Ionic species in a silane plasma

Abstract

The abundances A_j of groups of higher silane ions Si_jH⁺_k were measured mass spectrometrically in an rf glow discharge in SiH₄ under conditions used for preparation of hydrogenated amorphous silicon. The ratio A_j/A_j−1 is about 0.3 nearly independently of j, of pressure, of degree of ionization, and of rf power. The mean hydrogen to silicon ratio for j⩾3 is 1.5±0.1 and pressure independent in the 0.017–0.100‐Torr range. A mechanism postulating charge or hydride ion transfer and the addition of SiH₄ as the most rapid reactions of silane ions is consistent with the observations.