Fabrication of Deep Sub-lithographic Al-Based Nanointerconnects Utilizing a Wet Chemical Hard Mask Trim Process

A wet chemical trim of the SiO2 hard mask used for reactive ion etching of Al was developed to fabricate Al-based interconnects with line widths below those in today's most advanced semiconductor products. The electrical characterization of such narrow interconnects was done for a comparison with the data available for Cu Damascene interconnects with deep sub-100nm CDs. For very tight CDs very high electrical resistivities were obtained due to imperfect processing of Al. A fit of the combined compact model for size effects in Al to the experimental data obtained for CDs where process imperfections were not observed, allows an assessment of the expected increase of electrical resistivity of Al due to size effects for very tight feature sizes. The comparison of the data of Al- based interconnects fabricated with RIE using the trimmed SiO2 hard mask with Cu Damascene interconnects suggests a cross-over of electrical resistivities for CDs around 20nm.