Influence of Deposition Parameters on Surface Texturing of ZnO:Al Films Prepared by In-line RF Magnetron Sputtering

Abstract

A systematic study on the effect of sputtering deposition parameters on material properties of Al doped ZnO (ZnO:Al) films prepared by an in-line rf magnetron sputtering and on surface morphology of the films after wet etching process was carried out. For application to silicon thin film solar cells as a front electrode, the as-deposited films were surface-textured by a dilute HCl solution to improve the light scattering properties such as haze and angle resolved distribution of scattered light on the film surfaces. The microstructure of as-deposited films is affected significantly by the working pressure and film compactness decreases with increasing working pressure from 1.5 mTorr to 10 mTorr. High quality ZnO:Al films with electrical resistivity of 4.25 × 10^-4 Ω cm and optical transmittance of 80% in a visible range are obtained at low working pressure of 1.5 mTorr and substrate temperature of 100℃. Crater-like surface morphologies are observed on the textured ZnO:Al films after wet etching. The size and shape of craters are closely dependent on the microstructure and film compactness of as-deposited films. Haze values of the textured ZnO:Al films are improved in a whole wavelength of 300 – 1100 nm compared to commercial SnO2:F films (Asahi U type) and incident light on the textured films is scattered effectively with 30° angle.