Magnetoresistive device and method of manufacturing same, and thin-film magnetic head and method of manufacturing same

A reproducing head of a thin-film magnetic head incorporates an MR element, a pair of bias field applying layers located to be adjacent to the side portions of the MR element, and a pair of electrode layers that are located on the bias field applying layers and overlap the MR element. The electrode layers each have a first layer that is laid over part of the top surface of the MR element via a protection layer, and a second layer that overlaps the first layer. In the method of manufacturing the reproducing head, after forming the protection layer on an element-to-be film to make the MR element, a first electrode-to-be film to make the first layers is formed continuously without interposing a step of exposing the protection layer to the air.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a magnetoresistive device that incorporates a magnetoresistive element and a method of manufacturing same, and to a thin-film magnetic head that incorporates a magnetoresistive element and a method of manufacturing same.

2. Description of the Related Art

With recent enhancements in the areal recording density of hard disk drives, improved performance has been sought of thin-film magnetic heads. For the past few years in particular, hard disk drives have been doubling in areal recording density roughly each year. Lately, areal recording densities of 100 Gbit/(inch)2or more are required.

Among the thin-film magnetic heads, widely used are composite thin-film magnetic heads made of a layered structure including a recording head having an induction-type electromagnetic transducer for writing and a reproducing head having a magnetoresistive element (that may be hereinafter called an MR element) for reading.

MR elements include: an AMR element that utilizes the anisotropic magnetoresistive effect; a GMR element that utilizes the giant magnetoresistive effect; and a TMR element that utilizes the tunnel magnetoresistive effect.

For reproducing heads, a high sensitivity and a high output are required. Reproducing heads that meet these requirements are GMR heads incorporating spin-valve GMR elements. Such GMR heads have been mass-produced.

In general, a spin-valve GMR element incorporates: a nonmagnetic conductive layer having two surfaces that face toward opposite directions; a free layer that is located adjacent to one of the surfaces of the nonmagnetic conductive layer and has a direction of magnetization that varies in response to a signal magnetic field from a recording medium; a pinned layer that is located adjacent to the other of the surfaces of the nonmagnetic conductive layer and has a fixed direction of magnetization; and an antiferromagnetic layer that is located adjacent to one of surfaces of the pinned layer that is farther from the nonmagnetic conductive layer and fixes the direction of magnetization of the pinned layer. The free layer and the pinned layer are each made of a ferromagnetic layer. An electric resistance value of the free layer varies according to the direction of magnetization of the free layer. The spin-valve GMR element utilizes the variations in the electric resistance value of the free layer to reproduce data that is magnetically recorded on the recording medium.

Another characteristic required of reproducing heads is a small Barkhausen noise. Barkhausen noise results from transition of a domain wall of a magnetic domain of an MR element. If Barkhausen noise occurs, an abrupt variation in output results, which induces a reduction in signal-to-noise ratio (S/N ratio) and an increase in error rate.

To reduce Barkhausen noise, a bias magnetic field in the longitudinal direction (that may be hereinafter called a longitudinal bias field) is applied to the MR element. To apply the longitudinal bias field to the MR element, bias field applying layers may be provided on both sides of the MR element, for example. Each of the bias field applying layers is made of a laminate of a ferromagnetic layer and an antiferromagnetic layer, or a permanent magnet, for example.

In a reproducing head in which bias field applying layers are provided on both sides of the MR element, in general, a pair of electrode layers for feeding a current used for signal detection (hereinafter called a sense current) to the MR element are located to touch the bias field applying layers.

In general, the MR element is sandwiched between a bottom shield layer and a top shield layer. A bottom shield gap film that is an insulating film is interposed between the MR element and the bottom shield layer. Similarly, a top shield gap film that is an insulating film is interposed between the MR element and the top shield layer. A base layer may be provided between the MR element and the bottom shield gap film for the purpose of attaining better orientation and magnetic properties of magnetic layers that constitute the MR element. For example, a Ta or Cr compound may be used as a material of the base layer. Between the MR element and the top shield gap film, a protection layer may be formed after forming films making up the MR element, for the purpose of protecting those films. The protection layer may be made of Ta, for example.

Reference is now made toFIG. 25throughFIG. 28to describe an example of a method of manufacturing a reproducing head. In this manufacturing method, as shown inFIG. 25, a bottom shield gap film104made of alumina (Al2O3), for example, is first formed on a bottom shield layer103made of NiFe, for example. A base layer105is formed on the bottom shield gap film104. Then, an MR-element-to-be film106P to make the MR element is formed on the base layer105. A protection layer107is then formed on the MR-element-to-be film106P. Then, a mask108for patterning the MR-element-to-be film106P by etching is formed on the protection layer107. The mask108is made of a photoresist layer patterned by photolithography. For easy lift-off, the mask108is formed to have a T-shaped cross section, i.e., such a shape that a portion close to the bottom is smaller in width than a portion close to the top.

Next, as shown inFIG. 26, ion beam etching is performed so that ion beams travel at an angle of 5 to 10° with respect to the direction perpendicular to the top surface of the bottom shield layer103, thereby partially etching the protection layer107, the MR-element-to-be film106P, and the base layer105. The protection layer107, the MR-element-to-be film106P, and the base layer105are thus patterned. The MR-element-to-be film106P makes an MR element106as a result of the patterning.

Next, as shown inFIG. 27, a hard magnetic layer109P for making bias field applying layers is formed by sputtering on the entire top surface of the laminate obtained by the steps so far, with the mask108left unremoved. The hard magnetic layer109P is made of CoPt, for example. The mask108is then lifted off. Portions of the hard magnetic layer109P remaining after the liftoff make a pair of bias field applying layers109.

Next, as shown inFIG. 28, a pair of electrode layers110are formed on the pair of bias field applying layers109. The electrode layers110are made of a laminate of Au and Ta films, for example. A top shield gap film111made of alumina, for example, is then formed on the entire top surface of the laminate. Then, although not shown, a top shield layer is formed on the entire top surface of the laminate.

As disclosed in, e.g., Published Unexamined Japanese Patent Applications (KOKAI) Heisei 11-224411 and 2000-76629, it is known that, when the bias field applying layers are provided on both sides of the MR element, regions that may be hereinafter called lower-sensitivity regions develop near ends of the MR element that are adjacent to the bias field applying layers. In these regions, the magnetic field produced from the bias field applying layers limits variations of the direction of magnetization, and the sensitivity is thereby lowered. Consequently, if the electrode layers are located so as not to overlap the MR element, a sense current passes through the lower-sensitivity regions and the output of the reproducing head is thereby lowered. This problem becomes more noticeable as the track width of the reproducing head becomes smaller.

To solve this problem, each of the electrode layers is located such that a portion thereof is laid over part of (hereinafter expressed as “overlap”) the MR element, as disclosed in, e.g., Published Unexamined Japanese Patent Applications (KOKAI) Heisei 11-224411 and 2000-76629. It is possible to reduce Barkhausen noise while preventing a reduction in output of the reproducing head, if the reproducing head has a structure (hereinafter called an overlapping electrode layer structure) in which the bias field applying layers are located on both sides of the MR element, and the electrode layers overlap the MR element, as described above.

Reference is now made toFIG. 29throughFIG. 31to describe an example of a method of manufacturing a reproducing head having the overlapping electrode layer structure. This manufacturing method has the same steps as those described with reference toFIG. 25throughFIG. 27up to the step of forming the bias field applying layers109.

Then, in this manufacturing method, as shown inFIG. 29, a mask112for forming the electrode layers by a lift-off method is formed on the protection layer107after the mask108is lifted off. The mask112is made of a photoresist layer patterned by photolithography. The mask112has a width smaller than that of the mask108shown inFIG. 25throughFIG. 27. For easy lift-off, the mask112is formed to have a T-shaped cross section.

Next, as shown inFIG. 30, an electrode-to-be film113P to make the electrode layers is formed by sputtering on the entire top surface of the laminate. The electrode-to-be film113P is made of a laminate of Au and Ta films, for example.

Next, as shown inFIG. 31, the mask112is lifted off. Portions of the electrode-to-be film113P remaining after the liftoff make a pair of electrode layers113. The electrode layers113are located to overlap the MR element106. Then, although not shown, a top shield gap film and a top shield layer are formed in this order on the entire top surface of the laminate. In the reproducing head thus fabricated, the space between the pair of electrode layers113defines the optical track width of the reproducing head.

The method of manufacturing the reproducing head shown inFIG. 29throughFIG. 31requires two masks, that is, the mask108for defining the width of the MR element106and the space between the pair of bias field applying layers109, and the mask112for defining the space between the pair of electrode layers113. In typical reproducing heads of the overlapping electrode layer structure, the electrode layers113are formed to overlap the MR element106by a width of, e.g., 0.1 to 0.2 μm each from the end of each of the bias field applying layers109toward the center of the MR element106along the width thereof. The two electrode layers113are controlled to have the same overlap amount. Hence, alignment of the masks108and112is of extreme importance.

According to the method of manufacturing the reproducing head shown inFIG. 29throughFIG. 31, however, the MR element106and the bias field applying layers109are patterned by using the mask108while the electrode layers113are patterned by using the mask112. Hence, it is extremely difficult for this manufacturing method to locate the two electrode layers113in position as designed. As a result, this manufacturing method presents problems that the actual track width may deviate from a designed value, and that the overlap amount of at least one of the electrode layers113may fall below a designed value and the effect of the overlapping electrode layer structure against a drop in output of reproducing heads is thereby hampered.

To solve the foregoing problems, a method of manufacturing a reproducing head as described below is employable. In this manufacturing method, a single mask is used to pattern the MR element, the bias field applying layers and the electrode layers in a self-aligned manner. This manufacturing method will be described with reference toFIG. 32throughFIG. 34. This manufacturing method includes the same steps as those described with reference toFIG. 25up to the step of forming the protection layer107.

Then, in this manufacturing method, as shown inFIG. 32, a mask114for patterning the MR element, the bias field applying layers and the electrode layers is formed on the protection layer107. The mask114is made of a photoresist layer patterned by photolithography. For easy lift-off, the mask114is formed to have a T-shaped cross section. Hereinafter, a portion of the mask114that is closer to the bottom and smaller in width will be referred to as a root portion.

Then, ion beam etching is performed so that ion beams travel at an angle of 5 to 10° with respect to the direction perpendicular to the top surface of the bottom shield layer103, thereby partially etching the protection layer107, the MR-element-to-be film106P, and the base layer105. The protection layer107, the MR-element-to-be film106P, and the base layer105are thus patterned. The MR-element-to-be film106P makes the MR element106as a result of the patterning.

Next, ion beam deposition is performed so that ion beams travel at an angle of 0 to 5° with respect to the direction perpendicular to the top surface of the bottom shield layer103. The hard magnetic layer109P to make the bias field applying layers is thereby formed on the entire top surface of the laminate. The hard magnetic layer109P is made of CoPt, for example. InFIG. 32, the arrows represent ion beams.

Then, as shown inFIG. 33, ion beam deposition is performed so that ion beams travel at an angle of 45° with respect to the direction perpendicular to the top surface of the bottom shield layer103, with the mask114left unremoved. The electrode-to-be film113P to make the electrode layers is thereby formed on the entire top surface of the laminate. The electrode-to-be film113P is made of Au, for example. On the protection layer107, the electrode-to-be film113P is formed to extend to the vicinity of the root portion of the mask114. InFIG. 33, the arrows represent ion beams.

Next, as shown inFIG. 34, the mask114is lifted off. As a result, the remaining portions of the hard magnetic layer109P make a pair of bias field applying layers109, and the remaining portions of the electrode-to-be film113P make a pair of electrode layers113. Next, a top shield gap film115made of alumina, for example, is formed on the entire top surface of the laminate. Next, although not shown, a top shield layer is formed on the entire top surface of the laminate.

The manufacturing method shown inFIG. 32throughFIG. 34can solve the problems of the manufacturing method shown inFIG. 29throughFIG. 31. The method ofFIG. 32throughFIG. 34, however, has the following two problems.

A first problem will be described with reference toFIG. 35.FIG. 35is a cross section illustrating the reproducing head manufactured by the method shown inFIG. 32throughFIG. 34in detail. According to the manufacturing method ofFIG. 32throughFIG. 34, a region on top of the protection layer107near the root portion of the mask114is less exposed to ion beams during the ion beam deposition shown inFIG. 33. Accordingly, as shown inFIG. 35, portions of the electrode layers113located on the protection layer107become thinner than the other portions thereof.

In addition, in the manufacturing method shown inFIG. 32throughFIG. 34, after the protection layer107is formed, the laminate is exposed to air in order to form the mask114on the protection layer107. As a result, an upper part of the protection layer107is oxidized to form an oxide layer117. If the protection layer107is made of Ta, the oxide layer117is of TaO2.

For these reasons, the reproducing head manufactured by the method shown inFIG. 32throughFIG. 34has greater ohmic resistances between the electrode layers113and the MR element106near the portions of the electrode layers113located on the protection layer107. As a result, this reproducing head has the problem that less current flows between the MR element106and the portions of the electrode layers133located on the protection layer107, and the effect of the overlapping electrode layer structure against a drop in output of reproducing heads is thereby hampered.

To solve the above-mentioned problem, it is conceivable to remove the oxide layer117near the root portion of the mask114by dry etching before the electrode-to-be film113P is formed. To do so, for easy removal of the oxide layer117, it is preferable that the root portion of the mask114having a T-shaped cross section be made greater in height. However, this causes the following problem in turn.

The problem will be described with reference toFIGS. 36 and 37.FIG. 36is a cross section illustrating in detail a laminate after the electrode-to-be film113P is formed by the step shown inFIG. 33. As shown inFIG. 36, the ion beam deposition forms the electrode-to-be film113P even on the side surfaces of the root portion of the mask114. Hereinafter, the portions of the electrode-to-be film113P that are formed on the side surfaces of the root portion of the mask114will be referred to as sidewall portions118.

As shown inFIG. 37, after the mask114is lifted off, the sidewall portions118, which are electrically conductive, remain on the protection layer107. The sidewall portions118can come into contact with the top shield layer to cause a short between the top shield layer and the MR element106.

OBJECT AND SUMMARY OF THE INVENTION

It is an object of the invention to provide a magnetoresistive device, a thin-film magnetic head, and methods of manufacturing the same which make it possible to precisely define even a small track width for reading, and to improve sensitivity, output, and output stability.

A magnetoresistive device of the invention comprises:

a magnetoresistive element having two surfaces that face toward opposite directions and two side portions;

a pair of bias field applying layers that are adjacent to the side portions of the magnetoresistive element and apply a bias magnetic field to the magnetoresistive element; and

a pair of electrode layers that feed a current used for signal detection to the magnetoresistive element, each of the electrode layers being adjacent to one of surfaces of each of the bias field applying layers and overlapping one of the surfaces of the magnetoresistive element.

A thin-film magnetic head of the invention comprises:

a medium facing surface that faces toward a recording medium;

a magnetoresistive element located near the medium-facing surface and having two surfaces that face toward opposite directions and two side portions;

a pair of bias field applying layers that are adjacent to the side portions of the magnetoresistive element and apply a bias magnetic field to the magnetoresistive element; and

a pair of electrode layers that feed a current used for signal detection to the magnetoresistive element, each of the electrode layers being adjacent to one of surfaces of each of the bias field applying layers and overlapping one of the surfaces of the magnetoresistive element.

In the magnetoresistive device or the thin-film magnetic head of the invention, each of the electrode layers includes: a first layer laid over part of the one of the surfaces of the magnetoresistive element; and a second layer overlapping the first layer and electrically connected to the first layer.

According to the magnetoresistive device or the thin-film magnetic head of the invention, to form the electrode layers, an electrode-to-be film that is to be the first layers of the electrode layers is formed on the magnetoresistive element; the second layers are then formed on the electrode-to-be film; and then the electrode-to-be film is patterned by etching using the second layers as masks, to thereby make the first layers.

The magnetoresistive device or the thin-film magnetic head of the invention may further comprise a protection layer for protecting the magnetoresistive element, the protection layer being located between the one of the surfaces of the magnetoresistive element and the first layers.

A magnetoresistive device manufactured by a method of manufacturing a magnetoresistive device of the invention comprises:

a magnetoresistive element having two surfaces that face toward opposite directions and two side portions;

a pair of bias field applying layers that are adjacent to the side portions of the magnetoresistive element and apply a bias magnetic field to the magnetoresistive element;

a pair of electrode layers that feed a current used for signal detection to the magnetoresistive element, each of the electrode layers being adjacent to one of surfaces of each of the bias field applying layers and overlapping one of the surfaces of the magnetoresistive element; and

a protection layer for protecting the magnetoresistive element, the protection layer being located between the one of the surfaces of the magnetoresistive element and the electrode layers,

wherein each of the electrode layers includes: a first layer laid over part of the one of the surfaces of the magnetoresistive element via the protection layer; and a second layer electrically connected to the first layer.

A thin-film magnetic head manufactured by a method of manufacturing a thin-film magnetic head of the invention comprises:

a medium facing surface that faces toward a recording medium;

a magnetoresistive element located near the medium-facing surface and having two surfaces that face toward opposite directions and two side portions;

a pair of bias field applying layers that are adjacent to the side portions of the magnetoresistive element and apply a bias magnetic field to the magnetoresistive element;

a pair of electrode layers that feed a current used for signal detection to the magnetoresistive element, each of the electrode layers being adjacent to one of surfaces of each of the bias field applying layers and overlapping one of the surfaces of the magnetoresistive element; and

a protection layer for protecting the magnetoresistive element, the protection layer being located between the one of the surfaces of the magnetoresistive element and the electrode layers,

wherein each of the electrode layers includes: a first layer laid over part of the one of the surfaces of the magnetoresistive element via the protection layer; and a second layer electrically connected to the first layer.

The method of manufacturing the magnetoresistive device or the method of manufacturing the thin-film magnetic head of the invention comprises the steps of:

forming an element-to-be film that is to be the magnetoresistive element;

forming the protection layer on the element-to-be film;

forming a first electrode-to-be film that is to be the first layers of the electrode layers on the protection layer;

forming the bias field applying layers; and

forming the second layers of the electrode layers after the step of forming the bias field applying layers, wherein:

in the step of forming the first electrode-to-be film, the first electrode-to-be film is formed continuously after the step of forming the protection layer, without interposing a step of exposing the protection layer to the air.

The method of manufacturing the magnetoresistive device or the method of manufacturing the thin-film magnetic head of the invention may further comprise, after the step of forming the first electrode-to-be film, the steps of: forming a mask on the first electrode-to-be film, for patterning the first electrode-to-be film, the protection layer, and the element-to-be film by etching; and patterning the first electrode-to-be film, the protection layer, and the element-to-be film by etching using the mask. In this case, the bias field applying layers may be formed with the mask left unremoved in the step of forming the bias field applying layers. In addition, the second layers may be formed with the mask left unremoved in the step of forming the second layers.

In the method of manufacturing the magnetoresistive device or the method of manufacturing the thin-film magnetic head of the invention, the second layers may be formed to overlap the first layers. In this case, the method of manufacturing the magnetoresistive device or the method of manufacturing the thin-film magnetic head of the invention may further comprise the step of patterning the first electrode-to-be film by etching using the second layers as masks, in order to make the first layers. Alternatively, the method of manufacturing the magnetoresistive device or the method of manufacturing the thin-film magnetic head of the invention may further comprise the step of forming a coating layer to cover the second layers, and the step of patterning the first electrode-to-be film by etching using the coating layer as a mask, in order to make the first layers.

The method of manufacturing the magnetoresistive device or the method of manufacturing the thin-film magnetic head of the invention may further comprise the step of selectively removing portions of the bias field applying layers located on the first electrode-to-be film, between the step of forming the bias field applying layers and the step of forming the second layers.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Embodiments of the invention will now be described in detail with reference to the accompanying drawings.

Reference is now made toFIGS. 1 and 2to describe a thin-film magnetic head and a method of manufacturing the same of a first embodiment of the invention.FIG. 1is a cross section of the magnetic pole portion of the thin-film magnetic head parallel to the air bearing surface.FIG. 2is a cross section of the thin-film magnetic head orthogonal to the air bearing surface and the top surface of the substrate.

In the method of manufacturing the thin-film magnetic head of the embodiment, first, an insulating layer2made of alumina (Al2O3), for example, is formed on a substrate1made of aluminum oxide and titanium carbide (Al2O3—TiC), for example. Next, a bottom shield layer3of a magnetic material such as Permalloy (NiFe) is formed on the insulating layer2. The bottom shield layer3is selectively formed on the insulating layer2by plating using a photoresist film as a mask, for example. Then, although not shown, an insulating layer of alumina, for example, is formed on the entire top surface of the laminate obtained through the steps so far. The insulating layer is then polished by chemical mechanical polishing (hereinafter referred to as CMP), for example, to expose the bottom shield layer3, and the surface is thereby flattened. Then, a bottom shield gap film4serving as an insulating film is formed on the bottom shield layer3.

On the bottom shield gap film4, formed are an MR element5for magnetic signal detection, a pair of bias field applying layers6for applying a longitudinal bias field to the MR element5, and a pair of electrode layers7to be electrically connected to the MR element5. The MR element5is located near a region where to form an air bearing surface30to be described later. The MR element5has two surfaces that face toward opposite directions, and two side portions. The bias field applying layers6are located to be adjacent to the side portions of MR element5, over the bottom shield gap film4.

The electrode layers7feed a current used for signal detection (sense current) to the MR element5. The electrode layers7are each located to be adjacent to one of surfaces (top surface) of each of the bias field applying layers6and to overlap one of the surfaces (top surface) of the MR element5. Each of the electrode layers7includes: a first layer7alaid over part of the one of the surfaces of the MR element5; and a second layer7boverlapping the first layer7a. The second layers7bare electrically connected to the first layers7a. The first and second layers7aand7bare each made of a conductive material. The first and second layers7aand7bmay be made of the same material or of different materials. A method of forming the MR element5, the bias field applying layers6and the electrode layers7will be detailed later.

Next, a top shield gap film8serving as an insulating film is formed on the entire top surface of the laminate. A top shield layer9of a magnetic material is then selectively formed on the top shield gap film8. Then, although not shown, an insulating layer made of alumina, for example, is formed on the entire top surface of the laminate. The insulating layer is polished by CMP, for example, to expose the top shield layer9, and the surface is thereby flattened.

Next, an insulating layer10made of alumina, for example, is formed on the entire top surface of the laminate. On the insulating layer10, a first layer11aof a bottom pole layer11is formed. On the first layer11a, a second layer11band a third layer11cof the bottom pole layer11are formed. The first, second, and third layers11a,11b,11care each made of a magnetic material. The second layer11bforms the magnetic pole portion of the bottom pole layer11, and is connected to a surface of the first layer11a(the surface on the upper side inFIG. 2) that is closer to a recording gap layer to be described later. The third layer11cserves as a portion for connecting the first layer11aand a top pole layer to be described later to each other, and is located near the center of a thin-film coil to be described later. The second layer11bhas a portion opposed to the top pole layer, and the end of this portion farther from the air bearing surface30defines a throat height. The throat height is the length (height) of the magnetic pole portions, that is, the portions of the two pole layers opposed to each other with the recording gap layer in between, as taken from the end closer to the air bearing surface30to the other end.

Next, an insulating film12made of alumina, for example, is formed on the entire top surface of the laminate. A thin-film coil13made of copper (Cu), for example, is then formed on a portion of the insulating film12located on the first layer11a. The thin-film coil13is formed by frame plating, for example. InFIG. 2, the reference numeral13arepresents a connecting portion for connecting the thin-film coil13to a lead to be described later.

Next, an insulating layer14made of alumina, for example, is formed on the entire top surface of the laminate. The insulating layer14is polished by CMP, for example, so that the second and third layers11band11cof the bottom pole layer11are exposed, and the surfaces are thereby flattened.

Next, the recording gap layer15of an insulating material such as alumina is formed to cover the entire top surface of the laminate. Then, etching is performed to selectively remove portions of the recording gap layer15located on the third layer11cof the bottom pole layer11and on the connecting portion13aof the thin-film coil13, and to remove a portion of the insulating layer14located on the connecting portion13a. Contact holes are thereby formed over the third layer11cand the connecting portion13a.

Then, a top pole layer16patterned into a predetermined shape and a lead17are formed on the recording gap layer15. They are each made of a magnetic material. The top pole layer16is connected to the third layer11cthrough the contact hole located over the third layer11c. The lead17is connected to the connecting portion13athrough the contact hole located over the connecting portion13a.

The top pole layer16includes: a track width defining portion having one end located at the air bearing surface30and the other end located away from the air bearing surface30; and a yoke portion coupled to the other end of the track width defining portion. The yoke portion has a width equal to that of the track width defining portion at the interface with the track width defining portion. The width of the yoke portion gradually increases from this interface with an increase in distance from the track width defining portion, and finally becomes constant. The track width defining portion is the magnetic pole portion of the top pole layer16.

Next, the recording gap layer15is etched by using the top pole layer16as a mask. Then, using the track width defining portion of the top pole layer16as a mask, the second layer11bof the bottom pole layer11is partially etched around the track width defining portion. The etching forms a trim structure as shown inFIG. 1, in which sidewalls of the magnetic pole portion of the top pole layer16, the recording gap layer15and part of the bottom pole layer11are formed vertically in a self-aligned manner. The trim structure suppresses an increase in the effective track width due to expansion of a magnetic flux generated during writing in a narrow track. A portion of the second layer11bthat is opposed to the track width defining portion of the top pole layer16with the recording gap layer15in between is the magnetic pole portion of the bottom pole layer11.

Next, an overcoat layer18made of alumina, for example, is formed to cover the entire top surface of the laminate. Its surface is flattened, and electrode pads that are not shown are formed thereon. Finally, lapping of the slider including the foregoing layers is performed to form the air bearing surface30, thereby completing the thin-film magnetic head.

The thin-film magnetic head of this embodiment fabricated as described above comprises the air bearing surface30serving as a medium facing surface that faces toward a recording medium, a reproducing head (magnetoresistive device), and a recording head (induction-type electromagnetic transducer). The reproducing head incorporates: the MR element5located near the air bearing surface30; the bottom shield layer3and the top shield layer9for shielding the MR element5, portions of the bottom and top shield layers3and9located on a side of the air bearing surface30being opposed to each other with the MR element5in between; the bottom shield gap film4located between the MR element5and the bottom shield layer3; and the top shield gap film8located between the MR element5and the top shield layer9. The reproducing head further incorporates: a pair of bias field applying layers6located to be adjacent to the side portions of the MR element5; and a pair of electrode layers7that are located on the bias field applying layers6and over the bottom shield gap film4, and overlap the MR element5. The reproducing head functions as the magnetoresistive device according to the embodiment, too.

The recording head incorporates: the bottom pole layer11and the top pole layer16magnetically coupled to each other and including the magnetic pole portions that are opposed to each other and located in regions of the pole layers on a side of the air bearing surface30; the recording gap layer15provided between the magnetic pole portions of the bottom and top pole layers11and16; and the thin-film coil13at least part of which is located between the bottom and top pole layers11and16and insulated from the bottom and top pole layers11and16.

Reference is now made toFIG. 3to describe the configuration of the MR element5in this embodiment. InFIG. 3, the arrows indicate the directions of magnetization by way of example. The MR element5is located on a base layer20that is formed on the bottom shield gap film4. The MR element5includes an antiferromagnetic layer21, a pinned layer22, a nonmagnetic conductive layer23, and a free layer24that are laminated in this order on the base layer20. The free layer24is covered with a protection layer25. On the protection layer25, part of the electrode layers7and the top shield gap film8are to be placed.

The base layer20is provided for the purpose of attaining better orientation and magnetic properties of the antiferromagnetic layer21. The base layer20may be made of a Ta or Cr compound, for example. The base layer20has a thickness of 3 nm, for example.

The antiferromagnetic layer21fixes the direction of magnetization of the pinned layer22. The antiferromagnetic layer21is made of PtMn, for example. The antiferromagnetic layer21has a thickness of 25 nm, for example.

The pinned layer22is a layer whose direction of magnetization is fixed. The pinned layer22of the embodiment includes: a nonmagnetic spacer layer22b; and two ferromagnetic layers22aand22cthat sandwich the nonmagnetic spacer layer22b. The pinned layer22is fabricated by stacking the ferromagnetic layer22a, the nonmagnetic spacer layer22band the ferromagnetic layer22cin this order on the antiferromagnetic layer21. The two ferromagnetic layers22aand22care antiferromagnetic-coupled to each other and exhibit magnetizations whose directions are fixed in opposite directions. The ferromagnetic layers22aand22care each made of CoFe, for example. The nonmagnetic spacer layer22bis made of Ru, for example. The ferromagnetic layer22ahas a thickness of 2 nm, for example. The nonmagnetic spacer layer22bhas a thickness of 0.8 nm, for example. The ferromagnetic layer22chas a thickness of 2.5 nm, for example.

The nonmagnetic conductive layer23is made of Cu, for example. The nonmagnetic conductive layer23has a thickness of 2 nm, for example.

The free layer24is a layer in which the direction of magnetization varies in response to the signal magnetic field supplied from the recording medium. The free layer24is made of NiFe or CoFe, for example. The free layer24has a thickness of 2 to 3 nm, for example.

The protection layer25protects the films constituting the MR element5after the formation of these films. Thus, the protection layer25protects the MR element5. The protection layer25is made of Ta, for example. The protection layer25has a thickness of 5 nm, for example.

Thus, the MR element5includes: the nonmagnetic conductive layer23having two surfaces that face toward opposite directions; the free layer24adjacent to one of the surfaces (top surface) of the nonmagnetic conductive layer23; the pinned layer22, located adjacent to the other one of the surfaces (bottom surface) of the nonmagnetic conductive layer23, whose direction of magnetization is fixed; and the antiferromagnetic layer21that is adjacent to one of the surfaces of the pinned layer22farther from the nonmagnetic conductive layer23and fixes the direction of magnetization of the pinned layer22.

Reference is now made toFIG. 4throughFIG. 10to describe in detail the configuration of the reproducing head of this embodiment, that is, the magnetoresistive device of this embodiment, and the method of manufacturing the same.FIG. 4throughFIG. 10are cross sections for illustrating the method of manufacturing the magnetoresistive device of the embodiment.

In the method of manufacturing the magnetoresistive device of the embodiment, first, as shown inFIG. 4, the base layer20is formed on the bottom shield gap film4. Next, an MR-element-to-be film5P to make the MR element5is formed on the base layer20. The protection layer25is then formed on the MR-element-to-be film5P. The MR-element-to-be film5P is made up of a plurality of layers whose arrangement, materials, and thicknesses are the same as those of the layers making up the MR element5described with reference toFIG. 3. The materials and thicknesses of the base layer20and the protection layer25are also the same as those of the base layer20and the protection layer25described with reference toFIG. 3.

Next, a first electrode-to-be film31to make the first layers7aof the electrode layers7is formed on the protection layer25. The electrode-to-be film31is made of Au, for example. The electrode-to-be film31has a thickness of 30 nm, for example.

The base layer20, the MR-element-to-be film5P, the protection layer25, and the electrode-to-be film31are formed continuously in a vacuum by means of, e.g., sputtering, without interposing a step for atmospheric exposure.

Next, as shown inFIG. 5, a mask32for patterning the electrode-to-be film31, the protection layer25, the MR-element-to-be film5P and the base layer20by etching is formed on the electrode-to-be film31. The mask32is made of a photoresist layer patterned by photolithography. For easy lift-off, the mask32is formed to have a T-shaped cross section, i.e., such a shape that a portion close to the bottom is smaller in width than a portion close to the top. The mask32has a height of 600 nm, for example.

Next, as shown inFIG. 6, ion beam etching is performed so that ion beams travel at an angle of 10° with respect to the direction perpendicular to the top surface of the bottom shield layer3, thereby partially etching the electrode-to-be film31, the protection layer25, the MR-element-to-be film5P, and the base layer20. The electrode-to-be film31, the protection layer25, the MR-element-to-be film5P, and the base layer20are thus patterned. The MR-element-to-be film5P makes the MR element5as a result of the patterning.

Next, ion beam deposition is performed with the mask32left unremoved, so that ion beams travel at an angle of 0 to 5° with respect to the direction perpendicular to the top surface of the bottom shield layer3. A hard magnetic layer6P for forming the bias field applying layers6is thereby formed on the entire top surface of the laminate. The hard magnetic layer6P is made of CoPt, for example. The hard magnetic layer6P has a thickness of 30 to 50 nm, for example. InFIG. 6, the arrows represent ion beams.

Next, as shown inFIG. 7, ion beam deposition is performed with the mask32left unremoved, so that ion beams travel aslant with respect to the direction perpendicular to the top surface of the bottom shield layer3. A second electrode-to-be film33to make the second layers7bof the electrode layers7is thereby formed on the entire top surface of the laminate. The traveling direction of the ion beams forms an angle of, e.g., 40° to 75°, with respect to the direction perpendicular to the top surface of the bottom shield layer3. The ion beams may be allowed to sweep so that the angle formed between the traveling direction of the ion beams and the direction perpendicular to the top surface of the bottom shield layer3changes within a range of 10° to 75°, for example. The electrode-to-be film33is made of Au, for example. The electrode-to-be film33has a thickness of 50 to 80 nm, for example. The electrode-to-be film33is formed to cover the hard magnetic layer6P and to overlap the electrode-to-be film31. InFIG. 7, the arrows represent ion beams.

Next, as shown inFIG. 8, the mask32is lifted off. As a result, the remaining portions of the hard magnetic layer6P make a pair of bias field applying layers6, and the remaining portions of the electrode-to-be film33make a pair of second layers7b. Portions of the pair of second layers7blocated on the electrode-to-be film31are separated from each other with a predetermined space interposed therebetween.

Next, as shown inFIG. 9, the electrode-to-be film31is partially etched by dry etching with the second layers7bas masks. As a result, portions of the electrode-to-be film31remaining under the second layers7bmake a pair of first layers7a. The space between the pair of first layers7adefines the optical track width of the reproducing head. The etching of the electrode-to-be film31may be ion beam etching, sputter etching, reactive sputter etching, reactive ion etching, or plasma etching. The sputter etching may be of various types such as a direct current (DC) magnetron type and a radio frequency (RF) type. The etching of the electrode-to-be film31is performed in such gas as Ar, He, and Kr. Here, by way of example, sputter etching using argon gas ions shall be performed in a parallel plate sputter etching system to etch the electrode-to-be film31. As shown inFIG. 9, the etching of the electrode-to-be film31may be performed so that the space between one of the side portions of one of the first layers7aand one of the side portions of the other of the first layers7a, the ones of the side portions being opposed to each other, increases with increasing proximity to the top of the first layers7a. InFIG. 9, the arrows represent the traveling direction of ion beams in the etching.

Next, as shown inFIG. 10, the top shield gap film8is formed on the entire top surface of the laminate. The top shield layer9is then formed on the entire top surface of the laminate. The top shield gap film8has a thickness of 30 nm, for example. The top shield layer9has a thickness of 1.8 μm, for example.

As has been described, according to the magnetoresistive device and the thin-film magnetic head, and the methods of manufacturing the same according to the embodiment, the pair of bias field applying layers6are provided to be adjacent to the side portions of the MR element5, and the pair of electrode layers7are provided to overlap the top surface of the MR element5. According to the embodiment, it is thereby possible to reduce Barkhausen noise while preventing a reduction in output of the magnetoresistive device (reproducing head). The magnetoresistive device (reproducing head) can thus be improved in sensitivity, output, and output stability.

In this embodiment, the electrode layers7include: the first layers7aeach being laid over part of the one of the surfaces (top surface) of the MR element5via the protection layer25; and the second layers7boverlapping the first layers7aand electrically connected to the first layers7a. By making the electrode layers7to have the above-mentioned structure, it becomes possible to form the protection layer25and the electrode-to-be film31continuously and to pattern the MR elements5, the bias field applying layers6, and the electrode layers7in a self-aligned manner by using a single mask32.

Specifically, in the embodiment, the protection layer25and the electrode-to-be film31are continuously formed in a vacuum without interposing a step of exposing the protection layer25to the air. Thereafter, in the embodiment, the single mask32is used to pattern the MR element5and to form the bias field applying layers6and the second layers7bof the electrode layers7. Furthermore, in the embodiment, the electrode-to-be film31is partially etched by using the second layers7bas masks, so that portions of the electrode-to-be film31remaining under the second layers7bafter the etching make the first layers7aof the electrode layers7. Thus, according to the embodiment, it is possible to prevent an increase in ohmic resistance between the electrode layers7and the MR element5that would be caused by oxidation of the protection layer25. As a result, it is possible to prevent the advantageous effects of the overlapping electrode layer structure from being hampered.

According to the embodiment, the MR element5, the bias field applying layers6, and the electrode layers7are patterned in a self-aligned manner by using the single mask32. Thus, according to the embodiment, it is possible to precisely locate the electrode layers7at positions as designed. Consequently, the embodiment makes it possible to precisely define the track width, even if it is small, of the reproducing head for reading, and to prevent the advantageous effects of the overlapping electrode layer structure from being hampered.

In the embodiment, it is not necessary to remove the oxide layer on the protection layer before the formation of the electrode layers7. Therefore, the root portion of the mask32need not be rendered greater in height than necessary. Consequently, according to the embodiment, it is possible to avoid the problem that would arise in the case where the root portion of the mask32has a greater height, i.e., the problem that a short between the top shield layer and the MR element can be caused by the conductive sidewall portions.

Reference is now made toFIG. 11throughFIG. 14to describe a magnetoresistive device, a thin-film magnetic head, and methods of manufacturing the same according to a second embodiment of the invention.FIG. 11throughFIG. 14are cross sections for illustrating the method of manufacturing the magnetoresistive device of this embodiment.

The method of manufacturing the magnetoresistive device of the embodiment is the same as that of the first embodiment up to the step of forming the hard magnetic layer6P shown inFIG. 6. Then, in the embodiment, as shown inFIG. 11, ion beam deposition is performed with the mask32left unremoved, so that ion beams travel aslant with respect to the direction perpendicular to the top surface of the bottom shield layer3. A second electrode-to-be film33to make the second layers7bof the electrode layers7is thereby formed on the entire top surface of the laminate. The traveling direction of the ion beams forms an angle of, e.g., 40° to 75°, with respect to the direction perpendicular to the top surface of the bottom shield layer3. The ion beams may be allowed to sweep so that the angle formed between the traveling direction of the ion beams and the direction perpendicular to the top surface of the bottom shield layer3changes within a range of 10° to 75°, for example. The electrode-to-be film33is made of Au, for example. The electrode-to-be film33has a thickness of 40 to 60 nm, for example. The electrode-to-be film33is formed to cover the hard magnetic layer6P and to overlap the electrode-to-be film31. InFIG. 11, the arrows represent ion beams.

Next, a coating layer41is formed to cover the electrode-to-be film33. The coating layer41protects the electrode-to-be film33at steps after the formation of the electrode-to-be film33. The coating layer41may be made of a metal material with a high melting point or an insulating material. The metal material with a high melting point may be Ta, Mo, W, Ni, Cr, Ti, TiW, or TaN. The insulating material may be Al2O3, for example. The coating layer41has a thickness of 10 to 60 nm, for example. When a metal material with a high melting point is to be used as the material of the coating layer41, the coating layer41is formed by ion beam deposition, for example. When Al2O3is to be used as the material of the coating layer41, the coating layer41is formed by chemical vapor deposition (CVD), for example.

Next, as shown inFIG. 12, the mask32is lifted off. As a result, the remaining portions of the hard magnetic layer6P make a pair of bias field applying layers6, and the remaining portions of the electrode-to-be film33make a pair of second layers7b. Portions of the pair of second layers7blocated on the electrode-to-be film31are separated from each other with a predetermined space interposed therebetween.

Next, as shown inFIG. 13, the electrode-to-be film31is partially etched by dry etching using the coating layer41as a mask. As a result, portions of the electrode-to-be film31remaining under the second layers7bmake a pair of first layers7a. The space between the pair of first layers7adefines the track width of the reproducing head. The method of etching the electrode-to-be film31is the same as that in the first embodiment. InFIG. 13, the arrows represent the traveling direction of ion beams in the etching.

Next, as shown inFIG. 14, the top shield gap film8and the top shield layer9are formed in this order over the entire top surface of the laminate. Their thicknesses are the same as in the first embodiment.

As has been described, in this embodiment, the coating layer41is formed to cover the electrode-to-be film33that is to be the second layers7bof the electrode layers7. After that, the electrode-to-be film31is partially etched using the coating layer41as a mask, thereby making the first layers7a. Thus, according to the embodiment, the second layers7bare prevented from loosing shape during the etching of the electrode-to-be film31. It is thereby possible to define the track width of the reproducing head with precision.

In the embodiment, electric insulation between the top shield layer9and the electrode layers7is improved if the coating layer41is formed of an insulating material such as Al2O3. This also improves electric insulation between the MR element5and the top shield layer9.

The remainder of configuration, functions and effects of this embodiment are similar to those of the first embodiment.

Reference is now made toFIG. 15throughFIG. 17to describe a magnetoresistive device, a thin-film magnetic head, and methods of manufacturing the same according to a third embodiment of the invention.FIG. 15throughFIG. 17are cross sections for illustrating the method of manufacturing the magnetoresistive device of this embodiment.

The method of manufacturing the magnetoresistive device of this embodiment is the same as that of the first embodiment up to the step of forming the hard magnetic layer6P shown inFIG. 6. Then, in this embodiment, as shown inFIG. 15, ion beam etching is performed so that ion beams travel at an angle of 40 to 75° with respect to the direction perpendicular to the top surface of the bottom shield layer3, thereby selectively removing portions of the hard magnetic layer6P located on the electrode-to-be film31. InFIG. 15, the arrows represent ion beams.

Next, as shown inFIG. 16, the electrode-to-be film33is formed on the entire top surface of the laminate with the mask32left unremoved. The forming method, material, and thickness of this electrode-to-be film33are the same as in the second embodiment. The electrode-to-be film33is formed to cover the hard magnetic layer6P and to overlap the electrode-to-be film31.

Next, the coating layer41is formed to cover the electrode-to-be film33. The material, thickness, and forming method of the coating layer41are the same as in the second embodiment.

Next, the mask32is lifted off. As a result, the remaining portions of the hard magnetic layer6P make a pair of bias field applying layers6, and the remaining portions of the electrode-to-be film33make a pair of second layers7b. Portions of the pair of second layers7blocated on the electrode-to-be film31are separated from each other with a predetermined space interposed therebetween.

Next, as shown inFIG. 17, the electrode-to-be film31is partially etched by dry etching using the coating layer41as a mask, as in the second embodiment. As a result, portions of the electrode-to-be film31remaining under the second layers7bmake a pair of first layers7a. The space between the pair of first layers7adefines the track width of the reproducing head. The method of etching the electrode-to-be film31is the same as in the first embodiment.

Next, the top shield gap film8and the top shield layer9are formed in this order over the entire top surface of the laminate. Their thicknesses are the same as in the first embodiment.

As has been described, in this embodiment, the portions of the hard magnetic layer6P located on the electrode-to-be film31are selectively removed. This can increase the contact areas between the first layers7aand the second layers7bof the electrode layers7, thereby reducing the electric resistances therebetween.

The remainder of configuration, functions and effects of this embodiment are similar to those of the first or second embodiment.

Reference is now made toFIG. 18throughFIG. 24to describe a magnetoresistive device, a thin-film magnetic head, and methods of manufacturing the same according to a fourth embodiment of the invention.FIG. 18throughFIG. 24are cross sections for illustrating the method of manufacturing the magnetoresistive device of this embodiment.

The method of manufacturing the magnetoresistive device of this embodiment is the same as that of the first embodiment up to the step of forming the mask32on the electrode-to-be film31. Then, in this embodiment, as shown inFIG. 18, ion beam etching is performed so that ion beams travel at an angle of 10°, for example, with respect to the direction perpendicular to the top surface of the bottom shield layer3, thereby partially etching the electrode-to-be film31, the protection layer25, and the free layer24of the MR-element-to-be film5P. In this embodiment, at this time, the layers of the MR-element-to-be film5P below the free layer24and the base layer20are not etched. The MR-element-to-be film5P having undergone the etching makes the MR element5. In the MR element5of this embodiment, the two side portions of the free layer24make the two side portions of the MR element5.

Next, as shown inFIG. 19, ion beam deposition is performed so that ion beams travel at an angle of 0 to 5° with respect to the direction perpendicular to the top surface of the bottom shield layer3. The hard magnetic layer6P to make the bias field applying layers6is thereby formed on the entire top surface of the laminate. The material and thickness of the hard magnetic layer6P are the same as in the first embodiment.

Next, as shown inFIG. 20, ion beam etching is performed so that ion beams travel at an angle of 40° to 75°, for example, with respect to the direction perpendicular to the top surface of the bottom shield layer3, thereby selectively removing portions of the hard magnetic layer6P located on the electrode-to-be film31. InFIG. 20, the arrows represent ion beams.

Next, as shown inFIG. 21, the electrode-to-be film33is formed on the entire top surface of the laminate with the mask32left unremoved. The forming method, material, and thickness of this electrode-to-be film33are the same as in the second embodiment. The electrode-to-be film33is formed to cover the hard magnetic layer6P and to overlap the electrode-to-be film31.

Next, the coating layer41is formed to cover the electrode-to-be film33. The material, thickness, and forming method of the coating layer41are the same as in the second embodiment.

Next, as shown inFIG. 22, the mask32is lifted off. As a result, the remaining portions of the hard magnetic layer6P make a pair of bias field applying layers6, and the remaining portions of the electrode-to-be film33make a pair of second layers7b. Portions of the pair of second layers7blocated on the electrode-to-be film31are separated from each other with a predetermined space interposed therebetween.

Next, as shown inFIG. 23, the electrode-to-be film31is partially etched by dry etching using the coating layer41as a mask, as in the second embodiment. As a result, portions of the electrode-to-be film31remaining under the second layers7bmake a pair of first layers7a. The space between the pair of first layers7adefines the track width of the reproducing head. The method of etching the electrode-to-be film31is the same as in the first embodiment.

Next, as shown inFIG. 24, the top shield gap film8and the top shield layer9are formed in this order over the entire top surface of the laminate. Their thicknesses are the same as in the first embodiment.

The remainder of configuration, functions and effects of this embodiment are similar to those of any of the first through third embodiments.

The present invention is not limited to the foregoing embodiments but may be practiced in still other ways. For example, the MR element may be made up of the layers stacked in the order reverse to that of the foregoing embodiments.

In the foregoing embodiments, the thin-film magnetic head is disclosed, comprising the magnetoresistive device for reading formed on the base body and the induction-type electromagnetic transducer for writing stacked on the magnetoresistive device. Alternatively, the magnetoresistive device may be stacked on the electromagnetic transducer.

If the thin-film magnetic head is dedicated to reading, the thin-film magnetic head may comprise the magnetoresistive device for reading only.

The magnetoresistive device of the invention is applicable to not only a reproducing head of a thin-film magnetic head but also to a rotational position sensor, a magnetic sensor, a current sensor, and so on.

As has been described, in the magnetoresistive device or the thin-film magnetic head of the invention, the electrode layers include: the first layers each being laid over part of the one of the surfaces of the magnetoresistive element; and the second layers overlapping the first layers and electrically connected to the first layers. As a result, according to the invention, it is possible to prevent an increase in ohmic resistance between the magnetoresistive element and the electrode layers, and to precisely locate the electrode layers at positions as designed. Therefore, the invention makes it possible to precisely define even a small track width for reading, and to improve sensitivity, output, and output stability in a magnetoresistive device or a thin-film magnetic head.

In the method of manufacturing a magnetoresistive device or the method of manufacturing a thin-film magnetic head of the invention, the electrode layers include: the first layers each being laid over part of the one of the surfaces of the magnetoresistive element via the protection layer; and the second layers electrically connected to the first layers. In the method of manufacturing a magnetoresistive device or the method of manufacturing a thin-film magnetic head of the invention, the first electrode-to-be film that is to be the first layers of the electrode layers is formed continuously after forming the protection layer on the element-to-be film that is to be the magnetoresistive element, without interposing a step of exposing the protection layer to the air. Therefore, according to the invention, it becomes possible to prevent an increase in ohmic resistance between the magnetoresistive element and the electrode layers, and to precisely locate the electrode layers at positions as designed. Consequently, the invention makes it possible to improve sensitivity, output, and output stability of a magnetoresistive device or a thin-film magnetic head.