Characteristics of nucleation using the bias-enhanced nucleation method atlow pressure

The bias-enhanced nucleation (BEN) method is well, known as a pretreatment method for nucleation, and the nucleus is generated in the plasma sheath re gion during the BEN process. To utilize high-density nucleation at low pres sure and to expand the nucleation region in hot-filament chemical vapor dep osition (BFCVD), the BEN method was applied under a low-pressure condition in which the plasma and plasma sheath expanded. Some substrates were treate d in hydrogen plasma or activated hydrogen before nucleation. The purpose o f this study is to confirm the characteristics of nucleation at low pressur e and to determine the condition for realizing uniform, high-density and la rge-area nucleation. By using emitted electrons, bias voltage and current w ere 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 s ubstrate surface was treated in hydrogen plasma or activated hydrogen befor e 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 nucleat ion 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 dens ity distributions in the nucleation phase.