M.M. de Jong

Temperature Dependence of the Ion Energy Distribution in a Hydrogen Diluted Silane VHF Plasma

Using an energy resolved mass spectrometer we measured the ion energy and abundance of SinH2n+1+(n = 1…5) ions reaching the growing surface as a function of temperature and pressure in a very high frequency (VHF) hydrogen diluted silane plasma. We observed an increase in ion energy with increasing substrate temperature for all species. For low mass ions, we observe an increase in the number of ions reaching the growing surface with increasing temperature, whereas the count rate for high mass ions decreases with increasing temperature. This result confirms the hypothesis that a higher substrate temperature will prevent the plasma from going into the dusty γ′‐regime by suppressing the polymerization reactions of silyl into larger polysilanes which are the precursors for the dust formation.

An optical analysis tool for avoiding dust formation in very-high frequency hydrogen diluted silane plasmas at low substrate temperatures

Control of the formation of dust particles in a silane deposition plasma is very important for avoiding electrical shunts in devices, such as thin film silicon solar cells. In this work we present a noninvasive in situ method for identification of the plasma regime, based on optical emission spectroscopy (OES), which can be applied to silane/hydrogen plasmas at low substrate temperatures. By monitoring the OES spectra as a function of the position perpendicular to the plasma electrodes we developed a method to identify the transition of a plasma from the dust free to a dusty regime, which was confirmed by TEM images of layers deposited in both regimes. Using this technique we mapped this transition as a function of applied forward very-high frequency (VHF) power and hydrogen dilution at different substrate temperatures. The advantage of this technique is that the experiment is insensitive to optical transmission loss at the viewport due to deposition of silicon films. As the transition from the dust free ...