臺灣博碩士論文加值系統

MRAM是公認為極具潛力的新記憶體之一，其中所應用的主要元件為穿遂式磁阻元件。本論文主要探討穿隧式磁阻元件電磁特性之研究，首先了解在不同溫度下之多層膜磁性的變化，並運用電子迴旋共振離子蝕刻系統（ECR-IBE），透過光微影術、電子束微影術、鍍膜技術製作穿隧式磁阻元件，探討元件製成後不加外加磁場，改變不同退火對於磁阻變化量（MR%）的影響。並以掃描式電子顯微鏡及原子力顯微鏡了解蝕刻後樣品之表面型態，設法解決蝕刻所產生的反鍍以及反鍍造成的翹邊現象，並量測其MR%-V曲線特性及磁阻，探究製程中可能造成元件損害的因素。
在元件的製作過程中，離子蝕刻的反鍍容易造成穿隧式磁阻元件的短路，讓其無法達到穿遂的效果，因此我們利用高角度（離子束入射線與薄膜法線的夾角稱之）的蝕刻，來通過絕緣層，以期能達到反鍍最少；再者，加上高角度能夠蝕刻側邊，用此來清除反鍍。電子迴旋共振離子蝕刻系統為高密度均勻電漿，能達到蝕刻速率低，蝕刻範圍（直徑2cm）內均勻，對於元件的製成有很大的幫助。元件製成後的不加場退火，可以使上電極與元件的接合程度變好，降低整體的阻抗，但不會影響磁阻變化，進而提升MR%。隨著各種增加穿遂式磁阻元件穩定性的方式不斷地被研發，MRAM正式上市之期指日可待。

A new breed of magnetic random access memory (MRAM) based on a magnetic tunnel junction (MTJ) storage element has emerged as a promising candidate for nonvolatile memory application. The objective of this thesis is mainly to investigate the electric and magnetic properties of magnetic tunnel junction cells. Firstly, we get to know the magnetic property changes of multilayer under different temperatures. Though top-down processes, including electron beam lithography, photolithography, ECR ion-milling, reactive ion etching, sputtering and thermal evaporation, micron-patterned magnetic tunnel junction devices have been fabricated. We also investigated the influences on electric and magnetic properties of magnetic tunnel junction cells with different anneal temperature. Through AFM&SEM observe the surface texture of MTJ devices and try to resolve the re-deposition what is caused by etching process. By measuring the MR loop characteristic and magnetoresistance, factors which cause device damages in the fabrication process can be found.
In the fabrication process, shorting is caused by re-deposition. Then the tunneling effect disappeared. So we etching the cells by tilting an angle to clean the re-deposition. When devices were fabricated, the contact between top electrode and cells become more inseparably by annealing without applied magnetic field. And the TMR ratio was also increasing. We have a long-ranged nice view when MRAM enter to the market.

目次
第一章 緒論…………………………………………………………1
1-1前言……………………………………………………………1
1-2磁性的起源……………………………………………………2
1-3磁阻材料的發展與應用………………………………………3
1-3-1常磁電阻與異向性磁電阻……………………………4
1-3-2自旋相關磁電阻………………………………………5
第二章 理論及文獻探討………………………………………… 9
2-1前言……………………………………………………………9
2-2交換磁異向性……………………………………………… 12
2-3 Simmon’s模型…………………………………………… 14
2-4 自旋相關穿隧效應………………………………………… 20
2-5 Julliere's 模型……………………………………………23
第三章 實驗設備與實驗步驟……………………………………28
3-1 前言………………………………………………………… 28
3-2 實驗設備…………………………………………………… 28
3-2-1微影系統………………………………………………29
3-2-2蝕刻系統………………………………………………33
3-2-3鍍膜系統………………………………………………35
3-2-4量測系統………………………………………………37
3-3 樣品製程與量測…………………………………………… 41
3-3-1 樣品的製程………………………………………… 42
3-3-2樣品的量測……………………………………………46
第四章 實驗結果與討論………………………………………… 48
4-1 前言……………………………………………………………48
4-2 製程問題的解決………………………………………………49
4-2-1 蝕刻的反鍍……………………………………………49
4-2-2 SiN絕緣層鍍膜品質改善…………………………… 54
4-3磁穿遂多層膜與元件之磁性與電性探討…………………… 55
4-3-1磁穿遂多層膜…………………………………………55
4-3-2磁穿遂元件之電性測量………………………………56
第五章 結論…………………………………………………………… 63
參考文獻………………………………………………………………… 64

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