Effect of Sacrificial Layer Sizes and Fabrication Process on Deformation Caused by Residual Stress of Center-Anchored Circular Plate

During depositing a thin film as a structure layer, residual stress from thermal treatment of depositing process will cause deformation after release. Thus the yield ratio and deformation of the devices may be lowered. This work investigates the effect of sacrificial layer on deformation by residual stress causing when depositing a thin film as structure layer. A model is established by using theory of plates-and-shells to investigate the deformation caused by residual stress when the structure layers of the devices are center-anchored circular plate. Theoretically, it is found that the deformation would happen when depositing structure layer under higher temperature. And from the analysis, the thicker structure plate will cause less deformation. When the thickness of the structure layer is larger than 3μm , the maximum deformation will reduce to the order of μm. Furthermore, four cases of different sacrificial layer types and temperature distribution with effect on deformation are discussed. If the thickness of the structure layer is above 5μm, the deformation caused by residual stress is not so important. And it is found that if the thickness of structure layer is 10μm order or above, the residual stress effect on deformation can be neglected. It is found the sacrificial layer will affect the deformation. But it is found that with the same structure layer thickness, as the sacrificial layer thickness increasing, the four cases have different effect on deformation. The in-plane dimension effect is also considered. When the in-plane dimension of sacrificial layer is above 20 times of outer radius, the in-plane dimension effect is neglected and can considered as an infinite dimension.