Studies on radical generation mechanism in the atmospheric plasma etching

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In the atmospheric plasma etching, the stronger electric field is required for generating radiacals efficiently because of a short mean free path. But, the stronger electric field brings about spreading of a plasma and getting worse of machining resolution. Although the atmospheric plasma is doing very well as both a machining rate and a spatial resolution, it is difficult to combine them on the high level.In this study, a pulse modulated R.F.power is suggested to realize both a high machining rate and a fine spatial resolution. To modulate a continuous R.F.power to a pulse, an extremely strong electric field is generated in a moment. Then it is expected to generate radicals efficiently in a R.F.-ON cycle. And it is expected to these radicals are disappear before diffusing in a R.F.-OFF cycle.We gave the existence R.F.power supply a function of a pulse modulation, and made several experiments changing a pulse width and a peak R.F.power. As a result, we found relationship between these parameters and a density of radials, and understood a process of decomposition of reactive gases. Specially in the case of using SF6 as a reactive gas, it was found that both a high machining rate and a fine spatial resolution are realized.