Gap Detection And Numerical Simulation For Plasmonic Super-resolution Based On Traverse Chirp Grating

With the intergrated circuit technology heading towards larger scale,more requirements for inter-connection lines and density,push forward progress in the micro-nano processing lithography technology.Because only the transmission wave participates in the imaging and the evanescent wave that is an exponential decay is lost during the imaging process,that the highest resolution is only half the exposure wavelength.Surface plasmas(SP)with short wavelength transmission and evanescent wave coupling amplification break diffraction limit to achieve super-resolution imaging.However,the gap detection between the mask and the substrate in the proximity SP lithography is an urgent problem to be solved.Our research is funded by "Super-resolution lithography equipment development" project and the National Natural Science Foundation,which studies proximity SP super-resolution lithography gap detection technology based on chirped gratings.Although there are many articles reported in this technology,but the effect of chirped grating parameters,Fabry-Perot effect and Image processing method on the detection accuracy is rarely reported.In fact,these factors are closely related to the frequency and phase of the Moire fringes.Therefore,this paper will focus on the study of the gap detection technology in SP lithography and the impact of these factors on the detection.(1)An introduction is given on the typical gap detection technologies at home and abroad,and their advantages and disadvantages are analyzed.At the same time we propose optical interference measurement method based on chirped grating.(2)The mechanism of the formation of Moire fringes using chirped grating and the effect of chirped grating parameters on the Moire fringes are studied,and According to the gap measurement range,accuracy and real-time SP lithography,a chirped grating is designed,and method for the peak frequency and phase extraction method is investigated.The mathematical model of SP lithography gap detection is established,and the grating parameters are optimized for SP photometric measurement range using MATLAB mathematical software,is also designed to guarantee the a proper incident respect to the grating.(3)For the requirements of promximity lithography in accuracy,the frequency and phase extraction method based on Fourier window addition is proposed,the effect on spectrum leakage by several common windows is analyzed.(4)On the basis of theoretical research and numerical simulation,the proximity SP lithography gap experimental system is build up,and step-by-step experiments and repetitive experiments are conducted.At this stage,the system can achieve 0.1?m accuracy.A two-dimensional grating is designed,and the optical fiber laser beam is incident on the direction(X-Z)of the two-dimensional chirped grating at a angle of 18.5 °,vertical incidence in the direction of chirp changing.The corrected angle is smaller than 0.5°in X-Z direction and less than 0.01 °in Y-Z direction.According to the results,further improvements in the experiments and design are proposed.