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

本研究项目的目的是开发一种后处理技术，通过控制暴露在中性离子束中来平面化曲面自支撑薄膜微电子机械系统(MEMS)器件。该方法的工作原理是：(1)在离子束曝光的最初几秒钟内，通过靠近薄膜表面的原子重排影响薄的高应力层；以及(2)在额外的几分钟离子束曝光后，去除薄膜中的初始应力物质。这些效应可以以一种可控的方式组合在一起，以补偿微镜中的初始弛豫曲率。MEMS微镜是几种下一代光通信器件中的重要组成部分。独立式MEMS微镜通常在从主机基板释放之前采用逐层工艺制造；通透厚度尺寸可能小至1微米或更小。一旦这些薄结构被释放，加工过程中的残余应力就会被足够大的横向曲率松弛，从而使器件在光学上毫无用处。该计划包括理论工作和实验工作。利用解析和数值模型，将研究各种加工参数的影响；将进行实验以检验这些参数，并将对所得到的平面化反射镜的质量进行表征。

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.