阅读说明：本技术 具有可调的高垂直磁各向异性的磁隧道结 (Magnetic tunnel junction with tunable high perpendicular magnetic anisotropy ) 是由 薛林 程志康 王晓东 马亨德拉·帕卡拉 汪荣军 于 2019-02-19 设计创作，主要内容包括：本公开内容的实施方式提供了用于从设置在基板上的膜堆叠形成磁隧道结(MTJ)结构的方法,以用于磁随机存取存储器(MRAM)应用和相关联的MTJ器件。本文描述的方法包括从膜堆叠形成材料层的膜特性以产生具有足够高垂直磁各向异性(PMA)的膜堆叠。利用含铁氧化物覆盖层产生合乎需要的PMA。通过利用含铁氧化物覆盖层,可以更精细地控制覆盖层的厚度,并且减少了在磁性存储层和覆盖层的界面处对硼的依赖。(Embodiments of the present disclosure provide methods for forming Magnetic Tunnel Junction (MTJ) structures from film stacks disposed on a substrate for Magnetic Random Access Memory (MRAM) applications and associated MTJ devices. The methods described herein include forming film properties of a material layer from a film stack to produce a film stack having a sufficiently high Perpendicular Magnetic Anisotropy (PMA). Utilizing an iron-containing oxide capping layer produces a desirable PMA. By utilizing an iron-containing oxide capping layer, the thickness of the capping layer may be more finely controlled and the dependence on boron at the interface of the magnetic storage layer and the capping layer is reduced.)

1. A magnetic tunnel junction film stack comprising:

a buffer layer;

a seed layer disposed over the buffer layer;

a first pinning layer disposed over the seed layer;

a synthetic ferrimagnetic (SyF) coupling layer disposed over the first pinned layer;

a second pinning layer disposed over the SyF coupling layer;

a structural barrier layer disposed over the second pinning layer;

a magnetic reference layer disposed over the structural barrier layer;

a tunnel barrier layer disposed over the magnetic reference layer;

a magnetic storage layer disposed over the tunnel barrier layer;

a capping layer disposed over the magnetic storage layer, wherein the capping layer comprises a layer of Fe-containing oxide material.

2. The membrane stack of claim 1, wherein the cover layer further comprises:

one or more of an Ir-containing layer, a Ru-containing layer, or a combination thereof.

3. The film stack of claim 1, wherein the Fe-containing oxide material layer is a material selected from the group consisting of a CoFe oxide material, a CoFeB oxide material, a NiFe oxide material, a FeB oxide material, and combinations thereof.

4. The film stack of claim 1, wherein the SyF coupling layer comprises:

An Ir-containing layer.

5. The film stack of claim 1, wherein the buffer layer comprises:

a CoFeB-containing layer.

6. The film stack of claim 1, wherein the seed layer comprises:

(a) a NiCr-containing layer, or (b) one or more of a Pt-containing layer, an Ir-containing layer, and a Ru-containing layer.

7. The membrane stack of claim 6, wherein:

the seed layer comprises a NiCr-containing layer; and

the buffer layer further comprises one or more of a TaN containing layer and a Ta containing layer, wherein the CoFeB containing layer of the buffer layer is disposed over one or more of the TaN containing layer of the buffer layer and the Ta containing layer of the buffer layer.

8. The membrane stack of claim 6,

the seed layer comprises one or more of a Pt-containing layer, an Ir-containing layer, and a Ru-containing layer; and

the buffer layer further includes one or more of a TaN containing layer and a Ta containing layer, wherein the CoFeB containing layer of the buffer layer is disposed below one or more of the TaN containing layer of the buffer layer and the Ta containing layer of the buffer layer.

9. A magnetic tunnel junction film stack comprising:

a buffer layer, wherein the buffer layer comprises a CoFeB-containing layer;

a seed layer disposed over the buffer layer;

A first pinning layer disposed over the seed layer;

a synthetic ferrimagnetic (SyF) coupling layer disposed over the first pinning layer, wherein the SyF coupling layer comprises an Ir-containing layer;

a second pinning layer disposed over the SyF coupling layer;

a structural barrier layer disposed over the second pinning layer;

a magnetic reference layer disposed over the structural barrier layer;

a tunnel barrier layer disposed over the magnetic reference layer;

a magnetic storage layer disposed over the tunnel barrier layer;

a capping layer disposed over the magnetic storage layer, wherein the capping layer comprises a layer of Fe-containing oxide material; and

a hard mask disposed over the capping layer.

10. The film stack of claim 9, wherein the Fe-containing oxide material layer is disposed on and in contact with the magnetic storage layer.

11. The film stack of claim 10, wherein the Fe-containing oxide material layer is a material selected from the group consisting of a CoFe oxide material, a CoFeB oxide material, a NiFe oxide material, a FeB oxide material, and combinations thereof.

12. The film stack of claim 9, wherein an Ir-containing layer, a Ru-containing layer, or a combination thereof is disposed on and in contact with the Fe-containing oxide material layer.

13. A magnetic tunnel junction film stack comprising:

a buffer layer;

a seed layer disposed on and in contact with the buffer layer;

a first pinning layer disposed on and in contact with the seed layer;

a synthetic ferrimagnetic (SyF) coupling layer disposed on and in contact with the first pinning layer;

a second pinning layer disposed on and in contact with the SyF coupling layer;

a structural barrier layer disposed on and in contact with the second pinning layer;

a magnetic reference layer disposed on and in contact with the structural barrier layer;

a tunnel barrier layer disposed on and in contact with the magnetic reference layer;

a magnetic storage layer disposed on and in contact with the tunnel barrier layer;

a capping layer disposed on and in contact with the magnetic storage layer, wherein the capping layer comprises an Fe-containing oxide material layer; and

a hard mask disposed on and in contact with the capping layer.

14. The film stack of claim 13, wherein the Fe-containing oxide material layer is a material selected from the group consisting of a CoFe oxide material, a CoFeB oxide material, a NiFe oxide material, a FeB oxide material, and combinations thereof.

15. The film stack of claim 13, wherein an Ir-containing layer, a Ru-containing layer, or a combination thereof is disposed on and in contact with the Fe-containing oxide material layer.

Technical Field

Embodiments of the present disclosure relate to methods for fabricating structures and devices for use in spin transfer-torque magnetic random access memory (STT-MRAM) applications. More particularly, embodiments of the present disclosure relate to methods for fabricating magnetic tunnel junctions having tunable high perpendicular magnetic anisotropy, and to devices related to magnetic tunnel junctions having tunable high perpendicular magnetic anisotropy.

Background

Magnetic Random Access Memory (MRAM) is a storage device that contains an array of MRAM cells that use their resistance values, rather than electrical charges, to store data. Typically, each MRAM cell includes a Magnetic Tunnel Junction (MTJ) structure. MTJ structures typically include a stack of magnetic layers having a configuration in which two ferromagnetic layers are separated by a thin non-magnetic dielectric (e.g., an insulating tunnel layer). The MTJ structure is sandwiched with a top electrode and a bottom electrode such that current can flow between the top electrode and the bottom electrode.

One type of MRAM cell is a spin transfer-torque magnetic random access memory (STT-MRAM). In such a fabrication process flow, a stable Magnetic Tunnel Junction (MTJ) stack is utilized to maintain a high temperature back end heat treatment while still yielding a high Tunnel Magnetoresistance (TMR) ratio. MTJ stacks typically utilize a buffer layer to improve adhesion and seeding of subsequent layers. The MTJ stack also includes a synthetic ferrimagnetic (SyF) coupling layer that couples the first pinned layer and the second pinned layer in an anti-parallel manner. A capping layer is used on top of the MTJ stack that protects the stack from corrosion and also serves as an etch stop for the hard mask etch. The capping layer, which is bonded to the magnetic storage layer of the MTJ, is used to create sufficient Perpendicular Magnetic Anisotropy (PMA) to provide a data retention energy barrier.

Conventional capping layers at the interface with the magnetic storage layer utilize boron to maintain a sufficient PMA. However, after a high temperature heat treatment, boron diffuses from the interface and weakens the magnetic storage layer PMA. Such conventional capping layers use magnesium oxide (MgO) material, however, to maintain a suitable PMA, thicker MgO material is used. Thicker MgO material increases the surface roughness of the interface and reduces TMR.

Accordingly, there is a need in the art for improved methods for fabricating MTJ structures for STT-MRAM applications. There is also a need for an improved MTJ stack that can maintain a high temperature heat treatment while maintaining a high PMA.

Disclosure of Invention

In one embodiment, a magnetic tunnel junction film stack is provided. The film stack includes a buffer layer, a seed layer disposed over the buffer layer, a first pinning layer disposed over the seed layer, and a synthetic ferrimagnet coupling layer disposed over the first pinning layer. The second pinning layer is disposed over the synthetic ferrimagnet coupling layer, the structural barrier layer is disposed over the second pinning layer, the magnetic reference layer is disposed over the structural barrier layer, and the tunnel barrier layer is disposed over the magnetic reference layer. A magnetic storage layer is disposed over the tunnel barrier layer, and a capping layer is disposed over the magnetic storage layer. The capping layer includes an oxide material layer containing Fe.

In another embodiment, a magnetic tunnel junction film stack is provided. The film stack includes a buffer layer, wherein the buffer layer includes a CoFeB-containing layer, a seed layer disposed over the buffer layer, a first pinning layer disposed over the seed layer, and a synthetic ferrimagnetic coupling layer disposed over the first pinning layer, wherein the synthetic ferrimagnetic coupling layer includes an Ir-containing layer. The second pinning layer is disposed over the synthetic ferrimagnet coupling layer, the structural barrier layer is disposed over the second pinning layer, the magnetic reference layer is disposed over the structural barrier layer, and the tunnel barrier layer is disposed over the magnetic reference layer. A magnetic storage layer is disposed over the tunnel barrier layer, a capping layer is disposed over the magnetic storage layer, the capping layer includes an Fe-containing oxide material layer, and a hard mask is disposed over the capping layer.

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

Drawings

So that the manner in which the above recited features of the present disclosure can be understood in detail, a more particular description of the disclosure may be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only exemplary embodiments and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments.

FIG. 1 depicts a flow diagram illustrating a method for fabricating a Magnetic Tunnel Junction (MTJ) structure according to one embodiment described herein.

Fig. 2A shows a schematic view of a portion of a membrane stack according to embodiments described herein.

Fig. 2B shows a schematic view of a portion of a membrane stack according to embodiments described herein.

Fig. 2C shows a schematic view of a portion of a membrane stack according to embodiments described herein.

Fig. 3A shows a schematic view of a cover layer according to embodiments described herein.

Fig. 3B shows a schematic view of a cover layer according to embodiments described herein.

Fig. 3C shows a schematic view of a cover layer according to embodiments described herein.

Fig. 3D shows a schematic view of a cover layer according to embodiments described herein.

To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures. It is contemplated that elements and features of one embodiment may be beneficially incorporated in other embodiments without further recitation. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this disclosure and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments.

Detailed Description

Embodiments of the present disclosure provide methods for forming MTJ structures from film stacks disposed on a substrate for MRAM applications and associated MTJ devices. The methods described herein include forming film properties of a material layer from a film stack to produce a film stack having a sufficiently high Perpendicular Magnetic Anisotropy (PMA). Utilizing an iron-containing oxide capping layer produces a desirable PMA. By utilizing an iron-containing oxide capping layer, the thickness of the capping layer may be more finely controlled and the dependence on boron at the interface of the magnetic storage layer and the capping layer is reduced.

Fig. 1 depicts a flow chart illustrating a process 100 for fabricating an MTJ structure on a substrate for MRAM applications in accordance with one embodiment of the present disclosure. In some embodiments, process 100 is a process flow and operations 101-106 are separate processes. The process 100 is configured to be performed in a plasma processing chamber and a thermal processing chamber or other suitable plasma immersion ion implantation system or etch chamber. The process 100 may also use other tools, such as PVD chambers, CVD chambers, and photolithography tools.

The process 100 begins at operation 101 by providing a substrate having a film stack disposed thereon. In some embodiments, the substrate comprises metal or glass, silicon, dielectric materials and metal alloys or composite glasses, crystalline silicon (e.g., Si <100> or Si <111>), silicon oxide, strained silicon, silicon germanium, doped or undoped polysilicon, doped or undoped silicon wafers, and patterned or unpatterned wafers silicon-on-insulator (SOI), carbon doped silicon oxide, silicon nitride, doped silicon, germanium, gallium arsenide, glass or sapphire. The substrate may have various dimensions, such as about 200mm, about 300mm, about 450mm, or other diameters, as well as rectangular or square panels. Unless otherwise specified, embodiments described herein are performed on a substrate having a 200mm diameter, a 300mm diameter, or a 450mm diameter. In one embodiment, a substrate includes a film stack disposed on the substrate.

It should be noted that the pinned magnetic layer, optional structural decoupling layer, tunnel barrier layer, magnetic storage layer, magnetic reference layer, and capping layer may be formed by any suitable technique and in any suitable manner, such as a PVD process. Examples of systems that can be used to form these layers include those available from Applied materials Inc. (Applied materials Inc., Santa Clara, Calif.) of Santa Clara, Calif PVD systems. It is contemplated that other processing systems, including those available from other manufacturers, may be suitable for practicing the present disclosure.

Other processes may be utilized to form the transistor and interconnect layers known to those skilled in the art before performing the MTJ stack deposition at operation 102. After performing the post-patterning anneal at operation 106, additional operations may be performed, such as completing the operations for the remaining interconnect layers and contact pads.

At operation 102-. Operation 102-104 includes a patterning process, such as an etching process, performed to remove a portion of the film stack exposed and defined by the etch mask layer (not shown) from the substrate until the underlying substrate is exposed. The patterning process for patterning the film stack, which includes several separate operations or different recipes, is configured to provide different gas mixtures or etchants to etch different layers depending on the materials included in each layer. During patterning, an etching gas mixture or several gas mixtures with different etching species are sequentially supplied to the substrate surface to remove a portion of the film stack from the substrate. The endpoint of the patterning process at operation 104 is controlled by time or other suitable method. For example, the patterning process is terminated after performing the patterning process for about 200 seconds to about 10 minutes until the substrate is exposed. In another example, the patterning process is terminated by a determination from an endpoint detector.

A further deposition process is performed to form an encapsulation and insulation layer on the portion of the substrate, wherein the film stack is removed during the patterning process at operation 104. Encapsulation allows for proper step coverage and hermeticity and typically involves deposition of a material composed of a silicon nitride based substrate material. The insulating material utilizes an oxide-based material and includes a material deposited to a thickness greater than a thickness of the encapsulation material. The insulating layer is formed of a suitable insulating material and is subsequently processed through a series of etch and deposition processes to form an interconnect structure (e.g., back end processing) in the insulating layer to complete the device structure fabrication process. In one example, the insulating layer is a silicon oxide layer or other suitable material.

At operation 106, a thermal annealing process is performed. Examples of systems that may be used for annealing include rapid thermal annealing chambers. One example of a rapid thermal annealing chamber is available from applied materials, Inc. of Santa Clara, CalifA chamber. It is contemplated that other processing systems, including those available from other manufacturers, may be suitable for practicing the present disclosure. A thermal annealing process is performed to repair, densify, and strengthen the lattice structure of the film stack, particularly the magnetic memory layer and the magnetic reference layer included in the film stack. In that After the thermal annealing process, the magnetic storage layer and the magnetic reference layer are transformed into a crystalline magnetic storage layer and a crystalline magnetic reference layer having a crystal orientation substantially in a single plane. According to the obtained desired crystallization of the magnetic storage layer and the magnetic reference layer, the overall electrical characteristics of the film stack for manufacturing the MTJ device are improved.

In some implementations, one of operations 103 and 106 (or any other equivalent annealing process) may be used depending on the desired implementation. As described below, the MTJ film stack of the present disclosure is capable of maintaining high temperature thermal processes and improved electrical and magnetic properties.

Each of fig. 2A-2C respectively shows a schematic view of a portion 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 and is in contact with the substrate 200. Although not shown in fig. 2A-2C, other layers in the form of one or more layers, such as transistors and interconnect structures, may be disposed between the substrate 200 and the bottom contact 204. The differences between the film stacks shown in fig. 2B and 2C include buffer layer 205/205', seed layer 210/210', and first pinning layer 215/215 '. In some embodiments, the film stack includes a bottom contact, a buffer layer, a seed layer, a first pinning layer, a synthetic ferrimagnetic (SyF) coupling layer, a second pinning layer, a structural barrier layer, a magnetic reference layer, a tunnel barrier layer, a magnetic storage layer, a capping layer, and a hard mask. In some embodiments, each of these layers individually comprises one or more layers.

In some implementations, and as shown in fig. 2A-2C, a film stack for forming a Magnetic Tunnel Junction (MTJ) structure is disposed over the bottom contact 204. The MTJ structure includes: a buffer layer 205/205', a buffer layer 205/205' disposed over the bottom contact 204; a seed layer 210/210 'disposed on the buffer layer 205/205'; a first pinning layer 215/215 'disposed over seed layer 210/210'; a synthetic ferrimagnet (SyF) coupling layer 220 disposed on the first pinning layer 215/215'; a second pinning layer 225 disposed over the SyF coupling layer 220; a structural barrier layer 230 disposed over the second pinning layer 225; a magnetic reference layer 235 disposed over the structural barrier layer 230; a tunnel barrier layer 240 disposed over the magnetic reference layer 235; a magnetic storage layer 245 disposed over tunnel barrier layer 240; a capping layer 250 disposed over magnetic storage layer 245, wherein the capping layer comprises one or more layers; and a hard mask 255 disposed over the capping layer 250, wherein at least one of the capping layer, the buffer layer, and the SyF coupling layer is not fabricated from Ru. In one embodiment, when adjacent layers of a film stack are said to be disposed above or below adjacent layers, then each of these layers are said to be disposed on and in contact with each other.

The film stack includes a buffer layer 205/205' disposed over 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, buffer layer 205/205' improves adhesion and seeding of subsequently deposited layers. In one embodiment, buffer layer 205/205' includes one or more layers. In one embodiment, buffer layer 205/205' is not fabricated from Ru.

In one embodiment, buffer layer 205/205 'includes CoFeB-containing layers 205a/205 a'. The weight percent (wt%) of boron (B) in buffer layer 205/205' is between about 10 wt% and about 40 wt%, such as between about 20 wt% and 40 wt%, such as between about 25 wt% and about 40 wt%. The weight percentage of iron in buffer layer 205/205' is between about 20 wt% and about 60 wt%, such as 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 aboutAnd the combinationBetween, such as about

In one embodiment, buffer layer 205/205' includes TaN-containing layers 205b/205b ' and/or Ta-containing layers 205c/205c '. At one endIn one embodiment, the TaN-containing layer 205b/205b 'and the Ta-containing layer 205c/205c' are disposed over the CoFeB layer 205 a. Alternatively, the TaN-containing layer 205b/205b ' and the Ta-containing layer 205c/205c ' can be disposed below the CoFeB layer 205a '. The thickness of the TaN-containing layer and the Ta-containing layer is about

And the combinationBetween, such as about

The film stack includes a seed layer 210/210 'disposed over 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 '.

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 seed layer 210 having one or more of a Pt-containing layer, an Ir-containing layer, and a Ru-containing layer has a thickness of about

And the combinationBetween, such as aboutIn one embodiment, when the seed layer 210 comprises 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 below the TaN-containing layer 205b of the buffer layer 205/205' (and/or the Ta-containing layer 205 c).

In some embodiments, the seed layer 210' comprises a NiCr-containing layer. The seed layer 210' having a layer comprising NiCr has a thickness of about

And the combination

Between, such as about

In an embodiment, when the seed layer comprises a NiCr-containing layer, CoFeB-containing layer 205a ' of buffer layer 205/205' is disposed over TaN-containing layer 205b ' (and/or Ta-containing layer 205c ') of buffer layer 205/205 '.

In one embodiment, the film stack includes a first pinning layer 215/215 'disposed over 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 metal alloy with dopants, such as boron dopants, oxygen dopants, 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. Examples of suitable magnetic materials include Ru, Ta, Co, Pt, Ni, TaN, NiFeO _x、NiFeB、CoFeO_xB、CoFeB、CoFe、NiO_xB、CoBO_x、FeBO_xCoFeNiB, CoPt, CoPd, CoNi, and TaO_x。

In one embodiment, the first pinned layer 215 includes a Co-containing layer 215b disposed on a Ta/Pt-containing layer 215 a. The thickness of the Co-containing layer 215b is about

And aboutSuch as aboutThe Co/Pt-containing layer 215a may have a composition comprising

[Co_(x)/Pt_(y)]_m

Wherein x has a Co thickness of about

And the combination

E.g. in the range ofAnd the combinationAnd y has a Pt thickness of aboutAnd the combination

E.g. in the range ofAnd the combinationWherein m is an integer from about 3 to about 10, wherein m represents the number of Co/Pt-containing layers 215a repeatedly formed in the film stack. For example, when x is

When y is

And m is an integer of 2, the Co/Pt layer is composed of a Co layer

Layer of/PtLayer of/Co

Layer of/PtAnd (4) forming.

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 aboutAnd about

Such as aboutThe Co/Ni-containing layer 215a' may have a composition comprising

[Co_(x1)/Ni_(y1)]_n

Wherein the thickness of Co of x1 is aboutAnd the combination

E.g. in the range ofAnd the combination

Y1 has a Ni thickness of aboutTo about

E.g. aboutTo aboutAnd n is an integer between about 1 and about 10, where n is tabulatedShowing the number of Co/Ni containing layers 215a' repeatedly formed in the film stack.

In embodiments where the first pinned 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 embodiments where the first pinned layer 215 'includes a Co/Ni containing layer 215a', the seed layer 210 includes a Ni Cr containing layer.

The film stack includes a synthetic ferrimagnetic (SyF) coupling layer 220 disposed above the first pinned layer 215/215'. In one embodiment, the SyF coupling layer 220 is sandwiched between the first pinning layer 215/215' and the second pinning layer 225. The SyF coupling layer 220 is used to couple the first pinning layer 215/215' and the second pinning layer 225 in an antiparallel manner. In one embodiment, the SyF coupling layer 220 includes one or more of an Ir-containing layer, a Ru-containing layer, an Rh-containing layer, and a Cr-containing layer. In one embodiment, the SyF coupling layer is an Ir containing layer. In another embodiment, the SyF coupling layer is not made of Ru. The thickness of the SyF coupling layer 220 is aboutTo about

In the meantime. When the SyF coupling layer 220 is a Ru-containing layer, the thickness of the SyF coupling layer 220 is about

And aboutBetween or aboutAnd about

In the meantime. When the SyF coupling layer 220 is an Ir-containing layer, the thickness of the SyF coupling layer 220 is aboutTo about

In the meantime.

The film stack includes a second pinning layer 225 disposed over the SyF coupling layer 220. In one embodiment, the second pinning layer 225 is sandwiched between the SyF coupling layer 220 and the structural barrier 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 metal alloys with dopants, such as boron dopants, oxygen dopants, 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. Examples of suitable magnetic materials include Ru, Ta, Co, Pt, Ni, TaN, NiFeO _x、NiFeB、CoFeO_xB、CoFeB、CoFe、NiO_xB、CoBO_x、FeBO_xCoFeNiB, CoPt, CoPd, CoNi, and TaO_x。

In one embodiment, the second pinning layer 225 includes a Co-containing layer 225b disposed over the Co/Pt-containing layer 215 a. The thickness of the Co-containing layer 225b is about 0And about

Such as about

The Co/Pt-containing layer 215a may have a composition comprising

[Co_(x2)/Pt_(y2)]_p

Wherein the thickness of Co of x2 is aboutAnd the combination

E.g. in the range of

And the combination

Y2 is aboutAnd the combination

E.g. in the range ofAnd the combination

And p is an integer between about 0 and about 5, where p represents the number of Co/Pt-containing layers 225a that are repeatedly formed in the film stack.

The film stack includes a structural barrier layer 230 disposed over the second pinning layer 225. In one embodiment, structural barrier layer 230 is sandwiched between second pinning layer 225 and magnetic reference layer 235. In one embodiment, the structural barrier layer 230 includes one or more layers. In one embodiment, the structural barrier layer 230 includes one or more of a metal-containing material or a magnetic material, such as Mo, Ta, W, CoFe, and CoFeB, one or more of a Co-containing layer, a Mo-containing layer, and a W-containing layer. The second pinning layer 225 has a thickness of about

And about

Such as about

The film stack includes a magnetic reference layer 235 disposed over the structural barrier layer 230. In one embodiment, the magnetic reference layer 235 is sandwiched between the structural barrier layer 230 and the tunnel barrier layer 240. In one embodiment, the magnetic property Reference layer 235 includes one or more layers. The magnetic reference layer 235 is made of several magnetic materials, such as a metal alloy with dopants, such as boron dopants, oxygen dopants, 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. Examples of suitable magnetic materials include Ru, Ta, Co, Pt, Ni, TaN, NiFeO_x、NiFeB、CoFeO_xB、CoFeB、CoFe、NiO_xB、CoBO_x、FeBO_xCoFeNiB, CoPt, CoPd, CoNi, and TaO_x。

In one embodiment, one or more of the several layers of the magnetic reference layer 235 comprise a CoFeB-containing layer. The weight percent (wt%) of boron (B) in magnetic reference layer 235 is between about 10 wt% and about 40 wt%, such as between about 20 wt% and 40 wt%, such as between about 25 wt% and about 40 wt%. The weight percentage of iron in magnetic reference layer 235 is between about 20 wt% and about 60 wt%, such as between about 40 wt% and 60 wt%, such as between about 45 wt% and about 60 wt%. The thickness of the magnetic reference layer 235 is about

To about

Such as about

In one embodiment, the film stack includes a tunnel barrier layer 240 disposed over the magnetic reference layer 235. In an embodiment, tunnel barrier layer 240 is sandwiched between magnetic reference layer 235 and magnetic storage 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, HfO ₂、TiO₂、TaO_x、Al₂O₃Or other suitable material. In one embodiment, tunnel barrier 240 is MgO, which is approximately MgO thickAnd aboutSuch as about

The tunnel barrier layer 240 may be annealed during or after deposition, for example, using a rapid thermal annealing (RTP) process.

In one embodiment, the film stack includes a magnetic storage layer 245 disposed over the tunnel barrier layer 240. In one embodiment, magnetic storage layer 245 is sandwiched between tunnel barrier layer 240 and capping layer 250. Magnetic storage layer 245 is made of several magnetic materials, such as metal alloys with dopants, such as boron dopants, oxygen dopants, 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. Examples of suitable magnetic materials include Ru, Ta, Co, Pt, Ni, TaN, NiFeO_x、NiFeB、CoFeO_xB、CoFeB、CoFe、NiO_xB、CoBO_x、FeBO_xCoFeNiB, CoPt, CoPd, CoNi, and TaO_x。

In one embodiment, magnetic storage layer 245 is a CoFeB-containing material, a CoFeNiB-containing material, a Ta-containing material, a Mo-containing material, or a W-containing material, combinations of the above, or other suitable layers. For example, in the embodiment shown in fig. 2, magnetic storage layer 245 includes a first CoFeB-containing layer 245a and a second CoFeB-containing layer 245c sandwiching an intermediate layer 245 b. The thickness of the first CoFeB-containing layer 245A is about To aboutSuch as aboutThe weight percent (wt%) of boron (B) in the first CoFeB-containing layer 245a is aboutBetween 10 wt% and about 40 wt%, such as between about 20 wt% and 40 wt%, such as between about 25 wt% and about 40 wt%. The weight percent 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%.

The second CoFeB-containing layer 245c has a thickness of about

To about

A thickness of, such as aboutThe weight percent (wt%) of boron (B) in the second CoFeB-containing layer 245c is between about 10 wt% and about 40 wt%, such as between about 20 wt% and 40 wt%, such as between about 25 wt% and about 40 wt%. The weight percent 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%.

Intermediate layer 245b of magnetic storage layer 245 includes one or more layers of at least one or more of a Ta-containing layer, a Mo-containing layer, and a W-containing layer. The thickness of the intermediate layer 245b is aboutTo about

For example, about

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

The first layer 250a includes one or more oxygen-containing layers, 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, a FeB oxide material, and combinations thereof. The first layer 250a has a thickness of about

To about

E.g. between about

And about

In the meantime.

In one embodiment, first layer 250a is fabricated by sputtering (i.e., a PVD deposition process) an Fe-containing metal onto magnetic storage layer 245. In this embodiment, the Fe-containing metal is subsequently oxidized in an oxygen-containing ambient environment. An oxygen-containing ambient environment may be formed in the process chamber or the Fe-containing metal may be exposed to the atmosphere to form an Fe-containing oxide material. In another embodiment, the Fe-containing metal is reactively sputtered on magnetic storage 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 delivered to the processing ambient at a flow rate of between about 1sccm and about 60sccm, such as between about 10sccm and about 30sccm, such as about 20 sccm.

The oxygen is exposed to promote oxidation of the Fe material for a period of time 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 (atmospheric air or oxygen-containing gas) for a period of about 10 seconds, which results in the film stack exhibiting a coercive field (coercive field) of about 581Oe ld)(H_c) And a data retention barrier (E) of about 41kT_b). In another example, the Fe-containing metal is exposed to an oxygen-containing ambient (atmospheric air or oxygen-containing gas) for a period of about 30 seconds, which results in the film stack exhibiting a coercive field (Hc) of about 918Oe and a data retention barrier (Eb) of about 45 kT. In another example, the Fe-containing metal is exposed to an oxygen-containing environment (atmospheric air or an oxygen-containing gas) for a period of about 60 seconds, which results in the film stack exhibiting a coercive field (Hc) of about 1029Oe and a data retention barrier (Eb) of about 51 kT.

In yet another embodiment, an Fe-containing oxide material is sputtered directly on magnetic storage layer 245 to form an Fe-containing oxide material. In one or more of the foregoing embodiments, the oxidation of Fe metal is performed in situ to avoid subsequent atmospheric exposure and formation of native Fe oxides.

The use of an Fe-containing oxide material for capping layer 250a that is directly bonded to magnetic storage layer 245 enables a number of benefits. The Fe-containing oxide material has a stronger bulk PMA than the conventional capping layer material, which increases the PMA of the MTJ. Furthermore, as PMA increases, the dependence on boron at the interface between capping layer 250a and magnetic storage layer 245 may decrease, and in certain embodiments, substantially eliminate boron, which typically diffuses away from the interface during thermal processing of the MTJ. In addition, the PMA can be adjusted by controlling the thickness of the Fe-containing oxide material. Thus, a sufficiently thin layer of Fe-containing oxide material can be used, thus providing a suitable PMA, while avoiding an undesirable increase in film surface roughness, while avoiding an effect on the TMR of the MTJ. As a result, MTJ performance, such as electrical performance, material stability, tunability, and manufacturability, is improved.

The second layer 250b includes one or more Ru-containing layers and/or Ir-containing layers. The second layer 250b has a thickness of about

To aboutE.g. aboutThe third layer 250c includes one or more layers of a Ta-containing material. The thickness of the third layer 250c is aboutTo aboutSuch as aboutThe fourth layer 250d includes one or more Ir-containing layers and Ru-containing layers, e.g., one or more Ir-containing layers. The thickness of the fourth layer 250d is about

To aboutWithin a range such as about

In one embodiment, the overlay 250 includes an optional layer 250 x. Optional layer 250x is disposed between first layer 250a and second layer 250 b. In one embodiment, optional layer 250x comprises one or more Ir-containing layers and/or Ru-containing layers. In another embodiment, optional layer 250x is an Fe-containing oxide material, such as those described above. Optional layer 250x has a thickness of aboutTo aboutE.g. about

In an embodiment, when the overlay layer 250 includes the optional layer 250x, the second layer 250b is not used. In such an embodiment, optional layer 250x is above first layer 250 a. In one embodiment, the optional layer 250x is disposed directly on the first layer 250a and in contact with the first layer 250 a.

Fig. 3A-3D illustrate various embodiments of the overlay 250 as described above. Fig. 3A illustrates a cover layer 250 comprising: a first layer 250 a; an optional layer 250x disposed over the first layer 250 a; a second layer 250b disposed over the optional layer 250 x; a third layer 250c disposed over the second layer 250 b; and a fourth layer 250d disposed over the third layer 250 c. The materials, compositions, and thickness ranges for each of the layers 250a, 250x, 250b, 250c, 250d are discussed above.

Fig. 3B illustrates a cover layer 250 comprising: a first layer 250 a; a second layer 250b disposed over the first layer 250 a; a third layer 250c disposed over the second layer 250 b; and a fourth layer 250d disposed over the third layer 250 c. The materials, compositions, and thickness ranges for each of the layers 250a, 250b, 250c, 250d are discussed above.

Fig. 3C illustrates a cover layer 250 comprising: a first layer 250 a; an optional layer 250x disposed over the first layer 250 a; a third layer 250c disposed over the optional layer 250 x; and a fourth layer 250d disposed over the third layer 250 c. The materials, compositions, and thickness ranges for each of the layers 250a, 250x, 250c, 250d are discussed above.

Fig. 3D illustrates a cover layer 250 that includes a first layer 250a and an optional layer 250x disposed over the first layer 250 a. The materials, compositions, and thickness ranges for each of the layers 250a, 250x are discussed above.

Fig. 2A-2C illustrate an exemplary MTJ film stack where one or more of the buffer layer, the SyF coupling layer, and the capping layer are not fabricated from Ru. In some embodiments, the MTJ film stack includes CoFeB-based buffer layer 205/205', optionally including some TaN and/or Ta. The CoFeB layer can be disposed over or under the TaN and/or Ta containing layer. The CoFeB-based buffer layer should have a weight percent of boron greater than about 10 wt%, for example, greater than about 25 wt%. In some embodiments, Ir, Ru, Rh, and/or Cr may be used as the SyF coupling layer 220. In some embodiments, Ir and/or Ru may be the top layer metal for capping layer 250.

The use of a CoFeB-based buffer layer instead of a Ru-containing buffer layer has demonstrated an increase in Tunnel Magnetoresistance (TMR) with excellent magnetic pinning even after annealing at temperatures up to 450 ℃. High SyF coupling, high perpendicular magnetic anisotropy of the pinned and reference layers, and controllable perpendicular magnetic anisotropy of the free layer are achieved. Some embodiments implementing a CoFeB buffer layer (with 25 wt% boron) show an improvement in TMR (%) of more than 10% compared to conventional Ta/Ru/Ta buffer layers. The CoFeB layer prevents an increase in roughness from the bottom contact into the MTJ film stack.

Furthermore, the replacement of Ru with Ir in the SyF coupling layer and capping layer showed TMR (%) increase even when annealed at temperatures up to 450 ℃. Some embodiments implementing a SyF coupling layer comprising Ir show an improvement in TMR (%) of more than 10% compared to a conventional Ru-comprising SyF coupling layer. Furthermore, by eliminating Ru in the SyF coupling layer and the capping layer, the film TMR can be enhanced by eliminating Ru diffusion into MgO. IrO₂May have a thermal stability higher than RuO₄This helps to eliminate diffusion.

Such as the configurations of fig. 2A-2C, provide advantages over conventional film stacks. The first advantage is that the buffer layer remains amorphous and blocks the texture of the bottom contact even with high temperature heat treatment. A second advantage is the strong antiparallel coupling between the pinned layers brought about by Ir. A third advantage is improved TMR by using a new buffer layer and removing Ru from the stack. These advantages result in higher MTJ performance (e.g., high TMR, high SyF coupling, high perpendicular magnetic anisotropy of pinned and reference layers, and controllable perpendicular magnetic anisotropy of the free layer) and improved manufacturability . The MTJ film stack can be used to fabricate memory cells for STT-MRAM applications, as well as other memory and logic devices that use MTJs as cell building blocks. Physical vapor deposition systems (e.g., vapor deposition systems)MRAM) may be used to deposit the MTJ film stack for a high performance STT-MRAM chip. As described herein, MTJ film stacks capable of sustaining high temperature thermal processing improve the electrical and magnetic properties of the MTJ.

Tables 1 and 2 show exemplary compositions for forming a film stack of a Magnetic Tunnel Junction (MTJ) structure on a substrate. Materials, compositions, and thicknesses for the hardmask layer and the bottom contact layer are known to those of ordinary skill in the art.

As described above (represented by 250 x), an additional (and optional) Ir and/or Ru layer within the cap layer may be placed on top of the oxygen containing layer. The thickness of the layer may be about

To aboutIn the meantime. In some embodiments, when additional Ir and/or Ru layers are used, the CoFeB layer of the capping layer is not used.

TABLE 1

All values of composition and thickness are listed as approximate ranges.

TABLE 2

All values of composition and thickness are listed as approximate ranges.

Although the disclosure herein has been described with reference to particular embodiments, it is to be understood that these embodiments are merely illustrative of the principles and applications of the present disclosure. It will be apparent to those skilled in the art that various modifications and variations can be made in the method and apparatus of the present disclosure without departing from the spirit and scope of the disclosure. Thus, it is intended that the present disclosure encompass such modifications and variations as fall within the scope of the appended claims and equivalents thereof.