Nickel-based germanosilicide of n⁺-Si_0.83Ge _0.17 for various doping concentrations and rapid thermal annealing conditions

A Ni/n⁺-Si_0.83Ge_0.17 germanosilicide process has been investigated to understand the influence of temperature and doping concentration on the evolution of sheet resistance and microstructures. After depositing Ni film on Si_0.83Ge_0.17 epilayer and annealing for suicide reaction, sheet resistance and surface roughness were analyzed by using a four- point-probe and scanning probe micrograph. Favorable-quality Ni/Si_0.83Ge_0.17 contact was observed after annealing at around 500°C, but severe degradation occurred when the temperature was high, above 600°C, and this became even worse in heavily phosphorus-doped 1.2 × 10²⁰ cm^-3 Si _0.83Ge_0.17. In order to solve an inappropriate reaction, multilayer metal structures of Ni/Pt and Ni/Ti were employed. We found that a multilayer structure with 1-nm-thick Pt interlayer presented significant advantageous properties for germanosilicide of n⁺-Si _0.83Ge_0.17 with low sheet resistance and smooth surface morphology.