Capacitor and method for manufacturing capacitor

Abstract

A capacitor (10) includes a first structure (110) having a first electrode; a dielectric layer (103) disposed on the first structure (110); and a second structure (120) that is disposed on the dielectric layer (103) and that includes a second electrode. The first structure includes: a first oxide layer (111) containing 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) contains the first metal element and the second metal element. The second oxide layer (112) includes: 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) contains a crystal structure.

Description

Capacitor and method for manufacturing the same

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

[0002] Various capacitors have been proposed in the past. Patent Document 1 (Japanese Patent Laid-Open Publication No. 2006-135339) describes a step of forming a storage electrode, and depositing ZrO ２ Thin film and Al ２ O ３ A method for forming a capacitor in a semiconductor device is described, which comprises the steps of forming a multi-layer dielectric film made of thin films and forming a plate electrode on the multi-layer dielectric film.

[0003] Patent Document 2 (JP 2012-80095 A) describes a method for manufacturing a semiconductor device having a capacitor, the method for forming the capacitor comprising the steps of forming a lower electrode made of a titanium nitride film on a semiconductor substrate, forming a dielectric film made of a zirconium oxide film on the lower electrode, and forming an upper electrode including a titanium nitride film on the dielectric film, the step of forming the dielectric film including a step of depositing a film formed on at least the uppermost layer of the dielectric film by an atomic layer deposition (ALD) method, and the method further comprising the step of depositing a protective film on the film formed on the uppermost layer of the dielectric film between the step of forming the dielectric film and the step of forming the upper electrode without applying a temperature that exceeds the film deposition temperature of the ALD method by 70° C. or more.

[0004] JP 2006-135339 A JP 2012-80095 A

[0005] Capacitors using an oxide layer are known as capacitors with high heat resistance. To improve capacitor characteristics (e.g., high capacitance and low leakage current), it is important that the dielectric constant of the dielectric layer is high and that defects (e.g., cracks) in the dielectric layer are suppressed. In this context, one of the objectives of the present disclosure is to provide a capacitor that can achieve high capacitance and low leakage current.

[0006] A capacitor according to one embodiment of the present disclosure 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 an oxide layer disposed on the second oxide layer and 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 facing the first oxide layer and a second surface facing the dielectric layer, and the dielectric layer includes a crystalline structure.

[0007] A method for manufacturing a capacitor according to one embodiment of the present disclosure 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 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.

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

[0009] Fig. 1 is a diagram schematically showing a cross-sectional view of an example of a capacitor according to the present embodiment. Fig. 2 is a diagram schematically showing a cross-sectional view of another example of a capacitor according to the present embodiment. Fig. 3 is a diagram schematically showing a cross-sectional view of another example of a capacitor according to the present embodiment. Fig. 4 is a diagram schematically showing a cross-sectional view of another example of a capacitor according to the present embodiment.

[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, but 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 greater 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 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) Hereinafter, the capacitor according to this embodiment may be referred to as a "capacitor (C)." 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] Dielectric layers with a crystalline structure are affected by adjacent layers. For example, Al ２ O ３ ZrO ２ When a dielectric layer made of a first oxide layer (e.g., Al) is formed, defects (cracks) tend to occur in the dielectric layer due to the difference in the thermal expansion coefficients of the two. ２ O ３A second oxide layer is disposed between the first oxide layer and the dielectric layer. The second oxide layer contains the first metal element contained in the first oxide layer and the second metal element contained in the dielectric layer. Therefore, compared to when the dielectric layer is formed directly on the first oxide layer, the occurrence of defects in the dielectric layer due to differences in thermal expansion coefficients can be suppressed. As a result, it is possible to reduce the leakage current of the capacitor (C). It is also possible to improve the reliability of the capacitor (C) against thermal cycles.

[0013] Furthermore, by making the composition of the second surface of the second oxide layer closer to the composition of the dielectric layer, it is possible to reduce lattice mismatch and the difference in thermal expansion coefficient, and to improve the crystallinity of the dielectric layer formed on the second oxide layer. By improving the crystallinity of the dielectric layer, it is possible to further increase the capacitance of the capacitor (C).

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

[0015] By satisfying conditions (1) and (2), the occurrence 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 or be composed of a polycrystalline structure. The dielectric constant of a dielectric layer including a polycrystalline structure is preferably 30 or more. By bringing 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, crystallization of the dielectric layer is promoted. As a result, the dielectric constant of the dielectric layer can be made 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., ZrO ２ ), a hafnium oxide layer (e.g., HfO ２ ), and Hf Ｘ Zr １－Ｘ O ２ (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 a layer of tantalum oxide (e.g., Ta ２ O ５ ), titanium oxide (e.g., TiO ２ ), niobium oxide (e.g., NbO Ｘ In this specification, the oxygen composition ratio in the oxide composition formula is the composition ratio when it is assumed that there is no oxygen deficiency. An actual oxide may contain oxygen deficiency. For example, zirconium oxide is ZrO ２－Ｚ (Z is an 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, or may be 100 nm or less, 50 nm or less, 25 nm or less, or 10 nm or less. In the capacitor (C), even in a thin dielectric layer (e.g., a thickness of 50 nm or less) in which crystallization is difficult to occur, the second oxide layer can promote crystallization. As a result, the capacitance can be increased.

[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] (First 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 the metal layer include a metal layer disposed on a substrate, a metal foil, a metal substrate, a metal foil made porous by etching or the like, a sintered body of metal powder, and a metal layer disposed inside 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 (Al 2 O 3 ) formed by natural oxidation of the surface of the aluminum layer. ２ O ３ 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 one selected from the group consisting of 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 as a metal element, 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 complex oxide containing the first metal element and another element (an element other than oxygen). The other element other than oxygen may be one element or multiple elements. In the first oxide layer, the proportion of the first metal element in the element 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 M other than oxygen 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 RuO. ２ layer, IrO ２The first oxide layer may include a polycrystalline structure or may consist 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 may not be roughened. By using a first electrode having a non-roughened surface, the crystallinity of the dielectric layer can be easily improved.

[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 easy to achieve a 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 easy 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] The capacitor (C) may satisfy the following conditions (3) and / or (4): (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, and (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. In conditions (3) and (4), the composition ratio in the second oxide layer means the composition ratio in the entire second oxide layer. 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] The capacitor (C) may satisfy the following conditions (5) and / or (6): (5) In the second oxide layer, the composition ratio of the first metal element gradually decreases from the first surface toward the second surface, and (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] In conditions (5) and (6), the composition ratio in the second oxide layer refers to the composition ratio in the entire second oxide layer. 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 (e.g., 50 atomic % or more), and Rc(M1) is in the range of 20 to 80% (e.g., 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 (e.g., 50 atomic % or more), and Rc(M2) is in the range of 20 to 80% (e.g., 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 have a structure of aluminum substrate (metal layer) / amorphous aluminum oxide (first oxide layer) / Al-containing ZrO ２ It may have a laminated structure of (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 elements other than oxygen, M, 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 stacked structure of Mo layer (metal layer) / polycrystalline molybdenum oxide layer (first oxide layer) / polycrystalline molybdenum-zirconium composite oxide (second oxide layer) / 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 as the material for the first electrode. The thickness of the second electrode is not limited as long as it can 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 configuration 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 its corresponding layer of the second capacitor, but preferably has the same configuration.

[0043] (Method for manufacturing a capacitor) 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), capacitor (C) can be manufactured. However, capacitor (C) may also be manufactured by a method other than manufacturing method (M). Since the matters described for capacitor (C) can be applied to manufacturing method (M), duplicated explanations may be omitted. The matters described for 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, the second oxide layer, the third oxide layer, the fourth oxide layer, and the dielectric layer are not particularly limited. These layers may be formed by vapor deposition or liquid 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 accurate control of the composition ratio and the 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 through heat treatment is insufficient. In particular, in a polycrystalline layer or a layer made of a material with a high melting point, 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] The capacitor (C) preferably 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 enhance the crystallinity of the second oxide layer. Increasing the crystallinity of the second oxide layer can enhance 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, 1 minute or higher, and 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 a temperature lower than the melting point of the first electrode. For example, when the first electrode is made of aluminum (melting point: about 660° C.), the heat treatment temperature is set to a temperature lower than 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 embodiment 1. Although embodiment 1 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 example first structure 110 illustrated in FIG. 1 includes a first electrode 110a, a first oxide layer 111, and a second oxide layer 112. The example 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] Figure 2 shows a schematic cross-sectional view of an example of a capacitor having a first structure 110 different from the first structure 110 shown in Figure 1. The first structure 110 of the capacitor 10 in Figure 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 is a schematic cross-sectional view of an example of a capacitor having a second structure 120 different from the second structure 120 shown in FIG. 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 having two stacked capacitor elements is shown in Figure 4. The 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. The capacitor 10 can be considered to include a first capacitor 10a and a second capacitor 10b, which are stacked one on top of the other. The 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 the intermediate electrode 104, the first oxide layer 111, the second oxide layer 112, the dielectric layer 103, the third oxide layer 123, the fourth oxide layer 124, and the 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] (Additional Note) The above description discloses the following techniques.

[0063] (Technology 1) A capacitor comprising: 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, wherein the first structure comprises a first oxide layer including a first metal element and a second oxide layer disposed on the first oxide layer, the dielectric layer being an oxide layer disposed on the second oxide layer and including a second metal element different from the first metal element, the second oxide layer including the first metal element and the second metal element, the second oxide layer having a first surface on the first oxide layer side and a second surface on the dielectric layer side, and the dielectric layer including a crystalline structure.

[0064] (Technology 2) The capacitor according to Technology 1, wherein, when a composition ratio of the first metal element in the first oxide layer is M1f, a composition ratio of the first metal element in the second oxide layer is M1s, and a composition ratio of the first metal element in the dielectric layer is M1d, a relationship of M1d<M1s<M1f is satisfied; and, when a composition ratio of the second metal element in the first oxide layer is M2f, a composition ratio of the second metal element in the second oxide layer is M2s, and a composition ratio of the second metal element in the dielectric layer is M2d, a relationship of M2f<M2s<M2d is satisfied.

[0065] (Technology 3) The capacitor according to Technology 1 or 2, wherein the dielectric layer includes a polycrystalline structure.

[0066] (Technology 4) The capacitor according to any one of Technologies 1 to 3, wherein the dielectric layer is a layer of an oxide of at least one element selected from the group consisting of zirconium and hafnium.

[0067] (Technology 5) The capacitor according to any one of Technologies 1 to 4, wherein the first structure includes a metal layer containing the first metal element, and the first oxide layer is disposed on the metal layer.

[0068] (Technology 6) The capacitor according to any one of Technologies 1 to 5, wherein the first metal element is one selected from the group consisting of Al, Mo, Ni, Cu, Ti, Ta, Nb, and Si.

[0069] (Technology 7) The capacitor according to any one of Technologies 1 to 6, wherein the second oxide layer has a crystalline structure on the second surface.

[0070] (Technology 8) A capacitor according to any one of Technologies 1 to 7, wherein 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, and a composition ratio of the second metal element at the first surface of the second oxide layer is lower than a composition ratio of the second metal element at the second surface of the second oxide layer.

[0071] (Technology 9) The capacitor according to Technology 8, wherein in the second oxide layer, the composition ratio of the first metal element gradually decreases from the first surface toward the second surface, and in the second oxide layer, the composition ratio of the second metal element gradually increases from the first surface toward the second surface.

[0072] (Technology 10) A method for manufacturing a capacitor, comprising: a step (i) of forming a first structure including a first electrode; a step (ii) of forming a dielectric layer including a crystalline structure on the first structure; and a step (iii) of forming a second structure including a second electrode on the dielectric layer, wherein 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, and the second oxide layer includes the first metal element and the second metal element.

[0073] (Technology 11) The manufacturing method according to Technology 10, wherein the dielectric layer comprises a polycrystalline structure.

[0074] (Technology 12) The manufacturing method according to Technology 10 or 11, wherein the second oxide layer includes a first surface on the first oxide layer side and a second surface on the dielectric layer side, and the second oxide layer has a crystal structure on the second surface.

[0075] (Technology 13) The manufacturing method according to any one of Techniques 10 to 12, wherein 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, and a composition ratio of the second metal element at the first surface of the second oxide layer is lower than a composition ratio of the second metal element at the second surface of the second oxide layer.

[0076] (Technology 14) The manufacturing method according to Technology 13, wherein in the second oxide layer, a composition ratio of the first metal element gradually decreases from the first surface toward the second surface, and in the second oxide layer, a composition ratio of the second metal element gradually increases from the first surface toward the second surface.

[0077] (Technology 15) The manufacturing 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.

[0078] (Technology 16) The manufacturing method according to any one of Techniques 10 to 15, wherein the step (i) further includes 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.

[0079] (Technology 17) The manufacturing method according to any one of Techniques 10 to 16, wherein the step (ii) further includes a step of heat-treating the dielectric layer at a temperature higher than the temperature at which the dielectric layer is formed after the dielectric layer is formed.

[0080] The capacitor (C) according to the present disclosure will be described in more detail by way of examples.

[0081] (Experiment 1) In Experiment 1, a plurality of capacitors with different configurations were fabricated and evaluated.

[0082] (Capacitor A1) Capacitor A1 was produced by the following method.

[0083] (1) Metal layer and first oxide layer Aluminum foil was used as the metal layer. The first oxide layer was a natural oxide layer (aluminum oxide layer: Al) formed on the surface of the aluminum foil. ２ O ３ The native oxide layer had a thickness of about 3 nm.

[0084] (2) Second Oxide Layer: A zirconium oxide layer containing Al was formed as the second oxide layer. 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).

[0085] The thickness of the second oxide layer was 2 nm. The second oxide layer was formed by ALD. Trimethylammonium (TMA) was used as a precursor for the Al source. Tetrakis(dimethylamino)zirconium (TDMAZr) was used as a precursor for the Zr source. Ozone (O ３ In the aluminum oxide formation step, TMA was supplied, purged, ozone was supplied, and purged. In the zirconium oxide formation step, TDMAZr was supplied, purged, ozone was supplied, and purged. The deposition temperature was 200°C.

[0086] When the proportion of Al represented by element M was 10 atomic %, one aluminum oxide formation step and nine zirconium oxide formation steps were performed. When the proportion of Al represented by 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.

[0087] Next, the aluminum foil on which the second oxide layer was formed was heat-treated at 500°C for 1 minute in a nitrogen gas atmosphere, thereby forming a first structure. Also, in this way, a second oxide layer having a crystalline structure on the second surface on the dielectric layer side was formed.

[0088] (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 a precursor for the Zr source. Ozone (O ３ The deposition temperature was 200° C. A polycrystalline zirconium oxide layer was formed by the ALD method.

[0089] 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.

[0090] (Second 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 the titanium layer and the gold layer was formed. In this way, capacitor A1 was produced.

[0091] (Capacitors A2-A4, C1-C2) Capacitors A2-A4, C1-C2 were fabricated using the same method and conditions as capacitor A1, except that the thickness of the second oxide layer and / or the dielectric layer was changed. The thickness of the second oxide layer and the dielectric layer were changed as shown in Table 1. In the fabrication of capacitor C1, a second oxide layer was not formed. In the fabrication of 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.

[0092] The capacitance (capacitance per unit area) and leakage current density of the produced capacitors were measured. Some of the manufacturing conditions of the capacitors and the measurement results are shown in Table 1. 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 , and 1.05E-06 is 1.05 × 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.

[0093]

[0094] 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.

[0095] (Experiment 2) In Experiment 2, a plurality of capacitors were fabricated and evaluated using the same method and conditions as for fabricating 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.

[0096] The capacitance (capacitance per unit area) of the produced capacitor was measured. Table 2 shows some of the manufacturing conditions of the capacitor and the capacitance. 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)}. In Table 2, 1.44E-06 is 1.44×10 －６ , and 1.57E-06 is 1.57 x 10 －６ The same applies to other evaluation results.

[0097]

[0098] 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.

[0099] The present disclosure can be used for capacitors.

[0100] 10: Capacitor 10a: First capacitor 10b: Second capacitor 103: Dielectric layer 104: Intermediate electrode 110: First structure 110a: First electrode 111: First oxide layer 112: Second oxide layer 112a: First surface 112b: Second surface 120: Second structure 120a: Second electrode 123: Third oxide layer 124: Fourth oxide layer

Claims

1. A capacitor comprising: 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, wherein the first structure comprises a first oxide layer including a first metal element and a second oxide layer disposed on the first oxide layer, the dielectric layer being an oxide layer disposed on the second oxide layer and including a second metal element different from the first metal element, the second oxide layer including the first metal element and the second metal element, the second oxide layer having a first surface facing the first oxide layer and a second surface facing the dielectric layer, and the dielectric layer comprising a crystalline structure.

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

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

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

5. The capacitor of claim 1, wherein said first structure includes a metal layer containing said first metal element, and said first oxide layer is disposed on said metal layer.

6. The capacitor according to claim 1, wherein the first metal element is one selected from the group consisting of Al, Mo, Ni, Cu, Ti, Ta, Nb, and Si.

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

8. A capacitor according to any one of claims 1 to 7, wherein 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, and 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. The capacitor described in claim 8, wherein the composition ratio of the first metal element in the second oxide layer gradually decreases from the first surface toward the second surface, and 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) a step of forming a first structure including a first electrode; (ii) a step of forming a dielectric layer including a crystalline structure on the first structure; and (iii) a step of forming a second structure including a second electrode on the dielectric layer, wherein 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; and 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 manufacturing method according to claim 10, wherein the second oxide layer includes a first surface on the side of the first oxide layer and a second surface on the side of the dielectric layer, and the second oxide layer has a crystalline structure on the second surface.

13. A manufacturing method according to any one of claims 10 to 12, wherein 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, and 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.

14. The manufacturing method described in claim 13, wherein the composition ratio of the first metal element in the second oxide layer gradually decreases from the first surface toward the second surface, and 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 of 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 step (i) further comprises the step of heat-treating the second oxide layer after forming the second oxide layer at a temperature higher than the temperature at which the second oxide layer was formed.

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

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