Abstract:
The magnetoresistance effect film is capable of shortening time of ion mill treatment and improving resolution of a read-element. The magnetoresistance effect film includes a protection layer, which protects a magnetic layer and which is constituted by a specular layer and a cap layer. The specular layer and cap layer are made of the same metallic material, and the metallic material of the specular layer is oxidized.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     The present invention relates to a magnetoresistance effect film and a method of manufacturing the magnetoresistance effect film, more precisely relates to a magnetoresistance effect film, which is capable of shortening time of ion mill treatment and improving resolution of a read-element, and the method of manufacturing the magnetoresistance effect film.  
         [0002]     A constitution of a conventional GMR (giant magnetoresistance) film, which is an example of magnetoresistance effect film used in a magnetoresistance effect element, is shown in  FIG. 4 . The GMR film is formed by piling a seed layer  8 , an antiferromagnetic layer  7 , a pinned layer  6 , an intermediate layer  5 , a free layer  4 , a back layer  3 , a specular layer  2  and a cap layer  1  in that order.  
         [0003]     Various types of GMR films are used. For example, the seed layer  8  is made of NiCr; the antiferromagnetic layer  7  is made of PdPtMn; the pinned layer  6  is made of CoFe/Ru/CoFe; the intermediate layer  5  is mede of Cu; the free layer  4  is made of CoFe/NiFe; and the back layer  3  is made of Cu. Further, for example, the specular layer  2  is made of a plasma oxide film of Al; and the cap layer  1  is made of a plasma oxide film of Ta. The plasma oxide film of Al of the specular layer  2  is Al 2 O 3 , which is oxidized by the steps of: forming an Al film on the back layer  3 ; introducing Ar and oxygen into an oxidizing chamber, which is separated from a chamber for forming the Al film; and plasma-oxidizing the Al film in the oxidizing chamber.  
         [0004]      FIG. 5A  shows a step of applying resist  12  on a surface of the GMR film  10 ; and  FIG. 5B  shows a step of ion-milling the GMR film  10  so as to form a read-element. In the ion-milling step, ions are diagonally irradiated with respect to the surface of the GMR film  10 . The ions are partially sheltered by the resist  12 , so that side faces  10  and  10 b of the read-element are formed into tapered faces. Electrodes are respectively formed on the tapered faces  10 a and  10 b. By forming the tapered faces  10 a and  10 b in the GMR film  10 , the electrodes can be easily formed thereon. Further, contact area of the GMR  10  and the electrodes can be broader, so that electric connection can be secured. The above described GMR film is disclosed in Japanese Patent Gazette 2001-189503.  
         [0005]     As described above, after the GMR film  10  is formed, the side faces of the read-element are ion-milled so as to form the tapered faces  10 a and  10 b. However, the specular layer  2  of the conventional GMR film  10  is made of Al 2 O 3 , so it takes a long time to execute the ion mill treatment. Therefore, manufacturing efficiency of the conventional magnetoresistance effect film is low. One reason is that Al 2 O 3  is hard, so it cannot be easily removed by ion milling; and another reason is that the specular layer  2  is thick, so it takes a long time to execute the ion milling.  
         [0006]     As shown in  FIG. 5B , film materials  14  of the GMR film  10  stick on surfaces of the resist  12 . If a large amount of the film materials  14  stick on the resist  12 , width of the resist  12  is substantially widened, so that width of a read-core is also widened. By widening the read-core, resolution of the read-element must be lower. In the case of the conventional GMR film  10  whose specular layer  2  is made of Al 2 O 3 , it takes a long time to execute the ion milling, so that thickness of the film materials  14 , which stick on the resist  12 , is thick. Therefore, the resolution of the read-element must be lower.  
       SUMMARY OF THE INVENTION  
       [0007]     The present invention was invented to solve the problems of the conventional magnetoresistance effect film.  
         [0008]     An object of the present invention is to provide a magnetoresistance effect film, which is capable of shortening time of ion mill treatment and improving resolution of a read-element.  
         [0009]     Another object is to provide a method of manufacturing said magnetoresistance effect film.  
         [0010]     To achieve the objects, the present invention has following structures.  
         [0011]     The magnetoresistance effect film of the present invention includes a protection layer, which protects a magnetic layer and which is constituted by a specular layer and a cap layer, wherein the specular layer and cap layer are made of the same metallic material, and the metallic material of the specular layer is oxidized.  
         [0012]     On the other hand, the method of manufacturing a magnetoresistance effect film including a protection layer, which protects a magnetic layer and which is constituted by a specular layer and a cap layer, comprises the steps of: forming the specular layer, which is made of a metallic material, on the magnetic layer; oxidizing the metallic material of the specular layer; and forming the cap layer, which is made of the same metallic material.  
         [0013]     In the present invention, the metallic material may be Ta. Further, the magnetic layer may be constituted by a seed layer, an antiferromagnetic layer, a pinned layer, an intermediate layer and a free layer, which are formed in that order.  
         [0014]     In the present invention, the specular layer and the cap layer, which constitute the protection layer, are made of the same metallic material, and the material of the specular layer is oxidized. Therefore, time for forming a read-element by ion milling can be shortened, and efficiency of manufacturing the magnetoresistance effect film can be improved. Characteristics of the magnetoresistance effect film are almost equal to those of conventional films. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0015]     Embodiments of the present invention will now be described by way of examples and with reference to the accompanying drawings, in which:  
         [0016]      FIG. 1  is an explanation view showing a constitution of a GMR film manufactured by the method of the present invention;  
         [0017]      FIGS. 2A and 2B  are explanation views showing steps of forming a read-element by ion milling;  
         [0018]      FIG. 3  is a graph of GMR ratio of the GMR film;  
         [0019]      FIG. 4  is an explanation view showing a constitution of the conventional GMR film; and  
         [0020]      FIGS. 5A and 5B  are explanation views showing steps of forming the conventional read-element. 
     
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS  
       [0021]     Preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings.  
         [0022]     A constitution of a GMR film, which is manufactured by the method of the present invention, is shown in  FIG. 1 . A symbol  1  stands for a cap layer; a symbol  2  stands for a specular layer; a symbol  3  stands for a back layer; a symbol  4  stands for a free layer; a symbol  5  stands for an intermediate layer; a symbol  6  stands for a pinned layer; a symbol  7  sands for an antiferromagnetic layer and a symbol  8  stands for a seed layer. Note that, the constitution from the back layer  3  to the seed layer  8  is the same as that of the conventional GMR film shown in  FIG. 4 . The feature of the present embodiment is the cap layer  1  and the specular layer  2 , especially the specular layer  2 .  
         [0023]     In the present embodiment, for example, the seed layer  8  is made of NiCr; the antiferromagnetic layer  7  is made of PdPtMn; the pinned layer  6  is made of CoFe/Ru/CoFe; the intermediate layer  5  is made of Cu; the free layer  4  is made of CoFe/NiFe; and the back layer  3  is made of Cu. Further, the specular layer  2  is made of plasma oxide film of Ta; and the cap layer  1  is made of Ta film.  
         [0024]      FIG. 1  shows relative thickness of each layer of the GMR film of the present embodiment, and  FIG. 4  shows that of the conventional GMR film. According to  FIGS. 1 and 4 , thickness of the layers  3 - 8  shown in  FIG. 1  are equal to thickness of the layers  3 - 8  shown in  FIG. 4 .  
         [0025]     In the conventional GMR film shown in  FIG. 4 , the specular layer is made of plasma oxide film of Al; in the present embodiment, the specular film  2  is made of plasma oxide film of Ta. The plasma oxide film of Ta is formed by the steps of: forming Ta film on a surface of the back layer  3 ; and oxidizing the Ta film in an oxidizing chamber, which is separated from a chamber in which the Ta chamber has been formed. Namely, Ar and oxygen are introduced into the oxidizing chamber, then the Ta film is plasma-oxidized therein so that plasma oxide film of Ta (Ta 2 O 5 ) can be formed.  
         [0026]     In the conventional GMR film shown in  FIG. 4 , when the specular layer is formed, firstly the Al film is grown until reaching thickness of 2 nm, then the Al film is plasma-oxidized. On the other hand, in the present embodiment, the Ta film is grown until reaching thickness of 1.5 nm, then the Ta film is plasma-oxidized. Therefore, the specular layer  2  of the present embodiment is slightly thinner than the specular layer of the conventional GMR film.  
         [0027]     Further, thickness of the cap layer of the conventional GMR film is 3 nm; thickness of the cap layer  1  of the present embodiment is 1.5 nm.  
         [0028]     In comparison with the conventional specular layer made of plasma oxide film of Al, the specular layer  2  of the present embodiment, which is made of plasma oxide film of Ta, can be easily etched by ion milling. Therefore, time for etching the GMR film of the present embodiment by ion milling can be shortened.  
         [0029]     Etching rate ratio of the conventional GMR film, whose specular layer is made of plasma oxide film (Al 2 O 3 ) and whose cap layer is made of Ta, and that of the GMR film of the present embodiment, whose specular layer  2  is made of plasma oxide film (Ta 2 O 5 ) and whose cap layer  1  is made of Ta, are shown in  
                                         TABLE                                       GMR FILM OF           CONVENTIONAL   THE PRESENT           GMR FILM   EMBODIMENT                                    THICKNESS OF LAYERS   Al 2 O 3 (2 nm)/Ta(3 nm)   Ta 2 O 5 (1.5 mn)/       (SPECULAR LAYER       Ta(1.5 nm)       /CAP LAYER)           ETCHING   4   1       RATE           RATIO                      
 
         [0030]     According to the TABLE, speed of etching (or ion-milling) the GMR film of the present embodiment is four times faster than that of etching the conventional GMR film. In the present embodiment, the thickness of the specular layer  2  is thinner than that of the conventional specular layer made of Al 2 O 3 , the thickness of the cap layer  1  is also thinner than that of the conventional cap layer. However, a main reason of the difference of the etching rate ratio between the two is to employ the plasma oxide film of Ta, e.g., Ta 2 O 5 , instead of the plasma oxide film of Al because Ta can be easily ion-milled.  
         [0031]     The inventor compared time of completely etching the conventional GMR film with time of completely etching the GMR film of the present embodiment under the conditions shown in the TABLE. The time for completely etching the GMR film of the present embodiment was about 50% of the time for completely etching the conventional GMR film. According to the result, the time for ion milling the GMR film can be effectively shortened by employing the specular layer  2  made of the plasma oxide film of Ta and the cap layer  1  made of the Ta film.  
         [0032]      FIGS. 2A and 2B  show the steps of forming a read-element by ion milling the GMR film  10 , in which the specular layer  2  is made of the plasma oxide film of Ta and the cap layer  1  is made of the Ta film. In  FIG. 2A , resist  12  is applied on a surface of the GMR film  10 ; in  FIG. 2B , tapered faces  10 a and  10 b are respectively formed on both sides of a read-element by ion-milling the GMR film  10 . Since the GMR film  10  of the present embodiment can be ion-milled in a short time, amount of a film material  14  sticking on the resist  12  can be reduced so that extension of width of the resist  12  can be substantially restricted. Therefore, core width of the read-element can be restricted, and resolution of the read-element can be improved.  
         [0033]     In the present embodiment, after the Ta film is formed of the surface of the back layer  3 , the Ta film is plasma-oxidized in the oxidizing chamber so as to form the specular layer  2 . Variation of GMR ratio of the GMR film, which was oxidized in the oxidizing chamber, with respect to oxidizing time was observed. The result is shown in  FIG. 3 . The experiment was executed under the conditions shown in the TABLE. The result of the conventional GMR film, whose specular layer was made of plasma oxide film of Al shown in the TABLE, is also shown in  FIG. 3  as a comparable example.  
         [0034]     According to  FIG. 3 , when the Ta film was plasma-oxidized for 30 seconds, the GMR ratio was lower than that of the comparable example, namely oxidization was not enough. When the Ta film was plasma-oxidized for 60-90 seconds, the GMR ratio was almost equal to that of the comparable example. Namely, by employing the plasma oxide film of Ta, which is formed by plasma-oxidizing the Ta film for 60-90 seconds, as the specular layer  2 , the GMR film  10  can be suitably used for the magnetoresistance effect element.  
         [0035]     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.