Efficient Variation-Aware Delay Fault Simulation Methodology for Resistive Open and Bridge Defects

Abstract

SPICE offers an accurate method of simulating defect behavior. However, as demonstrated by recent research, it requires long computation time to simulate defect behavior, when considering process variation. To the best of our knowledge, there is no efficient variation-aware delay fault simulation methodology for resistive opens and resistive bridges. This paper presents a fast and accurate delay fault simulation methodology for these two defects. It is fast because it speeds up delay fault computation time by employing two efficient algorithms. The first algorithm is used to calculate transient gate output voltage, which is a key variable needed to compute delay faults. It employs a three step strategy to accelerate the computation of transient gate output voltage without compromising accuracy. The second algorithm uses bisection method to efficiently compute delay fault behavior of a fault-site. The proposed methodology (PM) has been incorporated in an open-source SPICE (NGSPICE) with BSIM4.7 transistor model. The methodology has been validated by comparing results with HSPICE using industrial designs from IWLS 2005 benchmarks and realistic fault-sites have been extracted from synthesized designs. Simulations are carried out using a 65-nm gate library (for illustration). When compared with HSPICE, results show that the PM is on average up to 52-times faster with ≤ 4.2% error in accuracy for resistive open and 39-times faster with ≤ 5.2% error in accuracy for resistive bridge defects.