Pixel Isolation Structure for HDR Image Sensor Blooming Control
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Solution Overview
Problem
Current image sensors face challenges in achieving high dynamic range and effective blooming control, particularly in preventing charge overflow between pixel regions, which affects image quality and signal integrity.
Innovation Solution
The image sensor design incorporates a semiconductor substrate with distinct pixel regions, photoelectric conversion elements, and a pixel isolation structure, along with switching elements and well impurity regions to manage charge storage and transfer, ensuring that charges are contained within their respective regions and preventing overflow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If photoelectric conversion elements are arranged in adjacent pixel regions without sufficient isolation, then device complexity is reduced and manufacturing is simplified, but charge overflow between regions occurs causing blooming effects and degraded image quality
Solution Approach 1:
The pixel array is divided into multiple pixel regions with pixel isolation structures positioned between adjacent photoelectric conversion elements. These isolation structures physically segment the semiconductor substrate into distinct regions, preventing charge carriers generated in one pixel from migrating to adjacent pixels, thereby eliminating blooming effects while maintaining a relatively simple overall device architecture.
Solution Approach 2:
Pixel isolation structures serve as intermediary elements positioned between adjacent photoelectric conversion elements. These structures act as barriers that block the movement of charge carriers between pixel regions, mediating the interaction between neighboring pixels and preventing harmful charge overflow while allowing each pixel to function independently.
2Reliability
If pixel isolation structures are made more extensive or deeper, then charge overflow between pixels is prevented improving blooming properties, but device complexity and manufacturing difficulty increase
Solution Approach 1:
Pixel isolation structures are implemented with specific local characteristics - they are positioned only where needed between adjacent photoelectric conversion elements and extend to a controlled depth within the semiconductor substrate. This localized approach provides effective charge containment at the pixel boundaries without requiring complex isolation throughout the entire device, thereby achieving blooming control with moderate structural complexity.
3Measurement precision
If photoelectric conversion elements are made larger to increase light sensitivity, then signal-to-noise ratio improves, but charge overflow to adjacent regions increases causing blooming effects
Solution Approach 1:
By implementing pixel isolation structures that physically segment the semiconductor substrate between photoelectric conversion elements, the patent enables larger photoelectric conversion elements to be used without increasing blooming effects. The segmentation creates independent charge collection regions, allowing each pixel to maximize its light-sensitive area while the isolation structures prevent charge carriers from overflowing into adjacent regions.
4Measurement precision
If pixel density is increased to improve resolution, then image quality improves, but the risk of charge overflow between adjacent pixels increases
Solution Approach 1:
Pixel isolation structures are positioned between adjacent photoelectric conversion elements to act as intermediary barriers. These structures prevent charge carriers generated in one pixel from migrating to neighboring pixels, even when pixels are densely packed. This allows the patent to achieve high image resolution through increased pixel density while the isolation structures mediate the interaction between pixels and prevent harmful charge overflow.
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 enhances blooming properties and improves the dynamic range, reducing charge overflow and distortion, thereby increasing the signal-to-noise ratio and overall image sensor performance.
Implementation Method 1
a first photoelectric conversion element on the first pixel region; a second photoelectric conversion element on the second pixel region
Data Source
AI summary
Disclosed is an image sensor including a semiconductor substrate including first and second pixel regions, first and second photoelectric conversion elements on the first and second pixel regions, a pixel isolation structure between the first and second photoelectric conversion elements, a first floating diffusion region on the first pixel region, a first transfer gate electrode between the first photoelectric conversion element and the first floating diffusion region, a second floating diffusion region on the second pixel region, a second transfer gate electrode between the second photoelectric conversion element and the second floating diffusion region, a first charge storage region on the first pixel region, a second charge storage region on the second pixel region, a first switching element between the first floating diffusion region and the first charge storage region, and a second switching element between the second floating diffusion region and the second charge storage region.