High Temperature In-situ Observation of Si on the Porous Ceramic Substrate Repelling Si Melt for Growth of Spherical Si Crystal

Abstract

The porous ceramic substrate repelling Si melt was developed for the growth of high quality spherical Si crystals with slow cooling of Si melt on the substrate. For the characterization of the developed porous ceramic substrate, high temperature insitu observation of Si melt on the substrate was carried out using the original furnace. Contact angle between Si melt and the substrate was measured for the porous substrates composed of Si 3 N 4 and SiO 2 at a weight ratio 4:1 with different size of pore (2, 5, 10 and 20 m). Developed porous ceramic substrate shows excellent repellency against Si melt and the maximum measured contact angle is 160°. The contact angle of Si was affected by the pore size of the porous substrate and the substrate with pore size 25 m is preferable for the growth of spherical Si crystals on the substrate. Grown spherical Si crystals are single or twin crystals and meet the impurity specifications of Si for solar cells.