Structure of twinned {113} defects in high-dose oxygen implanted silicon-on-insulator material
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John C. Barry Electron Microscope Centre, University of Queensland, St. Lucia, Brisbane, Queensland 4067, Australia (Received 29 August 1990; accepted 11 December 1990)
Conventional and high resolution electron microscopy (HREM) were used to study the structure of {113} defects in high-dose oxygen implanted silicon. The defects are created with a density of 1011 cm"2 below the buried oxide layer in the substrate region. The HREM images of the {113} defects are similar to the ribbon-like defects in bulk silicon. It is proposed that there is a third possible structure of the defects, in addition to coesite and/or hexagonal structures. Portions of some defects exhibit the original cubic diamond structure which is twinned across {115} planes. The atomic model shows that the {115} interface is a coherent interface with alternating five- and seven-membered rings and no dangling bonds.
I. INTRODUCTION
Silicon-on-insulator structures can be produced by implantation of a high dose of oxygen to form a buried oxide layer below a thin, top silicon layer. This material is referred to as SIMOX (Separation by IMplanted OXygen). The implantation generates defects not only in the top silicon layer, but also in the silicon substrate beneath the buried oxide layer. It has been previously reported that the defects present in the substrate region of as-implanted SIMOX are {113} defects and stacking faults.1"4 The {113} defects are very similar in shape to the oxygen-induced ribbon-like defects (RLDs) in the bulk silicon, which have been extensively studied in the last decade.5 Based on computer simulations of high resolution electron microscopy (HREM) images, the {113} defects were initially identified as ribbon of coesite, a high pressure phase of silicon oxide.6'7 More recently, Carpenter et al} have shown from high resolution analytical electron microscopy provided field emission gun, that oxygen is present in the central area of the RLDs in CZ-silicon. However, evidence was presented that the defects consist of hexagonal silicon and are thus formed by self-interstitial precipitation.5'910 A proposed nucleation and growth mechanism for the RLD is a pure silicon-interstitial agglomeration, as described by Salisbury and Loretto11 or Tan et al.12 More recently, Pirouz et al.,13M who had observed the cubic-hexagonal transformation in hot-indented silicon, discussed the
Present name and address: Supapan Seraphin, Department of Materials Sciences and Engineering, University of Arizona, Tucson, Arizona 85721. 792 http://journals.cambridge.org
J. Mater. Res., Vol. 6, No. 4, Apr 1991 Downloaded: 18 Mar 2015
fact that hexagonal silicon formation by aggregation of silicon self-interstitials in RLDs is unlikely because the hexagonal phase in silicon is not thermodynamically favored. Also, the parallelism of (011)cu || (0001)he and [011]cu || [12Tb]he are unexpected. It would be preferential to have the more natural orientation relationship of (lll) cu || (0001)he and [llb]cu || [1120]he. Thus, it presently appears that one or the other or
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