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CVD Boron Carbo-Nitride as Pore Sealant for Ultra Low-K Interlayer Dielectrics

Published online by Cambridge University Press:  01 February 2011

P. Ryan Fitzpatrick ,
Sri Satyanarayana ,
Yangming Sun ,
John M. White  and
John G. Ekerdt
P. Ryan Fitzpatrick
Affiliation:
Department of Chemical Engineering, University of Texas, Austin, TX 78712
Sri Satyanarayana
Affiliation:
SEMATECH, Austin, TX 78741
Yangming Sun
Affiliation:
Department of Chemistry and Biochemistry, University of Texas, Austin, TX 78712
John M. White
Affiliation:
Department of Chemistry and Biochemistry, University of Texas, Austin, TX 78712
John G. Ekerdt
Affiliation:
Department of Chemical Engineering, University of Texas, Austin, TX 78712
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Abstract

Blanket porous methyl silsesquioxane (pMSQ) films on a Si substrate were studied with the intent to seal the pores and prevent penetration of a metallic precursor during barrier deposition. The blanket pMSQ films studied were approximately 220 nm thick and had been etched and ashed. When tantalum pentafluoride (TaF5) is exposed to an unsealed pMSQ sample, X-ray photoelectron spectroscopy (XPS) depth profiling and secondary ion mass spectroscopy (SIMS) depth profiling reveal penetration of Ta into the pores all the way to the pMSQ / Si interface. Boron carbo-nitride films were grown by thermal chemical vapor deposition (CVD) using dimethylamine borane (DMAB) precursor with Ar carrier gas and C2H4 coreactant. These films had a stoichiometry of BC0.9N0.07 and have been shown in a previous study to have a k value as low as 3.8. BC0.9N0.07 films ranging from 1.8 to 40.6 nm were deposited on pMSQ and then exposed to TaF5 gas to determine the extent of Ta penetration into the pMSQ. Ta penetration was determined by XPS depth profiling and sometimes SIMS depth profiling. XPS depth profiling of a TaF5 / 6.3 nm BC0.9N0.07 / pMSQ / Si film stack indicates the attenuation of the Ta signal to < 2 at. % throughout the pMSQ. Backside SIMS of this sample suggests that trace amounts of Ta (< 2 at. %) are due to knock-in by Ar ions used for sputtering. An identical film stack containing 3.9 nm BC0.9N0.07 was also successful at inhibiting Ta penetration even with a 370°C post-TaF5 exposure anneal, suggesting the stability of BC0.9N0.07 to thermal diffusion of Ta. All BC0.9N0.07 films thicker than and including 3.9 nm prevented Ta from penetrating into the pMSQ.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 863: Symposium B – Materials, Technology and Reliability of Advanced Interconnects , 2005 , B6.8
Copyright
Copyright © Materials Research Society 2005

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