mcgill nanotools microfabrication processes matthieu nannini manager url :: miam2.physics.mcgill.ca
TRANSCRIPT
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Outline
Microfabrication• Add material• Remove material• Pattern material• To the outside world• Process flow example
Idea to device Conclusion
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Add material: Thermal processes
Atmospheric Chemical Vapour Deposition
Reaction between gases ans substrate at high temperature (900-1100°C)
Precise control of temperature High purity material Si + O2 SiO2 (dry SiO2) Si + H2O SiO2 (wet SiO2)
Available @ McGill: Oxide thermal growth up to 1.5µm
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Add material CVD (Chemical Vapor Deposition)
Low Pressure Chemical Vapour Deposition
Reaction between two gases at high temperature (500-800°C)
Precise control of temperature High purity material 3 SiH2Cl2 + 4 NH3 → Si3N4 + 6 HCl +
6 H2 (silicon nitride) SiH4 → Si + 2H2 (polysilicon)
Available @ McGill: Silicon Nitride LPCVD Amorphous and
polycristalline silicon LPCVD
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Add material: Plasma Enhanced CVD (PECVD)
Plasma Enhanced Chemical Vapour Deposition
Reaction between two gases @ 300-400°C and enhanced by plasma
Allow oxide, nitride or oxynitride to be deposited on metals for insulation or passivation/
High deposition rate: ~1000 A/min Available @ McGill: Silicon Oxide Silicon Nitride Silicon Oxynitride (under
dev.)
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Add material: PVD (Physical Vapor Deposition)
Evaporation• Heat the target material
until it melts and evaporates onto the sample
• Directional coating (shadow effect)
• Low to high etch rates• Stack of material• Materials available: Au,
Ti, Cr, Pd, Al, Ni, Pt …
sample
Add material and pattern at once: lift-off
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samplesample
sample
samplesample
Metal evaporation
Resist
coat
ing
UV pat
tern
ing
develo
pmen
t
Resist dissolution
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Add material: PVD (Physical Vapor Deposition)
Sputtering• Bombard the target with plasma
discharge that extracts atoms from the target onto the sample
• Conformal coating• Conductive and non conductive
material• Reactive sputtering with
additional gas• Stack of material• Co-sputtering alloys• Materials available: Au, Ti, Cr, Al,
AlN, TiN, TiO2, ITO, Cu, Pd, W, Si, SiC…
sample
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Outline
Microfabrication• Add material• Remove material• Pattern material• To the outside world• Process flow example
Idea to device Conclusion
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Remove material: Wet Etch
Wet Etch• Chemical solution• Usually Isotropic (can be
anisotropic in crystals)• Very selective: resist etch
rate vs. material etch rate• High etch rate• Difficult to control precisely• Resolution limitation• Batch processing
Etching
Masking material
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Remove material: Dry Etch
Dry Etch• Gas phase• Sputter + chemical etch• Anisotropic• Less selective• High resolution• Excellent control• Single wafer processing
Gas available @ McGill: Oxides/Nitrides: CF4, CHF3,
O2, Ar Silicon: HBr, Cl2, Ar Metals: HBr, Cl2, Ar, N2, NF3
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Remove silicon: Deep Reactive Ion Etching
DRIE• We need 2 gases, one for etching
and another one to deposit a protective polymer.
• We need to alternate etching and deposition then we pulse the gas injection
• We need energetic ions to remove the polymer on the feature bottom to allow Si etching during SF6 cycle.
available @ McGill: Tegal SDE 110
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Outline
Microfabrication• Add material• Remove material• Pattern material• To the outside world• Process flow example
Idea to device Conclusion
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Pattern material: Photolithography
UV exposition through mask Resolution (~800nm):
• Wavelength (432nm)• mask-substrate distance• resist thickness
To consider• Large exposed area (150mm)• Parallel• Fast• Limited resolution
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Pattern material: Mask design
Designing your mask• Knowing what kind of shapes
you need• How many mask level ?
Alignment needed ?
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Pattern material: Electrolithography
Electron beam direct exposition Principle:
• electron sensitive polymer• Direct beam writing
Resolution: 30nm• E-beam quality (focus,
stigmatism, alignment…)• Stability of stage• Thickness of polymer
To consider• Limited writing areas• Serial writing• slow
E-beam
expose
develop
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Outline
Microfabrication• Add material• Remove material• Pattern material• To the outside world• Process flow example
Idea to device Conclusion
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To the outside world: Dicing
Dicing: • Precision diamond saw to cut out wafer in small dies• Blade thicknesses from 100 to 250µm• Accurate alignment (~ 50µm)