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Electrochemical Measurements Demonstrate Performance of BTAH and Alternative Passivating Agents on Copper in a Hydroxylamine CMP System

Published online by Cambridge University Press:  01 February 2011

Melvi Keith Carter  and
Robert Small
Melvi Keith Carter
Affiliation:
DuPont Electronic Technologies, EKC Technology 2520 Barrington Court Hayward, CA 94545-1163
Robert Small
Affiliation:
DuPont Electronic Technologies, EKC Technology 2520 Barrington Court Hayward, CA 94545-1163
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Extract

Organic passivating agents have been measured by a galvanostatic method during abrasive free Chemical Mechanical Planarization (CMP) of copper coated silicon wafers. CMP process steps include (a) removal of the passivation layer to expose the metal surface, (b) wet chemical oxidation of the metal surface and (c) mechanical removal of the oxidation products by means of the pad with a colloidal polishing aid such as silica or alumina1. CMP of necessity seeks to establish a unique equilibrium between little or no metal removal due to corrosion effects and rapid metal removal resulting from a mechanically aided chemical oxidation or polishing. Chemical oxidizing agents can corrode the metal surface during polishing and non-polishing steps alike so protective passivation agents are necessary to inhibit or block surface corrosion. Historically, benzotriazole (BTAH) has been the copper protective agent of choice because it performed well at concentrations of 50 to 500ppm, however BTAH can scratch copper. Self-assembly of monolayers was reported by Sung et al2 demonstrating a tendency toward organizational energy of molecular surface protection. Cho et al3 have reported formation of a flat, well ordered BTAH based monolayer on copper supporting a three dimensional BTAH stack above it. Metrikos-Hukovic et al4 reported evidence for a monolayer of a CuBTA compound and additional adsorption/crystallization layers of 7nm thickness5 were measured. Discussions in this work refer to the combined adsorption/chelation layers on copper as passivation providing measurements that distinguish between them. It will be shown that addition of BTAH forms a thin layer of CuBTA covered by a second layer creating a protective film with relatively high electrical resistance. The purpose of this electrochemical effort is to measure the effect of BTAH during a non-Prestonian, slurry free CMP process, to affect a direct measure of bi-layer passivation and to identify other organic compounds that may also provide protection of the copper surface against corrosion.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 767: Symposium F – Chemical-Mechanical Planarization , 2003 , F6.2
Copyright
Copyright © Materials Research Society 2003

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References

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