Gate-All-Around Image Sensor Pixel Structure for Lower Leakage Noise
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Solution Overview
Problem
As the density of image sensors increases, the reduced size of pixels and components in the pixel circuit leads to leakage current and read noise, deteriorating image quality due to the close packing of high-resolution pixels.
Innovation Solution
The image sensor incorporates a semiconductor pattern with a gate-all-around structure, where a buried transmission gate electrode and a first gate electrode with a ring-shaped horizontal cross-section surround the side wall of the semiconductor pattern, reducing leakage current and read noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If pixel density is increased to achieve higher resolution, then image sensor resolution is improved, but leakage current increases and image quality deteriorates
Solution Approach 1:
The patent transitions from planar 2D transistor structures to vertical 3D structures by extending the semiconductor pattern and gate electrode in the depth direction (z-axis). The gate electrode wraps around the semiconductor pattern side wall, creating a gate-all-around structure that utilizes the third dimension to achieve better electrical control without increasing lateral pixel density.
Solution Approach 2:
The patent changes the geometric parameters of the transistor structure by forming the gate electrode with a ring-shaped horizontal cross-section that partially surrounds the semiconductor pattern side wall. This structural parameter change enables more effective electrical control of the channel, reducing leakage current while maintaining the same pixel footprint.
2Measurement precision
If pixel size is reduced to increase pixel density, then image sensor resolution is improved, but read noise increases and image quality deteriorates
Solution Approach 1:
The patent moves the transistor structure from lateral scaling to vertical stacking. By forming the semiconductor pattern and gate electrode in the depth direction, the design maintains larger effective transistor dimensions for noise performance while achieving higher pixel density through vertical integration rather than lateral compression.
Solution Approach 2:
The patent modifies the transistor geometry by creating a gate electrode that extends vertically and wraps around the semiconductor pattern. This parameter change in structural configuration improves the gate control efficiency, enabling reduced read noise through better electrical control without requiring larger lateral pixel dimensions.
3Quantity of substance
If component size is reduced to increase pixel density, then image sensor resolution is improved, but leakage current increases due to closer packing
Solution Approach 1:
The patent resolves the leakage current issue by transitioning to vertical transistor structures. The gate electrode wraps around the semiconductor pattern in the depth direction, creating effective electrical isolation and control that prevents leakage current even when pixels are closely packed in the lateral plane.
Solution Approach 2:
The patent changes the transistor structural parameters by forming a gate electrode with a ring-shaped cross-section that partially surrounds the semiconductor pattern side wall. This geometric parameter change enhances the gate's electrical control over the channel, effectively suppressing leakage current while allowing high pixel density through compact lateral arrangement.
Data Source
AI summary
An image sensor is provided. The image sensor includes a semiconductor substrate including a first surface and a second surface opposite to each other. A semiconductor pattern is disposed on the first surface of the semiconductor substrate and it extends in a first direction perpendicular to the first surface. A buried transmission gate electrode is disposed in a transmission gate trench extending from the first surface of the semiconductor substrate to an interior of the semiconductor substrate. A first gate electrode at least partially surrounds a side wall of the semiconductor pattern and has a ring-shaped horizontal cross-section. A color filter is disposed on the second surface of the semiconductor substrate.