We discuss the development, at Argonne National Laboratory, of a four-pixel camera suitable for photometry of distant
dusty galaxies located by Spitzer and SCUBA, and for study of other millimeter-wave sources such as ultra-luminous
infrared galaxies, the Sunyaev-Zeldovich (SZ) effect in clusters, and galactic dust. Utilizing Frequency Selective
Bolometers (FSBs) with superconducting Transition-Edge Sensors (TESs), each of the camera's four pixels is sensitive
to four colors, with frequency bands centered approximately at 150, 220, 270, and 360 GHz.
The current generation of these devices utilizes proximity effect superconducting bilayers of Mo/Au or Ti/Au for TESs,
along with frequency selective circuitry on membranes of silicon nitride 1 cm across and 1 micron thick. The operational
properties of these devices are determined by this circuitry, along with thermal control structures etched into the
membranes. These etched structures do not perforate the membrane, so that the device is both comparatively robust
mechanically and carefully tailored in terms of its thermal transport properties.
In this paper, we report on development of the superconducting bilayer TES technology and characterization of the FSB
stacks. This includes the use of new materials, the design and testing of thermal control structures, the introduction of
desirable thermal properties using buried layers of crystalline silicon underneath the membrane, detector stability control,
and optical and thermal test results. The scientific motivation, FSB design, FSB fabrication, and measurement results are