WO2021027404A1 - 磁隧道结及降低磁隧道结自由层工艺波动的方法 - Google Patents

磁隧道结及降低磁隧道结自由层工艺波动的方法 Download PDF

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WO2021027404A1
WO2021027404A1 PCT/CN2020/098497 CN2020098497W WO2021027404A1 WO 2021027404 A1 WO2021027404 A1 WO 2021027404A1 CN 2020098497 W CN2020098497 W CN 2020098497W WO 2021027404 A1 WO2021027404 A1 WO 2021027404A1
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layer
free layer
magnetic
tunnel junction
magnetic tunnel
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PCT/CN2020/098497
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English (en)
French (fr)
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孙一慧
孟凡涛
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浙江驰拓科技有限公司
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    • 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
    • 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
    • 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
    • H10N50/01—Manufacture or treatment
    • 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
    • H10N50/80—Constructional details
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N59/00—Integrated devices, or assemblies of multiple devices, comprising at least one galvanomagnetic or Hall-effect element covered by groups H10N50/00 - H10N52/00

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  • the invention relates to the technical field of magnetic random access memory, in particular to a magnetic tunnel junction and a method for reducing process fluctuations in the free layer of the magnetic tunnel junction.
  • Magnetic random access memory has the advantages of long life, low power consumption and non-volatility. It is mainly achieved by flipping the magnetization direction of the free layer to make it parallel or anti-parallel to the magnetization direction of the reference layer to switch between different resistances. Data "0" or “1” erasing and writing.
  • the reference layer it must remain stable enough during the working period of the device, so its coercivity must be large enough. Therefore, its requirement for the fluctuation of the coercive force is that the minimum value of the coercive force is greater than a certain critical threshold. .
  • the switching between "0" and “1" of the magnetic random access memory is achieved by flipping the free layer, so the smaller the free layer coercive force, the easier it is to flip, the smaller the driving force required and the lower the power consumption ; But if the coercivity is too small, there will be a risk that the read current/thermal disturbance will turn the free layer over, so the free layer must meet the requirements of a certain thermal stability factor.
  • the device design of the free layer must meet certain requirements at the upper and lower limits, and due to the existence of process fluctuations, when it crosses the lower limit, some bits have the problem of incorrect erasure; when it crosses the upper limit, then It will increase the power consumption of the overall array and reduce the service life.
  • the magnetic tunnel junction and the method for reducing the process fluctuation of the free layer of the magnetic tunnel junction provided by the present invention can improve the uniformity of the free layer and reduce the process fluctuation of the free layer.
  • the present invention provides a magnetic tunnel junction, comprising at least a reference layer, a barrier layer, a magnetic buffer layer, and a free layer stacked in sequence; wherein the ductility of the magnetic buffer layer is greater than that of the free layer. Strong.
  • the magnetism of the material of the magnetic buffer layer is stronger than the magnetism of the material of the free layer.
  • the thickness of the magnetic buffer layer is smaller than the thickness of the free layer.
  • the ratio of the thickness of the buffer layer to the thickness of the free layer is 0.5/9 to 1.5/8.5.
  • the magnetic buffer layer includes one or a combination of Co, Fe, CoFe, FeB, CoFeB, or Heusler alloy materials.
  • it further includes an anti-ferromagnetic coupling layer and a pinned layer that are stacked; a surface of the anti-ferromagnetic coupling layer facing away from the pinned layer is in contact with the reference layer.
  • the free layer includes a first free layer, a coupling layer, and a second free layer stacked in sequence, and a side of the first free layer away from the coupling layer is in contact with the barrier layer;
  • the materials of the first free layer and the second free layer are both magnetic materials.
  • the present invention is designed for the following situations: the magnetic tunnel junction with the free layer in the uppermost layer, due to the deposition of the multilayer film underneath, makes the barrier layer surface flatness reduced after the barrier layer is deposited, which is more likely to cause the free layer The magnetic process fluctuation becomes larger. Therefore, by adding a thin magnetic buffer layer on the surface of the barrier layer, the present invention uses its better ductility to provide a flatter substrate, so that the uniformity of the subsequently deposited free layer film is better without damaging the magnetic field.
  • the TMR effect of the tunnel is designed for the following situations: the magnetic tunnel junction with the free layer in the uppermost layer, due to the deposition of the multilayer film underneath, makes the barrier layer surface flatness reduced after the barrier layer is deposited, which is more likely to cause the free layer The magnetic process fluctuation becomes larger. Therefore, by adding a thin magnetic buffer layer on the surface of the barrier layer, the present invention uses its better ductility to provide a flatter substrate, so that the uniformity of the subsequently deposited free layer film is better without damaging the magnetic
  • the present invention provides a method for reducing process fluctuations in a magnetic tunnel junction free layer, including:
  • a magnetic buffer layer and a free layer are sequentially laminated on the barrier layer, and the ductility of the magnetic buffer layer is stronger than the ductility of the free layer.
  • the thickness of the buffer layer is controlled to be smaller than the thickness of the free layer.
  • the ratio of the thickness of the magnetic buffer layer to the thickness of the free layer is controlled to be 0.5/9 to 1.5/8.5.
  • a material with stronger magnetic properties than the material of the free layer is selected as the buffer layer material.
  • one or a combination of Co, Fe, CoFe, FeB, CoFeB, or Heusler alloy materials is selected as the material of the buffer layer.
  • forming the free layer includes:
  • a first free layer, a coupling layer and a second free layer are sequentially formed on the magnetic buffer layer.
  • the method further includes: sequentially stacking and forming a pinning layer and an antiferromagnetic coupling layer;
  • the reference layer is formed on the antiferromagnetic coupling layer.
  • a thin magnetic buffer layer is added on the surface of the barrier layer, and its better ductility is used to provide a smoother substrate, so that the uniformity of the free layer film deposited later is better, and the magnetic tunnel is not damaged. TMR effect.
  • Figure 1 is a schematic structural diagram of an embodiment of the present invention
  • Figure 2 is a schematic structural diagram of another embodiment of the present invention.
  • the embodiment of the present invention provides a magnetic tunnel junction, as shown in FIG. 1, comprising a reference layer 1, a barrier layer 2, a magnetic buffer layer 3, and a free layer 4 stacked in sequence; wherein the magnetic buffer layer 3 is more ductile than free Layer 4 is highly ductile.
  • the material of the reference layer 1 is a ferromagnetic material, and one or a combination of Co, Fe, CoFe, FeB, CoFeB or Heusler alloy materials can be selected, and the magnetization direction of the reference layer 1 is fixed.
  • the material of the barrier layer 2 is a non-magnetic material, and one or a combination of magnesium oxide, aluminum oxide, magnesium aluminum oxide, hafnium oxide, tantalum oxide, bismuth telluride or bismuth selenide can be selected Things.
  • the material of the magnetic buffer layer 3 is also a magnetic material, and one or a combination of Co, Fe, CoFe, FeB, CoFeB or Heusler alloy materials can be selected.
  • the material of the free layer 4 is a ferromagnetic material, and one or a combination of Co, Fe, CoFe, FeB, CoFeB or Heusler alloy materials can be selected.
  • the ductility of the magnetic buffer layer 3 needs to be better than that of the free layer 4.
  • a material with better ductility than the material of the free layer 4 can be selected. It is also possible to form a crystal structure with better ductility than the free layer 4 when forming the magnetic buffer layer 3.
  • Co is selected as the material of the magnetic buffer layer 3
  • CoFeB is selected as the material of the free layer 4.
  • This embodiment provides a magnetic tunnel junction, as shown in FIG. 2, comprising a pinning layer 6, an antiferromagnetic coupling layer 5, a reference layer 1, a barrier layer 2, a magnetic buffer layer 3, and a free layer 4 stacked in sequence; Among them, the ductility of the magnetic buffer layer 3 is stronger than the ductility of the free layer 4.
  • the free layer 4 includes a first free layer 41, a coupling layer 42, and a second free layer 43 that are sequentially stacked. The first free layer 41 is in contact with the buffer layer. In order to protect the second free layer 43, a cover layer 7 is further laminated on the second free layer 43.
  • the material of the pinning layer 6 can be selected from one or a combination of Co, Fe, CoFe, NiFe, NiFeCo, CoFeB, CoMnB or CoNbZr.
  • the antiferromagnetic coupling layer 5 can be selected from one or a combination of ruthenium, chromium, rhodium or iridium.
  • the material of the reference layer 1 is a ferromagnetic material, and one or a combination of Co, Fe, CoFe, FeB, CoFeB or Heusler alloy materials can be selected, and the magnetization direction of the reference layer 1 is fixed.
  • the material of the barrier layer 2 is a non-magnetic material, and one or a combination of magnesium oxide, aluminum oxide, magnesium aluminum oxide, hafnium oxide, tantalum oxide, bismuth telluride or bismuth selenide can be selected Things.
  • the material of the magnetic buffer layer 3 is also a magnetic material, and one or a combination of Co, Fe, CoFe, FeB, CoFeB or Heusler alloy materials can be selected.
  • the materials of the first free layer 41 and the second free layer 43 are ferromagnetic materials, and one or a combination of Co, Fe, CoFe, FeB, CoFeB, or Heusler alloy materials can be selected.
  • the coupling layer 42 can be selected from one or a combination of Ta, W, Nb, Ru, Ti, Cr, V, Mo, and Re.
  • the ductility of the magnetic buffer layer 3 needs to be better than that of the free layer 4.
  • a material with better ductility than the material of the free layer 4 can be selected. It is also possible to form a crystal structure with better ductility than the free layer 4 when forming the magnetic buffer layer 3.
  • the material selected for the magnetic buffer layer 3 has stronger magnetism than the material of the free layer 4.
  • the thickness of the magnetic buffer layer 3 is smaller than the thickness of the free layer 4.
  • the ratio of the thickness of the buffer layer to the thickness of the free layer 4 is 0.5/9 to 1.5/8.5.
  • This embodiment provides a method for reducing process fluctuations in the free layer of a magnetic tunnel junction, including:
  • a magnetic buffer layer and a free layer are sequentially laminated on the barrier layer, and the ductility of the magnetic buffer layer is stronger than the ductility of the free layer.
  • the specific formation process is as follows: one or a combination of Co, Fe, CoFe, FeB, CoFeB or Heusler alloy materials is selected as a raw material, so that the raw material forms a reference layer on the substrate.
  • One or a combination of Co, Fe, CoFe, FeB, CoFeB or Heusler alloy materials is selected as a raw material to form a magnetic buffer layer on the barrier layer.
  • One or a combination of Co, Fe, CoFe, FeB, CoFeB or Heusler alloy materials is selected as a raw material to form a free layer on the magnetic buffer layer.
  • the above-mentioned layers can be formed by processes such as physical vapor deposition (PVD), chemical vapor deposition (CVD), radio frequency sputtering (RF), ion spraying (PSC) and the like.
  • PVD physical vapor deposition
  • CVD chemical vapor deposition
  • RF radio frequency sputtering
  • PSC ion spraying
  • a material with greater ductility than that of the free layer material is selected.
  • the same material as the free layer material can also be selected when selecting the magnetic buffer layer material to form a crystal structure with better ductility than the free layer when forming the magnetic buffer layer.
  • a material with stronger magnetic properties than the material of the free layer is selected as the buffer layer material.
  • the thickness of the buffer layer is controlled to be smaller than the thickness of the free layer.
  • the ratio of the thickness of the magnetic buffer layer to the thickness of the free layer is controlled to be 0.5/9 to 1.5/8.5.
  • the surface flatness of the barrier layer is reduced, which is more likely to cause greater fluctuations in the magnetic process. Therefore, in this embodiment, by adding a thin magnetic buffer layer on the surface of the barrier layer, its better ductility is used to provide a flatter substrate, and its stronger magnetism is used to homogenize the magnetic moment of the free layer to enable subsequent deposition
  • the free layer film has better uniformity and will not harm the TMR effect of MTJ.
  • This embodiment provides a method for reducing process fluctuations in the free layer of a magnetic tunnel junction, including:
  • a pinning layer an anti-ferromagnetic coupling layer, a reference layer and a barrier layer that are sequentially stacked from bottom to top;
  • a magnetic buffer layer and a free layer are sequentially laminated on the barrier layer, and the ductility of the magnetic buffer layer is stronger than the ductility of the free layer.
  • the specific formation process is as follows: one or a combination of Co, Fe, CoFe, NiFe, NiFeCo, CoFeB, CoMnB, or CoNbZr is selected as a raw material to form a pinned layer on the substrate.
  • One or a combination of ruthenium, chromium, rhodium, or iridium is selected as a raw material to form an antiferromagnetic coupling layer on the pinned layer.
  • One or a combination of Co, Fe, CoFe, FeB, CoFeB or Heusler alloy materials is selected as a raw material to form a reference layer on the antiferromagnetic coupling layer.
  • One or a combination of Co, Fe, CoFe, FeB, CoFeB or Heusler alloy materials is selected as a raw material to form a magnetic buffer layer on the barrier layer.
  • the specific steps of forming the free layer include selecting one or a combination of Co, Fe, CoFe, FeB, CoFeB, or Heusler alloy materials as raw materials to form the first free layer on the magnetic buffer layer.
  • One or a combination of Ta, W, Nb, Ru, Ti, Cr, V, Mo, and Re is selected as a raw material to form a coupling layer on the first free layer.
  • One or a combination of Co, Fe, CoFe, FeB, CoFeB or Heusler alloy materials is selected as the raw material to form the second free layer on the coupling layer.
  • the above-mentioned layers can be formed by processes such as physical vapor deposition (PVD), chemical vapor deposition (CVD), radio frequency sputtering (RF), ion spraying (PSC) and the like.
  • PVD physical vapor deposition
  • CVD chemical vapor deposition
  • RF radio frequency sputtering
  • PSC ion spraying
  • a material with greater ductility than that of the free layer material is selected.
  • the same material as the free layer material can also be selected when selecting the magnetic buffer layer material to form a crystal structure with better ductility than the free layer when forming the magnetic buffer layer.
  • a material with stronger magnetic properties than the material of the free layer is selected as the buffer layer material.
  • the thickness of the buffer layer is controlled to be smaller than the thickness of the free layer.
  • the ratio of the thickness of the magnetic buffer layer to the thickness of the free layer is controlled to be 0.5/9 to 1.5/8.5.
  • a cover layer may also be formed on the free layer.
  • the surface flatness of the barrier layer is reduced, which is more likely to cause greater fluctuations in the magnetic process. Therefore, in this embodiment, by adding a thin magnetic buffer layer on the surface of the barrier layer, its better ductility is used to provide a flatter substrate, and its stronger magnetism is used to homogenize the magnetic moment of the free layer to enable subsequent deposition
  • the free layer film has better uniformity and will not harm the TMR effect of MTJ.

Abstract

本发明提供一种磁隧道结，至少包括依次层叠的参考层、势垒层、磁性缓冲层和自由层；其中，所述磁性缓冲层的延展性比所述自由层的延展性强。本发明通过在势垒层表面增加一层薄的磁性缓冲层，利用其较好的延展性提供更平整的基底，使随后沉积的自由层薄膜的均一性更好，且不会损害磁隧道的TMR效应。

Description

磁隧道结及降低磁隧道结自由层工艺波动的方法 技术领域
本发明涉及磁随机存储器技术领域，尤其涉及一种磁隧道结及降低磁隧道结自由层工艺波动的方法。
背景技术
磁性随机存储器具有长寿命、低功耗以及非易失等优点，其主要是通过翻转自由层的磁化方向，使其与参考层的磁化方向平行或反平行，以在不同电阻间切换，从而实现数据“0”或“1”的擦写。
受工艺波动影响，对于一个存储器阵列而言，其内所有位元的性能不可能完全一致，而是在某一范围内分布，在器件设计时必须将这种工艺波动提前规划进去。对磁性随机存储器而言，同样存在这样的工艺波动，而且对磁隧道结中不同的部分，对这种工艺波动的要求和考量也不一样。
对参考层而言，它在器件工作期间要保持足够稳定，因此其矫顽力要足够大，因此，其对矫顽力波动的要求就是，矫顽力的最小值大于某一临界阈值即可。
磁性随机存储器在“0”与“1”之间切换就是通过自由层的翻转来实现，所以自由层矫顽力越小，越容易翻转，则所需驱动力则越小，功耗则越低；但是矫顽力过小则会存在读电流/热扰动就会使自由层翻转的风险，因此自由层又必须满足一定的热稳定因子的要求。自由层的器件设计在上下限都必须满足一定的要求，而其本身由于工艺波动的存在，当与下限产生交叉时，则部分位元存在误擦写的问题；当与上限产生交叉时，则会提升整体阵列的功耗，同时降低使用寿命。
发明内容
本发明提供的磁隧道结及降低磁隧道结自由层工艺波动的方法，能够提高自由层的均一性，降低自由层的工艺波动。
第一方面，本发明提供一种磁隧道结，至少包括依次层叠的参考层、势垒层、磁性缓冲层和自由层；其中，所述磁性缓冲层的延展性比所述自由层的延展性强。
可选地，所述磁性缓冲层的材料的磁性比所述自由层的材料的磁性强。
可选地，所述磁性缓冲层的厚度小于所述自由层的厚度。
可选地，所述缓冲层的厚度与所述自由层的厚度比为0.5/9～1.5/8.5。
可选地，所述磁性缓冲层包括Co、Fe、CoFe、FeB、CoFeB或Heusler合金材料中的一种或几种的组合。
可选地，还包括层叠设置的反铁磁耦合层和钉扎层；所述反铁磁耦合层背离所述钉扎层的一侧表面与所述参考层接触。
可选地，所述自由层包括依次层叠设置的第一自由层、耦合层和第二自由层，所述第一自由层背离所述耦合层的一侧与所述势垒层接触；所述第一自由层和所述第二自由层的材料均为磁性材料。
本发明是针对如下情况设计：自由层在最上层的磁隧道结，由于其底下多层膜的沉积，使得在势垒层沉积完后，势垒层表面平整度有所降低，更易导致自由层磁性的工艺波动变大。因此，本发明通过在势垒层表面增加一层薄的磁性缓冲层，利用其较好的延展性提供更平整的基底，使随后沉积的自由层薄膜的均一性更好，且不会损害磁隧道的TMR效应。
第二方面，本发明提供一种降低磁隧道结自由层工艺波动的方法，包括：
提供由下向上依次层叠的参考层和势垒层；
在所述势垒层上依次层叠磁性缓冲层和自由层，所述磁性缓冲层的延展性比所述自由层的延展性强。
可选地，控制所述缓冲层的厚度小于所述自由层厚度。
可选地，控制所述磁性缓冲层的厚度与所述自由层的厚度比为0.5/9～1.5/8.5。
可选地，选取磁性强于所述自由层的材料的磁性的材料作为缓冲层材料。
可选地，选取Co、Fe、CoFe、FeB、CoFeB或Heusler合金材料中的一种或几种的组合物作为所述缓冲层的材料。
可选地，形成所述自由层包括：
在所述磁性缓冲层上依次形成第一自由层、耦合层和第二自由层。
可选地，还包括：依次层叠形成钉扎层和反铁磁耦合层；
所述参考层形成在所述反铁磁耦合层上。
本发明通过在势垒层表面增加一层薄的磁性缓冲层，利用其较好的延展性提供更平整的基底，使随后沉积的自由层薄膜的均一性更好，且不会损害磁隧道的TMR效应。
附图说明
图1为本发明一实施例的结构示意图；
图2为本发明另一实施例的结构示意图。
具体实施方式
为使本发明实施例的目的、技术方案和优点更加清楚，下面将结合本发明实施例中的附图，对本发明实施例中的技术方案进行清楚、完整地描述，显然，所描述的实施例仅仅是本发明一部分实施例，而不是全部的实施例。基于本发明中的实施例，本领域普通技术人员在没有做出创造性劳动前提下所获得的所 有其他实施例，都属于本发明保护的范围。
实施例1
本发明实施例提供一种磁隧道结，如图1所示，包括依次层叠的参考层1、势垒层2、磁性缓冲层3和自由层4；其中，磁性缓冲层3的延展性比自由层4的延展性强。
参考层1的材料为铁磁性材料，可以选择Co、Fe、CoFe、FeB、CoFeB或Heusler合金材料中的一种或几种的组合，参考层1的磁化方向固定。
势垒层2的材料为非磁性材料，可以选择镁氧化物、铝氧化物、镁铝氧化物、铪氧化物、钽氧化物、碲化铋或硒化铋中的一种或几种的组合物。
磁性缓冲层3的材料也为磁性材料，可以选择Co、Fe、CoFe、FeB、CoFeB或Heusler合金材料中的一种或几种的组合。
自由层4的材料为铁磁性材料，可以选择Co、Fe、CoFe、FeB、CoFeB或Heusler合金材料中的一种或几种的组合。
磁性缓冲层3的延展性需要比自由层4好，为了实现该目的，可以在材料选择时，依据已经选定的自由层4材料，选择延展性比自由层4材料好的材料。也可以在形成磁性缓冲层3时，形成比自由层4延展性好的晶体结构。
作为本实施例的可选实施方式，如下表：
Co/CoFeB 阻尼系数的标准差 阻尼系数测试点离散性 离散标准差
0/10 0.00074 186.4 13.8
1.0/9.0 0.00046 155.9 10.3
1.5/8.5 0.00041 139.2 8
在上述实施方式中，选用Co作为磁性缓冲层3的材料，选用CoFeB作为自由层4材料，在图表中可以看出，当缓冲层的厚度与自由层4的厚度比为1/9和 1.5/8.5时，可以看出Damping error bar、dH0、dH0error bar三个性能参数大幅下降，因此可以看出随着缓冲层的加入，自由层4的均一性有显著的改善。
本实施例通过在势垒层2表面增加一层薄的磁性缓冲层3，利用其较好的延展性提供更平整的基底，使随后沉积的自由层4薄膜的均一性更好，且不会损害磁隧道的TMR效应。
实施例2
本实施例提供一种磁隧道结，如图2所示，包括依次层叠的钉扎层6、反铁磁耦合层5、参考层1、势垒层2、磁性缓冲层3和自由层4；其中，磁性缓冲层3的延展性比自由层4的延展性强。自由层4包括依次层叠的第一自由层41、耦合层42和第二自由层43。其中第一自由层41与缓冲层接触。为了保护第二自由层43在第二自由层43上还层叠有覆盖层7。
钉扎层6的材料可以选择Co、Fe、CoFe、NiFe、NiFeCo、CoFeB、CoMnB或CoNbZr中的一种或几种的组合。
反铁磁耦合层5可以选用从钌、铬、铑或铱中的一种或几种的组合。
参考层1的材料为铁磁性材料，可以选择Co、Fe、CoFe、FeB、CoFeB或Heusler合金材料中的一种或几种的组合，参考层1的磁化方向固定。
势垒层2的材料为非磁性材料，可以选择镁氧化物、铝氧化物、镁铝氧化物、铪氧化物、钽氧化物、碲化铋或硒化铋中的一种或几种的组合物。
磁性缓冲层3的材料也为磁性材料，可以选择Co、Fe、CoFe、FeB、CoFeB或Heusler合金材料中的一种或几种的组合。
第一自由层41和第二自由层43的材料均为铁磁性材料，可以选择Co、Fe、CoFe、FeB、CoFeB或Heusler合金材料中的一种或几种的组合。耦合层42可以选择Ta、W、Nb、Ru、Ti、Cr、V、Mo和Re中的一种或几种的组 合。
磁性缓冲层3的延展性需要比自由层4好，为了实现该目的，可以在材料选择时，依据已经选定的自由层4材料，选择延展性比自由层4材料好的材料。也可以在形成磁性缓冲层3时，形成比自由层4延展性好的晶体结构。
本实施例通过在势垒层2表面增加一层薄的磁性缓冲层3，利用其较好的延展性提供更平整的基底，使随后沉积的自由层4薄膜的均一性更好，且不会损害磁隧道的TMR效应。
作为本实施例的可选实施方式，磁性缓冲层3选用的材料的磁性比自由层4的材料的磁性强。
作为本实施例的可选实施方式，磁性缓冲层3的厚度小于自由层4的厚度。
作为本实施例的进一步可选实施方式，缓冲层的厚度与自由层4的厚度比为0.5/9～1.5/8.5。
实施例3
本实施例提供了一种降低磁隧道结自由层工艺波动的方法，包括：
提供由下向上依次层叠的参考层和势垒层；
在所述势垒层上依次层叠磁性缓冲层和自由层，所述磁性缓冲层的延展性比所述自由层的延展性强。
具体形成过程如下：选择Co、Fe、CoFe、FeB、CoFeB或Heusler合金材料中的一种或几种的组合作为原料，使原料在衬底上形成参考层。
选择镁氧化物、铝氧化物、镁铝氧化物、铪氧化物、钽氧化物、碲化铋或硒化铋中的一种或几种的组合物作为原料，在参考层上形成势垒层。
选择Co、Fe、CoFe、FeB、CoFeB或Heusler合金材料中的一种或几种的组合作为原料，在势垒层上形成磁性缓冲层。
选择Co、Fe、CoFe、FeB、CoFeB或Heusler合金材料中的一种或几种的组合作为原料在磁性缓冲层上形成自由层。
上述各层在形成时可以使用物理气相沉积(PVD)、化学气相沉积(CVD)、射频溅射(RF)、离子喷涂(PSC)等工艺形成。
作为本实施例的可选实施方式，在选择磁性缓冲层的材料时，选择延展性比所述自由层材料的延展性强的材料。
作为本实施例的另一可选实施方式，还可以在选择磁性缓冲层材料时选择与自由层材料相同的材料，在形成磁性缓冲层时形成延展性比自由层延展性好的晶体结构。
作为本实施例的可选实施方式，选取磁性强于所述自由层的材料的磁性的材料作为缓冲层材料。
作为本实施例的可选实施方式，控制所述缓冲层的厚度小于所述自由层厚度。
作为本实施例进一步地可选实施方式，控制所述磁性缓冲层的厚度与所述自由层的厚度比为0.5/9～1.5/8.5。
对于自由层在最上层的MTJ结构，由于其底下多层膜的沉积，使得在势垒层沉积完后，势垒层表面平整度有所降低，更易导致磁性工艺波动变大。因此，本实施例通过在势垒层表面增加一层薄的磁性缓冲层，利用其较好的延展性提供更平整的基底，利用其较强的磁性均一化自由层的磁矩，使随后沉积的自由层薄膜的均一性更好，且不会损害MTJ的TMR效应。
实施例4
本实施例提供了一种降低磁隧道结自由层工艺波动的方法，包括：
提供由下向上依次层叠的钉扎层、反铁磁耦合层、参考层和势垒层；
在所述势垒层上依次层叠磁性缓冲层和自由层，所述磁性缓冲层的延展性比所述自由层的延展性强。
具体形成过程如下：选择Co、Fe、CoFe、NiFe、NiFeCo、CoFeB、CoMnB或CoNbZr中的一种或几种的组合作为原料在衬底上形成钉扎层。
选择钌、铬、铑或铱中的一种或几种的组合作为原料在钉扎层上形成反铁磁耦合层。
选择Co、Fe、CoFe、FeB、CoFeB或Heusler合金材料中的一种或几种的组合作为原料，使在反铁磁耦合层上形成参考层。
选择镁氧化物、铝氧化物、镁铝氧化物、铪氧化物、钽氧化物、碲化铋或硒化铋中的一种或几种的组合物作为原料，在参考层上形成势垒层。
选择Co、Fe、CoFe、FeB、CoFeB或Heusler合金材料中的一种或几种的组合作为原料，在势垒层上形成磁性缓冲层。
形成自由层的具体步骤包括选择Co、Fe、CoFe、FeB、CoFeB或Heusler合金材料中的一种或几种的组合作为原料在磁性缓冲层上形成第一自由层。选择Ta、W、Nb、Ru、Ti、Cr、V、Mo和Re中的一种或几种的组合作为原料在第一自由层上形成耦合层。选择Co、Fe、CoFe、FeB、CoFeB或Heusler合金材料中的一种或几种的组合作为原料在耦合层上形成第二自由层。
上述各层在形成时可以使用物理气相沉积(PVD)、化学气相沉积(CVD)、射频溅射(RF)、离子喷涂(PSC)等工艺形成。
作为本实施例的可选实施方式，在选择磁性缓冲层的材料时，选择延展性比所述自由层材料的延展性强的材料。
作为本实施例的另一可选实施方式，还可以在选择磁性缓冲层材料时选择与自由层材料相同的材料，在形成磁性缓冲层时形成延展性比自由层延展性好 的晶体结构。
作为本实施例的可选实施方式，选取磁性强于所述自由层的材料的磁性的材料作为缓冲层材料。
作为本实施例的可选实施方式，控制所述缓冲层的厚度小于所述自由层厚度。
作为本实施例进一步地可选实施方式，控制所述磁性缓冲层的厚度与所述自由层的厚度比为0.5/9～1.5/8.5。
作为本实施例的可选实施方式，在自由层上还可以形成覆盖层。
对于自由层在最上层的MTJ结构，由于其底下多层膜的沉积，使得在势垒层沉积完后，势垒层表面平整度有所降低，更易导致磁性工艺波动变大。因此，本实施例通过在势垒层表面增加一层薄的磁性缓冲层，利用其较好的延展性提供更平整的基底，利用其较强的磁性均一化自由层的磁矩，使随后沉积的自由层薄膜的均一性更好，且不会损害MTJ的TMR效应。
以上所述，仅为本发明的具体实施方式，但本发明的保护范围并不局限于此，任何熟悉本技术领域的技术人员在本发明揭露的技术范围内，可轻易想到的变化或替换，都应涵盖在本发明的保护范围之内。因此，本发明的保护范围应该以权利要求的保护范围为准。

Claims (14)

  1. 一种磁隧道结，其特征在于：至少包括依次层叠的参考层、势垒层、磁性缓冲层和自由层；其中，所述磁性缓冲层的延展性比所述自由层的延展性强。
  2. 如权利要求1所述磁隧道结，其特征在于：所述磁性缓冲层的材料的磁性比所述自由层的材料的磁性强。
  3. 如权利要求1所述磁隧道结，其特征在于：所述磁性缓冲层的厚度小于所述自由层的厚度。
  4. 如权利要求3所述磁隧道结，其特征在于：所述缓冲层的厚度与所述自由层的厚度比为0.5/9～1.5/8.5。
  5. 如权利要求1所述磁隧道结，其特征在于：所述磁性缓冲层包括Co、Fe、CoFe、FeB、CoFeB或Heusler合金材料中的一种或几种的组合。
  6. 如权利要求1所述磁隧道结，其特征在于：还包括层叠设置的反铁磁耦合层和钉扎层；所述反铁磁耦合层背离所述钉扎层的一侧表面与所述参考层接触。
  7. 如权利要求1所述磁隧道结，其特征在于：所述自由层包括依次层叠设置的第一自由层、耦合层和第二自由层，所述第一自由层背离所述耦合层的一侧与所述势垒层接触；所述第一自由层和所述第二自由层的材料均为磁性材料。
  8. 一种降低磁隧道结自由层工艺波动的方法，其特征在于：包括：
    提供由下向上依次层叠的参考层和势垒层；
    在所述势垒层上依次层叠磁性缓冲层和自由层，所述磁性缓冲层的延展性 比所述自由层的延展性强。
  9. 如权利要求8所述降低磁隧道结自由层工艺波动的方法，其特征在于：控制所述缓冲层的厚度小于所述自由层厚度。
  10. 如权利要求9所述降低磁隧道结自由层工艺波动的方法，其特征在于：控制所述磁性缓冲层的厚度与所述自由层的厚度比为0.5/9～1.5/8.5。
  11. 如权利要求8所述降低磁隧道结自由层工艺波动的方法，其特征在于：选取磁性强于所述自由层的材料的磁性的材料作为缓冲层材料。
  12. 如权利要求8所述降低磁隧道结自由层工艺波动的方法，其特征在于：选取Co、Fe、CoFe、FeB、CoFeB或Heusler合金材料中的一种或几种的组合物作为所述缓冲层的材料。
  13. 如权利要求8所述降低磁隧道结自由层工艺波动的方法，其特征在于：形成所述自由层包括：
    在所述磁性缓冲层上依次形成第一自由层、耦合层和第二自由层。
  14. 如权利要求8所述降低磁隧道结自由层工艺波动的方法，其特征在于：还包括：依次层叠形成钉扎层和反铁磁耦合层；
    所述参考层形成在所述反铁磁耦合层上。
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