Ion-Optical System For Maskless Ion Implantation With 100 nm Resolution

N. Anazawa; R. Aihara; E. Ban; M. Okunuki

doi:10.1117/12.935105

7 November 1983 Ion-Optical System For Maskless Ion Implantation With 100 nm Resolution

N. Anazawa, R. Aihara, E. Ban, M. Okunuki

Proceedings Volume 0393, Electron-Beam, X-Ray and Ion-Beam Techniques for Submicron Lithographies II; (1983) https://doi.org/10.1117/12.935105
Event: 1983 Microlithography Conferences, 1983, Santa Clara, United States

Abstract

Recent technology of a liquid-metal ion source makes it possible to realize maskless ion implantation with 100 nm resolution. A 100 kV implantation apparatus has been developed by using fine-focus technology of ion optics. Since alloy-metal ion sources have to be often used as the source of the apparatus, a mass filter (EXB) was equipped with for ion separation. Because the liquid-metal ion source has a large energy spread, a chromatic aberration is important to assess the optical performance of the apparatus. Particularly, the energy spread varies dependently on the emission current, so that the minimum probe size also varies with the emission current through the chromatic aberration. In order to optimize the design for such ion-optical systems, the dependency of the chromatic aberration upon the emission current must be taken into account. The optical system design was optimized under this consideration. As a result it was found that the optical system has an optimum aperture angle. Furthermore, the beam divergence in the mass filter was discussed. Ions passing through the mass filter undergo a dispersive force because of their velocity distribution. This is also a factor determining the minimum probe size. Numerical calculations of the optical property of the EXB filter showed that a weakly excited filter has a specified focal point where its velocity dispersion was apparently canceled. Therefore, if one let the focal point to be just located at a crossover point of the lens system, the effect of velocity dispersion can be reduced to the same level as the aberrations of the latter.

Citation Download Citation

N. Anazawa, R. Aihara, E. Ban, and M. Okunuki "Ion-Optical System For Maskless Ion Implantation With 100 nm Resolution", Proc. SPIE 0393, Electron-Beam, X-Ray and Ion-Beam Techniques for Submicron Lithographies II, (7 November 1983); https://doi.org/10.1117/12.935105

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