Integrated silicon sensors: technology and microstructures

The development of integrated sensor technology during the past decade, which has made possible the fabrication of a wide variety of microstructures on a high-volume basis, is discussed. Bulk micromachining is widely practiced using double-sided processes, while the single-sided dissolved-wafer bulk process offers advantages for many applications. Surface micromachining avoids the necessity of deep etching of the wafer bulk but requires careful control of stress in the deposited films and protection of the wafer during the sacrificial etch. Wafer-scale bonding processes such as electrostatic bonding and silicon fusion offer additional tools for the creation of three-dimensional microstructures. Electroforming processes such as LIGA allow structural thicknesses as great as 100 μm with micron or submicron lateral features. The application of these processes and microstructures to neuroelectronic interfaces, mass flow and microflow sensors, and multichannel submicron surface profilometers is described. The extension of these approaches to complete integrated microsystems, realized monolithically or as multichip hybrids, is discussed, and applications in areas such as millimeter-wave components and vacuum microelectronics are examined