單晶片微機電諧振結構完成之環境溫度感測器設計

Abstract

本論文提出可於標準CMOS 0.18μm 1P6M電路製程下，完成用於環境溫度感測之電容式微機電諧振器。在這個製程下，可以將驅動和讀出電路整合微機電諧振器於單晶片上，而不需要任何晶圓代工廠外的後製程步驟。本論文提出的諧振器之共振頻率被設計成與環境溫度變化呈線性關係，由鎖相迴路提供穩定的時脈來驅動諧振器，也利用鎖相迴路追蹤頻率、鎖定相位的特性，判別出具有溫度資訊的頻率飄移。本論文也提出了具高增益的振幅放大電路的設計，將諧振器輸出的小電流轉為方波電壓訊號，以利鎖相迴路中的相位頻率偵測器能夠準確判讀。 本論文提出的諧振器之量測結果如下，當壓力為760torr時，共振頻率為38.66kHz，有最大位移為648nm，品質因素為183；梳狀電容的覆蓋面積高達407.6μm2以上，代表初始電容值有高於模擬結果的92個百分比。環境溫度計的共同模擬結果如下，在-40~120°C的範圍，靈敏度為-5.7Hz/°C (-143ppm/°C)或-0.228V/°C，解析度為0.67°C。鎖相迴路電路功耗為17.23μW，而整體讀出電路的功耗為190.36μW。

A Micro Electro Mechanical Systems (MEMS) resonator that can be manufactured and monolithically integrated in the ASIC-compatible 0.18μm 1-poly-6-metal (1P6M) standard complementary metal-oxide-semiconductor (CMOS) process is proposed for measuring environmental temperature. It could be monolithically integrated with CMOS driving and readout circuitry without the need of any post-processing after fabrication from the foundry. The resonant frequency shifts designed proportionally to temperature variation. The phase locked loop (PLL) circuitry provides a stable clock to drive the resonator, and it can track the resonant frequency shifts due to the environmental temperature changes. A high-gain amplitude enhancement circuit is presented to transfer the small current from the resonator output to square wave voltage for the phase frequency detector of PLL proper functioning. The measurement results of the proposed resonator have been demonstrated that the maximum displacement was 648nm when the frequency was 38.66kHz under pressure being 760torr. The calculated Q-factor was 183, and the overlap area of comb fingers is larger than 407.6μm2, which represents more than 92% initial capacitance. The co-simulation result of the proposed resonator-based environmental temperature sensor has been demonstrated with a sensitivity -5.7Hz/°C (-143ppm/°C) or -0.228mV/°C and resolution 0.67°C in a temperature range from -40°C to 120°C. The power consumption of the PLL is 17.23μW and overall readout circuit is only 190.36μW.