Patent Publication Number: US-2009229112-A1

Title: Method of producing head slider

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to a method of producing a head slider, more precisely relates to a method of producing a head slider, which is capable of processing read-elements to have a prescribed size. 
     Head sliders are produced by the steps of: forming read-elements and write-elements on a surface of a wafer substrate, which is composed of, for example, ALTIC (Al 2 O 3 —TiC), by a film deposition process; cutting raw bars from the wafer substrate; processing air bearing surfaces of head sliders; and cutting the raw bar to form independent head sliders. 
       FIGS. 19A-25  show an outline of producing independent head sliders  20  from a wafer substrate  10 . 
       FIG. 19A  shows the wafer substrate  10 , which is a base material of the head sliders  20 .  FIG. 19B  is a sectional view of the wafer substrate  10  taken along a line A-A shown in  FIG. 19A . 
       FIG. 20A  shows the wafer substrate  10 , on which element sections  12 , each of which includes a read-element and a write-element, are formed by the film deposition process, etc.. A number of the element sections  12  are arranged in a matrix in a surface of the wafer substrate  10 .  FIG. 20B  shows a layer including the read-elements  12   a  and a layer including the write-elements  12   b , which are laminated on the wafer substrate  10 . 
     In  FIG. 21 , the wafer substrate  10 , on which the element sections  12  have been formed, is cut along array directions of the element sections  12  and divided into a plurality of blocks. Each of the blocks is a stack bar  14 , in which a plurality of raw bars are included. 
       FIG. 22  shows a step of forming raw bars  16  from the stack bar  14 . In this step, the stack bar  14  is adhered onto a support jig  15 , which is composed of an electrically conductive ceramic, and an exposed sensing surface (an air bearing surface) of the stack bar  14  is abraded on an abrasive plate  17  so as to form sensing sections having a prescribed size. 
     The sensing sections are processed by abrading the exposed sensing surface of the raw bar  16  until heights of the read elements (MR height) reach a prescribed height. For example, the abrasion process is performed with monitoring resistance values of MR elements until the resistance values reach a prescribed value. Upon reaching the prescribed resistance value, the abrasion process is stopped. 
     After completing the abrasion process, the outermost raw bars  16  in the stack bar  14  is cut from the stack bar  14  and set on a setting plate  18  (see  FIG. 23 ). A cut surface of the stack bar  14  is abraded every time the raw bar  16  is cut from the stack bar  14 , and then the new outermost raw bar  16  is cut and set on the setting plate  18 . These steps are repeated as shown in  FIG. 24 . 
     Next, step-shaped sections, which will be included in the air bearing surfaces of the head sliders, are formed in outer faces of the raw bars  16  set on the setting plate  18 . In  FIG. 24 , the step-shaped sections are formed in the outer faces of the raw bars  16 , which will be the air bearing surfaces of the head sliders. 
     Finally, the raw bar  16 , in which the air bearing surfaces of the head sliders have been processed, is adhered to a ceramic tool  19  and cut to form the independent head sliders (see  FIG. 25 ). 
     The above described conventional technology is disclosed in, for example, Japanese Patent Gazettes No. 2004-55028 and No. 2006-53999. 
     As described above, in the conventional method of producing the head slider, the raw bar is abraded until the heights of the read-elements (MR heights) reach the prescribed height. However, the conventional technology has following problems. 
     The MR heights are adjusted by abrading the entire raw bar  16 . Even if the raw bar  16  is supported by the jig  15 , the raw bar  16  is not always perfectly supported in a horizontal plane. If the raw bar  16  is waved in the height direction, the amount of abrading the raw bar  16  partially varied, so that the MR heights are partially varied in the raw bar  16 . 
     In  FIG. 22  which is an enlarged view, hardness of an ALTIC base member  10   a  of the raw bar  16  is quite different from that of materials of a read-element  12   a  and a write-element  12   b,  and an abrasion rate of the sensing section is greater than that of the base member  10   a.  Therefore, a step-shaped part is formed between the sensing section and the base member  10   a,  so a clearance between the sensing section and a surface of a storage medium cannot be shortened. 
     In the abrasion process, abrasive grains are used, so surfaces of the MR elements will be damaged. Further, smears will stick onto surfaces of the sensing sections during the abrasion process. 
     SUMMARY OF THE INVENTION 
     The present invention was conceived to solve the above described problems. 
     An object of the present invention is to provide a suitable method of producing a method of producing a head slider, which is capable of restraining variation of processing read-elements, forming the read-elements having a prescribed size, improving production yield and improving magnetoresistance characteristics. 
     To achieve the object, the present invention has following constitutions. 
     Namely, the method of producing a head slider comprises the steps of: forming grooves in a wafer substrate, wherein the grooves correspond to raw bars to be cut from the wafer substrate; filling the grooves with an insulating material; forming read-elements and write-elements on the surface of the wafer substrate, whose grooves have been filled with the insulating material; and cutting the wafer substrate, on which the read-elements and the write-elements have been formed, along the grooves so as to form the raw bars, whose base members are constituted by the wafer substrate and coated with the insulating material. 
     For example, the step of forming the read-elements and the write-elements comprises the steps of: firstly forming the read-elements; removing disused parts of the read-elements, whose boundaries are defined by positions of a prescribed MR height of the read-elements, by etching, so as to form the read-elements having the prescribed MR height; and forming the write-elements. Since the MR height of the read-elements are set by etching, the MR height thereof can be highly precisely set and forming smears, which are formed by abrasion, etc., can be prevented. 
     For example, the read-elements having the prescribed MR height are formed by the steps of: forming a resist pattern, whose opening sections correspond to the read-elements, on a surface of a film layer, in which the read-elements have been formed; and etching the film layer with using the resist pattern as a mask until the MR heights of the read-elements reach the prescribed height. In this case, the MR height of the read-elements can have a prescribed height. 
     For example, the film layer is etched by the steps of: forming grooves in the film layer until reaching the surfaces of the insulating material filling the grooves formed in the wafer substrate; and filling the grooves formed in the film layer with an insulating material. In this case, in the raw bar, the base member and the film layer too are coated with the insulating material. 
     For example, the each of the raw bars, whose base member has been coated with the insulating material, is cut from the wafer substrate by the steps of: abrading an air bearing surface of the raw bar to leave a layer of the insulating material on the air bearing surface; and cutting the raw bar from the wafer substrate. By leaving the layer of the insulating material on the air bearing surface, falling particles of the base member of the wafer substrate from the air bearing surface of the head slider can be prevented. 
     The method may further comprise the step of dry-etching surfaces of the raw bars, whose base members have been coated with the insulating material, as a finishing step. In this case, flatness of the air bearing surface of the head slider can be improved. 
     Preferably, the dry-etching step is performed with measuring electric currents passing through the read-elements so as to detect a terminal point of removing the insulating material stuck on the film layer, in which the read-elements have been formed. In this case, the insulating material coating the read-elements can be securely removed. 
     Preferably, the dry-etching step is performed with measuring resistances of the read-elements, and the dry-etching step is stopped when the resistances reach a prescribed value. In this case, the insulating material sticking on the film layer, in which the read-elements are formed, can be removed, and the read-elements can be trimmed so as to have prescribed resistance. 
     In the production method of the present invention, the surface of the base member of the raw bar is coated with the insulating material when the raw bar is cut from the wafer substrate. Therefore, the air bearing surface of the raw bar is constituted by the homogenous insulating material, the abrasion process can be highly precisely performed, variation of processing the head slider can be restrained, and the high quality head slider can be produced. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
       Embodiments of the present invention will now be described by way of examples and with reference to the accompanying drawings, in which: 
         FIG. 1  includes a plan view of a wafer substrate, in which grooves are formed, and a sectional view thereof taken along a line A-A; 
         FIG. 2  includes a plan view of the wafer substrate, in which the grooves are filled with an insulating material, and a sectional view thereof taken along a line A-A; 
         FIG. 3  includes a plan view of the wafer substrate, in which read-elements are formed, and a sectional view thereof taken along a line A-A; 
         FIGS. 4A and 4B  are explanation views showing steps of setting a MR height of the read-elements; 
         FIG. 5  includes a plan view of the wafer substrate, in which write-elements are formed, and a sectional view thereof taken along a line A-A; 
         FIG. 6  includes a plan view of stack bars cut from the wafer substrate, and a sectional view thereof taken along a line A-A; 
         FIG. 7  is an explanation view showing a step of forming a raw bar; 
         FIGS. 8A and 8B  are explanation views showing steps of processing the raw bar; 
         FIG. 9  is an explanation view of etching the insulating material; 
         FIG. 10  is an explanation view of the read-element, in which the insulating material has been removed from a surface; 
         FIG. 11  is a perspective view of the raw bar; 
         FIG. 12  is a perspective view of the raw bar, whose air bearing surface is coated with a protection film; 
         FIG. 13  is a perspective view of the raw bar, in which a resist pattern is formed on the air bearing surface so as to form an air bearing surface section; 
         FIG. 14  is a perspective view of the raw bar, in which the air bearing surface section is formed in the air bearing surface; 
         FIG. 15  is a perspective view of the raw bar, in which a resist pattern is formed on the air bearing surface so as to form a step section; 
         FIG. 16  is a perspective view of the raw bar, in which the step section is formed in the air bearing surface; 
         FIG. 17  is a plan view of the wafer substrate, in which grooves arranged in a waffle pattern are filled with an insulating material; 
         FIG. 18  is a perspective view of a head slider; 
         FIG. 19A  is a plan view of a wafer substrate, and  FIG. 19B  is a sectional view taken along a line A-A; 
         FIG. 20A  is a plan view of the wafer substrate, in which element sections are formed, and  FIG. 20B  is a sectional view thereof taken along a line A-A; 
         FIG. 21  is a plan view of stack bars cut from the wafer substrate; 
         FIG. 22  is an explanation view showing the conventional step of forming a raw bar; 
         FIG. 23  is a plan view of a setting plate, on which the raw bars are set; 
         FIG. 24  is a plan view of the raw bars, whose air bearing surfaces have been processed; and 
         FIG. 25  is an explanation views showing a step of forming independent head sliders from the raw bar. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS  
     Preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings. 
     In  FIG. 1 , grooves  20  are formed in a wafer substrate  10 , which is composed of ALTIC (Al 2 O 3 —TiC), by suitable means, e.g., cutting means, laser means. The grooves  20  are placed to correspond to raw bars to be formed, and they are extended and arranged parallel in the longitudinal direction of the raw bars. For example, each of the grooves  20  is formed on the air bearing surface side of each of the raw bars. A number of the raw bars will be formed parallel in the wafer substrate  10 , so each of the grooves  20  is formed between the adjacent raw bars. A width of the grooves  20  is about several tens of μm. 
     As shown in a sectional view of  FIG. 1  taken along a line A-A, the raw bars will be cut in the thickness direction of the wafer substrate  10 , so that one of cut surfaces of each of the raw bars will be an air bearing surface. In the process of forming the grooves  20 , a depth of each of the grooves  20  is made greater than a length of a head slider (an anteroposterior length of the head slider or a direction of streaming air on the air bearing surface). 
     The grooves  20  are filled with an insulating material, e.g., alumina. In the present embodiment, firstly a surface of the wafer substrate  10  is coated with resist  22 , and then the grooves  20  are formed in a base member  10   a  of the wafer substrate  10  together with the resist  22 . In another case, the grooves  20  may be formed by the steps of: coating the surface of the wafer substrate  10  with the resist  22 ; optically exposing and developing the resist  22  so as to form a resist pattern, in which parts corresponding to the grooves  20  are opened; and forming the grooves  20  in the opened parts of the resist pattern. 
     In  FIG. 2 , the grooves  20  are filled with an insulating material  24 , e.g., alumina, by sputtering. The resist has been removed after filling the grooves  20  with the insulating material  24 . 
     In  FIG. 3 , read-elements  26  are formed on the surface of the wafer substrate  10 . The read-elements  26  are formed by a known method. Namely, the read-elements  26  are formed by laminating magnetic films, insulating films, etc. on the surface of the wafer substrate  10 . Each of the read-elements  26  is formed for each of the head sliders. In  FIG. 3 , positions of the read-elements  26  correspond to the raw bars to be formed in the wafer substrate  10 . One line of the read-elements  26  correspond to one raw bar. In each of the head sliders, the read-element  26  is provided a position close to the air bearing surface. Thus, as shown in a sectional view of  FIG. 3  taken along a line A-A, the read-elements  26  are respectively formed on the insulating material  24  filling the grooves  20 . 
       FIGS. 4A and 4B  show the steps of processing the read-elements  26  to have a prescribed size. The present embodiment is characterized in that the size, i.e., a MR height, of the read-elements  26  is determined in the process stage of forming the read-elements  26 . 
     To form the read-elements  26  having the prescribed size, firstly the surface of the wafer substrate  10  is coated with resist  28 , and then the resist is optically exposed and developed, by a high performance photolithography apparatus, so as to form opening sections  28   a  at prescribed positions, at which the read-elements  26  will be etched or partially removed. 
     Each of the opening sections  28   a  of the resist  28  is formed to traverse the read-element  26 , and an end face of each of the opening sections  28   a  is set to define an end face of each of the read-elements  26  partially etched. Actually, the resist  28  is patterned so as to form each of the opening sections  28   a,  which corresponds to a position for etching the read-elements  26  and traverses each of the raw bars in the longitudinal direction. 
     Next, the read-elements  26  are etched, with using the patterned resist  28  as a mask, until the etched grooves reach upper faces of the insulating material  24  filling the grooves  20 . With this step, the MR heights of the read-elements  26  are determined. By etching the read-elements  26 , grooves are formed in a film layer  11 , in which magnetic layers, insulating layers, etc. are laminated. 
     Next, the resist  28  is removed, and then the grooves formed in the film layer  11  are filled with an insulating material  24   a,  which is the same as the insulating material  24  filling the grooves  20 . For example, in case of using alumina as the insulating material  24 , the grooves formed in the film layer  11  are filled with alumina by sputtering. By filling the grooves with the insulating material  24   a,  the insulating material  24   a  projects a surface of the film layer  11 , so the surface of the wafer substrate  10  is flattened by a chemical mechanical polishing method. 
     In  FIG. 4B , the surface of the wafer substrate  10  is flattened. The grooves  20  in the wafer substrate  10  are filled with the insulating material  24 ; the grooves formed in the thickness direction of the film layer  11  formed on the surface of the wafer substrate  10  are filled with the insulating material  24   a.    
     In  FIG. 5 , write-elements  30  are formed on the wafer substrate  10 , on which the read-elements  26  have been already formed. The write-elements  30  are formed at positions, each of which corresponds to the read-element  26 . The write-elements  30  too are formed by a known method. 
     In the former step, the surface of the wafer substrate  10  has been abraded and flattened. Magnetic layers, insulating layers and coils are formed in prescribed patterns so as to form the write-elements  30 . In a sectional view of  FIG. 5 , the layer including the read-elements  26  is formed on the base member  10   a  of the wafer substrate  10 , and the layer including the write-elements  30  is formed on the layer including the read-elements  26 . 
     After forming the write-elements  30 , a rear surface of the wafer substrate  10  is abraded so as to determine the length of the head sliders. As described above, the depth of the grooves  20  is greater than the length of the head sliders. So, in this step, the wafer substrate  10  is abraded beyond bottom faces of the grooves  20  formed in the wafer substrate  10 . 
     In  FIG. 6 , stack bars  32 , in each of which a plurality of the raw bars are integrated, are cut from the wafer substrate  10 . When the stack bars  32  are formed, the wafer substrate  10  is cut along the grooves  20 . 
     In a sectional view of  FIG. 6 , one raw bar is included in the stack bar  32 , but a plurality of the raw bars are integrally piled in the actual stack bar  32 . 
       FIG. 7  shows a step of cutting the raw bars  38  from the stack bar  32 . The stack bar  32  is adhered to and supported by a supporting jig  34 , which is composed of an electrically conductive ceramic, and the stack bar  32  is abraded by an abrasive plate  36 , but a layer of the insulating material is left on an air bearing surface of the stack bar  32  (raw bar  38 ). After abrading the air bearing surface of the stack bar  32 , the raw bar  38  is cut from the stack bar  32 . 
       FIGS. 8A and 8B  are enlarged explanation views, wherein one raw bar  38  in the stack bars  32  is abraded. 
       FIG. 8A  shows the raw bar  38  whose air bearing surface is not abraded. When the stack bar  32  is cut from the wafer substrate  10 , the wafer substrate  10  is cut along the groove  20 . Concretely, the wafer substrate  10  is cut along a line corresponding to end faces of disused parts, which are located on the other side of the read-elements  26  in the groove  20 . The insulating material  24  filling the groove  20  and the insulating material  24   a  filling the layer including the read-elements  26 , which is formed on the wafer substrate  10 , are exposed in the air bearing surface of the raw bar  38 . 
     By abrading the rear surface of the wafer substrate  10 , the entire surface of the base member  10   a  on the air bearing surface side are coated with the insulating material  24 , and the parts of the read-elements  26  are coated with the insulating material  24   a.    
     In the present embodiment, after cutting the stack bar  32  from the wafer substrate  10 , the air bearing surface of the stack bar  32 , which will be abraded, is coated with the insulating materials  24  and  24   a,  e.g., alumina. Therefore, the air bearing surface of the stack bar  32  has even hardness. In the layer including the write-elements  30 , magnetic layers and insulating layers composed of, for example, alumina are laminated, and hardness of the layer including the write-elements  30  is not significantly different from that of the insulating materials  24  and  24   a.    
     Therefore, unlike abrading the air bearing surface of the conventional stack bar (raw bar), the hardness of the air bearing surface of the stack bar  32  is even and lower than that of ALTIC, so that the air bearing surface of the stack bar  32  can be abraded, by the chemical mechanical polishing method, with using fine abrasive grains  37 , e.g., silica. 
     In  FIG. 8B , the stack bar  32  (raw bar  38 ) has been abraded. The abrasion process is performed until the insulating material  24   a  is slightly left on the surface of the layer including the read-elements  26 . By using the fine abrasive grains  37 , damaging the air bearing surfaces of the raw bar  38  can be prevented, remaining stress in the raw bar  38  can be prevented and the air bearing surface can be highly precisely abraded. Since the air bearing surface of the raw bar  38  is composed of the homogenous insulating materials  24  and  24   a,  the entire raw bar  38  can be evenly abraded and forming the step-shaped parts, which are formed between the base member and the element sections of the conventional raw bar, can be prevented. Further, forming smears during the abrasion process can be restrained. 
     After abrading the air bearing surface of the stack bar  32 , the outermost raw bar  38  is cut from the stack bar  32 , and then the new outermost raw bar  38  of the stack bar  32 , which has been adhered to and supported by the support jig  34 , is abraded again. Namely, the process of abrading the outermost raw bar  38  and the process of cutting the outermost raw bar  38  from the stack bar  32  are repeated in order, so that the raw bars  38 , whose air bearing surfaces have been abraded, can be obtained. 
     As shown in  FIG. 8B , in the obtained raw bar  38 , the surface of the base member  10   a  of the wafer substrate  10  on the air bearing surface side is coated with the insulating material  24 , and the insulating material  24   a  is slightly stuck on the read-elements  26 . 
       FIG. 9  shows the next step, wherein the insulating material  24   a,  e.g., alumina, slightly stuck on the read-elements  26  in the raw bar  38  is removed. 
     To remove the insulating material  24   a,  a reactive ion etching (RIE) method is used in the present embodiment as an example of a dry etching method. As shown in  FIG. 9 , the raw bars  38 , whose air bearing surfaces coated with the insulating materials  24  and  24   a  are faced upward, are set on an electrode plate  40  of a RIE apparatus, and then high-frequency voltage is applied between the electrode plate  40  and an electrode  41  so as to etch the insulating materials  24   a.    
     Purposes of the etching process is to remove the insulating material  24   a  from the surface including the read-elements  26  and to monitor resistance values of the read elements  26  and equalize the resistance values, so that the final MR height of the read-elements  26  can be determined. 
     Therefore, terminals  42  connected to the read-elements  26  are provided to each of the raw bars  38 , and a resistance measuring equipment is connected to the terminals  42  of each of the raw bars  38 . A terminal point detecting equipment  46  stops generating plasma when the insulating materials  24   a  are removed and the resistance values of the read-elements  26  reach a prescribed value (i.e., the MR heights of the read-elements  26  reach a prescribed MR height). 
     By generating plasma in the RIE apparatus, metal etching ions I and electrons E are generated therein. At the beginning of the etching process, the surfaces of the read-elements  26  are coated with the insulating materials  24   a , so no current passes through the read-elements  26  and the resistance measuring equipment  44  measures no resistance of the read-elements  26 . With the progress of the etching, the insulating materials  24   a  coating the read-elements  24   a  are gradually removed and ion currents can pass through the read-elements  26 , so that the resistance measuring equipment  44  can measure resistance values of the read-elements  26 . When the ion currents are increased with progressing the etching, the resistance measuring equipment  44  can correctly measure resistance values of the read-elements  26 . When the resistance values reach the prescribed value, the terminal point detecting equipment  46  stops the etching. 
     The resistance of the read-elements  26  can be measured when the insulating materials  24   a  stuck on the read-elements  26  are removed and the increased ion currents pass through the read-elements  26  as shown in  FIG. 10 . Further, the resistance values (MRR) are increased with etching the read-elements  26 , so the read-elements  26  can be trimmed until reaching the prescribed MR height or the prescribed resistance value. 
     Namely, by performing the etching process shown in  FIG. 9 , completely removing the insulating materials  24   a  from the read-elements  26  can be known, and the read-elements  26  can be trimmed so as to equalize the MR heights or the resistance values of the read-elements  26 . 
     Note that, the resistance values of the read-elements  26  may be equalized by the steps of: removing the insulating materials  24   a  by the RIE apparatus; and then abrading the read-elements  26 , by the known method, until the resistance values of the read-elements  26  reach the prescribed value. In this case, the ion currents passing through the read-elements may be detected by, for example, an ammeter while etching the insulating materials  24   a  by the RIE apparatus so as to detect the terminal points of removing the insulating materials  24   a,  and the etching may be stopped when the terminal points are detected. In the present embodiment too, the abrasion is executed with monitoring the resistance values of the read-elements  26  as well as the conventional method. Since the entire air bearing surface of the raw bar  38  is coated with the insulating material  24 , the abrasion process for determining the heights of the read-elements  26  can be precisely controlled. 
     After removing the insulating materials  24   a  and trimming the read-elements  26 , step-shaped sections (ABS sections and STEP sections) are formed in the air bearing surface of the head slider. 
       FIGS. 11-16  show the steps of processing the air bearing surfaces of the head sliders. Note that,  FIGS. 11-16  are enlarged perspective views of one of the head sliders included in the raw bar  38 . 
       FIG. 11  shows the surface of the raw bar  38 , which faces a storage medium. The surface of the base member  10   a  of the wafer substrate  10  is coated with the insulating material  24 , e.g., alumina. An element layer  26   a  including the read-elements  26  is formed on the bottom face of the raw bar  38 . 
       FIG. 12  shows the raw bar  38  whose surface is coated with a protection film. The protection film is composed of, for example, diamond-like carbon (DLC). 
     In  FIG. 13 , resist  48   a  and  48   b  are patterned so as to form the ABS sections (highest step-shaped sections in the air bearing surface). The resist patterns correspond to the planar shapes of the ABS sections. 
     In  FIG. 14 , the raw bar  38  is ion-milled, with using the resist  48   a  and  48   b  as masks, so as to form the ABS sections  50   a  and  50   b.  In this ion-milling step, the surface of the raw bar  38  is etched until reaching heights of the STEP sections, which are one step lower than the ABS sections. Since the surface of the raw bar  38  is coated with the insulating material  24 , the insulating material  24  is actually etched. After removing the resist  48   a  and  48   b,  the ABS sections  50   a  and  50   b  are formed into the step-shaped sections one step higher than outer regions thereof. 
     In  FIG. 15 , resist patterns  52   a  and  52   b,  which correspond to planar shapes of the STEP sections, are formed so as to form the STEP sections. To protect the ABS sections  50   a  and  50   b  while forming the STEP sections, resist patterns  52   c  and  52   s  are formed on the ABS sections  50   a  and  50   b.    
     In  FIG. 16 , the STEP sections  54   a  and  54   b  are formed, by ion milling, with using the resist patterns  52   a - 52   d  as masks. By the ion milling, peripherals of the ABS sections  50   a  and  50   b  and the STEP sections  54   a  and  54   b  become a lower region  55 , which is one step lower than the STEP sections  54   a  and  54   b . The ABS sections  50   a  and  50   b  are one step higher than the STEP sections  54   a  and  54   b.    
     After forming the ABS sections  50   a  and  50   b  and the STEP sections  54   a  and  54   b  in the air bearing surface, the raw bar  38  is adhered to and supported by the ceramic tool  19  as shown in  FIG. 25 , and then the raw bar  38  is cut to form the independent head sliders. 
     In each of the independent head sliders, the air bearing surface is coated with the insulating material  24 , and the insulating material  24  is etched to form the ABS sections  50   a  and  50   b  and the STEP sections  54   a  and  54   b  in the air bearing surface. 
     By coating the air bearing surface with the insulating material  24 , no base member  10   a  of the wafer substrate  10 , which is composed of ALTIC, is exposed in the air bearing surface, so that falling particles of the base member  10   a  of the wafer substrate  10  from the air bearing surface can be prevented. 
     In case of coating side faces of the independent head slider with an insulating material, e.g., alumina, the grooves  20  of the wafer substrate  10  are formed to correspond to the air bearing surfaces of the head sliders, and further grooves  20  are formed to correspond to side faces of the head sliders as shown in  FIG. 17 . By filling all of the grooves  20  with the insulating material, e.g., alumina, the air bearing surface and the side faces of the independent head slider can be coated with the insulating material. 
       FIG. 18  shows the independent head slider  60  cut from the raw bar. The side faces of the head slider  60  are coated with the independent material  24 . By coating the side face of the head slider  60  with the insulating material  24 , falling particles of the base member  10   a  of the wafer substrate  10  from the side faces can be prevented. Therefore, disk crush, which is caused by ALTIC particles fallen onto a surface of the storage medium, can be prevented. 
     Unlike the conventional method in which the read-elements are abraded, the method of the above described embodiment is capable of highly accurately determining the heights of the read-elements  26  by etching. The air bearing surface of the raw bar, which is substantially evenly coated with the insulating material, is abraded, so that the abrasion process can be performed with high accuracy. Further, variation of abrasion can be prevented, so that no step-shaped parts are formed between the base members and the sensing sections of the head sliders. Therefore, an amount of floating the sensing section from the surface of the storage medium can be restrained, and electromagnetic conversion characteristics of the head slider can be improved. 
     The invention may be embodied in other specific forms without departing from the spirit of essential characteristics thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.