An overview of uncooled infrared sensors technology based on amorphous silicon and silicon germanium alloys

Abstract

At the present time there are commercially available large un‐cooled micro‐bolometer arrays (as large as 1024×768 pixels) for a variety of thermal imaging applications. Different thermo‐sensing materials have been employed as thermo sensing elements as Vanadium Oxide (VOx), metals, and amorphous and polycrystalline semiconductors. Those materials present good characteristics but also have some disadvantages. As a consequence none of the commercially available arrays contain optimum pixels with an optimum thermo‐sensing material. This paper reviews the development of the un‐cooled bolometer technology and the research achievements on this area, with special attention on the key factors that would lead to improve the pixels performance characteristics. The work considers the R&D of microbolometer arrays and the integration with MEMS and IC technologies. A comparative study with the state of the art and data reported in literature is presented. Finally, further directions of uncooled bolometer based in thin films materials are also discussed in this paper. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

MEMS-Based Wavelength-Selective Bolometers

“…Prior to the fabrication of the membrane-supported bolometers, we fabricated bolometer films and examined their temperature coefficient of resistance (TCR) characteristics. In the past two decades, the a-Si and a-SiGe alloys bolometers (thermistors) have been intensively investigated in both scientific study and practical application due to its great success in achieving a high TCR with simple fabrication processes [20,41,42,43]. In this work, we also intended to choose a-Si film fabricated by sputtering for our MEMS-based wavelength-selective bolometers.…”

TiO2−x films for bolometer applications: recent progress and perspectives

“…Vanadium oxide (VO x ), amorphous silicon (a-Si), and carbon nanotubes (CNTs) are widely accepted heat-sensitive materials due to their high TCR and affordable noise level. These materials have high TCR (of approximately 2∼3 -%/K for VO x [5], 1∼4 -%/K for a-Si [6] and CNT for 0.26 -%/K [7]) and suitable noise characteristics (1/f noise parameter: low 10 -13 for VO x , low 10 -11 for a-Si) for bolometer. However, VO x has a drawback of its unstable reproducibility because it undergoes a phase change caused by the heating process that occurs after the formation of the oxide film [8].…”

Device-level vacuum packaged uncooled microbolometer on a polyimide substrate

“…Depending on the material, the resistance may increase or decrease with temperature. There are a variety of materials that can be used as the sensor material or thermometer for room temperature detection of infrared radiation, such as Y-Ba-Cu-O [1], SiGe [4], amorphous Si (a-Si) [5], polysilicon [6], and VO x [7]. The selection of the material depends on the compatibility of the fabrication process, sensitivity of the material with temperature variation, noise floor, and operating temperature.…”