Abstract: A method for dry etching metal films, specifically aluminum, is described. This process uses photoresist as a mask with a gas mixture of BCl3, Cl2 and N2 used for the RIE. The addition of specific amounts of N2 to the etching chemistry results in non-tapered or non-undercut aluminum shapes. These desired shapes are attributed to the creation of polymer on the sidewall of the aluminum during the etching procedure, thus protecting against the isotropic components of RIE process, which cause the tapering. This RIE process can also be conducted at high enough temperatures, needed to avoid deleterious microloading effects.

Abstract: This invention provides a method of forming contact holes and via holes in interlevel dielectric which insure good metal stepcoverage. The contact or via holes have tapered sides and smoothed edges. The method uses isotropic etching, anisotropic etching, and argon sputter etching in vacuum and does not require high temperature contact reflow. The final argon sputter etch is a timed etch that smoothes all sharp edges, exposes the regions where electrical contact will be made, and planarizes the interlevel dielectric.