The Influence of Implantation Conditions and Target Orientation in High Dose Implantation of Al + into Si
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THE INFLUENCE OF IMPLANTATION COWDITIONS AND TARGET ORIENTATION IN HIGH DOSE IMPLANTATION OF Al+ INTO Si
F. NAM-AVAR,* J. I. BUDNICK,* A. FASIHUDDIN,* H. C. HAYDEN,* D. A. PEASE,* F. A. OTTER,** AND V. PATARINI** *The University of Connecticut, Storrs, CT 06268; **United Technologies Research Center, East Hartford, CT 06108
ABSTRACT We report the preliminary results of a study to determine the dependence of the near surface composition and structure on total dose, dose rate, vacuum condition and substrate orientation for Al implgntation into Si (111) and 2 Si (100) with doses up to 2 x 101l ions/cm . Our studies include the results of Rutherford Back Scattering (RBS), Auger Electron Spectroscopy (AES) and x-ray diffraction measurements on samples implanted with a _00 keV energy in a diffusion pumped vacuum (DPV) system (10 Torr) with and without-g LN2 trap and in an ultra high vacuum (UHV) system (24) x 10 Torr. 2
Results of high dose rate (50 WA/cm ) implantation into Si (111) in an untrapped DPV system indicate that Al segregates with a preferred (111) orientation. For a dose 8 2 of 1 x 101 ions/cm the surface is Al-rich to a depth of 2500A while for lower doses the surface is silicon-rich. A carbon build-yp occurred for samples prepared by low dose rate (5 WA/cm ) implantation. However, no A1 segregation could be observed for doses of less than 101 ions/cm . A similar behavior has been observed for Si (100) except that Al segregation occurs with a polycrystalline structure. Moreover, the segregated Al is present at depths greater than the projected range. When implantation was carried out in a DPV system with a LN 2 trap, no carbon peaks could be observed by RBS regardless of the dose rate. For these conditions, as well as for the implantation of Al in an UHV system, we find Al segregation with a polycrystalline structure independent of the dose rates and target orientations we used. Al is observed at a depth greater by a factor of two than the expected value from the R calculations. The Al depth penetration increases with the dose of implantation.
INTRODUCTION We have recently shown Il] that, under certain conditions, the implantation of energetic Xe through the interface of deposited Al thin films on Si substrates can produce an Al-Si alloy layer which is uniform in texture. No segregation was observed for a long period of room temperature annealing. Our subsequent experiments demonstrated [2] that Al-Si alloy 0 layers are stable under heat treatments of up to 450 C where at this temperature a thin film of Al is formed at the sample surface. We have been very interested in understanding the reasons for this stability and in determining the dependence of stability on the presence of undersized and oversized impurities such as oxygen and Xe.
Mat. Res.
Soc. Symp. Proc. Vol.
27 (1984) OElsevier Science Publishing Co., Inc.
348
Since the production of an oxygen-free Al-Si interface is normally very difficult, we proceeded to prepare Al-Si mixtures by direct high dose implantation of Al into silicon. Our i
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