Properties of gallium oxide thin film sputtered from powder target for high temperature oxygen sensor

Gallium oxide thin film has properties of n-type semiconductor and high stability at high temperature. The resistivity of Ga₂O ₃ changes with the concentration of oxygen in the thin film. On the basis of this principle, gallium oxide thin film for an oxygen sensor was deposited on the Si substrate from a sintered powder target by an RF magnetron sputtering system using Ar as the sputtering gas. The sputtering condition is an important factor to control the oxygen content of the Ga₂O₃ thin film and hence the response characteristics of the sensor. It has been found that electrical conductivity, gas sensitivity and rising response time of the thin film depend on sputtering pressure of Ar during the deposition process. It has also been clarified that gallium oxide thin film deposited in lower sputtering pressure shows higher electrical conductivity and rising response time, whereas the thin film deposited in higher sputtering pressure shows high gas sensitivity. These differences in characteristics of the deposited thin films may be considered due to the surface structure including grain boundary as revealed from the AFM observation