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

Abstract: 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 35μm 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 20μm. The measured contact resistances on metal pads (Al, Cu, and Au) are all below 1Ω, whereas the maximum current leakage is 64pA for 3.3V voltage across two adjacent tips. After a probing reliability test of 100,000 cycles, the cantilever-tip shows no sign of any performance degradation. [Copyright &y& Elsevier]