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Moisture Adsorption in Plasma-Damaged Porous Low-k Dielectrics

Published online by Cambridge University Press:  01 February 2011

Ekaterina Vinogradova ,
Casey E Smith ,
DW Mueller ,
Andrew J McKerrow  and
Rick Reidy
Ekaterina Vinogradova
Affiliation:
Materials Science and Engineering, University of North Texas, PO Box 305310, Denton, TX, 76203-5310
Casey E Smith
Affiliation:
ces0102@unt.edu, University of North Texas, Materials Science and Engineering, PO Box 305310, Denton, TX, 76203-5310, United States
DW Mueller
Affiliation:
mueller@unt.edu, University of North Texas, Materials Science and Engineering, PO Box 305310, Denton, TX, 76203-5310, United States
Andrew J McKerrow
Affiliation:
mckerrow@ti.com, Texas Instruments, Dallas, TX, 75243, United States
Rick Reidy
Affiliation:
reidy@unt.edu, University of North Texas, Materials Science and Engineering, PO Box 305310, Denton, TX, 76203-5310, United States
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Abstract

Plasma etch/ash processes can induce changes in low-k film surface/bulk chemistries and topographies resulting in increased water absorption, surface roughness, and metal intrusion. After ashing, the altered surface character of the low-k can impact wetting, adhesion, and, consequently, the resistance of subsequently deposited barrier layers. In this work, we describe the use of deuterium oxide as means of measuring moisture penetration into low-k films. Film chemistries have been monitored using grazing angle attenuated total reflectance (GATR) and transmission Fourier transform infrared spectroscopy (FTIR). To study moisture absorption in porous spin-on and CVD low-k films, unashed and ashed films have been exposed to D2O liquid and vapor treatments under “dry” nitrogen. The extent of D2O uptake, removal and exchange reactions has been studied using transmission and GATR FTIR methods because the D2O and O-D adsorption peaks are distinct from water and O-H as well as other low-k adsorptions. This method can be used to study Si-OH species because deuterium can exchange with hydrogen within silanols under ambient conditions while methyl groups are much less likely to exchange. Three different low-k films, a porous spin-on MSQ (k=2.2), a porous CVD (k=2.3), and an organosilicate glass (OSG, k=2.85) have been used. In FTIR spectra, unashed low-k films show minimal D2O adsorption. In MSQ hydrogen-ashed films, the data suggest the presence of deuterium oxide and O-D peaks. Further, D2O adsorption appears to be considerably higher for ashed films as would be expected due to the hydrophobicity of these films. In the CVD films, there does not appear to be as marked a difference. This method permits the introduction of a chemical “marker” into low-k wet and ambient processes allowing one to distinguish among adsorptions from different aqueous sources.

Keywords

dielectricinfrared (IR) spectroscopyabsorption
Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 1079: Symposium N – Materials and Processes for Advanced Interconnects for Microelectronics , 2008 , 1079-N02-09
Copyright
Copyright © Materials Research Society 2008

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References

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