Directly patterning ferroelectric films by nanoimprint lithography with low temperature and low pressureOutlineWhy ferroelectric materials?Conventional NILDirect nanoimprint – previously…Method 1Method 2Results – FE gelResults – FE gel + Au filmSummary/Questions remainingM 2007 March 19 EE C235/NSE C203 1Directly patterning ferroelectric films by nanoimprint lithography with low temperature and low pressureK.C. Hsieh and H.L. ChienDepartment of Materials Science and Engineering, National Taiwan University, Taipei, TaiwanC.H. LinNational Nano Device Laboratories, Hsinchu, TaiwanC.Y. LeeDepartment of Materials Science and Engineering, National Taiwan University, Taipei, TaiwanJournal of Vacuum Science & Technology B 24(6). Nov/Dec 2006, p3234-3236.Joanne YimEE C235/NSE C203M 2007 March 19 EE C235/NSE C203 2Outline•Background–Why ferroelectric materials?–Conventional nanoimprint lithography–Direct nanoimprint on metals•Method–Gel precursor–Au/gel bilayer•Results•Summary/Questions RemainingM 2007 March 19 EE C235/NSE C203 3Why ferroelectric materials?•Apply electric field to induce electric dipole moment•Used for:–Memory, sensors, actuators, optoelectronics•Large-area patterns•Examples: BaTiO3, PbZrTiO3M 2007 March 19 EE C235/NSE C203 4Conventional NIL•Shape, then harden some soft material into relief of desired pattern•Transfer pattern to substrate by etching•Processing speed/resolution limited by etchingM 2007 March 19 EE C235/NSE C203 5Direct nanoimprint – previously…•Semiconductor material–Excimer laser-assisted–Requires high power and high pressure•Metal films–100MPa–Imprinted onto “soft” film•DIRECT = shape material, not some buffer–Must be malleable–Use “sharper” mold to reduce pressureM 2007 March 19 EE C235/NSE C203 6Method 1•MOD (metal organic decomposition) solution of Pb(Zr0.52Ti0.48)O3 with excess Pb•Spin coat ~200nm onto Si substrate•120°C anneal to remove solvent, make gel & maximize hardness difference•Si mold apply at RT, 10-20MPa•Dry @ 120°C, pyrolyze @ 450°C, anneal @ 650-800°C to obtain perovskite phase•(higher T anneal = more complete perovskite structure)M 2007 March 19 EE C235/NSE C203 7Method 2•FE require some metal contact to apply electric field•Apply metal thin film and shape along with FE layer•Better–Less sticking–Less relaxation after mold releaseM 2007 March 19 EE C235/NSE C203 8Results – FE gel• After imprint, features ~60nm high, much less than ~500nm mold height and gel depth• gel sticks to moldM 2007 March 19 EE C235/NSE C203 9Results – FE gel + Au filmDepth by AFM•14MPa (top) : 90nm•20MPa : 300nmM 2007 March 19 EE C235/NSE C203 10Summary/Questions remaining•Malleable precursor can be directly imprinted•Combining with top metal film improves transfer •Thickness of Au film?–When will cracking begin?•Applicability to other material
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