JP2010073960A - Semiconductor device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To efficiently inject a highly polarized spin current. <P>SOLUTION: A semiconductor device includes; a semiconductor substrate 2; and a ferromagnetic laminated film 20 which is arranged on the semiconductor substrate, including the first Heusler alloy layer 24, and the first non-magnetic layer 26 arranged on the first Heusler alloy layer. The magnetic resistance change rate of the ferromagnetic laminated film is vibrated in response to a bias voltage to be applied to the ferromagnetic laminated film. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a semiconductor device in which a ferromagnetic laminated film is provided on a semiconductor substrate.

  In recent years, an MTJ element having a magnetic tunnel junction (hereinafter also referred to as MTJ (Magnetic Tunnel Junction)) composed of a laminated structure of a ferromagnetic layer / insulator layer (tunnel barrier) / ferromagnetic layer is used as a memory element. A magnetic storage device (hereinafter also referred to as MRAM (Magnetic Random Access Memory)) has been proposed. In this MRAM, the spin of one ferromagnetic layer is fixed, and the spin of the other ferromagnetic layer is controlled (free layer) to change the resistance of the laminated structure. For example, it is stored corresponding to “0” or “1”. The resistance is small when the spins of the fixed layer and the free layer are parallel to each other, and the resistance is large when the spins are antiparallel. This MTJ element has a magnetoresistance change rate (MR ratio) of several tens of percent at room temperature up to several years ago, but has recently reached 500%, and is not limited to MRAM, but can be used as various spin devices. Is spreading. One of them is a spin MOSFET (for example, Non-Patent Document 1).

As described above, although the MR ratio is improved, it is necessary to further increase the MR ratio in order to realize a highly efficient magnetic memory device, spin MOSFET, and the like. In particular, when the MTJ is applied to a semiconductor device such as an MRAM or a spin MOSFET, it is necessary to obtain a high MR ratio in a resistance region having an area resistance RA of about 10 Ωμm ² or less. In an MTJ element capable of obtaining an MR ratio of 500%, it is known that if the thickness of the MTJ tunnel barrier is reduced to about 1 nm in order to make RA = 10 Ωμm ² or less, the MR ratio decreases to 200%. Yes. In order to solve this problem, it is a promising approach to use a ferromagnetic material having a high spin polarization (P) as the MTJ ferromagnetic material layer. According to Julliere's law, P = 100% half-metal If the material is used, the MR ratio is theoretically infinite. Candidates for half-metal materials include CrO ₂ , Fe ₃ O ₄ , and Heusler alloys. Recently, high MR ratios have been realized with Co-based Heusler alloys, and spin devices using these materials are expected. . Furthermore, in recent years, a device structure in which a Co-based Heusler alloy and a magnesium oxide (MgO) tunnel barrier are combined has attracted attention in MTJ (for example, see Non-Patent Document 2). This combination of Heusler alloy and MgO tunnel barrier is expected to be applied not only to MTJ but also to the source / drain portion of spin MOSFET.

  In a spin MOSFET, in order to control the spin-polarized current by the gate voltage, a current having a high ratio of spin-polarized electrons from the magnetic layer of the source portion into the channel (hereinafter also referred to as a high spin-polarized current). It is important to inject. In the spin MOSFET and MTJ, the basic operation principle of the device is the magnetoresistive effect (MR) controlled by the relative magnetization directions of the two magnetic layers sandwiching the nonmagnetic layer. In order to use these devices, it is necessary to extract a sufficiently large signal voltage, so that a bias voltage of about 0.15 V to 0.5 V is typically applied when reading information. However, it is generally known that in these magnetic devices, the MR ratio decreases as the bias voltage increases. In particular, it is known that the MT voltage using a Heusler alloy has a remarkable dependency on the applied voltage of the MR ratio.

  In the writing method using spin injection in the spin MOSFET and MTJ, when spin injection is performed, spin inversion does not occur unless a current having a very high current density is passed through the element. When a current having a high current density is passed through a magnetoresistive element having a tunnel barrier layer, a high electric field is applied to the tunnel barrier, which causes element destruction. Therefore, a structure in which spin inversion is performed at a low current density is required. In order to reduce the write current for magnetization reversal, the spin reversal current density is required to be low, and an MTJ structure capable of generating a high spin polarization current is required.

  In the MTJ using MgO as a tunnel barrier (barrier layer), MgO is a (001) -oriented crystal film, and the magnetic layer sandwiching the tunnel barrier is bcc (Body Centered Cubic) Fe, Co, Fe-Co, Alternatively, in the case of CoFeB, a high magnetoresistance ratio (MR ratio) is developed by selectively tunneling electrons having specific orbital symmetry.

In addition, when an extremely thin metal layer is sandwiched between two barrier layers, quantization due to resonance of electron wave derivatives occurs, and when current flows through these resonance levels, one normal barrier is generated. It is known that it is possible to extract a larger current density than in the case of a layer (for example, see Non-Patent Document 3). In this Non-Patent Document 3, in an MTJ having a laminated structure of Fe (001) / MgO (001) / Fe (001) formed by epitaxial growth on (001) oriented nonmagnetic metal chromium (Cr), It is disclosed that an electron selective effect is exhibited through a resonance level. This is because in an MTJ having a stacked structure of Cr (001) / Fe (001) / MgO (001) / Fe (001), the Fe layer sandwiched between Cr and MgO is a quantum well layer for Δ ₁ band electrons ( This is because the resonance tunnel effect is selectively exhibited only in the parallel arrangement of magnetization.
S. Sugahara and M. Tanaka, Appl. Phys. Lett. 84 (2004) 2307. N. Tezuka, et.al., Appl. Phys. Lett. 89 (2006) 112514. X.-G.Zhang et al., Phys. Rev. Lett. 94, 207210 (2005).

  As described above, in a semiconductor device having a spin MOSFET or a ferromagnetic laminated film formed on a semiconductor substrate, generation and injection of a high spin polarization current are indispensable for realizing a device and improving performance.

  However, up to now, no semiconductor device that enables efficient injection of spin-polarized current has been known.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a semiconductor device capable of efficiently injecting a spin-polarized current.

  A semiconductor device according to a first aspect of the present invention includes a semiconductor substrate, a first Heusler alloy layer provided on the semiconductor substrate, and a first nonmagnetic layer provided on the first Heusler alloy layer. And a magnetoresistance change ratio of the ferromagnetic multilayer film oscillates according to a bias voltage applied to the ferromagnetic multilayer film.

  A semiconductor device according to a second aspect of the present invention includes a semiconductor substrate, a first Heusler alloy layer provided on the semiconductor substrate and having a thickness of 0.28 nm to 5.6 nm, and the first Heusler alloy. A ferromagnetic multilayer film including a first nonmagnetic layer provided on the layer, wherein the first nonmagnetic layer is any one of chromium, vanadium, manganese, and alloys thereof, or It is a tunnel barrier.

  A semiconductor device according to a third aspect of the present invention includes a semiconductor substrate, copper, silver, gold, or an alloy thereof provided on the semiconductor substrate and having a thickness of 0.5 nm to 2.0 nm. And a second nonmagnetic layer, a first Heusler alloy layer provided on the second nonmagnetic layer, and a first nonmagnetic layer provided on the first Heusler alloy layer. And a laminated film.

  According to the present invention, a high spin polarized current can be efficiently injected.

  First, before explaining the embodiments of the present invention, the background to the present invention and the principle of the present invention will be described.

As described in the prior art, in an MTJ having a laminated structure of Fe (001) / MgO (001) / Fe (001) formed by epitaxial growth on (001) oriented nonmagnetic metal chromium (Cr), An electron selection effect is exhibited through the resonance level (see Non-Patent Document 3). This is because in an MTJ having a stacked structure of Cr (001) / Fe (001) / MgO (001) / Fe (001), the Fe layer sandwiched between Cr and MgO is a quantum well layer for Δ ₁ band electrons ( This is because the resonance tunnel effect is selectively exhibited only in the parallel arrangement of magnetization.

  As described in Non-Patent Document 3, in a semiconductor device having a structure in which a Cr layer oriented in (001) is formed on a semiconductor substrate and an MTJ is formed on the Cr layer, Spin injection is performed on the semiconductor substrate. However, according to the findings of the present inventors, since the Cr layer reflects spin, spin injection is not efficiently performed in the semiconductor device having the above structure.

  Therefore, as a result of diligent research, the present inventors include a Heusler alloy layer having an appropriate thickness on a semiconductor substrate, and a first nonmagnetic layer that is formed on the Heusler alloy layer and reflects spin. When a ferromagnetic laminated film is formed, quantum levels are formed in the Heusler alloy layer, and the magnetoresistive change ratio (hereinafter also referred to as TMR ratio) depends on the bias voltage due to the spin resonance tunneling effect via the quantum levels. It was found to vibrate. That is, the present inventors have found that the TMR ratio increases at a specific applied bias, and the deterioration of the bias voltage dependency of the TMR ratio is improved.

As the Heusler alloy used in the present invention, a Co-based full Heusler alloy (hereinafter also referred to as Co ₂ YZ (where Y and Z indicate element symbols)) is more preferable because its Curie temperature Tc is high. . It has been pointed out that some of the Co-based full Heusler alloys (Co ₂ YZ) are half-metal ferromagnets in which only one spin electron (one of up-spin and down-spin) exists at the Fermi level. Yes. Of Co ₂ YZ, Co ₂ MnSi, Co ₂ FeSi, Co ₂ FeAl, and the like have only an s electronic band equivalent to the Δ ₁ band at the Fermi level in the band structure. Therefore, for example, in the ferromagnetic laminated film structure of Si substrate / MgO (001) / Co ₂ YZ (001) / Cr (001) as shown in FIG. 1, the upspin band in the parallel magnetization arrangement by s electrons The resonance tunnel effect appears in the (majority spin band) (see FIG. 2A). In contrast, the down-spin band at magnetization antiparallel arrangement as shown in FIG. 2 (b), in addition to the absence of the down-spin state in the vicinity of the Fermi level E _F of the half-metallic ferromagnet, non A spin reflection layer made of Cr, which is a magnetic material, is also added, so that almost no current flows. Therefore, as shown in FIG. 3A, the conductance _GP in the parallel magnetization state vibrates according to the bias voltage due to the resonant tunneling effect. However, the conductance G _AP in the magnetization anti-parallel state is not the vibration increases or decreases monotonically in response to changes in a positive or negative bias voltage (Figure 3 (a)). Thus, TMR ratio defined by _TMR = _{G P /} G AP -1 is due to an increase in conductance _{G P} by resonant tunneling, so that a phenomenon that vibrates at a particular bias voltage level occurs (FIG. 3 (a ), 3 (b)).

  In the above description, the Cr layer is used as the nonmagnetic layer that reflects spin. Since the properties of the Cr layer as a spin reflection layer are derived from its electronic band structure, vanadium (V) and manganese (Mn) having the same electronic structure as Cr may be used as a nonmagnetic layer that reflects spin. .

In consideration of the effects found as described above, a MgO / Co ₂ YZ / Cr laminated film is grown in this order on the semiconductor substrate, and a Co ₂ YZ ferromagnetic layer is used as the spin quantum well layer. It has been found that the spin tunneling current can be efficiently injected into the semiconductor substrate by the resonant tunneling effect when the thickness is sufficiently functioning. Here, in order to function as a spin quantum well layer, the thickness of the Co ₂ YZ layer is preferably within 20 atomic layers (one atomic layer is about 0.28 nm), and a flat interface is formed at the atomic level. It is preferable that

Further, since Cu can be used as a spin quantum well layer because of its band structure, as shown in FIG. 4, Si (001) / Cu (001) / MgO (001) / Co ₂ YZ (001) / It has been found that if a ferromagnetic laminated film of Cr (001) is formed on a semiconductor substrate, a spin-polarized current is efficiently injected into the semiconductor substrate. Cu can be easily formed as an ultrathin layer, which is advantageous for controlling the conditions of the spin resonance effect.

  In the above-described ferromagnetic laminated film, each layer is not necessarily formed by single crystal epitaxial growth, and may have a polycrystalline laminated film structure as long as it has a (001) orientation.

Further, if the above-described ferromagnetic laminated film structure of Heusler alloy layer and nonmagnetic layer is used, even when the MgO tunnel barrier is deleted from the ferromagnetic laminated film shown in FIGS. High spin polarization current can be injected into the semiconductor. The reason for this is, FIG. 5 (a), the as shown in 5 (b), because that can form a Schottky barrier, the potential barrier for example delta ₁ band by the non-magnetic layer made of Cr. For the same reason, in the ferromagnetic laminated film shown in FIGS. 2 (a) and 2 (b), for example, a ferromagnetic laminated film using a nonmagnetic layer serving as a spin reflecting layer instead of a MgO tunnel barrier. (See FIGS. 6A and 6B), a low interface resistance (high current density) and a high spin injection efficiency can be realized simultaneously.

  In the above description, a Si substrate is used as the semiconductor substrate. However, a substrate having at least a Si single crystal, a Ge single crystal, a Si—Ge single crystal, a SiC single crystal, an SOI (Silicon on Insulator) substrate, GaAs The same effect can be obtained by using a III-V group compound semiconductor substrate or a II-VI group semiconductor substrate having a single crystal, InGaAs single crystal or the like on at least the surface.

  Next, embodiments of the present invention will be described below in detail with reference to the drawings.

(First embodiment)
A semiconductor device according to the first embodiment of the present invention is shown in FIG. The semiconductor device of this embodiment includes a ferromagnetic laminated film 20 provided on the semiconductor substrate 2. The ferromagnetic multilayer film 20 includes a tunnel barrier layer 22, a Heusler alloy layer 24 provided on the tunnel barrier layer 22, and a nonmagnetic layer 26 provided on the Heusler alloy layer 24. For example, it is used as a source part or a drain part of a spin MOSFET.

The tunnel barrier layer 22 is made of a material having an effective mass at the time of tunneling and transmitting s-electron conduction electrons having high symmetry. For example, MgO is suitable as the tunnel barrier layer 22. Not only MgO but also ZnSe or SrTiO ₃ or other insulators that can obtain the same effect may be used. However, it is preferable to use a material having good lattice matching with the Heusler alloy. From this point, MgO, ZnSe, or SrTiO ₃ is desirable. The MgO tunnel barrier layer 22 is formed by forming a (001) -oriented single crystal film or a (001) -oriented polycrystalline film of MgO on the semiconductor substrate 2 by sputtering, for example. In order to inject a high current density into the semiconductor substrate 2 and secure a drive current for the spin MOSFET, a tunnel resistance as low as possible is necessary. Therefore, it is desirable that the thickness of the tunnel barrier layer 22 of MgO be as thin as possible. However, since the lattice constant of MgO is about 0.42 nm, even if it is a single atomic layer, the film thickness needs to be at least 0.21 nm. Considering realistic interface roughness between the MgO layer 22 and the semiconductor substrate 2, the typical film thickness is preferably in the range of 0.5 nm to 3 nm. Here, the film thickness is not necessarily an integer multiple of the atomic layer, and may be considered as an average film thickness corresponding to the coverage. The method for forming the tunnel barrier layer is not limited to the sputtering method, and may be a vacuum deposition method, a CVD (Chemical Vapor Deposition) method, an MBE (Molecular Beam Epitaxy) method, a PLD (Pulsed Laser Deposition) method, etc. In order to obtain MgO, heat treatment may be performed during film formation or after film formation.

As the Heusler alloy layer 24, s electronic conduction is performed in a dispersion relation ([001] direction in the reciprocal lattice space) from the Γ point to the H point at the Fermi level of the majority spin band (up spin band) in the electronic band structure. Co ₂ MnSi, Co ₂ MnGe, or Co ₂ FeSi in which electrons are present is used. Not limited to these, a Heusler alloy having a similar electronic band structure and having a s-electron conduction electron in a dispersion relation from the Γ point to the H point at the Fermi level of the majority spin band (up spin band) is used. It ’s fine. Alternatively, these mixed crystals may be used. Thus, for example, _{Co 2 Mn 1-x Fe x} Si (0 ≦ x ≦ 1) may be used. As the Heusler alloy, a half-metal ferromagnet having an energy gap in the Fermi level of a minority spin band (down spin band) is desirable. However, in this embodiment and other embodiments described later, it is not always necessary to use a half-metal ferromagnetic material. Therefore, for example, Co ₂ FeAl _1-x Si _x (0 ≦ x ≦ 1) may be used. Further, Heusler alloy L2 ₁ structure capable of realizing the highest spin polarization is desirable. However, in this embodiment and other embodiments described later, a B2 structure or an A2 structure may be used. The Heusler alloy layer 24 is formed by forming a (001) -oriented single crystal film or a (001) -oriented polycrystalline film on the tunnel barrier layer 22 by using, for example, a sputtering method.

  In order to form a sufficiently discrete resonance level in the Heusler alloy layer 24, it is desirable that the Heusler alloy layer 24 is as thin as possible. However, since the lattice constant of Heusler alloy is typically about 0.56 nm, even if it is a single atomic layer, the film thickness needs to be at least 0.28 nm. Further, when the film thickness is thicker than 20 atomic layers, the resonance level cannot be discretized, and a mechanism that destroys the coherency of the electron wave function, such as electron-electron scattering and phonon scattering, becomes dominant. There is a possibility that the effect of the present embodiment cannot be obtained. Therefore, the film thickness of the Heusler alloy layer 24 is set to 1 to 20 atomic layers, in other words, in the range of 0.28 nm to 5.6 nm. The method of forming the Heusler alloy layer 24 is not limited to the sputtering method, and may be a vacuum deposition method, a metal CVD method, an MBE method, a PLD method, etc. In order to realize a crystalline Heusler alloy layer and control the crystal structure Heat treatment may be performed during film formation or after film formation.

  As the nonmagnetic layer 26, chromium (Cr), vanadium (V), manganese (Mn), or an alloy containing these that functions as a reflective layer of s-electron conduction electrons supplied from the Heusler alloy layer 24 is used. . Although not limited to these, a nonmagnetic layer that can achieve the same effect may be used, but chromium, vanadium, manganese, or an alloy containing these can be easily obtained because lattice matching with the Heusler alloy is good. . As the nonmagnetic layer 26, for example, a Cr layer is formed on the Heusler alloy layer 24 by sputtering, for example, to form a (001) -oriented thin film. The thickness of the Cr layer is typically 1 nm or more. However, it is desirable that the Cr layer is as thick as possible in order to function as a reflective layer for spin s-electron conduction electrons, and typically the thickness is 5 nm or more. It is desirable. However, it may be 5 nm or less as long as the function as the spin reflection layer is not impaired. The film formation method of the nonmagnetic layer 26 is not limited to the sputtering method, but may be a vacuum deposition method, a metal CVD method, an MBE method, a PLD method, etc. In order to realize a crystalline nonmagnetic layer and control the crystal structure Heat treatment may be performed during film formation or after film formation.

  As described above, according to the present embodiment, the semiconductor substrate having a high spin polarization current due to the resonance effect is provided because the ferromagnetic laminated film having the nonmagnetic layer serving as the spin reflection layer and the Heusler alloy layer is provided. It is possible to perform injection.

(Modification)
Next, as a semiconductor device according to a modification of the present embodiment, a spin MOSFET using the ferromagnetic multilayer film 20 according to the present embodiment as a source part and a drain part will be described. A section of this modification is shown in FIG. In the spin MOSFET according to this modification, a gate insulating film 4 is formed on the surface of the semiconductor single crystal substrate 2, and a gate electrode 6 is formed on the gate insulating film 4. Then, a source portion 20a and a drain portion 20b are formed in the regions of the semiconductor substrate on both sides of the gate electrode 4, and the source portion 20a and the drain portion 20b are respectively connected to the tunnel barrier layer 22 formed on the semiconductor substrate 2 and this tunnel. A Heusler alloy layer 24 formed on the barrier layer 22 and a nonmagnetic layer 26 formed on the Heusler alloy layer 24 are provided. In the spin MOSFET shown in FIG. 8, the impurity diffusion layers to be the source region and the drain region are not formed in the region of the semiconductor substrate 2 immediately below the source portion 20a and the drain portion 20b, but they may be formed. Also, one of the two Heusler alloy layers 24 can be a layer in which the magnetization is changed and the other is a layer in which the magnetization is not changed. That is, a difference is provided in the coercive force of the two Heusler alloy layers 24 by changing the thickness or providing an antiferromagnetic layer on one side.

Next, a method for manufacturing the spin MOSFET of this modification will be described. LOCOS fabrication, Gate fabrication, an ion implantation process for a semiconductor substrate, and an impurity activation process using RTA are performed in the same manner as in a normal MOSFET. Next, the tunnel barrier layer 22, the Heusler alloy layer 24, and the nonmagnetic layer 26 are formed in this order on the surface of the semiconductor substrate 2 where the source part 20a and the drain part 20b are formed, thereby obtaining a ferromagnetic laminated film. In this method of forming a ferromagnetic laminated film, an interlayer insulating film (not shown) made of SiO ₂ having openings is formed in a region where the source portion 20a and the drain portion 20b of the semiconductor substrate 2 are formed, and these openings are formed. There are a method of embedding by depositing a ferromagnetic laminated film by high-pressure RF sputtering and a method of forming the ferromagnetic laminated film by depositing the ferromagnetic laminated film on a semiconductor substrate and patterning by chlorine-based RIE. In the present embodiment, the former method is used.

FIG. 9 shows the MR bias dependence characteristics through the channel length in the spin MOSFET according to this modification formed as described above. In FIG. 9, the ferromagnetic layer 24 in the ferromagnetic laminated film of the source part 20a and the drain part 20b of the spin MOSFET is in a magnetization parallel arrangement (resonance state) by s electrons, and the source part 20a is grounded and the gate electrode 6 is grounded. applying a positive gate voltage V _g, which is a diagram showing characteristics of drain current I _d at the time of changing the drain voltage (bias voltage) V _d applied to the drain portion 20b. As can be seen from FIG. 9, the drain current I _d is vibrated in response to changes in the bias voltage V _d in the region of a bias voltage V _d, the peak of the vibration is in the resonance peak. As a result, it is understood that a high polarization current is injected from the ferromagnetic laminated film 20b to the semiconductor substrate 2 and MR is increased.

(Second Embodiment)
A semiconductor device according to a second embodiment of the present invention is shown in FIG. In the semiconductor device of this embodiment, as shown in FIG. 10, a ferromagnetic laminated film 20 </ b> A is provided on a semiconductor substrate 2. The ferromagnetic laminated film 20A is formed on the tunnel barrier layer 22 formed on the semiconductor substrate 2, the laminated film 23 including the Heusler alloy layer formed on the tunnel barrier layer 22, and the laminated film 23. And a nonmagnetic layer 26. The laminated film 23 includes a Heusler alloy layer 23a formed on the tunnel barrier layer 22, a tunnel barrier layer 23b formed on the Heusler alloy layer 23a, and a Heusler alloy layer 23c formed on the tunnel barrier layer 23b. And constitutes an MTJ.

  The tunnel barrier layer 22 and the tunnel barrier layer 23b can be the same as the tunnel barrier layer 22 described in the first embodiment, and the manufacturing method thereof can also be formed by the method described in the first embodiment. The Heusler alloy layer 23a and the Heusler alloy layer 23c can be the same as the Heusler alloy 24 described in the first embodiment, and the manufacturing method thereof can also be formed by the method described in the first embodiment. The nonmagnetic layer 26 can be the same as the nonmagnetic layer 26 of the first embodiment, and the manufacturing method thereof can also be formed by the method described in the first embodiment.

  As described above, according to this embodiment, since the ferromagnetic laminated film having the nonmagnetic layer 26 serving as the spin reflection layer and the Heusler alloy layer 23c is provided, a high spin-polarized current due to the resonance effect is provided. It is possible to perform implantation into the semiconductor substrate.

(Modification)
Next, as a semiconductor device according to a modification of the present embodiment, a spin MOSFET using the ferromagnetic multilayer film 20A according to the present embodiment as at least one of a source part and a drain part, for example, a drain part will be described. FIG. 11 shows a cross section of the spin MOSFET of this modification. The spin MOSFET according to this modification has a configuration in which the drain portion 20b of the spin MOSFET shown in FIG. 8 is replaced with a drain portion 20Ab. The drain portion 20Ab has the same stacked structure as the ferromagnetic stacked film 20A shown in FIG. That is, the drain portion 20Ab includes a tunnel barrier layer 22 formed on the semiconductor substrate 2, a stacked film 23 formed on the tunnel barrier layer 22 and including a Heusler alloy layer, and a non-layer formed on the stacked film 23. And a magnetic layer 26. The laminated film 23 includes a Heusler alloy layer 23a formed on the tunnel barrier layer 22, a tunnel barrier layer 23b formed on the Heusler alloy layer 23a, and a Heusler alloy layer 23c formed on the tunnel barrier layer 23b. And constitutes an MTJ. In the spin MOSFET shown in FIG. 11, the ferromagnetic laminated film 20A shown in FIG. 10 is used only as the drain part, but it may be used only as the source part, or may be used as both the source part and the drain part.

  In the spin MOSFET of this modification, since the drain portion 20Ab has an MTJ structure, the Heusler alloy layer 23a is formed as a magnetization free layer by making the film thickness of the Heusler alloy layer 23a smaller than the film thickness of the Heusler alloy layer 23b. It functions and enables magnetization reversal writing by injection of spin-polarized current. The spin MOSFET of this modification can be formed using the manufacturing method described in the first embodiment except that the formation of the ferromagnetic laminated film is different.

  In the spin MOSFET of this modification, as in the first embodiment, an increase in MR was confirmed with a specific bias.

(Third embodiment)
Next, FIG. 12 shows a semiconductor device according to the third embodiment of the present invention. The semiconductor device of this embodiment has a configuration in which a ferromagnetic laminated film 20B is provided on a semiconductor substrate. The ferromagnetic laminated film 20B is formed on the tunnel barrier layer 22 formed on the semiconductor substrate 2, the laminated film 23 including the Heusler alloy layer formed on the tunnel barrier layer 22, and the laminated film 23. A nonmagnetic layer 26, a ferromagnetic layer 28 formed on the nonmagnetic layer 26, and an antiferromagnetic layer 30 formed on the ferromagnetic layer 28 are provided. The laminated film 23 includes a Heusler alloy layer 23a formed on the tunnel barrier layer 22, a tunnel barrier layer 23b formed on the Heusler alloy layer 23a, and a Heusler alloy layer 23c formed on the tunnel barrier layer 23b. And constitutes an MTJ. The antiferromagnetic layer 30 fixes the magnetization direction of the ferromagnetic layer 28 by exchange coupling with the ferromagnetic layer 28.

  As the ferromagnetic layer 28, general Fe, Co, Ni, or an alloy thereof may be used, and a material mixed with another element may be used. However, materials other than these materials can be used if they have the same magnetic properties as Fe, Co, Ni, or alloys thereof. The film thickness of the ferromagnetic layer is typically about 2 nm to 5 nm, but is not limited to this film thickness as long as the magnetic properties are maintained. As the antiferromagnetic layer 30, a material capable of giving a sufficiently large exchange coupling energy to the ferromagnetic layer 28 is used. For example, IrMn, PtMn, and FeMn can be used as such an antiferromagnetic material. Or what mixed further another element to these can be used. However, the present invention is not limited to these, and other materials may be used as long as similar magnetic properties can be obtained. The film thickness of the antiferromagnetic layer 30 is typically 7 nm to 20 nm, but is not limited to this film thickness as long as the magnetic properties are maintained.

  In the three-layer structure of Heusler alloy layer 23c / nonmagnetic layer 26 / ferromagnetic layer 28, Heusler alloy layer 23c and ferromagnetic layer 28 are antiferromagnetically coupled. Therefore, the Heusler alloy layer 23c becomes a magnetization fixed layer of the MTJ 23. By processing the three-layer structure into a pillar shape, an antiferromagnetic magnetization arrangement is formed by magnetostatic coupling. Alternatively, the fact that an artificial ferrimagnetic structure can be realized by combining the three-layer structure in consideration of magnetic properties may be used.

  In the semiconductor device of this embodiment, since the magnetization fixed layer of MTJ formed in the drain portion 20Ab can be realized by exchange coupling, a structure more resistant to rewriting noise due to an external magnetic field can be realized.

  The spin MOSFET according to the modification of the present embodiment has a configuration in which at least one of the source part and the drain part of the spin MOSFET according to the modification of the first embodiment is replaced with the ferromagnetic multilayer film 20B according to the present embodiment shown in FIG. have. In the spin MOSFET according to this modification, as in the first embodiment, an increase in MR was confirmed with a specific bias.

  As described above, according to the present embodiment, the semiconductor substrate having a high spin polarization current due to the resonance effect is provided because the ferromagnetic laminated film having the nonmagnetic layer serving as the spin reflection layer and the Heusler alloy layer is provided. It is possible to perform injection.

(Fourth embodiment)
Next, FIG. 13 shows a semiconductor device according to the fourth embodiment of the present invention. The semiconductor device of this embodiment has a configuration in which a ferromagnetic laminated film 20C is provided on a semiconductor substrate 2. This ferromagnetic laminated film 20C has a laminated structure in which a tunnel barrier layer 22 / Heusler alloy layer 24 / nonmagnetic layer 26 / ferromagnetic layer 28 / antiferromagnetic layer 30 are formed on a semiconductor substrate 2 in this order. ing. The magnetization of the ferromagnetic layer 28 is fixed by exchange coupling with the antiferromagnetic layer 30. As the ferromagnetic layer 28 and the antiferromagnetic layer, the materials described in the third embodiment can be used, and the film thicknesses thereof can also be the same as those described in the third embodiment.

  The MTJ is composed of a three-layer structure of Heusler alloy layer 24 / nonmagnetic layer 26 / ferromagnetic layer 28. In this MTJ, Heusler alloy layer 24 and ferromagnetic layer 28 are antiferromagnetically coupled. That is, the MTJ having the three-layer structure is a magnetization fixed layer.

  By processing the three-layer structure into a pillar shape, an antiferromagnetic magnetization arrangement is formed by magnetostatic coupling. Alternatively, the fact that an artificial ferrimagnetic structure can be realized by combining the three-layer structure in consideration of magnetic properties may be used.

  As described above, according to the present embodiment, the semiconductor substrate having a high spin polarization current due to the resonance effect is provided because the ferromagnetic laminated film having the nonmagnetic layer serving as the spin reflection layer and the Heusler alloy layer is provided. It is possible to perform injection.

  Moreover, in the ferromagnetic laminated film according to the present embodiment, since the magnetization fixed layer serving as the MTJ can be realized by exchange coupling, a structure that is more resistant to rewriting noise due to an external magnetic field can be realized.

  The spin MOSFET according to the modification of the present embodiment has a configuration in which at least one of the source part and the drain part of the spin MOSFET according to the modification of the first embodiment is replaced with the ferromagnetic laminated film 20C according to the present embodiment shown in FIG. have. In the spin MOSFET according to this modification, as in the first embodiment, an increase in MR was confirmed with a specific bias.

(Fifth embodiment)
Next, FIG. 14 shows a semiconductor device according to the fifth embodiment of the present invention. The semiconductor device of this embodiment has a configuration in which a ferromagnetic laminated film 20D is provided on a semiconductor substrate 2. This ferromagnetic laminated film 20D has a configuration in which a nonmagnetic layer 21 is provided between the semiconductor substrate 2 and the tunnel barrier layer 22 in the ferromagnetic laminated film 20 according to the first embodiment shown in FIG. Yes. That is, as shown in FIG. 14, a non-magnetic layer 21 / tunnel barrier layer 22 / Heusler alloy layer 24 / non-magnetic layer 26 are laminated on the semiconductor substrate 2 in this order.

  In the ferromagnetic laminated film 20D, the nonmagnetic layer 21 functions as a spin accumulation layer and is sandwiched between the semiconductor substrate 2 and the tunnel barrier layer 22, so that a resonance level is formed in the nonmagnetic layer 21. . When the film thickness of the nonmagnetic layer 21 is thicker than the 10 atomic layer, the resonance level cannot be discretized. For this reason, the film thickness of the nonmagnetic layer 21 is preferably from 1 atomic layer to 10 atomic layer, typically in the range of 0.5 nm to 2 nm.

  The nonmagnetic layer 21 is made of a material that does not serve as an energy barrier against s-electron conduction electrons. The nonmagnetic layer 21 is preferably made of a material that has good lattice matching with the semiconductor substrate 2 and allows single crystal growth. Alternatively, the nonmagnetic layer 21 is preferably a (001) -oriented material even if it is polycrystalline on the semiconductor substrate 2. Copper (Cu) is most preferable as a material that satisfies these conditions, but is not limited to this, and a nonmagnetic material having similar characteristics, such as silver (Ag) or gold (Au), can be used.

  In the present embodiment, since a tunnel current is generated via the resonance level formed in the nonmagnetic layer 21, a high spin polarization current can be injected at a high current density from the Heusler alloy layer 24 to the semiconductor substrate. .

  The spin MOSFET according to the modification of the present embodiment has a configuration in which at least one of the source part and the drain part of the spin MOSFET according to the modification of the first embodiment is replaced with the ferromagnetic multilayer film 20D according to the present embodiment shown in FIG. have. In the spin MOSFET according to this modification, as in the first embodiment, an increase in MR was confirmed with a specific bias.

(Sixth embodiment)
FIG. 15 shows a semiconductor device according to the sixth embodiment of the present invention. The semiconductor device of this embodiment has a configuration in which a ferromagnetic laminated film 20E is provided on a semiconductor substrate 2. This ferromagnetic laminated film 20E has a configuration in which a tunnel barrier layer 27 is provided between the nonmagnetic layer 21 and the semiconductor substrate 2 in the ferromagnetic laminated film 20D according to the fifth embodiment shown in FIG. . That is, as shown in FIG. 15, the ferromagnetic laminated film 20 </ b> E has a tunnel barrier layer 27 / nonmagnetic layer 21 / tunnel barrier layer 22 / Heusler alloy layer 24 / nonmagnetic layer 26 in this order on the semiconductor substrate 2. It has a laminated structure.

  In the ferromagnetic laminated film 20E, the nonmagnetic layer 21 functions as a spin accumulation layer as in the fifth embodiment, and is sandwiched between the tunnel barrier layer 22 and the tunnel barrier layer 27. A resonance level is formed. When the film thickness of the nonmagnetic layer 21 is thicker than the 10 atomic layer, the resonance level cannot be discretized. Therefore, the film thickness of the nonmagnetic layer 21 is preferably 1 to 10 atomic layers, and is preferably in the range of 0.5 to 2 nm.

  As in the tunnel barrier layer of each embodiment, the tunnel barrier layer 27 is made of a material having a property of transmitting s-electron conduction electrons having high symmetry, which are electrons having a low effective mass when tunneling. For example, MgO is preferable. The tunnel barrier layer 27 is formed as a (001) oriented film.

  As in the fifth embodiment, the nonmagnetic layer 22 is made of a material that does not serve as an energy barrier against s-electron conduction electrons. For example, Cu is most preferable, and any of silver, gold, and alloys thereof can be used. There is a similar function. The ferromagnetic laminated film according to the present embodiment generates a tunnel current via the resonance level formed in the nonmagnetic layer 21, so that a high current density and a high spin polarization current are generated from the Heusler alloy layer 24 to the semiconductor substrate. Can be injected.

The spin MOSFET according to the modification of the present embodiment has a configuration in which at least one of the source part and the drain part of the spin MOSFET according to the modification of the first embodiment is replaced with the ferromagnetic multilayer film 20E according to the present embodiment shown in FIG. have. FIG. 16 shows the bias dependence characteristics of MR via the channel in the spin MOSFET according to this modification. In FIG. 16, the ferromagnetic layers in the ferromagnetic laminated film of the source part and the drain part of the spin MOSFET are in a magnetization parallel arrangement (resonance state) by s electrons, the source part is grounded, and a positive gate voltage V is applied to the gate electrode. the _g is applied is a diagram showing the characteristics of drain current I _d at the time of changing the drain voltage (bias voltage) V _d applied to the drain unit. As can be seen from Figure 16, the drain current I _d is vibrated in response to changes in the bias voltage V _d in the region of a bias voltage V _d, the peak of the vibration is in the resonance peak. Thereby, it can be seen that a high polarization current is injected from the ferromagnetic laminated film to the semiconductor substrate, and MR is increased. Further, it can be seen that the resonance peak current _Id is sharpened as compared with the MR bias dependence characteristics of the spin MOSFET according to the modification of the first embodiment shown in FIG.

(Seventh embodiment)
Next, FIG. 17 shows a semiconductor device according to the seventh embodiment of the present invention. The semiconductor device of this embodiment has a configuration in which a ferromagnetic laminated film 20F is provided on a semiconductor substrate 2. This ferromagnetic laminated film 20F has a configuration in which the tunnel barrier layer 22 between the semiconductor substrate 2 and the Heusler alloy layer 24 is removed from the ferromagnetic laminated film 20 according to the first embodiment shown in FIG. That is, as shown in FIG. 17, the semiconductor substrate 2 has a structure in which the Heusler alloy layer 24 / nonmagnetic layer 26 are laminated in this order.

  In the ferromagnetic laminated film 20F, the Heusler alloy layer 24 is sandwiched between the Schottky barrier formed at the interface with the semiconductor substrate 2 and the nonmagnetic layer 26, so that the up spin band of the Heusler alloy layer 24 is resonant. A level is formed. Since a tunnel current is generated via this resonance level, a high spin density current and a high spin polarization current can be injected from the Heusler alloy layer 24 to the semiconductor substrate 2. By not using the tunnel barrier layer 22, the structure can be simplified. For the growth of the Heusler alloy layer 24 on the semiconductor substrate 2, the same manufacturing method as that used when forming on the tunnel barrier layer of the first embodiment is used.

  The spin MOSFET according to the modification of the present embodiment has a configuration in which at least one of the source part and the drain part of the spin MOSFET according to the modification of the first embodiment is replaced with the ferromagnetic laminated film 20F shown in FIG. In the spin MOSFET of this modification, as in the first embodiment, an increase in MR was confirmed with a specific bias.

(Eighth embodiment)
Next, FIG. 18 shows a semiconductor device according to the eighth embodiment of the present invention. The semiconductor device of this embodiment has a configuration in which a ferromagnetic laminated film 20G is provided on a semiconductor substrate 2. This ferromagnetic laminated film 20G has a configuration in which a nonmagnetic layer 21 is provided in place of the tunnel barrier layer 22 in the ferromagnetic laminated film 20 according to the first embodiment shown in FIG. That is, as shown in FIG. 18, a nonmagnetic layer 21 / Heusler alloy layer 24 / nonmagnetic layer 26 are stacked on the semiconductor substrate 2 in this order.

  In the ferromagnetic laminated film 20G, the Heusler alloy layer 24 has a structure sandwiched between the two nonmagnetic layers 21 and 26, so that a resonance level is formed in the up spin band of the Heusler alloy layer 24. Since a tunnel current is generated via the resonance level, a high spin-polarized current can be injected at a high current density from the Heusler alloy layer 24 to the semiconductor substrate 2.

  In the case where it is difficult to grow the tunnel barrier layer on the semiconductor substrate 2, the present embodiment may be adopted to form a nonmagnetic metal layer that is easy to grow on the semiconductor. In the seventh embodiment, when heat treatment is applied when the Heusler alloy layer 24 is formed, mutual diffusion may occur between the Heusler alloy layer 24 and the semiconductor substrate 2, and the Heusler alloy layer 24 is magnetic. May stop functioning. On the other hand, in this embodiment, since the nonmagnetic layer 21 is inserted between the semiconductor substrate 2 and the Heusler alloy layer 24, this functions as a barrier layer for mutual diffusion. For this reason, the magnetic properties of the Heusler alloy layer 24 are not impaired. For the growth of the Heusler alloy layer 24 on the semiconductor substrate 2, the same manufacturing method as that used for the growth on the tunnel barrier layer of the first embodiment is used. The nonmagnetic layer 21 may be made of the same material as the nonmagnetic layer 26, and it is preferable to use chromium (Cr), vanadium (V), or manganese (Mn).

  The spin MOSFET according to the modification of the present embodiment has a configuration in which at least one of the source part and the drain part of the spin MOSFET according to the modification of the first embodiment is replaced with the ferromagnetic laminated film 20G shown in FIG. In the spin MOSFET of this modification, as in the first embodiment, an increase in MR was confirmed with a specific bias.

In each of the above embodiments, a tunnel barrier layer, between the Heusler alloy _{layer, C r xAl 1-x (} 40% ≦ x ≦ 60%), Cr x Ga 1-x (40% ≦ x ≦ 60 %) And the like can be obtained by inserting 3 angstroms to 6 angstroms, and the reduction of MR due to temperature dependence can be suppressed.

  In each of the embodiments described above, the material of the semiconductor substrate is at least a Si single crystal, a Ge single crystal, a substrate having a Si-Ge single crystal, a substrate having a SiC single crystal, an SOI (Silicon on Insulator) substrate, A III-V compound semiconductor substrate or a II-VI group semiconductor substrate having at least a GaAs single crystal, an InGaAs single crystal, or the like on the surface can be used.

  Even when spin MOSFETs are formed by changing the combinations of the embodiments described above, all are included in the scope of the present invention.

  In each of the above-described embodiments, a semiconductor layer (semiconductor substrate) and a tunnel barrier layer, or a semiconductor layer (semiconductor substrate) and a Heusler alloy layer, or a semiconductor natural layer between a semiconductor layer (semiconductor substrate) and a nonmagnetic layer are used. An oxide film may be formed. If a (001) -oriented thin film laminated structure is formed on this natural oxide film, the same effect as described in the above embodiment can be obtained.

  In each of the embodiments described above, a conventional CMOS process can be used up to the step immediately before the formation of the stacked structure of the source and drain portions.

In this specification, the name of the spin MOSFET is used. However, the MOSFET structure is not necessarily intended, and a MISFET in which the gate insulating film is formed of a film other than a semiconductor oxide film may be used. Specifically, for example, La ₂ O ₅ , La ₂ O ₃ , CeO ₂ , ZrO ₂ , HfO ₂ , SrTiO ₃ , PrO ₃ , LaAlO ₃ , Si ₃ N ₄ , Al ₂ O ₃ , Ta ₂ O ₅ , TiO ₂ or the like can be applied as the gate insulating film.

1 is a cross-sectional view showing a semiconductor device according to an embodiment of the present invention. The figure explaining the operation | movement principle of this invention. The figure explaining the operation | movement principle of this invention. The figure explaining the operation principle of this invention. The figure explaining the operation | movement principle of this invention. The figure explaining the operation principle of this invention. Sectional drawing which shows the semiconductor device by 1st Embodiment. Sectional drawing which shows the spin MOSFET by the modification of 1st Embodiment. The figure which shows the bias dependence characteristic of MR of spin MOSFET by the modification of 1st Embodiment. Sectional drawing which shows the semiconductor device by 2nd Embodiment. Sectional drawing which shows the spin MOSFET by the modification of 2nd Embodiment. Sectional drawing which shows the semiconductor device by 3rd Embodiment. Sectional drawing which shows the semiconductor device by 4th Embodiment. Sectional drawing which shows the semiconductor device by 5th Embodiment. Sectional drawing which shows the semiconductor device by 6th Embodiment. The figure which shows the bias dependence characteristic of MR of spin MOSFET by the modification of 6th Embodiment. Sectional drawing which shows the semiconductor device by 7th Embodiment. Sectional drawing which shows the semiconductor device by 8th Embodiment.

Explanation of symbols

2 Semiconductor substrate 4 Gate insulating film 6 Gate electrode 20 Ferromagnetic laminated film 20a Source part 20b Drain part 20Ab Drain part 21 Nonmagnetic layer 22 Tunnel barrier layer 23 Laminated film including Heusler alloy layer (MTJ)
23a Heusler alloy layer 23b Tunnel barrier layer 23c Heusler alloy layer 24 Heusler alloy layer 26 Nonmagnetic layer 27 Tunnel barrier layer 28 Ferromagnetic layer 30 Antiferromagnetic layer

Claims (7)

A semiconductor substrate;
A ferromagnetic multilayer film provided on the semiconductor substrate and including a first Heusler alloy layer and a first nonmagnetic layer provided on the first Heusler alloy layer;
With
2. A semiconductor device according to claim 1, wherein the magnetoresistance change ratio of the ferromagnetic multilayer film vibrates in accordance with a bias voltage applied to the ferromagnetic multilayer film. A semiconductor substrate;
A ferromagnetic laminate including a first Heusler alloy layer provided on the semiconductor substrate and having a thickness of 0.28 nm to 5.6 nm and a first nonmagnetic layer provided on the first Heusler alloy layer. A membrane,
With
The semiconductor device, wherein the first nonmagnetic layer is made of chromium, vanadium, manganese, or an alloy thereof, or is a tunnel barrier. A semiconductor substrate;
A second nonmagnetic layer which is provided on the semiconductor substrate and is one of copper, silver, gold, and alloys thereof having a film thickness of 0.5 nm to 2.0 nm; and the second nonmagnetic layer. A ferromagnetic multilayer film comprising: a first Heusler alloy layer provided; and a first nonmagnetic layer provided on the first Heusler alloy layer;
A semiconductor device comprising:   4. The semiconductor device according to claim 1, wherein a tunnel barrier layer is provided between the ferromagnetic laminated film and the semiconductor substrate. The ferromagnetic laminated film is
A first laminated film in which the second Heusler alloy layer / the third nonmagnetic layer are laminated in this order;
Second laminated film in which second Heusler alloy layer / nonmagnetic layer / ferromagnetic layer / antiferromagnetic layer are laminated in this order, and third laminated film in which ferromagnetic layer / antiferromagnetic layer are laminated in this order 5. The semiconductor device according to claim 1, wherein the laminated film is provided on the first nonmagnetic layer.   6. The semiconductor device according to claim 1, wherein all the layers of the ferromagnetic laminated film have a (001) crystal orientation. A gate insulating film provided on the semiconductor substrate; and a gate electrode provided on the gate insulating film;
The semiconductor device according to claim 1, wherein the ferromagnetic laminated film is provided in at least one of the regions of the semiconductor substrate that sandwich the gate electrode.

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