Enhanced Conduction Structure for Improving Infrared Microbolometer Sensors Without the Need for Cooling

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Block diagram of an infrared (IR) imager constructed in accordance with an embodiment of the inventionTop perspective view of an array of micro bolometers constructed in accordance with an embodiment of the inventionTop perspective view illustrating the structure of a micro bolometer formed in accordance with an embodiment of the invention
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Kevin Coffey, Ph.D.
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Andrea Adkins
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Conduction structure for infrared microbolometer sensors

US Patent 7,633,065 B2

Methods and apparatus for an enhanced conduction structure used in infrared (IR) microbolometer sensors.

The desire to “see” in complete darkness or through obscurants such as smoke or fog has driven the development and adoption of thermal imaging technology in numerous industries. Thermal imaging devices provide the observer with instruments that can collect and convert the thermal infrared (IR) radiation emitted (and also reflected) by objects into images that can be seen on a view screen or computer display. Two classes of IR thermal imagers systems are available in the market today: cooled and uncooled systems. Both of these systems generally include a bolometer or microbolometer device to detect incident electromagnetic radiation. Bolometers are essentially resistive thermometers that need to maintain a certain total resistance for optimum signal and noise properties. Accordingly, a material with a large thermal coefficient of resistivity (TCR) is preferred to produce better IR sensing. Microbolometers are a specific type of bolometers used as a detector in a thermal camera. Cooled IR imagers with bolometers, are often complex, larger in size, and costly. On the contrary, uncooled IR systems with microbolometers are less expensive and smaller in design. However, these uncooled systems must typically include a lower resistivity bolometer film material because of the in-plane conduction mode structure design of these bolometers, resulting in lower values of TCR, thus lower IR sensitivity and lower image quality. Therefore, there is a need for a novel conduction mode structure design for uncooled IR systems that will significantly improve performance while being cost effective.

Technical Details

The present invention introduces a novel conduction structure for uncooled IR systems, by changing the conduction mode of the microbolometer device from in-plane to a vertical conduction mode through the thickness of a bolometer film. This novel vertical structure significantly reduces the overall resistance of the microbolometer pixel device, allowing the device resistance to be essentially unchanged when much higher resistivity bolometer materials are used. Accordingly, this novel invention will allow the use of a bolometer material with a resistivity 4000 times higher and yet still achieve the same device resistance! By using vertical conduction structure, it is possible to use the material with high resistivity, resulting in higher TCR, thus high sensitivity of the IR sensors and better image quality. Furthermore, improvements on overall system performance and cost can be achieved. By allowing higher TCR materials to be used in a vertically conducting structure, this concept has the potential to revolutionize the development of the low cost, uncooled IR imager for better IR sensing performance.

Benefits

  • Significantly improves the thermal coefficient of resistivity (TCR) which results in enhanced sensitivity and image quality
  • Bolometer materials with large resistivity can be easily incorporated while achieving the same device resistance, resulting in enhanced image quality at lower costs
  • Easily scalable and inexpensive manufacturing process, therefore very attractive for many business applications

Applications

  • Security
  • First response industries
  • Automotive
  • Industrial
  • Infrared detectors


Additional Technology Numbers: 31284