MICROWAVE RAPID HEATING SYSTEM USING CARBON HEATING TUBE

A microwave heating system with a carbon heating tube (CHT) is reported. 2.45-GHz microwave at 200 W was introduced to a 300-dimameter metal cavity, in which the CHT made by 60-mm-long and 4-mm diameter quartz tube filled with 2-mu m diameter carbon particles and Ar gas at 1400 Pa was set at the central position. The numerical simulation with a finite element moment method demonstrated the standing wave of the electric field caused by three-dimensional Fresnel interference effect. The lowest average electric field intensity of 5 kV/m in the cavity space was achieved in the case of the electrical conductivity of carbon ranging from 10 to 55 S/m. Heating a CHT with 55 S/m was experimentally realized to 1200 degrees C by microwave irradiation at 200 W. This heating method was applied to activate 1.0x10(15)-cm(-2) boron and phosphorus implanted regions in n-type crystalline silicon substrate to fabricate pn junction and solar cells. The CHT heating at 1200 degrees C realized a solar cell characteristic with a conversion efficiency of 14.8% under illumination of air mass 1.5 at 0.1 W/cm(2).