EPITAXIAL-GROWTH AND LATTICE MATCH OF COBALT AND NICKEL DISILICIDES SI(111) GOLD AND COBALT DOPING OF NISI2/

We report on an X-ray diffraction study of the epitaxial growth of thi ck films of cobalt and nickel disilicides on silicon. The lattice para meters both parallel and normal to the interface are measured at room temperature (RT) for various samples prepared by solid phase epitaxy o r reactive deposition epitaxy with annealing at high temperature (600- 800 degrees C). The formation of a rigid disilicide:silicon interface with a dislocation network frozen below a critical temperature T-D, es timated at 600 degrees C for CoSi2 and at 710 degrees C for NiSi2, is the likely growth mechanism of the thick disilicide films. CoSi2 and N iSi2 layers are indeed tetragonally strained at RT with a lateral mism atch equal to that of the relaxed material at T-D, i.e. -0.87% and +0. 17% respectively. The tetragonal distortion results from the different thermal expansion coefficients of silicon and silicides. Doping NiSi2 with 10% Co, i.e. smaller atoms, leads to a close in-plane lattice ma tch. Introducing 6% Au atoms increases the lattice parameter of NiSi2, and also favours the relaxation of the film after annealing. With 12% Au-doping, quasi-total relaxation is observed but the layer is no lon ger uniform. Doping in all cases induces a decrease of the critical te mperature T-D of dislocation freezing.