Highly reliable probe card for wafer testing

A probe card with tungsten probes (needles) is conventionally used for wafer testing. However, the electrical contact between a probe and an aluminum bonding pad becomes unstable, due to the adhesive pick-up of aluminum on the probe tip. In order to maintain a low and stable contact resistance, the probe tip has to be cleaned frequently. A contact mechanism and an adhesion phenomenon are examined to improve the unstable contact. The relations between a tip shape and a plastic deformation of aluminum, and a surface roughness of tip and a adhesion of aluminum are discussed. It was found that the tungsten probe tip with a surface roughness of 0.1 /spl mu/m and a radius of 15 /spl mu/m can maintain stable testing over contact of 300,000 times.