Dynamic magnetic information storage or retrieval – Head – Core
Reexamination Certificate
1997-11-07
2003-06-17
Korzuch, William (Department: 2653)
Dynamic magnetic information storage or retrieval
Head
Core
Reexamination Certificate
active
06580583
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a thin-film magnetic head having a head face and a magnetic layer structure which is arranged on a semiconductor substrate which is provided with an integrated circuit. The invention also relates to a method of manufacturing such a magnetic head. In this method, a semiconductor substrate is provided with an integrated circuit, whereafter the layer structure is arranged on the semiconductor substrate and the head face is formed.
The magnetic layer structure may comprise a write element and/or a read element. In practice, a number of these elements will be formed in a side-by-side relationship on the semiconductor substrate. A thin-film magnetic head comprising a number of these elements enables a number of information tracks on a magnetic information carrier to be written or read simultaneously or successively. The integrated circuit can be used, for example, to enhance signals or to connect, successively and at desired points in time, said elements to a connection electrode.
In U.S. Pat. No. 5,506,737 a thin-film magnetic head of the type mentioned in the opening paragraph is disclosed, in which the semiconductor substrate is formed by a silicon wafer.
Integrated circuits can be formed in a relatively simple manner in the silicon wafer using known and customary techniques. It is practically impossible, however, to produce thin-film magnetic heads with a reproducible sensitivity on such a substrate. It has been found that magnetic heads which are provided on a silicon wafer exhibit properties which, both during writing and reading of information, can differ considerably from each other.
It is an object of the invention to obviate the above-mentioned drawback. To achieve this, the magnetic head mentioned in the opening paragraph is characterized in that the semiconductor substrate is secured to a carrier body by means of a securing layer. Such magnetic heads can be manufactured so as to have reproducible properties.
It has been found that magnetic heads on a silicon wafer cannot be fabricated so as to be reproducible because, owing to its relatively low rigidity, a silicon wafer can be subject to deformation during the manufacture of the magnetic head. As a result, magnetic layers provided on the substrate can also be subject to deformation during the manufacture of the magnetic head. Due to magnetostriction, these layers and hence also the magnetic head, exhibit properties which are influenced in an uncontrollable manner by this deformation. These properties manifest themselves as differences in sensitivity during reading of magnetic information and as differences in effectiveness during writing of magnetic information.
In the manufacture of the magnetic heads in accordance with the invention, the semiconductor substrate is first provided with an integrated circuit and then secured to a carrier body by means of a securing layer, whereafter the layer structure is formed on the exposed side of the semiconductor substrate facing away from the carrier body. Since the semiconductor substrate is secured to the carrier body prior to the formation of the layer structure, said deformation during the manufacture of the magnetic head is successfully counteracted by the rigidity of the carrier body.
Preferably, the integrated circuit is formed in the side of the semiconductor substrate facing the carrier body. By virtue thereof, the magnetic layer structure can be provided on a surface which, prior to the formation of the layer structure, can be processed in some way or other. For example, it may be subjected to a surface-grinding process or it may be provided with grooves. In practice, the side of the semiconductor substrate which is provided with the integrated circuit is not flat and exhibits some topography.
OBJECTS AND SUMMARY OF THE INVENTION
Further, a supporting body is secured to the layer structure by means of a second securing layer, with the head face intersecting the carrier body, the layer structure and this supporting body. Preferably, the carrier body and the supporting body are made of the same material. In this manner, a head face is formed past which a tape-shaped information carrier can be moved in a well-defined manner.
Preferably, the semiconductor substrate is secured, with the side provided with the integrated circuit, to the carrier body, whereafter, from the other side, a part of the thickness of the semiconductor substrate is removed. The integrated circuit can be provided in a silicon wafer. This wafer has a thickness of approximately 700 &mgr;m. After it has been secured to the carrier body, a very substantial part of the thickness of this wafer can be removed. The thickness can be reduced, for example, to approximately 20 &mgr;m. This enables the integrated circuit to be contacted in a simple manner via contact holes which are formed in this relatively thin semiconductor substrate. In this way, connections can be made in a simple manner between the integrated circuit, the layer structure and electrodes for external contact.
If the integrated circuit is formed in a top layer of the semiconductor substrate, which top layer is situated on a layer of an insulating material, and which substrate, after it has been secured to the carrier body, is etched away from the other side down to the layer of insulating material, then there remains a semiconductor substrate having a thickness below 1 &mgr;m. This enables the above-mentioned contact to be established even more readily.
If a head face is provided which intersects the carrier body, the semiconductor substrate, the layer structure and the supporting body, then the semiconductor substrate is exposed at the location of said head face. Silicon is a material with a low resistance to wear, so that during operation of the magnetic head, when a magnetic information carrier is fed past the head face of the magnetic head, this head face will wear relatively rapidly. This can be precluded by providing a wear-resistant layer between the semiconductor substrate and the head face. This can be achieved in a simple manner by replacing the semiconductor substrate at the location of the head face to be formed with a wear-resistant material prior to the formation of the layer structure, and by forming the head face in such a manner that it also intersects the wear-resistant material.
These and other aspects of the invention will be apparent from and elucidated with reference to the embodiments described hereinafter.
REFERENCES:
patent: 3987485 (1976-10-01), Sugaya et al.
patent: 4317147 (1982-02-01), Daughenbaugh et al.
patent: 4477853 (1984-10-01), Lemke
patent: 4516179 (1985-05-01), Imakoshi et al.
patent: 4809103 (1989-02-01), Lazzari
patent: 5506737 (1996-04-01), Lin et al.
patent: 5513057 (1996-04-01), Zieren et al.
patent: 5710683 (1998-01-01), Sundaram
Adelerhof Derk J.
Dekker Ronald
Maas Henricus G. R.
Gathman Laurie E.
Koninklijke Philips Electronics , N.V.
Korzuch William
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