NMTC Report 1

8/12/2019 NMTC Report 1

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A study report on Nano Manufacturing Technology Centre (NMTC)


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Introduction

Nanotechnologyis the manipulation of matter on an atomic and molecular level. It primarily

deals with synthesis, characterization, exploration, and exploitation of nanostructure materials.

These materials are characterized by at least one dimension in the nanometer range. A

nanometer (nm) is one billionth of a meter, or 109m.

Nano manufacturing

Manufacturing refers to the manipulation of raw material into required useful product. Based

on the type of manipulation of materials manufacturing can be achieved by two approaches.

Top down approach: Most conventional machining process follow top down approach to

manufacturing. This approach involves removal of stock material from a larger piece to obtain

required net shape. Material wastage is high in this approach

Bottom up approach: This is a relatively new concept in manufacturing. Also called as additive

manufacturing, this approach involves layer by layer building of the final product. Materialwastage is minimal.

Manufacturing can further be classified into various types. Based on the amount of material

removed from the work piece, it can be classified as follows

Precision Machining: 1 in 10mm Ultra Precision Machining: 1 in 100mm Micro Precision Machining: 1 in 999 m Nano Precision Machining: material manipulation in few nano-meters.

Need for Micro/Nano Precision Machining:

Advancements of materials require newer machining techniques. Components require minimal features such as micro-holes and micro-slots Materials require very high surface finish like optical surface finish.

Requirements for nano machining:

Low unit removal rate (URR): Unit removal refers to the minimum amount of material

manipulations that can be achieved in a process, for achieving nano level manipulation the

process has to be capable of achieving URR in nano meter scale.

Manufacturing accuracies: The machine for nano machining should have the capabilities to

achieve nano level positon control and feedback systems.

Some of the Nano manufacturing facilities in CMTI are:

1. Focused Ion beam Machining

Make and model: Carl Zeiss Neon 40 Crossbeam, Germany.


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Focused Ion beam machining is a top down manufacturing methodology which uses a finely

focused beam of ions that can be operated at high currents for site specific material removal by

sputtering.

Principle of operation:

A FIB utilizes a liquid metal ion source such as gallium.Of the existing ion source types, the LMIS

provides the most highly focused beam. There are a number of different types of LMIS sources;

the most widely used being a Ga-based blunt needle source. Ga is used because of its

combination of low melting temperature (30C), low volatility and low vapor pressure. Thegallium flows from a reservoir to a blunt tungsten pin with 10m end radius which acts as an

electrode. The gallium ions adhere to the tungsten pin by Coanda effect and Taylor cone

phenomenon. The machining takes place in vacuum conditions, So that the mean free path

available for the ions is more. The gallium ion source is concentrated at the tip and when a

voltage is applied the ions gain acceleration voltage up to 30 kEv.The ions beam is then scannedover the surface to be machined by means of electrostatic lenses. The molecules from the

substrate are removed upon collision by ions. The unit removal is of the order of 60 to 80

nm.Minimum material removed in the FIB system CMTI is 22nm.

The sputtering action also depends on the following factors:

Material Crystal orientation Incidence angle Extent of redeposition.


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FIB Construction

The process can also utilize precursor gasses for assisting machining or deposition. The machine

can achieve milling as well as deposition or etching operations. The precursor gasses can be

classified as enchant precursor (It releases with particular gas in conjunction with Ga and reacts

with substrate to facilitate easier removal of material from the substrate.Eg: XeF2and water

vapor) and deposition precursor (these are used in deposition of thin films or other materials

over the substrates.

Concepts in FIB

Ions: These are atoms having unequal number of protons and electrons.

Vacuum: It is a space devoid of matter. It is measured as the pressure at a particular point.

Atmospheric pressure is of the 760mm of Hg or 1.0132 bar or 101.32 kPa. Energy has to bespent to achieve pressures below this range.

Vacuum Classes:

Vacuum quality Torr Pa
https://en.wikipedia.org/wiki/Torrhttps://en.wikipedia.org/wiki/Pascal_(unit)https://en.wikipedia.org/wiki/Pascal_(unit)https://en.wikipedia.org/wiki/Pascal_(unit)https://en.wikipedia.org/wiki/Torr


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Atmospheric pressure 760 1.01310+5

Low vacuum 760 to 25 110+5

to 310+3

Medium vacuum 25 to 1103

310+3

to 1101

High vacuum 1103

to 1109

1101

to 1107

Ultra high vacuum 1109

to 11012

1107

to 11010

Extremely high vacuum


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FEMTO SECOND LASER MACHINING SYSTEM

Introduction

This method utilizes ultra short pulses(10-15

sec) of lasers for machining of materials.

Laser is an acronym for light amplification by stimulated emission. Laser has the followingproperties:

It is coherent It is unidirectional It is has high monochromaticity (all photon fall within a small frequency range).


Femtosecond (fs) lasers are also known as ultrafast and/or ultrashort-pulse (USP) lasers.

Femtosecond laser machining utilizes short laser pulses compared to continuous and long pulse

laser which reduces the Heat affected zone as the laser pulse duration is much smaller than thetimescale for the energy transfer between free electrons and material lattice. The finish and the

machining is achieved with high accuracies.

Two major mechanisms are studied 1. Thermal vaporization where the removed material

vaporizes without melting. 2. Coulomb explosion, where excited electrons escape from the bulk

material and form strong electric field and pulls out the ions in the impact area. For long-pulsed

lasers, ablation of materials occurs through melt expulsion driven by the vapor pressure and

the recoil pressure of light. This is an unstable process in which the dynamics of the fluid phase

and the driving vapor conditions are quite complicated. The melt layer is resolidified, resulting

in geometric changes to the holes (i.e. rough holes).

Machining with long pulse LASER


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Machining with Ultra short pulse laser

Important parameters used to describe femtosecond lasers are pulse duration (width) and

pulse repetition rate (PRR). The pulse duration (tp) is also referred to as full width at half

maximum (FWHM) amplitude.

The pulse repetition rate (PRR) describes the frequency with which pulses are emitted by the

laser. For instance, if the PRR was 1 kHz, then the period T would be equal to 0.001 seconds (T=

1/PRR).

Application

Sub-micron material processing: Material milling, hole drilling, and grid cutting.Surface structuring: Photolithographic mask repair, surface removal or smoothing

without imparting any thermal influence into the underneath sub-layers or the

substrate.

Photonics devices: Machining of optical waveguides in bulk glasses or silica, and

inscription of grating structure in fibers.

Biomedical devices: Use of Femto-second laser for stent manufactures or eye surgery.

Single point Diamond Turning:

The operation involves the use of a single point monocrystalline diamond for machining of nonferrous materials. This type of machining falls under the ductile machining regime

INTELLIGENT ULTRA PRECISION TURNING MACHINE (iUPTM)

Intelligent ultra-precision turning machine is state of the art machine, developed by CMTI, for

producing nonferrous components with high surface finish. The nano level surface finish

achieved on components are in the magnitude of


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The machine has excellent static dynamic and thermal behavior and has accuracies in order of

nano meters.

One of the advantages of using single point diamond turning is the ability to make lensshapes very accurately without expensive tooling.

The process isn't really suited for mass production since the rejection rate is highApplications:

Spherical and aspherical lenses and mirrors Metal mirrors for laser applications Special lenses and mirrors for space applications Incidence mirrors and telescopes Moulds for lens manufacturing Fresnel surfaces Precision bearing components

Machine Features

Spindle

The basic principle is that the spindle is supported by two aerostatic radial bearings made from

porous ceramic. The spindle can rotate precisely without restriction or friction. The spindle

houses an air chuck in order to prevent deformation to the workpeice. The spindle is positioned

in the axial direction, by utilizing a permanent magnet in the spindle air-core coils in the spindle

housing and a laser interferometric measurement system. An air turbine is used to rotate the

spindle, because an air turbine drive generates less heat and disturbance forces than an electric

motor

CNC system

The use of open architecture CNC is gaining importance in automation technology. It allows

integration of equipment and improved machine tool communication. Benefits of using an

open architecture when developing new CNC include lower-cost electronics and higher-

performance computers. Open architecture is based on a philosophy of removing the barriers,

limitations and planned imposed by proprietary CNC control systems. It places focus on

continuous improvement by allowing ongoing incorporation of upgrades. Adaptive Control

covers a set of techniques which provide a systematic approach for automatic adjustment of

controllers in real time, in order to achieve or to maintain a desired level of control systemperformance when the parameters unknown and/or change in time.

Spindle Health Monitoring

Any intelligent capability that can be added to a spindle for the purpose of monitoring the

health of the spindle and predicting its impending failure based on the sensor measurement

data will enhance the overall performance of machining systems. A spindle with such added


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capability is called a smart spindle. Smart spindles are key components of the next generation

of smart machine tools that will be capable of self-diagnosis, leading to condition-based,

ATOMIC FORCE MICROSCOPE

It is scanning probe microscopy technique which works on the principle of Van der Waals force

between two molecules. Van der Waals force is the interactions between dipole moments

between molecules. This technique utilizes a cantilever with a sharp tip to scan a object surface.

The tip dia used in this process are of 1 angstrom to 100 angstrom.

The van der waals force between the tip and the object causes the tip to deflect. These

deflections are measured to obtain the profile of the surface. The main components of the AFM

system are

o Scanner head (Cantilever an tip)o Photodetectoro Feedback system.

The cantilever position is controlled by the piezoelectric crystal, A laser beam is continuouslyincident the cantilever head and is reflected on to a photodetector, The change in position of

laser is used to measure the deflections in the cantilever. The feedback system adjusts the

position of the cantilever depending on the magnitude of van der waals force.


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The machine operates in three modes they are:

Contact mode ( constant force and constant height mode) Intermittent mode Non contact mode

Contact mode:

In contact mode the tip apex is in direct contact with the surface, and the force acting between

the atoms of tip and sample is counterbalanced by the elastic =force produced by the deflected

cantilever according to Hooke's law: F = - kz.

Cantilevers used in contact-mode have relatively small stiffness, allowing to provide high

sensitivity and to avoid undesirable excessive influence of the tip on the sample. The contact

mode may be carried out either at constant force or at constant height (distance between

probe and sample).

In constant height mode the scanner maintains fixed end of cantilever at the constant height.

Thus, deflection (DFL) of the cantilever under scanning reflects topography of a sample.

In constant force mode the scanner maintains constant value of constant bend, hence constant

force is maintained. Change of topography affects the DFL. To keep it constant, the feedback

system changes voltage applied to the Z-electrode of the scanner. Thus, changes of this voltage

will be proportional to the surface topography.

Intermittent mode

Here the tip is made to osscilate at their resonant frequency at high amplitudes (of the order of10-100nm). In the bottom half of the swing the cantilever comes in contact with the substrate

surface and is repelled. The repulsive force contribution to the amplitude is measured to get

the profile. This mode is used for biological sample to prevent damage to the sample and also in

thin film applications to prevent peeling off the thin films.

Non contact mode:

Here the AFMs work on the principle of amplitude modulation (AM) detection. The force

gradient leads to shift in frequency which causes change of the amplitude. The latter one is


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used by the detection system and converted into surface profile of the substrate. In NC AFM,

oscillation amplitude is typically small, a few nanometers (< 10nm). Here no force is exerted on

the sample surface.This method has lower lateral resolution (limited by the tip-sample

separation) and slower scan speeds to avoid contacting the surface.

Applications:

Three Dimensional topography Roughness measurement MEMS failure analysis Mechanical and Physical properties of thin film Phase distribution on polymers

Limitations:

Time consuming Laser interaction may lead to thermal stresses In contact mode, chances of tip breakage

OPTICAL PROFILEROptical profiler is a non-contact type used to get three-dimensional profile, topography,

roughness, step height, radius of curvature and surface finish.


It works primarily on the the principle of interferometry. The beam of monochromatic light

exiting from a light source is divided by a beam splitter in to 2 beams. One beam is reflected

from the reference mirror and other from the sample. Beam is recombined by beam splitter,

Interference pattern is obtained. For /4 displacement of the light source /2 path difference of

light is obtained resulting in the bright or dark fringes. This is called a interferogram for the

sample. The imaging lens images the interferogram on to a camera. It is then analyzed by the

software to give the surface profile of the sample.

PSI and VSI setups in optical profilers

The optical profiler works in 2 modes


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In vertical scanning interferometry (VSI), an internal translator scans vertically during the

measurement as the camera periodically records frames.As each point on the surface comes

into focus, the intensity of fringes for that point is maximum and reduces as translator passes

through focus. VSI, which uses a broadband light source, is effective for measuring objects with

rough surfaces, and those with adjacent pixel-height differences greater than /4.

In phase-shifting interferometry (PSI), Light focusing system precisely alters the optical pathlength of the test beam. Each optical path change causes a lateral shift in the fringe pattern.

The shifted fringes are periodically recorded by the camera, producing a series of

interferograms. Computerized calculations then combine these interferograms to determine

the surface height profile. PSI, which uses a monochromatic light source, is typically used to test

smooth surfaces (roughness less than 30 nm), such as mirrors, optics, or other highly polished

samples

X-RAY DIFFRACTOMETER

Fig: X-ray Diffractometer

Xray diffraction is a method used to find material composition, crystalline phase

identification, identification of structure of material, measurement of residual stresses. X-rays

are electromagnetic radiation similar to light, but with a much shorter wavelength (0.01 to

11.3nm). Xrays are produced when electrically charged particles are decelerated. In an X-ray

tube, the high voltage maintained across the electrodes draws electrons toward a metal target

(Copper, Cobalt and Chromium targets).When an incident X-ray beam encounters a crystal

lattice, general scattering occurs. Most scattering interferes with itself and is eliminated

(destructive interference), diffraction occurs when scattering in a certain direction is in phase

with scattered rays from other atomic planes. Under this condition the reflections combine to

form new enhanced wave fronts that mutually reinforce each other (constructive interference).

The relation by which diffraction occurs is known as the Bragg law or equation as given below,

n =2dsin

where n is an integer,

is wavelength of incident wave,

d is the distance between planes, and

is the angle between incident ray and the scattering.


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Crystalline materials have a characteristic atomic structure; therefore each of it will diffract X-

rays in a unique characteristic pattern. The X ray interacts with the innermost electrons of K-

shell and L-shell and dislodge them from the atom. The vacancy in the inner most shell results

in the displacement of electrons in to vacancies in the subsequent shells with a loss of energy in

the form of X-rays. The value for K shell radiation is constant for each element and is called the

characteristic radiation(brehmstrahlung). A database is available for each element; hence thismethod is useful in finding the composition of a given sample. The dislodged electron interacts

with atom; resulting energy loss is also converted into X rays (continuous radiation). A plot of

Intensity vs. photon energy is shown below

10.1 Components of an XRD:

X-ray Tube: the source of X Rays Incident-beam optics: condition the X-ray beam before it hits the sample The platform that holds and moves the sample, optics, detector, and/or tube The sample & sample holder Receiving-side optics: condition the X-ray beam after it has encountered the sample Detector: count the number of X Rays scattered by the sample Applications: Crystalline Phase Identification & Quantification of material Texture Analysis Identification of structure of material Measurement of residual stresses Residual Strain (macrostrain)Limitations:

Possible Peak overlay mixed material detection limit ~2% Amorphous structures cannot be studied


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RAMAN SPECTROSCOPY

Raman spectroscopy is a spectroscopic technique based on inelastic scattering of

monochromatic light, usually from a laser source. Spectroscopyis the study of the interaction

between matter and energy. The Raman Effect was discovered by Dr. Chandrasekhar Venkata

Raman (1888-1970) who received noble prize for the same in 1930. He stated that instead ofabsorption & emission, photon can also in elastically scatter, which is dependent on the

polarization of the molecule. When a sample is irradiated with an intense monochromatic

light source (usually a laser), most of the radiation is scattered by the sample at the same

wavelength as that of the incoming laser radiation in a process known as Rayleigh scattering.

Absorption & Emission of the radiation gives the information about the energy level

associated with particular degree of freedom.Also, some of the photons undergo inelastic

scattering meaning that the frequency of photons in monochromatic light changes upon

interaction with a sample. Frequency of the reemitted photons is shifted up or down in

comparison with original monochromatic frequency, which is called the Raman Effect

Fig: Principle of Raman Spectroscopy Fig: Raman Spectroscopy Setup

. Raman spectroscopy is used to study vibration modes of the molecule. It is used to study

composition, stress-strain, crystalline and amorphous phase study etc.

11.1 Applications:

Composition of material. Crystal symmetry & orientation. Amount of material.

NANO INDENTOR

Nano Indentor is a low load nano mechanical test system, ideal for measuring modulus

of elasticity, hardness, yield strength, fracture toughness and wear properties of thin films &

coatings by recording load and displacement. The range of loads can be varied from 1nN to

about 500mN. A low load nano-mechanical test system for loads ranging from 1nN to 500 N.A

high load nano-mechanical test system for loads ranging from 20 N to 500 mN. Various types

of tips used for indentation include a three sided pyramid (Berkowich indentor) having a tip


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radius of 20nm, spherical indenter, cube corner indenter & a conical indenter. The setup can be

operated in two different modes. The CSM Mode (Continuous Stiffness Measurement Mode) or

the DCM Mode (Dynamic Contact Mode).

Table: Comparison between CSM and DCM Modes

The low resolutions are achieved by using capacitive sensors. The displacements are measured

laser interferometers; the displacement resolution is 0.2nm. Factors like vibration, acoustics,

and thermal drift are responsible for measurement inaccuracies. The load is controlled by

electromagnetic coils. The depth of penetration should be 10% of the film thickness in thin filmapplications. To avoid errors in measurement due to surface roughness, surface preparation is

very important. The surface roughness has to be 5% of the depth of penetration. The Results

are obtained in a form of a graph of load v/s Displacement, from which various properties can

be obtained. The fracture toughness is measured by making cracks on a surface by a definite loa

and measuring the length of the cracks. Scratch tests are done by measuring the critical load at

which material is peeled off. The load is of the order of mN

Fig: Graph of Loading V/S Unloading

Table: Comparison between the types of indentor

Description Berkovich Conical Cube-corner Spherical

Shape 3-sided pyramid Conical 3-sided pyramid Spherical

Material Thin films Hard materials Ultra-thin filmsGenerally for Soft

Materials

Parameter CSM Mode DCM Mode

Max Load 500mN 10mN

Load resolution 50nN 1Nn

Displacement Resolution 0.01nm 0.0002nm


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Included Angle 142.35 60 90 -

TestsHardness,

Youngs modulus

Wear tests,

scratch test

Fracture

toughness

Yield points,

scratch test

Tool material Diamond Diamond Diamond Diamond

12.1 Applications:

Fracture analysis Anti-wear films Paints & coatings Nano machining Metals & ceramics Bio-materials Metal-matrix composites DLC coatings

Semi-conductors Polymers Thin films testing & Development

PLANETARY BALL MILLINGA ball mill is a type of grinder used to grind materials into extremely fine powder for use in

various processes. It works on the principle of impact, wherein size reduction of the sample is

done by impact as the balls.A ball mill consists of a hollow cylindrical shell rotating about its

axis. the vial or chamber is partially filled with balls.

Construction and working

The two grinding bowls have been sunk into the rotating disc, therefore allowing greater speedsof rotation, which hugely increases the impact energy. During milling, the grinding bowls rotate

around their own axis, whilst orbiting around a central axis. The inner surface of the cylindrical

shell is usually lined with an abrasion-resistant material such as Zirconium. The grinding balls

are made of steel, ceramics, zirconium, cemented carbides or tungsten carbide balls ranging

upto 10mm in diameter. The grinding balls are carried up the inner wall of the grinding bowl

and propelled off the wall; after crossing the grinding bowl, the balls and the material collide on

the opposite side of the grinding bowl wall. Milling speeds of up to 1100rpm are possible. The

grinding bowls sizes are 20ml, 45ml and 80ml, with each grinding bowl having a useful working

capacity of approximately half. The grinding bowl and supporting disc rotate in opposite

directions so that the centrifugal forces alternately act in the same and opposite directions. Thisresults in the grinding balls running along the inner wall of the grinding bowl as a frictional

effect and the balls impacting against the opposite wall of the grinding bowl as an impact

effect.

PROCESS PARAMETERS

Material dependent types of balls used (shape, surface area of balls)


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ratio of balls to powder space vaccant in vias (2/3 space should be left) duration of milling cycle Pause in between proces Inert atmosphere

PECVD (Plasma-Enhanced Chemical Vapour Deposition)Plasma-enhanced chemical vapour deposition (PECVD) is a process used to deposit thin films

from a gas state to a solid state on a substrate. Chemical reactions are involved in the process,

which occur after creation of a plasma of the reacting gases. Deposition take place due to a

chemical reaction between some reactants on the substrate. In this case reactant gases

(precursors) are pumped in to a reaction chamber (reactor).Under the right conditions (T, P),

they undergo a reaction at the substrate. One of the products of the reaction gets deposited on

the substrate. The by-products are pumped out. The key parameters are chemical (reaction

rates, gas transport, and diffusion).

The energy for the dissociation is mainly put in the electrons in the plasma while the gasremains relatively cold (typically room temperature or slightly above).The plasma is created

through inelastic collisions between gas molecules and electrons which gain adequate kinetic

energy in the electric field inside the discharge chamber. It uses electron energy (plasma) as the

activation method to enable deposition to occur at a low temperature and at a reasonable rate.

Supplying electrical power at high voltage to a gas at reduced pressures results in the breaking

down of the gas and generates glow discharge plasma consisting of electrons, ions and

electronically excited species. The vapor reactants are ionized and dissociated by electron

impact, and hence generating chemically active ions and radicals that undergo the

heterogeneous chemical reaction at or near the heated substrate surface and deposit the thin

film. PECVD can be operated using either direct or remote modes. The direct PECVD reactorssuch as rf diode, microwave and inductively coupled plasma involve gaseous precursors, inert

carrier gas and substrates being placed directly in the plasma source region. However, the

remote PECVD methods generate plasma away from the deposition zone. This can avoid

damaging the films caused by energetic ions and electrons in the plasma.

Fig: PECVD


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14.1 Advantages: Deposition at much lower temperatures and pressures than would be required for

thermal CVD.

A final important benefit of plasma deposition is the ability to easily clean the reactor.For example, by introducing a fluorine-containing gas (e.g. CF4) and igniting a plasma,

one can clean silicon, silicon nitride, or silicon dioxide from the electrodes and chamber

walls.

14.2 Disadvantages:Limited capacity

PECVD systems require wafers to lie flat on the bottom wafer. Only one wafer side can

be coated at a time unlike LPCVD (wafers loaded vertically). PECVD can coat 1~4 wafers

at one time whereas LPCVD can coat up to 25 wafers.

14.3 Applications:

Scratch resistant coatings. Corrosion protection. Anti-bonding, anti-soiling coatings. Barrier layers.

Scanning electron microscope

Rheometer

Surface area analysis

Confocal microscope


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