In this paper, we proposed a novel infrared absorbing structure for uncooled infrared detectors. The infrared absorber makes use of a quarter-wavelength structure composed of a dielectric layer, a protecting layer, an active layer, a supporting layer and a reflecting layer. Sputtered amorphous silicon is used as a dielectric layer because of its high refractive index. We fabricated the uncooled microbolometer with the proposed infrared absorbing structure by surface micromachining method. Then we characterized various bolometric properties such as thermal conductance, thermal time constant, responsivity and infrared absorptance. The fabricated bolometer showed the thermal conductance of 6.72 x 10(-7) W/K, the thermal mass of 4.43 x 10(-9) J/K, the thermal time constant of 6.6 ms and the responsivity of 7.76 x 10(3) V/W at 10 Hz chopper frequency and 9.22 mu A bias current. From the results, the estimated absorptance is about 80%. We expect that the proposed absorbing structure shows high infrared absorption and high performance of uncooled microbolometer. (C) 2007 Elsevier B.V. All rights reserved.