Electrochemical investigation of copper chemical mechanical planarization in alkaline slurry without an inhibitor

Abstract

This work investigates the static corrosion and removal rates of copper as functions of H 2 O 2 and FA/OIIconcentration, and uses DC electrochemical measurements such as open circuit potential (OCP), Tafel analysis, as well as cyclic voltammetry (CV) to study H 2 O 2 and FA/OIIdependent surface reactions of Cu coupon electrode in alkaline slurry without an inhibitor. An atomic force microscopy (AFM) technique is also used to measure the surface roughness and surface morphology of copper in static corrosion and polishing conditions. It is shown that 0.5 vol.% H 2 O 2 should be the primary choice to achieve high material removal rate. The electrochemical results reveal that the addition of FA/O II can dissolve partial oxide film to accelerate the electrochemical anodic reactions and make the oxide layer porous, so that the structurally weak oxide film can be easily removed by mechanical abrasion. The variation of surface roughness and morphology of copper under static conditions is consistent with and provides further support for the reaction mechanisms proposed in the context of DC electrochemical measurements. In addition, in the presence of H 2 O 2 , 3 vol.% FA/O II may be significantly effective from a surface roughness perspective to obtain a relatively flat copper surface in chemical mechanical planarization (CMP) process.

Chemical and Mechanical Aspects of a Co-Cu Planarization Scheme Based on an Alkaline Slurry Formulation

“…17 Additionally, to mitigate the surface defects caused by dissolution, alkaline slurries are an attractive option not only for barrier CMP, but also for Cu CMP. 18,19 To fully utilize these alkaline slurry chemistries, new advances have been made in recent years, 20,21 which include strategies for tackling alkaline damages to low-k materials. 22,23 In view of these developments, alkaline (pH = 10.3) slurry solutions are employed in z E-mail: samoy@clarkson.edu the present study.…”