Abstract:
Methods for fabricating magnetic sensor heads using a CMP defined hard bias to fabricate a magnetic sensor head reader with a flat reader gap. The method comprises defining a read sensor of the magnetic sensor head. The method further comprises depositing an insulator layer on the read sensor. The method further comprises performing a chemical mechanical polishing (CMP) process down to a protective layer on the read sensor deposited while defining the read sensor to remove an overfill portion of the hard bias layer above the protective layer and to remove a sensor pattern masking layer above the protective layer.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The invention is related to the field of magnetic recording head fabrication, and in particular, to improved methods of fabricating a read sensor which involve using a chemical mechanical polishing (CMP) defined hard bias and totally flat reader gap. 
         [0003]    2. Statement of the Problem 
         [0004]    Magnetic disk drive systems typically include a magnetic disk, a magnetic recording head having read and write elements, a suspension arm, and an actuator arm. As the magnetic head is rotated, air adjacent to the disk surface moves with the disk. This allows the recording head (also referred to as a slider) to fly on an extremely thin cushion of air, generally referred to as an air bearing. When the recording head flies on the air bearing, the actuator arm swings the suspension arm to place the recording head over selected circular tracks on the rotating magnetic disk where signal fields are written to and read by the write and read elements, respectively. The write and read elements are connected to processing circuitry that operates according to a computer program to implement write and read functions. 
         [0005]    The magnetic recording head read sensor is typically produced using thin-film deposition and patterning techniques. One process defines the stripe height of the read sensor, while another process defines the track width of the read sensor. In particular, the several material layers and processes which make up a read sensor for a magnetic recording head are typically formed by depositing full film sensor layers of the required materials on a wafer substrate, depositing and patterning a masking layer over the sensor layers to form a mask structure using a photolithographic process, etching the exposed portion of the sensor layers around the mask structure, and then removing the mask structure. In particular, the mask structure is removed using a chemical mechanical polishing (CMP) assisted lift-off process. Protective layers are deposited on the top of sensor layers and hard bias to protect the sensor layers during the CMP lift-off processes. These protective layers are then removed using any dry etching (e.g., reactive ion etching or ion milling) process. 
         [0006]    This prior art process has reached its limitations and problems are encountered when fabricating magnetic sensor heads with narrow track widths such as 60 microns and below for high density magnetic recording heads. First, there may not be a sufficient amount of photo resistive material left above the read sensor for the CMP lift-off process to completely remove the mask structure. Second, fencing may occur around the read sensor once the protective and masking layers are removed. Third, large reader gap flare and shield curvature occurs due to the narrow track width and thick hard bias, which may reduce reader resolution (side reading) and stability (shield curvature). 
         [0007]    It is evident from the above discussion that improved solutions are needed for fabricating magnetic sensor heads with narrow track width readers for high density magnetic recording heads. 
       SUMMARY OF THE SOLUTION 
       [0008]    The invention solves the above and other related problems with improved methods for fabricating a magnetic sensor head using a CMP defined hard bias and flat reader gap. 
         [0009]    An exemplary embodiment comprises an improved method for fabricating magnetic sensor heads in which a CMP process is utilized (1) to perform mask lift-off on the top of a patterned read sensor with a narrow track width, (2) to define a hard bias and (3) to reach a flat reader gap. A second protective layer is not deposited above the hard bias layer. Rather, the hard bias layer is deposited on side regions of a read sensor of the magnetic sensor head structure at a height above the protective layer. The overfill hard bias is removed by CMP which stops at the protective layer to define the thickness of hard bias. The protective layer may then be optionally removed through an etching process to complete the fabrication process. Advantageously, this eliminates the problems described above during the magnetic sensor head fabrication process. Further, features and aspects herein allow for the use of rhodium (Rh) as a protective layer, which is not removed during the fabrication process. Rather, the rhodium layer may be used as part of a sensor cap of a read sensor of the magnetic sensor head to achieve a totally flat reader gap. 
         [0010]    The invention may include other exemplary embodiments described below. 
     
    
     
       DESCRIPTION OF THE DRAWINGS 
         [0011]    The same reference number represents the same element or same type of element on all drawings. 
           [0012]      FIG. 1  is a flow chart illustrating a prior art method for fabricating a magnetic sensor head, and in particular for defining the track width of a read sensor of the magnetic sensor head. 
           [0013]      FIGS. 2-12  are cross-sectional views of a magnetic sensor head formed according to the method of  FIG. 1 . 
           [0014]      FIG. 13  is a flow chart illustrating an exemplary method for fabricating a magnetic sensor head using a CMP defined hard bias and flat reader gap. 
           [0015]      FIGS. 14-17  are cross-sectional views of a magnetic sensor head formed according to the method of  FIG. 13 . 
           [0016]      FIG. 18  is a flow chart illustrating another exemplary method for fabricating a magnetic sensor head with a totally flat reader gap using a CMP defined hard bias. 
           [0017]      FIG. 19  is a cross-sectional view of a magnetic sensor head formed according to the method of  FIG. 18 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0018]      FIG. 1  is a flow chart illustrating a prior art process used for defining the track width of a read sensor of a magnetic sensor head.  FIGS. 2-12  are schematic diagrams illustrating the layers of the magnetic sensor head during the track width fabrication process illustrated in  FIG. 1 . 
         [0019]    In step  102  of  FIG. 1 , sensor layers  204  are deposited on a wafer (see  FIG. 2 ). In prior art processes in which the stripe height is defined prior to the track width, the wafer may additionally comprise a stripe height under fill insulator layer  202  adjacent to the sensor layers  204 . Sensor layers  204  and insulator layer  202  are typically deposited over a shield layer (not shown). 
         [0020]    In step  104 , a first protective layer  302  is deposited on the sensor layers  204  (see  FIG. 3 ). In step  106 , a masking layer  402  is deposited over the first protective layer  302  (see  FIG. 4 ). Masking layer  402  is then patterned in a photolithographic process to form a mask structure  504  as illustrated in  FIG. 5 . 
         [0021]    In step  108 , the first protective layer  302  is etched using a reactive ion etching (RIE) process. Any exposed areas of the first protective layer  302  not protected by mask structure  504  are removed by exposure to the RIE process (see  FIG. 6 ). In step  110 , sensor layers  204  and insulator layer  202  are etched using an ion milling process to define read sensor  704  with desired dimensions as illustrated in  FIG. 7 . 
         [0022]    In step  112 , an insulator layer  802  is deposited over read sensor  704 , as illustrated in  FIG. 8 . In step  114 , a hard bias layer  902  is deposited over insulator layer  802 , as illustrated in  FIG. 9 . Additionally, a lead layer (not shown) may be fabricated over hard bias layer  902 . 
         [0023]    In step  116 , a second protective layer  1002  is deposited over hard bias layer  902  as a stop layer for a CMP process (see  FIG. 10 ). A CMP lift-off process is performed down to the stop layer. The CMP lift-off process removes mask structure  504  and material deposited above mask structure  504 . Portions of insulator layer  802 , hard bias layer  902  and second protective layer  1002  above mask structure  504  (e.g., above read sensor  704 ) are removed. The resulting structure is illustrated in  FIG. 11 . 
         [0024]    In step  118 , a second RIE process is used to remove first protective layer  302  and second protective layer  1002  as illustrated in  FIG. 12 . 
         [0025]      FIGS. 13-19  and the following description depict specific exemplary embodiments of the invention to teach those skilled in the art how to make and use the invention. For the purpose of teaching inventive principles, some conventional aspects of the invention have been simplified or omitted. Those skilled in the art will appreciate variations from these embodiments that fall within the scope of the invention. Those skilled in the art will appreciate that the features described below can be combined in various ways to form multiple variations of the invention. As a result, the invention is not limited to the specific embodiments described below, but only by the claims and their equivalents. 
         [0026]      FIG. 13  is a flow chart illustrating a method  1300  for fabricating magnetic sensor heads in an exemplary embodiment of the invention. The steps of the flow chart in  FIG. 13  are not all inclusive and may include other steps not shown. Fabrication of magnetic sensor heads is commonly performed at the wafer level, and those skilled in the art understand that wafer level fabrication is assumed even if the description and drawings refer to a magnetic sensor head. 
         [0027]    In step  1302 , sensor layers  204  (see  FIG. 2 ) for a magnetic sensor head  200  are deposited on a shield layer (not shown). The sensor layers  204  may be surrounded by insulating material  202 . Insulating material  202  may be any suitable dielectric material, such as alumina (Al 2 O 3 ) or SiO 2 . The sensor layers  204  and insulating material  202  may be deposited during a stripe height definition process defining the stripe height of a read sensor of magnetic sensor head  200  prior to defining the track width of the read sensor. The resulting structure of magnetic sensor head  200  is illustrated in  FIG. 2 . 
         [0028]    In step  1304 , a protective layer  302  (see  FIG. 3 ) is deposited on sensor layers  204 . Protective layer  302  acts as a stop layer during a later CMP process. Protective layer  302  may be any suitable material, such as carbon. The carbon may be sputtered carbon or diamond-like carbon (DLC). The resulting structure of magnetic sensor head  200  is illustrated in  FIG. 3 . 
         [0029]    In step  1306 , a masking layer  402  of  FIG. 4  is deposited on protective layer  302 . Masking layer  402  is a photo resistive layer used to define the track width of a read sensor of magnetic sensor head  200 . Masking layer  402  is etchable using reactive ion etching (RIE) for definition of a mask structure  504  (see  FIG. 5 ). 
         [0030]    To form mask structure  504 , masking layer  402  is light exposed in a pattern to remove regions of masking layer  402  to create mask structure  504 . If masking layer  402  is a positive photo resist, then masking layer  402  is light-exposed in regions to be removed. Otherwise, if masking layer  402  is a negative photo resist, then masking layer  402  is light-exposed in regions to be retained. 
         [0031]    In step  1308 , protective layer  302  is etched around mask structure  504  to remove a portion of protective layer  302  in end regions of sensor layers  204 . If carbon is used as protective layer  302 , then a reactive ion etching (RIE) process may be utilized to remove the end regions of protective layer  302 . The RIE process may be performed using any suitable etch gas, such as one containing carbon-dioxide (CO 2 ) or oxygen (O 2 ). As shown by the resulting structure of magnetic sensor head  200  in  FIG. 6 , end regions of sensor layers  204  are thereby exposed as a result of the etching process in step  1308 . 
         [0032]    In step  1310 , sensor layers  204  are etched to define a read sensor  704  of magnetic sensor head  200  (see  FIG. 7 ). The defined read sensor  704  is produced by removing portions of sensor layers  204  through the etching process. The etching process may define the track width of read sensor  704 . The etching process in step  1310  may be any suitable etching process, such as ion milling. Portions of insulating material  202  may also be removed. The resulting structure of magnetic sensor head  200  is illustrated in  FIG. 7 . 
         [0033]    In step  1312 , an insulating layer  802  is deposited on read sensor  704  (see  FIG. 8 ). In step  1314  a hard bias layer  1402  is deposited on insulating layer  802  (see  FIG. 14 ). Hard bias layer  1402  is deposited on side regions of read sensor  704  to a height above protective layer  302 . A second protective layer (e.g., a DLC layer) therefore does not need to be deposited during the fabrication process. The portion of hard bias layer  1402  (i.e., overfill hard bias) above read sensor  704  may then be removed during the CMP process to achieve a flat gap surface. The resulting structure of magnetic sensor head  200  is illustrated in  FIG. 14 . 
         [0034]    In step  1316 , a lift-off process is performed to remove mask structure  504  in the field of magnetic sensor head  200  (see  FIG. 15 ). In step  1318  of the present method, a CMP process is performed down to the stop layers. Any material above protective layer  302 , such as a portion of insulating material  802  and a portion of hard bias layer  1402  is removed with mask structure  504 . 
         [0035]    In step  1318  of method  1300 , portions of hard bias layer  1402  (see  FIG. 16 ) at a height above protective layer  302  are removed. Once the CMP process stops at protective layer  302 , hard bias layer  1402  will be planarized, as exemplified in  FIG. 16  to achieve a flat read gap. 
         [0036]    In step  1320 , remaining portions of protective layer  302  may be removed using an etching process. If carbon is used as protective layer  302 , then a reactive ion etching (RIE) process may be utilized to remove the end regions of protective layer  302 . The resulting structure of magnetic sensor head  200  is illustrated in  FIG. 17 . A second shield layer (not shown) may then be fabricated on the top of magnetic sensor head  200 . 
         [0037]    In another exemplary embodiment of the invention, protective layer  302  may comprise a conductive material, such as rhodium, which is not removed during an etching step. Rather, the rhodium remains as a sensor cap  1902  of read sensor  704  as illustrated in  FIG. 19 .  FIG. 18  is a flow chart illustrating a method  1800  for fabricating magnetic sensor heads in an exemplary embodiment of the invention in which a conductive material is used for the protective layer. The steps of the flow chart in  FIG. 18  are not all inclusive and may include other steps not shown. 
         [0038]    In step  1802 , sensor layers  204  (see  FIG. 2 ) for a magnetic sensor head  200  are deposited on a shield layer (not shown). The sensor layers  204  may be surrounded by insulating material  202 . Insulating material  202  may be any suitable dielectric material, such as alumina (Al 2 O 3 ) or SiO 2 . The sensor layers  204  and insulating material  202  may be deposited during a stripe height definition process defining the stripe height of a read sensor of magnetic sensor head  200  prior to defining the track width of the read sensor. The resulting structure of magnetic sensor head  200  is illustrated in  FIG. 2 . 
         [0039]    In step  1804 , a rhodium protective layer  302  (see  FIG. 3 ) is deposited on sensor layers  204 . Protective layer  302  acts as a stop layer during a later CMP process and forms part of a sensor cap of a read sensor of the magnetic sensor head  200 . The resulting structure of magnetic sensor head  200  is illustrated in  FIG. 3 . 
         [0040]    In step  1806 , a masking layer  402  of  FIG. 4  is deposited on protective layer  302 . Masking layer  402  is etchable for definition of a mask structure  504  (see  FIG. 5 ). 
         [0041]    In step  1808 , protective layer  302  and sensor layers  204  are etched around mask structure  504  to remove a portion of protective layer  302  in end regions of sensor layers  204  and define read sensor  704 . If rhodium is used as protective layer  302 , then an ion milling process may be utilized for the etching process. As shown by the resulting structure of magnetic sensor head  200  in  FIG. 6 , end regions of sensor layers  204  are thereby exposed as a result of the etching process in step  1808 . Portions of insulating material  202  may also be removed. The resulting structure of magnetic sensor head  200  is illustrated in  FIG. 7 . 
         [0042]    In step  1810 , an insulating layer  802  is deposited on read sensor  704  (see  FIG. 8 ). In step  1812 , a hard bias layer  1402  is deposited on insulating layer  802  (see  FIG. 14 ). Hard bias layer  1402  is deposited on side regions of read sensor  704  to a height above protective layer  302 . 
         [0043]    In step  1814 , a lift-off process is performed to remove mask structure  504  in the field of magnetic sensor head  200  (see  FIG. 15 ). In step  1316 , a CMP process is performed down to protective layer  302  to remove mask structure  504  and overfill hard bias material  902  to reach a flat surface. The resulting structure of magnetic sensor head  200  is illustrated in  FIG. 19 . The portion of protective layer  302  above read sensor  704  remains as part of a sensor cap  1902  (see  FIG. 19 ) of read sensor  704 , and protective layer  302  may also serve as the top lead as well as adjusting the gap thickness to the targeted reader gap thickness and obtain a totally flat reader gap. 
         [0044]    Although specific embodiments were described herein, the scope of the invention is not limited to those specific embodiments. The scope of the invention is defined by the following claims and any equivalents therein.