| Mass producing micro-and nanostructures over large areas are critical to the commercial applications of nanotechnology.Large-area micro/nano patterning has demonstrated great potential which can significantly enhance the performance of many devices and create innovative products,such as HD flat panel display,high efficiency solar cells,anti-reflective and self-cleaning glass,LED patterning,sub-wavelength optical elements,etc.However,creating large-area nanostructures,particularly nano imprinting(NIL)on various curved or non-flat surfaces,are extremely difficult using existing three patterning approaches(large-scale wafer imprinting,roll-to-face imprinting,roll-to-roll imprinting).In this paper,a new NIL process for large-scale non-flat rigid substrate and large-area micro-nano patterning of fragile substrate is proposed.The basic principle of composite NIL process is put forward,and the sequence of NIL process is clarified.Compared with the previous NIL process,the characteristics and advantages of new NIL process are revealed.It established the foundation for the design of the experimental device.The deformation of composite soft mold has important influence on the process of composite NIL.In this paper,the mechanism and regularity of the overall bending deformation and local deformation of composite soft mold are analyzed in theory and simulation.The relationship between the overall bending deformation of the composite soft mold and the thickness of the support layer is revealed.The critical vacuum pressure is deduced when deformation of mold is smallest.The effects of overall bending deformation and local deformation on imprinting result are revealed by ABAQUS engineering simulation software It laid the theoretical basis for the choice of the thickness of soft mold support layer.The manufacture of large-size composite soft mold is one of the most important technological elements to realize composite NIL.The quality of working mold will directly affect the precision,quality and graphic area of composite NIL process and imprinting result.Aiming at the manufacturing of double-layer soft mold used in composite NIL,the theoretical analysis and numerical simulation were studied systematically in this paper.The theoretical model of the composite soft mold demoulding and the bubble defect are put forward.The factors and the internal law of the large-scale composite soft mold are revealed by ABAQUS engineering simulation software.A large-size wafer-level double-layer composite mold manufacturing process is put forward.It provided a practical method for the manufacture of double-layer soft molds for composite NIL.The experimental research including the design of the composite NIL tool,the deformation of the composite soft mold(the choice of the thickness of the support layer),the manufacture of the composite soft mold,and the patterning of 200 mm × 200 mm glass are carried out.Based on the basic principle of composite NIL,a experiment platform was designed for micro/nano patterning of 200 mm × 200 mm rigid substrate.Based on the theoretical and simulation results,The thickness of the mold support layer is optimized.The composite soft mold manufacturing process which put forward in this paper is used to realize the high quality manufacturing of the 4-inch wafer-level double-layer composite soft mold.The process has successfully imprinted the lines and spaces structures with a pitch of 2?m and a line width 2.5?m(patterned area of 55mm×55mm)on glass substrates,the micro-pillar arrays with the diameter and height of 2?m and 2.5?m,the pitch of 3?m(the area of 132mm×119mm)and sub-micro-pillar arrays with the diameter and height of 300 nm and 500 nm,the pitch of 500nm(the area of 47mm×47mm)on PMMA substrates with high uniformity.This technique provides a new solution for mass producing large-area micro/nanostructures on patterning ultra-large sized and non-flat substrates at low cost and high throughput,and shows great potential in high volume production and industrial application prospects. |
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