真空镀膜中基底预应力的有限元分析

Finite Element Analysis for Substrate′s Initial Stress in Vacuum Deposition

真空镀膜过程中,基底因支撑、温度梯度造成的应变会对最终的薄膜-基底系统的面形产生影响。用有限元方法对不同支撑方式下不同尺寸基底的预应力以及烘烤过程中基底内部温度梯度造成的热应力进行了分析和计算,得到基底表面变形的峰谷值,并给出了不同工况下基底形变的等值线图。对于尺寸超过200 mm的基底,自重变形量和热应力变形量比较大,是影响最终薄膜面形的重要因素;装夹时随着基底倾角的增大,基底的形变与应力呈减小趋势;同样结构尺寸情况下,熔融石英基底的自重变形量略大于BK7基底,热变形量远小于BK7基底;热应力对基底预应力的贡献较大。

In vacuum deposition, the substrate deformation caused by sustentation and temperature grads can affect the final surface form of film-substrate system. By finite element analysis and calculation on initial stress of different substrates under different sustentation manner, and the thermal stress caused by the interior temperature grads of substrate, P-V values of the substrate surface deformation are gained, and the contours of substrate deformation in different situations are plotted. This analysis shows that the deformation induced by gravity and the thermal deformation are great when its size is over 200 mm, which become the important factor affecting the final film surface form, with the augmentation of substrate obliquity when fixed, the substrate deformation and the stress show decreasing trend; in the same situation, the deformation induced by gravity of the fused silica substrate is a little greater than that of the BK7 glass substrate, while the thermal deformation quantity of the former is further less than the latter; the thermal stress has made greater contribution on substrate＇s initial stress.