Characterization Of Tunable Ultra-deep Subwavelength Photolithography Using A Surface Plasmon Resonant Cavity

Photolithography has been a key technique in semiconductor industry 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 optical diffraction limit. The recent discovery of extraordinary transmission behavior through perforated metal films shows that the surface plasmon polaritons on the metal surface can greatly enhance the 1ight transmission and redistribute the electromagnetic field in nanometer scale. These features of the surface plasmon polaritons suggest a new technique of photolithography that is beyond the diffraction limit. In this thesis, we report an observation of a novel tunable ultra-deep subwavelength nanolithography technique using a surface plasmonic resonant cavity formed by a metallic grating and a metallic thin-film layer separated by a photoresist layer. The physical mechanism of the proposed technique is analyzed and verified by both Maxwell electromagnetic theory and the numerical calculation. It is found that an interference pattern with ultra-deep sub-wavelength resolution can be obtained by employing a surface plasmonic resonant cavity (under illumination of 436nm wavelength, line-width of the interference pattern can be as small as 16.5nm). Moreover, the period of interference pattern is tunable, which can be implemented by varying the cavity length ( i.e., the thickness of the photoresist) without the need of changing the phase mask. These features break the limitations of low resolution, non-tunability and shallow exposure depth imposed by the conventional"open"surface plasmonic photolithography. It opens a new way for further improving the resolution of photolithography and provides a new idea for flexible nano-manufacturing.