Size Detection And Quality Assessment In Laser Interference Nanomanufacturing

Laser interference nanolithography is one of effective technologies for generating periodical and nanoscale patterns, The technology has the advantages of high-resolution, low cost, large area and maskless patterning. However, in a laser interference nanolithography process, the quality of the fabricated patterns is often affected by various factors such as the laser intensity homogeneity, temperature variations, and noise. Therefore, quality inspection and assessment are essential in the laser interference nanolithography process.In this work, the methodology for detecting the parameters and evaluating the quality of patterns fabricated by laser interference photolithography are discussed. Firstly, the principle of correlation is introduced, and the computer-simulation patterns in the two beam laser interference as well as simulated CCD patterns in the laser interference system are measured using both ideal and added noisy fringes. The results show that the method is effective and antinoise in measuring the laser interference lithography patterns. Then, the principles of both Hough fitting and least squares fitting are introduced to measure the computer-simulation patterns in two beam laser interference and AFM images obtained in practical photolithography. The realization process was also discussed in detail, the measured results of the two fitting methods was analyzed and the combination fitting of Hough and least squares fittings was proposed. Experimental results indicate that the combination fitting method has advantages of high precision and good anti-noise property. Finally, by using the combination fitting method, the parameters in the actual laser interference patterns are successfully measured, and the simulated results obtained by Matlab agree well with the experimental patterns. By measuring the values of the binary images for the ideal and actual patterns, the influence of noise to the patterns produced by laser interference lithography, and the quality of the laser interference patterns is evaluated.