A robust MEMS probe card with vertical guide for a fine pitch test

A vertically guided MEMS probe card was designed to deflect 50 mu m at a force of 1.5 g and achieve less than 50 mu m of pad pitch. Based on our experimental results, the measured average contact resistance of a device under test (DUT) was approximately 0.2 Omega at 1.44 g of force and the leakage current between two tips in the distance of one pitch was about 10 pA. In addition, tip planarity was about +/- 6 mu m with x-y alignment errors within +/- 8 mu m. A reliability test showed that the average contact resistance was 0.34 Omega and the probe tip wear was less than 1 mu m after the 10 000 timed touchdowns. To be capable of fine pitch probing, a cantilever beam was constructed by dry etching using a positive photoresist. After the cantilever beam was formed by silicon etching using a deep RIE etcher inside a deep-recessed trench, a vertically guided structure was created from the cantilever beam. Furthermore, to make a horizontally stopped structure, the cantilever beam was designed to have a pyramid tip with a width bigger than that of the beam itself. This kind of structure is mechanically stable when the tip is applied with an oblique force. Because the probe card can be guided vertically and horizontally, it can be neither broken nor deformed by any directional force. In that respect, this newly proposed probe card is suitable for wafer-level testing and fine pitch device testing.