Crystallography of PtSi films on (001) silicon

Abstract

Platinum silicide is widely used to make Ohmic contacts and Schottky‐barrier diodes. These contacts are formed by evaporation of platinum on a (001) silicon substrate. During evaporation, two phases are formed: Pt₂Si and/or or PtSi, depending on the process used. After sintering, the final phase is PtSi. This study shows that PtSi grains in epitaxy on (001) silicon are oriented along two separate sets of orientation: the already known (11̄0) and a newly determined (12̄1) orientation. The ratio of the number of grains oriented along the latter and former orientations depends on the wafer temperature during evaporation. The two orientations may be caused by two different formation mechanisms: evaporation on silicon substrates at 320 °C under which Pt₂Si is formed at first and then transformed into the PtSi phase with the (11̄0) orientation during sintering and evaporation on silicon substrates at 400 °C under which PtSi is formed directly along the (12̄1) plane and undergoes no change during further heat treatments. For intermediate temperatures, both mechanisms are present.