Composite coating device and method of forming overcoat on magnetic head using the same

A composite coating device includes first to third processing chambers. The first processing chamber performs an ion beam etching as a pretreatment process in which an ion beam is irradiated on a surface of a magnetic head at a predetermined angle and the surface is removed for a predetermined depth. The second processing chamber performs a magnetron sputter deposition as a shock absorbing coating formation process in which a shock absorbing coating is formed on the pretreated surface. The third processing chamber performs an electron cyclotron resonance plasma chemical vapor epitaxy or a cathode arc discharge deposition as an overcoat formation process in which an overcoat is formed on the shock absorbing coating. A preparation chamber communicates with the first to third processing chambers through opening and closing devices for transferring the magnetic head.

BACKGROUND OF THE INVENTION AND RELATED ART STATEMENT

The present invention relates to a composite coating device for forming a composite coating on a magnetic head and a method of forming a composite coating on a magnetic head.

In a magnetic storage device, a magnetic head is used to record and retrieve data stored in a magnetic storage media. For example, in a hard drive (HD) magnetic storage device in which data is recorded on a magnetic disk, when a magnetic head records and retrieves (access) data, the magnetic head rises from a disk surface only for a predetermined distance. When the magnetic head does not access data, the magnetic head lands on the disk surface in a so-called CSS (contact start and stop) mechanism.

As described above, when the magnetic head does not access data, the magnetic head receives a shock from the disk. The magnetic head also receives a corrosive action through atmospheric moisture and the like, so that wear resistance and corrosion resistance are required for an overcoat of the magnetic head. In addition, as the recording density has been increasing, it is required to reduce a thickness of the overcoat to reduce a distance between an electrode of the magnetic head and a recording layer on the magnetic disk (flight height).

In general, an overcoat of the magnetic head is formed through a manufacturing process comprising (1) a pretreatment process in which a coating surface of a head body is cleaned; (2) a shock absorbing coating formation process in which an amorphous silicon coating is formed; and (3) an overcoat formation process in which a DLC coating is formed. A composite coating device is used to carry out the processes in three independent processing chambers, respectively. The composite coating device performs a sputter etching for the pretreatment process, sputter deposition for the shock absorbing coating formation process, and electron cyclotron resonance plasma chemical vapor epitaxy or cathode arc discharge deposition for the overcoat formation process (refer to Japanese Patent Publication (Kokai) No. 2001-195717).

When the sputter etching is used for the pretreatment process, there is the following problem. An overcoat is formed on a surface of a magnetic head. The surface includes a portion formed of a soft electrode metal, for example, Permalloy, and a portion formed of a hard base metal, for example, AlTic (Al2O3TiC). Accordingly, the portions of the surface are etched at different etch rates, i.e. the portion formed of Permalloy is etched at a higher speed, thereby forming a recessed portion on the surface. As a result, the flight height increases, thereby making it difficult to obtain high recording density.

In view of the problem described above, an object of the present invention is to provide a composite coating device and an overcoat formation method, in which an overcoat is formed on a magnetic head while a flight height in the magnetic recording is reduced.

SUMMARY OF THE INVENTION

In order to attain the objects described above, according to a first aspect of the present invention, a composite coating device includes a first processing chamber for performing ion beam etching as a pretreatment process in which an ion beam is irradiated on a surface of a magnetic head at a predetermined angle and the surface is removed for a predetermined depth; a second processing chamber for performing magnetron sputter deposition as a shock absorbing coating formation process in which a shock absorbing coating is formed on the pretreated surface; a third processing chamber for performing electron cyclotron resonance plasma chemical vapor epitaxy as an overcoat formation process in which an overcoat is formed on the surface with the shock absorbing coating formed thereon; and a preparation chamber communicating with the first to third processing chambers through opening and closing means for transferring the magnetic head.

According to a second aspect of the present invention, a composite coating device includes a first processing chamber for performing ion beam etching as a pretreatment process in which an ion beam is irradiated on a surface of a magnetic head at a predetermined angle and the surface is removed for a predetermined depth; a second processing chamber for performing magnetron sputter deposition as a shock absorbing coating formation process in which a shock absorbing coating is formed on the pretreated surface; a third processing chamber for performing cathode arc discharge deposition as an overcoat formation process in which an overcoat is formed on the surface with the shock absorbing coating formed thereon; and a preparation chamber communicating with the first to third processing chambers through opening and closing means for transferring the magnetic head.

According to a third aspect of the present invention, in the composite coating devices in the first and second aspects, an ion beam etching device includes an ion source provided with an electrode for obtaining ions having a first grid with positive potential and a second grid with negative potential; and a communicating portion for eliminating an effect of the potential of the second grid relative to an electron in a plasma production area and for communicating a plasma production area with an outside of the plasma production area. The ion beam etching device may be provided with a dielectric block for adjusting a plasma density distribution at a plasma production portion. The ion beam etching device may also be provided with a high-frequency induction coupled plasma source including an electric insulation dividing wall projecting into the plasma production area and separating the plasma production chamber from outside, and an excitation coil provided in an outer concave portion of the electric insulation dividing wall.

In the composite coating device, the shock absorbing coat is formed of a silicon layer, and the overcoat is formed of a carbon layer. Especially, the silicon layer may be formed of an amorphous silicon, and the carbon layer is formed of one of a diamond-like carbon (DLC) layer or a tetrahedral amorphous carbon (ta-C) layer.

According to the present invention, a method of forming the overcoat on the magnetic head includes steps of the ion beam etching, the magnetron sputter deposition, and the electron cyclotron resonance plasma chemical vapor epitaxy in this order using the composite coating device described above.

According to the present invention, a method of forming the overcoat on the magnetic head may include steps of the ion beam etching, the magnetron sputter deposition, and the cathode arc discharge deposition in this order using the composite coating device described above.

According to the present invention, the magnetic head is formed with one of the overcoat formation methods described above.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Hereunder, embodiments of the present invention will be described with reference to the accompanying drawings.FIG. 1is a schematic view showing a structure of a composite coating device according to an embodiment of the present invention.

As shown inFIG. 1, a composite coating device1includes a cassette chamber2wherein a substrate100with a plurality of magnetic heads arranged thereon is taken in and out; a conveyance chamber3wherein the substrate100is transferred; an IBE device10for performing ion beam etching (hereinafter, referred to as IBE); a MSD device30for performing magnetron sputter deposition (hereinafter, referred to as MSD); and an ECR-CVD device40for performing electron cyclotron resonance plasma chemical vapor epitaxy (hereinafter, referred to as ECR-CVD). The conveyance chamber3is connected with the IBE device10, the MSD device30, and the ECR-CVD device40through gates5,6and7, respectively. The substrate100inside the conveyance chamber3is conveyed to each device by a conveyance mechanism4, and the substrate100inside each device is carried in the conveyance chamber3by the conveyance mechanism4.

In the embodiment, the composite coating device1is used for forming an overcoat on the magnetic head. Before the overcoat formation, an electrode metal, a base metal, and the like are exposed on an overcoat formation surface (protected surface) of the substrate100. The composite coating device1carries out one process in one chamber, so that it is possible to prevent mutual contamination between the processing chambers. Also, the substrate100is consecutively processed without being exposed to the atmosphere in the middle of the processing, so that it is possible to prevent oxidation of the substrate100, sticking of a dust, and the like.

The substrate100is transferred to the IBE device10from the conveyance chamber3, and the etching process is carried out on the protected surface in the IBE device10. In the etching process, the protected surface of the substrate100is removed as much as 20 nm in depth as the cleaning process before the amorphous silicon coat is formed. As shown inFIG. 2, the IBE device10is provided with an ion source11and a process camber12wherein the etching process is carried out. The ion source11is formed of electrodes18for leading out ions in a plasma source13, i.e. plasma production means.

The plasma source13is a high-frequency induction coupled plasma source for generating plasma through high-frequency induction coupling. A high-frequency introductory window14is provided in a plasma chamber19of the plasma source13, and flat-surface excitation coils15are provided outside the high-frequency introductory window14for generating high frequencies. A RF power source16is connected to the excitation coils15for supplying a high-frequency electric current of 13.56 MHz. A dielectric material such as quartz, ceramic, and the like is used for the high-frequency introductory window14. A matching circuit (not shown) is provided between the excitation coil15and the RF power source16for matching impedance.

In the plasma chamber19, gas for plasma production is introduced via a gas supply source17. In the present embodiment, argon gas is used as an example. Grids18a,18b, and18cconstituting the electrodes18for leading out ions are provided at an opening of the plasma chamber19. A positive potential V1is supplied to the grids18avia a grid power source20a, and a negative potential (−V2) is supplied to the grids18bvia a grid power source20b. The grids18chave earth potential Vg, and the plasma chamber19has potential (V1) same as that of the grids18a.

In the embodiment, an electron port21made of a conductive material is provided in the electrodes18for leading out ions. The electron port21(described below) is attached to the grids18a, and has the same potential (V1) as that of the grids18a. A substrate holder23is provided in the process chamber12for holding the substrate100as an etching object. The substrate holder23is arranged to be tiltable as shown by R1, and rotatable as shown by R2. A vacuum pump (not shown) is connected to an exhaust port12afor evacuating the inside of the process chamber12.

When argon gas is introduced into the plasma chamber19and high frequency generated at the excitation coil15is introduced into the plasma chamber19from the high-frequency introductory window14, electrons are separated from argon atoms, and plasma including argon ions Ar+and electrons e are generated. The argon ions Ar+are accelerated with an electric field between each positive potential grid18aand each negative potential grid18band then, decelerated between each grid18band each earth potential grid18c. In the end, ion beams IB having energy corresponding to a potential difference between the grids18aand the grids18care formed.

The accelerated argon ions Ar+irradiate on the substrate100, and etch the surface of the substrate. When the substrate100is made of a conducting material, a positive charge of argon ions Ar+irradiating on the substrate100flows to the substrate holder23connected to the substrate100. When the substrate100is made of an insulation material such as SiO2, the positive charge is accumulated on the surface of the substrate and the potential of the substrate increases, as shown inFIG. 2. The electric field between the grids18aand the grids18bprevents electronegative electrons e from leaking in the process chamber12.

As shown inFIG. 2, a tubular portion of the electron port21with the same potential as the grids18aextends to the grids18c. Accordingly, the grids18bdo not affect the inside of the tubular portion, thereby forming an approximately equal potential inside the tubular portion. As a result, there is no electric field preventing the electrons e from moving, so that the electrons e can easily move toward the process chamber12. When the substrate100is positively charged, the electrons e can easily move toward the positive direction, so that the electrons e inside the plasma chamber19are led out of the electron port21toward the substrate100and irradiate on the substrate100.

When the positive charge is not accumulated on the substrate100, the electrons e are not led out through the electron port21. Accordingly, the electrons e corresponding to an amount of the positive charge accumulated on the substrate100irradiate on the substrate100through the electron port21from the plasma chamber19, so that the positive charge of the substrate100is neutralized.

As described above, the electron port21is provided in the electrodes18, and the grids18bdo not prevent the electrons e from moving toward the process chamber. As a result, the electrons e inside the plasma move toward the electropositive substrate100to neutralize the positive charge of the substrate100, so that the etching effect of the argon ion Ar+is maintained.

Also, the electrons e irradiate on the substrate100for the amount automatically determined by the charged amount of the substrate100, so that it is not necessary to adjust the amount of the electrons without a problem of too small or too large amount. The electrons e move faster compared to the argon ions Ar+, the electrons e neutralize quickly when the substrate100is charged in positive. Specifically, just the electron port21is provided in the electrodes18, thereby reducing cost as compared to a conventional method wherein a heater for thermal emission or another plasma source is provided.

Next, etching characteristics of the substrate100with the IBE device will be explained.FIG. 8(a) is a partial cross sectional view showing a state that the substrate100is etched with the IBE device.FIG. 8(b) is a partial cross sectional view showing a state wherein an amorphous silicon coat103and a DLC coat104are formed on the substrate100after the etching. A line A1indicates the surface (protected surface) formed of a base metal101and an electrode metal102before the etching. A line A2indicates a surface after only a depth D is removed by the etching with the IBE device.

As shown inFIGS. 8(a) and8(b), the base metal101and the electrode metal102have different etch rates, so that an actual A2looks more like A3shown inFIG. 8(c). For example, when Al2O3TiC is used for the base metal101and FeNi (Permalloy) is used for the electrode metal102, the softer Permalloy is deeply etched, and a step d is formed as shown inFIG. 8(c). Therefore, the flight height increases by the step, so that it is difficult to obtain a high record density.

In addition, when the step d is formed, it is difficult to properly form the amorphous silicon coat103and the DLC coat104. The amorphous silicon coat103and the DLC coat104have small thicknesses. Accordingly, even though the step d may be small, it is difficult to cover the step, thereby causing a micro-crack or residual stress, and lowering corrosion resistance.

As shown inFIG. 10, in conventional sputter etching (SE), an etch rate of FeNi is higher than that of Al2O3TiC. When RF electric power is 200 W, the etch rate of FeNi is three times higher than that of Al2O3TiC, and when the RF electric power is 300 W, the etch rate of FeNi is 3.2 times higher than that of Al2O3TiC. On the other hand, as shown inFIG. 9, in the IBE of the present embodiment, etch rates of the FeNi and Al2O3TiC are function of an inclined angle of the substrate100relative to the ion beam, and when the inclined angle is 75°, the difference becomes a minimum. The substrate holder23tilts as shown by R1to change the inclined angle. Since the ion beam has directivity, the etch rate of a different material can be adjusted by the inclined angle. As a result, the step d shown inFIG. 8(c) becomes very small, so that the magnetic head coated with the amorphous silicon coat103and the DLC coat104reduces the flight height. Also, since the step d is very small, it is easy to form the amorphous silicon coat103and the DLC coat104, so that the corrosion resistance of the overcoat is improved.

After the etching process, the substrate100is conveyed to the conveyance chamber3and then to the MSD device30through the gate5.FIG. 3is a view showing the DC type MSD device for forming the amorphous silicon coat, and the amorphous silicon coat is formed with a thickness of 0.5 nm. A silicone (Si) target31is placed on a target holder39provided in a sputter chamber37of the MSD device30. The target holder39is a cathode, and the substrate100is attached to an anode32. The substrate100is held in such a way that the coated surface faces down. A magnet33is provided in the target holder39, and a negative bias voltage is applied the Si target31from a bias power source34. The magnet33is provided for generating a parallel magnetic field around a surface of the Si target31. Argon gas (Ar) is supplied as process gas to the sputter chamber37. The argon gas is supplied from a supply source35through a mass-flow controller36aand a valve36bof a gas feeding device36.

In the coating process, the argon gas is supplied to the sputter chamber37, and a vacuum device38evacuates the inside of the sputter chamber37, so that the inside of the sputter chamber37has a predetermined process pressure and plasma is generated. The Si target31is sputtered by the argon ion in the plasma, and sputtered Si particles are accumulated on the coated surface of the substrate100and form the amorphous silicon coat.

After the coating process of the amorphous silicon coat, the substrate100is conveyed to the conveyance chamber3through the gate6, and then to the ECR-CVD device40through the gate7.FIG. 4is a view of the ECR-CVD device for forming the DLC (diamond-like carbon) coat, and the DLC coat is formed with a thickness of 1 nm. The ECR-CVD device40comprises a reaction chamber41for forming a thin coat on the substrate100with the amorphous silicon coat formed thereon; an ECR plasma generation portion42for introducing plasma into the reaction chamber41; a bias power source portion43for applying a bias voltage to the substrate100; and a control portion45for controlling the whole device, coating conditions, and a reaction gas introductory portion44to introduce reactive gas into the reaction chamber41.

The ECR plasma generation portion42is a mechanism for supplying microwave electric power to the magnetic field to generate the electron cyclotron resonance plasma, and for introducing the plasma flow into the reaction chamber41. A microwave source46generates a microwave of 2.45 GHz, and the microwave is introduced into a plasma chamber47through a wave guide46ato discharge the microwave. In addition, a magnetic flux density 875 G at the ECR condition is formed with the magnetic filed generated by coils46band46cto generate electron cyclotron resonance, so that activated ECR plasma is generated. The ECR plasma generated inside the plasma chamber47moves toward the substrate100inside the reaction chamber41along the divergent magnetic field from the plasma window47a.

In the bias power source portion43, a bias power source43ais connected to a substrate holding mechanism inside the reaction chamber41through a matching unit43b, and a negative bias voltage is applied to the substrate100disposed inside the reaction chamber41. A voltage monitor43cmeasures the bias voltage. The reactive gas introduced into the reaction chamber41from the reaction gas introductory portion44is ionized inside the high density plasma generated by the ECR, and the DLC coat is formed on the substrate100with the negative bias voltage. When the DLC coat is formed, ethylene (C2H4), methane (CH4), propane (C3H8), or the like is provided through the reaction gas introductory portion44as coating gas. An exhaust pump44dexhausts the reaction chamber20, and a pressure gauge44emeasures the pressure inside the reaction chamber20.

Instead of the ECR-CVD device forming the DLC coat, a cathode arc discharge deposition device may form a ta-C (tetrahedral amorphous carbon) coat.FIG. 5is a view of an FCVA (Filtered Cathode Vacuum Arc) device as the cathode arc discharge deposition device. A carbon ion generation source51generates a carbon ion C+via vacuum arc discharge between a cathode52and an anode53. The cathode52is formed in a disk shape made of high-purity graphite. The carbon ions C+generated at the carbon ion generation source51are coated on the substrate100after passing through a filter54. The filter54allows only required carbon ions to pass through using the electric field and the magnetic filed, and the filter54removes large carbon particles or neutral carbon atoms.

Magnetic coils55are provided near an exit of the filter54for scanning carbon ion beams, so that the ta-C coat is uniformly formed on the substrate100. A bias voltage is applied to the substrate100, and energy of the ions arriving at the substrate100depends on the bias voltage, so that the coating characteristics can be adjusted through the bias voltage.

FIG. 6is a view showing a modified example of the IBE device. The IBE device60is composed of a plasma production portion61and a vacuum chamber62. The substrate100, i.e. the etching object, is placed in the vacuum chamber62. The plasma production portion61is disposed at a position facing the substrate100inside the vacuum chamber62. The plasma production portion61comprises a plasma chamber63including a cylindrical plasma formation space; antenna coils64; and a high-frequency power65. The plasma production portion61generates plasma with an inductive coupled plasma excitation method.

A dielectric window63aformed of ceramic and the like is provided at a bottom surface of the plasma chamber63. The antenna coils64are provided at outside the dielectric window63a. The antenna coils64form a high-frequency magnetic field inside the plasma chamber63through the dielectric window63a. A cylindrical dielectric block66is provided inside the plasma chamber63for adjusting a plasma distribution. When plasma production gas (for example, argon gas) is supplied into the plasma chamber63through a gas supply device67and the antenna coils64form the high-frequency magnetic field, plasma P is generated inside the plasma chamber63. A porous electrode grid G for leading out ions is provided at an opening of the plasma chamber63. Charged particles such as ions are led out of the plasma chamber63via the grid G, and ion-beams IB are accelerated.

In the plasma production portion61, the cylindrical dielectric block66is disposed coaxially with the antenna coils64. At this moment, the plasma P does not enter an area of the dielectric block including the internal space of the dielectric block66. As a result, the plasma P is distributed around the dielectric block66in a doughnut shape. A density distribution of the plasma P is related to a distribution of an ion current value, i.e. a density distribution of the ion-beams IB. When the density distribution of the plasma has a doughnut shape around the coil shown inFIG. 6, the ion current value of the ion-beams IB led out of the plasma P has a two-top distribution wherein the center of the coil is a concave portion. It is possible to adjust the distribution of the current value by moving the dielectric block66inside the plasma P. In the etching process, the surface of the substrate100is removed as much as 20 nm in depth, and the cleaning is completed before the amorphous silicon coat is formed.

FIG. 7is a view showing another modified example of the IBE device. In an IBE device70, a stage71is provided inside a process chamber PC for placing the substrate100. A high-frequency induction coupled plasma source72is provided at a position facing the stage71in the process chamber PC. When the inside of the process chamber PC is evacuated via a vacuum pump VP during the etching process, the inside of a plasma production chamber73of the high-frequency induction coupled plasma source72is also evacuated in a decompressed state.

A protrusion73aprojecting into the plasma production chamber73is provided at a midsection of the plasma production chamber73. An excitation coil74is disposed in a concave portion formed outside the protrusion73afor forming an alternate current magnetic field M inside the plasma production chamber73. The protrusion73ais formed of an insulator such as glass, ceramic, and the like, and functions as a high-frequency introductory window for introducing the alternate current magnetic field formed by the excitation coil74into the plasma production chamber73. The excitation coil74is a solenoid-type coil, and connected to a RF power source76through a matching device75. Incidentally, in the present embodiment, the excitation coil74is the solenoid-type coil, and may be a flat-type coil with one tern.

The RF power source76uses a frequency from 1 to 100 MHz for an economical reason, and the high-frequency power of 13.56 MHz is used in the present embodiment. A capacitor for matching impedance is provided in the matching device75. By adjusting a capacitance of the capacitor, a matching condition can be adjusted. When plasma is generated, argon gas or the like is introduced into the plasma production chamber73from a gas supply source77.

Ring-shaped magnets78aand78bare provided on an outer periphery of the plasma production chamber73for forming a static magnetic field in the plasma production chamber73. The magnets78aand78bare formed of an electromagnet, and may be formed of a permanent magnet. The magnets78aand78bform a cusped magnetic field. When the high-frequency voltage is applied to the excitation coil74, argon gas is excited via inductive coupling, and plasma P1including the argon ions is generated in a ring-shaped space between the plasma production chamber73and the protrusion73a. Electrons in the plasma P1are trapped by the cusped magnetic field, thereby facilitating the plasma production and efficiently forming the plasma P1.

Grids G1, G2, and G3are provided at an opening of the plasma production chamber73for leading out the argon ions from the generated plasma P1. A grid power source79applies a grid voltage to the grids G1to G3. For example, a voltage of 800 V is applied to the grid G1and a voltage of 400 V is applied to the grid G2, respectively. The grid G3is grounded and has a potential of 0 V. When the voltages are applied to the grids G1to G3, the ion beams IB of the argon ions are led out of the plasma source72upwardly, and irradiate on the substrate100.

In the plasma source72shown inFIG. 7, the protrusion73aformed of an insulator projects into the plasma production chamber73, so that the plasma P1does not enter an area of the protrusion73a. As a result, the plasma P1is distributed between the protrusion73aand the plasma production chamber73in a ring shape around the protrusion73a. In the etching process, the surface of the substrate100is removed as much as 20 nm in depth, and the cleaning process is completed before the amorphous silicon coat is formed.

Finally, the amorphous silicon coat and the carbon coat formed with the composite coating device1of the present embodiment will be explained.FIG. 11is a graph showing spectral characteristics of the amorphous silicon coat formed with the MSD device30, wherein the vertical axis represents a refractive index n and the horizontal axis represents a wavelength.FIG. 12is a graph showing spectral characteristics of the amorphous silicon coat formed with the MSD device30, wherein the vertical axis represents an absorption coefficient k and the horizontal axis represents a wavelength. The refractive index n and the absorption coefficient k are indicators of a nature of the amorphous silicon coat.

FIGS. 13(a) and13(b) are graphs showing Raman spectra of the carbon layers formed with the ECR-CVD device and the FCVA device, wherein the vertical axis represents a signal strength and the horizontal axis represents a wavelength.FIG. 13(a) shows the carbon layer formed with the ECR-CVD device andFIG. 13(b) shows the carbon layer formed with the FCVA device. The spectra were analyzed with a peak resolution analysis to identify a component associated with a diamond structure (D) and a component associated with a graphite structure (G), and an area ratio of the peak areas, i.e. Area (D/G), was determined. The carbon layer formed with the ECR-CVD device has the Area (D/G) of 0.48, and the carbon layer formed with the FCVA device has the Area (D/G) of 0.34. The Area (D/G) is an indicator of a nature of the carbon layer.

As explained above, according to the present invention, the substrate is tilted by a predetermined angle using the IBE, so that the step between the base metals and the electrode metal can be reduced. Accordingly, it is possible to form the overcoat on the magnetic head with a small flight height.