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Anisotropic Elastic Properties of Low-k Dielectric Materials

Published online by Cambridge University Press:  17 March 2011

A.A. Maznev ,
A. Mazurenko ,
G. Alper ,
C.J.L. Moore ,
M. Gostein ,
Michelle T. Schulberg ,
Raashina Humayun ,
Archita Sengupta  and
Jia-Ning Sun
A.A. Maznev
Affiliation:
Philips Advanced Metrology Systems, Natick MA 01760
A. Mazurenko
Affiliation:
Philips Advanced Metrology Systems, Natick MA 01760
G. Alper
Affiliation:
Philips Advanced Metrology Systems, Natick MA 01760
C.J.L. Moore
Affiliation:
Philips Advanced Metrology Systems, Natick MA 01760
M. Gostein
Affiliation:
Philips Advanced Metrology Systems, Natick MA 01760
Michelle T. Schulberg
Affiliation:
Novellus Systems, Inc., San Jose, CA 95134
Raashina Humayun
Affiliation:
Novellus Systems, Inc., San Jose, CA 95134
Archita Sengupta
Affiliation:
Novellus Systems, Inc., San Jose, CA 95134
Jia-Ning Sun
Affiliation:
Novellus Systems, Inc., San Jose, CA 95134
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Abstract

A non-contact optical technique based on laser-generated surface acoustic waves (SAWs) was used to characterize elastic properties of two types of thin (150-1100 nm) low-k films: more traditional non-porous organosilicate glass PECVD films (k=3.0) and novel mesoporous silica films fabricated in supercritical CO2 (k=2.2). The acoustic response of the non-porous samples is well described by a model of an elastically isotropic material with two elastic constants, Young's modulus and Poisson's ratio. Both parameters can be determined by analyzing SAW dispersion curves. However, the isotropic model fails to describe the SAW dispersion in the mesoporous samples. Modifying the model to allow a difference between in-plane and out-of plane properties (i.e., a transversely isotropic material) results in good agreement between the measurements and the model. The in-plane compressional modulus is found to be 2-3 times larger than the out-of plane modulus, possibly due to the anisotropic shape of the pores. Elastic anisotropy should therefore be taken into account in modeling mechanical behavior of low-k materials.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 812: Symposium F – Materials, Technology and Reliability for Advanced Interconnects and Low-k Dielectrics-2004 , 2004 , F5.9
Copyright
Copyright © Materials Research Society 2004

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