Patent Publication Number: US-2004045671-A1

Title: Selective etching device

Description:
RELATED APPLICATIONS  
     [0001] The present application is based on and claims the benefit of U.S. provisional patent application Serial No. 60/409,480, filed Sep. 10, 2002, the content of which is hereby incorporated by reference in its entirety. 
    
    
     
       FIELD OF THE INVENTION  
       [0002] The present invention relates to the field of mass storage devices. More particularly, this invention relates to magnetoresistive (“MR”) heads and air bearing surfaces used in a data storage device.  
       BACKGROUND OF THE INVENTION  
       [0003] In the manufacturing of recording heads, the removal of material from the air bearing surface is a necessary process in order to define slider sensor heights. During this material removal process, a specified level of surface planarity and roughness is required to ensure proper operation of the recording head in a hard disc drive. The state of the art process for forming sensor height and maintaining acceptable surface finish is an abrasive lapping process. However, the abrasive lapping process has inherent limitations in sensor height control therefore, alternate methods have been pursued to define the slider sensor height with improved targeting capability. While these methods have shown some promise, the impact of these methods to the degradation of head surface planarity and roughness must be controlled as a requirement for implementing the technology in production.  
       [0004] A recording head is a composite of materials and the material removal rates generally depend on intrinsic chemical and physical properties. The air bearing surface includes materials such as the ceramic substrate, dielectric insulating films, and materials associated with the magnetoresistive element and writer. Some materials will have a removal rate slower than others on the air bearing surface.  
       [0005] What is needed is a method and apparatus that can be used to carefully control the rate of material removal in forming the stripe height dimension of individual MR elements within a row of MR elements, while simultaneously maintaining an acceptable level of planarity and roughness on the air bearing surface without being constrained by intricate and costly masking techniques. What is also needed is a method and apparatus for feedback control so that a property level of the MR element and the air bearing surface can be controlled during manufacture of the MR elements. What is also needed is a method and apparatus that is both reliable and quick, such that it can be used to produce MR elements and air bearing surfaces in large volume.  
       SUMMARY OF THE INVENTION  
       [0006] An apparatus for use in slider fabrication having at least one exposed substrate with an air bearing surface. The apparatus has a plurality of etching devices, wherein the plurality of etching devices is made up of a physical etch component and a chemical etch component and a controller for directing the physical etch component and the chemical etch component at the air bearing surface, wherein the physical etch component and chemical etch component are combined in a manner to provide a uniform etch rate throughout the plurality of materials 
     
    
    
     BRIEF DESCRIPTION OF THE DRAWING  
     [0007]FIG. 1 is an exploded view of a disc drive with a multiple disc stack.  
     [0008]FIG. 2 is a flow chart showing an overview of the manufacture of sliders according to the present invention.  
     [0009]FIG. 3 is a bottom view of a slider showing the air-bearing surface of a slider that includes a thin film write element and a magnetoresistive read element.  
     [0010]FIG. 4 is a schematic view of the etching device according to the present invention.  
     [0011]FIG. 5 is a front view of an embodiment of the present invention including a substrate selectively subject to a chemical and physical etch.  
     [0012]FIG. 6 is a front view of an embodiment of the present invention including a substrate selectively subject to a chemical etch and a physical etch consisting of focused ion beams.  
     [0013]FIG. 7 is a front view of an embodiment of the present invention including a substrate selectively subject to a chemical etch and a physical etch, the embodiment also including a shutter system.  
     [0014]FIG. 8 is a schematic view of a computer system. 
    
    
     DETAILED DESCRIPTION  
     [0015] In the following detailed description of the preferred embodiments, reference is made to the accompanying drawings, which form a part hereof, and in which are shown by way of illustration specific embodiments in which the invention may be practiced. It is to be understood that other embodiments may be utilized and structural changes may be made without departing from the scope of the present invention.  
     [0016] The invention described in this application is useful in any semiconductor fabrication process where it may be advantageous to control the process while it is occurring. One such process is during the removal of material from a bar of sliders  126  that will be used in a disc drive  100 . FIG. 1 is an exploded view of one type of disc drive  100 . The disc drive  100  includes a housing or base  112 , and a cover  114 . The base  112  and cover  114  form a disc enclosure. Rotatably attached to the base  112  on an actuator shaft  118  is an actuator assembly  120 . The actuator assembly  120  includes a comb-like structure  122  having a plurality of arms  123 . Attached to the separate arms  123  on the comb  122 , are load beams or load springs  124 . Load beams or load springs are also referred to as suspensions. Attached at the end of each load spring  124  is a slider  126  that carries a magnetic transducer  150 . The slider  126  with the transducer  150  form what is many times called the head. The slider  126  shown includes a transducer with a separate read element and a separate write element. On the end of the actuator arm assembly  120  opposite the load springs  124  and the sliders  126  is a voice coil  128 .  
     [0017] Attached within the base  112  is a pair of magnets  130  and  131 . The pair of magnets  130  and  131 , and the voice coil  128  are the key components of a voice coil motor that applies a force to the actuator assembly  120  to rotate it about the actuator shaft  118 . Also mounted to the base  112  is a spindle motor. The spindle motor includes a rotating portion called the spindle hub  133 . In this particular disc drive, the spindle motor is within the hub. In FIG. 1, a number of discs  134  are attached to the spindle hub  133 . In other disc drives a single disc or a different number of discs may be attached to the hub. The invention described herein is equally applicable to such other disc drives.  
     [0018] Moving the actuator assembly  120  moves all the load springs  124 . In operation, the actuator assembly  120  is moved to a park position when the disc drive is powered down. Moving the actuator to the park position causes the sliders to move to a non-data area of the disc. The non-data area is typically at the inner diameter (“ID”) of the disc  134 .  
     [0019] The present invention provides an apparatus for the formation of slider  126 . The slider  126  is shown in more detail in FIG. 3. FIG. 2 shows an overview of the process  200  for forming sliders according to the present invention. The process starts with a wafer. The first step in the process is to place the wafer in a semiconducting process machine as depicted by reference numeral  210 . While in the semiconducting process machine, magnetoresistive elements are formed on the wafer, as depicted by step  212 . The next step is to form write heads over the MR elements, as depicted by reference numeral  214 . It should be noted that a magnetic shield or shields may be placed between the magnetoresistive elements and the write heads formed. The shields may include several other layers formed by a semiconductive process. The combination of a magnetoresistive element and a write head form a transducer  150 . It should also be noted that there are a multiplicity or a very large number of transducers  150  formed on a wafer. The multiplicity of MR elements  320  and write elements  360  are organized in rows on the wafer so that the wafer may be cut or sliced to form a bar that includes a row with a plurality of transducers  150 . Once all of the transducers  150  are formed, the wafer is cut or sliced to form elongated bars containing rows of transducers of MR elements, as depicted by step  216  in process  200 . These elongated rows of transducers are placed in carriers and initially lapped to smooth the surface and provide a first rough removal of material, as depicted by step  218  in process  200 . The next step in the present invention is to remove additional material from the surface of the rowbar via a chemical and physical etch process to further define a property level of the transducer and to achieve an acceptable level of roughness and planarity of the air bearing surface, and as depicted by step  220 . A further explanation to achieve step  220  will be more fully described herein. After step  220 , the remaining features on the air-bearing surface are formed, as depicted by reference number  222  of process  200 . After forming the features, the rowbar is cut or diced into individual sliders  126 , as depicted by reference numeral  224  and process  200 .  
     [0020]FIG. 3 is a bottom view of rowbar  300 , more specifically slider  126  which shows an air-bearing surface subsequent the lapping process  220 , yet prior to the step of removing additional material  222 . Slider  126  is positioned between sliders  125  and  127 , which are only three sliders in a plurality of sliders present in a rowbar  200 . The air-bearing surface includes a leading edge  360  and trailing edge  370 , a substrate portion  380 , a transducer  150  including reading portion (MR element)  320  and writer portion  325 , and overcoat layer  350 . Substrate portion  380  may consist of Alumina Titanium-Carbide (AlTiC), the overcoat layer  350  may consist of alumina, and the transducer portion  150  generally consists of metallic and magnetic materials.  
     [0021] After lapping, a second general step for removing additional material from the lapped surface rows of transducers may be used. The second general step may be to expose all the rowbars to a general ion milling process. The bars of elongated rows of transducers are placed in a vacuum chamber and ion milled. This removes material at a slower, more controlled rate than the lapping process. The surface that is ion milled is the surface that corresponds to the air bearing surface  300  of a finished slider  126  and includes the transducer  150 .  
     [0022]FIG. 4 is a schematic view of the apparatus  400 , which is used to process a system comprising of multiple materials. One such system may be a rowbar of sliders used in data storage, which is shown in FIG. 3. Apparatus  400  includes slider  405 , a physical etch component or device  410  and a chemical etch component or device  420 . Slider  402  is essentially a cross-sectional view of slider  126  (of rowbar  300 ) in FIG. 3, including substrate portion  380 , transducer  150  and overcoat layer  350 . Physical etch component  410  can consist of an ion beam source of a type that can be either focused or collimated, which is further shown and described in FIG. 6. The physical etch component  410  can also implement a broad ion beam, which is more fully described and shown in FIG. 7. The chemical etch component  420  can be accomplished by gas-solid reactions with gas phase atoms, molecules, radicals, and/or ions. The chemical etch component  420  forms reaction byproducts that are either volatile or nonvolatile. Under certain conditions, materials in slider  402  may have a high physical sputter rate but low chemical etch rate, while other materials in slider  405  may have high chemical etch rates but low physical sputter rates. By adjusting the chemical and physical nature of the etching process, etch rate difference across several materials are reduced, thereby achieving air bearing surface requirements or desired property levels (such as planarity, cleanliness, pole tip characteristics and roughness), and the sensor definition (resistivity) requirements in one efficient and accurate processing step.  
     [0023] One example in which apparatus  400  could be implemented is as follows: Chemical etch component  420  provides a chemical flood gas locally to the air bearing surface. The gas may be comprised of, but is not limited to, O 2 , F 2 , orXeF 2 . Simultaneously, the physical etch component  410  etches the air bearing surface. The physical etch component  410  may comprise of, but is not limited to, accelerated ion species such as Ar +  and Xe + . The physical etch component  410  implements an acceleration energy approximately on the order of 100 eV to 5000 eV. The balance between the chemical and physical processes can be used to modify the etch rates of at least two of the constituent materials at the air bearing surface. In one example, two materials make up the substrate portion  380  of AlTiC. Under physically dominated etching, TiC will etch slower than Al 2 O 3 . By using a reactive flood gas, the TiC phase etch rate can be accelerated through a chemical means along with optimized partial pressure and/or flow rate of the flood gas. This concept is also applicable to the other materials on the air bearing surface (dielectrics, reader materials, writer materials) Material etch rates via chemically-assisted physical sputtering can be either enhanced or impeded relative to the etch rate from physical sputtering alone.  
     [0024] Chemical etch component  420  can also be an ionized reactive gas in which case both chemical and physical components are combined in a single source  420 . The extent of physical etching of the source  420  is varied by means of variable ion acceleration energy over a range of approximately 100 eV to 5000 eV. The chemical etch component of the source  420  is varied by the choice of reactive gas(es) and their respective partial pressure(s). The process gas may be comprised of, but not limited to, SF 6 , CF 4 , O 2 . This reactive ion source can still be used in combination with the physical etch component  410  consisting of accelerated ion species such as Ar +  and Xe +  to further extend the range of physical etch control by varying the ion acceleration energy over the range of approximately 100 eV to 5000 eV. In regard to the substrate portion  380 , comprised of AlTiC, a fluorine containing etch gas could be used to chemically-assist the etch process of the constituent TiC phase relative to the constituent Al 2 O 3  phase so that the two phases achieve an equalization in etch rates. In a similar manner, the etch rates of other materials on the air bearing surface can be manipulated in order to achieve more similar etch rates.  
     [0025]FIG. 5 is a schematic view of the apparatus  500  which is one example of how to implement apparatus  400  in order to remove material from rowbar  550  that includes a plurality of individual MR elements and write elements. The apparatus  500  includes a chemical etch component  510 , a physical etch component  520  and a carrier  512  situated within a vacuum chamber  505 . The carrier element  512  includes a stage  515 . The stage  515  moves with respect to the carrier  512 . Also included are control electronics  530 . The control electronics  530  control the chemical and physical etch components  510  and  520 , as well as the stage  512 . The chemical and physical etch components  510  and  520  are located within the vacuum chamber  505  to facilitate the fabrication of electrical devices in which the electrical performance depends upon the physical geometry of the device structure.  
     [0026] The process cycle, as described above in regard to apparatus  400 , generally includes chemically and physically etching based on known parameters for a predetermined amount of time. Parameters may include the etch rate of various materials. The control electronics  530  control the amount of time spent in each area of the rowbar  550 . Next, the etching process is stopped upon reaching a desired property level. Then, stage  515  is moved in order to redirect the etching devices  510  and  520  so that they are positioned on a new area of rowbar  300 .  
     [0027]FIG. 6 is a schematic view of the apparatus  600  which is another example of how to implement apparatus  400  in order to remove material from rowbar  550  that includes a plurality of material with varying etch rates. The apparatus  600  includes a chemical etch component  610 , a physical etch component  620  and a carrier  612 . The carrier element  612  includes a stage  615 . The stage  615  moves with respect to the carrier  612 . Also included are control electronics  630 . The control electronics  630  control the chemical and physical etch components  610  and  620 , as well as the stage  612 , and an electrical probe system which connects a probe or probes to individual transducers  152  on rowbar  650 . The electrical probes are shown or depicted by signal carrier  660 , which carries a signal related to a parameter being measured as the chemical and physical etch components  510  and  520  remove material from the air bearing surface of the rowbar  650 . The chemical and physical etch components  610  and  620  are combined within the vacuum chamber  605  to facilitate the fabrication of electrical devices in which the electrical performance depends upon the physical geometry of the device structure. Such a device is an MR element  152 . The resistivity of the MR element depends upon the stripe height of the MR element. The signal produced by the electrical probe system situated at the first area is fed back to the control electronics  630 . The signal from the probe electronics act as a feedback signal in a control loop and enables accurate targeting or specification of the magnitude of a desired electrical property or properties in the first area. As soon as the desired value of the properties of the first area is reached, the control electronics  630  stop the etching or removal of further material from the first area or the first particular device, such as an MR element  152 . Generally, the control electronics  630  will blank the etch components to the side where it will not remove material from other areas or another element or device on the rowbar  650 . The etch components are deflected until the control electronics move the stage  615  with respect to the carrier  612  so that second area will be positioned directly below the etch components. The process of removal of material using the chemical and physical etch components  610  and  620  is then repeated with the next area of the rowbar.  
     [0028] The process cycle, as described above in regard to apparatus  400 , generally includes chemically and physically etching until a desired property level of the selected area of the rowbar is reached. This is done partially by engaging the electrical probe  660  to one of the pads of the transducer  152 , then etching the transducer to an electrical end point where a particular electrical property being measured by the probe is at a desired level. The next step is to stop the etch upon reaching the end point and then disconnect the probe to devise a contact and then move the stage  615  or redirect the etching components  610  and  620  so that it is positioned on a new area which includes a new MR element or device to which the electrical probe  660  has been attached.  
     [0029] One skilled in the art will appreciate that certain aspects of FIGS. 5 and 6 may be altered without departing from the present invention. For instance, the chemical and physical etch devices  510  and  520  may be positioned differently in relation to the rowbar  750  in order to optimize certain etching angles. Also, the number of carriers, stages, probes, etch components, may be changed and still obtain the advantages realized by the present invention.  
     [0030]FIG. 7 is a schematic view of another apparatus  700  for selectively removing material from devices as contemplated by apparatus  400 . Apparatus  700  is similar in operation to the apparatus  600  shown in FIG. 6. Rather than describe the entire apparatus in detail, for the sake of clarity, the differences between the apparatus  700  and the apparatus  600  will be discussed. Apparatus  700  includes shutter system  780  (including multiple shutters  790 ) located between chemical and physical etch components  710  and  720 . Shutter system  780  is used to cover some or all of the transducer  152 . Shutter system  700  includes a plurality of shutters  790  that can be actuated or moved between a position where a portion of the rowbar is covered and a portion of the rowbar that is not covered. Controller  730  is electrically attached to the shutter system  780 . When the desired property level is reached for a particular area of the rowbar  750 , the controller  730  sends a signal to an actuator (not shown) that moves shutter  790  over the particular area of the rowbar so as to minimize or substantially halt further removal of material from that area. More specifically, etching continues while the various shutters  790  are moved from an uncovered position to a covered position. Each shutter  780  acts like a mask in that it shields or substantially shields the portion of the rowbar from this etching process.  
     [0031] One skilled in the art will appreciate that certain aspects of FIG. 7 may be altered without departing from the present invention. For instance, the chemical and physical etch devices  510  and  520  may be positioned differently in relation to the shutter system  780  and rowbar  750  in order to optimize certain etching angles. Also, the number of shutters  780 , carriers  712 , stages  715 , probes  760 , etch components  710  and  720 , may be changed and still obtain the advantages realized by the present invention.  
     [0032]FIG. 8 is a schematic view of a computer system  800  used as part of the control electronics. The computer system  800  may also be called an electronic system or an information handling system and includes a central processing unit, a memory and a system bus. The information handling system includes a central processing unit  804 , a random access memory  832 , and a system bus  830  for communicatively coupling the central processing unit  804  and the random access memory  832 . The information handling system  802  may also include an input/output bus  810  and several devices peripheral devices, such as  812 ,  814 ,  816 ,  818 ,  820 , and  822  may be attached to the input output bus  810 . Peripheral devices may include hard disc drives, magneto-optical drives, floppy disc drives, monitors, keyboards and other such peripherals. Any type of disc drive may use the slider having the surface treatment discussed above. The computer system is programmable and acts in response to program instructions. A software program is loaded onto the computer system  800 . The software program provides control functions which a user can use to select and implement the various processes described in the above paragraphs.