US20020093761A1 - Hard disk drive for perpendicular recording with transducer having submicron gap between pole tips - Google Patents

Abstract

An information storage system includes a transducer having a loop of ferromagnetic material with pole tips separated by an nonferromagnetic gap located adjacent to a medium such as a rigid disk. During writing the separation between the pole tips and the media layer of the disk is a small fraction of the gap separation. Due to the small separation between the pole tips and the media layer, the magnetic field generated by the transducer and felt by the media has a larger perpendicular than longitudinal component, favoring perpendicular recording over longitudinal recording. The media may have an easy axis of magnetization oriented substantially along the perpendicular direction, so that perpendicular data storage is energetically favored. The transducer may also include a magnetoresistive sensor for reading magnetic information from the disk.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS
• This application claims the benefit under 35 U.S.C. §120 of pending U.S. Pat. application Ser. No. 08/577,493, filed Dec. 22, 1995; pending U.S. Pat. application Ser. No. 08/528,890, filed Sep. 15, 1995; pending U.S. Pat. application Ser. No. 08/338,394, filed Nov. 14, 1994; abandoned U.S. Pat. application Ser. No. 08/673,281, filed Jun. 28, 1996; U.S. Pat. No. 6,212,047, filed Dec. 20, 1996; U.S. Pat. No. 6,198,607, filed Oct. 2, 1996; U.S. Pat. No. 6,160,685, filed Aug. 26, 1996; U.S. Pat. No. 5,949,612, filed Aug. 15, 1995 and U.S. Pat. No. 5,550,691, filed Oct. 22, 1992, all of which are incorporated by reference herein.[0001]
TECHNICAL FIELD
• The present disclosure relates to systems for electromagnetic storage and retrieval of information, such as disk drive system and components.[0002]
BACKGROUND
• Hard disk drives have traditionally employed electromagnetic transducers that are spaced from a rapidly spinning rigid disk by a thin layer of air that moves with the disk surface. Such a spacing is believed to be important in avoiding damage between the rapidly spinning disk and the transducer, which is constructed with an aerodynamic “slider” designed to “fly” slightly above the disk surface, buoyed by the moving air layer. This spacing or fly height, however, limits the density with which data can be stored and lowers the resolution and amplitude with which data can be retrieved.[0003]
• Data is conventionally stored in a thin media layer adjacent to the disk surface in a longitudinal mode, i.e., with the magnetic field of bits of stored information oriented generally along the direction of a circular data track, either in the same or opposite direction as that with which the disk moves relative to the transducer. In order to record such a longitudinal bit in the media layer, the transducer has a ring-shaped core of magnetic material with a gap positioned adjacent to the disk, while current in a coil inductively coupled to the core induces a magnetic field adjacent to the gap strong enough to magnetize a local portion of the media, creating the bit. This type of transducer is commonly termed a “ring head.” The media layer for this form of data storage has an easy axis of magnetization parallel to the disk surface, so that writing of bits in the longitudinal mode is energetically favored. Since adjacent bits within the plane of the thin film media have opposite magnetic directions, demagnetizing fields from adjacent bits limit the minimum length of a magnetic transition between such bits, thereby limiting the density with which data can be stored and lowering the signal-to-noise ratio at high bit densities. Moreover, at high bit densities, the transition location between longitudinal bits is more difficuly to control, increasing errors known as “bit shift”. Also, overlap between adjacent longitudinal bits of opposite polarity can result in reduced transition amplitude at higher bit densities, termed “partial erasure” and reducing the signal to noise ratio since a larger fraction of each bit is degraded by the transition. At very high densities, demagnetization of the oppositely directed longitudinal bits may occur over time, resulting in data loss.[0004]
• Perpendicular data storage, in which the magnetic data bits are oriented normally to the plane of the thin film of media, has been recognized for many years to have advantages including the relative absence of in-plane demagnetizing fields which are present in longitudinal data storage. In addition to potentially achieving sharper magnetic transitions due to the reduction of bit shift and partial erasure, perpendicular data storage may offer a more stable high density storage, at least for multilayered media. Despite these advantages, perpendicular data storage has not yet seen commercial success. The system typically proposed for perpendicular recording includes a transducer having a single pole, commonly termed a “probe head.” In order to form a magnetic circuit with the probe head, a magnetically soft underlayer adjoins the media layer opposite to the pole, the underlayer providing a path for magnetic flux that flows to or from the transducer through a return plane of the head separate from the pole.[0005]
• Several disadvantages of the probe head and underlayer system have been discovered. Comparison of a probe head with a ring head having a gap of a thickness equal to that of the single pole has revealed that the longitudinal fields from the ring head are more spatially localized than the perpendicular fields from the probe head, since the field lines in a ring head span from the closest edges of one pole to the other across the gap, while the field lines in the single pole probe head radiate from both the probe tip and the sides of the probe toward the underlayer (unless the pole tip contacts the underlayer), the field lines from the sides of the probe essentially broadening the transition beyond the dimensions of the probe tip. Moreover, the ring head has a single amagnetic gap, while the probe head has two gaps: one between the probe and underlayer and one between the return plane and the underlayer. The presence of this second gap renders the probe head extremely sensitive to external stray fields. Due to the high reluctance of the second gap, stray fields entering the head are channeled directly through the probe and across the media. Calculations show that a 5 Gauss (G) stray field can easily be amplified to 2000 G at the center of the media, large enough to cause erasure, which we have observed in the laboratory.[0006]
• One of the advantages of the probe head and underlayer recording system is that the write fields produced between the probe and underlayer are generally stronger than those attained underneath the gap of a ring head. There is a disadvantage to the high write fields, however, in heads of insufficient stability, since domains oriented parallel to the probe can induce fields at the media gap which are strong enough to erase data, another effect which we have observed empirically. Moreover, achieving an efficient magnetic circuit in the probe head and underlayer system is difficult. During head fabrication, great care is taken to magnetically align the easy axis of the permalloy yoke perpendicular to the direction of magnetic flux flow. While this may be relatively straightforward to accomplish in the small magnetic structures of the head, it is problematic for large circular structures such as the soft magnetic underlayer of the disk, which forms part of the magnetic flux circuit in the probe head system. As a result, the permeability of the underlayer has generally been unsatisfactory and inhomogeneous, and the magnetic circuit therefore inefficient.[0007]
• The possibility of employing a flying ring head in combination with media having a perpendicular anisotropy appears to have been originally proposed in an article entitled, “Self-Consistent Computer Calculations For Perpendicular Recording,” IEEE Transactions On Magnetics, September 1980, by Potter and Beardsley. A difficulty in the system described in this article is that the maximum perpendicular component of the magnetic field transmitted from the head to the medium is substantially less than the maximum longitudinal component of that field. Wang and Huang, in “Gap-Null Free Spectral Response of Asymmetric Ring Heads For Longitudinal and Perpendicular Recording”, IEEE Transactions On Magnetics, September 1990, calculate the magnetic fields transmitted from a ring head that has a gap angled away from normal to a media layer. Similarly, Yang and Chang, in an article entitled “Magnetic Field of an Asymmetric Ring Head with an Underlayer”, IEEE Transactions On Magnetics, March 1993, calculate the magnetic fields transmitted from a ring head with a slanted gap, and include a soft magnetic underlayer adjacent to the media to complete the magnetic circuit of the ring head.[0008]
• Osaka et al., in the article “Perpendicular Magnetic Recording Process Of Electroless-Plated CoNiReP/NiFeP Double Layered Media With Ring-Type Heads”, look at recording performance of flexible double layered magnetic media to measure the effect of various coercivity underlayers. And Onodera et al., in the article “Magnetic Properties And Recording Characteristics of CoPtB-O Perpendicular Recording Media” investigate how varying the proportion of oxygen can be used to control the perpendicular anisotropy and coercivity of that media, which is measured with a metal-in-gap video cassette recorder ring head. More recently, U.S. Pat. No. 5,455,730 to Dovek et al. proposes a disk drive system with a slider that skis on a liquid spread atop a wavy disk, with a transducer stepped back from the support surface having a magnetoresistive sensor and an electrical means for compensating for a baseline modulation induced by the temperature sensitive waviness of the disk. Unfortunately, the spacing added by the liquid and the distance between the bottom of the carrier and the transducer reduces data storage density and resolution.[0009]
• What is needed is a system that affords the advantages of perpendicular data storage in a durable, high density, hard disk drive system.[0010]
SUMMARY
• The present disclosure is directed to an information storage system employing a microscopic transducer having a loop of ferromagnetic material with pole tips separated by an nonferromagnetic gap located adjacent to a medium such as a rigid disk. During writing of a magnetic signal to the disk the separation between the pole tips and the media layer of the disk is maintained at a small fraction of the gap separation. Due to the small separation between the pole tips and the media layer, the magnetic field generated by the transducer and felt by the media has a larger perpendicular than longitudinal component, favoring perpendicular recording over longitudinal recording. Moreover, the head to media separation is small enough to allow a significant reduction in the gap size without causing the longitudinal field component to predominate over the perpendicular field component, providing further increases in data density. The media may have an easy axis of magnetization oriented substantially along the perpendicular direction, so that perpendicular data storage is energetically favored. The transducer may also include a magnetoresistive sensor for reading magnetic information from the disk.[0011]
BRIEF DESCRIPTION OF THE DRAWINGS
• FIG. 1 shows a greatly enlarged, simplified, cross-sectional view of a portion of a data storage system in accordance with the present invention.[0012]
• FIG. 2 shows a plot of longitudinal and perpendicular field components of the magnetic field transmitted from the pole tips to the medium of the data storage system of[0013]claim 1.
• FIG. 3 shows a plot comparing maximum strength perpendicular and longitudinal magnetic field components transmitted from the pole tips of FIG. 1 at various distances from the head.[0014]
• FIG. 4 is an enlarged perspective view of a generally plank-shaped embodiment of a transducer holding the pole tips of FIG. 1 in one of three disk-facing projections.[0015]
• FIG. 5 is a bottom view of the transducer of FIG. 4.[0016]
• FIG. 6 is a cross-sectional view of a magnetically active portion of the transducer of FIG. 4.[0017]
• FIG. 7 is an opened up bottom view of the magnetically active portion of FIG. 6.[0018]
• FIG. 8 is a further enlarged bottom view of the magnetic pole structure of FIG. 7.[0019]
• FIG. 9 is a fragmentary cross-sectional view of an embodiment having a pole structure including a high magnetic saturation material adjoining the gap and one of the pole tips.[0020]
• FIG. 10 is a plot of the field strength of the embodiment of FIG. 9.[0021]
• FIG. 11 is a fragmentary cross-sectional view of an embodiment having a pole structure including a high magnetic saturation material adjoining a slanted gap and one of the pole tips.[0022]
• FIG. 12 is a cross-section of the embodiment of FIG. 9 and including a magnetoresisitve sense element adjacent to the magnetic core and distal to the pole structure.[0023]
• FIG. 13 is an opened up top view of the magnetoresistive sense element and magnetic core of FIG. 12.[0024]
• FIG. 14 is an enlarged cross-sectional view illustrating the formation of the magnetoresistive sense element and magnetic core of FIG. 13.[0025]
• FIG. 15 is an enlarged cross-sectional view illustrating the formation of a conductive terminal and lead to connect with the magnetoresistive sense element of FIGS.[0026]11-13.
• FIG. 16 is a cross-sectional view shows later steps in the formation of the embodiment of FIG. 12.[0027]
• FIG. 17 is an opened up top view of the coil layer of the embodiment shown in FIGS. 11 and 14.[0028]
• FIG. 18 is a cross-sectional view illustrating a subsequent stage in the formation of the embodiment of FIG. 12 that focuses on the construction of the high magnetic saturation layer of FIG. 9.[0029]
• FIG. 19 is a cross-sectional view illustrating a subsequent step in the formation of the embodiment of FIG. 12 that focuses on the construction of the gap of FIG. 9.[0030]
• FIG. 20 is a cross-sectional view illustrating a later step in the formation of the embodiment of FIG. 12 that focuses on the construction of the pole tips of FIG. 9.[0031]
• FIG. 21 is a top view of the pole tip construction of FIG. 20.[0032]
• FIG. 22 is a cross-sectional view of the formation of a durable pad encasing the pole tips of FIG. 9.[0033]
• FIG. 23 is a cutaway bottom view of a flexure beam and gimbal to which the transducer of FIG. 12 is attached.[0034]
• FIG. 24 is an opened up top view of a disk drive system employing the transducer of FIG. 12 and the beam of FIG. 23.[0035]
• FIG. 25 is a highly magnified cross-sectional view of a magnetic recording surface having a high perpendicular anisotropy.[0036]
DETAILED DESCRIPTION
• Referring now to FIG. 1, a greatly enlarged cross-sectional view of an information storage system in accordance with the present invention focuses on a pair of[0037]pole tips20 and22 of anelectromagnetic transducer25 that are separated by anamagnetic gap27, the transducer sliding on a rigidmagnetic recording disk30. Thedisk30 in this simplified drawing has amedia layer33 disposed between asubstrate35 and aprotective overcoat38, and asurface40 on which thetransducer25 slides, the disk moving relative to the transducer in a direction shown byarrow41. As a descriptive aid, a direction normal todisk surface40 is termed the perpendicular or vertical direction, while a direction parallel to thedisk surface40 is defined in terms of lateral and longitudinal directions. Thegap27 has a longitudinal extent G separating thepole tips20 and22 that is several times a perpendicular distance D separating the pole tips from themedia layer33, distance D including the thickness λ of theovercoat38 and any lubricant, not shown, disposed atop the overcoat. Themedia layer33 has a thickness δ such that the perpendicular distance D from a midpoint of themedia layer33 and thepole tips20 and22 is a fraction of the gap extent G. A number of magnetic fields lines42 produced by thetransducer25 during writing of data on thedisk30 travel both directly across thegap27 and radiate in a semicircular fashion from onepole tip20 to the other22 through themedia layer33. The field lines42 that penetrate thedisk30 are most concentrated adjacent tocorners44 and46 ofrespective pole tips20 and22.
• In FIG. 2, the field lines[0038]42 of FIG. 1 are displayed in terms of the magnitude of longitudinal50 and perpendicular52 components felt by themedia layer33 at a perpendicular distance D from thepole tips20 and22 that is in the neighborhood of one-tenth the gap spacing G. The dimensions along the horizontal axis of this figure are depicted with the gap spacing G being equal to unity. Thelongitudinal component50 can be seen to have the shape of a symmetrical curve that peaks in themedia layer33 directly across from a center of thegap27. Theperpendicular component52, on the other hand, has zero strength directly opposite from the center of thegap27, and a peak in magnitude directly opposite both of thecorners44 and46, the peak oppositecorner46 having a negative value to reflect that the perpendicular component oppositecorner46 is oppositely directed relative to the perpendicular component oppositecorner44. Note that theperpendicular component52 of the magnetic field felt by the media has a magnitude nearest thecorners40 and44 that exceeds the maximum magnitude of thelongitudinal component50, encouraging perpendicular data storage in the media layer.
• FIG. 3 compares a maximum[0039]longitudinal field component55 with a maximum perpendicularly orientedfield component57 over various perpendicular distances D from thepole tips20 and22. As can be seen in the previous figure, the maximum longitudinal component is found directly opposite the center of the gap whereas the maximum perpendicular component occurs directly oppositecorners44 and46. In FIG. 3 the longitudinal field strength deep within thegap27 has been given a unitary value for reference, and the vertical distance D from thepole tips20 and22 is given in units for which a distance D equal to the gap width G is equal to one. It is apparent that the maximum perpendicularly orientedfields57 vary with distance D from thepole tips20 and22 much more dramatically than the maximum longitudinally orientedfields55 for distances D less than about one-quarter of the gap spacing G, such that the perpendicular fields are stronger than the longitudinal fields at vertical distances from the pole tips that are a small fraction of the gap width G, while the longitudinal fields are stronger than the perpendicular fields at distances D further than a fraction of the gap width.
• A gap-to-media spacing ratio of ten, which is in a range for which the perpendicular field component would dominate, is approximately present in a sliding contact hard disk drive embodiment having a gap G of 250 nm, an overcoat thickness λ of about 150 Å, including surface roughness and lubricant, and an[0040]active media layer33 with a thickness δ of 200 Å, or a half thickness of about 100 Å. By comparison, a conventional flying transducer having a similar gap spacing employed with a disk having a similar overcoat may have an additional spacing due to the flying height that adds perhaps 40 nm to 100 nm between the pole tips and the media layer, pushing the gap-to-media spacing ratio to a level at which the maximum longitudinal field component felt by the media is larger than the corresponding perpendicular field component. For a disk with amedia33 composed of a number of thin multilayers and a roughly 10 nm overcoat38 (including lubricant), thegap27 may have a width G as small as 0.15 μm and still enjoy a gap-to-media spacing ratio of ten. Such a small gap spacing provides sharper field gradients which afford higher density recording and reading, and a gap as small as 0.10 μm and smaller may be employed to record and read perpendicularly stored data. The employment of media having a high perpendicular anisotropy and low noise is also beneficial, particularly for the situation in which the perpendicular write fields from the head do not clearly dominate.
• As will be discussed below, data retrieval may be inductively accomplished or, preferably, a magneto-resistive (MR) reading element may be incorporated adjacent to the magnetic core. In the situation for which the MR element is separated from the core, the MR element senses perpendicular fields and thus receives a greater signal from perpendicularly magnetized media, rather than the perpendicular offshoots of longitudinally magnetized media, providing a clear advantage to perpendicular data storage. For a transducer which reads either inductively or with an MR element piggybacked to a magnetic core, the sensitivity of the head during reading will be proportional to the efficiency of that head during writing, via the rule of reciprocity. Moreover, the sensitivity of the head in reading signals involves head sensitivity fields that have a direction which mirrors that of the write fields of the head. Thus, just as the perpendicular component of the write fields tends to dominate the longitudinal component at head to media spacings that are a small fraction of the gap width, reading of the perpendicularly magnetized bits of the media is favored at such small head to media spacings, as the head sensitivity fields have a larger perpendicular than longitudinal component in this situation. An advantage of the extremely close head to media spacing afforded by the sliding contact can be seen by looking at the steep slope of the[0041]perpendicular field component57 for distances less than, for instance, one-fourth of the gap width, and realizing that the increase in field strength afforded by such close spacing applies for reading sensitivity as well as writing strength, thus compounding the overall increase in performance of the head for reading after writing.
• Referring now to FIGS. 4 and 5, a greatly enlarged view of a[0042]transducer60 which provides durably intimate head-media proximity, thereby enabling perpendicular data storage, is formed as a generallytrapezoidal chip62 with asurface65 designed to face a recording surface of a rigid magnetic storage disk. The transducer has a magnetically active pad (MAP)68 that projects from the disk-facingsurface65 at a location adjacent to afirst end70 of thechip62 and approximately equidistant between aright side73 and aleft side75 of the chip. A pair of magnetically inactive pads (MIPS)78 and80 project from the disk-facingsurface65 adjacent to asecond end72 of thechip62,MIP78 being disposed about the same distance fromside73 asMIP80 is fromside75. The threepads68,78 and80 are spaced apart from each other to provide a stable support structure for thetransducer60, like a table with three short legs that can maintain contact with any conventional disk surface. An exposed pair ofmagnetic pole tips20 and22 are located on a bottom surface ofMAP68, with anamagnetic gap27 disposed between thepole tips20 and22. The term “amagnetic” is used in the current disclosure to describe materials that are not ferromagnetic, including paramagnetic and diamagnetic materials. Preferably the gap is formed from a diamagnetic material so that a magnetic field across the gap is obstructed, encouraging a magnetic flux path that travels around the gap, increasing the perpendicular component of the field adjacent to the gap. Thepole tips20 and22 are ends of a loop-shaped core of magnetic material that is embedded in thechip62 and not shown in this figure.
• The loop-shaped core extends within a[0043]transduction section88 further in the longitudinal direction than in the vertical or lateral direction, and is inductively coupled within thatarea88 to a coil which winds repeatedly around the core, as will be seen in greater detail below. The protrusion of thepole tips20 and22 from the disk-facingsurface65 allows the core to contact the disk, reducing the spacing between the core and the media layer of the disk while lifting the disk-facing surface of thechip62 from the influence of the thin film of air moving with the disk. As will be seen, theentire chip62 is constructed of a composite of thin films, and any bulk substrate which was used as a work surface for forming many thousands of such chips is removed after formation of the chips. This thinfilm composite chip62 is much lighter than conventional hard disk drive sliders which include bulk substrate, the lighter weight decreasing the inertia of the chip and the power of impacts between the chip and a hard disk, thus reducing the probability of damage. Such a thin film composite transducer having pole tips separated by a submicron gap and contacting a hard disk is also disclosed in parent U.S. Pat. No. 5,041,932, along with perpendicular recording.
• The[0044]chip62 may have a thickness measured in the vertical direction between the disk-facingsurface65 and an opposed major surface, not shown in this figure, of between about 1 mil and about 5 mils, although other thicknesses may be possible, depending upon tradeoffs such as magnetic constraints and mass. The lateral width of this embodiment of thechip62 is about 20 mils, although this width can vary by more than a factor of two and is set primarily by the separation of theMIPS78 and80 required for stability. The width can be much smaller about theMAP68, as discussed below, while still encompassing thetransduction section88. TheMAP68 andMIPS78 and80 extend from thesurface65 an approximately equidistant amount, which may range between about 2 μm and 8 μm, which is sufficient to avoid aerodynamic lifting and to allow for gradual wear without engendering fracturing of those pads or instability of thetransducer60. The aerodynamic lifting force is believed to be primarily due to the disk-facing area of the chip which is in close proximity with the disk, including the contact area of the pads, and any bowing or tilting of the chip. As will be explained in greater detail below, thechip62 may be intentionally bowed, tilted and/or etched to create a negative pressure region between thechip62 and the spinning disk, so that the lifting force from the disk-facing area of the chip is more than overcome by downward force of the negative pressure. Anarea89 of each of theMIPS78 and80 may be as small as 25 μm²or as large as about 1000 μm², although other sizes are possible based upon tradeoffs including, for example, friction, pad wear and manufacturing tolerances. An aspect ratio of the vertical height to the lateral or longitudinal width of those pads should not be much over 2/1 to avoid fracturing and transducer inefficiency. The length of thechip72 of this embodiment as measured between thefirst end70 and the second end82 is about 40 mils, although this can be varied by a factor of two. This aspect ratio is determined primarily by mechanical considerations regarding the separation of theMIPS78 and80 and theMAP68, as limited by the space needed for thetransduction section88.
• In FIG. 6, a cross-section of the chip that focuses on the[0045]transduction section88 is shown along a cross-section bisecting theMAP68, thepole tips20 and22 and thegap27. Alower layer90 which preferably is made of alumina, but which alternatively may be made of another electrically insulative, amagnetic material such as doped silicon, silicon dioxide or diamond-like carbon (DLC) forms the disk-facingsurface65, while a hard,wearable casing92 which is preferably made of DLC or another hard amagnetic material such as silicon carbide or boron nitride forms the portion of theMAP68 surrounding thepole tips20 and22. Thegap27 is preferably formed of an insulative, amagnetic material such as silicon or silicon dioxide which is softer than the hard wear material of thecasing92. Hydrogenated carbon may also be adesirable gap27 material, having a hardness that can be adjusted to correspond with theparticular pole tips20 and22, casing92 and disk surface characteristics. The wear material of thecasing92 is preferably made of an amorphous material such as DLC which has a hardness similar to that of a surface layer of the disk with which thetransducer60 is to be employed, for matching wear between the transducer and the disk. The casing may be thicker closer to the disk-facingsurface65 for manufacturing and durability. Adjoining thepole tips20 and22 is abottom yoke95 of magnetic material which extends symmetrically from a pair of slantedsections98 to a pair of generallyplanar sections100. Thepole tips20 and22 andyoke sections98 and100 are formed from permalloy or other known magnetic materials, while at least one of the pole tips may include a high magnetic moment material, such as cobalt niobium zirconium (CoZrNb), iron nitride (FeN) or iron nitride alloys such as FeNAl adjacent to thegap27. Theyoke sections98 and100 are preferably formed in a laminated fashion, to be described below, in order to reduce eddy currents that impede transducer efficiency at high frequencies. Adjoining theyoke sections100 are a pair ofmagnetic studs101 and102 that extend to a generally planar magnetictop yoke104 interconnecting thestuds101 and102. Thepoles20 and22,bottom yoke95,studs101 and102 andtop yoke104 form a generally loop-shapedmagnetic core106, creating a contiguous magnetic circuit except for the smallamagnetic gap27. In a preferred embodiment discussed below, the studs are eliminated, and the core is formed in a shape having a cross-section that resembles a clamshell.
• A series of electrically[0046]conductive coil sections110 made of copper or other conductive metals or alloys is shown in cross-section in FIG. 3 to be spaced both within and without themagnetic core106. Interspaced between thecoil sections110 and thecore106 is an electricallyinsulative spacer material112 such as Al₂O₃, SiO₂or a hardbaked photoresist or other polymer. Thecoil sections110 can be seen to be divided into three generally horizontal layers in this embodiment, although more or less layers are possible, depending upon manufacturing and magnetic tradeoffs. These layers ofcoil sections110 can also be seen to fall into four horizontally separate groups. Proceeding from left to right, these groups are labeled114,116,118, and120, with a crossover section122 connectinggroups116 and118. Although difficult to see in the cross-sectional view of FIG. 6, thecoil sections110 are in actuality asingle coil124 which winds repeatedly about first one and then the other of the twostuds101 and102. Thegroups114 and120 which are disposed outside thecore106 have an electric current during writing or reading which is directed into or out of the plane of the paper opposite to that ofgroups116 and118 and crossover section122. The reader may wish to jump ahead temporarily to FIG. 17, which shows a top view of one layer of the spiralingcoil240 much likecoil124, includingcrossover section339, corresponding to crossover122.
• Thus a current traveling into the plane of the paper at[0047]coil section126 would spiral in the layer of thatsection126 aroundstud101 with a generally increasing distance from thestud101 until reachingcoil section128, which is connected tosection130 of the next layer. The current would then spiral inwardly aboutstud101 in the layer ofsection130 until reachingsection132, which is connected tosection134 of the next layer. The current would then spiral outwardly aroundstud101 in the layer that includessection134 until reaching crossover section122, at which point the current would begin to spiral inwardly aboutstud102, traveling to the second layer atsection135. The layered spiraling of the current aroundstud102 would continue in a similar but converse fashion to that described above for the spiraling aboutstud101, until the current exited the coil structure by traveling out of the plane of the paper atsection136. Thecoil124 thus resembles interconnected stacks of pancake-shaped spirals centered aboutstuds101 and102.
• Representative dimensions for this embodiment include an approximately 3 μm[0048]thick bottom yoke95 and atop yoke104 that is about 4 μm in thickness, andstuds101 and102 which each extend vertically about 23 μm between the yokes. The thickness of thebottom yoke95 is selected to saturate at a somewhat lower magnetic flux than the pole tips, thus limiting the flux through the pole tips and avoiding broadening of the transition that would occur during pole tip saturation. In order to achieve this flux limiting effect with pole tips of different sizes and materials, a function can be employed to determine the optimum bottom yoke parameters. Theindividual coil sections110 are about 3.5 μm thick measured in the vertical direction, and have a center to center spacing of about 5.5 μm in that direction. Longitudinally, thosesections110 may be about 2 μm to 4 μm thick within thecore106 with a center to center spacing of about 4 μm. Thetop yoke104 extends about 169 μm longitudinally, and thebottom yoke95 extends similarly but is, of course, split up by thepole tips20 and22 andgap27.
• In FIG. 7, a top view diagram of the[0049]magnetic core106 shows that thebottom yoke95 is shaped like a bow-tie, as theslanted sections98 are much narrower in lateral dimension than theplanar sections100. Diagonaltapered portions140 of theplanar sections100 funnel magnetic flux into thenarrower section98 during a write operation and offer a low reluctance path for such flux during a read operation. Centered atop the slantedsections98 are thepole tips20 and22, which are separated by theamagnetic gap27. Theplanar sections100 have a width of about 42 μm, which tapers at about a 45 degree angle to a width of about 7 μm at theslanted sections98. Thestuds101 and102 meet theplanar sections100 distal to thepole tips20 and22.
• An even more enlarged view in FIG. 8 shows that the[0050]pole tips20 and22 are shaped like baseball homeplates that nearly meet along parallel sides, separated by the long,narrow gap27. Thepole tips20 and22 andgap27 are exactingly tailored to precise dimensions that are chosen based on a number of parameters. The specific embodiment depicted in FIG. 8 has pole tips that each measure 3.25 μm in the lateral dimension and 4 μm in the longitudinal direction, before tapering to extend another 2 μm longitudinally. The peak-to-peak longitudinal dimension of thepole tips20 and22 andgap27 is 12 μm. Thegap27 of this embodiment has a precisely defined longitudinal dimension of 0.26 μm and a lateral dimension of 3.25 μm. As mentioned above, thelongitudinal gap27 dimension may be as small as 0.10 μm or less for extremely high density perpendicular data storage applications.
• Referring again to FIGS. 1 and 2, it is apparent that the[0051]perpendicular field component52 felt by themedia33 has an opposite direction adjacent topole tip20 compared to that adjacent topole tip22. As long as theperpendicular field component52 magnitude is sufficient to easily magnetize themedia33, the opposite direction of the field does not present a problem, since the field adjacent to thetrailing pole tip22 will write over the magnetization of the media induced by the leadingpole tip20. It is advantageous for high coercivity media, however, to transmit a stronger perpendicular field adjacent to thetrailing pole tip22 than that adjacent to theleading pole tip20. Although this may be accomplished, for example, by creating an asymmetric pair of pole tips such that the gap therebetween is angled rather than perpendicular to themedia layer33, a preferable means for achieving a stronger write field is to sandwich a layer of high magnetic saturation material between the gap and the remainder of the trailing pole tip.
• A cross-section of such a pair of[0052]pole tips155 and157 separated by anamagnetic gap160 and a high B_slayer162 is shown in FIG. 9. High B_s,layer162 is formed of Fe(Al)N or other known high B_smaterial, and magnetically acts as a part of trailingpole tip157 that does not saturate at flux levels significantly higher than those which induce saturation of leadingpole tip155.Gap160 is formed of silicon or other amagnetic material having suitable wear characteristics. Surroundingpole tips155 and157,gap160 and high B_slayer162 is a hard,durable material166 such as amorphous diamond-like carbon, which is constructed for lasting operational contact with a spinning rigid disk. Also shown in this figure arebottom yoke sections170 and172 of the magnetic core, anamagnetic pedestal175 upon which the yoke sections are formed, and anamagnetic isolation layer177 that forms a disk-facingsurface180. During writing, a magnetic field is induced in the core preferably at a strength which saturates the leadingpole tip155 without saturating thehigh B_s162 layer of the trailing pole tip, so that the field felt by the media is more spread out adjacent to theleading pole155 than the concentrated field adjacent to the high B_s,layer162 of trailingpole tip157. The shape of a magnetic pattern written on the disk depends substantially upon the shape of high B_slayer162, which is formed as a thin film having a longitudinal thickness of between 100 nm and 400 nm, a lateral thickness approximately equal to the track width of 3.25 μm, and a vertical depth of 3 μm to 8 μm. Alternatively, a high B_slayer may be formed on both edges of the gap to enhance writing gradients for the situation in which the resulting trailing write fields are sufficient to easily overcome the magnetization of the media caused by the leading edge.
• FIG. 10 shows a[0053]perpendicular component150 of a write field transmitted from a head having a high B_slayer adjoining a trailing pole tip and felt by a media layer located at about one-tenth the gap distance from the head. As in FIG. 2 the longitudinal distance is given in units of gap width G, so that zero represents the trailing edge of the gap adjoining the high B_slayer, and one represents the edge of the gap adjoining the leading pole tip. As can be seen, the field adjacent to the trailing pole tip reaches a much higher value than that adjacent to the leading pole tip, so that the media is magnetized with the trailing signal without remnant magnetization left from the oppositely directed leading field.
• FIG. 11 shows another embodiment of the MAP that provides an assymetric write field for perpendicular recording. To construct this embodiment atop the bottom yokes[0054]sections170 and172,pedestal175 andinsulation layer177 that were shown in FIG. 9, a photoresist is patterned atop a sputtered conductive seed layer of NiFe so that the resist has an angled overhang that causes the formation of aslanted edge182 during plating of a first pole layer which will be subsequently etched to formfirst pole tip184. Anamagnetic gap186 of silicon is then sputtered on theslanted edge182, on top of which a coating of high B_smaterial188 is deposited. Asecond pole tip190 is then formed by first electroplating, then lapping to create asurface192 coplanar withfirst pole section184, and then angled IBE as described above to define vertical, skirted edges ofpole tips184 and190.Durable wear material195 such as amorphous, diamond-like carbon then encases thepole tips184 and190, which is then etched and lapped to expose thepole tips184 and190, completing the formation ofassymetric MAP197. Theslanted edge182 facilitates uniform sputtering of thegap186 and high B_s, coating188, as compared to the angled sputtering described above for the vertically orientedgap160 and high B_scoating162 depicted in FIG. 9. The angled photoresist overhang which affords formation of the slantededge182 can be formed by a number of methods, including the use of either positive or negative photoresists and either angled coherent or incoherent light.
• Further improvement to the sliding ring head and perpendicular medium information storage system can be achieved by modifying the transducer of the above described contact planar ring head to include a magneto-resistive (MR) sensor, such a modified[0055]transducer220 being shown in cross-section in FIG. 12, the orientation of the cross-section being similar to that of the inductive-only transducer88 shown in FIG. 6. In the embodiment of FIG. 12, anMR element222 piggybacks the loop shaped core ofmagnetic material225 on a side opposite to thepole tips155 and157. Agap233 separates a top yoke of the core225 into first and secondtop yoke sections235 and237, providing an increase in magnetic flux passing throughMR element222 during reading of data. Since thepole tips155 and157 are closest to the disk during operation, theyoke sections235 and237 are termed top yokes, while the pair of yoke sections adjacent to the pole tips are termedbottom yoke sections170 and172. Only a single layer ofcoils240 is employed in this embodiment, which is sufficient for creating a large flux in thecore220 during writing, additional coil layers of the previous inductively-sensingtransducer88 embodiment not being needed due to the MR sensing element. Thebottom yoke sections170 and172 connect thetop yoke sections235 and237 and thepole tips155 and157 via a series of shallow, slanted steps, providing a low reluctance magnetic path which is especially helpful for high frequency operations. Theamagnetic gap160 and high B_slayer162 provide a sharp magnetic transition adjacent to the border between that gap and high B_slayer.
• Coupling the[0056]MR sensor222 to themagnetic core225 far from thepole tips155 and157 has a number of advantages over conventional MR elements. First, the resistance of MR sensors is known to depend greatly upon temperature, which may produce spurious readings of the sensor due to temperature rather than magnetic fluctuations. This temperature sensitivity is particularly problematic for transducers which contact the media, as the friction and thermal conductivity created by contact with the media can result in a thermally induced bias signal that can conceal the magnetic signal desired to be read. The placement of the MR sensor of the current embodiment far from the disk-contactingpole tips155 and157 and well within the interior of the thin-film slider that contains the transducer insulates the sensor from thermal fluctuations, which can improve the magnetic signal to thermal noise ratio by several orders of magnitude. In addition, piggybacking thesensor222 to themagnetic core225 allows the same pole tips that write data to the disk to read that data from the disk, eliminating misregistration problems that occur in the prior art due to placement of the MR reading element apart from an inductive writing element, an advantage that is particularly helpful at high skew angles. Moreover, since the MR element is typically very thin and is insulated in this embodiment from the core by another very thin layer, uniformity and purity of those layers is important. Surface irregularities and contaminants typically build up with each additional layer of thetransducer220, which is constructed in layers generally from thetop yoke sections235 and237 to thepole tip155. TheMR stripe222 is one of the first layers formed intransducer220, and benefits from the surface uniformity and lack of contamination available at that incipient stage. Finally, removing the electrically active MR element from exposure to the disk prevents shorting of that element to the disk surface.
• FIG. 13 shows a top view of the[0057]MR sensor222 andtop yoke sections235 and237 of themagnetic core225, as they appear during construction of the core prior to the formation of the coil layer. TheMR stripe222 is formed first, atop a planar layer of alumina which has been patterned in areas not shown in this figure to provide electrical interconnection for the coils and the MR element. TheMR stripe222 in this embodiment is made of a permalloy (approximately Ni_{0 8}Fe_0.2) layer formed to a thickness of about 200 Å and having an easy axis of magnetization along the directions of double headedarrow248, the permalloy layer then being covered with a patterned photoresist and ion beam etched to define a generally rectangular shape extending about 5 μm longitudinally and about 30 μm laterally, although the exact dimensions of the stripe may vary from these figures by 50%, depending upon tradeoffs involved in maximizing efficiency and stability. Next, a conductive pattern is formed which provides a pair ofconductive leads250 and252 to theMR stripe222, the leads having respective slantededges251 and253 which are parallel with each other. A bias layer of a permanent magnet or an antiferromagnetic material such as FeMn optionally underlies the conductive pattern adjoining theMR stripe222, in order to pin the magnetization of that stripe in the direction ofarrow249. An optionalconductive bar255 or bars shaped as a parallelogram having sides parallel toedges251 and253 is disposed atopMR stripe222 betweenleads250 and253, and additional spaced apart bars may be formed having sides parallel toedges251 and253. The leads250 and252 and any interveningconductive bars255 are so much more electrically conductive than theMR stripe222 that an electrical current betweenleads250 and252 insections257 of the MR stripe not adjoiningleads250 and252 or bar255 flows along the shortest path between theslanted edges251 and253 and bars as shown byarrows258, essentially perpendicular to those edges and the parallel sides of the interveningbars255 and at a slant to theeasy axis direction249.
• The magnetoresistance of the[0058]MR stripe222 varies depending upon an angle θ between the magnetic field and the current in the stripe such that the resistance is proportional to cos²θ. In the absence of a magnetic field from theyoke sections235 and237, the angle between theeasy axis249, along which the magnetization of thestripe222 is directed, and the current inmagnetoresistive sections257 as shown byarrow258, is between 0° and 90° and preferably near 45°. Upon exposure of the pole tips227 and230 to a magnetic pattern in a disk that results in a magnetic flux in theyoke sections235 and237 along a direction shown byarrows262 the magnetic moment of thestripe222 is rotated in a direction more parallel withcurrent arrows258 so that the magnetoresistance insections257 approaches zero. On the other hand, when the pattern on the disk creates a magnetic flux in theyoke sections235 and237 in the direction ofarrows264, the magnetic moment withinMR stripe222 is rotated to become more nearly perpendicular to current258 withinresistive sections257, so that magnetoresistance in thosesections257 rises. This differential resistance based upon the direction of magnetic flux inyoke sections235 and237 creates a voltage difference which is used to read the information from the disk.
• A process for constructing the[0059]transducer220 is shown beginning FIG. 14. Aconventional wafer substrate300 of silicon, alsimag or other known materials is used to form many thousand of thesliders62 of FIG. 4, each containing at least onesuch transducer220, after which the sliders are separated from each other and from the wafer. Separation of thesliders62 from the wafer is accomplished by selective etching either of the wafer or of a release layer such as copper formed atop the wafer before the sliders are formed. The formation of thesliders62 proceeds in layers generally from a back side of the slider designed to face away from the disk to the disk-facing side of the slider. Initially, electrically conductive interconnects for thecoils240 andMR element222 are formed of gold, including four spaced apart terminals that protrude from the back side and provide mechanical as well as conductive connections to a gimbal and flexure beam structure.
• A layer of[0060]alumina303 has been sputtered onto thesilicon substrate300 and is then polished and cleaned to provide a planar surface. An MR layer of Permalloy is then formed in the presence of a magnetic field by sputtering or ion beam deposition to a carefully controlled thickness of about 200 Å, the field creating an easy axis of the Permalloy film into or out of the plane of the paper of FIG. 14. A photoresist is then distributed atop that film and patterned to protectM stripe222 while the remainder of the Permalloy is removed by ion beam etching (IBE). TheMR stripe222 is then covered with another photoresist that is patterned to cover slanted portions of the stripe corresponding to barber pole shapedMR sections257 of FIG. 13. Abias layer305 of antiferromagnetic material such as FeMn is then deposited which pins the easy axis of the MR stripe in a single direction, as shown byarrow249 of FIG. 13. A conductive material such as copper is then deposited atop thebias layer305 forming the conductive pattern shown in FIG. 13 includingbar255. The photoresist that had covered areas such as257 andlayer303 is then removed, taking with it anybias layer305 and conductive layer that had been disposed on top of the photoresist. Aprotective layer310 of alumina is the deposited atop theMR element222,bar255 andalumina layer303 to a thickness in a range between 125 Å and 1000 Å. A photoresist is then distributed atoplayer310 and patterned to protect that portion oflayer310 coveringMR stripe222 andconductive bar255, while the remainder of that layer is removed by wet etch or IBE.
• Another photoresist layer is then patterned to cover a central portion of the[0061]insulation310 abovebar255 andMR section257. ANiFe seed layer313 is then sputtered to a thickness of about 1000 Å, whereupon a solvent is applied to remove the resist and to lift off any seed layer disposed on the resist. This photoresist lift-off process avoids the need for etching or other removal of the thin seed layer that would otherwise exist atop the central portion ofinsulation layer310, and thus avoids damage to that layer and the MR elements below.Top yoke sections235 and237 are then formed by window frame plating withgap233 left between those sections disposed above the central portion ofMR stripe222.Yoke sections235 and237 overlapMR stripe222 so as to minimize the interruption of magnetic flux between theyoke sections235 and237 and theMR stripe222. One should note that although a single MR stripe is shown, a connected series of such MR stripes may cross back and forth adjacent to the top yoke in order to increase the measurable magneto-resistance.
• FIG. 15 shows a portion of the substrate removed somewhat from and preferably formed subsequently to the[0062]MR stripe222 andyoke sections235 and237 in order to illustrate an electrical andmechanical interconnection320 that, after eventual removal of the substrate, will protrude from the non-disk-facingsurface322 ofalumnina layer303. Thelayer303 is covered with a patterned photoresist which exposes areas of that layer for etchingholes325, the holes being extended into thesubstrate300 by reactive ion etching (RIE) to form molds for the protrudingterminals320, which are then seeded with a TiCu layer327 while theyoke sections235 and237 andMR stripe222 are covered with a photoresist, after which another photoresist is patterned and copper is plated to defineleads330 as well asinterconnect terminals320. Two of theleads330, of which only one is shown, connect with theconductors250 and252, while another pair of leads provide connection to theelectrical coil240.
• FIG. 16 focuses on one half of generally[0063]symmetric transducer220 in order to better illustrate its formation. After formation of theyoke sections235 and237,MR stripe222 andconductive lead330, an approximately 1500 Å thicketch stop layer307 is then deposited and selectively etched by RIE to remove portions of thatlayer307 over theMR stripe222. Aconductive segment333 is then plated atop an end oflead330 while the rest of the construction is covered with photoresist. After that, an alumina layer is deposited, which is then lapped and cleaned to form a planar surface upon whichcoil240 is formed by through plating a spiral pattern of photoresist.
• A top view of[0064]coil section240 is shown in FIG. 17. Aninner section335 ofcoil240 is connected tosegment333, while asimilar section337 is connected to another segment, not shown, which is connected via a lead similar to lead330 to the exterior of the chip.Coil240 spirals outwardly aroundyoke section170 until crossing over atsection339 to spiral aboutyoke section172.
• Referring again to FIG. 16, another layer of alumina is deposited which encases and covers[0065]coil section240, the alumina layer then being lapped and cleaned to form aplanar surface342, upon which an etch stop layer of silicon carbide is formed. Atop the SiC etch stop layer344 a thicker layer of alumina is deposited, which is then planarized, masked with a patterned resist layer and isotropically etched to formpedestal175 having slantedsides346. The exposedetch stop layer344 is then covered with a photoresist patterned with a hole above an end ofyoke section348, after which an IBE or RIE removes the exposed portion ofetch stop344. An isotropic etch through the etch stop hole and a photoresist pattern results in sloping alumina sides350. Theend348 is then exposed by RIE or IBE removal of loweretch stop layer307. Next, abottom yoke350 is formed by window frame plating on theend348 ofbottom yoke section235 and over the terraced insulation that peaks atoppedestal175, providing a low profile, low reluctance magnetic path that projects above the pedestal. After deposit of anotherthicker alumina layer355 atop the structure of FIG. 17, that layer is lapped flat to alevel exposing pedestal175 and separatingbottom yoke sections170 and172.
• FIG. 18 focuses on the process for making the pole tips which adjoin the pedestal and incorporate a high BS layer in the trailing pole tip adjoining the gap, some advantages of which were discussed above. Instead of the[0066]solid yoke350 layer shown in the previous figure, laminatedbottom yoke360 is made of a pair ofmagnetic layers362 and365 of permalloy formed by window frame plating with a thinneramagnetic layer370 of alumina formed by sputtering disposed between the magnetic layers. Theyoke360 curves upward as before due to its formation atop theamagnetic pedestal175. Themagnetic layers362 and365 each have a thickness of 1 μm to 3 μm, while theamagnetic layer370 has a thickness between 100 and 200 nm. Another amagnetic,insulative layer377, preferably formed of alumina, is deposited atop the yoke layers362 and365, and then those layers are lapped to form a predetermined separation in the yoke layers atop thepedestal175, as discussed above with regard tolayer355. Afirst pole layer380 is then formed by window frame plating of permalloy on a NiFe seed layer, providing an essentiallyvertical edge382 to that pole layer. A high magnetic saturation material such as cobalt zirconium niobium or FeAl(N) is then sputtered at an angle385 to formhorizontal layers388 and avertical layer390 of high B_smaterial adjoining edge382.
• Referring now to FIG. 19, the[0067]horizontal layers388 have been removed by a vertically directed ion beam etch (113E) leaving the slightly shortenedvertical layer390 of high B_smaterial.Layer390, which has a precisely controlled longitudinal thickness that may range between 100 nm and 400 nm, is to become the portion of the head through which the highest flux passes during writing, and so the shape of thislayer390 is important in determining the bit shape written on the medium.Vertical layer395 andhorizontal layers397 of amagnetic material such as alumina, silicon or silicon dioxide are then formed by angled sputtering in a similar fashion as that described above for the high B_smaterial, after which thehorizontal layers397 are masked and etched to leave the “S” shape shown. Asecond pole layer400 is subsequently electroplated, after which lapping is used to remove the portion of that pole layer atop thefirst pole layer380 and the upperhorizontal layer397, leaving thevertical portion395.
• As shown in FIG. 19, the pole layers[0068]380 and400 are then masked with slightlyoversized photoresist pattern402 of thepole tips20 and22, not shown in this figure, after which a rotating IBE is performed at an angle α, removing the photoresist at about the same rate as the exposed pole layers, as shown by dashedlines404 and406, to create the home-plate-shaped pair of pole tips with thevertical portion395 left to serve as thegap27. The angled, rotating IBE leaves thepole tips20 and22 with vertical outside walls that rise from an angled skirt that is caused by shadowing during the angled IBE, the skirt providing an improved substrate for the subsequent formation of hard, durable material such as diamond like carbon that encases the pole tips and, like the pole tips, slides on the disk.
• Referring additionally now to FIG. 21, the[0069]photoresist mask402 has been formed in the elongated hexagonal shape desired for thepole tips20 and22 andgap27, however, themask402 is larger than the eventual pole tip area, to compensate for removal of a portion of the mask during etching. The etching is done by IBE with the ion beam directed at a preselected angle α to the surface of the pole layers380 and400, while the wafer is rotated, in order to form vertical sides of thepole tips20 and22, aside from a taperedskirt413, shown in FIG. 22, of thepole tips20 and22, theskirt413 acting as an aid to the subsequent formation of thehard wear material52 that will surround the pole tips. The vertical sides of thepole tips20 and22 allows operational wear of the pole tips to occur without changing the magnetic read write characteristics of the head. On the other hand, theskirt413 allows thewear material433 that wraps around thepole tips20 and22 to be formed without cracks or gaps which can occur, for example, in depositing DLC, preferably by plasma enhanced chemical vapor deposition (PECVD) onto a vertically etched pair ofpole tips20 and22. Although this taperedskirt413 can be achieved by a variety of techniques, an angled, rotating IBE is preferred to exactingly tailor thevertical pole tips20 and22 with taperedskirts413.
• The[0070]photoresist mask402 has an etch rate that is similar to that of the NiFe pole layers380 and400, so that when the angle α is approximately 45° thepole layer404 and the mask415 are etched a similar amount, as shown by dashed404.Pole layer380, however, is partially shielded from the angled IBE by the mask415, so that aportion420 oflayer380 that is adjacent to the mask is not etched, while another portion is etched as shown by dashedline406. As the wafer substrate is rotated, not shown,pole layer400 will have anon-etched portion425 adjacent to an opposite end of theelongated mask402, as willareas427 and428 adjacent sides of the elongated mask. Sinceareas427 and428 are adjacent larger widths of the mask215 than areas such as220 and225 and are thus more shielded and etch slower, the rotation of the wafer is preferably slower during periods when the IBE is angled along the elongated length of the mask (closest either toportion420 or425). The angle α may be changed to further control the shaping of thepole tips20 and22, for example to employ a greater angle such as about 60° toward the end of the IBE. This rotating, angled IBE is continued for an appropriate time to create a pair ofpole tips20 and22 having vertical sides with atapered skirt413 and a flat, elongated hexagonal top substantially centered about thegap27.
• After electrical testing, the wafer carrying the transducer is ready for the formation of the[0071]support pads68,78 and80, as shown in FIG. 22, which focuses on theMAP68 for clarity. Anadhesion layer430 of Si is deposited to a thickness of about 500 Å atop thepole tips44 andalumina layer377. Alayer433 of DLC is then sputtered onto theadhesion layer430. An approximately 1500 Åthick layer435 of NiFe is then deposited, which is then patterned by IBE with a lithographically definedphotoresist mask438 to leave, after IBE, a NiFe mask disposed over the DLC coveredpole tips20 and22 and over portions of the DLC layer at positions corresponding to theMIPS78 and80, not shown in this figure. TheDLC layer433 covered with the NiFe masks is then reactive ion etched with O₂plasma to leave projections of DLC that form theMAP68 andMIPS78 and80. TheMAP68 andMIPS78 and80 are then lapped to expose thepole tips20 and22. TheMAP68 andMIPS78 and80 are next protected with a photoresist which extends laterally and longitudinally beyond the edges of each pad, and then an RIE etch using CF4/O2 removes theSi layer430 not covered by the resist, leaving a flange of Si which helps to position undercutting of thealumina layer377 further from the MAP and MIPS, resulting in a stronger MAP and MIPS that are thicker closer to the disk-facing surface. Alternatively, theSi layer430 can be left over most of the surface to facilitate laser interferometer testing of chip flatness and tilt. Thechip62 is then laser scribed to provide lateral and longitudinal separations from other chips that have been simultaneously formed on the wafer substrate.
• FIG. 23 illustrates an end of a[0072]flexure beam450 that has been formed as agimbal460 employed to hold thechip62 in contact with a rapidly spinning rigid disk. Thebeam450 has fourconductive leads452,454,456 and458 that extend along most of the length of the beam and provide electrical circuits for thecoil240 and theMR element222, the leads being differentially shaded to facilitate their distinction. The leads452,454,456 and458 are connected with the terminals that protrude from the non-disk-facing side of thechip62 by ultrasonic or thermo-compressive bonding, soldering or other means atareas462,464,466 and468. The convoluted paths betweenleads452,454,456 and458 andareas462,464,466 and468 allows thechip62 to pitch and roll during sliding on the disk. Thebeam450 is laminated, having a stiffening layer connected to theconductors452,454,456 and458 on an opposite side from thechip62 by an adhesive damping layer.
• FIG. 24 shows an information storage system with the[0073]beam450 holding thechip62 in contact with arigid disk472 spinning rapidly (1,000 rpm to 8,000 rpm) in a direction ofarrow474. Thebeam450 is mounted to anarm477 of a rotary actuator which pivots aboutaxis480 to provide thechip62 access to themagnetic recording surface484. The recording media of the disk475 has a large perpendicular anisotropy and low noise, facilitating perpendicular data storage with the ringhead MR transducer220.
• FIG. 25 focuses on a tremendously magnified cross-section of the[0074]magnetic recording surface484 of the disk475. Amedia layer500 of the disk475 may be composed of a number of alternating atomic films of cobalt (Co) and either paladium (Pd) or platinum (Pt) which are grown on atextured seed layer505 of Tungsten (W), for example, on asubstrate510 of aluminum (Al) or glass, for instance. Whether formed by atomic layer deposition or as a cobalt based alloy, as shown in this figure,layer500 grows atop theseed layer505 in a number ofcolumns513 having a crystallographic C axis substantially perpendicular to thesurface484. Themedia layer500 has a thickness generally in a range of about100 Å to 1000 Å, with a preferable thickness of about 200 Å. On top of the media layer500 aprotective overcoat515 of nitrogenated or hydrogenated carbon, for example, is formed to a thickness of about 100 Å.
• The[0075]seed layer505 imparts a texture to thedisk surface484 which helps to reduce friction during sliding. Alternatively, the media layer can be composed of barrium ferrite (BaFeO), in which case a protective overcoat is not necessary and the head to media spacing is reduced further. After writing with a closely spaced ring head, not shown in this figure,columns513 are magnetized with fields shown by arrows318. Groups of adjoiningcolumns513 that are magnetized in the same direction represent a bit of stored information, such thatgroup520 represents an up bit, andgroup522 represents a down bit. For ultra high density recording, individual columns may represent single bits.

Claims (20)

1. An information storage system comprising:

a spinning, rigid disk having a surface and an associated media layer,

a slider contacting said surface, said slider including a microscopic transducer having a conductive coil inductively coupled to a core of ferromagnetic material shaped as a loop with pole tips separated by a submicron amagnetic gap, and

a beam mechanically coupled to said slider and having an elongate dimension oriented substantially along a direction of travel of a portion of said surface adjacent to said pole tips,

wherein a magnetic field from said pole tips writes upon said media layer with a strength oriented substantially perpendicular to said surface that is larger than a maximum strength oriented parallel to said surface.

2. The system ofclaim 1 wherein said transducer has an at least partially sliding relationship with said surface at a time of transmission of said magnetic signal.

3. The system ofclaim 1 wherein:

said pole tips are separated from each other by a first distance,

said pole tips are separated from said media layer by a second distance, and

said first distance is at least several times greater than said second distance when said magnetic field from said pole tips writes upon said media layer.

4. The system ofclaim 1 wherein an easy axis of magnetization of said media layer is substantially perpendicular to said surface.

5. The system ofclaim 1 wherein said pole tips are separated from each other by a distance less than one-fifth of a micron and at least 125 angstroms.

6. The system ofclaim 1 wherein said pole tips are separated from said media layer by less than thirty nanometers during transmission of said magnetic field.

7. The system ofclaim 1 wherein said second distance is at most one-fifth that of said first distance.

8. The system ofclaim 1 wherein at least one of said pole tips is exposed adjacent to said surface.

9. The system ofclaim 1 wherein said slider includes a magnetoresistive sensor.

10. An information storage system comprising:

a rigid disk having a disk surface and an associated magnetic media layer with an easy axis of magnetization oriented substantially perpendicular to said disk surface, and

a slider having a disk-facing surface with a projection, said slider including a transducer with a conductive coil that is inductively coupled to a loop of magnetic material partly disposed in said projection and having a pair of pole tips that are separated by a submicron amagnetic gap,

wherein said pole tips are separated from each other by a distance at least several times greater than that between one of said pole tips and said media layer when writing a magnetic signal from said pole tip to the media layer.

11. The system ofclaim 10 wherein said magnetic signal has a maximum strength at said media layer directed transversely to said disk surface.

12. The system ofclaim 10 wherein said slider contacts said disk surface during said writing.

13. The system ofclaim 10 wherein said pole tips are separated from each other by a distance less than one-fifth of a micron and at least 125 angstroms.

14. The system ofclaim 10 wherein said pole tips are separated from said media layer by less than thirty nanometers during said writing of said magnetic signal.

15. The system ofclaim 10 wherein said slider includes a magnetoresistive sensor.

16. An information storage system comprising:

a rigid disk having a disk surface and an associated magnetic media layer with an easy axis of magnetization oriented substantially perpendicular to said disk surface, and

a slider including a transducer with a conductive coil that is inductively coupled to a loop of magnetic material and having a pair of pole tips that are separated by a submicron nonferromagnetic gap, at least one of said pole tips being separated from said media layer by a distance less than one-fourth that between said pole tips and said media layer when writing a magnetic signal from said pole tip to the media layer, said slider including a magnetoresistive sensor to read said signal.

17. The system ofclaim 16 wherein:

said magnetic signal has a component directed perpendicular to said disk surface and a component directed parallel to said disk surface, and

at said media layer said component directed perpendicular to said disk surface has a strength greater than that of said component directed parallel to said disk surface.

18. The system ofclaim 16 wherein said slider contacts said disk surface during said writing.

19. The system ofclaim 16 wherein said pole tips are separated from each other by a distance less than one-fifth of a micron and at least 125 angstroms.

20. The system ofclaim 16 wherein said pole tips are separated from said media layer by less than thirty nanometers during said writing of said magnetic signal.

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