Recent interest in bolometers for heterodyne mixing applications has prompted development of microbridges which are small enough to allow electron diffusion to dominate over electron-phonon interaction as a cooling mechanism. Prior results at 533 GHz have demonstrated several GHz intermediate frequency (IF) bandwidth. Here we describe our processing method in which the bolometer element is a 10 nm thin film of niobium defined by electron beam lithography down to dimensions of 80 nm. This microbridge is embedded in a normal metal (Au) antenna structure for 1.2 and 2.5 THz applications.