JP2009176806A - Nonvolatile magnetic memory element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a nonvolatile magnetic memory capable of reversing magnetization efficiently with a low current density. <P>SOLUTION: The invention relates to a nonvolatile magnetic memory in which a magnetization inversion layer of a ferrimagnetic structure antiferromagnetically coupled weakly with a stationary layer is reversed by a magnetic field from magnetization inversion control layers and the magnetization directions of the magnetization inversion control layers are fixed being faced to both sides of the magnetization inversion layer. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a magnetization reversal mechanism and device structure of a nonvolatile magnetic memory element.

  One of the nonvolatile magnetic memory elements is a magnetic random access memory (MRAM). The MRAM has a configuration in which current wirings (bit lines and word lines) for recording and reading are provided above and below a tunneling magnetoresistive element (TMR). The TMR element has a structure in which an extremely thin insulating barrier layer is sandwiched between ferromagnetic layers, and utilizes a tunnel effect in which the resistance value in the film thickness direction varies greatly in accordance with the magnetization direction of the ferromagnetic layer.

  The main configuration of the TMR element is a substrate in which a fixed layer (antiferromagnetic layer) / a fixed magnetization layer (pinned layer) / an insulating layer (barrier layer) / a magnetization switching layer (free layer) are sequentially stacked. ing. In the MRAM, the magnetization reversal of the free layer is controlled by a synthetic magnetic field generated by currents flowing in the upper and lower wirings.

  However, if the TMR element is miniaturized to increase the density, the demagnetizing field of the magnetization reversal layer (free layer) increases, the current required for magnetization reversal increases and the power consumption increases. Problems such as a magnetic field affecting adjacent elements arise.

As one technique for solving these problems, a spin injection magnetization reversal technique for injecting a spin-polarized current has been proposed (Non-patent Document 1).
“Research Trends of Spin Injection Magnetization Reversal”, Kojiro Rooftop et al., Japan Society of Applied Magnetics, Vol. 28, no. 9 (2004)

However, although the miniaturization of the element can be dealt with by the spin injection magnetization reversal technique, at present, the current density necessary for the magnetization reversal is still as large as about 10 ⁷ A / cm ² . In order to realize a GBit-class non-volatile magnetic memory element, it is estimated that it is necessary to improve the current density with an element area of 0.1 μm ² or less and about two digits.

  Therefore, in the present invention, a method for efficiently inverting the magnetization switching layer at a low current density by providing a magnetization switching control layer for controlling the magnetization of the magnetization switching layer (free layer) in the nonvolatile magnetic memory element. I will provide a.

  A first invention is a nonvolatile magnetic memory element in which a first fixed layer / a fixed magnetization layer / barrier layer / magnetization inversion layer whose magnetization direction is fixed by the first fixed layer are sequentially stacked on a substrate. A first magnetization reversal control layer antiferromagnetically coupled to the fixed magnetization layer and a metal material layer on one side of both sides of the magnetization reversal layer, and the other of the magnetization reversal layers The present invention relates to a nonvolatile magnetic memory element characterized in that, on the side, a second magnetization reversal control layer that is directly ferromagnetically coupled to the fixed magnetization layer is formed.

  That is, according to the first invention, in the nonvolatile magnetic memory element using the tunnel magnetoresistive effect, the first magnetization reversal control layer includes the fixed magnetization layer and the metal material layer on one side of the magnetization reversal layer of the magnetoresistive element. And the second magnetization reversal control layer is directly ferromagnetically coupled to the fixed magnetization layer on the other side of the magnetoresistive element, thereby magnetizing the ferrimagnetic structure magnetization reversal layer. Current density, which can be reversed by a magnetic field from the reversal control layer, is applied to the magnetization reversal layer at the same time as applying a voltage to the magnetization reversal layer simultaneously with the first fixed layer during recording. Can be greatly reduced.

  A second invention relates to the nonvolatile magnetic memory element according to the first invention, wherein a second pinned layer made of an antiferromagnetic material is provided on the magnetization switching layer.

  In other words, according to the second invention, the magnetization reversal layer is weakly antiferromagnetically coupled to the pinned layer provided thinly thereon, so that the stray magnetic field from other elements and the magnetic field balance of the magnetization reversal control layers on both sides are obtained. It becomes possible to suppress the influence of the variation of.

  The third invention is characterized in that the magnetization directions of the first magnetization inversion control layer and the second inversion control layer formed on both sides of the magnetization inversion layer are fixed so as to face each other. The present invention relates to the nonvolatile magnetic memory element according to the first or second invention.

  That is, according to the third invention, the magnetization reversal control layer on one side is antiferromagnetically coupled via the pinned magnetization layer and the metal material layer, and the magnetization reversal control layer on the other side is Due to the direct ferromagnetic coupling, the magnetization direction of the magnetization reversal control layer can be fixed in a state facing each other on both sides of the magnetization reversal layer. The magnetization reversal in the magnetization reversal layer can be easily controlled with a small current.

  According to a fourth aspect of the present invention, during recording, one of the magnetization reversal control layers formed on both sides of the magnetization reversal layer is selected simultaneously with voltage application between the first fixed layer and the magnetization reversal layer. The present invention relates to the nonvolatile magnetic memory element according to any one of the first to third inventions, wherein a voltage is applied between the first fixed layer and the first fixed layer.

  That is, according to the fourth aspect of the invention, a voltage is applied between the one magnetization reversal control layer and the first fixed layer to cause a current to flow. Due to the effect of Joule heat, the magnetization of the magnetization reversal control layer becomes smaller, the leakage magnetic field from the other magnetization reversal control layer becomes dominant, and the magnetization of the magnetization reversal layer is reversed by this magnetic field. Recording status is possible.

  As described above, with the nonvolatile magnetic memory element of the present invention, the magnetization reversal control layers magnetized in opposite directions are provided on both sides of the magnetization reversal layer of the tunnel magnetoresistive (TMR) element, and either one of the magnetization reversal control layers is recorded during recording. By applying a voltage, the current density required for magnetization reversal is significantly reduced by one to two digits compared to the conventional case.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 shows an example of the basic structure of a nonvolatile magnetic memory element according to an embodiment of the present invention. The nonvolatile magnetic memory element (MRAM) of the present invention has a structure in which a resistance value in the film thickness direction varies greatly in accordance with the magnetization direction of the ferromagnetic film in a structure in which an extremely thin insulating film is sandwiched between ferromagnetic thin films. It uses the (TMR) effect.

  The TMR element is formed on the substrate in the order of the first pinned layer 1 (antiferromagnetic layer) / pinned magnetic layer 2 (pinned layer) / barrier layer 3 (insulating layer) / magnetization switching layer 4 (free layer) / second. The fixed layer 5 (antiferromagnetic layer) is laminated.

  In this TMR element, in order to efficiently reverse the magnetization of the magnetization switching layer 4 and reduce the current density at the time of writing, the barrier layer 3 / magnetization switching layer 4 / second layer constituting part of the TMR element. The first and second magnetization reversal control layers 6 and 7 are arranged on both sides of the laminated body including the fixed layer 5.

  In the magnetization reversal layer 4, when electrons having spins in the opposite direction are injected into the magnetic body, the magnetization direction in the magnetic material is reversed according to the injected electron spins. Further, by weakly antiferromagnetically coupling with the second pinned layer 5 provided thinly on the magnetization switching layer 4, the stray magnetic field from other elements and the variation in the magnetic field of the magnetization switching control layers 6 and 7 on both sides are obtained. It is possible to suppress the influence of. The magnetization reversal layer 4 may have a three-layer ferrimagnetic structure that is antiferromagnetically coupled instead of one layer. In this case, the net magnetization direction is aligned with the magnetization direction from the magnetization reversal control layer.

  The first magnetization reversal control layer 6 is antiferromagnetically coupled to the fixed magnetization layer 2 via a metal layer 9 made of a thin layer of nonmagnetic metal such as ruthenium (Ru) or copper (Cu). It is magnetized in the opposite direction to the fixed magnetization layer 2. The other second inversion control layer 7 is magnetized in the same direction as the pinned magnetic layer 2 by being directly ferromagnetically coupled to the pinned magnetic layer 2. In this way, a configuration is realized in which the magnetization directions of the magnetization reversal control layers 6 and 7 provided on both sides of the TMR element face each other.

  FIG. 2 shows the magnetization state (during reproduction) of the nonvolatile magnetic memory element according to the embodiment of the present invention. FIG. 2 shows a configuration when reading the magnetization state of the magnetization switching layer 4 in the nonvolatile magnetic memory element (during reproduction). The first magnetization reversal control layer 6 is antiferromagnetically coupled to the fixed magnetization layer 2 via a nonmagnetic metal layer 9 such as Ru or Cu, while the second magnetization reversal control layer 7 on the opposite side is directly The magnetization reversal control layers 6 on both sides of the laminate composed of the barrier layer 3 / magnetization reversal layer 4 / second pinned layer 5 constituting a part of the TMR element by being ferromagnetically coupled to the pinned magnetic layer 2. , 7 are in a state in which the magnetization directions face each other.

Here, the current I _R indicates a read current (constant current) that flows between the fixed layer 1 and the fixed layer 5. According to the magnetization directions “parallel” and “antiparallel” of the magnetization switching layer with respect to the fixed magnetization layer, the magnetic resistance differs, and the corresponding bits “0” and “1” are detected as a voltage difference.

  The power source 10 is a power source supplied during writing (recording) between the magnetization switching layer 6 or 7 / the first fixed layer 1, and is switched to the magnetization switching layer 6 or 7 by switching the switch A / B. Is supplied.

FIG. 3 shows a magnetization state diagram at the time of “0” recording according to the embodiment of the present invention. In order to reverse the magnetization direction of the magnetization switching layer 4, a write current I _W (downward) is passed, and a voltage is applied from the power supply 10 between the first magnetization switching control layer 6 and the fixed layer 1 to pass the current. At that time, the magnetization of the first magnetization reversal control layer 6 becomes smaller due to the influence of the generated Joule heat, and the leakage magnetic field from the other second magnetization reversal control layer 7 becomes dominant. 4 are aligned in the same direction as the magnetization direction of the pinned magnetic layer, and a “0” recording state is obtained.

FIG. 4 shows a magnetization state diagram at the time of “1” recording according to the embodiment of the present invention. In order to reverse the magnetization of the magnetization switching layer in the reverse direction, a write current I _W (upward) is passed and a voltage is applied between the second magnetization switching control layer 7 and the first fixed layer 1. Similar to FIG. 3, the magnetization of the second magnetization reversal control layer 7 becomes smaller, and the leakage magnetic field from the first magnetization reversal control layer 6 becomes dominant, so that the magnetization of the magnetization reversal layer 4 is reversed in the reverse direction. , “1” can be recorded.

  FIG. 5 shows a manufacturing procedure (No. 1) of the nonvolatile magnetic memory element according to the embodiment of the present invention. In the manufacturing procedure of the nonvolatile magnetic memory element of FIG.

  The structure of the TMR element produced below is the first pinned layer 1 (antiferromagnetic layer) / pinned magnetic layer 2 (pinned layer) / barrier layer 3 (insulating layer) / magnetization switching layer 4 (free layer). / Second pinned layer 5 (antiferromagnetic layer) / protective layer 11 In this element configuration, a protective film 11 is further laminated on the configuration of FIG.

In the examples, the material and thickness of each layer correspond to the above configuration, and IrMn (7 nm) / CoFeB (1.8 nm) / MgO (1.4 nm) / CoFeB (3 nm) / PtMn (1 nm) / Ta ( 10 nm). However, the present invention is not necessarily limited to this material, composition, and configuration.
Procedure 1: First, each layer of the TMR element is sequentially formed by a normal sputtering method.
Procedure 2: Next, in order to create a desired reproduction core width, a resist is applied on the TMR element, and then exposed and developed to leave a part of the resist.
Procedure 3: CF4 gas is introduced, and Ta as the protective film 11 is etched by a reactive etching (RIF) method.
Procedure 4: Subsequently, the resist is removed.

FIG. 6 shows a manufacturing procedure (No. 2) of the nonvolatile magnetic memory element according to the embodiment of the present invention. In the manufacturing procedure of the nonvolatile magnetic memory element of FIG.
Procedure 5: The layer from the protective layer 11 to the barrier layer 3 is etched at a time so as to have a predetermined width by ion beam etching (IBE). At this time, Ta acts as a mask, and a layer structure below the Ta protective layer 11 is formed.
Procedure 6: Next, an Al ₂ O ₃ insulating layer 8 is formed to a thickness of 4 nm by RF sputtering.
Procedure 7: Ar gas is introduced to mill the Al ₂ O ₃ insulating layer 8.
Procedure 8: Subsequently, Ru is formed as a metal layer 9 for antiferromagnetic coupling of the first magnetization reversal control layer 6 on one side to the fixed magnetization layer 2. The Ru metal layer 9 is finally provided to be 0.3 nm.

FIG. 7 shows a manufacturing procedure (No. 2) of the nonvolatile magnetic memory element according to the embodiment of the present invention. In the procedure for manufacturing the nonvolatile magnetic memory element in FIG. 7, procedures 9 to 11 are shown.
Procedure 9: Ar gas is introduced and the Ru metal layer 9 is milled obliquely so that only one side of the TMR element remains. The oblique milling is performed by shifting the electrode on which the wafer substrate is placed from the position opposite to the electrode of the target material.
Procedure 10: Next, a GdFe film is formed to a thickness of about 15 nm as the magnetization reversal control layers 6 and 7. The magnetization reversal control layer may be a general CoCrPt alloy as a hard film for a reproducing magnetic head, but here, the Curie temperature can be changed so that the magnitude of magnetization can be changed at a relatively low temperature (Joule heat). GdFe rare earth transition metal alloy of about 200 ° C.).

The saturation magnetization value of this magnetic film is about 250 emu / cc at room temperature, and its composition is a rare earth-dominated composition that decreases almost linearly to the Curie temperature, for example, Gd32Fe68. The leakage magnetic field from the magnetization reversal control layers 6 and 7 has a magnitude of several tens to several hundreds Oe depending on the temperature in the magnetization reversal layer 4 and assists the magnetization reversal of the magnetization reversal layer 4.
Procedure 11: Finally, planarization is performed by chemical mechanical polishing (CMP) until the Ta protective layer 11 is scraped by about 3 nm. After the magnetic memory element was completed, heat treatment was performed in a vacuum at a temperature of 350 ° C. in a magnetic field of 1.3 Tesla to fix the magnetization direction of the fixed magnetization layer.

Prior to the manufacture of the magnetic memory element, an element having a size of, for example, 0.06 μm ² without the magnetization reversal control layers 6 and 7 was formed, and the magnetization reversal operation was confirmed. The blocking temperature is a temperature at which the first pinned layer 1 is thinned and the exchange coupling force between the antiferromagnetic layer (first pinned layer 1) and the ferromagnetic layer (pinned magnetic layer 2) is eliminated. Is set to about 200 ° C., and the second pinned layer 5 on the magnetization switching layer is not provided.

  In confirmation, a pulse voltage of 100 μsec was applied while applying a magnetic field of 50 Oe in the opposite direction to the fixed magnetization layer, and the voltage at which magnetization reversal of the fixed magnetization layer was examined was about 700 mV. That is, it is considered that the blocking temperature was reached by applying a pulse voltage of 700 mV, and the magnetization was reversed.

  Therefore, in the case of a magnetic memory element structure, the magnitude of magnetization can be controlled without raising the magnetization reversal control layers 6 and 7 to 200 ° C. Therefore, the applied voltage at the time of recording is reduced to about half. Is possible.

As described above, the magnetization reversal operation of the magnetic memory element manufactured in the above manufacturing process according to the present invention was confirmed. As a result, at the time of recording, a current of 0.1 mA was passed through the TMR element, and at the same time, reversal of the magnetization reversal layer was observed when a pulse voltage of 100 μsec was applied to the magnetization reversal control layer 300 mV. This is a current density of about 1 × 10 ⁶ A / cm ² , which is about an order of magnitude lower than the conventional one. Furthermore, when the current passed through the TMR element was 0.07 mA, inversion was observed when the pulse voltage was 400 mV, and it was found that the current density could be reduced by nearly two orders of magnitude compared to the conventional case.

It is a figure which shows the example of a basic structure of the non-volatile magnetic memory element which becomes embodiment of this invention. It is a figure which shows the magnetization state (at the time of reproduction | regeneration) of the non-volatile magnetic memory element which becomes embodiment of this invention. FIG. 6 is a magnetization state diagram at the time of “0” recording according to an embodiment of the present invention. It is a magnetization state diagram at the time of “1” recording according to the embodiment of the present invention. It is a figure which shows the preparation procedures (the 1) of the non-volatile magnetic memory element which becomes embodiment of this invention. It is a figure showing the manufacture procedure (the 2) of the non-volatile magnetic memory element which becomes embodiment of this invention. It is a figure showing the manufacture procedure (the 3) of the non-volatile magnetic memory element which becomes embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 1st pinned layer 2 Pinned magnetization layer 3 Barrier layer 4 Magnetization reversal layer 5 2nd pinned layer 6 1st magnetization reversal control layer 7 2nd magnetization reversal control layer 8 Insulating layer 9 Metal layer 10 Power supply 11 Protective layer

Claims (4)

A non-volatile magnetic memory element in which a first fixed layer / a fixed magnetization layer / barrier layer / magnetization inversion layer whose magnetization direction is fixed by the first fixed layer are sequentially stacked on a substrate,
A first magnetization reversal control layer antiferromagnetically coupled to the fixed magnetization layer and a nonmagnetic metal material layer on one side of both sides sandwiching the magnetization reversal layer;
A second magnetization reversal control layer that is ferromagnetically coupled directly to the fixed magnetization layer on the other side of the magnetization reversal layer;
A nonvolatile magnetic memory element characterized by comprising:   The nonvolatile magnetic memory element according to claim 1, wherein a second pinned layer made of an antiferromagnetic material is provided on the magnetization switching layer.   3. The magnetization direction of the first magnetization reversal control layer and the second reversal control layer formed on both sides of the magnetization reversal layer is fixed so as to face each other. Non-volatile magnetic memory element.   At the time of recording, simultaneously with voltage application between the first fixed layer and the magnetization switching layer, one of the magnetization switching control layers formed on both sides of the magnetic switching layer is selected and the first switching layer is selected. The nonvolatile magnetic memory element according to claim 1, wherein a voltage is applied between the fixed layer and the fixed layer.

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