Nickel suicide thermal stability on polycrystalline and single crystalline silicon

The thermal stability of NiSi on polycrystalline silicon (poly-Si) or single crystalline silicon on sapphire (SOS) substrates has been investigated with scanning electron microscopy, transmission electron microscopy, and in-situ resistance measurements. For NiSi on poly-Si, suicide enhanced grain growth occurs in the poly-Si. The grain growth first occurs from the NiSi/poly-Si interface with poly-Si grains growing into the silicide, resulting in alternating grains of poly-Si and NiSi on the top surface. With further annealing, grain growth also occurs in the bottom layer of the poly-Si, with NiSi moving to the bottom interface and consuming the small poly-Si grains, resulting in an inverted structure. Agglomeration of NiSi is observed for NiSi on SOS substrates after high temperature annealing. The activation energies for inversion and agglomeration are similar, (3.0 ± 0.2 and 2.9 ± 0.2 eV, respectively) suggesting that the same mechanism is controlling both processes. The activation energy may correspond to that for adding a Si atom onto a growing Si grain, as suggested by L.H. Allen, K.N. Tu, L.C. Feldman, and J.W. Mayer, Phys. Rev. B, 41 (1990) 8213.