Via-Last TSV Stacking for Reliable Cross-Tier Wafer Interconnects

The patent divides the TSV formation process into separate steps: first forming TSVs through the first substrate, then forming additional TSVs through the second substrate after stacking. This segmentation allows each TSV formation step to be optimized independently, preventing volume deterioration that would occur if all TSVs were formed in a single step through the entire multi-stack wafer.

The patent performs preliminary TSV formation in the first substrate before stacking with the second substrate. This preliminary action allows the first substrate's TSVs to be formed with optimal dimensions and properties, and subsequent TSVs in the second substrate can be formed after stacking to connect to the already-formed first substrate TSVs, maintaining consistent volume throughout the process.

The patent segments the interconnect formation process by creating TSVs in each substrate separately before stacking, rather than forming all interconnects in a single complex process. This allows each substrate to be prepared independently with its own optimized TSV structure, reducing overall process complexity while supporting multiple interconnect levels.

The patent transitions from planar interconnect expansion to three-dimensional stacking, adding the vertical dimension for interconnection. By forming TSVs in each substrate before stacking and then creating additional TSVs through the stacked structure, the patent enables multiple interconnect levels without proportionally increasing process complexity, as each layer can be processed independently.

The patent divides the manufacturing process into separate TSV formation steps for each substrate, allowing standard, well-established TSV formation techniques to be used for each individual substrate. This segmentation avoids the need for complex, expensive single-step TSV formation through entire multi-stack wafers, reducing manufacturing cost and complexity while maintaining cross-tier interconnect capability.

The patent performs preliminary substrate preparation and TSV formation before stacking, utilizing existing, cost-effective manufacturing processes. This preliminary action allows each substrate to be manufactured using standard processes, and the stacking step simply combines these pre-prepared substrates with additional TSV formation, significantly reducing overall manufacturing cost and complexity compared to forming all TSVs in a single complex process.