本研究以微機電技術為基礎，提出一高音壓電式微型揚聲器設計，目標取代入耳式耳機市場中的磁致動單體。儘管多數文獻以低驅動電壓下達到市場需求的聲壓等級，然而頻寬普遍不足，因此本研究以懸臂式振膜多單體的結構特性，於3 x 3 mm2的有效振膜面積限制內設計八片三角懸臂振膜，並調整幾何尺寸與邊界條件等兩種設計手法改變各自振膜的剛性，增加元件的共振頻率數目，拓展聲壓等級目標以上的頻寬表現。然而相關文獻已提到多剛性陣列單體於正常驅動時面臨相位問題，使得相鄰頻率響應極點之間的聲壓驟降，因此沿用文獻中的反相驅動法改善此缺點，提升頻寬內的聲壓表現。本研究使用已沉積壓電薄膜PZT之SOI晶圓，藉壓電製程平台批量製作出微型揚聲器單體。於人工耳系統中通以0.707 Vrms輸入電壓，並以90 dB聲壓等級界線劃分頻寬界線，反相驅動後頻寬將預期達到4 kHz至14 kHz，實現拓寬目標聲壓以上之頻寬，成功實現小體積、低功耗、高聲壓與寬頻寬等多項優勢的高音入耳式應用微型揚聲器。

This study has presented a design of a piezoelectric microspeaker with wide bandwidth. The device features small size and low power consumption due to the MEMS technology with piezoelectric materials, targeting in ear applications, such as earphones, to replace traditional microspeakers nowadays. Many researchers have proposed piezoelectric MEMS microspeaker design, however, the bandwidths with sufficient SPL are not wide enough. The study takes the advantage of multi-way unit by designing cantilever type microspeaker to enhance the bandwidth. Eight different stiffness of triangular cantilevers have been implemented on the active area of 3 x 3 mm2. The design methods can be separated into two ways. Four of the cantilevers are adjusted by the length of the units, and the other four are revised by creating slits at the anchors. It is anticipated that the multi-way device faces phase issue and SPL cancellation. Therefore, the proposed microspeaker will be driven by the out-of-phase driving method from the literature. It was fabricated from a PZT thin film on SOI wafer with piezoelectric standard platform. The bandwidth with SPL over 90 dB is from 4 kHz to 14 kHz by 0.707 Vrms driving signal in the ear simulator, which shows promising performance with small size, low power consumption, high SPL with wide bandwidth at high frequency range.

摘要 I
Abstract II
誌謝 III
目錄 VIII
圖目錄 XII
表目錄 XIX
第一章 緒論 1
1-1 前言 1
1-2 文獻回顧 5
1-2-1 靜電式 5
1-2-2 動圈式 8
1-2-3 壓電式 10
1-3 研究動機 19
1-4 全文架構 21
第二章 元件設計與聲學性能 38
2-1 聲學參數 38
2-1-1 聲壓等級 38
2-1-2 量測場域 39
2-1-3 總諧波失真 41
2-2 壓電材料 42
2-2-1 逆壓電效應 44
2-2-2 製備方法 45
2-3 設計概念 46
2-3-1 壓電材料選擇 47
2-3-2 高頻振膜 49
2-3-3 振膜幾何形狀 52
2-3-4 元件外觀與尺寸 53
2-3-5 中央三角懸臂振膜設計 55
2-3-6 外圍三角懸臂振膜設計 56
2-4 聲學表現及模擬結果 57
2-4-1 頻率響應 59
2-4-2 反相驅動法 60
第三章 製程流程與結果 76
3-1 製程流程 76
3-1-1 壓電層濕蝕刻製程 78
3-1-2 鉻金薄膜蒸鍍與上電極掀舉製程 79
3-1-3 白金下電極乾蝕刻 81
3-1-4 矽元件層乾蝕刻 83
3-1-5 背面深矽蝕刻 84
3-2 製程結果與討論 87
第四章 量測結果與討論 102
4-1 元件機械性能量測 102
4-1-1 介電常數與介電損失 102
4-1-2 楊氏模數 103
4-1-3 壓電係數 105
4-1-4 極化率—電場強度曲線 107
4-1-5 殘餘應力 108
4-1-6 元件共振頻率 111
4-2 元件聲學性能量測 112
4-2-1 頻率響應 113
4-2-2 線性度 116
4-2-3 總諧波失真 117
第五章 結論與未來工作 136
5-1 結論 136
5-2 未來工作 137
5-2-1 封裝與聲學表現 137
5-2-2 製作與初步量測結果 139
參考文獻 146
附錄A 空氣耦合 154
A-1 耦合背景 154
A-2 空氣耦合模擬 155
A-3 空氣耦合量測 157

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