OVERLAY ACCURACY OF CANON SYNCHROTRON-RADIATION STEPPER XFPA FOR 0.15-MU-M PROCESS

Canon has been developing a synchrotron radiation stepper system for x -ray lithography feasibility studies. We have developed a novel accura te alignment system using the dual grating lens (DGLs) method. In this article, we explain the principle of the DGL, and the results of the alignment accuracy and process applicability tests. We have evaluated alignment performance for translation (X, Y) and rotation (theta) at t he center of every exposure area. We obtained the alignment accuracy 3 sigma of 19 nm (X), 15 nm (Y) and 0.8 mu rad (theta), using etched Si N patterns on Si substrates, and the overlay accuracy in an actual dyn amic random access memory fabrication process 3 sigma of 34 nm (X), 31 nm( Y), and 2.1 mu rad (theta). After eliminating the alignment offse t in each shot, the values (3 sigma) are 18 nm, 21 nm, 1.4 mu rad, res pectively. These results show that the alignment method is promising f or 0.15 mu m level device fabrication. (C) 1996 American Vacuum Societ y.