| Summary: | 碩士 === 國立中央大學 === 光電科學與工程學系 === 101 === Experiments of this paper is the use of electron cyclotron resonance chemical vapor deposition system (ECRCVD) for microcrystalline silicon thin film growth to explore its film properties and application in pin-type thin-film solar cell intrinsic active layer. ECRCVD system has the advantages that low working pressure (10-4~10-1torr), low evaporation temperature, low ion energy, high gas dissociation and plasma density (1011~1013cm-3), low ion bombardment of the substrate, and ions flow as well as ion energy can be separately controlled. In experiments we use modulation process parameters such as process gas flow, gas ratio, the magnetic field coil current and the process chamber pressure to investigate the characteristics of microcrystalline silicon thin films.
According to the experimental results, the hydrogen dilution ratio, process pressure is the important factor affecting the film crystallization rate. And we found that the crystallization rate limit is about 80%. By raising the total gas flow rate, we can enhance the microcrystalline silicon thin film deposition rate up to 11.2Å/sec. And in ECRCVD system, we could obtain crystalline phase without large amount of hydrogen dilution. The hydrogen dilution ratio minimum is about 2.4, well below the PECVD process required that is about 20 to 50 or more. For intrinsic layers used in solar cells, as the film crystallinity is 35%, we can obtain the cell efficiency of 0.95%, showing that the mix of microcrystalline and amorphous phase would be the most suitable for the intrinsic layer. Yet its efficiency cannot be good due to the high hydrogen plasma density. It corrodes TCO substrate and results in insufficient light transmittance caused by layers interface damage.
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