Layout and EB data reduction: comparison of OASIS based approach with format-specific reversible compressions

Abstract

With rapid increase in the number of geometries in a chip and aggressive RET carried out on layout data, it has become very much imperative to address the issue of layout and EB data explosion during IC design. Currently, the most widely used GDSII format for layout data as well as the widely used data formats for EB data, are incapable of handling the huge amount of data prevalent in the UDSM regime. The new non-proprietary standardized formats of OASIS for layout data and OASIS.VSB for EB data are the way the industry is likely to go in the near future to address the issue of data explosion. But, the process of adoption of these new formats is too slow as it takes a long time for new design flows to mature. The speed of adoption is especially slow in the post-layout domain as it is very close to manufacturing and the cost of error is too high. However, the issue of layout and EB data explosion is real and immediate and hence, it should be addressed in short term without waiting for the long term solution to arrive.This paper discusses about an alternative approach of employing format-specific lossless reversible layout and EB data compression schemes to compress the layout and EB data. The performance and the advantage of this approach are compared with the currently prevalent approach of using OASIS primarily and solely for on-disk file size reduction. It is argued that the reversible compression techniques could be a better approach for on-disk data file size reduction as they would not only reduce the file sizes but could also almost seamlessly get integrated into the current tool flow without necessitating major changes in the tool flow. The possibility of using OASIS itself as a format for lossless reversible compression of GDSII and MEBES data is also discussed. It is also argued that for successful adoption of OASIS formats by the industry mere on-disk file size reduction may not be sufficient. Higher value additions such as reduction in in-core database size, enabling higher performance in data processing etc. may have to be addressed by the tool flows which adopt OASIS based formats natively.