METHOD OF MANUFACTURING A THIN-FILM MAGNETIC HEAD

Abstract: A method of manufacturing a thin-film magnetic head which is wear-resistant, on the one hand, but has only minimal transducing losses, on the other hand. A layer structure (3) is formed on a substrate (1), whereafter a wear-resistant material (9) is deposited on a surface constituted by a face of the substrate and a face of the layer structure. Before deposition of the wear-resistant material, the surface is selectively etched chemically, with the face of the substrate being moved backwards with respect to the face of the layer structure. After deposition of the wear-resistant material, wear-resistant material is removed from the face of the layer structure by means of a mechanical treatment, and a head face (10) is formed.

Description: Method of manufacturing a thin-film magnetic head. The invention relates to a method of manufacturing a thin-film magnetic head having a head face, in which method a layer structure is formed on a substrate, whereafter a wear-resistant material is deposited on a surface constituted by a face of the substrate and a face of the layer structure. The invention also relates to a method of manufacturing a thin-film magnetic head having a head face, in which method a layer structure is formed on a substrate, whereafter a protective body is provided on the layer structure, and subsequently a wear-resistant material is deposited on a surface constituted by a face of the substrate, a face of the layer structure and a face of the protective body. Such a method is known from GB-A 2 269 931. The known method starts from a substrate, particularly a ferrite substrate, on which a layer structure constituted by magnetic layers, electrically conducting layers and insulation layers is formed, in which method the structure is realized in such a way that flux guides, transducing elements and transducing gaps are formed in the layer structure. The layer structure is protected by a counterblock of a non-magnetic material. After formation of the assembly of substrate, layer structure and counterblock, a face is formed by grinding and/ or polishing, on which face Cr 2 O 3 is deposited for forming a wear-resistant layer constituting a contact face and having a thickness of between 10 and 100 nm. Although the layer formed gives the magnetic head sufficient protection against the abrasive action of magnetic media moving across the contact face during operation, the magnetic head has the drawback that the wear-resistant layer which is present renders the head-to-medium distance, measured at the most critical position, namely at the location of the layer structure, relatively large so that considerable losses of information transfer which are coherent with said distance may occur during use. It is an object of the invention to provide a method of the type described in the opening paragraph, with which magnetic heads can be manufactured which are wear- resistant, on the one hand, but have only minimal transducing losses, on the other hand. The method according to the invention, in which a layer structure is formed on a substrate, whereafter a wear-resistant material is deposited on a surface constituted by a face of the substrate and a face of the layer structure is therefore characterized in that, prior to depositing the wear-resistant material, the surface is selectively etched chemically, the face of the substrate being moved backwards with respect to the face of the layer structure, and subsequently, after deposition of the wear-resistant material, wear- resistant material is removed from the face of the layer structure by means of a mechanical treatment, and the head face is formed. The method according to the invention, in which a layer structure is formed on a substrate, whereafter a protective body is provided on the layer structure, and subsequently a wear-resistant material is deposited on a surface constituted by a face of the substrate, a face of the layer structure and a face of the protective body is therefore characterized in that, prior to depositing the wear-resistant material, the surface is selectively etched chemically, the face of the substrate and the face of the protective body being moved backwards with respect to the face of the layer structure, and subsequently, after deposition of the wear-resistant material, wear-resistant material is removed from the face of the layer structure by means of a mechanical treatment, and the head face is formed. During selective chemical etching, the face of the substrate and the face of the protective body, if any, are etched, but the face of the layer structure is not etched or etched only to a small extent so that, after etching, the layer structure projects at a head face side constituted by the surface with respect to the substrate and the protective body, if any. A non-magnetic material is preferably used as a wear-resistant material. Suitable, known materials are, for example, diamond-like carbon, CrN, CrO x and Cr 2 O 3 . A polishing and/or grinding treatment are examples of mechanical treatments. The mechanical treatment preferably includes lapping, such as band lapping, or polishing. A magnetic head obtained in accordance with one of the methods according to the invention has the advantage that the substrate and the protective body, if any, is, or are, protected adequately against wear during co-operation with a magnetic tape or magnetic disc without the protection used, i.e. the wear-resistant layer formed, necessarily leading to an increase of the head-to-medium distance. The transfer of information may therefore be equal to that of a magnetic head without a wear-resistant layer. In other words, the wear-protecting measure is not at the expense of loss of output of the magnetic head. For the sake of completeness, it is to be noted that the layer structure may comprise one or more write elements and/or one or more read elements, as well as one or more magnetic flux guides. Optimal results are achieved if, in the methods according to the invention. the wear-resistant material which is present on the face of the layer structure is removed completely. In this treatment, some material of the layer structure may also be removed. In the magnetic heads thus obtained, a magnetic information medium to be scanned and/or to be written directly bounds the layer structure during operation, so that transducing losses may be minimal. The methods according to the invention are eminently suitable for use with relatively soft substrate materials. For this reason, an embodiment is characterized in that the method starts from a substrate of a semiconductor material. The substrate is preferably provided with an integrated circuit. The semiconductor substrate is further preferably constituted by a silicon wafer. Integrated circuits may be formed, or may have been formed relatively easily in such a silicon wafer by means of known and conventional techniques. A silicon substrate can be chemically structured in a relatively easy manner, but such a substrate has the problem of a relatively small wear resistance. However, this problem is completely solved by using one of the methods according to the invention, in which the substrate is protected on the head face by a wear-resistant layer. If a protective body is used, it is preferred to use a body of a semiconductor material, particularly silicon. Because of the etching process, the substrate and the protective body are preferably made of one and the same material. When monocrystalline materials are used, the same crystal arrangement is preferably used for the same reason in the substrate and the protective body. The invention also relates to a magnetic head obtainable by means of one of the methods according to the invention. The magnetic head according to the invention is preferably implemented as defined in claim 8, 9 or 10. With reference to the claims, it is to be noted that various combinations of measures defined in the dependent method claims are possible. These and other aspects of the invention will be apparent from and elucidated with reference to the embodiments described hereinafter. In the drawings: Fig. 1 is a diagrammatic perspective view of an embodiment of an assembly of a substrate, a layer structure and a protective body, Fig. 2 is a diagrammatic perspective view of the assembly after performing a selective etching process, Fig. 3 is a diagrammatic perspective view of the assembly after performing the selective etching process and subsequently depositing wear-resistant material, Fig. 4 is a diagrammatic perspective view of an embodiment of a magnetic head according to the invention, and Fig. 5 is a diagrammatic cross-section of the embodiment of the magnetic head under operating conditions. An embodiment of the method according to the invention will be described with reference to Figs. 1 to 4. The method starts from a substrate 1 on which a layer structure 3 is formed, whereafter a counterblock or a protective body 5 is provided. The assembly thus formed is provided, for example, by means of polishing with a slightly curved surface 7 in this embodiment, constituting a head face side of the assembly. The surface 7 actually comprises a face la of the substrate 1 , a face 3a of the layer structure 3 and a face 5a of the protective body 5. The material of the substrate 1 and the protective body 5 is silicon in this embodiment. The layer structure 3 comprises layers of a magnetic material, such as SiO 2 or Al 2 O 3 , and layers of a ferromagnetic material such as an NiFe alloy or a CoZrNb alloy. When performing the method according to the invention, the surface 7 is etched by using a chemical etching process which is selective for silicon but does not attack or hardly attacks the materials of the layer structure 3. When the etching process is being performed, the faces la and 5a of the substrate 1 and the protective body 5, respectively, are therefore moved backwards with respect to the face 3 a of the layer structure 3. The resultant new faces are denoted by la' and 5a', respectively, in Fig. 2. Silicon may be selectively etched, for example, in a KOH solution, preferably after a short HF immersion in a solution for the purpose of removing an oxide layer which may be present. Another suitable possibility is the use of reactive ion etching in SF 6 . In one experiment, etching took place for 20 seconds in a 1 % HF solution and for 100 seconds in a KOH solution at 70°C. The layer structure was hardly etched, while the face of the substrate and the protective body had moved backwards through a distance of approximately 500 nm. An experiment in which reactive ion etching was used in an SF 6 plasma for 60 seconds yielded a result in which the face of the layer structure projected approximately 200 nm with respect to the face of the substrate and the protective body. In accordance with the method according to the invention, a wear-resistant material 9 such as CrN, CrO x or Cr 2 O 3 is deposited on the faces la', 3a and 5a' until a layer having a thickness of, for example, 50 or 100 nm is formed. Subsequently, the wear- resistant material 9 is removed from the face 3 a of the layer structure 3 by means of a mechanical treatment, for example a grinding and/or polishing treatment. During the mechanical treatment, a head face 10 is formed which actually comprises a face 1 la of a wear-resistant layer 11 formed on the substrate 1, a face 13a of the layer structure 3 and a face 15a of a wear-resistant layer 15 formed on the protective body 5. This face of the layer structure 3 mentioned here may be the face 3 a but may be alternatively a new face obtained during the mechanical treatment if material of the layer structure 3 itself is removed during said treatment. The faces 11a, 13a and 15a are preferably flush with each other, i.e. they merge steplessly. The embodiment of the magnetic head according to the invention, shown in Fig. 5, has a substrate 2, a layer structure 3 and a protective body 5. The layer structure 3 comprises a magnetoresistive element 101, possibly provided with equipotential strips, a bias winding 103 and a magnetic yoke comprising a first magnetic layer 105 and a second, interrupted magnetic layer 107a, 107b. The layers 105 and 107a, 107b are formed, for example, from an NiFe alloy or a CoZrNb alloy. The layer structure 3 has a plurality of insulation layers 109 of, for example, SiO 2 or Al 2 O 3 which are used for insulating the magnetoresistive element 101, the bias winding 103 and the magnetic yoke with respect to one another. The magnetic head according to the invention has a head face 10 which comprises a face 11a of a wear-resistant layer 11 present on the substrate 1, a face 13a of the layer structure 3 and a face 15a of a wear-resistant layer 15 present on the protective body 5. In the situation shown in Fig. 5, the magnetic head co-operates with a magnetic recording medium, in this example a magnetic tape 201 which is movable with respect to the magnetic head in a direction x. It is to be noted that the invention is not limited to the embodiments shown. For example, the layer structure may be implemented in many other ways than is shown in the Figures. Instead of only one magnetoresistive element, several of these elements may be used. The layer structure may be alternatively provided with inductive elements. Moreover, materials other than the ones mentioned may be used.

Claims: CLAIMS: 1. A method of manufacturing a thin-film magnetic head having a head face, in which method a layer structure is formed on a substrate, whereafter a wear-resistant material is deposited on a surface constituted by a face of the substrate and a face of the layer structure, characterized in that, prior to depositing the wear-resistant material, the surface is selectively etched chemically, the face of the substrate being moved backwards with respect to the face of the layer structure, and subsequently, after deposition of the wear- resistant material, wear-resistant material is removed from the face of the layer structure by means of a mechanical treatment, and the head face is formed. 2. A method of manufacturing a thin-film magnetic head having a head face, in which method a layer structure is formed on a substrate, whereafter a protective body is provided on the layer structure, and subsequently a wear-resistant material is deposited on a surface constituted by a face of the substrate, a face of the layer structure and a face of the protective body, characterized in that, prior to depositing the wear-resistant material, the surface is selectively etched chemically, the face of the substrate and the face of the protective body being moved backwards with respect to the face of the layer structure, and subsequently, after deposition of the wear-resistant material, wear-resistant material is removed from the face of the layer structure by means of a mechanical treatment, and the head face is formed. 3. A method as claimed in claim 1 or 2, characterized in that the wear- resistant material present on the face of the layer structure is removed completely. 4. A method as claimed in claim 1 or 2, characterized in that the method starts from a substrate of a semiconductor material. 5. A method as claimed in claim 2, characterized in that a protective body of a semiconductor material is used. 6. A method as claimed in claim 1 or 2, characterized in that a non-magnetic wear-resistant material is deposited. 7. A method as claimed in claim 1 or 2, characterized in that lapping or polishing is used during the mechanical treatment. 8. A magnetic head obtainable by means of a method as claimed in any one of the preceding claims. 9. A magnetic head as claimed in claim 8, having a head face and comprising a substrate provided with a layer structure, the head face comprising a face of a wear-resistant layer which is present on the substrate and adjoining the layer structure and a face of the layer structure, both faces being at least substantially flush with each other. 10. A magnetic head as claimed in claim 9, comprising a protective body, in which the layer structure extends between the substrate and the protective body, and the head face comprises a face of a wear-resistant layer which is present on the protective body and adjoins the layer structure, the last-mentioned face and the face of the layer structure being at least substantially flush with each other.

Inventors: ADELERHOF DERK J, ADELERHOF, DERK, J.
Applicants: KONINKL PHILIPS ELECTRONICS NV, KONINKLIJKE PHILIPS ELECTRONICS N.V.
Application year: 1999
Main classification: G11B5
IPC codes: G11B5