Headway Technologies, Incorporated

Magic Technologies, Inc.

Po Kang Wang

Tai Min

Moris Musa Dovek

Glen A Garfunkel

Jibin Geng

Cheng Tzong Horng

Mao-Min Chen

Cherng-Chyi Han

Xizeng Shi

Hsu Kai Yang

Fenglin Liu

Qiang Chen

As track densities increase, it becomes increasingly important, while writing in a given track, not to inadvertently write data in adjoining tracks. This problem has been overcome by limiting the width of material in the ABS plane to what it is at the write gap. The part of the lower pole that is wider than this is recessed back away from the ABS, thereby greatly reducing its magnetic influence on adjacent tracks. Four different embodiments of write heads that incorporate this notion are described together with a description of a general process for their manufacture.

Write head having recessed magnetic material in gap region

Process to manufacture a magnetic write head

An MRAM array of MTJ memory cells is provided wherein each such cell is a layered MTJ structure located at an intersection of a word and bit line and has a small circular horizontal cross-section of 1.0 microns or less in diameter and wherein the ferromagnetic free layer of each such cell has a magnetic anisotropy produced by a magnetic coupling with a thin antiferromagnetic layer that is formed on the free layer. The array of MTJ memory cells so provided is far less sensitive to shape irregularities and edge defects of individual cells than arrays of the prior art.

Array of magnetic tunneling junction film structures with process determined in-plane magnetic anisotropy

A CPP MTJ MRAM unit cell utilizes transfer of spin angular momentum as a mechanism for changing the magnetic moment direction of a free layer. The strength of the switching field, Hof the cell is controlled by the magnetic anisotropy of the cell which, in turn, is controlled by a combination of the shape anisotropy and the stress and magnetostriction of the cell free layer. The coefficient of magnetostriction of the free layer can be adjusted by methods such as adding Nb or Hf to alloys of Ni, Fe, Co and B or by forming the free layer as a lamination of layers having different values of their coefficients of magnetostriction. Thus, by tuning the coefficient of magnetostriction of the cell free layer it is possible to produce a switching field of sufficient magnitude to render the cell thermally stable while maintaining a desirable switching current.

MRAM with means of controlling magnetic anisotropy

An MRAM array structure and a method of its operation that is not subject to accidental writing on half-selected elements. Each element of the MRAM is an MTJ (magnetic tunneling junction) cell operating in accord with an STT (spin torque transfer) scheme for changing its free layer magnetization state and each cell is patterned to have a C-shape in the horizontal plane. The cell thereby operates by C-mode switching to provide stability against accidental writing by half-selection. During operation, switching of a cell's magnetization is accomplished with the assist of the pulsed magnetic fields of additional word lines that are formed either orthogonal to or parallel to the existing bit lines and that can carry currents in either direction as required to provide the assist.

Pulse field assisted spin momentum transfer MRAM design

An MTJ memory cell and/or an array of such cells is provided wherein each such cell has a small circular horizontal cross-section of 1.0 microns or less in diameter and wherein the ferromagnetic free layer of each such cell has a magnetic anisotropy produced by a magnetic coupling with a thin antiferromagnetic layer that is formed on the free layer. The MTJ memory cell so provided is far less sensitive to shape irregularities and edge defects than cells of the prior art.

Magnetic tunneling junction film structure with process determined in-plane magnetic anisotropy

An MRAM that is not subject to accidental writing of half-selected memory elements is described, together with a method for its manufacture. The key features of this MRAM are a C-shaped memory element used in conjunction with a segmented bit line architecture.

MRAM with enhanced programming margin

As track density requirements for disk drives have grown more aggressive, GMR devices have been pushed to narrower track widths to match the track pitch of the drive width. Narrower track widths degrade stability, cause amplitude loss, due to the field originating from the hard bias structure, and side reading. This problem has been overcome by adding an additional layer of soft magnetic material above the hard bias layers. The added layer provides flux closure to the hard bias layers thereby preventing flux leakage into the gap region. A non-magnetic layer must be included to prevent exchange coupling to the hard bias layers. In at least one embodiment the conductive leads are used to accomplish this. A process for manufacturing the device is also described.

Side reading reduced GMR for high track density

As track density requirements for disk drives have grown more aggressive, GMR devices have been pushed to narrower track widths to match the track pitch of the drive width. Narrower track widths degrade stability and can cause amplitude loss and side reading. This problem has been overcome by placing an additional layer of soft magnetic material on the conductive layer. The added layer prevents flux leakage into the gap region. A non-magnetic layer must be included to prevent exchange coupling to nearby magnetic layers. In at least one embodiment the conductive leads are used to accomplish this. A process for manufacturing the device is also described.

A trimmed upper pole piece for a magnetic write head, said pole piece having a tapered profile that is widest at its trailing edge. Such a pole piece is capable of writing narrow tracks with sharply and well defined patterns and minimal overwriting of adjacent tracks. The necessary taper is produced by using NiCr, NiFeCr, Rh or Ru as write gap filling materials which have an etch rate which is substantially equal to the etch rate of the other layers forming the pole piece and are highly corrosion resistant. As a result, the write gap does not protrude to mask the effects of the ion-beam etch used to form the taper.

Magnetic write head having a wider trailing edge pole structure

An MRAM array is formed of MTJ cells shaped so as to have their narrowest dimension at the middle of the cell. A preferred embodiment forms the cell into the shape of a kidney or a peanut. Such a shape provides each cell with an artificial nucleation site at the narrowest dimension, where an applied switching field can switch the magnetization of the cell in manner that is both efficient and uniform across the array.

Magnetic random access memory designs with controlled magnetic switching mechanism

A magnetic tunneling junction (MTJ) memory cell for a magnetic random access memory (MRAM) array is formed as a chain of magnetostatically coupled segments. The segments can be circular, elliptical, lozenge shaped or shaped in other geometrical forms. Unlike the isolated cells of typical MTJ designs which exhibit curling of the magnetization at the cell ends and uncompensated pole structures, the present multi-segmented design, with the segments being magnetostatically coupled, undergoes magnetization switching at controlled nucleation sites by the fanning mode. As a result, the multi-segmented cells of the present invention are not subject to variations in switching fields due to irregularities an structural defects.

Magnetic random access memory designs with controlled magnetic switching mechanism by magnetostatic coupling

As track density requirements for disk drives have grown more aggressive, GMR devices have been pushed to narrower track widths to match the track pitch of the drive width. Narrower track widths degrade stability, cause amplitude loss, due to the field originating from the hard bias structure, and side reading. This problem has been overcome by adding an additional layer of soft magnetic material above the hard bias layers. The added layer provides flux closure to the hard bias layers thereby preventing flux leakage into the gap region. A non-magnetic layer must be included to prevent exchange coupling to the hard bias layers. In at least one embodiment the conductive leads are used to accomplish this.

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San Jose, CA, United States of America

Po Kang Wang