Application of a new grain boundary technology for quasi-single crystalline silicon ingots

Abstract

A new functional grain boundary group (FGBG) technology was employed to generate quasi-single crystalline silicon ingots with a high single crystalline area ratio. Fabrication of the FGBG structure was achieved and special grain boundaries were formed between adjacent seed crystal strips with 〈100〉 crystal orientation, with a 30° crystal orientation angle between the special grain boundaries. The influence of FGBG on the evolution of grains, dislocation, and surface morphology was analyzed by photoluminescence and electron back-scattered diffraction. FGBG effectively suppressed the side polycrystalline grains (spontaneous nucleation on the crucible wall) intrusion at the early stage of solidification. Additionally, when the crystal growth height was increased, FGBG acted as a barrier layer for the external polycrystalline grains under the control of an appropriate horizontal temperature gradient and slightly convex solid–liquid interface shape, preventing most of the polycrystalline grains around the ingot from growing into the crystal, and blocking the dislocations generated by polycrystalline grains near the grain boundary. The application of this FGBG technology will greatly improve the quality of quasi-single crystalline silicon ingots with a weight of 1400 kg (G7).