What Is Ion Beam Machining?- Working and Application

What is Ion Beam Machining?

Ion beam machining (IBM) is a non-conventional manufacturing process that uses a stream of accelerated ions to remove atoms from a solid surface. The process is used in micro and nano-fabrication and is useful in the electronics manufacturing industry.

In IBM a stream of charged atoms (ions) of inert gas, such as argon, is accelerated in a vacuum by high energies and directed toward a solid workpiece. The beam removes atoms from the workpiece by transferring energy and momentum to atoms on the surface of the object.

When an atom strikes a cluster of atoms on the workpiece, it dislodges between 0.1 and 10 atoms from the workpiece material. IBM permits the accurate machining of virtually any material and is used in the semiconductor industry and in the manufacture of aspheric lenses.

The technique is also used for texturing surfaces to enhance bonding, for producing atomically clean surfaces on devices such as laser mirrors, and for modifying the thickness of thin films and membranes.

How Does Ion Beam Machining Work?

Ion beam machining (IBM) is an atomic-bit machining process, which is used to machine a product with a high resolution of the order of 0.1 μm.

Ions of inert gases like argon with a high kinematic energy of 10 KeV are used to bombard and eject atoms from the workpiece surface by elastic collision.

Unlike machine tool technologies of cutting, grinding, and lapping, IBM has no inherent reference surface; the patterning mask acts as a reference.

IBM could be used as micromachining with a 1–2 μm diameter micro-ion beam and a high-precision position control machine tool.

IBM can also be used for aphorizing lenses, sharpening of diamond microtones knives and cutting tools, IC pattern etching, etc. The cost of an IBM machine is very high, which increases the machining cost and makes the process uneconomical.

Here’s how IBM works:

• In a vacuum, a stream of ions from an inert gas, like argon, or metal, like gallium, is accelerated to high energies.
• The ions are directed at the solid workpiece.
• The ions transfer kinetic energy and momentum to the atoms on the surface of the workpiece, knocking them off. This process is called sputtering.

IBM is similar to sandblasting but uses individual atoms in an ion beam to ablate a target. The process can achieve a resolution of around 0.1 μm.

Performance Characteristics

• Practical etching rates – about 2000 Å/min or 2×10-4 mm/min
  • Varies for different materials & Tungsten etches at half the rate of Aluminium.
  • external means to cool the workpiece.
• Machining of small dimensions such as 10 to 100 nanometers are possible
• Accuracy levels of plus-minus 1 percent
• Repeatability of plus-minus 1 percent has been reported.
• Smoothening to a surface finish of less than 1 micrometer can be obtained.
• Depth-to-width ratios up to is to 1.

Applications of Ion-Beam Machining

• Micro/Nanofabrication of electronic components like computer memories and figuring optical surfaces.
• Fabrication of fine wire dies in refractory materials.
• Smoothening of laser mirrors.
• Production of closely packed, textured cones in copper, nickel, stainless steel, gold & silver.
• Atomically clean surfaces are used in the adhesion of gold films to silicon & aluminum oxide substrates.
• Removing surface oxide layers by using higher ion energies.
• Milling a line width of 0.2 micrometers used in the fabrication of bubble memory devices.

Advantages of Ion Beam Machining

Ion-beam has many advantages which include:

• Almost any material can be machined.
• No chemical reagents or etchants are required.
• No residue.
• Resolution is only limited by that of the mask.
• No undercutting as in chemical etching.
• Etching rates are easily controllable.

Disadvantages of Ion Beam Machining

However, the process has many disadvantages which are as follows:

• Relatively expensive.
• Slow etching rates.
• Thermal or radiation damage may occur in some cases.

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