Magnetic tunnel junction element and memory device including same

Abstract

A magnetic tunnel junction element and a memory device including the same are provided. The magnetic tunnel junction element includes: a pinned layer and a free layer facing each other; a buffer layer on the pinning layer; an auxiliary layer on the buffer layer; a polarization enhancement layer between the auxiliary layer and the free layer; and a tunnel barrier layer between the polarization enhancement layer and the free layer, in which the buffer layer is amorphous and includes CoFeBX, and X is W, Mo, Re, or Ta, and the auxiliary layer includes W, Mo, or Ta.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the priority of Korean Patent Application No. 10-2023-0161053 filed in the Korean Intellectual Property Office on November 20, 2023, the disclosure of which is incorporated herein by reference in its entirety. Technical Field

[0003] The present disclosure relates to a magnetic tunnel junction element and a memory device including the magnetic tunnel junction element. Background Art

[0004] Magnetic random access memory (MRAM) devices utilize magnetic tunnel junction elements to store data by using the resistance change of the element. The resistance of the magnetic tunnel junction element changes based on the magnetization direction of the free layer. For example, if the magnetization direction of the free layer is the same as that of the pinned layer, the magnetic tunnel junction element has a low resistance. On the contrary, if the magnetization direction of the free layer is opposite to that of the pinned layer, the magnetic tunnel junction element has a high resistance. This principle enables MRAM devices to represent binary data, for example, a low resistance state indicates data "0" and a high resistance state indicates data "1". Summary of the invention

[0005] The present disclosure provides a magnetic tunnel junction element having high tunneling magnetoresistance and exchange field, and a memory device including the magnetic tunnel junction element.

[0006] According to an embodiment of the present disclosure, a magnetic tunnel junction element is provided, comprising: a pinned layer and a free layer facing each other; a buffer layer on the pinned layer; an auxiliary layer on the buffer layer; a polarization enhancement layer between the auxiliary layer and the free layer; and a tunnel barrier layer between the polarization enhancement layer and the free layer, wherein the buffer layer is amorphous and comprises CoFeBX, and X is W, Mo, Re or Ta, and the auxiliary layer comprises W, Mo or Ta.

[0007] According to an embodiment of the present disclosure, a magnetic tunnel junction element is provided, comprising: a pinned layer and a free layer facing each other; a buffer layer on the pinned layer; a polarization enhanced layer between the buffer layer and the free layer; and a tunnel barrier layer between the polarization enhanced layer and the free layer, wherein the buffer layer is amorphous and comprises CoFeBX, and X is W, Mo, Re or Ta, the polarization enhanced layer comprises a first polarization enhanced layer and a second polarization enhanced layer, the second polarization enhanced layer is between the first polarization enhanced layer and the free layer, and the boron concentration contained in the second polarization enhanced layer is lower than the boron concentration contained in the first polarization enhanced layer.

[0008] According to an embodiment of the present disclosure, a memory device is provided, comprising: a plurality of memory cells, each memory cell comprising a magnetic tunnel junction element and a switching element connected to the magnetic tunnel junction element, wherein the magnetic tunnel junction element comprises: a pinned layer and a free layer facing each other; a buffer layer on the pinned layer; an auxiliary layer on the buffer layer; a polarization enhancement layer between the auxiliary layer and the free layer; and a tunnel barrier layer between the polarization enhancement layer and the free layer, wherein the buffer layer is amorphous and comprises CoFeBX, and X is W, Mo, Re or Ta, and the auxiliary layer comprises W, Mo or Ta. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 is a cross-sectional view showing a schematic structure of a magnetic tunnel junction element according to an embodiment of the present disclosure.

[0010] Figure 2 Shows the change according to Figure 1 Hysteresis curves measured when the materials of the buffer layer and the auxiliary layer of the magnetic tunnel junction element of the embodiment are used.

[0011] Figure 3 Another embodiment of the present disclosure is shown. Figure 1 Same cross-section.

[0012] Figure 4 Another embodiment of the present disclosure is shown. Figure 1 Same cross-section.

[0013] Figure 5 A memory cell including a magnetic tunnel junction element according to an embodiment of the present disclosure is briefly shown.

[0014] Figure 6 It schematically shows a plurality of Figure 5 A circuit diagram of a memory device showing a configuration of a memory cell. DETAILED DESCRIPTION

[0015] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. As those skilled in the art will appreciate, the described embodiments may be modified in various different ways without departing from the spirit or scope of the present disclosure.

[0016] The drawings and descriptions are to be regarded as illustrative in nature, and not restrictive. Throughout the specification, like reference numerals denote like elements.

[0017] For better understanding and ease of description, the size and thickness of each constituent element (eg, layer, film, panel, region, etc.) in the drawings are shown. Therefore, the following embodiments are not limited thereto.

[0018] It will be understood that when an element such as a layer, film, region, or substrate is referred to as being "on" another element, it can be directly on the other element or intervening elements may also be present. When an element is referred to as being "directly" "on" another element, there are no intervening elements. In addition, when an element is referred to as being "on" a reference element, it can be located above or below the reference element.

[0019] In addition, unless explicitly described to the contrary, the word “comprise” and variations such as “comprises” or “comprising” will be understood to imply the inclusion of stated elements but not the exclusion of any other elements.

[0020] In addition, the phrase "in plane" may refer to a view observed from a position above the object (e.g., from the top), and the phrase "in section" may refer to a view of a section cut vertically from the side of the object.

[0021] Figure 1 2 is a cross-sectional view showing a schematic structure of a magnetic tunnel junction element according to an embodiment. Figure 1 According to the embodiment, the magnetic tunnel junction element may include an electrode 101, a seed layer 110 on the electrode 101, a pinned layer 120 on the seed layer 110, a buffer layer 151 on the pinned layer 120, an auxiliary layer 152 on the buffer layer 151, a polarization enhancement layer 160 on the auxiliary layer 152, a tunnel barrier layer 130 on the polarization enhancement layer 160, and a free layer 140 on the tunnel barrier layer 130. In addition, a capping metal may be further disposed on the free layer 140.

[0022] The electrode 101 may include a conductive material so that the electrode 101 can apply current to the magnetic tunnel junction element. The electrode 101 may include a low resistance metal or a metal nitride. For example, the electrode 101 may include TiN or TaN. The electrode 101 may be part of a magnetic tunnel junction element; however, the electrode 101 may be part of a memory device including a magnetic tunnel junction element.

[0023] The seed layer 110 may be located on the electrode 101. For example, the seed layer 110 may be in direct contact with the electrode 101. The seed layer 110 may include Ru, Pt, Pd, or a combination thereof. In an embodiment, an intermediate layer may be located between the electrode 101 and the seed layer 110. The intermediate layer may be used to match the crystal structure of the electrode 101 and the seed layer 110 in the region between the electrode 101 and the seed layer 110. For example, the intermediate layer may include Ta.

[0024] The pinned layer 120 and the free layer 140 can be made of a ferromagnetic metal material with magnetism. For example, the pinned layer 120 and the free layer 140 can include iron (Fe), cobalt (Co), nickel (Ni), manganese (Mn), ruthenium (Ru), Fe-containing alloys, Co-containing alloys, Ni-containing alloys, Mn-containing alloys, Ru-containing alloys, Hosler alloys or combinations thereof. The pinned layer 120 can have a fixed magnetization direction, and the free layer 140 can have a variable magnetization direction. When the magnetization directions of the pinned layer 120 and the free layer 140 are the same (e.g., parallel), the magnetic tunnel junction element can have a low resistance. When the magnetization directions of the pinned layer 120 and the free layer 140 are opposite (e.g., antiparallel), the magnetic tunnel junction element can have a high resistance. This phenomenon is called tunneling magnetoresistance (TMR). By applying TMR, the magnetic tunnel junction element 100 can be used in a memory device.

[0025] As will be described in detail below, the magnetic tunnel junction element according to the present embodiment can alleviate the challenges of exchange field (Hex) degradation and tunneling magnetoresistance (TMR) reduction. These problems are usually caused by diffusion and crystal collision between layers in the magnetic tunnel junction element.

[0026] The pinned layer 120 and the free layer 140 may have a high perpendicular magnetic anisotropy (PMA), in particular an interface perpendicular magnetic anisotropy (IPMA). In other words, the energy associated with the perpendicular magnetic anisotropy of the pinned layer 120 and the free layer 140 may exceed the energy associated with the out-of-plane demagnetization. In this case, the magnetic moments of the pinned layer 120 and the free layer 140 may be stabilized in a direction perpendicular to the layer direction. The magnetic tunnel junction element may be applied to a spin transfer torque magnetic RAM (STT-MRAM) or a spin-orbit coupling torque (SOT) MRAM.

[0027] In order to improve the operating speed of the memory device using the magnetic tunnel junction element, the free layer 140 may have a low saturation magnetization (Ms). In order to reduce the saturation magnetization of the free layer 140, the free layer 140 may also be doped with a non-magnetic metal element. For example, the free layer 140 may be doped with a metal such as calcium (Ca), scandium (Sc), yttrium (Y), magnesium (Mg), strontium (Sr), barium (Ba), zirconium (Zr), beryllium (Be), titanium (Ti), hafnium (Hf), vanadium (V), zinc (Zn), niobium (Nb), manganese (Mn), aluminum (Al), chromium (Cr), lithium (Li), cadmium (Cd), lead (Pb), indium (In), gallium (Ga), tantalum (Ta) or a combination thereof. The non-magnetic metal doped into the free layer 140 may have an oxygen affinity higher than that of the ferromagnetic metal material of the free layer 140.

[0028] In addition, the free layer 140 may have two or more multilayer structures, the multilayer structure including a layer containing only a ferromagnetic metal material and a layer doped with a non-magnetic metal. By using the material and structure of the free layer 140, diffusion of oxygen or metal elements at the interface between the tunnel barrier layer 130 and the free layer 140 may be reduced or prevented, which will be described later.

[0029] The tunnel barrier layer 130 provides a magnetic tunnel junction between the pinned layer 120 and the free layer 140. The tunnel barrier layer 130 may include a crystalline metal oxide. For example, the tunnel barrier layer 130 may include MgO, MgAl 2 O 4 MgTiO x In an embodiment, the tunnel barrier layer 130 may include MgO.

[0030] The pinned layer 120 may be a synthetic antiferromagnet (SAF). The pinned layer 120 may include a first ferromagnetic layer 120a, a second ferromagnetic layer 120c, and a synthetic antiferromagnet (SAF) coupling layer 120b between the first ferromagnetic layer 120a and the second ferromagnetic layer 120c. The first ferromagnetic layer 120a may be in direct contact with the seed layer 110.

[0031] The SAF coupling layer 120b may include a conductive metal. For example, the SAF coupling layer 120b may include at least one of iridium (Ir), ruthenium (Ru), aluminum (Al), copper (Cu), silver (Ag), and alloys thereof.

[0032] Each of the first ferromagnetic layer 120a and the second ferromagnetic layer 120c may have a single-layer structure made of a ferromagnetic metal or an alloy of a ferromagnetic metal and a transition metal. Alternatively, each of the first ferromagnetic layer 120a and the second ferromagnetic layer 120c may have a multilayer structure including a plurality of layers, and the plurality of layers include a ferromagnetic metal or an alloy of a ferromagnetic metal and a transition metal. For example, each of the first ferromagnetic layer 120a and the second ferromagnetic layer 120c may include a single-layer structure or a multilayer structure, and the single-layer structure or the multilayer structure includes Co, Fe, CoPt, CoPtCr, FePt, CoFe, etc. In an embodiment, the first ferromagnetic layer 120a may include CoPt, and the second ferromagnetic layer 120c may include Co.

[0033] In such a structure of the pinned layer 120, due to the Ruderman-Kittel-Kasuya-Yosida (RKKY) interaction, the first ferromagnetic layer 120a and the second ferromagnetic layer 120c can form an antiferromagnet with the help of the SAF coupling layer 120b. In other words, when the magnetization direction of the first ferromagnetic layer 120a and the magnetization direction of the second ferromagnetic layer 120c are opposite to each other, the pinned layer 120 can have a stable state. For example, the first ferromagnetic layer 120a can be magnetized toward the lower surface, and the second ferromagnetic layer 120c can be magnetized toward the upper surface. Alternatively, the first ferromagnetic layer 120a can be magnetized toward the upper surface, and the second ferromagnetic layer 120c can be magnetized toward the lower surface. The first ferromagnetic layer 120a and the second ferromagnetic layer 120c magnetized in opposite directions (for example, antiparallel to each other) can cause the stray magnetic fields to cancel each other. Therefore, the first ferromagnetic layer 120 a and the second ferromagnetic layer 120 c magnetized in opposite directions reduce or prevent the stray magnetic field generated in the pinned layer 120 from affecting the free layer 140 .

[0034] Reference Figure 1 , the buffer layer 151 may be located on the second ferromagnetic layer 120c. The buffer layer 151 may be in direct contact with the second ferromagnetic layer 120c. The buffer layer 151 is amorphous and may mitigate crystal collision between a lower layer and an upper layer.

[0035] The buffer layer 151 may include CoFeBX. In this case, X may be W, Mo, Re, or Ta. The thickness of the buffer layer 151 may be to If the thickness of the buffer layer 151 is less than It may not be sufficient to mitigate crystal collisions, and if the thickness is greater than Since the buffer layer 151 is amorphous, the buffer layer 151 can alleviate crystal collision caused by the crystal structure difference between the second ferromagnetic layer 120c located at the bottom and the polarization enhanced layer 160 located at the top. The specific effect will be described separately later.

[0036] The auxiliary layer 152 may be located on the buffer layer 151. The auxiliary layer 152 may include W, Mo, or Ta. The auxiliary layer 152 includes a material having high temperature heat resistance, which can prevent diffusion of cobalt and boron in the magnetic tunnel junction element. The following Table 1 shows the structure and melting point of various materials.

[0037]

Table 1

[0038] Material Co W Mo Ta structure HCP BCC BCC BCC Melting point 1495℃ 3422℃ 2623℃ 3017℃

[0039] Referring to Table 1, W, Mo, and Ta contained in the auxiliary layer 152 have higher melting points than Co. Therefore, when the auxiliary layer 152 containing these materials is placed between the second ferromagnetic layer 120c and the polarization enhanced layer 160, diffusion of cobalt and boron may be prevented.

[0040] However, it can be seen from Table 1 above that the crystal structures of Co, W, Mo and Ta are different. In other words, Co has a hexagonal close-packed (HCP) structure, and W, Mo and Ta have a body-centered cubic (BCC) structure. Therefore, if W, Mo or Ta is formed directly above the Co layer, crystal collisions may occur at the interface. However, in the magnetic tunnel junction element according to the embodiment, the amorphous buffer layer 151 is located between the second ferromagnetic layer 120c containing Co and the auxiliary layer 152 containing W, Mo or Ta, so that crystal collisions can be prevented.

[0041] The thickness of the auxiliary layer 152 may be to The auxiliary layer 152 is formed as or less is not easy, and if the thickness of the auxiliary layer 152 is greater than Decoupling may occur. Although described in detail later, the auxiliary layer 152 may have the same crystal structure as the polarization enhancement layer 160 to be formed later, and therefore, the auxiliary layer 152 may act as a seed layer during the formation of the polarization enhancement layer 160, thereby enhancing the crystallinity of the polarization enhancement layer 160. For example, the auxiliary layer 152 may have a body-centered cubic (BCC) structure. The thickness of the auxiliary layer 152 may be thinner than that of the buffer layer 151.

[0042] The polarization enhancement layer 160 may be located on the auxiliary layer 152. The polarization enhancement layer 160 may help the tunnel barrier layer 130 and the free layer 140 grow. In addition, the polarization enhancement layer 160 has a crystal structure similar to that of the tunnel barrier layer 130 or the free layer 140. Therefore, the polarization enhancement layer 160 may further improve the crystal quality of the tunnel barrier layer 130 and the free layer 140. To achieve this, the polarization enhancement layer 160 may include a ferromagnetic material similar to the free layer 140.

[0043] The polarization enhanced layer 160 may include a first polarization enhanced layer 161 and a second polarization enhanced layer 162. The second polarization enhanced layer 162 may be located between the first polarization enhanced layer 161 and the tunnel barrier layer 130. For example, the second polarization enhanced layer 162 may directly contact the first polarization enhanced layer 161 and the tunnel barrier layer 130.

[0044] The first polarization enhancement layer 161 and the second polarization enhancement layer 162 may include the same material and have different composition ratios. The first polarization enhancement layer 161 and the second polarization enhancement layer 162 may include, for example, CoFeB. The proportion of boron (B) in the second polarization enhancement layer 162 may be less than the proportion of boron (B) in the first polarization enhancement layer 161. For example, the proportion of boron (B) in the first polarization enhancement layer 161 may be about 30 mol% to about 50 mol%, and the proportion of boron (B) in the second polarization enhancement layer 162 may be about 5 mol% to about 25 mol%.

[0045] In addition, the thickness of the second polarization enhanced layer 162 may be less than the thickness of the first polarization enhanced layer 161. For example, the thickness of the first polarization enhanced layer 161 may be about to about The thickness of the second polarization enhanced layer 162 may be about to about The composition ratio in the polarization enhanced layer 160 may be gradually adjusted to easily change the crystal structure from the pinned layer 120 to the free layer 140. Therefore, the crystal quality of the tunnel barrier layer 130 and the free layer 140 may be further improved.

[0046] Alternatively, the first polarization enhancement layer 161 and the second polarization enhancement layer 162 may have different compositions. Specifically, the first polarization enhancement layer 161 may include cobalt, and the second polarization enhancement layer 162 may not include cobalt. For example, the first polarization enhancement layer 161 may include CoFeB, and the second polarization enhancement layer 162 may include FeB.

[0047] The second polarization enhanced layer 162 is adjacent to the tunnel barrier layer 130. For example, the second polarization enhanced layer 162 may be in direct contact with the tunnel barrier layer 130. When the second polarization enhanced layer 162 adjacent to the tunnel barrier layer 130 does not contain cobalt, the performance of the magnetic tunnel junction element may be improved. For example, in the heat treatment process, cobalt may diffuse in both the direction of the pinned layer 120 and the direction of the free layer 140. Therefore, cobalt may diffuse toward the tunnel barrier layer 130, which may affect the performance of the magnetic tunnel junction element. However, when the second polarization enhanced layer 162 does not contain cobalt, the diffusion of cobalt toward the tunnel barrier layer 130 may be reduced.

[0048] In the magnetic tunnel junction element according to this embodiment, the first ferromagnetic layer 120a constitutes a lower pinned layer, the second ferromagnetic layer 120c, the buffer layer 151, the auxiliary layer 152 and the polarization enhancement layer 160 constitute an upper pinned layer, and the SAF coupling layer 120b is located between the lower pinned layer and the upper pinned layer. The first ferromagnetic layer 120a as the lower pinned layer may include CoPt. In addition, the upper pinned layer may use Co as the second ferromagnetic layer 120c and use CoFeB as the polarization enhancement layer 160. The Co / CoFeB combination should have a high tunneling magnetoresistance (TMR) value.

[0049] However, since Co is an HCP structure and CoFeB is a BCC structure, crystal collision occurs when CoFeB is formed directly above Co. In addition, during the high-temperature heat treatment process of manufacturing the magnetic tunnel junction element, diffusion occurs at the interface between Co and CoFeB, thereby reducing the tunneling magnetoresistance characteristics of the magnetic tunnel junction element. In other words, diffusion changes the crystallinity of Co and CoFeB, which may cause a reduction in the exchange field (Hex).

[0050] Therefore, the magnetic tunnel junction element according to the embodiment is designed to maintain the inherent crystallinity of each material even under high-temperature heat treatment by placing an amorphous buffer layer 151 containing CoFeBX (X=W, Mo, Re or Ta) between the second ferromagnetic layer 120c containing Co and the polarization enhancement layer 160 containing CoFeB. In other words, the magnetic tunnel junction element as described in the embodiment can maintain the inherent crystallinity of each material even when subjected to high-temperature heat treatment. This is achieved by incorporating an amorphous buffer layer 151 containing CoFeBX between the second ferromagnetic layer 120c containing Co and the polarization enhancement layer 160 containing CoFeB.

[0051] The buffer layer 151 is amorphous, which can alleviate the crystal collision between the HCP structure of Co and the BCC structure of CoFeB. In other words, if the BCC structure is formed directly above the HCP structure, crystal collision may occur at the interface due to the difference in crystal structure. However, as in the present embodiment, if the amorphous buffer layer is located between the HCP and the BCC, such crystal collision can be prevented.

[0052] In addition, in the present embodiment, the auxiliary layer 152 may be located on the buffer layer 151. The auxiliary layer 152 may include W, Mo, or Ta. The auxiliary layer 152 has a BCC structure and may be used as a seed layer for growing CoFeB having a BCC structure. Therefore, the crystallinity of CoFeB formed on the auxiliary layer 152 may be enhanced. In addition, the auxiliary layer 152 includes a high temperature resistant material, so that element diffusion between the second ferromagnetic layer 120c and the polarization enhanced layer 160 may be prevented.

[0053] In addition, in the magnetic tunnel junction element according to the present embodiment, the buffer layer 151 and the auxiliary layer 152 are located between Co and CoFeB. Therefore, the overall thickness of the Co and CoFeB junction increases, and the saturation magnetization (Ms) value can be reduced due to the increase in thickness. This can increase the exchange field.

[0054] In this case, the thickness of the buffer layer 151 may be thicker than that of the auxiliary layer 152. The thickness of the buffer layer 151 may be to And the thickness of the auxiliary layer 152 may be to If the thickness of the buffer layer 151 is less than Then it may not have sufficient crystal mismatch mitigation effect. In addition, when the thickness of the buffer layer 151 exceeds or the thickness of the auxiliary layer 152 becomes greater than In other words, the sum of the thickness of the buffer layer 151 and the auxiliary layer 152 between the Co-containing layer and the CoFeB-containing layer should not exceed 1000 Å. When the sum of the thickness of the buffer layer 151 and the auxiliary layer 152 exceeds When , decoupling may occur between Co and CoFeB.

[0055] Hereinafter, the effects of the magnetic tunnel junction element according to the present embodiment will be described through specific experimental examples.

[0056] Figure 2 Hysteresis curves measured when the materials of the buffer layer 151 and the auxiliary layer 152 of the magnetic tunnel junction element according to the embodiment are changed are shown.

[0057] In addition, Table 2 shows Figure 2 The resistance per unit area (RA, Ωμm) of the materials of the buffer layer 151 and the auxiliary layer 152 tested in 2 ) and tunneling magnetoresistance (TMR). Experimental Examples 1 and 2 changed the order of the auxiliary layer / buffer layer for the same material, and the improvement rate of Experimental Example 2 when the efficiency of Experimental Example 1 was set to 100 was shown. In the case of Experimental Examples 3 and 4, the improvement rate of Experimental Example 4 when the efficiency of Experimental Example 3 was set to 100 by changing the order of the auxiliary layer / buffer layer for the same material was shown. In the case of Experimental Examples 5 and 6, the improvement rate of Experimental Example 6 when the efficiency of Experimental Example 5 was set to 100 by changing the order of the auxiliary layer / buffer layer for the same material was shown. In Table 2 below, Experimental Examples 2, 4, and 6 are included in the embodiments of the present disclosure.

[0058]

Table 2

[0059]

[0060]

[0061] First, refer to Figure 2 In the case of the experimental example 1 (auxiliary layer CFBMo / buffer layer W) combination, the inflection point of the hysteresis curve appears near about 18 kOe. The portion where this inflection point appears corresponds to the exchange field (Hex) value of the magnetic tunnel junction element. However, in the case of experimental examples 2, 4, and 6 included in the embodiments of the present disclosure, Figure 2 No inflection point of the magnetic tunnel junction element appears in the graph, and it can be seen that the exchange field (Hex) value is 18 kOe or more.

[0062] In addition, referring to Table 2, it can be seen that Experimental Example 2 included in the embodiment of the present disclosure has a higher tunneling magnetoresistance (TMR) value than Experimental Example 1, and Experimental Example 4 has a higher tunneling magnetoresistance (TMR) value than Experimental Example 3.

[0063] In other words, it can be seen that the magnetic tunnel junction element including the buffer layer and the auxiliary layer as in this embodiment has a high exchange field (Hex) and a high tunneling magnetoresistance (TMR). This is because the buffer layer alleviates the crystal collision between cobalt and CoFeB, as described above. In addition, the auxiliary layer plays a role in preventing the diffusion of cobalt and boron, and acts as a seed layer on which the CoFeB of the BCC structure can grow. In Table 3 and above Figure 2 It was confirmed that the combination of the buffer layer CFBMo and the auxiliary layer W of Experimental Example 2 was the most effective. When the polarization enhancement layer 160 of different materials was used for this combination of the buffer layer CFBMo and the auxiliary layer W, the resistance per unit area (RA, Ωμm) was measured. 2 ) and tunneling magnetoresistance TMR and are shown in Table 3.

[0064]

Table 3

[0065]

[0066]

[0067] In Table 3, the number next to B indicates the boron content. In other words, CoFeB30 contains 30 mol% of boron, while FeB20 contains 20 mol% of boron.

[0068] Experimental Example 7 was conducted using a single-layer polarization enhanced layer. Experimental Example 8 was conducted in the case where the boron content in the second polarization enhanced layer was lower than that in the first polarization enhanced layer, and cobalt was not contained in the second polarization enhanced layer.

[0069] Experimental Example 9 was conducted when the boron concentrations in the first and second polarization enhanced layers were the same and the first polarization enhanced layer did not contain Co. Experimental Example 10 was conducted when the first polarization enhanced layer did not contain Co and the second polarization enhanced layer did not contain Boron.

[0070] Referring to Table 3, it can be seen that Experimental Example 8 corresponding to the present embodiment has the highest tunneling magnetoresistance (TMR) value.

[0071] In other words, if the first polarization enhanced layer 161 includes CoFeB and the second polarization enhanced layer 162 includes FeB and does not include cobalt, diffusion of cobalt toward the tunnel barrier layer 130 may be reduced, thereby improving tunneling magnetoresistance (TMR).

[0072] The magnetic tunnel junction element according to the present embodiment has the buffer layer 151 and the auxiliary layer 152 located between the second ferromagnetic layer 120 c and the polarization enhanced layer 160 , for example, between Co and CoFeB in the stacked structure of the magnetic tunnel junction element.

[0073] The buffer layer 151 alleviates the crystal collision between the HCP structure of cobalt and the BCC structure of CoFeB, and the auxiliary layer 152 having the BCC structure serves as a seed layer for the growth of CoFeB, thereby enhancing the crystallinity of the CoFeB layer. In addition, the auxiliary layer 152 can prevent the diffusion of cobalt and boron during a high temperature process of 400°C or higher. In addition, the polarization enhanced layer 160 has a multilayer structure, and the boron concentration of the upper layer is lower than that of the lower layer, thereby reducing the diffusion of boron into the tunnel barrier layer. According to an embodiment, when the polarization enhanced layer 160 has a multilayer structure, the upper layer may not contain cobalt. In this case, the diffusion of cobalt toward the tunnel barrier layer 130 can be reduced, thereby improving the tunneling magnetoresistance (TMR).

[0074] Hereinafter, other embodiments of the present disclosure will be described. In the magnetic tunnel junction element according to the present embodiment, heat treatment of the auxiliary layer 152 may be performed after the auxiliary layer 152 is formed. In other words, after the auxiliary layer 152 is formed, the crystallinity of the auxiliary layer 152 may be enhanced by heat treating the auxiliary layer 152. When the crystallinity of the auxiliary layer 152 is enhanced by heat treatment of the auxiliary layer 152, the crystallinity of the subsequently formed polarization enhanced layer 160 may also be improved. This is because when the crystallinity of the auxiliary layer 152 as a seed layer is improved, the crystallinity of the polarization enhanced layer 160 formed thereon is also improved.

[0075] exist Figure 1 , a configuration including the buffer layer 151, the auxiliary layer 152, the first polarization enhanced layer 161, and the second polarization enhanced layer 162 is shown, but in other embodiments, only some of these configurations may be included.

[0076] Figure 3 Another embodiment is shown with Figure 1 Same cross section. Figure 3 , except that the polarization enhancement layer 160 is a single layer, the magnetic tunnel junction element according to this embodiment is Figure 1 For example, in Figure 3 In the embodiment of the present invention, the polarization enhanced layer 160 may be made of a single layer. For example, the polarization enhanced layer 160 may be a single layer including CoFeB. Figure 3 The description of other layers in Figure 1 Same, so omitted.

[0077] In this case, with Figure 1 Similar to the embodiment of the present invention, the crystal collision between the HCP structure of Co and the BCC structure of CoFeB is alleviated by the buffer layer 151, and the auxiliary layer 152 having BCC enhances the crystallinity of CoFeB by serving as a seed layer for the growth of CoFeB. The auxiliary layer 152 prevents the diffusion of cobalt and boron, which can improve the tunneling magnetoresistance (TMR) and the exchange field (Hex).

[0078] Figure 4 Another embodiment is shown with Figure 1 Same cross section. Figure 4 , except that it does not include the auxiliary layer 152, the magnetic tunnel junction element according to this embodiment is Figure 1 The same as the embodiment.

[0079] Detailed description of the same components is omitted. Figure 4 As shown, even when the auxiliary layer 152 is not included, the buffer layer 151 alleviates the crystal collision between the HCP structure of cobalt and the BCC structure of CoFeB, thereby improving the tunneling magnetoresistance (TMR) and the exchange field (Hex).

[0080] Hereinafter, a memory cell and a memory device including a magnetic tunnel junction element according to the present embodiment will be described with reference to the accompanying drawings. However, this description is only an example, and the present disclosure is not limited thereto.

[0081] Figure 5 A memory cell including a magnetic tunnel junction element according to an embodiment is briefly shown. Figure 5, the memory cell MC may include the above-mentioned magnetic tunnel junction element 100 and a switching element (TR) connected thereto. The switching element TR may be a transistor, such as a thin film transistor, for example, a field effect transistor. The memory cell MC may be connected between a bit line BL and a word line WL. The bit line BL and the word line WL may cross each other, and the memory cell MC may be disposed at their intersection. The bit line BL may be electrically connected to the free layer 140 of the magnetic tunnel junction element 100, and the word line WL may be connected to the gate of the switching element TR. In addition, a first source / drain electrode of the switching element TR may be electrically connected to an electrode 101 of the magnetic tunnel junction element 100, and a second source / drain electrode of the switching element TR may be electrically connected to a selection line SL. For example, the selection line SL may extend parallel to the word line WL. In this structure, a write current, a read current, an erase current, etc. may be applied to the memory cell MC through the word line WL and the bit line BL. In Figure 5 , the memory cell MC is shown as comprising Figure 1 The magnetic tunnel junction element 100 shown in FIG. 1 is a schematic diagram of a memory cell MC. However, the memory cell MC may also include a magnetic tunnel junction element according to other embodiments, such as Figure 3 and Figure 4 Those magnetic tunnel junction elements shown.

[0082] Figure 6 It schematically shows a plurality of Figure 5 A circuit diagram of the structure of a memory device having a memory cell is shown. Figure 6 , the memory device 600 may include a plurality of bit lines BL, a plurality of word lines WL, a plurality of selection lines SL, a plurality of memory cells MC disposed at each intersection of the plurality of bit lines BL and the plurality of word lines WL, a bit line driver 601 for applying current to the plurality of bit lines BL, a word line driver 602 for applying current to the plurality of word lines WL, and a selection line driver 603 for applying current to the plurality of selection lines SL. Each memory cell MC may have Figure 5 The structure shown. Figure 6 The illustrated memory device 600 may be, for example, a 1T1MTJ element including one transistor and one magnetic tunnel junction element.

[0083] Figure 6 The memory device 600 shown may be a magnetic random access memory (MRAM) and may be used in electronic devices using non-volatile memory. For example, Figure 6 The memory device 600 shown may be an STT-MRAM in which the magnetization direction of the free layer is changed by a spin current directly applied to the free layer of the magnetic tunnel junction element. Since the STT-MRAM does not require a separate conductor to generate an external magnetic field, it is useful for high integration and has a simple operation method. In addition, Figure 6The illustrated memory device 600 may also be applied to SOT-MRAM.

[0084] As described above, the magnetic tunnel junction element and the memory device including the magnetic tunnel junction element according to the present embodiment include the buffer layer 151 and the auxiliary layer 152. Therefore, by adopting the buffer layer 151, crystal collision between the upper layer and the lower layer can be prevented, diffusion of elements in the magnetic tunnel junction element can be prevented by the auxiliary layer 152, and crystallinity of the upper layer can be enhanced.

[0085] In addition, polarization enhanced layer 160 is formed in multiple layers, the boron content of the upper layer is less than that of the lower layer, and the upper layer does not contain cobalt, thereby preventing diffusion. The magnetic tunnel junction element according to this embodiment can have high tunneling magnetoresistance (TMR) and exchange field (Hex).

[0086] Although the embodiments of the present disclosure have been described above, it should be understood that the present disclosure is not limited to the disclosed embodiments. For example, the present disclosure is intended to cover various modifications and equivalent arrangements included in the spirit and scope of the appended claims.

Claims

1. A magnetic tunnel junction element, comprising: A pinned layer and a free layer facing each other; a buffer layer on the pinned layer; an auxiliary layer on the buffer layer; a polarization enhancement layer between the auxiliary layer and the free layer; as well as a tunnel barrier layer between the polarization enhanced layer and the free layer, The buffer layer is amorphous and includes CoFeBX, and X is W, Mo, Re or Ta. The auxiliary layer includes W, Mo or Ta.

2. The magnetic tunnel junction element according to claim 1, wherein: The auxiliary layer is thinner than the buffer layer.

3. The magnetic tunnel junction element according to claim 1, wherein: The thickness of the buffer layer is to 4. The magnetic tunnel junction element according to claim 1, wherein: The thickness of the auxiliary layer is to 5. The magnetic tunnel junction element according to claim 1, wherein: The sum of the thickness of the buffer layer and the thickness of the auxiliary layer is less than 6. The magnetic tunnel junction element according to claim 1, wherein: The polarization enhancement layer includes a first polarization enhancement layer and a second polarization enhancement layer, and The second polarization enhanced layer is between the first polarization enhanced layer and the free layer.

7. The magnetic tunnel junction element according to claim 6, wherein: The second polarization enhanced layer includes a boron concentration lower than a boron concentration included in the first polarization enhanced layer.

8. The magnetic tunnel junction element according to claim 6, wherein: The first polarization enhancement layer comprises CoFeB, The second polarization enhanced layer includes Co or does not include Co.

9. The magnetic tunnel junction element according to claim 1, wherein: The pinning layer has a multi-layer structure, The pinning layer includes Co.

10. The magnetic tunnel junction element according to claim 1, wherein: The auxiliary layer and the polarization enhanced layer have a body-centered cubic (BCC) structure.

11. The magnetic tunnel junction element according to claim 1, wherein: The pinned layer and the polarization enhanced layer have different crystal structures.

12. A magnetic tunnel junction element, comprising: A pinned layer and a free layer facing each other; a buffer layer on the pinned layer; a polarization enhancement layer between the buffer layer and the free layer; as well as a tunnel barrier layer between the polarization enhanced layer and the free layer, The buffer layer is amorphous and includes CoFeBX, and X is W, Mo, Re or Ta. The polarization enhancement layer includes a first polarization enhancement layer and a second polarization enhancement layer, The second polarization enhanced layer is between the first polarization enhanced layer and the free layer, and The second polarization enhanced layer includes a boron concentration lower than a boron concentration included in the first polarization enhanced layer.

13. The magnetic tunnel junction element according to claim 12, wherein: The first polarization enhancement layer comprises CoFeB, The second polarization enhanced layer includes Co or does not include Co.

14. The magnetic tunnel junction element according to claim 13, further comprising: an auxiliary layer between the buffer layer and the first polarization enhanced layer, The auxiliary layer includes W, Mo or Ta.

15. The magnetic tunnel junction element according to claim 12, wherein: The pinning layer has a multi-layer structure, The pinning layer includes Co.

16. A storage device comprising: a plurality of memory cells, each memory cell comprising a magnetic tunnel junction element and a switch element connected to the magnetic tunnel junction element, Wherein, the magnetic tunnel junction element comprises: A pinned layer and a free layer facing each other; a buffer layer on the pinned layer; an auxiliary layer on the buffer layer; a polarization enhanced layer between the auxiliary layer and the free layer; and a tunnel barrier layer between the polarization enhanced layer and the free layer, The buffer layer is amorphous and includes CoFeBX, and X is W, Mo, Re or Ta. The auxiliary layer includes W, Mo or Ta.

17. The memory device according to claim 16, wherein: The polarization enhancement layer includes a first polarization enhancement layer and a second polarization enhancement layer, The second polarization enhanced layer is between the first polarization enhanced layer and the free layer, and The second polarization enhanced layer includes a boron concentration lower than a boron concentration included in the first polarization enhanced layer.

18. The memory device according to claim 17, wherein: The first polarization enhancement layer comprises CoFeB, The second polarization enhanced layer includes or excludes Co.

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