Classifications

• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10B—ELECTRONIC MEMORY DEVICES
  • H10B61/00—Magnetic memory devices, e.g. magnetoresistive RAM [MRAM] devices
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10N50/00—Galvanomagnetic devices
  • H10N50/10—Magnetoresistive devices

Definitions

• the present invention relates to an element and a method for manufacturing the element.
• Patent Document 1 discloses technology relating to a magnetoresistance effect element with a magnesium oxide passivation layer and a high-speed, ultra-low power consumption nonvolatile memory using the same.
• This memory has a tunnel magnetoresistance effect (TMR) film consisting of a ferromagnetic free layer, an insulating layer, and a ferromagnetic fixed layer, and a protective layer, and an MgO passivation layer on the side walls of the orientation control layer, thereby suppressing element diffusion from each layer of the tunnel magnetoresistance effect (TMR) element due to heat treatment at 350 degrees or more, and realizing a magnetic memory cell and magnetic random access memory with stable high output read and low current write characteristics.
• TMR tunnel magnetoresistance effect
• MgO passivation layer has a (001) orientation.
• an element includes a memory layer, an insulating layer, and a fixed layer.
• Each of the memory layer and the fixed layer is configured to have spontaneous magnetization.
• the insulating layer is disposed between the memory layer and the fixed layer, and is configured to form a tunnel magnetic junction between the memory layer and the fixed layer.
• the magnetization direction of the fixed layer is configured to be fixed regardless of data written to the element.
• the magnetization direction of the memory layer is configured to be reversible depending on data written to the element.
• At least one of the memory layer and the fixed layer is an anomalous Hall layer made of an antiferromagnetic material that exhibits an anomalous Hall effect.
• the sign of the anomalous Hall coefficient of the antiferromagnetic material is configured to be reversible depending on data written to the element. At least a portion of the anomalous Hall layer is configured to contain a contaminating element that is at least one element selected from the group consisting of H, B, C, and N.
• This configuration makes it possible to provide a new memory device.
• FIG. 1 is a front view showing an example of the structure of a memory element 10 according to an embodiment of the present invention.
• FIG. 1 is a diagram showing an example of MH curves of samples according to Experimental Examples 1 to 4.
• FIG. 13 is a diagram showing the relationship between the MR ratio of the sample according to Experimental Example 1 and the external magnetic field.
• FIG. 1 is a diagram showing an example of the relationship between the composition ratio x/y of Mn and Sn in MnxSnyAz and the MR ratio for each type of contaminant element A.
• the program for implementing the software used in this embodiment may be provided as a non-transitory computer-readable recording medium, or may be provided so that it can be downloaded from an external server, or may be provided so that the program is started on an external computer and its functions are implemented on a client terminal (so-called cloud computing).
• a "unit” can also include, for example, hardware resources implemented by a circuit in the broad sense, and software information processing that can be specifically realized by these hardware resources.
• this embodiment handles various types of information, which can be represented, for example, by physical values of signal values representing voltage and current, high and low signal values as a binary bit collection consisting of 0 or 1, or quantum superposition (so-called quantum bits), and communication and calculations can be performed on a circuit in the broad sense.
• a circuit in the broad sense is a circuit that is realized by at least appropriately combining a circuit, circuitry, a processor, and memory.
• ASICs application specific integrated circuits
• SPLDs simple programmable logic devices
• CPLDs complex programmable logic devices
• FPGAs field programmable gate arrays
• FIG. 1 is a front view showing an example of the structure of a memory element 10 according to this embodiment.
• the memory element 10 shown in FIG. 1 is an example of an element, and includes a substrate 100, an electrode 102, a fixed layer 104, a barrier layer 106 as an insulating layer, a free layer 108 as a memory layer, an intermediate layer 110, and an upper layer 112.
• the memory element 10 according to this embodiment is a so-called MTJ (Magnetic Tunnel Junction) element, which reads out data 1 or 0 based on the difference in tunnel magnetic resistance between the parallel and antiparallel states of spins due to the tunnel magnetoresistance effect.
• MTJ Magnetic Tunnel Junction
• a memory including the memory element 10 can be used as an MTJ element in, for example, MRAM (Magnetoresistive Random Access Memory), a magnetic head of a HDD (Hard Disk Drive), a racetrack memory, etc.
• the memory element 10 is expected to be used in, for example, STT (Spin Transfer Torque) type MRAM or SOT (Spin Orbit Torque) type MRAM, but may also be used in conventional Vertical MRAM.
• STT Spin Transfer Torque
• SOT Spin Orbit Torque
• the substrate 100 is made of any material used for memory applications, such as Si. Such a substrate 100 may be provided with an electrode made of W or the like.
• the electrode 102 is a layer made of a metal such as Ti or Ta. There are no particular limitations on the material.
• the electrode 102 is layered on the substrate 100, for example.
• the fixed layer 104 is a layer made of a ferromagnetic material or an antiferromagnetic material.
• the ferromagnetic material may be a ferromagnetic material used in ferromagnetic MTJ elements, such as CoFeB or CoFe.
• the pinned layer 104 of this embodiment is configured to have spontaneous magnetization.
• An antiferromagnetic material having spontaneous magnetization is, for example, a material having an antiferromagnetic magnetic order, such as a tilted antiferromagnetic material or a ferrimagnetic material.
• the magnetization direction of the pinned layer 104 is configured to be fixed regardless of the data written in the memory element 10 as the element.
• the antiferromagnetic material according to this embodiment is, for example, an antiferromagnetic material that exhibits an anomalous Hall effect.
• Such an antiferromagnetic material is, for example, an antiferromagnetic material in which an anomalous Hall effect is observed under conditions without a magnetic field.
• Such an antiferromagnetic material is, for example, an antiferromagnetic material in which an anomalous Hall effect is observed at a temperature above room temperature.
• Such an antiferromagnetic material is, for example, an antiferromagnetic material that can take two values by spin rotation.
• Such an antiferromagnetic material is, for example, a non-collinear antiferromagnetic material.
• the non-collinear antiferromagnetic material is, for example, an Mn3X -based alloy such as Mn3Sn , Mn3Ge , or Mn3Ga .
• the crystal structure of these alloys may be hexagonal.
• the material constituting the pinned layer 104 contains at least one of light elements such as hydrogen, nitrogen, carbon, and boron in an amount of 0.1 atomic % or more and 20 atomic % or less.
• the content (amount of substance) of Mn is, for example, 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5, or 8 times the content (amount of substance) of Sn, Ge, or Ga (including those containing a plurality of these), and may be within a range between any two of the values exemplified here.
• the content (amount of substance) of Mn is 2 to 6 times, preferably 2.3 to 5.5 times, and more preferably 2.5 to 5 times the content (amount of substance) of Sn, Ge, or Ga (including those containing a plurality of these).
• the fixed layer 104 is, for example, laminated on the substrate 100. In this embodiment, the fixed layer 104 is laminated on the substrate 100 via the electrode 102.
• the barrier layer 106 is a non-magnetic insulating layer provided to realize TMR.
• the barrier layer 106 is not particularly limited as long as it functions as an insulating layer, and may be, for example, MgO, AlOx, TiOx, etc.
• the barrier layer 106 is layered, for example, on the fixed layer 104.
• the free layer 108 is a layer made of an antiferromagnetic material.
• the free layer 108 can also be configured to have spontaneous magnetization, similar to the fixed layer 104.
• the antiferromagnetic material according to this embodiment is an antiferromagnetic material that exhibits an anomalous Hall effect.
• such an antiferromagnetic material is an antiferromagnetic material in which an anomalous Hall effect is observed under conditions without a magnetic field.
• such an antiferromagnetic material is an antiferromagnetic material in which an anomalous Hall effect is observed at a temperature above room temperature.
• such an antiferromagnetic material is an antiferromagnetic material that can take two values due to spin rotation.
• such an antiferromagnetic material is a non-collinear antiferromagnetic material.
• the non-collinear antiferromagnetic material is an Mn 3 X-based alloy such as Mn 3 Sn, Mn 3 Ge, or Mn 3 Ga.
• the antiferromagnetic material can contain at least one element of Mn, Sn, and Ge as a main component. More specifically, the antiferromagnetic material is composed of Mn3Sn. These alloys can easily rotate spins, for example, by polarization due to magnetic octopoles. The crystal structure of these alloys can be hexagonal.
• the material constituting the fixed layer 104 contains at least one of light elements such as hydrogen, nitrogen, carbon, and boron in an amount of 0.1 atomic % or more and 20 atomic % or less.
• the content of Mn is preferably 2.5 times or more and 5 times or less than the content of Sn, Ge, or Ga (including those containing a plurality of these).
• the barrier layer 106 as an insulating layer is disposed between the free layer 108 as a memory layer and the fixed layer 104, and is configured to form a tunnel magnetic junction (TMJ) between the free layer 108 and the fixed layer 104.
• TMJ tunnel magnetic junction
• the free layer 108 can function as an anomalous hole layer.
• the anomalous hole layer is a layer composed of an antiferromagnetic material that exhibits the anomalous Hall effect.
• the fixed layer 104 may include an anomalous Hall layer, that is, at least one of the free layer 108 and the fixed layer 104 may include an anomalous Hall layer made of an antiferromagnetic material that exhibits the anomalous Hall effect.
• An antiferromagnet that exhibits the anomalous Hall effect and has spontaneous magnetization can reverse the direction of the spontaneous magnetization, for example, by applying an external magnetic field.
• a change in the direction of the spontaneous magnetization means a change in the magnetic structure in the antiferromagnet.
• Such a change in the magnetic structure causes a reversal of the sign of the anomalous Hall coefficient.
• a reversal of the sign of the anomalous Hall coefficient means a reversal of the direction of the effective magnetic field inside the antiferromagnet. In this way, the sign of the anomalous Hall coefficient of the antiferromagnet is configured to be reversible depending on the data written to the element.
• the memory layer is not limited to being composed only of an anomalous Hall layer.
• the memory layer can be configured to have an anomalous Hall layer and a ferromagnetic layer.
• the reversal of the effective magnetic field accompanying the reversal of the sign of the anomalous Hall coefficient of the antiferromagnetic material is transmitted to the ferromagnetic layer via the magnetic coupling between the anomalous Hall layer and the ferromagnetic layer, and the direction of the spontaneous magnetization of the ferromagnetic layer can be linked to the reversal of the sign of the anomalous Hall coefficient, thereby increasing the response speed of the element to external signals (e.g., external magnetic fields).
• the intermediate layer 110 as a metal layer is provided between the free layer 108 and the upper layer 112 and can support the perpendicular magnetization of the free layer 108.
• the material constituting the intermediate layer 110 is preferably at least one metal selected from the group consisting of Ti, Zr, Hf, Ta, Nb, and W.
• the intermediate layer 110 can be stacked on the free layer 108.
• the memory element 10 may include a metal layer.
• the metal layer is configured to have an interface with at least one of the memory layer (the free layer 108 in this embodiment) and the fixed layer 104.
• the metal layer is stacked so as to be in contact with the barrier layer 106. This can improve the binding between the barrier layer 106 and the fixed layer 104 or the free layer 108.
• the metal layer can be made of a material containing at least one of elements belonging to the 4th, 5th, or 6th groups.
• the metal layer can be made of at least one element selected from the group consisting of Ti, Zr, Hf, Ta, Nb, and W.
• the upper layer 112 is a layer provided on top of the intermediate layer 110.
• the upper layer 112 is composed of, for example, Ta or TaN, but the material is not particularly limited.
• the upper layer 112 can be laminated on the intermediate layer 110.
• At least a part of the anomalous hole layer of the free layer 108 may be configured to contain a contaminating element, which is at least one element selected from the group consisting of hydrogen (H), nitrogen (N), carbon ( C), and boron (B).
• a contaminating element which is at least one element selected from the group consisting of hydrogen (H), nitrogen (N), carbon ( C), and boron (B).
• the film is easily made amorphous immediately after deposition, and when a magnetic tunnel junction film is formed using a crystalline insulating layer, the lattice mismatch at the interface between the crystalline insulating layer and the antiferromagnetic layer is alleviated, thereby increasing the tunnel magnetoresistance change rate
• the contaminating elements make it easier to temporarily keep the anomalous Hall layer in an amorphous state, making it easier to obtain an element having a free layer 108 or a fixed layer 104 that includes an antiferromagnetic material with higher crystallinity.
• the anomalous Hall layer can be configured to contain the contaminating elements at the interface with the insulating layer. With this configuration, it is possible to increase the crystallinity of the anomalous Hall layer while suppressing the deterioration of the magnetic properties of the anomalous Hall layer.
• the layers 102, 104, 106, 108, 110, and 112 are laminated on the substrate 100 by performing sputtering while changing the atmosphere or target.
• a layer into which a contaminating element is introduced such as the fixed layer 104 or the free layer 108
• the layers are laminated under conditions in which the element is introduced from the element source of the contaminating element toward the sputtering target.
• a gas containing the contaminating element e.g., H2 gas, N2 gas, etc.
• a target containing the contaminating element is used for sputtering.
• a light element (one example of a contaminating element, particularly H, B, C, and N) can be injected into each layer by mixing not only Ar but also hydrogen or nitrogen gas into the sputtering atmosphere gas, or by performing ion implantation, etc.
• the gas ratio, etc. can be adjusted as appropriate.
• Sputtering is performed, for example, at room temperature under ultra-high vacuum.
• a heat treatment process may be performed after the deposition of all layers. This can promote crystallization of the fixed layer 104 or the free layer 108, which is in a state where it is easily made amorphous due to the presence of the contaminating element.
• the heat treatment process may involve annealing for 5 hours at a heating temperature of 350° C.
• the heating temperature and heating time in the annealing can be appropriately adjusted according to the film characteristics and film structure. That is, the manufacturing method of the memory element 10 includes a process of stacking the free layer 108, the barrier layer 106 as an insulating layer, and the fixed layer 104 in the presence of an element source configured to release the contaminating element, and this process releases the contaminating element from the element source at least when stacking the anomalous hole layer.
• the element source may be included in the atmosphere during stacking, or may be a target capable of releasing the plasmatized element. Therefore, the manufacturing method is not limited to one using sputtering, and any method such as chemical vapor transport (CVT) and molecular beam epitaxy (MBE) can be used.
• CVT chemical vapor transport
• MBE molecular beam epitaxy
• the configuration of the memory element 10 described above can also be used as an element of a magnetic sensor such as a TMR sensor.
• the memory element 10 is an example of an element, and is not limited to this.
• Example 1 In Experimental Example 1, a Si substrate prepared in advance was first placed on a sample stage of a sputtering apparatus. The sample stage was housed in a sample chamber.
• the sample chamber in which the sample stage was stored was evacuated, and Ar gas (99.999% purity) was introduced as an inert gas.
• Ar gas (99.999% purity) was introduced as an inert gas.
• a Ti film was deposited on the Si substrate by sputtering using a Ti target to a thickness of 5 nm.
• the Ti film can function as the electrode 102.
• H2 gas (purity 99.99%) was introduced into the sample chamber to form an atmosphere composed of a mixed gas of Ar gas and H2 gas.
• the partial pressure ratio of each gas contained in the mixed gas was 95% for Ar gas and 5% for H2 gas, assuming that the partial pressure ratio of the entire mixed gas was 100%.
• sputtering was performed using a target composed of Mn3Sn alloy, and a fixed layer 104 was laminated on the Ti film to a film thickness of 10 nm.
• the target was changed from the Mn 3 Sn alloy to MgO, and an MgO film was laminated as a barrier layer on the fixed layer 104 to a thickness of 1 nm.
• the target was changed back from MgO to the Mn3Sn alloy, and further sputtering was performed in a mixed gas atmosphere, and a free layer 108 was further laminated on the MgO film to a thickness of 5 nm.
• the target was changed to Zr metal, and the atmosphere was replaced with Ar again before sputtering was performed, depositing a Zr film on the free layer 108 to a thickness of 5 nm.
• the target was changed to Ta metal and sputtering was performed to laminate a Ta film to a thickness of 5 nm on the Zr film.
• the Zr film and Ta film can function as both the intermediate layer 110 and an electrode. Note that the fabrication of the upper layer was omitted in this experimental example.
• Experimental Example 2 similar to Experimental Example 1, a pre-prepared Si substrate was first placed on the sample stage of the sputtering device.
• the sample chamber in which the sample stage was stored was evacuated and Ar gas was introduced as an inert gas.
• Ar gas was introduced as an inert gas.
• a Ta film was laminated on the Si substrate by sputtering using a Ta target to a thickness of 5 nm.
• the Ta film can function as the electrode 102.
• sputtering was performed using a target composed of a sintered body of Mn3Sn alloy and boron (B), and a fixed layer 104 was laminated on the laminated Ta film to a thickness of 15 nm.
• the target was changed from the sintered body of Mn3Sn alloy and B to MgO, and an MgO film was laminated as a barrier layer on the fixed layer 104 to a thickness of 1 nm.
• sputtering was performed using a target composed of a sintered body of Mn3Sn alloy and graphite (C), and a free layer 108 was further laminated on the MgO film to a thickness of 5 nm.
• the target was changed to W metal, and sputtering was performed to deposit a W film on the free layer 108 to a thickness of 5 nm.
• the target was changed to Ta metal and sputtering was performed to deposit a Ta film on the W film to a thickness of 5 nm.
• the fixed layer 104 and the free layer 108 were each configured to be an anomalous hole layer, and a sample was obtained as the memory element 10 of Experimental Example 2, in which the fixed layer 104 contained B and the free layer 108 contained C as contaminating elements.
• Experimental Example 3 similar to Experimental Examples 1 and 2, a pre-prepared Si substrate was first placed on the sample stage of the sputtering device.
• the sample chamber in which the sample stage was stored was evacuated and Ar gas was introduced as an inert gas. After that, a Ta film was deposited on the Si substrate by sputtering using a Ta target to a thickness of 5 nm.
• sputtering was performed using a target composed of an iron-cobalt-boron alloy (Fe 60 Co 20 B 20 ), and a fixed layer 104 was deposited on the deposited Ta film to a thickness of 1.8 nm.
• Fe 60 Co 20 B 20 iron-cobalt-boron alloy
• the target was changed from iron-cobalt-boron alloy to MgO, and an MgO film was laminated as a barrier layer on the fixed layer 104 to a thickness of 1 nm.
• N2 gas (purity 99.99%) was introduced into the sample chamber to form an atmosphere composed of a mixed gas of Ar gas and N2 gas.
• the partial pressure ratio of each gas contained in the mixed gas was 99% for Ar gas and 1% for N2 gas, assuming that the partial pressure ratio of the entire mixed gas was 100%.
• sputtering was performed using a target composed of Mn3Ge alloy, and a free layer 108 was further laminated on the MgO film to a thickness of 5 nm.
• the target was changed to Hf metal, and sputtering was performed to deposit an Hf film on the free layer 108 to a thickness of 2 nm.
• the target was changed to tantalum nitride (TaN) and sputtering was performed to deposit a TaN film on the Hf film to a thickness of 5 nm.
• TaN tantalum nitride
• Example 4 In Experimental Example 4, a Si substrate prepared in advance was first placed on the sample stage of a sputtering apparatus. The sample stage was housed in a sample chamber.
• the sample chamber in which the sample stage was stored was evacuated and replaced with an inert gas, Ar gas (99.999% purity).
• a Ta film was laminated on the Si substrate by sputtering using a Ta target to a thickness of 5 nm.
• the Ta film can function as the electrode 102.
• sputtering was performed in an Ar gas atmosphere using a target composed of a Mn 3 Sn alloy, and a fixed layer 104 was laminated on the laminated Ta film so as to have a film thickness of 15 nm.
• the target was changed from the Mn 3 Sn alloy to MgO, and an MgO film was laminated as a barrier layer on the fixed layer 104 to a thickness of 1 nm.
• the target was changed back from MgO to an Mn 3 Sn alloy, and further sputtering was performed in a mixed gas atmosphere to laminate a free layer 108 to a thickness of 10 nm on the MgO film.
• the target was changed to Ta metal and sputtering was performed to deposit a Ta film on the free layer 108 to a thickness of 5 nm.
• the fixed layer 104 and the free layer 108 were each configured to be an anomalous hole layer, and a sample was obtained as the memory element 10 of Experimental Example 4 in which no contaminating elements such as H were contained except as unavoidable impurities.
• compositions of the pinned layer 104 and the free layer 108 for each of the above Experimental Examples 1 to 3 were identified using X-ray photoelectron spectroscopy and mass spectrometry, resulting in the following table.
• the fixed layer 104 in Experimental Examples 1 and 2 contained H and B as contaminating elements, whereas Experimental Examples 3 and 4 contained no contaminating elements.
• the free layer 108 in Experimental Examples 1 to 3 contained H, C, and N as contaminating elements, whereas Experimental Example 4 contained no contaminating elements.
• Figure 2 shows an example of the M-H curves for the samples according to Experimental Examples 1 to 4.
• the magnetization of the samples according to Experimental Examples 1 to 4 was saturated when an external magnetic field of approximately 1 T was applied. It was shown that the saturation magnetization of the samples according to Experimental Examples 1, 2, and 3 at this time was greater than that of Experimental Example 4. This shows that the magnetic properties are improved by introducing contaminating elements such as H, B, C, and N into the fixed layer 104 and free layer 108.
• the saturation magnetization of the sample of Experimental Example 3 was particularly large compared to the saturation magnetization of the samples of Experimental Examples 1 and 2. This suggests that N is a preferable contaminating element.
• the retention force of the sample of Experimental Example 3 was smaller than the retention forces of the samples of Experimental Examples 1, 2, and 4. This suggests that the sample of Experimental Example 3 has a higher responsiveness to an external magnetic field compared to the other samples.
• MR ratio magnetoresistance ratio
• Table 3 shows an example of the measurement results of the MR ratio. The measurement results were obtained by measuring the magnetoresistance of the samples used in the measurement of the above M-H curves using a tunneling magnetoresistance measurement (CIPT) device.
• Figure 3 is a diagram showing the relationship between the MR ratio of the sample according to Experimental Example 1 and the external magnetic field.
• Fig. 4 is a diagram showing an example of the relationship between the composition ratio x/y of Mn and Sn and the MR ratio in Mn x Sn y A z for each type of contaminant element A. As shown in Fig. 4, it is estimated that for any contaminant element A, the MR ratio tends to be maximum when x/y is approximately 3 to 5. It is also estimated that when H is used as the contaminant element A, it has a higher MR ratio than other elements.
• An element comprising a memory layer, an insulating layer, and a fixed layer, each of the memory layer and the fixed layer being configured to have spontaneous magnetization, the insulating layer being disposed between the memory layer and the fixed layer, thereby forming a tunnel magnetic junction between the memory layer and the fixed layer, the magnetization direction of the fixed layer being configured to be fixed regardless of data written to the element, the magnetization direction of the memory layer being configured to be reversible depending on data written to the element, at least one of the memory layer and the fixed layer being an anomalous Hall layer made of an antiferromagnetic material that exhibits an anomalous Hall effect, the sign of the anomalous Hall coefficient of the antiferromagnetic material being configured to be reversible depending on data written to the element, and at least a portion of the anomalous Hall layer being configured to contain a contaminating element that is at least one element selected from the group consisting of H, B, C, and N.
• the contaminating elements make it easier to temporarily keep the anomalous Hall layer in an amorphous state, making it easier to obtain an element with a memory layer or fixed layer that contains a highly crystalline antiferromagnetic material.
• metal layer is composed of at least one element selected from the group consisting of Ti, Zr, Hf, Ta, Nb, and W.
• the anomalous Hall layer when stacking antiferromagnetic materials that exhibit the anomalous Hall effect, the anomalous Hall layer can be easily maintained in an amorphous state temporarily by the contaminating elements, making it easier to obtain an element having a memory layer or fixed layer that includes an antiferromagnetic material with higher crystallinity. Of course, this is not the case.

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