ElliCalc
Manual
Version 3.5.23 8.2.2011
Ocean Optics Germany GmbH 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
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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
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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”.
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1.1
Measurement setup
white light
source
spectrometer
polarizer
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.
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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.
70°
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):
layer
substrate
70°
transmitted (and
absorbed) intensity
reflected intensity
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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.
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Product support
Please contact your local distributor for product support. Here you can find additional information:
www.OceanOptics.de
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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. Now click on the button “init” and wait for some seconds. The motors of the ellipsometer will move to
their starting positions.
10. 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.
11. 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.
12. Now click the button “measure”. The measurement will take some seconds.
13. Now you see the measured data with the typical interference wiggles.
14. Then click on the button „analyze“ and wait for the result. You should get meaningful results.
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ElliCalc:
SpecEl
SCOUT
ElliCalc:
SpecEl
5
User modes of ElliCalc
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.
• 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 !
calculation
SCOUT sc2-recipe ElliCalc lrc--recipe
measure spectrum
display results
ellipsometer
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.
Ocean Optics Germany GmbH Thin Film Metrology
ElliCalc lrc-recipe
define layer stack
measure spectrum
calculate thickness
display thickness
ellipsometer
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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.
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5.4
List of all menus and buttons
Main menu Sub-menu SCOUT
mode
FILES menu Load Scout layer recipe x x
Load ElliCalc layer recipe
Save as layer recipe x
Change layer recipe x
Export raw data x x
Import raw data x x
Show all results x
Exit x x
SCREEN menu Spectrometer data x X
Limits x x
Dispersion x x
Psi/Delta or tan(Psi)/cos(Delta) x
EXTERNALS Mapping x x
Analyze mapped data x x
Online/multipoint x x
Analyze online data x x
RS232 x x
Video camera x x
Show plot x x
OPTIONS Change buttons x x
Roughness (x) x
Special modes x
Fit parameters x
Some setups ElliCalc (motor steps) x x
Some setups SCOUT (stoptime) x
Some setups (change colors) x x
VERSION NanoCalc_1 x x
NanoCalc_10nk x x
HELP Contents x x
About x x
EDITSTRUCTURE x
Internal
mode
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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)
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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.
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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.
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7
Detailed features of ElliCalc
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
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).
Load layer recipe
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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.
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.
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
Import raw data
Export raw data
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