JP2005063656A - Substrate for thin-film magnetic head and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a substrate for thin-film magnetic heads that is excellent in thermal conductivity and electric insulation properties. <P>SOLUTION: The substrate for thin-film magnetic heads comprises a ceramic substrate 1; an undercoat film 3 made of an aluminum oxide; and an intermediate layer that is sandwiched by the ceramic substrate 1 and the undercoat film 3 and is made of metal. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a thin film magnetic head substrate used for a thin film magnetic head slider of a hard disk drive device and a method for manufacturing the same.

  In recent years, with the development of the communication / information technology field, the amount of information that can be handled by a computer has increased dramatically. In particular, information such as voice, music, and images that can be handled only as an analog signal in the past can be converted into a digital signal and processed by a personal computer. Since such multimedia data such as music and images contain a lot of information, it is required to increase the capacity of an information recording device used for a personal computer or the like.

  The hard disk drive device is a typical information recording device conventionally used in personal computers and the like. In order to meet the above-described requirements, it is required to increase the capacity of the hard disk drive and reduce the size of the apparatus. In addition, hard disk recorders that record images directly on a hard disk drive and audio players that record music on a hard disk drive have become widespread. Even in such devices, it is required to reduce the size of the hard disk drive in order to increase the capacity and improve the portability.

  FIG. 7 schematically shows a cross section of a thin film magnetic head slider portion of a conventional hard disk drive device. As shown in the drawing, an undercoat film 13 is formed on the side surface of the substrate 12 held by the gimbal 10. On the undercoat film 13, a reading element 16 that is a reproducing head is provided, and a writing element 14 that is a recording head is provided adjacent to the reading element 16. Usually, a unit including the substrate 12, the writing element 14, and the reading element 16 held by the gimbal 10 is called a head slider or simply a slider.

  The write element 14 is made of a magnetic material. A coil 15 is wound inside the ring, and when a recording signal is applied to the coil 15, a magnetic field is generated in the writing element 14 and data is written in the magnetic recording medium 17.

  On the other hand, the reading element 16 as a reproducing head is a magnetoresistive effect element (MR or GMR) that converts a change in magnetic field into a change in electrical resistance, and reads the change in magnetism recorded on the magnetic recording medium 17. , Convert to electrical signal.

The substrate 12 that holds the writing element 14 and the reading element 16 is conventionally formed of an Al ₂ O ₃ —TiC ceramic sintered body. This is because Al ₂ O ₃ —TiC (hereinafter abbreviated as “AlTiC”) is excellent in balance in terms of thermal characteristics, mechanical characteristics, and workability. However, since AlTiC is an electrically good conductor, if the read / write element 14 ′ and the write element 14 are arranged in contact with such a conductor, the read element 16 and the write element 14 are short-circuited and operate correctly. do not do. Further, the substrate made of AlTiC had pores on the surface, and the surface smoothness was not so good. Therefore, an undercoat film 13 formed of Al ₂ O _{3 is} formed on the substrate 12 in order to increase the insulation between the reading element 16 or the writing element 14 and the substrate 12 and to make the surface of the substrate 12 smooth. It is provided on the side. This is because Al ₂ O ₃ has excellent insulating characteristics and excellent surface smoothness.

  However, such a conventional slider has various problems to be solved.

  First, as miniaturization of the hard disk drive device is required, it is necessary to reduce the size of the slider. For this purpose, as shown in FIG. 7B, the area occupied by the coil 15 of the write element 14 must be reduced. More specifically, the inner diameter of the coil 15 must be reduced, and the windings should not overlap as much as possible. However, if the area of the coil is reduced in this way, the amount of heat generated per unit area increases when a current flows through the coil 15 via the terminal 18.

However, Al ₂ O ₃ that has been conventionally used for the undercoat film 13 does not have a good thermal conductivity. For this reason, the heat generated by applying a signal to the coil 15 is blocked by the undercoat film 13 made of Al ₂ O ₃ and is not sufficiently diffused to the substrate 12, and is accumulated in the reading element 16 and the writing element 14. End up. As a result, the reading element 16 and the writing element 14 expand due to heat, and jump out toward the magnetic recording medium 17 as indicated by arrows in FIG. Since the distance between the reading element 16 and the writing element 14 and the magnetic recording medium 17 is only about 10 nm, the expanded reading element 16 and writing element 14 come into contact with the magnetic recording medium 17.

  This problem is called TPTR (Thermal Pole Tip Recession), and the magnetic recording medium is damaged by the physical contact between the reading element 16 or the writing element 14 and the magnetic recording medium, or the reading element 16 or the writing element 14 is damaged. It will destroy itself. As a result, it causes a serious failure that the hard disk drive device does not function.

  Even when the reading element 16 and the writing element 14 are not in contact with the magnetic recording medium 17, the distance between the magnetic recording medium 17 and the reading element 16 and the writing element 14 due to thermal expansion of the reading element 16 and the writing element 14. Will change. For example, when the reading element 16 and the writing element 14 expand several nanometers, the distance between the magnetic recording medium 17 and the reading element 16 and the writing element 14 changes by 10% or more. For this reason, writing characteristics and reading characteristics are greatly changed, and there is a possibility that an error occurs in a signal written to the magnetic recording medium or a signal read from the magnetic recording medium.

  In order to solve this problem, it is conceivable to reduce the thickness of the undercoat film 13 so that heat can be easily released to the substrate 12. However, in this case, electrostatic breakdown due to static electricity and a decrease in withstand voltage occur as new problems.

Specifically, in the hard disk drive device, the magnetic recording medium rotates at high speed, so that static electricity is easily generated. For this reason, static electricity is accumulated in the reading element 16 and the writing element 14 formed on the undercoat film 13 made of Al ₂ O ₃ having high electrical insulation. At this time, if the thickness of the undercoat film 13 is small, the accumulated static electricity tends to be discharged to the substrate 12 adjacent to the undercoat film 13. As a result, breakdown of the undercoat film 13 and destruction of the reading element 16 and the writing element 14 occur. Further, if the thickness of the undercoat film 13 is small, even if the dielectric breakdown does not occur, the insulation property of the undercoat film 13 is reduced and the leakage current is increased. As a result, the reading element 16 and the writing element 14 do not operate correctly.

  In order to solve these problems, Patent Document 1 forms a conventional undercoat film 13 on a substrate 12 and further forms a film made of amorphous alumina having a thickness of 100 to 55000 nm formed thereon by ECR sputtering. It is disclosed. According to Patent Document 1, since an amorphous alumina film formed by ECR sputtering is dense, it is disclosed that excellent voltage resistance can be obtained by this structure.

However, in order to obtain such a structure, it is necessary to use an ECR sputtering apparatus, and it is necessary to use an apparatus different from the conventional apparatus in which the undercoat film 13 is formed. For this reason, there has been a problem that the cost of manufacturing the substrate is remarkably increased.
JP-A-11-283221 Japanese Patent No. 1899891 US Pat. No. 4,769,127 Japanese Patent No. 1659501 U.S. Pat. No. 4,814,915 JP 2000-260999 A

  The present invention has been made in order to solve the above-mentioned problems, and the object of the present invention is to prevent the occurrence of the above-mentioned problems and improve the reliability of the apparatus in a small-sized and high recording density hard disk drive apparatus. Provided are a substrate for a thin film magnetic head suitably used and a method for manufacturing the same.

  A thin film magnetic head substrate of the present invention comprises a ceramic substrate, an undercoat film made of aluminum oxide, and an intermediate layer made of a material other than aluminum oxide, sandwiched between the ceramic substrate and the undercoat film. I have.

  In a preferred embodiment, the intermediate layer is made of a material other than an Al—Ti—O compound.

  In a preferred embodiment, the thickness of the intermediate layer has a value in the range of 1 nm to 1 μm.

  In a preferred embodiment, the intermediate layer is made of metal or Si.

  In a preferred embodiment, the intermediate layer is any one of Cu, Cr, Si, an alloy containing Cu, an alloy containing Cr, or a compound containing Si.

  In a preferred embodiment, the thickness of the undercoat film is a value in the range of 50 nm to 0.4 μm.

In a preferred embodiment, the ceramic substrate is made of an alumina-based ceramic material containing 24-75 mol% α-Al ₂ O ₃ and 2 mol% or less of an additive.

  In a preferred embodiment, the ceramic substrate further includes a metal carbide or a metal carbonitride.

  A thin film magnetic head slider of the present invention includes any one of the above thin film magnetic head substrates, and a writing element and a reading element held on the thin film magnetic head substrate.

  A hard disk drive device of the present invention includes the thin film magnetic head slider.

  The method for manufacturing a thin film magnetic head substrate of the present invention includes a step of forming an intermediate layer made of a material other than aluminum oxide on a ceramic substrate by a sputtering method, and an aluminum oxide by sputtering on the intermediate layer. Forming an undercoat film comprising:

  In a preferred embodiment, the step of forming the intermediate layer is performed by a sputtering method without applying a bias.

  In a preferred embodiment, the step of forming the undercoat film is performed by a sputtering method to which a bias is applied.

  In a preferred embodiment, the intermediate layer is formed by sputtering using a metal element as a target.

  A method of manufacturing a thin film magnetic head slider according to the present invention includes a step of preparing any one of the above thin film magnetic head substrates comprising a ceramic substrate, an intermediate layer, and an undercoat film, and a writing element on the undercoat film. And arranging the reading element.

  According to the present invention, by forming the intermediate layer, the surface of the substrate on which the undercoat film is formed is made uniform, or part of the aluminum oxide formed as the undercoat film is not changed into a conductive compound. can do. Therefore, even if the undercoat film is thin, the undercoat film exhibits excellent electrical insulation, and a thin film magnetic head substrate having excellent electrostatic breakdown resistance, thermal conductivity, and electrical insulation can be obtained.

  As a result of examining the conventional thin film magnetic head substrate in detail, the inventors of the present application reduced the thickness of the undercoat film made of aluminum oxide. It has been found that the electrical insulation characteristics actually provided are getting worse. There are two possible reasons for this.

  In general, a ceramic substrate such as AlTiC is a mixture of an insulator and a conductor, and an insulating region and a conductive region exist on the surface of the ceramic substrate. For this reason, when an undercoat film is formed on a ceramic substrate by sputtering or the like, the surface of the substrate is not uniform, so the plasma is locally unstable or non-uniform, and in the vicinity of the substrate interface of the formed undercoat film The uniformity of the structure and composition is reduced, or defects are generated near the substrate interface.

  Such non-uniform structure and composition or defects in the film are eliminated as the undercoat film becomes thicker. However, when the undercoat film is thin, the structure or composition is non-uniform or defects in the film remain. It is conceivable that the electrical insulation characteristics deteriorate.

Further, when a cross section of a conventional thin film magnetic head substrate was observed, an Al—Ti—O compound layer of about 0.1 μm was found on the undercoat film side from the interface between the AlTiC substrate and the undercoat film made of aluminum oxide. Was formed. Since the Al—Ti—O compound is a conductor having a volume resistivity of about 1 × 10 ⁻⁴ to 1 × 10 ⁴ Ω · cm, the formation of the layer of the Al—Ti—O compound results in the actual undercoat film. Is a value obtained by subtracting the thickness of the Al—Ti—O compound layer from the apparent thickness of the formed undercoat film. That is, it is considered that the thickness of the undercoat film is smaller than it appears due to the formation of the conductive layer.

  Therefore, by making the surface of the substrate on which the undercoat film is formed uniform and preventing a part of the aluminum oxide formed as the undercoat film from being changed into a conductive alteration layer such as an Al-Ti-O compound, A substrate for a thin film magnetic head having high insulation can be obtained.

  Hereinafter, an example of the thin film magnetic head substrate of the present invention will be described. As shown in FIG. 1, the thin film magnetic head substrate according to the present embodiment includes a ceramic substrate 1, an undercoat film 3, and an intermediate layer 2 sandwiched between the ceramic substrate 1 and the undercoat film 3.

The ceramic constituting the ceramic substrate 1 preferably has a volume resistivity in a range where static electricity does not accumulate in order to prevent electrostatic breakdown. Specifically, the volume resistivity is preferably 1 × 10 ⁹ Ω · cm or less. This value is also the upper limit value of the volume resistivity of a material called a semiconductive material. On the other hand, from the viewpoint that static electricity hardly accumulates, the volume resistivity of ceramics is preferably as low as possible. However, if the volume resistivity is too low, the ceramic becomes metal-bonding, the cutting resistance is high, and the tribological properties are deteriorated. Therefore, the volume resistivity is preferably 1 × 10 ⁻⁵ Ω · cm or more. For the above reasons, the volume resistivity of the ceramic substrate is preferably in the range of 1 × 10 ⁻⁵ to 1 × 10 ⁹ Ω · cm.

  The ceramic substrate 1 is preferably composed of a material having high thermal conductivity. In order to efficiently diffuse into the ceramic substrate 1 through the undercoat film 3 and the intermediate layer 2 without accumulating heat generated in the reading element and the writing element, the thermal conductivity may be 5 W / mK or more. Preferably, it is 15 W / mK or more.

  Further, if the surface roughness of the ceramic substrate 1 is rough, the surface roughness of the undercoat film 3 becomes rough, and the surface roughness of the undercoat film 3 cannot be set within a predetermined range described later in the polishing process. Therefore, before the formation of the intermediate layer 2, the average roughness (Ra) of the surface of the ceramic substrate 1 is preferably 2.5 nm or less.

As long as the ceramic has the above-described characteristics, ceramics having various compositions can be used as the material of the ceramic substrate 1, and in particular, by using a substrate made of composite ceramics of two or more systems having different conductivity or insulation. The remarkable effect of the present invention can be obtained. For example, the ceramic substrate 1 may include 24-75 mol% α-Al ₂ O ₃ , and the balance may be composed of a metal carbide or carbonitride and 2 mol% or less of a sintering aid. The substrate material having the above-described composition is suitable as a substrate used for a thin film magnetic head slider because it has very few opening pores and can be finished with high precision surface roughness. In particular, a substrate made of ceramics containing Al ₂ O ₃ having the above composition ratio, 24-75 mol% TiC and 2 mol% or less of a sintering aid is suitably used for a thin film magnetic head slider.

In addition to the above, ceramic substrates that can be used in the present invention include substrates using SiC-Al ₂ O ₃ -based ceramic materials disclosed in Patent Document 2 and Patent Document 3, Patent Document 4 and Patent Document 5, and the like. A substrate using the disclosed ZrO ₂ —Al ₂ O ₃ ceramic material, a substrate using a ZrO ₂ —SiC ceramic material well known as a conductive ceramic material, and the like can also be used. However, materials that are difficult to process such as silicon carbide and have poor tribological properties are not suitable for the ceramic substrate 1.

  As described above, the intermediate layer 2 makes the surface of the substrate on which the undercoat film 3 is formed uniform, and prevents a part of the undercoat film 3 from reacting with the ceramic substrate 1 and changing into a conductive compound. In order to do so, it is formed on the ceramic substrate 1. Therefore, it is preferable that the intermediate layer 2 has a uniform composition and can cover the entire surface of the ceramic substrate 1 so that the surface state of the ceramic substrate 1 can be made uniform. Moreover, it is preferable that the intermediate | middle layer 2 is formed with the material excellent in heat conductivity and adhesiveness.

  Specifically, if the surface roughness of the ceramic substrate 1 and the conditions for forming the intermediate layer are appropriately selected, the entire surface of the ceramic substrate 1 can be uniformly covered with the intermediate layer having a thickness of 1 nm or more. . Moreover, if the thickness of the intermediate layer 2 is 3 nm or more, the entire surface of the ceramic substrate 1 can be more reliably covered uniformly. However, if the intermediate layer 2 is thinner than 1 nm, it is difficult to cover the entire surface of the ceramic substrate 1, and the surface of the ceramic substrate 1 is likely to be exposed. For this reason, when the undercoat film 3 is formed, the state of the plasma near the base on which the undercoat film 3 is formed becomes non-uniform, and there is a possibility that the same problem as in the conventional case occurs.

  On the other hand, as long as the surface of the substrate on which the undercoat film 3 is formed can be made uniform, the effect of the present invention can be obtained even if the intermediate layer 2 is thickened. However, if the thickness of the intermediate layer 2 exceeds 100 nm, it takes time to form the intermediate layer 2 and the productivity of the thin film magnetic head substrate decreases. On the other hand, if the thickness of the intermediate layer 2 exceeds 1 μm, the cross-sectional area of the intermediate layer 2 exposed on the ABS surface increases when the slider is configured, and the gap between the ceramic substrate 1 and the undercoat film 3 and the intermediate layer 2 is increased. Due to the difference in coefficient of thermal expansion and the difference in hardness, large steps are likely to occur on the ABS surface. For these reasons, the intermediate layer 2 preferably has a thickness of 1 nm or more and 1 μm or less, and more preferably has a thickness of 3 nm or more and 100 nm or less.

As the intermediate layer 2 having such characteristics, it is preferable to use a film or layer made of metal or silicon. In particular, since the adhesion and thermal conductivity are excellent, it is preferable that the intermediate layer 2 is formed from an alloy containing Cu, Cr, Si, Cu, an alloy containing Cr, or a compound containing Si. As other metals, Ni, Au, Ag, Fe, Co, and Ti can be used for the intermediate layer 2. Examples of substances that can be used as the intermediate layer 2 other than metal include SiC and SiO ₂ . As a result of detailed experiments, it was found that even when Ti was used as the intermediate layer 2, a conductive altered layer was not formed in the undercoat film 3. This seems to be because the reactivity of Ti in the AlTiC substrate and Ti in the Ti film with respect to aluminum oxide is different.

  Since aluminum oxide generally has poor adhesion, it is not preferable to use aluminum oxide as the intermediate layer 2. In addition, a layer made of an Al—Ti—O compound generated as an altered layer in an undercoat film made of aluminum oxide, or a surface modification made of Al—Ti—O used for improving adhesion in Patent Document 6. It is not preferable to use an Al—Ti—O compound as the intermediate layer 2 such as a layer. This is because, since titanium or titanium oxide is contained, a conductive altered layer may be formed in the undercoat film 3 when these are diffused or mixed into the undercoat film 3.

  For the formation of the intermediate layer 2, it is preferable to use a sputtering method without applying a bias. In this specification, the bias in the sputtering method refers to a voltage for accelerating ions and particles to such an extent that the ions and particles in the chamber collide with the substrate for film formation and the surface of the substrate can be sputtered. Therefore, the condition of “no bias applied” is that particles constituting the substrate are knocked out from the surface of the substrate, and the particles and atoms constituting the substrate are substantially included in the film formed on the substrate. This includes the case of applying a voltage for accelerating ions and particles to such an extent that

  When a bias is applied to the formation of the intermediate layer 2, ions and particles accelerated by the sputtering bias collide with the substrate. Then, particles and atoms constituting the ceramic substrate 1 are knocked out and attached to the target, and the attached particles and atoms are deposited as an intermediate layer 2 by sputtering together with a substance constituting the target, whereby the ceramic substrate 1 is formed. Constructed particles and atoms are included in the intermediate layer 2. For this reason, when the substance which comprises the ceramic substrate 1 reacts with the substance which comprises the undercoat film | membrane 3, and forms what forms a conductive alteration layer, the intermediate | middle layer 2 does not contain such a substance. In both cases, a conductive altered layer may be formed in the undercoat film 3.

  The undercoat film 3 is made of an amorphous aluminum oxide. In order to have an insulating characteristic that indicates a predetermined withstand voltage or more, the undercoat film 3 preferably has a thickness of at least 10 nm. In addition, the undercoat film 3 may have a thickness of 1 μm or less in order to quickly conduct heat generated by the writing element and reading element formed on the undercoat film 3 to the ceramic substrate 1 side. preferable. When the thickness of the undercoat film 3 is 0.4 μm or less, the effect of providing the intermediate layer 2 is remarkable as described in the following examples.

  In general, since aluminum oxide does not have sufficient adhesion, the undercoat film 3 is preferably formed by a sputtering method to which a bias is applied. As described above, the atoms constituting the intermediate layer 2 are selected so as not to form a conductive altered layer in the undercoat film 3 even if diffused or mixed into the undercoat film 3. For this reason, even if atoms constituting the intermediate layer 2 are mixed or diffused into the undercoat film 3 by the sputtering method to which a bias is applied, a conductive deteriorated layer does not occur.

  According to the thin film magnetic head substrate having such a structure, the composition and structure of the undercoat film to be formed are uniform, and the conductive alteration layer does not occur in the undercoat film. Even when thin, it exhibits excellent electrical insulation properties. Therefore, it is possible to realize a thin film magnetic head substrate that maintains excellent electrical insulation characteristics while improving thermal conductivity by thinning the undercoat film. In particular, a thin-film magnetic head substrate using a metal layer as an intermediate layer is based on a completely new concept that is not found in the prior art in that a metal layer is used to enhance insulation.

  Hereinafter, examples in which a substrate for a thin film magnetic head was produced and electrical insulation characteristics were measured will be described.

On the AlTiC substrate 1 containing 70 vol% α-Al ₂ O ₃ and 30 vol% TiC, intermediate layers 2 made of Cr, Cu, and Si having various thicknesses were formed by sputtering without applying a bias. Thereafter, an undercoat film 3 made of aluminum oxide having various thicknesses was formed. The undercoat film 3 was formed by sputtering using an Al ₂ O ₃ target while applying a bias voltage.

  As a comparative example, a sample prepared using the same conditions except that the intermediate layer 2 was not formed was prepared.

  In order to evaluate the sample, the withstand voltage of the prepared sample was measured. An AlCu film having a thickness of 1 μm was formed on the undercoat film 3 of each sample, and a resist pattern in which 240 μm square patterns were formed at intervals of 240 μm was formed on the AlCu film. Thereafter, using the resist pattern as a mask, the AlCu film, the undercoat film 3 and the intermediate layer 2 were removed by wet etching, and the resist was peeled off.

  After measuring the thickness of the undercoat film 3 at the portion where the withstand voltage is measured by Nanospec 6100 manufactured by Nanometrics, it was connected to one end of a microammeter 34 (R8340 manufactured by Advantest) as shown in FIG. Each sample 32 was adsorbed on the stage 31, and the probe 33 connected to the other end of the microammeter 34 was brought into contact with the AlCu pattern. The applied voltage was increased from 0V to 100V at a time, and the flowing current was measured. When a current of 100 μA or more flows, it was determined that dielectric breakdown had occurred, and the voltage at that time was taken as the withstand voltage.

  FIG. 3 is a graph plotting the withstand voltage value with respect to the thickness of the intermediate layer 2 made of Cr. The thickness of the undercoat film 3 is 0.2 μm, and the withstand voltage is indicated by a value divided by the thickness of the undercoat film. As shown in FIG. 3, when the intermediate layer 2 is not formed (thickness is 0 nm), the withstand voltage is 10 MV / cm, but when the intermediate layer 2 of 3 nm is provided, the withstand voltage is 17 MV / cm. It has improved to cm. If the thickness of the intermediate layer 2 is 3 nm or more, the withstand voltage value is substantially constant. From this, it can be seen that if the surface of the ceramic substrate 3 can be covered almost completely, the withstand voltage can be improved regardless of the thickness of the intermediate layer 2.

  FIG. 4 is a graph plotting the withstand voltage value with respect to the thickness of the undercoat film. The intermediate layer is made of Si, Cr, or Cu, and a metal film having a thickness of 30 nm is used. The withstand voltage is indicated by a value divided by the thickness of the undercoat film. Further, the withstand voltage when the undercoat film is formed without providing the intermediate layer is also shown. As shown in the figure, when the intermediate layer is not provided and the thickness of the undercoat film is 0.3 μm or less, the withstand voltage is deteriorated. On the other hand, when the intermediate layer is provided, a withstand voltage of about 14.5 MV / cm is shown regardless of the thickness of the undercoat film. That is, when the intermediate layer is provided, the withstand voltage per unit thickness of the undercoat film is equal, and the undercoat film shows a withstand voltage value calculated from the thickness.

The withstand voltage value of the undercoat film when the intermediate layer is formed and the withstand voltage value of the under film without the intermediate layer coincide with each other when the thickness of the undercoat film is about 0.4 μm.
This is because, even if a conductive Al—Ti—O compound is generated in the conventional structure, if the undercoat film 3 becomes sufficiently thick, the influence of the conductive Al—Ti—O compound. Because it becomes possible to ignore. Therefore, it can be said that the effect of improving the electrical insulation characteristics by providing the intermediate layer 2 is remarkable when the thickness of the undercoat film 3 is in the range of 10 nm to 0.4 μm.

  FIG. 5 is a graph plotting leakage current against applied voltage when the thickness of the undercoat film 3 is 0.15 μm. In FIG. 5, the applied voltage is indicated by a bias electric field divided by the thickness of the undercoat film 3. As shown in FIG. 5, in the sample according to the present invention having the intermediate layer 2, as the bias electric field increases, the leakage current increases monotonously, and the dielectric breakdown occurs when the bias electric field becomes about 8.5 MV / cm. Has occurred. On the other hand, in the case of the comparative sample not having the intermediate layer 2, the leakage current increases rapidly as the bias electric field increases, and dielectric breakdown occurs when the bias electric field reaches about 6 MV / cm. The leakage current immediately before dielectric breakdown occurs is about 1 nA in the case of the sample according to the present invention having the intermediate layer 2, whereas it is about 10 mA in the case of the comparative sample not having the intermediate layer 2. That is, it can be seen that the comparative sample without the intermediate layer 2 has increased leakage current before dielectric breakdown, and does not cause dielectric breakdown, but has deteriorated electrical insulation characteristics. On the other hand, it can be seen that the sample according to the present invention having the intermediate layer 2 maintains good electrical insulation characteristics until dielectric breakdown occurs.

Hereinafter, an example of an embodiment of a thin film magnetic head slider according to the present invention will be described.

  FIG. 6 is a perspective view showing the main part of the thin film magnetic head slider 80. Although the gimbal of the thin film magnetic head slider 80 is not shown in FIG. 6, the main part shown in FIG. 6 is attached to the gimbal as in FIG.

  The thin film magnetic head slider 80 includes a ceramic substrate 1, an intermediate layer 2 deposited on the ceramic substrate 1, an undercoat film 3 deposited on the intermediate layer 2, and a shield film 85 deposited on the undercoat film 3. And. In this embodiment, a Cr film having a thickness of 10 nm is formed as the intermediate layer 2, and an aluminum oxide having a thickness of 1 μm is deposited as the undercoat film 3.

  A gap 86 of about 0.4 μm is provided on the shield film 85, and a reproducing GMR element 87 is arranged in the gap 86. The GMR element 87 has a known configuration including an electrode (not shown) and a GMR film. The gap 86 is formed of an insulating film such as alumina deposited on the shield film 85 so as to cover the GMR element 87. The thickness of the GMR element 87 is, for example, about 0.1 μm. The magnetic element (reproducing element) formed on the shield film 85 is not limited to the GMR element. Other types of elements such as MR elements and TMR elements may be used.

  A shield film 88 is deposited on the insulating film functioning as the gap 86. The shield films 85 and 88 are made of a soft magnetic material such as permalloy, for example, and also function as a magnetic shield film. A top pole (thickness: 2 to 3 μm) 90 is formed on the shield film 88 via a write gap 89 of 0.4 to 0.6 μm. Between the shield film 88 and the top pole 90, a coil pattern 91 formed by patterning a Cu film having a thickness of about 5 μm is provided. The periphery of the coil pattern 91 is covered with an organic insulating film. The recording head portion is constituted by the bottom pole 88, the coil pattern 91, the top pole 90, and the like. By energizing the coil pattern 91, a magnetic field is formed in the vicinity of the write gap 89, and data is written (recorded) on a recording medium (not shown). The recording head portion is covered with an overcoat 92 (thickness: 40 μm, for example).

  As the thin film magnetic head slider 80, for example, a wafer-shaped thin film magnetic head substrate in which the intermediate layer 2 and the undercoat film 3 are formed on the ceramic substrate 1 is prepared, and the shield film 85 to the overcoat 92 are formed on this substrate. The structure is formed using conventional thin film deposition techniques or lithography techniques. Thereafter, the substrate is divided into chips, and the head portion shown in FIG. 7 is completed. Then, an ABS (Air Bearing Surface) is processed and attached to the gimbal to complete the thin film magnetic head slider.

  According to the present embodiment, since the intermediate layer 2 is formed, excellent electrical insulation can be maintained even if the thickness of the undercoat film 3 is 1 μm and the thermal conductivity is improved. For this reason, TPTR due to heat generated from the writing element can be prevented by excellent heat dissipation, and electrostatic breakdown and dielectric breakdown of the thin film magnetic head slider can also be prevented. Therefore, it is possible to make the thin film magnetic head slider smaller.

  Since the thin film magnetic head substrate of the present invention is excellent in thermal conductivity and electrical insulation, it can be suitably used for a highly reliable thin film magnetic head slider and high density recording hard disk drive.

It is sectional drawing which shows the structure of the board | substrate for thin film magnetic heads by this invention. It is a schematic diagram which shows the structure of the apparatus for measuring a withstand voltage. It is a graph which shows the relationship of withstand voltage with respect to the thickness of an intermediate | middle layer. It is a graph which shows the relationship of withstand voltage with respect to the thickness of an undercoat film. It is a graph which shows the relationship between a bias electric field and leakage current. It is a perspective view which shows the principal part of the thin film magnetic head slider of this invention. (A) is sectional drawing which shows the structure of the conventional thin film magnetic head slider typically, (b) is a top view which shows typically the shape of a writing element.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,12 Ceramic substrate 2 Intermediate layer 3, 13 Undercoat film 14 Writing element 16 Reading element

Claims (15)

  A thin film magnetic head substrate comprising: a ceramic substrate; an undercoat film made of aluminum oxide; and an intermediate layer made of a material other than aluminum oxide and sandwiched between the ceramic substrate and the undercoat film.   The thin film magnetic head substrate according to claim 1, wherein the intermediate layer is made of a material other than an Al—Ti—O compound.   3. The thin film magnetic head substrate according to claim 1, wherein the thickness of the intermediate layer is a value in the range of 1 nm to 1 μm.   4. The thin film magnetic head substrate according to claim 1, wherein the intermediate layer is made of metal or Si.   4. The thin film magnetic head substrate according to claim 1, wherein the intermediate layer is any one of Cu, Cr, Si, an alloy containing Cu, an alloy containing Cr, or a compound containing Si.   6. The thin film magnetic head substrate according to claim 1, wherein the thickness of the undercoat film is a value in the range of 10 nm to 0.4 μm. The ceramic substrate, 24~75mol% of alpha-Al ₂ and O _3, the substrate for a thin film magnetic head according to any one of claims 1 to 6 made of alumina-based ceramic material containing 2 mol% or less of the additives.   The thin film magnetic head substrate according to claim 7, wherein the ceramic substrate further contains a metal carbide or a metal carbonitride.   9. A thin film magnetic head slider comprising: the thin film magnetic head substrate according to claim 1; and a writing element and a reading element held on the thin film magnetic head substrate.   A hard disk drive device comprising the thin film magnetic head slider according to claim 9. Forming an intermediate layer made of a material other than aluminum oxide on the ceramic substrate by sputtering;
Forming an undercoat film made of aluminum oxide by sputtering on the intermediate layer;
For manufacturing a thin film magnetic head substrate.   12. The method of manufacturing a thin film magnetic head substrate according to claim 11, wherein the step of forming the intermediate layer is performed by a sputtering method without applying a bias.   13. The method for manufacturing a substrate for a thin film magnetic head according to claim 11, wherein the step of forming the undercoat film is performed by a sputtering method to which a bias is applied.   14. The method for manufacturing a thin film magnetic head substrate according to claim 11, wherein the intermediate layer is formed by sputtering using a metal element as a target. Preparing a thin film magnetic head substrate according to any one of claims 1 to 8, comprising a ceramic substrate, an intermediate layer, and an undercoat film;
Arranging a writing element and a reading element on the undercoat film;
For manufacturing a thin film magnetic head slider.

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