Crystallization of 640 kg mc-silicon ingots under traveling magnetic field by using a heater-magnet module

For the first time a heater-magnet module (HMM), simultaneously generating heat and a traveling magnetic field (TMF), was constructed for an industrial scale G5 multi-crystalline Si crystallizer and extensively tested. Effective melt mixing and precise control of the interface shape have been demonstrated using TMF, which resulted in ingots exhibiting superior properties, clearly proving the beneficial effects of the advanced convection control without affecting the stability of the Si3N4 crucible coating. Hence, most of the solidified Si volume showed very homogeneous IR transmission without inclusions. Dislocation densities were relatively low and bunching was only rarely observed, resulting in overall high carrier lifetimes. Therefore, our results demonstrate that a HMM configuration in an industrial Si crystallizer may successfully accomplish the following tasks: (i) good thermal stability and controllability of the melt-solid interface morphology, (ii) suppression of second phase inclusions, such as SiC and Si3N4, by mastering the mixing of the melt during the whole crystallization process, and (iii) no pronounced interaction between melt and container wall.