Method for forming self-aligned vias in multi-level metal integrated

Abstract

A process for forming a via in a semiconductor device using a self-aligned metal pillar to connect metal layers separated by a dielectric. A first aluminum layer is formed on an oxide layer overlying a semiconductor substrate, and a thin tungsten layer is formed and patterned overlying the first aluminum layer. The pattern in this tungsten layer will determine the pattern for the first level of metal interconnect to be formed later in the first aluminum layer. The tungsten layer is etched using the underlying first aluminum layer as an etch stop. A second aluminum layer is then formed overlying the patterned tungsten layer and the exposed regions of the first aluminum layer. In one continuous etching step the second aluminum layer is patterned and etched to form a pillar, and the first aluminum layer is etched to form the first level of metal interconnect in the semiconductor device using the pattern formed earlier in the tungsten layer and to expose regions of the oxide layer. A dielectric is deposited overlying the exposed regions of the oxide layer, the formed pillar, and the thin tungsten layer. This dielectric is etched back to expose the top of the pillar, and then a third aluminum layer is deposited overlying the dielectric to make electrical contact to the exposed surface of the pillar.