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Reaction Engineering: Chemical Vapor Deposition CVD. Quak Foo Lee Department of Chemical and Biological Engineering The University of British Columbia 2003. What is CVD?. Thin film formation from vapor phase reactants. Deposited films range from metals to semiconductors to insulators.

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Reaction Engineering: Chemical Vapor Deposition CVD

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Reaction Engineering:Chemical Vapor DepositionCVD

Quak Foo Lee

Department of Chemical and Biological EngineeringThe University of British Columbia

2003


What is CVD?

  • Thin film formation from vapor phase reactants. Deposited films range from metals to semiconductors to insulators.

  • 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.

  • All CVD involves using an energy source to break reactant gases into reactive species for deposition.


Applications of CVD

  • Thin films for electronic and optical devices

  • Protective and decorative coatings

  • Particle production

  • Microelectronic chips

  • Optoelectronics

  • Silicon technology (the largest application)  semiconductor


Deposition Sequences

  • 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…)

  • 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

Nucleation and Island Growth

Step Growth

Adsorption of Film Precursor


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

  • 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

  • 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


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