PLASMA REACTIVE ION ETCHING OF 193 NM ATTENUATED PHASE-SHIFT MASK MATERIALS

This article gives details on plasma etch process development for pote ntial attenuated phase shift masking materials for use at 193 nm. Mask ing films investigated include materials based on aluminum nitride, zi rconium nitride, molybdenum-silicon oxide, tantalum-silicon nitride, a nd tantalum-silicon oxide. A variety of halogenated etch plasmas were investigated, including fluorine-based chemistries (CF4 and SF6) and c hlorine-based chemistries (Cl-2, CCl4) combined with oxygen, argon, an d hydrogen. Thin films of TaN, MoSiO, SixNy, and TaO that allow for su fficient volatility in fluorine plasma and processes using SF6 were ch osen for optimization. Fluorides of aluminum and zirconium exhibit ver y low vapor pressure so Cl-2+Ar mixtures were chosen for study. Al and Zr chlorides can be made volatile but ion assistance is generally nee ded to produce sufficiently high etch rates. Because of this, selectiv ity to resist is generally poor. Of all the materials evaluated, atten uated phase shift mask films of TaN/Si3N4 etched with SF6 allow the la rgest etch selectivity to both fused silica and resist. (C) 1997 Ameri can Vacuum Society.