Browse Prior Art Database

Thin Exit Window for Soft X-Ray Beam Line

IP.com Disclosure Number: IPCOM000102234D
Original Publication Date: 1990-Nov-01
Included in the Prior Art Database: 2005-Mar-17
Document File: 2 page(s) / 54K

Publishing Venue

IBM

Related People

Rippstein, R: AUTHOR

Abstract

The current trend in step and repeat aligners for use with electron storage ring X-ray sources is for the aligner to operate in a normal clean-room environment at ambient atmospheric pressure. The storage ring, however, requires ultra-high vacuum conditions to prevent atomic collisions from annihilating the circulating electron beam. The beam line serves to connect the aligner and soft X-ray source, and is also maintained under high vacuum conditions in order to deliver a maximum of useful flux to the stepper. At the end of the beam line nearest the aligner is a thin exit window, typically made of beryllium, which serves to separate the high vacuum of the beamline from the surrounding atmospheric gasses while being thin enough to allow a reasonable amount of the X-ray flux to arrive at the X-ray mask.

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Thin Exit Window for Soft X-Ray Beam Line

       The current trend in step and repeat aligners for use
with electron storage ring X-ray sources is for the aligner to
operate in a normal clean-room environment at ambient atmospheric
pressure.  The storage ring, however, requires ultra-high vacuum
conditions to prevent atomic collisions from annihilating the
circulating electron beam.  The beam line serves to connect the
aligner and soft X-ray source, and is also maintained under high
vacuum conditions in order to deliver a maximum of useful flux to the
stepper.  At the end of the beam line nearest the aligner is a thin
exit window, typically made of beryllium, which serves to separate
the high vacuum of the beamline from the surrounding atmospheric
gasses while being thin enough to allow a reasonable amount of the
X-ray flux to arrive at the X-ray mask.

      The stresses produced in the beryllium foil depend upon the
foil edge mounting conditions and the geometric curvature imparted to
the foil by the mount.  When the foil surface is bent in the form of
a cylinder, as shown in Fig. 1, the maximum stress is approximated
as:
                          P x R
                  Smax = -------
                          2 x T

      where P is the applied pressure (14.7 PSI), R is the radius of
curva ture of the cylindrical section, and T is the foil thickness.
The ratio of R/T is selected to provi...