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Browse Prior Art Database

Low Backscatter Surface for Scanning Electron Beam

IP.com Disclosure Number: IPCOM000112801D
Original Publication Date: 1994-Jun-01
Included in the Prior Art Database: 2005-Mar-27
Document File: 2 page(s) / 55K

Publishing Venue

IBM

Related People

Christensen, KK: AUTHOR [+4]

Abstract

Disclosed is a device for stopping high energy electron beams used for lithography on X-ray lithographic masks. The electrons are transmitted through the mask and can backscatter from the stage or holder below, producing a "background noise" or fogging which reduces contrast.

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Low Backscatter Surface for Scanning Electron Beam

      Disclosed is a device for stopping high energy electron beams
used for lithography on X-ray lithographic masks.  The electrons are
transmitted through the mask and can backscatter from the stage or
holder below, producing a "background noise" or fogging which reduces
contrast.

      The lowest backscattering coefficient material known,
beryllium, can not be used to stop the beam because of safety
considerations.  The remaining low coefficient materials, boron,
carbon, and nitrogen, give too many backscattered electrons.

      Using a honeycomb structure of carbon, boron nitride, or a
polymeric hydrocarbon to stop the electrons, as sketched in Fig. 1,
is proposed.  If the average diameter of the "pore" 1 in the material
is large compared to the "wall thickness" 3, the backscattered
electrons 4 from the surface will be reduced by nearly the area ratio
of the walls to the pores.  With high-aspect-ratio pores 1, electrons
2 which penetrate the cores and strike the bottom 5 may backscatter
but will probably then be absorbed in the walls.  The backscatter
coefficient of an aluminum honeycomb with a wall area-to-pore area
ratio of .05 has been measured to be less than 2%  for strongly
divergent electrons.  The backscatter coefficient could be lowered
substantially by producing the structure from a low z material.

      The structure sketched in Fig. 1 can be made by molding and
sintering boron nitri...