臺灣博碩士論文加值系統

本文完成多層堆疊電容式麥克風的設計、製作與特性分析。以矽製程微機電系統技術為基礎，完成微結構相關特性模擬分析後，設計不同尺寸與多樣式結構的電容式麥克風，相關電容式麥克風製程由MEMSCAP協助完成。本文基於最佳化設計之結果完成晶片尺寸的設計、利用半導體製程製作以及電腦來進行模擬分析對照，最後再進行封裝及性能測試，以不斷改善麥克風設計來適應工業界嚴格之需求。此外，關於電容式麥克風特性的量測。在雷射都卜勒的動態檢測中，可以明顯的觀測橫隔薄膜受到聲壓而產生的規律振動，其振動的最大位移量約在１微米之間，在頻率響應的量測中，可以發現雜訊對其元件的干擾影響，在經由治具的改善與放大器的增益輸出後，應可以得到一個完整訊號的頻率響應曲線，在取樣頻率1 kHz時，約可得到-80 dB/Pa的增益輸出（ref. to 0.1mV/Pa）。經由量測結果證實，此微電容式麥克風簡單的微機電結構與高靈敏度的特徵是能夠被預測的。未來工作將研究改善犧牲層蝕刻的長時間釋放技術，並調整元件微機電結構設計，使具高靈敏度的薄膜應力變化感測效能，以期能建立微感測器相關技術於日後的應用中。

The multi-layer stacking capacitive types of microphones are designed and fabricated based on theoretical analysis, simulations and silicon-based MEMS fabrication technology. The microphones in different physical sizes and functional structures are designed on the same chip. Micro-fabrication of the micro-microphones has been performed by the MEMSCAP Company. The MEMS microphone had been produced based on the optimum design and analysis. Two approaches are adopted in experimental validation --- one under static input voltage while another subjected to vibratory sound in wide frequency range. In the case with 6 Pa sound pressure applied to the membrane, the largest displacement of 1 m over the entire membrane is measure by a laser Doppler vibrometer, and furthermore pull-in phenomenon is present with acquisition of corresponding pull-in voltage and membrane deflection. In the second case with vibratory sound as the excitation, the frequency responses are obtained with moderate levels of noise present, giving less satisfactory sensitivities of the manufactured microphone. This is probably due to high residual stress remained inside the membrane. This residual stress is primarily caused the heat release from bulk micro-machining etching process on the backplate. When the sampling frequency reaches 1 kHz, gain output is about -80 dB/Pa (ref. to 0.1mV/Pa). Future works should be focused on developing the fabrication process to reduce residual stress for improving long-term sacrificial layer release etching technology and to adjust microstructures for compensating non-specific effects reduced film stress variations.

Table of Contents
Figure Captions I
Table Titles V
1 Introduction 1
1.1 Introduction 1
1.2 Literature Review of Miniaturized Microphones 2
2 Theory and Modeling 6
2.1 Microphone performance simulation using equivalent circuit method 6
2.1.1 Sensitivity Analysis 6
2.1.2 Pull in Voltage evaluation 7
2.2 Structure simulation using FEM 12
2.2.1 Modeling 12
2.2.2 Numerical Results 15
3 Fabrication Process 17
3.1 Sacrificial Layer Technology 17
3.2 Introduction to the MUMPs™ Process 18
3.3 Design Features 19
3.4 The manufacturing process result explains 21
4 Measurements 22
4.1 Microphone characteristic 22
4.2 Pull-in voltage measures results and discussion 23
5 Conclusions and Future Works 24
References 26
Figures 29
Tables 72
簡歷 73

Figure Captions
Fig. 1 Several read out techniques for micromachined silicon microphones: (a)
piezo -electric, (b) piezoresistive, and (c) capacitive.
Fig. 2 Design of silicon condenser microphone which can be use for feedback.(a)
top view showing the electrode configuration for actuating the membrane, (b)
cross section of the microphone.
Fig. 3 Schematic cross section of a single wafer fabricated silicon condenser
microphone.
Fig. 4 Fabrication process of a polyimide condenser microphone
(a) Deposition of Cr/Pt/Cr diaphragm electrode and polyimide diaphragm.
(b) Deposition of Al sacrificial layer and Cr/Pt/Cr backplate electrode.
(c) Deposition of polyimide backplate and Cr etchmask on the back of the
substrate.
(d) Etching of sacrificial layer and substrate.
Fig. 5 (a) Cross section of the polysilicon diaphragm condenser microphone.
(b) Equivalent electrical circuit of the condenser microphone.
Fig. 6 Calculated sensitivity frequency response for a 2 mm microphone with (a) 400, (b) 256 backplate holes/ .
Fig. 7 Linearization of the electrostatic force about zero displacement.
Fig. 8 (a) Lumped parameter model of a parallel plate transducer and (b) its equivalent circuit.
Fig. 9 The relation between central deflection and the bias voltage(square).
Fig. 10 The computed electric field and potential distribution in the quarter
condenser microphone.
Fig. 11 (a) Schematic TRANS126 element (b) TRANS126 Electro-mechanical
Transducer Element.
Fig. 12 The diaphragm is meshed with four node Solid 45 element. And the top and
bottom electrodes are separated by air gap, which is modeled using distributed TRANS126 transducer element.
Fig. 13 The membrane deflection of the diaphragm for 13 DC bias voltage.
Fig. 14 The membrane deflection of the diaphragm for 20 DC bias voltage.
Fig. 15 The relation between central deflection and the bias voltage (squared).
Fig. 16 Overview of PolyMUMPs
Fig. 17 Overview of SOIMUMPs
Fig. 18 Type 1 Condenser Microphone standards
Fig. 19 Type 2 Condenser Microphone standards
Fig. 20 Type 3 Condenser Microphone standards
Fig. 21 Type 4 Condenser Microphone standards
Fig. 22 Type 5 Condenser Microphone standards
Fig. 23 Type 6 Condenser Microphone standards
Fig. 24 Type 7 Condenser Microphone standards
Fig. 25 Type 8 Condenser Microphone standards
Fig. 26 Type 9 Condenser Microphone standards
Fig. 27 Simplified fabrication process of the microphone.
Fig. 28 MEMS PRO Layout.
Fig. 29 One chip contains nine kind of different shapes microphones. In term of the
size of microphone, it is the smallest. This is because that the size has
something to do with sensitivity.
Fig. 30 As the above diagram has shown, the identification was done on the DRC.
Fig. 31 Miniature microphones of nine different mechanical structure, the area of
each chip: 1Cm X 1Cm (One chip contains nine kinds of different shapes
microphones).
Fig. 32 (a) and (b) is the optical microscope . (c) The place where the light focuses
is the position of miniature microphone.
Fig. 33 Close up view of the back plate and holes.
Fig. 34 Observe the RIE based upon the ICP process has approached 90° sidewall
profiles possible through wafer by using the scanning electron microscope.
Fig. 35 Observe the accomplished sound hole structure on the backplate by using
scanning electron microscope (SEM).
Fig. 36 The back side situation of the condenser microphones.
Fig. 37 Show the measured capacitance versus bias voltage of the microphone with
a 2 mm diaphragm.
Fig. 38 With 6 Pa sound pressure applied to the membrane, the largest displacement
of 1 m over the entire membrane.
Fig. 39 2671 B&K Microphone Preamplifier standard.
Fig. 40 Block diagram of the microphone measurement setup.
Fig. 41 Frequency response of a 2.0 mm wide microphone (a) With a bias voltage of
4.5 V, the microphone exhibits sensitivity between -65 and -58 dB from 100 to 10 KHz. (b) With a bias voltage of 2 V, the 2 mm-wide microphone has a sensitivity between -58 and -64 dB.
Fig. 42 The laser Doppler vibrometer measurement system. In this case with static input voltage applied to the membrane, different displacements over the entire membrane is measure by a laser Doppler vibrometer.
Fig. 43 Comparison of Analytical, FEA, and Experimental Deflection Results. (Consider 100 MPa residual stress remained inside the membrane)

Table Titles
Table 1：Material Parameters and Microphone Dimensions.
Table 2：Cahnged the depth of Anchor 2 in the process of the PolyMUMPs from the
previous 2 to 3.75 . This change will increase the airgap value to prevent the collapse phenomenon

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