Dynamic magnetic information storage or retrieval – Head – Magnetoresistive reproducing head
Reexamination Certificate
1998-01-26
2001-07-10
Letscher, George J. (Department: 2754)
Dynamic magnetic information storage or retrieval
Head
Magnetoresistive reproducing head
Reexamination Certificate
active
06259585
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a thin film magnetic head comprising a substrate made of an electrically insulating and non-magnetic material, and an inductive magnetic converting element including first and second magnetic films each having pole portions provided in the vicinity of an air bearing surface and being magnetically coupled at portions remote from the air bearing surface, a gap film arranged between the first and second magnetic films at least at the pole portions, and a thin film coil having a portion provided between said first and second magnetic films.
The present invention also relates to an inverted hybrid or composed type thin film magnetic head, in which an inductive magnetic recording element is provided on a substrate and a magnetoresistive reading element is arranged on the inductive recording element.
2. Related Art Statement
A hybrid type thin film magnetic head including a inductive recording element and a magnetoresistive reading element has been known from, for instance Japanese Patent Application Publication No. 59-35088 and U.S. Pat. No. 3,908,194. In this known thin film magnetic head, the magnetoresistive reading element is provided on a substrate and the inductive recording element is provided on the magnetoresistive reading element. However, this structure has various problems particularly in a view point of the mass production. Hereinafter, the inductive recording element is sometimes called the inductive element and the magnetoresistive reading element is often called the MR element for the sake of simplicity.
In the known structure in which the inductive element is provided on the MR element, the previously manufactured MR element is subjected to all process steps for manufacturing the inductive element. This causes a serious decrease in characteristics, reliability and manufacturing yield of the magnetic head.
In order to realize a hybrid type thin film magnetic head which can offer a high surface recording density, it is desirable to form the MR element by a giant magnetoresistive (GMR) film such as spin bulb film, super lattice film and granular film, instead of a normal anisotropic magnetoresistive film. Such a GMR film is liable to be damaged by a thermal treatment during the formation of the inductive element and an output of the MR element is reduced to a large extent. For instance, in a spin bulb film including an alternate stack of magnetic layers of Ni—Fe and non-magnetic layers of Cu, at a temperature of about 200-250° C. which is usually employed for manufacturing the inductive element, Ni and Cu atoms are mutually diffused and the stacking structure of the spin bulb film is destroyed.
An over-write property of the inductive element is largely dependent upon an apex angle of an coil supporting and isolating insulating film for supporting the thin film coil such that conductive turns thereof are isolated from each other, and upon a throat height of the pole portion. Therefore, in order to improve the stability, reliability and yield, it is very important to control precisely said apex angle and throat height.
Particularly, in order to improve the manufacturing yield of the thin film magnetic head, not only the above mentioned throat height of the inductive element, but also an MR height of the MR element have to be formed precisely. As is well known in the art, the throat height and MR height are determined by a position of the lowermost insulating layer of the coil supporting and isolating insulating film and a working precision of an air bearing surface which is opposed to a magnetic recording medium with a very small space during the recording and reading. For the sake of simplicity, hereinafter the air bearing surface is called ABS. In the known hybrid type thin film magnetic head having the inductive element formed on the MR element, in order to obtain desired throat height MR height precisely corresponding to designed values, it is necessary to perform a mask alignment for the formation of the lowermost insulating layer with a minimum alignment error with respect to the already formed MR film. However, the MR film has very small thickness such as several hundreds Å and a pole portion of a relatively thick first magnetic film of the inductive element is formed on the MR film, a contour of the MR film could not be seen clearly during the mask alignment. Therefore, the precise mask alignment for the lowermost insulating layer could be carried out only with difficulty. It should be noted that the mask alignment for the lowermost insulating layer is also important for obtaining a desired throat height.
In order to mitigate the above problem of the mask alignment, an alignment pattern may be formed and the mask alignment may be performed with respect to this pattern. However, in this case, an alignment error of the alignment pattern is introduced, and thus the mask alignment for the lowermost insulating layer could not be carried out precisely. Furthermore, the manufacturing process becomes complicated and cost is increased.
Usually the thin film coil has a plurality of coil layers, and after a coil layer is formed, its insulating layer, e.g. photoresist is subjected to a heat treatment at a temperature of about 250° C. for forming a flat surface. This flat surface of the insulating layer is required for forming a next coil layer. During this heating process, the photoresist is softened or melt and its pattern size is varied largely. Moreover, when a patterning for forming a coil layer is conducted by milling, a pattern of the coil supporting and isolating insulating film constituting a positional reference for the MR element is etched again, and the retardation of pattern occurs. When such a variation of the pattern in the insulating layer occurs, even if the photomask for the photoresist is aligned precisely, a positional relationship of the photoresist with respect to the MR element might be changed. The variation of the photoresist pattern might amount to 0.5-0.6 &mgr;m when a thickness of the photoresist is large. Particularly, a hybrid type thin film magnetic head for high frequency has been required to have the throat height not longer than 1.00 &mgr;m. Therefore, it is necessary to control precisely the variation of the photoresist pattern in the order to sub-microns.
The known technique including a large variation in the photoresist pattern could not meet such a requirement, and many thin film magnetic heads whose inductive and/or magnetoresistive element have not desired properties are wasted after a polishing process for forming the ABS.
The known hybrid type thin film magnetic head has encountered another problem. Since after the MR film has been formed, a shield gap film is formed and then a first magnetic film of the inductive element is formed on the shield gap film, a pole portion of the first magnetic film could not have a flat surface due to the MR film and shield gap film. When a second magnetic film is formed on the first magnetic film via the writing gap film, the pole portion of the second magnetic film also could not have a flat surface. Such non-flat pole portions results in a degradation in a high frequency property of the inductive recording element. In order to avoid such a degradation, in the known manufacturing method, after forming the first magnetic film, a planarizing process is performed by a chemical-mechanical polishing (CMP) which has been known in the semiconductor device manufacturing technique. This planarizing process apparently increases the manufacturing cost and time.
In Japanese Patent Laid-open Publication Kokai Hei 3-263603, there is proposed a inverted or reversed type thin film magnetic head, in which a magnetoresistive reading element is formed on an inductive recording element. However, this-prior art publication does not teach a structure suitable for alignment between the MR element and the photoresist supporting the thin film coil, and does not disclose a useful technique for suppressing the variation of the photores
Koyanagi Tsutomu
Oyama Nobuya
Sasaki Yoshitaka
Yoshida Makoto
Letscher George J.
Oliff & Berridg,e PLC
TDK Corporation
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