Evaluating the merit of ALD coating as a barrier against hydrogen degradation in capacitor components

Abstract

The degradation of the properties of electronic materials due to exposure to hydrogen gas is a common problem in electro-ceramic device components. In this study, we explore atomic layer deposition (ALD) coatings as a potential barrier against hydrogen gas. Three ALD chemistries of ZnO, Al₂O₃, and HfO₂ with different thicknesses were coated onto BaTiO₃ capacitors, and their merit as hydrogen gas barriers at high temperatures was evaluated by I–V and impedance spectroscopy which could monitor the degradation of resistivity. These experimental investigations provide the temperature of merit (T₀) and the proton (H-ion) diffusion coefficients of the ALD layers, which can be used to evaluate their barrier effectiveness. Transmission electron microscopy (TEM) analysis was applied to examine the ALD layers before and after the I–V tests and find out the physical dimensions, conformity, and structure (amorphous and crystalline) of the ALD layers. We determine that the failure of the barrier characteristics at elevated temperatures is due to crystallization. The diffusion coefficient associated with protons before and after crystallizations in ALD layers was determined. Within the chemistries investigated here, the most effective ALD layers are made of HfO₂ with an amorphous structure.