1.Silicon Manufacturing
a) Czochralski method.
b) Wafer Manufacturing
c) Crystal structure
2.Photolithography
a) Photoresists
b) Photomask and Reticles
c) Patterning
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.
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.
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.
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.
Are you looking to buy Si Wafer? We are a leading supplier of Silicon wafers across six continents in over 45 countries. Call (561) 842-4441 or Shop at our website.
Different types of Nanolithography technique.
Types: Electron beam lithography, Photolithography, electron-beam writing, ion- lithography, X-ray lithography, and related images, concepts and graphical views.
I hope this presentation helpful for you.
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Are you looking to buy Si Wafer? We are a leading supplier of Silicon wafers across six continents in over 45 countries. Call (561) 842-4441 or Shop at our website.
Different types of Nanolithography technique.
Types: Electron beam lithography, Photolithography, electron-beam writing, ion- lithography, X-ray lithography, and related images, concepts and graphical views.
I hope this presentation helpful for you.
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Silicon Quest International, Inc is a first-rate supplier of Wafer Thinning, LED Wafers, and SiGe on Silicon, SiGe Wafers, and Float Zone Ingots, Silicon Wafers for MEMS and Wafer Reclaim and Services.
MONOLITHIC IC PROCESSES A monolithic integrated circuit (IC) is a set of circuitry on a single semiconductor plate or chip rather than built of separate elements as a discrete circuit is.
Lithographic photomasks are typically transparent fused silica blanks covered with a pattern defined with a chrome metal-absorbing film. Photomasks are used at wavelengths of 365 nm, 248 nm, and 193 nm. Photomasks have also been developed for other forms of radiation such as 157 nm, 13.5 nm (EUV), X-ray, electrons, and ions; but these require entirely new materials for the substrate and the pattern film.
Fabrication of microfluidic channels in glass and siliconYichen Sun
Microfluidic channels in glass and silicon chips are fabricated in the cleanroom. Their acoustic focusing properties are then tested and reported in this project report (MEMS 5801).
Kerala Engineering Architecture Medical is an entrance examination series for admissions to various professional degree courses in the state of Kerala, India. It is conducted by the Office of the Commissioner of Entrance Exams run by the Government of Kerala
Paleontology is the study of the history of life on Earth as based on fossils. Fossils are the remains of plants, animals, fungi, bacteria, and single-celled living things that have been replaced by rock material or impressions of organisms preserved in roc
The ways in which an element—or compound such as water—moves between its various living and nonliving forms and locations in the biosphere is called a biogeochemical cycle. Biogeochemical cycles important to living organisms include the water, carbon, nitrogen, phosphorus, and sulfur cycles.
The AC and DC bridge both are used for measuring the unknown parameter of the circuit. The AC bridge measures the unknown impedance of the circuit. The DC bridge measures the unknown resistance of the circuit.
The Wien bridge is a type of bridge circuit that was developed by Max Wien in 1891. The bridge consists of four resistors and two capacitors. At the time of the Wien bridge's invention, bridge circuits were a common way of measuring component values by comparing them to known values.
For most of us, our name existed even before we did.
In anticipation of our arrival, our parents went through an ultra stressful process of narrowing down dozens of potential names until they chose the perfect one.
Luckily they did, because whatever your name is, it has followed you throughout your entire life; and in some cases, people may have heard of your name before they’ve ever met you.
When it comes to how to name an app, it’s of similar importance as naming a child. The name of your app will follow your brand forever, and in many cases, potential users will hear the name before they ever actually use your app.
flora and fauna of himachal pradesh and keralaAJAL A J
flora and fauna of himachal pradesh and kerala
A green pearl in the Himalayan crown, Himachal Pradesh is blessed with a rich flora and fauna that graces the land with grandeur and majesty. Other animals that can be sighted in the wild include the ibex, wild yak, ghoral deer, musk deer, Himalayan black bear, brown bear, leopards and the Himalayan Thar. Also kerala is gods on country
Bachelor of Science in Cardio-vascular technology is an undergraduate course in cardiology. These technologists assist the physicians in the diagnosis and the treatment of cardiac (heart) and peripheral vascular conditions (blood vessels). The cardiovascular technologists are also responsible for preparing the patients for open-heart surgeries and pacemaker implantation surgeries. The technologists also monitor the patient’s cardiac parameters while they undergo the surgery. B. Sc. in Cardiovascular technology is a three years’ full-time undergraduate course and is an interesting and important course in medicine.
`Remove Unprofitable Products and Services. The products or services with the highest gross profit margin are the most important to your business. ...
Find New Customers. New customers can help grow your business. ...
Increase your Conversion Rate. ...
Review Current Pricing Structure. ...
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Polycystic ovary syndrome (PCOS) is a hormonal disorder common among women of reproductive age. Women with PCOS may have infrequent or prolonged menstrual periods or excess male hormone (androgen) levels. The ovaries may develop numerous small collections of fluid (follicles) and fail to regularly release eggs
Are you an NRI and aiming to come back to India to pursue graduation from the top-tier colleges of India?
Then, you’re halfway there. Being an NRI, your top preference would be IITs and NITs of India. If that's the case, you must know the fee structure of both the IITs, NITs (under DASA scheme), Centrally Funded Institutions and State-Level Govt. Engineering Colleges.
Note: According to the latest update from DASA, from session 2021-22 onwards, JEE Rank is made mandatory for NRI/PIO/OCI Students to be eligible for DASA & CIWG Schemes. Hence, 2020-21 will be the last year when SAT 2 scores will be considered for DASA/CIWG Scheme.
Subjects to study if you want to work for a charityAJAL A J
The charity sector can be competitive and experience, volunteer or otherwise, can count for a lot. But there are ways to make that third sector CV stand out from the competition. Why not take some courses? A course can be a great way to make your application shine and an opportunity to learn new skills and ideas.
Joint Entrance Examination - Main or commonly known as JEE Main is a national level entrance exam conducted by the NTA to offer admission to BE/BTech, BPlan and BArch courses at the IIITs (Indian Institute of Information Technology), NITs (National Institute of Technology) and other Centrally Funded Technical Institutions (CFTIs) across the country.
Vaccine management system project report documentation..pdfKamal Acharya
The Division of Vaccine and Immunization is facing increasing difficulty monitoring vaccines and other commodities distribution once they have been distributed from the national stores. With the introduction of new vaccines, more challenges have been anticipated with this additions posing serious threat to the already over strained vaccine supply chain system in Kenya.
Student information management system project report ii.pdfKamal Acharya
Our project explains about the student management. This project mainly explains the various actions related to student details. This project shows some ease in adding, editing and deleting the student details. It also provides a less time consuming process for viewing, adding, editing and deleting the marks of the students.
Automobile Management System Project Report.pdfKamal Acharya
The proposed project is developed to manage the automobile in the automobile dealer company. The main module in this project is login, automobile management, customer management, sales, complaints and reports. The first module is the login. The automobile showroom owner should login to the project for usage. The username and password are verified and if it is correct, next form opens. If the username and password are not correct, it shows the error message.
When a customer search for a automobile, if the automobile is available, they will be taken to a page that shows the details of the automobile including automobile name, automobile ID, quantity, price etc. “Automobile Management System” is useful for maintaining automobiles, customers effectively and hence helps for establishing good relation between customer and automobile organization. It contains various customized modules for effectively maintaining automobiles and stock information accurately and safely.
When the automobile is sold to the customer, stock will be reduced automatically. When a new purchase is made, stock will be increased automatically. While selecting automobiles for sale, the proposed software will automatically check for total number of available stock of that particular item, if the total stock of that particular item is less than 5, software will notify the user to purchase the particular item.
Also when the user tries to sale items which are not in stock, the system will prompt the user that the stock is not enough. Customers of this system can search for a automobile; can purchase a automobile easily by selecting fast. On the other hand the stock of automobiles can be maintained perfectly by the automobile shop manager overcoming the drawbacks of existing system.
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Industrial Training at Shahjalal Fertilizer Company Limited (SFCL)MdTanvirMahtab2
This presentation is about the working procedure of Shahjalal Fertilizer Company Limited (SFCL). A Govt. owned Company of Bangladesh Chemical Industries Corporation under Ministry of Industries.
Quality defects in TMT Bars, Possible causes and Potential Solutions.PrashantGoswami42
Maintaining high-quality standards in the production of TMT bars is crucial for ensuring structural integrity in construction. Addressing common defects through careful monitoring, standardized processes, and advanced technology can significantly improve the quality of TMT bars. Continuous training and adherence to quality control measures will also play a pivotal role in minimizing these defects.
TECHNICAL TRAINING MANUAL GENERAL FAMILIARIZATION COURSEDuvanRamosGarzon1
AIRCRAFT GENERAL
The Single Aisle is the most advanced family aircraft in service today, with fly-by-wire flight controls.
The A318, A319, A320 and A321 are twin-engine subsonic medium range aircraft.
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About
Indigenized remote control interface card suitable for MAFI system CCR equipment. Compatible for IDM8000 CCR. Backplane mounted serial and TCP/Ethernet communication module for CCR remote access. IDM 8000 CCR remote control on serial and TCP protocol.
• Remote control: Parallel or serial interface.
• Compatible with MAFI CCR system.
• Compatible with IDM8000 CCR.
• Compatible with Backplane mount serial communication.
• Compatible with commercial and Defence aviation CCR system.
• Remote control system for accessing CCR and allied system over serial or TCP.
• Indigenized local Support/presence in India.
• Easy in configuration using DIP switches.
Technical Specifications
Indigenized remote control interface card suitable for MAFI system CCR equipment. Compatible for IDM8000 CCR. Backplane mounted serial and TCP/Ethernet communication module for CCR remote access. IDM 8000 CCR remote control on serial and TCP protocol.
Key Features
Indigenized remote control interface card suitable for MAFI system CCR equipment. Compatible for IDM8000 CCR. Backplane mounted serial and TCP/Ethernet communication module for CCR remote access. IDM 8000 CCR remote control on serial and TCP protocol.
• Remote control: Parallel or serial interface
• Compatible with MAFI CCR system
• Copatiable with IDM8000 CCR
• Compatible with Backplane mount serial communication.
• Compatible with commercial and Defence aviation CCR system.
• Remote control system for accessing CCR and allied system over serial or TCP.
• Indigenized local Support/presence in India.
Application
• Remote control: Parallel or serial interface.
• Compatible with MAFI CCR system.
• Compatible with IDM8000 CCR.
• Compatible with Backplane mount serial communication.
• Compatible with commercial and Defence aviation CCR system.
• Remote control system for accessing CCR and allied system over serial or TCP.
• Indigenized local Support/presence in India.
• Easy in configuration using DIP switches.
COLLEGE BUS MANAGEMENT SYSTEM PROJECT REPORT.pdfKamal Acharya
The College Bus Management system is completely developed by Visual Basic .NET Version. The application is connect with most secured database language MS SQL Server. The application is develop by using best combination of front-end and back-end languages. The application is totally design like flat user interface. This flat user interface is more attractive user interface in 2017. The application is gives more important to the system functionality. The application is to manage the student’s details, driver’s details, bus details, bus route details, bus fees details and more. The application has only one unit for admin. The admin can manage the entire application. The admin can login into the application by using username and password of the admin. The application is develop for big and small colleges. It is more user friendly for non-computer person. Even they can easily learn how to manage the application within hours. The application is more secure by the admin. The system will give an effective output for the VB.Net and SQL Server given as input to the system. The compiled java program given as input to the system, after scanning the program will generate different reports. The application generates the report for users. The admin can view and download the report of the data. The application deliver the excel format reports. Because, excel formatted reports is very easy to understand the income and expense of the college bus. This application is mainly develop for windows operating system users. In 2017, 73% of people enterprises are using windows operating system. So the application will easily install for all the windows operating system users. The application-developed size is very low. The application consumes very low space in disk. Therefore, the user can allocate very minimum local disk space for this application.
CFD Simulation of By-pass Flow in a HRSG module by R&R Consult.pptxR&R Consult
CFD analysis is incredibly effective at solving mysteries and improving the performance of complex systems!
Here's a great example: At a large natural gas-fired power plant, where they use waste heat to generate steam and energy, they were puzzled that their boiler wasn't producing as much steam as expected.
R&R and Tetra Engineering Group Inc. were asked to solve the issue with reduced steam production.
An inspection had shown that a significant amount of hot flue gas was bypassing the boiler tubes, where the heat was supposed to be transferred.
R&R Consult conducted a CFD analysis, which revealed that 6.3% of the flue gas was bypassing the boiler tubes without transferring heat. The analysis also showed that the flue gas was instead being directed along the sides of the boiler and between the modules that were supposed to capture the heat. This was the cause of the reduced performance.
Based on our results, Tetra Engineering installed covering plates to reduce the bypass flow. This improved the boiler's performance and increased electricity production.
It is always satisfying when we can help solve complex challenges like this. Do your systems also need a check-up or optimization? Give us a call!
Work done in cooperation with James Malloy and David Moelling from Tetra Engineering.
More examples of our work https://www.r-r-consult.dk/en/cases-en/
2. HISTORY
19th
Century - Solid-State Rectifiers
1907 - Application of Crystal
Detector in Radio Sets
1947 - BJT Constructed by Bardeen
and Brattain
1959 – Integrated Circuit
Constructed by Kilby
5. 3.Oxide Growth & Removal
a) Oxide Growth & Deposition
b) Oxide Removal
c) Other effects
d) Local Oxidation
4. Diffusion & Ion Implantation
a) Diffusion
b) Other effects
c) Ion Implantation
Semiconductor Manufacturing
Process (cont)
7. FABRICATING
SILICON
Quartz, or Silica, Consists of Silicon Dioxide
Sand Contains Many Tiny Grains of Quartz
Silicon Can be Artificially Produced by
Combining Silica and Carbon in Electric
Furnice
Gives Polycrystalline Silicon (multitude of
crystals)
Practical Integrated Circuits Can Only be
Fabricated from Single-Crystal Material
8. CRYSTAL GROWTH
Czochralski Process is a
Technique in Making
Single-Crystal Silicon
A Solid Seed Crystal is
Rotated and Slowly
Extracted from a Pool of
Molten Si
Requires Careful Control
to Give Crystals Desired
Purity and Dimensions
9. CYLINDER OF
MONOCRYSTALLINE
The Silicon Cylinder is
Known as an Ingot
Typical Ingot is About 1 or 2
Meters in Length
Can be Sliced into Hundreds
of Smaller Circular Pieces
Called Wafers
Each Wafer Yields Hundreds
or Thousands of Integrated
Circuits
10. WAFER MANUFACTURING
The Silicon Crystal is Sliced by Using a Diamond-Tipped Saw
into Thin Wafers
Sorted by Thickness
Damaged Wafers Removed During Lapping
Etch Wafers in Chemical to Remove any Remaining Crystal
Damage
Polishing Smoothes Uneven Surface Left by Sawing Process
11. THE CRYSTAL STRUCTURE
OF SILICON
A Unit Cell Has 18
Silicons Atoms
Weak Bonding Along
Cleavage Planes
Wafer Splits into 4 or 6
Wedge-Shaped
Fragments
Miller Indices is Used to
Assign to Each Possible
Plane Passing Through
the Crystal Lattice
14. Photolithography
Photoresist
The first step in the photolithography process is to
develop a mask, which will be typically be a chromium
pattern on a glass plate.
Next, the wafer is then coated with a polymer which is
sensitive to ultraviolet light called a photoresist.
Afterward, the photoresist is then developed which
transfers the pattern on the mask to the photoresist
layer.
15. Photolithography
Photoresist
There are two basic types of Photoresists Positive and
Negative.
Positive resists.
Positive resists decomposes ultraviolet light. The resist is exposed with UV
light wherever the underlying material is to be removed. In these resists,
exposure to the UV light changes the chemical structure of the resist so
that it becomes more soluble in the developer. The exposed resist is then
washed away by the developer solution, leaving windows of the bare
underlying material. The mask, therefore, contains an exact copy of the
pattern which is to remain on the wafer.
16. Photolithography
Photoresist
Negative resists
Exposure to the UV light causes the negative resist to become
polymerized, and more difficult to dissolve. Therefore, the negative resist
remains on the surface wherever it is exposed, and the developer solution
removes only the unexposed portions. Masks used for negative
photoresists, therefore, contain the inverse (or photographic "negative")
of the pattern to be transferred.
17. Photolithography
Model
Figure 1a shows a thin film of
some material (eg, silicon
dioxide) on a substrate of some
other material (eg, a silicon
wafer).
Photoresist layer (Figure 1b )
Ultraviolet light is then shone
through the mask onto the
photoresist (figure 1c).
18. Photolithography
Model (cont)
The photoresist is then
developed which transfers the
pattern on the mask to the
photoresist layer (figure 1d).
A chemical (or some other
method) is then used to remove
the oxide where it is exposed
through the openings in the
resist (figure 1e).
Finally the resist is removed
leaving the patterned oxide
(figure 1f).
19. Photolithography
Photomasks and Reticles
Photomask
This is a square glass plate with a patterned emulsion of
metal film on one side. The mask is aligned with the
wafer, so that the pattern can be transferred onto the
wafer surface. Each mask after the first one must be
aligned to the previous pattern.
20. Photolithography
Photomasks and Reticles
When a image on the photomask is projected several time side
by side onto the wafer, this is known as stepping and the
photomask is called a reticle.
An common reticle is the 5X
The patterns on the 5X reticle are reduced 5 times when projected
onto the wafer. This means the dies on the photomask are 5 times
larger than they are on the final product. There are other kinds of
reduction reticles (2X, 4X, and 10X), but the 5X is the most
commonly used. Reduction reticles are used on a variety of steppers,
the most common being ASM, Canon, Nikon, and GCA.
22. Photolithography
Photomasks and Reticles
Once the mask has been accurately aligned with the pattern
on the wafer's surface, the photoresist is exposed through the
pattern on the mask with a high intensity ultraviolet light.
There are three primary exposure methods: contact,
proximity, and projection.
23. Photolithography
Patterning
The last stage of Photolithography is a process called ashing.
This process has the exposed wafers sprayed with a mixture of
organic solvents that dissolves portions of the photoresist .
Conventional methods of ashing require an oxygen-plasma ash,
often in combination with halogen gases, to penetrate the crust
and remove the photoresist. Usually, the plasma ashing process
also requires a follow-up cleaning with wet-chemicals and
acids to remove the residues and non-volatile contaminants that
remain after ashing. Despite this treatment, it is not unusual to
repeat the "ash plus wet-clean" cycle in order to completely
remove all photoresist and residues.
25. SiO2 growth is a key process step in manufacturing all
Si devices
- Thick (- 1µm) oxides are used for field oxides
(isolate devices from one another )
- Thin gate oxides (-100 Å) control MOS devices
- Sacrificial layers are grown and removed to
clean up surfaces
The stability and ease of formation of SiO2 was one of
the reasons that Si replaced Ge as the semiconductor
of choice.
26. The simplest method of producing an oxide layer
consists of heating a silicon wafer in an oxidizing
atmosphere.
27. Dry oxide - Pure dry oxygen is employed
Disadvantage
- Dry oxide grows very slowly.
Advantage
- Oxide layers are very uniform.
- Relatively few defects exist at the oxide-silicon
interface (These defects interfere with the proper
operation of semiconductor devices)
- It has especially low surface state charges and thus make
ideal dielectrics for MOS transistors.
28. Wet oxide - In the same way as dry oxides, but steam
is injected
Disadvantage
- Hydrogen atoms liberated by the decomposition of the
water molecules produce imperfections that may
degrade the oxide quality.
Advantage
- Wet oxide grows fast.
- Useful to grow a thick layer of field oxide
29. Deposited Oxides
Oxide is frequently employed as an insulator between two
layers of metalization. In such cases, some form of
deposited oxide must be used rather than the grown oxides.
Deposited oxides can be produced by various reactions
between gaseous silicon compounds and gaseous oxidizers.
Deposited oxides tend to possess low densities and large
numbers of defect sites. Not suitable for use as gate
dielectrics for MOS transistors but still acceptable for use as
insulating layers between multiple conductor layers, or as
protective overcoats.
30. Key Variables in Oxidation
Temperature
- reaction rate
- solid state diffusion
Oxidizing species
- wet oxidation is much faster than dry oxidation
Surface cleanliness
- metallic contamination can catalyze reaction
- quality of oxide grown (interface states)
31. Etching
Etching is the process where unwanted areas of films are
removed by either dissolving them in a wet chemical
solution (Wet Etching) or by reacting them with gases in a
plasma to form volatile products (Dry Etching).
Resist protects areas which are to remain. In some cases a
hard mask, usually patterned layers of SiO2 or Si3N4, are used
when the etch selectivity to photoresist is low or the etching
environment causes resist to delaminate.
This is part of lithography - pattern transfer.
32.
33. Wet Chemical Etching
Wet etches:
- are in general isotropic
(not used to etch features less than ≈ 3 µm)
- achieve high selectivities for most film
combinations
- capable of high throughputs
- use comparably cheap equipment
- can have resist adhesion problems
- can etch just about anything
34. Example Wet Processes
For SiO2 etching
- HF + NH4F+H20 (buffered oxide etch or BOE)
For Si3N4
- Hot phosphoric acid: H3PO4 at 180 °C
- need to use oxide hard mask
Silicon
- Nitric, HF, acetic acids
- HNO3 + HF + CH3COOH + H2O
Aluminum
- Acetic, nitric, phosphoric acids at 35-45 °C
- CH3COOH+HNO3+H3PO4
35. What is a plasma
(glow discharge)?
A plasma is a partially ionized gas made up of equal parts
positively and negatively charged particles.
Plasmas are generated by flowing gases through an electric
or magnetic field.
These fields remove electrons from some of the gas
molecules. The liberated electrons are accelerated, or
energized, by the fields.
The energetic electrons slam into other gas molecules,
liberating more electrons, which are accelerated and
liberate more electrons from gas molecules, thus sustaining
the plasma.
38. Dry or Plasma Etching
Combination of chemical and physical etching –
Reactive Ion Etching (RIE)
Directional etching due to ion assistance.
In RIE processes the wafers sit on the powered
electrode. This placement sets up a negative bias on the
wafer which accelerates positively charge ions toward the
surface. These ions enhance the chemical etching
mechanisms and allow anisotropic etching.
Wet etches are simpler, but dry etches provide better
line width control since it is anisotropic.
39. Other Effects of Oxide
Growth and Removal
Oxide Step
- The differences in oxide thickness and in the depths
of the silicon surfaces combine to produce a
characteristic surface discontinuity
The growth of a thermal oxide affects the doping levels
in the underlying silicon
The doping of silicon affects the rate of oxide growth
40. Local Oxidation of Silicon
(LOCOS)
LOCOS: localized oxidation of silicon using silicon
nitride as a mask against thermal oxidation.
A technique called local oxidation of silicon (LOCOS)
allows the selective growth thick oxide layers
CMOS and BiCMOS processes employ LOCOS to grow
a thick field oxide over electrically inactive regions of the
wafer
42. WN-Junction Fabrication (Earliest method)
Process:
Opposite polarity doping atoms are added to molten silicon
during the Czochralski process to create in-grown junctions in
the ingot.
Repeated counterdopings can produce multiple junctions within
the crystal.
Disadvantages
Inability to produce differently doped areas in different parts of
the wafer.
The thickness and planarity of grown junctions are difficult to
control.
Repeated counterdopings degrade the electrical properties of the
silicon.
43. The Planar Process
Advantages:
• The planar process does not require multiple
counterdopings of the silicon ingot.
• This process allows more precise control of junction
depths and dopant distributions.
44. Methods of planar process
Diffusion
• A uniformly doped ingot is
sliced into wafers.
• An oxide film is then grown
on the wafers.
• The film is patterned and
etched using photolithography
exposing specific sections of
the silicon.
• The wafers are then spun with
an opposite polarity doping
source adhering only to the
exposed areas.
• The wafers are then heated in
a furnace (800-1250 deg.C) to
drive the doping atoms into
the silicon.
Ion Implantation
• A particle accelerator is used
to accelerate a doping atom so
that it can penetrate a silicon
crystal to a depth of several
microns
•
Lattice damage to the crystal
is then repaired by heating
the wafer at a moderate
temperature for a few
minutes. This process is called
annealing.
46. Comparison of Diffusion and Ion
Implantation
Diffusion is a cheaper and more simplistic method, but
can only be performed from the surface of the wafers.
Dopants also diffuse unevenly, and interact with each
other altering the diffusion rate.
Ion implantation is more expensive and complex. It does
not require high temperatures and also allows for
greater control of dopant concentration and profile. It is
an anisotropic process and therefore does not spread the
dopant implant as much as diffusion. This aids in the
manufacture of self-aligned structures which greatly
improve the performance of MOS transistors.
47. References
The Art of Analog Layout by Alan Hastings 2001 Prentice-
Hall
Semiconductor Devices by Mauro Zambuto 1989 McGraw-
Hill
Semiconductor Manufacturing Technology by Quirk and
Serda 2001 Prentice-Hall