Abstract

New modification of por-Si have been discovered [1] to be formed as a 30 nm microporous layer (30 nm) as a result of laser annealing of c-Si implanted by krypton (:wave length of 694,3 nm, pulse width of 50 ns, energy density of 0.3 J/cm²).In the present work,in order to study influence of high dose implantation and laser annealing regimes on pecularities of formiation of such microporous layers, the p-silicon samples with (111) orientation were examined at higher doses of krypton ions (6*10¹⁵-2.4*10¹⁷ ion/cm²) and laser energy density (0-2.3 J/cm²).The ellipsometric measurements were performed with LEF-3M1 ellipsometer at a probe wave length 632.8 nm,room temperature and normal pressure.The angle of probe beam incidence was 70 degrees. Measuring the ellipsometric parameters followed by calculating of the optical constants n and k in the case of step by step anodic etching we have studied depthward transformation of the disordered undersurface layers depending on laser energy density.The profiles of complex refractive coefficient are shown in Fig.1. Behaviour of the n-profiles (Fig.1a,curves 2-4) has no agreement with ordinary data because, nearly to the surface, n is as little as monocrystalline silicon’s one (curve 5). Such a transformation of structure of nearsurface layer is due to formation of dense grid of micropores that results in considerable increase of k-coefficient as well (Fig.1b).Recrystallization of the disordered layer due to laser annealing takes place while increasing laser energy density., In dependence on regimes of irradiation the transformation process of nearsurface layer structure has some interesting features,for instance, diffusion of cryplon and moving of micropores to the surface at lower energy density.

© 1996 IEEE