Nuclear Instruments and Methods in Physics Research B 120 (1996) 68-73 zyxwvutsrqponmlkjihgfedcbaZYXWVU a __ __ k!iB ELSEVIER NOM zyxwvutsrqpon B Beam Interactions with Yeteriats & Atoms Investigation of BF; implants in silicon through SiO, films Redistribution of fluorine and boron under rapid thermal annealing L. Kaabi a,17* , C. Gontrand a, M. Lemiti a, B. Remaki b, B. Balland a, J. Meddeb ‘,*, O.Marty’ a zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA Lahoratoire de Physique de la MatGre, U.M.R., C.N.R.S. CSS-Il. Institut National des Sciences Applique’es de Lyon, 20 avenue A. Einstein, F-69621 Villeurbanne Cedex, France b Laboratoire d’ilech-onique des Solides, Biit. 201, Universifi Claude Bernard Lyon I, Boulevard I1 Novembre, F-69622 Villeurbanne Cedex, France ’ Diparrement de Physique des MattGiaux, Universik Claude Bernard de Lyon I. 43 Bd I I Novembre 1918, F-69622 Villeurbanne Cedex, France zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPO Abstract Boron difluoride (BFC) ions implantation through protecting oxide films was investigated to understand the behaviour of fluorine in damaged region under rapid thermal annealing (RTA) as well as in attempt to form shallow p’/n junctions. The implants redistribution profiles as a function of annealing temperatures and time have been monitored by the secondary ion mass spectrometry (SIMS). Implantation induced point-defects are detected by means of deep level transient spectroscopy (DLTS) technique. The effects of both fluorine and the RTA ion-implant damage annihilation on the transient enhanced boron diffusion are investigated. In particular, the fluorine segregation behaviour near the post implantation disturbed/crys- talline interface, resulting in clustering and void formation, as well as near the initial oxide/crystalline silicon is closely related to used technological data. 1. Introduction Implanting through protecting oxide films, allowing to mitigate channeling effects as well as to minimise the dopant enhanced diffusion, is in current use in microelec- tronic technologies. In the circumstances, this procedure is used for channel doping of MOSFETs for threshold volt- age readjustment and for shallow and steep doped junction formation (p’ doped source/drain). The ’ 'B' ionic boron implantation through oxide films, to create p-type surface conductive layers in n-type substrates, has been reported in several studies [l-3]. Depending on whether the position of the implanted dopant peak is localised in oxide far from the SiO,/mono-Si interface, the boron diffusion is largely reduced. However, an accelerated movement of dopants persists in the tail profiles region if the distribution range is of the same order or greater than the protecting oxide thickness [4]. Therefore, implantation of more massive * Corresponding author. ’ Future address: Institut National des Sciences Appliqu&s et de Technologie, B.P. 676, 1080 Tunis Cedex, Tunisia. ‘Permanent address: Dkpartement de Physique, faculti des Sciences, 5000 Monastir, Tunisia. molecular ions, resulting in shorter intrinsic range, reduces the boron enhanced diffusion in the profile tail region [5-81. Taking into consideration the effective role played by the molecular ion mass related to boron on the accelerated diffusion kinetics as well as the opportunity of reducing the junction depth, boron is implanted in the form of boron difluoride (BFC). Only approximately 22%, the atomic ratio of B to BFC, of the implant energy is transferred to the boron in this case. It is useful to operate at higher energy since the yield of the ion source is usually higher for the BFC ions. Therefore, this procedure present the opportunity to implant even at very low-energy boron at higher beam current by boron difluoride implantation. However, to the best of our knowledge, there is little data focused on the behaviour of fluorine in disturbed regions formed by implanting BFC, at moderate energy, through different surface oxides thicknesses. In this paper, we report on the effect of different rapid thermal treat- ments on the fluorine implanted into crystalline silicon through screen oxide layers. In particular, the effect of fluorine and of the implantation defects on the various enhanced boron diffusion processes, during several rapid thermal treatments, is investigated. 0168-583X/%/$15.00 Copyright 0 1996 Published by Elsevier Science B.V. All rights reserved PII SOl68-583X(96)00481-8