The stability of SiO2 films prepared using a magnetron sputter type negative ion source (MSNIS)

Aging effect of SiO2 films was investigated. SiO2 films were prepared using a magnetron sputter type negative ion source (MSNIS) utilizing the direct ion beam deposition (DIBD) method. Thin SiO2 films are known as suffering from aging effect after the deposition. To minimize the variation of the refractive index or thickness of the film after the long period of time, a dense film is desirable. The optical properties such as refractive index (n), extinction coefficient (k) and thickness were analyzed using an UV spectrometer-combined thin-film measurement system. The surface morphology and roughness were measured using an atomic force microscope (AFM). The thickness and refractive index variance after 1-month period was less than 3% for the 100 nm thickness films. The average roughness of the film on silicon substrate was less than 1 nm in most cases. The resultant films show that the film properties were strongly dependent on the ion beam energy and oxygen partial pressure of deposition. In high power density (3.2 W/cm2), the aging effect was more noticeable. The wet-etch test of SiO2 films with respect to Cs flow rate showed that Cs flow rate is an important parameter in operation of a MSNIS.