Microtechnology/Materials

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Materials[edit]

Overview[edit]

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:

Overview table of microfabrication materials[edit]

Microfabrication Materials Overview Table
Material Typical use Density [g/cm3] Atm. Mass[g/mol] Youngs Modulus[GPa] Shear modulus [GPa] El. Conductivity Therm. Cond.[W·m−1·K−1] Melting point[K] Notes
Aluminium Leads 2.70 26.98 70 26 26.50 nΩ·m 237 933.47 K (660.32 °C) Add notes
Gallium Arsenide Light emitter 5.3176 144.645 youngs bulk el. therm. 1238°C (1511 K) Bandgap 1.424 eV
Gallium Nitride Blue Light emitter 6.1 83.7297 youngs bulk el. therm. K ( °C) Add notes
Polysilicon solar cells den amu youngs bulk el. therm. K ( °C) highly dependent on doping and annealing. Se detailed table in the silicon section
Silicon Wafers, semiconductor 2.33 28.0855(3) 47 bulk el. 149 1687 K (1414 °C) highly dependent on doping. Se detailed table in the silicon section
Silicon dioxide, silica insulator, light waveguide den amu youngs bulk el. therm. K ( °C) Add notes
Silicon nitride insulator den amu youngs bulk el. therm. K ( °C) Add notes
Gold Coating of leads 19.3 196.966569 78 220 22.14 nΩ·m 318 1337.33 K (1064.18 °C) Add notes
Nickel MEMS, leads den amu youngs bulk el. therm. K ( °C) Add notes
Platinum Contact pads den amu youngs bulk el. therm. K ( °C) Add notes
PMMA 1.19 50.000-950.000 youngs bulk el. therm. 378 K (105°C) glass trans. Refractive index 1.492
SU8 polymer den amu youngs bulk el. therm. K ( °C) Add notes
Tungsten den amu youngs bulk el. therm. K ( °C) Add notes

This table should be merged with the above...

Metal Material Properties
Mechanical Thermal Electrical
Yield Str. Youngs. Pois. Density Th. Cond. Th. Exp. Melting El. cond. α
Highest Z Material GPa GPa ? kg/m³ (W/cmK) (ppm/K) K Ωm promille/K
Metals
34 Al 0.17 70 0.34 2698 2.36 23 660 26.5*10?? 4.3
55 Au ? 78-80 0.44-0.25 19281 3.12 14 1064 23-22.1*10?? 3.7
66 Cr ? ? ? 7194 ? ? 1860 ?
55 Ti 0.23 116 0.32 4508 0.2 8.5 1670 420*10?? 3.8
80 Pt 0.12 168 0.38 21450 0.73 8.9 1772 0.0981? 3.9
78 W 0.12 411 0.28 19254 1.8 4.5 3387 0.0489? 4.8
65 Ag ? ? ? ? ? ? 960 15.9*10??
56 Fe 12.6 196 0.29 7873 0.803 11.7-12 1540 89E 6.6
Semimetals
12 Graphite ? ? ? 2266 ? ? 3700 7-60E -0.4
Semiconductors
25 Si intrinsic 7 190 ? 2329 1.57 2.33 1410 2.5*10³
25 poly Si ? 150-170 0.3-0.066 2320 0.5-0.34 2.6 ? 22000
25 SiC 21 700 ? 3200 3.5 3.3 ? ?
45 InP ? 7.1E11 dyn cm-2 ? 4810 0.68 W cm-1 °C-1 4.60·10-6 °C-1 1060 ?
Insulators
12 Diamond 53 1035 ? 3500 20 1 ? 2.7
34 Al2O3 15.4 530 ? 4000 0.5 5.4 ? ?
25 SiO2 (bulk) 8.4 73 ? 25-2150 0.014 0.55 ? E-12

Units[edit]

  • 1 g/cm3 = 1 kg/L = 1000 kg/m3
  • g/mol = amu = Da

Applications and Uses[edit]

  • Microprocessors
  • Transistors
  • Lab-on-a-chip
  • MEMS

Product Life-Cycles[edit]

Cheap and disposable point-of-care microfluidic chips require very different materials compared to high performance microprocessors.

Environmental Considerations[edit]

The environmental footprint of microfabriaction is not discussed very often. If anyone has knowledge about this I hope they will contribute!!

Wafers and Substrates[edit]

Overview of wafer types, flats, cleaving planes etc.

References[edit]

See also notes on editing this book about how to add references Microtechnology/About#How to Contribute.