Monolithic two-dimensional arrays of micromachined microstructures for infrared applications

Abstract

Small micromachined structures (typically 10/sup -5/ cm/sup 2/) have been fabricated that have very small thermal mass (c, about 10/sup -9/ J/K) and that are suspended from the underlying silicon substrate by supports of such delicacy that the structures are extremely well thermally isolated from the substrate (thermal conductance to the substrate g of 10/sup -7/ W/K). This thermal conductance is close to the smallest value possible (about 10/sup -8/ W/K) due to radiative energy exchange. This high thermal isolation allows the microstructure temperature to be readily controlled by very small heating currents, or very small amount of infrared (IR) incident IR flux. Large arrays of such microstructures have been fabricated on silicon wafers, complete with complex integrated electronic circuits, and operated as (1) sensitive room-temperature IR sensors ("microbolometers") for night-vision IR imaging and (2) large arrays of individually controllable IR microemitters. The latter provide dynamic infrared "scene generators" that allow realistic simulations of IR scenes, an important tool for the development of IR cameras and IR missile seekers.