Abstract:
A slider includes an air bearing surface (ABS) including a plurality of separate coplanar pads, a cavity recessed to a certain depth beneath the level of the ABS, and a plurality of steps in which each step is disposed at a level between that of the ABS and that of the cavity. The plurality of steps include a trailing edge step and a leading edge step, and in some embodiments a first side step and a second side step. The leading edge step is provided at a level deeper than that of the trailing edge step. The first side step and the second side step may be provided at the same or different levels to tailor the flight characteristics of the slider. A process is also disclosed for the fabrication of a slider of the present invention. The process includes at least three cycles of masking, etching, and stripping in order to form at least three successively deeper levels, the deepest level being the cavity. Selective masking of the substrate allows portions of the substrate to be preserved through successive etching operations to become the ABS and the plurality of steps.

Description:
BACKGROUND OF THE INVENTION 
     This invention relates generally to methods for fabricating air bearing surfaces of sliders for magnetic disk drives and the sliders so produced. 
     Magnetic disk drives are used to store and retrieve data for digital electronic apparatus such as computers. In FIGS. 1A and 1B, a magnetic disk drive  1  of the prior art includes a sealed enclosure  2 , a disk drive motor  3 , a magnetic disk  4 , supported for rotation by a spindle  5  of motor  3 , an actuator  6  and an arm  7  attached to a spindle  8  of actuator  6 . A suspension  9  is coupled at one end to the arm  7 , and at its other end to a read/write head or slider  10 . The slider  10  typically includes an inductive write element with a sensor read element As the motor  3  rotates the disk  4 , as indicated by the arrow R, a layer of air proximate to the surface of the disk  4  is swept along with the disk  4 . This layer of air, commonly known as windage, pushes against the slider  10  and allows the slider  10  to lift off the surface of the disk  4  and “fly” on an air bearing formed beneath it. Various magnetic “tracks” of information can be read from the magnetic disk  4  as the actuator  6  is caused to pivot in a short arc as indicated by the arrows P. The design and manufacture of magnetic disk drives  1  is well known to those skilled in the art. 
     FIG. 2 shows a slider  10  of the prior art. The side of the slider  10  facing up in the drawing is the side that faces the disk  4 . Thus, the highest features in the drawing are those that are closest to the disk  4  when the disk drive  1  is in operation. The slider  10  has a generally rectangular shape with a leading edge  20 , a trailing edge  22 , a first side  24  and a second side  26 . Slider  10  further includes an air bearing surface (ABS) comprising a trailing edge pad  28 , a first leading pad  30  and a second leading pad  32 , and in some prior art designs also includes a first side pad  34  and a second side pad  36 . The slider  10  additionally includes a leading edge step  38 , a trailing edge step  40 , and a cavity  42 . In some prior art embodiments the slider  10  also includes a first side step  44  and a second side step  46 . 
     During manufacture, the slider  10  is etched from a single body, typically made of a two phase mixture of aluminum oxide and titanium carbide. The steps of the manufacturing process are generally illustrated in FIGS. 3A-3H and employ photolithography methods that are well known in the art. FIGS. 3A-3H show a crosssection of the slider  10  along the line  3 — 3  in FIG.  2  through successive steps. In FIG. 3A a body  48  that may have a nominally curved surface is covered with a photoresist layer  50 . The photoresist layer  50  is patterned and developed, and then any undeveloped material is washed away to leave a photoresist mask  52  as shown in FIG.  3 B. Next, the body  48  is etched to remove material that is not protected by the photoresist mask  52 . As shown in FIG. 3C, the etching creates a first surface that is recessed below the level of the initial surface by a depth H 1 . FIG. 3D shows the formed trailing edge pad  28  after the first photoresist mask  52  is stripped away. The steps of FIGS. 3A-3D are then repeated in FIGS. 3E-3H. A second photoresist layer  56  is formed over the body  48  as shown in FIG.  3 E. The photoresist layer is formed into a second photoresist mask  58  in FIG. 3F, and the body  48  is again etched in FIG. 3G to create a second surface recessed below the initial surface by a depth H 2 . FIG. 3H shows the slider  10  after the second photoresist mask  58  has been stripped away to reveal the leading edge step  38  and the cavity  42 . 
     Accordingly, as can be seen in FIG. 2, the prior art provides for two etching steps to create features at three different heights. The pads  28 ,  30 ,  32 ,  34 , and  36  that form the ABS represent the only portions of the initial surface that remain after the two etching operations. The steps  38 ,  40 ,  44 , and  46  all are recessed beneath the ABS by a depth of H 1 , while the cavity  42  is recessed beneath the ABS by a depth of H 2 . 
     During operation of the disk drive  1  air that is swept along with the spinning disk  4 , commonly known as windage, first encounters the leading edge  20 , and leading edge pads  30 ,  32  and leading edge step  38 . As the air flow passes between the leading edge pads  30 ,  32  and the disk  4  a lifting force is developed that tends to drive the slider  10  away from the disk  4 . Another portion of the air flow, however, passes through a gap  60  between the leading edge pads  30 ,  32 , over the leading edge step  38 , and over the cavity  42 . As the air expands over cavity  42  the pressure drops and a partial vacuum is developed that tends to draw the slider  10  towards the disk  4 . In stabile flight, the downward force and the upward force are in equilibrium and the slider  10  maintains a generally constant height above the disk  4 , commonly known as the fly height (FH). 
     FIG. 4 illustrates an attitude of a slider  10  in stabile flight over a disk  4 . The drawing shows how the slider  10  flies with the leading edge  20  elevated relative to the trailing edge  22  such that the plane defined by the ABS forms an angle α to the disk  4 . The fly height, FH, of the slider  10  is typically defined as the distance between the trailing edge  22  and the disk  4  since the transducer is commonly located along the trailing edge  22  adjacent to the trailing pad  28 . Pads  28 ,  34 ,  36  of the ABS are designed to cooperate with the leading edge pads  30 ,  32  to regulate, for example, the pressure drop experienced over the cavity  42 . The combination of the pads  28 ,  30 ,  32 ,  34 ,  36  and the steps  38 ,  40 ,  44 ,  46  also influences the angle α, also known as the pitch, the degree of rotation around the longitudinal line  33  known as roll, and the resistance slider  10  exhibits to changes in its flight characteristics, commonly referred to as stiffness. Stiffness with respect to fly height is especially desirable, but additionally stiffness is also desirable with respect to pitch and roll. 
     In prior art designs, in order to increase the pitch angle of a slider, the combined surface area of the leading edge pads  30 ,  32  is increased at the expense of the surface area of the cavity  42 . Increasing the surface area of the leading edge pads  30 ,  32  creates greater lift under the leading edge  20  causing the pitch to rise. Reducing the cavity surface area, however, reduces the volume enclosed by the cavity surface and the surrounding pads and steps. It has been found that reducing this volume also reduces the stiffness of the slider in flight. Therefore, in the prior art raising the pitch angle has been found to result in a tradeoff in stiffness. 
     Another well known configuration for a slider  10 , commonly referred to as side rail design, positions the trailing pad  28  and the transducer (not shown) close to either first side  24  or second side  26  of the slider  10 . A slider  10  with a side rail design preferably will have a controlled degree of roll so that the side  24  or  26  nearest to the transducer will be closest to the disk  4 . 
     As will be appreciated by those skilled in the art, the dimensions of the various features of slider  10  are carefully designed to control flight characteristics such as fly height, pitch, roll, and their respective stiffnesses. It will also be appreciated that the design process must also take into account factors such as the rotation rate of the disk  4  and the need to avoid the accumulation of debris on the slider  10 . Modifications to the dimensions of the various features in the design process necessarily creates tradeoffs in the flight characteristics of slider  10 . For example, increasing the size of the cavity  42  at the expense of the size of the leading edge pads  30 ,  32  will tend to cause the slider  10  to fly closer to the disk  4 . 
     Further, during the manufacturing process, deviations in the dimensions of the various features within the established tolerance ranges will create deviations in the flight performances of individual sliders  10 . Thus, deviations in the surface area of trailing edge pad  28  around some nominal value will tend to result in deviations in the fly height of slider  10 . For example, a variation of 1 microinch (μ″) in the depth H 1  of the leading edge step  38  and the trailing edge step  40  in a particular prior art slider  10  might result in a variation in its fly height of 0.1μ″. In the foregoing example the sensitivity of the fly height to step depth H 1  would be 0.1μ″/μ″ or just 0.1. It will be readily appreciated that lower sensitivity values are desired as they indicate that sliders  10  will be more uniform one to the next in operation which can permit lower fly heights to be achieved reliably. Therefore, it is desirable to identify designs that reduce the sensitivities of the various flight characteristics to deviations within the manufacturing tolerances of the various features on the slider  10 . 
     What is desired, therefore, is a process for manufacturing a slider that allows for greater flexibility in its design. It is further desired to create a slider with flight characteristics that are less sensitive to deviations within set manufacturing processes. 
     SUMMARY OF THE INVENTION 
     The present invention provides for an improved slider for a magnetic disk drive. The slider is provided with an air bearing surface (ABS) comprising a pair of leading edge pads and a trailing edge pad having surfaces that are substantially coplanar, a cavity that is a surface recessed below the ABS, and a plurality of steps disposed at heights intermediate between the ABS and the cavity. The steps include at least a leading edge step and a trailing edge step, each at a different depth beneath the ABS. The trailing edge step, located at a first depth, is positioned such that it is disposed between the ABS and the leading edge step, located at a second depth. The leading edge step is likewise disposed between the trailing edge step at a first depth and the cavity at a third depth. This configuration provides an advantage to a slider of the present invention over those of the prior art in that it allows the slider to fly with a larger pitch angle without sacrificing stiffness. It has been found that the pitch angle can be increased by increasing the difference between the depths of the trailing edge step and the leading edge step. 
     By increasing the difference in the depths between the trailing and leading edges, a slider of the present invention flies with a higher pitch angle without reducing the cavity volume and therefore without reducing the stiffness. In other embodiments of the present invention the combined surface area of the leading edge pads is reduced in order to increase the cavity volume to achieve greater stiffness. Pitch angle is not sacrificed in these embodiments because the leading edge step can be made deeper relative to the trailing edge step in order to compensate for the loss of lift created by the loss of leading edge pad surface area. 
     A further advantage of the present invention relates to the sensitivities of the various flight characteristics, such as fly height, to deviations in the depths within manufacturing tolerances of the leading and trailing edges. It has been found, for example, that the sensitivity of the fly height to the depth of the trailing edge step combined with the sensitivity of the fly height to the depth of the leading edge step is less than the sensitivity of the fly height to the depth H 1  in sliders of the prior art in which the two steps are always at substantially the same depth. Consequently, sliders manufactured according to the present invention have a lower overall sensitivity for the fly height when all the various manufacturing tolerances are summed together. 
     Additional embodiments of the invention can further include side pads and side steps where the side pads also form part of the ABS and the side steps may be disposed at any intermediate height between the ABS and the cavity. The ability to alter the depths of the side steps allows their relative heights to be used as a method for adjusting flight characteristics such as roll. It will be readily appreciated that a side step closer to the disk will experience greater lift than one further away and that a slider with such an asymmetry will tend to roll in flight. In side rail sliders of the prior art, for example, a certain degree of roll is desirable in order to position the side with the transducer as close to the disk as possible. It is therefore a further advantage of the present invention that roll and other flight characteristics can be adjusted by appropriately controlling the relative depths of the side steps. 
     A process is also disclosed for the fabrication of a slider of the present invention. The process includes a first cycle of masking, etching, and stripping to form a first level, a second cycle to form a second level, and a third cycle to form a cavity. In the first cycle those portions of the substrate that are to be retained as the ABS are masked and the remainder of the substrate is etched to a first depth. In the second cycle those portions of the substrate that are to be retained as the ABS and those portions that are to be retained as a trailing edge step are masked and the remainder of the surface is etched to a second depth. In the third cycle those portions of the substrate that are to be retained as the ABS, the trailing edge step, and the leading edge step are masked and the remainder of the surface is etched to the depth of the cavity. This process also allows portions of the substrate to be masked and retained to form side pads and side steps in any of the three cycles. The present invention further allows for additional cycles of masking, etching, and stripping to be included so that side steps can be placed at heights other than those of the leading and trailing edge steps. The various embodiments of the process of the present invention are generally advantageous for allowing greater flexibility in the design of sliders that have improved flight characteristics, stiffnesses, and sensitivities. 
     These and other advantages of the present invention will become apparent to those skilled in the art upon a reading of the following descriptions of the invention and a study of the several figures of the drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1A is a partially sectioned, front elevational view of a magnetic disk drive assembly of the prior art; 
     FIG. 1B is a cross section taken along line  1 B— 1 B of FIG. 1A; 
     FIG. 2 is a perspective view of a slider of the prior art; 
     FIGS. 3A-3H show a crosssection of the slider along the line  3 — 3  in FIG. 2 as it processed through successive steps; 
     FIG. 4 is shows a side elevational view of the slider of FIG. 2 in flight relative to a magnetic disk; 
     FIG. 5 is a front elevational view of a slider of the present invention; 
     FIG. 6 is a flow chart illustrating a process of making a slider according to the present invention; and 
     FIGS. 7A-7J show a crosssection of the slider of FIG. 5 along the line  7 — 7  as it is formed according to the process of FIG.  6 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIGS. 1-4 have previously been discussed with reference to the prior art. FIG. 5 shows a slider  62  of the present invention. The side  63  of the slider  62  seen in this figure faces the disk  4  (not shown) of the disk drive  1 . The slider  62  has a generally rectangular shape with a leading edge  64 , a trailing edge  66 , a first side  68  and a second side  70 . Since the slider  62  flies over the disk  4  with a certain degree of pitch, the leading edge  64  is further from the disk  4  than the trailing edge  66 . Slider  62  further includes an ABS comprising a trailing edge pad  72 , a first leading pad  74  and a second leading pad  76 , and in some embodiments optionally also includes a first side pad  78  and a second side pad  80 . The slider  62  additionally includes a leading edge step  82 , a trailing edge step  84 , and a cavity  86 . In additional embodiments the slider  62  also includes a first side step  88  and a second side step  90 . 
     The ABS, comprising pads  72 ,  74 , and  76 , and in some embodiments additionally comprising pads  78  and  80 , are formed from the same initial surface of a substrate and therefore have top surfaces that are substantially coplanar. Steps  82  and  84 , and in some embodiments steps  88  and  90  are each formed by removing material from the substrate down to an appropriate depth. According to the present invention, each of these steps can be recessed a different distance below the ABS. The only limitation imposed by the present invention on the relative depths of the several steps  82 ,  84 ,  88 , and  90  is that the leading edge step  82  must be recessed below the ABS more than the trailing edge step  84 . It is another limitation of the present invention that the cavity  86  is recessed below the ABS further than any of the several steps  82 ,  84 ,  88 , and  90 . 
     In some embodiments of the present invention the trailing edge step  84  is recessed about 3μ″ to about 8μ″ below the ABS, and in preferred embodiments the trailing edge step  84  is recessed about 5μ″ below the ABS. In some embodiments of the present invention the leading edge step  82  is recessed about 6μ″ to about 12μ″ below the ABS, and in preferred embodiments the leading edge step  82  is recessed about 8μ″ below the ABS. In further embodiments the leading edge step  82  is recessed below the level of the trailing edge step  84  by about 3μ″ to about 5μ″. The cavity  86 , in some embodiments, is recessed below the ABS about 30μ″ to about 80μ″, and in preferred embodiments is recessed about 50μ″ below the ABS. 
     Additional embodiments of the present invention are directed to sliders  62  including a first side step  88  but without a second side step  90 . In some of these embodiments the first side step  88  is recessed below the ABS by substantially the same distance as the trailing edge step  84 , while in other embodiments the first side step  88  is recessed below the ABS by substantially the same distance as the leading edge step  82 . 
     Yet other embodiments are directed to sliders  62  including both a first side step  88  and a second side step  90 . In some of these embodiments both side steps  88 ,  90  are recessed below the ABS by substantially the same distance as the trailing edge step  84 , while in other embodiments both side steps  88 ,  90  are recessed below the ABS by substantially the same distance as the leading edge step  82 . In further embodiments the first side step  88  is recessed below the ABS by substantially the same distance as the leading edge step  82  and the second side step  90  is recessed below the ABS by substantially the same distance as the trailing edge step  84 . In still other embodiments the first side step  88  is recessed below the ABS by substantially the same distance as either the leading edge step  82  or the trailing edge step  84 , while the second side step  90  is recessed below the ABS by a distance substantially different from either the leading edge step  82  or the trailing edge step  84 . In yet other embodiments the first side step  88  and the second side step  90  are both recessed below the ABS by a distance substantially different from either the leading edge step  82  or the trailing edge step  84 . 
     It should be noted that the present invention is directed to creating greater variation in the relative depths of the several steps  82 ,  84 ,  88 , and  90  to allow for sliders  62  with improved flight characteristics. Therefore, it should be understood that other parameters of the various pads  72 ,  74 ,  76 ,  78 ,  80 , steps  82 ,  84 ,  88 ,  90 , and the cavity  86 , such as surface area, crosssection shape, and relative positions are not meant to be limited by their representations in FIG.  5 . 
     FIG. 6 shows a process  100  for making a slider in accordance with the present invention. As indicated, the process  100  for fabricating a slider  62  comprises the acts or operations of providing a substrate  102 , forming a first photoresist mask  104 , forming a first level  106 , removing the first photoresist mask  108 , forming a second photoresist mask  110 , forming a second level  112 , removing the second photoresist mask  114 , forming a third photoresist mask  116 , forming a cavity  118 , and removing the third photoresist mask  120 . FIGS. 7A-7J show a crosssection of a substrate  122  as it is processed into a finished slider  62 . The cross-section in FIGS. 7A-7J corresponds to the line  7 — 7  in FIG.  5 . FIGS. 7A-7J further illustrate the process  100 . 
     Act or operation  102  is directed to providing a substrate  122  as shown in FIG.  7 A. The substrate  122  is preferably a two-phase mixture of alumninum oxide and titanium carbide, but in other embodiments may be silicon dioxide. The type of material employed is not essential to the present invention so long as it has materials properties similar to those of the materials just mentioned. At a minimum, the substrate material should be electrically insulating and exhibit good wear resistance. As provided, the top surface of the substrate  122 , hereinafter known as the initial surface  124 , can be either planar or slightly curved. Providing a slight convex curvature to the initial surface  124  can impart improved flight characteristics to the finished slider  62  as well as reduce the contact area between the slider  62  and the disk  4  when the disk drive  1  is not in operation and the slider  62  is parked. 
     As also shown in FIG. 7A, act or operation  104  of forming a first photoresist mask  128  is preferably accomplished by depositing a layer of an undeveloped photoresist material  126  over the substrate, projecting a pattern of radiation, such as visible light, onto the undeveloped photoresist  126  to selectively alter its chemistry and to create a latent image therein, and exposing the photoresist layer  126  to a developer to selectively remove either the unaltered material or the altered material. Following this series of steps, all of which are well known in the photolithography art, a first photoresist mask  128  will remain above and in contact with the substrate  122  as seen in FIG.  7 B. The mask  128  thus formed retains the pattern that was originally projected onto the undeveloped photoresist  126  such that some portions of the substrate  122  remain covered and protected by the mask  128  while other portions are intentionally exposed for further processing. In act or operation  104  the first photoresist mask  128  is formed such that it covers at least the portions of the substrate  122  that ultimately will become the ABS of the finished slider  62 . The ABS of the fmished slider  62  will include at least a first leading edge pad  74 , a second leading edge pad  76 , and a trailing edge pad  72 , and may additionally include in some embodiments a first side pad  78  and a second side pad  80 . 
     Act or operation  106  of forming a first level  130 , shown in FIG. 7C, is accomplished by selectively removing, to a desired first depth H 3 , portions of the substrate  122  left exposed by the first photoresist mask  129 . This is preferably achieved with an etching process such as reactive ion etching (RIE). Act or operation  106  should remove material to substantially the first dept H 3  that the trailing edge step  84  is intended to be recessed relative to the ABS. For purposes of the present invention first depth H 3  should be about 3μ″ to about 8μ″ below an initial surface  124  of the substrate  122 . More ideally, first depth H 3  should be about 5μ″ below the initial surface  124 . Etching processes useful for removing material from substrate  122  are well known in the art. 
     Act or operation  108 , removing the first photoresist mask  128 , commonly referred to as stripping, is performed in order to clean the substrate  122  for additional photolithography processing steps. Chemical solvents that can readily dissolve the first photoresist mask  128  but that do not attack the material of the substrate  122  are preferred in act or operation  108 . Techniques for stripping away photoresist masks are well known in the art, as is represented in FIG.  7 D. 
     Forming a second photoresist mask  132  in act or operation  110  is accomplished in much the same manner as forming a first photoresist mask  128  in act or operation  104 . The second photoresist mask  132  is formed such that it is above and in contact with the substrate  122 . As illustrated in FIG. 7E, the second photoresist mask  132  preferably covers and protects at least the portions of the substrate  122  that include the ABS as well as a portion of the first level  130  in a suitable position for the subsequent formation of a trailing edge step  84 . In some embodiments the second photoresist mask  132  will additionally cover a portion of the first level  130  that will be retained as a first side step  88 . In further embodiments the second photoresist mask  132  will additionally cover a portion of the first level  130  that will be retained as a first side step  88  and another portion of the first level  130  that will be retained as a second side step  90 . 
     As shown in FIG. 7F, forming a second level  134  in act or operation  112  is accomplished by selectively further removing, to a desired second depth H 4 , portions of the substrate  122  left exposed by the second photoresist mask  132 . Second depth H 4  should be substantially the distance that the leading edge step  82  will be recessed relative to the ABS. For purposes of the present invention second depth H 4  should be about 6μ″ to about 12μ″ below the initial surface  124  of the substrate  122 . More ideally, second depth H 4  should be about 8μ″ below the initial surface  124 . 
     The trailing edge step  84  is formed in act or operation  112 . Step  84  is formed by removing material from the substrate  122  around an isolated portion of the second photoresist mask  132  located in a suitable position on the first level  130 . It will be appreciated by those skilled in the art that the trailing edge step  84  is essentially a pillar with a planar top surface disposed on the surface of the substrate  122 . It will be further appreciated that trailing edge step  84  is further formed in subsequent acts or operations as progressively more of the substrate  122  is removed around it and it becomes a lengthier pillar while maintaining the particular cross-section defined in act or operation  112 . Lastly, it will be appreciated that the forgoing is true for each of the various pads and steps of the present invention. 
     In some embodiments act or operation  112  further includes forming a first side step  88  simultaneously with forming the trailing edge step  84 . The first side step  88  may be formed nearer to either side  68 ,  70  of the slider  62 , though it happens to be represented in FIG. 5 as being near the first side  68 . First side step  88  is formed by removing material from the substrate  122  around a portion of the second photoresist mask  132  located in a suitable position on the first level  130 . In further embodiments act or operation  112  further includes forming a first side step  88  and a second side step  90 . In these embodiments the second side step  90  will be formed nearer to the side  68 ,  70  that is opposite to the side  68 ,  70  nearest the first side step  88 . This is accomplished by removing material from the substrate  122  around separate isolated portions of the second photoresist mask  132  located in suitable positions on the first level  130 . 
     Removing the second photoresist mask  132  in act or operation  114  is accomplished in much the same manner as removing the first photoresist mask  128  in act or operation  108 , as can be seen in FIG.  7 G. Forming a third photoresist mask  136  in act or operation  116  is accomplished in much the same manner as forming a first photoresist mask  128  in act or operation  104  and a second photoresist mask  132  in act or operation  110  and is represented in FIG.  7 H. The third photoresist mask  136  is formed such that it is above and in contact with the substrate  122 . The third photoresist mask  136  preferably covers and protects at least the portions of the substrate  122  that include the ABS and the trailing edge step  84 , and also serves to cover and protect a portion of second level  134  in a suitable position for the subsequent formation of a leading edge step  82 . In those embodiments in which a first side step  88  was formed during act or operation  112  the third photoresist mask  136  additionally covers first side step  88 . In those embodiments in which both a first side step  88  and a second side step  90  was formed during act or operation  90  the third photoresist mask  136  additionally covers both steps  88  and  90 . 
     In those embodiments in which a first side step  88  was not formed during act or operation  112 , the third photoresist mask  136  in act or operation  116  can additionally cover a portion of the second level  134  to be retained as a first side step  88 , and may additionally cover a portion of the second level  134  that will be retained as a second side step  90 . In those embodiments in which a first side step  88  was formed during act or operation  112  but a second side step  90  was not formed, the third photoresist mask  136  in act or operation  116  can additionally cover a portion of the second level  134  to be retained as a second side step  90 . Put another way, any portion of the substrate  122  that is intended to become either a pad or a step in the finished slider should be covered by the third photoresist mask  136  in this act or operation. 
     Forming a cavity  86  in act or operation  118 , as shown in FIG. 7I, is accomplished in much the same manner as forming a first level  130  in act or operation  106  and forming a second level  134  in act or operation  112 . Forming the cavity  86  is accomplished by selectively removing, to a desired third depth H 5 , portions of the substrate  122  left exposed by the third photoresist mask  136 . Act or operation  118  should remove material to substantially the third depth H 5  that the cavity  86  is intended to be recessed relative to the ABS. For purposes of the present invention third depth H 5  should be about 30μ″ to about 80μ″ below the initial surface  124  of the substrate  122 . More ideally, third depth H 5  should be about 50μ″ below the initial surface  124 . The cavity  86  is formed in act or operation  118  by removing material to the third depth H 5  from all portions of the substrate  122  that are not protected by the third photoresist mask  136 . Removing the third photoresist mask  136  in act or operation  120 , as shown in FIG. 7J, is accomplished in much the same manner as removing the first photoresist mask  128  in act or operation  108  and removing the second photoresist mask  132  in act or operation  114 . 
     While this invention has been described in terms of several preferred embodiments, it is contemplated that alternatives, modifications, permutations and equivalents thereof will become apparent to those skilled in the art upon a reading of the specification and study of the drawings. For example, one of skill in the art will readily appreciate that a first side step  88  can be formed in a separate set of acts or operations from those used to form the trailing edge step  84  and the leading edge step  82  by including into process  100  an additional cycle of mask formation, level formation, and mask removal. Thus, embodiments of slider  62  can be formed in which a first side step  88  and a second side step  90  are both recessed below the ABS by distances substantially different from each other and substantially different from either the leading edge step  82  or the trailing edge step  84 . 
     It will further be appreciated that the present invention encompasses processes, and the sliders  62  formed thereby, in which a pad or a step, such as first side step  88 , formed in one act or operation is left either partially or entirely uncovered in a subsequent masking operation Consider, for example, an embodiment of slider  62  in which a first side step  88  is at a depth 1μ″ below the depth of a trailing edge step  84 , and a second side step  90  is at a depth 1μ″ below the depth of a leading edge step  82 . To form this slider  62  the first side step  88  could be formed concurrently with the trailing edge step  84  and the second side step  90  could be formed concurrently with the leading edge step  82 . In a subsequent series of acts or operations the ABS, the trailing edge step  84 , and the leading edge step  84  could all be masked while the first and second side steps  88 ,  90  are left unmasked so that in the next round of etching both steps  88 ,  90  are etched 1μ″ deeper. This process would include fewer steps than one in which the trailing edge step  84  is formed at a first level, the first side step  88  is formed at a second level, the leading edge step  82  is formed at a third level, and the second side step is formed at a fourth level. 
     It is therefore intended that the following appended claims include all such alternatives, modifications, permutations and equivalents as fall within the true spirit and scope of the present invention.