Short feedback loop for OPC model based on wafer level CD

A calibrated Optical Proximity Correction Model (OPC) allows the accurate prediction of wafer printing results based on the geometrically defined layout of features. Therefore the OPC Model takes physical parameter of the mask, optical parameter of the printing system and chemical parameter of the resist into account. In order to find a good correlation between OPC simulated data and real wafer prints, the mentioned parameter needs to be calibrated. In the past, this calibration was done based only on the wafer CD SEM measurements. To speed up the calibration process, this paper investigates the possibility to use the aerial image measured by a wafer level critical dimension measurement tool (WLCD) to shorten the feedback loop and to reduce the amount of wafer prints needed for calibration.