Optimization of resolution-enhancement technology and dual-layer bottom-antireflective coatings in hypernumerical aperture lithography

Resolution-enhancement technique (RET) and dual-layer bottom-antireflective coatings (DL-BARC) must be adopted in hypernumerical aperture (NA>1) lithography for a 45 nm half-pitch device. However, interactions of RET, polarization effect, and the resist process significantly impact on lithography performance. An in-house program and PROLITH 9.0 were employed to perform comprehensive optimization of RET and DL-BARC structures in order to improve pattern fidelity with a reasonable process window (PW). High-fidelity resist patterns are obtained when we employed optimum DL-BARC structures in conjunction with optimum RET. An alternating phase-shift mask and a conventional illumination is one kind of optimum combination of RET. An attenuated phase-shift mask and a cross-dipole illumination is the other one. Line-width changes are controlled within 4 nm. Sidewall angles are greater than 88°.