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Evaluation of the thermal stability of TiW/Cu heterojunctions using a combined SXPS and HAXPES approach

Kalha, C; Reisinger, M; Thakur, PK; Lee, T-L; Venkatesan, S; Isaacs, M; Palgrave, RG; ... Regoutz, A; + view all (2022) Evaluation of the thermal stability of TiW/Cu heterojunctions using a combined SXPS and HAXPES approach. Journal of Applied Physics , 131 (16) , Article 165301. 10.1063/5.0086009. Green open access

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Abstract

Power semiconductor device architectures require the inclusion of a diffusion barrier to suppress or at best prevent the interdiffusion between the copper metallization interconnects and the surrounding silicon substructure. The binary pseudo-alloy of titanium–tungsten (TiW), with >70 at. % W, is a well-established copper diffusion barrier but is prone to degradation via the out-diffusion of titanium when exposed to high temperatures ([Formula: see text]400 [Formula: see text]C). Here, the thermal stability of physical vapor deposited TiW/Cu bilayer thin films in Si/SiO[Formula: see text](50 nm)/TiW(300 nm)/Cu(25 nm) stacks were characterized in response to annealing at 400 [Formula: see text]C for 0.5 h and 5 h, using a combination of soft and hard x-ray photoelectron spectroscopy and transmission electron microscopy. Results show that annealing promoted the segregation of titanium out of the TiW and interdiffusion into the copper metallization. Titanium was shown to be driven toward the free copper surface, accumulating there and forming a titanium oxide overlayer upon exposure to air. Annealing for longer timescales promoted a greater out-diffusion of titanium and a thicker oxide layer to grow on the copper surface. However, interface measurements suggest that the diffusion is not significant enough to compromise the barrier integrity, and the TiW/Cu interface remains stable even after 5 h of annealing.

Type: Article
Title: Evaluation of the thermal stability of TiW/Cu heterojunctions using a combined SXPS and HAXPES approach
Open access status: An open access version is available from UCL Discovery
DOI: 10.1063/5.0086009
Publisher version: https://doi.org/10.1063/5.0086009
Language: English
Additional information: © 2022 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).
UCL classification: UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Chemistry
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL
URI: https://discovery.ucl.ac.uk/id/eprint/10148238
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