Transcript Reaction Engineering: Chemical Vapor Deposition

Reaction Engineering:
Chemical Vapor Deposition
CVD
Quak Foo Lee
Department of Chemical and Biological Engineering
The University of British Columbia
2003
What is CVD?
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Thin film formation from vapor phase reactants.
Deposited films range from metals to
semiconductors to insulators.
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An essential process step in the manufacturing
of microelectronic devices. High temperatures
and low pressures are the most common
process conditions, but are not necessary.
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All CVD involves using an energy source to
break reactant gases into reactive species for
deposition.
Applications of CVD
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Thin films for electronic and optical devices
Protective and decorative coatings
Particle production
Microelectronic chips
Optoelectronics
Silicon technology (the largest application) 
semiconductor
Deposition Sequences
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Mass transport in the bulk gas flow region from
the reactor inlet to the deposition zone
Gas phase reactions leading to the formation
of film precursors and byproducts
Mass transport of film precursors to the growth
surface
Adsorption of film precursors to the growth
surface
Deposition Sequences (cont…)
5.
6.
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Surface diffusion of film precursors to growth
sites
Incorporation of film constituents into the
growing film
Desorption of byproducts of the surface
reactions
Mass transport of byproducts in the bulk gas
flow region away from the deposition zone
towards the reactor exit
Transport and Reaction Processes
underlying CVD
Main Gas Flow Regime
Gas Phase Reactions
Desorption of
Volatile Surface
Reaction Products
Redesorption of
Film Precursor
Transport to Surface
Surface Diffusion
Adsorption of Film Precursor
Nucleation
and Island
Growth
Step Growth
Rule I
CVD reactors must be designed and operated in
such a manner that film thickness, crystal structure,
surface morphology, and interface composition
changes can be accurately controlled.
Typical CVD Reactors
 Horizontal
reactor
 Vertical reactor
 Barrel reactor
 Pancake reactor
 Multiple-wafer-in-tube LPCVD reactor
Thermal Diffusion
Examples of CVD
 Metals/Conductors
– W, Al, Cu, doped
poly-Si
 Insulators (dielectries) – BPSG, Si3N4,
SiO2
 Semiconductors – Si, Ge, InP, GaAsP
 Silicides – TiSi2, WSi2
 Barriers – TiN, TaN
Types of CVD Processes
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Atmospheric Pressure Chemical Vapor Deposition
(APCVD)
Low Pressure Chemical Vapor Deposition (LPCVD)
Metal-Organic Chemical Vapor Deposition (MOCVD)
Plasma Assisted Chemical Vapor Deposition (PAVCD) or
plasma Enhanced Chemical Vapor Deposition (PECVD)
Laser Chemical Vapor Deposition (LCVD)
Photochemical Vapor Deposition (PCVD)
Chemical Vapor Infiltration (CVI)
Chemical Beam Epitaxy (CBE)
Advantages of CVD
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Versatile – can deposit any element or compound
High Purity – typically 99.99 to 99.999%
High Density – nearly 100% of theoretical
Material Formation well below the melting point
Coatings Deposited by CVD are conformal and
near net shape
Economical in production, since many parts can be
coated at the same time