TEM Characterisation of Silicide Phase Formation in Ni-Based Ohmic Contacts to 4H n-SiC

抄録

Nickel silicide ohmic contacts to 4H n-SiC were investigated using electron microscopy. Ni/Si multilayer structures were fabricated using magnetron sputtering technique. The Ni to Si layer thickness ratio was chosen to achieve the stoichiometry of Ni₂Si phase. The deposited structure was subjected to a two-step annealing procedure. First annealing step was performed at 600°C, the second at 1050°C or 1100°C. Microstructure and morphology after each annealing step were characterized using scanning and transmission electron microscopy. The specific voids and discontinuities of the layer were observed after annealing at high temperature. Phase compositions were investigated with electron diffraction technique. After annealing at 600°C the phases Ni₂Si, Ni₃Si₂ and Ni₃₁Si₁₂ were detected. High temperature annealing resulted in the presence of only Ni₂Si phase. The influence of phase transformations on the morphology of the contacts is discussed. Explanation of the origin of layer discontinuities is proposed.