Headway Technologies, Incorporated

Magic Technologies, Inc.

International Business Machines Corporation

Applied Spintronics, Inc.

Cheng Tzong Horng

Ru-Ying Tong

Kochan Ju

Min Li

Simon H Liao

Mao-Min Chen

Witold Kula

Chyu-Jiuh Torng

Jei-Wei Chang

Liubo Hong

Robert Otto Schwenker

Cherng-Chyi Han

Yimin Guo

Tai Min

Wei Cao

Chyu Jiuh Torng

Po-Kang Wang

Bernard Dieny

Youfeng Zheng

Chen-Jung Chien

Cherng Chyi Han

Hui-Chuan Wang

Rongfu Xiao

Yu-Hsia Chen

Hans S Rupprecht

Yun-Fei Li

Richard R Konian

Ru Ying Tong

Masashi Sano

Kiyoshi Noguchi

Kunliang Zhang

Tom Zhong

Robert Beach

Po Kang Wang

Guangli Liu

Wai-Ming Johnson Kan

You Feng Zheng

Terry Kin Ting Ko

Chyu-Jinh Torng

Ru-Yin Tong

You Fong Zheng

Guenole Jan

Yue Liu

Paul J Tsang

Joseph R Cavaliere

Michael R Poponiak

Charles C Lin

Henry C Chang

Chien-Li Lin

Alwin E Michel

Yong-Chang Feng

Allen P Ho

Chyu-Jiuh Trong

Ruying Tong

Alfred Grill

Yuchen Zhou

Vishnubhai Vitthalbhai Patel

Tong Zhao

Bernard S Meyerson

Christopher H Bajorek

Bernard M Kemlage

Shao-Fu S Chu

Michael A Russak

Edward T Yen

PoKang Wang

Rong-Fu Xiao

Arthur Hungshin Tao

Rachid Sbiaa

Arkadi Galicki

Harold V Lillja

David K Seto

Armin W Wieder

Armin W Weider

Chyu-Jiuh Tomg

Ku-Ying Tong

Tong Ru-Ying

Kunliag Zhang

Mao Min Chen

A MTJ in an MRAM array is disclosed with a composite free layer having a lower crystalline layer contacting a tunnel barrier and an upper amorphous layer for improved bit switching performance. According to one embodiment, the amorphous layer has a NiFeM/NiFeMconfiguration where Mand Mare Mg, Hf, Zr, Nb, or Ta, and M1 is unequal to M2. The crystalline layer is Fe, Ni, or FeB with a thickness of at least 6 Angstroms that affords a high magnetoresistive ratio. The Mand Melements in the NiFeMand NiFeMlayers each have a content of 5 to 30 atomic %. The NiFeM/NiFeMconfiguration substantially reduces bit line switching current and number of shorted bits. In an alternative embodiment, the crystalline layer may be a Fe/NiFe bilayer. Annealing at 300&#xb0; C. to 360&#xb0; C. provides a high magnetoresistive ratio of about 150%.

Magnetic tunnel junction for MRAM applications

A STT-RAM MTJ is disclosed with a MgO tunnel barrier formed by natural oxidation and containing an oxygen surfactant layer to form a more uniform MgO layer and lower breakdown distribution percent. A CoFeB/NCC/CoFeB composite free layer with a middle nanocurrent channel layer minimizes Jcwhile enabling thermal stability, write voltage, read voltage, and Hc values that satisfy 64 Mb design requirements. The NCC layer has RM grains in an insulator matrix where R is Co, Fe, or Ni, and M is a metal such as Si or Al. NCC thickness is maintained around the minimum RM grain size to avoid RM granules not having sufficient diameter to bridge the distance between upper and lower CoFeB layers. A second NCC layer and third CoFeB layer may be included in the free layer or a second NCC layer may be inserted below the Ru capping layer.

Structure and method to fabricate high performance MTJ devices for spin-transfer torque (STT)-RAM application

A MTJ in an MRAM array is disclosed with a composite free layer having a lower crystalline layer contacting a tunnel barrier and an upper amorphous NiFeX layer for improved bit switching performance. The crystalline layer is Fe, Ni, or FeB with a thickness of at least 6 Angstroms which affords a high magnetoresistive ratio. The X element in the NiFeX layer is Mg, Hf, Zr, Nb, or Ta with a content of 5 to 30 atomic %. NiFeX thickness is preferably between 20 to 40 Angstroms to substantially reduce bit line switching current and number of shorted bits. In an alternative embodiment, the crystalline layer may be a Fe/NiFe bilayer. Optionally, the amorphous layer may have a NiFeM/NiFeMconfiguration where Mand Mare Mg, Hf, Zr, Nb, or Ta, and M1 is unequal to M2. Annealing at 300&#xb0; C. to 360&#xb0; C. provides a high magnetoresistive ratio of about 150%.

A magnetic element is disclosed wherein first and second interfaces of a free layer with a Hk enhancing layer and tunnel barrier, respectively, produce enhanced surface perpendicular anisotropy to lower switching current or increase thermal stability in a magnetic tunnel junction (MTJ). In a MTJ with a bottom spin valve configuration where the Hk enhancing layer is an oxide, the capping layer contacting the Hk enhancing layer is selected to have a free energy of oxide formation substantially greater than that of the oxide. The free layer may be a single layer or composite comprised of an Fe rich alloy such as CoFeB. With a thin free layer, the interfacial perpendicular anisotropy may dominate the shape anisotropy to generate a magnetization perpendicular to the planes of the layers. The magnetic element may be part of a spintronic device or serve as a propagation medium in a domain wall motion device.

Magnetic element with improved out-of-plane anisotropy for spintronic applications

A multi-layered bottom electrode for an MTJ device on a silicon nitride substrate is described. It comprises a bilayer of alpha tantalum on ruthenium which in turn lies on a nickel chrome layer over a second tantalum layer.

Bottom electrode for MRAM device

A STT-RAM MTJ is disclosed with a composite tunnel barrier comprised of a CoMgO layer that contacts a pinned layer and a MgO layer which contacts a free layer. A CoMg layer with a Co content between 20 and 40 atomic % is deposited on the pinned layer and is then oxidized to produce Co nanoconstrictions within a MgO insulator matrix. The nanoconstrictions control electromigration of Co into an adjoining MgO layer. The free layer may comprise a nanocurrent channel (NCC) layer such as FeSiO or a moment dilution layer such as Ta between two ferromagnetic layers. Furthermore, a second CoMgO layer or a CoMgO/MgO composite may serve as a perpendicular Hk enhancing layer formed between the free layer and a cap layer. One or both of the pinned layer and free layer may exhibit in-plane anisotropy or perpendicular magnetic anisotropy.

Spin torque transfer magnetic tunnel junction fabricated with a composite tunneling barrier layer

A MTJ in an MRAM array is disclosed with a composite free layer having a lower crystalline layer contacting a tunnel barrier and an upper amorphous NiFeX layer for improved bit switching performance. The crystalline layer is Fe, Ni, or FEB with a thickness of at least 6 Angstroms which affords a high magnetoresistive ratio. The X element in the NiFeX layer is Mg, Hf, Zr, Nb, or Ta with a content of 5 to 30 atomic % NiFeX thickness is preferably between 20 to 40 Angstroms to substantially reduce bit line switching current and number of shorted bits. In an alternative embodiments, the crystalline layer may be a Fe/NiFe bilayer. Optionally, the amorphous layer may have a NiFeM/NiFeMconfiguration where Mand Mare Mg, Hf, Zr, Nb, or Ta, and M1 is unequal to M2. Annealing at 300&#xb0; C. to 360&#xb0; C. provides a high magnetoresistive ratio of about 150%.

A STT-RAM MTJ that minimizes spin-transfer magnetization switching current (Jc) is disclosed. The MTJ has a MgO tunnel barrier layer formed with a natural oxidation process to achieve a low RA (10 ohm-um) and a Fe or Fe/CoFeB/Fe free layer which provides a lower intrinsic damping constant than a CoFeB free layer. A Fe, FeB, or Fe/CoFeB/Fe free layer when formed with a MgO tunnel barrier (radical oxidation process) and a CoFeB APpinned layer in a MRAM MTJ stack annealed at 360&#xb0; C. provides a high dR/R (TMR)&#x3e;100% and a substantial improvement in read margin with a TMR/Rp_cov=20. High speed measurement of 100 nm&#xd7;200 nm oval STT-RAM MTJs has shown a Jfor switching a Fe free layer is one half that for switching an amorphous CoFeBfree layer. A Fe/CoFeB/Fe free layer configuration allows the Hc value to be increased for STT-RAM applications.

High performance MTJ element for conventional MRAM and for STT-RAM and a method for making the same

A dual spin filter that minimizes spin-transfer magnetization switching current (Jc) while achieving a high dR/R in STT-RAM devices is disclosed. The bottom spin valve has a MgO tunnel barrier layer formed with a natural oxidation process to achieve low RA, a CoFe/Ru/CoFeB&#x2014;CoFe pinned layer, and a CoFeB/FeSiO/CoFeB composite free layer with a middle nanocurrent channel (NCC) layer to minimize Jc. The NCC layer may have be a composite wherein conductive M(Si) grains are magnetically coupled with adjacent ferromagnetic layers and are formed in an oxide, nitride, or oxynitride insulator matrix. The upper spin valve has a Cu spacer to lower the free layer damping constant. A high annealing temperature of 360&#xb0; C. is used to increase the MR ratio above 100%. A Jcof less than 1&#xd7;10A/cmis expected based on quasistatic measurements of a MTJ with a similar MgO tunnel barrier and composite free layer.

Method of forming a spin-transfer torque random access memory (STT-RAM) device

An MRAM structure is disclosed in which the bottom electrode has an amorphous TaN capping layer to consistently provide smooth and dense growth for AFM, pinned, tunnel barrier, and free layers in an overlying MTJ. Unlike a conventional Ta capping layer, TaN is oxidation resistant and has high resistivity to avoid shunting of a sense current caused by redeposition of the capping layer on the sidewalls of the tunnel barrier layer. Alternatively, the &#x3b1;-TaN layer is the seed layer in the MTJ. Furthermore, the seed layer may be a composite layer comprised of a NiCr, NiFe, or NiFeCr layer on the &#x3b1;-TaN layer. An &#x3b1;-TaN capping layer or seed layer can also be used in a TMR read head. An MTJ formed on an &#x3b1;-TaN capping layer has a high MR ratio, high Vb, and a RA similar to results obtained from MTJs based on an optimized Ta capping layer.

Underlayer for high performance magnetic tunneling junction MRAM

An MRAM array of MTJ memory cells is provided wherein each such cell is a layered MTJ structure located at an intersection of a word and bit line and has a small circular horizontal cross-section of 1.0 microns or less in diameter and wherein the ferromagnetic free layer of each such cell has a magnetic anisotropy produced by a magnetic coupling with a thin antiferromagnetic layer that is formed on the free layer. The array of MTJ memory cells so provided is far less sensitive to shape irregularities and edge defects of individual cells than arrays of the prior art.

Array of magnetic tunneling junction film structures with process determined in-plane magnetic anisotropy

A STT-RAM MTJ is disclosed with a MgO tunnel barrier formed by natural oxidation process. A CoFeB/NCC/CoFeB, CoFeB/NCC/CoFeB/NCC, or CoFeB/NCC/CoFeB/NCC/CoFeBfree layer configuration where NCC is a nanocurrent channel layer made of Fe(20%)-SiOis used to minimize Jcwhile enabling higher thermal stability, write voltage, read voltage, Ho, and Hc values that satisfy 64 Mb design requirements. The NCC layer is about 10 Angstroms thick to match the minimum Fe(Si) grain diameter size. The MTJ is annealed with a temperature of about 330&#xb0; C. to maintain a high magnetoresistive ratio while maximizing Hk&#x22a5;(interfacial) for the free layer thereby reducing Heff and lowering the switching current. The CoFeBlayers are sputter deposited with a low pressure process with a power of about 15 Watts and an Ar flow rate of 40 standard cubic centimeters per minute to lower Heff for the free layer.

Structure and method for enhancing interfacial perpendicular anisotropy in CoFe(B)/MgO/CoFe(B) magnetic tunnel junctions

A MTJ that minimizes spin-transfer magnetization switching current (Jc) in a Spin-RAM to &#x3c;1&#xd7;10A/cmis disclosed. The MTJ has a CoFeB/MgO/CoFeBconfiguration where the CoFeB AP1 pinned and free layers are amorphous and the crystalline MgO tunnel barrier is formed by a ROX or NOX process. The capping layer preferably is a Hf/Ru composite where the lower Hf layer serves as an excellent oxygen getter material to reduce the magnetic 'dead layer' at the free layer/capping layer interface and thereby increase dR/R, and lower He and Jc. The annealing temperature is lowered to about 280&#xb0; C. to give a smoother CoFeB/MgO interface and a smaller offset field than with a 350&#xb0; C. annealing. In a second embodiment, the AP1 layer has a CoFeB/CoFe configuration wherein the lower CoFeB layer is amorphous and the upper CoFe layer is crystalline to further improve dR/R and lower RA to &#x2266;10 ohm/&#x3bc;m.

Magnetic tunnel junction (MTJ) to reduce spin transfer magnetization switching current

A STT-MTJ MRAM cell that utilizes transfer of spin angular momentum as a mechanism for changing the magnetic moment direction of a free layer includes an IrMn pinning layer, a SyAP pinned layer, a naturally oxidized, crystalline MgO tunneling barrier layer that is formed on an Ar-ion plasma smoothed surface of the pinned layer and a free layer that comprises an amorphous layer of CoFeBof approximately 20 angstroms thickness or an amorphous ferromagnetic layer of CoFeBof approximately 15 angstroms thickness formed between two crystalline layers of Fe of 3 and 6 angstroms thickness respectively. The free layer is characterized by a low Gilbert damping factor and by very strong polarizing action on conduction electrons. The resulting cell has a low critical current, a high dR/R and a plurality of such cells will exhibit a low variation of both resistance and pinned layer magnetization angular dispersion.

High performance MTJ elements for STT-RAM and method for making the same

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San Jose, CA, United States of America

Cheng Tzong Horng