WO2010041719A1 - Storage element - Google Patents

Storage element Download PDF

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WO2010041719A1
WO2010041719A1 PCT/JP2009/067576 JP2009067576W WO2010041719A1 WO 2010041719 A1 WO2010041719 A1 WO 2010041719A1 JP 2009067576 W JP2009067576 W JP 2009067576W WO 2010041719 A1 WO2010041719 A1 WO 2010041719A1
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magnetic layer
tunnel magnetoresistive
magnetization
value
resistance value
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幸男 菊地
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株式会社アルバック
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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
    • G11C11/56—Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor using storage elements with more than two stable states represented by steps, e.g. of voltage, current, phase, frequency
    • G11C11/5607—Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor using storage elements with more than two stable states represented by steps, e.g. of voltage, current, phase, frequency using magnetic storage elements
    • 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
    • G11C11/16—Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor using magnetic elements using elements in which the storage effect is based on magnetic spin effect
    • G11C11/161—Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor using magnetic elements using elements in which the storage effect is based on magnetic spin effect details concerning the memory cell structure, e.g. the layers of the ferromagnetic memory cell
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N50/00—Galvanomagnetic devices
    • H10N50/10—Magnetoresistive devices

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Abstract

Provided is a storage element with a high storage capacity.  Electrodes composing a tunneling magnetoresistance element are each configured to have magnetic layers selected from among a magnetic layer having a weak coercive force, a magnetic layer having an intermediate coercive force stronger than the weak coercive force, and a magnetic layer having a strong coercive force stronger than the intermediate coercive force, the coercive forces of electrodes are different in the same tunneling magnetoresistance element, and a combination of the coercive forces of magnetic layers of one tunneling magnetoresistance element out of two tunneling magnetoresistance elements and a combination of the coercive forces of magnetic layers of the other tunneling magnetoresistance element are different.  The electrodes of each tunneling magnetoresistance element are magnetized in the same direction or opposite directions to each other, and ternary or quaternary storage is enabled by changing the magnetization directions of the magnetic layer having the weak coercive force and the magnetic layer having the intermediate coercive force without changing the magnetization direction of the magnetic layer having the strong coercive force.

Description

記憶素子Memory element
　本発明は記憶素子に関する。 The present invention relates to a memory element.
　従来より、トンネル磁気抵抗効果（Ｔｕｎｎｅｌｉｎｇ　Ｍａｇｎｅｔｏ　Ｒｅｓｉｓｔａｎｃｅ　Ｅｆｆｅｃｔ）を利用した素子は、ＭＲＡＭ（Ｍａｇｎｅｔｉｃ　Ｒａｎｄｏｍ　Ａｃｃｅｓｓ　Ｍｅｍｏｒｙ）等の不揮発性メモリや、ＨＤＤ（Ｈａｒｄ　Ｄｉｓｋ　Ｄｒｉｖｅ）の読取ヘッド等に利用されている。 Conventionally, elements using the tunneling magnetoresistance effect (Tunneling Magneto Resistance Effect) have been used in nonvolatile memories such as MRAM (Magnetic Random Access Memory), HDD (Hard Disk Drive) read heads, and the like.
　図５の符号１１０は従来技術の記憶素子を示している。記憶素子１１０は磁化方向（磁力の向き）が固定された固定層１１５と、固定層１１５よりも保磁力が小さい自由層１１２と、固定層１１５と自由層１１２の間に配置された絶縁層１１９とを有している。 5 indicates a memory element of the prior art. The memory element 110 includes a fixed layer 115 whose magnetization direction (direction of magnetic force) is fixed, a free layer 112 having a smaller coercive force than the fixed layer 115, and an insulating layer 119 disposed between the fixed layer 115 and the free layer 112. And have.
　自由層１１２の保磁力を超える外部磁界を発生させると、自由層１１２の外部磁界の方向を向く。固定層１１５の磁化方向が固定されている範囲では、自由層１１２の磁化方向は、固定層１１５の磁化方向と同じ場合と、固定層１１５の磁化方向と逆方向になる場合の二通りがある。 When an external magnetic field exceeding the coercive force of the free layer 112 is generated, the external magnetic field of the free layer 112 is directed. In the range in which the magnetization direction of the fixed layer 115 is fixed, the magnetization direction of the free layer 112 may be the same as the magnetization direction of the fixed layer 115 or may be opposite to the magnetization direction of the fixed layer 115. .
　記憶素子１１０の固定層１１５が配置された側の面上と、自由層１１２が配置された側の面上には、第一、第二の電極１２１、１２２が配置されている。絶縁層１１９の膜厚は薄く、第一、第二の電極１２１、１２２間に電圧を印加すると、トンネル効果により、固定層１１５と自由層１１２の間に挟まれる絶縁層１１９を通して各膜の積層に垂直にトンネル電流が流れる。 The first and second electrodes 121 and 122 are disposed on the surface of the memory element 110 on the side where the fixed layer 115 is disposed and on the surface on which the free layer 112 is disposed. The insulating layer 119 is thin, and when a voltage is applied between the first and second electrodes 121 and 122, each film is stacked through the insulating layer 119 sandwiched between the fixed layer 115 and the free layer 112 by the tunnel effect. A tunnel current flows perpendicularly to.
　記憶素子１１０のトンネル抵抗は、自由層１１２の磁化方向と固定層１１５の磁化方向が同じ場合に小さく、自由層１１２の磁化方向と固定層１１５の磁化方向が逆の場合に大きい。従って、自由層１１２の磁化方向を変えることで情報を記憶し、第一、第二の電極１２１、１２２間にセンス電流を流すことによって情報を読み取ることができる。
特開平７－２８２４６６号公報 特許第２８７２４９５号公報 The tunnel resistance of the memory element 110 is small when the magnetization direction of the free layer 112 and the magnetization direction of the fixed layer 115 are the same, and is large when the magnetization direction of the free layer 112 and the magnetization direction of the fixed layer 115 are opposite. Therefore, information can be stored by changing the magnetization direction of the free layer 112, and information can be read by flowing a sense current between the first and second electrodes 121 and 122.
JP-A-7-282466 Japanese Patent No. 2872495
　自由層の磁化方向は二通りであるため、従来は記憶素子１個に対し、「０」又は「１」の二通りのデータしか記憶できず、記憶媒体の記憶容量を増やすためには、記憶素子の個数（密度）を増やす必要がある。記憶素子の密度を増やすためには、記憶素子を微細化する必要があるが、記憶素子の微細化には限界がある。 Since the magnetization direction of the free layer is two ways, conventionally, only two kinds of data “0” or “1” can be stored for one storage element. In order to increase the storage capacity of the storage medium, It is necessary to increase the number (density) of elements. In order to increase the density of the memory element, it is necessary to miniaturize the memory element, but there is a limit to the miniaturization of the memory element.
　上記課題を解決するために、本発明は記憶素子であって、絶縁層を磁性を有する二層の電極で挟み、前記電極間にトンネル電流が流れると、前記電極間には、二層の前記電極の磁化方向が同じ方向を向く場合に磁化同方向抵抗値を生じさせ、反対方向を向く場合に前記磁化同方向抵抗値よりも大きな磁化反対方向抵抗値を生じさせるトンネル磁気抵抗素子を二個直列に接続して直列接続回路を形成し、前記直列接続回路の抵抗値の大きさによって三以上の値を記憶する記憶素子であって、同一のトンネル磁気抵抗素子の内部では、前記電極は、弱保磁力の磁性層と、前記弱保磁力よりも強い中保磁力の磁性層と、前記中保磁力よりも強い強保磁力の磁性層のうちから保磁力が異なるように選択し、前記二個のトンネル磁気抵抗素子では、一方のトンネル磁気抵抗素子の磁性層の保磁力の組合せと、他方のトンネル磁気抵抗素子の磁性層の保磁力の組み合わせが異なるようにされ、前記各トンネル磁気抵抗素子の電極は、互いに同一方向か又は反対方向に磁化された記憶素子である。
　また、本発明は、前記一方のトンネル磁気抵抗素子は、前記絶縁層が前記強保磁力の磁性層と前記中保磁力の磁性層とで挟まれ、他方の前記トンネル磁気抵抗素子は、前記絶縁層が前記強保磁力の磁性層と前記弱保磁力の磁性層とで挟まれた記憶素子である。
　また、本発明は、前記一方のトンネル磁気抵抗素子の前記強保磁力の磁性層と、前記他方のトンネル磁気抵抗素子の前記強保磁力の磁性層とは、離間して配置された記憶素子である。
　また、本発明は、前記一方のトンネル磁気抵抗素子は、前記絶縁層が前記中保磁力の磁性層と前記弱保磁力の磁性層とで挟まれ、他方の前記トンネル磁気抵抗素子は、前記中保磁力の磁性層と前記弱保磁力の磁性層のうちのいずれか一方の磁性層と前記強保磁力の磁性層で挟まれた記憶素子である。
　また、本発明は、前記一方のトンネル磁気抵抗素子の前記中保磁力の磁性層と前記弱保磁力の磁性層とで前記絶縁層が挟まれて、他方の前記トンネル磁気抵抗素子が構成された記憶素子である。
　また、本発明は、前記一方のトンネル磁気抵抗素子と前記他方のトンネル磁気抵抗素子とは積層された記憶素子である。
　また、本発明は、上記いずれかの記憶素子であって、前記各磁性層の磁化方向は、前記磁性層の表面と平行な方向に向けられた水平磁化記憶方式の記憶素子である。
　また、本発明は、前記強保磁力の磁性層には、反強磁性層が密着された記憶素子である。
　また、本発明は、上記いずれかの記憶素子であって、前記各磁性層の磁化方向は、前記磁性層の膜厚方向と平行な方向に向けられた垂直磁化記憶方式の記憶素子である。
　また、本発明は、前記強保磁力の磁性層は前記中保磁力の磁性層よりも膜厚が厚く、前記中保磁力の磁性層は、前記弱保磁力の磁性層よりも膜厚が厚い記憶素子である。
　また、本発明は、前記一方のトンネル磁気抵抗素子の前記磁化反対方向抵抗値から前記磁化同方向抵抗値を差し引いた値と、前記他方のトンネル磁気抵抗素子の前記磁化反対方向抵抗値から前記磁化同方向抵抗値を差し引いた値とが、異なる大きさになるように形成された記憶素子である。
　また、本発明は、上記いずれかの記憶素子を用いて第一、第二、第三の値を記憶する記憶方法であって、前記第一の値を記憶するために、直列接続された前記トンネル磁気抵抗素子のうち、両方の前記トンネル磁気抵抗素子が前記磁化同方向抵抗値を示すように前記磁性層の磁化方向を同方向とし、前記第二の値を記憶するために、両方の前記トンネル磁気抵抗素子が前記磁化反対方向抵抗値を示すように前記磁性層の磁化方向をそれぞれ反対方向に向け、第三の値を記憶するために、いずれか一方の前記トンネル磁気抵抗素子が前記磁化同方向抵抗値を示すように前記磁性層の磁化方向を同方向に向け、他方の前記トンネル磁気抵抗素子の前記磁性層の磁化方向を反対方向に向ける記憶方法である。
　また、本発明は、前記直列接続回路の抵抗値を測定し、前記抵抗値から記憶された値を読み取る記憶方法であって、前記記憶素子の抵抗値を測定して基準値と比較し、両方の前記トンネル磁気抵抗素子の抵抗値が前記磁化同方向抵抗値であると判別した場合を前記第一の値とし、両方の前記トンネル磁気抵抗素子の抵抗値が前記磁化反対方向抵抗値であると判別した場合を前記第二の値とし、一方の前記トンネル磁気抵抗素子が前記磁化同方向抵抗値であり他方の前記トンネル磁気抵抗素子が前記磁化反対方向抵抗値であると判別した場合を第三の値とする記憶方法である。
　また、本発明は、上記記憶素子を用いて第一、第二、第三、第四の値を記憶する記憶方法であって、前記第一の値を記憶するために、直列接続された前記トンネル磁気抵抗素子のうち、両方の前記トンネル磁気抵抗素子が前記磁化同方向抵抗値を示すように前記磁性層の磁化方向を同方向とし、前記第二の値を記憶するために、両方の前記トンネル磁気抵抗素子が前記磁化反対方向抵抗値を示すように前記磁性層の磁化方向をそれぞれ反対方向に向け、第三の値を記憶するために、いずれか一方の前記トンネル磁気抵抗素子が前記磁化同方向抵抗値を示すように前記磁性層の磁化方向を同方向に向け、他方の前記トンネル磁気抵抗素子の前記磁性層の磁化方向を反対方向に向け、第四の値を記憶するために、前記他方のトンネル磁気抵抗素子が前記磁化同方向抵抗値を示すように前記磁性層の磁化方向を同方向に向け、前記一方のトンネル磁気抵抗素子の前記磁性層の磁化方向を反対方向に向ける記憶方法である。
　また、本発明は、前記直列接続回路の抵抗値を測定し、前記抵抗値から記憶された値を読み取る記憶方法であって、前記記憶素子の抵抗値を測定して基準値と比較し、両方の前記トンネル磁気抵抗素子の抵抗値が前記磁化同方向抵抗値であると判別した場合を前記第一の値とし、両方の前記トンネル磁気抵抗素子の抵抗値が前記磁化反対方向抵抗値であると判別した場合を前記第二の値とし、前記一方のトンネル磁気抵抗素子が前記磁化同方向抵抗値であり前記他方のトンネル磁気抵抗素子が前記磁化反対方向抵抗値であると判別した場合を第三の値とし、前記一方のトンネル磁気抵抗素子が前記磁化同方向抵抗値であり前記他方のトンネル磁気抵抗素子が前記磁化反対方向抵抗値であると判別した場合を第四の値とする記憶方法である。 In order to solve the above problems, the present invention is a memory element, in which an insulating layer is sandwiched between two magnetic electrodes, and when a tunnel current flows between the electrodes, a two-layered electrode is interposed between the electrodes. Two tunnel magnetoresistive elements that generate the same magnetization resistance value when the magnetization directions of the electrodes are in the same direction, and generate a magnetization opposite resistance value that is larger than the magnetization same direction resistance value when they are in the opposite direction. A storage element that is connected in series to form a series connection circuit, and stores three or more values according to the magnitude of the resistance value of the series connection circuit, and in the same tunnel magnetoresistive element, the electrodes are: The coercive force is selected from among a magnetic layer having a weak coercivity, a magnetic layer having a medium coercivity stronger than the weak coercivity, and a magnetic layer having a strong coercivity stronger than the medium coercivity, In one tunnel magnetoresistive element, The combination of the coercive force of the magnetic layer of the tunnel magnetoresistive element is different from the combination of the coercive force of the magnetic layer of the other tunnel magnetoresistive element, and the electrodes of the tunnel magnetoresistive elements are in the same direction or opposite to each other. A storage element magnetized in the direction.
Further, the present invention provides the one tunnel magnetoresistive element, wherein the insulating layer is sandwiched between the strong coercive magnetic layer and the intermediate coercive magnetic layer, and the other tunnel magnetoresistive element is the insulating magnetoresistive element. The storage element is a memory element sandwiched between the magnetic layer having the strong coercive force and the magnetic layer having the weak coercive force.
Further, the present invention is a storage element in which the strong coercive magnetic layer of the one tunnel magnetoresistive element and the strong coercive magnetic layer of the other tunnel magnetoresistive element are spaced apart. is there.
Further, the present invention provides the one tunnel magnetoresistive element, wherein the insulating layer is sandwiched between the intermediate coercive magnetic layer and the weak coercive magnetic layer, and the other tunnel magnetoresistive element is the intermediate tunnel magnetoresistive element. The storage element is sandwiched between one of a magnetic layer having a coercive force and a magnetic layer having a weak coercive force, and the magnetic layer having a strong coercive force.
Further, in the present invention, the insulating layer is sandwiched between the intermediate coercive magnetic layer and the weak coercive magnetic layer of the one tunnel magnetoresistive element, and the other tunnel magnetoresistive element is configured. It is a memory element.
Further, the present invention is a memory element in which the one tunnel magnetoresistive element and the other tunnel magnetoresistive element are stacked.
The present invention is also the storage element of any of the above, wherein the magnetization direction of each magnetic layer is a horizontal magnetization storage type storage element oriented in a direction parallel to the surface of the magnetic layer.
The present invention is also a memory element in which an antiferromagnetic layer is adhered to the magnetic layer having the strong coercive force.
Further, the present invention is any one of the above storage elements, wherein the magnetization direction of each magnetic layer is a perpendicular magnetization storage type storage element in which the direction is parallel to the film thickness direction of the magnetic layer.
Further, according to the present invention, the strong coercive magnetic layer is thicker than the intermediate coercive magnetic layer, and the intermediate coercive magnetic layer is thicker than the weak coercive magnetic layer. It is a memory element.
Further, the present invention provides a value obtained by subtracting the same magnetization direction resistance value from the opposite magnetization direction resistance value of the one tunnel magnetoresistive element and the magnetization opposite direction resistance value of the other tunnel magnetoresistive element. The memory element is formed such that the value obtained by subtracting the resistance value in the same direction has a different size.
Further, the present invention is a storage method for storing the first, second, and third values using any one of the storage elements described above, wherein the first value is stored in series in order to store the first value. Among the tunneling magnetoresistive elements, both the tunneling magnetoresistive elements have the same direction of magnetization so that both of the tunneling magnetoresistive elements exhibit the same direction resistance value of magnetization, and both of the above described values are stored in order to store the second value. In order to store a third value by directing the magnetization directions of the magnetic layers in opposite directions so that the tunnel magnetoresistive element exhibits the resistance value opposite to the magnetization, one of the tunnel magnetoresistive elements is In this storage method, the magnetization direction of the magnetic layer is directed in the same direction so as to exhibit the same direction resistance value, and the magnetization direction of the magnetic layer of the other tunnel magnetoresistive element is directed in the opposite direction.
Further, the present invention is a storage method for measuring a resistance value of the series connection circuit and reading a value stored from the resistance value, and measuring a resistance value of the storage element and comparing it with a reference value. When the resistance value of the tunnel magnetoresistive element is determined to be the same magnetization direction resistance value as the first value, the resistance value of both of the tunnel magnetoresistive elements is the opposite magnetization direction resistance value The case where it is determined is the second value, and the case where it is determined that one of the tunnel magnetoresistive elements has the same magnetization direction resistance value and the other tunnel magnetoresistive element has the opposite magnetization direction resistance value is the third value. This is a storage method.
Further, the present invention is a storage method for storing the first, second, third, and fourth values using the storage element, wherein the first value is stored in series in order to store the first value. Among the tunneling magnetoresistive elements, both the tunneling magnetoresistive elements have the same direction of magnetization so that both of the tunneling magnetoresistive elements exhibit the same direction resistance value of magnetization, and both of the above described values are stored in order to store the second value. In order to store a third value by directing the magnetization directions of the magnetic layers in opposite directions so that the tunnel magnetoresistive element exhibits the resistance value opposite to the magnetization, one of the tunnel magnetoresistive elements is In order to store the fourth value by directing the magnetization direction of the magnetic layer in the same direction to indicate the same direction resistance value, orienting the magnetization direction of the magnetic layer of the other tunnel magnetoresistive element in the opposite direction, The other tunnel magnetoresistive element Wherein directing the magnetization direction of the magnetic layer to exhibit a magnetization in the same direction the resistance value in the same direction, which is a storage method for directing the magnetization direction of the magnetic layer of said one of the tunnel magneto-resistance element in the opposite direction.
Further, the present invention is a storage method for measuring a resistance value of the series connection circuit and reading a value stored from the resistance value, and measuring a resistance value of the storage element and comparing it with a reference value. When the resistance value of the tunnel magnetoresistive element is determined to be the same magnetization direction resistance value as the first value, the resistance value of both of the tunnel magnetoresistive elements is the opposite magnetization direction resistance value The case where it is determined is the second value, and the case where it is determined that the one tunnel magnetoresistive element has the same magnetization direction resistance value and the other tunnel magnetoresistive element has the opposite magnetization direction resistance value is the third value. And when the one tunnel magnetoresistive element has the same magnetization direction resistance value and the other tunnel magnetoresistive element has the opposite magnetization direction resistance value, a fourth method is used. is there.
　本発明は上記のように構成されており、弱保磁力の磁性層と、弱保磁力よりも保磁力が強い中保磁力の磁性層と、中保磁力の磁性層よりも保磁力が強い強磁性層の三種類の磁性層を用いており、一般に、強保磁力の磁性層を固定層と呼び、強保磁力の磁化方向を変化させるような強度の外部磁界は印加しないようにされている。 The present invention is configured as described above, and has a weak coercivity magnetic layer, a medium coercivity magnetic layer whose coercivity is stronger than the weak coercivity, and a strong coercivity stronger than the medium coercivity magnetic layer. Three types of magnetic layers are used. Generally, a magnetic layer having a strong coercive force is called a fixed layer, and an external magnetic field that changes the magnetization direction of the strong coercive force is not applied. .
　本発明では、中保磁力又は弱保磁力のいずれか一方の磁性層を第一の自由層、他方の磁性層を第二の自由層と呼んでいる。
　磁性層は導電性を有しており、絶縁膜と、絶縁膜の表面側の磁性層と裏面側の磁性層とでトンネル磁気抵抗素子を形成し、二個のトンネル磁気抵抗素子を直列接続すると、その直列接続回路の磁気抵抗値は、二個のトンネル磁気抵抗Ｑ1、Ｑ2の合計値になる。
　磁性層の磁化方向は、磁性層表面に平行な方向の水平磁化記憶方式と、磁性層の膜厚方向と平行な方向(これは、磁性層の表面とは垂直な方向である)の垂直磁化記憶方式との二種類がある。 In the present invention, one of the medium coercive force and the weak coercive force is called the first free layer, and the other magnetic layer is called the second free layer.
The magnetic layer has conductivity. When a tunnel magnetoresistive element is formed by an insulating film, a magnetic layer on the front surface side of the insulating film, and a magnetic layer on the back surface side, and two tunnel magnetoresistive elements are connected in series The magnetoresistance value of the series connection circuit is the total value of the two tunnel magnetoresistances Q 1 and Q 2 .
The magnetization direction of the magnetic layer is the horizontal magnetization storage method in the direction parallel to the magnetic layer surface and the perpendicular magnetization in the direction parallel to the film thickness direction of the magnetic layer (this is the direction perpendicular to the magnetic layer surface). There are two types of storage methods.
　トンネル磁気抵抗素子では、水平磁化と垂直磁化のいずれの場合でも、同じトンネル磁気抵抗素子内の二枚の電極の磁化方向が反対向きのときの方が、同方向のときよりも抵抗値が大きいことが知られている。
　同方向のときをＱ1＝Ｒ1、Ｑ2＝Ｒ2とし、反対方向のときをＱ1＝Ｒ1＋ΔＲ1、Ｑ2＝Ｒ2＋ΔＲ2 とすると、二個のトンネル磁気抵抗素子内の磁性層の方向により、直列抵抗Ｑ1＋Ｑ2は、
　Ｒ1＋Ｒ2、Ｒ1＋Ｒ2＋ΔＲ1 、Ｒ1＋Ｒ2＋ΔＲ2 、Ｒ1＋Ｒ2＋ΔＲ1＋ΔＲ2 ……(１)
の四個の式で表せる場合のうちのいずれかの場合の値をとる。 In a tunnel magnetoresistive element, the resistance value is larger when the magnetization directions of two electrodes in the same tunnel magnetoresistive element are opposite to each other in both cases of horizontal magnetization and vertical magnetization. It is known.
When Q 1 = R 1 and Q 2 = R 2 in the same direction, and Q 1 = R 1 + ΔR 1 and Q 2 = R 2 + ΔR 2 in the opposite direction, Depending on the direction of the magnetic layer, the series resistance Q 1 + Q 2 is
R 1 + R 2 , R 1 + R 2 + ΔR 1 , R 1 + R 2 + ΔR 2 , R 1 + R 2 + ΔR 1 + ΔR 2 (1)
It takes the value in any of the cases that can be expressed by the following four expressions.
　ΔＲ1とΔＲ2の大きさが異なれば、直列抵抗Ｑ1＋Ｑ2は、四種類の異なる値を取るのでＲ1＋Ｒ2＋ΔＲ1とＲ1＋Ｒ2＋ΔＲ2の大きさを区別できれば、トンネル磁気抵抗素子の抵抗値により、四種類の値を表すことができる。
　この場合、直列抵抗の抵抗値が四個の式のいずれであるかを区別するためには、三種類の値の基準値Ｒref1～Ｒref3が用いられ、ΔＲ1＜ΔＲ2とすると、基準値Ｒref1～Ｒref3は、直列抵抗Ｑ1＋Ｑ2に対して下記のような関係にある値が選択される。
　Ｒ1＋Ｒ2＜Ｒref1＜Ｒ1＋Ｒ2＋ΔＲ1＜Ｒref2＜Ｒ1＋Ｒ2＋ΔＲ2＜Ｒref3＜Ｒ1＋Ｒ2＋ΔＲ1＋ΔＲ2   ……(２) If the magnitudes of ΔR 1 and ΔR 2 are different, the series resistance Q 1 + Q 2 takes four different values. Therefore, if the magnitudes of R 1 + R 2 + ΔR 1 and R 1 + R 2 + ΔR 2 can be distinguished, the tunnel magnetism Four types of values can be represented by the resistance value of the resistance element.
In this case, three types of reference values Rref 1 to Rref 3 are used in order to distinguish which of the four resistance values of the series resistance, and when ΔR 1 <ΔR 2 , As the values Rref 1 to Rref 3 , values having the following relationship with respect to the series resistance Q 1 + Q 2 are selected.
R 1 + R 2 <Rref 1 <R 1 + R 2 + ΔR 1 <Rref 2 <R 1 + R 2 + ΔR 2 <Rref 3 <R 1 + R 2 + ΔR 1 + ΔR 2 (2)
　従って、測定した直列抵抗Ｑ1＋Ｑ2と基準値Ｒref1～Ｒref3を比較すると、二個のトンネル磁気抵抗素子で形成される記憶素子の四種類の状態を区別することができる。
　Ｒ1＋Ｒ2＋ΔＲ1とＲ1＋Ｒ2＋ΔＲ2の大きさを区別しない場合は、Ｒ1＋Ｒ2の大きさと、Ｒ1＋Ｒ2＋ΔＲ1又はＲ1＋Ｒ2＋ΔＲ2の大きさと、Ｒ1＋Ｒ2＋ΔＲ1＋ΔＲ2の大きさとを区別することで、三種類の値を表すことができる。基準値をＲrefa、Ｒrefbとし、ΔＲ1＜ΔＲ2とすると、基準値をＲrefa、Ｒrefbは直列抵抗Ｑ1＋Ｑ2に対して下記のような関係にある値が選択される。
　Ｒ1＋Ｒ2＜Ｒrefa＜Ｒ1＋Ｒ2＋ΔＲ1＜Ｒ1＋Ｒ2＋ΔＲ2＜Ｒrefb＜Ｒ1＋Ｒ2＋ΔＲ1＋ΔＲ2 ……(３) Therefore, by comparing the measured series resistance Q 1 + Q 2 with the reference values Rref 1 to Rref 3 , it is possible to distinguish the four types of states of the memory element formed by two tunnel magnetoresistive elements.
When the magnitudes of R 1 + R 2 + ΔR 1 and R 1 + R 2 + ΔR 2 are not distinguished, the magnitude of R 1 + R 2 , the magnitude of R 1 + R 2 + ΔR 1 or R 1 + R 2 + ΔR 2 , and R 1 + R By distinguishing from the magnitude of 2 + ΔR 1 + ΔR 2 , three types of values can be expressed. When the reference values are Rref a and Rref b, and ΔR 1 <ΔR 2 , the reference values Rref a and Rref b are selected to have the following relationship with respect to the series resistance Q 1 + Q 2 .
R 1 + R 2 <Rref a <R 1 + R 2 + ΔR 1 <R 1 + R 2 + ΔR 2 <Rref b <R 1 + R 2 + ΔR 1 + ΔR 2 (3)
　直列接続された二個のトンネル磁気抵抗素子に同じ外部磁界を印加して、上記（１）式中の四式の抵抗値の組合せを実現するためには、強保磁力、中保磁力、弱保磁力の三種類から、異なる保持力の磁性層を二種選択してトンネル磁気抵抗を形成した場合に、弱保磁力よりも強く且つ中保磁力よりも弱く、中保磁力及び強保磁力の磁性層の磁化方向は反転させないで弱保磁力の磁性層の磁化方向を反転させることができる弱外部磁界と、中保磁力よりも強く強保磁力よりも弱く、強保磁力の磁性層の磁化方向を反転させないで、弱保磁力と中保磁力の磁性層の磁化方向を反転させることができる強外部磁界のいずれかの外部磁界により、トンネル磁気抵抗素子の片方の磁性層の磁化方向を反転させることができる。 In order to realize the combination of the four resistance values in the above equation (1) by applying the same external magnetic field to the two tunnel magnetoresistive elements connected in series, the strong coercive force, the medium coercive force, the weak When two types of magnetic layers having different coercive forces are selected from the three types of coercive force and tunneling magnetoresistance is formed, the coercive force is stronger than the weak coercive force and weaker than the intermediate coercive force. A weak external magnetic field that can reverse the magnetization direction of the weakly coercive magnetic layer without reversing the magnetization direction of the magnetic layer, and a magnetization of the magnetic layer having a strong coercive force that is stronger than the intermediate coercive force and weaker than the strong coercive force The magnetization direction of one magnetic layer of the tunnel magnetoresistive element is reversed by one of the strong external magnetic fields that can reverse the magnetization direction of the magnetic layer of weak coercive force and medium coercive force without reversing the direction. Can be made.
　弱保磁力の磁性層と中保磁力の磁性層でトンネル磁気抵抗素子を形成した場合、強外部磁界によって、両方の磁性層の磁化方向を、外部磁界と同じ向きにすることができる。
　このように、本発明では、磁性材料の近くにある配線に電流を流すことで外部磁界を発生させ、その外部磁界が磁性層の磁化方向を変化させる方式や、記憶素子に磁石を近接させて磁石が発生する外部磁界を用いて磁性層の磁化方向を磁気抵抗素子変化させることができる。 When a tunnel magnetoresistive element is formed of a magnetic layer having a weak coercive force and a magnetic layer having a medium coercive force, the magnetization direction of both magnetic layers can be made the same as that of the external magnetic field by a strong external magnetic field.
As described above, in the present invention, an external magnetic field is generated by passing a current through a wiring near the magnetic material, and the external magnetic field changes the magnetization direction of the magnetic layer. The magnetization direction of the magnetic layer can be changed by using an external magnetic field generated by the magnet.
　しかし、外部磁界を用いる方法では、磁石は微小な記憶素子には不向きであり、電流により外部磁界を発生させる場合はパターンが小さくなる程大電流を必要とし、また、近接する他の磁性層にも影響を与えてしまう。
　磁性層の中の電子は、磁化方向と同じ向きにスピンの向きがそろっているが、この磁性層に、スピンが磁化方向と逆向きにそろっている電子を流すと、注入された電子と磁性層中の電子が相互作用を起こし、磁性層中の電子がスピンと垂直方向に揺れだす。この振幅が一定以上に大きくなると、スピンの方向が一斉に反転する。 However, in the method using an external magnetic field, the magnet is not suitable for a small memory element. When an external magnetic field is generated by an electric current, a larger current is required as the pattern becomes smaller. Will also affect.
The electrons in the magnetic layer have the same spin direction as the magnetization direction. However, if electrons with the spin direction opposite to the magnetization direction are passed through this magnetic layer, the injected electrons and the magnetism are magnetized. The electrons in the layer interact, and the electrons in the magnetic layer sway in the direction perpendicular to the spin. When this amplitude becomes larger than a certain level, the spin directions are reversed simultaneously.
　本発明では、磁石が発生する外部磁界や電流を流して発生させる外部磁界の他、上記のような磁性層に電子スピンの方向が偏った電流を磁性材料に流すことで、材料の磁化方向を変化させるスピン注入磁化反転方法も用いることができる。
　この場合、弱外部磁界や強外部磁界に替え、弱保磁力の磁性層の磁化方向を反転させることができるが中保磁力及び強保磁力の磁性層の磁化方向は反転させることができない弱スピン注入電流と、強保磁力の磁性層の磁化方向を反転させることはできないが、弱保磁力と中保磁力の磁性層の磁化方向を反転させることができる強スピン注入電流を用いて、三値、四値の記憶素子や記憶方法を得ることができる。 In the present invention, in addition to an external magnetic field generated by a magnet and an external magnetic field generated by passing a current, a current in which the direction of electron spin is biased in the magnetic layer is passed through the magnetic material, thereby changing the magnetization direction of the material. A changing spin injection magnetization reversal method can also be used.
In this case, it is possible to reverse the magnetization direction of the weak coercive magnetic layer instead of the weak external magnetic field or the strong external magnetic field, but the magnetization direction of the medium coercive force and strong coercive force magnetic layer cannot be reversed. The injection current and the magnetization direction of the magnetic layer with strong coercive force cannot be reversed, but the ternary can be obtained by using a strong spin injection current that can reverse the magnetization direction of the weak coercive force and the medium coercive force magnetic layer. A quaternary storage element and a storage method can be obtained.
　二個のトンネル磁気抵抗素子のうち、一方のトンネル磁気抵抗素子の磁性層の保磁力の組み合わせと、他方のトンネル磁気抵抗素子の磁性層の保磁力の組み合わせと異ならせると、直列抵抗の値は、磁性層の磁化方向の向きにより、上記(１)式中の四式のうち、いずれかの式で算出することができる。 If the combination of the coercive force of the magnetic layer of one tunnel magnetoresistive element and the coercive force of the magnetic layer of the other tunnel magnetoresistive element are different from each other, the value of the series resistance is Depending on the direction of the magnetization direction of the magnetic layer, it can be calculated by any one of the four formulas in the formula (1).
　三値の場合は、(３)式から、ΔＲ1とΔＲ2とを等しく(ΔＲ1＝ΔＲ2)してもよいことが分かる。
　四値の場合は、(２)式から、ΔＲ1とΔＲ2は等しくしない(ΔＲ1≠ΔＲ2）必要があることが分かる。 In the case of ternary values, it can be seen from the equation (3) that ΔR 1 and ΔR 2 may be equal (ΔR 1 = ΔR 2 ).
In the case of four values, it can be seen from the equation (2) that ΔR 1 and ΔR 2 need not be equal (ΔR 1 ≠ ΔR 2 ).
　強保磁力の磁性層と、中保磁力の磁性層と、弱保磁力の磁性層を用いることで、三値や四値の記憶素子が得られる。
　従って、記憶素子の密度を増やさなくても、二値の記憶媒体よりも記憶容量を増やすことができる。 By using a strong coercive magnetic layer, a medium coercive magnetic layer, and a weak coercive magnetic layer, a ternary or quaternary storage element can be obtained.
Accordingly, the storage capacity can be increased as compared with the binary storage medium without increasing the density of the storage elements.
本発明第一例の記憶素子を説明する断面図Sectional drawing explaining the memory element of 1st example of this invention 本発明第二例の記憶素子を説明する断面図Sectional drawing explaining the memory element of 2nd example of this invention （ａ）～（ｄ）：磁化方向の向きの組み合わせを説明する模式的な断面図(A) to (d): Schematic cross-sectional views illustrating combinations of magnetization directions 本発明の記憶素子を用いた記憶媒体の一例を説明する断面図Sectional drawing explaining an example of the storage medium using the memory element of this invention 従来技術の記憶素子を説明する断面図Sectional drawing explaining the memory element of a prior art 垂直磁化記憶方法の記憶素子の積層構造の一例を示す図The figure which shows an example of the laminated structure of the memory element of a perpendicular magnetization memory method 垂直磁化記憶方法の記憶素子の積層構造の他の一例を示す図The figure which shows another example of the laminated structure of the memory element of a perpendicular magnetization memory | storage method （ａ）～（ｄ）：磁化方向の変化と抵抗値の関係を説明するための模式的な図(A) to (d): Schematic diagrams for explaining the relationship between the change in magnetization direction and the resistance value （ａ）～（ｄ）：積層構造が変わった場合の磁化方向の変化と抵抗値の関係を説明するための模式的な図(A) to (d): Schematic diagrams for explaining the relationship between the change in magnetization direction and the resistance value when the laminated structure is changed 本発明の記憶素子の構造の他の第一例を示す図The figure which shows the other 1st example of the structure of the memory element of this invention 本発明の記憶素子の構造の他の第二例を示す図The figure which shows the other 2nd example of the structure of the memory element of this invention
　１……記憶媒体
１０、３０、５０、６０……記憶素子
１１……第一の自由層
１２……第二の自由層
１３、１４……絶縁層
２０、４０……磁場固定部材
２１～２３……固定層
２５～２７……反強磁性層
４１～４４……強磁性層
４７……第一の電極
４８……第二の電極 DESCRIPTION OF SYMBOLS 1 ... Storage medium 10, 30, 50, 60 ... Storage element 11 ... 1st free layer 12 ... 2nd free layer 13, 14 ... Insulating layer 20, 40 ... Magnetic field fixing member 21-23 ...... Fixed layers 25 to 27 ...... Antiferromagnetic layers 41 to 44 ...... ferromagnetic layer 47 ...... first electrode 48 ...... second electrode
　図１の符号１０は本発明第一例の記憶素子を示し、図２の符号３０は本発明第二例の記憶素子を示している。記憶素子１０、３０は、第一、第二の電極４７、４８と、第一、第二の電極４７、４８間に配置された磁場固定部材２０、４０とを有している。 1 indicates the memory element of the first example of the present invention, and numeral 30 of FIG. 2 indicates the memory element of the second example of the present invention. The memory elements 10 and 30 have first and second electrodes 47 and 48 and magnetic field fixing members 20 and 40 disposed between the first and second electrodes 47 and 48.
　磁場固定部材２０、４０は、磁化方向が固定されている層である固定層２１～２３を一又は二以上有している。第一例の記憶素子１０は固定層２１、２２の数が複数（ここでは二つ）であり、固定層（第一、第二の固定層）２１、２２は、反強磁性層２５、２６と、反強磁性層２５、２６の片面に配置された強磁性層４１、４２とを有している。
　第二例の記憶素子３０は固定層２３の数が一つであり、固定層２３は反強磁性層２７と、反強磁性層２７の表面及び裏面に配置された強磁性層４３、４４とを有している。 The magnetic field fixing members 20 and 40 have one or more fixed layers 21 to 23 which are layers whose magnetization directions are fixed. The memory element 10 of the first example has a plurality of (in this case, two) fixed layers 21 and 22, and the fixed layers (first and second fixed layers) 21 and 22 are antiferromagnetic layers 25 and 26. And ferromagnetic layers 41, 42 disposed on one side of the antiferromagnetic layers 25, 26.
The memory element 30 of the second example has one fixed layer 23, and the fixed layer 23 includes an antiferromagnetic layer 27 and ferromagnetic layers 43 and 44 disposed on the front and back surfaces of the antiferromagnetic layer 27. have.
　第一例、第二例の記憶素子１０、２０は両方とも強磁性層４１～４４の数は二以上（ここでは二つ）であり、各強磁性層４１～４４は反強磁性層２５～２７と積層されることによりＮ極とＳ極の向きである磁化方向が固定されている。
　強磁性層４１～４４の表面上には、絶縁層１３、１４（トンネル障壁）を介して磁性材料からなり、磁化方向が変更可能な第一、第二の自由層１１、１２が配置されている。 In both of the memory elements 10 and 20 of the first and second examples, the number of the ferromagnetic layers 41 to 44 is two or more (here, two), and each of the ferromagnetic layers 41 to 44 includes the antiferromagnetic layers 25 to 27, the magnetization direction which is the direction of the N pole and the S pole is fixed.
On the surfaces of the ferromagnetic layers 41 to 44, first and second free layers 11 and 12 made of a magnetic material and capable of changing the magnetization direction are arranged via insulating layers 13 and 14 (tunnel barriers). Yes.
　第一例の記憶素子１０では、第一、第二の固定層２１、２２が、反強磁性層２５、２６を外側（第一、第二の電極４７、４８側）に向け、強磁性層４１、４２を内側に向けて配置され、第一、第二の自由層１１、１２は第一、第二の固定層２１、２２の間に位置している。第一、第二の自由層１１、１２間には非磁性金属からなる隔壁保護膜１９が配置されている。 In the memory element 10 of the first example, the first and second pinned layers 21 and 22 have the antiferromagnetic layers 25 and 26 facing outward (first and second electrodes 47 and 48 side), and the ferromagnetic layers. The first and second free layers 11 and 12 are positioned between the first and second fixed layers 21 and 22. A partition protective film 19 made of a nonmagnetic metal is disposed between the first and second free layers 11 and 12.
　ここで、本記憶素子を作成するための積層構造は、これのみに限定されない。例えば、図１の反強磁性層２６と、強磁性層４２と、絶縁層１３と、第二の自由層１２の積層構造を、隔壁保護膜１９を介して単に重ね合わせてもよい。即ち、反強磁性層２６、強磁性層４２、絶縁層１３、自由層、隔壁保護膜１９、反強磁性層２６、強磁性層４２、絶縁層１３、自由層…の順番に積層してもよい。 Here, the laminated structure for creating this memory element is not limited to this. For example, the laminated structure of the antiferromagnetic layer 26, the ferromagnetic layer 42, the insulating layer 13, and the second free layer 12 in FIG. That is, the antiferromagnetic layer 26, the ferromagnetic layer 42, the insulating layer 13, the free layer, the partition protective film 19, the antiferromagnetic layer 26, the ferromagnetic layer 42, the insulating layer 13, the free layer. Good.
　第二例の記憶素子３０では、第一、第二の自由層１１、１２は、絶縁層１４、１３を介して、一方が固定層２３の表面上に位置し、他方が裏面上に位置する。
　いずれの記憶素子１０、３０も、第一、第二の自由層１１、１２は反強磁性層２５～２７と接触して配置されておらず、第一、第二の自由層１１、１２と反強磁性層２５～２７の間に強磁性層４１～４４があるから、第一、第二の自由層１１、１２の磁化方向は固定されない。従って、第一、第二の自由層１１、１２は保磁力を超える外部磁界により、磁化方向が変更可能になっている。 In the memory element 30 of the second example, one of the first and second free layers 11 and 12 is positioned on the surface of the fixed layer 23 and the other is positioned on the back surface via the insulating layers 14 and 13. .
In any of the memory elements 10 and 30, the first and second free layers 11 and 12 are not arranged in contact with the antiferromagnetic layers 25 to 27, and the first and second free layers 11 and 12 Since there are ferromagnetic layers 41 to 44 between the antiferromagnetic layers 25 to 27, the magnetization directions of the first and second free layers 11 and 12 are not fixed. Therefore, the magnetization directions of the first and second free layers 11 and 12 can be changed by an external magnetic field exceeding the coercive force.
　図３（ａ）～（ｄ）は、強磁性層４１～４４の磁化方向Ｆ0と、第一、第二の自由層１１、１２の磁化方向Ｆ1、Ｆ2を模式的に示す断面図である。
　この図３（ａ）～（ｄ）及び後述する各図中の矢印の向きは磁化方向を表している。
　第一例の記憶素子１０内の強磁性層４１、４２の磁化方向Ｆ0は互いに同じであり、また、第二例の記憶素子３０内の強磁性層４３、４４の磁化方向Ｆ0も互いに同じであり、右向きの矢印で表す。
　記憶素子１０、３０の各層１１～１４、１６、１７、１９、２５～２７は、各強磁性層４１～４４の磁化方向Ｆ0に対して平行な方向に磁化されている。第一、第二の自由層１１、１２の磁化方向Ｆ1、Ｆ2は、強磁性層４１～４４の磁化方向Ｆ0と平行であって、強磁性層４１～４４の磁化方向Ｆ0と同じ向き、又は逆向きになる。 3A to 3D are cross-sectional views schematically showing the magnetization direction F 0 of the ferromagnetic layers 41 to 44 and the magnetization directions F 1 and F 2 of the first and second free layers 11 and 12. It is.
The directions of arrows in FIGS. 3A to 3D and the drawings to be described later indicate the magnetization direction.
The magnetization directions F 0 of the ferromagnetic layers 41 and 42 in the memory element 10 of the first example are the same, and the magnetization directions F 0 of the ferromagnetic layers 43 and 44 in the memory element 30 of the second example are also mutually different. Same and represented by a right-pointing arrow.
The layers 11 to 14, 16, 17, 19, 25 to 27 of the memory elements 10 and 30 are magnetized in a direction parallel to the magnetization direction F 0 of the ferromagnetic layers 41 to 44. The magnetization directions F 1 and F 2 of the first and second free layers 11 and 12 are parallel to the magnetization direction F 0 of the ferromagnetic layers 41 to 44, and the magnetization directions F 0 of the ferromagnetic layers 41 to 44 are The same direction or the opposite direction.
　第一の自由層１１の保磁力（第一の保磁力）は、第二の自由層１２の保磁力（第二の保磁力）よりも大きく、第一の自由層１１の磁化方向Ｆ1よりも、第二の自由層１２の磁化方向Ｆ2の方が弱い外部磁界で向きが変るようになっている。
　図３（ａ）は強磁性層４１～４４と第一、第二の自由層１１、１２の磁化方向Ｆ0、Ｆ1、Ｆ2が同じ場合を示す。 The coercive force (first coercive force) of the first free layer 11 is larger than the coercive force (second coercive force) of the second free layer 12 and from the magnetization direction F 1 of the first free layer 11. also, who magnetization direction F 2 of the second free layer 12 is adapted to orientation changes by a weak external magnetic field.
FIG. 3A shows a case where the magnetization directions F 0 , F 1 and F 2 of the ferromagnetic layers 41 to 44 and the first and second free layers 11 and 12 are the same.
　図３（ａ）の状態の記憶素子１０、３０を、強磁性層４１～４４の磁化方向Ｆ0と逆向きであって、第二の保磁力以上第一の保磁力未満に相当する外部磁界Ｈrに曝すと、第二の自由層１２の磁化方向Ｆ2が強磁性層４１～４４の磁化方向Ｆ0に対して逆向きになるが、第一の自由層１１の磁化方向Ｆ1は変化しない。その状態を図３（ｂ）に表す。 An external magnetic field corresponding to the second coercive force or more and less than the first coercive force of the storage elements 10 and 30 in the state of FIG. 3A is opposite to the magnetization direction F 0 of the ferromagnetic layers 41 to 44. When exposed to H r , the magnetization direction F 2 of the second free layer 12 is opposite to the magnetization direction F 0 of the ferromagnetic layers 41 to 44, but the magnetization direction F 1 of the first free layer 11 is It does not change. This state is shown in FIG.
　図３（ａ）又は図３（ｂ）の状態の記憶素子１０、３０を、強磁性層４１～４４の磁化方向Ｆ0と逆向きであって、第一の保磁力以上に相当する外部磁界Ｈrに曝すと、第一、第二の自由層１１、１２の両方の磁化方向Ｆ1、Ｆ2が強磁性層４１～４４の磁界方向Ｆ0とは逆向きになる。その状態を図３（ｃ）に表す。 The external magnetic field corresponding to the first coercive force or more in the direction opposite to the magnetization direction F 0 of the ferromagnetic layers 41 to 44 is used for the memory elements 10 and 30 in the state of FIG. When exposed to H r , the magnetization directions F 1 and F 2 of both the first and second free layers 11 and 12 are opposite to the magnetic field direction F 0 of the ferromagnetic layers 41 to 44. This state is shown in FIG.
　図３（ｃ）の状態の記憶素子１０、３０を、強磁性層４１～４４の磁化方向Ｆ0と同じ向きであって、第二の保磁力以上第一の保磁力未満に相当する外部磁界Ｈrに曝すと、第二の自由層１２の磁化方向Ｆ2は強磁性層４１～４４の磁化方向Ｆ0と同じ向きに変るが、第一の自由層１１の磁化方向Ｆ1は変らない。その状態を図３（ｄ）に表す。 The storage elements 10 and 30 in the state of FIG. 3C have the same direction as the magnetization direction F 0 of the ferromagnetic layers 41 to 44 and an external magnetic field corresponding to a second coercive force or more and less than the first coercive force. When exposed to H r , the magnetization direction F 2 of the second free layer 12 changes to the same direction as the magnetization direction F 0 of the ferromagnetic layers 41 to 44, but the magnetization direction F 1 of the first free layer 11 does not change. . This state is shown in FIG.
　更に、図３（ｃ）又は図３（ｄ）の状態の記憶素子１０、３０を、強磁性層４１～４４の磁化方向Ｆ0と同じ向きであって、第一の保磁力以上に相当する外部磁界Ｈrに曝すと、図３（ａ）に示す状態になる。このように、自由層（１１、１２）の数が二つの場合は、磁化方向Ｆ0、Ｆ1、Ｆ2は４通りの組み合わせになる。 Furthermore, the storage elements 10 and 30 in the state of FIG. 3C or FIG. 3D have the same direction as the magnetization direction F 0 of the ferromagnetic layers 41 to 44 and correspond to the first coercive force or more. When exposed to the external magnetic field H r , the state shown in FIG. Thus, when the number of free layers (11, 12) is two, the magnetization directions F 0 , F 1 , F 2 are four combinations.
　第一、第二の電極４７、４８は、記憶素子１０、３０の各層１１～１４、１６、１７、１９、２５～２７、４１～４４に対して図のように設置され、第一、第二の電極４７、４８間に電圧を印加すると、各層１１～１４、１６、１７、１９、２５～２７、４１～４４に対して垂直な方向に電流が流れる。 The first and second electrodes 47 and 48 are disposed as shown in the figure with respect to the respective layers 11 to 14, 16, 17, 19, 25 to 27, and 41 to 44 of the memory elements 10 and 30, respectively. When a voltage is applied between the two electrodes 47 and 48, a current flows in a direction perpendicular to each of the layers 11 to 14, 16, 17, 19, 25 to 27, and 41 to 44.
　このとき、絶縁層１３、１４を挟んで隣接する強磁性層４１～４４と自由層１１、１２との間のトンネル抵抗は、強磁性層（４１～４４）と自由層（１１、１２）の磁化方向Ｆ0、Ｆ1、Ｆ2が同じ場合に最小になり、逆向きの場合に最大になる。
　従って、第一、第二の自由層１１、１２と強磁性層４１～４４の磁化方向Ｆ0、Ｆ1、Ｆ2が同じ場合、記憶素子１０、３０のトンネル抵抗（第一、第二の電極４７、４８間の電気抵抗）が最小値Ｒになる（図３（ａ））。 At this time, the tunnel resistance between the ferromagnetic layers 41 to 44 and the free layers 11 and 12 adjacent to each other with the insulating layers 13 and 14 interposed therebetween is that of the ferromagnetic layers (41 to 44) and the free layers (11, 12). It becomes minimum when the magnetization directions F 0 , F 1 , and F 2 are the same, and becomes maximum when they are reversed.
Therefore, when the magnetization directions F 0 , F 1 , F 2 of the first and second free layers 11, 12 and the ferromagnetic layers 41 to 44 are the same, the tunnel resistance (first, second, The electric resistance between the electrodes 47 and 48 becomes the minimum value R (FIG. 3A).
　絶縁層１３、１４の片面に接触する強磁性層４１～４４と、反対側の面に接触する自由層１１、１２との間のトンネル抵抗の、最大値と最小値の差を、強磁性層４１又は４４と第一の自由層１１との間では第一の抵抗差ΔＲ１とし、強磁性層４２、４３と第二の自由層１２との間では第二の抵抗差ΔＲ２とすると、第一、第二の自由層１１、１２の磁化方向Ｆ1、Ｆ2の両方が、強磁性層４１～４４の磁化方向Ｆ0と逆向きな場合、記憶素子１０、３０のトンネル抵抗はＲ＋ΔＲ１＋ΔＲ２で表される最大値となる（図３（ｃ））。 The difference between the maximum value and the minimum value of the tunnel resistance between the ferromagnetic layers 41 to 44 that are in contact with one side of the insulating layers 13 and 14 and the free layers 11 and 12 that are in contact with the opposite side is expressed as a ferromagnetic layer. 41 or 44 and the first free layer 11 is the first resistance difference ΔR1, and the ferromagnetic layers 42 and 43 and the second free layer 12 are the second resistance difference ΔR2. When the magnetization directions F 1 and F 2 of the second free layers 11 and 12 are opposite to the magnetization directions F 0 of the ferromagnetic layers 41 to 44, the tunnel resistance of the memory elements 10 and 30 is expressed by R + ΔR1 + ΔR2. Is the maximum value (FIG. 3C).
　第一の自由層１１と強磁性層４１～４４の磁化方向Ｆ0、Ｆ1が同じ向きであり、第二の自由層１２と強磁性層４１～４４の磁化方向Ｆ0、Ｆ2が逆向きの場合、記憶素子１０、３０のトンネル抵抗はＲ＋ΔＲ２であり、最小値Ｒと最大値Ｒ＋ΔＲ１＋ΔＲ２の間になる（図３（ｂ））。 The magnetization directions F 0 and F 1 of the first free layer 11 and the ferromagnetic layers 41 to 44 are the same, and the magnetization directions F 0 and F 2 of the second free layer 12 and the ferromagnetic layers 41 to 44 are reversed. In the case of the orientation, the tunnel resistance of the memory elements 10 and 30 is R + ΔR2, which is between the minimum value R and the maximum value R + ΔR1 + ΔR2 (FIG. 3B).
　また、第二の自由層１２と強磁性層４１～４４の磁化方向Ｆ2、Ｆ0が同じであり、第一の自由層１１と強磁性層４１～４４の磁化方向Ｆ1、Ｆ0が逆向きの場合、記憶素子１０、３０のトンネル抵抗はＲ＋ΔＲ１であり、この場合も最小値Ｒと最大値Ｒ＋ΔＲ１＋ΔＲ２の間になる（図３（ｄ））。 Also, the magnetization directions F 2 and F 0 of the second free layer 12 and the ferromagnetic layers 41 to 44 are the same, and the magnetization directions F 1 and F 0 of the first free layer 11 and the ferromagnetic layers 41 to 44 are the same. In the reverse direction, the tunnel resistance of the memory elements 10 and 30 is R + ΔR1, which is also between the minimum value R and the maximum value R + ΔR1 + ΔR2 (FIG. 3 (d)).
　従って、第一、第二の抵抗差ΔＲ１、ΔＲ２が等しい場合も異なる場合も、第一又は第二の自由層１１、１２のいずれか一方の磁化方向が強磁性層４１～４４の磁化方向と同じ向きであり、他方の自由層の磁化方向が強磁性層４１～４４の磁化方向と逆向きであれば、記憶素子１０、３０のトンネル抵抗は、最小値Ｒを超え、かつ、最大値Ｒ＋ΔＲ１＋ΔＲ２未満の間（中間値）になる。
　このように、自由層の数が二つの場合、記憶素子１０、３０のトンネル抵抗は、最大値、最小値に加え、最大値と最小値の間の値である中間値の３通りになる。
　Ｒ＋ΔＲ１とＲ＋ΔＲ２とが異なる値であり、区別できる第一の中間値と第二の中間値とすれば、４通りになる。
　例えば自由層の材料（材質）を異ならせると、ΔＲ１とΔＲ２の値が異なり、４通りになる。 Therefore, regardless of whether the first and second resistance differences ΔR1 and ΔR2 are equal or different, the magnetization direction of one of the first or second free layers 11 and 12 is the same as the magnetization direction of the ferromagnetic layers 41 to 44. If the magnetization direction of the other free layer is opposite to the magnetization direction of the ferromagnetic layers 41 to 44, the tunnel resistance of the memory elements 10, 30 exceeds the minimum value R and the maximum value R + ΔR1 + ΔR2 Less than (intermediate value).
As described above, when the number of free layers is two, the tunnel resistance of the memory elements 10 and 30 becomes three kinds of intermediate values which are values between the maximum value and the minimum value in addition to the maximum value and the minimum value.
R + ΔR1 and R + ΔR2 are different values. If the first intermediate value and the second intermediate value that can be distinguished are used, there are four values.
For example, if the materials (materials) of the free layer are different, the values of ΔR1 and ΔR2 are different and become four.
　次に、本発明の記憶素子を用いた記憶装置を説明する。図４はＭＲＡＭ等の記憶装置１の一例を示す断面図である。
　記憶装置１は第一、第二の配線５、６を複数本ずつ有している。第一の配線５は所定間隔を空けて互いに平行に配置され、第二の配線６は第一の配線５が配置された平面と平行な平面内で、第一の配線５と交差するように配置されている。ここでは、第一、第二の配線５、６はＳｉＯ2等の絶縁層２に埋設されている。 Next, a memory device using the memory element of the present invention will be described. FIG. 4 is a cross-sectional view showing an example of the storage device 1 such as an MRAM.
The storage device 1 has a plurality of first and second wirings 5 and 6. The first wiring 5 is arranged parallel to each other with a predetermined interval, and the second wiring 6 intersects the first wiring 5 in a plane parallel to the plane where the first wiring 5 is arranged. Has been placed. Here, the first and second wirings 5 and 6 are embedded in an insulating layer 2 such as SiO 2 .
　第一、第二の配線５、６が交差する位置では、第一、第二の配線５、６は離間しており、交差部分の近くには、本発明の記憶素子１０又は３０が配置されている。第一、第二の配線５、６の交差位置は複数個あり、行列状に配置されている。従って、記憶素子１０又は３０は行列状に配置されている。
　記憶素子１０又は３０の第一、第二の電極４７、４８は、当該記憶素子１０、３０の近傍で交差する第一、第二の配線５、６にそれぞれ接続されている。 At the position where the first and second wirings 5 and 6 intersect, the first and second wirings 5 and 6 are separated from each other, and the memory element 10 or 30 of the present invention is disposed near the intersection. ing. There are a plurality of intersecting positions of the first and second wirings 5 and 6, which are arranged in a matrix. Therefore, the memory elements 10 or 30 are arranged in a matrix.
The first and second electrodes 47 and 48 of the memory element 10 or 30 are respectively connected to first and second wirings 5 and 6 that intersect in the vicinity of the memory element 10 or 30.
　第一、第二の配線５、６は制御装置８に接続されている。制御装置８には、記憶素子１０、３０の位置情報と、各記憶素子１０、３０がどの配線５、６に接続されているかの情報が記憶されている。
　第一、第二の配線５、６は、制御装置８を介して測定装置９に接続されている。情報を読み出す場合、制御装置８は、第一、第二の配線５、６を選択して所望の記憶素子１０、３０に電流を流し、測定装置９は電流が流れた記憶素子１０、３０のトンネル抵抗を測定し、測定結果を制御装置８へ伝達する。 The first and second wirings 5 and 6 are connected to the control device 8. The control device 8 stores position information of the storage elements 10 and 30 and information on which wiring 5 and 6 each storage element 10 and 30 is connected to.
The first and second wirings 5 and 6 are connected to the measuring device 9 via the control device 8. When reading out information, the control device 8 selects the first and second wirings 5 and 6 to pass a current through the desired storage elements 10 and 30, and the measuring device 9 The tunnel resistance is measured and the measurement result is transmitted to the control device 8.
　上述したように、本発明の記憶素子１０、３０のトンネル抵抗は、最大値、最小値、中間値の３通りになり、制御装置８には少なくともトンネル抵抗の最大値と最小値が設定されている。
　制御装置８は測定装置９の測定結果と設定されたトンネル抵抗の値とを比較し、測定結果が最大値、最小値、又は最大値と最小値の間（中間値）のいずれかに相当するか判断する。制御装置８は、判断した結果をそれぞれ「０」、「１」、「２」等の情報に関連付け、情報として読み出す。
　従って、この記憶装置１では、第一、第二の配線５、６と、制御装置８と、測定装置９とで、情報を読み出す読み出し手段が構成される。 As described above, the tunnel resistances of the memory elements 10 and 30 of the present invention are the maximum value, the minimum value, and the intermediate value, and at least the maximum value and the minimum value of the tunnel resistance are set in the control device 8. Yes.
The control device 8 compares the measurement result of the measurement device 9 with the set tunnel resistance value, and the measurement result corresponds to the maximum value, the minimum value, or between the maximum value and the minimum value (intermediate value). Judge. The control device 8 associates the determined result with information such as “0”, “1”, “2”, etc., and reads it as information.
Therefore, in the storage device 1, the first and second wirings 5 and 6, the control device 8, and the measurement device 9 constitute a reading unit that reads information.
　次に、情報の書き換えについて説明する。この記憶装置１では、第一の配線５の配線に沿って書き換え配線４が延設されている。第一の配線５は第二の配線６と交差するから、書き換え配線４も第二の配線６と交差する。
　各記憶素子１０、３０は、書き換え配線４と第二の配線６とが交差した位置で、書き換え配線４と第二の配線６の間に配置されている。書き換え配線４は記憶素子１０、３０及び第一、第二の配線５、６と非接触であり、絶縁されている。 Next, information rewriting will be described. In the storage device 1, the rewrite wiring 4 is extended along the wiring of the first wiring 5. Since the first wiring 5 intersects with the second wiring 6, the rewrite wiring 4 also intersects with the second wiring 6.
Each storage element 10, 30 is disposed between the rewrite wiring 4 and the second wiring 6 at a position where the rewrite wiring 4 and the second wiring 6 intersect each other. The rewrite wiring 4 is not in contact with the memory elements 10 and 30 and the first and second wirings 5 and 6 and is insulated.
　書き換え配線４は制御装置８に接続されている。制御装置８には、書き換え配線４及び第二の配線６と、記憶素子１０、３０との位置関係が設定されている。
　制御装置８は格子状に配置された書き換え配線４と第二の配線６との間に配置されている中で目的とする記憶素子の一つを選択し、通電する。通電により、書き換え配線４と第二の配線６の周囲に磁場が発生し、書き換え配線４と第二の配線６が交差位置近傍に合成磁場が発生し、他の素子には磁場の影響を与えない。従って、行列状に配置された複数の記憶素子１０、３０のうち、選択した配線４、６の交差位置にある記憶素子１０、３０だけが合成磁場に曝される。 The rewrite wiring 4 is connected to the control device 8. In the control device 8, the positional relationship between the rewrite wiring 4 and the second wiring 6 and the storage elements 10 and 30 is set.
The control device 8 selects one of the target storage elements among the rewrite wirings 4 and the second wirings 6 arranged in a grid pattern and energizes them. When energized, a magnetic field is generated around the rewrite wiring 4 and the second wiring 6, a combined magnetic field is generated near the intersection of the rewriting wiring 4 and the second wiring 6, and the other elements are affected by the magnetic field. Absent. Therefore, only the memory elements 10 and 30 at the intersection of the selected wirings 4 and 6 among the plurality of memory elements 10 and 30 arranged in a matrix are exposed to the synthesized magnetic field.
　書き換え配線４と第二の配線６に流す電流の向きや強さ等の通電条件を変えると、合成磁場の向きや強さが変る。トンネル抵抗を最大値、最小値、中間値にする各合成磁場を作る通電条件は予め求められ、制御装置８に設定されている。
　制御装置８は記憶したい情報とトンネル抵抗を関連付け、トンネル抵抗を関連付けた値にする通電条件で、書き換え配線４と第二の配線６に電流を流し、記憶素子１０、３０に所望の記憶情報をトンネル抵抗として記憶する。 When the energization conditions such as the direction and strength of the current flowing through the rewrite wiring 4 and the second wiring 6 are changed, the direction and strength of the synthesized magnetic field changes. The energization conditions for creating each combined magnetic field that sets the tunnel resistance to the maximum value, the minimum value, and the intermediate value are obtained in advance and set in the control device 8.
The control device 8 associates the information to be stored with the tunnel resistance, and supplies current to the rewrite wiring 4 and the second wiring 6 under the energization condition that sets the tunnel resistance to an associated value, and stores desired storage information in the storage elements 10 and 30. Memorize as tunnel resistance.
　このように、第二の配線６と、書き換え配線４と、制御装置８とが情報を書き換える書き換え手段となるが、書き換え手段はこれに限定されない。例えば、書き換え手段を書き換え配線４と制御装置８だけで構成してもよい。この場合、制御装置８は、書き換え配線４を選択して通電し、選択した書き換え配線４上にある記憶素子１０、３０の情報を書き換える。 Thus, the second wiring 6, the rewriting wiring 4, and the control device 8 serve as a rewriting means for rewriting information, but the rewriting means is not limited to this. For example, the rewriting means may be composed of only the rewrite wiring 4 and the control device 8. In this case, the control device 8 selects the rewrite wiring 4 and energizes it, and rewrites the information of the storage elements 10 and 30 on the selected rewrite wiring 4.
　また、書き換え配線４を設けず、第一、第二の配線５、６と制御装置８で書き換え手段を構成してもよい。この場合、制御装置８は、第一、第二の配線５、６を選択して通電し、選択された第一、第二の配線５、６の交差位置で合成磁場を発生させ、当該交差位置近傍の記憶素子１０、３０の情報を書き換える。 Further, the rewriting means may be constituted by the first and second wirings 5 and 6 and the control device 8 without providing the rewriting wiring 4. In this case, the control device 8 selects and energizes the first and second wirings 5 and 6, generates a synthetic magnetic field at the crossing position of the selected first and second wirings 5 and 6, and Information in the memory elements 10 and 30 near the position is rewritten.
　要するに、書き換え手段は制御装置８と配線とを有し、制御装置８が配線を選択して通電することにより、配線上の記憶素子１０、３０の情報を書き換える。
　書き換え手段は記憶装置１に設ける必要も無い。書き換え手段（例えばごく微小な電磁石等の磁界形成手段）を記憶装置１の外側に設け、書き換えの必要な記憶素子１０、３０に外部から書き換え手段を近づけることで、情報の書き換えを行ってもよい。 In short, the rewriting means has the control device 8 and the wiring, and the control device 8 rewrites the information of the storage elements 10 and 30 on the wiring when the wiring is selected and energized.
There is no need to provide the rewriting means in the storage device 1. Information may be rewritten by providing rewriting means (for example, magnetic field forming means such as a very small electromagnet) outside the storage device 1 and bringing the rewriting means close to the storage elements 10 and 30 that need rewriting from the outside. .
　第一、第二の自由層１１、１２の積層順は特に限定されないが、保磁力の小さい第二の自由層１２を、第一の自由層１１よりも書き換え配線４に近づけることが望ましい。
　以上は、書き換え手段が発生する磁界により磁化方向Ｆ1、Ｆ2を変える電流発生磁場方式について説明したが、本発明はこれに限定されない。 The order of stacking the first and second free layers 11 and 12 is not particularly limited, but it is desirable that the second free layer 12 having a small coercive force be closer to the rewrite wiring 4 than the first free layer 11.
The current generation magnetic field method in which the magnetization directions F 1 and F 2 are changed by the magnetic field generated by the rewriting means has been described above, but the present invention is not limited to this.
　自由層１１、１２の数は二層に限定されない。保磁力が異なる自由層を３層以上設け、記憶素子１０、３０のトンネル抵抗の値を４通り以上にし、４通り以上の情報を記憶させることもできる。自由層を３層以上設ける場合、強磁性層の数は少なくとも自由層と同じにし、自由層と強磁性層の間に絶縁層を配置する。自由層は反強磁性層で磁化方向が固定されないように、自由層と反強磁性層の間に強磁性層を配置する。 The number of free layers 11 and 12 is not limited to two. It is also possible to provide three or more free layers having different coercive forces, to set the tunnel resistance values of the memory elements 10, 30 to four or more, and to store four or more types of information. When three or more free layers are provided, the number of ferromagnetic layers is at least the same as that of the free layers, and an insulating layer is disposed between the free layers and the ferromagnetic layers. The free layer is an antiferromagnetic layer, and a ferromagnetic layer is disposed between the free layer and the antiferromagnetic layer so that the magnetization direction is not fixed.
　強磁性層４１～４４の磁化方向は反強磁性層２５～２７で固定する場合に限定されず、強磁性層４１～４４の保磁力が、第一、第二の自由層１１、１２の保磁力よりも十分高くなるのであれば、反強磁性層２５～２７を設けなくてもよい。 The magnetization directions of the ferromagnetic layers 41 to 44 are not limited to the case where the antiferromagnetic layers 25 to 27 are fixed, and the coercive force of the ferromagnetic layers 41 to 44 is such that the coercive force of the first and second free layers 11 and 12 is increased. If it is sufficiently higher than the magnetic force, the antiferromagnetic layers 25 to 27 need not be provided.
　しかし、通常、磁性層の保磁力は数十ガウス程度であるのに対し、反強磁性層２５～２７で磁化方向を固定した場合には、保磁力が６００ガウス～８００ガウス程度に上昇するから、反強磁性層２５～２７で磁化方向を固定した方が、第一、第二の自由層１１、１２との保磁力の差をより大きくできる。 However, the coercive force of the magnetic layer is usually several tens of gauss, whereas when the magnetization direction is fixed by the antiferromagnetic layers 25 to 27, the coercive force increases to about 600 to 800 gauss. If the magnetization direction is fixed by the antiferromagnetic layers 25 to 27, the difference in coercive force between the first and second free layers 11 and 12 can be further increased.
　第一、第二の電極４７、４８の構成材料は導電性材料であれば特に限定されないが、例えばＣｕ、Ａｌ、Ｔａ、Ｒｕ等である。
　素子の機能上は、固定層２１～２３や第一、第二の自由層１１、１２を、第一、第二の電極４７、４８に直接接触させてもよいが、図１、２の符号１６、１７に示す下地層（保護層）を、固定層２１～２３及び第一、第二の自由層１１、１２と、第一、第二の電極４７、４８との間に配置した方が、第一、第二の自由層１１、１２を保護でき、また、多層構造の作製上好ましい。下地層１６、１７は特に限定されないが、例えば、Ｔａ等の金属材料である。 The constituent materials of the first and second electrodes 47 and 48 are not particularly limited as long as they are conductive materials, but are, for example, Cu, Al, Ta, Ru, and the like.
In terms of the function of the element, the fixed layers 21 to 23 and the first and second free layers 11 and 12 may be in direct contact with the first and second electrodes 47 and 48. 16 and 17 are preferably disposed between the fixed layers 21 to 23 and the first and second free layers 11 and 12 and the first and second electrodes 47 and 48. The first and second free layers 11 and 12 can be protected, and it is preferable for producing a multilayer structure. Although the underlayers 16 and 17 are not particularly limited, for example, a metal material such as Ta is used.
　反強磁性層２５～２７の構成材料は例えばＰｔＭｎ、ＩｒＭｎ等である。強磁性層４１～４４の構成材料は例えばＣｏＦｅＢである。第一、第二の自由層１１、１２の構成材料は保磁力が１桁程度異なる。例えばＣｏＦｅＢと、ＮｉＦｅである。
　強磁性層４１～４４及び第一、第二の自由層１１、１２の磁化方向を、各層１１～１４、１６、１７、１９、２５～２７、４１～４４に対して垂直にした垂直磁化方式の記憶素子１０、３０も本発明に含まれる。 The constituent material of the antiferromagnetic layers 25 to 27 is, for example, PtMn, IrMn, or the like. The constituent material of the ferromagnetic layers 41 to 44 is, for example, CoFeB. The constituent materials of the first and second free layers 11 and 12 differ in coercive force by about one digit. For example, CoFeB and NiFe.
Perpendicular magnetization method in which the magnetization directions of the ferromagnetic layers 41 to 44 and the first and second free layers 11 and 12 are perpendicular to the respective layers 11 to 14, 16, 17, 19, 25 to 27, and 41 to 44. The memory elements 10 and 30 are also included in the present invention.
　絶縁層１３、１４の構成材料は特に限定されず、例えばＭｇＯとアルミナ（Ａｌ2Ｏ3）のいずれか一方又は両方を用いることができるが、ＭｇＯを用いると記憶素子１０、３０の抵抗変化率が高くなるから特に好ましい。 The constituent materials of the insulating layers 13 and 14 are not particularly limited. For example, either or both of MgO and alumina (Al 2 O 3 ) can be used. When MgO is used, the rate of change in resistance of the memory elements 10 and 30 is increased. Is particularly preferable because of high.
　本発明の記憶素子では、例えば、自由層の数が二つであり、第一の自由層１１がＣｏＦｅＢ層、第二の自由層１２がＮｉＦｅ層、絶縁層１３、１４が同じ厚みの場合、第一の自由層１１によるＭＲ比（抵抗変化率）は約１００％であり、第二の自由層１２によるＭＲ比は約４０％である。以上により、最低抵抗状態に対して約１．４倍の中間抵抗状態と、約２倍の高抵抗状態が実現され、かつ、各高抵抗状態は保磁力の違いにより書き換えが可能である。尚、ＭＲ比とは最大抵抗値から最小抵抗値を引いた値を、最大抵抗値で除した値である。 In the memory element of the present invention, for example, when the number of free layers is two, the first free layer 11 is a CoFeB layer, the second free layer 12 is a NiFe layer, and the insulating layers 13 and 14 have the same thickness, The MR ratio (resistance change rate) by the first free layer 11 is about 100%, and the MR ratio by the second free layer 12 is about 40%. As described above, an intermediate resistance state that is about 1.4 times the minimum resistance state and a high resistance state that is about twice that of the lowest resistance state are realized, and each high resistance state can be rewritten by a difference in coercive force. The MR ratio is a value obtained by dividing a value obtained by subtracting the minimum resistance value from the maximum resistance value by the maximum resistance value.
　以上説明した構造では、第一の自由層１１と絶縁層１４と固定層２１又は２３とを積層させて第一のトンネル磁気抵抗素子を形成し、また、第二の自由層１２と絶縁層１３と固定層２２又は２３とを積層させて第二のトンネル磁気抵抗素子を形成して、三値又は四値のデータを記憶する記憶素子を構成させたが、二枚の電極が絶縁膜を間に挟んでトンネル磁気抵抗素子を形成する場合、二枚の電極の磁化方向が変化する場合も、二枚の電極の磁化方向の組合せによって、トンネル抵抗の大きさが異なるようになる。 In the structure described above, the first free layer 11, the insulating layer 14, and the fixed layer 21 or 23 are laminated to form the first tunnel magnetoresistive element, and the second free layer 12 and the insulating layer 13 are formed. And the fixed layer 22 or 23 are stacked to form a second tunnel magnetoresistive element to form a storage element for storing ternary or quaternary data, but the two electrodes sandwich the insulating film. When the tunnel magnetoresistive element is formed between the two electrodes, even when the magnetization directions of the two electrodes change, the magnitude of the tunnel resistance varies depending on the combination of the magnetization directions of the two electrodes.
　従って、三値又は四値のデータを記憶する記憶素子を構成させる場合は、上記と同様に、固定層２１又は２３と絶縁層１４と第一の自由層１１とを積層させて第一のトンネル磁気抵抗素子を形成すると共に、第一の自由層１１と絶縁層１３と第二の自由層１２とを積層させて第三のトンネル磁気抵抗素子を形成させ、この第一、第三のトンネル磁気抵抗素子によって記憶素子を構成させてもよい。 Therefore, in the case of configuring a storage element that stores ternary or quaternary data, the fixed layer 21 or 23, the insulating layer 14, and the first free layer 11 are stacked to form the first tunnel, as described above. In addition to forming the magnetoresistive element, the first free layer 11, the insulating layer 13, and the second free layer 12 are stacked to form a third tunnel magnetoresistive element. The memory element may be configured by a resistance element.
　この構造の記憶素子を図１０の符号７０で示す。この構造では、第二の電極４７上に保護層(下地層)１６が配置されており、固定層２１は保護層１６上に配置されている。
　固定層２１は、保護層１６上に形成された反強磁性層２５と、反強磁性層２５上に形成された強磁性層４１とで構成されている。
　強磁性層４１上には、絶縁層１４、第一の自由層１１、絶縁層１３、第二の自由層１２がこの順序で配置されている。第二の自由層１２上には、保護層１７と第一の電極４８とが積層されている。 A memory element having this structure is denoted by reference numeral 70 in FIG. In this structure, the protective layer (underlying layer) 16 is disposed on the second electrode 47, and the fixed layer 21 is disposed on the protective layer 16.
The fixed layer 21 includes an antiferromagnetic layer 25 formed on the protective layer 16 and a ferromagnetic layer 41 formed on the antiferromagnetic layer 25.
On the ferromagnetic layer 41, the insulating layer 14, the first free layer 11, the insulating layer 13, and the second free layer 12 are arranged in this order. On the second free layer 12, a protective layer 17 and a first electrode 48 are stacked.
　絶縁層１３、１４にはＭｇＯ薄膜が用いられており、第一、第二の自由層１１、１２にはＣｏＦｅＢの薄膜が用いられている。強磁性層４１は、ＣｏＦｅ膜と、Ｒｕ膜と、ＣｏＦｅＢ膜を反強磁性層２５上に積層して構成されている。そして後述するように、ＭｇＯ薄膜から成る二層の絶縁層１３、１４は、その配向のために、いずれもＣｏＦｅＢ層上に形成されている。反強磁性層２５には、ＰｔＭｎ薄膜が用いられている。 The insulating layers 13 and 14 are made of MgO thin films, and the first and second free layers 11 and 12 are made of CoFeB thin films. The ferromagnetic layer 41 is configured by laminating a CoFe film, a Ru film, and a CoFeB film on the antiferromagnetic layer 25. As will be described later, the two insulating layers 13 and 14 made of the MgO thin film are both formed on the CoFeB layer because of their orientation. For the antiferromagnetic layer 25, a PtMn thin film is used.
　また、他の構造として、図１１に示すように、第二の電極４７上に固定層２２と絶縁層１３と第二の自由層１２とを積層して第二のトンネル磁気抵抗素子を形成すると共に、第二の自由層１２上に他の絶縁層１４と第一の自由層１１とを積層させて第三のトンネル磁気抵抗素子を形成させ、第一、第三のトンネル磁気抵抗素子とで記憶素子８０を構成させてもよい。 As another structure, as shown in FIG. 11, the fixed layer 22, the insulating layer 13, and the second free layer 12 are stacked on the second electrode 47 to form a second tunnel magnetoresistive element. At the same time, another insulating layer 14 and the first free layer 11 are stacked on the second free layer 12 to form a third tunnel magnetoresistive element. The memory element 80 may be configured.
　要するに、二個のトンネル磁気抵抗素子によって、三値又は四値の記憶素子を構成させる場合、二個のトンネル磁気抵抗素子のうち、第一のトンネル磁気抵抗素子の一方の電極には強保磁力の固定層を用い、他方の電極には弱保磁力の自由層又は中保磁力の自由層を用いて構成し、且つ、第二のトンネル磁気抵抗素子の一方の電極は、強保磁力の固定層を用い、他方の電極には、弱保磁力の自由層と中保磁力の自由層のうち、第一のトンネル磁気抵抗素子で用いなかった保磁力の自由層の組み合わせるとよく、更に又、固定層を用いた第一のトンネル磁気抵抗素子に対し、第二のトンネル磁気抵抗素子は、一方の電極には弱保磁力の自由層を用い、他方の電極には中保磁力の自由層を用いて構成することができる。 In short, when a ternary or quaternary storage element is constituted by two tunnel magnetoresistive elements, one of the two tunnel magnetoresistive elements has a strong coercive force on one electrode. The other electrode is composed of a weak coercive force free layer or a medium coercive force free layer, and one electrode of the second tunnel magnetoresistive element is fixed with a strong coercive force. The other electrode may be a combination of a free layer of weak coercive force and a free layer of intermediate coercive force, which is not used in the first tunnel magnetoresistive element, and further, In contrast to the first tunnel magnetoresistive element using a fixed layer, the second tunnel magnetoresistive element uses a weak coercive force free layer for one electrode and a medium coercive force free layer for the other electrode. Can be configured.
　なお、固定層２１は、上記のように反強磁性層２５と強磁性層４１とを密着して形成する他、固定層を、第一、第二の自由層１１、１２と同材質で第一、第二の自由層１１、１２よりも膜厚の厚い薄膜で構成することもできる。第一、第二の自由層１１、１２も、薄い方を弱保持力の自由層、厚い方を中保持力の自由層にすることができる。 The fixed layer 21 is formed by adhering the antiferromagnetic layer 25 and the ferromagnetic layer 41 as described above, and the fixed layer is made of the same material as the first and second free layers 11 and 12. The first and second free layers 11 and 12 can be formed of a thin film having a larger film thickness. The first and second free layers 11 and 12 can also be a thin layer having a weak holding force and a thicker layer having a medium holding force.
＜垂直磁化方法＞
　次に、垂直磁化方法を使用する記憶素子と、その記憶素子を使用した四値又は三値記憶方法について説明する。
　近年垂直磁化膜を利用したTMR膜の開発が進んでおり、異なる材料を用いた磁気固定層を利用しない膜構造で比較的高いMR比が得られており、垂直磁化膜を採用したトンネル磁気抵抗効果を用いた記憶素子は微細化を実現できるため注目されている。
　垂直磁化方法を採用することに加え、“０”、“１”の二値による二進法に替えて三値、四値による三進法、四進法を採用することができれば、更に記憶素子の集積化に大きく貢献することができる。 <Vertical magnetization method>
Next, a storage element using the perpendicular magnetization method and a quaternary or ternary storage method using the storage element will be described.
In recent years, the development of TMR films using perpendicularly magnetized films has progressed, and a relatively high MR ratio has been obtained with a film structure that does not use a magnetic pinned layer using different materials, and tunnel magnetoresistive using perpendicularly magnetized films. A memory element using the effect has attracted attention because it can be miniaturized.
In addition to adopting the perpendicular magnetization method, if ternary, quaternary, and quaternary methods can be adopted instead of the binary method of “0” and “1”, storage elements can be further integrated. Can greatly contribute to the development.
　図６に示されている膜構造は、垂直磁化方法で膜厚方向と同方向に磁化された記憶素子５０であり、磁化方向が固定された磁場固定部材(固定層)２０と、絶縁性薄膜である第一の絶縁層１３と、磁化方向が変更可能な第一の自由層１１と、絶縁性薄膜である第２の絶縁層１４と、磁化方向が変更可能な第二の自由層１２とが、この順序で第二の電極層４７上に形成されている。
　従って、磁場固定部材(固定層)２０と、第一の絶縁層１３と、第一の自由層１１とで形成されるトンネル磁気抵抗素子と、第一の自由層１１と、第２の絶縁層１４と、第二の自由層１２とで形成されたトンネル磁気抵抗素子とが直列接続されている。第一の自由層１１である同一薄膜が両方のトンネル磁気抵抗素子で共通に用いられている。ここでは磁場固定部材(固定層)２０は磁性層を有しているが、反強磁性層は用いられていない。 The film structure shown in FIG. 6 is a memory element 50 magnetized in the same direction as the film thickness direction by a perpendicular magnetization method, a magnetic field fixing member (fixed layer) 20 having a fixed magnetization direction, and an insulating thin film. A first insulating layer 13 that can change the magnetization direction, a second insulating layer 14 that is an insulating thin film, and a second free layer 12 that can change the magnetization direction. Are formed on the second electrode layer 47 in this order.
Accordingly, the tunnel magnetoresistive element formed by the magnetic field fixing member (fixed layer) 20, the first insulating layer 13, and the first free layer 11, the first free layer 11, and the second insulating layer. 14 and a tunnel magnetoresistive element formed by the second free layer 12 are connected in series. The same thin film as the first free layer 11 is commonly used in both tunnel magnetoresistive elements. Here, the magnetic field fixing member (fixed layer) 20 has a magnetic layer, but no antiferromagnetic layer is used.
　磁場固定部材２０と、第一の自由層１１と、第二の自由層１２とはＦｅＰｔ薄膜から成る磁性層によって構成されている。
　磁性層を、磁性層の表面と平行な方向に磁化させる水平磁化の場合、磁性層と反強磁性層を接触させると、磁性層の保磁力が増大するため、反強磁性層を用いれば固定層を形成しやすいが、垂直磁化の場合、反強磁性層を用いて固定層を形成することは困難である。 The magnetic field fixing member 20, the first free layer 11, and the second free layer 12 are constituted by a magnetic layer made of a FePt thin film.
In the case of horizontal magnetization in which the magnetic layer is magnetized in a direction parallel to the surface of the magnetic layer, if the magnetic layer and the antiferromagnetic layer are brought into contact with each other, the coercive force of the magnetic layer increases. Although it is easy to form a layer, in the case of perpendicular magnetization, it is difficult to form a fixed layer using an antiferromagnetic layer.
　同じ組成の磁性材料から成る磁性層の保磁力の大小関係は、磁性層の膜厚の大小関係と等しくなっており、同一組成の磁性層が有する磁界の方向を逆方向に変更する場合、磁性層の膜厚が厚い方が、膜厚が薄い方の磁性層よりも大きな外部磁界が必要となる。
　従って、同一組成で強保磁力、中、弱の三種類の磁性層を形成する場合、膜厚が、厚みが厚い磁性層Ａ、厚みが中程度の磁性層Ｂ、厚みが薄い磁性層Ｃ(厚みは、磁性層Ａ>磁性層Ｂ>磁性層Ｃ)の三種類の磁性層を形成すればよい。 The magnitude relationship of the coercive force of the magnetic layers made of magnetic materials of the same composition is equal to the magnitude relationship of the film thickness of the magnetic layer. When changing the direction of the magnetic field of the magnetic layer of the same composition to the opposite direction, A thicker layer requires a larger external magnetic field than a thinner magnetic layer.
Therefore, when three types of magnetic layers having the same composition and strong coercive force, medium and weak are formed, the magnetic layer A having a large thickness, the magnetic layer B having a medium thickness, and the magnetic layer C having a thin thickness ( The thickness may be three types of magnetic layers: magnetic layer A> magnetic layer B> magnetic layer C).
　磁場固定部材２０は、磁性層の膜厚が、第一、第二の自由層１１、１２の膜厚よりも厚く形成されており、第一、第二の自由層１１、１２の磁化方向を変更する外部磁界の大きさよりも、磁場固定部材２０の磁化方向を変更する外部磁界の大きさの方が大きくなるようにされている。 The magnetic field fixing member 20 is formed such that the thickness of the magnetic layer is larger than the thickness of the first and second free layers 11 and 12, and the magnetization direction of the first and second free layers 11 and 12 is changed. The magnitude of the external magnetic field that changes the magnetization direction of the magnetic field fixing member 20 is made larger than the magnitude of the external magnetic field to be changed.
　また、第一、第二の自由層１１、１２のうち、いずれか一方の自由層の膜厚が他方の自由層の膜厚よりも厚くなり、膜厚の厚い方の磁界方向を変更する外部磁界の大きさが、膜厚が薄い方の磁界方向を変更する外部磁界の大きさよりも大きくなるようにされている。
　ここでは、第一の自由層１１の方が、第二の自由層１２よりも膜厚が厚くなっており、固定層２０が強保磁力の磁性層、第一の自由層１１が中保磁力の磁性層、第二の自由層１２が弱保磁力の磁性層である。 In addition, the thickness of one of the first and second free layers 11 and 12 is larger than the thickness of the other free layer, and the external magnetic field direction is changed to change the direction of the larger magnetic field. The magnitude of the magnetic field is set to be larger than the magnitude of the external magnetic field that changes the direction of the magnetic field with the thinner film thickness.
Here, the first free layer 11 is thicker than the second free layer 12, the fixed layer 20 is a strong coercive magnetic layer, and the first free layer 11 is a medium coercive force. The second free layer 12 is a magnetic layer having a weak coercive force.
　図８(ａ)～(ｄ)は、磁化方向の変化を示しており、強保磁力の磁性層、中保磁力の磁性層、弱保磁力の磁性層の磁化方向が揃っている。
　中保磁力の磁性層の磁化方向を反転させることはできないが、流れる電子のスピンの向きにより、弱保磁力の磁性層の磁化方向を反転させることができる電流を弱スピン注入電流、流れる電子のスピンの向きにより、弱保磁力の磁性層と中保磁力の磁性層の磁化方向を反転させることができるスピン電流を強スピン注入電流と呼ぶ。
　二個のトンネル磁気抵抗素子の磁性層の垂直磁化方向が同じ向きであり、二個のトンネル磁気抵抗素子の抵抗値が磁化方向が同じときに示される最小抵抗値である場合（図８(ａ)：Ｒ1＋Ｒ2)は、弱保磁力の磁性層(第二の自由層１２)の磁化方向Ｆ2だけを反転させる弱スピン注入電流が、第一、第二の電極４８、４７に印加された電圧により二個のトンネル磁気抵抗素子に流されて弱保磁力の磁性層(第二の自由層１２)を有するトンネル磁気抵抗素子の抵抗値が増加し(図８(ｂ)：Ｒ1＋Ｒ2＋ΔＲ2）、次に、スピンの向きが弱スピン注入電流と同じで、弱保磁力と中保磁力の磁性層の磁化方向も反転させることができる強スピン注入電流が流れると、ここでは中保磁力の磁性層(第一の自由層１１)の磁化方向Ｆ1が反転し、流れる前とは異なる抵抗値になる(図８(ｃ)：Ｒ1＋Ｒ2＋ΔＲ1)。 FIGS. 8A to 8D show changes in the magnetization direction, and the magnetization directions of the strong coercivity magnetic layer, the medium coercivity magnetic layer, and the weak coercivity magnetic layer are aligned.
Although the magnetization direction of the magnetic layer with medium coercivity cannot be reversed, the current that can reverse the magnetization direction of the magnetic layer with weak coercivity depends on the direction of the spin of flowing electrons. A spin current that can reverse the magnetization directions of the weak coercivity magnetic layer and the medium coercivity magnetic layer depending on the spin direction is called a strong spin injection current.
When the perpendicular magnetization directions of the magnetic layers of the two tunnel magnetoresistive elements are the same, and the resistance values of the two tunnel magnetoresistive elements are the minimum resistance values shown when the magnetization directions are the same (FIG. 8A ): R 1 + R 2 ) is a weak spin injection current that reverses only the magnetization direction F 2 of the weakly coercive magnetic layer (second free layer 12) is applied to the first and second electrodes 48 and 47. The resistance value of the tunnel magnetoresistive element having the weak coercive magnetic layer (second free layer 12) is caused to flow through the two tunnel magnetoresistive elements by the applied voltage (FIG. 8 (b): R 1 + R 2 + ΔR 2 ) Next, when a strong spin injection current flows in which the spin direction is the same as the weak spin injection current and the magnetization direction of the magnetic layer of the weak coercive force and the medium coercive force can be reversed, magnetization direction F 1 is inverted in the magnetic layer of the mediation force (first free layer 11), different from the previous flow It becomes the resistance value (FIG. 8 (c): R 1 + R 2 + ΔR 1).
　次に、スピンが逆向きの弱スピン注入電流が流されて弱保磁力の磁性層(第二の自由層１２)の磁化方向Ｆ2が再度反転し、抵抗値が最大になる（図８(ｄ)：Ｒ1＋Ｒ2＋ΔＲ1＋ΔＲ2)。
　この場合も、最小値、最大値、最小値と最大値の間の値である中間値の三値の記憶素子ができる。ΔＲ1とΔＲ2とが異なれば、Ｒ1＋Ｒ2＋ΔＲ1とＲ1＋Ｒ2＋ΔＲ2のうちの小さい方を第一の中間値、大きい方を第二の中間値とすると、最小値と第一の中間値と第二の中間値と最大値の四値の記憶素子ができる。 Next, a weak spin injection current having a reverse spin is applied to reverse the magnetization direction F 2 of the magnetic layer (second free layer 12) having a weak coercive force, and the resistance value is maximized (FIG. 8 ( d): R 1 + R 2 + ΔR 1 + ΔR 2 ).
Also in this case, a ternary storage element having a minimum value, a maximum value, and an intermediate value that is a value between the minimum value and the maximum value can be obtained. If ΔR 1 and ΔR 2 are different from each other, the smaller one of R 1 + R 2 + ΔR 1 and R 1 + R 2 + ΔR 2 is the first intermediate value and the larger one is the second intermediate value. A quaternary storage element having one intermediate value, a second intermediate value, and a maximum value is formed.
　図９は、強保磁力の固定層２０と絶縁層１３と第二の自由層１２とで構成したトンネル磁気抵抗素子と、第二の自由層１２と絶縁層１４と第一の自由層１１とで構成したトンネル磁気抵抗素子とを直列接続した記憶素子であり、この記憶素子でも、弱スピン注入電流と強スピン注入電流とを用いたり、弱外部磁界と強外部磁界を用いることで、三値、四値の記憶素子ができる。 FIG. 9 shows a tunnel magnetoresistive element composed of a pinned layer 20 having a strong coercive force, an insulating layer 13, and a second free layer 12, a second free layer 12, an insulating layer 14, and a first free layer 11. This is a memory element that is connected in series with a tunneling magnetoresistive element composed of a ternary element by using a weak spin injection current and a strong spin injection current, or by using a weak external magnetic field and a strong external magnetic field. A quaternary storage element can be formed.
　なお、図７の記憶素子６０に示すように、垂直磁化方法であって、直列接続する二個のトンネル磁気抵抗素子のうち、一方のトンネル磁気抵抗素子を第一の自由層１１と、絶縁層１４と、固定層２１で形成し、他方のトンネル磁気抵抗素子を第二の自由層１２と絶縁層１３と、固定層２２とで構成してもよい。
　磁化方向が垂直な磁性層としては、ＦｅＰｔ膜を用いることができる。 As shown in the memory element 60 of FIG. 7, in the perpendicular magnetization method, one of the two tunnel magnetoresistive elements connected in series is designated as the first free layer 11 and the insulating layer. 14 and the fixed layer 21, and the other tunnel magnetoresistive element may be composed of the second free layer 12, the insulating layer 13, and the fixed layer 22.
An FePt film can be used as the magnetic layer having a perpendicular magnetization direction.
　また、トンネル層となるＭｇＯの絶縁膜をＦｅＰｔ膜上に形成する場合、ＭｇＯトンネル層を（００１）に配向させるために、ＦｅＰｔ膜の表面に薄いアモルファス状ＣｏＦｅＢ膜を成膜してＦｅＰｔ膜とＣｏＦｅＢ膜とが積層された構造の電極とし、その表面にＭｇＯの絶縁層を形成し、更に、ＭｇＯの絶縁層の表面に、薄いアモルファス状ＣｏＦｅＢ膜とＦｅＰｔ膜とをこの順序で積層して電極として、各電極が垂直方向に磁化されたトンネル磁気抵抗素子を形成することができる。
　そして、電極中のＦｅＰｔの厚みを変えることで、電極の保磁力を変えて、自由層や固定層を形成することができる。
  When an MgO insulating film to be a tunnel layer is formed on the FePt film, a thin amorphous CoFeB film is formed on the surface of the FePt film in order to orient the MgO tunnel layer to (001). An electrode having a structure in which a CoFeB film is laminated, an MgO insulating layer is formed on the surface, and a thin amorphous CoFeB film and an FePt film are laminated in this order on the surface of the MgO insulating layer. As a result, a tunnel magnetoresistive element in which each electrode is magnetized in the vertical direction can be formed.
And by changing the thickness of FePt in an electrode, the coercive force of an electrode can be changed and a free layer and a fixed layer can be formed.

Claims (15)

  1. 　絶縁層を磁性を有する二層の電極で挟み、前記電極間にトンネル電流が流れると、前記電極間には、二層の前記電極の磁化方向が同じ方向を向く場合に磁化同方向抵抗値を生じさせ、反対方向を向く場合に前記磁化同方向抵抗値よりも大きな磁化反対方向抵抗値を生じさせるトンネル磁気抵抗素子を二個直列に接続して直列接続回路を形成し、前記直列接続回路の抵抗値の大きさによって三以上の値を記憶する記憶素子であって、
    　同一のトンネル磁気抵抗素子の内部では、前記電極は、弱保磁力の磁性層と、前記弱保磁力よりも強い中保磁力の磁性層と、前記中保磁力よりも強い強保磁力の磁性層のうちから保磁力が異なるように選択し、
    　前記二個のトンネル磁気抵抗素子では、一方のトンネル磁気抵抗素子の磁性層の保磁力の組合せと、他方のトンネル磁気抵抗素子の磁性層の保磁力の組み合わせが異なるようにされ、
    　前記各トンネル磁気抵抗素子の電極は、互いに同一方向か又は反対方向に磁化された記憶素子。     When an insulating layer is sandwiched between two layers of magnetized electrodes and a tunnel current flows between the electrodes, when the magnetization directions of the two layers of the electrodes are in the same direction, a magnetization co-directional resistance value is obtained. Two tunnel magnetoresistive elements that generate a resistance value in the opposite direction of magnetization that is larger than the resistance value in the same direction of magnetization when facing in the opposite direction to form a series connection circuit, A storage element that stores three or more values depending on the magnitude of the resistance value,
    Inside the same tunneling magnetoresistive element, the electrode includes a magnetic layer having a weak coercive force, a magnetic layer having an intermediate coercive force stronger than the weak coercive force, and a magnetic layer having a stronger coercive force stronger than the intermediate coercive force. Choose the coercive force to be different,
    In the two tunnel magnetoresistive elements, the combination of the coercive force of the magnetic layer of one tunnel magnetoresistive element is different from the combination of the coercive forces of the magnetic layer of the other tunnel magnetoresistive element,
    The electrodes of the tunnel magnetoresistive elements are storage elements magnetized in the same direction or in opposite directions.
  2. 　前記一方のトンネル磁気抵抗素子は、前記絶縁層が前記強保磁力の磁性層と前記中保磁力の磁性層とで挟まれ、他方の前記トンネル磁気抵抗素子は、前記絶縁層が前記強保磁力の磁性層と前記弱保磁力の磁性層とで挟まれた請求項１記載の記憶素子。 In the one tunnel magnetoresistive element, the insulating layer is sandwiched between the magnetic layer having the strong coercive force and the magnetic layer having the intermediate coercive force, and in the other tunnel magnetoresistive element, the insulating layer has the strong coercive force. The memory element according to claim 1, wherein the memory element is sandwiched between the magnetic layer and the magnetic layer having the weak coercive force.
  3. 　前記一方のトンネル磁気抵抗素子の前記強保磁力の磁性層と、前記他方のトンネル磁気抵抗素子の前記強保磁力の磁性層とは、離間して配置された請求項２記載の記憶素子。 3. The memory element according to claim 2, wherein the strong coercive magnetic layer of the one tunnel magnetoresistive element and the strong coercive magnetic layer of the other tunnel magnetoresistive element are arranged apart from each other.
  4. 　前記一方のトンネル磁気抵抗素子は、前記絶縁層が前記中保磁力の磁性層と前記弱保磁力の磁性層とで挟まれ、他方の前記トンネル磁気抵抗素子は、前記中保磁力の磁性層と前記弱保磁力の磁性層のうちのいずれか一方の磁性層と前記強保磁力の磁性層で挟まれた請求項１記載の記憶素子。 In the one tunnel magnetoresistive element, the insulating layer is sandwiched between the magnetic layer having the intermediate coercive force and the magnetic layer having the weak coercive force, and the other tunnel magnetoresistive element includes the magnetic layer having the intermediate coercive force. The memory element according to claim 1, wherein the memory element is sandwiched between any one of the weak coercive magnetic layers and the strong coercive magnetic layer.
  5. 　前記一方のトンネル磁気抵抗素子の前記中保磁力の磁性層と前記弱保磁力の磁性層とで前記絶縁層が挟まれて、他方の前記トンネル磁気抵抗素子が構成された請求項４記載の記憶素子。 5. The memory according to claim 4, wherein the insulating layer is sandwiched between the intermediate coercivity magnetic layer and the weak coercivity magnetic layer of the one tunnel magnetoresistive element, and the other tunnel magnetoresistive element is configured. element.
  6.  前記一方のトンネル磁気抵抗素子と前記他方のトンネル磁気抵抗素子とは積層された請求項１乃至請求項５のいずれか１項記載の記憶素子。 6. The memory element according to claim 1, wherein the one tunnel magnetoresistive element and the other tunnel magnetoresistive element are stacked.
  7. 　請求項１乃至請求項５のいずれか１項記載の記憶素子であって、前記各磁性層の磁化方向は、前記磁性層の表面と平行な方向に向けられた水平磁化記憶方式の記憶素子。 6. The storage element according to claim 1, wherein the magnetization direction of each magnetic layer is oriented in a direction parallel to the surface of the magnetic layer.
  8. 　前記強保磁力の磁性層には、反強磁性層が密着された請求項７記載の記憶素子。 The memory element according to claim 7, wherein an antiferromagnetic layer is adhered to the magnetic layer having the strong coercive force.
  9. 　請求項１乃至請求項５のいずれか１項記載の記憶素子であって、前記各磁性層の磁化方向は、前記磁性層の膜厚方向と平行な方向に向けられた垂直磁化記憶方式の記憶素子。 6. The storage element according to claim 1, wherein the magnetization direction of each magnetic layer is a perpendicular magnetization storage type memory in which the magnetization direction is parallel to the film thickness direction of the magnetic layer. element.
  10. 　前記強保磁力の磁性層は前記中保磁力の磁性層よりも膜厚が厚く、前記中保磁力の磁性層は、前記弱保磁力の磁性層よりも膜厚が厚い請求項１乃至請求項５のいずれか１項記載の記憶素子。 The magnetic layer with a strong coercive force is thicker than the magnetic layer with a medium coercive force, and the magnetic layer with a medium coercive force is thicker than the magnetic layer with a weak coercive force. The memory element according to any one of 5.
  11. 　前記一方のトンネル磁気抵抗素子の前記磁化反対方向抵抗値から前記磁化同方向抵抗値を差し引いた値と、前記他方のトンネル磁気抵抗素子の前記磁化反対方向抵抗値から前記磁化同方向抵抗値を差し引いた値とが、異なる大きさになるように形成された請求項１乃至請求項５のいずれか１項記載の記憶素子。 A value obtained by subtracting the magnetization unidirectional resistance value from the magnetization opposite direction resistance value of the one tunnel magnetoresistive element, and a value obtained by subtracting the magnetization unidirectional resistance value from the magnetization opposite direction resistance value of the other tunnel magnetoresistive element. The memory element according to claim 1, wherein the storage element is formed to have a different value.
  12. 　請求項１乃至請求項５のいずれか１項記載の記憶素子を用いて第一、第二、第三の値を記憶する記憶方法であって、
    　前記第一の値を記憶するために、直列接続された前記トンネル磁気抵抗素子のうち、両方の前記トンネル磁気抵抗素子が前記磁化同方向抵抗値を示すように前記磁性層の磁化方向を同方向とし、
    　前記第二の値を記憶するために、両方の前記トンネル磁気抵抗素子が前記磁化反対方向抵抗値を示すように前記磁性層の磁化方向をそれぞれ反対方向に向け、
    　第三の値を記憶するために、いずれか一方の前記トンネル磁気抵抗素子が前記磁化同方向抵抗値を示すように前記磁性層の磁化方向を同方向に向け、他方の前記トンネル磁気抵抗素子の前記磁性層の磁化方向を反対方向に向ける記憶方法。     A storage method for storing a first value, a second value, and a third value using the storage element according to any one of claims 1 to 5,
    In order to store the first value, among the tunnel magnetoresistive elements connected in series, the magnetization direction of the magnetic layer is the same direction so that both the tunnel magnetoresistive elements exhibit the same magnetization direction resistance value. age,
    In order to store the second value, the magnetization directions of the magnetic layers are respectively directed in opposite directions so that both the tunnel magnetoresistive elements exhibit the opposite magnetization direction resistance value,
    In order to store the third value, the magnetization direction of the magnetic layer is directed in the same direction so that any one of the tunnel magnetoresistive elements exhibits the same magnetization resistance value, and the other tunnel magnetoresistive element A storage method for directing the magnetization direction of the magnetic layer in the opposite direction.
  13. 　前記直列接続回路の抵抗値を測定し、前記抵抗値から記憶された値を読み取る請求項１２記載の記憶方法であって、
    　前記記憶素子の抵抗値を測定して基準値と比較し、
    　両方の前記トンネル磁気抵抗素子の抵抗値が前記磁化同方向抵抗値であると判別した場合を前記第一の値とし、
    　両方の前記トンネル磁気抵抗素子の抵抗値が前記磁化反対方向抵抗値であると判別した場合を前記第二の値とし、
    　一方の前記トンネル磁気抵抗素子が前記磁化同方向抵抗値であり他方の前記トンネル磁気抵抗素子が前記磁化反対方向抵抗値であると判別した場合を第三の値とする記憶方法。     The storage method according to claim 12, wherein a resistance value of the series connection circuit is measured, and a value stored from the resistance value is read.
    Measuring the resistance value of the memory element and comparing it to a reference value;
    The case where it is determined that the resistance value of both of the tunnel magnetoresistive elements is the magnetization same direction resistance value as the first value,
    The case where it is determined that the resistance values of both of the tunnel magnetoresistive elements are the resistance values opposite to the magnetization, the second value,
    A storage method in which a third value is obtained when it is determined that one of the tunnel magnetoresistive elements has the same magnetization direction resistance value and the other tunnel magnetoresistive element has the opposite magnetization direction resistance value.
  14. 　請求項１１記載の記憶素子を用いて第一、第二、第三、第四の値を記憶する記憶方法であって、
    　前記第一の値を記憶するために、直列接続された前記トンネル磁気抵抗素子のうち、両方の前記トンネル磁気抵抗素子が前記磁化同方向抵抗値を示すように前記磁性層の磁化方向を同方向とし、
    　前記第二の値を記憶するために、両方の前記トンネル磁気抵抗素子が前記磁化反対方向抵抗値を示すように前記磁性層の磁化方向をそれぞれ反対方向に向け、
    　第三の値を記憶するために、いずれか一方の前記トンネル磁気抵抗素子が前記磁化同方向抵抗値を示すように前記磁性層の磁化方向を同方向に向け、他方の前記トンネル磁気抵抗素子の前記磁性層の磁化方向を反対方向に向け、
    　第四の値を記憶するために、前記他方のトンネル磁気抵抗素子が前記磁化同方向抵抗値を示すように前記磁性層の磁化方向を同方向に向け、前記一方のトンネル磁気抵抗素子の前記磁性層の磁化方向を反対方向に向ける記憶方法。     A storage method for storing first, second, third, and fourth values using the storage element according to claim 11,
    In order to store the first value, among the tunnel magnetoresistive elements connected in series, the magnetization direction of the magnetic layer is the same direction so that both the tunnel magnetoresistive elements exhibit the same magnetization direction resistance value. age,
    In order to store the second value, the magnetization directions of the magnetic layers are respectively directed in opposite directions so that both the tunnel magnetoresistive elements exhibit the opposite magnetization direction resistance value,
    In order to store the third value, the magnetization direction of the magnetic layer is directed in the same direction so that any one of the tunnel magnetoresistive elements exhibits the same magnetization resistance value, and the other tunnel magnetoresistive element Directing the magnetization direction of the magnetic layer in the opposite direction,
    In order to store the fourth value, the magnetization direction of the magnetic layer is directed in the same direction so that the other tunnel magnetoresistive element exhibits the same magnetization resistance value, and the magnetism of the one tunnel magnetoresistive element is set. A storage method in which the magnetization direction of a layer is directed in the opposite direction.
  15. 　前記直列接続回路の抵抗値を測定し、前記抵抗値から記憶された値を読み取る請求項１４記載の記憶方法であって、
    　前記記憶素子の抵抗値を測定して基準値と比較し、
    　両方の前記トンネル磁気抵抗素子の抵抗値が前記磁化同方向抵抗値であると判別した場合を前記第一の値とし、
    　両方の前記トンネル磁気抵抗素子の抵抗値が前記磁化反対方向抵抗値であると判別した場合を前記第二の値とし、
    　前記一方のトンネル磁気抵抗素子が前記磁化同方向抵抗値であり前記他方のトンネル磁気抵抗素子が前記磁化反対方向抵抗値であると判別した場合を第三の値とし、
    　前記一方のトンネル磁気抵抗素子が前記磁化同方向抵抗値であり前記他方のトンネル磁気抵抗素子が前記磁化反対方向抵抗値であると判別した場合を第四の値とする記憶方法。     The storage method according to claim 14, wherein a resistance value of the series connection circuit is measured, and a value stored from the resistance value is read.
    Measuring the resistance value of the memory element and comparing it to a reference value;
    The case where it is determined that the resistance value of both of the tunnel magnetoresistive elements is the magnetization same direction resistance value as the first value,
    The case where it is determined that the resistance values of both of the tunnel magnetoresistive elements are the resistance values opposite to the magnetization, the second value,
    The case where it is determined that the one tunnel magnetoresistive element has the same magnetization direction resistance value and the other tunnel magnetoresistive element has the opposite magnetization direction resistance value is a third value,
    A storage method in which the fourth value is obtained when it is determined that the one tunnel magnetoresistive element has the same magnetization direction resistance value and the other tunnel magnetoresistive element has the opposite magnetization direction resistance value.
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