Improvement of Substrate Holder for Evaporation and Film Uniformity Verification

In general,infrared filters have thicker films,especially infrared optical films with high spectral requirements such as medium and long-wave infrared narrowband filters.The film thickness can reach tens of microns and the demand for film materials is very large.The uniformity has a very obvious influence on the spectral performance.If the coating vacuum chamber is large,the primary material will often not meet the requirement of the film material consumption,which is usually solved by reducing the evaporation distance,but this will bring about problems such as poor film thickness uniformity.According to the analysis of the coating theory,under the condition of satisfying the film uniformity,a set of rotating flat substrate support plate with freely adjustable height and size is designed to reduce the distance between the evaporation source and substrate.When the ratio of the vertical height between the work plate and the evaporation source to the distance between the evaporation source and the rotating shaft of the work plate is 1.8,the unevenness of the film thickness is 0.20% for a small area source.The prepared mid-wave infrared short-wave pass filter has a maximum spectral difference of 8 nm between the center point and the edge position of the work plate,which is consistent with the uniformity of the film thickness obtained by theoretical calculations.