Magnetic tunnel junction having a tunable large perpendicular magnetic anisotropy

Abstract

To provide a magnetic tunnel junction (MTJ) laminate which endures high-temperature heat treatment while holding a large PMA.SOLUTION: A method of forming an MTJ structure from a film laminate placed on a substrate for a magnetic random access memory (MRAM) application and a related MTJ device includes forming a film characteristic of a material layer of a film laminate to produce the film laminate having sufficiently large perpendicular magnetic anisotropy (PMA). To produce desired PMA, a thickness of a capping layer can be more finely controlled by utilizing an iron-containing oxide capping layer 250. Dependency on boron in a boundary surface between a magnetic storage layer 245 ana the capping layer is reduced.SELECTED DRAWING: Figure 2C

Description

Technical Field

[0001]

[0001] Embodiments of the present disclosure relate to structures and methods for manufacturing devices used in spin-transfer torque magnetic random access memory (STT-MRAM) applications. More specifically, embodiments of the present disclosure relate to methods and devices for manufacturing magnetic tunnel junctions having tunable large perpendicular magnetic anisotropy.

Background Art

[0002]

[0002] Magnetic random access memory (MRAM) is a type of memory device that includes an array of MRAM cells that store data using resistance values instead of the charge of electrons. Generally, each MRAM cell includes a magnetic tunnel junction (MTJ) structure. The MTJ structure typically includes a stack of magnetic layers having a configuration in which two ferromagnetic layers are separated by a thin non-magnetic dielectric, such as an insulating tunnel layer. An upper electrode and a lower electrode are used to sandwich the MTJ structure so that a current flows between the upper electrode and the lower electrode.

[0003]

[0003] One type of MRAM cell is spin-transfer torque magnetic random access memory (STT-MRAM). In such a manufacturing process flow, a stable magnetic tunnel junction (MTJ) stack is utilized to generate a high tunnel magnetoresistance (TMR) ratio while withstanding high-temperature backend heat treatment. The MTJ stack often utilizes a buffer layer to improve adhesion and seeding of subsequent layers. The MTJ stack also includes a synthetic ferrimagnetic (SyF) coupling layer for anti-parallel coupling of a first pinning layer and a second pinning layer. A capping layer is utilized on top of the MTJ stack to protect the stack from corrosion and also acts as an etch stop layer for hard mask etching. A capping layer in interface contact with the magnetic storage layer of the MTJ is utilized to generate sufficient perpendicular magnetic anisotropy (PMA) to provide a data retention energy barrier.

[0004]

[0004] Conventional capping layers utilize boron at the interface with the magnetic memory layer to maintain sufficient PMA. However, after high-temperature heat treatment, boron diffuses away from the interface and weakens the PMA of the magnetic memory layer. Such conventional capping layers utilize magnesium oxide (MgO) materials, but thicker MgO materials are used to maintain appropriate PMA. Thicker MgO materials increase the surface roughness of the interface and decrease TMR.

[0005]

[0005] Therefore, in the art, there is a need for an improved method for manufacturing an MTJ structure for STT-MRAM applications. There is also a need for an improved MTJ stack that can withstand high-temperature heat treatment while retaining a large PMA.

Summary of the Invention

[0006]

[0006] In one embodiment, a magnetic tunnel junction film stack is provided. The film stack includes a buffer layer, a seed layer disposed on the buffer layer, a first pinning layer disposed on the seed layer, and a synthetic ferrimagnetic coupling layer disposed on the first pinning layer. A second pinning layer is disposed on the synthetic ferrimagnetic coupling layer, a structure blocking layer is disposed on the second pinning layer, a magnetic reference layer is disposed on the structure blocking layer, a tunnel barrier layer is disposed on the magnetic reference layer. A magnetic memory layer is disposed on the tunnel barrier layer, and a capping layer is disposed on the magnetic memory layer. The capping layer includes an Fe-containing oxide material layer.

[0007]

[0007] In another embodiment, a magnetic tunnel junction film stack is provided. The film stack includes a buffer layer containing a CoFeB layer, a seed layer disposed on the buffer layer, a first pinning layer disposed on the seed layer, and a synthetic ferrimagnetic coupling layer containing an Ir-containing layer disposed on the first pinning layer. A second pinning layer is disposed on the synthetic ferrimagnetic coupling layer, a structure blocking layer is disposed on the second pinning layer, a magnetic reference layer is disposed on the structure blocking layer, a tunnel barrier layer is disposed on the magnetic reference layer. A magnetic memory layer is disposed on the tunnel barrier layer, a capping layer containing an Fe-containing oxide material layer is disposed on the magnetic memory layer, and a hard mask is disposed on the capping layer.

[0008]

[0008] In yet another embodiment, a magnetic tunnel junction film stack is provided. The film stack includes a buffer layer, a seed layer disposed in contact with the buffer layer on the buffer layer, a first pinning layer disposed in contact with the seed layer on the seed layer, and a synthetic ferrimagnetic coupling layer disposed in contact with the first pinning layer on the first pinning layer. A second pinning layer is disposed in contact with the synthetic ferrimagnetic coupling layer on the synthetic ferrimagnetic coupling layer, a structure blocking layer is disposed in contact with the second pinning layer on the second pinning layer, a magnetic reference layer is disposed in contact with the structure blocking layer on the structure blocking layer, a tunnel barrier layer is disposed in contact with the magnetic reference layer on the magnetic reference layer. A magnetic memory layer is disposed in contact with the tunnel barrier layer on the tunnel barrier layer, a capping layer containing an Fe-containing oxide material layer is disposed in contact with the magnetic memory layer on the magnetic memory layer, and a hard mask is disposed in contact with the capping layer on the capping layer.

[0009]

[0009] To enable a more detailed understanding of the above features of the present disclosure, a more specific description of the present disclosure, briefly summarized above, can be provided by referring to the embodiments, some of which are shown in the accompanying drawings. However, it should be noted that the accompanying drawings illustrate only exemplary embodiments and should not be considered as limiting the scope thereof, and other equally effective embodiments can be recognized.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2A

Figure 2B

Figure 2C

Figure 3A

Figure 3B

Figure 3C

Figure 3D

Modes for Carrying Out the Invention

[0011]

[0018] For ease of understanding, the same elements common to the drawings are indicated using the same reference numbers whenever possible. It is contemplated that the elements and features of one embodiment can be beneficially incorporated into other embodiments without further recitation. However, note that the accompanying drawings show only typical embodiments of the present disclosure, and thus the present disclosure should not be regarded as limiting its scope, as other equally valid embodiments can be recognized.

[0012]

[0019] Embodiments of the present disclosure provide a method for forming an MTJ structure from a film stack disposed on a substrate for MRAM applications and related MTJ devices. The methods described herein include forming the film properties of the material layers of the film stack to produce a film stack having a sufficiently large perpendicular magnetic anisotropy (PMA). An iron-containing oxide capping layer is utilized to produce the desired PMA. By utilizing the iron-containing oxide capping layer, the thickness of the capping layer can be more finely controlled, and the dependence on boron at the interface between the magnetic memory layer and the capping layer is reduced.

[0013]

[0020] FIG. 1 shows a flowchart illustrating a process 100 for manufacturing an MTJ structure on a substrate for MRAM applications, according to one embodiment of the present disclosure. In some embodiments, process 100 is a process flow, and steps 101-106 are individual processes. Process 100 is configured to be executed in a plasma processing chamber and a heat treatment chamber or other suitable plasma immersion ion implantation system or etching chamber. Process 100 can also use other tools such as PVD chambers, CVD chambers, and lithography tools.

[0014]

[0021] Process 100 starts at step 101 by providing a substrate with a film stack disposed thereon. In some embodiments, the substrate includes metal or glass, silicon, dielectric bulk material and metal alloy or composite glass, crystalline silicon (e.g., Si<100> or Si<111>), silicon oxide, strained silicon, silicon germanium, germanium, doped or undoped polysilicon, doped or undoped silicon wafers and patterned or unpatterned wafer silicon on insulator (SOI), carbon-doped silicon oxide, silicon nitride, doped silicon, germanium, gallium arsenide, glass, or sapphire. The substrate can have various dimensions such as about 200 mm, about 300 mm, about 450 mm or other diameters, and can further be a rectangular or square panel. Unless otherwise specified, the examples described herein are implemented on substrates with a diameter of 200 mm, 300 mm, or 450 mm. In one embodiment, the substrate includes a film stack disposed on the substrate.

[0015]

[0022] Note that the fixed magnetic layer, optional structural decoupling layer, tunnel barrier layer, magnetic memory layer, magnetic reference layer, and capping layer can be formed by appropriate techniques and methods such as a PVD process. Examples of systems that can be used to form these layers include the ENDURA® PVD system available from Applied Materials, Santa Clara, California. It is contemplated that other processing systems, including those available from other manufacturers, can be adapted to implement the present disclosure.

[0016]

[0023] Prior to performing MTJ stack deposition in step 102, other processes can be utilized to form transistors and interconnect layers known to those skilled in the art. After performing post-patterning annealing in step 106, additional steps such as steps for completing the remaining interconnect layers and contact pads can be performed.

[0017]

[0024] In processes 102 to 104, MTJ stack deposition, pre-patterning annealing, and MTJ patterning are performed. Processes 102 to 104 are patterning processes, such as etching processes, performed to remove a part of the film stack exposed and defined by an etching mask layer (not shown) from the substrate until the underlying substrate is exposed. The patterning process for patterning the film stack includes several individual processes or different recipes configured to supply different gas mixtures or etchants for etching different layers according to the materials contained in each layer. During patterning, several gas mixtures with etching gas mixtures or different etching species are sequentially supplied to the substrate surface to remove a part of the film stack from the substrate. The end point of the patterning process in process 104 is controlled by time or other appropriate methods. For example, the patterning process is terminated after performing the time patterning process for a time between about 200 seconds and about 10 minutes until the substrate is exposed. In another example, the patterning process is terminated by a determination from an end point detector.

[0018]

[0025] A further deposition process is performed to form a sealing and insulating layer on the portion of the substrate from which the film stack has been removed during the patterning process in process 104. Sealing enables appropriate step coverage and airtightness and often includes the deposition of a material composed of a silicon nitride-based material. Insulation utilizes an oxide-based material and includes the deposition of a material thicker than the thickness of the sealing material. The insulating layer is formed from an appropriate insulating material and is then processed by a series of etching and deposition processes to form an interconnect structure within the insulating layer (e.g., back-end process) to complete the device structure manufacturing process. In one example, the insulating layer is a silicon oxide layer or other appropriate material.

[0019]

[0026] In process 106, a thermal annealing process is performed. Examples of systems that can be used for annealing include rapid thermal annealing chambers. One example of a rapid thermal annealing chamber is the RADIANCE® chamber available from Applied Materials, Santa Clara, California. It is contemplated that other processing systems, including those available from other manufacturers, can be adapted to implement the present disclosure. The thermal annealing process is performed to repair, densify, and strengthen the lattice structure of the film stack, specifically the magnetic memory layer and the magnetic reference layer included in the film stack. After the thermal annealing process, the magnetic memory layer and the magnetic reference layer are converted into a crystallized magnetic memory layer and a crystallized magnetic reference layer having a crystal orientation in a substantially single plane. When the desired crystallization of the magnetic memory layer and the magnetic reference layer is obtained, the overall electrical characteristics of the film stack for manufacturing the MTJ device are improved.

[0020]

[0027] In some embodiments, depending on the desired implementation, one of processes 103 and 106 (or any other equivalent annealing process) can be used. As will be described below, the MTJ film stack of the present disclosure can withstand high-temperature thermal processes and improve electrical and magnetic characteristics.

[0021]

[0028] Each of FIGS. 2A-2C separately shows a schematic view of a part of a film stack according to various embodiments. The film stack includes a substrate 200 and a bottom contact 204. In one embodiment, the bottom contact 204 is patterned. In one embodiment, the bottom contact 204 is disposed on the substrate 200 in contact with the substrate 200. Although not shown in FIGS. 2A-2C, other layers such as transistors and interconnect structures in the form of one or more layers may be disposed between the substrate 200 and the bottom contact 204. The differences between the film stacks shown in FIGS. 2B and 2C include buffer layers 205 / 205', seed layers 210 / 210', and first pinning layers 215 / 215'. In some embodiments, the film stack includes one or more of a bottom contact, a buffer layer, a seed layer, a first pinning layer, a synthetic ferrimagnetic (SyF) bonding layer, a second pinning layer, a structural blocking layer, a magnetic reference layer, a tunnel barrier layer, a magnetic memory layer, a capping layer, and a hard mask. In some embodiments, each of these layers individually includes one or more layers.

[0022]

[0029] In some embodiments, as shown in FIGS. 2A-2C, the film stack used to form the magnetic tunnel junction (MTJ) structure is disposed on the bottom contact 204. The MTJ structure includes a buffer layer 205 / 205' disposed on the bottom contact 204, a seed layer 210 / 210' disposed on the buffer layer 205 / 205', a first pinning layer 215 / 215' disposed on the seed layer 210 / 210', a synthetic ferrimagnetic (SyF) coupling layer 220 disposed on the first pinning layer 215 / 215', a second pinning layer 225 disposed on the SyF coupling layer 220, a structural blocking layer 230 disposed on the second pinning layer 225, a magnetic reference layer 235 disposed on the structural blocking layer 230, a tunnel barrier layer 240 disposed on the magnetic reference layer 235, a magnetic memory layer 245 disposed on the tunnel barrier layer 240, a capping layer 250 disposed on the magnetic memory layer 245, the capping layer including one or more layers, and a hard mask 255 disposed on the capping layer 250, wherein at least one of the capping layer, the buffer layer, and the SyF coupling layer is not made of Ru. In one embodiment, when adjacent layers of the film stack are referred to as being disposed on top of or below an adjacent layer, each layer is considered to be disposed in contact with each other.

[0023]

[0030] The film stack includes a buffer layer 205 / 205' disposed on the bottom contact 204. The buffer layer 205 / 205' is sandwiched between the bottom contact 204 and the seed layer 210 / 210'. In one embodiment, the buffer layer 205 / 205' improves the adhesion and seeding of the layers subsequently deposited. In one embodiment, the buffer layer 205 / 205' includes one or more layers. In one embodiment, the buffer layer 205 / 205' is not made of Ru.

[0024]

[0031] In one embodiment, the buffer layer 205 / 205' includes a CoFeB-containing layer 205a / 205a'. The weight percentage (wt%) of boron (B) in the buffer layer 205 / 205' is between about 10 wt% and about 40 wt%, for example, between about 20 wt% and 40 wt%, for example, between about 25 wt% and about 40 wt%. The wt% of iron in the buffer layer 205 / 205' is between about 20 wt% and about 60 wt%, for example, between about 40 wt% and 60 wt%, for example, between about 45 wt% and about 60 wt%. The thickness of the CoFeB-containing layer 205a / 205a' is between about 0 Å and about 20 Å, for example, about 10 Å.

[0025]

[0032] In one embodiment, the buffer layer 205 / 205' includes a TaN-containing layer 205b / 205b' and / or a Ta-containing layer 205c / 205c'. In one embodiment, the TaN-containing layer 205b / 205b' and the Ta-containing layer 205c / 205c' are disposed on the CoFeB layer 205a. Alternatively, the TaN-containing layer 205b / 205b' and the Ta-containing layer 205c / 205c' may be disposed under the CoFeB layer 205a'. The thickness of the TaN-containing layer and the Ta-containing layer is between about 0 Å and about 40 Å, for example, about 15 Å.

[0026]

[0033] The film stack includes a seed layer 210 / 210' disposed on the buffer layer 205 / 205'. The seed layer 210 / 210' is sandwiched between the buffer layer 205 / 205' and the first pinning layer 215 / 215'.

[0027]

[0034] In some embodiments, the seed layer 210 includes one or more of a Pt-containing layer, an Ir-containing layer, and a Ru-containing layer. The thickness of the seed layer 210 having one or more of a Pt-containing layer, an Ir-containing layer, and a Ru-containing layer is between about 0 Å and about 60 Å, for example, about 25 Å. In an embodiment, when the seed layer 210 includes one or more of a Pt-containing layer, an Ir-containing layer, and a Ru-containing layer, the CoFeB-containing layer 205a of the buffer layer 205 / 205' is disposed under the TaN-containing layer 205b (and / or the Ta-containing layer 205c) of the buffer layer 205 / 205'.

[0028]

[0035] In some embodiments, the seed layer 210' includes a NiCr-containing layer. The thickness of the seed layer 210' having the NiCr-containing layer is between about 0 Å and about 100 Å, for example, about 50 Å. In an embodiment, when the seed layer includes a NiCr-containing layer, the CoFeB-containing layer 205a' of the buffer layer 205 / 205' is disposed on the TaN-containing layer 205b' (and / or Ta-containing layer 205c') of the buffer layer 205 / 205'.

[0029]

[0036] In one embodiment, the film stack includes a first pinning layer 215 / 215' disposed on the seed layer 210 / 210'. The first pinning layer 215 / 215' is sandwiched between the seed layer 210 / 210' and the SyF coupling layer 220. The first pinning layer 215 / 215' may include one or more layers. The first pinning layer 215 / 215' is made of several magnetic materials such as a dopant, for example, a boron dopant, a metal alloy containing an oxygen dopant, or other suitable materials. Suitable metal alloys include Ni-containing materials, Pt-containing materials, Ru-containing materials, Co-containing materials, Ta-containing materials, and Pd-containing materials. Suitable examples of magnetic materials include Ru, Ta, Co, Pt, Ni, TaN, NiFeOx, NiFeB, CoFeOxB, CoFeB, CoFe, NiOxB, CoBOx, FeBOx, CoFeNiB, CoPt, CoPd, CoNi, and TaOx.

[0030]

[0037] In one embodiment, the first pinning layer 215 includes a Co-containing layer 215b disposed on a Co / Pt-containing layer 215a. The thickness of the Co-containing layer 215b is between about 0 Å and about 10 Å, for example, about 5 Å. The Co / Pt-containing layer 215a is [Co (x) / Pt (y) m ​It is possible to have a composition including, where x has a thickness of Co between about 0 Å and about 10 Å, for example, between about 0.5 Å and about 7 Å, y has a thickness of Pt between about 0 Å and about 10 Å, for example, between about 0.5 Å and about 8 Å, and m is an integer between about 3 and about 10, where m represents the number of Co / Pt-containing layers 215a repeatedly formed in the film stack. For example, when x is 5 Å, y is 3 Å, and m is the integer 2, the Co / Pt layer is composed of Co layer (5 Å) / Pt layer (3 Å) / Co layer (5 Å) / Pt layer (3 Å).

[0031]

[0038] In one embodiment, the first pinning layer 215’ includes a Co-containing layer 215b’ disposed on the Co / Ni-containing layer 215a’. The thickness of the Co-containing layer 215b is between about 0 Å and about 10 Å, for example, about 5 Å. The Co / Ni-containing layer 215a’ is [Co (x1) / Ni (y1) n It is possible to have a composition including, where x1 has a thickness of Co between about 0 Å and about 10 Å, for example, between about 1 Å and about 8 Å, y1 has a thickness of Ni between about 0 Å and about 10 Å, for example, between about 1 Å and about 8 Å, and n is an integer between about 1 and about 10, where n represents the number of Co / Ni-containing layers 215a’ repeatedly formed in the film stack.

[0032]

[0039] In an embodiment, when the first pinning layer 215 includes a Co / Pt-containing layer 215a, the seed layer 210 includes one or more of a Pt-containing layer, an Ir-containing layer, and a Ru-containing layer. In an embodiment, when the first pinning layer 215’ includes a Co / Ni-containing layer 215a’, the seed layer 210 includes a NiCr-containing layer.

[0033]

[0040] ​The film stack includes a synthetic ferrimagnetic (SyF) bonding layer 220 disposed on the first pinning layer 215 / 215'. In one embodiment, the SyF bonding layer 220 is sandwiched between the first pinning layer 215 / 215' and the second pinning layer 225. The SyF bonding layer 220 is used to antiferromagnetically couple the first pinning layer 215 / 215' and the second pinning layer 225. In one embodiment, the SyF bonding layer 220 includes one or more of an Ir-containing layer, a Ru-containing layer, a Rh-containing layer, and a Cr-containing layer. In one embodiment, the SyF bonding layer is an Ir-containing layer. In another embodiment, the SyF bonding layer is not made of Ru. The thickness of the SyF bonding layer 220 is between about 3 Å and about 10 Å. When the SyF bonding layer 220 is a Ru-containing layer, the thickness of the SyF bonding layer 220 is between about 4 Å and about 5 Å, or between about 7 Å and about 9 Å. When the SyF bonding layer 220 is an Ir-containing layer, the thickness of the SyF bonding layer 220 is between about 4 Å and about 6 Å.

[0034]

[0041] The film stack includes a second pinning layer 225 disposed on the SyF bonding layer 220. In one embodiment, the second pinning layer 225 is sandwiched between the SyF bonding layer 220 and the structural blocking layer 230. In one embodiment, the second pinning layer 225 includes one or more layers. The second pinning layer 225 is made of several magnetic materials, such as a metal alloy containing a dopant, for example, a boron dopant, an oxygen dopant, or other suitable materials. Suitable metal alloys include Ni-containing materials, Pt-containing materials, Ru-containing materials, Co-containing materials, Ta-containing materials, and Pd-containing materials. Suitable examples of magnetic materials include Ru, Ta, Co, Pt, Ni, TaN, NiFeOx, NiFeB, CoFeOxB, CoFeB, CoFe, NiOxB, CoBOx, FeBOx, CoFeNiB, CoPt, CoPd, CoNi, and TaOx.

[0035]

[0042] In one embodiment, the second pinning layer 225 includes a Co-containing layer 225b disposed on a Co / Pt-containing layer 215a. The thickness of the Co-containing layer 225b is between about 0 Å and about 10 Å, for example, about 5 Å. The Co / Pt-containing layer 215a is [Co (x2) / Pt (y2) p It can have a composition containing, where x2 has a Co thickness between about 0 Å and about 10 Å, for example, between about 0.5 Å and about 7 Å, y2 has a Pt thickness between about 0 Å and about 10 Å, for example, between about 0.5 Å and about 8 Å, and p is an integer between about 0 and about 5, where p represents the number of Co / Pt-containing layers 225a repeatedly formed in the film stack.

[0036]

[0043] The film stack includes a structure blocking layer 230 disposed on the second pinning layer 225. In one embodiment, the structure blocking layer 230 is sandwiched between the second pinning layer 225 and the magnetic reference layer 235. In one embodiment, the structure blocking layer 230 includes one or more layers. In one embodiment, the structure blocking layer 230 includes one or more of a metal-containing material or a magnetic material, for example, one or more of Mo, Ta, W, CoFe, and CoFeB, a Ta-containing layer, a Mo-containing layer, and a W-containing layer. The thickness of the second pinning layer 225 is between about 0 Å and about 8 Å, for example, about 4 Å.

[0037]

[0044] The film stack includes a magnetic reference layer 235 disposed on the structure blocking layer 230. In one embodiment, the magnetic reference layer 235 is sandwiched between the structure blocking layer 230 and the tunnel barrier layer 240. In one embodiment, the magnetic reference layer 235 includes one or more layers. The magnetic reference layer 235 is made of several magnetic materials such as a metal alloy containing a dopant, for example, a boron dopant, an oxygen dopant, or other suitable materials. Suitable metal alloys include Ni-containing materials, Pt-containing materials, Ru-containing materials, Co-containing materials, Ta-containing materials, and Pd-containing materials. Suitable examples of magnetic materials include Ru, Ta, Co, Pt, Ni, TaN, NiFeOx, NiFeB, CoFeOxB, CoFeB, CoFe, NiOxB, CoBOx, FeBOx, CoFeNiB, CoPt, CoPd, CoNi, and TaOx.

[0038] ​

[0045] In one embodiment, one or more layers of the magnetic reference layer 235 include a CoFeB-containing layer. The weight percentage (wt%) of boron (B) in the magnetic reference layer 235 is between about 10 wt% and about 40 wt%, for example, between about 20 wt% and 40 wt%, for example, between about 25 wt% and about 40 wt%. The wt% of iron in the magnetic reference layer 235 is between about 20 wt% and about 60 wt%, for example, between about 40 wt% and 60 wt%, for example, between about 45 wt% and about 60 wt%. The thickness of the magnetic reference layer 235 is between about 5 Å and about 20 Å, for example, about 10 Å.

[0039]

[0046] In one embodiment, the film stack includes a tunnel barrier layer 240 disposed on the magnetic reference layer 235. In one embodiment, the tunnel barrier layer 240 is sandwiched between the magnetic reference layer 235 and the magnetic memory layer 245. In one embodiment, the tunnel barrier layer 240 is an oxide barrier layer. In this embodiment, the tunnel barrier layer 240 includes MgO, HfO2, TiO2, TaOx, Al2O3, or other suitable materials. In one embodiment, the tunnel barrier layer 240 is MgO having a thickness between about 1 Å and about 15 Å, for example, about 10 Å. The tunnel barrier layer 240 may be annealed either during or after deposition, for example, using a rapid thermal annealing (RTP) process.

[0040]

[0047] In one embodiment, the film stack includes a magnetic memory layer 245 disposed on the tunnel barrier layer 240. In one embodiment, the magnetic memory layer 245 is sandwiched between the tunnel barrier layer 240 and the capping layer 250. The magnetic memory layer 245 is made of several magnetic materials such as a metal alloy containing a dopant, for example, a boron dopant, an oxygen dopant, or other suitable materials. Suitable metal alloys include Ni-containing materials, Pt-containing materials, Ru-containing materials, Co-containing materials, Ta-containing materials, and / or Pd-containing materials. Suitable examples of magnetic materials include Ru, Ta, Co, Pt, Ni, TaN, NiFeOx, NiFeB, CoFeOxB, CoFeB, CoFe, NiOxB, CoBOx, FeBOx, CoFeNiB, CoPt, CoPd, CoNi, and TaOx.

[0041]

[0048] In one embodiment, the magnetic memory layer 245 is a CoFeB-containing material, a CoFeNiB-containing material, a Ta-containing material, a Mo-containing material, or a W-containing material, a combination thereof, or other suitable layers. For example, in the embodiment shown in FIG. 2, the magnetic memory layer 245 includes a first CoFeB-containing layer 245a and a second CoFeB-containing layer 245c sandwiching an intermediate layer 245b. The first CoFeB-containing layer 245a has a thickness of from about 5 Å to about 20 Å, for example, about 10 Å. The weight percentage (wt%) of boron (B) in the first CoFeB-containing layer 245a is between about 10 wt% and about 40 wt%, for example, between about 20 wt% and 40 wt%, for example, between about 25 wt% and about 40 wt%. The wt% of iron in the first CoFeB-containing layer 245a is between about 20 wt% and about 60 wt%, for example, between about 40 wt% and 60 wt%, for example, between about 45 wt% and about 60 wt%.

[0042]

[0049] The second CoFeB-containing layer 245c has a thickness of from about 5 Å to about 20 Å, for example, about 10 Å. The weight percentage (wt%) of boron (B) in the second CoFeB-containing layer 245c is between about 10 wt% and about 40 wt%, for example, between about 20 wt% and 40 wt%, for example, between about 25 wt% and about 40 wt%. The wt% of iron in the second CoFeB-containing layer 245a is between about 20 wt% and about 60 wt%, for example, between about 40 wt% and 60 wt%, for example, between about 45 wt% and about 60 wt%.

[0043]

[0050] The intermediate layer 245b of the magnetic memory layer 245 includes at least one layer of one or more of a Ta-containing layer, a Mo-containing layer, and a W-containing layer. The intermediate layer 245b has a thickness of from about 0 Å to about 8 Å, for example, about 3 Å.

[0044]

[0051] The film stack includes a capping layer 250 disposed on the magnetic memory layer 245. In one embodiment, the capping layer 250 is sandwiched between the magnetic memory layer 245 and the hard mask 255. The capping layer 250 is utilized on top of the MTJ stack to protect the stack from corrosion and also acts as an etch stop layer for hard mask etching. In one embodiment, the capping layer 250 includes a single layer. In another embodiment, the capping layer 250 is formed from multiple layers. In this embodiment, the capping layer 250 includes a first layer 250a, a second layer 250b, a third layer 250c, and a fourth layer 250d.

[0045]

[0052] The first layer 250a includes one or more layers of an oxygen-containing layer such as an Fe-containing oxide material. In one embodiment, the oxygen-containing layer is one or more of an Fe oxide material, a CoFe oxide material, a CoFeB oxide material, a NiFe oxide material, an FeB oxide material, and combinations thereof. The first layer 250a has a thickness between about 0 Å and about 15 Å, for example, between about 2 Å and about 10 Å.

[0046]

[0053] In one embodiment, the first layer 250a is manufactured by sputtering (i.e., a PVD deposition process) an Fe-containing metal onto the magnetic memory layer 245. In this embodiment, the Fe-containing metal is subsequently oxidized in an oxygen-containing ambient environment. An oxygen-containing ambient environment can be formed within the process chamber or the Fe-containing metal can be exposed to the atmosphere to form an Fe-containing oxide material. In another embodiment, the Fe-containing metal is reactively sputtered onto the magnetic memory layer 245 in the presence of an oxygen-containing gas to form an Fe-containing oxide material. In this embodiment, the oxygen-containing gas is fed into the process environment at a flow rate between about 1 sccm and about 60 sccm, for example, between about 10 sccm and about 30 sccm, for example, about 20 sccm.

[0047]

[0054] The period of oxygen exposure to promote the oxidation of the Fe material is between about 1 second and about 180 seconds, for example, between about 5 seconds and about 60 seconds. In one example, the Fe-containing metal is exposed to an oxygen-containing environment (either air or an oxygen-containing gas) for about 10 seconds, and as a result, the film laminate exhibits a coercive magnetic field (Hc) of about 581 Oe and a data retention barrier (Eb) of about 41 kT. In another example, the Fe-containing metal is exposed to an oxygen-containing environment (either air or an oxygen-containing gas) for about 30 seconds, and as a result, the film laminate exhibits a coercive magnetic field (Hc) of about 918 Oe and a data retention barrier (Eb) of about 45 kT. In another example, the Fe-containing metal is exposed to an oxygen-containing environment (either air or an oxygen-containing gas) for about 60 seconds, and as a result, the film laminate exhibits a coercive magnetic field (Hc) of about 1029 Oe and a data retention barrier (Eb) of about 51 kT.

[0048]

[0055] In yet another embodiment, the Fe-containing oxide material is directly sputtered onto the magnetic memory layer 245 to form the Fe-containing oxide material. In one or more of the foregoing embodiments, the oxidation of the Fe metal is performed in situ to avoid subsequent exposure to air and the formation of native Fe oxide.

[0049]

[0056] Utilizing the Fe-containing oxide material for the capping layer 250a in direct interfacial contact with the magnetic memory layer 245 enables the realization of several advantages. The Fe-containing oxide material has a stronger bulk PMA than conventional capping layer materials that increase the PMA of the MTJ. Further, the increase in PMA reduces the dependence on boron at the interface between the capping layer 250a and the magnetic memory layer 245 and, in certain embodiments, substantially eliminates it, and boron typically diffuses away from the interface during the heat treatment of the MTJ. Further, the PMA can be adjusted by controlling the thickness of the Fe-containing oxide material. Thus, it is possible to avoid an undesirable increase in film surface roughness and the impact on the TMR of the MTJ while utilizing a sufficiently thin layer of the Fe-containing oxide material that provides an appropriate PMA. As a result, the performance of the MTJ, such as electrical performance, material stability, tunability, manufacturability, etc., is improved.

[0050]

[0057] The second layer 250b includes one or more layers of a Ru-containing layer and / or an Ir-containing layer. The second layer 250b has a thickness between about 0 Å and about 30 Å, for example, about 20 Å. The third layer 250c includes one or more layers of a Ta-containing material. The third layer 250c has a thickness between about 0 Å and about 30 Å, for example, about 10 Å. The fourth layer 250d includes one or more layers of an Ir-containing layer and a Ru-containing layer, for example, one or more Ir-containing layers. The fourth layer 250d has a thickness between about 0 Å and about 50 Å, for example, about 30 Å.

[0051]

[0058] In one embodiment, the capping layer 250 includes an optional layer 250x. The optional layer 250x is disposed between the first layer 250a and the second layer 250b. In one embodiment, the optional layer 250x includes one or more layers of an Ir-containing layer and / or a Ru-containing layer. In another embodiment, the optional layer 250x is an Fe-containing oxide material such as the above. The optional layer 250x has a thickness between about 0 Å and about 30 Å, for example, about 20 Å.

[0052]

[0059] In an embodiment, when the capping layer 250 includes the optional layer 250x, the second layer 250b is not used. In such an embodiment, the optional layer 250x is on the first layer 250a. In one embodiment, the optional layer 250x is disposed in direct contact with the first layer 250a on the first layer 250a.

[0053]

[0060] FIGS. 3A - 3D show various embodiments of the capping layer 250 as discussed above. FIG. 3A shows a capping layer 250 including a first layer 250a, an optional layer 250x disposed on the first layer 250a, a second layer 250b disposed on the optional layer 250x, a third layer 250c disposed on the second layer 250b, and a fourth layer 250d disposed on the third layer 250c. The respective materials, compositions, and thickness ranges of the layers 250a, 250x, 250b, 250c, 250d are as discussed above.

[0054]

[0061] Figure 3B shows a capping layer 250 including a first layer 250a, a second layer 250b disposed on the first layer 250a, a third layer 250c disposed on the second layer 250b, and a fourth layer 250d disposed on the third layer 250c. The range of the material, composition, and thickness of each of the layers 250a, 250b, 250c, and 250d has been discussed above.

[0055]

[0062] Figure 3C shows a capping layer 250 including a first layer 250a, an optional layer 250x disposed on the first layer 250a, a third layer 250c disposed on the optional layer 250x, and a fourth layer 250d disposed on the third layer 250c. The range of the material, composition, and thickness of each of the layers 250a, 250x, 250c, and 250d has been discussed above.

[0056]

[0063] Figure 3D shows a capping layer 250 including a first layer 250a and an optional layer 250x disposed on the first layer 250a. The range of the material, composition, and thickness of each of the layers 250a and 250x has been discussed above.

[0057]

[0064] Figures 2A - 2C show exemplary MTJ film laminates in which one or more of the buffer layer, the SyF bonding layer, and the capping layer are not made of Ru. In some embodiments, the MTJ film laminate includes a CoFeB - based buffer layer 205 / 205’, which may optionally include some TaN and / or Ta. The CoFeB layer can be disposed above or below the layer including TaN and / or Ta. The wt% of boron in the CoFeB - based buffer layer must be greater than about 10 wt%, for example, greater than about 25 wt%. In some embodiments, Ir, Ru, Rh, and / or Cr can be used as the SyF bonding layer 220. In some embodiments, Ir and / or Ru can be the top - layer metal of the capping layer 250.

[0058]

[0065] Using a CoFeB-based buffer layer instead of a Ru-containing buffer layer has been demonstrated to increase the tunneling magnetoresistance (TMR) with excellent magnetic pinning even after annealing at temperatures up to 450°C. Strong SyF bonding, large perpendicular magnetic anisotropy in the fixed and reference layers, and controllable perpendicular magnetic anisotropy in the free layer are realized. Some embodiments implementing a CoFeB buffer layer (containing 25 wt% boron) show an improvement in TMR (%) of more than 10% over conventional Ta / Ru / Ta buffer layers. The CoFeB layer blocks the increased roughness from reaching the MTJ film stack from the bottom contact.

[0059]

[0066] Furthermore, replacing Ru with Ir in the SyF bonding layer and the capping layer has been demonstrated to increase the TMR (%) even after annealing at temperatures up to 450°C. Some embodiments implementing an Ir-containing SyF bonding layer show an improvement in TMR (%) of more than 10% over conventional Ru-containing SyF bonding layers. Further, removing the Ru from the SyF bonding layer and the capping layer improves the TMR of the film by removing the diffusion of Ru into the MgO. The higher thermal stability of IrO2 compared to RuO4 may play a role in removing the diffusion.

[0060]

[0067] Configurations such as FIGS. 2A to 2C provide advantages superior to those of conventional film stacks. The first advantage is that the buffer remains amorphous even in high-temperature thermal processes and blocks the texture from the bottom contact. The second advantage is the strong antiferromagnetic coupling between the pinned layers brought about by Ir. The third advantage is the improvement in TMR by using a new buffer layer and removing Ru from the stack. Due to these advantages, the performance of the MTJ is improved (such as high TMR, strong SyF coupling, large perpendicular magnetic anisotropy of the fixed and reference layers, controllable perpendicular magnetic anisotropy of the free layer, etc.), and manufacturability is improved. The MTJ film stack can be used in the manufacture of memory cells for STT-MRAM applications and other memories and logic devices that use the MTJ as a unit building block. A physical vapor deposition system (such as ENDURA® STTMRAM) can be used to deposit the MTJ film stack for high-performance STT-MRAM chips. As described herein, an MTJ film stack capable of withstanding high-temperature thermal processes improves both the electrical and magnetic properties of the MTJ.

[0061]

[0068] Tables 1 and 2 show exemplary compositions of film stacks utilized to form a magnetic tunnel junction (MTJ) structure on a substrate. The materials, compositions, and thicknesses of the hard mask layer and the bottom contact layer are known to those skilled in the art.

[0062]

[0069] As described above (represented by 250x), additional (and optional) Ir and / or Ru layers in the capping layer can be disposed on top of the oxygen-containing layer. The thickness of this layer can be between about 0 Å and about 30 Å. In some embodiments, when additional Ir and / or Ru layers are used, the CoFeB layer of the capping layer is not used.

[0063] TIFF0007708905000001.tif253170 All values of composition and thickness are given as approximate ranges.

[0064] All values of the composition and thickness are given as approximate ranges in TIFF0007708905000002.tif234170.

[0065]

[0070] Although the disclosure herein has been described with reference to specific embodiments, it should be understood that these embodiments are merely illustrative of the principles and applications of the disclosure. It will be apparent to those skilled in the art that various modifications and variations can be made to the methods and apparatuses of the disclosure without departing from the spirit and scope of the disclosure. Accordingly, the disclosure is intended to cover modifications and variations that come within the scope of the appended claims and their equivalents.

Claims

1. forming a film stack including at least a magnetic memory layer; forming a first layer of an Fe-containing oxide capping layer on the magnetic memory layer, depositing an Fe-containing metal on the magnetic memory layer and then oxidizing the Fe-containing metal in an environment containing oxygen; reactively sputtering an Fe-containing metal on the magnetic memory layer in the presence of an oxygen-containing gas; or directly depositing an Fe-containing oxide material on the magnetic memory layer, forming a first layer of an Fe-containing oxide capping layer on the magnetic memory layer, including at least one of the above; forming a second layer of the Fe-containing oxide capping layer including one or more layers of a Ru-containing layer, an Ir-containing layer, or a combination thereof on the first layer; forming a third layer of the Fe-containing oxide capping layer including one or more layers of a Ta-containing material on the second layer; A method for manufacturing a magnetic tunnel junction film stack including the above.

2. The method according to claim 1, wherein the first layer of the Fe-containing oxide capping layer is formed in direct contact with the magnetic memory layer.

3. The method according to claim 1, wherein a direct interface between the first layer of the Fe-containing oxide capping layer and the magnetic memory layer is substantially free of boron.

4. Forming the film stack includes forming a buffer layer; forming a seed layer on the buffer layer; forming a synthetic ferrimagnetic (SyF) bonding layer on the seed layer; forming a magnetic reference layer on the SyF bonding layer; forming a tunnel barrier layer on the magnetic reference layer; and forming the magnetic memory layer on the tunnel barrier layer, The method according to claim 1 including the above.

5. The method according to claim 1, further including forming a fourth layer of the Fe-containing oxide capping layer on the third layer, the fourth layer including one or more layers of a Ru-containing layer, an Ir-containing layer, or a combination thereof.

6. The method according to claim 1, wherein the first layer of the Fe-containing oxide capping layer includes one or more of an Fe oxide material, a CoFe oxide material, a CoFeB oxide material, a NiFe oxide material, an FeB oxide material, or a combination thereof.

7. a magnetic memory layer; an Fe-containing oxide capping layer disposed on the magnetic memory layer; A magnetic tunnel junction film stack including wherein the Fe-containing oxide capping layer a first layer containing an Fe-containing oxide material, a second layer disposed on the first layer and including one or more layers of a Ru-containing layer, an Ir-containing layer, or a combination thereof, a third layer disposed on the second layer and including one or more layers of a Ta-containing material, a magnetic tunnel junction film stack. **Claim 8** The first layer of the Fe-containing oxide capping layer includes one or more of an Fe oxide material, a CoFe oxide material, a CoFeB oxide material, a NiFe oxide material, an FeB oxide material, or a combination thereof, the magnetic tunnel junction film stack according to claim 7. **Claim 9** The Fe-containing oxide capping layer further includes a fourth layer disposed on the third layer, and the fourth layer includes one or more layers of a Ru-containing layer, an Ir-containing layer, or a combination thereof, the magnetic tunnel junction film stack according to claim 7. **Claim 10** a buffer layer, a seed layer disposed on the buffer layer, a synthetic ferrimagnetic (SyF) coupling layer disposed on the seed layer, a magnetic reference layer disposed on the SyF coupling layer, a tunnel barrier layer disposed on the magnetic reference layer, wherein the magnetic memory layer is disposed on the tunnel barrier layer, the magnetic tunnel junction film stack according to claim 7. **Claim 11** The thickness of the first layer of the Fe-containing oxide capping layer is from about 2 Å to about 10 Å, the magnetic tunnel junction film stack according to claim 7. **Claim 12** forming a film stack including at least a magnetic memory layer, forming a first layer of an Fe-containing oxide capping layer on the magnetic memory layer, forming a second layer of the Fe-containing oxide capping layer including one or more layers of a Ru-containing layer, an Ir-containing layer, or a combination thereof on the first layer, forming a third layer of the Fe-containing oxide capping layer including one or more layers of a Ta-containing material on the second layer, a method for manufacturing a magnetic tunnel junction film stack including. **Claim 13** Forming the first layer of the Fe-containing oxide capping layer depositing an Fe-containing metal on the magnetic memory layer, subsequently oxidizing the Fe-containing metal in an environment containing oxygen, the method according to claim 12 including. **Claim 14** Depositing the Fe-containing metal is the method according to claim 13, including a physical vapor deposition process.

15. Oxidizing the Fe-containing metal includes exposing the Fe-containing metal to oxygen for a period of about 5 seconds to about 60 seconds, which is the method according to claim 13.

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