JP7000882B2 - Oxynitride thin film and capacitive element - Google Patents

Description

The present invention relates to a dielectric thin film having a main composition composed of an oxynitride and a capacitive element containing the same.

In recent years, with the miniaturization and higher performance of digital devices, there is a demand for capacitive elements using high-performance dielectric thin films.

Conventionally, a thin film using a metal oxide material has been widely used as a dielectric thin film. However, the improvement of the characteristics of the dielectric thin film by the metal oxide material is reaching the limit, and a new material having higher characteristics is required.
Examples of the material of the dielectric thin film include oxynitride. The oxynitride can be represented by ABO ₂ N. For example, in the oxynitride represented by the composition formula SrTaO ₂ N, the oxide as a precursor thereof is Sr ₂ Ta ₂ O ₇ . SrTaO ₂ N can be synthesized directly from compounds containing Sr, Ta, O and N, but can also be obtained by nitriding Sr ₂ Ta ₂ O ₇ . The relative permittivity of Sr ₂ Ta ₂ O ₇ varies depending on the synthesis method, but is about 100 (Non-Patent Document 1). On the other hand, the relative permittivity of _SrTaO 2N has been reported to have a value of several thousand or more (Non-Patent Document 2 and Patent Document 1). That is, the relative permittivity increases dramatically by incorporating nitrogen into the crystal lattice of the oxynitride.
Among such oxynitrides, one of the candidates for a new material is a metal oxynitride material in which some of the oxygen atoms in the oxygen octahedron of the perovskite crystal structure are replaced with nitrogen atoms. However, it is difficult to obtain a dielectric thin film having a metal oxynitride material.

For example, Patent Document 2 and Patent Document 3 describe a method for producing a powder of perovskite _- type oxynitride ABO 2N. However, Patent Document 2 and Patent Document 3 do not disclose anything about obtaining a thin film using the perovskite _- type oxynitride ABO 2N.

Further, Non-Patent Document 3 and Non-Patent Document 4 describe that a thin film made of perovskite _- type oxynitride ABO 2N was produced. However, the thin films obtained in Non-Patent Document 3 and Non-Patent Document 4 are epitaxial films.

The epitaxial film has the drawback that it takes a very long time to manufacture. Non-Patent Document 1 describes that it takes a long time of 530 hours or less to produce an epitaxial film having a thickness of 20 nm or less.

Japanese Unexamined Patent Publication No. 2004-296603 Japanese Unexamined Patent Publication No. 61-122108 Japanese Unexamined Patent Publication No. 2013-001625

Journal of Materials Science: Materials in Electronics, 11 (2000), p.575-578 Chem. Master., Vol.16, No.7, 2004, p.1267-1276 Scientific Reports 4. DOI: 10.1038 / srep04987 KAST 2013 Research Overview Page 32-33

The present invention has been made in view of such an actual situation, and an object of the present invention is to provide a dielectric thin film having a main composition made of an oxynitride having high production efficiency and excellent dielectric properties, and a capacitive element containing the same.

The dielectric thin film according to the present invention is
A dielectric thin film having a main composition composed of an oxynitride represented by the composition formula A _a B _b O _o N _n (a + b + o + n = 5).
The A is any one or more of Sr, Ba, Ca, La, Ce, Pr, Nd, and Na.
B is any one or more of Ta, Nb, Ti, and W, and is
The crystal particles constituting the dielectric thin film are polycrystals that are not oriented in a specific crystal plane orientation, and are characterized by being composed of columnar particles.

The dielectric thin film according to the present invention has the above-mentioned characteristics, so that the dielectric characteristics can be enhanced.

Preferably, the columnar particles extend in a direction intersecting the substrate on which the dielectric thin film is formed.

Preferably, the composition ratio of the columnar particles penetrating from the front surface to the back surface of the dielectric thin film is 30% or more.

Preferably, when the nitrogen composition ratio is measured at a depth position of 1/4, a depth position of 1/2, and a depth position of 3/4 in the thickness direction from the surface of the dielectric thin film, the nitrogen composition ratio is measured. The maximum fluctuation rate of nitrogen composition at these three positions is within ± 55 %.

Preferably, A is Sr, B is Ta and / or Nb, and n is greater than zero and less than 1.

The capacitive element according to the present invention has the dielectric thin film.

It is a schematic diagram of the thin film capacitor which concerns on one Embodiment of this invention. It is a schematic diagram which showed the shape of the columnar particle in the dielectric thin film which concerns on one Embodiment of this invention by the broken line. It is a TEM image of the dielectric thin film sample of Example 1. The dashed line indicates the shape of the particle. It is a TEM image of the dielectric thin film sample of Example 2. The dashed line indicates the shape of the particle.

Hereinafter, the present invention will be described based on the embodiments.

FIG. 1 shows a schematic diagram of a thin film capacitor (capacitive element) according to this embodiment. The thin film capacitor 1 shown in FIG. 1 is formed on a substrate 11 in the order of a lower electrode 12 and a dielectric thin film 13, and includes an upper electrode 14 on the dielectric thin film 13.

The material of the substrate 11 is not particularly limited, but using a Si single crystal substrate as the substrate 11 is excellent in availability and cost. Ni foil can also be used as a substrate when flexibility is important.

The materials of the lower electrode 12 and the upper electrode 14 are not particularly limited, and may function as electrodes. For example, Pt, Ag, Ni and the like can be mentioned. The thickness of the lower electrode 12 is preferably 0.01 to 10 μm. The thickness of the upper electrode 14 is preferably 0.01 to 10 μm.

The dielectric thin film 13 has a main composition composed of an oxynitride represented by the composition formula A _a B _b O on _N (a + b + _o + n = 5).

A is one or more elements selected from Sr, Ba, Ca, La, Ce, Pr, Nd, and Na. Preferably, A is one or more elements selected from Sr, Ba, La and Nd. More preferably, A is Sr. By using the above element as A, a high capacity can be obtained. B is one or more elements selected from Ta, Nb, Ti, and W. Preferably, B is one or more elements selected from Ta and Nb. More preferably, B is Ta. By using the above element as B, a dielectric thin film 13 having few different phases can be obtained.

Further, in the composition formula A _a B _{b O} N _n , a <1 is preferable. Further, a / b> 1 is preferable, and a / b ≧ 1.05 is more preferable. Further, 1>n> 0 is preferable, 1> n ≧ 0.3 is more preferable, and 1> n ≧ 0.5 is more preferable. By setting a, b and n in the above range, good dielectric properties can be obtained.

The crystal particles constituting the dielectric thin film 13 are polycrystals that are not oriented in a specific crystal plane orientation. Then, as shown in FIG. 2, the crystal particles constituting the dielectric thin film 13 are composed of columnar particles X, and the columnar particles X are preferably with respect to the substrate 11 on which the dielectric thin film 13 is formed. Extends in the direction of intersection. Further, as shown in FIG. 2, it is preferable that the columnar particles X penetrate from the front surface of the dielectric thin film 13 on the upper electrode 14 side to the back surface of the substrate 11 side. In the present embodiment, the crystal particles constituting the dielectric thin film 13 are polycrystals that are not oriented in a specific crystal plane orientation, and the dielectric characteristics are improved by being composed of columnar particles X.

The crystal particles constituting the dielectric thin film 13 are polycrystals that are not oriented in a specific crystal plane orientation and are composed of columnar particles X, so that nitrogen is efficiently incorporated into the crystal particles to form a dielectric. It is considered that the dielectric properties of the thin film are improved.
Normally, the alignment film is formed at a relatively slow film formation rate in order to obtain its orientation, but at such a slow film formation rate, a grain boundary in the film thickness direction, which is a diffusion path for nitrogen, is sufficiently obtained. do not have. In the present embodiment, it is considered that since the crystal particles constituting the dielectric thin film 13 have a columnar particle shape, a nitrogen diffusion path is formed in the film thickness direction, and nitrogen can be efficiently taken into the crystal. Be done. As a result, the dielectric thin film of the present embodiment has an improved relative permittivity and high dielectric properties can be obtained.

Further, the composition ratio of the columnar particles X penetrating the dielectric thin film 13 to the total crystal particles constituting the dielectric thin film 13 is preferably 30% or more. The composition ratio is the ratio of the number of penetrating columnar particles X to the total number of crystal particles observed based on the transmission electron microscope (TEM) image of the dielectric thin film 13. The dielectric property is improved by setting the composition ratio of the penetrating columnar particles X within the above range.

Further, the nitrogen composition of the dielectric thin film 13 has a depth position of 1/4 (surface layer side), a depth position of 1/2 (center of the film), and a depth position of 3/4 in the thickness direction from the surface thereof. It is preferable that there is little variation with (the substrate side). More preferably, the maximum volatility of the nitrogen composition at each of the above depth positions is preferably within ± 55%, more preferably within ± 25%, still more preferably within ± 20%, and particularly preferably within ± 20%. Is within ± 16%. By setting the maximum volatility of the nitrogen composition within the above range, the dielectric properties are improved. The nitrogen composition of the dielectric thin film 13 can be confirmed by X-ray photoelectron spectroscopy.

The maximum volatility X is calculated as follows. First, the nitrogen compositions at five or more points that differ at each of the above depth positions are measured. Next, the nitrogen average composition at each depth position is obtained based on the nitrogen compositions of the above five or more different points. That is, at the above five or more different points, the nitrogen average composition X ₁ at the depth position of 1/4, the nitrogen average composition X ₂ at the depth position of 1/2, and the nitrogen average at the depth position of 3/4. The composition X ₃ is calculated. Here, the average value (X ₁ + X ₂ + X ₃ ) / 3 of the nitrogen composition at each depth position is defined as the average value X _a of the nitrogen composition of the thin film. Then, the volatility X _n '= (X _n −X _a ) / X _a at each depth position is obtained (n = 1, 2, 3). That is, the volatility X 1'at the 1/4 depth position and the volatility X 2'at the _1/2 depth position and the volatility X _3'at the _3/4 depth position are calculated. Of X ₁ ', X ₂ ', and X ₃ ', the volatility having the largest difference from the average value X _a is defined as the maximum volatility X.

For the quantification of nitrogen, a nitride single crystal wafer such as AlN is desirable, but a sensitivity factor can be calculated from the oxynitride powder composed of the same composition to correct the quantification value. When compensating with the oxynitride powder, it is advisable to quantify the oxynitride powder in advance by using an impulse heating melt extraction method or the like. In addition, the standard in the device can be used as a substitute.

The thickness of the dielectric thin film 13 is not particularly limited, but is preferably 10 nm to 2 μm, and more preferably 10 nm to 1 μm.

The dielectric loss tangent (tan δ) of the dielectric thin film is preferably 60% or less, more preferably 40% or less, still more preferably 15% or less, and particularly preferably 10% or less. By setting the dielectric loss tangent (tan δ) in the above range, a dielectric thin film having excellent dielectric properties can be obtained.
The dielectric loss tangent (tan δ) of the dielectric thin film can be measured using an LCR meter under the conditions of a voltage of 1 V / rms and a frequency of 1 kHz.

The relative permittivity of the dielectric thin film is preferably 355 or more, more preferably 450 or more, still more preferably 700 or more, and particularly preferably 1110 or more. By setting the relative permittivity within the above range, a dielectric thin film having excellent dielectric properties can be obtained.
The relative permittivity can be calculated based on the capacitance, the thickness of the dielectric thin film, and the electrode area by measuring the capacitance at a voltage of 1 V / rms and a frequency of 1 kHz using an LCR meter.

Method for Manufacturing Thin Film Capacitor 1 Next, a method for manufacturing the thin film capacitor 1 will be described. Hereinafter, in the dielectric thin film 13 having a main composition composed of an oxynitride represented by the composition formula A _a B _{b O} N _n , a case where the A atom is Sr and the B atom is Ta will be described. The same applies when other types of atoms are used.

There is no particular limitation on the method for forming a thin film that finally becomes the dielectric thin film 13. For example, vacuum vapor deposition method, sputtering method, PLD method (pulse laser vapor deposition method), MO-CVD (organic metal chemical vapor deposition method), MOD (organic metal decomposition method), sol gel method, CSD (chemical solution deposition method). ) Etc. are exemplified. Further, the raw material used at the time of film formation may contain minute impurities and auxiliary components, but there is no particular problem as long as the amount does not significantly impair the performance of the thin film. Further, the dielectric thin film 13 according to the present embodiment may also contain minute impurities and subcomponents so as not to significantly impair the performance.

Of the above film forming methods, when a film is formed by a method such as a PLD method, a sputtering method, or a CSD method, the finally obtained thin film tends to be a polycrystalline film. Although synthesis is possible by the CVD method, the PLD method and the sputtering method have higher composition controllability due to the large number of component elements. In this embodiment, a film forming method by the PLD method will be described.

First, a Si single crystal substrate is prepared as the substrate 11. Next, a film is formed on a Si single crystal substrate in the order of SiO ₂ , TiO _x , and Pt to form a lower electrode 12 made of Pt. There is no particular limitation on the method of forming the lower electrode 12. For example, a sputtering method or a CVD method can be mentioned.

Next, a metal oxide thin film is formed on the lower electrode 12 by the PLD method. A metal mask may be used to expose a portion of the lower electrode 12 to form a region where the thin film is not partially formed.

In the PLD method, first, a target containing a constituent element of a target dielectric thin film is installed in a film forming chamber. Next, a pulsed laser is irradiated on the surface of the target. The strong energy of the pulsed laser instantly evaporates the surface of the target. Then, the evaporation material is deposited on the substrate arranged so as to face the target to form a metal oxide thin film.

As the target, for example, a precursor having the composition formula A ₂ B ₂ O ₇ can be used. This precursor is preferably a perovskite layered compound, called a perovskite slab, in which perovskite units and O excess layers are alternately stacked.

The type of target is not particularly limited, and pellets formed by compressing oxynitride powder can also be used. However, since it is necessary to sufficiently control the amount of _N contained, it is better to use _pellets of _A2B2O7 for better controllability. Further, it is preferable that each element is evenly distributed in the target, but the distribution may vary within a range that does not affect the quality of the obtained dielectric thin film. Further, the number of targets does not necessarily have to be one, and it is possible to prepare a plurality of targets containing a part of the constituent elements of the dielectric thin film and use them for film formation. There is no limitation on the shape of the target, and the shape may be suitable for the film forming apparatus to be used. Further, by adjusting the film forming conditions (oxygen gas pressure, nitrogen gas pressure, film forming chamber size, position of gas introduction tube, etc.), a and b of the finally obtained dielectric thin film are controlled. can. For example, if the a / b of the target is increased, the a / b in the film formed can be increased.

For example, when the composition of the finally obtained dielectric thin film is Sr _a Tab O _{o N n ,} a sintered body containing Sr ₂ Ta ₂ O ₇ is prepared as a target. Then, by adjusting the film forming conditions (for example, oxygen gas pressure, nitrogen gas pressure, film forming chamber size, position of gas introduction tube, etc.), the finally obtained dielectric thin films a and b can be obtained. Can be controlled.

Film formation conditions are also important. This is because the metal element evaporated from the target by the pulse laser is affected by the elements constituting the atmosphere in the film forming chamber and reaches the film forming surface of the substrate. The PLD method is characterized by the ability to take a wide range of atmospheric pressure from ultra-high vacuum to near atmospheric pressure, but the higher the vacuum, the easier it is to obtain a highly crystalline film, while the higher the atmospheric pressure, such as oxygen, the better. It is easy to obtain a film with few defects such as oxygen. When plasma is used in combination, the pressure range width that plasma can maintain is determined, so an appropriate pressure may be determined within that range in consideration of crystallinity, defects, and the like. When oxygen and nitrogen are introduced to form an oxynitride, the pressure is preferably low because oxygen inhibits the uptake of nitrogen into the film. It is possible to form a perovskite structure by introducing nitrogen activated by plasma without introducing oxygen. In the spattering method, it is desirable to use argon together as the atmosphere in the film forming chamber.

Further, in the PLD method, it is preferable to heat the substrate 11 with an infrared laser at the time of film formation in order to crystallize the metal oxide thin film to be filmed. The heating temperature of the substrate 11 at the time of film formation varies depending on the metal oxide thin film, the constituent elements and the composition of the substrate 11, but is preferably 550 to 850 ° C, more preferably 600 to 800 ° C, still more preferable. Is 650 to 750 ° C. By setting the heating temperature of the substrate at the time of film formation within the above range, columnar particles are likely to be formed. In addition, voids are less likely to be formed and the dielectric properties are improved. Further, by setting the temperature of the substrate 11 to an appropriate temperature, the metallic oxynitride thin film can be easily crystallized and cracks generated during cooling can be prevented.

By introducing nitrogen radicals into the film and performing nitriding treatment, a dielectric thin film 13 made of perovskite-type oxynitride can be obtained. After forming a metal oxide film, nitrogen radicals may be introduced to perform nitriding treatment, but introducing nitrogen radicals during film formation should increase the amount of nitrogen in the formed thin film. Can be done.

The dielectric thin film 13 on the substrate may be subjected to a high-speed thermal annealing treatment (RTA) after the film formation. By performing the annealing at a temperature 100 ° C. higher than the film formation temperature, more preferably at a film formation temperature or lower, the columnar structure formed at the time of film formation can be maintained. When annealing is performed below the film formation temperature, no significant change is confirmed in the XRD pattern of the obtained film before and after annealing, so the columnar crystal structure is determined at the time of film formation, and defect compensation and stress are performed in annealing. It is presumed that relaxation has occurred.

Finally, the thin film capacitor 1 can be manufactured by forming the upper electrode 14 on the dielectric thin film 13. The material of the upper electrode 14 is not particularly limited, and Ag, Au, Cu, or the like can be used. Further, the method of forming the upper electrode 14 is not particularly limited. For example, it can be formed by a sputtering method or vapor deposition.

An intermediate layer 15 may be provided between the dielectric thin film 13 and the lower electrode 12, and between the dielectric thin film 13 and the upper electrode 14. The intermediate layer 15 may be made of an insulating material or a conductive material. As the insulating material, a compound such as an oxide or a nitride containing at least one of aluminum, silicon, strontium, and tantalum can be used. As the conductive material, Cu, Al, Ni, Au, Ni—Cr and the like can be used. As a method for forming the intermediate layer 15, a method similar to the above-mentioned method for forming the dielectric thin film 13 or the method for forming the lower electrode 12 and the upper electrode 14 can be adopted. The intermediate layer 15 can function as an insulating layer, a stress relaxation layer, a layer for smoothing irregularities on the electrode surface, and the like.
The intermediate layer 15 may be located between the dielectric thin film 13 and the lower electrode 12, and may be located between the dielectric thin film 13 and the upper electrode 14, or may be located in either one of them. When there are a plurality of intermediate layers, each intermediate layer may have a different function.
The thickness of the intermediate layer 15 is preferably 20% or less, more preferably 10% or less of the thickness of the dielectric thin film 13.

The dielectric thin film according to the present embodiment can be used as a dielectric layer of, for example, a voltage-tunable capacitor or a high-density capacitor device such as a decoupling thin film capacitor.

The capacitive element according to the present embodiment is an element utilizing the excellent dielectric property of the dielectric thin film according to the present embodiment, and is a capacitor, a thermista, a filter, a diplexer, a resonator, a transmitter, an antenna, a piezoelectric element, and the like. Includes transistors, ferroelectric memories, etc. The dielectric thin film according to the present embodiment is suitably used for a capacitive element that is particularly required to have high dielectric properties.

As the capacitive element according to the present embodiment, for example, as a method of manufacturing a capacitor, a method of forming a high tuning device structure having an appropriate electrode on a substrate can be mentioned. The high tuning device structure is not particularly limited, and is, for example, a SAW duplexer, a switch by RF-MEMS, a piezoelectric driven MEMS air gap varicap, a fixed (low tuning) high density thin film capacitor, a TFBAR circuit, a resistor, an inductor, and the like. Those integrated with other thin film devices such as oxide-based TFTs and sensors may be used.

Although the embodiments of the present invention have been described above, the present invention is not limited to these embodiments, and it is needless to say that the present invention can be carried out in various different modes without departing from the gist of the present invention. ..

Hereinafter, the present invention will be described based on more detailed examples, but the present invention is not limited to these examples.

Example 1
First, SrCO ₃ powder and Ta ₂ O ₅ powder were prepared as raw materials for the Sr ₂ Ta ₂ O ₇ sintered body used as a film forming target. The SrCO ₃ powder and the Ta ₂ O ₅ powder were weighed so that the molar ratio of Sr / Ta was 1.

Next, the SrCO ₃ powder and the Ta ₂ O ₅ powder were mixed with a wet ball mill using an ethanol solvent for 16 hours to obtain a mixed slurry.

Next, the mixed slurry was dried at 80 ° C. for 12 hours in a constant temperature dryer to obtain a mixture.

Next, the mixture was lightly crushed in a mortar and placed in a ceramic crucible. Then, it was heat-treated at 1000 ° C. for 2 hours in an air atmosphere using an electric furnace to obtain a calcined product.

Next, the calcined product was mixed again with a wet ball mill using an ethanol solvent for 16 hours to obtain a slurry after calcining.

The obtained post-pre-baked slurry was dried at 80 ° C. for 12 hours in a constant temperature dryer to obtain a post-pre-baked mixture.

A polyvinyl alcohol solution was added as a binder to the pre-baked mixture and mixed to obtain a granulated product. The amount of the polyvinyl alcohol solution added was 0.6% by weight with respect to 100% by weight of the pulverized product.

The granulated product was formed into a cylindrical shape having a diameter of about 23 mm and a height of about 9 mm to obtain a molded product. The molding method was CIP molding.

The molded product was fired at 1400 ° C. for 2 hours in an air atmosphere using an electric furnace to obtain a sintered product. Further, the upper surface and the lower surface of the sintered body were mirror-polished to obtain a film-forming target having a height of 5 mm. It was confirmed that the relative density of the obtained film forming target was 96 to 98%.

The film-forming target obtained as described above was installed in the film-forming apparatus, and the Si substrate was installed so as to face the film-forming target. As the Si substrate, a substrate having a Pt film as a lower electrode on the surface was used.

In Example 1, a pulse laser was irradiated at a frequency of 10 Hz by the PLD method, and a film was formed so as to have a thickness of 500 nm. At this time, nitrogen was not introduced into the film forming chamber, but only oxygen was introduced to form a dielectric oxide film. Further, during the film formation, plasma was irradiated for 0.5 hours. The film formation temperature was 700 ° C. Immediately after the film formation, nitrogen radicals were introduced and nitriding treatment was performed for 30 minutes to obtain a dielectric thin film sample. The obtained dielectric thin film samples were evaluated as follows.

Evaluation of polycrystal film and its orientation The obtained sample was subjected to XRD measurement using a fully automatic horizontal multipurpose X-ray diffractometer SmartLab manufactured by Rigaku Corporation, and the alignment film oriented to a specific surface from the XRD pattern. It was confirmed whether or not it had polycrystalline properties. It was evaluated as "good" when it was not an alignment film having polycrystallity and oriented with respect to a specific surface, and was evaluated as "poor" when it was not polycrystalline and it was an alignment film. The composition of the oxynitride contained in the obtained thin film sample is ULVAC-PHI, Inc. It was quantified by photoelectron spectroscopy using PHI Quantera II ^TM manufactured by PHI. The composition of the thin film in the depth direction was quantified while performing Ar etching.

Measurement of fluctuation rate of nitrogen composition With respect to the obtained sample, the nitrogen composition (atm%) at 5 different points at a depth of 1/4 in the thickness direction from the surface of the thin film was measured by an X-ray photoelectron spectroscopy analyzer, and the measurement thereof was performed. The average was calculated. The nitrogen composition (atm%) was similarly measured at the depth position of 1/2 and the depth position of 3/4 in the thickness direction from the surface of the thin film, and the average was calculated for each. The maximum volatility was calculated from those averages. The results are shown in Table 1.

Presence or absence of voids and evaluation of columnar particles The cross section of the thin film of the obtained sample was observed using a scanning electron microscope (SEM). From the SEM image, it was confirmed whether or not there was a void of 30 nm or more in the observation field of view of 3 fields of 1.2 μm × 1.5 μm. In addition, the presence or absence of columnar particles was confirmed from the TEM images obtained using a transmission electron microscope (TEM). Furthermore, if there were columnar particles, it was confirmed whether or not the columnar particles extended in the direction intersecting the substrate. Then, the ratio of the penetrating columnar particles was calculated based on the TEM image. The results are shown in Table 1. The TEM image obtained in Example 1 is shown in FIG.

Measurement of Dielectric Characteristics (tan δ and Relative Permittivity) Using an LCR meter, the capacitance and tan δ of the sample were measured at a voltage of 1 V / rms and a frequency of 1 kHz. Then, the relative permittivity was calculated based on the thickness of the thin film, the electrode area, and the capacitance.

Crystal structure The crystal structure of the obtained sample was confirmed by XRD measurement.

Example 2
In Example 2, a dielectric oxide film was formed so as to have a thickness of 1000 nm by the PLD method. In addition, nitrogen radicals were introduced during film formation to perform nitriding treatment, but nitrogen radicals were not introduced after film formation. A dielectric thin film sample was obtained in the same manner as in Example 1 under other conditions. It was evaluated in the same manner as in Example 1. The results are shown in Table 1. The TEM image is shown in FIG.

Example 3
In Example 3, a dielectric oxide film was formed so as to have a thickness of 500 nm by the PLD method. The film formation temperature was 600 ° C. A dielectric thin film sample was obtained in the same manner as in Example 1 under other conditions. It was evaluated in the same manner as in Example 1. The results are shown in Table 1.

Example 4
A dielectric thin film sample was obtained in the same manner as in Example 1 except as shown below. That is, in Example 4, La ₂ O ₃ powder and TiO ₂ powder were prepared as raw materials for the La ₂ Ti ₂ O ₇ sintered body used as a film forming target. The La ₂ O ₃ powder and the TiO ₂ powder were weighed so that the molar ratio of La / Ti was 1. Further, a dielectric oxide film was formed so as to have a thickness of 500 nm by the PLD method. It was evaluated in the same manner as in Example 1. The results are shown in Table 1.

Example 5
A dielectric thin film sample was obtained in the same manner as in Example 1 except as shown below. That is, in Example 5, BaCO ₃ powder and Ta ₂ O ₅ powder were prepared as raw materials for the sintered body of the oxide having a Ba / Ta molar ratio of 1 used as the target for film formation. The Ba ₂ CO ₃ powder and the Ta ₂ O ₅ powder were weighed so that the Ba / Ta molar ratio was 1. Further, a dielectric oxide film was formed so as to have a thickness of 500 nm by the PLD method. Since there is no composition of Ba ₂ Ta ₂ O ₇ , even if the molar ratio of Ba / Ta of the target sintered body is adjusted to 1, the molar ratio of the thin film obtained depending on the film forming conditions is the target. The composition is difficult to transfer. Therefore, the partial pressure at the time of film formation was adjusted, and the Ba / Ta molar ratio of 1 was evaluated in the same manner as in Example 1. The results are shown in Table 1.

Example 6
In Example 6, a dielectric thin film sample was obtained in the same manner as in Example 1 except that the film formation temperature was set to 500 ° C. It was evaluated in the same manner as in Example 1. The results are shown in Table 1.

Example 7
In Example 7, a dielectric thin film sample was obtained in the same manner as in Example 1 except that the film formation temperature was set to 850 ° C. It was evaluated in the same manner as in Example 1. The results are shown in Table 1.

Comparative Example 1
In Comparative Example 1, a dielectric thin film sample was obtained in the same manner as in Example 2 except that the film formation temperature was set to 400 ° C. It was evaluated in the same manner as in Example 1. The results are shown in Table 1.

Comparative Example 2
In Comparative Example 2, a dielectric thin film sample was obtained in the same manner as in Experimental Example 2, except that the film formation temperature was set to 300 ° C. It was evaluated in the same manner as in Example 1. The results are shown in Table 1.

Comparative Example 3
In Comparative Example 3, a dielectric thin film sample was obtained in the same manner as in Example 1 except that the film formation temperature was 900 ° C. It was evaluated in the same manner as in Example 1. The results are shown in Table 1.

From the TEM images of Tables 1 and FIGS. 3 and 4, in Examples 1 to 7, the polycrystal has no voids and is not oriented in a specific crystal plane orientation, and extends in a direction intersecting the substrate. A dielectric thin film sample composed of columnar particles was obtained, and it was confirmed that the maximum fluctuation rate of the N composition was ± 55 % or less and that it was uniform in the film thickness direction. On the other hand, in the dielectric thin film sample of Comparative Example 1, voids were observed and no columnar particles were observed. In the thin film sample of Comparative Example 2, no voids were observed, but no crystal structure was observed, and no columnar particles were observed. In addition, nitrogen was not detected in Comparative Examples 1 and 2. In the thin film sample of Comparative Example 3, no columnar particles were observed, and the maximum volatility of the N composition was more than ± 55% .

Example 8
In Example 8, a dielectric thin film sample was obtained in the same manner as in Example 1 except that the plasma irradiation time at the time of film formation was made longer. It was evaluated in the same manner as in Example 1. The results are shown in Table 2. As for the crystal structure, the result of "no peak shift" was obtained as compared with Example 1. “No peak shift” means that the peak position of the pattern obtained by X-ray diffraction is not shifted, and the size of the crystal lattice is larger than that of Example 1 regardless of the nitrogen N content. Indicates that has not changed.

Example 9
In Example 9, a dielectric thin film sample was obtained in the same manner as in Example 1 except that the plasma irradiation time at the time of film formation was further lengthened. It was evaluated in the same manner as in Example 1. The results are shown in Table 2. As for the crystal structure, the result of "no peak shift" was obtained as compared with Example 1 as in Example 8.

Examples 10 and 11
In Examples 10 and 11, a dielectric thin film sample was obtained in the same manner as in Example 1 except that the frequency of the pulsed laser and the film forming atmosphere were changed. It was evaluated in the same manner as in Example 1. The results are shown in Table 2. As for the crystal structure, the result of "no peak shift" was obtained as compared with Example 2. That is, it was found that in Examples 10 and 11, the size of the crystal lattice did not change as compared with Example 2 regardless of the nitrogen N content.

1 ... Thin film capacitor 11 ... Substrate 12 ... Lower electrode 13 ... Dielectric thin film 14 ... Upper electrode 15 ... Intermediate layer X ... Columnar particles

Claims (5)

A dielectric thin film having a main composition composed of an oxynitride represented by the composition formula AaBbOoNn (a + b + o + n = 5).
The A is any one or more of Sr, Ba, Ca, La, Ce, Pr, Nd, and Na.
B is any one or more of Ta, Nb, Ti, and W, and is
The crystal particles constituting the dielectric thin film are polycrystals that are not oriented in a specific crystal plane orientation, and are characterized by being composed of columnar particles. The dielectric thin film according to claim 1, wherein the columnar particles extend in a direction intersecting the substrate on which the dielectric thin film is formed. The dielectric thin film according to claim 2, wherein the composition ratio of the columnar particles penetrating from the front surface to the back surface of the dielectric thin film is 30% or more. When the nitrogen composition ratio is measured at the depth position of 1/4, the depth position of 1/2, and the depth position of 3/4 in the thickness direction from the surface of the dielectric thin film, these The dielectric thin film according to any one of claims 1 to 3, wherein the maximum fluctuation rate of the nitrogen composition at the three positions is within ± 55%. The capacitive element having the dielectric thin film according to any one of claims 1 to 4 .

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