Free-Standing CMOS-MEMS IR Sensor for Higher Sensitivity
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Solution Overview
Problem
Conventional uncooled infrared detectors, such as microbolometers, require mechanical components for calibration, increasing manufacturing complexity and cost, and are less suitable for compact or reliable small-device applications due to their mechanical nature.
Innovation Solution
The development of monolithic integrated CMOS-MEMS devices with free-standing MEMS sensors that eliminate the need for support dielectrics, enhancing sensor sensitivity and response time by integrating CMOS components with MEMS structures, including a substrate with a CMOS region and a MEMS region, where the MEMS sensor is formed over a lower sensor cavity without a support dielectric, and utilizing a double-release process to create a free-standing sensor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If microbolometers are used for uncooled infrared detection, then infrared detection capability is achieved, but mechanical components are required for calibration increasing device complexity
Solution Approach 1:
The patent replaces mechanical calibration components with electrical calibration mechanisms. The microbolometer array is integrated with CMOS readout circuitry that performs offset correction and non-uniformity correction through electrical means, eliminating the need for mechanical shutters and calibration mirrors. This substitution reduces mechanical complexity while maintaining infrared detection capability.
Solution Approach 2:
The patent merges the microbolometer sensor array with CMOS readout circuitry into a single integrated device. The CMOS circuitry includes pixel-level readout circuits, column-level signal processing, and digital signal processing capabilities, all integrated with the microbolometer elements. This integration eliminates separate mechanical calibration systems and reduces overall device complexity.
2Ease of operation
If mechanical components are added for calibration, then offset correction is enabled, but manufacturing complexity and cost increase
Solution Approach 1:
The patent replaces mechanical calibration components with electrical calibration mechanisms. The microbolometer array is integrated with CMOS readout circuitry that performs offset correction and non-uniformity correction through electrical means, eliminating the need for mechanical shutters and calibration mirrors. This substitution reduces mechanical complexity while maintaining infrared detection capability.
Solution Approach 2:
The patent implements self-calibration capabilities through integrated CMOS circuitry that automatically performs offset correction and non-uniformity correction. The device includes on-chip digital signal processing that continuously monitors and corrects sensor drift without external mechanical intervention, enabling the device to self-correct during operation.
3Measurement precision
If mechanical components are used for calibration, then sensor accuracy is maintained, but device size increases reducing compactness
Solution Approach 1:
The patent merges the microbolometer sensor array with CMOS readout circuitry into a single integrated device. The CMOS circuitry includes pixel-level readout circuits, column-level signal processing, and digital signal processing capabilities, all integrated with the microbolometer elements. This integration eliminates separate mechanical calibration systems and reduces overall device complexity.
Solution Approach 2:
The patent transitions from mechanical calibration in three-dimensional space to electrical and digital calibration in the circuit domain. The CMOS readout circuitry performs calibration functions through electrical signals and digital processing, effectively moving the calibration function from a spatial/mechanical dimension to an electrical/digital dimension, thereby reducing physical device size.
4Ease of operation
If mechanical shutters are used for calibration, then offset correction is achieved, but reliability decreases due to mechanical failure points
Solution Approach 1:
The patent replaces mechanical calibration components with electrical calibration mechanisms. The microbolometer array is integrated with CMOS readout circuitry that performs offset correction and non-uniformity correction through electrical means, eliminating the need for mechanical shutters and calibration mirrors. This substitution reduces mechanical complexity while maintaining infrared detection capability.
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 cost-effective, compact, and highly sensitive infrared detectors with improved response time, reducing manufacturing complexity and enhancing reliability, making them suitable for various applications including thermal imagers and IoT devices.
Implementation Method 1
free-standing MEMS infrared sensors
Implementation Method 2
thermoelectric-based infrared detector
Data Source
AI summary
A CMOS-MEMS integrated device and a method for forming such a device are disclosed. The integrated device includes a double released MEMS infrared sensor. The double released MEMS sensor is a free-standing sensor over a lower sensor cavity which is etched into the substrate of the device. The free-spending MEMS sensor is devoid of a support dielectric membrane which supports the MEMS sensor, resulting in the MEMS sensor being suspended over the lower sensor cavity. The support dielectric is removed by a second release process. The second release process may also remove a protective dielectric layer over the MEMS sensor. The MEMS sensor without the protective dielectric layer enhances sensor sensitivity. In other cases, the free-standing MEMS sensor may include an absorber thereover. The absorber enhances sensor sensitivity.