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Nanoindentation Analysis of Mechanical Properties of Low to Ultralow Dielectric Constant SiCOH Films

Published online by Cambridge University Press:  01 August 2005

Lugen Wang ,
M. Ganor ,
S.I. Rokhlin  and
Alfred Grill
Lugen Wang
Affiliation:
The Ohio State University, Laboratory for Multiscale Materials Processing and Characterization, Edison Joining Technology Center, Columbus, Ohio 43221
M. Ganor
Affiliation:
The Ohio State University, Laboratory for Multiscale Materials Processing and Characterization, Edison Joining Technology Center, Columbus, Ohio 43221
S.I. Rokhlin*
Affiliation:
The Ohio State University, Laboratory for Multiscale Materials Processing and Characterization, Edison Joining Technology Center, Columbus, Ohio 43221
Alfred Grill
Affiliation:
IBM—Thomas J. Watson Research Center, Yorktown Heights, New York 10598
*
a) Address all correspondence to this author. e-mail: [email protected]
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Abstract

Carbon-doped oxide SiCOH films with low to ultralow dielectric constants were prepared on a Si substrate by plasma-enhanced chemical vapor deposition (PECVD) from mixtures of SiCOH precursors with organic materials. The films have different levels of nanoscale porosity resulting in different dielectric constants and mechanical properties. The mechanical properties of the films have been characterized by continuous-stiffness nanoindentation measurements. To study the effect of film thickness, each group of samples with the same dielectric constant was composed of samples prepared with different film thicknesses. It is shown that the effective hardness and modulus of the SiCOH/Si substrate system depends significantly on indentation depth due to substrate constraint effects. The “true” film properties were determined using both an empirical formulation of the effective modulus and direct inversion based on a finite element model. The hardness and modulus of three groups of samples with different degrees of dielectric constants have been measured. The hardness increases from 0.7 to 2.7 GPa and modulus from 3.6 to 17.0 GPa as the dielectric constants change from 2.4 to 3.0. While for stiffer films the modulus measured at an indentation depth 10% of the film thickness is close to the “true” value for films thicker than 0.5 μm, the measured value can give an overestimate of up to 35% for softer films. Thin film cracking and film–substrate debonding have been observed with scanning electron and atomic force microscopy at the indentation sites in softer films. The damage initiation is indicated by pop-in events in the loading curve and sharp peaks in the normalized contact stiffness curves versus indentation depth.

Type
Articles
Information
Journal of Materials Research , Volume 20 , Issue 8 , August 2005 , pp. 2080 - 2093
Copyright
Copyright © Materials Research Society 2005

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References

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