Carbon Heating Tube Used for Rapid Heating System

Abstract

We report a microwave heating system with a carbon heating tube (CHT) which was made by a 4-mm diameter quartz tube filled with carbon particles and Ar gas at 1400 Pa. A 60-mm-long CHT was set in a cavity in which 2.45-GHz microwave was introduced. Via nearly complete absorption of a microwave power of 200 W by carbon in the CHT during multi-reflection of the microwave in the cavity, the CHT was effectively heated to 1279 °C at 33 s after the microwave initiation, which was observed by the radiation-type thermometer. Moreover, the control of the CHT temperature was demonstrated with a home-made proportional-integral-differential feedback circuit which regulated the magnetron power source using a signal of the thermometer. The control of temperature at 1100 °C was successfully realized. Crystallization of a 58-nm-thick amorphous silicon thin film formed on the glass substrate was demonstrated by mechanically moving the silicon sample just below the heated CHT. A high crystalline volume ratio of 0.92 was achieved. Furthermore, heating of 500-μm-thick-n-type silicon substrate implanted with cm-2 phosphorus and boron atoms with the CHT resulted in activation of the doped regions. Rectified diode characteristics were achieved.

Keywords

• Electromagnetic interference
• heat treatment
• low-microwave power electronics
• PID temperature control
• silicon