Unreleased Thermopile IR Sensor Using Material Transfer
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Solution Overview
Problem
The manufacturing process for thermopile infrared sensors is complex, costly, and time-consuming, and the suspended membrane structure is fragile and prone to damage, while non-suspended sensors suffer from low sensitivity due to inadequate thermal isolation materials that are not CMOS compatible at high temperatures.
Innovation Solution
The use of ultra-thin 2D materials combined with new thermally isolating materials like Parylene, which are stable at high temperatures, eliminates the need for a suspended membrane by providing effective thermal isolation between the sensor and the substrate, allowing for enhanced sensitivity and durability without the complexity of vacuum packaging and membrane suspension.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a suspended membrane structure is used to provide thermal isolation and enhance sensitivity, then the sensitivity is improved, but the device complexity and manufacturing cost increase significantly
Solution Approach 1:
The patent extracts and removes the complex suspended membrane structure, including the membrane, support beams, and vacuum cavity, retaining only the essential thermal isolation function through simplified thermally isolating material layers deposited directly on the substrate. This eliminates the need for extensive mask layers and complex fabrication processes while maintaining the core sensitivity enhancement through thermal isolation.
Solution Approach 2:
The patent applies local quality by using thermally isolating materials with specific low thermal conductivity properties only where thermal isolation is needed (between the thermocouple and substrate), rather than creating a fully suspended structure. This localized application of thermal isolation properties achieves sensitivity enhancement without the global complexity of a suspended membrane design.
2Measurement precision
If a suspended membrane structure is used to provide thermal isolation and enhance sensitivity, then the sensitivity is improved, but the manufacturing time and cost increase
Solution Approach 1:
The patent applies preliminary action by depositing the thermally isolating material layers (such as silicon oxide or silicon nitride) directly onto the substrate before fabricating the thermocouple structure. This pre-established thermal isolation eliminates the need for subsequent membrane suspension steps, vacuum cavity formation, and complex assembly operations, significantly reducing manufacturing time and process steps.
3Measurement precision
If a suspended membrane structure is used to provide thermal isolation and enhance sensitivity, then the sensitivity is improved, but the reliability decreases due to fragility and damage susceptibility
Solution Approach 1:
The patent inverts the conventional approach by instead of suspending the membrane above the substrate, depositing thermally isolating material layers directly onto the substrate surface. This inversion transforms the fragile suspended membrane into a robust integrated structure that is mechanically supported by the substrate, eliminating tearing and damage issues while maintaining thermal isolation functionality.
4Device complexity
If non-suspended sensor structure is used to simplify manufacturing, then the device complexity is reduced, but the sensitivity decreases due to inadequate thermal isolation
Solution Approach 1:
The patent uses composite materials by combining the thermocouple structure with multiple layers of thermally isolating materials (such as silicon oxide and silicon nitride) deposited directly on the substrate. This composite structure provides adequate thermal isolation to enhance sensitivity while maintaining a non-suspended, simplified device architecture that is easier to manufacture and more reliable.
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 results in a more robust, cost-effective, and efficient thermopile IR sensor with improved sensitivity, reducing manufacturing time and costs while maintaining structural stability, outperforming conventional polycrystalline silicon-based sensors.
Implementation Method 1
disposable thermally isolating material layer disposed between the ultra-thin material and the substrate
Implementation Method 2
An absorber is further deposited as an upper layer so as to absorb IR radiation
Implementation Method 3
The collected IR energy creates a temperature gradient across the thermocouple, causing the thermocouple to generate an output voltage via the Seebeck effect
Data Source
Figure 1A~1G
Figure 2A~2G
Figure 3
AI summary
An unreleased thermopile IR sensor and method of fabrication is provided which includes a new thermally isolating material and an ultra-thin material based sensor which, in combination, provide excellent sensitivity without requiring a released membrane structure. The sensor is fabricated using a wafer transfer technique in which a substrate assembly comprising the substrate and new thermally isolating material is bonded to a carrier substrate assembly comprising a carrier substrate and the ultra-thin material, followed by removal of the carrier substrate. As such, temperature restrictions of the various materials are overcome.