Dynamic magnetic information storage or retrieval – Head – Core
Reexamination Certificate
2001-08-16
2003-11-25
Tupper, Robert S. (Department: 2652)
Dynamic magnetic information storage or retrieval
Head
Core
Reexamination Certificate
active
06654203
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a thin-film magnetic head having at least an induction-type electromagnetic transducer and a method of manufacturing the same, and to a head gimbal assembly and a hard disk drive.
2. Description of the Related Art
Recently, performance improvements in thin-film magnetic heads have been sought as areal recording density of hard disk drives has increased. Such thin-film magnetic heads include composite thin-film magnetic heads that have been widely used. A composite thin-film magnetic head is made of a layered structure including a write (recording) head having an induction-type electromagnetic transducer for writing and a read (reproducing) head having a magnetoresistive (MR) element for reading.
The write head has a bottom pole layer and a top pole layer each of which has a magnetic pole portion. The magnetic pole portions of the bottom and top pole layers are located on a side of the air bearing surface and opposed to each other. The write head further has a write gap layer provided between the magnetic pole portions of the bottom and top pole layers, and a thin-film coil provided such that at least a part of the coil is insulated from the bottom and top pole layers.
What is required of the write head for achieving a high recording density is, in particular, reduction in a magnetic pole width that defines a write track width and improvement in recording characteristics. For example, in order to achieve a thin-film magnetic head having an areal recording density exceeding 30 gigabits per square inch, a magnetic pole width of 0.4 &mgr;m or less is required. On the other hand, when the pole width is reduced, the recording characteristics, one of which is overwrite property that is a parameter indicating one of characteristics when data is overwritten, deteriorate. Hence, the more the pole width is reduced, the more the recording characteristics need to be improved.
Conventionally, NiFe (Permalloy) is often used as a material of the magnetic pole. However, in order to achieve the recording characteristics that meet the need for a high recording density as discussed above, high saturation magnetic flux density materials having a higher saturation magnetic flux density than that of NiFe, for example, those having a saturation magnetic flux density of 1.8 T or higher, have been used recently as a material of the magnetic pole. Among such high saturation magnetic flux density materials, magnetic materials including FeCo or CoNiFe are often used.
As disclosed in Published Unexamined Japanese Patent Application (KOKAI) No. Hei 7-262519, for example, frame plating is used as a method of forming the magnetic pole that defines the write track width. In the frame plating, a base film that will serve as an electrode for plating is formed on a base by sputtering, for example, and a photoresist layer is formed on the base film. The photoresist layer is then patterned through a photolithography process, thereby forming a frame to be used for plating. The frame has an opening in the portion where the magnetic pole is to be formed. Using this frame, electroplating is performed with the previously formed base film as an electrode. A plating layer that will be made into the magnetic pole is thereby formed on the base film. Subsequently, the frame is removed, and unwanted portions of the base film that are other than the portion present under the plating layer are removed by dry etching such as ion milling. Thus, the base film remains under the magnetic pole formed in the above manner.
Conventionally, when NiFe is used as the material of the magnetic pole, NiFe is also used for the base film. The saturation magnetic flux density of NiFe is approximately 0.9 to 1.4 T. Accordingly, when a high saturation magnetic flux density material is intended to be used as the material of the magnetic pole to improve the recording characteristics as discussed above, a high saturation magnetic flux density material having a saturation magnetic flux density of, for example, 1.8 T or higher, is required for the base film, too. Like in the case of the magnetic pole, a high saturation magnetic flux density material used for the base film may be, for example, a magnetic material including FeCo or CoNiFe.
Published Unexamined Japanese Patent Application (KOKAI) No. Hei 5-73839 discloses a technique of forming a base film from a material having a saturation magnetic flux density higher than that of the magnetic pole.
It has been found, however, that there arise various problems as discussed below when a high saturation magnetic flux density material containing Co is used as the material of the base film.
A first problem is that, when forming the frame by patterning the photoresist layer formed on the base film through the photolithography process, a part of the photoresist that should be removed often adheres to the base film and remains thereon within the opening of the frame. If the unwanted part of the photoresist remains on the base film within the opening of the frame, a magnetic pole cannot be formed into a desired shape. Increasing a quantity of exposure onto the photoresist layer during the photolithography process can prevent the unwanted part of the photoresist from remaining on the base film. However, this enlarges the opening of the frame, thereby making it difficult to reduce the pole width.
A second problem is that a high saturation magnetic flux density material including Co has poor resistance to corrosion compared with NiFe, and for this reason, the base film is subject to corrosion before the magnetic pole is formed by frame plating. For example, in the plating process, during the period from the time when the base film is brought into contact with a plating liquid to the time when application of a predetermined voltage to the base film is started, the base film is subject to etching by a plating liquid and damaged by corrosion. When the base film is thus damaged by corrosion, a magnetic pole cannot be formed into a desired shape, either.
Corrosion on the base film before formation of the magnetic pole also occurs in the case of forming the frame for plating from a multi-layer film having three or more layers. A technique of forming the frame for plating from a multi-layer film having three or more layers is disclosed in, for example, Published Unexamined Japanese Patent Application (KOKAI) Nos. Hei 10-3613 and 11-175915. Here, a method of forming the frame for plating from a three-layer film will be briefly described. According to the method, a three-layer film is first formed. The uppermost layer of this film is a relatively thin photoresist layer; the layer beneath the same is the intermediate layer made of metal, ceramic, etc.; and the lowermost layer is a photoresist layer. According to this method, the photoresist layer provided as the uppermost layer is patterned by photolithography. Then, using the patterned photoresist as a mask, the intermediate layer is patterned by reactive ion etching. Subsequently, using the patterned intermediate layer as a mask, the photoresist layer provided as the lowermost layer is patterned by reactive ion etching.
The above method makes it possible to form a frame for plating having a narrow opening. In this method, however, if a high saturation magnetic flux density material containing Co is used for the base film, the base film is subject to etching by a reactive gas and damaged by corrosion when the lowermost photoresist layer is patterned by reactive ion etching.
Published Unexamined Japanese Patent Application (KOKAI) No. Hei 5-73839 discloses that, when a Co—Zr—Ta amorphous film is used as the base film and an NiFe plating layer is used as the magnetic pole, the base film and the plating layer react with each other and it is therefore necessary to provide a thin film (having a thickness of approximately 0.1 &mgr;m) of metal such as Ti and Cr between the base film and the plating layer. However, it is not preferable to provide a film of a non-magnetic metal such as Ti and Cr
Hokushin Jun-ichi
Ishizaki Kazuo
Maekawa Kazuya
Mino Tetsuya
Sato Jun-ichi
Oliff & Berridg,e PLC
TDK Corporation
Tupper Robert S.
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