Image Sensor Vertical Stacking for Sensitivity
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Solution Overview
Problem
Miniaturization of image sensors has led to reduced pixel sizes, resulting in decreased absorption areas and sensitivity due to the use of silicon photodiodes, which increases light loss and reduces pixel sensitivity.
Innovation Solution
An image sensor design incorporating a semiconductor substrate with vertically overlapping first and second photo-sensing devices for different wavelength spectra, along with a third photo-sensing device positioned proximate to the front surface to selectively absorb longer wavelength light, utilizing a p-type and n-type semiconductor photo-sensing layer between light-transmitting electrodes to enhance light absorption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If pixel sizes are reduced to increase resolution, then the number of pixels increases, but the absorption area decreases and sensitivity is reduced
Solution Approach 1:
The patent transitions from a planar arrangement of photo-sensing devices to a three-dimensional stacked configuration. Multiple photo-sensing devices are arranged vertically at different heights above the semiconductor substrate, enabling light absorption in the thickness direction while maintaining small footprint area. This dimensional change allows resolution to be improved without sacrificing sensitivity, as each pixel can capture light across multiple vertical layers.
2Ease of manufacture
If silicon photodiodes are used for photo-sensing, then manufacturing is simplified, but light loss increases and sensitivity is reduced
Solution Approach 1:
The patent employs photo-sensing devices with diverse light-absorbing materials rather than relying solely on silicon photodiodes. Different materials with complementary absorption characteristics are used to capture various wavelengths of light more efficiently. This composite approach reduces overall light loss while maintaining manufacturability through established semiconductor fabrication processes.
3Reliability
If vertically overlapping photo-sensing devices are used, then light absorption efficiency improves, but device complexity increases
Solution Approach 1:
The patent divides the photo-sensing function into multiple independent devices positioned at different vertical levels. Each photo-sensing device operates independently, sensing light in its specific spatial region. This segmentation allows the system to achieve high light absorption efficiency through vertical stacking while managing complexity by keeping each individual device relatively simple and modular.
4Adaptability or versatility
If multiple wavelength spectra are sensed simultaneously, then color information is improved, but manufacturing process becomes more complex
Solution Approach 1:
The patent designs photo-sensing devices that can sense multiple wavelength spectra through the use of diverse light-absorbing materials with different absorption characteristics. Rather than requiring separate dedicated devices for each wavelength, the system achieves multi-wavelength sensing capability within a unified stacked architecture, simplifying the manufacturing process while maintaining versatility.
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 design reduces light loss, improves sensitivity, and simplifies the manufacturing process by eliminating the need for a color filter and wavelength separation layer, while increasing the light-absorptive area and optical characteristics of the image sensor.
Implementation Method 1
the photo-sensing layer configured to selectively absorb the third wavelength spectrum of visible light
Implementation Method 2
an image sensor that dissembles the incident light into separate components according to incident light wavelength and converts each component to an electrical signal
Data Source
AI summary
An image sensor includes a semiconductor substrate integrated with at least one of a first photo-sensing device that may sense a first wavelength spectrum of visible light and a second photo-sensing device that may sense second wavelength spectrum of visible light, and a third photo-sensing device on the semiconductor substrate that may selectively sense third wavelength spectrum of visible light in a longer wavelength spectrum of visible light than the first wavelength spectrum of visible light and the second wavelength spectrum of visible light. The first photo-sensing device and the second photo-sensing device may overlap with each other in a thickness direction of the semiconductor substrate.