Study On Peel Demolding And Flexible Composite Molds For Full Wafer Nanoimprint Lithography

There's a massive market demand for large-area micro/nanostructures in the fields of micro/nano-electronic technology,high performance glass,high performance display devices and bioinstrumentation.However,the existing micro/nano manufacturing technologies cannot better meet the needs of industrial-scale production with low cost and high resolution.Nanoimprint lithography(NIL)has been considered as one of the most potential large-area patterning processes.The current process however still face many challenging issues,which hinder the industrialization of NIL,such as uneven imprinting force in large area,the poorness of conformal-contacting between the mold and uneven substrate,difficulty of demolding and the flaw of air bubbles.Therefore,the research on existing problems of large-area NIL has important significance on the development of Micro-nano technology,which can massive makes complex 3D micro/nanostructures over large-area,uneven or fragile substrates with low cost and high resolution.To resolve the current problems on large-area NIL,our research team invented the8-inch full wafer NIL device(NIL-200)independently,which uses flexible composite molds and implements full wafer NIL in a sealed air chamber under the force of air pressure.Based on this processing,This paper investigated the mechanism of peel demolding,flexible composite molds of conformal contacting NIL,parameter optimization of imprinting device and imprinting process.As the key factor of nanoimprint lithography,demolding has significantly influence on the imprinted pattern area,quality of duplicated structures and mold lifetime.Peel demolding approach has been proven to be an effective way implementing large-area nanoimprint lithography.A model estimated demolding force was established based on the interfacial adhesion energy.A modeling predicted the critical speed of peel demolding was derived by the combination of the strain energy method and theconservation of energy in demolding stage.Furthermore,the influence and laws of the demolding process parameters were revealed by numerical simulation using ABAQUS software.Large-area nanoimprint lithography using flexible molds is an emerging nanopatterning approach for mass producing large-area micro/nano scale structures with low cost,high throughput and high resolution.A theoretical model which can predict the deformation of flexible molds and determine suitable thickness of composite stamps was proposed.Furthermore,the influence of the thickness,the material properties and imprinting pressure for the flexible composite molds were revealed by numerical simulation using ABAQUS software.The mechanism and rule of the mold deformation were also discussed in detailed.Some fundamental design rules for flexible composite molds were put forwarded.In NIL-200 imprinting process,the bending deformation of flexible composite molds has a decisive effect on the initial separation distance between molds and substrates,which significantly influenced both on the setting of imprinting's key parameters and on the quality of ultimate patterning.Based on the bending deformation of flexible composite molds,the initial separation distance between molds and substrates was revealed by using ABAQUS software.What's more,The optimal contacting level was revealed based on the conformal-contact imprinting process between flexible composite molds and uneven substrates.The imprinting experiments based on conformal-contact imprinting were implemented to check the research results of flexible composite molds and optimized parameters,which got high-quality patterning based on both nano-scale and micro-scale templates.