Spin-orbit torque MRAMs and method for fabricating the same

A spin-orbit torque MRAM is provided. The spin-orbit torque MRAM includes a spin Hall metal layer, a free magnetic layer disposed on the spin Hall metal layer, a barrier layer, and a pinned layer. The free magnetic layer includes a first area and a second area located on both sides thereof. The barrier layer includes a first area and a second area located on both sides thereof. The first area of the barrier layer is disposed on that of the free magnetic layer, and the second area of the barrier layer is disposed on that of the free magnetic layer. The pinned layer is disposed on the first area of the barrier layer.

CROSS REFERENCE TO RELATED APPLICATIONS

This Application claims priority of Taiwan Patent Application No. 106141350, filed on Nov. 28, 2017, the entirety of which is incorporated by reference herein.

TECHNICAL FIELD

The disclosure relates to a spin-orbit torque MRAM, and relates to a spin-orbit torque MRAM with a uniform ultra-thin metal layer and a method for fabricating the same.

BACKGROUND

A spin-orbit torque (SOT) MRAM is a magnetic memory technology which is able to improve an operating speed to 1 ns and achieve an unlimited number of operations, and is considered as an important technology to undertake the spin torque transfer (STT) MRAM. The highest efficiency of the spin Hall effect can be achieved in a 3-nm ultra-thin heavy metal layer. Therefore, how to fabricate a 3-nm metal layer structure with high uniformity is the key to mass production.

SUMMARY

For a magnetic tunnel junction (MTJ) device with a top pinned layer, an etching process stops at an ultra-thin spin Hall metal layer. The bottom ultra-thin heavy metal layer of the average spin-orbit torque (SOT) MRAM can become damaged during the etching process, and this may result in uneven operation characteristics and component failure. In order to overcome this problem, the disclosure provides a spin-orbit torque (SOT) MRAM with a uniform ultra-thin heavy metal layer and a method for fabricating the SOT MRAM.

In accordance with one embodiment of the disclosure, a spin-orbit torque (SOT) MRAM is provided. The spin-orbit torque MRAM comprises a spin Hall metal layer, a free magnetic layer, a barrier layer, and a pinned layer. The free magnetic layer is disposed on the spin Hall metal layer. The barrier layer is disposed on the free magnetic layer. The barrier layer comprises a first area and a second area located on both sides of the first area, and the thickness of the second area is equal to or smaller than that of the first area. The pinned layer is disposed on the first area of the barrier layer.

In accordance with one embodiment of the disclosure, a spin-orbit torque (SOT) MRAM is provided. The spin-orbit torque MRAM comprises a spin Hall metal layer, a free magnetic layer, a barrier layer, and a pinned layer. The free magnetic layer is disposed on the spin Hall metal layer. The free magnetic layer comprises a first area and a second area located on both sides of the first area, and the thickness of the second area is equal to or smaller than that of the first area. The barrier layer is disposed on the first area of the free magnetic layer. The pinned layer is disposed on the barrier layer.

In accordance with one embodiment of the disclosure, a high-efficiency method for fabricating a spin-orbit torque (SOT) MRAM is provided, comprising the following steps. A spin Hall metal layer is provided. A free magnetic layer is disposed on the spin Hall metal layer. The free magnetic layer comprises a first area and a second area located on both sides of the first area. A barrier layer is disposed on the free magnetic layer. The barrier layer comprises a first area and a second area located on both sides of the first area. The first area of the barrier layer is disposed on the first area of the free magnetic layer. The second area of the barrier layer is disposed on the second area of the free magnetic layer. A pinned layer is disposed on the barrier layer. A patterned photoresist layer is disposed on the pinned layer. The pinned layer is etched using the patterned photoresist layer as a mask to expose the second area of the barrier layer.

The present disclosure provides a top-pinned layer MTJ structure which is able to terminate etching processes at either any thickness position of a barrier layer or any thickness position of a bottom free magnetic layer, used as a component to develop the optimized process technology of the spin-orbit torque (SOT) MRAM. The uniformity of various layers can be achieved using etch selectivity ratios between various materials, for example, the etch selectivity ratio between the top pinned layer and the barrier oxide layer or between the barrier oxide layer and the free magnetic layer. In addition, a bottom ultra-thin heavy metal layer can be protected by the residual material of the barrier layer or the free magnetic layer. This component structure not only generates the splitting of the upper and lower spin currents by spin Hall effect, but it also achieves the magnetic moment reversal of the free magnetic layer by the spin-orbit effect. Simultaneously, this component structure can overcome problems with the bottom ultra-thin metal layer of a top-pinned layer MTJ of a conventional spin-orbit torque (SOT) structure getting damaged in the etching process and causing uneven operation characteristics and component failure. This process-optimized component structure can significantly improve the production yield of the spin-orbit torque (SOT) MRAM.

DETAILED DESCRIPTION

The following description is of the best-contemplated mode of carrying out the disclosure. This description is made for the purpose of illustrating the general principles of the disclosure and should not be taken in a limiting sense. The scope of the disclosure is best determined by reference to the appended claims.

Referring toFIG. 1, in accordance with one embodiment of the disclosure, a spin-orbit torque magnetoresistive random access memory (SOT MRAM)10is provided.FIG. 1is a cross-sectional view of the SOT MRAM10.

In this embodiment, the SOT MRAM10comprises a spin Hall metal layer12, a free magnetic layer14, a barrier layer16, and a pinned layer18.

The free magnetic layer14is disposed on the spin Hall metal layer12. The free magnetic layer14comprises a first area20and a second area22. The second area22is located on both sides of the first area20. The thickness h2of the second area22is equal to the thickness h1of the first area20.

The barrier layer16comprises a first area24and a second area26. The second area26is located on both sides of the first area24. The first area24of the barrier layer16is disposed on the first area20of the free magnetic layer14. The second area26of the barrier layer16is disposed on the second area22of the free magnetic layer14.

The pinned layer18is disposed on the first area24of the barrier layer16.

The thickness h4of the second area26is equal to the thickness h3of the first area24of the barrier layer16.

In some embodiments, the spin Hall metal layer12comprises heavy metal materials capable of producing large spin Hall effect, for example, tantalum (Ta), platinum (Pt), hafnium (Hf), tungsten (W), zirconium (Zr), or an alloy thereof.

In some embodiments, the thickness of the spin Hall metal layer12is smaller than about 10 nm.

In some embodiments, the free magnetic layer14may comprise a single layer or a composite layer.

In some embodiments, the free magnetic layer14may comprise a single layer of, for example, iron (Fe), cobalt (Co), nickel (Ni), gadolinium (Gd), terbium (Tb), cobalt iron boron (CoFeB) alloy, or cobalt iron (CoFe) alloy.

In some embodiments, the free magnetic layer14may comprise a composite layer of, for example, cobalt iron boron (CoFeB) alloy/tantalum (Ta)/cobalt iron boron (CoFeB) alloy or cobalt iron (CoFe) alloy/tantalum (Ta)/cobalt iron (CoFe).

In some embodiments, the thickness h1of the first area20of the free magnetic layer14is in a range from about 1 nm to about 3 nm.

In some embodiments, the barrier layer16may comprise magnesium oxide (MgO) or aluminum oxide (AlOx).

In some embodiments, the thickness h3of the first area24of the barrier layer16is in a range from about 0.5 nm to about 2 nm.

In some embodiments, the pinned layer18may comprise a single layer or a composite layer.

In some embodiments, the pinned layer18may comprise a single layer of, for example, cobalt iron (CoFe) alloy, cobalt iron boron (CoFeB) alloy, or cobalt nickel (CoNi) alloy.

In the SOT MRAM10, the free magnetic layer14, the barrier layer16and the pinned layer18form a magnetic tunnel junction (MTJ) device30.

In this embodiment, the shape of the patterned pinned layer18may be a circle, an ellipse, a square, or a rectangle, from a top view.

In some embodiments, the magnetic tunnel junction (MTJ) device30may be disposed at any position on the spin Hall metal layer12without limitation.

Referring toFIGS. 2A-2B, in accordance with one embodiment of the disclosure, a method for fabricating a spin-orbit torque magnetoresistive random access memory (SOT MRAM)10is provided.FIGS. 2A-2Bare cross-sectional views of the fabrication method of the SOT MRAM10.

As shown inFIG. 2A, a spin Hall metal layer12is provided.

Next, a free magnetic layer14is disposed on the spin Hall metal layer12. The free magnetic layer14comprises a first area20and a second area22. The second area22is located on both sides of the first area20.

Next, a barrier layer16is disposed on the free magnetic layer14. The barrier layer16comprises a first area24and a second area26. The second area26is located on both sides of the first area24. The first area24of the barrier layer16is disposed on the first area20of the free magnetic layer14. The second area26of the barrier layer16is disposed on the second area22of the free magnetic layer14.

Next, a pinned layer18is disposed on the barrier layer16.

Next, a patterned photoresist layer28is disposed on the pinned layer18.

Next, the pinned layer18is etched using the patterned photoresist layer28as a mask to expose the second area26of the barrier layer16. The patterned photoresist layer28is then removed, as shown inFIG. 2B.

In some embodiments, the pinned layer18is etched by, for example, a plasma etching (PE) process, a reactive ion etching (RIE) process, an ion beam etching (IBE) process, or an inductively coupled plasma etching (ICPE) process.

In some embodiments, the pinned layer18is etched by, for example, a reactive ion etching (RIE) process.

In some embodiments, the etching gas used in the reactive ion etching (RIE) process may comprise carbon monoxide (CO), ammonia (NH3), oxygen, hydrogen, or fluorine (F2) and argon (Ar).

In this embodiment, the stop time of the etching process is controlled and determined by the difference in the etching rate between various materials, and by simultaneously employing an end point detector (EPD) so that the second area26of the barrier layer16can maintain the desired thickness; that is, the thickness h4of the second area26corresponds to the thickness h3of the first area24of the barrier layer16.

Referring toFIG. 3, in accordance with one embodiment of the disclosure, a spin-orbit torque magnetoresistive random access memory (SOT MRAM)10is provided.FIG. 3is a cross-sectional view of the SOT MRAM10.

In this embodiment, the SOT MRAM10comprises a spin Hall metal layer12, a free magnetic layer14, a barrier layer16, and a pinned layer18.

The free magnetic layer14is disposed on the spin Hall metal layer12. The free magnetic layer14comprises a first area20and a second area22. The second area22is located on both sides of the first area20. The thickness h2of the second area22is equal to the thickness h1of the first area20.

The barrier layer16comprises a first area24and a second area26. The second area26is located on both sides of the first area24. The first area24of the barrier layer16is disposed on the first area20of the free magnetic layer14. The second area26of the barrier layer16is disposed on the second area22of the free magnetic layer14.

The pinned layer18is disposed on the first area24of the barrier layer16.

The thickness h4of the second area26is smaller than the thickness h3of the first area24of the barrier layer16. For example, the thickness h4of the second area26is about half the thickness h3of the first area24of the barrier layer16.

In some embodiments, when the thickness h4of the second area26is smaller than the thickness h3of the first area24of the barrier layer16, the thickness h4of the second area26may be any proportionality to the thickness h3of the first area24of the barrier layer16.

In some embodiments, the spin Hall metal layer12comprises heavy metal materials capable of producing large spin Hall effect, for example, tantalum (Ta), platinum (Pt), hafnium (Hf), tungsten (W), zirconium (Zr), or an alloy thereof.

In some embodiments, the thickness of the spin Hall metal layer12is smaller than about 10 nm.

In some embodiments, the free magnetic layer14may comprise a single layer or a composite layer.

In some embodiments, the free magnetic layer14may comprise a single layer of, for example, iron (Fe), cobalt (Co), nickel (Ni), gadolinium (Gd), terbium (Tb), cobalt iron boron (CoFeB) alloy, or cobalt iron (CoFe) alloy.

In some embodiments, the free magnetic layer14may comprise a composite layer of, for example, cobalt iron boron (CoFeB) alloy/tantalum (Ta)/cobalt iron boron (CoFeB) alloy or cobalt iron (CoFe) alloy/tantalum (Ta)/cobalt iron (CoFe).

In some embodiments, the thickness h1of the first area20of the free magnetic layer14is in a range from about 1 nm to about 3 nm.

In some embodiments, the barrier layer16may comprise magnesium oxide (MgO) or aluminum oxide (AlOx).

In some embodiments, the thickness h3of the first area24of the barrier layer16is in a range from about 0.5 nm to about 2 nm.

In some embodiments, the pinned layer18may comprise a single layer or a composite layer.

In some embodiments, the pinned layer18may comprise a single layer of, for example, cobalt iron (CoFe) alloy, cobalt iron boron (CoFeB) alloy, or cobalt nickel (CoNi) alloy.

In the SOT MRAM10, the free magnetic layer14, the barrier layer16and the pinned layer18form a magnetic tunnel junction (MTJ) device30.

In this embodiment, the shape of the patterned pinned layer18and the first area24of the barrier layer16may comprise a circle, an ellipse, a square, or a rectangle, from a top view.

In some embodiments, the magnetic tunnel junction (MTJ) device30may be disposed at any position on the spin Hall metal layer12without limitation.

Referring toFIGS. 4A-4B, in accordance with one embodiment of the disclosure, a method for fabricating a spin-orbit torque magnetoresistive random access memory (SOT MRAM)10is provided.FIGS. 4A-4Bare cross-sectional views of the fabrication method of the SOT MRAM10.

As shown inFIG. 4A, a spin Hall metal layer12is provided.

Next, a free magnetic layer14is disposed on the spin Hall metal layer12. The free magnetic layer14comprises a first area20and a second area22. The second area22is located on both sides of the first area20.

Next, a barrier layer16is disposed on the free magnetic layer14. The barrier layer16comprises a first area24and a second area26. The second area26is located on both sides of the first area24. The first area24of the barrier layer16is disposed on the first area20of the free magnetic layer14. The second area26of the barrier layer16is disposed on the second area22of the free magnetic layer14.

Next, a pinned layer18is disposed on the barrier layer16.

Next, a patterned photoresist layer28is disposed on the pinned layer18.

Next, the pinned layer18is etched using the patterned photoresist layer28as a mask to expose the second area26of the barrier layer16.

Next, the second area26of the barrier layer16is continuously etched such that the thickness h4of the second area26is smaller than the thickness h3of the first area24of the barrier layer16.

The patterned photoresist layer28is then removed, as shown inFIG. 4B.

In some embodiments, the pinned layer18and the barrier layer16are etched by, for example, a plasma etching (PE) process, a reactive ion etching (RIE) process, an ion beam etching (IBE) process, or an inductively coupled plasma etching (ICPE) process.

In some embodiments, the pinned layer18and the barrier layer16are etched by, for example, a reactive ion etching (RIE) process.

In some embodiments, the etching gas used in the reactive ion etching (RIE) process may comprise carbon monoxide (CO), ammonia (NH3), oxygen, hydrogen, or fluorine (F2) and argon (Ar).

In some embodiments, the etch selectivity ratio between the pinned layer18and the barrier layer16is about 3:1 or above.

In this embodiment, the stop time of the etching process is controlled and determined by the difference in the etching rate between various materials and by simultaneously employing an end point detector (EPD) so that the second area26of the barrier layer16can maintain the desired thickness; that is, the thickness h4of the second area26is smaller than the thickness h3of the first area24of the barrier layer16.

Referring toFIG. 5, in accordance with one embodiment of the disclosure, a spin-orbit torque magnetoresistive random access memory (SOT MRAM)10is provided.FIG. 5is a cross-sectional view of the SOT MRAM10.

In this embodiment, the SOT MRAM10comprises a spin Hall metal layer12, a free magnetic layer14, a barrier layer16, and a pinned layer18.

The free magnetic layer14is disposed on the spin Hall metal layer12. The free magnetic layer14comprises a first area20and a second area22. The second area22is located on both sides of the first area20. The thickness h2of the second area22is equal to the thickness h1of the first area20.

The barrier layer16is disposed on the first area20of the free magnetic layer14.

The pinned layer18is disposed on the barrier layer16.

The barrier layer16does not cover the second area22of the free magnetic layer14. That is, the thickness of the second area26of the barrier layer16is substantially zero in this embodiment.

In some embodiments, the spin Hall metal layer12comprises heavy metal materials capable of producing large spin Hall effect, for example, tantalum (Ta), platinum (Pt), hafnium (Hf), tungsten (W), zirconium (Zr), or an alloy thereof.

In some embodiments, the thickness of the spin Hall metal layer12is smaller than about 10 nm.

In some embodiments, the free magnetic layer14may comprise a single layer or a composite layer.

In some embodiments, the free magnetic layer14may comprise a single layer of, for example, iron (Fe), cobalt (Co), nickel (Ni), gadolinium (Gd), terbium (Tb), cobalt iron boron (CoFeB) alloy, or cobalt iron (CoFe) alloy.

In some embodiments, the free magnetic layer14may comprise a composite layer of, for example, cobalt iron boron (CoFeB) alloy/tantalum (Ta)/cobalt iron boron (CoFeB) alloy or cobalt iron (CoFe) alloy/tantalum (Ta)/cobalt iron (CoFe).

In some embodiments, the thickness h1of the first area20of the free magnetic layer14is in a range from about 1 nm to about 3 nm.

In some embodiments, the barrier layer16may comprise magnesium oxide (MgO) or aluminum oxide (AlOx).

In some embodiments, the thickness of the barrier layer16is in a range from about 0.5 nm to about 2 nm.

In some embodiments, the pinned layer18may comprise a single layer or a composite layer.

In some embodiments, the pinned layer18may comprise a single layer of, for example, cobalt iron (CoFe) alloy, cobalt iron boron (CoFeB) alloy, or cobalt nickel (CoNi) alloy.

In the SOT MRAM10, the free magnetic layer14, the barrier layer16and the pinned layer18form a magnetic tunnel junction (MTJ) device30.

In this embodiment, the shape of the patterned pinned layer18and the barrier layer16may comprise a circle, an ellipse, a square, or a rectangle, from a top view.

In some embodiments, the magnetic tunnel junction (MTJ) device30may be disposed at any position on the spin Hall metal layer12without limitation.

Referring toFIGS. 6A-6B, in accordance with one embodiment of the disclosure, a method for fabricating a spin-orbit torque magnetoresistive random access memory (SOT MRAM)10is provided.FIGS. 6A-6Bare cross-sectional views of the fabrication method of the SOT MRAM10.

As shown inFIG. 6A, a spin Hall metal layer12is provided.

Next, a free magnetic layer14is disposed on the spin Hall metal layer12. The free magnetic layer14comprises a first area20and a second area22. The second area22is located on both sides of the first area20.

Next, a barrier layer16is disposed on the free magnetic layer14. The barrier layer16comprises a first area24and a second area26. The second area26is located on both sides of the first area24. The first area24of the barrier layer16is disposed on the first area20of the free magnetic layer14. The second area26of the barrier layer16is disposed on the second area22of the free magnetic layer14.

Next, a pinned layer18is disposed on the barrier layer16.

Next, a patterned photoresist layer28is disposed on the pinned layer18.

Next, the pinned layer18is etched using the patterned photoresist layer28as a mask to expose the second area26of the barrier layer16.

Next, the second area26of the barrier layer16is continuously etched until the second area22of the free magnetic layer14is exposed.

The patterned photoresist layer28is then removed, as shown inFIG. 6B.

In some embodiments, the pinned layer18and the barrier layer16are etched by, for example, a plasma etching (PE) process, a reactive ion etching (RIE) process, an ion beam etching (IBE) process, or an inductively coupled plasma etching (ICPE) process.

In some embodiments, the pinned layer18and the barrier layer16are etched by, for example, a reactive ion etching (RIE) process.

In some embodiments, the etching gas used in the reactive ion etching (RIE) process may comprise carbon monoxide (CO), ammonia (NH3), oxygen, hydrogen, or fluorine (F2) and argon (Ar).

In some embodiments, the etch selectivity ratio between the pinned layer18and the barrier layer16is about 3:1 or above.

In this embodiment, the stop time of the etching process is controlled and determined by the difference in the etching rate between various materials and by simultaneously employing an end point detector (EPD) so that the second area22of the free magnetic layer14can maintain the desired thickness; that is, the thickness h2of the second area22corresponds to the thickness h1of the first area20of the free magnetic layer14.

Referring toFIG. 7, in accordance with one embodiment of the disclosure, a spin-orbit torque magnetoresistive random access memory (SOT MRAM)10is provided.FIG. 7is a cross-sectional view of the SOT MRAM10.

In this embodiment, the SOT MRAM10comprises a spin Hall metal layer12, a free magnetic layer14, a barrier layer16, and a pinned layer18.

The free magnetic layer14is disposed on the spin Hall metal layer12. The free magnetic layer14comprises a first area20and a second area22. The second area22is located on both sides of the first area20.

The barrier layer16is disposed on the first area20of the free magnetic layer14.

The pinned layer18is disposed on the barrier layer16.

The thickness h2of the second area22is smaller than the thickness h1of the first area20of the free magnetic layer14. For example, the thickness h2of the second area22is about half the thickness h1of the first area20of the free magnetic layer14.

In some embodiments, when the thickness h2of the second area22is smaller than the thickness h1of the first area20of the free magnetic layer14, the thickness h2of the second area22may be any proportionality to the thickness h1of the first area20of the free magnetic layer14.

In some embodiments, the spin Hall metal layer12comprises heavy metal materials capable of producing large spin Hall effect, for example, tantalum (Ta), platinum (Pt), hafnium (Hf), tungsten (W), zirconium (Zr), or an alloy thereof.

In some embodiments, the thickness of the spin Hall metal layer12is smaller than about 10 nm.

In some embodiments, the free magnetic layer14may comprise a single layer or a composite layer.

In some embodiments, the free magnetic layer14may comprise a single layer of, for example, iron (Fe), cobalt (Co), nickel (Ni), gadolinium (Gd), terbium (Tb), cobalt iron boron (CoFeB) alloy, or cobalt iron (CoFe) alloy.

In some embodiments, the free magnetic layer14may comprise a composite layer of, for example, cobalt iron boron (CoFeB) alloy/tantalum (Ta)/cobalt iron boron (CoFeB) alloy or cobalt iron (CoFe) alloy/tantalum (Ta)/cobalt iron (CoFe).

In some embodiments, the thickness h1of the first area20of the free magnetic layer14is in a range from about 1 nm to about 3 nm.

In some embodiments, the barrier layer16may comprise magnesium oxide (MgO) or aluminum oxide (AlOx).

In some embodiments, the thickness of the barrier layer16is in a range from about 0.5 nm to about 2 nm.

In some embodiments, the pinned layer18may comprise a single layer or a composite layer.

In some embodiments, the pinned layer18may comprise a single layer of, for example, cobalt iron (CoFe) alloy, cobalt iron boron (CoFeB) alloy, or cobalt nickel (CoNi) alloy.

In the SOT MRAM10, the free magnetic layer14, the barrier layer16and the pinned layer18form a magnetic tunnel junction (MTJ) device30.

In this embodiment, the shape of the patterned pinned layer18, the barrier layer16and the first area20of the free magnetic layer14may comprise a circle, an ellipse, a square, or a rectangle, from a top view.

In some embodiments, the magnetic tunnel junction (MTJ) device30may be disposed at any position on the spin Hall metal layer12without limitation.

Referring toFIGS. 8A-8B, in accordance with one embodiment of the disclosure, a method for fabricating a spin-orbit torque magnetoresistive random access memory (SOT MRAM)10is provided.FIGS. 8A-8Bare cross-sectional views of the fabrication method of the SOT MRAM10.

As shown inFIG. 8A, a spin Hall metal layer12is provided.

Next, a free magnetic layer14is disposed on the spin Hall metal layer12. The free magnetic layer14comprises a first area20and a second area22. The second area22is located on both sides of the first area20.

Next, a barrier layer16is disposed on the free magnetic layer14. The barrier layer16comprises a first area24and a second area26. The second area26is located on both sides of the first area24. The first area24of the barrier layer16is disposed on the first area20of the free magnetic layer14. The second area26of the barrier layer16is disposed on the second area22of the free magnetic layer14.

Next, a pinned layer18is disposed on the barrier layer16.

Next, a patterned photoresist layer28is disposed on the pinned layer18.

Next, the pinned layer18is etched using the patterned photoresist layer28as a mask to expose the second area26of the barrier layer16.

Next, the second area26of the barrier layer16is continuously etched until the second area22of the free magnetic layer14is exposed. The second area22of the free magnetic layer14is then continuously etched such that the thickness h2of the second area22is smaller than the thickness h1of the first area20of the free magnetic layer14.

The patterned photoresist layer28is then removed, as shown inFIG. 8B.

In some embodiments, the pinned layer18, the barrier layer16and the free magnetic layer14are etched by, for example, a plasma etching (PE) process, a reactive ion etching (RIE) process, an ion beam etching (IBE) process, or an inductively coupled plasma etching (ICPE) process.

In some embodiments, the pinned layer18, the barrier layer16and the free magnetic layer14are etched by, for example, a reactive ion etching (RIE) process.

In some embodiments, the etching gas used in the reactive ion etching (RIE) process may comprise carbon monoxide (CO), ammonia (NH3), oxygen, hydrogen, or fluorine (F2) and argon (Ar).

In some embodiments, the etch selectivity ratio between the pinned layer18and the barrier layer16is about 3:1 or above.

In some embodiments, the etch selectivity ratio between the barrier layer16and the free magnetic layer14is about 1:3 or above.

In this embodiment, the stop time of the etching process is controlled and determined by the difference in the etching rate between various materials and by simultaneously employing an end point detector (EPD) so that the second area22of the free magnetic layer14can maintain the desired thickness; that is, the thickness h2of the second area22is smaller than the thickness h1of the first area20of the free magnetic layer14.

In some embodiments, the spin Hall metal layer12comprises heavy metal materials capable of producing large spin Hall effect, for example, tantalum (Ta), platinum (Pt), hafnium (Hf), tungsten (W), zirconium (Zr), or an alloy thereof.

In some embodiments, the thickness of the spin Hall metal layer12is smaller than about 10 nm.

In some embodiments, the free magnetic layer14may comprise a single layer or a composite layer.

In some embodiments, the free magnetic layer14may comprise a single layer of, for example, iron (Fe), cobalt (Co), nickel (Ni), gadolinium (Gd), terbium (Tb), cobalt iron boron (CoFeB) alloy, or cobalt iron (CoFe) alloy.

In some embodiments, the free magnetic layer14may comprise a composite layer of, for example, cobalt iron boron (CoFeB) alloy/tantalum (Ta)/cobalt iron boron (CoFeB) alloy or cobalt iron (CoFe) alloy/tantalum (Ta)/cobalt iron (CoFe).

In some embodiments, the thickness of the free magnetic layer14is in a range from about 1 nm to about 3 nm.

In some embodiments, the barrier layer16may comprise magnesium oxide (MgO) or aluminum oxide (AlOx).

In some embodiments, the thickness of the barrier layer16is in a range from about 0.5 nm to about 2 nm.

In some embodiments, the pinned layer18may comprise a single layer or a composite layer.

In some embodiments, the pinned layer18may comprise a single layer of, for example, cobalt iron (CoFe) alloy, cobalt iron boron (CoFeB) alloy, or cobalt nickel (CoNi) alloy.

In the SOT MRAM10, the free magnetic layer14, the barrier layer16and the pinned layer18form a magnetic tunnel junction (MTJ) device30.

In this embodiment, the shape of the patterned pinned layer18, the barrier layer16and the free magnetic layer14may comprise a circle, an ellipse, a square, or a rectangle, from a top view.

In some embodiments, the magnetic tunnel junction (MTJ) device30may be disposed at any position on the spin Hall metal layer12without limitation.

Referring toFIG. 9, in accordance with one embodiment of the disclosure, a spin-orbit torque magnetoresistive random access memory (SOT MRAM)10is provided.FIG. 9is a top view of the SOT MRAM10.

In this embodiment, the SOT MRAM10comprises a spin Hall metal layer12and a magnetic tunnel junction (MTJ) device30.

The magnetic tunnel junction (MTJ) device30is disposed on the spin Hall metal layer12.

In this embodiment, the magnetic tunnel junction (MTJ) device30comprises a free magnetic layer, a barrier layer and a pinned layer (not shown).

In this embodiment, the shape of the magnetic tunnel junction (MTJ) device30is circular from a top view.

In this embodiment, the SOT MRAM10is arranged with a vertical magnetic tunnel junction (MTJ) device.

Referring toFIG. 10, in accordance with one embodiment of the disclosure, a spin-orbit torque magnetoresistive random access memory (SOT MRAM)10is provided.FIG. 10is a top view of the SOT MRAM10.

In this embodiment, the SOT MRAM10comprises a spin Hall metal layer12and a magnetic tunnel junction (MTJ) device30.

The magnetic tunnel junction (MTJ) device30is disposed on the spin Hall metal layer12.

In this embodiment, the magnetic tunnel junction (MTJ) device30comprises a free magnetic layer, a barrier layer and a pinned layer (not shown).

In this embodiment, the shape of the magnetic tunnel junction (MTJ) device30is elliptical from a top view.

In this embodiment, the SOT MRAM10is arranged with a horizontal magnetic tunnel junction (MTJ) device.

Referring toFIGS. 11A-11D, in accordance with one embodiment of the disclosure, a spin-orbit torque magnetoresistive random access memory (SOT MRAM)10is provided.FIGS. 11A-11Dare top views of the SOT MRAM10.

As shown inFIG. 11A, in this embodiment, the SOT MRAM10comprises a spin Hall metal layer12and a magnetic tunnel junction (MTJ) device30.

The magnetic tunnel junction (MTJ) device30is disposed on the spin Hall metal layer12.

In this embodiment, the magnetic tunnel junction (MTJ) device30comprises a free magnetic layer, a barrier layer and a pinned layer (not shown).

In this embodiment, the shape of the magnetic tunnel junction (MTJ) device30is elliptical from a top view.

In this embodiment, the magnetic tunnel junction (MTJ) device30is disposed at a central position of the spin Hall metal layer12.

As shown inFIG. 11B, in this embodiment, the SOT MRAM10comprises a spin Hall metal layer12and a magnetic tunnel junction (MTJ) device30.

The magnetic tunnel junction (MTJ) device30is disposed on the spin Hall metal layer12.

In this embodiment, the magnetic tunnel junction (MTJ) device30comprises a free magnetic layer, a barrier layer and a pinned layer (not shown).

In this embodiment, the shape of the magnetic tunnel junction (MTJ) device30is elliptical from a top view.

In this embodiment, the magnetic tunnel junction (MTJ) device30is disposed at an upper-left position of the spin Hall metal layer12.

As shown inFIG. 11C, in this embodiment, the SOT MRAM10comprises a spin Hall metal layer12and a magnetic tunnel junction (MTJ) device30.

The magnetic tunnel junction (MTJ) device30is disposed on the spin Hall metal layer12.

In this embodiment, the magnetic tunnel junction (MTJ) device30comprises a free magnetic layer, a barrier layer and a pinned layer (not shown).

In this embodiment, the shape of the magnetic tunnel junction (MTJ) device30is elliptical from a top view.

In this embodiment, the magnetic tunnel junction (MTJ) device30is disposed at a lower-left position of the spin Hall metal layer12.

As shown inFIG. 11D, in this embodiment, the SOT MRAM10comprises a spin Hall metal layer12and a magnetic tunnel junction (MTJ) device30.

The magnetic tunnel junction (MTJ) device30is disposed on the spin Hall metal layer12.

In this embodiment, the magnetic tunnel junction (MTJ) device30comprises a free magnetic layer, a barrier layer and a pinned layer (not shown).

In this embodiment, the shape of the magnetic tunnel junction (MTJ) device30is elliptical from a top view.

In this embodiment, the magnetic tunnel junction (MTJ) device30is disposed on the right side of the spin Hall metal layer12.

Referring toFIGS. 12A-12D, in accordance with one embodiment of the disclosure, a spin-orbit torque magnetoresistive random access memory (SOT MRAM)10is provided.FIGS. 12A-12Dare top views of the SOT MRAM10.

As shown inFIG. 12A, in this embodiment, the SOT MRAM10comprises a spin Hall metal layer12and a magnetic tunnel junction (MTJ) device30.

The magnetic tunnel junction (MTJ) device30is disposed on the spin Hall metal layer12.

In this embodiment, the magnetic tunnel junction (MTJ) device30comprises a free magnetic layer, a barrier layer and a pinned layer (not shown).

In this embodiment, the shape of the magnetic tunnel junction (MTJ) device30is circular from a top view.

In this embodiment, the magnetic tunnel junction (MTJ) device30is disposed at a central position of the spin Hall metal layer12.

As shown inFIG. 12B, in this embodiment, the SOT MRAM10comprises a spin Hall metal layer12and a magnetic tunnel junction (MTJ) device30.

The magnetic tunnel junction (MTJ) device30is disposed on the spin Hall metal layer12.

In this embodiment, the magnetic tunnel junction (MTJ) device30comprises a free magnetic layer, a barrier layer and a pinned layer (not shown).

In this embodiment, the shape of the magnetic tunnel junction (MTJ) device30is circular from a top view.

In this embodiment, the magnetic tunnel junction (MTJ) device30is disposed at an upper-left position of the spin Hall metal layer12.

As shown inFIG. 12C, in this embodiment, the SOT MRAM10comprises a spin Hall metal layer12and a magnetic tunnel junction (MTJ) device30.

The magnetic tunnel junction (MTJ) device30is disposed on the spin Hall metal layer12.

In this embodiment, the magnetic tunnel junction (MTJ) device30comprises a free magnetic layer, a barrier layer and a pinned layer (not shown).

In this embodiment, the shape of the magnetic tunnel junction (MTJ) device30is circular from a top view.

In this embodiment, the magnetic tunnel junction (MTJ) device30is disposed at a lower-left position of the spin Hall metal layer12.

As shown inFIG. 12D, in this embodiment, the SOT MRAM10comprises a spin Hall metal layer12and a magnetic tunnel junction (MTJ) device30.

The magnetic tunnel junction (MTJ) device30is disposed on the spin Hall metal layer12.

In this embodiment, the magnetic tunnel junction (MTJ) device30comprises a free magnetic layer, a barrier layer and a pinned layer (not shown).

In this embodiment, the shape of the magnetic tunnel junction (MTJ) device30is circular from a top view.

In this embodiment, the magnetic tunnel junction (MTJ) device30is disposed on the right side of the spin Hall metal layer12.

The Electrical Test of the SOT MRAM (1)

The electrical test was performed on the spin-orbit torque (SOT) MRAM10as shown inFIG. 1.

By applying a magnetic field, the magnetic tunnel junction (MTJ) device30of the SOT structure was read and written to obtain a complete R-H loop, as shown inFIG. 13. It represents that this process-optimized component can conduct normal read and write operations.

The Electrical Test of the SOT MRAM (2)

The electrical test was performed on the spin-orbit torque (SOT) MRAM10as shown inFIG. 1.

By applying current on the spin Hall metal layer12and the spin Hall effect to generate the spin Hall current, the magnetic tunnel junction (MTJ) device30was read and written to obtain a complete R-J loop, as shown inFIG. 14. It represents that this process-optimized component can conduct read and write operations by the SOT operation mechanism.

The present disclosure provides a top-pinned layer MTJ structure which is able to terminate an etching process at either any thickness position of a barrier layer or any thickness position of a bottom free magnetic layer, used as a component to develop the optimized process technology of the spin-orbit torque (SOT) MRAM. The uniformity of various layers can be achieved using etch selectivity ratios formed between various materials, for example, the etch selectivity ratio between the top pinned layer and the barrier oxide layer or between the barrier oxide layer and the free magnetic layer. In addition, a bottom ultra-thin heavy metal layer can be protected by the residual material of the barrier layer or the free magnetic layer. This component structure not only generates the splitting of the upper and lower spin currents by spin Hall effect, but also achieves the characteristics of the magnetic moment reversal of the free magnetic layer by the spin-orbit effect. Simultaneously, this component structure can overcome the problems that, due to an etching process, a bottom ultra-thin metal layer of a top-pinned layer MTJ of a conventional spin-orbit torque (SOT) structure is damaged which results in uneven operation characteristics and component failure. This process-optimized component structure can significantly improve the production yield of the spin-orbit torque (SOT) MRAM.