Ion implantation
Ion implantation is used in semiconductor device fabrication and in metal finishing, as well as in materials science research.
The crystal structure of the target can be damaged or even destroyed by the energetic collision cascades, and ions of sufficiently high energy (tens of MeV) can cause nuclear transmutation.
Therefore, ion implantation finds application in cases where the amount of chemical change required is small.
Energies lower than this result in very little damage to the target, and fall under the designation ion beam deposition.
Thus, ion implantation is especially useful in cases where the chemical or structural change is desired to be near the surface of the target.
The loss of ion energy in the target is called stopping and can be simulated with the binary collision approximation method.
[1][2][3] All varieties of ion implantation beamline designs contain general groups of functional components (see image).
Crucibles often last 60–100 hours and prevent ion implanters from changing recipes or process parameters in less than 20–30 minutes.
[18] Ion implantation was developed as a method of producing the p-n junction of photovoltaic devices in the late 1970s and early 1980s,[32] along with the use of pulsed-electron beam for rapid annealing,[33] although pulsed-electron beam for rapid annealing has not to date been used for commercial production.
In this process, ions are implanted at a high enough energy and dose into a material to create a layer of a second phase, and the temperature is controlled so that the crystal structure of the target is not destroyed.
The structural change caused by the implantation produces a surface compression in the steel, which prevents crack propagation and thus makes the material more resistant to fracture.
In some applications, for example prosthetic devices such as artificial joints, it is desired to have surfaces very resistant to both chemical corrosion and wear due to friction.
[42] Each individual ion produces many point defects in the target crystal on impact such as vacancies and interstitials.
Interstitials result when such atoms (or the original ion itself) come to rest in the solid, but find no vacant space in the lattice to reside.
For this reason, most implantation is carried out a few degrees off-axis, where tiny alignment errors will have more predictable effects.
Ion channelling can be used directly in Rutherford backscattering and related techniques as an analytical method to determine the amount and depth profile of damage in crystalline thin film materials.
In fabricating wafers, toxic materials such as arsine and phosphine are often used in the ion implanter process.
Other common carcinogenic, corrosive, flammable, or toxic elements include antimony, arsenic, phosphorus, and boron.
Semiconductor fabrication facilities are highly automated, but residue of hazardous elements in machines can be encountered during servicing and in vacuum pump hardware.
In addition, high-energy atomic collisions can generate X-rays and, in some cases, other ionizing radiation and radionuclides.
