Atomic layer deposition for high aspect ratio through silicon vias

The paper presents atomic layer deposition (ALD) processes and process integration for the deposition of insulating liners, copper diffusion barriers, and seed layers for direct copper plating in high aspect ratio (>20:1) through silicon vias. A TaN-based copper diffusion barrier was deployed on an aluminum oxide insulating liner. The latter has the potential to act also as a dielectric barrier against copper diffusion according to BTS and TVS measurements. Furthermore, ruthenium ALD films applied as seed layers for direct copper plating were deposited with an intermediate annealing step to improve film adhesion and ensure the deposition of thick films without any delamination. The step coverage of the presented ALD processes was confirmed by SEM measurements on cross-sections of coated TSV structures. Finally a subsequent electrochemical deposition (ECD) of copper was conducted revealing the satisfying functionality of the Ru seed layer.

Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Atomic layer deposition was used to deposit functional films in high aspect ratio through silicon vias. ► The step coverage of the deployed processes was verified by scanning electron microscopy. ► Direct copper plating was demonstrated in TSV structures coated with an ALD film stack.