Composite metal etching for submicron integrated circuits

To define metal lines for composite metal structures for integrated circuits with small pitches (<2 μm), the etch selectivity and dimensional control must be improved from existing values of ~1.5:1 and >0.1 μm/line, respectively, without leaving metallic residue and without undercutting the masking layer. These goals have been achieved for a layered metal structure of Ti-W/Al-Cu(2%)/Ti-W with an Applied Materials AME 8330 batch system after examining process parameter spaces defined by the following: (i) reactor pressure, (ii) dc bias voltage, and (iii) gas composition for these two films. The selectivity between Al-Cu(2%) and photoresist increases with decreasing dc bias voltage and increasing Cl₂ content of Cl₂/BCl₃/CHF₃ gas mixtures. In comparison, the selectivity between Ti-W and photoresist increases only with increasing CF₄ content of CF₄/Cl₂ gas mixtures; changes in the other variables examined in this work with Ti-W have no significant effect on selectivity