Image Sensor Vertical Diffusion Layer Arrangement
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Solution Overview
Problem
Conventional solid-state image sensors face a reduction in light receiving area and sensitivity due to the arrangement of diffusion layers, leading to a decrease in the amount of electric charge generated by photoelectric conversion, which affects their sensitivity and performance.
Innovation Solution
The image sensor design includes an accumulation unit and a readout unit arranged along the optical axis of a microlens, with the accumulation unit on one surface and the readout unit on the other, allowing for efficient charge accumulation and signal readout, reducing pixel size and enhancing sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the first diffusion layer and second diffusion layer are arranged along the surface of the semiconductor substrate, then the device complexity is reduced, but the light receiving area is reduced
Solution Approach 1:
The patent transitions from a two-dimensional surface arrangement to a three-dimensional vertical arrangement. The first diffusion layer is positioned at a first depth from the front surface, while the second diffusion layer is positioned at a second depth greater than the first depth, both within the semiconductor substrate. This vertical stacking along the depth dimension increases the light receiving area without complicating the surface layout, effectively resolving the contradiction between arrangement simplicity and light receiving area.
2Productivity
If the number of pixels is increased, then the productivity is improved, but the light receiving area per pixel is reduced
Solution Approach 1:
By arranging diffusion layers vertically at different depths within the semiconductor substrate rather than horizontally on the surface, the patent enables increased pixel density without sacrificing individual pixel light receiving area. The vertical positioning allows more pixels to be packed into the same surface area while each pixel maintains sufficient depth for effective photoelectric conversion.
Solution Approach 2:
The patent implements a nested structure where the first diffusion layer and second diffusion layer are positioned at different depths within the semiconductor substrate volume. This vertical nesting allows multiple functional layers to coexist within the same lateral footprint, enabling higher pixel counts while maintaining adequate light receiving area for each pixel.
3Manufacturing precision
If the first diffusion layer and second diffusion layer are arranged along the surface of the semiconductor substrate, then the manufacturing precision requirements are reduced, but the sensitivity is reduced
Solution Approach 1:
The patent positions the first diffusion layer at a first depth and the second diffusion layer at a second depth greater than the first depth within the semiconductor substrate. This vertical arrangement leverages the depth dimension to achieve proper layer separation and functionality without requiring extremely precise lateral positioning, thereby maintaining manufacturing feasibility while significantly improving sensitivity through increased light receiving area.
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 configuration reduces pixel size and improves sensitivity by allowing charge signals to flow in the thickness direction of the semiconductor substrate, enhancing photoelectric conversion efficiency and maintaining a high signal-to-noise ratio even at high frame rates.
Implementation Method 1
a photoelectric conversion unit that photoelectrically converts incident light transmitted through a microlens
Data Source
AI summary
An image sensor includes: an accumulation unit that accumulates an electric charge generated by a photoelectric conversion unit that photoelectrically converts incident light transmitted through a microlens; and a readout unit that reads out a signal based on a voltage of the accumulation unit, wherein the accumulation unit and the readout unit are included along an optical axis direction of the microlens.