Measurement results of a 12 μm pixel size microbolometer array based on a novel thermally isolating structure using a 17 μm ROIC

Abstract

In this paper a novel concept for the fabrication of highly sensitive uncooled microbolometers is presented. The approach is based on the realization of thermal isolation and simultaneous electrical contacting of the microbolometers by means of sufficiently long and thin coated nanotubes, which can be fabricated by post processing on top of CMOS wafers comprising the ROIC. Thus, the effective area of the absorption layer is maximized at a given pixel size, as lateral legs, which have been the main component of the thermal isolation commonly, are completely omitted. The resulting thermal conductance can be tuned independently from the pixel size by varying the geometry and structuring of the nanotubes. Based on test structures the nanotube microbolometers are characterized with respect to electro-optical and mechanical properties. The focus in this paper is on nanotube microbolometers with a pixel size of 12 μm

Uncooled infrared focal plane arrays

“…Figure shows the trends in pixel reduction. While the pixel pitch of the first microbolometer reported in 1992 was 50 μm , it was reduced to 25 μm by 2002 , 17 μm by 2007 , and 12 μm in 2013 . Today, the most advanced microbolometer IRFPA has a pixel pitch of 10 μm .…”

Per-Pixel Time Constant Measurement of Bolometer Cameras

“…There are many reported methods of measuring τ depending on the level of control one has over the system or component. One common method for test structures is to electrically excite the bolometer array with a controlled current to raise the temperature through Joule heating and simultaneously measure the voltage across the device [2][3][4][5]. The device resistance is then used to calculate a temperature change over time based on knowledge of the thermal coefficient of resistance (TCR) of the device material.…”

Modeling of Thermal Conductivity for a CMOS-Compatible MEMS-ROIC Contact by TiN Nanotubes

“…T HE selection of contact materials for microelectromechanical systems (MEMS) with free-standing membranes like microheaters [1] or microbolometers [2], [3] is mainly process-related and leads to metals or alloys, where phonons as well as electrons contribute to thermal conductivity. Recent manufacturing techniques like atomic layer deposition (ALD) allow the deposition of thin films in geometries with a high aspect ratio.…”

“…Recent manufacturing techniques like atomic layer deposition (ALD) allow the deposition of thin films in geometries with a high aspect ratio. The combination of thin layer deposition with a sacrificial material can be used for the manufacturing of nanotubes [3], [4]. An overview about ALD compatible materials for such kind of nanotubes, made of metals or alloys as conducting layer is given by Johnson [5].…”