Effect of oxygen to argon ratio on the properties of thin SiO x films deposited by r.f. sputtering

Energy Dispersive X-ray and X-ray Photoelectron (XPS) spectroscopies show that SiO (x) films deposited by reactive r.f. magnetron sputtering at partial pressure ratios R between oxygen and argon in a wide range (1-0.005) have compositions close to the stoichiometric one. For these films high temperature annealing at 1,000 A degrees C shifts the band in the Fourier Transform-Infrared spectrum due to the Si-O-Si stretching vibration to values typical of stoichiometric SiO2. Further decrease of R leads to splitting of the Si 2p XPS line indicating increase of the Si content and formation of a second phase in a SiO2 matrix. The electrical properties of test MOS structures with SiO (x) gate dielectric, regarding defect density in the oxide and at the SiO (x) /c-Si interface, degrade with the decrease of R. High temperature annealing at 1,000 A degrees C strongly improves the properties of all films regarding leakage current and properties of the interface.