Faculty Profiles - TOYOTA Yoshitaka

MISC - TOYOTA Yoshitaka

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Yield Measurement of Secondary Electrons Emitted from Silicon Dioxide Film in Negative-Ion Bombardment.

Toyota Yoshitaka, Tsuji Hiroshi, Gotoh Yasuhito, Ishikawa Junzo

Japanese Journal of Applied Physics 35 ( 9A ) 4785 - 4788 1996

Language：English Publisher：The Japan Society of Applied Physics

The yield of secondary electrons emitted from insulating materials subjected to negative-ion bombardment was studied. In general, such measurements for insulating materials are difficult because surface charging due to ion implantation makes the apparent yield unity. We used silicon dioxide (SiO₂) film and a small ion current for the yield measurements. As a result, charge compensation due to the leakage current minimized the surface charging and the true yield was obtained. The experimental results showed that secondary electrons emitted due to negative-ion bombardment consist of electrons due to both kinetic emission and detachment from negative ions. In addition, it was found that the yield depends on the ion species. It was concluded that the same tendencies as those for negative-ion-implanted conductive materials are observed.

DOI： 10.1143/JJAP.35.4785

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Negative-Fluorine-Ion Extraction from RF Plasma-Sputter-Type Heavy Negative-Ion Source using SF_6 Gas

TSUJI Hiroshi, TOMITA Tetsuo, TOYOTA Yoshitaka, GOTOH Yasuhito, ISHIKAWA Junzo

38 ( 9 ) 769 - 769 1995.9

Negative-ion implantation technique

Junzo Ishikawa, Hiroshi Tsuji, Yoshitaka Toyota, Yasuhito Gotoh, Koji Matsuda, Masayasu Tanjyo, Shigeki Sakai

Nuclear Inst. and Methods in Physics Research, B 96 ( 1-2 ) 7 - 12 1995.3

Language：English

Negative-ion implantation is a promising technique for charging-free implantation for the forthcoming ULSI fabrication, in which the water charging by positive-ion implantation will become a troublesome problem even with an electron shower. The negative-ion implantation technique remarkably ameliorates such a charging problem since the incoming negative charge of implanted negative ions is easily balanced by the outgoing negative charge of a part of secondary electrons. Thus, the surface charging voltage is maintained to within about ± 10 V for isolated conducting materials and insulators, and is free from space and time fluctuations. A high-current negative-ion source and a medium current negative-ion implanter developed for this technique are described with the design concepts. In addition, the fundamental measurements of interactions between the negative-ion beam and the gas/solid are also described. © 1995.

DOI： 10.1016/0168-583X(94)00444-7

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The charging mechanism of insulated electrode in negative-ion implantation

Shigeki Sakai, Yasuhito Gotoh, Hiroshi Tsuji, Yoshitaka Toyota, Junzo Ishikawa, Masayasu Tanjyo, Koji Matsuda

Nuclear Inst. and Methods in Physics Research, B 96 ( 1-2 ) 43 - 47 1995.3

Language：English

The wafer charging during ion implantation is a serious problem with greater levels of circuit integration in semiconductor device fibracations. Positive charges are accumulated on insulated electrodes or insulators and cause dielectric breakdown if there is no compensation of charging. Ion implantation with negative ions is one of the hopeful techniques to solve this problem. Since an incident ion is a negative charge, an incoming negative charge and an outgoing negative charge of secondary electrons will achieve electrical equilibrium on the insulated electrode. Therefore the charging voltage is extremely low because of this electrical equilibrium. We have measured the charging voltage at several energies of negative ions and also simulated the charging voltage with varying secondary-electron emission factor. We have found that the charging voltage depends on the secondary-electron emission factor. © 1995.

DOI： 10.1016/0168-583X(94)00451-X

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Evaluation of Charging Model in Negative-Ion Implantation

Yoshitaka Toyota, Hiroshi Tsuji, Shoji Nagumo, Shigeki Sakai, Yasuhito Gotoh, Junzo Ishikawa, Koji Matsuda

Shinku 38 ( 3 ) 224 - 227 1995

Charging Potential Measurement of Photoresist-Layer Surface during Negative-Ion Implantation from Ion-Induced Secondary Electron Energy Analysis

Hiroshi Tsuji, Shoji Nagumo, Yoshitaka Toyota, Shigeki Sakai, Yasuhito Gotoh, Junzo Ishikawa

Shinku 38 ( 3 ) 221 - 223 1995

Energy distribution and yield measurement of secondary electrons to evaluate the equilibrium charging voltage of an isolated electrode during negative-ion implantation

Yoshitaka Toyota, Hiroshi Tsuji, Yasuhito Gotoh, Junzo Ishikawa

Japanese Journal of Applied Physics 34 ( 12 ) 6487 - 6491 1995

Language：English

The negative-ion implantation method has the advantage that the charging voltage of an isolated electrode, or electrically insulated conductive material, stays as low as at most +10 V during implantation without any charge neutralization. The significant parameters, the energy distribution and the yield of secondary electrons in negative-ion implantation, have been measured in the energy range below 40 keV. The results show that the energy distribution, which is independent of ion energy in shape, has a low energy peak together with a long tail extending toward the high-energy region, and that the yield increases with ion energy. Furthermore, the equilibrium charging-voltage equation of an isolated electrode during negative-ion implantation is presented. The charging voltages estimated according to the equation are found to be in good agreement with those measured directly with a high-input-impedance voltmeter. It is also demonstrated that the charging voltage is proportional to the yield and to ion velocity in the linear region of the kinetic electron emission. © 1995 The Japan Society of Applied Physics.

DOI： 10.1143/JJAP.34.6487

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Negative-Ion Current Density Dependence of the Surface Potential of Insulated Electrode During Negative-Ion Implantation

Hiroshi Tsuji, Shigeki Sakai, Yoshio Okayama, Yoshitaka Toyota, Yasuhito Gotoh, Kouji Matsuda, Masayasu Tanjyo, Junzo Ishikawa

Shinku 37 ( 3 ) 135 - 138 1994

Surface Potential Measurement of the Insulator with Secondary Electron Caused by Negative Ion Implantation

Hiroshi Tsuji, Yoshitaka Toyota, Syoji Nagumo, Yasuhito Gotoh, Junzo Ishikawa, Shigeki Sakai, Masayasu Taniyo, Kohji Matsuda

Shinku 37 ( 3 ) 139 - 142 1994

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