Improved binary collision approximation ion implant simulators

Abstract

An efficient binary collision approximation ͑BCA͒ ion implant code with good prediction capabilities for semiconductor materials ͑Si, GaAs, SiC͒ with only one fitting parameter for low implantation doses is presented. It includes specific interatomic potentials and recent improvements in physical models for inelastic stopping. A periodic ab initio full bond electron density for the target is used. Damage accumulation is supported using a modified Kinchin-Pease model ͓G. H. Kinchin and R. S. Pease, Rep. Prog. Phys. 18, 1 ͑1955͔͒. Also, some of the BCA integration algorithms and target selection procedure have been refined. An algorithm commonly used for statistical noise reduction has been modified to also improve the noise reduction in the lateral and shallow zones. The agreement with experiments is good, even under channeling conditions and for different target materials. A comparison with experimental secondary ion mass spectroscopy results for several projectiles and targets is presented.

Molecular dynamics simulations of damage production by thermal spikes in Ge

“…41 In most BCA simulators, a value of 15 eV is commonly assumed for both materials, providing a good description of damage. 25,38,42 In this work, the E d value for Ge and Si described by several potentials was calculated by means of MD simulations. Simulations were performed at 0 K, in cubic cells containing 7840 atoms, in which periodic boundary conditions were applied in all directions.…”

“…For this purpose, we have analyzed the energy distribution in the different damage generation events by means of the simulator Ion Implantation in Semiconductors (IIS). 25 This Monte Carlo code, based on the BCA, can simulate ion and recoils distributions, taking into account both elastic and inelastic stopping powers. 5 keV cascades of B, Si, Ge, and Sb ions were implanted in Ge and Si lattices.…”

Atomistic modeling of ion implantation technologies in silicon

“…We gave a certain amount of kinetic energy to a number of Si atoms located in a sphere with velocities in random directions. The initial energy of moving Si atoms was varied between 0 and 20 eV per atom, around the displacement threshold for Si [25,26], and the total deposited energy between 50 and 500 eV. At the end of the simulations we counted the number of atoms displaced from perfect lattice positions.…”

Improved physical models for advanced silicon device processing

“…These collisions can be numerically solved from the energy and momentum conservation laws [37][38][39]. The target atoms are placed in crystalline lattice sites (such as in MARLOWE [37,40,41] and IIS [42] codes) or in random positions to reproduce an amorphous material (such as in SRIM code [43]). This has consequences in the channeling of the implanted ions and therefore in the tails of the profiles.…”

“…To take into account such effect, advanced BCA simulators include the feedback of accumulated damage for the next cascades [40,42,[127][128][129][130]. Figure 11 shows KMC simulation results of the evolution of the a-layer thickness with dose [131], compared with experimental data from Maszara et al [132], for 150 keV Si implants at 82 K. There is an initial fast increase of the a/c interface depth with dose until a given depth is reached, and then, the increase is very slow.…”