氮化矽薄膜由於具有電絕緣作用、及在高溫高濕度的環境之下不易被破壞和被氧化及水氣滲透的特性以及可當作機械材料等特性，故常應用於半導體製程或IC元件，然而當使用氮化矽薄膜應用半導體製程或IC元件時，薄膜的機械性質容易影響到半導體製程的良率或微系統元件的可靠度，例如：當薄膜應用在IC元件或MEMS可動元件時，可能受到溫度變化所造成的熱疲勞或週期性外力所造成的機械疲勞，對元件造成破壞，因而降低薄膜元件的可靠度與性能，由此可知薄膜材料的性質是影響微元件的良率與可靠度的重大因素。本文以在兩種不同PECVD製程壓力環境下沉積於單晶矽底材的 PECVD 氮化矽薄膜為測試對象，探討薄膜經過不同退火溫度與時間之快速熱退火製程以及機械疲勞後之破壞性質。本文藉由微米與奈米壓痕測試儀，經由觀測薄膜裂縫，推估薄膜之殘留應力、破壞韌性、介面強度及疲勞裂縫傳播等材料破壞特性。實驗結果顯示上述機械性質與薄膜沉積製程參數相關，例如: 在較低壓下沉積之薄膜，其殘留應力較低，且擁有較佳之介面強度。另外，快速熱退火製程雖可提升薄膜的介面強度，使薄膜不容易與基材產生脫層，但其伴隨生成之高殘留張應力卻在實質上減少了氮化矽薄膜之破壞韌性，此外，也使的薄膜表面的裂紋在機械疲勞的過程中容易成長，不利結構安全。研究結果可提供相關微系統結構可靠度評估應用，以提升微系統元件與積體電路結構可靠度與機械良率。

PECVD silicon nitride films are commonly used in microsystems and integrated circuits as structural or transduction medias and the reliability of nitride films subjected to external mechanical loading and thermal annealing are traditional major concerns for structural and process designs. In particular, the post-deposition thermal annealing dependent elastic and fracture properties should be investigated for device performance evaluation and the design optimization for post-deposition thermal annealing process. In addition, it is also important to evaluate its fatigue properties since the associated devices may encounter possible mechanical and thermal fatigue loadings. In this work, the mechanical properties of PECVD silicon nitride deposited on silicon substrates by two different processing temperatures (i.e., 300 and 350C) and pressures (i.e., 1 and 5 torrs) subjected to rapid thermal annealing between 200 – 800 C for 1 to 5 minutes are investigated. Their residual stress and elastic modulus are characterized by examining the specimen curvature and by a MTS nanoindentor. On the other hand, by examining the crack length of pre-indented specimens and performing data reduction using Marshall/Lawn or Zhang’s relations, it is possible to deduce their fracture toughness. Finally, by utilizing a self-designed and assembled fatigue testing machine, the crack propagations of pre-cracked specimens can be monitored and the associated fatigue life can be estimated. The experimental results indicate that the residual stress, fracture toughness and interfacial strength, as well as the fatigue crack propagation were strongly depend on the processing conditions such as deposition temperatures and chamber pressures. Preliminary results indicate that the specimen deposited at a lower temperature and a lower pressure exhibited a much less residual tensile stress and a better interface strength. On the other hand, it is found that RTA can enhance the interfacial strength but the generated high tensile strength can actually reduce the equivalent toughness and leads to structural reliability concerns. For example, the experimental results also indicate that a larger temperature ramp down rate can induce a higher residual stress in nitride and this could be critical for process design. In summary, the characterization results should be possible to provide useful information for correlating the mechanical reliability with the processing parameters for future structural design optimization and for improving the structural integrity of PECVD silicon nitride films for MEMS and IC fabrication.

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