The Ion Charge Fluctuation Effect on Impurity Depth Distributions for High‐Energy Ion Implantation. The Backward Transport Equation‐Based Simulation

Abstract

A model of high-energy ion implantation is formulated with allowance for fluctuations of the charge state of ions and the corresponding backward transport equation for post-implantation spatial distributions of an impurity. Simulation results of experiments concerned with boron ion implantation into silicon by numerical solving the backward transport equation are reported. It is shown that the account of ion charge fluctuations in the high-energy range leads to an increase of the range straggling of the implanted impurity and provides a better agreement with the experiment than the traditional methods of modelling based on the use ofthe Monte-Carlo method or the backward transport equations.

Effects of Latent Tracks Formed by High-Energy Ion Implantation in Crystals

“…There are other specific effects relating to the ion tracks in semiconductors. They are migration of atomic species along the tracks 45 and channeling of ions in tracks formed at a previous stage of irradiation. , The “tube”-like structure of tracks with low atomic density can result in the acceleration of diffusion.…”

“…The channeling through the ion tacks is quite similar to the common axial crystallographic channeling. For a description of the movement of energetic ions in such tracks, the low-energy version of the Fokker−Plank equation developed by Beloshitsky and Kumakhov (see ref 52) for proton and α-particles channeling in crystals was adopted for track channeling, , namely where F ( x,E ⊥ ) is the distribution of channeled ion through the transversal energy E ⊥ at the depth x . D ( E ⊥ ) and (d E ⊥ /d x ) loss are the diffusivity and the drift velocity for the transversal energy, respectively.…”

“…All distributions are normalized to 1. The ordinate values are cm -1 .

8 Depth distribution of optical reflectivity at a wavelength of 650 nm (1) on silicon implanted with 335-MeV Ni + ions at a dose of 5 × 10 14 cm -2 . The bevel angle is 10 o .

…”

“…This shoulder spreads up to 10 μm from the main distribution peak. Such a shoulder can be described theoretically by involving the effect of ion channeling through tracks . The parameters used in these calculations were r o = 9 Å, N d = 0.02 N a , and L tr = 30 μm.…”

“…

9 Depth distribution profiles of nuclear stopping power for 60-MeV Ni + ions in diamond (1), taking into account the ion channeling through tracks (2). The circles are the experimental values of cathodoluminescence intensity of the implanted nickel centers

…”