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研究生: 林文浩
Wen-Hao Lin
論文名稱: <110>垂直致動微掃描面鏡
A Micro Scanning Mirror Actuated by <110> Vertical Comb Actuators
指導教授: 劉承賢
Dr. Cheng-Hsien Liu
口試委員:
學位類別: 碩士
Master
系所名稱: 工學院 - 動力機械工程學系
Department of Power Mechanical Engineering
論文出版年: 2004
畢業學年度: 92
語文別: 英文
論文頁數: 77
中文關鍵詞: wet etchingvertical comb drive actuators<110> siliconV-shape springKOH
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  • 在光學微機電的領域裡,微掃描面鏡是其中應用最廣泛且最重要的一個基礎元件。像是可應用在光調變(optical modulator)的光開關(optical switch),光遮斷器(optical chopper)和光快門(optical shutter),或是具光掃描功能的掃描器(scanner),條碼讀取器(barcode reader),甚至可整合於光對準(optical positioning)等等。
    然而,傳統上利用面型微加工技術所製作的微掃描面鏡,卻因為受限於犧牲層的厚度而無法達到較大的旋轉角度,另外在做高頻掃描時也因為鏡面較薄,容易產生動態變形而影響到掃描的解析度。於是,我們利用<110>矽晶圓在濕蝕刻製程後會產生垂直<111>晶格面的特性,設計出一個整合垂直梳狀致動器的微掃描面鏡,此元件擁有一般垂直致動器低電壓大旋轉角度的優點,更具有製程上較為單純且便宜的優勢。另外,我們更利用硼擴散的技術製作支撐的V型彈簧來減少高電壓致動所可能引起的側向吸附(stiction)現象。
      本研究已完成大部分的理論分析並加以數值模擬來輔佐應證,如垂直梳狀致動器上下電極間隔與靜電力的關聯,V型彈簧角度在垂直掃描與水平旋轉的彈力係數比的最佳化等等。另外,在製程方面遇到的許多濕蝕刻上不穩定的問題,我們也在此論文全部整理出來並一一提出解決之道。雖然在最後一道製程屢次因一些外在因素而導致失敗,不過仍可證明了此元件的可行性,相信在不久的將來就可以將此元件順利完成。


    Scanning micromirrors are one of the key components in MOEMS (Micro-opto-Electro- mechanical systems). They have been applied for a variety of applications such as optical switches, optical data storage, barcode readers, laser printers and image displays. Micro scanners via various MEMS techniques generally have the advantages of low power consumption, high speed actuation, compact size and low cost due to batch fabrication.
    Compared with surface type micromirrors, bulk micromachined scanning mirrors have many advantages such as larger scan range and thicker mirror. Therefore, in this research we present a novel <110> micromirror with vertical comb-drive actuators via wet etching to simplify the process with low cost process but still hold high performance. The springs are formed by boron diffusion that can make silicon resistive to KOH etching. Our device targets for a wide-angle but low cost scanning applications.
    We have done most of the theoretical analyses and numerical simulations including the relationship between electrostatic torque and vertical gap of vertical comb actuators, the optimum tilt angle of V-shape springs. Finally, we demonstrate the feasibility of the <110> scanning mirror with vertical comb actuators. This research covers most of fundamental studies and gives some suggestions and comments for the future design.

    Chapter 1 Introduction 1-1 Background........................................1 1-2 Literature of Vertical Comb-drive Actuators.......2 1-3 Motivation and Goal...............................6 Chapter 2 Design Concept 2-1 Characteristic of anisotropic wet etching........12 2-1.1 Orientation of <110> wafer.....................12 2-1.2 Characteristic of KOH etchant..................13 2-1.3 The Influence of Boron Diffusion in KOH Etching.15 2-1.4 Comparison of Anisotropic Wet Etchants.........17 2-1.5 Fan-shape Alignment Key........................18 2-1.6 Length Etching rate of <110> beams.............19 2-2 Fabrication Process..............................20 2-2.1 Original Fabrication Process...................20 2-2.2 Modified Fabrication Process...................21 Chapter 3 Theorem Analysis and Simulation 3-1 Theorem Analysis.................................33 3-1.1 Electrostatic Torque...........................33 3-1.2 The Design of V-shape Springs..................37 3-1.3 Optical resolution.............................40 3-2 Simulation Results...............................43 3-2.1 Simulation Results of <110> Si Wet Etching.....43 3-2.2 Effect of Vertical Gap.........................44 3-2.3 Simulation of V-shape Spring...................45 3-2.4 Device Performance.............................45 Chapter 4 Experiment Results 4-1 Etching Performance..............................59 4-2 Problems and Discussions.........................60 4-3 Experiment result................................63 Chapter 5 Conclusions & Future Work..................71 References............................................74

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