DESIGN CONSIDERATIONS OF METAL-FILM BOLOMETER WITH MICROMACHINED FLOATING MEMBRANE

Abstract

A metal-film microbolometer formed on a glass membrane suspended on a silicon substrate has been fabricated by the anisotropic etching technique. The rectangular glass membrane is supported by its four leads connected to the corners of an etched V-groove cavity. This structure allows flexible thermal management and sensitivity optimization of the bolometer for different kinds of application, with a trade-off between lead thermal impedance and device active area. Optimizations of the structure applied to both a focal-plane array and a single detector are interpreted. A thermal impedance as high as 4 x 10(5)-degrees-C/W with a response time of several milliseconds can be achieved. For a 320-mu-m x 320-mu-m detector, theoretical predictions give a responsivity and normalized detectivity of over 700 V/W and 10(9) cm square-root Hz/W, respectively. For dimensions of 128-mu-m x 128-mu-m, suitable for a focal-plane-array detector, theory predicts a D* of 5.5 x 10(8). A discrepancy exists between the experiment and the theory, which is also discussed.