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Title: Al/Ti{sub x}W{sub 1{minus}x} metal/diffusion-barrier bilayers: Interfacial reaction pathways and kinetics during annealing

Abstract

Polycrystalline bcc Ti{sub x}W{sub 1{minus}x} layers with mixed 011 and 002 texture were grown on oxidized Si(001) substrates at 600{degree}C by ultrahigh-vacuum (UHV) sputter deposition from W and Ti{sub 0.33}W{sub 0.67} targets using both pure Ar and Xe discharges. Ti concentrations in the 100-nm-thick layers were 0, 6, and 33 at.{percent} depending on target composition and sputtering gas. Al overlayers, 190 nm, thick with strong 111 preferred orientation, were then deposited in Ar at 100{degree}C. Changes in bilayer sheet resistance R{sub s} were monitored as a function of time t{sub a} and temperature T{sub a} during subsequent UHV annealing. Thermal ramping of Al/W and Al/Ti{sub 0.06}W{sub 0.94} bilayers at 3{degree}C min{sup {minus}1} resulted in large ({gt}fourfold) increases in R{sub s} at T{sub a}{approx_equal}550{degree}C, whereas R{sub s} in the Al/Ti{sub 0.33}W{sub 0.67} bilayers did not exhibit a similar increase until {approx_equal}610{degree}C. Interfacial reactions and microstructural changes were followed as a function of annealing conditions. Results indicate that Al/W and Al/Ti{sub 0.06}W{sub 0.94} bilayer reactions proceed along a very similar pathway in which monoclinic WAl{sub 4} forms first as a discontinuous interfacial phase followed by the nucleation of bcc WAl{sub 12} whose growth is limited by the rate of W diffusion, withmore » an activation energy of 2.7 eV, into Al. In contrast, the W diffusion rate during the early stages of Al/Ti{sub 0.33}W{sub 0.67} annealing is significantly higher allowing the formation of a continuous WAl{sub 4} interfacial blocking layer which increases the overall activation energy E{sub a}, still limited by W diffusion, to 3.4 eV and strongly inhibits further reaction. We attribute observed increases in WAl{sub 4} nucleation and growth rates in interfacial Al/Ti{sub 0.33}W{sub 0.67} to a vacancy wind effect associated with the very rapid (E{sub a}=1.7 eV) diffusion of Ti into Al. (Abstract Truncated)« less

Authors:
; ;  [1]
  1. Coordinated Science Laboratory, Materials Research Laboratory, and Department of Materials Science, University of Illinois, Urbana, Illinois 61801 (United States)
Publication Date:
Research Org.:
Univ. of Illinois at Urbana-Champaign, IL (United States)
OSTI Identifier:
550377
DOE Contract Number:  
AC02-76ER01198
Resource Type:
Journal Article
Journal Name:
Journal of Applied Physics
Additional Journal Information:
Journal Volume: 82; Journal Issue: 5; Other Information: PBD: Sep 1997
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; ALUMINIUM; INTERFACES; TITANIUM ALLOYS; DIFFUSION; TUNGSTEN BASE ALLOYS; NUCLEATION; CHEMICAL REACTIONS; SPUTTERING; ANNEALING; MICROSTRUCTURE; PHASE STUDIES; TEMPERATURE DEPENDENCE

Citation Formats

Bergstrom, D B, Petrov, I, and Greene, J E. Al/Ti{sub x}W{sub 1{minus}x} metal/diffusion-barrier bilayers: Interfacial reaction pathways and kinetics during annealing. United States: N. p., 1997. Web. doi:10.1063/1.366039.
Bergstrom, D B, Petrov, I, & Greene, J E. Al/Ti{sub x}W{sub 1{minus}x} metal/diffusion-barrier bilayers: Interfacial reaction pathways and kinetics during annealing. United States. https://doi.org/10.1063/1.366039
Bergstrom, D B, Petrov, I, and Greene, J E. Mon . "Al/Ti{sub x}W{sub 1{minus}x} metal/diffusion-barrier bilayers: Interfacial reaction pathways and kinetics during annealing". United States. https://doi.org/10.1063/1.366039.
@article{osti_550377,
title = {Al/Ti{sub x}W{sub 1{minus}x} metal/diffusion-barrier bilayers: Interfacial reaction pathways and kinetics during annealing},
author = {Bergstrom, D B and Petrov, I and Greene, J E},
abstractNote = {Polycrystalline bcc Ti{sub x}W{sub 1{minus}x} layers with mixed 011 and 002 texture were grown on oxidized Si(001) substrates at 600{degree}C by ultrahigh-vacuum (UHV) sputter deposition from W and Ti{sub 0.33}W{sub 0.67} targets using both pure Ar and Xe discharges. Ti concentrations in the 100-nm-thick layers were 0, 6, and 33 at.{percent} depending on target composition and sputtering gas. Al overlayers, 190 nm, thick with strong 111 preferred orientation, were then deposited in Ar at 100{degree}C. Changes in bilayer sheet resistance R{sub s} were monitored as a function of time t{sub a} and temperature T{sub a} during subsequent UHV annealing. Thermal ramping of Al/W and Al/Ti{sub 0.06}W{sub 0.94} bilayers at 3{degree}C min{sup {minus}1} resulted in large ({gt}fourfold) increases in R{sub s} at T{sub a}{approx_equal}550{degree}C, whereas R{sub s} in the Al/Ti{sub 0.33}W{sub 0.67} bilayers did not exhibit a similar increase until {approx_equal}610{degree}C. Interfacial reactions and microstructural changes were followed as a function of annealing conditions. Results indicate that Al/W and Al/Ti{sub 0.06}W{sub 0.94} bilayer reactions proceed along a very similar pathway in which monoclinic WAl{sub 4} forms first as a discontinuous interfacial phase followed by the nucleation of bcc WAl{sub 12} whose growth is limited by the rate of W diffusion, with an activation energy of 2.7 eV, into Al. In contrast, the W diffusion rate during the early stages of Al/Ti{sub 0.33}W{sub 0.67} annealing is significantly higher allowing the formation of a continuous WAl{sub 4} interfacial blocking layer which increases the overall activation energy E{sub a}, still limited by W diffusion, to 3.4 eV and strongly inhibits further reaction. We attribute observed increases in WAl{sub 4} nucleation and growth rates in interfacial Al/Ti{sub 0.33}W{sub 0.67} to a vacancy wind effect associated with the very rapid (E{sub a}=1.7 eV) diffusion of Ti into Al. (Abstract Truncated)},
doi = {10.1063/1.366039},
url = {https://www.osti.gov/biblio/550377}, journal = {Journal of Applied Physics},
number = 5,
volume = 82,
place = {United States},
year = {1997},
month = {9}
}