Thermal and oxidation stability of Tix W1−x diffusion barriers investigated by soft and hard x-ray photoelectron spectroscopy

DOI: 10.1063/5.0048304

Authors: C. Kalha (University College London (UCL)) , S. Bichelmaier (Kompetenzzentrum Automobil- und Industrieelektronik GmbH) , N. K. Fernando (University College London) , J. V. Berens (Kompetenzzentrum Automobil- und Industrieelektronik GmbH) , P. K. Thakur (Diamond Light Source) , T.-L. Lee (Diamond Light Source) , J. J. Gutiérrez Moreno (Barcelona Supercomputing Center (BSC)) , S. Mohr (Barcelona Supercomputing Center (BSC); Nextmol (Bytelab Solutions SL)) , L. E. Ratcliff (Imperial College London) , M. Reisinger (Kompetenzzentrum Automobil- und Industrie-Elektronik GmbH) , J. Zechner (Kompetenzzentrum Automobil- und Industrie-Elektronik GmbH) , M. Nelhiebel (Kompetenzzentrum Automobil- und Industrie-Elektronik GmbH) , A. Regoutz (University College London)
Co-authored by industrial partner: Yes

Type: Journal Paper
Journal: Journal Of Applied Physics , VOL 129

State: Published (Approved)
Published: May 2021
Diamond Proposal Number(s): 19885

Abstract: The binary alloy of titanium-tungsten (TiW) is an established diffusion barrier in high-power semiconductor devices, owing to its ability to suppress the diffusion of copper from the metallization scheme into the surrounding silicon substructure. However, little is known about the response of TiW to high-temperature events or its behavior when exposed to air. Here, a combined soft and hard x-ray photoelectron spectroscopy (XPS) characterization approach is used to study the influence of post-deposition annealing and titanium concentration on the oxidation behavior of a 300 nm-thick TiW film. The combination of both XPS techniques allows for the assessment of the chemical state and elemental composition across the surface and bulk of the TiW layer. The findings show that in response to high-temperature annealing, titanium segregates out of the mixed metal system and upwardly migrates, accumulating at the TiW/air interface. Titanium shows remarkably rapid diffusion under relatively short annealing timescales, and the extent of titanium surface enrichment is increased through longer annealing periods or by increasing the bulk titanium concentration. Surface titanium enrichment enhances the extent of oxidation both at the surface and in the bulk of the alloy due to the strong gettering ability of titanium. Quantification of the soft x-ray photoelectron spectra highlights the formation of three tungsten oxidation environments, attributed to WO2, WO3, and a WO3 oxide coordinated with a titanium environment. This combinatorial characterization approach provides valuable insights into the thermal and oxidation stability of TiW alloys from two depth perspectives, aiding the development of future device technologies.

Journal Keywords: Alloys; Annealing; X-ray photoelectron spectroscopy; News and events; Depth profiling techniques; Metallization process; Microfabrication; Density functional theory; Diffusion barriers; Semiconductor devices

Diamond Keywords: Alloys; Semiconductors

Subject Areas: Physics, Chemistry, Materials


Instruments: I09-Surface and Interface Structural Analysis

Added On: 18/05/2021 12:46

Documents:
5.0048304.pdf

Discipline Tags:

Surfaces Physics Physical Chemistry Chemistry Materials Science interfaces and thin films Metallurgy

Technical Tags:

Spectroscopy X-ray Photoelectron Spectroscopy (XPS) Hard X-ray Photoelectron Spectroscopy (HAXPES)