EFFECTS OF A THIN SiO₂ LAYER ON THE FORMATION OF METAL-SILICON CONTACTS.

The reactions that occur between different metals and silicon wafers with a thin oxide layer were studied. The oxides were formed by either exposing the chemically cleaned wafer to air at room temperature or by thermally growing 30 A of oxide at 700 degree C in dry O//2. Al, Pt, and Au contacts were investigated. The interfacial reactions before and after heat treatment at 400 degree C for 1 h were characterized using Auger and ESCA sputter profiling. The air grown oxides were found not to prevent intimate contact between the metal and the silicon, and reactions were observed for both heat treated and unheated samples. At 400 degree C the 30 A thermal oxide was found to be an effective diffusion barrier for Pt but less effective for Au. The Al reduced the 30 A of SiO//2 to form Al//2O//3 at the interface in what appeared to be a self-limiting reaction.