Bolometer Absorber Pillar Structure for Thermal Shorting
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Solution Overview
Problem
Bolometer infrared sensors face reliability and accuracy issues due to heat transference, process variations, drift, and Joule-heating, which introduce variations and offsets in sensor output, requiring compensation values based on historical data.
Innovation Solution
A bolometer sensor configuration with an absorber element that can be thermally shorted to the substrate in a controllable manner, allowing for correlated double sampling to measure and adjust output characteristics, reducing offset and drift by measuring differences in sensor output before and after thermal shorting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the absorber element is suspended above the substrate to minimize heat transference, then heat loss is reduced, but the ability to perform thermal shorting for compensation measurements is lost
Solution Approach 1:
The absorber element is designed with a pillar structure that can dynamically change its thermal contact state with the substrate. By applying an actuating voltage, the absorber element can be pulled toward the substrate to establish thermal contact for compensation measurements, then released to return to its suspended state for normal operation. This dynamic transition allows the system to adapt between minimizing heat loss and enabling thermal shorting for compensation.
2Measurement precision
If compensation values based on historical data are used to correct drift and offset, then sensor accuracy is improved, but the complexity of the measurement system increases
Solution Approach 1:
The system performs compensation measurements by thermally shorting the absorber element to the substrate before taking the actual infrared radiation measurement. This preliminary action establishes a known reference state (zero temperature difference between absorber and substrate) that allows for calculation of compensation values. By performing this thermal shorting action beforehand, the system obtains real-time compensation data without requiring complex historical databases or external calibration equipment.
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 improves the accuracy and reliability of the sensor by compensating for variations and drift, ensuring precise measurement of infrared radiation.
Implementation Method 1
infrared radiation incident upon the bolometer is absorbed by the absorber element and transferred to the transducer element in the form of heat
Implementation Method 2
enables the absorber element of the sensor to be thermally shorted to the substrate by bringing a part of the absorber element into contact with the substrate
Implementation Method 3
a transducer element that has an electrical resistance that varies with temperature
Implementation Method 4
Joule-heating results when an electric current is passed through the transducer element to detect heat induced changes in the electrical resistance. The electric current generates heat in the transducer element
Data Source
AI summary
A semiconductor device includes a substrate having an electrode structure. An absorber structure is suspended over the electrode structure and spaced a first distance apart from the first electrode structure. The absorber structure includes i) suspension structures extending upwardly from the substrate and being electrically connected to readout conductors, and ii) a pillar structure extending downwardly from the absorber structure toward the first electrode structure. The pillar structure has a contact portion located a second distance apart from the first electrode structure, the second distance being less than the first distance. The absorber structure is configured to flex toward the substrate under a test condition. The second distance is selected such that the contact portion of the pillar structure is positioned in contact with the first electrode structure when the absorber structure is flexed in response to the test condition.