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Nanostructures for High Resolution Measurements of Magnetic Fields

IP.com Disclosure Number: IPCOM000061044D
Original Publication Date: 1986-Jun-01
Included in the Prior Art Database: 2005-Mar-09
Document File: 3 page(s) / 47K

Publishing Venue

IBM

Related People

Best, JS: AUTHOR [+5]

Abstract

Described below are methods of fabricating high resolution sensors using electron beam nanolithography. The two methods discussed are contamination and lift-off nanolithography. The sensors, so produced, can measure magnetic field variations over distances as small as 10 nm. The operation of a number of devices (for example, magnetic recording heads) is dependent on the magnetic properties of the device. An accurate determination of these properties is an important contributing factor in the optimization of the device performance. Inductive microloops [1], magnetoresistive sensors [2], and miniature Hall probes [3] have all been developed to measure the distribution of magnetic fields on a local scale. The resolution of these sensors has been limited from 0.

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Nanostructures for High Resolution Measurements of Magnetic Fields

Described below are methods of fabricating high resolution sensors using electron beam nanolithography. The two methods discussed are contamination and lift-off nanolithography. The sensors, so produced, can measure magnetic field variations over distances as small as 10 nm. The operation of a number of devices (for example, magnetic recording heads) is dependent on the magnetic properties of the device. An accurate determination of these properties is an important contributing factor in the optimization of the device performance. Inductive microloops [1], magnetoresistive sensors [2], and miniature Hall probes
[3] have all been developed to measure the distribution of magnetic fields on a local scale. The resolution of these sensors has been limited from 0.5 um to 1 um by the lithographic techniques used to fabricate the devices. Electron beam nanolithography, however, can be used to form lines almost two orders of magnitude smaller than this, using either contamination resist [4] or lift-off [5] techniques. The very small magnetic field sensors made using these techniques will have over 50 times better resolution than those currently in use. This enhanced field characterization capability will permit a controlled miniaturization of magnetic devices. Referring to Fig. 1, in contamination nanolithography, an electron beam is rastered over the surface of a metal film 13 where a sensor is to be formed. Contamination resist 12 forms where the electron beam 11 interacts with organic contamination in an electron microscope. Since the contamination resist has a much lower sputtering yield than metals, subsequent ion milling removes all metal not protected by the contamination resist, but leaves a magnetic sensor formed from very narrow line under the resist. Lines 8 nm wide have been formed using this technique. These lines are used in high resolution magnetic sensors. In lift-off nanolithography, an election beam exposes certain regions of a thin layer of resist. The exposed region is then selectively dissolved away in various solvents. A metallic film is then deposited over both the remaining resist and the exposed substrate. Dissolving the remaining resist under the metallic film leaves very narrow lines for a magnetic sensor. A variation on this process is to use a starting material consisting of a thin layer of metal on top of a substrate. A layer of resist on top of the metal is exposed with electrons and developed so that resist only remains on top of the metal to be used as the sensor. Subtractive etching is then used to remove all metal not covered by resist, leaving a hig...