Silicon cantilever arrays with by-pass metal through-silicon-via (TSV) tips for micromachined IC testing probe cards

In this paper, an integrated probe card is proposed and developed for wafer-level IC testing. Based on micromachining technology, totally about 26,000 cantilever-tip probes can be formed simultaneously in one 4-in. silicon wafer, with the minimum pitch of 35 μm for adjacent probing tips. The probe card is designed with a novel composite structure that combines both single-crystalline silicon and electroplated metals. In the composite structure, a novel bypass through-silicon-via with a low aspect ratio can be high-yield fabricated for transferring the testing signals from the probing sided (at the wafer bottom side) to the I/O interface (at the front side). The probe card makes full use of the advantages of the single-crystal silicon and the electroplated nickel and copper. Bulk micromachined silicon cantilevers behave uniform probing height and a good elastic deformation property, while the electroplated nickel probing tips promise high hardness and satisfactory electric contact performance with the dies-under-test (DUT). Measurements show that the fabricated cantilever is able to withstand a contact force of 80mN by a tip displacement of 20 μm. The measured contact resistances on metal pads (Al, Cu, and Au) are all below 1 Ω, whereas the maximum current leakage is 64 pA for 3.3 V voltage across two adjacent tips. After a probing reliability test of 100,000 cycles, the cantilever-tip shows no sign of any performance degradation.