Stacked Color and Infrared Image Sensor with Global Shutter
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Solution Overview
Problem
Designing a color and infrared image sensor that simultaneously achieves high resolution, global shutter capability, small pixel size, and high filling factor is challenging due to the need to balance color and infrared image acquisition requirements.
Innovation Solution
The image sensor employs a silicon substrate with MOS transistors, multiple photosensitive layers, and electrodes to absorb and filter visible and infrared spectra, along with an array of lenses and readout circuits that control charge collection in sub-pixels for simultaneous integration phases, allowing for high-resolution color and infrared imaging with a global shutter method.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a color and infrared image sensor is designed to simultaneously acquire both color and infrared images, then the functional versatility is improved, but the device complexity increases due to multiple photosensitive layers and filtering structures
Solution Approach 1:
The sensor divides the pixel structure into multiple photosensitive layers, with the first photosensitive layer dedicated to infrared detection and the second photosensitive layer dedicated to color detection. Each layer has specialized electrodes and filtering structures, segmenting the detection functions to achieve dual imaging capability while managing complexity through modular design
Solution Approach 2:
The patent implements a nested structure where the first photosensitive layer and its associated infrared filter are positioned above the second photosensitive layer. The infrared filter is nested within the stack covering the substrate, and the first photodiodes are formed within the first photosensitive layer, creating a compact multi-functional pixel structure
2Measurement precision
If the pixel size is reduced to increase resolution, then the measurement precision is improved, but the filling factor decreases reducing the active capture area
Solution Approach 1:
The patent transitions from a planar single-layer photodiode structure to a three-dimensional stacked architecture with multiple photosensitive layers formed above the substrate. This vertical dimensionality allows each pixel to capture both infrared and color information independently, effectively increasing the active capture area without increasing the lateral pixel footprint, thus maintaining high filling factor while achieving high resolution
3Reliability
If a global shutter mechanism is implemented for simultaneous charge collection, then the temporal synchronization is improved, but the device complexity increases due to additional control circuits and electrodes
Solution Approach 1:
The patent implements a global shutter mechanism where all first photodiodes and all second photodiodes simultaneously enter their respective integration phases at the same time. The control circuit is designed to apply voltages to all electrodes across the entire sensor array simultaneously, ensuring synchronized charge collection for both infrared and color channels before readout, thus achieving temporal synchronization for global shutter operation
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
The solution enables image sensors with resolutions greater than 2,560 ppi, pixel sizes smaller than 10 μm, and filling factors greater than 50%, effectively addressing the constraints of color and infrared image acquisition while maintaining global shutter functionality.
Implementation Method 1
The first photosensitive layer is configured to absorb the electromagnetic waves of the visible spectrum and of a first portion of the infrared spectrum
Implementation Method 2
the second photosensitive layer is configured to absorb the electromagnetic waves of the visible spectrum
Implementation Method 3
the infrared filter being configured to give way to the electromagnetic waves of the visible spectrum, to give way to the electromagnetic waves of said first portion of the infrared spectrum, and to block the electromagnetic waves of at least a second portion of the infrared spectrum
Data Source
AI summary
A color and infrared image sensor includes a silicon substrate, MOS transistors formed in the substrate, a stack covering the substrate and including a first photosensitive layer, an electrically-insulating layer, a second photosensitive layer, and color filters. The image sensor further includes electrodes on either side of the first photosensitive layer and delimiting first photodiodes, and electrodes on either side of the second photosensitive layer and delimiting second photodiodes. The first photosensitive layer absorbs the electromagnetic waves of the visible spectrum and of a portion of the infrared spectrum and the second photosensitive layer absorbs the electromagnetic waves of the visible spectrum and gives way to the electromagnetic waves of the portion of the infrared spectrum.