Effect of oxygen on the formation of end-of-range disorder in implantation amorphized silicon
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N. Q. Khanh Joint Institute for Experimental Physics of the Technical University of Budapest and of the Central Research Institute of Physics, H-1525 Budapest, P. O. Box 49, Hungary (Received 13 June 1990; accepted 15 April 1991)
Formation of End-of-Range (EOR) disorder was studied in (lOO)-oriented silicon, when subjected to amorphization by implantation of Ge+ ions, followed by a 10 s Rapid Thermal Annealing (RTA) at 1050 °C. XTEM, RBS/channeling, and SIMS were used to analyze Czochralski grown (CZ) silicon wafers with oxygen concentrations of 6.5, 7.0, and 8.0 x 10 17 /cm 3 and Float Zone (FZ) silicon, as "low oxygen" wafers. Amorphization on neighboring parts of the 4" wafers was made either by 60 keV Ge+ implantation or by 110 keV Ge+ implantation and by sequential (60 keV + 110 keV) Ge+ implantation. Parts of each wafer were additionally implanted with 13 keV boron. In FZ silicon, no defects were found for 60 keV Ge+ implantation and RTA at 1050 °C. For 110 keV Ge+ and sequential (60 keV + 110 keV) Ge+ implantation in FZ-silicon the majority of the samples showed perfect annealing. Two wafers, however, subjected to sequential implantation still contained defects but with a defect density that was one order of magnitude lower than for CZ wafers. For one of them, not even a continuous layer of defects was formed. In contrast, CZ wafers contained defect bands, except for the 60 keV Ge+ implantation [in accord with the findings of Ozturk et al., IEEE Trans, on Electronic Dev. 35, 659 (1988)]. The presence of boron had no visible effect on the defect structure.
I. INTRODUCTION +
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Formation of defect-free shallow p n or n p junctions is the focus of microelectronics today. Ion implantation is one of the prospective candidates to produce such junctions. However, the deep ion penetration due to channeling and the transient diffusion of boron during damage regrowth have to be avoided or, at least, have to be kept under control.1 One approach is for a low-mass dopant, like boron, to preamorphize by implantation of a nondoping species, e.g., of self-ions.2 Preamorphization prevents channeling and, simultaneously, improves conditions for a low-temperature solid phase epitaxial growth, which keeps dopant distribution at an acceptable level. The formation of extended defects at the original amorphous/crystalline interface (xa being the depth of the EOR defects) during annealing presents a problem. Low-energy Ge+ ion implantation for amorphization and additional BF 2 + doping3 are recommended to solve this problem.4 Simultaneous amorphization and doping by implantation of BF 2 + is widely used,5 but disadvantageous properties of the fluorine make elemental boron implantation the preferred method.6
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'On leave from Joint Institute for Experimental Physics of the Technical University of Budapest and of the Central Research Institute of Physics, H-1525 Budapest, P.O. Box 49, Hungary. J. Mater. Res., Vol. 6, No. 8, Aug 1991
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