PVD-CVD..............................pdf

VLSI Technology
(EC 325)
Dr. Vivek Garg
Department of Electronics Engineering
S. V. National Institute of Technology (SVNIT)
Surat
email: vivekg@eced.svnit.ac.in; vivekgarg0101@gmail.com

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Course Text and Materials
Additional:
• Relevant Journals and Conferences
• Materials and Sources shared in the lectures

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Physical/Chemical Vapor Deposition
PVD CVD

Chemical Vapor Deposition

Physical Vapor Deposition
Physical vapor deposition (PVD) refers to a family of processes in
which a material is converted to its vapor phase in a vacuum
chamber and condensed onto a substrate surface as a thin film.
PVD can be used to produce coatings of a wide variety of materials:
• metals alloys
• ceramics glasses
• semiconductors polymers

 All PVD processes consist of the
following steps:
• synthesis of coating vapor,
• vapor transport to the substrate,
• condensation of vapors onto the
substrate surface to form a thin
film.
 These steps are carried out inside a
vacuum chamber, so evacuation of
the chamber always precedes the
PVD process.

Thin Film Deposition

 The two most common PVD processes are:
• Evaporation: Thermal, e-beam
• Sputtering
 For evaporation, the background pressure in the vacuum
chamber is typically ~10-6 Torr (~10-4 Pa) or lower.
 For sputtering, the background pressure in the vacuum
chamber is typically 10-3 to 10-2 Torr (~1 Pa).

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Evaporation
 In order to evaporate a material, it must be heated to a
temperature at which its vapor pressure is 10-3 Torr or higher.
 There are two common ways to heat the source material:
• resistive heating
• electron-beam heating.
 Resistive heating uses electric current flow through a tungsten
filament to heat the source material.
 The source material can be placed directly on the tungsten
filament, or it can be put in a crucible that is heated by the
filament.

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Thermal Evaporation

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Thermal Evaporation

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 In electron-beam (e-beam) evaporation
systems, a high intensity beam of
electrons, with energy up to 15 keV, is
focused on the source material.
 Electron bombardment heats the source
material to the temperature required for
evaporation.
 Heating can be restricted to the source
material itself .  The surroundings stay
cool.
 Because pressure is so low in the vacuum
chamber, in evaporation the source
material travels in a straight line from the
source to the substrate  shadowing

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Sputtering

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Sputtering
• Sputtering takes place after kinetic energy
of the bombarding particles are much high
compared to the thermal energies.
• It results in more pure and precise thin film
deposition compared to evaporation.
• The number of atoms sputtered off from the
target is called the sputter yield.
• Sputter yield can be controlled by:
a) energy and incidence angle of ions
b) relative mass of the ions
c) surface binding energy of the target atom
• There are different variants of sputtering
systems based on supply, sputtering
mechanism.

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Sputtering
Types of sputtering
a) DC/RF Diode Sputtering
b) DC/RF Magnetron Sputtering
c) Ion beam Sputtering
d) Pulsed DC sputtering
e) High Power Impulse Magnetron Sputtering (HIPIMS)
f) Co Sputtering

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DC Diode Sputtering
• Chamber pressure is usually from 1 to 100 mTorr
• DC power is usually preferred for electrically
conductive target materials as it’s effective and
economical.
• Target is held at negative potential and substrate/body
at positive potential.
• Positive ions bombard the target and eject neutral
atoms.
• In DC diode sputtering electrons are accelerated
away from the target and ionize the process gases to
sustain the discharge.
• To maintain the discharge optimum gas density is
required.
• If the gas density is too low electrons will hit the
anode without ionizing the Ar atoms.
Sputtering

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DC Diode Sputtering
• If the gas density is too high, electrons will not gain
enough energy to ionize the Ar atoms.
• Ar ions hitting the cathode results in secondary
electrons emission.
• This interaction results in the heating of the targets,
therefore cooling arrangement is required.
• Disadvantages:
Low deposition rates
High discharge voltages
Low plasma density
High gas density
• Triode Sputtering
Sputtering

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RF Sputtering
• Initially, developed to coat insulating layers.
• The power source is AC (13.6 MHz).
• RF peak to peak voltage is 1kV, electron
densities are 109 to 1011 cm-3, chamber pressure
0.5 to 10 mTorr.
• RF sputtering has a wider range of applications
and is suitable for all the materials for conductive
• The deposition rate is lower compare with DC
sputtering.
• It is used for smaller substrate sizes due to the
high cost.
• Higher cost is because of the supplies and
matching components.
Sputtering

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RF Sputtering
• The RF sputtering involves two processes. In
the first cycle, the target material is
negatively charged.
• This results in atoms’ polarization, and the
sputtering gas atoms are attracted to the
source, where they knock out source atoms.
• Due to polarization, the source atoms and
ionized gas ions remain on the target
surface.
• In the second cycle, the target is positively
charged. Due to reverse polarization, this
causes the ejection of gas ions and source
atoms. These ions and atoms accelerated
toward the substrate to form deposition.
Sputtering
Disadvantages:
a) low deposition rates
b) High cost
c) Non-uniform plasma

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DC/RF Magnetron Sputtering
• Magnetic confinement of electrons to enhance
the plasma density near the target.
• Magnetic field is added to the cathode provides
E x B drift path for the electrons.
• Proper alignment of the magnetic field results in
the confinement of the electrons near the surface
of the target.
• The secondary electrons leaving the surface with
speed v, experience the Lorentz force and begin
to move in the circular path with radius r.
• It significantly increases the ion density.
• Low pressure requirements.
Sputtering

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Ion Beam Sputtering

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 Deposition Source
Assist Source
Deposition Source

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 Deposition Source
Ion Source

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 Targets
 Vacuum Pump
 Sample Holder
 Robotic Arm

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Pressure Gauge Turbo Pump

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Mechanical Pumps
Positive Displacement
Pressure Range: 1- 0.1 Torr

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Turbo Molecular Pumps
Momentum Transfer
Pressure Range: 10-6 to 10-7 Torr

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Cryogenic Pumps
Entrapment or condensation
Pressure Range: 10-8 to 10-9 Torr

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Reactive Sputtering
Sputtering
• It utilizes oxygen or nitrogen separately or
along with the Ar gas.
• Ionized non-inert gas can react chemically with
the target material vapor and produce the
compound.
• The reactive gas is chemically consumed during
the process.
• An arrangement is required for the continuous
desired compound formation.
• One such arrangement is called gas ring.
• There is the possibility of the creation of the
compound over the surface of the target. This is
called as poisoning of the substrate.
• It results in the charging effects.
• Pulsed DC sputtering is developed to tackle this
issue.

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Pulsed DC Sputtering
Sputtering
• It is used to coat conducting as well as insulating
materials.
• It is used with the reactive configuration.
• It is widely used to grow Alumina, Titania, and
Silica.
• A pulsed DC electrical current in the few
hundred voltage range applied to the target.
• During the On time of the pulse sputtering will
takes place.
• During off voltage is turned off for one tenth of
the on time duration. It will cleanse the surface
for next on time duration.
• Two configurations: Micro Arc, Hard Arc
• Advantages:
Optimized pulse freq. and duty cycles
Higher deposition rates.

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High Power Impulse Magnetron Sputtering (HiPIMS)
Sputtering
• Pulsed source along with Magnetron source.
• High voltage pulse with the 100us length.
• Duty cycle less than 10 percent.
• Large amount of the material will sputtered
out without heating the target.
• It creates very dense plasma.
• As the off time is quite large compared to on
time gives ample amount of time for the
cooling of target.
• Provides high performance dense coatings,
good adhesion and smooth morphology.
• Traditional system can be converted to the
HIPIMIS by adding the pulsed source in the
existing system.
• Disadvantage:
high power requirements

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High Power Impulse Magnetron Sputtering (HiPIMS)
Sputtering

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Co-evaporation/Co-sputtering

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• Vapor deposition process are used to deposit thin layers of films
• Highly sensitive to atmospheric conditions and contaminants.
• Must be carried out in vacuum chambers at low pressure.
• It can be used to improve the substrate material or to grow a layer
of composite structure.
• Tuning of the material properties: temperature, gas mixture,
pressure, substrate material, etc.

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Types of CVD:
 Pressure
Atmospheric Pressure (APCVD)
Low Pressure (LPCVD)
Ultrahigh Vacuum (UHVCVD)
 Stimulus
Plasma Enhanced (PECVD)
Photo Initiated (PICVD)
Rapid Thermal (RTCVD)
Hot Filament (HFCVD)
Microwave Plasma (MPCVD)
 Source
Atomic Layer Deposition (ALD)
Metal Organic (MOCVD)

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CVD Reactors: Horizontal

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CVD Reactors: Barrel

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CVD Reactors: Rotating Disk Vertical CVD Reactor

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CVD Reactors: Pancake or Planetary

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Thermal CVD

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Thermal CVD

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Thermal CVD

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Thermal CVD

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CVD: Pressure

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LP-CVD

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LP-CVD

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LP-CVD

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Atomic Layer Deposition
Precursors are sequentially introduced in the chamber to grow one atomic layer at a time.
Cycle
1
Cycle
2

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• Low temperature requirement
• Precise Thickness Formation
Disadvantages
• Chemical Limitations
• Slow Process
Advantages

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Plasma Enhanced CVD (PECVD)
• Utilizes plasma energy for the deposition
process
• Operates at lower temperature
• Plasma is the stimulus for the deposition
process.
• Primarily used to deposit Dielectrics:
Oxides, Nitrides.

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Plasma Enhanced CVD

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Microwave Plasma Enhanced CVD
• Microwaves are used to create
dense plasma.
• Substrate bias is applied.
• Widely used to create diamond
coatings.

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Photo Initiated CVD
• More efficient energy consumption
• Can be operated at normal condition
• Better polymer growth

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Metal Organic- CVD or Vapor Phase Epitaxy
Epitaxy Types: a) Homo Epitaxy
b) Hetero Epitaxy

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Example Reaction:
Ga(CH3)3 + AsH3  3CH4 + GaAs
Trimethal
Gallium Gas
Arsene
Gas
Methane
Gas
on the
substrate
• The reaction occurs in a sealed container (reactor)
NOTE!! Arsene gas is highly toxic & highly flammable!
Trimethal gallium gas is highly toxic!!
Methane gas is highly explosive!

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Metal Organic CVD

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Oxides and Metals in MOS Devices
Silicon Dioxide
Deposition Processes
• LP CVD
• RF Sputtering
• Oxidation

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Poly Silicon
• LP CVD
• RF Sputtering

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Silicon Nitride
• PE CVD
• MOCVD

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High K Dielectric

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High K Dielectric
• ALD
• PE CVD
• MOCVD
• Pulsed Laser Deposition
• RF Sputtering
• E-Beam Evaporation

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High K Dielectric

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High K Dielectric

PVD-CVD..............................pdf

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