Ion implantation
It is defined as the process by which impurity ions are accelerated to high velocity and physically lodged into the target material.
It is a process by which energetic impurity atoms can be introduced into a single crystal substrate in order to change its electronic properties.
Dopant atoms are vapourized , accelerated , and directed at silicon substrate.
They enter the crystal lattice , collide with silicon atoms , and gradually loose energy , finally coming to rest at some depth within the lattice.
The gas containing the desired impurity is ionized within the ion source.
The ions are generated and repelled from their source in a diverging beam that is focused by the 1st electrical lens before it passes through a mass separator.
The 2nd electrical lens focuses this resolved beam which then passes through an accelerator.
Accelerator brings the ions to their required energy before they strike the target and become implanted in the exposed areas of the silicon wafers.
Advantages:
- Mass separation techniques can be used to obtain highly pure form of impurity atoms
- Wide range of dopant doses
- It can be carried out at room temperature
- Provides independent control of dose and penetration depth
Disadvantages:
- Equipments are highly sophisticated and expensive
- Results in damage to conductor
- At high temp , annealing is needed
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