Modifying Mask To Improve The Uniformity Of Film Thickness

Film optics has become an important branch of modern optics after a hundred years of development. The technology of film optics has formed complete system in theory, design, calculation and preparation craft. A lot of different functional films have been produced which made optical films technology be widely used in emerging scientific research area. Film technology has gradually become a significant method in processing technology of high technology products. During the process of preparation, the uniformity of the films is a problem which has to be paid a lot of attention.The uniformity of the films is the change of the film on the substrate with the change of the location in the vacuum chamber. The uniformity of the films contains two parts:one part is the similar thickness distribution in different location in the same process of preparation; the other part is error distribution in the limited range of each film. The former guarantees the industry efficiency and the latter ensures the property of the products. The uniformity of films is a vital index to measure the property of the device and the quality of the film. Uniformity and adhesion, which largely affects the productivity of optical and photoelectric devices, will directly affect the reliability, stability and consistency of the products. Therefore, we have to know the distribution regular of the thickness of films to obtain the best uniform thickness films with large area.The principles and characteristics of vacuum evaporation, sputtering and ion plating have been produced in this article. The influence factors of the uniformity of the thickness of the films have been analyzed. The factors are evaporation sources, temperature of the substrate, the relative position between substrate and evaporation sources, geometric disposition in the vacuum chamber and the effect of the rotation angle of the substrate. The thick uniformity of the TiO2 films which prepared by electron beam evaporation have improved by adding the amended plate. The distribution of the thickness of the films have been analyzed and checked by experiments. The distributions of the thickness of the films prepared by different fixtures have been introduced, such as plate rotation jig, sphere rotation jig, planetary fixture. The calculation of optical constants of weak absorption optical films is also mentioned in this article. The distribution curves of thickness are fitted after the calculation of the optical constants.The technique of still closure for catching vapor stream is used to design modifying mask. The thick uniformity affection with different voltages has been analyzed. The modifying mask is designed by the thickness distribution which is mostly closed to theoretical curve, and then verified by experiments. The final modifying mask successfully improved the uniformity of the thickness. It can be controlled in 5%o during 200mm and the total uniformity in2.52%.