Subhalf-micron patterning of negative working resist by using new phase-shifting masks

A lithographic technique using phase-shifting masks combined with i-line reduction projection printing in negative working results has been evaluated for subhalf-micron patterning. The combination of a ‘‘standard’’ phase-shifting mask and image reversal resist, AZ 5214E (from Hoechst), makes it possible to resolve 0.3-μm line and space patterns with practically enough focus latitude on a 0.42 numerical aperture i-line aligner (σ:0.5). New phase-shifting masks which are adapted to isolated spaces and holes for negative working resist have been developed. Of these new masks, a mask whose patterns consist of only shifter film gives excellent results. By using this mask and the i-line aligner, 0.3-μm hole patterns are clearly resolved in LMR-UV (low-molecular-weight resist for UV lithography resist) film.