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8/12/2019 Ibm manual
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Ion Beam Machining (IBM)
Thermal Type AMPs: Ion Beam Machining (IBM) Dr. Neelesh K. Jain
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Ion beam machining (IBM) is closely associated
with the phenomenon of 'sputtering', first
reported by Grove in1852
Ion beam machining takes place in a vacuumchamber, with charged atoms (ions) fired from
an ion source towards a target by means of an
accelerating voltage
Thermal Type AMPs: Ion Beam Machining (IBM) Dr. Neelesh K. Jain
[1] Process Principle
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[1] Process Principle (Contd)
The surface atoms are dislodged (sputtering)
by incident bombarding ions
Ions are formed by knocking of electrons from
the atoms and are accelerated in an electric
fieldwhich collide with the work surface
Transfer of kinetic energy takes place on the
work surface to finally dislodge its surface atoms
Thermal Type AMPs: Ion Beam Machining (IBM) Dr. Neelesh K. Jain
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[2] IBM System
An ion beam machine has three main
components:
1. Plasma Source which generates the ions
2. Extraction Grids for removing the ions from
the plasma, and accelerating them towards
the substrate (or the specimen)
3. Tablefor holding the specimen
Thermal Type AMPs: Ion Beam Machining (IBM) Dr. Neelesh K. Jain
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Fig.-1: Main features of ion beam machining (Melliar-Smith, 1976)
Thermal Type AMPs: Ion Beam Machining (IBM) Dr. Neelesh K. Jain
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[2.1] Plasma source
A heated filament, usually tungsten, acts as
the cathode, from which electrons areacceleratedby means of a high voltage above
1 kV, towards the anode
During the passage of the electrons from the
cathode to the anode, they interact with argon
atoms in the plasma source
The following reaction then occurs:
2Ar e Ar e
Thermal Type AMPs: Ion Beam Machining (IBM) Dr. Neelesh K. Jain
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[2.2] Extraction Grids
The grids are normally made of two or three arrays of
perforated sheets of carbon or molybdenum The outer grid is usually kept at ground potential,
which is a more negative level than that of the anode.
The second grid is held at a negative potential belowtheground value
A third grid, which is maintained at the anode potential,
is sometimes placed between the plasma and the
electron suppressor grid
Thermal Type AMPs: Ion Beam Machining (IBM) Dr. Neelesh K. Jain
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[2.3] Substrate mounting
When the ions have been removed from the
source, they drift in a field-free region to thecomponent/ specimen/ substrate which is to be
machined or milled
The specimen is usually mounted on a water-cooled table which can be tilted through an angle
of 0 to 090
Thermal Type AMPs: Ion Beam Machining (IBM) Dr. Neelesh K. Jain
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[3] Collision MechanismBy Stuart (1983): when an ion strikes the
surface of a material it usually collides with anatom there
Primary Collision
Secondary Collision If the incident ion strikes the surface obliquely,
the ejection is very likely to result from the
primary collision between the incident ion andthe surface atom
Thermal Type AMPs: Ion Beam Machining (IBM) Dr. Neelesh K. Jain
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Fig. 3: Ion (shaded) bombardment at normal incidence to
surface (Stuart, 1983)
Thermal Type AMPs: Ion Beam Machining (IBM) Dr. Neelesh K. Jain
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Mechanism continued
Spencer and Schmidt (1972) explain material
removal in terms of the transfer of momentumfrom the incident ions to atoms on the surface
of the material
The higher the energy of the incident ion, themore deeply this cascading effect occurs into
the material
Yield: Number of Atoms Removed per Incident
Ion
Thermal Type AMPs: Ion Beam Machining (IBM) Dr. Neelesh K. Jain
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Fig. 4: Collision (mass of ion less than that of atom)Thermal Type AMPs: Ion Beam Machining (IBM) Dr. Neelesh K. Jain
S d S h idt (1972) d S kh
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Spencer and Schmidt (1972) and Somekh
(1976) confirmed that the yield depends on:
Material being treated
Type of Atoms and their Energy
Angle of Incidence Gas Pressure
Thermal Type AMPs: Ion Beam Machining (IBM) Dr. Neelesh K. Jain
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The Current Associated with the Extraction of the Ion may be
calculated from Childslaw:
3/ 2 1/ 2 2
0( / )(2* / ) ( / )eI V q q m d l
To achieve the highest current,
Lowest Spacing between the Grids
Grids should have the Largest number of Holes of the Smallest Size
Thermal Type AMPs: Ion Beam Machining (IBM) Dr. Neelesh K. Jain
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Fig.-7: Variation of yield with ion energy(Spencer and Schmidt, 1972)
Thermal Type AMPs: Ion Beam Machining (IBM) Dr. Neelesh K. Jain
Applications
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Applications
Smoothing
Ion Beam texturing
Ion beam Cleaning Shaping, polishing and thinning by IBM
Ion milling
Thermal Type AMPs: Ion Beam Machining (IBM) Dr. Neelesh K. Jain
4) Widely used for:
Cleaning -Removing surface contamination
Polishing glass -Not to crystalline
Etching -Study of micro structure wire dies
Micromachining -Integrated circkt, bearings
Sputter deposition -Atomic deposition i.e. thin film deposition
Material Applications
Fair: Al, Steel, Super alloys, Titanium, Refractory, Plastics and Glass
Good: Ceramics
Advantages
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Advantages
1) Process is almost universal.
2) No chemical reagents etchants
3) No under cutting
4) Etching rates controllable
Thermal Type AMPs: Ion Beam Machining (IBM) Dr. Neelesh K. Jain
Disadvantages
1) Relatively expensive
2) Slow etching rates
3) Little possibility of some thermal or reaction damage
[7] SUMMARY of PROCESS CAPABILITIES and OPERATIONAL CHARACTERISTICS of IBM PROCES
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Thermal Type AMPs: Ion Beam Machining (IBM) Dr. Neelesh K. Jain
Type Capability/Characteristics Common Value/Range
FinishingCapabilities
Surface Roughness [CLA in m] 0.2 0.8
Dimensional Tolerance or Accuracy [ m] 50 125
Minimum Corner Radii (mm) 2 m
Minimum Overcut (mm)
Minimum Surface Damage(m) Chemical Damage NoMechanical Damage No
Thermal Damage 0.005 m
DrillingCapabilities
Hole Diameter (mm) Fair for Micro-holes (d < 0.03 mm) andgood for small holes (0.15 < d