CHANNELED ION-BEAM SYNTHESIS - A NEW TECHNIQUE FOR FORMING HIGH-QUALITY RARE-EARTH SILICIDES

High dose Er-166 Or Gd-160 implantations are used to form rare-earth ( RE) silicides in Si. After implanting 0.8-2.0 x 10(17) at./cm(2) with 90 keV into Si(lll) substrates kept at similar to 450 to 530 degrees C , we found that using conventional non-channeled implantation (tilted over 7 degrees), it is impossible to form a continuous RESi(1.7) layer . On the contrary, using channeled implantation, a continuous epitaxia l ErSi1.7 layer with very good crystalline quality can be synthesized; a lowest chi(min) value of 1.5% for a surface ErSi1.7 layer is obtain ed. This different behaviour is explained using a model based on the d ifference in implantation depth, defect density and sputtering yield b etween random and channeled implantation, and the results are compared with Monte Carlo simulations. Such a high-quality RESi(1.7)/Si system offers a rare opportunity to study the structure, orientation and str ain comprehensively using Rutherford backscattering and channeling spe ctrometry, X-ray diffraction and TEM. We found that the azimuthal orie ntation of the hexagonal RESi(1.7) layer to the cubic Si substrate is RESi(1.7)[0001]parallel to Si[111] and RESi(1.7){<11(2)over bar 0>}par allel to Si{110}. It is further observed that the ErSi1.7 epilayer is compressively strained and quasi-pseudomorphic. In the case of GdSi1.7 the most difficult rare-earth silicide to form, an enhanced stabiliza tion of the hexagonal over the orthorhombic phase is observed.