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"SIMULATED ANNEALING" ALGORITHM FOR LIGHT SOURCE PARAMETRIC OPTIMIZATION IN PHOTOLITHOGRAPHY

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Subject of Research. The paper deals with methods of resolution enhancement, as well as stability and repeatability of photolithographic process with the use of complex shape light source. Possibilities of source shapeoptimization to be used with specific patterns or pattern groups are shown. Methods. We applied "Simulated annealing" stochastic algorithm for source optimization for periodic patterns with a various pitch. The periodic patterns contrast with a various pitch (including "forbidden" pitch) was used as a merit function, as well as the area of elliptical process window for photolithographic setup.  Research was carried out with the aid of Sentaurus Lithography program (Synopsys Inc). Main Results. Optimization of periodic patterns with 150-300 nm pitch, 193 nmwavelength and optical system numerical aperture equal to 0.93 is shown as an example. The case of optimization algorithmwith focus-expose matrix is considered. It is shown, that proposedsource optimization with the use of the algorithm allows increasing image contrast for various pitches, as well as the area of process windowforphotolithographic setup. The convergence study shows that 100 iterations are enough for the source optimization for 600-800 nm mask pitch and further increasing of iteration number has no impact to the contrast. Practical Relevance.The studied algorithm can be used as a replacement for more complex algorithms of source optimization for reducing the minimum element size and the process stability enhancement. The algorithm has high convergence.

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