Principle, Processes and Materials for Nanoimprint Lithography pp. 1-44
Authors: (Hongbo Lan, Yucheng Ding, Hongzhong Liu, State Key Laboratory for Manufacturing System Engineering, Xi’an Jiaotong University, China, and others)
Abstract: Lithography, the fundamental fabrication process of semiconductor devices, has been playing a critical role in micro-nanofabrication technologies and manufacturing of Integrated Circuits (IC). Optical lithography (photolithography) was the first and the earliest microfabrication technology used in semiconductor IC manufacturing. It is still the main tool of lithography in today’s VLSI (Very Large Scale Integrated Circuit) and MEMS. Traditional optical lithography including contact and project photolithography has contributed significantly to the semiconductor device advancements. As of 2009 the most advanced form of photolithography is immersion lithography, in which water is used as an immersion medium for the final lens. It is being applied to the 45 nm and 32 nm nodes. Several companies, including IBM, Intel and TSMC, have prepared for the continued use of current lithography, using double patterning, for the 22 nm and 16 nm nodes, and extending double patterning beyond 11 nm. However, as the resolution requirement increases for fabrication of finer and smaller components and devices, the technological dependence on photolithography becomes a serious problem since the photolithography resolution is restricted by the diffraction limitation of optics [1, 2]. Currently, maintaining the rapid pace of half-pitch reduction requires overcoming the challenge of improving and extending the incumbent optical projection lithography technology while simultaneously developing alternative, next generation lithography (NGL) technologies to be used when optical projection lithography is no longer more economical than the alternatives . Candidates for next generation lithography include: extreme ultraviolet lithography (EUV-lithography), electron beam lithography (EBL), focused ion beam lithography (FIB), X-ray lithography, maskless lithography (ML2), interference lithography, and nanoimprint lithography, etc. Among NGL candidates and emerging nanopatterning techniques, nanoimprint lithography (NIL) has several important advantages over conventional optical lithography and other NGLs; it is nonoptical by design, and the resolution appears to be limited only by the resolution of structures that can be generated in the template or mold. It is neither limited by diffraction nor scattering effects nor secondary electrons, and does not require any sophisticated radiation chemistry. In particular, the prominent advantage of NIL compared to other lithography techniques, NGL and micro/nanomanufacturing technologies, is the prominent ability to create 3-D and largearea micro/nano structures with low cost and high throughput. In addition, due to the parallel nature of NIL, it has very high production rate which is well suitable for mass production. It has been considered as one of the most promising NGLs due to its unique principle and outstanding advantages. Furthermore, NIL is also one of the most promising low-cost, highthroughput technologies for manufacturing nanostructures [3,4,5].