Editing MEMS (section)

== Materials ==
[[File:BioMEMS with X-shpaed cantilever.png|thumb|Electron microscope pictures of X-shaped TiN beam above ground plate (height difference 2.5&nbsp;μm). Due to the clip in the middle, an increasing reset force develops when the beam bends downwards. The right figure shows a magnification of the clip.<ref name=JAP2013>{{cite journal | display-authors = 3 | author1 = M. Birkholz | author2 =  K.-E. Ehwald | author3 =  T. Basmer | author4 =  P. Kulse | author5=  C. Reich | author6 =  J. Drews | author7 =  D. Genschow | author8 =  U. Haak | author9 =  S. Marschmeyer | author10 =  E. Matthus | author11 =  K. Schulz | author12 =  D. Wolansky | author13 =  W. Winkler | author14 =  T. Guschauski | author15 =  R. Ehwald | title = Sensing glucose concentrations at GHz frequencies with a fully embedded Biomicro-electromechanical system (BioMEMS) | journal = J. Appl. Phys. | volume = 113 | issue = 24 | pages = 244904–244904–8 | year = 2013 | doi = 10.1063/1.4811351| pmid = 25332510 | pmc = 3977869 | bibcode = 2013JAP...113x4904B }}</ref>]]

The fabrication of MEMS evolved from the process technology in [[semiconductor device fabrication]], i.e. the basic techniques are [[Deposition (chemistry)|deposition]] of material layers, patterning by [[photolithography]] and etching to produce the required shapes.<ref>{{cite book|title=MEMS Materials and Processes Handbook|vauthors=Ghodssi R, Lin P|publisher= Springer |year=2011|isbn=978-0-387-47316-1 }}</ref>

; Silicon: Silicon is the material used to create most [[integrated circuit]]s used in consumer electronics in the modern industry. The [[economies of scale]], ready availability of inexpensive high-quality materials, and ability to incorporate electronic functionality make silicon attractive for a wide variety of MEMS applications. Silicon also has significant advantages engendered through its material properties. In single crystal form, silicon is an almost perfect [[Hooke's law|Hookean]] material, meaning that when it is flexed there is virtually no [[hysteresis]] and hence almost no energy dissipation. As well as making for highly repeatable motion, this also makes silicon very reliable as it suffers very little [[Fatigue (material)|fatigue]] and can have service lifetimes in the range of [[1000000000 (number)|billions]] to [[1000000000000 (number)|trillions]] of cycles without breaking. [[Semiconductor nanostructures]] based on silicon are gaining increasing importance in the field of microelectronics and MEMS in particular. [[Silicon nanowire]]s, fabricated through the [[thermal oxidation]] of silicon, are of further interest in [[electrochemistry|electrochemical]] conversion and storage, including nanowire batteries and [[photovoltaic]] systems.
; Polymers: Even though the [[electronics industry]] provides an economy of scale for the silicon industry, crystalline silicon is still a complex and relatively expensive material to produce. Polymers on the other hand can be produced in huge volumes, with a great variety of material characteristics. MEMS devices can be made from polymers by processes such as [[injection molding]], [[Embossing (manufacturing)|embossing]] or [[stereolithography]] and are especially well suited to [[microfluidic]] applications such as disposable blood testing cartridges.
; Metals: Metals can also be used to create MEMS elements. While metals do not have some of the advantages displayed by silicon in terms of mechanical properties, when used within their limitations, metals can exhibit very high degrees of reliability. Metals can be deposited by electroplating, evaporation, and sputtering processes. Commonly used metals include gold, nickel, aluminium, copper, chromium, titanium, tungsten, platinum, and silver.
; Ceramics: The [[nitride]]s of silicon, aluminium and titanium as well as [[silicon carbide]] and other [[ceramic]]s are increasingly applied in MEMS fabrication due to advantageous combinations of material properties. [[aluminium nitride|AlN]] crystallizes in the [[wurtzite structure]] and thus shows [[pyroelectricity|pyroelectric]] and [[piezoelectricity|piezoelectric]] properties enabling sensors, for instance, with sensitivity to normal and shear forces.<ref name="PC2009">{{cite journal|vauthors=Polster T, Hoffmann M|date=2009|title=Aluminium nitride based 3D, piezoelectric, tactile sensors|journal=Procedia Chemistry|volume=1|issue=1|pages=144–7|doi=10.1016/j.proche.2009.07.036|doi-access=free}}</ref> [[titanium nitride|TiN]], on the other hand, exhibits a high [[electrical conductivity]] and large [[elastic modulus]], making it possible to implement electrostatic MEMS actuation schemes with ultrathin beams. Moreover, the high resistance of TiN against biocorrosion qualifies the material for applications in biogenic environments. The figure shows an electron-microscopic picture of a MEMS [[biosensor]] with a 50&nbsp;nm thin bendable TiN beam above a TiN ground plate. Both can be driven as opposite electrodes of a capacitor, since the beam is fixed in electrically isolating side walls. When a fluid is suspended in the cavity its viscosity may be derived from bending the beam by electrical attraction to the ground plate and measuring the bending velocity.<ref name=JAP2013/>