To get the accurate physical layout information a special file format is needed. In the early 1970’s a file format called Masterslice used to represent the physical layout of a design which is developed by calma company. But Masterslice had limitations, and designs became more complex and advanced, the need for the a more efficient format arose. This led to the development of the GDS file format.

GDS

GDS means “Graphic Design system”. It is commonly used file format in semiconductor industry. And it was also developed by the calma company in the early 1980’s. Later GDS file was updated and improved, it became known as “GDSII”. Both terms represent the same binary file format used for representing geometric layouts of the designs.

Currently GDSII is widely using in the semiconductor industry for transferring design data between different EDA tools and for manufacturing photomasks.

What is GDSII?

GDSII is a binary file format that represents geometric layout data for electronic circuit designs. It is commonly used in VLSI design to represent the various layers, shapes, and components of a semiconductor chip.

Usage in VLSI Design

During the VLSI design process, engineers use various EDA tools to create and modify circuit layouts. Once the design is complete, it is typically converted into a GDSII file format for further processing and manufacturing.

GDSII stream Format vs Database Format

GDSII is available in two formats:

• GDSII Stream Format:It is human-readable but can result in large file sizes due to its ASCII representation.
• GDSII Database Format: It is more compact as it is in binary format but not human-readable.

Manufacturing and Photomask Generation

Once the GDSII is ready, it is used for manufacturing purposes. Photomasks, used in the semiconductor fabrication process, are generated from the GDSII data. These photomasks help to transfer the circuit pattern onto silicon wafers during the chip manufacturing process.

OASIS

OASIS means Open Artwork System Interchange Standard.It is also similar to GDSII file format, OASIS is used to represent geometric layout data of the design. It was developed by a consortium (an association of several companies) of companies within the semiconductor industry. It was developed to address some of the limitations of the older GDSII format, particularly in handling the increasing complexity of modern designs.OASIS was introduced into market around in early 2000s.

OASIS supports a hierarchical structure for describing complex chip layouts, and uses binary format that is more compact and efficient than the ASCII-based GDSII format. This efficiency aids in the management and processing of the massive amounts of data generated by current semiconductor designs. Due to its compactness managing storage and data transfer is easy.And it supports for various advanced features that were not present in GDSII. This includes support for advanced compression techniques, and better handling of various design rules.

Almost all EDA tool vendors were recognized OASIS format as industry standard. For high complexity designs mostly OASIS file formats are using. Many EDA tools offering features to convert between GDSII and OASIS formats.