紫外压印长波红外亚波长结构的涂胶工艺研究

Spin coating of UV-curable resist for imprinting long-wave infrared subwavelength structures

采用旋涂法进行了Si表面紫外固化胶涂布研究,并压印出了长波红外亚波长结构图形。用激光共聚焦显微镜观察了旋转涂布胶层的表面形貌,测量了表面粗糙度(Ra);用椭圆偏振仪测试了胶层厚度,扫描电子显微镜观察了压印图形的表面形貌,并用扫描探针显微镜测量了压印图形的结构高度。结果显示:当匀胶转速较小(如300r/min)时,胶层中不会产生气泡及针孔等缺陷,胶层的Ra小,但胶层均匀性差;提高转速可以改善胶层均匀性,但同时胶层中会产生大量气泡和针孔等缺陷,且它们不会随匀胶时间的延长而消除。文中提出用四转速匀胶法来同时解决胶层均匀性和膜层气泡等问题,获得的胶层无气泡,Ra为317nm时与Si衬底表面相当(324nm),均匀性(最小厚度值与最大厚度值之比)为89.17%,胶层平均厚度为626nm。结果表明:四转速涂胶法获得的胶层满足紫外压印长波红外亚波长结构的要求,压印的图形均匀、完整、保真性好。

The ultraviolet-curing imprinting resist on Si substrates was explored by spin coating method,and the long wave subwavelength structures were imprinted.The surface topography of the coated resist layers was observed by a Laser Scanning Co-focal Microscope （LSCM）,and their surface roughnesses（Ra） were tested.The thicknesses of the resist layers were tested by an ellipsometer,then the surface morphology and the structure heights of the imprinted patterns were tested by a Scanning Electron Microscope （SEM） and a Scanning Probe Microscopy（SPM）,respectively.Results show when spin velocities are as low as 300 r/min,the resist layers have negligible defects,such as gas bubbles,pinholes and very low Ra,meanwhile,it shows a bad uniformity.The uniformity can be improved by increasing spin velocity,however,the bubbles and pinholes in the resist layers are also increased and cannot be decreased by extending the spin time at elevated velocities.A four-spin-velocity coating method was proposed to eliminate the bubbles and pinholes and obtain the resist layers with high uniformity.The obtained resist layers show the roughness to be 317 nm,lower than that of the Si substrate （324 nm） and its uniformity is 89.17％,mean thickness is 626 nm.These results well satisfy the requirement of UV imprinting of long-wave infrared antireflective subwavelength structures and imprinted patterns have the advantages of good uniformity,integrity,and higher fidelity.