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Characterizing STI CMP Processes with an STI Test Mask Having Realistic Geometric Shapes

Published online by Cambridge University Press:  15 March 2011

Xiaolin Xie
Affiliation:
Microsystems Technology Laboratories, MIT, Cambridge, MA
Tae Park
Affiliation:
Microsystems Technology Laboratories, MIT, Cambridge, MA
Duane Boning
Affiliation:
Microsystems Technology Laboratories, MIT, Cambridge, MA
Aaron Smith
Affiliation:
National Semiconductor, South Portland, ME
Paul Allard
Affiliation:
National Semiconductor, South Portland, ME
Neil Patel
Affiliation:
National Semiconductor, South Portland, ME
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Abstract

Chemical mechanical polishing (CMP) has become the enabling planarization method for shallow trench isolation (STI) of sub 0.25μm technology. CMP is able to reduce topography over longer lateral distances than earlier techniques; however, CMP still suffers from pattern dependencies that result in large variation in the post-polish profile across a chip. In the STI process, insufficient polish will leave residue nitride and cause device failure, while excess dishing and erosion degrade device performance.

Our group has proposed several chip-scale CMP pattern density models [1], and a methodology using designed dielectric CMP test mask to characterize CMP processes [2]. The methodology has proven helpful in understanding STI CMP; however, it has several limitations as the existing test mask primarily consists of arrays of lines and spaces of large feature size varying from 10 to 100 μm. In this paper, we present a new STI characterization mask, which consists of various rectangular, L-shape, and X-shape structures of feature sizes down to submicron. The mask is designed to study advanced STI CMP processes better, as it is more representative of real STI structures. The small feature size amplifies the effects of edge acceleration and oxide deposition bias, and thus enables us to study their impact better. Experimental data from an STI CMP process is shown to verify the methodology, and these secondary effects are explored. The new mask and data guide ongoing development of improved pattern dependent STI CMP models.

Type
Research Article
Copyright
Copyright © Materials Research Society 2004

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References

[1] Ouma, D. O., Boning, D. S., Chung, J. E., Easter, W. G., Saxena, V., Misra, S., and Crevasse, A., “Characterization and Modeling of Oxide Chemical Mechanical Polishing Using Planarization Length and Pattern Density Concepts,” IEEE Trans. Semiconduct. Manufact., vol. 15, no. 2, pp. 232244, May 2002.Google Scholar
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[3] Xie, X., Park, T., Lee, Brian, Tugbawa, T., Cai, H. and Boning, D., “Re-examining the Physical Basis of Planarization Length in Pattern Density CMP Models,” MRS Spring Meeting, Symposium F: Chemical Mechanical Planarization, San Francisco, CA, April 2003 Google Scholar
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[5] Vlassak, J. J., “A contact-mechanics based model for dishing and erosion in chemicalmechanical polishing,” Material Research Society (MRS) Spring Meeting, 2001 Google Scholar