WO2010125941A1

WO2010125941A1 - Screening method for magnetoresistive storage device

Info

Publication number: WO2010125941A1
Application number: PCT/JP2010/056945
Authority: WO
Inventors: 有光加藤
Original assignee: 日本電気株式会社
Priority date: 2009-04-28
Filing date: 2010-04-19
Publication date: 2010-11-04

Abstract

A screening method for a magnetoresistive storage device comprising a first magnetic body, and a storage element which stores data in the magnetization direction of the first magnetic body. The method is provided with a step of setting a magnetization direction of the first magnetic body; a step of applying a storage element with a first magnetic field which includes a component in a direction different from the directions of axis of easy magnetization and axis of hard magnetization of the first magnetic body, and opposite to the magnetization direction of the first magnetic body; a step of assessing a resistance of the storage element; a step of determining whether or not the storage element is defective, on the basis of the assessment result; and a step of storing and/or setting so that the storage element which has been determined as defective should not be used.

Description

Magnetoresistive memory device screening method

The present invention relates to a screening method for a magnetoresistive memory device, and more particularly, to a defective cell screening method for a magnetic random access memory (MRAM).

MRAM is a promising nonvolatile memory from the viewpoint of high integration and high-speed operation. In the MRAM, a magnetoresistive memory element exhibiting a “magnetoresistance effect” such as a TMR (Tunnel MagnetoResistance) effect is used. In the magnetoresistive memory element, for example, a magnetic tunnel junction (MTJ) is formed in which a tunnel barrier layer is sandwiched between two ferromagnetic layers. The two ferromagnetic layers are composed of a pinned layer (magnetization pinned layer) whose magnetization direction is fixed and a free layer (magnetization free layer) whose magnetization direction can be reversed. For example, Roy Scheuerlein et al. , “A 10 ns Read and Write Non-Volatile Memory Array Usage a Magnetic Tunnel Junction and FET SwitchinEtErPNeSNRC” 128-129 (Non-Patent Document 1) discloses such an MRAM.

The resistance value (R + ΔR) of the MTJ when the magnetization directions of the pinned layer and the free layer are “anti-parallel” is larger than the resistance value (R) when they are “parallel” due to the magnetoresistance effect. It is known. The MRAM uses a magnetoresistive storage element having this MTJ as a memory cell, and stores data in a nonvolatile manner by utilizing the change in the resistance value. Data is written to the memory cell by reversing the magnetization direction of the free layer.

Conventionally, the asteroid method is known as a method of writing data to the MRAM. For example, M.M. Durlam et al. , “Nonvolatile RAM based on Magnetic Tunnel Junction Elements”, 2000 IEEE International Solid-State Circuits Conference, DIGEST OF TECHNICPAPER. 130-131 (Non-Patent Document 2) discloses such an asteroid system.

FIG. 1 is a perspective view showing an example of a non-volatile memory using TMR as a storage element. In this nonvolatile memory, the TMR 505 is arranged in an array. A pair of

wirings

506 and 509 that intersect is provided above and below the TMR 505. The free layer of the TMR 505 is connected to the upper wiring 506. The pin layer of the TMR 505 is connected to the drain of the transistor 508 formed in the lower layer through the wiring layer 507. By passing a current through the two wirings (B) 506 and (D) 509, a synthetic magnetic field is generated near the intersection (near TMR 505), and the magnetization direction of the free layer is set (data is written). The magnetization direction (data to be written) of the free layer is set according to the direction of current. Thereby, the resistance value of the TMR 505 can be changed (data can be written). To read data, the transistor 508 connected to the TMR 505 to be read is turned on by the wiring (W) 510, a voltage is applied to the TMR 505 from the wiring (B) 506, and the resistance value of the TMR 505 is evaluated by the current flowing through the TMR 505. To do. According to the asteroid method, the reversal magnetic field necessary for reversing the magnetization of the free layer is substantially in inverse proportion to the size of the memory cell. That is, the write current tends to increase as the memory cell is miniaturized.

A “spin transfer method” has been proposed as a write method capable of suppressing an increase in write current accompanying miniaturization. For example, Yamami and Suzuki, “Research Trends in Spin Transfer Magnetization Switching” (Research Trends of Spin Injection Magnetization Reversal), Journal of Japan Society of Applied Magnetics, Vol. 28, no. 9, 2004, pp. No. 937-948 (Non-patent Document 3) discloses such a spin injection method. According to the spin injection method, a spin-polarized current is injected into the ferromagnetic conductor, and the magnetization is reversed by a direct interaction between the spin of the conduction electron carrying the current and the magnetic moment of the conductor. (Hereinafter referred to as “Spin Transfer Magnetization Switching”).

FIG. 2 is a schematic cross-sectional view showing an outline of the spin injection magnetization reversal of the magnetoresistive memory element. The magnetoresistive memory element includes a free layer 601, a pinned layer 603, and a tunnel barrier layer 602 that is a nonmagnetic layer sandwiched between the free layer 601 and the pinned layer 603. Here, the pinned layer 603 whose magnetization direction is fixed is formed to be thicker than the free layer 601, and plays a role as a mechanism (spin filter) for creating a spin-polarized current. The state where the magnetization directions of the free layer 601 and the pinned layer 603 are parallel is associated with data “0”, and the state where they are antiparallel is associated with data “1”. The spin-injection magnetization reversal shown in FIG. 2 is realized by a CPP (Current Perpendicular to Plane) method, and a write current is injected perpendicularly to the film surface. Specifically, current flows from the pinned layer 603 to the free layer 601 at the time of transition from data “0” to data “1”. In this case, electrons having the same spin state as the pinned layer 603 serving as a spin filter move from the free layer 601 to the pinned layer 603. Then, the magnetization of the free layer 601 is reversed by a spin transfer (spin angular momentum transfer) effect. On the other hand, at the time of transition from data “1” to data “0”, the direction of the current is reversed, and the current flows from the free layer 601 to the pinned layer 603. In this case, electrons having the same spin state as the pinned layer 603 serving as a spin filter move from the pinned layer 603 to the free layer 601. Due to the spin transfer effect, the magnetization of the free layer 601 is reversed. Thus, in spin injection magnetization reversal, data is written by movement of spin electrons. The direction of magnetization of the free layer 601 can be defined by the direction of the spin-polarized current injected perpendicular to the film surface.

As a related technology, Japanese Patent No. 3866701 (corresponding US Pat. No. 6,950,334 (B2)) discloses a magnetic random access memory and a test method thereof. The magnetic random access memory includes a memory cell array, a write word line and a write bit line, a first driver, a second driver, a first sinker, a third driver, a fourth driver, 2 sinkers, first means, and second means. In the memory cell array, magnetoresistive storage elements are arranged in a matrix. A write word line is arranged in each row of the memory cell array. Write bit lines are arranged in each column of the memory cell array. The first driver is selectively connected to both ends of the write word line. The second driver has a higher driving capability than the first driver. The third driver was connected to one end of the write bit line. The fourth driver has a higher driving capability than the third driver. The second sinker was connected to the other end of the write bit line. The first means collectively writes the information of the plurality of memory cells by uniaxial writing in the hard axis direction by the second driver. The second means simultaneously applies a larger current to the plurality of memory cells by uniaxial writing in the easy axis direction than the biaxial writing in the normal operation by the fourth driver.

Also, Japanese Patent Application Laid-Open No. 2003-338199 discloses a semiconductor memory device and a method for using the same. This semiconductor memory device uses a plurality of magnetoresistive memory elements as memory cells. This semiconductor memory device has a function of determining stored data of a memory cell, and a function of comparing a characteristic value correlated with the absolute value of the resistance value of each memory cell with a desired threshold value to determine whether the memory cell is good or bad And have.

Also, Japanese Patent Application Laid-Open No. 2005-311167 (corresponding US Pat. No. 7,236,392 (B2)) discloses a tunnel magnetoresistive effect element inspection method and apparatus. In this tunnel magnetoresistive effect element inspection method, the initial resistance value of the tunnel magnetoresistive effect element is measured to obtain a first resistance value, and a current is passed through the tunnel magnetoresistive effect element from the non-substrate direction to the substrate direction. The resistance value after energization for a predetermined time is measured to obtain a second resistance value, and the tunnel magnetoresistive effect element is evaluated by comparing the first resistance value and the second resistance value.

JP-A-2006-269907 (corresponding US Pat. No. 7,737,282 (B2)) discloses a tunnel magnetoresistive element inspection method and apparatus, a tunnel magnetoresistive element manufacturing method, and a tunnel magnetoresistive element. . In this tunnel magnetoresistive effect element inspection method, the resistance values of the tunnel magnetoresistive effect element are respectively measured in a state where a plurality of voltages having mutually different voltage values are applied to the tunnel magnetoresistive effect element. The tunnel magnetoresistive element is evaluated by obtaining the resistance change amount from the value.

Also, JP 2007-123637 A (corresponding US Pat. No. 7,394,684 (B2)) discloses a spin injection magnetic random access memory. This spin-injection magnetic random access memory executes writing to a magnetoresistive element using spin-polarized electrons generated by a spin-injection current. The spin injection magnetic random access memory includes means for applying a magnetic field in the hard axis direction of the magnetoresistive effect element to the magnetoresistive effect element at the time of writing.

The inventor has newly discovered the following findings as a result of this research.
In the magnetoresistive memory element in which the magnetization direction of the free layer described above is used for data storage, the magnetic characteristics may be shifted, deformed, or rotated. The reason is that there is a non-uniform part in the magnetic characteristics due to abnormal shape of the free layer and defects in the magnetic film, stress due to nearby wiring, etc., the use of an adjacent magnetoresistive memory element or magnetic material For example, it is affected by the leakage magnetic field from the dummy pattern. FIG. 3 is an asteroid curve showing conditions under which magnetization reversal occurs in the free layer when a magnetic field is applied. The vertical axis represents the magnitude of the magnetic field in the direction of the hard axis in the free layer. The horizontal axis indicates the magnitude of the magnetic field in the direction of the easy axis of magnetization in the free layer. A thick arrow indicates the magnetization direction of the free layer. In the figure, the magnetization of the free layer is reversed to a data “1” state when a magnetic field exceeding the solid line A of the asteroid curve is applied, and to a data “0” state when a magnetic field exceeding the broken line B is applied. . As can be seen from the figure, the magnetization can be reversed with the smallest magnetic field by applying the magnetic field in the direction of 45 degrees with respect to the easy axis direction.

However, when the magnetic properties are shifted or deformed, the asteroid curve in FIG. 3 moves or deforms. 4A and 4B show an example of an asteroid curve when the magnetic characteristics are changed. When the asteroid curve is shifted and deformed, for example, in the lower right direction as shown in FIG. 4A, or when the asteroid curve is shifted, for example, in the lower right direction as shown in FIG. 4B The magnetization reversal itself has a good balance regardless of the data to be written, and the value is the same as in the case of FIG. However, the origin, which is in the state of holding no magnetic field data, is close to the asteroid curve indicating the boundary where magnetization reversal occurs. This means that magnetization reversal occurs due to thermal disturbance during data retention, and data is easily destroyed. For these reasons, it is not desirable for the asteroid curve in the free layer to shift, rotate or deform. Therefore, it is necessary to perform a screening process for detecting a memory cell (defective cell) having a magnetoresistive memory element exhibiting such magnetic characteristics and not using it as a memory cell. However, magnetization reversal due to thermal disturbance is a phenomenon that occurs stochastically and does not necessarily occur just because data is retained for a certain period of time. Therefore, in the magnetoresistive memory element that stores data using the magnetization direction, it is difficult to screen a defective cell in which magnetization reversal occurs with probability and to obtain a highly reliable magnetoresistive memory device. is there.

Japanese Patent No. 3866701 JP 2003-338199 A JP 2005-311167 A JP 2006-269907 A JP 2007-123637 A

An object of the present invention is to provide a method for effectively screening defective cells of a magnetoresistive memory device such as an MRAM.

A screening method for a magnetoresistive storage device according to a first aspect of the present invention is a screening method for a magnetoresistive storage device that includes a first magnetic body and includes a storage element that stores data in the direction of magnetization of the first magnetic body. It is. In the screening method, the step of setting the magnetization direction of the first magnetic body is different from the magnetization easy axis direction and the magnetization difficult axis direction of the first magnetic body. Applying a first magnetic field including a direction component opposite to the direction to the storage element; evaluating a resistance of the storage element; determining whether the storage element is defective based on the evaluation result; Storing and / or setting not to use the memory element determined to be defective.

Also, the magnetoresistive storage device according to the second aspect of the present invention includes a storage element, a writing unit, an applying unit, an evaluating unit, and a control unit. The storage element includes a first magnetic body and stores data in the magnetization direction of the first magnetic body. The writing unit sets the magnetization direction of the first magnetic body. The application unit stores a first magnetic field that has a direction component that is different from an easy magnetization direction and a hard magnetization direction of the first magnetic body and includes a direction component opposite to the magnetization direction of the first magnetic body. Apply to. The evaluation unit evaluates the resistance of the memory element. The control unit determines whether or not the storage element is defective based on the evaluation result, and stores and / or sets the storage element that is determined to be defective so as not to be used.

The screening method of the magnetoresistive memory device of the present invention enables efficient defective cell screening. Thereby, a highly reliable magnetoresistive memory device can be realized.

FIG. 1 is a perspective view showing an example of a nonvolatile memory using TMR as a memory element. FIG. 2 is a schematic cross-sectional view showing an outline of spin injection magnetization reversal of the magnetoresistive memory element. FIG. 3 is an asteroid curve showing conditions under which magnetization reversal occurs in the free layer when a magnetic field is applied. FIG. 4A is an example of an asteroid curve when the magnetic properties change. FIG. 4B is another example of an asteroid curve when the magnetic properties are changed. FIG. 5A is a schematic diagram showing the principle of the screening method for the magnetoresistive storage device according to the embodiment of the present invention. FIG. 5B is a schematic diagram illustrating the principle of the screening method for the magnetoresistive storage device according to the embodiment of the present invention. FIG. 5C is a schematic diagram showing the principle of the screening method for the magnetoresistive storage device according to the embodiment of the present invention. FIG. 5D is a schematic diagram showing the principle of the screening method of the magnetoresistive storage device according to the embodiment of the present invention. FIG. 6 is a sectional view showing the main part of the memory cell according to the first embodiment of the present invention. FIG. 7 is a plan view showing the main part of the memory cell according to the first embodiment of the present invention. FIG. 8 is a circuit diagram showing a configuration example of the memory cell according to the first embodiment of the present invention. FIG. 9 is a block diagram showing a configuration example of a magnetoresistive memory device in which memory cells according to the first embodiment of the present invention are integrated. FIG. 10A is a conceptual diagram illustrating a memory cell screening method according to the first embodiment of the present invention. FIG. 10B is a conceptual diagram illustrating a memory cell screening method according to the first embodiment of the present invention. FIG. 11 is a plan view showing an example of an external magnetic field according to the first embodiment of the present invention. FIG. 12 is a sectional view showing the main part of a memory cell according to the second embodiment of the present invention. FIG. 13 is a plan view showing the main part of a memory cell according to the second embodiment of the present invention. FIG. 14A is a conceptual diagram illustrating a memory cell screening method according to a second embodiment of the present invention. FIG. 14B is a conceptual diagram illustrating a memory cell screening method according to a second embodiment of the present invention. FIG. 15 is a sectional view showing the main part of a memory cell according to the third embodiment of the present invention. FIG. 16 is a plan view showing the main part of a memory cell according to the third embodiment of the present invention. FIG. 17A is a conceptual diagram illustrating a memory cell screening method according to a third embodiment of the present invention. FIG. 17B is a conceptual diagram illustrating a memory cell screening method according to a third embodiment of the present invention.

Hereinafter, an embodiment of a screening method for a magnetoresistive storage device of the present invention will be described with reference to the accompanying drawings.

5A to 5D are schematic diagrams showing the principle of the screening method for the magnetoresistive memory device according to the embodiment of the present invention.

The magnetoresistive memory device 10 is exemplified by an MRAM in which a plurality of memory cells are arranged in an array, and the memory cell includes a magnetoresistive memory element 1. As shown in FIG. 5A and FIG. 5C, the magnetoresistive memory device 10 includes a memory cell (magnetoresistance memory element 1), a writing unit 4, an applying unit 2, an evaluating unit 3, and a control unit 5. is doing.

The magnetoresistive memory element 1 includes a first magnetic layer 11 whose magnetization state changes according to data, a second magnetic layer 13 whose magnetization direction is fixed, a first magnetic layer 11 and a second magnetic layer 13. And a tunnel barrier layer 12 which is a nonmagnetic material sandwiched between the two. The first magnetic layer 11, the tunnel barrier layer 12, and the second magnetic layer 13 constitute an MTJ element. The first magnetic layer 11 is exemplified as a free layer of a typical or spin-injection magnetoresistive memory element or a reference layer of a domain wall motion type magnetoresistive memory element. The second magnetic layer 13 is exemplified by a pin layer of a typical or spin-injection magnetoresistive memory element or a magnetization recording layer of a domain wall motion type magnetoresistive memory element. 5A and 5C show that in the magnetoresistive memory element 1 (memory cell), the first magnetic layer 11 and the second magnetic layer 13 have perpendicular magnetic anisotropy, and data “0” (first magnetic layer) is shown. The body layer 11 and the second magnetic layer 13 have parallel magnetization directions) and data “1” (same as the antiparallel magnetization direction) are stored.

The writing unit 4 changes the magnetization state of the first magnetic layer 11 and writes data to the magnetoresistive memory element 1. As the writing unit 4, a circuit for writing a memory cell and a wiring for writing can be used. The application unit 2 applies a screening magnetic field to at least the first magnetic layer 11 during screening. As the application unit 2, it is possible to apply a desired magnetic field to the memory cell, and use a wiring in the vicinity of the memory cell through which a screening current can flow, a wiring diverted from other uses, a circuit for them, and the like. it can. An external magnetic field may be used. The evaluation unit 3 evaluates the magnitude of the resistance of the magnetoresistive memory element 1 and reads data of the magnetoresistive memory element 1. As the evaluation unit 3, a memory cell read circuit and a read wiring can be used. The control unit 5 determines whether the memory cell is good or defective using the evaluated resistance value or the characteristic value corresponding to the resistance value, and handles the memory cell (defective cell) determined as defective in advance. Set as follows. 5A and 5C show a case where screening is performed by applying a magnetic field Hs for screening to the magnetoresistive memory element 1 (memory cell). In addition, the structure of the magnetoresistive memory element 1, the application part 2, the evaluation part 3, the writing part 4, and the control part 5 in a figure are typical illustrations, and are not limited to this example.

In the screening method, the writing unit 4 sets the direction of magnetization of the first magnetic layer 11 (writes data to the memory cell), and the applying unit 2 applies the screening magnetic field Hs (screening) to the first magnetic layer 11. A magnetic field), a step in which the evaluation unit 3 evaluates the magnitude of the resistance of the magnetoresistive memory element 1 after the magnetic field Hs is applied (reads data in the memory cell), and a resistance value evaluated by the control unit 5 Alternatively, the step of determining whether the memory cell is good or defective using a characteristic value (read data) corresponding to the resistance value, and the control unit 5 to handle the memory cell determined to be defective in advance. And a step of setting to However, the magnetic field Hs is a magnetic field having such a magnitude and direction that does not cause magnetization reversal in a memory cell that is not defective, but may be capable of magnetization reversal in a defective memory cell.

5B and 5D show the range of the magnetic field Hs (screening magnetic field) to be applied when screening is performed in FIGS. 5A and 5C, respectively. The vertical axis represents the easy axis direction (also referred to as easy axis direction) of the first magnetic layer 11, and the horizontal axis represents the hard axis (plane) direction (also referred to as hard axis direction). Is the direction of magnetization of the first magnetic layer 11. The direction of the magnetic field Hs applied by the application unit 2 has a component opposite to the direction of magnetization of the first magnetic layer 11, and further includes an easy axis direction and a hard axis direction of the first magnetic layer 11. Are in different directions. For example, in the case of FIG. 5B, the range α1 of the direction of the magnetic field Hs is a range having a component opposite to the direction of magnetization of the first magnetic layer 11, and the direction of the angle θ1 from the hard axis (plane) direction. To the direction of the angle θ2 from the easy axis direction. On the other hand, in the case of FIG. 5D, the range α2 of the direction of the magnetic field Hs is a range having a component in the opposite direction to the magnetization direction of the first magnetic layer 11, and the direction of the angle θ3 from the hard axis (plane) direction. To the direction from the easy axis direction to the direction of the angle θ4.

In particular, it is preferable that the magnetic field Hs (screening magnetic field) applied by the application unit 2 has an angle component in the direction of 45 degrees from the easy axis direction of the first magnetic layer 11 larger than the easy axis direction component and the difficult axis direction component. More preferably, the magnetic field Hs is 45 degrees from the easy axis direction of the first magnetic layer 11. As can be seen from the shape of the asteroid curve (Fig. 3), there is the smallest reversal magnetic field between the easy axis direction and the hard axis direction, so the position is 45 degrees between the easy axis direction and the hard axis direction. This is because is optimal.

Further, in the magnetoresistive storage device 10 that performs writing by setting the magnetization direction of the first magnetic layer 11 using the write magnetic field Hw, the write magnetic field Hw applied by the writing unit 4 has the magnetization direction to be set. It has a component, and the direction of about 45 degrees from the easy axis direction of the first magnetic layer 11 is desirable. On the other hand, as described above, the direction of the magnetic field Hs has a component opposite to the direction of magnetization set in the first magnetic layer 11 and is about 45 degrees from the easy axis direction of the first magnetic layer 11. Direction. For this reason, when viewed from the writing magnetic field Hw, the direction of the magnetic field Hs applied in the screening is about 90 degrees (about 45 degrees + about 45 degrees).

The application of the magnetic field Hs is performed for each of the two magnetization states of the first magnetic layer 11 set corresponding to the data “0” and “1”, and a plurality of application of the magnetic field Hs is performed for each of the two magnetization states. It is effective when performed in the direction of. This is particularly effective when the hard axis direction forms a surface. Thereby, when there is a problem in the magnetic characteristics, magnetization reversal or the like is likely to occur in the retained state, and screening can be performed reliably.

The evaluation unit 3 performs the resistance evaluation of the memory cell (the magnetoresistive memory element 1) before applying the magnetic field Hs, after applying the magnetic field Hs and stopping the magnetic field Hs, or while applying the magnetic field Hs. Or you may perform combining those evaluation. Based on the evaluated resistance value or the characteristic value corresponding to the resistance value, the control unit 5 determines whether the memory cell is good or defective based on a predetermined determination criterion. As the predetermined determination criterion, a screening-determination criterion that is provided separately from the determination criterion for determining a defective cell by normal memory cell operation may be used. Alternatively, the control unit 5 performs resistance evaluation a plurality of times, and determines whether the memory cell is good or bad based on the magnitude relationship between the values or the magnitude relationship between the difference between the values and a predetermined value. The control unit 5 stores the address of the defective cell so as not to be used thereafter, or replaces the defective cell or a memory cell group including the defective cell with another memory cell group, depending on the generation position and number. It can be used in the same way as a normal memory cell and control such as correction of data by parity check can be performed.

According to the present embodiment, by reversing the characteristics of the magnetoresistive memory element by applying a magnetic field for screening, magnetization reversal occurs in the holding state, or resistance change occurs, and this is evaluated. It is possible to effectively detect a cell that may become abnormal, and a highly reliable magnetoresistive memory device can be obtained.

(First embodiment)
Next, a first embodiment of the present invention will be described.
6 and 7 are a sectional view and a plan view, respectively, showing the main part of the memory cell according to the first embodiment of the present invention. However, FIG. 6 is an AA ′ sectional view of FIG. In the memory cell, a Ta film 72, NiFe film 73, PtMn film 74, CoFe film 75, Ru film 76, CoFe film 77, MgO film 78, NiFe film 79, Ta film 84, and AlCu film 89 are laminated in this order. .

The NiFe film 79 is a free layer as the first magnetic layer 11 in FIGS. 5A and 5C, has a magnetization direction in the in-plane direction of the film, and has an elliptical pattern. The

CoFe films

75 and 77 antiferromagnetically coupled via the Ru film 76 of the conductor layer are pinned layers as the second magnetic layer 13 in FIGS. 5A and 5C. The MgO film 78 is the tunnel barrier layer 12 provided between the free layer and the pinned layer in FIGS. 5A and 5C. These free layer, pinned layer, and tunnel barrier layer function as an MTJ element (magnetoresistance memory element 1). A pin layer portion (Ta film 72 / NiFe film 73 / PtMn film 74 / CoFe film 75 / Ru film 76 / CoFe film 77) extending in one direction functions as a write wiring. The AlCu film 89 electrically connected to the free layer via the Ta film 84 as the upper electrode functions as a read wiring and a current wiring that induces a screening magnetic field. The Ta film 72 which is a lower electrode in the pin layer is electrically connected with other wiring for read current and write current via a W plug 70. The MTJ element is arranged so that the long side direction of the ellipse is oriented in a direction inclined by about 45 degrees with respect to the extending direction of the write wiring.

Next, with reference to FIGS. 6A and 6B, description will be made on a manufacturing method of the main part (including the MTJ element) of the memory cell according to the first embodiment of the present invention. First, a transistor including a selection transistor (described later) and a wiring including a bit line and a word line (described later) are formed on a semiconductor substrate (not shown). Thereafter, a SiO ₂ film 71 as an interlayer insulating film is formed with a film thickness of 300 nm on the semiconductor substrate. A W plug 70 connected to the lower layer wiring is formed at a predetermined position of the SiO ₂ film 71. Next, a Ta72 film with a film thickness of 20 nm, a NiFe film 73 with a film thickness of 2 nm, an antiferromagnetic PtMn film 74 with a film thickness of 20 nm, a CoFe film 75 with a pin layer underlayer magnetic material with a film thickness of 4 nm, Conductor layer Ru film 76 for antiferromagnetic coupling between pinned layers, 4 nm thick pinned layer

magnetic CoFe film

77, 1 nm thick tunnel insulating

film MgO film

78, 2 nm thick free layer NiFe film A Ta film 84 having a thickness of 79 and a thickness of 100 nm is formed by sputtering. Annealing is performed in the in-plane magnetic field of about 1 T (Tesla) at 275 ° C. for 2 hours, and the magnetization direction of the pinned layer is set by exchange coupling with the PtMn film 74. The Ta film 84 is processed by a photolithography technique and a reactive ion etching technique (RIE: Reactive Ion Etching). After removing the resist by ashing, the NiFe film 79 is processed into an MTJ shape by a milling method using the Ta film 84 as a mask. The free layer shape of this example is an ellipse having a long side of 0.4 μm and a short side of 0.2 μm as shown in FIG. Next, a SiN film 86 having a thickness of 30 nm is formed by a CVD method to protect the sidewall of the NiFe film 79. Subsequently, the MgO film 78 to the Ta film 72 are processed into a write wiring shape by a photolithography technique and a milling method. Thereby, a write wiring (Ta film 72, NiFe film 73, PtMn film 74, CoFe film 75, Ru film 76, CoFe film 77) is formed. Subsequently, a 200 nm thick SiO ₂ film 88 is formed by a CVD method. Thereafter, the surface is flattened by chemical mechanical polishing (CMP) to expose the surface of the Ta film 84. Next, an AlCu film 89 is formed and processed into a readout wiring shape. Thereby, a read wiring (AlCu film 89) is formed. Through these steps, the MTJ element (magnetoresistance memory element 1) can be formed.

Next, the configuration and operation of the memory cell and the magnetoresistive memory device including the memory cell will be described.
FIG. 8 is a circuit diagram showing a configuration example of the memory cell according to the first embodiment of the present invention. In the magnetoresistive effect element 1 of the memory cell 180, a terminal connected to the first magnetic layer 11 (NiFe film 79 in the first embodiment, the same applies hereinafter) as a free layer is a read word line WR for reading. Connected to (AlCu film 89). One of the two terminals connected to the second magnetic layer 13 (Ta film 72 / NiFe film 73 / PtMn film 74 / CoFe film 75 / Ru film 76 / CoFe film 77) as the pinned layer is the source of the transistor TRa. The other is connected to one of the source / drain of the transistor TRb. The other of the sources / drains of the transistors TRa and TRb is connected to the bit lines BLa and BLb for writing, respectively. Further, the gates of the transistors TRa and TRb are connected to the word line WL. However, the configuration of the memory cell 180 is not limited to this example.

FIG. 9 is a block diagram showing a configuration example of a magnetoresistive memory device in which memory cells according to the first embodiment of the present invention are integrated. An MRAM 190 as a magnetoresistive storage device includes a memory array 191 in which a plurality of memory cells 180 are arranged in a matrix. The memory array 191 includes a reference cell 180r that is referred to when reading data, in addition to the memory cell 180 used for data recording described in FIG. In the example of this figure, one column is a reference cell 180r. The structure of the reference cell 180r is the same as that of the memory cell 180. In this case, the MTJ element of the reference cell 180r has an intermediate resistance value R0.5 between the resistance value R0 when data “0” is stored and the resistance value R1 when data “1” is stored. However, two columns can be used as reference cells 180r, one of which can be used as a reference cell 180r having a resistance value R0, and the other column can be used as a reference cell 180r having a resistance value R1. In this case, a resistance value of 0.5 is created from the reference cell 180r having the resistance value R0 and the reference cell 180r having the resistance value R1, and is used for reading. However, the data may be determined by comparison with a reference voltage from the reference voltage generation circuit.

The word line WL and the read word line WR each extend in the X direction. One end of the word line WL is connected to the X-side control circuit 192. The X-side control circuit 192 selects the word line WL connected to the target memory cell 180 as the selected word line WL during the data write operation and the read operation. In the read operation, the read word line WR connected to the target memory cell 180 is selected as the selected read word line WR. Each of the bit lines BLa and BLb extends in the Y direction, and one end thereof is connected to the Y side control circuit 193. The Y-side control circuit 193 selects the bit lines BLa and BLb connected to the target memory cell 180 as the selected bit lines BLa and BLb during the data write operation and the read operation. The control circuit 194 controls the X-side control circuit 192 and the Y-side control circuit 193 during a data write operation and a read operation. In addition, the control circuit 194 determines whether the memory cell is good or bad, stores an address for the defective cell, and controls the memory cell so as not to be used thereafter, or sets a memory cell group including the defective cell or the defective cell to another memory. Control is performed such as replacement with a cell group, correction of data by parity check using the same as a normal memory cell depending on the generation position and number.

Next, a writing method and a reading method in the MRAM shown in FIGS. 6 to 9 will be described.
First, a case where writing is performed will be described. Based on the control of the control circuit 194, the X-side control circuit 192 selects the selected word line WL. As a result, the selected word line WL is pulled up to the “high” level, and the transistors TRa and TRb are turned “ON”. The Y-side control circuit 193 selects the selected bit lines BLa and BLb. Accordingly, one of the selected bit lines BLa and BLb is pulled up to the “high” level, and the other is pulled down to the “Low” level. As a result, a write current Iw flows through the pinned layer 13 that functions as a write wiring. Which of the selected bit lines BLa and BLb is pulled up to a “high” level and which is pulled down to a “Low” level is determined by data to be written in the magnetoresistive effect element 1. That is, it is determined according to the direction of the write current Iw that flows through the pinned layer functioning as the write wiring. The X-side control circuit 192, the Y-side control circuit 193, the word line WL and the read word line WR, the bit lines BLa and BLb, and the control circuit 194 that controls them constitute the writing unit 4.

That is, the write unit 4 writes a write current to the pin layer portion (Ta film 72 / NiFe film 73 / PtMn film 74 / CoFe film 75 / Ru film 76 / CoFe film 77) that functions as a write wiring of the memory cell 180 that writes data. Iw, for example, 1 mA is applied. The magnetic field Hw generated by the write current Iw changes the magnetization direction of the free layer (NiFe film 79) of the MTJ element (CoFe film 75 / Ru film 76 / CoFe film 77, MgO film 78, NiFe film 79). At this time, the direction of magnetization of the free layer is set by the direction of the write current Iw flowing through the write wiring. Thus, desired data “0” and “1” can be written to the MTJ element according to the direction of the write current Iw.

Next, a case where reading is performed will be described. Based on the control of the control circuit 194, the X-side control circuit 192 selects the selected word line WL and the selected read word line WR. As a result, the selected word line WL is pulled up to the “high” level, and the transistors TRa and TRb are turned “ON”. A predetermined read current IR is supplied to the memory cell 180 from the selected read word line WR. On the other hand, the Y-side control circuit 193 selects the selected bit lines BLa and BLb. Accordingly, one of the selected bit lines BLa and BLb is set to the ground level, and the other is set to “open” (floating). At this time, the read current IR flows from the selected read word line WR to one of the selected bit lines BLa and BLb via the MTJ element (the first magnetic layer 11, the tunnel barrier layer 12, and the second magnetic layer 13). The potential of the selected read word line WR through which the read current IR flows or the magnitude of the read current IR depends on a change in the resistance value of the magnetoresistive element 1 due to the magnetoresistive effect. Therefore, compared with the output of the reference bit line BLr of the reference cell 180r through which the read current IR flows (or the reference voltage from the reference voltage generation circuit), the change in resistance value is expressed as a voltage signal or a current signal. For example, high-speed reading can be performed by detection in the X-side control circuit 192 or the Y-side control circuit 193. The X-side control circuit 192, the Y-side control circuit 193, the word line WL and the read word line WR, the bit lines BLa and BLb, and the control circuit 194 for controlling them constitute the evaluation unit 3.

That is, the evaluation unit 3 sets the pin layer portion (Ta film 72 / NiFe film 73 / PtMn film 74 / CoFe film 75 / Ru film 76 / CoFe film 77) to 0 V, and the read wiring as the selective read word line WR ( A read current of 20 μA is applied to the AlCu film 89). When the MTJ element (CoFe film 75 / Ru film 76 / CoFe film 77, MgO film 78, NiFe film 79) has a resistance value of 10 kΩ and 20 kΩ according to data “0” and “1”, it is connected to the pinned layer. When the on-resistance of the selection transistor TRa (or TRb) is 1 kΩ, the potential of the read wiring through the MTJ element is 0.21 V and 0.41 V, respectively. The differential sense amplifier of the evaluation unit 3 can discriminate data by using the potential of the read wiring and the reference potential Vref (or the output potential of the reference cell) set to 0.3V as inputs.

Next, a memory cell screening method will be described. 10A and 10B are conceptual diagrams illustrating a memory cell screening method according to the first embodiment of the present invention. As shown in FIG. 10A, first, the writing unit 4 writes data corresponding to the magnetization direction in the memory cell 180 so that the magnetization is oriented in the upper right direction (45 degrees direction from the + x direction and the + y direction). To do. That is, the write current Iw1 is supplied to the write wiring in the −x direction corresponding to the data to be written. Thereby, when writing is performed satisfactorily, a magnetization M1 oriented in a desired direction (direction of 45 degrees from the + x direction and the + y direction) is generated. At this time, the magnetization M1 is a direction parallel to the easy axis direction (+ side). The data write operation is as described above.

Next, the evaluation unit 3 reads data by evaluating the resistance value of the memory cell 180 to which data has been written. The control unit 5 as the control circuit 194 evaluates based on the data read by the evaluation unit 3 whether the written data is actually written, that is, whether the direction of the magnetization M1 is in a desired direction. As a result, when the written data and the read data do not match, the memory cell 180 is detected as a defective bit and stored. The data read operation is as described above.

Subsequently, based on the control of the control circuit 194, the X-side control circuit 192 selects the selected read word line WR. As a result, a predetermined screening current Is flows through the selected read word line WR passing through the vicinity of the memory cell 180. However, in this case, the screening current Is does not flow into the MTJ element. The magnetic field Hs generated by the screening current Is flowing through the selected read word line WR affects the magnetization of the free layer of the memory cell 180. The X-side control circuit 192, the read word line WR, and the control circuit 194 that controls them constitute the application unit 2.

That is, the application unit 2 applies a screening current Is1 in the + y direction to the selected read word line WR as a read wiring, and applies a leftward (−x direction) magnetic field Hs1 to the free layer. In this case, the direction of the magnetic field Hs1 (−x direction) is inclined 45 degrees from the easy axis direction (− side) of the free layer, and the component is opposite to the magnetization direction of the free layer (45 degrees direction from the + x direction and the + y direction). It becomes the direction with. At this time, in the memory cell 180 having magnetic characteristics as shown in FIGS. 4A and 4B, magnetization reversal occurs due to the magnetic field Hs1 that does not cause magnetization reversal in a normal memory cell.

Thereafter, after the screening current Is1 is stopped, the evaluation unit 3 performs a data read process of the memory cell 180. The control unit 5 detects and stores defective bits. The data read operation and defective bit determination are as described above.

Furthermore, these procedures are performed by applying a magnetic field Hs2 in the reverse direction after writing the magnetization M2 in the reverse direction. That is, as shown in FIG. 10B, first, the writing unit 4 writes data corresponding to the magnetization direction so that the magnetization is directed in the lower left direction (45 ° direction from the −x direction and the −y direction). To the memory cell 180. That is, the write current Iw2 is supplied to the write wiring in the + x direction corresponding to the data to be written. Thereby, when writing is performed satisfactorily, a magnetization M2 oriented in a desired direction (a direction of 45 degrees from the −x direction and the −y direction) is generated. At this time, the magnetization M2 is a direction parallel to the easy axis direction (− side). Next, the evaluation unit 3 reads data by evaluating the resistance value of the memory cell 180 to which data has been written. The control unit 5 evaluates based on the data read by the evaluation unit 3 whether the written data is actually written, that is, whether the direction of the magnetization M2 is in a desired direction. As a result, when the written data and the read data do not match, the memory cell having the MTJ element is detected as a defective bit and stored.

Subsequently, the application unit 2 applies a screening current Is2 in the −y direction to the readout wiring, and applies a magnetic field Hs2 in the right direction (+ x direction) to the free layer. In this case, the direction of the magnetic field Hs2 (+ x direction) is inclined 45 degrees from the easy axis direction (+ side) of the free layer, and is opposite to the magnetization direction of the free layer (45 degrees direction from the -x direction and -y direction). The direction has a component. At this time, in the memory cell 180 having magnetic characteristics as shown in FIGS. 4A and 4B, magnetization reversal occurs due to the magnetic field Hs2 that does not cause magnetization reversal in a normal memory cell. Next, after the screening current Is2 is stopped, the evaluation unit 3 performs a reading process in the same manner as described above to detect and store a defective bit.

The memory cells stored as defective in each of the series of operations described above are not used as memory cells, and the control unit 5 performs control so that alternative memory cells are allocated.

Instead of passing the screening current Is, an external magnetic field Hs having a desired direction and strength may be applied to the entire wafer. FIG. 11 is a plan view showing an example of an external magnetic field according to the first embodiment of the present invention. As shown in the figure, the direction of the external magnetic field Hs has a component opposite to the direction of the magnetization M of the free layer in the in-plane direction of the free layer and is, for example, 5 degrees, 30 degrees, 60 degrees from the easy axis direction. , With an inclination of 85 degrees or the like. You may test by applying one after another about not only one direction but several directions (angle). Although the angle in the film thickness direction of the free layer is also conceivable, in this case, since the film thickness is thin, it may be applied in the direction in the film plane.

These series of operations or a part of time for applying the magnetic field Hs may be performed at a temperature higher than room temperature. This is because an asteroid curve is generally small at high temperatures, and it becomes easier to detect defective cells. In the above example, the reading is performed when the magnetic field Hs is not applied. However, the reading may be performed while the magnetic field Hs is being applied. At this time, a threshold for determining that the controller 5 is defective may be provided for screening separately from the normal reading condition, and may be used by switching between normal reading and screening. By making it possible to adjust the defect determination in this way, it is possible to detect a cell whose resistance is temporarily changed significantly by applying the magnetic field Hs as an abnormal cell even if it is not reversed by the screening process. become.

In the present embodiment, in the screening process, the asteroid curve is shifted by applying the screening magnetic field Hs to cause magnetization reversal or a large resistance change in a memory cell having an abnormal magnetic characteristic. By detecting and discriminating as the magnitude of a value or the difference between a plurality of values, a defective cell can be detected effectively.

(Second embodiment)
Next, a second embodiment of the present invention will be described.
12 and 13 are a sectional view and a plan view, respectively, showing the main part of the memory cell according to the second embodiment of the present invention. However, FIG. 12 is a BB ′ sectional view of FIG. In the memory cell, a Cu film 90, Ta film 91, PtMn film 92, CoPt film 93, Ru film 94, CoPt film 95, MgO film 78, CoPt film 96, Ta film 84, and AlCu film 89 are laminated in this order. .

Unlike the first embodiment, this memory cell is a spin injection type memory cell. The CoPt film 96 is a free layer as the first magnetic layer 11, has a magnetization direction perpendicular to the film surface, and has a circular pattern. The

CoPt films

93 and 95 antiferromagnetically coupled through the Ru film 94 of the conductor layer are the pinned layer 13 as the second magnetic layer 13. The MgO film 78 is the tunnel barrier layer 12 provided between the free layer and the pinned layer. These free layer, pinned layer, and tunnel barrier layer function as an MTJ element (magnetoresistance memory element 1). The AlCu film 89 that is electrically connected to the free layer via the Ta film 84 that is the upper electrode functions as a read current and write current wiring. The Cu film 90 as the lower electrode is electrically connected to the pin layer through the W plug 70 and other wiring for the read current and the write current. The screening wiring 130 is a wiring for a current that induces a screening magnetic field, and is provided at a distance that allows the current-induced magnetic field to be applied to the free layer.

Next, with reference to FIGS. 12A to 12C, description will be made on a manufacturing method of the main part (including the MTJ element) of the memory cell according to the second embodiment of the present invention. First, a transistor including a selection transistor and a wiring including a bit line and a word line are formed on a semiconductor substrate (not shown). Thereafter, a SiO ₂ film 71 as an interlayer insulating film is formed with a film thickness of 300 nm on the semiconductor substrate. A W plug 70 connected to the lower layer wiring is formed at a predetermined position of the SiO ₂ film 71. Next, a Cu film 90 having a thickness of 20 nm, a Ta film 91 having a thickness of 2 nm, an antiferromagnetic PtMn film 92 having a thickness of 20 nm, a CoPt film 93 having a pin layer lower magnetic layer having a thickness of 4 nm, and a thickness of 0.8 nm. Conductor layer Ru film 94 that antiferromagnetically couples the pinned layers of each other, 4 nm thick pinned layer upper

magnetic CoPt film

95, 1 nm thick tunnel insulating

film MgO film

78, 2 nm thick free layer CoPt A film 96 and a Ta film 84 with a thickness of 100 nm are formed by sputtering. The magnetization direction of the pinned layer is set by annealing in a perpendicular magnetic field of about 1 T (Tesla) at 275 ° C. for 2 hours, and exchange coupling with the PtMn film 92. The Ta film 84 is processed by photolithography and RIE. After removing the resist by ashing, the CoPt film 96 is processed into an MTJ shape by a milling method using the Ta film 84 as a mask. The free layer shape of this embodiment is circular as shown in FIG. Next, a SiN film 86 having a thickness of 30 nm is formed by a CVD method to protect the side wall of the CoPt film 96. Subsequently, the MgO film 78 to the Cu film 90 are processed by a photolithography technique and a milling method. Thereafter, a SiN film 87 having a film thickness of 30 nm is formed on the entire surface to protect the side wall of the MTJ. Next, after a 200 nm-thickness SiO ₂ film 88 is formed by a CVD method, it is flattened by CMP to expose the surface of the Ta film 84. Next, an AlCu film 89 is formed and processed into a readout wiring shape. Through these steps, the MTJ element (magnetoresistance memory element 1) can be formed.

Next, the configuration and operation of the memory cell and the magnetoresistive memory device including the memory cell will be described.
First, the configuration example of the memory cell is basically the same as the case of FIG. 8 according to the first embodiment. However, the transistor TRb is unnecessary and is omitted, and the bit line BLb is different from the first embodiment in that it functions as the screening wiring 130 in FIG. 13 independently.

Next, the configuration example of the magnetoresistive memory device including the memory cells is basically the same as that in FIG. 9 according to the first embodiment. However, as described above, the bit line BLb is different from the first embodiment in that it functions as the screening wiring 130.

Next, a writing method and a reading method in the MRAM shown in FIGS. 12 to 13 and FIGS. 8 to 9 will be described.
First, a case where writing is performed will be described. Based on the control of the control circuit 194, the X-side control circuit 192 selects the paired selected word line WL and selected read word line WR. As a result, the selected word line WL is pulled up to the “high” level, and the transistor TRa is turned “ON”. The Y-side control circuit 193 selects the selected bit line BLa. One of the selected read word line WR and the selected bit line BLa is pulled up to the “high” level, and the other is pulled down to the “Low” level. As a result, the write current Iw flows through the first magnetic layer 11 / tunnel barrier layer 12 / second magnetic layer 13. Which of the selected read word line WR and the selected bit line BLa is pulled up to the “high” level and which is pulled down to the “Low” level is determined by data to be written in the magnetoresistive effect element 1. That is, it is determined according to the direction of the write current Iw flowing through the magnetoresistive effect element 1. The X-side control circuit 192, the Y-side control circuit 193, the word line WL and the read word line WR, the bit line BLa, and the control circuit 194 for controlling them constitute the writing unit 4.

That is, the write unit 4 applies a write current Iw, for example, 0.5 mA, between the free layer (CoPt film 96) and the pinned layer (CoPt film 95 / Ru film 94 / CoPt film 93) of the memory cell 180 into which data is written. Shed. Spin electrons are transferred between the free layer and the pinned layer by the write current Iw. Thereby, the magnetization direction of the free layer can be set by the direction of the write current Iw as described above. Thus, desired data “0” and “1” can be written to the MTJ element according to the direction of the write current Iw.

Next, a case where reading is performed will be described. Based on the control of the control circuit 194, the X-side control circuit 192 selects the selected word line WL and the selected read word line WR. As a result, the selected word line WL is pulled up to the “high” level, and the transistor TRa is turned “ON”. A predetermined read current IR is supplied to the memory cell 180 from the selected read word line WR. On the other hand, the Y-side control circuit 193 selects the selected bit line BLa. Thereby, the selected bit line BLa is set to the ground level. At this time, the read current IR flows from the selected read word line WR to the selected bit line BLa via the MTJ element (the first magnetic layer 11, the tunnel barrier layer 12, and the second magnetic layer 13). Compared with the potential of the selected read word line WR or the magnitude of the read current IR and the output of the reference bit line BLr of the reference cell 180r (or the reference voltage from the reference voltage generation circuit), this change in resistance value is a voltage signal. Alternatively, as a current signal, for example, detection at the X-side control circuit 192 or the Y-side control circuit 193 enables high-speed reading. The X-side control circuit 192, the Y-side control circuit 193, the word line WL, the read word line WR, the bit line BLa, and the control circuit 194 that controls them constitute the evaluation unit 3.

That is, the evaluation unit 3 sets the pinned layer 13 (CoPt film 95 / Ru film 94 / CoPt film 93) to 0 V and applies a read current of 20 μA to the read wiring (AlCu film 89) as the selected read word line WR. When the MTJ element (CoPt film 95 / Ru film 94 / CoPt film 93, MgO film 78, CoPt film 96) has a resistance value of 10 kΩ and 20 kΩ respectively by data “0” and “1”, it is connected to the pinned layer. When the on-resistance of the selection transistor TRa is 1 kΩ, the potential of the read wiring through the MTJ element is 0.21 V and 0.41 V, respectively. The differential sense amplifier of the evaluation unit 3 can discriminate data by using the potential of the read wiring and the reference potential Vref (or the output potential of the reference cell) set to 0.3V as inputs.

Next, a memory cell screening method will be described. 14A and 14B are conceptual diagrams illustrating a memory cell screening method according to a second embodiment of the present invention. As shown in FIG. 14A, first, the writing unit 4 writes data corresponding to the magnetization direction to the memory cell 180 so that the magnetization is directed upward (+ z direction) in the figure. That is, the write current Iw1 is supplied to the MTJ element in the −z direction corresponding to the data to be written. Thereby, when writing is performed satisfactorily, magnetization M1 oriented in a desired direction (+ z direction) is generated. At this time, the magnetization M1 is a direction parallel to the easy axis direction (+ side). The data write operation is as described above.

Subsequently, based on the control of the control circuit 194, the Y-side control circuit 193 selects the selected bit line BLb. As a result, a predetermined screening current Is flows through the selected bit line BLb as the screening wiring 130 passing through the vicinity of the memory cell 180. The magnetic field Hs1 generated by the screening current Is flowing through the selected bit line BLb affects the magnetization of the free layer (first magnetic layer 11) of the memory cell 180. The Y-side control circuit 192, the bit line BLb, and the control circuit 194 that controls them constitute the application unit 2.

That is, the application unit 2 causes the screening current Is1 to flow in the −y direction through the selected bit line BLb as the screening wiring 130, and the magnetic field Hs1 having a downward (−z direction) component to the free layer (first magnetic layer 11). Is applied. In this case, the direction of the magnetic field Hs1 (having a −z direction component) is slightly inclined from the easy axis direction (− side) of the free layer, and has a direction opposite to the magnetization direction of the free layer (+ z direction). Become. At this time, in the memory cell 180 having magnetic characteristics as shown in FIGS. 4A and 4B, magnetization reversal occurs due to the magnetic field Hs1 that does not cause magnetization reversal in a normal memory cell.

Furthermore, these procedures are performed by applying a magnetic field Hs2 in the reverse direction after writing the magnetization M2 in the reverse direction. That is, as shown in FIG. 14B, the writing unit 4 first writes data corresponding to the magnetization direction to the memory cell 180 so that the magnetization is directed downward (−z direction) in the figure. That is, the write current Iw2 is supplied to the MTJ element in the + z direction corresponding to the data to be written. Thereby, when writing is performed satisfactorily, magnetization M2 oriented in a desired direction (−z direction) is generated. At this time, the magnetization M2 is a direction parallel to the easy axis direction (− side). Next, the evaluation unit 3 reads data by evaluating the resistance value of the memory cell 180 to which data has been written. The control unit 5 evaluates based on the data read by the evaluation unit 3 whether the written data is actually written, that is, whether the direction of the magnetization M2 is in a desired direction. As a result, when the written data and the read data do not match, the memory cell 180 is detected as a defective bit and stored.

Subsequently, the application unit 2 applies a screening current Is2 in the + y direction to the screening wiring 130, and applies a magnetic field Hs2 having an upward component (+ z direction) to the free layer (first magnetic layer 11). In this case, the direction of the magnetic field Hs2 (having a + z direction component) is slightly inclined from the easy axis direction (+ side) of the free layer 11 and has a component opposite to the magnetization direction of the free layer 11 (−z direction). It becomes the direction. At this time, in the memory cell 180 having magnetic characteristics as shown in FIGS. 4A and 4B, magnetization reversal occurs due to the magnetic field Hs2 that does not cause magnetization reversal in a normal memory cell.

Next, after the screening current Is2 is stopped, the evaluation unit 3 performs a process of reading data from the memory cell 180. The control unit 5 detects and stores defective bits. The data read operation and defective bit determination are as described above.

The memory cells stored as defective in each of the series of operations described above are not used as memory cells, and the control unit 5 performs control so as to allocate alternative memory cells.

Instead of passing the screening current Is, an external magnetic field Hs having a desired direction and strength may be applied to the entire wafer. The magnetization direction has a component opposite to the magnetization direction of the free layer (−z direction or + z direction) and has an inclination of, for example, 5 degrees, 30 degrees, 60 degrees, 85 degrees, etc. from the easy axis direction. To do. Since the difficult axis direction of the present embodiment is a plane (xy plane), the in-plane direction of the free layer of the applied magnetic field Hs can be all 0 ° to 360 °. You may test by applying one after another about not only one direction but several directions (angle). It is clear that the magnetization reversal of the defective cell can be effectively induced when the application of the three angles not in the same plane is performed.

These series of operations or a part of time for applying the magnetic field Hs may be performed at a temperature higher than room temperature. This is because an asteroid curve is generally small at high temperatures, and it becomes easier to detect defective cells. In the above example, the reading is performed when the magnetic field Hs is not applied. However, the reading may be performed while the magnetic field Hs is being applied. At this time, a threshold for determining that the controller 5 is defective may be provided for screening separately from the normal reading condition, and may be used by switching between normal reading and screening. By making it possible to adjust the defect determination in this way, it is possible to detect a cell whose resistance is temporarily changed significantly from a normal cell by application of the magnetic field Hs as an abnormal cell without going through reversal by the screening process. become.

In this embodiment, even in a spin-electron-injection write-type memory cell, in a screening process, a magnetic field reversal or a large resistance change is applied to a memory cell with abnormal magnetic characteristics by applying a screening magnetic field Hs to shift the asteroid curve. By causing this to occur, and detecting and discriminating this, a defective cell can be detected effectively.

(Third embodiment)
Next, a third embodiment of the present invention will be described.
15 and 16 are a cross-sectional view and a plan view, respectively, showing the main part of the memory cell according to the third embodiment of the present invention. 15 is a cross-sectional view taken along the line BB ′ of FIG. The memory cell includes Ta film 100, Pt film 101, CoPt film 93, Ru film 94, CoPt film 95, MgO film 78, CoPt film 96, Ru film 102, PtMn film 103, CoPt film 104, Ta film 83, Ta film. 84 and an AlCu film 89 are laminated in this order.

Unlike the first embodiment, this memory cell is a domain wall motion type memory cell. The CoPt film 96 is a magnetization recording layer as the second magnetic layer 13, has a magnetization direction perpendicular to the film surface, and has a line pattern (cuboid shape). One end of the magnetization recording layer is antiferromagnetically coupled to the PtMn film 103 via the Ru film 102 of the conductor layer to form a first pin region (also referred to as a first magnetization fixed region) 14a. Similarly, the other end of the magnetization recording layer is antiferromagnetically coupled to the CoPt film 104 via the Ru film 102 of the conductor layer to form a second pin region (also referred to as a second magnetization fixed region) 14b. Yes. The magnetization directions of the first magnetization fixed region 14a and the second magnetization fixed region 14b are the -z direction and the + z direction, respectively, and are in antiparallel relation to each other. The magnetization free region 15 (functioning as a free layer) in the center of the magnetization recording layer can take both the −z direction and the + z direction, and stores data according to the magnetization direction. A domain wall is formed at the boundary between the magnetization free region 15 and the magnetization fixed region 14 whose magnetization directions are antiparallel to each other. During the write operation, data is written by moving the domain wall by exchanging spin electrons by passing a write current Iw from one of the first magnetization fixed region 14a and the second magnetization fixed region 14b to the other. The first magnetization fixed region 14 a is connected to the AlCu film 89 as the second wiring through the Ta film 83. The second magnetization fixed region 14 b is connected to another AlCu film 89 as a third wiring via the Ta film 84.

The

CoPt films

93 and 95 antiferromagnetically coupled via the Ru film 94 of the conductor layer are reference layers (functioning as pinned layers) as the first magnetic layer 11. The reference layer is connected to the first wiring (not shown) via the W plug 70. The MgO film 78 is the tunnel barrier layer 12 provided between the magnetization recording layer and the reference layer. The magnetization free region 15 (free layer), reference layer (pinned layer), and tunnel barrier layer of the magnetization recording layer function as an MTJ element (magnetoresistance memory element 1).

Next, with reference to FIGS. 15A to 15C, description will be made on a manufacturing method of the main part (including the MTJ element) of the memory cell according to the third embodiment of the present invention. First, a transistor including a selection transistor and a wiring including a bit line and a word line are formed on a semiconductor substrate (not shown). Thereafter, a SiO ₂ film 71 as an interlayer insulating film is formed with a film thickness of 300 nm on the semiconductor substrate. A W plug 70 connected to the lower layer wiring is formed at a predetermined position of the SiO ₂ film 71. Next, a Ta film 100 having a thickness of 2 nm, a Pt film 101 having a thickness of 20 nm, a CoPt film 93 of a magnetic material having a lower reference layer having a thickness of 4 nm, and a conductor that antiferromagnetically couples the reference layers having a thickness of 0.8 nm. Ru film 94 as a layer, CoPt film 95 as a reference layer upper layer magnetic material with a thickness of 4 nm, tunnel insulating film MgO film 78 with a thickness of 1 nm, free CoPt film 96 with a thickness of 2 nm, Ru film 102 with a thickness of 1 nm, film A PtMn film 103 with a thickness of 30 nm and a Ta film 83 with a thickness of 100 nm are formed by sputtering. After patterning the Ta film 83 and the PtMn film 103 by photolithography and milling, a CoPt film 104 having a thickness of 3 nm and a Ta film 84 having a thickness of 100 nm are respectively formed on the entire surface by sputtering and patterned. Annealing is performed in a film surface vertical direction magnetic field of about 1 T (Tesla) at 275 ° C. for 2 hours, and the magnetization direction of the first pin region (first magnetization fixed region) using the PtMn film 103 is set. Next, a magnetic field is applied in the opposite direction at room temperature, and the magnetization directions of the second pin region (second magnetization fixed region) and the reference layer using the

CoPt films

104, 93, and 95 are set in the opposite directions. Thereby, the magnetization directions of the two pin regions can be set in opposite directions. For this reason, a domain wall is formed in a free layer (magnetization recording layer). Subsequently, the free layer portion is processed and formed using the resist and the pinned layer as a mask. The subsequent steps are the same as in the second embodiment. Through these steps, the MTJ element (magnetoresistance memory element 1) can be formed.

Next, the configuration and operation of the memory cell and the magnetoresistive memory device including the memory cell will be described.
First, the configuration example of the memory cell is basically the same as the case of FIG. 8 according to the first embodiment. However, the transistors TRa and TRb are respectively connected to the first magnetization fixed region 14a and the second magnetization fixed region 14b of the magnetization recording layer, and the read word line WR is connected to the reference layer. In this case, the second wiring (AlCu film 89) connected to the first pin region and the third wiring (AlCu film 89) connected to the second pin region are the bit lines BLa and BLb, respectively. The first wiring connected to the reference layer is the read word line WR.

Next, the configuration example of the magnetoresistive memory device including the memory cells is basically the same as that in FIG. 9 according to the first embodiment.

Next, a writing method and a reading method in the MRAM shown in FIGS. 15 to 16 and FIGS. 8 to 9 will be described.
First, a case where writing is performed will be described. Based on the control of the control circuit 194, the X-side control circuit 192 selects the selected word line WL. As a result, the selected word line WL is pulled up to the “high” level, and the transistors TRa and TRb are turned “ON”. The Y-side control circuit 193 selects the selected bit lines BLa and BLb. Accordingly, one of the selected bit lines BLa and BLb is pulled up to the “high” level, and the other is pulled down to the “Low” level. As a result, the write current Iw flows from one pin region of the magnetization recording layer (second magnetic layer 13) to the other pin region. Which of the selected bit lines BLa and BLb is pulled up to a “high” level and which is pulled down to a “Low” level is determined by data to be written in the magnetoresistive element 1. That is, it is determined according to the direction of the write current Iw flowing through the magnetization recording layer (second magnetic layer 13). The X-side control circuit 192, the Y-side control circuit 193, the word line WL and the read word line WR, the bit lines BLa and BLb, and the control circuit 194 that controls them constitute the writing unit 4.

That is, the writing unit 4 includes two pin regions 14a (PtMn film 103 / Ru film 102 / CoPt film 96) and 14b (CoPt film 104) at both ends of the magnetization recording layer (CoPt film 96) of the memory cell 180 to which data is written. / Ru film 102 / CoPt film 96) is supplied with a write current Iw, for example, 0.5 mA from one to the other. Spin electrons are exchanged in the domain wall portion in the magnetization recording layer by the write current Iw. Thereby, the magnetization direction of the magnetization free region 15 can be set to one of the magnetization directions of the two

pin regions

14a and 14b depending on the direction of the write current Iw flowing in the magnetization recording layer. Thus, desired data “0” and “1” can be written to the MTJ element according to the direction of the write current Iw.

Next, a case where reading is performed will be described. Based on the control of the control circuit 194, the X-side control circuit 192 selects the selected word line WL and the selected read word line WR. As a result, the selected word line WL is pulled up to the “high” level, and the transistors TRa and TRb are turned “ON”. A predetermined read current IR is supplied to the memory cell 180 from the selected read word line WR. On the other hand, the Y-side control circuit 193 selects the selected bit lines BLa and BLb. Accordingly, one of the selected bit lines BLa and BLb is set to the ground level, and the other is set to “open” (floating). At this time, the read current IR flows from the selected read word line WR to one of the selected bit lines BLa and BLb via the MTJ element (the first magnetic layer 11, the tunnel barrier layer 12, and the second magnetic layer 13). The potential of the selected read word line WR through which the read current IR flows or the magnitude of the read current IR depends on a change in the resistance value of the magnetoresistive element 1 due to the magnetoresistive effect. Therefore, compared with the output of the reference bit line BLr of the reference cell 180r through which the read current IR flows (or the reference voltage from the reference voltage generation circuit), the change in resistance value is expressed as a voltage signal or a current signal. For example, the detection can be performed at a high speed by the detection by the X-side control circuit 192 or the Y-side control circuit 193. The X-side control circuit 192, the Y-side control circuit 193, the word line WL and the read word line WR, the bit lines BLa and BLb, and the control circuit 194 for controlling them constitute the evaluation unit 3.

That is, the evaluation unit 3 sets the magnetization recording layer (CoPt film 96) to 0 V via the AlCu film 89 as the selected bit line BLa (or BLb), and the reference layer (CoPt film 93/90) via the selective read word line WR. A read current of 20 μA is applied from the Ru film 94 / CoPt film 95). When MTJ elements (CoPt film 93 / Ru film 94 / CoPt film 95, MgO film 78, CoPt film 96) have resistance values of 10 kΩ and 20 kΩ, respectively, by data “0” and “1”, they are connected to the pin region. When the on-resistance of the selection transistor TRa (or TRb) is 1 kΩ, the potential of the read wiring through the MTJ element is 0.21 V and 0.41 V, respectively. The differential sense amplifier of the evaluation unit 3 can discriminate data by using the potential of the read wiring and the reference potential Vref (or the output potential of the reference cell) set to 0.3V as inputs. However, since the resistance value between the

pin regions

14a and 14b and the reference layer does not change regardless of data, this structure has a feature that the resistance change amount is small.

Next, a memory cell screening method will be described. 17A and 17B are conceptual diagrams showing a memory cell screening method according to a third embodiment of the present invention. As shown in FIG. 17A, first, the writing unit 4 writes data corresponding to the magnetization direction to the memory cell 180 so that the magnetization is directed upward (+ z direction) in the figure. That is, the write current Iw1 is passed through the magnetization free region 15 of the magnetization recording layer (first magnetic layer 11) in the −x direction corresponding to the data to be written. Thereby, when writing is performed satisfactorily, magnetization M1 oriented in a desired direction (+ z direction) is generated. At this time, the magnetization M1 is a direction parallel to the easy axis direction (+ side). The data write operation is as described above.

Subsequently, based on the control of the control circuit 194, the Y-side control circuit 193 selects the selected bit line BLa. As a result, a predetermined screening current Is1 flows through the selected bit line BLa passing through the vicinity of the memory cell 180. The magnetic field Hs1 generated by the screening current Is1 flowing through the selected bit line BLa affects the magnetization of the free layer (magnetization free region 15 (first magnetic layer 11)) of the memory cell 180. The Y-side control circuit 192, the bit line BLa, and the control circuit 194 that controls them constitute the application unit 2.

That is, the application unit 2 causes the screening current Is1 to flow in the −y direction through the selected bit line BLa, and a magnetic field having a downward (−z direction) component in the free layer (magnetization free region 15 (first magnetic layer 11)). Apply Hs1. In this case, the direction of the magnetic field Hs1 (−z direction) is slightly inclined from the easy axis direction (−side) of the free layer, and has a direction opposite to the magnetization direction (+ z direction) of the free layer. At this time, in the memory cell 180 having magnetic characteristics as shown in FIGS. 4A and 4B, magnetization reversal occurs due to the magnetic field Hs1 that does not cause magnetization reversal in a normal memory cell.

Next, after the screening current Is1 is stopped, the evaluation unit 3 performs a data read process for the memory cell 180. The control unit 5 detects and stores defective bits. The data read operation and defective bit determination are as described above.

Furthermore, these procedures are performed by applying a magnetic field Hs2 in the reverse direction after writing the magnetization M2 in the reverse direction. That is, as shown in FIG. 17B, the writing unit 4 first writes data corresponding to the magnetization direction to the memory cell 180 so that the magnetization is directed downward (−z direction) in the figure. That is, the write current Iw2 is passed through the magnetization free region 15 of the magnetization recording layer (first magnetic layer 11) in the + x direction corresponding to the data to be written. Thereby, when writing is performed satisfactorily, magnetization M2 oriented in a desired direction (−z direction) is generated. At this time, the magnetization M2 is a direction parallel to the easy axis direction (− side). Next, the evaluation unit 3 reads data by evaluating the resistance value of the memory cell 180 to which data has been written. The control unit 5 evaluates based on the data read by the evaluation unit 3 whether the written data is actually written, that is, whether the direction of the magnetization M2 is in a desired direction. As a result, when the written data and the read data do not match, the memory cell having the MTJ element is detected as a defective bit and stored.

Subsequently, the application unit 2 supplies a screening current Is2 to the selected bit line BLa in the + y direction, and a magnetic field Hs2 having an upward (+ z direction) component in the free layer (magnetization free region 15 (first magnetic layer 11)). Is applied. In this case, the direction (+ z direction) of the magnetic field Hs2 is slightly inclined from the easy axis direction (+ side) of the free layer, and has a direction opposite to the magnetization direction (−z direction) of the free layer. At this time, in the memory cell 180 having magnetic characteristics as shown in FIGS. 4A and 4B, magnetization reversal occurs due to the magnetic field Hs2 that does not cause magnetization reversal in a normal memory cell. Next, after the screening current Is2 is stopped, the evaluation unit 3 performs a reading process in the same manner as described above to detect and store a defective bit.

In the present embodiment, even in a domain wall motion writing type memory cell by spin electron injection, a screening magnetic field Hs is applied in the screening process to shift the asteroid curve, whereby a memory cell having an abnormal magnetic characteristic is reversed in magnetization or large. By causing a resistance change and detecting and discriminating this, a defective cell can be detected effectively.

Further, the present invention is not limited to the above-described embodiments, and it is obvious that each embodiment can be appropriately changed within the scope of the technical idea of the present invention. Further, the techniques shown in the embodiments can be implemented in combination as long as no contradiction occurs.

As described above, according to the present invention, in the screening process, by applying the screening magnetic field Hs and shifting the asteroid curve, magnetization reversal or large resistance change is caused in a cell having abnormal magnetic characteristics. Thus, it is possible to efficiently detect a cell having abnormal magnetic characteristics. Thereby, a highly reliable magnetoresistive memory device can be realized.

The present invention can also be described as follows. However, the content is not limited.
The screening method for a magnetoresistive storage device is a screening method for a magnetoresistive storage device that includes a first magnetic body and includes a storage element that stores data in the direction of magnetization of the first magnetic body. The method for screening a magnetoresistive storage device includes a step of setting a magnetization direction of the first magnetic body and a direction different from a magnetization easy axis direction and a magnetization difficult axis direction of the first magnetic body, Applying a first magnetic field including a direction component opposite to the direction of magnetization of one magnetic body to the memory element, evaluating a resistance of the memory element, and based on the evaluation result, the memory element Determining whether or not the memory element is defective, and storing and / or setting the storage element determined to be defective so as not to be used.

In the above-described screening method for a magnetoresistive storage device, the first magnetic field may have a directional component of 45 degrees with respect to the easy axis direction greater than the easy axis direction component.

In the magnetoresistive storage device screening method, the first magnetic field may have a direction component of 45 degrees with respect to the easy axis direction larger than a component in the hard axis direction.

In the above-described screening method for a magnetoresistive storage device, the direction of the first magnetic field may be approximately 45 degrees with respect to the easy axis direction.

In the above-described screening method for a magnetoresistive storage device, the direction of the first magnetic field may be approximately 90 degrees with respect to the direction of the second magnetic field that sets the direction of magnetization of the first magnetic body. .

In the magnetoresistive memory device screening method, the step of determining uses, as the evaluation result, a resistance value of the memory element after the application of the first magnetic field or a characteristic value correlated with the resistance value is used. May be.

In the magnetoresistive memory device screening method, the determining step may use, as the evaluation result, a resistance value of the memory element during application of the first magnetic field or a characteristic value correlated with the resistance value. good.

In the magnetoresistive storage device screening method, the determining step includes, as the evaluation result, a resistance value of the storage element before application of the first magnetic field or a characteristic value correlated with the resistance value, or the A characteristic value correlated with the resistance value or resistance value of the memory element after the application of the first magnetic field, and a characteristic value correlated with the resistance value or the resistance value of the memory element during the application of the first magnetic field. And may be used.

In the screening method of the magnetoresistive storage device, the determining step includes a plurality of the resistance values as the evaluation result or a characteristic value correlated with the plurality of resistance values, or a difference between them and a predetermined value. A step of determining whether or not the storage element is defective based on a magnitude relationship with a value may be provided.

In the above-described screening method for a magnetoresistive memory device, the applying step may include a step of raising the temperature of the memory element above room temperature during at least a part of the time during which the first magnetic field is applied.

In the above-described screening method for a magnetoresistive memory device, the step of determining may be performed using a defective cell determining unit during normal reading.

In the screening method of the magnetoresistive memory device, the determining step refers to a determination criterion at the time of screening different from a determination criterion at the time of normal reading, and determines whether or not the storage element is defective May be provided.

In the above-described screening method for a magnetoresistive memory device, the applying step includes a step of applying a plurality of the first magnetic fields to the memory element from a plurality of directions. The step of evaluating includes a step of evaluating a resistance of the memory element with respect to the plurality of first magnetic fields. The step of determining may include a step of determining whether or not the storage element is defective based on the plurality of evaluation results.

In the above-described screening method for a magnetoresistive storage device, the application step, the evaluation step, and the discrimination step may be performed on each of a plurality of magnetization state magnetism possessed by the first magnetic body.

A magnetoresistive storage device according to the present invention includes a first magnetic body, a storage element that stores data in a magnetization direction of the first magnetic body, and a write that sets a magnetization direction of the first magnetic body And a first magnetic field including a direction component opposite to a magnetization direction of the first magnetic body and having a direction component opposite to the magnetization direction of the first magnetic body. An application unit for applying to the storage element, an evaluation unit for evaluating the resistance of the storage element, and determining whether or not the storage element is defective based on the evaluation result, and using the storage element determined to be defective And a control unit for storing and / or setting so as not to be performed.

This application is based on Japanese Patent Application No. 2009-109590 filed on April 28, 2009, and claims the benefit of the priority of the application, the disclosure of that application should be cited Is incorporated here as it is.

Although the present invention has been described above with reference to the embodiment, the present invention is not limited to the above embodiment. Various changes that can be understood by those skilled in the art can be made to the configuration and details of the present invention within the scope of the present invention.

Claims

A screening method for a magnetoresistive storage device including a first magnetic body and comprising a storage element that stores data in the direction of magnetization of the first magnetic body,
Setting the direction of magnetization of the first magnetic body;
A first magnetic field having a direction component different from an easy magnetization axis direction and a hard magnetization axis direction of the first magnetic body and having a direction component opposite to the magnetization direction of the first magnetic body is applied to the storage element. Applying, and
Evaluating the resistance of the memory element;
Determining whether or not the memory element is defective based on the evaluation result;
A method of screening a magnetoresistive storage device, comprising: storing and / or setting the storage element determined to be defective so as not to be used.
The method for screening a magnetoresistive storage device according to claim 1,
A screening method for a magnetoresistive storage device, wherein the first magnetic field has a direction component of 45 degrees with respect to the easy axis direction of magnetization greater than a component of the easy axis direction.
In the screening method of the magnetoresistive memory device according to claim 1 or 2,
A screening method for a magnetoresistive storage device, wherein the first magnetic field has a direction component of 45 degrees with respect to the easy axis direction of magnetization greater than a component of the hard axis direction.
In the screening method of the magnetoresistive memory device according to any one of claims 1 to 3,
The method for screening a magnetoresistive storage device, wherein the direction of the first magnetic field is a direction of approximately 45 degrees with respect to the easy axis direction.
In the screening method of the magnetoresistive memory device according to any one of claims 1 to 4,
The method of screening a magnetoresistive storage device, wherein the direction of the first magnetic field is approximately 90 degrees with respect to the direction of the second magnetic field that sets the direction of magnetization of the first magnetic body.
In the screening method of the magnetoresistive memory device according to any one of claims 1 to 5,
The step of determining includes
A screening method for a magnetoresistive memory device, wherein the evaluation result uses a resistance value of the memory element after the application of the first magnetic field or a characteristic value correlated with the resistance value.
In the screening method of the magnetoresistive memory device according to any one of claims 1 to 5,
The step of determining includes
A screening method for a magnetoresistive memory device, wherein the evaluation result uses a resistance value of the memory element during application of the first magnetic field or a characteristic value correlated with the resistance value.
In the screening method of the magnetoresistive memory device according to any one of claims 1 to 5,
The step of determining includes
As the evaluation result, a resistance value of the memory element before application of the first magnetic field or a characteristic value correlated with the resistance value, or a resistance value or resistance of the memory element after completion of application of the first magnetic field A screening method for a magnetoresistive memory device, using a characteristic value correlated with a value and a resistance value of the memory element during application of the first magnetic field or a characteristic value correlated with the resistance value.
In the screening method of the magnetoresistive memory device according to any one of claims 6 to 8,
The step of determining includes
Whether or not the storage element is defective based on the magnitude of the plurality of resistance values or the characteristic values correlated with the plurality of resistance values as the evaluation result, or on the magnitude relationship between the difference and a predetermined value A method for screening a magnetoresistive storage device, comprising the step of:
In the screening method of the magnetoresistive memory device according to any one of claims 1 to 9,
The applying step includes:
A method for screening a magnetoresistive storage device, comprising the step of raising the temperature of the storage element above room temperature during at least a part of time during which the first magnetic field is applied.
In the screening method of the magnetoresistive memory device according to any one of claims 1 to 10,
The step of determining includes
A method for screening a magnetoresistive memory device, wherein the discrimination is performed using a defective cell discrimination unit during normal reading.
In the screening method of the magnetoresistive memory device according to any one of claims 1 to 11,
The step of determining includes
A method for screening a magnetoresistive storage device, comprising: determining whether or not the storage element is defective by referring to a determination criterion at the time of screening different from a determination criterion at the time of normal reading.
In the screening method of the magnetoresistive memory device according to any one of claims 1 to 12,
The applying step includes:
Applying a plurality of the first magnetic fields from a plurality of directions to the storage element,
The step of evaluating comprises
Evaluating the resistance of the memory element with respect to the plurality of first magnetic fields;
The step of determining includes
A method for screening a magnetoresistive storage device, comprising: determining whether or not the storage element is defective based on the plurality of evaluation results.
The method of screening a magnetoresistive memory device according to claim 13,
A method for screening a magnetoresistive storage device, wherein the applying step, the evaluating step, and the determining step are performed on each of a plurality of magnetization state magnetisms of the first magnetic body.
A storage element including a first magnetic body and storing data in a magnetization direction of the first magnetic body;
A writing unit for setting the direction of magnetization of the first magnetic body;
A first magnetic field having a direction component different from an easy magnetization axis direction and a hard magnetization axis direction of the first magnetic body and having a direction component opposite to the magnetization direction of the first magnetic body is applied to the storage element. An application unit to apply,
An evaluation unit for evaluating the resistance of the memory element;
A magnetoresistive storage device comprising: a control unit that determines whether or not the storage element is defective based on the evaluation result, and stores and / or sets the storage element determined not to be used.