A silicon cantilever probe card with tip-to-pad electric feed-through and automatic isolation of the metal coating

摘要

A new microfabrication technology for a silicon cantilever array probe card is developed, with technical requirements from Sino IC Technology Co. Ltd for dies under test of 8 inch wafers. A probe card consisting of 96 silicon probes for simultaneously testing two dies is designed and fabricated with bulk micromachining technologies. According to the requirements, a probing force of 25 mN is designed for over-drive displacement no lower than 20 mu m. By using a double- sided metal overlapping scheme, electric feed-through is realized from the probe tips at the bottom to the automatic testing equipment interface on the topside. A recessed concave step is designed and formed to automatically isolate the adjacent probes when a conductive metal layer is sputtered on the surface of the cantilever tips. Characterization of the probe card shows that the resistance at the feed-through via holes is generally lower than 0.8 Omega. In addition, the parasitic capacitance between adjacent probes is as low as 0.02-0.03 pF. The spring constant of the cantilevers is measured as 1126.8 N m-1, which agrees well with the design.