Image Sensor Refractive Structure for Infrared Sensitivity
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Solution Overview
Problem
Infrared image sensors have low sensitivity due to a low infrared absorption rate of semiconductor substrates, which is exacerbated by the damage caused by etching processes used to improve sensitivity, leading to increased dark current noise.
Innovation Solution
A refractive structure is implemented on the semiconductor substrate's surface, comprising a first anti-reflective layer, a refractive pattern made of polysilicon, an insulation layer, and a second anti-reflective layer, which refracts incoming light at a great inclination angle, increasing absorption and reducing noise by avoiding etching damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If etching processes are used to improve infrared light absorption, then sensitivity is improved, but dark current noise increases due to substrate damage
Solution Approach 1:
The patent divides the light incident surface into multiple regions with different structures: flat regions for normal light reception and recessed regions with refractive patterns for enhanced infrared absorption. This segmentation allows different areas to serve different functions, improving overall sensitivity without requiring etching of the entire substrate surface.
Solution Approach 2:
The patent introduces a vertical dimension by forming recessed regions with refractive patterns that extend into the substrate. This dimensional change creates multiple interfaces for light refraction and absorption, enhancing infrared detection capability without damaging the overall substrate crystalline quality through extensive etching.
2Reliability
If the semiconductor substrate infrared absorption rate is increased, then sensitivity is improved, but the signal to noise ratio decreases due to inherent substrate properties
Solution Approach 1:
The patent applies different structural qualities to different locations on the substrate surface. Recessed regions with refractive patterns provide enhanced light absorption quality, while flat regions maintain original substrate properties. This local differentiation optimizes the balance between absorption and noise across the sensor surface.
3Reliability
If refractive patterns are added to enhance light absorption, then sensitivity is improved, but device complexity increases
Solution Approach 1:
The patent employs curved refractive patterns with specific radius of curvature in the recessed regions. These curved structures efficiently refract incoming light at multiple angles to enhance absorption probability, achieving improved sensitivity through geometric optics rather than complex material compositions or multi-layer structures.
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 refractive structure enhances infrared light absorption and sensitivity while reducing dark current noise, improving the overall performance of the image sensor by maintaining the crystalline quality of the semiconductor substrate.
Implementation Method 1
a refractive structure on the second surface of the semiconductor substrate... which refracts incoming light at a great inclination angle, increasing absorption
Implementation Method 2
The image sensors include a photodiode region in a semiconductor substrate to receive light and convert the light into an electrical signal
Implementation Method 3
The refractive structure includes a first anti-reflective layer on the second surface of the semiconductor substrate... and a second anti-reflective layer on the refractive pattern and the insulation layer
Data Source
AI summary
An image sensor includes a semiconductor substrate having opposite first and second surfaces, a wiring structure on the first surface of the semiconductor substrate, and a refractive structure on the second surface of the semiconductor substrate. The refractive structure includes a first anti-reflective layer on the second surface of the semiconductor substrate, a refractive pattern on the first anti-reflective layer, an insulation layer on the first anti-reflective layer, and a second anti-reflective layer on the refractive pattern and the insulation layer. The refractive pattern includes first refractive parts spaced apart from each other in a first direction parallel to the second surface of the semiconductor substrate, and the insulation layer fills spaces between the first refractive parts.