Fast model for positive tone development (PTD) source mask optimization (SMO) calibrated by dose tuning

The measurement of critical dimension (CD) using scanning electron microscopy (SEM) brings the blur of CD measured compared with the absolute CD from optical simulation. Although optical property is dominant in PTD process, the CD bias between measurement and simulation with optical model will disqualify the accuracy of CD prediction, EPE calculation and mask correction in SMO. In this paper, using multiple different 1D patterns with different exposure latitude (EL) could discovery the global bias between simulation with optical model and wafer data measured. Due to the property of photoresist shrinkage and the identical profile of PTD through pitches, this bias works well in 1D patterns and assists in anchor re-matching between wafer data and simulation, which could control dose shift between wafer situation and simulation under 1mJ. This bias is also not relevant to source type and will improve the accuracy of PTD SMO highly without resist model.