WO2019208340A1 - CAPACITOR AND METHOD FOR MANUFACTURING HfO2 FILM - Google Patents

Abstract

Provided is a capacitor including a dielectric layer constituted of a metal oxide having a high dielectric constant. This capacitor comprises a first electrode layer 2, a dielectric layer 3 formed on the first electrode layer 2, and a second electrode layer 4 formed on the dielectric layer 3, wherein the dielectric layer 3 is made of a metal oxide, and the metal oxide includes Hf, Bi, and a pentavalent or higher element. The metal oxide including Hf, Bi, and a pentavalent or higher element is, for example, HfO2 where a part of Hf is substituted by Bi and a pentavalent or higher element. The metal oxide may have, for example, a fluorite structure. The pentavalent or higher element may be, for example, one or more elements selected from Nb, Ta, Mo and W.

Description

Capacitor and method for manufacturing HfO2 film

The present invention relates to a capacitor, and more particularly to a capacitor containing Hf in a metal oxide constituting a dielectric layer.

The present invention also relates to a method for manufacturing an HfO ₂ film suitable for use in manufacturing the capacitor of the present invention.

Highly reliable capacitors that do not fail even when used at high temperatures or when a high voltage is applied due to static electricity or the like are demanded as capacitors for various applications including in-vehicle applications.

As a material for such a highly reliable capacitor dielectric layer, HfO ₂ having high insulation, high strength, high toughness, and the like is a promising candidate. However, conventional HfO ₂ has a low dielectric constant of about 20, so far it has been necessary to increase the area of the electrode in order to use it as a material for the dielectric layer of the capacitor.

It is an object of the present invention to improve the dielectric constant of a metal oxide containing HfO ₂ and to provide a capacitor having both high reliability (such as high insulation) and high dielectric constant. Yes.

In considering the use of a metal oxide containing HfO ₂ as a material for a dielectric layer of a capacitor, the following technical information is helpful.

First, Non-Patent Document 1 (Nano Letters, 12, 4318 (2012)) discloses that a thin film of HfO ₂ produced by an ALD (Atomic Layer Deposition) method exhibits ferroelectricity. Yes.

In Non-Patent Document 2 (Journal of Solid State Science and Technology, 4 (12), 419 (2015)), even a thin film of HfO ₂ produced by spin coating replaces a part of Hf with La. It is disclosed that it exhibits ferroelectricity.

Further, capacitors that use an antiferroelectric material for the dielectric layer and exhibit a high dielectric constant under a bias electric field are disclosed in Patent Document 1 (Japanese Patent Publication No. 2013-518400) and Patent Document 2 (Japanese Patent Publication No. 2015-518458). ), Patent Document 3 (Japanese Patent Laid-Open No. 52-153200), and the like. For example, Patent Document 1 discloses a capacitor (capacitor) using an antiferroelectric positive bias characteristic made of Pb _1-1.5y La _y Ti _1-z Zr _z O ₃ .

Furthermore, Non-Patent Document 3 (Journal of Applied Physics 122, 144105 (2017)) reports that even a thin film of HfO ₂ may exhibit antiferroelectricity. Specifically, it is disclosed that a thin film of HfO ₂ to which Si is added exhibits antiferroelectric properties. More specifically, it is disclosed that a thin film of HfO ₂ to which Si is added and produced by the ALD method exhibits antiferroelectric properties, and the dielectric constant increases under a bias electric field.

Special table 2013-518400 gazette Special table 2015-518459 gazette JP-A-52-153200

As described above, it has been reported that metal oxides containing HfO ₂ may exhibit antiferroelectric properties (Non-Patent Document 3). However, in order to actually use a metal oxide containing HfO ₂ for the dielectric layer of the capacitor, it is desired that the dielectric constant be improved by applying a small bias electric field. It is also desirable that the increase in the dielectric constant due to the application of the bias electric field is large. Furthermore, it is desirable to provide a high dielectric constant even when no bias electric field is applied.

The present invention has been made to solve the above-described conventional problems, and as a means therefor, a capacitor according to an embodiment of the present invention includes a first electrode layer and a dielectric formed on the first electrode layer. And a second electrode layer formed on the dielectric layer. The dielectric layer is made of a metal oxide, and the metal oxide contains Hf, Bi, and an element having a valence of 5 or more. Shall be. Note that the metal oxide containing Hf, Bi, and a pentavalent or higher element includes, for example, HfO ₂ in which a part of Hf is substituted with Bi and a pentavalent or higher element.

Further, one manufacturing method of the HfO ₂ film with an embodiment of the present invention, HfO _2, or a HfO ₂ film manufacturing method, including Hf and O and HfO ₂ containing other elements, the film-forming target A step of preparing a material, a step of preparing a chemical solution as a raw material of the HfO ₂ film, a step of spin-coating the chemical solution on the film-forming target, and a heat treatment to spin-coat on the film-forming target And a step of precipitating an HfO ₂ film containing at least one of a tetragonal crystal and an orthorhombic crystal phase from a chemical solution. Incidentally, HfO ₂ containing Hf and O and other elements, for example, a HfO ₂ some Hf is substituted with another element.

The capacitor of the present invention has high reliability. In addition, even when a bias electric field is not applied, the dielectric layer has a high dielectric constant. Furthermore, even when a small bias electric field is applied, the dielectric constant of the dielectric layer is greatly improved.

Further, according to the method for producing the HfO ₂ film of the present invention, the capacitor of the present invention can be easily produced.

1 is a cross-sectional view of a capacitor 100 according to a first embodiment. 2 is an X-ray diffraction spectrum of a dielectric layer of a capacitor 100. FIG. 3 is a dielectric constant-electric field curve of a capacitor 100 and capacitors 1100 and 1200 of comparative examples. 7 is a relative dielectric constant-electric field curve of a capacitor 210 according to a comparative example and capacitors 220 to 270 according to the second embodiment. 10 is a relative dielectric constant-electric field curve of capacitors 310 and 320 according to the third embodiment. 12 is a relative dielectric constant-electric field curve of capacitors 410 to 440 according to the fourth embodiment. It is a dielectric constant-electric field curve of the capacitor 500 concerning 5th Embodiment.

Hereinafter, modes for carrying out the present invention will be described.

As described above, a capacitor according to an embodiment of the present invention includes a first electrode layer, a dielectric layer formed on the first electrode layer, and a second electrode layer formed on the dielectric layer. The dielectric layer is made of a metal oxide, and the metal oxide includes Hf, Bi, and a pentavalent or higher element. Note that the metal oxide containing Hf, Bi, and a pentavalent or higher element includes, for example, HfO ₂ in which a part of Hf is substituted with Bi and a pentavalent or higher element. In the capacitor of this embodiment, the metal oxide constituting the dielectric layer has a high dielectric constant. This is presumably because the crystal structure is easily distorted and the dielectric constant is improved by replacing part of Hf with Bi. In addition, when Bi is replaced by Bi alone, there is a risk that the valence does not match and oxygen vacancies are generated and the characteristics are deteriorated. It is considered that the generation of oxygen vacancies was suppressed and the high dielectric constant could be obtained.

The metal oxide can have a fluorite structure, for example.

The pentavalent or higher element can be, for example, one or more kinds of elements selected from Nb, Ta, Mo, and W.

When the total amount of metal oxides excluding O is 100 mol%, the addition amounts of Bi and pentavalent or higher elements can each be 15 mol% or less. In this case, a decrease in insulation is suppressed.

When the pentavalent or higher element is a pentavalent element, the molar ratio of Bi to the pentavalent element is 1: 1, and when the pentavalent or higher element is a hexavalent element, Bi And the molar ratio of the hexavalent element to 2: 1. In this case, the valence of the element is adjusted, and the generation of oxygen vacancies is satisfactorily suppressed.

Furthermore, a group IV element may be added to the metal oxide. In this case, the dielectric constant can be further improved. The group IV element can be, for example, one or both of Si and Ge. Further, when the total amount of metal oxides excluding O is 100 mol%, the amount of Group IV element added can be 3 mol% or less. In this case, the dielectric constant can be improved satisfactorily. Further, the amount of Group IV element added can be 2 mol% or less. In this case, the dielectric constant can be further improved. When the addition amount of the group IV element is 1 mol% or less, the dielectric constant can be further improved.

When the thickness of the dielectric layer is 10 nm or more, it is preferable to add a stabilizer. When the thickness of the dielectric layer is less than 10 nm, the metal oxide mainly has one or more crystal structures of tetragonal, orthorhombic, and cubic without adding a stabilizer, Good antiferroelectricity can be expressed. However, when the film thickness of the dielectric layer is 10 nm or more, the crystal structure of the metal oxide may be monoclinic, and good antiferroelectricity may not be exhibited. Therefore, when the film thickness of the dielectric layer is 10 nm or more, it is preferable to add a stabilizer as described above to suppress the crystal structure of the metal oxide from being monoclinic. As the stabilizer, for example, one or more kinds of elements selected from La, Al, Y, Zr, and Ce can be used. Even when the thickness of the dielectric layer is less than 10 nm, a stabilizer may be added. Also in this case, it is possible to suppress the crystal structure of the metal oxide from being monoclinic.

Hereinafter, a plurality of embodiments will be described. However, each embodiment shows an embodiment of the present invention by way of example, and the present invention is not limited to the content of the embodiment. Moreover, it is also possible to implement combining the content described in different embodiment, and the implementation content in that case is also included in this invention. Further, the drawings are for helping the understanding of the specification, and may be schematically drawn, and the drawn components or the ratio of dimensions between the components are described in the specification. There are cases where the ratio of these dimensions does not match. In addition, the constituent elements described in the specification may be omitted in the drawings or may be drawn with the number omitted.

[First Embodiment]
FIG. 1 shows a capacitor 100 according to the first embodiment. FIG. 1 is a cross-sectional view of the capacitor 100.

The capacitor 100 includes a substrate 1. The material, characteristics, thickness and the like of the substrate 1 are arbitrary, but in this embodiment, a Si (100) substrate having a thickness of 500 μm was used.

A first electrode layer 2 is formed on the substrate 1. The material, characteristics, thickness, etc. of the first electrode layer 2 are arbitrary, but in this embodiment, a Pt (111) film having a thickness of 100 nm is formed.

A dielectric layer 3 is formed on the first electrode layer 2. The dielectric layer 3 is made of a metal oxide having a fluorite structure. The metal oxide contains HfO ₂ in which a part of Hf is substituted with Bi and a pentavalent or higher element.

In this embodiment, pentavalent Nb is used as the pentavalent or higher element. That is, in the metal oxide, a part of tetravalent Hf is substituted with trivalent Bi and pentavalent Nb. Bi is mainly added to improve the dielectric constant. Nb is added mainly to adjust the valence of the element to suppress the generation of oxygen vacancies and to suppress deterioration of characteristics (decrease in dielectric constant).

Furthermore, in this embodiment, La is added to the metal oxide as a stabilizer. The stabilizer (La) is added in order to avoid that the metal oxide film has a monoclinic crystal structure and does not exhibit good antiferroelectricity. In addition, when the thickness of the dielectric material layer 3 is less than 10 nm, it is thought that favorable antiferroelectric property is obtained even if it does not add a stabilizer. The stabilizer is not limited to La, for example, one or more kinds selected from La, Ce, Al, Ti, Sn, Zr, Sc, Mg, Zn, Y, Ca, Sr, Ba These elements can be used.

In the present embodiment, the dielectric layer 3 has a thickness of 60 nm. In the following, the dielectric layer 3 may be referred to as an HfO ₂ film.

The dielectric layer 3 has antiferroelectric properties. Therefore, the dielectric layer 3 exhibits a high dielectric constant by applying a bias electric field.

A second electrode layer 4 is formed on the dielectric layer 3. The material, characteristics, thickness, etc. of the second electrode layer 4 are arbitrary, but in this embodiment, a Pt (111) film having a thickness of 100 nm is formed.

The capacitor 100 according to the first embodiment having the above-described structure can be used as a capacitor that develops a high capacitance by applying a bias electric field. Note that the capacitor 100 exhibits a high capacitance even when no bias electric field is applied.

The capacitor 100 according to the first embodiment can be manufactured, for example, by the following method.

First, the substrate 1 is prepared.

Also, a chemical solution is prepared in parallel with the preparation of the substrate 1.

As raw material salts of the chemical solution, 0.952 g of hafnium isopropoxide, 0.052 g of bismuth acetate, 0.052 g of niobium isopropoxide, and 0.042 g of lanthanum isopropoxide are prepared.

Also, prepare 2 ml of acetic acid and 4 ml of 2-methoxyethanol as the solvent for the chemical solution.

In a container, add acetic acid and 2-methoxyethanol and stir. Furthermore, each raw material salt is added to the container and stirred to obtain a chemical solution.

Next, the first electrode layer 2 made of a Pt (111) film is formed on the substrate 1 by sputtering.

Next, a chemical solution is coated on the first electrode layer 2 by spin coating.

Specifically, as the first coating, the substrate 1 on which the first electrode layer 2 is formed is attached to a turntable, and the turntable is rotated at 3000 rpm, and the first electrode layer 2 is formed on the first electrode layer 2. A chemical solution is dropped, and a film of a chemical solution having a thickness of 60 nm is coated on the first electrode layer 2. In addition, let the chemical solution dripped be the quantity of 1/3 of the produced chemical solution. Subsequently, the substrate 1 on which the film of the chemical solution is formed on the first electrode layer 2 is heated to 500 ° C. at a heating rate of 300 ° C./min in an oxygen atmosphere with an oxygen flow rate of 200 ml / min. Hold for a minute. As a result, a first HfO ₂ film is formed on the first electrode layer 2.

Subsequently, on the first HfO ₂ film, as a second coating, a chemical solution is coated by a spin coating method under the same conditions as the first coating, and heated to form a second HfO ₂ film. To do. In addition, let the chemical solution dripped be the quantity of 1/3 of the produced chemical solution.

Subsequently, on the second HfO ₂ film, as a third coating, a chemical solution is coated by a spin coat method under the same conditions as the first and second times, and heated to form a third HfO 2 film. _Two films are formed. In addition, let the chemical solution dripped be the quantity of 1/3 of the produced chemical solution.

As a result, the dielectric layer 3 in which the first HfO ₂ film, the second HfO ₂ film, and the third HfO ₂ film having the same thickness are laminated on the first electrode layer 2 is formed.

Next, the second electrode layer 4 made of a Pt (111) film is formed on the dielectric layer 3 by sputtering.

Next, heat treatment is performed to improve the crystallinity of the dielectric layer (HfO ₂ film) 3. Specifically, the substrate 1 on which the first electrode layer 2, the dielectric layer 3, and the second electrode layer 4 are formed is heated at a rate of temperature increase of 300 ° C./min in an oxygen atmosphere with an oxygen flow rate of 200 ml / min. Heat to 700 ° C. and hold for 10 minutes.

Thus, the capacitor 100 is completed.

Table 1 shows the composition of the dielectric layer of the capacitor 100, the type of raw material salt, and the weight.

The X-ray diffraction spectrum of the dielectric layer (HfO ₂ film) 3 of the completed capacitor 100 was measured. FIG. 2 shows an X-ray diffraction spectrum of the dielectric layer 3 of the capacitor 100. From FIG. 2, the diffraction lines appearing near 30 ° and 35 ° can be attributed to cubic, tetragonal or orthorhombic fluorite structures, and HfO having a fluorite structure in which a part of Hf is substituted with Bi, Nb, and La. _It can be confirmed that _two films are formed.

Further, the bias characteristic of the relative dielectric constant of the dielectric layer (HfO ₂ film) 3 of the capacitor 100 was measured using an LCR meter. FIG. 3 shows a relative dielectric constant-bias electric field curve of the capacitor 100.

For comparison, capacitors 1100 and 1200 according to comparative examples were produced. Each of the capacitors 1100 and 1200 is a part of the configuration of the capacitor 100. Specifically, in the capacitor 1100, In was added instead of Bi. The capacitor 1200 did not add Nb. Note that the capacitors 1100 and 1200 were manufactured by the same method as the capacitor 100.

Table 2 shows the composition of the dielectric layers of the capacitors 1100 and 1200.

FIG. 3 shows a relative dielectric constant-bias electric field curve of the dielectric layers of the capacitors 1100 and 1200.

The capacitor 100 according to the first embodiment was compared with the capacitors 1100 and 1200 according to the comparative example.

The relative permittivity of the capacitor 100 was increased by application of a bias electric field, and a relative permittivity of 75 was exhibited at 0.7 MV / cm. That is, by applying a small bias electric field, the relative dielectric constant was greatly improved and good antiferroelectric properties were exhibited.

On the other hand, the capacitor 1100 showed only a relative dielectric constant of 36 even when a bias field of 2 MV / cm was applied. That is, the relative dielectric constant of the capacitor 1100 was low, and the bias electric field indicating the maximum value of the relative dielectric constant was high. That is, the capacitor 1100 did not show good antiferroelectricity.

The capacitor 1200 showed only a relative dielectric constant of 35 even when a bias electric field of 1.5 MV / cm was applied. That is, the relative dielectric constant of the capacitor 1200 was low, and the bias electric field indicating the maximum value of the relative dielectric constant was high. That is, the capacitor 1200 also did not show good antiferroelectricity.

Further, in a state where no bias electric field was applied, the capacitor 100 had a relative dielectric constant of 50, indicating a high value. In contrast, in the state where no bias electric field was applied, the capacitor 1100 had a relative dielectric constant of 28, and the capacitor 1100 had a relative dielectric constant of 29, both of which were low values.

As described above, in the capacitor 100 according to the first embodiment, the dielectric layer (HfO ₂ film) 3 easily responds to an electric field, and exhibits a higher relative dielectric constant under a lower bias electric field than in the past, and has a high static It was found that electric capacity was developed. This effect of the capacitor 100 is an effect obtained by substituting a part of Hf with Bi and Nb at the same time, and is an effect that cannot be obtained by replacing Bi alone or replacing it with In instead of Bi.

It is not clear why the co-substitution with Bi and Nb has resulted in a high dielectric constant in the absence of a bias field and under a relatively low bias field. However, it is thought that Bi caused distortion in the crystal, and the crystal became more responsive to the electric field.

In the capacitor 1100 of the comparative example, In was substituted for Bi instead of Bi. In is the same trivalent element as Bi, but when it was substituted with In, the dielectric constant did not improve, and good antiferroelectricity was not exhibited. The reason for the remarkable improvement in dielectric properties in the case of Bi compared to In is that Bi ³⁺ ions have unshared electron pairs and are trying to take a more distorted structure in the crystal structure. It is thought that there is not.

In the capacitor 1200 of the comparative example, Bi and Nb are not co-replaced, and Bi is substituted only. However, the substitution with Bi alone did not show a sufficient effect. Regarding the reason why a high dielectric constant was obtained by co-substitution of Bi and Nb, the valence of the element was adjusted by substituting tetravalent Hf with trivalent Bi and pentavalent Nb, This is probably because the generation of oxygen vacancies was suppressed and the deterioration of characteristics (decrease in dielectric constant) was suppressed.

In the present embodiment, La is added as a stabilizer in order to adjust the crystal structure of HfO ₂ . However, the stabilizer is not limited to La, and the same effect can be obtained by adding other elements such as Ce. Therefore, the characteristic improvement (improvement of dielectric constant, good antiferroelectric expression) in the present embodiment is due to co-substitution of a part of Hf with Bi and Nb rather than addition of La. Conceivable. In addition to La and Ce, for example, Al, Ti, Sn, Zr, Sc, Mg, Zn, Y, Ca, Sr, Ba, etc. can be used as the stabilizer.

[Second Embodiment]
Capacitors 210, 220, 230, 240, 250, 260, 270 and 280 according to the second embodiment were produced. Reference numerals 210 to 280 denote sample numbers. Although not shown, each capacitor has the same structure as the capacitor 100 according to the first embodiment shown in FIG. However, of the capacitors 210 to 280, the capacitor 210 is a comparative example.

In the capacitors 210 to 280 according to the second embodiment, Bi and Nb are changed by changing the addition amount to the metal oxide constituting the dielectric layer (HfO ₂ film) 3 of the capacitor 100 according to the first embodiment. The amount of La added is optimized according to the amount added. Therefore, in any of the examples and comparative examples, the total amount of Hf, Bi, Nb, and La becomes 100 mol%.

Specifically, the capacitor 210 was added with 5 mol% of La without adding Bi and Nb. The capacitor 220 was added with 0.5 mol% of Bi and Nb and 5 mol% of La. The capacitor 230 was added with 1 mol% of Bi and Nb, respectively, and 5 mol% of La. The capacitor 240 was added with 3 mol% of Bi and Nb and 5 mol% of La. In the capacitor 250, 7.5 mol% of Bi and Nb were added, and 5 mol% of La was added. The capacitor 260 was added with 10 mol% of Bi and Nb and 3 mol% of La. The capacitor 270 was added with 15 mol% of Bi and Nb and 1 mol% of La. Capacitor 280 was added with 17.5 mol% of Bi and Nb and 1 mol% of La, respectively.

Other items of the capacitors 210 to 280, for example, the type of raw material salt used in the chemical solution, the type and amount of the solvent contained, and the manufacturing method were the same as those of the capacitor 100.

Table 3 shows the composition of the dielectric layer of each of the capacitors 210 to 280. In Table 3, the numerical value of the capacitor 100 is also shown.

In the second embodiment, part of Hf of HfO ₂ contained in the dielectric layer is replaced with Bi, Nb, and La. Hf is a tetravalent element, La and Bi are trivalent elements, and Nb is a pentavalent element.

FIG. 4 shows relative dielectric constant-electric field curves of the dielectric layers of the capacitors 100 and 210 to 270, respectively. In addition, in the capacitor 280 to which 17.5 mol% of Bi and Nb were added respectively, the insulation was lowered and the relative dielectric constant could not be measured.

As can be seen from FIG. 4, in each of the capacitors 220 to 270 to which Bi and Nb were added, the relative dielectric constant increased compared to the capacitor 210 to which Bi and Nb were not added (Comparative Example). Among the capacitors 210 to 270, those having a relative dielectric constant that is as large as the capacitor 100 and increased are indicated by ◎, those having a relative dielectric constant increased by the capacitor 210, and capacitors 210 by ×. The evaluation results are shown in Table 3.

The relative dielectric constant was increased by adding Bi and Nb and could be increased up to about 80. This is probably because Bi and Nb were added simultaneously, while maintaining the charge neutrality, the Bi substitution caused distortion in the crystal and the crystal became more responsive to the electric field. However, when the added amounts of Bi and Nb exceeded a certain amount, the insulating properties of the film deteriorated. This is thought to be because Bi and Nb formed impurity levels in the band gap of HfO ₂ and the conduction carriers increased.

As described above, it was confirmed that the dielectric constant could be increased by replacing part of Hf of the metal oxide film constituting the dielectric layer (HfO ₂ film) with Bi and Nb. However, it has been found that Bi and Nb are preferably replaced with 15 mol% or less, because Bi and Nb are excessively substituted to deteriorate the insulating properties.

[Third Embodiment]
Capacitors 310 and 320 according to the third embodiment were produced. Reference numerals 310 and 320 are sample numbers. Although not shown, each capacitor has the same structure as the capacitor 100 according to the first embodiment shown in FIG.

In the capacitors 310 and 320 according to the third embodiment, a part of the configuration of the capacitor 100 according to the first embodiment is changed. Specifically, in the capacitor 100, Nb was added to the metal oxide constituting the dielectric layer (HfO ₂ film) 3 simultaneously with Bi. The capacitor 310 changed this and added Ta instead of Nb. In addition, the capacitor 320 is changed, and Wa is added instead of Nb.

Specifically, the capacitor 310 is added with 5 mol% of Bi and Ta and 5 mol% of La (the amount of Hf is reduced by 15 mol%, and 5 mol% of Bi and Ta are added instead, and 5 mol% of La is added. Added). Capacitor 320 was added with 6.6 mol% Bi, 3.3 mol% W, and 5 mol% La (the amount of Hf was reduced by 14.9 mol%, and Bi 6.6 mol% was added instead. W was added at 3.3 mol%, and La was added at 5 mol%).

In the capacitor 310, tantalum isopropoxide was used as a Ta raw material salt. In the capacitor 320, tungsten ethoxide was used as a raw material salt of W.

The other matters of the capacitors 310 and 320, for example, the type and amount of the solvent contained in the chemical solution, and the manufacturing method are the same as those of the capacitor 100.

Table 4 shows the composition of the dielectric layer of each of the capacitors 310 and 320. In Table 4, the numerical value of the capacitor 100 is also shown for comparison.

In the third embodiment, a part of Hf of HfO ₂ contained in the metal oxide of the dielectric layer of the capacitor 310 is replaced with Bi, Ta, and La. In addition, a part of Hf of HfO ₂ contained in the metal oxide of the dielectric layer of the capacitor 320 is replaced with Bi, W, and La.

Hf is a tetravalent element, Bi and La are trivalent elements, Ta is a pentavalent element, and W is a hexavalent element. When Bi, which is a trivalent element, and Ta, which is a pentavalent element, are added simultaneously, the molar ratio of Bi and Ta is preferably 1: 1. When Bi, which is a trivalent element, and W, which is a hexavalent element, are added simultaneously, the molar ratio of Bi and W is preferably 2: 1. This is because the valence of the element is adjusted and the generation of oxygen vacancies is suppressed.

FIG. 5 shows relative dielectric constant-electric field curves of the dielectric layers of the capacitors 100, 310, and 320, respectively.

As can be seen from FIG. 5, the capacitor 310 added with 5 mol% of Bi and Ta each showed a high relative dielectric constant of 61 when no bias electric field was applied. When a bias electric field was applied to the capacitor 310, the relative dielectric constant was improved, and a relative dielectric constant of 75 was exhibited at a bias electric field of 0.7 MV / cm. The capacitor 320 to which 6.6 mol% Bi and 3.3 mol% W were added showed a high relative dielectric constant of 42 in a state where no bias electric field was applied. When a bias electric field was applied to the capacitor 320, the relative dielectric constant was improved, and a relative dielectric constant of 62 was exhibited at a bias electric field of 1.2 MV / cm.

The relative dielectric constants of the capacitors 310 and 320 are equivalent to those of the capacitor 100 to which Nb is added, and it is considered that the effects of adding Nb, Ta, and W are similar.

As described above, it was confirmed that the dielectric constant could be increased by adding Bi, Ta or Bi, W to the dielectric layer (HfO ₂ film). In addition to Nb, Ta, and W, the element added simultaneously with Bi may be Mo or the like.

[Fourth Embodiment]
Capacitors 410, 420, 430, and 440 according to the fourth embodiment were produced. Reference numerals 410 to 440 are sample numbers. Although not shown, each capacitor has the same structure as the capacitor 100 according to the first embodiment shown in FIG.

The capacitors 410 to 440 according to the fourth embodiment are obtained by adding Si to the dielectric layer (HfO ₂ film) 3 of the capacitor 100 according to the first embodiment while changing the addition amount.

Specifically, the capacitor 410 is added with 5 mol% of Bi and Nb, 5 mol% of La, and 1 mol% of Si (the amount of Hf is reduced by 16 mol%, and Bi and Nb are each 5 mol% instead. And 5 mol% La and 1 mol% Si were added). In the capacitor 420, 5 mol% of Bi and Nb were added, 5 mol% of La was added, and 2 mol% of Si was added. The capacitor 430 was added with 5 mol% of Bi and Nb, 5 mol% of La, and 3 mol% of Si. In the capacitor 440, 5 mol% of Bi and Nb were added, 5 mol% of La was added, and 4 mol% of Si was added.

In capacitors 410 to 440, silicon ethoxide was used as a raw material salt of Si.

The other matters of the capacitors 410 to 440, for example, the type, amount, and manufacturing method of the solvent included are the same as those of the capacitor 100.

Table 5 shows the composition of the dielectric layer of each of the capacitors 410 to 440. In Table 5, the numerical value of the capacitor 100 is also shown for comparison.

In the fourth embodiment, part of Hf of HfO ₂ contained in the dielectric layer is replaced with Bi, Nb, La, and Si. Hf and Si are tetravalent elements, La and Bi are trivalent elements, and Nb is a pentavalent element.

FIG. 6 shows the relative permittivity-electric field curves of the dielectric layers of the capacitors 410 to 440, respectively.

As can be seen from FIG. 6, in the capacitor 410 to which 1 mol% of Si was added, the relative permittivity was greatly increased. In the capacitor 420 to which 2 mol% of Si was added, the increase amount of the relative dielectric constant was equal to that of the capacitor 100, but the bias electric field necessary for the increase of the relative dielectric constant was increased. In the capacitor 430 to which 3 mol% of Si was added, the increase amount of the relative dielectric constant was smaller than that of the capacitor 100, and the bias electric field required for increasing the relative dielectric constant was also increased. In the capacitor 440 to which 4 mol% of Si was added, the relative dielectric constant was greatly reduced and the antiferroelectric property was not exhibited.

Table 5 shows that the capacitor 100 is ◯, that the relative permittivity is larger than that of the capacitor 100, ◎, that the relative permittivity is increased to the same level as the capacitor 100, and that the relative permittivity is decreased from the capacitor 100. Δ, where the relative permittivity is greatly reduced as compared with the capacitor 100 and the antiferroelectric property is not shown.

The relative dielectric constant changed corresponding to the amount of Si added, and could be increased up to about 87 by adding Si. This is considered to be because the crystal structure can be easily fluctuated by the Si substitution, and the response to the electric field becomes easier. However, when the added amount of Si exceeded a certain amount, the relative dielectric constant decreased conversely. The reason why the relative permittivity is decreased is considered to be that when the added amount of Si exceeds a certain amount, Si cannot be dissolved in HfO ₂ and the crystallinity is lowered. The amount of Si added is preferably 3 mol% or less, and more preferably 2 mol% or less.

As described above, it was confirmed that the dielectric constant could be increased by adding Si to the dielectric layer (HfO ₂ film) to which Bi and Nb were added. Note that the element added to increase the dielectric constant is not limited to Si, and may be, for example, Ge.

[Fifth Embodiment]
A capacitor 500 according to the fifth embodiment was produced. Reference numeral 500 denotes a sample number. Although not shown, the capacitor 500 has the same structure as the capacitor 100 according to the first embodiment shown in FIG.

In the capacitor 500 according to the fifth embodiment, a part of the configuration of the capacitor 100 according to the first embodiment is changed. Specifically, in the capacitor 100, La is added as a stabilizer to the metal oxide constituting the dielectric layer (HfO ₂ film) 3. The capacitor 500 changed this and added Ce instead of La.

In the capacitor 500, cerium isopropoxide was used as a raw material salt of Ce.

Other items of the capacitor 500, for example, the type, amount and manufacturing method of the solvent contained in the chemical solution were the same as those of the capacitor 100.

Table 6 shows the composition of the dielectric layer of the capacitor 500. In Table 6, the numerical value of the capacitor 100 is also shown for comparison.

In the fifth embodiment, a part of Hf of HfO ₂ contained in the metal oxide of the dielectric layer of the capacitor 500 is replaced with Bi, Nb, and Ce.

FIG. 7 shows the relative permittivity-electric field curve of the dielectric layers of the capacitors 100 and 500.

As can be seen from FIG. 7, the capacitor 500 to which Ce is added instead of La shows a high relative dielectric constant of 76 when a bias electric field of 0.6 MV / cm is applied. It has a dielectric constant-electric field curve.

La and Ce are added as stabilizers for adjusting the crystal structure of HfO ₂ . Specifically, it is considered that the addition of La and Ce suppresses the crystal structure from becoming monoclinic. The stabilizer is not limited to La and Ce, and may be an element such as Al, Y, or Zr. Further, not only one type but also a plurality of types of elements may be added in combination.

The method for manufacturing the capacitor and the HfO ₂ film according to the first to fifth embodiments has been described above. However, the present invention is not limited to the contents described above, and various modifications can be made in accordance with the spirit of the invention.

For example, the composition of the dielectric layer is arbitrary within the scope of the invention and is not limited to the above-described contents.

Also, the kind and weight of the raw material salt for producing the dielectric layer of the capacitor are arbitrary, and other kinds of raw material salts can be used. For example, in the capacitor 100, hafnium isopropoxide is used as a raw material salt of Hf. Instead of or in addition to this, other hafnium alkoxides such as hafnium ethoxide, hafnium-t-butoxide, and hafnium carboxylate are used. One type or a plurality of types such as hafnium chloride, hafnium nitrate, and hafnium acetate may be used.

DESCRIPTION OF SYMBOLS 1 ... Substrate 2 ... 1st electrode layer 3 ... Dielectric layer 4 ... 2nd electrode layer

Claims (13)

1. A first electrode layer;
   A dielectric layer formed on the first electrode layer;
   A capacitor comprising: a second electrode layer formed on the dielectric layer;
   The dielectric layer is made of a metal oxide;
   The metal oxide includes Hf, Bi, and a pentavalent or higher element.
2. The capacitor according to claim 1, wherein the metal oxide has a fluorite structure.
3. The capacitor according to claim 1 or 2, wherein the pentavalent or higher element is one or more kinds of elements selected from Nb, Ta, Mo, and W.
4. When the total amount of the metal oxide excluding O is 100 mol%,
   4. The capacitor according to claim 1, wherein addition amounts of the Bi and the pentavalent or higher element are each 15 mol% or less. 5.
5. When the pentavalent or higher element is a pentavalent element, the molar ratio of Bi to the pentavalent element is 1: 1.
   5. The element according to claim 1, wherein when the pentavalent or higher element is a hexavalent element, a molar ratio of Bi to the hexavalent element is 2: 1. Capacitor.
6. The capacitor according to claim 1, further comprising a group IV element added to the metal oxide.
7. The capacitor according to claim 6, wherein the group IV element is one or both of Si and Ge.
8. When the total amount of the metal oxide excluding O is 100 mol%,
   The capacitor according to claim 6 or 7, wherein an additive amount of the group IV element is 3 mol% or less.
9. The capacitor according to claim 8, wherein the amount of the group IV element added is 2 mol% or less.
10. The thickness of the dielectric layer is 10 nm or more;
    The capacitor according to any one of claims 1 to 9, further comprising a stabilizer.
11. The stabilizer is one or more kinds of elements selected from La, Ce, Al, Ti, Sn, Zr, Sc, Mg, Zn, Y, Ca, Sr, and Ba. 10. The capacitor described in 10.
12. HfO _2, or a method for producing a HfO ₂ film containing HfO ₂ containing Hf and O and other elements,
    Preparing a film formation target;
    Preparing a chemical solution as a raw material for the HfO ₂ film;
    Spin-coating the chemical solution on the film formation target;
    By heat treatment, the production of the film from the chemical solution was spin-coated on the object, tetragonal and orthorhombic HfO ₂ film and a step of precipitating the HfO ₂ film containing at least one crystalline phase Method.
13. The chemical solution as a raw material of the HfO ₂ film is a chemical solution in which one or more selected from hafnium alkoxide, hafnium carboxylate, hafnium chloride, hafnium nitrate, and hafnium acetate are mixed in an organic solvent. A method for producing an HfO ₂ film according to claim 12.

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