Capacitor and manufacturing method of capacitor

Abstract

To provide a capacitor capable of increasing capacitance and reducing leakage current.SOLUTION: A disclosed capacitor 10 includes a first structure 110 including a first electrode, a dielectric layer 103 disposed on the first structure 110, and a second structure 120 disposed on the dielectric layer 103 and including a second electrode. The first structure includes a first oxide layer 111 including a first metal element and a second oxide layer 112 disposed on the first oxide layer 111. The dielectric layer 103 is disposed on the second oxide layer 112 and is an oxide layer containing a second metal element different from the first metal element. The second oxide layer 112 includes the first metal element and the second metal element. The second oxide layer 112 has a first surface 112a on the first oxide layer 111 side and a second surface 112b on the dielectric layer 103 side. The dielectric layer 103 includes a crystalline structure.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to capacitors and methods for manufacturing capacitors. [Background technology]

[0002] Various capacitors have been proposed in the past. Claim 1 of Patent Document 1 (JP 2006-135339 A) states: "forming a storage electrode; forming a multi-layer dielectric film consisting of a ZrO2 thin film and an Al2O3 thin film on the storage electrode; forming a plate electrode on the multiple dielectric film; "A method for forming a capacitor in a semiconductor device, comprising:

[0003] Claim 1 of Patent Document 2 (JP 2012-80095 A) states: "A method for manufacturing a semiconductor device having a capacitor, The method for forming a capacitor comprises: forming a lower electrode made of a titanium nitride film on a semiconductor substrate; forming a dielectric film made of zirconium oxide on the lower electrode; forming an upper electrode including a titanium nitride film on the dielectric film; Equipped with the step of forming the dielectric film includes a step of forming a film to be formed on at least the uppermost layer of the dielectric film by an atomic layer deposition (ALD) method; The document states, "A method for manufacturing a semiconductor device further comprising, between the step of forming the dielectric film and the step of forming the upper electrode, a step of forming a first protective film on the film formed on the uppermost layer of the dielectric film, without applying a temperature that exceeds the film formation temperature of the ALD method for the film by 70°C or more." [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-135339 [Patent Document 2] Japanese Patent Application Laid-Open No. 2012-80095 Summary of the Invention [Problem to be solved by the invention]

[0005] Capacitors using an oxide layer are known as capacitors with high heat resistance. To improve the characteristics of a capacitor (for example, to increase capacitance and reduce leakage current), it is important that the dielectric constant of the dielectric layer is high and that defects (such as cracks) in the dielectric layer are suppressed. In this situation, one of the objectives of the present disclosure is to provide a capacitor that can increase capacitance and reduce leakage current. [Means for solving the problem]

[0006] One aspect of the present disclosure is a capacitor, comprising: a first structure including a first electrode; a dielectric layer disposed on the first structure; a second structure disposed on the dielectric layer and including a second electrode; the first structure includes a first oxide layer including a first metal element and a second oxide layer disposed on the first oxide layer; the dielectric layer is an oxide layer disposed on the second oxide layer and containing a second metal element different from the first metal element; the second oxide layer contains the first metal element and the second metal element, the second oxide layer has a first surface on the first oxide layer side and a second surface on the dielectric layer side; The dielectric layer relates to a capacitor, wherein the dielectric layer includes a crystalline structure.

[0007] Another aspect of the present disclosure is a method for manufacturing a capacitor, comprising: (i) forming a first structure comprising a first electrode; (ii) forming a dielectric layer including a crystalline structure on the first structure; and (iii) forming a second structure on the dielectric layer, the second structure including a second electrode; the first structure includes a first oxide layer including a first metal element and a second oxide layer disposed on the first oxide layer; the dielectric layer is disposed on the second oxide layer and includes a second metal element different from the first metal element; The second oxide layer includes the first metal element and the second metal element. [Effects of the Invention]

[0008] According to the present disclosure, a capacitor with high heat resistance can be obtained. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a schematic cross-sectional view of an example of a capacitor according to this embodiment. [Figure 2] FIG. 2 is a schematic cross-sectional view of another example of the capacitor according to this embodiment. [Figure 3] FIG. 3 is a schematic cross-sectional view of another example of the capacitor according to this embodiment. [Figure 4] FIG. 4 is a schematic cross-sectional view of another example of the capacitor according to this embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] The following describes embodiments of the present disclosure using examples, but the present disclosure is not limited to the examples described below. In the following description, specific numerical values ​​and materials may be exemplified. However, other numerical values ​​and other materials may be applied as long as the invention of the present disclosure can be implemented. In this specification, the term "numerical value A to numerical value B" includes numerical value A and numerical value B and can be read as "numerical value A or more and numerical value B or less." In the following description, when lower and upper limits of numerical values ​​related to specific physical properties or conditions are exemplified, any of the exemplified lower limits and any of the exemplified upper limits can be arbitrarily combined, as long as the lower limit is not equal to or greater than the upper limit. In the following description, when examples of components or methods are listed, only one of the listed examples may be used, or multiple of the listed examples may be used in combination, unless otherwise specified.

[0011] (Capacitor) The capacitor according to this embodiment may be referred to as "capacitor (C)" below. The capacitor (C) includes a first structure including a first electrode, a dielectric layer disposed on the first structure, and a second structure disposed on the dielectric layer and including a second electrode. The first structure includes a first oxide layer including a first metal element and a second oxide layer disposed on the first oxide layer. The dielectric layer is disposed on the second oxide layer and is an oxide layer including a second metal element different from the first metal element. The second oxide layer includes the first metal element and the second metal element. The second oxide layer has a first surface on the first oxide layer side and a second surface on the dielectric layer side. The dielectric layer includes a crystalline structure.

[0012] A dielectric layer having a crystal structure is affected by an adjacent layer. For example, when a dielectric layer made of ZrO2 is formed on an Al2O3 layer, due to the difference in thermal expansion coefficients between the two, defects (cracks) are likely to occur in the dielectric layer. In a capacitor (C), a second oxide layer is disposed between a first oxide layer (e.g., an Al2O3 layer) and the dielectric layer. The second oxide layer contains a first metal element included in the first oxide layer and a second metal element included in the dielectric layer. Therefore, compared with the case where the dielectric layer is directly formed on the first oxide layer, the generation of defects in the dielectric layer due to the difference in thermal expansion coefficient can be suppressed. As a result, the leakage current of the capacitor (C) can be reduced. Also, the reliability of the capacitor (C) against thermal cycles can be improved.

[0013] Furthermore, by making the composition of the second surface of the second oxide layer closer to the composition of the dielectric layer, the lattice mismatch and the difference in thermal expansion coefficient can be reduced, and the crystallinity of the dielectric layer formed on the second oxide layer can be enhanced. By enhancing the crystallinity of the dielectric layer, further increase in the capacitance of the capacitor (C) becomes possible.

[0014] In the capacitor (C), it is preferable that the following conditions (1) and (2) are satisfied. <000010,7>(1) The composition ratio M1f of the first metal element in the first oxide layer, the composition ratio M1s of the first metal element in the second oxide layer, and the composition ratio M1d of the first metal element in the dielectric layer satisfy the relationship M1d < M1s < M1f. (2) The composition ratio M2f of the second metal element in the first oxide layer, the composition ratio M2s of the second metal element in the second oxide layer, and the composition ratio M2d of the second metal element in the dielectric layer satisfy the relationship M2f < M2s < M2d.

[0015] By satisfying conditions (1) and (2), the generation of defects in the dielectric layer can be particularly suppressed. In conditions (1) and (2), the composition ratio in the first oxide layer means the composition ratio in the entire first oxide layer. In conditions (1) and (2), the composition ratio in the second oxide layer means the composition ratio in the entire second oxide layer.

[0016] (Dielectric layer) The dielectric layer may include a polycrystalline structure or may be composed of a polycrystalline structure. The relative permittivity of the dielectric layer including a polycrystalline structure is preferably 30 or more. By making the composition of the second surface of the second oxide layer closer to the composition of the dielectric layer and reducing the lattice mismatch and the difference in thermal expansion coefficient, the crystallization of the dielectric layer is promoted. As a result, it is possible to make the relative permittivity of the dielectric layer be 30 or more.

[0017] The dielectric layer may be a layer of an oxide of at least one element selected from the group consisting of zirconium and hafnium. For example, the dielectric layer may be a zirconium oxide layer (e.g., ZrO2), a hafnium oxide layer (e.g., HfO2), and Hf X Zr 1-X O2 (0 < X < 1), etc. Alternatively, the dielectric layer may be a layer of an oxide other than these. For example, the dielectric layer may be tantalum oxide (e.g., Ta2O5), titanium oxide (e.g., TiO2), niobium oxide (e.g., NbO X ), etc. In this specification, the composition ratio of oxygen in the composition formula of the oxide is the composition ratio assuming no oxygen deficiency. The actual oxide may contain oxygen deficiency. For example, zirconium oxide may be represented by ZrO 2-Z (Z is oxygen deficiency).

[0018] The thickness of the dielectric layer is not particularly limited. The thickness of the dielectric layer may be 5 nm or more, or 10 nm or more, and may also be 100 nm or less, 50 nm or less, 25 nm or less, or 10 nm or less. In the capacitor (C), even a thin dielectric layer (e.g., with a thickness of 50 nm or less) where crystallization is unlikely to occur can be promoted in crystallization by the second oxide layer. As a result, it is possible to increase the capacitance.

[0019] The first electrode may be a conductive layer. The first electrode may be composed of only a metal layer. The first electrode may include a metal layer and a first oxide layer formed on the metal layer. The first oxide layer may be a conductive layer or an insulating layer.

[0020] (1st structure) The first structure includes multiple layers. The first structure includes a first oxide layer and a second oxide layer formed on the first oxide layer. The first structure may include layers other than the first oxide layer and the second oxide layer.

[0021] The first structure may include a metal layer containing a first metal element. In this case, the first oxide layer is disposed on the metal layer. The metal layer functions as a first electrode. The metal constituting the metal layer is not limited and may be at least one selected from the group consisting of Al, Mo, Ni, Cu, Ti, Ta, Nb, and alloys thereof. Examples of metal layers include metal layers disposed on a substrate, metal foils, metal substrates, metal foils made porous by etching or other processes, sintered bodies of metal powders, and metal layers disposed within a dielectric.

[0022] The first oxide layer may be a layer formed by a vapor deposition method or the like. Alternatively, the first oxide layer may be a layer formed by oxidizing a metal layer. Alternatively, the first oxide layer may be a natural oxide layer of the metal layer. When the metal layer is an aluminum layer (e.g., aluminum foil), the first oxide layer may be an aluminum oxide layer (Al2O3 layer) formed by natural oxidation of the surface of the aluminum layer.

[0023] The first metal element is one type of element, and the second metal element is one type of element. The first metal element may be Al, Mo, Ni, Cu, Ti, Ta, Nb, or Si. Although Si is sometimes classified as a metalloid element, Si can constitute metallic Si, and therefore, in this specification, Si will be described as a metal element. When Si is not included in the metal elements, the first metal element can be interpreted as "a first element that is a metal element or Si." The first oxide layer may be a layer of an oxide of the first metal element, or a layer of a composite oxide containing the first metal element and other elements (elements other than oxygen). The other elements other than oxygen may be one element or multiple elements. In the first oxide layer, the proportion of the first metal element in the elements other than oxygen M may be 50 atomic % or more, or 90 atomic % or more, but is 100 atomic % or less. In the second oxide layer, the proportion of the first metal element in the elements other than oxygen M may be 50 atomic % or more, or 90 atomic % or more, but is 100 atomic % or less.

[0024] The first electrode may be a conductive layer. The first electrode may be composed of only a metal layer, or may be composed of only a conductive layer other than a metal layer. Alternatively, the first electrode may be a laminate of a metal layer and a conductive layer other than a metal layer. The first electrode may include a metal layer and a first oxide layer disposed on the metal layer. The first oxide layer may be a conductive layer or an insulating layer. The first oxide layer may be amorphous. Alternatively, the first oxide may have a crystalline structure. For example, the first oxide may be composed of an amorphous and a polycrystalline structure, or may be composed of a polycrystalline structure. The metal layer may include at least one element selected from the group consisting of Al, Mo, Ni, Cu, Ti, Ta, Nb, and Si. The metal layer may be composed of an alloy containing at least one of these elements.

[0025] The first electrode may include a first oxide layer. In this case, the first oxide layer is made of an oxide having electrical conductivity. Examples of the first oxide layer having electrical conductivity include a RuO2 layer and an IrO2 layer. The first oxide layer may include a polycrystalline structure or may be made of a polycrystalline structure. When the first oxide layer has a polycrystalline structure, the crystallinity of the second oxide layer can be increased.

[0026] The thickness of the first electrode is not limited as long as it can ensure the necessary conductivity. The surface of the first electrode may be roughened or not. Using a first electrode with a non-roughened surface makes it easier to improve the crystallinity of the dielectric layer.

[0027] (Second oxide layer) The second oxide layer may have a crystalline structure on the second surface. For example, the second surface of the second oxide layer may have a polycrystalline structure. The presence of a crystalline structure on the second surface can enhance the crystallinity of the dielectric layer.

[0028] The second oxide layer may be entirely polycrystalline, or the second oxide layer may be amorphous on the first surface side and polycrystalline on the second surface side.

[0029] When the first oxide layer is a conductive layer, the second oxide layer may be a conductive layer or an insulating layer, and when the first oxide layer is an insulating layer, the second oxide layer may be an insulating layer.

[0030] The thickness of the first oxide layer may be 1 nm or more, or 5 nm or more, or 10 nm or less, or 5 nm or less. By making the thickness of the first oxide layer 5 nm or less, it becomes easier to achieve high capacity. The thickness of the second oxide layer may be 2 nm or more, or 5 nm or more, or 10 nm or less, or 5 nm or less. By making the thickness of the second oxide layer 2 nm or more, it becomes easier to increase the crystallinity of the second oxide layer.

[0031] Examples of combinations of the first metal element and the second metal element include molybdenum and zirconium, aluminum and zirconium, molybdenum and hafnium, and aluminum and hafnium.

[0032] In the capacitor (C), the following conditions (3) and / or (4) may be satisfied: (3) The composition ratio of the first metal element at the first surface of the second oxide layer is higher than the composition ratio of the first metal element at the second surface of the second oxide layer. (4) The composition ratio of the second metal element at the first surface of the second oxide layer is lower than the composition ratio of the second metal element at the second surface of the second oxide layer.

[0033] By satisfying condition (3) and / or (4), defects in the dielectric layer due to differences in thermal expansion coefficients can be particularly suppressed. The composition ratio of the first metal element may decrease in the order of the first oxide layer, the second oxide layer, and the dielectric layer. The composition ratio of the second metal element may increase in the order of the first oxide layer, the second oxide layer, and the dielectric layer.

[0034] In the capacitor (C), the following conditions (5) and / or (6) may be satisfied: (5) In the second oxide layer, the composition ratio of the first metal element gradually decreases from the first surface toward the second surface. (6) In the second oxide layer, the composition ratio of the second metal element gradually increases from the first surface toward the second surface.

[0035] When the composition ratio of a specific element gradually increases from the first surface to the second surface, the composition ratio may increase continuously or in steps. When the composition ratio of a specific element gradually decreases from the first surface to the second surface, the composition ratio may decrease continuously or in steps.

[0036] At the first surface of the second oxide layer, the ratio of the first metal element to the elements other than oxygen is defined as R1(M1). At the second surface of the second oxide layer, the ratio of the first metal element to the elements other than oxygen is defined as R2(M1). At the center in the thickness direction of the second oxide layer, the ratio of the first metal element to the elements other than oxygen is defined as Rc(M1). At the first surface, the ratio R1(M1) of the first metal element to the elements other than oxygen M may be 10 atomic % or more, 50 atomic % or more, or 90 atomic % or more, or may be 100 atomic % or less. At the second surface, the ratio R2(M1) of the first metal element to the elements other than oxygen M may be 0 atomic % or more, 50 atomic % or less, 10 atomic % or less, or 5 atomic % or less. In one example of the second oxide layer, R1(M1) is 10 atomic % or more (for example, 50 atomic % or more), and Rc(M1) is in the range of 20 to 80% (for example, 30 to 70%) of R1(M1).

[0037] At the first surface of the second oxide layer, the ratio of the second metal element to the elements other than oxygen is defined as R1(M2). At the second surface of the second oxide layer, the ratio of the second metal element to the elements other than oxygen is defined as R2(M2). At the center in the thickness direction of the second oxide layer, the ratio of the second metal element to the elements other than oxygen is defined as Rc(M2). At the first surface, the ratio R1(M2) of the second metal element to the elements other than oxygen M may be 0 atomic % or more, 50 atomic % or less, 10 atomic % or less, or 5 atomic % or less. At the second surface, the ratio R2(M2) of the second metal element to the elements other than oxygen M may be 10 atomic % or more, 50 atomic % or more, or 90 atomic % or more, or 100 atomic % or less. In one example of the second oxide layer, R2(M2) is 10 atomic % or more (for example, 50 atomic % or more), and Rc(M2) is in the range of 20 to 80% (for example, 30 to 70%) of R2(M2).

[0038] In one example, the second oxide layer has a crystal structure that changes from amorphous to polycrystalline from the first surface to the second surface. In this case, the above conditions (5) and (6) may be satisfied. Furthermore, the proportion of the first metal element in the elements other than oxygen, M, may change from 10 atomic % to 0 atomic % from the first surface to the second surface. In this example, the first structure and the dielectric layer may have a layered structure of aluminum substrate (metal layer) / amorphous aluminum oxide (first oxide layer) / Al-containing ZrO2 (second oxide layer) / zirconium oxide layer (dielectric layer).

[0039] In another example of the second oxide layer, the first oxide layer is polycrystalline and satisfies the above conditions (5) and (6). In this case, the proportion of the first metal element in the element M other than oxygen may gradually decrease from 100 atomic % to 0 atomic % from the first surface to the second surface. In this example, the first structure and the dielectric layer may have a layered structure of Mo layer (metal layer), polycrystalline molybdenum oxide layer (first oxide layer), polycrystalline molybdenum-zirconium composite oxide (second oxide layer), and zirconium oxide layer (dielectric layer).

[0040] (Second structure) The second structure includes a second electrode. The second electrode may be a conductive layer. The second electrode may be made of any of the materials exemplified for the first electrode. The thickness of the second electrode is not limited as long as it is thick enough to ensure the required conductivity.

[0041] The second structure may include another layer disposed between the dielectric layer and the second electrode. For example, the second structure may include a third oxide layer disposed on the dielectric layer and a fourth oxide layer disposed on the third oxide layer. In this case, the third oxide layer may have a first surface facing the second electrode and a second surface facing the dielectric layer. The third oxide layer may have the structure described for the second oxide layer. For example, the third oxide layer may have a composition gradient symmetrical to that of the second oxide layer across the dielectric layer. The fourth oxide layer may be a layer described for the first oxide layer.

[0042] The capacitor (C) may include a stacked first capacitor and a second capacitor. This configuration can approximately double the capacitance per unit area and approximately halve the equivalent series resistance (ESR). In this case, the second electrode of the first capacitor may be used as the first electrode of the second capacitor. The first capacitor may have a configuration of first electrode / first oxide layer / second oxide layer / dielectric layer / third oxide layer / fourth oxide layer / intermediate electrode. The second capacitor may have a configuration of intermediate electrode / first oxide layer / second oxide layer / dielectric layer / third oxide layer / fourth oxide layer / second electrode. The intermediate electrode functions as the second electrode of the first capacitor and the first electrode of the second capacitor. If the first oxide layer and the fourth oxide layer are layers that can function as electrodes, the first electrode and the second electrode may be omitted. Each layer of the second capacitor may have a different configuration from the corresponding layer of the second capacitor, but preferably has the same configuration.

[0043] (Capacitor manufacturing method) The manufacturing method according to this embodiment may be referred to as "manufacturing method (M)" below. Manufacturing method (M) is a method for manufacturing a capacitor. According to manufacturing method (M), a capacitor (C) can be manufactured. However, capacitor (C) may also be manufactured by a method other than manufacturing method (M). Since matters explained about capacitor (C) can be applied to manufacturing method (M), duplicated explanations may be omitted. Matters explained about manufacturing method (M) may also be applied to capacitor (C).

[0044] The manufacturing method (M) includes the steps of: (i) forming a first structure including a first electrode; (ii) forming a dielectric layer including a crystalline structure on the first structure; and (iii) forming a second structure including a second electrode on the dielectric layer. The first structure includes a first oxide layer including a first metal element and a second oxide layer formed on the first oxide layer. The dielectric layer is formed on the second oxide layer and includes a second metal element different from the first metal element. The second oxide layer includes the first metal element and the second metal element. The manufacturing method (M) achieves the effects described for the capacitor (C).

[0045] Step (i) at least includes forming a second dielectric layer on the first oxide layer. Step (i) may include forming a first oxide layer. Step (ii) at least includes forming a second electrode. Step (iii) may include forming a third oxide layer and a fourth oxide layer on the dielectric layer. Step (iii) may include forming a third oxide layer, a fourth oxide layer, and a second electrode on the dielectric layer.

[0046] The methods for forming the first oxide layer, second oxide layer, third oxide layer, fourth oxide layer, and dielectric layer are not particularly limited. They may be formed by vapor deposition or liquid phase deposition. Examples of vapor deposition methods include atomic layer deposition (ALD), chemical vapor deposition (CVD), sputtering, and evaporation. The first oxide layer may be formed by oxidizing the surface of the metal layer. Alternatively, the first oxide layer may be formed by natural oxidation of the metal layer.

[0047] The ALD method allows for precise control of the composition ratio and composition gradient. Furthermore, the ALD method allows for the formation of a layer with high crystallinity. Therefore, the ALD method is a preferred example of a method for forming the second oxide layer, the dielectric layer, and the third oxide layer.

[0048] In the ALD method, the composition ratio can be controlled by changing the number of times each precursor is supplied when different precursors are supplied. In the CVD method, the composition ratio can be controlled by changing the flow rate ratio of each source gas when multiple source gases are supplied. The source gases used in the vapor phase deposition method are not limited and can be selected depending on the composition of the layer to be formed. For example, the precursors used in the ALD method are not limited and can be selected depending on the composition of the layer to be formed.

[0049] However, it is difficult to form a second oxide layer by diffusing the first metal element in the first oxide layer and the second metal element in the dielectric layer through heat treatment because the diffusion of the elements by heat treatment is insufficient. In particular, in polycrystalline layers and layers made of materials with high melting points, the elements hardly diffuse even after heat treatment.

[0050] As described above, the first electrode may be a metal foil, a metal substrate, a metal foil whose surface has been made porous by etching or the like, a sintered body of metal powder, or a metal layer disposed within a dielectric. Alternatively, the first electrode may be formed by vapor deposition. The second electrode may be formed by vapor deposition.

[0051] The dielectric layer may include a polycrystalline structure, and the dielectric constant of the dielectric layer may be equal to or greater than 30. A layer including a crystalline structure (e.g., a polycrystalline structure) can be formed by selecting a composition that can form a crystalline structure, and by selecting a formation method and formation conditions (e.g., deposition temperature) that allow the crystalline structure to be formed.

[0052] The second oxide layer may include a first surface on the first oxide layer side and a second surface on the dielectric layer side, and the second oxide layer may have a crystalline structure on the second surface.

[0053] It is preferable that the capacitor (C) satisfies the above conditions (1) and (2). The capacitor (C) may also satisfy the above conditions (3) and / or (4). The capacitor (C) may also satisfy the above conditions (5) and / or (6).

[0054] In step (i), the second oxide layer may be formed by atomic layer deposition.

[0055] Step (i) may further include a step of heat-treating the second oxide layer after forming the second oxide layer. For example, step (i) may further include a step of heat-treating the second oxide layer at a temperature higher than the temperature at which the second oxide layer was formed after forming the second oxide layer. The heat treatment can increase the crystallinity of the second oxide layer. Increasing the crystallinity of the second oxide layer can increase the crystallinity of the dielectric layer. The heat treatment temperature can be selected depending on the temperature at which the second oxide layer was formed and the composition of the second oxide layer. The heat treatment temperature may be 300°C or higher or 500°C or higher, and may be 1000°C or lower or 500°C or lower. The heat treatment time may be 30 seconds or higher or 1 minute or higher, and may be 1 hour or lower or 30 minutes or lower. When the second oxide layer is a zirconium oxide layer containing Al, the heat treatment temperature may be in the range of 400°C to 800°C. However, the heat treatment temperature is set to be lower than the melting point of the first electrode. For example, if the first electrode is made of aluminum (melting point: approximately 660°C), the heat treatment temperature is set to a temperature below the melting point of aluminum. The heat treatment may be performed in an atmosphere of an inert gas (nitrogen gas, rare gas, etc.) or in the air.

[0056] Step (ii) may further include a step of heat-treating the dielectric layer after forming the dielectric layer. For example, step (ii) may further include a step of heat-treating the dielectric layer at a temperature higher than the temperature at which the dielectric layer was formed after forming the dielectric layer. The heat treatment can enhance the crystallinity of the dielectric layer. The temperature and time of the heat treatment may be within the ranges exemplified for the heat treatment of the second oxide layer.

[0057] Examples of embodiments according to the present disclosure will be specifically described below with reference to the drawings. The components described above can be applied to the components of the examples described below. Furthermore, the examples described below can be modified based on the above description. Furthermore, the matters described below may be applied to the above embodiments. Furthermore, in the embodiments described below, components that are not essential for the capacitor according to the present disclosure may be omitted. Note that the following drawings are schematic and may differ from the actual configuration.

[0058] (Embodiment 1) FIG. 1 is a cross-sectional view schematically illustrating a portion of a capacitor according to a first embodiment. Although the first embodiment illustrates an example of a parallel-plate capacitor, the capacitor configuration is not particularly limited. The capacitor 10 illustrated in FIG. 1 includes a first structure 110, a dielectric layer 103, and a second electrode 120a (second structure 120). The first structure 110 illustrated in FIG. 1 includes a first electrode 110a, a first oxide layer 111, and a second oxide layer 112. The second structure 120 illustrated in FIG. 1 is the second electrode. The first oxide layer 111 and the second oxide layer 112 are in contact with each other, and the second oxide layer 112 and the dielectric layer 103 are in contact with each other. In other words, the second oxide layer 112 is adjacent to the first oxide layer 111, and the dielectric layer 103 is adjacent to the second oxide layer 112. The second oxide layer 112 has a first surface 112a on the first oxide layer 111 side and a second surface 112b on the dielectric layer 103 side.

[0059] Fig. 2 is a schematic cross-sectional view of an example of a capacitor having a first structure 110 different from the first structure 110 shown in Fig. 1. The first structure 110 of the capacitor 10 in Fig. 2 includes a first oxide layer 111 and a second oxide layer 112. In this case, the first oxide layer 111 functions as a first electrode.

[0060] FIG. 3 shows a cross-sectional view of an example of a capacitor having a second structure 120 different from the second structure 120 shown in FIG. 3. The example second structure 120 shown in FIG. 3 includes a third oxide layer 123, a fourth oxide layer 124, and a second electrode 120a. The third oxide layer 123 is formed on the dielectric layer 103. The fourth oxide layer 124 is formed on the third oxide layer 123. The second electrode 120a is formed on the fourth oxide layer 124. In the capacitor 10 of FIG. 3, the first structure 110 may be the first structure 110 shown in FIG. 2.

[0061] A cross-sectional view of an example of a capacitor in which two capacitor elements are stacked is shown in Figure 4. Capacitor 10 in Figure 4 has a structure of first electrode 110a / first oxide layer 111 / second oxide layer 112 / dielectric layer 103 / third oxide layer 123 / fourth oxide layer 124 / intermediate electrode 104 / first oxide layer 111 / second oxide layer 112 / dielectric layer 103 / third oxide layer 123 / fourth oxide layer 124 / second electrode 120a. Capacitor 10 can be considered to include a first capacitor 10a and a second capacitor 10b, which are stacked together. First capacitor 10a has a structure of first electrode 110a / first oxide layer 111 / second oxide layer 112 / dielectric layer 103 / third oxide layer 123 / fourth oxide layer 124 / intermediate electrode 104. The second capacitor 10b has a structure of an intermediate electrode 104, a first oxide layer 111, a second oxide layer 112, a dielectric layer 103, a third oxide layer 123, a fourth oxide layer 124, and a second electrode 120a. The intermediate electrode 104 functions as the second electrode of the first capacitor 10a and as the first electrode of the second capacitor 10b.

[0062] (Addendum) Based on the above description, the following techniques are disclosed. (Technology 1) A capacitor, a first structure including a first electrode; a dielectric layer disposed on the first structure; a second structure disposed on the dielectric layer and including a second electrode; the first structure includes a first oxide layer including a first metal element and a second oxide layer disposed on the first oxide layer; the dielectric layer is an oxide layer disposed on the second oxide layer and containing a second metal element different from the first metal element; the second oxide layer contains the first metal element and the second metal element, the second oxide layer has a first surface on the first oxide layer side and a second surface on the dielectric layer side; The capacitor, wherein the dielectric layer includes a crystalline structure. (Technology 2) The composition ratio M1f of the first metal element in the first oxide layer, the composition ratio M1s of the first metal element in the second oxide layer, and the composition ratio M1d of the first metal element in the dielectric layer satisfy the relationship M1d < M1s < M1f, The composition ratio M2f of the second metal element in the first oxide layer, the composition ratio M2s of the second metal element in the second oxide layer, and the composition ratio M2d of the second metal element in the dielectric layer satisfy the relationship M2f < M2s < M2d, The capacitor according to Technique 1. (Technique 3) The dielectric layer includes a polycrystalline structure, The capacitor according to Technique 1 or 2. (Technique 4) The dielectric layer is a layer of an oxide of at least one element selected from the group consisting of zirconium and hafnium, The capacitor according to any one of Techniques 1 to 3. (Technique 5) The first structure includes a metal layer containing the first metal element, The first oxide layer is disposed on the metal layer, The capacitor according to any one of Techniques 1 to 4. (Technique 6) The first metal element is Al, Mo, Ni, Cu, Ti, Ta, Nb, or Si, The capacitor according to any one of Techniques 1 to 5. (Technique 7) The second oxide layer has a crystal structure on the second surface, The capacitor according to any one of Techniques 1 to 6. (Technique 8) The composition ratio of the first metal element on the first surface of the second oxide layer is higher than the composition ratio of the first metal element on the second surface of the second oxide layer, The composition ratio of the second metal element on the first surface of the second oxide layer is lower than the composition ratio of the second metal element on the second surface of the second oxide layer, The capacitor according to any one of Techniques 1 to 7. (Technique 9) In the second oxide layer, the composition ratio of the first metal element gradually decreases from the first surface toward the second surface, 9. The capacitor according to claim 8, wherein the composition ratio of the second metal element in the second oxide layer gradually increases from the first surface toward the second surface. (Technology 10) A method for manufacturing a capacitor, comprising: (i) forming a first structure comprising a first electrode; (ii) forming a dielectric layer including a crystalline structure on the first structure; and (iii) forming a second structure on the dielectric layer, the second structure including a second electrode; the first structure includes a first oxide layer including a first metal element and a second oxide layer disposed on the first oxide layer; the dielectric layer is disposed on the second oxide layer and includes a second metal element different from the first metal element; The second oxide layer includes the first metal element and the second metal element. (Technology 11) The manufacturing method according to technique 10, wherein the dielectric layer comprises a polycrystalline structure. (Technology 12) the second oxide layer includes a first surface on the first oxide layer side and a second surface on the dielectric layer side; 12. The manufacturing method according to claim 10 or 11, wherein the second oxide layer has a crystalline structure on the second surface. (Technology 13) a composition ratio of the first metal element at the first surface of the second oxide layer is higher than a composition ratio of the first metal element at the second surface of the second oxide layer; 13. The manufacturing method according to any one of techniques 10 to 12, wherein a composition ratio of the second metal element in the first surface of the second oxide layer is lower than a composition ratio of the second metal element in the second surface of the second oxide layer. (Technology 14) In the second oxide layer, the composition ratio of the first metal element gradually decreases from the first surface toward the second surface, 14. The manufacturing method according to claim 13, wherein the composition ratio of the second metal element in the second oxide layer gradually increases from the first surface toward the second surface. (Technology 15) 15. The method according to any one of techniques 10 to 14, wherein in the step (i), the second oxide layer is formed by atomic layer deposition. (Technology 16) 16. The manufacturing method according to any one of techniques 10 to 15, wherein the step (i) further comprises a step of heat-treating the second oxide layer at a temperature higher than the temperature at which the second oxide layer was formed, after the second oxide layer is formed. (Technology 17) 17. The manufacturing method according to any one of claims 10 to 16, wherein the step (ii) further comprises a step of heat-treating the dielectric layer at a temperature higher than the temperature at which the dielectric layer was formed after the dielectric layer was formed. [Example]

[0063] The capacitor (C) according to the present disclosure will be described in more detail with reference to examples.

[0064] (Experiment 1) In Experiment 1, several capacitors with different configurations were fabricated and evaluated.

[0065] (Capacitor A1) The capacitor A1 was fabricated in the following manner. (1) Metal layer and first oxide layer The metal layer was made of aluminum foil. The first oxide layer was made of a natural oxide layer (aluminum oxide layer: Al2O3 layer) formed on the surface of the aluminum foil. The thickness of the natural oxide layer was approximately 3 nm.

[0066] (2) Second oxide layer The second oxide layer was a zirconium oxide layer containing Al. In the second oxide layer, the proportion of Al in the element M other than oxygen was gradually decreased from 10 atomic % to 0 atomic % from the first surface (the surface on the first electrode side) to the second surface (the surface on the dielectric layer side).

[0067] The thickness of the second oxide layer was 2 nm. The second oxide layer was formed by the ALD method. Trimethylammonium (TMA) was used as the precursor for the Al source. Tetrakis(dimethylamino)zirconium (TDMAZr) was used as the precursor for the Zr source. Ozone (O3) was used as the oxidizing agent for the O source. The aluminum oxide formation step involved supplying TMA, purging, supplying ozone, and purging. The zirconium oxide formation step involved supplying TDMAZr, purging, supplying ozone, and purging. The deposition temperature was 200°C.

[0068] When the proportion of Al shown in element M was 10 atomic %, one aluminum oxide formation step and nine zirconium oxide formation steps were performed. When the proportion of Al shown in element M was 5 atomic %, one aluminum oxide formation step and 19 zirconium oxide formation steps were performed. On the second surface, only the zirconium oxide formation step was performed.

[0069] Next, the aluminum foil on which the second oxide layer was formed was heat-treated in a nitrogen gas atmosphere at 500°C for 1 minute. In this way, the first structure was formed. In this way, the second oxide layer having a crystalline structure on the second surface on the dielectric layer side was formed.

[0070] (dielectric layer) A zirconium oxide layer (thickness: 13 nm) was used as the dielectric layer. The zirconium oxide layer was formed by the ALD method. Tetrakis(dimethylamino)zirconium (TDMAZr) was used as the precursor for the Zr source. Ozone (O3) was used as the oxidizing agent for the O source. The deposition temperature was 200°C. A polycrystalline zirconium oxide layer was formed by the ALD method.

[0071] Next, the aluminum foil on which the dielectric layer was formed was heat-treated in a nitrogen gas atmosphere at 500° C. for 1 minute. This heat treatment increased the crystallinity of the zirconium oxide layer.

[0072] (2nd electrode) As the second electrode, a titanium layer (thickness: 100 nm) and a gold layer (thickness: 100 nm) were formed on the dielectric layer by electron beam evaporation. In this way, a second electrode consisting of a titanium layer and a gold layer was formed. In this way, capacitor A1 was produced.

[0073] (Capacitors A2 to A4, C1 to C2) Capacitors A2 to A4, C1, and C2 were fabricated using the same method and conditions as those for fabricating capacitor A1, except that the thickness of the second oxide layer and / or the dielectric layer was varied. The thickness of the second oxide layer and the dielectric layer were varied as shown in Table 1. In fabricating capacitor C1, a second oxide layer was not formed. In fabricating capacitor C2, a dielectric layer was not formed. As described above, the proportion of Al in the elements other than oxygen, M, in the second oxide layer was gradually decreased from 10 atomic % to 0 atomic % from the first surface to the second surface.

[0074] The capacitance (capacitance per unit area) and leakage current density of the fabricated capacitors were measured. Table 1 shows some of the manufacturing conditions for the capacitors and the measurement results. Table 1 also shows the ratio of the thickness T2 of the second oxide layer to the sum of the thickness Td of the dielectric layer and the thickness T2 of the second oxide layer {T2 / (Td+T2)}. In Table 1, 9.08E-07 is 9.08×10 -7 1.05E-06 means 1.05 x 10 -6 The same applies to other evaluation results. The leakage current density indicates the leakage current density when a voltage of 2 V is applied. It is preferable that the capacitance is high. It is preferable that the leakage current density is low.

[0075] [Table 1]

[0076] Capacitors A1 to A4 are capacitors (C) according to the present disclosure. Capacitors C1 and C2 are comparative examples. As shown in Table 1, the capacitances of capacitors A1 to A4 were higher than those of capacitors C1 and C2. The leakage current densities of capacitors A1 to A4 were lower than that of capacitor C1. Capacitors A1 to A4 were able to achieve both high capacitance and low leakage current density.

[0077] (Experiment 2) In Experiment 2, several capacitors were fabricated and evaluated using the same method and conditions as for the fabrication of capacitor A1 in Experiment 1, except that the thickness Td of the dielectric layer and the thickness T2 of the second oxide layer were varied. The thickness Td of the dielectric layer and the thickness T2 of the second oxide layer were varied as shown in Table 2.

[0078] The capacitance (capacitance per unit area) of the fabricated capacitors was measured. Some of the manufacturing conditions for the capacitors and the capacitances are shown in Table 1. Table 2 also shows the ratio of the thickness T2 of the second oxide layer to the sum of the thickness Td of the dielectric layer and the thickness T2 of the second oxide layer {T2 / (Td+T2)}.

[0079] [Table 2]

[0080] Capacitors A5 to A14 are capacitors (C) according to the present disclosure. Capacitors C3 to C7 are comparative examples. As shown in Table 2, when comparing capacitors with the same (Td+T2) value, the capacitance of capacitor (C) was higher than the capacitance of the comparative capacitors. [Industrial Applicability]

[0081] The present disclosure can be used for capacitors. [Explanation of symbols]

[0082] 10: Capacitor 10a: First capacitor 10b: Second capacitor 103: Dielectric layer 104: Intermediate electrode 110 :1st structure 110a: 1st electrode 111: First oxide layer 112: Second oxide layer 120:Second structure 120a: 2nd electrode 123: Third oxide layer 124: Fourth oxide layer

Claims

1. A capacitor, a first structure including a first electrode; a dielectric layer disposed on the first structure; a second structure disposed on the dielectric layer and including a second electrode; the first structure includes a first oxide layer including a first metal element and a second oxide layer disposed on the first oxide layer; the dielectric layer is an oxide layer disposed on the second oxide layer and containing a second metal element different from the first metal element; the second oxide layer contains the first metal element and the second metal element, the second oxide layer has a first surface on the first oxide layer side and a second surface on the dielectric layer side; The capacitor, wherein the dielectric layer includes a crystalline structure.

2. a composition ratio M1f of the first metal element in the first oxide layer, a composition ratio M1s of the first metal element in the second oxide layer, and a composition ratio M1d of the first metal element in the dielectric layer satisfy the relationship M1d<M1s<M1f; 2. The capacitor of claim 1, wherein a composition ratio M2f of the second metal element in the first oxide layer, a composition ratio M2s of the second metal element in the second oxide layer, and a composition ratio M2d of the second metal element in the dielectric layer satisfy the relationship M2f<M2s<M2d.

3. The capacitor of claim 1 , wherein the dielectric layer comprises a polycrystalline structure.

4. 2. The capacitor of claim 1, wherein the dielectric layer is a layer of an oxide of at least one element selected from the group consisting of zirconium and hafnium.

5. the first structure includes a metal layer including the first metal element; The capacitor of claim 1 , wherein the first oxide layer is disposed on the metal layer.

6. The capacitor of claim 1 , wherein the first metal element is Al, Mo, Ni, Cu, Ti, Ta, Nb, or Si.

7. The capacitor of claim 1 , wherein the second oxide layer has a crystalline structure on the second surface.

8. a composition ratio of the first metal element at the first surface of the second oxide layer is higher than a composition ratio of the first metal element at the second surface of the second oxide layer; The capacitor according to any one of claims 1 to 7, wherein the composition ratio of the second metal element at the first surface of the second oxide layer is lower than the composition ratio of the second metal element at the second surface of the second oxide layer.

9. In the second oxide layer, a composition ratio of the first metal element gradually decreases from the first surface toward the second surface, 9. The capacitor according to claim 8, wherein the composition ratio of the second metal element in the second oxide layer gradually increases from the first surface toward the second surface.

10. A method for manufacturing a capacitor, comprising: (i) forming a first structure comprising a first electrode; (ii) forming a dielectric layer including a crystalline structure on the first structure; and (iii) forming a second structure on the dielectric layer, the second structure comprising a second electrode; the first structure includes a first oxide layer including a first metal element and a second oxide layer disposed on the first oxide layer; the dielectric layer is disposed on the second oxide layer and includes a second metal element different from the first metal element; The second oxide layer includes the first metal element and the second metal element.

11. The method of claim 10 , wherein the dielectric layer comprises a polycrystalline structure.

12. the second oxide layer includes a first surface on the first oxide layer side and a second surface on the dielectric layer side; The method of claim 10 , wherein the second oxide layer has a crystalline structure on the second surface.

13. a composition ratio of the first metal element at the first surface of the second oxide layer is higher than a composition ratio of the first metal element at the second surface of the second oxide layer; The manufacturing method according to any one of claims 10 to 12, wherein a composition ratio of the second metal element in the first surface of the second oxide layer is lower than a composition ratio of the second metal element in the second surface of the second oxide layer.

14. In the second oxide layer, a composition ratio of the first metal element gradually decreases from the first surface toward the second surface, The manufacturing method according to claim 13 , wherein the composition ratio of the second metal element in the second oxide layer gradually increases from the first surface toward the second surface.

15. The method according to claim 13 , wherein in step (i), the second oxide layer is formed by atomic layer deposition.

16. The manufacturing method according to claim 13 , wherein the step (i) further comprises the step of heat-treating the second oxide layer at a temperature higher than the temperature at which the second oxide layer was formed, after the second oxide layer is formed.

17. The manufacturing method according to claim 13 , wherein the step (ii) further comprises the step of heat-treating the dielectric layer at a temperature higher than the temperature at which the dielectric layer was formed, after the dielectric layer is formed.

Images