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Simultaneous Shift And Scan in an Sem Using "SCAN" Coils

IP.com Disclosure Number: IPCOM000100792D
Original Publication Date: 1990-Jun-01
Included in the Prior Art Database: 2005-Mar-16
Document File: 2 page(s) / 69K

Publishing Venue

IBM

Related People

Christenson, KK: AUTHOR [+2]

Abstract

Disclosed is a method of tilting the electron beam in a Scanning Electron Microscope (SEM) by varying the currents in the upper and lower shift coils. Tilting the beam changes the "visual" orientation of the image and is useful for obtaining 3-D or "stereo" information.

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Simultaneous Shift And Scan in an Sem Using "SCAN" Coils

       Disclosed is a method of tilting the electron beam in a
Scanning Electron Microscope (SEM) by varying the currents in the
upper and lower shift coils.  Tilting the beam changes the "visual"
orientation of the image and is useful for obtaining 3-D or "stereo"
information.

      When scanning the beam in an SEM, it is common practice to
deflect the beam twice with upper and lower deflection coils.  The
ratios (or balance) of these deflections are typically chosen such
that the scan is a pure shift, the angle of incidence on the sample
does not change (Fig. 1A) or such that the beam always passes through
the center of the lens which improves resolution (Fig. 1B).

      There is also a ratio which produces a pure tilt that rocks the
beam on a fixed position on the sample (Fig. 1C). These deflections
can be combined linearly for small tilts and shifts.  The deflections
required to produce a beam with the shift of 1A and the tilt of 1C
are the sum of the individual tilt and shift deflections (Fig. 1D).

      A schematic illustration of a technique for simultaneous shift
and tilt control is shown in Fig. 2.

      Analog signals for shift and tilt are completely separated for
ease of operation.

      The deflections required for large tilts and shifts are
themselves nonlinear and also do not sum linearly.  These
nonlinearities can be easily dealt with when using
computer-controlled sca...