AVS 50th International Symposium
    Manufacturing Science and Technology Monday Sessions
       Session MS-MoM

Paper MS-MoM7
Two-Gas Reactive Sputtering

Monday, November 3, 2003, 10:20 am, Room 309

Session: Process and Equipment Integration and Development
Presenter: D.C. Carter, Advanced Energy Industries, Inc.
Authors: W.D. Sproul, Advanced Energy Industries, Inc.
D.J. Christie, Advanced Energy Industries, Inc.
D.C. Carter, 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. Experiments have confirmed the model. The reactive sputtering of titanium or silicon in a combined oxygen/nitrogen atmosphere is shown. In this study, individual partial pressure signals for each of the oxygen and nitrogen reactive gases were available from a mass spectrometer. A combination where one of the gases is controlled in the partial pressure mode and the other in a flow mode can lead to unstable operating conditions under certain process conditions. The gas operating in flow control can trap the target in a poisoned state, and the target cannot return to the unpoisoned state until both gases are removed. Both target voltage and mass spectrometer data show the existence of a high partial pressure of the flow controlled reactive gas that traps the target in the poisoned mode even when the partial pressure controlled reactive gas is removed from the system. To have a fully stable process when two reactive gases are used requires that the partial pressure of each gas be controlled individually. When the individual partial pressures are controlled, the target does not get trapped in a poisoned state, and there is complete freedom to adjust the reactive gas partial pressures to achieve the desired film composition.