Mechanism and kinetics of near-surface dopant pile-up during post-implant annealing

Abstract

Dopant pile-up within 1-2 nm of Si/SiO2 interfaces during post-implant annealing can influence the performance of microelectronic devices using silicon-on-insulator technology or super-steep retrograde channels. Pile-up results from changes in the dopant interstitial charge state induced by band bending at the interface. But, there exists little mechanistic understanding of the specific conditions needed for pile-up or of the kinetics of temporal evolution. The present work uses continuum simulations coupled with experiments in the case of B implanted into Si to show that pile-up requires a zone near the interface wherein the Fermi level exceeds the ionization level for dopant interstitials to change their charge state. The spatial extent of pile-up corresponds closely to the width of this zone unless the annihilation probability of defects at the interface is large. The time and temperature dependences of pile-up closely track those of the free dopant interstitials concentration.

Interface-Mediated Photostimulation Effects on Diffusion and Activation of Boron Implanted into Silicon

“…However, the magnitude of pileup is rather small, consistent with a value of V s that is fairly close to the ionization energy for B interstitials. 37 Even very modest decreases in the dark value of V s for thermal oxides would be consistent with the observed disappearance of pile-up for that type of interface. Thus, the presence or absence of pile-up does not offer much help in deconvoluting the relative contributions of S and V s in mediating photostimulation effects.…”

Surface-based manipulation of point defects in rutile TiO2

“…The near-surface accumulation probably has an electrostatic origin, arising from the migration of charged defects under the influence of the electric field in the space-charge region near the surface. Related effects have been explained in detail for Si, 19 and the present work will focus instead on the deeper profile extensions.…”

Suppression of uphill diffusion caused by phosphorus deactivation using carbon implantation

“…However, the impact of generated interstitials on ultrashallow junctions has not been discussed. Because the surface acted as a sink of excess interstitials [11], interstitial generation may produce a retrograde interstitial profile near the surface [12]. Pairing of phosphorus and excess interstitials provided a kinetic driving force for phosphorus diffusion toward the surface.…”