In-Situ Studies of Growth, Defects and Reconstruction at Epitaxial Silicide/Silicon Interfaces

The cubic metallic silicides CoSi 2 and NiSi 2 have been grown epitaxially on silicon with great success, and provide model systems for the study of Schottky barriers. The lattice mismatch with Si of these silicides is less than 1.2% and layers with abrupt interfaces can be grown by Molecular Beam Epitaxy (MBE). 1 A common method of growth is by deposition of pure metal at room temperature followed by in-situ solid phase epitaxy of the disilicide by annealing at 400–550°C. In such experiments it has been found that the thickness of the deposited metal layer has a profound effect on the final microstructure of the disilicide. For example, for (111) NiSi 2 formation, the orientation is found to depend on the thickness of deposited Ni: for 8–12A deposited Ni single crystals of type-B orientation NiSi 2 result on annealing. For thickness of 16–20A Ni, type-A NiSi 2 results. 1 The type-B orientation has a twinned heterointerface whereas the type-A is normally epitaxed. For (100) NiSi 2 and CoSi 2 formation, good quality films result only from annealing of metal deposits of thickness ≤15A.