本研究運用CMOS MEMS技術設計出電容式超音波感測器，特色
是整合電路和感測器於單一晶片，能有效的降低寄生電容。本研究製
作出電容式超音波傳感器並結合峰值感測電路（Peak Detection
Circuit），在傳感器接收到超音波並轉換為電壓訊號後放大並取樣峰
值，將峰值記錄形成數值表，並將數值對應影像之明暗度即可快速成
像。本研究所使用的製程為TSMC 0.18 m 1P6M CMOS Process，利
用該製程製作出超音波感測器，並沉積2.4 m之Parylene C做封裝，
感測器成功在水中進行超音波量測，實驗結果顯示感測薄膜之共振頻
率為3.8 MHz，感測頻寬為2.8 MHz，感測度為494.505 mV􀭮􀭮⁄MPa/V。
峰值感測電路以頻率為1 MHz 至 10 MHz、振幅為0.1 V至1 V之作測
試，輸入振幅為0.1 V至0.5 V之誤差在 ±20% 以內，輸入振幅為0.5 V
至1 V之誤差可降為 ±12% 以內。若峰值感測電路採用矯正機制可減
少峰值誤差，將可提升影像解析度，於醫療將有更大應用。

This work presents a capacitive ultrasonic sensor chip fabricated by
the 0.18-m CMOS-MEMS technology. The unique feature of this work
is integrating the circuit and the sensor on the same chip, which can
efficiently reduce the parasitic capacitance. The study combines
capacitive ultrasonic sensors with peak-detection circuits. Ultrasonic
waves produced by the photoacoustic effect are received by the sensing
pixels, followed by signal amplification, peak detection, and collection of
all the detected values. These values correspond to the brightness of the
image. The time for image production is significantly reduced. The
CMOS MEMS technology allows convenient signal processing to
enhance scalability of the array and sensor miniaturization to increase
image resolution. The structure is successfully released by wet etching
and sealed by 2.4-μm Parylene C. The fabricated capacitive ultrasonic
sensor is tested in water. The measured resonant frequency, band width
and sensitivity are 3.8 MHz, 2.8 MHz, and 494.505 mV􀭮􀭮⁄MPa/V. In the
experiment we successfully detect and hold the peak values by using
input signals with frequencies from 1 MHz to 10 MHz and amplitudes
from 0.1V to 1V. The errors are within ±20% for inputs from 0.1V to
0.5V. The errors reduce to less than ±12% when input voltage is from
0.5V to 1 V. The peak detection circuit design can be improved by the
calibration. Therefore, a better image resolution can achieved.

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