PtSi contact metallurgy using electron-beam evaporated Pt films and different annealing processes

Abstract

Pt films deposited by electron-beam evaporation onto both heated and unheated Si substrates have been used to form PtSi by different annealing sequences and ambients. Pt films deposited on substrates at 350 °C show complete formation of PtSi. Subsequent annealing at 550 °C is needed to form the protective oxide desired for device processing, with little dependence on the annealing ambients used. Pt films deposited on unheated substrates, on the other hand, show a partial formation of Pt2Si. The formation of PtSi by further annealing of such films is clearly dependent on the annealing sequence and ambient used. A three-temperature sequence at 200/300/550 °C in forming gas is shown to allow a complete reaction between Pt and Si, and to develop a surface protective oxide of excellent resistance against etching in aqua regia. PtSi films formed by single-temperature annealing at 550 °C in various ambients, however, show incomplete reactions between Pt and Si, leaving unreacted Pt and traces of Pt2Si, and a surface passivating oxide of poor resistance against aqua regia. The results on such evaporated Pt films are therefore similar to those reported earlier for the sputtered Pt. Film structures and compositions, phases formed, and Schottky diodes using different processes are analyzed and compared with those using sputtered Pt.