Recent Situation of the UV Imprint Lithography and Its Application to the Photonics Devices

Optical communication systems with large capacity that support the today’s global information and communication society are made up from high-performance photonic devices. To develop higher functional photonic devices, nanotechnology plays an important role for their production. There are two major optical elements of the photonic device, that is, diffraction grating with one-dimensional periodic structure and photonic crystal with two-dimensional periodic structure. In general electron beam lithography (EBL) is used to fabricate the nano-structure on a semiconductor substrate. EBL has also been utilized to produce masks employing in other lithographic technologies, such as photolithography, X-ray lithography, imprint lithography (IL), and others. However, EBL is not suitable for making large-scale microstructure, because the throughput time is extremely low, which corresponds mainly to exposure time of curing EB-resins. The authors have focused on UV imprint lithography (UV-IL), which enables pattern transfer with high-throughput time and comparatively lowcost in order to solve the EBL-problem, and have applied the production process of a diffraction grating for a DFB laser [1]. In this paper, a detailed description of imprinting technique has been made to fabricate fine microstructures on both substrates, lithium niobate and sapphire, which are difficult to produce high-aspect patterns by using conventional method, and some examples for application to photonic devices are mentioned.