JP4944315B2 - Magnetoresistive film, memory element including the same, and memory using the same - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a magnetoresistive effect film using a method for reducing a magnetization reversal magnetic field of a perpendicular magnetization film, a memory element including the same, and a memory using the same.
[0002]
[Prior art]
In recent years, semiconductor memories, which are solid-state memories, are widely used in information equipment, and there are various types such as DRAM, FeRAM, and flash EEPROM. These semiconductor memories have advantages and disadvantages, and there is no memory that satisfies all of the specifications required for current information equipment. For example, DRAM has a high recording density and a large number of rewritable times, but it is volatile and information is lost when the power is turned off. In addition, the flash EEPROM is non-volatile, but the erasure time is long and is not suitable for high-speed information processing.
[0003]
In contrast to the current state of the semiconductor memory as described above, the memory (MRAM) using the magnetoresistive effect has specifications required by many information devices in terms of recording time, reading time, recording density, number of rewritable times, power consumption, etc. It is promising as a memory that fills everything. In particular, MRAM using the spin-dependent tunneling magnetoresistance (TMR) effect is advantageous for high recording density or high-speed reading because a large read signal can be obtained, and recent research reports have demonstrated its feasibility as MRAM. ing.
[0004]
The basic configuration of a magnetoresistive film used as an MRAM element is a sandwich structure in which a magnetic layer is formed adjacent to a nonmagnetic layer. Cu and Al are commonly used as nonmagnetic films.₂O_ThreeIs mentioned. A magnetoresistive film that uses a conductor such as Cu as the nonmagnetic layer is called a giant magnetoresistive film (GMR film).₂O_ThreeThose using insulators such as are called spin-dependent tunnel magnetoresistive films (TMR films). In general, a TMR film shows a larger magnetoresistance effect than a GMR film.
[0005]
When the magnetization directions of the two magnetic layers are parallel as shown in FIG. 13 (a), the electric resistance of the magnetoresistive film is relatively small, and when the magnetization directions are antiparallel as shown in FIG. 13 (b). The electrical resistance is relatively large. Therefore, information can be read by using one of the magnetic layers as a recording layer and the other as a reading layer and utilizing the above properties. For example, the magnetic layer 13 located above the nonmagnetic layer 12 is a recording layer, the magnetic layer 14 located below is a readout layer, and the magnetization direction of the recording layer is rightward, `` 1 '', and the leftward direction is `` 0 '' And When the magnetization directions of both magnetic layers are rightward as shown in FIG. 14A, the electric resistance of the magnetoresistive film is relatively small, and as shown in FIG. 14B, the magnetization direction of the readout layer is rightward and When the magnetization direction of the recording layer is leftward, the electric resistance is relatively large. In addition, when the magnetization direction of the reading layer is leftward and the magnetization direction of the recording layer is rightward as shown in FIG. 14C, the electric resistance is relatively large, and as shown in FIG. When the magnetization direction is leftward, the electrical resistance is relatively small. That is, when the magnetization direction of the readout layer is fixed to the right, if the electrical resistance is large, “0” is recorded in the recording layer, and if the electrical resistance is small, “1” is recorded. Will be. Alternatively, when the magnetization direction of the readout layer is fixed to the left, if the electrical resistance is large, “1” is recorded in the recording layer, and if the electrical resistance is small, “0” is recorded. Will be.
[0006]
If the element size is reduced in order to increase the recording density of the MRAM, the MRAM using the in-plane magnetization film has a problem that information cannot be retained due to the effect of demagnetizing field or end surface magnetization curling. In order to avoid this problem, for example, the shape of the magnetic layer can be rectangular. However, since the element size cannot be reduced by this method, the recording density is not expected to be improved much. Therefore, for example, as described in Japanese Patent Laid-Open No. 11-213650, a proposal has been made to avoid the above problem by using a perpendicular magnetization film. In this method, the demagnetizing field does not increase even when the element size is reduced. Therefore, a magnetoresistive film having a size smaller than that of the MRAM using the in-plane magnetization film can be realized.
[0007]
A magnetoresistive film using a perpendicular magnetized film, like a magnetoresistive film using an in-plane magnetized film, has a relatively small electrical resistance if the magnetization directions of the two magnetic layers are parallel. If the magnetization direction is antiparallel, the electrical resistance becomes relatively large. The magnetic layer 23 located above the nonmagnetic layer 22 is the recording layer, and the magnetic layer 21 located below is the readout layer.When the magnetization direction of the recording layer is upward, it is `` 1 '', and when it is downward, it is `` 0 '' To do. When the magnetization directions of both magnetic layers are upward as shown in FIG. 15A, the electric resistance of the magnetoresistive film is relatively small, and the magnetization direction of the readout layer is downward as shown in FIG. When the magnetization direction of the recording layer is upward, the electric resistance is relatively large. Therefore, if a magnetic field is applied so that the magnetization direction of the readout layer is downward after a magnetic layer is applied so that the magnetization direction of the readout layer is upward with “1” recorded, the magnetoresistive film The electrical resistance changes so as to increase, and “1” can be read from this change. However, the magnetic field applied at the time of reading is such a magnitude that the magnetization direction of the recording layer does not change. Further, when the magnetization direction of the reading layer is upward and the magnetization direction of the recording layer is downward as shown in FIG. 15B, the electric resistance becomes relatively large, and both magnetic layers are shown as shown in FIG. 15D. When the magnetization direction is downward, the electrical resistance is relatively small. Therefore, when “0” is recorded, it is possible to read “0” because the electrical resistance changes so as to decrease when the reading operation is performed.
[0008]
[Problems to be solved by the invention]
As the perpendicular magnetization film, an alloy film or artificial lattice film of at least one element selected from rare earth metals such as Gd, Dy, Tb and at least one element selected from transition metals such as Co, Fe, Ni, Co Main examples include artificial lattice films of transition metals such as / Pt and noble metals, and alloy films having crystal magnetic anisotropy in the direction perpendicular to the film surface, such as CoCr. The magnetization reversal field of the perpendicular magnetization film is generally larger than that having in-plane magnetic anisotropy due to transition metals, for example, the magnetization reversal field of permalloy, which is an in-plane magnetization film, is about several hundred A / m. The Co / Pt artificial lattice film, which is a perpendicular magnetization film, is remarkably large at several tens of kA / m. In an alloy film of a rare earth metal and a transition metal, since the sublattice magnetization of the rare earth metal and the sublattice magnetization of the transition metal are antiparallel, the apparent magnetization differs depending on the film composition. Therefore, the magnetization reversal field varies depending on the composition. The GdFe alloy film has a relatively small magnetization reversal field among the rare earth metal and transition metal alloy films, but the magnetization reversal is usually about several thousand A / m near the critical composition where the squareness ratio of the magnetization curve starts to decrease from 1. Has a magnetic field.
[0009]
When a sensor, memory, or the like is configured with a magnetoresistive film using a perpendicular magnetization film, it does not operate unless a large magnetic field is applied for the above reason. Therefore, for example, in the sensor, the stray magnetic field needs to be concentrated on the magnetic layer of the magnetoresistive effect film, and in the memory, a device for generating a large magnetic field is required. The magnetic field applied to the memory is generally generated by passing a current through the conducting wire, but in the case of a memory used for a portable terminal in particular, it is not preferable to flow a large current because of power supply capacity limitations. For this reason, it is necessary to take measures such as winding a conductive wire for generating a magnetic field around a memory element made of a magnetoresistive film. However, such a countermeasure complicates the structure and electric circuit around the magnetoresistive film, making it difficult to produce, and causes a problem of a decrease in yield and a significant increase in cost.
[0010]
In view of this point, the present invention provides a magnetoresistive film that reduces the magnetization reversal field of the perpendicular magnetization film, is easy to produce, and does not cause a decrease in yield or a significant increase in cost. The purpose is to provide less memory.
[0011]
[Means for Solving the Problems]
The magnetoresistive film of the present invention is
In a magnetoresistive film having a structure in which a nonmagnetic film is sandwiched between magnetic films, at least one of the magnetic films is a perpendicular magnetization film, and is in a position in contact with the perpendicular magnetization film and not in contact with the nonmagnetic film. And a magnetic film having an easy axis of magnetization inclined from the direction perpendicular to the film surface.
[0012]
Further, at least one easy axis of magnetization of the magnetic film may be inclined from the direction perpendicular to the film surface.
[0013]
Moreover, the magnetic film and the magnetic film whose easy axis of magnetization is inclined from the direction perpendicular to the film surface may be exchange coupled.
Furthermore, a layer having a higher spin polarizability than that of the perpendicular magnetization film may be inserted between the perpendicular magnetization film and the nonmagnetic film.
[0014]
Further, the perpendicular magnetization film and the layer having a high spin polarizability may be exchange coupled.
[0015]
In addition, the first magnetic film, the second magnetic film, the nonmagnetic film, the third magnetic film, and the easy magnetization axis are inclined from the film surface perpendicular direction. A fourth magnetic film is formed in this order, and at least one of the second magnetic film and the third magnetic film is a perpendicular magnetization film, the first magnetic film and the second magnetic film, and The third magnetic film and the fourth magnetic film may be exchange coupled.
[0016]
In addition, the easy magnetization axis of at least one of the second magnetic film or the third magnetic film may be inclined from the direction perpendicular to the film surface.
[0017]
A layer having a higher spin polarizability than that of the second magnetic film may be formed between the second magnetic film and the nonmagnetic film.
[0018]
Furthermore, a layer having a higher spin polarizability than that of the third magnetic film may be formed between the third magnetic film and the nonmagnetic film.
[0019]
The layer having a high spin polarizability and the second magnetic film, and the layer having a high spin polarizability and the third magnetic film may be exchange-coupled.
[0020]
In addition, the layer having a high spin polarizability may have a grain shape.
[0021]
Further, the magnetization of the magnetic film in which the easy axis of magnetization is inclined from the direction perpendicular to the film surface may be directed in the direction perpendicular to the film surface by a magnetic field having a magnitude of 4 kA / m or less.
[0022]
In addition, the magnetization of the magnetic film whose easy axis is oriented in the direction tilted from the direction perpendicular to the film surface is at least partially inclined with respect to the direction perpendicular to the film surface in the state of exchange coupling with the perpendicular magnetization film. Also good.
[0023]
The perpendicular magnetization film may be a ferrimagnetic material.
[0024]
The ferrimagnetic material may be an alloy of a rare earth metal and a transition metal.
[0025]
The alloy of rare earth metal and transition metal may be amorphous.
[0026]
Further, the ferrimagnetic material may be an artificial lattice film of a rare earth metal and a transition metal.
[0027]
The rare earth metal is one or more elements selected from Gd, Tb, and Dy, and transition gold
The genus may be one or more elements selected from Fe, Co, and Ni.
[0028]
The nonmagnetic film may be an insulator.
[0029]
The memory element of the present invention is
The memory element including the magnetoresistive film described above includes means for applying a magnetic field in the direction perpendicular to the film surface of the magnetoresistive film and means for detecting the electrical resistance of the magnetoresistive film.
[0030]
Further, the means for applying the magnetic field may be a conducting wire.
[0031]
Furthermore, a means for applying a magnetic field in a direction inclined from the direction perpendicular to the film surface of the magnetoresistive film may be provided.
[0032]
The memory of the present invention
In a memory using the above-described magnetoresistive film as a memory element, it is provided in contact with a magnetic film whose easy axis is inclined from the direction perpendicular to the film surface among magnetic films sandwiching a non-magnetic film when recording information. Information is recorded and reproduced without changing the magnetization direction of the magnetic film, and changing the magnetization direction of the other magnetic film.
[0033]
Of the magnetic films formed in contact with the non-magnetic film, the magnetic film whose magnetization is oriented in the direction perpendicular to the film surface in a zero magnetic field is used as the recording layer, and the magnetic film whose magnetization is inclined from the direction perpendicular to the film surface May be used as a readout layer.
[0034]
In addition, among the magnetic films formed adjacent to the nonmagnetic film against the magnetic field applied during recording or reading, the magnetization of the magnetic film formed in contact with one film surface of the nonmagnetic film is The magnetization of the magnetic film formed in contact with the other film surface of the nonmagnetic film may be reversed without being reversed.
[0035]
Further, a plurality of magnetoresistive effect films may be arranged, a means for selectively recording on the desired magnetoresistive effect film, and a means for selectively reading information recorded on the desired magnetoresistive effect film.
[0036]
Therefore, the magnetoresistive film of the present invention can be reversed in magnetization with a relatively small magnetic field. In particular, a memory using this magnetoresistive film can reduce power consumption.
[0037]
DETAILED DESCRIPTION OF THE INVENTION
An example of the magnetoresistive film of the present invention is shown in FIG. A magnetic film in which the magnetization is oriented in a direction inclined from the perpendicular direction of the film surface in the absence of a magnetic field and no exchange force with another magnetic substance, i.e., the magnetization easy axis is inclined from the perpendicular direction of the film surface. One magnetic film 111, a second magnetic film 112 that is a perpendicular magnetization film, a nonmagnetic film 113, and a third magnetic film 114 that is a perpendicular magnetization film are sequentially formed. The first magnetic film 111 and the second magnetic film 112 are exchange coupled. The magnetization of the second magnetic film 112 is oriented in the direction perpendicular to the film surface at least near the interface with the nonmagnetic film 113 in a zero magnetic field, or easily applied in the direction perpendicular to the film surface when a magnetic field is applied in the direction perpendicular to the film surface. Keep it facing. In the MRAM, it is preferable that the magnitude of the magnetic field that can be applied to the memory element is 4 kA / m or less because of the limitation of the current density that flows in the conducting wire. Therefore, the magnetization tilted from the vertical direction of the film surface in the zero magnetic field should be oriented in the vertical direction by applying a magnetic field of 4 kA / m or less. When a magnetic film whose magnetization is directed from the direction perpendicular to the film surface is exchange-coupled to the perpendicular magnetization film in the absence of a magnetic field and in the state where no exchange force with another magnetic material is working, the perpendicular magnetization film is Perpendicular magnetic anisotropy apparently decreases. Therefore, the magnetization reversal magnetic field in the direction perpendicular to the film surface can be reduced.
[0038]
A magnetoresistive film using an exchange coupling film of a perpendicular magnetization film and an in-plane magnetization film is disclosed in Japanese Patent Laid-Open No. 2000-306374. The main difference between the present invention and the present invention is the position where a magnetic film whose magnetization is oriented in a direction inclined from the direction perpendicular to the film surface is disposed. In Japanese Patent Laid-Open No. 2000-306374, the purpose is to obtain a large magnetoresistance effect, and a means is to form a magnetic film having a large spin polarizability so as to be in contact with the nonmagnetic film. An in-plane magnetization film is used for a magnetic film having a large spin polarizability, but the magnetization of the magnetic film must be oriented in the direction perpendicular to the film surface. Is achieved by the exchange coupling force.
[0039]
On the other hand, the present invention aims to reduce the magnetization reversal magnetic field with respect to the magnetic field applied in the direction perpendicular to the film surface. Magnetization is performed in the absence of a magnetic field and in the absence of exchange force with other magnetic materials. The magnetic film oriented in the direction inclined from the direction perpendicular to the film surface is not in contact with the nonmagnetic film, and the magnetization of the magnetic film need not be oriented in the direction perpendicular to the film surface.
[0040]
Even if a magnetic film with a magnetization oriented in a direction inclined from the direction perpendicular to the film surface in the absence of a magnetic field and no exchange force with another magnetic material is formed so as to contact the non-magnetic film, it will not contact However, the magnetization reversal field of the exchange coupling film between the magnetic film and the perpendicular magnetization film is smaller than that in the case of the perpendicular magnetization film single layer. However, the magnetization reversal in the direction perpendicular to the film surface depends on the thickness of the magnetic film whose magnetization is directed in the direction inclined from the direction perpendicular to the film surface, and the film thickness of the magnetic film is determined by the magnitude of the magnetization reversal magnetic field. It is done. In Japanese Patent Laid-Open No. 2000-306374, as described above, since the magnetization needs to be directed in the direction perpendicular to the film surface, the in-plane magnetization film cannot be increased in thickness, and the in-plane magnetization film has a thickness of 2 nm. Since it is necessary to make the following, the amount of decrease in the magnetization reversal magnetic field cannot be expected so much. On the other hand, in the magnetoresistive film of the present invention, it is not necessary to direct the magnetization of the magnetic film whose magnetization is inclined from the direction perpendicular to the film surface in the direction perpendicular to the film surface. It is possible to make it relatively thick, and for this reason, it is easy to sufficiently reduce the magnetization switching magnetic field in the direction perpendicular to the film surface.
[0041]
As described above, the film configuration shown in FIG. 1 can be cited as an example of the embodiment of the present invention. In the state of exchange coupling with the second magnetic film 112, the magnetization of the first magnetic film 111 may be oriented in the direction perpendicular to the film surface or may be inclined from the direction perpendicular to the film surface. However, when a magnetoresistive film whose magnetization is inclined from the direction perpendicular to the film surface is used as a memory element, it is necessary that both the magnetization of the third magnetic film 114 and the magnetization of the second magnetic film 112 can be reversed. The third magnetic film 114 is a recording layer, and the second magnetic film 112 is a reading layer. When a current is passed through a conducting wire and recording is performed with a magnetic field generated by this current, it is generally difficult to generate a magnetic field larger than 4 kA / m. Therefore, recording on the third magnetic film 114 is 4 kA / m. The following magnetic field is preferably used, and at the time of reading, the magnetization of the second magnetic film 112 inclined from the direction perpendicular to the film surface is caused by a magnetic field smaller than the reversal magnetic field of the third magnetic film 114. It is preferable to face in the direction perpendicular to the film surface. Further, the magnetization of the second magnetic film 112 is reversed by a magnetic field smaller than the magnetization of the third magnetic film 114.
[0042]
As the perpendicular magnetization film, as described above, an alloy film of at least one element selected from rare earth metals such as Gd, Dy, and Tb and at least one element selected from transition metals such as Co, Fe, and Ni, or an artificial film is used. Lattice films, artificial lattice films of transition metals and noble metals such as Co / Pt, and alloy films having crystal magnetic anisotropy in the direction perpendicular to the film surface, such as CoCr, can be mainly used. As a magnetic film in which the magnetization is directed in a direction tilted from the direction perpendicular to the film surface in a non-magnetic field and in a state in which no exchange force with other magnetic materials is acting, the magnetic film having the perpendicular magnetic anisotropy described above is used. Using similar materials, Ku-2πMs²It can be obtained by adjusting the film forming conditions so that <0. This makes it possible to obtain a magnetic film whose easy axis is inclined from the direction perpendicular to the film surface. Here, Ku is the perpendicular magnetic anisotropy energy constant, and Ms is the saturation magnetization. An in-plane magnetization film using a film made of one kind of element selected from transition metals such as Co, Fe, Ni, or an alloy film made of two or more kinds of elements can also be used.
[0043]
As the nonmagnetic film 113, a conductor such as Cu or Cr or Al₂O_ThreeInsulators such as NiO can be used. When an insulator is used for the nonmagnetic film 113, a relatively large change in magnetoresistance can be obtained, which is preferable when used as a memory element.
[0044]
When the magnetoresistive film having the film configuration shown in FIG. 1 is used as a memory element, the magnetization of the second magnetic film 112 can be reversed by an applied magnetic field, and the magnetization of the third magnetic film 114 can be reversed. Either is possible or not. However, when the magnetization of the third magnetic film 114 cannot be reversed, the voltage of the element is directly read without changing the magnetization direction so as not to destroy the recorded information at the time of reading. Is preferred. When the magnetization of the third magnetic film 114 is reversible, the exchange coupling film of the first magnetic film 111 and the second magnetic film 112 having a relatively small magnetization reversal magnetic field is used as a readout layer, and the magnetization is relatively The third magnetic film 114 having a large reversal magnetic field can be used as the recording layer, and information recorded by reading the voltage change of the element caused by reversing the magnetization direction of the second magnetic film 112 is recorded. Can be read nondestructively.
[0045]
FIG. 2 is a cross-sectional view schematically showing a film configuration as an example of the embodiment of the present invention, which is different from the film configuration shown in FIG. 1 in that a fourth magnetic film 115 is formed. The fourth magnetic film 115 is a magnetic film in which the magnetization is directed in a direction inclined from the direction perpendicular to the film surface in a state where there is no magnetic field and no exchange force with another magnetic material is applied. Exchange coupled with membrane 114. That is, like the first magnetic film 111, it functions to reduce the magnetization reversal field of the perpendicular magnetization film. With such a configuration, both the second magnetic film 112 and the third magnetic film 114 can be reversed in magnetization with a small applied magnetic field. However, the magnitude of the magnetization reversal field of the second magnetic film 112 and the magnetization reversal field of the third magnetic film 114 are different. When the magnetoresistive film having such a configuration is used as a memory, the exchange coupling film of the first magnetic film 111 and the second magnetic film 112 and the exchange coupling film of the third magnetic film 114 and the fourth magnetic film 115 are used. Of these, the relatively small magnetization reversal field is the readout layer, and the relatively large magnetization reversal field is the recording layer. The magnitude of the magnetization reversal field can be adjusted by the composition, film thickness, film forming conditions, etc. of each magnetic film.
[0046]
Further, as shown in FIG. 3, it is possible to increase the magnetic resistance by forming magnetic films 116 and 117 made of a material having a high spin polarizability at the interface between the nonmagnetic film 113 and the magnetic film. In FIG. 3, such a film is formed on both interfaces, but only one of them may be formed. The magnetic films 116 and 117 formed at the interface may be either the one whose magnetization is oriented in the direction inclined from the film surface perpendicular direction or the perpendicular magnetization film, but the second magnetic film 112 and the third magnetic film, respectively. In the state of exchange coupling with 114, the magnetization in the vicinity of the interface with the nonmagnetic film 113 needs to be perpendicular to the film surface.
[0047]
Further, the magnetic film 116 and the magnetic film 117 may have a grain shape.
[0048]
In the above magnetoresistive film of the present invention, the nonmagnetic film may be a metal such as Cu or Al.₂O_ThreeHowever, when using it as a memory, it is preferable to use a nonmagnetic film as a dielectric because the change in magnetoresistance is large.
[0049]
A plurality of magnetoresistive films having any of the above film structures are arranged side by side, and a relatively large magnetic field is applied to only one desired element, whereby a memory cell capable of selective recording can be obtained. it can.
[0050]
【Example】
(Example-1)
FIG. 4 is a cross-sectional view schematically showing a magnetoresistive film of the present invention. Using a Si wafer as the substrate 001, this surface was oxidized and about 1 μm SiO₂A film 002 is formed. SiO₂On the top of the film 002, the first magnetic film 111 is an in-plane magnetic film of 5 nm thick Fe film, and the second magnetic film 112 is a perpendicular magnetic film of 30 nm thick Gd.₂₀Fe₈₀2nm thick Al film as non-magnetic film 113₂O_Three10nm Tb which is a perpendicular magnetized film as the third magnetic film 114_{twenty two}Fe₇₈A 5 nm Pt film was sequentially formed as a film and a protective film 118. Where Fe film and Gd₂₀Fe₈₀The film is exchange-coupled, and the Pt film is a protective film for preventing corrosion such as oxidation of the magnetic film. Gd₂₀Fe₈₀Membrane and Tb_{twenty two}Fe₇₈Both films are transition metal sublattice magnetization dominant. Next, a 1 μm square resist film is formed on top of the obtained multilayer film, and the Pt film and Tb of the part not covered with the resist by dry etching_{twenty two}Fe₇₈The membrane was removed. 15nm thickness Al after etching₂O_ThreeA film is formed, and the resist and Al₂O_ThreeRemove the film, upper electrode and Fe film and Gd₂₀Fe₈₀An insulating film 121 for preventing a short circuit with the lower electrode made of the film was formed. After that, the upper electrode 122 is made of an Al film by a lift-off method, and the Al at a position shifted from the upper electrode is formed.₂O_ThreeAn electrode pad for removing the film and connecting the measurement circuit was obtained. Further, the obtained magnetoresistive film applied a magnetic field of 2 MA / m in the direction perpendicular to the film surface, and Tb_{twenty two}Fe₇₈Magnetization was performed with the magnetization of the film directed in the direction of the applied magnetic field. However, 1cm square Tb_{twenty two}Fe₇₈The coercive force of the film is as large as 1.6 MA / m, and the coercive force of the obtained magnetoresistive film is expected to be as large as the same.
[0051]
Connect a constant current power supply to the upper and lower electrodes of the magnetoresistive effect film₂₀Fe₈₀Membrane and Tb_{twenty two}Fe₇₈Al between membranes₂O_ThreeA constant current is passed so that electrons tunnel through the film. A magnetic field was applied in the direction perpendicular to the film surface of the magnetoresistive effect film, and the change (magnetoresistive curve) of the voltage of the magnetoresistive effect film was measured by changing the magnitude and direction. The result is shown in FIG. According to this measurement result, the magnetization reversal was about 3 kA / m.
[0052]
(Example-2)
FIG. 6 is a cross-sectional view schematically showing the magnetoresistive film of the present invention. Using a Si wafer as the substrate 001, this surface was oxidized and about 1 μm SiO₂A film 002 is formed. SiO₂On the top of the film 002, the first magnetic film 111 is an in-plane magnetic film of 3 nm thick Fe film, and the second magnetic film 112 is a perpendicular magnetic film of 50 nm thick Gd._{twenty five}Fe₇₅As a fifth magnetic film 116 having a larger spin polarizability than the second magnetic film, a Co film having a thickness of 1 nm is an in-plane magnetization film.₅₀Fe₅₀2nm thick Al film as non-magnetic film 113₂O_ThreeAs a sixth magnetic film 117 exhibiting a larger spin polarizability than that of the third magnetic film, a Co film having a thickness of 1 nm is an in-plane magnetization film.₅₀Fe₅₀Tb with a thickness of 30 nm which is a perpendicular magnetization film as the third magnetic film 114_{twenty five}Fe₇₅A 3 nm thick Fe film, which is an in-plane magnetized film, was formed as the fourth magnetic film 115, and a 5 nm Pt film was sequentially formed as the protective film 118. Where Fe film and Gd_{twenty five}Fe₇₅Membrane, Gd_{twenty five}Fe₇₅Membrane and Co₅₀Fe₅₀Each membrane is exchange-coupled and Co₅₀Fe₅₀Membrane and Tb_{twenty five}Fe₇₅Membrane, Tb_{twenty five}Fe₇₅The film and the Fe film are exchange coupled. Gd_{twenty five}Fe₇₅Membrane and Tb_{twenty five}Fe₇₅Both films are rare earth metal sublattice magnetization dominant. 2 layers of Co₅₀Fe₅₀The film is Gd_{twenty five}Fe₇₅Membrane or Tb_{twenty five}Fe₇₅The spin polarizability is larger than that of the film, and the direction of magnetization is oriented in the direction perpendicular to the film surface due to the exchange coupling force. The Pt film is a protective film for preventing corrosion such as oxidation of the magnetic film. Next, a 1 μm square resist film is formed on top of the obtained multilayer film, and the Pt film and Tb of the part not covered with the resist by dry etching_{twenty five}Fe₇₅The membrane was removed. 39nm thickness Al after etching₂O_ThreeA film is formed, and the resist and Al₂O_ThreeRemove the film, upper electrode and Fe film and Gd_{twenty five}Fe₇₅An insulating film 121 for preventing a short circuit with the lower electrode made of the film was formed. After that, the upper electrode 122 is made of an Al film by a lift-off method, and the Al at a position shifted from the upper electrode is formed.₂O_ThreeAn electrode pad for removing the film and connecting the measurement circuit was obtained.
[0053]
Connect a constant current power supply to the upper and lower electrodes of the magnetoresistive effect film_{twenty five}Fe₇₅Membrane and Tb_{twenty five}Fe₇₅Al between membranes₂O_ThreeA constant current is passed so that electrons tunnel through the film. A change in voltage of the magnetoresistive effect film was measured by applying a magnetic field in a direction perpendicular to the film surface of the magnetoresistive effect film and changing its magnitude and direction. The result is shown in FIG. Magnetization reversal occurs at about 2.5 kA / m and 3.8 kA / m.
[0054]
(Example-3)
FIG. 8 is an electric circuit diagram of a memory cell when the magnetoresistive films 101, 102, 103, 104, 105, 106, 107, 108, 109 used in Example-2 are arranged in 3 rows and 3 columns as memory elements. And shown in FIG. FIG. 8 is a circuit for generating a magnetic field applied to the magnetoresistive effect film, and FIG. 9 is a circuit for detecting a resistance change of the magnetoresistive effect film.
[0055]
A method for selectively reversing the magnetization of the magnetic film of an arbitrary element will be described. For example, when the magnetization of the magnetoresistive film 105 is selectively reversed, the transistors 212, 217, 225, and 220 are turned on, and the other transistors are turned off. In this way, current flows through the conductors 312, 313, 323, 322 and generates a magnetic field around them. Therefore, if the magnetic field in the same direction is applied only from the four conducting wires to the magnetoresistive effect film 105 and these combined magnetic fields are adjusted so as to be slightly larger than the magnetization reversal field of the magnetic film of the element, it is possible to selectively Only the magnetization of the magnetoresistive film 105 can be reversed. When applying a magnetic field in the reverse direction to the magnetoresistive film 105, the transistors 213, 216, 224, and 221 are turned on, and the other transistors are turned off. In this way, the current flows in the direction opposite to the previous direction through the conducting wires 312, 313, 323, and 322, and a reverse magnetic field is applied to the magnetoresistive film 105.
[0056]
Next, the operation during reading will be described. For example, when information recorded on the magnetoresistive film 105 is read, the transistor 235 and the transistor 241 are turned on. Then, a circuit in which the power supply 412, the fixed resistor 100, and the magnetoresistive film 105 are connected in series is obtained. Therefore, the power supply voltage is divided into the respective resistors at the ratio of the resistance value of the fixed resistor 100 and the resistance value of the magnetoresistive effect film 105. Since the power supply voltage is fixed, when the resistance value of the magnetoresistive effect film changes, the voltage applied to the magnetoresistive effect film changes accordingly. This voltage value is read by the sense amplifier 500. Here, there are mainly two reading methods. One is a method of detecting the magnitude of the voltage value applied to the magnetoresistive effect film and identifying information based on the magnitude, and this is called absolute detection. The other is a method in which only the magnetization direction of the readout layer of the magnetoresistive film is changed, and information is identified by the difference in voltage change that occurs at that time. When the magnetization of the readout layer is reversed, if the voltage value drops, for example, to “1”, the voltage value rises to “0”. Such a reading method is called relative detection.
[0057]
FIG. 10 is a cross-sectional view schematically showing a peripheral portion of one element. Two n-type diffusion regions 119 and 120 are formed on a p-type Si substrate 011, and a word line (gate electrode) 342 is formed therebetween via an insulating layer 123. A ground line 356 is connected to the n-type diffusion region 013, and the magnetoresistive effect film 105 is connected to the other via contact plugs 352, 353, 354, 357 and local wiring 358. The magnetoresistive film is further connected to the bit line 332. Next to the magnetoresistive effect film 105, a conducting wire 322 and a conducting wire 323 for generating a magnetic field are arranged.
[0058]
(Comparative example)
FIG. 11 is a cross-sectional view schematically showing a conventional magnetoresistive film. Using a Si wafer as the substrate 001, this surface was oxidized and about 1 μm SiO₂A film 002 is formed. SiO₂Gd with a thickness of 30 nm is a perpendicular magnetization film as a magnetic film 21 having a relatively small magnetization reversal magnetic field on the film 002₂₀Fe₈₀2nm thick Al film as non-magnetic film 22₂O_Three10 nm Tb which is a perpendicular magnetization film as a magnetic film 23 having a relatively large coercive force_{twenty two}Fe₇₈A 5 nm Pt film was sequentially formed as a film and a protective film 118. Here, the Pt film is a protective film for preventing corrosion such as oxidation of the magnetic film. Gd₂₀Fe₈₀Membrane and Tb_{twenty two}Fe₇₈Both films are transition metal sublattice magnetization dominant. Next, a 1 μm square resist film is formed on top of the obtained multilayer film, and the Pt film and Tb of the part not covered with the resist by dry etching_{twenty two}Fe₇₈The membrane was removed. 15nm thickness Al after etching₂O_ThreeA film is formed, and the resist and Al₂O_ThreeRemove the membrane, top electrode and Gd₂₀Fe₈₀An insulating film 121 for preventing a short circuit with the lower electrode made of the film was formed. After that, the upper electrode 122 is made of an Al film by a lift-off method, and the Al at a position shifted from the upper electrode is formed.₂O_ThreeAn electrode pad for removing the film and connecting the measurement circuit was obtained. Further, the obtained magnetoresistive film applied a magnetic field of 2 MA / m in the direction perpendicular to the film surface, and Tb_{twenty two}Fe₇₈Magnetization was performed with the magnetization of the film directed in the direction of the applied magnetic field. However, 1cm square Tb_{twenty two}Fe₇₈The coercive force of the film is as large as 1.6 MA / m, and the coercive force of the obtained magnetoresistive film is expected to be as large as the same.
[0059]
Connect a constant current power supply to the upper and lower electrodes of the magnetoresistive effect film₂₀Fe₈₀Membrane and Tb_{twenty two}Fe₇₈Al between membranes₂O_ThreeA constant current is passed so that electrons tunnel through the film. A magnetic field was applied in the direction perpendicular to the film surface of the magnetoresistive effect film, and the change (magnetoresistive curve) of the voltage of the magnetoresistive effect film was measured by changing the magnitude and direction. The result is shown in FIG. According to this measurement result, the magnetization reversal field was about 24 kA / m.
[0060]
【The invention's effect】
As described above, the magnetoresistive film of the present invention can be reversed in magnetization with a relatively small magnetic field, and in particular, a memory using this magnetoresistive film has an effect that power consumption can be reduced. .
[Brief description of the drawings]
FIG. 1 is a diagram schematically showing a cross section showing an example of a magneto-resistive film of the present invention.
FIG. 2 is a diagram schematically showing a cross section showing an example of a magneto-resistive film of the present invention.
FIG. 3 is a view schematically showing a cross section showing an example of a magneto-resistive film of the present invention.
FIG. 4 is a diagram schematically showing a cross section of a magnetoresistive film used in Example-1.
FIG. 5 is a diagram showing a magnetoresistance curve of a magnetoresistive film used in Example-1.
6 is a view schematically showing a cross section of a magnetoresistive film used in Example-2. FIG.
7 is a diagram showing a magnetoresistance curve of a magnetoresistive film used in Example-2. FIG.
8 is a schematic diagram of an electric circuit for applying a magnetic field to the magnetoresistive film used in the memory of Example-3. FIG.
FIG. 9 is a schematic diagram of a read circuit used in the memory of Example-3.
FIG. 10 is a schematic diagram showing a cross section of a part of the memory of Example-3;
FIG. 11 is a schematic diagram showing a cross section of a magnetoresistive film used in a comparative example.
FIG. 12 is a diagram showing a magnetoresistance curve of a magnetoresistive film used in a comparative example.
FIG. 13A is a cross-sectional view schematically showing a state in which the magnetization of the magnetoresistive effect film is parallel.
(B) It is sectional drawing which shows typically the state by which the magnetization of a magnetoresistive effect film is antiparallel.
FIG. 14 is a diagram for explaining the principle of recording / reproducing in a conventional magnetoresistive film using an in-plane magnetization film.
(A) It is sectional drawing which shows typically the state of the magnetization in the case of reading the recording information "1".
(B) It is sectional drawing which shows typically the state of the magnetization in the case of reading recording information "0".
(C) It is sectional drawing which shows typically the state of the magnetization in the case of reading recording information "1".
(D) It is sectional drawing which shows typically the state of the magnetization in the case of reading recording information "0".
FIG. 15 is a diagram for explaining the principle of recording / reproducing in a conventional magnetoresistive film using a perpendicular magnetization film.
(A) It is sectional drawing which shows typically the state of the magnetization in the case of reading the recording information "1".
(B) It is sectional drawing which shows typically the state of the magnetization in the case of reading recording information "0".
(C) It is sectional drawing which shows typically the state of the magnetization in the case of reading recording information "1".
(D) It is sectional drawing which shows typically the state of the magnetization in the case of reading recording information "0".
[Explanation of symbols]
001 Si substrate
002 SiO₂film
011 p-type Si substrate
12, 22 Nonmagnetic layer
13, 14, 21, 23 Magnetic layer
100 fixed resistance
101-109 magnetoresistive film
111 First magnetic film
112 Second magnetic film
113 Non-magnetic film
114 Third magnetic film
116, 117 Magnetic film made of material with high spin polarizability
118 Protective film
119, 120 n-type diffusion region
121, 123 Insulating film
122 Upper electrode
211 to 226, 231 to 242 transistors
311 to 314, 321 to 324 Conductor (write line)
331 to 333 bit line
341 to 343 Word line (gate electrode)
351 to 355, 357 Contact plug
356 Ground wire
357 Local wiring
411, 412 power supply
500 sense amplifiers

Claims (17)

In a magnetoresistive film having a structure in which a nonmagnetic film is sandwiched between first and second magnetic films,
The first and second magnetic films are perpendicular magnetization films, and the easy axis of magnetization is tilted from the direction perpendicular to the film surface at a position in contact with the first magnetic film and not in contact with the nonmagnetic film. A magnetoresistive film characterized in that a magnetic film is disposed and exchange-coupled with the first magnetic film, and the magnetization reversal field of the first magnetic film is smaller than the magnetization reversal field of the second magnetic film Effect film. In a magnetoresistive film having a structure in which a nonmagnetic film is sandwiched between first and second magnetic films,
The first and second magnetic films are perpendicular magnetization films, and the easy axis of magnetization is tilted from the direction perpendicular to the film surface at a position in contact with the first magnetic film and not in contact with the nonmagnetic film. A magnetic reversal field of the first magnetic film in which a magnetic film is arranged and exchange-coupled to the first magnetic film, and the easy magnetization axis is exchange-coupled to a magnetic film inclined from the direction perpendicular to the film surface Is smaller than when the first magnetic film is provided as a single layer. Furthermore, a layer having a higher spin polarizability than that of the perpendicular magnetization film is inserted between the perpendicular magnetization film and the nonmagnetic film, and the perpendicular magnetization film and the layer having a higher spin polarization rate are exchange coupled. The magnetoresistive film according to claim 1 or 2. The first magnetic film, the second magnetic film, the nonmagnetic film, the third magnetic film, and the easy magnetization axis are inclined from the film surface perpendicular direction. A fourth magnetic film is formed in this order,
The second magnetic film and the third magnetic film are perpendicular magnetization films;
The first magnetic film and the second magnetic film, and the third magnetic film and the fourth magnetic film are exchange-coupled, respectively.
The magnetic reversal field of the second magnetic film exchange-coupled to the first magnetic film is larger than the magnetization reversal field of the third magnetic film exchange-coupled to the fourth magnetic film. Effect film. Characterized in that said second layer magnetic film spin polarization than are exchange-coupled to the magnitude rather the second magnetic film is formed between the second magnetic film and the nonmagnetic film The magnetoresistive film according to claim 4 . Moreover, said third layer spin polarization than that of the magnetic film is exchange-coupled to the magnitude rather the third magnetic film is formed between said third magnetic film and the nonmagnetic film The magnetoresistive film according to claim 5 . The magnetoresistive film according to claim 3 , wherein the layer having a high spin polarizability has a grain shape. Magnetization of the magnetic film in which the easy axis of magnetization is inclined from the direction perpendicular to the film surface is, by a magnetic field of 4 kA / m or less in size, according to claim 1, 2 or 4, wherein the facing in a direction perpendicular to the film surface Magnetoresistive film. The magnetization of the magnetic film in which the easy axis is oriented in a direction inclined from the direction perpendicular to the film surface is at least partially inclined with respect to the direction perpendicular to the film surface in the state of exchange coupling with the perpendicular magnetization film. The magnetoresistive film according to any one of claims 1 to 8 , wherein It said non-magnetic film is the magnetoresistive film of any one of claims 1 to 9, characterized in that an insulator. A memory device comprising the magnetoresistive film according to any one of claims 1 to 10 ,
Means for applying a magnetic field in a direction perpendicular to the film surface of the magnetoresistive film;
And a memory element for detecting an electric resistance of the magnetoresistive film. The memory element according to claim 11 , wherein the means for applying the magnetic field is a conductive wire. 12. The memory element according to claim 11 , further comprising means for applying a magnetic field in a direction inclined from a direction perpendicular to the film surface of the magnetoresistive film. In a memory using the magnetoresistive film according to claim 1 as a memory element,
When recording information, among the magnetic films sandwiching the non-magnetic film, the magnetization direction of the magnetic film provided in contact with the magnetic film whose easy axis is inclined from the direction perpendicular to the film surface is changed, and the other magnetic A memory which records and reproduces information without changing the magnetization direction of the film. In a memory using the magnetoresistive film according to claim 1 as a memory element,
Among the magnetic films formed in contact with the non-magnetic film, a magnetic film whose magnetization is oriented in the direction perpendicular to the film surface in a zero magnetic field is used as a recording layer, and a magnetic film whose magnetization is inclined from the direction perpendicular to the film surface, A memory comprising a reading layer for reading information recorded on the recording layer. A memory using the magnetoresistive film according to any one of claims 1 to 10 as a memory element,
Of the magnetic film formed adjacent to the nonmagnetic film, the magnetization of the magnetic film formed in contact with one surface of the nonmagnetic film is reversed with respect to the magnetic field applied during recording or reading. A memory characterized in that the magnetization of the magnetic film formed in contact with the other film surface of the nonmagnetic film is reversed. A memory using the magnetoresistive film according to any one of claims 1 to 10 as a memory element,
Means for arranging a plurality of magnetoresistive films and selectively recording on a desired magnetoresistive film;
A memory comprising: means for selectively reading information recorded on a desired magnetoresistive film.

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