Directional solidification of polycrystalline silicon ingots by successive relaxation of supercooling method

sPolycrystalline silicon ingots were directionally solidified by the conventional traveling heater method and the newly proposed method, named the successive relaxation of supercooling (SRS) method. The grown ingots were evaluated by measurements of minority carrier lifetime, etch-pit density, and substitutional carbon concentration. Although there were many small grains (<1 mm) in the ingots grown by the conventional method, the number of small grains in the ingot grown by the SRS method were few. The average lifetime of the SRS ingot was improved by a factor of three to five times compared to that of the conventional ingot. The etch-pit density and substitutional carbon concentration of the SRS ingot were also improved as compared to those of the conventional ingots.