磁場感測器之研究

Abstract

在本論文中，我們分別從磁場感測器的元件結構及材料兩方面的改變 來探討其對靈敏度的影響。在結構方面，使用埋層通道金氧半場效電晶 體(Buried-channel MOSFET)結構來取代傳統的表層通道金氧半場效電晶 體(Surface-channel MOSFET)結構，因為其通道產生在基板內部而非在介 面上，可減少介面散射效應，故可提高載子移動率，實驗顯示當其應用於 磁場感測器時，可使靈敏度增加，雜訊減低。在材料方面，我們以超高真 空化學氣相沈積系統所成長的矽鍺異質結構應用於磁場感測器，因為在矽 鍺異質結構中會產生二維電洞氣體(2DH)而使載子移動率增加，亦可增加 靈敏度，實驗發現其靈敏度為一般矽基板磁場感測器的10至30倍。最後， 為了提高元件的靈敏度，我們在元件的背面鍍上一層磁性材料並探討磁性 材料厚度對靈敏度的影響。 In this thesis, we try to improve the sensitivity of magnetic field sensorsfrom two considirations: the structure and the material. Considering the structure, buried channel MOSFET devices are used to substitute for conventional surface channel MOSFET devices. Thanks to the separation between the conductingchannel and the interface, the surface scattering is avoided. Therefore, the mobility of buried channel devices is higher and we obtain higher sensitivity.In addition, the noise and the offset voltage of the buried channel devices aresmaller. Considering the materials, different types of Si/SiGe heterostructuregrowm by ultra-high vacuum chemical vapor deposition(UHV-CVD) are used. Due to the formation of 2DHG, the mobility in Si/SiGe is higher than the mobility in bulk Si. The sensitivity in Si/SiGe is 10 to 30 times better than that in bulkSi. Finally, the ferromagnetic materials are used to coat on the bottom of the devices. The sensitivity of coating devices is larger than that of uncoated devices.