阅读说明：本技术 自旋力矩转移（stt）-磁性随机存取存储器（mram）之氮化物盖层 (Nitride cap layer for Spin Torque Transfer (STT) -Magnetic Random Access Memory (MRAM) ) 是由 裘地·玛丽·艾维塔 真杰诺 童儒颖 维格纳许·桑达 朱健 刘焕龙 于 2019-01-25 设计创作，主要内容包括：公开一种磁性穿隧结(MTJ),其中自由层(FL)与第一金属氧化物(垂直非等向性增强层)及第二金属氧化物(穿隧阻障)的第一及第二界面各别产生垂直磁非等向性(PMA)以增加热稳定性。在一些实施例中,盖层为导电金属氮化物(例如,MoN)相对于第一界面接触垂直非等向性增强层的相反表面,相较于TiN盖层,减少氧及氮的相互扩散并保持可接受的电阻面积(RA)乘积。在其他实施例中,盖层可以包括绝缘氮化物,例如AlN,其与导电金属合金以最小化RA。此外,可以在盖层与垂直非等向性增强层之间插入金属缓冲层。因此,减少电性短路并且增加磁阻比。(A Magnetic Tunneling Junction (MTJ) is disclosed in which first and second interfaces of a Free Layer (FL) and a first metal oxide (vertical anisotropy enhancement layer) and a second metal oxide (tunneling barrier) each produce a vertical magnetic anisotropy (PMA) to increase thermal stability. In some embodiments, the capping layer is a conductive metal nitride (e.g., MoN) that contacts an opposite surface of the vertical anisotropic enhancement layer relative to the first interface, reducing interdiffusion of oxygen and nitrogen and maintaining an acceptable Resistance Area (RA) product compared to a TiN capping layer. In other embodiments, the cap layer may comprise an insulating nitride, such as AlN, alloyed with a conductive metal to minimize RA. In addition, a metal buffer layer may be interposed between the cap layer and the vertical anisotropy enhancing layer. Thus, electrical shorts are reduced and the magnetoresistance ratio is increased.)

1. A perpendicular magnetic tunneling junction (p-MTJ), comprising:

(a) a tunnel barrier layer which is a first metal oxide layer;

(b) a vertical anisotropic enhancement layer which is a second metal oxide layer or a metal oxynitride layer;

(c) a Free Layer (FL) having a first surface forming a first interface with the tunneling barrier layer, the free layer having a second surface forming a second interface with the vertical anisotropy enhancement layer, wherein the first and second interfaces each create a vertical magnetic anisotropy (PMA) in the free layer; and

(d) a metal nitride or metal oxynitride cap or barrier layer contacting a side of the vertical anisotropy enhancement layer opposite the second interface.

2. The mtj of claim 1 wherein the free layer is one or more layers selected from Co, Fe, CoFe, CoFeB, CoB, FeB, CoFeNi and CoFeNiB or alloys thereof, wherein Fe is greater than 50 at% (iron-rich) of the total magnetic element/component content.

3. The mtj of claim 1 wherein the free layer is a heusler alloy of Ni₂MnZ、Pd₂MnZ、Co₂MnZ、Fe₂MnZ、Co₂FeZ、Mn₃Ge or Mn₂Ga, wherein Z is one of Si, Ge, Al, Ga, In, Sn and Sb, or the free layer is an ordered L10 or L11 material, is one of MnAI, MnGa or RT, wherein R is Rh, Pd, Pt, Ir or alloys thereof, T is Fe, Co, Ni or alloys thereof, or the free layer is a rare earth alloy of TbFeCo, GdCoFe, FeNdB or SmCo.

4. The mtj of claim 1 wherein the metal in the el layer is one or more of Mg, Si, Ti, Ba, Ca, La, Al, Mn, V, and Hf, and the el layer is a single layer or a stack.

5. The mtj of claim 1 wherein the capping or barrier layer has a composition of M1N or M1ON, where M1 is a metal or alloy of one or more of Ti, V, Cr, Zr, Nb, Mo, Hf, Ta, and W.

6. The mtj of claim 1 wherein the capping or barrier layer has a composition of M2M3N or M2M3ON, where M2 is one of B, Al, Si, Ga, In, and TI, and M3 is one or more of Pt, Au, Ag, Mg, Ca, Sr, Ba, Sc, Y, La, Co, Fe, Mn, Ru, Rh, Ir, Ni, Pd, Zn, Cu, TI, V, Cr, Zr, Nb, Mo, Hf, Ta, and W.

7. The mtj of claim 1 wherein the capping or barrier layer comprises an M2N or M2ON matrix with conductive paths of M3 metal, wherein M2 is one of B, Al, Si, Ga, In, and Tl and M3 is one or more of Pt, Au, Ag, Mg, Ca, Sr, Ba, Sc, Y, La, Co, Fe, Mn, Ru, Rh, Ir, Ni, Pd, Zn, Cu, Ti, V, Cr, Zr, Nb, Mo, Hf, Ta, and W.

8. The mtj of claim 1 wherein the free layer has a thickness of about 5 a to about 5 a

9. The mtj of claim 1 wherein the tunnel barrier is MgO, Al₂O₃、MgAlO、TiO_x、AlTiO、MgZnO、Al₂O₃、ZnO、ZrO_x、HfO_xAnd MgTaO or a stack thereof.

10. The perpendicular magnetic tunneling junction according to claim 1, further comprising a pinning layer adjacent to the tunneling barrier layer, wherein the perpendicular magnetic tunneling junction is part of a Magnetoresistive Random Access Memory (MRAM), spin torque transfer-magnetic random access memory (STT-MRAM), spin torque oscillator, spin hall effect device, magnetic sensor, or biosensor.

11. A perpendicular magnetic tunneling junction (p-MTJ) structure, comprising:

(a) a tunnel barrier layer which is a first metal oxide layer;

(b) a vertical anisotropic enhancement layer which is a second metal oxide layer or a metal oxynitride layer;

(c) a Free Layer (FL) having a first surface forming a first interface with the tunneling barrier layer, the free layer having a second surface forming a second interface with the vertical anisotropy enhancement layer, wherein the first and second interfaces each create a vertical magnetic anisotropy (PMA) in the free layer; and

(d) a metal nitride or metal oxynitride cap or barrier layer; and

(e) a metal buffer layer having a first surface in contact with the vertical anisotropy enhancement layer and a second surface adjacent to the capping layer or the barrier layer.

12. The magnetic element of claim 11 wherein the free layer is one or more layers and is one or more of Co, Fe, CoFe, CoFeB, CoB, FeB, CoFeNi, and CoFeNiB or alloys thereof, with Fe content greater than 50 atomic% of the total magnetic element/component content (iron-rich).

13. The mtj of claim 11 wherein the free layer is a Heusler (Heusler) alloy that is one of Ni2MnZ, Pd2MnZ, Co2MnZ, Fe2MnZ, Co2FeZ, Mn3Ge, or Mn2Ga, where Z is one of Si, Ge, Al, Ga, In, Sn, and Sb, or the free layer is an ordered L10 or L11 material that is one of MnAI, MnGa, or RT, where R is Rh, Pd, Pt, Ir, or alloys thereof, T is Fe, Co, Ni, or alloys thereof, or the free layer is a rare earth alloy of TbFeCo, GdCoFe, FeNdB, or SmCo.

14. The mtj of claim 11 wherein the metal in the el layer is one or more of Mg, Si, Ti, Ba, Ca, La, Al, Mn, V, and Hf, and the el layer is a single layer or a stack.

15. The mtj of claim 11 wherein the capping or barrier layer has a composition of M1N or M1ON, where M1 is a metal or alloy of one or more of Ti, V, Cr, Zr, Nb, Mo, Hf, Ta, and W.

16. The mtj of claim 11 wherein the capping or barrier layer has a composition of M2M3N or M2M3ON, where M2 is one of B, Al, Si, Ga, In, and TI, and M3 is one or more of Pt, Au, Ag, Mg, Ca, Sr, Ba, Sc, Y, La, Co, Fe, Mn, Ru, Rh, Ir, Ni, Pd, Zn, Cu, TI, V, Cr, Zr, Nb, Mo, Hf, Ta, and W.

17. The mtj of claim 11 wherein the capping or barrier layer comprises an M2N or M2ON matrix with conductive paths of M3 metal or alloy, wherein M2 is one of B, Al, Si, Ga, In, and Tl and M3 is one or more of Pt, Au, Ag, Mg, Ca, Sr, Ba, Sc, Y, La, Co, Fe, Mn, Ru, Rh, Ir, Ni, Pd, Zn, Cu, Ti, V, Cr, Zr, Nb, Mo, Hf, Ta, and W.

18. The mtj of claim 11 wherein the free layer has a thickness of about 5 a to about 5 a

19. The mtj of claim 11 wherein the tunnel barrier is MgO, Al₂O₃、MgAlO、TiO_x、AlTiO、MgZnO、Al₂O₃、ZnO、ZrO_x、HfO_xAnd MgTaO or a stack thereof.

20. The perpendicular magnetic tunneling junction according to claim 11, further comprising a pinning layer adjacent to the tunneling barrier layer, wherein the perpendicular magnetic tunneling junction is part of a Magnetoresistive Random Access Memory (MRAM), spin torque transfer-magnetic random access memory (STT-MRAM), spin torque oscillator, spin hall effect device, magnetic sensor, or biosensor.

21. The mtj of claim 11 wherein the metal buffer layer is one or more of Ti, V, Cr, Zr, Nb, Mo, Hf, Ta, and W.

22. A method of forming a perpendicular magnetic tunneling junction (p-MTJ), comprising:

(a) forming a tunnel barrier layer on a substrate;

(b) depositing a Free Layer (FL) on the tunnel barrier layer;

(c) forming a vertical anisotropic enhancement layer on the free layer, wherein the vertical anisotropic enhancement layer is a metal oxide or a metal oxynitride; and

(d) forming a metal nitride or metal oxynitride cap layer on the vertical anisotropic enhancement layer.

23. The method of claim 22, wherein the metal in the vertical anisotropy enhancing layer is one or more of Mg, Si, Ti, Ba, Ca, La, Al, Mn, V, and Hf, and the vertical anisotropy enhancing layer is a single layer or a stack.

24. The method of claim 22, wherein the capping layer has a composition of M1N or M1ON, wherein M1 is a metal or alloy of one or more of Ti, V, Cr, Zr, Nb, Mo, Hf, Ta, and W.

25. The method of claim 22, wherein the capping layer has a composition of M2M3N or M2M3ON, wherein M2 is one of B, Al, Si, Ga, In, and TI, and M3 is one or more of Pt, Au, Ag, Mg, Ca, Sr, Ba, Sc, Y, La, Co, Fe, Mn, Ru, Rh, Ir, Ni, Pd, Zn, Cu, TI, V, Cr, Zr, Nb, Mo, Hf, Ta, and W.

26. The method of claim 22, wherein the cap layer comprises a matrix of M2N or M2ON having a plurality of conductive paths formed of M3 metal or alloy, wherein M2 is one of B, Al, Si, Ga, In and Tl, and M3 is one or more of Pt, Au, Ag, Mg, Ca, Sr, Ba, Sc, Y, La, Co, Fe, Mn, Ru, Rh, Ir, Ni, Pd, Zn, Cu, Ti, V, Cr, Zr, Nb, Mo, Hf, Ta and W

27. A method of forming a perpendicular magnetic tunneling junction (p-MTJ), comprising: .

(a) Forming a tunnel barrier layer on a substrate;

(b) depositing a Free Layer (FL) on the tunnel barrier layer;

(c) forming a vertical anisotropic enhancement layer on the free layer, wherein the vertical anisotropic enhancement layer is a metal oxide or a metal oxynitride;

(d) depositing a metal buffer layer on the vertical anisotropic enhancement layer; and

(e) forming a metal nitride or metal oxynitride cap layer on the metal buffer layer.

28. The method of claim 27, wherein the metal in the vertical anisotropy enhancing layer is one or more of Mg, Si, Ti, Ba, Ca, La, Al, Mn, V, and Hf, and the vertical anisotropy enhancing layer is a single layer or a stack.

29. The method of claim 27, wherein the capping layer has a composition of M1N or M1ON, wherein M1 is a metal or alloy of one or more of Ti, V, Cr, Zr, Nb, Mo, Hf, Ta, and W.

30. The method of claim 27, wherein the cap layer has a composition of M2M3N or M2M3ON, wherein M2 is one of B, Al, Si, Ga, In, and TI, and M3 is one or more of Pt, Au, Ag, Mg, Ca, Sr, Ba, Sc, Y, La, Co, Fe, Mn, Ru, Rh, Ir, Ni, Pd, Zn, Cu, TI, V, Cr, Zr, Nb, Mo, Hf, Ta, and W.

31. The method of claim 27, wherein the cap layer comprises a matrix of M2N or M2ON having a plurality of conductive paths formed of M3 metal or alloy, wherein M2 is one of B, Al, Si, Ga, In and Tl, and M3 is one or more of Pt, Au, Ag, Mg, Ca, Sr, Ba, Sc, Y, La, Co, Fe, Mn, Ru, Rh, Ir, Ni, Pd, Zn, Cu, Ti, V, Cr, Zr, Nb, Mo, Hf, Ta and W

32. The method of claim 27, wherein the metal buffer layer is one or more of Ti, V, Cr, Zr, Nb, Mo, Hf, Ta, and W.

33. A method of forming a perpendicular magnetic tunneling junction (p-MTJ), comprising:

(a) forming a metal nitride or metal oxynitride barrier layer on a substrate;

(b) forming a vertical anisotropic enhancement layer on the barrier layer, wherein the vertical anisotropic enhancement layer is a metal oxide or a metal oxynitride;

(c) depositing a Free Layer (FL) on the vertical anisotropic enhancement layer; and

(d) a tunnel barrier layer is formed over the free layer.

34. The method of claim 33, wherein the metal in the vertical anisotropy enhancing layer is one or more of Mg, Si, Ti, Ba, Ca, La, Al, Mn, V, and Hf, and the vertical anisotropy enhancing layer is a single layer or a stack.

35. The method of claim 33 wherein the barrier layer has a composition of M1N or M1ON wherein M1 is a metal or alloy of one or more of Ti, V, Cr, Zr, Nb, Mo, Hf, Ta, and W.

36. The method of claim 33 wherein the barrier layer has a composition of M2M3N or M2M3ON, wherein M2 is one of B, Al, Si, Ga, In and TI, and M3 is one or more of Pt, Au, Ag, Mg, Ca, Sr, Ba, Sc, Y, La, Co, Fe, Mn, Ru, Rh, Ir, Ni, Pd, Zn, Cu, TI, V, Cr, Zr, Nb, Mo, Hf, Ta and W.

37. The method of claim 33, wherein the barrier layer comprises a matrix of M2N or M2ON having a plurality of conductive paths formed of M3 metal or alloy, wherein M2 is one of B, Al, Si, Ga, In and Tl, and M3 is one or more of Pt, Au, Ag, Mg, Ca, Sr, Ba, Sc, Y, La, Co, Fe, Mn, Ru, Rh, Ir, Ni, Pd, Zn, Cu, Ti, V, Cr, Zr, Nb, Mo, Hf, Ta and W.

38. A method of forming a perpendicular magnetic tunneling junction (p-MTJ), comprising:

(a) forming a metal nitride or metal oxynitride barrier layer on a substrate;

(b) depositing a metal buffer layer on the barrier layer;

(c) forming a vertical anisotropic enhancement layer on the barrier layer, wherein the vertical anisotropic enhancement layer is a metal oxide or a metal oxynitride;

(d) depositing a Free Layer (FL) on the vertical anisotropic enhancement layer; and

(e) a tunnel barrier layer is formed over the free layer.

39. The method of claim 38, wherein the metal in the vertical anisotropy enhancing layer is one or more of Mg, Si, Ti, Ba, Ca, La, Al, Mn, V, and Hf, and the vertical anisotropy enhancing layer is a single layer or a stack.

40. The method of claim 38, wherein the barrier layer has a composition of M1N or M1ON, wherein M1 is a metal or alloy of one or more of Ti, V, Cr, Zr, Nb, Mo, Hf, Ta, and W.

41. The method of claim 38 wherein the barrier layer has a composition of M2M3N or M2M3ON, wherein M2 is one of B, Al, Si, Ga, In and TI, and M3 is one or more of Pt, Au, Ag, Mg, Ca, Sr, Ba, Sc, Y, La, Co, Fe, Mn, Ru, Rh, Ir, Ni, Pd, Zn, Cu, TI, V, Cr, Zr, Nb, Mo, Hf, Ta and W.

42. The method of claim 38, wherein the barrier layer comprises a matrix of M2N or M2ON having a plurality of conductive paths formed of M3 metal or alloy, wherein M2 is one of B, Al, Si, Ga, In and Tl, and M3 is one or more of Pt, Au, Ag, Mg, Ca, Sr, Ba, Sc, Y, La, Co, Fe, Mn, Ru, Rh, Ir, Ni, Pd, Zn, Cu, Ti, V, Cr, Zr, Nb, Mo, Hf, Ta and W.

43. The method of claim 38, wherein the metal buffer layer is one or more of Ti, V, Cr, Zr, Nb, Mo, Hf, Ta, and W.

Technical Field

A magnetic element includes a free layer that interfaces with a tunnel barrier layer and a vertical anisotropy enhancement layer and with a nitride cap layer to prevent oxygen diffusion from the vertical anisotropy enhancement layer and to minimize diffusion of metal and nitrogen through the vertical anisotropy enhancement layer to the free layer, thereby maintaining an acceptable magnetoresistance ratio (DRR) and reducing the Resistance Area (RA) product when the cap layer is conductive.

Background

MRAM, based on the integration of silicon Complementary Metal Oxide Semiconductor (CMOS) and Magnetic Tunneling Junction (MTJ) technologies, is an emerging technology that is very competitive with existing semiconductor memories, such as SRAM, DRAM, and flash memory. Further, spin-transfer torque (STT) magnetization switching, described by j.c. slonczewski in "current-driven excitation of multilayer magnetic materials" (j.magn.magn.mater.v159, L1-L7(1996)), has facilitated the development of spintronic devices, such as gigabit STT-MRAM.

Both field-type MRAM and STT-MRAM have MTJ elements based on Tunneling Magnetoresistive (TMR) effects. In which the stacked layers have a configuration in which two Ferromagnetic (FM) layers are separated by a thin non-magnetic dielectric layer. The FM layer is a pinned layer whose magnetic moment is fixed in a first direction, while the other FM layer is called a Free Layer (FL) whose magnetic moment is free to rotate in a direction parallel (P-state) or anti-parallel (AP-state) to the first direction, corresponding to a "0" or "1" magnetic state, respectively. STT-MRAM has the advantage over conventional MRAM of avoiding the half-select problem and write interference between adjacent cells. The spin transfer effect arises from the spin-dependent electron transport properties of ferromagnetic-spacer-ferromagnetic multilayers. When a spin-polarized current passes through the magnetic multilayer in a current perpendicular to the plane (CPP), the spin angular momentum of electrons incident on the FM layer interacts with the magnetic moment of the FM layer near the interface between the FM layer and the nonmagnetic spacer. Through this interaction, the electrons transfer a portion of the angular momentum to the FL. Therefore, if the current density is sufficiently high and the size of the multilayer film is small, the spin-polarized current can switch the magnetization direction of the FL.

P-MTJs are MTJ cells with Perpendicular Magnetic Anisotropy (PMA) in the pinned layer and FL, and are the basis for the construction of STT-MRAM and other spintronic devices. Generally, there is one nonmagnetic tunnel oxide layer, called a tunnel barrier layer, between the pinned layer and the FL. When the FL has a PMA, the critical current (ic) required to switch the FL and P-MTJ from the P-state to the AP-state (or vice versa) is proportional to the perpendicular magnetic anisotropy field, as shown in equation (1):

where e is the electronic charge, a is the Gilbert damping constant, M_sIs the FL saturation magnetization, h is the reduced Planck constant, g is the gyromagnetic ratio,

is the out-of-plane anisotropy field of the magnetic region to be switched, and V is the volume of the free layer.

Δ＝kV/k_BThe value of T is the thermal stability of FL, where kV is also referred to as E_bOr energy barrier between P and AP magnetic states, k_BIs the Boltzmann constant and T is the temperature. Thermal stability is a function of the vertical anisotropy field, as shown in equation (2):

vertical anisotropy field (H) of FL_k) Expressed in equation (3) as:

wherein M is_sIs the saturation magnetization, d is the thickness of the free layer, H_fcX is a crystal anisotropy field in the vertical direction,is the surface vertical anisotropy of the FL top and bottom surfaces. This high temperature requirement leads to new p-MTJ designs since the FL must be able to withstand 400 ℃ in the annealing process required for CMOS fabrication, where the FL has a larger PMA. One way to enhance PMA in FL is to form metal oxide interfaces on its top and bottom surfaces. Thus, in addition to the first FL interface with the tunnel barrier, the second FL interface forms a so-called vertical anisotropy enhancement layer to produce the higher surface vertical anisotropy in equation (3).

Since the vertical anisotropy enhancement layer is typically not fully oxidized to minimize RA in the p-MTJ cell, metal or other species from the upper cap layer or hardmask tend to migrate to the FL and lower DRR through vacancies in the vertical anisotropy enhancement layer. DRR is expressed as dR/R, where dR is the difference in resistance between the P and AP states, and R is the resistance of the P state. A larger DRR means a higher read margin (margin). In addition, oxygen may migrate out of the vertical anisotropy enhancement layer, thereby reducing the surface vertical anisotropy at the FL/vertical anisotropy enhancement layer interface, resulting in reduced FL thermal stability. Therefore, there is a need for an improved p-MTJ structure to maintain the integrity of the vertical anisotropy enhancement layer, thereby maintaining the thermal stability of the FL, while providing the DRR and RA values required for high magnetic performance in advanced memory designs, where the critical dimension (FL width) is substantially less than 100 nm.

Disclosure of Invention

It is an object of the present disclosure to provide a p-MTJ in which the barrier of metal and other species from the hardmask layer or cap layer, through the vertical anisotropy enhancement layer, to the FL in the bottom spin valve structure, and from the seed layer or Bottom Electrode (BE), through the vertical anisotropy enhancement layer, to the FL in the top spin valve structure, is improved.

A second object of the present disclosure is to provide an improved barrier in accordance with the first object, wherein the barrier also substantially minimizes diffusion of oxygen from the vertical anisotropic enhancement layer to the cap layer/hardmask or to the seed layer/BE.

A third object of the present disclosure is to provide a process flow method for forming p-MTJ that is compatible with CMOS fabrication.

According to one embodiment, these objects are achieved by providing a nitride or oxynitride cap layer that acts as a barrier between a vertical anisotropy enhancement layer and a hard mask in a p-MTJ with a bottom spin valve configuration. Thus, an optional seed layer, pinning layer, tunnel barrier layer, FL, vertical anisotropy enhancement layer, nitride or oxynitride cap layer, and hard mask are sequentially formed on the substrate, which may BE the Bottom Electrode (BE). The pinned layer preferably has a synthetic antiparallel (SyAP) configuration in which the outer AP2 layer is in contact with the seed layer, or BE in the absence of the seed layer, and the inner AP1 layer abuts the tunnel barrier layer. In addition, there is an Antiferromagnetic (AF) coupling layer between the AP1 and AP2 layers. Thus, the FL has a first interface with the tunnel barrier layer and a second interface with the vertical anisotropy enhancement layer, which may be a metal oxide or a metal oxynitride.

A key feature of the first embodiment is the composition of the cap layer, which is a metal nitride or metal oxynitride, wherein the metal (M1) is selected from the group consisting of Ti, Zr, Hf, V, Nb, Ta, Cr, Mo and W to provide a conductive nitride (M1N) or oxynitride (M1ON) that is advantageous for minimizing RA compared to the corresponding metal oxide. In addition, a layer of powder (passivation layer) may be inserted between the vertical anisotropic enhancement layer and the conductive nitride or oxynitride cap layer to reduce interdiffusion associated with the vertical anisotropic enhancement layer/M1N interface or the vertical anisotropic enhancement layer/M1 ON interface. Preferably, the powder layer is one or more of M1 metal, Ti, V, Cr, Zr, Nb, Mo, Hf, Ta or W.

According to a second embodiment, the capping layer may comprise an insulating metal (M2) nitride or oxynitride, wherein M2 is one of B, Al, Si, Ga, In, or TI, alloyed with a conductive metal or alloy (M3), and M3 is one or more selected from Pt, Au, Ag, Mg, Ca, Sr, Ba, Sc, Y, La, Co, Fe, Mn, Ru, Rh, Ir, Ni, Pd, Zn, Cu, TI, V, Cr, Zr, Nb, Mo, Hf, Ta, and W, to render the resulting M2M3 nitride (M2M3N) or M2M3 oxynitride (M2M3ON) conductive. A dusting (buffer) layer formed of one or more M1 metals may be disposed between the vertical anisotropic reinforcement layer and the M2M3N or M2M3ON cap layer.

According to a third embodiment, the capping layer comprises insulating M2 nitride or M2 oxynitride, wherein a conductive path is formed in contact with the vertical anisotropy enhancing layer and the hard mask. Preferably, the conductive path is formed from one or more of the M3 metals described above. In addition, a layer of M1 powder may be included between the vertical anisotropic reinforcement layer and the cap layer.

The present disclosure also includes a p-MTJ structure with a top spin valve configuration in which an optional seed layer, a nitride or oxynitride barrier layer, a vertical anisotropy enhancement layer, a FL, a tunnel barrier layer, a pinning layer, and a hard mask are sequentially formed on a substrate. The nitride or oxynitride barrier layer may have a composition of M1N or M1ON, M2M3N or M2M3ON, or a composite with an M3 conductive pathway formed in the M2N or M2ON layer. In each example, a buffer layer may be included between the barrier layer and the vertical anisotropic enhancement layer to prevent interdiffusion at the barrier layer/vertical anisotropic enhancement layer interface.

The present disclosure also includes a method of fabricating a p-MTJ with a metal nitride or metal oxynitride cap layer having a structure according to one of the above embodiments. In general, the M1N, M1ON, M2M3N, and M2M3ON layers are sputter deposited in a single step. However, a multi-step process may be employed in which the M1 or M2M3 layer is sputter deposited first, followed by a second step involving nitridation or oxynitridation to form a nitride or oxynitride, respectively. The formation of the M3 conductive path in the M2N or M2ON layer is accomplished by a series of steps: (1) depositing an M3 layer, (2) depositing an M2 layer on the M3 layer, and (3) nitriding or oxynitriding with a plasma, or by a first step of ion implantation and a second step of an annealing process.

Drawings

FIG. 1 is a cross-sectional view of a magnetic tunneling junction (p-MTJ) including a nitride cap layer between a vertical anisotropy enhancement layer and a hard mask according to a first embodiment of the disclosure.

FIG. 2 is a cross-sectional view of a p-MTJ including a lower buffer layer and an upper nitride cap layer stack between a vertical anisotropy enhancement layer and a hard mask according to a second embodiment of the disclosure.

FIG. 3 is a cross-sectional view of a p-MTJ including a nitride cap layer according to a third embodiment of the present disclosure where a conductive current path is formed between the vertical anisotropy enhancement layer and the hard mask.

FIG. 4 is a cross-sectional view of the p-MTJ of FIG. 3 instead including a buffer layer between the vertical anisotropy enhancement layer and the nitride cap layer, according to a fourth embodiment of the present disclosure.

FIG. 5 is a cross-sectional view of a p-MTJ having a top spin valve configuration where a nitride barrier layer is formed between a seed layer and a vertical anisotropy enhancement layer, according to a fifth embodiment of the present disclosure.

FIG. 6 is a cross-sectional view of the p-MTJ of FIG. 5 instead including a buffer layer between the nitride barrier layer and the vertical anisotropy enhancement layer in accordance with a sixth embodiment of the disclosure.

FIG. 7 is a cross-sectional view of a p-MTJ having a top spin valve configuration where a nitride barrier layer with current conduction paths is formed between a seed layer and a vertical anisotropy enhancement layer, according to a seventh embodiment of the present disclosure.

FIG. 8 is a cross-sectional view of the p-MTJ of FIG. 7 instead including a buffer layer between the vertical anisotropy enhancement layer and the nitride barrier layer, according to an eighth embodiment of the present disclosure.

Fig. 9a-9d are dot line graphs showing measured hysteresis loops (hysterissops) for p-MTJs formed with different nitride barrier layers between a vertical anisotropy enhancement layer and a hard mask according to embodiments of the disclosure.

Fig. 10 is a table of free energy of a plurality of metals to form oxides.

Fig. 11-14 are cross-sectional views depicting various methods of forming conductive paths in a metal nitride or metal oxynitride substrate, in accordance with embodiments of the present disclosure.

FIG. 15 is a top view of a memory array with a plurality of p-MTJ cells insulated by an encapsulation layer according to an embodiment of the disclosure.

Detailed Description

A p-MTJ structure and method of fabrication are disclosed in which a barrier layer formed between a vertical anisotropy enhancement layer and a hard mask (or seed layer) reduces electrical shorts and improves DRR by substantially minimizing diffusion of oxygen from the vertical anisotropy enhancement layer and reduces diffusion of metal or nitrogen through the vertical anisotropy enhancement layer into the adjacent free layer. The present disclosure relates to p-MTJ structures having bottom and top spin valve configurations or dual spin valve configurations. The p-MTJ can be incorporated into MRAM, STT-MRAM, or other spintronic devices, such as spin torque oscillators, spin Hall effect devices, magnetic sensors, and biosensors. The thickness of each p-MTJ layer is in the z-axis direction, and the plane of each layer is formed in the x-axis and y-axis directions. The terms "barrier layer" and "cap layer" may be used interchangeably.

In related patent application No. 15/461,779, we disclose an MTJ structure in which the free layer forms a first interface with a first oxide layer (tunnel barrier layer) and a second interface with a second oxide layer (vertical anisotropy enhancement layer), preferably MgO, to improve PMA and thermal stability. In addition, a TiN barrier layer is interposed between the vertical anisotropic enhancement layer and the overlying hard mask to maintain the integrity of the MgO layer. However, energy dispersive X-ray spectroscopy (EDS) showed extensive interdiffusion at the MgO/TiN interface, indicating the presence of oxygen in the TiN layer and nitrogen in the FL.

In the present disclosure, we disclose an improved barrier layer designed to substantially reduce oxygen diffusion from the vertical anisotropic enhancement layer and significantly minimize diffusion of metal or nitrogen into the FL through the vertical anisotropic enhancement layer. When replacing Ti in a TiN barrier with another metal, an important concept we consider is that this replacement metal preferably has a lower oxygen affinity than Ti, which is consistent with the lower (less negative) oxide formation free energy shown in fig. 10. Second, by interposing a metal buffer layer between the vertical anisotropy enhancement layer and the metal nitride/oxynitride barrier layer, the effect of the metal nitride barrier layer on the vertical anisotropy enhancement layer and the FL can be mitigated to some extent. While a conductive metal nitride/oxynitride barrier layer is preferred, an insulating metal nitride/oxynitride is feasible if alloyed with a conductive metal or a conductive path is formed through the insulating barrier layer matrix.

Referring to fig. 1, a first embodiment of the present disclosure is illustrated in the form of a p-MTJ 1 with a bottom spin valve configuration, in which an optional seed layer 11, pinning layer 12, tunnel barrier layer 13, FL 14, vertical anisotropy enhancement layer 15, metal nitride or oxynitride cap layer 16, and hard mask 17 are sequentially formed on a substrate 10. In some embodiments, the substrate may BE a Bottom Electrode (BE) in a STT-MRAM or another spintronic device. The BEs are typically embedded in an insulating layer (not shown) and are electrically connected to bit lines or word lines (not shown) driven by the underlying transistors.

The seed layer 11 is single or multi-layered and may comprise one or more of NiCr, Ta, Ru, Ti, TaN, Cu, Mg or other materials commonly used to promote a smooth and uniform grain structure of the overlying layers. The pinned layer 12 may have a SyAP configuration represented by AP2/AFC layer/AP 1, with an AF-coupling (AFC) layer formed, for example, of Ru, Rh, or Ir, sandwiched between an AP2 magnetic layer and an AP1 magnetic layer (not shown). When the AP1 layer abuts the tunnel barrier layer 13, the AP2 layer contacts the seed layer (or BE). The AP1 and AP2 layers may include CoFe, CoFeB, Co, or combinations thereof. In other embodiments, the pinning layer may be a lamination stack with intrinsic PMA, e.g. (Co/Ni)_n、(CoFe/Ni)_n、(Co/NiFe)_n、(Co/Pt)_n、(Co/Pd)_nOr the like, where n is the number of stacked layers. In addition, a transition layer, such as CoFeB or Co, may be interposed between the uppermost layer of the build-up stack and the tunnel barrier layer.

In a preferred embodiment, the tunnel barrier layer 13 is MgO formed by sputter deposition of an MgO target, or by depositing one or more Mg layers, followed by oxidation of the Mg layer or layers using known free Radical Oxidation (ROX) or Natural Oxidation (NOX) methods. However, other metal oxides or metal oxynitrides known in the art may be used with or in place of MgO. For example, the tunneling barrier may comprise Al₂O₃、MgAlO、TiO_x、AlTiO、MgZnO、Al₂O₃、ZnO、ZrO_x、HfO_xOr MgTaO. The present disclosure also contemplates that the tunneling barrier can be a stack of one or more of the aforementioned metal oxides.

FL 14 thickness of 5 toIs of single or multilayer structure and is one or more of Co, Fe, CoFe, CoFeB, CoB and FeB, or its alloy including CoFeNi and CoFeNiB, wherein the content of Fe is more than 50 atom% (rich in Fe) of the total content of magnetic elements/components. For example, at Co_(100-x)Fe_xIn layer B, x is greater than 50 atomic%. In other embodiments, the FL may comprise a material with a high crystalline anisotropic energy constant (Ku) with intrinsic PMA, including Heusler alloys, ordered L1₀Or L1₁Materials and rare earth alloys. The hassler alloy comprises Ni₂MnZ、Pd₂MnZ、Co₂MnZ、Fe₂MnZ、Co₂FeZ、Mn₃Ge、Mn₂Ga and the like, wherein Z is one of Si, Ge, Al, Ga, In, Sn and Sb. Ordered L1₀Or L1₁The material has a composition, such as MnAI, MnGa or RT, where R is Rh, Pd, Pt, Ir or alloys thereof and T is Fe, Co, Ni or alloys thereof. Rare earth alloys include, but are not limited to, TbFeCo, GdCoFe, FeNdB, or SmCo.

Due to this arrangement of the tunnel barrier (metal oxide) 13 and the vertical anisotropy enhancement layer (metal oxide) 15 forming interfaces with the bottom and top surfaces, respectively, FL 14 has a strong vertical surface anisotropy,

andlocated at the first and second interfaces, respectively, helps to enhance the above equation (3)An item.

According to one embodiment, the vertical anisotropy enhancement layer 15 is a metal oxide or metal oxynitride layer having a thickness and an oxidation state controlled such that its RA product is less than the thickness and oxidation state of the MgO layer in the tunnel barrier layer 13 to minimize DRR reduction. Thus, the vertical anisotropy enhancing layer may be a single layer that is an oxide or oxynitride of one or more of Mg, Si, Ti, Ba, Ca, La, Al, Mn, V, and Hf. Furthermore, the vertical anisotropy enhancement layer may be a stack including one or more of the above-described metal oxides or oxynitrides. In all embodiments, the vertical anisotropic enhancement layer may have a stoichiometric or non-stoichiometric oxygen content. Stoichiometry is defined as the oxidation state in which substantially all non-metal lattice sites in the metal oxide are occupied by oxygen, while in the non-stoichiometric oxidation state, there are a plurality of unoccupied lattice sites.

A key feature of MTJ 1 is that cap layer 16 has a metal nitride or metal oxynitride composition. According to a first embodiment, the capping layer comprises a metal or alloy (M1), wherein the metal or alloy is preferably one or more of Ti, Zr, Hf, V, Nb, Ta, Cr, Mo and W, to provide a conductive nitride (M1N) or oxynitride (M1ON) to minimize the contribution of RA to the p-MTJ. It should be noted that the total RA value of the p-MTJ is determined by the contributions of each of the metal oxide and metal nitride/oxynitride layers and is given by the equation RA_TOTAL＝(RA₁₃+RA₁₅+RA₁₆) Is shown in which RA₁₃、RA₁₅And RA₁₆Respectively, the RA products of the tunnel barrier layer, the vertical anisotropy enhancement layer, and the cap layer. Preferred is RA_TOTALLess than 5 ohm-mum²To obtain the best p-MTJ performance. Since the maximum contribution to the total amount comes from the tunnel barrier, the vertical anisotropy enhancement layer is often not fully oxidized to avoid exceeding the desired RA_TOTAL，RA₁₆Should provide a minimum RA contribution and ideally should be close to zero.

The cap layer advantageously acts as a barrier to oxygen migration out of the adjoining vertical anisotropic enhancement layer 15 and preferably has a thickness of 5 to 5

Is measured. In other embodiments, the cap layer may be as thick asThus, the affinity of the metal or alloy M1 for oxygen should be less than that of Mg, since the vertical anisotropy enhancement layer is preferably chosen to be MgO. Preferably, M1 should be one or more of the elements listed in fig. 10, which form oxides with less negative free energy than Mg. More preferably, M1 should have an oxide-forming free energy that is less negative than Ti,since the Ti buffer layer adjacent to the vertical anisotropy enhancing layer was found to reduce DRR due to the oxygen gettering property of the vertical anisotropy enhancing layer.

The M1N cap layer may be formed by sputter depositing an M1 target in a reactive ambient including N and Ar species, where the term "species" is defined as ions or radicals. The M1N (or M1ON) layer may have a non-stoichiometric nitrided state in which the metal nitride matrix has vacancies not occupied by M1 or N atoms. Thus, we found that when the ratio of 0.6: 1 (higher N content in MoN) and 5: 1 (lower N content in MoN) Ar: n flow ratio deposition, a significant PMA is found in FL 14 to yield a FL/MgO/MoN stack of FL/vertical anisotropic enhancement layer 15 and cap layer 16.

It is also important to minimize nitrogen migration from the cap layer through the vertical anisotropic enhancement layer and into the FL 14 so as not to degrade DRR. In particular, nitrogen migration from the M1N or M1ON capping layer should be less than from the same thickness of TiN. As previously described, we found that nitrogen does migrate into the FL in a p-MTJ comprising a FL/MgO/TiN stack, where MgO is the vertical anisotropy enhancement layer and TiN is the capping layer. The above-mentioned M1 metals and alloys are believed to provide improvements in this regard.

Alternatively, the capping layer 16 may comprise an insulating metal (M2) nitride or oxynitride, where M2 is one of B, Al, Si, Ga, In, and TI, alloyed with a conductive metal or alloy (M3), and M3 is selected from one or more of Pt, Au, Ag, Mg, Ca, Sr, Ba, Sc, Y, La, Co, Fe, Mn, Ru, Rh, Ir, Ni, Pd, Zn, Cu, TI, V, Cr, Zr, Nb, Mo, Hf, Ta, and W, to render the resulting M2M3 nitride (M2M3N) or M2M3 oxynitride (M2M3ON) conductive. M2M3N or M2M3ON layers may be formed by using N₂The flow and RIE conditions generate plasma and are formed by sputter depositing M2 and M3 targets in a reaction chamber or by sputtering M2M3 alloy in the presence of a nitrogen plasma.

The hard mask 17 may comprise one or more layers. For example, the hard mask may be a single layer of Ta or Ru, or have a Ru/Ta or Ru/Ta/Ru configuration. However, the present disclosure is not limited to a particular configuration, which means that other hard mask materials used in the art are acceptable. In general, the hard mask may serve as a RIE or IBE etch mask during patterning of the p-MTJ, and also as a barrier to Chemical Mechanical Polishing (CMP) steps that are typically used to planarize the encapsulation layers for insulating the p-MTJ cells.

According to the second embodiment of the present disclosure shown in fig. 2 and illustrated as p-MTJ 2, nitrogen migration from the cap layer 16 to the FL 14 may be further reduced by inserting a metal buffer layer 18 between the vertical anisotropy enhancement layer 15 and the cap layer. In addition, all aspects previously described with respect to p-MTJ 1 remain in p-MTJ 2 with sidewall 2 s. It is believed that the metal lattice in the buffer layer, also referred to as the soot layer, absorbs or reacts with nitrogen without allowing the nitrogen to diffuse to and above the vertical anisotropic enhancement layer. Preferably, the powder layer is one or more of the previously described elements M1, which have a lower affinity for oxygen than Mg, and more preferably, an oxygen affinity that is less than that of Ti according to fig. 10. The metal buffer layer also has conductivity to prevent RA_TOTALAn undesirable increase occurs. In some embodiments, the metal buffer layer has a thickness of 0.3 toPreferably, the metal buffer layer has a minimum thickness required to form a continuous film of aboutThus, the metal buffer/cap layer stack according to the second embodiment may have a M1/M1N, M1/M1ON, M1/M2M3N, or M1/M2M3ON configuration.

It should BE understood that in all exemplary embodiments shown herein, the p-MTJ sidewalls are substantially orthogonal to BE top surface 10 t. In other embodiments, the p-MTJ sidewalls may form an angle between 65 degrees and 90 degrees with respect to the top surface 10t depending on the RIE or IBE conditions used to create the sidewalls during patterning of the p-MTJ.

The present disclosure also includes a third embodiment depicted in FIG. 3, where the p-MTJ 3 with sidewall 3s is a modification of p-MTJ 2. In detail, the M3 metal or alloy forms the conductive path 19 in the insulating M2N or M2ON substrate 16x, rather than alloying with the nitride M2 or oxynitride M2. This approach is desirable when M3 is not alloyed with M2 nitride or oxynitride, or if the maximum M3 content in the M2M3N or M2M3ON cap layers is not sufficient to produce acceptable conductivity (minimum RA). In a subsequent section, a method of forming a conductive path in an M2N or M2ON matrix is provided. The conductive path may have a size (width) that varies from a single atom to a plurality of atoms in the in-plane direction. Preferably, each path extends from the vertical anisotropic enhancement layer 15 to the hard mask 17. Further, the path need not be orthogonal to the substrate 10, but may have an in-plane component other than a direction substantially perpendicular or perpendicular to the plane.

According to the fourth embodiment shown in FIG. 4, where the p-MTJ 4 has a sidewall 4s, the p-MTJ in the third embodiment is modified to include the metal buffer layer 18 previously described with respect to the second embodiment. Again, the buffer layer is beneficial in substantially reducing nitrogen migration from the metal M2 nitride or oxynitride portion of the capping layer 16x to the vertical anisotropy enhancement layer 15 and FL 14. All aspects of the buffer layer, including thickness and M1 metal composition, remain from the second embodiment.

In a fifth embodiment shown in FIG. 5, the bottom spin valve configuration in FIG. 1 is modified by preserving all the p-MTJ layers, but changing the deposition sequence to produce a p-MTJ 5 with sidewalls 5s and with a top spin valve configuration, where a seed layer 11, a barrier layer 16, a vertical anisotropy enhancement layer 15, a FL 14, a tunnel barrier layer 13, a pinning layer 12, and a hard mask 17 are formed sequentially on BE 10. The FL continues to have a first interface with the tunnel barrier layer and a second interface with the vertical anisotropy enhancement layer to enhance PMA in the FL. In this case, when the pinned layer has a SyAP configuration (not shown), the inner AP1 layer contacts the top surface of the tunnel barrier layer, while the outer AP2 layer abuts the bottom surface of the hard mask. It should be noted that for all top spin valve embodiments, the term "cap layer" is replaced by a "barrier layer" because layer 16 is no longer located above the FL and vertical anisotropy enhancement layer, but below the layer.

A sixth embodiment is depicted in FIG. 6, where all layers in the p-MTJ 2 are retained but stacked in a different order to produce a p-MTJ 6 with sidewall 6s and with a top spin valve configuration. In detail, the metal buffer layer 18 is inserted between the barrier layer 16 and the vertical anisotropy enhancing layer 15 to reduce the diffusion of nitrogen from the M1N, M1ON, M2M3N or M2M3ON barrier layer into the vertical anisotropy enhancing layer and the FL. Thus, seed layer 11, barrier layer 16, buffer layer 18, vertical anisotropy enhancement layer 15, FL 14, tunnel barrier layer 13, pinning layer 12, and hard mask 17 are sequentially formed on BE 10.

In a seventh embodiment shown in FIG. 7, the p-MTJ 3 in FIG. 3 is reconfigured to provide a p-MTJ 7 with sidewalls 7s, where a seed layer 11, an insulating matrix 16x with a conductive path 19 formed therein, a vertical anisotropy enhancement layer 15, a FL 14, a tunnel barrier layer 13, a pinning layer 12, and a hard mask 17 are formed sequentially on BE 10.

According to the eighth embodiment shown in FIG. 8, in which the p-MTJ 8 has a sidewall 8s, the p-MTJ in the seventh embodiment is modified to include the metal buffer layer 18 as described previously. The buffer layer advantageously substantially reduces nitrogen migration from the metal M2 nitride or oxynitride portion of the insulating matrix 16x to the vertical anisotropy enhancement layer 15 and FL 14. All aspects of the buffer layer, including thickness and M1 metal composition, remain from the sixth embodiment.

The present disclosure also includes methods of fabricating the p-MTJ cells described herein. All of the layers in the p-MTJ cell described herein may be formed in the Anelva C-7100 thin film sputtering system or similar system, which typically includes a plurality of Physical Vapor Deposition (PVD) chambers, each of which may house five targets, one oxidation chamber and one sputter etch chamber. Typically, the sputter deposition process includes a noble gas, such as argon, and does not include oxygen unless a tunneling barrier or a vertical anisotropic enhancement layer is desired in the oxidation chamber. Once all the layers in the p-MTJ stack are placed on the bottom electrode, a high temperature anneal at a temperature of about 360 ℃ to 400 ℃ may be performed in a vacuum oven for 1 to 5 hours to convert the amorphous tunnel barrier and the vertical anisotropy enhancement layer and the amorphous FL to crystalline layers for lattice matching in the tunnel barrier/FL/vertical anisotropy enhancement layer stack to improve DRR.

Thereafter, the array of p-MTJ cells can be fabricated by conventional lithographic patterning processes and Reactive Ion Etching (RIE) and/or Ion Beam Etching (IBE) processes known in the art. Subsequently, an encapsulation layer (not shown) is deposited to electrically insulate the p-MTJ cell. A Chemical Mechanical Polishing (CMP) process is typically used to form a smooth surface on the encapsulation layer that is coplanar with the upper surface of the hard mask in each p-MTJ cell. Then, an array of top electrodes (not shown) including conductive lines (e.g., bit lines or word lines) is formed over the p-MTJ array and the packaging layer to continue fabrication of the magnetic device. During a read or write operation, current flows from the BE through the p-MTJ to the top wire, or vice versa.

With respect to the formation of the conductive paths 19 in the metal nitride or metal oxynitride matrix 16x shown in fig. 3-4, a method similar to the method of forming the doped metal oxide layer described in the related application No. 15/728,818 may be employed. According to one embodiment illustrated in fig. 11, a conductive path formed from a M3 metal or alloy is formed in a M2N matrix in a reactive gas ambient generated by a Chemical Vapor Deposition (CVD), Physical Vapor Deposition (PVD), plasma-assisted CVD (pecvd) process, wherein the M3 species, the M2 species, and the nitrogen species N are simultaneously directed toward the top surface 15t of the vertical anisotropic enhancement layer 15 and react to form a film thereon. The conductive path may be formed during CVD, PVD or PECVD, or during a subsequent annealing step that promotes diffusion and aggregation of M3. It should be understood that when an M2ON substrate is desired, the reactive gas environment also includes oxygen species.

According to a second embodiment shown in fig. 12, during the first step, an M2 layer 16M having a top surface 16t is deposited on the vertical anisotropy enhancement layer 15. Then, a second step is performed in which the reactive gas ambient mentioned in the previous embodiments is limited to nitrogen species N and M3 species, providing conductive M3 channels 19 in the M2N matrix 16x, or to N, O and M1 species to form M3 channels in the M2ON matrix of fig. 3. Alternatively, the M2 layer may be first deposited on a metal buffer layer (not shown) and then a second step is performed to create a conductive M3 channel in the M2N or M2ON matrix in fig. 4 using N and M3 species (or N, O and M1 species), respectively.

In a third embodiment shown in fig. 13, where the M2N or M2ON layer 16x is deposited over the vertical anisotropy enhancement layer. Thereafter, as shown in FIG. 3, a reactive gas ambient comprising M3 species is generated and reacted with layer 16x to provide conductive paths 19 therein. Alternatively, the method shown in fig. 13 represents ion implantation of M3 species into the M2N or M2ON layers. One or more annealing steps may then be used to form the conductive M3 channel.

In yet another embodiment shown in FIG. 14, a stack of three layers 16x1/16d/16x2 is formed over the vertical anisotropy enhancement layer, followed by deposition of a hard mask 17. It should be noted that the layers 16x1, 16x2 are M2N or M2ON layers, while the layer 16d is an M3 layer. Alternatively, one of the 16x1 and 16x2 layers may be omitted to provide a bi-layer stack. Thereafter, one or more annealing steps diffuse M3 into the M2N or M2ON layer to form conductive pathways 19 in the M2N or M2ON matrix 16x shown in fig. 3.

In all embodiments, the p-MTJs 1-8 are patterned by a conventional sequence involving patterning in a photoresist mask (not shown) on the hard mask top surface 17t, followed by transferring the pattern through the p-MTJ stack using one or more IBE or RIE steps to form the sidewalls 1s-8s, respectively.

FIG. 15 is a top view after patterning the p-MTJ stack with the uppermost layer 17 and depositing and planarizing an encapsulation layer 20 to insulate adjacent p-MTJs in the array of rows and columns. In an exemplary embodiment, each p-MTJ has a circular shape with a critical dimension w that may be less than 100 nm. In other embodiments, each p-MTJ may have an elliptical or polygonal shape.

The performance of inserting a metal nitride layer in a p-MTJ according to embodiments of the present disclosure depends on forming a p-MTJ stack of layers first, with a CoFeB pinning layer, a MgO tunnel barrier layer, a CoFeB FL, a MgO vertical anisotropy enhancement layer, and a metal nitride layer deposited on a substrate. The hysteresis loops of the patterned p-MTJ stack were measured at room temperature and shown in fig. 9a for reference with the TiN cap layer disclosed in related application No. 15/461,779, and in fig. 9b-9d for respective MoN, WN and AlN layers formed in accordance with the first embodiment and shown in fig. 1. All the displaysExamples show PMA in FL and abrupt switching. Each p-MTJ is circular with a width of 100nm and the target thickness of the metal nitride cap layer is

In a second experiment, according to a second embodiment of the present disclosure shown in FIG. 2, the thickness in the p-MTJ was set to beThe Mo buffer layer is inserted at a target thickness of

Between the M1N capping layer and the MgO vertical anisotropy enhancement layer. The results of the experiments are collated in table 1 below. It should be noted that the thickness of the non-TiN capping layer has not been optimized, and further studies are expected to provide one or more of enhanced DRR, higher Hc, and lower RA relative to the TiN capping layer. The normalized Hc column shows that the best Hc was observed for p-MTJs with Mo/M1N stack, but may not correspond to the example providing the largest DRR.

TABLE 1 magnetic Properties of p-MTJs with seed layer/CoFeB/MgO/CoFeB/MgO/buffer/capping layer configurations

We confirm that the insertion of a metal buffer layer between a metal nitride (M1N) capping layer and a MgO vertical anisotropy enhancement layer is effective to reduce interdiffusion between M1N and MgO, according to the second embodiment in fig. 2. In detail, when the MgO vertical anisotropic enhanced layer and the thickness are

With the insertion of a Mo buffer layer between the TiN layers, DRR is increased by 10% compared to the prior art MgO/TiN stack. Furthermore, according to the second embodiment, when the thickness and the vertical anisotropy of the MgO layer are as followsWhen the Mo buffer layer is inserted between the MoN layers, DRR is increased by 3% compared to the MoN cap layer without the buffer layer. It should be noted that all the results in table 1 have been normalized and compared to the relative value of 1.00 for the TiN cap layer. Rp and RA_TOTALOn, Vc is the measure of the switching voltage and Hc is the coercive force (coercivity).

All of the embodiments described herein may be incorporated into a manufacturing scheme by standard tools (tools) and processes. Significant improvements in overall magnetic performance are achieved by observing higher DRR and FL PMA and fewer electrical shorts, while maintaining or reducing RA to further improve 64Mb and 256Mb STT-MRAM technology and related spintronic devices, where switching current, RA, DRR, FL PMA and thermal stability are all key parameters. Since more components can be used per unit of production time, reducing electrical shorts can lead to higher device yields and lower manufacturing costs. When the MoN cap layer according to the first embodiment was used in place of the TiN cap layer previously disclosed in related application No. 15/461,779, we observed a significant increase in the percentage of good devices (80nm p-MTJ cells) from 6% to 26%.

While the preferred embodiments of the present disclosure have been illustrated and described, it will be appreciated by those skilled in the art that changes may be made in these embodiments without departing from the principles and spirit of the disclosure.