Method of preventing resist poisoning in dual damascene structures

A method, for forming a dual damascene interconnect in a dielectric, comprising:

• etching a first aperture in the dielectric, wherein the dielectric is a low-K dielectric;
• forming a poison barrier layer over part of the dielectric, which prevents resist poisoning;
• forming a patterned mask over the poison barrier layer;
• etching a second aperture into the low-K dielectric layer, wherein at least part of the first aperture shares the same area as at least part of the second aperture, wherein the first aperture is a via and the second aperture is a trench, wherein the via is within the trench, wherein the forming the poison barrier layer comprises plasma treating surfaces of the first aperture to neutralize nitrogen on the surfaces of the first aperture;
• placing a copper diffusion barrier layer over surfaces of the first aperture and second aperture;
• and
• filling the first aperture and second aperture with copper.