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Measuring of Calibration Standards for Atomic Force Microscope Tips

IP.com Disclosure Number: IPCOM000118624D
Original Publication Date: 1997-Apr-01
Included in the Prior Art Database: 2005-Apr-01
Document File: 4 page(s) / 67K

Publishing Venue

IBM

Related People

Wagner, D: AUTHOR

Abstract

Disclosed is a method which uses a modified confocal microscope to determine the definition of the edge of a test structure used to calibrate Atomic Force Microscope (AFM) tips.

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Measuring of Calibration Standards for Atomic Force Microscope Tips

      Disclosed is a method which uses a modified confocal microscope
to determine the definition of the edge of a test structure used to
calibrate Atomic Force Microscope (AFM) tips.

      The form of an AFM tip is characterized by a polysilicon
structure slightly underetched in a defined way (Fig. 1) and
manufactured using known lithography steps.  Measuring the line width
of the polysilicon structure requires to exactly define the edge of
the structure.

      In an edge detector, a focussed laser beam is diffracted
forward and backward at the edge of the calibration structure (Fig.
2).  The forwardly diffracted light is reflected at the base plane of
the calibration structure and interferes with the backwardly
diffracted light.  This results in an undefined edge definition
error.

      To achieve precise measuring results, a laserscanner with a
high S/N-ratio is proposed (Fig. 3).  The numeric aperture of the
objective should be 0.95 and the wave length of the laser beam should
be in the range from 250 nm to 325 nm.  These conditions will allow a
resolution of between 160 nm and 200 nm which is comparable to the
resolution of an AFM.

      The laser beam is focussed onto the calibration structure.  The
light reflected at the structure is of no interest and leaves the
laser along the same way it came in.  The diffracted light is
focussed onto a  limiting aperture with the h...