Metastable acceptor centers in boron implanted silicon

Abstract

The evolution of the electrical activation with the annealing time in B1 implanted (5.0 31014 cm22, 50 keV! Si was studied as a function of the annealing temperature. Electrical activation yields of 15%–30% were observed after annealing for 2 s at temperatures above 550 °C. Prolonging the annealing time from 2 to 900 s we observed that the electrical activation evolves differently according to the temperature: ~i! at 550 °C,T,700 °C it decreases toward an equilibrium level, ~ii! at 700 °C,T,800 °C it decreases during the first minutes and subsequently increases again, and ~iii! at temperatures ,550 °C or T.800 °C it increases continuously. In order to explain the carrier removal observed during annealing at 550–800 °C we proposed that metastable acceptor centers are formed during the B1 implantation and/or the initial period of the annealing time. Interaction of Si self-interstitial atoms with these centers leads to their neutralization and/or dissociation with consequent decreasing of the carrier concentration.