Abstract:
Methods for fabricating TMR and CPP GMR magnetic heads using a chemical mechanical polishing (CMP) process with a patterned CMP conductive protective layer for sensor stripe height patterning. The method comprises defining a stripe height of a read sensor of a magnetic head reader. The method further comprises refill depositing an insulator layer on the read sensor. The method further comprises performing a CMP process down to the conductive protective layer on the read sensor deposited while defining the read sensor to remove an overfill portion of the insulator layer above the conductive protective layer and to remove a sensor pattern masking structure on the conductive protective layer. As a result, the insulator layer is planarized and smooth with the read sensor, eliminating fencing and alumina bumps typically encountered in the insulator layer at the edge of the patterned sensor.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     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) process with a patterned conductive CMP protective layer for sensor stripe height patterning. 
     2. Statement of the Problem 
     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 disk is rotated, air adjacent to the disk surface moves with the disk. This allows the magnetic 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 magnetic recording head flies on the air bearing, the actuator arm swings the suspension arm to place the magnetic 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. 
     The magnetic recording head is typically produced using thin-film deposition and patterning techniques. The magnetic head reader fabrication involves two separate patterning processes. 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 which make up a read sensor for a magnetic reader 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, etching the exposed portion of the sensor layers around the mask structure, and then removing the mask structure. 
     The mask structure is removed using a CMP assisted lift-off process. CMP protective layers (also called CMP stop layers) are deposited between various layers of the fabricated structure to protect other layers, such as sensor layers and insulation during the CMP lift-off process. These protective layers are then removed using another etching process (e.g., reactive ion etching or ion milling). 
     Problems are encountered in the prior art process because alumina bumps or fencing may occur at edges of sensor after the stripe height definition process. This added topography may cause shield shorts and sensor shunt subsequent to the track width definition process because the insulator layer is not fabricated flat with the read sensor. It is evident from the above discussion that improved solutions are needed for fabricating magnetic readers using new processes. 
     SUMMARY OF THE SOLUTION 
     The invention solves the above and other related problems with improved methods for fabricating a magnetic reader using a CMP process with a patterned CMP conductive protective layer for sensor stripe height patterning. After a sensor is patterned and an insulator layer is deposited, the CMP process is used to planarize the insulator layer. The CMP process stops at the CMP conductive protective layer. The CMP conductive protective layer may be left in place as sensor cap of a read sensor of the magnetic reader. The invention eliminates the alumina bumps typically encountered by prior art stripe height definition processes using DLC protective layers. The invention also allows for the elimination of a second protective layer (e.g., a DLC layer) used in prior art stripe height definition processes. 
     A first exemplary embodiment comprises a method for fabricating magnetic readers. The method comprises defining a read sensor of a magnetic reader. The method further comprises depositing an insulator layer on the read sensor. The method further comprises performing a CMP process down to a conductive protective layer deposited while defining the read sensor to remove an overfill portion of the insulator layer above the conductive protective layer and to remove a sensor pattern mask structure above the conductive protective layer. 
     A second exemplary embodiment of the invention comprises a method for fabricating magnetic readers. The method comprises defining a stripe height of a read sensor of a magnetic reader. The read sensor has a field on side regions of the read sensor. During the stripe height definition process a conductive protective layer is formed above a top portion of the read sensor to protect the read sensor. The method further comprises depositing an insulator layer on the read sensor. The insulator layer is deposited in the field of the read sensor to a height above the conductive protective layer. The method further comprises performing a CMP process down to the conductive protective layer. The CMP process removes an overfill portion of the insulator layer above the conductive protective layer, planarizes the insulator layer with the conductive protective layer and removes a sensor pattern mask structure above the conductive protective layer. The method further comprises defining a track width of the read sensor. The method further comprises depositing a bi-layer photo resistive structure on the magnetic reader. The method further comprises milling the magnetic reader to remove material on side regions of the bi-layer photo resistive structure. The method further comprises depositing insulator material on side regions of the bi-layer photo resistive structure. The method further comprises performing a lift-off process to remove the bi-layer photo resistive structure. As a result, the insulator layer is planarized and flush with the read sensor, eliminating fencing typically encountered at the edges of the insulator layer. 
     A third exemplary embodiment is a method for fabricating magnetic readers. The method comprises depositing sensor layers. The method further comprises depositing a conductive protective layer on the sensor layers. The method further comprises depositing a masking layer on the conductive protective layer. The masking layer is etchable for definition of a mask structure. The method further comprises etching the conductive protective layer around the mask structure to remove a portion of the conductive protective layer. The method further comprises etching the sensor layers to define a stripe height of a read sensor of the magnetic reader. The method further comprises depositing an insulator layer on the read sensor. The method further comprises performing a CMP process down to the conductive protective layer. 
     The invention may include other exemplary embodiments described below. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
       The same reference number represents the same element or similar type of element on all drawings. 
         FIG. 1  is a flow chart illustrating a prior art method for fabricating a magnetic reader, and in particular for defining the stripe height of a read sensor of the magnetic reader. 
         FIGS. 2-10  are cross-sectional views of a magnetic reader formed according to the method of  FIG. 1 . 
         FIG. 11  is a flow chart illustrating an exemplary method for fabricating a magnetic reader using a CMP process for sensor stripe height patterning. 
         FIGS. 12-16  are cross-sectional views of a magnetic reader formed according to the method of  FIG. 11 . 
         FIG. 17  is a top view of a magnetic reader formed according to the method of  FIG. 11 . 
         FIG. 18  is a flow chart illustrating an exemplary method for fabricating a magnetic reader. 
         FIGS. 19-24  are cross-sectional views of a magnetic reader formed according to the method of  FIG. 18 . 
         FIG. 25  is a top view of a magnetic reader formed according to the method of  FIG. 18 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  is a flowchart illustrating a prior art process used for defining the stripe height of a read sensor of a magnetic reader.  FIGS. 2-10  are cross-sectional views illustrating the layers of the magnetic reader during the stripe height fabrication process illustrated in  FIG. 1 . 
     In step  102  of  FIG. 1 , sensor layers  206  are deposited on shield layer  202  (see  FIG. 2 ). In step  104 , a first diamond like carbon (DLC) protective layer  302  is deposited on the sensor layers  206  (see  FIG. 3 ). In step  106 , a masking layer  402  is deposited over the first DLC protective layer  302 . In step  108 , masking layer  402  is etched in a photolithographic process to form a mask structure  402  (see  FIG. 4 ).  FIG. 4  illustrates a sensor pattern mask structure  402 . Those of ordinary skill in the art will recognize that mask structure  402  may also be formed in the field. 
     In step  110 , the first DLC protective layer  302  is etched using a reactive ion etching (RIE) process. Any exposed areas of the first DLC protective layer  302  not protected by mask structure  402  are removed by exposure to the RIE process (see  FIG. 5 ). In step  112 , sensor layers  206  are etched using an ion milling process to define read sensor  602  with desired dimensions as illustrated in  FIG. 6 . 
     In step  114 , an insulator layer  702  is deposited over read sensor  602 , as illustrated in  FIG. 7 . In step  116 , a second DLC protective layer  802  is deposited over insulator layer  702  as a stop layer for a CMP lift-off process (see  FIG. 8 ). In step  118 , a CMP lift-off process is performed down to the stop layer. The CMP lift-off process removes mask structure  402  and material deposited above mask structure  402 , such as overfill insulator material  702 . The resulting structure is illustrated in  FIG. 9 . 
     In step  120 , a second RIE process is used to remove first DLC protective layer  302  and second DLC protective layer  802 . The resulting structure is illustrated in  FIG. 10 . The prior art process described in  FIG. 1  typically encounters fencing or alumina bumps at edges of read sensor  602  fabricated by the stripe height definition process. This added topography may cause shield shorts and sensor shunts subsequent to the track width definition process because insulator layer  702  is not fabricated flush with read sensor  602 . 
       FIGS. 11-25  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. 
     As described in  FIG. 1 , the typical fabrication process for magnetic readers involves depositing various layers of a magnetic reader on a wafer substrate. Two such layers are a first and second DLC protective layer, which act as stop layers during CMP lift-off. Such protective layers are typically removed before the fabrication process is completed. An exemplary embodiment of the invention eliminates the need for a second protective layer and uses only one protective layer. A patterned and conductive protective layer forms part of the sensor cap of the read sensor. The insulator layer is polished using a CMP process to achieve a flat reader gap. Thus, the exemplary embodiment eliminates the need for deposition of an entire layer in the fabrication process, which thereby also eliminates many of the negative byproducts of such deposition and removal, such as fencing and alumina bumps. 
       FIG. 11  is a flow chart illustrating a method  1100  for fabricating magnetic readers in an exemplary embodiment of the invention. Method  1100  will be described in reference to magnetic reader  1200  in  FIGS. 12-17 . The steps of the flow chart in  FIG. 11  are not all inclusive and may include other steps not shown. Fabrication of magnetic readers 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 single magnetic reader. 
     In step  1102 , sensor layers  206  (see  FIG. 12 ) for a magnetic reader  1200  are deposited on a shield layer  202 . The sensor layers may be deposited during a stripe height definition process defining the stripe height of a read sensor of magnetic reader  1200 . 
     In step  1104 , a conductive protective layer  1202  (see  FIG. 12 ) is deposited on sensor layers  206 . Conductive protective layer  1202  acts as a stop layer during a later CMP process, and forms the sensor cap of magnetic reader  1200 . Conductive protective layer  1202  may be any suitable conductive material, such as Rhodium (Rh). Rh has a CMP material removal rate (2 Angstroms/min) that is comparable to DLC (2 Angstroms/min). The removal rate of Rh is significantly lower than other materials used in magnetic reader fabrication (e.g., Ru (60 A/min), Cr (70 A/min), Ta (1200 A/min) and Al 2 O 3  (3000 A/min)). 
     In step  1106 , a masking layer  402  is deposited on conductive protective layer  1202 . Masking layer  402  is a photo resistive layer used to define the stripe height or track width of a read sensor of magnetic reader  1200 . Masking layer  402  may be made of Duramide®, a registered trademark of Cambrex Bio Science Rockland, Inc. 
     In step  1108 , a mask structure  402  is formed from masking layer  402 . To form mask structure  402 , masking layer  402  is light exposed in a pattern to remove desired regions of masking layer  402 . 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. The resulting structure of magnetic reader  1200  is illustrated in  FIG. 12 . 
     In step  1110 , conductive protective layer  1202  is etched through mask structure  402  using an ion milling process to pattern sensor layers  206  and conductive protective layer  1202 . The ion milling process defines a read sensor  1302  of magnetic reader  1200  (see  FIG. 13 ). The defined read sensor  1302  is produced by removing portions of sensor layers  206  through the ion milling process. The etching process may define the stripe height of read sensor  1302 . Read sensor  1302  has a field on side regions of read sensor  1302 . The resulting structure of magnetic reader  1200  is illustrated in  FIG. 13 . 
     In step  1112 , an insulator layer  1402  is deposited on read sensor  1302  (see  FIG. 14 ). Insulator layer  1402  is deposited on side regions (i.e., in the field) of read sensor  1302  to a height above conductive protective layer  1202  (i.e., on read sensor  1302 ). The overfill portion of insulator layer  1402  above read sensor  1302  may then be removed during the CMP process. 
     In step  1114 , a lift-off process is performed down to conductive protective layer  1202  to remove mask structure  402  on side regions of read sensor  1302 . Any material above mask structure  402  in the field of read sensor  1302 , such as an overfill portion of insulator layer  1402  is removed with mask structure  402 . The resulting structure of magnetic sensor  1200  is illustrated in  FIG. 15 . 
     In step  1116 , a CMP process is performed to remove masking layer  402  (i.e., sensor pattern mask structure  402 ) above read sensor  1302 . The CMP process planarizes insulator layer  1402  with conductive protective layer  1202 . Overfill portions of insulator layer  1402  (see  FIG. 15 ) at a height above conductive protective layer  1202  are polished and removed. Once the CMP process stops at conductive protective layer  1202 , insulator layer  1402  will be planarized, as exemplified in  FIG. 16 . Insulator layer  1302  is thus fabricated flush with read sensor  1302  to achieve a flat reader gap. Conductive protective layer  1202  remains above read sensor  1302  and sensor layers  206  in the field area (i.e., on side regions of read sensor  1302 ). 
       FIG. 17  illustrates a top view of magnetic reader  1200 . Read sensor  1302  is below protective layer  1202  in the center portion of magnetic reader  1200 . Sensor layers  206  are below conductive protective layer  1202  in the outer portion of magnetic reader  1200 . Sensor layers  206  may be removed during the subsequent fabrication process and the resulting gap may be filled with insulator material to fabricate magnetic reader  1200  with a flat reader gap. Additionally, a track width of read sensor  1302  may be defined to complete the fabrication of read sensor  1302 . 
       FIG. 18  is a flow chart illustrating a method  1800  for fabricating magnetic readers in an exemplary embodiment of the invention. Method  1800  will be described in reference to magnetic reader  1200  in  FIGS. 12-17  and  19 - 25 . The steps of the flow chart in  FIG. 18  are not all-inclusive and may include other steps not shown. 
     In step  1802 , read sensor  1302  is etched to define a track width of read sensor  1302 . Defining a track width of read sensor  1302  may involve depositing a masking layer over magnetic reader  1200  (i.e., over conductive protective layer  1202 ) to form a mask structure, ion milling protective layer  1202  and read sensor  1302  to define the track width of read sensor  1302 , depositing an insulator layer  1904  and a hard bias layer  1902 , and then removing the mask structure.  FIG. 19  illustrates magnetic reader  1200  after completion of the track width definition process. 
     In step  1804 , a bi-layer photo resistive structure  2002  is deposited on magnetic reader  1200 . The resulting structure of magnetic reader  1200  is illustrated in  FIG. 20 . In step  1806 , an ion milling process is performed on read sensor  1200  around bi-layer photo resistive structure  2002  to remove sensor layers  206  and conductive protective layer  1202  in the field (i.e., on side regions) of read sensor  1302 . The resulting structure of magnetic reader  1200  is illustrated in  FIG. 21 . 
     In step  1808 , a refill insulator layer  2202  is deposited on magnetic reader  1200 . Refill insulator layer  2202  may be Alumina (Al 2 O 3 ), and may be deposited to a height above conductive protective layer  1202 . The resulting structure of magnetic reader  1200  is illustrated in  FIG. 22 . 
     In step  1810 , a lift-off process is performed to remove bi-layer photo resistive structure  2002 . The resulting structure of magnetic reader  1200  is illustrated in  FIG. 23 . In step  1812 , a shield layer  2402  may then be deposited on magnetic reader  1200 . The resulting structure of magnetic reader  1200  is illustrated in  FIG. 24 .  FIG. 25  illustrates a top view of magnetic sensor  1200  fabricated by method  1800 . 
     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.