Thermal Diode Current Path Redirection for 1/f Noise Reduction
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Solution Overview
Problem
Conventional thermal imaging camera sensors face challenges in minimizing noise, particularly 1/f noise, due to surface defects in semiconductor materials, which affect the signal-to-noise ratio and thermal resolution.
Innovation Solution
A thermal diode design with doped structures and a deep doped base, along with a thin absorption layer, directs current flow away from the surface into deeper semiconductor layers, reducing 1/f noise and enhancing signal-to-noise ratio by forming a p-n junction and using silicon dioxide for improved infrared absorption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If current flows through the semiconductor substrate near the surface, then the sensor element can detect infrared radiation, but 1/f noise increases due to surface defects and trapped charge carriers
Solution Approach 1:
The patent extends the current path from the two-dimensional surface region into the third dimension by utilizing deeper layers of the semiconductor substrate. The increased depth of the doped structures directs current flow away from the noisy surface region into cleaner, deeper substrate regions, effectively adding a dimensional aspect to the current path to avoid surface defects.
Solution Approach 2:
The patent introduces an intermediate region in the semiconductor substrate that acts as a mediator between the surface and the deep substrate. This intermediate region, formed by specific doping profiles and depths, guides and redistributes the current flow, preventing direct current passage through the high-noise surface defect regions while maintaining efficient charge carrier collection.
2Measurement precision
If the sensor element is exposed micromechanically to increase heating and signal, then thermal resolution improves, but mechanical stability with respect to vibrations deteriorates
Solution Approach 1:
The patent applies local quality by differentiating the mechanical and thermal properties of different regions within the sensor element. The sensor element is selectively exposed micromechanically in specific local areas to maximize thermal sensitivity and signal generation, while other regions maintain their structural integrity and mechanical stability, allowing the element to withstand vibrations.
3Measurement precision
If the sensor element area is increased to be greater than the wavelength used, then absorption of infrared radiation improves, but device complexity increases
Solution Approach 1:
The patent divides the sensor element into multiple functional segments: an extended active area for maximum infrared absorption, selectively exposed regions for enhanced thermal sensitivity, and structured doped regions for optimized current flow. This segmentation allows each region to perform its specific function efficiently without requiring the entire element to be overly complex.
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 design significantly reduces 1/f noise, thereby improving the thermal resolution and signal-to-noise ratio of the thermal diode and photosensor, allowing for more accurate infrared radiation detection.
Implementation Method 1
two doped structures set apart from each other on the surface... forming a p-n junction
Implementation Method 2
each sensor element should have its own absorption layer in order to ensure the best possible absorption of the infrared radiation to be received. For example, silicon dioxide may be used for that purpose
Implementation Method 3
Due to the infrared radiation, the sensor elements warm up by amounts on the order of a few mK. The heating of the sensor element caused by the infrared radiation leads to a change in the current-voltage characteristic
Data Source
AI summary
A thermal diode for a photosensor of a thermal imaging camera includes a semiconductor substrate having a surface and two doped structures set apart from each other on the surface. Furthermore, a device is provided for influencing a current between the first and the second structure, in order to reduce a current density in an area near to the surface and to increase it in an area far from the surface. In addition, a topology having an even absorption layer is proposed. The measures proposed have the aim of realizing a low-noise diode for thermal applications.