AVS 59th Annual International Symposium and Exhibition
    Plasma Science and Technology Thursday Sessions
       Session PS-ThA

Paper PS-ThA3
A Grid Reactor with Low Ion Energy Bombardment for Large Area PECVD of Thin Film Silicon Solar Cells

Thursday, November 1, 2012, 2:40 pm, Room 25

Session: Plasma Sources
Presenter: M. Chesaux, Ecole Polytechnique Fédérale de Lausanne (EPFL), Switzerland
Authors: M. Chesaux, Ecole Polytechnique Fédérale de Lausanne (EPFL), Switzerland
A.A. Howling, Ecole Polytechnique Fédérale de Lausanne (EPFL), Switzerland
U. Kroll, Oerlikon Solar-Lab SA, Switzerland
D. Dominé, Oerlikon Solar-Lab SA, Switzerland
Ch. Hollenstein, Ecole Polytechnique Fédérale de Lausanne (EPFL), Switzerland
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This study presents a PECVD reactor using localized remote plasma in a grid electrode. The aim is to reduce the ion energy bombardment inherent in RF capacitively-coupled parallel plate reactors conventionally used to deposit large area thin film silicon solar cells. This bombardment could cause defects in silicon layers and deteriorate electrical interfaces. Here, low ion bombardment energy is obtained by inserting a grounded grid close to the RF electrode of a parallel plate reactor. The plasma is then localized in the grid holes and remote from the substrate. This grid also increases the negative self-bias by increasing the effective area of grounded electrode in contact with the plasma while retaining the lateral uniformity required for large area deposition. The self-bias reduces the ion energy bombardment, but retarding field energy analyzer measurements show that the ion energy is even lower than expected from the self-bias effect alone. This reduced ion energy could be caused by a non sinusoidal RF cycle of the plasma potential as was measured with a capacitive probe and supported by phase resolved optical emission spectroscopy. Measurements were done in hydrogen at 0.5 mbar and 13.56 MHz.