PVD aluminum dual damascene interconnection: yield comparison between counterbore and self aligned approaches

A comparative study of the counterbore dual damascene (CBDD) and self-aligned dual damascene (SADD) approaches with aluminum interconnects was carried out for application to 0.18 /spl mu/m ULSI multilevel interconnects. It is shown that the defect density is lower with the SADD approach. Yield degradation with the CBDD approach is explained by photoresist residues in the bottom of vias, which are difficult to remove due to the high aspect ratio of the holes. The Al-CMP process was optimized by introducing dummy structures to reduce Al dishing on wide interconnect lines. Equivalent yield was demonstrated with the SADD approach in comparison with the standard subtractive aluminum etch process on 0.25 /spl mu/m SRAM technology.