二維頻率偏移式微型加速度計結構設計

Abstract

此研究提出了一個雙軸加速度計，它具有以線性響應來反應所感測到之加速度，高抗擾動之結構剛性來減低發自垂直於感測方向之加速度或重力所造成的形變影響，結構對稱性以有效解耦平面加速度，以及對加速度具有高偵測靈敏度等優點。而它的設計考慮便是以頻率偏移原理，高深寬比結構設計，結構幾何對稱以及尺寸最佳化來達成上述的優點。另外，UV-LIGA製程則被採用，藉以驗證此型結構的製作可行性。結果是，在所提出的振動式雙軸加速度計的模擬範例中，其響應之線性誤差小於4%，因重力造成的結構變形小於0.01微米，跨軸靈敏度小於0.002%，而感測靈敏度則可藉尺寸最佳化而被提升到8%/G。此外，由於此結構優異的解耦特性，所推得的一維解析模型也可以用來推算受測的二維平面加速度。至於所採用的UL-LIGA製程則可製作出，深寬比大於5，細長比大於100，而絕對尺寸為4×20×500 µm的鎳材電鍍結構。由此等結果相較於早先提出的加速度計，可了解所提的振動式雙軸加速度計確實在性能上被顯著的提升，並且可以用簡單，經濟的製程來製作。

This research proposes a structure of a 2D frequency shift microaccelerometer with good characteristics on linear response to respond the detected acceleration, high structure rigidity to resist influence from non-sensing axis acceleration, geometry symmetry to decouple a planar acceleration, and high sensitivity for sensing acceleration. In this design, the frequency shift principle, structure with symmetry geometry and also high-aspect ratio and the dimension optimization are adopted to fulfill the mentioned advantages. The results show that, the response linearity error for the simulated illustration is less than 4%, the deformation of the proof mass along gravitation direction is smaller than 0.01 µm, the cross-axis sensitivity is negligible less than 0.002%, and the sensitivity could be raised to 8%/G after dimension optimization. In addition, owing to the superior decoupling capability, the derived 1D analytical model can successfully calculate the sensed 2D planar acceleration. On the other side, the fabrication result of the adopted UV-LIGA process shows that, a 4 (w) × 20 (h) × 500 (l) µm nickel microbeam with high-aspect ratio 5 and slender ratio larger than 100 can be electroplated. In contrast to the previous design, the proposed 2D frequency shift microaccelerometer structure has a significant performance promotion and can be fabricated by using a simple and economic process.