Chemical vapor deposition and its types. You can learn easily its to much easy to understand.

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Chemical Vapor deposition
Prepared by:
Adnan Majeed

2. Table of contents
 Introduction
 Chemical Vapor deposition
 Apparatus
 CVD techniques
 Applications
 Advantages
 Disadvantages
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Chemical Vapor deposition

3. Introduction:
 Chemical vapour deposition (CVD) is a process whereby a
solid material is deposited from a vapour by a chemical
reaction occurring on or in the vicinity of a normally heated
substrate surface.
 The solid material is obtained as a coating, a powder, or as
single crystals.
 CVD is an example for Solid-Vapour Reaction.
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4. Chemical Vapour Depositions:
 Chemical Vapor Deposition (CVD) is a chemical process used
to produce high purity, high performance solid materials.
 In a typical CVD process, the substrate is exposed to one or
more volatile precursors which react and decompose on the
substrate surface to produce the desired deposit.
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5. APPARATUS:
 Gas delivery system.
 Reactor chamber
 Substrate loading mechanism
 Energy source
 Vacuum system
 Exhaust system
 Exhaust treatment systems
 Process control equipment.
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 It works at atmospheric pressure.
 It is used to deposit a layer of material typically several
micro meters thick onto a wafer or other type of substrate.
 It is also used as a surface finishing process for items such
as tools and turbine blades to improve lifetime and
performance.
 Since a vacuum system is not required, APCVD systems
have a relatively low operating cost.
Atmospheric Pressure CVD:

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Limitations:
• Film thickness uniformity cannot be maintained.
• Large number of pinhole defects can occur.
• The deposits get contaminated very easily.
• APCVD has inherently poor utilization.

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 In this process the deposition of thin film is performed
using low pressure.
 The deposition of Silicon carbide thin film is performed
using low pressure CVD of Dichlorosilane / Acetylene /
Hydrogen reaction system.
 LPCVD coatings exhibit excellent uniformity, high
purity, and good step coverage.
Low pressure CVD:

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• The pressure for LPCVD is usually around1000 Pa
while standard atmospheric pressure is 101,325 Pa

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Metal-organic chemical vapour deposition:
• Metal-organic compounds are used as molecular
precursors to deposit, a wide variety of thin film
materials for new industrial applications .
• The great advantage of MOCVD precursors are their
high volatility at moderate to low temperatures, therefore
reaction temperatures are lower (750 to 1100 K) than
conventional CVD .
• The main disadvantages are the precursors tend to be
very expensive and are very volatile .

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The thickness of the layer is only determined by the
number of drops injected.

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Laser chemical vapour deposition:
• LCVD uses a focussed laser beam to heat the
substrate.
• Laser chemical vapour deposition (LCVD) is a
chemical process used to produce high purity, high
performance films, fibres, and mechanical hardware.
• The process is used in the semiconductor industry
for spot coating.
• Laser chemical vapour deposition (LCVD) is one of
several recently developed deposition techniques
using laser sources.

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CVD Reactors:
Hot-wall reactor:
• In this the substrate (wafer) and the walls of the
reactor are heated, i.e. a homogeneous temperature
is maintained inside the reaction chamber.
Disadvantage of hot-wall reactor:
• Contamination

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 This reactors uses heating systems that minimize
the heating up of the reactor walls while the
wafer is being heated up. The temperature is not
homogeneous inside the reaction chamber.
Cold-wall reactor:
Disadvantage of cold-wall reactor:
• It is difficult to get a uniform layer of
the film.

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• Versatile –any element or compound can be
deposited.
• High purity can be obtained.
• High density – nearly 100% of theoretical value.
• Economical in production, since many parts can
be coated at the same time.
Advantages of CVD:

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 High deposition temperatures (often greater than
600 °C) are often unsuitable for structures already
fabricated on substrates.
 Restrictions on the kind of substrates that can be
coated.
 Film may not be pure.
 Some time cases contaminations.
Disadvantages of CVD:

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 Coatings – Coatings for a variety of applications such as
wear resistance, corrosion resistance, high temperature
protection.
 Semiconductor and related devices.
 Integrated circuits.
 Sensors and optoelectronic devices.
 Optical Fibers – For telecommunications.
 Catalysts.
 Nano machines.
Applications:

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• Powder production – Production of novel powders
and fibers.
• Use in microelectronics industry to make films
serving as dielectric, conductors.

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