Method of etching self-aligned vias and trenches in a multi-layer film stack

Abstract

A multi-step etch process wherein elliptical via openings and trench openings are formed in a dielectric layer includes supporting a multi-layer film stack on a temperature controlled electrostatic chuck in a plasma etch reactor. The multi-layer film stack has a dielectric layer and a patterned metal hard mask layer above the dielectric layer. An etchant gas is supplied to the plasma etch reactor. The etchant gas is energized into a plasma state, and via openings in a photo resist are transferred into a planarization layer and then into elliptical portions of the trench openings in a patterned hard mask layer while maintaining the chuck at a temperature of about 30 to 50° C. The elliptical openings are extended into a lower layer of the hard mask and into an underlying dielectric layer while maintaining the chuck at a temperature of 20° C. or below. After stripping the planarization layer to expose the trench pattern in the hard mask, trench openings are formed in the dielectric layer while maintaining the chuck at a temperature of about 55° C. or higher. The process can thus provide enlarged via contact areas while etching trenches with pitches of 80 nm or less.