應用於指紋辨識之壓阻式壓力感測器 暨平行處理介面電路設計

Abstract

本論文提出可以在混和訊號微機電製程下，完成指紋辨識壓力感測器以及讀出電路設計。單一指紋辨識壓力感測器尺寸50μm×50μm 以符合指紋辨識影像解析度規格500dpi 操作範圍在0~1Mpa，採用壓阻式架構以改善電容式架構需要濕蝕刻後製程之缺點，在0~1MPa壓力範圍內電阻由23.55kΩ變化至24.6kΩ，電阻變化範圍0~1.05kΩ隨壓力呈現線性變化，靈敏度為1.05kΩ/MPa。 我們提出平行化處理技術，用以讀取指紋感測器陣列並增加讀取速度，採用電阻轉時間以及時間轉數位電路完成電阻轉數位電路，靈敏度為318.04(digits/ kΩ)，在不須任何類比轉數位電路情況下，能將輸入壓力範圍轉出為數位訊號，以便後續數位訊號處理。

A monolithic fingerprint pressure sensor with integrated resistance to digital readout circuit in 0.18um CMOS MEMS process is proposed to demonstrate sensor to bit integration. The sensing range of the fingerprint pressure sensor is designed from 0~1MPa and the variation of the resistance is from 23.55kΩ to 24.6kΩ, the resistance difference in sensing range is 0Ω to 1.05kΩ. The sensitivity of the pressure sensor is 1.05kΩ/MPa. The resistance value of the sensing range is readout by the resistance to pulse-width circuit to readout. We proposed the parallel processing to readout the fingerprint pressure sensors array and increase through put rate, it composed of resistance to pulse converter and time to digital converter with sensitivity 576.8(digits/ kΩ). Therefore, without any analog to digital module, the output signal can be directly interface to digital signal process by the time-to-digital converter. In order to get the accurate value of monolithic front-end circuits, the computer aided design flow for MEMS and IC integration is used to co-simulate the and to provide comprehensive analysis of the difference between the simulation and the measurement results.