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.
Highlights
Three-dimensional (3D) wafer-level packaging (WLP) is a mainstream advanced packaging technology to meet the various requirements of semiconductor industries, including low cost, low profile, high input/output (I/O), high electrical performances, and high reliability [1,2]
We propose a novel design for a MEMS vertical probe for wafer-level testing, to improve its current-carrying capacity and minimize damage to various interconnect structures, including solder balls, Cu pillar microbumps, and through-silicon vias (TSVs) structures
For the 4000 μm-long probe, the allowable current was less than 900 mA. These results indicated that the proposed Au–NiCo probe had a superior current-carrying capacity compared with the conventional vertical probe
Summary
Three-dimensional (3D) wafer-level packaging (WLP) is a mainstream advanced packaging technology to meet the various requirements of semiconductor industries, including low cost, low profile, high input/output (I/O), high electrical performances, and high reliability [1,2]. A wafer testing before the bonding process, known as a prebond test, is commonly required to enhance the test yield in 3D WLP [10] Wafer testing on these advanced packages is more difficult because they have unique, weaker, and more complex interconnect structures than the conventional flat metal electrode on the wafer. Excessive heating will cause changes in the physical properties and mechanical behavior of the probe, and eventually lead to the probe burning or melting [9,16] For these reasons, highly elastic and robust materials such as Ni–Co, tungsten, Be–Cu, and Paliney are commonly used to fabricate the vertical probe [9,16,17]. We propose a novel design for a MEMS vertical probe for wafer-level testing, to improve its current-carrying capacity and minimize damage to various interconnect structures, including solder balls, Cu pillar microbumps, and TSV structures. Contact behavior such as deformation, contact force, and the stress of the probe and various interconnect structures with different overdrives (OD) were numerically analyzed
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