Room-temperature remote-plasma sputtering of c-axis oriented zinc oxide thin films

Abstract

Highly c-axis oriented ZnO films have been deposited at room temperature with high rates (∼50 nm·min−1) using an innovative remote plasma sputtering configuration, which allows independent control of the plasma density and the sputtering ion energy. The ZnO films deposited possess excellent crystallographic orientation, high resistivity (>109 Ω·m), and exhibit very low surface roughness. The ability to increase the sputtering ion energy without causing unwanted Ar+ bombardment onto the substrate has been shown to be crucial for the growth of films with excellent c-axis orientation without the need of substrate heating. In addition, the elimination of the Ar+ bombardment has facilitated the growth of films with very low defect density and hence very low intrinsic stress (<100 MPa for 3 μm-thick films). This is over an order of magnitude lower than films grown with a standard magnetron sputtering system.