Single-Wafer Photoacoustic Gas Sensor Cavity Integration
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Solution Overview
Problem
Existing photoacoustic gas sensors face limitations in robustness, miniaturization, and cost-effectiveness due to the use of multiple wafers joined by welding, soldering, or anodic joining processes, which increase manufacturing effort and costs.
Innovation Solution
A production method for a photoacoustic gas sensor using a single silicon wafer with a buried insulation layer to create separated cavities for the thermal emitter and acoustically sensitive element, implemented through photolithographic and etching processes, eliminating the need for wafer joining.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple wafers are joined by welding, soldering, or anodic joining processes to create photoacoustic gas sensors, then the sensor functionality is achieved, but robustness decreases and manufacturing complexity increases
Solution Approach 1:
The patent merges the thermal emitter wafer and the acoustically sensitive element wafer into a single integrated wafer structure. The first cavity (thermal emitter) and second cavity (acoustically sensitive element) are created in the same wafer, eliminating the need for separate wafers and joining processes. This integration directly improves robustness by removing joint interfaces and simplifies manufacturing by reducing the number of components and assembly steps.
Solution Approach 2:
The single wafer is segmented into functionally distinct regions: the first cavity for the thermal emitter and the second cavity for the acoustically sensitive element. These segments are separated by a common wall formed within the wafer structure. This segmentation allows each functional element to be optimized independently while maintaining structural integrity and eliminating the need for external joining processes.
2Ease of manufacture
If multiple wafers are joined to create photoacoustic gas sensors, then the sensor can be assembled, but manufacturing effort and costs increase
Solution Approach 1:
By combining both functional elements into a single wafer, the patent eliminates multiple joining operations (welding, soldering, or anodic joining) that are required when using separate wafers. This reduction in assembly steps directly decreases manufacturing effort and eliminates the time-consuming joining processes, thereby improving manufacturing efficiency and productivity.
3Volume of moving object
If multiple wafers are joined to create photoacoustic gas sensors, then the sensor structure is formed, but miniaturization is limited
Solution Approach 1:
The integration of both cavities into a single wafer allows for compact arrangement of the thermal emitter and acoustically sensitive element in close proximity. The common wall between the cavities serves dual purposes: separating the functional regions and providing structural support. This merged structure enables miniaturization by reducing the overall sensor footprint compared to separate-wafer designs that require additional spacing for joining interfaces.
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 method enables a robust, miniaturized, and cost-effective photoacoustic gas sensor with high sensitivity and selectivity, allowing for mass production without the need for photodetectors and adhesive layers.
Implementation Method 1
when a gas sample to be analyzed is irradiated in a measuring cell with a pulsed light source, then the gas molecules absorb the light, and the gas sample heats up
Implementation Method 2
With a constant volume size of the measuring cell, this causes acoustic waves to be produced whose frequency corresponds to the modulation frequency of the light source
Data Source
AI summary
A method for producing a photoacoustic gas sensor for a target gas, having the steps of a) providing a wafer made of silicon, having a front face and a rear face. The wafer having a buried insulating layer within the silicon. The method including b) providing a suspended thermal emitter having a first cavity on the rear face of the wafer. The method including c) providing a sound-sensitive element on the front face of the wafer, the sound-sensitive element having a second cavity in which the target gas is enclosed. The additionally relates to a photoacoustic gas sensor for a target gas.