Stacked Image Sensor Capacitance Layout for Smaller Chips
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Solution Overview
Problem
Existing image sensors face challenges in reducing chip area while maintaining high capacitance values, often resulting in increased space requirements due to the need for numerous capacitances in the pixel region and surrounding analog/digital conversion circuits.
Innovation Solution
The image sensor design incorporates accumulation units stacked on the semiconductor substrate within the pixel region, allowing for high capacitance values without expanding the chip area by providing capacitances corresponding to each pixel column and reducing the need for additional wiring layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a large number of capacitances are provided in the pixel region to achieve high capacitance values, then the signal accumulation capability is improved, but the chip area increases
Solution Approach 1:
The patent transitions from a two-dimensional planar arrangement of capacitances to a three-dimensional stacked architecture. Accumulation units are formed by stacking multiple capacitance structures vertically above the substrate, enabling high capacitance values without increasing the horizontal chip area. This vertical dimensionality change resolves the contradiction between capacitance quantity and area occupation.
Solution Approach 2:
The patent implements nested capacitance structures where multiple capacitance elements are stacked and integrated within a vertical column above each pixel column. The accumulation units contain nested conductive plates and dielectric layers, allowing multiple capacitances to occupy the same horizontal footprint, thus achieving high total capacitance without area expansion.
2Quantity of substance
If numerous capacitances are provided in the pixel region and surrounding circuits, then the signal accumulation capability is improved, but the device complexity increases
Solution Approach 1:
The patent merges multiple capacitance functions into integrated accumulation units. Instead of providing separate capacitances for each pixel, the stacked capacitance structures in accumulation units serve multiple pixels simultaneously. This consolidation reduces the total number of discrete capacitance components while maintaining the required signal accumulation capability, thereby reducing device complexity.
Solution Approach 2:
The accumulation units with stacked capacitance structures serve multiple functions: they accumulate signals from multiple pixel columns, provide noise management capabilities, and enable parallel readout operations. This multi-functionality reduces the need for separate dedicated capacitances for each function, simplifying the overall device architecture.
3Measurement precision
If signals are read out sequentially from pixels, then the readout accuracy is improved, but the frame rate decreases
Solution Approach 1:
The patent segments the pixel array into multiple pixel columns, each with its own accumulation unit. This segmentation enables independent parallel readout of multiple columns simultaneously, increasing the overall frame rate while maintaining accurate signal accumulation in each column's dedicated accumulation unit.
Solution Approach 2:
The patent enables continuous parallel operation where multiple pixel columns are read out simultaneously through their respective accumulation units. This continuous parallel processing maintains high frame rates without compromising the accuracy of signal accumulation, as each column's signals are accumulated and read out concurrently rather than sequentially.
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 approach enables efficient signal accumulation and noise management, reducing the overall chip area and enabling high frame rates by parallelizing horizontal transfers during readout periods.
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.