近年來微機電技術已逐漸發展成熟，其商品及功能需求也漸漸邁向多元化，其中可動元件在微機電結構裡扮演了極重要的角色，舉凡微機電感測器及致動器大部分均含有可動結構，且均須被長期的反覆使用，在這種情形下，結構便會產生疲勞現象，而由於製程的不確定性，造成微機電結構的材料特性會隨著不同批次的製程而改變，尤其以微機電結構的疲勞現象最為顯著，以多晶矽材料而言，其疲勞壽命的實驗結果有數十秒到數十天的差距，材料特性測試的最終目的是為了能提供結構設計者作為結構設計上的參考，對於這樣分散的實驗結果並無法提供結構設計者一個衡量的標準，有鑑於此，本文的研究目的即在於對疲勞實驗的結果引入機率化的特性，以提供結構設計者一套衡量材料特性的方法，本文以大量的多晶矽微懸浮結構進行疲勞實驗，以符合結構機率化的精神，並為了能方便的觀察及統計實驗結果，本文設計了一套新的疲勞實驗方法，實驗結果則以Weibull 機率分佈來描述，並引入NASA –CARES/LIFE 可靠度分析程式裡所運用的理論，提供了一套疲勞實驗簡化的模型，以減少長時間的疲勞實驗因外在實驗環境的改變而影響實驗結果。

　With the rapid growth of microelectromechanical systems (MEMS),many micro actuators and sensors, such as valves, pumps, accelerometers, and pressure transducers, have been developed and utilized in industrial applications. These devices are all subjected to cyclic loading during service and therefore their long term reliability due to fatigue is a significant concern. Due to the probabilistic nature of micro flaw distribution and further imposed　by the limitation on the resolution of available instruments for crack growth detection, the conventional fatigue properties characterization methods may not yield a practical results for subsequent structure design. This thesis presents two major issues: First, a novel methodology for structural reliability　assessment is presented. Based on the probabilistic nature of brittle materials,this method integrates the scholastic material strength with fatigue crack extension rules such as Walker’s or Paris laws to forecast the residual strength of MEMS structures after a certain period of service and thus it provides the necessary information for structural design. Second, specimens for fatigue properties characterization are designed and fabricated. An array of bothfixed-fixed and cantilever beams is designed in order to capture the nature of　probabilistic fatigue parameters of polysilicons and provides necessary material parameters for the proposed design flow. The fabrication of these specimens are carried in National Nano-Device Laboratory (NDL) and　Center
for Micro/Nano Technology (MINA) at NCKU. Although the initial fabrication and test results for these specimens cannot yield a satisfied result,the experience and lessen learned form this work is certainly invaluable for the subsequent design modification and optimization. By the approach proposed by this work, a more reasonable structural reliability evaluation methodology could be established for enhancing the robustness for MEMS structures.

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