THE GROWTH OF PINHOLE-FREE EPITAXIAL DYSI2-X FILMS ON ATOMICALLY CLEAN SI(111)

The growth of pinhole-free epitaxial DySi2-x films on atomically clean Si(111) has been achieved by depositing a 2-nm-thick Dy layer onto Si (111) with a 1.5-nm- thick capping amorphous Si (a-Si) layer at room t emperature followed by annealing at 700 degrees C in ultrahigh vacuum. The thickness of the a-Si was selected to be such that the consumptio n of Si atoms from the substrate is minimized by taking into account t he formation of an amorphous interlayer at the Dy/Si(111) interface. B ased on our experimental findings, a new mechanism for the formation o f pinhole is proposed. The Stranski-Krastanov growth behavior of epita xial DySi2-x on Si(111) by solid phase epitaxy leads to the apparently random formation of a high density of recessed regions at the initial stage of silicidation. Polycrystalline DySi2-x was found to be presen t at the areas inside and epitaxial DySi2-x outside the recessed regio ns. Large numbers of Si atoms from the substrate can therefore diffuse through the recessed regions. As a result, the depth and size of the recessed regions increase with annealing time. Finally, the DySi2-x th in layer inside the recessed regions with higher interface energy is t hermally unstable and breaks apart to form pinholes. (C) 1998 American Institute of Physics. [S0021-8979(98)08719-2].