多晶硅薄膜制备工艺研究

【作者】 李瑞；

【导师】 卢景霄；

【作者基本信息】 郑州大学 ， 材料物理与化学， 2005， 硕士

【摘要】 作为绿色能源,太阳能电池在能源危机和环境危机的今天,突显其研究和应用价值。多晶硅薄膜集晶体硅和非晶硅材料优点于一身,克服了光致衰退,与现有的太阳能电池研究生产技术具有兼容性,有可能成为制作太阳能电池的廉价优质材料。 等离子体辅助化学气相沉积方法(PECVD)是制备薄膜材料的几种方法中技术最为成熟、操作较为简单的一种,并且可以制备均匀性高的大面积薄膜。但是采用PECVD方法沉积多晶硅薄膜仍面临着两大难题:一是薄膜的晶化率有待提高;二是薄膜的生长速率也有待提高。薄膜的晶化率决定电池的性能,生长速率决定其成本,因此高速制备优质薄膜是制作太阳能电池的关键。为解决这些问题,目前研究人员多致力于沉积条件的优化以及如“二次晶化”等辅助手段的采用。 本文采用PECVD方法,系统研究了沉积温度、衬底、射频功率、氢稀释比、磷掺杂等沉积参数对多晶硅薄膜结晶状态及光电性能的影响,并对沉积出的多晶硅薄膜进行了固相晶化。结果表明:1)在一定范围内随着沉积温度的升高、射频功率的增大、硅烷含量的降低,薄膜的晶化率提高;但进一步提高温度、射频功率反而会使薄膜晶化效果变差。硅烷含量的降低大大减慢沉积速率。2)衬底的导电性能、及表面形貌对薄膜的晶化率有很大的影响。3)快速光退火与常规炉子退火的结果有一定的差异;4)磷掺杂导致沉积时晶化率降低,但对固相晶化有利。5)晶化越好薄膜的暗电导越大,光学带隙越小,逐渐靠近晶硅的带隙。发现固相晶化后的薄膜表面出现孔洞,建立理论模型给出解释。固相晶化后样品的反射谱显示它同时起到一定的减反射功能。更多还原

【Abstract】 Solar cell as one kind of green energy resource exhibits important role because of the resource crisis and environmental crisis. Polycrystalline silicon thin film possesses the excellences of both crystalline silicon and amorphous thin film silicon. It not only is immune from "optical-induced degradation" but also can be compatible with the existing solar cell technology. It is promising cheap and excellent material for solar cell.Plasma enhanced chemical vapor deposition （PECVD） is one of the matured and simple manipulated among the thin film deposition methods. It suits to be used depositing large area high-uniformity film. But now this method faces two big difficulties: one is the crystalline ratio of the deposited film should be improved, the other is the deposition velocity is slow. The crystalline ratio decides the electric character and the deposition velocity influence the cost. So preparing high quality thin film rapidly is key element for solar cell. Aiming at this target scientists try to optimize the deposition parameters and use recrystallization method.PECVD method is used to deposit polycrystalline silicon thin films at low temperature. The influences of deposition parameters include temperature, substrate, rf power, ratio of SiH₄ and doping on the crystalline and electric character was studied systematically. Solid Phase Crystallization was also carried out using the thin film had deposited. It shows that: 1) In some range increasing the temperature, rf power and decrease the ratio of SiH₄, will improve the crystalline ratio. But going on increase temperature and power will depress it; decrease the SiH₄ ratio will slow down the deposition. 2) Conductivity and surface condition influence the crystallization. 3) There is difference between the furnace annealing and the rapid thermal annealing. 4) Phosphorus doping degenerates the crystalline ratio of deposited film but benefits recrystallization. 5) Dark conductivity increases and optical energy gap decreases when the crystalline ratio increases. Holes were found on the film surface and model was given to explain their formation. It was also found that recrystallization can also make antireflecting surface.更多还原