Abstract:
Methods for improving within wafer and wafer to wafer yields during fabrication of notched trailing shield structures are disclosed. Ta/Rh CMP stop layers are deposited prior to planarization and notch formation to ensure a planar surface for trailing shield structures. These stop layers may be blanket deposited or patterened prior to CMP. Patterned stop layers produce the highest yields.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    This invention relates to structures and methods for fabricating perpendicular write heads. More specifically, the invention relates to improved methods for fabricating notched trailing shields using metallic CMP stop layers to improve yields within wafer and wafer to wafer. 
         [0003]    2. Description of the Related Art 
         [0004]    Perpendicular write heads are currently well known in the art. A particular variant of such heads, known as the perpendicular write head with a notched trailing shield, has also been recently disclosed. See, for example US Patent Application Publications 2005/0264931, 2006/0023352, 2005/0190491, and 2005/0068671, all assigned to Hitachi Global Storage Technologies, Netherlands B.V. During the fabrication of the notched trailing shield, the tapered write pole is produced by ion milling, and the area around and above the tapered pole is filled with alumina. The alumina deposition leaves a “bump” or high spot directly above the tapered pole which must be removed to create a notch directly above the pole. The trailing shield layer is then deposited above the pole and within the notch. Removal of the “bump” is typically done with a CMP process. However, the CMP process may produce rounding and damage to the region proximate to where the notch is formed, altering the critical gap thickness and producing non-planar trailing shields. What is needed is a better process for producing the notched trailing shield for the perpendicular write head. U.S. Patent Application Publication 2005/0264931 discloses fabrication of a perpendicular write head in a wafer, wherein at least two sides of a write pole are defined (e.g. by ion milling) while a third side of the write pole is protected by a masking material. At this stage, a material that is to be located in the write gap is already present between the write pole and the masking material. After definition of the write pole surfaces, a layer of dielectric material is deposited. During this deposition, the masking material is still present. Thereafter, the masking material (and any dielectric material thereon) is removed, to form a hole in the dielectric material. Next, a trailing shield is formed in the structure, so that at least one portion of the trailing shield is located in the hole, and another portion of the trailing shield is located over the dielectric material, in an area adjacent to the hole. Note that the gap material is now sandwiched between the portion of the trailing shield in the hole, and the write pole. 
         [0005]    U.S. Patent Application Publication 2005/0259355 discloses a perpendicular write head including a main pole and a trailing shield, the main pole being made of a diamond-like carbon (DLC) layer as hard mask and a rhodium (Rh) layer as shield gap, both DLC and Rh layers being CMP stop layers so as to avoid corner rounding and damage from chemical mechanical planarization (CMP) process, the DLC layer being removed by reactive ion etching (RIE) to create a trench, the trailing shield being deposited into the trench for self alignment. 
         [0006]    U.S. Patent Application Publication 2006/0023352 discloses a method and apparatus for providing a reverse air bearing surface head with trailing shield design for perpendicular recording. A reverse air bearing surface head for perpendicular recording is provided with an inversed bevel shape to handle skew when recording data on a magnetic recording medium. 
         [0007]    U.S. Patent Application Publication 2005/0190491 discloses a perpendicular magnetic write head having a notched, self aligned trailing shield for canting a magnetic field emitted there from. 
         [0008]    U.S. Patent Application Publication 2005/0068671 discloses a magnetic transducer with separated read and write heads for perpendicular recording. The write head has a trailing shield that extends from the return pole piece toward the main pole piece to form the write gap at the air-bearing surface. One embodiment of the trailing shield is a two part structure with a pedestal and a much smaller tip that confronts the main pole piece at the gap. In one embodiment a sink of non-magnetic, electrically conductive material is disposed in the separation gap between the read head and the flux bearing pole piece. The sink is preferably made of copper and does not extend to the ABS. 
         [0009]    U.S. Patent Application Publication 2005/0102820 discloses that conventional liftoff processes used to define track width in magnetic read heads can produce an uneven etch-depth of dielectric materials around the sensor and cause shorting to the overlay top lead layer. This problem has been overcome by printing the images of track width and stripe height onto an intermediate layer to form a hard mask. Through this hard mask, the GMR stack can be selectively etched and then back-filled with a high-resistivity material by using newly developed electroless plating processes. 
         [0010]    U.S. Patent Application Publication 2005/0068665 discloses a method and materials to fabricate a trailing shield write pole that resolve the problems of controlling the write gap and preventing damages to the write gap or pole during fabrication of the subsequent structure: This process also introduces a CMP assisted lift-off process to remove re-deposition and fencing (increase yields) and a method to create dishing in the top of the write pole. Moreover, also included in this disclosure are suitable materials that can function as an ion mill transfer layer, CMP layer, and RIEable layer. 
         [0011]    U.S. Patent Application Publication 2004/0012894 discloses a magnetic head including a substrate and a data transducer positioned upon the substrate. The data transducer includes a reader comprised of a top shield and a bottom shield characterized by at least one of the shields including a layer for compensating a thermally-caused expansion of the reader. 
         [0012]    U.S. Pat. No. 6,757,141 discloses a perpendicular recording head having a second pole piece which includes a bottom ferromagnetic shaping layer and a top ferromagnetic probe layer. Each of these layers has a flare point where the layers first commence to widen after the ABS with the flare point of the shaping layer being located between an air bearing surface (ABS) of the head and the flare point of the probe layer. Further, the probe layer has a probe at the ABS which has a decreasing width from its top to its bottom to provide a trapezoidal shape which minimizes side writing due to skew of the probe at outermost and innermost circular tracks of a rotating magnetic disk. 
       SUMMARY OF THE INVENTION 
       [0013]    It is an object of the present invention to provide a method for making a perpendicular head comprising fashioning a pole structure on a surface of a substrate, the pole structure having a tapered pole section in contact with the substrate, a gap layer deposited on the tapered pole section, and a spacer layer deposited on the gap layer. The method further includes depositing a dielectric layer on the surface of the substrate, enclosing the pole structure, the dielectric layer having a first portion of thickness T 1  and a second raised portion of thickness T 2 , the first portion of the dielectric layer having a surface approximately parallel to the surface of the substrate, the second raised portion of the dielectric layer being approximately centered over the pole structure, thickness T 2  being greater than thickness T 1 ; and depositing a stop layer on the dielectric layer. The dielectric layer is then planarized by a CMP process, a portion of the stop layer deposited on the first portion of the dielectric layer serving to terminate the CMP process. 
         [0014]    It is another object of the present invention to provide a method for making a perpendicular head comprising fashioning a pole structure on a surface of a substrate, the pole structure having a tapered pole section in contact with the substrate, a gap layer deposited on the tapered pole section, and a spacer layer deposited on the gap layer; and depositing a dielectric layer on the surface of the substrate, enclosing the pole structure, the dielectric layer having a first portion of thickness T 1  and a second raised portion of thickness T 2 , the first portion of said dielectric layer having a surface approximately parallel to the surface of the substrate, the second raised portion of the dielectric layer being approximately centered over the pole structure, thickness T 2  being greater than thickness T 1 . The method further includes depositing a stop layer on the first portion and the second raised portion of the dielectric layer; depositing a photo resist layer on the stop layer; removing a portion of the photo resist layer over the second raised portion of the dielectric layer; and removing a portion of the stop layer deposited over the second raised portion of the dielectric layer. The dielectric layer is then planarized by a CMP process, a portion of the stop layer deposited on the first portion of the dielectric layer serving to terminate the CMP process. 
         [0015]    It is yet another object of the present invention to provide a method for making a perpendicular head comprising fashioning a pole structure on a surface of a substrate, the pole structure having a tapered pole section in contact with the substrate, a gap layer deposited on the tapered pole section, and a spacer layer deposited on the gap layer; and depositing a dielectric layer on the surface of the substrate, enclosing the pole structure, the dielectric layer having a first portion of thickness T 1  and a second raised portion of thickness T 2 , the first portion of said dielectric layer having a surface approximately parallel to the surface of the substrate, the second raised portion of the dielectric layer being approximately centered over the pole structure, thickness T 2  being greater than thickness T 1 . The method further includes depositing a photo resist layer on the dielectric layer; removing a first portion of the photo resist layer over the first portion of the dielectric layer; depositing a stop layer subsequent to removing the photo resist; and, removing a second portion of the photo resist deposited on the second raised portion of the dielectric layer, wherein a portion of the stop layer deposited on the second portion of the photo resist is removed. The dielectric layer is then planarized by a CMP process, a portion of the stop layer deposited on the first portion of said dielectric layer serving to terminate the CMP process. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0016]    The present invention will be better understood when consideration is given to the following detailed description thereof. Such description makes reference to the annexed drawings, wherein: 
           [0017]      FIG. 1  is a partial cross sectional view looking into the air bearing surface (ABS) of a blanket deposited film stack prior to fabrication of a perpendicular write head with a notched trailing shield, in accordance with an embodiment of the present invention; 
           [0018]      FIG. 2  is a partial cross sectional view looking into the air bearing surface (ABS) of the film structure following the imaging and development of photo-resist layer  102  in accordance with an embodiment of the present invention; 
           [0019]      FIG. 3  is a partial cross sectional view looking into the air bearing surface (ABS) of the film structure subsequent to the transfer of patterned feature  102 ′ into layers  106  and  108 , in accordance with an embodiment of the present invention; 
           [0020]      FIG. 4  is a partial cross sectional view looking into the air bearing surface (ABS) of the film structure subsequent to ion milling and formation of the pole structure, in accordance with an embodiment of the present invention; 
           [0021]      FIG. 5  is a partial cross sectional view looking into the air bearing surface (ABS) of the film structure subsequent to deposition of dielectric layer  502  in accordance with an embodiment of the present invention; 
           [0022]      FIG. 6  is a partial cross sectional view looking into the air bearing surface (ABS) of the film structure subsequent to planarization by CMP in accordance with an embodiment of the present invention; 
           [0023]      FIG. 7  is a partial cross sectional view looking into the air bearing surface (ABS) of the film structure subsequent to ion milling of layer  502  in accordance with an embodiment of the present invention; 
           [0024]      FIG. 8  is a partial cross sectional view looking into the air bearing surface (ABS) of the film structure subsequent to reactive ion etching of feature  108 ′ in accordance with an embodiment of the present invention; 
           [0025]      FIG. 9  is a partial cross sectional view looking into the air bearing surface (ABS) of the film structure subsequent to deposition of notched trailing shield  902  in accordance with an embodiment of the present invention; 
           [0026]      FIG. 10  is a partial cross sectional view looking into the air bearing surface (ABS) of the film structure subsequent to deposition of CMP stop layer  1002  in accordance with an embodiment of the present invention; 
           [0027]      FIG. 11  is a partial cross sectional view looking into the air bearing surface (ABS) of the film structure subsequent to planarization of the structure of  FIG. 10  in accordance with an embodiment of the present invention; 
           [0028]      FIG. 12  is a partial cross sectional view looking into the air bearing surface (ABS) of the film structure subsequent to deposition of photo resist layer  1202  in accordance with an embodiment of the present invention; 
           [0029]      FIG. 13  is a partial cross sectional view looking into the air bearing surface (ABS) of the film structure subsequent to imaging and development of photo resist layer  1202  in accordance with an embodiment of the present invention; 
           [0030]      FIG. 14  is a partial cross sectional view looking into the air bearing surface (ABS) of the film structure subsequent to deposition of stop layer  1402  in accordance with an embodiment of the present invention; 
           [0031]      FIG. 15  is a partial cross sectional view looking into the air bearing surface (ABS) of the film structure subsequent to removal of photo resist feature  1202 ′ in accordance with an embodiment of the present invention; 
           [0032]      FIG. 16  is a partial cross sectional view looking into the air bearing surface (ABS) of the film structure subsequent to planarization of the structure of  FIG. 15  in accordance with an embodiment of the present invention; 
           [0033]      FIG. 17  is a partial cross sectional view looking into the air bearing surface (ABS) of the film structure subsequent to deposition of photo resist layer  1702  in accordance with an embodiment of the present invention; 
           [0034]      FIG. 18  is a partial cross sectional view looking into the air bearing surface (ABS) of the film structure subsequent to imaging and development of photo resist layer  1702  in accordance with an embodiment of the present invention; 
           [0035]      FIG. 19  is a partial cross sectional view looking into the air bearing surface (ABS) of the film structure subsequent to removal of a portion of stop layer  1002  in accordance with an embodiment of the present invention; 
           [0036]      FIG. 20  is a schematic block diagram of the basic process for fabricating a notched trailing shield, in accordance with an embodiment of the present invention; 
           [0037]      FIG. 21  is a schematic block diagram of Process A for fabricating a notched trailing shield, in accordance with an embodiment of the present invention; 
           [0038]      FIG. 22  is a schematic block diagram of Process B for fabricating a notched trailing shield, in accordance with an embodiment of the present invention; and, 
           [0039]      FIG. 23  is a schematic block diagram of Process C for fabricating a notched trailing shield, in accordance with an embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0040]    The features and description of the present invention are best understood while viewing the cross sectional structure views ( FIGS. 1-19 ) in light of the process block diagrams ( FIGS. 20-23 ). A basic process for fabricating a notched trailing shield is disclosed in  FIG. 20 , and  FIGS. 1-9 . Improved variants of the basic process are disclosed in Process A ( FIG. 21 ), Process B ( FIG. 22 ), and Process C ( FIG. 23 ). 
         [0041]      FIG. 20  is a schematic block diagram of the basic process for fabricating a notched trailing shield, in accordance with an embodiment of the present invention. The process begins at step  2002 , wherein the layer stack  100  of  FIG. 1  is deposited.  FIG. 1  is a partial cross sectional view looking into the air bearing surface (ABS) of a blanket deposited film stack  100  prior to fabrication of a perpendicular write head with a notched trailing shield. The film stack comprises blanket layers  102 - 112  deposited on substrate  114 , which is typically alumina (at the air bearing surface), but may be other materials such as magnetic pole shaping layers deeper (further from the ABS) into the structure. For the purposes of this disclosure, substrate  114  can be a bulk material on which all subsequent layers are deposited, or it can be a layer deposited over previously deposited under-layers. For example, when fabricating a combined read and write head structure, the latter is usually the case, as the read head structure is generally deposited first (not shown). Layer  112  makes up the magnetic pole material, and is typically a laminated, multilayer structure comprising layers of magnetic and non-magnetic materials. Layer  112  is nominally 240 nm thick. Above pole layer  112  is gap layer  110 , typically 50 nm thick, comprised of alumina or other non-magnetic materials. A spacer layer  108  is deposited above gap layer  110 , and is comprised of Durimide, approximately 1000 nm thick. Above spacer layer  108 , layers  102 ,  104 , and  106  are deposited. Layer  102  comprises the imaging photo resist layer that defines the width and location of the write pole. Layers  104  and  106  aid in transferring the developed features of photo resist layer  102  to the spacer layer  108 . Layer  106  is typically comprised of silica nominally 100 nm thick, and layer  104  is typically comprised of Durimide nominally 60 nm thick. 
         [0042]    In step  2004  of  FIG. 20 , photo resist layer  102  is imaged and developed, creating feature  102 ′ in  FIG. 2 .  FIG. 2  is a partial cross sectional view looking into the air bearing surface (ABS) of the film structure  200  following the imaging and development of photo-resist layer  102 . 
         [0043]    In step  2006  of  FIG. 20 , photo resist feature  102 ′ is transferred to layers  106  and  108 , creating features  106 ′ and  108 ′.  FIG. 3  is a partial cross sectional view looking into the air bearing surface (ABS) of the film structure  300  subsequent to the transfer of patterned feature  102 ′ into layers  106  and  108 . The transfer is carried out with three consecutive RIE process steps comprising a first oxidation step to etch layer  104 , a second fluorine etch step to etch silica layer  106 , followed by a third oxidation step to etch spacer layer  108 . Details of the RIE processes are well known to those skilled in the art. During the oxidation steps, photo resist layer  102  is removed, resulting in structure  300 . 
         [0044]    In step  2008  of  FIG. 20 , the structure of  FIG. 3  is ion milled to form the pole structure comprising features  108 ′,  110 ′ and  112 ′.  FIG. 4  is a partial cross sectional view looking into the air bearing surface (ABS) of the film structure  400  subsequent to ion milling and formation of the pole structure. The width of the pole structure ( 108 ′,  110 ′,  112 ′) is W p    402 . Details of the formation of the tapered pole section  112 ′ have been previously disclosed in the prior art and are well known. 
         [0045]    In step  2010  of  FIG. 20 , dielectric layer  502  is deposited around pole structure  108 ′,  110 ′,  112 ′.  FIG. 5  is a partial cross sectional view looking into the air bearing surface (ABS) of the film structure  500  subsequent to deposition of dielectric layer  502 . Layer  502  typically comprises alumina. Due to the conformal nature of the deposition, a raised portion of layer  502  (or “bump feature”  502 ′) is created directly above the buried pole structure  108 ′,  110 ′,  112 ′. The thickness T 2  (ref  508 ) of this raised portion  502 ′, as measured from the substrate  114  surface, is greater than thickness T 1  (ref  510 ). T 1  is the thickness of the generally flat portion of layer  502 , having a surface  504  that is approximately parallel to the surface of substrate  114 . Typically, the width  506  of the “bump feature” (W bf ) is many times that of the pole width  402 . To proceed further with the device fabrication, this “bump feature”  502 ′ must be removed and a surface co-planar with the surface  504  of layer  502  created. This is typically done by planarization via CMP. 
         [0046]    In step  2012  of  FIG. 20 , structure  500  is planarized by CMP.  FIG. 6  is a partial cross sectional view looking into the air bearing surface (ABS) of the film structure  600  subsequent to planarization by CMP. No stop layer is employed in this process, also known as a “touch down” process because the planarization is carried out in such manner as to only remove the bump feature. However, termination of the process is tricky, and if carried out too far, will result in removal of spacer layer  108 ′ and potential damage to or thinning of the gap layer  110 ′. If the thickness of spacer layer  108 ′ is reduced significantly or eliminated, no notch will be created for the trailing shield, which is undesirable. 
         [0047]    In step  2014  of  FIG. 20 , layer  502  in structure  600  is ion milled to set the notch depth above the gap layer.  FIG. 7  is a partial cross sectional view looking into the air bearing surface (ABS) of the film structure  700  subsequent to ion milling of layer  502 . In step  2016  of  FIG. 20 , spacer layer  108 ′ is removed by RIE to create the notch for the trailing shield.  FIG. 8  is a partial cross sectional view looking into the air bearing surface (ABS) of the film structure  800  subsequent to reactive ion etching of layer  108 ′. In step  2018  of  FIG. 20 , a seed layer (not shown) is deposited, followed by electroplating of trailing shield  902 .  FIG. 9  is a partial cross sectional view looking into the air bearing surface (ABS) of the film structure  900  subsequent to deposition of notched trailing shield  902 . 
         [0048]    The foregoing basic process of  FIG. 20  is suitable for producing write heads with notched trailing shields, but there are a number of aspects which can be improved upon. In particular, the CMP process in step  2012  may result in some undesirable results. It is difficult to control the termination of the process, making precise control of the notch depth difficult. In extreme cases, the gap depth may also be reduced or damaged, making the heads unusable. The basic process of  FIG. 20  also produces larger than acceptable within wafer and wafer to wafer variations, affecting yields of die produced within the wafer. The preferred embodiments disclosed below in Processes A, B, and C address many of these shortcomings, providing a more reliable method for fabricating notched trailing shields, having better within wafer and wafer to wafer uniformities, and higher yields. 
         [0049]      FIG. 21  is a schematic block diagram of Process A for fabricating a notched trailing shield, in accordance with a preferred embodiment of the present invention. Process steps  2002 - 2010  and  2014 - 2018  are the same as previously described in the basic process of  FIG. 20 . The previously disclosed steps are placed in shaded, dotted outline boxes to clearly distinguish them from the new steps. Following the deposition of layer  502  in step  2010 , a CMP stop layer  1002  is deposited in a blanket layer over all features, including the “bump feature”  502 ′, located above the pole structure.  FIG. 10  is a partial cross sectional view looking into the air bearing surface (ABS) of the film structure  1000  subsequent to deposition of CMP stop layer  1002  in accordance with an embodiment of the present invention. The purpose of stop layer  1002  is to terminate the planarization process more precisely, and is the result of the hardness of the stop layer in comparison to alumina layer  502 . Typically, DLC (diamond like carbon) is commonly used as a stop layer due to it&#39;s extreme hardness and low planarization rate of about 2 angstroms/minute. Although DLC can be used as the stop layer in this process, it is not preferred due it&#39;s brittle nature, which may chip or crack in the vicinity of “bump feature”  502 ′. Other materials suitable for the stop layer include Rh, Ru, Cr, and Ta. Out of these choices, Ta is the least desirable, due to a planarization rate of about 200 angstroms/minute. It may still be usable, however, since it&#39;s planarization rate is less than one tenth that of alumina (3000 angstroms/minute). Rh is the most desirable, having a planarization rate of about 2 angstroms/minute, which is as good as DLC, without the brittleness of DLC. Ru and Cr are usable, better than Ta but not as good as Rh, with planarization rates of about 60 and 70 angstroms/minute, respectively. When Rh is used as stop layer  1002 , a Ta layer may be used underneath the Rh layer to improve adhesion to layer  502 . Deposition thickness for a Rh stop layer can range from 15 to 35 nm, preferably about 25 nm. If a Ta layer is used, it can range from 3-7 nm in thickness, preferably about 5 nm. 
         [0050]    In step  2104  of  FIG. 21 , structure  1000  is planarized by CMP to the stop layer.  FIG. 11  is a partial cross sectional view looking into the air bearing surface (ABS) of the film structure  1100  subsequent to planarization of the structure  1000  of  FIG. 10  in accordance with an embodiment of the present invention. Although the “bump feature”  502 ′ is coated with the stop layer, planarization is still possible due to the reduced surface area of the “bump feature” in comparison to the surface area of surface  504 . Once the planarization process has cut though the stop layer covering the top surface of the “bump feature”, the process will proceed rapidly until the stop layer  1002  covering surface  504  is reached. At that point, the large surface area of the remaining stop layer will effectively terminate the planarization process. With an appropriate thickness for layer  502 , the process can be designed in such a manner as to have little or no impact on spacer layer  108 ′ or gap layer  110 ′. 
         [0051]    In step  2014  of  FIG. 21 , structure  1100  is ion milled to remove the remaining stop layer  1002  and a portion of layer  502 . The resulting structure  700  is shown in  FIG. 7 . The degree of ion milling determines the gap depth, which is not affected by the planarization process of step  2104 . Process steps  2016  and  2018  complete the process as previously described above. 
         [0052]    One disadvantage of Process A is the requirement to planarize through the stop layer deposited on the “bump feature”  502 ′. The hardness of the stop layer slows planarization of the “bump features” when compared to the basic process of  FIG. 20 , for example. An improvement on this process would be realized if the stop layer could be selectively deposited only where needed, on the planar surfaces of layer  502  parallel to the substrate  114 , exclusive of the “bump features”. This is the object of Process B and Process C of the present invention. 
         [0053]      FIG. 22  is a schematic block diagram of Process B for fabricating a notched trailing shield, in accordance with a preferred embodiment of the present invention. Process steps  2002 - 2010  and  2014 - 2018  are the same as previously described in the basic process of  FIG. 20 . The previously disclosed steps are placed in shaded, dotted outline boxes to clearly distinguish them from new steps  2202 - 2210 . Following the deposition of layer  502  in step  2010 , a blanket photo resist layer  1202  is deposited in step  2202 .  FIG. 12  is a partial cross sectional view looking into the air bearing surface (ABS) of the film structure  1200  subsequent to deposition of photo resist layer  1202  in accordance with an embodiment of the present invention. 
         [0054]    In step  2204  of  FIG. 22 , photo resist layer  1202  is imaged and developed to create feature  1202 ′.  FIG. 13  is a partial cross sectional view looking into the air bearing surface (ABS) of the film structure  1300  subsequent to imaging and development of photo resist layer  1202  in accordance with an embodiment of the present invention. Photo resist feature  1202 ′, having width  1302  (W pr ) is designed to cover the entire width W bf  of the “bump feature”  502 ′, and terminates on the planar portion of layer  502  on either side of the “bump feature”. The actual width  1302  of feature  1202 ′ is not critical, as long as the “bump feature”  502 ′ is completely enclosed, or W pr &gt;W bf . 
         [0055]    In step  2206  of  FIG. 22 , a blanket stop layer  1402  is deposited on structure  1300 .  FIG. 14  is a partial cross sectional view looking into the air bearing surface (ABS) of the film structure  1400  subsequent to deposition of stop layer  1402  in accordance with an embodiment of the present invention. Materials suitable for the stop layer include Rh, Ru, Cr, and Ta. Out of these choices, Rh is preferred, due to it&#39;s low planarization rate (previously discussed above). DLC is not suitable for this process. Ru, Cr, and Ta may also be used, but are not preferred. When Rh is used as stop layer  1402 , a Ta layer may be used underneath the Rh layer to improve adhesion to layer  502 . Deposition thickness for a Rh stop layer can range from 15 to 35 nm, preferably about 25 nm. If a Ta layer is used, it can range from 3-7 nm in thickness, preferably about 5 nm. 
         [0056]    In step  2208  of  FIG. 22 , feature  1 - 202 ′ is removed.  FIG. 15  is a partial cross sectional view looking into the air bearing surface (ABS) of the film structure  1500  subsequent to removal of photo resist feature  1202 ′ in accordance with an embodiment of the present invention. Feature  1202 ′ and the portion of stop layer  1402  covering feature  1202 ′ are removed by a combination of baking and photo resist stripping processes. The baking step, known as “wrinkle baking” causes the photo resist feature  1202 ′ to expand, cracking and rupturing the stop layer covering it. This allows an oxidizing strip chemistry (either wet or dry) to attack the exposed resist and remove it from the “bump feature”  502 ′. Portions of stop layer  1402  adherent to surface  504  of layer  502  are not affected and remain on the structure  1500 . 
         [0057]    In step  2210  of  FIG. 22 , structure  1500  is planarized by CMP.  FIG. 16  is a partial cross sectional view looking into the air bearing surface (ABS) of the film structure  1600  subsequent to planarization of the structure of  FIG. 15 , in accordance with an embodiment of the present invention. The “bump feature”  502 ′ is effectively removed at a faster rate than in Process A, because only the alumina material of layer  502  is being planarized. Stop layer  1402  terminates the planarization process due to its very low planarization rate, before any damage to the pole structure can be realized. 
         [0058]    In step  2104  of  FIG. 22 , structure  1600  is ion milled to remove the remaining stop layer  1402  and a portion of layer  502 . The resulting structure  700  is shown in  FIG. 7 . The degree of ion milling determines the gap depth, which is not affected by the planarization process of step  2104 . Process steps  2016  and  2018  complete the process as previously described above. 
         [0059]      FIG. 23  is a schematic block diagram of Process C for fabricating a notched trailing shield, in accordance with a preferred embodiment of the present invention. Process steps  2002 - 2010 ,  2102 ,  2210  and  2014 - 2018  are the same as previously described. The previously disclosed steps are placed in shaded, dotted outline boxes to clearly distinguish them from new steps  2302 - 2308 . In Process C, a blanket stop layer  1002  is deposited on structure  500  of  FIG. 5 , as was done in step  2102  of  FIG. 21  (Process A). The limitations and preferences for the stop layer  1002  disclosed above under the discussion of Process A apply here as well, including the use of DLC as a stop layer material. Although not preferred, DLC layers may be used in Process C. 
         [0060]    In step  2302  of  FIG. 23 , a blanket photo resist layer  1702  is deposited over stop layer  1002 .  FIG. 17  is a partial cross sectional view looking into the air bearing surface (ABS) of the film structure  1700  subsequent to deposition of photo resist layer  1702  in accordance with an embodiment of the present invention. 
         [0061]    In step  2304  of  FIG. 23 , photo resist layer  1702  is imaged and developed.  FIG. 18  is a partial cross sectional view looking into the air bearing surface (ABS) of the film structure  1800  subsequent to imaging and development of photo resist layer  1702  in accordance with an embodiment of the present invention. In this step, photo resist is removed from a channel of width W ( 1802 ) surrounding “bump feature”  502 ′, leaving photo resist features  1702 ′ which cover the surface  504  of layer  502  on either side of the “bump feature”. The amount of photo resist layer  1702  removed is not critical, as long as “bump feature”  502 ′ is fully exposed (having no photo resist coverage). Extending the photo resist removal zone beyond the width  1802  of the “bump feature” is allowed, as long as there is sufficient coverage of stop layer on surface  504  of layer  502  to provide a planarization stop. That is, W&gt;W bf . 
         [0062]    In step  2306  of  FIG. 23 , the stop layer  1002  exposed by removal of the photo resist in the previous step is removed.  FIG. 19  is a partial cross sectional view looking into the air bearing surface (ABS) of the film structure  1900  subsequent to removal of a portion of stop layer  1002  in accordance with an embodiment of the present invention. Ion milling can be used to remove Rh, Ru, Cr, and Ta. For the special case of DLC, an oxidizing RIE process can be used. This process may also damage the photo resist features  1702 ′ remaining, but this are not critical, and a small degree of undercutting of layer  1002  under the photo resist near the boundaries is not a problem. 
         [0063]    In step  2308  of  FIG. 23 , the remaining photo resist is removed from the surface of the stop layer  1002 . The resulting structure is depicted in  FIG. 15 , with the exception that the stop layer is labeled  1002 , not  1402 . In step  2210 , the “bump feature” is planarized by CMP as in preceding processes. It is also possible to combine these two steps, and planarize structure  1900  of  FIG. 19  without a separate photo resist removal step, since the CMP process could remove the photo resist layer and the “bump feature” in a single step; 
         [0064]    Steps  2014 - 2018  complete the process and are described above. 
         [0065]    The present invention is not limited by the previous embodiments heretofore described. Rather, the scope of the present invention is to be defined by these descriptions taken together with the attached claims and their equivalents.