Yong-Hee Han

Fabrication of vanadium oxide thin film with high-temperature coefficient of resistance using V2O5/V/V2O5 multi-layers for uncooled microbolometers

Vanadium oxide thin film is a promising material for uncooled microbolometers due to its high temperature coefficient of resistance (TCR) at room temperature. It is, however, very difficult to deposit vanadium oxide thin films having a high temperature coefficient of resistance and low resistance because of the process limits in microbolometer fabrication. We present a novel fabrication method for vanadium oxide thin films having good electrical properties. Through the formation of a sandwich structure of V2O5 (100 A)/V (∼80 A)/V2O5 (500 A) by a conventional sputter method and post-annealing at 300 °C in oxygen, a mixed phase of VOx is formed. The results show that the mixed phase formed by this process has a high TCR of more than −2%/°C and low resistivity of <0.1 Ω cm at room temperature.

Enhanced characteristics of an uncooled microbolometer using vanadium–tungsten oxide as a thermometric material

To produce a highly sensitive uncooled microbolometer, the development of a high-performance thermometric material is essential. In this work, amorphous vanadium–tungsten oxide was developed as a thermometric material at a low temperature of 300°C, and the microbolometer, coupled with the material, was designed and fabricated using surface micromachining technology. The vanadium–tungsten oxide showed good properties for application to the microbolometer, such as a high-temperature coefficient of resistance of over −4.0%∕K and good compatibility with the surface micromachining and integrated circuit fabrication process due to its low fabrication temperature. As a result, the uncooled microbolometer could be fabricated with high detectivity over 1.0×109cmHz1∕2∕W at a bias current of 7.5μA and a chopper frequency of 10–20Hz.

Enhanced Characteristics of V0.95W0.05OX-Based Uncooled Microbolometer

In this work, high-performance uncooled microbolometer was fabricated by using vanadium tungsten oxide as a infrared-sensitive material and its bolometric properties was characterized. As a bolometric material, the optimized V_0.95W_0.05O_x thin film has a high TCR value over - 3.0%/K and low noise properties compared with VOx thin film. The fabricated V_0.95W_0.05O_x-based microbolometer was vacuum-packaged and equipped with thermal electric cooler for the measurement of bolometric properties. The TCR value of the fabricated device was -3.49%/K at room temperature resistance of 71 kOmega and the measured thermal conductance was 6.1times10^-7 W/K. Finally, we obtained high responsivity over 1.8times10⁴ W/K and high detectivity over 1.3times10⁹ cmHz^frac12/W at a chopper frequency of 10 Hz and a bias current of 7.4 muA

A floated absorbing structure for uncooled microbolometer

We propose a versatile infrared (IR) absorbing structure for uncooled infrared detectors. We have designed an infrared absorber consisting of five thin film layers (dielectric layer/protection layer/active layer/supporting layer/reflecting layer) that produce a quarter-wavelength resonance condition. It has excellent thermal properties, which are not influenced by the deformation of the thermal isolation structure. We fabricated a microbolometer with the proposed IR absorption structure by a surface micromachining technology. We estimated an IR absorptance of 80%. This IR absorption structure can be applied to both surface micromachining and bulk micromachining.