Browse Prior Art Database

Submicron Resolution Dynamic Magnetic Force Sensor

IP.com Disclosure Number: IPCOM000121102D
Original Publication Date: 1991-Jul-01
Included in the Prior Art Database: 2005-Apr-03
Document File: 4 page(s) / 147K

Publishing Venue

IBM

Related People

Bayer, T: AUTHOR [+4]

Abstract

Based on the atomic force microscope (AFM) principle, a magnetic force sensor is proposed which is capable of detecting magnetic domains at a resolution of 100 nm or less. The measuring principle used is the force active on a live conductor in a magnetic field, so that the sensor may be referred to as a magnetic force sensor. The conductor volume determines the local resolution and may be less than 0.1 x 0.1 x 0.1 mm3 .

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Submicron Resolution Dynamic Magnetic Force Sensor

      Based on the atomic force microscope (AFM) principle, a
magnetic force sensor is proposed which is capable of detecting
magnetic domains at a resolution of 100 nm or less.  The measuring
principle used is the force active on a live conductor in a magnetic
field, so that the sensor may be referred to as a magnetic force
sensor.  The conductor volume determines the local resolution and may
be less than 0.1 x 0.1 x 0.1 mm3 .

      Magnetic force microscopy (MFM) is based on the concept of
measuring interactive forces between a ferromagnetic tip and a
magnetic substrate.  As in AFMs, the tip is positioned on a sensitive
cantilever.  The force or force gradient is derived from the
cantilever's deflection.  The tips used for this purpose so far have
been exclusively ferromagnetic ones.

      In lieu of a ferromagnetic tip, the (Lorentz) force on a live
conductor in a magnetic stray field is used as a measuring principle.
In one embodiment described in this article, this live conductor is
fitted to the tip of an AFM. The design of this magnetic force sensor
permits a high local resolution of & 100 nm.  With low currents, the
sensor does not affect the magnetization of the substrate.  In the
case of alternating currents, the sensor may be resonance-operated,
which affords much higher sensitivities.

      Thus, the design of the sensor determines its resolution and
sensitivity.  Two examples of realizing such a sensor are described
below.  The sensor of the first example is shown in the
cross-sectional view in Fig. 1.  It consists of a handling element 1,
a fine beam 2 and a tip 3. Starting from the bottom, the sensor is
provided with the following:
      -    A first insulator of about 30 nm (consisting, for example,
of Si3N4, SiO2, SiC, C), preferably thermal oxide, which is blanket
deposited.
      -    A first conductor of about 100 nm (consisting, for
example, of gold, platinum, Cu) which is deposited by oblique
incidence.
      -    A second insulator which is deposited such that it stops
at the front side of the tip.  This protects the tip during the
deposition process.  The tip may also be protected by forcing it
against a pad. In the latter case, the second insulator must be
applied by CVD (chemical vapor deposition) or PECVD (plasma enhanced
chemical vapor deposition). In that way, even covered structures are
reached and coated.  The curvature radius obtainable for AFM tips is
about 10 nm.  This allows protecting a tip length of & 100 nm during
deposition...