USING SCANNING FORCE MICROSCOPY (SFM) TO INVESTIGATE VARIOUS CLEANINGPROCEDURES OF DIFFERENT TRANSPARENT CONDUCTING OXIDE SUBSTRATES

Cleaning of substrate surfaces prior to deposition of thin film semico nductors is an important processing step. Determining the surface clea nliness is essential to ascertain whether the cleaning method used is effective or not. Two types of glass substrates coated with transparen t conducting indium tin oxide or fluorine doped tin oxide were cleaned using various solvents. The efficiency of the cleaning methods were e xamined using the topography, lateral force microscopy (LFM), and forc e modulation images from the scanning force microscope (SFM), as well as the calculated root mean square roughness values of the surfaces. T he SFM was found to have a unique ability to relate organic contaminat ion patches to adsorbed surface particle density, and it is shown how removing the one can help in removing the other. The two substrates ha d different morphologies and reacted differently to the cleaning metho ds. Contamination and surface particles on the relatively smooth subst rate were effectively removed using one method, while the same method on the rougher substrate proved to be ineffective, thus emphasising th e influence of substrate type and texture on cleaning. CdS layers that were electrodeposited on these substrates were examined in a field em ission scanning electron microscope. The morphology of the deposited l ayers correlates with the results obtained on the SFM. (C) 1998 Elsevi er Science B.V. All rights reserved.