Crystal structures can be single crystal, polycrystalline, or amorphous. Single crystal silicon is used to manufacture solar cells and semiconductors due to its precise electronic properties. The Czochralski method is commonly used to grow large single crystal silicon ingots from melted, purified silicon in quartz crucibles. The ingots are sliced, polished, and cleaned to produce thin round wafers for semiconductor fabrication. Larger diameter wafers allow more chips to be produced from each wafer, increasing manufacturing efficiency.
Semiconductor device fabrication is the process used to create the integrated circuits that are present in everyday electrical and electronic devices. It is a multiple-step sequence of photo lithographic and chemical processing steps during which electronic circuits are gradually created on a wafer made of pure semiconducting material. Silicon is almost always used, but various compound semiconductors are used for specialized applications.
1.Silicon Manufacturing
a) Czochralski method.
b) Wafer Manufacturing
c) Crystal structure
2.Photolithography
a) Photoresists
b) Photomask and Reticles
c) Patterning
Ion implantation is used in semiconductor device fabrication and in metal finishing, as well as in material science research.
it is a low temperature process that includes the acceleration of ions of a particular element towards a target, altering the chemical and physical properties of the target.
Semiconductor device fabrication is the process used to create the integrated circuits that are present in everyday electrical and electronic devices. It is a multiple-step sequence of photo lithographic and chemical processing steps during which electronic circuits are gradually created on a wafer made of pure semiconducting material. Silicon is almost always used, but various compound semiconductors are used for specialized applications.
1.Silicon Manufacturing
a) Czochralski method.
b) Wafer Manufacturing
c) Crystal structure
2.Photolithography
a) Photoresists
b) Photomask and Reticles
c) Patterning
Ion implantation is used in semiconductor device fabrication and in metal finishing, as well as in material science research.
it is a low temperature process that includes the acceleration of ions of a particular element towards a target, altering the chemical and physical properties of the target.
Semiconductors are materials that have electrical conductivity between conductors such as most metals and nonconductors or insulators like ceramics. How much electricity a semiconductor can conduct depends on the material and its mixture content.
Semiconductors can be insulators at low temperatures and conductors at high temperatures. As they are used in the fabrication of electronic devices, semiconductors play an important role in our lives.
Have an overview of the most conventionally utilized crystal growth techniques: process, diagrams, advantages, and disadvantages. This is the presentation of my "PV cells and materials" course at the MSc Engg. level.
Semiconductors are materials that have electrical conductivity between conductors such as most metals and nonconductors or insulators like ceramics. How much electricity a semiconductor can conduct depends on the material and its mixture content.
Semiconductors can be insulators at low temperatures and conductors at high temperatures. As they are used in the fabrication of electronic devices, semiconductors play an important role in our lives.
Have an overview of the most conventionally utilized crystal growth techniques: process, diagrams, advantages, and disadvantages. This is the presentation of my "PV cells and materials" course at the MSc Engg. level.
One can get full description of metallic glasses which contains history, preparation methods, effects on metallic glasses, properties and application part is also there with diagrams, tables and graphs
Ring n chain compounds
Silicates
Types of silicates
Principle of Silicate minerals
Soluble silicates
Amphiboles, Zeolites, Ultramarines,
Feldspars
Silicates in technology
Glass, quartz, micas
DENTAL CASTING ALLOYS
Mostly metals used in dentistry are in the form of alloys or mixture of one or more metals.
Alloy: two or more metal that are mutually soluble in each other in the molten state.
Metal: Any strong and relatively ductile substance that provide electropositive ions to a corrosive environment and that can be polished to a high luster.
Uses of metal or alloys in dentistry:
For direct intra-coronal restoration such as using direct filling gold.
Fabrication of extra-coronal restoration such as inlays, onlays, crown and fixed partial denture.
For fabricating superstructure, cast frameworks, cast partial denture etc.
For surgical use such as making titanium plates, screws etc.
For orthodontic use in making wires, brackets, bands etc.
For making laboratory instruments etc.
Properties of metal:
Should have high strength.
Should be malleable and ductile.
Should have good thermal and electrical conductivity.
Should have high luster.
Should have high corrosion resistance .
Structure of metal:
All metals are crystalline in nature.it refers to regular arrangement of atoms. There are six different type of crystal structure:
a) Cubic
- Simple
- Body-centered
- Face conferred
b) Tetragonal
- Simple
- Body-centered
- Rhombohedric
c) Orthorhombic
- Simple
- Body-centered
- Face-centered
- Base centered
d) Monoclinic
- Simple
- Base centered
e) Triclinic
f) Hexagonal
Crystal lattice structure
Classification of dental casting alloys
On the basis of use
alloys for all metal and resin veneer restorations
alloys for metal ceramic restoration
alloys for post and core
alloys for removable partial denture
alloys for dental implants
on the basis of major elements
gold based alloys
palladium based
silver based
nickel based
cobalt based
titanium based
on the basis of three major elements
gold-palladium-silver
palladium-silver-tin
nickel-chromium-molybdenum
cobalt-chromium-molybdenum
iron-nickel-chromium
titanium-aluminum-vanadium
on the basis of nobility
o high noble metal alloy
o noble metal alloy
o Predominantly base metal alloy
o Base metal alloy
On the basis of dominant phase system
Single phase or solid solution alloys
Eutectic alloys
Peritectic alloys
Intermetallic compound
Alloys for all metal restoration
Earlier days metal restoration was choice for replacement of missing teeth, but as an advancement of new material and because of color of metal, the uses of metallic restoration have reduced. However, the metal alloys continue to be used in metal-ceramic restoration to enhance strength, wear resistance and hardness.
Classification:
Based on their yield strength, percentage elongation and use, alloys for all metal restorations are classified into
Type I soft
Small inlays, class III and class IV cavities which are not subjected to wear great stress.
Type II medium
For inlay, onlays and partial veneer crown, abutm
Silicones are a group of organosilicon polymers which are also known as siloxanes. Organosilicon compounds are those in which organic group is attached to silicon. preparations properties, types and applications of silicones.
references for study of silicones.
The radio frequency microelectromechanical system (RF MEMS) Materials Jitendra Jangid
RF technologies. Besides RF MEMS technology, III-V compound semiconductor (GaAs, GaN, InP, InSb), ferrite, ferroelectric, silicon-based semiconductor (RF CMOS, SiC and SiGe), and vacuum tube technology are available to the RF designer. Each of the RF technologies offers a distinct trade-off between cost, frequency, gain, large-scale integration, lifetime, linearity, noise figure, packaging, power handling, power consumption, reliability, ruggedness, size, supply voltage, switching time and weight.
Ceramic materials are inorganic , nonmetallic
materials
made from compounds of a metal and a non metal.
Ceramic materials may be crystalline or partly crystalline.
The word ceramic comes from the Greek word keramiko
of pottery" or for pottery from keramos.
Ceramics materials are the phases containing a
compounds of metallic and nonmetallic
elements. In short
ceramics are the inorganic non metallic materials such as
silicates, aluminates, oxides, carbides, borides and
hydroxides. Since there are many possible combinations
of metallic and nonmetallic
atoms and there are many
several structural arrangement of each combination.
Ceramics always composed of more than one element.
Bonds are partially or totally ionic, can have combination
of ionic and covalent bonding (electronegativity)
Ceramic materials are inorganic, non-metallic materials made from compounds of a metal and a non metal. Ceramic materials may be crystalline or partly crystalline.
The word ceramic comes from the Greek word keramiko of pottery" or for pottery from keramos
Ceramic materials are inorganic, non-metallic materials made from compounds of a metal and a non metal. Ceramic materials may be crystalline or partly crystalline.
The word ceramic comes from the Greek word keramiko of pottery" or for pottery from keramos.
Ceramic materials are inorganic , nonmetallic
materials
made from compounds of a metal and a non metal.
Ceramic materials may be crystalline or partly crystalline.
The word ceramic comes from the Greek word keramiko
of pottery" or for pottery from keramos.
Ceramics materials are the phases containing a
compounds of metallic and nonmetallic
elements. In short
ceramics are the inorganic non metallic materials such as
silicates, aluminates, oxides, carbides, borides and
hydroxides. Since there are many possible combinations
of metallic and nonmetallic
atoms and there are many
several structural arrangement of each combination.
Ceramics always composed of more than one element.
Bonds are partially or totally ionic, can have combination
of ionic and covalent bonding (electronegativity)
nano whiskers r thread like structure compared to the nano rods and nano wires but still controversy is there that they can be put under springs too.......... check to know more abt the whiskers
Students, digital devices and success - Andreas Schleicher - 27 May 2024..pptxEduSkills OECD
Andreas Schleicher presents at the OECD webinar ‘Digital devices in schools: detrimental distraction or secret to success?’ on 27 May 2024. The presentation was based on findings from PISA 2022 results and the webinar helped launch the PISA in Focus ‘Managing screen time: How to protect and equip students against distraction’ https://www.oecd-ilibrary.org/education/managing-screen-time_7c225af4-en and the OECD Education Policy Perspective ‘Students, digital devices and success’ can be found here - https://oe.cd/il/5yV
Model Attribute Check Company Auto PropertyCeline George
In Odoo, the multi-company feature allows you to manage multiple companies within a single Odoo database instance. Each company can have its own configurations while still sharing common resources such as products, customers, and suppliers.
The Indian economy is classified into different sectors to simplify the analysis and understanding of economic activities. For Class 10, it's essential to grasp the sectors of the Indian economy, understand their characteristics, and recognize their importance. This guide will provide detailed notes on the Sectors of the Indian Economy Class 10, using specific long-tail keywords to enhance comprehension.
For more information, visit-www.vavaclasses.com
2024.06.01 Introducing a competency framework for languag learning materials ...Sandy Millin
http://sandymillin.wordpress.com/iateflwebinar2024
Published classroom materials form the basis of syllabuses, drive teacher professional development, and have a potentially huge influence on learners, teachers and education systems. All teachers also create their own materials, whether a few sentences on a blackboard, a highly-structured fully-realised online course, or anything in between. Despite this, the knowledge and skills needed to create effective language learning materials are rarely part of teacher training, and are mostly learnt by trial and error.
Knowledge and skills frameworks, generally called competency frameworks, for ELT teachers, trainers and managers have existed for a few years now. However, until I created one for my MA dissertation, there wasn’t one drawing together what we need to know and do to be able to effectively produce language learning materials.
This webinar will introduce you to my framework, highlighting the key competencies I identified from my research. It will also show how anybody involved in language teaching (any language, not just English!), teacher training, managing schools or developing language learning materials can benefit from using the framework.
How to Create Map Views in the Odoo 17 ERPCeline George
The map views are useful for providing a geographical representation of data. They allow users to visualize and analyze the data in a more intuitive manner.
We all have good and bad thoughts from time to time and situation to situation. We are bombarded daily with spiraling thoughts(both negative and positive) creating all-consuming feel , making us difficult to manage with associated suffering. Good thoughts are like our Mob Signal (Positive thought) amidst noise(negative thought) in the atmosphere. Negative thoughts like noise outweigh positive thoughts. These thoughts often create unwanted confusion, trouble, stress and frustration in our mind as well as chaos in our physical world. Negative thoughts are also known as “distorted thinking”.
Instructions for Submissions thorugh G- Classroom.pptxJheel Barad
This presentation provides a briefing on how to upload submissions and documents in Google Classroom. It was prepared as part of an orientation for new Sainik School in-service teacher trainees. As a training officer, my goal is to ensure that you are comfortable and proficient with this essential tool for managing assignments and fostering student engagement.
Palestine last event orientationfvgnh .pptxRaedMohamed3
An EFL lesson about the current events in Palestine. It is intended to be for intermediate students who wish to increase their listening skills through a short lesson in power point.
1. Crystal Structure
&
Wafer Fabrication
Abu Syed Md. Jannatul Islam
Lecturer, Dept. of EEE, KUET, BD
1
Department of Electrical and Electronic Engineering
Khulna University of Engineering & Technology
Khulna-9203
3. 3
Single Crystal
A single crystal/mono-crystal, is a crystalline solid in which the crystal lattice of the
entire sample is continuous and unbroken to the edges of the sample, with no grain
boundaries.
Mono/single Si serves as light-absorbing material in the manufacture of solar cells.
Insulin crystals Gallium, a metal that easily
forms large single crystals Quartz crystal
Silicon
4. 3
Polycrystalline
Polycrystalline materials are solids that are composed of many crystallites of
varying size and orientation.
The crystallites are referred to as grains.
The variation in direction can be random (called random texture) or directed,
possibly due to growth and processing conditions.
Fiber texture is an example of the latter. Almost all common metals, and many
ceramics are polycrystalline.
5. 3
Amorphous Solid
The amorphous structure of glassy Silica (SiO2).
No long range order is present, however there is
local ordering with respect to the tetrahedral
arrangement of Oxygen (O) atoms around the
Silicon (Si) atoms.
An amorphous solid is a solid in which there is no long-range order of the
positions of the atoms
Most classes of solid materials can be found or prepared in an amorphous form.
For instance, common window glass is an amorphous ceramic, many polymers
(such as polystyrene) are amorphous, and even foods such as cotton candy are
amorphous solids.
6. 3
Si and atomic number 14 14. The atomic mass is 28.0855.
Silicon, like carbon and other group IV elements form face-centered diamond cubic
crystal structure.
Silicon, in particular, forms a face-centered cubic structure with a lattice spacing of
5.430710 A (0.5430710 nm).
II III IV V VI
B
Boron
C
Carbon
N
Nitrogen
O
Oxygen
Al
Aluminum
Si
Silicon
P
Phosphorus
S
Sulfur
Zn
Zinc
Ga
Galium
Ge
Germanium
As
Arsenic
Se
Selenium
Cd
Cadmium
In
Indium
Sn
Tin
Sb
Antimony
Te
Tellurium
Silicon
7. 16
Why Silicon?
Silicon is abundant in the earth crest as an ore in the form of
quartzite and it is a low cost material.
Other reason:
► It forms an oxide that is of very high quality, seals the surface with very few pin
holes or gaps.
► This allows gap MOSFET to be more easily made as the SiO2 forms the insulating
layer for the Gate,
► Protects and passivates underlying circuitry helps in patterning and useful for
dopant masking.
► It forms a very tough Nitride- Si3N4 (Silicon Nitride) forms a very high band gap
insulator which is impermeable.
► This is used to passivate (seal) the die.
► This also used to make hard masks and in other process steps
► Si has a very nice bandgap of ~ 1.12 eV, not too high so that room temperature
can't ionize it, and not so low that it has to high leakage current.
8. 8
17
Why Silicon?
►Silicon has relatively high dielectric strength and therefore is suitable for power
devices.
►It forms a very nice gate material. Most modern FET's used in VLSI (up until the
latest generations) have been called MOSFET but in actual fact have used Si as
the gate material.
►Stable and strong material & crystal structure like diamond
►Higher operating temperature (125-175ºC vs. ~85 ºC) and thus become intrinsic at
higher temp.
►Large variety of process steps possible without the problem of decomposition
(as in the case of compound semiconductors)
►GeO2 - is partially soluble
►GaAs - does not form a oxide
►CO2 - is a gas
►Recently, SiC becoming popular due to high temperature tolerance and high
power, high frequency operation. …
9. 18
Crystal structure : diamond cubic
Magnetic ordering: diamagnetic
Electric resistivity : (20 °C) 103 Ω·m
Thermal conductivity: (300 K) 149 W·m−1·K−1
Thermal expansion : (25 °C) 2.6 µm·m−1·K−1
Speed of sound : (thin rod) (20 °C) 8433 m/s
Young’s modulus: 185 GPa
Shear modulus : 52 GPa
Bulk modulus :100 GPa
Band gap energy at 300 K : 1.12eV
Why Silicon?
10. 3
Importance of Single Crystal Silicon
Semiconductor devices and VLSI (very large scale integrated) circuits require high-
purity single-crystal semiconductors. Because:
Difficult to control properties of amorphous or poly-crystals.
By doping, electronic properties (carrier density, mobility, conductivity, carrier
lifetime) of a single crystal can be controlled more precisely.
Amorphous silicon is used in photovoltaic cells, electronic displays (large-area).
Polycrystalline silicon is used as a gate contact in MOSFETs (VLSI circuits).
Single crystal Si wafers
Diameters: currently up to 300mm (500mm?)
Wafer thickness: 650μm
Wafer purity: 150 parts/trillion
Impurities: 99.99999999% Si
11. 3
Crystals are
characterized by a unit
cell which repeats in the
x, y, z directions.
Planes and directions
are defined using an x,
y, z coordinate system.
[111] direction is defined
by a vector having
components of 1 unit in
x, y and z.
Planes are defined by
Miller indices -
reciprocals of the
intercepts of the plane
with the x, y and z axes.
Crystallography
15. 3
Quartzite (sand, SiO2) is placed in a hot (1800oC) furnace with carbon releasing materials,
and reacts as shown, forming metallurgic grade silicon (MGS):
2SiO2(solid) + 2C(solid) Si(liquid) + 2CO(gas)
Metallurgical Grade Silicon
Metallurgical grade silicon (~98% pure) production and typical impurity levels.
Over 50% MGS is used to make Al alloys. The fraction used for semiconductors is very
small.
16. 3
Electrical Grade Silicon (polycrystalline)
Basically, the solid Si is first converted into a liquid form (SiHCl3) for purification,
then converted back into solid Si.
Both reactions occur at high temperatures.
Metallurgical grade silicon is treated with hydrogen chloride to form tri-
chlorosilane:
Si + 3HCl SiHCl3(g) + H2(g) (use catalyst)
SiHCl3 is liquid at room temperature, boiling point 32oC. Multiple distillation of the
liquid removes the unwanted impurities (99.9999% pure).
The purified SiHCl3 is then used in a hydrogen reduction reaction to prepare the
electronic grade Si (EGS):
SiHCl3(g) + H2(g) Si(s) + 3HCl(g)
(this is the reverse reaction of the above reaction)
EGS is the raw material for Si single crystal production.
17. 3
Jan Czochralski (1885 - 1953) was a Polish chemist who invented
the Czochralski process, which is used to grow single crystals
and is used in the production of semiconductor wafers.
He discovered the Czochralski method in 1916 when he
accidentally dipped his pen into a crucible of molten tin rather
than his inkwell. He immediately pulled his pen out to discover
that a thin thread of solidified metal was hanging from the nib.
The nib was replaced by a capillary, and Czochralski verified that
the crystallized metal was a single crystal.
Czochralski Method
18. 3
Czochralski Method
It is widely employed for Si, GaAs, and InP.
The EGS is broken into small pieces and placed in an SiO2 crucible.
In an argon ambient, the crucible is heated to just above 1417oC.
Dopant is added to the melt to intentionally dope the resulting crystal.
A single crystal seed is then lowered into the melt (crystal orientation and wafer
diameter determined by seed orientation and pull rate), and withdrawn slowly.
19. 3
Melt flows up the seed and cools as crystal begins to grow.
Seed rotated about its axis to produce a circular cross-section crystal. The
rotation inhibits the natural tendency of the crystal to grow along certain
orientations to produce a faceted crystal.
Long ingots (boules) 100 kg, with very good circular cross-section are
produced.
The oxygen and carbon (from graphite furnace components), contribute about
1017-1018/cm3 contaminants.
Czochralski Method
23. 3
Oxygen and Carbon in CZ silicon
The CZ growth process inherently introduces O (from SiO2 crucible) and C (from
graphite susceptor/supporter).
Typically, CO ≈ 1018 cm-3 and CC ≈ 1016 cm-3.
The O in CZ silicon often forms small SiO2 precipitates in the Si crystal under
normal processing conditions.
O and these precipitates can actually be very useful: provide mechanical
strength, internal gettering.
24. 3
Dopant Incorporation
Dopants are added to the melt to provide a controlled N or P doping level in the
wafers.
However, the dopant incorporation process is complicated by dopant segregation.
Generally, impurities “prefer to stay in the liquid” as opposed to being incorporated
into the solid.
This process is known as segregation. The degree of segregation is characterized
by the segregation coefficient, ko, for the impurity.
CS
CL
kO
CS
CL
CS and CL are the
impurity concentration
just on the either side
of the solid/liquid
interface.
25. 3
kO
CS
CL
Most k0 values are <1 which means the impurity prefers to stay in
the liquid. Thus as the crystal is pulled, dopant concentration will
increase. In other words, the distribution of dopant along the ingot
will be graded.
Dopant behavior during crystal growth
28. 3
Ingot Grinding
This means first
precisely aligning the
crystals, then
cylindrical grinding of
the ingot pieces to the
required diameter.
The final step is
grinding orientation
markings, such as
notches for large-
diameter wafers or
straight edges (flats)
on the side of small
wafers.
29. 3
Wafer Slicing
The first step when wafering the silicon
ingots is multi-wire slicing, which is the
slicing method commonly employed
today.
A very thin metal wire, which can be many
miles long, is pulled over the wire guide
rollers in such a way that a wire web with
very precise spacing is spanned.
Nozzles apply the slurry to the web while
the silicon ingot is slowly pushed through
the web. This technology makes it
possible to slice complete silicon ingots
into hundreds of silicon wafers in just one
step.
The individual process parameters must
be carefully monitored in order to
guarantee that the wafers are uniformly
thick and that the two faces of each wafer
are parallel to each another.
After slicing, edge rounding, mechanical
lapping and wet chemical etching is
performed before final chemical mechanical
polishing. The wet etching is typically:
3Si + 4HNO3 + 18HF 3H2SiF6 + 4NO + 8H2O
30. 3
Edge Rounding
Monocrystalline silicon is a very
brittle material with a high risk of
breaking.
Special care is consequently needed
in order to avoid mechanical
damages on the edge of the wafer.
The unrounded silicon wafer is mounted onto a grinding chuck and a profile rounding wheel
rounds the edge of the wafer.
The edge profile is rounded to match the customer specifications.
Each wafer is optimized in order to avoid processing damages and maximize the yields in the
component processes, such as CMP and lithography.
31. 3
Laser Marking
Laser marking is used to identify individual wafers or wafer batches in order to
allow manufacturing traceability.
Laser marking can take place in accordance with either industry standard or
customer specifications. As a rule, the markings contain information on the wafer
supplier, some technical information, and an individual wafer number.
32. 3
Wafer Lapping
For lapping, the silicon wafers are held in carrier wheels (lapping carriers) between
the upper and lower lapping plates, which rotate in opposite directions. The addition
of an abrasive (lapping slurry) helps remove roughly ten micrometers of silicon from
each wafer surface.
After the wafers have
been sliced and the
edges have been
rounded, the wafers are
lapped (or alternatively
ground) in order to
increase the parallelism
of the silicon wafer
surfaces and to remove
any damage below the
surface caused by the
slicing process.
33. 3
Wafer Etching and Cleaning
the silicon wafers are etched and cleaned in order to eliminate any remaining
mechanical damage. Alkaline solutions, acids, or a combination of the two can be
used for the etching.
34. 3
Wafer Polishing
Polishing makes the silicon
wafer surface smooth as
glass and further improves
the flatness.
The wafers are mounted on
support plates and pressed
against a polishing cloth
that lies on a polishing
plate.
Wafers with a diameter of 200mm or less are usually polished on one side.
Wafers with a diameter of 300mm are polished on both sides.
Like in the lapping process, the wafers are held by plates and simultaneously polished on the
front and back by upper and lower polishing plates.
The polishing agent (polishing slurry) and the pressure scheme determine the finished wafer’s
surface quality and flatness.
Chemical mechanical polishing
37. 3
Steps for Wafer Preparation
Crystal Growth
Remove seed and
Other end of ingot
Wafer Slicing by
diamond saw
Wafer Lapping and
Edge Grind by Al2O3
and glycerine
Etching for removing
surface damage
Polishing
Cleaning
Inspection
Packaging
Grinding to special
diameter and ground
some flat region