本研究為與台亞半導體股份有限公司合作開發之電容式超聲波元件製程，以因應近年來高速發展之智慧物聯網應用下，針對個人隱私保障之指紋辨識元件開發需求。此元件具備微小電容傳感間隙，可大幅提高元件機電轉換效率，並操作於指紋辨識頻段，且完全使用CMOS製程，因此預期能更有利於與後端電路整合，以達成單晶片系統之指紋辨識功能。
由於快速熱退火後，金屬與非晶矽會形成矽化物，並造成本身體積微縮。因此本研究在CMUT元件膜層堆疊全數完成後，透過快速熱退火製程於CMUT兩電極之間形成微小空氣間隙，實現等效電容間隙60 nm之CMUT元件，大幅提高CMUT元件之機電轉換效率。

There is an increasing demand on personal security for consumer electronics due to the mobile payments and communications on smart phones. Ultrasonic fingerprint scanner features better security characteristic and is convenient as compared to other sensing methods. In this work, a novel capacitive micromachined ultrasound transducer (CMUT) device which is designed to meet the fingerprint scanner requirements through tiny gap is developed thanks to the innovative process on the formation of tiny transducer gap. Therefore, it features higher electromechanical coupling coefficient, operates at fingerprint scanning frequency, and most importantly is compatible with CMOS process. As a result, a single-chip system of a fingerprint scanner can be potentially realized in near future.
This CMUT device is developed by a rapid thermal annealing (RTA) process. In such an RTA process, metal and silicon will form alloy through silicidation and lead to a volumetric shrinkage to enable a tiny transducer gap. After all layers of the CMUT are deposited, we perform RTA to create a 60-nm effective gap, leading to a higher electromechanical coupling coefficient of such a capacitive transducer targeting for CMUT fingerprint applications.

摘要 ……………………………………..………….………………….I
Abstract …………………………………………………………………II
總目錄 ……………………………………..…………………………...III
圖目錄 …………………………………………..………………………VI
表目錄……………………………………………...…………………..XII
第一章 緒論 1
1-1 研究動機與背景 1
1-2 文獻回顧 5
1-3 內容架構 8
第二章 原理分析與設計 10
2-1 超聲波傳遞原理 10
2-1-1介面反射 10
2-1-2現今之超聲波應用 11
2-2 電容式元件分析 12
2-2-1電容式超聲波元件 13
2-2-2電容式超聲波元件結構 16
2-2-3電容式超聲波元件等效模型 17
2-3 釋放薄膜間隙 22
2-3-1釋放薄膜間隙的方法 22
2-3-2矽化物釋放薄膜間隙 24
2-4 電容式超聲波元件模擬 26
2-4-1機械共振模擬 26
2-4-2頻率響應模擬 28
2-4-3聲場模擬 30
2-5 元件應力模擬 30
2-5-1殘餘應力 30
2-5-2殘餘應力模擬 31
2-5-3熱製程應力模擬 34
2-6 電容式超聲波元件設計 35
第三章 製作過程與結果 36
3-1 Silicidation-Induced-CMUT元件製程簡介 36
3-1-1 Silicidation-Induced-CMUT元件製程流程 36
3-1-2 Silicide-Induced-CMUT元件製程結果 59
第四章 元件量測結果與討論 60
4-1 CMUT動態量測 60
4-1-1 網路分析儀量測(Network Analyzer) 60
4-1-2 去嵌化後處理(De-embedding) 62
4-1-3 機電模型 64
4-1-4 雷射都普勒振動儀 65
4-2 CMUT超音波量測 68
4-2-1 CMUT發射器量測 68
4-2-2 CMUT接收器量測 70
第五章 結論與未來研究 79
5-1 結論 79
5-2 未來工作 79
5-2-1 較大間距Silicide-Induced CMUT實驗 79
5-2-2 單晶片CMUT元件與電路全整合應用實作 80
參考文獻 85

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