Characterisation of Device Grade Soi Structures formed by Implantation of High Doses of Oxygen
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CHARACTERISATION OF DEVICE GRADE SO1 STRUCTURES FORMED BY IMPLANTATION OF HIGH DOSES OF OXYGEN * *t P.L.F. HEMMENT, E.A. MAYDELL-ONDRUSZ , K.G. STEPHENS, 0 A.C. GLACCUMk, J.A. KILNER and J.B. BUTCHERA
R.P. ARROWSMITH
+
+Dept. of Electronic & Electrical Engineering, Universitg of Surrey, U.K.; British Telecom Research Laboratory, Martlesham Heath; Imperial College, London; AMiddlesex Polytechnic, Bounds Green, London. tPermanent address: Institute of Nuclear Physics,
Krakow, Poland
ABSTRACT SO1 structures have been formed in (100) silicon by implantinq 400 keV molecular oxygen to a dose of l. SxlO 0 atoms cm . These samples were annealed at 1150°C for 2 hours with a SILOX cap. Oxygen depth profiles have been determined by SIMS and wafers implanted at about 500°C have been characterized by studying the regrowth kinetics, As drive in and oxidation rate in the top silicon overlay. INTRODUCTION Silicon on insulator (SOI) structures formed by the implantation of high doses of oxygen ions have been studied recently by a number of groups [1],[2],[3]. Very high doses of oxygen (> 1018 0 cm-2) are required to synthesise the buried oxide layer and, consequently, the supply of wafers has been very limited but, nevertheless, the material has been shown to be a suitable substrate for LSI circuits. As the material is compatible with current silicon processing technology it is expected to be suitable also for VLSI circuits. In this paper we report further results from experiments to characterize the material, the work being part of an "on going" study of this SOI technology [4]. EXPERIMENTAL DETAILS Synthesised SO1 structures have been formed by impl~nting 400 keV 18 molecular oxygen ions to a dose of l.8xlO atomic 0 cminto device grade (100) silicon wafers of diameter 50 mm and 75mm using the Heavy Ion Accelerator at the University of Surrey [3]. Wafers have been implanted 0 within the temperature range 325 C to 600 C. After implantation the wafers were furnaced annealed at 11500C for 2 hours in flowing N2 , using a SILOX cap. Batches of samples (5mm x 5mm) have been cleaved from wafers implanted at about 500 C and further processed (i) by implantation with lxlO16 As+ cm-2 at 40 keY and annealed and (ii) oxidized in dry oxygen at 950°C. Samples have been surface analysed by the SIMS [5] and Rutherford backscattering (RBS) methods. Test batches of wafers have also been fully processed to 5 pm NMOS and 3 pm CMOS rules [6]. RESULTS AND DISCUSSION Figure I shows SIMS depth profiles from samples implanted with 1.8 x 1018 0 cm-2 at substrate temperatures of 325°C, 400°C, 5000C and 6000C. Figure l(a) shows the profiles from the as implanted samples. The profiles are smooth, asymmetric and show saturation of the oxygen volume concentration at the value corresponding to stoichiometric Si0 2 . Independent analyses
Mat. Res. Soc.Symp. Proc. Vol. 27 (1984)(
Elsevier science Publishing Co.,Inc.
282
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FIG. 1. Oxygen dept
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