Abstract:
A perpendicular magnetic recording (PMR) head comprises a PMR pole having at least one side, a bottom, and a top wider than the bottom, a first portion of the at least one side being substantially vertical, a second portion of the at least one side being nonvertical, the top portion having a width not greater than one hundred fifty nanometers. The PRM head further comprises a nonmagnetic layer surrounding the bottom and the at least one side of the PMR pole, an intermediate layer substantially surrounding at least the second portion of the at least one side of the PMR pole, and a hard mask layer adjacent to the first portion of the at least one side of the PMR pole.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a divisional of U.S. patent application Ser. No. 12/121,624, filed on May 15, 2008, which is hereby incorporated by reference in its entirety. 
    
    
     BACKGROUND 
       FIG. 1  is a flow chart depicting a conventional method  10  for fabricating a conventional perpendicular magnetic recording (PMR) transducer. For simplicity, some steps are omitted. The conventional method  10  is used for providing a PMR pole. An intermediate layer, chemical mechanical planarization (CMP) stop layer and hard mask layer are provided, via step  12 . The intermediate layer is typically aluminum oxide. The CMP stop layer may include Ru, while the hard mask layer may include NiCr. A photoresist mask is provided on the hard mask layer, via step  14 . The photoresist mask includes an aperture above the portion of the intermediate layer in which the PMR pole is to be formed. A conventional aperture is formed in the hard mask layer, via step  16 . Typically, this is accomplished through using a conventional ion mill. Step  16  also includes forming a conventional aperture in the CMP stop layer. Thus, through ion milling in step  16 , the pattern of the photoresist mask is transferred to both the hard mask and the CMP stop layer in a conventional manner. 
     Using the hard mask and photoresist mask, a trench is formed in the aluminum oxide layer, via step  18 . Step  18  is typically performed using an alumina reactive ion etch (RIE). The top of the trench  66  is desired to be wider than the trench bottom. In addition, the trench may extend through the aluminum oxide intermediate layer. As a result, the PMR pole formed therein will have its top surface wider than its bottom. Consequently, the sidewalls of the PMR pole will have a reverse angle. The conventional PMR pole materials are deposited, via step  20 . A CMP is then performed, via step  22 . The stop layer provided in step  12  is used to terminate the CMP. Thus, the conventional PMR pole is provided. Subsequent structures, such as a write gap and shields, may then be provided. 
     Although the conventional method  10  may provide the conventional PMR transducer, there may be drawbacks. Use of the photoresist mask and hard mask may result in relatively large variations in the critical dimension of the conventional PMR pole. The critical dimension corresponds to the track width of the conventional PMR pole. Such variations in track width may adversely affect fabrication and performance. In addition, the conventional PMR pole may be relatively large in size. Using conventional photolithography, the critical diameter of the apertures formed in step  16 , and thus the trench provided in step  18 , is typically greater than 150 nm. Consequently, without more, the conventional PMR poles formed using the conventional method  10  may not be usable in high density magnetic recording technology. 
     Accordingly, what is needed is an improved method for fabricating a PMR transducer. 
     SUMMARY 
     A method and system for providing a PMR pole in a magnetic recording transducer are disclosed. The magnetic recording transducer includes an intermediate layer. The method and system include providing a mask including a line on the intermediate layer. The method further include providing a hard mask layer on the mask and removing the line. Thus, an aperture in a hard mask corresponding to the line is provided. The method and system also include forming a trench in the intermediate layer under the aperture. The trench has a bottom and a top wider than the bottom. The method further includes providing a PMR pole, at least a portion of which resides in the trench. 
    
    
     
       BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS 
         FIG. 1  is a flow chart depicting a conventional method for fabricating a PMR head. 
         FIG. 2  is a flow chart depicting an exemplary embodiment of a method for fabricating a PMR transducer. 
         FIG. 3  is a flow chart depicting another embodiment of a method for fabricating a PMR transducer. 
         FIGS. 4-13  are diagrams depicting an exemplary embodiment of a perpendicular magnetic recording transducer during fabrication. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       FIG. 2  is a flow chart depicting an exemplary embodiment of a method  100  for fabricating a PMR pole for a PMR transducer. For simplicity, some steps may be omitted. The PMR transducer being fabricated may be part of a merged head that also includes a read head (not shown) and resides on a slider (not shown). The method  100  also may commence after formation of other portions of the PMR transducer. The method  100  is also described in the context of providing a single PMR pole in a single magnetic recording transducer. However, the method  100  may be used to fabricate multiple transducers at substantially the same time. The method  100  and system are also described in the context of particular layers, such as a BARC layer. However, in some embodiments, such layers may include multiple sub-layers. 
     In one embodiment, the method  100  commences after formation of the intermediate layer(s) in which the PMR pole is to reside. In one embodiment, the intermediate layer is an insulator such as alumina. The intermediate layer may reside on an underlayer. Further, in one embodiment, the underlayer layer may be an etch stop layer. A mask is provided on the intermediate layer, via step  102 . The mask includes a line that corresponds to the location of the PMR pole. In one embodiment, the mask is a photoresist mask and may be formed using photolithographic techniques. For example, a BARC might be used in order to improve formation of the line. The BARC reduces reflections in forming a photoresist mask on the BARC layer. In such an embodiment, formation of the mask may further include removal of any BARC exposed by the mask. A hard mask layer is provided on the mask, via step  104 . For example, step  104  may include deposition of a material such as NiCr, Cr, and/or Ru. 
     The line in the mask is removed, via step  106 . In one embodiment, step  106  may include removal of corresponding structures, such as any BARC residing beneath the line. In one embodiment, step  106  includes performing a planarization, such as a CMP, and a lift-off of any remaining photoresist. The hard mask is thus formed. In particular, removal of the line forms an aperture corresponding to the line. The aperture in the hard mask resides in substantially the position occupied by the line. 
     A trench is formed in the intermediate layer under the aperture, via step  108 . The trench has a bottom and a top wider than the bottom. Consequently, the trench formed is appropriate for a PMR pole. In one embodiment, the trench extends through the intermediate layer. However, in another embodiment, the trench might extend only partially through the intermediate layer. In one embodiment, step  108  includes performing a RIE. 
     A PMR pole is provided, via step  110 . At least a portion of the PMR pole resides in the trench. In one embodiment, only part of the PMR pole resides within the trench in the intermediate layer. Thus, the top of the PMR pole would be above the top of intermediate layer. In an alternate embodiment, the entire PMR pole resides within the trench. Formation of the PMR pole in step  110  may include providing a nonmagnetic layer in the trench. Such a nonmagnetic layer might be used to adjust the critical dimension, and thus the track width, of the PMR pole. Thus, the PMR pole would reside on such a nonmagnetic layer. In one embodiment, the nonmagnetic layer may be provided using atomic layer deposition (ALD). As part of step  110  a planarization stop layer might also be provided. In one embodiment, the planarization stop layer is provided on the nonmagnetic layer. The planarization stop layer may be a CMP stop layer. In one such embodiment, the planarization stop layer includes Ru. A seed layer for the PMR pole may also be provided on the planarization stop layer. In another embodiment, the planarization stop layer may also function as a seed layer. The layer(s) for the PMR pole may then be blanket deposited. A planarization, such as a CMP, may be performed. In addition, the geometry of the PMR pole might be further adjusted using an ion beam etch. Thus, the PMR pole may be formed. Although described above as part of formation of the PMR pole, at least some of the steps of providing the nonmagnetic layer, the planarization stop layer and/or the seed layer may be considered separate from providing the PMR pole. 
     Using the method  100 , at least part of a PMR transducer may be formed. The method  100  utilizes the photoresist line to provide the aperture in the hard mask. In one embodiment, the line in the mask may have a critical dimension, or width, that is not larger than one hundred-fifty nanometers. The critical dimension of the line might also be not more than one hundred nanometers. As a result, the critical dimension for the PMR pole may be not more than one hundred-fifty nanometers in one embodiment. In another embodiment, the critical dimension might be not more than on hundred nanometers. The PMR transducer formed may thus be used at higher densities. For example, the PMR transducer formed might be usable in 400 Gb/in 2  or higher density transducers. Using the method  100 , therefore, a PMR transducer usable at higher densities may be fabricated. 
       FIG. 3  is a flow chart depicting another exemplary embodiment of a method  150  for fabricating a PMR transducer. For simplicity, some steps may be omitted.  FIGS. 4-13  are diagrams depicting an exemplary embodiment of a PMR transducer  200  as viewed from the ABS during fabrication. For clarity,  FIGS. 4-13  are not to scale. Referring to  FIGS. 3-13 , the method  150  is described in the context of the PMR transducer  200 . However, the method  150  may be used to form another device (not shown). The PMR transducer  200  being fabricated may be part of a merged head that also includes a read head (not shown) and resides on a slider (not shown). The method  150  also may commence after formation of other portions of the PMR transducer  200 . The method  150  is also described in the context of providing a single PMR transducer. However, the method  150  may be used to fabricate multiple transducers at substantially the same time. The method  150  and device  200  are also described in the context of particular layers, such as a bottom antireflective coating (BARC) layer. However, in some embodiments, such layers may include multiple sublayers. 
     The method  150  commences after an intermediate layer is provided. The intermediate layer may be an alumina layer. A BARC is provided on the intermediate layer, via step  152 . A photoresist mask is provided on the BARC, via step  154 . The photoresist mask includes a line that corresponds to the location of the PMR pole.  FIG. 4  depicts a portion of the PMR transducer  200  after step  154  is performed. In the embodiment shown, an underlayer  202  that may also functions as an etch stop layer  202 , is shown. In addition, an intermediate layer  204  is also depicted. The PMR transducer  200  also includes a BARC  206  and a mask  208 . In the embodiment shown, the mask  208  is shown as consisting of a line. However, in another embodiment, the mask  208  may include other features. 
     The pattern of the mask  208  is transferred to the BARC  206 , via step  156 .  FIG. 5  depicts the PMR transducer  200  after step  156  is performed. Thus, the BARC  206 ′ resides only under the line  208 . A hard mask layer is provided on the PMR transducer  200 , via step  158 . Step  158  may include deposition of a material such as NiCr, Cr, and/or Ru.  FIG. 6  depicts the PMR transducer  200  after step  158  is performed. Thus, a hard mask layer  210  has been provided. 
     A planarization, such as a CMP, is performed to expose the line of the mask  208 , via step  160 .  FIG. 7  depicts the PMR transducer after step  160  has been performed. Thus, a hard mask  210 ′ has been formed from the hard mask layer  210 . The hard mask  210 ′ includes an aperture  212 . In addition, a remaining portion  208 ′ of the line of the mask is shown. Because of the CMP, the top surface of the PMR transducer  210  is substantially flat. Thus, the remaining portion  208 ′ of the line and the hard mask  210 ′ have top surfaces at substantially the same level. The aperture  212  corresponds to the line of the mask  208 . As a result, the location and size of the aperture  212  match that of the line. 
     A lift-off is performed, via step  162 . As a result, the remaining portion  208 ′ of the line is removed. In addition, the remaining portion  206 ′ of the BARC that was under the line is removed, via step  164 .  FIG. 8  depicts the PMR transducer  200  after step  164  is completed. Thus, the aperture  212  in the hard mask  210 ′ exposes the underlying intermediate layer  204 . 
     A RIE is performed to form a trench in the intermediate layer  204 , via step  166 . In one embodiment, the RIE is performed utilizing a Cl-containing gas.  FIG. 9  depicts the PMR transducer after step  166  is performed. Thus, a trench  213  has been formed in the intermediate layer  204 ′. For clarity, the aperture  212  is no longer labeled. However, the trench  213  is formed under the aperture  212 . The trench  213  has a bottom and a top wider than the bottom. 
     The PMR pole is then formed. This may occupy a number of steps. In one embodiment, a nonmagnetic layer is provided in the trench  213 , via step  168 . At least a portion of the nonmagnetic layer resides in the trench  213 . In one embodiment, step  168  may be performed using ALD. However, in another embodiment, another method for providing the nonmagnetic layer may be used. Alternatively, step  168  might be omitted. Because it is magnetically separate from the pole being formed, the nonmagnetic layer may be used to reduce the critical diameter of the pole being formed. Stated differently, the nonmagnetic layer may be considered to make the trench  213  less wide and, in one embodiment, shallower. Thus, the thickness of the nonmagnetic layer may be used to tune the width of the PMR pole being formed. In particular, the width the PMR pole being formed may be reduced by twice the thickness of the nonmagnetic layer. For example, in one embodiment, the nonmagnetic layer may be at least fifty and not more than four hundred Angstroms. Consequently, use of a nonmagnetic layer in such an embodiment allows the width of the PMR pole being formed to be reduced by one hundred to eight hundred Angstroms. 
     A planarization stop layer is provided on the nonmagnetic layer, via step  170 . In one embodiment, the planarization stop layer is a CMP stop layer and may include materials such as Ru. A seed layer may also be provided on the CMP stop layer, via step  172 . Such a seed layer may be nonmagnetic or magnetic. If magnetic, the seed layer may be magnetically indistinct from the PMR pole. Thus, the seed layer may be considered part of the PMR pole. In another embodiment, the seed layer may be nonmagnetic. In such an embodiment, the seed layer would be magnetically distinct from the PMR pole. In one embodiment, the seed layer and the planarization stop layer may function as a single layer or be merged into a single layer.  FIG. 10  depicts the PMR transducer  200  after step  172  is performed. Thus, a nonmagnetic layer  214 , a CMP stop layer  216 , and a seed layer  218  are all shown. A portion of each of the nonmagnetic layer  214 , the CMP stop layer  216 , and the seed layer  218  resides in the trench  213 . However, another portion of each of the nonmagnetic layer  214 , the CMP stop layer  216 , and the seed layer  218  also resides on and next to the hard mask  210 ′. Thus, a portion of the nonmagnetic layer  214  is above the top of the intermediate layer  204 ′. 
     A PMR pole layer(s) may be provided, via step  174 . Step  174  may include plating the PMR pole layer(s). In one embodiment, a single layer is used. However, in another embodiment, multiple layers might be used for the PMR pole. Consequently, multiple layers might be deposited in step  174 . In the embodiment described, the PMR pole layer(s) are blanket deposited. However, in another embodiment, masking might be used. In one embodiment, the PMR pole layer is plated on the planarization stop layer  216 . In an embodiment in which a separate seed layer is used, the PMR pole layer may also be plated on the seed layer  218  and, if used, the nonmagnetic layer  214 . 
       FIG. 11  depicts the PMR transducer  200  after step  174  is performed. Thus, the PMR pole layer  220  resides in the trench  213 . However, another portion of the PMR pole layer  220  also resides on and next to the hard mask  210 ′. Thus, a portion of the PMR pole layer  220  is above the top of the intermediate layer  204 ′. A CMP, or other planarization selected, is performed, via step  176 . The CMP planarization may terminate when at least a portion of the planarization stop layer  216  remains. In addition, an ion beam etch might also be performed in step  176  to further configure the geometry of the PMR pole. 
       FIG. 12  depicts the PMR transducer  200  after step  176  has been performed. Consequently, the PMR pole  220 ′ has been formed from the PMR pole layer(s)  220 . In addition, a portion of the seed layer  218  and, in some embodiments, a portion of the CMP stop layer  216  have been removed. Consequently, only portions of the seed layer  214 ″, portions of CMP stop layer  216 ′, and nonmagnetic layer  214  remain after step  176  is performed. In the embodiment shown, only a portion of the PMR pole  220 ′ resides within the trench  213 . This portion of the PMR pole  220 ′ has a top wider than the bottom. Stated differently, there is a negative angle (as measured from vertical) for these portions of the sidewalls of the PMR pole  220 ′. A remaining portion of the PMR pole  220 ′ is next to the hard mask layer  210 ′, nonmagnetic layer  220 , and remaining planarization stop layer  222 ′. The sidewalls for this portion of the PMR pole  220 ′ are s substantially vertical. 
     Fabrication of the PMR transducer  200  might then be completed. For example, a write gap, a shield, and other structures might be provided.  FIG. 13  depicts the PMR transducer  200  after such structure are provided. Thus, the write gap  222  and top shield  224  are shown. In one embodiment, the write gap  228  may be an insulator, such as aluminum oxide. In another embodiment, other material(s) may be used. 
     Using the method  150 , at least part of the PMR transducer  200  may be formed. The method  150  utilizes the photoresist line of the mask  208  to provide the aperture  212  in the hard mask  210 ′. In one embodiment, the line in the mask  208 ′ may have a critical dimension, or width, that is not larger than one hundred-fifty nanometers. The critical dimension of the line  208  might also be not more than one hundred nanometers. As a result, the critical dimension for the PMR pole  220 ′ may be not more than one hundred-fifty nanometers in one embodiment. In another embodiment, the critical dimension might be not more than one hundred nanometers. The PMR transducer  200  may thus be used at higher densities. For example, the PMR transducer  200  might be usable in 400 Gb/in 2  or higher density transducers. Using the method  150 , therefore, a PMR transducer  200  usable at higher densities may be fabricated.