Institute of Solid State Physics. Technische Universität Graz. Deposition. Franssila: Chapters 5 & 6. Peter Hadley

Transcription

1 Technische Universität Graz Institute of Solid State Physics Deposition Franssila: Chapters 5 & 6 Peter Hadley

2 Silicon wafers Total Thickness Variation: a good 8" Prime wafer would be < 15 m Site flatness measurement: < 0.3 m flatness across each mm site. Bow: < 30 m concave or convex Warp: < 20 m (like a potato chip) Resistivity variation: 2%-15%

3 Physical Vapor Deposition (PVD) Thermal evaporation E-beam evaporation Knudsen cell, Effusion cell Molecular Beam Epitaxy (MBE) Sputtering Laser ablation

4 Thermal evaporation Coil Boat Knudsen cell Covers substrate features like snow. Polycrystalline films.

5 Titanium Sublimation Pump (TSP) This is a kind of getter pump

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7 Electron-beam evaporation

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9 Electron-beam evaporation Electron accelerating voltages: 3 kv 40 kv kw power High vacuum x-rays and secondary electrons are emitted deposition rate from 0.1 μm / min to 100 μm / min Alloys can be difficult because the components evaporate at different rates Co-evaporation is sometimes used for alloys line-of-sight deposition process Not suitable for large areas or coating complex shapes

10 Molecular Beam Epitaxy (MBE)

11 RHEED (Reflection high-energy electron diffraction)

12 RHEED M. Ohring, The Material Science of Thin Films, Academic Press, 1992.

13 Molecular dynamics Calculate the motions of the atoms at the surface.

14 Growth modes

15 Evaporated atoms or molecules may form layers, needles, or clusters.

16 Fransila Heteroepitaxy

17 Strain induced by lattice mismatch

18 Stoney's formula f Eh s 2 s 6 h (1 ) f s The stress f in the film depends on E s Young's modulus in the substrate v s Poisson's ratio of the substrate h s thickness of the substrate h f thickness of the film curvature Only holds for uniform curvature

19 Sputtering Sputtering can be used to clean a surface and to deposit material. Low-emissivity coatings on double-pane window glass.

20 Sputtering

21 Sputtering Depending of the particle energy and angle, it may be implanted or bounce off. The sputter gas can bounce off the target and get implanted in the film htm

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24 Sputtering You can almost sputter anything Chemical composition of the film is the same as the target High melting point materials can be deposited Better step coverage than evaporation Large areas (2x2 meters) are possible Sputter gases are incorporated in the film

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26 Laser ablation RHEED J. Phys. D: Appl. Phys. 47 (2014)

27 Laser ablation J. Phys. D: Appl. Phys. 47 (2014)

28 Electrochemical Deposition (ECD) Copper

29 Lithography and Galvanic plating (LIGA) Fransila

30 Chemical vapor deposition image from wikipedia Epitaxial silicon CVD SiH 4 (silane) or SiH 2 Cl 2 (dichlorosilane) PH 3 (phosphine) for n-doping or B 2 H 6 (diborane) for p-doping.

31 Si CVD Fransila

32 Epi - layers Chemically purer than substrate Doping controlled independently Commonly used in CMOS and bipolar device technology Epi-wafers can be purchased

33 epitaxial lateral overgrowth (ELO) Defect density can be high where the films meet

34 Tungsten CVD

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36 Through Silicon Vias (TSVs)

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38 PECVD SiO 2 Silicon nitride SiC: Carbon:

39 PECVD Bring substrate to the desired temperature Establish correct gas flow conditions Strike plasma for deposition Turn off plasma, purge with cleaning gasses

40 Elastic constant, hardness, density, optical constant, etc. depend on deposition conditions

41 Atomic Layer Deposition(ALD) AlO x for diffusion barriers OLED displays

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