STRESS IN SILICON RIBBONS CRYSTALLISED FROM A MOLTEN ZONE: A STUDY OF THE INFLUENCE OF GROWTH PARAMETERS

摘要

Stress is frequently the limiting factor in silicon ribbon production processes. This is particularly true for processes using perpendicular growth from the liquid, such as EFG, SSP, S-ribbon or those being studied in our laboratory, based on growth from a molten zone. Here, we report the results of a study of stress in silicon ribbons produced by one of our techniques. A series of samples were grown specifically for this study, in which only a few parameters were varied. Growth rate ranged from quasi-stationary conditions (6 mm/min) to very high (120 mm/min). The samples were grown in different atmospheres: argon, nitrogen and oxygen. Residual stress was measured by infrared photoelasticity. The general behaviour of the residual stress field is reasonably understood. It was shown that there is a concentration of stress near the edges of the ribbons. The asymmetry of the stress distribution is shown to increase with the growth rate and the incorporation of impurities in the material.