Spatially confined nickel disilicide formation at 400 °C on ion implantation preamorphized silicon

Abstract

The localized formation of continuous silicide layers via solid state reaction of nickel atoms with ion implantation preamorphized silicon is described. Ni films 12 nm thick were evaporated on 65 nm deep amorphized surface layers. The silicidation reaction was induced by two stage thermal annealing at 360 and 400 °C, well below the solid phase epitaxial regrowth temperature for amorphous Si and the normal NiSi2 formation temperature. Rutherford backscattering with channeling, XTEM, and four-point-probe measurements were used to determine the structure, interfacial morphology, composition, and resistivity of the silicide films. After the lower temperature annealing stage a continuous layer of NiSi2 is formed with an underlying residual amorphous region located above the crystalline substrate. During a second annealing the residual amorphous areas recrystallize epitaxially with respect to the substrate via lateral silicide growth. The process leads to formation of a continuous 35 nm thick nickel disilicide layer completely confined within the original amorphous region. Silicide resistivity was 44 μΩ cm. The process may be viewed as a low-temperature process enhancement to self-aligned silicide (SALICIDE) technology since silicide growth proceeds only on preamorphized areas of the silicon substrate.