Engineers at National Yang Ming Chiao Tung University and TSMC say molybdenum-based quasi phase-only masks can beat the tantalum absorbers that dominate extreme ultraviolet photomasks today. Their paper, published in August, rests on electromagnetic simulation rather than wafer data.
The reported gains are 35 percent higher image contrast, roughly a fivefold wider common focus window, and 92 percent lower peak telecentricity error. The stack also supports 12.5-nanometre half-pitch resolution on 0.33 numerical aperture scanners with monopole illumination, a combination conventional absorbers struggle to hold.
Phase-shifting masks work by manipulating the phase of reflected light instead of simply blocking it. Tantalum absorbs a meaningful share of the 13.5-nanometre light it is meant to shape, and that loss grows more expensive as chipmakers push single-exposure patterning toward finer pitches. Molybdenum reflects more and absorbs less, which is why the authors frame the change as a redesign rather than a tweak.
The work lands as the mask supply chain prepares for high-numerical-aperture EUV, where larger 12-inch photomasks are being developed for pilot production later this decade. Wider process windows matter most at tighter geometries, because depth of focus shrinks as pitch falls.
Simulation results are not wafer results. The contrast and telecentricity figures still need experimental confirmation before mask makers commit to a molybdenum absorber stack. No production timeline was disclosed.
