Multispectral Infrared Photodetector Filtering for Low Crosstalk
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Solution Overview
Problem
Infrared multi-spectral photo-detection devices face challenges in achieving low crosstalk and homogeneous quantum efficiency due to flatness defects and thermal expansion coefficient differences between materials, which affect color reconstruction.
Innovation Solution
The implementation of an anti-reflective coating between the adhesive layer and the support substrate, combined with a thin adhesive layer and a filtering stage with distinct spectral bands, reduces parasitic reflections and compensates for flatness defects, ensuring low crosstalk and high quantum efficiency homogeneity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the adhesive layer thickness is reduced to minimize crosstalk, then crosstalk between pixels is reduced, but quantum efficiency homogeneity deteriorates due to flatness defects
Solution Approach 1:
An anti-reflective coating is introduced as an intermediary layer between the adhesive layer and the support substrate. This coating minimizes parasitic reflections that would otherwise be exacerbated by the thin adhesive layer configuration, thereby maintaining quantum efficiency homogeneity while allowing the adhesive layer to remain thin for low crosstalk performance
Solution Approach 2:
The patent modifies the optical parameters of the interface between the adhesive layer and support substrate by applying an anti-reflective coating. This changes the reflection and transmission characteristics of light at this interface, compensating for the effects of variable adhesive layer thickness and support substrate flatness variations
2Manufacturing precision
If the support substrate flatness is improved to enhance quantum efficiency homogeneity, then manufacturing complexity increases, but thermal expansion differences still cause flatness defects at cryogenic temperatures
Solution Approach 1:
The patent accepts the inevitability of flatness defects due to thermal expansion differences and converts this harmful effect into a manageable parameter. By using an anti-reflective coating, the system compensates for the flatness variations rather than attempting to eliminate them, thereby reducing manufacturing complexity while maintaining performance
Solution Approach 2:
Instead of requiring the entire support substrate to have high flatness, the patent applies a localized solution (anti-reflective coating) at the critical interface where light interacts with the adhesive layer. This approach maintains quantum efficiency homogeneity without requiring complex substrate flatness control across the entire device
3Object-affected harmful factors
If the adhesive layer is made thinner to bring the filtering stage closer to the photodiode matrix, then crosstalk is reduced, but parasitic reflections increase
Solution Approach 1:
The anti-reflective coating serves as an intermediary optical element between the adhesive layer and support substrate. It specifically targets and reduces parasitic reflections that would otherwise increase with thinner adhesive layers, enabling the system to maintain both low crosstalk and low parasitic reflections simultaneously
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 configuration enhances color reconstruction by minimizing crosstalk and quantum efficiency variations across pixels, improving the overall performance of the multi-spectral photo-detection device.
Implementation Method 1
an anti-reflective coating, which extends between the adhesive layer and the support substrate, and which is configured to reduce inner reflections in the infrared
Implementation Method 2
each formed of an interference filter and each capable of transmitting the wavelengths of a first spectral band and of blocking the wavelengths of a second spectral band
Implementation Method 3
an active layer made of a semiconductor material, incorporating a matrix of photodiodes
Data Source
AI summary
A device for multi-spectral photo-detection in the infrared includes a photo-detection stage and a filtering stage superimposed on top of one another. The photo-detection stage includes a read circuit, an active layer incorporating a matrix of photodiodes, and a support substrate, superimposed together in that order. The filtering stage includes filtering areas of a first type, each formed of an interference filter capable of transmitting the wavelengths of a first spectral band and of blocking the wavelengths of a second spectral band, and filtering areas of a second type, capable of transmitting at least part of the wavelengths of the second spectral band. The device further includes an adhesive layer, located between the photo-detection stage and the filtering stage, on the support substrate side, and an anti-reflective coating, located between the adhesive layer and the support substrate.