Technical Issues - FilmStar News 2007

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January 12    Lambda 19, Reverse Synthesis

1. Lambda 19 with Ascanis AX board...

Further testing by Ascanis indicates 100% reliability with FilmStar MEASURE version Mpe19AX.exe. A Windows 2000/XP Pentium 4 computer > 1.5 MHz with built-in parallel port and available PCI slot is required. The price for the board is $2250 plus shipping from Germany.

2. On the Reliability of Optical Thin Film Inverse Synthesis...

You obtain an out-of-spec coating curve and ask "which layer(s) is responsible??" You convert the curve to targets, run the optimizer and get an answer. Is it the CORRECT answer?

While this question cannot be answered in general, it occurred to me that the process can be simulated in FilmStar BASIC:

  1. Randomize a design
  2. Convert the resulting spectrum to optimization targets.
  3. Restore the original (ideal) design and optimize in order to solve for the randomized design.
  4. If each layer is close (say within 0.5%) to the known value, reverse synthesis is considered to be successful, otherwise we have an incorrect solution.

An update to Sub RandCalc in DESIGN 2.50.0842 makes it possible to run two new BASIC programs: FilmSolve1.bas and FilmSolve2.bas. The programs are nearly identical. FilmSolve1.bas calculates targets at normal incidence while FilmSolve2.bas adds 45 deg P and S pol targets. The update to RandCalc provides a switch which retains the randomized design. The new BASIC programs are included in the full installation and in basic32.zip (DESIGN password required).

**** Complex design ****

Initial results for a 26 layer laser output mirror (optimized laser.faw) indicate that, for a given spectral range (in this case a range exceeding the design performance range), angular measurements are exceedingly important! Normal incidence solutions with near-perfect spectral matching are most always wrong, while solutions with 45 deg P and S are most always correct. (DLS is the optimization method that should be used; L-M also works, but is much slower.)

**** Simple design ****

Initial results for a 4 layer AR design (optimized bbar.faw) indicate that normal incidence measurements will be sufficient for inverse synthesis. It may, however, be necessary that the spectral range exceeds the performance range.

If our conclusions are correct (please verify for yourself), it has implications for the types of measurements required in thin film production. If anyone knows of any papers on this subject, please inform me by return e-mail. Further ideas on this subject: add index variations, add measurement errors (as in AddNoise.bas).

3. Mr. Shoji's BASIC programs...

We have uploaded two documented BASIC programs authored by Mr. H. Shoji of Tokai Optical who has kindly made these available to all FilmStar users. One program calculates TACT time for a given coating design and the other imports binary Hitachi spectra (*.uds). The link to shoji.zip is on the Updates page.


March 19

1. New beta versions DESIGN 2.60 and MEASURE 2.50 include an updated FSPlot graphics driver. The benefits are mainly for monochrome printing.

2. DESIGN 2.60.0002 adds the Layer Error Analyzer. This important facility helps you understand coating errors and computes monitor corrections as a function of layer thickness or total thickness.

3. Need a better way to organize designs and designers?

DESIGN 2.60 adds a File Properties List dialog for FILM Archive designs. File Properties are enabled in File.. Configuration.. Directories. When enabled, the DESIGN File menu adds a File Properties command leading to Edit and List functions.

In the File Properties List dialog, click the column header to sort and click a row to open the design. Right-clicking displays the file Comments field.

4. With MEASURE 2.50, OCX versions are discontinued.

These versions were added for compatibility with Galactic Industries (now Thermo Electron) MyInstrument specification. This allowed FTG scanning modules to be accessed inside of GRAMS/AI spectroscopy software for chemists. Since MyInstrument failed failed in the marketplace (perhaps because chemists did not understand its benefits), we see no reason to continue OCX development at this time.

MEASURE can, however, still save files in GRAMS .spc format and DESIGN can open them. This is important when working in the deep UV because McPherson uses the GRAMS .spc file format.


April 2    Log Wavelength Scale

1. Following a discussion with users specializing in IR coatings, log wavelength scales were added to the DESIGN (2.60.0003) Interactor (Options box under Graph) and to the INDEX (2.50.0002) main screen (Graph..Plot Axes <Ctrl+W>).

The log scale benefits anyone working in very wide wavelength ranges (i.e. 0.5 to 10 Ám) by eliminating the need for different graph axes in UV/Vis and IR regions. Note that a log wavelength scale was already included in the FSPlot Module.

A log scale was also added to the vertical axis; this makes it possible to examine filter performance in blocking regions without using an OD scale. The feature is especially useful when comparing designs to measured spectra.

Need to look at graph details? Did you realize that the Interactor supports zooming? Zoom mode is activated with Ctrl+Z or Shift+Click. Just hit <Esc> to exit zoom mode. Right Click brings up the Graph Axes dialog while Right Click in the CIE graph brings up the CIE Setup Parameters dialog.

Haven't upgraded in a while and wondering how the Interactor works? We'll be pleased to show you via our web conferencing facility.

2. You don't need to open INDEX to view the wavelength ranges covered in n,k tables. That information is conveniently available in the Film Indices dialog under File...List <Ctrl+L>. (I point this out because, in a recent conversation with users, I forgot where it was!)

3. New FilmStar DESIGN BASIC Property PlotNumber returns the number of plots currently in the FSPlot Module. This helps users develop macros which manipulate plot legends.


June 18    CSV Peculiarity

An Excel CSV peculiarity is that the format depends on country settings for decimal symbol and list separator. I used a text editor to change ", to "." and ";" to ",".

Eliminating this step, DESIGN and MEASURE have been modified to open 'foreign' Excel-compatible CSV spectra files. That is, if your computer is set for USA, a European CSV file can be opened and vice-versa. Normally, this is only a problem when exchanging files with European colleagues.

USA standard...
"." is decimal symbol, "," is list separator

380,0.6587843
381,0.6533251
...

European standard...
"," is decimal symbol, ";" is list separator

380;0,6587843
381;0,6533251
...

Two column (Wave, R or T) and three column formats (Wave, R, T) both work. You can also open FilmStar-format CSV files that include a two line header as shown below. These files are country-independent.

"Optional description"
139
400,.1456623,.7819613
402,.1041717,.8222814
...

Check 'For Excel' in Spectra... Format Options if creating files for ultimate use in Excel. Saving CSV files in Excel format (*.xls) eliminates country-setting problems. When sending us spectra in Excel, we prefer that you include all spectra in a single .xls file (just use multiple sheets).


July 10

1. Need to automate CIE color calculations? DESIGN 2.60.0100 adds BASIC subroutine CieOptimize and property CieYield.

2. Working with active films? The DESIGN Interactor has been updated to plot absorptance in specified layers. Selecting Absorptance in Setup Parameters adds an Absorptance entry (under Graph) in the Interactor options dialog. If a triple plot is selected, the following are displayed: absorptance in a specified layer, total absorptance, ratio of layer absorptance to total.

3. Hint: In the Interactor Compare or Difference modes, use Spectra Copy followed by Spectra Paste to retain a particular curve (plotted in blue). This helps visualize changes as layers or angle are modified.


July 31    NTFS File Property Update

1. Have hundreds of designs and perhaps thousands of spectra in the same directories?

FilmStar's NTFS file property capabilities have been updated. File properties are now available for FILM Archive, Index Table and Spectra (MEASURE users) files. File properties can be listed, sorted and selected.

The INDEX File Properties list can be accessed from DESIGN's Film Indices editor. Suppose you have 20 TiO2 files mixed in with 200 others. Using the File Properties dialog instead of the usual Dispersion pull-down lets you select just TiO2 files, making it easier to find the file you need. Similarly, the MEASURE Spectra list can be accessed in DESIGN.

Clicking a row in the File Properties dialog loads the file. In Film Indices it inserts the n,k Table name into the current index grid row under Dispersion. Right clicking a row displays the Comment field in a separate box.

2. You can also organize data in specific directories. You might put all AR designs in one directory, etc.

When users e-mail files for us to analyze, we transfer them to a new ..\Winfilm subdirectory. BASIC macro 'SetPath.bas' makes it easy. Restore default directories with macro 'DefPath.bas'. You'll find these in ..\Winfilm\Basic32.


Aug 27

1. CIE Color Module... Following a user's suggestion, it is now possible (CIE Setup Menu) to specify R or T independently of Graph Axes settings. In addition, color values are now displayed in the dialog's title bar (top) and copied to the clipboard.

2. Interactor... A new 'Merit Function' option lets you continuously monitor the optimization merit function. This is useful when manually examining different starting designs. The result appears in the status bar. (If the merit is exactly zero, you did not define any optimization targets.)

Evaluate...Merit Function gives the same result in the Main Menu or when the Interactor Merit Function option is set to 'Hide'. Useful short cut... Right-click the CIE plot in the Interactor to bring up the CIE Setup Parameters dialog. You can also do this from the Setup Menu.

3. FilmStar Administrator... We have implemented new NTFS File Property capabilities for users who need to share design files!

Are designs and index tables in numerous user-directories? That might be secure, but it makes it more difficult to share designs and index tables. A FilmStar Adminstrator can specify that only the file author may re-save FILM Archive and Index Table files. If the current User Name does not match the author's, the user is prompted to change the file name.

Since your current files won't include Author information, the Administrator can retroactively assign an Author to any number of files. This would typically be implemented when adding files from a particular user's directory. FilmStar Administrator status is enabled via a specially programmed Security ID Module. Contact FTG for further details.


September 17

1. New BASIC Property Get IDModInfo returns a text string with Security ID Module information. The string looks like

User: FTG Software; ID: 3B70B850

This feature was added in response to a MEASURE user's request, and has been implemented in all FilmStar programs.

2. Reminder...When using reverse reflectance targets ('% R Rev' in the targets editor), the substrate should be treated as a massive layer. While this subtle point is documented in the on-line help and printed manual, it can easily be overlooked.


October 8

A recent inquiry revealed that users are not familiar with FilmStar's new NTFS File Properties capabilities.

File Properties were first added to assist companies with large numbers of shared designs ('who designed it?'). Index files and spectra were added later.

We think the File Properties capability is extremely useful; it provides a simple alternative for those not wishing to implement the FileMaker Pro-based FilmStar Database. It includes comments and enables you to search file names, sort by date, etc.

If you enable the FilmStar Administrator you can also make sure that no one overwrites another engineer's designs, etc. (A FilmStar Adminstrator owns a special HASP Security ID Module which enables one to set security functions on users' computers.Contact us for further details.)

Note: There was a minor bug in INDEX which did not let you enable and disable File Properties. This was fixed in 2.50.0063.


October 29    Adjust Indices in Interactor

*********************************************************
**** Important Interactor update in DESIGN 2.60.1000 ****
*********************************************************

Responding to a request from a FilmStar user in California, Film indices can now be varied in the Interactor. In Interactor mode, click Setup...Adjust Indices <Ctrl+A> to display the Adjust Film Indices dialog. This dialog can be used at the same time as the main Interactor screen.

Once you drag the Adjust Film Indices dialog above or below the main Interactor window, its position is remembered. The normal Film Indices dialog can also be used, but not at the same time.

This new facility provides means to analyze materials which intentionally or unintentionally vary according to deposition conditions and/or environment. It extends FilmStar's ability to define dispersive materials as functions of up to three look-up tables (Setup...Index Functions...User Defined).

An example: let's say that TiO2 dispersion can be approximated by a mixture of 'good' and 'bad' TiO2. We define a linear User Index Function 'TiO2Mix' as

n = A*N1 + (1-A)*N2, k = A*K1 + (1-A)*K2 

where Table 1 is 'TiO2 Good' and Table 2 is 'TiO2 Bad'. The important advantage of this approach is that there is only one coefficient 'A' to be varied either manually or by optimization; this simplifies analysis significantly.

Is the combination model valid? Informal discussions with users indicated that it agrees with experience. (Anyone able to supply references on the subject?) Multiple overlaid n,k plots in INDEX are useful in analyzing models.

Intentional index variations provide new design tools. In such cases, index coefficients might include deposition conditions (sputtering rates, gas partial pressure, etc.) or environment (temperature, electric field, etc.).


November 12

1. BASIC Sub SetLayersIgnore has been added. This allows macro control of the Ignore Layers feature found in the Layers Mode design editor. The new subroutine helps facilitate strategies for setting up broadband optical monitors such as the Eddy Company Spectra Lock 2010-C.

In broadband optical monitors there arises the question of when to change the witness chip. Should the next layer be deposited on the same chip or a new one? The analysis is made considerably easier by being able to evaluate subdesigns, say layers 20 to 26, without breaking up the original design.

2. A new web page discusses connecting the FilmStar Database to the enterprise (corporate) database.

3. To assist a user who is modeling materials with complex n,k properties, we revisited the ability to implement User Defined Index Functions in Excel. We noted that the documentation referred to a very old version of Excel with XLM macros. Testing revealed that everything worked as before, except for a slight change in specifying the optional Excel macro. Replacing

[RUN("INDXFNC.XLM!AconstCalc")] by [RUN("AconstCalc")] 

where Sub AconstCalc() is a VBA subroutine was the only change required.

4. Users have reported convergence problems with built-in Index Function CAUCHY. Please use CAUCHYM instead. We suggest that you uncheck CAUCHY in the Built-in Index Functions dialog (unless already using it successfully).
 


November 19

1. DESIGN INDEX TABLES: If referenced index table (*.itw) files are renamed or deleted, designs do not load. This raises havoc when engineers, who share designs, haphazardly change index files.

In DESIGN 2.60.1031 a missing Index Table no longer halts the File.. Open process; the design is still loaded. This gives an opportunity to access Setup.. Film Indices and re-specify index files. Prefer the way it was before? Uncheck 'Can open designs with index table errors' in File.. Configuration.. Preferences.

Hint: Check File.. Archive n,k Data if you want to create a design with embedded and unchangeable index tables.

2. DESIGN THICKNESS AXES: When plotting vs. layer thickness (simulating an optical monitor), there is a possibility to specify different wavelengths for each layer. This feature is triggered by checking 'Specify evaluation wavelengths...' in the Graph Axes dialog:

A user accidentally checked this box and then failed to specify any wavelengths. This resulted in frustrating error messages. We addressed this issue in DESIGN 2.60.1031 through menu and dialog changes: Setup.. Wavelength List is now Evaluate.. Wavelengths and there is a new 'Evaluation Wavelengths' button in the Calculate Dialog as shown at the right.

As an aid to entering wavelengths, note the new Edit...Spawn Cell command in the Evaluation Wavelengths dialog. This repeats the wavelength value in following cells. Having said all this, MONITOR should really be used for multi-wavelength optical monitoring anyway.

3. MONITOR DESIGN OPEN: Opening a new design in MONITOR may cause error messages when the design changes the number of layers. This flummoxed a new user who did not realize that Edit.. Clear Worksheet would have solved his problem. MONITOR 2.50.0030 now prompts users to clear the Worksheet when a new design is opened.

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