Abstract:
A method makes a magnetic head at first, second, third, fourth and fifth regions on a substrate including forming a read sensor material layer in all regions, forming a first capping layer on the read sensor material layer in all regions, removing the first capping layer and the sensor material layer in all regions except the first, second and third regions wherein the first region is definable by a read sensor and the second and third regions abut opposite side edges of the first region, forming a low resistance material lead layer and a second capping layer in the fourth and fifth regions wherein the fourth and fifth regions abut the second and third regions respectively, selectively removing portions of the first capping layer in the second and third regions, selectively removing portions of the read sensor material layer in the second and third regions and portions of the second capping layer in the fourth and fifth regions and forming a high resistance material lead layer in the second, third, fourth and fifth regions.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a read sensor with self-aligned low resistance leads and a method of making wherein the method employs protective capping layers during milling steps for eliminating a masking step in the construction of low resistance lead layer portions of the lead structure. 
     2. Description of the Related Art 
     The heart of a computer is an assembly that is referred to as a magnetic disk drive. The magnetic 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. 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 read head includes a read sensor that is located between first and second gap layers and the first and second gap layers are located between first and second shield layers. The first and second gap layers magnetically insulate the read sensor from the shield layers and the shield layers protect the read sensor from stray magnetic fields. Accordingly, the read sensor is sensitive to flux signals from the rotating disk within the distance between the first and second shield layers. This distance defines the linear density capability of the read head. The smaller this distance the greater the linear density and the more information that can be read by the read head per track length. 
     The flux signals imposed on the read head change the resistance of the read sensor. By conducting a sense current through the read sensor the processing circuitry can detect a change in potential when the flux signal changes the resistance of the read sensor. In a digital scheme where ones and zeros convey information the flux signal can represent a one and the absence of a flux signal can represent a zero. Accordingly, incremental lengths of the track represent bits of information in the digital scheme. The greater the linear density, the greater the number of bits of information that can be read by the read head from the track on the rotating disk. 
     The read sensor can be an anisotropic magnetoresistive (AMR) sensor or a spin valve (SV) sensor. Either of these sensors is sensitive to flux incursions so that when the sense current is conducted through the sensor potential changes can be detected by the processing circuitry. The sense current is conducted through the read sensor by first and second leads that are connected at opposite ends of the read sensor. The first and second leads are located between the first and second gap layers which electrically insulate the leads from the shield layers. A portion of each of the leads is exposed at the aforementioned ABS where they are subjected to corrosion. An anticorrosion and mechanically stable material is selected for these lead portions, such as tantalum (Ta). Unfortunately, Ta is also highly resistive. These lead portions are referred to as the high resistance lead portions. At a recessed location in the head a low resistance lead portion is stitched (overlapping connection) to a respective high resistance portion. The stitching approach also reduces the topography of the lead structure at the ABS. The lead topology, normally replicated into the second shield (first pole piece), can degrade the performance of the write head because of write gap curvature. In the past the high resistance portions extend along the ABS after which they make a bend inwardly for connection to the low resistance portions. This bend has been necessary because of the alignment tolerances in the photomasking process. It would be desirable if the lengths of the high resistance portions could be reduced so as to reduce resistance of the lead structure and heat generated thereby. 
     The aforementioned lead structure is typically made with three photopatterning (masking) steps. Each photopatterning step involves spinning a layer of photoresist on a wafer where multiple heads are being constructed, light imaging the photoresist layer to prepare portions of the photoresist layer that are to be removed and then removing the photoresist portions with a developer. Milling, such as ion milling or etching is then employed to remove layer portions exposed by the open portions of the photoresist layer. 
     After applying a layer of read sensor material to the wafer a first mask may be employed for making the high resistance lead portions and defining the track width of the read sensor. Read sensor material exposed by the openings are milled away and high resistance material is deposited to form the high resistance lead portions. By this method side edges of a partially completed read sensor and the high resistance leads abut one another making them self-aligned with respect to one another. A second mask covers the high resistance lead portions and a read sensor site. Milling is then employed to remove a remainder of the read sensor material leaving only the read sensor and the high resistance lead portions connected thereto. A third mask then covers the read sensor and portions of the high resistance lead portions leaving each high resistance lead portion with a stitch region. Low resistance material is then deposited which forms low resistance lead portions that are stitched to the high resistance lead portions and which extend to terminals. It would be desirable if one of the masking steps could be eliminated without degrading the lead structure. 
     SUMMARY OF THE INVENTION 
     The present invention employs only two masking steps in the construction of the lead structure of the read head. The third masking step, which is employed for constructing the low resistance lead portions, is eliminated by the present invention. This is accomplished by employing protective capping layers that are deposited at various stages of the construction so that milling without a photoresist mask can be employed for constructing the low resistance lead portions. The capping layers are different materials and the dry etching is of different types so that preferential etching can be performed. Preferential etching means that during a selected etching step one or more of the capping layers is etched significantly slower than the other layers. The capping layers are preferably selected from the group C, Al 2 O 3  and SiO 2  and the etching is based from the group O 2 , Ar, fluorocarbon and chlorine containing gases. As an example, an O 2  based reactive etching will remove the C cap and leave a Ta cap essentially intact, an Ar based milling will remove the Ta cap and unwanted read sensor material, a fluorocarbon based etching will remove the Ta cap without essentially etching the C and Al 2 O 3  caps and the Ar based milling will remove the unwanted copper or gold without significantly etching the C and Al 2 O 3  caps. By appropriately locating these capping layers and selecting appropriately based etching a lead structure with low overall resistance can be produced with less photomasking steps. 
     The present method lends itself to constructing a lead structure that has a lower resistance than prior art lead structures. Each of the low resistance lead portions has a front edge that is coextensive with a back edge of the read sensor. Each of first and second high resistance lead portions has a side edge that is contiguous with a side edge of the read sensor (self-aligned) and has a recessed portion that overlaps a respective low resistance portion. Accordingly, the lengths of the high resistance portions is minimized. The widths of the high resistance portions at the ABS is greatly reduced. Instead of making a bend each high resistance portion extends straight back into the head and overlaps a respective low resistance lead portion. With this arrangement resistance is reduced and corrosion of the lead structure at the ABS is reduced. 
     An object of the present invention is to provide an improved method of making a lead structure of a read head. 
     Another object is to make a read sensor and first and second leads connected to the read sensor with only two masking steps. 
     A further object is to selectively employ various capping layers and chemically based dry etching for eliminating a masking step in the construction of a lead structure of a read head. 
     Still another object is to provide a method of making a read head that enables a reduction in the resistance of a lead structure and reduced corrosion of the lead structure at an air bearing surface. 
     Still a further object is to provide a lead structure that has a reduced resistance. 
     Other objects and advantages of the present 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 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 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 second pole piece removed; 
     FIG. 9 is a plan view of a read sensor (SV) and a first and second leads of a prior art structure; 
     FIG. 10 is a plan view of a read sensor (SV) and first and second leads of the present structure; 
     FIG. 11 is a plan view of a first insulative gap layer deposition step of a previous method; 
     FIG. 12 is a view taken along plane  12 — 12  of FIG. 11; 
     FIG. 13 is a cross-sectional view taken along plane  13 — 13  of FIG. 11; 
     FIG. 14 is a plan view of a wafer wherein a mask is employed for defining the track width of the MR sensor and for depositing hard bias and first lead layer films of first and second lead layers of a previous MR read head; 
     FIG. 15 is a view taken along plane  15 — 15  of FIG. 14; 
     FIG. 16 is a cross-sectional view taken along plane  16 — 16  of FIG. 14; 
     FIG. 17 is a plan view of a wafer wherein a mask is employed for defining the height of the previous MR sensor; 
     FIG. 18 is a cross-sectional view taken along plane  18 — 18  of FIG. 17; 
     FIG. 19 is a cross-sectional view taken along plane  19 — 19  of FIG. 17; 
     FIG. 20 is a plan view of a mask employed in a previous process for depositing a second lead layer film of each lead layer; 
     FIG. 21 is a cross-sectional view taken along plane  21 — 21  of FIG. 20; 
     FIG. 22 is a view taken along plane  22 — 22  of FIG. 20; 
     FIG. 23 is a plan view of the MR read head made by the previous process; 
     FIG. 24 is a cross-sectional view taken along plane  24 — 24  of FIG. 23; 
     FIG. 25 is a cross-sectional view taken along plane  25 — 25  of FIG. 23; 
     FIG. 26 is a cross-sectional view taken along plane  26 — 26  of FIG. 23; 
     FIG. 27 is a plan view of a portion of a wafer at a read head site where read sensor material (SV) and a first capping layer have been deposited on top of a first gap layer and a first shield layer; 
     FIG. 28 is the same as FIG. 27 except a first mask has been formed over a read sensor site; 
     FIG. 29 is the same as FIG. 28 except the first capping layer (C) and the read sensor (SV) layer exposed by the first mask have been etched away; 
     FIG. 30 is the same as FIG. 29 except an alumina layer (Al 2 O 3 ), second lead layer (Au) and a second capping layer (Ta) have been deposited; 
     FIG. 31 is the same as FIG. 30 except the first mask has been removed leaving read sensor material (SV) capped by the first capping layer (C) at a read sensor site; 
     FIG. 32 is the same as FIG. 31 except a second mask has been formed with spaced apart openings defining the track width of the read sensor, as well as locations for first and second leads; 
     FIG. 33 is the same as FIG. 32 except the first capping layer (C) has been etched; 
     FIG. 34 is the same as FIG. 33 except the read sensor material (SV) and second capping layer (Ta) have been removed at the first and second lead sites; 
     FIG. 35 is the same as FIG. 34 except a bias layer, a first lead material layer (Ta) and a third capping layer (Al 2 O 3 ) have been deposited; 
     FIG. 36 is the same as FIG. 35 except the second mask has been removed; 
     FIG. 37 is the same as FIG. 36 except the second capping layer (Ta) has been removed from field regions about the second mask; 
     FIG. 38 is the same as FIG. 37 except first lead layer material (Au) has been removed in the field regions about the second mask; 
     FIG. 39 is the same as FIG. 38 except the first capping layer (C) has been removed from the read sensor (SV); and 
     FIG. 40 is a block diagram showing steps for the completion of the magnetic head. 
    
    
     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 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 an 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 , 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 the merged MR head  40 , which has a write head portion  70  and a read head portion  72 , the read head portion employing a spin valve sensor  74  of the present invention. Optionally, the sensor may be an AMR sensor. 
     FIG. 7 is an ABS view of FIG.  6 . The spin valve sensor  74  is sandwiched between first and second gap layers  76  and  78  and the gap layers are sandwiched between first and second shield layers  80  and  82 . In response to external magnetic fields, the resistance of the spin valve 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 MR head 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. 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. A wear layer  128  may be employed for protecting the sensitive elements of the magnetic head, as shown in FIGS. 2,  4 ,  6  and  7 . 
     FIG. 9 illustrates a portion of a wafer  150  where a read sensor (SV)  152  and first and second leads  154  and  156  have been constructed. The first lead  154  includes a high resistance lead layer (LI)  158  and a low resistance lead layer (LII)  160 . The second lead  156  includes a high resistance lead layer (LI)  162  and a low resistance lead layer (LII)  164 . The high resistance lead layers  158  and  162  make contiguous junctions with the read sensor  152  at edges  166  and  168  and, after lapping, have exposed surfaces  170  and  172  at an air bearing surface (ABS). The high resistance lead layers  158  and  162  are preferably (Ta) which is corrosion resistant. Unfortunately, (Ta) has a high resistance. The high resistance leads  158  and  162  extend along the ABS and make a bend into the head where they are overlapped by the low resistance lead layers  160  and  164  at stitch regions  174  and  176  for making electrical connection therebetween. Because of these lengths significant resistance is added to the read head circuit which degrades the signal to noise ratio and unduly heats the head. It should be noted that if a high resistance lead is made thicker to reduce its resistance that this will increase the topology in the leads and the first pole piece as mentioned previously. 
     FIG. 10 illustrates a wafer portion  180  of the present invention where a read sensor  182  and first and second leads  184  and  186  have been constructed. The first lead  184  includes a high resistance lead layer (LI)  188  and a low resistance lead layer (LII)  190  and the second lead layer  186  includes a high resistance lead layer (LI)  192  and a low resistance lead layer (LII)  194 . The high resistance lead layers  188  and  192  do not make a bend into the head. Accordingly, there is less resistance in the read head circuit. The low resistance lead layers  190  and  194  have forward edges  195  and  196  that are coextensive with a back edge  197  which defines a stripe height of the read sensor  182 . The high resistance lead layer portions  188  and  192  extend straight back from the ABS without a bond and overlap the low resistance lead layer portions  190  and  194 . The exposed edges  198  and  199  of the high resistance lead layers is less than that in the prior art. 
     Exemplary Method of Making 
     FIGS. 11-26 illustrate an exemplary method of making the lead structure shown in FIG.  9  and FIGS. 27-40 illustrate the present method of making the lead structure shown in FIG.  10 . In both methods, ion beam deposition or sputter deposition is employed for depositing the metal and insulation layers. The masks are preferably bilayer photoresist layers wherein a bottom photoresist layer is recessed from a top photoresist layer so that a dissolvent can dissolve the bottom layer, thereby permitting the mask to be lifted from the wafer carrying with it the sputtered material deposited thereon. Stippled layers are insulation layers in FIGS. 11-26 and heavy lines show the outlines of the masks. Also, the masks are defined by light cross-hatching. L(I) represents a high resistance lead layer film for the first lead layer and L(II) represents a low resistance lead layer film for the first lead layer. While the lead layers L(I) and L(II) are described primarily in reference to a first lead, these layers apply equally as well to a second lead. S 1  and S 2  designate first and second shield layers and G 1  and G 2  designate first and second read gap layers. 
     FIG. 11 is a plan view of a portion  200  of a wafer where a magnetic spin valve (SV) read head is to be constructed along with other SV read heads (not shown) arranged in rows and columns (not shown) on the wafer. The wafer portion  200  shows an SV site  202 , first and second via sites  204  and  206 , and first and second lead layer sites  208  and  210  which electrically connect side edges of the SV sensor to the via sites. Each via site  204  and  206  is a vertically disposed (out of paper) electrical conductor connecting a lead to a respective terminal (see  104  and  106  in FIG.  2 ). As shown in FIG. 12, a first shield layer  212 , a first gap layer  214  and an SV material layer  216  have been formed while as shown in FIG. 13, the first shield layer  212 , the first insulative gap layer  214 , a first insulation layer  218  and the SV material layer  216  have been formed. In this process, a first mask (not shown) was employed for constructing the first insulation layer  218  on top of the first gap layer  214  behind the SV sensor site along line  222 . The purpose of the first insulation layer  218  is to provide extra insulation for the first and second lead layers that are to be constructed at the lead layer sites  208  and  210 . The extra insulation prevents shorting of the leads through pinholes in the first gap layer  214  to the first shield layer  212 . It should be noted that a front portion of each lead layer site below line  222  is left unprotected by the first insulation layer  218 . 
     In FIG. 14 a liftoff mask (Mask I)  224  is employed for covering the entire wafer portion except openings  226  and  228  at the first and second lead layer sites. As shown in FIGS. 15 and 16, the SV material layer  216  within the front lead layer sites  226  and  228  is milled away and hard bias and first lead layer films (shown as one film  230 ) are deposited on the first gap layer  214 . It should be noted that the film  230  is formed as a full film deposition in which a portion of the film  230  is deposited on top of the mask  224 . As stated hereinabove, the mask  224  is a bilayer photoresist mask (shown as one layer) with the bottom layer recessed from the top layer so that a dissolvent can dissolve the bottom. This allows the mask  224  to be removed from the wafer along with the film  230 , which is done in a subsequent step. It should be noted in FIGS. 14 and 16 that the SV sensor material  216  at the SV sensor site  202  has been formed with a side edge  232  which directly abuts an end  234  of the film  230  at the first lead layer site to form a contiguous junction therebetween. An opposite side edge  236  of the SV sensor also forms a contiguous junction with an end  238  of the film  230  at the second lead layer site  228 . 
     In FIGS. 17,  18  and  19 , the mask  224  in FIG. 19 has been removed and a second mask (Mask II)  240  has been formed covering only the SV sensor site  202  and slightly smaller portions of  226  and  228  of the first and second lead layer sites. As shown in FIGS. 18 and 19, the remainder of the SV material  216  is ion milled away so as to define the height of the MR sensor, which is shown at  242 . 
     In FIGS. 20,  21  and  22 , the second mask  240  of FIG. 17 has been removed and a third mask (Mask III)  244  has been formed over the entire wafer portion  200 , except rear portions  246  and  248  of the first and second lead layer sites. A second lead layer film  250  is deposited in the openings  246  and  248  so as to overlap and make connection with the underlying first lead layer films so that the lead layer films extend to the via sites  204  and  206 . In FIG. 26, a second insulation layer  256  is formed in the rear portion of the head outside of the SV sensor frame, a front boundary thereof being shown at  258  in FIG. 23. A fourth mask (not shown) is employed for forming the second insulation layer  256 . After removing the fourth mask a full film of a second insulative gap layer (G 2 )  260  is formed, as shown in FIGS. 23-26. 
     It should be noted that five separate masking steps are required to form the SV sensor  216 , the first and second lead layer films  230  and  250  and the first and second insulation layers  218  and  256 . Each masking step requires the wafer to be removed from the deposition chamber, thereby breaking vacuum and allowing the metallic layers  230  and  250  already deposited to become oxidized. This reduces adherence between the metal layers  230  and  250  and the insulation layers  214 ,  218  and  256  shown in FIGS. 24-26. While the sensor has been described as a spin valve (SV) sensor it could optionally be a magnetoresistive (MR) sensor. 
     Present Method of Making 
     FIGS. 27-40 illustrate the present method of making the read sensor and lead structure shown in FIG.  10 . This method employs only two masks thereby eliminating a third mask employed in the method described in FIGS. 11-26. The third mask is eliminated by employing first, second and third capping layers which are deposited during various stages of the construction of the read sensor and the lead structure and which protects desired components of the structures during milling steps which will be explained in detail hereinbelow. The perimeters of the masks will be shown by heavy lines and areas covered will be shown by light cross hatchings. 
     FIG. 27 illustrates a wafer portion  300  where a read sensor and first and second leads are to be constructed. After depositing a first shield layer (S 1 ) and a first gap layer (G 1 ) a spin valve (SV) material layer and a first capping layer (C) are formed on the wafer by any suitable means such as sputter deposition. The first capping layer (C) will be employed during subsequent steps to protect the spin valve sensor. The spin valve material includes multiple films (not shown), namely: a pinning layer, such as iron manganese (FeMn), a pinned layer, such as Permalloy (nickel iron) (NiFe), a spacer layer, such as copper (Cu), and a free layer, such as permalloy (NiFe) and a top protective layer such as tantalum (Ta). 
     In FIG. 28 a first photoresist mask (Mask I)  302  has been formed which covers a read sensor site, as well as extensions on both sides thereof. In FIG. 29 milling, such as ion milling, has been employed to remove the first capping material (C) and the spin valve material (SV) about the first mask  302  so that the first gap layer (G 1 ) is exposed. In FIG. 30 an alumina (Al 2 O 3 ) layer, a low resistance lead layer material, such as gold (Au), and a second capping layer such as tantalum (Ta) has been deposited on the wafer by any suitable means such as sputter deposition. In FIG. 31, the first mask has been removed exposing the spin valve (SV) material portion and the first capping layer (C). 
     In FIG. 32 a second mask (Mask II)  304  has been formed with first and second openings  306  and  308 . The openings  306  and  308  are elongated and expend perpendicular to an ABS site of the partially completed read head. The openings  306  and  308  have side edge portions  310  and  312  which will define a track width of the read sensor in subsequent steps. The first opening  306  exposes a high resistance lead material region  314  where a spin valve layer (SV) and a first capping layer (C) are located and a low resistance lead layer site  316  where an alumina (Al 2 O 3 ) layer, a low resistance lead layer (Au) and the second capping layer (Ta) are located. The second opening  308  has the same arrangement in a high resistance lead layer site  318  and a low resistance lead layer site  320 . The alumina (Al 2 O 3 ) layers in the low resistance lead layer sites  316  and  320  are optional, but preferred for the purpose of insulating the partially completed low resistance lead layer portions from the first gap (G 1 ). 
     In FIG. 33 oxygen reactive ion etching (RIE) or ion milling is employed for removing the first capping layer (C) in the high resistance lead layer sites  314  and  318 . In FIG. 34 spin valve sensor material (SV) is removed from the high resistance lead layer sites  314  and  318  and the second capping layer (Ta) is removed from the low resistance lead layer sites  316  and  320  by milling such as an (Ar) etch. This leaves the first gap layer (G 1 ) exposed in the high resistance lead layer sites  314  and  318  and the low resistance lead layer material (Au) exposed in the low resistance lead layer sites  316  and  320 . 
     In FIG. 35 a hard bias material layer, a high resistance material layer (Ta) and a third capping layer (Al 2 O 3 ) is formed on the wafer by any suitable means such as sputter deposition. In FIG. 36 the second mask is removed leaving a partially formed spin valve (SV) sensor and a first capping layer (C) at a spin valve site  322 , a hard bias layer, a second capping layer (Ta) and a third capping layer (Al 2 O 3 ) in the first and second high resistance lead layer sites  314  and  318 , a low resistance lead layer (Au), a hard bias layer, a second capping layer (Ta) and a third capping layer (Al 2 O 3 ) in the low resistance lead layer sites  316  and  320  and an alumina layer (Al 2 O 3 ), a low resistance material layer (Au) layer and a second capping layer (Ta) layer in field regions about the read sensor and lead structure sites. 
     In FIG. 37 a fluorocarbon gas reactive ion etching (RIE) or milling or argon (Ar) ion milling is employed for removing the second capping layer (Ta) in the field regions about the read sensor and first and second lead structure sites. In FIG. 38 milling, such as an argon (Ar) etch is employed for removing low resistance lead layer material (Au) in the field regions about the read sensor and first and second lead structure sites. This leaves only (Al 2 O 3 ) in the field regions with the first and second lead layers protected by the third capping layer (Al 2 O 3 ) and the read sensor (SV) protected by the first capping layer (C). 
     In FIG. 39 the first capping layer (C) is removed by oxygen RIE, such as an oxygen (O 2 ) etch. As shown in FIG. 40, the read head is then completed by forming the second gap layer (G 2 ) on the wafer followed by forming the second shield layer (S 2 ). Thereafter, the write head may be formed completing the merged head described hereinabove. It should be noted that the high resistance leads (LI) extend from the ABS and overlap the low resistance leads (LII). The high resistance leads LI make contiguous junctions with the side edges  310  and  312  of the spin valve (SV) sensor. With this construction, the resistance of the high resistance lead layers LI is minimized. 
     While FIGS. 27-39 set forth preferred materials and etching, it should be understood that other materials and milling may be substituted. The first, second and third capping layers may be selected from the group carbon (C), alumina (Al 2 O 3 ), silicon oxide (SiO 2 ), Ta and tungsten (W) and the etching may be ion milling or RIE based on the group oxygen (O 2 ), argon (Ar), fluorocarbons (FC), etching and chlorine containing gases. Suitable materials for the first, second and third caps, the read sensor, the high resistance lead and the low resistance lead as well as removal of these various materials by ion milling or RIE based upon various chemicals are set forth in the following chart. The milling (Ar miling) rate of various materials in Å/min are as follows: w=340, Ni=530, Mn=880, Ta=420, c=110, Al 2 O 3 =100, Au=1080 and Cu=880. 
     
       
         
               
               
               
               
               
               
             
               
               
               
               
               
               
             
           
               
                   
                   
               
               
                   
                 1st Cap 
                 2nd Cap 
                 3rd Cap 
                 Sensor 
                 Lead(L.R.) 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                 Material 
                 C 
                 Ta or W 
                 Al 2 O 3   
                 NiFe 
                 Au or Cu 
               
               
                 Removal 
                 O 2   
                 FC 
                   
                 Ar 
                 Ar 
               
               
                 Material 
                 SiO 2   
                 Al 2 O 3   
                 SiO 2   
                 NiFe 
                 Cu 
               
               
                 Removal 
                 FC 
                 BCl 3 Cl 2   
                   
                 Ar 
                 BCl 3 /Cl 2   
               
               
                 Material 
                 Al 2 O 3   
                 SiO 2   
                 Al 2 O 3   
                 NiFe 
                 Au or Cu 
               
               
                 Removal 
                 BCl 3 Cl 2   
                 FC 
                   
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     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.