PRESENTED BY:
S.CHAITANYA

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Ion Beam Machining
Ion source
The Ion Source has arrays of permanent magnets to produce a multi-cusp magnetic field in regions remote from the plasma grid and the RF antenna.
The field confines the plasma by lengthening the path of ionizing electrons and reducing their drift to the walls.
Plasma sources generate plasmas.
Excitation of plasma requires partial ionization of neutral atoms and/or molecules of a medium.
There are several ways to cause ionization: collisions of energetic particles, strong electric fields acting on bond electrons, or ionizing radiation.
- The following reaction occurs:
Argon ions are thereby produced.
A magnetic field, obtained from an electromagnetic coil or a permanent magnet, is often applied between the anode and cathode to make the electrons spiral.
Spiraling increases the path length of the electrons and hence increases ionization.
The ions are removed from the plasma by means of extraction grids.
The grids are normally made of two or three arrays of perforated sheets of carbon or molybdenum; these materials can withstand erosion by ion bombardment.
The perforations in each of the sheets are aligned above one another.
- The outer grid
The outer grid is usually kept at ground potential, which is a more negative level than that of the anode.
This grid therefore provides the negative field that is needed to remove the ions from the plasma.
- A third grid
A third grid, which is maintained at the anode potential, is sometimes added placed between the plasma and the electron suppressor grid to improve the performance of the source.
Output voltages and currents are precisely controlled from the front panel or by remote programming.
Digital displays on the front panel directly monitor the voltage and current outputs.
Remote analog signals proportional to each output are provided at the rear panel I/O connector.
Focusing of the Ion Beam
Focusing of the Ion Beam is also provided by the construction and shape of the electrodes.
The suppression electrode produces an inner zero electrostatic field, and an outer electrostatic on a field such that ions entering this outer field are deflected by an amount that is a function of their distance from the edge of the inner field.
The result is a focused beam having a uniform intensity over a given target area and at a given distance from the lens.
Ion beams can be used for sputtering or ion beam etching and for ion beam analysis.
Ion beam etching, or sputtering, is a technique conceptually similar to sandblasting, but using individual atoms in an ion beam to ablate a target.
Reactive ion etching is an important extension that uses chemical reactivity to enhance the physical sputtering effect.
Advantages of IBM
Low temperature processing reduces handling an stress problems.
No dimensional changes
Good adhesion of treated surface
New alloys possible
Can improve corrosion, oxidation, wear, hardness, friction, fatigue
Disadvantages of IBM
Very shallow treatment (< 1 μm)
High cost
The surface can be weakened by radiation effects