Crystallographic aspects of thin PtSi films on Si substrates

The structural characteristics of a reacted ohmic contact, platinum silicide, have been investigated using X-ray diffraction, electron diffraction and electron microscopy techniques. The contacts were formed by depositing Pt metal onto Si substrates and sintering at various temperatures in the range 225 to 725°C. Some slight initial reaction occurred at 225°C (the nominal substrate temperature) giving rise to both the thermodynamically stable PtSi and the intermediate reaction product Pt₃Si. Complete reaction was accomplished when the contacts were sintered at temperatures in excess of 650°C. The compositions of the silicide contacts were independent of the method of metal deposition. The PtSi phase occurred as two distinct crystallographic components, one being moderately oriented, the other having a very high degree of the (010) type orientation. The relative proportions of these two components were solely dependent on the substrate temperature during deposition; the formation of the moderately oriented component could be suppressed by raising the substrate temperature above 500°C.