Analysis of electrostatic coupling in monolithic 3D integrated circuits and its impact on delay testing

Monolithic 3D (M3D) integration is a promising technology that offers considerable performance and area benefits. A number of techniques have been proposed in the literature for the design and fabrication of M3D integrated circuits (ICs). Despite these advances, test challenges have remained unexplored. As a first step towards the development of test solutions, we analyze electrostatic coupling in M3D ICs and quantify its impact on delay testing. We carry out a detailed study of coupling between device layers, and quantify the change in threshold voltage of transistors in the top layers. Such variations in threshold voltage can significantly impact circuit timing. Next, we analyze the impact of coupling on the effectiveness of delay-test patterns using the statistical delay quality level (SDQL) as a metric. Our results show that significant rethinking in test generation is needed to effectively screen delay defects in M3D ICs.