Automated testing of bare die-to-die stacks

Stacking singulated dies is an efficient way to create die stacks; IMEC uses this so-called die-to-die (D2D) stacking approach often to manufacture small to medium volumes of test chips. There is a need to perform a post-bond test on still-unpackaged (`bare´) D2D stacks, if only to avoid unnecessary packaging costs. This paper presents an approach to perform automatic stepping and probing on arrays of D2D stacks pick-n-placed (PnP´d) on a carrier substrate. We describe an algorithm for Cascade Microtech´s CM300 probe station to automatically correct small PnP misalignments. Subsequently we present experimental results for PnP´d D2D stacks on three types of carriers: (1) dicing tape on tape frames for φ100mm wafers, (2) sheets of single-sided thermal-release tape, and (3), φ 300mm carrier wafers with double-sided thermal-release tape. Finally, we describe adaptations to the CM300 probe station to be able to handle 400mm-wide tape frames for, φ 300mm wafers.