Image Sensors Group

Microbolometer Type Uncooled Infrared Detectors in Standard CMOS Technology

Uncooled infrared detectors have recently gained wide attention for infrared imaging applications, due to their advantages such as low cost, low weight, low power, wide spectral response, and long-term operation compared to those of photon detectors. Microbolometers are most widely used uncooled infrared detectors due to their compatibility with CMOS technology. They can be monolithically integrated with CMOS circuitry which allows their cost to be low.

The application areas of the uncooled detectors can be summarized as:

Military Applications

Civilian Applications

Simple surveillance

Night vision enhancers for drivers

Light weight helmet sights

Fire fighting

Munitions

Handheld camera

Rifle sights

Process control

Unattended ground sensors

Medical imaging

Advanced threat warning

Navigation

Long range scouts

Security systems

Missile seeker

Satellite instruments

In this project we have implemented the lowest-cost uncooled infrared microbolometer, where the CMOS n-well layer is used as the active sensor material. The suspended n-well structure have been obtained by post-etching of the fabricated CMOS dies, while the n-well was protected from etching by the electrochemical etch-stop technique in TMAH.

We have two types of n-well microbolometers. In the first generation n-well microbolometers, the n-well structure is used as a resistor. A 16x16 array was fabricated with this approach. In the second generation microbolometers, n-well is used as a diode in order to increase the performance of the detectors. 16x16, 64x64, and 128x128 detector arrays are fabricated with these detectors. Below you can see some pictures of the fabricated n-well microbolometers.

The main advantage of these detectors is that they can be fabricated in any CMOS technology together with their readout circuits, which makes the cost of the detectors very low. Our research have shown that n-well microbolometers can provide a reasonable performance for low-cost uncooled imaging especially for civil applications.

 


Resistor type n-well microbolometer from 16x16 array

Single pixel diode type n-well microbolometer (underneath)

Diode type n-well detectors from 128x128 array 

Diode type n-well microbolometers from 128x128 array (underneath)