A new Al plasma etching technology for fine metallization of highly packed LSI´s

An Al plasma etching method that utilizes a BCl3+CF4+O2gas mixture followed by an anti-corrosion treatment has been developed. This process produces highly packed LSI metallizations of Al-Si and Al-Cu-Si alloys. This etching technology has the following features: (1) The CF4and O2added to BCl3to enhance BCl3decomposition in the plasma increase the Al etching rate and selectivity. (2) Side etching can be controlled to within 0.1 µm or less using a self bias (Vdc) of approximately -200 V. (3) Corrosion of the AI is prevented by treatment with CF4plasma. This method produces 3 µm pitch metallizations on rugged underlayers and can produce submicron patterns. It has been successfully used for the fabrication of two-level metallizations for highly packed LSI´s.