Scheduling Tests for 3D Stacked Chips under Power Constraints

This paper addresses Test Application Time (TAT) reduction under power constraints for core- based 3D Stacked ICs (SICs) connected by Through Silicon Vias (TSVs). Unlike non-stacked chips, where the test flow is well defined by applying the same test schedule both at wafer sort and at package test, the test flow for 3D TSV-SICs is yet undefined. In this paper we present a cost model to find the optimal test flow. For the optimal test flow, we propose test scheduling algorithms that take the particulars of 3D TSV-SICs into account. A key challenge in testing 3D TSV-SICs is to reduce the T AT by co-optimizing the wafer sort and the package test while meeting power constraints. We consider a system of chips with cores that are accessed through an on-chip JTAG infrastruc- ture and propose a test scheduling approach to reduce T AT while considering resource conflicts and meeting the power constraints. Depending on the test schedule, the JTAG interconnect lines that are required can be shared to test several cores. This is taken into account in experiments with an implementation of the proposed scheduling approach. The results show significant sav- ings in T AT.