[18a-C212-1~11] 15.7 Crystal characterization, impurities and crystal defects

▲ [18a-C212-8] 3D Numerical investigation on 200 mm (8-inch) floating zone (FZ) silicon process

〇(P)Xuefeng Han¹, Satoshi Nakano¹, Xin Liu¹, Hirofumi Harada¹, Yoshiji Miyamura¹, Koichi Kakimoto¹ (1.RIAM, Kyushu Univ.)

Keywords:Floating zone, Simulation, melt flow

Floating zone (FZ) process is a crucible-free technique to produce silicon single crystals with low oxygen content and diameter up to 200 mm (8 inches). Ratnieks has proposed the first 2D asymmetric global model for 8-inch FZ process in the previous study to investigate the fluid flow and the shape of liquid-solid interface [1]. However, a needle-eye inductor with one main slit and three side slits is used in the FZ process. This asymmetric configuration induces the asymmetric heating on the free surface of the silicon melt. Therefore, in the present study, we propose a 3D 8-inch model to investigate the fluid flow and solid-liquid interface. The 3D local model is developed based on the previous 4-inch FZ model [2]. To investigate the effect of asymmetric electromagnetic (EM) heating on the melt flow, 3D EM and heat transfer calculations are conducted by using COMSOL program and open-source library OpenFOAM. Marangoni force and EM force at the free surface have been considered. Fig. 1 shows the surface current density distribution at the free surface as a result of asymmetric high-frequency inductor. The strong EM field below the three side slits causes high thermal gradient and high EM force at the free surface. Fig. 2 shows that the melt flow velocity vector is not homogeneous. Under the effect of Marangoni and EM forces, the melt flow velocity in the vicinity of the side slits and inner triple point (ITP) is high. By considering 3D Marangoni force and EM force at the free surface, more accurate melt flow distribution has been obtained.