Ion Beam Machining to Eliminate Stress-Induced Curvature in Microelectromechanical Systems (MEMS) Optical Devices

该研究项目的目标是开发一种后处理技术，通过受控的中性离子束曝光来平坦化弯曲的独立式薄膜微机电系统 (MEMS) 器件。该方法的工作原理是：(1) 在离子束照射的最初几秒钟内，通过薄膜表面附近的原子重排影响薄的高应力层； (2)在离子束暴露另外几分钟后去除膜中最初受应力的材料。 这些效应可以以受控的方式组合起来，以抵消微镜中的初始弛豫曲率。 MEMS 微镜是多种下一代光通信设备的重要组件。 独立式 MEMS 微镜通常采用逐层工艺制造，然后从主基板上剥离；厚度方向的尺寸可以小至一微米或更小。一旦这些薄结构被释放，由于加工产生的残余应力就会被足够大的横向曲率所松弛，从而使器件在光学上变得无用。该计划包括理论和实验工作。 使用分析和数值模型，研究各种加工参数的影响；将进行实验来测试这些参数，并对所得平面镜的质量进行表征。

The objective of this research project is to develop a post-processing technique to planarize curved freestanding thin film microelectromechanical systems (MEMS) devices by means of controlled exposure to a neutral ion beam. The method works by (1) affecting a thin highly stressed layer in the first few seconds of ion beam exposure through atomic rearrangement near the surface of the film; and, (2) removing initially stressed material in the film after several additional minutes of ion beam exposure. These effects can be combined in a controlled way to offset the initial relaxation curvature in the micro-mirror. MEMS micro-mirrors are important components in several next-generation optical communications devices. Freestanding MEMS micro-mirrors are often fabricated in a layer-by-layer process before being released from a host substrate; through-thickness dimensions may be as small as one micron or less. Once these thin structures are released, residual stresses due to processing are relaxed by transverse curvatures large enough to render the devices optically useless. The program includes both theoretical and experimental work. Using analytical and numerical models, the effects of various processing parameters will be studied; experiments will be carried out to test these parameters, and the quality of the resulting planarized mirrors will be characterized.