The Influence of Cleaning on SiO2 Growth

The oxidation rate of single crystalline silicon depends on the preoxidation cleaning procedure. Various cleaning procedures were compared using aqueous solutions of NH4OH-H2O2, HCl-H2O2 and H2SO4·H2O2· A dip in 10% HF was used either at the beginning or at the end of the cleaning procedure. Thermal oxidation was carried out at 885°C, 985°C and 1085°C in a conventional diffusion furnace. The oxidation rates are maximum for the samples treated with HF as a final step in the cleaning procedure whereas a final treatment with NH4OH leads to a minimum oxidation rate. ESCA measurements were performed to investigate the chemical state of the SiO2-Si interface. The oxide contains more silicon after HF etching than after NH4OH etching.