CHARACTERIZATION OF POROUS SILICON BY NRA, RBS AND CHANNELING

Porous silicon could be an interesting material for microelectronic applications if the quality of porous films is significantly improved. This material has the ability to be easily oxidized at relatively low temperatures (< 850° C). Moreover, it preserves the single-crystal characteristics of the substrate, allowing epitaxial growth of Si and GaAs at moderate temperatures. The aim of this work was to determine the impurity content of porous films and to test their crystalline quality, as a function of preparation conditions, using ion beam analysis: NRA, ERDA, RBS and channeling. Relatively good channeling was observed in some porous materials (Xmin = 15%) in spite of the adsorbed impurities and the disorder due to the enormous surface area of the pores: 400 times higher than the geometrical surface area for a 2 μm thick porous layer. The surface density of the impurities is relatively low and can be decreased significantly by adequate surface preparation. Typical results are: 0.6 × 1015 O-at./cm2, 3 × 1015 C-at./cm2, 1015 H-at./cm2 and 0.1 × 1015 F-at./cm2. © 1990.