鐵鉑薄膜之磁性質及其阻態變化之應用

本文透過調控快速真空退火製程，在矽/二氧化矽基板上使鐵鉑薄膜在2, 3, 4.5奈米的厚度下序化並達成(001)優選取向。並在矽/二氧化矽基板，以鐵鉑作為底電極下在4.5奈米鐵鉑達成垂直異向性，以提供異常霍爾量測上進行進一步的量測。元件製作上透過黃光微影製程製作了鐵鉑薄膜作為層霍爾十字，並以二氧化矽、氧化鎂/二氧化矽作為絕緣層的元件。透過氧化鎂/二氧化矽以及二氧化矽絕緣層作為施加電場的介電層，進行異常霍爾效應量測，發現異常霍爾電壓以及矯頑磁場並未隨施加電壓以及時間有顯著改變，推測可能原自於較厚的鐵鉑薄膜以及電場屏蔽效應的影響，造成電場效應不顯著。另一方面透過金屬遮罩製作的元件上，絕緣層使用鈦酸鍶作為絕緣層，並以鉑、鐵鉑作為底電極，鉑作為頂電極。發現了透過不同的形成過程(forming process)可以達到單極性(uni-polar)以及雙極性(bi-polar)的阻態變化行為，並在IV量測上看到類似鐵電特性的曲線，以供後續進一步的研究確定此類似鐵電的性質是否為真正的鐵電特性。

關鍵字

鐵鉑；電場控制；磁記憶體；電阻式記憶體；鈦酸鍶；鐵白金

並列摘要

The electric field control of magnetism has drawn a lot of attention due to the need of reducing writing current densities on MRAM devices. This thesis focus on tuning FePt for ordering and (001) preferred orientation. On Si / SiO¬2 ¬ substrates, we tune the rapid thermal annealing process and FePt composition and introduce FeOx as capping layer or underlayer. We obtain ordering in FePt films of thickness 2, 3, and 4.5 nm with (001) preferred orientation. The reduction of FeOx to Fe on rapid thermal annealing process promotes the diffusion of Fe and Pt atoms, which leads to a better (001) preferred orientation. The perpendicular anisotropy is suit for analogous Hall measurement, which is often needed after device patterning and further spin Hall angle measurement. FePt on Pt 5 nm electrode also achieve perpendicular anisotropy by inserting ultrathin SiO2 insertion layer. The insoluble SiO2 insertion layer will diffuse through gran boundaries of FePt during rapid thermal annealing process and also promote the diffusion of Fe and Pt atoms. That leads to a lower ordering temperature. The RRAM characteristic of SrTiO3 dielectric layer is also tested. With different forming process, SrTiO3 can achieve unipolar switching and bipolar switching. The ferroelectric like IV curves also been observed. Further examination is needed to ensure the properties of SrTiO3 is ferroelectric or not. The cycling test and retention test shows stable RRAM characteristic of SrTiO3.

並列關鍵字

FePt ； E field control ； MRAM ； RRAM ； SrTiO3

參考文獻

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[4] Liang-Wei Wang, Wen-Chieh Shih, Yun-Chung Wu, and Chih-Huang Lai, ” Promotion of [001]-oriented L10-FePt by rapid thermal annealing with light absorption layer” Applied Physics Letters, vol. 101, p. 252403, 2012

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[9] Wang Kang et al. Voltage-Controlled MRAM for Working Memory: Perspectives and Challenges 2017 Design, Automation and Test in Europe (DATE), At Lausanne, Switzerland

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鐵鉑薄膜之磁性質及其阻態變化之應用

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