Solid-State Image Sensor Charge Holding Depth Optimization
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Solution Overview
Problem
Existing solid-state image sensors suffer from insufficient light-shielding performance in the charge holding portion, leading to noise generation and degradation of image quality due to incident light.
Innovation Solution
A solid-state image sensor design where the charge holding portion is positioned at least 4 μm deeper than the light-receiving surface, utilizing the light absorption characteristics of silicon to absorb most incident light, and optionally incorporating a light-shielding layer or optical filter to further suppress noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the charge holding portion is positioned closer to the light-receiving surface, then the device complexity is reduced, but light-shielding performance deteriorates causing noise generation
Solution Approach 1:
The patent positions the charge holding portion at a depth of not less than 4 μm from the light-receiving surface, utilizing the depth dimension to achieve light shielding. This spatial arrangement in the depth direction allows the charge holding portion to be shielded from incident light while maintaining a relatively simple overall structure without requiring additional light-shielding layers.
2Object-affected harmful factors
If a light-shielding layer is added to improve light-shielding performance, then noise generation is suppressed, but device complexity increases
Solution Approach 1:
The patent changes the positional parameter of the charge holding portion, specifying that it should be located at a depth of not less than 4 μm from the light-receiving surface. This parameter change utilizes the light absorption characteristics of silicon to achieve effective light shielding without adding structural complexity.
3Object-affected harmful factors
If the charge holding portion is positioned deeper in the substrate, then light-shielding performance is improved, but manufacturing precision requirements increase
Solution Approach 1:
The patent specifies a minimum depth parameter (not less than 4 μm) for the charge holding portion, which balances light-shielding performance with manufacturing feasibility. This parameter setting ensures sufficient light absorption while remaining achievable with conventional manufacturing 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 design effectively reduces noise generation and image quality degradation by ensuring that most incident light is absorbed by the substrate before reaching the charge holding portion, thereby enhancing the signal-to-noise ratio and allowing for a global shutter function with improved image quality.
Implementation Method 1
utilizing the light absorption characteristics of silicon to absorb most incident light
Implementation Method 2
charges generated by photoelectric conversion element
Data Source
AI summary
A solid-state image sensor is provided. The sensor includes a substrate having a light-receiving surface. The substrate includes a charge accumulation portion that forms part of a photoelectric conversion element, a charge holding portion arranged at a position deeper than the charge accumulation portion from the light-receiving surface, and a first transfer portion configured to transfer charges generated by the photoelectric conversion element to the charge holding portion along a depth direction of the substrate. A distance between the charge holding portion and the light-receiving surface is not less than 4 μm.