單晶片雙軸電容式微加速規的改進與測試

Abstract

本論文研究重點在於承接先前所提出對稱式線圈型懸吊雙軸微加速度計，並加以改進結構與製作流程、整合電路與機械結構並量測電性輸出，致力於完成單晶片電容式微加速規的開發。 結構設計上，使用差動式感測懸臂來作電容的感測，且沿用對稱懸吊結構，但是在感測懸臂設計上屏棄先前單邊固定並提供應力補償的設計，而改採用兩端固定的設計以確保完全去除側向沾黏。同時為了減低殘留應力值和部分製程缺陷，再次修改製作流程，並訂定製程規範，確定製程的穩定性。 製程結果量測方面，結構尺寸部分的量測將用到本實驗室之電子顯微鏡及三維輪廓量測儀。結構翹曲量部分則由國家晶片系統設計中心提供之白光干涉儀(white-light interferometer)來量測，而頻率響應部份則透過國家晶片系統設計中心的微機電系統動態分析儀(MEMS Motion Analyzer, MMA)來量測。 在輸出特性方面，兩軸動態範圍在±5G時，靈敏度即可達300mv/G，而兩軸偶合度約有15%符合當初所訂定之規格，同時所設計的自我測試致動器在製作及測試有效，並可提供靜電力使質量塊產生一微小的位移。而封裝測試方面，也初步達成封蓋的動作，未來將進一步開發完整封裝製程。

Based on the previous design of our group, with symmetric coil-type suspension in the micro accelerometer, here the fabrication process is further improved, sensing circuit and MEMS structure are integrated, and the electrical output signal are measured for the development of a single-chip capacitive micro accelerometer. For the structural design of micro accelerometer, differential sensing pair we used to achieve the capacitive measurement. In order to reduce side stiction, the sensing fingers are fixed at both ends in current design. At the same time, fabrication process is modified to reduce residual stress of polysilicon structure and the flaws during the whole process. For the result of the fabrication process, scanning electron microscope (SEM, NCTU) and 3D profiler (ET-4000, NCTU) are used to measured geometric sizes of fabricated accelerometers. The optical profiler (white-light interferometer, CIC) and MEMS motion analyzer (MMA, CIC) are used to characterize the deflection of proof mass and the dynamic response of accelerometer, respectively. For the electrical signal output, sensitivity of dual-axial accelerometers is shown to reach above 300 mv/G with the dynamic range of ±5G, however cross sensitivity is about 15%. The all signal self-test actuator is shown to successfully provide electrostatic force to move the proof mass. Currently, capping process of the micro accelerometer has been developed, and further package process in under way.