Hybrid Image Sensor with Graded SiGe Layer
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Solution Overview
Problem
Existing image sensors face challenges in integrating infrared and visible light detection technologies, resulting in hybrid sensors with low IR sensitivity and visible light contamination due to difficulties in fabricating hybrid visible-IR image sensors using low-band gap materials.
Innovation Solution
A visible and infrared image sensor pixel array is developed, incorporating a SixGey layer with a gradated germanium content grown using atomic layer deposition, which allows for efficient absorption of infrared photons and integration with traditional silicon-based visible light detection, enhancing IR sensitivity and reducing lattice strain.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If low-band gap materials are used for infrared detection, then infrared sensitivity is improved, but integration with traditional image sensor fabrication processes becomes difficult
Solution Approach 1:
The patent employs a composite material structure consisting of a silicon-germanium (SiGe) layer formed on a silicon substrate. The SiGe layer contains germanium atoms substituted in the silicon crystal lattice, creating a material with tailored band gap properties that enable infrared detection while maintaining compatibility with silicon-based fabrication processes. This composite approach allows the sensor to detect both visible and infrared light by leveraging the unique properties of the SiGe material system.
Solution Approach 2:
The patent utilizes parameter changes by varying the germanium concentration in the SiGe layer. By controlling the amount of germanium substitution in the silicon lattice, the band gap energy of the material is adjusted to enable infrared photon absorption. This parameter adjustment allows the same silicon-based fabrication process to produce materials with different optical properties for different detection wavelengths.
2Adaptability or versatility
If hybrid visible-IR image sensors are fabricated, then detection capability is improved, but visible light contamination and semiconductor defects increase
Solution Approach 1:
The patent divides the sensor into distinct functional regions: a first region with silicon-based pixels for visible light detection and a second region with SiGe pixels for infrared detection. This segmentation is achieved by selectively forming the SiGe layer only in the infrared detection regions, while leaving the visible light detection regions as pure silicon. The segmentation prevents visible light contamination in the infrared channels and reduces semiconductor defects by isolating the different material systems into separate functional zones.
Solution Approach 2:
The patent applies local quality by creating spatially varying material composition across the sensor array. The SiGe layer is formed only in specific regions where infrared detection is required, while other regions maintain pure silicon composition optimized for visible light detection. This local differentiation allows each region to be optimized for its specific detection function, improving overall sensor quality while maintaining versatility.
3Measurement precision
If SiGe layer with high germanium content is formed, then infrared absorption is improved, but lattice strain increases
Solution Approach 1:
The patent employs parameter changes by using a gradient germanium concentration profile in the SiGe layer. Rather than using a uniform high germanium content throughout, the germanium concentration varies through the layer thickness, with lower germanium content near the silicon substrate interface and higher germanium content toward the top surface. This gradient approach allows the layer to achieve high infrared absorption capability while progressively accommodating lattice strain, preventing defect formation that would occur with abrupt high-concentration interfaces.
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 the formation of a hybrid image sensor with superior performance and versatility, capable of detecting both visible and infrared light, overcoming the limitations of conventional IR imaging systems.
Implementation Method 1
A visible and infrared image sensor pixel array is developed, incorporating a SixGey layer with a gradated germanium content grown using atomic layer deposition, which allows for efficient absorption of infrared photons
Implementation Method 2
A visible and infrared image sensor pixel array is developed, incorporating a SixGey layer with a gradated germanium content grown using atomic layer deposition
Data Source
AI summary
A method of image sensor fabrication includes forming a second semiconductor layer on a back side of a first semiconductor layer. The method also includes forming one or more groups of pixels disposed in a front side of the first semiconductor layer. The one or more groups of pixels include a first portion of pixels separated from the second semiconductor layer by a spacer region, and a second portion of pixels, where a first doped region of the second portion of pixels is in contact with the second semiconductor layer. Pinning wells are also formed and separate individual pixels in the one or more groups of pixels, and the pinning wells extend through the first semiconductor layer. Deep pinning wells are also formed and separate the one or more groups of pixels.