Plasma‐Enhanced Atomic Layer Deposition of Semiconductor Grade ZnO Using Dimethyl Zinc

Abstract

Abstract Zinc oxide films are deposited over the temperature range 25–120 °C by plasma‐enhanced atomic layer deposition (PEALD) using dimethyl zinc (DMZ, Zn(CH 3 ) 2 ) as the metal precursor. DMZ is unreactive with molecular oxygen under process conditions, facilitating its utility for PEALD. The deposition rate is independent of plasma exposure (1–5 s) and saturates for DMZ exposures ≥75 mTorr s. The saturated growth per cycle increases from 1.6 to 2.9 Å per cycle as the temperature is increased from 25 to 85 °C, and remains constant in the range 85–120 °C. Over the narrow range explored, substrate temperature has a dramatic impact on film structure and properties. Polycrystalline films with a (100) texture are obtained at room temperature, with the preferred orientation evolving to the (002) direction as the temperature increases. The electrical resistivity decreases exponentially from 270 at room temperature to values of ∼5 Ω cm within the ALD window. Compositional analysis shows that films at low temperature are contaminated by carbon and hydroxyl impurities, however these defects are attenuated with temperature and not detected in films deposited within the ALD window. Room temperature photoluminescence is dominated by strong emission from ZnO defects in most films, however these signals are attenuated and strong band edge emission is observed for films deposited at 120 °C.