2013 年 38 巻 3 号 p. 337-340
The cutting loss of Si ingot in conventional manufacturing process of Si wafers for solar cells is one of the main obstacles to reduce the cost of solar power generation. Growth of Si crystals without the cutting process is possible using substrates repelling Si melt. In this study, the porous ceramic substrate repelling Si melt was successfully developed and spherical Si and Si sheet crystals were directly prepared using this substrate. Effect of cooling rate on the quality of grown spherical Si crystals was also investigated. Spherical Si crystals consist of less than three grains were stably grown with cooling rate less than 100 K/h when the undercooling of Si melt was estimated to be 40 K. Slow cooling of Si melt on the substrate leads to low undercooling of Si melt that enables the growth of high quality spherical Si crystals. Carbon and oxygen concentration in the grown Si sheet crystal was below the specification value of Si for solar cells. Sticking or infiltration of Si against the substrate was not observed after the growth of Si crystals so the developed substrate is reusable multiple times.
