Mass spectrometry of a silane glow discharge during plasma deposition of a-Si: H films

We undertook a mass spectrometric investigation of the ionic and neutral species present during the deposition of a-Si: H using an r.f. glow discharge in silane (mixed with helium or hydrogen). A correlation between the neutral composition of the plasma and the nature of the IR vibrational modes in the deposited film is proposed. The ionic species extracted from the silane discharge are not characteristic of the direct ionization of SiH₄. The predominance of the SiH₃⁺ ion is attributed to the ion-molecule reaction $\text{SiH}{}_2{}^{\mathrm{+}}\text{+ SiH}{}_4\text{→ SiH}{}_3{}^{\mathrm{+}}\text{+ SiH}{}_3$ Secondary ions Si₂H_n⁺ (n = 1?7) are also observed. Mass spectrometry of the ionic species resulting from the interaction of a hydrogen plasma with the a-Si: film suggests that atomic hydrogen plays an active role during the growth of the film.