Pixel Separation Layout for Variable-Capacitance Imaging Dynamic Range
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Solution Overview
Problem
Solid-state imaging devices face limitations in layout flexibility due to the presence of capacitive elements, which restrict the arrangement of pixels and wiring lines, affecting their dynamic range and efficiency.
Innovation Solution
Incorporating a first pixel separation section with electrically conductive material between adjacent pixels, coupled to the conversion efficiency switching transistor through the floating diffusion region, adds capacitance without requiring new elements or circuit wiring, thereby enhancing layout freedom and reducing optical crosstalk.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a capacitive element is provided to increase dynamic range, then the dynamic range is improved, but the layout freedom of pixel and wiring line is reduced
Solution Approach 1:
The pixel separation section is merged with the capacitive element function. The same conductive structure serves dual purposes: optically separating adjacent pixels and providing capacitance to the floating diffusion region, thereby eliminating the need for separate capacitive elements and maintaining layout freedom
Solution Approach 2:
The pixel separation section is designed to perform multiple functions simultaneously: optical isolation between pixels and capacitance storage. This multi-functionality resolves the contradiction by making the layout-constrained element (pixel separation section) also serve as the capacitive element, thus improving dynamic range without sacrificing layout freedom
2Reliability
If a capacitive element is provided to improve dynamic range, then the dynamic range is improved, but the device complexity is increased
Solution Approach 1:
The pixel separation section is merged with the capacitive element function. The same conductive structure serves dual purposes: optically separating adjacent pixels and providing capacitance to the floating diffusion region, thereby eliminating the need for separate capacitive elements and maintaining layout freedom
Solution Approach 2:
The pixel separation section is designed to perform multiple functions simultaneously: optical isolation between pixels and capacitance storage. This multi-functionality resolves the contradiction by making the layout-constrained element (pixel separation section) also serve as the capacitive element, thus improving dynamic range without sacrificing layout freedom
3Reliability
If capacitance of floating diffusion region is increased to improve dynamic range, then the dynamic range is improved, but the conversion efficiency is reduced
Solution Approach 1:
The pixel separation section is configured to enable variable capacitance of the floating diffusion region. By controlling the potential of the pixel separation section, the capacitance can be dynamically adjusted, allowing optimization between dynamic range and conversion efficiency depending on imaging conditions
Solution Approach 2:
The capacitance value of the floating diffusion region is made variable through control of the pixel separation section potential. This parameter change capability allows the system to adapt capacitance to different imaging scenarios, improving dynamic range when needed while maintaining high conversion efficiency when possible
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 solution allows for increased layout flexibility of pixels and wiring lines, improves dynamic range, and maintains high conversion efficiency while controlling capacitance values, reducing coupling capacitance and optical crosstalk.
Implementation Method 1
The photoelectric conversion section generates electric charge through photoelectric conversion. The electric charge corresponds to an amount of received light.
Data Source
AI summary
A solid-state imaging device as disclosed includes: a semiconductor substrate; a floating diffusion region; a conversion efficiency switching transistor; and a first pixel separation section. The semiconductor substrate has a first surface and a second surface that are opposed to each other. The semiconductor substrate has a photoelectric conversion section formed therein for each of the pixels. The photoelectric conversion section generates electric charge through photoelectric conversion. The electric charge corresponds to an amount of received light. The floating diffusion region is provided in the semiconductor substrate, and accumulates the electric charge generated by the photoelectric conversion section. The conversion efficiency switching transistor causes capacitance of the floating diffusion region to be variable. The first pixel separation section is provided in the semiconductor substrate and includes an electrically conductive material that separates the adjacent pixels and that is coupled to the floating diffusion region through the conversion efficiency switching transistor.