Investigation into trans-scale 3D fabrication process for fabrication of precise metallic microdevices

Abstract

The photolithography process has been the dominant technique for microscale patterning for the past fifty years. To reduce the size of electronic and photonic components, various processes have been proposed. Among various alternatives, the two-photon stereolithography (TPS) process offers direct fabrication of true three-dimensional shapes with sub-100 nm resolution, which might be difficult to obtain by general miniaturization technologies. Previous studies using TPS have focused on a fabrication using polymer materials. Until now the conventional TPS process employing only polymer materials has been limited to the fabrication of functional nano/micro-devices. Direct metal patterning methods using the TPS process have been investigated for various electronic applications. A low-temperature, ultra-high-resolution direct metal patterning process for the fabrication of nanoscale electronics, in which the metal nanoparticles are sintered by applying a TPS process, has been developed. To achieve homogeneous dispersion of the silver nanoparticles, the nanoparticles are encapsulated using a functional self-assembled monolayer. Because the femtosecond laser produces a relatively small heat-affected zone the selective thermal sintering area can be limited to sub-wavelength scale. Also, controlling the position of the laser beam focus within a 10 nm resolution allows for the uniform sintering of the metal nanoparticles. Through this process, metal conductors on a flexible substrate with nanometer features and high conductivity were successfully fabricated. Hybrid material (metal coatable polymer and polymer) patterning is achieved using two-photon stereolithography with a dual-stage scanning system (TPS-D). For effective laser scanning, the sequential scanning method and the 3D continuous-path scanning method are used. For the precise alignments of the metal coatable polymer and polymer structures, the pattern-to-pattern comparison method is used. Selective metallizat...