This document discusses various thin film deposition techniques used in experimental research, with a focus on vacuum deposition methods. It describes sample preparation using physical vapor deposition processes like sputtering and evaporative deposition as well as chemical vapor deposition approaches like atmospheric pressure CVD, low pressure CVD, and plasma enhanced CVD. For each method, it outlines the basic process steps, advantages, disadvantages, and applications for depositing materials like silicon dioxide, silicon nitrides, polysilicon and metals.

1. Experimental Techniques for
Interdisciplinary Research Work
(Sample Preparation: Use of Vacuum Technology)
By
Dr. C.L. Saini
(clsaini52@gmail.com, clsaini52@uniraj.ac.in)
(Mobile No. : +91-9413119927)
(Assistant Professor)
Solar and H2 storage Laboratory
Department of Physics
University of Rajasthan, Jaipur
JLN Marg Jaipur, Rajasthan – 302004, India
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2. Sample Preparation by
Different techniques
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3. Purpose of Deposition
• Conductive or insulating layers on a substrate
• It creates locally conductive paths that can be
used to interconnect devices
• Deposition can be used to build up more
complex structures one layer at a time (which
is known as multilayer)
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4. Deposition Types
1) Silicon Dioxide SiO2
– Insulating layers
– Protective coatings
– Gate oxides
2) Silicon Nitrides
– Protective layers
– Isolation
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3) Polysilicon
– Heavily doped silicon
– Conductive
– Used for interconnects and gate
4) Metals
– Aluminum/Aluminum-Copper
– Tungsten
– Titanium Alloys

5. Deposition Processes
• Physical or Chemical (or both?)
– Physical Processes Deposit the material without
chemical reactions
– Chemical processes utilize liquid or vapor forms
of precursors that react with the surface to form
the desired deposition
– To combine the processes and gain the benefits of
each
– Many processes are carried out in reduced
pressure (limited vacuum range) environments
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6. Requirements of Deposition
• Any deposited layer must be compatible in many customs with
the following properties:
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i. Film Stress
ii. Conformality
Good Poor
iii. Uniformity
iv. Step Coverage
v. Thermal compatibility
Source file From
MATEC Module 45

7. • Deposition rate
• Film uniformity:
• Materials that can be deposited: metal, dielectric, polymer.
• Quality of film:
Physical and chemical properties
Electrical property, breakdown voltage
Mechanical properties, stress and adhesion to substrate
Optical properties, transparency, refractive index
Composition, stoichiometry
Film density, defect (pinhole…) density
Texture, grain size, boundary property, and orientation
Impurity level, doping
• Deposition directionality:
Directional - good for lift-off, trench filling
Non-directional - good for step coverage
• Cost of operation.
General characteristics of thin film deposition
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8. Physical Deposition Processes
• Sputtering
– Plasma is created by RF or HV DC source
– Inert gas (such as Ar) is used in a low pressure
environment (~ 10-3 Torr)
– Free electrons strike Ar atoms, causing positive
ions to be formed
– Negatively charged target material attracts ions
– Ions dislodge particles that are deposited on
substrate
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9. Sputtering
(Process and mechanism)
Source: www.wikipedia.com
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10. Sputtering
• Advantages
– Low temperature process
– Good Conformal Coating
– Good Step Coverage
• Disadvantages
– Dielectrics require RF Source
– RF environment may affect other depositions
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11. Evaporative Deposition
• Utilizes the principle of vapor pressure
– Metallic species are melted in a low pressure environment
– Higher vapor pressure metals evaporate first
– Deposition of the vapor on the surface occurs
– A low temperature process on the substrate
– Alternatives include laser ablation (Laser strikes a target, causing local melting)
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Source file: Wikipedia

12. Evaporative Deposition
• Advantages
– Uniformly covers substrate
– Simple process without chemicals or gases
• Disadvantages
– Alloys are difficult to deposit
• Different metals have different vapor pressures
– High aspect ratio features are difficult to cover
• Trajectory of evaporated particles tends to be vertical, which
may not pattern sidewalls evenly
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13. Spin On Coating
• A Physical Deposition Process
– Similar to photoresist spin-on
– Si-based liquid is applied
– Coating is baked on to remove volatile liquid
• Used to planarize or flatten wafer surface
– Can be patterned and etched for contacts
• Adds steps to process
• Alternatives – Chemical Mechanical Polish
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Experimental Set-up
Different size chucks

14. Basic principle and working mechanism
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Device fabrication using Spin Coating
unit
Device architecture
XRD data
Optical properties
I-V Curve

16. Chemical Deposition Processes
• Wet or Dry Method?
– Wet processes use liquids and immersion
Electroplating
Electro-less deposition
Wet growth of SiO2 insulating layer (water vapor)
– Dry processes use chemical vapors
a) Atmospheric Pressure Chemical Vapor Deposition
b) Low Pressure Chemical Vapor Deposition
c) Plasma Enhanced Chemical Vapor Deposition
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17. Types of Chemical Vapour Deposition (CVD)
For Research & Development, PECVD is most popular, followed by LPCVD.
(can be higher)
and epitaxy Si…
(can have high
deposition rate)
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18. Chemical Deposition Processes
• Atmospheric Chemical
Vapor Deposition (CVD)
• Main steps for deposition
considerations:
i. Wafers are heated
ii. Chemical gases are
introduced
iii. A temperature
dependent deposition
rate
iv. Mass transport limited
at higher temperatures
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Source file: Wikipedia

19. Chemical Deposition Processes
• Plasma Enhanced Low
Pressure (CVD)
Steps to be considered:
 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
Source file: From MATEC Module 54
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20. Chemical Deposition Processes
• Use of chemical deposition process to
deposits Anti-reflective coatings
a) Utilize thin film deposition to create coatings
that have λ/2 thickness at the exposure lamp
wavelength
b) This results in destructive interference
canceling reflection in the photo-resist layer
c) Reflection from glossy layers below photo-resist
causes indistinct features
d) By this method better lithography is possible
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Thank you
very much
Suggestions are invited for improvement in the ppt file.
Send your feedbacks at Email: clsaini52@gmail.com