The influence of implanted impurities on the thermally-induced epitaxial recrystallization of CoSi 2
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R. G. Elliman Department of Electronic Materials Engineering, Research School of Physical Sciences, Australian National University, Canberra, Australia, and Microelectronics and Materials Technology Centre, Royal Melbourne Institute of Technology, Melbourne, Australia
M. Petravic Department of Electronic Materials Engineering, Research School of Physical Sciences, Australian National University, Canberra, Australia
R. P. Thornton Microelectronics and Materials Technology Centre, Royal Melbourne Institute of Technology, Melbourne, Australia
J. S. Williams Department of Electronic Materials Engineering, Research School of Physical Sciences, Australian National University, Canberra, Australia, and Microelectronics and Materials Technology Centre, Royal Melbourne Institute of Technology, Melbourne, Australia (Received 22 October 1990; accepted 11 January 1991)
The influence of implanted impurities (B, O, P, Ar, Xe, Pb, and Bi) on the rate of low-temperature (138 °C), solid-phase epitaxial growth (SPEG) of amorphized CoSi2 has been studied. SPEG rates of impurity-implanted CoSi2, as determined from time-resolved reflectivity measurements, were retarded for all impurities compared to that of Si-implanted CoSi2. The extent of retardation varied from a factor of 1.5 for P to 9.4 for Xe. Channeling measurements of impurity-implanted CoSi2 indicated that Xe and Bi atoms were located on nonsubstitutional lattice sites while —40% of Pb atoms occupied either substitutional sites or vacant interstitial cation sites following annealing. The presence of impurities did not affect the CoSi2 post-anneal crystalline quality, and no significant impurity diffusion was apparent at 138 °C from secondary-ion mass spectrometry measurements.
I. INTRODUCTION
Low-resistivity metal silicides such as CoSi2 have important applications for the fabrication of integrated circuits including contact, gate, and inter-connect metallization. CoSi2 has a crystallographic structure (fluorite1) and lattice parameter (0.5365 nm1) suitable for the growth of epitaxial CoSi2 layers on crystalline Si substrates.2 Such epitaxial metal silicide heterostructures have potential use in advanced devices, including metal-base transistors.3'4 Ion implantation of CoSi2 layers is of technological interest as a means of shallow junction formation by thermal diffusion of implanted dopants into an underlying Si substrate.5 The redistribution of B and As in CoSi2 during rapid thermal annealing at temperatures >500 °C has been reported previously6'7 and the stability of such structures has recently been discussed in terms of thermodynamic considerations.8'9 In addition", the J. Mater. Res., Vol. 6, No. 5, May 1991
diffusion of implanted impurities (B, P, Ge, Ga, As, and Sb) in polycrystalline CoSi2 layers at temperatures of >400 °C has been investigated,10'11 although, in such studies, the CoSi2 layer was not amorphized during implantation. However, crystalline CoSi2 layers can be amorphized by Si implantation at temperatures of 196 CC.12 During annealing, such layers r
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