针对高深宽比结构的脱模问题，利用压缩试验获得了材料的力学性能，并用Ogden模型对其进行描述，建立了卷对卷紫外光(UV)固化-脱模工艺过程的有限元模型.分析了光照时长、残余层厚度、微结构深宽比以及结构间隙等参数对脱模最大应力的影响规律.结果表明：在结构深宽比为4∶1时，界面粘接力是导致脱模缺陷的主要原因；光照时长越长，残余层厚度越薄；微结构深宽比越小以及结构间隙越大，固化-脱模应力越小、越有利于脱模.
Focusing on the demolding issues of high aspect ratio structures, this paper attempts to explain the reasons behind this problem. Firstly, the material properties of the cured resist was measured, and Ogden model was used to describe its behavior. Then, a roll to roll UV curing and demolding numerical model was constructed and analyzed. It was found that the adhesive forces between mold and structures is the major cause of maximum stress in cured resist when aspect ratio is set to 4∶1. Moreover, a longer curing time, a thinner residual layer thickness, a smaller structure aspect ratio and a bigger structure gap can lead to smaller maximum stress during the curing and demolding process.
［1］CHANG C Y, YANG S Y, HUANG L S, et al. Fabrication of polymer microlens arrays using capillary forming with a soft mold of micro-holes array and UV-curable polymer［J］. Optics Express, 2006, 14(13): 6253-6258.
［2］CHANG C Y, YANG S Y, CHU M H. Rapid fabrication of ultraviolet-cured polymer microlens arrays by soft roller stamping process［J］. Microelectronic Engineering, 2007, 84(2): 355-361.
［3］CHANPARK M B, YAN Y, NEO W K, et al. Fabrication of high aspect ratio poly(ethylene glycol)-containing microstructures by UV embossing［J］. Langmuir, 2003, 19(10): 4371-4380.
［4］WANG X, GE L, LU J, et al. Fabrication of enclosed nanofluidic channels by UV cured imprinting and optimized thermal bonding of SU-8 photoresist［J］. Microelectronic Engineering, 2009, 86(4-6): 1347-1349.
［5］LIU S, ROEDER G, AYGUN G, et al. Simulation of 3D inclined/rotated UV lithography and its application to microneedles［J］. Optik-International Journal for Light and Electron Optics, 2012, 123(10): 928-931.
［6］LIU H Z, JIANG W T, DING Y C, et al. A novel loading and demoulding process control in UV nanoimprint lithography［J］. Microelectronic Engineering, 2009, 86(1): 4-9.
［7］LIU H Z, DING Y C, JIANG W T, et al. Novel imprint lithography process used in fabrication of micro/nanostructures in organic photovoltaic devices［J］. Journal of Micro/Nanolithography, MEMS, and MOEMS, 2009, 8(2): 021170.
［8］AHN S H, GUO L J. High-speed roll-to-roll nanoimprint lithography on flexible substrate and mold-separation analysis［C］∥Advanced Fabrication Technologies for Micro/Nano Optics and Photonics II. San Jose, California, United States: International Society for Optics and Photonics, 2009: 72050U-72050U.
［9］CHANPARK M B, LAM Y C, LAULIA A P, et al. Simulation and investigation of factors affecting high aspect ratio UV embossing［J］. Langmuir the Acs Journal of Surfaces & Colloids, 2005, 21(5): 2000-2007.
［10］AMIRSADEGHI A, LEE J J, PARK S. A simulation study on the effect of cross-linking agent concentration for defect tolerant demolding in UV nanoimprint lithography［J］. Langmuir the Acs Journal of Surfaces & Colloids, 2012, 28(31): 11546-11554.
