Carbon Enhancement of SiO[sub 2] Nucleation in Buried Oxide Synthesis Computer Simulations and Secondary Ion Mass Spectroscopy Depth Profiling

Abstract

Physical mechanisms of oxygen transport and precipitation in silicon during the synthesis of buried oxide layers are reviewed. Different effects caused by the interaction of weakly bonded oxygen with mobile point defects and static defect complexes are analyzed. As a result, the possibility of controlling the evolution of the spatial distribution of implanted oxygen by means of gettering and defect engineering are studied and validated by computer simulations based on a quasi-chemical description of the kinetics. Special attention is given to carbon induced gettering mechanisms involved in the buried oxide synthesis known as low-dose approach combined with defect engineering. Secondary ion mass spectroscopy profiling data together with the results of computer simulations show a rather complicated behavior of the carbon and point toward an important role of the carbon-vacancy and carbon-oxygen complexes in the oxygen accumulation. Some effects in the early stage of the oxygen redistribution are revealed and discussed. The influence of an inhomogeneous distribution of bonded oxygen in silicon on the yield of different single atomic and cluster secondary ions ͑SIs͒ during oxygen sputtering is studied. The role of different oxygen containing phases in SI formation is discussed. It is shown that carbon acts on SiO 2 precipitates not only in a local but also in a global manner.The formation of a buried oxide ͑BOX͒ layer in a Si substrate is accompanied by a redistribution of the implanted oxygen, independent of the used SIMOX technology. Both vacancy and interstitial defects induced by the oxygen implantation play a very important role in this process. Another key factor is the presence of oxygen precipitates. Their parameters strongly depend on the thermal history of the sample, i.e., temperature and duration of previous heat treatments, heating and cooling rates, and to some extent, on the presence of other impurities such as C, N, Fe, etc. The details of the oxygen redistribution become even more important for the recently developed low dose, stimulated technology, since in that case oxygen must be accumulated in a very thin layer of the matrix. 1 In all low dose approaches the control of the accumulation of oxygen becomes an important issue and the use of gettering, for obtaining the required control, would be very desirable. This paper is devoted to a study ͑both experimentally and by computer simulations͒ of the mechanisms lying at the basis of the functioning of an oxygen getter formed by the implantation of carbon. This type of getter allows one to grow ultrathin ͑ϳ50 nm͒ stoichiometric buried oxides, by using a two-step oxygen ion implantation ͑the total oxygen dose is about 2 ϫ 10 17 cm Ϫ2 ͒ and intermediate annealing cycles. 1,2 It is shown that in this case gettering is only possible due to the synergetic action of both carbon and vacancies and depends on the local atomic environment of the carbon atoms in the silicon lattice.Buried SiO x in silicon prepared by a relatively low dose ( ϳ 10 17 cm Ϫ2 ) oxygen...

Computer Modelling of SiO₂ Precipitation in Cz-Si Doped with Nitrogen

“…The second term in the denominator, DG el is the change in the total elastic energy of the spherical nucleus related to the change of the unit volume, g and b are the numbers of self-interstitials and vacancies emitted and absorbed (per one oxygen atom) by the precipitate for partial strain relief. It is known that nitrogen causes the effect of vacancy enrichment (C V /C* V ratio increases) [11] and create additional free volume [12] similar to carbon. Therefore, because of nitrogen, the denominator in (9) increases and a lot of potential centers of nucleation became additionally suitable for precipitation in N-enriched Si.…”