Patent Description:
Magnetoresistive random-access memory ("MRAM") is a non-volatile memory technology that stores data through magnetic storage elements. These elements are two ferromagnetic plates or electrodes that can hold magnetization and are separated by a nonmagnetic material, such as a non-magnetic metal or insulator. In general, one of the plates has its magnetization pinned (i.e., a "reference layer"), meaning that this layer has a higher coercivity than the other layer and requires a larger magnetic field or spin-polarized current to change the orientation of its magnetization. The second plate is typically referred to as the free layer and its magnetization direction can be changed by a smaller magnetic field or spin-polarized current relative to the reference layer.

MRAM devices store information by changing the orientation of the magnetization of the free layer. In particular, based on whether the free layer is in a parallel or antiparallel alignment relative to the reference layer, either a "<NUM>" or a "<NUM>" can be stored in each MRAM cell. Due to the spin-polarized electron tunneling effect, the electrical resistance of the cell change due to the orientation of the magnetization of the two layers. The cell's resistance will be different for the parallel and anti-parallel states and thus the cell's resistance can be used to distinguish between a "<NUM>" and a "<NUM>". One important feature of MRAM devices is that they are non-volatile memory devices, since they maintain the information even when the power is off. The two plates can be sub-µm in lateral size and the magnetization direction can still be stable with respect to thermal fluctuations.

Spin transfer torque or spin transfer switching, uses spin-aligned ("polarized") electrons to change the magnetization orientation of the free layer in the magnetic tunnel junction. In general, electrons possess a spin, a quantized number of angular momentum intrinsic to the electron. An electrical current is generally unpolarized, i.e., it consists of <NUM>% spin up and <NUM>% spin down electrons. Passing a current though a magnetic layer polarizes electrons with the spin orientation corresponding to the magnetization direction of the magnetic layer (i.e., polarizer), thus produces a spin-polarized current. If a spin-polarized current is passed to the magnetic region of a free layer in the magnetic tunnel junction device, the electrons will transfer a portion of their spin-angular momentum to the magnetization layer to produce a torque on the magnetization of the free layer. Thus, this spin transfer torque can switch the magnetization of the free layer, which, in effect, writes either a "<NUM>" or a "<NUM>" based on whether the free layer is in the parallel or antiparallel states relative to the reference layer.

<FIG> illustrates a magnetic tunnel junction ("MTJ") stack <NUM> for a conventional MRAM device. As shown, stack <NUM> includes one or more seed layers <NUM> provided at the bottom of stack <NUM> to initiate a desired crystalline growth in the above-deposited layers. Furthermore, MTJ <NUM> is deposited on top of SAF layer <NUM>. MTJ <NUM> includes reference layer <NUM>, which is a magnetic layer, a non-magnetic tunneling barrier layer (i.e., the insulator) <NUM>, and the free layer <NUM>, which is also a magnetic layer. It should be understood that reference layer <NUM> is actually part of SAF layer <NUM>, but forms one of the ferromagnetic plates of MTJ <NUM> when the non-magnetic tunneling barrier layer <NUM> and free layer <NUM> are formed on reference layer <NUM>. As shown in <FIG>, magnetic reference layer <NUM> has a magnetization direction perpendicular to its plane. As also seen in <FIG>, free layer <NUM> also has a magnetization direction perpendicular to its plane, but its direction can vary by <NUM> degrees.

The first magnetic layer <NUM> in the SAF layer <NUM> is disposed over seed layer <NUM>. SAF layer <NUM> also has a antiferromagnetic coupling layer <NUM> disposed over the first magnetic layer <NUM>. Furthermore, a nonmagnetic spacer <NUM> is disposed on top of MTJ <NUM> and a polarizer <NUM> is disposed on top of the nonmagnetic spacer <NUM>. Polarizer <NUM> is a magnetic layer that has a magnetic direction in its plane, but is perpendicular to the magnetic direction of the reference layer <NUM> and free layer <NUM>. Polarizer <NUM> is provided to polarize a current of electrons ("spin-aligned electrons") applied to MTJ structure <NUM>. Further, one or more capping layers <NUM> can be provided on top of polarizer <NUM> to protect the layers below on MTJ stack <NUM>. Finally, a hard mask <NUM> is deposited over capping layers <NUM> and is provided to pattern the underlying layers of the MTJ structure <NUM>, using a reactive ion etch (RIE) process.

Various mechanisms have been proposed to assist the free-layer magnetization switching in magnetic tunnel junction (MTJ) devices such as orthogonal spin transfer for in plane magnetic tunnel junction devices. One issue has been that to realize the orthogonal spin transfer effect for in-plane MTJ structures, large spin currents may be required for switching. The need for large switching currents may limit such device's commercial applicability. One way proposed to reduce switching current is to lower the magnetization of the free layer. However, if the effective magnetization of the free layer is lowered significantly, the orthogonal effect has to be limited so that the free-layer does not go into precessional mode that would make the end state of the free-layer magnetization un-deterministic. This defines the operation window for the in-plane OST structures. In an in-plane device, unlike that shown in <FIG>, the magnetization direction of the reference layer and free layer are in the plane of the layer. Another aspect of in-plane devices is that the thermal stability requirements may limit the size of the MTJ devices to approximately sixty nanometers or higher.

For perpendicular MTJ structures such as those shown in <FIG>, the precession is not an issue. The orthogonal polarizer acts on the free layer magnetization at the initial state, but when the precession takes hold, the fixed orthogonal polarizer <NUM> helps only half the cycle of the free-layer magnetization rotation while it harms the other half of the cycle. This is demonstrated with reference to <FIG> and <FIG>. <FIG> show switching of a free layer <NUM> of an MTJ. As is seen, free layer <NUM> has a magnetization direction <NUM> perpendicular to that of the polarizer <NUM>. The magnetization direction <NUM> of the free layer <NUM> can rotate by <NUM> degrees. <FIG> show precession about the axis of the magnetization vector of free layer <NUM>. During precession, magnetic vector <NUM> begins to rotate about its axis in a cone-like manner such that its magnetization vector <NUM>' deflects from the perpendicular axis <NUM> of free layer <NUM>. For an ideal case, prior to initiating precession, no component of magnetic vector <NUM> is in the plane of free layer <NUM>, once precession starts, a component of magnetic vector <NUM>' can be found both in-plane and orthogonal to free layer <NUM>. As magnetic vector <NUM>' continues to precess (i.e., switch), the rotation of vector <NUM>' extends further from the center of free layer <NUM>, as is seen in <FIG>.

In prior MTJ devices using a polarizer such as polarizer <NUM>, the magnetization direction of polarizer <NUM> is fixed, which is shown in <FIG> and <FIG>. See also <CIT>, which states that the direction of the magnetization of the polarizing layer cannot vary in the presence of current. Prior to current passing through the MTJ, the free layer <NUM> has a magnetization direction <NUM> substantially perpendicular to that of the polarizer <NUM>. While the magnetization direction <NUM> of the free layer <NUM> can rotate by <NUM> degrees, such rotation is normally precluded by the free layer's inherent damping ability <NUM>, which is represented by a vector <NUM> pointing to axis <NUM> (shown as a dashed line in <FIG> as well as <FIG>). Axis <NUM> is perpendicular to the plane of free layer <NUM>. This damping <NUM> has value, defined by the damping constant, which maintains the magnetization direction of the free layer <NUM>.

Passing a current through polarizer <NUM> produces a spin-polarized current, which creates a spin transfer torque <NUM> in the direction of the polarizer <NUM> on the magnetization vector <NUM>. This spin transfer torque from the polarizer adds to the main spin transfer torque that causes free layer magnetization direction switching. In devices like those shown in <FIG>, when the spin transfer torque <NUM> begins to help overcome the damping <NUM> inherent to the free layer <NUM>, the magnetic direction <NUM>' begins to precess about its axis, as shown in <FIG>. As seen in <FIG>, spin transfer torque <NUM> helps the magnetization direction of the free layer <NUM> to precess in a cone-like manner around an axis <NUM> perpendicular to the plane of the layers. When a spin polarized current traverses the stack <NUM>, the magnetization of the free layer <NUM> precesses in a continuous manner (i.e. it turns on itself in a continuous manner as shown in <FIG>) with maintained oscillations until the magnetic direction of free layer <NUM> is opposite the magnetic direction prior to the spin torque causing precession, i.e., the magnetic direction of free layer <NUM> switches by <NUM> degrees.

<FIG> illustrates precession of a free layer <NUM> of an MTJ assisted by spin polarized current provided by polarizing magnetic layer <NUM>. The spin polarized electrons from polarizer <NUM> provide torque <NUM> that helps overcome the damping <NUM> in the first half of the precession <NUM> because the torque <NUM> provided by the spin polarized current is opposite that of the inherent damping <NUM> of the free layer <NUM>. This is shown on the right-hand side of the middle portion of <FIG>. However, the spin polarized electrons from polarizer <NUM> actually harm the switching process during the second half of the precession <NUM>. The reason for this is that the spin of the electrons in the spin polarized current only apply a torque <NUM> in the direction of their polarization. Thus, when the magnetic vector is in the half of the precession cycle <NUM> that is opposite the spin of the polarized electrons, the spin transfer torque <NUM> actually works with the inherent damping <NUM> of free layer <NUM> to make rotation more difficult. This is shown in the left-hand side of the middle portion of <FIG>. Indeed, it is the magnetization vector of the reference layer <NUM> (not shown in <FIG>) that overcomes the damping of free layer <NUM> as well as the spin transfer torque <NUM> during the half of a precession cycle where the spin of the electrons harms precession, and thus it is the reference layer <NUM> that allows for completion of precession.

In these prior devices, because magnetization direction of polarizer <NUM> is fixed, once the precession holds, it has no positive effect on the switching mechanism for a full one-hundred eighty degree precession. This is because polarized electrons will help the spin transfer torque the most when all vectors are closely aligned.

In <CIT>, filed by the same Applicant as the present patent document and published as <CIT>, discloses an MRAM device having a precessional spin current magnetic layer that is physically separated from the free magnetic layer of a magnetic tunnel junction and which is coupled to the free magnetic layer by a non-magnetic spacer. In the device described in this co-pending application, the magnetization direction of the precessional spin current magnetic layer follows precession of the magnetization direction of the free magnetic layer, thereby causing spin transfer torque to assist switching of the magnetization vector of the free magnetic layer.

When using an in-plane precessional spin current magnetic layer with a perpendicular magnetic tunnel junction, it is desirable to maintain the magnetic moment of the precessional spin current magnetic layer in-plane while also reducing its magnetic moment. Unfortunately, many ferromagnetic materials such as CoFeB have interface perpendicular magneto crystalline anisotropy ("IPMA"), thus resulting in a magnetic direction that is out of plane. To avoid IPMA, the thickness of the CoFeB must be increased, generally to thickness greater than <NUM>. However, a <NUM> thick layer of CoFeB layer increases the magnetic moment such that it is equal to or greater than the magnetic moment of the free layer, hence losing the ability to set the in-plane magnetization for low magnetic moment of the precessional spin current magnetic layer independently. This is undesirable because the precessional spin current magnetic layer should remain in plane, and, as discussed, performance may be enhanced with the magnetic moment of the precessional spin current magnetic layer is reduced. This results in strong dipolar fields in the vicinity of the free layer of the magnetic tunnel junction, which decreases free layer stability.

According to an aspect of the present invention, there is provided a method of manufacturing a magnetic device over a substrate as claimed in claim <NUM>. An MRAM device fabricated according to the invention has a magnetic tunnel junction stack having a significantly improved performance of the free layer in the magnetic tunnel junction structure that requires significantly lower switching currents and which significantly reduces switching times for MRAM applications.

A magnetic device manufactured according to the inventive method includes a first synthetic antiferromagnetic structure in a first plane. The synthetic antiferromagnetic structure includes a magnetic reference layer, where the magnetic reference layer has a magnetization vector that is perpendicular to the first plane and has a fixed magnetization direction. The device also includes a non-magnetic tunnel barrier layer in a second plane and disposed over the magnetic reference layer. The device further includes a free magnetic layer in a third plane and disposed over the non-magnetic tunnel barrier layer. The free magnetic layer has a magnetization vector that is perpendicular to the third plane and has a magnetization direction that can precess from a first magnetization direction to a second magnetization direction. The magnetic reference layer, the non-magnetic tunnel barrier layer and the free magnetic layer form a magnetic tunnel junction. The device further includes a non-magnetic spacer in a fourth plane that is disposed over the free magnetic layer. The magnetic coupling layer comprises MgO.

In the magnetic device manufactured according to the inventive method, a precessional spin current magnetic layer is present in a fifth plane that is physically separated from the free magnetic layer and coupled to the free magnetic layer by the non-magnetic spacer. The precessional spin current magnetic layer has a magnetization vector with a magnetization component in the fifth plane which can freely rotate in any magnetic direction. The precessional spin current magnetic layer comprising a material has a face centered cubic (fcc) crystal structure. The device further includes a capping layer in a sixth plane that is disposed over the precessional spin current magnetic layer. During operation of the manufactured device, electrical current is directed through the capping layer, the precessional spin current magnetic layer, the non-magnetic spacer, the free magnetic layer, the non-magnetic tunnel barrier layer, and the magnetic reference layer, wherein electrons of the electrical current are aligned in the magnetic direction of the precessional spin current magnetic layer. The magnetization direction of the precessional spin current magnetic layer is free to follow precession of the magnetization direction of the free magnetic layer, thereby causing spin transfer torque to assist switching of the magnetization vector of the free magnetic layer.

In an embodiment, the magnetization direction of the magnetization vector of the precessional spin current magnetic layer is in the fifth plane.

In an embodiment, the magnetization direction of the precessional spin current magnetic layer has a magnetization component in the fifth plane which can freely rotate in the fifth plane.

In an embodiment, the precessional spin current magnetic layer further comprises a CoFeB layer disposed over the Fe layer and under the fcc crystal structure layer.

In an embodiment, the precessional spin current magnetic layer further comprises a first CoFeB layer and the fcc crystal structure layer comprising the material having the fcc crystal structure and a second CoFeB layer, the Fe layer being disposed over the non-magnetic spacer, the Ru layer being disposed over the Fe layer, the first CoFeB layer being disposed over the Fe layer, the fcc crystal structure layer being disposed over the first CoFeB layer, and the second CoFeB layer being disposed over the fcc crystal structure layer.

In an embodiment, the material having the face centered cubic crystal structure is permalloy comprising nickel (Ni) and iron (Fe).

In an embodiment, the capping layer comprises a layer of TaN.

In an embodiment, the capping layer comprises a layer of MgO.

In an embodiment, the capping layer comprises a layer Ru.

In an embodiment the material having the fcc crystal structure is a NiFe layer, and the precessional spin current magnetic layer further comprises a layer being disposed over the NiFe layer.

In an embodiment, the layer disposed over the NiFe layer comprises CoFeB.

In an embodiment, the precessional spin current magnetic layer is magnetically coupled to the free magnetic layer.

In an embodiment, the precessional spin current magnetic layer is electronically coupled to the free magnetic layer.

In an embodiment, precession of the precessional spin current magnetic layer is synchronized to precession of the free magnetic layer.

In an embodiment, the precessional spin current magnetic layer has a rotation frequency greater than zero.

In an embodiment, the free magnetic layer has an effective magnetic anisotropy such that its easy magnetization axis points away from the perpendicular direction and forms an angle with respect to its perpendicular plane.

The accompanying drawings, which are included as part of the present specification, illustrate the presently preferred embodiments and, together with the general description given above and the detailed description given below, serve to explain and teach the principles of the MTJ devices described herein.

The figures are not necessarily drawn to scale and the elements of similar structures or functions are generally represented by like reference numerals for illustrative purposes throughout the figures. The figures are only intended to facilitate the description of the various embodiments described herein; the figures do not describe every aspect of the teachings disclosed herein and do not limit the scope of the claims.

The following description is presented to enable any person skilled in the art to create and use a precessional spin current structure for a magnetic semiconductor device such as an MRAM device. Representative examples utilizing many of these additional features and teachings, both separately and in combination, are described in further detail with reference to the attached drawings. This detailed description is merely intended to teach a person of skill in the art further details for practicing preferred aspects of the present teachings and is not intended to limit the scope of the claims. Therefore, combinations of features disclosed in the following detailed description may not be necessary to practice the teachings in the broadest sense, and are instead taught merely to describe particularly representative examples of the present teachings. The invention is only defined and limited by the claims.

In the following description, for purposes of explanation only, specific nomenclature is set forth to provide a thorough understanding of the present teachings. However, it will be apparent to one skilled in the art that these specific details are not required to practice the present teachings.

This present patent document discloses a MRAM device that does not use a polarization layer having a fixed magnetization direction. Instead of a polarization layer having a fixed magnetization direction, the MRAM device described in this patent document utilizes a precessional spin current (PSC) magnetic layer <NUM> in conjunction with a perpendicular MTJ <NUM> where the in-plane magnetization component direction of the PSC layer is free to rotate (and is shown, for example, in <FIG> and <FIG>). The PSC magnetic layer <NUM> can rotate with the free-layer magnetization precessional dynamics. This will significantly improve the impact of the spin current in overcoming the inherent damping of the free layer <NUM> since the PSC layer will help the spin torque overcome this damping through the entire orbital motion of the precession cycle rather on only half of the precession. This precessional spin current effect throughout the entire one-hundred eighty degree rotation significantly enhances the freelayer magnetization switching.

<FIG> shows the concept behind the MRAM device using a PSC magnetic layer <NUM> having magnetization vector <NUM> that rotates instead of a polarization layer <NUM> having a magnetic vector with a fixed magnetization direction. The free layer <NUM> in this embodiment is similar to the free layer <NUM> previously discussed, in that it has an inherent damping characteristic <NUM> that can be overcome with the assistance of spin transfer torque. However, the embodiment shown in <FIG> replaces polarizing layer <NUM> with PSC magnetic layer <NUM>. As seen in the bottom portion of <FIG>, the direction of the spin transfer torque <NUM> created by spin current passing through free layer <NUM> changes with the rotation of the magnetization direction of the PSC magnetic layer <NUM>. As seen in the middle of <FIG>, spin transfer torque <NUM> helps the magnetization direction <NUM>' of the free layer <NUM> to precess in a cone-like manner around an axis <NUM> perpendicular to the plane of the layers. <FIG> shows a progression of rotation of the magnetic direction <NUM>' about axis <NUM>. As discussed, when a spin polarized current traverses the device, the magnetization of the free layer <NUM> precesses in a continuous manner (i.e. it turns on itself in a continuous manner as shown in <FIG>) with maintained oscillations until the magnetic direction of free layer <NUM> is opposite the magnetic direction prior to the spin torque causing precession, i.e., the magnetic direction of free layer <NUM> switches by <NUM> degrees. The precessional spin current layer <NUM> and the free-layer <NUM> are magnetically and/or electronically coupled such that the magnetization direction of the magnetization vector <NUM> of the PSC magnetic layer <NUM> is free to follow the precessional rotation of the magnetic vector of the free layer <NUM>. This can be seen in <FIG>.

As seen in on the right-hand side of <FIG>, the spin polarized electrons provide torque <NUM> helps to overcome the damping <NUM> in the first half of the precession <NUM> because the torque <NUM> provided by the spin polarized current is opposite that of the inherent damping <NUM> of the free layer <NUM>. As discussed, the magnetization direction of magnetization vector <NUM> of PSC magnetic layer <NUM> rotates. Thus, the polarization of electrons of the spin current created by PSC magnetic layer <NUM> changes as well. This means that the direction of torque <NUM> exerted on magnetic vector of free layer <NUM> changes as well, which is seen on the bottom of <FIG>. Thus, unlike prior devices having a fixed polarization magnetic layer <NUM>, the spin of the electrons in the spin polarized current applies a torque <NUM> in both halves of the precession cycle, including the half of the precession cycle <NUM> where devices with fixed polarization magnetic layers <NUM> actually harmed precession. This is seen in the left-hand side of <FIG>. As is seen, the torque <NUM> continues to help overcome the inherent damping <NUM> of free layer <NUM> throughout the entire precession cycle. Thus, devices using PSC magnetic structure <NUM> can provide spin transfer torque <NUM> for an entire switching cycle.

The precessional vector <NUM> of the PSC magnetic layer <NUM> is free to follow the precessional rotation of the magnetic vector of the free layer <NUM>. The magnetization direction of the free layer is switched by the spin torque <NUM> from the reference layer <NUM> where the direction of the current defines the final state.

A memory cell with a precessional spin current MTJ structure <NUM> is shown in <FIG>. Memory cell <NUM> is formed on a substrate, which can be silicon or other appropriate materials, and can include complementary metal oxide semiconductor (CMOS) circuitry fabricated thereon. MTJ structure <NUM> includes one or more seed layers <NUM> provided at the bottom of stack <NUM> to initiate a desired crystalline growth in the above-deposited layers. A first synthetic antiferromagnetic (SAF) layer <NUM> is disposed over seed layer <NUM>. First SAF layer <NUM> is a magnetic layer having a magnetization direction that is perpendicular to its plane. Details of the construction of first SAF layer <NUM> will be discussed below. An anti-ferromagnetic (AFM) coupling layer <NUM> is disposed over first SAF layer <NUM>. AFM coupling layer <NUM> is a non-magnetic layer. A second SAF layer <NUM> is disposed over AFM coupling layer <NUM>. Second SAF layer <NUM> has a magnetic direction that is perpendicular to its plane. The magnetic direction of first SAF layer <NUM> and second SAF layer <NUM> are antiparallel, as is shown in <FIG>. Details of the construction of second SAF layer <NUM> will also be discussed below. A ferromagnetic coupling layer <NUM> is placed over second SAF layer <NUM>. Ferromagnetic coupling layer <NUM> is a non-magnetic layer. MTJ <NUM> is deposited over ferromagnetic coupling layer <NUM>. MTJ <NUM> includes reference layer <NUM>, tunneling barrier layer (i.e., the insulator) <NUM> and free layer <NUM>. Reference layer <NUM> of MTJ <NUM> is fabricated over ferromagnetic coupling layer <NUM>. Tunneling barrier layer <NUM> of MTJ <NUM> is fabricated over reference layer <NUM>. Free layer <NUM> of MTJ <NUM> is fabricated over tunneling barrier layer <NUM>. Note that synthetic antiferromagnetic layer <NUM> technically also includes ferromagnetic coupling layer <NUM> and reference layer <NUM>, but are shown separately here for explanation purposes.

As shown in <FIG>, the magnetization vector of reference layer <NUM> has a magnetization direction that is perpendicular to its plane. As also seen in <FIG>, free layer <NUM> also has a magnetization vector that is perpendicular to its plane, but its direction can vary by <NUM> degrees. In addition, free layer <NUM> design may include magnetization of the free layer <NUM> pointing a few degrees away from its perpendicular axis. The tilted angle of the free layer magnetization can be due to interaction with the PSC magnetic layer <NUM> or due to magnetocrystalline anisotropy, will additionally help switching of the free layer magnetization by improving the initiation of the switching. Because reference layer <NUM> and free layer <NUM> each have a magnetic direction that is perpendicular to their respective planes, MTJ <NUM> is known as a perpendicular MTJ.

A nonmagnetic spacer <NUM> is disposed over of MTJ <NUM>. PSC magnetic layer <NUM> is disposed over nonmagnetic spacer <NUM>. In one embodiment, PSC magnetic layer <NUM> has a magnetization vector having a magnetic direction parallel to its plane, and is perpendicular to the magnetic vector of the reference layer <NUM> and free layer <NUM>. One or more capping layers <NUM> are provided on top of PSC layer <NUM> to protect the layers below on MTJ stack <NUM>.

Nonmagnetic spacer <NUM> has a number of properties. For example, nonmagnetic spacer <NUM> physically separates free layer <NUM> and PSC layer <NUM>. Nonmagnetic spacer <NUM> promotes strong magnetic and/or electronic coupling such that the magnetic direction of the PSC magnetic layer <NUM> is free to follow the precession cycle of the free layer <NUM>. In other words, nonmagnetic spacer <NUM> couples the magnetic direction of the PSC magnetic layer <NUM> to the magnetic direction of the free layer <NUM>. Nonmagnetic spacer <NUM> transmits spin current efficiently from the PSC magnetic layer <NUM> into the free layer <NUM> because it preferably has a long spin diffusion length. Nonmagnetic spacer <NUM> also promotes good microstructure and high tunneling magnetoresistance (TMR) and helps keep the damping constant of the free layer <NUM> low.

PSC magnetic layer <NUM> has at least the following properties. First, in one embodiment, the magnetization direction of PSC magnetic layer <NUM> is in the plane of the layer but is perpendicular to magnetization direction of free layer <NUM>. In other embodiments such as shown in <FIG>, the magnetization direction of PSC magnetic layer <NUM> can have a horizontal component X and perpendicular component Z such that the angle Θ between the plane of free layer <NUM> and the magnetic direction <NUM> of PSC magnetic layer <NUM> can be anywhere between <NUM> and less than <NUM> degrees, although, as discussed, the angle is as close to zero as feasible so that the magnetic direction remains in-plane. Likewise, as shown, the magnetization vector can also spin in a rotational vector, shown in <FIG> as cone-like rotation <NUM> while precessing about its perpendicular axis. Note that the angle Θ between the plane of free layer <NUM> and the magnetic direction <NUM> of PSC magnetic layer <NUM> will vary in this situation.

As seen in <FIG> and discussed above, PSC magnetic layer <NUM> has a magnetic direction that is in the plane of the layer. Because materials having face centered cubic (fcc) crystalline structures tend to have high in-plane anisotropy, they are used in the embodiments described herein for in-plane PSC magnetic layer <NUM>. In an embodiment, PSC magnetic layer <NUM> comprises a NiFe alloy having an fcc crystal structure. Ni-Fe compositions like permalloy (which comprises approximately <NUM>% nickel and <NUM>% Fe iron) have high magnetic permeability, soft magnetic properties (e.g., low easy axis coercivity and virtually no hard axis coercivity) and provide good spin polarization of electrons passing there through. Note also that permalloy does not possess perpendicular magneto crystalline anisotropy ("PMA"). PMA is undesirable for in-plane magnetic layers, and is another reason to use permalloy.

Using a Ni-Fe permalloy results in an in-plane PSC layer <NUM> with magnetic moments that are lower than the magnetic moment of free layer <NUM>, and can facilitate desired magnetization of PSC layer <NUM>.

Seed layer <NUM> in the MTJ structure shown in <FIG> preferably comprises Ta, TaN, Cr, Cu, CuN, Ni, Fe or alloys thereof. First SAF layer <NUM> preferably comprises either a Co/Ni or Co/Pt multilayer structure. Second SAF layer <NUM> preferably comprises either a Co/Ni or Co/Pt multilayer structure plus a thin non-magnetic layer comprised of tantalum having a thickness of two to five Angstroms and a thin CoFeB layer (. <NUM> to three nanometers). Anti-ferromagnetic coupling layer <NUM> is preferably made from Ru having thickness in the range of three to ten Angstroms. Ferromagnetic coupling layer <NUM> can be made of Ta, W, Mo or Hf having a thickness in the range of one to eight Angstroms. Tunneling barrier layer <NUM> is preferably made of an insulating material such as MgO, with a thickness of approximately ten Angstroms. Free layer <NUM> is preferably made with CoFeB deposited on top of tunneling barrier layer <NUM>. Free layer <NUM> can also have layers of Fe, Co, Ni or alloys thereof. Spacer layer <NUM> over MTJ <NUM> is made of <NUM>-<NUM> Angstroms of MgO.

The manner in which a bit is written using the precessional spin current MTJ structure <NUM> will now be described. In particular, an electrical current is supplied, for example, by a current source <NUM>, which passes electrical current through the precessional spin current magnetic layer <NUM>, the non-magnetic spacer <NUM>, the free magnetic layer <NUM>, the non-magnetic tunneling barrier layer <NUM>, and the reference layer <NUM>. The electrons of the electrical current passing through the precessional spin current magnetic layer <NUM> become spin polarized in the magnetic direction thereof, thus creating a spin polarized current that passes through non-magnetic spacer layer <NUM>, free magnetic layer <NUM>, tunneling barrier layer <NUM>, and reference magnetic layer <NUM>. The spin polarized current exerts a spin transfer torque on free magnetic layer <NUM>, which helps overcome the inherent damping of the magnetic material making up the free layer <NUM>. This assists the free magnetic layer <NUM> to precess about its axis, which is shown in <FIG>.

Once the magnetic direction of the free magnetic layer <NUM> begins to precess, the magnetic direction of the PSC magnetic layer <NUM> begins to rotate, as is also seen in <FIG>. This rotation is caused by the magnetic and/or electronic coupling between the free magnetic layer <NUM> and the PSC magnetic layer <NUM> through the non-magnetic spacer <NUM>. The rotation of the magnetic direction of the PSC magnetic layer <NUM> causes the spin polarization of the electrons of the electrical current to change in a manner corresponding to the magnetic direction of the PSC magnetic layer <NUM>. Because the spin of the electrons of the spin polarized current corresponds to the magnetic direction of PSC magnetic layer <NUM>, and the magnetic direction of PSC magnetic layer <NUM> follows the precession of free magnetic layer <NUM>, the spin of the electrons applies spin transfer torque to the free layer <NUM> in a direction that varies through an entire switching cycle. Thus, devices using PSC magnetic layer <NUM> can provide spin transfer torque <NUM> for an entire switching cycle.

In particular, the structure described herein utilizing PSC magnetic layer <NUM> and spacer layer <NUM> creates precessional magnetization that provides spin current to the free layer <NUM> of an MTJ throughout the whole precession cycle and therefore significantly enhance the free layer switching process, which will result in faster write times.

A flowchart showing a method <NUM> of manufacturing an embodiment of an MRAM stack <NUM> is illustrated in Figs. MRAM stack <NUM> is illustrated in <FIG>. MRAM stack will be formed on a substrate, which in an embodiment can be a silicon substrate and in other embodiments can be any other appropriate substrate material. In step <NUM> seed layer <NUM> is deposited. In an embodiment, seed layer <NUM> can be constructed by depositing, at step <NUM>, a TaN layer <NUM> and then, at step <NUM>, depositing a Cu layer <NUM>. In an embodiment, TaN layer <NUM> is a thin film having a thickness of five nanometers and Cu layer <NUM> is a thin film having a thickness of five nanometers. In alternative embodiments, TaN layer <NUM> can have a thickness ranging from <NUM> to <NUM> nanometers while Cu layer <NUM> can have a thickness ranging from <NUM> to <NUM> nanometers.

At step <NUM>, first perpendicular synthetic antiferromagnetic layer <NUM> is deposited. In an embodiment, first perpendicular synthetic antiferromagnetic layer <NUM> can comprise a Pt layer <NUM> (deposited at step <NUM>), a Co/Pt multilayer <NUM> (deposited at step <NUM>) and a Co layer <NUM> (deposited at step <NUM>). In an embodiment, Pt layer <NUM> is a Pt thin film having a thickness of <NUM> nanometers. In other embodiments, Pt layer <NUM> can comprise a Pt thin film having a thickness ranging from <NUM> to <NUM> nanometers. Co/Pt multilayer <NUM> can comprise a thin film of Co having a thickness of <NUM> nanometers and a thin film of Pt having a thickness of <NUM> nanometers. In other embodiments, the Co layer of Co/Pt multilayer <NUM> can have a thickness of <NUM> to <NUM> nanometers and the Pt layer of Co/Pt multilayer <NUM> can have a thickness ranging from <NUM> to <NUM> nanometers. In an embodiment, Co/Pt multilayer <NUM> is repeated such that Co/Pt multilayer <NUM> comprises six Co/Pt multilayers. In an embodiment, Co layer <NUM> is a thin film having a thickness of <NUM> nanometers. In other embodiments, Co layer <NUM> can have a thickness ranging from <NUM> to <NUM> nanometers.

As seen in <FIG>, first perpendicular synthetic antiferromagnetic layer <NUM> has a magnetic vector having a direction perpendicular to its plane. The magnetic direction of first perpendicular synthetic antiferromagnetic layer <NUM> is fixed and will not change directions (i.e., rotate or precesses) under normal operating conditions. The thickness of the layers are selected to have high anisotropy while managing stray fields on free layer <NUM>.

At step <NUM>, exchange coupling layer <NUM> is deposited. In an embodiment, exchange coupling layer <NUM> comprises an Ru thin film having a thickness of <NUM> nanometers, and in other embodiments can range from <NUM> to <NUM> nanometers.

At step <NUM>, second perpendicular synthetic antiferromagnetic layer <NUM> is fabricated. Fabrication of second perpendicular synthetic antiferromagnetic layer <NUM> (step <NUM>) comprises many steps, and includes fabrication of reference layer <NUM> of magnetic tunnel junction <NUM>, as will be discussed. At step <NUM>, Co layer <NUM> is deposited. In an embodiment, Co layer <NUM> is a thin film having a thickness of <NUM> nanometers and in other embodiments, can have a thickness of <NUM> to <NUM> nanometers. Thereafter, at step <NUM>, a Co/Pt multilayer <NUM> is deposited. In an embodiment, Co/Pt multilayer <NUM> comprises a thin film of Co having a thickness of <NUM> nanometers and a thin film of Pt having a thickness of <NUM> nanometers. In other embodiments, the thin film of Co can have a thickness of <NUM> to <NUM> nanometers while the thin film of Pt can have a thickness of <NUM> to <NUM> nanometers. Moreover, Co/Pt multilayer <NUM> can comprise multiple Co/Pt layers as described herein. In an embodiment, Co/Pt multilayer <NUM> has two Co/Pt multilayers with the thickness properties described above. After depositing Co/Pt multilayer <NUM> at step <NUM>, the method described herein deposits a cobalt layer <NUM> at step <NUM>. In an embodiment, Co layer <NUM> is a thin film having a thickness of <NUM> nanometers, while other embodiments, Co layer <NUM> can have a thickness in the range of <NUM> to <NUM> nanometers. Together, Co layer <NUM>, Co/Pt layer <NUM> and Co layer <NUM> form a magnetic structure. The magnetic direction of the combination of Co layer <NUM>, Co/Pt layer <NUM> and Co layer <NUM> is fixed, perpendicular to the plane of each layer, and antiparallel to the magnetic direction of first perpendicular synthetic antiferromagnetic layer <NUM>. The magnetic properties of the combination of Co layer <NUM>, Co/Pt layer <NUM> and Co layer <NUM> will interact with the magnetic properties of reference layer <NUM> of second perpendicular synthetic antiferromagnetic layer <NUM> to generate a magnetic vector having a fixed magnetic direction that is also perpendicular to the plane of each layer of second perpendicular synthetic antiferromagnetic layer <NUM> (although variations of a several degrees are within the scope of what is considered perpendicular) and antiparallel to the magnetic direction of first perpendicular synthetic antiferromagnetic layer <NUM>. These magnetic vectors are illustrated and <FIG>, where it can be seen that the perpendicular synthetic antiferromagnetic layer <NUM> has a fixed and perpendicular magnetic direction that is antiparallel to the magnetic direction of first perpendicular synthetic antiferromagnetic layer <NUM>.

After deposition of Co layer <NUM> (step <NUM>), a ferromagnetic coupling layer <NUM> is deposited (step <NUM>). In an embodiment, ferromagnetic coupling layer <NUM> is a thin film of Ta having a thickness of <NUM> nanometers. In other embodiments, ferromagnetic coupling layer <NUM> can be a thin film of Ta, W, Hf or Mo (or other appropriate material) having a thickness ranging from <NUM> to <NUM> nanometers.

After deposition of ferromagnetic coupling layer <NUM> at step <NUM>, reference layer <NUM> is deposited (step <NUM>). Step <NUM>, fabrication of reference layer <NUM>, comprises several steps, including deposition of magnetic layer <NUM> (step <NUM>), deposition of a tungsten (W) layer <NUM> (step <NUM>) and deposition of magnetic layer <NUM> (step <NUM>). In an embodiment, magnetic layer <NUM> comprises a thin film of CoFeB having a thickness of <NUM> nanometers, where the alloy is sixty (<NUM>) percent Fe, twenty (<NUM>) percent Co and twenty (<NUM>) percent B. W layer <NUM> comprises a thin film of W having a thickness of <NUM> nanometers. Magnetic layer <NUM> comprises a thin film of CoFeB having a thickness of <NUM> nanometers, where the alloy is sixty (<NUM>) percent Fe, twenty (<NUM>) percent Co and twenty (<NUM>) percent B. In other embodiments, magnetic layer <NUM> can comprise a thin film of CoFeB having a thickness ranging from <NUM> to <NUM> nanometers, W layer <NUM> can comprise a thin film having a thickness of <NUM> to <NUM> nanometers, and magnetic layer <NUM> can comprise a thin film of CoFeB having a thickness of <NUM> to <NUM> nanometers.

Reference layer <NUM> is constructed using magnetic materials so that it has a magnetic vector having a magnetic direction perpendicular to its plane, is fixed in direction, and is antiparallel to the magnetic direction of first perpendicular synthetic antiferromagnetic layer <NUM>. As discussed and as seen in <FIG>, the collective materials of the second perpendicular synthetic antiferromagnetic layer <NUM> have a magnetic vector having a magnetic direction that is perpendicular to the plane of each of its collective layers, is fixed in direction and antiparallel to the magnetic direction of first perpendicular synthetic antiferromagnetic layer <NUM>. Note that the particular magnetic direction of first perpendicular synthetic antiferromagnetic layer <NUM> and second perpendicular synthetic antiferromagnetic layer <NUM> is not important, so long as they are perpendicular to their respective planes and antiparallel to each other.

As discussed, reference layer <NUM> is one of the structures forming magnetic tunnel junction <NUM>. The flowchart showing the method of manufacturing MRAM stack <NUM>, including magnetic tunnel junction <NUM>, continues on <FIG>. At step <NUM>, non-magnetic tunneling barrier layer <NUM> is deposited on reference layer <NUM>. In an embodiment, nonmagnetic tunneling barrier <NUM> is formed as a thin film of an insulating material, e.g., MgO. The purpose of non-magnetic tunneling barrier <NUM> is discussed above. Manufacture of magnetic tunnel junction <NUM> continues at step <NUM>, when free layer <NUM> is deposited over non-magnetic tunneling barrier <NUM>. Fabrication of free layer <NUM> comprises several steps. At step <NUM>, a magnetic layer <NUM> is deposited over nonmagnetic tunneling barrier <NUM>. In an embodiment, magnetic layer <NUM> is comprised of a thin film of CoFeB having a thickness of <NUM> nanometers, where the alloy is sixty (<NUM>) percent Fe, twenty (<NUM>) percent Co and twenty (<NUM>) percent B. In other embodiments, magnetic layer <NUM> can comprise a thin film of CoFeB or other suitable magnetic material having a thickness ranging from <NUM> to <NUM> nanometers. Manufacture of free layer <NUM> continues at step <NUM>, where a W layer <NUM> is deposited. In an embodiment, W layer <NUM> comprises a thin film of W having a thickness of <NUM> nanometers, and in other embodiments can a thickness ranging from <NUM> to <NUM> nanometers. At step <NUM>, manufacture of free layer <NUM> continues with forming magnetic layer <NUM>. In an embodiment, magnetic layer <NUM> can comprise a thin film of CoFeB having a thickness of <NUM> nanometers, where the alloy is sixty (<NUM>) percent Fe, twenty (<NUM>) percent Co and twenty (<NUM>) percent B. In other embodiments, magnetic layer <NUM> can comprise a thin film of CoFeB or other suitable magnetic material having a thickness ranging from <NUM> to <NUM> nanometers.

Collectively, magnetic layers <NUM> and <NUM>, along with non-magnetic W layer <NUM>, form free magnetic layer <NUM>. Free magnetic layer <NUM> has a magnetic vector having a magnetic direction perpendicular to its plane. In addition, free magnetic layer <NUM> design may include magnetization of the free layer <NUM> pointing a few degrees away from its perpendicular axis. The tilted angle of the free layer magnetization can be due to interaction with the PSC magnetic layer <NUM> or due to magnetocrystalline anisotropy, will additionally help switching of the free layer magnetization by improving the initiation of the switching. As seen in <FIG>, the magnetic direction of free magnetic layer <NUM> can switch one hundred eighty (<NUM>) degrees from one direction to another, antiparallel, direction.

After fabrication of magnetic tunnel junction <NUM> at step <NUM>, step <NUM> is performed in which a spacer <NUM> is deposited. In an embodiment, spacer <NUM> can comprise a thin film of MgO having a thickness of <NUM> nanometers. In other embodiments, spacer layer <NUM> can comprise a thin film of MgO having a thickness ranging from <NUM> to <NUM> nanometers.

After deposition of spacer layer <NUM>, precessional spin current magnetic layer <NUM> is deposited (step <NUM>). As seen in <FIG>, manufacture of precessional spin current magnetic layer <NUM> comprises several steps. At step <NUM>, magnetic Fe layer <NUM> is fabricated over spacer layer <NUM>. In an embodiment, magnetic Fe layer <NUM> comprises a thin film of Fe having a thickness of <NUM> nanometers. In other embodiments, magnetic Fe layer <NUM> can comprise a thin film of Fe having a thickness ranging from <NUM> to <NUM> nanometers.

At step <NUM>, Ru layer <NUM> is deposited over magnetic Fe layer <NUM>. In an embodiment, Ru layer <NUM> can comprise a thin film of Ru having a thickness of <NUM> nanometers, and in other embodiments can comprise a thin film of Ru having a thickness ranging from <NUM> to <NUM> nanometers.

At step <NUM>, a magnetic NiFe layer <NUM> is deposited. In an embodiment, magnetic NiFe layer <NUM> comprises eighty (<NUM>) percent Ni and twenty (<NUM>) percent Fe, and has a thickness of <NUM> nanometers. In other embodiments, NiFe layer <NUM> can have a thickness ranging between <NUM> to <NUM> nanometers. NiFe layer <NUM> can also comprise multiple layers. In one such embodiment, layer <NUM> comprises a thin film of CoFeB and NiFe. In another embodiment, layer <NUM> comprises NiFe layer in between layers of CoFeB.

After manufacture of precessional spin current magnetic layer <NUM> at step <NUM>, a capping layer <NUM> is deposited (step <NUM>). Manufacture of capping layer <NUM> can comprise depositing TaN layer <NUM> (step <NUM>) and depositing Ru layer (step <NUM>). In an embodiment, TaN layer <NUM> comprises a thin film of TaN having a thickness of <NUM> nanometers, while in other embodiments, TaN layer <NUM> can have a thickness ranging from <NUM> to <NUM> nanometers. In an embodiment, Ru layer <NUM> comprises a thin film of Ru having a thickness of ten (<NUM>) nanometers, while in other embodiments, Ru layer <NUM> can have a thickness ranging from <NUM> to <NUM> nanometers. In other embodiments, capping layer <NUM> comprise a layer of Ru (with no TaN) or a layer of MgO. The selection of a particular capping structure is influenced, among several reasons, by the particular annealing temperature to be used. This is due to the fact that these particular materials will have different characteristics depending on the annealing temperature.

Finally, at step <NUM>, a hard mask <NUM> is deposited. Hard mask <NUM> can comprise a layer of TaN having a thickness of <NUM> nanometers.

As shown in <FIG>, precessional spin current magnetic layer <NUM> has magnetic direction that is in in-plane, and which can freely rotate in any magnetic direction. It is desirable for the magnetic vector of precessional spin current magnetic layer <NUM> to remain in-plane while it rotates. This is due to the fact, as seen in <FIG>, that the more the magnetic vector of precessional spin current magnetic layer <NUM> remains in plane during rotation, the more torque can be excerpted on the magnetic free layer <NUM>, which aids in overcoming the damping <NUM> of free layer <NUM>. Because it is desirable to keep the magnetic vector of precessional spin current magnetic layer <NUM> in-plane during rotation, the embodiments described herein utilize materials having high in-plane anisotropy.

Permalloy is a NiFe alloy having a face centered crystal structure. Permalloy comprised of approximately eighty (<NUM>) percent Ni and twenty (<NUM>) percent Fe and has soft magnetic properties (e.g., low easy axis coercivity and almost no hard axis coercivity), and has good spin polarization. Using permalloy for layer <NUM> of precessional spin current magnetic layer <NUM> (which resides at the PSC layer <NUM>-TaN layer <NUM> interface) thus provides an in-plane magnetic direction with magnetic moments that can be lower than the free layer magnetization.

Thus, in addition to NiFe layer <NUM>, precessional spin current magnetic layer <NUM> can include an additional layer of Co, CoFeB or other Co alloys at the interface with TaN layer <NUM> and also at the interface of NiFe layer <NUM> and Ru layer <NUM>. One example of which could be a thin film of CoFeB (not shown in <FIG>) in between NiFe layer <NUM> and TaN layer <NUM> as well as between NiFe layer <NUM> and Ru layer <NUM>. In such an embodiment, the CoFeB layer in between NiFe layer <NUM> and Ru layer <NUM> can have a thickness ranging from one Angstrom to ten Angstroms. Use of CoFeB layer can avoid the strong intermixing of NiFe layer <NUM> with TaN layer <NUM>. Note that in other embodiments, precessional spin current magnetic layer <NUM> may also have other layers to improve the interface properties/performance in between NiFe layer <NUM>, TaN layer <NUM> and Ru layer <NUM>. Examples of such additional materials include Co or alloys including Co.

Other materials can be used at the interface of precessional spin current magnetic layer <NUM> and TaN layer <NUM>, examples of which include Co, Fe, and alloys containing these elements such as CoFeB. Likewise, choosing different Co-Fe ratios with various interfacial layers may make it possible to obtain desired magnetizations for precessional spin current magnetic layer <NUM>. Other embodiments of MRAM stack devices that may not be fabricated by the inventive method are shown in <FIG> and <FIG>. In these embodiments, the structures are similar to the embodiment described in the context of Figs. 6A-6B and <FIG>, the difference being the structure of the precessional spin current magnetic layer <NUM>. In the MRAM device <NUM> shown in <FIG>, precessional spin current magnetic layer <NUM> comprises Fe layer <NUM> disposed over spacer <NUM>. Fe layer <NUM> can comprise a thin film of Fe having a thickness of <NUM> to <NUM> nanometers. In this embodiment, precessional spin current magnetic layer <NUM> further comprises CoFeB layer <NUM>. CoFeB layer <NUM> can have a thickness ranging from <NUM> to <NUM> nanometers.

Another embodiment of MRAM stack <NUM> is shown in <FIG>. In the embodiment shown in <FIG>, precessional spin current magnetic layer <NUM> comprises Fe layer <NUM> over spacer <NUM>. Fe layer <NUM> comprises a thin film of Fe having a thickness ranging from <NUM> to <NUM> nanometers. NiFe layer <NUM> is disposed over Fe layer <NUM>. NiFe layer <NUM>, such as permalloy, as discussed, is a material having a face centered cubic crystal structure and can have a thickness ranging from <NUM> to <NUM> nanometers. As in embodiments discussed herein, NiFe layer <NUM> can be eighty percent Ni and twenty percent Fe. In this embodiment, precessional spin current magnetic layer <NUM> also comprises CoFeB layer <NUM>. CoFeB layer <NUM> can have a thickness ranging from <NUM> to <NUM> nanometers.

The materials are chosen so that the magnetization of precessional spin current magnetic layer <NUM> can be set independently while also controlling the out of plane magnetization component of the PSC layer that impacts the freelayer switching performance.

<FIG> is a graph of the thin film vibrating sample magnetometer (VSM) major hysteresis loop data for perpendicular magnetic tunnel junction devices having a precessional spin current magnetic layer <NUM>. To obtain this VSM) major hysteresis loop (labeled as <NUM> in <FIG>), a DC field was applied. The applied field started at -<NUM> kA/m (-<NUM> Oersteds), which then decreased to <NUM> kA/m (<NUM> Oersteds), before rising to +<NUM> kA/m (<NUM> Oersteds). The applied field was then decreased steadily from +<NUM> kA/m (<NUM> Oersteds) to <NUM> kA/m (<NUM> Oersteds), before increasing to -<NUM> kA/m (-<NUM> Oersteds). Positive and negative signs of the DC applied field indicate in-plane applied field directions of the field sweep. VSM measurements, shown as normalized magnetic moment on the Y axis of the graph in <FIG>, were taken with the DC magnetic field applied in the plane of the sample, i.e., along the hard axis of the magnetic tunnel junction <NUM>. The sharp transition around zero applied field (<NUM> kA/m (<NUM> Oersteds)) pointed to by arrows 1110A and 1110B, indicates that precessional spin current magnetic layer <NUM> is in-plane magnetized, i.e., magnetized along the easy axis.

<FIG> shows the ferromagnetic resonance of a magnetic tunnel junction device <NUM> having precessional spin current magnetic layer <NUM> measured at twenty four (<NUM>) GHz. The magnetic field was applied in perpendicular direction. Dashed line <NUM> at <NUM> kA/m (<NUM> Oersteds) indicates the region boundary ω)/γ ~<NUM> kA/m (<NUM> kGauss) at <NUM> between in-plane precessional spin current magnetic layer <NUM> and perpendicular magnetized free magnetic layer <NUM>. According to the resonance equation: ω/γ = Hres - 4πMeff, resonance of precessional spin current magnetic layer <NUM> indicates strong in-plane magnetization. The effective magnetization values show effective perpendicular anisotropy of the free layer (4πMeff ~ -<NUM> kA/m (-<NUM>. 0kGauss)) and strong effective in-plane anisotropy of the PSC layer (4πMeff ~ <NUM> kA/m (<NUM> kGauss)).

An alternative embodiment that may also not be fabricated according to the inventive method is shown in <FIG>. In this embodiment, magnetic device <NUM> has had its MTJ stack inverted with respect to the embodiment shown in <FIG>. In particular, magnetic device <NUM> includes a seed layer <NUM>. Precessional spin current magnetic layer <NUM> is placed over seed layer <NUM>. Precessional spin current magnetic layer <NUM> can comprise any of the embodiments described in the context of <FIG> and <FIG>, with the layers inverted. As an example, precessional spin current magnetic layer <NUM> can comprise a magnetic NiFe permalloy layer <NUM> over seed layer <NUM>, Ru layer <NUM> over NiFe permalloy layer <NUM>, and magnetic Fe layer over Ru layer <NUM>. As discussed, NiFe permalloy layer <NUM> can be replaced with other face centered materials without departing from the scope of the teachings of the patent document.

Nonmagnetic spacer <NUM> is placed over PSC layer <NUM>. Nonmagnetic spacer <NUM> has the same properties, construction and characteristics as nonmagnetic spacer <NUM> and <NUM>, discussed above. MTJ <NUM> is placed over nonmagnetic spacer <NUM>. MTJ <NUM> is generally constructed of free layer <NUM> (which is placed over nonmagnetic spacer <NUM>) and reference layer <NUM>. Free layer <NUM> and reference layer <NUM> are spatially separated from each other by tunneling barrier layer <NUM>, which is made of an insulating material such as MgO. As above, MTJ <NUM> is a perpendicular MTJ in that the magnetic direction of both reference layer and free layer are perpendicular to their respective planes. As discussed with respect to other embodiments, free magnetic layer <NUM> design may include magnetization of the free layer <NUM> pointing a few degrees away from its perpendicular axis. The tilted angle of the free layer magnetization can be due to interaction with the PSC magnetic layer <NUM> or due to magnetocrystalline anisotropy, will additionally help switching of the free layer magnetization by improving the initiation of the switching. Ferromagnetic coupling layer <NUM> is placed over reference layer <NUM>. A synthetic antiferromagnetic (SAF) layer <NUM> is disposed over ferromagnetic coupling layer <NUM>. An antiferromagnetic coupling layer <NUM> is placed over SAF layer <NUM>. Another synthetic antiferromagnetic layer <NUM> is placed over antiferromagnetic coupling layer <NUM>. Note that SAF layer <NUM> technically also includes ferromagnetic coupling layer <NUM> and reference layer <NUM>, but are shown separately here for explanation purposes. SAF layers <NUM> and <NUM> also perpendicular magnetic directions. Finally, capping layer <NUM> is placed over SAF layer <NUM>. Current can be provided by a current source <NUM>. Other than the ordering of the layers, magnetic device operates in the same manner as described with respect to the embodiment shown in <FIG> and <FIG>. Thus, just as shown in <FIG> and <FIG>, PSC magnetic layer <NUM> rotates in such a way that spin transfer torque <NUM> is applied in a beneficial manner throughout the entire precession cycle of free layer <NUM>.

All of the layers of devices <NUM>, <NUM>, <NUM>, <NUM> and <NUM> illustrated in <FIG>, <FIG> and <FIG> can be formed by a thin film sputter deposition system as would be appreciated by one skilled in the art. The thin film sputter deposition system can include the necessary physical vapor deposition (PVD) chambers, each having one or more targets, an oxidation chamber and a sputter etching chamber. Typically, the sputter deposition process involves a sputter gas (e.g., argon, krypton, xenon or the like) with an ultra-high vacuum and the targets can be made of the metal or metal alloys to be deposited on the substrate. Thus, when the present specification states that a layer is placed over another layer, such layer could have been deposited using such a system. Other methods can be used as well. It should be appreciated that the remaining steps necessary to manufacture MTJ stack <NUM> are well-known to those skilled in the art and will not be described in detail herein so as not to unnecessarily obscure aspects of the disclosure herein.

It should be appreciated to one skilled in the art that a plurality of MTJ structures <NUM> can be manufactured and provided as respective bit cells of an STT-MRAM device. In other words, each MTJ stack <NUM>, <NUM>, <NUM>, <NUM> and <NUM> can be implemented as a bit cell for a memory array having a plurality of bit cells.

Claim 1:
A method of manufacturing a magnetic device over a substrate, comprising:
forming (<NUM>, <NUM>, <NUM>) a synthetic antiferromagnetic structure in a first plane, the synthetic antiferromagnetic structure comprising a magnetic reference layer (<NUM>), the magnetic reference layer having a magnetization vector that is perpendicular to the first plane and having a fixed magnetization direction;
forming (<NUM>) a non-magnetic tunnel barrier layer (<NUM>) in a second plane and over the magnetic reference layer;
forming (<NUM>) a free magnetic layer (<NUM>) in a third plane and over the non-magnetic tunnel barrier layer, the free magnetic layer having a magnetization vector that is perpendicular to the third plane and having a magnetization direction that can precess from a first magnetization direction to a second magnetization direction, the magnetic reference layer, the non-magnetic tunnel barrier layer and the free magnetic layer forming a magnetic tunnel junction (<NUM>);
forming (<NUM>) a non-magnetic spacer (<NUM>) in a fourth plane and over the free magnetic layer, the non-magnetic spacer comprising MgO having a thickness in the range of <NUM> to <NUM>;
forming (<NUM>) a precessional spin current magnetic layer (<NUM>) in a fifth plane that is physically separated from the free magnetic layer and coupled to the free magnetic layer by the nonmagnetic spacer, the precessional spin current magnetic layer having a magnetization vector with a magnetization component that is located within the fifth plane and can freely rotate in any magnetic direction in the fifth plane, the precessional spin current magnetic layer comprising an Fe layer (<NUM>), a Ru layer (<NUM>), and a face centered cubic, fcc, crystal structure layer (<NUM>) comprising a material having a fcc crystal structure, the Fe layer being disposed over the non-magnetic spacer, the Ru layer being disposed over the Fe layer, and the fcc crystal structure layer being disposed over the Ru layer; and
forming (<NUM>) a capping layer (<NUM>) in a sixth plane and over the precessional spin current magnetic layer.