Improvement of iterative error-correction method in laser direct writing

In order to further correct the optical proximity effect in laser direct writing,the Iterative Error-Correction Method (IECM) proposed by Rajesh Menon is improved from two aspects. Firstly,one virtual acoustooptic modulator with high resolution is used to correct the direct writing pattern,and then the exposure data obtained are converted and rounded to that corresponding to the low resolution acoustooptic modulator to avoid the degradation during correction. Secondly,the exposure dose of writing spot that is the nearest to each error area barycenter is modulated by taking the minimum whole pattern error as a yardstick to achieve serial global optimization,which avoids a failure to correct the optical proximity effect when the number of positive errors is equal to that of negative errors. By taking the centerless block diagram as the test pattern,numerical simulation results indicate that the optical proximity effect of pattern with a low resolution acoustooptic modulator can be preferably corrected and the corrected pattern error value is decreased by 91.78% as compared with the initial error value. Furthermore,the optical proximity effect of pattern with a high resolution acoustooptic modulator can be further improved after being corrected by IECM,and the corrected pattern error value is further decreased by 1% based on 92.32% as compared with the initial error value.