Hostname: page-component-78c5997874-lj6df Total loading time: 0 Render date: 2024-11-09T09:44:27.605Z Has data issue: false hasContentIssue false

Advances in Understanding and Control of CMP Performance: Contact-Hydrodynamics at Wafer, Groove, and Asperity Scale

Published online by Cambridge University Press:  01 February 2011

Gregory P. Muldowney*
Affiliation:
[email protected], tba, tba, tba, tba, DE, tba, United States
Get access

Abstract

Examining CMP at any scale, one finds coupled contact mechanics and fluid mechanics. Increasingly sophisticated experimental and computational techniques have revealed aspects of solid-solid interaction and slurry flow at the wafer and groove scale and, more recently, at the texture scale. Successful prediction of CMP performance hinges on identifying universal physics that span these scales. In this paper we first review results of novel asperity-scale experiments that characterize the pad texture both as a solid topography subject to contact deformation and as an equivalent porous medium for slurry flow. These measures reveal that much of the texture volume is inactive as flow space, a feature confirmed quantitatively by computational modeling of flow across a conditioned CMP pad surface built from 3-D microscopy images. For hydrodynamics, the findings establish active fluid volume per unit area as the property that bridges from asperity scale to wafer scale. We then derive a fundamental basis for CMP removal rate prediction based on contact and hydrodynamics, using a Sommerfeld number defined across the groove and texture length scales. The resulting equation, containing a single unknown proportionality constant, demonstrates that the often used product of downforce and table speed tracks removal rate only when the hydrodynamic state affords adequate pad-wafer contact. Departures from the Preston equation attributed in other models to chemically-limited regimes of CMP are explained in the present treatment as changes in hydrodynamic film thickness and contact area—a fact confirmed by direct measurement. Removal rate predictions are discussed for ILD, STI, and copper processes using both conventional and non-Prestonian slurries, including variations in downforce, table speed, temperature, pad properties, and groove design. Finally, the influence of regional pad-wafer hydrodynamics is illustrated by applying the contact-hydrodynamics equation to grooves specially configured to vary the slurry film thickness from wafer center to edge. Local removal rates are well predicted using locally defined values of the groove-texture Sommerfeld number, confirming the generality of the contact-hydrodynamic description at least from wafer to asperity scale. Findings are further discussed in the context of next-generation pad architectures—not only to achieve more effective pad-wafer contact and slurry delivery, but also to favorably decouple contact and fluid mechanics in CMP pad design.

Type
Research Article
Copyright
Copyright © Materials Research Society 2007

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

References

REFERENCES

1. Elmufdi, C. L. and Muldowney, G. P., MRS Spring Meeting (2007).Google Scholar
2. Elmufdi, C. L. and Muldowney, G. P., Proceedings of MRS Spring Meeting (2006).Google Scholar
3. Muldowney, G. P., Proceedings of AIChE Fall Meeting (2003).Google Scholar
4. Ergun, S., Chem. Engr. Prog., 48, 89 (1952).Google Scholar
5. Muldowney, G. P. et al, Proceedings of CMP-MIC Conference (2006).Google Scholar
6. Muldowney, G. P., Proceedings of CAMP 11th International Symposium on CMP (2006).Google Scholar
7. Muldowney, G. P. and Tselepidakis, D. P., Proceedings of ECS Spring Meeting (2004).Google Scholar
8. Jiang, B. and Muldowney, G. P., MRS Spring Meeting (2007).Google Scholar
9. Cook, L. M., in Journal of Non-Crystalline Solids (1990).Google Scholar
10. Stein, D. and Hetherington, D., Proceedings of ECS Spring Meeting (1999).Google Scholar
11. Lawing, A. S., unpublished results (2005).Google Scholar
12. Sorooshian, J. et al, Proceedings of MRS Spring Meeting (2004).Google Scholar
13. Duong, C. H., unpublished results (2003).Google Scholar
14. Elmufdi, C. L., Hendron, J. J., and Muldowney, G. P., United States Patent 7,131,895.Google Scholar
15. Muldowney, G. P., Duong, C. H., VanHanehem, M. R., and Kuo, C. C., Proceedings of ISTC Conference (2007).Google Scholar