Image Sensor Pixel Stack for High-Capacitance Signal Accumulation
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Solution Overview
Problem
Existing image sensors face challenges in reducing chip area while maintaining high capacitance values, leading to increased noise and reduced efficiency in signal processing.
Innovation Solution
The image sensor incorporates an accumulation unit stacked on the photoelectric conversion unit, allowing for signal accumulation without increasing the chip area, and provides a large capacitance value by arranging accumulation units in the pixel region.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a large number of capacitances are provided in one pixel column to horizontally transfer signals, then signal transfer capability is improved, but chip area increases
Solution Approach 1:
The patent transitions from a two-dimensional planar arrangement of capacitances to a three-dimensional stacked configuration. The accumulation unit is positioned above the pixel array in the vertical dimension, allowing signal accumulation without occupying additional horizontal chip area. This spatial reconfiguration resolves the contradiction by enabling sufficient capacitance functionality while maintaining compact chip footprint.
Solution Approach 2:
The accumulation unit is nested within the vertical structure of the pixel column, stacking above the photoelectric conversion units. This nesting approach allows the accumulation capacitance to be integrated into the existing pixel column architecture rather than requiring separate lateral space, thus improving signal transfer capability without increasing chip area.
2Productivity
If capacitance value is increased to improve signal accumulation, then signal processing efficiency is improved, but chip area increases
Solution Approach 1:
The patent achieves high capacitance values by extending the accumulation structure vertically rather than horizontally. The accumulation unit stacked above the pixel array provides sufficient capacitance for efficient signal processing while utilizing the vertical dimension, thereby avoiding the need to expand chip area.
3Productivity
If readout speed is increased to achieve higher frame rates, then productivity is improved, but noise increases
Solution Approach 1:
The accumulation unit performs preliminary signal accumulation before the final readout operation. By pre-integrating signals from multiple pixels in the vertical stacking direction, the system achieves faster effective readout speeds without requiring individual pixel readout at excessively high speeds that would generate noise. The accumulation process prepares the signal in advance, enabling high frame rates while maintaining signal quality.
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 the chip area and enhances signal processing efficiency by providing a high capacitance value without increasing noise, enabling faster readout times and higher frame rates.
Implementation Method 1
a photoelectric conversion unit that converts incident light into an electric charge
Data Source
AI summary
An image sensor includes: a plurality of pixels each having a photoelectric conversion unit that converts incident light into an electric charge, the incident light being incident from one side of a substrate, and an output unit that outputs a signal caused by the electric charge, the plurality of pixels being arranged in a first direction and a second direction intersecting the first direction; and an accumulation unit provided to be stacked on the photoelectric conversion unit on a side opposite to the one side of the substrate, the accumulation unit accumulating the signal.