Uncooled Microbolometer Pixel for Terahertz Detection
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Solution Overview
Problem
Current uncooled microbolometer arrays face challenges in extending their absorption spectrum beyond 30 μm wavelengths and efficiently detecting terahertz radiation due to material absorption and diffraction issues, as well as incompatibility with existing fabrication and packaging processes.
Innovation Solution
The design of an uncooled microbolometer pixel array featuring a thermistor assembly and an absorber assembly with elongated resonators that determine a specific absorption spectrum, allowing for broadband or multi-frequency absorption of electromagnetic radiation, including terahertz wavelengths, by forming a resonant cavity with a reflector and optimizing the arrangement of absorbers and resonators to achieve wavelength- and polarization-selective absorption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional infrared microbolometer detectors include a reflector deposited on the underlying substrate to form a quarter-wavelength optical resonant cavity, then radiation absorption is optimized in the desired spectral band, but forming such a resonant cavity for detecting electromagnetic radiation at wavelengths longer than 10 μm is generally not practical with surface micromachining techniques
Solution Approach 1:
Instead of depositing the reflector on the substrate and forming the resonant cavity from the bottom up (conventional approach), the patent inverts the sequence by first forming the suspended platform and then depositing the reflector underneath it. This allows the resonant cavity to be formed with a height corresponding to quarter-wavelength of terahertz radiation, making it practical with surface micromachining techniques while maintaining absorption optimization.
2Object-affected harmful factors
If the pitch of terahertz-sensitive pixels is increased to avoid diffraction effects, then diffraction is reduced, but the pixel pitch becomes larger than that of infrared-sensitive pixels
Solution Approach 1:
The patent makes the resonant cavity height a variable parameter that can be tuned to match quarter-wavelength of different terahertz frequencies. By dynamically adjusting the cavity height rather than relying solely on increased pixel pitch, the system reduces diffraction effects while maintaining compact pixel dimensions suitable for array fabrication.
3Manufacturing precision
If broadband thin-film absorbers such as metallic blacks, organic blacks, and carbon nanotubes are used to improve spectral response beyond 30 μm, then absorption is improved, but fabricating these thin-film absorbers requires special deposition and processing techniques that are generally not fully compatible with standard microfabrication and packaging processes
Solution Approach 1:
The patent extracts the complex thin-film absorber materials (metallic blacks, organic blacks, carbon nanotubes) and replaces them with a simpler reflector-based resonant cavity structure. This extraction eliminates the need for special deposition techniques while maintaining improved spectral response beyond 30 μm, achieving full compatibility with standard microfabrication processes.
4Measurement precision
If antenna-coupled microbolometer detectors are used for terahertz sensing, then detection capability is improved, but fabricating these detectors involves electron-beam or deep-ultraviolet lithography and a redesign of the underlying readout integrated circuit
Solution Approach 1:
The patent replaces the complex antenna-coupled detector design with a simpler resonant cavity-based microbolometer that uses standard lithography techniques. By adopting this simpler, more disposable-friendly design, the system achieves terahertz detection capability without requiring expensive electron-beam or deep-ultraviolet lithography equipment, and without redesigning the readout integrated circuit.
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 enables the microbolometer array to achieve continuous broadband absorption spectra, effectively detecting electromagnetic radiation in the terahertz region while maintaining compatibility with standard microfabrication techniques, thus overcoming previous limitations in spectral response and fabrication compatibility.
Implementation Method 1
the optical absorber comprising a set of elongated resonators determining an absorption spectrum of the optical absorber
Implementation Method 2
broadband or multi-frequency absorption of electromagnetic radiation, including terahertz wavelengths
Implementation Method 3
forming a resonant cavity with a reflector
Implementation Method 4
The thermistor may, for example, be composed of a material having a high temperature coefficient of resistance (TCR)
Data Source
AI summary
An uncooled microbolometer pixel for detection of electromagnetic radiation is provided that includes a substrate, a thermistor assembly and an absorber assembly. The thermistor assembly includes a thermistor platform suspended above the substrate, one or more thermistors on the thermistor platform, and an electrode structure electrically connecting the thermistors to the substrate. The absorber assembly includes an optical absorber over the thermistor assembly and a reflector provided under and forming a resonant cavity with the optical absorber. The optical absorber is in thermal contact with the thermistors and exposed to the electromagnetic radiation. The optical absorber includes a set of elongated resonators determining an absorption spectrum of the optical absorber. An array of microbolometer pixels is also provided, in which the resonators of different pixels can have different lengths determining different absorption spectra, thereby enabling configurable broadband and/or multi-frequency detection, in particular in the terahertz region.