Modeling optical equipment for wafer alignment and line-width measurement

A methodology is presented for modeling a wide variety of optical metrology equipment currently utilized in integrated circuit manufacturing. These tools include steppers for wafer alignment and optical microscopes for linewidth measurement. Rigorous models have been developed to facilitate this task, and the simulator METRO, based on these models, has been implemented. By utilizing this simulator, process engineers can gain more insight into the equipment under operation so as to obtain more accurate alignment and measurement results. These models are general enough so that optics designers can use the simulator to design innovative alignment and metrology schemes