Hard phase-shifting masks for the 65-nm node: a performance comparison

The lithographic potential of various mask types for the printing of 65nm features has been investigated by simulation and experimentation. As key parameters process window, mask error enhancement factor, balancing performance, and phase and CD error susceptibility have been analyzed. Alternating chromeless phase-shifting masks (PSM) show the smallest mask error enhancement factor (MEEF), but the largest phase and CD error sensitivity. Alternating PSM have a larger MEEF but require less tight mask specifications. Double edge chromeless PSM combine small MEEF value with relaxed phase and CD control specifications when an appropriate illumination is chosen. Good intra-field CD control and sufficient large process window for 65nm pattern can be obtained for this mask type. The impact of aberrations and pupil imperfections on the CD control has been investigated. The mask processes will be discussed and mask performance data introduced.