Photolithographic mask aligner based on modified moire technique

This paper presents an automatic, accurate mask aligner based on modified moire technique. In this technique the alignment marks are in the form of gratings. The high slope region of moire signal is used to obtain higher sensitivity and better position control accuracy. Automatic alignment is achieved by using difference of moire signal and its inverted signal obtained by computer. Accuracy for alignment, under the present experimental conditions, is of the order of +/- 0.06 micrometers . Our alignment technique by virtue of its higher alignment accuracy is suitable to X-ray lithography. However, due to nonavailability of a X- ray source the lithography was performed by UV source. Nevertheless, the effort is worth it so as to prove the workability of this technique. The overlay accuracy is estimated to be 0.8 micrometers which is limited by the diffraction effects of the exposure optics.© (1995) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.