Pixel Charge Leak Layout for High-Illuminance Linearity
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Solution Overview
Problem
In photoelectric conversion apparatuses, varying signal charge amounts between multiple photoelectric conversion elements can lead to an inappropriate signal, and existing solutions like signal charge leak regions increase pixel area, limiting layout flexibility and linearity under high illuminance.
Innovation Solution
A photoelectric conversion apparatus with a first charge leak region of the same conductivity type as the charge accumulation region, positioned overlapping the floating diffusion portion and at a deeper depth, helps in signal charge leakage between photoelectric conversion elements without increasing pixel area, improving linearity and layout freedom.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a signal charge leak region is arranged between photoelectric conversion elements, then signal charge leakage is improved, but pixel area increases
Solution Approach 1:
The patent applies dimensionality change by arranging the first charge leak region at a different depth level than the floating diffusion portion. Specifically, the charge leak region is positioned at a second depth that is deeper than the first depth of the floating diffusion portion, allowing vertical stacking in the depth direction. This enables the charge leak function to be achieved without increasing the planar area occupied by these structures, effectively resolving the contradiction between signal charge leakage performance and pixel area.
Solution Approach 2:
The patent implements nesting by placing the charge leak region and floating diffusion portion at different depth levels within the same pixel structure. The charge leak region is nested at a deeper level beneath the floating diffusion portion, allowing both structures to coexist within the same vertical space. This nested arrangement enables the charge leak region to perform its signal charge leakage function while occupying minimal additional planar area, thus resolving the area expansion issue.
2Reliability
If a signal charge leak region is arranged between photoelectric conversion elements, then signal charge leakage is improved, but layout flexibility decreases
Solution Approach 1:
By transitioning to three-dimensional spatial arrangement, the patent allows the charge leak region and floating diffusion portion to be positioned at different depths rather than requiring separate planar space. This vertical stacking approach provides greater layout freedom in the planar direction, enabling more flexible arrangement of other pixel components while maintaining the charge leakage function.
3Reliability
If a signal charge leak region is arranged between photoelectric conversion elements, then signal charge leakage is improved, but linearity under high illuminance deteriorates
Solution Approach 1:
The patent addresses linearity improvement by positioning the charge leak region at a deeper depth level, which creates a more effective charge leakage path. This deeper positioning allows excess signal charge under high illuminance conditions to be properly leaked through the charge leak region without interfering with the floating diffusion portion's signal collection function, thereby maintaining better input-output linearity while still providing necessary charge leakage capability.
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 enables appropriate signal acquisition while suppressing pixel area expansion and enhancing linearity of the pixel input-output characteristic, especially under high illuminance conditions.
Implementation Method 1
a charge accumulation region arranged in each of the plurality of photoelectric conversion elements and configured to accumulate signal charge
Implementation Method 2
a floating diffusion portion arranged between the plurality of photoelectric conversion elements in a plan view from a side of the first surface
Implementation Method 3
an array of a plurality of photoelectric conversion elements
Data Source
AI summary
A photoelectric conversion apparatus includes a pixel having first and second surfaces and including photoelectric conversion elements, a charge accumulation region arranged in each of the elements and configured to accumulate signal charge, a transfer gate arranged on the first surface and configured to transfer the signal charge, a floating diffusion (FD) portion arranged between the elements in a plan view from a first surface side, and a charge leak region arranged between the elements and being in contact with the elements in the plan view. The charge leak region and the charge accumulation region have the same conductivity type. The FD portion is at a first depth from the first surface. The charge leak region is at a second depth deeper than the first depth from the first surface. In the plan view, the charge leak region is at a position overlapping at least part of the FD portion.