Research on critical dimensions variation based on improved optical lithography imaging model

Stray light exists in optical lithography, and causes the CD (Critical Dimension) Variation. Therefore, it is important to obtain an appropriate description model of imaging with stray light. An improved optical lithography imaging model considering medium-range and long-range flare is proposed by using the PSFF (Point Spread Function of Flare) model and the Kirk flare model. The proposed simulation model is confirmed to have much better precision when compared to the experiment data. The effect of flare on CD is studied, in which the total flare is the same but the ratio of medium-range and long-rang flares are varied. The simulation results show that long-range flare has a bigger impact on CD than medium-range flare. The greater the proportion of long-rang flare, the smaller line-width of CD will be. Thus, long-range flare should be taken fully into account in optical lithography.