Shielding Unit for Optical Black Area Light Blocking
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional solid-state imaging devices using Cu interconnects in damascene processes face challenges with dishing effects, making it difficult to utilize Cu for large-area components, leading to increased shielding layer height and difficulties in determining the black reference level due to inclined light entry, which hinders downsizing and sensitivity improvements.
Innovation Solution
The implementation of a solid-state imaging device with a first photoelectric conversion unit at the imaging area, a second photoelectric conversion unit for black reference observation, an insulating film, and a shielding unit formed by connecting contacts and interconnects in an accumulating direction from the semiconductor substrate to the insulating film surface, effectively shielding inclined light and reducing the need for dummy pixels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If Cu interconnect is utilized in damascene process for fine interconnect, then fine processing and low power consumption are improved, but dishing occurs in large area shielding layers making it difficult to utilize Cu for large area components
Solution Approach 1:
The patent applies different interconnect materials to different areas: Cu interconnect is used for fine processing in lower layers and logic circuits, while Al interconnect is used for large area shielding layers in upper layers. This local differentiation resolves the dishing problem in large area shielding while maintaining fine processing capability where needed.
2Productivity
If multi-layer peripheral circuits are implemented with Cu interconnect, then integration and signal processing speed are improved, but shielding layer position becomes high causing inclined light entry into OB area
Solution Approach 1:
The patent introduces a light shielding film as an intermediary element positioned between the imaging area and the optical black area. This film blocks inclined light from entering the OB area, thereby protecting the black reference level determination accuracy while allowing multi-layer peripheral circuits to be implemented for high-speed signal processing.
3Device complexity
If shielding layer position is raised due to multi-layer peripheral circuits, then integration is improved, but precise determination of black reference level becomes difficult
Solution Approach 1:
The light shielding film acts as a mediator that blocks inclined light paths from the imaging area to the optical black area. This allows the shielding layer position to be raised for better integration while maintaining accurate black reference level determination by preventing light contamination.
4Measurement precision
If invalid area is enlarged to ensure black reference level, then black reference determination is improved, but downsizing of solid state imaging device becomes difficult
Solution Approach 1:
The light shielding film provides an effective barrier against inclined light entry, which maintains accurate black reference level determination without requiring an enlarged invalid area. This enables device downsizing while preserving measurement precision.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration prevents inclined light from entering the optical black area, stabilizes the black reference level, allows for downsizing, and enhances imaging characteristics without the need for additional dummy pixels, thereby improving integration and speed of peripheral circuits.
Implementation Method 1
a shielding unit which shields light incident from imaging area to optical black area
Data Source
AI summary
An imaging device according to an example of the invention comprises a first photoelectric conversion unit which is formed at an imaging area of a substrate, a second photoelectric conversion unit for black reference observation which is formed at an optical black area between the imaging area of the substrate and a peripheral circuit area where a peripheral circuit is formed, an insulating film which is formed on the imaging area and the optical black area of the substrate, and a shielding unit which is formed by connecting a contact and a interconnect in an accumulating direction of the insulating film from the substrate surface to the insulating film surface.