Source Follower Gate Layout for Low-Noise Image Sensors
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Image sensing devices face challenges in reducing noise in electrical signals due to limited gate regions of source follower transistors, which affect the quality of captured images.
Innovation Solution
The image sensing device incorporates a structure that enlarges the gate region of the source follower transistor, allowing it to overlap photoelectric conversion elements and reduce noise by increasing the area of the gate, thereby improving signal quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the gate region of the source follower transistor is enlarged to reduce noise, then the noise level decreases, but the device area increases
Solution Approach 1:
The gate of the source follower transistor is positioned on the second surface of the semiconductor substrate, utilizing the vertical dimension and overlapping with photoelectric conversion elements. This three-dimensional arrangement allows the gate region to be enlarged without increasing the planar footprint, thereby reducing noise while maintaining compact device area.
2Object-affected harmful factors
If the gate of the source follower transistor overlaps with photoelectric conversion elements, then noise is reduced through increased gate area, but the structural complexity increases
Solution Approach 1:
The gate of the source follower transistor is merged with the photoelectric conversion elements by positioning them to overlap in the vertical dimension. This integration allows the gate to serve dual purposes: as a control element for the transistor and as a noise-reduction feature by increasing its effective area without adding separate structural components.
3Object-affected harmful factors
If pixel isolation structures are arranged to create a gap region for the gate, then the gate region area increases for noise reduction, but the manufacturing precision requirements increase
Solution Approach 1:
Instead of requiring precise lateral positioning of pixel isolation structures to create gap regions, the gate is positioned on the second surface overlapping with existing photoelectric conversion elements. This vertical positioning approach reduces the manufacturing precision requirements compared to lateral gap creation, while still achieving increased gate area for noise reduction.
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 in electrical signals output from pixels, enhancing the image sensing device's performance and quality of captured images.
Implementation Method 1
first and second photoelectric conversion elements that are supported by the semiconductor substrate and are spaced apart from each other, each photoelectric conversion element configured to receive incident light and generate photocharges by sensing the incident light
Data Source
AI summary
An image sensing device including a source follower transistor is disclosed. The image sensing device includes first and second photoelectric conversion elements that supported by the semiconductor substrate and are spaced apart from each other, a first pixel isolation structure recessed from the second surface and configured to surround the first and second photoelectric conversion elements; second and third pixel isolation structures disposed between the first photoelectric conversion element and the second photoelectric conversion element and spaced apart from each other; and a source follower transistor supported by the semiconductor substrate and configured to include a gate disposed on the second surface in at least a portion of a gap region between the second pixel isolation structure and the third pixel isolation structure.