Abstract:
A method of making a magnetic head that has a read head with a track width includes the steps of depositing a read track width defining material layer on a read sensor material layer; forming a bi-layer photoresist mask on the read track width defining material layer that masks a read track width defining layer portion of the read track width defining material layer; removing by reactive ion etching (RIE) a portion of the read track width defining material layer not masked by the photoresist mask to form the read track width defining layer portion with exposed first and second side edges that are spaced apart a distance equal to the track width; removing by ion milling a first portion of the read sensor material layer not masked by the read track width defining layer portion to form a second portion of the read sensor material layer with exposed first and second side edges that have a width equal to the track width; depositing hard bias and lead material layers on the photoresist mask in contact with the first and second side edges of each of the second portion of the read sensor material layer and the read track width defining layer portion; and removing the photoresist mask, thereby lifting off a portion of the hard bias and lead material layers leaving first and second hard bias and lead layers connected to the first and second side edges of each of the second portion of the read sensor material layer and the read track width defining layer portion.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a read head that has a read track width defining layer that planarizes the write gap layer of a write head and, more particularly, to a read head and method of making wherein a read track width defining layer is located between the read sensor of the read head and the write gap layer of the write head and has a thickness which substantially planarizes the read head at the level of first and second hard bias and lead layers which, by replication of subsequent layers, planarizes the write gap layer. 
     2. Description of the Related Art 
     The heart of a computer is an assembly that is referred to as a magnetic disk drive. The disk drive includes a rotating magnetic disk, write and read heads that are suspended by a suspension arm above the rotating disk and an actuator that swings the suspension arm to place the read and write heads over selected circular tracks on the rotating disk. The read and write heads are directly mounted on a slider that has an air bearing surface (ABS). 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 the ABS to cause the slider to ride on an air bearing a slight distance from the surface of the rotating disk. The write and read heads are employed for writing magnetic impressions to and reading magnetic impressions 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. 
     The write head includes a coil layer embedded in first, second and third insulation layers (insulation stack), the insulation stack being sandwiched between first and second pole piece layers. A write gap layer between the first and second pole piece layers forms a magnetic gap at an air bearing surface (ABS) of the write head. The pole piece layers are connected at a back gap. Current conducted to the coil layer induces a magnetic field across the magnetic gap between the pole pieces. This field fringes across the magnetic gap for the purpose of writing information in tracks on moving media, such as the circular tracks on the aforementioned rotating disk, or a linearly moving magnetic tape in a tape drive. 
     The read head includes first and second shield layers, first and second gap layers, a read sensor and first and second lead layers that are connected to the read sensor for conducting a sense current through the read sensor. The first and second gap layers are located between the first and second shield layers and the read sensor and the first and second lead layers are located between the first and second gap layers. The distance between the first and second shield layers determines the linear read density of the read head. The read sensor has first and second side edges that define a track width of the read head. The product of the linear density and the track density equals the areal density of the read head which is the bit reading capability of the read head per square inch of the magnetic media. 
     Rows and columns of combined read and write heads are made on a wafer substrate located in various chambers where layers are deposited and then defined by subtractive processes. A plurality of substrate wafers may be located on a turntable which rotates within the chamber and which may function as an anode. One or more targets, which comprise materials that are to be deposited on the wafer substrates, may also be located in the chamber. The target functions as a cathode and a DC or RF bias may be applied to the cathode and/or the anode. The chamber contains a gas, typically argon (Ar), which is under a predetermined pressure. Material is then sputtered from a target onto the wafer substrates forming a layer of the desired material. Layers may also be deposited by ion beam deposition wherein an ion beam gun directs ionized atoms (ions) onto a target which causes the target to sputter material on the wafer substrate. A subtractive process may employ a gas in the chamber, such as argon (Ar), under pressure which causes sputtering of the material from portions of the wafer substrate not covered by a mask. Alternatively, the subtractive process may employ an ion beam gun that discharges high velocity ions, such as argon (Ar) ions, which impact and remove portions of the wafer substrate that are not covered by a mask. 
     First and second hard bias and lead layers are typically joined at first and second side edges of the read sensor in what is known in the art as a contiguous junction. A first step in making this junction is forming a read sensor material layer over the entire wafer. Then, for each magnetic head a bilayer photoresist is formed over the desired read sensor site with a top layer portion that has first and second side edges for defining the first and second side edges of the read sensor and a bottom layer portion directly on the read sensor material layer that is recessed from the top layer portion so as to provide undercuts for the purpose of lifting off subsequently deposited unwanted layer portions. The wafer is then rotated by the turntable and a subtractive process, such as ion milling, is employed for removing all of the read sensor material layer except the read sensor under the bilayer photoresist. Unfortunately, the read sensors on the outside of the wafer are subjected to a different ion milling angle than wafers on the inside of the wafer, resulting in magnetic heads which have different characteristics. A first side edge of the read sensors on the outside of the wafer is notched while a second side edge is not notched. This is due to the fact that the turntable is rotated about an axis that is at an angle to the milling direction for the purpose of minimizing redeposition of the milled material. While the bilayer photoresist is still in place a hard bias and lead layer material is deposited on the entire wafer substrate. The bilayer photoresist is then removed lifting off the bias and lead layer material deposited thereon. The result is that a first hard bias and lead layer makes good abutting engagement with the first side edge of the read sensor, however, the second hard bias and lead layer may make only partial abutting engagement with the notched second side edge of the read sensor. This occurs because the angle of deposition of the hard bias and lead layer material is different than the angle of ion milling of the second side of the read sensor. The result is that the hard bias material adjacent the notched side edge may not make sufficient abutting contact for magnetically stabilizing the magnetic domains of the read sensor. This would degrade the performance of the read head. 
     Another problem is that the undercut of the bilayer photoresist permits ion milling to mill, to some extent, under the undercut. This results in an unpredictable track width of the read sensor. 
     A further problem noted with the above process is that upon deposition of the hard bias and lead layer material there is some overlap of the hard bias and/or lead layer material on a top surface portion of the read sensor adjacent each of the first and second side edges. This can cause an exchange coupling between the hard bias material and the read sensor which adversely affects the magnetics of the read sensor and may alter the expected track width of the read sensor. 
     Still another problem with the above process is that the first and second hard bias and lead layers have a higher profile than the read sensor. When the second gap, the second shield/first pole piece layer and the write gap layer of the write head are deposited there is a dip in the gap layer. This dip is known in the art as write gap curvature and can significantly degrade the performance of the write head. With a curved write gap the write head writes curved magnetic impressions into a rotating disk which are then read by a linearly extending read sensor. The read sensor will only read the center portion of the curved impression which reduces read signal performance. 
     SUMMARY OF THE INVENTION 
     The present invention provides a read and write head combination wherein the read head is planarized so as to overcome write gap curvature. A method of making is also provided where a read track width defining layer is employed for defining the track width of the read sensor with improved side edges. In a preferred embodiment the read track width defining layer remains in the head for planarizing the read head and overcoming the write gap curvature problem. 
     In the method a read track width defining material layer is formed on a read sensor material layer. The bilayer photoresist mask is then formed for masking the aforementioned read track width defining layer. A first selective removing process is then employed for removing the read track width defining material layer, except for the read track width defining layer that is masked by the photoresist mask. The first selective removing forms the read track width defining layer with exposed first and second side edges. Then a second selective removing process is employed for removing the read sensor material layer, except for a read sensor layer portion masked by the read track width defining layer. The second selective removing process forms a read sensor layer with exposed first and second side edges. Then, hard bias and lead material layers are deposited on the photoresist mask adjacent the first and second side edges of each of the read sensor layer and the read track width defining layer. Finally, the photoresist mask is removed thereby lifting off a portion of the hard bias and lead material layer leaving first and second hard bias and lead layers connected to the first and second side edges of each of the read sensor layer and the read track width defining layer. 
     In a preferred embodiment the track width defining layer is carbon. When the read track width defining layer is carbon the first selective removing is preferably a reactive ion etch with an oxygen (O 2 ) base. Other materials for the read track width defining layer may be silicon (Si) or silicon dioxide (SiO 2 ). When the read track width defining layer is silicon (Si) or silicon dioxide (SiO 2 ) the first selective removing process may be a reactive ion etch with a freon (CF 4 ) base. In the preferred embodiment the read track width defining layer has a thickness which is the difference between the thickness of the hard bias and lead layer and the thickness of the read sensor. With this arrangement the read track width defining layer planarizes the read head at the hard bias and lead layer level so that subsequent layers formed on the read sensor and the first and second hard bias and lead layers do not replicate a curvature to the write gap of the write head. If desired, however, the read track width defining layer may be removed by ashing in the presence of oxygen (O 2 ) within a chamber. 
     An object of the present invention is to provide a combined read and write head wherein the read head is planarized so as to obviate write gap curvature of the write head. 
     Another object of the present invention is to provide a read head wherein contiguous junctions are made between first and second hard bias and lead layers and first and second side edges of a read sensor respectively wherein the first and second hard bias and lead layers do not overlap first and second surface portions adjacent the first and second side edges of the read sensor. 
     A further object of the present invention is to provide a read and write head wherein each of first and second hard bias and lead layers make a continuous abutting junction with precisely located first and second side edges of the read sensor. 
     Still another object is to provide a method of making a read and write magnetic head wherein a bilayer photoresist mask is employed for defining a read track width defining layer which, in turn, is employed for defining the read track width of a read sensor. 
     Still a further object is to provide a method of making a read and write magnetic head which substantially eliminates any portion of first and second hard bias and lead layers covering a top surface of the read sensor, implements complete abutting engagement of the first and second hard bias and lead layers with first and second side edges of the read sensor and planarizes the read head so that no curvature is replicated to the write gap layer of the write head. 
     Other objects and advantages of the present invention will become apparent upon reading the following description taken together with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a planar view of an exemplary magnetic disk drive; 
     FIG. 2 is an end view of a slider with a magnetic head of the disk drive as seen in plane  2 — 2 ; 
     FIG. 3 is an elevation view of the magnetic disk drive wherein multiple disks and magnetic heads are employed; 
     FIG. 4 is an isometric illustration of an exemplary 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 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 prior art magnetic head; 
     FIG. 8 is a view taken along plane  8 — 8  of FIG. 6 with the insulation stack removed; 
     FIGS. 9 and 9B are block diagrams of various methods of depositing and milling layers within a chamber; 
     FIG. 10 is a side elevation view of a bilayer photoresist on a read sensor material layer; 
     FIG. 11 is the same as FIG. 10 except ion milling has been implemented for removing the read sensor material layer except a read sensor under the bilayer photoresist; 
     FIG. 12 is the same as FIG. 11 except first and second hard bias and lead layers have been formed, 
     FIG. 13 is the same as FIG. 12 except a second gap layer, a second shield/first pole piece layer, a write gap layer, a second pole tip layer and an overcoat layer have been formed on the read sensor and the first and second hard bias and lead layers; 
     FIG. 14 is a side elevation view of a first step in the present method of making a read head; 
     FIG. 15 is the same as FIG. 14 except a read track width defining material layer of carbon has been formed on the read sensor material layer; 
     FIG. 16 is the same as FIG. 15 except a bilayer photoresist has been formed on the track width defining material layer; 
     FIG. 17 is the same as FIG. 16 except reactive ion etching (RIE) has been implemented to remove all of the track width defining material layer except a track width defining material layer portion (track width defining layer) below the bilayer photoresist; 
     FIG. 18 is the same as FIG. 17 except ion milling has been employed for removing the read sensor material layer except for a read sensor layer directly below the track width defining layer; 
     FIG. 19 is the same as FIG. 18 except first and second hard bias and lead layers have been formed; 
     FIG. 20 is the same as FIG. 19 except the bilayer photoresist has been removed; 
     FIG. 21 is the same as FIG. 20 except the write head and additional layers of the read head are shown; 
     FIG. 22 is a side view of the first and second hard bias lead layers connected to the first and second side edges of the read sensor layer which is the same as that shown in FIG. 20; 
     FIG. 23 is the same as FIG. 22 except the track width defining layer has been removed; 
     FIG. 24 is the same as FIG. 23 except the second gap layer, the second shield/first pole piece layer, the write gap layer, the second pole tip layer and an overcoat layer have been formed; 
     FIG. 25 is the same as FIG. 17 except silicon (Si) or silicon dioxide (SiO 2 ) is employed for the track width defining layer and RIE is employed with a fluorine base as a removal process, and; 
     FIG. 26 is the same as FIG. 25 except ion milling is employed for defining the first and second side edges of the read sensor layer. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring now to the drawings wherein like reference numerals designate like or similar parts throughout the several views there is illustrated in FIGS. 1-3 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 motor  36  that is controlled by a motor controller  38 . A combined read and write magnetic head  40  is mounted on a slider  42  that is supported by a suspension  44  and actuator arm  46 . 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  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 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 motor drive signals for rotating the magnetic disk  34 , and provides control signals for moving the slider to various tracks. In FIG. 4 the slider  42  is shown mounted to the suspension  44 . The components described hereinabove may be mounted on a frame  54  of a housing  55 , 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. 
     Merged Magnetic Head 
     FIG. 6 is a side cross-sectional elevation view of the merged MR or spin valve head  40  which has a write head portion  70  and a read head portion  72 , the read head portion employing an MR or spin valve sensor  74 . FIG. 7 is an ABS view of FIG.  6 . The sensor  74  is located between first and second gap layers  76  and  78  and the gap layers are located between 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 of the merged head includes a coil layer  84  located 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 located 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. As shown in FIGS. 2 and 4, first and second connections  104  and  106  connect leads from the sensor  74  to leads  112  and  114  on the suspension  44  and third and fourth connections  116  and  118  connect leads  120  and  122  from the coil  84  (see FIG. 8) to leads  124  and  126  on the suspension. It should be noted that the merged head  50  employs a single layer  82 / 92  to serve a double function as a second shield layer for the read head and as a first pole piece for the write head. A piggyback head employs two separate layers for these functions. 
     After placing a wafer substrate in a chamber  150 , as shown in FIG. 9, various deposition processes  152  and various subtractive processes  154  may be employed in implementing the present invention. Deposition processes may include sputter deposition  156 , magnetron sputter deposition  158  or ion beam sputter deposition  160 . The subtractive processes  154  may include sputter etching  162 , reactive ion etching (RIE)  164 , ion beam milling  166  or reactive ion beam milling  168 . The sputter deposition  156  may include providing argon (Ar) gas and a target of material to be deposited in the chamber  170 , providing radio frequency (rf) or direct current (dc) bias between the target and the wafer substrate  172  and sputtering the target to deposit material from the target on the wafer substrate  174 . The magnetron sputter deposition  158  may include providing a target of material to be deposited in the chamber between a magnetron and the wafer substrate  176  and then sputtering the target in the field of the magnetron to deposit material from the target on the wafer substrate  178 . The ion beam sputter deposition  160  may include providing an inert gas, such as argon (Ar), krypton (Kr) or xenon (Xe), and a target of the material to be deposited in the chamber  180  and then ion beaming the target to sputter deposit the material from the target on the wafer substrate  182 . The sputter etching  162  may include providing argon (Ar) gas in the chamber  184 , applying rf or dc bias to the wafer substrate  186  and then sputter etching the wafer substrate  188 . The reactive ion etching  164  includes placing argon (Ar) and reactive gases in the chamber  189 , applying a dc or rf bias to the wafer substrate  190  and then reactive ion etching the wafer substrate  192 . The ion beam milling  166  includes grounding the wafer substrate  193  and then ion beam milling the wafer substrate  194 . The reactive ion beam milling  168  may include placing an inert gas, such as argon (Ar) or helium (He), and reactive gases in an ion beam gun  196 , grounding the wafer substrate  197  and then reactive ion beaming to mill the wafer substrate  198 . The chambers are placed under various preselected pressures in order to implement the aforementioned processes. Full film deposition is made without a mask, however, when features are to be formed a mask is provided with openings where the features are to be formed. A mask is also employed for covering areas to be retained when the subtractive processes  154  are employed. 
     FIGS. 10-13 illustrate a prior art process for making contiguous junctions between first and second hard bias and lead layers and first and second side edges of a read sensor, respectively. In FIG. 10 a read sensor material layer  220  may be formed on a nonconductive electrically insulative first gap layer (G 1 )  222  by depositions  156 ,  158  or  160  in FIG. 9A. A bilayer photoresist  224  is then formed on the read sensor material layer  220  that has first and second layer portions  226  and  228 . The first layer portion  226  has a width that is less than the second layer portion  228  so as to provide the bilayer photoresist with first and second undercuts. This bilayer photoresist may be formed by forming the first and second layer portions  226  and  228 , light exposing the second layer portion and developing the second layer  228  with a developer that also etches the first layer  226 . The second layer portion  228  has first and second side edges  230  and  232  that define a desired track width of a subsequently formed read sensor. 
     In FIG. 11 the wafer substrate is subjected to ion beam milling ( 166  in FIG. 9B) as the wafer substrate is rotated, which removes all of the read sensor material layer except for the read sensor  232  between the first and second side edges  234  and  236 . When a head is located near the outer perimeter of the wafer substrate the side edges  234  and  236  are significantly asymmetrical. This is because of an angle of incidence θ with respect to a normal to the read sensor surface and the divergence of the beam from a source above the center of the wafer substrate. The result is that the second side edge  234  is milled with a large taper while the first side edge  236  is fairly well defined with a small taper. The problem is not as bad for heads near the center of the wafer. In FIG. 12 first and second hard bias and lead layers  238  and  240  are formed by depositions  156 ,  158  or  160  in FIG. 9A wherein each hard bias and lead layer has a side edge that is formed adjacent a respective side edge of the read sensor. Unfortunately, however, the full thickness of the second hard bias and lead layer  238  does not make complete abutting contact with the second side edge  234  of the read sensor due to a notching or depression of each of the hard bias (H.B.) and lead layers  238  as shown. This is also due to the angle of incidence θ and the divergence of the beam, and is worst for heads near the outer perimeter of the wafer substrate. This reduced abutting contact can seriously degrade the magnetostatic coupling between the hard bias layer and the read sensor which can, in turn, affect the magnetic stabilization of the magnetic domains of the read sensor and render the read head inoperative. 
     In FIG. 13 the photoresist has been removed and a second gap layer  242 , a second shield/first pole piece layer  244 , a write gap layer  246 , a second pole tip layer  248  and an overcoat layer  250  have been formed by any of the depositions  156 ,  158  or  160  in FIG.  9 A. Because of the higher profile of the hard bias and lead layers  238  and  240  relative to the read sensor  232  the second gap layer  242 , the second shield/first pole piece layer  244  and the write gap layer  246  make a dip which results in write gap curvature of the write gap layer  246 . This is not desirable since the read head reads curved magnetic impressions in a rotating magnetic disk which degrades read signal performance. It should also be noted that the first and second hard bias and lead layers overlap first and second surface portions of the read sensor adjacent the first and second side edges  234  and  236 . If the hard bias layer overlaps these portions this results in an exchange coupling which can degrade the magnetic performance of the read sensor layer. The overlap can also change the track width of the read sensor. Still another problem is that the side edges  234  and  236  of the read sensor are not directly under the side edges  230  and  232  of the second layer of the bilayer photoresist. This results in a read sensor with an unreliable track width. 
     The Invention 
     FIGS. 14-21 illustrate various steps of the present method of making the read head. In FIG. 14 a ferromagnetic first shield layer (S 1 )  300  is formed on the wafer substrate (not shown), a nonmagnetic electrically insulative first gap layer (G 1 )  302  is formed on the first shield layer and a read sensor material layer  304  is formed on the first gap layer  302  by any of the depositions  156 ,  158  or  160  in FIG.  9 A. The read sensor material layer  304  may comprise multiple layers such as an antiferromagnetic pinning layer, a ferromagnetic pinned layer, an electrically conductive spacer layer, a ferromagnetic free layer and a capping layer, which layers constitute a spin valve sensor. The ferromagnetic pinned layer may be an antiparallel (AP) pinned layer as described in U. S. Pat. No. 5,018,037, which is incorporated by reference herein, or a pinned layer consisting of a single thin film. The layers can differ depending upon different types of spin valve sensors or anisotropic magnetoresistive (AMR) sensors employed. In FIG. 15 a track width defining material layer  306  of carbon is formed on the read sensor material layer  304 . The track width defining material layer has a predetermined thickness which will be described in more detail hereinbelow. 
     In FIG. 16 a bilayer photoresist  308  is formed on the track width defining material layer  306  which is the same as the bilayer photoresist  224  shown in FIG.  10 . In FIG. 17 a reactive ion etch (RIE) with an oxygen (O 2 ) base, as shown in  164  of FIG. 9B, is employed in a chamber (not shown) for removing all of the track width defining material layer except for a track width defining layer  310  below the bilayer photoresist  308 . The chamber may contain 20% oxygen (O 2 ) and 80% argon (Ar) with a pressure of 5 millitorr. An rf bias of 150 watts may be applied to the wafer substrate. We have found that the first and second side edges  312  and  314  of the track width defining layer portion  310  are substantially aligned with first and second side edges  316  and  318  of the bilayer photoresist. This is because the RIE process is selective by a ratio of 4 to 1 to the track width defining material layer over the materials of the read sensor material layer  304  and the bilayer photoresist  308 . Accordingly, the read track width defining material layer is quickly removed, except the read track width defining layer  310 , without any substantial removal of the read sensor material layer  304  or the bilayer photoresist  308 . 
     In FIG. 18 ion beam milling, as shown in  166  of FIG. 9B, is employed for removing all of the read sensor material layer except for a read sensor layer  320  directly below the read track width defining layer  310 . This milling is selective by a ratio of 4 to 1 to the read sensor material layer  304  (FIG. 17) over the carbon of the read track width defining layer  310 . It should be noted from FIG. 17 that the first and second side edges  312  and  314  of the read track width defining layer are immediately adjacent the read sensor material layer  304  so that first and second side edges  322  and  324  of the read sensor in FIG. 18 are accurately located and defined with less asymmetry between the two edges  322  and  324  for heads located nearest the outer perimeter of the wafer substrate. In FIG. 19 first and second hard bias and lead layers  326  and  328  are formed which have side edges that make complete abutting engagement with respective side edges  322  and  324  of the read sensor and the first and second side edges  312  and  314  of the read track width defining layer. In FIG. 20 the bilayer photoresist  308  is removed leaving top surfaces  330  and  332  of the first and second hard bias and lead layers substantially planar with the top surface  334  of the read sensor. 
     In order to accomplish this the thickness of the read track width defining layer portion  310  should be substantially the difference between the thickness of the hard bias and lead layers  330  and  332  and the thickness of the read sensor  320 . This thickness is preferably 100-500Å and, more preferably, is about 200Å thick. The thickness of either the first and second hard bias and lead layers  330  and  332  is typically thicker than the thickness of the read sensor  320  so that when the thickness of the read sensor  320  is subtracted from the thickness of one of the hard bias and lead layers the result will be the desired thickness of the read track width defining layer  310 . It should be noted that each of the first and second hard bias and lead layers have a slight rise or “bird&#39;s beak”  336  and  338 . It has been found that this height is less than 100Å, and does not affect the planarity of the read head. In FIG. 21 the complete read head is shown with a nonmagnetic electrically insulative second gap layer (G 2 )  340  on the read sensor  310  and the first and second hard bias and lead layers  326  and  328 , a second shield/first pole piece (S 2 /P 1 ) layer  342  on the second gap layer  340 , a write gap layer  344  on the second shield/first pole piece layer  342 , a second pole tip layer  346  on the write gap layer  344  and an overcoat layer  348  on the second pole tip layer  346  by any of the depositions  156 ,  158  or  160  in FIG.  9 A. 
     It can be seen that with this method of construction there is substantially no write gap curvature of the write gap layer  344  since the read head is planarized at the first and second hard bias and lead layer level by the read track width defining layer  310 . Further, it should be noted that the first and second hard bias and lead layers  326  and  328  do not overlap any portion of the top surface  334  of the read sensor adjacent its first and second side edges  312  and  314 . Accordingly, the magnetic properties of the read sensor  310  are preserved as well as the desired track width. 
     FIGS. 22-24 illustrate various steps in an alternate construction of the present read head. FIG. 22 is the same as FIG.  20 . If desired, the read track width defining layer portion  310  in FIG. 22 may be removed in FIG. 23 by any suitable process such as ashing which is implemented by the presence of oxygen (O 2 ) in a chamber. This removal may be desirable if it is undesirable to have the carbon material at the ABS or if the carbon has a substantially different coefficient of expansion than other layers in the head which may stress the read sensor or protrude other layers at the ABS under high heat conditions. After forming the second gap layer (G 2 )  350 , the second shield/first pole piece layer (S 2 /P 1 )  352  and the write gap layer  354  it can be seen that the write gap layer  354  has curvature under the second pole tip layer  356 . Accordingly, the preferred embodiment is the method shown in FIGS. 14-20 and the embodiment shown in FIG. 21 since write gap curvature has been eliminated. However, the embodiment shown in FIGS. 22-24 has the advantage over the read head made by the process in FIGS. 10-13 since the read head in FIG. 24 does not have an overlap of the first and second hard bias and lead layers on top surface portions of the read sensor  320 . 
     FIGS. 25 and 26 illustrate alternate steps to the steps shown in FIGS. 17 and 18. In FIG. 25 a silicon (Si) or silicon dioxide (SiO 2 ) material is employed for the read track width defining layer portion  360  instead of carbon as shown in FIG.  17 . The chamber may contain 20% freon (CF 4 ) and 80% helium (He) under a pressure of 5 millitorr. An rf bias of 150 watts may be applied to the wafer substrate. In this instance all of the read track width defining material layer is removed by reactive ion etching (RIE) with a fluorine base, such as freon (CF 6 ), which is selective by a ratio of 5 to 1 to the silicon (Si) or silicon dioxide (SiO 2 ) with respect to the read sensor material layer  304  and the photoresist  308 . In FIG. 26 ion beam milling is employed for defining the first and second side edges  322  and  324  of the read sensor  320 . The rate of ion beam milling of the read sensor material layer with respect to the read track width defining layer  360  and the photoresist layer  308  is about 1/1. 
     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 following claims, which include all such embodiments and modifications when viewed in conjunction with the above specification and accompanying drawings.