Porous Metal Oxide Sensor Seed Layer for Grain Boundary Density
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Solution Overview
Problem
Existing MOS gas sensors have limited sensitivity due to fewer grain boundaries in their gas-sensitive portions, which restricts the degree of electrical change in response to target gases.
Innovation Solution
A method is developed to form a gas sensor device using atomic layer deposition, where a seed layer is structured with trenching or chemical activation to encourage spaced-apart nucleation of a sensing material, resulting in a porous sensing layer with numerous grain boundaries, enhancing the sensor's sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a dense sensing layer is formed using conventional deposition methods, then the layer provides good electrical continuity, but the number of grain boundaries is reduced, limiting sensitivity
Solution Approach 1:
The patent applies porous silicon dioxide as a seed layer structure that maintains electrical continuity while providing numerous grain boundaries. The porous structure creates multiple nucleation sites for the sensing material, increasing grain boundary density without compromising the electrical pathways needed for sensor operation.
Solution Approach 2:
The patent performs preliminary structuring of the silicon dioxide seed layer before depositing the sensing material. By pre-forming trenches or porous structures in the seed layer, the patent establishes predetermined nucleation sites that will generate the desired grain boundary distribution in the final sensing layer, ensuring both continuity and sensitivity.
2Speed
If the sensing layer is made thinner to improve response rate, then the response time decreases, but the electrical signal strength is reduced
Solution Approach 1:
The porous seed layer structure enables the formation of a thinner sensing layer with increased surface area to volume ratio. The porosity compensates for the reduced thickness by providing more grain boundaries per unit volume, maintaining signal strength while improving response rate through faster gas diffusion and more active sites.
3Ease of manufacture
If conventional deposition methods are used without seed layer structuring, then the manufacturing process is simple, but the grain boundary density is insufficient for high sensitivity
Solution Approach 1:
The patent introduces preliminary structuring of the silicon dioxide seed layer through trenching or porous formation before sensing material deposition. This pre-structuring step creates controlled nucleation sites that guarantee sufficient grain boundary density in the final sensing layer, achieving high sensitivity while maintaining a relatively simple overall manufacturing process.
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 approach increases the number of grain boundaries, leading to a more significant electrical change in response to target gases, improving the sensor's detection capabilities and response rate.
Implementation Method 1
ion-milling the deposited seed layer at spaced-apart nucleation sites
Implementation Method 2
nucleating, at spaced apart sites on the seed layer, a sensing material, thereby forming a porous sensing layer
Implementation Method 3
The grain boundaries 22 are target sites to which molecules of the target gas bind through a process referred to as adsorption
Implementation Method 4
The heating element is activated to heat the gas-sensitive portion to a temperature that is suitable for detecting a target gas
Data Source
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AI summary
A semiconductor sensor device includes a substrate, a non-suitable seed layer located above the substrate, at least one electrode located above the non-suitable seed layer, and a porous sensing layer supported directly by the non- suitable seed layer and in electrical communication with the at least one electrode, the porous sensing layer defining a plurality of grain boundaries formed by spaced-apart nucleation on the non-suitable seed layer using atomic layer deposition.