Design and fabrication of an electrostatically actuated MEMS probe card

Abstract

We have designed and fabricated a new type of MEMS probe card consisting of electrostatically-driven microprobes, which can be used for a next generation wafer probe card with the fritting-contact method. MEMS probe cards are requisite to higher pad-density and smaller pad-pitch chips, and are effective in high frequency testing. If a probe card consists of an array of actuator-integrated microprobes, it has some further advantages. Since the deflection of each probe can individually be controlled, probe-pad contact force can be uniform by compensating the probe-pad distance deviation with probe deflection. Furthermore, since contacts can directly be switched on and off, it could be suitable for a wafer-level test/burn-in probe card. To obtain a design guideline of actuator-integrated probes, we investigated the characteristics of fritting contact between electroplated Ni probes and Al electrodes. As a result, it has been found that both the contact and disconnection forces of Ni probes in fritting contact process could be as small as 10 /spl mu/N. We proposed a MEMS probe card that is composed of an array of Ni microcantilevers with a rolling-contact touch-mode electrostatic actuator and developed a micromachining process which includes electroplating deposition of two layers having different internal stress and etching of Cu sacrifice layer.