NIOMI zyxwvutsrq B Nuclear Instruments and Methods in Physics Research B 85 (1994) 921-924 North-Holland Beam Interactions w ith Materials A Atoms Observation of local SIMOX layers by microprobe RBS A. Kinomura *, Y. Horino, Y. Mokuno, A. Chayahara, M. Kiuchi, K. Fujii zyxwvutsrqponmlkjihgfedc Government Industrial Research Institute Osaka, Midorigaoka, Ikeda, Osaka 563, Japan M. Takai, T. Lohner ’ Faculty of Engineering Science and Research Center for Extreme Materials, Osaka University, Toyonaka, Osaka 560, Japan H. Ryssel, R. Schork Fraunhofer Arbeitsgmppe fuer Integrierte Schaltungen, Artilleriestrasse 12, 08520 Erlangen, Germany Buried oxide layers locally formed by oxygen implantation in silicon were analyzed by Rutherford backscattering with a 1.5 MeV He+ microprobe. Lateral and cross-sectional images of 0 and Si atoms in the buried oxide layers could be successfully obtained by scanning the microprobe over the sample. The Si images showed better contrasts than the 0 images. A process-failure region was detected by RBS mapping images. 1. Introduction A SIMOX (separation by implanted oxygen) pro- cess, which realizes uniform silicon-on-insulator (SOI) structures by high dose oxygen implantation into sili- con, has been widely studied as one of the most promising technologies for device isolation [1,2]. It is necessary to investigate local structures in SIMOX layers to improve quality of buried oxide and top silicon layers. Moreover, a local SIMOX process has been recently studied with implantation through pat- terned mask layers such as silicon dioxide [3,4]. Uniform SIMOX layers were analyzed by various methods such as cross-sectional TEM (transmission electron microscopy) and conventional RBS (Ruther- ford backscattering). However, it is not easy to investi- gate microareas by conventional methods. Microprobe RBS can be a useful tool for such local structures, because it is possible to analyse three-dimensional structures without special sample preparation such as etching or cleaving [5,6]. In this study, locally formed SIMOX layers were analyzed by an RBS-mapping method with a 1.5 MeV He+ microprobe. Lateral and cross-sectional images of silicon and oxygen in local SIMOX layers were ob- * Corresponding author, phone +81 727 519 531, fax +81 727 519 631. Data acquisition was fully controlled by a personal computer. The computer system had a random access memory of 11 Mbytes and a built-in histogram memory directly combined with a computer bus, so that a set of 4096 RBS spectra, corresponding to 64 X 64 pixels within a scanning area, could be collected and stored. This facility made it possible to obtain a full three-di- mensional (3D) data set for RBS mapping analysis [s]. Median filters with sizes of 7 X 7, 9 X 9 and 11 X 11 pixels were used to suppress the influence of statistical error in the images [9]. The filter sizes were selected by taking account of average scattering yields and spatial resolution of the images. ’ On leave from Central Research Institute for Physics, Hun- Local SIMOX layers were prepared by 180 keV gary. oxygen implantation into Si to a dose of 1.6 x 1018 tained by scanning the microprobe. A process-failure region of the local SIMOX layers was detected by the RBS mapping method. 2. Experimental A microbeam line combined with a Van de Graaff accelerator in Government Industrial Research Insti- tute Osaka was used to form a 1.5 MeV He+ micro- probe for local RBS analysis [7]. The spot size was 4 x 4 km2 with a beam current of 20 pA. The scanning area was 120 x 120 km’. Backscattered particles were detected by a silicon surface barrier detector @SD) of an annular type with a scattering angle of 170”. 0168-583X/94/$07.00 0 1994 - Elsevier Science B.V. All rights reserved SSDI 0168-583X(93)E0572-X XV. SEMICONDUCTORS