Using scanning force microscopy (SFM) to investigate various cleaning procedures of different transparent conducting oxide substrates

Abstract

Cleaning of substrate surfaces prior to deposition of thin film semiconductors is an important processing step. Determining the surface cleanliness is essential to ascertain whether the cleaning method used is effective or not. Two types of glass substrates coated with transparent conducting indium tin oxide or fluorine doped tin oxide were cleaned using various solvents. The efficiency of the cleaning methods were examined using the topography, lateral force microscopy (LFM), and force modulation images from the scanning force microscope (SFM), as well as the calculated root mean square roughness values of the surfaces. The SFM was found to have a unique ability to relate organic contamination patches to adsorbed surface particle density, and it is shown how removing the one can help in removing the other. The two substrates had different morphologies and reacted differently to the cleaning methods. Contamination and surface particles on the relatively smooth substrate were effectively removed using one method, while the same method on the rougher substrate proved to be ineffective, thus emphasising the influence of substrate type and texture on cleaning. CdS layers that were electrodeposited on these substrates were examined in a field emission scanning electron microscope. The morphology of the deposited layers correlates with the results obtained on the SFM.