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Magnetic Mask Used for Deposition Field

IP.com Disclosure Number: IPCOM000095812D
Original Publication Date: 1964-Jul-01
Included in the Prior Art Database: 2005-Mar-07
Document File: 1 page(s) / 11K

Publishing Venue

IBM

Related People

Daughton, JM: AUTHOR [+3]

Abstract

Coupled films are now evaporated through slits in nonmagnetic masks in the presence of a uniform magnetic field. Uniform fields greater than about 50 oe are not easily achieved by coils external to the bell jar. The direction of this applied field determines the easy direction of the films, and, hence, must be quite uniform. The magnitude of the deposition field is not critical so long as it is above a threshold value, about 50 oe. Because of demagnetizing fields caused by the film itself as it is deposited, the effective deposition field can well fall below the necessary threshold value in some parts of the film. This results as the strip becomes narrower.

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Magnetic Mask Used for Deposition Field

Coupled films are now evaporated through slits in nonmagnetic masks in the presence of a uniform magnetic field. Uniform fields greater than about 50 oe are not easily achieved by coils external to the bell jar. The direction of this applied field determines the easy direction of the films, and, hence, must be quite uniform. The magnitude of the deposition field is not critical so long as it is above a threshold value, about 50 oe. Because of demagnetizing fields caused by the film itself as it is deposited, the effective deposition field can well fall below the necessary threshold value in some parts of the film. This results as the strip becomes narrower.

Very large deposition fields are obtained by using a saturated magnetic material for a mask. For example, if a 10 mil thick mask of cobalt which has 20 mil slits with 20 mil spacings is saturated perpendicular to the slots, the stray field near the center of the slot is greater than 1000 oe, and is the largest near the edge of the slit where the largest deposition field is needed. The direction of the field should be uniform across the slit.

Two ways of obtaining a saturated mask are possible. A permanent-magnet material can be used, such as vicalloy or cunife which are easily machinable. Use can also be made of a soft magnetic material, such as permalloy, as a low reluctance path for either a permanent magnet or an electromagnet.

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