WO1998002715A1 - Revetement destine au controle simultane des proprietes optiques et tribologiques de surfaces de reference interferometrique - Google Patents

Revetement destine au controle simultane des proprietes optiques et tribologiques de surfaces de reference interferometrique Download PDF

Info

Publication number
WO1998002715A1
WO1998002715A1 PCT/US1997/012095 US9712095W WO9802715A1 WO 1998002715 A1 WO1998002715 A1 WO 1998002715A1 US 9712095 W US9712095 W US 9712095W WO 9802715 A1 WO9802715 A1 WO 9802715A1
Authority
WO
WIPO (PCT)
Prior art keywords
coating
disk
recited
tester
transparent
Prior art date
Application number
PCT/US1997/012095
Other languages
English (en)
Inventor
Ashok R. Machcha
Kok Lue
Kenneth H. Womack
Blasius Brezoczky
Daniel L. Abraham
Original Assignee
Phase Metrics
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Phase Metrics filed Critical Phase Metrics
Publication of WO1998002715A1 publication Critical patent/WO1998002715A1/fr

Links

Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B11/00—Measuring arrangements characterised by the use of optical techniques
    • G01B11/14—Measuring arrangements characterised by the use of optical techniques for measuring distance or clearance between spaced objects or spaced apertures

Definitions

  • the present invention relates to a coated transparent substrate that is used in a flying height tester which measures the height of an air bearing between a disk and a recording head of a hard disk drive.
  • Hard disk drives contain magnetic recording heads which magnetize and sense the magnetic field of a rotating magnetic disk(s).
  • the recording head is integrated into a slider which has aerodynamic features that create an air bearing between the head and the rotating disk. The air bearing prevents contact and corresponding mechanical wear of the recording head.
  • the sliders are typically tested in a flying height tester before being installed into a hard disk drive assembly.
  • Flying height testers measure the height of the air bearing to insure that the slider complies with manufacturing specifications.
  • Flying height testers typically contain a loader which places each slider adjacent to a rotating transparent disk. A beam of light is directed through the substrate and reflected off of the disk/slider interface. The reflected light creates an interference pattern that is detected and analyzed by the tester to determine the flying height of the slider.
  • the transparent disk of the flying height tester is typically constructed from a glass material such as BK-7.
  • the glass is susceptible to scratching and wear particularly when the slider strikes or otherwise makes contact with the disk. Damage in the glass may disturb the interference pattern of the reflected light, reducing the accuracy of the tester. Extensive damage can adversely influence the flying characteristics of sliders. Thus, it would be desirable to provide an optical reference surface that is not susceptible to scratching and wear.
  • sliders are designed to operate in or near contact with the disk.
  • the contact may create undesirable wear on the slider or disk during the flying height test . It would therefore be desirable to provide a transparent disk having an optical reference surface that reduced the friction and wear between the disk surface and an adjacent slider.
  • the present invention is a coated transparent interferometric reference for an optical tester.
  • the coated reference surface provides improved tribological and optical properties as would be desirable for a disk in an interferometric flying height tester.
  • the disk for example may comprise a diamond like coating that covers a surface of a glass substrate.
  • the coating has a wear resistance which prevents scratching of the underlying glass substrate.
  • the disk may also have an optical bias layer which compensates for the optical phase shift created by the protective coating.
  • the disk may have an overlaying lubricant that is applied to the disk or disk coating to reduce friction and stiction.
  • Figure 1 is a schematic of a flying height tester having a disk of the present invention
  • Figure 2 is a cross-sectional view of an alternate embodiment of the disk
  • Figure 3 is a cross-sectional view of another alternate embodiment of the disk.
  • Coatings on glass disks offer a way to improve the tribological properties of the glass surface as well as the interferometer signal produced by a gap between the glass and a second reflective surface of interest.
  • Specific applications of interest include measuring flying height of a disk drive slider on a rapidly spinning glass disk and the measurement of pole-tip recession using a slider positioned at a small gap distance beneath a glass reference flat.
  • an amorphous diamond-like-carbon (D C) layer is deposited on a glass disk.
  • a deposition can introduce a phase shift in the light reflected off the surface.
  • another material layer of suitable optical constants e.g., Si ⁇ 2 or MgF2
  • the phase shift on reflection that would exist for DLC alone with no underlay can be effectively nulled out by introduction of an appropriate thickness of lower index material between the DLC and the disk.
  • the DLC coated glass can be made to behave in reflection as a simple bulk dielectric even though a multiple layer coating is actually present.
  • the index and thickness of the intermediate layer the phase shift on reflection can be over-compensated so that the phase shift "at contact' occurs well away from an interference minimum.
  • either hydrogenated or nitrogenated DLC coatings can be used for improving the tribological properties of a glass disk.
  • the DLC layer improves the tribology with respect to friction, stiction, corrosion resistance, lubricant adsorption and bonding, and also changes in environmental conditions such as humidity, temperature and gas composition.
  • Such an overcoat has been extensively used for the protection and improved durability of thin film magnetic media.
  • amorphous hydrogenated DLC coatings have been used in various applications.
  • nitrogen incorporated in DLC films results in some attractive properties. The internal stresses of the films are found to be lower without much change in the surface hardness. The optical properties are as also changed.
  • Nitrogenated DLC films have a higher conductivity and may possess a different surface polarity due to the structural changes introduced in the bonding by the presence of nitrogen atoms.
  • the polarity change may improve the lubricant adsorption of the DLC surface when it is applied.
  • the degree of conductivity may be controlled by changing the amount of nitrogen incorporated into the film by changing the process parameters. This may play an important role in reducing the amount of tribo- charging and hence the amount of contamination or wear debris that might accumulate at the interfaces which have tribological interaction. It would also play an important role in reducing the amount of accumulation of charge from other sources in the vicinity of the surface and thus decrease the need for a separate de-ionization unit.
  • ESD electro-static discharge
  • Sensors such as magneto- resistive sliders (also known as MR heads) and the future GMR (giant magneto-resistive) heads may benefit from the reduced charging associated with a nitrogenated DLC coating. This may be important in future use of these types of heads with flying height testers.
  • improvements in the wear resistance of the glass disk surface may be obtained by coating an ultra- thin layer of lubricant to either the uncoated or a DLC-coated glass surface.
  • This thin layer of lubricant may consist of a single layer or multiple layers of molecules. Such lubricant layers have been used for thin film magnetic media. However, the thickness of the lubricant should be only be a fraction of the slider flying height ( ⁇ 10%).
  • the implementation of the ultra thin lubricant may be achieved by spin coating, dip-coating, Langmuir-Blodgett (LB) or self assembling mono-layer (SAM ) techniques.
  • the bonding of the lubricant molecules to the glass or overcoated surface may be achieved by spontaneous chemical reaction between the surface active head group of the lubricant and the substrate surface. Temperature, UV light, electron beam, plasma or surface treatment or a combination of the above may all impart the degree of bonding.
  • Figure 1 shows a flying height tester 10.
  • the flying height tester 10 is typically used to measure the height of an air bearing 12 created between a slider 14 of a recording head and a rotating transparent disk 16.
  • the slider 14 is typically mounted to a loader (not shown) which can allow an operator to place a new head thereon.
  • the flying height tester 10 can therefore test a number of different sliders 14.
  • a flying height tester 10 is shown and described, it is to be understood that the disk 16 of the present invention can be configured in other shapes and used in other optical testers such as an optical profilometer that utilizes an optical reference surface.
  • the transparent disk 16 Used in the flying height tester 10, the transparent disk 16 is rotated by a spindle (not shown) . Rotation of the disk 16 induces a flow of air below the slider 14.
  • the recording head 14 has aerodynamic features which induce the formation of the air bearing 12 between the slider 14 and the rotating disk 16.
  • the flying height tester 10 further includes a light source 18 which directs a beam of light 20 through the disk 16.
  • the light beam 22h is reflected off of the slider 14 and back through the disk 16. Part of the light beam 22s also reflects off of the interface between the disk 16 and the air bearing 12.
  • the two reflected light beams 22h and 22s create an interference pattern that is detected by a photodetector 24.
  • the photodetector 24 is coupled to a computer 26 that can determine the height of the air bearing 12 from the interference pattern.
  • the disk 16 has a substrate 28 which has a first surface 30 and an opposite second surface 32.
  • the substrate 28 is typically constructed from a glass material such as BK-7 that is transparent to light.
  • Other optical quality materials may also be used such as quartz, fused silicon or sapphire.
  • the tribological and optical coatings of the present invention will alleviate the need to use a more expansive material such as sapphire.
  • the slider 14 is typically constructed from a ceramic material such as AlTiC. A considerable problem with flying height testers as described herein is that the slider material is typically much harder than the glass disk substrate 28. If the slider 14 comes into contact with the glass, the glass will scratch and wear.
  • the first surface 30 of the substrate 28 may be covered with a protective coating 34.
  • the protective coating 34 is a material which has a hardness that is greater than the hardness of the glass.
  • the protective coating 34 is preferably a diamond-like-carbon (DLC) material.
  • the coating 34 may be applied using sputtering or
  • the DLC thickness should be less than about V , where ⁇ is the wavelength of light and n is the refractive index of the coating. In the preferred embodiment, the thickness of the DLC coating is preferably less than lOnm.
  • the minimum thickness of the DLC coating 34 will be determined by the mechanical stresses encountered in use. However, the preferable thickness will also depend upon the desired optical properties of the combination disk and coating. Specifically, the coating 34 will induce an additional phase shift in the light beam 22s which reflects from the air-coating outerface, thereby influencing the measured interference pattern.
  • the protective coating thickness may be adjusted to optically bias the interference pattern, thereby achieving high sensitivity to flying height variations at a predetermined flying height (e.g. contact between disk and slider) .
  • preferred interlayers may be used to adjust or null the phase offset caused by the protective coating 34. Multi-layer coatings are described in more detail below.
  • the coating 34 may be a hydrogenated or nitrogenated DLC material or any combination thereof. In addition to providing a hard protective surface the coating 34 may also provide other favorable tribological properties such as lower stiction, lower friction and corrosion resistance. Additionally, the nitrogen content of nitrogenated DLC may be varied to reduce the amount of tribo-charging and resulting accumulation of debris and contamination on the surface of the disk 16. Reduced tribo-charging will play an important role in testing MR heads. Furthermore, the DLC 34 will also improve the adsorption of a lubricant that may also be applied to the disk 16 as described in more detail below.
  • Figure 2 shows another embodiment of the disk 16.
  • the existence of the DLC coating 34 may create a phase shift in the reflected light beam 22s which influences the interference pattern and the sensitivity of the tester 10.
  • the disk 16 may include an optical bias layer 36 located between the protective coating 34 and the substrate 28.
  • the bias layer 36 preferably has an index of refraction and a thickness which will adjust the phase shift of the reflected light beam 22s.
  • the bias layer thickness is adjusted to compensate the phase shift induced by the protective coating 34.
  • the multi-layered disk behaves as a dielectric medium having a net phase shift on reflection adjusted to approximately 180°.
  • the bias layer 36 is preferably a transparent material such as Si ⁇ 2 or MgF2 having an index of refraction lower than the glass substrate 28 with a thickness of 10-30 nanometers.
  • the bias layer 36 may be applied by sputtering, ion-beam deposition or any other means.
  • the thickness and index of refraction may be selected so that the phase shift biases the interference pattern to a point of high sensitivity at slider- disk contact.
  • interlayers may achieve enhanced interferometric properties.
  • the interlayer may be a single dielectric layer having an index and thickness adjusted to phase bias the interference pattern.
  • reflective interlayers may be added to enhance the contrast ratio ⁇ !--- of the interference pattern, and sensitivity over a predetermined air bearing spacing 12.
  • the protective coating 34 prevents damage to a carefully designed and fabricated interferometric reference surface.
  • FIG. 3 shows another embodiment of the disk 16.
  • the disk 16 may have a lubricant 38 applied to the DLC coating 34.
  • the lubricant 38 passivates the surface and reduces the friction and wear between the slider 14 and the disk 16.
  • the lubricant 38 may comprise perfluoropolyether (PFPE) or a mixture of a PFPE with other lubricants applied with known processes such as spin coating, dip coating, Langmuir-Blodgett , or self assembling mono-layer (SAM) techniques.
  • PFPE perfluoropolyether
  • SAM self assembling mono-layer
  • the lubricant 38 may consist of a single layer, or multiple layers of molecules.
  • the lubricated disk 16 may be treated with heat, ultraviolet light, electron beam or other means to bond the lubricant 38 to the underlying disk material.
  • the transparent disk 16 is periodically cleaned to remove debris and contaminants that may accumulate on the outer surfaces of the disk 16.
  • the disk 16 may be cleaned with a cleaning solution which contains the lubricant 38 so that - li ⁇
  • the surface of the disk 16 is replenished with residual lubricant by the cleaning process.
  • a cleaning/lubricating process will utilize a cleaning solution having a lubricant concentration of less than 10%.
  • the lubricant 38 can be applied to a disk 16 which does not have the protective coating 34 or the bias layer 36.
  • a preferred class of lubricants for application directly to the transparent substrate 28 comprise PFPE lubricants.
  • the specific PFPE lubricant should have a refractive index closely matched to the substrate 28. It snould also have low surface tension for uniformly wetting the substrate surface, and be non-corrosive (ph 7) . While it is believed that many possible PFPE lubricants such as Z-DOL may be used to lubricate the transparent substrate 28, it has been found that Demmum S-200 (Daiken Industries Ltd.) substantially satisfies the aforementioned criteri .
  • a sufficient clearing process may comprise rinsing m a combination of solvents including de- ionized water, ultrasonic clearing, and spin drying.
  • the glass disk 16 is exposed to a plasma cleaning process comprising 02 or more preferably Ozone.
  • Lubricant is applied to the cleaned substrate 28 by a dipping or gravity process, or by spin coating. In both cases, the lubricant is preferably used in solutions having a concentration to yield lubricating layers typically 1-10 molecular layers thick.
  • a UV curable phosphozene e.g. X-1P, Dow Chemical
  • the lubricant layer is UV cured to achieve good adhesion to the glass surface.

Landscapes

  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Manufacturing Of Magnetic Record Carriers (AREA)

Abstract

Référence (34) interférométrique à revêtement transparent, destinée à un testeur optique (10). Selon l'un des aspects de la présente invention, la surface de référence (34) à revêtement possède des propriétés optiques et tribologiques identiques à celles souhaitables pour un disque (16) dans un testeur (10) interférométrique de la hauteur de survol.
PCT/US1997/012095 1996-07-12 1997-07-11 Revetement destine au controle simultane des proprietes optiques et tribologiques de surfaces de reference interferometrique WO1998002715A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US67951196A 1996-07-12 1996-07-12
US08/679,511 1996-07-12

Publications (1)

Publication Number Publication Date
WO1998002715A1 true WO1998002715A1 (fr) 1998-01-22

Family

ID=24727202

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/US1997/012095 WO1998002715A1 (fr) 1996-07-12 1997-07-11 Revetement destine au controle simultane des proprietes optiques et tribologiques de surfaces de reference interferometrique

Country Status (1)

Country Link
WO (1) WO1998002715A1 (fr)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US7273655B2 (en) 1999-04-09 2007-09-25 Shojiro Miyake Slidably movable member and method of producing same
US7771821B2 (en) 2003-08-21 2010-08-10 Nissan Motor Co., Ltd. Low-friction sliding member and low-friction sliding mechanism using same
US8096205B2 (en) 2003-07-31 2012-01-17 Nissan Motor Co., Ltd. Gear
US8152377B2 (en) 2002-11-06 2012-04-10 Nissan Motor Co., Ltd. Low-friction sliding mechanism

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5473431A (en) * 1993-04-29 1995-12-05 Conner Peripherals, Inc. Interferometric flying height measuring device including an addition of a spacer layer

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5473431A (en) * 1993-04-29 1995-12-05 Conner Peripherals, Inc. Interferometric flying height measuring device including an addition of a spacer layer

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US7273655B2 (en) 1999-04-09 2007-09-25 Shojiro Miyake Slidably movable member and method of producing same
US8152377B2 (en) 2002-11-06 2012-04-10 Nissan Motor Co., Ltd. Low-friction sliding mechanism
US8096205B2 (en) 2003-07-31 2012-01-17 Nissan Motor Co., Ltd. Gear
US7771821B2 (en) 2003-08-21 2010-08-10 Nissan Motor Co., Ltd. Low-friction sliding member and low-friction sliding mechanism using same

Similar Documents

Publication Publication Date Title
US6099981A (en) Magnetic recording medium having a lubricant film coated on optimum conditions and method of evaluating the lubricant film
Pit et al. Formation of lubricant “moguls” at the head/disk interface
US5565266A (en) Multilayer magnetooptic recording media
EP0700505B1 (fr) Dispositif interferometrique de mesure de la hauteur de sustentation
KR20010021674A (ko) 다층의 탄소 함유 보호 오버코팅부를 포함하는 자기 기록매체
US5919560A (en) Magnetic recording medium having a lubricant film
WO1998002715A1 (fr) Revetement destine au controle simultane des proprietes optiques et tribologiques de surfaces de reference interferometrique
US6491798B2 (en) Magnetic recording medium and magnetic storage apparatus
JPH0712714A (ja) 磁気記録媒体のカーボン保護膜の評価方法
US8607425B2 (en) Method for lubed tape burnish for producing thin lube media
US6477011B1 (en) Magnetic recording device having an improved slider
Li et al. Limitations and corrections of optical profilometry in surface characterization of carbon coated magnetic recording disks
US6757115B2 (en) Magnetic transfer apparatus and magnetic recording medium
Karis et al. Pin‐on‐disk tribology of thin‐film magnetic recording disks
US6804010B1 (en) Optical coating thickness optimization for fly height test media
US6369900B1 (en) Glide head with features on its air bearing surface for improved fly height measurement
Smallen et al. Pole tip recession measurements on thin film heads using optical profilometry with phase correction and atomic force microscopy
US6322880B1 (en) Magneto-resistance recording media comprising a foundation layer and a C-overcoat
Dai et al. Tribological issues in perpendicular recording media
US5675463A (en) Slider with a transparent coating on a rail and a reflective material within a recess of the rail
US6704103B2 (en) Coatings for sensitivity enhancement of signal from glass disks
Tsai et al. Tribological phenomena at the head–disk interface of thin‐film rigid disks
Phetdee Development of High-Durability and High-Sensitivity Glass Disk for Flying Height Measurement Process
JPH10153543A (ja) 磁気記録媒体のカーボン膜質評価方法及び磁気記録媒体
US20040258873A1 (en) Flexible magnetic disc medium

Legal Events

Date Code Title Description
AK Designated states

Kind code of ref document: A1

Designated state(s): JP KR SG

AL Designated countries for regional patents

Kind code of ref document: A1

Designated state(s): AT BE CH DE DK ES FI FR GB GR IE IT LU MC NL PT SE

121 Ep: the epo has been informed by wipo that ep was designated in this application
NENP Non-entry into the national phase

Ref country code: JP

Ref document number: 98506174

Format of ref document f/p: F

122 Ep: pct application non-entry in european phase