压印光刻工艺中光刻胶填充流变模拟与试验研究

Simulation and Experimental Study on Photoresist Flow and Deforming Behavior in Imprint Lithography Process

压印光刻工艺中,为了实现高质量的压印复型,必须能够理解和预测压印载荷作用下光刻胶的流变填充行为。根据实际采用的光刻胶的特性,建立了基于粘性流体的光刻胶流变填充有限元模型,采用体积率法对光刻胶流场的运动边界进行追踪,研究模板特征几何尺寸、胶层厚度及及尺度效应对压印填充过程的影响及其作用机理。结果表明,光刻胶流变填充以单峰或双峰两种模式进行,模式的转变点可由特征凹槽宽度和初始胶厚度的比值来预测,并受表界面效应的影响;最有利于填充的特征深宽比约为0.8;最佳初始胶层厚度约为特征深度的2倍。进行了相应的压印试验,试验结果与模拟计算的结论吻合,说明仿真结果可信,可以作为压印光刻工艺中模板图形几何特征、胶厚以及模板表面处理的工艺设计依据。

It is necessary to understand and predict the photoresist flow and filling behavior in imprint lithography process to obtain high fidelity replication of the template patterns. The finite element model based on viscosity fluid for resist flow and filling is established considering the properties of the resist adopted in this study and the influences of geometric characteristics of template patterns, initial resist film thickness and micro/nano effect on resist rheologic properties are investigated to distinguish different flow driving mechanisms by tracing the resist moving boundary by using volume of fluid （VOF） method. The calculation results show that the resist filling is accomplished in single or dual peak deformation mode. The mode transition point can be predicted from the ratio of characteristic groove width to initial resist film thickness and the transition point is influenced by the surface/interface effects. The required from pressure is minimized when the aspect ratio of the template patterns is approximately 0.8. The optimal initial resist thickness is about twice of the depth of the patterns on the template considering both the pattern transfer quality and residual resist thickness. The numerical simulations are compared with the related experimental results in imprint lithography and it shows that the calculation results are in good agreement with the experimental results, which indicates that the conclusions from simulation analysis are valid and can be used as the process layout rules for the template pattern geometry, initial resist thickness and template surface treatment.