Formation of conducting and insulating layered structures in Si by ion implantation - Process control using FTIR spectroscopy

Fourier transform infrared (FTIR) spectroscopy was employed to characterize the formation process of conducting and/or insulating layers in silicon by arsenic or oxygen ion implantation, respectively. Two methods of buried in sulating layer formation were studied. The first involved implantation of 2 00 keV oxygen ions at a dose of 1.8 x 10(18) cm(-2) at implantation tempera ture in the range 500-550 degreesC followed by annealing at 1300 degreesC f or 5 h. The second involved 190 keV oxygen implantation in three cycles, ea ch cycle followed by annealing at 1315 degreesC for 2 h. The Si overlayer o f these substrates as well as bulk Si wafers were then implanted with 70 ke V As+ ions at a nominal dose of 5 x 10(15) cm(-2). Annealing at 950 or 1150 degreesC led to dopant activation and the formation of conducting layers. The optical multilayer modeling of such inhomogeneous structures is given i n detail. Depth profiles of oxygen atomic concentration or free carrier con centration as well as the corresponding refractive index depth profiles are quantified in a fast, cheap, accurate, and contactless way using FTIR spec troscopy. Furthermore, layer thickness, chemical composition, crystallinity , interface quality, and the electrical and transport properties are also e valuated. The results are in good agreement with ion beam analysis and elec trical measurements and it is demonstrated that FTIR spectroscopy can act a s a complementary technique to ion beam analysis techniques, taking over th e role of the electrical methods (which are destructive) and giving much mo re information. (C) 2001 The Electrochemical Society.