假塑性流体纳米压印中影响填充度的因素

Factors influencing filling degree in nanoimprint lithography with pseudoplastic fluid

作为新一代的半导体加工工艺,直接金属纳米压印以其步骤简单、成本低等显著优点得到迅速的发展.然而目前纳米压印中所采用的转移介质在流动状态下为牛顿流体,牛顿流体的黏度是一个常量,而假塑性流体具有黏度随着剪切速率的增大而逐渐减小的趋势,更适用于纳米压印.综合假塑性流体的剪切稀化特性以及直接金属图形转移的优点,将不同大小的金属纳米粒子分散在基液中制成假塑性金属纳米流体并将其作为转移介质用于纳米压印中.基于假塑性流体的Carreau流变模型利用COMSOL软件仿真分析金属纳米粒子假塑性流体参数集对图形压印转移的影响,完成假塑性流体与牛顿流体分别作为转移介质实现图形转移的对比分析.同时还得到了压印过程中影响填充度的各个因素,如流体黏度、施加压强、掩模板移动速度等.研究工作为金属纳米粒子假塑性流体制备以及纳米压印流程的设计提供了理论基础.

As a novel development of semiconductor process, direct metallic patterning has the advantages of simple steps, low cost, etc. However, almost all transfer media are Newtonian fluids in traditional nanoimprint lithography. Newtonian fluid viscosity is constant. Too high a viscosity is adverse to filling the small space, and if viscosity is too low, it is harmful to solidify graphics. So an appropriate viscosity range that can both realize a high filling degree and benefit solidification is difficult to determine. Pseudoplastic fluid viscosity decreases with the increase of shear rate. The problem would be solved well when pseudoplastic fluid is used as a transfer medium. Synthesizing the advantages of direct metallic patterning and pseudoplastic fluid feature, a novel idea is put forward. The pseudoplastic metal nanofluids, which would be fabricated with metal nanoprticals, can take the place of transfer medium in nanoimprint lithography. Based on the finite element method, COMSOL software is used to compute the filling degree of pseudoplastic fluid, and the results are compared with those of Newtonian fluid under the same conditions. Factors, such as viscosity, imprinting speed, pressure, etc., which would affect filling degree, can be obtained from simulation results. These parameters provide a theoretical basis for designing technological process and fabricating pseudoplastic fluids in future work.