A
system comprises a
processing chamber for maintaining a
hydrogen plasma at low pressure. The
processing chamber has a long, wide, thin geometry to favor deposition of thin-film
silicon on sheet substrates over the chamber walls. The sheet substrates are moved through between ends. A pair of opposing
radio frequency electrodes above and below the workpieces are electrically driven hard to generate a flat, pancaked
plasma cloud in the middle spaces of the
processing chamber. A collinear series of gas
injector jets pointed slightly up on a
silane-jet manifold introduce 100%
silane gas at
high velocity from the side in order to roll the
plasma cloud in a coaxial vortex. A second such
silane-jet manifold is placed on the opposite side and pointed slightly down to further help roll the plasma and maintain a
narrow band of silane concentration. A silane-concentration monitor observes the relative amplitudes of the spectral signatures of the silane and the
hydrogen constituents in the roll-vortex plasma and outputs a
process control feedback
signal that is used to keep the silane in
hydrogen concentration at about 6-7%.