Development of surface morphology of epitaxial Al2O3 on silicon by controlling reaction between oxygen and silicon surface

Epitaxial growth of Al2O3 on Si has been investigated using ultrahigh-vacuum chemical vapor deposition (UHV-CVD). The uniformity of Al2O3 growth in a wafer was improved by UHV-CVD with a hot-wall heating system, but the surface morphology of grown films was degraded compared with that of films grown by low-pressure chemical vapor deposition (LP-CVD) with a cold-wall heating system. Using oxygen for Al2O3 growth instead of N2O, crystalline quality and electrical properties of Al2O3 films were improved, but microroughness still exist at the Al2O3 surface. A new Al2O3 growth method is proposed taking into account thermochemical considerations. The growth temperature of Al2O3 was lowered at a temperature below 780 degrees C to improve the surface morphology. Although the surface morphology of Al2O3 film was improved, its crystalline structure was degraded by the low-temperature growth. Then, a high-temperature growth was performed on the Al2O3 layer grown at the low temperature, to recover the crystalline structure of the grown films. Using two complementary growth steps with different temperatures, the surface morphology and electrical properties of epitaxial Al2O3 films on Si substrates were improved.