OASIS stands for Open Artwork System Interchange Standard. OASIS is similar to GDSII in function and purpose. OASIS is a new electronic pattern layout language created as a commercial successor to GDSII. It was developed to solve the problem of large GDSII files that were unable to keep up with the growth of integrated circuit layout complexity. OASIS is a binary file format developed by SEMI for expressing electronic patterns in integrated circuit design and manufacture. It defines the code for geometric shapes, their properties, organization into cells, and relative placement. OASIS includes 25 types of trapezoids, variable-length numeric format for coordinates, and gzip-like compression algorithm to reduce data size, and was adopted by integrated circuit design, equipment, photomask, fabless, 3rd party Intellectual Property (IP) and manufacturing companies worldwide.
Why OASIS is Better Than GDS :
With advancements in process technology, IC layout designers can deliver more functionality in the same chip area. However, this leads to larger file sizes, with full-chip GDSII/GDS™ layouts that can be hundreds of gigabytes or even terabytes in size. This can result in longer loading times for EDA tools, which can frustrate users and impact tape-out schedules. Zipping GDS layouts may reduce file size, but it can increase loading times. A better solution is to switch to the OASIS format, which is accepted by major foundries and can reduce both file sizes and loading times.
Compression: GDS Vs OASIS :
OASIS data uses variable byte lengths to represent numerical values, while GDS format uses fixed byte lengths. OASIS can recognize complex patterns and store them as repetitions, reducing file size. OASIS CBLOCKs feature applies internal Gzip compression to individual cells within a layout, enabling parallelized unzipping and faster loading times. Strict mode OASIS layouts contain an internal lookup table, which improves loading time efficiency by allowing the reader to parallelize the loading of the layout. A word of caution , zipping an OASIS layout as it only provides minimal file size reductions and increases loading times since tools must uncompress the file twice. While in some cases, zipping an uncompressed OASIS layout may reduce file sizes more than using CBLOCKs, layout readers cannot load a zipped OASIS layout in parallel without first unzipping the file, leading to increased loading times. The recommended approach is to use CBLOCKs, which offer internal compression within the file and can be uncompressed in parallel, providing significant loading time improvements.
Why OASIS is choice of present ?
Oasis is a system that reduces the size of a database by optimizing file structures, suppressing redundancies, and compacting values. It reduces the size of geometric descriptions by reducing the number of coordinates needed to describe a polygon and reducing the size of each individual coordinate. It also overcomes the limited precision of numerical values by storing them with variable length encoding. Oasis optimizes the layers, data type values, and geometric repetitions of a design, and it allows for the hierarchical structure of a chip. Oasis also enables compression of some blocks in a file using a gzip-like format. An Oasis file is between five and 20 times smaller than one encoded in GDSII.
Checks before switching to OASIS:
Most major foundries and commercial EDA tools now support OASIS. However you must double check at this point at your own company. If you work with a smaller foundry or use internal layout tools, it's recommended to check if both of them support OASIS. Additionally, if you use IP from 3rd-party suppliers, it's important to ensure they can provide the IP in OASIS format or have a discussion with them about changing the format without contract issues.
What is Open Access(OA) Then ?
OpenAccess is a language-based interface to information used in IC design and manufacturing. It consists of a set of C++ functions that operate on a hierarchical set of class definitions, known as the OpenAccess API. OpenAccess offers many advantages, such as a freely provided reference database implementation that supports the API and is tested and of production level quality and performance. The reference database is highly structured, modular, and open- source, making it accessible to the public and able to be used by commercial applications and within IC design and manufacture flows. The goal of OpenAccess is to achieve industry acceptance of the API as a standard, rather than standardizing the use of the reference database code.
Open Access (OA) and OASIS :
Conclusion:
The Oasis format has limitations and can add potential sources of error during the transition from GDSII. Different EDA vendors offer various methods for generating Oasis files, and there is still some resistance to the new format. However, it is believed that extending disk and RAM capacities is not a better deal than changing to Oasis. The complexity of Oasis means there are more possible errors than GDSII, and databases in the new format require careful validation. Despite this, the same detailed checking process built confidence in GDSII, and the arrival of Oasis format reader software is necessary for building a platform for the new standard.
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