A New Phase Shifting Method for High Resolution Microlithography
Cavallaro, Joseph R.
Wilson, William L.
Tittel, Frank K.
One of the most promising lithographic technique for the future designs of DRAMs is the phase-shifting mask technique. Conventional phase shifting-masks, however, are difficult to fabricate as they require regions of different optical thickness. We present a new phase shifting technique that does not use any phase shifting materials. A special interferometer and a mask that has both transmitting areas and reflective areas accomplish the required phase-shift at the image plane. Using this technique we have demonstrated phase shifting effects using a CCD camera. We also present the results of a computer simulation for the critical resolution of this new method in comparison with the conventional phase shifting approach.