Image Sensor Silicon Microstructures for Light Absorption
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Solution Overview
Problem
Conventional image sensor devices suffer from reduced light absorption due to the smooth surface of silicon substrates, leading to decreased signal-to-noise ratio (SNR) and photosensitivity due to reflected light, and increased pixel cross-talk.
Innovation Solution
The implementation of microstructures on the surface of semiconductor substrates corresponding to photo-conversion devices, which differ in design and dimensions for various light sources, reduces reflectivity and enhances light absorption by creating a tailored environment for each pixel region to optimize light absorption efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a smooth silicon substrate surface is used, then the manufacturing process is simple, but light absorption efficiency is reduced due to reflection
Solution Approach 1:
The patent applies curvature by forming microlens structures on the substrate surface. These microlenses have curved surfaces that focus incident light onto the photo-conversion devices, reducing reflection and improving light absorption efficiency while maintaining manufacturing feasibility through standard photolithography and reflow processes
Solution Approach 2:
The patent introduces a light-trapping layer with porous or rough surface structure between the substrate and color filter array. This layer creates multiple internal reflections that trap light within the pixel region, significantly reducing light reflection loss and improving absorption efficiency without complicating the overall manufacturing process
2Ease of manufacture
If a smooth substrate surface is used, then manufacturing is easier, but pixel cross-talk increases due to scattered light
Solution Approach 1:
The patent segments the pixel region by introducing a light-trapping layer with localized structures that confine light within each pixel boundary. This segmentation prevents light from escaping to adjacent pixels, reducing cross-talk while maintaining simple manufacturing through patterned deposition processes
Solution Approach 2:
The light-trapping layer with porous or rough surface structure creates multiple internal reflections that trap light within the pixel region. This structure effectively confines light paths, preventing scattered light from reaching adjacent pixels and reducing cross-talk while maintaining manufacturing simplicity
3Ease of manufacture
If uniform microstructures are applied to all pixels, then manufacturing is simpler, but light absorption optimization for different wavelengths is reduced
Solution Approach 1:
The patent applies local quality by assigning different microlens parameters (focal length, curvature radius, aperture size) to different pixel regions based on their specific wavelength requirements. This allows optimization of light absorption for different wavelengths while maintaining relatively simple manufacturing through selective photolithography and reflow processes
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 approach effectively increases the quantum efficiency and reduces cross-talk between pixels, enhancing the signal-to-noise ratio and photosensitivity of the image sensor device by optimizing light absorption across different wavelengths.
Implementation Method 1
a large amount of incident light (not shown) is reflected from the silicon substrate 100 and cannot be absorbed efficiently by the photo-conversion devices 101 due to the smooth surface of the silicon substrate
Implementation Method 2
The surface of the semiconductor substrate corresponding to the first photo-conversion device and the second photo-conversion device has a first microstructure and a second microstructure, respectively, permitting a reflectivity of the first pixel region with respect to the first light source to be lower than a reflectivity of the second pixel region with respect to the first light source
Data Source
AI summary
An image sensor device is disclosed. The image sensor device includes a semiconductor substrate having a first pixel region and a second pixel region. A first photo-conversion device is disposed within the first pixel region of the semiconductor substrate to receive a first light source. A second photo-conversion device is disposed within the second pixel region of the semiconductor substrate to receive a second light source different from the first light source. The surface of the semiconductor substrate corresponding to the first photo-conversion device and the second photo-conversion device has a first microstructure and a second microstructure, respectively, permitting a reflectivity of the first pixel region with respect to the first light source to be lower than a reflectivity of the second pixel region with respect to the first light source. The invention also discloses a fabrication method of the image sensor device.