United States Patent [19]
`Brand et al.
`
`US005853959A
`[11] Patent Number:
`[45] Date of Patent:
`
`5,853,959
`Dec. 29, 1998
`
`[54] METHOD OF FABRICATING A CONTOURED
`SLIDER SURFACE FEATURE WITH A
`SINGLE MASK
`
`[75] Inventors: John L. Brand, Burnsville; Daniel P.
`Burbank, Minneapolis, both of Minn.
`
`[73] Assignee: Seagate Technology, Inc., Scotts
`Valley, Calif.
`
`[21] Appl. No.: 695,374
`[22] Filed:
`Aug. 9, 1996
`
`Int. Cl.6 ..................................................... .. G03C 5/00
`[51]
`[52] US. Cl. .......................... .. 430/320; 430/396; 216/22;
`216/41; 216/58; 29/630.2; 29/630.18; 29/630.15;
`29/630.12
`[58] Field of Search ................................... .. 430/320, 396,
`430/929; 29/ 03.2, 603.18, 603.15, 603.12;
`216/22, 41, 58
`
`[56]
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`
`1/1986 Blaske et al. ......................... .. 430/313
`4,564,585
`1/1992 Aronoff et a1. ..
`360/103
`5,079,657
`6/1992 Gau ................ ..
`430/320
`5,126,232
`8/1992 Amin e161. .... ..
`427/116
`5,137,750
`5,162,073 11/1992 Aronoff et al. .... ..
`156/625
`5,509,554
`4/1996 Samuelson et a1. .................... .. 215/22
`
`5,626,941
`
`5/1997 Ouano ................................... .. 428/141
`
`Primary Examiner—M. NuZZolillo
`Assistant Examiner—Steven H. VerSteeg
`Attorney, Agent, or Firm—Westman, Champlin & Kelly,
`PA.
`
`[57]
`
`ABSTRACT
`
`A method of fabricating a contoured surface feature to
`multiple depths on a surface of a hydrodynamic bearing
`slider With a single mask includes applying a lithographic
`resist layer to the slider surface and forming the single mask
`With a mask pattern Which includes a masked area, an
`unmasked area and an intermediate area betWeen the masked
`area and the unmasked area. The lithographic resist layer is
`then exposed through the single mask and removed as a
`function of exposure to form a patterned resist layer and to
`thereby uncover portions of the slider surface Within the
`patterned resist layer. The uncovered portions of the slider
`surface and the patterned resist layer are etched, With the
`uncovered portions being etched to a ?rst depth beloW the
`slider surface. The multiple depth surface feature is created
`by providing the intermediate mask area With a geometry of
`masked and unmasked features that is unresolvable by one
`of the steps of exposing an etching such that an area of the
`slider surface corresponding to the intermediate mask area is
`etched to a second depth Which is less than the ?rst depth.
`
`26 Claims, 7 Drawing Sheets
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`1
`METHOD OF FABRICATING A CONTOURED
`SLIDER SURFACE FEATURE WITH A
`SINGLE MASK
`BACKGROUND OF THE INVENTION
`The present invention relates to disc drive data storage
`systems and, more particularly, to a method of fabricating a
`multiple depth surface feature on a hydrodynamic bearing
`slider With a single mask.
`Disc drives of the “Winchester type” are Well known in
`the industry. Such drives use rigid discs coated With a
`magnetiZable medium for storage of digital information in a
`plurality of circular, concentric, data tracks. The discs are
`mounted on a spindle motor Which causes the discs to spin
`and the surfaces of the discs to pass under respective head
`gimbal assemblies
`The HGAs carry transducers
`Which Write information to and read information from the
`disc surface. An actuator mechanism moves the HGAs from
`track to track across the surface of the discs under control of
`electronic circuitry. The actuator mechanism includes a track
`accessing arm and a load beam for each HGA. The load
`beam provides a preload force Which presses the HGA
`toWard the disc surface.
`The HGA includes a hydrodynamic (e.g. air) bearing
`slider and a gimbal. The gimbal is positioned betWeen the
`slider and the load beam to provide a resilient connection
`that alloWs the slider to pitch and roll While folloWing the
`topography of the disc. The slider includes a slider body
`having an air bearing surface Which faces the disc surface.
`As the disc rotates, the disc drags air under the slider along
`the air bearing surface in a direction approximately parallel
`to the tangential velocity of the disc. Skin friction on the air
`bearing surface causes the air pressure betWeen the disc and
`the air bearing surface to increase Which creates a hydro
`dynamic lifting force that causes the slider to lift and ?y
`above the disc surface. The preload force supplied by the
`load beam counteracts the hydrodynamic lifting force. The
`preload force and the hydrodynamic lifting force reach an
`equilibrium based upon the hydrodynamic properties of the
`slider and the speed of rotation of the disc. The transducer
`is typically mounted at or near the trailing edge of the slider.
`A conventional catamaran slider includes a pair of raised
`side rails Which face the disc surface and form the air
`bearing surfaces. The raised side rails and other surface
`features on the slider are typically formed through a photo
`lithography process folloWed by an ion milling or reactive
`ion etching process. Traditional photolithography processes
`use masks With hard edges to create Well-de?ned patterns in
`the slider surface. Angled ion milling is often used to
`decrease redeposition of the milled substrate. Angled ion
`milling does decrease someWhat the slope of the edge
`feature in the slider surface. With angled ion milling, an ion
`beam is directed to the slider surface at an angle With respect
`to the slider surface. The ion beam is then rotated about an
`aXis perpendicular to the slider surface. Angled ion milling
`results in Well de?ned sideWalls With relatively large slopes.
`These edges tend to accumulate lubricant and debris during
`disc drive operation.
`Photolithography techniques have also been used to
`recess portions of the pole tips of the read/Write transducers
`at the trailing edge of the slider to improve performance,
`such as undershoot performance. The edges of the recesses
`can also serve as debris and lubricant collection areas.
`There is a continuing need for improved fabrication
`processes of slider surface features Which improve perfor
`mance of the slider or read/Write head While minimiZing
`collection of debris and lubrication.
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`SUMMARY OF THE INVENTION
`
`The fabrication process of the present invention forms a
`multiple depth surface feature on a surface of a hydrody
`namic bearing slider With a single mask. The method
`includes applying a lithographic resist layer to the slider
`surface and forming the single mask With a mask pattern
`Which includes a masked area, an unmasked area and an
`intermediate area betWeen the masked area and the
`unmasked area. The lithographic resist layer can include a
`positive resist or a negative resist material. The lithographic
`resist layer is then eXposed through the single mask and
`removed as a function of eXposure to form a patterned resist
`layer and to thereby uncover portions of the slider surface
`Within the patterned resist layer. The uncovered portions of
`the slider surface and the patterned resist layer are etched,
`With the uncovered portions being etched to a ?rst depth
`beloW the slider surface. The intermediate mask area has a
`geometry that is unresolvable by one of the steps of eXposing
`and etching such that an area of the slider surface corre
`sponding to the intermediate mask area is etched to a second
`depth Which is less than the ?rst depth.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`FIG. 1 is a perspective vieW of a hydrodynamic bearing
`slider, as vieWed from its trailing edge and air bearing
`surface.
`FIGS. 2A—2F are cross-sections of a slider substrate,
`Which illustrate the processing steps performed on the
`substrate according to one embodiment of the present inven
`tion.
`FIG. 3 is a plan vieW of a portion of a photolithography
`mask according to the present invention.
`FIGS. 4A—4C are plan vieWs of masks having various
`shaped masked features, in accordance With the present
`invention.
`FIG. 5A is a plan vieW of an aspect ratio limited photo
`lithography mask, in accordance With the present invention.
`FIG. 5B is a plan vieW of an eXposed photoresist pattern
`resulting from the mask shoWn in FIG. 5A.
`FIGS. 6A—6F are cross-sections of a photoresist pattern
`and a slider substrate during progression through an ion
`milling process.
`FIG. 7 is a plan vieW of a mask having saW-tooth shaped
`masked features.
`FIGS. 8A is plan vieW of a mask having a plurality of
`differently siZed circular masked areas.
`FIG. 8B is a photograph of a slider substrate material
`having a plurality of milled holes resulting from the mask
`shoWn in FIG. 8A.
`FIGS. 8C and 8D are graphs illustrating pro?les of tWo of
`the holes shoWn in FIG. 8B.
`FIGS. 9A—9C illustrate a process for fabricating raised air
`bearing surface features according to the present invention.
`FIGS. 10A—10C illustrate a process for fabricating
`recessed air bearing surface features according to the present
`invention.
`
`DETAILED DESCRIPTION OF THE
`PREFERRED EMBODIMENTS
`
`FIG. 1 is a perspective vieW of a hydrodynamic bearing
`slider, as vieWed from a trailing edge. Slider 10 includes a
`substrate 12 (eg ceramic), a leading edge 14, a trailing edge
`16, raised side rails 18 and 20, cross rail 22 and subambient
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`pressure cavity 24. Raised side rails 18 and 20 form air
`bearing surfaces With inside and outside edges 26 and 28. A
`typical fabrication process forms rails 18 and 20 With hard,
`Well-de?ned edges. It has been found that these edges tend
`to accumulate lubricant and debris 30 during operation.
`Different air bearing shapes have different lubricant and
`debris accumulation properties.
`Collection of lubricant and debris can be limited by
`forming the edges of side rails 18 and 20 With relatively
`smooth, shalloW slopes. These shalloW slopes can be fabri
`cated according to the present invention With a single
`lithographic mask and etching process by providing the
`mask With additional features that are unresolvable by the
`imaging apparatus or the etching apparatus.
`1. Resolution Limited Photolithography
`FIGS. 2A—2F are cross-sections of slider substrate 12 in
`schematic form, Which illustrate the processing steps per
`formed on the substrate according to one embodiment of the
`present invention. The dimensions shoWn in FIGS. 2A—2F
`are greatly exaggerated for clarity. In FIG. 2A, a positive
`photolithography resist (“photoresist”) layer 40 is applied to
`surface 42 of substrate 12. Avariety of photoresist materials
`can be used, such as a diaZonapththoquinone sulfonic ester,
`Which is sold under the name NOVOLAK.
`In FIG. 2B, an imaging apparatus 44 exposes photoresist
`layer 40 through a photolithography mask 46. Imaging
`apparatus 44 includes a light source 48 and a lens 50, Which
`are Well knoWn in the art. Mask 46 has a plurality of masked
`and unmasked areas Which are arranged in a desired pattern
`for exposing photoresist layer 40. For example, mask 46
`includes masked areas 52 and unmasked area 54. Light 58
`generated by light source 48 is blocked by masked areas 52
`and passes through unmasked area 54. Lens 50 focuses light
`58 passing through mask 46 onto photoresist layer 40 and
`thereby projects the desired pattern onto photoresist layer
`40.
`Light 58 exposes portion 60 of photoresist layer 40 Which
`correspond to unmasked area 54, While portions 62 remain
`unexposed. Exposing portions 60 to light 58 induces a
`chemical change in the positive photoresist material Which
`causes the portions to be susceptible to etching, as is Well
`knoWn in the art. Unexposed portions 62 resist etching.
`According to the present invention, mask 46 includes
`additional, intermediate areas 56 betWeen masked area 52
`and unmasked areas 54. Intermediate areas 56 have geom
`etries that are beyond the resolution capability of imaging
`apparatus 44. The light pattern passing through intermediate
`areas 56 becomes blurred as represented by Wavy lines 64.
`As a result, the blurred light pattern only partially exposes
`intermediate portions 66 of photoresist layer 40.
`In FIG. 2C, photoresist layer 40 is removed through a
`chemical dissolution process as a function of the level of
`exposure to form a patterned photoresist. With the positive
`resist, fully exposed portion 60 is completely stripped from
`slider surface 42, unexposed portions 62 remain on surface
`42 and partially exposed portions 66 are partially stripped.
`After milling, the partial stripping of portions 66 provides
`sloping sideWalls betWeen the stripped and unstripped resist
`portions.
`In FIG. 2D, the unstripped portions of the patterned
`photoresist layer 40 and the uncovered portions of slider
`surface 42 are etched to form the desired pattern in slider
`surface 42. This pattern includes side rails 18 and 20.
`Etching can include various types of etching, such as reac
`tive or nonreactive ion milling for example. The sloping
`sideWall contour of partially stripped photoresist portions 66
`
`4
`are transferred to slider surface 42 to create smooth, sloped
`transitions along inside edges 26 of side rails 18 and 20,
`shoWn in FIG. 1.
`After etching, a small portion of photoresist layer 40
`remains on slider surface 42. In FIG. 2E, the remaining
`portions of photoresist layer 40 are removed, leaving the
`desired surface pattern in slider substrate 12. Preferably,
`inside edges 26 have a maximum slope 70 of 20 degrees as
`measured from a plane de?ned by the air bearing surfaces of
`side rails 18 and 20. Most preferably, the slope 70 is a
`maximum of 15 degrees. Further photolithography steps can
`then be performed to form additional surface features on
`slider substrate 12. For example, in FIG. 2F the subambient
`pressure cavity 24 has been formed betWeen side rails 18 and
`20.
`FIG. 3 is a plan vieW of a portion of mask 46 Which
`illustrates one of the intermediate, partially masked areas 56
`in greater detail. Intermediate area 56 is positioned betWeen
`masked area 52 and unmasked area 54. Intermediate area 56
`includes a plurality of masked and unmasked features hav
`ing a geometry that is smaller than the resolution of imaging
`apparatus 44. The resolution capability of imaging apparatus
`44 can be reduced by controlled defocus. Each vertical line
`68 Within intermediate area 56 represents a masked feature.
`The gaps betWeen the vertical lines represent unmasked
`features. The Width of each masked feature is smaller than
`the imaging capabilities of image apparatus 44 such that the
`masked features are not accurately reproduced on photore
`sist layer 40.
`In the embodiment shoWn in FIG. 3, lines 68 have equal
`Widths and are separated by distance D1 Which progres
`sively increases from masked area 52 toWard unmasked area
`54. This provides a gradient in the level of light 58 passing
`through intermediate area 56, Which results in a gradient in
`the level of exposure in partially exposed portions 66
`(shoWn in FIG. 2B) from unexposed portion 62 toWard
`unexposed portion 60. At the left edge of intermediate area
`56, the mask lines 68 are spaced close together such that the
`photoresist layer 40 is mostly unexposed. At the right edge
`of intermediate area 56, the mask lines 68 are Widely spaced
`such that the photoresist layer 40 is mostly exposed. In an
`alternative embodiment, the spacing D1 betWeen lines 68
`remains equal, but the Width of each line progressively
`decreases from masked area 52 toWard unmasked area 54.
`This also provides a gradient in the level of light passing
`through intermediate area 56.
`In the embodiment shoWn in FIGS. 2 and 3, the photoli
`thography mask includes additional, unresolvable mask fea
`tures at the edge of the masked areas. The features are too
`small for the imaging system to image accurately. These
`optically, unresolvable features result in a continuous “grey”
`area at the edge of the masked areas. By varying the spacing,
`Width and shape of the features, the extent of the “grey” area
`can be controlled. The unresolvable mask features can
`include shapes other than the lines shoWn in FIG. 3. These
`shapes can include circles, dots, ovals, cross-hatches,
`diamonds, saW-teeth, scallops or other shapes. The shapes
`can form either the intermediate masked features or the
`intermediate unmasked features. The shapes can be arranged
`in any desired pattern With ?xed or varying density.
`FIG. 4A is a plan vieW of a mask 72 having a plurality of
`circular shaped apertures 74 Within intermediate area 56.
`Apertures 74 increase in diameter from masked area 52
`toWard unmasked area 54 to provide increasing exposure
`from masked area 52 toWard unmasked area 54.
`Alternatively, apertures 74 can be siZed equally and increase
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`in density toward unmasked area 54. FIGS. 4B and 4C are
`plan views of masks 76 and 78 Which have saW-tooth and
`scallop shaped masked features 80 and 82 Within interme
`diate area 56, respectively. These features decrease in
`density, from masked area 52 toWard unmasked area 54.
`Various other shapes and patterns can also be used in
`accordance With the present invention.
`In an alternative embodiment, the photolithography mask
`is physically applied to the surface of the slider on top of,
`and in controlled proximity to, the layer of photoresist. In
`this embodiment, the proximity of the mask is decreased
`such that, due to the solid angle subtended by the light
`projected toWard the mask, the ?ne feature resolution of the
`proximity exposure is inhibited by penumbral shadoWing.
`The mask pattern cannot be accurately reproduced on the
`photoresist. The thickness of the mask causes the mask to be
`beyond the optical resolution of the imaging apparatus.
`2. Aspect Ratio Limited Photolithography
`The sloped edges can also be formed in the slider surface
`by adding features to the photolithography mask that are
`unresolvable by the etching process (eg ion milling), as
`opposed to the imaging process. While these features can be
`reproduced accurately onto the photoresist, the resulting
`etched pattern is altered by limitations of the etch process to
`transfer small features into the etched surface. As a result,
`the slider surface is formed With smooth or contoured,
`sloped transitions betWeen milled and unmilled areas. The
`unresolvable mask features are de?ned such that the result
`ing pattern in the photoresist has a high aspect ratio in that
`the height of the photoresist is large compared to either the
`spacing betWeen the photoresist features or the Width of the
`photoresist features.
`FIG. 5A is a plan vieW of an aspect ratio limited photo
`lithography mask 84 having additional masked features that
`are altered during transfer into the ion milled surface by
`process resolution limitations. Mask 84 includes a masked
`area 86, an unmasked area 88 and an intermediate area 90.
`Intermediate area 90 has a plurality of intermediate masked
`features 91 Which are optically resolvable and can be
`accurately reproduced on the photoresist. HoWever, the
`intermediate masked features 91 have a Width
`Which is
`small compared to the height of the photoresist.
`FIG. 5B is a top plan vieW of an exposed photoresist
`pattern 94 resulting from the aspect ratio limited mask 84
`shoWn in FIG. 5A. The photoresist material includes a
`negative photoresist. In an alternative embodiment, a posi
`tive photoresist is used. Photoresist pattern 94 includes a
`fully exposed portion 96 corresponding to unmasked area
`88, an unexposed resist portion 98 corresponding to masked
`area 86 on mask 46 and a plurality of intermediate exposed
`and unexposed portions 100 and 102, respectively, corre
`sponding to intermediate area 90 of mask 84.
`FIGS. 6A—6F are cross sections of the photoresist pattern
`94 and slider substrate 104 during progression through the
`ion milling process. FolloWing stripping, photoresist pattern
`94 has a plurality of spaced resist features 106 and 107,
`Which correspond to exposed portions 96 and 100,
`respectively, shoWn in FIG. 5B. Resist features 106 and 107
`have a height
`on slider substrate 104 and are separated
`by gaps having the Width
`Ion milling begins in FIG. 6B. Ion beam 110 is directed
`toWard photoresist pattern 94 and the uncovered surface of
`slider substrate 104 at an angle 6 Which is measured from a
`vector Within a plane parallel to the surface of slider sub
`strate 104. In one embodiment, ion beam 110 is rotated about
`an axis 112 Which is perpendicular to the surface of slider
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`substrate 104. As discussed above, the intermediate photo
`resist features have a high aspect ratio
`In a preferred
`embodiment, the aspect ratio
`is de?ned as H/Witan
`0. As seen by the progression through FIGS. 6B—6F, the
`intermediate resist features 107 initially “shadoW” one
`another from right to left. As the ion milling progresses, the
`resist on the right of the ?gures becomes milled and no
`longer shadoWs the adjacent features. The resist features on
`the right are milled at a faster rate than the resist features on
`the left, Which creates a sloped edge 114 in the surface of
`slider substrate 104. Edge 114 has a slope 116 Which is
`preferably a maximum of 20 degrees and, most preferably,
`a maximum of 15 degrees as measured from the slider
`surface. Although the process shoWn in FIGS. 6A—6F are
`discussed With reference to ion milling, other directed beam
`anisotropic etching processes can also be used to achieve the
`shadoWing effect caused by the high aspect ratio photoresist
`features. Although FIGS. 6A—6F shoW the milling process
`creating sharp features in the slider surface, the topography
`of the features are much more rounded.
`The intermediate resist features can have a variety of
`shapes in addition to the rectangles shoWn in FIGS. 5 and 6.
`For example, the intermediate resist features can include
`circles, dots, ovals, cross hatches, diamonds, saW-teeth,
`scallops and other shapes. FIG. 7 illustrates a mask 120
`Which creates intermediate resist features having a saW-tooth
`shape. Mask 120 includes a masked area 122, an unmasked
`area 124 and an intermediate area 126. Intermediate area 124
`has a plurality of saW-tooth shaped intermediate mask
`features 128. As in the embodiment shoWn in FIGS. 5 and
`6, intermediate masked features 128 create patterns in the
`photoresist Which shadoW one another during the initial
`stages of the ion milling process.
`3. Example
`FIG. 8A is a schematic of a mask 150 having a plurality
`of differently siZed circular masked areas 152A—152E. FIG.
`8B is a photograph of a slider substrate material 154 having
`a plurality of milled holes 156A—156E resulting from the
`mask shoWn in FIG. 8A. The largest hole 156A is 60
`micrometers in diameter. The smallest hole 156E is 22
`micrometers in diameter. The photoresist used during the
`milling process Was about 30 micrometers high.
`Consequently, the aspect ratio (height of photoresist to Width
`of hole) of the largest resist feature Was 0.5 and the aspect
`ratio of the smallest resist feature Was 1.35. The ion milling
`angle 0 Was 45 degrees (tan(0)=1.0).
`FIG. 8C is a plot of the cross section of the largest hole
`156A. The edge of hole 156A has a slope of 18—21 degrees
`as measured from the surface adjacent the hole. The center
`of hole 156A has a slope of about 3 degrees.
`FIG. 8D is a plot of a cross section of the smallest hole
`156E. The edge of hole 156E has a constant slope of about
`5 degrees. The slope of hole 156E is much less than the slope
`of hole 156A because of the higher aspect ratio. In other
`Words, the height of the photoresist surrounding hole 156E
`Was suf?ciently large as compared to the diameter of the
`hole that the photoresist shadoWed the hole during the
`angled ion milling process. Initially, the ions Were unable to
`reach the substrate surface until the edge of the photoresist
`Was milled to less than the Width of the hole.
`The resolution limited and aspect ratio limited photoli
`thography fabrication processes of the present invention
`permits a transition from non-milled to milled areas on the
`slider surface to extend over a controlled Width. By shaping
`the edges of the slider surface in a controlled manner, debris
`and lubricant accumulation can be minimiZed during disc
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`drive operation. Also, the fabrication processes of the
`present invention allow the slider surface to be milled at
`multiple depths With a single mask pattern and photoresist.
`This can be used to form the edges of air bearing surfaces or
`edges of other features on the slider surface. For example,
`the fabrication processes can be used to perform multiple
`depth patterning of pole tips in the read/Write head to
`improve performance of the head While limiting debris and
`lubricant collection. Pole tips have been contoured to pro
`vide undershoot reduction. Current processes only permit
`single level pole patterning depths. With the present
`invention, pole patterning features can be created With
`complex contours to optimiZe the edges of the poles for
`reduced debris and lubricant accumulation.
`4. Use of Aspect Ratio Limited Photolithography for
`Creating Raised or Recessed Air Bearing Features
`In another aspect of the present invention, the aspect ratio
`limited photolithography process can be used to created
`raised or recessed air bearing surface features. According to
`the present invention, photolithographic techniques are used
`to create photoresist patterns With high aspect ratios that
`cannot be reproduced during the ion milling process.
`Consequently, the resulting surface features on the slider
`have curved edges and contoured topographies. The con
`toured typographies create reduce debris collection and
`provide strength to the protruding surfaces.
`FIGS. 9A—9C illustrate a process for fabricating raised air
`bearing surface features according to the present invention.
`FIG. 9A is a plan vieW of a mask 210 having a plurality of
`circular, unmasked apertures of various diameters. FIG. 9B
`is a cross section of a patterned photoresist layer 212 on the
`surface of a slider substrate 214, Which results from the
`mask shoWn in FIG. 9A. FIG. 9C is a cross section of slider
`substrate 214 after milling.
`Patterned photoresist layer 212 includes a plurality of
`resist features 216 and 218 having a height
`and a Width
`The aspect ratio of each feature is de?ned as H/W.
`Resist features 216 have high aspect ratios (greater than 1.5)
`and are thus not completely resolvable during the ion milling
`process. Since the aspect ratios of resist features 216 are
`high, the resist features are milled from the top and sides
`Which causes surface features 220 formed in substrate 214 to
`become rounded.
`Resist features 218 have conventional, loWer aspect ratios
`(less than 1.0). Resist features 218 remain on the surface of
`substrate 214 during the entire milling process, Which pre
`vents any substrate removal. The corresponding surface
`features 224 formed in substrate 214 therefore have sharp
`sideWalls.
`FIGS. 10A—10C illustrate a fabrication process for fab
`ricating recessed features, as opposed to raised features on
`the air bearing surface. FIG. 10A is a plan vieW of a mask
`230 having a plurality of unmasked apertures 232A—232E.
`Apertures 232A and 232B are spaced closely together Which
`causes the resulting photoresist features to shadoW one
`another during the milling process and therefore create
`surface features in the slider surface With rounded slopes. In
`contrast, apertures 232B—232E are spaced further apart.
`FIG. 10B is a cross section of a patterned photoresist layer
`234 on the surface of a slider substrate 236, Which results
`from the mask shoWn in FIG. 10A. Patterned photoresist
`layer 234 includes resist features 238A—238E corresponding
`to apertures 232A—232E. Resist features 238A—238E have a
`height
`and are separated by a gap having a Width
`FIG. 10C is a cross section of substrate 236 after milling.
`Recessed features 240A—240D are formed in substrate 236
`
`10
`
`15
`
`25
`
`35
`
`45
`
`55
`
`65
`
`8
`at the gaps betWeen resist features 238A—238E. Since the
`gap betWeen resist features 238A and 238B is small com
`pared to the height H, recessed feature 240A has shalloW,
`sloping sideWalls. Since the gap betWeen resist features
`238B and 238E is larger, recessed features 240B—240D have
`relatively sharply de?ned, steep sideWalls. There is little or
`no shadoWing betWeen resist features 238B—238E.
`Although the present invention has been described With
`reference to preferred embodiments, Workers skilled in the
`art Will recogniZe that changes may be made in form and
`detail Without departing from the spirit and scope of the
`invention. For example, the present invention has been
`described With respect to a photolithography process.
`HoWever, the present invention is equally applicable to other
`lithography processes such as electron beam and x-ray
`lithography.
`What is claimed is:
`1. A method of fabricating a multiple depth feature on a
`surface of a hydrodynamic bearing slider, the method com
`prising:
`applying a lithographic resist layer to the slider surface;
`forming a single mask having a mask pattern Which
`includes a masked area, an unmasked area and an
`intermediate area betWeen the masked area and the
`unmasked area;
`exposing the lithographic resist layer through a single
`mask;
`removing the lithographic resist layer as a function of
`exposure to form a patterned resist layer and to thereby
`uncover portions of the slider surface Within the pat
`terned resist layer;
`etching the uncovered portions of the slider surface and
`the patterned resist layer, With the uncovered portions
`being etched to a ?rst depth beloW the slider surface;
`and
`Wherein the step of forming the single mask includes
`providing the intermediate area With a geometry that is
`unresolvable by one of the steps of exposing and
`etching such that an area of the slider surface corre
`sponding to the intermediate mask area is etched to a
`second depth beloW the slider surface Which is less than
`the ?rst depth.
`2. The method of claim 1 Wherein:
`the step of forming the single mask comprises de?ning the
`geometry of the intermediate mask area With a linear
`dimension; and
`the step of exposing comprises projecting the single mask
`onto the resist layer With an imaging apparatus having
`a resolution that is larger than the linear dimension such
`that a ?rst portion of the lithographic resist layer
`corresponding to the unmasked area is exposed at a ?rst
`exposure level, a second portion of the lithographic
`resist layer corresponding to the masked area is unex
`posed and a third portion of the lithographic resist layer
`corresponding to the intermediate area is partially
`exposed at a second exposure level Which is loWer than
`the ?rst exposure level.
`3. The method of claim 1 Wherein:
`the step of applying comprises applying to the slider
`surface a lithographic resist layer having a height, H;
`the step of forming the single mask comprises de?ning the
`geometry of the intermediate mask area such that the
`step of removing forms the patterned resist layer With
`?rst and second resist features on the slider surface
`Which are separated by a gap having a Width, W; and
`
`

`
`9
`the step of etching comprises performing a directed,
`anisotropic etch at an angle 6 Which is measured from
`a vector Within a plane of the slider surface, Wherein
`H/W Ztan 6.
`4. The method of claim 1 Wherein:
`the step of removing comprises forming the patterned
`resist layer With a resist feature having a height, H, and
`a Width, W; and
`the step of etching comprises performing a directed,
`anisotropic etch at an angle 6 Which is measured from
`a vector Within a plane of the slider surface, Wher