Semiconductor structures with improved metal capping layers

Abstract

Semiconductor structures and fabrication methods are provided. In one example, a method includes forming a first dielectric layer on a semiconductor structure. The semiconductor structure includes a substrate and a multi-layer interconnect (MLI) structure on the substrate. The MLI structure includes multiple metallization layers. The first dielectric layer is formed on a topmost metallization layer. The method further includes forming a through-substrate-via (TSV) opening extending vertically through the first dielectric layer and the multiple metallization layers into the substrate, forming a TSV in the TSV opening, performing a first planarization process to planarize the TSV, forming multiple first metal vias and first metal lines in the first dielectric layer after the first planarization process, forming multiple first metal capping layers respectively on the multiple first metal lines, and performing a second planarization process to planarize the first metal capping layers.