Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B82—NANOTECHNOLOGY
  • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
  • B82Y25/00—Nanomagnetism, e.g. magnetoimpedance, anisotropic magnetoresistance, giant magnetoresistance or tunneling magnetoresistance
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
  • G01R33/00—Arrangements or instruments for measuring magnetic variables
  • G01R33/02—Measuring direction or magnitude of magnetic fields or magnetic flux
  • G01R33/06—Measuring direction or magnitude of magnetic fields or magnetic flux using galvano-magnetic devices
  • G01R33/09—Magnetoresistive devices
  • G01R33/093—Magnetoresistive devices using multilayer structures, e.g. giant magnetoresistance sensors
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10N50/00—Galvanomagnetic devices
  • H10N50/01—Manufacture or treatment
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10N50/00—Galvanomagnetic devices
  • H10N50/10—Magnetoresistive devices

Definitions

• the present invention relates to magnetoresistive and giant magnetoresistive devices, and more particularly to magnetoresistive (MR) and giant magnetoresistive (GMR) devices and sensors fabricated using electrochemistry to deposit resistive material onto a conductive or partially conductive substrate and to methods for fabricating same.
• MR magnetoresistive
• GMR giant magnetoresistive
• Magnetoresistive sensors are traditionally used to read data (memory) and when used in conjunction with a magnet, to monitor the position of moving objects. These sensors generally find use in a wide variety of applications, including navigational, ferromagnetic metal detection and location, position and proximity sensing, etc. Resistive elements may also be used as switches or relays integrated as part of, for example, tunable antennas and bipolar MOS type transistors to reduce source to drain current leakage and in other microelectronic applications requiring resistance variation.
• a magnetoresistive or magnetoresistance (“MR”) sensor is generally made up of electrically connected (or “bridged") regions of active material (resistors) that can detect changes in an applied magnetic field. These regions of active material have an electrical resistivity that changes as a function of both the magnitude and the direction of the magnetic field. In other words, the region of active material acts as a variable resistor when placed in a changing external magnetic field.
• the source of this magnetic field can be for example internal, originating from a region in close proximity on the same integrated circuit or external as for example, from the earth's magnetic field.
• the "sensitivity" of such resistors is measured as the ratio of the change in resistivity ( ⁇ R) to the change in the magnetic field ( ⁇ H) .
• the magnetic field rotates the internal magnetization vector in the film, and the varying angle of this vector with the current flow affects the resistance.
• the sensitivity of a particular resistor depends on both the structural and chemical composition of the active material and, in the case of magnetoresistive devices, the value of the applied field.
• the region of active material can comprise several different layers, which are generally deposited using any number of different deposition techniques.
• a typical material for use as the active layer (s) in MR devices is an alloy such as one containing, e.g., cobalt, nickel, copper, or iron.
• An example of such an appropriate alloy is one containing 78.5% nickel and 21.5% iron known generically and sold as PERMALLOY.
• the alloy PERMALLOY is useful for MR sensors because it has high magnetic permeability and electrical resistivity.
• a region (or regions) of active material is formed by depositing thin films of the various layers onto a substrate.
• these thin films have been deposited by relatively expensive methods such as vacuum- based deposition, i.e., sputtering and molecular beam epitaxy and in some instances by electron beam (E-beam) or chemical vapor deposition (CVD) .
• Current commercially available MR sensors are fabricated by using electron beam, or sputtering techniques to deposit Permalloy as an active material on silicon chips.
• a prototypical commercial sensor is manufactured by sputtering to deposit layers of PERMALLOY (NiFe) onto a silicon substrate.
• resistors manufactured by CVD, sputtering, and MBE are difficult to manufacture in high volume because of the limits on the size of the substrate. Attempts in the past have been made at manufacturing resistors by other means . These have however resulted in sensors that are not sensitive nor reliable enough for modern applications.
• deposition techniques such as melt-spinning and ball-milling. However, these techniques are usually restricted to the production of heterogeneous alloys.
• Giant Magnetoresitive (“GMR”) sensors are made up of regions of active material and are less sensitive than MR sensors even though they exhibit larger total changes in resistance.
• Some GMR sensors are made up of magnetic layers separated by layers of diamagnetic or non-magnetic material while others are made of granular metals. The change in resistivity of these materials is attributed in part to conduction electrons moving across the non-magnetic layers and the accompanying spin-dependent scattering at or near the layer interfaces. It is believed that the in-plane resistance between two magnetic layers varies approximately as the cosine of the angle between the magnetization in the two layers.
• U.S. Patent No. 5,277,991 to Satomi et al . is directed to an example of such a GMR type material .
• the manufacturing process is further limited, in that the relatively small area of the silicon wafer substrate, limits large-scale production.
• This article which is herein incorporated by reference in its entirety, explains various techniques for electroplating thin metallic films.
• electrochemical deposition involves providing metal ions in a solution.
• the ions receive electrons from one of two electrodes (the cathode) and are thereby reduced to a solid form that deposits onto some type of substrate material.
• An example of a typical electrodeposition half reaction is shown below: Cu 2+ (aq) + 2 e- - Cu (B)
• Electrodeposited GMR films as sensors for magnetic data storage is suggested but is also limited by the requirement of electrodepositing the thin films onto a copper substrate and the accompanying need to dissolve the copper substrate to avoid short circuiting the resistor.
• electrodeposition has not heretofore been used to fabricate MR or GMR sensors.
• problems inherent in using this method to fabricate sensors have in the past been numbered and varied.
• the technique of electrodeposition requires that the material be deposited onto a conductive or partially conductive substrate, such as for example copper. Since the substrate must be conductive, it has heretofore been commercially impractical to form regions of active material thereon (resistors) without requiring the step of dissolving away the copper to avoid short circuiting the active resistive element.
• Electroplating methods as well as electrochemical treatments and plating apparatus for the electrodeposition of thin film alloys on a substrate, are well known.
• Castellani et al in U.S. Patent No. 4,103,756, issued July 25, 1978, teaches methods and apparatus for electroplating
• Permalloy NiFe
• Electrodeposition has also been used to fabricate magnetic thin films, as for example, magnetic recording heads.
• Such recording heads are fabricated in U.S. Patent No. 4,756,816 to Liao et al .
• the CoFe thin films deposited in Liao et al have acceptable permeability for recording purposes.
• these films are not magnetorestrictive and therefore cannot be used for sensor manufacture .
• electrodeposition in MR or GMR device or sensor fabrication could enable the relatively inexpensive, rapid production of large quantities of devices or sensors on large area substrates such as glass.
• the necessity of having an appropriately conductive substrate versus the tendency for such a substrate to short circuit the resistive material has kept this technology from being commercially implemented.
• the inability to deposit and permanently affix appropriate materials on otherwise suitable substrates has heretofore also prevented their use. Specifically, it has heretofore been virtually impossible to adhere thin films of electrodeposited metals such as copper onto large scale substrates such as planar glass that has been appropriately coated with a layer of conductive or partially conductive material to facilitate electrodeposition.
• magnetoresistors and giantmagnetoresistors and devices such as sensors made therefrom that: (1) can be fabricated in high volume and at low cost using electrodeposition techniques and (2) are sensitive and reliable enough for the demands of modern applications .
• the present invention is based, in part, on using electrodeposition techniques to deposit regions of active (resistive) material onto a large area conductive (or partially conductive) substrate to produce reliable as well as low cost MR and GMR devices such as sensors.
• the present invention also provides thin film magnetoresistive sensor (s) comprised of resistors having a line pattern wherein the width of the lines of magnetorestrictive material making up the resistors is maximized so as to enhance the sensitivity of the resulting sensor .
• an insulated substrate is covered with a conductive coating.
• At least one region of magnetically active material is deposited on the substrate or conductive coating using electrodeposition.
• the region of active material is patterned, using photofabrication to form variable resistors having a line pattern.
• These resistors can detect changes in a magnetic field either resulting from an external source such as a remote magnet or internal source such as an adjacent magnetic source on the IC.
• the resistance of each resistor changes as a function of the applied field and its direction.
• high permeability material is electrochemically deposited to concentrate the magnetic flux delivered to a region of active material.
• pole pieces or magnetic flux concentrators are deposited as either part of the electrodeposition sequence or added at a later stage.
• magnetic layers separated by non-magnetic layers are alternately deposited onto a conductive substrate using electrochemical deposition techniques.
• the magnetic/non-magnetic layers are patterned to form a GMR resistor having increased magnitude of resistive change.
• the layer structures can be assembled in such a way to produce spin valve behavior.
• the regions of active material are electrically connected to additional circuits (e.g., voltage sources, current sources, resistors, and capacitors) or even directly to a preamplifier chip to make up a MR or GMR device or sensor.
• the present invention also provides a process whereby magnetically active material is adherently electrodeposited onto a conductive substrate without electrically short circuiting the active material.
• Suitable substrates for use in the present invention include, but are not limited to indium tin oxide [ITO] coated glass, doped silicon, gallium-arsenide, germanium, or doped diamond.
• Fig. 1 is a cross section of a magnetoresistive layer [MR] on ITO coated glass.
• Fig. 2 is an isolated MR resistor situated on a ITO coated glass substrate.
• Fig. 3 is a block diagram illustrating the steps for deposition of magnetically active material [both MR and GMR] onto ITO coated glass.
• Fig. 4 is a cross section of a giant magnetoresistive [GMR] material electroplated onto ITO coated glass.
• Fig. 5 is an isolated GMR resistor sitting on a planar ITO coated glass substrate.
• Fig. 6 is a schematic top view of a complete magnetoresistive (MR) sensor made up of four (4) resistors and four (4) pole pieces.
• MR magnetoresistive
• Fig. 7 is an optical micrograph (17x magnification) of a sensor according to the present invention.
• Fig. 8 is a schematic of a typical mask for photomasking the present invention sensors.
• a magnetoresistive device for detecting a change in a magnetic field in accordance with the present invention comprises an insulated substrate having at least one region of less than about 2000 A thickness of a conductive or partially conductive coating disposed thereon. It is preferable to limit the thickness of the conductive coating in order to prevent short circuiting problems associated with the application of resistive material onto conductive material.
• the insulated substrate is preferably planar glass.
• Optical quality glass of the Glaverbel type is particularly suitable.
• other suitable materials for the substrate include, but are not limited to, a member selected from the group consisting of stainless steel, gallium arsenide and doped silicon.
• the coating on the substrate is preferably selected from the group consisting of indium tin oxide (ITO) , indium oxide, and tin oxide and has a resistivity value of from about 10 ohms/square to about 100 ohms/square.
• ITO indium tin oxide
• Indium tin oxide is a particularly preferred material for use as the coating in this invention.
• There is at least one resistor region comprising at least one layer of from about 0.5 ⁇ m to about 2 ⁇ m of an electrodeposited metallic material disposed on each of the region (s) of conductive or partially conductive coating. This layer is intentionally kept at minimal thickness to prevent short circuiting of the resistive material deposited thereon.
• Suitable metals for use as the metallic material in this invention include, but are not limited to one or more of chromium, platinum, gold, palladium, silver, copper and alloys and combinations thereof, with copper being especially preferred.
• the electrodeposited metallic material is at least substantially permanently affixed onto the coated substrate. It has heretofore been impossible to obtain this permanent adherance of the metallic material on a substrate such as ITO coated glass. There is a least one layer of from about 15 A to about
• an electrodeposited ferromagnetic material disposed on the layer (s) of electrodeposited metallic material.
• the ferromagnetic material is preferably comprised of a member selected from the group consisting of iron, nickel, copper, cobalt and alloys and combinations thereof.
• Preferred ferromagnetic metals for use in this invention include iron and nickel and a preferred ferromagnetic alloy is permalloy.
• Fig. 1 illustrates the aforedescribed device showing a region of magnetoresistive material disposed on a planar glass substrate having a partially conductive coating thereon.
• Substrate 11 can be of any shape, thickness, or size.
• substrate 11 has a thickness of from about 0.8 ⁇ m to about 14 ⁇ m and is most preferably about 0.8 ⁇ m to about 2 ⁇ m in thickness .
• substrate 11 has conductive coating 12 disposed thereon.
• Conductive coating 12 is preferably a thin film or layer of a metal, oxide, or semiconductor.
• Thin metallic layer 13 is disposed on conductive coating 12.
• Ferromagnetic material layer 14 is disposed on thin metallic layer 13.
• the deposition of metallic layer 13 and ferromagnetic material layer 14 is performed by electrochemical deposition.
• the deposition preferably takes place in an electrochemical cell (not shown) .
• a typical electrochemical cell for use in the present invention comprises a rectangular box made up of polypropylene.
• a "U" shaped magnet is affixed on the outside of the box and is of sufficient strength to provide a magnetic field of between 500-1000 gauss for MR material deposition. Uniformly distributed across the volume of the cell is a cathode affixed to one end of the cell and an anode at an opposite end of the cell exactly parallel to the cathode.
• a reference electrode is positioned in close proximity to a center of a cathode plate.
• a means of agitating the solution in a very uniform manner is provided.
• the solution is typically pumped through appropriate filters and there is a thermostat for controlling the temperature affixed to the cell.
• These resistors can be fabricated using electrodeposition cells and techniques known in the art .
• Thin film 13 is a metallic material affixed onto the conductive coating.
• Thin film 13 preferably has a thickness of from about 10 nm to about 200 nm.
• the metallic material of thin film 13 is at least substantially permanently affixed to the conductive coating, as explained below.
• substantially permanently affixed is intended to mean that for all practical purposes the film does not readily peel off of the coating on the glass (substrate) .
• Copper is a particularly preferred material for use as the thin film affixed to the conductive coating.
• the second thin film 14 is ferromagnetic material disposed on the metallic material 13 and as discussed above, has a preferred thickness of from about 50 nm to about 2000 nm.
• An MR sensor in accordance with the present invention comprises at least two electrically interconnected resistors on an insulated substrate having at least two regions of a conductive or partially conductive coating disposed thereon.
• Each of the resistors making up a sensor in accordance with the present invention comprises a magneto-resistive device as earlier described.
• the resistors are preferably electrically interconnected in a Wheatstone Bridge configuration.
• the present invention MR sensor preferably further comprises at least one pole piece disposed on the coated substrate.
• the pole piece preferably comprises a region of electrodeposited pole piece material disposed on at least one region of the coated substrate.
• the region of electrodeposited pole piece material is preferably situated relative to the resistors such that the pole piece material acts to focus a magnetic field onto the resistors without shielding the resistors from same.
• the pole piece element focuses the magnetic field along its axis onto the resistors.
• Suitable material for use as pole piece material should preferably be a permeable material . Examples of such suitable pole piece material include, but are not limited to nickel-iron, cobalt- iron and combinations thereof.
• an MR sensor in accordance with the present invention comprises at least one pole piece having a thickness of from about .5 ⁇ m to about 5 ⁇ m thick.
• the pole piece preferably comprises at least one layer of from about 0.5 ⁇ m to about 5 ⁇ m thick of metallic material selected from the group consisting of chromium, platinum, gold, palladium, silver, copper and alloys and combinations thereof.
• the pole piece further comprises at least one layer of from about 15 A to about 30 A of an electrodeposited ferromagnetic material.
• the electrodeposited ferromagnetic material is preferably selected from the group consisting of iron, nickel, copper, cobalt and alloys and combinations thereof and is disposed on the layer (s) of metallic material.
• the pole piece is comprised of the same material making up the reistors .
• Each of the resistors is configured in a linear pattern having a preferred line width of from about 15 ⁇ m to about 25 ⁇ m.
• linear patterbs having the preferred line width maximize sensitivity of the sensor. Any given portion of the linear pattern should be spatially separated from another given portion by a distance of from about 2 ⁇ m to about 20 ⁇ m.
• the present MR sensor comprises four magnetoresistive regions (resistors) .
• Each of two of the four regions are preferably situated on the substrate at an angle that is about 90° relative to each of the other two of the four magnetoresistive regions (resistors) .
• the resistor (s) are "patterned" and the pole pieces delineated using multiple steps of photofabrication.
• the resulting resistive material is photo masked with photo resist in a specific designed pattern such as that shown for exemplary purposes only in Fig. 8.
• Photo resist overlays a portion of the resistive material and protects it from subsequent etching steps.
• the conductive coating, the metallic layer and the ferrogmagnetic layer in any exposed region are etched away.
• FIG. 6 illustrates a configuration of variable resistors in a sensor according to the present invention. Region 172,
• 272, 372, 472 are each one of four resistors, and regions 173,
• variable resistors 172, 272, 372, and 472 are electrically interconnected through pole pieces 173, 273, 373, and 473 in a configuration commonly referred to as a Wheatstone Bridge. Additionally, contact points for connecting to an outside circuit can be spot welded or gold bonded onto the resistive material to connect with packaging case . During sensor operation, the contact points should be electrically connected across a voltage meter, voltage source, or capacitor (not shown) .
• An MR sensor in accordance with the present invention can have a hysteresis measurement of about 1 gauss and a resistance measurement of from about 500 ohms to about 3000 ohms when measured using a Hall probe and applying a constant current of about 10 ma at a frequency of 1 KHz.
• the maximum sensitivity of this specially designed sensor is along arrow 101 direction.
• the pole pieces 173, 273, 373 and 473 will align the magnetic flux along their axis and focus the field on resistors 172 and 372.
• resistor 272 and 472 have a electrical resistance that changes reversely proportional to the magnitude of the applied magnetic field 100.
• resistor 272 and 472 have a resistance that changes proportional to the magnitude of the applied magnetic field 100.
• This reverse MR response function combined with Wheatstone Bridge circuit increases the sensitivity in this MR sensor.
• the pole pieces can be very thick to focus the magnetic field 100 to the resistors 172 and 372, the sensitivity of resistors 172 and 372 can be largely increased.
• the resistors 272 and 472 are mostly shielded from magnetic field 100 by the pole pieces 173, 273,
• this invention is directed to a giant magnetoresistive device for detecting a change in a magnetic field.
• the device comprises an insulated substrate having at least one region of less than about 2000 A of a conductive or partially conductive coating disposed thereon.
• the insulated substrate is planar glass having a thickness of from about 0.8 ⁇ m to about 2.0 ⁇ m and the partially conductive coating is indium titanium oxide having a thickness of from about 0.2 ⁇ m to about 2.0 ⁇ m.
• the coating has a resistivity value of from about 10 ohms/square to about 100 ohms/square.
• Alternative coating materials include indium oxide and tin oxide and alternative substrate materials include stainless steel, gallium arsenide and doped silicon.
• the resistor region comprises at least one layer of from about 0.5 ⁇ m to about 1.0 ⁇ m of an electrodeposited metallic material disposed on each of the region (s) of conductive or partially conductive coating.
• the electrodeposited metallic material is at least substantially permanently affixed onto the coated substrate.
• Suitable material for use as the metallic material includes chromium, platinum, gold, palladium, silver, copper, aluminum, titanium and alloys and combinations thereof, with copper being preferred.
• each layer couple comprises at least one layer and preferably from about 5 to about 15 layers of from about 20 A to about 30 A of electrodeposited ferromagnetic material in each of said at least one layer couple and at least one layer and preferably from about 3 to about 10 layers of from about 8 A to about 13 A of an electrodeposited non-ferromagnetic material.
• the number of layer couples, the number and thickness of the individual layers making up the couples will vary according to the materials being used and the ultimate use of the resistive material. For example, when depositing a cobalt/copper multilayer, it is preferred to have from about 30-100 couples of layer cobalt and one layer copper.
• Suitable ferromagnetic material for use in the present GMR resistive device includes iron, nickel, copper, cobalt and alloys and combinations thereof.
• Example of such ferromagnetic alloys include Co-Ni-Cu, Ni-Cu, Ni-Fe, Co-Fe, Co-Ni, Co-Pt, Fe-Rh, with Co-Ni and Co-Ni-Cu being preferred.
• the present embodiment also comprises a GMR sensor comprising an insulated substrate having at least two regions of less than about 2000 A thickness of a conductive or partially conductive coating disposed thereon.
• the coating has a resistivity value of from about 10 ohms/square to about 100 ohms/square.
• the electrical interconnection can be in a wheatstone bridge configuration.
• FIG. 4 illustrates a GMR resistor in accordance with the present invention.
• Substrate 111 can be of any shape, thickness, or size. As shown in Fig. 4 the substrate 111 has conductive coating 112 disposed thereon.
• conductive coating 112 is preferably a metal, an oxide, or a semiconductor.
• the conductive coating is a thin film comprising indium tin oxide (ITO) .
• ITO indium tin oxide
• the conductive coating has a preferred resisitivity value of from about 10 ohms/square to about 100 ohms/square, and alternatively can be comprised of for example, but not limited to, stainless steel, gallium arsenide or doped silicon.
• the GMR sensors according to the present invention can further comprise a pole piece element .
• the pole piece element comprises a region of electrodeposited pole piece material disposed on at least one region of the coated substrate.
• the region of electrodeposited pole piece material is situated relative to the resistors such that the pole piece material acts to focus a magnetic field onto the resistors without shielding the resistors from same.
• the pole piece focuses the magnetic field along its axis onto the resistors.
• a thin layer of metal 131 is disposed on the conductive coating 112 and has a preferred thickness of about 10 nm to about 200 nm.
• the metallic material of layer 131 is at least substantially permanently affixed to the conductive coating, as explained below.
• the metallic material should not be construed as being limited to copper, but is preferably selected from the group consisting of chromium, platinum, gold, palladium, silver, copper and alloys and combinations thereof.
• the active layer 114 is made of a number of alternative ferro-magnetic and non-magnetic layers. This multilayered film 114 is disposed directly onto the metallic layer 131.
• Each layer of the ferromagnetic material has a preferred thickness of from about 20 A to about 30 A, and preferably comprises a member of the group consisting of iron, nickel, copper, cobalt and alloys and combinations thereof. Suitable alloys for use as the ferromagnetic material include, but are not limited to a member of the group consisting of Co-Ni-Cu, Ni-Cu, Ni-Fe, Co-Fe, Co-Ni, Co-Pt, Fe-Rh, and combinations thereof (see table 1).
• Each of the layer (s) of non- ferromagnetic material has a preferred thickness of about from about 8 A to about 50 A.
• Suitable material for use as the non- ferromagnetic material includes, but is not limited to a member selected from the group consisting of copper, silver, platinum, palladium, titanium, chromium, rhodium and combinations thereof .
• the deposition of multilayer 114 is performed by electrochemical deposition. The relative thickness of each of these layers influences the sensitivity relative to the noise of the resultant sensor structure.
• a copper layer having a thickness of about 12 A alternating with a cobalt layer having a thickness of about 20 A results in a more sensitive but "noisier" (more hystereses) sensor than a copper layer having a thickness of about 24 A alternating with a cobalt layer having a thickness of about 20 A.
• the later would be less sensitive than the former and would typically respond linearly with the magnetic field.
• layers 131 is electrodeposited onto the conductive coating, it is peeled off and layer 131 is replated on the conductive surface thereby substantially, permanently affixing this layer onto this substrate.
• a similar photo masking process as that described for the MR sensors above is carried out on the GMR sensor material .
• a relatively thick pole piece would be necessary to shield the resistor 272 and 472 from magnetic field 100, because all four resistors 172, 272, 372 and 472 have the same response function to the magnetic field 100 (as shown in Fig. 6) .
• resistors 272 and 472 can be replaced by constant resistors to balance the bridge circuit.
• the two balancing resistors 272 and 472 are optionally situated on a circuit board or integrated into a preamplifier circuit when such GMR sensors are used therewith.
• Fig. 3 schematically illustrates a process for fabricating a sensor in accordance with the present invention.
• Conductive material coated substrate 11 (as shown in Fig. 1) substrate is used for electrochemical deposition. Tthe size of substrate 11 is primarily limited only by the size of the electrochemical cell in which the electrodeposition step is performed.
• the substrate comprises Glaverbel-type glass having a thickness that is about 1.1 ⁇ m and a coating thereon comprising indium tin oxide having a thickness from about .02 ⁇ m to about 0.2 ⁇ m and a resistivity value of from about 10 to about 100 ohms per centimeter.
• Pre-cleaner 10 prepares substrate 11 and conductive coating 12 for electrochemical deposition thereon. Each substrate is cleaned using ultrasonic cleaning, de-ionized water, and an acid solution. Each substrate is attached to an electric contact and a copper loop.
• a thin metallic layer 131 (shown in Fig. 4) is electrochemically deposited onto conductive coating 112.
• thin film depositor 20 comprises an electrochemical cell and a copper electrolyte.
• Thin film depositor 20 deposits at least one first layer (not shown) of from about 0.01 ⁇ m to about 0.2 ⁇ m of copper onto the conductive coating on the substrate.
• a film peeler (not shown) peels off the at least one first metal layer.
• the substrate is removed from the electrochemical cell and the first metal layer is peeled off by hand.
• thin film depositor 20 deposits preferably from about 10 nm to about 200 nm of at least one second layer of copper onto the region on conductive coating 112 from which the first layer of copper is peeled so as to provide requisite electrical conductivity for further deposition.
• This second layer of copper is thereby substantially permanently affixed to the coated glass.
• Magnetically active material depositor 30 deposits at least one thin film of magnetoresistive material 14 (shown in FIG. 1) onto the thin metallic layer 13.
• active material depositor 30 comprises an electrochemical cell and a solution for depositing a single magnetic element or magnetic alloy.
• the magnetic alloy comprises nickel and iron.
• Magnetoresistive material depositor 30 preferably deposits between 50nm and 2000nm of the magnetic alloy onto thin film 13.
• GMR deposition includes providing a substrate having a conductive coating thereon requires an additional step wherein a thin film depositor deposits a layer of non- ferromagnetic material alternatively with the ferromagnetic material being deposited.
• the present invention is also directed to a method for electrodepositing magnetoresistive material onto an insulated substrate and at least substantially permanently affixing same thereon.
• the method comprises the steps of providing an insulated substrate having a conductive or partially conductive coating to a thickness of from about 0.2 ⁇ m to about 2.0 ⁇ m thereon and electrodepositing at least one first layer of metallic material onto at least one region of the conductive or partially conductive coating.
• the conductive or partially conductive coating is selected from indium tin oxide (ITO) , indium oxide, and tin oxide, with indium tin oxide being preferred.
• the first layer has a preferred thickness of from about 0.5 ⁇ m to about 2.0 ⁇ m.
• Preferred material for use as the metallic material in the present invention includes, but is not limited to chromium, platinum, gold, palladium, silver, copper and alloys and combinations thereof, with copper being preferred.
• the next step comprises removing the first layer of metallic material from conductive or partially conductive coating.
• a second layer of metallic material having a thickness of from about 0.5 ⁇ m to about 2.0 ⁇ m is electrodeposited onto the region (s) of conductive or partially conductive coating.
• At least one layer of magnetoresistive material is electrodeposited onto the second layer of metallic material.
• the preferred manner in which to remove the first layer of metallic material is by peeling it off the coated substrate.
• a magnetic field should preferably be provided during the electrodeposition steps, the value of the magnetic field is preferably from about 500 gauss to about 2 kilo-gauss.
• the present invention is directed to a method for producing a sensor.
• the method comprises providing an insulated substrate having a conductive or partially conductive coating disposed thereon.
• a layer of from about 0.5 ⁇ m to about 2.0 ⁇ m of copper is at least substantially permanently affixed on the conductive or partially conductive coating.
• At least one layer of from about 15 A to about 30 A of ferromagnetic material is electrodeposited onto the layer of copper.
• At least one portion of the ferromagnetic material and the copper layer and conductive or partially conductive coating are etched away thereunder to thereby form at least two spatially separated regions of active material.
• Fig. 5 illustrates a GMR resistor in accordance with the present invention. Each of the regions of active material are then interconnected in an electrical bridge configuration.
• the substrate has a preferred thickness of from about 0.8 ⁇ m to about 2 ⁇ m.
• the conductive or partially conductive coating is selected from the group consisting of indium tin oxide (ITO) , indium oxide, and tin oxide, with indium tin oxide being preferred.
• the step of electrodepositing at least one layer of ferromagnetic material onto the layer of copper comprises electrodepositing from about 10 mono-layers to about 100 layers of one of the group consisting of iron, nickel, copper, cobalt and alloys and combinations thereof. Nickel and the alloy permalloy are preferred.
• the method can further comprise forming at least pole piece on said substrate by forming a region of electrodeposited pole piece material on the conductive or partially conductive coating.
• the region of electrodeposited pole piece material is situated such that it acts to focus a magnetic field being applied to the device onto the magnetoresistive region (s) without shielding it from same.
• the pole piece element focuses the magnetic field along its axis onto the magnetoresistive region (s) .
• the pole piece is preferably permeable and selected from the group consisting of nickel-iron, cobalt-iron and combinations thereof .
• the present invention is directed to a method of making a giant magnetoresistive device for detecting a change in a magnetic field.
• the substrate and substrate coating are the same as those used in MR device fabrication.
• At least one resistor region is produced.
• the steps for depositing the GMR resistor comprise electrodepositing at least one layer of from about 0.5 ⁇ m to about 1.0 ⁇ m of a metallic material on each of the region of conductive or partially conductive coating on the substrate.
• the metallic material is at least substantially permanently affixed thereto.
• At least one layer couple is electrodeposited onto the at least substantially permanently affixed layer of electrodeposited metallic material.
• Each of the layer couple (s) comprises at least one layer of from about 20 A to about 30 A of a ferromagnetic material and at least one layer of from about 8 A to about 13 A of an non- ferromagnetic material.
• the ferromagnetic material is comprised of a member selected from the group consisting of iron, nickel, copper, cobalt and alloys and combinations thereof.
• the alloys are selected from the group consisting of Co-Ni-Cu, Ni-Cu, Ni-Fe, Co-Fe, Co-Ni, Co-Pt, Fe-Rh, and combinations thereof, with Cu-Ni and Co-Ni-Cu being preferred.
• the non-magnetic material is preferably selected from copper, silver, platinum, palladium, titanium, chromium, rhodium and combinations thereof .
• This method comprises electrodepositing from about 30 to about 100 layer couples onto the layer of electrodeposited metallic material.
• This method like the one for fabricating the MR sensors can further comprise the step of forming at least one pole piece being situated relative to the giant magnetoresistive region such that the pole piece material acts to focus a magnetic field being applied to the device onto the giant magnetoresistive region (s) without shielding the region from same .
• the active material is deposited in an electrochemical cell 30.
• photo resist will cover the whole surface of active layer and a window will be open only in pole pieces region 173, 273, 373 and 473 as shown in Fig. 6 to enable the deposition of additional pole piece layer through the windows.
• the pole piece depositor 50 deposits pole piece material on the active layer in the open regions.
• Pole piece depositor 50 can be the same or different electrochemical cell as active magnetic layer depositor with a solution for depositing a single magnetic element or magnetic alloy.
• the thickness of the pole piece layer varies from about 0.1 ⁇ m to 5 about ⁇ m.
• a photo resist cleaner cell 60 is used to remove the photo resist on the surface after pole piece deposition.
• Photo masking process (2) 70 will mask the sample as the final pattern showed in Fig. 6.
• the etcher 80 is responsible for removing regions between resistor lines and the region between the pole pieces as shown in Fig. 6. It is preferable to remove all conductive materials in the region mentioned, including active layer 14 for MR sensors and 114 for GMR sensors, conductive layer 13 and ITO layer 112.
• the enchant used in etcher 80 can be one or several in sequence to etch the metallic layers and ITO layer. If conductive coating 12 is not removed, variable resistor is not insulated from adjacent variable resistors (not shown) . When a variable resistor is electrically connected to additional circuits to form a sensor, the underlying ITO layer becomes a path for electrical current, the current in adjacent resistor lines will conduct laterally instead of along the path of lines making up the resistor.
• the reduced current that results along the intended path decreases the overall effectiveness of the sensor.
• the scriber 90 is responsible for making final cuts, if necessary, to the substrate 11.
• the scriber 90 should make whatever cuts are necessary to prepare substrate 11 and the resistors formed thereon for use in the ultimate application.
• the individual sensors will be packed in step
• Thickness 1.1 ⁇ m
• ITO Coating 15 ohms/square 2 .
• Pre - clean steps a) Samples preparation: the ITO glass is cut into
• Pre-deposition cleaning ultrasonic cleaning: 4 Oz/Gal Micro, 50°C, 3min rinse with deionized water: 50°C, 3 min dip into 2.5% H 2 S0 4 etching for 1 min.
• Copper deposition a) electrolyte for copper conductive layer deposition: copper pyrophosphate strike solution: 333 ml/L; water: 666 ml/L; pH: 8.8 b) deposition condition :
• the permalloy is electro-deposited to a layer thickness of 250 nm as measured by a coulometer
• sample is placed back on spinner and developer is poured on at stopping mode for 60 seconds, the spin cycle is turned on, the sample is spun at low speed (500RPM) with developer and water for 10 extra seconds followed by water for 55 seconds.
• the sample is subjected to a high speed spin (4000RPM) for 1 minute to dry.
• the sample is hard baked at 120°C for 20 minutes.
• Fig. 6 is an optical micrograph of a sensor made in accordance with this example .
• Example 2 GMR resistor and sensor fabrication 1.
• Substrate Glass type: Glaverbel
• Thickness 1.1 ⁇ m
• Pre-deposition cleaning ultrasonic cleaning: 4 Oz/Gal Micro, 50°C, 3min rinse with deionized water: 50°C, 3 min dip into 2.5% H 2 S0 4 etching for 1 min. Rinse with D.I. water.
• Copper deposition a) electrolyte for copper conductive layer deposition: copper pyrophosphate strike solution: 333 ml/L; water: 666 ml/L; pH : 8.8 b) deposition condition:
• Plating potential potentiostatic deposition at -2.0V SCE (saturated calomel electrode) Temperature: ambient Cathode and anode are kept parallel to achieve uniform film layer thickness c) copper layer deposition and bonding treatment:
• GMR multilayer deposition Electrolyte : cobalt sulfamate 500 ml/L; copper sulfate: 2.947 g
• Photo-etching a) Cleaning: the sample is rinsed with Acetone, Isopropanol and D.I. water while sample is placed on a spinner at low spin speed (-500 RPM) for a total of 60 second; then spin dried at 4000 RPM for 60 seconds. b) the sample is baked in an oven at 120°C for 15 minutes. The sample is allowed to cool for 3 minutes. c) photo-resist is spun on (Shipley, Inc. #1813) : set time and speed as 6 sec at 700 RPM followed by
• sample is baked in an oven for 20 minutes at 120°C, then is allowed to cool for 3 minutes; e) the sample is masked, aligned and exposed to UV light at 15mV/cm 2 (setting on the exposure meter for 14 seconds) . f) developing: sample is placed back on spinner and developer is poured on at stopping mode for 60 seconds, the spin cycle is turned on, the sample is spun at low speed (500RPM) with developer and water for 10 extra seconds followed by water for 55 seconds. The sample is subjected to a high speed spin (4000RPM) for 1 minute to dry. g) the sample is hard baked at 120°C for 20 minutes.

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