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 PMR 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 planarization stop 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. 12/121,540, 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 method and system include providing a mask including a line on the intermediate layer. The line has at least one side, a top, and a bottom. The side(s) have an undercut such that the top of the line is wider than the bottom. The method further includes providing a hard mask on the PMR transducer. The hard mask includes an aperture corresponding to the line. Thus, an aperture in the 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. 4-12  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. 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. The sides of the line are undercut. As a result, the bottom of the line is smaller than the top of the line. In one embodiment, the mask is a bilayer with the lower layer having a smaller critical dimension, or width, than the top layer. For example, the line may include a polydimethylglutarimide (PMGI) layer and photoresist layer. In such an embodiment, the PMGI and photoresist layers have different critical dimensions, or widths. In addition, the mask may be formed using photolithographic techniques. In one embodiment, the mask may not be formed directly on the intermediate layer. For example, the mask may be formed on a planarization stop layer, such as a CMP stop layer. In another embodiment, the planarization stop layer might be provided at another time. 
     A hard mask is provided on the mask, via step  104 . For example, the hard mask provided in step  104  may include a material such as NiCr and/or Cr. Furthermore, the hard mask includes an aperture corresponding to the line in the mask. The aperture in the hard mask resides in substantially the position occupied by the line. In one embodiment, step  104  includes depositing a hard mask layer, then removing the line for the mask without removing all of the hard mask layer. For example, in one embodiment, the line may be removed for example through a lift-off process. Substantially only the portion of the hard mask layer on the line would be removed. Thus, the aperture in the hard mask corresponding to the line may be provided. 
     A trench is formed in the intermediate layer under the aperture, via step  106 . 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  106  includes performing a RIE. 
     A PMR pole is provided, via step  108 . 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  108  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. The nonmagnetic layer may also be used to adjust the height of the PMR pole. The PMR pole would reside on such a nonmagnetic layer. In one embodiment, the nonmagnetic layer may be provided using atomic layer deposition (ALD). A seed layer for the PMR pole may also be provided, for example on the nonmagnetic layer. In another embodiment, the nonmagnetic 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 line having undercut sides 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. In one such embodiment, the line and thus the PMR pole may have a critical dimension on the order of fifty nanometers or less. Consequently, a low critical dimension PMR pole may be formed. 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. In addition to improved resolution, formation of the line in the mask in step  102  may have improved depth of focus and greater robustness than for the conventional method  10 . Moreover, in one embodiment, the hard mask may be formed in step  104  using a lift-off of the line for the mask. Variations in the critical dimension of the hard mask may thus be reduced because the hard mask may be formed in step  104  without the use of an ion beam etch. Consequently, processing may be simplified and more readily extended to higher resolutions. The higher resolution PMR transducer may thus be made more manufacturable. 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. 4-12  are diagrams depicting an exemplary embodiment of a PMR transducer  200  as viewed from the ABS during fabrication. For clarity,  FIGS. 4-12  are not to scale. Referring to  FIGS. 3-12 , 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 PMR pole layer(s) and planarization stop layer(s). 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 planarization stop layer is provided on the intermediate layer, via step  152 . In one embodiment, the planarization stop layer is a CMP stop layer and may include materials such as Ta and/or Ru. 
     A mask having undercut side(s) is provided on the CMP stop layer, via step  154 . The mask includes a line that corresponds to the location of the PMR pole. Moreover, the side(s) of the line are undercut. Consequently, the bottom of the line has a smaller width than the top of the line. In one embodiment, the undercut is sharp. However, in another embodiment, the undercut may not be.  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. The underlayer  22  may include materials such as NiCr. In addition, an intermediate layer  204  is also depicted. The PMR transducer  200  also includes a planarization stop layer  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 mask  208  includes undercuts  209 . In the embodiment shown, the mask  208  is a bilayer having layers  210  and  212 . The lower layer  210  has a smaller critical dimension, or width, than the top layer  212 . For example, the line may include a PMGI layer  210  and a photoresist layer  212 . However, in another embodiment, the undercuts  209  might be achieved in another manner. 
     A hard mask layer is provided on the PMR transducer  200 , via step  156 . More specifically, the hard mask layer may be deposited on the mask  208 . In one embodiment, step  158  includes deposition of a material such as NiCr and/or Cr, for example using an ion beam deposition process.  FIG. 6  depicts the PMR transducer  200  after step  156  is performed. Thus, a hard mask layer  214  has been provided. Because of the geometry of the mask  208 , particularly the undercuts  209 , the hard mask layer  214  is discontinuous. Thus, the hard mask  214  includes portions  214 A,  214 B, and  214 C. 
     The line  208  is removed, via step  158 . In an embodiment in which other structures (not shown) are present for the mask  208 , step  158  may be performed such that only the line  208  is removed. In another embodiment, the entire mask  208  may be removed. In one embodiment, a lift-off process is used in step  158 .  FIG. 7  depicts the PMR transducer  200  after step  158  is completed. Because the line  208  has been removed, the portion  214 C of the hard mask layer  214  has also been removed. Consequently, hard mask  214 ′ remains. The hard mask  214 ′ includes portions  214 A and  214 B. The hard mask  214 ′ include aperture  216  that corresponds to the line  208 . The aperture  216  resides in substantially the position occupied by the line  208 . 
     A RIE is performed to form a trench in the intermediate layer  204 , via step  160 . In one embodiment, the RIE is performed utilizing a Cl-containing gas. The RIE performed in step  204  removes both the exposed portion of the planarization stop layer  206  and at least a portion of the underlying intermediate layer  204 .  FIG. 7  depicts the PMR transducer after step  160  is performed. Thus, an aperture  218  has been formed in the planarization stop layer  206 ′. Further, a trench  220  has been formed in the intermediate layer  204 ′. The aperture  218  and the trench  2220  are formed under the aperture  216 . The trench  220  has a bottom and a top wider than the bottom. In addition, the trench  220  is shown as extending through the intermediate layer  204 ′, exposing the layer  202 . However, in an alternate embodiment, the trench  220  may not extend through the intermediate layer  204 ′. 
     The PMR pole is then formed. This may occupy a number of steps. In one embodiment, a nonmagnetic layer is provided in the trench  220 , via step  162 . At least a portion of the nonmagnetic layer resides in the trench  220 . In one embodiment, step  162  may be performed using ALD. However, in another embodiment, another method for providing the nonmagnetic layer may be used. Alternatively, step  162  might be omitted. 
       FIG. 8  depicts the PMR transducer  200  after step  162  is performed. Thus, a nonmagnetic layer  222  has been deposited. Because the nonmagnetic layer  222  is magnetically separate from the pole being formed, the nonmagnetic layer  222  may be used to reduce the critical diameter of the PMR pole. Stated differently, the nonmagnetic layer may be considered to make the trench  220  less wide and, in one embodiment, shallower. Thus, the thickness of the nonmagnetic layer  222  may be used to tune the width and height of the PMR pole being formed. The width the PMR pole being formed may be reduced by twice the thickness of the nonmagnetic layer  222 , while the height of the PMR pole is reduced by the thickness of the nonmagnetic layer. For example, in one embodiment, the nonmagnetic layer  222  might be at least fifty and not more than four hundred Angstroms. Consequently, use of a nonmagnetic layer  222  in such an embodiment allows the width of the PMR pole being formed to be reduced by one hundred to eight hundred Angstroms. 
     A seed layer may optionally be provided on the nonmagnetic layer  222 , via step  164 . 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 nonmagnetic stop layer may function as a single layer or be merged into a single layer.  FIG. 9  depicts the PMR transducer  200  after step  164  is performed. Thus, the nonmagnetic layer  222  and a seed layer  2224  are shown. A portion of each of the nonmagnetic layer  222  and the seed layer  224  resides in the trench  220 . However, another portion of each of the nonmagnetic layer  222  and the seed layer  2224  also resides on and next to the hard mask  214 ′ and the planarization stop layer  206 ′. Thus, a portion of the nonmagnetic layer  222  and a portion of the seed layer  224  are above the top of the intermediate layer  204 ′ 
     A PMR pole layer(s) may be provided, via step  166 . Step  166  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  166 . 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 seed layer  224  and/or the nonmagnetic layer  222 .  FIG. 10  depicts the PMR transducer  200  after step  166  is performed. For simplicity, the apertures  216  and  218  are no longer separately labeled. Thus, the PMR pole layer  226  resides in the trench  220 . However, another portion of the PMR pole layer  226  also resides on and next to the hard mask  214 ′ and the planarization stop layer  206 ′. Thus, a portion of the PMR pole layer  226  is above the top of the intermediate layer  204 ′. 
     A CMP, or other planarization selected, is performed, via step  168 . The CMP planarization may terminate when at least a portion of the planarization stop layer  206 ′ remains. In addition, an ion beam etch or other processing might also be performed in step  168  to further configure the geometry of the PMR pole.  FIG. 11  depicts the PMR transducer  200  after step  168  has been performed. Consequently, the PMR pole  226 ′ has been formed from the PMR pole layer(s)  226 . In addition, a portion of the nonmagnetic layer  222  and a portion of the seed layer  224 , if present, have been removed. Consequently, only portions of the seed layer  224 ′ and nonmagnetic layer  222 ′ remain. In the embodiment shown, only a portion of the PMR pole  226 ′ resides within the trench  220 . This portion of the PMR pole  226 ′ 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  226 ′. A remaining portion of the PMR pole  226 ′ is next to the planarization stop layer  206 ′ and remaining portions of the nonmagnetic layer  222 ′ and seed layer  224 ′. The sidewalls for this portion of the PMR pole  226 ′ 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. 12  depicts the PMR transducer  200  after such structures are provided. Thus, the write gap  228  and top shield  230  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 line  208  having undercuts  209  in the side to provide the aperture  216  in the hard mask  214 ′. Use of a line  208  may have improved resolution. In one embodiment, the line  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  226 ′ 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. In one such embodiment, the critical dimension may be fifty nanometers or less. 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. In addition, the lift-off process used to remove the line  208 ′ may eliminate etching of the hard mask layer  214 . Thus, variations in the critical dimension of the aperture  216  may be reduced. Further, processing is simplified. Use of the nonmagnetic layer  222  and/or seed layer  224  may allow for further tailoring of the critical dimension of the PMR pole  226 ′. Consequently, processing may be simplified and more readily extended to higher resolutions. The higher resolution PMR transducer  200  may thus be made more manufacturable.