Carbon Heating Tube Rapid Heating System for Fabricating Silicon Solar Cells

We report 2.45-GHz microwave heating system with a carbon heating tube (CHT) made by a 4-mm-diameter and 60-mm-long-quartz tube filled with conductive carbon particles and Ar gas at 1400 Pa set in a 300-mm-diameter-sized metal cavity. The three-dimensional finite element numerical simulation method resulted in the most effective electrical conductivity of CHT ranged from 10 to 55 S/m to absorb the microwave power. A proportional-integral-differential feedback CHT temperature control system was used to activate 1.0×1015-cm−2-boron and phosphorus implanted regions in n-type crystalline silicon substrate from 1000 to 1200°C. The CHT heating at 1200°C realized decrease in the sheet resistivity to 146 Ω/sq, decrease in the density of defect states to 1.3×1011 and 9.2×1010 cm−2 for boron (p+) and phosphorus (n+) implanted surfaces, and solar cell characteristic with a conversion efficiency of 15% under illumination of air mass 1.5 at 0.1 W/cm2.