Photoresist distribution and topology over GaAs mesa structures and their dependence on inter-mesa separations are studied and analyzed for different types of resists and spin parameters. The cross-sectional observations give insight into the flow of photoresist over mesa edges and in identifying the difficult region as ’mesa edge’ for pattern openings. These observations are important where small geometry patterns are required to be opened near to the mesa edge and for interconnecting metal lines running down the mesa Experimental parameters have been identified for achieving specific GaAs mesa/resist profile combination.