JP2005183852A - Capacitor and its manufacturing method and semiconductor device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a capacitor capable of miniaturizing a device with a dielectric film having a high dielectric constant by forming the dielectric film, a manufacturing method for the capacitor capable of manufacturing the capacitor at a low cost and a semiconductor device with such a capacitor. <P>SOLUTION: The capacitor has a structure in which a dielectric film 3 is held between a first electrode 2 and a second electrode 4. The dielectric film 3 mainly comprises BiFeO<SB>3</SB>while BiFeO<SB>3</SB>has a crystalline texture composed of an amorphous phase and a crystalline phase. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

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

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-sized and high-capacitance capacitor inside the circuit, it is desired to increase the capacity by forming the dielectric film from a material having a high dielectric constant from the viewpoint of leakage current. ing. 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 fabricated 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 low dielectric constant of 10 or less, and therefore 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.

As materials having a high dielectric constant, for example, ferroelectric materials such as lead zirconate titanate (PbTiO ₃ ) and barium titanate (BaTiO ₃ ) are known. When forming a dielectric film made of such a ferroelectric material, the film forming temperature must be 450 ° C. or lower due to the influence on other semiconductor elements and wirings provided in the same semiconductor device. There is. 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 have 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.

  In particular, in a piezoelectric element having a dielectric film such as PZT containing Pb in the composition, since Pb is a harmful substance, it is considered that this may contribute to environmental pollution. The production of piezoelectric elements using this material is urged to be reviewed in the future.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a capacitor that has a dielectric film having a high dielectric constant, thereby enabling downsizing of a device including the dielectric film, and to reduce the cost of the capacitor. It is in providing the manufacturing method of the capacitor which can be manufactured by, and the semiconductor device provided with such a capacitor.

In order to solve the above-described problem, 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 contains BiFeO ₃ as a main component. The BiFeO ₃ is provided with a capacitor comprising an amorphous phase and a crystalline phase of the BiFeO ₃ .
According to this capacitor, the dielectric film is composed of BiFeO ₃ as a main component and the BiFeO ₃ has a crystal structure composed of an amorphous phase and a crystalline phase, which is higher than before. A dielectric constant can be obtained, and a small and high-capacitance capacitor can be obtained. Therefore, it is possible to reduce the size of the apparatus provided with this. Since the dielectric film according to the present invention has the above-described crystal structure, it has a ferroelectricity (that is, a relationship between the polarization amount and the voltage) of BiFeO ₃ that is originally a ferroelectric substance. ), And a high dielectric constant can be obtained. In addition, since the crystal structure can be obtained by low-temperature firing, there is little thermal influence on the existing semiconductor elements and wirings in the device when the capacitor is manufactured. By using the capacitor of the present invention, the device is manufactured. And the degree of freedom in device design is improved.

  In the capacitor of the present invention, it is preferable that the crystal phase is formed discontinuously between the first electrode and the second electrode. With such a configuration, the residual polarization in the dielectric film can be more effectively reduced, and a capacitor having excellent behavior controllability can be obtained.

  In the capacitor of the present invention, it is preferable that the crystal phase is oriented with a polarization axis in a direction intersecting with the film thickness direction of the dielectric film, and the polarization axis is substantially orthogonal to the film thickness direction. It is more preferable. With such a configuration, the dielectric constant of the dielectric film can be further increased, and a small and high-capacitance capacitor can be obtained.

In the capacitor of the present invention, it is preferable that the dielectric film contains Si and / or Ge. With such a configuration, the Si or Ge acts as a catalyst for promoting crystallization of BiFeO _{3 in} the step relating to the formation of the dielectric film, and even when baked at a low temperature, the BiFeO ₃ A crystal phase can be generated, and a capacitor having a high dielectric constant can be easily obtained, and a thermal influence on an existing semiconductor element or wiring can be reduced.

In the capacitor of the present invention, the content of Si and / or Ge is preferably 0.1 mol% or more and 30.0 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. When the total addition amount exceeds 30.0 mol%, the amount of BiFeO _{3 as} a main component is increased. This is because the dielectric constant is decreased by relatively decreasing.

Next, a method for manufacturing a capacitor according to the present invention is 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 the step of forming the first electrode on a substrate. And a step of disposing a precursor compound of BiFeO ₃ on the first electrode, and a step of forming the dielectric compound containing BiFeO ₃ by heat-treating the precursor compound, and heat-treating the liquid material In this step, the heat treatment temperature is 500 ° C. or lower.
According to this manufacturing method, the BiFeO ₃ precursor compound is baked at a low temperature of 450 ° C. or lower, and BiFeO ₃ composed of a mixed phase of an amorphous phase and a crystalline phase is generated in the dielectric film. A dielectric film having a dielectric constant and good behavior controllability by effectively suppressing the ferroelectricity of BiFeO ₃ (reducing residual polarization) is provided between the first and second electrodes. Can be formed. In particular, since the baking is performed at a low temperature of 500 ° C. or less, there is little thermal influence on the semiconductor elements, wirings, and the like that are already provided on the substrate, and the ease of manufacturing and the degree of design freedom can be improved. Furthermore, since the obtained dielectric film does not contain Pb, it is advantageous for environmental pollution.

In the method for manufacturing a capacitor of the present invention, a liquid material containing a BiFeO ₃ precursor compound is disposed on the first electrode, and then the liquid material is heat-treated to form the dielectric film containing BiFeO _3. It is preferable to use a droplet discharge method when arranging the liquid material on the first electrode. By forming the dielectric film by such a liquid phase method, a dielectric film having a uniform crystal structure can be easily formed. In addition, by using the droplet discharge method, it is possible to dispose only a necessary amount of the liquid material at a predetermined position, which is an advantageous manufacturing method in terms of manufacturing cost with extremely high material use efficiency.

In the capacitor manufacturing method of the present invention, a mixture of Bi ₂ O ₃ and Fe ₂ O ₃ is disposed on the first electrode, and then the dielectric film containing BiFeO ₃ is formed by heat-treating the mixture. You can also. The dielectric film of the capacitor according to the present invention can be formed not only by the liquid phase method but also by a solid synthesis method.

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.

In the present embodiment, each of the first electrode 2 and the second electrode 4 is formed of a metal sintered body formed by sintering metal fine particles. Specifically, fine particles made of at least one selected from platinum (Pt), iridium (Ir), ruthenium (Ru), gold (Au), and silver (Ag) are sintered and formed.
The dielectric film 3 is formed using bismuth iron oxide (BiFeO ₃ ) as a main component. The dielectric film 3 has an extremely high dielectric constant compared to, for example, silicon oxide, silicon nitride, or silicon oxynitride. Therefore, the capacitor 1 having the dielectric film 3 has a higher capacity than the conventional one. In addition, when the capacity is designed to be equal to that of the conventional one, the size can be reduced.

In the dielectric film 3, Si and / or Ge may be added as a component other than the BiFeO _{3 serving as} a main component. The Si may be added to the dielectric film 3 as a metal silicate. When Si or Ge is added in this way, the added Si and Ge, as will be described later, fire the precursor material of the dielectric film 3 to form an oxide containing BiFeO ₃ as a main component. Acts as a catalyst. That is, due to this catalytic action, a crystal phase of BiFeO ₃ is formed even at a low firing temperature, and thus a high dielectric constant can be obtained. In addition, since the firing temperature can be lowered, the thermal influence on other semiconductor elements (such as CMOS) and wiring on the base 53 can be reduced.
In the dielectric film 3 according to the present embodiment, “having BiFeO ₃ as a main component” is allowed to contain Si, Ge, or other impurity components to some extent in addition to BiFeO ₃ , and BiFeO _{3. 3} is contained at 50 mol% or more.

The total amount of Si and Ge is preferably in the range of 0.1 mol% to 30 mol%. When the total amount of added Si and Ge is less than 0.1 mol%, the effect of Si and Ge as a catalyst is not exhibited satisfactorily, and when it exceeds 30.0 mol%, BiFeO _{3 as} a main component is not obtained. The dielectric constant is lowered by relatively reducing the amount of. 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, it is 0 mol% or more and 5.0 mol% or less.

Here, as described later, when the precursor material of the dielectric film 3 is baked to form the composite metal oxide (dielectric film 3) containing BiFeO ₃ as a main component, the obtained dielectric film 3 is obtained as follows. It becomes a mixed phase (mixed state) of an amorphous phase and a crystalline phase. In particular, when Si and / or Ge is added as described above, the generation of the crystalline phase is promoted and the mixed phase is easily obtained.
Thus, since the dielectric film 3 is a phase having an amorphous phase, the behavior of the dielectric film 3 is easy to control, and therefore, the design of a circuit incorporating the dielectric film 3 becomes easy, and energy loss is reduced. Yes. More specifically, since it is a mixed phase of an amorphous phase and a crystalline phase, a high dielectric constant can be obtained without exhibiting the ferroelectricity of BiFeO ₃ , and hysteresis appears in the relationship between voltage and polarization amount. Instead, it is a dielectric film that behaves as a paraelectric material whose polarization changes with voltage almost linearly.

The crystal phase of BiFeO ₃ contained in the dielectric film 3 is preferably formed in a discontinuous state instead of a continuous state between the first electrode 2 and the second electrode 4. Since the crystal phase is formed in a discontinuous state between the first electrode 2 and the second electrode 4, the ferroelectricity can be more effectively suppressed, and the relationship between the polarization amount and the voltage Has no hysteresis.
In addition, since such a mixed phase dielectric film can be formed by firing at a relatively low temperature, thermal influence on other semiconductor elements (such as CMOS) and wiring on the substrate 53 is achieved. However, there are few things.

Furthermore, the crystal phase of BiFeO ₃ contained in the dielectric film 3 is preferably oriented with a polarization axis in a direction intersecting with the film thickness direction of the dielectric film 3, and desirably the film thickness It is preferable to have an orientation having a polarization axis substantially orthogonal to the direction. That is, it is preferable that the alignment state has a polarization axis that intersects the direction in which the electric field is applied, and that the alignment has a polarization axis that is substantially orthogonal to the voltage application direction. When the polarization axis and the electric field application direction are orthogonal to each other, the maximum dielectric constant can be obtained in the dielectric film 3.
In the capacitor of the present invention, a plurality of layers of the electrodes and dielectric films can be alternately laminated, and the capacitance of the capacitor can be further increased by adopting such a laminated structure.

(Capacitor manufacturing method)
Next, an embodiment of a method for manufacturing a capacitor according to the present invention will be described based on the method for manufacturing the capacitor 1 having such a configuration. 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.
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 generic term for an ink jet method. 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.

  First, an example of an ejection head used for a droplet ejection method will be described prior to a description of a specific method for manufacturing the capacitor 1. As shown in FIGS. 3A and 3B, the discharge head 34 includes, for example, a stainless steel nozzle plate 12 and a diaphragm 13, and both are joined via a partition member (reservoir plate) 14. . A plurality of cavities 15 and reservoirs 16 are formed between the nozzle plate 12 and the diaphragm 13 by the partition member 14, and the cavities 15 and the reservoirs 16 communicate with each other via a flow path 17. Yes.

  Each cavity 15 and the inside of the reservoir 16 are filled with a liquid material, and a flow path 17 between them functions as a supply port for supplying the liquid material from the reservoir 16 to the cavity 15. . In addition, a plurality of hole-shaped nozzles 18 for injecting a liquid material from the cavity 15 are formed in the nozzle plate 12 in a state of being aligned vertically and horizontally. On the other hand, a hole 19 that opens into the reservoir 16 is formed in the diaphragm 13, and a liquid tank (not shown) is connected to the hole 19 via a tube (not shown).

  Also, a piezoelectric element (piezo element) 20 is joined to the surface of the diaphragm 13 opposite to the surface facing the cavity 15 as shown in FIG. The piezoelectric element 20 is sandwiched between a pair of electrodes 21 and 21 and is configured to bend so as to protrude outward when energized.

The diaphragm 13 to which the piezoelectric element 20 is bonded in such a configuration is bent together with the piezoelectric element 20 at the same time, thereby increasing the volume of the cavity 15. Then, the cavity 15 and the reservoir 16 communicate with each other, and when the reservoir 16 is filled with the liquid material, the liquid material corresponding to the increased volume in the cavity 15 flows from the reservoir 16. It flows in through the path 17.
When the energization to the piezoelectric element 20 is released from such a state, both the piezoelectric element 20 and the diaphragm 13 return to their original shapes. Accordingly, since the cavity 15 also returns to its original volume, the pressure of the liquid material inside the cavity 15 rises, and the liquid droplet 22 is discharged from the nozzle 18.

  The discharge means of the discharge head may be other than the electromechanical transducer using the piezoelectric element (piezo element) 20, for example, a method using an electrothermal transducer as an energy generating element, a charge control type, It is also possible to employ a continuous method such as a pressure vibration type, an electrostatic suction method, or a method in which an electromagnetic wave such as a laser is irradiated to generate heat and a liquid material is discharged by the action of this heat generation.

<First Electrode Formation Process>
First, as shown in FIG. 4A, a liquid material containing metal fine particles is placed on a substrate 53 (on the interlayer insulating film 52) by a droplet discharge method (inkjet method) using the discharge head 34 described above. That is, it is arranged on the embedded wiring 5. The metal fine particles contained in the liquid, that is, the metal fine particles used as the material for forming the first electrode 2 are one or more selected from platinum, iridium, ruthenium, gold, silver, etc., and these metal fine particles are dispersed. It is dispersed in a medium and adjusted to a liquid material. The particle diameter of the metal fine particles is preferably 50 nm or more and 0.1 μm or less. By setting the particle size within such a range, it is easy to disperse in the dispersion medium, and the ejection property from the ejection head 34 is improved. In addition, about the metal fine particle, the dispersibility in a dispersion medium may be improved by coating the surface with organic substance etc.

  As the dispersion medium for dispersing the metal fine particles, those having a vapor pressure at room temperature of 0.001 mmHg to 200 mmHg are preferable. This is because if the vapor pressure exceeds 200 mmHg, the dispersion medium evaporates first when a coating film is formed by discharge, and it becomes difficult to form a good coating film. On the other hand, when the vapor pressure at room temperature is less than 0.001 mmHg, the drying rate is slow, and the dispersion medium tends to remain in the coating film, making it difficult to obtain a high-quality conductive film after the subsequent heat-light treatment. Because. In particular, when the vapor pressure of the dispersion medium is 50 mmHg or less, nozzle clogging due to drying hardly occurs when droplets are ejected from the ejection head 34 and stable ejection is more preferable.

  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, ether solvents are preferred, and more preferred solvents are the dispersibility of the metal fine particles, the stability of the dispersion, and the ease of application to the ink jet method. Can include water and hydrocarbon-based dispersion media. 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.

In the metal fine particle dispersion, a trace amount of a surface tension adjusting material such as a fluorine-based material, a silicon-based material, or a non-ionic material may be added as necessary within a range not impairing the intended function.
Nonionic surface tension modifiers improve the wettability of the dispersion to the object to be applied, improve the leveling of the applied film, and help prevent the occurrence of coating crushing and distortion skin. Become. The metal fine particle dispersion prepared by adding this nonionic surface tension adjusting agent preferably has a viscosity of 1 mPa · s to 50 mPa · s. When the viscosity is less than 1 mPa · s, the peripheral portion of the nozzle of the droplet discharge head 34 is likely to become dirty due to the outflow of the liquid material, and when the viscosity exceeds 50 mPa · s, the clogging frequency in the nozzle holes is increased. It will be expensive.

  Furthermore, it is desirable that the metal fine particle dispersion thus prepared has a surface tension in the range of 20 dyn / cm to 70 dyn / cm. When the surface tension is less than 20 dyn / cm, the wettability of the ink composition with respect to the nozzle surface increases, and thus flight bending easily occurs. When the surface tension exceeds 70 dyn / cm, the shape of the meniscus at the nozzle tip is not stable. This is because it becomes difficult to control the discharge amount and discharge timing of the composition.

When such a metal fine particle dispersion is disposed at a desired position on the interlayer insulating film 52 by the ejection head 34 and applied in a predetermined pattern with the metal fine particle dispersion, the substrate 53 is heated to form the metal fine particle dispersion. Apply heat treatment. Then, the dispersion medium is removed from the metal fine particle dispersion, and further, the metal fine particles are sintered, so that the electrical contact between the fine particles is sufficiently good as shown in FIG. 4B. 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 thickness of the obtained first electrode 2 is, for example, about 0.1 μm.
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.

<Dielectric film formation process>
Next, a dielectric film 3 containing BiFeO ₃ as a main component is formed on the first electrode 2. As a BiFeO ₃ precursor material, each constituent metal of this oxide, that is, a metal salt such as a metal alkoxide or carbonate containing Bi or Fe, is prepared for each metal element. Apart from these, for example, a Si precursor compound is prepared. Then, these metal compounds are mixed so that the composition ratio of Bi and Fe is 1: 1. Further, for Si, the composition ratio of Bi and Fe does not impair the above conditions, so that Si is not less than 0.1 mol% and not more than 30.0 mol% in the finally obtained dielectric film. The Si precursor compound is mixed with the BiFeO ₃ precursor material so that it is contained in the range. As the Bi and Fe precursor compounds, for example, bismuth 2-ethylhexanoate and triisopropoxy iron can be used. In addition to Si precursor compounds, Ge precursor compounds can also be used, and examples of Si and Ge precursor compounds include tetraethoxysilane and tetraethoxygermanium.
In order to give the precursor compound thus mixed with physical properties suitable for ejection by the droplet ejection method, for example, by adding an appropriate solvent or dispersion medium such as alcohols, the sol It is preferable to prepare it in the form of a liquid.

Subsequently, the sol-like liquid material thus prepared is arranged (applied) on the first electrode 2 by the discharge head 34 so as to have a uniform thickness.
Next, 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, 400 ° 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, 450 ° C. or less, preferably 400 ° C. to 450 ° C., more preferably 450 ° C. while oxygen flows in an RTA (Rapid Thermal Annealing) furnace, and the metal oxide is baked to obtain FIG. As shown in (c), a dielectric film 3 is formed on the first electrode 2 to a thickness of about 0.2 μm. In the production method according to the present invention, even when the firing temperature is lowered in this firing step, the crystallization of BiFeO ₃ is promoted by the catalytic action of Si, and a mixed phase containing an amorphous phase and a crystalline phase. It is possible to form the dielectric film 3 mainly composed of BiFeO ₃ .
In addition, since the heat treatment is performed at 450 ° C. or lower, the thermal influence on these can be reduced particularly when other semiconductor elements or wirings are formed on the base 53. The heat treatment is not limited to the RTA furnace.

<Liquid repellent part forming step>
Here, when the dielectric film 3 is formed of the sol-like liquid material as described above, when the liquid material is discharged, the liquid material 3 wets and spreads, so that the desired shape, that is, the entire surface of the first electrode 2 is substantially covered. It becomes difficult to become a simple shape. Therefore, prior to the formation of the dielectric film 3, a self-assembled film using, for example, fluoroalkylsilane is formed on the surface of the base 53 (interlayer insulating film 52) on which the first electrode 2 is formed, and the sol-like film is formed. A liquid repellent portion having a low affinity for the liquid may be formed.

For example, as shown in FIG. 5, the liquid-repellent portion is formed on the surface of the base 53, that is, on the surface of the first electrode 2 and the exposed surface of the interlayer insulating film 52 with respect to the sol-like liquid material. A self-assembled film 1001 made of fluoroalkylsilane or the like is formed so as to have a predetermined contact angle. The contact angle is preferably 20 [deg] or more and 60 [deg] or less.
The organic molecular film for treating the surfaces of the first electrode 2 and the interlayer insulating film 52 has a first functional group capable of binding to them and a surface property of a substrate such as a lyophilic group or a liquid repellent group on the opposite side. Each of the surfaces is provided with a second functional group that controls surface energy, and a linear or partially branched carbon chain that connects the first and second functional groups to each other. To form a molecular film, for example, a monomolecular film.

  The self-assembled film 1001 is composed of a binding functional group capable of reacting with constituent atoms of the first electrode 2 and the interlayer insulating film 52 serving as an underlayer and other linear molecules, and the mutual relationship between the linear molecules. It is a film formed by orienting a compound having extremely high orientation by action. Therefore, the self-assembled film 1001 is formed by aligning single molecules, so that the film thickness becomes extremely thin, and the film becomes uniform at the molecular level. Further, since the same molecule is located on the surface of the film, the film surface is imparted with uniform and excellent liquid repellency and lyophilicity.

As the compound having high orientation, that is, the compound forming the self-assembled film 1001, fluoroalkylsilane (FAS) is used for the reason of providing adhesion to the base 53 side and good liquid repellency. Preferably used. When fluoroalkylsilane is used, each compound is oriented so that the fluoroalkyl group is located on the surface of the film and the self-assembled film 1001 is formed, so that uniform liquid repellency is imparted to the surface of the film.
Examples of such fluoroalkylsilanes include heptadecafluoro-1,1,2,2 tetrahydrodecyltriethoxysilane, heptadecafluoro-1,1,2,2 tetrahydrodecyltrimethoxysilane, heptadecafluoro-1, 1,2,2 tetrahydrodecyltrichlorosilane, tridecafluoro-1,1,2,2 tetrahydrooctyltriethoxysilane, tridecafluoro-1,1,2,2 tetrahydrooctyltrimethoxysilane, tridecafluoro-1, 1,2,2 tetrahydrooctyltrichlorosilane, trifluoropropyltrimethoxysilane and the like are preferably used. In use, one compound (FAS) may be used alone, or two or more compounds (FAS) may be used in combination.

In order to form such a self-assembled film 1001, the raw material compound (FAS) and the base 53 are placed in the same sealed container. Then, in the case of room temperature, the self-assembled film 1001 is formed on the substrate 53 by leaving it for about 2 to 3 days. Further, if the entire sealed container is kept at 100 ° C., the self-assembled film 1001 is formed on the substrate 53 in about 3 hours.
Further, instead of the formation method from the gas phase, the self-assembled film 1001 can be formed from the liquid phase. For example, the self-assembled film 1001 can be formed on the substrate by immersing the substrate in a solution containing the raw material compound, washing, and drying.
Note that before the self-assembled film 1001 is formed, it is desirable to perform pretreatment by irradiating the substrate surface with ultraviolet light or washing with a solvent.

In this way, the surface of the first electrode 2 and the surface of the interlayer insulating film 52 are made liquid repellent, and in particular, the sol-like liquid disposed on the surface of the first electrode 2 is made difficult to wet and spread. It is possible to prevent the dielectric film 3 obtained from spreading out to the surface of the insulating film 52 and greatly different from the desired shape.
In order to make the dielectric film 3 have a desired shape, that is, a shape that covers almost the entire surface of the first electrode 2, at least the surface of the interlayer insulating film 52 (base 53) around the first electrode 2 is liquid repellent. A part may be formed. The surface of the first electrode 2 may not necessarily be a liquid repellent part, but may be a lyophilic part (a part having a high affinity for the sol-like liquid material), for example.

  In order to make the surface of the first electrode 2 a lyophilic part, for example, the self-assembled film is passed through a mask (not shown) in which an opening pattern corresponding to a desired pattern, that is, the surface shape of the first electrode 2 is formed. 1001 is irradiated with ultraviolet light or the like. Then, in the region irradiated with ultraviolet light, the self-assembled film 1001 is removed, and, for example, a hydroxyl group is exposed on the surface. Thereby, it becomes a lyophilic part which shows the property which becomes very wet easily compared with the area | region of FAS.

  Further, the second self-assembled film may be formed in the region where the FAS is removed as described above. The compound that forms this second self-assembled film also has a binding functional group and a functional group that modifies the surface in the same manner as FAS, and the binding functional group binds to a hydroxyl group or the like on the substrate surface. It is supposed to form a self-assembled film. However, the functional group for modifying the surface of the second self-assembled film is different from FAS in that it exhibits lyophilicity or has a strong binding force with metal fine particles. Or thiol group. By forming such a second self-assembled film, it is possible to more reliably distribute the sol-like liquid material on the first electrode 2 and form the dielectric film 3 having a desired shape. Become. In addition, the adhesion of the obtained dielectric film 3 to the first electrode 2 is also increased. Examples of the compound forming the second self-assembled film include 3-mercaptopropyltriethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, and 3-aminopropyltrimethoxysilane. Can be mentioned.

<Step of forming second electrode>
When the dielectric film 3 is formed in this way, the second electrode 4 is subsequently formed on the dielectric film 3 as shown in FIG. The formation of the second electrode 4 can be performed by substantially the same formation method as the formation method of the first electrode 2 described above. That is, a liquid material containing metal fine particles is disposed on the dielectric film 3 by a droplet discharge method (inkjet method) using the discharge head 34, and then heat treatment is performed to sinter the metal fine particles. The second electrode 4 is formed. As a result, the capacitor 1 (1a, 1b) is obtained.
As the metal fine particles contained in the liquid, that is, the metal fine particles used as the material for forming the second electrode 4, as in the case of the first electrode 2, one kind selected from platinum, iridium, ruthenium, gold, silver, etc. Multiple species are used. Further, the heat treatment is preferably performed at 400 ° C. or lower.

Prior to the formation of the second electrode 4, a liquid repellent part forming step performed as a pretreatment for forming the dielectric film 3 may be performed. That is, the above-described liquid repellent portion made of fluoroalkylsilane (FAS) or the like is formed on the surface of the dielectric film 3 and the surface of the interlayer insulating film 52 to prevent the liquid from spreading and preventing the second electrode 4 from becoming dielectric. It may be selectively formed on the body film 3. Also, when forming the first electrode 2 described above, a liquid repellent portion may be formed on the surface of the base 53 (interlayer insulating film 52) prior to the formation. Further, when the liquid repellent part is formed as a pretreatment for the formation of the electrodes 2 and 4 as described above, the part where the liquid material is directly arranged is made a lyophilic part by ultraviolet light irradiation or the like as described above. Also good.
Moreover, about the 1st electrode 2 and the 2nd electrode 4, you may make it employ | adopt a vapor deposition method, a sputtering method, etc., without employ | adopting the droplet discharge method as the formation method.
When the second electrode 4 is formed in this way, the semiconductor device 50 is obtained by forming the wiring connected to the second electrode 4, the protective layer covering them, and the insulating layer.

In the capacitor 1 thus obtained, the dielectric film 3 has a crystal structure composed mainly of BiFeO ₃ and a mixed phase of an amorphous phase and a crystalline phase. Therefore, the capacitor 1 having the high dielectric constant can be increased in capacity compared to the conventional one, and the capacitance is designed to be equal to that of the conventional one. The size can be reduced, and since it has no polarization amount hysteresis, it has excellent behavior controllability.

  Further, in such a manufacturing method of the capacitor 1, since the dielectric film 3 is formed by arranging a sol-like liquid material by a droplet discharge method and heat-treating it, a large-scale film formation is performed. No device is required, and the cost can be reduced because it is advantageous in terms of material use efficiency and energy consumption. Furthermore, by disposing the liquid material at a desired position, patterning by etching becomes unnecessary, so that it is possible to improve the characteristics without damaging the dielectric film due to etching. In addition, since the dielectric film 3 having a high dielectric constant can be formed as described above, the capacity of the capacitor 1 can be increased or the size can be reduced.

  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. In particular, since the dielectric film 3 is formed using a droplet discharge method, the manufacturing cost can be reduced. Furthermore, since the dielectric film 3 of the capacitor 1 does not contain Pb, it is advantageous against environmental pollution. Therefore, the semiconductor device provided with this is also environmentally advantageous.

In the manufacturing method according to the above embodiment, a metal alkoxide or metal salt is used as the BiFeO ₃ precursor compound, and a liquid material in which the metal alkoxide or metal salt is dissolved is disposed on the first electrode 2 and baked to form the dielectric film 3. The method of forming the dielectric film 3 has been described by way of example. However, the method of forming the dielectric film 3 is not limited to such a liquid phase method. For example, a powder containing Bi and Fe is used as a precursor compound. A solid synthesis method in which sinter is formed can also be applied. In this case, a powder in which Bi ₂ O ₃ powder and Fe ₂ O ₃ powder are mixed at a ratio of 1: 1 is placed on the first electrode 2 and fired at about 450 ° C., whereby an amorphous phase and a crystalline phase are obtained. The dielectric film 3 containing BiFeO ₃ made of a mixed phase with the above can be formed. You may use the powder which pre-baked the said mixed powder.

The technical ideas derived from the above embodiments are listed below.
In the method for manufacturing a capacitor according to the present invention, before the step of disposing the liquid material containing the precursor compound on the first electrode by a droplet discharge method, the surface of the substrate and the first electrode is provided. A step of forming a self-assembled film can be included.
According to this manufacturing method, it is possible to control the arrangement state of the liquid material by utilizing the surface modification action by the self-assembled film, and for example, it is possible to selectively arrange the liquid material in a predetermined region. Become.

  Furthermore, the method for manufacturing a capacitor of the present invention preferably includes a step of irradiating light on the self-assembled film formed on the first electrode. According to this manufacturing method, the affinity between the self-assembled film and the liquid material can be controlled by the light irradiation. If the liquid material is disposed in the light-irradiated region, the liquid material spreads in the outer region. Can be prevented. Therefore, according to the present method, the dropping position of the liquid can be easily controlled.

  Further, in the capacitor manufacturing method of the present invention, it is preferable that the self-assembled film is formed using fluoroalkylsilane. When a self-assembled film made of fluoroalkylsilane is used, the formation area of the self-assembled film becomes a liquid repellent part with respect to the liquid, and the light-irradiated area becomes a lyophilic part. Thus, the selective arrangement of the liquid material on the first electrode can be performed accurately and easily.

Furthermore, in the method for manufacturing a capacitor of the present invention, the step of forming the first electrode includes a step of disposing a first liquid material in which first metal fine particles are dispersed in a first dispersion medium on the substrate by a droplet discharge method. And a step of removing the first dispersion medium by heat-treating the first liquid and a step of sintering the first metal fine particles.
In this manufacturing method, the liquid material is also selectively disposed by the droplet discharge method for the first electrode and is formed by heat treatment, so that a large-scale film forming apparatus is not required and the use efficiency of the material is reduced. Since this is advantageous also in terms of energy consumption, a reduction in manufacturing cost can be realized.

Furthermore, in the method for manufacturing a capacitor according to the present invention, the step of forming the second electrode includes a step of disposing a second liquid material in which the second metal fine particles are dispersed in the second dispersion medium on the substrate by a droplet discharge method. And a step of removing the second dispersion medium by heat-treating the second liquid and a step of sintering the second metal fine particles.
In this manufacturing method, the liquid material is also selectively disposed by the droplet discharge method for the second electrode, and this is heat-treated, so that a large-scale film forming apparatus is not required, and the use efficiency and energy consumption of the material are not required. However, since it becomes advantageous, the manufacturing cost can be reduced.

Furthermore, in the method for producing a capacitor according to the present invention, the first metal particles are fine particles made of at least one of platinum, iridium, ruthenium, gold, or silver, and a heat treatment temperature when the first metal fine particles are sintered. Is preferably 400 ° C. or lower.
Furthermore, in the method for producing a capacitor according to the present invention, the second metal fine particles are fine particles composed of at least one of platinum, iridium, ruthenium, gold, or silver, and heat treatment for sintering the second metal fine particles. The temperature is preferably 400 ° C. or lower.
According to these manufacturing methods, it is possible to form an electrode made of a stable metal film with low resistance and resistance to oxidation. Further, since the heat treatment temperature is set to 400 ° C. or lower, for example, when other semiconductor elements or wirings are formed on the base, it is possible to reduce the thermal influence on them.

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 discharged to a predetermined position on an interlayer insulating film 52 made of polyimide provided on a substrate 53 by a droplet discharge method, and further heated at 300 ° C. for 30 minutes by a hot plate. By performing the treatment, 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 BiFeO ₃ precursor compound was disposed on the first conductive film 2A by a droplet discharge method. As this precursor compound, bismuth 2-ethylhexanoate and tetraisopropoxy iron are used for each metal, that is, Bi and Fe, respectively, and tetraethoxysilane (Si (OC ₂ H ₅ ) for the purpose of adding Si. ₄ ) was prepared. 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 (1 to 5 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, a liquid material in which fine particles of Pt are dispersed on the metal oxide film 3A is disposed on the dielectric film by a droplet discharge method, and is further heat-treated, whereby the second conductive film 2A is formed in the same manner as the first conductive film 2A. A second conductive film 4A for forming the electrode 4 was formed to a thickness of about 0.1 μm using Pt.
The capacitor 1 was obtained through the above steps.

  With respect to the capacitor obtained by the above steps, a plurality of types of samples were prepared by varying the addition amount of Si or Ge (1 to 5 mol%) and the firing temperature (300 to 600 ° 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 400 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 600. A dielectric film having a dielectric constant of 400 or more can be obtained when the temperature is set to ℃ or higher, and in Sample 2 (1 mol% Si added), a dielectric film having a dielectric constant of 400 or more when the firing temperature is set to 500 ° C or higher. Is obtained.

As shown in Table 1, the addition of Si or Ge can lower the firing temperature at which a high dielectric constant of 400 or more can be obtained. These additive elements act as a catalyst during firing, and BiFeO ₃ crystals. It was confirmed to improve the performance. Therefore, in the manufacturing method according to the present invention, a dielectric film having a high dielectric constant can be obtained even by low-temperature firing conditions of 500 ° C. or less by adding Si, and by adding Ge, a high dielectric constant can be obtained by low-temperature firing conditions of 500 ° C. A dielectric film 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 of a capacitor according to an embodiment. FIG. 2 is a side sectional view of the semiconductor device. FIG. 3 is a perspective view (a) of a main part of the ejection head and a side sectional view (b) of the main part. FIG. 4 is a sectional process diagram of the capacitor according to the embodiment. FIG. 5 is a side sectional view showing an example where a liquid repellent portion is formed.

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

Claims (11)

A capacitor having a structure in which a dielectric film is sandwiched between a first electrode and a second electrode,
The dielectric film includes BiFeO ₃ as a main component,
The BiFeO ₃ is composed of an amorphous phase and a crystalline phase of the BiFeO ₃ .   The capacitor according to claim 1, wherein the crystal phase is formed discontinuously between the first electrode and the second electrode.   3. The capacitor according to claim 1, wherein the crystal phase is oriented with a polarization axis in a direction intersecting with a film thickness direction of the dielectric film.   The capacitor according to claim 1, wherein the dielectric film contains Si and / or Ge.   5. The capacitor according to claim 4, wherein the content of Si and / or Ge is not less than 0.1 mol% and not more than 30.0 mol%. A method of manufacturing a capacitor having a structure in which a dielectric film is sandwiched between a first electrode and a second electrode,
Forming a first electrode on a substrate;
Disposing a precursor compound of BiFeO ₃ on the first electrode;
Forming the dielectric compound containing BiFeO ₃ by heat-treating the precursor compound,
A method for manufacturing a capacitor, wherein a heat treatment temperature in the step of heat-treating the liquid is 500 ° C. or less. The liquid material containing a BiFeO ₃ precursor compound is disposed on the first electrode, and then the liquid material is heat-treated to form the dielectric film containing BiFeO _3. Manufacturing method of capacitor.   The method for manufacturing a capacitor according to claim 7, wherein a droplet discharge method is used when the liquid material is disposed on the first electrode. 7. The dielectric film containing BiFeO ₃ is formed by arranging a mixture of Bi ₂ O ₃ and Fe ₂ O ₃ on the first electrode and then heat-treating the mixture. The manufacturing method of the capacitor of description.   10. The precursor compound according to claim 6, wherein a precursor compound of Si and / or Ge is mixed in the precursor compound, a liquid containing the precursor compound, or the mixture. Manufacturing method of capacitor.   A semiconductor device comprising the capacitor according to any one of claims 1 to 5, or the capacitor obtained by the manufacturing method according to any one of claims 6 to 10.

Images