Micromechanics: an emerging technology

Summary form only given, substantially as follows. Micromechanics deals with sensors and actuators. Sensors are devices which measure some property of their environment. They should do this non-invasively. This implies small physical size and low power transfer with large sensitivity. These requirements demand very stable material characteristics which are available in single crystal silicon. Smallness can be accommodated via surface rather than bulk micromachining. In this procedure three-dimensionality is achieved by using a sacrificial layer which supports the sensor structure temporarily and is eventually removed by lateral etching. Silicon systems in which n-doped silicon is removed and p⁺-doped silicon is retained have been used successfully. The most commonly used material system consists of silicon dioxide as a sacrificial layer with single crystal silicon and deposited polycrystalline silicon as the construction material. Actuators are devices which interfere with their environment. They fundamentally use energy storing volumes and therefore are 3-dimensional devices. Construction techniques must recognize this and are evaluated by computing the output force per unit chip area. Deep X-ray lithography, the LIGA process, has many of the required attributes for actuator construction. This process can be further extended by combining it with surface micromachining which leads to assembled structures such as fully integrated magnetic micromotors and linear motors. These structures can be fabricated on most planar substrates