Silicon Pixel Nanostructures for Low-Scattering Light Steering
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Solution Overview
Problem
Silicon pixel image sensors face challenges in maximizing quantum efficiency and minimizing scattering and crosstalk, leading to reduced signal-to-noise ratio due to scattering nanostructures that can cause dark noises and parasitic light sensitivity.
Innovation Solution
The implementation of non-scattering nanostructures with specific refractive index layers and microlenses that steer electromagnetic radiation linearly towards photodetectors, minimizing scattering and crosstalk, and avoiding chemical etching effects that introduce dark states.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If scattering nanostructures are used to increase light absorption, then quantum efficiency is improved, but scattering and crosstalk increase leading to reduced signal-to-noise ratio
Solution Approach 1:
The patent applies local quality by creating nanostructures with specific refractive index profiles at different locations within the pixel. The nanostructures have a core region with one refractive index and a surrounding region with a different refractive index, allowing different parts of the same structure to perform different optical functions - the core for light absorption and the surrounding region for controlling light direction and reducing scattering.
2Ease of manufacture
If conventional nanostructure fabrication is used, then device functionality is achieved, but chemical etching introduces dark states causing dark noises
Solution Approach 1:
The patent extracts the harmful chemical etching step from the fabrication process by using a lift-off technique. The nanostructures are formed by depositing material layers that are subsequently removed from areas where nanostructures should not exist, eliminating the need for chemical etching that would otherwise introduce dark states and dark noises in the photodetector region.
3Reliability
If microlenses are used to focus light, then light collection is improved, but parasitic light sensitivity increases
Solution Approach 1:
The patent employs composite materials by combining the microlens structure with carefully engineered refractive index layers and dielectric materials. The microlens is integrated with nanostructures that have specific refractive index profiles, creating a composite optical system that focuses light effectively while the refractive index engineering prevents parasitic light sensitivity by controlling light propagation paths.
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 enhances quantum efficiency, reduces crosstalk and parasitic light sensitivity, and improves signal-to-noise ratio by directing incident light effectively and preventing dark noise generation, suitable for various electromagnetic spectra including infrared and visible light.
Implementation Method 1
a back reflector formed on a substrate layer of the pixel, the back reflector configured to reflect electromagnetic radiation incident on the pixel
Implementation Method 2
a photodetector formed within the substrate layer of the pixel and configured to generate photoelectrons based on the electromagnetic radiation
Implementation Method 3
a nanostructure formed on the passivation layer and configured to allow the electromagnetic radiation to pass through the nanostructure and reflected electromagnetic radiation from back reflector through the substrate with zero to minimal to steer the electromagnetic radiation towards the photodetector
Implementation Method 4
a microlens positioned on the nanostructure, the microlens including at least one of a flat coat layer or a curved lensing layer
Data Source
AI summary
Provided are systems, methods, and apparatuses for non-scattering nanostructures of silicon pixel image sensors. In one or more examples, the systems, devices, and methods include forming a metal layer on a substrate layer of the pixel, the metal layer to reflect electromagnetic radiation incident on the pixel; forming a photodetector on a silicon layer of the pixel, the photodetector to generate photoelectrons based on the electromagnetic radiation; and forming a passivation layer over the silicon layer, the passivation layer including a thin film dielectric. In one or more examples, the systems, devices, and methods include forming a nanostructure on the passivation layer, the nanostructure to allow the electromagnetic radiation to pass through the nanostructure and steer the electromagnetic radiation linearly towards the photodetector, and forming a microlens on the nanostructure, the microlens including at least one of a flat coat layer or a curved lensing layer.