Abstract:
A method of making a magnetic head, which has an air bearing surface (ABS) and a back gap (BG), comprising the steps of: forming a second pole tip of a second pole piece with a top surface and a bottom surface at an ABS site for said ABS; the top surface of the second pole tip having a write region located at the ABS site and a stitch region which is recessed in its entirety from the ABS site toward said back gap; depositing a protective sacrificial layer on the write region of the second pole tip; removing said sacrificial layer from only the stitch region of the second pole tip; and forming a second pole piece yoke of a second pole piece magnetically connected to the stitch region of the second pole tip.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a method of protecting a second pole tip thickness during fabrication of a write head and, more particularly, to preventing a reduction in the thickness of the second pole tip during subsequent processing steps, such as seed layer removal, sputter cleaning the wafer and formation of studs for terminals. 
     2. Description of the Related Art 
     The heart of a computer is a magnetic disk drive which includes a rotating magnetic disk, a slider that has read and write heads, a suspension arm above the rotating disk and an actuator arm that swings the suspension arm to place the read and write heads over selected circular tracks on the rotating disk. The suspension arm biases the slider into contact with the surface of the disk when the disk is not rotating but, when the disk rotates, air is swirled by the rotating disk adjacent an air bearing surface (ABS) of the slider causing the slider to ride on an air bearing a slight distance from the surface of the rotating disk. When the slider rides on the air bearing the write and read heads are employed for writing magnetic impressions to and reading magnetic signal fields from the rotating disk. The read and write heads are connected to processing circuitry that operates according to a computer program to implement the writing and reading functions. 
     A write head typically employs ferromagnetic first and second pole pieces which are capable of carrying flux signals for the purpose of writing magnetic impressions into a track on a magnetic medium, such as a rotating magnetic disk. Each of the first and second pole pieces has a yoke region which is located between a pole tip region and a back gap region. The pole tip region is located at the ABS and the back gap region is spaced from the pole tip region at a recessed location within the write head. At least one coil layer is embedded in an insulation stack which is located between the first and second pole pieces in the yoke region. A nonmagnetic write gap layer is located between the pole tip regions of the first and second pole pieces. The thinner the thickness of the write gap layer, the greater the number of bits the write head can write into the track of a rotating magnetic disk. The first and second pole pieces are magnetically connected at the back gap. Processing circuitry digitally energizes the write coil which induces flux into the first and second pole pieces so that flux signals bridge across the write gap at the ABS to write the aforementioned magnetic impressions or bits into the track of the rotating disk. The second pole piece has a second pole piece yoke (P2 yoke) which is magnetically connected to the second pole tip (P2 tip) and extends to the back gap for connection to the first pole piece. 
     A write head is typically rated by its areal density which is a product of its linear bit density and its track width density. The linear bit density is the number of bits which can be written per linear inch along the track of a rotating magnetic disk and the track width density is the number of tracks that can be written per inch along a radius of the rotating magnetic disk. The linear bit density is quantified as bits per inch (BPI) and the track width density is quantified as tracks per inch (TPI). As discussed hereinabove, the linear bit density depends upon the thickness of the write gap layer. The track width density is directly dependent upon the width of the second pole tip at the ABS. Efforts over the years to increase the areal density of write heads has resulted in computer storage capacities increasing from kilobytes to megabytes to gigabytes. 
     The first and second pole pieces, including the second pole tip, are typically fabricated by plating techniques. The strong-felt need to fabricate second pole tips with submicron widths is limited by the resolution of the fabrication techniques. The second pole tip is typically fabricated by frame plating. Photoresist is employed to provide the frame and a seed layer is employed to provide a return path for the plating operation. A typical sequence for fabricating a second pole tip, as well as other components of the first and second pole pieces, is to sputter clean the wafer, sputter deposit a seed layer, such as nickel iron, on the wafer, spin a layer of photoresist on the wafer, light-image the photoresist layer through a mask to expose areas of the photoresist that are to be removed (assuming that the photoresist is a positive photoresist), develop the photoresist to remove the light-exposed areas to provide an opening in the photoresist at the pole tip region and then plate the second pole tip in the opening up to a desired height. 
     It is necessary that a second pole tip have a sufficient amount of volume at the ABS in order to conduct the required amount of flux for writing the signals into the magnetic disk. If the second pole tip is made thinner, it must be made higher in order to provide the necessary volume of magnetic material. Unfortunately, as the track width becomes narrower the resolution of the photoresist decreases. Resolution is quantified as aspect ratio which is the width of the second pole tip versus the thickness of the photoresist. As the thickness of the photoresist increases the light penetration during the light-imaging step loses its columnation as it travels toward the bottom of the photoresist. The result is that the side walls of the photoresist frame are jagged which results in jagged side walls of the second pole tip. 
     The aforementioned problems are particularly manifested when the second pole tip and the yoke of the second pole piece are plated simultaneously in a common photoresist frame. In addition to loss of resolution with an increasing height of the second pole tip, there is also notching of the side walls of the photoresist frame, and consequently the second pole tip, due to reflection of light from a seed layer on the insulation stack immediately behind the pole tip region. One method to overcome this problem has been to employ a stitched “T”-shaped second pole piece which is fabricated by first making only the second pole tip portion with a photoresist frame and then subsequently making the yoke portion of the second pole piece with a second photoresist frame with the yoke portion being stitched (magnetically connected) to a stitch region at the top of the second pole tip. This type of second pole piece is referred to as a stitched “T” because the yoke portion extends laterally across the top of the pole tip portion, forming the configuration of a “T”. The yoke portion can be stitched across the entire top surface of the second pole tip in which case it is exposed at the ABS or it may be recessed from the ABS, as desired. 
     Unfortunately, processing steps subsequent to the construction of the second pole tip decrease the height of the second pole tip and can seriously damage its side walls. When the second pole piece is a continuous pole tip and yoke combination these processing steps are removal of the seed layer by sputter etching after removal of the photoresist frame and the fabrication of studs for write head and read head terminals which involves sputter etching to clean the wafer, depositing a seed layer, photoresist framing the areas involved, plating the studs, removing the photoresist layer and sputter etching the exposed seed layer. While these steps lessen the height of the second pole tip of the continuous second pole tip and yoke combination, it is even more aggravated with the stitched “T” type of second pole piece. After the second pole tip of the stitched “T” is fabricated, sputter etching is required to remove the seed layer employed to fabricate the pole tip which further reduces the height of the second pole tip. Further, if chemical mechanical polishing (CMP) is employed for planarizing the wafer, preparation steps for this operation can further reduce the height of the second pole tip. 
     In order to overcome the loss of height of the second pole tip while maintaining a narrow track width (width of the second pole tip) the second pole tip can be frame plated to a greater height so that after the processing steps the remaining height of the second pole tip is at a desired level. Unfortunately, this requires the photoresist frames to be thicker which increases the aforementioned aspect ratio. Consequently, the resolution of the photoresist frame is lessened which degrades the resolution of the finally plated second pole tip. 
     SUMMARY OF THE INVENTION 
     The present invention provides a stitched “T” type of second pole piece wherein the second pole tip portion is protected from a reduction in height due after subsequent processing steps. In the present invention the top surface of the second pole tip has a write region which is located at the ABS and a stitch region which is recessed from the ABS toward the back gap. A protective sacrificial layer is deposited on the write region of the second pole tip and the second pole piece yoke is magnetically connected to the stitch region. The method includes first depositing the sacrificial layer on both the write region and the stitch region of the second pole tip. The sacrificial layer is then removed from only the stitch region of the second pole tip leaving a portion of the sacrificial layer covering the write region of the second pole tip. 
     Several methods are employed for accomplishing these steps. In a first embodiment, the sacrificial layer is deposited over the entire wafer. The sacrificial layer is then chemically mechanically polished (CMP) until it is flat, but stopping the CMP before the top surface of the second pole tip is exposed, and then before forming the second pole piece yoke, removing the sacrificial layer from only the stitch region by sputter etching or ion milling until the stitch region is exposed. The second pole piece yoke is then stitched to the exposed stitch region of the second pole tip. In another embodiment the second pole tip is provided with an upstanding pedestal which is located in the stitch region. Again the sacrificial layer is deposited over the entire wafer, the sacrificial layer is then chemically mechanically polished until it is flat and until the pole tip pedestal in the stitch region is exposed, but stopping the chemical mechanical polishing before the write region of the second pole tip is exposed. The second pole piece yoke is then magnetically connected to the second pole tip pedestal. The invention provides a unique method of obtaining the second pole tip pedestal by forming an insulation layer directly below the second pole tip before its formation and then forming a second pole tip so that the profile of the insulation layer forms the second pole tip with the pedestal. 
     In a preferred embodiment of the invention the write head employs first and second coil layers which are embedded in first and second insulation stacks which are stacked on top of each other. This is accomplished by providing the first pole piece with a first pole piece layer and first and second spaced-apart pedestals which are magnetically connected to the first pole piece layer. The first pedestal is located at the ABS and the second pedestal is located at the back gap. The first insulation stack with the first write coil embedded therein is located in the space between the first and second pedestals and is separated from the first pole piece layer by a first insulation layer. The write gap layer is located on the first pedestal and may extend all the way from the ABS to the back gap. The second pole piece includes the second pole tip portion at the ABS and a back gap pedestal at the back gap with a yoke portion extending between the second pole tip and the back gap pedestal and magnetically connected thereto. The second pole tip is separated from the first pedestal of the first pole piece by the write gap layer. The second insulation stack with the write coil embedded therein is located between the second pole tip and the back gap pedestal and may be separated or further separated from the first write coil by a second insulation layer. The sacrificial layer is then formed over the entire wafer and the stitch region of the second pole tip is exposed by one of the methods described hereinabove followed by fabrication of the second pole piece yoke. In a preferred embodiment, the aforementioned first insulation layer, the second insulation layer and the sacrificial layer are chemically mechanically polished (CMP). Further, the composition of each of the first and second insulation layers and the sacrificial layer is preferably alumina. 
     An object of the present invention is to protect a pole tip portion of a second pole tip in a stitched “T” second pole piece from subsequent processing steps. 
     Another object is to provide unique methods for exposing a stitch region of the second pole tip for stitching a yoke portion of a second pole piece thereto. 
     A further object is to accomplish the aforementioned objects with first and second insulation stacks with first and second write coils embedded therein. 
     Still another object is to provide the various write heads fabricated by the aforementioned methods. 
     Other objects and attendant advantages of the invention will be appreciated upon reading the following description taken together with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a plan view of an exemplary prior art magnetic disk drive; 
     FIG. 2 is an end view of a prior art slider with a magnetic head of the disk drive as seen in plane  2 — 2  of FIG. 1; 
     FIG. 3 is an elevation view of the prior art magnetic disk drive wherein multiple disks and magnetic heads are employed; 
     FIG. 4 is an isometric illustration of an exemplary prior art suspension system for supporting the slider and magnetic head; 
     FIG. 5 is an ABS view of the magnetic head taken along plane  5 — 5  of FIG. 2; 
     FIG. 6 is a partial view of the slider and a prior art merged magnetic head as seen in plane  6 — 6  of FIG. 2; 
     FIG. 7 is a partial ABS view of the slider taken along plane  7 — 7  of FIG. 6 to show the read and write elements of the magnetic head; 
     FIG. 8 is a view taken along plane  8 — 8  of FIG. 6 with all material above the coil layer and leads removed; 
     FIG. 9 is a side view of a first embodiment of the write head similar to the view shown in FIG. 6; 
     FIG. 10 is the same as FIG. 9 except a portion of a photoresist layer has been removed; 
     FIG. 11 is the same as FIG. 10 except a thick layer of alumina has been deposited on the wafer; 
     FIG. 12 is the same as FIG. 11 except the alumina layer has been chemically mechanically polished (CMP); 
     FIG. 13 is the same as FIG. 12 except the alumina layer has been removed from a stitch region of a second pole tip; 
     FIG. 14 is the same as FIG. 13 except a second pole piece yoke has been formed; 
     FIG. 14A is a view taken along plane  14 A— 14 A of FIG. 14; 
     FIG. 15 is a side view of a second embodiment of the present invention which is a similar view to FIG. 11 after depositing a thick alumina layer; 
     FIG. 16 is the same as FIG. 15 except the thick alumina layer has been chemically mechanically polished (CMP); 
     FIG. 17 is the same as FIG. 16 except a second pole piece yoke has been stitched to the second pole tip; 
     FIG. 18 is a side view of a third embodiment of the present invention; and 
     FIG. 19 is a side view of a fourth embodiment of the present invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Magnetic Disk Drive 
     Referring now to the drawings wherein like reference numerals designate like or similar parts throughout the several views, FIGS. 1-3 illustrate a magnetic disk drive  30 . The drive  30  includes a spindle  32  that supports and rotates a magnetic disk  34 . The spindle  32  is rotated by a spindle motor  36  that is controlled by a motor controller  38 . A slider  42  has a combined read and write magnetic head  40  and is supported by a suspension  44  and actuator arm  46  that is rotatably positioned by an actuator  47 . A plurality of disks, sliders and suspensions may be employed in a large capacity direct access storage device (DASD) as shown in FIG.  3 . The suspension  44  and actuator arm  46  are moved by the actuator  47  to position the slider  42  so that the magnetic head  40  is in a transducing relationship with a surface of the magnetic disk  34 . When the disk  34  is rotated by the spindle motor  36  the slider is supported on a thin (typically, 0.05 μm) cushion of air (air bearing) between the surface of the disk  34  and the air bearing surface (ABS)  48 . The magnetic head  40  may then be employed for writing information to multiple circular tracks on the surface of the disk  34 , as well as for reading information therefrom. Processing circuitry  50  exchanges signals, representing such information, with the head  40 , provides spindle motor drive signals for rotating the magnetic disk  34 , and provides control signals to the actuator for moving the slider to various tracks. In FIG. 4 the slider  42  is shown mounted to a suspension  44 . The components described hereinabove may be mounted on a frame  54  of a housing, as shown in FIG.  3 . 
     FIG. 5 is an ABS view of the slider  42  and the magnetic head  40 . The slider has a center rail  56  that supports the magnetic head  40 , and side rails  58  and  60 . The rails  56 ,  58  and  60  extend from a cross rail  62 . With respect to rotation of the magnetic disk  34 , the cross rail  62  is at a leading edge  64  of the slider and the magnetic head  40  is at a trailing edge  66  of the slider. 
     FIG. 6 is a side cross-sectional elevation view of a merged magnetic head  40 , which includes a write head portion  70  and a read head portion  72 , the read head portion employing a sensor  74 . FIG. 7 is an ABS view of FIG.  6 . The sensor  74  is sandwiched between nonmagnetic electrically insulative first and second read gap layers  76  and  78 , and the read gap layers are sandwiched between ferromagnetic first and second shield layers  80  and  82 . In response to external magnetic fields, the resistance of the sensor  74  changes. A sense current I s  conducted through the sensor causes these resistance changes to be manifested as potential changes. These potential changes are then processed as readback signals by the processing circuitry  50  shown in FIG.  3 . 
     The write head portion  70  of the magnetic head  40  includes a coil layer  84  sandwiched between first and second insulation layers  86  and  88 . A third insulation layer  90  may be employed for planarizing the head to eliminate ripples in the second insulation layer caused by the coil layer  84 . The first, second and third insulation layers are referred to in the art as an “insulation stack”. The coil layer  84  and the first, second and third insulation layers  86 ,  88  and  90  are sandwiched between first and second pole piece layers  92  and  94 . The first and second pole piece layers  92  and  94  are magnetically coupled at a back gap  96  and have first and second pole tips  98  and  100  which are separated by a write gap layer  102  at the ABS. Since the second shield layer  82  and the first pole piece layer  92  are a common layer this head is known as a merged head. In a piggyback head these layers are separate layers which are separated by an insulation layer. As shown in FIGS. 2 and 4, first and second solder connections  104  and  106  connect leads from the spin valve sensor  74  to leads  112  and  114  on the suspension  44 , and third and fourth solder connections  116  and  118  connect leads  120  and  122  from the coil  84  (see FIG. 8) to leads  124  and  126  on the suspension. 
     First Embodiment of the Invention 
     The magnetic head  200  in FIG. 14 illustrates a first embodiment of the present invention constructed on a wafer  201 . The magnetic head may include the read head portion  72  in FIG. 6 which includes the read sensor  74  which is located between first and second read gap layers  76  and  78  which are, in turn, located between first shield layer (S1)  80  and the combined second shield/first pole piece layer (S2/P1)  82 / 92 . The write head portion of the head also includes a first pole piece pedestal  202  which is magnetically connected to the first pole piece  92  and is located at the air bearing surface (ABS). The first pole piece also includes a second pedestal which is located at a back gap and will be described in a second embodiment of the present invention, as shown in FIG. 17. A first insulation stack  204  with a write coil layer  206  embedded therein is located between the first and second pedestals. The first insulation stack  204  may include a first insulation layer  208  which separates the write coil  206  from the first pole piece  92 , a second insulation layer  210  of baked photoresist which partially insulates the write coil  206  between its coils and is located below the top of the write coil and a third insulation layer  212  which is also located between the turns of the write coil and is flush with the top of the write coil. 
     The second pole piece includes a second pole tip  214 , a back gap pedestal which is located at the back gap and spaced from the second pole tip  214  which will be described in the second embodiment of the invention, as shown in FIG. 17, and a second pole piece yoke  216 . A second insulation stack  218  is located in the space between the second pole tip  214  and the back gap yoke and has a second write coil  220  embedded therein. The second insulation stack  218  may include a fourth insulation layer  222 , a fifth insulation layer  224  of baked photoresist which partially insulates between the turns of the write coil  220  and is located a distance below a top surface thereof, and a fifth insulation layer  226  which also insulates between the turns of the write coil  220  and is located above and insulates the top of the write coil  220 . The second pole tip  214  is separated from the first pedestal  202  by a write gap layer  228 . The write gap layer  228  may extend into the yoke region and provide the only insulation or extra insulation between the first and second write coil layers  206  and  220 . 
     According to the present invention the second pole tip  214  has a pole tip region  232 , which is located at the ABS, and a stitch region  234  which is recessed from the ABS. The yoke  216  is magnetically connected to the stitch region  234  of the second pole tip and is magnetically connected to the back gap pedestal, which will be described in the second embodiment. The write portion  232  of the second pole tip is provided with insulation, such as a portion of insulation layer  226 , before fabrication of the second pole piece yoke  216 . This protects the height of the second pole tip from subsequent processing steps, such as sputter etching the seed layers for the second pole tip as well as the yoke, and subsequent construction of studs for read and write terminals of the head. The insulation layers  208 ,  212 ,  222 ,  226  and the write gap layer  228  are preferably alumina. In the preferred embodiment chemical mechanical polishing (CMP) is employed for planarizing the wafer at various stages in the fabrication, such as flattening layers  208 ,  212  and  226 . 
     It should be understood that the magnetic head is constructed as one head in an array of magnetic heads on a wafer substrate which are arranged in rows and columns. After completion of the magnetic heads, which includes the studs for terminals (not shown) and an overcoat layer  242 , the magnetic heads are diced into rows of magnetic heads after which they are lapped to the ABS, as shown in FIG.  14 . The row of heads is then diced into individual heads and mounted on the magnetic disk drive shown in FIGS. 3 and 4. CMP may be first employed after depositing a thick alumina layer and then CMP the thick alumina layer until the top of the S2/P1 layer  82 / 92  is exposed. Then the first insulation layer  208  is formed with a proper thickness. Before or after constructing the write coil  206  the first pedestal  202  and a second pedestal can be formed on the first pole piece layer  92  after etching away a portion of the first insulation layer  208  so that magnetic connections can be made. The second CMP may be employed after depositing a thick alumina layer on top of the write coil  206  until the top of the coil layer  206  is exposed. Then the insulation layer  222  can be formed. A front portion of this insulation layer may then be etched away and the write gap layer  228  of a predetermined thickness may be formed on top of the pedestal  202 . After constructing the second write coil layer  220  another thick alumina layer may be deposited and CMP until the fifth insulation layer  226  is flat without exposing the top surface of the second pole tip  214  and the top portion of the write coil  220 . A portion of the insulation layer  226  is then etched away from the stitch region  224  of the second pole tip and the second pole piece yoke  216  is formed. The CMP operations planarize the head which enables the yoke  216  to be more planar and better able to conduct flux to the second pole tip  214 . 
     Method of Fabricating First Embodiment 
     FIGS. 9-14 illustrate various steps in the construction of the write head  200  shown in FIG.  14 . After constructing the first write coil  206  a thick layer of alumina is deposited on the wafer  201  and the wafer is CMP until the top surfaces of the write coil layer  206 , the pedestal  202  and the alumina layer  212  are planar. The insulation layer  222  covers the top surface of the write coil layer  206  and the photoresist layer  224  is formed between the turns of the write coil  220  as shown in FIG.  9 . 
     In FIG. 10 oxygen-based reactive ion etching (O 2  RIE) may be employed for removing a top portion of the resist layer  224  below a top of the write coil  220 . In FIG. 11, a thick layer of alumina  240  is deposited over the wafer with a thickness greater than the thickness of the write coil layer  220  and a thickness of the second pole tip  214  filling in a remainder of the turns of the write coil  220 . In FIG. 12 CMP is employed for polishing the alumina layer  240  in FIG. 11 until the insulation layer  226  is formed flat a distance above the top of the second pole tip  214  and optionally above the top of the write coil  220 . Important in this step is that the CMP be terminated before it touches the top surface of the second pole tip  214  so that a portion of the insulation layer  226  remains thereon. In FIG. 13 an insulation layer  227  may be deposited and the insulation layers  226  and  227  are etched to expose the stitch region  234  of the second pole tip. In FIG. 14 the second pole piece yoke  216  is magnetically connected to the second pole tip at the stitch region  234  and is extended over the insulation layer  226  above the write coil  220 . An overcoat layer  242  may be subsequently formed. 
     It should be noted that the insulation layer  226  protects the pole tip region  232  when a seed layer for the yoke  216  is removed by etching and studs are formed for terminals for the read and write head portions of the head. FIG. 14A is an ABS illustration of the magnetic head shown in FIG.  14 . 
     Second Embodiment of the Invention 
     FIGS. 15,  16  and  17  illustrate a second embodiment of the present head  300 , as shown in FIG. 17, and its method of making. The write head  300  is similar to the write head in FIGS. 14 and 14A and shows the aforementioned second pedestal  302  of the first pole piece and the back gap pedestal  304  of the second pole piece. It can be seen that these two pedestals are magnetically connected at the back gap and that the yoke  216  is magnetically connected to the pedestal  304 . A first difference in the write head  300  is that an insulation layer  306 , such as baked photoresist, is formed on top of the insulation layer  212  and extends into the stitch region  234  of the second pole tip. The insulation layer  222  in FIG. 14 may now be omitted. More importantly, however, is that the insulation layer  306  provides a profile which elevates the stitch region of the second pole tip into a pedestal which is shown at  234  upon the plating of the second pole tip  214 . The write gap layer  228  is located between the P1 pedestal and the second pole tip  214  and may extend over the insulation layer  306  if desired. 
     Important steps in fabrication of the head  300 , shown in FIG. 17, are shown in FIGS. 15 and 16. In FIG. 15 a thick layer of alumina  308  is deposited over the entire wafer. In FIG. 16 the alumina layer is CMP until a top surface of the pedestal  234  (stitch region) and the top surfaces of the write coil layer  220  are exposed with these surfaces and a top surface of an alumina layer  310  being planar, as shown in FIG.  16 . However, the CMP is terminated before a remaining layer portion  310  of the alumina is removed from the write portion  232  of the second pole tip. It should be noted in this embodiment that the alumina layer fills in between the coils of the write coil  220  and that the baked photoresist layer  224  in FIG. 14 is omitted. In FIG. 17 the yoke  216  is formed magnetically connected to the exposed pedestal  234  of the second pole tip and magnetically connected to the back gap pedestal  304 . Before depositing the yoke  216  a baked photoresist layer  312  (I5) may be formed on top of the write coil  220  for insulating it from the yoke  216 . Again, it should be noted that the insulation layer portion  310  at the write portion  232  has protected the height of the second pole tip from the yoke seed layer removal and subsequent construction of studs (not shown) to terminals of the read and write head portions of the head  300 . It should be understood that the pedestal  234  may be constructed in other ways than as shown in FIGS. 15-17, such as by etching the write portion  232  to a desired depth or performing two plating steps wherein the pedestal  234  is plated separately from a main body of the second pole tip therebelow. After completion of the P2 yoke  216  an overcoat layer  314  may be formed. 
     Still another embodiment  400  of the present invention is illustrated in FIG. 18 which employs a single write coil layer  402 . The write coil layer  402  is located within an insulation stack  404  which includes a first insulation layer  406 , a baked photoresist layer  408  between the turns of the coil and a third insulation layer  410  on top of the coil layer which may be constructed by first depositing a thick layer of alumina and then CMP. This last step may be employed for leaving a small amount of insulation  412  over a write portion  414  of the second pole tip  416 . This also planarizes the head and also maintains the yoke  418  flat as it extends across the head and it is extended to a stitch region  420  of the second pole tip. 
     The head  400  may include an insulation layer  422  which is inset within the first pole piece (P1)  92  at a location recessed from the ABS and between the ABS and a commencement of the write coil layer  402 . The front end of the insulation layer  422  defines a location of the zero throat height (ZTH) of the magnetic head where the first and second pole pieces first commence to separate after the ABS. This minimizes flux leakage between the first and second pole pieces. 
     FIG. 19 illustrates still another head  500  of the present invention which is the same as the head  400  in FIG. 18 except a second pole tip  502  has a pedestal  504  and a zero throat height (ZTH) defining insulation layer  506 . The ZTH defining insulation layer  506  is recessed from the ABS and is located entirely between the ABS and the commencement of the write coil layer  402 . The front portion of the layer  506  defines the ZTH as described hereinabove. However, the ZTH insulation layer  506  also provides a profile which forms the pedestal  504  at the stitch region of the second pole tip when the second pole tip is formed by plating. Accordingly, the ZTH insulation layer  506  performs a double function in the embodiment shown in FIG.  19 . 
     Discussion 
     Exemplary materials for the various components of the aforementioned heads may be nickel iron (Ni 89 Fe 21 ) for the layers of the first and second pole pieces, copper (Cu) for the write coil layers, alumina (Al 2 O 3 ) or silicon dioxide (SiO 2 ) for the write gap layer and the insulation layers that are CMP and copper or nickel iron for the various seed layers. In a broad concept of the invention it should be understood that the write portion of the second pole tip at the ABS is simply protected by an insulation layer from subsequent processing steps regardless of the remainder of the configuration of the head. 
     Clearly, other embodiments and modifications of this invention will occur readily to those of ordinary skill in the art in view of these teachings. Therefore, this invention is to be limited only by the following claims, which include all such embodiments and modifications when viewed in conjunction with the above specification and accompanying drawings.