WO2004081943A1 - 磁気メモリデバイスおよびその読出方法 - Google Patents
磁気メモリデバイスおよびその読出方法 Download PDFInfo
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- WO2004081943A1 WO2004081943A1 PCT/JP2004/003362 JP2004003362W WO2004081943A1 WO 2004081943 A1 WO2004081943 A1 WO 2004081943A1 JP 2004003362 W JP2004003362 W JP 2004003362W WO 2004081943 A1 WO2004081943 A1 WO 2004081943A1
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- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10B—ELECTRONIC MEMORY DEVICES
- H10B61/00—Magnetic memory devices, e.g. magnetoresistive RAM [MRAM] devices
- H10B61/20—Magnetic memory devices, e.g. magnetoresistive RAM [MRAM] devices comprising components having three or more electrodes, e.g. transistors
- H10B61/22—Magnetic memory devices, e.g. magnetoresistive RAM [MRAM] devices comprising components having three or more electrodes, e.g. transistors of the field-effect transistor [FET] type
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B82—NANOTECHNOLOGY
- B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
- B82Y10/00—Nanotechnology for information processing, storage or transmission, e.g. quantum computing or single electron logic
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- G—PHYSICS
- G11—INFORMATION STORAGE
- G11C—STATIC STORES
- G11C11/00—Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor
- G11C11/02—Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor using magnetic elements
- G11C11/14—Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor using magnetic elements using thin-film elements
- G11C11/15—Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor using magnetic elements using thin-film elements using multiple magnetic layers
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- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10B—ELECTRONIC MEMORY DEVICES
- H10B61/00—Magnetic memory devices, e.g. magnetoresistive RAM [MRAM] devices
- H10B61/10—Magnetic memory devices, e.g. magnetoresistive RAM [MRAM] devices comprising components having two electrodes, e.g. diodes or MIM elements
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- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10B—ELECTRONIC MEMORY DEVICES
- H10B61/00—Magnetic memory devices, e.g. magnetoresistive RAM [MRAM] devices
- H10B61/20—Magnetic memory devices, e.g. magnetoresistive RAM [MRAM] devices comprising components having three or more electrodes, e.g. transistors
Definitions
- the present invention relates to a magnetic memory device including a magnetoresistive element and a reading method thereof.
- volatile memories such as DRAM (Dynamic Random Access Memory) and SRAM (Static RAM) have been used as general-purpose memories used in information processing devices such as computers and mobile communication devices. These volatile memories lose all information unless they are constantly powered. Therefore, it is necessary to provide a means for storing information, that is, a nonvolatile memory, and a flash EEPROM or a hard disk device is used. In these non-volatile memories, speeding up access has become an important issue as data processing speeds up. Furthermore, with the rapid spread of portable information devices and the advancement of their performance, the development of information devices aiming at so-called “upikitas computing”, which enables information processing to be performed at any time and at any place, is rapidly progressing. As a key device in the development of such equipment, the development of high-speed nonvolatile memory is strongly required.
- MRAM Magnetic Random Access Memory
- MRAM Magnetic Random Access Memory
- individual memory cells arranged in a matrix are composed of magnetic elements with two ferromagnetic layers.
- the information is stored by making the magnetization of the ferromagnetic layer of the element parallel or anti-parallel along the easy axis, corresponding to the binary information of “0” and “1”.
- the resistance of a magnetic element in a specific direction differs depending on whether the magnetization direction of the ferromagnetic layer is parallel or antiparallel. Therefore, information is read from the memory cell by detecting a difference in resistance corresponding to the information as a change in current or voltage.
- MRAM requires a resistance change in order to perform stable writing and reading. It is important that the rate be as large as possible.
- GMR giant magneto-resistive
- GMR—MRAM is available in two types: coercive force difference type (Pseudo Spin Valve type) and exchange bias type (Spin Valve type).
- a Pseudo Spin Valve type MRAM is composed of a GMR element composed of two ferromagnetic layers and a non-magnetic layer sandwiched between them, and uses the difference in coercive force between the two ferromagnetic layers to store information. This is for writing / reading.
- two ferromagnetic layers are composed of a fixed layer having a fixed magnetization direction and a free layer whose magnetization direction can be changed by an external magnetic field.
- the magnetization of the fixed layer is stably fixed by antiferromagnetic coupling with the antiferromagnetic layer with the nonmagnetic layer interposed therebetween.
- the resistance change rate of each type of GMR element is about 6 to 8% for a Pseudo Spin Valve type element with a (NiFe / Cu / Co) laminated structure, and (PtMn / Co It is about 10% even for SpinValve-type devices with a multilayer structure of FeCu / CoFe). For this reason, readouts that use the difference in resistance as the difference between current and voltage have not yet been obtained, and it is said that it is difficult to improve storage capacity and access speed.
- TMR-MRAM tunneling magneto-resistive
- TMR-MRAM tunneling magneto-resistive
- TMR-MRAM since the resistance of the TMR element is high, it is said that it is easy to achieve matching when combined with a semiconductor device such as a metal oxide semiconductor field effect transistor (MOSFET). From the above advantages, TMR-MRAM is easier to achieve higher output than GMR-MRAM, and is expected to improve storage capacity and access speed.
- a semiconductor device such as a metal oxide semiconductor field effect transistor (MOSFET).
- MOSFET metal oxide semiconductor field effect transistor
- TMR-MRAM information is written by changing the magnetization direction of the ferromagnetic layer using a current magnetic field induced by a current flowing through a conductor.
- the binary information is stored corresponding to the relative magnetization direction (parallel or antiparallel) between the ferromagnetic layers.
- a method is adopted in which a current is applied to the insulating layer in a direction perpendicular to the layer surface to detect a tunnel current value or a tunnel resistance. This difference in the relative magnetization direction (parallel or antiparallel) between the ferromagnetic layers appears as a difference in the output current value or cell resistance value.
- the cell array structure it is proposed to connect multiple TMR elements in parallel on the data line and arrange semiconductor elements for selection corresponding to each TMR element, or to arrange each semiconductor element for each data line.
- semiconductor element a MOS FET, a diode formed by short-circuiting the gate and drain of the FET, a pn junction diode, a Schottky diode, and the like are used.
- TMR elements are arranged in a matrix using row data lines and column data lines, and a selection transistor is arranged for each data line.
- the structure that has the best characteristics in terms of power consumption efficiency during readout is the structure in which a semiconductor device for selection is arranged for each TMR device.
- the noise caused by the variation cannot be ignored.
- the S / N ratio of the output voltage of the memory cell is only a few dB. there is a possibility.
- a commonly used method is to compare the output voltage V of one selected memory cell with a reference voltage Vref and differentially amplify the difference voltage Vsig.
- the purpose of differential amplification is, firstly, to remove noise generated in the data line pair to which the storage cell is connected, and secondly, due to the characteristic variation of the semiconductor element for driving the sense line or for selecting the cell. It is to remove the offset of the force voltage.
- the circuit for generating the reference voltage Vrei is realized by a circuit using a dummy cell or a semiconductor element.Since there is a variation in element characteristics between this circuit and the storage cell, the offset of the output voltage is completely removed. It is impossible in principle.
- a storage cell is constituted by a pair of TMR elements and the outputs from the elements forming the pair are differentially amplified.
- writing is performed such that the magnetization directions of the magneto-sensitive layers of the paired TMR elements are always antiparallel to each other. That is, in one element, writing is performed complementarily so that the magnetization of the free layer and the magnetization of the fixed layer are parallel to each other, and the magnetization of both layers is antiparallel to each other, and the output of the two elements is compared.
- dynamic amplification and reading common-mode noise is removed and the SZN ratio is improved.
- Such a differential amplification type circuit configuration is disclosed in Japanese Patent Application Laid-Open Nos. 2001-236781, 2001-266567 and ISSCC 2000 Digest paper TA7.2.
- the first TMR constituting a memory cell is disclosed.
- the element and the second TMR element are individually connected at one end to a pair of first and second data lines, and at the other end to the bit line via the same cell selection semiconductor element. It has become.
- the word line is connected to the cell selection semiconductor element.
- Information is read by applying a potential difference between the bit line and the first and second data lines while maintaining the first data line and the second data line at the same potential. This is done by outputting the difference value of the amount of current flowing through the data line.
- the second TMR element has one end connected separately to the pair of first and second data lines, and the other end connected to the bit line via the same cell selection semiconductor element. Despite this configuration, the reduction in the SZN ratio of the output signal due to the variation in resistance has not yet been resolved.
- a large number of TMR elements are connected to the first and second data lines, and a number of cell selection semiconductor elements in the bit column direction are connected to the third bit line, so that the number of memory cells is reduced. Since a matrix is configured, in order to obtain a stable read signal output, the resistance variation between the TMR elements connected to each data line and the selection semiconductor element connected to the same bit line It is necessary to sufficiently suppress the variation in characteristics between them. However, the readout method of giving the equal potential voltage difference between the first data line and the second data line cannot in principle suppress the above variation. Therefore, it was extremely difficult to take thorough countermeasures against noise due to these variations.
- An object of the present invention is to provide a magnetic memory device and a method for reading a magnetic memory device which are excellent in operation stability such as read accuracy and can perform highly reliable read operation by using power.
- a magnetic memory device includes a plurality of magnetoresistive elements each having a magneto-sensitive layer whose magnetization direction changes according to an external magnetic field, and is configured such that one storage cell includes a pair of magnetoresistive elements.
- a memory device comprising: a pair of read lines provided to extend along the first direction for each pair of magnetoresistive elements and supplying a read current to the pair of magnetoresistive elements; and a pair of magnetoresistive elements. The sum of a pair of read currents that are provided in common for a ground side read line that guides the read current flowing through the effect element to the ground and a plurality of ground side read lines and that flow through a pair of magnetoresistive elements in one storage cell. And a read circuit for reading information from a memory cell based on a difference between a pair of read currents.
- “external magnetic field” means a magnetic field generated by a write current.
- the constant current circuit provided in common for a plurality of ground-side read lines for guiding the read current flowing through the pair of magnetoresistive elements to the ground causes the memory cells in each memory cell to have different functions.
- the sum of the pair of read currents flowing through the pair of magnetoresistive elements is made constant. For this reason, the read current is controlled so that the sum of the pair of read currents always flows by a fixed amount, and the variation in the output current among the memory cells is reduced.
- the constant current circuit may be provided between the plurality of magnetoresistive elements and the ground, and may be configured using a band gap reference.
- the constant current circuit includes a current control transistor, a diode connected between the base of the current control transistor and ground, and a current control transistor between the emitter and the ground of the current control transistor. It is desirable to include a connected current control resistor.
- the magnetic memory device of the present invention further includes a pair of rectifying elements provided on a current path of a read current supplied to the pair of magnetoresistive elements.
- a pair of rectifying elements provided on a current path of a read current supplied to the pair of magnetoresistive elements.
- the pair of rectifying elements is connected between the pair of magnetoresistive elements and the ground side read line. May be provided between the readout line pair and the pair of magnetoresistive elements.
- the rectifying element is a Schottky diode or a PN junction diode
- the rectifying element is disposed between the constant current circuit and each of the plurality of ground-side read lines, for example, orthogonal to the first direction which is the bit string direction of the magnetic memory device.
- a first semiconductor switch for selecting any one of a plurality of second direction memory cell groups arranged along a second direction which is a row direction of the memory cells may be provided.
- a rectifying element that also functions as a second semiconductor switch for selecting one of a plurality of second-direction storage cell groups arranged in the second direction is used. May be present.
- the second semiconductor switch a bipolar transistor or an MS transistor is suitable.
- This magnetic memory device takes advantage of the fact that the current value when a current flows in the direction perpendicular to these layers depends on the relative magnetization direction of the magneto-sensitive layer of the magnetoresistive element forming a pair. Can be read. Regarding information reading, it is preferable that a read current is supplied to each of the pair of magnetoresistive elements from each read line in the read line pair, and information is read from the memory cell based on a difference between the pair of read currents. . According to this method, since the read current is differentially output, noise generated in each read line in the read line pair and an offset component included in the output value of each magnetoresistive element are canceled and removed.
- the “rectifying element” of the present invention refers to an element that allows a current to pass only in one direction and blocks the current from flowing in the opposite direction.
- the “current path” refers to the entire path that the read current follows in order to flow into the magnetoresistive element, passes through the magnetoresistive element, and flows out.
- the rectifying element has a rectifying function of causing a current to flow in the ground direction (ground-side readout line side) on the current path. This rectifier prevents current from sneaking into each storage cell to be read from another storage cell connected to the common ground-side read line.
- the magnetic memory device of the present invention is further provided for each of the plurality of first-direction storage cell groups arranged along the first direction, and includes a plurality of ground-side read lines for each of the first-direction storage cell groups.
- One of the plurality of first-direction storage cell groups which is provided between each of the plurality of shared read lines and the plurality of shared read lines and the constant current circuit; May be provided.
- the selection switch is controlled to open and close by a selection signal for selecting which of the first direction storage cell groups the read current flows.
- the magnetic memory device of the present invention further includes a plurality of first write lines, and a plurality of second write lines extending so as to intersect with the plurality of first write lines, respectively.
- a magnetoresistive element including a magneto-sensitive layer whose magnetization direction is changed by an external magnetic field, wherein the magneto-resistance effect element is configured to allow a current to flow in a direction perpendicular to the lamination plane; and a lamination on one side of the lamination. It is preferable to include an annular magnetic layer arranged so that the direction along the plane is the axial direction and configured to be penetrated by the first and second write lines.
- the “external magnetic field” means a magnetic field generated by a current flowing through the first and second write lines, or a return magnetic field generated in the annular magnetic layer.
- the “annular” of the “annular magnetic layer” means that at least the first and second write lines that penetrate the inside of the annular magnetic layer completely and magnetically and electrically continuously surround each other. And a cross section in a direction crossing the first or second write line is closed. Therefore, the annular magnetic layer allows the insulator to be contained as long as it is magnetically and electrically continuous. It is a matter of course that an oxide film generated in the manufacturing process may be included.
- the “axial direction” refers to the opening direction when focusing on the single annular magnetic layer, that is, the extending direction of the first and second write lines penetrating therethrough.
- disposed on one surface side of the laminated body means that the annular magnetic layer is disposed separately from the laminated body on one side of the laminated body. This is intended to include a case where the magnetic layer is provided so as to include a part of the laminate.
- one unit information is stored by using two magnetoresistive elements capable of storing one unit information independently. Further, each of the magnetoresistive elements forms a closed magnetic path in the annular magnetic layer by passing a current through the first and second write lines. As a result, a current flowing in a direction perpendicular to the stacking plane of the stack flows from the free layer to the annular magnetic layer.
- the magnetic memory device further comprises a pair of magnetoresistive effect elements formed by a magnetic field generated by a current flowing through both the first and second write lines passing through the annular magnetic layer. It is desirable that the magnetization direction of each magneto-sensitive layer in step (1) changes so as to be antiparallel to each other, and information is stored in the memory cell.
- “the magnetization directions are antiparallel to each other” means that the magnetization directions of each other, that is, the angle formed by the average magnetization direction in the magnetic layer is exactly 180 degrees, This also includes the case where the angle between the magnetization directions deviates from each other by a predetermined angle from 180 degrees due to an error or the like that occurs because the axis is not completely uniaxial.
- “Information” is generally a binary value represented by “0”, “1”, or “High” or “Low” depending on the current or voltage value in the input / output signal to the magnetic memory device. Refers to information.
- information is stored in a pair of magnetoresistive elements in a state where the magnetization directions of the magnetosensitive layers are antiparallel to each other.
- one of the pair of magneto-sensitive layers in the pair of magneto-resistance effect elements is magnetized in the first magnetization direction and the other is magnetized in the second magnetization direction which is antiparallel to the first magnetization direction.
- a second state in which one of the pair of magnetosensitive layers is magnetized in the second magnetization direction and the other is magnetized in the first magnetization direction. It is desirable that information be stored in the storage cell in accordance with the second state.
- the magnetizations of both magneto-sensitive layers of the pair of magnetoresistive elements face each other or are opposite to each other. The binary information corresponds to this.
- a reading method of a magnetic memory device includes a plurality of magnetoresistive elements each having a magneto-sensitive layer whose magnetization direction changes by an external magnetic field, and one storage cell includes a pair of magnetoresistive elements.
- a read current is supplied to a pair of magnetoresistive elements via a read line pair extending along the first direction, and a pair of magnetoresistive elements is provided.
- the read current flowing through the storage element is led to ground via the ground-side read line, and a constant current circuit is provided in common for a plurality of ground-side read lines.
- the sum of a pair of read currents flowing through the memory cell is made constant, and information is read from the memory cell based on the difference between the pair of read currents. For this reason, the read current is controlled such that the sum of the pair of read currents always flows by a fixed amount, and the variation in the output current among the memory cells is reduced.
- FIG. 1 is a block diagram showing an overall configuration of a magnetic memory device according to a first embodiment of the present invention.
- FIG. 2 is a diagram showing a configuration of a storage cell and a read circuit of the magnetic memory device shown in FIG.
- FIG. 3 is a circuit diagram for explaining the configuration of the entire sense amplifier in the read circuit shown in FIG.
- FIG. 4 is a configuration diagram showing a state of mounting of the memory cell group shown in FIG. 1 around a Y-direction drive circuit unit.
- FIG. 5 is a diagram showing an actual circuit arrangement of the Y-direction drive circuit section shown in FIG.
- FIG. 6 is a pattern layout diagram of a sense amplifier area in the unit drive circuit shown in FIG.
- FIG. 7 is a cross-sectional view showing a specific configuration of the memory cell shown in FIG.
- FIG. 8 is a diagram showing a storage cell of the magnetic memory device shown in FIG. 1 and a wiring structure for writing the same.
- FIG. 9 is a diagram showing an equivalent circuit of the storage cell shown in FIG.
- FIG. 10A and FIG. 10B are diagrams for explaining a method of storing information in the storage cell shown in FIG.
- FIG. 11 is a diagram for explaining a method of writing information in the storage cell shown in FIG.
- FIG. 12 is a diagram for explaining the principle of reading operation from a storage cell in the magnetic memory device shown in FIG.
- FIG. 13 is a circuit diagram for explaining a comparative example of the read circuit shown in FIG.
- FIG. 14 is a diagram showing a rectifying element according to a modification of the backflow preventing diode in the readout circuit shown in FIG. 2 and an arrangement thereof.
- FIG. 15 is a diagram showing a rectifying element according to a modification of the backflow prevention diode in the readout circuit shown in FIG. 2 and its arrangement.
- FIG. 16 is a diagram showing an arrangement according to a modification of the backflow prevention diode in the read circuit shown in FIG.
- FIG. 17 is a diagram showing a rectifying element according to a modification of the backflow prevention diode in the readout circuit shown in FIG. 2 and an arrangement thereof.
- FIG. 18 is a diagram showing a rectifying element according to a modification of the backflow prevention diode in the readout circuit shown in FIG. 2 and an arrangement thereof.
- FIG. 19 is a diagram of a read circuit according to an embodiment of the magnetic memory device of the present invention.
- FIG. 20 is a diagram showing the relationship between the bit decode voltage in the read circuit shown in FIG. 19 and the measured current values at the measurement points P1 to P4.
- FIG. 21 is a diagram showing the relationship between the pit decode voltage and the measured current values at the measurement points P1 to P9 in the read circuit shown in FIG.
- FIG. 22 is a diagram showing the relationship between the resistance change of each storage cell of the magnetoresistive element in the read circuit shown in FIG. 19 and the output voltage.
- FIG. 23 is an equivalent circuit diagram for explaining a read circuit of a comparative example with respect to the embodiment shown in FIG.
- FIG. 24 is a diagram showing a relationship between a resistance variation between a pair of magnetoresistive elements and an output voltage in the read circuit shown in FIG.
- FIG. 25 is a diagram showing a configuration of a storage cell and a read circuit of the magnetic memory device according to the second embodiment of the present invention.
- FIG. 26 is a configuration diagram for explaining a modification 2-1 in the readout circuit shown in FIG.
- FIG. 27 illustrates a modification 2-2 of the readout circuit shown in FIG. 25.
- FIG. 28 is a configuration diagram for describing Modification 2-3 of the readout circuit shown in FIG.
- FIG. 29 is a block diagram for explaining a modified example 2-4 of the readout circuit shown in FIG.
- FIG. 30 is a partial cross-sectional view showing a cross-sectional configuration around a memory cell corresponding to the read circuit shown in FIG.
- FIG. 31 is a configuration diagram for explaining a modification 2-5 in the readout circuit shown in FIG. 25.
- FIG. 32 is a configuration diagram for explaining Modifications 2-6 in the readout circuit shown in FIG. 25.
- FIG. 1 is a diagram showing an overall configuration of a magnetic memory device according to one embodiment of the present invention.
- This magnetic memory device is an MRAM embodied as a so-called semiconductor memory chip, and includes an address buffer 101, a data buffer 102, a control logic unit 103, a memory cell group 104, a Y-direction drive circuit unit.
- the main components are 106 and the X-direction drive circuit 108.
- the memory cell group 104 is arranged in a wide area in the center of the silicon chip, and circuit components and wiring such as the drive circuit sections 106 and 108 are arranged in a small area around the silicon memory chip. It has been implemented. '
- the storage cell group 104 has a large number of storage cells 12 arranged in a word line direction (X direction) and a bit line direction (Y direction) so as to form a matrix as a whole.
- Each memory cell 12 is a minimum unit for storing data, and bit data of “1” and “0” is stored.
- each column of the storage cells 12 in the storage cell group 104 is referred to as a word string X n , and each row is referred to as a bit string Y nie.
- the ⁇ direction drive circuit section 106 is ⁇ direction address decoder 106 ⁇ , And a Y-direction current drive 106 C for writing, each of which has a bit string ⁇ ⁇ ( ⁇ ,, ⁇ 2 ,... ⁇ ) Each is connected.
- the X-direction drive circuit section 108 is composed of an X-direction address decoder 108 ⁇ , a constant current circuit for reading 108 ⁇ , and an X-direction current drive 108 C for writing, each of which is a memory cell group.
- word sequence chi "of the memory cells 1 2 (X,, chi 2, ⁇ ⁇ ⁇ ) are connected to each.
- memory cell Le 1 2 is one, as shown , X-direction address decoder 1 08 a, Upsilon direction address decoder 1 0 word direction and the bit direction input from 6 Alpha Adoresu ( ⁇ ", ⁇ ⁇ ) is selected uniquely by.
- the address buffer 101 has external address input terminals AO to ⁇ 20, and has a 7-way address line 105, 107, and a 4-way address decoder 106 A, an X-direction address decoder 108 It is connected to the.
- the address buffer 101 receives a selection signal for selecting the memory cell 12 from the external address input terminals A0 to A20, and the Y and X direction address decoders 106A and 108A in the internal buffer amplifier. (Hereinafter, if there is no need to distinguish between the two, they are simply referred to as address decoders 106A and 108A), and they have the function of amplifying to the required voltage level.
- the amplified selection signal is divided into two selection signals in the word column direction (X direction) and the bit column direction (Y direction) of the memory cell 12, and the signals are respectively applied to the address decoders 106 A and 108 A.
- the address buffer 101 When the magnetic memory device has a plurality of storage cell groups 104, the address buffer 101 also has an address signal for selecting one storage cell group 104 from the plurality of storage cell groups 104. It is also input.
- the bit string direction (Y direction) corresponds to the “first direction” in the present invention
- the word string direction (X direction) corresponds to the “second direction” in the present invention.
- the data buffer 102 includes external data terminals D0 to D7 for exchanging digital data signals with the outside, and is connected to the control logic unit 103 by a control signal line 113.
- the data buffer 102A is composed of an input buffer 102A and an output buffer 102B. It operates according to these control signals.
- the input buffer 102 is connected to the Y-direction current drive 106 C and the X-direction current drive 108 C via the write data bus 110, 111, respectively.
- the data signals are captured from the evening terminals D0 to D7, and the data signals are amplified to the required voltage level by the internal buffer amplifier. If there is no need to distinguish between them, they are simply abbreviated as current drive 106C and 108C).
- the output buffer 102B is connected to the sense amplifier 106B via the read data path 112, and is input from the sense amplifier 106B at the time of memory read by using the internal buffer amplifier. It has a function of outputting a read data signal to external data terminals D 0 to D 7 with low impedance.
- the control logic section 103 includes an input terminal CS and an input terminal WE, and is connected to the data buffer 102 via a control signal line 113.
- the control logic section 103 controls the operation of the memory cell group 104. From the input terminal CS, a signal (chip select; whether or not to make the write Z read operation of the magnetic memory device active) is provided. CS) is input. Also, a write enable signal (write enable; WE) for switching between writing and reading is input from the input terminal WE.
- the control logic section 103 converts the signal voltage taken from the input terminal CS and the input terminal WE by the internal buffer amplifier into the Y-direction and X-direction drive circuit sections 106 and 108 (hereinafter, it is necessary to distinguish between the two). If not, they are simply abbreviated as drive circuit sections 106 and 108).
- FIG. 2 is a configuration diagram of a circuit system including a memory cell group and a readout circuit.
- This readout circuit system is a differential amplification type in which a memory cell 12 is composed of a pair of magnetoresistive elements 12A and 12B.
- the reading of information from each memory cell 12 is performed based on the sensing current flowing through each of the magnetoresistive elements 12 A and 12 B (the sensing bit decode lines 21 A and 2 IB (described later)).
- the difference between the currents flowing into the elements 12 A and 12 B and flowing out to the common sense word decode line 31 (described later) The value is output as output.
- the pair of magnetoresistive elements 12A and 12B is a specific example corresponding to the "pair of magnetoresistive elements" in the present invention.
- the storage cell 12 for each bit string Y thoroughof the storage cell group 104 and a part of the readout circuit including the sense amplifier 106 06 are a bit direction unit readout circuit which is a repetition unit of the readout circuit.
- 80 (..., 80 ⁇ , 80 n ⁇ 1 , ⁇ ), which are arranged in parallel in the bit string direction Bit direction unit readout circuit 80 (..., 80 ⁇ , 80 ⁇ + 1 , )
- the bit decoder 106 A via the bit decode line 20 ( ⁇ , 20 20, 20 ⁇ + 1 , ⁇ )
- the output buffer 102 B It is connected via the read data bus 112.
- bit direction unit readout circuit 80 since there is not enough space and the entire bit direction unit readout circuit 80 cannot be drawn, it is represented by two columns. The same applies to the memory cell group 104, which is represented by two columns of bit strings Y Y and YntI .
- the magnetoresistive elements 12A and 12B of each memory cell 12 will be described as TMR elements utilizing the TMR effect, but the detailed configuration will be described later.
- the memory cell group 104 includes a sense word line 31 for sense arranged in the X direction (hereinafter abbreviated as a sense word line 31) and a pair of bit lines for sense arranged in the Y direction.
- the lines 21 A and 21 B (hereinafter, abbreviated as sense bit lines 21 A and 2 IB) form a matrix wiring.
- the individual memory cells 12 are arranged at these intersections, and the memory cells 12 connected in parallel to the common sense bit lines 21A and 21B form a bit string ⁇ ,.
- the memory cells 12 cascaded to the sense line 31 form a word string ⁇ ⁇ .
- one end of each of a pair of magnetoresistive elements 12 ⁇ and 12 ⁇ is connected to sense bit lines 21 ⁇ and 21 B, and the other is connected to each other.
- the end is connected to a common sense word line 31 via each of a pair of backflow prevention diodes 13 1 and 13 ⁇ .
- the current path of the sensing current to each of the magnetoresistive elements 1.2 mm and 1.2 mm starts from the node between the conductor from each element and the sense bit lines 21 A and 21 B, and goes from the node to the conductor from each element. It is a path to a node with the sense word line 31.
- the sense bit lines 21 ⁇ , 21 1 Correspond to the “read line pair” of the present invention
- the sense word line 31 corresponds to the “ground side read line” of the present invention.
- Sense bit lines 2 1 A, 2 1 B, the bit string of the memory cells 1 2 ⁇ ⁇ ( ⁇ ,, ⁇ 2, I) for each, are arranged in pairs. These sense bit lines 21 1 and 21 1 extend in the direction ⁇ so as to penetrate the memory cell group 104, and one end is connected to the power supply Vcc. On one end side of the sense bit lines 21 A and 2 IB (power supply Vcc side), current-voltage conversion resistors 23 A and 23 B (hereinafter, resistors 23 A and 23 B) and transistor 22 are connected, respectively. The collector and emitter of A and 22B are connected in series. Further, the plurality of storage cells 12 forming the bit string Y meritare connected to both the sense bit line 21 1 and the sense pit line 21 ⁇ B. One end of the effect element 12A is connected to the sense bit line 21A, and one end of the magnetoresistive element 12B is connected to the sense bit line 21B.
- bit decode line 20 is connected to the base sides of the transistors 22A and 22B.
- the bit decode line 20 is connected to the Y-direction address decoder 106 A. From the Y-direction address decoder 106 A, the pit row Y n to which the storage cell 12 to be written / read is to belong. A selection signal that is selectively output is input.
- the pit decode line 20 (..., 2 0 ", 20" +1, 7) is the storage cell 1 2 is provided corresponding to each bit string Upsilon eta, Upsilon direction ⁇ address decoder 1 06 It has the function of transmitting the selection signal from ⁇ to the bit string Y practicallyto be operated
- the transistors 22 ⁇ and 22 ⁇ ⁇ are input from the bit decode line 20 as a pair of semiconductor switches. It has a function to open and close according to the value of the selection signal (bit decode value).
- bit decode line 20 and the sense bit lines 21 A and 21 B have the same decoding function as described above, but they are clearly distinguished in operation. That is, the bit decode line 20 is a signal line for transmitting the selected cell from the ⁇ directional address decoder 106 ⁇ , and its value is a binary digital signal of "High” and “Low”, while Bit lines 21A and 21B are connected to magnetoresistive elements 12A and 12B. This is an analog signal line for detecting a weak current flowing therein. The same can be said for the word decod line 30 and the sense line 31.
- the sense amplifier input lines 40 A and 4 OB (Hereafter, input lines 40A and 40B) are derived.
- Resistors 23 A and 23 B function as bias resistors for sense amplifier 106 B. That is, to convert the sensing current flowing from the power supply Vcc through the sense bit lines 21 A and 21 B into a voltage due to its own voltage drop, and to lead it to the sense amplifier 106 B from the input lines 4 OA and 40 B. Installed in The resistors 23A and 23B also have a function of creating an intermediate voltage level that is lower by one ⁇ than the supply voltage of the power supply Vcc.
- resistors 23A and 23B In order to obtain a large voltage drop at resistors 23A and 23B because the sensing current is weak, and to maximize the voltage input to input lines 40A and 40B, resistors 23A and 23B It is necessary to increase the resistance value of B. Therefore, it is desirable that the resistors 23 A and 23 B have a high resistance value of, for example, about 100 kQ, and at least a resistance value larger than the resistance value of the magnetoresistive elements 12 A and 12 B. It is desirable to have.
- Each of the sense word line 3 1, the same word sequence X n (X,, ⁇ 2 , ⁇ ' ⁇ ) storage cell 1 2 is connected which is arranged.
- diodes 13 ⁇ , 13 ⁇ for backflow prevention as rectifying elements hereinafter abbreviated as diodes 13 A, 13 ⁇ ).
- diodes 13 A, 13 ⁇ for backflow prevention as rectifying elements
- Each of the backflow preventing diodes 13A, 13 ⁇ corresponds to the magnetoresistive element 12A, 12 2, and is individually connected.
- the magnetoresistive element 12 1 and the diode 13A, and the magnetoresistive element 12B and the diode 13B are insulated from each other.
- the diodes 13A and 13B are provided as unidirectional elements for preventing current from flowing back from the sense word line 31 to the magnetoresistive elements 12A and 12B.
- Diodes 13A and 13B include, for example, ⁇ junction diode, Schottky diode, or bipolar 'junction, transistor (BJT: Bipolar Junction Transistor) can be used as a diode with a short circuit between the base and collector, or a diode with a short circuit between the gate and drain of the MOS FET.
- the collector side of the transistor 33 is connected to the ground side of the sense word line 31, and the base side of the transistor 33 is connected to the word decode lines 30 (..., 30 réelle, 30 ⁇ + 1 , ⁇ ).
- the pad decode line 30 is connected to the X-direction address decoder 108A.
- a selection signal for selecting the row Xn is input from the X-direction address decoder 108A, and the selection signal is transferred to a transistor. It has the function of sending out to 33 bases.
- the transistor 33 functions as a semiconductor switch that opens and closes in accordance with the value of the selection signal (bit decode value) input to the base, and controls the conduction Z cutoff of the sense word line 31.
- a BJT or a MOS FET can be used.
- a current control resistor 34 is provided on the emitter side of the transistor 33.
- a constant current circuit 108 B is further provided on the ground side of sense word line 31.
- the constant current circuit 108B has a function of making the current flowing through the sense word line 31 constant, and is composed of a diode 32 for generating a constant voltage, a transistor 33, and a current control resistor 34. Therefore, the transistor 33 has a current control function of flowing a constant current in the collector emitter in addition to the function as a semiconductor switch for word decoding, and the base side is a diode 32. It is also connected to the agent node.
- the diode 32 in this case is one in which two diodes are connected in series. .
- One sense amplifier 106B is provided in the bit-direction unit readout circuit 80, and in each bit-direction unit readout circuit 80, takes in the potential difference between a pair of sense bit lines 21A and 21B, and obtains the potential difference.
- the sense amplifier 106 B of each bit direction unit read circuit 80 is connected to the corresponding sense bit line 21 A, 21 B via input lines 4 OA, 40 B, respectively, and all are connected to a common sense amplifier output line.
- 51 A, 5 IB hereafter, output lines 51 A, 5 IB
- it is connected to the output buffer 102B by the read data bus 112.
- the sense amplifier 106 B itself is configured as a so-called differential amplifier, and includes an amplification stage including transistors 41 A and 4 IB, and resistors 42 A and 42 B which are bias resistors for extracting a voltage output. It has a diode 43 for voltage drop, a transistor 44 having a current control function and a selection switch function, and a resistor 45 for voltage drop.
- FIG. 3 shows a portion of the sense amplifier 106B extracted from the entire readout circuit.
- the sense amplifier 106B provided in each bit direction unit read circuit 80 is cascaded to the output lines 51A and 51B.
- the resistors 42A and 42B are bias resistors shared by all sense amplifiers 106B connected in cascade.
- the transistor lines 41 A and 41 B are connected to the input lines 4 OA and 40 B on the base side and the resistors 42 A and 42 B on the collector side (via the output lines 51 A and 51 B). Is connected. These emitters are both connected to the collector of transistor 44.
- the bit-decoded line 20 is connected to the base side of the transistor 44 via a diode 43, and the emitter side is grounded via a resistor 45.
- resistors it is desirable to use resistors with high precision for the resistors 42 A and 42 B, and it is important that the transistors 41 A and 41 B have good characteristics.
- the diode 43 uses the bandgap reference to create an intermediate voltage level that is one ⁇ lower than the voltage level of the bit-decoded line 20, and uses this voltage value as the base-side input of the transistor 44. Used to generate voltage.
- the transistor 44 has both a current limiting function and a function as a semiconductor switch that opens and closes according to the bit decode value from the bit decode line 20.
- FIG. 4 shows a state of mounting around the Y-direction drive circuit unit of the memory cell group
- FIG. 5 shows an actual circuit arrangement of the Y-direction drive circuit unit.
- the Y-direction drive circuit section 106 is formed on one side of the memory cell group 104, and a bonding pad 122 is provided above the Y-direction drive circuit section.
- each of the Y-direction address decoder 106A, the sense amplifier 106B, and the Y-direction current drive 106C is provided with each pit string ⁇ nourish( ⁇ , , ⁇ 2 ,...)
- one constituent unit of these circuits 106 ⁇ to 106 C is defined as a corresponding bit string ⁇ réelle( ⁇ ,, ⁇ 2 ,...)
- the unit drive circuit DU n has a width equal to the storage cell 1. It is formed so as to fit to the second width W, and so as to be exactly positioned on the end of the corresponding bit string Y n.
- FIG. 5 shows one unit drive circuit.
- Circuit area ⁇ direction address decoder 1 0 6A includes a power source line 1 22 (Vcc), the power supply line 1 23 (V m) of the intermediate potential, is formed between the ground line 1 24 (GND).
- the power line 123 at the intermediate potential is a voltage source that supplies a voltage corresponding to the band gap + 2 ⁇ to the current limiting transistor ⁇ , and the constant current circuit 108 B in the X direction.
- An address line 105 extends so as to traverse the circuit area, and is connected to the Y-direction address decoder 106A of each unit drive circuit DU #.
- the circuit error of the sense amplifier 106B is formed between the power supply line 125, the power supply line 123 of the intermediate potential, and the ground line 124.
- the output lines 51A and 51B extend so as to traverse, and wiring is performed so that the sense amplifier 106B of each unit drive circuit DU livingis cascaded.
- the circuit area of the Y-direction current drive 106C is formed between the power supply line 125, the power supply line 126 of the intermediate potential, and the ground line 127.
- FIG. 6 specifically shows a circuit pattern arrangement of only a sense amplifier among the unit drive circuits.
- the sense amplifier 106 B is not only associated with each bit string ⁇ ⁇ ( ⁇ ,, ⁇ 2 ,. 2, 21 ⁇ are connected to the power supply Vcc side. Therefore,
- the transistors 22A and 22B and the resistors 23A and 23B are integrated with the sense amplifier 106B in the circuit area of the sense amplifier 106B.
- the pair of transistors 22A and 22B, the pair of resistors 23A and 23B, and the sense amplifier 106B are all differential pairs, and have the same characteristics as the mating partner. This is important for operation. Therefore, the output characteristics may be different, for example, when the temperature conditions of the installation locations of the circuit elements are different, although the characteristics are of course equalized in advance.
- the circuit elements forming the pair are arranged close to each other, so that both receive the same temperature change, the characteristics of each other change similarly, and there is almost no difference. . Thereby, the change in the output value caused by the temperature change can be reduced.
- FIG. 7 is a cross-sectional view illustrating a configuration of a storage cell.
- the memory cell 12 has a pair of left and right magnetoresistive elements 12 A and 12 B mounted on the substrate 10.
- Each of these magnetoresistive elements 12 A and 12 B has a laminated body in which a first magnetic layer 1, a non-magnetic layer 2, and a second magnetic layer 3 are laminated, and one side of the laminated body. And is penetrated by the write bit line 6a and the write pad line 6b (first and second write lines).
- Annular magnetic layer 5 configured as It is comprised including.
- the second magnetic layer 3 and the annular magnetic layer 5 are joined via the nonmagnetic conductive layer 4 and are electrically connected.
- each of the magnetoresistive elements 12 A and 12 B is provided with a reading sensing wire 11 on the upper surface of the laminated body (the surface opposite to the annular magnetic layer 5), and is directed toward the substrate 10. Thus, it is configured such that a current can flow through the stacked body in a direction perpendicular to the stacked surface.
- the first magnetic layer 1 is a ferromagnetic layer having a fixed magnetization direction
- the second magnetic layer 3 is a ferromagnetic layer (magnetic sensing layer) whose magnetization direction is changed by an external magnetic field.
- These are stacked with a few nm (a few 10 A) and a very thin nonmagnetic layer 2 interposed therebetween.
- a tunnel current flows to the first magnetic layer 1. That is, the nonmagnetic layer 2 here is a tunnel barrier layer.
- This tunnel current changes depending on the relative angle between the spin of the first magnetic layer 1 and the spin of the second magnetic layer 3 at the interface with the nonmagnetic layer 2. That is, when the spin of the first magnetic layer 1 and the spin of the second magnetic layer 3 are parallel to each other, the resistance value of the magnetoresistive element 12A (12B) is minimum and antiparallel. Is the largest. .
- the magnetization of the second magnetic layer 3 is changed by a magnetic field induced by the write pit line 6a and the write word line 6b.
- the magnetization of the second magnetic layer 3 is inverted by the induced magnetic field, whereby the relative angle with respect to the magnetization of the first magnetic layer 1 is inverted.
- the memory cell 12 to be written is selected by a so-called matrix driving method, current is supplied not only to either the write pit line 6a or the write word line 6b but also to both of them.
- the magnetic properties and dimensions of the second magnetic layer 3 are set so that the magnetization reversal is possible only when the magnetic flux flows in the same direction. This is the basic structure of the magnetoresistive element 12A (12B) as a TMR element.
- the annular magnetic layer 5 has a cylindrical shape having an axis perpendicular to the paper surface in FIG. 7, and is parallel to the write bit line 6a and the write word line 6b. Part is included. That is, the axial direction of the annular magnetic layer 5 is a, the extending direction of the write word line 6b, and a closed ring in a cross-sectional direction crossing the axial direction.
- the annular magnetic layer 5 is made of a high-permeability magnetic material, and the magnetic flux generated by the currents of the write bit lines 6a and the write lead lines 6b contained therein is confined in the layer to form a second layer. It has a function of efficiently changing the magnetization direction of the magnetic layer 3.
- the annular magnetic layer 5 has a closed loop in cross section as shown in the figure, and the generated induction magnetic field flows through the layer along a plane parallel to the cross section.
- the annular magnetic layer 5 has an electromagnetic shielding effect that does not generate a leakage magnetic flux to the outside.
- the second magnetic layer 3 since the second magnetic layer 3 is configured so as to be in contact with the entire surface of the second magnetic layer 3, it is easy to transmit a magnetic field to the second magnetic layer 3, and the second magnetic layer 3 having a high magnetic flux density has a high magnetic flux density. The magnetization direction can be changed more efficiently.
- FIG. 8 shows the wiring structure of the write bit line 6a and the write word line 6b.
- the magnetic memory device of the present embodiment has a plurality of write pit lines 6a and a plurality of write lead lines 6b extending so as to intersect with the write pit lines 6a, respectively. And although they extend so as to intersect, they extend partially in parallel in the intersecting region, and the magnetoresistive elements 12 A and 12 B are formed in the parallel portions.
- the term “parallel” includes a manufacturing error range of ⁇ 10 °.
- the magnetization of the second magnetic layer 3 is reversed by using the composite magnetic field of the parallel write pit line 6a and the parallel write line 6b. It is larger than the combined magnetic field when each wiring crosses. Thus, the write operation can be performed efficiently.
- each layer of the laminate except the nonmagnetic layer 2 through which a tunnel current flows, and the nonmagnetic conductive layer 4 and the annular magnetic layer 5 are all made of a conductive material.
- a cobalt iron alloy (CoFe) is used, and other simple cobalt (Co) and a cobalt platinum alloy (CoPt) are used.
- Nickel-iron-cobalt alloy (NiFeCo) can be used.
- the first magnetic layer 1 and the second magnetic layer 3 have magnetization directions parallel or anti-parallel to each other.
- the thickness of the nonmagnetic layer 2 is determined based on tunnel resistance and the like. Generally, in a magnetic memory element using a TMR element, a tunnel resistance of about several 10 k ⁇ ⁇ (Mm) 2 is appropriate in order to match a semiconductor device such as a transistor. However, in order to increase the density and speed of operation in a magnetic memory device, the tunnel resistance should be less than 101 ⁇ (m) 2 , and more preferably less than 1 k ⁇ ( ⁇ ) 2 . Is preferred.
- the thickness of the nonmagnetic layer 2 is desirably 2 nm or less, and more desirably 1.5 nm or less. However, if the thickness of the non-magnetic layer 2 is too small, the tunnel resistance can be reduced, but the leakage current due to the unevenness of the junction interface between the first magnetic layer 1 and the second magnetic layer 3 occurs. However, the MR ratio may be reduced. In order to prevent this, the thickness of the nonmagnetic layer 2 needs to have a thickness that does not allow a leak current to flow, and specifically, it is desirable that the thickness be 0.3 nm or more.
- the non-magnetic conductive layer 4 functions to provide antiferromagnetic coupling between the second magnetic layer 3 and the annular magnetic layer 5, and is made of, for example, ruthenium (Ru), copper (Cu), or the like.
- ruthenium Ru
- Cu copper
- iron Fe
- NiFe nickel-iron alloy
- Co CoFe
- NiFeCo Co
- the magnetic permeability of the annular magnetic layer 5 is preferably as large as possible. It is 0 or more, more preferably 600 or more.
- Each of the write bit line 6a and the write word line 6b has a structure in which titanium (T i), titanium nitride (T i N), and aluminum (A 1) are sequentially stacked. It is electrically insulated from each other by the rim.
- the write pit line 6a and the write word line 6b may be made of, for example, at least one of aluminum (A 1), copper (Cu), and tantalum (W).
- the magnetoresistive element 12 A (12 B) is a TMR element here, it is also a CPP (Current Perpendicular to the Plane) GMR element, which also has a structure in which current flows perpendicular to the magnetic layer stacking surface. It may be.
- the element structure is the same as that described above except that the nonmagnetic layer 2 is changed from an insulating layer to a nonmagnetic metal layer. This can be the same as that of the magnetoresistive effect element 12A (12B).
- An epitaxial layer 9 is formed on a substrate 10 on which the magnetoresistive elements 12A and 12B are formed, and a conductive layer 8 and an insulating layer 7 are further formed thereon.
- the conductive layer 8 includes conductive layers 8A and 8B insulated from each other via the insulating layer 7.
- the magnetoresistive elements 12 A and 12 B are formed on the upper surfaces of the conductive layer 8 and the insulating layer 7, respectively, and at least a part of the formation region is formed by the formation region of the conductive layers 8 A and 8 ⁇ And are positioned so as to overlap. Therefore, the magnetoresistive element 12A and the magnetoresistive element 12B are individually joined to the separately insulated conductive layers 8A and 8B, respectively, and are electrically insulated from each other. That is, here, the wiring is made such that the magnetoresistive element 12A and the magnetoresistive element 12B are electrically non-conductive.
- the substrate 10 is an n-type silicon wafer.
- an n-type silicon wafer is subjected to impurity diffusion of P (phosphorus), and a substrate 10 which becomes n "-type due to high-concentration diffusion of P (phosphorus) is used.
- the epitaxial layer 9 is made to be n-type by diffusing P (phosphorus) at a low concentration, and a metal is used for the conductive layer 8. At this time, the epitaxial layer which is an n-type semiconductor is used. A band gap is generated when contact is made between 9 and metal conductive layer 8. Short-circuit diodes are formed, which are diodes 13A and 13B in the present embodiment.
- a Schottky diode has a leakage current that is several hundred times or more larger than that of a PN junction diode, and in addition, the leakage current increases with a rise in temperature. If this magnetic memory device is an MRAM semiconductor memory chip and several thousand Schottky diodes are connected in parallel for each of the storage cells 12 and 12, the leakage current will increase considerably, and the SZN ratio of the read output will increase. Can be considered as a cause.
- a Schottky diode that is advantageous in terms of cost and manufacturing is used as the diodes 13A and 13B, but if leakage current cannot be ignored, the diode 13A, 13B It is also possible to form 13B with a PN junction diode, a BJT with a short between base and collector, or a MOS FET with a short between gate and drain.
- FIG. 9 is a circuit diagram of the storage cell.
- the magnetoresistive element 12 A (12 B) has a low resistance state where the current density of the tunnel current that can flow is high and a high resistance state where the current density is small.
- information is stored with one of the magnetoresistive effect elements 12A and 12B having a low resistance and the other having a high resistance.
- the two magnetoresistive elements 12 A and 12 B are differentially amplified and read. Therefore, the two magnetoresistive elements 12 A and 12 B forming a pair need to be manufactured so that the resistance value, the magnetoresistance change rate, and the magnitude of the reversal magnetic field of the second magnetic layer 3 are equal. There is.
- FIGS. 1OA and 10B show the memory cells in the same manner as FIG. 9, and show the first magnetic layer 1 and the second magnetic layer of the magnetoresistive elements 12 A and 12 B, respectively. It represents the magnetization of layer 3.
- the white arrow represents the magnetization of the first magnetic layer 1, and the magnetization is fixed to the right in both the magnetoresistive elements 12A and 12B.
- the black arrows indicate the magnetization of the second magnetic layer 3, and are magnetized in anti-parallel directions in the magnetoresistive elements 12A and 12B.
- information is stored in a state where the magnetization directions of the second magnetic layers 3 of the pair of magnetoresistive elements 12A and 12B are antiparallel to each other.
- the combination of the magnetization directions of the first magnetic layer 1 and the second magnetic layer 3 is always (parallel, antiparallel) Or the second state of (anti-parallel, parallel). Therefore, by associating binary information “0” and “1” with these two states, one bit of information is stored in one storage cell 12.
- the magnetoresistive element 12A (1 2 B) If the magnetization directions of the first magnetic layer 1 and the second magnetic layer 3 are parallel, a low resistance state where a large tunnel current flows is obtained, and if the magnetization directions are antiparallel, a high resistance state where only a small tunnel current flows .
- the magnetoresistive element 12 A and the magnetoresistive element 12 B forming a pair always store information with one having a low resistance and the other having a high resistance.
- FIG. A current is applied to the write bit line 6a and write word line 6b of each of the elements 12A and 12B so as to be relatively opposite to each other (see FIG. 8).
- FIG. 11 shows the direction of the write current when the “1” bit shown in FIG. 1OA and FIG. 10B is written into the storage cell 12.
- the effective magnetic field strength contributing to the magnetization reversal of the second magnetic layer 3 becomes larger than before.
- the magnetization of the second magnetic layer 3 can be reversed with a necessary and sufficient magnetic field strength, and an efficient writing operation can be performed.
- the magnetization of the second magnetic layer 3 is aligned so as to be sufficiently large in a predetermined direction. Therefore, the possibility that the magnetization direction of the second magnetic layer 3 is disturbed by the external disturbance magnetic field can be reduced, and the information once written can be prevented from being unexpectedly erased or rewritten. That is, information can be written reliably.
- the address buffer 101 captures the signal voltage of the external address input terminals AO to A20, amplifies it with the internal buffer, and passes through the address lines 105, 107 in the Y direction and X direction.
- Direction address decoder 1 0 6 A, 1 0 8 Communicate to A.
- the data buffer 102 takes in the signal voltages of the external data terminals D0 to D7, amplifies them in the internal buffer, and outputs the currents in the Y and X directions through the write data buses 110 and 111. Transmit to drive 106C and 108C (Fig. 1).
- the address decoders 106A and 108A select the write bit line 6a and the write word line 6b having the corresponding decode value according to the selection signal.
- the direction of the current flowing through the write bit line 6a and the write word line 6b is determined by the current drives 106C and 108C.
- the storage cell 12 in which the current flows through both the write bit line 6a and the write word line 6b is intentionally selected, and predetermined bit data is written therein.
- the directions of the currents of the write bit line 6a and the write word line 6b are indicated by arrows, and the state where the memory cell 12 is selected is shown.
- the magnetic memory device reads information written in each storage cell 12 as follows.
- FIG. 12 shows the basic configuration of a memory cell. D
- Each storage cell 12 is in a state where the magnetoresistive elements 12 A and 12 B have magnetization directions as shown and information is stored.
- the storage cell 12 from which information is read is selected by inputting a selection signal to the bit decode line 20 in the Y direction and to the word decode line 30 in the X direction in accordance with the address. For example, if the memory cell 12 to be selected is in the Y facilitatorcolumn and the ⁇ ⁇ + ⁇ row, the ⁇ ⁇ - th bit decoder line 20 and ⁇ ⁇ + the first decoder line 30 ⁇ The signal is input to +1 .
- Reading of information is performed by detecting a difference between current values flowing through the magnetoresistive elements 12A and 12B of the memory cell 12 respectively.
- the current flowing through them is almost equal to the sensing current flowing through the sense bit lines 21 1 and 21 1.
- a voltage drop due to the sensing current occurs in the resistor 23 A (23 B) connected in series to the sense pit line 21 A (21 B).
- the voltage drop Va is determined by Equation 1 if the magnitude of the sensing current is I sense and the resistance value of the resistor 23A (23B) is Ra.
- Va (Volt) I sense (A) XRa ( ⁇ )
- Equation 1 it can be seen that if the values of the resistor 23 A and the resistor 23 B are well aligned, the sensing current I sense is converted to a voltage by the voltage drop Va and detected. Therefore, the voltage drop of the resistor 23A and the resistor 23B is taken out from the input lines 40A and 40B as the read output signal, and the difference is detected. As described above, by using the two magnetoresistive elements 12A and 12B and extracting the difference between the respective output values, a large output value from which noise is removed can be obtained as the storage cell 12. Can be
- the magnitude of the sensing current flowing through the selected memory cell 12 is determined by the current control resistor 34 provided on the ground side of the sense word line 31. Is adjusted by The current control resistor 34 alone has the effect of limiting the amount of current. However, here, a constant current circuit 108 composed of a combination of the current control resistor 34, the transistor 33, and the diode 32 is also used. B operates to keep the current within a certain range.
- the two diodes 32 connected in series generate a fixed intermediate voltage level + 2 ⁇ higher than the ground by a diode band gap reference. . Therefore, the intermediate voltage level is applied to the base terminal of the transistor 33, and the transistor 33 is turned on. At this time, the magnitude I sense of the sensing current flowing from the sense word line 31 is obtained by Expression 2 when the resistance value of the current control resistor 34 is Rc.
- I sense (A) (2 ⁇ '— ⁇ ") (Volt) / Rc ( ⁇ )
- Equation 2 is the forward voltage of the two series-connected diodes 32, and “is the forward voltage between the base and the emitter of the transistor 33. Since these are values specific to the semiconductor device, Equation 2 is It shows that if the resistance value Rc is determined, the sensing current I sense takes a constant value, and that the sensing current I sense can be uniquely determined using the resistance value Rc as a parameter.
- a weak sensing current I sense flows in the sense word line 31 stably at a value within a certain range.
- the sensing current I sense in Equation 2 is a current flowing through the sense word line 31 and is sense bit line 21 A and sense bit line 21 B, or magnetoresistive element 12 A and magnetoresistive element 1 It is the sum of the currents flowing through both 2B.
- the sensing current I sense by the constant current circuit 108B is approximately 15 / iA become.
- the pair of magnetoresistive elements 12A and 12B differ in the range of resistance values that can be taken for driving operation due to manufacturing reasons, the current flowing through both elements may be different.
- the sum is always approximately equal to 15 A.
- the variation in the resistance value of the anti-effect element 12 A (12 B) means that the non-magnetic layer 2 has a thickness of only a few atomic units of several nm (a few 10 A), and the thickness and atomic arrangement are different.
- the resistance value changes due to slight disturbance. Therefore, great care is taken to form the non-magnetic layer 2 with a uniform thickness, but in reality, the resistance of the magnetoresistive element 12 A (12 B) is 15 to 50%. When the conditions such as the degree and the production equipment are bad, more variation occurs.
- Variations in the resistance values of the magnetoresistive elements 12A and 12B can be considered in two cases for each factor.
- the first case is that the resistance values of the magnetoresistive elements 12A and 12B at the time of low resistance and at the time of high resistance are different between the memory cells 12 due to variations in the thickness of the nonmagnetic layer 2 and the like. It is. In general, as the thickness of the nonmagnetic layer 2 increases, the resistance of the pair of magnetoresistive elements 12A and 12B takes a large value both when the resistance is low and when the resistance is high.
- the second is that the magnetoresistive elements 12A and 12B, which make a pair in each memory cell 12, have irregularities at the junction interface, differences in the thickness of the nonmagnetic layer 2, and other causes. In this case, the ratio between the resistance when a large tunnel current flows and the resistance when only a small tunnel current flows, that is, the MR ratio varies.
- each current flowing through the sense pit lines 21A and 21B is obtained by distributing a certain amount of current according to the resistance ratio. Therefore, the deviation of each current value is smaller than the degree of variation of the resistance value.
- the diodes 13 A and 13 B provided on the current path on the sense line 31 side of each of the magnetoresistive elements 12 A and 12 B have the current From the sense word line 31 to the magnetoresistive elements 12A and 12B.
- the magnetoresistive elements 12 ⁇ and 12 ⁇ are connected to the common sense bit lines 21 A, 21 ⁇ and the common sense word line 31.
- Part of the sensing current deviates from the normal path, flows out to another path via the magnetoresistive element 12 A, 12 ⁇ that is not the target of reading, and goes to ground as it is. There is a danger that it will run down or re-enter the legitimate route. Nevertheless, the reason why such a wiring structure is adopted is to simplify the wiring by sharing the selection switch of the memory cell 12 with a single switch for each column in both the bit direction and the directional direction. This is for sharing the constant current circuit 108 08 for each column.
- FIG. 13 shows, as a comparative example for the present embodiment, the path (i) of the leakage current when the diodes 13A and 13B are not on the current path of the magnetoresistive elements 12A and 12B.
- a part of the sensing current flows backward from the sense lead line 31 to the magnetoresistive elements 12 A and 12 B adjacent in the word column direction, for example, as shown by a path (i), and It flows to the bit line 2 0 n.
- the same leakage also occurs in a large number of magnetoresistive elements 1 2A and 12B (not shown) commonly connected to the same sense line 31.
- the sense pit line 21 A is further descended, and is adjacent in the pit row direction, passes through the low-resistance magnetoresistive element 12 A, and is further connected to the sense pit line 31 via the sense line 31. The current flows backward to the magnetoresistive element 12 A on the low resistance side of the memory cell 12 adjacent in the direction.
- the sense pit line 21 A which is different from the normal path, rises to the magnetoresistive element 12 A connected to the selected sense word line 31 (adjacent in the bit string direction in the figure), It flows into the low-resistance magnetoresistive element 12 A, and finally flows into the selected sense word line 31.
- a similar wraparound is caused by a large number of magnetoresistive elements 12 A (not shown) connected to the same sense bit line 21 A, and a sense word line 31 1 connected to those magnetoresistive elements 12 A. This also occurs for a large number of magnetoresistive elements 12 A and 12 B (not shown) that make the same. When the magnetoresistive element 12B has a low resistance, the wraparound also occurs in the same manner.
- a wraparound is a route (out).
- the magnetoresistive element 12 A low resistance side
- the magnetoresistive effect element 12 B high resistance side
- By flowing back one of A and the magnetoresistive element 12B it passes through one storage cell 12. Further, it goes up the sense bit line 21 B on the opposite side and goes around from the magnetoresistive element 12 B of the storage cell 12 to be read to the normal path.
- Diodes 13A and 13B of the present embodiment can be replaced with transistors that are also elements having a rectifying action.
- FIG. 14 shows such a modified example in which bipolar transistors 63 A and 63 B are provided between the magnetoresistive elements 12 A and 12 B and the sense lead line 31. ing.
- the bipolar transistors 63A and 63B are connected to the sense bit lines 21A and 2IB or the sense word line 31 when the base terminal is connected to the bit decode line 20 or the negative decode line 30. be able to. In addition .. In such a case, it is not necessary to have Transit Areas 22A and 22B.
- Such bipolar transistors 63A and 63B also function as one-way elements.
- the advantage of using the bipolar transistors 63A and 63B is that the voltage at the time of conduction is considerably lower than the forward voltage of the diode.
- Transistor The collector-emitter voltage when conducting in the evening is very low (about 0.2V), but the diode has a forward voltage of band gap ⁇ (0.65V to 0.75V).
- the current path is connected in series from the power supply Vcc to the ground, the current-voltage conversion resistor 23 A (23 B), the transistor 22 A (22 B), the magnetoresistive element 1 It has a five-stage configuration consisting of 2 A (1 2 B), diode 13 A (1 3 B)., Transistor 33, and current control resistor 34.
- the bipolar transistors 63A and 63B operate at a power supply voltage as low as 0.5 V as compared to the diodes 13A and 13B. Can be done. In addition, by distributing the surplus of this voltage, it is possible to raise the circuit from five stages to several stages and to perform more complicated control operations.
- Diodes 13A and 13B can also be replaced with MS transistors 73A and 73B, as shown in Fig. 15.
- the drain-source voltage during conduction is as low as about 0.1 IV, and its operation and effect are almost the same as those of the bipolar transistors 63A and 63B.
- These rectifying elements are provided between the sense bit lines 21A and 21B and the magnetoresistive elements 12A and 12B as shown in FIGS. 16 to 18. It may be.
- the transistors 22A and 22B, the resistors 23A and 23B, and the sense amplifier 106B are integrated in a region having the same width W as that of the memory cell 12; Of these, the elements forming a differential pair have almost the same temperature change during operation. This suppresses fluctuations in the output value caused by temperature changes.
- the output of the sense amplifier 106B is finally input to the output buffer 102B via the output lines 51A and 51B and the read data bus 112.
- the output buffer 102B amplifies the input signal voltage and outputs it from the external data terminals D0 to D7 as a binary voltage signal.
- the magnetoresistive elements 12A and 12B are provided with the annular magnetic layer 5, so that writing can be performed efficiently and at the same time, the second magnetic layer Information can be reliably written with the magnetization directions of 3 fully aligned. You. When information is read in turn, if the magnetization of the second magnetic layer 3 is sufficiently aligned in a predetermined direction as described above, the magnetoresistive effect element 1 is determined by the relative magnetization direction to the first magnetic layer 1.
- the tunnel current value at 2 A (12 B) also clearly shows a large and small binary state, and an output value with a high SZN ratio can be obtained.
- the memory cell 12 is composed of a pair of magnetoresistive elements 12 A and 12 B, and the current flowing through both is differentially output. The noise coupled to 2 1 B is removed.
- a constant current circuit 108 B is provided on the ground side of the sense word line 31 so that the total sum of the sensing current flowing through the read circuit is kept constant.
- the difference between the current values of the sense bit lines 21 A and 21 B is always kept within a certain range.
- normalizing the total current value to a constant value requires the sense bit lines 21 A, 21 1 to prevent variations in resistance between the pair of magnetoresistive elements 12 A, 12 B. This has the effect of suppressing the fluctuation of each current value of B.
- the transistor 33 of the constant current circuit 108 B also functions as a semiconductor switch for the decoupling line 30, it can be manufactured relatively easily and is advantageous in circuit design.
- the diodes 13A and 13B are provided as unidirectional elements between each of the magnetoresistive elements 12A and 12B and the sense lead line 31, the sense lead line is provided. Current is prevented from flowing back from 31 to the magnetoresistive elements 12 A and 12 B. As a result, the magnetoresistance effect between the storage cells 12 connected to the common sense bit lines 21 A and 21 B or the common sense line 31 and in one storage cell 12 A current path is prevented from being formed between the element 12A and the magnetoresistive element 12B, and leakage or sneak of the sensing current is cut off, so that noise can be reduced.
- transistors 22 A and 22 B and resistors 23 A and 23 B are integrated with the sense amplifier 106 B in the circuit area of the sense amplifier 106 B. Since they are arranged, a differential amplifier circuit is formed together with the sense amplifier 106B, and the paired circuit elements are formed at positions close to each other. Therefore, these Since these circuit elements are driven under the same temperature condition, variation in characteristics due to temperature changes is suppressed, and noise in the differential amplifier circuit can be prevented.
- noise due to variation in characteristics of each storage cell 12 and variation in resistance between the pair of magnetoresistive elements 12A and 12B In addition to reducing noise, noise coupled to the data lines, noise due to variations in the characteristics of the sense amplifier 106B and other differential pairs, and noise in peripheral circuits wrapping around from the power supply circuit were reduced.
- the SZN ratio of the output signal output can be greatly improved and improved. Therefore, this magnetic memory device can perform a stable operation with little reading error.
- since a large signal output value can be obtained by improving the S / N ratio it is possible to obtain a sufficient output even when the storage cells 12 are highly integrated. It is also possible to realize current and low voltage driving.
- the voltage applied to the element in a magnetic memory device, when a tunnel current is passed through a magnetoresistive element, the voltage applied to the element must be set to an appropriate value in order to prevent dielectric breakdown of an extremely thin tunnel barrier layer.
- the magnetic memory device of the present embodiment is provided with the constant current circuit 108B to reduce the tunnel current and drive the non-magnetic layer 2 by lowering the voltage applied to the non-magnetic layer 2 to a voltage sufficiently lower than its electric breakdown voltage. be able to.
- the read circuit of the present embodiment is configured such that the current path is connected in series from the power supply Vcc to the ground, the resistor 23A (23B), the transistor 22A (22B), and the magnetoresistive element 12A (1 2B), diode 13A (1 3B), transistor 33, and current control resistor 34. From the relationship of the voltage division, the voltage drop in these magnetoresistive elements 12 A (12 B) can be actually suppressed to as low as about 0.1 V to 0.3 V. Of course, in such a case, the voltage output (voltage drop in the resistors 23A and 23B) directly obtained from the magnetic recording elements 12A and 12B is weak, but the sensing current is defined as a constant current. As a result, the SZN ratio is high.
- this output is further amplified by several stages of differential amplifier circuits to obtain a final output, sufficient readout sensitivity can be obtained.
- this magnetic memory device is driven by a tunnel current that is extremely weak compared to the conventional one, preventing dielectric breakdown of the magnetoresistive elements 12A and 12B, and at the same time, having a sufficiently large value.
- the current value at each measurement point was measured using a current probe during the reading of information.
- the measurement points are nine points P1 to P9 shown in FIG.
- FIG. 20 shows the measurement results at the measurement points P 1 to P 4.
- the current flowing through the sense bit line 21 A on the side connected to the magnetoresistive element 12 A is the emitter current of the transistor 22 A, that is, the collector current of the transistor 22 A and the base current.
- the measurement results show that the collector voltage at the measurement point P1 is large enough to ignore the base current at the measurement point P3. Therefore, it can be seen that the currents flowing at the collector and emitter terminals of the transistor 22 A are almost equal.
- the relationship between the collector current of the measurement point P 2 for the transistor 22 B and the base current of the measurement point P 4 is the same, and it can be seen that the currents flowing at the collector end and the emitter end of the transistor 22 B are almost equal. .
- Fig. 21 shows the measurement results at measurement points P1 to P9 (Fig. The scale of the current value is different).
- the current flowing through the resistors 23A and 23B branches off, and the current flows through the collector terminals of the transistors 22A and 22B, which are switches for selecting bit strings, and the differential pair of the sense amplifier 106B, respectively. It flows into the base terminals of certain transistors 41A and 41B. Further, the sum of the collector current and the base current of the transistors 41 A and 41 B is the respective emitter current, and the emitter currents are combined by a common wiring and flow into the collector terminal of the transistor 44. ⁇
- the collector currents of the transistors 41A and 41B are obtained by amplifying the respective base currents (currents at the measurement points P7 and P8). From the measurement results, the difference between the collector current of the transistor 41A at the measurement point P5 and the collector current of the transistor 41B at the measurement point P6 is determined by the sense bit lines 21A and 2IB which are the original outputs. It can be seen that the current difference is extremely large as compared with the current difference. The ratio of the current difference reaches about 200 times in the case of the measurement data shown. Therefore, it can be seen that in this magnetic memory device, a very large output can be obtained by amplifying the read signal by such a sense amplifier 106B.
- FIG. 22 shows the measurement results.
- the horizontal axis shows the resistance value R RMR1 of the magnetoresistive element
- the vertical axis shows the output voltage value normalized by the power supply voltage Vcc.
- the open circles indicate the output voltage value from the magnetoresistive element 12 A (1 2 B) that takes the resistance value R H when the resistance is high
- the X indicates the resistance value R when the resistance is low.
- the output voltage value from the magnetoresistive effect element 12 B (12 A) with the L is shown.
- the measured values are connected by a solid line, and the dotted line shows a comparative example of a configuration in which a current flows through a pair of magnetoresistive elements and a voltage drop of the magnetoresistive elements is directly sensed. This is the result.
- FIG. 23 shows an equivalent circuit diagram of the comparative example.
- This reading circuit reads the voltage difference between a pair of magnetoresistive elements (shown as variable resistances R 1 and R 2), one of which has high resistance and the other has low resistance, and stores information.
- Each of the magnetoresistive effect elements is connected in series to a current source and a cell-selecting semiconductor switch, and the series wiring is independent of each other.
- the MR ratio of each memory cell 12 was changed by fixing the resistance value R H and changing the resistance value RL, and the respective output voltages were measured.
- Figure 24 shows the measurement results.
- the horizontal axis shows the MR ratio (%), and the vertical axis shows the output voltage value (V) normalized by the power supply voltage Vcc.
- the open circle indicates the output voltage value from the magnetoresistive effect element 12 A (12B) having the resistance value R H
- the X mark indicates the magnetoresistive effect element 1 having the resistance value RL.
- the output voltage value from B (12 A) is shown.
- the measured values are connected by a solid line, and the dotted line is the offset reference value due to the constant current effect for each of the resistance values RH and RL .
- the output voltage from the resistance value RL and the output voltage from the resistance value RH tend to approach each other as the MR ratio decreases. That is, if the MR ratio varies for each of the memory cells 12, the effect appears in the voltage output in this manner. Nevertheless, the output voltage on the resistance value RL and the output voltage on the resistance value RH are each within a certain range with respect to the reference value. In this case, if the MR ratio is about 15% or more, the difference between the two is sufficient as an output. It is running low.
- the sum of the currents flowing through the magnetoresistive elements 12 A and 12 B is always equal, the sum of the currents is always equal to the ratio of the element resistance at that time. It takes a value that is symmetrical about the half value.
- the offset reference value shown by the dotted line in Fig. 24 is exactly this value converted to voltage, and its position remains unchanged unless the total current is changed. Therefore, if a voltage level serving as a threshold when differential amplification is performed by the sense amplifier 106 B matches the offset reference value, a voltage output of an appropriate value can be obtained from the sense amplifier 106 B. This is also an effect of adding a constant current circuit.
- FIGS. 25 to 32 a second embodiment of the present invention will be described in detail with reference to FIGS. 25 to 32. Will be described.
- This embodiment has a different feature from the first embodiment in a part of the configuration of the readout circuit.
- the same reference numerals are given to substantially the same components as those in the first embodiment, and the description will be appropriately omitted.
- the magnetic memory device has a sense bit line 21A, 21 as a read line pair extending along the bit column direction and supplying a read current to a pair of magnetoresistive elements 12A, 12B.
- a sense word line 31 serving as a ground-side read line for guiding a read current flowing through a pair of magnetoresistive elements 12 A, 12B to the ground, and a plurality of sense gate lines 31
- a constant current circuit 108B that defines the sum of a pair of read currents flowing through a pair of magnetoresistive elements 12A and 12B in one storage cell 12;
- a bit direction unit read circuit 80 as a read circuit for reading information from the memory cell 12 based on the difference is provided.
- FIG. 25 is a configuration diagram of a circuit system including a memory cell group and a read circuit thereof, and is similar to the configuration diagram shown in FIG.
- the storage cell 12 is a differential amplification type comprising a pair of magnetoresistive elements 12A and 12B, and each storage cell 12A , 12B is read as the output of the difference value of the sensing current flowing through each of the magnetoresistive elements 12A, 12B.
- the internal configuration of the sense amplifier 106B is omitted.
- the transistors 22A and 22B and the resistors 23A and 23B have the same configuration as that shown in FIG.
- Each of the sense word lines 31 includes a magnetoresistive element 12 A, 12 B arranged in the same word string X n (X,, X 2 ,...), And a diode 13 3 as a rectifier. Connected via A, 13B. However, in the present embodiment, a constant current circuit 108 B is provided in common on the ground side of each sense word line 31. Each sense line 31 is provided with a read switch 83, and a selection signal is inputted from the X-direction address decoder 108A via the word decode line 30. The constant current circuit 108B is connected to the power save (PS) —The break signal 84 is input.
- PS power save
- the diodes 13A and 13B are composed of Schottky diodes or PN junction diodes.
- the read switch 83 is provided between each of the constant current circuit 108B and each of the code lines 30 so as to select one of a plurality of memory cell groups 104X along the word column direction. Function.
- the constant current circuit 108 B has a function of stabilizing the current flowing through the sense word line 31, and as shown in FIG. 2, generates a constant voltage using a band gap reference. And a current controlling transistor 33 and a current controlling resistor 34. However, they are omitted in FIG. 25.
- the readout switch 83 is a specific example corresponding to the “first semiconductor switch” in the present invention.
- the “memory cell group 104 XJ” is a specific example corresponding to the “second direction memory cell group” in the present invention.
- a sensing current flows through the following path during a read operation.
- Reading of information is performed based on the difference between a pair of current values supplied to the magnetoresistive elements 12A and 12B of the storage cell 12 as in the first embodiment. Is
- the magnitude of the sensing current flowing through the selected storage cell 12 is controlled by the current control resistor 34 provided on the ground side of the sense word line 31.
- the current control resistor 34 has the effect of limiting the amount of current by itself, but in this case, the current control resistor 34 further includes a transistor 33 and a diode 32.
- the current circuit 108 B operates so as to keep the amount of current within a certain range.
- the two diodes 32 connected in series are connected to the ground by + 2 ⁇ from the ground using the diode band gap reference. Only a high intermediate voltage level is fixedly produced. Therefore, a constant intermediate voltage level is applied to the base terminal of the transistor 33, the transistor 33 is turned on, and the function of the constant current circuit 108B makes the sense lead line 3 1 , A sensing current of a certain magnitude flows stably.
- the constant current circuit 108 B for each of the word strings, it is possible to reduce the variation in the resistance value caused by the components of the memory cell 12 for each of the word strings, A read current standardized to a constant value can always flow through each memory cell 12. However, in this case, there is a variation in the characteristics of the components in each of the constant current circuits 108 B, so that mutual variation in each of the constant current circuits 108 B cannot be completely eliminated.
- a constant current circuit 108 B is provided in common for the plurality of sense word lines 31 in the readout circuit system, and the cause of the variation in the resistance value caused by the components is removed.
- a read current standardized to a constant value is always supplied to each memory cell 12.
- the constant current circuit 108 B in common, the relative number of components in the entire magnetic memory device is smaller than when the constant current circuit 108 B is provided for each row. Reduce it can. This makes it possible to reduce manufacturing costs. Further, since the number of constant current circuits 108 B that need to constantly supply a constant current can be reduced, the effect of reducing power consumption in the entire magnetic memory device can be obtained.
- the diodes 13 A and 13 B as rectifiers can be replaced with bipolar transistors or MOS transistors.
- the rectifying element also functions as a second semiconductor switch for selecting the storage cell group 104X arranged along the word column direction. A specific example thereof will be described later.
- the voltage level of the PS pin is set to "Low", and the standby current (base-emitter current) is prevented from flowing, and the non-standby state is set.
- the response speed during the read operation may slightly decrease when transitioning from the non-standby state to the standby state, the power consumption can be kept low. Can be reduced.
- FIG. 26 shows a modified example 2-1.
- the diodes 13A and 13B shown in FIG. 25 are replaced with bipolar transistors 63A and 63B.
- the bipolar transistors 63A and 63B also function as a second semiconductor switch for selecting any one of the plurality of memory cell groups 104X.
- a read shared line 85 is provided for each of the plurality of storage cell groups 104 Y, and bundles the plurality of sense word lines 31 for each storage cell group 104 Y.
- the storage cell group 104 Y is a specific example corresponding to the “first direction storage cell group” of the present invention.
- a sensing current flows through the following path during a read operation.
- Reading of information is performed based on a difference between a pair of current values supplied to each of the magnetoresistive elements 12A and 12B of the storage cell 12 as in the first embodiment.
- the modified example 2-2 shown in FIG. 27 is the same as the modified example 2-1 shown in FIG. 26, except that each of the plurality of shared read lines 85 and the constant current circuit 108 B And a selection switch 86 for selecting any one of the plurality of memory cell groups 104Y.
- the selection switch 86 is controlled to be opened and closed by a selection signal for selecting which of the plurality of storage cell groups 104 Y should receive a read current. In such a case, during a read operation, Sensing current flows.
- the selection signal is input to +:
- the selection signal input to the bit decode line 20 is input to the sense amplifier 106 6 and the selection switch 86, respectively. Therefore, assuming that the voltage level at the ⁇ ⁇ ⁇ th bit decode line 20 personallyis“ High ”, the sense bit lines 21 A and 2 IB of the bit direction unit readout circuit 80 ⁇ are connected to the opposite side from the power supply Vure side. The sensing current flows toward. At the same time, the selection switch 86 is turned on.
- the pair of bipolar transistors 63A and 63B in the Xn + 1- th row are energized. Therefore, the sensing current is allowed to flow through the storage cell 12 in the Y n column, ⁇ réelle +1 row. Specifically, the sensing current is supplied from the ⁇ ⁇ th sense bit line 21 1 and 21 ⁇ from the magnetoresistive element 12 ⁇ and the bipolar transistor 63 ⁇ and the magnetoresistive element 12 ⁇ , respectively. And the bipolar transistor 6 3, both of which flow into the ⁇ + 1st sense line 3 1 consider+, pass through the selection switch 8 6 ⁇ via the readout shared line 85, and Flow into circuit 1 08 ⁇ .
- Information reading is performed based on the difference between a pair of current values supplied to the magnetoresistive elements 12 1 and 12 ⁇ of the memory cell 12 as in the first embodiment.
- each memory cell 12 in the memory cell group 104 is connected to each other by the sense line 31 or the shared read line 85. Since the sense amplifier 106 # provided for each bit string has a potential slightly higher than the ground level potential, the bit string is not selected (the memory cell 12 to be read is not included). Even in this case, a weak current continues to flow through the sense bit lines 21 ⁇ and 21 1. Further, in the read circuit configuration shown in FIG. 25 and FIG. 26, each memory cell 12 in the memory cell group 104 is connected to each other by the sense line 31 or the shared read line 85. Since the sense amplifier 106 # provided for each bit string has a potential slightly higher than the ground level potential, the bit string is not selected (the memory cell 12 to be read is not included). Even in this case, a weak current continues to flow through the sense bit lines 21 ⁇ and 21 1. Further, in the read circuit configuration shown in FIG.
- the bipolar transistors 63 A and 63 B shown in FIG. 27 can be replaced with MOS transistors 73 A and 73 B.
- the sensing currents from the magnetoresistive elements 12 A and 12 B in each memory cell 12 flow into the drains of the MOS transistors 73 A and 73 B, respectively, and then merge via the sources. Then, it is led to the readout common line 85 provided for each of the memory cell groups 104 Y.
- the gates of the MOS transistors 73 A and 73 B are controlled to be opened and closed by a selection signal from a code line 30.
- the pair of rectifying elements provided for backflow prevention are connected to the sense bit lines 21 A, 21 B and the magnetoresistive element. It may be provided between the effect elements 12 A and 12 B.
- FIG. 29 corresponds to FIG. 25, in which a pair of diodes 13 A, 13 B is connected between the sense bit lines 21 A, 21 B and the magnetoresistive elements 12 A, 12 B. They are provided between them.
- FIG. 30 shows a cross-sectional configuration of the pair of magnetoresistive elements 12A and 12B and the vicinity thereof in such a circuit configuration.
- FIG. 3.0 is similar to FIG. 7 described in the first embodiment, but FIG. 30 is a diagram showing the TMR film 112 A, 1 1 2B and the write bit line 6a and the write lead line 6b.
- the formed annular magnetic layer 5 is formed in order.
- the sense bit lines 21A and 21B are connected to the epitaxial layer 9 via the connection layer 21T, and the read current is applied to the TMR film 112A via the conductive layers 8A and 8B, respectively. , 1 1 2B.
- the read currents passing through the TMR films 112A and 112B respectively flow into the sense line 31 via the annular magnetic layer 5.
- FIG. 31 corresponds to FIG. 27, in which a pair of bipolar transistors 63 A and 63 B are connected between the sense pit lines 21 A and 21 B and the magnetoresistive elements 12 A and 12 B, respectively. This is provided (Modification 2-5).
- FIG. 32 corresponds to FIG. 28, in which a pair of MS transistors 73 A, 73 B are connected to the sense bit lines 21 A, 21 B and the magnetoresistive elements 12 A, 12 B. They are provided between them (Modifications 2-6).
- a bipolar transistor is used for the sense amplifier 106 B, the constant current circuit 108 B, and the switching elements such as the transistors 22 A and 22 B. (Complementary MOS).
- the magnetic memory device of the present invention may be any device that stores one unit of information by using two magnetoresistive elements having a ring-shaped magnetic layer. It is not limited to the form. For example, the same information can be stored in two magnetoresistive elements, and reading can be performed from only one element in a normal state, and reading can be performed from the other element when a reading error occurs. . As described above, since two elements can be used for one unit of information, the magnetic memory device of the present invention has more applicable write and read methods than the case where one unit of information corresponds to one element. The degree of freedom is increasing. Further, in the above embodiment, the storage cell 12 is described as a CD which is a TMR element as a magnetoresistive element including a stacked body in which a current flows in a direction perpendicular to the stacking plane. May be replaced by
- the constant current circuit of the present invention is not particularly limited in the element structure of a pair of magnetoresistive elements forming a storage cell, and can be widely applied to a magnetic memory device that performs so-called differential reading. That is, the pair of magnetoresistive elements need not have the same configuration as the storage cell 12 described in the embodiment.
- the pair does not have the annular magnetic layer 5, and has the first magnetic layer 1,
- a read sensing conductor is connected to the laminated body including the magnetic layer 2 and the second magnetic layer 3 which is a magnetically sensitive layer, and a current is read perpendicularly to the laminated surface to read information. May be.
- the pair of magnetoresistance effect elements may be a magnetoresistance effect element (CIP (Current Flows In the Plane) -GMR) including a laminate in which current flows in a direction parallel to the lamination plane.
- CIP Current Flows In the Plane
- the read line is particularly limited, except that a plurality of storage cells are connected to the read line in one direction (ground-side read line). In such a case, the constant current circuit of the present invention can exhibit the same operation and effect as those of the embodiment.
- the sense pit lines 21 A and 21 B correspond to the read line pairs
- the sense word lines 31 correspond to the ground-side read lines.
- the wiring direction of the readout line is not limited to the embodiment, and may have a correspondence opposite to the above.
- the magnetic memory device includes a plurality of magnetoresistive elements each having a magneto-sensitive layer whose magnetization direction changes according to an external magnetic field, and one storage cell includes a pair of storage cells.
- a magnetic memory device configured to include a magnetoresistive element, a read line pair extending along a first direction and supplying a read current to the pair of magnetoresistive elements;
- a ground-side read line for guiding the read current flowing through the effect element to the ground and a plurality of ground-side read lines are provided in common, and the sum of a pair of read currents flowing through a pair of magnetoresistive elements in one storage cell is calculated.
- a constant current circuit for stabilizing and a read circuit for reading information from a memory cell based on a difference between a pair of read currents are provided, this is caused by using a plurality of constant current circuits. Variation in resistance value can be eliminated, and variation in read current value can be further reduced. Also, by providing a constant current circuit in common, the relative number of components in the entire magnetic memory device can be reduced as compared with a case in which a constant current circuit is provided for each ground-side read line. Can be reduced. Furthermore, since the number of constant current circuits that need to always supply a constant current can be reduced, the power consumption of the entire magnetic memory device can be reduced.
- a read-out common line is provided for each of the plurality of first-direction storage cell groups arranged along the first direction, and bundles a plurality of ground-side read lines for each first-direction storage cell group.
- a selection switch provided between each of the plurality of shared read lines and the constant current circuit, for selecting any one of the plurality of first-direction storage cell groups.
- Each of the laminates includes a magneto-sensitive layer whose magnetization direction changes due to an external magnetic field, and is configured so that a current flows in a direction perpendicular to the lamination plane, and a direction along the lamination plane on one side of the laminate.
- an annular magnetic layer arranged so as to extend in the axial direction and penetrated by the first and second write lines. The magnetization of the magnetosensitive layer can be efficiently reversed by the action of the annular magnetic layer.
- one unit of information is stored using two magnetoresistive elements, information can be efficiently and reliably written, and the degree of freedom in the information writing method and the information reading method is increased. be able to.
- a reading method of a magnetic memory device includes a plurality of magnetoresistive elements each having a magneto-sensitive layer whose magnetization direction changes by an external magnetic field, and one storage cell includes a pair of magnetoresistive elements.
- the first method is used for each pair of magnetoresistive elements.
- a read current is supplied to a pair of magnetoresistive elements via a pair of read lines provided so as to extend along the direction, and the read current flowing through the pair of magnetoresistive elements is supplied via a ground side read line.
- the sum of a pair of read currents flowing through a pair of magnetoresistive elements in one memory cell is made constant, and a pair of read currents Information is read from the memory cell based on the difference between the resistance values, it is possible to eliminate the variation in the resistance value caused by using multiple constant current circuits, and to obtain a read current with smaller variation Can be. Furthermore, since the number of constant current circuits that need to always supply a constant current can be reduced, the power consumption of the entire magnetic memory device at the time of reading can be reduced.
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Abstract
Description
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US10/547,508 US7209380B2 (en) | 2003-03-13 | 2004-03-12 | Magnetic memory device and method of reading the same |
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JP5551129B2 (ja) * | 2011-09-07 | 2014-07-16 | 株式会社東芝 | 記憶装置 |
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WO2013043738A1 (en) * | 2011-09-19 | 2013-03-28 | The Regents Of The University Of California | Body voltage sensing based short pulse reading circuit |
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Also Published As
Publication number | Publication date |
---|---|
US7209380B2 (en) | 2007-04-24 |
JP4283011B2 (ja) | 2009-06-24 |
TWI240928B (en) | 2005-10-01 |
US20060120145A1 (en) | 2006-06-08 |
EP1610339A1 (en) | 2005-12-28 |
TW200428385A (en) | 2004-12-16 |
EP1610339B1 (en) | 2011-10-19 |
EP1610339A4 (en) | 2007-03-28 |
JP2004280910A (ja) | 2004-10-07 |
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