Fatigue Characteristics of Silicon Micromechanism for Micromachine

微结构的弹性变形，如弹性铰链，是MEMS中的一种可动机构，微结构的制造过程中经常会产生应力集中。静态和疲劳强度进行评估的缺口型试样由硅晶片的微机械加工，即PVD和光刻工艺。主要研究结果如下：1.研制了一种微材料四点弯曲试验机，用于静载和循环载荷下的试验。改进了计算机图像处理测量试件变形的算法.从能量定律出发，分析了加载频率与试件变形之间的界限。在疲劳试验条件下，实验得到的最大频率是理论值的一半.介绍了一种用于单晶硅V形槽的各向异性腐蚀方法。从SEM观察，缺口根部的半径为亚微米量级.研究发现，除了极浅缺口外，缺口试样的静强度可以用应力强度因子来评价.对缺口试样进行了10^6次循环的疲劳试验，但在缺口根部周围没有观察到变化。

Elastic deformation of the microstructure such as an elasticity hinge was used for a movable mechanism of MEMS.The fabrication process of the microstructure often yielded the stress concentration. Static and fatigue strength are evaluated for notched type specimens fabricated from silicon wafers by micromachining, that is, PVD and the photo-etching processes. Results are summarized as follows :1. A micromaterial testing machine is developed for four points bending under statically and cyclic loading. An algorithm for the computer image processing to measure the specimen deformation is improved.2. Limitation between the loading frequency and deformation of the specimen is examined base on the energy law. Maximum frequency experimentally obtained under the fatigue test is half of the theory.3. An anisotropy etching has been applied to single crystalline silicon and V-groove is introduced. From the SEM observation a notch root has a radius of sub-micron order.4. It is found that the static strength of the notched specimen can be evaluated by the stress intensity factor, except for the extremely shallow notch.5. Fatigue test for 10^6 cycles is done for notched specimen, however no change is observed around the root of the notch.