Enhanced performance of microbolometer using coupled feed horn antenna

Abstract

In the paper, we improved the performance of the microbolometer using coupled feed horn antenna. The response time of the device was improved by reducing thermal time constant as the area of the absorption layer was reduced. We designed the shape of an absorption layer as circular structure in order to reduce the coupling loss between the antenna and the bolometer. A supporting leg for thermal isolation also has circular structure and its length increased up to 82micrometers , it reduced the thermal conductance to 4.65x 10<SUP>-8</SUP>[W/K]. The directivity of the designed antenna has 20.8dB. So the detectivity of the bolometer was improved to 2.37x 10<SUP>-9</SUP> [cm ROOT(Hz)/W] as the noise characteristics of the bolometer was enhanced by coupling feed horn antenna. The fabrication of the bolometer are carried out by a surface micromachining method that uses a polyimide as a sacrificial layer. The absorption layer material of the bolometer is VO<SUB>x</SUB> and its TCR value has above 2%/K. The 3-D feed horn antenna structure can be constructed by using a PMER negative photoresist. The antenna and the bolometer can be bonded by Au-Au flip chip bonding method.