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

DOI: 10.1063/5.0086009

Authors: C. Kalha (University College London) , M. Reisinger (Kompetenzzentrum Automobil- und Industrie-Elektronik GmbH) , P. K. Thakur (Diamond Light Source) , T.-L. Lee (Diamond Light Source) , S. Venkatesan (Infineon Technologies AG) , M. Isaacs (University College London; Harwell XPS, Research Complex at Harwell (RCaH)) , R. G. Palgrave (University College London) , J. Zechner (Kompetenzzentrum Automobil- und Industrie-Elektronik GmbH) , M. Nelhiebel (Kompetenzzentrum Automobil- und Industrie-Elektronik GmbH) , A. Regoutz (Imperial College London)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Journal Of Applied Physics , VOL 131

State: Published (Approved)
Published: April 2022
Diamond Proposal Number(s): 24248

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 (≥400 ∘C). Here, the thermal stability of physical vapor deposited TiW/Cu bilayer thin films in Si/SiO2(50 nm)/TiW(300 nm)/Cu(25 nm) stacks were characterized in response to annealing at 400 ∘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.

Diamond Keywords: Semiconductors; Electric Vehicles

Subject Areas: Physics, Materials, Chemistry


Instruments: I09-Surface and Interface Structural Analysis

Added On: 09/05/2022 14:56

Documents:
5.0086009.pdf

Discipline Tags:

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

Technical Tags:

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