Design of New Au–NiCo MEMS Vertical Probe for Fine-Pitch Wafer-Level Probing

Abstract

As fine-pitch 3D wafer-level packaging becomes more popular in semiconductor industries, wafer-level prebond testing of various interconnect structures has become increasingly challenging. Additionally, improving the current-carrying capacity (CCC) and minimizing damage to the probe and micro-interconnect structures are very important issues in wafer-level testing. In this study, we propose an Au–NiCo MEMS vertical probe with an enhanced CCC to efficiently reduce the damage to the probe and various interconnect structures, including a solder ball, Cu pillar microbump, and TSV. The Au–NiCo probe has an Au layer inside the NiCo and an Au layer outside the surface of the NiCo probe to reduce resistivity and contact stress. The current-carrying capacity, contact stress, and deformation behavior of the probe and various interconnect structures were evaluated using numerical analyses. The Au–NiCo probe had a 150% higher CCC than the conventional NiCo probe. The maximum allowable current capacity of the 5000 µm-long Au–NiCo probe was 750 mA. The Au–NiCo probe exhibited less contact force and stress than the NiCo probe. The Au–NiCo probe also produced less deformation of various interconnect structures. These results indicate that the proposed Au–NiCo probe will be a prospective candidate for advanced wafer-level testing, with better probing efficiency and higher test yield and reliability than the conventional vertical probe.