The surface roughness of silicon wafers after different stages of chemomechanical polishing was investigated by light scattering topography, soft-x-ray scattering, and atomic-force microscopy. Quantitative values of the rms roughness, the lateral correlation length, and the roughness exponent are extracted. The results suggest deviations from the ‘‘ideal’’ polishing process at large length scales.

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The polishing technology used for manufacturing ultraflat and smooth Si surfaces on a large scale is the chemomechanical polishing (CMP) technique. This technique combines the chemical corrosive removal of silicon atoms and the mechanical transport of the agents. The removal rates strongly depend on the interaction of mechanical parameters and the chemistry involved in the polishing process like the pH of the alkaline polishing slurry used. Removal of Si during CMP is explained by a nucleophilic attack of OH− to silicon atoms catalyzing the corrosive reaction of H2O resulting in cleavage of silicon backbonds. Characterization of the surface chemistry of the silicon wafer after polishing by X-Ray Photoelectron Spectroscopy and High-Resolution Electron Energy Loss Spectroscopy reveals an oxide free, predominantly hydride covered silicon surface displaying hydrophobic properties. Morphological features like microroughness as well as localized surface irregularities on the silicon surface, also referred to as Light Point Defects, depend on different strongly interacting process parameters. Microroughness is reduced by CMP by several orders of magnitude as characterized by lightscattering techniques and Atomic Force Microscopy.

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High-temperature annealing in hydrogen, argon, and oxygen ambients improves the electrical performance of Czochralski Si wafers considerably. The gate oxide integrity of such wafers can approach values close to 100% yield after annealing for 1 to 2 h at 1200~ in argon and hydrogen ambient which is related to a significant reduction of near-surface crystal defects as compared to nonannealed polished wafers. The perfection of epitaxial wafers is, however, not obtained. The high-temperature treatment deteriorates the surface of polished wafers depending on the ambient used. A protective oxide layer grown during annealing in an oxygen ambient prevents roughening due to desorption of SiO. A more pronounced roughening occurs by annealing in hydrogen or argon which is tightly connected to the chemical composition of the Surface. A hydrogen terminated 2 • ] reconstructed Si (i00) surface is observed after annealing in hydrogen. An oxygen-denuded zone is formed close to the surface during high-temperature annealing preventing oxygen precipitation in this region of the wafer. The oxygen precipitation in the bulk of the wafers depends significantly on the details of the annealing process. A precipitation behavior similar to nonannealed Si wafers can be obtained by appropriate process parameters.