Determination of Interconnect Structural Parameters for Best- and Worst-Case Delays

Toshinori INOSHITA
Zhangcai HUANG
Yasuaki INOUE

IEICE TRANSACTIONS on Fundamentals of Electronics, Communications and Computer Sciences   Vol.E89-A    No.4    pp.856-864
Publication Date: 2006/04/01
Online ISSN: 1745-1337
DOI: 10.1093/ietfec/e89-a.4.856
Print ISSN: 0916-8508
Type of Manuscript: Special Section PAPER (Special Section on Selected Papers from the 18th Workshop on Circuits and Systems in Karuizawa)
interconnect,  worst-case delay,  static timing analysis,  process variation,  capacitance extraction,  

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In general, a corner model with best- and worst-case delay conditions is used in static timing analysis (STA). The best- and worst-case delays of a stage are defined as the fastest and slowest delays from a cell input to the next cell input. In this paper, we present a methodology for determining the parameters that yield the best- and worst-case delays when interconnect structural parameters have the minimum and maximum values with process variations. We also present analysis results of our circuit model using the methodology. The min and max conditions for the time constant are found to be (+Δw, +Δt, +Δh) & (-Δw, -Δt, -Δh), respectively. Here, +Δ or -Δ means the max or min corner value of each parameter variation, where w is the width, t is the interconnect thickness, and h is the height. Best and worst conditions for delay time are as follows: 1) given a circuit with an optimum driver, dense interconnects, and small branch capacitance, the best and worst conditions are respectively (-Δw, +Δt, +Δh) & (+Δw, +Δt, -Δh), 2) given driver and/or via resistances that are higher than the interconnect resistance, dense interconnects, and small branch capacitance, they are (-Δw, -Δt, +Δh) & (+Δw, +Δt, -Δh), and 3) for other conditions, they are (+Δw, +Δt, +Δh) & (-Δw, -Δt, -Δh). Moreover, if there must be only one condition each for the best- and worst-case delays, they are (+Δw, +Δt, +Δh) & (-Δw, -Δt, -Δh).