基于遮挡矩阵的膜厚修正挡板的设计

Design of uniformity correction masks based on shadow matrix

为了在光学元件镀膜过程中精确控制膜厚均匀性,通常需要有针对性地设计并制作膜厚修正挡板。然而,由于基底在真空室内运动方式复杂,实际工作中通常采用多次试验,反复进行局部修正的方法来确定挡板形状。为解决这一问题,本文提出了遮挡矩阵的概念。基于这一概念,提出了膜厚修正挡板的设计方法。通过对挡板进行合理的划分,对膜厚空间分布与挡板形状建立起精确的定量关系,从而可在不需进行事后修正的情况下,准确计算出修正挡板的形状。针对平面行星夹具,设计并制作了膜厚修正挡板,在φ300mm的口径上实现了膜厚均匀性的PV值优于0.3%、rms值优于0.1%。这些结果验证了这一方法的有效性,表明该方法满足光学元件镀膜过程中高效、可靠地调整膜厚均匀性的要求。

To control the thickness distribution accurately in optical coatings for optical elements, cor- rection masks should be designed according to details of coating machines and substrates. However, the shapes of correction masks are hard to predict for restrictions from many factors. Normally, a la- borious method is used to correct masks by slightly adjusting their shapes repeatedly. To solve this problem, the concept of the shadow matrix was proposed. Based on this concept, a design method of correction masks for coating thickness was proposed. The relation between thickness distribution and mask shape was established based on partitioning of the mask reasonably. Therefore, mask shapes could be derived without additional mending processes. A uniformity mask was designed and manufac- tured for a planetary fixture by using this method. Experiments show that the measured uniformity is better than 0.3% PV or 0.1% rms on the range of φ300 ram. The results prove the validity of this method and indicate that it can meet the requirement of optical elements in coating processing for ad- justing thickness uniformity in higher efficiency and reliability.