Microstructural Characterization of High Dose Oxygen Implanted Silicon
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MICROSTRUCTURAL CHARACTERIZATION OF HIGH DOSE OXYGEN IMPLANTED SILICON
J.L.BATSTONE, ALICE E.WHITE, K.T.SHORT, D.C.JACOBSON AT&T Bell Laboratories, Murray Hill, NJ 07974.
J.M.GIBSON
AND
ABSTRACT The microstructure of oxygen implanted silicon for use in silicon-on- insulator technology has been examined by transmission electron microscopy. A variety of buried oxide layers prepared using oxygen doses below and above that required for stoichiometric SiO 2 formation have been studied. High resolution imaging in crosssection has revealed exceptionally flat Si-Si0 2 interfaces, comparable to the best thermally grown Si-SiO 2 interfaces. Examination of as-implanted material shows a complex interwoven crystalline/amorphous structure which evolves during high temperature (1350-1400 ° C) annealing into a buried oxide layer.
INTRODUCTION Implantation of high doses (1018 0 cm- 2 ) of oxygen ions into crystalline silicon at energies exceeding 100keV is rapidly becoming an attractive method of fabricating silicon-on-insulator structures [1]. High temperature post-implantation annealing[2] results in the diffusion of oxygen to form a stoichiometric buried Si0 2 layer beneath good quality single crystal silicon. Several factors influence the final quality of the layer. Of particular importance for device applications is the density of dislocations in the surface silicon layer which is influenced by both the implanted oxygen dose [3] and the temperature and duration of post implantation annealing [4]. Moreover, the formation of the buried oxide layer and its continuity are strongly affected by the substrate temperature (T,) during implantation [3,5,6]. Determination of the oxygen distribution in implanted structures is usually performed using bulk analytical techniques such as Rutherford backscattering and channelling, Auger electron spectroscopy and secondary ion mass spectrometry. However, detailed information regarding the microstructure of buried oxide layers is best obtained using transmission electron microscopy (TEM), and a complete understanding of buried oxide layer formation is obtained by a correlation of TEM with the above analytical techniques. In studying defects, precipitates and their removal during annealing, a combination of planview and cross-sectional TEM imaging has proven essential. Similarities between high dose implanted layers and low concentration oxygen precipitation in Czochralski (Cz) silicon have been observed. The detailed TEM study of the samples presented here is indicative of the results observed after a careful study of various implantation and annealing conditions [5]. EXPERIMENTAL DETAILS Buried oxide layers have been formed in Si(100) wafers by implantation at 17 temperatures in the range 25--700'C in the dose range 1xl0 to 2x10t8 0 ions was performed annealing Post implantation 1200 keV. cm-2 at energies from 100 to in an A12 0 3 tube furnace in an argon + 1% oxygen ambient at 1300-1400 C [3]. Mat. Res. Soc. Symp. Proc. Vol. 74. 1987 Materials Research Society
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Samples were subseque
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