Study of surface control during barrier layer etch

摘要

The etching characteristics of Ta/TaN bilayer barrier films are investigated using a commercial capacitively coupled plasma (CCP) etch system. The challenge of the barrier layer etch is that the by-product is very difficult to remove even with lengthy CF4/O2 strip and ST250 (alkali solvent) wet strip. Two typical chemistry bases for barrier layer etch are studied in this paper. With the first chemistry base (C4F8 and C4F6), the dielectric layer sidewall has no etch by-product residue, but the copper surface underneath the barrier layer has barrier residue and worse pinhole. With the other chemistry base (CF4 with high flow and low pressure), the following can be achieved with CO addition: no etch by-product adhesion to the sidewall, no pinhole and barrier layer residue on copper surface underneath the barrier layer.