Vibration analysis of micromechanical elements

The development of solid-state sensors and actuators during the last decade is reviewed, with emphasis on solid-state physical transducers for the measurement or control of the physical parameters in biomedical instrumentation systems. The principles and performance of electrodes, sensors for temperature, position, motion, pressure, fluid flow, and humidity, as well as actuators, are briefly discussed. Selective references on physical sensors and actuators are listed.

Solid-State Physical Transducers for Biomedical Research

Results are presented for deep implantation of nitrogen into n‐type GaAs. The main purpose of these investigations is to clarify whether deep implantation can be a suitable process to create buried, selectively etchable layers for the fabrication of micromechanical structures in GaAs. The implanted layers have been characterized by x‐ray photoelectron spectroscopy (XPS) combined with sputter profiling, electrical measurements using test Schottky diodes, and selected etching techniques. XPS depth profiling shows the formation of a GaAs1−xNy layer with y<x that can be etched with high selectivity with respect to the GaAs using alkaline agents. The degree of radiation damage introduced during implantation is determined by planar test diodes located at different depth levels in the implanted structure. It can be shown that implantation damage recovers to a certain extent after annealing at a temperature of about 750 °C although the optimum annealing conditions have not yet been found.

Deep implantation of nitrogen into GaAs for selective three‐dimensional microstructuring

Two separate schemes for bulk micromachining are presented together with experimental results on microfabricated cantilever beam structures indicating that conventional lithography and wet etching techniques can be used to produce geometrically well-defined, high-strength GaAs elements (fracture limits >

Bulk and surface micromachining of GaAs structures

Micromechanical structures on GaAs are fabricated by making use of the different chemical properties of heterostructures, epitaxially grown on GaAs. One of the most advanced heterosystems on GaAs substrates is the AlGaAs/GaAs system. Due to the large technological relevance of this system a number of wet chemical etchants exist that are capable to either etch GaAs selectively to AlGaAs or vice versa. This is the prerequisite for a large number of different types of integrated sensors making use of micromechanical elements such as membranes, cantilevers etc. In this paper the realization of an anemometer integrated on GaAs is presented.

E. Gustafsson

Papers

Batch fabrication of micromechanical elements in GaAs–AlxGa1–xAs