Evaluation of the new oasis format for layout fill compression
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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

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


Overview
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


Cmp and interlevel dielectric thickness

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


Motivation
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?


Repetition operators in gdsii
Repetition Operators in GDSII

AREF = array reference

SREF = structure reference


Repetition operators in oasis
Repetition Operators in OASIS

Type 1

Type 2

Type 3

Type 5

Type 4

Type 7

Type 6

Type 8


Compression ratio of oasis repetitions
Compression Ratio of OASIS Repetitions

  • Compression Ratio CR=

    size flat OASIS / size compressed OASIS

CR ( , ) = Θ(MN)

CR ( , , ) = Θ(M)


Compression ratio of oasis repetitions1
Compression Ratio of OASIS Repetitions

  • Compression Ratio of Types 4,5 and 8

CR ( , ) = 7

CR ( ) = 3.5


Compressible fill

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



Compressible fill generation gzip
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)


Compressible fill generation results
Compressible Fill Generation Results

I = Restricted OASIS (= GDSII)

II = Full OASIS

III = Types 1,2,3,4,5

IV = Types 4,5


Fill compression problem
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



Fill compression results
Fill Compression Results

Rest = GDSII

Full = Full OASIS

ESBG = Exhaustive search

RSBG = Regularity search



Conclusions suggestions

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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