Sayed Shady, Selvaganapathy P R
Department of Mechanical Engineering, McMaster University, Hamilton, ON L8S 4L8, Canada.
Nanotechnology. 2021 Sep 22;32(50). doi: 10.1088/1361-6528/ac244d.
Nanoimprint lithography is an emerging technology to form patterns and features in the nanoscale. Production of nanoscale patterns is challenging particularly in the sub-50 nm range. Pre-stressed polymer films with embedded microscale pattern can be miniaturized by shrinking induced due to thermal stress release. However, when pre-stressed films are thermally nanoimprinted with sub-micron features and shruken, they lose all the topographical features due to material recovery. Here we report a new approach that prevents recovery and allows retention of shrunken patterns even at the scale of <50 nm. We have discovered that when the shrinking process is mechanically constrained in one direction, the thermal treatment only relieves the stress in the orthogonal direction leading to a uniaxial shrinkage in that direction while preserving the topographical features. A second step, with the constraint in the orthogonal direction leads to biaxial shrinkage and preservation of all of the topographical features. This new technique can produce well defined and high resolution nanostructures at dimensions below 50 nm. The process is programmable and the thermal treatment can be tuned to shrink features to various dimension below the original imprint which we use to produce tunable and gradient plasmonic structures.
纳米压印光刻技术是一种用于在纳米尺度上形成图案和特征的新兴技术。纳米尺度图案的制作具有挑战性，尤其是在低于50纳米的范围内。具有嵌入式微尺度图案的预应力聚合物薄膜可通过热应力释放引起的收缩而实现小型化。然而，当预应力薄膜通过热纳米压印形成亚微米特征并收缩时，由于材料恢复，它们会失去所有的形貌特征。在此，我们报告一种新方法，该方法可防止恢复，甚至在小于50纳米的尺度下也能保留收缩后的图案。我们发现，当收缩过程在一个方向上受到机械约束时，热处理仅能释放正交方向上的应力，从而导致该方向上的单轴收缩，同时保留形貌特征。第二步，在正交方向上施加约束会导致双轴收缩并保留所有的形貌特征。这种新技术能够在低于50纳米的尺寸下制造出定义明确且高分辨率的纳米结构。该过程是可编程的，并且可以调整热处理，将特征收缩至低于原始印记的各种尺寸，我们利用这一点来制造可调节的梯度等离子体结构。
