UC San Diego

Plasma discharge sputter coaters have been used to create uniform thin layers of practically any target material. For Inertial Confinement Fusion research, a batch of several 1-2 mm diameter inertial fusion target shells are grown using several sputter coaters that run for 2-3 weeks and use 2-3 targets per gun. As the targets are consumed, a well documented ring or "race track" indentation develops on the target surface. The changing geometry of the target has been shown to affect the operating parameters of the sputter gun, as well as the quality of the deposition. Current methods do not achieve the quality and reproducibility that specifications demand. The purpose of this thesis is to characterize the sputtering process as it evolves through the life of a target, to better understand the sputtering process and ultimately to provide the means to produce higher quality, reproducible shells. Several production sputter coaters were automated to provide enhanced control and process data as a function of time. An experiment was then conducted that documented the deposition from an unused copper target through 90% of its initial thickness in three separate runs. It was found that the sputter yield matches with the empirical calculation, and is determined by the cathode voltage. The distribution of coated material for small theta; retains the cosine to the fourth power dependence, even as the sputter yield decreases with increasing target erosion. As the target erodes, the sputtered material is focused around small theta; because of changing target geometry and resputtering.