Recoils

• If the target is composed is composed of two layers, atoms from one layer will be displaced into the next during ion implantation.

• For example, in implantation through a thin oxide layer into silicon, the oxygen atoms are displaced from the oxide layer into the silicon, giving a profile composed of two roughly exponential regions.

• Close to the interface, the displacement cascades push many very-low-energy oxygen atoms just across the interface but after the Si and SiO₂ interface, primary oxygen recoils form a deeper exponential tail.

• From the Fig. 6 note that the oxygen concentration near the interface exceeds the implanted arsenic concentration. This high dose of oxygen can degrade carrier mobility and introduce deep-level traps.

• Recoil can be use for introducing dopant atoms by implanting silicon through the film (containing dopant atoms), that pushes dopant atoms into the silicon. This is called silicon self-implantation.

Fig. 6 Oxygen recoils from the implantation of arsenic through an oxide layer. [2]