| Project/Area Number |
13555001
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 展開研究 |
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| Research Field |
Applied materials science/Crystal engineering
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| Research Institution | Tohoku University |
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Principal Investigator |
KUBOTA hitoshi Tohoku University, Gradate School of Engineering, Research associate, 大学院・工学研究科, 助手 (30261605)
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| Co-Investigator(Kenkyū-buntansha) |
KUMAGAI Seiji Sony, CNC DSC Magnetic Devices Division, Manager, CNC DSC磁気デバイス事業部, 課長(研究職)
MIYAZAKI Terunobu Tohoku University, Graduate School of Engineering, Professor, 大学院・工学研究科, 教授 (60101151)
ANDO Yasuo Tohoku University, Graduate School of Engineering, Associate professor, 大学院・工学研究科, 助教授 (60250726)
NAKASHIO Eiji Sony, CNC DSC Magnetic Devices Division, Researcher, CNC DSC磁気デバイス事業部, 研究員
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| Project Period (FY) |
2001 – 2002
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| Keywords | focused ion beam / carbon / tungsten / microfabrication / spin tunnel / magnetoresistance effect / epitaxial film / bias dependence |
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| Research Abstract |
Development of micro-fabrication processes of small magnetic tunnel junctions (MTJs) using focused ion beam induced deposition (FIBID) has been examined. FIBID technique was applied to make small carbon or tungsten patterns, those were used as Ar etching masks and/or electrical leads. The deposition tecnique has some advantages: Pattern location can be controlled freely and precisely, pattem shaps a easily designed, pattem height can be controlled widely, and sub-micron patterns should ha easily fabricated. The smallest lateral size of the carbon and tungsten mask patterns deposited were about 100 nm and 140 nm, repectively. The C mask patterns were hard for Ar etching and soft for O_2 ashing. Resistivity of the Wpatterns was enough small, thus, the W patterns can be used as electrical leads. MTJs were fabricated using C masks or W masks/leads. During Ar ion etching, redeposition at side walls of the mask patterns were formed, resulted in short-circuiting. It is necessary to avoid the redeposition to establish the fabrication process of small MTJs using FIBID technique.
To improve the quality of insulating layers in MTJs, we have used epitaxially grown Ag/Cu/Ni-Fe films on Si (111) substrates as bottom electrodes. Epitaxial growth of the trilayers was confirmed using X-ray diffraction and low energy electron diffraction. The MTJs fabricated showed large tunnel magnetoresistance (TMR) ratios of about 50%. The bias dependence of the TMR ratio was greatly improved in those MTJs. The insulating layers grown on the epitaxial bottom electrodes would have fewer defects than the those grown on textured bottom electrodes.
Further experiments are necessary to complete the fabrication process to apply to the MTJs with epitaxially grown bottom electrodes. The switching characteristics of epitaxially grown MTJs with an area of about 100 nm square would be investigated.
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