Formation and ordering of self-assembled Si islands by ultrahigh vacuum annealing of ultrathin bonded silicon-on-insulator structure

Thermal agglomeration of Si in an ultrathin (< 10 nm) bonded silicon-on-ins ulator (SOI) wafer was studied by means of X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). It was found that annealing in an ultrahigh vacuum (UHV) causes the formation of square-shaped holes whose s ides are parallel to the (011) directions. Within the hole, single-crystall ine Si islands are densely formed on the buried SiO2 with an ordered alignm ent in the (013) directions. The lateral size and the height of a typical i sland near the center of the hole are about 500 and 70 nm, respectively, an d the island is surrounded by facets of {111}, {113} and {100} crystal plan es. The initial process of hole opening and island formation is discussed. (C) 2000 Elsevier Science B.V. All rights reserved.