Hai, Deposition rates of about 10 nm per minute and controlling the temperature of the substrate to room temperature will help to get rather flat thin film of Al on quartz. Oil free vacuum and moderate temperature to maintain stream line flow of Al to quartz will definetly improve the film quality.. Using all this you should be able to get RMS roughness of the order of about 2-5 nm with reduced number of pinholes and almost no micro-bumps on surface. If you are not looking for specific application of Al thin film then Al(1%Ti) will also be a good option to improve the things. regards, Pradeep Sharma.