Slurry for chemical mechanical polishing of cobalt

Abstract

A slurry for chemical mechanical polishing of Co. The slurry comprises components by weight as follows, Inhibitor 0.01-2%, Oxidant 0-5%, Abrasive 0.1-10%, Complexing agent 0.001-10%, and the rest of water. The pH value of the slurries is adjusted to 3-5 by a pH value adjustor. The inhibitor is chosen from one or more kinds of five-membered heterocycle compound containing S and N atoms or containing S or N atom. The oxidant is one or more chosen from H2O2, (NH4)2S2O8, KIO4, and KClO5. The abrasive is one or more chosen from SiO2, CeO2, and Al2O3. The complexing agent is one or more chosen from amino acid and citric acid. The slurry can effectively prevent Co over corrosion and reduce the polishing rate of Co in the polishing process.

Description

TECHNICAL FIELD [0001]The present invention relates to microelectronics technology, especially relates to chemical mechanical polishing (CMP) slurries and related applications.BACKGROUND OF THE INVENTION[0002]With the continuous shrink of feature size in ultra large scale integrated Circuits (ULSI) technology, the size of the copper interconnect structure is getting more and more smaller. To reduce the RC delay, the thickness of barrier or adhesion layer in the copper interconnect structure is getting thinner. The traditional copper barrier / adhesion layer stack—Ta / TaN is not suitable any more, as the resistivity of Ta is relatively high and copper cannot be directly electroplated onto Ta. Compared with Ta, cobalt has lower resistivity and is relatively cheaper. The adhesion between Cu and Co is good. Cu can easily nucleate on Co, also copper can be directly electroplated on cobalt.[0003]Porous low k dielectrics material has been already used in the current interconnect structures. I...

AI Technical Summary

Benefits of technology

The present invention provides a slurry for chemical mechanical polishing in microelectronics technology that can prevent reliability issues caused by over polishing or corrosion. The slurry includes an inhibitor that reduces corrosion rates of copper (Cu) and cobalt (Co) in the slurry, resulting in improved efficiency of planarization, reduced dishing defects, and prevention of adhesion layer dissolution along the sidewall of the interconnect structure. The inhibitor is selected from five-membered heterocycle compounds containing S and N atoms or their derivatives. Additionally, the slurry includes a complexing agent, such as amino acid or citric acid, which reacts with metal ions on the metal surface or in the slurry, reducing metal particles and preventing metal ion contamination. Overall, the present invention is a slurry that effectively inhibits Co corrosion rate and reduces polishing rate of Co, resulting in reduced defects after polishing process.

Problems solved by technology

The traditional copper barrier / adhesion layer stack—Ta / TaN is not suitable any more, as the resistivity of Ta is relatively high and copper cannot be directly electroplated onto Ta.

It is reported that low k can be easily damaged by plasma or polishing slurries.

But it is observed that copper and cobalt easily suffered from dissolution in acidic solution containing oxidant (H2O2).

The dissolution of the cobalt adhesion layer on the sidewall of the copper interconnect structure can lead to the delamination of copper lines and cause reliability problem.

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