Solid-State Imaging Charge Transfer via Localized Light Intensity
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Solution Overview
Problem
The dynamic range of solid-state imaging apparatuses is reduced due to changes in floating diffusion potential during charge transfer, leading to saturation issues, especially at high luminance levels.
Innovation Solution
A solid-state imaging apparatus design with a semiconductor portion having a first face for light incidence and an optical system on the second face, where a photoelectric conversion portion surrounds a first semiconductor region, and a gate electrode is positioned between semiconductor regions to enhance charge transfer efficiency by creating a higher light intensity in the second semiconductor region compared to the first, thereby improving charge transfer while maintaining dynamic range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If photoelectric conversion is performed in the floating diffusion region, then charge transfer efficiency is improved, but dynamic range is reduced
Solution Approach 1:
The patent applies local quality by creating different light intensity zones within the semiconductor structure. Specifically, the optical system is designed to make light intensity in the second semiconductor region (where photoelectric conversion occurs) higher than in the first semiconductor region (floating diffusion), enabling localized photoelectric conversion without affecting the entire structure uniformly. This resolves the contradiction by allowing efficient charge transfer in the photoelectric conversion region while preventing saturation in the floating diffusion region.
Solution Approach 2:
The patent utilizes the depth dimension (from first face to second face of semiconductor portion) to separate functions. The floating diffusion is positioned in the first semiconductor region while photoelectric conversion occurs in the second semiconductor region deeper in the structure. This spatial separation in the depth dimension allows both charge transfer efficiency and dynamic range to be optimized simultaneously.
2Productivity
If light intensity is increased to improve charge transfer, then charge transfer efficiency is improved, but saturation occurs at high luminance levels
Solution Approach 1:
The optical system creates a localized high light intensity region specifically in the second semiconductor region where photoelectric conversion occurs, while maintaining lower light intensity in the first semiconductor region (floating diffusion). This localized illumination improves charge transfer efficiency without causing saturation in the floating diffusion, thereby resolving the contradiction between charge transfer efficiency and saturation prevention.
3Productivity
If floating diffusion is positioned in the center of pixel region, then charge transfer efficiency is improved, but photoelectric conversion in FD causes dynamic range reduction
Solution Approach 1:
The patent maintains the floating diffusion in the center position for efficient charge transfer but applies local quality by creating a differentiated light intensity distribution. The optical system ensures that light intensity is higher in the second semiconductor region (photoelectric conversion portion) than in the first semiconductor region (floating diffusion), enabling the floating diffusion to remain in a low-light state while the surrounding photoelectric conversion portion operates at high efficiency.
Solution Approach 2:
The patent resolves the contradiction by utilizing the depth dimension to separate the floating diffusion from the photoelectric conversion region. The floating diffusion is positioned in the first semiconductor region while photoelectric conversion occurs in the second semiconductor region, allowing both functions to coexist without interference even when the floating diffusion is centrally positioned.
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 charge transfer efficiency and maintains dynamic range, allowing for improved light sensitivity and frame rate by optimizing light intensity distribution and reducing dark current.
Implementation Method 1
a photoelectric conversion portion configured to be provided in the semiconductor portion so as to surround the first semiconductor region
Data Source
AI summary
A solid-state imaging apparatus which includes a semiconductor portion having a first face on the light incident side and a second face opposite to the first face, and an optical system arranged on the first face, comprising a first semiconductor region of a first conductivity type provided on the second face side in the semiconductor region, a photoelectric conversion portion provided in the semiconductor portion so as to surround the first semiconductor region, including a second semiconductor region of the first conductivity type, and a gate electrode arranged between the first and the second semiconductor regions on the second face, for transferring a charge generated in the photoelectric conversion portion to the first semiconductor region, wherein the optical system is configured so that a light intensity in the second semiconductor region is higher than that in the first semiconductor region.