Stacked Image Sensor Layout for Visible-IR Crosstalk Reduction
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Solution Overview
Problem
Existing image sensors face challenges in achieving improved performance without increasing physical size, particularly in effectively sensing both visible and infrared light spectra while minimizing crosstalk and maintaining optical and electrical performance.
Innovation Solution
The image sensor design incorporates a stacked structure with a visible light sensing device and an infrared photo-sensing device, utilizing an organic photoelectric conversion layer and an inorganic photodiode, respectively, along with a filtering element such as a color filter and bandpass filter to selectively transmit and absorb light across the visible and infrared spectra, and includes a fullerene or fullerene derivative in the n-type semiconductor to enhance light absorption and reduce crosstalk.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a stacked structure with visible light sensing device and infrared photo-sensing device is used, then sensitivity to both visible and infrared light is improved, but device complexity increases
Solution Approach 1:
The image sensor is divided into distinct functional layers: a visible light sensing device layer and an infrared photo-sensing device layer. Each layer is optimized for its specific wavelength range, with the visible light sensing device positioned closer to the light incident surface and the infrared photo-sensing device positioned deeper in the substrate. This segmentation allows each component to specialize in detecting its target wavelength range, improving overall sensitivity while managing complexity through functional separation.
Solution Approach 2:
The patent transitions from a planar single-layer sensor design to a three-dimensional stacked architecture. By stacking the visible light sensing device and infrared photo-sensing device at different depths within the semiconductor substrate, the design utilizes the vertical dimension to accommodate multiple sensing functions. This dimensional transition enables simultaneous detection of visible and infrared light without requiring lateral expansion, thus improving sensitivity while controlling device footprint.
2Object-affected harmful factors
If the thickness of the visible light sensing device is reduced, then optical crosstalk is minimized, but manufacturing precision requirements increase
Solution Approach 1:
The visible light sensing device is designed with a reduced thickness specifically in the region where it interfaces with the infrared photo-sensing device. This localized thinning minimizes the path length for visible light photons, reducing the probability of visible light being detected by the infrared sensor and thereby minimizing optical crosstalk. The selective modification of thickness in critical regions achieves crosstalk reduction without requiring uniform thinning across the entire device.
Solution Approach 2:
The design proactively addresses optical crosstalk by pre-configuring the visible light sensing device with reduced thickness before light detection occurs. This preliminary structural adjustment creates an inherent barrier against crosstalk, preventing visible light from penetrating deeply enough to reach the infrared photo-sensing device. By building anti-crosstalk capability into the device architecture itself, rather than relying on post-processing or active compensation, the design reduces harmful optical interference while establishing clear manufacturing specifications.
3Use of energy by moving object
If an organic photoelectric conversion layer with fullerene is used, then light absorption in visible spectrum is improved, but electrical performance stability may be affected
Solution Approach 1:
The photoelectric conversion layer employs a composite material system combining organic semiconductors with fullerene derivatives. The fullerene components serve as electron acceptors and transport channels, while the organic semiconductor materials provide light absorption capabilities across the visible spectrum. This composite structure leverages the complementary strengths of different materials: the organic components broaden light absorption coverage and the fullerene components enhance charge separation and transport efficiency, achieving improved light absorption while maintaining electrical performance through synergistic material interactions.
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 enables high sensitivity and improved performance by reducing the thickness of the visible light sensing device, minimizing optical crosstalk, and maintaining electrical performance, allowing for effective sensing of both visible and infrared light spectra without increasing the sensor's size.
Implementation Method 1
an organic photoelectric conversion device... configured to photoelectrically convert light in a visible wavelength spectrum of light
Implementation Method 2
an inorganic photodiode... configured to sense light in an infrared wavelength spectrum of light
Implementation Method 3
Each color filter of the plurality of color filters may be configured to transmit light in at least one wavelength spectrum of light of a red wavelength spectrum of light, a green wavelength spectrum of light, and a blue wavelength spectrum of light
Implementation Method 4
a bandpass filter on the plurality of color filters and configured to selectively transmit light in the visible wavelength spectrum of light and light in the infrared wavelength spectrum of light
Implementation Method 5
The p-type semiconductor and the n-type semiconductor may be collectively configured to absorb light in an entirety of the visible wavelength spectrum of light
Data Source
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AI summary
An image sensor may include a photodiode within a semiconductor substrate and configured to sense light in an infrared wavelength spectrum of light, a photoelectric conversion device on the semiconductor substrate and configured to sense light in a visible wavelength spectrum of light, and a filtering element configured to selectively transmit at least a portion of the infrared wavelength spectrum of light and the visible wavelength spectrum of light. The filtering element may include a plurality of color filters on the photoelectric conversion device. The photoelectric conversion device may include a pair of electrodes facing each other and a photoelectric conversion layer between the pair of electrodes and configured to selectively absorb light in a visible wavelength spectrum of light. The filtering element may be between the semiconductor substrate and the photoelectric conversion device and may selectively absorb the infrared light and selectively transmit the visible light.