Abstract:
A method for providing a perpendicular magnetic recording (PMR) head is disclosed. The method comprises: providing an insulating layer; covering the insulating layer with a hard mask material; forming a pre-defined shape in the hard mask material; forming a pole trench and a yoke area in the insulating layer by a first reactive ion etching (RIE) process in which the yoke area includes a loading prevention pattern; performing a wet etching process to remove the hard mask material from the pole trench and the yoke area; performing a second RIE process to remove the loading prevention pattern of the yoke area, wherein the pole trench and the remainder of the yoke area are not removed and remain having similar side wall angles; and providing a PMR pole in which at least a portion of the PMR pole resides in the pole trench.

Description:
BACKGROUND 
     A huge market exists for disk drives for mass-market computing devices such as desktop computers and laptop computers, as well as small form factor (SFF) disk drives for use in mobile computing devices (e.g. personal digital assistants (PDAs), cell-phones, digital cameras, etc.). To be competitive, a disk drive should be relatively inexpensive and provide substantial capacity, rapid access to data, and reliable performance. 
     One example of a disk drive is a hard disk drive. A conventional hard disk drive includes a rotating magnetic disk, write and read heads that are suspended by a suspension arm adjacent to a surface of the rotating magnetic 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 located on a slider that has an air bearing surface (ABS). The suspension arm biases the slider towards the surface of the disk, and when the disk rotates, air adjacent to the disk moves along with the surface of the disk. The slider flies over the surface of the disk on a cushion of the moving air. 
     When the slider rides on the air bearing, the write and read heads are employed for writing magnetic transitions to and reading magnetic transitions from the rotating disk. The read and write heads are connected to processing circuitry that operates according to a program to implement writing and reading functions. 
     Perpendicular magnetic recording (PMR) transducers are now being utilized to increase the data density of hard disk drives. Such perpendicular magnetic recording transducers record magnetic bits of a data in a direction that is perpendicular to the surface of the magnetic disk. A write head is used that generally includes a write pole having a relatively small cross section at the air bearing surface (ABS) and a return pole having a larger cross section at the ABS. A magnetic write coil induces a magnetic flux to be emitted from the write pole in a direction generally perpendicular to the plane of the magnetic disk. 
     Thus, a conventional magnetic recording head may include a PMR transducer residing on the slider. As previously described, the slider also includes an air-bearing surface (ABS) that faces the disk. A conventional PMR transducer may include a PMR pole and a top shield separated by a write gap. The top shield may also act as a pole during writing. The conventional PMR pole may be surrounded by an insulating layer. Similarly, the top shield may also be surrounded by another insulating layer. 
     The conventional PMR pole may have sidewalls. In some applications, the height of the conventional PMR pole may be less than approximately three-tenths micrometer. The conventional PMR pole may also have a negative angle such that the top of the conventional PMR pole is wider than the bottom of the conventional PMR pole. Stated differently, the angle of the sidewalls may be less than 90 degrees. A pole having this height and shape is desirable for use in PMR applications. 
     However, in the case of conventional PMR pole fabrication, when a reactive ion etching (RIE) process is used in an insulating layer, an undesirable sidewall angle difference between the yoke and trench occurs due to an inevitable RIE loading effect caused by the different etching area between the trench area and the yoke area. Unfortunately, because of the sidewall angle difference between the yoke area and the trench area, the overall writing performance of the PMR pole of the write head is decreased. 
     Accordingly, there is a need for an improved PMR pole fabrication method in which the sidewalls of both the yoke area and trench area are formed having similar sidewall slopes. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a flow chart illustrating a method to fabricate a PMR transducer, according to one embodiment of the invention. 
         FIG. 2  is a diagram that illustrates a top view of the yoke area and the pole trench area and cross-sectional views of the yoke area and the pole trench area, according to one embodiment of the invention. 
         FIG. 3  is a diagram illustrating top views of the pole trench area and the yoke area and cross-sectional views of the pole trench and yoke area in order to illustrate steps to remove the loading prevention pattern from the yoke area, according to one embodiment of the invention. 
         FIG. 4  illustrates a portion of a PMR transducer as viewed toward the air-bearing surface (ABS) that may be formed by the previously-described processes, according to one embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION 
     In the following description, various embodiments of the invention will be described in detail. However, such details are included to facilitate understanding of the invention and to describe exemplary embodiments for implementing the invention. Such details should not be used to limit the invention to the particular embodiments described because other variations and embodiments are possible while staying within the scope of the invention. Furthermore, although numerous details are set forth in order to provide a thorough understanding of the present invention, it will be apparent to one skilled in the art that these specific details are not required in order to practice the present invention. In other instances details such as, well-known methods, devices, procedures, components, electrical structures, circuits, etc., related to the fabrication of PMR transducers and PMR transducers themselves are not described in detail, or are shown in block diagram or reduced form, in order not to obscure the present invention. 
       FIG. 1  is a flow chart illustrating a method  100  to fabricate a PMR transducer, according to one embodiment of the invention. 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), along with other known elements, that reside on a slider (not shown). Method  100  may commence after the formation of a first pole and the formation of layers that will reside under a second pole. Method  100  is described in the context as providing a single PMR transducer. However, method  100  may be used to fabricate multiple transducers at substantially the same time. 
     To begin with, an insulating layer is provided (block  102 ). The insulating layer may be an alumina insulating layer, according to one embodiment. In one particular embodiment, the alumina insulating layer may be an Al 2 O 3  insulating layer. The insulating layer may cover a stop layer. For example, the stop layer may be formed of Cr or NiCr or Ru material. Next, the alumina insulating layer may be covered with a hard mask material (block  104 ). For example, the hard mask material may be a NiFe material. 
     A pre-defined shape may then be formed in the hard mask material (block  106 ). After the pre-defined shape is formed, a pole trench and a yoke area may then be formed in the alumina insulating layer by a first reactive ion etching (RIE) process (block  108 ). The yoke area may include a loading prevention pattern. 
     With reference now to  FIG. 2 , a diagram  200  is shown that illustrates a top view of the yoke area  202  and the pole trench area  204  and cross-sectional views of the yoke area and the pole trench area  210 ,  220 , according to one embodiment of the invention. These cross-sectional yoke and pole trench areas are taken along lines  209  and  211 . 
     It should be appreciated that the yoke area and the pole trench area are formed from a flat wafer. In particular, first a stop layer  205  is formed. The stop layer  205  may be formed of Cr or NiCr or Ru material. An alumina insulating layer  206  is formed over the stop layer  205 . A Ta layer  207  may be formed over the alumina insulating layer  206 . A hard mask material (e.g., NiFe)  208  may then be used to cover the Ta layer  207  and the alumina insulating layer  206 . 
     In particular, as previously described, a pre-defined shape material may be formed in the hard mask material  208 . In one embodiment, a lithography pattern may form a Y-shape pre-defined shape  212  in the hard mask material  208 . Afterwards, the first RIE process is performed to form the pole trench  222  in the pole area  220  and a pair of trenches  221  in the yoke area  210  but the loading prevention pattern  203  and  213  remain. As can be seen in  FIG. 2 , both the pole trench and yoke trenches  222  and  221  have similar sidewall angles or slopes. 
     Thus, a first step of this process is to etch the pole trench  222  along with a portion of a yoke (e.g., yoke trenches  221 ) that is not covered by the loading prevention pattern  203 , and as will be described, the second step is to etch out the loading prevention pattern  203  inside the yoke. As will be described, embodiments of the invention include a deposition, wet etching, and second RIE process scheme to remove the loading prevention pattern  203  as part of damascene PMR processing. 
     As shown in  FIG. 1 , in process  100 , a wet etching process is performed to remove the hard mask material from the pole trench and the yoke area (block  110 ). Next, a second RIE process is performed to remove the loading prevention pattern of the yoke area (block  112 ). After this, a PMR pole may be provided (block  114 ) and a write gap may be provided (block  116 ). Further, a top shield may be provided (block  118 ). 
     Turning now to  FIG. 3 ,  FIG. 3  is a diagram  300  illustrating top views of the pole trench area  204  and the yoke area  202  and cross-sectional views of the pole trench and yoke area  220  and  210  in order to illustrate steps ( 310 ,  320 ,  330 , and  340 ) to remove the loading prevention pattern  203  from the yoke area, according to one embodiment of the invention. At step  310 , a wet etching process is performed to remove the hard mask material  208  from the pole trench area  220  and the yoke area  210 . For example, the wet etch process may be utilized to remove the NiFe hard mask material. 
     Next, at step  320 , a photo-resist process is performed to cover the pole trench area  220  and the yoke area  210 , excluding the loading prevention pattern  203  of the yoke area  210 , with photoresist material  325 . Any suitable type of photoresist material may be utilized. 
     At step  330 , a second RIE process  333  is performed to remove the loading prevention pattern  203  of the yoke area  210 . It should be noted that the pole trench  220  and the remainder of the yoke area  210  are not removed due to the photoresist material  325  covering them. It should be further noted that the pole trench  222  and the remaining yoke area trench  338  remain with similar sidewall angles  339 . 
     In one embodiment, the second RIE process to remove the loading prevention pattern  203  of the yoke area is an alumina RIE process, such as, an Al 2 O 3  RIE process. 
     Lastly, at step  340 , a lift off photoresist process may be performed to lift off the photoresist material. 
     Thus, the previously-described process  300  utilizes deposition, wet-etching and RIE processing to remove the loading prevention pattern  203  for damascene PMR processing. Accordingly, as previously described, in one embodiment, the first step includes the first Al 2 O 3  RIE process which generates the pole trench and the yoke area trench having a loading prevention pattern inside the yoke trench, and the second step includes deposition, wet-etching and the second Al 2 O 3  RIE process to remove the loading prevention pattern  203 . 
     Embodiments of the invention therefore relate to a damascene process utilizing an alumina RIE process to generate a pole trench and a yoke area. A two-set patterning and etching process is used to prevent the RIE loading effect that generates an undesirable sidewall angle difference between the yoke areas and the pole trench areas. In particular, the previously described process removes the loading prevention pattern  203  inside the yoke area. 
     It has been found that by first utilizing NiFe as the hard mask material that the NiFe hard mask material can then be successfully removed by wet-etching. This wet-etching may then be followed by a second alumina RIE process to remove all the alumina inside the yoke area including the loading prevention pattern of the yoke area. Further, it should be noted that these patterning and etching processes are relatively simple and easy to implement and that these tools and materials are basic fabrication tools and materials. 
     With reference now to  FIG. 4 ,  FIG. 4  illustrates a portion of a PMR transducer  400  as viewed toward the air-bearing surface (ABS) that may be formed by the previously-described processes. In particular, the PMR transducer  400  may include a base layer  416 , an alumina insulating layer  420  having a PMR pole  418  formed with embodiments of the previously-described invention, a write gap  426 , and a top shield  428 . 
     In particular, PMR pole  418  may have sidewalls  422  and  424 . These sidewalls  422  and  424  may be formed as part of the pole trench forming operations previously described. In particular, the sidewall angles of the pole trench area and the yoke area are formed, as previously described, such that they have similar sidewall angles or slopes which improve the overall performance of the PMR transducer, and in particular, create better writing performance. 
     Using the previously-described methods, PMR pole  418  may be provided using a damascene process. In particular, because the pole trench and yoke areas are formed having similar sidewall angles, the performance of the PMR transducer  400  is improved.