Advanced timing analysis based on post-OPC extraction of critical dimensions

ABSTRACT

While performance specifications are verified before sign-off for a modern nanometer scale design, extensive application of optical proximity correction substantially alters the layout introducing systematic variations to the simulated and verified performance. As a result, actual on-silicon chip performance is quite different from sign-off expectations. This paper presents a new methodology to provide better estimates of on-silicon performance. The technique relies on the extraction of residual OPC errors from placed and routed full chip layouts to derive actual (i.e., calibrated to silicon) CD values that are then used in timing analysis and speed path characterization. This approach is applied to a state-of-the-art microprocessor and contrasted with traditional design flow practices where ideal (i.e., drawn) L_gate values are employed, leading to a subsequent lack of predictive power. We present a platform for diagnosing and improving OPC quality on gates with specific functionality such as critical gates or matching transistors. Furthermore, with more accurate timing analysis we highlight the necessity of a post-OPC verification embedded design flow, by showing substantial differences in the Si-based timing simulations in terms of significant reordering of speed path criticality and a 36.4% increase in worst-case slack. Extensions of this methodology to multi-layer extraction and timing characterization are also proposed.

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INDEX TERMS

Primary Classification:
  B. Hardware
  B.7 INTEGRATED CIRCUITS
      B.7.2 Design Aids
          Subjects: Layout

Additional Classification:
  B. Hardware
  B.7 INTEGRATED CIRCUITS
      B.7.2 Design Aids
          Subjects: Verification
  B.8 Performance and Reliability

General Terms:
Algorithms, Design, Performance

Keywords:
OPC, design flow, layout, process CD