Semiconductor Manufacturing Techniques Quiz

Nanofabrication Part I

• Nanofabrication is a crucial area in physics
• Key technologies are covered, along with their applications
• Different tools and processes are highlighted.

SEM Cross Section Silicon Device

• This image is a Scanning Electron Microscope (SEM) cross-section of a silicon device.
• The image shows the detailed structure and features of the silicon device at the nanometer level.
• Technical information is included (e.g. voltage, current, magnification, etc.) about the SEM image

Intel unveils 22nm 3D Ivy Bridge processor

• Intel introduced the 22nm 3D Ivy Bridge processor in 2011
• This processor utilized new Tri-Gate "3D" transistors to improve efficiency compared to earlier planar chip designs.
• The Tri-Gate transistors were a key component to improve performance.

Moore's Law

• The number of transistors on a chip doubles approximately every two years.
• Intel has played a significant role in the development and adoption of this technology.
• The original graph from 1965 illustrated the exponential increase in transistor counts over time.

Evolution of Transistor

• The implementation of high-k and metal materials represents a significant advancement in transistor technology.
• This advancement follows the introduction of polysilicon gate MOS transistors in the late 1960s.
• The introduction of high-k and metal materials was a major breakthrough from previous transistors.

Lithography

• Photolithography is the process of transferring a pattern from a template to a substrate.
• A common approach using photoresist involves exposing, developing, and etching procedures.
• This technique is essential for fabricating microchips and other nanostructures.

Pattern Transfer

• Integrated circuits (ICs) and micro-fabricated MEMS devices are formed by defining patterns in various layers.
• The desired pattern is transferred photographically from an optical plate to a photosensitive film coating the wafer.
• Subsequent chemical and physical processes remove or add materials to create the final pattern.

Main steps in Lithography

• Photoresist (light-sensitive material) is coated on a wafer.
• Certain areas of the wafer are exposed to light.
• Exposed and Unexposed areas of the photoresist are etched differently.
• The photoresist acts as a mask.

Photoresist

• Photoresist is a liquid film that can be placed on a substrate.
• It's typically composed of three components: resin, sensitizer, and solvent.
• Exposure patterns selectively harden parts of the photoresist.

Lithographic Process

• Preparation of the substrate surface follows:
• Coating, Pre-bake, Alignment, Exposure, Development, Post-bake
• Etching of material using photoresist as a mask, Stripping, Cleaning
• This sequence enables the fabrication of various patterns onto the substrate.

Top Down Processing Techniques

• Two major techniques are used for patterning :
• Subtractive etching and Lift-off
• In subtractive etching photoresist is applied to a layer to be patterned and then the undesired material is removed.
• In Lift-off the patterned layer is deposited on top of the photoresist and the undesired material is lifted off when the resist is removed.

Subtractive and Additive Creation of Nanostructures

• Subtractive etching techniques can be applied to nanotechnology processes.
• High precision and increased lateral resolution are necessary in nanofabrication processes.
• The volume of material is drastically decreased in nanofabrication.

Nanostructure Generation by Lift-off Processes

• Similar to subtractive methods, the material layer is deposited on top of a mask.
• Lift-off process is independent of the characteristics of the patterned layer to be achieved.
• The quality of the final patterned material depends heavily on the quality of the mask and the ability to deposit the material properly.

Novel Lithographic Processes

• E-beam lithography
• Ion-beam lithography
• X-ray lithography
• These methods offer advanced capabilities for nanoscale patterning.

Energy of Light Source

• Key parameter values for various UV and x-ray wavelengths and energies are provided
• The energy of photons is directly associated with their wavelength.

Electron Beam Lithography

• A direct writing technique used to fabricate patterns on wafers.
• Throughput and cost are disadvantages.
• Resolution stops at 20nm due to diffraction limitation.

Implantation

• Essential in modern IC manufacturing for doping semiconductors.
• lons are steered into the substrate to modify or dope the material's properties.
• The most commonly implanted species include Arsenic, Phosphorus, Boron, Boron Difluoride, Indium, Antimony, Germanium, Silicon, Nitrogen, Hydrogen, and Helium.

Molecular Beam Epitaxy (MBE)

• MBE is a deposition technique used to create atomically perfect layers.
• The growth happens under ultra-high vacuum (UHV) conditions using evaporation.
• Methods include homoepitaxy and heteroepitaxy.

Surface interactions during MBE growth

• Adsorption, desorption, migration, and incorporation into the film are crucial processes concerning surface interactions.
• Doping of substrates is another significant use of MBE.
• Lattice integrity is maintained during the doping process.

###Basic Process Chamber and Source Layout

• Visual diagram illustrating a typical layout for MBE equipment
• The arrangement of different sources/substrates is explained.

Assessment

• The assessment criteria for relevant courses are provided for a module.
• Percentage breakdowns are present for each task/exercise.

Nanofabrication Part II

• The next section of procedures and applications related to nanofabrication.

Assessment Topics and Date

• Upcoming assessment dates, including topics to be covered for an exam
• Details about the format are provided for the assessment/exam.

The preparation of Nanostructures

• The techniques are present for the preparation of nanostructures
• Details about different materials and related information are included.

Miniaturization to the nanometer scale

• Important trends in science and technology
• Chemistry, engineering, and physics are connected for research

Nanofabrication: Top down and bottom-up fabrication

• Two main approaches - top-down and bottom-up
• Top-down approach miniaturizes using current technologies, Bottom-up involves construction atom by atom using molecular building blocks.

Planar Technology

• Realization of this technology through layer by layer technique.
• Thickness ranges from 100μm to 1nm.

The subtractive method

• This method starts with a thin layer deposition, followed by a masking layer.
• Then undesired parts of the required layer are etched away.

The additive or lift-off process

• The mask is deposited first on the substrate.
• The required layer is then deposited.
• Removal of the masking layer results in just the required layer.

Plasma Applications in Nanofabrication

• Application areas of plasma and its techniques
• The key ones included are Sputtering, Etching, Deposition, and Lithography among others
• These techniques modify surface properties in numerous ways.

Surface Processes

• Physical and chemical processes involving plasma and substrate interactions, are considered.
• Sputtering, a physical process, involves removal of materials due to collisions with energetic ions or fast neutals.
• Chemical processes refer to the chemical reactions between the substrate and plasma ions or neutrals with high chemical potentials

Consequences of such surface processes

• Examples of consequences are material removal, insertion, and modifications that affect the chemical composition of the wafer.
• Etching and Deposition are examples of the process outputs.

Deposition

• The methods for depositing thin coatings are included
• The processes for generating and transporting the reactants are listed
• The material deposition method involves the generation and transportation of the reactants.

Physical Vapour Deposition (PVD) and Sputtering

• Thin film deposition by a physical method
• Evaporation, transportation, reaction, and deposition are the main steps.
• Independent of the target material.

Evaporation

• A key step in PVD, where the target material is heated to create a plume.

Transport

• This refers to the movement/transfer of atoms/molecules from the target to the substrate.
• This process generally results in a linear motion.

Reaction

• Involves reaction between target atoms and reactants (e.g., gases).
• If products are formed, this step is necessary for the creation of alloys or materials like oxides.

Advantages of the Physical Vapour Deposition Process

• Improved properties, especially for inorganic and some organic materials
• Relatively environmentally friendly

Disadvantages of the Physical Vapour Deposition Process

• Line of sight technique so it's hard to coat undercuts, high costs, and slow deposition rates

Applications

• PVD coatings improve hardness, wear resistance, and oxidation resistance
• Aerospace, Automotive, Surgical/Medical, Dies/molds, and Cutting tools are some application areas.

Various Physical Vapour Deposition Techniques

• This section discusses different techniques for PVD, including thermal evaporation, magnetron sputtering, and pulsed laser deposition (PLD).

Magnetron Sputtering

• A technique that uses magnetic fields to confine charged particles within a vacuum chamber, leading to enhanced sputtering

Pulsed Laser Deposition (PLD)

• A deposition method using laser pulses to ablate materials, creating a plasma plume containing the ablated particles, which are subsequently deposited on a substrate.

Nanofabrication Part III

• The next set of procedures and application areas related to nanofabrication.

Continuous with Nanofabrication Processes

• The process of continuing nanofabrication processes.

Chemical Vapor Deposition (CVD)

• A process that involves controlled chemical reactions at low pressures to deposit materials.
• This process often requires heating the substrate to promote the activation of the reactants.

Atomic Layer Deposition (ALD)

• The process involves introducing reactants successively and sequentially in a controlled manner.
• The deposited material builds one layer at a time, resulting in a conformal layer without defects.

ALD Applications

• High-k gate oxides and storage capacitor dielectrics are typical applications.
• Other applications include passivation of crystal structures, and the creation of highly conformal coatings.

Etching

• Removal of unwanted material from substrates
• Wet or Dry chemical or physical processes may be used.

Wet etching vs dry etching

• Wet etching uses liquid reactants while dry etching employs gaseous reactants.
• Dry etching is often preferred for selectivity and anisotropy due to its less contamination
• Its also easier to control and stop processes involved

The three important parameters

• A process measure include Etch Rate, Selectivity, and Uniformity.

Selectivity

• The ability to etch one material without etching another is crucial for making complex patterns.

Uniformity

• Uniformity across a wafer is important to prevent variation in the quality of the resulting structure due to non-uniform plasma exposure.

Advantages of plasma etching

• Ease of automation, high purity and a reduction in chemical hazards and waste treatment
• Its is also anisotropic for achieving good geometries
• Useful for achieving high line-width resolution

Physical-Chemical Plasma Etching Process

• Plasma creation is the first step in generating plasma
• Chemical reaction on the substrate takes place with the assistance of ions

Order of the etching process

• Generation of etching species, Diffusion to surfaces, Adsorption, Reaction, and Desorption

Sidewall Passivation

• Deposition of non-volatile fluorocarbons on surfaces during etching.
• This technique is used to increase the degree of anisotropy and prevent etching through side walls.

Scanning Probe Microscopy (SPM)

• Techniques include Scanning Tunneling Microscopy (STM) and Atomic Force Microscopy (AFM)
• Scanning probe microscopes image surfaces at the atomic level.
• SPM images surfaces using a probe to scan.

Scanning Tunneling Microscopy (STM)

• Developed by Binning and Rohrer in 1981 and awarded a Nobel prize in 1986.
• Measures the current flowing through a very small gap between a sharp probe and the sample.
• This is necessary for mapping out surface profiles at atomic resolution at a fixed tip height

Scanning Tunneling Microscopy (STM)

• The sharpness of the tip determines the lateral resolution.
• Useful for analyzing surface structures at nanometer scales.
• Different types of STM operation exist and each has its own benefits
• Constant current and constant height are typical examples

Scanning Tunneling Microscopy (STM)

• An atomically sharp metallic tip mounted on a set of piezoelectric transducers.
• The spacing between the tip and the surface is measured within a few angstroms.
• A voltage difference drives electrons to tunnel through the vacuum gap.

The Vacuum Gap and Tunneling

• The tunneling current and distance relationship is exponential.
• The larger the gap, the smaller the tunneling current.
• A very small gap permits electrons to tunnel quantum mechanically across the vacuum gap.

Scanning Tunneling Microscopy (STM)

• The decay constant is crucial to work functions for determining the sensitivity of the STM method.

Scanning Tunneling Microscopy(STM)

• The piezoelectric transducer stage in the STM allows fine positioning and careful control of the tip.
• The tip is biased relative to the sample and a feedback mechanism allows for control or variations, enabling a variety of modes to be controlled.

Scanning Tunneling Microscopy (STM)

• Piezoelectric transducers are exceptionally sensitive to voltage differences.
• This sensitivity allows precise tip positioning.
• A proper STM setup normally involves special dampening features to minimise outside interference.

Scanning Tunneling Spectroscopy (STS)

• STS is a type of analysis that can be carried out at any point on a surface at a particular distance which is often fixed.
• The bias is varied from a negative to positive value, and the current tunneling characteristic is measured as the voltage changes.
• The IV characteristic plot gives information about the physical and electronic properties of the surface.

Atomic Force Microscopy (AFM)

• A related scanning-probe technique similar to STM in principle but involves less challenging setup procedures.
• A tiny cantilever with a tip is moved over the surface.
• Tiny forces between tip and sample atoms deflect the cantilever.

Atomic Force Microscopy (AFM)

• AFM uses a laser beam to measure the deflection of a very small cantilever which is part of a nano-mechanical "lever" and the deflection is measured using a laser.
• It is relatively simpler to set up than an STM method with less challenging setup procedures.
• The resolution is not as good as STM but is still good enough for useful analysis.

Atomic Force Microscopy (AFM)

• Insulators can be studied more easily with AFM because there is no tunneling current involved
• Surface magnetism can be probed as magnetic force microscopy (MFM).
• Chemical species can be probed with chemically active tips to get a molecular sensitivity map (CPM)

Surface Analysis Techniques

• Techniques are useful for studying various aspects like chemical composition, surface structures, and electronic properties.
• No one technique is sufficient to address all the needed information at once.

Electron Microscopy (SEM)

• SEM is a well-established instrument for imaging physical properties.
• It uses a focused electron beam scanned across the sample surface.
• Measurements in the SEM system include the current from specimen to ground.

Electron Microscopy (SEM)

• Alternatively, characteristic x-rays or secondary electron fluxes can be registered
• The image gives areas, variations, and chemical compositions that are displayed using colour.
• The sample has to be conducting as a current is needed.

Optical Methods

• Optical methods are advantageous because they don't need any vacuum.
• The relatively low energy of photons means the methods are generally much safe.
• Spectroscopic ellipsometry is a significant optical method.

Vacuum Science

• Principles and types of vacuum pumps and general operational aspects
• The basic physical principles at the heart of diverse ways of producing vacuum
• Different types of pumps are considered and how they operate mechanically to remove gas molecules

Vacuum Pumps

• Pumps are classified either as : Mechanical(momentum removal) or Non-mechanical (entrapment)
• The different types of pumps that fit into each category are also listed as examples.

Rotary Vane Pump

• This is a first-stage backing pump that operates over a range from atmosphere to low 10-3 mbar.
• Vane design helps in gas collection/compression and displacement to the outlet to achieve this range.

Roots Pump or Roots Blower

• This second stage pump is usually used with a backing pump.
• It consists of two precision figure-eight or similarly shaped symmetrical rotors which rotate in opposite directions.
• The rotors are synchronised and do not touch each other or the chamber wall

Roots Pump or Roots Blower

• These are suited to processes with large gas loads as found in plasma reactors.
• Speed of these pumps is high as there is minimal friction due to the small gap between rotors, and without any lubrication.

Turbomolecular (turbo) pump

• These are second-stage pumps, generally needed to follow a Rotary type pump.
• The system consists of a stack of spinning rotor discs that are interleaved with stators to impart momentum to gas molecules, forcing them out of the chamber.

Turbomolecular Pump

• Disc thickness and slot angle variations influence the achieved pumping speed.

Diffusion Pump

• These second-stage pumps use the principle of vapour diffusion to generate a high flow of molecules.
• The process involves heating a suitable fluid (e.g. hydrocarbons, mercury) and generating a supersonic vapour stream through a nozzle.

Diffusion Pump

• The vapour interacts with the incoming gas, removing it from the chamber through adsorption mechanisms on the cooled walls.

Sorption (Sorb) Pump

• These physically simple pumps use a molecular sieve sorbent material.
• The material is porous, high surface area to effectively adsorb gas by physical adsorption.

Getter-ion or Sputter-Ion(ion) pump

• Used for third or fourth stage pumping
• Effective for the range from low 10-5 - 10-12 mbar

Getter-ion or Sputter-Ion pump

• The sputtering of titanium from cathodes to give a fresh film of titanium deposited in the anodes.
• This process is based on the adsorption of ions and uses a massively parallel array of elements.

Getter ion or sputter ion pump

• This method involves ionising gas and colliding positive ions with titanium cathodes, sputtering and further ionising more gas molecules
• The magnetic field confines electrons to spiral paths, thus increasing the likelihood of gas ionisation.

The ion Pump and its operation

• This final stage operates at pressures of 10-5mbar or below
• These pumps are mainly used to remove gas from the chambers which have been roughened or brought down sufficiently
• Ions are pumped to the electrodes and no need for regular regeneration.

The current flow

• Due to the motion of gas ions, the current represents a direct measure of gas pressure.
• The nature of the pump is suited to applications where it's crucial to have a vibration free environment.

Ion Pumps commonly used

• These pumps are used as a final stage in UHV pumps.
• A range of sizes are available - the smaller ones are often used to evacuate tube attachments.
• High speeds of hundreds of litres per second can be obtained in larger ion pumps.

Sublimation (TSP) pump

• Fourth stage vacuum pump for ultra-high-vacuum (UHV) applications.
• Relies on the principle of gettering.

Sublimation (TSP) pump

• Usually uses titanium as getter material as it has high efficiency
• The metal is placed in the chamber to evaporate and form a thin film layer.
• Gases get trapped on this surface due to the process of chemisorption.

Cryopump

• An increasingly popular pump in UHV applications.
• Consists of a series of manifolds which produces a large surface area for physisorption.
• The surface is maintained at extremely low temperatures.

Cryopump and operation

• Cryopumps are quiet, clean and efficient as they are vibration free.
• Require a constant supply of liquid helium, which makes it expensive.
• An entrapment pump with limited capacity, and needs backing from another vacuum chamber to operate.

Pressure Measurement

• A broad range of pressure values are employed in industrial and research contexts.
• Different types of gauges are employed depending on the range of pressure values.
• Location and calibration of the gauge are crucial to obtain accurate and meaningful measurements.

Capacitance Manometer

• A type of absolute gauge that uses a metal diaphragm to measure the pressure.
• This approach provides a stable measurement across a wide range of pressures from high pressures to very low ones (UHV)
• It employs a very sensitive capacitance bridge to measure the diaphragm displacement and converts that into a measurement.

Pirani Gauge

• A thermal conductivity gauge that measures the conductivity of gas to judge or estimate the pressure..
• Useful over a wide range of pressure range, from regular High pressures (atm) to Low pressures (HV)
• However, the sensitivity is lower in comparison to other gauges used at high vacuum or ultra-high vacuum

Ionisation Gauge

• A gauge that relies on ionising gas molecules to measure pressure.
• A popular configuration is the Bayard-Alpert gauge, which uses a heated filament to generate electrons.
• The emitted electrons will collide with gas molecules to produce ions.

Ionisation Gauge for UHV

• The geometry of the Bayard-Alpert gauge minimizes the effect of x-rays at low pressures.

A Typical UHV Vent/Pump Routine

• A typical Procedure involved in a UHV chamber venting/pumping routine.
• Steps associated with this procedure for the different components are given as well.

Sample Vent Process

• The steps for venting a high vacuum chamber to atmospheric pressure are illustrated.
• Prior to any opening procedures, the chamber needs to be filled with pure nitrogen to minimise possible contamination.

Sample Pump-down Process

• A typical procedure for pumping a vacuum chamber from atmospheric conditions to reach UHV conditions
• Various components that are switched on/off are indicated
• The pressure levels being reached for every phase of operation are given.

Plasma Physics cont.

• This part covers the continued discussion and evaluation of Plasma Physics.

Plasma Sheaths in Plasma Physics

• A study or evaluation of the plasma sheaths and related topics in plasma physics is present here.

Sheaths and Ambipolar Diffusion

• At all solid surfaces, in plasmas, high field regions known as sheaths develop.
• The question is whether or not such sheaths are always there when considering a plasma.
• It is argued that sheaths are inevitable in plasmas and can't be entirely eliminated.

Plasma Sheaths

• The formation of sheaths relates to the different average velocities between electrons and ions involved in the plasma

Plasma Sheaths

• A slab of plasma between two plates forms the context here.
• In the initial conditions there's a uniform plasma with no potential differences between the plasma and plates.
• The situation can't last long because of the differences in escape rates of ions and electrons.

Plasma Sheaths

• The high rate of electron escape versus ion escape results in more electrons lost than ions.
• This leaves extra positive charges between the plates.
• The positive charge forms the basis of the potential difference development
• The region where this occurs is called the sheath which is characterized by a lower electron density than in the region of the plasma.

Plasma Sheaths

• The electric field in the sheath reflects electrons back into the plasma regions.
• The sheath field accelerates ions towards the plates.
• The extra ions in the sheath region are concentrated.

Steady State of Plasma

• At steady-state conditions for plasma, ions and electrons are lost at identical rates.
• Sheath reflects only a portion of electrons, enough so that the random thermal fluxes are comparable to the ion fluxes in the walls

Contrast the characteristics of electrons and ions

• The contrast of electron and ion behaviour is highlighted through discussions about their temperatures
• Ions are cold while electrons are considerably hotter compared to ions in plasmas.

Two important questions / Discussion points

• Relevant discussion points concerning the steady state flux of ions at walls and the plasma density profile in steady-state conditions are present.

Fick's Law

• Fick's Law is a description or mathematical formulation of diffusion
• This law focuses on the flux of particles and its relationship with the density gradient
• A steeper gradient leads to a higher flux and faster diffusion

The Bohm Sheath Criterion and lon Energy

• Characteristics of the sheath and the presheath in plasmas are differentiated
• The high electric field region where electrons get reflected is termed as the sheath.
• The ions are accelerated to the wall in the sheath region, and this energy is beneficial in numerous types of surface treatments.

The Bohm Sheath Criterion and lon Energy

• The energy of ions within the sheath is notably higher than average thermal energy in the main body of the plasma.
• There exists a transition layer called the presheath between sheath and plasma

The Bohm Sheath Criterion and lon Energy

• At the sheath-presheath boundary, we assume ions have acquired a directed velocity (Bohm velocity) which affects the ion energy.
• This simplification suggests the kinetic energy of ions striking surfaces is related to the sheath voltage.

Discussion points regarding RF Sheath Structure and Scaling

• The sheath in RF plasmas has a structure notably influenced by oscillating voltages across the electrodes.
• The voltage across the sheath fluctuates at RF frequencies.

Electron Escape into the Sheath

• Electrons can overcome the sheath voltage due to short, brief periods of time that the voltage across the sheath is quite low.
• Electrons need to move fast through the sheath to utilize these moments, and are in fact very responsive to the voltage changes, which is why it is easier to deal with in theory.

Electron Escape into the Sheath

• The smaller mass of electrons leads them to be able to respond rapidly to these oscillations.
• Ions respond only to average (time-averaged) electric fields

Electron Escape into the Sheath

• The ion density remains relatively unaffected by the voltage fluctuations, and thus is similar to the ion density profiles found in DC sheaths.
• The electrons, meanwhile, change their density in time with the oscillations in voltage.

Particle and energy balance

• Process optimisation in plasma applications relies on knowing how characteristics of plasma will respond to changes in external parameters.
• The parameters that can be controlled or changed include gas pressure & flow, the proportion of each gas in a mixture/types of gas used, the duration of the processes, and the applied RF power.

Process Optimisation

• Conservation laws are fundamental and powerful principles used in physics.
• These laws are used to predict how plasmas respond to changes in processes and parameters.
• The two most significant parameters used/controlled are the applied RF power and the gas pressure

The Two Fundamental Conservation Laws

• Particle conservation, i.e. the total number of ions and electrons remains constant.
• Energy conservation, i.e. energy is supplied, ultimately conducted to the walls of the device.
• These can be used to understand a lot about the behaviour of plasmas when parameters are altered or controlled.

Welcome and Introductions

• Welcome statement regarding beginning of a new semester in college.

Course Outline

• Course information and structure including which modules, lectures, timetable, etc are present.

Course Outline

• Specific session details for each module to be taught.

• Details regarding how to complete the module

Delivery of Course

• Course material will be delivered as PDFs online for each module/week

Importance of Engagement in the module

• Importance is given to the engagement effort required for students to effectively comprehend and understand the course material

Course Description

• Nanoscience requires a fundamental concept of a wide range of materials, manufacturing and analysis, techniques.
• A wide variety of industry types rely heavily on vacuum technology in different processes
• An introduction is planned to cover the fundamentals of vacuum and system design within a broad range of applications in advanced manufacturing processes.

Vacuum Science and Technology

• An illustration of applications in which vacuum technology can be used is included here.

Vacuum Science and Technology

• Illustrations of different applications of vacuum science, including the materials used in the construction of different devices are included
• An array of applications in different areas to demonstrate the principles associated with applications are present.

Module Content

• The structure and parts of the module are delineated here - Gas Fundamentals, Plasma Physics, Vacuum Science and so on.

Part 2 Plasma Physics

• Introduction to plasmas, with an emphasis on the context of industrial applications, such as chemical processing, plasma surface interactions, and aspects of damage, sputtering, etching, ashing, deposition, implantation, manipulating friction, material hardness, and biomaterial treatments.

Vacuum Science

• Ideal environment conditions or specific conditions are needed for implementing controlled reactions/processes.
• This part deals with the details of achieving a well-controlled process at a nanometer scale.
• The importance of vacuum environments and vacuum systems

Introduction

• History of vacuum, definitions, and the reasons why controlling or producing vacuum environments is required
• A short history of vacuum methods and understanding, relevant concepts and applications.

Gas Fundamentals

• Discussion concerning the structure and properties of gases to understand gas behaviour at the molecular/atomic level, and associated physical properties.
• Definitions and measures (Mole, moles per unit volume etc. are introduced for gases as are relative molecular masses).

Avogadro's Law

• A description or mathematical formulation of the law
• Important relations concerning pressure, molecular mass, pressure, number of molecules
• Example calculations to illustrate the theory.

Vacuum Science Lecture 2

• Revision or recap of the previous lecture is present here.

Using Vacuum Chambers as processing tools

• The concepts relating concepts discussed from the previous lecture, together with ideas of how and why using such chambers/environments is important in particular modern day technologies/experiments.

Energy Distribution – Maxwell Boltzmann Statistics

• Pressure definitions, with an example of quantifying the force resulting from collisions between molecules and the surfaces of the contained vessel

Maxwell Boltzmann Theory

• The relationship between gas behaviour (in terms of velocity distribution e.g.), is studied/described by using a theory.
• Properties of gases are included.

Maxwell Boltzmann Theory

• A theory that defines the distribution of molecular energy given a specific temperature, or describes the distribution of velocities of gas molecules/particles

Pressure - Kinetic Theory

• Pressure is defined as the force per unit area exerted by gas molecules
• Properties associated with the behaviour of ideal gases given that collisions are elastic and momentum changes are considered
• Concepts relating to pressure with gas speeds (rms speeds)

Pressure - Kinetic Theory

• A theoretical explanation of pressure exerted by molecules
• Key concepts are the magnitude of velocity, the change in velocity on impact, and associated momentum change

Pressure - Kinetic Theory

• Calculating the frequency of collisions - the average distance covered by each molecule per unit time

Pressure - how does a gas exert pressure

• From Newton's Second Law, momentum change per time is equivalent to the force felt

Pressure measurement - units

• Different units for pressure (e.g., atm, mmHg, Torr, mbar, Pa) are used
• Converting between these different units is important, especially when taking into account that the different engineering contexts are included.

Example calculations regarding Pressure Measurement

• Calculating average gas molecule velocity, given the pressure of air at STP, and relative molecular mass of Nitrogen

Average energy of an atom

Pressure in terms of temperature

• This relation is critical and it is noted that the type of gas does not affect the pressure for a given temperature / given n, the molecular number.
• Important results associated with these relationships between pressure and temperature.

Mean Free Path

• Mean free path of molecules, and its link to a gas's pressure and molecular behaviour.

Mean Free Path and frequency of collisions

• The average distance travelled by a molecule between collisions is determined by the mean free path
• The relationship between these characteristics is highlighted at low pressures

Example calculations regarding Mean Free Path

• Frequency calculated from mean free path and average gas molecule velocity at normal atmospheric conditions

Vacuum Science Lecture 3

• Study notes for Lecture 3 of the Vacuum Science course

Gas Flow

• The various types or regions/stages of gas flow (continuum, viscous, and laminar flows) will be studied, and relationships identified.

Gases in real systems

• Classification of vacuum regimes (e.g. high vacuum and ultra high vacuum) is given
• These divisions or regimes are arbitrary in definition or assignment in terms or naming.

Requirements for Pressure Reduction

• Chamber pressure reduction
• Several technical elements needed to reach the lowest pressure
• Issues or considerations for achieving low pressure are presented

Vacuum Valving

• The function and importance of vacuum valves for isolating or sealing and controlling the movement of gases are presented

Vacuum seals

• Various properties of the sealing materials and the reasons why different materials are used for seals are highlighted

Bulk air gas load

• The constituents of air and a more detailed consideration or investigation, with partial pressures.

Adsorption Processes

• Two fundamental ways or types of adsorption (chemisorption and physisorption) are presented/discused
• The distinction between adsorption and absorption are highlighted
• The process or interaction of a molecule or atom arriving on a surface

Outgassing Processes

• The process of molecules leaving or desorbing surfaces of a vacuum chamber are discussed.
• This can be particularly important at low pressures (lower HV, UHV, etc.)

Proper treatment of construction materials

• Proper handling of materials, in terms of design, to reduce outgassing loads is key
• Issues can result from high levels of impurities, or improper materials selection/handling methods.

Leaks

• Leaks or permeation in vacuum are discussed.
• This is a consideration when developing a system to be resistant to leaks or other types of problems

Virtual Leaks

• Trapped gas in areas, like inside screw threads or under imperfect welds can be a problem source.
• The magnitude of the trapped gas and associated pressure contribution can be significant, especially in ultra-high vacuum

Virtual Leaks

• High level of concern from these type of virtual leaks during vacuum design steps
• Methods to deal with virtual leaks and avoid potential issues are highlighted

Vacuum Components and Fittings

• A typical seal, called Conflat, is shown and described in its use and properties.
• The properties of this type of seal and the benefits are also discussed

Klein Flange (KF) Seal

• The advantages and considerations for a Klein Flange (KF) seal with o-rings compared to Conflat® (CF) seals are discussed

Valves

• This part describes various types of valves that are used to control the flow of gas in a vacuum chamber.

Leak Valve

• A detailed description of its design, including a lever-controlled conical obstruction for gas input control.

Butterfly valve

• A description of a valve using an o-ring seal for controlling gas input.
• This part discusses or deals with how its design and possible disadvantages differ

Gate Valve

• Gate valves allow for unrestricted gas flow when open, a useful property given the conditions of a device through which elements may pass or need to be passed.

Introduction to Plasma Physics Lecture 5

• Introduction to a plasma and the distinct characteristics of it
• The particles in plasmas behave differently due to their charged nature

Motion of Charged Particles in a Plasma

• The paths of charged particles in plasmas aren't always straight, due to interactions with other charged particles.
• Instead, a collective behaviour develops as charged particles affect one another over long distances.

Solid to Liquid to Gas to Plasma

• The process involving increasing energy to induce a change in state (solid, liquid, gas to plasma).

Solid to Liquid to Gas to Plasma

• The gradual changes or transformations of a substance as the amount of energy input increases from a solid to a plasma state are depicted and discussed here.

Plasma Physics

• Plasma physics overview or review; relevant concepts presented/discussed here include the different types of plasmas (which is useful given the different types of plasmas).

Why are electrons hotter than any other particle in a plasma?

• Electrons absorb field energy and don't easily share it with heavier particles
• Heat transfer from electrons to other particles (ions or neutrals) is poor

The great advantage of plasmas

• High temperature chemistry at low physical temperatures due to the fact that electrons are much hotter in plasmas

Although plasmas are not in thermodynamic equilibrium

• Electrons and ions can quite efficiently share energy within the plasma

Plasmas are generally not in equilibrium

• The term 'steady state' describes when characteristics of a plasma are constant over time, suitable for industrial or similar processes
• Examples regarding applications, e.g. etching, are given

Methods of Plasma Generation

• The mechanisms used for generating charged particles
• Two fundamental ways are described: Electron impact and Photoionisation(photon impact)
• The different types of plasma generation methods are highlighted.

DC Sources

• A discussion of different types of DC sources and their applications.

RF Sources

• Different types of RF sources
• Their applications are presented/discussed

Plasma Properties

• The aims and theoretical concepts associated with introducing specific plasma theory are mentioned
• Estimation/calculation of crucial plasma parameters is presented
• The role of sheaths and associated considerations are included

RF Plasma Generation

• The behaviour of electrons and

Test your knowledge on various semiconductor manufacturing techniques, including lithography, etching, and deposition methods. This quiz covers essential concepts related to top-down processing and advanced technologies like molecular beam epitaxy and ion implantation. Perfect for students and professionals in the field of semiconductor engineering.