SpecEl Software

SpecEl Software
ElliCalc
Software
Manual
Version 3.5
Ocean Optics
8.2.2011
Thin Film Metrology
CONTENTS
CONTENTS ....................................................................................................................................................................... 1
1 Introduction .................................................................................................................................................................... 3
1.1
Measurement setup ............................................................................................................................................. 4
1.2
Measurement signal ............................................................................................................................................ 4
1.3
Physical principle ................................................................................................................................................ 5
2
Installation .................................................................................................................................................................. 6
3
Product support ........................................................................................................................................................... 6
4
Getting started ............................................................................................................................................................. 7
5
User modes of ElliCalc ............................................................................................................................................... 9
5.1
SCOUT mode ..................................................................................................................................................... 9
5.2
Internal mode ...................................................................................................................................................... 9
5.3
Combiversion with NanoCalc ........................................................................................................................... 10
5.4
List of all menus and buttons ............................................................................................................................ 12
6
Basic features of ElliCalc ......................................................................................................................................... 13
6.1
Init ..................................................................................................................................................................... 13
6.2
Auto intensity.................................................................................................................................................... 13
6.3
Simulate ............................................................................................................................................................ 13
6.4
Measure............................................................................................................................................................. 14
6.5
Analyze ............................................................................................................................................................. 14
6.6
Continuous mode .............................................................................................................................................. 15
6.7
Fitness ............................................................................................................................................................... 15
7
Detailed features of ElliCalc .................................................................................................................................... 16
7.1
Main menu “File” ............................................................................................................................................. 16
7.1.1
Load layer recipe ...................................................................................................................................... 16
7.1.2
Import raw data ......................................................................................................................................... 17
7.1.3
Export raw data ......................................................................................................................................... 17
7.1.4
Print report ................................................................................................................................................ 18
7.1.5
Show all results ......................................................................................................................................... 18
7.1.6
Exit ............................................................................................................................................................ 18
7.1.7
Function keys ............................................................................................................................................ 18
7.2
Main menu “Screen” ......................................................................................................................................... 19
7.2.1
Spectrometer data ..................................................................................................................................... 19
7.2.2
Limits ........................................................................................................................................................ 21
7.2.3
Dispersion ................................................................................................................................................. 23
7.3
Main menu “Externals”..................................................................................................................................... 25
7.3.1
Mapping .................................................................................................................................................... 25
7.3.2
Result List ................................................................................................................................................. 31
7.3.3
Analyze mapped data ................................................................................................................................ 32
7.3.4
Structure of .map-file ................................................................................................................................ 32
7.3.5
Online/multipoint measurements .............................................................................................................. 32
7.3.6
Analyze online/multipoint data ................................................................................................................. 36
7.3.7
Structure of .onl-file .................................................................................................................................. 36
7.3.8
RS232 ....................................................................................................................................................... 36
7.3.9
Vision system............................................................................................................................................ 37
7.4
Main menu “Options” ....................................................................................................................................... 38
7.4.1
Change buttons ......................................................................................................................................... 38
7.4.2
Fit parameters ........................................................................................................................................... 39
7.4.3
Some setups .............................................................................................................................................. 39
7.4.4
Operator mode .......................................................................................................................................... 40
7.4.5
Remote control .......................................................................................................................................... 41
7.5
Main menu “Version” ....................................................................................................................................... 42
7.6
Chart and chartdesigner .................................................................................................................................... 42
8
Special features for “SCOUT mode” ........................................................................................................................ 43
8.1
Main menu “File” ............................................................................................................................................. 43
Ocean Optics
Thin Film Metrology
1
8.1.1
Change layer recipe................................................................................................................................... 43
8.2
Main menu “Screen” ......................................................................................................................................... 44
8.2.1
Psi/Delta or tan(Psi)/cos(Delta) ................................................................................................................ 44
8.3
Main menu “Options” ....................................................................................................................................... 44
8.3.1
Some setups .............................................................................................................................................. 44
9
Special features for “internal mode” ......................................................................................................................... 45
9.1
EditStructure button .......................................................................................................................................... 45
9.1.1
General ...................................................................................................................................................... 46
9.1.2
Catalogues ................................................................................................................................................. 47
9.1.3
Materials ................................................................................................................................................... 47
9.1.4
Thickness .................................................................................................................................................. 47
9.1.5
Estimates ................................................................................................................................................... 47
9.1.6
Fixed limits ............................................................................................................................................... 48
9.1.7
Narrow Limits ........................................................................................................................................... 48
9.1.8
Wide Limits .............................................................................................................................................. 48
9.1.9
User limits ................................................................................................................................................. 48
9.1.10
Number of layers ...................................................................................................................................... 48
9.1.11
Layer commands ....................................................................................................................................... 49
9.2
Main menu “Options” ....................................................................................................................................... 51
9.2.1
Roughness ................................................................................................................................................. 51
10
Experimental setups and problems ....................................................................................................................... 52
10.1 General .............................................................................................................................................................. 52
10.1.1
Experimental setup ................................................................................................................................... 52
10.1.2
Maximum intensity ................................................................................................................................... 52
10.1.3
Polarization ............................................................................................................................................... 52
10.1.4
Signal to noise ratio .................................................................................................................................. 52
10.1.5
Stray light.................................................................................................................................................. 52
10.1.6
Fiber .......................................................................................................................................................... 52
10.1.7
Absorbing media ....................................................................................................................................... 52
10.1.8
Passwords ................................................................................................................................................. 53
10.1.9
Function buttons ....................................................................................................................................... 53
11
Physical explanations ............................................................................................................................................ 54
11.1 Refraction index and absorption indices ........................................................................................................... 54
11.2 Cauchy coefficients........................................................................................................................................... 54
11.3 Interference ....................................................................................................................................................... 55
12
Thinfilm.ini ........................................................................................................................................................... 56
13
APPENDIX........................................................................................................................................................... 58
13.1 ElliCalc-Quick-Setup ........................................................................................................................................ 58
Ocean Optics
Thin Film Metrology
2
1 Introduction
ElliCalc is an ellipsometric software to extract thickness and optical data from thin, transparent layers on
different substrates. ElliCalc uses Ocean Optics microspectrometers.
ElliCalc offers a lot of different options like:
• Simulation and measurement of multilayer systems (weakly absorbing or transparent)
• A powerful software engine in the background (“SCOUT”)
• Additionally: an easy-to-use “internal “ mode for thickness extraction and/or Cauchy dispersion
• A graphical user interface that is very easy to use (recipes)
• Simulation of up to 10 layers (weakly absorbing or transparent)
• Highly accurate thickness measurements between some nanometers up to about 25 µm.
• Extraction of dispersion n(λ) and k(λ), roughness, EMA-fractions and other layer parameters, if
using SCOUT add-on (and Cauchy models in internal mode)
• 3D - mapping mode with a motor driven xy(z)-stage (=function of position)
• Online/multipoint measurements (=function of time)
• Remote control via OLE-commands from external software
• Video
• Combination with reflectometry (“NanoCalc”)
Measurement principle
A thin layer is illuminated with white light via a collimating optics and a spectrometer measures the change
of polarization (that occurs after reflection) as a function of wavelength. ElliCalc software determines
thickness (and optical parameters) of the layer.
The mathematics to extract useful data about the film is quite ambitious, but the user is separated from
these problems. The internally measured properties are called “Psi” and “Delta” (in degrees) or sometimes
tan(Psi) and cos(Delta). Of course in spectroscopic ellipsometry these 2 properties are measured as a
function of wavelength (in contrast to single wavelength ellipsometry)
ElliCalc has 2 different modes of operation:
1. data extraction via an optional software tool called “SCOUT”. This SCOUT software is very powerful
and works more or less in the background. SCOUT is able to handle very complicated dispersion
curves, but needs some experience with optical modeling. ElliCalc acts as a user interface to simplify
the data extraction process. Even without deep understanding of the underlying physics it is possible to
measure complex layer systems by using a recipe concept. A layer recipe has to be loaded and the
rest is a “one-button-solution” (of course there must be an expert in the beginning to establish this
recipe. Ask your software supplier…)
2. data extraction by ElliCalc itself (without SCOUT). In this “internal mode” it is very easy to extract
thicknesses and –to some extent- dispersion values without optical modeling. Recipes may be used,
but even without recipes it is extremely simple to get results. This “internal mode” does not need an
expert, but it is not as powerful as the “SCOUT mode”.
Ocean Optics
Thin Film Metrology
3
1.1
Measurement setup
spectrometer
polarizer
white light
source
analyzer
A broadband white light source is focused on a thin layer under oblique incidence. The incoming light is
polarized by a “polarizer”, the reflected light is analyzed by an other polarizer, the so called “analyzer”. The
intensity as a function of wavelength is measured by a spectrometer, a PC extracts the wanted information.
1.2
Measurement signal
The typical modulated signal of such a spectroscopic thin film measurement might look like this (after some
data manipulations):
On the screen you see two different curves (Ψ/∆or tan(Ψ) and cos(∆) as a function of wavelength. ElliCalc
uses these signals to extract thicknesses and optical data for this (SiO2 ) layer on Si.
Ocean Optics
Thin Film Metrology
4
1.3
Physical principle
The measurement principle of ElliCalc is the well-known fact of oblique reflection and interference of light
in thin layers. Light is reflected (and normally transmitted), resulting in different phase shifts and different
intensities for different wavelengths. Ellipsometry measures the change of phases and intensities between
vertically and horizontally oriented light and calculates different layer parameters like dispersion or
thickness.
reflected intensity
70°
70°
layer
substrate
transmitted (and
absorbed) intensity
After some calculations ElliCalc will show a result (here: 998 nm) nm as the best fit to the experimental
data (blue and magenta curves=measured signals, black curves = theoretical curves):
Ocean Optics
Thin Film Metrology
5
2
Installation
ElliCalc (and SCOUT) is delivered on a CD-ROM.
Insert the CD-ROM in your CD-ROM drive, use Microsoft Explorer to run „ElliCalc-Setup.exe “. Do not call
“ElliCalc.exe” at this level, if you happen to find it in some subdirectory.
ElliCalc will ask you for a directory (and propose a directory „c:\programs\ElliCalc“).
If you prefer other names, change this to "c:\MyPrograms\ElliCalc” or any convenient directory name).
Reboot the PC after installation.
Deinstallation:
If you want to deinstall ElliCalc from your computer, go to „system control“, „software“ and deinstall ElliCalc.
Do NOT just delete it because ElliCalc adds some files to your windows\system directory !! Always deinstall the software properly.
3
Product support
Please contact your local distributor for product support. Here you can find additional information:
www.OceanOptics.de
Ocean Optics
Thin Film Metrology
6
4
Getting started
After installation of your hardware and software you should be ready to make your first measurements.
An example:
1. For the first steps it is a good idea to use a special “step wafer” with different oxide thicknesses. You
can use this wafer to check the correct functionality of the ellipsometer. Please ask your hardware
supplier for information about step wafers.
Otherwise use a really well known sample with good optical properties (not rough, homogenous,
simple layer structure, like SiO2 on Si). Put the wafer on the stage.
2. Choose a room without too much light, avoid full sunlight and reflections (you might run into problems
with stray light).
3. Load a layer recipe (via “files/load layer recipe”) corresponding to your sample, e.g. “SiO2 on Si.lrc”.
Then the structure in Setup picture shows a correct layer system
4. Then put your wafer in the middle of the chuck and switch on your power supply and lamps
5. Start ElliCalc.exe (there should be no warnings or error messages) and wait unil all messages “please
wait” have disappeared.
6. click on the button „init“and wait unil all wait and progress messages have disappeared.
7. Now the ellipsometer motors are initialized. There is no absolute need to press the button “auto
intensity”, as this action has been performed by “init” (but are allowed to do it….)
8. Now press the button “continuous”, you should see a live signal. Try to maximize this signal by using
the height adjustment and the tilt adjustment of your stage. In case that these 2 adjustments were
considerable: press “auto intensity” to optimize the integration time again.
9.
10.
11.
12.
13.
14.
Now click on the button “init” and wait for some seconds. The motors of the ellipsometer will move to
their starting positions.
Click on the black button “continuous”. The button turns to red and you should see an intensity signal
on the screen. Manually adjust the height of your stage to maximize this signal. Click on the (red)
button “continuous” again to stop this mode.
Click on the button “auto intensity”. The integrations times are chosen automatically so that the
maximum signal height is about 75% of the maximum to avoid saturation. If you change your sample
now or later and the new sample has a different reflectivity you have to press the button “auto
intensity” again. If the new sample is of the same type as before this is not necessary but advisable.
Now click the button “measure”. The measurement will take some seconds.
Now you see the measured data with the typical interference wiggles.
Then click on the button „analyze“ and wait for the result. You should get meaningful results.
Ocean Optics
Thin Film Metrology
7
Ocean Optics
Thin Film Metrology
8
User modes of ElliCalc
5
ElliCalc has two different user modes, the “SCOUT-mode” and the “ElliCalc internal mode”. At the moment
the “SCOUT-mode” is the normal mode, the “internal mode” can only extract thicknesses and Cauchy
dispersion
The “SCOUT-mode” requires that another software, called “SCOUT” is installed on this PC, the “internal
mode” only uses ElliCalc.
5.1
SCOUT mode
ElliCalc works as a graphical user interface for a sophisticated film software “SCOUT” working in the
background.
The whole process is necessarily driven by recipes.
SCOUT sc2-recipe
SCOUT
calculation
•
•
•
•
ElliCalc lrc--recipe
ElliCalc:
measure spectrum
display results
SpecEl
ellipsometer
within ElliCalc you have to load a “recipe”, e.g. “SiO2 on Si.lrc”. This ASCII-readable recipe
contains a link to a SCOUT recipe like “SiO2 on Si.sc2”. All necessary layer informations are
contained in this SCOUT recipe and are read by ElliCalc, but only for display purposes.
ElliCalc now controls the hardware, measures the sample and sends the measured Psi/Delta-values
to SCOUT (via a file EC_Data.xy in directory “ElliCalc\Internal_Files”).
SCOUT does the calculation of all parameters
the results are given back to ElliCalc via OLE-connection. The main fit parameters (thickness,
refraction, absorption, roughness and EMA-fractions) are displayed by ElliCalc, as well as all other
SCOUT fit parameters.
This SCOUT mode relies totally on good SCOUT recipes. So there must be someone (you or the
administrator or OceanOptics) in the background being familiar with the details and the physics of SCOUT.
The advantage is a “one-button-ellipsometry” for the user and an enormous calculation power !
5.2
Internal mode
In this internal mode the user can create own layer stacks and does not need the external SCOUT software
at all. There is no need to work with recipes, but is is recommended. BUT: At the moment only thickness
values and a Cauchy dispersion can be extracted.
ElliCalc lrc-recipe
ElliCalc:
define layer stack
measure spectrum
calculate thickness
display thickness
Ocean Optics
Thin Film Metrology
SpecEl
ellipsometer
9
5.3
Combiversion with NanoCalc
If you bought a combiversion ElliCalc + NanoCalc (= ellipsometry and reflectometry) you will see an extra
menu “version”. Here you can switch from one application to the other.
Ocean Optics
Thin Film Metrology
10
Ocean Optics
Thin Film Metrology
11
5.4
List of all menus and buttons
Main menu
Sub-menu
FILES menu
Load Scout layer recipe
Load ElliCalc layer recipe
Save as layer recipe
Change layer recipe
Export raw data
Import raw data
Show all results
Exit
Spectrometer data
Limits
Dispersion
Psi/Delta or tan(Psi)/cos(Delta)
Mapping
Analyze mapped data
Online/multipoint
Analyze online data
RS232
Video camera
Show plot
Change buttons
Roughness
Special modes
Fit parameters
Some setups ElliCalc (motor steps)
Some setups SCOUT (stoptime)
Some setups (change colors)
NanoCalc_1
NanoCalc_10nk
Contents
About
SCREEN menu
EXTERNALS
OPTIONS
VERSION
HELP
EDITSTRUCTURE
Ocean Optics
Thin Film Metrology
SCOUT
mode
x
Internal
mode
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
(x)
x
x
x
x
x
x
x
x
x
x
X
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
12
6
Basic features of ElliCalc
6.1
Init
This button performs 2 tasks:
• initialize the motors for polarizer and analyzer (e.g. end positions)
• automatically set the integration times to good values (so there is no need to press “auto intensity”
directly after an init procedure). But: If you change the stage height you should apply “auto intensity”
hint:
If you change your sample you may run into saturation of the spectrometer = a (nearly) horizontal part in
some of the measured curves near to the upper limit of the plot.
6.2
Auto intensity
This option automatically adjusts integration times.
This button has to be pressed if you use a completely different sample (each sample has a different reflectivity, so a different integration time). Normaly the “init button” already has performed such an auto intensity
procedure.
If your sample is of the same type as your last sample (=has nearly the same reflectivity) it is not necessary
to press this button.
AutoIntensity tries to get 75% of the maximum allowed value. You can change this value by manually editing
the file “thinfilm.ini”
6.3
Simulate
This routine simulates a spectrum.
• in SCOUT-mode:
from the .sc2-layer recipe data within SCOUT
• in ElliCalc internal mode: from the data in EditStructure (identical to the data in Thinfilm.ini-file)
Ocean Optics
Thin Film Metrology
13
Hint:
If you want to have a short check which structure is simulated at the moment, put the mouse cursor over
the appropriate layer for some seconds and you see the layer thickness.
OR:
Leave your mouse cursor for some seconds over the button SIMULATE and look at the text in the status
bar.
6.4
Measure
This routine measures the ellipsometric spectra of your test device.
If you use a double spectrometer, you had to adjust the crossover wavelength. Below this wavelength the
data are collected from channel A ("master spectrometer"), above this wavelength they are collected from
channel B ("slave spectrometer").
6.5
Analyze
This routine analyzes a spectrum (either simulated or measured) within the data extraction limits.
• In SCOUT-mode: SCOUT is doing the calculations. The structure that is simulated may only be
changed within SCOUT.
• In ElliCalc’s internal mode: ElliCalc is doing the calculations (only thickness and Cauchy parameters at
the moment)
Hint:
To have a short check which structure is simulated at the moment, put the mouse cursor over the
appropriate layer for some seconds and you see the layer thickness.
OR:
Leave your mouse cursor for some seconds over the button SIMULATE and look at the text in the status
bar.
Ocean Optics
Thin Film Metrology
14
6.6
Continuous mode
The continuous button switches between continuous mode (=red button) and “stop continuous” (button
=black). Then there will be a continuous measurement of the signal (necessary to adjust the height and tilt
of your stage !!)
All others buttons of ElliCalc are disabled until you finish the continuous mode.
6.7
Fitness
Any extraction of parameters is accompanied by a value of "fitness". This is the sum of the mean square
deviations between measured and simulated curve (normalized to the range of extraction). The fitness is a
rough guide whether your thickness value is "good" or not.
In the file “Thinfilm.ini” you will find 3 entries in section [fit]:
Failure_RedLevel=1
Failure_YellowLevel=0.1
RYG_LevelsAreDisplayed=False
If you change the variable RYG_LevelsAreDisplayed from “False” to “True” (in main menu “Fitparameters”),
the usual rainbow pattern on the screen will disappear and a simple color will show up.
• If the fitness is below Failure_YellowLevel=0.1 you will see a GREEN color.
• If the fitness is between Failure_YellowLevel=0.1 and Failure_RedLevel=1 you will see a
YELLOW color.
• If the fitness is above Failure_RedLevel=0.1 you will see a RED color
Attention:
If you measure very thick layers (with a good correlation between maxima positions, but bad correlation
between signal heights) you may end up with high values of fitness, but nevertheless the thickness results
may be o.k.
Ocean Optics
Thin Film Metrology
15
Detailed features of ElliCalc
7
In this chapter the most common commands and menus of ElliCalc are decribed.
Special commands and menus for “SCOUT mode” and for ElliCalc’s “internal mode” are decribed in later
chapters.
7.1
Main menu “File”
Internal mode
SCOUT mode
Load layer recipe
7.1.1
This routine loads a layer recipe that has been saved earlier (extension: .lrc). Do not change the extension
.lrc.
In SCOUT mode you may either load another SCOUT recipe (“load Scout layer recipe”) or you may switch
to ElliCalcs internal mode (“Load Ellicalc layer recipe”). See the screenshots above.
In SCOUT mode all buttons captions are in italic, otherwise in normal.
It is assumed that all .lrc-files are in the default directory “ElliCalc\recipes\layer_recipes”, but you can
change the directory path to any other directory on your PC (provided that you did not use "UseLastFilenames_EC=False" in section [Filenames_EC] in Thinfilm.ini).
Ocean Optics
Thin Film Metrology
16
There is a section [Scout] in this layer recipe with an entry for "Scout_Recipename_EC". This entry is a link
to the corresponding SCOUT .sc2-recipe in the directory "c:\programs\scout\scout_sc2_recipes" (or similar
directory name).
If this linked .sc2-recipe is existent, SCOUT will be used for calculations = “SCOUT mode”. If this link is
empty, ElliCalc will calculate without SCOUT = “internal mode” (at the moment only for thicknesses and
Cauchy parameters!)
Example for SCOUT-mode (in ellipsometry):
[Scout]
Scout_DirPath=c:\programs\scout
ScoutStopTime=15
Scout_RecipeName_NC=
Scout_RecipeName_EC=SiO2 (table) on Si.sc2
Example for ElliCalc internal mode:
[Scout]
Scout_DirPath=c:\programs\scout
ScoutStopTime=15
Scout_RecipeName_NC=
Scout_RecipeName_EC=
The *.lrc-file is an ASCII file that contains most parameters of the software, but NO measured or simulated
values of psi/delta (or tan(psi) /cos(delta)) as a function of the wavelength.
If you load a recipe you will not see any curve on the screen, but a change in the setup or the limits.
Import raw data
7.1.2
(internal mode and SCOUT mode)
You are asked for an import- directory. The imported values are displayed in blue (=similar to measured
values). The scale of the screen is not adjusted.
Export raw data
7.1.3
(internal mode and SCOUT mode)
If a curve was produced by simulation or measurement it may be exported as ASCC-file (“raw data”). This
file has a very simple structure: (lambda, tan(Psi), cos(Delta)
350,0.796,0.064
351,0.780,0.050
352,0.764,0.034
353,0.749,0.014
354,0.736,-0.009
355,0.722,-0.035
356,0.710,-0.064
357,0.697,-0.096
You are asked for a directory to save this file. Please use the default directory \RawData_Files\Ellipsometry
Ocean Optics
Thin Film Metrology
17
Print report
7.1.4
This routine allows you to enter some user data (names of operator, of sample and so on), shows a
preview and prints on the Windows standard printer. Changing the printer is possible only within Windows
itself.
Entering of user data: you may also change the names of the labels (empty labels: this line is not shown on
the final print). In the preview window you may zoom in and out. After pressing the print button you have
the chance to change some printer options.
If you want to get a printout of the complete screen or parts of it:
It is recommended to use a hardcopy program to print the different parts of the software with enough
options to change colors, resolution etc.
We recommend a shareware ”HC.EXE” (http://www.sw4you.de and on the CD-ROM in : tools\general),
which will include a small button in every (!) window of your system near to the close button.
For online-users: we recommend to buy the OPTION ElliCalc-Online for printouts of Multipoint
Measurement, Result-Windows with Statistic Data’s and Excel-Connection.
Show all results
7.1.5
See chapter “Special features for SCOUT mode”
Exit
7.1.6
This routine exits ElliCalc and SCOUT and closes all windows. All important data have been written to the
Thinfilm.ini -file before and will be reloaded in the next run.
Important warning:
Do NOT close SCOUT separately !!! This would break the OLE-connection between SCOUT and ElliCalc.
The only way to restore this connection is to exit ElliCalc and restart the software !
Function keys
7.1.7
If you click on the button F1, you get access to help functions.
Ocean Optics
Thin Film Metrology
18
7.2
7.2.1
Main menu “Screen”
Spectrometer data
The 4 spectrometer coefficients are
displayed for information purposes. They
are automatically set by the Thinfilm.ini file
which is specific for each single system.
Changing these values will screw up the
system and is therefore password
protected and only accessible for technical
service.
For calibration purposes you may change
these values (with a password and only
within several percent deviation from your
original values).
physical meaning:
These 4 numbers are the coefficients in a formula that shows the dependence between wavelength (in
nanometers) and pixel number of your spectrometer according to the following formula:
λ = I + C1 ⋅ P + C 2 ⋅ P 2 + C3 ⋅ P 3
with:
I
C1
C2
C3
P
= intercept
= first coefficient
= second coefficient
= third coefficient
= pixel number
Hint:
Ask your hardware supplier if you have the impression that it might be necessary to recalibrate the
spectrometer (a red HeNe-laser should show 632.8 nm)
7.2.1.1 Integration time
Whenever you change this value, it is written to disk (in file “Thinfilm.ini”) and will be used as a startup
value.
How to change integration time:
1. method = “auto intensity” button (or “init” button !): This method starts with the lowest available integration times for different positions of the polarizer and checks the resulting spectra (every 10 nm) to find
an optimum integration time. The software will try to achieve a maximum signal of 75 % of the total
range and will try to avoid saturation. The absolute value of the integration time will depend very much
on the reflectivities of your reference materials, your substrate material and your layer material.
2. method = use the menu "options/spectrometer data" and and enter a value. Be careful: this may lead to
bad results ...
Ocean Optics
Thin Film Metrology
19
You may check the value of integration time at any time without entering the menu OPTIONS: Put your
mouse cursor over the button MEASURE and wait for about 2 seconds: a small window will pop up to inform you about integration time, samples to average and boxcar width.
These values correspond to the channel A ("master spectrometer") if you use a double spectrometer.
7.2.1.2 Boxcar width
physical meaning:
The OceanOptics spectrometer is able to average over some pixels to increase signal/noise-ratio.
A boxcar width of 1 pixel means no averaging at all (which is an ideal situation and would correspond to a
very narrow fiber). This has to be used if you want to measure very thick layers (like 50 micrometers of resist)
A boxcar width of 5 pixels means an averaging over 2 pixels on the left side and 2 pixels on the right side
(= 5 pixels altogether). This averaging routine is shifted from the left side of the simulated spectrum to the
right side with a step size of 1 pixel only. Values of 5-9 are recommended if you want to measure films in
the range of 1 micrometer or less as you get a better signal-to-noise ratio.
hint:
You may check boxcar width at any instance without entering the menu OPTIONS: Put your mouse cursor
over the button REFERENCE or MEASURE and wait for about 2 seconds: a small window will pop up to
inform you about integration time, samples to average and boxcar width.
These values correspond to the channel A spectrometer if you use a double spectrometer.
7.2.1.3 Samples to average
Whenever you change this value, it is written to disk (in file “Thinfilm.ini”) and will be used as a startup
value.
physical meaning:
The Ocean Optics /spectrometer is able to average over some runs to increase signal/noise-ratio.
Tips:
Try to use small values for Samples To Average while keeping the lamp intensity as high as possible (to
get short measuring times). This is especially important in mapping mode.
You may check Samples To Average at any instance without entering the menu OPTIONS: Put your
mouse cursor over the button MEASURE and wait for about 2 seconds: a small window will pop up to
inform you about integration time, samples to average and boxcar width.
7.2.1.4 Internal correct for dark
If you choose this option, dark current is corrected automatically (see button “measure”).
The Ocean Optics Spectrometer is able to measure the dynamic dark current internally within a couple of
pixels that are NOT irradiated by external light, and is correcting dynamically.
7.2.1.5
Dark button
Ocean Optics
Thin Film Metrology
20
If you choose this option, dark current is corrected mathematically. This is only necessary if you can’t
protect your system against ambient light or stray light.
7.2.1.6 Maximum intensity
This value describes the maximum intensity in the spectrum of your (halogen ?) lamp.
This value helps ElliCalc to achieve an automatic adjustment of the integration time within the limits of the
screen (=without saturation)
If you use a double spectrometer there are TWO such wavelengths corresponding to the different lamps
and the different sensitivities of the two spectrometers.
If you use a double spectrometer with different sensitivity regions, e.g. 200-600 nm for channel A ("master
spectrometer") and 500-1100 nm for channel B ("slave spectrometer"), ElliCalc joins the 2 spectra to get a
single spectrum (200-1100 nm). The wavelength where the two overlapping spectra are joined is called
"crossover wavelength". (any value is possible, 550 nm would be a good choice in this case).
7.2.1.7 Crossover wavelength
If you use a double spectrometer with different sensitivity regions, e.g. 200-600 nm for channel A ("master
spectrometer") and 500-1100 nm for channel B ("slave spectrometer"), ElliCalc joins the 2 spectra to get a
single spectrum (200-1100 nm). The wavelength where the two overlapping spectra are joined is called
"crossover wavelength". (any value is possible, 550 nm would be a good choice in this case).
Limits
7.2.2
The spectrometer limits in magenta colors are showing the maximum range of your specific system.
7.2.2.1 Plot limits
The plot limits are the left and right side of the plot on your screen and coincide with limits of measurement.
The adjustable values of the plot limits depend on the grating in your Ocean Optics spectrometer and are
noted in the calibration sheet of your system.
Ocean Optics
Thin Film Metrology
21
The plot limits may be changed within ElliCalc in steps of 1 nm.
1. normal mode to change the limits:
open the menu “spectrometer data \ limits” and enter numbers or use the up-down arrows
2. fast and rough method to change the limits:
If you click in the field near the LOWER numbers you may change the plot limits without entering the
menu option/limits:
If you click in the LEFT half with your LEFT mouse button you will decrease the lower plot limit.
If you click in the LEFT half with your RIGHT mouse button you will increase the lower plot limit.
If you click in the RIGHT half with your LEFT mouse button you will decrease the lower plot limit.
If you click in the RIGHT half with your RIGHT mouse button you will increase the lower plot limit.
The same feature applies to plot limits and reflectivity limits.
3. fast and precise method to change the limits:
If you move your mouse very near to the lower part of the plot window (but still in the grey part) you will
see a little vertical arrow and the value of the wavelength is displayed. If you now click with the left
mouse button, you are able to change the lower plot limit (right mouse button=upper plot limit). The
same applies to the other 2 grey zones = extraction and reflectivity limits (see picture)
4. Zoom
You may zoom by dragging the
mouse from one point to
another within the plot area.
If you click with the right mouse
button a small popup window
will appear with the chance to
undo this zoom.
You can also change the plot
limits back to the full range
(according to your spectrometer
limitations).
You can also set the current plot
limits as a standard or return to
a previously set standard.
ATTENTION:
Tto be consistent with data handling, ALL materials files contain n and k data between 150 nm and
1100 nm. Usually only parts of these data are measured data (e.g. between 206 nm and 840 nm or
between 300 nm and 1100 nm). If you simulate, the valid part of the curve is shown in black while the
rest is shown in grey (and you get a message).
Extraction limits are restricted to the range of valid n and k data.
7.2.2.2 Extraction limits
These limits cannot be larger than the plot limits. Try to use a large extraction range as long as your signal
is “good”.
1. normal mode to change the limits:
open the menu “spectrometer data \ limits” and enter numbers or use the up-down arrows
2. fast and rough method to change the limits:
If you click in the field near the UPPER numbers you may change the extraction limits without entering
the menu “spectrometer data \ limits”.
If you click in the LEFT half with your LEFT mouse button you will decrease the lower extraction limit.
If you click in the LEFT half with your RIGHT mouse button you will decrease the lower extraction limit.
If you click in the RIGHT half with your LEFT mouse button you will decrease the lower extraction limit.
Ocean Optics
Thin Film Metrology
22
If you click in the RIGHT half with your RIGHT mouse button you will decrease the lower extraction limit.
The same feature applies to plot limits and reflectivity limits.
3. Fast and precise method to change the limits:
If you move your mouse very near to the upper part of the plot window (but still in the grey part) you will
see a little vertical arrow and the value of the wavelength is displayed. If you now click with the left
mouse button, you are able to change the lower extraction limit (right mouse button=upper extraction
limit)
ATTENTION:
To be consistent with data handling, ALL materials files contain n and k data between 150 nm and 1100
nm. Usually only parts of these data are measured data (e.g. between 206 nm and 840 nm or between 300
nm and 1100 nm).
If you simulate, the valid part of the curve is shown in black while the rest is shown in grey (and you get a
message).
Extraction limits are restricted to the range of valid n and k data.
7.2.2.3 Y limits
To zoom in the plot and to see some more details you may change the Y limits. In most cases you will not
need this option.
1. normal mode to change the limits:
open the menu “spectrometer data \ limits” and enter numbers or use the up-down arrows
2. fast and rough method to change the limits:
If you click in the field near the LEFT numbers you may change the reflectivity limits without entering
the menu option \ limits:
If you click in the LOWER half with your LEFT mouse button you will decrease the lower reflectivity limit.
If you click in the LOWER half with your RIGHT mouse button you will decrease the lower reflectivity
limit.
If you click in the UPPER half with your LEFT mouse button you will decrease the lower reflectivity limit.
If you click in the UPPER half with your RIGHT mouse button you will decrease the lower reflectivity
limit.
The same feature applies to plot limits and reflectivity limits.
2. Fast and precise method to change the limits:
If you move your mouse very near to the left part of the plot window (but still in the grey area) you will
see a little horizontal arrow and the value of the wavelength is displayed. If you now click with the left
mouse button, you are able to change the lower reflectivity limit (right mouse button=upper reflectivity
limit)
Dispersion
7.2.3
This form shows the refraction index n and the absorption index k (within the plot limits) for different layers.
This form is just a tool to control your data, nothing can be really changed in this form.
There are two cursors available for n and k (press the cursor symbol and drag them with the mouse, atrthe
beginning they are on top of oneanother)
• You may use 2 cursors (symbol #4). At start time of the cursors both cursors are painted on top of
one another, move them with the mouse. The cursor values are shown in blue (= k(λ)) and red (=n(λ))
• You may also zoom in and out and in an area (symbols #1 - #3)
Ocean Optics
Thin Film Metrology
23
You may also save these dispersion values
as a dat-file, but be very careful about the
target directory !!
ATTENTION:
To be consistent with data handling, ALL materials files contain n and k data between 150 nm and 1100
nm. Usually only parts of these data are measured data (e.g. between 206 nm and 842 nm or between 300
nm and 1100 nm).
If you simulate, the valid part of the curve is shown in black while the rest is shown in grey (and you get a
message).
Extraction limits are restricted to the range of valid n and k data.
Ocean Optics
Thin Film Metrology
24
7.3
7.3.1
Main menu “Externals”
Mapping
You need a mapping-xy-stage and a special mapping
add-on software for ElliCalc to measure in mapping
mode. In this mode it is possible to measure and
display your film parameters as a function of x and y.
Ocean Optics
Thin Film Metrology
25
main menus of mapping mode
1. menu “Recipes”
• Save as map recipe
• Load map recipe
Here you may save or load ALL the settings you have done in all the various possibilities. It is
recommended to save your usual settings in a recipe. It is possible to use a special recipe name like
“myownRecipe”. Recipes for mapping will receive the extension “.mrc” and will be saved in menu
“Recipes\Map_Recipes”
2. menu “Teach in”
This will be explained later in the following section
3.menu “help”
this is the usual access to help functions
main buttons (lower right side)
init stage
you can initialize your ellipsometer (right mouse button=time adjustments possible)
auto intensity
you can adjust the nintegration times automatically (right mouse button=time adjustments possible)
measure
you can take a real (test) measurement with your sample. Thus you can control all settings before you
start the mapping
clear
clears the screen
conti
this will make a continuous mode for measurement
analyze
you can analyze the layer parameters your sample. Thus you can control all settings before you start
the mapping
initialize stage:
After starting mapping mode you have to initialize the xy-mapping stage first.
Until the xy-mapping stage is initialized the function start mapping is deactivated.
start mapping
this will start the mapping sequence
cancel
leave mapping mode
Scan mode:
a. shape of the wafers:
1. You may use square or round wafers.
2. To use your own design as a background you need to edit the file
OwnDesign.bmp within the ElliCalc directory (this is possible with
lots of drawing programs, or ask your software supplier for help).
b. wafer size
Wafer size may be changed between 50 mm and 300 mm (= 8''). A
grid is shown with a constant grid distance (e.g. 10 mm).
c. scan region
It is possible to change:
- the x and y coordinates of the origin in steps of 0.1 mm
- the number of rows and the number of columns of the scanning
grid
(from 1 to 100)
- the size of the x and y steps (in multiples of 0.1 mm)
The wafer plot shows what you are doing.
d. rotation
Ocean Optics
Thin Film Metrology
26
here you can rotate the scan region
e. mapping positions
measuring position:
If you press one of the position buttons, the mapping stage will immediately go to this point and a red circle
is displayed on the screen. Additionally the coordinates of this point are displayed. If option "measure on
each click" in Tab2 is activated, a measurement will be performed.
You may reach any point by clicking with the LEFT mouse button or by entering the coordinates and
pressing the xy-button.
You may move up and down or left and right by pressing the appropriate arrow buttons. If you press the
arrow buttons with the left mouse button the cursor will move in increments of xSteps. If you press the arrow
buttons with the right mouse button the cursor will move in smaller increments of xSteps/10
f. position buttons:
1. home position
Typically this is in the right lower corner of the xy-stage. The hardware of the stage will define this point
at the beginning of the mapping experiment (and it can be changed manually in the ini-File in section
[mapping], HomepositionX/Y=.... The numbers mean the percentage compared to wafersize (0.05 =5%
of wafersize)
2. scan position
this is the origin of the scanning coordinate system
3. center position
this is the center of the (round) wafer stage
The wafer plot shows what you are doing.
Wafer:
The shape of the substrate may be:
a. circular (between 50 and 300mm)
b. square (between 50 and 300 mm)
c. your own design (change file "OwnDesign.bmp" with any drawing
software)
example:
Wafer size may be changed between 50 mm (= 2'') and 300 mm
(=8””).
Ocean Optics
Thin Film Metrology
27
Stage:
Ocean Optics can deliver an xy-stage for 8'' (=300mm).
a. serial port:
The port is used for communication with the mapping-stage. Ask your
hardware supplier for details..
To drive the mapping-stage you need one COM-port for xy-stages (or
a USB port and a converter).
b. wait interval:
After each measurement the scanning may be interrupted for a
certain interval of time
c. single step:
If you activate this option each single measurement is waiting for a
trigger signal (a keystroke with ENTER key or an external TTL trigger
signal which is applied to the spectrometer. Ask your hardware
supplier…)
Data extract:
a. plot during map
With this option you choose the layer you want to "extract" = to
display.
You cannot choose more than one parameter as only one
parameter can be displayed at a time. If you use ElliCalc_10nk you
may calculate up to 10 layers (but display ONE of these)
b. analyzing options
Analyze parameters on each left mouse click. This is a very useful
feature to make a quick check on film parameter distributions on
your wafer (do not forget to activate option "plot value during
mapping").
Fitness limit: if your results are completely wrong for some
reasons, all measured values with a fitness greater than this fitness
limit here will be set to zero. This feature is useful, if dust causes a
measurement error during mapping. Without this feature you might
get enormous spikes.
c. visible during map
You have the choice between 1D-plots for line scans, 2D-plots
and/or 3D-plots.
The 2D-plot and the 3D-plot contain the same data.
A 1D-plot is possible only if you measure along ONE row or
column (and not a two-dimensional field.)
d. number of runs
You have the choice between a single run (for real measurement
purposes) and a nearly infinite number of runs (=30000) for
demonstration purposes.
Ocean Optics
Thin Film Metrology
28
Data export:
You may choose the following options during a mapping experiment:
1. plot the simulated curve
2. plot parameter value
It is more informative to see the analyzed curve and the calculated
parameter value during the simulation, but this is time-consuming. If
the mapping takes a longer time it is recommended to switch off
these 2 features.
You may choose the following options after a mapping experiment:
1. write data as map-file
2. insert comments in map or Excel-files
3. show results window
1. Write data as map-file
All parameter and fitness data together with some coordinate
information are written to a ASCII-file in directory
“ElliCalc\data\map_files”.
examples can be found in the directory “ElliCalc\data\map_files”
2. insert comments in map or Excel-files
you may enter text like “sample #1, “Paul McCartney” or
“myfirsttest”.
This text will be a header for your map-files and also for all
exported Excel_files
3. show result window
If you accept this option a results window with possibility for Excel
export will open after the mapping process.
Scan data:
This feature is used in microscope arrangement (e.g. for measuring
structured wafers) if you want to hit the xy-positions with higher
accuracy.
Usually the wafer or sample will be positioned on the chuck with
some mechanical adjustments (like pins on 2 sides of the wafer and
adjustment to the wafer flat). This will result in a medium accuracy,
but not comparable to fine positioning like in semiconductor
photolithography.
How to get a higher accuracy:
1. click on “marker 1”:
The stage will move to this position. If you now look through the
microscope you will see a slight deviation between the illuminated
spot and the real marker on your wafer.
2. Correct this deviation by moving the stage (use the keyboard
arrows: clicking or pressing once = 10 micrometer, SHIFT +
clicking or pressing once = 1 millimeter). The red circle on the
screen will move slightly off the marker.
3. Repeat step 1 and 2 for marker 2
4. Now the software knows both deviations and is able to calculate
what to do: shifting the origin and rotating the scan pattern a little
bit. Press the button: “accept teach-in”
5. Control the values of rotation angle and xy-origin
6. Start mapping as usual
Ocean Optics
Thin Film Metrology
29
Teach in:
Teach in is an interactive tool to write new map-recipes without using text editors to edit the map recipe file.
Now the method with teach-in-mode:
1. Open the mapping window (main menu “map data”) and then the menu “TeachIn”
2. You will see this window:
3. To set the first marker position, click on “marker 1”, then move the measuring position
with the arrow keys on the keyboard
or by clicking somewhere in the wafer area
or by typing values in the text box
4. To set the second marker position, click on “marker 2”, then move the measuring position as before
5. To set the first data point, click on “data”, then move the measuring position as before
6. To set the next data point, click on the up down counter (now it should show the value 2 instead of 1)
and then move to the measuring position as before
7. Save the new recipe (like test.mrc) with the extension .mrc
Ocean Optics
Thin Film Metrology
30
It is possible to change any or these values by clicking on the first columns in the appropriate row. Then the
stage moves to that position and you are able to change it.
It is NOT possible to interchange or delete rows.
Result List
7.3.2
As soon as the mapping is finished you will see a result list:
On the first page you see the measured thickness values for each layer. In the picture above there was just
one layer and 3 x 3 = 9 measured data points. In the last page you can see the associated fitness values for
each coordinate. In the text windows below the data window you see mean values, maximum and minimum
values and standard deviation σ, the 3σ-value and the number of failures (according to the measured fitness
and your fitness limit).
If you did not choose a regular scan pattern, you will see a one-dimensional list.
If you click on the buttons with the numbers in a row or a column you will highlight a certain number of data
points (in the picture above column 3 was highlighted). Now you can control these selected values in a oneor two-dimensional plot by pressing the appropriate button in the last row. You may also choose a smaller
amount of data by dragging with the mouse (e.g. 2 x 2 = 4 points).
Ocean Optics
Thin Film Metrology
31
If you press “write data to EXCEL-file” EXCEL will be opened (if installed on your PC) and the data will be
transferred to a spreadsheet.
With “close all windows” you will return to NanoCalc main window and all mapping windows will be closed.
If you enter a value for “fitness limit” and press ENTER, the screen will be updated and all cells with a higher
fitness than your limit will be plotted in red (cells in grey show that this point was outside the wafer).
Analyze mapped data
7.3.3
This feature helps to analyze mapped data that have been measured earlier.
You are asked for a file name (extension .map) in directory ElliCalc\data\map_files. Then the results window is opened and you may inspect your data, plot the data or export them to Microsoft Excel.
Structure of .map-file
7.3.4
The first 2 lines are comments, the file format is very strict.
test4
user4
***
xy-ScanMode
1 Layer(s)
1 Layer(s)ToExtract
2 Row(s)
2 Col(s)
4 total points
5 xStep
5 yStep
***
IndexNo, row, col, x, y, fitness, d1
1, 1, 1, 30.000, 30.000, 0.048, 132.880717
2, 1, 2, 35.000, 30.000, 0.048, 132.806642
3, 2, 1, 35.000, 35.000, 0.048, 132.918102
4, 2, 2, 30.000, 35.000, 0.048, 132.858514
7.3.5
Online/multipoint measurements
Ocean Optics
Thin Film Metrology
32
load online recipe:
The online setup window contains lots of input data, so
usually you will want to use an online recipe to do that job
for you.
You will be asked for a file name (usually in directory
“ElliCalc\recipes\online_recipes”). After loading this file
nothing happens except new parameters in setup, like
different y-axis or other trigger parameters.
save as online/multipoint recipe:
The online setup window contains lots of input data, so usually you will want to use an online recipe to do
that job for you.
If you changed some setup parameters you can save them as a new online recipe.
You will be asked for a new file name (usually in directory “ElliCalc\recipes\online_recipes”).
online/multipoint setup:
Depending on the switch “show setup first” in menu “online\setup” the setup window for online
measurements is shown at first or not. If you want to rename your files at the beginning of each
measurement cycle it is recommended to open the setup window first.
Ocean Optics
Thin Film Metrology
33
The setup window contains lots of input data, so usually you will want to use an online recipe to do that job
for you.
Save mode:
In this first part of online setup you can
choose:
a. Option “save mode“
1. Do not save the online data
all data are lost and only visible on screen
2. save online data to RAM
At the end of the run you may observe
and analyze your data in the results
window
3. save online data to disk
according to option “write_to_file_interval”
all data are written to file in smaller
portions with filenames that are
determined in option “filenames”
b. Option “filenames“
1. Choose a name like “series 1“ or “test4” or
alike
2. Choose one or more options “add…..”
example: a filename might look like:
test156.onl
c. Option “trigger interval”
You might want to save the value (not the
file !) every trigger, but for some reasons
you might want to save only every third
trigger.
d. Option “write_to_file_interval”
You might want to save the file (not the
value !) every trigger, but for some
reasons you might want to save only
every third trigger.
Trigger:
In this second part of online setup you can
choose:
a. option “trigger mode“
You can trigger continuously by adjusting
the appropriate software parameters like
trigger interval.
you can trigger externally with a TTLsignal to your spectrometer. Please
consult your hardware supplier…
b. option “trigger interval”
Here you choose the time interval between two
software triggers. Pay attention on the correct
unit.
You may test the trigger interval empirically with
“test recommended time”. Add some safety
margins.
Ocean Optics
Thin Film Metrology
34
c. option “number of runs”
You might want to run a certain number of
data points only or (nearly) infinitely.
Attention: “infinite” means about 999999
data points.
Result list for online/multipoint mode
On the first page you see the measured thickness values for each layer. In the picture above there 5
measured data points. In the last page you can see the associated fitness values for each measurement. In
Ocean Optics
Thin Film Metrology
35
the text windows below the data window you see mean values, maximum and minimum values and
standard deviation σ, the 3σ-value and the number of failures (according to the measured fitness and your
fitness limit).
If you press “write data to EXCEL-file” the data are transferred to an .xls-file (Excel need not be installed on
this PC).
If you press this Excel-button together with the SHIFT-key the text will switch to “write data as csv-file” and
such a csv-file will be generated instead of an .xls-file.
With “close all windows” you will return to ElliCalc main window and all online windows will be closed.
Analyze online/multipoint data
7.3.6
This feature helps to analyze online/ multipoint data that have been measured earlier.
You are asked for a file name (extension: .onl) in directory ElliCalc\data\online_files. Then the results window is opened and you may inspect your data, plot the data or export them to Microsoft Excel.
Structure of .onl-file
7.3.7
The first line is a comment, the file format is very strict.
test1
***
55 total points
***
triggercounter, time, fitness, d1
1, 10:35:19, 0.010, 128.3
2, 10:35:19, 0.010, 128.1
3, 10:35:20, 0.014, 128.1
4, 10:35:20, 0.009, 128.3
5, 10:35:21, 0.008, 128.2
RS232
7.3.8
If you own an xy-stage or any other arrangement with Faulhaber motors you may use this menu to drive
the motors and to test their behaviour. You find a list of commands on the left side, for more information
please consult the motor manuals.
Ocean Optics
Thin Film Metrology
36
You may open and close each virtual port separately. If you send the signal "ver" the motors of the xystage should answer (more precise: this command is "1ver" for motor1 and "2ver" for motor2). Ask your
hardware supplier for the motor numbers.
Vision system
7.3.9
If you own a vision system with an IDS uEye-camera you may turn on the camera with this menu
Ocean Optics
Thin Film Metrology
37
7.4
7.4.1
Main menu “Options”
Change buttons
witout SCOUT = internal mode
with SCOUT
In this window you can make visible or invisible:
- The startup image:
The picture will disappear after some seconds or you might “click it away”
- measure and analyze-button:
to combine the functions to the measure and the analyze button
- show fit checkboxes (in internal mode of ElliCalc only):
in the menu Edit Structure there are some fit checkboxes that can be made visible or not. In the
current software version only thickness and n and k (for Cauchy models) are activated
- show fit sliders (in internal mode of ElliCalc only):
you may use fit sliders to check for variations of thickness, n or k
- show dark button:
to measure any dark current separately
- show SCOUT recipe button:
it is not necessary to see the SCOUT window, but for experienced users this might be helpful
Ocean Optics
Thin Film Metrology
38
- show ElliCalc recipe button:
to make it easier to load recipes
- show mapping button:
to make it easier to use mapping
- quality slider is allowed
With this feature it is possible to set the speed (or the precision of the fit) for each individual
measurement
7.4.2
Fit parameters
In the 1st Tab “General” you may change the time for simulation = the number of Simplex fits. A longer time
usually means more precise data (up to some limit…)
In the 2nd Tab “Traffic lights” you may change the fitness values for the trafficlight = good/medium/bad
7.4.3
Some setups
7.4.3.1 ElliCalc setups
Here you can change:
• Number of polarizer steps
Typically ElliCalc uses 18 steps per revolution of the polarizer = a measurement every 20°. This is
good for most purposes. If you use less steps (e.g. only 9 steps) you might loose presicion (but you
may try, it’s faster…)
• Analyzer angle
Normally this value is 45°. BUT: if you have measured your signal and see that the mean value of Psi
is totally different from 45° (e.g. around 15°) then reset the analyzer angle to this mean Psi-value (15°)
and repeat the whole mesurement. This will increase the quality of your data and is especially useful
for thin layers
7.4.3.2 Change colors
In this menu you may change the colors of your layers in the layer stack. It is just an optical effect and has
nothing to do with calculations.
Ocean Optics
Thin Film Metrology
39
First click on the layer area on the left side. Then move the mouse over the large colored area and click if
the color pleases you. Then press OK
Operator mode
7.4.4
NanoCalc can be used in administrator or operator mode.
7.4.4.1
administrator mode
In user mode certain restrictions apply: e.g. the user is not allowed to edit the structure or to change the
parameters of the spectrometer.
The default password to come back to administrator mode is: ”admin”. This password can be changed
arbitrarily, there are no severe restrictions concerning passwords. Please use letters and numbers only.
7.4.4.2 administrator mode
In administrator mode no restrictions apply.
This mode is reserved for the administrator of the system.
The default password to come back to administrator mode is: ”admin”. This password can be changed
arbitrarily, there are no severe restrictions concerning passwords. Please use letters and numbers only.
The administrator may define the options that will work for a standard user. To get this Rights of User window just click ”administrator mode”.
7.4.4.3 Rights of user
The administrator may set the rights for the user for nearly every single feature of the software.
Ocean Optics
Thin Film Metrology
40
Remote control
7.4.5
There is a very powerful OLE remote control as well.
Ask your software supplier...
Ocean Optics
Thin Film Metrology
41
7.5
Main menu “Version”
This menu is visible only if you own a “combiversion” = a combined version of NanoCalc and ElliCalc. You
may switch to the other application
7.6
Chart and chartdesigner
If you produced a 1Dplot or 2Dplot or 3D-plot
you may change nearly
ALL parameters of the
plot by clicking with the
RIGHT mouse button
Hint:
To change the view
position: keep CTRL
button pressed and
move the mouse at the
same time.
For further information
see VCFI5.hlp in the
help directory of your ElliCalc installation.
1D-plot
2D-plot
3D-plot
During mapping it is possible to produce 1D-plots, 2D-plots and 3D-plots.
These plot types can be changed interactively after the mapping was finished. Click on the plot with right
mouse button to get access to the "chart designer“.
Ocean Optics
Thin Film Metrology
42
8
Special features for “SCOUT mode”
8.1
Main menu “File”
8.1.1 Change layer recipe
If you load a (.lrc)-recipe containing a link to a SCOUT .sc2-recipe and measure your sample, SCOUT will
analyze in the background and the results will be displayed in the graphical user interface of ElliCalc.
The layer stack and all layer parameters are defined within SCOUT and are extracted by SCOUT. ElliCalc
is only a user interface. There are lots of data in ElliCalc's internal .lrc-recipe, but most of them are not important in this context: SCOUT is the "master".
With "change layer recipe" you may change some of the layer and fit parameters of SCOUT (but not all).
Your changes are NOT permanently saved to the SCOUT recipe on the harddisk, only to the running
SCOUT instance. If you are convinced that your changes are good enough you may also save them permanently (at the moment only via Scout itself).
To switch to a completely new recipe you have to load another .lrc-recipe with a different SCOUT .sc2recipe (do NOT use SCOUT directly !). With "change layer recipe" it is not possible to change the layer
structure, only values of the recipe.
SCOUT fit parameters: Changing a value
SCOUT fit parameters: Changing a range for parameters
Ocean Optics
Thin Film Metrology
43
SCOUT fit parameters: Changing an extraction method
8.2
Main menu “Screen”
8.2.1
Psi/Delta or tan(Psi)/cos(Delta)
Here you may switch between a display in Psi/Delta or in tan(Psi)/cos(Delta), whichever you prefer. The
data transfer to SCOUT (via a file EC_data.xy in Internal_Files) is done in tan(Psi)/cos(Delta)
8.3
Main menu “Options”
8.3.1
Some setups
Scout stoptime in seconds.
You may enter a number (in sec) to stop SCOUT calculations independent of the quality of the data. This is
equivalent to the above mentioned slider in menu “Fit parameters” / Tab1
Ocean Optics
Thin Film Metrology
44
9
Special features for “internal mode”
This internal mode can only extract thicknesses in layer stacks, so this is much more restricted than
“SCOUT mode”. You do not need the SCOUT software and it may be faster than SCOUT in simple cases.
To reach this mode you have to use a lrc-recipe without an internal link to a SCOUT .sc2-recipe. There are
different possibilities to do do this:
• Press SHIFT+CTRL+F12
• Or: load a special .lrc-recipe, called “no_recipe.lrc”
• Or: edit any .lrc-recipe manually: just remove the name of the .sc2-recipe after
“Scout_FileName_EC=name.sc2” in section [Scout]. Be careful with this manual editing, make a safety
copy! Finally the line should read: “Scout_FileName_EC=”
After this change, you will see a new button “EditStructure”, which allows you to edit your own layer stack.
9.1
EditStructure button
You will see this button and this window only if you do not use a SCOUT recipe = if you use ElliCalc’s
internal mode. You get good results, but only for the extraction of thicknesses (not dispersion)
In this menu “edit layer structure” you have to define your own layer structure
Ocean Optics
Thin Film Metrology
45
9.1.1 General
The full menu EditStructure is only available if you do not use SCOUT.
In the menu EditStructure you may enter:
1. The type of catalogue like:
oxides
nitrides
semiconductors
.....
2. The type of material within one specified catalogue, like „oxides“:
SiO2
CuO
TiO2
......
3. The number of layers (in the present version: 1 to10)
4.
The thickness of all layers in nanometers. This value is regarded as an EXACT value for simulations
and as a GUESS for analyzing measured spectra. Whether this guess is used (or not) will depend on
the measurement mode.
5.
A lower and an upper limit of the thickness. These values are NOT used in simulations. Whether these
limits are used for measuring purposes (or not) will depend on the measurement mode.
6. An option „fixed“:
If you press this option, the lower and upper limits are fixed to the value of the thickness of the layer.
Such a layer is regarded as „well known“.Of course it does not make sense to use three fixed layers,
there is nothing left to analyze.
7. An option „narrow limits“
If you press this option the lower and higher limits are set to about 80-100 nm below and above the
value of the thickness. This is equivalent to having a FAIRLY GOOD KNOWLEDGE of the thickness
8.
An option „wide limits“
If you press this option the lower and upper limits are set to a wider range. This range depends on the
Ocean Optics
Thin Film Metrology
46
settings of the menu EditStructureSetup and may be set to:
-- well defined values like: lower limit=200 nm and upper limit=800 nm
(with any thickness value between 200 and 800 nm)
-- constant range like lower limit=thickness-100 nm and upper limit=thickness+100 nm
Thus the search region is restricted to a rather wide, but more or less "reasonable" range. Of course
you may also set the limits very narrow, even to a search range of zero.
9. An option „user limits“
If you press this option you may set the lower and upper limit to any value between 0 and 300000
nanometers. These values are equivalent to having absolutely NO KNOWLEDGE of any thickness.
10. A submenu “layers” with lots of commands to delete, insert or switch layers. Especially important is the
possibility to include “thick layers” = include the calculation of backside reflections.
9.1.2 Catalogues
In the menu EditStructure you find a row “catalogues” for each layer. You may choose the TYPE of material
like: glasses, semiconductors, metals etc. In the next row “materials” you may choose the actual material of
your layer.
There are different catalogues for photoresists (for different companies like Shipley, MRT and others).
You may add a new catalogue manually or use the menu Edit Refraction Index.
9.1.3 Materials
In the menu EditStructure you find a row “materials” for each layer. You may choose the material itself: Si,
GaAs, Ge etc.
In the previous row “catalogues” you first have to choose the TYPE of material of your layer (like
“semiconductors”). There are different catalogues for photoresists (for different companies like Shipley,
MRT and others).
You may add a new material manually or use the menu Edit Refraction Index.
9.1.4 Thickness
ElliCalc uses values for the thickness between 0 and 300000 nm (=300 micrometers).
9.1.5 Estimates
ElliCalc uses a maximum value for the estimates of 300000 nm (=300 micrometers).
In automatic mode it is NOT necessary to add values for the upper and lower estimate.
You should give reasonable values for these limits in fitting mode as this influences the time for calculation
considerably.
Ocean Optics
Thin Film Metrology
47
9.1.6 Fixed limits
If you fix a layer you force the upper and lower limit to have the same value as the thickness value. This
means that the thickness of a fixed layer is regarded to be “well-known” = exact.
Example: thickness = 500 nm
upper limit = 500 nm
lower limit = 500 nm
9.1.7 Narrow Limits
If you click “narrow limits”, ElliCalc uses rather narrow
low and high limits range of about 100 nm above and
below your thickness estimate (depending on the
material of the layer)
Example1: thickness = 500 nm
upper limit = 600 nm
lower limit = 400 nm
Example2: thickness = 3500 nm
upper limit = 3600 nm
lower limit = 3400 nm
If you need a larger range of limits you have to choose the options WideLimits or UserLimits (up to 300000
nm).
9.1.8 Wide Limits
To use this option you should consult the menu EditStructure \ Setup first:
You have the choice between relative and absolute wide limits
If you choose “relative wide limits” (e.g. ±500 nm and a thickness of 4000 nm), ElliCalc will search between
3500 nm and 4500 nm.
If you choose “absolute wide limits” (e.g. 1500 nm and 6000 nm and a thickness of 4000 nm), ElliCalc will
search between 1500 nm and 6000 nm. The value of 4000 nm is of no importance in this case.
9.1.9 User limits
If you click “user limits”, ElliCalc accepts your values for lower and upper limits (up to 300000 nm = 300
micrometers).
9.1.10 Number of layers
In its internal mode ElliCalc is doing all simulations with a maximum of 10 layers and am maximum of 12 fit
parameters (=thickness and Cauchy).
An example of 3 layers:
Ocean Optics
Thin Film Metrology
48
Layer commands
only available in "internal mode"
9.1.11
In menu EditStructure there is a submenu "layers" which helps to insert, remove or shift layers within a stack.
application 1: show layer commands
If this option is activated a small list of commands is shown (like PageDown, PageUp, ...)
application 2: select a layer
To delete, insert or switch layers you first have to select a layer.
You have 2 possibilities:
a. click on the label of the layer, e.g. L0 with a left mouse click
b. in submenu "layers" there is a command "select a layer"
Ocean Optics
Thin Film Metrology
49
application 3: delete a layer
First select the layer that is to be deleted (see application 2). Then press the delete button on your keyboard
Or: select the layer and use the command "delete a layer" in submenu "layers"
application 4: insert a layer (above another)
First select a layer (see application 2). Then press the insert button on your keyboard
Or: select the layer and use the command "insert a layer above" in submenu "layers"
application 5: switch layers
First select a layer (see application 2). Then press the PageUp or PageDown button on your keyboard
Ocean Optics
Thin Film Metrology
50
9.2
Main menu “Options”
9.2.1
Roughness
General:
It is quite difficult to measure interference if the substrate or the layers are rough, as the interference
patterns get lost.
Example: Roughness is quite common for thick layers like 20 micrometers of photoresist, as the drying
process is very critical and the shrinking of the resist does not lead to perfect surfaces.
Roughness is also quite common for technical surfaces like aluminum or brass or steel that are to be
covered with protection layers (like DLC=diamond like carbon layers).
Methods:
In ElliCalc internal mode (not in SCOUT mode!) an empirical method is implemented to deal with
roughness:
1. no roughness
No roughness is included in the calculation (=default).
2. constant roughness
You will see some textboxes in the setup area which show
“R-factors” for each interface. This value means a
percentage of light that is regarded as lost at this interface.
So there is no real physical roughness model. Such a
physical model cannot be given as the typical size of the
roughness is absolutely unknown. This means that even the
scattering mechanism (Mie scattering, Rayleigh scattering
etc) is unknown. There are some formulae in the literature
but in our case these are not better than the above
mentioned method of light loss via some empirical RFactors.
An R-factor of R=0 means a perfect surface = no roughness
An R-factor of R=50 means a loss of 50% light at this
interface.
There is no wavelength dependency of these empirical
factors.
In
the current version there is no wavelength dependency of
these empirical factors.
constant roughness
Attention:
You have to input roughness values in the setup roughness textboxes.
At each interface a certain amount of light is regarded as lost. This percentage has to be input via
roughness textboxes in the setup area. These R-factors are not dependent on wavelength.
This algorithm does NOT manipulate measured data, but the measured amplitude might still differ
considerably from the simulated amplitudes. This means that the fit procedure might still have problems to
find a good solution.
Ocean Optics
Thin Film Metrology
51
10
Experimental setups and problems
10.1 General
10.1.1 Experimental setup
Ellipsometer setup:
• carefully adjust the height of your stage to get maximized in intensity
• if your samples are not really perfectly plane thin about installing an autocollimator
• try to avoid stray light in the lab
• as your spot size is so small: pay attention on dust particles which may give wrong results
10.1.2 Maximum intensity
This value describes the maximum intensity in the spectrum of your lamp (can be easily checked in “auto
intensity” mode).
If you use a double spectrometer there are TWO wavelengths corresponding to the sensitivities of the two
spectrometers and your light source.
10.1.3 Polarization
In case of oblique incidence polarization plays an important role. In a vertical arrangement (like NanoCalc)
the polarization does not play any role. “angle of incidence” is defined as the angle between the direction of
incoming light and an axis vertical to the surface.
10.1.4 Signal to noise ratio
The intensity of your acquired signal depends on:
the adjustment of the lamp (see light source or ElliCalc-2000 manual)
the integration time (see menu options)
the number of averages (see samples to average in menu options)
the diameter of the fiber
the distance between fiber and wafer
the sample itself
Do not extend the extraction limits into regions with a high signal-to-noise-ratio !
10.1.5 Stray light
There is a slight risk to catch stray light from your laboratory lamps. Try to avoid this as much as. External
light sources usually change and will produce errors.
10.1.6 Fiber
Your ellipsometer may be equipped with different fibers with core diameters between 50 and 600
micrometers.
The spot size is directly proportional to the fiber diameter, of course the signal intensity decraeses
quadratically.
Consult your hardware supplier.
10.1.7 Absorbing media
It is not too easy to measure absorbing media like polycrystalline silicon as their refractive and absorption
indices usually depend strongly on preparation conditions.
Try to find good optical models for n(λ) and k(λ).
Ocean Optics
Thin Film Metrology
52
10.1.8 Passwords
There are several passwords within ElliCalc:
As a start for user mode and administrator mode there is a password “admin”. This password can be
changed.
To change intercept, first coefficient and second coefficient and third coefficient (to recalibrate your own
spectrometer) there is another password corresponding to the serial number of your Ocean Optics
spectrometer. This number is displayed on a separate sheet or on the backside of your spectrometer
system. If you could not find this serial number ask your hardware supplier…
10.1.9 Function buttons
If you click on the button F1, you get access to help functions.
If you click on the buttons F2 - F7 different spectra or recipes together with their layer data are loaded for
demonstration purposes.
Ocean Optics
Thin Film Metrology
53
11
Physical explanations
11.1 Refraction index and absorption indices
The refraction index n of a substance is defined as
n=
cvacuum
cmaterial
with c = speed of light
The absorption index k of a substance describes the absorption behavior of materials. Glasses and
photoresists have negligible absorption in the visible range.
n and k are a function of the wavelength lambda: n = n(λ). This phenomenon is called „dispersion“.
n(λ) and k(λ) are closely interrelated via the complex dielectric function ε(λ).
11.2 Cauchy coefficients
These coefficients empirically describe dispersion as a function lambda
n =n1 +
n2
λ
2
+
n3
λ
4
k =k1 +
k2
λ
2
+
k3
λ4
In many cases the 6 Cauchy coefficients are sufficient to describe the spectral behavior of resists, glasses
etc. Normally ElliCalc uses „nanometers“ as a unit dimension. If you add your own cauchy parameters in a
.dat-file, pay attention on the correct dimension !! It is possible to use other dimensions within the software
but not in the .dat-files.
Structure of a .dat-file:
SiO2_(therm)
name of the material
# this is my own comment 1 arbritrary comment (beginning with #)
# this is my own comment 2
633,1.4570,0
lambda, n and k at 633 nm
150,900
measured data between these limits
Table
(or CAUCHY)
150,1.5510,0
n and k at 150 nm
151,1.5504,0
n and k at 151 nm
152,1.5491,0
n and k at 152 nm
153,1.5477,0
n and k at 153 nm
154,1.5464,0
n and k at 154 nm
and so on......
The first lines are not used by the software for calculation.
ATTENTION: Do not use any blanks in the name of the file !
The third line (150,900) means that measured data are measured (=available) between these limits
(LowerLimit=150 nm and UpperLimit=900 nm) and all extracted and displayed data (drawn in light Grey
instead of black) between 900-1100 nm have NO meaning !!
Ocean Optics
Thin Film Metrology
54
11.3 Interference
The arrangement in the picture below shows the case of an oblique incidence.
The measurement of ellipsometry of thin films is a good example of an interference problem:
reflected intensity
70°
70°
layer
substrate
transmitted (and
absorbed) intensity
The incoming wave splits up in a reflected and a transmitted wave at each external or internal surface. The
amplitudes of these partial waves depend on:
1.angle of incidence (if this angle is >0, then polarization plays
an important role)
2.refraction index and absorption index of all layers
Now the superposition of ALL waves (with different phase relations, amplitudes) has to be done. If the
layers are thin and flat you have to add amplitudes and not intensities (see your physics text book). So
you may end up with „destructive and constructive interference“: a positive amplitude and a negative
amplitude may add up to zero. This is why your measured intensities usually have maxima and minima.
Ocean Optics
Thin Film Metrology
55
12
Thinfilm.ini
This *.ini-file has to be located in the working directory of ElliCalc and should NOT be changed manually.
In emergency cases (= a corrupt file Thinfilm.ini) you may try to overwrite Thinfilm.ini with the default file
Thinfilm.ini (on your CD).
ATTENTION: All files from CD-ROMs are write-protected. Click on the file name in Windows Explorer with
your right mouse button and remove the write-protection.
Section [UserEdits]
In the file Thinfilm.ini there is a section [UserEdits] very near to the beginning of the file. You may edit the
file Thinfilm.ini with any text editor like notepad.exe or wordpad.exe (do not use Microsoft Word or similar
programs). These entries are in part only for special customers and special equipment: they are NOT
supported !!
Attention: be careful in editing this file ! Make a backup before you edit Thinfilm.ini !!
The section [UserEdits] contains some parameters which cannot be changed within the graphical user
interface of ElliCalc because only special users need these features.
[UserEdits]
WriteTmpFile=False
WriteRefFile=False
MinimumSearch=False
AllowPixels=True
Plot_During_Online=True
Save_During_Mapping=False
CCD_StartCounts=0
WindowShift=175
AdjustRecipes=False
Special_FFTLayer=-1
Plot_After_FFT=False
YScale_FFTLayer=0
CsvExcelExport=xls
CsvExcelSeparator=;
CsvExcelNumberFormatter=.
ExcelMargins_LRTB=2;2;2;1
UseShutter=False
SpecialLambda=-1
UseClipBoard=True
HideElliCalc=False
StopMappingStage=False
SpectrometerSleepTime=30
WriteTmpFile:
if this flag is set to TRUE then ElliCalc will write a temporary file after each measurement. In rare cases the
PC together with its network connection may be very slow and it is advisable to set the flag to FALSE. Then
it will no longer be possible to use the feature “load last file”
WriteRefFile
if this flag is set to TRUE then ElliCalc will write a file after each reference measurement. In rare cases the
PC together with its network connection may be very slow and it is advisable to set the flag to FALSE. Then
it will no longer be possible to use the feature “load last reference”
MinimumSearch
this is reserved for a special customer (using antireflective coatings)
AllowPixels
If you disable this feature by setting the flag to FALSE it will not be possible to use the pixel mode. You
gain some speed as no recalculation for pixels is done with each measurement.
Plot_During_Online
if you set this flag to FALSE then you gain some speed during online measurements as no plots are shown
Save_During_Mapping
Ocean Optics
Thin Film Metrology
56
allows to save all spectra during mapping (time-consuming !)
Online_StartCounts
some spectrometers need a certain number of calls to the CCD pixels before they give stable results. If you
set this number to any value less than 10 (e.g. Online_StartCounts =5) you will have to wait until 5 dummy
measurements have been done. If you use a short integration time it is recommended to use values of 510. If you use a longer integration time and you do not want to wait for some seconds it is recommended to
set the value to zero (but be aware that the first 1-5 measurements may not be completely correct)
AdjustRecipes
True: the main menu will contain a possibility to change a certain parameter in ALL recipe or ini-files
simultaneously
Special_FFTLayer
for NanoCalc and special customer only
if any valid layer number is set to some number <> -1 (=default), the FFT result will be changed to get the
thickness result of this special layer and not the total sum of all layers (ask your software supplier for details).
There is also an application to extract the refraction index instead of thickness (ask your software supplier
for details).
Plot_After_FFT
for NanoCalc and special customer only
If this variable is set to FALSE only the FFT peak wil be plotted and not the extracted (=simulated) curve
YScale_FFTLayer
for NanoCalc and special customer only
this number gives a zoom factor for the main FFT peak (it can be changed within the software by pressing
the + and – buttons)
csvEXcelExport
you may enter csv oder xls (example: csvEXcelExport=csv). Csv is the well-known “comma separated
value” format.
csvEXcelSeparator
here you may enter the separator for the csv-format, like “;” oder”,” (example: csvEXcelSeparator=;)
csvExcelNumberFormatter
here you may enter the number formatter for the csv-format, like “,” oder”.” (example:
csvExcelNumberFormatter=.)
ExcelMargins_LRTB
To print Excel sheets: this sets Left, Right, Top,Bottom
UseShutter
If you need control over the shutter of the light source (True/False)
SpecialLambda
for NanoCalc and special customer only
UseClipBoard=True
To avoid copying measured data to clipboard
HideElliCalc
To avoid ElliCalc in windows taskline
StopMappingStage
To enable/disable the xy-motors after 1 step
SpectrometerSleepTime
A time in minutes. After this time the spectrometer is asked up to 10 times to “reactivate” it.
Ocean Optics
Thin Film Metrology
57
13
APPENDIX
13.1 ElliCalc-Quick-Setup
This Appendix helps you step by step to get a first measurement. This description is using the
reference stepwafer from OceanOptics, SiO2-Steps on Si-Wafer.
Install the ElliCalc software and AD-Converter (see Appendix A)
Start the computer, the power supply for the motors (black box) and the ellipsometer itself
(front side)
Plug-In the USB-Cable (or blue AD-Cable), then install the fibercable between the
spectrometer and the lightsource.
Put the sample (step-wafer ?) on the chuck
Start the ElliCalc software (WITH a reflecting sample on the chuck !!)
Load a SCOUT layer recipe that is good for your sample (files\load layer recipe)
Click "init" and wait until this operation is finished (about 15 seconds)
Maximize signal intensity (continuous button) by adjusting stage height
Eventually re-adjust intensity by pressing “auto intensity”
Click "measure"
During the measurement (some seconds) you see the measured raw data and finally the
Psi/Delta spectrumFehler! Keine gültige Verknüpfung.A result is displayed in the upper right half
of the screen
Now you are ready !!!
Ocean Optics
Thin Film Metrology
58
Was this manual useful for you? yes no
Thank you for your participation!

* Your assessment is very important for improving the work of artificial intelligence, which forms the content of this project

Download PDF

advertisement