Resonant Heterodyne Interferometer for Plasma Process Control

Improvements in plasma processors used in industry can lead to greater efficiences, reduced energy use, and overall improvements in manufacturing. For example, in the deposition of metal-diamond-like carbon coatings on gears and other wear surfaces, the coatings are not reproducible enough to meet design standards; therefore, improvements in plasma process control are needed. This project will adapt a previously-developed, resonant heterodyne interferometer for use on a magnetron sputtering system used to deposit these hard coatings. This interferometer is capable of making absolute density measurements in Tokamak plasmas with high spectral and spatial resolution. Previous work has demonstrated that the level of hydrogen in the plasma correlates with the composition of the deposited films. Therefore, in Phase I, the interferometer will be used to further investigate the observed correlation between the plasma properties and the ultimate coating, and a control strategy will be developed. In Phase II, the control system will be fully developed, and the ultility of the interferometer, as a high level diagnostic for other industrial plasma processes, will be investigated. Commercial Applications and Other Benefits as described by the awardee: A plasma-depostion control system using the resonant heterdyne interferometer should lead directly to significant improvements in the manufacturing of drive train components used in heavy equipment. Since the sensor can be applied to almost any plasma species, it also would have broad application in the diagnosis, monitoring, and control of any industrial plasma processor. It has been estimated that the successful control of the deposition of hard coatings could lead to annual savings of $6 billion in the auto industry alone.