JP5118766B2 - Magnetoresistive element, magnetoresistive head, magnetic storage device, and magnetic memory - Google Patents

Description

  The present invention relates to a magnetoresistive effect element, a magnetoresistive effect head, a magnetic storage device, and a magnetic memory that detect magnetism by flowing a sense current in a direction perpendicular to the film surface of the magnetoresistive effect film.

 The discovery of the giant magneto-resistive effect (GMR) has dramatically improved the performance of magnetic devices, particularly magnetic heads. In particular, the application of a spin-valve (SV film) to a magnetic head, MRAM (Magnetic Random Access Memory), etc. has brought great technical progress in the field of magnetic devices.

  A “spin valve film” has a structure in which a nonmagnetic spacer layer is sandwiched between two ferromagnetic layers, and is called one of the ferromagnetic layers (“pinned layer”, “magnetization pinned layer”, etc.) ) Is fixed by an antiferromagnetic layer, and the magnetization of the other ferromagnetic layer (referred to as “free layer” or “magnetization free layer”) is rotated in response to an external magnetic field. A membrane. In the spin valve film, a huge change in magnetoresistance can be obtained by changing the relative angle between the magnetization directions of the pinned layer and the free layer.

  The conventional spin valve film is a CIP (Current In Plane) -GMR element in which a sense current is passed in parallel to the film surface. In recent years, a CPP (Current Perpendicular to Plane) -GMR element (hereinafter referred to as a “CPP element”) that supplies a sense current in a direction substantially perpendicular to the film surface exhibits a greater GMR effect than a CIP-GMR element. Has attracted attention.

Considering the application of these magnetoresistive elements to magnetic heads, problems arise in terms of shot noise and high frequency response when the element resistance increases. Regarding the element resistance, it is appropriate to evaluate by RA (resistance x energization area). Specifically, RA is required to be several hundred mΩμm ^{2 to} 1Ωμm ² at a recording density of 200 Gbpsi (Gigabit per square inch) and 500 mΩμm ² or less at a recording density of 500 Gbpsi.

  In response to such demands, the CPP element has a potential to obtain a large MR change rate even when the resistance is low under the tendency that the magnetic device is increasingly miniaturized. From such a background, the CPP element and the magnetic head using the CPP element are considered to be promising candidates for realizing a recording density of 200 Gbpsi to 1 Tbpsi (Terabit per square inch).

  However, in a metal CPP element in which a pinned layer / spacer layer / free layer (these three-layer structures are called spin-dependent scattering units or spin valve films) are formed of a metal layer, the amount of resistance change due to magnetization is small, and high It is difficult to detect a weak magnetic field accompanying the increase in density.

  In order to solve this problem, a CPP element using an oxide layer [NOL (nano-oxide layer)] including a current path in the thickness direction as a nonmagnetic spacer layer has been proposed (see, for example, Patent Document 1). ). In such a CPP element, both the element resistance and the MR change rate can be increased by a current confinement [CCP (Current-confined-path)] effect. Hereinafter, such an element is referred to as a CCP-CPP element.

  Here, with the trend toward miniaturization of elements (magnetic devices), it is required that the size of the CPP spin valve film in the planar direction be smaller than 100 nm × 100 nm. For example, a track width of 0.1 μm or less is required due to the high density of the magnetic disk.

  It has been reported that when a sense current flows in the direction perpendicular to the film surface of a CPP spin valve film having a small area as described above, noise due to spin transfer torque occurs (STI (Spin-Transfer Induced) noise is (See Patent Documents 1 and 2).

  The spin transfer effect is a phenomenon in which the magnetization direction of the free layer changes even when no external magnetic field is applied when a current of a certain critical value or more is passed through the CPP spin valve film. At this time, if the energization direction changes, the magnetization direction of the free layer may be reversed. In other words, if the energization direction is fixed in one direction, the magnetization stable direction of the free layer is also fixed in one direction.

  The magnetization stable direction at this time is as follows. When electrons flow from the pinned layer to the free layer (current flows from the free layer to the pinned layer), a spin torque is applied so that the magnetization direction of the free layer is aligned with the direction of the pinned layer. On the other hand, when electrons flow from the free layer to the pinned layer (current flows from the pinned layer to the free layer), spin torque acts in such a direction that the magnetization direction of the free layer is aligned antiparallel to the pinned layer.

  In the magnetic head, the magnetization direction of the free layer changes depending on the direction of the medium magnetic field. For this reason, when the energization direction is constant, depending on the magnetization direction of the free layer, the free layer may become magnetically unstable, and noise may be generated.

  Thus, even in a state where a sense current is passed without applying an external magnetic field, the magnetization in the free layer becomes unstable, and the noise of the element may increase. This noise is referred to as STI (Spin Transfer Induced) noise because it is noise induced by the spin transfer effect.

  When STI noise occurs, the noise increases even if the signal output is constant, so that the S / N ratio of the magnetic head deteriorates and the BER (Bit Error Rate) in the HDD increases. As a result, it is difficult to detect a weak medium magnetic field at the time of high-density recording with an element, and there is a risk that it is practically impossible to use it for a magnetic head or the like.

JP 2002-208744 A

M. Covington et al., Phys. Rev. B69, 184406 (2004) M. Covington et al., J. Magn. Magn. Mater. 287, 325 (2005) H. Yuasa et al., J. Appl. Phys. 92 (5), 2646 (2002) H. Fukuzawa et al., Appl. Phys. Lett. 87, 082507 (2005)

  Non-Patent Documents 1 and 2 show STI noise in a metal CPP spin valve film using a metal Cu layer as a spacer layer. In a CCP-CPP spin valve film using a NOL spacer layer having CCP, there is a possibility that the situation around STI noise is more complicated than a metal CPP spin valve film.

  In the CCP-CPP spin-valve film, electrons are injected from the free layer to the pinned layer or from the pinned layer to the free layer through the CCP current constricted spacer layer in a state where the current is locally concentrated. . The local current density is much larger than that of a normal metal CPP spin valve film. Considering that the STI noise is sensitive to the current density, the STI noise in the CCP-CPP spin valve film may be larger than the STI noise in the metal CPP spin valve film. Thus, suppression of STI noise is an important issue in the CCP-CPP spin valve film.

  In view of the above, an object of the present invention is to provide a magnetoresistive effect element, a magnetoresistive effect head, a magnetic storage device, and a magnetic memory in which noise is reduced.

A magnetoresistive effect element according to the present invention includes a magnetization pinned layer having a pinning layer, an insulating layer disposed on the magnetization pinned layer, and a conductor that passes a current in a layer direction of the insulating layer. A spin valve film having a magnetic layer and a magnetization free layer having a NiFe layer disposed on the nonmagnetic layer and having a CoFe layer inserted at an interface with the nonmagnetic layer, and disposed inside the magnetization free layer A predetermined layer having a thickness of 0.1 nm or more and 1 nm or less (excluding 1 nm), including Ti or Pd, one or more layers away from the nonmagnetic layer by 1 nm or more, and the spin valve film And a pair of electrodes that are perpendicular to the film surface of the spin valve film, and have an fcc (111) peak of the spin valve film, an fct (111) peak of the pinning layer, or bcc ( Half width of the rocking curve at 10), characterized in that a 3.5 to 6 degrees.

It is a perspective view showing the magnetoresistive effect element concerning the 1st Embodiment of this invention. It is a flowchart showing the manufacturing process of the magnetoresistive effect element which concerns on the 1st Embodiment of this invention. It is a schematic diagram which shows the schematic of the film-forming apparatus used for manufacture of a magnetoresistive effect element. It is a schematic diagram showing the structure of an oxidation chamber. It is a perspective view showing the magnetoresistive effect element concerning the 2nd Embodiment of this invention. It is a flowchart showing the manufacturing process of the magnetoresistive effect element which concerns on the 2nd Embodiment of this invention. It is sectional drawing of the magnetic head which concerns on embodiment of this invention. It is sectional drawing of the magnetic head which concerns on embodiment of this invention. 1 is a perspective view of a magnetic recording / reproducing apparatus according to an embodiment of the present invention. 1 is a perspective view of a magnetic head assembly according to an embodiment of the present invention. It is a figure which shows an example of the matrix structure of the magnetic memory which concerns on embodiment of this invention. It is a figure which shows the other example of the matrix structure of the magnetic memory which concerns on embodiment of this invention. It is sectional drawing which shows the principal part of the magnetic memory which concerns on embodiment of this invention. It is sectional drawing which follows the A-A 'line of FIG.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following embodiments, the composition of the alloy is expressed in atomic%.

(First embodiment)
FIG. 1 is a perspective view showing a magnetoresistive effect element (CCP-CPP element) according to a first embodiment of the present invention. Note that FIG. 1 and the subsequent drawings are all schematic views, and the ratio between the film thicknesses in the figure does not necessarily match the ratio between the actual film thicknesses.

  As shown in FIG. 1, the magnetoresistive effect element according to the present embodiment has a magnetoresistive effect film 10, and a lower electrode 11 and an upper electrode 20 that sandwich the magnetoresistive effect film 10 from above and below, and is configured on a substrate (not shown). .

  The magnetoresistive film 10 includes an underlayer 12, a pinning layer 13, a pin layer 14, a lower metal layer 15, a spacer layer (CCP-NOL) 16, an upper metal layer 17, a free layer 18, and a cap layer 19 stacked in this order. Composed. Among them, the pinned layer 14, the spacer layer 16, and the free layer 18 as a whole correspond to a spin valve film in which a nonmagnetic spacer layer is sandwiched between two ferromagnetic layers. For ease of viewing, the spacer layer 16 is shown separated from the upper and lower layers (the lower metal layer 15 and the upper metal layer 17).

  In the present embodiment, STI noise is reduced by inserting a damping factor (DF) adjustment layer 21 into at least one of the pinned layer 14 and the free layer 18.

  The CCP-CPP element in FIG. 1 is a bottom type in which the pinned layer 14 is disposed at the bottom, but may be a top type in which the pinned layer 14 is disposed at the top. That is, it is possible to reverse the top and bottom of the laminated structure of the lower electrode 11, the base layer 12 to the cap layer 19, and the upper electrode 20.

  Hereinafter, components of the magnetoresistive element will be described.

  The lower electrode 11 is an electrode for energizing in the direction perpendicular to the spin valve film. When a voltage is applied between the lower electrode 11 and the upper electrode 20, a current flows through the inside of the spin valve film along the direction perpendicular to the film. By detecting a change in resistance caused by the magnetoresistive effect with this current, magnetism can be detected. As a specific material, NiFe that also serves as a lower shield, or a non-magnetic metal layer such as Cu, Ta, Ru, or Cr is used.

  The underlayer 12 can be divided into, for example, a buffer layer 12a and a seed layer 12b.

The buffer layer 12a is a layer for reducing the roughness of the surface of the lower electrode 11. The seed layer 12b is a layer for controlling the crystal orientation and crystal grain size of the spin valve film formed thereon.

  As the buffer layer 12a, Ta, Ti, W, Zr, Hf, Cr, or an alloy thereof can be used. The thickness of the buffer layer 12a is preferably about 2 to 10 nm, and more preferably about 3 to 5 nm. If the buffer layer 12a is too thin, the buffer effect is lost.

On the other hand, if the buffer layer 12a is too thick, the series resistance that does not contribute to the MR ratio is increased, which is not preferable. In addition, when the seed layer 12b formed on the buffer layer 12a also has a buffer effect, the buffer layer 12a is not necessarily provided.

  The seed layer 12b may be any material that can control the crystal orientation of a layer formed thereon, but it may have an hcp structure (hexagonal close-packed structure) or an fcc structure (face-centered cubic structure: A metal layer having a face-centered cubic structure is preferred. By using Ru as the seed layer 12b, the crystal orientation of the spin valve film thereon can be changed to the fcc (111) orientation. Further, the fct structure (face-centered tetragonal structure) in which the crystal orientation of the pinning layer 13 (for example, PtMn) is regularized, or bcc (body-centered cubic structure) (110) orientation It can be.

  The crystal orientation of the spin valve film and the pinning layer 13 can be measured by X-ray diffraction. Good orientation is obtained by setting the full width at half maximum of the rocking curve at the fcc (111) peak of the spin valve film, the fct (111) peak of the pinning layer 13 (PtMn), or the bcc (110) peak to 3.5 to 6 degrees. be able to. The orientation dispersion angle can also be determined from a diffraction spot using a cross-sectional TEM.

  In addition, by providing the seed layer 12b, the crystal grain size of the spin valve film can be controlled to 10 to 40 nm, and even if the size of the CCP-CPP element is reduced, a high MR change rate without causing variation in characteristics. Can be realized.

As the seed layer 12b, instead of Ru, for example, Ni _x Fe _100-x (x = 90 to 50%, preferably 75 to 85%) or the third element X is added to NiFe to make it nonmagnetic (Ni _{x Fe 100-x) 100-} y X y (X = Cr, V, Nb, Hf, Zr, Mo) can also be used NiFe-based alloy such as. It is easier for the NiFe base to obtain better crystal orientation as the seed layer 12b than Ru, and the half width of the rocking curve measured in the same manner as described above can be 3 to 5 degrees.

  In order to obtain an appropriate crystal grain size of 10 to 40 nm as described above, the composition y of the third element X is preferably about 0 to 30% (including the case where y is 0%). In order to make the crystal grain size coarser than 40 nm, it is preferable to use a larger amount of additive element. For example, in the case of NiFeCr, it is preferable to use a composition having a Cr amount of about 35 to 45% and a boundary phase between fcc and bcc.

  However, when used as a reproducing head compatible with high-density recording, the element size is 100 nm or less, and if the crystal grain size is too large, there may be variations in characteristics, and it is not preferable to use large crystal grains. Absent. On the other hand, when used as an MRAM, for example, the element size may be 100 nm or more, and therefore a seed layer 12b for increasing the crystal grain size may be used.

  The thickness of the seed layer 12b is preferably about 1.5 nm to 6 nm, and more preferably 2 to 4 nm. If the thickness of the seed layer 12b is too thin, effects such as crystal orientation control are lost. On the other hand, if the seed layer 12b is too thick, the series resistance may be increased and the interface irregularity of the spin valve film may be caused.

  The pinning layer 13 has a function of fixing magnetization by imparting unidirectional anisotropy to a ferromagnetic layer to be a pinned layer 14 formed thereon. As a material of the pinning layer 13, an antiferromagnetic material such as PtMn, PdPtMn, IrMn, RuRhMn can be used.

  In order to impart sufficient strength of unidirectional anisotropy, the film thickness of the pinning layer 13 is appropriately set. When the pinning layer 13 is PtMn or PdPtMn, the film thickness is preferably about 8 to 20 nm, and more preferably 10 to 15 nm. When the pinning layer 13 is IrMn or RuRhMn, unidirectional anisotropy can be imparted even with a thinner film thickness such as PtMn. Therefore, 5 to 18 nm is preferable, and 7 to 15 nm is more preferable.

Since the specific resistance of the antiferromagnetic layer such as PtMn is as large as about 100 μΩcm or more, there is a possibility that the pinning layer 13 increases the series resistance that does not directly contribute to the MR change rate and increases the value of RA. In order to prevent an increase in series resistance, a hard magnetic layer can be used as the pinning layer 13 instead of the antiferromagnetic layer. Examples of the hard magnetic layer include CoPt (Co = 50 to 85%), (Co _x Pt _100-x ) _100-y Cr _y (x = 50 to 85%, y = 0 to 40%), FePt (Pt 40 to 60%) can be used. Since the hard magnetic layer (particularly CoPt) has a relatively small specific resistance, it is possible to suppress an increase in series resistance and RA.

The pinned layer 14 has a three-layer structure including a lower pinned layer 141 (for example, Co ₉₀ Fe ₁₀ ), a magnetic coupling layer 142 (for example, Ru), and an upper pinned layer 143 (for example, Co ₉₀ Fe ₁₀ [4 nm]). It can be a synthetic pinned layer. The pinning layer 13 (for example, PtMn) and the lower pinned layer 141 immediately above it are exchange-magnetically coupled so as to have unidirectional anisotropy. The lower pinned layer 141 and the upper pinned layer 143 above and below the magnetic coupling layer 142 are strongly magnetically coupled so that the magnetization directions are antiparallel to each other.

The lower pinned layer 141 is, for example, a Co _x Fe _100-x alloy (x = 0 to 100%), a Ni _x Fe _100-x alloy (x = 0 to 100%), or a material in which a nonmagnetic element is added thereto Can be used.

The lower pinned layer 141 is preferably designed such that the magnetic film thickness, that is, the saturation magnetization Bs × the film thickness t (Bs · t product) is substantially equal to the upper pinned layer 143. As an example, when the upper pinned layer 143 is (Fe ₅₀ Co ₅₀ [1 nm] / Cu [0.25 nm]) × 2 / Fe ₅₀ Co ₅₀ [1 nm], the saturation magnetization of FeCo is about 2.2 T. Therefore, the magnetic film thickness is 2.2T × 3 nm = 6.6 Tnm. Since the saturation magnetization of Co ₉₀ Fe ₁₀ is about 1.8 T for the lower pinned layer 141, the film thickness t of the lower pinned layer 141 giving a magnetic film thickness equal to the above is 6.6 Tnm / 1.8T = 3.66 nm. . Therefore, it is desirable to use Co ₉₀ Fe ₁₀ having a film thickness of about 3.6 nm.

  The thickness of the magnetic layer used for the lower pinned layer 141 is preferably about 2 to 5 nm. This is based on the viewpoint of the unidirectional anisotropic magnetic field strength by the pinning layer 13 (for example, PtMn) and the antiferromagnetic coupling magnetic field strength between the lower pinned layer 141 and the upper pinned layer 143 via Ru. If the lower pinned layer 141 is too thin, the MR change rate becomes small. On the other hand, if the lower pinned layer 141 is too thick, it is difficult to obtain a sufficient unidirectional anisotropic magnetic field necessary for device operation.

  The magnetic coupling layer 142 (for example, Ru) has a function of forming an antiferromagnetic coupling in the upper and lower magnetic layers to form a synthetic pin structure. The film thickness of the Ru layer as the magnetic coupling layer 142 is preferably 0.8 to 1 nm. A material other than Ru may be used as long as it is a material that causes sufficient antiferromagnetic coupling in the upper and lower magnetic layers (lower pinned layer 141 and upper pinned layer 143).

The upper pinned layer 143 (Co ₉₀ Fe ₁₀ [4 nm]) forms part of the spin-dependent scattering unit. When FeCo having a bcc structure or the like is used as the upper pinned layer 143 instead of Co ₉₀ Fe ₁₀ having an fcc structure, a large MR change rate can be realized because the spin-dependent interface scattering effect is large. Examples of the FeCo-based alloy having the bcc structure include Fe _x Co _100-x (x = 30 to 100%) and those obtained by adding an additive element to Fe _x Co _100-x . Since the metal material used for the spin valve film often has an fcc structure or an fct structure, only the upper pinned layer 143 may have a bcc structure.

  If the film thickness of the upper pinned layer 143 is too thin, it becomes difficult to keep the bcc structure stable and a high MR ratio cannot be obtained. Therefore, the film thickness of the upper pinned layer 143 is preferably 2 nm or more. On the other hand, in order to obtain a large pin fixing magnetic field, the film thickness of the upper pinned layer 143 is preferably 5 nm or less.

  When the upper pinned layer 143 is formed of a magnetic layer having a bcc structure that can easily achieve a high MR ratio, the thickness of the layer having the bcc structure is 2 nm or more in order to keep the bcc structure more stable. Preferably there is.

In order to achieve both a large pinned magnetic field and the stability of the bcc structure, the thickness of the layer having the bcc structure is preferably about 2.5 nm to 4 nm. Regarding FeCo-based magnetic films, Fe ₇₅ Co _{25 to} Fe ₈₅ Co ₁₅ can be cited as a composition range in which a more stable bcc structure can be obtained on the phase diagram.

  For the upper pinned layer 143, a CoFe alloy having an fcc structure or a cobalt alloy having an hcp structure can be used instead of a magnetic material having a bcc structure. Any single metal such as Co, Fe, Ni, or an alloy material containing any one of these elements can be used. When the magnetic material of the upper pinned layer 143 is arranged from those that are advantageous for obtaining a large MR ratio, it has an alloy material having a bcc structure, a cobalt alloy having a cobalt composition of 50% or more, and an Ni composition of 50% or more. Nickel alloy order.

  A damping factor (DF) adjustment layer 21 can be inserted into the upper pinned layer 143 to suppress STI noise. Details of this will be described later.

  The lower metal layer 15 is used when forming the current path 162, and so to speak, is a supply source of the current path 162. However, it is not necessary to remain as a clear metal layer even after the current path 162 is formed.

  The spacer layer (CCP-NOL) 16 includes an insulating layer 161 and a current path 162. The spacer layer 16, the lower metal layer 15, and the upper metal layer 17 can also be handled as a spacer layer.

The insulating layer 161 is made of oxide, nitride, oxynitride, or the like, and may be Al ₂ O ₃ formed of amorphous material or may have a crystal structure such as MgO.

As a typical insulating material used for the insulating layer 161, there are a material using Al ₂ O ₃ as a base material and a material obtained by adding an additive element thereto. Examples of additive elements include Ti, Hf, Mg, Zr, V, Mo, Si, Cr, Nb, Ta, W, B, and C. The ratio of these additive elements can be appropriately changed at a ratio of about 0% to 50%.

For the insulating layer 161, instead of Al oxide such as Al ₂ O ₃ , Ti oxide, Hf oxide, Mg oxide, Zr oxide, Cr oxide, V oxide, Ta oxide, Nb oxidation Materials, Mo oxides, Si oxides, and the like can also be used. Even in the case of these oxides, the above-described materials can be used as additive elements. Further, the amount of the additive element can be appropriately changed at a ratio of about 0% to 50%.

  Instead of these oxides, oxynitrides and nitrides based on Al, Si, Hf, Ti, Mg, Zr, V, Mo, Nb, Ta, W, B, and C as described above are used. Also good.

  The current path 162 is for constricting the current, functions as a conductor that allows the current to pass in the layer direction of the insulating layer 161, and can be made of a nonmagnetic metal such as Cu, for example. That is, the spacer layer 16 has a current confinement structure (CCP structure). The element resistance and MR change rate can be increased by the current confinement effect.

  The current path 162 is a region where the oxygen and nitrogen contents are significantly lower than that of the insulating layer 161 (there is at least a two-fold difference in oxygen and nitrogen content), and is generally a crystalline phase. Since the crystalline phase has a smaller resistance than the amorphous phase, it easily functions as the current path 162.

  The upper metal layer 17 functions as a barrier layer that protects the free layer 18 formed thereon from being oxidized in contact with the oxide of the spacer layer 16.

  Since the oxidation of the free layer 18 can be avoided by optimizing the annealing conditions, the upper metal layer 17 is not necessarily provided. However, considering the manufacturing margin, it is preferable to form the upper metal layer 17 on the spacer layer 16.

  As a constituent material of the upper metal layer 17, Au, Ag, Ru, or the like can be used in addition to Cu. The material of the upper metal layer 17 is preferably the same as the material of the current path 162 of the spacer layer 16. When the material of the upper metal layer 17 is different from the material of the current path 162, the interface resistance is increased. However, if both are the same material, the interface resistance is not increased.

  The thickness of the upper metal layer 17 is preferably 0 to 1 nm, and more preferably 0.1 to 0.5 nm. If the upper metal layer 17 is too thick, the current confined by the spacer layer 16 spreads in the upper metal layer 17 and the current confinement effect becomes insufficient, leading to a reduction in MR ratio.

The free layer 18 is a layer having a ferromagnetic material whose magnetization direction is changed by an external magnetic field. For example, Co ₉₀ Fe ₁₀ [1 nm] / Ni ₈₃ Fe ₁₇ [3. Three layers of 5 nm] may be used. In order to obtain a high MR ratio, selection of the magnetic material of the free layer 18 located at the interface of the spacer layer 16 is important. In this case, it is preferable to provide a CoFe alloy at the interface with the spacer layer 16 rather than a NiFe alloy. In the case where the NiFe layer is not used, Co ₉₀ Fe ₁₀ [4 nm] can be used.

Among the CoFe alloys, Co ₉₀ Fe ₁₀ is preferable because the soft magnetic characteristics are stable. When a CoFe alloy near Co ₉₀ Fe ₁₀ is used, the film thickness is preferably 0.5 to 4 nm.

  Further, as the free layer 18, a CoFe layer or Fe layer having a thickness of 1 to 2 nm and an ultrathin Cu layer having a thickness of about 0.1 to 0.8 nm may be alternately stacked.

Also in the case of the free layer 18, as in the case of the pinned layer 14, when the spacer layer 16 is formed of a Cu layer, the MR ratio can be increased by using a bcc FeCo layer as an interface material with the spacer layer 16. Therefore, a bcc FeCo alloy can be used instead of the fcc CoFe alloy as the interface material with the spacer layer 16. In this case, Fe _x Co _100-x (x = 30 to 100) in which a bcc layer is easily formed, or a material obtained by adding an additive element thereto can also be used.

  Here, a damping factor (DF) adjustment layer 21 can be inserted into these free layers 18 to suppress STI noise. Details of this will be described later.

  The cap layer 19 has a function of protecting the spin valve film. The cap layer 19 can have, for example, a plurality of metal layers, for example, a two-layer structure of a Cu layer and a Ru layer. At this time, the thickness of the Cu layer is preferably about 0.5 to 10 nm. The film thickness of the Ru layer can be about 0.5 to 10 nm.

  As the cap layer 19, a Ru layer having a thickness of about 0.5 to 10 nm may be directly provided on the free layer 18 without using a Cu layer. Further, another metal layer may be provided instead of the Ru layer. The configuration of the cap layer 19 is not particularly limited, and other materials may be used as long as the cap can protect the spin valve film.

  The upper electrode 20 is an electrode for energizing in the direction perpendicular to the spin valve film. When a voltage is applied between the lower electrode 11 and the upper electrode 20, a current flows through the inside of the spin valve film along the direction perpendicular to the film.

(Details of damping factor (DF) adjustment layer 21)
The damping factor adjustment layer 21 is a layer for reducing STI noise. As described above, STI noise is generated by torque that moves the magnetization direction. A direction in which magnetization information is aligned in parallel with each other when electrons having spin torque (in other words, electrons having magnetization information of the magnetic layer) flow from the pinned layer 14 to the free layer 18 or vice versa, Alternatively, torque that is aligned in an antiparallel direction is generated, and this torque causes noise. Suppressing the torque that moves the magnetization direction (stabilizing the magnetization torque caused by current application) is effective in reducing STI noise. A parameter representing damping to the torque is a damping factor.

  In this embodiment, it is possible to increase the damping factor to reduce STI noise and to maintain the MR change rate at a high value. As a specific method, for example, an ultrathin Pt layer of about 0.5 nm is inserted as the damping factor adjustment layer 21 in the magnetic layer of the CCP-CPP spin valve film. As a result, the spin transfer torque phenomenon and thus the STI noise are suppressed.

  Here, it is effective to use a material having a large atomic number or a non-magnetic 3d transition metal ultrathin layer as the damping factor adjustment layer 21 in order to increase the damping factor. The damping factor adjustment layer 21 is inserted into the pinned layer 14 or the free layer 18.

  However, mixing a material having a large atomic number into the magnetic layer of a normal metal CPP spin valve film has a risk of causing adverse effects. Specifically, when a material having a large atomic number is mixed in the magnetic layer, the GMR effect is reduced by the spin orbit interaction. In particular, in the metal CPP spin valve film, the influence on the GMR effect is significant. This is due to the fact that the spin-dependent interface scattering effect and the spin-dependent bulk scattering effect are two in CPP-GMR, but the spin-dependent bulk scattering effect is more prominent in a normal metal CPP spin valve film.

  The spin-dependent interface scattering effect is a GMR effect at the interface between the spacer layer 16 and the pinned layer 14 or the free layer 18, and is a phenomenon that occurs only in the vicinity of the interface. On the other hand, the spin-dependent bulk scattering effect is a GMR effect generated inside the magnetic layer of the pinned layer 14 or the free layer 18. Since the spin-dependent bulk scattering effect is a phenomenon in the magnetic layer, the thicker the magnetic layer, the larger the spin-dependent bulk scattering effect and the higher the MR change rate.

  In a normal metal CPP spin valve film, the GMR phenomenon due to the spin-dependent interface scattering effect is small, and most of the GMR phenomenon is caused by the spin-dependent bulk scattering effect (Non-Patent Document 3: H. Yuasa et al., J. Appl. Phys. 92 (5), 2646 (2002)). In FIG. 5 of Non-Patent Document 3, compared to AdR (area resistance change amount) in the limit where the magnetic layer thickness is zero (this value corresponds to the spin-dependent interface scattering effect), the magnetic layer thickness is larger. This fact can be understood from the fact that AdR is much larger (the sum of the spin-dependent interface scattering effect and the spin-dependent bulk scattering effect is seen where the magnetic layer is thick).

  That is, in the normal metal CPP spin valve film, the contribution of the spin bulk scattering effect is very large. For this reason, it is not preferable to insert a material having a large atomic number that reduces the spin-dependent bulk scattering effect into the magnetic layer from the viewpoint of a decrease in MR ratio and a decrease in head output. That is, it is difficult to achieve both low STI noise and high output. Thus, in a metal CPP spin valve film having a normal metal spacer layer 16, it is difficult to say that inserting an element having a large atomic number into the magnetic layer of the pinned layer 14 or the free layer 18 is a preferable method.

  On the other hand, in the CCP-CPP spin valve film, the influence of the spin-dependent interface scattering effect is much greater than the spin-dependent bulk scattering effect (Non-patent Document 4: H. Fukuzawa et al., Appl. Phys. Lett. 87, 082507 (2005)). This is because the influence of the interface effect in the vicinity of the CCP is large because the contribution of the CCP portion to the total resistance of the spin valve film is very large. That is, in the CCP-CPP spin valve film, even if there is a slight decrease in the spin-dependent bulk scattering effect, the MR ratio and the head output are unlikely to decrease unless the spin-dependent interface scattering effect decreases. For this reason, it is easy to achieve both low STI noise and a high MR ratio.

  For the above reason, in the CCP-CPP element, the damping factor adjustment layer 21 can suppress STI noise without substantially reducing MR.

  As the damping factor adjustment layer 21, in addition to Pt, atomic numbers such as Zr, Nb, Mo, Ru, Rh, Pd, Ag, La, Hf, Ta, W, Re, Os, Ir, Pt, and Au are relatively used. Large materials and non-magnetic 3d transition metals such as Ti, V, Cr, and Mn can also be used.

  By inserting a nonmagnetic material, there is a possibility that the magnetic coupling in the pinned layer 14 or the free layer 18 (that is, the upper and lower magnetic layers via the damping factor adjusting layer 21) may be broken. In order to keep the magnetic coupling through the damping factor adjustment layer 21 at a sufficiently large value, the film thickness of the damping factor adjustment layer 21 is preferably 0.1 to 1 nm, more preferably 0.1 nm to 0.7 nm.

  The damping factor adjustment layer 21 may be inserted into only one of the pinned layer 14 and the free layer 18.

  If the damping factor adjustment layer 21 is inserted in the vicinity of the spacer layer 16, the MR change rate is decreased, which is not preferable. It is preferable to insert the damping factor adjustment layer 21 at a position at least 1 nm away from the spacer layer 16. That is, the damping factor adjustment layer 21 is disposed at a position away from the spacer layer 16 to some extent in consideration of the influence on the MR change rate.

  As described above, the damping factor adjustment layer 21 is arranged at a position about 1 nm away from the vicinity of the interface with the spacer layer 16, thereby suppressing the damping factor without adversely affecting the spin-dependent interface scattering effect. it can. That is, in the case of CCP-CPP, STI noise can be efficiently suppressed without sacrificing the MR change rate.

  Depending on the material, it is also possible to insert the damping factor adjustment layer 21 in a region of 1 nm or less from the vicinity of the interface with the spacer layer 16. Specifically, when Ti, Zr, Pd, Nb, or the like is used as the damping factor adjustment layer 21, the influence of the spin-dependent interface scattering effect is relatively not disturbed, so that it is 1 nm or less from the interface with the spacer layer 16. The damping factor adjustment layer 21 may be inserted in the region. More specifically, it can also be used at an insertion position at a distance from the interface with the spacer layer 16 (that is, a distance of 0 nm from the interface) to 1 nm. Of course, these materials can be inserted at any location, such as at greater distances.

  These materials such as Ti, Zr, Pd, and Nb are materials that can be easily used as the damping factor adjustment layer 21 from the viewpoint that the influence on the MR ratio is small.

  A plurality of damping factor adjustment layers 21 may be inserted in a magnetic layer such as the pinned layer 14 or the free layer 18. In this case, when the material such as Ti, Zr, or Nb is used, the first layer is inserted at a distance of 1 nm or less from the spacer layer 16, and the distance from the spacer layer 16 is used when other elements such as Pt are used. The first layer is inserted at a distance of more than 1 nm.

 Then, a laminated film such as a second layer and a third layer is inserted at a position farther from the spacer layer 16 than the first layer. The distance between the first layer and the second layer, or the distance between the second layer and the third layer is preferably about 1 nm to 2 nm. However, when a thick magnetic layer is used, it is possible to use a thicker interval than this range.

  As an advantage of using a plurality of damping factor adjustment layers 21 in the free layer 18 or the pinned layer 14, there is a point that the effect of adjusting the damping factor and, moreover, the effect of noise reduction are further increased. A plurality of damping factor adjustment layers 21 may be inserted only in the free layer 18 or only in the pinned layer 14, and both the pinned layer 14 and the free layer 18 may be laminated.

  Disadvantages of using a plurality of damping factor adjustment layers 21 may be that the MR ratio is reduced or the magnetic coupling between the magnetic layers via the damping factor adjustment layer 21 is weakened, which may deteriorate the magnetic characteristics. . In order to prevent magnetic characteristics, the total thickness of the free layer 18 or the damping factor adjustment layer 21 in the pinned layer 14 is preferably in the same film thickness range as that of one layer. In addition, as described above, the distance between the plurality of damping factor adjustment layers 21 in one magnetic layer is preferably in the range of 1 to 2 nm.

  Here, instead of using the damping factor adjustment layer 21 as in the present embodiment, a material (for example, an alloy) in which the ST effect is suppressed in the constituent material itself of the magnetic layer (the pinned layer 14 and the free layer 18). It is conceivable to select a material.

  However, in this case, the MR change rate decreases. In a CPP spin valve film having a CCP structure, the MR effect near the interface of the spacer layer 16 is large, and it is not preferable that an additive element that lowers the MR ratio be present near this interface.

  In the vicinity of the interface with the spacer layer 16, a magnetic material that does not impair high MR is used, and an extremely thin layer (damping factor adjustment layer 21) is inserted inside the magnetic layer (pinned layer 14, free layer 18). The effect can be suppressed. By doing so, it becomes easy to achieve both suppression of the ST effect and maintenance of the MR ratio.

  Hereinafter, this embodiment will be described in comparison with a comparative example.

A. Comparison with the case where Pt is added to the entire magnetic layer As a comparative example, a case where Pt is used as an additive element to the entire magnetic layer is considered. When Pt is added as a whole to a laminated magnetic layer such as CoFe / NiFe used as the free layer 18, a free layer 18 of CoFePt / NiFePt is obtained. In this case, the damping factor increases and STI noise can be suppressed. However, on the other hand, since the MR change rate is reduced, the head output is reduced. Specifically, the MR change rate, which was 9% in the free layer to which Pt is not added, is 4% in the free layer to which Pt is added, and the MR change rate is significantly reduced.

  On the other hand, in this embodiment, the effect of adjusting the damping factor is exhibited while maintaining a large spin-dependent interface scattering effect by inserting the Pt ultrathin layer at a distance from the CCP interface. Specifically, by inserting a 0.5 nm ultra-thin Pt layer into the NiFe layer, the MR change rate is slightly reduced to 8.5%, but this is not a significant decrease, and STI noise is greatly suppressed. It becomes possible to do. That is, in this embodiment, the advantage of improving the S / N ratio by reducing noise is greater than the effect of slightly reducing the MR change rate and the signal output, resulting in a BER (Bit Error Rate). ) Is reduced, and good characteristics can be obtained.

B. Comparison with Metal CPP Spin Valve Film In the case of a metal CPP spin valve film having no CCP structure, the spin-dependent interface scattering effect is not the main effect, and the spin-dependent bulk scattering effect contributes very much. For this reason, even if an ultrathin Pt layer is inserted at a position away from the interface of the spacer layer 16, the MR change rate decreases, and the function as the damping factor adjustment layer 21 cannot be exhibited.

  As a specific example, in the case of a normal metal CPP spin valve film having a 5 nm Cu spacer layer without a CCP spacer layer and a standard CoFe / NiFe free layer, the MR ratio is 2%. It is. At this time, if a 0.5 nm ultrathin Pt layer or the like is inserted in the NiFe layer, the MR ratio will be 1%. In the case of a simple metal CPP spin-valve film, it is difficult to obtain a sufficient output as a magnetic head with an original MR change rate as small as 1 to 3%. The amount of MR change rate deterioration caused by inserting the damping factor adjustment layer 21 into the metal CPP spin valve film is larger than that in the CCP-CPP. For this reason, as a total performance, it is difficult to use an ultrathin Pt layer as the damping factor adjustment layer 21 of the metal CPP spin valve film.

  Thus, a great effect is exhibited by combining the CCP spin valve film and the damping factor adjustment layer 21.

C. Effect of changing the damping factor adjustment layer 21 The basic CCP-CPP spin valve film is fixed, and the influence on the MR change rate when the damping factor adjustment layer 21 is changed is examined.

As the configurations of the pinned layer 14, the spacer layer 16, and the free layer 18 that have a great influence on the MR ratio, the following configurations were examined. First, as the pinned layer 143, a layer in which 0.2 nm of ultra-thin Cu was laminated for every 1 nm of FeCo on 2-3 nm of Fe ₅₀ Co ₅₀ was used. The spacer layer 16 is a 1.5 to 2 nm spacer layer 16 using Al ₂ O ₃ having a CCP structure as an insulating layer and Cu as a metal path. The free layer 18 has a basic film configuration of CoFe 1 nm / NiFe 3.5 nm.

In such a CCP-CPP spin valve film, Table 1 below shows the material and insertion position dependency of the damping factor adjusting layer 21 when the damping factor adjusting layer 21 is used.

Table 1 shows the dependency of the MR ratio on the material and the insertion position (distance: distance from the CCP interface) when the damping factor adjustment layer 21 is inserted only in the free layer 18. Comparative Example 0 is a case where the damping factor adjustment layer 21 is not provided.

  As can be seen from Table 1, when a standard damping factor adjustment layer 21 such as Pt is inserted at the interface of the spacer layer 16, the MR ratio is greatly reduced, which is not effective. Usually, it is desirable to insert the damping factor adjustment layer 21 at a position 1 nm or more away from the interface of the spacer layer 16.

  On the other hand, when the damping factor adjustment layer 21 is Ti, Zr, Pd or Hf, even if it is inserted in the vicinity of the interface of the spacer layer 16, the degree of decrease in the MR ratio is relatively small, and it is also used in the vicinity of the interface. be able to. However, the insertion into the magnetic layer rather than the interface is preferable from the viewpoint of the MR change rate because the influence on the decrease in MR change rate is reduced.

  Depending on the specific STI noise situation, it is optimized whether it is provided near the interface or inside the magnetic layer. Since the free layer 18 is responsible for the magnetization response to the magnetic field of the medium and the pinned layer 14 is fixedly magnetized regardless of the direction of the medium magnetic field, inserting the damping factor adjustment layer 21 in the free layer 18 is effective in reducing STI noise. It is. Therefore, it is preferable to insert in the free layer 18 as in Examples 1 to 11 as a configuration in which the MR change rate and the STI noise reduction are compatible.

Examples 21 to 31 in the case where the damping factor adjustment layer 21 is inserted only into the pinned layer 14 are shown in Table 2. Also in this case, the dependence on the material is qualitatively the same as in Examples 1-11. However, in the case of the pinned layer 14, the increase in the spin-dependent interface scattering effect is large because bcc-FeCo having a large spin-dependent interface scattering effect is used. For this reason, the damage to the decrease in MR change rate due to the insertion of the damping factor adjustment layer 21 is larger than that in the case of the free layer 18.

Tables 3 to 51 show Examples 41 to 51 when both the pinned layer 14 and the free layer 18 are inserted. The tendency is the same as before. Compared with the case where only the pinned layer 14 and only the free layer 18 are inserted, the MR change rate is reduced, but the STI noise suppressing effect is increased.

(Method for manufacturing magnetoresistive element)
Hereinafter, the manufacturing method of the magnetoresistive effect element in this Embodiment is demonstrated in detail.

  FIG. 2 is a flowchart showing manufacturing steps of the magnetoresistive effect element according to the first embodiment of the present invention.

  FIG. 3 is a schematic diagram showing an outline of a film forming apparatus used for manufacturing a magnetoresistive effect element. FIG. 4 is a schematic view showing an oxidation chamber 60 in the film forming apparatus.

  As shown in FIG. 3, a load lock chamber 51, a pre-cleaning chamber 52, a first metal film forming chamber (MC1) 53, and a second metal film forming chamber (MC2) 54 are centered on a transfer chamber (TC) 50. Each of the oxidation chambers (OC) 60 is provided via a gate valve. In this film forming apparatus, the substrate can be transported in vacuum between the chambers connected via the gate valve, so that the surface of the substrate is kept clean.

  The metal film forming chambers 53 and 54 have multi-targets (5 to 10 yuan). Examples of the film formation method include sputtering methods such as DC magnetron sputtering and RF magnetron sputtering, ion beam sputtering methods, and vapor deposition methods.

  As shown in FIG. 4, the oxidation chamber 60 is evacuated by a vacuum pump 61, and oxygen gas whose flow rate is controlled by a mass flow controller (MFC) 63 is introduced into the oxidation chamber 60 from an oxygen supply pipe 62.

  An ion source 70 is provided in the oxidation chamber 60. Examples of the ion source include ICP (Inductive coupled plasma) type, Capacitive coupled plasma type, ECR (Electron-cyclotron resonance) type, and Kaufmann type.

  The substrate holder 80 and the substrate 1 are arranged so as to face the ion source 70. Three grids 71, 72, and 73 that adjust ion acceleration are provided at the ion emission port from the ion source 70. A neutralizer 74 for neutralizing ions is provided outside the ion source 70. The substrate holder 80 is supported to be tiltable. Although the incident angle of ions on the substrate 1 can be varied in a wide range, a typical incident angle value is 15 ° to 60 °.

  Hereinafter, the manufacturing process of the magnetoresistive effect element will be described.

  On a substrate (not shown), the lower electrode 11, the base layer 12, the pinning layer 13, the pin layer 14, the lower metal layer 15, the spacer layer 16, the upper metal layer 17, the free layer 18, the cap layer 19, and the upper electrode 20 Are formed in order. Note that the order of formation may be reversed.

The substrate is set in the load lock chamber 51, and metal film formation is performed in the metal film formation chambers 53 and 54, and oxidation is performed in the oxidation chamber 60. The ultimate vacuum of the metal film forming chamber is preferably 1 × 10 ⁻⁸ Torr or less, and generally about 5 × 10 ⁻¹⁰ Torr to 5 × 10 ⁻⁹ Torr. The ultimate vacuum of the transfer chamber 50 is on the order of 10 ⁻⁹ Torr. The ultimate vacuum of the oxidation chamber 60 is 8 × 10 ⁻⁸ Torr or less.

(1) Formation of lower electrode 11, foundation layer 12, and pinning layer 13 (step S11) The lower electrode 11 is formed on a substrate (not shown).

  On the lower electrode 11, for example, Ta [5 nm] / Ru [2 nm] is formed as the base layer 12. As described above, Ta is the buffer layer 12a for reducing the roughness of the lower electrode. Ru is a seed layer 12b for controlling the crystal orientation and crystal grain size of the spin valve film formed thereon.

  A pinning layer 13 is formed on the underlayer 12. As a material of the pinning layer 13, an antiferromagnetic material such as PtMn, PdPtMn, IrMn, RuRhMn can be used.

(2) Formation of Pinned Layer 14 (and Damping Factor Adjusting Layer 21) (Step S12) The pinned layer 14 is formed on the pinning layer 13. The pinned layer 14 can be, for example, a synthetic pinned layer including a lower pinned layer 141 (Co90Fe ₁₀ ), a magnetic coupling layer 142 (Ru), and an upper pinned layer 143 (Co90Fe ₁₀ [4 nm]).

The damping factor adjustment layer 21 can be inserted by switching the material to be deposited during the deposition of the upper pinned layer 143. Specifically, by switching the film forming material from Co90Fe ₁₀ to Pt, also by returning the _Co 90 _{Fe 10,} the damping factor adjustment layer 21 made of Pt in the upper pinned layer 143 is inserted.

(3) Formation of spacer layer 16 (step S13)
Next, the spacer layer 16 having a current confinement structure (CCP structure) is formed. An oxidation chamber 60 is used to form the spacer layer 16.

In order to form the spacer layer 16, the following method is used. Here, a case where the spacer layer 16 including the current path 162 made of Cu having a metal crystal structure is formed in the insulating layer 161 made of Al ₂ O ₃ having an amorphous structure will be described as an example.

  1) After forming a lower metal layer 15 (for example, Cu) serving as a current path supply source on the upper pinned layer 143, an oxidized metal layer (for example, AlCu or the like) that is converted into an insulating layer on the lower metal layer 15 Al) is deposited.

  Pretreatment is performed by irradiating the metal layer to be oxidized with an ion beam of a rare gas (eg, Ar). This pretreatment is called PIT (Pre-ion treatment). As a result of this PIT, a part of the lower metal layer is sucked and invaded into the metal layer to be oxidized.

2) An oxidizing gas (for example, oxygen) is supplied to oxidize the metal layer to be oxidized. By this oxidation, the metal layer to be oxidized is converted into an insulating layer 161 made of Al ₂ O _3, and a current path 162 penetrating the insulating layer 161 is formed to form the spacer layer 16.

For example, an oxidizing gas (for example, oxygen) is supplied while irradiating an ion beam of a rare gas (Ar, Xe, Kr, He, etc.) to oxidize a metal layer to be oxidized (ion beam assisted oxidation (IAO)). Oxidation)). By this oxidation treatment, the spacer layer 16 in a form in which the Al ₂ O _{3 as} the insulating layer 161 and the Cu as the current path 162 are separated is formed. This is a process that utilizes the difference in oxidation energy that Al is easily oxidized and Cu is not easily oxidized.

(4) Formation of upper metal layer 17 and free layer 18 (and damping factor adjusting layer 21) (step S14)
On the spacer layer 16, for example, Cu [0.25 nm] is formed as the upper metal layer 17.

A free layer 18, for example, Co ₉₀ Fe ₁₀ [1 nm] / Ni ₈₃ Fe ₁₇ [3.5 nm] is formed on the upper metal layer 17.

The damping factor adjustment layer 21 can be inserted by switching the material to be formed during the formation of the free layer 18. Specifically, by switching the film forming material from the Ni ₈₃ Fe ₁₇ to Pt, also by returning the Ni ₈₃ Fe _17, the damping factor adjustment layer 21 made of Pt into the Ni ₈₃ Fe ₁₇ free layer 18 is inserted The

(5) Formation of cap layer 19 and upper electrode 20 (step S15)
On the free layer 18, for example, Cu [1 nm] / Ru [10 nm] is laminated as the cap layer 19. An upper electrode 20 is formed on the cap layer 19 to vertically apply current to the spin valve film.

(Example)
As an example of an embodiment of the present invention, the following configuration can be exemplified. In this embodiment, a 0.5 nm Pt layer is disposed as the damping factor adjustment layer 21 in the upper pinned layer 143 and in the Fe ₅₀ Co ₅₀ layer of the free layer 18. By using the damping factor adjustment layer 21, it is possible to suppress STI noise while maintaining a high value of RA of 300 to 1000 mm ² and MR change rate of 8 to 15%.

・ Lower electrode 11
・ Underlayer 12: Ta [5 nm] / Ru [2 nm]
Pinning layer 13: Pt ₅₀ Mn ₅₀ [15 nm]
Pinned layer 14: Co ₉₀ Fe ₁₀ [4 nm] / Ru [ _0.9 nm] / Fe ₅₀ Co ₅₀ [
2 nm] / Pt _0.5 nm / Fe ₅₀ Co ₅₀ [2 nm]
Lower metal layer 15: Cu [0.5 nm]
Spacer layer (CCP-NOL) 16: Insulating layer 161 made of Al ₂ O ₃ and current path 162 made of Cu (after oxidation of Al ₉₀ Cu ₁₀ [ _0.9 nm])
Upper metal layer 17: Cu [0.25 nm]
Free layer 18: Co ₉₀ Fe ₁₀ [1 nm] / Ni ₈₃ Fe ₁₇ [1 nm] / Pt [0
. 5 nm] / Ni ₈₃ Fe ₁₇ [1 nm]
Cap layer 19: Cu [1 nm] / Ru [10 nm]
・ Upper electrode 20
(Second Embodiment)
FIG. 5 is a perspective view showing a magnetoresistive effect element (CCP-CPP element) according to the second embodiment of the present invention.

  As shown in FIG. 5, the magnetoresistive effect element according to the present embodiment includes a magnetoresistive effect film 10a, and a lower electrode 11 and an upper electrode 20 that sandwich the magnetoresistive effect film 10a from above and below, and is configured on a substrate (not shown). .

  The magnetoresistive effect film 10a includes a base layer 12, a pinning layer 13, a pin layer 14a, a lower metal layer 15, a spacer layer (CCP-NOL) 16, an upper metal layer 17, a free layer 18a, and a cap layer 19 stacked in this order. Composed. Since the magnetoresistive film 10a is not essentially different from the magnetoresistive film 10, a detailed description of the underlayer 12 to the cap layer 19 is omitted.

  In this embodiment, the STI noise is reduced by disposing an electron diffuse reflection layer (Diffusive Electron Scattering Layer: DESL) 22 at the interface (the boundary between the free layer 18a and the cap layer 19) on the free layer 18a. Unlike the first embodiment, the electron irregular reflection layer 22 is not disposed in the pinned layer 14a.

  The electron irregular reflection layer 22 is disposed under the cap layer 19 and diffuses electrons. By irregularly reflecting electrons with the electron irregular reflection layer 22, the electron reflection at the outer interface (interface opposite to the spacer layer 16) of the ferromagnetic layer (free layer 18 a) is limited, and the ST effect and consequently STI noise are suppressed. can do. It is also possible to include the electron irregular reflection layer 22 in the cap layer 19.

  (1) The electron irregular reflection layer 22 can be formed of a nonmagnetic amorphous material. Electrons are diffusely reflected by the amorphous structure of the nonmagnetic amorphous material, and STI noise is suppressed.

  As the nonmagnetic amorphous material, a single metal such as Ta, Ti, Zr, Hf, Nb, B, Si, W, or an alloy material containing at least 50% of these elements can be used. As the nonmagnetic amorphous material, an amorphous material having an alloy composition such as AlB, AlSiB, or AlSi may be used.

  Since the STI noise is suppressed by utilizing the irregular reflection of electrons due to the amorphous structure of the nonmagnetic amorphous material, it is not preferable that the electron irregular reflection layer 22 has a crystal structure. In order to suppress crystallization in the electron irregular reflection layer 22, it is preferable that the electron irregular reflection layer 22 is thin to some extent.

From the viewpoint of a narrow gap, it is preferable that the electron irregular reflection layer 22 is thin to some extent. Specifically, the thickness of the electron irregular reflection layer 22 is preferably 0.5 to 5 nm, and more preferably 1 to 3 nm.

  (2) Moreover, the electron irregular reflection layer 22 can be comprised by a mixing layer. The mixing layer can cause irregular reflection of electrons and suppress STI noise.

  Two layers can be laminated and a mixing layer can be formed at the interface. That is, at least two kinds of alloy materials having a solid solution relationship can be laminated in two layers, and a solid solution mixing layer can be formed at the interface. Examples of combinations of mutually solid materials include Cu and Al (form a CuAl alloy), Cu and Ni (form a CuNi alloy), and the like.

(Method for manufacturing magnetoresistive element)
FIG. 6 is a flowchart showing the manufacturing process of the magnetoresistive effect element according to the second embodiment of the invention.

  FIG. 6 differs from FIG. 2 in that an electron irregular reflection layer 22 is formed instead of the damping factor adjustment layer 21. In other respects, FIG. 6 is not essentially different from FIG. 2, and only the formation of the electron irregular reflection layer 22 will be described below.

  Any of the following methods (1) to (3) can be applied to the formation of the electron irregular reflection layer 22 in step S25 of FIG.

(1) Formation of amorphous layer A nonmagnetic amorphous material layer is formed by depositing the above-described simple metal such as Ta, an alloy material containing at least 50% of these elements, or an alloy material such as AlB. . For this film formation, sputtering methods such as DC magnetron sputtering and RF magnetron sputtering, ion beam sputtering, and vapor deposition can be used.

  Since these materials are easily amorphized, means for promoting the amorphization such as cooling may not be applied at the time of film formation.

(2) Formation of mixing layer 1) As described above, at least two or more kinds of alloy materials having a solid solution relationship with each other are laminated into a first layer and a second layer so that a solid layer is formed at the interface. A soluble mixing layer can be formed. A sputtering method such as DC magnetron sputtering or RF magnetron sputtering, an ion beam sputtering method, or a vapor deposition method can be used for this lamination.

  For example, on the free layer 18a, 0.5 nm of Al is stacked as the first layer, and 0.5 nm of Cu is stacked as the second layer. Since Al and Cu are in a solid solution relationship, a mixing layer is formed at the interface, and electrons are irregularly reflected by this mixing layer.

  In addition, following Al [0.5 nm] / Cu [0.5 nm], Ru can be laminated by 10 nm to form the cap layer 19 (step S26 in FIG. 6).

  2) It is also possible to promote the formation of the mixing layer by applying a surface treatment to the interface between the first layer and the second layer.

  For example, on the free layer 18a, Al is deposited to a thickness of 0.5 nm as a first layer, and then Cu is deposited as a second layer to a thickness of 0.5 nm, and then a treatment such as plasma or ion beam is applied to the surface. By performing the surface treatment, it is possible to enhance (promote) the formation of the mixing layer at the interface between the Al layer and the Cu layer. The formation of the mixing layer is promoted by moving and intermingling atoms at the interface between the Al layer and the Cu layer by incident energy such as ions.

  This surface treatment may be performed not only after the film formation of the first and second layers but also during the film formation. For example, after the first layer is formed, the surface treatment can be performed during the formation of the second layer.

  For this surface treatment, an inert gas such as Ar or Ne can be used after being plasmatized or ionized. At this time, neutral atoms can contribute to the surface treatment in addition to ions of the rare gas. If it has a certain amount of energy when it is incident on the interface, atoms at the interface can be moved regardless of the presence or absence of ionization.

  The promotion of the formation of the mixing layer by the surface treatment is also effective in the case of a combination of other materials (for example, Ni and Cu) besides the combination of Al and Cu.

(Example)
As an example of an embodiment of the present invention, the following configuration can be exemplified. Here, the Ta layer in the cap layer 19 functions as the electron irregular reflection layer 22. That is, here, the electron irregular reflection layer 22 is considered to be included in the cap layer 19. The nonmagnetic layer inside the free layer 18 and the nonmagnetic layer at the interface with the spacer layer 16 are considered as the damping factor adjustment layer 21, but the nonmagnetic layer laminated on the top of the free layer 18 is the cap layer 19. Can be considered part of

Here, (Fe ₅₀ Co ₅₀ / Cu) is repeatedly laminated twice to form the upper pinned layer 143a. As shown in Non-Patent Document 3, FeCo is used because it has a large spin-dependent interface scattering effect, and Cu is stacked in order to improve the spin-dependent bulk scattering effect.

Note that the upper pinned layer 143a may be formed of only Fe ₅₀ Co ₅₀ .

・ Lower electrode 11
・ Underlayer 12: Ta [5 nm] / Ru [2 nm]
Pinning layer 13: Pt ₅₀ Mn ₅₀ [15 nm]
Pinned layer 14: Co ₉₀ Fe ₁₀ [4 nm] / Ru [ _0.9 nm] / (Fe ₅₀ Co ₅₀
[1 nm] / Cu [0.25 nm]) × 2 / Fe ₅₀ Co ₅₀ [1 nm]
Lower metal layer 15: Cu [0.5 nm]
・ Spacer layer (CCP-NOL) 16
Upper metal layer 17: Cu [0.25 nm]
Free layer 18: Co ₉₀ Fe ₁₀ [1 nm] / Ni ₈₃ Fe ₁₇ [3.5 nm]
Cap layer 19: Ta [1 nm] / Cu [10 nm]
-Upper electrode 20
(Magnetic head)
7 and 8 show a state in which the magnetoresistive effect element according to the embodiment of the present invention is incorporated in a magnetic head. FIG. 7 is a cross-sectional view of the magnetoresistive element cut in a direction substantially parallel to a medium facing surface facing a magnetic recording medium (not shown). FIG. 8 is a cross-sectional view of the magnetoresistive element cut in a direction perpendicular to the medium facing surface ABS.

  The magnetic head illustrated in FIGS. 7 and 8 has a so-called hard abutted structure. The magnetoresistive film 10 is the CCP-CPP film described above. A lower electrode 11 and an upper electrode 20 are provided above and below the magnetoresistive effect film 10, respectively. In FIG. 7, a bias magnetic field application film 41 and an insulating film 42 are laminated on both sides of the magnetoresistive effect film 10. As shown in FIG. 8, a protective layer 43 is provided on the medium facing surface of the magnetoresistive film 10.

  The sense current for the magnetoresistive film 10 is energized in a direction substantially perpendicular to the film surface as indicated by the arrow A by the electrodes 11 and 20 disposed above and below it. A bias magnetic field is applied to the magnetoresistive film 10 by a pair of bias magnetic field application films 41, 41 provided on the left and right. By this bias magnetic field, the magnetic anisotropy of the free layer 18 of the magnetoresistive effect film 10 is controlled to form a single magnetic domain, thereby stabilizing the magnetic domain structure and suppressing Barkhausen noise due to the domain wall movement. can do.

  Since the S / N ratio of the magnetoresistive film 10 is improved, high sensitivity magnetic reproduction is possible when applied to a magnetic head.

(Hard disk and head gimbal assembly)
The magnetic head shown in FIGS. 7 and 8 can be mounted on a magnetic recording / reproducing apparatus by being incorporated in a recording / reproducing integrated magnetic head assembly.

  FIG. 9 is a main part perspective view illustrating a schematic configuration of such a magnetic recording / reproducing apparatus. That is, the magnetic recording / reproducing apparatus 150 of the present invention is an apparatus using a rotary actuator. In the figure, a magnetic disk 200 is mounted on a spindle 152 and rotated in the direction of arrow A by a motor (not shown) that responds to a control signal from a drive device control unit (not shown). The magnetic recording / reproducing apparatus 150 of the present invention may include a plurality of magnetic disks 200.

  A head slider 153 that records and reproduces information stored in the magnetic disk 200 is attached to the tip of a thin-film suspension 154. The head slider 153 has a magnetic head including the magnetoresistive effect element according to any one of the above-described embodiments mounted near its tip.

  When the magnetic disk 200 rotates, the medium facing surface (ABS) of the head slider 153 is held with a predetermined flying height from the surface of the magnetic disk 200. Alternatively, a so-called “contact traveling type” in which the slider contacts the magnetic disk 200 may be used.

  The suspension 154 is connected to one end of the actuator arm 155. A voice coil motor 156, which is a kind of linear motor, is provided at the other end of the actuator arm 155. The voice coil motor 156 includes a drive coil (not shown) wound around a bobbin portion, and a magnetic circuit including a permanent magnet and a counter yoke arranged so as to sandwich the coil.

  The actuator arm 155 is held by ball bearings (not shown) provided at two positions above and below the spindle 157, and can be freely rotated and slid by a voice coil motor 156.

  FIG. 10 is an enlarged perspective view of the head gimbal assembly ahead of the actuator arm 155 as viewed from the disk side. That is, the assembly 160 has an actuator arm 155, and a suspension 154 is connected to one end of the actuator arm 155. A head slider 153 including a magnetic head including the magnetoresistive effect element according to any one of the above-described embodiments is attached to the tip of the suspension 154. The suspension 154 has a lead wire 164 for writing and reading signals, and the lead wire 164 and each electrode of the magnetic head incorporated in the head slider 153 are electrically connected. In the figure, reference numeral 165 denotes an electrode pad of the assembly 160.

  According to the present embodiment, by providing the magnetic head including the magnetoresistive element described above, it is possible to reliably read information magnetically recorded on the magnetic disk 200 at a high recording density.

(Magnetic memory)
Next, a magnetic memory equipped with the magnetoresistive effect element according to the embodiment of the present invention will be described. That is, by using the magnetoresistive effect element according to the embodiment of the present invention, a magnetic memory such as a random access magnetic memory (MRAM) in which memory cells are arranged in a matrix can be realized.

  FIG. 11 is a diagram showing an example of a matrix configuration of the magnetic memory according to the embodiment of the present invention. This figure shows a circuit configuration when memory cells are arranged in an array. In order to select one bit in the array, a column decoder 350 and a row decoder 351 are provided, and the switching transistor 330 is turned on by the bit line 334 and the word line 332 to be uniquely selected and detected by the sense amplifier 352. As a result, the bit information recorded in the magnetic recording layer (free layer) in the magnetoresistive film 10 can be read. When writing bit information, a magnetic field generated by applying a write current to a specific write word line 323 and bit line 322 is applied.

  FIG. 12 is a diagram showing another example of the matrix configuration of the magnetic memory according to the embodiment of the present invention. In this case, bit lines 322 and word lines 334 wired in a matrix are selected by decoders 360 and 361, respectively, and specific memory cells in the array are selected. Each memory cell has a structure in which a magnetoresistive element 10 and a diode D are connected in series. Here, the diode D has a role of preventing the sense current from bypassing in the memory cells other than the selected magnetoresistive effect element 10. Writing is performed by a magnetic field generated by supplying a write current to the specific bit line 322 and the write word line 323, respectively.

  FIG. 13 is a cross-sectional view showing the main part of the magnetic memory according to the embodiment of the present invention. FIG. 14 is a cross-sectional view taken along the line A-A ′ of FIG. 13. The structures shown in these drawings correspond to 1-bit memory cells included in the magnetic memory shown in FIG. This memory cell has a memory element portion 311 and an address selection transistor portion 312.

  The memory element portion 311 includes the magnetoresistive effect element 10 and a pair of wirings 322 and 324 connected thereto. The magnetoresistive effect element 10 is the magnetoresistive effect element (CCP-CPP element) according to the above-described embodiment.

  On the other hand, the selection transistor portion 312 is provided with a transistor 330 connected via a via 326 and a buried wiring 328. The transistor 330 performs a switching operation according to the voltage applied to the gate 332, and controls opening and closing of a current path between the magnetoresistive effect element 10 and the wiring 334.

  Further, below the magnetoresistive effect element 10, a write wiring 323 is provided in a direction substantially orthogonal to the wiring 322. These write wirings 322 and 323 can be formed of, for example, aluminum (Al), copper (Cu), tungsten (W), tantalum (Ta), or an alloy containing any of these.

  In the memory cell having such a configuration, when writing bit information to the magnetoresistive effect element 10, a write pulse current is supplied to the wirings 322 and 323, and a composite magnetic field induced by these currents is applied to thereby apply the magnetoresistive effect element. The magnetization of the recording layer is appropriately reversed.

  When reading bit information, a sense current is passed through the wiring 322, the magnetoresistive effect element 10 including the magnetic recording layer, and the lower electrode 324, and the resistance value of the magnetoresistive effect element 10 or a change in the resistance value is measured. To do.

  The magnetic memory according to the embodiment of the present invention uses the magnetoresistive effect element (CCP-CPP element) according to the embodiment described above to reliably control the magnetic domain of the recording layer even if the cell size is reduced. Reliable writing can be ensured and reading can be performed reliably.

(Other embodiments)
Embodiments of the present invention are not limited to the above-described embodiments, and can be expanded and modified. The expanded and modified embodiments are also included in the technical scope of the present invention.

  The specific structure of the magnetoresistive film, and other shapes and materials of the electrode, bias application film, insulating film, etc., are appropriately implemented by those skilled in the art, and the present invention is similarly implemented. The effect of can be obtained.

  For example, when applying a magnetoresistive element to a reproducing magnetic head, the detection resolution of the magnetic head can be defined by providing magnetic shields above and below the element.

  The embodiment of the present invention can be applied not only to a longitudinal magnetic recording system but also to a perpendicular magnetic recording system magnetic head or magnetic reproducing apparatus.

  Furthermore, the magnetic reproducing apparatus of the present invention may be a so-called fixed type having a specific recording medium constantly provided, or a so-called “removable” type in which the recording medium can be replaced.

  In addition, all magnetoresistive elements, magnetic heads, magnetic storage / reproduction devices, and magnetic memories that can be appropriately designed and implemented by those skilled in the art based on the magnetic head and magnetic storage / reproduction device described above as embodiments of the present invention Are also within the scope of the present invention.

  DESCRIPTION OF SYMBOLS 10 ... Magnetoresistance effect film (magnetoresistance effect element), 11 ... Lower electrode, 12 ... Underlayer, 13 ... Pinning layer, 14 ... Pin layer, 141 ... Lower pin layer, 142 ... Magnetic coupling layer, 143 ... Upper pin layer 15 ... Lower metal layer, 16 ... Spacer layer, 161 ... Insulating layer, 162 ... Current path, 17 ... Upper metal layer, 18 ... Free layer, 19 ... Cap layer, 20 ... Upper electrode, 21 ... Damping factor adjustment layer, 22 ... Electron diffuse reflection layer

Claims (6)

A non-magnetic layer having a pinned layer, a non-magnetic layer disposed on the pinned layer, and having an insulating layer and a conductor that passes a current in a layer direction of the insulating layer, on the non-magnetic layer A spin valve film having a magnetization free layer having a NiFe layer arranged and having a CoFe layer inserted at an interface with the nonmagnetic layer;
Predetermined to be disposed inside the magnetization free layer, including Ti or Pd, one or more layers away from the nonmagnetic layer by 1 nm or more, and having a thickness of 0.1 nm to 1 nm (excluding 1 nm) Layer of
A pair of electrodes provided above and below the spin valve film and energized perpendicularly to the film surface of the spin valve film;
Comprising
A magnetoresistive element in which a half-value width of a rocking curve at the fcc (111) peak of the spin valve film, the fct (111) peak of the pinning layer, or bcc (110) is 3.5 to 6 degrees.   The magnetoresistive element according to claim 1, wherein the predetermined layer is disposed on the magnetization free layer and includes any one of Ti and Pd.   2. The magnetoresistive element according to claim 1, wherein the spin valve film has a crystal grain size of 10 to 40 nm.   A magnetoresistive head comprising the magnetoresistive element according to claim 1.   A magnetic storage device comprising the magnetoresistive head according to claim 4.   The magnetic memory which comprises the magnetoresistive effect element of any one of Claims 1-3.

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