Stacked Image Sensor Resolving Resolution Sensitivity Trade-off
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Solution Overview
Problem
Conventional image sensors using silicon photodiodes face sensitivity deterioration due to small pixel sizes, which affect their resolution and light absorption efficiency.
Innovation Solution
An image sensor design incorporating a semiconductor substrate with separate photo-sensing devices for blue, red, and green wavelength regions, along with a semi-transmitting layer and photoactive layer, enhances light absorption and sensitivity by using a p-type and n-type semiconductor material pn junction to selectively absorb green light and transmit other wavelengths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If pixel size is reduced to achieve high resolution, then resolution is improved, but light absorption area is reduced causing sensitivity deterioration
Solution Approach 1:
The patent transitions from planar photodiode structures to vertically stacked three-dimensional photo-sensing devices. Multiple photo-sensing devices are stacked in the vertical direction on the semiconductor substrate, each detecting different wavelength regions (blue, green, red). This vertical stacking enables high resolution through small pixel footprints while maintaining sensitivity through increased light absorption volume in the vertical dimension.
Solution Approach 2:
The patent employs composite material structures including color filter layers with specific optical properties, semi-transmitting layers with controlled transmittance, and photoactive layers with wavelength-selective absorption characteristics. These composite material arrangements optimize light absorption across different wavelength regions while maintaining compact pixel dimensions for high resolution.
2Measurement precision
If pixel size is reduced to achieve high resolution, then resolution is improved, but absorption area is reduced
Solution Approach 1:
The patent extends light absorption into the vertical dimension through stacked photo-sensing devices. Each device in the stack contributes to the total absorption area, effectively increasing the absorption cross-section without expanding the lateral pixel footprint. This enables high resolution while compensating for reduced in-plane absorption area.
Solution Approach 2:
The patent implements nested structures where color filter layers, semi-transmitting layers, and photoactive layers are arranged in concentric or stacked configurations within each pixel. This nesting maximizes the use of available space, allowing multiple functional layers to coexist in a compact volume, thereby increasing effective absorption area without increasing pixel size.
3Adaptability or versatility
If multiple wavelength regions are detected using separate photo-sensing devices, then spectral detection capability is improved, but device complexity increases
Solution Approach 1:
The patent combines multiple photo-sensing devices detecting different wavelength regions (blue, green, red) into a single integrated pixel structure. The color filter layer and semi-transmitting layer are shared across all devices, and the stacked arrangement allows compact integration. This merging approach enables full spectral detection capability while minimizing the increase in device complexity through shared components and compact three-dimensional packaging.
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 design improves light absorption efficiency and sensitivity, particularly in the green wavelength region, while maintaining a compact size, thus enhancing the performance of the image sensor and electronic devices that utilize it.
Implementation Method 1
A photoelectric device converts light into an electrical signal using photoelectric effects
Implementation Method 2
The semi-transmitting layer may include a plurality of first and second layers alternately stacked on the semiconductor substrate, the plurality of first layers having different refractive indices from the plurality of second layers
Implementation Method 3
the photoactive layer includes a p-type semiconductor material and an n-type semiconductor material, at least one of the p-type semiconductor material and the n-type semiconductor material configured to selectively absorb light in the green wavelength region
Data Source
AI summary
An image sensor includes a semiconductor substrate integrated with at least one first photo-sensing device configured to sense light in a blue wavelength region and at least one second photo-sensing device configured to sense light in a red wavelength region, a color filter layer on the semiconductor substrate and including a blue color filter configured to selectively absorb light in a blue wavelength region and a red color filter configured to selectively absorb light in a red wavelength region, and a third photo-sensing device on the color filter layer and including a pair of electrodes facing each other, and a photoactive layer between the pair of electrodes and configured to selectively absorb light in a green wavelength region.