Scan FF Reordering for Test Volume Reduction in Chiba-scan Architecture

Abstract

Scan architecture is one of designs for tests (DFTs). In scan architecture, some or all of flip-flops (FFs) in a circuit are serially connected and form a scan chain. The Chiba-scan is one of scan architectures facilitating delay testing. The Chiba-scan has many advantages such as small area overhead comparable to that of the standard scan architecture and complete fault coverage for robust testable path delay faults. However, its test volume is much larger than that of other scan architectures. This paper presents a test volume reduction method for robust path delay fault testing on the Chiba-scan. In this method, scan FFs are reordered. The experimental results give evidence that the proposed method reduces the number of test vectors by 18.4% for ISCAS89 benchmark circuits. Furthermore, the proposed method enables testing with 16.8% shorter test application time (TAT) and 18.3% lower required memory size for automatic test equipment (ATE) compared with those for the enhanced scan architecture.