FEOL Metal Coupling Structure for Damage-Free TSV Landing
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Solution Overview
Problem
Forming through substrate vias (TSVs) to connect with BEOL metal interconnect structures is challenging due to the difficulty in etching through semiconductor substrates without damaging narrower and thinner wires, especially when using extremely low-K dielectrics, which can lead to damage during the etching process.
Innovation Solution
The formation of a metal coupling structure during FEOL processing, which is harder than the BEOL metal interconnect wires, allows TSVs to land on this structure without causing damage by adhering to FEOL design rules, using substructures that are coplanar with FEOL metal interconnects or gate strips, and forming a notched end to ensure proper connection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If through substrate vias are etched to connect to BEOL metal interconnect structures, then electrical interconnection is achieved, but the narrower and thinner wires and extremely low-K dielectrics are damaged during the etching process
Solution Approach 1:
A metal coupling structure is formed during FEOL processing before the BEOL metal interconnect wires are formed. This coupling structure serves as a protective landing pad that is already in place before the subsequent etching of through substrate vias, preventing damage to the narrower BEOL wires and extremely low-K dielectric materials during the via etching process.
Solution Approach 2:
The metal coupling structure acts as an intermediary element between the through substrate via and the BEOL metal interconnect structure. It provides a robust landing surface for the via that is harder and more damage-resistant than the BEOL wires, while still enabling electrical connection to the interconnect structure through subsequent via formation.
2Reliability
If a metal coupling structure is formed during FEOL processing, then damage-free TSV landing is enabled, but process complexity increases
Solution Approach 1:
The metal coupling structure is formed by merging it with existing FEOL metal interconnect structures or gate strips. By using the same metal layers and processing steps already required for FEOL, the coupling structure is created without adding separate processing steps, thus avoiding increased process complexity while still providing the protective landing surface.
Solution Approach 2:
The FEOL metal interconnect structures and gate strips serve dual functions: their original purpose in the FEOL circuitry and as protective coupling structures for TSV landing. This multi-functionality eliminates the need for dedicated additional structures, maintaining process simplicity while achieving damage-free via connection.
Data Source
AI summary
The problem of connecting a TSV to a BEOL metal interconnect structure without damaging the BEOL metal interconnect structure is solved by landing the TSV on a metal coupling structure formed during FEOL processing. The metal coupling structure is produced in accordance with design rules that apply to FEOL processing. The metal coupling structure may include substructures that have the composition and shape of wires in a transistor level metal interconnect and substructures that have the composition and shape of metal gate strips. The metal coupling structure may include pluralities of the substructures arrayed across the TSV landing area. The substructures that make up the metal coupling structure are connected to the BEOL metal interconnect through vias.