Influence of germanium on the formation of NiSi1−xGex on (111)-oriented Si1−xGex

Abstract

The formation of NiSi1−xGex on Si1−xGex(111) substrates with x=0, 0.05, and 0.20 at an annealing temperature of 500°C has been studied by x-ray diffraction, transmission electron microscopy, and pole-figure measurements. NiSi formed preferentially oriented on Si, with (100), (001), and (102) parallel to Si(111) and NiSi[010]‖Si⟨211⟩. In NiSi0.95Ge0.05, (001) and (102) maintained their preferential orientations, whereas NiSi0.95Ge0.05(100) was rotated by 30°, so that NiSi0.95Ge0.05[010]‖Si0.95Ge0.05⟨011⟩. An epitaxial alignment in the form of a double axiotaxy, with NiSi0.95Ge0.05(2±11) as well as (20−2)‖Si0.95Ge0.05{220}, simultaneously with NiSi0.95Ge0.05(0±13) as well as (020)‖Si0.95Ge0.05{022}, caused NiSi0.95Ge0.05(100) to tilt over the range of 0°–7.5°. The Ge addition also enhanced the preferentially oriented structure by reinforcing NiSi0.95Ge0.05(123)‖Si0.95Ge0.05(111) through the axiotaxial alignments, NiSi0.95Ge0.05(211) and (−112)‖Si0.95Ge0.05{220}. Observed was also the presence of NiSi0.95Ge0.05(011)‖Si0.95Ge0.05(111), with NiSi0.95Ge0.05[100]‖Si0.95Ge0.05⟨011⟩. In the case of NiSi0.80Ge0.20, the preferential orientations were sharply reduced in favor of NiSi0.80Ge0.20(100)‖Si0.80Ge0.20(111), with NiSi0.80Ge0.20[010]‖Si0.80Ge0.20⟨011⟩ and the 30° rotation thus preserved. The observed Ge influence is shown to be consistent with a model suggested earlier for Si1−xGex(001) substrates, which is based on the nonexistence of Ni(Si1−xGex)2 for all except the smallest values of x. High-resolution transmission electron microscopy was used to show that the surface steps typical of molecular-beam-deposited epitaxial Si1−xGex substrate films do not influence the growth of the NiSi1−xGex.