ECN publication
Microwave Plasma Assisted VHF-PECVD of Micro-Crystalline Silicon
Soppe, W.J.; Bailat, J.; Droz, C.; Graf, U.; Kroll, U.; Meier, J.; Shah, A.
Published by: Publication date:
ECN Solar Energy 1-4-2002
ECN report number: Document type:
ECN-RX--02-012 Conference Paper
Number of pages: Full text:
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Presented at: 2002 MRS Spring Meeting, San Francisco, USA, 1-5 april 2002.

Growth of intrinsic micro-crystalline silicon layers by means of VHF-PECVD,assisted by remote microwave (MW) plasma has been investigated. The aim of the microwave plasma is to enhance the deposition rate by introducing additional excited hydrogen and Ar atoms in the VHF deposition zone. For this purpose a remote microwave plasma source was constructed in which a H2/Ar plasma is generated in a 20 mm diameter quartz tube. A gas-shower has been constructed for homogeneous distribution of the flow of excited gas species from the microwave source into the deposition zone of the VHF-PECVD reactor where the dissociation of silane takes place. At high microwave power (> 500 W) and undiluted hydrogen in the MW source, an increase of the deposition rate of silicon by 20 % with respect to pure VHF deposition was observed. The silicon layers grown with MW assistance had a high oxygen content as a result of a strong reduction of the quartz tube by the hydrogen plasma. In a second series of experiments Ar dilution and reduced MW power were used to eliminate the effect of etching of the tube by the microwave hydrogen plasma. In this series of experiments an increase of the growth rate of micro-crystalline silicon by about 15 % due to assistance of the microwave plasma was found. Optical emission spectroscopy indicates that ? in these experiments ? the main mechanism for the increased dissociation of silane is through molecular quenching reaction of Ar * metastables.

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