Molybdenum thin films with low resistivity and superior adhesion deposited by radio-frequency magnetron sputtering at elevated temperature

Molybdenum (Mo) thin films are widely used as back contact layers for thin film solar cells. In this work, Mo layers were deposited by radio-frequency (RF) magnetron sputtering at elevated substrate temperature, and their electrical and adhesion properties were investigated with regard to sputtering power and sputtering gas pressure. The crystal structure and morphology of the films were studied using X-ray diffractometry, scanning electron microscopy and atomic force microscopy. It was found that lower pressure and higher power of RF sputtering resulted in lower resistivity of Mo films due to increased kinetic energy of sputtered particles, which improved the crystallinity and compactness of the films. However, bad adhesion was observed for those films with desirable resistivity, exhibiting compressive stress. Through continuous deposition under higher and then lower sputtering gas pressures, a bi-layer Mo film was obtained with desired microstructure and surface morphology, possessing of a low resistivity of 11.1 mu Omega cm and excellent adhesion property. (C) 2014 Elsevier B.V. All rights reserved.