Reentrant Through-Substrate Via Structure for Liner Damage Mitigation
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Solution Overview
Problem
The existing through-substrate-via (TSV) formation process often damages the dielectric liner and substrate sidewalls due to etching, leading to insufficient insulation and reliability issues in integrated chips, particularly in back-side illuminated CMOS image sensors.
Innovation Solution
The integration of a TSV with a reentrant profile is achieved by forming an intermediate TSV hole with increasing width from the back-side of the substrate, which laterally sets back the dielectric liner sidewalls from the etching process, protecting them from damage and ensuring sufficient insulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a conventional TSV etching process is used, then the TSV hole can be formed through the substrate, but the dielectric liner and substrate sidewalls are damaged due to etching
Solution Approach 1:
The patent applies preliminary action by forming a mandrel structure with a reentrant profile before the TSV etching process. This mandrel creates a protective overhang that prevents the etchant from directly contacting and damaging the dielectric liner and substrate sidewalls during the etching process, thus protecting these structures in advance while still allowing the TSV hole to be formed through the substrate
2Ease of operation
If the TSV hole is etched directly through the substrate, then the through-substrate connection is achieved, but insulation is insufficient due to dielectric liner damage
Solution Approach 1:
The patent uses an intermediary mandrel structure with reentrant profile that acts as a mediator between the etching process and the dielectric liner. This mandrel protects the dielectric liner from direct etchant exposure while still allowing the TSV hole to pass through the substrate, thereby maintaining both the through-connection capability and the insulation quality
3Ease of manufacture
If conventional etching is used to form TSV, then the via hole is created, but structural integrity is compromised due to sidewall damage
Solution Approach 1:
The mandrel structure with reentrant profile is formed in advance before the TSV etching process. This preliminary structure creates a physical barrier that protects the substrate sidewalls from etchant damage while still allowing the TSV hole to be etched through the substrate, thus maintaining structural integrity while achieving via hole formation
Data Source
AI summary
The present disclosure relates an integrated chip. The integrated chip includes a semiconductor device arranged along a first side of a semiconductor substrate. The semiconductor substrate has one or more sidewalls extending from the first side of the semiconductor substrate to an opposing second side of the semiconductor substrate. A dielectric liner lines the one or more sidewalls of the semiconductor substrate. A through-substrate-via (TSV) is arranged between the one or more sidewalls and is separated from the semiconductor substrate by the dielectric liner. The TSV has a first width at a first distance from the second side and a second width at a second distance from the second side. The first width is smaller than the second width and the first distance is smaller than the second distance.