Comparison study of diffraction based overlay and image based overlay measurements on programmed overlay errors

In this paper we will present the comparison study of these two methods on programmed errors of critical layers of 14nm technology node. Programmed OVL errors were made on certain fields during the exposure. Full coverage OVL measurements were performed using both IBO and DBO. Linear, HOPC and iHOPC modeling has been done from non-programmed fields. Then modeling has been subtracted from these certain programmed fields, and Reticle contribution was also calculated and subtracted. In this study, metrology measurement accuracy and stability can be feasible and more accurate OVL control is enabled by selecting better OVL measurement techniques.