The effects of nickel germanosilicide contacts on the biaxial compressive stress in thin epitaxial silicon-germanium alloys on silicon

Abstract

When a thin Si1−xGex epitaxial layer is grown on Si, it is under biaxial compression. In this letter, it is shown that a nickel germanosilicide (NiSi1−xGex) layer formed on Si1−xGex can significantly reduce the in-plane compressive strain in Si1−xGex. It is proposed that the observed reduction is due to the biaxial tensile stress applied by the NiSi1−xGex layer. Because the Si1−xGex bandgap is a strong function of the strain, this is expected to have a strong impact on the metal-semiconductor barrier height and the contact resistivity of the interface if the metal Fermi level is pinned near the Si1−xGex midgap.