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The initiation of arcs on a metal surface stained by contamination and exposed to a plasma has been studied experimentally and with the use of a calculation model. It is assumed in the calculation model that a negative voltage is applied to a metal specimen with respect to the plasma potential, arcs are initiated when the electric field strength due to the voltage drop produced in the contaminant layer is large enough to induce dielectric breakdown in the layer, and that the conditions for arc initiation in the gap between the plasma and the metal surface are fulfilled by the burst of vapor produced when dielectric breakdown occurs. The variation of the arc initiation voltage with the plasma density and the variation of the time lag before arc initiation with the applied voltage were obtained experimentally. These experimental results can be qualitatively explained by the results obtained from the calculation model.

The bias-enhanced nucleation (BEN) method is well known as a pretreatment method for nucleation, and the nucleus is generated in the plasma sheath region during the BEN process. To utilize high-density nucleation at low pressure and to expand the nucleation region in hot-filament chemical vapor deposition (HFCVD), the BEN method was applied under a low-pressure condition in which the plasma and plasma sheath expanded. Some substrates were treated in hydrogen plasma or activated hydrogen before nucleation. The purpose of this study is to confirm the characteristics of nucleation at low pressure and to determine the condition for realizing uniform, high-density and large-area nucleation. By using emitted electrons, bias voltage and current were controlled to be steady at the low pressure of 0.1 Torr. The nucleation density increased and the width of the nucleation area expanded when the substrate surface was treated in hydrogen plasma or activated hydrogen before nucleation. It was proposed that the nucleation mechanism is as follows. (1) A substrate surface was treated by H ions and H radicals, (2) a nucleation site was formed on the treated position and (3) nucleation occurred on the nucleation site. To achieve high-density and large-area nucleation, it is necessary to obtain the treated substrate surface and to generate carbon-containing cations, H ions and H radicals with appropriate ratios and density distributions in the nucleation phase.

To study the change in characteristics of a double probe exposed to silane plasma, we measured the V–I characteristics of a double probe for various a-Si thicknesses, and compared the experimental results with results calculated by a simple model. It is found that the change in V–I characteristics of the double probe was caused by the deposition of resistive material on probe surface, and it is expected that the change in the V–I characteristics of a double probe will be utilized to monitor the thickness of a-Si deposition.

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