The Low-Pressure, Chemical Vapor Deposition of SiO2 Layers Using CO2 as the Oxygen Source

Silicon Dioxide (SiO2), useful in microelectronics and microfabrication, is often deposited via low pressure CVD (LPCVD). One method is to use dichlorosilane (DCS) and an oxidizer such as N2O:SiH2Cl2+2N2O-\u3eSiO2+2N2+2HCl. Carbon dioxide (CO2) is isoelectric and should be able to replace N2O as an oxidizer. Little work has been done with CO2 and DCS at low pressure. We deposited rich SiO2 on silicon wafers using CO2 and DCS over the ranges of .6 to 5 Torr and 800 to 950ºC. We used ellipsometry and SEM-EDX to measure the thickness, refractive index, and chemical composition of each sample. We found that most of the films were hazy, i.e. light scattering off the surface was obvious to the eye. So little SiO2 formed at .6 Torr and 800ºC that we concluded substrate oxidation rather than deposition occurred. It was the least silicon rich and least hazy. Around 5 Torr we achieved SiO2 deposition with a refractive index of 1.6, atomic ratio of Si to O of 40:60, and the haziest surface