MEMS Gas Sensor Vertical Cavity Interaction Length
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Solution Overview
Problem
Existing gas sensors for air quality monitoring in consumer electronics are either large or slow, and current miniaturization efforts face challenges with light throughput, complex optical alignment, and high reflectivity requirements, making them unsuitable for compact, high-performance devices.
Innovation Solution
A MEMS component with a semiconductor substrate stack featuring a cavity and reflection elements that increase the interaction length of radiation with the environment, allowing for efficient gas detection without the need for highly reflective mirrors, enabling a compact and high-performance optical gas sensor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multi pass cells are used to increase interaction length, then gas detection sensitivity is improved, but device complexity and optical alignment requirements increase significantly
Solution Approach 1:
The device is segmented into distinct functional layers (semiconductor substrates, cavity, reflection elements, radiation source, and detector) that can be independently fabricated and then assembled. This segmentation allows each component to be optimized separately and simplifies the overall integration process, reducing the complexity of optical alignment while maintaining high gas detection sensitivity through the extended interaction path in the cavity.
2Measurement precision
If highly reflective mirrors are used to increase interaction length, then gas detection sensitivity is improved, but manufacturing complexity and difficulty increase
Solution Approach 1:
The invention changes the key parameter from requiring extremely high reflectivity (R>99.99%) to using moderate reflectivity reflection elements. This parameter change is achieved by using semiconductor substrates with inherent optical properties that provide sufficient reflection without requiring complex high-reflectivity mirror coatings, thereby significantly simplifying the manufacturing process while still achieving the necessary interaction length for sensitive gas detection.
3Volume of moving object
If Fabry-Pérot resonators are used for miniaturization, then device size is reduced, but wavelength selectivity limitations arise
Solution Approach 1:
The invention transitions from planar optical paths to a three-dimensional vertical cavity structure. By stacking semiconductor substrates and creating a vertical resonance cavity, the device achieves miniaturization in the lateral dimensions while maintaining an extended interaction path in the vertical dimension. This dimensional change allows the device to function as a compact sensor without the wavelength selectivity constraints of traditional Fabry-Pérot resonators, as the cavity supports multiple modes and wavelengths 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
The MEMS component achieves a significant increase in interaction length for gas detection, enhancing sensitivity and reducing complexity, while maintaining a small form factor, thus addressing the limitations of existing sensors.
Implementation Method 1
The invention relates to a MEMS component (MEMS: microelectromechanical system), and in particular to a gas sensor having an integrated vertical cavity, said gas sensor being embodied as a MEMS component
Implementation Method 2
Two mutually spaced apart reflection elements for reflecting the emitted radiation are arranged in a beam path between the radiation source and the radiation detector
Data Source
AI summary
A MEMS component includes a semiconductor substrate stack having a first semiconductor substrate and a second semiconductor substrate, wherein the semiconductor substrate stack has a cavity formed within the first and second semiconductor substrates, and wherein at least the first or the second semiconductor substrate has an access opening for gas exchange between the cavity and an environment. A radiation source is arranged at the first semiconductor substrate, and a radiation detector is arranged at the second semiconductor substrate. Two mutually spaced apart reflection elements are arranged in a beam path between the radiation source and the radiation detector, wherein one reflection element is partly transmissive to the emitted radiation from the cavity in the direction of the radiation detector, and wherein an interspace between the two mutually spaced apart reflection elements has a length that is at least ten times the wavelength of the emitted radiation.