Metal working – Method of mechanical manufacture – Electrical device making
Patent
1979-08-03
1983-11-22
Hall, Carl E.
Metal working
Method of mechanical manufacture
Electrical device making
29602R, 360123, 360124, 427116, G11B 542, H01F 4104
Patent
active
044160569
DESCRIPTION:
BRIEF SUMMARY
DESCRIPTION
1. Technical Field
The present invention relates to a process for the preparation of film coils for use in, for example, thin-film magnetic heads, utilizing the technique of photolithography, and more particularly, the invention relates to a process for the preparation of a flattened multi-layer, multi-winding conductor coil.
2. Background Art
In forming a multi-layer pattern structure on the surface of a semiconductor in the field of semiconductor integrated circuits, there has heretofore been adopted a method in which patterns of respective layers are laminated in sequence from a lower layer to a higher layer according to the ordinary photolithographic technique. In this method, if a layer is not a flat but includes convexities and concavities, corresponding convexities and concavities are formed in the layers laminated thereon. Accordingly, the flatness of the topmost layer is influenced by the convexities and concavities of all the layers and, even if the convexities and concavities of the respective layers are small, the flatness of the topmost layer is considerably degraded. When another pattern layer is formed on a certain layer through a photomask, the presence of such convexities and concavities results in a non-uniformity of the gap between the photomask and the layer surface, and therefore, the precision of the pattern is drastically lowered.
This problem of degradation of the flatness has a close relationship to the subject matter of the present invention. Accordingly, this problem will now be described in detail by reference to the case of a film coil for use in a thin-film magnetic head.
In a conventional thin-film magnetic head, as illustrated in FIG. 1, a lower magnetic layer 2 is formed on a substrate 1, and an upper magnetic layer 4 is formed thereon. A coil 3 is interposed between the layers 2 and 4. Further, a gap 5 for generating a leakage magnetic field for writing and reading is formed between these magnetic layers 2 and 4. In principle, as illustrated in FIG. 2, such a coil 3 is formed by forming a first layer conductor pattern 6 having a spiral shape according to the photolithographic technique, piling a second layer conductor pattern 7 on the first layer conductor pattern 6 with the interposition of insulating layer therebetween, not illustrated in the drawing, connecting one of the ends of these conductor patterns to each other by means of a conductor exposing window 8 formed by etching the insulating layer on the lower layer pattern 6, and forming conductor exposing windows 6A and 7A for connection of a cable on the other ends of the conductor patterns 6 and 7.
Similar procedures to those described above are repeated according to the number of conductor layers to be laminated, and as the number of conductor layers to be laminated is increased, the number of lower layer conductor exposing windows should be increased. More specifically, in case of an n-layer structure, (n-1) windows should be formed. Accordingly, the number of steps in the forming operation is increased and the efficiency of the operation is reduced. Further, when the first conductor layer 6 is formed and the second conductor layer 7 is formed thereon with the interposition of the insulating layer therebetween, a stepped portion is formed between the portion where the second layer conductor 7 is piled on the first layer conductor 6 and the portion where the second layer conductor 7 is not piled on the first layer conductor 6. More specifically, a stepped portion is formed in an area 9 where the first layer conductor 6 does not exist (such area is inevitably present) when the second layer conductor 7 is formed.
Ordinarily, in photolithography, if there is present a stepped portion, the thickness of the resulting resist film in this portion is different from the thickness in the other portion, and as is well-known, a stress imposed on the conductor film in such stepped portion causes various troubles in formation of the pattern. For example, if the thickness of the film conductor pattern 7 formed in the
REFERENCES:
patent: 3685144 (1972-08-01), Trimble
patent: 3798059 (1974-03-01), Astle et al.
Fujitsu Limited
Hall Carl E.
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