具垂直異向性的鈷鐵硼/氧化鎂之高熱穩定性結構研究

Perpendicular-anisotropy CoFeB/MgO free layer with high thermal stability structure

蔡弘益(Tsai, Hung Yi)

指導教授 ： 賴志煌

國立清華大學/工學院/材料科學工程學系/碩士(2016年)

摘要

本論文探討以具有垂直異向性之鈷鐵硼/氧化鎂作為自由層，量測不同尺寸元件之熱穩定性，及熱穩定量測之實驗架設。此外，製備出具較高熱穩定性之雙層鈷鐵硼結構試片。並進一步量測通入電流後因為Rashba效應和自旋霍爾效應產生的有效磁場以及臨界翻轉電流。
磁性質部分，藉由鈷鐵硼厚度的調整和退火條件達到最佳垂直異向性。接著鍍製雙層鈷鐵硼薄膜部分，藉由調控下層鈷鐵硼厚度和中間層鉭的鍍膜條件，得到MS*t上升較多，HK不會衰減的雙層膜結構。
微小化製程部分，藉由黃光微影製程和電子束微影製程搭配乾式蝕刻製作霍爾十字架結構，以異常霍爾效應得到霍爾電壓訊號藉以量測小尺寸元件之性質。
熱穩定性量測主要以脈衝磁場翻轉機率和動態矯頑場法為主，量測微米尺寸和奈米尺寸元件，並分析其中的關係。最後比較單層鈷鐵硼結構和雙層鈷鐵硼結構通入電流後產生的有效磁場和臨界翻轉電流。

關鍵字

熱穩定性 ； 鈷鐵硼 ； 氧化鎂 ； 臨界翻轉電流密度

並列摘要

This work has been focused on the deposition of perpendicular-anisotropy CoFeB/MgO free layer, measurement of thermal stability in different size devices, and the experimental setup of measuring thermal stability. Moreover, develop a new double CoFeB structure with higher thermal stability. Then, evaluate the effective field when a current passed and the threshold switching current density.
In the single CoFeB layer, I have tuned the thickness of CoFeB and the condition of annealing to get the better perpendicular anisotropy. After that, I have tuned the thickness of bottom CoFeB and sputter condition to get a double CoFeB structure with higher MS*t and a constant HK value.
In order to fabricate different size devices, I have used photolithography and E-beam lithography to pattern the Hall cross structure. I would like to use the Hall voltage which had been measured by AHE to investigate the properties of small-sized devices.
I mainly used pulse magnetic switching probability and dynamic coercivity method to measure the thermal stability of micro-sized and nano-sized devices. In the last part, I would like to compare the effective field and threshold switching current density between single CoFeB and double CoFeB structure.

並列關鍵字

thermal stability ； CoFeB ； MgO ； threshold switching current density

參考文獻

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