Microwave rapid heating used for diffusing impurities in silicon

Abstract

We report diffusing boron and phosphorus dopant atoms in silicon with impurity sources of BOx and POx layers formed on the top surfaces of n- and p-type crystalline silicon substrates. The silicon samples with impurity sources were subsequently covered with carbon powders to effectively absorb 2.45 GHz microwave power. Microwave irradiation at 1000 W for 27 s rapidly heated the carbon powders to 1265°C. The sheet resistivity of the samples decreased to 29 and 16 Ω/sq because of boron and phosphorus doping by 29-s-microwave heating. The photo-induced minority carrier lifetime increased to 2.0×10-5 and 3.5×10-5 s by 20- and 14-s-microwave heating for the boron- and phosphorus-doped samples. Boron atoms with a concentration above 1020 cm-3 diffused 150 nm deep by 26-s-microwave heating. Achievements of diode rectified characteristics and photovoltaic effect demonstrate pn junction formation at the top surface region by the present doping method.