Detailed placement for improved depth of focus and CD control

Abstract

Sub-resolution assist features (SRAFs) provide an absolutely essential technique for critical dimension (CD) control and process window enhancement in subwavelength lithography. However, as focus levels change during manufacturing, CDs at a given "legal" pitch can fail to achieve manufacturing tolerances required for adequate yield. Furthermore, adoption of off-axis illumination (OAI) and SRAF techniques to enhance resolution at minimum pitch worsens printability of patterns at other pitches. This paper describes a novel dynamic programming-based technique for Assist-Feature Correctness (AFCorr) in detailed placement of standard-cell designs. For benchmark designs in 130nm and 90nm technologies, AFCorr achieves improved depth of focus and substantial improvement in CD control with negligible timing, area, or CPU overhead. The advantages of AFCorr are expected to increase in future technology nodes.

Temperature- and Cost-Aware Design of 3D Multiprocessor Architectures

“…A problem is that placement perturbation at the post-route stage or at near the signoff stage can always introduce new timing violations due to the changes in parasitic RC from ECO routing, unless the placement and routing changes are very localized. In [10], assist-feature correctness (AF-Corr) is achieved by dynamic programming (DP) that minimizes displacement of cells while ensuring space for correct assist-feature insertion.…”

On-Line Adjustable Buffering for Runtime Power Reduction

“…Our approach modifies the pitches themselves to reduce leakage and is complementary to theirs. Gupta et al [11] proposed a placement perturbation approach to increase the number of scattering bars that can be inserted. Scattering bars are very thin, non-printing lines that assist printability by reducing through-pitch variation.…”

“…Scattering bars are very thin, non-printing lines that assist printability by reducing through-pitch variation. While [11] can increase the number of scattering bars and reduce through-pitch variations, design objectives such as delay and leakage are not targeted. The approach of [11] is also limited to perturbing cells in the neighboring free space in a single row, which limits the opportunities for optimization.…”

“…While [11] can increase the number of scattering bars and reduce through-pitch variations, design objectives such as delay and leakage are not targeted. The approach of [11] is also limited to perturbing cells in the neighboring free space in a single row, which limits the opportunities for optimization. The use of detailed placement to enhance the printability of cells has also attracted interest from the industry recently [8].…”

Lithography-Aware Physical Design

“…Lithoaware routing can be performed not just at the post-layout stage, but through the correct-by-construction routing using proper litho-cost to explore the design/manufacturing tradeoff. Furthermore, litho-aware placement shall be done to make sure no forbidden pitches exist between adjacent cells [14]. The placement also affects the overall interconnection, thus should be considered together with litho-aware routing.…”