以氮化矽及二氧化矽薄膜組合之雙層薄膜結構應用相當廣泛，其應用於太陽能板及微致動器中具有較佳的電性及絕緣能力，然而多層結構的內部應力對於結構可靠度有很大的影響，必須深入討論，在製程此兩種薄膜時，主要使用電漿輔助化學氣相沉積，其優點為沉積溫度較低，薄膜內應力較小，但薄膜內部結構較鬆散，包含氫鍵、空孔及差排，造成薄膜的介電性能較差等，因此薄膜必須經過熱處理，改善內部結構，但產生遲滯應力造成薄膜應力過大，必須評估薄膜內應力避免破壞發生，本文主要目的為評估雙層結構中薄膜的內應力，且提出理論討論退火過程中內應力改變行為。由於薄膜內部應力來自氫氣擴散所造成的孔洞受熱收縮，因此本文將以氫氣擴散的形式模擬薄膜受熱收縮行為，進行內應力分析，主要考慮內部氫氣濃度、擴散速率、及氫鍵活化能為主要參數，模擬薄膜內應力及退火時間及溫度關係，且應用於多層薄膜結構上之應力預測，另外以實驗輔助量測由氮化矽及二氧化矽所組成之四組薄膜結構之機械性質，如殘留應力、楊氏模數及破壞行為，比較薄膜經不同退火條件後性質的改變。結果顯示雙層薄膜可以改善薄膜的翹曲量，但薄膜內部各層應力與Stoney方程式所量測出的結果不同，在實驗的觀察中，由二氧化矽於上層之薄膜較能抵抗壓痕器的破壞，應選擇材料性質接近的材料互相排列，此外退火的溫度必須超過400℃以上才能改變薄膜的楊氏係數，本文提出一個有效的內應力模型，於工程上的使用中，可選擇較佳的製程參數增加薄膜的可靠度，應用於更複雜之結構。

Plasma-enhanced chemical vapor deposited (PECVD) dielectric films such as silicon nitride and silicon oxide have been widely used for passivation and inter-metal dielectrics. Multi-layer structures constructed by nitride and oxide films have been shown to have better performance in solar cell and RF MEMS switches applications, on which the device reliability, such as fracture and delamination failures, is also an important concern. It is mainly controlled by the residual stress existed in the film. However, the stress states of the films during deposition and after post-deposition thermal annealing are process-dependent due to the interaction of thermal stress, void-driven intrinsic stress generation, and stress relaxations. Without an effective stress evaluation model, it is difficult for performing the subsequent structural integrity evaluation. The goal of this study is therefore to develop an efficient method to model the process-dependent stress for subsequent device reliability applications This thesis firstly proposed an effective intrinsic stress model by lumping the simultaneously considering the diffused void-generation and subsequent void shrinkage effect and implementing it as an equivalent state-dependent thermal expansion coefficient and realized by using finite element method. The model predictions agree with that performed by previous experimental investigations. The result is then combined with material viscoelasticity and a multi-layer structure model for evaluating the stress existed in each layer during thermal processing is then proposed and can be solved by using Matlab. The prediction results agree with that performed by axisymmetric finite element simulation very well using a three-layer structure. In parallel, multi-layer film structures are fabricated. The material characterization results in associated with the model prediction have been applied for evaluating residual stress of each layer and provide necessary explanations for observed structure failures under indentation load. In summary, this thesis provides a novel and effective approach to model the stress behavior in multi-layered films. By this approach, we believe that it should be possible to provide more precise information for optimizing the deposition and the subsequent thermal annealing processes for improving structure longevity of MEMS and IC devices.

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