THE CONSTRUCTION OF A CVD PROCESS WITH MATERIAL RECYCLE TO PRODUCE EFFICIENT SOLAR CELLS AT LOW-COST.

我们试图通过构建原料气体的回收方法，建立低成本、高效率的沉积多晶硅的CVD工艺，以形成太阳能电池的电子发电层。1996年，为了了解氯硅烷作为原料气体的沉积和蚀刻特性，获取反应器出口气体的信息，我们制作了沉积硅薄膜的设备。该设备为热壁常压CVD系统，由原料气供应系统、反应炉、气相色谱和出口气处理系统组成。以三氯硅烷（SiHCl_3）和四氯硅烷（SiCl_4）为原料气，氢气为载气。我们进行了沉积实验，然后根据管式反应器的生长速率曲线确定了速率常数，并计算了反应器中的转化率。同时，通过气相色谱法分析反应物气体，通过反应器进出口气体组成的差异来了解氯硅烷的质量平衡，从而获得气相反应的信息。1997年，我们从热力学角度估计了平衡态。通过与实验结果的比较，证明了以氯硅烷为原料气的CVD反应反映了平衡态。因此，通过操作平衡态来控制硅的沉积和蚀刻是可能的。因此，我们提出了一种新的太阳能电池生产工艺，我们可以利用Si/H/Cl体系的这些特性，利用蚀刻反应再生和回收原料气体。

We have tried to establish low-costly and high-efficient CVD process of depositing poly-silicon for the formation of electronic power generation layr of the solar cell, by constructing the recycling methods of raw gases.In 1996, we made an equipment to deposit silicon thin films for the purposeof understanding characteristics of deposition and etching of chlorosilane as raw gases and obtaining information of the gases from the reactor outlet. The equipment is a hot-wall atmospheric pressure CVD system which consists of supplying system of raw gases, reactor furnace, gas chromatography and disposing system of outlet gases. We used trichlorosilane (SiHCl_3) and tetrachlorosilane (SiCl_4) as raw gases, and hydrogen as carrier gas. We operated depositing experiments, and then detremined rate constants from the growth rate profile of the tubular reactor and calculated the conversion in the reactor. Also, we analyzed reactant gases by gas chromatography to understand the mass balance of chlorosilane from the difference of gas composition between inlet and outlet of the reactor, so that we obtained information of gas-phase reactions.In 1997, we estimated equilibrium states thermodynamically. From the comparison between the estimation and the experimental results, we proved that the CVD reactions using chlorosilane as raw gases reflect the equilibrium state. Therefore, it is possible to control deposition and etching of silicon by operating equilibrium state. Consequently, we suggested newly process for producing solar cell that we can reproduce and recycle raw gases using etching reactions on the basis of these characteristics of Si/H/Cl system.