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マグネティック・ナノイメージングと次世代磁気応用に関する研究会 2003.2.2 7. EB描画ダマシン法によるSi埋め込み磁性体サブミクロン構造の作製と MFM観察と非線形磁気光学効果 . 東京農工大学 佐藤勝昭. 21世紀COE「ナノ未来材料」推進研究室. 協力者:石橋隆幸・森下義隆・纐纈明伯・松本剛・手塚智之・鶴我真紀子. Fabrication of permalloy nanostructure by Damascene technique.
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マグネティック・ナノイメージングと次世代磁気応用に関する研究会 2003.2.27マグネティック・ナノイメージングと次世代磁気応用に関する研究会 2003.2.27 EB描画ダマシン法によるSi埋め込み磁性体サブミクロン構造の作製とMFM観察と非線形磁気光学効果 東京農工大学 佐藤勝昭 21世紀COE「ナノ未来材料」推進研究室 協力者:石橋隆幸・森下義隆・纐纈明伯・松本剛・手塚智之・鶴我真紀子
Fabrication of permalloy nanostructure by Damascene technique ①Preparation of substrate: Spin-coating of ZEP resist with high etching resistance ②EB-exposition: Write patterns by EB ③Development: Formation of mask-pattern by development ④Etching:By dry-etching process mask-pattern is transferred to the substrate ⑤Deposition of magnetic film: Deposition of magnetic films by sputter or evaporation ⑥Polishing: Obtain flat buried structure using chemical-mechanical polishing Process is simplified by abbreviation of lift-off and repeated spin-coating
EB-patterning process Spin coating of resist 〔1〕Dot size 100nm×300nm rectangular dot with 300nm-spacing 100nm square dot with 300nm-spacing 〔2〕Patterned area: 3mm×3mm 〔3〕EB-resist thickness: 300 nm ・・・by spin-coating with 5000 rpm rotation 〔4〕Baking160℃20min EB exposure Development Si substrate
Clean Room Laboratory • Electron beam lithography
Dry etching process Etching Resist removal 300nm 100nm 〔1〕Etching gas: CF4 〔2〕Vacuum3.0×10-3Pa 〔3〕Gas pressure 9.2Pa 〔4〕RF power: 400W 〔5〕Etching rate: 0.1μm/min Silicon surface after etching
Embedding of permalloy 〔1〕material:permalloy(Ni80Fe20) 〔2〕Vacuum3.0×10-6Torr 〔3〕Accelerating voltage 4kV 〔4〕Deposition rate1.0Å/sec Embedding of permalloy film by electron beam deposition Chemical mechanical polishing 〔1〕Polishing chemicals:Si wafer grain-size~20nm 〔2〕pH11 〔3〕polishing rate:60nm/min flatting
Laboratory EB deposition RF magnetron sputtering
Ni80Fe20 約150nm Si Buried permalloy dot array 300nm 300nm 100nm 300nm 1μm 300nm 100nm 100nm 1μm Rectangular dots Circular dots Square dots
Observation • AFM/MFM FE-SEM
1m square dot array MFM Square dots AFM
0.6μm 3μm SEM observation 300nm×100nmsquare dot, 300 nm space Rectangular dots
0.6μm 100nm Cross sectional SEM observation Dot depth?
Cross section SEM image of Line and space pattern (width =100nm) 0.3μm
AFM and MFM observationof 300 nm x 100 nm dot array 1μm AFM Line scan ・・・Surface roughness~10nm MFM image ・・・magnetization axis along the longer side direction
Comparison between two scans after magnetization in opposite direction 5kOe 5kOe
0° 15° 30° 45° 60° 75° 90° Pattern variation with scan direction
0.0004 0.0002 M(emu) 0 -0.0002 Longer axis Shorter axis -0.0004 -2 -1 0 1 2 H(kOe) In-plane VSM measurement Perpendicular
0.5μm 100nm circular dotswith 300 nm spacing SEM AFM Surface roughness ~10nm
VSM measurement of circular dot array Parallel to the plane Perpendicular to the plane
MFM measurement of circular dots Magnetic field applied Perpendicular to the plane Demagnetized
Influence of stray field from the MFM probe tip MFM measurenment AFM sensing (2-3nmlevitation) MFM probe 80nm A B A B Magnetization Magnetization Reading by second scan Recording by first scan
A MFM image A B C B Magnetization Magnetization MFM image Models to explain MFM images MFM image Magnetization
MFM image of 300nm x 100nm dot with a low-moment probe tip MFM AFM
300nm x 100nm dot (wide scan)with a low-moment probe tip AFM MFM
Observation of dot-array structures using magnetically induced second harmonic generation (MSHG)
l=810nm Pulse=150fs P=600mW rep80MHz LD pump SHG laser Ti: sapphire laser Mirror l=532nm Electromagnet Filter Berek compensator Stagecontroller Mirror Sample Chopper Analyzer lens polarizer Lens Photon counting Filter PMT Photon counter Computer MSHG Measureing System
Laboratory • Nonlinear MO measurement system
Sample Longitudinal Kerr configuration 試料回転 Sample stage w (810nm) P-polarized or S-polarized light Pole piece 45° Rotating analyzer w (810nm) Analyzer Filter 2w (405nm)
Polar Kerr configuration 磁場:面直 Electromagnet Rotating stage S P P sample S B
Azimuthal angle dependence of SHG from unpatterned permalloy film PinPout Longitudinal (counts/10sec) Unstructured permalloy film: H=±2.5kOe
Azimuthal angle dependence of SHG from unpatterned Si wafer Longitudinal PinPout (counts/10sec) H=±2.5kOe
90 120 60 10000000 8000000 30 150 6000000 4000000 2000000 0 0 180 0 2000000 4000000 6000000 330 210 8000000 10000000 240 300 270 Azimuthal angle dependence of SHG from GaAs wafer
Azimuthal angle dependence of MSHG from the square dot array Londitudinal PinPout PinSout SHG強度(counts/10sec) SHG強度(counts/10sec) SinPout SinSout SHG強度(counts/10sec) SHG強度(counts/10sec)
Azimuthal angle dependence of MSHG from 1m square dot array PinPout (counts/10sec) Longitudinal Kerr configuration H=±4kOe
Longitudinal Nonlinear Kerr rotation In 1m square dots Nonlinear Kerr rotation2.80 Nonlinear Kerr rotation6.00 SHGカウント(counts/10sec) SHGカウント(counts/10sec) Analyzer angle(deg) Analyzer angle(deg) 〈Pin〉 〈Sin〉
Azimuthal angle dependence of rectangular dots longitudinal PinPout PinSout SHG強度(counts/10sec) SHG強度(counts/10sec) SinPout SinSout SHG強度(counts/10sec) SHG強度(counts/10sec)
Azimuthal angle dependence of MSHG from 300nm x 100nm rectangular dot array (Longitudinal) PinPout (counts/10sec) H=±4kOe
Azimuthal angle dependence of MSHG from 300nm x 100nm rectangular dot array (Polar) PinPout (counts/10sec) H=±6kOe
longitudinal Nonlinear Kerr rotation in rectangular dot array Nonlinear Kerr rotation 0.25 SHGカウント(counts/10sec) Analyzer angle(deg) 〈Sin〉
Azimuthal angle dependence of MSHG in circular dots longitudinal PinPout PinSout SHG強度(counts/10sec) SHG強度(counts/10sec) SinPout SinSout SHG強度(counts/10sec) SHG強度(counts/10sec)
Summary • Square, rectangular and circular dot arrays of 0.1-1 m in dimension buried in Si wafer have been successfully obtained by Damascene technique using EB lithography • MFM observation in square dot clearly shows closure domain pattern. • MFM images of smaller dots show influence of magnetic field from the probe tip • MSHG reflects symmetry of dot-arrangements