Extending microcontact printing for patterning of thick polymer layers: semi-drying of inks and contact mechanisms
Extending microcontact printing for patterning of thick polymer layers: semi-drying of inks and contact mechanisms
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DOI：
10.1088/0960-1317/24/12/125019
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发表时间：
2014-12-01
影响因子：
2.3
通讯作者：
Ushijima, Hirobumi
中科院分区：
文献类型：
--
作者：
Kusaka, Yasuyuki;Miyashita, Kaori;Ushijima, Hirobumi
我们研究了微接触印刷技术对于厚度为微米级的聚合物抗蚀刻层图案化的适用性。与微接触印刷中通常使用的硫醇和硅烷偶联剂等小分子材料相比，厚层的图案化需要调整墨膜的流变性能，以防止图案变形并获得高质量的转印。通过评估微接触印模材料（即聚二甲基硅氧烷（PDMS））的膨胀率和溶剂的蒸发率，我们找到了最佳的油墨配方，以达到聚合物层印刷所需的半干燥状态。在固含量低于最佳限度的聚合物薄膜中，根据墨膜的附着力和变形能力，会出现裂痕或皱纹型变形，而过度干燥的聚合物薄膜则无法转移。这些现象与胶体探针显微镜测量获得的变形曲线定性一致，成功揭示了半干聚合物薄膜的变形性和粘附性。进一步研究印模刚度对图案形成的影响表明，当使用较硬的 PDMS 印模时，厚度轮廓具有较小曲率半径的图案区域无法转移。此类缺陷被认为是由于聚合物薄膜的半圆形帽结构和印模变形不足导致薄膜与基材之间接触不完全造成的。在此，基于赫兹接触模型讨论了高质量图案化的详细接触机制。使用开发的抗蚀刻墨水和优化的印刷工艺条件，可以获得硅基板的精细蚀刻结构。
We investigate the applicability of the microcontact printing technique for the patterning of polymeric etch-resistant layers with thicknesses in the order of micrometers. In contrast to small molecular materials such as thiols and silane coupling agents typically used in microcontact printing, the patterning of thick layers requires tuning of the rheological properties of an ink film to prevent pattern deformation and attain high-quality transfer. By evaluating the swelling rate of a microcontact stamp material (i.e. poly(dimethylsiloxane) (PDMS)) and the evaporation rate of solvents, we find an optimal ink formulation to attain the desired semi-dried state for the printing of polymer layers. In polymer films with solid content below the optimal limit, split-or wrinkle-type deformations were found depending on the adhesion force and deformability of ink films, while overly-dried polymer films failed to be transferred. These phenomena are in qualitative agreement with deformation curves obtained from colloidal probe microscopy measurements that successfully revealed the deformability and adhesion of semi-dried polymer films. Further investigation of the effects of stamp stiffness on pattern formation reveals that a pattern region in which the thickness profile has a small curvature radius failed to be transferred when a stiffer PDMS stamp was used. This type of defect is thought to be caused by incomplete contact between the film and substrate due to a semi-circular cap structure of the polymer film and insufficient deformation of the stamp. Herein, a detailed contacting mechanism for high-quality patterning is discussed on the basis of the Hertz contact model. Using the developed etch-resistant ink and optimized printing process conditions, a finely defined etched structure for a silicon substrate is obtained.