IMPROVEMENT OF CZOCHRALSKI SILICON-WAFERS BY HIGH-TEMPERATURE ANNEALING

High-temperature annealing in hydrogen, argon, and oxygen ambients imp roves 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 degrees C in argon an d hydrogen ambient which is related to a significant reduction of near -surface crystal defects as compared to nonannealed polished wafers. T he perfection of epitaxial wafers is, however, not obtained. The high- temperature treatment deteriorates the surface of polished wafers depe nding on the ambient used. A protective oxide layer grown during annea ling in an oxygen ambient prevents roughening due to desorption of SiO . A more pronounced roughening occurs by annealing in hydrogen or argo n which is tightly connected to the chemical composition of the surfac e. A hydrogen terminated 2 x 1 reconstructed Si (100) surface is obser ved after annealing in hydrogen. An oxygen-denuded zone is formed clos e to the surface during high-temperature annealing preventing oxygen p recipitation in this region of the wafer. The oxygen precipitation in the bulk of the wafers depends significantly on the details of the ann ealing process. A precipitation behavior similar to nonannealed Si waf ers can be obtained by appropriate process parameters.