Slide 1OutlineNanoimprint Lithography - BasicsCapillary ActionCapillary Forces at WorkSingle Layer Resist NILIssues with a Single Layer ResistProcess for 17nm ½ pitchSlide 9ConclusionDepartment of Electrical Engineering and Computer SciencesUniversity of California, Berkeley, CA 94720-1770 USANanoimprint LithographyPeter MatheuEE 235 – “Nanoscale Fabrication”Professor Connie Chang-HasnainApril 14, 2008EE 235 ‘Nanoscale Fabrication’Peter Matheu 2OutlineIntroduction to Nanoimprint Lithography (NIL)PromiseUV curing for NILMotivation for workCross-bar circuitsSingle layer resist NILIssuesBest line patterns with NILG. Y. Jung, et al, App. Phys. A, 81, 2005.EE 235 ‘Nanoscale Fabrication’Peter Matheu 3Nanoimprint Lithography - BasicsBy using a patterned mold, or a shallow 3D pattern, we can transfer a pattern with dimensions below traditional optical lithographic limits.Can be used in either a lift-off or etch mask pattern transfer method.For smallest features sizes the resist is cured to the substrate using UV lightG. Y. Jung, et al, Nano Letters, 6, 2006.EE 235 ‘Nanoscale Fabrication’Peter Matheu 4Capillary ActionCapillary forces spread the resist throughout the moldBy engineering the surface energies of the mold and the substrate, very little resist is left between the edge of the mold and the substrate.G. Y. Jung, et al, Nano Letters, 4, 2004.EE 235 ‘Nanoscale Fabrication’Peter Matheu 5Capillary Forces at WorkOf course, the capillary forces take time to reach a uniform resist thickness. ~30min.G. Y. Jung, et al, Nano Letters, 4, 2004.EE 235 ‘Nanoscale Fabrication’Peter Matheu 6Single Layer Resist NILThe single layer recipe for:RigidityReleaseViscosityUV responseG. Y. Jung, et al, App. Phys. A, 81, 2005.G. Y. Jung, et al, Nano Letters, 4, 2004.EE 235 ‘Nanoscale Fabrication’Peter Matheu 7Issues with a Single Layer ResistGoal: Avoid etch mask simplicityNIL challenge no undercut with a moldLift-off desire an undercut for resistIssue rabbit earsEE 235 ‘Nanoscale Fabrication’Peter Matheu 8Process for 17nm ½ pitchSNAP transfer method:1. Selectively etch a superlattice2. Shadow (tilted) evaporation3. Transfer to sacrificial layer4. Transfer to underlying layers/substrateUniform pressure for the NIL process is accomplished by employing optically patterned disks in the vicinity of the NIL template.G. Y. Jung, et al, Nano Letters, 6, 2006.EE 235 ‘Nanoscale Fabrication’Peter Matheu 9A. The nanoimprint mold from the SNAP processB. Transferred pattern in resistC. Pattern in resist transferred to form metal nanowiresG. Y. Jung, et al, Nano Letters, 6, 2006.EE 235 ‘Nanoscale Fabrication’Peter Matheu 10ConclusionMotivation for further workA molecular monolayer of switching ‘material’A 34x34 cross-bar structure at 50nm ½ pitch10Gbit/cm2At 17nm ½ pitch (with 15nm wide lines)
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