超高集積化した磁性メモリセル

• Project/Area Number: 12305041
• Research Category: Grant-in-Aid for Scientific Research (A)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: Physical properties of metals
• Research Institution: Osaka University
• Principal Investigator: 山本 雅彦 阪大, 工学(系)研究科(研究院), 教授 (30029160)
• Co-Investigator(Kenkyū-buntansha): 遠藤 恭 大阪大学, 大学院・工学研究科, 助手 (50335379) ; 中谷 亮一 大阪大学, 大学院・工学研究科, 助教授 (60314374) ; 鎌田 康寛 大阪大学, 大学院・工学研究科, 助手 (00294025)
• Project Period (FY): 2000 – 2002
• Project Status: Completed (Fiscal Year 2002)
• Budget Amount: ¥43,460,000 (Direct Cost: ¥39,500,000、Indirect Cost: ¥3,960,000); Fiscal Year 2002: ¥7,540,000 (Direct Cost: ¥5,800,000、Indirect Cost: ¥1,740,000); Fiscal Year 2001: ¥9,620,000 (Direct Cost: ¥7,400,000、Indirect Cost: ¥2,220,000); Fiscal Year 2000: ¥26,300,000 (Direct Cost: ¥26,300,000)
• Keywords: 情報記憶デバイス / MRAM / メモリアル / 磁性薄膜 / 静磁エネルギー / 情報記録層 / 磁性ドットアレイ / 還流磁区 / メモリセル / 薄膜 / 磁性 / 表面物理 / 微細加工 / 人工格子 / 電気伝導性

Research Abstract

新世代の情報記憶デバイスであるMRAM(Magnetic Random Access Memory)における磁性薄膜メモリセルについての検討を行った。本研究では、情報記録層の静磁エネルギーを低減する新積層構造を提案し、4Gbit級のMRAMに用いられるメモリセルの基本構造を構築することを目的とした。
(1)走査型プローブ顕微鏡を用いたメモリセルの材料構造観察、磁気構造観察を行った。検討は主に、0.5μm×0.5μmから2μm×2μmのサイズの正方形メモリセルに関して行った。従来型の厚さ10nmのNi-20at%Fe単層膜情報記憶磁性層は、面内還流磁区構造となり情報を失うのに対して、本研究で提案した基本構造であるNi-Fe(10nm)/Hf(2nm)/Ni-Fe(10nm)積層膜情報記憶磁性層は、面内方向には還流磁区構造とならずに情報を安定に保持することができることを明らかにした。また、長方形メモリセルについても同様の結果を得た。
(2)Ni-Fe(10nm)/Hf(2nm)/Ni-Fe(tnm)積層膜情報記憶磁性層における下部磁性層の厚さtを薄くし、厚さ5nm以下にすると、上下の磁性層の磁化のバランスが崩れ、面内還流磁区構造となり情報を失うことを明らかにした。
(3)超高集積化が可能であると予想している閉磁路構造を有するリング型メモリセルについての検討を行い、上記リング型メモリセルでは漏洩磁界がなく、隣接するメモリセルの記録情報に与える影響がないことを明らかにした。

Research Products

• [Publications] Ryoichi Nakatani, Masahiko Yamamto, Hirotaka Yakame, Yasuhiro Kamada, Yoshio Kawamura: "Uniaxial magnetic anisotropy of Ni-Fe films exchange-coupled with Fe dotarras"J.Magn.& Magn.Master.. (印刷中).
• [Publications] Ysuhiro Kamada, Akihiro Itoh, Daisuke Takama, Masahiko Yamamoto: "Effects of hydrogenation on structure, transport and magnetic properties of the multilayers composed of transition metals and rare-earth metals"J.Trans.Magn.Soc.Japan.. 2・2(印刷中). (2002)
• [Publications] Ryoichi Nakatani, Takayuki Kusano, Masahiko Yamamoto: "Magnetic and electric properties of C/Mn/C/Si multilayers"4th International Symposium on Metallic Multilayers. 291 (2001)
• [Publications] Ysuhiro Kamada, Yoshitaka Hitomi, Toshiki Kingetsu, Masahiko Yamamotom: "In situ observation of epitaxial growth of [Au/Co/Cu] and [Cu/Co/Au] superlattices and their magnetic interface anisotroies"J.Appl.Phys.. 90・10. 5104-5110 (2001)
• [Publications] Ryoichi Nakatani, Hirotaka Yamne, Masahiko Yamamoto, Yasuhiro Kamada, Yoshio Kawamura: "Magnetic anisotropy of Ni-Fe films induced by overlying Fe dot-arrays"4th International Symposium on Metallic Multilayers. 54 (2001)
• [Publications] Toshiki Kingetsu, Masahiko Yamamoto: "Epitaxial growth of short-period metallic superlattices for soft X-ray mirrors"0yobuturi. 70. 428-432 (2001)
• [Publications] Gyu Bong Cho, Yasuhiro Kamada, Masahiko Yamamoto: "Studies of self-organized steps and terraces in inclined SrTi0_3(001) substrate"Jan.J.Appl.Phys.. 40・7A. 4666-4671 (2001)
• [Publications] Toshiki Kingetsu, Yasuhiro kamada, Masahiko Yamomoto: "Epitaxial growth of binary and metallic strained superlattices and their magnetic properties"Sci.Tech.Adv.Mat. 2. 331-347 (2001)
• [Publications] Yasuhiro kamada, Akihiro Itoh, Masahiko Yamomoto: "Magnetic properties of amorphous Fe/La and BCC-Fe/La multilayers"Proc. of 4th Pacific Rim Intern. Conf. on Advanced Mat. and Processing. 127-130 (2001)
• [Publications] Yasuhiro kamada, Daisuke Takama, Akihiro Itoh, Hiroyuki Naka, Masahiko Yamomoto: "Towards fabrication of new functional multilayers by hydrogenation"Proc. of 4th Pacific Rim Intern. Conf. on Advanced Mat. and Processing. 425-428 (2001)
• [Publications] Toshiki Kingetsu, Yasuhiro kamada, Masahiko Yamomoto: "Epitaxial Growth and magnetic anisotropies of binary and ternary metallic strained superlattices"J.Magn.&Magn.Mater.. 239・1-3. 262-264 (2002)
• [Publications] Toshiki Kingetsu, Yasuhiro kamada, Masahiko Yamomoto: "Interface structure of metallic strained epitaxially superlattices"Proc. of 4th Pacific Rim Intern. Conf. on Advanced Mat. and Processing. 721-724 (2001)
• [Publications] Toshiki Kingetsu, Yasuhiro kamada, Masahiko Yamomoto: "Structure and magnetic properties of metallic strained superlattices"J.Trans.Magn.Soc.Japan.. 2・2(印刷中). (2002)
• [Publications] Toshiki Kingetsu, Masahiko Yamamoto: "Growth of short-period epitaxial superlattices for X-ray multilayer mirrors"Surface Science Report. 45(印刷中). (2002)
• [Publications] Cho Gyu-Bong,Yu Shiratsuchi,Yasuhiro Kamada and Masahiko Yamaoto: "Self-organized SrTiO3 and sapphire substrates with inclined angles for fabrication of magnetic wire and dot arrays"Proc.of Intern.Conf.on Trend in Nanotechnology.. 30 (2000)
• [Publications] Yasuhiro Kamada,Masaya Sakaguchi,Daisuke Takama and Masahiko Yamamoto: "Effects of Hydrogen on the Interface Structure and Magnetic,Electric Properties of Co/La Multilayers"Proc.of Int.Symp.on Nanoscale Magnetism and Transport.. 45 (2000)
• [Publications] Yasuhiro Kamada,Masaya Sakaguchi,Daisuke Takama and Masahiko Yamamoto: "Magnetic Properties and Interface Structure of Co/La and Co/LaHx Multilayers"Digests of 8th Int.Conf.on Ferrites.. 267 (2000)
• [Publications] Ryoichi Nakatani,Masahiko Yamamoto,Yasuhiro Kamada,Noritsugu Takahashi,Hirotaka Yakame and Yoshio Kawamura: "Magnetic Domain Structures in Microfabricated Fe/Cr and Fe/Cr/Fe/Cr Dots"Digests of 8th Int.Conf.on Ferrites.. 248 (2000)
• [Publications] Ryoichi Nakatani,Masahiko Yamamoto,Yasuhiro Kamada,Hirotaka Yakame,Noritsugu Takahashi and Yoshio Kawamura: "Uniaxial Magnetic Anisotropy in Fe/Cr Films with Microstructures Formed by Electron Beam Lithography"Digests of 8th Int.Conf.on Ferrites.. 270 (2000)
• [Publications] Toshiki Kingetsu,Yasuhiro Kamada and Masahiko Yamamoto: "Stranski-Krastanov Growth of Al on Cr layers during Molecular-Beam Epitaxial Growth and lts Influence on the Structure of Epitaxial(100)Al/Cr Super lattices"J.Appl.Phys.. 87. 159 (2000)
• [Publications] Toshiki Kingetsu,Yasuhiro Kamada and Masahiko Yamamoto: "Dependence of Stranski-Krastanov growth of Al layer on thickness of Cr underlayer in molecular-beam epitaxy of(001)Al/Cr superlattices"J.Appl.Phys.. 88,No.4. 1838 (2000)