Electronics, Army STTR, Phase I
Engineered Bolometer Leg Materials Toward Physics-Limited Thermal Infrared Imaging Arrays
Objective
The vendor must demonstrate an engineered materials system that can deposit and pattern with semiconductor foundry techniques, offer very low thermal conductivity, and have reasonable electrical conductivity for use as a bolometer leg.
Description
Bolometer technology is prevalent in nearly all uncooled, longwave imaging sensors worldwide. Commercial and military applications use these sensors on ground, personnel-carried and air platforms. This technology supports targeting, autonomy, situational awareness, security and many other application spaces. With its inclusion into numerous Army Programs of Record, the technology is increasingly relevant for inputs to artificial intellgience and machine-learning-powered algorithms. This is because bolometer-based sensors can provide low-cost imaging in the longwave infrared band.
Domestic U.S. industry holds strong advantages in performance and the number of manufactured sensor units. However, high levels of investment by foreign companies and countries have eroded this advantage. This topic seeks to extend the power of the U.S.’capabilities.
A bolometer-based imaging sensor comprises a focal plane where each pixel is a bolometer structure, a read-out integrated circuit, supporting electronics, optics and a mechanical housing. The basic bolometer structure itself, a microelectromechanical structure, comprises a transducing body and two legs. The legs serve to mechanically support the body and thermally isolate it while passing an electric current to read out the transducing body’s signal.
The leg, and the materials that comprise it, are key to a highly-sensitive and manufacturable pixel. Higher thermal isolation results in a more sensitive pixel. However, the typical way to increase thermal isolation is to make the leg longer and thinner, often wrapping around the pixel many times. This decreases the pixel manufacturability and sensor robustness in operational use. This is especially important as bolometer pixels shrink in support of higher resolution devices.
The topic seeks a new material or engineered material system, which is inherently more thermally isolating, while maintaining electrical conductivity and mechanical robustness. This would enable a shorter, wider leg that helps push bolometers closer to their physical performance limit and away from the practical structural limits imposed today. This requires a material system that breaks the usual Wiedemann–Franz relationship between electrical and thermal conductivity.
To be applicable to high-rate bolometer fabrication, the material must deposit and lithographically pattern via standard CMOS foundry equipment used in bolometer fabrication. It should also be compatible with other portions of the fabrication and packaging processes. A low-noise ohmic contact must form with the substrate and bolometer body material (commonly vanadium oxide, but sometimes α-silicon, titanium oxide or other materials). Overall, the total leg thermal mass must be low to avoid degrading sensor performance.
The Army will not be consider proposals for material systems with other bolometer components (e.g., the body/transducing material), alternate sensing technologies, other components of the camera module, or anything else that is not a bolometer leg capable of mechanical support, thermal isolation and electrical conductivity.
Phase I
The businesses must describe one or more material systems and propose a method of fabricating the material compatible with the constraints of a semiconductor fabrication facility. Through a combination of modeling, theory and/or experimental evidence, the vendor should demonstrate that the system meets all requirements to act as a bolometer leg and is superior to materials used in current production devices.
The Army will evaluate the material system based on low thermal conductivity (< 250 pW/K, ideally approaching 0), low overall thermal mass (<0.3 pJ/K), moderate electrical conductivity (ideally resistance < 250 kΩ, but up to 2 MΩ for certain readouts), its ability to form low-noise ohmic contacts, a low deposition thermal budget (<200°C), and an overall thermal and mechanical robustness (withstand 300°C, mechanical shock and vibration). The business shall deliver this in a final technical volume.
Phase II
Vendors should further develop, fabricate and characterize the material system. Businesses need to show that the material system can meet the requirements of bolometer legs. The Army does not require a particular physical form for this demonstration. However, it desires that the final material system demonstration be as high-fidelity as possible in replicating its end use as a bolometer leg (though a complete bolometer is not necessary).
Vendors must formulate a fabrication process flow that is fully compatible, with bolometer fabrication flows used by. industry to promote the transition of the material system. Vendors should collaborate with industry to show the buy-in of the material system and compatibility with production flows. Businesses need to demonstrate or otherwise show that this fabrication method is low-cost, high yield and high uniformity.
Phase III
Vendors must work with a U.S.-based bolometer fabricator to transition the material system to a high-rate production environment. It needs to support the bolometer fabricator in developing an imaging demonstration prototype LWIR bolometer sensor system. It may be based on an existing camera/sensor product to prove the viability and benefits of the material system for increasing performance and/or manufacturing yield.
Such a material system is useful to all domestic bolometer manufacturers and could improve any existing or future bolometer product (domestic or commercial use) as a 100% drop-in replacement. The enhanced sensors could then qualify for use in any COTS, Program of Record or acquisition program. Since sensors utilizing this material system would be a 100% drop-in replacement, it could help future programs utilizing uncooled thermal technologies.
Submission Information
All eligible businesses must submit proposals by noon ET.
To view full solicitation details, click here.
For more information, and to submit your full proposal package, visit the DSIP Portal.
STTR Help Desk: usarmy.rtp.devcom-arl.mbx.sttr-pmo@army.mil
References:
- Hopkins, P.E. (2013). Thermal Transport across Solid Interfaces with Nanoscale Imperfections: Effects of Roughness, Disorder, Dislocations, and Bonding on Thermal Boundary Conductance. ISRN Mech Eng. 2013. http://dx.doi.org/10.1155/2013/682586
- Xiong, S., Sääskilahti, K., Kosevich, Y. A., Han, H., Donadio, D., & Volz, S. (2016). Blocking Phonon Transport by Structural Resonances in Alloy-Based Nanophononic Metamaterials Leads to Ultralow Thermal Conductivity. Phys Rev Lett, 117(2), 025503-9. http://dx.doi.org/10.1103/PhysRevLett.117.025503
- Maldovan, M. (2013). Sound and heat revolutions in phononics. Nature, 503(7475), 209-217. https://doi.org/10.1038/nature12608
- Davis, B. L. & Hussein, M. I. (2014). Nanophononic Metamaterial: Thermal Conductivity Reduction by Local Resonance. Phys Rev Lett, 112(5), 055505-10. https://doi.org/10.1103/PhysRevLett.112.055505
- Wilson, A. A., Sharar, D. J., Smith, G. L. & Knick, C. R. (2021) Phonon disruptors for increased thermal resistance without sacrificing electrical signal quality in thermal sensors (U.S. Patent No. US20220381623A1). U.S. Patent and Trademark Office. https://patents.google.com/patent/US20220381623A1/en
- Wilson, A. A., Waldron, D. L., Knick, C. R. & Sharar, D. J. (2022) Phonon disruptors for increased thermal resistance without sacrificing electrical signal quality in thermal sensors using alloy and intermetallic materials (U.S. Patent No. US20220373395A1). U.S. Patent and Trademark Office. https://patents.google.com/patent/US20220373395A1/en
- KEYWORDS: Bolometer, microbolometer, longwave, LWIR, sensor, thermal, conductivity, MEMS
Objective
The vendor must demonstrate an engineered materials system that can deposit and pattern with semiconductor foundry techniques, offer very low thermal conductivity, and have reasonable electrical conductivity for use as a bolometer leg.
Description
Bolometer technology is prevalent in nearly all uncooled, longwave imaging sensors worldwide. Commercial and military applications use these sensors on ground, personnel-carried and air platforms. This technology supports targeting, autonomy, situational awareness, security and many other application spaces. With its inclusion into numerous Army Programs of Record, the technology is increasingly relevant for inputs to artificial intellgience and machine-learning-powered algorithms. This is because bolometer-based sensors can provide low-cost imaging in the longwave infrared band.
Domestic U.S. industry holds strong advantages in performance and the number of manufactured sensor units. However, high levels of investment by foreign companies and countries have eroded this advantage. This topic seeks to extend the power of the U.S.’capabilities.
A bolometer-based imaging sensor comprises a focal plane where each pixel is a bolometer structure, a read-out integrated circuit, supporting electronics, optics and a mechanical housing. The basic bolometer structure itself, a microelectromechanical structure, comprises a transducing body and two legs. The legs serve to mechanically support the body and thermally isolate it while passing an electric current to read out the transducing body’s signal.
The leg, and the materials that comprise it, are key to a highly-sensitive and manufacturable pixel. Higher thermal isolation results in a more sensitive pixel. However, the typical way to increase thermal isolation is to make the leg longer and thinner, often wrapping around the pixel many times. This decreases the pixel manufacturability and sensor robustness in operational use. This is especially important as bolometer pixels shrink in support of higher resolution devices.
The topic seeks a new material or engineered material system, which is inherently more thermally isolating, while maintaining electrical conductivity and mechanical robustness. This would enable a shorter, wider leg that helps push bolometers closer to their physical performance limit and away from the practical structural limits imposed today. This requires a material system that breaks the usual Wiedemann–Franz relationship between electrical and thermal conductivity.
To be applicable to high-rate bolometer fabrication, the material must deposit and lithographically pattern via standard CMOS foundry equipment used in bolometer fabrication. It should also be compatible with other portions of the fabrication and packaging processes. A low-noise ohmic contact must form with the substrate and bolometer body material (commonly vanadium oxide, but sometimes α-silicon, titanium oxide or other materials). Overall, the total leg thermal mass must be low to avoid degrading sensor performance.
The Army will not be consider proposals for material systems with other bolometer components (e.g., the body/transducing material), alternate sensing technologies, other components of the camera module, or anything else that is not a bolometer leg capable of mechanical support, thermal isolation and electrical conductivity.
Phase I
The businesses must describe one or more material systems and propose a method of fabricating the material compatible with the constraints of a semiconductor fabrication facility. Through a combination of modeling, theory and/or experimental evidence, the vendor should demonstrate that the system meets all requirements to act as a bolometer leg and is superior to materials used in current production devices.
The Army will evaluate the material system based on low thermal conductivity (< 250 pW/K, ideally approaching 0), low overall thermal mass (<0.3 pJ/K), moderate electrical conductivity (ideally resistance < 250 kΩ, but up to 2 MΩ for certain readouts), its ability to form low-noise ohmic contacts, a low deposition thermal budget (<200°C), and an overall thermal and mechanical robustness (withstand 300°C, mechanical shock and vibration). The business shall deliver this in a final technical volume.
Phase II
Vendors should further develop, fabricate and characterize the material system. Businesses need to show that the material system can meet the requirements of bolometer legs. The Army does not require a particular physical form for this demonstration. However, it desires that the final material system demonstration be as high-fidelity as possible in replicating its end use as a bolometer leg (though a complete bolometer is not necessary).
Vendors must formulate a fabrication process flow that is fully compatible, with bolometer fabrication flows used by. industry to promote the transition of the material system. Vendors should collaborate with industry to show the buy-in of the material system and compatibility with production flows. Businesses need to demonstrate or otherwise show that this fabrication method is low-cost, high yield and high uniformity.
Phase III
Vendors must work with a U.S.-based bolometer fabricator to transition the material system to a high-rate production environment. It needs to support the bolometer fabricator in developing an imaging demonstration prototype LWIR bolometer sensor system. It may be based on an existing camera/sensor product to prove the viability and benefits of the material system for increasing performance and/or manufacturing yield.
Such a material system is useful to all domestic bolometer manufacturers and could improve any existing or future bolometer product (domestic or commercial use) as a 100% drop-in replacement. The enhanced sensors could then qualify for use in any COTS, Program of Record or acquisition program. Since sensors utilizing this material system would be a 100% drop-in replacement, it could help future programs utilizing uncooled thermal technologies.
Submission Information
All eligible businesses must submit proposals by noon ET.
To view full solicitation details, click here.
For more information, and to submit your full proposal package, visit the DSIP Portal.
STTR Help Desk: usarmy.rtp.devcom-arl.mbx.sttr-pmo@army.mil
References:
- Hopkins, P.E. (2013). Thermal Transport across Solid Interfaces with Nanoscale Imperfections: Effects of Roughness, Disorder, Dislocations, and Bonding on Thermal Boundary Conductance. ISRN Mech Eng. 2013. http://dx.doi.org/10.1155/2013/682586
- Xiong, S., Sääskilahti, K., Kosevich, Y. A., Han, H., Donadio, D., & Volz, S. (2016). Blocking Phonon Transport by Structural Resonances in Alloy-Based Nanophononic Metamaterials Leads to Ultralow Thermal Conductivity. Phys Rev Lett, 117(2), 025503-9. http://dx.doi.org/10.1103/PhysRevLett.117.025503
- Maldovan, M. (2013). Sound and heat revolutions in phononics. Nature, 503(7475), 209-217. https://doi.org/10.1038/nature12608
- Davis, B. L. & Hussein, M. I. (2014). Nanophononic Metamaterial: Thermal Conductivity Reduction by Local Resonance. Phys Rev Lett, 112(5), 055505-10. https://doi.org/10.1103/PhysRevLett.112.055505
- Wilson, A. A., Sharar, D. J., Smith, G. L. & Knick, C. R. (2021) Phonon disruptors for increased thermal resistance without sacrificing electrical signal quality in thermal sensors (U.S. Patent No. US20220381623A1). U.S. Patent and Trademark Office. https://patents.google.com/patent/US20220381623A1/en
- Wilson, A. A., Waldron, D. L., Knick, C. R. & Sharar, D. J. (2022) Phonon disruptors for increased thermal resistance without sacrificing electrical signal quality in thermal sensors using alloy and intermetallic materials (U.S. Patent No. US20220373395A1). U.S. Patent and Trademark Office. https://patents.google.com/patent/US20220373395A1/en
- KEYWORDS: Bolometer, microbolometer, longwave, LWIR, sensor, thermal, conductivity, MEMS