Image Sensor Separation Impurity Layer for Blooming Suppression
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Solution Overview
Problem
Current image sensors face challenges in enhancing blooming characteristics, which affect the quality of images by allowing overflowing charges to move into photoelectric conversion layers, leading to reduced image sharpness and resolution.
Innovation Solution
The image sensor design includes a semiconductor layer with a separation impurity layer that creates distinct potential levels to manage photoelectric conversion and readout circuit regions, allowing charges to be drained through specific paths, preventing blooming and maintaining high resolution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If photoelectric conversion layers are enlarged to increase light sensitivity, then image brightness is improved, but blooming phenomenon worsens as charges overflow into adjacent regions
Solution Approach 1:
The semiconductor layer is divided into distinct photoelectric conversion regions and readout circuit regions by the separation impurity layer. This segmentation prevents charge carriers generated in photoelectric conversion regions from overflowing into adjacent regions, thereby suppressing the blooming phenomenon while maintaining large photoelectric conversion layer areas for high light sensitivity
Solution Approach 2:
The separation impurity layer acts as an intermediary barrier between photoelectric conversion regions and readout circuit regions. This intermediate layer with different conductivity type creates a potential barrier that blocks charge overflow, resolving the conflict between large photoelectric conversion area and blooming suppression
2Reliability
If separation impurity layer is introduced to prevent blooming, then blooming characteristics are improved, but device complexity increases
Solution Approach 1:
The separation impurity layer is formed by extending the same impurity layer used for creating readout circuit regions into the photoelectric conversion region area. This merging approach uses a single continuous impurity layer to serve dual purposes: defining readout circuit regions and separating photoelectric conversion regions, thereby preventing blooming without significantly increasing device complexity
Solution Approach 2:
The separation impurity layer performs multiple functions: it defines the boundary between photoelectric conversion regions and readout circuit regions, creates a potential barrier to prevent charge overflow, and maintains electrical isolation between adjacent pixels. This multi-functionality achieves blooming suppression without adding excessive structural complexity
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 the blooming phenomenon, ensuring that overflowing charges are properly managed, thereby enhancing image sensor performance and maintaining high resolution and sharpness.
Implementation Method 1
the separation impurity layer is configured to have a first potential level around the photoelectric conversion layer and a second potential level on a portion between the photoelectric conversion layer and the impurity regions of the readout circuit region
Implementation Method 2
Image sensors may convert optical images into electrical signals
Data Source
AI summary
An image sensor includes a separation impurity layer in a semiconductor layer and defining a photoelectric conversion region and a readout circuit region, a photoelectric conversion layer in the semiconductor layer of the photoelectric conversion region and surrounded by the separation impurity layer, a floating diffusion region spaced apart from the photoelectric conversion layer and in the semiconductor layer of the photoelectric conversion region, a transfer gate electrode between the photoelectric conversion layer and the floating diffusion region, and impurity regions in the semiconductor layer of the readout circuit region. When the photoelectric conversion layer is integrated with photo-charges, the separation impurity layer has a first potential level around the photoelectric conversion layer and a second potential level on a portion between the photoelectric conversion layer and the impurity regions of the readout circuit region. The second potential level is greater than the first potential level.