Techniques for the crystal growth of silicon ingots and ribbons

Abstract

Traditional techniques for silicon crystal growth - Czochralski pulling and float-zoning - have developed to a stage where dislocation-free, high purity crystals over 10 cm in diameter and 10 kg in weight are routinely produced. Needs of the integrated circuit industry have been the main driving force for these advances. In recent years, the needs of terrestrial photovoltaics have driven research to make these techniques more cost-effective, to develop new and simpler ingot crystallization methods, and to explore numerous silicon ribbon or sheet growth approaches for photovoltaic applications. A classification of silicon sheet growth methods by meniscus geometry permits them to be discussed in three groups: short meniscus techniques, high meniscus techniques, and extended meniscus or large solid/liquid interface area techniques. A second parameter, meniscus shaper interaction with the liquid silicon, is also instrumental in determining the characteristics of the various sheet processes. The current status of each process is discussed in the context of meniscus geometry and shaper/melt interaction. One aspect of sheet growth, surface area generation rate, is quantitatively compared with combined ingot growth and wafering surface area generation rates.