Spectroscopic analysis of ultra-thin TiN as a diffusion barrier for lithium-ion batteries by ToF-SIMS, XPS, and EELS

On-chip integration of solid-state thin-film lithium-ion batteries (LIBs) can be a feasible solution for integrating energy storage devices directly into microchips. Constituting an energy source in such devices requires an implementation of the battery on a silicon substrate and prevent lithium ions diffusing from the active battery materials into other components. In this paper, we compare 10 nm titanium nitride, deposited with two techniques: thermal atomic layer deposition (ALD) and pulsed chemical vapor deposition (pCVD). TiN films feasibility as a barrier layer is investigated before and after electrochemical cycling by time of flight secondary ion mass spectrometry and x-ray photoelectron spectroscopy. The results show the superior performance of the TiN prepared with ALD in comparison to pCVD. This drawback of pCVD identify the dependency of TiN stability on the composition ratio between nitrogen and oxygen, and the co-existence of surface/interface impurities. Moreover, 35 nm films prepared with pCVD compared with 10 nm films to show the effectiveness of increasing the thickness. Finally, we show that the concentration of oxygen atoms at grain boundaries can be a leading cause of TiN abruption. For the pCVD sample, this can be related to the higher number of crystal defects in comparison to ALD.