具有數位輸出的CMOS MEMS電感式加速度計

CMOS MEMS Variable Inductance Accelerometer with Digital Output

劉軒吾(Hsuan-Wu Liu)

指導教授 ： 邱一 ； 洪浩喬

國立交通大學/電機學院/電機與控制工程系所/碩士(2018年)

摘要

本論文使用TSMC 1P6M 0.18μm CMOS MEMS製程設計出一個具數位輸出的電感式加速度計，此設計使用彈簧作為可變電感，並額外串聯一個High Q的電感，透過並聯一個固定的MIM電容形成一個LC振盪器，當晶片受到一個外部的加速度時，會使質量塊受力而產生位移，此位移會造成彈簧電感線圈面積的變化並使電感值改變，最後改變LC振盪器的頻率，且此頻率變化與加速度大小成正比，故可以透過輸出頻率的變化來偵測加速度大小。此外，本設計在晶片內加入一個計數器電路，頻率輸出可連接至計數器中做頻率計數，並將頻率輸出轉換為數位輸出，方便後續的量測與應用，同時避免使用外部的儀器量測造成額外的寄生效應影響感測器性能。量測結果顯示，震盪頻率為1.38 GHz，靈敏度為37.8 kHz/g。

關鍵字

微機電 ； 加速度計 ； 可變電感 ； 振盪器 ； 頻率輸出 ； 數位輸出

並列摘要

This thesis proposes an inductive accelerometer with digital output, which is fabricated by TSMC 1P6M 0.18μm CMOS MEMS process. In this design, the LC oscillator is composed of a variable spring-inductor which is connected with a high Q inductor in series and is paralleled with a MIM capacitor. When an external acceleration acts on the chip, displacement of the mass occurs and, at the same time, the spring-inductor area and inductance value change. The change of the inductance value causes the oscillation frequency changes. Furthermore, the changes of frequency and acceleration are in direct proportion. Therefore, the acceleration can be detected by the frequency change. In addition, a counter circuit is added in the chip. The oscillator output is connected to the counter for frequency counting which converts the frequency output to the digital output for subsequent measurement and application. The counter also avoids using the external instruments that may cause additional parasitic effects and affect sensor performance. In this thesis, the measurement result shows the oscillation frequency is 1.38 GHz and sensitivity is 37.8 kHz/g.

並列關鍵字

CMOS MEMS ； Accelerometer ； Variable Inductance ； Oscillator ； Frequency Output ； Digital Output

參考文獻

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