Thermal study of the Pt-Al reaction and its effects on contact resistance to silicon

Abstract

The sintering reaction of a thin film of platinum on a silicon substrate followed by a thicker aluminum overlayer has been studied. The metal layers were deposited on 〈100〉 oriented p- and n-type silicon. Aluminum is the major contaminant found in sputtered platinum films. Possible deleterious metallurgical reactions between platinum and several possible metal contaminants during subsequent processing were previously discussed. In the present study the metallization system was exposed to harsh thermal and chemical conditions. The results do not indicate the existence of detrimental effects on the ohmic contact properties due to a platinum-aluminum reaction, following the usual treatment in aqua regia, if a thick enough (∼500 Å) layer of platinum is used. In fact, the formation of a PtAl2 intermetallic compound seems to result in low values for the specific contact resistance.