Comparison of charge generation from hot wires between AC and DC power supply and its effect on deposition behavior during hot-wire chemical vapor deposition of silicon

The generation behavior of electric charges was different between DC and AC powered wires of hot-wire chemical vapor deposition (HWCVD), which is attributed to the different electric fields formed around the hot wire powered by DC and AC. When the AC and DC powers were used to heat the wire, the currents measured 1.5 cm below the input position of the hot wire were −3.65×104 and −0.11 nA/cm2, respectively, under the same processing conditions of the wire temperature of 1800 °C, reactor pressure of 40 Pa and a reactant gas mixture of 5% SiH4–95% H2. Deposited thin films showed different crystalline fraction depending on the type of power supply. The AC power produced more negative current and a thin film with a higher crystalline fraction than the DC power. When the additional DC bias was applied to the hot wire with respect to the ground, the electric field around the hot wire changed, which affected both the measured current and deposition behavior. Thin films with a higher crystalline fraction could be deposited when the negative wire bias was applied for both AC and DC powers. In this case also thin films deposited under AC power showed higher crystallinity than those under DC power.