A far infrared VGA detector based on uncooled microbolometers for automotive applications

Warm bodies like humans or animals emit radiation in the long-wave infrared band (8 to 14 µm) which can be used for pedestrian detection in an automotive application. Fraunhofer-IMS has developed an advanced 640 x 480 (VGA) IR detector (IRFPA=infrared focal plane array) based on uncooled micro bolometers with a pixel-pitch of 25µm. The IRFPA is designed for thermal imaging applications with a full-frame frequency of 30 Hz and a high sensitivity with a NETD < 100 mK @ f/1. The microbolometer as the sensing element is based on amorphous silicon as the sensing layer. A novel readout architecture which utilizes massively parallel on-chip Sigma-Delta-ADCs located under the microbolometer array re sults in a high performance digital readout. Since packaging is a significant part of a IRFPA's price Fraunhofer-IMS uses a chip-scaled package consisting of an IR-transparent window with antireflection coating and a soldering frame for maintaining the vacuum. The IRFPAs are completely fabricated at Fraunhofer-IMS on 8" CMOS wafers with an additional surface micromachining process.