本論文利用磁控濺鍍系統成長CoFeB/MgO/CoFeB之垂直式穿隧結多層膜磁阻,並進行兩種不同階段性覆蓋製膜,而後進行磁滯曲線(M-H)量測;再經由蝕刻將多層膜製作出5um*10um之橢圓形元件並且進行磁阻曲線(R-H)量測。實驗主要分為三個部分 (1) 量測磁阻時經由改變偏壓發現當偏壓越大時,磁阻率會下降,其中,我們發現利用二次覆蓋製膜的樣品V1/2比一次製模大,其衰減的幅度較小,另外我們發現到一次製膜之樣品磁阻曲線的矯完場(Hc)會因為外加正或負的偏壓隨之增加或減少,然而二次覆蓋製膜之樣品變化幅度較小。 (2) 成長多層膜樣品P一次製膜與S二次覆蓋製膜 Ta(5)/Ru(5)/Ta(5)/ Co4Fe4B2 (1.2)/MgO(1.1)/ Co2Fe6B2 (1.4) /(Ta5)/Ru(5) (in nm) 與Ta(5)/Ru(5)/Ta(5)/ Co4Fe4B2 (1.2)/MgO(1.1)/ Co2Fe6B2 (1.3)/ Ta(1)/(Ta5)/Ru(5) (in nm) 兩種樣品分別為一次製膜與二次覆蓋製膜在室溫下我們量測磁滯曲線觀察到是由兩層垂直式鐵磁層所疊加而成的,並且發現此兩層鐵磁層分別在不同樣品製成下扮演不同腳色,我們進而量測磁阻同樣發現此兩樣品如磁滯曲線般鐵磁層扮演著不同之腳色,利用此法可以調控不同之垂直式磁阻。 (3) 我們另外成長一組上層結構Ta10/Mgo(1)/CoFeB1.3/Ta(X)/Ta5/Ru5 (in nm) X=0.6 , 1, 2(nm) 利用二段式覆蓋製膜,探討其介面氧化之效應並量測其磁滯曲線,發現三組樣品二次覆蓋並且退火後垂直異向能、介面異向能等有變大的趨勢,並且其繳完場(Hc)也因為二次式覆蓋也明顯變大。
We have fabricated a series of Ta/CoFeB/MgO/CoFeB/Ta magnetic tunnel junctions by sputtering. In order to vary the interface, the top Ta cap layer was partially oxidized by controlling the growth process. The magnetoresistance ratio reaches over 90% with strong perpendicular magnetic anisotropy. The most striking observation is that the electrical bias voltage measurements show that the V1/2 almost doubled compared to the films without interface oxidation. This study may provide a simple route to enhance the application to higher bias region. In addition, the direct evidence of the interface varies the role of reference/free layer will be also discussed.