Taiwan Semiconductor Manufacturing Comp. Ltd.

Headway Technologies, Incorporated

Magic Technologies, Inc.

Guenole Jan

Ru-Ying Tong

Huanlong Liu

Yu-Jen Wang

Jian Zhu

Yuan-Jen Lee

Po-Kang Wang

Jodi Mari Iwata

Luc Thomas

Witold Kula

Vignesh Sundar

Sahil Patel

Ru Ying Tong

Santiago Serrano Guisan

Son Le

Yu Jen Wang

Robert Beach

Dongna Shen

Cheng Tzong Horng

John De Brosse

Yi Yang

PoKang Wang

Ruth Tong

Santiago Serrano

Huanlong Lui

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 magnetic device for magnetic random access memory (MRAM), spin torque MRAM, or spin torque oscillator technology is disclosed wherein a magnetic tunnel junction (MTJ) with a sidewall is formed between a bottom electrode and a top electrode. A passivation layer that is a single layer or multilayer comprising one of B, C, or Ge, or an alloy thereof wherein the B, C, and Ge content, respectively, is at least 10 atomic % is formed on the MTJ sidewall to protect the MTJ from reactive species during subsequent processing including deposition of a dielectric layer that electrically isolates the MTJ from adjacent MTJs, and during annealing steps around 400° C. in CMOS fabrication. The single layer is about 3 to 10 Angstroms thick and may be an oxide or nitride of B, C, or Ge. The passivation layer is preferably amorphous to prevent diffusion of reactive oxygen or nitrogen species.

Protective passivation layer for magnetic tunnel junctions

A perpendicularly magnetized magnetic tunnel junction (p-MTJ) is disclosed wherein a boron containing free layer (FL) is subjected to a plasma treatment with inert gas, and a natural oxidation (NOX) process to form BObefore overlying layers are deposited. A metal layer such as Mg is deposited on the FL as a first step in forming a Hk enhancing layer that increases FL perpendicular magnetic anisotropy, or as a first step in forming a tunnel barrier layer on the FL. One or more anneal steps are essential in assisting BOsegregation from the free layer and thereby increasing the FL magnetic moment. A post-oxidation plasma treatment may also be used to partially remove BOproximate to the FL top surface before the metal layer is deposited. Both plasma treatments use low power (<50 Watts) to remove a maximum of 2 Angstroms FL thickness.

Magnetic layer for magnetic random access memory (MRAM) by moment enhancement

A magnetic tunnel junction is disclosed wherein the reference layer and free layer each comprise one layer having a boron content from 25 to 50 atomic %, and an adjoining second layer with a boron content from 1 to 20 atomic %. One of the first and second layers in each of the free layer and reference layer contacts the tunnel barrier. Each boron containing layer has a thickness of 1 to 10 Angstroms and may include one or more B layers and one or more Co, Fe, CoFe, or CoFeB layers. As a result, migration of non-magnetic metals along crystalline boundaries to the tunnel barrier is prevented, and the MTJ has a low defect count of around 10 ppm while maintaining an acceptable TMR ratio following annealing to temperatures of about 400° C. The boron containing layers are selected from CoB, FeB, CoFeB and alloys thereof including CoFeNiB.

Magnetic tunnel junction with low defect rate after high temperature anneal for magnetic device 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 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 fabrication process for an STT MTJ MRAM device includes steps of cooling the device at individual or at multiple stages in its fabrication. The cooling process, which may be equally well applied during the fabrication of other multi-layered devices, is demonstrated to produce an operational device that is more resistant to adverse thermal effects during operation that would normally cause a similar device not so fabricated to lose stored data and otherwise fail to operate properly.

Cooling for PMA (perpendicular magnetic anisotropy) enhancement of STT-MRAM (spin-torque transfer-magnetic random access memory) devices

A synthetic antiferromagnetic structure for a spintronic device is disclosed and has an FL2/Co or Co alloy/antiferromagnetic coupling/Co or Co alloy/CoFeB configuration where FL2 is a ferromagnetic free layer with intrinsic PMA. Antiferromagnetic coupling is improved by inserting a Co or Co alloy dusting layer on top and bottom surfaces of the antiferromagnetic coupling layer. The FL2 layer may be a L10 ordered alloy, a rare earth-transition metal alloy, or an (A1/A2)n laminate where A1 is one of Co, CoFe, or an alloy thereof, and A2 is one of Pt, Pd, Rh, Ru, Ir, Mg, Mo, Os, Si, V, Ni, NiCo, and NiFe, or A1 is Fe and A2 is V. A method is also provided for forming the synthetic antiferromagnetic structure.

Minimal thickness synthetic antiferromagnetic (SAF) structure with perpendicular magnetic anisotropy for STT-MRAM

A ferromagnetic layer is capped with a metallic oxide (or nitride) layer that provides a perpendicular-to-plane magnetic anisotropy to the layer. The surface of the ferromagnetic layer is treated with a plasma to prevent diffusion of oxygen (or nitrogen) into the layer interior. An exemplary metallic oxide layer is formed as a layer of metallic Mg that is plasma treated to reduce its grain size and enhance the diffusivity of oxygen into its interior. Then the plasma treated Mg layer is naturally oxidized and, optionally, is again plasma treated to reduce its thickness and remove the oxygen rich upper surface.

Reduction of capping layer resistance area product for magnetic device applications

A magnetic tunnel junction (MTJ) 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 increase thermal stability. In some embodiments, a capping layer that is a conductive metal nitride such as MoN contacts an opposite surface of the Hk enhancing layer with respect to the first interface to reduce interdiffusion of oxygen and nitrogen compared with a TiN capping layer and maintain an acceptable resistance×area (RA) product. In other embodiments, the capping layer may comprise an insulating nitride such as AlN that is alloyed with a conductive metal to minimize RA. Furthermore, a metallic buffer layer may be inserted between the capping layer and Hk enhancing layer. As a result, electrical shorts are reduced and the magnetoresistive ratio is increased.

Nitride capping layer for spin torque transfer (STT) magnetoresistive random access memory (MRAM)

A magnetic device for magnetic random access memory (MRAM), spin torque MRAM, or spin torque oscillator technology is disclosed wherein a magnetic tunnel junction (MTJ) with a sidewall is formed between a bottom electrode and a top electrode. A passivation layer that is a single layer or multilayer comprising one of B, C, or Ge, or an alloy thereof wherein the B, C, and Ge content, respectively, is at least 10 atomic % is formed on the MTJ sidewall to protect the MTJ from reactive species during subsequent processing including deposition of a dielectric layer that electrically isolates the MTJ from adjacent MTJs, and during annealing steps around 400&#xb0; C. in CMOS fabrication. The single layer is about 3 to 10 Angstroms thick and may be an oxide or nitride of B, C, or Ge. The passivation layer is preferably amorphous to prevent diffusion of reactive oxygen or nitrogen species.

A magnetic tunnel junction (MTJ) is disclosed wherein a free layer (FL) interfaces with a first metal oxide (Mox) layer and second metal oxide (tunnel barrier) to produce perpendicular magnetic anisotropy (PMA) in the FL. In some embodiments, conductive metal channels made of a noble metal are formed in the Mox that is MgO to reduce parasitic resistance. In a second embodiment, a discontinuous MgO layer with a plurality of islands is formed as the Mox layer and a non-magnetic hard mask layer is deposited to fill spaces between adjacent islands and form shorting pathways through the Mox. In another embodiment, end portions between the sides of a center Mox portion and the MTJ sidewall are reduced to form shorting pathways by depositing a reducing metal layer on Mox sidewalls, or performing a reduction process with forming gas, H, or a reducing species.

Low resistance MgO capping layer for perpendicularly magnetized magnetic tunnel junctions

A magnetic element is disclosed wherein a composite seed layer such as TaN/Mg enhances perpendicular magnetic anisotropy (PMA) in an overlying magnetic layer that may be a reference layer, free layer, or dipole layer. The first seed layer is selected from one or more of Ta, Zr, Nb, TaN, ZrN, NbN, and Ru. The second seed layer is selected from one or more of Mg, Sr, Ti, Al, V, Hf, B, and Si. A growth promoting layer made of NiCr or an alloy thereof is inserted between the seed layer and magnetic layer. In some embodiments, a first composite seed layer/NiCr stack is formed below the reference layer, and a second composite seed layer/NiCr stack is formed between the free layer and a dipole layer. The magnetic element has thermal stability to at least 400&#xb0; C.

Seed layer for multilayer magnetic materials

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 MgO layer is formed using a process flow wherein a Mg layer is deposited at a temperature &#x3c;200&#xb0; C. on a substrate, and then an anneal between 200&#xb0; C. and 900&#xb0; C., and preferably from 200&#xb0; C. and 400&#xb0; C., is performed so that a Mg vapor pressure &#x3e;10Torr is reached and a substantial portion of the Mg layer sublimes and leaves a Mg monolayer. After an oxidation between &#x2212;223&#xb0; C. and 900&#xb0; C., a MgO monolayer is produced where the Mg:O ratio is exactly 1:1 thereby avoiding underoxidized or overoxidized states associated with film defects. The process flow may be repeated one or more times to yield a desired thickness and resistance&#xd7;area value when the MgO is a tunnel barrier or Hk enhancing layer. Moreover, a doping element (M) may be added during Mg deposition to modify the conductivity and band structure in the resulting MgMO layer.

Growing community of inventors

San Jose, CA, United States of America

Guenole Jan