JP4058164B2 - Magnetic recording / reproducing device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a magnetic recording / reproducing apparatus, and more particularly to a high recording density magnetic recording / reproducing apparatus.
[0002]
[Prior art]
Japanese Patent Laid-Open No. 4-103014 describes a ferromagnetic tunnel effect film using an antiferromagnetic material and a magnetoresistive effect element using the same. Japanese Patent Application Laid-Open No. 9-128714 describes a magnetic transducer having a structure in which the film thickness of a ferromagnetic layer is changed in the film plane.
[0003]
[Problems to be solved by the invention]
The conventional technology supports the increase in recording density, and supports elements using the magnetoresistive effect as reproducing elements for magnetic recording and reproducing devices that reproduce weak magnetic signals from fine recording with sufficiently high sensitivity and output. However, at present, there is a technical need for a storage device that solves the problem of reduction in reproduction sensitivity, output, and noise due to further miniaturization.
[0004]
In recent years, it has been known that a large magnetoresistive effect is generated in a tunnel current observed when a ferromagnetic metal film is laminated through a very thin insulating layer and a current is passed in the film thickness direction. In this case, the tunnel magnetoresistive effect and the giant magnetoresistive effect element known in the art measure the decrease in which the resistance changes depending on the direction of the external magnetic field as the output while the current flows in the film surface direction. The effect film has a structure in which current flows in the film thickness direction, and it is necessary to adopt a head structure different from the conventional one.
[0005]
On the other hand, in terms of magnetic structure, this tunnel-type magnetoresistive effect element is similar to the structure of a spin valve that has been developed in the past, and has a magnetic film separated into two layers with an intermediate layer interposed therebetween. The need for proper control is as important as the spin valve structure. In addition, the tunnel magnetoresistive element needs to control current leakage and dielectric breakdown. Therefore, there are problems in the magnetization characteristics of the fixed layer, the regulation of the magnetization rotation of the free layer, and the control of magnetic domain generation in the free layer, which are the magnetic characteristics of the tunnel magnetoresistive element. In the conventional magnetoresistive film, for example, a structure in which hard magnetic films for magnetic domain control are arranged at both ends of the magnetoresistive film as in a mechanism called hard bias is used. Since current leaks in the tunnel type magnetoresistive effect element, it is difficult to apply current to the tunnel type magnetoresistive effect film in this structure. Furthermore, a pair of electrodes for applying a current to the magnetoresistive effect film has been formed side by side in the magnetic gap, but in the tunnel type magnetoresistive effect film, it is necessary to form the electrodes in the thickness direction. It is difficult to manufacture. Further, the actual film size is used as a factor for determining the track width.
[0006]
Also, in the tunnel type magnetoresistive effect element, an electric current flows in the thickness direction of the magnetic film sandwich structure through an insulating film whose active region is an extremely thin film, so this portion is a surface facing the magnetic head, that is, a surface close to the recording medium. When exposed to light, current may be short-circuited due to proximity to or contact with the recording medium. For this reason, it is difficult to process the opposing surface at the same time.
[0007]
In addition, with regard to the structure of the electrodes, there is a problem that the element size is miniaturized with the realization of high-density recording, and accordingly, the electric resistance of the element itself is reduced and the output is reduced.
[0008]
Accordingly, an object of the present invention is to provide a tunnel type magnetoresistive magnetic head compatible with high-density recording and a magnetic recording apparatus using the same, and specifically, the reproduction sensitivity associated with the above-mentioned miniaturization. Another object of the present invention is to provide a memory device having a structure that solves problems such as output reduction, noise reduction, and current short circuit.
[0009]
[Means for Solving the Problems]
First, in order to prevent a short circuit of the tunnel-type magnetoresistive multilayer film on the opposite surface, the thickness of the peripheral part of the insulating barrier film of the tunnel-type magnetoresistive multilayer film is increased or a process for increasing the insulation is performed. Therefore, the insulating property of the peripheral portion is increased, and a structure is adopted in which a short circuit between the free-side magnetic film and the fixed-side magnetic film on the opposing surface of the element is prevented. In addition, the magnetic signal can be handled in a region that is not affected by other processes magnetically, so that it is considered effective for reducing noise.
[0010]
Secondly, to connect the electrodes of the element, the upper surface of the tunnel magnetoresistive laminated film is covered with a high resistance film, and a hole is made in a portion corresponding to the active region of the element, and this is used as a contact hole to produce an electrode A structure that can be considered. Since current flows through the region defined by this contact hole, the effective track width can be defined by this contact hole, and current short circuit in the peripheral portion can be minimized. In addition, magnetic domain control can be performed by selecting an antiferromagnetic or hard magnetic material for the high resistance film.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
The magnetic head of the present invention comprises a pair of magnetic shields forming a magnetic gap as a basic structure and a tunnel type magnetoresistive effect element disposed in the magnetic gap. The tunnel magnetoresistive element is configured by sequentially laminating a lower magnetic shield, a lower conductive gap, a tunnel magnetoresistive laminated film, an upper conductive gap, and an upper magnetic shield. In particular, with respect to the tunnel magnetoresistive laminated film, the thin film constituting the tunnel type magnetoresistive laminated film was produced by a high frequency magnetron sputtering apparatus as follows. The following materials were sequentially laminated on a ceramic substrate in an atmosphere of 1 to 6 mTorr of argon.
[0012]
As a material (target) used for sputtering, each target of tantalum, nickel 20 atomic% -iron alloy, copper, cobalt, chromium-manganese alloy, and alumina was used. If necessary, the composition was adjusted by placing a tip of one centimeter square of the additive element on the target. The chip was made of platinum, nickel, iron, or cobalt.
[0013]
In the laminated film, high frequency power was applied to each cathode on which each target was placed to generate plasma in the apparatus, and each layer was sequentially formed by opening and closing the shutters arranged for each cathode. When the film was formed, a permanent magnet was used to apply a magnetic field of about 80 oersted in a direction parallel to the substrate to provide uniaxial anisotropy, and the direction of an exchange coupling magnetic field such as a chromium manganese film was induced in each direction.
[0014]
Element formation on the substrate was patterned by a photoresist process.
[0015]
There are several methods for changing the film thickness in the same layer as in the present invention as follows. When a thick layer is grown and the layer is partially removed, patterning by a photoresist process, CMP, or FIB is used. Further, a method is used in which a film is formed at a thin part, a lift-off pattern is formed thereon, and the same film is grown around the pattern. The choice of these methods depends on the area, nature and material of the layer that changes film thickness.
[0016]
Similarly, as a method of changing electric resistance in the same layer, a method of partially forming a reaction layer by irradiating ions of oxygen, nitrogen, carbon, sulfur, etc. using a focused ion beam, and an ion implantation method, These ions were implanted. The substrate thus produced was processed with a slider and mounted on a magnetic recording apparatus.
[0017]
Hereinafter, specific embodiments of the present invention will be described with reference to the drawings.
[0018]
FIG. 1 is a schematic view showing a configuration example of a tunnel type magnetic head of the present invention. A lower magnetic shield 35, a lower conductive gap 33, a tunnel type magnetic laminate 101, an insulating gap film 40, an upper conductive gap 34, an upper magnetic shield / lower magnetic core 36, a coil 42, and an upper magnetic core 83 are formed on a base 50. Formed and configured. A conductive material was used for the upper magnetic shield 36 and the lower magnetic shield 35, and these were drawn out to form an electrode to apply a current and detect a reproduction output. At this time, the upper magnetic core 83 and the upper magnetic shield / lower magnetic core 36 write around the write gap formed on the surface facing the recording medium by the magnetomotive force generated by applying a current to the coil 42. Generate a magnetic field.
[0019]
The orientation of the magnetic head is determined by the facing surface and the substrate surface, and a track width direction 61, an element height direction 62, and a magnetic head driving direction 63 are defined. When viewed from the opposite surface, the lower magnetic shield 35, the lower conductive gap 33, and the tunnel-type laminated film 101 are directly connected, and the upper conductive gap 34 and the upper magnetic shield / lower magnetic core 36 are connected. The tunnel-type magnetoresistive film sandwiched between the lower magnetic shield 35 and the upper magnetic shield 36 has a structure as shown in FIG. For this reason, the barrier film 17 made of an insulating material is sandwiched between the fixed-side magnetic film 11 and the free-side magnetic film 12 on the facing surface. The barrier film is made of an oxide, carbide, or nitride such as Al ₂ O ₃ , Zr ₂ O ₃ , or SiO ₂ .
[0020]
As a method for forming this film, there are a method in which a metal thin film is prepared and chemical bonding is forcibly performed by plasma irradiation or ion implantation, and a method in which it is left in an oxygen or nitrogen atmosphere or heat-treated. For simplicity, these processes are referred to as chemical reaction processes here. As described above, the periphery of the layer called the fixed-side magnetic film and the free-side insulating barrier layer is thick, and the thickened portion is exposed to the opposing surface.
[0021]
As a manufacturing method, when a barrier film is formed by oxidizing a metal film, a metal film is formed, and this is thinly processed by milling or FIB (focused ion beam milling method), and then a chemical reaction process is performed. Then, a film made of a material corresponding to the barrier film is created from the beginning, and this is processed and subjected to a chemical reaction treatment, or a film made of a material corresponding to the barrier film is created and processed as it is. Although there are some differences in the size of these, the tunnel magnetoresistance effect was recognized. In addition, by partially implanting conductive ions or a high energy light element on the surface of the film corresponding to the barrier film without changing the film thickness, oxygen bonds are broken to partially change electric conductivity. The method is also effective.
[0022]
3A and 3B show an example of a film configuration of a general tunnel type magnetoresistive laminate. The tunnel-type magnetoresistive laminate 102 has a structure in which a free-side magnetic layer 12, a barrier layer 17, and a fixed-side magnetic layer 11 are laminated. The fixed-side magnetic layer 11 is composed of an antiferromagnetic bias film 71 and a fixed ferromagnetic film 72, and the fixed ferromagnetic film 72 is applied with unidirectional anisotropy by exchange coupling with the antiferromagnetic bias film 71 directly overlapped and joined. ing. The free-side magnetic film is formed by laminating a free ferromagnetic film 12, a magnetic separation film / underlayer film 18, and a magnetic domain control film 16. The free-side magnetic film 12 may be a single-layer magnetic film. A laminated body of a soft magnetic film and a magnetoresistive film is more effective. The magnetic domain control film 16 includes a hard magnetic film and a base film. The base film can be omitted, but the presence of the base film stabilizes the characteristics of the hard magnetic film.
[0023]
The magnetic separation film / underlying film 18 has a function of sufficiently weakening and separating the interaction through the film surface of the magnetic domain control film 16 and the free-side magnetic film 12, and stabilizes the characteristics of the film formed thereon. It has a function to let you. The composition of each film used in this example is shown in the figure. The antiferromagnetic bias film 71 is Cr45Mn45Pt1030 nanometers, the fixed ferromagnetic film 72 is Co film 3 nanometers, and the barrier film 17 is Al ₂ O ₃ partially thinned from 10 nanometers to 3 nanometers. Co1 nanometer as the increase film 74, Ni81Fe19 film 5 nanometer as the soft magnetic film 75, Ta film 20 nanometer as the magnetic separation and underlayer 18, CoPt film 10 nanometer as the hard magnetic film 77, and Cr film as the underlayer 78 Each 5 nanometer was used.
[0024]
FIG. 4 is a diagram showing the direction of application of magnetic anisotropy of the film constituting the tunnel magnetoresistive laminate. The magnetic domain control film 16 is magnetized so that the residual magnetization is parallel to the track width direction 61. The free ferromagnetic film 12 induces a weak anisotropy in a direction parallel to the track width direction 61 in order to take a mechanism of rotating the magnetization while the magnetic field to be detected enters parallel to the element height direction 62. The fixed-side magnetic film 11 induces exchange coupling so that the residual magnetization is in a direction parallel to the element height direction 63.
[0025]
As a result of testing the tunnel magnetoresistive effect element of the present invention and the magnetic recording / reproducing apparatus equipped with the tunnel magnetoresistive effect element according to the present invention as described above, it has a sufficient output and a good bias characteristic and has a good operation reliability.
[0026]
On the other hand, as shown in FIG. 5, in the tunnel-type laminated film 102, the fixed side magnetic layer 11 is on the lower side and the free side magnetic layer 12 is on the upper side, and the high resistance is formed on the free side magnetic layer 12. The structure in which the magnetic domain control film 16 is stacked and the upper electrode / upper magnetic shield / lower magnetic core 36 is formed on the magnetic domain control film 16 is studied. NIO was used as the material of the high resistance magnetic domain control film 16. The film thickness of the high resistance magnetic domain control film 16 is thin on the tunnel type laminated film and is electrically connected to the shield 36. CMP (chemical mechanical polishing), FIB, or the like was used as a method for changing the film thickness in the film.
[0027]
In this way, by forming a partially thin portion or a hole to be a contact hole on the magnetic domain control film 16, a structure in which the electrode on the magnetic domain control film and the tunnel magnetoresistive film are electrically connected is formed. Created. At this time, the size of the hole formed on the magnetic domain control film 16, particularly the length in the track width direction 61 is set to a size corresponding to the actual track width, and the length of the shield is set to the track of the tunnel magnetoresistive effect active region 102. If the track width is smaller than the track width determined by the length in the width direction 61, the actual track width is defined by the size of the hole formed on the magnetic domain control film 16. This is because current flows almost straight from the upper shield 36 to the lower shield 35 in the tunnel magnetoresistive film. By adopting such a structure, a structure having a structure for defining the actual track width was also produced.
[0028]
For this reason, the active region of the tunnel magnetoresistive film can be formed with a sufficient size, the track width can be determined by the size of the upper contact hole, and a structure that can handle high-density recording can be obtained. It was. As a result of testing the tunnel magnetoresistive effect element of the present invention and the magnetic recording / reproducing apparatus of FIG. 6 equipped with the tunnel magnetoresistive effect element of the present invention with the above-described configuration, it has a sufficient output and good bias characteristics and has a good operation reliability. there were.
[0029]
【The invention's effect】
As described above in detail, according to the present invention, a head having good bias characteristics, an electrically stable and noise-reduced head can be obtained, and the reproduction track width is also the size of the active portion of the tunnel magnetoresistive film. Since the controllability that can be defined by the size of the different holes opened on the magnetic domain control film is improved, it is possible to obtain a magnetic head and a high recording density reproducing apparatus having good reproduction output and bias characteristics that can withstand high recording density Can do.
[Brief description of the drawings]
FIG. 1 is a perspective view showing a configuration example of a tunnel type magnetoresistive head of the present invention.
FIG. 2 is a side sectional view showing a configuration example of a tunneling magnetoresistive laminated film of the present invention.
3A and 3B are cross-sectional views showing a configuration example of a tunneling magnetoresistive laminated film of the tunneling magnetoresistive head of the present invention.
FIG. 4 is an explanatory diagram showing the direction of application of magnetic anisotropy of a film constituting the tunnel magnetoresistive stack of the tunnel magnetoresistive head of the present invention.
FIG. 5 is an explanatory view showing a configuration example of magnetic anisotropy of a tunnel magnetoresistive laminated film of the tunnel magnetoresistive head of the present invention.
FIG. 6 is an explanatory view showing a configuration example of a magnetic reproducing apparatus equipped with a tunnel type magnetoresistive head of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 101 ... Tunnel type magnetoresistive laminated body exposure part, 102 ... Tunnel type magnetoresistive laminated body of active region, 11 ... Fixed side magnetic film, 12 ... Free side magnetic film, 15 ... Free ferromagnetic film, 16 ... Magnetic domain control film, DESCRIPTION OF SYMBOLS 17 ... Barrier film, 18 ... Magnetic separation film | membrane and base film, 33 ... Lower conductive gap, 34 ... Upper conductive gap, 35 ... Lower magnetic shield, 36 ... Upper magnetic shield, 40 ... Insulating gap film, 41 ... Electrode terminal, 42 ... Coil, 50 ... Base, 61 ... Track width direction, 62 ... Element height direction, 63 ... Driving direction of magnetic head, 64 ... Opposing surface, 65 ... Active region of tunnel-type magnetoresistive laminate, 66 ... Free strength Direction of anisotropy of magnetic film, 67: Direction of residual magnetization of magnetic domain control film, 68: Direction of residual magnetization of fixed side magnetic film, 71: Antiferromagnetic film, 72: Fixed ferromagnetic film, 74: Magnetoresistance Increase film, 75 ... soft magnetic Film, 77 ... hard magnetic film, 78 ... underlayer film, 81 ... magnetic disk, 82 ... motor, 83 ... actuator, 84 ... control mechanism, 85 ... data reproducing composite systems.

Claims (2)

In a magnetic recording / reproducing apparatus having a magnetic head for reproducing a signal recorded on the recording medium through an opposing surface close to the recording medium,
The magnetic head includes a tunnel type magnetoresistive element;
The tunnel magnetoresistive element is composed of a lower magnetic shield, a lower conductive gap, a tunnel magnetoresistive laminated film, an upper conductive gap, and an upper magnetic shield, which are sequentially laminated. A fixed-side magnetic film to which magnetic anisotropy is applied in a direction parallel to the magnetic field direction to be detected so as to be fixed, and a direction orthogonal to the in-plane with respect to the magnetic field direction to be detected And a barrier film made of an insulating material formed between the fixed-side magnetic film and the free-side magnetic film. At least in the active region of the tunnel magnetoresistive element,
In the barrier film, the film thickness at the outer peripheral portion of the barrier film surface is thicker than the critical film thickness having insulation against a predetermined current, and the film thickness at the central portion of the film surface is thinner than the outer peripheral portion. Magnetic recording / reproducing apparatus characterized by the above. In a magnetic recording / reproducing apparatus having a magnetic head for reproducing a signal recorded on the recording medium through an opposing surface close to the recording medium,
The magnetic head has a tunnel type magnetoresistive effect element, and the tunnel type magnetoresistive effect element has a lower magnetic shield, a lower conductive gap, a tunnel magnetoresistive laminated film, an upper conductive gap, and an upper magnetic shield sequentially laminated. The tunneling magnetoresistive laminated film has a fixed-side magnetic film in which magnetic anisotropy is applied in a direction parallel to the magnetic field direction to be detected so that the magnetization direction is fixed; A free side magnetic film in which anisotropy is applied weaker than the fixed side magnetic film in a direction perpendicular to the plane of the power magnetic field, and the fixed side magnetic film and the free side magnetic film Having at least an active region of the tunnel-type magnetoresistive effect element having a sandwich structure having a barrier film made of an insulating material formed therebetween,
In the barrier film, the electric resistance of the outer peripheral portion of the barrier film surface is sufficiently insulating with respect to a predetermined voltage,
A magnetic recording / reproducing apparatus characterized in that the central portion of the film surface has a lower electrical resistance than the outer peripheral portion.

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