靜電式振動電能轉換器之改良與測試

Abstract

微機電系統MEMS 是以半導體產業中的平面製造觀念為基礎的一種整合技術。微機電系統中的各種感測器或致動器的發展，均以和IC整合而形成智慧型的模組或系統作為最終目標。當微系統的技術越來越成熟時，各種利用微感測器或微傳感器所形成的智慧型網路或系統應用也隨之而生。在這些應用上，每一個標器或節點的模組都可能有微型獨立電源的需求。拜先進的超大型積體電路與CMOS技術所賜，現今這些微系統節點的電能需求已降至數十μW的程度。因此，利用微機電技術將環境中的能源轉換成電能來取代傳統的電池會是一個具有吸引力的方法。 靜電式振動電能轉換器可將生活中普遍存在的振動轉換為可用之電源，其運作原理在於，利用由振動驅動的可變電容器的改變，搭配直流電壓源產生電流輸出。轉換器的核心可變電容是利用SOI晶片搭配深蝕刻製程，製造梳齒狀電極而成。本實驗室先前已完成此轉換器之設計與製造，然而，系統分析及模擬並未考慮輸出端負載的效應，輸出電壓過高也造成無法與後端功率管理電路相容，而製作完成的元件因為寄生電阻電容的存在影響了轉換器特性，因此，根據先前的經驗和實驗結果，本篇論文的重點在於此轉換器之改良與測試。 系統分析及模擬平台已經修正，第二代元件的設計、製作流程及測試平台亦完成改良。根據設計，轉換器在3.3 V的輸入電壓下，考慮8 Mohm的輸出負載，輸出功率能達到200 μW (功率密度每立方公分105 μW)，以及約40 V的輸出電壓。元件成品大小約0.8x1.4x1.7 cm3。雖然製程良率太低導致經過機械特性測試之後，沒有元件能夠進行輸出功率量測，但透過更完整的振動測試已得到元件共振頻率與振幅。元件的電性量測也顯示，寄生電容和電阻並不存在。此外，製程條件的影響和良率過低的原因也完成討論。

Micro-Electro-Mechanical System (MEMS) is a technology platform based on the planar fabrication processes in the IC industry. The goal of MEMS actuators and sensors is the integration with circuits to form a smart module or system. Recent advances in the CMOS technology have reduced the power consumption of the micro system nodes to tens to hundreds of microwatts. Therefore, it is attractive to scavenge and transform the energy in the environment into electric energy. An electrostatic vibration-to-electric energy converter can convert vibrations into electric energy. The device produces an current output from a DC voltage source. The core of the converter is a variable capacitor formed by comb fingers fabricated in a SOI wafer with DRIE processes. In our previous work, the effect of load on the output port was not considered in the device design. The output voltage was too high to be compatible to the power management circuit. Besides, parasitic conductance affected the characteristics of the fabricated device. Therefore, this thesis focuses on the improvement and testing of the electrostatic vibration-to-electric energy converter. In this thesis, system analysis and simulation were improved for the design of the second generation device. The measurement setup and new fabrication processes were also developed. For the 3.3 V supply voltage and the optimal load of 8 Mohm, the output power was 200 μW with the output voltage of 40 V. The fabricated device had a size of 0.8x1.4x1.7 cm3. The low yield of device fabrication caused no device with fine electrical properties to survive, and thus the output power measurement could not be conducted. However, the complete mechanical characteristics were recorded, and the unwanted parasitic conductance was eliminated. Finally, explanations for the problems in the fabrication as well as proposed solutions are discussed.