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

• The formation of NiSi1-xGex on Si1-xGex(111) substrates with x=0, 0.05, and 0.20 at an annealing temperature of 500 degrees 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]parallel to Si < 211 >. In NiSi0.95Ge0.05, (001) and (102) maintained their preferential orientations, whereas NiSi0.95Ge0.05(100) was rotated by 30 degrees, so that NiSi0.95Ge0.05[010]parallel to 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)parallel to Si0.95Ge0.05{220}, simultaneously with NiSi0.95Ge0.05(0 +/- 13) as well as (020)parallel to Si0.95Ge0.05{022}, caused NiSi0.95Ge0.05(100) to tilt over the range of 0 degrees-7.5 degrees. The Ge addition also enhanced the preferentially oriented structure by reinforcing NiSi0.95Ge0.05(123)parallel to Si0.95Ge0.05(111) through the axiotaxial alignments, NiSi0.95Ge0.05(211) and (-112)parallel to Si0.95Ge0.05{220}. Observed was also the presence of NiSi0.95Ge0.05(011)parallel to Si0.95Ge0.05(111), with NiSi0.95Ge0.05[100]parallel to Si0.95Ge0.05< 011 >. In the case of NiSi0.80Ge0.20, the preferential orientations were sharply reduced in favor of NiSi0.80Ge0.20(100)parallel to Si0.80Ge0.20(111), with NiSi0.80Ge0.20[010]parallel to Si0.80Ge0.20< 011 > and the 30 degrees 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.

Nyckelord

thin-films

single-crystal

stress

nickel

nisi

nisi1-ugeu

silicides

growth

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