International Business Machines Corporation

John V Powers

Kie Y Ahn

Michael Hatzakis

Lubomyr Taras Romankiw

Mitchell S Cohen

Christopher H Bajorek

Robert J Miller

Paul S Ho

Eugene E Castellani

Lung-jo Tao

Daniel E Cox

Susan M Kane

A single level masking process for producing microelectronic structures, such as magnetic bubble domain devices, which require very fine line widths. This is a subtractive dry process using a very thin, additively plated mask in order to obtain optimum lithographic resolution. Use of the very thin plated mask eliminates the need for a thick resist layer which would adversely affect resolution. In one example, a double layer metallurgy comprising a conductor layer (such as Au) and an overlying magnetically soft layer (such as NiFe) is patterned using a thin Ti (or Cr) mask. The Ti mask is subtractively patterned using a NiFe mask which is itself patterned by electroplating through a thin resist layer. The double layer NiFe/Au structure is patterned to provide devices having high aspect ratio, good pattern acuity, and uniform thicknesses, where the minimum feature is 1 micron or less.

Bubble device fabrication

A laminated conductor includes a lower thin film of nickel-X alloy or pseudo alloy deposited upon a substrate containing silicon or upon a substrate intended for use as a magnetic bubble storage device. Upon the film of nickel-X alloy, a thicker film of gold is deposited as the conductive portion of the conductor. On the upper surface of the gold layer is deposited a thin film of nickel-X alloy. Failure of the conductor because of electromigration is reduced dramatically as compared with use of molybdenum instead of nickel in the laminated structure. The nonmagnetic nickel-X alloy does not interfere with magnetic fields or produce unwanted magnetic fields.

Nickel-X/gold/nickel-X conductors for solid state devices where X is

An improved magnetic bubble domain chip and processes for making the chip are described. The chip is comprised of a magnetic bubble domain film in which small bubble domains can be moved, and overlying layers of metallurgy. The layer of metallurgy closest to the bubble film is an electrically conductive layer having apertures (or recesses) therein. This layer is patterned to provide current carrying conductors. The next overlayer is a layer of magnetic material having in-plane magnetization which is patterned to provide the propagation elements used to move the bubble domains. In a particular embodiment, the magnetic layer is comprised of a magnetically soft material, such as permalloy. The chip is characterized by the provision of insulating pedestals located in the apertures of the conductive layer. These insulating pedestals are located in the regions of the chip used for sensing (and/or bubble generation). That is, they take the place of the thick conductive material in those areas of the chip. The sensor and bubble generators are usually portions of the in-plane magnetic layer. If the height of the insulating pedestals is the same as the height of the conductive layer, planarization is achieved and each overlayer lies in a single plane, where the planes are parallel to one another. However, the pedestal can be of any desired height. This chip is particularly advantageous for use with bubble domains having diameters of about 1 micron and less, since the pedestal magnetic chip can be provided by single level masking techniques in which only a single critical masking step is required. The insulating pedestal can be formed prior to deposition of the current carrying conductive layer, or subsequent to deposition of this layer.

Pedestal bubble domain chip and processes for making same

A thin film of low magnetostriction Permalloy 80% nickel - 20% iron .+-. 1% is electroplated in a bath having a ratio of about 1.8:1 to 24:1 g/liter ratio of Ni to Fe ions with a plating current density from 10 ma/cm.sup.2 - 200 ma/cm.sup.2 when plating in sheet form or an Ni/Fe ratio of 25:1 to 85:1 with a current density of 2 ma/cm.sup.2 - 110 ma/cm.sup.2 when plating through a mask. The fluid in the system is constantly mixed, replenished with fresh iron, acid, and other reagents, is adjusted in temperature and subjected to a continuous laminar regime of mixing. Fresh solution is added to the bath from a reservoir where the above adjustments are made. The inlet for the fresh solution is at the lower end of the plating chamber and directed at a bath mixer which includes a slot through which the fresh solution is directed to optimize mixing in the plating chamber. Complexing agents are avoided. High speed plating is obtained with about 24.4 g/l of Ni.sup.++, 1.05 g/l of Fe.sup.++, 25 g/l of H.sub.3 BO.sub.3, 0.2 g/l of Na saccharin and a pH of 1.5 to 3.6.

Nickel-iron (80:20) alloy thin film electroplating method and

A fabrication process for fabricating multiple layer magnetic bubble domain devices using only a single masking step. As a specific example, a thin conductor film (which could be a magnetic material, such as NiFe) is deposited on a substrate comprising a magnetic bubble domain material. This conductor film is coated with a resist which is exposed with an electron beam or an X-ray beam. The exposure density in a first area of the resist is different than that in a second area of the resist. Subsequent development of the resist will uncover the thin film only in the area which has received the greater exposure density. This area can then be used as a plating base for electro-plating another conductive layer, such as a thick gold film. Further development of the resist is used to uncover the second area (which initially received a lower exposure density). Another layer then can be plated which will plate onto the thin conductive base film which is now uncovered and onto the second conductive layer which was formed in the previous electro-plating step. After this, the remaining resist and the unwanted remaining thin film is etched away to leave a final circuit structure.

Single lithography for multiple-layer bubble domain devices

A method for making multilayer devices, such as magnetic bubble domain devices, which are comprised of a plurality of layers that are deposited using only a single critical masking step. A first metallic layer is deposited on a substrate including a magnetic bubble domain film, which may or may not have a nonmagnetic material thereon. A first resist layer is then applied, selectively exposed, and developed to expose at least two areas of the first metallic film. A thicker metallic layer is then deposited in the exposed areas, or is electroplated. After this, another resist layer is applied without deforming the pattern in the first layer, selectively exposed, and developed to protect certain areas of the thick metallic layer from subsequent formation of another metallic layer. During this subsequent formation, a second metallic film is formed using the first resist layer as a mask. After this, the resists are removed and the now uncovered portions of the original thin metallic layer are etched away. In a particular embodiment, a magnetic bubble domain chip is provided in which the second resist layer is used to protect the sensor region of the chip. The second resist layer need not be critically aligned as it only functions as a protect mask. Exposure and development of the second resist layer does not adversely affect the underlying metal layers.

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Shenorock, NY, United States of America

John V Powers