Micro-RBS Analysis of Masklessly Fabricated Structures
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MICRO-RBS
ANALYSIS
OF
MASKLESSLY
FABRICATED
STRUCTURES
A. Kinomura, M. Takai, T. Matsuo, M. Satou*, M. Kiuchi*, K. Fujii* and S. Namba Faculty of Engineering Science and Research Center for Extreme Materials, Osaka University, Toyonaka, Osaka 560, Japan *Government Industrial Research Institute Osaka, Ikeda, Osaka 563, Japan ABSTRACT Rutherford backscattering (RBS) analysis of small-sized structures, fabricated by laser chemical vapor deposition (LCVD) with a focused laser beam and ion implantation with a focused ion beam (FIB), has been performed by a microprobe with focused 1.5 MeV helium ions. Micro-RBS spectra and RBS-mapping images revealed a local distribution of masklessly deposited Mo layers on GaAs and local doses of masklessly implanted Au atoms in Si. INTRODUCTION Maskless fabrication processes of semiconductor integrated circuits have recently attracted considerable attention due to increasing requirements for repairing and customizing circuits [1]. A focused ion beam (FIB) system has made it possible to masklessly implant ions in semiconductors with minimum spot sizes close to ion ranges [2]. Local chemical-reactions induced by focused laser or ion beams have also realized maskless etching or deposition in micro areas from several microns down to submicron [3,4]. Such local interactions or reactions have unique characteristics which cannot be observed in processes for large areas [1]. Therefore, a microprobe technique suitable for characterization of the local structures is needed. An RBS analysis can provide information on elemental distribution in depth without etching a substrate. Although a spot size of conventional RBS systems ranges about 0.5 - 1 mm, recent developments of MeV ion microprobe have realized a minimum spot size of several microns down to submicron [5-7]. The MeV ion microprobe has made it possible to perform not only RBS analysis of micro areas but also three-dimensional elemental mapping which cannot be obtained by electron microprobes [6-9]. In this study, RBS analyses of Mo lines, delineated by a maskless LCVD process, and gold lines, masklessly implanted by a focused ion beam system, were made by the microprobe with focused 1.5 MeV helium ions. Micro-RBS spectra of the delineated line and elemental mapping image by an RBSmapping method were obtained. Distributions of the deposited Mo and local dose of implanted Au atoms were discussed. EXPERIMENTAL PROCEDURE Figure 1 shows the schematic diagram of the analytical system. The microprobe was realized with piezo-driven objective collimators and a magnetic quadrupole doublet. 1.5 MeV helium ions or protons supplied by a Van de Graaff accelerator can be focused down to a spot sizes of 0.9 pm x 1.2 pm and 1.2 pm x 1.4 pm, respectively. A spot size used in this study was 3 pm x 3 pm to increase a beam current for obtaining good statistics in the RBS analysis. The beam current was 100 pA for this spot size. The detailed parameters of the ion optics used in this study has been published elsewhere [6,7,10]. A target position to be an
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