Low temperature deposition of Al-doped zinc oxide films by ICP-assisted reactive DC magnetron sputtering

Al doped ZnO (AZO) films were synthesized by inductively coupled plasma (ICP) assisted DC magnetron sputtering at low temperatures (<150 °C). A two-turn rf coil was inserted in the process chamber between the substrate and magnetron to generate the ICP. In order to obtain the optimum film properties even at a low temperature, high-density plasma was used to activate the sputtered metals and oxygen. The deposition process could be stabilized by controlling the target voltage in the transition region. The electrical resistivity of the films was ∼10−3 Ω cm, and the optical transmittance in the visible range was >80%. As the working pressure was increased, the visible transmittance of films was increased but the low resistivity processing window became narrower.