High Aspect Ratio (>10:1) Via-Middle TSV with High-k Dielectric Liner Oxide

Abstract

Downward scaling of TSV feature-size provides benefits in terms of increased interconnection density, which translates to increased data bandwidth between devices/chips at both ends of the TSVs. However, there is little motivation in the reduction of TSV depth. As a result, the aspect ratio of TSV increased as its critical dimension (CD) decreases. In cases where the TSV CD becomes too small, deposition of the liner oxide becomes a critical issue. A thicker layer is needed to ensure sufficient coverage at the TSV bottom but there is a risk of the TSV opening closing up when the deposited layer is too thick. Atomic Layer Deposition (ALD) process offers excellent coverage and a higher dielectric constant with respect to silicon dioxide. This paper evaluates the use of ALD high-k dielectric (HfO2 and Al2O3) as an alternative for TSV liner.