SUB 20 NM STITCHING AND OVERLAY FOR NANO LITHOGRAPHY APPLICATIONS

The typical placement, stitching and overlay performance of high resolution electron beam lithography systems is not compatible with the minimum linewidth which can be achieved. Linewidths of 20 nm or less can be obtained, but placement accuracy is typically 3 times higher. The major components in the error distribution of the stitching and overlay performance of the Leica EBPG-5FE have been analysed and indicate that the number of stage movements and stage reproducibility are the predominant factors in the error budget. A direct write algorithm has been developed which reduces the influence of the stage. The calculated 3 sigma stitching and overlay errors for this new algorithm are 14 nm. Experimental results showed 8 nm stitching and 10 nm overlay (3 sigma), obtained in a 546 mu m field.