Image Sensor Pixel Capacitor Sidewall Extension for Dynamic Range
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Solution Overview
Problem
Conventional image sensors have a limited dynamic range, failing to capture the full range of luminance levels encountered in scenes, leading to issues such as high memory requirements, high power consumption, loss in resolution, and motion artifacts in high dynamic range (HDR) applications.
Innovation Solution
The implementation of a pixel circuit design with increased capacitance by extending capacitors over two sidewalls and the upper surface of the epitaxial substrate layer in image sensors, utilizing high-k dielectric materials and conductive materials like indium tin oxide, allows for improved charge storage and dynamic range without sacrificing pixel area, enhancing quantum efficiency and sensor performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If intra-frame multi-exposure or interlaced exposures are used to provide HDR, then the luminance capture range is improved, but memory requirements increase
Solution Approach 1:
The patent changes the capacitance parameter of the pixel by extending the capacitor structure over two sidewalls and the upper surface of the epitaxial substrate layer. This structural modification increases the pixel capacitance, allowing the sensor to handle a wider range of luminance levels within a single exposure, thereby achieving HDR without requiring multiple exposures and reducing memory requirements for storing multiple exposure frames.
2Illumination intensity
If intra-frame multi-exposure or interlaced exposures are used to provide HDR, then the luminance capture range is improved, but power consumption increases
Solution Approach 1:
By modifying the pixel capacitance parameter through the extended capacitor structure, the patent enables the sensor to capture HDR in a single exposure. This eliminates the need for multiple exposures or interlaced scanning, thereby reducing the power consumption associated with repeated readout operations and processing multiple frames.
3Device complexity
If conventional image sensors are used, then the device complexity is low, but the dynamic range is limited
Solution Approach 1:
The patent extends the capacitor structure from a conventional planar configuration into the vertical dimension by covering two sidewalls and the upper surface of the epitaxial substrate layer. This three-dimensional configuration increases the effective capacitance area without significantly increasing the lateral footprint, thereby maintaining relatively simple device architecture while achieving enhanced dynamic range.
4Illumination intensity
If pixel area is increased to improve charge storage, then the dynamic range is improved, but the resolution is reduced
Solution Approach 1:
The patent resolves this contradiction by utilizing the vertical dimension for capacitor extension. The capacitor covers two sidewalls and the upper surface of the epitaxial substrate layer, effectively increasing the charge storage capacitance without increasing the lateral pixel area. This maintains the pixel density and resolution while enhancing the dynamic range through increased capacitance.
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 image sensors to capture a wider luminance range, improving scene capture capabilities, reducing costs, and maintaining high resolution while minimizing motion artifacts, thus overcoming the limitations of conventional image sensors.
Implementation Method 1
The pixel circuit comprises a photodetector and a capacitor configured to convert light (photons) into an electric charge consisting of electrons and holes
Implementation Method 2
The capacitor is connected to two sidewalls and/or an upper surface of the epitaxial substrate layer in which the photodetector is formed
Data Source
AI summary
Various embodiments of the present technology may comprise methods and apparatus for increasing dynamic range of an image sensor. According to an exemplary embodiment, the image sensor comprises a backside-illuminated hybrid bonded stacked chip image senor having a pixel circuit array. A capacitor is formed on each pixel circuit along two adjacent sidewalls of an epitaxial substrate layer facing a deep trench isolation region. The capacitor may also extend along an upper surface of the epitaxial substrate layer.