Aluminum oxide thin film deposition by reactive ion plating using the cathode system composed of LaB6 disc and Ta pipe

Abstract

New type reactive ion plating with the pressure gradient plasma gun is used to deposit aluminum oxide thin films. The plasma gun has a cathode system composed of a LaB6 disc and a tantalum pipe. The 650 ℓ process chamber is made of an aluminum alloy. A 1800 ℓ/s compound molecular pump is used for the main pump. The ultimate pressure of the process chamber is 7.8×10−9 Torr. Argon is used for the carrier gas for the plasma, and oxygen is introduced to the process chamber to produce the oxygen plasma. The electron beam in plasma concentrated with magnetic field is applied to aluminum pellets in the hearth to vaporize the pellets. Aluminum vapor and oxygen radicals interact to make aluminum oxide thin films. The typical deposition rate of an aluminum oxide thin film is 60 Å/s. This film is regarded as a nonequilibrium phase of oxide or hydroxide film. The aluminum oxide thin film deposited on an aluminum alloy plate with constant contents of aluminum and oxygen was locally corroded in wet chlorine gas, but the film with the gradient in oxygen concentration was not corroded. The outgassing of an aluminum oxide thin film with gradient in oxygen concentration deposited on an aluminum plate was one order of magnitude lower than a conventional anodic oxide film formed on an aluminum alloy in sulfuric acid.