The effects of argon gas flow rate and furnace pressure on oxygen concentration in Czochralski-grown silicon crystals

The effects of argon gas flow rate and furnace pressure on oxygen concentration in Czochralski (CZ) grown silicon crystals were examined through experimental crystal growth. A newly designed gas controller was used for this study. Increase in the oxygen concentration with an increase in argon gas flow rate or with a decrease in furnace pressure was demonstrated for the first time. The results of oxygen concentration changes were analyzed in terms of calculated velocity of argon gas flow along the gas controller over the silicon melt surface. The flow velocity of argon gas was affected both by the argon gas flow rate and the furnace pressure. The flow velocity of argon gas was found to increase with an increase in argon gas flow rate under a fixed furnace pressure or with a decrease in furnace pressure under a fixed argon gas flow rate. The oxygen concentration in the CZ silicon crystals was found to be proportional to the flow velocity of argon gas. Two possible mechanisms which could explain this relationship were discussed.