International Business Machines Corporation

Magic Technologies, Inc.

Headway Technologies, Incorporated

Grace Lim Gorman

Yimin Guo

Cherngye Hwang

Randall George Simmons

Vedantham Raman

Pei C Chen

Yuchen Zhou

Po-Kang Wang

Kurt A Rubin

Xuhui Jin

Devendra S Chhabra

Martin Y Chen

Roger W Barton

Vincent Marrello

Jack Dana Cook

Charles Raymond Davis

A method by which portions of a wafer level fabrication can be selectively heated by forming plasmon generating layers of specific size, shape, orientation and material on the fabrication and then illuminating the formation with electromagnetic radiation of such wavelength and polarization as will optimally be absorbed by the plasmon generating layers so as to generate plasmons therein. The generated plasmons thereupon produce thermal energy which is transferred to portions of the fabrication with which the plasmon generation layer has thermal contact. This method is particularly advantageous for producing multiple anneals and different magnetic pinning directions for the anti-ferromagnetic pinning layer in each of an array of GMR or TMR devices. In that process, the anti-ferromagnetic layer must be raised above its Curie temperature at which point it loses its anti-ferromagnetic properties and can have a magnetization imposed by application of an external magnetic field. The method can equally well be applied to any wafer level fabrication or deposited film fabrication in which it is desired to heat specific regions to obtain some specified result that is temperature dependent.

Multi-directional pin anneal of MR sensors with plasmon heating

Simultaneous setting of exchange pinning field magnetization in more than one direction for several thin film structures on a single substrate has been achieved by first orienting the structures as needed. A layer of hard magnetic material is then deposited, suitably patterned to control the direction of its flux, and then magnetized through a single exposure to a strong magnetic field. The assemblage is then thermally annealed (in the absence of any applied field) at a temperature higher than the AFM material blocking temperature, following which the thin film structures are magnetically pinned in the intended directions.

Method for providing AFM exchange pinning fields in multiple directions on same substrate

An apparatus and a general method to measure a magnetic field using magneto-resistive sensors in an open-loop configuration are disclosed. A key feature is the regular in-situ normalization of the sensors to compensate for the effects of sensor aging.

Open loop magneto-resistive magnetic field sensor

The problem of magneto-resistive sensor drift with age has been solved by normalizing the sensor's output relative to its output when it is in a selected reproducible state. Details for the method to accomplish this normalization are disclosed together with several examples of how the method can be utilized.

Elimination of errors due to aging in magneto-resistive devices

The invention discloses a method and apparatus for determining the rotational status of a gear wheel whether or not it is actually turning. A key feature is the magnetic angle sensor that is used. Said sensor comprises a bridge structure of four MR devices in a square array. The direction of the pinned reference layer is the same for all four devices and lies along one of the diagonals of said square array. A single wafer process is used to manufacture the invented device.

Gear tooth sensor (GTS) with magnetoresistive bridge

Presented herein is a shunted MTJ sensor formed of a plurality of electrically connected MTJ cells for measuring magnetic fields and currents and its method of fabrication. To provide stable single domain magnetic moments of the MTJ cells and to ensure that the magnetic moments return to a fixed bias point in the absence of external magnetic fields, the cells are formed of sufficiently small size and with elliptical cross-section of aspect ratio greater than 1.2. To eliminate the possibility of ESD damage to the cells, they are protected by a parallel shunt, formed as a trace of sufficiently high resistance that directs accumulated charges harmlessly to ground while bypassing the cells.

MTJ based magnetic field sensor with ESD shunt trace

The invention discloses a rotation sensor suitable for gear wheels. MR (magneto-resistive) sensors are placed inside a zero field region generated by at least two permanent magnets. The sensors are divided into two groups that are immersed in different locally generated magnetic environments. A differential signal taken between the two groups then senses the movement of the wheel's teeth. A single wafer method for manufacturing the device is also briefly described.

Gear tooth sensor with single magnetoresistive bridge

An AMR gear tooth rotation sensor and a method for utilizing it are disclosed. These facilitate easy manufacture of the device without sacrificing either high sensitivity or high signal output. This is achieved by forming individual sensing elements out of AMR stripes and then connecting four such sensing elements as a Wheatstone bridge. The latter is attached to a permanent magnet that provides a bias field whose value rises and falls as wheel teeth and valleys (respectively) move past the rotation sensor.

Highly sensitive AMR bridge for gear tooth sensor

The invention discloses a sensor for 360-degree magnetic field angle measurement. It comprises multiple GMR (or MTJ) stripes with identical geometries except for their orientations. These are used as the building blocks for a pair of Wheatstone bridges that signal the direction of magnetization of their environment. The design greatly enhances sensitivity within GMR stripes and does not require an additional Hall sensor in order to cover the full 360 degree measurement range.

Magnetic field angle sensor with GMR or MTJ elements

The process margin for the manufacture of devices formed from multi-element MTJ or GMR devices has been widened by providing a method and structure to reset the magnetization directions of all pinned layers simultaneously so that their directions of magnetization become evenly distributed. This has the effect of minimizing non-linearity and hysteresis in these devices during their subsequent operation.

Method and structure to reset multi-element MTJ

A method of forming a waveguide comprising the following steps. A structure is provided. An underclad layer is formed over the structure and a core layer is formed over the underclad layer. Patterning: the core layer to form the waveguide; and partially into the underclad layer, forming an overetched underclad layer having a projection underneath the waveguide. The waveguide having stress gradients and the overetched underclad layer having stress gradients.

Method to produce stress-free optical waveguides to reduce stress-induced birefringence in planar lightwave circuit (PLC) devices

A silicon coating on an air bearing surface for magnetic thin film heads. A thick silicon layer is provided to replace metallic layers such as TiW as an overcoat for thin film heads. The silicon layer will provide a durable head-disk interface and act as a reflective surface for fly height measurement. The silicon layer can be planarized with the pole tips to avoid any magnetic spacing loss. The thickness of the silicon coating is preferably between 125 and 6500 angstroms thick. The slider body may be fabricated from silicon such that the silicon coating is substantially identical to the silicon slider body, thereby preventing thermal mismatch therebetween. The silicon coating is preferably applied using a magnetron sputtering technique which provides a high rate of deposition of silicon to form a dense, low stress silicon layer.

Silicon coating on air bearing surface for magnetic thin film heads

A method for protecting magnetic read/write head assembly against electrostatic discharge during disk drive manufacturing are disclosed. The magnetic head assembly is supported on a substrate having a magnetoresistive sensor element disposed in spaced relationship between several magnetic shield elements. Before a focused ion beam fabrication operation, at least a portion of an air bearing surface of the magnetic head assembly is coated with a thin and transparent layer of conductive material. This layer of conductive material is subsequent removed after the focused ion beam fabrication operation.

Method for protecting magnetic read/write transducers against electrostatic discharge during disk drive manufacturing

A silicon coating on an air bearing surface for magnetic thin film heads. A thick silicon layer is provided to replace metallic layers such as TiW as an overcoat for thin film heads. The silicon layer will provide a durable head-disk interface and act as a reflective surface for fly height measurement. The silicon layer can be planarized with the pole tips to avoid any magnetic spacing loss. The thickness of the silicon coating is preferably between 125 and 6500 Angstroms thick. The slider body may be fabricated from silicon such that the silicon coating is substantially identical to the silicon slider body, thereby preventing thermal mismatch therebetween. The silicon coating is preferably applied using a magnetron sputtering technique which provides a high rate of deposition of silicon to form a dense, low stress silicon layer.

A single layer wear coating is provided for a magnetic head assembly. The single layer is silicon or silicon-based material with a thickness in the range of 30-75 .ANG.. The single layer may be formed by a single step of deposition employing a DC magnetron. The single layer wear coating improves the wear performance of the magnetic head assembly and protects one or more sensitive elements of a magnetic head without significant reduction of spacing loss.

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San Jose, CA, United States of America

Grace Lim Gorman