Staggered ATPG with capture-per-cycle observation test points

Abstract

This paper presents a new staggered test pattern generation scheme. It produces deterministic stimuli in the course of a test-per-clock-based process by using dedicated capture-per-cycle observation test points. These observation points, once inserted into a design, form dedicated scan chains with the capability of capturing test responses during shift cycles when other regular scan cells are loading test patterns. This new scan infrastructure enables one to generate more compact test patterns, reduce test pattern counts, systematically detect many additional faults, and keep the resultant silicon real-estate at the acceptable level. It appears that original scan cells of a design can provide good observability for staggered test patterns. Thus, capture-per-cycle observation test points are directly inserted at selected scan cells' inputs with a minimal impact on the design. Experimental results obtained for large industrial designs illustrate feasibility of the proposed ATPG and are reported herein.