外延生长讲义

KINETICS (Chemical Control, Surface Limited) Rate increases exponentially with increasing temperature Independent
Ch.14 : Epitaxial Growth
VT 2004/5; Micro and NanoProcessing Technologies
Ch.14 : Epitaxial Growth
VT 2004/5; Micro and NanoProcessing Technologies
Ch.14 : Epitaxial Growth
VT 2004/5; Micro and NanoProcessing Technologies
Ch.14 : Epitaxial Growth
Four main CVD Reactions
• Pyrolysis: heat driven break down • Reduction: usually react with Hydrogen • Oxidation: react with oxygen to form oxides • Nitradation: create nitrides with nitrogen compounds
TYPE OF CONTROL MASS TRANSFER TYPE 1 Inpu Rate Limited Equilibrium Process MASS TRANSFER TYPE 2 Diffusion Controlled Mass Transfer Limited
RATE LIMITING STEPS Input rate of reactants to epitaxial growth region
Transfer of reactants or products between main gas streaqm and sbstrate surfah as diffusion or convection Adsorption of reactants Desorption of products Surface reaction Site incorporation
Kinetics Control Surface Limited Chemically Controlled
After D.W. Shaw, Mechanisms in Vapour Phase epitaxy of Semiconducors, Crystal Growth Vol1, Ed. C.H.L. Goodman, Plenum press, NY, 174 VT 2004/5; Micro and NanoProcessing Technologies
VT 2004/5; Micro and NanoProcessing Technologies
Ch.14 : Epitaxial Growth
Epitaxy techniques - the spectrum of options
Chemical Vapour Deposition (CVD) • Atmospheric pressure – APCVD • Low pressure CVD – LPCVD • Plasma enhanced CVD – PECVD Vapor phase Epitaxy (hydrodynamic flow) • Hydride • Chlorine Metallo-Organic CVD (MOCVD) Liquid Phase Epitaxy Molecular Beam Epitaxy (MBE) (ballistic flow) • Solid source • Gas source • Chemical beam • Organo-metallic source
SURFACE DIFFUSION SURFACE REACTION SUBSTRATE
Sequence of events in thermal CVD or VPE reactor
VT 2004/5; Micro and NanoProcessing Technologies
Ch.14 : Epitaxial Growth
VT 2004/5; Micro and NanoProcessing Technologies
Ch.14 : Epitaxial Growth
VT 2004/5; Micro and NanoProcessing Technologies
Ch.14 : Epitaxial Growth
VT 2004/5; Micro and NanoProcessing Technologies
VT 2004/5; Micro and NanoProcessing Technologies
Ch.14 : Epitaxial Growth
CVD Applications
• Thin insulating films oxides, silicon nitride • Polysilicon (gates/conductors) • Epitaxial silicon (single crystal on wafer) • Silicide materials • III-V compounds
外延生长讲义 vt2004/5; micro nano-processing technologies ch.14 epitaxialgrowth micro nano-processing technologies epitaxial growth mahdad sadeghi mahdad.sadeghi@mc2.chalmers.se 031-7721902 vt 2004/5; micro nano-processing technologies ch.14 epitaxialgrowth control thicknesscomposition throughput (growth rate) uniformitiy doping concentration junctions (x-tal) quality, defects reproducibility growthtemperature gas flow rate- flowmeter source temperature flux cutoff valves/shuttersx-tal orientation geometry/ environment source/gas purity precleaning epitaxy well-controlledphase transition which leads (singlecrystalline) solid. vt 2004/5; micro nano-processing technologies ch.14 epitaxialgrowth epitaxy techniques optionschemical vapour deposition (cvd) atmosphericpressure lowpressure cvd plasmaenhanced cvd pecvdvapor phase epitaxy (hydrodynamic flow) chlorinemetallo-organic cvd (mocvd) liquid phase epitaxy molecular beam epitaxy (mbe) (ballistic flow) solidsource gassource chemicalbeam organo-metallicsource vt 2004/5
VT 2004/5; Micro and NanoProcessing Technologies
Ch.14 : Epitaxial Growth
Major CVD Processes
• Reactants diffuse to surface • Chemical reaction(s) at surface • Film reformed at surface • Products desorbed and diffuse from surface
VT 2004/5; Micro and NanoProcessing Technologies
Ch.14 : Epitaxial Growth
CVD Important film parameters • Stoichiometery: exact composition of film • Physical parameters: hardness, optical density • Electrical parameters: dielectric constant, breakdown voltage • Purity of film: lack of contamination • Thickness and uniformity • Conformality and step coverage • pin hole and particle free • Adhesion
MASS TRANSPORT TYPE 2 (Diffusion control) Slight dependence due to concentration gradient changes Rate increases with flow rate increase Rate increases with increasing veocity Independent Dependent Dependent on apparent or geometrical surface area
Epitaxy techniques - the spectrum of options
Chemical Vapour Deposition (CVD) • Atmospheric pressure – APCVD • Low pressure CVD – LPCVD • Plasma enhanced CVD – PECVD Vapor phase Epitaxy (hydrodynamic flow) • Hydride • Chlorine Metallo-Organic CVD (MOCVD) Liquid Phase Epitaxy Molecular Beam Epitaxy (MBE) (ballistic flow) • Solid source • Gas source • Chemical beam • Organo-metallic source
VT 2004/5; Micro and NanoProcessing Technologies
Ch.14 : Epitaxial Growth
LPE GaAs/AlGaAs InP+related 750825oC 600660oC
VPE 500650oC
MBE 600700oC 480560oC
Epitaxy is a well-controlled phase transition which leads to a (single crystalline) solid.
VT 2004/5; Micro and NanoProcessing Technologies
Ch.14 : Epitaxial Growth
Micro and Nano- Processing Technologies
EPITAXIAL GROWTH
Mahdad Sadeghi
mahdad.sadeghi@mc2.chalmers.se 031-7721902
VT 2004/5; Micro and NanoProcessing Technologies
CARRIER GAS + REACTANTS CARRIER GAS + UNREACTED REACTANTS + PRODUCTS
TRANSFER OF REACTANTS TO SURFACE
ADSORPTION OF REACTANTS
DESORPTION OF PRODUCTS
TRANSFER OF PRODUCTS TO MAIN FLOW
Ch.14 : Epitaxial Growth
EXPERIMENTAL PARAMETERS Growth temperature
MASS TRANSPORT TYPE 1 (Eqm. process) Dependence predicted by thermodynamics Rate increases with total flow rate due to increase in total mass input rate Independent Independent Independent Total amount deposited independent of surface area
VT 2004/5; Micro and NanoProcessing Technologies
Ch.14 : Epitaxial Growth
Chemical Vapour Deposition (CVD)
Chemical reactions (Gas phase reactions) in a reactor to create a thin film layer at surface
Ch.14 : Epitaxial Growth
CONTROL
BY Growth temperature Gas flow rate- Flowmeter Source temperature Flux cutoff – valves/shutters X-tal orientation Geometry/ Environment Source/Gas purity Precleaning OF Thickness Composition Throughput (growth rate) Uniformitiy Doping concentration Junctions (X-tal) Quality, defects Reproducibility