Effect of Bias Applied to Hot Wires on Generation of Positive and Negative Charges during Silicon Hot-Wire Chemical Vapor Deposition

Hot-wire chemical vapor deposition of silicon films has been studied focusing on the generation of electric charge during the process. The currents measured 1.5 cm below the input and output positions, with respect to the DC power supply, of the hot wires at 2000 °C were +4 and −544 nA/cm2, respectively, and those 4.5 cm below the input and output positions were +3 and −64 nA/cm2, respectively. These data imply that both positive and negative charges are generated presumably by surface ionization of gas molecules on the hot wires, but an appreciable fraction of negative charges was attracted to the electric field around the hot wires, which have the input and output potentials of +18 and 0 V, respectively, provided by the DC power supply. The additional biases of +25 and −25 V applied to the hot wires produced +2.38 and −4.86 × 104 nA/cm2, respectively, 1.5 cm below the input position of the hot wires. The absolute value of the current measured under the negative bias is much larger than that under the po...