Microtechnology/Materials

Materials Overview thumb|400px| Overview of the electronic structure of the different fundamental classes of materials. Atoms have discrete energy levels for each electronic state. Electronic transitions by eg. optical excitation can change the state of the atom. Molecules can also have discrete energy levels, but the more complex structure also gives a much more complex diagram of electronic states. In addition, the molecules can rotate and vibrate which modulates the observed energy levels. Insulators can be seen as a condensed phase of molecules with little electronic connection between neighboring molecules for conducting a current. Only when excitation is made with an energy above the several eV bandgap will conduction be possible. Semiconductors have a more narrow bandgap and even at room temperature a few conduction electrons will be excited into the conductance band. Doped Semiconductors have higher electrical conductance because added dopants provide conduction electrons. Metals can be considered as ionized metal atoms in a sea of free electrons, giving a high conductivity and high reflectivity of light (as long as it is not too high in frequency) Resources with overviews of materials and their most prominent uses: Semiconductor materials Ioffe NSM data archive overview of microfabrication materials overview of microfabrication materials Semiconductor materials polymers Overview table of microfabrication materials + Microfabrication Materials Overview TableMaterialTypical useDensity [g/cm3]Atm. Mass[g/mol]Youngs Modulus[GPa]Shear modulus [GPa]El. ConductivityTherm. Cond.[W·m−1·K−1]Melting point[K]NotesAluminiumLeads2.7026.98702626.50 nΩ·m237933.47 K (660.32 °C)Add notesGallium ArsenideLight emitter5.3176144.645 youngsbulkel.therm.1238°C (1511 K)Bandgap 1.424 eVGallium NitrideBlue Light emitter6.1 83.7297youngsbulkel.therm. K ( °C)Add notesPolysiliconsolar cellsdenamuyoungsbulkel.therm. K ( °C)highly dependent on doping and annealing. Se detailed table in the silicon sectionSiliconWafers, semiconductor2.3328.0855(3) 47bulkel.149 1687 K (1414 °C)highly dependent on doping. Se detailed table in the silicon sectionSilicon dioxide, silicainsulator, light waveguidedenamuyoungsbulkel.therm. K ( °C)Add notesSilicon nitrideinsulatordenamuyoungsbulkel.therm. K ( °C)Add notesGoldCoating of leads19.3196.9665697822022.14 nΩ·m318 1337.33 K (1064.18 °C)Add notesNickelMEMS, leadsdenamuyoungsbulkel.therm. K ( °C)Add notesPlatinumContact padsdenamuyoungsbulkel.therm. K ( °C)Add notesPMMA1.1950.000-950.000youngsbulkel.therm. 378 K (105°C) glass trans.Refractive index 1.492 SU8 polymerdenamuyoungsbulkel.therm. K ( °C)Add notesTungstendenamuyoungsbulkel.therm. K ( °C)Add notes This table should be merged with the above... + Metal Material Properties MechanicalThermalElectrical Yield Str.Youngs.Pois.DensityTh. Cond.Th. Exp.MeltingEl. cond.αHighest ZMaterialGPaGPa?kg/m³(W/cmK)(ppm/K)KΩmpromille/KMetals34Al0.17700.3426982.362366026.5*10??4.355Au?78-800.44-0.25192813.1214106423-22.1*10??3.766Cr???7194??1860?55Ti0.231160.3245080.28.51670420*10??3.880Pt0.121680.38214500.738.917720.0981?3.978W0.124110.28192541.84.533870.0489?4.865Ag??????96015.9*10??56Fe12.61960.2978730.80311.7-12154089E6.6Semimetals12Graphite???2266??37007-60E-0.4Semiconductors25Si intrinsic7190?23291.572.3314102.5*10³25poly Si?150-1700.3-0.06623200.5-0.342.6?2200025SiC21700?32003.53.3??45InP?7.1E11 dyn cm-2?48100.68 W cm-1 °C-14.60·10-6 °C-11060?Insulators12Diamond531035?3500201?2.734Al2O315.4530?40000.55.4??25SiO2 (bulk)8.473?25-21500.0140.55?E-12 Units 1 g/cm3 = 1 kg/L = 1000 kg/m3 g/mol = amu = Da Applications and Uses Microprocessors Transistors Lab-on-a-chip MEMS Product Life-Cycles Cheap and disposable point-of-care microfluidic chips require very different materials compared to high performance microprocessors. Environmental Considerations The environmental footprint of microfabriaction is not discussed very often. If anyone has knowledge about this I hope they will contribute!! Wafers and Substrates Overview of wafer types, flats, cleaving planes etc. References See also notes on editing this book about how to add references Microtechnology/About#How to Contribute.