製程參數對薄膜殘餘應力影響研究

Studying on the Effect of Fabrication Process on the Residual Stress in Thin Film

范介凱(Chieh-Kai Fan)

指導教授 ： 江國寧

國立清華大學/工學院/動力機械工程學系/碩士(2012年)

https://doi.org/10.6843/NTHU.2012.00151

摘要

製程流程對半導體元件之可靠度有相當大影響。在薄膜製造過程中薄膜會產生殘餘應力，此應力可能會導致結構產生非預期變形、破損或破壞，故為了提升元件之可靠度與性能，製程過程與薄膜殘餘應力影響是需要深入進行分析。本研究中將透過實驗設計方式，並以物理模型與模擬分析探討薄膜厚度與溫度效應對薄膜殘餘應力之影響。
為分析薄膜之殘餘應力，首先必須建立完善之物理模型與實驗進行分析。研究中以能量法方式推導修正之Stoney模型，模型可同時考慮厚度與溫度效應下之殘餘應力變化，其中將殘餘應力分為熱應力、沉積過程產生之應力及差排所產生之應力。利用實驗所得之結果可用來比對改善之模型，進而提供適當之物理解釋。此外，研究中設計鋁矽銅薄膜與氮化鈦薄膜之熱循環實驗，並透過基礎理論分析薄膜機械性質與溫度之影響。實驗結果顯示薄膜會發生應力釋放之現象，此現象可利用所提出之Stoney模型與差排理論解釋其殘餘應力變化。實驗也將不同厚度薄膜進行機械性質分析，其厚度變化對機械性質並無太大差異。研究以有限元素分析軟體建構薄膜殘餘應力之模型，分析薄膜應力受非等向性基板之影響與熱循環過程之殘餘應力變化。薄膜殘餘應力分析結果顯示，使用非等向基板不會影響薄膜應力分佈，然而模擬所描述之殘餘應力變化會接近厚度較大之薄膜，厚度小的薄膜容易低估其本質應力變化而有較大誤差。

關鍵詞：Stoney方程式、殘餘應力、本質應力、鋁矽銅薄膜、氮化鈦薄膜、製程模擬

關鍵字

Stoney方程式 ； 殘餘應力 ； 本質應力 ； 鋁矽銅薄膜 ； 氮化鈦薄膜 ； 製程模擬

並列摘要

Manufacturing processes are essential factors in determining structural reliability of many semiconductor devices. Fabrication of thin film typically results in residual stress in the film leading uncertain deformation, failure or damage. Thus, this study sets out to examine film thickness and temperature effect on residual stresses which could provide a guideline to improve reliability and performance of products.
To analyze the influence of residual stresses, a physical model and experiments are needed in research. An energy-based modified Stoney’s model is proposed to improve the stress conversion by simultaneously considering the thermal effect and thickness effect. Here, residual stresses are categorized into thermal stresses, stresses induced from dislocation and stresses generated in film structure. Solutions obtained by this method were used to compare with experiment results which provided appropriate explanation to the stress variation in different thickness films. In addition, thermal cycling experiments were carried out to investigate thermal impact and mechanical properties of Al-Si-Cu and TiN films. The results show that residual stresses in thin films could be explained by using modified Stoney’s model and dislocation theory. Also, the observed mechanical properties difference between films with various thickness in this study is not significant. Finite element simulation is also included to analyze stress distribution in the film and stress conversion in thermal cycle processes. Simulation results indicate that the anisotropic substrate does not affect the stress distribution in the film and mechanical properties of thin films are only in good agreement with thicker films, while films of small thickness might underestimate the effect of intrinsic stress.

Key words: Stoney’s formula, Residual stress, Intrinsic stress, Al-Si-Cu film, TiN film, Process modeling

並列關鍵字

Stoney’s formula ； Residual stress ； Intrinsic stress ； Al-Si-Cu film ； TiN film ； Process modeling

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