Magnetic head including a gap-depth defining layer on protruding layer and method for manufacturing the same

A recording thin-film magnetic head includes a gap-depth defining layer, lower magnetic pole layers and gap layers on the front and rear sides of the gap-depth defining layer, and an upper magnetic pole layer. The entire top surface of the gap-depth defining layer is covered with a first seed layer. The rear end surfaces of the lower magnetic pole layer and the gap layer on the front side are in contact with the front end surface of the gap-depth defining layer. The upper magnetic pole layer is formed on the gap layers by plating.

This application claims the benefit of priority to Japanese Patent Application No. 2003-066221, herein incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to recording thin-film magnetic heads for use in, for example, floating magnetic head devices and their manufacturing methods. In particular, the present invention relates to a thin-film magnetic head that can precisely define tracks having a predetermined width, be properly compatible with narrower tracks, have a shorter magnetic path, and prevent flux leakage to improve the recording characteristics, and its manufacturing method.

2. Description of the Related Art

FIG. 28is a longitudinal sectional view of a known thin-film magnetic head, where X indicates a track-width direction; Y indicates a height direction of the magnetic head; and Z indicates a traveling direction of the magnetic head over a magnetic recording medium such as a hard disc. The front surface (the leftmost surface in the drawing) of this magnetic head parallel to plane X-Z faces the recording medium.

InFIG. 28, a lower core layer6, which is made of, for example, Ni—Fe alloy, has a protrusion6aextending upward (in the Z direction in the drawing) along the front surface of the magnetic head. A back gap layer7of a magnetic material is formed on the lower core layer6at the rear of the magnetic head in the height direction (in the Y direction in the drawings). The space between the protrusion6aand the back gap layer7on the lower core layer6includes some portions of a coil layer8of, for example, copper, and is filled with an insulating layer9. The protrusion6a, the insulating layer9, and the back gap layer7have flat top surfaces6b,9a, and7a, respectively.

A gap layer10of, for example, Al2O3is formed on the top surfaces6band9aof the protrusion6aand the insulating layer9. A nonmagnetic layer12is formed on this gap layer10away from the front surface of the magnetic head in the height direction by a predetermined distance. An upper magnetic pole layer11is further formed over the top surfaces of the gap layer10, the nonmagnetic layer12, and the back gap layer7.

Such a thin-film magnetic head is disclosed in, for example, Japanese Unexamined Patent Application Publication No. 2001-319311.

In recent years, smaller thin-film magnetic heads and higher-speed magnetic head devices have been developed with higher recording densities and higher frequency. This trend imposes more severe requirements on thin-film magnetic heads.

In the magnetic head shown inFIG. 28, a seed layer13for plating the upper magnetic pole layer11is substantially separated into a seed layer13aformed on the nonmagnetic layer12and a seed layer13bformed on the protrusion6aof the lower core layer6. These seed layers13aand13bare spaced in the height direction by a distance S.

Smaller magnetic heads demand that the upper magnetic pole layer11have a smaller thickness. Unfortunately, if the seed layer13is substantially separated, such a thin upper magnetic pole layer11cannot be reliably formed on the nonmagnetic layer12.

Smaller magnetic heads have difficulty in connecting an electrode to the seed layer13aon the nonmagnetic layer12during their formation. Therefore, the electrode is connected to the seed layer13bon the protrusion6ato form the upper magnetic pole layer11on the seed layer13bby plating. This upper magnetic pole layer11is allowed to grow until it extends over the nonmagnetic layer12and reaches the seed layer13a.

If the upper magnetic pole layer11reaches the seed layer13a, current can be passed through the seed layer13ato grow the upper magnetic pole layer11entirely over the seed layer13a. However, if the upper magnetic pole layer11has a small thickness, it may fail to reach the seed layer13a. Then, as shown inFIG. 29, the upper magnetic pole layer11cannot be formed over the nonmagnetic layer12, thus producing a magnetic head that cannot perform magnetic recording or, even if possible, that has significantly poor recording characteristics.

As described above, this magnetic head cannot be properly compatible with higher recording densities and higher frequency in future, nor can it improve the recording characteristics.

SUMMARY OF THE INVENTION

Accordingly, embodiments of the present invention is to provide a thin-film magnetic head that can be properly compatible with narrower tracks, have a shorter magnetic path, and improve the recording characteristics.

Embodiments of the present invention also provide an easy method for manufacturing this magnetic head.

The present invention provides a thin-film magnetic head including a lower core layer extending from the front surface of the magnetic head in the height direction of the magnetic head, the front surface facing a recording medium; a protruding layer formed on the lower core layer, extending from the front surface of the magnetic head in the height direction by a predetermined length; a back gap layer formed on the lower core layer away from the rear end surface of the protruding layer in the height direction by a predetermined distance; a coil layer that is at least partially included in a space surrounded by the lower core layer, the protruding layer, and the back gap layer; a coil-insulating layer covering the coil layer; a gap-depth defining layer composed of a nonmagnetic material and disposed on the top surface of the protruding layer away from the front surface of the magnetic head in the height direction by a predetermined distance; a first seed layer composed of a metal, covering the entire top surface of the gap-depth defining layer; a lower magnetic pole layer formed on the protruding layer on the front side of the gap-depth defining layer, the rear end surface of the lower magnetic pole layer being in contact with the front end surface of the gap-depth defining layer; a gap layer formed on the lower magnetic pole layer, the rear end surface of the gap layer being in contact with the front end surface of the gap-depth defining layer; and an upper magnetic pole layer connected to the back gap layer through the top surfaces of the gap layer and the gap-depth defining layer.

This magnetic head has two features. The first feature is that the gap-depth defining layer of a nonmagnetic material is disposed on the top surface of the protruding layer away from the front surface of the magnetic head in the height direction by a predetermined distance; and that the first seed layer of a metal covers the entire top surface of the gap-depth defining layer. The second feature is that the lower magnetic pole layer and the gap layer, in this order, are formed on the protruding layer on the front side of the gap-depth defining layer; that the rear end surfaces of the lower magnetic pole layer and the gap layer are in contact with the front end surface of the gap-depth defining layer; and that the upper magnetic pole layer is connected to the back gap layer through the top surfaces of the gap layer and the gap-depth defining layer.

According to the first feature, the first seed layer, covering the entire top surface of the gap-depth defining layer, allows reliable formation of the upper magnetic pole layer over the gap-depth defining layer, providing a magnetic head having stable recording characteristics.

According to the second feature, the upper magnetic pole layer, which is formed on the gap layer disposed on the lower magnetic pole layer, may be allowed to grow from a level closer to the first seed layer by plating. This ensures that the upper magnetic pole layer reaches the first seed layer to cover the gap-depth defining layer, providing a magnetic head having stable recording characteristics.

The front end surfaces of the gap-depth defining layer and the first seed layer are preferably continuous. Such continuous surfaces allow the upper magnetic pole layer to reach the first seed layer more reliably.

The front end surface of the gap-depth defining layer is preferably perpendicular to the top surface of the protruding layer. Such a perpendicular surface allows precise definition of the gap depth of the magnetic head, provides less side fringing than one curved or not perpendicular to the top surface of the protruding layer, and allows the upper magnetic pole layer to reach the first seed layer more reliably. Side fringing is a phenomenon in which a recording magnetic field occurs outside a predetermined track width.

The total thickness of the gap-depth defining layer and the first seed layer is preferably 0.5 μm or less. Such thicknesses can increase the magnetic flux passing through the upper magnetic pole layer, the lower magnetic pole layer, and the lower core layer.

The nonmagnetic material for the gap-depth defining layer may be selected from the group consisting of SiO2, SiN, Ta2O5, Si3N4, and a resist.

The top surfaces of the protruding layer, the coil-insulating layer, and the back gap layer are preferably flat and continuous.

Such flat top surfaces allow the upper magnetic pole layer, the gap layer, and the upper magnetic pole layer to have a predetermined shape and enable precise definition of a predetermined track width, which is a width of the upper magnetic pole layer at the front surface of the magnetic head. These advantages lead to a thin-film magnetic head properly compatible with higher recording densities.

In addition, the upper magnetic pole layer, the gap layer, and the upper magnetic pole layer can provide a shorter magnetic path because these layers are formed on the flat top surfaces. Therefore, even if the coil layer has a smaller number of turns, the magnetic head can retain its recording characteristics. A smaller number of turns can decrease the coil resistance, thereby preventing heat generation in the magnetic head during operation and, for example, the protrusion of the gap layer from the front surface of the magnetic head.

This magnetic head preferably further includes another lower magnetic pole layer and another gap layer on the coil-insulating layer on the rear side of the gap-depth defining layer.

The lower magnetic pole layer and gap layer on the rear side allow the upper magnetic pole layer to be flat and provide a shorter magnetic path.

In this manufacturing method, the lower magnetic pole layer, the gap layer, and the upper magnetic pole layer may have the same planar shape. Then, the width of the upper magnetic pole layer at the front surface of the magnetic head determines a track width.

The rear end surface of the gap-depth defining layer may be positioned on the protruding layer, the coil-insulating layer, or the back gap layer.

The lower magnetic pole layer, the gap layer, and the upper magnetic pole layer are preferably formed by plating to form the upper magnetic pole layer on the gap layer continuously and to facilitate the connection between the upper magnetic pole layer and the first seed layer.

In addition, plating eliminates the need for trimming the upper magnetic pole layer to achieve narrower tracks.

Preferably, this magnetic head further includes an upper core layer on the upper magnetic pole layer; the upper core layer has the same planar shape as the upper magnetic pole layer; and the upper and lower magnetic pole layers have a higher saturation magnetic flux density than the upper core layer.

This upper core layer can be directly formed on the upper magnetic pole layer in the present invention. The top surface of the upper magnetic pole layer, which is substantially flat, allows precise formation of the upper core layer having a predetermined shape.

In addition, the upper and lower magnetic pole layers, if having a higher saturation magnetic flux density than the upper core layer, can increase the magnetic flux efficiency to improve the recording characteristics.

The upper and lower magnetic pole layers preferably have a higher saturation magnetic flux density than the lower core layer, the protruding layer, and the back gap layer.

The planar shape of the upper magnetic pole layer is preferably composed of a front portion having a width that corresponds to the track width at the front surface of the magnetic head and that remains constant or increases in the height direction; and a rear portion having a width that increases from the side base ends at the rear of the front portion in the height direction. Such an upper magnetic pole layer can concentrate a magnetic flux on the front portion, which functions as a magnetic pole, and can increase the magnetic flux efficiency at the rear portion, which functions as a yoke.

Preferably, this magnetic head further includes a second seed layer of a magnetic material, and the lower magnetic pole layer is formed on the protruding layer with the second seed layer disposed therebetween.

The second seed layer, which is exposed in the front surface of the magnetic head, needs to be made of a magnetic material. The second seed layer, if made of a nonmagnetic metal, acts as a pseudogap.

Preferably, this magnetic head further includes a third seed layer extending from the rear end surface of the gap-depth defining layer onto the back gap layer; the second and third seed layers are separately formed; the gap-depth defining layer is disposed between the second and third seed layers; and another lower magnetic pole layer and another gap layer are formed on the third seed layer. Then, the third seed layer may be made of a nonmagnetic metal.

The coil layer may surround the back gap layer on a plane parallel to the top surface of the lower core layer. Alternatively, the coil layer may helically surround the upper magnetic pole layer or the lower core layer.

The present invention further provides a method for manufacturing a thin-film magnetic head. This method includes the steps of (a) forming a lower core layer extending from the front surface of the magnetic head in the height direction of the magnetic head, the front surface of the magnetic head facing a recording medium; (b) forming a coil-insulating seed layer on the lower core layer; and a coil layer at predetermined areas on the coil-insulating seed layer; (c) forming a protruding layer and a back gap layer on the lower core layer before or after step (b), the protruding layer extending from the front surface of the magnetic head to a position not in contact with the front end surface of the coil layer in the height direction; and the back gap layer being separated from the rear end surface of the protruding layer in the height direction such that the back gap layer is not in contact with the coil layer; (d) covering the coil layer with a coil-insulating layer; (e) forming a nonmagnetic material layer and a first seed layer on the protruding layer, the coil-insulating layer, and the back gap layer; (f) patterning the first seed layer into a predetermined shape such that the first seed layer is separated from the front surface of the magnetic head by a predetermined distance; (g) removing a portion of the nonmagnetic material layer uncovered by the patterned first seed layer to form a gap-depth defining layer; and (h) forming a lower magnetic pole layer on the protruding layer on the front side of the gap-depth defining layer such that the rear end surface of the lower magnetic pole layer is in contact with the front end surface of the gap-depth defining layer; a gap layer on the lower magnetic pole layer such that the rear end surface of the gap layer is in contact with the front end surface of the gap-depth defining layer; and an upper magnetic pole layer connected to the back gap layer through the top surfaces of the gap layer and the gap-depth defining layer.

According to this manufacturing method, the first seed layer, which serves as a mask for processing the nonmagnetic material layer to form the gap-depth defining layer at step (g), can cover the entire top surface of the gap-depth defining layer.

Therefore, at step (h), the upper magnetic pole layer can be readily formed over the first seed layer, providing a magnetic head having stable recording characteristics.

Additionally, at step (h), the upper magnetic pole layer, which is formed on the gap layer disposed on the lower magnetic pole layer, may be allowed to grow from a level closer to the first seed layer by plating. This ensures that the upper magnetic pole layer reaches the first seed layer to cover the gap-depth defining layer, providing a magnetic head having stable recording characteristics.

At step (b), the coil layer, if having a helical shape, is only partially formed on the coil-insulating seed layer, as will be described later in detail.

At step (g), the gap-depth defining layer and the first seed layer may be formed such that the front end surfaces thereof are continuous, that is, are formed in the same flat plane or the same curved plane.

At step (g), the gap-depth defining layer is preferably formed such that the front end surface thereof is perpendicular to the top surface of the protruding layer.

If the front end surface of the gap-depth defining layer is perpendicular to the top surface of the protruding layer, the upper magnetic pole layer need not extend over the gap-depth defining layer to reach the first seed layer. Thus, the upper magnetic pole layer can reliably reach the first seed layer.

Preferably, at step (e), the nonmagnetic material layer is formed with a material selected from the group consisting of SiO2, SiN, Ta2O5, Si3N4, and a resist; and, at step (g), the uncovered portion of the nonmagnetic material layer is removed by reactive ion etching. Through such steps (e) and (g), the gap-depth defining layer can be formed such that the front end surface thereof is perpendicular to the top surface of the protruding layer.

At step (e), the nonmagnetic material layer and the first seed layer are preferably formed such that the total thickness thereof is 0.5 μm or less. Such thicknesses can increase the magnetic flux passing through the upper magnetic pole layer, the lower magnetic pole layer, and the lower core layer.

At step (d), the top surfaces of the protruding layer, the coil-insulating layer, and the back gap layer are preferably processed into a continuous, flat surface after the coil layer is covered with the coil-insulating layer.

Such a continuous, flat surface can facilitate precise formation of the three-layer structure of the lower magnetic pole layer, the gap layer, and the upper magnetic pole layer having a predetermined shape, providing a thin-film magnetic head properly compatible with higher recording densities.

At step (h), the lower magnetic pole layer, the gap layer, and the upper magnetic pole layer are preferably continuously formed by plating. Such continuous plating facilitates the formation of the three-layer structure having a predetermined shape and, particularly, to enable precise definition of the track width.

Preferably, this manufacturing method further includes a step of continuously forming an upper core layer on the upper magnetic pole layer by plating after step (h), at which the upper and lower magnetic pole layers are formed with a material having a higher saturation magnetic flux density than the upper core layer.

At step (h), the upper and lower magnetic pole layers are preferably formed with a material having a higher saturation magnetic flux density than the lower core layer, the protruding layer, and the back gap layer.

In the present invention, the lower magnetic pole layer, the gap layer, the upper magnetic pole layer, and the upper core layer can be formed on the flat surface described above, providing broad options for the materials for the individual layers. Therefore, the lower and upper magnetic pole layers, which function as a magnetic pole at the front surface of the magnetic head, may be made of a material having high saturation magnetic flux density. Furthermore, another lower magnetic pole layer may be formed on the rear side of the gap-depth defining layer, and the upper magnetic pole layer may extend to the rear side of the gap-depth defining layer. These lower and upper magnetic pole layers, which function as a yoke on the rear side of the gap-depth defining layer, also have high saturation magnetic flux density, providing a thin-film magnetic head having excellent magnetic flux efficiency.

At step (h), preferably, the upper magnetic pole layer is formed in a planar shape composed of a front portion having a width that corresponds to the track width at the front surface of the magnetic head and that remains constant or increases in the height direction; and a rear portion having a width that increases from the side base ends at the rear of the front portion in the height direction, and the lower magnetic pole layer, the gap layer, and the upper core layer are formed in the same planar shape as the upper magnetic pole layer.

At step (f), the first seed layer is preferably patterned such that the rear end surface thereof is positioned above any one of the top surfaces of the protruding layer, the coil-insulating layer, and the back gap layer. Thereby, the gap-depth defining layer may also be patterned such that its rear end surface is positioned above any one of the top surfaces of the protruding layer, the coil-insulating layer, and the back gap layer.

This manufacturing method preferably further includes a step of forming a second seed layer of a magnetic material on the protruding layer between steps (d) and (e).

In addition, preferably, this manufacturing method further includes between steps (d) and (e) a step of forming a third seed layer such that it is disposed between the rear end surface of the gap-depth defining layer and the front end surface of the back gap layer; at step (f), the first seed layer is patterned to remain above the area between the protruding layer and the third seed layer; and, at step (h), another lower magnetic pole layer and another gap layer are formed on the third seed layer by plating.

If the first seed layer is patterned to remain above the area between the protruding layer and the third seed layer at step (f), the gap-depth defining layer is formed at step (g) to bridge the protruding layer and the third seed layer. The third seed layer is exposed after the formation of the gap-depth defining layer. Therefore, the additional lower magnetic pole layer and gap layer can be formed on the third seed layer by plating at step (h).

The third seed layer may be formed with a nonmagnetic metal.

The coil layer may be formed so as to surround the back gap layer on a plane parallel to the top surface of the lower core layer. Alternatively, the coil layer may be formed in a helical shape composed of first coil segments in a space surrounded by the lower core layer, the protruding layer, and the back gap layer, the first coil segments extending in a direction crossing the height direction; and second coil segments on the upper magnetic pole layer with an insulating layer disposed therebetween, the second coil segments extending in a direction crossing the height direction. Then, ends of the first coil segments opposed to ends of the second coil segments in the thickness direction of the upper magnetic pole layer may be connected to the ends of the second coil segments.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1is a longitudinal sectional view of a thin-film magnetic head according to a first embodiment of the present invention.

In the drawings, X indicates a track-width direction; Y indicates a height direction of magnetic heads orthogonal to the track-width direction; and Z indicates a traveling direction of the magnetic heads over a recording medium (magnetic disc). InFIG. 1, F indicates the front surface (the leftmost surface in the drawing) of the magnetic head. This front surface faces the recording medium.

An Al2O3layer21is formed on a substrate20of, for example, alumina-titanium carbide (Al2O3—TiC).

A lower shield layer22of, for example, Ni—Fe alloy or sendust is formed on this Al2O3layer21, and a lower gap layer23of, for example, Al2O3is formed on this lower shield layer22.

A magnetoresistive device24, typically a giant magnetoresistive (GMR) device such as a spin-valve thin-film device, is formed on this lower gap layer23near the front surface of the magnetic head. An electrode layer25extends from both sides of this magnetoresistive device24in the track-width direction (the X direction in the drawings) to the rear of the magnetic head in the height direction (the Y direction in the drawings).

An upper gap layer26of, for example, Al2O3is formed on the magnetoresistive device24and the electrode layer25, and an upper shield layer27of, for example, Ni—Fe alloy is formed on this upper gap layer26.

The above-described layers from the lower shield layer22to the upper shield layer27are collectively referred to as a read head (MR head).

A separating layer28of, for example, Al2O3is formed on the upper shield layer27. The magnetic head of the present invention need not include the upper shield layer27and the separating layer28. Without these two layers27and28, a lower core layer30, which will be described below, may be directly formed on the upper gap layer26. Then, the lower core layer30concurrently functions as the upper shield layer27.

On the other hand, with the two layers27and28, the lower core layer30is formed on the separating layer28. This lower core layer30is made of a magnetic material such as Ni—Fe alloy and has a predetermined length from the front surface of the magnetic head in the height direction (in the Y direction in the drawings).

A protruding layer31is formed on this lower core layer30, having a predetermined length L2from the front surface of the magnetic head in the height direction (in the Y direction in the drawings). In addition, a back gap layer32is formed on the lower core layer30away from the rear end surface of the protruding layer31in the height direction (in the Y direction in the drawings) by a predetermined distance.

The protruding layer31and the back gap layer32are made of a magnetic material, which may be the same as or different from that of the lower core layer30. These layers31and32may each be formed in a monolayer or a multilayer, and are magnetically connected to the lower core layer30.

A coil-insulating seed layer33of an insulating material such as Al2O3and SiO2is formed in a space surrounded by the lower core layer30, the protruding layer31, and the back gap layer32. First coil segments34are formed on this coil-insulating seed layer33, crossing the height direction.

Viewed from above, as shown inFIG. 3, these first coil segments34are parallel to the track-width direction (the X direction in the drawings). The space accommodating the first coil segments34is filled with a coil-insulating layer35of, for example, Al2O3.

The first coil segments34, which extend in a direction crossing the height direction, may be nonparallel. In addition, these first coil segments34may be linear, curved, or bent.

The top surfaces of the protruding layer31, the coil-insulating layer35, and the back gap layer32form a continuous, flat surface along a reference plane A inFIG. 1.

A gap-depth defining layer36is formed on this flat surface, extending from a position separated from the front surface of the magnetic head in the height direction (in the Y direction in the drawings) by a minimum length L1. This gap-depth defining layer36is made of a material selected from the group consisting of SiO2, SiN, Ta2O5, Si3N4, and a resist.

In this embodiment, a front end surface36b(see alsoFIG. 4) of the gap-depth defining layer36is disposed above the protruding layer31while a rear end surface36c(see alsoFIG. 4) of the gap-depth defining layer36is disposed above the coil-insulating layer35.

A second seed layer37of a magnetic material is formed on the protruding layer31. In addition, a third seed layer38extends from the rear end surface36cof the gap-depth defining layer36to the top surface of the back gap layer32. The second and third seed layers37and38are separately formed.

The gap-depth defining layer36is disposed between the second and third seed layers37and38.

The second and third seed layers37and38are made of, for example, Ni40Fe60, Fe70Co30, or Fe60Co30Ni10, which have saturation magnetic flux densities of about 1.9 T, about 2.3 T, and about 2.1 T, respectively. These seed layers37and38may be formed by sputtering to provide a sufficient corrosion resistance.

A lower magnetic pole layer39and a gap layer40, in this order, are formed on the protruding layer31with the second seed layer37disposed therebetween, extending from the front surface of the magnetic head to the front end surface36bof the gap-depth defining layer36. On the other hand, another lower magnetic pole layer39and another gap layer40, in this order, are formed on the coil-insulating layer35and the back gap layer32with the third seed layer38disposed therebetween, extending from the rear end surface36cof the gap-depth defining layer36in the height direction. The lower magnetic pole layers39and the gap layers40on the front and rear sides are formed by plating in this embodiment.

An upper magnetic pole layer41is formed on the gap layers40and the gap-depth defining layer36by plating, and an upper core layer42is formed on this upper magnetic pole layer41by plating. The upper magnetic pole layer41is connected to the back gap layer32through the top surface36aof the gap-depth defining layer36.

An insulating layer43of an insulating material such as Al2O3and a resist is formed on a four-layer structure52composed of the lower magnetic pole layers39, the gap layers40, the upper magnetic pole layer41, and the upper core layer42. Second coil segments44are formed on this insulating layer43, extending in a direction crossing the height direction.

Viewed from above, as shown inFIG. 3, these second coil segments44are, for example, inclined with respect to the track-width direction (in the X direction in the drawings).

The second coil segments44, which cross the height direction, may be nonparallel. In addition, the second coil segments44may be linear, curved, or bent.

The second coil segments44are nonparallel to the first coil segments34. Referring toFIGS. 2 and 3, ends34aof the first coil segments34opposed to ends44aof the second coil segments44in the thickness direction of the four-layer structure52(in the Z direction in the drawing) are connected through connections51to the opposed ends44aof the second coil segments44. A connection51illustrated with a dotted line on the right inFIG. 2connects an end34aof a first coil segment34behind a first coil segment34visible inFIG. 2and an end44aof a second coil segment44visible inFIG. 2.

The connections51connect the first and second coil segments34and44to form a coil layer54in a helical shape. A protective layer55inFIG. 1is made of, for example, Al2O3; a layer53is made of, for example, a resist; and a lead layer56inFIGS. 1 and 3is formed at a step of forming the second coil segments44.

The coil layer54can be formed in a helical shape because the four-layer structure52can be formed on the flat surface composed of the top surfaces of the protruding layer31, the coil-insulating layer35, and the back gap layer32. Consequently, the top surface of the upper core layer42can also be flat, on which, therefore, the second coil segments44can be easily and precisely formed into a predetermined shape.

Features of the magnetic head inFIG. 1will now be described with reference toFIG. 4, which is an enlarged partial sectional view of the magnetic head inFIG. 1and shows the gap-depth defining layer36and its periphery. InFIG. 4, the same reference numerals as inFIG. 1indicate the same parts as inFIG. 1and, therefore, are not described.

A top surface36aof the gap-depth defining layer36is entirely covered with a metallic first seed layer60.

This first seed layer60is exemplified by nonmagnetic films such as Ti films and Ti/Au laminated films and magnetic films such as FeCo films and FeCo/Ti/Au laminated films. Among them, nonmagnetic films are preferred as the first seed layer60because nonmagnetic films have a higher corrosion resistance in a plating solution than magnetic films.

The gap-depth defining layer36entirely covered with the first seed layer60ensures reliable formation of the upper magnetic pole layer41on the gap-depth defining layer36. That is, the upper magnetic pole layer41can be reliably connected to the back gap layer32through the top surface of the gap layer40on the front side and the top surface36aof the gap-depth defining layer36, providing a magnetic head having stable recording characteristics.

The gap-depth defining layer36, if partially covered with a seed layer, poses a problem described below.

Referring toFIG. 5, for example, after the formation of the second seed layer37, the third seed layer38, and the gap-depth defining layer36, a resist layer R1is applied on these layers37,38, and36. This resist layer R1is exposed and developed to form an opening R1a. Then, a metal is sputtered onto both of the top surface of the resist layer R1and an exposed part of the top surface36aof the gap-depth defining layer36in the opening R1ato deposit a seed layer70on the gap-depth defining layer36.

This seed layer70only partially covers the top surface36aof the gap-depth defining layer36. Therefore, the front end surface36bof the gap-depth defining layer36and the front end surface70aof the seed layer70are not continuous and are separated by a discontinuous portion N.

Smaller magnetic heads have difficulty in connecting an electrode to the seed layer70. Therefore, the electrode is connected to the second seed layer37, and then the upper magnetic pole layer39, the gap layer40, and the upper magnetic pole layer41are formed on the second seed layer37by plating.

The upper magnetic pole layer41is allowed to grow and extend over the discontinuous portion N, which exposes the top surface36aof the gap-depth defining layer36. If the upper magnetic pole layer41reaches the seed layer70beyond the discontinuous portion N, current can be passed through the seed layer70to grow the upper magnetic pole layer41entirely over the seed layer70.

The size reduction of magnetic heads, a decrease in inductance, and the suppression of heat generated by eddy currents require that the upper magnetic pole layer41have a smaller thickness. However, if the upper magnetic pole layer41has a small thickness, it may fail to reach the seed layer70. Then, as shown inFIG. 6, the upper magnetic pole layer41cannot be formed on the gap-depth defining layer36and, therefore, is separated by the gap-depth defining layer36. This separation results in a magnetic head that cannot perform magnetic recording or, even if possible, that has significantly poor recording characteristics.

InFIG. 4, the lower magnetic pole layer39and the gap layer40on the front side are formed on the protruding layer31. Rear end surfaces39aand40aof these layers39and40are in contact with the front end surface36bof the gap-depth defining layer36, which is made of an insulating material.

This contact provides the lower magnetic pole layer39and the gap layer40on the front side with flat top surfaces ranging from the front surface of the magnetic head to the front end surface36bof the gap-depth defining layer36.

Referring toFIG. 7, for example, after the formation of the gap-depth defining layer36, the protruding layer31, the coil-insulating layer35, and the gap-depth defining layer36are entirely covered with a metallic seed layer71, which is also formed on the front end surface36bof the gap-depth defining layer36. Then, the lower magnetic pole layer39and the gap layer40on the front side grow unnecessarily from the seed layer71on the front end surface36bby plating. Referring toFIG. 8, as a result, these layers39and40cause curved portions39band40bnear the gap-depth defining layer36and, therefore, cannot be flat, leading to a magnetic head having poor recording characteristics.

A method for forming the gap-depth defining layer36and its periphery inFIGS. 1 and 4will be described later in detail.

InFIG. 4, the front end surface36bof the gap-depth defining layer36and the front end surface60aof the first seed layer60form a continuous surface C, which indicates that these front end surfaces36band60aare formed in the same flat plane or the same curved plane.

The front end surface36bof the gap-depth defining layer36is perpendicular to the top surface31aof the protruding layer31, allowing precise definition of the gap depth of the magnetic head. The gap depth has ascertain length of the plane between the gap layer40on the front side and the upper magnetic pole layer41in the height direction. The gap depth is a significant factor for the recording characteristics such as overwrite characteristics and non-linear transition shift (NLTS) characteristics, has a certain length of the plane between the gap layer40and the upper magnetic pole layer41in the height direction.

If the front end surface36bof the gap-depth defining layer36is curved or not perpendicular to the top surface31aof the protruding layer31, the gap depth varies with changes in the thicknesses of the lower magnetic pole layer39and the gap layer40on the front side. On the other hand, inFIG. 1, if the front end surface36bof the gap-depth defining layer36is perpendicular to the top surface31aof the protruding layer31, the gap depth is equal to the minimum length L1from the front surface of the magnetic head to the gap-depth defining layer36. The gap depth, therefore, is kept constant even if the lower magnetic pole layer39and the gap layer40on the front side change in thickness.

In addition, if the front end surface36bof the gap-depth defining layer36is perpendicular to the top surface31aof the protruding layer31, it provides less side fringing than one curved or not perpendicular to the top surface31aof the protruding layer31. Side fringing is a phenomenon in which a recording magnetic field occurs outside a predetermined track width.

The upper magnetic pole layer41is formed on the gap layers40disposed on the lower magnetic pole layers39. The upper magnetic pole layer41, therefore, may be allowed to grow from a level closer to the first seed layer60by plating. Therefore, the upper magnetic pole layer41, even if it has a small thickness, can reliably reach the first seed layer60.

The total thickness t1of the gap-depth defining layer36and the first seed layer60is preferably 0.5 μm or less to increase the magnetic flux passing through the upper magnetic pole layer41, the lower magnetic pole layers39, and the lower core layer30.

As described above, the top surfaces of the protruding layer31, the coil-insulating layer35, and the back gap layer32form a flat surface, on which the four-layer structure52is formed by plating.

This flat surface allows precise formation of the four-layer structure52having a predetermined shape. In particular, the flat surface allows precise definition of a track width Tw (see alsoFIG. 9), which is a width of the upper magnetic pole layer41in the track-width direction (in the X direction in the drawing) at the front surface of the magnetic head. In this embodiment, this track width Tw can be defined within the range of 0.1 to 0.3 μm.

The four-layer structure52can form a linear magnetic path from the protruding layer31to the back gap layer32. This magnetic path, therefore, is shorter than that formed by the four-layer structure52curved under the upper core layer42.

Even if, therefore, the coil layer54has a smaller number of turns, the magnetic head can retain its recording characteristics. A smaller number of turns can decrease the coil resistance, thereby preventing heat generation in the magnetic head during operation and, for example, the protrusion of the gap layer40from the front surface of the magnetic head.

In addition, a smaller number of turns can increase the inversion speed of magnetic fields, providing a magnetic head having excellent high-frequency characteristics.

The coil-insulating layer35may be made of an inorganic insulating material to decrease the thermal expansion coefficient of the magnetic head.

In this magnetic head, the lower magnetic pole layers39, the gap layers40, and the upper magnetic pole layer41function as magnetic pole layers on the front side of the gap-depth defining layer36and function as yoke layers on the rear side of the gap-depth defining layer36.

In other words, the lower magnetic pole layers39, the gap layers40, and the upper magnetic pole layer41are functionally separated by the gap-depth defining layer36. This functional separation can provide an improvement in the recording characteristics of the magnetic head.

According to this embodiment, the four-layer structure52may be easily formed by plating with the same frame. Such a four-layer structure52allows precise definition of a predetermined track width Tw with no reduction by, for example, trimming.

This four-layer structure52, which is formed with the same frame, can have the same planar shape.

FIG. 9is a perspective view of an example of this four-layer structure52. InFIG. 9, the four-layer structure52has a planar shape consisting of a front portion B and a rear portion C. The front portion B extends from the front surface of the magnetic head in the height direction (in the Y direction in the drawings) with a constant width; on the other hand, the rear portion C extends from side base ends B1of the front portion B in the height direction with a gradually increasing width. The track width Tw, as described above, is defined by the width of the upper magnetic pole layer41in the track-width direction (in the X direction in the drawings) at the front surface of the magnetic head.

The front portion B may have a width gradually. increasing from the front surface of the magnetic head in the height direction. Then, the rear portion C has a width further increasing from the side base ends B1of the front portion B in the height direction.

The side base ends B1, which are positioned closer to the rear of the magnetic head than the rear end surface36cof the gap-depth defining layer36inFIG. 9, may be positioned above the gap-depth defining layer36.

As shown inFIG. 9, the gap depth is defined by a length of the top surface40cof the gap layer40on the front side from the front surface of the magnetic head to the gap-depth defining layer36in the height direction (in the Y direction in the drawings). To define a proper gap depth, preferably, the gap layer40on the front side is separated from that on the rear side by the gap-depth defining layer36. The gap depth is preferably about 0.3 to 2.0 μm. Therefore, the front end surface36bof the gap-depth defining layer36is preferably positioned such that the minimum length L1(seeFIG. 1) from the front surface of the magnetic head to the front end surface36bof the gap-depth defining layer36ranges from about 0.3 to about 2.0 μm.

The lower and upper magnetic pole layers39and41will now be described. The lower and upper magnetic pole layers39and41, which are opposed to the gap layer40, are preferably made of a material having a higher saturation magnetic flux density Bs than the lower and upper core layers30and42, the protruding layer31, and the back gap layer32. Such lower and upper magnetic pole layers39and41can concentrate a recording magnetic field around the gap layers40to improve the recording density.

The lower and upper magnetic pole layers39and41extend beyond the gap-depth defining layer36in the height direction, providing an area with high saturation magnetic flux density Bs near the coil layer54. This area improves the magnetic flux efficiency to provide a magnetic head having excellent recording characteristics.

The lower and upper magnetic pole layers39and41may be made of a magnetic material such as Ni—Fe alloy, Co—Fe alloy, and Co—Fe—Ni alloy. The composition of this magnetic material may be adjusted to provide a higher saturation magnetic flux density Bs, which is 1.8 T or more in this embodiment.

The lower and upper magnetic pole layers39and41may each be formed in a monolayer or a multilayer.

The gap layers40will now be described. The gap layers40are formed on the lower magnetic pole layers39by plating with a nonmagnetic metal, which is preferably at least one material selected from the group consisting of NiP, Ni—Pd alloy, Ni—W alloy, Ni—Mo alloy, Ni—Rh alloy, Au, Pt, Rh, Pd, Ru, and Cr. The gap layers40may be formed in a monolayer or a multilayer.

The gap layers40of NiP have advantages such as easy continuous plating, high thermal resistance, and good adhesion to the lower and upper magnetic pole layers39and41. In addition, such gap layers40can have a hardness equivalent to the lower and upper magnetic pole layers39and41. The gap layers40, therefore, can have an equivalent required processing amount to the lower and upper magnetic pole layers39and41during the processing of their front end surfaces facing the recording medium by, for example, ion milling, thereby improving the processability.

More preferably, the gap layers40are made of NiP containing phosphorus of 8% to 15% by weight to remain nonmagnetically stable against external factors such as heat generation. The composition of the gap layers40may be measured by, for example, X-ray spectroscopy in combination with scanning electron microscopy (SEM) or transmission electron microscopy (TEM) or wavelength dispersive X-ray spectroscopy.

The upper core layer42will now be described. The upper core layer42is formed together with the lower magnetic pole layer39, the gap layer40, and the upper magnetic pole layer41by plating. In addition, the upper core layer42has the same planar shape as these layers39,40, and41. The upper core layer42, having a predetermined planar shape, can be easily and precisely formed on the upper magnetic pole layer41because the upper magnetic pole layer41is substantially flat.

The upper core layer42may be made of, for example, the same magnetic material as the lower core layer30and may be formed in a monolayer or a multilayer.

This upper core layer42, though not being essential, is preferably provided in the magnetic head. For layers having high saturation magnetic flux density, such as the lower and upper magnetic pole layers39and41, it is difficult to provide a large thickness because of their slow growth in plating. On the other hand, the upper core layer42does not need high saturation magnetic flux density and, therefore, does not face tough plating conditions. The upper core layer42having a large thickness can improve the recording characteristics.

The upper core layer42has a thickness of about 1 to 3 μm. For reference, the lower magnetic pole layers39, the gap layers40, and the upper magnetic pole layer41have thicknesses of about 0.1 to 0.5 μm, about 0.05 to 0.15 μm, and about 0.1 to 1 μm, respectively.

The protruding layer31will now be described. In this embodiment, the protruding layer31is separated from the lower core layer30and magnetically connected to the lower core layer30. The protruding layer31and the lower core layer30may be formed as an unseparated layer. The material for the protruding layer31may be the same as or different from the lower core layer30. The protruding layer31may be formed in a monolayer or a multilayer.

InFIG. 9, the protruding layer31has a larger width T1in the track-width direction (in the X direction in the drawing) at the surface facing the recording medium than the lower magnetic pole layer39, the gap layer40, the upper magnetic pole layer41, and the upper core layer42. This width T1ranges from about 5 to about 30 μm; a length L2of the protruding layer31in the height direction ranges from about 1.5 to about 3 μm; and a thickness H1of the protruding layer31ranges from about 2.5 to about 4 μm.

The second and third seed layers37and38for forming the lower magnetic pole layers39will now be described. InFIG. 4, the second seed layer37extends on the protruding layer31from the front surface of the magnetic head in the height direction (in the Y direction in the drawings). The third seed layer38extends on the coil-insulating layer35and the back gap layer32from a position separated from the rear end surface of the second seed layer37in the height direction by a predetermined distance.

The gap-depth defining layer36bridges a space61between the second and third seed layers37and38.

The lower magnetic pole layers39are formed on the second and third seed layers37and38by plating, and the gap layers40are formed on the lower magnetic pole layers39by plating.

The second and third seed layers37and38are separated by the space61to prevent magnetic loss, which leads to a deterioration in the recording characteristics. If these seed layers37and38are formed as an unseparated seed layer of a magnetic material, some flux passes through this unseparated seed layer, which is not the correct route, to leak out and result in magnetic loss. The gap-depth defining layer36can prevent such magnetic loss.

The third seed layer38may be made of a nonmagnetic metal such as copper while the second seed layer37needs to be made of a magnetic material. If the second seed layer37, which is exposed in the front surface of the magnetic head, is made of a nonmagnetic metal, the second seed layer37acts as a pseudogap, resulting in a deterioration in the recording characteristics. On the other hand, the third seed layer38, which is not exposed in the front surface of the magnetic head, does not have such a limitation.

The second seed layer37is not essential because the top surface31aof the protruding layer31may function as a seed layer. The third seed layer38only needs to extend from the rear end surface36cof the gap-depth defining layer36to the front end surface32aof the back gap layer32. Rather, the third seed layer38does not preferably overlap with the back gap layer32to prevent a magnetic loss. A part of the third seed layer38overlapping the back gap layer32may be removed before the formation of the lower magnetic pole layer39. Alternatively, the third seed layer38may be formed so as not to overlap the back gap layer32.

The second and third seed layers37and38may be formed at the same time. Then, a magnetic material is deposited onto the flat surface along the reference plane A by sputtering and is patterned by, for example, photolithography or ion milling to form the second and third seed layers37and38.

Next, a method for manufacturing the magnetic head, mainly a process of forming the layers30to42, will now be described with reference toFIGS. 10 to 16, which are longitudinal sectional views of the magnetic head in the manufacturing process.

Referring toFIG. 10, first, the lower core layer30of, for example, Ni—Fe alloy is formed by plating and polished to form a flat top surface.

Referring toFIG. 11, the protruding layer31and the back gap layer32are formed on the flat top surface of the lower core layer30. Specifically, a resist is exposed and developed to form a pattern, which is filled with a magnetic material layer by, for example, plating. This resist is then removed to form the protruding layer31and the back gap layer32.

The protruding layer31and the back gap layer32are formed such that their top surfaces are aligned at substantially the same level in the thickness direction.

Referring toFIG. 12, the coil-insulating seed layer33of an insulating material such as Al2O3and SiO2is formed in the space surrounded by the lower core layer30, the protruding layer31, and the back gap layer32by, for example, sputtering. Then, the first coil segments34crossing the height direction are formed on this coil-insulating seed layer33by plating with a nonmagnetic material such as copper. The connections51inFIGS. 2 and 3are formed at the same time.

Referring toFIG. 13, the coil-insulating layer35of, for example, Al2O3is formed over the first coil segments34, the protruding layer31, and the back gap layer32by, for example, sputtering.

This coil-insulating layer35is trimmed to line D—D in parallel to the X-Y plane by, for example, chemical mechanical polishing (CMP).FIG. 14shows the trimmed coil-insulating layer35.

InFIG. 14, the top surfaces of the protruding layer31, the coil-insulating layer35, and the back gap layer32form the flat surface along the reference plane A. The first coil segments34are completely embedded in the coil-insulating layer35.

Referring toFIG. 15, after the second and third seed layers37and38are formed on this flat surface by, for example, sputtering, the gap-depth defining layer36is formed away from the front surface of the magnetic head in the height direction (in the Y direction in the drawings) by a predetermined distance. This gap-depth defining layer36bridges the space61between the second and third seed layers37and38.

As described above, the third seed layer38may be made of a nonmagnetic metal and need not overlap with the back gap layer32. If a part of the third seed layer38overlaps with the back gap layer32, this part may be removed by etching. In addition, the second seed layer37is not essential and, if formed, needs to be made of a magnetic material. The third seed layer38may be made of either magnetic or nonmagnetic material.

Referring toFIG. 16, after the formation of a resist layer having a pattern of, for example, the front portion B and the rear portion C inFIG. 9, the lower magnetic pole layers39, the gap layers40, the upper magnetic pole layer41, and the upper core layer42, in this order, are continuously formed in this pattern by plating.

As described above, the lower magnetic pole layers39, the gap layers40, the upper magnetic pole layer41, and the upper core layer42have the planar shape consisting of the front portion B and the rear portion C. The front portion B has a small width and extends from the front surface of the magnetic head in the height direction (in the Y direction in the drawings). On the other hand, the rear portion C has a width gradually increasing from the side base ends B1of the front portion B in the height direction. The track width Tw is defined by the width of the upper magnetic pole layer41in the track-width direction (in the X direction in the drawings) at the front surface of the magnetic head. After the formation of these layers39,40,41, and42, the resist layer is removed.

In this step, the lower magnetic pole layers39and the gap layers40are formed on the front and rear sides of the gap-depth defining layer36by plating. The upper magnetic pole layer41is then formed on these layers39and40by plating, extending from the front surface of the magnetic head to the top surface of the back gap layer32. The upper core layer42is continuously formed on the upper magnetic pole layer41by plating.

Originally, the lower magnetic pole layers39, the gap layers40, and the upper magnetic pole layer41are required to constitute a magnetic pole. Therefore, in general, only the lower magnetic pole layer39and gap layer40on the front side of the gap-depth defining layer36are formed, and the upper magnetic pole layer41only needs to extend from the front surface of the magnetic head onto the gap-depth defining layer36.

In this step, however, the lower magnetic pole layers39and the gap layers40are formed on the front and rear sides of the gap-depth defining layer36, and the upper magnetic pole layer41extends to the back gap layer32. The lower magnetic pole layer39, the gap layer40, and the upper magnetic pole layer41on the rear side of the gap-depth defining layer36function as a yoke, as does the upper core layer42.

Thus, the upper core layer42can be continuously formed on the lower magnetic pole layers39, the gap layers40, and the upper magnetic pole layer41by plating.

If, as described above, the lower magnetic pole layer39, the gap layer40, and the upper magnetic pole layer41are not formed on the rear side of the gap-depth defining layer, an additional layer, such as a coil layer and an insulating layer, is generally formed on the rear side of the gap-depth defining layer36. The entire top surfaces of the upper magnetic pole layer41and such an additional layer require flattening by, for example, CMP to form the upper core layer42. The step inFIG. 16, however, does not require such flattening, because the lower magnetic pole layers39and the gap layers40are formed on the front and rear sides and the upper magnetic pole layer41extends to the back gap layer32. The upper core layer42, therefore, can be directly formed on the upper magnetic pole layer41by plating. Thus, with such a simpler step, the upper core layer42having a predetermined shape can be readily and precisely formed on the flat top surface of the upper magnetic pole layer41.

In the step inFIG. 16, the lower and upper magnetic pole layers39and41may be made of a material having a higher saturation magnetic flux density than the lower and upper core layers30and42, the protruding layer31, and the back gap layer32. Such magnetic pole layers39and41can collect a recording magnetic field around the gap layers40to increase the recording density. In addition, such magnetic pole layers39and41can provide an area with high saturation magnetic flux density near the coil layer54to increase the magnetic flux efficiency, improving the recording characteristics.

The gap layers40, which are formed by plating, are preferably made of a nonmagnetic metal that can be used in plating. More preferably, the gap layers40are made of at least one material selected from the group consisting of NiP, Ni—Pd alloy, Ni—W alloy, Ni—Mo alloy, Ni—Rh alloy, Au, Pt, Rh, Pd, Ru, and Cr. These materials allow the gap layers40to be nonmagnetic and to have a predetermined thickness.

The gap layers40of NiP have advantages such as easy plating, high thermal resistance, and good adhesion to the upper magnetic pole layer41. More preferably, the gap layers40are made of NiP containing phosphorus of 8% to 15% by weight to remain nonmagnetically stable against external factors such as heat generation. The composition of the gap layers40may be measured by, for example, X-ray spectroscopy in combination with scanning electron microscopy (SEM) or transmission electron microscopy (TEM) or wavelength dispersive X-ray spectroscopy.

The insulating layer43of an insulating material such as Al2O3is formed on the upper core layer42. The second coil segments44crossing the height direction are formed on this insulating layer43.

When the second coil segments44are formed, as shown inFIGS. 2 and 3, the ends34aof the first coil segments34and the ends44aof the second coil segments44, which are opposed in the thickness direction of the four-layer structure52(in the Z direction in the drawings), are connected through the connections51.

The connections51connect the first and second coil segments34and44to form the coil layer54in a helical shape. Before the formation of the second coil segments44, as shown inFIG. 2, the layer53of, for example, a resist is formed to cover the corners of the four-layer structure52. The lead layer56is formed together with the second coil segments44, and then the protective layer55of, for example, Al2O3is formed, finally providing the magnetic head inFIG. 1.

Next, a process of forming the gap-depth defining layer36and the first, second, and third seed layers60,37, and38will now be described with reference toFIGS. 17 to 22.

FIG. 17is an enlarged partial sectional view of the protruding layer31, the coil-insulating layer35, and their periphery after the step inFIG. 14.

In a step inFIG. 18, the second seed layer37is deposited on the protruding layer31and the third seed layer38is deposited on the coil-insulating layer35and the back gap layer32by, for example, sputtering. As described above, these seed layers37and38are spaced by a predetermined distance in the height direction.

The second and third seed layers37and38are made of, for example, Ni40Fe60, Fe70Co30, or Fe60Co30Ni10, which have saturation magnetic flux densities of about 1.9 T, about 2.3 T, and about 2.1 T, respectively. These seed layers37and38may be formed by sputtering to provide a sufficient corrosion resistance. The third seed layer38may be made of a nonmagnetic metal.

Referring toFIG. 19, a nonmagnetic material layer73is deposited on the top surfaces of the protruding layer31, the coil-insulating layer35, and the back gap layer32, and then the first seed layer60is formed on this nonmagnetic material layer73. The nonmagnetic material layer73will be patterned to form the gap-depth defining layer36later.

This nonmagnetic material layer73is formed by sputtering with an inorganic material that can be used for reactive ion etching, such as SiO2, SiN, Ta2O5, and Si3N4. Alternatively, a resist may be applied and cured by heating to form the nonmagnetic material layer73.

The first seed layer60is exemplified by nonmagnetic films such as Ti films and Ti/Au laminated films; and magnetic films such as FeCo films and FeCo/Ti/Au laminated films. Among them, nonmagnetic films are preferred because nonmagnetic films have higher corrosion resistance to a plating solution than magnetic films.

The first seed layer60has a thickness of 100 to 200 Å while the nonmagnetic material layer73has a thickness of 0.2 to 0.45 μm. The total thickness of these layers60and73is preferably 0.5 μm or less.

Referring toFIG. 20, a resist layer R2is formed on the first seed layer60and is patterned to remain at an area separated from the front surface of the magnetic head by a predetermined distance. Then, uncovered parts of the first seed layer60are removed by ion milling or reactive ion etching to form the first seed layer60having the same planar shape as the gap-depth defining layer36.

InFIG. 20, the rear end surface of the first seed layer60overlaps with the third seed layer38while the front end surface of the first seed layer60overlaps with the second seed layer37.

Referring toFIG. 21, the resist layer R2is removed, and then uncovered parts of the nonmagnetic material layer73are removed to form the gap-depth defining layer36, which is the remaining nonmagnetic material layer73.

If the nonmagnetic material layer73is made of a material selected from the group consisting of SiO2, SiN, Ta2O5, and Si3N4, the uncovered parts of the nonmagnetic material layer73may be removed by reactive ion etching with CF4. On the other hand, if the nonmagnetic material layer73is a resist layer cured by heating, the uncovered parts of the nonmagnetic material layer73may be removed by reactive ion etching with O2. Such reactive ion etching provides the gap-depth defining layer36having the front end surface36bperpendicular to the top surface31aof the protruding layer31.

Thus, the gap-depth defining layer36is formed to bridge the second and third seed layers37and38.

After the formation of the gap-depth defining layer36, the exposed top surfaces of the second and third seed layers37and38are precleaned, that is, trimmed by tens of angstroms by ion milling at an incident angle of 30° to 60° from the normal direction to these top surfaces.

Referring toFIG. 22, after the precleaning, the lower magnetic pole layers39, the gap layers40, the upper magnetic pole layer41, and the upper core layer42are continuously formed by plating.

The lower magnetic pole layer39and the gap layer40on the front side are formed on the second seed layer37such that their rear end surfaces are in contact with the front end surface36bof the gap-depth defining layer36. On the other hand, the lower magnetic pole layer39and the gap layer40on the rear side are formed on the third seed layer38. The upper magnetic pole layer41is formed such that it is connected to the gap layer40on the back gap layer32through the top surface of the gap layer40on the protruding layer31and the top surface36aof the gap-depth defining layer36.

According to the manufacturing method described above, the nonmagnetic material layer73is processed to form the gap-depth defining layer36, with the patterned first seed layer60used as a mask. Therefore, the first seed layer60can cover the entire top surface36aof the gap-depth defining layer36.

Such a first seed layer60allows reliable formation of the upper magnetic pole layer41over the first seed layer60, providing a magnetic head having stable recording characteristics.

The rear end surfaces of the lower magnetic pole layer39and the gap layer40on the front side are in contact with the front end surface36bof the gap-depth defining layer36. The upper magnetic pole layer41, which is formed on the gap layers40, may be allowed to grow by plating from a level closer to the first seed layer60. Thus, the upper magnetic pole layer41can reliably reach the first seed layer60and can be readily formed on the gap-depth defining layer36, providing a magnetic head having stable recording characteristics.

The gap-depth defining layer36is formed with the first seed layer60as a mask. Therefore, the front end surfaces36band60aof the gap-depth defining layer36and the first seed layer60form a continuous surface, which indicates that these front end surfaces36band60aare formed in the same flat plane or the same curved plane.

The front end surface36bof the gap-depth defining layer36is perpendicular to the top surface31aof the protruding layer31. The upper magnetic pole layer41, therefore, need not extend over the gap-depth defining layer36to reach the first seed layer60. Thus, the upper magnetic pole layer41can reliably reach the first seed layer60.

Another process of forming the first seed layer60so as to cover the entire top surface36aof the gap-depth defining layer36will now be described.FIG. 23is a partial sectional view of the magnetic head in this process.

This process includes the same steps as the above-described process except for the steps after the formation of the nonmagnetic material layer73. In this process, as shown inFIG. 23, a resist layer R3is applied on the nonmagnetic material layer73instead of depositing the first seed layer60on the entire top surface of the nonmagnetic material layer73. Then, an opening R3ais formed in the resist layer R3, and the first seed layer60is deposited on an exposed area of the first seed layer60in the opening R3aof the resist layer R3by, for example, sputtering. At the same time, a layer60aof the same material as the first seed layer60is formed on the top surface of the resist layer R3.

The opening R3aand the first seed layer60have the same planar shape as the gap-depth defining layer36to be formed.

The rear end surface of the first seed layer60overlaps with the third seed layer38while the front end surface of the first seed layer60overlaps with the second seed layer37.

Referring toFIG. 24, the resist layer R3is removed, and then uncovered parts of the nonmagnetic material layer73are removed to form the gap-depth defining layer36, which is the remaining nonmagnetic material layer73.

If the nonmagnetic material layer73is made of a material selected from the group consisting of SiO2, SiN, Ta2O5, and Si3N4, the uncovered parts of the nonmagnetic material layer73may be removed by reactive ion etching with CF4. On the other hand, if the nonmagnetic material layer73is a resist layer cured by heating, the uncovered parts of the nonmagnetic material layer73may be removed by reactive ion etching with O2. Such reactive ion etching provides the gap-depth defining layer36having the front end surface36bperpendicular to the top surface31aof the protruding layer31.

Thus, the gap-depth defining layer36is formed to bridge the second and third seed layers37and38.

FIG. 25is a partial longitudinal sectional view of a magnetic head according to a second embodiment of the present invention.

This magnetic head inFIG. 25has a similar structure to that inFIG. 1. Therefore, the same parts as the magnetic head inFIGS. 1 to 4will be indicated by the same numbers and not described in detail.

The magnetic head inFIG. 25is different from that inFIG. 1in that the rear end surface36cof the gap-depth defining layer36is positioned on the back gap layer32.

Alternatively, the rear end surface36cof the gap-depth defining layer36may be positioned on the boundary between the top surface and front end surface of the back gap layer32.

In this magnetic head, the gap-depth defining layer36overlaps entirely with the first coil segments34to strengthen the insulation between the first coil segments34and the upper magnetic pole layer41.

The upper magnetic pole layer41can be insulated even if the first coil segments34extend to the reference plane A to be in contact with the bottom surface of the gap-depth defining layer36. Such first coil segments34can have a larger sectional area and, therefore, a smaller resistance.

In this magnetic head, as shown inFIG. 26, the width W3of the gap-depth defining layer36is preferably slightly larger than the maximum width W2of the upper core layer42in the track-width direction. The reason for this will now be described.

A thickness T2of the gap-depth defining layer36, on which the magnetic pole layer41is formed, results in steps on the upper magnetic pole layer41. The upper core layer42is formed on the upper magnetic pole layer41with a seed layer that is not shown in the drawings disposed therebetween. Therefore, the steps on the upper magnetic pole layer41are also formed on the upper core layer42. Then, if the width W3of the gap-depth defining layer36is smaller than the maximum width W2of the upper core layer42to be formed, the upper magnetic pole layer41causes two steps extending in the height direction along side edges36dand36eand a step extending in the track-width direction along the rear end surface36cof the gap-depth defining layer36. These steps readily impair the seed layer for forming the upper core layer42to make it difficult to reliably form the upper core layer42by plating.

On the other hand, if the width W3of the gap-depth defining layer36is larger than the maximum width W2of the upper core layer42to be formed, the side edges36dand36eof the gap-depth defining layer36are positioned outside those of the upper magnetic pole layer41. Thus, the upper magnetic pole layer41cause no step extending in the height direction, allowing reliable formation of the upper core layer42and, therefore, improving the quality of the magnetic head.

The rear end surface36cof the gap-depth defining layer36may be positioned on the coil-insulating layer35.

FIG. 27is a partial longitudinal sectional view of a magnetic head according to a third embodiment of the present invention. This magnetic head inFIG. 27has a similar structure to that inFIG. 1. Therefore, the same parts as the magnetic head inFIGS. 1 to 4will be indicated by the same numbers and not described in detail.

The magnetic head inFIG. 27has a different coil layer82from that inFIG. 1.

This magnetic head includes a leveling layer80that has a top surface at the same level as that of the lower core layer30and that is disposed behind the lower core layer30. The leveling layer80is separated from the rear end surface30aof the lower core layer30by a predetermined distance. The space between the lower core layer30and the leveling layer80is filled with a nonmagnetic layer81made of, for example, Al2O3. The lower core layer30, the leveling layer80, and the nonmagnetic layer81form a continuous, flat top surface.

The coil-insulating seed layer33is formed on the lower core layer30and the leveling layer80. The coil layer82, which surrounds the back gap layer32, is formed on the coil-insulating seed layer33.

Segments of the coil layer82in the front side of the back gap layer32are included in the space surrounded by the lower core layer30, the protruding layer31, and the back gap layer32.

The spaces including the coil layer82are filled with the coil-insulating layer35of, for example, Al2O3. Extension layers83are formed on coil ends82aand82band are connected to the lead layer84. These extension layers83are made of, for example, the same magnetic material as the protruding layer31and the back gap layer32.

Also in the magnetic heads inFIGS. 25 and 27, the first seed layer60covers the entire top surface of the gap-depth defining layer36and has a front end surface perpendicular to the top surface of the protruding layer31.

The magnetic heads described above in detail are built in, for example, a magnetic head device for use in hard disc drives. These magnetic heads may be built in either floating magnetic head devices or contact magnetic head devices. Alternatively, these magnetic heads may be used in, for example, magnetic sensors.