Abstract:
A magnetic slider for magnetic data recording constructed by a process that allows for careful control of seed layer and overcoat thickness. The slider is treated by a process that result in surface pits and scratches. A refill layer is used to fill in the pits and scratches, the refill layer being constructed of a material that does not include Si or carbon. An angled ion beam etching can be used to remove portions of the refill layer that extend outside of the pits and scratches. Then, a seed layer comprising Si and a protective layer comprising C are deposited over the surface. Because the refill layer does not contain either of Si or C, the thickness of the seed layer and carbon overcoat can be acurately measured and controlled, without the refill layer being mistaken for seed or overcoat material.

Description:
FIELD OF THE INVENTION 
     The present invention relates to magnetic data recording and more particularly to a novel refill process for an air bearing surface of a magnetic head. 
     BACKGROUND OF THE INVENTION 
     The heart of a computer is an assembly that is referred to as a magnetic disk drive. The magnetic 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 into contact with the surface of the disk when the disk is not rotating, but when the disk rotates air is swirled by the rotating disk. When the slider rides on the air bearing, the write and read heads are employed for writing magnetic impressions to and reading magnetic impressions from the rotating disk. The read and write heads are connected to processing circuitry that operates according to a computer program to implement the writing and reading functions. 
     A magnetoresistive sensor such as a Giant Magnetoresistive (GMR) sensor or a Tunnel Junction Magnetoresistive (TMR) sensor can be employed to read a magnetic signal from the magnetic media. The write head includes at least one coil, a write pole and one or more return poles. When a current flows through the coil, a resulting magnetic field causes a magnetic flux to flow through the write pole, which results in a magnetic write field emitting from the tip of the write pole. This magnetic field is sufficiently strong that it locally magnetizes a portion of the adjacent magnetic disk, thereby recording a bit of data. The write field, then, travels through a magnetically soft under-layer of the magnetic medium to return to the return pole of the write head. 
     The magnetic read and write heads are formed on a slider body that can be constructed of a material such as Al—Ti—C. Various processing procedures, such as polishing of the slider and ion milling used to recess the magnetic read and write heads slightly from the air bearing surface, result in surface roughness on the air bearing surface portion of the magnetic read and write heads. 
     SUMMARY OF THE INVENTION 
     The present invention provides a slider for magnetic data recording that includes a slider body having a surface with a roughness that includes troughs and peaks, and a refill material filling at least some of the troughs, the refill material being a material that does not include silicon or carbon. A seed layer comprising Si is formed over the slider body surface and refill material, and a protective overcoat comprising carbon is formed over the seed layer. 
     The seed layer can also be referred to as an adhesion layer. This layer promotes adhesion of the carbon layer. By using a refill material that does not contain either of Si or C, the thickness of the seed layer and protective overcoat can be much more easily controlled. During deposition, the thickness of the seed layer and protective overcoat can be measured and controlled using an ellipsometer. After deposition, the thickness of the seed layer and protective overcoat can be measured by a process such as XRF or Auger measurement to confirm that thickness of these layers. Because the refill layer does not contain either of Si or C, the material of the refill layer will not interfere with the measurement of the thickness of the seed layer or protective overcoat during deposition of these layers or after deposition. 
     In addition, the refill layer can be constructed of a material having a high affinity for oxygen, such as AlOx, TaOx, CrOx, TaN, CrN which will help to protect the barrier layer of the read sensor, advantageously resulting in improved sensor performance. 
     These and other features and advantages of the invention will be apparent upon reading of the following detailed description of preferred embodiments taken in conjunction with the Figures in which like reference numerals indicate like elements throughout. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For a fuller understanding of the nature and advantages of this invention, as well as the preferred mode of use, reference should be made to the following detailed description read in conjunction with the accompanying drawings which are not to scale. 
         FIG. 1  is a schematic illustration of a disk drive system in which the invention might be embodied; 
         FIG. 2  is a perspective view of an air bearing surface of a slider; and 
         FIGS. 3-6  are enlarged sectional views of a portion of the slider shown in various intermediate stages of manufacture in order to illustrate treatment of the air bearing surface of the slider. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The following description is of the best embodiments presently contemplated for carrying out this invention. This description is made for the purpose of illustrating the general principles of this invention and is not meant to limit the inventive concepts claimed herein. 
     Referring now to  FIG. 1 , there is shown a disk drive  100  embodying this invention. As shown in  FIG. 1 , at least one rotatable magnetic disk  112  is supported on a spindle  114  and rotated by a disk drive motor  118 . The magnetic recording on each disk is in the form of annular patterns of concentric data tracks (not shown) on the magnetic disk  112 . 
     At least one slider  113  is positioned near the magnetic disk  112 , each slider  113  supporting one or more magnetic head assemblies  121 . As the magnetic disk rotates, slider  113  moves radically in and out over the disk surface  122  so that the magnetic head assembly  121  can access different tracks of the magnetic disk where desired data are written. Each slider  113  is attached to an actuator arm  119  by way of a suspension  115 . The suspension  115  provides a slight spring force which biases slider  113  against the disk surface  122 . Each actuator arm  119  is attached to an actuator means  127 . The actuator means  127  as shown in  FIG. 1  may be a voice coil motor (VCM). The VCM comprises a coil movable within a fixed magnetic field, the direction and speed of the coil movements being controlled by the motor current signals supplied by controller  129 . 
     During operation of the disk storage system, the rotation of the magnetic disk  112  generates an air bearing between the slider  113  and the disk surface  122  which exerts an upward force or lift on the slider. The air bearing thus counter-balances the slight spring force of suspension  115  and supports slider  113  off and slightly above the disk surface by a small, substantially constant spacing during normal operation. 
     The various components of the disk storage system are controlled in operation by control signals generated by control unit  129 , such as access control signals and internal clock signals. Typically, the control unit  129  comprises logic control circuits, storage means and a microprocessor. The control unit  129  generates control signals to control various system operations such as drive motor control signals on line  123  and head position and seek control signals on line  128 . The control signals on line  128  provide the desired current profiles to optimally move and position slider  113  to the desired data track on disk  112 . Write and read signals are communicated to and from write and read heads  121  by way of recording channel  125 . 
     With reference to  FIG. 2 , slider  113  has an air bearing surface  202  that is configured to optimize the flight characteristics when the slider  113  flies over the surface of the magnetic disk  112 . To this end, the air bearing surface  202  can be formed with a topography that can include one or more pads  204  and/or rails  206 . The configuration of this topography can vary with design requirements. The magnetic head  121 , which includes a magnetic sensor and a magnetic write element, is formed at a trailing edge of the slider  113 . 
     The topography of the air bearing surface  202  can be formed by one or more masking and etching processes. For example, starting with a flat air bearing surface, one or more etching masks can be formed over the air bearing surface  202  so as to cover areas where raised portions are desired. Then, an etching process such as a dry or wet etching can be performed to remove portions of the air bearing surface  202  that are not protected by the etch mask. 
     In addition a polishing process and possibly an etching process can also be performed to provide a desired amount of recessing of the read and write heads. This recession of the magnetic head compensates for thermal expansion of the magnetic head during operation. Current flow through the magnetic write head during operation generates heat, which results in thermal expansion of and protrusion of the magnetic head during operation. Recessing of the read and write heads assures that a desired fly height is maintained during operation without any contact between the magnetic head and the media. 
       FIG. 3  shows a greatly enlarged cross sectional view of a portion of the slider  113  and the air bearing surface  202  in the region of the magnetic head  121 . In  FIG. 3  it can be seen that the air bearing surface has various troughs  302  and raised portions  304 . It is desirable that the air bearing surface  202  be as smooth as possible in this region. In addition, in order to protect the magnetic head  121  ( FIG. 2 ) as well as the disk from corrosion and from contact between the slider  113  and disk  112  it is desirable to deposit one or more protective layers and lubricant layers onto the air bearing surface  202 . In order for these layers to be effective it is further desirable that the air bearing surface  202  be as smooth as possible. 
     The present invention provides a process for optimizing the smoothness of the air bearing surface  202  in the area of the magnetic head  121  prior to depositing a protective layer or lubricant layer. With reference to  FIG. 4 , a refill material  402  is deposited over the air bearing surface. This refill layer is a  402  is a material that does not contain either Si or C, which is advantageous for reasons that will become clearer below. To this end, the refill layer  402  can be constructed of a material such as AlOx, TaOx, CrOx, TaN, CrN, etc. The refill layer  402  can be deposited by sputter deposition, such as ion beam deposition (IBD) or physical vapor deposition (PVD). 
     With reference now to  FIG. 5 , an angled ion beam etching process is performed to preferentially remove portions of the refill layer that extend out of the trenches, leaving a structure where the trenches are filled with refill material, but the peaks are generally exposed. This greatly smoothens the air bearing surface of the slider  113 . The ion beam etch is preferably a two step glancing angled ion beam etching, wherein a first etching is performed at an angle of 70-80 degrees (or about 75 degrees) relative to normal. This is followed by a second ion beam etching that is performed at an angle of 55-65 degrees (or about 60 degrees) relative to normal. 
     Then, with reference to  FIG. 6 , a seed layer  602  is deposited, followed by a protective overcoat layer  604 . The seed layer  602  is a Si containing material, preferably Si or SiN, which is deposited very thin, (e.g. 1-10 Angstroms). The protective overcoat layer  604  is preferably carbon or diamond like carbon (DLC), which can be deposited to a thickness of 5 to 20 Angstroms. Both the seed layer  602  and the protective overcoat  604  can be deposited by sputter deposition. The thickness of the seed layer  602  and overcoat layer  604  are important to the performance of the magnetic data recording system. The thickness of these layers  602 ,  604  contributes to the magnetic spacing between the read/write heads and the recording layer of the magnetic medium. Since the strength of the magnetic field (either being written or being read) drops off exponentially with distance, reducing the thickness of these layers  602 ,  604  greatly improves the performance of the recording system. On the other hand, these layers  602 ,  604  must be sufficiently thick to protect the slider, magnetic head and media itself from damage, and also to protect the read and write heads from corrosion. If these layers  602 ,  604  are too thin, there will invariably be places where there is no protection and the reliability of the system will suffer. 
     The thickness of the layers  602 ,  604  during deposition can be monitored and controlled by use of an ellipsometer. After deposition, the final thicknesses of the layers  602 ,  604  can be confirmed by a process such as XRF or Auger measurement. This can be used to very carefully control the thickness of the layers  602 ,  604 . It will be recalled that the refill layer  402  was constructed of a material that does not contain Si or C. This advantageously prevents the refill  402  from being detected during the measurement of the thickness of the layers  602 ,  604 . The inventors have found that, when a material such as SiN is used as the refill layer, this layer is mistakenly detected during the measurement of seed and overcoat layer  602 ,  604  thicknesses. Therefore, the use of a Si containing material such as SiN leads to inaccurate thicknesses of the layer  602 ,  604 , which as discussed above can lead to decreased performance or compromised reliability. 
     Therefore, the use of a non-silicon containing non-carbon containing material for the refill layer  402  greatly improves the control of the thickness of the layers  602 ,  604 . In addition, refill materials  402  having a high affinity for oxygen also advantageously improve sensor performance. For example, as those skilled in the art will appreciate, a TMR sensor has a barrier layer that is constructed of an oxide such as MgO, NiO or Al 2 O 3 . A refill layer  402  that is constructed of a material having a high affinity for oxygen helps to preserve the barrier layer for better sensor performance and reliability. 
     While various embodiments have been described above, it should be understood that they have been presented by way of example only and not limitation. Other embodiments falling within the scope of the invention may also become apparent to those skilled in the art. Thus, the breadth and scope of the invention should not be limited by any of the above-described exemplary embodiments, but should be defined only in accordance with the following claims and their equivalents.