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Characterization of CMP Pad Surface Texture and Pad-Wafer Contact

Published online by Cambridge University Press:  15 March 2011

Gregory P. Muldowney  and
David B. James
Gregory P. Muldowney
Affiliation:
Advanced Research and Pad Technology Groups Rohm and Haas Electronic Materials, CMP Technologies, Newark, DE, USA
David B. James
Affiliation:
Advanced Research and Pad Technology Groups Rohm and Haas Electronic Materials, CMP Technologies, Newark, DE, USA
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Abstract

Surface texture of CMP polishing pads varies considerably with the intrinsic microstructure of the pad, the addition of perforations or grooves, and the means of surface conditioning. The state of pad-wafer contact is determined by both large and small-scale texture in the top pad asperity layer and by the interaction of the top pad and sub-pad.

A flow-based texture characterization test was applied to several types of CMP polishing pads to describe the asperity layer as a porous media having a void fraction and characteristic length. Fluid pressure loss profiles were measured in a radial flow geometry across pad samples pressed against a flat instrumented plate. Symmetry of the profiles revealed the extent of contact between the pad and the plate, and curvature of the profiles showed the relative contributions of viscous and inertial flow among the asperities. Sub-pads, grooving, and conditioning all increased padwafer contact and the effective resistance of the surface texture, improving flow uniformity. Soft pads showed higher inertial flow influence than fixed abrasives with regularly spaced asperities. The results demonstrate that pad surface texture has a strong influence on heat and mass transfer at the wafer surface in CMP. Implications are discussed for both pad design and CMP modeling.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 816: Symposium K – Advances in Chemical-Mechanical Polishing , 2004 , K5.2
Copyright
Copyright © Materials Research Society 2004

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