Ma. Szymanski et al., The roles of charged and neutral oxidising species in silicon oxidation from ab initio calculations, MICROEL REL, 40(4-5), 2000, pp. 567-570
We examine the roles of charged oxidising species based on extensive ab ini
tio density functional theory calculations. Six species are considered: int
erstitial atomic O, O-, O2- and molecular species: O-2, O-2(-), O-2(2-) We
calculate their incorporation energies into bulk silicon dioxide, vertical
electron affinities and diffusion barriers. In our calculations, we assume
that the electrons responsible for the change of charge state come from the
silicon conduction band, however, the generalisation to any other source o
f electrons is possible, and hence, our results are also relevant to electr
on-beam assisted oxidation and plasma oxidation. The calculations yield inf
ormation about the relative stability of oxidising species, and the possibl
e transformations between them and their charging patterns. We discuss the
ability to exchange O atoms between the mobile species and the host lattice
during diffusion, since this determines whether or not isotope exchange is
expected. Our results show very clear trends: (1) the molecular species ar
e energetically preferable over alo,nic ones, (2) the charged species are e
nergetically more favourable than neutral ones, (3) diffusion of atomic spe
cies (O, O-, O2-) will result in oxygen exchange, whereas the diffusion of
nzoleculai species (O-2, O-2(-), O-2(2-)) is not likely to lead to a signif
icant exchange with the lattice. On the basis of our calculation, we predic
t that charging of oxidising species may play a key role in silicon oxidati
on process. (C) 2000 Elsevier Science Ltd. All rights reserved.