This document discusses semiconductor doping techniques used in the electronics industry. It describes intrinsic and extrinsic semiconductors and the two main types of doping: n-type and p-type. The two major doping techniques discussed are diffusion and ion implantation. Diffusion involves moving dopant atoms into the semiconductor through heating, while ion implantation accelerates dopant ions to implant them into the surface. Both techniques have advantages and disadvantages, with diffusion causing less damage but having less control over depth and concentration. Ion implantation offers more precise control but requires annealing to repair surface damage.

1. SURFACE ENGINEERING IN
ELECTRONICS INDUSTRY
SEMICONDUCTOR DOPING
Abhishek Anand
Gaole Dai
Harmeet Singh
Ishank Chopra
Yunzhe He

2. Introduction
• Semiconductor plays key role in the applications
in area of thermostat, IR sensors, diodes,
transistors etc.
• The gradient of concentration of a dopant in a
substrate provides different properties like
variable conductivity, light emission etc.
• Most popular material used in substrate are
silicon and germanium.

3. Type of semiconductors
Two kind of semiconductors:-
• Intrinsic semiconductor- Intrinsic semiconductor
is pure . It has poor electric conduction.
• Extrinsic semiconductor- Extrinsic semiconductor
is also known as impurity semiconductor.
• It is lightly or moderately doped and it has great
capacity of electric conduction.
• A semiconductor doped to high levels such as it
acts like conductor called degenerate.

4. Impurity semiconductor is classified in two types
• N-type
• P-type

5. • For N-type semiconductor , impurities are chosen
from range of pentads, mostly phosphorus
• For P-type semiconductors , the selected
impurities should be trivalent elements, mostly
boron.
• The following table shows the various materials
used in semiconductor industry

6. Techniques of Semiconductor
doping
There are numerous techniques being followed
in the industry for doping, most widely used
techniques are
• Ion implantation
• Diffusion
• Oxidation
We are going to focus on two major techniques;
Diffusion and Ion implantation

7. Diffusion
What is Diffusion?
 The movement of impurity atoms (dopant) at high temperature
into a semiconductor material due to concentration gradient is
known as diffusion.
 Diffusion of impurities in the silicon lattice takes place at
temperatures in the range of 900-1100o C.

8. There are two major ways in which diffusion
doping process can be carried out:
• Predeposition: The impurities diffuse into the
parent material with a constant concentration
gradient.
• Drive-in: A layer of the dopant is deposited on
the surface. In this case, the impurity gradient
at the surface of the substrate decreases with
time.
Predeposition Drive-In

9. Diffusion at microscopic level
Substitution diffusion
Interstitial diffusion

10. Diffusion process parameters
• Temperature
• Type of impurity
• Diffusion time
• Defects in silicon crystal
Challenges:-
• Crystal structure:
• Junction depth control
• Doping concentration control:

11. Advantages:-
• No damage to surface
• Batch fabrication is possible
• An isotropic process
• Cost associated with process is low
Disadvantages:-
• Low dose doping is difficult to carry out
• Shallow junctions are difficult to fabricate
• Cant be carried out at room temperature

12. Ion implantation
• What is ion implantation?
Ions of the desired dopant are first accelerated
using an electric field resulting in formation of
a beam of ions. The beam is then projected
upon the parent lattice material causing a
bombardment of the ions on the substrate
resulting in a uniform deposition of dopant on
the parent lattice.

13. The Process
• In order to form a beam of ions, the first step is to
generate ions.
• The dopants are heated on a hot filament causing
generation of ions.
• The ions generated are accelerated away from the
source by electric field.
• The ions then pass through a magnetic field
which diverts the ions and separates them
according to their size or according to the
requirement using a predesigned aperture.

14.  The separated ions are brought to the desired energy by accelerating
them again using an electric field and are bombarded on the
substrate after passing through a focusing lens.
 The focused accelerated ions strike the substrate and get implanted
in the area exposed to the beam.

15. Advantages:-
• It is a low temperature process and fast
process.
• The dose of ion can be controlled
• Precise depth control possible
• It can be used to implant ions through thin
layers of oxide
• The method can be used to obtain extremely
low as well as extremely high dope.

16. Parameters effecting ion implantation process:-
• The energy of the incoming impurity
• Intensity
• Project range
Challenges:-
• Damage to the surface during implantation
• Formation of amorphous regions
• Annealing for a longer time causes the
implanted ion undergo diffusion.
• Channeling effect

17. Disadvantages:-
• It causes physical damage to the surface
• Annealing is required to relive the stresses and
remove physical damage to the material
• Amorphous regions are formed in the crystal
lattice
• Channeling occurs, causing irregular
distribution of ions.
• It is expensive and one of the most hazardous
process.

18. Comparative study:-

19. Conclusion:-
• The driving force in the diffusion process is the
difference between the concentrations of the
materials involved, is carried out at high
temperature. It is a non-destructive process and
causes no damage to the material surface. Batch
formation is possible with diffusion process,
increasing the overall output
• The Ion Implantation process offers better doping
concentration control, precise junction depth
control, and easy reproducibility and doesn’t
require high temperature for being carried out.
The ion implanted product has to undergo
annealing process to repair the damage which
makes this process relatively expensive.

20. Feedback
• An improvement to the ion implantation process is the plasma
immersion ion implantation (PIII). In PIII process, the parent
material is directly immersed in a plasma chamber. The chamber has
plasma of ions of the impurity to be implanted. The chamber is then
impulse with a very high negative potential.
• This potential drives the electron and lead to formation of a positive
cloud around the parent material. The positive ion round the parent
material is attracted towards the material due to its negative
potential and it gets implanted on the surface uniformly.
• PIII is a non-line of sight technique unlike the conventional process
and it doesn’t require all the complexities and sophisticated
mechanisms of the conventional Ion Implantation Method.
• It is a simpler, cheaper, less time consuming, less hazardous and
flexible process than the conventional Ion Implantation.

21. References
1. J D Plummer, M D Deal and P B Griffin, “Silicon VLSI Technology: fundamentals,
practice and modelling”, Pearson Edu. Inc., 2001
2. Razeghi and Manijeh, “Technology of Quantum Devices”, Springer, 2010
3. Bose D.N., “Semiconductor Material and Devices”, New Age Publishers, 2012
4. F.G, Tseng, “IC Fabrication Process 2: Diffusion, Ion Implantation, Film Deposition,
Interconnection and contacts”. Lecture conducted from National Tsing Hua University,
Taiwan.
5. John (2010, June 1), “Diffusion of impurities for IC fabrication”
6. R.C. Jaeger (vol.5), Introduction to Microelectronic fabrication, Pearson Education
Inc., New Jersey,USA ,2002
7. Advancements in ion implantation Modelling for Doping of Semiconductors, Sivaco,
Inc. Available [Online] http://www.silvaco.com/content/kbase/ion_implantation.pdf
8. Plummer D. James, Deal Michael , Griffin D. Peter, “Silicon VLSI Technology:
Fundamentals, Practise and Modelling”, Prentice Hall , 2000.
9. Gupta Dushyant (2011) , “Plasma Immersion Ion Implantation Process Physics and
Technology", International Journal of Advancements in Technology.

22. THANK YOU
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