While some people are proud of the fact that they never have to fabricate structures but can keep on peddling with bits and bytes and writing electromagnetic simulation software, most of the people in our group get involved in fabrication somewhere in the course of their PhD.

The design of a lithography mask, be it for e-beam lithography, contact lithography or deep UV lithography in Leuven is not a trivial task. This page should help you on the way to making mask layouts in GDSII file format. It contains basically two sections:

1. Generating a Mask Layout. In our group, this is most often done using scripts that generate GDSII files. The are a few options for these.
2. Inspecting the layout with a GDSII viewer. Some software for this purpose is also discussed, and made available on this web site (internal use only)

Mask Layout Libraries

Scripts are a flexible way of generating masks, as the parameters of the layout can easily be adjusted in the script. There are a number of options.

• GDS_KEY: This is th most recent library written in the group. It is possible to generate GDSII files directly using python scripts. Because it is based on python, it is possible to use very concise scripts and employ all the existing libraries of python. It doesn't require a separate compilation step.
  This library was written because it the alternatives did not provide for hierarchy in the GDSII files (In hierarchical files, repeated structures are only defined once and are referred to at every occurence. This reduces the file size dramatically).
  Instead of the binary GDSII file format, it also supports the KEY file format, which is a textual representation of GDSII and which can be read with the Boolean viewer.
  ( GDS_KEY home page)
• The older alternative is a libary in C which generates EGS files. These files can be converted to GDSII using the HP-ADS viewer. While the library is more focused on waveguide structures, it does not support hierarchy.
  (more information will be available soon)

Mask Viewers

• HP-ADS: This design software package runs on wsbob and can read/write EGS files and GDSII files. It is not very well suited for large files and hierarchy, and should only be used in conjunction with the older C library which generates EGS files
• CleWin: CleWin is a mask layout editor. This commercial package is available from Wieweb (now merged with Phoenix software). A demo version, which cannot save files, can be downloaded here. Extract the zip file and start the executable.
• Boolean: This is a somewhat buggy viewer/editor for GDSII files. Unless for the conversion between KEY files and GDSII files, it should not be used, as it introduces corrupt AREFs and conversion errors. A Zip file containing the software and installations instructures (readme.txt)  can be found here. (Boolean GDSII Viewer/Editor)
• SoC GDS Seduction: This is a very efficient GDSII viewer that can handle extremely large and complex files with remarkable ease. While it it free, it requires a per-computer license, which is locked to a specific machine using its MAC network address. The software can be downloaded from the site of Dolphin Integration.