Backside-Illuminated Image Sensor TSV Seal Ring for Interface Protection
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Solution Overview
Problem
Existing image sensors face challenges in improving light receiving efficiency, particularly for specific light wavelengths, and require enhanced protection against contaminants at the interface between through-silicon-vias (TSVs) and metal landing pads.
Innovation Solution
The implementation of a TSV edge seal ring surrounding a portion of the TSV in the contact layer, extending to a depth coextensive with the TSV, and coupled to diffusion barrier layers and shallow-trench-isolation regions, provides a barrier against contaminants like moisture, mobile ions, and hydrogen, while enhancing light reception.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a through-silicon-via (TSV) is formed to extend through the die to a metal landing pad, then light receiving efficiency is improved, but contamination at the TSV-metallization interface increases
Solution Approach 1:
An edge seal ring is introduced as an intermediary structure between the TSV and the metallization layer. This seal ring acts as a barrier that prevents contaminants from reaching the critical interface region, while allowing the TSV to maintain its light-receiving function. The seal ring is positioned at the edge of the TSV opening in the metallization layer, creating a protective barrier without interfering with the optical path.
Solution Approach 2:
The edge seal ring functions as a thin film structure that seals the perimeter of the TSV opening. This thin film barrier effectively blocks contaminant ingress paths along the sidewalls and interface regions, while maintaining the overall structural integrity and optical performance of the sensor device.
2Reliability
If the TSV extends deeply into the die to reach the metal landing pad, then electrical connectivity is improved, but vulnerability to contaminants increases
Solution Approach 1:
The edge seal ring serves as a mediator that protects the deep TSV structure from contaminant ingress. By positioning the seal ring at the metallization interface, it creates a barrier that prevents contaminants from traveling along the TSV sidewalls to the landing pad, thereby protecting the electrical connectivity without compromising the deep via structure.
Solution Approach 2:
The seal ring is formed in advance to prevent contaminant ingress before contamination can occur. This preliminary protective structure is integrated into the fabrication process, creating a barrier that proactively prevents contaminant accumulation at the TSV-metallization interface throughout the device lifetime.
3Object-affected harmful factors
If additional protective structures are added around the TSV, then contamination protection is improved, but device complexity increases
Solution Approach 1:
The protective function is segmented and localized to only where it is most needed - at the edge of the TSV opening in the metallization layer. Rather than providing comprehensive protection throughout the entire TSV structure, the seal ring focuses protection at the critical interface region where contaminant ingress is most likely to occur, thereby reducing overall structural complexity.
Solution Approach 2:
The edge seal ring provides localized protection at the TSV-metallization interface rather than uniformly protecting the entire TSV structure. This local quality approach places protective features only where contamination risk is highest, optimizing the balance between protection and structural simplicity.
Data Source
AI summary
Implementations of image sensor devices may include a through-silicon-via (TSV) formed in a backside of an image sensor device and extending through a material of a die to a metal landing pad. The metal landing pad may be within a contact layer. The devices may include a TSV edge seal ring surrounding a portion of the TSV in the contact layer and extending from a first surface of the contact layer into the contact layer to a depth coextensive with a depth of the TSV.