반도체 소자 응용을 위한 복합 나노패터닝 공정기술 연구

Abstract

For the past few decades, various semiconductor devices have been widely fabricated by optical nanopatterning technologies due to the reasonable process cost, excellent reproducibility, and high throughput. However, photo-based nanopatterning methods have several difficulties for structural miniaturization owing to the physical pattern limitation. Therefore, more practical and useful patterning methods need to be developed to overcome these obstacles. Recently, several patterning research group members suggested a lot of advanced nanolithography technologies for realization of controlled pattern formation of complex nanostructures, such as directed self-assembly (DSA), nanoimprint lithography (NIL), extreme ultraviolet lithography (EUV), and nano stereolithography (nSLA). Among them, nanotransfer printing (nTP) as one of soft NIL processes has much attention due to its process simplicity with low cost, reliable pattern-tunability, and excellent pattern resolution. Furthermore, the nTP process has good compatibility with other lithography techniques, generating various two-dimensional (2D) and/or 3D complex nanostructures by combining two or three different patterning methods. In this paper, we show advanced combined nanopatterning methods based on nTP process to obtain various complex and unique nanopatterns over a large area, showing outstanding scalability and versatility of the nTP process. Specifically, we present three candidates of replica materials and novel patterning method, and combined processes using conventional SLA 3D printer. First, we show that polymethyl methacrylate (PMMA), polystyrene (PS), and poly(4-vinlypyridine) (P4VP) are suitable materials for effective replication, showing well-duplicated polymer patterns from a Si master mold with nanoscale patterns. Then, we display successfully transfer-printing of high-resolution metal (Pt) and oxides (NiO, Li2CO3) line pattern on the arbitrary substrate by using the soft replica nanostructures. In addition, we show a state-of-the-art solvent spray assisted nanotransfer printing (SS-nTP) method for effective pattern formation of 3D metallic nanosheets on diverse substrates. We demonstrate how to form uniform convex nanostructures with various filling factors (e.g., dot, ring, hole, zig-zag, wave and hexagon). The SS-nTP provides outstanding patternability on diverse receiver surfaces such as Cu foil, flexible PET, leather and slippery curved surface. Finally, we introduce very simple and useful nanopatterned film-assisted stereolithography (NF-SLA) process, which is a combined nanopatterning method to generate high-resolution nanostructures with functionality on surface of 3D printed model that greatly overcomes the resolution limit of conventional SLA printers. Also, we show nanopattern formation on the surface of desired area by controlling the contact area between nanopatterned film and cured part through masking process. In particular, the versatile NF-SLA method shows pattern generation of various/complex structures without using any special laser and resin, showing excellent large-area-patternability by repeated attachment of replica patterns. We expect that this practical and useful approach would be applicable to various 3D electronic devices with complex circuits.