41
Contemporary Machining Processes
Thus, both efficiency of the process and the machining depth depend on the power P b ,
cross-section area of the beam, and thermal characteristics of a machined material.
The main advantages of this process are a high degree of automation, high productivity, high precision, and the ability to machine all types of materials (Bhattacharyya,
2015). However, since static electrical load defocuses the electron beam, conductive
materials are preferable.
1.9 ION BEAM MACHINING
Ion beams are useful in such applications as doping of semiconductors or depth profiling in surface spectroscopies. Ion beam techniques are used for surface treatment or
depositing coatings on engineering materials to enhance resistance to corrosion and
wear of metallic and ceramic materials (Halada and Clayton, 2012). Ion beam machining (IBM) is an important nonconventional manufacturing technology for micro- and
nanofabrication. A stream of accelerated ions in a vacuum chamber is able to remove,
add, or modify atoms on the surface of an object, mainly as a result of an energetic
collision cascade. Transfer of sufficient ion energy and momentum to target atoms
forces parts of the ions to be finally implanted into a substrate after losing their energy
(Fang and Xu, 2018). IBM does not produce any HAZ as melting and evaporation of
workpiece materials does not take place. In effect, the process does not introduce any
mechanical strain in the workpiece. Unlike traditional machine tool technologies of
cutting, grinding, and lapping, IBM has no inherent reference surface. The process
can be used for unusual and difficult tasks like aspherizing of lenses, sharpening of
diamond microtone knives and cutting tools, IC pattern etching, etc. Very high cost of
an IBM machine makes the process uneconomical (Bhattacharyya, 2015).
IBM can be classified as ion sputtering/etching (remove material), ion sputter
coating/ion-induced deposition (add material), and ion implantation (implant modification), according to the function (Fang and Xu, 2018).
Sputtering is a very important process in ion beam machining of micro- and
nanostructured devices. Ion milling can be performed using a dedicated system
employing a broad-beam ion source to generate a beam of usually Ar ions with
beam energy typically in the range 600–1,000 eV (Hindmarch et al., 2012). The ion
beam is able to etch away any regions of a thin-film or device heterostructure left
unprotected by an overlying resist pattern. Usually, ions sputter and remove atoms
near the surface of a target, but a small part of recoil cascade atoms exiting the target
might originate from deep inside it (Fang and Xu, 2018).
Ion sputtering efficiency is measured with the number of atoms ejected from
the target surface by every incident ion. Generally, higher ion sputter yields can be
achieved by choosing heavier ion sources or lower binding-energy target materials,
since atom’s energy received by collision must be larger than its surface binding
energy E surf . High sputtering efficiency can be obtained by using ions with energies
ranging from 10 to 100 keV, and the ion energy of up to 30 keV is usually selected
in commercial focused ion beams (FIB) (Allen et al. 2009; Xu et al. 2015). Higher
energy than the order of 100 keV allows ions to penetrate into the substrate, decreasing the ion sputtering yield or causing ion implantation (Fang and Xu, 2018).
Contemporary Machining Processes
Thus, both efficiency of the process and the machining depth depend on the power P b ,
cross-section area of the beam, and thermal characteristics of a machined material.
The main advantages of this process are a high degree of automation, high productivity, high precision, and the ability to machine all types of materials (Bhattacharyya,
2015). However, since static electrical load defocuses the electron beam, conductive
materials are preferable.
1.9 ION BEAM MACHINING
Ion beams are useful in such applications as doping of semiconductors or depth profiling in surface spectroscopies. Ion beam techniques are used for surface treatment or
depositing coatings on engineering materials to enhance resistance to corrosion and
wear of metallic and ceramic materials (Halada and Clayton, 2012). Ion beam machining (IBM) is an important nonconventional manufacturing technology for micro- and
nanofabrication. A stream of accelerated ions in a vacuum chamber is able to remove,
add, or modify atoms on the surface of an object, mainly as a result of an energetic
collision cascade. Transfer of sufficient ion energy and momentum to target atoms
forces parts of the ions to be finally implanted into a substrate after losing their energy
(Fang and Xu, 2018). IBM does not produce any HAZ as melting and evaporation of
workpiece materials does not take place. In effect, the process does not introduce any
mechanical strain in the workpiece. Unlike traditional machine tool technologies of
cutting, grinding, and lapping, IBM has no inherent reference surface. The process
can be used for unusual and difficult tasks like aspherizing of lenses, sharpening of
diamond microtone knives and cutting tools, IC pattern etching, etc. Very high cost of
an IBM machine makes the process uneconomical (Bhattacharyya, 2015).
IBM can be classified as ion sputtering/etching (remove material), ion sputter
coating/ion-induced deposition (add material), and ion implantation (implant modification), according to the function (Fang and Xu, 2018).
Sputtering is a very important process in ion beam machining of micro- and
nanostructured devices. Ion milling can be performed using a dedicated system
employing a broad-beam ion source to generate a beam of usually Ar ions with
beam energy typically in the range 600–1,000 eV (Hindmarch et al., 2012). The ion
beam is able to etch away any regions of a thin-film or device heterostructure left
unprotected by an overlying resist pattern. Usually, ions sputter and remove atoms
near the surface of a target, but a small part of recoil cascade atoms exiting the target
might originate from deep inside it (Fang and Xu, 2018).
Ion sputtering efficiency is measured with the number of atoms ejected from
the target surface by every incident ion. Generally, higher ion sputter yields can be
achieved by choosing heavier ion sources or lower binding-energy target materials,
since atom’s energy received by collision must be larger than its surface binding
energy E surf . High sputtering efficiency can be obtained by using ions with energies
ranging from 10 to 100 keV, and the ion energy of up to 30 keV is usually selected
in commercial focused ion beams (FIB) (Allen et al. 2009; Xu et al. 2015). Higher
energy than the order of 100 keV allows ions to penetrate into the substrate, decreasing the ion sputtering yield or causing ion implantation (Fang and Xu, 2018).