Precipitation, ripening and chemical effects during annealing of Ge+ implanted SiO2 layers

The Ge redistribution and nanocrystal formation in Ge+ implanted SiO2 layer s have been systematically studied by RES, TEM and XPS. Annealing in N-2 or Ar leads to a dramatic change of the as-implanted Gaussian-like Ge depth d istribution to a bimodal profile and, additionally, an accumulation of Ge a t the Si/SiO2 interface. XTEM images show no Ge nanocrystals in the region of the sub-surface peak, whereas the deeper peak can be clearly related to Ge nanocrystals. A similar Ge redistribution occurs after annealing in pure O-2, but in this case amorphous GeOx clusters have been found too. The ann ealing behaviour is explained by the in-diffusion of an oxidant (O-2 or a f ew ppm of moisture) from the annealing ambient and its subsequent reaction with dissolved and/or clustered Ge. Kinetic 3D lattice Monte-Carlo simulati ons have been performed to prove this model of the Ge redistribution and na nocluster evolution. (C) 1999 Elsevier Science B.V. All rights reserved.