Czochralski Silicon Crystal Growth for Photovoltaic Applications

The fast growing photovoltaic market is mainly based on crystalline silicon. The strong demand on silicon requires wafer manufacturers to produce high-quality material through high productivity processes with low-cost. Due to the higher energy conversion efficiency of single crystalline silicon (sc-i), the Czochralski (Cz) pulling remains the key technology in photovoltaics. However, when compared with the multicrystalline silicon (mc-Si) production by the directional solidification, the current Cz technology is still more costly, due to the lower throughput and more energy consumption. Therefore, to retain the competition of sc-Si in the PV market, high efficient Cz ingot pulling is needed. In this chapter, we discuss some important issues in the Cz sc-Si production. Special focuses will be on the hot-zone design and multiple charges. The implementation of these concepts has led to significant cost reduction and yield improvement for both 6 in. and 8 in.-diameter solar-grade silicon in production. Some comments for the future development are also given.