Thyratron modulators in plasma source ion implantation

Plasma source ion implantation (PSII) is an emerging technology which can be used to harden metal surfaces in a conformal manner. North Star Research Corp. (NSRC) is building a unique implanter system for Empire Hard Chrome which will be the first truly commercial implanter of this type. The choice of pulsed power technology for this application is important from the standpoint of both reliability and compatibility with the basic plasma processes under consideration. In this paper, the authors evaluate the various possible pulsed power system choices including thyratron modulators, hard tube modulators and crossatron modulators in the context of compatibility with the plasma and implantation process. Currents in the hundreds of amperes at 80-100 kV are clearly found to be desirable based on the requirements of the process. This leads to the logical choice of thyratron/transformer modulators at lower average powers, or crossatron modulators at higher average powers. They also discuss pulse forming network design for thyratron modulators for the universal PSII-type waveform. A thyratron modulator was selected for the Empire implanter due to the requirements for low cost and high peak current.