JP2005191153A - Capacitor and its production process, and semiconductor device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a process for producing a capacitor inexpensively while reducing the size by employing a dielectric film having a high dielectric constant, and to provide a semiconductor comprising such a capacitor. <P>SOLUTION: The capacitor has such a structure as a dielectric film 3 is sandwiched between a first electrode 2 and a second electrode 4 wherein the dielectric film 3 principally comprises a bismuth layer compound represented by a general formula Bi<SB>2</SB>A<SB>m-1</SB>B<SB>m</SB>O<SB>3m+3</SB>(where, m=2, 4, A is a metal element being selected from among Ba, Ca, Sr and Bi, and B is a metal element being selected from among Fe, Ga, Ti, Ta, Nb, V, Mo and W), and contains at least one of Si and Ge wherein the bismuth layer compound has c-axis oriented in the film thickness direction of the dielectric film. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a capacitor, a manufacturing method thereof, and a semiconductor device including the capacitor.

In a semiconductor device, various capacitors are used as its constituent elements (see, for example, Patent Document 1, Patent Document 2, Patent Document 3, and Patent Document 4). For example, capacitors are used in an oscillation circuit, a power supply circuit, and the like in a semiconductor device for the purpose of preventing operational amplifier oscillation, stabilizing, smoothing, and boosting circuits.
As such a capacitor, in the case where the capacitor is built in a circuit, a dielectric film such as a silicon oxide film, a silicon nitride film, or a silicon oxynitride film is formed by using silicon, metal, titanium nitride, aluminum nitride, etc. A structure sandwiched between upper and lower electrode films is often used. In addition, capacitors that are externally attached to a circuit or the like are known, such as a multilayer capacitor provided with a ceramic dielectric film such as barium titanate.
In manufacturing such a capacitor, in particular, a sputtering method, a CVD method, a laser ablation method, or the like is used to form the dielectric film.

By the way, the capacitance of the capacitor is proportional to the dielectric constant and area of the dielectric film and inversely proportional to the thickness. Therefore, when it is desired to form a small, high-capacitance capacitor internal to the circuit, in order to increase the film thickness from the viewpoint of leakage current, the dielectric film is formed of a material having a high dielectric constant, thereby increasing the capacitance. It is hoped that On the other hand, in the case of an external capacitor, there is a demand for reducing the assembly cost and increasing the yield, and it is desired that the capacitor can be easily manufactured with a thin film.
From this background, the dielectric constant of the dielectric film of the capacitor is preferably 300 or more in the case of an internal circuit and 1000 or more in the case of an external connection in consideration of the area and film thickness. Has been.
JP-A-7-226485 JP-A-9-139480 JP-A-5-82801 Japanese Patent Laid-Open No. 5-47587

  However, in the capacitor manufactured inside the circuit, a silicon oxide film, a silicon nitride film, a silicon oxynitride film, or the like is used as a dielectric film. However, these dielectric films have a dielectric constant as low as 10 or less. In order to increase the capacity, it is necessary to increase the area. If the area of the capacitor is increased in this way, the area occupied by the capacitor in the circuit increases, which hinders downsizing of the circuit. In order to increase the capacity, a means of reducing the film thickness is conceivable. However, if the film thickness is reduced, there is a problem in that the leakage current increases and the efficiency decreases. Furthermore, there is a problem that dielectric breakdown is likely to occur when the film thickness is reduced.

  As insulator materials having a high dielectric constant, ferroelectric materials such as lead zirconate titanate (PZT) and barium titanate are known. In such a ferroelectric material, the film forming temperature is preferably set to about 550 ° C. or less because of influence on other semiconductor elements and wirings provided in the same semiconductor device. However, crystallization hardly occurs at such a low temperature, and thus the obtained dielectric film has a higher dielectric constant than a silicon oxide film or the like, but does not reach a desired high dielectric constant. Absent. In addition, the change in dielectric constant with respect to the change in frequency and temperature is large, so that it is inferior to a silicon oxide film or the like.

  On the other hand, when a capacitor made of ceramics such as barium titanate is formed externally, the cost of the capacitor itself is low, but it requires assembly costs such as alignment and bonding with other elements. In addition, since there are problems such as yield, sufficient cost reduction has not yet been achieved.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a dielectric film having a high dielectric constant, thereby enabling downsizing of a device including the dielectric film, and manufacturing the capacitor at a low cost. An object of the present invention is to provide a capacitor manufacturing method and a semiconductor device including such a capacitor.

In order to solve the above problems, the present invention provides a capacitor having a structure in which a dielectric film is sandwiched between a first electrode and a second electrode, and the dielectric film has a general formula Bi _{2 Am −. 1} B _m O _{3m + 3} (where m = 2, 4, A is a metal element selected from Ba, Ca, Sr, Bi, B is a metal selected from Fe, Ga, Ti, Ta, Nb, V, Mo, W) Element)) and containing at least one of Si and Ge, and the bismuth layered compound is c-axis oriented in the film thickness direction of the dielectric film. A capacitor is provided.

According to this capacitor, the dielectric film has the general formula Bi ₂ A _m−1 B _m O _{3m + 3} ((B ₂ O ₂ ) ²⁺ (A _m−1 B _m O _{3m + 1} ) ²⁻ ) m = The main component is a bismuth layered compound of 2 or m = 4, and the c-axis is oriented in the film thickness direction of the dielectric film, so that a higher dielectric constant can be obtained as compared with the prior art, Therefore, it is possible to reduce the size of the apparatus provided with this. In addition, since at least one of Si and Ge is added to the dielectric film, it is easy to obtain a bismuth layered compound having good crystallinity at the time of manufacture. In particular, the precursor compound is baked to form the dielectric film. In this case, the firing temperature can be lowered, the influence on other semiconductor elements and wirings can be reduced, and the use of the capacitor of the present invention improves the ease of manufacturing the device, Design freedom is improved.
Further, since the dielectric film does not contain Pb, it is advantageous for environmental pollution, and the capacitor provided with this is also environmentally advantageous.

In the capacitor according to the present invention, the bismuth layered compound contains SrBi ₄ Ti ₄ O ₁₅ (m = 4), SrBi ₂ (Ta _x Nb _1-x ) ₂ O ₉ (where 0 ≦ x ≦ 1) (m = 2). ), Bi ₃ Ti (Ta _x Nb _1-x ) ₂ O ₉ (where 0 ≦ x ≦ 1) (m = 2) or a mixed phase. Of the bismuth layered compounds having m = 2, 4, particularly those having the above composition are used, so that by-products are hardly formed during film formation, and a high dielectric constant can be obtained.

  In the capacitor of the present invention, the total content of Si and Ge is preferably 0.1 mol% or more and 10.0 mol% or less. When the total addition amount of Si and Ge is less than 0.1 mol%, the effect of Si and Ge as a catalyst is not satisfactorily exhibited, and when it exceeds 10.0 mol%, the amount of the bismuth layered compound as the main component This is because the relative permittivity decreases and the dielectric constant decreases.

  In the capacitor of the present invention, the first electrode and / or the second electrode is an electrode made of one or more metal materials selected from platinum, iridium, ruthenium, gold, and silver, or an oxide of these metal materials. There can be a certain configuration. If these metal materials are used, an electrode can be formed easily and efficiently.

The capacitor of the present invention may be configured such that the first electrode and / or the second electrode is an electrode composed mainly of a perovskite metal oxide. Furthermore, in the capacitor of the present invention, it is preferable that the first electrode is an electrode made of SrRuO ₃ .
In the capacitor of the present invention, the main orientation direction of the metal oxide constituting the first electrode is preferably pseudo-cubic and (100) orientation. More preferably, a buffer layer is formed below the first electrode, and the buffer layer is formed using ion beam assist and has a (100) orientation.
Also in this configuration, the definition of the “main component” is as described above, and in addition to the metal oxide, there are no additives or impurities within a range that does not impair the crystallinity of the metal oxide. It shows that it may be.
In particular, if a perovskite-type metal oxide is used for the first electrode, the bismuth layered compound constituting the dielectric film can be c-axis oriented in the film thickness direction and the crystallinity can be improved. It is possible to increase the capacitor capacity by further increasing the dielectric constant. In addition, the primary orientation of the metal oxide of the first electrode is pseudo cubic (cubic) and (100) orientation so that the crystallinity of the bismuth layered compound formed on the first electrode is better. It becomes. Furthermore, if the buffer layer formed by the ion beam assist method is used, the orientation can be easily obtained and the restriction on the surface state of the substrate on which the capacitor is formed can be relaxed.

In order to solve the above-mentioned problems, the present invention provides a method for manufacturing a capacitor having a structure in which a dielectric film is sandwiched between a first electrode and a second electrode, and has a chemical formula Bi ₂ A _m-1 B _m O. _{3m + 3} (where m = 2, 4, A is a metal element selected from Ba, Ca, Sr, Bi, and B is a metal element selected from Fe, Ga, Ti, Ta, Nb, V, Mo, W) A step of disposing a precursor containing a bismuth layered compound and a liquid containing at least one of Si and Ge on a substrate, and heat-treating the liquid containing the precursor compound, And a step of forming the dielectric film containing the bismuth layered compound, wherein the heat treatment temperature is set to 550 ° C. or lower in the step of heat treating the liquid.
According to this capacitor manufacturing method, it is possible to form a dielectric film containing the bismuth compound as a main component and the c-axis of the compound being oriented substantially perpendicular to the surface of the first electrode. As a result, it is possible to reduce the size of the device including the capacitor having the dielectric film. In addition, since such a dielectric film having excellent crystallinity can be obtained by low-temperature firing at 550 ° C. or lower, for example, when other semiconductor elements or wirings are formed on the substrate, the thermal influence on them Can be reduced. Further, if the baking temperature is set to 450 ° C. by adjusting the addition amount of Si or Ge, the thermal influence can be further reduced, which is preferable. Furthermore, since the dielectric film does not contain Pb, it is advantageous against environmental pollution. Therefore, the capacitor itself obtained by manufacturing a capacitor having the dielectric film is also environmentally advantageous. .

Next, a semiconductor device of the present invention is characterized by including the capacitor of the present invention described above or the capacitor obtained by the manufacturing method according to the present invention described above.
According to this configuration, it is possible to provide a semiconductor device that can be easily miniaturized and highly integrated by providing a capacitor that is miniaturized by having a dielectric film having a high dielectric constant. In particular, if the dielectric film is formed using a droplet discharge method, the manufacturing cost can be reduced.

(Capacitor)
The present invention will be described in detail below.
FIG. 1 is a diagram showing an embodiment of a capacitor according to the present invention, and reference numeral 1 in FIG. 1 denotes a capacitor. For example, in the semiconductor device 50 according to an embodiment of the semiconductor device of the present invention shown in FIG. 2, the capacitor 1 is further replaced with a capacitor external to the circuit as a capacitor 1a that is replaced with a conventional circuit internal capacitor. It is used as the capacitor 1b.

  Here, in the semiconductor device 50, various transistors such as CMOS transistors and memory elements are formed on the substrate 51, and various wirings that electrically connect between these and the capacitors 1a and 1b. A plug or the like is formed on or in the interlayer insulating film. Note that the layers up to the interlayer insulating film 52 on which the capacitors 1a and 1b are formed are referred to as a base 53 in the present invention. Although not shown, a protective layer, wiring, and the like are formed on the capacitors 1a and 1b, and an insulating layer is formed to cover them.

  As shown in FIG. 1, the capacitor 1 used as the capacitors 1 a and 1 b is formed on the interlayer insulating film 52 (on the base 53) made of, for example, polyimide, and is formed on the interlayer insulating film 52. The first electrode 2, the dielectric film 3 formed on the first electrode 2, and the second electrode 4 formed on the dielectric film 3. That is, the capacitor 1 has a structure in which the dielectric film 3 is sandwiched between the first electrode 2 and the second electrode 4, and the embedded wiring 5 formed in the interlayer insulating film 52 is formed on the first electrode 2. Are connected, and another wiring (not shown) is connected to the second electrode 4.

  For the first electrode 2 and the second electrode 4, a metal material such as platinum, iridium (or iridium oxide), ruthenium, gold, silver, or a perovskite-type metal oxide can be used. In particular, if a perovskite-type metal oxide is used for the first electrode 2, the crystallinity of the dielectric film 3 formed thereon can be improved and a higher dielectric constant can be obtained. Further, these electrodes may be formed of a sintered metal body obtained by sintering fine particles of the metal materials listed above. An example using a perovskite type metal oxide will be described in detail later.

The dielectric film 3, the general formula _{Bi 2 A m-1 B m} O 3m + 3 ( i.e. ^{_{(Bi 2 O 2) 2+ (}} A m-1 B m O 3m + 1) 2-) ( where, m = 2, 4, A Is a metal element selected from Ba, Ca, Sr and Bi, B is a metal element selected from Fe, Ga, Ti, Ta, Nb, V, Mo and W), and Si, It is formed by adding at least one of Ge, and the bismuth layered compound is c-axis oriented in the film thickness direction of the dielectric film 3. Specifically, the bismuth layered compound is SrBi ₄ Ti ₄ O ₁₅ (m = 4), SrBi ₂ (Ta _x Nb _1-x ) ₂ O ₉ (where 0 ≦ x ≦ 1) (m = 2) Bi ₃ Ti (Ta _x Nb _1-x ) ₂ O ₉ (where 0 ≦ x ≦ 1) (m = 2) or a mixed phase is preferable.

  Here, in the present invention, the above-mentioned main component allows a certain amount of impurities other than Si and Ge as a component of the dielectric film 3 and the bismuth layered compound accounts for 50 mol% or more of the whole. It means that The dielectric film 3 has a dielectric constant higher than that of a dielectric film such as a silicon oxide film, a silicon nitride film, or a silicon oxynitride film. Therefore, the capacitor 1 having the dielectric film 3 has a higher dielectric constant than that of the conventional one. The capacity can be increased, and when the capacity is designed to be the same as the conventional capacity, the size can be reduced.

In the dielectric film 3, at least one of Si and Ge is added as a component other than the bismuth layered compound as a main component. These Si or Ge are preferably added to the dielectric film 3 in a total amount (total amount) of 0.1 mol% or more and 10.0 mol% or less, preferably 0.5 mol% or more and 8.0 mol%. % Or less, more preferably 1.0 mol% or more and 5.0 mol% or less. When Si and Ge are added in such a total addition amount, as will be described later, these Si and Ge fire the precursor material of the dielectric film 3 to form an oxide mainly composed of the bismuth layered compound. It will act as a catalyst. That is, due to this catalytic action, a crystal layer of a bismuth layered compound is formed even at a low firing temperature, and thus a high dielectric constant can be obtained. Conventionally, when a bismuth layered compound is obtained by firing a precursor compound, it is necessary to make the firing temperature higher than a material such as Pb (Zr, Ti) O ₃ (PZT), and when the above Si or Ge is not added, It was necessary to set the firing temperature to about 700 to 800 ° C. On the other hand, in the dielectric film 3 according to this embodiment, the addition of Si or Ge having the catalytic action described above makes it possible to obtain a bismuth layered compound having good crystallinity even when fired at a low temperature. Specifically, the firing temperature can be lowered to 550 ° C. or lower. As a result, the thermal influence on other semiconductor elements (such as CMOS) and wiring on the base 53 can be reduced.

  When the total addition amount of Si and Ge is less than 0.1 mol%, the action as a catalyst is not exhibited satisfactorily, and when it exceeds 10.0 mol%, the amount of the bismuth layered compound as the main component is exceeded. The relative permittivity decreases and the dielectric constant decreases. Moreover, it is preferable that the amount of addition that does not cause a decrease in the dielectric constant at the same time that the catalytic action of Si and Ge is exhibited is preferably 0.5 mol% or more and 8.0 mol% or less. More preferably, the content is set to 0.0 mol% or more and 5.0 mol% or less.

  In the dielectric film 3 according to the present embodiment, the bismuth layered compound as the main component is preferentially oriented in the c-axis substantially parallel to the film thickness direction of the dielectric film 3 (the normal direction of the electrodes 2 and 4). . In this way, in the bismuth layered compound preferentially oriented in the c-axis in the film thickness direction, the main polarization axis is the plane direction of the dielectric film 3, and m = 2 or m = 4 as in the dielectric film 3 of the present embodiment. When a bismuth layered compound is used, the polarization axis is limited to the plane direction of the dielectric film 3. With this configuration, the dielectric film 3 according to the present embodiment can obtain a high dielectric constant, does not cause hysteresis in its voltage characteristics, and therefore has excellent behavior controllability and a low energy loss. Yes. Therefore, according to the capacitor of this embodiment, the design of a circuit incorporating the capacitor is facilitated, and the miniaturization and performance enhancement thereof are facilitated.

Here, a case where a perovskite metal oxide is used for the first electrode 2 of the capacitor 1 according to the present embodiment will be described. By using an electrode made of such a metal oxide, the crystallinity of the dielectric film 3 formed immediately above can be increased, a higher dielectric constant can be obtained, and the c-axis preferred orientation degree of the dielectric film 3 can be obtained. By increasing the value, it is possible to effectively suppress the expression of the polarization axis in the thickness direction and to make it difficult to cause energy loss.
As the perovskite metal oxide, at least one selected from SrRuO ₃ , Nb—SrTiO ₃ , La—SrTiO ₃ , (La, Sr) MnO ₃ , (La, Sr) CoO ₃ is preferably used. It is done. Here, Nb—SrTiO ₃ is obtained by doping SrTiO ₃ with Nb, and La—SrTiO ₃ is obtained by doping SrTiO ₃ with La. Since these metal oxides are excellent in conductivity and chemical stability, the lower electrode 4 formed from them is also excellent in conductivity and chemical stability. In particular, when SrRuO ₃ is used, the present inventors have confirmed that the bismuth layered compound composing the dielectric film 3 is favorably crystal-grown. Furthermore, if the perovskite oxide has a (100) orientation, the degree of c-axis orientation of the bismuth layered compound is increased, which is convenient.

  As described above, in a capacitor mounted on a semiconductor device, the surface of the interlayer insulating film 52 on which the lower first electrode 2 is formed does not necessarily have an orientation plane convenient for crystal growth. When the 1st electrode 2 is comprised with a metal oxide in order to improve the crystallinity of the body film 3, it is preferable that the 1st electrode 2 has favorable crystallinity on arbitrary surfaces. Therefore, it is preferable to provide a buffer layer on the lower side (base side) of the first electrode 2 in order to control the orientation of the first electrode 2. This buffer layer may be provided for each of the capacitors, or a plurality of capacitors formed in the same layer may share a single buffer layer.

  The buffer layer may be a single orientation (alignment orientation is aligned only in the thickness direction), but is further in-plane orientation (alignment orientation is aligned in all three-dimensional directions). Are preferred). This is because by providing such a buffer layer, it is possible to obtain excellent bondability (adhesion) between the interlayer insulating film 52 and the first electrode 2.

  The buffer layer preferably includes at least one of a metal oxide having a NaCl structure, a metal oxide having a fluorite structure, a metal oxide having a perovskite structure, and the metal oxide having a NaCl structure. Alternatively, a structure in which a metal oxide having a fluorite structure and a metal oxide having a perovskite structure are stacked is preferable. A metal oxide having a NaCl structure or a metal oxide having a fluorite structure has a small lattice mismatch with a metal oxide having a perovskite structure. Therefore, when a first electrode 2 having a perovskite structure is formed, This is because it is advantageous for forming a layer having a perovskite structure as a base.

For the above reasons, as the buffer layer of the first electrode 2, for example, in order from the interlayer insulating film 52 side, a first buffer layer and a second buffer made of a metal oxide having a NaCl structure or a metal oxide having a fluorite structure are used. A layer and a third buffer layer made of a metal oxide having a perovskite structure formed on the second buffer layer may be stacked.
The first buffer layer formed on the interlayer insulating film 52 is made of cubic (100) -oriented yttria stabilized zirconia (hereinafter referred to as YSZ) having a thickness of, for example, about 100 nm. However, as YSZ, what is represented by the following formula | equation is used arbitrarily.
_{Zr 1-x Ln x O y} 0 ≦ x ≦ 1.0 (Ln; Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu)

Here, the first buffer layer is formed directly on the interlayer insulating film 52. However, as described above, the interlayer insulating film 52 is formed of an organic insulating material, silicon oxide, or the like. It is difficult to epitaxially grow YSZ on the interlayer insulating film 52 by a general film forming method. Therefore, if the first buffer layer is formed by epitaxial growth using the ion beam assist method, the crystallinity of the second buffer layer formed on the first buffer layer can be further increased. Is possible. The ion beam assist method in the present invention is an inert ion (ion of Ar, He, Ne, Xe, Kr, etc.) or inert to the substrate surface during film formation by laser ablation method, sputtering method or the like. In this film forming method, mixed ions of ions and oxygen ions are irradiated with a beam.
Next, the second buffer layer can be made of cubic (100) oriented CeO _2, and it is preferable to use a layer epitaxially grown to a thickness of, for example, about 100 nm on the first buffer layer.

The first buffer layer and the second buffer layer are not limited to YSZ and CeO ₂ listed above, and any metal oxide having a NaCl structure or metal oxide having a fluorite structure may be used. Can do. Examples of the metal oxide having a NaCl structure include MgO, CaO, SrO, BaO, MnO, FeO, CoO, NiO, or a solid solution containing these, and among these, MgO, CaO, SrO, BaO are particularly preferable. Alternatively, it is preferable to use at least one of solid solutions containing these. Such a metal oxide having a NaCl structure has a particularly small lattice mismatch with a metal oxide having a perovskite structure. When MgO is used instead of YSZ, the thickness of the first buffer layer is set to about 20 nm, for example.

On the other hand, examples of the metal oxide having a fluorite structure include YSZ (yttria-stabilized zirconia), CeO ₂ , ZrO ₂ , ThO ₂ , UO ₂ , and solid solutions containing these, among these, It is preferable to use at least one of YSZ, CeO ₂ , ZrO ₂ , or a solid solution containing these. Such a metal oxide having a fluorite structure also has a particularly small lattice mismatch with a metal oxide having a perovskite structure.

The third buffer layer can be formed of YBa ₂ Cu ₃ O _x (x is, for example, 7), which is a layered perovskite oxide, and is epitaxially grown on the second buffer layer to have a thickness of, for example, about 30 nm (orthorhombic crystal). (001) oriented) can be used. Since the third buffer layer is made of the metal oxide having the perovskite structure as described above, the lattice mismatch between the third buffer layer and the second buffer layer is particularly small as described above. Therefore, it has a good crystal structure free from defects and the like, and the perovskite type first electrode 2 can be favorably epitaxially grown on the third buffer layer.
The third buffer layer is not limited to YBa ₂ Cu ₃ O _x , and other perovskite metal oxides can also be used. For example, CaRuO ₃ , SrRuO ₃ , BaRuO ₃ , SrVO ₃ , (La, Sr) MnO ₃ , (La, Sr) CrO ₃ , (La, Sr) CoO ₃ , or a solid solution containing these can be used. .

(Capacitor manufacturing method)
Next, an embodiment of a method for manufacturing a capacitor according to the present invention will be described with reference to FIG. In this embodiment, the capacitor manufacturing method of the present invention is shown as an example in the case of being applied to the manufacturing of the capacitor 1 (1a, 1b) in the semiconductor device 50 shown in FIG.

<Process for Forming First Conductive Film (First Electrode)>
First, as shown in FIG. 3A, a first conductive film 2 </ b> A that should become the first electrode 2 is formed on the interlayer insulating film 52. In forming the first conductive film 2A, a vapor phase film formation method such as a sputtering method or a vapor deposition method, or a liquid phase film formation method using a droplet discharge method, a spin coating method, a printing method, or the like can be used. . Below, the case where the 1st electrically conductive film 2A is formed by the liquid phase film-forming method is demonstrated.
In the present invention, the droplet discharge method is a method for forming a desired pattern on a substrate by discharging droplets made of a liquid material into a desired pattern, and is a general term for an inkjet method or the like. However, the liquid material (droplet) to be ejected is not a so-called ink used for printed matter, but a liquid material containing various material substances constituting the device. Specifically, the material substance is a conductive substance or an insulating substance. The substance etc. which can function as are mentioned.

  In order to form the first conductive film 2A by the liquid phase film formation method, a liquid material in which metal fine particles are dispersed is applied on the interlayer insulating film 52 and then baked. The metal fine particles used as the material for forming the first conductive film 2A are one or more selected from platinum, iridium, ruthenium, gold, silver, and the like, and a liquid prepared by dispersing these metal fine particles in a dispersion medium. It is supplied on the interlayer insulating film 52 in the form of a body. The particle size of the metal fine particles is preferably 50 nm or more and 0.1 μm or less. By setting the particle size within this range, the metal fine particles are easily dispersed in the dispersion medium, and the diffusibility on the insulating film 52 is improved. In addition, about the metal microparticle, the dispersibility in a dispersion medium can be improved by coating the surface with organic substance etc.

  The solvent to be used is not particularly limited as long as the metal fine particles can be dispersed well without causing aggregation. Specifically, in addition to water, alcohols such as methanol, ethanol, propanol, butanol, n-heptane, n-octane, decane, toluene, xylene, cymene, durene, indene, dipentene, tetrahydronaphthalene, decahydronaphthalene , Hydrocarbon solvents such as cyclohexylbenzene, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycol methyl ethyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol methyl ethyl ether, 1,2-dimethoxyethane, bis (2-methoxy Ethyl) ether, ether solvents such as p-dioxane, propylene carbonate, γ-butyrolactone, N-methyl 2-pyrrolidone, dimethylformamide, dimethyl sulfoxide, can be mentioned polar solvents such as cyclohexanone. Of these, water, alcohols, hydrocarbon solvents, and ether solvents are preferred from the viewpoint of the dispersibility of the metal fine particles and the stability of the dispersion liquid, and more preferred solvents include water and hydrocarbon dispersion media. Can do. These dispersion media can be used alone or as a mixture of two or more.

  When forming the dispersion by dispersing the metal fine particles in a dispersion medium, the concentration of the metal fine particles in the dispersion is preferably 1 wt% or more and 80 wt% or less, particularly in this range. It is desirable to adjust according to the film thickness of the metal film (first electrode 2). If it exceeds 80% by weight, aggregation of metal fine particles tends to occur and it becomes difficult to obtain a uniform coating film. If it is less than 1% by weight, it takes a long time for drying to evaporate the dispersion medium. This is because productivity decreases.

When such a metal fine particle dispersion (liquid) is applied on the interlayer insulating film 52, the metal fine particle dispersion is subjected to heat treatment by heating the substrate 53. Then, the dispersion medium is removed from the metal fine particle dispersion, and further, the metal fine particles are sintered, whereby the first conductive film in which the electrical contact between the fine particles is sufficiently good as shown in FIG. 2A is formed.
The conditions for the heat treatment are not particularly limited, and general conditions can be adopted. For example, the heat treatment atmosphere may be performed in the air, or may be performed in an inert gas atmosphere such as nitrogen, argon, or helium as necessary. The heat treatment temperature is appropriately determined in consideration of the boiling point (vapor pressure) of the dispersion medium, the pressure, and the thermal behavior of the metal fine particles, but is preferably 400 ° C. or less. By setting the temperature to 400 ° C. or lower, for example, when another semiconductor element, Al wiring, a protective layer made of resin, an insulating layer, or the like is formed on the base 53, the thermal influence on these may be sufficiently reduced. Because it can.

As a heating method in the heat treatment, lamp annealing can be performed in addition to the treatment by a normal hot plate, electric furnace or the like. When heat treatment is performed with a hot plate or an electric furnace, the conditions are, for example, a heat treatment temperature of 300 ° C. and a treatment time of 30 minutes. By forming the first electrode 2 under such conditions, the resulting first conductive film 2A has a thickness of about 0.1 μm, for example.
The light source used for lamp annealing is not particularly limited, but excimers such as infrared lamps, xenon lamps, YAG lasers, argon lasers, carbon dioxide lasers, XeF, XeCl, XeBr, KrF, KrCl, ArF, ArCl, etc. A laser or the like can be used as a light source. In general, these light sources have an output in the range of 10 W to 5000 W, but in the present embodiment, a range of 100 W to 1000 W is sufficient.

In the case where a perovskite type metal oxide (SrRuO ₃ , Nb—SrTiO ₃ , La—SrTiO ₃ , (La, Sr) MnO ₃ , (La, Sr) CoO _3, etc.) is formed as the first electrode 2. A laser ablation method can be cited as a suitable film forming method. Prior to the formation of the metal oxide, for example, a buffer layer having a three-layer structure is preferably formed on the interlayer insulating film 52. By forming the metal oxide first conductive film 2A through the buffer layer in this way, a perovskite metal oxide having good crystallinity on the interlayer insulating film 52 made of an amorphous insulating material such as polyimide or silicon oxide. Since the first conductive film 2A (first electrode 2) can be formed, the crystallinity of the metal oxide film formed on the first conductive film 2A in the subsequent process can be improved. This makes it easier to obtain a dielectric film having a high dielectric constant.

<Metal oxide film (dielectric film) formation process>
Once the first conductive film 2A is formed, a metal oxide film 3A to be the dielectric film 3 is formed on the first conductive film 2 next. In forming the metal oxide film 3A, a laser ablation method that is a vapor deposition method, a MOCVD method (chemical vapor deposition method using an organic metal), or a MOD method (metal that is a liquid phase deposition method). Any film forming method such as a coating method using an organic acid salt), a sol-gel method (a coating method using a metal alkoxide), a droplet discharge method, or the like can be used. Below, the formation process of the metal oxide film 3A using the MOD method will be described as an example.

As a precursor material of the bismuth layered compound constituting the dielectric film 3, each constituent metal of this oxide, that is, an organic acid salt containing Sr, Bi, Ti, Ta (or Nb) is used for each metal element. prepare. Apart from these, a compound such as an oxide containing at least one of Si or Ge is prepared.
Specific examples of the organic acid salt include strontium 2-ethylhexanoate (Sr), bismuth ethylhexanoate (Bi), tantalum ethylhexanoate (Ta), niobium ethylhexanoate (Nb), Titanium 2-ethylhexanoate (Ti) or the like can be used, and all are used by dissolving in a solvent such as octane, butoxyethanol, or xylene. In order to add Si, a predetermined amount of tetraethoxysilane (TEOS) may be added to these solutions. In addition, when adding Ge, a predetermined amount of tetraethoxygermanium may be added to these solutions.

These metal compounds are converted into molar ratios of elements constituting the bismuth layered compound (for example, in the case of the bismuth layered compound SrBi ₂ (Ta, Nb) ₂ O ₉ with m = 2), Sr: Bi: (Ta, Nb) = Mix 1: 2: 2). Further, Si or Ge is also mixed so that the total addition amount thereof is contained in the range of 0.1 mol% to 10.0 mol% in the finally obtained dielectric film. Here, when a metal compound containing Sr, Bi, Ti, Ta, or Nb is used as the precursor compound of Si and Ge, the content of these elements is the above-described condition, that is, the composition ratio of the bismuth layered compound. It is necessary to add so as not to impair the conditions. In order to improve the coatability of the precursor compound thus mixed, for example, an appropriate solvent such as alcohols or a dispersion medium may be added to prepare a sol-like liquid.

  Subsequently, the liquid prepared as described above is applied on the first conductive film 2A so as to have a uniform thickness by using a dip coating method, a spin coating method, a printing method, or the like. Thereafter, drying is performed at a predetermined temperature for a predetermined time, and the liquid content in the liquid is removed. Furthermore, after this drying, degreasing is performed at a predetermined high temperature (for example, 450 ° C.) for a predetermined time (for example, 30 minutes) in an air atmosphere, thereby thermally decomposing an organic component coordinated to the metal and oxidizing the metal. Metal oxide. And each process of such application | coating → drying → degreasing is repeated predetermined times, and a metal oxide is made into desired thickness.

  Thereafter, heat treatment is performed at a predetermined temperature, for example, 550 ° C. or less, preferably 450 ° C. to 550 ° C. while oxygen flows in an RTA (Rapid Thermal Annealing) furnace, and the metal oxide is baked, as shown in FIG. A metal oxide film 3A is formed to a thickness of about 0.2 μm on the first conductive film 2A. By performing the heat treatment at 450 ° C. or lower, particularly when other semiconductor elements or wirings are formed on the base 53, the thermal influence on them can be reduced. The heat treatment is not limited to the RTA furnace.

<Step of Forming Second Conductive Film (Second Electrode)>
When the metal oxide film 3A is formed in this way, the second conductive film 4A is subsequently formed on the metal oxide film 3A as shown in FIG. The formation of the second conductive film 4A can be performed by substantially the same formation method as the formation method of the first conductive film 2A. That is, the liquid film containing metal fine particles is applied onto the dielectric film 3, and then heat treatment is performed to sinter the metal fine particles, thereby forming the second conductive film 4A. As the metal fine particles contained in the liquid, that is, the metal fine particles used as the material for forming the second conductive film 4A, as in the case of the first electrode 2, one kind selected from platinum, iridium, ruthenium, gold, silver, etc. Alternatively, a plurality of types or perovskite type metal oxides (SrRuO ₃ or the like) are used. Further, the heat treatment is preferably performed at 400 ° C. or lower. Needless to say, when forming the second conductive film 4A, a vapor phase film forming method such as a sputtering method or a vapor deposition method, or a liquid phase method such as a droplet discharge method or a spin coating method may be used.

<Layered film patterning process>
If the laminated film which consists of the 1st electrically conductive film 2A, the metal oxide film 3A, and the 2nd electrically conductive film 4A is formed on the interlayer insulation film 52 by the above process, the laminated film will be patterned by predetermined plane shape. Thus, the capacitor 1 (1a, 1b) having a structure in which the first electrode 2, the dielectric film 3, and the second electrode 4 are stacked as shown in FIG. 3D can be obtained. As illustrated, the first electrode 2 is in contact with and electrically connected to the embedded wiring 5. Then, after the capacitor 1 is formed in this way, the semiconductor device 50 is obtained by forming the wiring connected to the second electrode 4 of the capacitor 1 and the protective layer and insulating layer covering them.
Incidentally, as a patterning means for the laminated film in this step, an etching method using a known photolithography technique, an ion milling method, or the like can be applied.

In the capacitor 1 thus obtained, the dielectric film 3 has the general formula (Bi ₂ O ₂ ) ²⁺ (A _m−1 B _m O _{3m + 1} ) ²⁻ (where m = 2, 4, A Is a metal element selected from Ba, Ca, Sr and Bi, and B is a metal element selected from Fe, Ga, Ti, Ta, Nb, V, Mo and W). The dielectric constant becomes high, and therefore the capacitor 1 having this can be made higher in capacity than the conventional one, and can be reduced in size when designed to have the same capacity as the conventional one. It has become.

In addition, in such a method for manufacturing the capacitor 1, a liquid phase film forming method in which a sol-like liquid material is applied to form a film can be applied, and the dielectric film 3 is formed by heat-treating the applied film made of the liquid material. Therefore, a large-scale film forming apparatus is not required, and it is advantageous in terms of material use efficiency and energy consumption. Therefore, cost reduction can be achieved. Furthermore, since Si and Ge are added to the liquid, a bismuth layered compound having good crystallinity can be obtained even when the firing temperature is set to a low temperature of 550 ° C. or less. The thermal influence on the semiconductor elements and wirings can be reduced. In particular, if a perovskite-type metal oxide is used for the first electrode 2 on which the dielectric film 3 is formed, the bismuth layered compound can be more satisfactorily c-axis oriented and a dielectric having a higher dielectric constant can be obtained. The body membrane 3 can be obtained. Since the dielectric film 3 having a high dielectric constant can be formed, the capacitor 1 can be increased in capacity or reduced in size.
Further, in the semiconductor device 50 including the capacitor 1, since the capacitor 1 includes the dielectric film 3 having a high dielectric constant, the semiconductor device 50 itself can be reduced in size. Can be realized.

Next, the present invention will be described more specifically with reference to examples. In this example, the capacitor 1 shown in FIG. 1 was manufactured based on the manufacturing method shown in FIGS.
First, a liquid material in which fine particles of Pt are dispersed is ejected by a spin coating method to a predetermined position on an interlayer insulating film 52 made of polyimide provided on a base 53, and further heated at 300 ° C. for 30 minutes by a hot plate. As a result, the first conductive film 2A for forming the first electrode 2 was formed to a thickness of about 0.1 μm.

Next, a liquid material containing a precursor compound of SrBi ₄ Ti ₄ O _{15 was} disposed on the first conductive film 2A by spin coating. As this precursor compound, each metal, ie, metal organic acid salt of each of Sr, Bi, and Ti was used, and tetraethoxysilane (Si (OC ₂ H ₅ ) ₄ ) was prepared for the purpose of adding Si. The precursor compound is mixed so that the molar ratio of the metal is a predetermined ratio to prepare a sol-like liquid, and tetraethoxysilane is added in a predetermined amount (0 to 3 mol%) of Si component. Thus, the liquid was prepared.

Subsequently, the liquid disposed on the first conductive film 2A was dried and degreased. Then, after repeating the steps of applying the liquid, drying, and degreasing a predetermined number of times, heat treatment is performed at a predetermined temperature (for example, 450 ° C.) while flowing oxygen in the RTA furnace, and the metal oxide is fired to form the first conductive material. On the film 2A, a metal oxide film 3A for forming the dielectric film 3 was formed to a thickness of about 0.2 μm.
Next, the second electrode 4 should be formed in the same manner as the first conductive film 2A by discharging a liquid in which fine particles of Pt are dispersed on the metal oxide film 3A by a spin coating method and further performing a heat treatment. The second conductive film 4A was formed to a thickness of about 0.1 μm using Pt.
Then, the capacitor 1 was obtained by patterning to a predetermined planar shape.

  With respect to the capacitor obtained by the above steps, a plurality of types of samples were prepared by varying the amount of addition of Si or Ge (0 to 3 mol%) and the firing temperature (400 to 900 ° C.). The dielectric constant of the dielectric film was measured. The measurement results are shown in Table 1 below. “Baking temperature” shown in Table 1 indicates the minimum baking temperature at which a dielectric constant of 1000 or more can be obtained with the corresponding addition amount of Si or Ge. For example, in Sample 1 (without addition of silicon), the baking temperature is 850. A dielectric film having a dielectric constant of 1000 or more is obtained when the temperature is higher than or equal to 1000 ° C., and in Sample 2 (1 mol% Si added), a dielectric film having a dielectric constant of 1000 or higher when the firing temperature is 650 ° C. or higher Is obtained.

  As shown in Table 1, by adding Si or Ge, the firing temperature at which a high dielectric constant of 1000 or more can be lowered, these additive elements act as a catalyst during firing, and the bismuth layered compound It was confirmed that the crystallinity was improved. Therefore, in the manufacturing method according to the present invention, a dielectric film having a high dielectric constant can be obtained by adding Si even under a low-temperature firing condition of 450 ° C., and by adding Ge, a dielectric film having a high dielectric constant can be obtained under a low-temperature firing condition of 550 ° C. A body membrane can be obtained. And since such low-temperature firing is made possible, the influence on the existing semiconductor elements and wirings on the base material can be reduced, and a semiconductor device equipped with capacitors can be manufactured at a high yield. Become. In addition, it increases the degree of design freedom of a semiconductor device including a capacitor, contributing to higher integration and higher performance of the semiconductor device.

FIG. 1 is a side sectional view showing an embodiment of a capacitor of the present invention. FIG. 2 is a side sectional view showing an embodiment of the semiconductor device of the present invention. FIG. 3 is a side sectional view showing a manufacturing process of the capacitor according to the embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1, 1a, 1b ... Capacitor, 2 ... 1st electrode, 3 ... Dielectric film, 4 ... 2nd electrode, 50 ... Semiconductor device, 51 ... Substrate, 52 ... Interlayer insulation film, 53 ... Base | substrate, 2A ... 1st conductivity Film, 3A ... Metal oxide film, 4A ... Second conductive film

Claims (10)

A capacitor having a structure in which a dielectric film is sandwiched between a first electrode and a second electrode,
The dielectric film has the general formula _{Bi 2 A m-1 B m} O 3m + 3 ( where, m = 2, 4, A is Ba, Ca, Sr, metal element selected from Bi, B is Fe, Ga, Ti, A bismuth layered compound represented by a metal element selected from Ta, Nb, V, Mo, and W) and containing at least one of Si and Ge;
The capacitor, wherein the bismuth layered compound is preferentially c-axis oriented in the film thickness direction of the dielectric film. The bismuth layered compound contains SrBi ₄ Ti ₄ O ₁₅ (m = 4), SrBi ₂ (Ta _x Nb _1-x ) ₂ O ₉ (where 0 ≦ x ≦ 1) (m = 2), Bi ₃ Ti ( The capacitor according to claim 1, wherein Ta _x Nb _1-x ) ₂ O ₉ (where 0 ≦ x ≦ 1) (m = 2) or a mixed phase.   3. The capacitor according to claim 1, wherein the total content of Si and Ge is 0.1 mol% or more and 10.0 mol% or less.   The first electrode and / or the second electrode is an electrode made of one or more metal materials selected from platinum, iridium, ruthenium, gold, and silver, or an oxide of these metal materials. The capacitor according to any one of claims 1 to 3.   4. The capacitor according to claim 1, wherein the first electrode and / or the second electrode is an electrode containing a perovskite metal oxide as a main component. 5.   The capacitor according to claim 5, wherein the main orientation direction of the metal oxide constituting the first electrode is pseudo-cubic and (100) orientation. The capacitor according to claim 5, wherein the first electrode is made of SrRuO ₃ .   The capacitor according to claim 6, wherein a buffer layer is formed below the first electrode, the buffer layer is formed using ion beam assist, and has a (100) orientation. A method of manufacturing a capacitor having a structure in which a dielectric film is sandwiched between a first electrode and a second electrode,
Formula _{Bi 2 A m-1 B m} O 3m + 3 ( where, m = 2,4, A is Ba, Ca, Sr, metal element selected from Bi, B is Fe, Ga, Ti, Ta, Nb, V, A step of disposing on a substrate a liquid material containing a precursor compound of a bismuth layered compound represented by (metal element selected from Mo and W) and at least one of Si and Ge;
Forming a dielectric film containing the bismuth layered compound by heat-treating a liquid containing the precursor compound,
A method of manufacturing a capacitor, wherein in the step of heat-treating the liquid, a heat treatment temperature is set to 550 ° C. or lower.   A semiconductor device comprising the capacitor according to claim 1 or a capacitor obtained by the manufacturing method according to claim 9.

Images