Gaikwad Abhaysinh, Desai Salil
Center for Excellence in Product Design and Advanced Manufacturing, North Carolina A & T State University, Greensboro, NC 27411, USA.
Materials (Basel). 2021 May 14;14(10):2548. doi: 10.3390/ma14102548.
Understanding the deformation behavior during nanoimprint lithography is crucial for high resolution patterning. Molecular dynamics modeling was implemented to investigate the effect of different mold profiles (cylindrical, rectangular, and spherical) on the von Mises stress, lattice dislocations, and material deformation. Relatively higher von Mises stress (1.08 × 10 Pa) was observed for the spherical mold profile compared to the rectangular and cylindrical profiles due to the larger surface area of contact during the mold penetration stage of NIL. Substantial increases in the von Mises stress were observed for all the mold geometries during the mold penetration stage. The von Mises stresses had a reduction in the relaxation and mold retrieval stages based on the rearrangement of the gold atoms. The lattice dislocation during the deformation process revealed the formation of the BCC structure which further reverted to the FCC structure after the mold retrieval. The polyhedral template matching (PTM) method was used to explain the retention of the FCC structure and subsequent ductile behavior of the substrate. The cylindrical mold had the lowest percentage spring back in both of the orthogonal directions and thus replicated the mold profile with high-fidelity as compared to the spherical and rectangular molds. The findings of this research can aid the design of molds for several applications.
了解纳米压印光刻过程中的变形行为对于高分辨率图案化至关重要。采用分子动力学模拟研究了不同模具轮廓（圆柱形、矩形和球形）对冯·米塞斯应力、晶格位错和材料变形的影响。由于在纳米压印光刻模具穿透阶段的接触表面积较大，与矩形和圆柱形模具相比，球形模具轮廓的冯·米塞斯应力相对较高（1.08×10 Pa）。在模具穿透阶段，所有模具几何形状的冯·米塞斯应力都有显著增加。基于金原子的重新排列，冯·米塞斯应力在松弛和模具回收阶段有所降低。变形过程中的晶格位错揭示了体心立方结构的形成，该结构在模具回收后进一步转变为面心立方结构。采用多面体模板匹配（PTM）方法解释了面心立方结构的保留以及随后衬底的延性行为。与球形和矩形模具相比，圆柱形模具在两个正交方向上的回弹百分比最低，因此能够以高保真度复制模具轮廓。本研究结果有助于多种应用的模具设计。
