AVS 51st International Symposium
    Advanced Surface Engineering Monday Sessions
       Session SE-MoA

Paper SE-MoA9
The Dominance of Oxygen in Two-Gas Reactive Sputtering of Oxynitride Films

Monday, November 15, 2004, 4:40 pm, Room 303D

Session: Structure Control of Hard Coatings in Sputtering Processes
Presenter: W.D. Sproul, Advanced Energy Industries, Inc.
Authors: W.D. Sproul, Advanced Energy Industries, Inc.
D.C. Carter, Advanced Energy Industries, Inc.
D.J. Christie, Advanced Energy Industries, Inc.
Correspondent: Click to Email
Reactive sputtering with two reactive gases and one target material presents special problems. Both reactive gases affect the state of the target surface and the plasma conditions, which means that both affect common feedback control signals such as the cathode voltage and optical emission signals. Modeling has shown that the way to control the two-gas reactive sputtering process is to produce individual control signals for each gas and to control the partial pressure of each reactive gas. Experiments have confirmed the model. When oxygen and nitrogen are the two reactive gases, oxygen usually dominates the reaction. A small change in the amount of oxygen results in large changes in the properties of the films, whereas it usually takes a large change in the nitrogen partial pressure to change the film properties. These results were found during two-gas reactive sputtering of the oxynitrides of aluminum, silicon, and titanium where a differentially pumped mass spectrometer was used to produce individual partial pressure feedback signals for the oxygen and nitrogen. For these three oxynitride systems, oxygen strongly dominated the reaction. Very slight changes in the oxygen to nitrogen partial pressure ratios result in large changes in rate and optical properties for these oxynitrides. The dominance of oxygen is particularly acute when flow control is used for the oxygen and the nitrogen is in partial pressure control. In this situation, it is possible for the oxygen to trap the target in a poisoned state that cannot be reversed until both gases are removed. To avoid this problem, partial pressure control should be used to control both reactive gases. Experimental results showing the dominance of oxygen over nitrogen for the two-gas reactive sputtering of AlOxNy, SiOxNy, and TiOxNy will be shown and discussed.