Pixel Metal Grid Connection Through Buffer Dielectric Openings
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Solution Overview
Problem
In back-illuminated CMOS image sensors, the metal grid formed in the pixel area is physically connected but not electrically connected to the underlying substrate and deep-trench fill structures, limiting the optimization of electrical performance.
Innovation Solution
A semiconductor device is fabricated with a substrate, trench fill structure, and a buffer dielectric layer that exposes portions of the substrate, allowing a metal grid layer to be directly electrically connected to the substrate and trench fill structures, thereby enhancing electrical performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the metal grid is separated from the underlying substrate by a buffer dielectric layer, then the optical performance is improved, but the electrical connection between the metal grid and substrate is lost
Solution Approach 1:
The buffer dielectric layer is segmented to create localized openings, allowing the metal grid to maintain electrical connection with the substrate at specific points while remaining optically isolated in other areas. This segmentation resolves the contradiction by enabling both optical performance improvement and electrical connection preservation through spatial differentiation.
Solution Approach 2:
The buffer dielectric layer exhibits different properties in different regions: it provides electrical isolation in covered areas for optimal optical performance, while creating openings in specific locations to maintain necessary electrical connections. This local quality variation allows simultaneous achievement of both optical and electrical performance goals.
2Stability of the object's composition
If the metal grid is physically connected to the substrate, then the structural stability is improved, but the electrical performance cannot be optimized
Solution Approach 1:
The buffer dielectric layer is divided into regions with and without openings, enabling the metal grid to have both physical support from the substrate (through openings) and electrical isolation (through dielectric coverage). This segmentation allows structural stability and electrical performance optimization to coexist.
Solution Approach 2:
The buffer dielectric layer acts as an intermediary between the metal grid and substrate, providing mechanical support while controlling electrical interaction. By strategically placing openings in this intermediary layer, the system achieves both structural stability and optimized electrical performance.
Data Source
AI summary
A semiconductor device is disclosed. The semiconductor device includes: a substrate defining a pixel area; a trench fill structure formed in the substrate in the pixel area; a buffer dielectric layer formed over a surface of the substrate in the pixel area, the buffer dielectric layer defining a first opening, which at least exposes a portion of the substrate surrounding the trench fill structure; and a metal grid layer formed on the buffer dielectric layer, the metal grid layer filling the first opening to at least directly contact with and electrically connect to the exposed portion of the substrate. The present invention provides a technical solution that brings the metal grid layer into electrical connection with the exposed portion of the substrate, thus allowing optimization or amelioration of the semiconductor device's electrical performance.