Metal Surface Structure Of The Surface Plasmon Interference Lithography Resolution

Photolithography has been a key technique in semiconductor nanofacture and microfabrication for several decades. With the development of Super Large Scale Integration (SLSI) and integrated optics, high resolution photolithography has become more and more important. However the traditional photolithography is limited by the illuminating wavelength due to the optical diffraction limit. Many nanoscale lithography techniques like the electron beam lithography and deep ultraviolet (UV) lithography have been applied to achieve high resolution, but these techniques require quite expensive equipment and cannot meet the industrial mass fabrication needs. The recent discovery of extraordinary transmission through perforated metal films shows that the surface plasmons (SPs) on the metal surface can greatly enhance the light transmission and redistribute the electromagnetic field in nanometer scale. These give us a novel method of photolithography beyond the diffraction limit. The photolithography based on the surface plasmons is researched for several years. Sub-50 nm lines have been patterned at the wavelength of 436 nm by using Surface Plasmons Resonant interference nanolithography technique. In this technique, the resolution greatly depends on the periodicity and thickness of the metallic mask. The resolution could be further enhanced by adding two symmetrical grooves in a grating cell on its output side. Thus the optical field can be subtly modulated, the formatted pattern is expected to be adjusted more uniform. Therefore, the high resolution could be achieved.In this paper, the electric field distribution of the micro-structured metal grating is investigated by using the Finite-Difference Time-Domain method. The simulation results show that the electric field distribution is strongly dependent on the structure's periodicity, the groove's depth and the distance between groove and slit. Adjusting the parameters of the grating can modify the transmitted field distribution, which provides a valid way for high resolution photolithography.