ROUGHNESS OF THERMAL OXIDE LAYERS GROWN ON ION-IMPLANTED SILICON-WAFERS

We have studied by atomic force microscopy (AFM) the surface morpholog y of SiO2 layers grown by thermal oxidation of silicon wafers implante d with As, B, Ge, or Si ions. In order to grow oxides having comparabl e thickness at different temperatures, we have employed both dry and w et processes. Roughness values up to 0.4 nm have been measured on the surface of these oxides. Surface morphology is not influenced by the o xidation ambient, while temperature-related effects are predominant. F or low temperature oxidation (920 degrees C), the predominating effect s are due to the behavior of the implanted species, and mainly consist in segregation phenomena, that are the result of a complex competitio n among different factors, including the segregation coefficient, the relative diffusion rates in the oxide and silicon, and the oxidation r ate. At higher temperature (1100 degrees C), impurity segregation is i nhibited or considerably reduced by the increased diffusivity, and def ects formation, due to the evolution of the radiation damage, becomes the main effect. Finally, the comparison among AFM, Rutherford backsca ttering spectrometry, and transmission electron microscopy data has al lowed to demonstrate that the morphologies of the SiO2 surfaces are ti ghtly related to the corresponding SiO2/Si interfaces. (C) 1998 Americ an Vacuum Society. [S0734-211X(98)01402-4].