Chemical Vapour Deposition
Chemical Vapour Deposition
Chemical Vapour Deposition
Presented by:
-Priyasi Singh
-Pooja Singh
Chemical Vapour Deposition
(CVD)
Definition:
Chemical Vapor Deposition is the formation of a non-
volatile solid film on a substrate by the reaction of vapor
phase chemicals (reactants) that contain the required
constituents.
Cold wall
Types of CVD process
1. APCVD (atmospheric pressure CVD)
2. LPCVD (low Pressure CVD)
3. PECVD (plasma enhanced CVD)
Hot wall
Parallel type
Single wafer
4. MOCVD (metal organic CVD)
5. LCVD (laser CVD)
6. PCVD (photochemical CVD)
7. CVI (chemical vapor infiltration)
8. CBE (chemical beam epitaxy)
1. APCVD
APCVD reactors operate in mass transport limited region
So they are designed such that equal flow of reactants is delivered
This ensures uniform film deposition
This is done by placing the wafer horizontally and then moving
them under gas stream
They are used for depositing low temperature oxide films
Samples are carried through the reactor on a conveyer belt
Reactant gases flowing through the centre of the reactor are
containing by gas curtains formed by fast flow of nitrogen
Advantages:
Simple
High deposition rate
Low temp
Disadvantages:
Poor step coverage
Particle contamination
Require excess wafer handling
Application:
Doped & undoped low temp oxides
2. LPCVD
The reactor consists of a quartz tube heated
by a three zone furnace
Gas introduced from one end & pumped out
from the other end
Wafers stand vertically, perpendicular to the
gas flow
They are placed in a quartz holder
It operates in a surface reaction rate limited
mode
Therefore supply of equal flux of reactants is
not required
Therefore geometry can be such that it can
accommodate a large no. of wafers approx
200 wafers at a time
Advantages:
Excellent purity
Comfortable step coverage
Large wafer capacity
Disadvantage
High temp
Low deposition rate
Application
Doped & undoped high temp oxides
3. PECVD
PECVD system use an RF induced glow
discharge to transfer energy into reactant
gases
This procedure allows the substrate to remain
at a low temp than APCVD & LPCVD
Types:
Parallel plate type
Hot wall type
Single wafer type
a) Parallel plate type
Reaction chamber is cylinder &
constructed of Al- coated stainless
steel
There are Al plates on the top &
bottom
Samples lie on the grounded bottom
electrode
RF is applied to the top electrode
which creates a glow discharge
between 2 plates
Gases flow radially through the
discharge
Resistance heater heat the bottom,
grounded electrode to a temp b/w
100-400C
Gases are flowing from outer edges to
the center
Advantages:
Low temp deposition
b) Hot wall type
The reaction takes place in a quartz tube heated
by a furnace
Samples are held parallel to the gas flow
The electrode assembly contains long graphite or
al slabs to support the wafers
Alternating slabs are connected to power supply
to generate discharge in the space between the
electrode (long slabs serve both as electrode &
holder)
Advantage:
Uniformity
Large no. of wafer deposition
Disadvantage:
Contamination while loading
and unloading
c)Single wafer type
The reactor is load locked
It offers cassette to cassette operation
It offers rapid radiant heating of each
wafer
Wafer larger than 200mm can be loaded
MOCVD
MOCVD stands forMetal-
OrganicChemicalVapourDepositio
n. This is a technique for
depositing thin layers of atoms
onto a semiconductor wafer. Using
MOCVD you can build up many
layers, each of a precisely
controlled thickness, to create a
material which has specific optical
and electrical properties
devices
Dense structural parts CVD can be used to produce components that are difficult or
uneconomical to produce using conventional fabrication techniques. Dense parts produced via
CVD are generally thin walled and maybe deposited onto a mandrel or former.
Composites Preforms can be infiltrated using CVD techniques to produce ceramic matrix
Catalysts
Nanomachines
PHYSICAL VAPOR
DEPOSITION
PVD is a process by which a thin film of
material is deposited on a substrate acc to
following steps:
1) The material to be deposited is converted
into vapour by physical means
2) The vapor is transported across a region
of low pressure from its source to the
substrate
3) Vapor undergoes condensation on the
substrate to form the thin film
EVAPORATION