Requirements for Enhanced Mid-Frequency Dual Magnetron Sputtering Process Stability

D. J. Christie, E. A. Seymour

Mid-frequency dual magnetron reactive sputtering has become a common means for depositing transparent fi lms on glass. Even so, process stability is still an ongoing concern. Plasma stability and reactive gas partial pressure stability must both be addressed. Process stability in the short term is strongly affected by the process power system characteristics, including generator, cabling, and arc handling method.

Sputtering process electrical characteristics vary wildly as gas pressure and content change, demonstrating extreme hysteresis in some cases. Short term plasma stability is the result of careful process power system confi guration and design. We show power system requirements for enhanced process stability, without generator circuit tuning, and experimental data for a process in the 100 kW range.

When the power supply output turns off for arc handling, the partial pressure of the reactive gas will rise, since getter pumping by the target atoms on the chamber surfaces decreases. The power supply must handle an arc quickly for reactive gas pressure to stay within limits. We present a simple model used to simulate reactive gas partial pressure variation during the arc response time, and develop rapid arc detection and response time scale requirements.

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