Large modification of crystal–melt interface shape during Si crystal growth by using electromagnetic Czochralski method (EMCZ)

Large-diameter, high-quality Si wafers are required for further advance of ultra large-scale integrated circuit (ULSI) device processing. Therefore, a new crystal growth technique is needed to obtain large-diameter, high-quality Si crystals containing homogeneously distributed oxygen and reduction of grown-in defect density in the concentration required for ULSI device processing. To address this requirement, we developed a new crystal growth technique using electromagnetic force (EMF), which we call the electromagnetic Czochralski (EMCZ) method. Using the EMCZ method, we were able to grow defect-free Si crystals of 200 mm diameter with a higher pulling rate rather than those grown under the conventional CZ crystal growth conditions. High-speed pulling of defect-free crystals by the EMCZ method is due to large modifications of the crystal–melt interface. In this method, the interface shape is largely modified to the upward convexly toward the crystal. The large upward convex shape of the crystal–melt interface during EMCZ growth results from the temperature distribution at the interface by the controlled melt flow generated by the EMF. We confirmed this large modification of interface shape by experiments and numerical simulations. The mechanism of this modification of interface shape is discussed from the viewpoint of melt flow around the growing interface.