Reduction of oxygen concentration by heater design during Czochralski Si growth

Publication date: 1 February 2018
Source:Journal of Crystal Growth, Volume 483
Author(s): Bing Zhou, Wenliang Chen, Zhihui Li, Ruicun Yue, Guowei Liu, Xinming Huang
Oxygen is one of the highest-concentration impurities in single crystals grown by the Czochralski (CZ) process, and seriously impairs the quality of the Si wafer. In this study, computer simulations were applied to design a new CZ system. A more appropriate thermal field was acquired by optimization of the heater structure. The simulation results showed that, compared with the conventional system, the oxygen concentration in the newly designed CZ system was reduced significantly throughout the entire CZ process because of the lower crucible wall temperature and optimized convection. To verify the simulation results, experiments were conducted on an industrial single-crystal furnace. The experimental results showed that the oxygen concentration was reduced significantly, especially at the top of the CZ-Si ingot. Specifically, the oxygen concentration was 6.19 × 10¹⁷ atom/cm³ at the top of the CZ-Si ingot with the newly designed CZ system, compared with 9.22 × 10¹⁷ atom/cm³ with the conventional system. Corresponding light-induced degradation of solar cells based on the top of crystals from the newly designed CZ system was 1.62%, a reduction of 0.64% compared with crystals from the conventional system (2.26%).