SOT (Spin-Orbit Torque) MTJ (Magnetic Tunnel Junction) devices, MAMR (Microwave Assisted Magnetic Recording) write heads, MRAM (Magnetoresistive Random Access Memory) devices

Abstract

To provide a device comprising a BiSb layer having a high spin hole angle and a high conductivity.SOLUTION: A spin orbit torque (SOT) magnetic tunnel junction (MTJ) device includes a substrate, a buffer layer 10 formed on the substrate, and a bismuth antimony (BiSb) layer 20 formed on the buffer layer 10. The BiSb layer 20 is (012) oriented.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to SOT (Spin Orbit Torque) MTJ (Magnetic Tunnel Junction) devices.

[0002] (CROSS-REFERENCE TO RELATED APPLICATIONS) This application claims the benefit of U.S. Provisional Patent Application No. 62 / 975,661, filed February 12, 2020, which is incorporated herein by reference. [Background technology]

[0003] Bismuth antimonide (BiSb) is a narrow-gap topological insulator that has been proposed as a spin Hall layer for spin torque oscillators (STO) and magnetoresistive random access memory (MRAM) devices. BiSb possesses both a giant spin Hall effect and high electrical conductivity.

[0004] Non-Patent Document 1 discloses that BiSb with a (012) crystal orientation has a higher spin-Hall angle and higher conductivity than BiSb with a (001) crystal orientation. BiSb with a (012) crystal orientation was formed on an MnGa film with a (001) crystal orientation, which was formed on a GaAs substrate with a (001) crystal orientation.

[0005] Non-Patent Document 2 shows that the growth, crystal orientation, spin Hall angle, and high conductivity of BiSb are not consistent among several experiments.

[0006] In Non-Patent Document 3, an ultrathin BiSb layer with a (012) orientation is grown on Si(111), but the junction of the BiSb layer with a (012) orientation on Si(111) is insufficient. [Prior art documents] [Non-patent literature]

[0007] [Non-Patent Document 1] N.H.D. Khang, Y. Ueda, and P.N. Hai, “A conductive topological insulator with large spin Hall effect for ultralow power spin-orbit torque switching,” Nature Materials, v. 17, 808 (2018) [Non-Patent Document 2] N. Roschewsky, E.S. Walker, P. Gowtham, S. Muschinske, F. Hellman, S.R. Bank, and S. Salahuddin, “Spin-orbit torque and Nernst effect in Bi-Sb / Co heterostructures”, Phys. Rev. B, vol. 99, 195103 (2 May 2019), [Non-Patent Document 3] E.S. Walker, S. Muschinske, C.J. Brennan, S.R. Na, T. Trivedi, S.D. March, Y. Sun, T. Yang, A. Yau, D. Jung, A.F. Briggs, E.M. Krivoy, M.L. Lee, K.M. Liechti, E.T. Yu, D. Akinwande, and S.R. Bank, “Composition-dependent structural transition in epitaxial Bi1?xSbx thin films on Si (111)”, Phys. Rev. Materials 3, 064201 (7 June 2019), [Summary of the Invention][[ID=I1]] [Problems to be Solved by the Invention]

[0008] In this situation, there is a need for improved processes for forming BiSb with high spin Hall angles and high electrical conductivity, and improved devices having BiSb layers with high spin Hall angles and high electrical conductivity. [Means for solving the problem]

[0009] The present disclosure generally relates to buffer layers that facilitate the growth of bismuth antimony (BiSb) layers with a (012) orientation.

[0010] In one embodiment, a spin-orbit torque (SOT) magnetic tunnel junction (MTJ) device includes a substrate, a buffer layer on the substrate, and a BiSb (bismuth antimony) layer having a (012) orientation formed on the buffer layer. The buffer layer includes a pre-seed layer on the substrate, a seed layer on the pre-seed layer, and a crystalline layer on the seed layer. The pre-seed layer includes a material selected from the group consisting of Si, NiTa, NiFeTa, CoZrTa, NiNb, NiFeTa, NiFeW, CoHf, CoFeHf, CoFeHfB, NiFeB, CoFeB, Ge, Co, CoFe, NiCr, Ni, Cu, NiFe, Ru, Pt, Rh, silicon oxide, aluminum oxide, magnesium oxide, TiN, AlN, and alloys thereof. The seed layer comprises a material selected from the group consisting of Co, CoFe, Ni, NiFe, NiCr, NiTa, NiFeTa, Cu, CuAgNi, RuX, CuX, CuNiX, CoFeX, CoNiX, FeX, NiX, and CoX, (where X = Cr, Ag, Pt, Ir, Rh), and combinations thereof. The crystalline layer comprises a material selected from the group consisting of Co, CoFe, Ni, NiFe, NiCr, NiTa, NiFeTa, Cu, CuAgNi, RuX, CuX, CuNiX, CoFeX, CoNiX, FeX, NiX, and CoX, (where X = Cr, Ag, Pt, Ir, Rh), and combinations thereof.

[0011] Another embodiment of a microwave-assisted magnetic recording (MAMR) write head includes a main pole and a trailing shield, and a spin-orbit torque (SOT) device disposed in the gap between the main pole and the trailing shield. The SOT device includes a substrate, a buffer layer formed on the substrate, and a BiSb (bismuth antimony) layer formed on the buffer layer, the BiSb layer having a (012) orientation and serving as a spin Hall layer.

[0012] An MRAM device according to another embodiment includes a recording layer, a buffer layer formed on the recording layer, and a BiSb (bismuth antimony) layer having a (012) orientation formed on the buffer layer. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a schematic cross-sectional view of one embodiment of a BiSb layer having a (012) orientation formed on a buffer layer formed on a substrate. [Figure 2] 1 is a schematic plan view illustrating one embodiment of a BiSb layer with a (012) orientation formed on a buffer layer with a (111) fcc orientation or a (002) hcp orientation. [Figure 3] 1 is a schematic diagram of an embodiment of a magnetic media drive including a MAMR write head. [Figure 4] 2 is a fragmented cross-sectional side view of a read / write head facing a magnetic medium in an embodiment. [Figure 5A] FIG. 1 is a schematic cross-sectional view of an SOT device for use in a MAMR write head. [Figure 5B] FIG. 5B is a schematic MFS diagram of an embodiment of a portion of a MAMR write head with the SOT device of FIG. 5A. [Figure 5C] FIG. 5B is a schematic MFS diagram of an embodiment of a portion of a MAMR write head with the SOT device of FIG. 5A. [Figure 6] FIG. 1 is a schematic cross-sectional view of an SOT-MTJ used as an MRAM device. [Figure 7]1A-1C show X-ray diffraction (XRD) 2θ scans of BiSb layers formed on various material layers. [Figure 8] 1A-1C show X-ray diffraction (XRD) 2θ scans of BiSb layers formed on various material layers. [Figure 9] 1A-1C show X-ray diffraction (XRD) 2θ scans of BiSb layers formed on various material layers. DETAILED DESCRIPTION OF THE INVENTION

[0014] For ease of understanding, where possible, like reference numerals have been used to designate like elements common to the figures, and it is intended that elements disclosed in one embodiment may be beneficially utilized on other embodiments without specific description.

[0015] While reference will be made below to embodiments of the present disclosure, it should be understood that the disclosure is not limited to the specific described embodiments. Any combination of the following features and elements, whether associated with different embodiments, is intended to realize and practice the present disclosure. Furthermore, embodiments of the present disclosure may achieve advantages over other possible solutions and / or the prior art, but whether a particular advantage is achieved by an embodiment does not limit the present disclosure. Accordingly, the following aspects, features, embodiments, and advantages are merely exemplary and should not be considered elements or limitations of the appended claims unless expressly recited in the claims. Similarly, references to "disclosure" should not be construed as a generalization of the inventive subject matter disclosed herein, and should not be considered elements or limitations of the appended claims unless expressly recited in the claims.

[0016] Embodiments of the present disclosure generally relate to a buffer layer that facilitates the growth of a (012)-oriented bismuth antimonide (BiSb) layer. The buffer layer can be grown on a silicon or alumina substrate with or without an oxide layer formed thereon. The (012)-oriented BiSb layer exhibits a large spin Hall effect and high electrical conductivity. A (012)-oriented BiSb layer can be used to form a spin-orbit torque (SOT) magnetic tunnel junction (MTJ) device. For example, a (012)-oriented BiSb layer can be used as a spin Hall layer in a spin-orbit torque device in a microwave-assisted magnetic recording (MAMR) write head. In another example, a (012)-oriented BiSb layer can be used as a spin Hall electrode layer in a magnetoresistive random access memory (MRAM) device.

[0017] In one embodiment, a spin-orbit torque (SOT) magnetic tunnel junction (MTJ) device includes a substrate, a buffer layer on the substrate, and a BiSb (bismuth antimony) layer formed on the buffer layer with a (012) orientation. The buffer layer includes a pre-seed layer on the substrate, a seed layer on the pre-seed layer, and a crystalline layer on the seed layer. The pre-seed layer includes a material selected from the group consisting of Si, NiTa, NiFeTa, CoZrTa, NiNb, NiFeTa, NiFeW, CoHf, CoFeHf, CoFeHfB, NiFeB, CoFeB, Ge, Co, CoFe, NiCr, Ni, Cu, NiFe, Ru, Pt, Rh, silicon oxide, aluminum oxide, magnesium oxide, TiN, AlN, and alloys thereof. The seed layer comprises a material selected from the group consisting of Co, CoFe, Ni, NiFe, NiCr, NiTa, NiFeTa, Cu, CuAgNi, RuX, CuX, CuNiX, CoFeX, CoNiX, FeX, NiX, and CoX, (where X = Cr, Ag, Pt, Ir, Rh), and combinations thereof. The crystalline layer comprises a material selected from the group consisting of Co, CoFe, Ni, NiFe, NiCr, NiTa, NiFeTa, Cu, CuAgNi, RuX, CuX, CuNiX, CoFeX, CoNiX, FeX, NiX, and CoX, (where X = Cr, Ag, Pt, Ir, Rh), and combinations thereof.

[0018] FIG. 1 is a schematic cross-sectional view of one embodiment of a BiSb layer 20 having a (012) crystal orientation formed on a buffer layer 10 formed on a substrate 1. The substrate 1 can be a silicon substrate or an alumina substrate. The silicon substrate has a cubic structure with a (111), (100), or other crystal orientation. The alumina substrate has a hexagonal structure with a (001) orientation or other crystal orientation, or has an amorphous structure. The substrate 1 can be bare or have one or more layers formed thereon, such as a thermally grown or deposited oxide layer.

[0019] The buffer layer 10 includes a pre-seed layer 12 formed on the substrate 1, a seed layer 14 formed on the pre-seed layer 12, and a crystal layer 16 formed on the seed layer 14.

[0020] The pre-seed layer 12 provides adhesion to the substrate 1. The pre-seed layer 12 includes an amorphous material or a crystalline material. Examples of amorphous materials include Si, NiTa, NiFeTa, CoZrTa, NiNb, NiFeTa, NiFeW, CoHf, CoFeHf, CoFeHfB, NiFeB, CoFeB, Ge, and alloys thereof. In one embodiment, the pre-seed layer 12 includes amorphous materials such as Si, NiTa, NiFeTa, and alloys thereof. Examples of crystalline materials include Co, CoFe, NiCr, Ni, Cu, NiFe, Ru, Pt, Rh, silicon oxide, aluminum oxide, magnesium oxide, TiN, AlN, and alloys thereof. In one embodiment, the pre-seed layer 12 includes crystalline materials such as NiCr, Cu, NiFe, Co, and CoFe, and alloys thereof.

[0021] The seed layer 14 provides an interface between the pre-seed layer 12 and the crystalline layer 16 and is useful for growing the crystalline layer 16 with fewer crystalline defects. The seed layer 14 can be a crystalline material such as a face-centered cubic (fcc) material or a hexagonal close-packed (hcp) material. Examples of the seed layer 14 include Co, CoFe, Ni, NiFe, NiCr, NiTa, NiFeTa, Cu, CuAgNi, metal alloys, and combinations thereof. Examples of the metal alloys for the seed layer 14 include RuX, CuX, CuNiX, CoFeX, CoNiX, FeX, NiX, and CoX, where X is Cr, Ag, Pt, Ir, Rh, Al, Mn, and combinations thereof. In one embodiment, the seed layer 14 includes Co, CoFe, Ni, NiFe, Cu, CuNiAg, and alloys thereof.

[0022] The crystalline layer 16 helps to provide growth of the BiSb layer 20 with a (012) orientation. The crystalline layer 16 can be an fcc material or an hcp material. Examples of the crystalline layer 16 include Co, CoFe, Ni, NiFe, NiCr, NiTa, NiFeTa, Cu, CuAgNi, metal alloys, and combinations thereof. Examples of metal alloys for the crystalline layer 16 include RuX, CuX, CuNiX, CoFeX, CoNiX, FeX, NiX, and CoX, where X is Cr, Ag, Pt, Ir, Rh, Al, Mn, and combinations thereof. In one embodiment, the crystalline layer 16 includes Co, CoFe, Ni, NiFe, Cu, CuNiAg, and alloys thereof.

[0023] The seed layer 14 and the crystalline layer 16 can comprise the same or different materials. The seed layer 14 and the crystalline layer 16 can have similar properties. In some embodiments, the seed layer 14 and the crystalline layer 16 provide a lattice structure gradient from large to small or small to large to enhance the lattice match of the crystalline layer 16 and the BiSb layer 20.

[0024] In one embodiment, the seed layer 14 and the crystalline layer 16 include one or more fcc materials having a (111) orientation with an a-axis of about 3.52 Å to about 3.71 Å, which the inventors have discovered surprisingly provides for the growth of a (012)-oriented BiSb layer. For example, the fcc material having a (111) orientation can be Cu or a CuAg alloy with an atomic percent silver content of greater than zero to about 18%. The a-axis of the Cu or CuAg alloy is about 3.60 Å to about 3.71 Å.

[0025] In one embodiment, seed layer 14 and crystalline layer 16 comprise one or more hcp materials with an a-axis of about 2.49 Å to about 2.62 Å and a (002) orientation, which the inventors have discovered surprisingly provides for the growth of a (012) oriented BiSb layer.

[0026] In one embodiment, the buffer layer 10 is deposited by physical vapor deposition (PVD), such as sputtering, molecular beam epitaxy, ion beam deposition, other suitable PVD processes, and combinations thereof. In one embodiment, the buffer layer 10 is deposited at an ambient temperature, such as 20° C. to about 25° C. In one aspect, forming the buffer layer 10 at ambient temperature reduces thermal migration of the pre-seed layer 12, the seed layer 14, and the crystalline layer 16. In another aspect, forming the buffer layer 10 at ambient temperature minimizes changes in the magnetization direction of magnetic materials formed on the substrate 1 prior to forming the buffer layer 10. In one embodiment, the pre-seed layer 12 is formed to a thickness of about 2 Å to about 50 Å, such as about 5 Å to about 30 Å. In one embodiment, the seed layer 14 is formed to a thickness of about 2 Å to about 20 Å, such as about 3 Å to about 12 Å. In one embodiment, the crystalline layer 16 is formed to a thickness of about 1 Å to about 15 Å, such as about 2 Å to about 7 Å. A thickness of the crystalline layer 16 of about 1 Å to about 15 Å helps maintain current flow from the buffer layer 10 through the BiSb layer 20 in an SOT device. A crystalline layer 16 having a thickness greater than 15 Å can cause current shunting of current through the buffer layer 10 and away from the BiSb layer 20 in an SOT device.

[0027] In one embodiment, post-etching of the buffer layer 10 is performed. For example, the buffer layer 10 can be post-etched by ion etching, such as by irradiating the crystalline layer 16 with argon ions. The post-etching is believed to clean the surface of the crystalline layer 16 and / or strain the crystalline layer 16 to promote (012) growth and strengthen the interface between the crystalline layer 16 and the BiSb layer 20.

[0028] The BiSb layer 20 has a (012) orientation. <x<1であるBi 1-x Sb x In one embodiment, the BiSb layer 20 has an x ​​of 0.05 <x<0.2であるBi 1-x Sb xor about 7% to about 22% atomic percent antimony content. In one embodiment, the BiSb layer 20 is formed to a thickness of about 20 Å to about 200 Å, for example, about 50 Å to about 150 Å.

[0029] Table 1 shows an example of the properties of a BiSb layer with a (012) orientation compared with beta-tantalum and a BiSb layer with a (001) orientation. [Table 1] The (012)-oriented BiSb layer has similar electrical conductivity and a much larger spin-Hall angle than beta-tantalum (Beta-Ta) or (001)-oriented BiSb layers. Therefore, the relative power consumption to generate the spin-Hall effect is lower in BiSb(012) compared to beta-tantalum or BiSb(001).

[0030] 2 is a schematic plan view illustrating one embodiment of a BiSb layer 20 with a (012) orientation formed on a buffer layer 10 with a (111) fcc or (002) hcp orientation. Different symbols in each layer indicate atoms of the material at different depths in the layer.

[0031] In one embodiment, a BiSb layer 20 having a (012) orientation is formed on a buffer layer 10 having a (111) fcc orientation or a (002) hcp orientation due to the a-axis lattice constant of the buffer layer having a ratio of about 2:3 to the a-axis of silicon in the Si(111) plane. For example, as shown in FIG. 2, a NiSb layer 20 having an x ​​of about 0.5 is formed on a buffer layer 10 having a (111) fcc orientation or a (002) hcp orientation due to the a-axis lattice constant of the buffer layer having a ratio of about 2:3 to the a-axis of silicon in the Si(111) plane. x Fe 1-xThe (111)-containing buffer layer 10 has an a-axis lattice parameter that is approximately 2:3 with respect to the a-axis of silicon in the Si(111) plane. The NiFe(111) plane can be aligned with the Si(111) plane. The rectangular outline of the NiFe(111) plane with dimensions a = approximately 4.40 Å and b = approximately 5.08 Å depicted in the bottom of Figure 2 indicates that the NiFe(111) plane is aligned with the approximately rectangular BiSb(012) plane with dimensions a = 4.54 Å and b = 4.75 Å (shown in the top of Figure 2) with a 3% mismatch in one direction. Therefore, a NiFe thin film with a (111) structure can be used as the buffer layer 10 to grow a BiSb layer 20 with a (012) structure. fcc From a hcp Conversion to a fcc / √2 to a hcp Therefore, a hcp The axes have a ratio of 2:3.

[0032] In the example described with reference to FIG. 7 , a highly structured BiSb(012) surface is grown on a highly structured NiFe layer. Amorphous Si promotes the growth of (111) NiFe thereon. The example shows that BiSb(012) structures can be formed from polycrystalline epitaxy using (111) textured fcc lattice-matched thin films, such as (111) NiFe layers, or (002) structured hcp lattice-matched thin films, such as (002) Co layers. These structured films are useful for manufacturing BiSb(012) structures on a production scale. It is believed that BiSb(012) epitaxial films can be grown by crystalline epitaxy on single-crystal Si(111) surfaces. For example, a NiFe(111) buffer layer can be epitaxially grown on single crystal Si(111), and a BiSb(012) layer can be epitaxially grown on the NiFe(111) buffer layer, thereby forming an epitaxial film stack of Si(111) / NiFe(111) / BiSb(012).

[0033] In one embodiment, the fcc material with a (111) orientation, the hcp material with a (002) orientation, and combinations thereof shown in FIG. 2 can be substantially aligned with the BiSb layer 20 with a (012) orientation. The (111) orientation of the fcc material or the (002) orientation of the hcp material promotes BiSb growth in a (012) orientation rather than growth in a (001) orientation. The (012)-oriented BiSb layer 20 has a higher spin-Hall angle and better performance in SOT-MTJ devices than the (001)-oriented BiSb layer. The SOT-MTJ device can be configured with a vertical stack or an in-plane stack. SOT-MTJ devices can be used, for example, in MAMR write heads, MRAM, artificial intelligence chips, and other applications.

[0034] 3 is a schematic diagram of an embodiment of a magnetic media drive including a MAMR write head with a SOT-MTJ device. The magnetic media drive may be a single drive or may include multiple drives. For simplicity of explanation, a single disk drive 100 is shown in the embodiment. At least one rotatable magnetic disk 112 is supported on a spindle 114 and rotated by a drive motor 118. Magnetic recording on each magnetic disk 112 is in the form of data tracks (not shown) in any suitable pattern, such as a concentric annular pattern.

[0035] At least one slider 113 is positioned near the magnetic disk 112, and each slider 113 supports one or more magnetic head assemblies 121, each including a SOT device. As the magnetic disk 112 rotates, the slider 113 moves radially inward and outward over the disk surface 122, allowing the magnetic head assemblies 121 to access different tracks on the magnetic disk 112 where desired data is written. Each slider 113 is attached to an actuator arm 119 via a suspension 115. The suspension 115 provides a small spring force that holds the slider 113 toward the disk surface 122. Each actuator arm 119 is attached to an actuator means 127. The actuator means 127, as shown in FIG. 2, may be a voice coil motor (VCM). The VCM includes a coil movable within a fixed magnetic field, and the direction and speed of the coil's movement are controlled by motor current signals provided by a control unit 129.

[0036] During operation of disk drive 100, the rotation of magnetic disk 112 forms an air bearing between slider 113 and disk surface 122, which exerts an upward force, or lift, on slider 113. The air bearing thus counterbalances the slight spring force of suspension 115 and supports slider 113 slightly above disk surface 122, a small, substantially constant spacing during normal operation.

[0037] During operation, the various components of disk drive 100 are controlled by control signals, such as access control signals and internal clock signals, generated by control unit 129. Control unit 129 typically includes logic control circuits, storage means, and a microprocessor. Control unit 129 generates control signals to control various system operations, such as drive motor control signals and head position signals on lines 123, and searches for control signals on lines 128. The control signals on lines 128 provide the desired current profiles to optimally move and position slider 113 toward the desired data track on disk 112. Write and read signals are transmitted to and from the write and read heads on assembly 121 via recording channel 125.

[0038] The above description of a typical magnetic media drive and the description of Figure 3 are merely representative. A magnetic media drive can include multiple media or disks and actuators, and each actuator can support multiple sliders.

[0039] 4 is a fragmented cross-sectional side view of one embodiment of a read / write head 200 having a SOT-MTJ device. The read / write head 200 faces the magnetic medium 112. The read / write head 200 may correspond to the magnetic head assembly 121 described in FIG. 3. The read / write head 200 includes a medium-facing surface (MFS) 212, such as a gas bearing surface, that faces the disk 112, a MAMR write head 210, and a magnetic read head 211. As shown in FIG. 4, the magnetic medium 112 moves past the MAMR write head 210 in the direction indicated by arrow 232, and the read / write head 200 moves in the direction indicated by arrow 234.

[0040] In some embodiments, the magnetic read head 211 is a magnetoresistive (MR) read head and includes an MR sensing element 204 disposed between MR shields S1 and S2. In other embodiments, the magnetic read head 211 is a magnetic tunnel junction (MTJ) read head that includes an MTJ sensing device 204 disposed between MR shields S1 and S2. The magnetic fields of adjacent magnetized regions in the magnetic disk 112 are detectable by the MR (or MTJ) sensing element 204 as recorded bits.

[0041] The MAMR write head 210 includes a main pole 220, a leading shield 206, a trailing shield 240, a spin-orbit torque (SOT) device 250, and a coil 218 that excites the main pole 220. The coil 218 may have a "pancake" structure wrapped around the back contact between the main pole 220 and the trailing shield 240 instead of the "spiral" structure shown in FIG. 4. The SOT device 250 is formed in a gap 254 between the main pole 220 and the trailing shield 240. The main pole 220 includes a trailing taper 242 and a leading taper 244. The trailing taper 242 extends from a recessed position from the MFS 212. The leading taper 244 extends from a recessed position from the MFS 212 to the MFS 212. The trailing taper 242 and the leading taper 244 may have similar tapers. The degree of taper is measured relative to the longitudinal axis 260 of the main pole 220. In some embodiments, the main pole 220 may not include a trailing taper 242 or a leading taper 244. Instead, the main pole 220 includes a trailing side (not shown) and a leading side (not shown) that are substantially parallel. The main pole 220 may be made of a magnetic material such as an FeCo alloy. The leading shield 206 and the trailing shield 240 may be made of a magnetic material such as a NiFe alloy. In one embodiment, the trailing shield 240 may include a trailing shield hot seed layer 241. The trailing shield hot seed layer 241 may include a high-momentum sputtered material such as CoFeN or FeXN, where X is Rh, Al, Ta, Zr, or Ti. In one embodiment, the trailing shield 240 does not include a trailing shield hot seed layer.

[0042] 5A is a schematic cross-sectional view of an SOT device 250 for use in a MAMR write head, such as the MAMR write head of drive 100 of FIG. 3 or other suitable magnetic media drive. SOT device 250 includes a BiSb layer 20 with a (012) orientation formed on a buffer layer 10 formed on a substrate 1. A spin torque layer (STL) 570 is formed on BiSb layer 20. STL 570 includes one or more layers of a ferromagnetic material, such as CoFe, CoIr, NiFe, or a CoFeX alloy (where X is B, Ta, Re, or Ir).

[0043] In some embodiments, the current shunt blocking layer 560 is disposed between the BiSb layer 20 and the spin torque layer 570. The current shunt blocking layer 560 reduces current flow from the BiSb layer 20 to the spin torque layer 570 while allowing spin-orbit torque between the BiSb layer 20 and the spin torque layer 570. In some embodiments, the current shunt blocking layer 560 includes a magnetic material that provides a greater spin-orbit torque than a non-magnetic material between the BiSb layer 20 and the spin torque layer 570. In some embodiments, the current shunt blocking layer 560 includes a magnetic material such as FeCo, FeCoM, FeCoMO, FeCoMMeO, an FeCoM / MeO stack, an FeCoMNiMnMgZnFeO, an FeCoM / NiMnMgZnFeO stack, multiple layers thereof, multiple stacks thereof, and combinations thereof. M is one or more of B, Si, P, Al, Hf, Zr, Nb, Ti, Ta, Mo, Mg, Y, Cu, Cr, and Ni, and Me is Si, Al, Hf, Zr, Nb, Ti, Ta, Mg, Y, or Cr. In some embodiments, the current shunt blocking layer 560 is formed to a thickness of about 10 Å to about 100 Å. In certain aspects, a current shunt blocking layer 560 having a thickness greater than 100 Å can reduce spin-orbit torque between the BiSb layer 20 and the spin torque layer 570. In some aspects, a current shunt blocking layer having a thickness less than 10 Å may not sufficiently reduce current from the BiSb layer 20 to the spin torque layer 570.

[0044] In some embodiments, additional layers, such as a spacer layer 580 and a pinned layer 590, are formed on the STL 570. The pinned layer 590 can partially pin the STL 570. The pinned layer 590 includes one or more layers of PtMn, NiMn, IrMn, IrMnCr, CrMnPt, FeMn, other antiferromagnetic materials, and combinations thereof. The spacer layer 580 includes one or more layers of magnesium oxide, aluminum oxide, other nonmagnetic materials, and combinations thereof.

[0045] 5B-5C are schematic MFS diagrams of one embodiment of a portion of a MAMR write head 210 with an SOT device 250 of FIG. 5A. The MAMR write head 210 may be the write head of FIG. 4 or any other suitable write head for the drive 100 of FIG. 3 or any other suitable magnetic media drive, such as a tape drive. The MAMR write head 210 includes a main pole 220 and a trailing shield 240 in the track direction. The SOT device 250 is disposed in the gap between the main pole and the trailing shield 240.

[0046] During operation, a charge current passing through the BiSb layer 20, which functions as a spin Hall layer, generates a spin current in the BiSb layer. The spin-orbit torque between the BiSb layer and the spin torque layer (STL) 570 causes the magnetization of the STL 570 to switch or precess due to the spin-orbit torque of the spin current from the BiSb layer 20. The STL 570 can generate an assist AC field to the write field. Energy-assisted write heads based on SOT have several times the power efficiency compared to MAMR write heads based on spin-transfer torque. As shown in FIG. 5B, the easy axis of the magnetization direction of the STL 570 is perpendicular to the MFS due to the shape anisotropy of the STL 570, coupling from the pinned layer 590 in FIG. 5A, and / or bias from a hard bias element adjacent to the STL 570. As shown in FIG. 5C, the easy axis of magnetization of STL 570 is parallel to the MFS due to shape anisotropy of STL 570, coupling from pinned layer 590 of FIG. 5A, and / or bias from hard bias elements proximate to STL 570.

[0047] 6 is a schematic cross-sectional view of a SOT-MTJ 250 used as an MRAM device 600. The MRAM device includes a reference layer (RL) 610, a spacer layer 620 on the RL 610, a recording layer 630 on the spacer layer 620, a buffer layer 10 on the recording layer 630, and a BiSb layer 20 on the buffer layer 10.

[0048] The RL 610 includes a single layer or multiple layers of CoFe, other ferromagnetic materials, and combinations thereof. The spacer layer 620 includes a single layer or multiple layers of magnesium oxide, aluminum oxide, other dielectric materials, and combinations thereof. The recording layer 630 includes a single layer or multiple layers of CoFe, NiFe, other ferromagnetic materials, and combinations thereof.

[0049] In one embodiment, the current shunt blocking layer 640 is disposed between the buffer layer 10 and the recording layer 630. The current shunt blocking layer 640 reduces current flow from the BiSb layer 20 to the recording layer 630 while allowing spin-orbit torque between the BiSb layer 20 and the recording layer 630. For example, writing to an MRAM device may be achieved by the spin-orbit torque between the BiSb layer 20 and the recording layer 630, which enables switching of the magnetization of the recording layer. In one embodiment, the current shunt blocking layer 640 includes a magnetic material that provides a greater spin-orbit torque between the BiSb layer 20 and the recording layer 630 than a non-magnetic material. In one embodiment, the current shunt blocking layer 640 includes a magnetic material such as FeCo, FeCoMO, FeCoMMeO, an FeCoM / MeO stack, an FeCoMNiMnMgZnFeO, an FeCoM / NiMnMgZnFeO stack, multiple layers thereof, multiple stacks thereof, and combinations thereof. M is one or more of B, Si, P, Al, Hf, Zr, Nb, Ti, Ta, Mo, Mg, Y, Cu, Cr, and Ni, and Me is Si, Al, Hf, Zr, Nb, Ti, Ta, Mg, Y, or Cr.

[0050] 6 may include other layers, such as a pinned layer, a pinned structure (e.g., a synthetic antiferromagnetic (SAF) pinned structure), electrodes, gates, and other structures. Other MRAM devices than the structure of FIG. 6 can be formed using a (012)-oriented BiSb layer on the buffer layer 10 to form a SOT-MTJ.

[0051] Embodiments of the present disclosure generally relate to a buffer layer that facilitates the growth of a (012)-oriented bismuth antimonide (BiSb) layer. The buffer layer can include one or more layers and can be grown on a silicon or alumina substrate with or without an oxide layer formed thereon. The (012)-oriented BiSb layer exhibits a large spin Hall effect and high electrical conductivity. The (012)-oriented BiSb layer can be used to form a spin-orbit torque (SOT) magnetic tunnel junction (MTJ) device.

[0052] In one embodiment, a spin-orbit torque (SOT) magnetic tunnel junction (MTJ) device includes a substrate, a buffer layer formed on the substrate, and a bismuth antimonide (BiSb) layer formed on the buffer layer and having a (012) orientation. The buffer layer includes a pre-seed layer on the substrate, a seed layer on the pre-seed layer, and a crystalline layer on the seed layer. The pre-seed layer includes a material selected from the group consisting of Si, NiTa, NiFeTa, CoZrTa, NiNb, NiFeTa, NiFeW, CoHf, CoFeHf, CoFeHfB, NiFeB, CoFeB, Ge, Co, CoFe, NiCr, Ni, Cu, NiFe, Ru, Pt, Rh, silicon oxide, aluminum oxide, magnesium oxide, TiN, AlN, and alloys thereof. The seed layer comprises a material selected from the group consisting of Co, CoFe, Ni, NiFe, NiCr, NiTa, NiFeTa, Cu, CuAgNi, RuX, CuX, CuNiX, CoFeX, CoNiX, FeX, NiX, and CoX, (where X = Cr, Ag, Pt, Ir, Rh), and combinations thereof. The crystalline layer comprises a material selected from the group consisting of Co, CoFe, Ni, NiFe, NiCr, NiTa, NiFeTa, Cu, CuAgNi, RuX, CuX, CuNiX, CoFeX, CoNiX, FeX, NiX, and CoX, (where X = Cr, Ag, Pt, Ir, Rh), and combinations thereof.

[0053] In another embodiment, a microwave-assisted magnetic recording (MAMR) write head includes a main pole, a trailing shield, and a spin-orbit torque (SOT) device disposed in the gap between the main pole and the trailing shield. The SOT device includes a substrate, a buffer layer formed on the substrate, a bismuth antimony (BiSb) layer formed on the buffer layer, and a spin torque layer formed on the BiSb layer. The BiSb layer has a (012) orientation and is a spin Hall layer.

[0054] In another embodiment, a magnetoresistive random access memory (MRAM) device includes a recording layer, a buffer layer formed on the recording layer, and a bismuth antimony (BiSb) layer formed on the buffer layer, wherein the BiSb layer has a (012) orientation.

[0055] The following are examples illustrating various embodiments of BiSb layers, such as BiSb layer 20 of Figures 1 and 2, magnetic drive 100 of Figure 3, write head 210 of Figure 4, SOT device 250 of Figures 5A-5C and 6, and other magnetic drives, SOT devices, and variations thereof. These examples are not intended to limit the scope of the claims unless specifically recited in the claims.

[0056] Example A In Example A (FIG. 7), a BiSb layer 710 is deposited by PVD directly onto a silicon (111) substrate to a thickness of about 100 Å. A BiSb layer 720 is deposited by PVD directly onto a NiFe layer to a thickness of about 100 Å. A NiFe layer is deposited by PVD onto a silicon (111) substrate to a thickness of about 6 Å. A BiSb layer 730 is deposited by PVD directly onto the NiFe layer to a thickness of about 100 Å. A NiFe layer is deposited by PVD onto a silicon (111) substrate to a thickness of about 50 Å.

[0057] 7 shows X-ray diffraction (XRD) 2θ scans of BiSb layers 710, 720, and 730. BiSb layer 710 formed directly on a thermal oxide-coated silicon substrate exhibits a (001) orientation, whereas BiSb layers 720 and 730 formed directly on NiFe layers on thermal oxide-coated silicon substrates exhibit a (012) orientation.

[0058] Example B In Example B (FIG. 8), a BiSb layer 1010 is deposited by PVD to a thickness of approximately 100 Å directly on a Cu layer. The Cu layer is deposited by PVD to a thickness of approximately 20 Å on a thermal oxide-coated silicon substrate. A BiSb layer 1020 is deposited by PVD to a thickness of approximately 100 Å directly on a NiFe layer. The NiFe layer is deposited by PVD to a thickness of approximately 10 Å on a thermal oxide-coated silicon substrate. A BiSb layer 1030 is deposited by PVD to a thickness of approximately 100 Å directly on a NiTa layer. The NiTa layer is deposited by PVD to a thickness of approximately 20 Å on a thermal oxide-coated silicon substrate. A BiSb layer 1040 is deposited by PVD to a thickness of approximately 100 Å directly on the NiFe layer. The NiFe layer is deposited by PVD to a thickness of approximately 5 Å directly on the Cu layer. A Cu layer is deposited by PVD to a thickness of approximately 20 Å on a thermal oxide coated silicon substrate. A BiSb layer 1050 is deposited by PVD to a thickness of approximately 100 Å directly on the Cu layer. The Cu layer is deposited by PVD to a thickness of 20 Å directly on the Ta layer. The Ta layer is deposited by PVD to a thickness of approximately 20 Å on a thermal oxide coated silicon substrate.

[0059] A BiSb layer 1060 is deposited by PVD to a thickness of approximately 100 Å directly on the NiFe layer. A NiFe layer is deposited by PVD to a thickness of approximately 6 Å directly on the Ta layer. A Ta layer is deposited by PVD to a thickness of 20 Å on a thermal oxide-coated silicon substrate. A BiSb layer 1070 is deposited by PVD to a thickness of approximately 100 Å directly on the Si layer. An amorphous Si layer is deposited by PVD directly on the Ta layer. A Ta layer is deposited by PVD on a thermal oxide-coated silicon substrate. A BiSb layer 1080 is deposited by PVD to a thickness of approximately 100 Å directly on the NiFe layer. A NiFe layer is deposited by PVD directly on the Si layer. A Si layer is deposited by PVD on a thermal oxide-coated silicon substrate.

[0060] Figure 8 shows XRD 2θ scans of BiSb layers 1010, 1020, 1030, 1040, 1050, 1060, 1070, and 1080. BiSb layers 1010, 1020, 1030, 1040, 1050, 1060, 1070, and 1080 exhibit a (012) orientation.

[0061] Example C In Example C (FIG. 9), a BiSb layer 1110 is deposited by PVD to a thickness of about 100 Å directly on a NiTa layer having a thickness of about 20 Å on a thermal oxide-coated silicon substrate. A BiSb layer 1120 is deposited by PVD to a thickness of about 100 Å directly on a NiFe layer. The NiFe layer is deposited by PVD to a thickness of about 6 Å on a thermal oxide-coated silicon substrate. A BiSb layer 1130 is deposited by PVD to a thickness of about 100 Å directly on the NiFe layer. The NiFe layer is deposited by PVD to a thickness of about 50 Å on a thermal oxide-coated Si wafer. A BiSb layer 1140 is deposited by PVD to a thickness of about 100 Å directly on a CuAgNi layer. The CuAgNi layer is deposited by PVD to a thickness of about 10 Å directly on the NiFe layer. The NiFe layer is deposited by PVD to a thickness of about 20 Å on a thermal oxide-coated silicon substrate. The BiSb layer 1150 is deposited by PVD to a thickness of approximately 100 Å directly on the NiFe layer. The NiFe layer is deposited by PVD to a thickness of approximately 6 Å on a PVD-deposited amorphous Si layer having a thickness of approximately 30 Å on a thermal oxide-coated silicon substrate. The BiSb layer 1160 is deposited by PVD to a thickness of approximately 100 Å on a Co seed layer. The Co seed layer is deposited by PVD to a thickness of approximately 3 Å on a Co / Pt laminate deposited by PVD. The Co / Pt laminate is a multilayer stack of P on Co: Co 3 Å / Pt 5 Å / Co 3 Å / Pt 5 Å. The Co / Pt laminate is deposited on a Pt pre-seed layer. The Pt pre-seed layer is deposited by PVD to a thickness of approximately 15 Å on a thermal oxide-coated Si wafer. The BiSb layer 1170 is deposited by PVD to a thickness of approximately 100 Å on the CuAgNi layer, which is deposited by PVD to a thickness of approximately 5 Å on the NiFe layer, which is deposited by PVD to a thickness of approximately 7 Å on the amorphous Si layer, which is deposited to a thickness of approximately 20 Å.

[0062] 9 shows XRD 2θ scans of BiSb layers 1110, 1120, 1130, 1140, 1150, 1160, and 1170. The BiSb layers 1110, 1120, 1130, 1140, 1150, 1160, and 1170 exhibit a (012) plane orientation.

[0063] The SOT-MRAM device 600 of FIG. 6 formed from BiSb layers 20 including BiSb layers with a (012) plane orientation as disclosed in Examples A, B, and C, has a lattice loss of about 110 MA / cm 2 or less, for example 100 MA / cm 2 The switching current density is estimated to be equal to or less than that, assuming a BiSb layer 20 forming a 170 nm wide SOT track with a 60 nm circular MTJ.

[0064] Example D The shunt block layers are deposited by PVD. The composition and properties of each shunt block layer are listed in Table 2. [Table 2]

[0065] While the foregoing description is directed to embodiments of the present disclosure, other and further embodiments of the present disclosure may be devised without departing from the basic scope thereof, which scope is determined by the following claims. [Explanation of symbols]

[0066] 1 board 10 Buffer layer 12 Pre-seed layer 14 Seed layer 16 Crystal Layer 20 BiSb layer 100 Drive 112 discs 113 Slider 114 Spindle 115 Suspension 118 Drive motor 119 Actuator Arm 121 Assembly 122 Disc Surface 123 Line 125 recording channels 127 Actuator means 128 lines 129 Control Unit 200 head 204 Detector element 206 Leading Shield 210,211 heads 212 MFS 218 Coil 220 Main pole 240 Trailing Shield 241 Trailing Shield Hot Seed Layer 242 Trailing Taper 244 Leading Taper 250 SOT devices 254 Gap 560 Current Shunt Block Layer 570 Spin Torque Layer 580 spacer layer 590 Fixed layer 600 MRAM devices 610RL 620 spacer layer 630 Recording Layer 640 Current Shunt Block Layer

Claims

1. A SOT (Spin Orbit Torque) MTJ (Magnetic Tunnel Junction) device, comprising: A substrate; a buffer layer on the substrate; a BiSb (bismuth antimony) layer having a (012) orientation and formed on the buffer layer; Equipped with The buffer layer is a pre-seed layer on the substrate comprising a material selected from the group consisting of Si, NiTa, NiFeTa, CoZrTa, NiNb, NiFeTa, NiFeW, CoHf, CoFeHf, CoFeHfB, NiFeB, CoFeB, Ge, Co, CoFe, NiCr, Ni, Cu, NiFe, Ru, Pt, Rh, silicon oxide, aluminum oxide, magnesium oxide, TiN, AlN, and alloys thereof; a seed layer on the pre-seed layer comprising a material selected from the group consisting of Co, CoFe, Ni, NiFe, NiCr, NiTa, NiFeTa, Cu, CuAgNi, RuX, CuX, CuNiX, CoFeX, CoNiX, FeX, NiX, and CoX, where X = Cr, Ag, Pt, Ir, Rh, and combinations thereof; a crystalline layer on the seed layer comprising a material selected from the group consisting of Co, CoFe, Ni, NiFe, NiCr, NiTa, NiFeTa, Cu, CuAgNi, RuX, CuX, CuNiX, CoFeX, CoNiX, FeX, NiX, and CoX (where X=Cr, Ag, Pt, Ir, Rh) and combinations thereof.

2. 10. The SOT-MTJ device of claim 1, wherein the pre-seed layer comprises a material selected from the group consisting of Si, NiTa, NiFeTa, NiCr, Co, CoFe, Cu, NiFe, and alloys thereof.

3. 3. The SOT-MTJ device of claim 1, wherein the crystalline layer comprises a material selected from the group consisting of Co, CoFe, Ni, NiFe, Cu, CuNiAg, and alloys thereof.

4. The SOT-MTJ device according to any one of claims 1 to 3, wherein the material of the seed layer and the material of the crystalline layer have a (111) orientation with an a-axis of 3.52 Å to 3.71 Å.

5. The SOT-MTJ device according to any one of claims 1 to 4, wherein the material of the seed layer and the material of the crystalline layer have a (002) orientation with an a-axis of 2.49 Å to 2.62 Å.

6. The SOT-MTJ device according to any of claims 1 to 5, wherein the BiSb layer contains antimony with an atomic percent content of 5% to 20%.

7. The SOT-MTJ device according to any one of claims 1 to 6, wherein the substrate is selected from the group consisting of silicon and alumina.

8. The SOT-MTJ device of any of claims 1 to 7, further comprising a current shunt blocking layer comprising a magnetic material.

9. 9. The SOT-MTJ device of claim 8, wherein the current shunt blocking layer comprises a magnetic material selected from the group consisting of FeCo, FeCoM, FeCoMO, FeCoMMeO, FeCoM / MeO stack, FeCoMNiMnMgZnFeO, FeCoM / NiMnMgZnFeO stack, multiple layers thereof, multiple stacks thereof, and combinations thereof, where M is one or more of B, Si, P, Al, Hf, Zr, Nb, Ti, Ta, Mo, Mg, Y, Cu, Cr, and Ni, and Me is Si, Al, Hf, Zr, Nb, Ti, Ta, Mg, Y, or Cr.

10. A MAMR (Microwave Assisted Magnetic Recording) write head, comprising: a main pole and a trailing shield; a spin-orbit torque (SOT) device disposed in the gap between the main pole and the trailing shield; The SOT device comprises: A substrate; a buffer layer formed on the substrate; a BiSb (bismuth antimony) layer having a (012) orientation and serving as a spin Hall layer formed on the buffer layer; a spin torque layer formed on the BiSb layer; Including, The buffer layer is a pre-seed layer on the substrate comprising a material selected from the group consisting of Si, NiTa, NiFeTa, CoZrTa, NiNb, NiFeTa, NiFeW, CoHf, CoFeHf, CoFeHfB, NiFeB, CoFeB, Ge, Co, CoFe, NiCr, Ni, Cu, NiFe, Ru, Pt, Rh, silicon oxide, aluminum oxide, magnesium oxide, TiN, AlN, and alloys thereof; a seed layer on the pre-seed layer comprising a material selected from the group consisting of Co, CoFe, Ni, NiFe, NiCr, NiTa, NiFeTa, Cu, CuAgNi, RuX, CuX, CuNiX, CoFeX, CoNiX, FeX, NiX, and CoX, where X = Cr, Ag, Pt, Ir, Rh, and combinations thereof; a crystalline layer on the seed layer comprising a material selected from the group consisting of Co, CoFe, Ni, NiFe, NiCr, NiTa, NiFeTa, Cu, CuAgNi, RuX, CuX, CuNiX, CoFeX, CoNiX, FeX, NiX, and CoX (wherein X = Cr, Ag, Pt, Ir, Rh) and combinations thereof; 1. A MAMR write head comprising:

11. 11. The MAMR write head of claim 10, wherein the crystalline layer comprises a material selected from the group consisting of Co, CoFe, Ni, NiFe, Cu, CuNiAg, and alloys thereof.

12. The MAMR write head of claim 10 or 11, further comprising a current shunt blocking layer between the BiSb layer and the spin torque layer, the current shunt blocking layer comprising a magnetic material.

13. 13. The MAMR write head of claim 12, wherein the current shunt blocking layer comprises a magnetic material selected from the group consisting of FeCo, FeCoM, FeCoMO, FeCoMMeO, FeCoM / MeO stack, FeCoMNiMnMgZnFeO, FeCoM / NiMnMgZnFeO stack, multiple layers thereof, multiple stacks thereof, and combinations thereof, where M is one or more of B, Si, P, Al, Hf, Zr, Nb, Ti, Ta, Mo, Mg, Y, Cu, Cr, and Ni, and Me is Si, Al, Hf, Zr, Nb, Ti, Ta, Mg, Y, or Cr.

14. A magnetic media drive including the MAMR write head of any one of claims 10 to 13.

15. a recording layer; a buffer layer formed on the recording layer; a BiSb (bismuth antimony) layer having a (012) orientation formed on the buffer layer; Equipped with The buffer layer is a pre-seed layer on the recording layer, the pre-seed layer comprising a material selected from the group consisting of Si, NiTa, NiFeTa, CoZrTa, NiNb, NiFeTa, NiFeW, CoHf, CoFeHf, CoFeHfB, NiFeB, CoFeB, Ge, Co, CoFe, NiCr, Ni, Cu, NiFe, Ru, Pt, Rh, silicon oxide, aluminum oxide, magnesium oxide, TiN, AlN, and alloys thereof; a seed layer on the pre-seed layer comprising a material selected from the group consisting of Co, CoFe, Ni, NiFe, NiCr, NiTa, NiFeTa, Cu, CuAgNi, RuX, CuX, CuNiX, CoFeX, CoNiX, FeX, NiX, and CoX, where X = Cr, Ag, Pt, Ir, Rh, and combinations thereof; a crystalline layer on the seed layer comprising a material selected from the group consisting of Co, CoFe, Ni, NiFe, NiCr, NiTa, NiFeTa, Cu, CuAgNi, RuX, CuX, CuNiX, CoFeX, CoNiX, FeX, NiX, and CoX (wherein X = Cr, Ag, Pt, Ir, Rh) and combinations thereof; 1. An MRAM device comprising:

16. 16. The MRAM device of claim 15, wherein the crystalline layer comprises a material selected from the group consisting of Co, CoFe, Ni, NiFe, Cu, CuNiAg, and alloys thereof.

17. 17. The MRAM device of claim 15, further comprising a current shunt blocking layer between the buffer layer and the recording layer, the current shunt blocking layer comprising a magnetic material.

18. 18. The MRAM device of claim 17, wherein the current shunt blocking layer comprises a magnetic material selected from the group consisting of FeCo, FeCoM, FeCoMO, FeCoMMeO, FeCoM / MeO stack, FeCoMNiMnMgZnFeO, FeCoM / NiMnMgZnFeO stack, multiple layers thereof, multiple stacks thereof, and combinations thereof, where M is one or more of B, Si, P, Al, Hf, Zr, Nb, Ti, Ta, Mo, Mg, Y, Cu, Cr, and Ni, and Me is Si, Al, Hf, Zr, Nb, Ti, Ta, Mg, Y, or Cr.

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