Conformal High-Aspect-Ratio Solid Electrolyte Thin Films for Li-Ion Batteries by Atomic Layer Deposition

Area of Science:

• Materials Science
• Electrochemistry
• Thin-Film Deposition Technology

Background:

• Lithium phosphorus oxynitride (LiPON) is a key solid electrolyte for thin-film microbatteries.
• Conformal thin films are crucial for 3D microbattery architectures.
• Atomic Layer Deposition (ALD) is a promising technique for achieving conformal films.

Purpose of the Study:

• To quantify the conformality of ALD-grown LiPON films on high-aspect-ratio 3D structures.
• To compare the effects of different lithium precursors on LiPON film conformality.
• To understand how precursor properties influence film deposition in complex geometries.

Main Methods:

• Utilized lateral high-aspect-ratio test structures to evaluate film conformality.
• Investigated two lithium precursors: lithium tert-butoxide (LiOBu) and lithium bis(trimethylsilyl)amide (Li-HMDS).
• Employed diethyl phosphoramidate as the oxygen, phosphorus, and nitrogen source.

Main Results:

• LiPON films grown using LiOBu exhibited deeper penetration into 3D cavities.
• Li-HMDS-based LiPON films showed more uniform initial growth at cavity entrances.
• Differences in conformality are attributed to precursor diffusion and reactivity variations.

Conclusions:

• ALD offers a viable method for depositing conformal LiPON films for microbatteries.
• Precursor selection significantly impacts LiPON film conformality on 3D surfaces.
• Optimized LiPON deposition could enable high-surface-area electrodes for faster charging batteries.