Abstract:
The method of making the magnetic resistance element comprises the steps of: forming a first magnetizable layer, a non-magnetizable layer and a second magnetizable layer, in this order, on an insulating layer; providing a resist layer for forming a main part of the magnetic resistance element on the second magnetizable layer; etching side faces of the first magnetizable layer, the non-magnetizable layer and the second magnetizable layer to form into slope faces by ion milling from the second magnetizable layer side; forming terminals on the slope faces; and removing the resist layer, wherein a part of the first megnetizable layer which is located outside of the slope faces is left on the insulating layer when the side faces of the first magnetizable layer, the non-magnetizable layer and the second magnetizable layer are etched by ion milling.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    The present invention relates to a method of making a magnetic resistance element, which is employed in a magnetic head of a magnetic disc drive unit, etc..  
           [0002]    The magnetic resistance element is capable of detecting a magnetic field by the megnetic resistance effect, and it is employed in the magnetic head of the magnetic disc drive unit, which is capable of reading high density data from a magnetic disc. These days, the disc drive units are made smaller in size but they have large capacity of memory, further high power magnetic heads are required, so the magnetic resistance elements, in which magnetic domains are controlled by ferromagnetic layers, draw engineers&#39; attention.  
           [0003]    The magnetic resistance element, in which the magnetic domains are controlled by the ferromagnetic layers, is shown in FIG. 6. An insulating layer  10  is made of an insulator, e.g., alumina, silicon oxide. A first magnetizable layer  12  is formed on the insulating layer  10 ; a non-magnetizable layer  14  is formed on the first magnetizable layer  12 ; and a second magnetizable layer  16  is formed on the non-magnetizable layer  14 . One of the first and the second magnetizable layers  12  and  16  is a magnetic resistance layer (MR layer), and the other is a bias layer (SAL layer). The SAl layer applies a bias magnetic field to the MR layer so as to detect magnetic data with high sensivity. The non-magnetizable layer  14  is provided between the first and the second magnetizable layers  12  and  16  as a shielding layer. A Ni—Fe laver is employed as the MR layer; an alloy layer, which is made of two or more selected from a group of Ni, Fe, Cr, Rh, Co, etc., is employed as the SAL layer; and a layer made of Ta, Ti or Cr is employed as the non-magnetizable layer.  
           [0004]    Planar shapes of the first magnetizable layer  12 , the non-magnetizable layer  14  and the second magnetizable layer  16  are rectangular shapes; their side faces are formed into slope faces on which terminals  18  are formed; and they constitute a main part of the magnetic resistance element. The terminals  18  are formed on the slope faces of the main part. Since the terminals  18  are formed on the slope faces, contact area between the terminals  18  and the first and the second magnetizable layers  12  and  16  can be broader, so that resistance of the magnetic resistance element can be reduced.  
           [0005]    A conventional method of making the magnetic resistance element is shown in FIGS.  7 A- 7 C. In FIG. 7A, the insulating layer  10 , the first magnetizable layer  12 , the non-magnetizable layer  14  and the second magnetizable layer  16  are formed on a substrate, e.g., a ceramic member. The layers can be formed, in said order, by spattering.  
           [0006]    As shown in FIG. 6, in the case of the magnetic resistance element of the magnetic head, etc., the terminals  18  are formed on the side slope faces. Thus, a resist layer  20 , which is formed into a prescribed shape, is formed on an upper face of the second magnetizable layer  16 , which is the uppermost layer as a mask, then the layers are etched, with the mask of the resist layer  20 , by ion milling, as shown in FIG. 7A.  
           [0007]    In FIG. 7B, the slope faces, on which the terminals  18  are formed, are formed in the first magnetizable layer  12 , the non-magnetizable layer  14  and the second magnetizable layer  16  by ion milling. A sectional shape of the resist layer  20  has undercut sections, namely a wider section  20   a  is supported by a supporting section  20   b , which is narrower than the wider section  20   a . When ions are radiated by ion milling, the slope faces for the terminals  18  are formed by partially shading the ion radiation by the wider section  20   a ; the terminals  18  can be formed on each slope face.  
           [0008]    To form the slope faces in the first magnetizable layer  12 , the non-magnetizable layer  14  and the second magnetizable layer  16  by ion milling, They are gradually etched from the second magnetizable layer  16  toward the lower layers. In an are located outside of the slope faces on which the terminals  18  are formed, the insulating layer  10  is exposed, so the surface of the insulating layer  10  is slightly overetched, by ion milling, so as to leave no layers on the insulating layer  10 . In FIG. 7B, a symbol “L” stands for depth of overetching the insulating layer  10 .  
           [0009]    In the conventional method, to correctly etch the first magnetizable layer  12 , the non-magnetizable layer  14  and the second magnetizable layer  16  by ion milling, the etching is stopped on the basis of operator&#39;s visual observation or on the basis of required time to completely remove the first magnetizable layer  12 , which has been previously known. Therefore, the overetching of the insulating layer  10  cannot be avoided so as to completely remove the first magnetizable layer  12  from the surface of the insulating layer  10 .  
           [0010]    If the insulating layer  10  is overetched after the slope faces are formed in the first magnetizable layer  12 , the non-magnetizable layer  14  and the second magnetizable layer  16 , the insulating materials of the insulating layer  10  are scattered and stick onto the slope faces, on which the terminals  18  are formed. In FIG. 7C, the insulating materials  10   a  of the insulating layer  10  stick on the slope faces, and the terminals  18  are formed thereon.  
           [0011]    If the terminals  18  are formed on the slope faces on which the materials  10   a  have stuck, the magnetic resistance element has following disadvantages: resistance between the terminals  18  and the main part is unstable; and resistance of the magnetic resistance element must be greater.  
           [0012]    Further, the first and the second magnetizable layers are heated while forming on the insulating layer  10 , atoms of the first magnetizable layer  12  are spread in the insulating layer  10 , so that magnetic characteristic of the magnetic resistance element must be worse. In the case that the first magnetizable layer  12  is the SAL layer, if the atoms of the first magnetizable layer  12  are spread in the insulating layer  10 , magnetic characteristic of the first magnetizable layer  12  is changed, and a prescribed bias magnetic field cannot be applied.  
         SUMMARY OF THE INVENTION  
         [0013]    The present invention is invented to solve above described disadvantages of the conventional magnetic resistance elements, and an object of the present invention is to provide a method of making a magnetic resistance element, which includes the MR layer, the bias layer and the non-magnetizable layer and which has a stable magnetic characteristic and high reliability.  
           [0014]    To achive the object, the present invention has following steps.  
           [0015]    Namely, the method comprises the steps of: forming a first magnetizable layer, a non-magnetizable layer and a second magnetizable layer, in this order, on an insulating layer; providing a resist layer for forming a main part of the magnetic resistance element on the second magnetizable layer; etching side faces of the first magnetizable layer, the non-magnetizable layer and the second magnetizable layer to form into slope faces by ion milling from the second magnetizable layer side; forming terminals on the slope faces; and removing the resist layer, wherein a part of the first megnetizable layer which is located outside of the slope faces is left on the insulating layer when the side faces of the first magnetizable layer, the non-magnetizable layer and the second magnetizable layer are etched by ion milling. With this method, scattering and sticking the materials of the insulating layer onto the slope faces while the etching step can be prevented, so the highly reliable magnetic resistant element can be provided.  
           [0016]    In the method, thickness of the first magnetizable layer may be detected by an end sensor while the first magnetizable layer, the non-magnetizable layer and the second magnetizable layer may be etched by ion milling, so that the first magnetizable having a prescribed thickness can be left on the insulating layer. With this method, the thickness of the first magnetizable layer, which is on the insulating layer, can be precisely controlled.  
           [0017]    In the method, the end sensor may be capable of detecting the intensity of the light from metallic elements in the first magnetizable layer, and the ion milling may be stopped when a predetermined time is lapsed from a time point at which the end sensor detects the peak of the intensity of the light.  
           [0018]    In the method, the thickness of the first magnetizable layer left may be about 30 Å.  
           [0019]    And, another method of the present invention comprises the steps of: forming a first magnetizable layer, a non-magnetizable layer and a second magnetizable layer, in this order, on an insulating layer; providing a resist layer for forming a main part of the magnetic resistance element on the second magnetizable layer; etching side faces of the first magnetizable layer, the non-magnetizable layer and the second magnetizable layer to form into slope faces by ion milling from the second magnetizable layer side; forming terminals, each of which is formed on the insulating layer and the slope faces; and removing the resist layer, wherein an intermediate layer, whose resistivity is greater than that of the first and the second magnetizable layers, is formed between the insulating layer and the first magnetizable layer, and wherein a part of the intermediate layer which is located outside of the main part is left on the insulating layer when the main part is etched by ion milling.  
           [0020]    In the method, the intermediate layer may be made of a non-magnetizable material such as Ti, Ta, Cr.  
           [0021]    In the methods, one of the first and the second magnetizable layers is an MR layer, and the other is an SAL layer.  
           [0022]    In the method of the present invention, the magnetizable layer is left on the insulating layer when the layers are etched by ion milling, so the main part of the magnetic resistance element can be formed without sticking the insulating materials of the insulating layer onto the slope faces, on which the terminals are formed, and the magnetic resistance element having excellent magnetic characteristic and high reliability can be made. And, the magnetic resistance element having excellent magnetic characteristic can be made by providing the magnetizable layer between the insulating layer and the first magnetizable layer.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0023]    Embodiments of the present invention will now be described by way of examples and with reference to the accompanying drawings, in which:  
         [0024]    FIGS.  1 A- 1 D are explanation views showing the method of making the magnetic resistance element of an embodiment of the present invention;  
         [0025]    [0025]FIG. 2 is a graph showing change of intensity of light while etching the magnetizable layer, etc. by ion milling;  
         [0026]    [0026]FIG. 3 is a graph showing change of the intensity of the light while etching the magnetizable layer, etc. by ion milling;  
         [0027]    [0027]FIG. 4 is a graph showing change of the intensity of the light while etching the magnetizable layer, etc. by ion milling;  
         [0028]    FIGS.  5 A- 5 C are explanation views showing the method of making the magnetic resistance element of another embodiment of the present invention;  
         [0029]    [0029]FIG. 6 is a sectional view of the magnetic resistance element; and  
         [0030]    FIGS.  7 A- 7 C are explanation views showing the conventional method of making the magnetic resistance element.  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0031]    Preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings.  
         [0032]    FIGS.  1 A- 1 D are the explanation views showing the method of making the magnetic resistance element of a first embodiment of the present invention. In the method of the present embodiment, the MR layer, the bias layer and the non-magnetizable layer are formed on the insulating layer, and the layers are etched by ion milling as well as the conventional magnetic resistance element.  
         [0033]    In FIG. 1A, the first magnetizable layer  12  is formed on the insulating layer  10 ; the second magnetizable layer  16  is formed on the first magnetizable layer  12  as the MR layer. In the present embodiment, thickness of the first magnetizable layer  12 , which works as the SAL layer, is 0.01 μm; thickness of the non-magnetizable layer  14 , which is made of Ta, is 0.01 μm; thickness of the second magnetizable layer  16 , which is made of Ni—Fe alloy, is 0.01 μm. The layers are formed by spattering.  
         [0034]    The resist layer  20  is provided to form the slope faces, on which the terminals  18  are formed, and the main part of the magnetic resistance element by ion milling. The wider section  20   a  may be made of alumina instead of the resist.  
         [0035]    The characteristic point of the method of the present embodiment is that the layers are etched by ion milling and the ion milling is stopped, by an end sensor  30 , immediately before the insulating layer  10  is exposed.  
         [0036]    In FIG. 1B, the etching has been executed from the second magnetizable layer  16 , which is the uppermost layer, to the first magnetizable layer  12 .  
         [0037]    In FIG. 1C, end of the etching the first magnetizable layer  12  is detected. It is to be desired that the first magnetizable layer  12  should be removed from the surface of the insulating layer  10 . However, if the insulating layer  10  is etched by ion milling, the insulating materials will stick onto the slope faces, which are formed by etching the first and the second magnetizable layers  12  and  16 , as well as the conventional method, so the ion milling is stopped when the thickness of the first magnetizable layer  12 , which is left on the surface of the insulating layer  10 , reaches about 30 Å in the present embodiment.  
         [0038]    The thickness of the first magnetizable layer  12 , which is left on the insulating layer  10 , is about 30 Å, so the resistance of the magnetic resistance element is not badly influenced even if the terminals  18  are formed onto the insulating layer  10 . By the conventional ion milling method too, the thin first magnetizable layer  12  can be left on the surface of the insulating layer  10 . However, it is difficult to precisely control the thickness of the layer left by visual observation or time control, so the thickness of the layer left will be widely dispersed, and the characteristic of the magnetic resistance element will be influenced if the thickness of the layer left on the insulating layer  10  is thicker.  
         [0039]    In the present embodiment, the thickness of the first magnetizable layer  12 , which is left on the insulating layer  10 , can be precisely controlled by using the end sensor  30 .  
         [0040]    The end sensor  30  of the present embodiment detects intensity of light, which is radiated from metallic elements constituting the magnetizable layer while the ion milling. For example, the first and the second magnetizable layers  12  and  16  include nickel as the metallic element, so the intensity of the light radiated from nickel is analyzed while the ion milling so as to detect the thickness of the layer or layers.  
         [0041]    The results of analyzing the intensity of the light are shown in FIGS.  2 - 4 . In FIGS.  2 - 4 , the axes of abscissas indicate the time of the ion milling; the axes of ordinates indicate the intensity of the radiated light.  
         [0042]    [0042]FIG. 2 shows the change of the intensity of the light while executing the ion milling from the second magnetizable layer  16  to the first magnetizable layer  12  via the non-magnetizable layer  14 . In a part “A”, the second magnetizable layer  16  radiates the light; in a part “B”, the thickness of the second magnetizable layer  16  is gradually made thinner, the non-magnetizable layer  14  is etched, and the intensity of the light radiated from the first magnetizable layer  12  reaches the peak. Since no nickel is included in the non-magnetizable layer  14 , the intensity is minimum while etching the intermediate non-magnetizable layer  14 .  
         [0043]    As shown in FIG. 2, the intensity of the light, which is detected by the sensor  30 , changes according to the thickness of the magnetizable layers, so the thickness of the first magnetizable layer  12 , which will be left on the insulating layer  10 , can be controlled by monitoring the change of the intensity of the light after the etching reaches the first magnetizable layer  12 . For example, as shown in FIGS. 3 and 4, firstly the peak “P” of the intensity of the light while etching the first magnetizable layer  12  is detected, then the the ion milling is stopped when a predetermined time is lapsed from the peak “P”.  
         [0044]    In FIGS. 3 and 4, a symbol “T” indicates the time point at which the first magnetizable layer  12  is completely removed from the insulating layer  10  by ion milling; a symbol “S” indicates the time point at which the ion milling is stopped so as to leave the first magnetizable layer  12  whose thickness is about 30 Å on the insulating layer  10 . The end of etching the first magnetizable layer  12  can be know as described above, so the thickness of the first magnetizable layer  12 , which will be left on the insulating layer  10 , can be properly controlled by stopping the ion milling proper time prior to the end time point (the time point “T”).  
         [0045]    In the present embodiment, the peak point (the point “P”) of the intensity of the light radiated from the first magnetizable layer  12  is detected, then the ion milling is stopped when the predetermined time is lapsed from the time point “P”. The relationship between the thickness of the layers and the etching rate by ion milling are previously known, so the time point “S” at which the ion milling is stopped is selected according to products so as to precisely control the thickness of the layer left on the surface of the insulating layer  10 . FIG. 4 is the results of another example in which the thickness of the layers are different. By selecting the time point of stopping the ion milling (the time point “S”) according to products, the thickness of the layers can be properly controlled.  
         [0046]    In FIG. 1D, the etching is executed until reaching the first magnetizable layer  12 , then the terminals  18  are formed. Since the first magnetizable layer  12  left on the insulating layer  10  is quite thin, it is not shown therein. After the terminals  18  are formed, the resist  20  is melt and removed, so that the magnetic resistance element, in which the MR layer and the SAL layer are magnetically separated by the non-magnetizable layer, can be made.  
         [0047]    To control the thickness of the magnetizable layer by analyzing the intensity of the light radiated from the metallic elements in the magnetizable layer while the ion milling is much more advantageous than the conventional method, in which the thickness is controlled by visual observation or controlling the etching time. In the present embodiment, dispersion of the thickness of the first magnetizable layer  12  left on the insulating layer  10  cannot be avoided, but the degree of the dispersion of the present embodiment can be reduced to ⅓ of the conventional method&#39;s or less.  
         [0048]    By leaving the first magnetizable layer  12  on the surface of the insulating layer  10 , the insulating materials, which are scattered from the insulating layer  10  by ion milling, can be prevented to stick onto the surfaces of the first and the second magnetizable layers  12  and  16 , so that the resistance of the magnetic resistance element can be reduced. Since the degree of the dispersion of the thickness of the magnetizable layer left on the surface of the insulating layer  10  can be reduced, the magnetic resistance elements, whose dispersion of characteristics is small and which have high reliability, can be provided.  
         [0049]    In the present embodiment, the first and the second magnetizable layers  12  and  16  include nickel, so the thickness of the layers are detected on the basis of the intensity of the light radiated from nickel. Various materials may be employed in the magnetizable layers, so the thickness of the layers can be controlled by detecting the intensity of the light radiated from the metallic element, which is selected on the basis of the wave length, etc..  
         [0050]    In the present embodiment, the first magnetizable layer  12  works as the SAL layer and the second magnetizable layer  16  works as the MR layer; in the case that the first magnetizable layer  12  is MR layer and the second magnetizable layer  16  is the SAL layer, the thickness of the layers can be controlled as well.  
         [0051]    Another method, in which the magnetic resistance element is made without etching the insulating layer  10 , will be explained in FIGS.  5 A- 5 . The characteristic point of this embodiment is an intermediate layer  22 , which is formed between the insulating layer  10  and the first magnetizable layer  12  and which prevents the insulating layer  10  from being overetched while the ion milling. In FIG. 5A, the intermediate layer  22  is formed on the insulating layer  10 , and the first magnetizable layer  12 , the non-magnetizable layer  14  and the second magnetizable layer  16  are also formed on the insulating layer  10 .  
         [0052]    The intermediate layer  22  protects and prevents the insulating layer  10  from being etched while the ion milling, so it covers over a part of the insulating layer  10  to which ions are radiated while the ion milling.  
         [0053]    In FIG. 5B, the first magnetizable layer  12 , the non-magnetizable layer  14  and the second magnetizable layer  16  are etched by ion milling. The intermediate layer  22  is exposed by etching the first magnetizable layer  12 , the non-magnetizable layer  14  and the second magnetizable layer  16 , but the insulating layer  10  is covered with the intermediate layer  22  and protected from the ion milling, so the insulating layer  10  is not etched until the the intermediate layer  22  is removed by etching.  
         [0054]    Namely, the ion milling is stopped when the first magnetizable layer  12  is etched until the intermediate layer  22  is exposed, so that etching the insulating layer  10  can be prevented. To stop the etching when the first magnetizable layer  12  is removed and the intermediate layer  22  is exposed, the end sensor  30  is employed to detect the end of the first magnetizable layer  12  as well as the foregoing embodiment; further, if the thickness of-the intermediate layer  22  has proper thickness, the stop of etching may be controlled on the basis of time length of the ion milling. In the case of the time control, the insulating layer  10  is not etched even if the time length of the ion milling is set to slightly overetch the intermediate layer  22 . The thickness of the intermediate layer  22  may be about 20-100 Å.  
         [0055]    In the case of forming the intermediate layer  22 , the intermediate layer  22  must be made of a material having greater resistivity. The reason is that the terminals  18  are formed on the first and the second magnetizable layers  12  and  16  in a state in which the intermediate layer  22  is left as shown in FIG. 5C, so electric current passing between the terminals  18  via the intermediate layer  22  must be prevented. Namely, the resistivity of the intermediate layer  22  must be greater than that of the first and the second magnetizable layers  12  and  16 .  
         [0056]    The intermediate layer  22  may be made of a non-magnetizable material such as Ti, Ta, Cr, whose resistivity is twice or more as great as that of the MR layer.  
         [0057]    Note that, the first magnetizable layer  12 , the non-magnetizable layer  14 , the second magnetizable layer  16 , etc. are heated during the forming process, but the intermediate layer  22  prevents the atoms of the first magnetizable layer  12  from spreading into the insulating layer  10 . For example, in the case of forming the intermediate layer  22  on the insulating layer  10  which is made of alumina, silicon oxide, etc., the atoms of the first magnetizable layer  12  cannot spread into the insulating layer  10  even if the first and the second magnetizable layers  12  and  16  are heated. With this structure, the characteristic of the first magnetizable layer  12  can be kept even if it is heated during the forming process. It is important for the magnetic resistance elements having higher stability and reliability to keep the characteristics of the first magnetizable layer  12 , etc. during the process of making the magnetic resistance elements.  
         [0058]    The invention may be embodied in other specific forms without departing the spirit or 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.