Mechanism of via etch striation and its impact on contact resistance & breakdown voltage in 65nm cu low-k interconnects

The mechanism of two kinds of via etch striation (type I and type II) has been investigated to improve contact resistance (Rc) uniformity and solve breakdown voltage (VBD) issue in 65 nm Cu low-k interconnects. Heavy etching polymer deposition on the sidewall of capping layer and rapid photo-resist (PR) consumption on PR shoulder are two main resources to result in via etch striation. The effects of both via etch striations on Rc and VBD can be decoupled. Type I striation related to barc open (BO) step leads to worse Rc uniformity while type II striation formed in main etch (ME) and over-etch (OE) step degrades VBD performance.