AVS 49th International Symposium
    Plasma Science Thursday Sessions
       Session PS+TF-ThM

Paper PS+TF-ThM7
Correlation between Cluster Amount and Qualities of a-Si:H Films for SiH@sub 4@ Plasma CVD

Thursday, November 7, 2002, 10:20 am, Room C-103

Session: Plasma Enhanced Deposition
Presenter: K. Koga, Kyushu University, Japan
Authors: K. Koga, Kyushu University, Japan
K. Imabeppu, Kyushu University, Japan
M. Kai, Kyushu University, Japan
A. Harikai, Kyushu University, Japan
M. Shiratani, Kyushu University, Japan
Y. Watanabe, Kyushu University, Japan
Correspondent: Click to Email
Recently, clusters below a few nanometers in size formed in SiH@sub 4@ high frequency discharges have been pointed out to be a possible cause of light-induced degradation of hydrogenated amorphous silicon (a-Si:H) films. Hence, suppression of cluster growth is an important issue for depositing high quality a-Si:H films at a high rate. To realize such suppression, we have developed a cluster-suppressed plasma CVD method utilizing gas flow and gas temperature gradient.@footnote 1@ The following results have been obtained in our experiments. 1) Even under so-called device quality conditions, a large amount of clusters (> 10@super 4@ cps) exist in the conventional plasma CVD reactor. 2) Microstructure parameter R@alpha@ of a- Si:H films decreases with decreasing the cluster amount. The developed cluster-suppressed plasma CVD reactor can decrease both R@alpha@ and cluster amount below detection limits of our measurement systems (R@alpha@< 0.003 and cluster amount < 0.001 cps, respectively). These results suggest that a-Si:H films of high qualities can be prepared at a high deposition rate by suppressing the cluster growth. 3) A ratio of cluster amount to deposition rate for a discharge frequency of 60 MHz is 1/20 of that for 13.56 MHz, indicating that the VHF discharge is effective in suppressing cluster growth. 4) Preliminary evaluation of fill factor (FF) of a n@super +@Si/a-Si:H/Ni Schottky solar cell using a-Si:H films of R@alpha@= 0.057 shows the high initial value FF@sub i@= 0.57 and high stabilized value after-light soaking FF@sub a@= 0.53, compared to FF@sub i@= 0.51 and FF@sub a@= 0.47 of cell using conventional device quality a-Si:H films of R@alpha@~ 0.1. @FootnoteText@ @footnote 1@ K. Koga, M. Kai, M. Shiratani, Y. Watanabe and N. Shikatani, Jpn. J. Appl. Phys., 41, L168 (2002).