極低頻磁場對於晶圓廠製程之良率有不良的影響，當製程低於14奈米，極低頻磁場對製程與檢測設備之影響更為嚴重，因此晶圓廠針對易受極低頻磁場影響之設備，如電子顯微鏡SEMs、TEMs、STEMs、FIB writers、E-beam writers相關設備，強烈要求須在磁場強度低於0.6毫高斯的環境下運作。因此需透過主動或被動式磁場消除的方式，使環境磁場能低於0.6毫高斯以下。
本論文是專注在主動消磁系統研究，透過磁感測器、主動消磁原型機與赫姆茲線圈所組成。作法則是利用磁感測器偵測環境雜訊場，並將偵測到之訊號做簡易處理後，送入原型機做完整訊號處理，包含放大、反向、濾波等，最後將輸出訊號送至赫姆茲線圈，藉此產生一大小相等，方向相反之磁場，以抵消原環境雜訊場。
透過本論文實做之主動消磁系統，可將60赫茲、10.6毫高斯之環境雜訊場，消磁至0.8毫高斯，消磁率可達92.5%，對於100赫茲以及150赫茲，也能達到80%以上之效能。

The extremely low frequency (ELF) magnetic field has significant impact on yield rate especially while the processing is lower than 14 nanometer in nano-Fab. For sensitive equipments such as the SEMs、TEMs、STEMs、FIB writers, and E-beam writers, it suggests that the ELF magnetic field should be lower than 0.6 milli-Gauss to guarantee good yield. Therefore, mitigating the magnetic field by active/passive approaches such as the material shielding, wire permutation, or active canceling has been highly demanded.
This thesis focuses on the development of an active magnetic field canceling system which consists of sensors, current driven unit, and Helmholtz coils. First of all, a sensor is used to detect the magnetic field. A number of procedures such as amplifying, reversing and filtering are then involved to process the signals. Finally, the current driven unit, i.e. the power amplifier, delivers a reversed current to the Helmholtz coil to create a canceling magnetic field which is in equal magnitude but almost out of phase with respect to the environmental one.
According to our experiments, the prototype design is able to reduce the magnetic field intensity from 10.6mG to 0.8mG at 60Hz, the canceling also reaches 92.5% and 80% for 100Hz and 150Hz, respectively.

[1] Keita Yamazaki, Shigetaka Hirosato , Kazuhiro Muramatu , Masayuki Hirayama, Kiyotaka Kamata , Takanori Onoki , Koichiro Kobayashi, Akira Haga , Kazuhiro Katada, Yutaka Kinomura , and Yoshifumi Kuwayama ,“Open-Type Magnetically Shielded Room Using Only Canceling Coil Without a Ferromagnetic Wall for Magnetic Resonance Imaging,” IEEE Trans. On Magnetics, vol. 43, no. 6, pp. 2480-2482, jun 2007
[2] Takeshi Saito, “Features of a Wall With Open-Type Magnetic Shielding Method,” IEEE Trans. On Magnetics, vol. 44, no. 11, pp. 4191-4194, Nov 2008
[3] Pablo Moreno and Robert G. Olsen, “A Method for Estimating Magnetic Shielding by 2-D-Thick Planar Plates for Distribution Systems Shielding,” IEEE Trans. On Power Delivery, vol. 25, no. 4, pp 2710-2716, Oct 2010
[4] Y.-L. Song, C. Yu, F.-C. Chuang, Y.-C. Tseng, J.-Y. Zou, S.-K. Hsu, T.-G. Ma, T.-L. Wu, and L.-M. Chang, “Evaluation of magnetic field from varied permutation power transmission line at high technology nano-fab,” in Int. Conf. Power Electron. Systems Applications, Jun. 2011
[5] F.-C. Chuang, Y.-L. Song, C. Yu, S.-K. Hsu, T.-L. Wu, and L.-M. Chang, “Active field canceling system in next generation nano-fab,” in Int. Conf. Power Electron. Systems Applications, Jun. 2011
[6] Stefan Mayer Instruments “MR-3 Triaxial Magnetic Field Compensation System、Compensation coil design and system installation guide,” January 2003
[7] 劉人傑，「最新電子學寶典(下) 第三版」，鼎茂圖書
[8] Honeywell spec “3-Axis Magnetic Sensor Hybrid”
[9] Texas Instruments spec “TL071, TL071A, TL071B, TL072 TL072A, TL072B, TL074, TL074A, TL074B LOW-NOISE JFET-INPUT OPERATIONAL AMPLIFIERS”
[10] Linear Technology spec “LT1210 ,1.1A, 35MHz Current Feedback Amplifier”
[11] National Instruments spec “User Guide NI sbRIO-961x/963x/964x and NI sbRIO-9612XT/9632XT/9642XT Single-Board RIO OEM Devices”