0.5 MeV Submicron Ion Probe System for RBS/PIXE
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0.5 MeV
SUBMICRON
ION PROBE SYSTEM
FOR
RBS/PIXE.
K. ISHIBASHI* , Y. KAWATA* , N. SUZUKI* K. INOUE* , M. TAKAI, AND S. NAMBA Faculty of Engineering Science and Research Center for Extreme Materials, Osaka University, Toyonaka, Osaka 560, Japan. 673-02, * Electronics Technology Center, Kobe Steel Ltd., Nishi-ku, Kobe Japan ABSTRACT A nuclear microprobe-forming system for the microscopic RBS/PIXE measurement of micro devices has been developed and installed at the Research Center for Extreme Materials, Osaka University. The use of precision quadrupole magnets and an objective collimator ensures a final spot size of less than 1pm. INTRODUCTION MeV ion beams with a typical beam size of 0.5-1 mm for RBS and channeling effect measurements have been successfully used to study ionimplanted semiconductors [1-3]. At the same time, however, the feature sizes of semiconductor processing have been reduced to the submicron range. Maskless processes using focused ion or laser beams, for example, are being developed. Furthermore, fabrication of multilayered wirings or interconnections of metals between gates is being studied for ULSI's. In such situations, a nondestructive three-dimensional microanalyzing method with a lateral resolution in the micron-tosubmicron range becomes indispensable to realize future devices. It is, in particular, important to get information on three dimensional structures, crystallinity, atomic composition and distribution. In conventional microscopic analysis, such as Auger electron spectroscopy (AES), a sample surface layer must be sputtered by Ar ions to analyze the subsurface layers. This repeated pre-treatment makes such analysis time-consuming and results in inexact readings of depth. Use of a microbeamline for MeV ions with a beam-spot diameter of less than 3um is one way to deal with the above problem. Several groups have developed such systems [4-10]. The first such system in Japan was constructed and is already in operation by a group including several of the present authors at the Government Industrial Research Institute Osaka (GIRIO) [10-12]. This study reported on a new microbeamline with 0.5 MeV helium ions developed at the Research Center for Extreme Materials at Osaka University. Each of the components and the adjusting mechanism of the system were carefully designed to attain a submicron spot size, building on the experiences gained from the research on the GIRIO system. This paper includes full descriptions of the quadrupole magnet and objective collimator. BEAMLINE Table 1 and Fig. I show the specifications and the schematic diagram of the beamlines, respectively. The Disktron-type accelerator supplies the probe-forming system with helium ions or protons with an energy of 0.5 MeV. Typically it provides a current of over ten Mal. Res. Soc. Symp. Proc. Vol. 128. "1989 Materials Research Society
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Table 1 Specification of the microbeamline at Osaka University (Ion source system) Accelerator Ion source Momentum analyzer (Beam characteristics) Ion Acceleration voltage Energy spread
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