Model based correction of placement error in EBL and its verification

In maskmaking, the main source of error contributing to placement error is charging. DISPLACE software corrects the placement error for any layout, based on a physical model. The charge of a photomask and multiple discharge mechanisms are simulated to find the charge distribution over the mask. The beam deflection is calculated for each location on the mask, creating data for the placement correction. The software considers the mask layout, EBL system setup, resist, and writing order, as well as other factors such as fogging and proximity effects correction. The output of the software is the data for placement correction. One important step is the calibration of physical model. A test layout on a single calibration mask was used for calibration. The extracted model parameters were used to verify the correction. As an ultimate test for the correction, a sophisticated layout was used for the verification that was very different from the calibration mask. The placement correction results were predicted by DISPLACE. A good correlation of the measured and predicted values of the correction confirmed the high accuracy of the charging placement error correction.