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Theoretical Analysis of Film Thickness Uniformity of Coating on Hemispherical Substrate

2021-01-07 14:15  Times of view:

A theoretical analysis and research on the uniformity of the film thickness of the film coated on the surface of a special non-planar substrate-hemisphere is carried out. First, the film thickness equation of each point on the spherical surface when the hemispherical surface is at rest and the area where the hemispherical surface can be coated are derived. Then the film thickness equation at each position of the spherical surface after the hemispheric surface rotates along the axis passing through the vertical direction of the spherical center is calculated. In addition, when the horizontal distance between the evaporation source and the spherical center is less than the radius of the hemispherical surface, there is a certain area that cannot be coated. Carry out theoretical calculations. Finally, the distribution of film thickness on the surface of the hemisphere is analyzed by calculating the relative film thickness. Choosing an appropriate geometric configuration between the evaporation source and the substrate can obtain a relatively uniform coating area in a small area. This research work has theoretical guiding significance for the study of film thickness uniformity on the hemispherical complex non-planar substrate, and at the same time provides relevant theoretical basis for the research on improving the film thickness distribution on this surface.

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In the vacuum coating work, the unevenness of the film thickness is an important factor restricting the function of various functional films. This type of impact not only involves optical films, which have greater requirements for thickness control, but also has greater impact on various functional films used in optoelectronics, microelectromechanical systems (MEMS) and other devices. Therefore, the work on the uniformity of the film thickness of the thin film layer on the flat substrate has attracted the attention of many coating workers. These studies include various coating methods, such as evaporation, magnetron sputtering, laser pulse deposition, plasma Enhanced Chemical Vapor Deposition (PECVD), etc., but these studies are based on flat substrates in flat fixtures or spherical fixtures.

With the complexity and diversification of modern coating work, the surface that needs to be coated with a thin film layer is no longer limited to flat substrates, and more and more coatings on the hemispherical surface, such as some hemispherical shields, Shell etc. Obviously, the thickness distribution of the film coating on this type of hemispherical surface is more complicated than that of the flat substrate, which severely restricts the normal use of various functional films coated on such special surfaces. The research of film thickness distribution is indispensable, but there has been almost no research work on the film thickness distribution of such non-planar substrate-hemispherical substrate coating film layer.

This paper conducts a theoretical study on the uniformity of the coating thickness on the hemispherical surface under evaporation. Since the coating on the hemispherical surface is similar to the coating on the small plane substrate under the spherical fixture, this paper only conducts the uniformity of the coating thickness on the hemispherical surface. theoretical analysis. In the analysis process, evaporation sources are regarded as two common types of evaporation sources, namely, point sources that emit uniformly around and small plane surface sources that obey the cosine distribution. First, the film thickness formula of the hemispherical substrate at each point at rest is deduced, and then the film thickness equation at each position after the hemispherical surface rotates is calculated on this basis. Finally, the theoretical analysis of the film thickness distribution of the hemispherical coating was carried out, and the corresponding uniformity equation was calculated and the corresponding function graph was drawn.

Zunhua Baorui Titanium Equipment

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in conclusion

In this paper, a theoretical study on the film thickness distribution of the hemispherical coating on a special surface is carried out. During the study, the evaporation source is used as a point source and a small plane surface source. First, the film thickness equation of each point on the hemispherical surface when the spherical surface is at rest and the corresponding coating range are calculated. On this basis, the film thickness equation of the hemispherical surface after the hemispherical surface rotates along the axis passing through the center of the sphere is calculated. When R >n ≥0, the corresponding uncoated area. Finally, the formula for the film thickness distribution on the hemispherical surface is calculated. The results show that the film thickness distribution of this type of hemispherical surface is affected by the vertical distance between the evaporation source and the center of the hemisphere and the ratio of the horizontal parallel distance to the center of the hemisphere and the radius of the hemisphere. Big. Through computer programming, the film thickness distribution curve when h/R=2, different nR values and n/R=2, different hR are drawn. Choosing a proper geometric configuration between the substrate and the evaporation source can obtain a film with uniform thickness within a certain range, but the range is relatively small. Under the theoretical guidance of this article, further work is needed to improve the uniformity of the hemispherical film thickness.

Founded in 2015,Zunhua Baorui Titanium Equipment Co.,Ltd. is a manufacturer specializing in pvd vacuum ion coating equipment. The company’s products mainly include large plate coating machine, large tube collating machine, tool coating machine and LOW-E glass production line. Mr.Wang baijiang ,general manager of the company ,has been engaged in vacuum coating industry for more than 30 years. He continuously improve production technology, improve product performance and devote himself to provide customers with better product experience and higher production efficiency.

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