Radiant energy – Inspection of solids or liquids by charged particles – Electron probe type
Reexamination Certificate
1999-03-23
2001-05-15
Berman, Jack (Department: 2878)
Radiant energy
Inspection of solids or liquids by charged particles
Electron probe type
C250S397000, C250S398000, C250S3960ML, C250S3960ML
Reexamination Certificate
active
06232601
ABSTRACT:
The invention relates to a charged particle beam device according to the preamble of claim
1
and to a method for inspecting a specimen according to the preamble of claim
9
.
Charged particle beam devices are known comprising
a source for generating a charged particle beam,
an objective lens with an optical axis for focussing said charged particle beam on a specimen which consists of a magnetic lens and a superimposed electrostatic lens having at least two electrodes,
deflection means for deflecting said charged particle beam on said specimen
and detector means for detecting charged particles released at said specimen.
By using a combination of a magnetical single pole lens and an electrostatic retarding field lens excellent low axial aberration coefficients and correspondingly high axial resolution can be achieved. However, those lenses have a limited image field, in which uniform image brightness and high optical performance can be achieved.
In secondary electron microscopes the secondary electrons and/or backscattered electrons released by the primary electron beam are detected, whereby preferably in-lens detectors and/or pre-lens detectors are used. Known arrangements are
off-axial detectors, partially using a beam deflector,
axial detectors with a rotational symmetry or divided into segments,
or detectors having means for influencing the released particles.
However, the image quality of these known arrangements becomes worse with increasing image field size.
It is, therefore, an object of this invention to provide a charged particle beam device according to the preamble of claim
1
or a method for inspecting a specimen according to the preamble of claim
9
which has an improved efficiency of detecting charged particles released at image areas being located on the specimen with a distance from the optical axis.
This object is solved by the characterizing features of claims
1
and
9
. According to the invention there are control means co-acting with the deflection means and one of the electrodes of the electrostatic lens for applying a dynamic voltage to said electrode, the amount of the voltage being dependent on the distance of said charged particle beam from said optical axis at the specimen.
Further improvements and embodiments of the invention are the subject matter of the subclaims and will be explained in greater detail by means of the description of some embodiments and the drawing.
REFERENCES:
patent: 5412209 (1995-05-01), Otaka et al.
Frosien Jurgen
Lanio Stefan
Schmitt Reinhold
Schonecker Gerald
Advantest Corporation
Berman Jack
Reising Ethington, Barnes, Kisselle, Learman & McCulloch, P.C.
Wells Nikita
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