High rate etching of GaAs and GaP by gas cluster ion beams
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High rate etching of GaAs and GaP by gas cluster ion beams Masahiro Nagano1, Shingo Houzumi2, Noriaki Toyoda2, Susumu Yamada1, Shirabe Akita1 and Isao Yamada2 1 Electrical Physics Department, Komae Research Laboratory, Central Research Institute of Electric Power Industry (CRIEPI), 2-11-1 Iwado Kita, Komaeshi, Tokyo 201-8511, Japan 2 Laboratory of Advanced Science & Technology for Industry, Himeji Institute of Technology, 3-1-2 Kouto, Kamigori, Ako, Hyogo 678-1205, Japan ABSTRACT Gas cluster ion beam (GCIB) techniques have recently been proposed as new processing methods. We have been investigating the characteristics of GCIB techniques through sputtering GaAs and GaP by Ar gas cluster ion beams as a function of cluster size and acceleration energy. The Ar cluster size was selected by a magnetic spectrometer, and was obtained from the mass spectra measured by a time of flight mass spectrometer. The average sputtering yields of GaAs and GaP were 0-47 and 0-66 atoms/ion for 5-30 kV, respectively. The sputtering yields of GaAs and GaP were higher than those of an Ar monomer ion. INTRODUCTION Many types of nano-structure devices have been developed and many varieties of etching, deposition, and lithography processes are used for nano-structure fabrication. Etching by conventional ion beam processing has been applied to nano-structure fabrication. Gas cluster ion beam (GCIB) techniques have been proposed as new processing methods[1]. GCIB may have potential use in etching where etching by conventional ion beams has been found to cause significant damage[2,3]. The cluster consists of several thousands of atoms, so it impacts a surface with equivalent low energy and high density[4]. As the energy per atom within a cluster ion is equal to the total acceleration energy divided by the cluster size, GCIB realizes the equivalent of an ultra low energy ion beam. For example, when the acceleration energy and the cluster size are 10 keV and 1000 atoms, respectively, the energy per atom is only 10 eV. As a result, cluster ions exhibit unique irradiation effects, such as high sputtering yield and formation of a shallow junction. It is important to study the dependence of the sputtering yield on the cluster size. Although it has been difficult to control the cluster size of an ion beam, a gas cluster ion beam system with a permanent magnetic spectrometer has been
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developed by Epion corporation[5]. In addition, etching of Si and various kinds of metals have been reported by Matsuo et al. with Ar GCIB[6]. They reported that the sputtering yield obtained with Ar GCIB was approximately two orders of magnitude higher than that obtained with Ar mononer ion beam[6]. GCIB is very effective for ion beam processing of metals. However, etching of GaAs and GaP has not yet been reported. In this study, we report GCIB etch results for GaAs and GaP as a function of ion cluster size and acceleration energy, and their sputtering yields. EXPERIMENTAL DETAILS Figure 1 shows a schematic diagram of a size-selected GCIB irradiation sys
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