Precipitation as the Phenomenon Responsible for the Electrically Inactive Arsenic in Silicon

Abstract

The physical nature of the electrically inactive arsenic in silicon was investigated by annealing experiments performed on specimens doped in a wide range of concentration, up to 4 x 1021 cm ~, obtained by ion implantation and laser annealing. Thermal treatments of these alloys at temperatures of 800 ~ 900 ~ and 1000~ provided solid solubility values which correspond to the carrier density in equilibrium with excess dopant. Additiona] confirmation that the electrically inactive arsenic is a precipitated phase was obtained by the kinetics of the annealing process. The occurrence of precipitation in an amount which is consistent with that of the electrically inactive dopant was confirmed by small angle x-ray scattering which provided also details on the size and shape of the particles. The latter are in form of thin platelets and match the structure of the silicon lattice. These results clearly contradict the models developed to account for the difference between carrier and arsenic concentration which hypothesize the formation of a high equilibrium concentration of complex point defects making the excess dopant electrically inaetive.

Reply to ‘‘Comment on ‘Atomistic models of vacancy-mediated diffusion in silicon’ ’’ [J. Appl. Phys. 78, 2362 (1995)]

“…In fact, there is direct experimental evidence to the contrary in that laser annealed or molecular-beam-epitaxygrown samples can show active donor concentrations more than an order of magnitude above the equilibrium solubility level. [18][19][20] The work of Bakeman and Borrego 21 is cited to support the approach used by Antoncik. 1,7 As in Refs.…”

Lattice compression of Si crystals and crystallographic position of As impurities measured with x-ray standing wave spectroscopy

“…The definite nature of the conclusion contrasts with results from other techniques. Varied mechanisms have been suggested to explain the primary cause for deactivation, including the following: the formation of small As clusters, 18 the formation of As precipitates, 19 the creation of structural defects working as traps, 20 and the migration of As from substitutional to interstitial sites. 21,22 Although the substitutional nature of deactivated As impurities is not longer under discussion, 23,24 the details of the responsible defect are still under debate.…”

Suppression of uphill diffusion caused by phosphorus deactivation using carbon implantation

“…Because solid solubility of dopants increases with temperature, laser annealing was performed to minimize dopant diffusion and improve dopant activation [3]. Unfortunately, dopant deactivation may occur during low-temperature processes after laser annealing [4][5][6]. Deactivation of laser annealed arsenic was demonstrated to generate point defects, causing diffusion of the boron layer embedded in silicon substrates [7].…”