Low pressure chemical vapor deposition of oxide from SiH₄/O ₂: Chemistry and effects on electrical properties

The low pressure chemical vapor deposition (CVD) process of SiO2 from SiH4 and O2 has been analyzed. For deposition at pressures ranging from 10-3 to 3 Torr, with no carrier gas, the process is dominated by fast gas-phase reactions. In situ analytical techniques, such as mass spectrometry and high-resolution electron energy loss spectroscopy, indicate that hydroxyl groups are reaction products and are imbedded into the growing oxide at temperatures from 300 to 600°C. Presence of these groups is detrimental to the electrical properties of metal-oxide-semiconductor (MOS) structures, e.g., by causing low-field breakdown and by increasing the interface state density. Low-pressure (SiH 4/O2) oxides are thus principally not well suited for gate-oxide applications because of their underlying chemistry.