Study of fluorinated silicon-based resist material and photoreactive underlayer for defect reduction in step and repeat ultraviolet nanoimprint lithography S. Takei 1,2,3 , T. Ogawa 3 , C. Grant Willson 3 1 Toyama Prefectural University, Imizu, Toyama 939-0398, Japan 2 Osaka University, Toyonaka, Osaka 560-8531, Japan 3 The University of Texas, Austin, TX 78712-1167, USA E-mail: takeis@pu-toyama.ac.jp Published in Micro & Nano Letters; Received on 20th April 2011 Step and repeat ultraviolet (UV) nanoimprint lithography has advantages such as metal-direct patterning, develop-less process, low line-edge- roughness and easy operation. However, the dirty-template-causing resist pattern peeling and the defect present challenges that must be resolved for mass-produce nano-devices. The approach to use the chemical adhesion by cationic polymerisation between resist material and the photoreactive underlayer during UV irradiation was investigated asthe next generation of clean separation technology between tem- plate and resist material in step and repeat UV nanoimprint lithography. The obtained chemical adhesion between epoxy groups of the new fluorinated sol–gel silicon-based resist polymer and epoxy groups of novolac-type photoreactive underlayer was achieved with excellent 80nm patterning dimensional accuracy by replication of imprint process cycles over 32 times, and was one of the key to reduce the resist pattern peeling and defect numbers. 1. Introduction: Nanoimprint lithography includes the fabrication of very small structures that have features on the order of 10 mm or smaller [1–4]. The nanoimprint lithography is expected to be applicable to ultra-high-speed metal –oxide semiconductor field- effect transistors, metal semiconductor field-effect transistors and high-speed single-electron transistor memory. Other areas of development in which the nanoimprint lithography fabrication has been employed include high density magnetic storage devices, microelectromechanical systems, optical film material, next-gener- ation high-density compact disks, photodetectors and solar panel. The nanoimprint lithography appears as a simple, cost reduction in manufacturing, fast operation, develop-less patterning application compatible with conventional pattern transfer techniques. The step and repeat UV nanoimprint lithography to solve the res- olution and cost issues using semiconductor fabrication methods was investigated by Willson [5], and the resist materials [6–8] and the hard mask underlayer materials were reported [9]. The resist pattern peeling and defect generated in step and repeat UV nanoimprint lithography present challenges that must be resolved to mass-produce advanced electronic devices. Fig. 1 shows the scanning electron micrograph images of (a) dirty-template- causing resist pattern peeling and (b) defect in step and repeat UV nanoimprint lithography [10]. Further technical progress associated with generated resist pattern peeling and defects is needed in the step and repeat UV nanoimprint lithography. Fig. 2 shows a proposed multi-layer process of step and repeat UV nanoimprint lithography using the fluorinated silicon-based resist material on photoreactive underlayer as an etching transfer layer, usually with high carbon concentration. A typical fluorinated silicon-based resist material has no cross-linking reaction with the surface of underlayer. However, to obtain the chemical adhesion by cationic polymerisation between the resist material and the underlayer during UV irradiation process, the new fluorinated silicon-based resist material and the photoreactive underlayer were developed to improve the dirty-template-causing resist pattern peeling and defect to avoid template contamination. A low viscosity fluorinated silicon-based resist material is filled into the nanostruc- tures while maintaining a certain interval between the template and the underlayer. Subsequently, at the time of completion of the filling, the template is in contact with the resist material and the photoreactive groups remaining on the surface of underlayer reacts with fluorinated silicon-based resist material by irradiating with UV light at room temperature. The template is then separated from the imprinted substrate, and the nanostructure is transferred on the substrate through the underlayer by the reactive ion etching and the lift-off processes. The strong chemical adhesion between resist material and photoreactive underlayer was expected to reduce the Figure 1 Scanning electron micrograph images of resist profiles on under- layer by shortage of adhesion between resist (a) and underlayer in the rep- etition of nanoimprint process cycle (b) Figure 2 Multi-layer process of step and repeat UV nanoimprint lithography using fluorinated silicon-based resist material on photoreactive underlayer 422 Micro & Nano Letters, 2011, Vol. 6, Iss. 6, pp. 422–424 & The Institution of Engineering and Technology 2011 doi: 10.1049/mnl.2011.0213