Taiwan Semiconductor Manufacturing Comp. Ltd.

International Business Machines Corporation

Headway Technologies, Incorporated

Luc Thomas

Guenole Jan

Ru-Ying Tong

Santiago Serrano Guisan

Jodi Mari Iwata

Son Le

Vignesh Sundar

Huanlong Liu

Jian Zhu

Yuan-Jen Lee

Yu-Jen Wang

Po-Kang Wang

Sahil Patel

Stuart P Parkin

Anthony J Annunziata

Michael C Gaidis

William Joseph Gallagher

Stuart Stephen Papworth Parkin

See-Hun Yang

Rai Moriya

Moris Musa Dovek

Yuhui Tang

Dongna Shen

Yue Liu

Tom Zhong

Yaguang Wei

Jesmin Haq

Stuart Stephen Parkin

Zhongjian Teng

Xiaomin Liu

Feiyue Li

Ruth Tong

Santiago Serrano

A seed layer stack with a uniform top surface having a peak to peak roughness of 0.5 nm is formed by sputter depositing an amorphous layer on a smoothing layer such as Mg where the latter has a resputtering rate 2 to 30× that of the amorphous layer. The uppermost seed layer is NiW, NiMo, or one or more of NiCr, NiFeCr, and Hf while the bottommost seed layer is one or more of Ta, TaN, Zr, ZrN, Nb, NbN, Mo, MON, TIN, W, WN, and Ru. Accordingly, perpendicular magnetic anisotropy in an overlying magnetic layer is substantially maintained during high temperature processing up to 400° C. and is advantageous for magnetic tunnel junctions in embedded MRAMs, spintronic devices, or in read head sensors. The amorphous seed layer is SiN, TaN, or CoFeM where M is B or another element with a content that makes CoFeM amorphous as deposited.

Multilayer structure for reducing film roughness in magnetic devices

An improved magnetic tunnel junction with two oxide interfaces on each side of a ferromagnetic layer (FML) leads to higher PMA in the FML. The novel stack structure allows improved control during oxidation of the top oxide layer. This is achieved by the use of a FML with a multiplicity of ferromagnetic sub-layers deposited in alternating sequence with one or more non-magnetic layers. The use of non-magnetic layers each with a thickness of 0.5 to 10 Angstroms and with a high resputtering rate provides a smoother FML top surface, inhibits crystallization of the FML sub-layers, and reacts with oxygen to prevent detrimental oxidation of the adjoining ferromagnetic sub-layers. The FML can function as a free or reference layer in an MTJ. In an alternative embodiment, the non-magnetic material such as Mg, Al, Si, Ca, Sr, Ba, and B is embedded by co-deposition or doped in the FML layer.

Perpendicularly magnetized ferromagnetic layers having an oxide interface allowing for improved control of oxidation

A dual magnetic tunnel junction (DMTJ) is disclosed with a PL/TB/free layer/TB/PL/capping layer configuration wherein a first tunnel barrier (TB) has a substantially lower resistance x area (RA) product than RAfor an overlying second tunnel barrier (TB) to provide an acceptable net magnetoresistive ratio (DRR). Moreover, magnetizations in first and second pinned layers, PLand PL, respectively, are aligned antiparallel to enable a lower critical switching current than when in a parallel alignment. An oxide capping layer having a RAis formed on PLto provide higher PLstability. The condition RA<RAand RA<RAis achieved when TBand the oxide capping layer have one or both of a smaller thickness and a lower oxidation state than TB, are comprised of conductive (metal) channels in a metal oxide or metal oxynitride matrix, or are comprised of a doped metal oxide or doped metal oxynitride layer.

Dual magnetic tunnel junction (DMTJ) stack design

A three terminal spin-orbit-torque (SOT) device is disclosed wherein a free layer (FL) with a switchable magnetization is formed on a Spin Hall Effect (SHE) layer comprising a Spin Hall Angle (SHA) material. The SHE layer has a first side contacting a first bottom electrode (BE) and an opposite side contacting a second BE where the first and second BE are separated by a dielectric spacer. A first current is applied between the two BE, and the SHE layer generates SOT on the FL thereby switching the FL magnetization to an opposite perpendicular-to-plane direction. The SHE layer is a positive or negative SHA material, and may be a topological insulator such as BiSb. A top electrode is formed on an uppermost hard mask in each SOT device. A single etch through the FL and SHE layer ensures a reliable first current pathway that is separate from a read current pathway.

Integration scheme for three terminal spin-orbit-torque (SOT) switching devices

A perpendicular magnetic tunnel junction is disclosed wherein a metal insertion (MIS) layer is formed within a free layer (FL), a partially oxidized Hk enhancing layer is on the FL, and a nitride capping layer having a buffer layer/nitride layer (NL) is on the Hk enhancing layer to provide an improved coercivity (Hc)/switching current (Jc) ratio for spintronic applications. Magnetoresistive ratio is maintained above 100%, resistance×area (RA) product is below 5 ohm/μm, and thermal stability to 400° C. is realized. The FL comprises two or more sub-layers, and the MIS layer may be formed within at least one sub-layer or between sub-layers. The buffer layer is used to prevent oxygen diffusion to the NL, and nitrogen diffusion from the NL to the FL. FL thickness is from 11 Angstroms to 25 Angstroms while MIS layer thickness is preferably from 0.5 Angstroms to 4 Angstroms.

Magnetic element with perpendicular magnetic anisotropy (PMA) and improved coercivity field (Hc)/switching current ratio

A ferromagnetic resonance (FMR) measurement method is disclosed wherein a magnetic film or stack of layers is patterned into elongated structures having a length along a long axis. A magnetic field (H) is applied in two different orientations with respect to the long axis (in-plane parallel and perpendicular to the long axis) or one orientation may be perpendicular-to-plane. In another embodiment, H is applied parallel to a first set of elongated structures with a long axis in the x-axis direction, and perpendicular to a second set of elongated structures with a long axis in the y-axis direction. From the difference in measured resonance frequency (&#x394;fr) (for a fixed magnetic field and sweeping through a range of frequencies) or the difference in measured resonance field (&#x394;Hr) (for a fixed microwave frequency and sweeping through a range of magnetic field amplitudes), magnetic saturation Ms is determined using formulas of demagnetizing factors.

Method for measuring saturation magnetization of magnetic films and multilayer stacks

A magnetic tunnel junction with perpendicular magnetic anisotropy (PMA MTJ) is disclosed wherein a free layer interfaces with a tunnel barrier and has a second interface with an oxide layer. A lattice-matching layer adjoins an opposite side of the oxide layer with respect to the free layer and is comprised of CoFeNiLMor an oxide or nitride of Ru, Ta, Ti, or Si, wherein L is one of B, Zr, Nb, Hf, Mo, Cu, Cr, Mg, Ta, Ti, Au, Ag, or P, and M is one of Mo, Mg, Ta, Cr, W, or V, (x+y+z+w+v)=100 atomic %, x+y&#x3e;0, and each of v and w are &#x3e;0. The lattice-matching layer grows a BCC structure during annealing thereby promoting BCC structure growth in the oxide layer that results in enhanced free layer PMA and improved thermal stability.

Maintaining coercive field after high temperature anneal for magnetic device applications with perpendicular magnetic anistropy

A dual magnetic tunnel junction (DMTJ) is disclosed with a PL1/TB1/free layer/TB2/PL2 configuration wherein a first tunnel barrier (TB1) has a substantially lower resistance&#xd7;area (RA) product than RAfor an overlying second tunnel barrier (TB2) to provide an acceptable magnetoresistive ratio (DRR). Moreover, first and second pinned layers, PL1 and PL2, respectively, have magnetizations that are aligned antiparallel to enable a lower critical switching current that when in a parallel alignment. The condition RA1&#x3c;RA2 is achieved with one or more of a smaller thickness and a lower oxidation state for TB1 compared with TB2, with conductive (metal) pathways formed in a metal oxide or metal oxynitride matrix for TB1, or with a TB1 containing a dopant to create conducting states in the TB1 band gap. Alternatively, TB1 may be replaced with a metallic spacer to improve conductivity between PL1 and the FL.

Dual magnetic tunnel junction devices for magnetic random access memory (MRAM)

A scanning ferromagnetic resonance (FMR) measurement system is disclosed with a radio frequency (RF) probe and one or two magnetic poles mounted on a holder plate and enable a perpendicular-to-plane or in-plane magnetic field, respectively, at test locations. While the RF probe tip contacts a magnetic film on a whole wafer under test (WUT), a plurality of microwave frequencies (f) is sequentially transmitted through the probe tip. Simultaneously, a magnetic field (H) is applied to the contacted region thereby causing a FMR condition in the magnetic film for each pair of (H, f) values. RF output signals are transmitted through or reflected from the magnetic film to a RF diode and converted to voltage signals which a controller uses to determine effective anisotropy field, linewidth, damping coefficient, and/or inhomogeneous broadening for a sub-mm area. The WUT is moved to preprogrammed locations to enable multiple FMR measurements at each test location.

Ferromagnetic resonance (FMR) electrical testing apparatus for spintronic devices

A perpendicular magnetic tunnel junction is disclosed wherein a metal insertion (MIS) layer is formed within a free layer (FL), a partially oxidized Hk enhancing layer is on the FL, and a nitride capping layer having a buffer layer/nitride layer (NL) is on the Hk enhancing layer to provide an improved coercivity (Hc)/switching current (Jc) ratio for spintronic applications. Magnetoresistive ratio is maintained above 100%, resistance&#xd7;area (RA) product is below 5 ohm/&#x3bc;m, and thermal stability to 400&#xb0; C. is realized. The FL comprises two or more sub-layers, and the MIS layer may be formed within at least one sub-layer or between sub-layers. The buffer layer is used to prevent oxygen diffusion to the NL, and nitrogen diffusion from the NL to the FL. FL thickness is from 11 Angstroms to 25 Angstroms while MIS layer thickness is preferably from 0.5 Angstroms to 4 Angstroms.

A perpendicular magnetic tunnel junction is disclosed wherein first and second interfaces of a free layer (FL) with a first metal oxide (Hk enhancing layer) and second metal oxide (tunnel barrier), respectively, produce perpendicular magnetic anisotropy (PMA) to provide thermal stability to 400&#xb0; C. Insertion of an oxidation control layer (OCL) such as Mg and a magnetic moment tuning layer (MMTL) like Mo or W enables FL thickness to be reduced below 10 Angstroms while providing sufficient PMA for a switching voltage substantially less than 500 mV at a 10 ns pulse width and 1 ppm defect rate. Magnetoresistive ratio is &#x2265;1, and resistance&#xd7;area (RA) product is below 5 ohm-&#x3bc;m. Embodiments are provided where MMTL and OCL materials interface with each other, or do not contact each other. Each of the MMTL and OCL materials may be deposited separately, or at least one is co-deposited with the FL.

Minimal thickness, low switching voltage magnetic free layers using an oxidation control layer and magnetic moment tuning layer for spintronic applications

A ferromagnetic resonance (FMR) measurement system is disclosed with a plurality of 'm' RF probes and one or more magnetic assemblies to enable a perpendicular-to-plane or in-plane magnetic field (H) to be applied simultaneously with a sequence of microwave frequencies (f) at a plurality of 'm' test locations on a magnetic film formed on a whole wafer under test (WUT). A FMR condition occurs in the magnetic film (stack of unpatterned layers or patterned structure) for each pair of (H, f) values. RF input signals are distributed to the RF probes using RF power distribution or routing devices. RF output signals are transmitted through or reflected from the magnetic film to a plurality of &#x201c;n&#x201d; RF diodes where 1&#x2264;n&#x2264;m, and converted to voltage signals which a controller uses to determine effective anisotropy field, linewidth, damping coefficient, and/or inhomogeneous broadening at the predetermined test locations.

Multi-probe ferromagnetic resonance (FMR) apparatus for wafer level characterization of magnetic films

A ferromagnetic resonance (FMR) measurement system is disclosed with a waveguide transmission line (WGTL) connected at both ends to a mounting plate having an opening through which the WGTL is suspended. While the WGTL bottom surface contacts a portion of magnetic film on a whole wafer, a plurality of microwave frequencies is sequentially transmitted through the WGTL. Simultaneously, a magnetic field is applied to the contacted region thereby causing a FMR condition in the magnetic film. After RF output is transmitted through or reflected from the WGTL to a RF detector and converted to a voltage signal, effective anisotropy field, linewidth, damping coefficient, and/or inhomogeneous broadening are determined based on magnetic field intensity, microwave frequency and voltage output. A plurality of measurements is performed by controllably moving the WGTL or wafer and repeating the simultaneous application of microwave frequencies and magnetic field at additional preprogrammed locations on the magnetic film.

Scanning ferromagnetic resonance (FMR) for wafer-level characterization of magnetic films and multilayers

A magnetic tunnel junction (MTJ) is disclosed wherein a nitride diffusion barrier (NDB) has a L2/L1/NL or NL/L1/L2 configuration wherein NL is a metal nitride or metal oxynitride layer, L2 blocks oxygen diffusion from an adjoining Hk enhancing layer, and L1 prevents nitrogen diffusion from NL to the free layer (FL) thereby enhancing magnetoresistive ratio and FL thermal stability, and minimizing resistance x area product for the MTJ. NL is the uppermost layer in a bottom spin valve configuration, or is formed on a seed layer in a top spin valve configuration such that L2 and L1 are always between NL and the FL or pinned layer, respectively. In other embodiments, one or both of L1 and L2 are partially oxidized. Moreover, either L2 or L1 may be omitted when the other of L1 and L2 is partially oxidized. A spacer between the FL and L2 is optional.

Nitride diffusion barrier structure for spintronic applications

A dual magnetic tunnel junction (DMTJ) is disclosed with a PL/TB/free layer/TB/PL/capping layer configuration wherein a first tunnel barrier (TB) has a substantially lower resistance&#xd7;area (RA) product than RAfor an overlying second tunnel barrier (TB) to provide an acceptable net magnetoresistive ratio (DRR). Moreover, magnetizations in first and second pinned layers, PLand PL, respectively, are aligned antiparallel to enable a lower critical switching current than when in a parallel alignment. An oxide capping layer having a RAis formed on PLto provide higher PLstability. The condition RA&#x3c;RAand RA&#x3c;RAis achieved when TBand the oxide capping layer have one or both of a smaller thickness and a lower oxidation state than TB, are comprised of conductive (metal) channels in a metal oxide or metal oxynitride matrix, or are comprised of a doped metal oxide or doped metal oxynitride layer.

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San Jose, CA, United States of America

Luc Thomas