JP2009146530A - Method for adjusting head resistance of current-confined-path cpp-gmr head - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To adjust a head resistance of a CPP-GMR using a screen layer to improve its yield. <P>SOLUTION: The head resistance can be adjusted within a desired range without significantly degrading a magnetic resistance change rate by feeding a current for resistance adjustment into the head whose head resistance is higher than the desired resistance range. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a magnetoresistive head utilizing a current confinement effect and a manufacturing method thereof.

  Along with the increase in the density of magnetic recording, a tunnel magnetoresistive element having a high output is used as a reproducing head of an HDD device (for example, Patent Document 1). The tunnel magnetoresistive element has a structure in which an insulating layer is formed between two magnetic layers, and a current flows in a direction perpendicular to the film surface. The phenomenon is that the electric resistance of the magnetoresistive effect element changes depending on the parallel / antiparallel state of magnetization of the two magnetic layers, and the output is very high. The tunnel magnetoresistive effect element has problems such as an increase in head resistance accompanying a reduction in element size and deterioration of read characteristics for high frequency recording. Patent Document 2 discloses a method of lowering the tunnel magnetoresistive head resistance by applying stress due to voltage or current.

On the other hand, as an alternative element of the tunneling magnetoresistive element, CPP (C urrent- P erpendicular to the P lane) -GMR has been proposed (for example, Non-Patent Document 1). The CPP-GMR element has a structure in which a metal layer such as Cu is formed between two magnetic layers. A current flows in a direction perpendicular to the film surface, and the magnetization of the two magnetic layers is caused by an external magnetic field. A phenomenon is used in which the electrical resistance changes due to the change in parallel / antiparallel. However, in this structure, the output of CPP-GMR is low and it is difficult to apply to a reproducing head.

  On the other hand, as a CPP-GMR structure capable of obtaining a high output, CPP-GMR in which an insulating film having a pinhole with low electric resistance is formed in an element is disclosed (Non-patent Document 2). Hereinafter, the insulating layer having pinholes is referred to as a screen layer. By narrowing the current flowing in the film thickness direction by pinholes in the screen layer, high output is obtained, and the CPP-GMR element to which the screen layer is applied can be sufficiently applied to a reproducing head.

  Patent Document 3 discloses a method in which a material for phase separation is applied as a screen layer, and a current is narrowed down by a difference in electric resistance between two phases. Patent Document 4 discloses a method of forming a pinhole by forming an insulating film above or in a CPP-GMR and applying a high voltage to cause dielectric breakdown.

Japanese Patent No. 319000661 JP 2007-81091 A JP 2004-153248 A US Pat. No. 7,093,347 Journal of Japan Society of Applied Magnetics, vol.25, pp.807-810 (2001) Journal of Japan Society of Applied Magnetics, vol.26, pp.979-985 (2002)

  CPP-GMR to which a screen layer is applied has high output, but it is difficult to control pinholes in the screen layer. When applied to a reproducing head compatible with high recording density, the head resistance varies greatly depending on the size and number of pinholes existing in the screen layer as the element size becomes smaller in the future.

  In Patent Document 4, after forming an insulating layer, pinholes are formed by dielectric breakdown. In particular, in the case of a magnetic head, after processing to a slider and forming a protective film on the air bearing surface, if a voltage is applied, the protective film is conductive, so that current flows near the air bearing surface and the insulating layer near the air bearing surface is destroyed. Thus, pinholes are formed near the air bearing surface. As a characteristic of CPP-GMR to which a screen layer is applied, in order to obtain a high magnetoresistance change rate, it is necessary to make the electrical resistivity of the pinhole as small as possible, but when the pinhole is formed by breaking the insulating film It is difficult to form a pinhole having a low electrical resistivity. Further, at the time of dielectric breakdown, migration occurs due to a high current flowing for a moment, which causes a decrease in the rate of change in magnetoresistance. As a result, the head output becomes low, and a highly reliable head cannot be expected.

  Patent Document 2 described above describes a method of reducing the head resistance by applying stress due to current or voltage to the tunnel magnetoresistive effect element. In this case, unlike the screen layer, the insulating film has no pinhole. Patent Document 2 does not describe any mechanism that can reduce the resistance by applying stress. However, a good insulating film is probably formed due to disappearance of defects in the insulating film or disappearance of pinholes. It can be inferred that it became easier to flow. Therefore, another mechanism needs to be considered for adjusting the head resistance of the CPP-GMR to which the screen layer is applied.

  An object of the present invention is to provide a method for suppressing variation in resistance that occurs as the element size decreases in a CPP-GMR element to which a screen layer is applied.

  The perpendicular current type magnetoresistive head to which the present invention is applied includes a fixed layer, a free layer, an intermediate layer sandwiched between the fixed layer and the free layer, and a screen layer in which a pinhole having a low electric resistance is embedded in an insulating film. And a shield that also serves as an electrode above and below the CPP-GMR element. In the present invention, in the manufacturing process of the magnetic head, the height of the magnetic head or the element after completion of the wafer process (step of forming a large number of magnetic heads on one substrate using photolithography technology: FIG. 2) is determined. In any step of the magnetic head on the bar after polishing the air bearing surface for adjustment, the magnetoresistance change rate is increased by passing a resistance adjustment current to the head whose head resistance is higher than the desired resistance range. The head resistance is adjusted to a desired range without deteriorating. It is considered that the head resistance is high because the number of pinholes in the screen layer is small or small. Compared with the current density flowing in the pinhole in the screen layer of the head having a desired resistance, the current density flowing in the pinhole in the screen layer of the head having a high resistance is large, so heat is generated. This heat is thought to increase the pinhole size gradually and reduce the head resistance. For this reason, variation in head resistance is reduced and yield is improved.

  In the present invention, a resistance adjustment current is applied in a stepwise manner to a magnetic head having high resistance, and the head resistance is observed. When the head resistance reaches a desired magnitude, the resistance adjustment current is stopped and the output is checked. If the increase in head resistance is caused by the number and size of pinholes, the head resistance can be reduced by the process of the present invention without reducing the magnetoresistance change rate.

  In the present invention, the current value applied for resistance adjustment is set lower than the current value at which the head resistance is deteriorated in the magnetic head having the desired head resistance. By doing this, even if a current for resistance adjustment is applied to all the heads on the bar or all the heads on the wafer, the head having a high resistance without deteriorating the characteristics of the head whose resistance is in the desired range. Only the desired resistance can be lowered. When this method is used, it is not necessary to select the head, and the resistance can be adjusted easily.

  As the screen layer, it is preferable to apply a layer made of any metal of Co, CoFe or Co alloy and its oxide. This is because in the screen layer made of a metal and its oxide, oxygen can be moved by heat, so that the pinhole can be expanded relatively easily. In addition, a screen layer in which other nonmagnetic metal materials such as Cu, Au, Ag, Pt, Pd, Rh, Ir, and Ru and Al oxide, Si oxide, etc., which are insulating materials are mixed may be applied. Almost the same effect can be obtained.

  A magnetoresistive head to which this CPP-GMR is applied is mounted on a magnetic recording / reproducing apparatus in combination with an inductive thin film magnetic recording head or a perpendicular recording head.

  According to the present invention, in a magnetic head using a CPP-GMR to which a screen layer in which a pinhole having a low electrical resistance exists in an oxide layer is applied, the resistance of the magnetic head exhibiting a resistance higher than a desired resistance value is obtained. The head resistance can be lowered and the yield can be improved without reducing the magnetoresistance change rate.

  Hereinafter, an embodiment of the present invention will be described and more specifically described with reference to the drawings.

  FIG. 1 is a schematic view of a magnetoresistive head according to the present invention as viewed from the air bearing surface. As shown in FIG. 1, a CPP-GMR head using a screen layer has an underlayer 121, an antiferromagnetic layer 122, a first ferromagnetic pinned layer 123, an antiparallel coupling on a lower shield 11 that also serves as an electrode. A layer 124, a second ferromagnetic pinned layer 125, an antioxidant layer 126, a screen layer 127, an intermediate layer 128, a ferromagnetic free layer 129, and a cap layer 130 are formed. Here, the screen layer 127 includes an oxidized portion 131 and a metal portion 132, and a protruding portion of the metal portion 132 that is not covered with the oxide layer becomes a pinhole. The underlayer 121 to the cap layer 130 are CPP-GMR, and after the CPP-GMR film is patterned by photolithography, insulation for preventing conduction between the lower shield 11 also serving as an electrode and the upper shield 16 also serving as an electrode The hard bias layer 15 for controlling the magnetic domain of the film 14 and the ferromagnetic free layer 129 is formed, and finally the upper shield 16 also serving as an electrode is formed.

In this embodiment, the lower shield 11 is a 1 μm thick NiFe plating film, the underlayer 121 is Ta (2 nm) / NiFeCr (3 nm) / NiFe (1 nm), and the antiferromagnetic layer 122 is Mn-20 at%. Ir (6 nm), Co-25 at% Fe (3.7 nm) for the first ferromagnetic pinned layer 123, Ru (0.8 nm) for the antiparallel coupling layer 124, and the second ferromagnetic pinned layer 125. Co-10 at% Fe (3 nm) was used for the anti-oxidation layer 126 and Cu (0.5 nm) was used. As the screen layer 127, a layer composed of a Co oxide portion 131 and a Co metal portion 132 formed by natural oxidation of Co (2 nm) in an oxidizing gas pressure of 700 Pa for 1 minute was used. Further, Cu (2 nm) was used for the intermediate layer 128, and a two-layer free layer made of CoFe (1 nm) / NiFe (2.5 nm) was used for the ferromagnetic free layer 129. As the cap layer 130, Cu (2 nm) / Ru (7 nm) / Ta (2 nm) was formed. The cap layer is cleaned before the upper shield 16 is formed in order to reduce contact resistance. For this reason, in the cap layer of the actual head, a part of Ta and Ru is cut off. As the insulating film 14, an Al ₂ O ₃ film having a thickness of 8 nm was formed. The film thickness in the vicinity of the actual CPP-GMR is as thin as about 4 nm. In the hard bias layer 15, CoCrPt is formed, and the magnitude of the magnetic domain control magnetic field applied to the ferromagnetic free layer is changed with the thickness of CoCrPt.

  FIG. 2 shows a part of a process of a magnetic head having a CPP-GMR element as one embodiment of the present invention. As shown in FIG. 2A, a large number of magnetic heads 22 are formed in a matrix on the wafer 21. The magnetic head 22 includes a reproducing magnetic head using a CPP-GMR element having a screen layer and a perpendicular magnetic recording head for recording. FIG. 2B is a schematic enlarged view of one magnetic head as viewed from the upper surface of the wafer. As described above, since the magnetic head 22 has two heads, ie, a reproducing head and a recording head, two electrode terminals are provided for each of them, for a total of four electrode terminals. Other electrode terminals other than the above are omitted here. Here, the two terminals 23 on the right side are electrode terminals for the reproducing head. FIG. 2C shows a state in which the probe 24 is brought into contact with the two electrode terminals 23 and the resistance and output of the element are observed.

  FIG. 3 shows the size dependency of the sheet resistance (RA) of the CPP-GMR element applied to the reproducing head, and FIG. 4 shows the size dependency of the magnetoresistance change rate (MR ratio). Here, the area resistance is a product of the element area and the resistance. When comparing heads having the same element area, the higher the sheet resistance, the higher the head resistance. As shown in FIG. 3, the variation in the sheet resistance of the element increased as the element size decreased. On the other hand, as shown in FIG. 4, the magnetoresistance change rate showed a substantially constant value regardless of the size. The largest cause of variation in the area resistance of the element is considered to be due to the size and number of pinholes in the screen layer. Therefore, the following experiment was performed on the smallest element.

The reference measurement current of the element on the wafer is 2 mA. After measuring the area resistance of the element with the reference current value, after applying a high current value for 3 seconds, the area resistance is measured again with the reference current value. Here, the current value applied intermittently was gradually increased. This process is shown in FIG. FIG. 6 shows changes in sheet resistance RA and applied current in several elements measured in this way. Here, an element having an area of about 0.1 μm ² was evaluated. The element having a high area resistance in FIG. 6 is considered to be an element having a small pinhole area or a small number of pinholes. Therefore, when the same current value is applied as compared with other elements having low sheet resistance, it is considered that the current density flowing through the pinhole is effectively increased and heat is likely to be generated. When the current value is gradually increased as shown in FIG. 5, the pinhole begins to expand, and the electrical resistance of the pinhole portion gradually decreases. Therefore, as shown in FIG. 6, the resistance starts to decrease at a lower current value as the element has a higher area resistance, and the area resistance of all the elements shows the same value by increasing the current value.

FIG. 7 shows the applied current dependence of the value _{RAσ / ave} obtained by dividing the variance of the _sheet resistance by the average in the element shown in FIG. 6 and the value MRσ _{/ ave} obtained by dividing the variance of the magnetoresistance change rate by the average. . These values are indexes indicating variations in sheet resistance and magnetoresistance change rate. In this embodiment, as shown in FIG. 7, when a current of 40 mA or more is applied, the value of RA _{σ / ave} starts to decrease. That is, the variation becomes smaller. On the other hand, the MR _{σ / ave} value does not change even when the value of RA _{σ / ave} starts to decrease, but when a current exceeding 60 mA is applied, the magnetoresistance change rate starts to vary. This indicates that the magnetoresistance change rate has started to deteriorate. That is, even if a large amount of current is applied to the CPP-GMR element, the damage to the portion of the CPP-GMR that generates the magnetic resistance is small, and it can be interpreted that the pinhole of the screen layer is simply enlarged. In this embodiment, by applying a current of about 60 mA, the element resistance can be reduced without reducing the rate of change in magnetoresistance of the element having an increased area resistance.

The upper limit of the current applied for resistance adjustment is the current value at which the resistance of an element having a desired element resistance starts to deteriorate. For example, in the example of FIG. 6, since the desired sheet resistance RA of the wafer is 0.23 Ωμm ² , the upper limit is 60 mA at which the element resistance near the RA starts to deteriorate. Even if a current lower than this current value is applied, an element having a desired sheet resistance value is not deteriorated. On the other hand, the element resistance having a high area resistance can be adjusted to a desired area resistance value without reducing the magnetoresistance effect ratio.

FIG. 8 shows the horizontal axis of FIG. 6 not by current but by voltage value. In the case of the voltage value, the reduction in sheet resistance starts at almost the same voltage value for all heads. In other words, when a constant current value is applied to a magnetic head having variations in resistance, the voltage applied to the magnetic head having a high resistance is higher than the voltage applied to the magnetic head having a desired head resistance. Indicates that it is high. Therefore, the maximum value of the applied current for resistance adjustment can be said to be a value obtained by dividing the voltage value at which the element resistance starts to deteriorate in the magnetic head having the desired head resistance by the head resistance. The area on the wafer of the element evaluated in this example was about 0.1 μm ² , but when the element area is halved, the element resistance is doubled, so the maximum that can be applied for resistance adjustment Current is half, 30 mA. When the element area is reduced to ¼, the element resistance is quadrupled, so that the maximum current cut off by application for resistance adjustment is ¼, 15 mA.

  In many cases, the bias voltage when operating the magnetic head is 50 to 70% of the voltage at which the element deteriorates from the viewpoint of reliability. Therefore, the maximum value of the applied current for resistance adjustment is a value obtained by dividing the bias voltage value at the time of operation by 0.5 to 0.7 and further dividing by the element resistance. Therefore, it can be said that the applied current for resistance adjustment is typically a value obtained by dividing twice the bias voltage value by the head resistance.

  In this embodiment, the time for applying the resistance adjustment current is 3 seconds as shown in FIG. 5, but it is preferable to set it to 1 second or longer. As described above, the resistance is adjusted by enlarging the pinhole by heat, so that a current may be applied for a long time. However, from the viewpoint of shortening the head process, the applied current time is preferably as short as possible. However, if the current application time is 1 second or less, the temperature rise due to the heat of the pinhole portion due to the applied current is small, and it is necessary to further increase the applied current value for resistance adjustment. In this case, the current density is increased and the rate of change in magnetoresistance due to migration is reduced, so the application time is preferably set to 1 second or longer. In this embodiment, the current value is changed stepwise, but the current value for adjusting the element resistance may be applied only once. Thereby, the head process can be shortened.

  Further, in this embodiment, the natural oxidation of Co is used as the screen layer, but the same effect can be obtained by using Co, Fe, or an alloy thereof, or an alloy containing CoFe as a main component. This is because a screen layer made of a metal and its oxide can move oxygen relatively easily by heat and can widen a pinhole. Further, the screen layer may be formed by reactive sputtering.

In this embodiment, MnIr is used as the antiferromagnetic film, but the same effect can be obtained by using an antiferromagnetic material such as MnPt, MnPtPd, or MnRh. Further, when a film in which Mn, Cr, Al, Si, Ga, Ge, In, Sn, Zn, Au, Ag, Au is added to Co, CoFe or Co, CoFe is applied to the magnetic layer, a high magnetoresistance change is achieved. This is preferable because the rate is obtained. Further, even when Co ₂ MnGe or Co ₂ MnSi called Heusler alloy is used, a high magnetoresistance change rate can be obtained.

  The element resistance adjusting process of the present invention was applied to a processed magnetic head for forming the element height. As shown in FIG. 9A, a magnetic head having a large number of CPP-GMRs is produced on a wafer 31 in a matrix. On the magnetic head 32, a reproducing magnetic head using a CPP-GMR having a screen layer and a perpendicular magnetic recording head are overlaid. After completing the head wafer process, the magnetic head is cut into a plurality of bars 33 arranged in a line. FIG. 9B shows one of the cut out bars 33. The air bearing surface side of this bar is polished so that the element height becomes a desired value. After the element height reaches a desired value, a protective film is formed on the air bearing surface. When the bar is cut after the rail processing, the head slider chip shown in FIG. 9C is obtained. In the state of the bar 33 in which a plurality of magnetic heads 32 are arranged in a row in FIG. It was. As shown in FIG. 9D, the probe 35 for current application was brought into contact with the electrode terminal of the reproducing head in the same manner as in Example 1.

  FIG. 10 shows a process flow. With respect to all the elements formed on the bar 33, the element resistance and the output are measured with a reference sense current (here, 0.4 mA). Thereafter, the applied current is increased at a step of 0.4 mA, and the head resistance and output are measured by returning to the reference sense current of 0.4 mA each time. If the upper limit of the applied current is not set here, even if an abnormal magnetic head is present, even a good element is broken. Here, the upper limit value was 2.4 mA. This time, the current was applied stepwise to the element at the end of the bar, and the element resistance of the next element was adjusted if the element resistance was in the desired value range. After the evaluation of all the elements is completed, the head slider chip is cut.

FIG. 11 shows the result of resistance adjustment with an actual magnetic head. In FIG. 11, the horizontal axis represents head resistance, and the vertical axis represents frequency. The element size used was a film having a target of 60 nm square and RA of 0.5 Ωμm ² . The head resistance derived from these was 140Ω, and the allowable resistance value was 200Ω. The voltage at which the resistance of the magnetoresistive element used in this example starts to decrease was about 300 mV. As shown in FIG. 11, by increasing the maximum applied current to 2.4 mA, all the elements having a head resistance of 200Ω or more became 200Ω or less.

  FIG. 12 shows the change rate of the magnetoresistance and the change of the magnetic head resistance when the resistance adjustment current is gradually increased and applied in the element having the head resistance of 200Ω or more. As shown in the figure, by increasing the applied current for resistance adjustment, most of the elements could reduce the head resistance without greatly reducing the rate of change in magnetoresistance. The reason why the magnetoresistance change rate is slightly decreased is that the current confinement effect is slightly reduced as the pinhole is enlarged. In FIG. 12, the two magnetic head groups 41 whose magnetoresistance change rates have fallen are considered to be provided with surplus resistance in areas other than the screen layer, and can be selected as defective.

  Here, the reason why the voltage value of 300 mV at which the magnetic head resistance starts decreasing is different from the value of 150 mV in Example 1 is that the effect of heat sinking is different due to the difference in the film thickness of the screen layer, the difference in element size, and the head structure. it is conceivable that. Even if these change, the effect of lowering the element resistance to a desired resistance without lowering the magnetoresistance change rate of the element having substantially high resistance is not affected.

  In this example, a process of applying a current to each CPP-GMR head formed on the bar was applied. As a result, head variations can be easily reduced, and the yield is improved. In order to shorten the process, the head resistance may be adjusted by applying this process only to the head that has become higher than the desired resistance value. Further, the process can be further shortened by using a process step of adjusting the head resistance by applying an appropriate current value to all elements at once.

  In the present embodiment, the same effect can be obtained regardless of the process of the present invention after the air bearing surface polishing process is performed. Further, after cutting into head sliders, only the heads with high resistance can be extracted and a desired current can be applied to each head to suppress variations in electrical resistance. This is preferable because a good head is not destroyed by mistake.

A CPP-GMR film different from that in Example 1 was examined. The reproducing head having this example CPP-GMR is almost the same as the film structure of the reproducing head used in Examples 1 and 2 except that a mixed layer of Al ₂ O ₃ and Cu is applied as the material of the screen layer. . In this example, the head wafer was cut into a bar and examined in the same manner as in Example 2. The element size used was a film with a target of 60 nm square and RA of 0.3 Ωμm ² . The head resistance derived from these was 83Ω, and the allowable resistance value was 160Ω.

The head resistance was adjusted by applying the process steps shown in FIG. 10 to these heads. The result is shown in FIG. As shown in FIG. 13, it was found that the magnetoresistance change rate hardly decreased to almost 100 Ω in the vicinity of the head, the head resistance could be reduced, and the effect was also obtained by the screen layer material of this example. Further, in the group 41 of two magnetic heads in FIG. 13, the rate of change in magnetoresistance is reduced from the beginning, and it is considered that surplus resistance is applied in a portion other than the screen layer. However, as compared with Example 1, there were many magnetic heads in which the rate of change in magnetoresistance suddenly decreased (group 42 in the figure). This is originally a phase-separated screen material, and the element resistance can be reduced without greatly reducing the rate of change in magnetoresistance due to the release of oxygen from the Cu portion that initially becomes pinholes. since the mixing of the Al ₂ O _3, or the migration of Al ₂ O ₃ is generated, when compared to the screen layer mainly composed of CoFe, it seems magnetoresistance ratio decreases suddenly. For this reason, when the screen layer material is changed, it is necessary to pay attention to the upper limit value of the applied current.

In this embodiment, a mixed layer of Cu and Al ₂ O ₃ was used as a screen. However, a mixture of Au, Ag, which are other metal materials, and SiO ₂ , MgO, Ta ₂ O ₅ , Nb ₂ O ₅ , HfO, or the like. A similar effect can be obtained by applying the layer as a screen.

  FIG. 14 is a conceptual diagram of a recording / reproducing separated magnetic head for perpendicular recording equipped with a magnetoresistive effect element whose element resistance is adjusted according to the present invention. The reproducing head is composed of an electrode / lower 1 shield 51 formed on a substrate also serving as a slider, a CPP-GMR film 52 having a screen layer, an insulating film 53, a magnetic domain control film 54, a conductive gap film 55, and an upper shield 56. The A perpendicular recording head including a sub magnetic pole 57, a coil 58, a main magnetic pole 59, and a yoke portion 60 is formed on the upper side of the reproducing head.

  The present invention relates to a magnetoresistive head, and can be applied to whether the recording head side is a perpendicular recording head or an in-plane recording head. However, a more effective function can be realized by combining with a perpendicular recording head.

A magnetic disk device using the recording / reproducing separated magnetic head for perpendicular recording shown in FIG. 14 was produced. FIG. 15 shows a schematic diagram of a magnetic disk device. FIG. 15A is a schematic plan view of the magnetic disk device, and FIG. 15B is a sectional view taken along line AA ′. As the magnetic recording medium 61, a granular medium for perpendicular recording made of CoCrPt and SiO ₂ was used. The head shown in FIG. 14 was used as the magnetic head 63. A recording medium 61 on which information is magnetically recorded is rotated by a spindle motor 62, and the head 63 is guided onto a track of the recording medium 61 by an actuator 64. That is, in the magnetic disk apparatus, the reproducing head and the recording head formed on the head 63 move relative to a predetermined recording position on the recording medium 61 by this mechanism, and sequentially write and read signals. The recording signal is recorded on the medium by the recording head through the signal processing system 65, and the output of the reproducing head is obtained as a signal through the signal processing system 65.

  As a result of testing the magnetic head of the present invention and the magnetic recording / reproducing apparatus equipped with the magnetic head of the present invention as described above, it showed sufficient output, good bias characteristics, and good operation reliability. This is because the screen layer-applied CPP-GMR head with the element resistance adjusted according to the present invention was used.

The figure which shows the structural example of the CPP-GMR head seen from the medium opposing surface. Schematic explaining the process of this invention in a wafer process. The figure which shows the element size dependence of sheet resistance. The figure which shows the element size dependence of a magnetoresistive change rate. The figure which shows the example of an electric current application step. The figure which shows the applied current dependence for resistance adjustment of the area resistance of a reproducing head. The figure which shows the relationship between the dispersion | variation in the area resistance of a read head and a magnetoresistive change rate, and the applied current for resistance adjustment. The figure which shows the relationship between the area resistance of a reproducing head, and an applied voltage. Schematic explaining the process of this invention in the state of a bar. The figure of a head resistance adjustment flow. The figure which shows distribution of magnetic head resistance immediately after a process and after a resistance adjustment process. The figure which shows the change of the relationship between head resistance and a magnetoresistive change rate when the applied current for resistance adjustment is made to increase. The figure which shows the change of the relationship between head resistance and a magnetoresistive change rate when the applied current for resistance adjustment is made to increase. FIG. 3 is a conceptual diagram of a recording / reproducing separated magnetic head for perpendicular recording. 1 is a conceptual diagram of a magnetic disk device.

Explanation of symbols

11, 51 Electrode and lower shield 121 Underlayer 122 Antiferromagnetic layer 123 First ferromagnetic pinned layer 124 Antiparallel coupling layer 125 Second ferromagnetic pinned layer 126 Antioxidation layer 127 Screen layer 128 Intermediate layer 129 Ferromagnetic free Layers 130 and 25 Cap layer 131 Metal part 132 Oxidation part 21 and 31 Magnetic head wafers 22 and 32 Magnetic heads 23 and 34 Playback head terminals 24 and 35 Current and voltage application probes 33 Bars 14 and 53 Insulating layers 15 and 54 Magnetic domains Control layers 16, 56 Electrode and upper shield layer 52 CPP-GMR
57 Sub magnetic pole 58 Coil 59 Main magnetic pole 60 Yoke 61 Magnetic recording medium 62 Spindle motor 63 Magnetic head 64 Actuator 65 Recording / reproducing signal processing system

Claims (9)

Between the upper and lower shields also serving as electrodes, a fixed layer, a free layer, an intermediate layer sandwiched between the fixed layer and the free layer, and a screen layer having a pinhole with low electric resistance in the insulating film are provided. A first step of forming a magnetoresistive element;
And a second step of reducing element resistance by applying a current in a direction perpendicular to the film surface of the magnetoresistive effect element.   2. The method of manufacturing a magnetoresistive head according to claim 1, wherein the second step is performed after a processing and polishing step for determining an element height.   2. The method of manufacturing a magnetoresistive head according to claim 1, wherein the current application in the second step is intermittent and the current value is increased stepwise. .   2. The method of manufacturing a magnetoresistive head according to claim 1, wherein the current applied in the second step is equal to or less than a current value at which the element resistance of the magnetic head showing the element resistance within an allowable range starts to deteriorate. A method of manufacturing a magnetoresistive head characterized by the above.   2. The method of manufacturing a magnetoresistive head according to claim 1, wherein the current applied in the second step is set to a desired head resistance that is twice the bias voltage value applied when reading recorded information from the medium. A method of manufacturing a magnetoresistive head, wherein the magnetoresistive head is equal to or less than the value divided by.   2. The method of manufacturing a magnetoresistive head according to claim 1, wherein the second step is performed after the wafer process is completed.   2. The method of manufacturing a magnetoresistive head according to claim 1, wherein the screen layer is made of any one of Co, CoFe, and a Co alloy and an oxide thereof. . Between the upper and lower shields also serving as electrodes, a fixed layer, a free layer, an intermediate layer sandwiched between the fixed layer and the free layer, and a screen layer having a pinhole with low electric resistance in the insulating film are provided. A first step of forming a magnetoresistive element;
A magnetic head comprising: a magnetoresistive head manufactured through a second step of reducing element resistance by applying a current in a direction perpendicular to the film surface of the magnetoresistive element.   9. The magnetic head according to claim 8, further comprising a recording head.

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