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Evaluation of the New OASIS Format for Layout Fill Compression

Supported by Cadence Design Systems Inc., U.S. National Science Foundation, and the Packard Foundation. Evaluation of the New OASIS Format for Layout Fill Compression. Yu Chen, Andrew B. Kahng, Gabriel Robins, Alexander Zelikovsky and Yuhong Zheng UCLA, UCSD, UVA, GSU vlsicad.ucsd.edu.

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Evaluation of the New OASIS Format for Layout Fill Compression

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  1. Supported by Cadence Design Systems Inc., U.S. National Science Foundation, and the Packard Foundation Evaluation of the New OASIS Format for Layout Fill Compression Yu Chen, Andrew B. Kahng, Gabriel Robins, Alexander Zelikovsky and Yuhong Zheng UCLA, UCSD, UVA, GSU vlsicad.ucsd.edu

  2. Overview • CMP and Interlevel Dielectric Thickness • Motivation • Repetition Operators in GDSII • Repetition Operators in OASIS & their Compression Ratios • Compressible Fill Generation: algorithms and results • Fill Compression Problem: algorithms and results • Conclusions & Suggestions

  3. Chemical-Mechanical Planarization (CMP) = wafer surface planarization Uneven features cause polishing pad to deform Area fill features CMP and Interlevel Dielectric Thickness Post-CMP ILD thickness Features • Interlevel-dielectric (ILD) thickness  feature density • Insert dummy features to decrease variation Post-CMP ILD thickness

  4. Motivation • Dummy features grow layout size to terabytes •  Need in more compressible format • New format: OASIS = Open Artwork System Interchange Standard • Our focus: • How to exploit new compression capabilities of OASIS? • How to improve proposed OASIS for further fill compression?

  5. Repetition Operators in GDSII AREF = array reference SREF = structure reference

  6. Repetition Operators in OASIS Type 1 Type 2 Type 3 Type 5 Type 4 Type 7 Type 6 Type 8

  7. Compression Ratio of OASIS Repetitions • Compression Ratio CR= size flat OASIS / size compressed OASIS CR ( , ) = Θ(MN) CR ( , , ) = Θ(M)

  8. Compression Ratio of OASIS Repetitions • Compression Ratio of Types 4,5 and 8 CR ( , ) = 7 CR ( ) = 3.5

  9. Filled layout with area features in 9 operators Compressible Fill • Compressible Fill Generation Problem (CFGP) Given a design rule-correct layout, create the minimum number of OASIS operators to represent area fill features that keep window density variation within the given bounds (L,U) Filled layout with 82 area features Original layout

  10. Greedy Compressible Fill Generation

  11. Compressible Fill Generation & GZIP GZIP applied to compressible fill compress slower and worse than native generator GCF GZIP and GCF are orthogonal to each other C_Ratio(GCF+GZIP) =C_Ratio(GCF)×C_Ratio(GZIP)

  12. Compressible Fill Generation Results I = Restricted OASIS (= GDSII) II = Full OASIS III = Types 1,2,3,4,5 IV = Types 4,5

  13. Fill Compression Problem • OASIS Fill Data Compression Problem Given a layout containing are fill features, represent these area fill features using OASIS repetition operators in a way that minimizes the resulting data volume Finding regularities

  14. Exhaustive Search Greedy Fill Compression

  15. Fill Compression Results Rest = GDSII Full = Full OASIS ESBG = Exhaustive search RSBG = Regularity search

  16. Fill Compression Results

  17. Contributions: New algorithms for compressible fill generation New fill compression algorithms for OASIS format Comparison of GDSII and OSIS formats Conclusions & Suggestions • Suggestions to enhance OASIS • Add irregular array OASIS repetition = combination of 4 & 5 • Include pseudo-random number generator in OASIS, for fast and simple generation of irregular area fill

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