Crystal Growth

Crystal Growth
Arpan Deyasi
Dept of ECE, RCCIIT, Kolkata, India
1/6/2021 Arpan Deyasi, RCCIIT

Fabrication processes
Growth Techniques
Basic growth methods available for crystal growth
1. Growth from melt
2. Growth from vapour
3. Growth from solution
4. Growth from solid

Silicon Crystal Growth from Melt
Czocharlski Technique
method of crystal growth used to obtain single crystals of
semiconductors (e.g. silicon, germanium and gallium arsenide),
metals (e.g. palladium, platinum, silver, gold), salts and synthetic
gemstones
also known as Pulling Technique
widely used for growing semi conducting material crystal. The
shape of the crystal is free from the constraint due to the shape
of the crucible

1/6/2021
Arpan Deyasi, RCCIIT
Czocharlski
Technique

Czocharlski Technique: kinetics
SiC (solid) + SiO2 (solid) Si (solid) + SiO (gas) + CO (gas)
produces metallurgical grade Silicon (MGS) with 98% purity
Si (solid) + 3HCl(gas) SiHCl3 (solid) + H2 (gas)
trichlorosilane (TCS) is produced
SiHCl3 (solid) + H2 (gas) Si (solid) + 3HCl(gas)
electronic grade Silicon (EGS) is formed

Czocharlski Technique: Mathematical formulation
As crystal pulled from melt, doping concentration of
crystal (CS) is different from doping of melt (CL)
Equilibrium segregation coefficient
0
S
L
C
k
C
=

For incremental amount of crystal weight dM, corresponding
reduction of dopant (dS) from the melt is
0
( )
M M
−
Remaining weight of the melt is
S
dS C dM
= −
0
L
S
C
M M
=
−

0
S
L
C
dS dM
S C M M
= −
−
0
0
dS dM
k
S M M
= −
−

0 0
0
0
0
S M
C M
dS dM
k
S M M
= −
−
∫ ∫
0
( 1)
0 0
0
1
k
S
M
C k C
M
−
 
= −
 
 

Growth from free surface
Growth of large oriented crystals
Convenient chemical composition
Control of atmosphere
Czocharlski Technique: Advantages

Czocharlski Technique: Disadvantages
High vapour pressure materials
Liquid phase encapsulation
Possible contamination of the melt by the crucible
No reproductive ability of the crystal shape

Growth of single crystal materials from the vapour phase
Deposition from the Vapour Phase is the most preferred
techniques for the fabrication of thin layer of metal,
insulator and semiconductor materials
The crystal often have perfectly flat external surfaces and
less imperfections
Crystal Growth from Vapor

Crystal Growth from Vapor

• Convenient for large large-scale operation
• Coat irregular-shaped substrates including growth on
inner surfaces
• Offer maximum control of material properties such as
thickness and composition
• Does not involve contacting of growing surface with
liquid/ solid phase
Crystal Growth from Vapor: Advantages

Physical Vapour Deposition (PVD)
Physical vapour deposition (PVD) is a thin-film coating process
which produces coatings of pure metals, metallic alloys and
ceramics with a thickness usually in the range 1 to 10µm.
Physical vapour deposition, as its name implies, involves
physically depositing atoms, ions or molecules of a coating
species on to a substrate.
• thermal evaporation
• sputtering
• ion plating

1/6/2021
PVD:
Thermal
evaporation
uses the heating of a
material to form a
vapour which
condenses on a
substrate to form the
coating. Heating is
achieved by various
methods including
hot filament,
electrical resistance,
electron or laser
beam and electric
arc.

1/6/2021
PVD:
Sputtering
involves the
electrical
generation of a
plasma between
the coating species
and the substrate

1/6/2021
PVD:
Ion
plating
essentially a
combination of
thermal
evaporation and
sputtering

Advantages of PVD
Materials can be deposited with improved properties
compared to the substrate material
Almost any type of inorganic material can be used as
well as some kinds of organic materials
The process is more environmentally friendly than
processes such as electroplating

Disadvantages of PVD
It is a line of sight technique meaning that it is extremely
difficult to coat undercuts and similar surface features
High capital cost
Some processes operate at high vacuums and temperatures
requiring skilled operators
Processes requiring large amounts of heat require
appropriate cooling systems
The rate of coating deposition is usually quite slow

Chemical Vapour Deposition (CVD)
Chemical vapour deposition (CVD) is a coating process that
uses thermally induced chemical reactions at the surface of
a heated substrate, with reagents supplied in gaseous form.
These reactions may involve the substrate material itself,
but often do not.
MOCVD
enables very thin layers of atoms to be deposited on a
semiconductor wafer and is a key process for
manufacturing III-V compound semiconductors,
especially gallium nitride (GaN)-based semiconductors.

MOCVD

Epitaxial Growth
• Deposition of a layer on a
substrate which matches the
crystalline order of the
substrate
• Homo-epitaxy
– Growth of a layer of the
same material as the
substrate
– Si on Si
• Hetero-epitaxy
– Growth of a layer of a
different material than the
substrate
– GaAs on Si
Ordered,
crystalline
growth;
NOT
epitaxial
Epitaxial
growth:

Types of epitaxial deposition
• Vapor Phase Epitaxy
• Liquid Phase Epitaxy
• Molecular Beam Epitaxy

Vapor Phase Epitaxy

1/6/2021
Liquid Phase Epitaxy

1/6/2021
Molecular Beam Epitaxy

Molecular Beam Epitaxy
– Very promising technique
– Beams created by evaporating solid source in UHV
– Evaporated beam of particle travel through very high vacuum
and then condense to shape the layer
– Doping is possible to by adding impurity to source gas
– Deposition rate is the most important aspect of MBE
– Thickness of each layer can be controlled to that of a single
atom
– Development of structures where the electrons can be
confined in space, giving quantum structures

Modern Epitaxial Techniques

Crystal Growth

More Related Content

What's hot

Similar to Crystal Growth

More from RCC Institute of Information Technology

Recently uploaded

Crystal Growth