Atomistic modeling of deactivation and reactivation mechanisms in high-concentration boron profiles

Abstract

We use kinetic nonlattice Monte Carlo atomistic simulations to investigate the physical mechanisms for boron cluster formation and dissolution at very high B concentrations, and the role of Si interstitials in these processes. For this purpose, high-dose, low-energy B implants and theoretical structures with fully active box shaped B profiles were analyzed. Along with the theoretical B profile, different Si interstitial profiles were included. These structures could be simplifications of the situation resulting from the regrowth of preamorphized or laser annealed B implants. While for B concentrations lower than 1020 cm−3, B clusters are not formed unless a high Si interstitial concentration overlaps the B profile, our simulation results show that for higher B concentrations, B clusters can be formed even in the presence of only the equilibrium Si interstitial concentration. The existence of a residual concentration of Si interstitials along with the B boxes makes the deactivation faster and more severe.

Below-band-gap electroluminescence related to doping spikes in boron-implanted siliconpndiodes

“…Following the model which was proposed by Pelaz et al, 28,29 boron clustering occurs at the very early stage of annealing when the supersaturation of silicon interstitials is very high in ion implanted silicon. 30,31 Boron gathering during the nucleation of the extended defects was also observed by Bonafos and Xia et al 16,17 The preformed B clusters grow by adding interstitial boron in the presence of a high boron concentration, resulting in boron complexes with a high interstitial content. With increasing annealing time the Si interstitial supersaturation decreases and preformed B-Si interstitial clusters start emitting Si interstitials, leaving more stable boron clusters with a low silicon interstitial content.…”

Deactivation of ultrashallow boron implants in preamorphized silicon after nonmelt laser annealing with multiple scans

“…13 The interstitials flow towards the surface and decorate the boron profile, producing boron interstitial clusters. [14][15][16][17] In this letter, multiple laser scan annealing at 1150°C followed by isochronal rapid thermal postannealing at lower temperatures is used to investigate the role of end-of-range defects in the redistribution and deactivation of ultrashallow B profiles in preamorphized and nonmelt laser-annealed silicon.N-type ͑100͒ Czochralski-silicon wafers were preamorphized with 5 keV Ge + to a dose of 1 ϫ 10 15 cm −2 producing a surface amorphous layer to a depth of ϳ15 nm. 500 eV B + was implanted into the amorphous layer to a dose of 1 ϫ 10 15 cm −2 .…”

Atomistic analysis of B clustering and mobility degradation in highly B‐doped junctions

“…These processes are highly transient and its dynamics needs to be captured by models in order to define the optimum processes that provide maximal dopant activation with minimal diffusion. Predictive process simulation has stimulated the development of detailed models about dopant diffusion, evolution of extended defects and formation and dissolution of dopant-defect clusters [2][3][4]. Although continuum models are the mainstay in process simulators used in the semiconductor industry, atomistic process models are very helpful to extract relevant parameters (diffusivity, binding energies, etc.…”