Deposition Technique
A physical vapor deposition process that combines a sputtering metal target with a reactive gas in a vacuum chamber produces compound thin films with high chemical purity. When fabricating dielectrics or transition layers, reactive magnetron sputtering allows for the deposition of oxides and nitrides from pure metal targets. This method provides precise control over the chemical composition and microstructure of the deposited film.
By adding trace amounts of oxygen to the argon plasma, operators can deposit stoichiometric alumina from a pure aluminum target.
Chemical Control
Oxygen or nitrogen is introduced into the argon plasma to react with the sputtered metal atoms on the substrate surface and form the desired compound. Sputtering parameters, such as the flow rate of the reactive gas and the discharge power, are controlled to maintain the correct stoichiometry. This process requires a balance to avoid target poisoning, which reduces the deposition rate.
Process Challenge
Target poisoning occurs when the reactive gas forms a compound layer on the target surface, reducing the sputtering efficiency. This phenomenon leads to instability in the sputtering discharge and alters the properties of the growing film. Active closed loop feedback systems are used to monitor the plasma emission and adjust the gas flow to maintain stable operating conditions.
Characterization Practice
Electrical and structural measurements are performed to verify that the deposited films have the required properties. This testing ensures that the oxide or nitride layer provides high electrical insulation and has the correct phase composition. The process remains the primary method for producing high temperature ceramic buffers.
