Preparation Of Solid Phase Crystallization (spc) Polysilicon Thin Film Research

This paper demonstrated the meaning and necessity of developing polycrystalline silicon thin film solar cells, starting from the current development state of solar cells. And then starting from the current research condition and the difficulties that people were confronted with in the developing of the polycrystalline silicon thin film solar cells, argued why it is necessary to use the recrystallization technology of a-Si:H thin films in preparing polycrystalline silicon thin films. Then it summarized several main recrystallization techniques employed at home and abroad, including conventional furnace annealing, rapid thermal annealing, metal-induced crystallization, microwave-induced crystallization, laser crystallization and so on. After analysis, it is considered that the two techniques of rapid thermal annealing and conventional furnace annealing are most fitful and most probably applicable to the industrial productivity of polycrystalline silicon thin-film solar cells. This paper is about the careful research on them and especially on rapid thermal annealing technique. 1. Research on rapid thermal annealing technique.The rapid thermal annealing technique is a relatively new annealing technique. Researches on this field at home and abroad are relatively few. So this paper focused most of work on the research in the technique. First, the influence of annealing temperature on the crystallization of a-Si:H thin films was studied. It was found that when the temperature is below 700 degrees centigrade, it is very difficult for a-Si:H thin films to crystallize. When annealing temperature is above 750 degrees centigrade, it is very ease for a-Si:H thin films to crystallize. That is to say, there exists a temperature transition field between 700 to 750 degrees centigrade. Then the crystallization condition of a-Si:H was studied thoroughly when it is above 750 degrees centigrade and below 700 degrees centigrade. The results turned out that annealing temperature and time have great influence on particle size and dark conductivity. There exists the best annealing condition of a-Si:H thin films. In addition, the influence of using conventional furnace annealing to warm up beforephoto-thermal annealing and the substrate temperature when a-Si:H film was deposited on the crystallization of a-Si:H thin films was also studied. It was found that to use normal high temperature stove to warm up before photo-thermal annealing is helpful to increase the size of polycrystalline silicon thin film and improve its electronic property and that the higher the substrate temperature is, the more easy to crystallize the a-Si:H thin films are.The pulse rapid photo-thermal annealing is an excellent and new rapid photo-thermal annealing way, especially fitful for the crystallization of a-Si:H thin films on cheap low temperature substrate. This paper also tried on this method and experimental results proved that this method can realize the crystallization of a-Si:H thin films. But compared with the polycrystalline silicon thin film by the normal rapid thermal annealing methods, the films prepared by this method have smaller size and worse electronic property.Finally, we studied the annealing mechanism of rapid photo-thermal annealing technique and found that in rapid photo-thermal annealing, short wave length light has great influence on the crystallization of a-Si:H film. Both for the pulse rapid photo-thermal annealing and the normal rapid photo-thermal annealing, under the same annealing temperature, compared with not filtrating short wave length light, when short wave length light is filtrated the crystalline fraction of polycrystalline silicon thin films prepared is lower and the particle size is smaller. So this also proved the existence of the quantum effect in rapid photo-thermal annealing process. 2. Research on the conventional furnace annealingThe conventional furnace annealing technique is one of the earliest employed annealing techniques. So far, much work has been done on this field. But most of them are only focused on the crystallization condition of a-Si:H thin films under low temperature. This paper emphasized on the crystallization condition under a higher temperature. The results turned out that with the increase of annealing temperature, the size of the polycrystalline silicon thin films has a trend of gradually decreasing. But the difference is not obvious and the change of dark conductivity with annealing temperature is also not obvious. In addition, comparing the polycrystalline silicon thinfilms made by this method and polycrystalline silicon thin films by rapid photo-thermal annealing method, we found that the polycrystalline silicon thin films produced by the latter are superior in the quality of crystallology and electronic qualities.