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Understanding the Impact of Porosity and Pore Structure in Ultra Low Dielectric Constant Organosilicate Glasses

Published online by Cambridge University Press:  30 July 2012

Irene J. Hsu ,
Raymond N. Vrtis ,
Jennifer E. Al-Rashid ,
Anupama Mallikarjunan ,
Kathleen E. Theodorou  and
John M. Zielinski
Irene J. Hsu
Affiliation:
Electronics Technology, Air Products and Chemicals, Inc., Allentown, PA, United States.
Raymond N. Vrtis
Affiliation:
Electronics Technology, Air Products and Chemicals, Inc., Allentown, PA, United States.
Jennifer E. Al-Rashid
Affiliation:
Electronics Technology, Air Products and Chemicals, Inc., Allentown, PA, United States.
Anupama Mallikarjunan
Affiliation:
Electronics Technology, Air Products and Chemicals, Inc., Allentown, PA, United States.
Kathleen E. Theodorou
Affiliation:
Electronics Technology, Air Products and Chemicals, Inc., Allentown, PA, United States.
John M. Zielinski
Affiliation:
Intertek Analytical Sciences Americas, Allentown, PA, United States.
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Abstract

Recently there have been a number of reports indicating concern relating to the effect of porosity, pore size distribution, and pore interconnectivity on the integration of highly porous ultra low-k organosilicate glasses (OSGs) as back-end-of-line (BEOL) interconnect dielectrics. In an effort to address these concerns a number of options to control the skeleton and pore structure of OSGs have been proposed, from adding alternative OSG precursors to alternative porogen precursors. In all these options there is a need to balance pore structure modification with critical film properties such as dielectric constant and mechanical strength. In this context, this paper examines porosity and its impact on film properties for highly porous ultra low dielectric constant films. A series of PDEMS® porous OSG films were deposited by plasma enchanced chemical vapor deposition (PECVD) from DEMS® precursor (diethoxymethylsilane) and porogen ATRP (alpha-terpenine). The percent porosity and pore interconnectivity of these films relative to the dielectric constant were measured by ellipsometric porosimetry (EP) and positron annihilation spectroscopy (PALS) respectively. Porosity and pore-size distribution for films deposited using several different species (structure former or porogen precursors) were examined using EP in an effort to understand the impact of the chemical nature of the precursor on pore morphology. Results from these depositions show that it is possible to deposit films with smaller pores using alternative structure formers (ASFs) with bulky organic groups, although there are tradeoffs with respect to other film characteristics. The addition of a separate porogen (ATRP) to the ASF lowered the dielectric constant and the addition of DEMS® precursor to the ASF/ATRP mix gave the films added structural integrity and mechanical strength. Such a fundamental understanding of structure-property relationships will help support successful integration of these porous OSG films.

Keywords

porositydielectricmicroelectronics
Type
Articles
Information
MRS Online Proceedings Library (OPL) , Volume 1428: Symposium C – “Interconnect Challenges for CMOS Technology--Materials, Processes and Reliability for Downscaling, Packaging and 3D Stacking” , 2012 , mrss12-1428-c01-10
Copyright
Copyright © Materials Research Society 2012

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