高性能トンネル磁気抵抗効果TMR膜を形成するためのスパッタ成膜技術(<特集>「磁性薄膜作製技術」)

概要

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This paper describes novel sputter-deposition techniques, such as low-pressure sputtering, sputtering using Kr gas, and rf sputtering, for fabrication of high-performance GMR and TMR films. A surface morphology study using AFM showed that low-pressure sputtering is effective in obtaining a smooth film surface for almost any material. Sputtering with Kr gas was also found to be effective for improving the surface smoothness, although only in materials with a large mass number. Through these techniques, the interlayer coupling field can be reduced in both GMR and TMR films. We also studied the differences between Al_2O_3 and MgO tunnel barrier layers prepared by oxidation of Al and Mg metal layers, and found that the molar volume of Mg is reduced when it is oxidized, which is the opposite of the case for Al. This may explain why it is difficult to fabricate MgO by using an oxidation process with an metallic Mg film. Finally, a fabrication technique for obtaining a high magnetoresistance ratio in a TMR film using an MgO barrier layer is described.
社団法人日本磁気学会の論文
2005-09-01