MEMS Active Probe for Wafer-level Switching Contacter

本研究的目的是提出一种新型IC探针卡，该探针卡由集成执行器的MEMS探头组成，能够实现触点的直接切换。此外，我们还试图开发基本的制造工艺来实现这一点。具体地说，我们研究了熔块接触过程，这是一种电击穿过程，对于使用MEMS探头进行低力接触是必不可少的。重要结果描述如下1.实现了力分辨率为10μN的熔接触点特性测量系统，并测量了几种探头与铝、铜焊盘冶金膜之间的接触特性。(1)接触电阻随熔接电压和电路电阻所确定的最大熔接电流的增大而减小。(2)镍探头是传统探头中接触电阻最小的。当极限电流大于100mA时，即使接触力在10ΩN.2左右，电阻也可以小于1μ。电镀镍微悬臂梁的研制利用电镀镍双层内应力的差异，提出了微机械加工镍卷起悬臂梁，并对其制作工艺进行了改进。在低应力层采用柳胺酸浴，高应力层采用瓦茨浴，成功地获得了约4 0 0 Mpa的内应力差。通过测量微探头的弹性常数为计算值的70%，证明了镍微悬臂梁探头可用于焊盘间距小于20μm的集成电路测试，其烧结特性与传统针状探头相当。

The purpose of this stude is to propose the new IC probe card which consists of actuator-integrated MEMS probes and enables the direct switching of contacts. Also, we have attempted to develop basic fabrication processes to realize it. Specifically, we have studied the fritting contact process which is a kind of electrical breakdown and is indispensable to make contact to Al pads with low forces using the MEMS probe. The important results are described below.1. Characterization of fritting contact using newly developed measurement systemsWe have realized the systems which can measure the fritting-contact characteristics with the force resolution of 10 μN and measured the characteristics of the contacts between several kinds of probes and pad metallurgy films of Al and Cu.(1) Contact resistance decreases with increasing the maximum fritting current determined by the fritting voltage and circuit resistance.(2) Ni probe can have lowest contact resistance among the conventional probes. When the limit current is larger than 100 mA, the resistance can be smaller than 1 Ω, even if the contact force is around 10μN.2. Development of electroplated Ni microcantilever probesWe have proposed the micromachined Ni curl-up cantilever utilizing the difference of internal stress in electroplated Ni double layers and developed its fabrication process. The internal stress difference of about 400 MPa has successfully been obtained utilizing a salfamic acid bath for the lower low-stress layer and a Watts bath for the upper high-stress layer.We have demonstrated that the Ni microcantilever probes can be applied to the test of IC with the pad pitch of less than 20 μm, by measuring the spring constant of the fabricated microprobes as 70 % of calculated value and showing their fritting characteristics are comparable to those of the conventional needle probes.