Effect of the Substrate Cleaning Process on Pinhole Formation in Sputtered CdTe Films

Seven cleaning methods for glass substrates were proposed and their role on pinhole formation of deposited CdTe films was examined. AFM micrographs of the cleaned substrates show the presence of surface particles after cleaning. RMS-roughness of the cleaned glass substrates is associated with the remaining particles at the surface after the cleaning processes. CdTe thin films deposited by the sputtering technique onto the cleaned substrates were analyzed to evaluate the pinhole formation. Parameters such as the occupied area, size, and circularity of the formed pinholes in the CdTe thin films were investigated by microscopy technique through image processing software. Some illustrative 2.5-D images of the pinholes in CdTe films were obtained for each cleaning method. For all the investigated cleaning methods, the mean pinhole diameters ranged from 30 to 55 μm. Correlations between the pinhole formation and the cleaning method were observed, which highlight the importance of the cleaning process selection.