A Low-Stress Low-Temperature "Micro-Soldering" Technique for Making Electrical Contacts to Semiconductor Crystals and Thin Film Materials

A new method for the creation of electrical contacts to semiconductor materials is described. The method utilizes a standard thermocompression bonder apparatus to carry out the bonding motions but does not utilize the compression action to effect the bonding. A small ball is formed at the end of a length of an appropriate contact metal wire by the bonder flame-off system, and a metal or metal alloy is picked up by the ball. Subsequently the ball and alloy metal is brought into contact with the surface of the material to be contacted without pressure. The material contacted in such a manner is not subjected to global heating, significant localized high temperatures, or thermal or mechanical shock, in contrast to the thermocompression or ultrasonic bonding methods. This technique generates contacts with good characteristics, but no degradation of device properties or electrical characteristics is induced by the contacting process. Metal-semiconductor and metal-metal contacts may be formed by the micro-soldering method.