Novel Low-Cost Scalable Nanofabrication Technologies by Soft Lithography, Plasmonic Lithography, and Electrochemical Processes

Abstract

As wide variety of devices such as optical devices, wearable devices, and color filters have become more common, the demand for technologies which can fabricate these devices at a low cost is at an all-time high. Photolithography is currently the most widely used patterning technology in industries, but its resolution is physically limited by the diffraction of light. Although there have been many technologies developed to improve the resolution limit of photolithography, the increasing cost remains one of the biggest concerns. As another key technology, material depositions are also an important factor in determining the fabrication cost for nanotechnology devices. The most common technologies are vacuum depositions, such as physical vapor deposition and chemical vapor deposition, due to their high controllability and plainness. However, the high vacuum required for this process increases the cost significantly, since it limits the size of substrates, takes a long time to pump, and requires many expensive tools. There have been many studies on alternative technologies for the main processes used in nanotechnology fabrications, e.g., nanoimprint lithography, plasmonic lithography, and electrochemical depositions. Despite the fact that they have some advantages in cost, practical applications are still very limited because of their complexities. In this dissertation, nanoimprint lithography technologies aimed at practical applications will be discussed first. Moreover, a newly developed technique based on metal transfer assisted nanolithography will be introduced to expand its ability to fabricate various devices on a wider choice of materials. As the second topic, plasmonic lithography, a super resolution optical lithography utilizing surface plasmon polaritons excited by evanescent waves will be discussed. While there have been many studies on plasmonic lithography to achieve sub-diffraction limit patterns, attempts to scale up this technology for larger sizes and higher productivity have not been well investigated, which has created a barrier in putting this technology to practical use in mass production. In this thesis, large area plasmonic photo roller lithography by epsilon-near-zero hyperbolic metamaterials will be introduced as a potential solution for higher productivity. Although the experiment requires a somewhat complex fabrication process and setup, plasmonic lithography by the 5th order diffraction has been successfully performed. Lastly, electroplating and electroless plating will be discussed as low-cost material deposition technologies. Even though these technologies have a long history and have been used in industries for various purposes, the potential application to nanotechnology fields has been very limited. This dissertation focuses on the optics and photonics applications of electrochemistry, in particular, broadband light absorbers and structural colors. Electroless plating of Pt was performed on a porous substrate to fabricate a device showing excellent light absorptance in a wide range of wavelengths and electroplating of metals and metal oxides was employed to fabricate Fabry-Pérot cavities to create color filters. Both experimental and computational work are reported to characterize their performances.