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

我们试图建立低成本和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，通过构建原料气体的回收方法，1996年，我们制作了一台设备来沉积存款硅薄膜，以了解作为原料气体的氯硅烷的沉积和蚀刻特性，并从反应器出口获得气体的信息。该设备为热壁常压CVD系统，由原料气供给系统、反应炉、气相色谱仪和出口气体处理系统组成。我们以三氯氢硅（SiHCl_3）和四氯硅烷（SiCl_4）为原料气，氢气为载气。进行了沉积实验，由管式反应器的生长速率曲线确定了反应速率常数，并计算了反应器中的转化率。此外，我们还利用气相色谱法分析了反应气体，从反应器进出口气体组成的差异来了解氯硅烷的质量平衡，从而获得了气相反应的信息。通过估算值与实验值的比较，证明了以氯硅烷为原料的CVD反应是平衡反应。因此，可以通过操作平衡状态来控制硅的沉积和蚀刻。因此，我们提出了新的太阳能电池的生产工艺，我们可以再生和回收原料气体使用蚀刻反应的基础上的Si/H/Cl系统的这些特性。

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.