Optical Properties Of SiO₂ Thin Film Deposited By Variant Sputtering Method

Silicon oxide (SiO2) thin film is an ideal optical material for its low refractive index, low extinction coefficient, small dispersion, strong adhesion, small surface roughness and high transmission in visible and near infrared region; meanwhile, the mechanical properties of silicon oxide thin film are also outstanding, such as high hardness, chemical inert, high abrasive corrosion resistance and high laser induced damage threshold. So the SiO2 thin film is widely used in optics, mechanical manufacture and microelectronics. At present, the SiO2 thin film attracts more attention in the development of high power laser and especially in the laser weapon for its high laser induced damage threshold.There are many methods to deposit SiO2 thin film. The reactive magnetron sputtering (RMS) and reactive ion-beam sputtering (RIBS) deposition are recognized as the main methods for preparing SiO2 thin film. In this paper, SiO2 thin film was deposited on stainless successfully by RMS and RIBS deposition to improve its characteristics.The optical properties of SiO2 thin film were measured by spectroscopic ellipsometer. The results showed that when the O2 content in working gas mixture more than 16%, the refractive index of SiO2 film deposited by RMS was 1.46～1.5 at 630nm wavelength and the extinction coefficient was less than 10"5. When the O2 content in working gas mixture more than 80%, the refractive index of SiO2 film deposited by RIBS was 1.45-1.47 at 630nm wavelength and the extinction coefficient was less than 10-5. The analysis of the XPS prove that the stoichiometry of silicon oxide was 2.05. By 1 on 1 test method, when the laser wave was 1064nm, the laser induced damage threshold of the film deposited by RMS was 8.89J/cm2, the laser induced damage threshold of the film deposited with RIBS was 25.01 J/cm2.The experiments showed that RMS and RIBS deposition could deposit SiO2 thin film with low refractive index and low extinction coefficient. The optimal technological parameters of the RMS were described as follows:the current was 0.7A, the flow rate of Ar was 65sccm, and the flow rate of O2 was 22sccm. The optimal technological parameters of the RIBS were described as follows:the voltage was 3.7KV, the current was 120mA, and the flow rate of O2 was 22sccm.