Thin Ni-silicides for low resistance contacts and growth of thin crystalline Si layers

A new technological method of producing the Ni silicide with metal-like conductivity by deposition of a thin Si film over an ultrathin Ni prelayer at low temperature has been developed. The interaction of a metallic Ni with the Si atoms provided by the deposition source leads to the formation of the Ni-rich silicide phases immediately after the onset of Si deposition. Continued Si deposition results in the transformation of the Ni-rich silicide phases into the more Si-rich ones which implies that the phase composition is controlled by the Ni-to-Si concentration ratio rather than temperature. After Ni is completely consumed, the Si grains grow epitaxially on the disilicide crystals. The silicide layer has been studied in detail with respect to both the dynamics of the silicide growth and the electrical properties. The Ni silicide resistivity was found to be 2x 10^-4 Ω-cm. The technique has advantages in two respects: it provides a high crystallinity Si film and allows fabrication of an ohmic contact directly on the substrate thus leaving the front surface of the film available for the formation of the active device junction.