GDSII

GDSII

Developed by	Calma

A rendering of a small GDSII standard cell with three metal layers (dielectric has been removed). The sand-colored structures are metal interconnect, with the vertical pillars being contacts, typically plugs of tungsten. The reddish structures are polysilicon gates, and the solid at the bottom is the crystalline silicon bulk.

GDS II stream format, common acronym GDSII, is a database file format which is the de facto industry standard for data exchange of integrated circuit or IC layout artwork. It is a binary file format representing planar geometric shapes, text labels, and other information about the layout in hierarchical form. The data can be used to reconstruct all or part of the artwork to be used in sharing layouts, transferring artwork between different tools, or creating photomasks.

History of the GDS II format

GDS = Graphic Database System

Initially, GDS II was designed as a format used to control integrated circuit photomask plotting. Despite its limited set of features and low data density, it became the industry conventional format for transfer of IC layout data between design tools of different vendors, all of which operated with proprietary data formats.

It was originally developed by Calma for its layout design software, "Graphic Data System" ("GDS") and "GDS II". Now the format is owned by Cadence Design Systems.

GDS II files are usually the final output product of the IC design cycle and are given to IC foundries for IC fabrication. GDS II files were originally placed on magnetic tapes. This moment was fittingly called tape out though it is not the original root of the term.

Objects contained in a GDS II file are grouped by assigning numeric attributes to them including a "layer number", "datatype" or "texttype". While these attributes were designed to correspond to the "layers of material" used in manufacturing an integrated circuit, their meaning rapidly became more abstract to reflect the way that the physical layout is designed.

As of October 2004, many EDA software vendors have begun to support a new format, OASIS, which may replace GDS II.

GDS II utilities

As the GDS II stream format is a de facto standard, it is supported by nearly all EDA software. Besides the commercial vendors there are plenty of free GDSII utilities. These free tools include editors,, viewers, utilities to convert the 2D layout data into common 3D formats, utilities to convert the binary format to a human readable ASCII format and program libraries.

Software that supports GDSII

The following software can read/write the GDSII file format:

• CleWin (WieWeb)[1]
• Electric [2]
• Glade [3]
• Klayout [4]
• LayoutEditor [5]
• L-Edit (Tanner EDA)[6]
• Zeni EDA [7]
• PowerGDS (GDS Suite) [8]

See also

• Computer Aids for VLSI Design - Appendix C: GDS II Format by Steven M. Rubin
• The GDSII Stream Format by Jim Buchanan
• List of various layout editors/viewers
• GDSII Suite for Converting GDSII files to BMP/TXT/BIN Formats

References

* Clein, Dan. (2000). CMOS IC Layout. Newnes. ISBN 0-7506-7194-7