Basic introduction about thin films, their importance and some methods of their synthesis.

1. INTRODUCTIONTO THINFILMS
TECHNOLOGY
Presented by :
Sumit Kumar

2. Thin Films ???
 Thin films are just a layer of materials, thickness ranging
between (10-500) nanometers
 If there is no substrate then it is a “foil”.
fig: Zno thin film deposited on a substrate

3. Why Thin Films ???
 Maintain surface uniformity
 Simple fabrication
 Manufacturing requires less material
 Reduce light absorbing material
 Strange electrical, optical and mechanical properties

4. • Nowadays thin film technology used in many applications,
including microelectronics, optics, magnetic, hard resistant
coatings, micro-mechanics, etc.
• Better results in these areas depend on selective and
controlled deposition.
• There are a vast number of deposition methods available, all
methods have their specific advantages as well as
disadvantages based on substrate and source material,
thickness of deposited film.
• This makes it difficult to select the best technique for any
specific application. Some of these methods are discussed.
Technology Focus

5. Deposition Techniques
 Glow Discharge Processes
1. Sputtering
2. Plasma processes
 Gas phase chemical processes
1. Low Pressure CVD
2. Metal Organic CVD
3. Laser induced CVD
 Liquid Phase Chemical Processes
1. Electroplating
2. Spin on Techniques

6. .
• Vacuum evaporation Techniques
1. Convential Vacuum Evaporation
2. Molecular Beam evaporation
3. Molecular Beam Epitaxy
4. Reaction Evaporation

7. .Deposition based on Physical or
Chemical Processes
Deposition
Techniques
PhysicalVapor
Deposition
Vacuum
Evaporation
Techniques
Sputtering Spin Coatings
Chemical
Vapor
Deposition
Electroplating PECVD LPCVD

8. Plasma Enhanced CVD
.
• Lower Temperature Process
due to Plasma Enhancement
• Dissociation of precursor gas
molecules (Homogeneous
reactions)
• Ions bombard surface
making it more reactive
• Higher rates of deposition
are possible than with
LPCVD

9. Low Pressure CVD
 .
• Surface reaction limited
at low pressure
• Chamber may also be
heated or unheated
• Low pressure
environment increases
mean free path
• Better Step Coverage
and conformality than
APCVD

10. Electroplating

11. Sputtering
• It is basically an etching process which was first discovered in
1892 and developed as a thin film deposition techniques in
1920 by Langmuir.

12. Spin Coating

13. Evaporation Deposition
The material is heated in high vacuum chamber (P < 10-5 Torr)
to minimize the collision in source atoms, it is also called
Vacuum Deposition.
Heating is done by resistive or e-beam sources.
Surface interactions are physical, can be very fast (>1m/min
possible)
High sticking coefficient leading to poor conformal
coverage/significant shadow. But this also makes evaporation
the most popular thin film deposition for nanofabrication using
liftoff process.
Deposition rate is determined by emitted flux and by geometry
of the source and wafer.
Evaporation is not widely used by industry as sputter
13

14.  Evaporator based on heating process
1. Thermal Evaporator(Resistive heating)
2. Electron beam Evaporator(Heating by electron beam)
3. Inductive Evaporator (Inductive heating – most unpopular
one)

15. Thermal Evaporator
 Used for material whose vapor pressure can be reasonable at
(1600-1800)°C or less than that. Common evaporant materials
are Au, Ag, Al, Sn, Cds, Pbs, Cdse etc.

16.  Thermal Evaporator
1. Simple, used at large scale
2. W, Ta filaments are used as heaters.
3. Filament produces current to (200-300) ampere.
4. Substrate exposes to Infrared or Visible rays
5. Contamination from heated boat
 E-Beam Evaporator
1. More complex and can be used for almost all kind of
materials .
2. Less contamination and heating to wafer.
3. Exposes substrate to secondary electron radiation
4. X-Ray can be generated by high voltage electron beam.
As it produces X-ray beams so it can’t be used for
MOSFET(X-ray may damage substrate as well as dielectrics)

17. Issues with Evaporation System
 Step Coverage
 Alloy Evaporation
 Shadow Evaporation

18. Types of Thin Films
 Si based thin films
 CdTe Thin Films
 CIGS Thin Films
 CZTS Thin Films

19. Applications
• Microelectronics - electrical conductors, electrical barriers,
diffusion barriers.
• Magnetic sensors - sense I, B or changes in them
• Gas sensors, SAW devices.
• Tailored materials - layer very thin films to develop materials with
new properties
• Optics- anti-reflection coatings
• Corrosion protection
• Wear resistance

20. Thank You