摘要
针对MEMS(micro electro mechanicalsystem)和NEMS(nano electro mechanicalsystem)对薄膜应力测试的要求,开发了一种新型高灵敏度薄膜应力测试技术,使用自行搭建的准纳米光学干涉测试系统,利用局部基底弯曲来检测薄膜的内应力.该方法不仅保留了传统基底弯曲法的所有优点,而且消除了其系统误差.使用ANSYS对测试结构进行了模拟和优化,对于30nm厚的薄膜,应力检测的分辨率为1.5MPa,优于目前国际上的相关报道.本测试结构使用各向异性腐蚀和DRIE(deepreactiveionetching)完成,加工工艺简单实用.文中使用该测试技术对常用MEMS薄膜的残余应力进行了测量,结果与其他测试方法得到的结果基本一致,测量重复性优于1%.该技术可以用于测试纳米级薄膜及超低应力薄膜的内应力.
Novel local curvature test structures combined with a sub-nanometer optical interferometry measurement setup are developed to detect stresses in nanometer-scale films and ultra low stresses in thin films. Several ＂localized＂ test structures based on the bending plate measurement method are designed to improve its sensitivity and accuracy. FEM analysis is performed to calculate the deviation of boundary-introduced stress from that predicted by the Stoney formula. Optimized structures are fabricated with anisotropic etching and DRIE. Stress values obtained with this metrology are in good agreement with those extracted by other methods,and repeatability within 1% is achieved. Stress differences as small as 1.5MPa in the 30nm film can be resolved. Such resolution is among the finest in the world.
基金
国家自然科学基金资助项目(批准号:50535030)~~
关键词
微机械系统
内应力
纳米级薄膜
基底弯曲法
光学干涉测量
MEMS
internal stress
nano-film
bending-plate measuring methodology
optical interferometry measurement
