Characteristic Investigation Of Nanometer Direct-Writing Lithography Focusing Based On Bowtie Nanostructure

Near-field direct-writing nanolithography technology has the advantages of simply operation, flexibly writing and maskless. And compared to the traditional lithography technology, it can overcome diffraction limit to obtain the subwavelength nano-patterns with higher resolution. SPs with the characteristic of shorter wavelength are electromagnetic excitations propagating at the interface between a dielectric and a conductor, evanescently confined in the perpendicular direction. This will give rise to difficulty in controlling the work distance and making the nano-patterns depth shallow,edge fuzzy. That seriously is going to hinder the further development of direct write lithography technology. To solve these problems, single bowtie(SB) aperture structure which is a novel nanostructure based on localized surface plasmon resonance(LSPSR)was proposed. The electric field intensity of the light spots has been greatly enhanced and the size has been compressed with SB structure. But due to the asymmetry of SB structure, the light spots size is compressed only in parallel to the polarization direction but still is broadened obviously in the vertical direction. This problem in a large extent limits the development of near-field nanometer direct write lithography technology.1. To solve the asymmetrical spot problem, DB structure based on SB structure was proposed. Compared with the symmetrical characteristic of spots for both structures with COMSOL, simulate results indicated that the spots were elliptic with SB structure but were circular with DB structure. So DB structure proposed figured out availably the problem of asymmetrical spots. Secondly, studied the enhanced characteristic of electric field in simulation and the electric field intensity of transmission was enhanced through the DB structure from the simulation results but only near the DB structure.2. Though asymmetrical spots problem has been solved with SB structure, the characteristic of enhanced electrical field is confined to the SB structure surface. To extend the working distance, single bowtie combined with metal-insulator-metal(SB-MIM), a novel lithography structure, was put forward. Which solved availably the shorter working distance. So to compress the spots and extant the working distance,double bowtie combined with metal-insulator-metal(DB-MIM) structure based on SB-MIM structure was proposed. Firstly, analyzed the polarization feature of DB structure and the results show that symmetrical spots were achieved with the selection of circle polarization modes. Then, the focal spot of 45 nm FWHM with the theoretical simulation was achieved and the working distance was prolonged. Finally, analyze theoretically the factors of influencing light spots quality, including: the size of DB structure, each layer thickness of DB-MIM structure, the material of mask.