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GDSII Info, Links

What is GDSII

GDSII is a binary file format which is classified as a "data interchange format", used for transferring mask-design data between the IC designer and the fabrication facility ("Fab"). At the Fab, the GDSII data is converted into a machine-readable language called CATS (for Computer Aided Transcription Software) which transcribes the data so that it can be read by the photomask systems used in the manufacture of semiconductors.

GDSII stands for "Graphic Design System II". Alternative names are "Calma Stream Format" (CSF) or just "Stream Format". Alternative spellings to GDSII you might encounter on the Net: GDS, GDSIII, GDSIV, GDS2, and various alternatives with a dash or space between the "GDS" and number part.

GDSII History

The GDSII format was invented in the early 1970's at Calma Co. in Sunnyvale, Calif, a then wholly owned subsidiary of General Electric Company, U.S.A.
Some of the people who helped write the GDSII format while working for Calma at the time were Roger Sturgeon, Tom Hedges, Tom Schaefer, Carl Smith, and Mark Zimmer. You can see their pictures and read a little more about them over at the 29th Annual SEMI Dinner and Award Ceremony page, where the above were "honored for their significant contributions to the advancement of semiconductor manufacturing technology". Anyway, Calma Company later sold the rights to GDSII to Valid Logic Systems, which later merged with Cadence Design Systems, Inc..

GDSII Format

Because it has become an EDA industry standard, GDSII is an open standard- you can even find open-source libraries and tools on the Net (but more on that in the next section). Apart from that, you can also read about the file format from several places, which provide descriptions ranging from the general to specific technical details and the BNF for the GDSII format. For example:

  • If you want a detailed technical PDF you can read and print, the Stream Format description is perfect for you.
  • For those who prefer HTML, the GDSII Format page is a great technical resource in HTML format.
  • Section 2.9 of the "SPIE Handbook Of Microlithography, Micromachining And Microfabrication" reprints portions of the GDSII Stream Format Manual, with permission from Cadence.
  • Additional descriptions can be found at buchanan1.net and Appendix C of the online book "Computer Aids for VLSI Design".

GDSII Tools

There are many companies which offer free GDSII tools or free demo versions of commercial tools. A number of examples are listed below. If you know of a good tool that is not listed, please let us know.

Free GDSII Viewers

  • SoC GDS Seduction is a free GDSII viewer from Dolphin Integration. Registration is required for the free download.
  • UQ GDSII Viewer is a free GDSII viewer. It doesn't doesn't perform well with large files, but is Java based and runs on most platforms. There are also a number of other GDSII utilities at the site.

GDSII Conversion Utilities

  • GdsDump is "a command-line based application that prints out the contents of a GDS II file in a human-useable form." GdsDump runs on machines running MacOSX, NeXTSTEP 3.3, OpenStep/Mach 4.X, and Solaris/Sparc 2.5 or greater.
  • gdsreader is a GPL'd "reader/parser/print tool". It can read GDSII files and output a postscript or HPGL-2 file.
  • gds2pov is "a program to take a GDS2 layout file and output a POV-Ray scene description file of the GDS2 data. This allows the creation of attractive 3D pictures of a layout."
  • Anuvad is a free suite of source code of GDSII and OASIS data exchange libraries and tools.
  • The gds2oasis utility is a stand-alone translator from GDSII to OASIS, made available by Mentor Graphics.

Other GDSII Tools

  • LASI "(LAyout System for Individuals) is a suite of general purpose layout and design programs", for use under the Windows platform. Non-commercial use is free.
  • Electric is "a sophisticated electrical CAD system that can handle many forms of circuit design", released by the GNU foundation under the GPL.
  • Magic is a GPL'd VLSI layout tool, which one can use to edit/view GDSII files.
  • Boolean is a GDSII viewer/editor.
  • Alliance is "a complete set of free CAD tools and portable libraries for VLSI design."

The Future of GDSII

There's a problem with GDSII -- it's OLD. The format was not designed to compactly handle the amount of data a modern layout requires, a problem that can cause modern GDSII files to reach as much as 50GB in size. In fact, this problem was already considered severe enough for a paper titled GDSII Considered Harmful to be published in October 2001. So what's to be done? Well, the above paper suggests improvments to the GDSII format, or even a replacement based on XML.

However, an organization called SEMI has decided to replace GDSII with a new format, called OASIS(*), for "Open Artwork System Interchange Standard". The OASIS specification, SEMI P39-0304E2, is available for online purchase.

It now remains to be seen how wide industry support will be for OASIS. As there are currently no other contenders for the crown of GDSII replacement, OASIS seems like it will eventually catch on.

*OASIS is a registered trademark of Semiconductor Equipment and Materials International.

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