The Methodological Research Of Wavefront Modulation On Improving The Resolution Of Super-resolution Imaging Lithography

The key requirements for manufacturing integrated circuits are Critical Dimension(CD) control, and defect control. But,suffering from the diffraction behavior of light, the resolution of conventional imaging optics is limited to about half of the used light wavelength. Recently, research about abnormal characteristics of surface Plasmon shows the possibility of breaking the diffraction limit. Hereafter, a great deal of efforts including wavefront engineering techniques, for example phase-shifting mask, has been made to improve imaging resolution and contrast of plasmonic lens lithography. In the conventional projecting optics lithography, Off-axis illumination(OAI) which is proposed to improve resolution and focus depth is widely used.In this thesis, we carried out the research on the off-axis illumination applied to enhance sub-diffraction imaging performance of superlens lithography. We mainly concentrate on the theoretical research, optimization design and lithography experiments. The main work and conclusions as follow:1. Off-axis illumination plasmonic lens(OAIPL) is proposed and demonstrated to improve the imaging contrast in the case of non-contact manner. The spatial spectra components of nano-patterns in the mask are greatly enhanced due to the shifting of wave vectors, which resultantly delivers image performance improvement including high resolution and contrast, good fidelity and elongation of air gap. Compared to the normal illumination, the elongation of air gap for 30 nm and 60 nm half-pitch is extended to 25 nm and 100 nm by OAIPL with numerical aperture NA=1.55, respectively.2. For 60 nm half-pitch mask, we optimized numerical aperture of illumination and achieved high image contrast. Furthermore, we simulate and investigate the contrast and the intensity of image field in the photoresist layer for variant thickness of air gap. Compared to the normal illumination case, the thickness of air gap with numerical aperture NA=1.52 for the Ag-Pr- Ag structure is extended to ~100nm.3. Based on the previous theoretical investigation and numerical simulation, we focus on the design of experimental equipment and accomplish the super-resolution lithography experiment. This method is believed to find potential applications like nano lithography, optical storage and nanoscope etc. The illumination angle and the light wavelength are 60° and 365 nm respectively. We achieve sub-diffraction imaging with a feature size of 60 nm.