電流磁場印加引上げ法(EMCZ法)によるシリコン単結晶中の酸素濃度制御(<小特集>シリコン結晶成長における酸素輸送と欠陥制御)

抄録

When using the Czochralski method for growing large-diameter (>300 mm) silicon crystals, the control of oxygen concentration and its distribution in the crystals by crucible rotation is a serious problem. We have developed a new method to control oxygen concentration and its distribution by the electromagnetic force without crucible rotation. The electromagnetic force in the azimuthal direction in the silicon melt is generated by the interaction between the electric current (/) through the melt (in the radial direction) using an electrode and the vertical magnetic field (5). Using this method, the oxygen concentration in a small crystal (the diameter of 40 mm and the length of 200mm) was continuously changed from 10^<17> to 10^<18> atoms/cm^3. The homogeneous oxygen distributions in both the radial and the pulling directions were also achieved by gradually increasing melt rotation rate. Numerical simulation results of melt flow during EMCZ (Electromagnetic Czochralski) crystal growth showed that natural convection is almost suppressed and forced flow generated by electromagnetic force is dominant in the melt. From the results of experiment and numerical simulation, the continues change of oxygen concentration and the homogenization of oxygen distribution along the radial direction are attributed to the control of the diflusion-boundary-layer at both the melt/crucible and crystal/melt by forced flow due to the electromagnetic force. These things suggest that EMCZ method would be effective for the control of oxygen concentration and its distribution even in the large diameter silicon crystal.