19 Sputtering and Evaporation Presentation-Ravi Chawla
-
Upload
prashant-verma -
Category
Documents
-
view
224 -
download
0
Transcript of 19 Sputtering and Evaporation Presentation-Ravi Chawla
-
8/12/2019 19 Sputtering and Evaporation Presentation-Ravi Chawla
1/44
By Ravi Chawla
-
8/12/2019 19 Sputtering and Evaporation Presentation-Ravi Chawla
2/44
MOTIVATION
-
8/12/2019 19 Sputtering and Evaporation Presentation-Ravi Chawla
3/44
Film growth/deposition
-
8/12/2019 19 Sputtering and Evaporation Presentation-Ravi Chawla
4/44
-
8/12/2019 19 Sputtering and Evaporation Presentation-Ravi Chawla
5/44
-
8/12/2019 19 Sputtering and Evaporation Presentation-Ravi Chawla
6/44
-
8/12/2019 19 Sputtering and Evaporation Presentation-Ravi Chawla
7/44
-
8/12/2019 19 Sputtering and Evaporation Presentation-Ravi Chawla
8/44
-
8/12/2019 19 Sputtering and Evaporation Presentation-Ravi Chawla
9/44
Physical Vapor Deposition (PVD)
The physical vapor deposition technique is based on the formation ofvapor of the material to be deposited as a thin film. The material insolid form is either heated until evaporation (thermal evaporation) orsputtered by ions (sputtering). In the last case, ions are generated by a
plasma discharge usually within an inert gas (argon). It is also possibleto bombard the sample with an ion beam from an external ion source.This allows to vary the energy and intensity of ions reaching the targetsurface.
-
8/12/2019 19 Sputtering and Evaporation Presentation-Ravi Chawla
10/44
-
8/12/2019 19 Sputtering and Evaporation Presentation-Ravi Chawla
11/44
a) Physical Vapor Deposition (PVD) systems -
continued
The range of materials that may be deposited using thesemethods include:
Metals such as:
Al
Cu
Au
Ag
etc.
Compound & hard materials such as: Cr
TiN
CrN
AlCuSi
etc.
-
8/12/2019 19 Sputtering and Evaporation Presentation-Ravi Chawla
12/44
PhysicalVapor
Deposition
ThermalEvaporation
Sputtering
Resistive
Inductive
Electron Beam
DC
RF
Magnetron(RF or DC)
ReactiveSputtering
-
8/12/2019 19 Sputtering and Evaporation Presentation-Ravi Chawla
13/44
-
8/12/2019 19 Sputtering and Evaporation Presentation-Ravi Chawla
14/44
THERMAL EVAPORATION
Thermal evaporation, using different types of heat sources, was theearliest method used for achieving supersaturated vapor. Preparationof nanoparticles from supersaturated vapor produced by thermalevaporation was first established in 1930 to prepare nanoparticles ofelements.
Oxides were later prepared by the same method by introducingoxygen to the metal vapor.
-
8/12/2019 19 Sputtering and Evaporation Presentation-Ravi Chawla
15/44
The material to be deposited is placed
in a crucible within a high-vacuum
chamber.
After the chamber is pumped down, the
source is heated via (typically) resistive
or e-beam heating. The material isheated to its boiling point such that it
sublimates onto all exposed surfaces in
the vacuum chamber.
The amount of material deposited is
controlled via a thickness monitor which
is placed within the deposition chamber.
The source material must be of high
purity.
Vacuum levels are on the order of 10-5
to 10-7Torr.
Thermal Evaporation
Resistive Heating
Thermal Evaporation
e-Beam
Thermal Evaporation - General
-
8/12/2019 19 Sputtering and Evaporation Presentation-Ravi Chawla
16/44
-
8/12/2019 19 Sputtering and Evaporation Presentation-Ravi Chawla
17/44
-
8/12/2019 19 Sputtering and Evaporation Presentation-Ravi Chawla
18/44
-
8/12/2019 19 Sputtering and Evaporation Presentation-Ravi Chawla
19/44
Fig: Example of an inductively heated crucibleused to create moderately charged temperatures
-
8/12/2019 19 Sputtering and Evaporation Presentation-Ravi Chawla
20/44
Single Source Evaporation : Method of evaporatingmulticomponent film
-
8/12/2019 19 Sputtering and Evaporation Presentation-Ravi Chawla
21/44
-
8/12/2019 19 Sputtering and Evaporation Presentation-Ravi Chawla
22/44
-
8/12/2019 19 Sputtering and Evaporation Presentation-Ravi Chawla
23/44
-
8/12/2019 19 Sputtering and Evaporation Presentation-Ravi Chawla
24/44
-
8/12/2019 19 Sputtering and Evaporation Presentation-Ravi Chawla
25/44
-
8/12/2019 19 Sputtering and Evaporation Presentation-Ravi Chawla
26/44
Thermal Evaporation - drawbacks
Resistive heating is the simplest method of evaporating metals such as Al or Au,
but it is also the dirtiest in that contaminants which find their way onto the
filament tend to be evaporated along with the metal.
The purity issue can be addressed via e-beam evaporation since the cooled,non-molte high-purity material to be deposited acts as a crucible during the
process (as seen on one of the schematic previously ).
In the case of resistive heating, temperature uniformity across the filament is
difficult to control and therefore, evaporation uniformity onto the substrates may
be a problem. This is not an issue with e-beam evaporation
E-beam evaporation may cause surface damage due to ionizing radiation and/or
X-rays (@ voltages above 10kV, the incident electron beam will give rise to X-ray
emission).
-
8/12/2019 19 Sputtering and Evaporation Presentation-Ravi Chawla
27/44
SPUTTERING
-
8/12/2019 19 Sputtering and Evaporation Presentation-Ravi Chawla
28/44
Sputtering: General
-
8/12/2019 19 Sputtering and Evaporation Presentation-Ravi Chawla
29/44
The Mechanism of Sputtering
-
8/12/2019 19 Sputtering and Evaporation Presentation-Ravi Chawla
30/44
Sputtering Deposition
-
8/12/2019 19 Sputtering and Evaporation Presentation-Ravi Chawla
31/44
Sputtering
The substrate is placed in a vacuum chamber with the source material, named a target,and an inert gas (such as argon) is introduced at low pressure. A gas plasma is struckusing an RF power source, causing the gas to become ionized. The ions are acceleratedtowards the surface of the target, causing atoms of the source material to break off from
the target in vapor form and condense on all surfaces including the substrate.
-
8/12/2019 19 Sputtering and Evaporation Presentation-Ravi Chawla
32/44
-
8/12/2019 19 Sputtering and Evaporation Presentation-Ravi Chawla
33/44
-
8/12/2019 19 Sputtering and Evaporation Presentation-Ravi Chawla
34/44
-
8/12/2019 19 Sputtering and Evaporation Presentation-Ravi Chawla
35/44
Sputtering Process
-
8/12/2019 19 Sputtering and Evaporation Presentation-Ravi Chawla
36/44
Physical vapor deposition (PVD): Sputtering
W= kV i
PTd
-V working voltage- i discharge current- d, anode-cathode distance- PT, gas pressure- k proportionality constant
Momentum transfer
The sputter yield depends on: (a) the energy of the
incident ions; (b) the masses of the ions and target
atoms; (c) the binding energy of atoms in the solid
and (d) the incident angle of ions.
-
8/12/2019 19 Sputtering and Evaporation Presentation-Ravi Chawla
37/44
Reactive Sputtering
Sputtering metallic target in the presence of
a reactive gas mixed with inert gas (Ar)
37
oxides Al2O3, SiO2, Ta2O5 (O2)nitrides TaN, TiN, Si3N4 (N2, NH3)carbides TiC, WC, SiC (CH4, C2H4, C3H8)
A mixture of inert +reactive gases used for sputtering
-
8/12/2019 19 Sputtering and Evaporation Presentation-Ravi Chawla
38/44
Reactive Sputtering (Cont.)
chemical reaction takes place on substrate and target
can poison target if chemical reactions are faster thansputter rate
adjust reactive gas flow to get good stoichiometry
without incorporating excess gas into film
-
8/12/2019 19 Sputtering and Evaporation Presentation-Ravi Chawla
39/44
Reactive Magnetron Sputtering
Zinc Oxide Thin films
Zinc oxide is one of the most interesting semiconductors It has been investigated
extensively because of its interesting electrical, optical and piezoelectric
properties
Reactive sputtering isthe best technique forZinc Oxidedeposition.
-
8/12/2019 19 Sputtering and Evaporation Presentation-Ravi Chawla
40/44
Process Parameters
The physical properties of ZnO films are influenced not only by
the deposition techniques, but also by process parameters.
The film deposited on hightemperature substrate willshow finer uniform grainsand smoother surface
-
8/12/2019 19 Sputtering and Evaporation Presentation-Ravi Chawla
41/44
Process Parameters
41
Quality of the film dependents on deposition conditions, such assubstrate temperature, deposition power, deposition pressure andargonoxygen flow.
-
8/12/2019 19 Sputtering and Evaporation Presentation-Ravi Chawla
42/44
Conclusion
Sputter deposition is a widely used technique for depositing
thin metal layers on semiconductor wafers.
The range of applications of sputtering and the variations of the
basic process, is extremely wide.
42
-
8/12/2019 19 Sputtering and Evaporation Presentation-Ravi Chawla
43/44
Sputtering advantages/disadvantages
-
8/12/2019 19 Sputtering and Evaporation Presentation-Ravi Chawla
44/44
Thank You!