Abstract
This paper reviews the recent development of the silicon continuous-charging Czochralski (CCZ) process with a double-crucible method and discusses some problems and their solutions based on the author's work. The newly developed double-crucible (DC) method, which characterizes an inner crucible held at an upper portion during the meltdown process, is effective to avoid the troubles usually caused in conventional DC methods. The dopant concentration of the CCZ crystal could be precisely controlled by setting the concentration of the inner and the outer melts equal before starting the pulling. Granular polysilicon was used as continuous-charging material in the pulling. The accumulation of heavy-metal impurities in the melt was evaluated by a numerical calculation considering both the resolution of quartz crucibles and the inherent concentration of continuously charged poly-silicon. The CCZ crystals showed the same contamination level with the conventional CZ crystals at the top and the tail portion, though they showed a little higher concentration at the middle portion. The possibility of a long CCZ crystal growth was also investigated by using an incidence of structure-loss.
