Abstract
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 to the dusty regime is substrate
temperature dependent and the transition from amorphous to nanocrystalline growth mainly
depends on hydrogen dilution, a limited parameter window has been defined in which dust-free
amorphous silicon can be deposited at low substrate temperatures. A single simple OES technique
can be used for in situ monitoring of amorphous to nanocrystalline transition as well as the onset of
the dusty regime in a thin film silicon cell fabrication process.
Original language | English |
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Article number | 020703 |
Pages (from-to) | 020703/1-020703/5 |
Number of pages | 5 |
Journal | Physics of Plasmas |
Volume | 19 |
Issue number | 2 |
DOIs | |
Publication status | Published - 2012 |