Ion Implantation

Kinetic Displacement

High-energy ions transfer their kinetic energy to the target silicon atoms through a series of collisions, which displaces them from their lattice positions. This cascade of collisions disrupts the long-range crystalline order and can turn the surface region completely amorphous. The degree of damage is determined by the mass of the implanted species and the acceleration voltage of the tool.

Heavy ions create dense damage cascades that must be addressed in subsequent manufacturing steps.

Depth Distribution

The distribution of implanted ions follows a Gaussian profile, where the peak concentration lies at a depth determined by the acceleration energy. In-line metrology uses secondary ion mass spectrometry to measure the atomic depth profile and confirm that the dopant dose matches the design parameters. Wafers are scanned across the ion beam to ensure uniform distribution across the entire surface.

Lattice Recovery

Annealing is required to restore the crystalline structure of the damaged wafer and move the dopant atoms into active substitutional lattice sites. If this thermal budget is neglected, the device will exhibit poor electrical conductivity and high leakage.