Temperature Dependence of Ion Assisted Epitaxial Growth of Chemical Vapor Deposited Si Layers
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TEMPERATURE DEPENDENCE OF ION ASSISTED EPITAXIAL GROWTH OF CHEMICAL VAPOR DEPOSITED SI LAYERS. A. La Ferla*, E. Rimini C. Spinella Dipartimento di Fisica - Corso
Italy.
SGS
-
Thomson
-
Stradale
Italia
and G. Ferla 57 - 195129
Primosole
50-
195100
Catania
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Catania -
Italy.
ABSTRACT Thin layers of Si were chemical vapor deposited onto as received p-type Si wafers and implanted with 80 KeV of As 1 5 2 or Ge to a fluence of I x 10 /cm . Irradiation at 450°C with 600 KeV Kr++ ions causes the epitaxial growth of the entire deposited and amorphized Si layer. At lower irradiation temperatures the regrowth rate of the deposited layers is substantially reduced with respect that of the implanted amorphous layers. The presence of As enhances the regrowth rate of a factor 2.5. The results are explained qualitatively in terms of a dynamical bond breaking of SiO 2 , and of a dopant influence on the migration energy of the defects responsible for the growth.
INTRODUCTION Solid phase epitaxial growth (SPEG) of amorphous silicon has been mainly investigated for layers formed by ion implantation of either silicon or impurity atoms[1-2]. In the case of deposited amorphous layer the presence of contaminants at the interface with the single crystal retards or impedes the 3 1 Substrates cleaned by the usual procedurer growth. epitaxial before e-gun deposition of Si have at least still a monola er of native oxide. The crystallization of these samples occurs[4] by columnar growth of the amorphous film in some regions randomly distributed on the surface, where the oxide is absent or negligible. The columnar growth is followed by a lateral growth and at the end a uniform single crystal is obtained. Th.e epitaxial, layer by layer growth has been found instead for ultrahigh vacuum deposited amorphous films[5] SPEG can be enhanced by ion beam irradiation. The activation energy of the ion assisted crystallization process is about ý 0.3 eV one order of magnitude lower than that of the pure thermal process. Also the dependence on substrate orientation and impurities of ion beam assisted growth is considerably reduced with respect the pure thermal[7] case. For instance the presence of Ar atoms up to concentrations of few 2 0 3 times 10 /cm in the amorphous layer don't [8] impede the ion beam assisted regrowth as seen instead in the thermal annealing[9], due to the clustering of Ar atoms into bubbles which stop the advancing amorphous/single crystal interface. A preliminar investigation[I01 has shown that chemical
Mat. Res. Soc. Symp. Proc. Vol. 100. C1988 Materials Research Society
382
vapor deposited Si layers onto Si substrates regrow epitaxially under ion beam irradiation at temperature of 450 *C. No cleaning procedure was adopted for the substrates and the deposition was performed on as - received samples with a thin native oxide of about 2 - 3 nm thickness. In the present work we report a more detailed investigation on the temperature dependence of such a growth of deposited films and on the influence of impurities presen
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