Browse Prior Art Database

Ultra-Sensitive Probes for Magnetic Resonance Force Microscopy

IP.com Disclosure Number: IPCOM000116466D
Original Publication Date: 1995-Sep-01
Included in the Prior Art Database: 2005-Mar-30
Document File: 2 page(s) / 99K

Publishing Venue

IBM

Related People

Bayer, T: AUTHOR [+3]

Abstract

Described is the fabrication of silicon single crystal probes for high-resolution Magnetic Resonance Force Microscopy (MRFM). The method allows for the manufacturing of extremely thin single crystal cantilevers with integrated tips. The lever thickness is extremely uniform and can be made even thinner as the original diffusion depth by isotropic "material removal" procedures like isotropic wet etching and/or "oxidation thinning". The method allows probes having a cantilever thickness of less than 100 nm, which is key to achieve extremely low spring constants of about 10(-5) N over m.

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Ultra-Sensitive Probes for Magnetic Resonance Force Microscopy

      Described is the fabrication of silicon single crystal probes
for high-resolution Magnetic Resonance Force Microscopy (MRFM).  The
method allows for the manufacturing of extremely thin single crystal
cantilevers with integrated tips.  The lever thickness is extremely
uniform and can be made even thinner as the original diffusion depth
by isotropic "material removal" procedures like isotropic wet etching
and/or "oxidation thinning".  The method allows probes having a
cantilever thickness of less than 100 nm, which is key to achieve
extremely low spring constants of about 10(-5)  N over m.

      An additional advantage of this method is, that it creates a
"hollow" tip, which is adding only very little "weight" to the
cantilever, which is also crucial to achieve the requirements.

      Magnetic resonance force microscopy is a new "SXM" probe
technique (1,2,3) In contrast to all other SXM techniques, the
method is not only a "Surface Technique" but has the potential for 3
D detection of single atoms and molecules.  The basic feasibility
with a resolution in the micron range has been demonstrated already.
The availability of an instrument, based on the proposed method
(1,2,3) would have broad implications in molecular biology, polymer
science, surface science and nanotechnologies.  The biomedical
applications could be particularly important since, in principle,
such a device could be used to determine protein structures based on
a single molecular copy.

      The most crucial component in the MRFM is the ultra-sensitive
micromechanical force sensor.  The development of cantilever
technology that can detect forces as small as 10(-19) N is key to the
success of MRFM project.  So far, thin nitride levers (thinner than
100 nm) have been used.

      Single crystal levers offer the advantage of having a higher
Quality factor than amorphous or poly crystalline materials.
Preferably they are made of silicon due to the amount of processing
techniques available for silicon.

      Key to success is uniformity and process control.  Both factors
can be achieved by choosing the "right" processes and sequences; a
typical fabrication sequence is shown in the Figure.

      Fig. 1a shows the start of the process.  An appropriate mask
opening in SiO(2) defines the tip size and position.  A variety of
etching procedures (mostly dry etching) allows the definition of a
"mold" for the later tip.  With mod...