| abstract |
A method for making planar metal interconnections and T-shaped metal plugs for integrated circuits is achieved. The method involves forming a planar insulating (SiO 2 ) and a hard mask film over a first level of interconnections. A patterned first photoresist layer is then formed for etching trenches in the hard mask film and partially into the planar insulating layer (SiO 2 ) in which a second level of interconnections are to be formed. The patterned photoresist layer is then laterally etched to expose the hard mask adjacent to the trenches in the SiO 2 , and the hard mask is then removed adjacent to the trenches to form a self-aligned mask for the metal plug contact openings. A patterned second photoresist mask aligned over the trenches is then used to etch the contact openings in the trenches, using the hard mask to form T-shaped plug contact openings to the first level of interconnections. The trenches and plug contact openings are concurrently filled with CVD aluminum and chem/mech polished back to form the second level of interconnections with T-shaped metal plugs. The T-shaped metal plugs improve the edge coverage while making it easier to fill the narrow contact openings with aluminum without voids in the metal plugs. |