US20030049496A1 - Thin film protective layer with buffering interface - Google Patents
Thin film protective layer with buffering interface Download PDFInfo
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- US20030049496A1 US20030049496A1 US09/952,872 US95287201A US2003049496A1 US 20030049496 A1 US20030049496 A1 US 20030049496A1 US 95287201 A US95287201 A US 95287201A US 2003049496 A1 US2003049496 A1 US 2003049496A1
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- thin film
- overcoat
- nitrogen
- protective layer
- layer
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- 239000010409 thin film Substances 0.000 title claims abstract description 43
- 239000011241 protective layer Substances 0.000 title claims abstract description 34
- 230000003139 buffering effect Effects 0.000 title abstract description 4
- 239000010408 film Substances 0.000 claims abstract description 48
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims abstract description 41
- 239000010410 layer Substances 0.000 claims abstract description 41
- 230000005291 magnetic effect Effects 0.000 claims abstract description 38
- 238000000034 method Methods 0.000 claims abstract description 35
- 238000000151 deposition Methods 0.000 claims abstract description 22
- 229910052757 nitrogen Inorganic materials 0.000 claims abstract description 20
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims abstract description 19
- 229910052799 carbon Inorganic materials 0.000 claims abstract description 18
- 230000008021 deposition Effects 0.000 claims abstract description 13
- 239000000696 magnetic material Substances 0.000 claims description 5
- 230000007704 transition Effects 0.000 claims description 5
- 229910000531 Co alloy Inorganic materials 0.000 claims description 3
- 230000005294 ferromagnetic effect Effects 0.000 claims 2
- 238000004544 sputter deposition Methods 0.000 abstract description 13
- 150000002500 ions Chemical class 0.000 abstract description 12
- 239000000463 material Substances 0.000 abstract description 7
- 230000008569 process Effects 0.000 abstract description 6
- 238000005468 ion implantation Methods 0.000 abstract description 4
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 10
- 239000001257 hydrogen Substances 0.000 description 10
- 229910052739 hydrogen Inorganic materials 0.000 description 10
- 239000000758 substrate Substances 0.000 description 10
- 230000001681 protective effect Effects 0.000 description 4
- 238000005260 corrosion Methods 0.000 description 3
- 230000007797 corrosion Effects 0.000 description 3
- 238000002474 experimental method Methods 0.000 description 3
- 239000000203 mixture Substances 0.000 description 3
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 2
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 description 2
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 2
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 2
- 230000003466 anti-cipated effect Effects 0.000 description 2
- 230000008901 benefit Effects 0.000 description 2
- 229910052804 chromium Inorganic materials 0.000 description 2
- 239000011651 chromium Substances 0.000 description 2
- 238000009792 diffusion process Methods 0.000 description 2
- 238000009826 distribution Methods 0.000 description 2
- 239000007789 gas Substances 0.000 description 2
- 239000011521 glass Substances 0.000 description 2
- 239000000725 suspension Substances 0.000 description 2
- 238000012360 testing method Methods 0.000 description 2
- ZOXJGFHDIHLPTG-UHFFFAOYSA-N Boron Chemical compound [B] ZOXJGFHDIHLPTG-UHFFFAOYSA-N 0.000 description 1
- 229910000599 Cr alloy Inorganic materials 0.000 description 1
- 229910000640 Fe alloy Inorganic materials 0.000 description 1
- 229910000990 Ni alloy Inorganic materials 0.000 description 1
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 description 1
- 229910045601 alloy Inorganic materials 0.000 description 1
- 239000000956 alloy Substances 0.000 description 1
- 229910052786 argon Inorganic materials 0.000 description 1
- 230000004888 barrier function Effects 0.000 description 1
- 229910052796 boron Inorganic materials 0.000 description 1
- 150000001721 carbon Chemical class 0.000 description 1
- 239000000788 chromium alloy Substances 0.000 description 1
- 239000004020 conductor Substances 0.000 description 1
- 238000011109 contamination Methods 0.000 description 1
- 230000001419 dependent effect Effects 0.000 description 1
- 229910001873 dinitrogen Inorganic materials 0.000 description 1
- 230000009977 dual effect Effects 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 239000003302 ferromagnetic material Substances 0.000 description 1
- 229910002804 graphite Inorganic materials 0.000 description 1
- 239000010439 graphite Substances 0.000 description 1
- 238000010849 ion bombardment Methods 0.000 description 1
- 229910001004 magnetic alloy Inorganic materials 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 230000035515 penetration Effects 0.000 description 1
- 230000009993 protective function Effects 0.000 description 1
- 238000000926 separation method Methods 0.000 description 1
- 229910052715 tantalum Inorganic materials 0.000 description 1
- GUVRBAGPIYLISA-UHFFFAOYSA-N tantalum atom Chemical compound [Ta] GUVRBAGPIYLISA-UHFFFAOYSA-N 0.000 description 1
- 229910052719 titanium Inorganic materials 0.000 description 1
- 239000010936 titanium Substances 0.000 description 1
Images
Classifications
-
- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C14/00—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material
- C23C14/22—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material characterised by the process of coating
- C23C14/34—Sputtering
- C23C14/3435—Applying energy to the substrate during sputtering
- C23C14/345—Applying energy to the substrate during sputtering using substrate bias
-
- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C14/00—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material
- C23C14/06—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material characterised by the coating material
- C23C14/0641—Nitrides
- C23C14/0658—Carbon nitride
-
- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
- G11B5/62—Record carriers characterised by the selection of the material
- G11B5/72—Protective coatings, e.g. anti-static or antifriction
- G11B5/726—Two or more protective coatings
- G11B5/7262—Inorganic protective coating
- G11B5/7264—Inorganic carbon protective coating, e.g. graphite, diamond like carbon or doped carbon
- G11B5/7268—Inorganic carbon protective coating, e.g. graphite, diamond like carbon or doped carbon comprising elemental nitrogen in the inorganic carbon coating
-
- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
- G11B5/74—Record carriers characterised by the form, e.g. sheet shaped to wrap around a drum
- G11B5/82—Disk carriers
-
- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
- G11B5/84—Processes or apparatus specially adapted for manufacturing record carriers
- G11B5/8408—Processes or apparatus specially adapted for manufacturing record carriers protecting the magnetic layer
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H01F41/00—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties
- H01F41/32—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties for applying conductive, insulating or magnetic material on a magnetic film, specially adapted for a thin magnetic film
-
- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
- G11B5/012—Recording on, or reproducing or erasing from, magnetic disks
Definitions
- the invention relates to thin film protective layers and to methods for the deposition of thin film protective layers and more particularly to films comprising carbon and nitrogen (CNx) and even more particularly to such films as used on magnetic thin film media.
- CNx carbon and nitrogen
- FIG. 1 A typical prior art head and disk system 10 is illustrated in FIG. 1.
- the magnetic transducer 20 is supported by the suspension 13 as it flies above the disk 16 .
- the magnetic transducer 20 usually called a “head” or “slider,” is composed of elements that perform the task of writing magnetic transitions (the write head 23 ) and reading the magnetic transitions (the read head 12 ).
- the electrical signals to and from the read and write heads 12 , 23 travel along conductive paths (leads) 14 which are attached to or embedded in the suspension 13 .
- the magnetic transducer 20 is positioned over points at varying radial distances from the center of the disk 16 to read and write circular tracks (not shown).
- the disk 16 is attached to a spindle 18 that is driven by a spindle motor 24 to rotate the disk 16 .
- the disk 16 comprises a substrate 26 on which a plurality of thin films 21 are deposited.
- the thin films 21 include ferromagnetic material in which the write head 23 records the magnetic transitions in which information is encoded.
- the thin film protective layer (not shown in FIG. 1) is typically the last or outermost layer.
- the conventional disk 16 typically has a substrate 26 of AlMg or glass.
- the thin films 21 on the disk 16 typically include a chromium or chromium alloy underlayer that is deposited on the substrate 26 .
- the magnetic layer in the thin films 21 is based on various alloys of cobalt, nickel and iron. For example, a commonly used alloy is CoPtCr. However, additional elements such as tantalum and boron are often used in the magnetic alloy.
- FIG. 2 illustrates one common internal structure of thin films 21 on disk 16 .
- the protective overcoat layer 37 is used to improve wearability and corrosion.
- the materials and/or compositions which are optimized for one performance characteristic of an overcoat are rarely optimized for others.
- the most commonly used protective layer materials for commercial thin film disks have been carbon, hydrogenated carbon (CHx), nitrogenated carbon (CNx) and CNxHy.
- CHx hydrogenated carbon
- CNx nitrogenated carbon
- CNxHy CNxHy
- Efforts to optimize overcoat properties have included use of a layer structure using different materials and/or compositions for each of two or more layers in the overcoat structure. For example, U.S. Pat. No. 5,942,317 issued to R.
- White describes the use of a graded CHx protective layer wherein the hydrogen content is highest at the film's surface to take advantage of the lower polar surface energy characteristic of higher hydrogen levels (which improves corrosion resistance) and is lowest at the interface with the magnetic layer to optimize the adhesion properties.
- the midlevel of the CHx film is likewise optimized by having an intermediate hydrogen concentration which has a high hardness to improve wearability.
- the variations in the hydrogen content can be continuous or discrete.
- a protective layer structure with three sublayers with lower hydrogen concentration nearest the magnetic layer, intermediate hydrogen concentration in the middle sublayer and high hydrogen concentration at the surface is suggested in White '317. Hardness and density are reduced by the presence of hydrogen in certain percentage ranges; thus, the overcoat structure of White '317 is hardest and densest at the interface with the magnetic layer.
- U.S. Pat. No. 6,086,730 to Liu, et al. describes a method for sputtering a carbon protective layer with a high sp 3 content which involves applying relatively high voltage pulses to the carbon target. Liu '730 asserts that the resulting carbon overcoat has good durability and corrosion resistance down to low thicknesses.
- the protective overcoat 37 must be made as thin as possible to reduce the separation from the magnetic transducer 20 and the magnetic thin film 33 while maintaining the protective function.
- the applicants disclose a method for sputtering a protective layer which allows the protective layer to be ultra-thin with improved durability over prior art films.
- the method reduces the kinetic energy of the impinging ions during the initial period of deposition to form a buffering interface which reduces the interpenetration of the atoms of the protective layer into the underlying film.
- the lower energy ions form a less dense and softer film than do higher energy ions.
- the sputtering of the overcoat preferably begins with zero (or very low) bias voltage applied to the underlying film. This “low energy” phase of the deposition results in minimal ion implantation in the underlying film.
- the “low energy” deposition continues only as long as it takes to form a buffer layer of the overcoat material on the underlying film.
- the buffer layer deposited in this phase is relatively soft and is, therefore, not sufficient for a complete overcoat.
- the “high energy” phase of the process begins with increases in the magnitude of the negative bias voltage applied to the underlying film.
- the higher energy imparted to ions in the plasma result in a denser and harder film being formed over the initial buffer layer.
- the initial buffer layer reduces the interpenetration of the higher energy ions into the underlying film.
- the protective layer preferably comprises carbon and nitrogen.
- the protective layer structure of the invention is preferably used over a magnetic layer on thin film magnetic media.
- the protective film produced by the method of the invention has a relatively lower density at the interface with the underlying film and a relatively higher density at the surface.
- FIG. 1 is a symbolic illustration of the prior art showing the relationships between the head and associated components in a disk drive.
- FIG. 2 is an illustration of a layer structure for a magnetic thin film disk according to the invention.
- FIG. 3 is a graph of the anticipated distribution of the depth of 50 ev carbon ion implantation into a CoPtCr magnetic film.
- FIG. 2 illustrates a cross section of a magnetic thin film disk embodying the protective layer structure of the invention.
- the film structure illustrated contains only one magnetic layer 33 and one underlayer 31 .
- the protective layer structure of the invention is not dependent on any particular underlying film structure so long as the final layer below the overcoat is conductive.
- the protective layer of the invention therefore, may be used on any combination of multiple magnetic layers, underlayers and seed layers.
- the interface 42 between the magnetic layer 33 and the protective layer 37 is the region of the protective layer 37 that has the lowest density (indicated by the spacing of the small circles in the drawing) and the surface of the protective layer 37 has the highest density.
- the preferred material for the protective layer 37 is CNx.
- Other elements such as hydrogen may be added to the film in relatively small atomic percentages.
- the preferred method of depositing the protective layer 37 of the invention is by sputtering using known techniques for forming a CNx film with the exceptions noted below.
- a graphite target is used and nitrogen is introduced into the sputtering chamber as a gas.
- the relative concentration of nitrogen in the deposited film is controlled by modulating the partial pressure of the nitrogen gas in the chamber. Lower partial pressures of nitrogen result in lower concentrations of nitrogen in the film as would be expected.
- the precise partial pressures of nitrogen and the working gas typically argon
- the preferred embodiment of the invention has from 5 to 25 at. % nitrogen in the protective layer.
- the preferred thickness of the protective layer is from 2 to 9 nanometers.
- the method of the invention includes modulating the bias voltage applied to underlying film.
- the use of negative bias voltages applied to metallic substrates is well known. The larger the magnitude of the voltage, the more kinetic energy is imparted to the positive ions as they are accelerated toward the substrate. Higher energy ions result in a denser, harder and smoother overcoat film due, at least in part, to resputtering effects. The higher energy ions also interpenetrate the underlying film to a greater depth than do lower energy ions. This interpenetration is considered to be negligible for many applications since the depth of penetration is small in comparison to the film thickness.
- FIG. 3 is a graph of the anticipated distribution of the depth of 50 ev carbon ion implantation into a CoPtCr magnetic film.
- the initial bias voltage is essentially zero which reduces the average energy of the impinging ions to a few electron volts.
- the interpenetration of the overcoat atoms into the magnetic film is negligible at this energy level.
- a second batch of otherwise identical disks was prepared using the method of the invention to sputter 2.5 nm CNx overcoats.
- the particular sputtering setup required approximately four (4) seconds to deposit 2.5 nm of CNx.
- no voltage bias was applied to the underlying CoPtCr film.
- the underlying film was then subjected to ⁇ 50 v dc bias for the remainder of the deposition.
- This second batch of disks was then burnished and tested for flyability. These disks passed the flyability test 87% of the time representing nearly a six-fold increase in yield over the prior art disks.
- the bias was rapidly switched from 0 to ⁇ 50 v dc after the initial period in which the lower density CNx material for the buffering interface was formed.
- the bias can also be increased gradually, as long as the low and high density portions of the film are given adequate time to form.
- the preferred range of dc bias voltages for the high voltage period is from ⁇ 50 v to ⁇ 400 v.
- the method of the invention can also be used with dual cathode pulsed sputtering techniques.
- this technique the pulsing of opposing targets provides considerable ion bombardment of the films deposited on grounded substrates, therefore, for this embodiment the preferred bias voltages are in the range of 0 (ground) to ⁇ 200 v.
- the contact points for delivery of the bias voltage to the conductive film on which the protective layer of the invention is to be formed must not have been shadowed during the deposition of the conductive film(s). This condition is satisfied if the disk is held at different points during the deposition of the overcoat other than the points at which the disk was held during the deposition of the conductive film. A small rotation of the disk after the deposition of the conductive film is sufficient to move the contact points to locations where the conductive has been adequately formed. Since the magnetic thin films in question are on the order of ten's of nanometers thick care must be taken not to overheat the thin film through which the bias current flows.
Abstract
Description
- The invention relates to thin film protective layers and to methods for the deposition of thin film protective layers and more particularly to films comprising carbon and nitrogen (CNx) and even more particularly to such films as used on magnetic thin film media.
- A typical prior art head and
disk system 10 is illustrated in FIG. 1. In operation themagnetic transducer 20 is supported by thesuspension 13 as it flies above thedisk 16. Themagnetic transducer 20, usually called a “head” or “slider,” is composed of elements that perform the task of writing magnetic transitions (the write head 23) and reading the magnetic transitions (the read head 12). The electrical signals to and from the read and writeheads suspension 13. Themagnetic transducer 20 is positioned over points at varying radial distances from the center of thedisk 16 to read and write circular tracks (not shown). Thedisk 16 is attached to aspindle 18 that is driven by aspindle motor 24 to rotate thedisk 16. Thedisk 16 comprises asubstrate 26 on which a plurality ofthin films 21 are deposited. Thethin films 21 include ferromagnetic material in which thewrite head 23 records the magnetic transitions in which information is encoded. The thin film protective layer (not shown in FIG. 1) is typically the last or outermost layer. - The
conventional disk 16 typically has asubstrate 26 of AlMg or glass. Thethin films 21 on thedisk 16 typically include a chromium or chromium alloy underlayer that is deposited on thesubstrate 26. The magnetic layer in thethin films 21 is based on various alloys of cobalt, nickel and iron. For example, a commonly used alloy is CoPtCr. However, additional elements such as tantalum and boron are often used in the magnetic alloy. - FIG. 2 illustrates one common internal structure of
thin films 21 ondisk 16. Theprotective overcoat layer 37 is used to improve wearability and corrosion. The materials and/or compositions which are optimized for one performance characteristic of an overcoat are rarely optimized for others. The most commonly used protective layer materials for commercial thin film disks have been carbon, hydrogenated carbon (CHx), nitrogenated carbon (CNx) and CNxHy. Efforts to optimize overcoat properties have included use of a layer structure using different materials and/or compositions for each of two or more layers in the overcoat structure. For example, U.S. Pat. No. 5,942,317 issued to R. White describes the use of a graded CHx protective layer wherein the hydrogen content is highest at the film's surface to take advantage of the lower polar surface energy characteristic of higher hydrogen levels (which improves corrosion resistance) and is lowest at the interface with the magnetic layer to optimize the adhesion properties. The midlevel of the CHx film is likewise optimized by having an intermediate hydrogen concentration which has a high hardness to improve wearability. The variations in the hydrogen content can be continuous or discrete. For example, a protective layer structure with three sublayers with lower hydrogen concentration nearest the magnetic layer, intermediate hydrogen concentration in the middle sublayer and high hydrogen concentration at the surface is suggested in White '317. Hardness and density are reduced by the presence of hydrogen in certain percentage ranges; thus, the overcoat structure of White '317 is hardest and densest at the interface with the magnetic layer. - In U.S. Pat. No. 5,679,431 Chen, et al., describe the use of a bilayer protective overcoat in which the initial sublayer is carbon, titanium or chromium and the surface sublayer is CHx or CNx. The problem being addressed in Chen '431 is diffusion of nitrogen or hydrogen into the magnetic layer over time. The initial sublayer is intended to act as a diffusion barrier.
- U.S. Pat. No. 6,086,730 to Liu, et al., describes a method for sputtering a carbon protective layer with a high sp3 content which involves applying relatively high voltage pulses to the carbon target. Liu '730 asserts that the resulting carbon overcoat has good durability and corrosion resistance down to low thicknesses.
- In order to improve the performance of magnetic thin film media the
protective overcoat 37 must be made as thin as possible to reduce the separation from themagnetic transducer 20 and the magneticthin film 33 while maintaining the protective function. - The applicants disclose a method for sputtering a protective layer which allows the protective layer to be ultra-thin with improved durability over prior art films. The method reduces the kinetic energy of the impinging ions during the initial period of deposition to form a buffering interface which reduces the interpenetration of the atoms of the protective layer into the underlying film. The lower energy ions form a less dense and softer film than do higher energy ions. In the method of the invention the sputtering of the overcoat preferably begins with zero (or very low) bias voltage applied to the underlying film. This “low energy” phase of the deposition results in minimal ion implantation in the underlying film. The “low energy” deposition continues only as long as it takes to form a buffer layer of the overcoat material on the underlying film. The buffer layer deposited in this phase is relatively soft and is, therefore, not sufficient for a complete overcoat. The “high energy” phase of the process begins with increases in the magnitude of the negative bias voltage applied to the underlying film. The higher energy imparted to ions in the plasma result in a denser and harder film being formed over the initial buffer layer. The initial buffer layer reduces the interpenetration of the higher energy ions into the underlying film. The protective layer preferably comprises carbon and nitrogen. The protective layer structure of the invention is preferably used over a magnetic layer on thin film magnetic media. The protective film produced by the method of the invention has a relatively lower density at the interface with the underlying film and a relatively higher density at the surface.
- FIG. 1 is a symbolic illustration of the prior art showing the relationships between the head and associated components in a disk drive.
- FIG. 2 is an illustration of a layer structure for a magnetic thin film disk according to the invention.
- FIG. 3 is a graph of the anticipated distribution of the depth of 50 ev carbon ion implantation into a CoPtCr magnetic film.
- FIG. 2 illustrates a cross section of a magnetic thin film disk embodying the protective layer structure of the invention. The film structure illustrated contains only one
magnetic layer 33 and oneunderlayer 31. However, the protective layer structure of the invention is not dependent on any particular underlying film structure so long as the final layer below the overcoat is conductive. The protective layer of the invention, therefore, may be used on any combination of multiple magnetic layers, underlayers and seed layers. Theinterface 42 between themagnetic layer 33 and theprotective layer 37 is the region of theprotective layer 37 that has the lowest density (indicated by the spacing of the small circles in the drawing) and the surface of theprotective layer 37 has the highest density. - The preferred material for the
protective layer 37 is CNx. Other elements such as hydrogen may be added to the film in relatively small atomic percentages. The preferred method of depositing theprotective layer 37 of the invention is by sputtering using known techniques for forming a CNx film with the exceptions noted below. In the typical process for forming a CNx film a graphite target is used and nitrogen is introduced into the sputtering chamber as a gas. The relative concentration of nitrogen in the deposited film is controlled by modulating the partial pressure of the nitrogen gas in the chamber. Lower partial pressures of nitrogen result in lower concentrations of nitrogen in the film as would be expected. As is well known to those in the sputtering arts, the precise partial pressures of nitrogen and the working gas (typically argon) are derived empirically for each unique combination of equipment used in the sputtering process. - The preferred embodiment of the invention has from 5 to 25 at. % nitrogen in the protective layer. The preferred thickness of the protective layer is from 2 to 9 nanometers.
- The method of the invention includes modulating the bias voltage applied to underlying film. The use of negative bias voltages applied to metallic substrates is well known. The larger the magnitude of the voltage, the more kinetic energy is imparted to the positive ions as they are accelerated toward the substrate. Higher energy ions result in a denser, harder and smoother overcoat film due, at least in part, to resputtering effects. The higher energy ions also interpenetrate the underlying film to a greater depth than do lower energy ions. This interpenetration is considered to be negligible for many applications since the depth of penetration is small in comparison to the film thickness. However, in applications such as magnetic thin film media, the films are sufficiently thin that the interpenetration of atoms into the lattice of magnetic materials is undesirable. FIG. 3 is a graph of the anticipated distribution of the depth of 50 ev carbon ion implantation into a CoPtCr magnetic film. Using the method of the invention the initial bias voltage is essentially zero which reduces the average energy of the impinging ions to a few electron volts. The interpenetration of the overcoat atoms into the magnetic film is negligible at this energy level.
- Moreover, for ultra-thin overcoats (for example, 0.5 to 2.5 nm) the performance of the overcoat depends critically on the nature of the interface with the underlying film. Although negative voltage bias improves the overcoat itself, it has been found by the applicants to degrade the interface for overcoats on the order of 2.5 nm thick.
- In an experiment performed by the applicants, prior art sputtering techniques using −50 v bias were used to deposit 2.5 nm CNx overcoats on a batch of thin film magnetic disks. The disks were then subjected to the finishing and testing process that is normally used for large scale manufacturing of magnetic disks which includes burnishing the surface of the disks using special heads with leading edges designed to cut off the higher protrusions. To be commercially usable the overcoat on the disks must be able to withstand this burnishing and still present a surface to the slider of the magnetic transducer over which the slider can “fly” without excessive disturbance. In the experiment 85% of the prior art disks with 2.5 nm CNx overcoats failed to provide a flyable surface after burnishing, i.e., the usable yield was 15%.
- A second batch of otherwise identical disks was prepared using the method of the invention to sputter 2.5 nm CNx overcoats. The particular sputtering setup required approximately four (4) seconds to deposit 2.5 nm of CNx. For the initial one (1) second, no voltage bias was applied to the underlying CoPtCr film. The underlying film was then subjected to −50 v dc bias for the remainder of the deposition. This second batch of disks was then burnished and tested for flyability. These disks passed the flyability test 87% of the time representing nearly a six-fold increase in yield over the prior art disks.
- In the experiment described above the bias was rapidly switched from 0 to −50 v dc after the initial period in which the lower density CNx material for the buffering interface was formed. The bias can also be increased gradually, as long as the low and high density portions of the film are given adequate time to form. The preferred range of dc bias voltages for the high voltage period is from −50 v to −400 v.
- The method of the invention can also be used with dual cathode pulsed sputtering techniques. With this technique the pulsing of opposing targets provides considerable ion bombardment of the films deposited on grounded substrates, therefore, for this embodiment the preferred bias voltages are in the range of 0 (ground) to −200 v.
- Applying bias to disks with conductive substrates such as the NiP coated AlMg substrates is a straightforward process. The edges of the disk are held during sputtering by conductive material to which the bias voltage is applied. Whether the points of electrical contact are blocked or shadowed during the deposition is irrelevant since the substrate itself is conductive. However, for nonconductive substrates such as glass the bias voltage must be applied to a conductive film on the disk, so shadowing must be taken into account. There are several different types of mechanical systems used to load and support disks while they are being sputtered. Regardless of what type of system is being used, the contact points for delivery of the bias voltage to the conductive film on which the protective layer of the invention is to be formed must not have been shadowed during the deposition of the conductive film(s). This condition is satisfied if the disk is held at different points during the deposition of the overcoat other than the points at which the disk was held during the deposition of the conductive film. A small rotation of the disk after the deposition of the conductive film is sufficient to move the contact points to locations where the conductive has been adequately formed. Since the magnetic thin films in question are on the order of ten's of nanometers thick care must be taken not to overheat the thin film through which the bias current flows.
- The atomic percent compositions given above are given without regard for the small amounts of contamination that invariably exist in sputtered thin films as is well known to those skilled in the art.
- The invention has been described with respect to use on thin film magnetic disks, but other uses and applications which can benefit from the properties of the protective layer structure of the invention will be apparent to those skilled in the art.
Claims (20)
Priority Applications (2)
Application Number | Priority Date | Filing Date | Title |
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US09/952,872 US20030049496A1 (en) | 2001-09-11 | 2001-09-11 | Thin film protective layer with buffering interface |
US10/756,556 US6969447B2 (en) | 2001-09-11 | 2004-01-12 | Thin film protective layer with buffering interface |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
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US09/952,872 US20030049496A1 (en) | 2001-09-11 | 2001-09-11 | Thin film protective layer with buffering interface |
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US10/756,556 Division US6969447B2 (en) | 2001-09-11 | 2004-01-12 | Thin film protective layer with buffering interface |
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US20030049496A1 true US20030049496A1 (en) | 2003-03-13 |
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US09/952,872 Abandoned US20030049496A1 (en) | 2001-09-11 | 2001-09-11 | Thin film protective layer with buffering interface |
US10/756,556 Expired - Fee Related US6969447B2 (en) | 2001-09-11 | 2004-01-12 | Thin film protective layer with buffering interface |
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US10/756,556 Expired - Fee Related US6969447B2 (en) | 2001-09-11 | 2004-01-12 | Thin film protective layer with buffering interface |
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Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
CN115261774A (en) * | 2022-08-26 | 2022-11-01 | 集美大学 | Gradient superhard composite film layer of high-speed blanking die cutting edge of aluminum alloy pop can cover and preparation method thereof |
Families Citing this family (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP4005976B2 (en) * | 2004-03-03 | 2007-11-14 | Tdk株式会社 | Magnetic recording medium |
JP4382843B2 (en) * | 2007-09-26 | 2009-12-16 | 株式会社東芝 | Magnetic recording medium and method for manufacturing the same |
Family Cites Families (12)
Publication number | Priority date | Publication date | Assignee | Title |
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JP2830544B2 (en) | 1991-10-25 | 1998-12-02 | 松下電器産業株式会社 | Magnetic recording media |
US5773124A (en) | 1993-02-22 | 1998-06-30 | Hitachi, Ltd. | Magnetic recording medium comprising a protective layer having specified electrical resistivity and density |
US6330131B1 (en) | 1993-09-17 | 2001-12-11 | Read-Rite Corporation | Reduced stiction air bearing slider |
JP3058066B2 (en) * | 1995-11-06 | 2000-07-04 | 富士電機株式会社 | Magnetic recording medium and method of manufacturing the same |
US5808832A (en) | 1996-02-27 | 1998-09-15 | International Business Machines Corporation | Ultrathin silicon wear coating for a slider and thin film magnetic head elements at an ABS |
US5855746A (en) | 1996-02-28 | 1999-01-05 | Western Digital Corporation | Buffered nitrogenated carbon overcoat for data recording disks and method for manufacturing the same |
DE19651615C1 (en) | 1996-12-12 | 1997-07-10 | Fraunhofer Ges Forschung | Sputter coating to produce carbon layer for e.g. magnetic heads |
US5942317A (en) | 1997-01-31 | 1999-08-24 | International Business Machines Corporation | Hydrogenated carbon thin films |
US6069769A (en) | 1997-09-30 | 2000-05-30 | International Business Machines Corporation | Air bearing slider having rounded corners |
US6086949A (en) | 1998-02-25 | 2000-07-11 | International Business Machines Corporation | Thin film protective coating with two thickness regions |
US6303214B1 (en) | 1999-04-14 | 2001-10-16 | Seagate Technology Llc | Magnetic recording medium with high density thin dual carbon overcoats |
US6086730A (en) | 1999-04-22 | 2000-07-11 | Komag, Incorporated | Method of sputtering a carbon protective film on a magnetic disk with high sp3 content |
-
2001
- 2001-09-11 US US09/952,872 patent/US20030049496A1/en not_active Abandoned
-
2004
- 2004-01-12 US US10/756,556 patent/US6969447B2/en not_active Expired - Fee Related
Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
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CN115261774A (en) * | 2022-08-26 | 2022-11-01 | 集美大学 | Gradient superhard composite film layer of high-speed blanking die cutting edge of aluminum alloy pop can cover and preparation method thereof |
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US20040170871A1 (en) | 2004-09-02 |
US6969447B2 (en) | 2005-11-29 |
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