Combined attenuated-alternating phase shifting mask structure and fabrication methods therefor

Abstract

Abstract A structure and fabrication method for a phase-shifting lithographic mask wherein an attenuated phase-shifting mesh structure (Att PSM) is combined with an alternating-element phase shifting mask (Alt PSM) to provide a mask combination consisting of phase-shifted and unshifted attenuated backgrounds in which the phase-shifted attenuated backgrounds surrounds the unshifted components and the unshifted attenuated background surrounds the phase-shifted components. A substrate (10), composed for example of quartz, has discrete layers of phase shift material (12) such as silicon nitride (Si₃N₄). The phase shifter (12) provides a 180 degree phase shift to light transmitted through it. Transparent regions (14) which also may be composed of quartz are disposed on the phase shifters (12) and attenuator material (16) is disposed on the top of regions (14). The majority of the attenuator regions of the mask are slightly transmissive absorbers and π shifted openings such as the background (K) with respect to openings (C, E, G and J). The slightly transmissive, π shifted absorber (H, A and I) is composed, for example, of chromium plus a phase shifting layer. In the areas where isolated, small, opaque features are required, the unattenuated phase shifter (B) is used instead of the Att PSM. Where there are closely packed patterns (C, D, E, F and G), every other element (D and G) is shifted by -π. The shifted elements are each decorated by a rim that has the same transmission as the Att PSM but shifts 3π. In the present configuration, each of the closely packed elements is surrounded by an attenuated phase shifter; whereas, it is also π-shifted respect to its close neighbor. The extra opaque line between the shifted and unshifted elements (H and I) do not print, because they are imbedded in a background of low transmission. These elements are 3π shifted (equivalent to π shift) while the background area (K) is 4π shifted (equivalent to zero phase shift).

Inventors

• 👤 Jeng Lin Burn

Bibliographic Details