JP2014053546A - Voltage drive spintronics three-terminal element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a voltage drive spintronics three terminal element which can be made extremely thin while reducing power consumption, and can produce a large signal output while ensuring stable operation at room temperature.SOLUTION: A voltage drive spintronics three terminal element has a multi-layer film structure sequentially consisting of a ferromagnetic magnetization fixed layer, a nonmagnetic spacer layer, and a ferromagnetic magnetization rotation layer, and exhibiting magneto-resistance effect, and has an electrode layer for voltage application covering any one of the upper surface, lower surface or side face of the magnetization rotation layer entirely, with an insulator layer interposed therebetween. A first terminal, i.e., an input terminal, is connected with the electrode layer for voltage application, a second terminal is connected with the magnetization rotation layer, and a third terminal is connected with magnetization fixed layer.

Description

  The present invention relates to a voltage-driven spintronics three-terminal element. This three-terminal device is useful for power amplification, voltage amplification, fan-out, and the like.

  In recent years, with the miniaturization of metal oxide semiconductor field effect transistors (MOSFETs) represented by complementary metal oxide semiconductors (CMOS), the leakage current of the gate insulating film has increased and the carrier density in the channel has fluctuated. These problems are becoming apparent, and there are concerns about the limit of scaling (scaling limit) of semiconductor transistors. In order to break through the miniaturization limit of CMOS technology, realization of transistor technology based on a new principle that does not depend on the electric field effect of a semiconductor channel, so-called Beyond CMOS technology is desired.

  The field of technology that creates new device functions by utilizing both the charge and electron spin of electrons in solid-state devices is called “spintronics”, and it is expected to create new functional devices that cannot be realized by semiconductor electronic technology alone. . Already using spintronics technology, a giant magnetoresistive effect element (GMR element) based on a ferromagnetic layer / nonmagnetic metal layer / ferromagnetic layer or a multilayer structure of a ferromagnetic layer / tunnel barrier layer / ferromagnetic layer The tunnel magnetoresistive element (also called TMR element or MTJ element) is realized, and new application devices such as high-sensitivity magnetic sensors and nonvolatile memories (MRAM) using these elements are created. Spintronics is also expected as Beyond CMOS technology, and basic research on not only two-terminal GMR elements and TMR elements but also three-terminal elements that include GMR elements and TMR elements as components has begun.

  Typical prior art documents related to spintronics three-terminal devices that have been studied so far are listed below.

Japanese Laid-Open Patent Publication No. 11-238924 Toshiba (猪 俣) “Resonant Tunnel of Double Barrier MTJ” JP 2007-305610 JP Tohoku University (Ohno) “Resonant tunnel of double barrier MTJ” JP 2011-205007 Publication NEC (Fukami) "Domain Wall Moving Three Terminals" JP 2008-066479 Publication Osaka University (Suzuki) "Domain Wall Drive Transistor" International Publication WO2009 / 133650 Publication Osaka University (Suzuki / Nozaki) “Magnetization Control Method, Information Storage Method, Information Storage Element, and Magnetic Functional Element”

“Current-Field Driven‘ ‘Spin Transistor’ ’, Katsunori Konishi et al., Applied Physics Express vol.2, 063004 (2009). May 29, 2009. “Three-Terminal Device Based on the Current-Induced Magnetic Vortex Dynamics with the Magnetic Tunnel Junction”, S. Kasai et al., Applied Physics Express vol.1, 091302 (2008). "RF amplification in a three-terminal magnetic tunnel junction with a magnetic vortex structure", T. Nozaki et al., APPLIED PHYSICS LETTERS vol.95, 022513 (2009). `` Induction of coherent magnetization switching in a few atomic layers of FeCo using voltage pulses '', Y. Shiota et al., NATURE MATERIALS vol.11, p.39-43 (2012). `` Large voltage-induced magnetic anisotropy change in a few atomic layers of iron '', T. Maruyama et al., NATURE NANOTECHNOLOGY, vol.4, p.158-161 (2009).

  In Patent Documents 1 and 2, a resonant tunneling transistor type spintronics three-terminal using an ultrathin nonmagnetic layer as an intermediate electrode layer having a double tunnel barrier structure and utilizing a quantum well level formed in the nonmagnetic layer Devices have been proposed theoretically. However, it is difficult to actually manufacture such a resonant tunneling spintronics three-terminal device, even with the most advanced technology at present, and this type of three-terminal device is actually a practical performance as a resonant tunneling transistor. No example has been realized yet.

  In Non-Patent Document 1, the direction of magnetization of the magnetization free layer of the TMR element is changed using a magnetic field (referred to as a current magnetic field) generated by passing a current through a metal wiring, and this magnetization direction is determined using the TMR effect. There has been reported a three-terminal element characterized in that an output is obtained by converting the amount of change into an electrical signal. A major problem with this type of three-terminal element is that power consumption increases with the miniaturization of the element, that is, there is no scalability of miniaturization.

In Patent Documents 3 and 4, a domain wall is introduced into a ferromagnetic layer, and the position of the domain wall is displaced using spin torque generated by passing a current between two electrode terminals arranged at both ends of the ferromagnetic layer. There has been proposed a “domain wall drive type” spintronics three-terminal device characterized in that an output signal is obtained by detecting displacement of a domain wall using a magnetoresistive element formed on a ferromagnetic layer. This type of three-terminal element is promising as a non-volatile memory in which an input circuit and an output circuit are separated, and high-speed operation of the non-volatile memory by input / output separation becomes possible.
In addition, in the structure of Patent Document 4, a proposal has been made to give an amplification function by appropriately designing the domain wall introduction thin wire and the magnetoresistive element. However, the domain wall in the ferromagnetic layer has various different structures, so that there are many practical problems such as incomplete reproducibility and reliability of element operation and large variation in characteristics among many elements. . Also, the domain wall motion is so complex that this type of three-terminal element is not well suited for signal amplification.

  In Non-Patent Documents 2 and 3, a magnetic vortex structure is formed in a disk-shaped ferromagnetic layer, and spin torque generated by passing a current between two electrode terminals arranged at both ends of the ferromagnetic layer disk is used. The magnetic vortex drive type spintronics, characterized in that the position of the magnetic vortex is displaced and the output signal is obtained by detecting the displacement of the magnetic vortex using a magnetoresistive element formed on the ferromagnetic layer. Terminal elements have been reported. This type of three-terminal element is suitable for signal amplification, but the biggest problem is that a magnetic disk larger than a certain size is required to form a magnetic vortex structure, so that the element can be miniaturized. This is a difficult point.

The main difference between the above-described domain wall drive type three-terminal element and the magnetic vortex drive type three terminal element of Patent Document 3 is the difference between the magnetic structure formed in the ferromagnetic layer being the domain wall or the magnetic vortex, and the ferromagnetic layer. A common point is that the magnetic structure is displaced by passing a current through the magnetic field, and the displacement is read out by the magnetoresistive effect.
Another problem of these elements utilizing spin torque is that it is difficult to reduce power consumption because of current-driven elements. A spintronic device using a spin torque is superior in terms of power consumption and scalability as compared with a device using a current magnetic field, but it is still difficult to reduce power consumption as compared with a voltage-driven device. If this problem is compared to a semiconductor transistor, a three-terminal element using spin torque is equivalent to a bipolar transistor.

  Regarding the technology for controlling the magnetization direction of the ferromagnetic layer, as a third basic technology following the current magnetic field and the spin torque, the following “voltage-driven” spintronic device is recently attracting attention, not the current-driven type. Collecting. In Non-Patent Documents 4 and 5, in the two-terminal element, by applying a voltage to the ferromagnetic layer through the insulator layer, an electric field is applied in the vicinity of the interface “with the insulator layer” in the ferromagnetic layer, There has been reported an “electric field induced magnetic anisotropy change” phenomenon in which the magnetic anisotropy of the ferromagnetic layer, particularly the perpendicular magnetic anisotropy component, is changed by this electric field. When this electric field induced magnetic anisotropy change is used, theoretically, it is possible to change or reverse the magnetization direction of the ferromagnetic layer using a voltage with almost no current flowing. The magnetization control technique using the electric field induced magnetic anisotropy change is referred to herein as “voltage-driven” magnetization control. The advantage of this voltage-driven magnetization control is that, in principle, the direction of magnetization can be controlled only by the voltage without passing a current other than the displacement current, so that the power consumption can be further reduced compared to the magnetization control by spin torque. is there.

  In Patent Document 5, not only a voltage-driven spintronics two-terminal element using a TMR element but also a concept of a three-terminal element is proposed, and the fifth embodiment (FIG. 13) to the eighth embodiment (FIG. 16) are proposed. A specific voltage-driven spintronic three-terminal device structure has been proposed. However, there is almost no description about the operation principle. By analogizing the operation principle of the three-terminal element shown in Patent Document 5 from the element structure shown in FIGS. 13-16, all of these three-terminal elements have practical problems.

  In the three-terminal element of the fifth embodiment (FIG. 13) of Patent Document 5, the electrode 30 (corresponding to the voltage applying electrode layer of the present invention) through the insulating layer 11 (corresponding to the insulator layer of the present invention) are used. By applying an electric field to the magnetic layer 10 (corresponding to the magnetization rotation layer of the present invention), the magnetization direction of the magnetic layer 10 is changed. However, in the three-terminal element of FIG. 13 of Patent Document 5, the dimension in the in-film direction of the electrode 30 and the insulating layer 11 is smaller than the dimension in the in-film direction of the magnetic layer 10, and therefore only in a part of the magnetic layer 10. No electric field is applied. As a result, the direction of magnetization of the portion of the magnetic layer 10 to which the electric field is applied first changes, and the change in magnetization propagates to other portions of the magnetic layer 10 in the form of “domain wall movement”. . When the domain wall is formed in the magnetic layer during the operation of the element as described above, the same problem as in Patent Documents 3 and 4 described above occurs. Even in the three-terminal element of the seventh embodiment (FIG. 15) of Patent Document 5, a domain wall is formed in the magnetic layer during the operation of the element as in the case of the three-terminal element of FIG.

In the three-terminal element of the sixth embodiment (FIG. 14) and the seventh embodiment (FIG. 15) of Patent Document 5, the electrode 43 and the electrode 44 functioning as signal output electrodes are the same magnetic layer (reference numerals in FIG. 14). 42 or the reference numeral 10) in FIG. 15 and a signal output current flows through the magnetic layer 42 and the magnetic layer 10 in the in-film direction. In such an arrangement of the electrode 43 and the electrode 44, the magnetoresistive effect of the signal output portion of the three-terminal element becomes very small, so that the signal output of the three-terminal element also becomes very small. There is a problem.
Incidentally, according to the present inventors' elucidation, in order to increase the signal output of the three-terminal element, the two signal output electrodes are in contact with different magnetic layers, and the signal output current is applied directly to the film surface. It is necessary to flow in the direction.

  Since the three-terminal element of the eighth embodiment (FIG. 16) of Patent Document 5 uses spin injection into a semiconductor, room temperature operation is very difficult at the current technical level.

As a result of intensive studies, the present inventors have invented a voltage-driven spintronics three-terminal element that solves the practical problems of the three-terminal element of Patent Document 5, even if it is a voltage-driven spintronics three-terminal element. .
The present invention comprises a number of inventions. The first invention of the present invention is “a multilayer film having a magnetoresistive effect comprising, in order, a ferromagnetic magnetization fixed layer, a nonmagnetic spacer layer, and a ferromagnetic magnetization rotation layer. A voltage application electrode layer that covers the entire upper surface, lower surface, or side surface of the magnetization rotation layer via an insulator layer, and the voltage application electrode layer serves as an input terminal. A voltage-driven spintronics three-terminal element having a terminal connected, a second terminal connected to the magnetization rotation layer, and a third terminal connected to the magnetization fixed layer, wherein a voltage is applied from the voltage application electrode layer As a result, the magnetization direction of the magnetization rotation layer changes, and depending on the relative angle between the magnetization directions of the magnetization pinned layer and the magnetization rotation layer, the magnetization rotation layer and the magnetization pinned layer pass through the nonmagnetic spacer layer. Output signal that the electrical resistance between Utilized as a power amplifier, to provide a voltage-driven spintronic three-terminal element ", characterized in that to obtain such a voltage amplification or fan-out.
The second invention of the present invention has a multilayer film structure showing a magnetoresistive effect composed of a ferromagnetic magnetization fixed layer, a nonmagnetic spacer layer, and a ferromagnetic magnetization rotation layer in order. A voltage applying electrode layer that covers the entire upper surface, lower surface, or side surface through an insulator layer; a first terminal that is an input terminal is connected to the voltage applying electrode layer; and A voltage-driven spintronics three-terminal element having a second terminal connected to the remaining surface and a third terminal connected to the magnetization fixed layer is provided.
According to a third aspect of the present invention, in the voltage-driven spintronics three-terminal element according to the first or second invention, the nonmagnetic spacer layer is a tunnel barrier layer. Device ".
According to a fourth aspect of the present invention, in the voltage-driven spintronics three-terminal element according to any one of the first to third aspects, by applying a voltage from the voltage application electrode layer, There is provided a voltage-driven spintronics three-terminal device characterized in that the direction of magnetization changes between an in-plane direction and a direction perpendicular to the film plane.
According to a fifth aspect of the present invention, in the voltage-driven spintronics three-terminal element according to any one of the first to fourth aspects, the magnetization direction of the magnetization fixed layer is in an in-plane direction. "Voltage-driven spintronics three-terminal device".
According to a sixth aspect of the present invention, in the voltage-driven spintronics three-terminal element according to any one of the first to fourth aspects, the magnetization direction of the magnetization fixed layer is perpendicular to the film surface. A voltage-driven spintronics three-terminal device.
According to a seventh aspect of the present invention, in the voltage-driven spintronic three-terminal element according to any one of the first to sixth aspects, the voltage applying electrode layer surrounds a side surface of the magnetization rotation layer. A voltage-driven spintronics three-terminal device is provided.
According to an eighth aspect of the present invention, in the voltage-driven spintronics three-terminal element according to any one of the first to seventh aspects, the magnetization rotation layer has a single magnetic domain structure. A three-terminal device is provided.
According to a ninth aspect of the present invention, in the voltage-driven spintronics three-terminal element according to any one of the first to eighth aspects, the magnetization rotation layer is grounded. Device ".
According to a tenth aspect of the present invention, in the voltage-driven spintronics three-terminal element according to the ninth aspect of the invention, a signal output load circuit is connected to the magnetization fixed layer. A terminal element is provided.

According to the present invention, a voltage-driven spintronics three-terminal device is the first (1) that a domain wall is not formed in a magnetic layer, that is, a magnetization fixed layer or a magnetization rotation layer, and (2) for signal output. Current does not flow through the magnetic layer, that is, the magnetization fixed layer or the magnetization rotation layer, so that the magnetoresistive effect is very large, so that the signal output is also very large, and (3) the semiconductor Since (spin injection into the inside) is not used, room temperature operation can be easily performed at the current technical level.
In addition, the three-terminal element of the present invention can realize a power amplification factor greatly exceeding 5, a voltage amplification factor exceeding 1, and a fan-out greatly exceeding 5.
When the single-domain structure (“single-domain” is ideal and may be a structure close to it) is used as the magnetization rotation layer, the three-terminal element of the present invention is reliable in element operation and has characteristic variations. There are few advantages that can be made ultra-fine.
Furthermore, compared to a semiconductor transistor typified by CMOS, since a single crystal semiconductor substrate is not necessary, the three-terminal element of the present invention can be fabricated on an arbitrary underlayer at a low manufacturing cost, and can be easily multilayered. A metal with a high carrier density has no problem of carrier fluctuation, and thus has any advantage that enables stable operation even with an element smaller than 10 nm.

It is a cross-sectional schematic diagram of the three-terminal element concerning the Example of this invention. (A) is a cross-sectional schematic diagram of the three-terminal element of FIG. 1 in which the magnetization fixed layer has in-plane magnetization. The arrow schematically represents the direction of magnetization. Similarly, (b) is a schematic cross-sectional view of the three-terminal element of FIG. 1 in which the magnetization fixed layer has perpendicular magnetization. The arrow schematically represents the direction of magnetization. FIG. 6 is a schematic perspective view of an element for measuring the rotation of magnetization due to application of a voltage using the magneto-optical Kerr effect. It is a graph which shows the measurement result of magnetization direction (phi) and applied voltage Vin _{in a} magnetization rotation layer. It is a cross-sectional schematic diagram of the three-terminal element concerning another Example of this invention. (A) is a cross-sectional schematic diagram of the three-terminal element concerning another Example of this invention, (b) is the top view. (A) is the same cross-sectional schematic diagram as FIG. 5, but with the name as an electric circuit. (B) is an equivalent circuit diagram of FIG. (C) is a circuit symbol of FIG. (D) is the electric circuit diagram of the minimum unit incorporating the circuit symbol of the (c) figure. (A) is an electric circuit diagram which shows an example of the electric circuit incorporating the three-terminal element made into the circuit symbol. (B) is an electric circuit diagram of another example. It is a graph which shows the gate resistance _RG dependence of the power gain PG of a three-terminal element. It is a graph which shows the gate resistance _RG dependence of the voltage gain VG of a three-terminal element. It is an electric circuit diagram showing an example of cascade connection of three terminal elements. It is a cross-sectional schematic diagram of a prototype three-terminal element. It is the scanning electron micrograph which observed the prototype 3 terminal element from the top.

Next, embodiments of the present invention will be specifically described with reference to the drawings.
<Example>
FIG. 1 is a schematic sectional view of a voltage-driven spintronics three-terminal element in this embodiment. The element is composed of a voltage application electrode layer 11, an insulator layer 12, a ferromagnetic magnetization rotation layer 13, a nonmagnetic spacer layer 14, and a ferromagnetic magnetization fixed layer 15 in order from the lower side of FIG. An input terminal (first terminal) 16 is connected to the voltage application electrode layer 11, and an output terminal (second terminal) 17 and an output terminal (third terminal) are connected to the magnetization rotation layer 13 and the magnetization fixed layer 15, respectively. 18 is connected. A voltage signal is input to the input terminal (first terminal) 16, and a current signal or a voltage signal generated between the output terminal (second terminal) 17 and the output terminal (third terminal) 18 becomes an output signal.
The three-layer structure of the ferromagnetic magnetization rotation layer 13, the nonmagnetic spacer layer 14, and the ferromagnetic magnetization fixed layer 15 exhibits a magnetoresistive effect. For example, when the nonmagnetic spacer layer 14 is a nonmagnetic metal, it functions as a GMR element, and when the nonmagnetic spacer layer 14 is a tunnel barrier layer made of an insulator, it functions as a TMR element.

Next, the basic operation principle of this embodiment will be described with reference to FIGS. 2 (a) and 2 (b). The difference between FIG. 2 (a) and FIG. 2 (b) is in-plane magnetization in which the magnetization of the magnetization fixed layer faces the in-plane direction in FIG. 2 (a), and in FIG. The only point is that the magnetization is perpendicular magnetization in the direction perpendicular to the film surface.
As a typical example of element operation, the output terminal (second terminal) 17 is grounded, and the voltage Vin is applied to the input terminal (first terminal) 16. At this time, a DC voltage, a pulse voltage, an AC voltage, or the like can be used as Vin. As a result of an electric field being induced in the vicinity of the interface “with the insulator layer 12” in the magnetization rotation layer 13 by the application of the voltage Vin, the perpendicular magnetic anisotropy energy Ku of the magnetization rotation layer 13 changes. Using this change in Ku, the magnetization angle φ of the magnetization rotation layer 13 can be changed. For example, if the shape magnetic anisotropy of the magnetization rotation layer 13 is larger than Ku, the magnetization is in the in-plane direction (φ = 0) in the state of Vin = 0. Ku can be increased by applying Vin having an appropriate polarity and size. Φ can take any value between 0 ° and 90 ° depending on the relative relationship between Ku, shape magnetic anisotropy, and external magnetic field, and φ can be changed between 0 ° and 90 ° by changing Vin. It is theoretically possible to change continuously between.

  Next, an example of a demonstration experiment showing that it is actually possible to continuously change the magnetization angle φ between 0 ° and 90 ° by changing Vin will be described. In this example, in order to accurately measure the relationship between the applied voltage Vin and the magnetization angle φ, an element (sample) having a structure as shown in FIG. 3 was produced. In this sample, the magnetization fixed layer is intentionally omitted in order to measure the magnetization direction of the magnetization rotation layer by the polar magneto-optical Kerr effect. Further, in order to measure the polar magneto-optical Kerr effect, it is necessary to irradiate the magnetization rotation layer with laser light from the upper surface of the sample. Therefore, the transparent electrode ITO is applied to the voltage application electrode layer 11, and the insulator layer 12 is applied Uses a laminate of transparent polyimide and MgO. For this reason, parameters such as the applied voltage Vin and the external magnetic field are different from those of a practical three-terminal element. This example is only an experiment for demonstrating that the magnetization angle φ continuously changes depending on the voltage Vin. FIG. 4 shows the voltage Vin dependency of the magnetization angle φ measured when a 50 Oe stationary magnetic field is applied in the vertical direction. FIG. 4 shows that the magnetization angle φ of the magnetization rotation layer 13 is continuously changed from 90 ° (perpendicular magnetization) to 12 ° by changing Vin from −200 V to +200 V. It is also possible to change the magnetization angle φ in the range from 0 ° to 90 ° with a smaller applied voltage Vin by appropriately selecting the sample structure, the thickness of each layer, and the material to be used. In particular, if the insulating layer 12 is made thin and an insulating material having a high relative dielectric constant is used, Vin can be significantly reduced. For example, in this experiment, the electric field strength applied to the MgO layer when a voltage of 200 V is applied is about 50 mV / nm, and assuming that the film thickness of the MgO tunnel barrier layer used in a normal TMR element is 2 nm, for example. A similar effect can be obtained at about 100 mV. That is, drastic low-voltage driving is possible only by making the insulating layer 12 a single MgO layer. In this experiment, a stationary magnetic field was applied from the outside. However, a permanent magnetic layer was placed around the sample and a stationary magnetic field was applied to the sample, or exchange coupling from a magnetization fixed layer adjacent to the magnetization rotation layer 13 was used. If a technique such as this is used, it is possible to change the magnetization angle φ between 0 ° and 90 ° using only the voltage Vin without applying an external magnetic field.

Since it has been demonstrated that the magnetization direction φ of the magnetization rotation layer 13 can be continuously changed between 0 ° and 90 ° by applying a voltage as described above, FIG. 2A and FIG. Returning to the explanation of the operating principle of the three-terminal element having the structure shown in FIG. When the magnetization angle φ of the magnetization rotation layer 13 changes, the relative angle θ of magnetization between the magnetization fixed layer 15 and the magnetization rotation layer 13 also changes. In the case of FIG. 2A in which the magnetization fixed layer 15 has in-plane magnetization, | θ | = | φ |, and in the case of FIG. 2B in which the magnetization fixed layer 15 has perpendicular magnetization, | θ | = 90 ° −. | φ |. In either case, | θ | can be continuously changed between 0 ° and 90 ° by applying the voltage Vin. Here, since the three-layer structure of the magnetization rotation layer 13, the nonmagnetic spacer layer 14, and the magnetization fixed layer 15 exhibits a magnetoresistive effect, the electrical resistance (or the output terminal 17 and the output terminal 17 between the magnetization rotation layer 13 and the magnetization fixed layer 15). The electrical resistance between 18) R varies depending on θ. Hereinafter, the case of FIG. 2A (in the case where the magnetization fixed layer 15 is in-plane magnetization) will be described as an example. The electrical resistance R takes a minimum value (denoted as R _P ) at θ = 0 °, and θ = It shows a maximum value (denoted as R _AP) at 180 °. The electrical resistance at θ = 90 ° (denoted as R ₉₀ ) is (R _P + R _AP ) / 2. That is, by inputting a voltage Vin to the voltage application voltage layer 11, the electric resistance R between the magnetization rotation layer 13 and the magnetization fixed layer 15, can be continuously changed between the R _P and R ₉₀ . The magnetoresistance ratio (MR ratio) of the magnetoresistive element structure is defined as MR = (R _AP −R _P ) / R _P.

  If the electric resistance R changes depending on the input voltage Vin, an output signal can be obtained between the output terminals 17 and 18. For example, if a voltage is applied in advance between the output terminal (second terminal) 17 and the output terminal (third terminal) 18, the output can be taken out as a current signal. Alternatively, if a current is passed between the output terminal (second terminal) 17 and the output terminal (third terminal), the output can be taken out as a voltage signal. Based on the principle described above, the three-terminal element shown in FIGS. 2A and 2B operates as a transistor.

  How much amplification performance can be obtained with the three-terminal element of FIG. 2 will be described later. Before that, an example of a more specific element structure based on the structure of the three-terminal element shown in FIG. 2 is shown in FIGS. The three-terminal element of FIG. 5 has a multilayer structure of a voltage application electrode layer 11, an insulator layer 12, a magnetization rotation layer 13, a nonmagnetic spacer layer 14, and a magnetization fixed layer 15 in order from the bottom. Usually, since the magnetization rotation layer 13 is very thin, for example, 0.5 nm to 3 nm, it is desirable to provide an electrode layer 19 in order to connect the output terminal (second terminal) 17 thereto. As the electrode layer 19, the magnetization rotation layer 13 itself can also be used. That is, the magnetization rotation layer 13 may be made larger than the nonmagnetic spacer layer 14 and the magnetization fixed layer 15, and the output terminal (second terminal) 17 may be directly connected to the magnetization rotation layer 13. In the three-terminal element shown in FIG. 5, the element manufacturing process is easier if the voltage application terminal 11 is arranged on the substrate side, but it is theoretically possible to arrange the magnetization fixed layer 15 on the substrate side. .

  The three-terminal element of FIG. 6 has a concentric circular shape as shown in FIG. 6B (plan view), and the inside of a small circle close to the center is “magnetization rotation layer 13 / nonmagnetic spacer layer 14 / magnetization fixed layer”. 15 is a multi-layered structure showing a magnetoresistive effect ”, and the ring-shaped portion between the middle circle and the small circle is the insulator layer 12, and is between the outermost great circle and the middle circle. The ring-shaped portion is the voltage application electrode layer 11. The voltage application electrode layer 11 covers the entire side surface of the magnetization rotation layer 13 via the insulator layer 12. The structure of the three-terminal element of FIG. 6 is more complicated in the manufacturing process than the structure of FIG. 5, but the application efficiency of voltage to the magnetization rotation layer 13 is improved as the element is miniaturized, which is superior in terms of scalability. Yes. In the three-terminal element of FIG. 6, the magnetization rotation layer 13 can be disposed on the substrate side, or the magnetization fixed layer 15 can be disposed on the substrate side.

Next, the signal amplification performance of the above three-terminal element will be described. Here, the amplification performance is estimated by using the magnetization fixed layer 15 having in-plane magnetization shown in FIG. 2A and the element structure shown in FIG. 5 as an example. Note that even when the perpendicular magnetization magnetization fixed layer as shown in FIG. 2B or the element structure as shown in FIG. 6 is used, the amplification performance can be basically estimated in the same manner. 7A is a name as an electric circuit of the components of the three-terminal element shown in FIG. 5, FIG. 7B is an equivalent circuit diagram of the three-terminal element, and FIG. 7C is a circuit of the three-terminal element. Symbol definition, FIG. 7 (d) represents the smallest unit of a circuit incorporating a three-terminal element. In FIG. 7B, R _G and C _G are the electric resistance and capacitance between the gate electrode and the source electrode, respectively, and R _MTJ is the electric resistance between the source electrode and the drain electrode (variable that changes depending on the magnetoresistance effect). Resistance), R _S represents the electrical resistance of the wiring portion of the source electrode. A three-terminal element composed of such components is denoted by a circuit symbol shown in FIG. FIG. 7D shows an example of the minimum unit when this three-terminal element is incorporated in a circuit. In this case, the source terminal is grounded, and the voltage V _D is applied to the drain terminal in advance. R _MTJ is changed when the gate terminal inputs a V _G as a voltage signal, the transistor operation is achieved by taking out an output signal variation which the current I _D flowing into the drain terminal changes.

ここで、数式１は、交流電圧源の出力インピーダンスに比べてR_Gが非常に大きい場合の近似式である。 Next, a description will be given of a power amplification factor (hereinafter, “Power Gain” is abbreviated as “PG”) obtained by the circuit shown in FIG. In order to extract the signal output, a load resistor R _L is connected to the drain terminal of the three-terminal element as shown in FIG. 8A, and the power output is estimated from the power consumed in the load resistor. Amplitude v _in, the AC voltage having a frequency ω as the voltage V _in input to the gate terminal _{(V in = v in · exp} (-iωt), t is time) using a load and an AC power P _in input to the gate terminal The power amplification factor of the three-terminal element is estimated from the ratio of the AC component ΔP _out of the power consumed by the resistor. Input power P _in the case where the input AC voltage amplitude required to change the magnetization direction of the magnetization rotation layer from in-plane direction to the perpendicular direction (v referred to as _90), as the following equation (Equation 1) Become.

Here, Formula 1 is an approximate formula when _RG is very large compared to the output impedance of the AC voltage source.

ゲート端子に振幅v₉₀の交流電圧を入力した場合、θは0°と90°の間で振動する。その結果、負荷抵抗R_Lに生じる交流電力の振幅ΔP_outは、次式（数３）のようになる。

ここで、数式３の右辺は、出力電力振幅が最大になるようにR_Lの値を選択した場合、つまりインピーダンス・マッチングを取った場合に得られる最大の出力電力振幅である。 The power P _out (function of the relative angle θ of magnetization) consumed by the load resistance when the DC voltage V _D is applied to the drain terminal is expressed by the following equation (Equation 2).

When an AC voltage with an amplitude of ₉₀ is input to the gate terminal, θ oscillates between 0 ° and 90 °. As a result, the amplitude ΔP _{out of the} AC power generated in the load resistance R _L is expressed by the following equation (Equation 3).

Here, the right side of Equation 3 is the maximum output power amplitude obtained when the value of _RL is selected so that the output power amplitude is maximized, that is, when impedance matching is taken.

The power amplification factor PG of the three-terminal element is obtained by dividing Equation 3 by Equation 1 and is given by the following equation (Equation 4).

Next, an actual element parameter is put into Formula 4, and the power amplification factor PG of the three-terminal element is estimated. Actual measured values of R _P = 2.3 kΩ, R _S = 0.5 kΩ, MR = 120%, R ₉₀ = 1.6 kΩ were obtained from the actually manufactured three-terminal element (described later). substitute. Further, v as the ₉₀ to about 1 V since a realistic maximum value, this value is used. As V _D , a value of V _D = 3 V is used in consideration that the voltage applied to the tunnel barrier layer is sufficiently lower than the element breakdown voltage. FIG. 9 shows the power gain PG obtained by substituting these parameters into Equation 4 as a function of the gate resistance _RG . Here, the reason why the gate resistance _RG is used as a variable is that the value of the gate resistance _RG can be easily changed within a range of several digits by changing the material and thickness of the gate insulating layer.

As can be seen from FIG. 9, if the gate resistance _RG is set to 10 kΩ or more, for example, a large power amplification factor exceeding 10 can be obtained. This is because the input power can be reduced by increasing the gate resistance _RG . For example, since the value of the gate resistance _RG of the actually manufactured three-terminal element (described later) is 30 kΩ, the power amplification factor is 30. As described above, the three-terminal element of the present invention can obtain a large power amplification factor.

Next, the voltage amplification factor (hereinafter, “Voltage Gain” is abbreviated as VG) obtained by the circuit of FIG. In order to extract the voltage signal, a voltage output terminal is set between the drain terminal of the three-terminal element shown in FIG. 8B and the load resistor R _L , and the output voltage V _out is extracted therefrom. This output voltage _Vout is expressed by the following equation (Equation 5).

ここで、数式６の右辺は、出力電圧振幅が最大になるようにR_Lの値を選択した場合、つまりインピーダンス・マッチングを取った場合に得られる最大の出力電圧振幅である。 Similar to the case where the power amplification factor is estimated, it is obtained when an AC voltage of AC voltage amplitude v ₉₀ necessary to change the magnetization direction of the magnetization rotation layer from the in-plane direction to the vertical direction is input to the gate terminal. The AC amplitude ΔV _out of the output voltage V _out is expressed by the following equation.

Here, the right side of Equation 6 is the maximum output voltage amplitude obtained when the value of _RL is selected so that the output voltage amplitude is maximized, that is, when impedance matching is taken.

The voltage amplification factor VG of the three-terminal element is obtained by dividing Equation 6 by the input voltage amplitude v ₉₀ and is given by the following equation (Equation 7).

Next, an actual element parameter is put into Formula 7, and the power amplification factor PG of the three-terminal element is estimated. FIG. 10 shows the voltage amplification factor VG obtained by substituting the same parameter as the parameter used when estimating the power amplification factor PG into Equation 7 as a function of the gate resistance _RG . When a value of about 1 kΩ or more is used as the gate resistance _RG , a voltage amplification factor VG exceeding 2 is obtained. For example, since the value of the gate resistance _RG of the actually manufactured three-terminal element (described later) is 30 kΩ, a voltage amplification factor exceeding 2 can be obtained.

Next, the fan-out obtained by the three-terminal element of the present invention will be described. As a basic circuit for estimating fan-out, a “circuit in which the output side of one three-terminal element and the input side of a plurality of three-terminal elements are cascade-connected” shown in FIG. 11 is used. Leave applying a voltage V _D to advance the drain terminal, the input to the gate terminal of the three terminal element circuit upstream of the pulse voltage signal V _in, a pulse voltage signal V _out corresponding thereto is outputted from the source terminal. By inputting this voltage signal _Vout to the gate terminals of a plurality of three-terminal elements connected in cascade, a plurality of three-terminal elements can be driven by one three-terminal element. In such a cascade connection, the number indicating how many three-terminal elements can be driven by the output from one three-terminal element is the fan-out. When the fan-out is 1, one three-terminal element can drive only one three-terminal element, so that a logic circuit cannot be configured. On the other hand, if there are two or more fan-outs, one three-terminal element can drive two or more three-terminal elements, so that a logic circuit can be configured. The device of the present invention is useful because it can obtain fan-outs in excess of 5.

  The formula for estimating the fan-out is omitted because it is extremely complicated. However, if the fan-out is estimated using the cascade connection circuit shown in FIG. 11 and the circuit parameters described above, the voltage gain VG is smaller than 1. Fan out is less than 1. On the other hand, when the voltage amplification factor VG is larger than 1, a large fan-out exceeding 5 is obtained. Qualitatively explaining such characteristics, since the three-terminal element has a very large power amplification factor PG as shown in FIG. 9, a voltage signal larger than the first input voltage signal is applied to the lower stage. This is because as long as the input can be made to the three-terminal element, the driving ability is sufficient to drive a large number of three-terminal elements.

In the cascade connection circuit as described above, it is necessary to apply the voltage V _D to the drain terminal in advance, but if the drain voltage V _D is always applied, a leakage current always flows to the drain terminal, Static power consumption, that is, standby power increases. This problem also using a pulse voltage to the drain voltage V _D, can be solved by applying a drain voltage V _D only at the moment the circuit is operating.

  Next, a description will be given of a three-terminal element that is prototyped to accurately grasp circuit parameters. FIG. 12 shows a schematic diagram of the cross-sectional structure of the prototype device. The three-layer structure of the magnetization pinned layer 105, the ruthenium layer 106, and the cobalt iron layer 107 is a laminated structure called a laminated ferrimagnetic structure, and the magnetization pinned layer 105 and the cobalt iron layer 107 have antiparallel magnetization arrangement via the ruthenium layer 106. It has become. The direction of magnetization of the laminated ferrimagnetic structure is fixed by the exchange bias antiferromagnetic layer 108 laminated thereon, and as a result, the direction of magnetization of the magnetization fixed layer 105 is one direction in the film plane. It is fixed. Perpendicular magnetic anisotropy is induced at the interface “with the magnesium oxide layer located above and below it” in the magnetization rotation layer 103. A photograph observed from above the three-terminal element using a scanning electron microscope is shown in FIG. The element parameters as described above were measured from this three-terminal element.

  In the element of FIG. 12, the transverse dimension of the magnetization fixed layer 105 is 340 nm and the transverse method of the source terminal is 5 μm, but a three-terminal element smaller than 100 nm is manufactured by using the most advanced microfabrication technology. Is possible. Furthermore, if a perpendicular magnetization film having strong perpendicular magnetic anisotropy is used as the magnetization fixed layer, it is theoretically possible to produce a magnetization fixed layer smaller than 10 nm. 12 has the structure shown in FIG. 5. However, if the three-terminal element having the structure shown in FIG. 6 is fabricated, the gate can be efficiently formed on an ultrafine magnetization rotation layer of about 10 nm. A voltage can be applied. The three-terminal element shown in FIG. 12 is merely an example, and other elements having various structures such as the three-terminal element shown in FIG. 1 can be manufactured.

Next, materials that can be used for the voltage application electrode layer, the ferromagnetic layer, and the insulator layer of the three-terminal element will be described.
Examples of the material for the voltage application electrode layer include gold (Au), silver (Ag), copper (Cu), platinum (Pt), aluminum (Al), tungsten (W), chromium (Cr), and tantalum (Ta). Metals such as titanium (Ti) and ruthenium (Ru), noble metals or transition metals or alloys of those metals, polycrystalline silicon, silicides and carbons that are compounds of refractory metals such as silicon and nickel, cobalt or titanium Carbon materials such as nanotubes and graphene can be used. This electrode layer may be a laminated structure. In some cases, the electrode layer material is preferably non-magnetic.
As the film thickness of the voltage application electrode layer, unnecessarily thickening is not desirable because it not only adversely affects device miniaturization and shortens the manufacturing process time, but also impairs compatibility with the current CMOS process. If the thickness is extremely reduced, the electrical resistance increases. For this reason, the film thickness of the voltage application electrode layer depends on the material, but is preferably 5 nm to 1 μm, more preferably 10 nm to 100 nm, for example.
From the viewpoint of obtaining stable magnetoresistance characteristics at room temperature, it is preferable to use a transition metal / alloy containing at least one element among iron (Fe), cobalt (Co), and nickel (Ni) for the magnetization rotation layer. In particular, when an insulator is used for the nonmagnetic spacer layer, it is more preferable to use a ferromagnetic metal / ferromagnetic alloy containing iron for the magnetization rotation layer in order to obtain a high magnetoresistance ratio. More specifically, CoFeB to which perpendicular magnetic anisotropy is imparted by interfacial magnetic anisotropy with magnesium oxide can be mentioned.

  Originally, a material having a large perpendicular magnetic anisotropy tends to have a larger change in perpendicular magnetic anisotropy induced by voltage application. From this point of view, materials that can be applied to the magnetization rotation layer include (1) alloys of L10 ordered structure such as Fe-Pt, Fe-Pd, Co-Pt, Co-Pd, Mn-Ga, and (2) heterogeneous ferromagnetic metals. Or a multilayer film of an alloy thereof, or (3) a multilayer film in which “ferromagnetic metal or alloy thereof” and “nonmagnetic metal or alloy thereof” are laminated, (4) rare earth element neodymium (Nd), samarium (Sm), terbium A compound containing a magnetic element such as (Tb) or an alloy thereof; (5) a metal having HCP structure containing Co or an alloy thereof; and (6) a thin Co—Fe—B alloy layer utilizing interfacial magnetic anisotropy. Layers can also be used. For the magnetization fixed layer, various magnetic materials and multilayer films similar to the magnetization rotation layer can be used.

The film thickness of the magnetization rotation layer needs to be designed appropriately in consideration of different requirements from the output terminal side and the input terminal side. Regarding the control of the magnetization rotation layer by the voltage on the input side, it is desirable to be able to induce a large change in the magnetization direction at a low voltage, so it is desirable to make it as thin as possible. For example, the thickness of the magnetization rotation layer may be 5 nm or less, more preferably 3 nm or less, and even more preferably 2 nm or less. On the other hand, from the viewpoint of the output side, if the magnetization rotation layer is made too thin, (i) the magnetoresistive effect is reduced and (ii) the output is reduced due to the increase in source resistance. It is not preferable to make it thinner than nm. For this reason, the thickness of the magnetization rotation layer is preferably about 0.5 nm or more, more preferably 1 nm or more, and further preferably 1.5 nm or more.
Although there is no major limitation on the thickness of the magnetization pinned layer, device fabrication is easy if it is between about 2 nm and 10 nm.

As the material for the nonmagnetic spacer layer, oxides, nitrides, and fluorides of metals such as aluminum, magnesium, hafnium, cerium, strontium, tantalum, and titanium that exhibit the tunnel magnetoresistance effect (TMR) can be used. Of these, oxides of elements containing magnesium and oxides of elements containing magnesium and aluminum are preferred. Of these, single crystal or polycrystalline magnesium oxide having a (001) crystal plane preferentially oriented is particularly effective.
In addition, noble metals and transition metal elements such as gold (Au), silver (Ag), copper (Cu), aluminum (Al), chromium (Cr), ruthenium (Ru), etc., exhibiting giant magnetoresistance effect (GMR) are also used. The
The film thickness of the nonmagnetic spacer layer is preferably in the range of about 1 nm to 3 nm for a spacer layer such as magnesium oxide, and in the range of about 1 nm to 10 nm for a metal spacer layer. .

As the material of the insulator layer, (1) a nonmagnetic insulator material containing an oxide, nitride, fluoride or the like of metal such as aluminum, magnesium, hafnium, cerium, strontium, tantalum and titanium, or (2 ) Use of a ferromagnetic or ferrimagnetic transition metal oxide containing a magnetic element such as Fe, Co, or Ni, and (1) a laminated structure of (1) a nonmagnetic insulating material and (2) a magnetic oxide. it can.
Since the magnetization direction control of the magnetization rotation layer by voltage depends on the amount of accumulated charge induced near the interface with the “insulator layer” in the magnetization rotation layer by applying voltage, the material used for the insulator layer is room temperature. It is more preferable to use a dielectric having a high relative dielectric constant. Specifically, a material in which the ferroelectric Curie temperature and dielectric constant are controlled by adding Sr, Sn, La, Zr, Ca, Y, Nd, Sm, Dy, etc. to BaTiO ₃ which is a ferroelectric material, iron or BaTiO ₃ , IIIB element oxides (such as Y ₂ O ₃ and La ₂ O ₃ ), and IVB element oxides (ZrO ₂ and HfO ₂ ), which have a small lattice mismatch with iron-cobalt alloy of 1 to 2% and can be epitaxially grown. Etc.), oxides of VB elements (Ta ₂ O ₅ etc.), TiO _{2 and the} like are effective. In addition, the RA product of the insulator layer is preferably about 1 kΩ or more in order to obtain the above-described voltage gain.

Since the three-terminal element of the present invention is not voltage driven but current driven, it has low power consumption, can be operated at room temperature, and can be miniaturized. It is useful as an amplifying element, a logical operation element, etc.

DESCRIPTION OF SYMBOLS 11 ... Voltage application electrode layer, 12 ... Insulator layer, 13 ... Ferromagnetic magnetization rotation layer, 14 ... Nonmagnetic spacer layer, 15 ... Ferromagnetic magnetization fixed layer, 16 ... Input terminal (1st terminal), 17 Output terminal (second terminal) 18 Output terminal (third terminal) 19 Electrode layer 101 Gate electrode layer 102 Insulator layer (magnesium oxide (001) layer: RA product 1.7 MΩμm ² ) DESCRIPTION OF SYMBOLS 103 ... Magnetization | rotation layer (2 nm-thickness cobalt iron boron layer), 104 ... Tunnel barrier layer (magnesium oxide (001) layer: RA product 70 Ωμm ² ), 105 ... Magnetization fixed layer (2.2 nm-thickness cobalt iron Boron layer), 106 ... ruthenium layer (thickness 0.9 nm), 107 ... cobalt iron layer (thickness 2.5 nm), 108 ... antiferromagnetic layer for exchange bias (platinum manganese layer 15 nm thick)

Claims (10)

In order, it has a multilayer structure showing a magnetoresistive effect composed of a ferromagnetic magnetization fixed layer, a nonmagnetic spacer layer, and a ferromagnetic magnetization rotation layer,
A voltage applying electrode layer that covers the entire upper surface or lower surface or side surface of the magnetization rotation layer via an insulator layer;
A first terminal which is an input terminal is connected to the voltage applying electrode layer;
A second terminal connected to the magnetization rotation layer;
A voltage-driven spintronics three-terminal element having a third terminal connected to the magnetization fixed layer,
By applying a voltage from the voltage application electrode layer, the magnetization direction of the magnetization rotation layer changes, and the nonmagnetic spacer layer depends on the relative angle of the magnetization direction of the magnetization fixed layer and the magnetization rotation layer A voltage-driven spintronics three-terminal device that obtains power amplification, voltage amplification, fan-out, etc., using as an output signal the change in electrical resistance between the magnetization rotation layer and the magnetization fixed layer via element. In order, it has a multilayer structure showing a magnetoresistive effect composed of a ferromagnetic magnetization fixed layer, a nonmagnetic spacer layer, and a ferromagnetic magnetization rotation layer,
A voltage applying electrode layer that covers the entire upper surface or lower surface or side surface of the magnetization rotation layer via an insulator layer;
A first terminal which is an input terminal is connected to the voltage applying electrode layer;
A second terminal connected to the magnetization rotation layer;
A voltage-driven spintronics three-terminal element having a third terminal connected to the magnetization fixed layer.   3. The voltage-driven spintronic three-terminal element according to claim 1, wherein the nonmagnetic spacer layer is a tunnel barrier layer.   The voltage-driven spintronics three-terminal element according to any one of claims 1 to 3, wherein a voltage is applied from the voltage application electrode layer so that the magnetization direction of the magnetization rotation layer is in a film plane direction and a film plane. A voltage-driven spintronics three-terminal device characterized by changing between vertical directions.   5. The voltage-driven spintronic three-terminal element according to claim 1, wherein the magnetization direction of the magnetization fixed layer is in an in-plane direction. 6.   5. The voltage-driven spintronic three-terminal element according to claim 1, wherein the magnetization direction of the fixed magnetization layer is perpendicular to the film surface. .   The voltage-driven spintronics three-terminal element according to any one of claims 1 to 6, wherein the voltage application electrode layer surrounds a side surface of the magnetization rotation layer.   8. The voltage-driven spintronics three-terminal element according to claim 1, wherein the magnetization rotation layer has a single domain structure.   9. The voltage-driven spintronics three-terminal element according to claim 1, wherein the magnetization rotation layer is grounded.   10. The voltage-driven spintronics three-terminal element according to claim 9, wherein a load circuit for signal output is connected to the magnetization fixed layer.

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