靜電式微功率產生器之最佳化設計與改良

Abstract

近年來微機電系統科技已成為世界各國於半導體產業之後相繼追求的新興整合型科技產業。目前各種微機電系統的發展均以和IC整合為最終目標。在此技術層面應用上，每一個節點的模組也都可能有獨立電源的需求。拜先進的低功率超大型積體電路與CMOS技術，元件的電能需求已降至數十μW的等級。因此，利用微機電技術將環境中的能源轉換成電能已成為一種可行的方式。 本論文將有別於前幾代的元件結構，針對無外加質量球的元件來做最佳化功率的設計，利用理論模型及分析找出最佳的參數來得到元件可輸出的最大功率。在l cm2元件面積及120 Hz操作頻率的限制下，元件輸出功率為0.51 μW (功率密度為 12 μW/cm3)，輸出電壓約5V，元件質量約36.5 mg。在製程方面，元件製作將針對上一代的漏電電阻問題進行改善，利用SOI 晶圓並搭配深蝕刻的製程，定義出梳指狀電極以形成電容，再經由外加振動源驅動來產生可變電容的改變，以達到電能轉換的功效。透過低壓化學絕緣層的沉積以及精確的遮罩定義金屬電極，使結構有良好的絕緣性以達到隔絕短路的效果。元件的共振頻率經由微機電動態干涉儀及激振器的測試皆符合設計值。經由電容放電時間常數的量測也顯示寄生電阻的改善。元件在3.33 MΩ□負載及182 Hz 振動頻率下，量到的交流輸出功率為17.5 nW，功率輸出的頻率問題已完成討論。此外，元件上機械式開關經由靜態和動態的量測也已完成測試。

In recent years, Micro-Electro-Mechanical System (MEMS) technology has become an emerging and integrated industry which every company in the world have been following after the IC industry. The goal of MEMS is the integration with circuits. Each node of module may have an independent power demand. Advances in low power VLSI and CMOS technology have reduced the power consumption of electronic devices to a few tens of microwatts. Therefore, it is feasible to scavenge and transform energy in the environment into electric energy. The optimal power design without external mass attachment which differs from the previous device was presented in this thesis. The optimal parameter was obtained by using theoretical model and analysis in order to get maximum output power. With a device area constraint of 1cm2 and operation frequency of 120 Hz, the output power was 0.51 μW (power density of 12 μW/cm3), output voltage was 5 V, and the mass of device was about 36.5 mg. The leakage resistance of the previous device was improved. The device was fabricated in SOI wafer by deep silicon etching technology. The comb finger structure was defined to form a capacitance. The capacitance variation was caused by the external vibration source in order to convert the electrical energy. By depositing LPCVD isolation layer and defining electrical pad with an accurate shadow mask, the device has better isolation and the leakage problem removal. The resonant frequencies measured by MMA and shaker agreed with the design value. Parasitic resistance improvement was verified by the discharge time constant measurement. The measured AC output power was 17.5 nW with a load of 3.33 MΩ□and frequencies of 182 Hz. The issue of the frequency of AC power was discussed. Finally, the mechanical switch on the device was tested.