High-rate deposition of Sb-doped SnO2 films by reactive sputtering using the impedance control method

SnO2 films doped with Sb (ATO) were deposited both on unheated glass substrates and on glass substrates that had been heated at 200 °C by reactive sputtering of an Sb–Sn alloy target with a plasma control unit (PCU) and mid-frequency (mf, 50 kHz) unipolar pulsing. The PCU feedback system monitors the oxidation states of target surface by detecting the sputtering cathode voltage (impedance control method). The mf pulse wave is approximately square-shaped; this helps to reduce arcing on the target when high power density is applied on the cathode. In case of the ATO depositions on the heated substrate at 200 °C in the “transition region” of reactive sputtering, the deposition rate was 280 nm/min, the lowest resistivity of the ATO films was 4.6 × 10− 3 Ω cm and the optical transmittance was over 80% in the visible region of light.