SOI Gas Sensor Trench Isolation for Thermal Stress Reduction
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Solution Overview
Problem
Existing semiconductor gas sensors face challenges with high power consumption and vulnerability due to thermal expansion coefficients mismatch in their multi-layer structures, leading to heat emission issues and potential film distortion or cracking, especially in suspended-film type sensors where integrating sensing material and film is difficult under high operating temperatures.
Innovation Solution
A manufacturing method for a gas sensor using a Silicon-On-Insulator (SOI) substrate with an oxide layer between the device layer and carrier, where a trench is etched around the conducting line to reduce power consumption, and the integrated circuit region is suspended on a cavity formed by etching the carrier and oxide layer, with a connecting arm electrically connecting to the circuit region, allowing for reduced heat transfer and improved thermal insulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a multi-layer structure is used in semiconductor gas sensors, then the sensor can achieve high temperature operation and sensitivity, but thermal expansion coefficient mismatch causes film distortion or cracking
Solution Approach 1:
The patent introduces a trench structure that segments the multi-layer film into isolated islands, separating the heater circuit layer from the sensing material layer. This segmentation prevents thermal stress from propagating across the entire film structure, thereby preventing distortion and cracking while maintaining high temperature operation capability
Solution Approach 2:
The patent extracts the heater circuit from the continuous film structure by removing material to form trenches around it. This isolation removes the source of thermal expansion mismatch stress from the sensing material, preventing film distortion and cracking while preserving the heating function
2Use of energy by moving object
If suspended-film type structure is used, then power consumption is reduced, but integrating sensing material and film is difficult under high operating temperatures
Solution Approach 1:
The patent applies preliminary action by forming the trench structure around the heater circuit before depositing the sensing material. This pre-formed isolation structure guides the subsequent material deposition process, making integration easier while maintaining the low power consumption suspended-film configuration
3Measurement precision
If heater circuit provides high temperature micro-environment, then gas sensor achieves consistency and sensitivity, but power consumption is greater than 1 watt
Solution Approach 1:
The patent applies local quality by concentrating the heating function in a localized trench-isolated region rather than heating a large continuous film area. This localized heating approach maintains the high temperature micro-environment needed for sensitivity while reducing the total power consumption below 1 watt
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 approach reduces power consumption and enhances the structural integrity of the gas sensor by minimizing heat loss and stress from thermal expansion, making it more efficient and reliable under high operating temperatures.
Implementation Method 1
an oxide layer, wherein the oxide layer is disposed between the device layer and the carrier
Implementation Method 2
the trench is formed around the conducting line and excavated to the oxide layer for reducing the power consumption of the heater circuit
Implementation Method 3
the heat emission paths are limited to the cantilevered beam in the suspended-film type gas sensor; therefore, the suspended-film type gas sensor has much lower power consumption
Data Source
AI summary
A gas sensor manufacturing method comprises the following steps: providing a SOI substrate, including an oxide layer, a device layer, and a carrier, wherein the oxide layer is disposed between the device layer and the carrier; etching the device layer to form an integrated circuit region, an outer region, a trench and at least one conducting line; coating or imprinted a sensing material on the integrated circuit region; and etching the carrier and the oxide layer to form a cavity up to the gap so as to form a film structure which is suspended in the cavity by the cantilevered connecting arm.