Reactive ion etching of ZnO using the H₂/CH₄ and H₂/CH₄/Ar mixtures

This work investigates the reactive ions etching (RIE) physical properties of n-type ZnO using H₂/CH₄ and H₂/CH ₄/Ar mixtures by varying the gas flow ratio, the radio-frequency (rf) plasma power and the chamber pressure. Atomic force microscopy (AFM) results and surface topographies are discussed. Although the etching rate of the n-ZnO at an H₂/CH₄ flow rate of 100/0 sccm, a work pressure of 100 mTorr and an rf power of 300 W is lower than under any other conditions, the rms roughness of 43.78 nm is the highest, and supports the application of roughened transparent contact layer (TCL) in light-emitting diodes (LEDs). The dynamics associated with the high etching rate were highly efficient at an H₂/CH₄/Ar flow rate of 38/5/57 sccm, a work pressure of 150 mTorr and an rf power of 300 W. In addition, the ZnO with thermal annealing were studied. The slower etching rate of annealed n-ZnO is observed due to an increase the crystal quality of the ZnO films after thermal annealing which consists with the x-ray diffraction (XRD) results.