JP2002025855A - Thin-film capacitor and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thin-film capacitor which is high in quality and reliability and can prevent increase in leakage current due to heating, ensure constant electrostatic capacity and reduce electrical resistance in a lower electrode, and its manufacturing method, by forming a conductor thin film which is made mainly of two elements and can be anodized, especially a tantalum nitride thin film and anodizing it thereafter. SOLUTION: When a tantalum nitride thin film 2 is formed on an insulation layer through sputtering, partial pressure of nitrogen in a sputtering gas is changed at a prescribed interval of time, so that the concentration of nitrogen varies in the film-thickness direction of the tantalum nitride, and three layers of tantalum films 11 to 13 are formed, and they are anodized to form an oxide film as a dielectric body.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a thin film capacitor and a method for manufacturing the same. In particular, the present invention relates to a high-quality and high-reliability thin-film capacitor that does not increase leakage current due to heating, secures a constant capacitance value, and has a lower electrode with low electric resistance, and a method for manufacturing the same.

[0002]

2. Description of the Related Art In recent years, electronic circuits have been required to have higher density year by year due to higher speed of signals to be transmitted, adoption of highly integrated circuits, and downsizing of devices. The same is true for electronic components that make up an electronic circuit. For example, for a capacitor, there is a demand for a technique of reducing the size while maintaining a predetermined capacitance. As is well known, the capacitance of a capacitor is proportional to the dielectric constant of a dielectric and the area of an electrode, and inversely proportional to the thickness of the dielectric.
Therefore, as means for reducing the size of the capacitor and obtaining a desired capacitance, it is conceivable to select a material having a high dielectric constant or to reduce the thickness of the dielectric, that is, to use a thin film capacitor. In addition to satisfying the above conditions, when a thin film capacitor is mounted on an electronic circuit board or the like, the area occupied by the capacitor becomes substantially zero when an LSI chip or the like is mounted thereon, so that the electronic circuit board has a high density. It also has the feature of greatly contributing to the development.

[0003] Actually, a wide variety of thin film capacitors have been developed so far in order to produce products having good characteristics. One of the solutions is a so-called thin film tantalum capacitor using a tantalum oxide thin film as a dielectric. A capacitor using tantalum oxide as a dielectric has high reliability and high quality stability such as a high dielectric constant and a small leakage current as compared with silicon oxide and aluminum oxide (alumina). There are many reports on the development of thin film tantalum capacitors, for example, JP-A-2-302016 and JP-A-3-38809.

[0004]

As described above, there is a case where a thin film capacitor is mounted inside an electronic circuit board as one of the usage methods. Electronic circuit boards are mainly composed of metal wiring layers and insulating layers, but in electronic circuit boards that are required to transmit high-frequency signals at high speed,
In order to obtain good electronic circuit characteristics, it is common to apply an organic compound such as polyimide having a low dielectric constant as a material of the insulating layer. In other words, when an electronic circuit that has a capacitor mounted in an electronic circuit, has high-density wiring, and has good circuit characteristics is required, the insulating layer is made of polyimide, the capacitor is made of a thin film tantalum capacitor, and this is called a substrate. One solution is to use a form of an electronic circuit board built in the device. Therefore, in order to obtain such a high-performance electronic circuit board, it is a precondition that a thin film tantalum capacitor can be formed on a polyimide film.

[0005] Tantalum oxide dielectrics are mainly formed by directly forming a tantalum oxide film by CVD or reactive sputtering, or by forming a tantalum metal thin film by sputtering or the like, and anodizing a part of the thin film. This is roughly classified into two methods of forming a tantalum oxide film. In the former case, the leakage current is large in the untreated state after the oxide film is formed.
0 ° C.). In such a temperature range, the polyimide film used for the thin film insulating layer of the electronic circuit board is completely thermally decomposed, so that such a forming method cannot be applied. Therefore, when a thin film tantalum capacitor is formed on a polyimide film, an anodic oxidation method that does not undergo high-temperature treatment is necessarily selected. However, a thin film tantalum capacitor formed by anodic oxidation, which is said to have a relatively small leakage current, may not be able to fall below the upper limit of the leakage current required for a capacitor for an electronic circuit board.

When used as a capacitor in an electronic circuit board, the leakage current is desirably less than about 10 to ⁶ A / cm ² . In a thin film tantalum capacitor, this condition can be satisfied if the applied voltage is about 5 V. However, if a voltage of 10 V or more is applied, the leakage current may exceed the above upper limit. Further, if the thin film tantalum capacitor is subjected to a heat treatment in a reducing atmosphere at 350 ° C. for about 60 minutes, the leakage current increases several thousand times. This is because oxygen in the thin film diffuses into the tantalum metal as the upper or lower electrode, resulting in oxygen deficiency in the oxide film, or the film stress of the metal tantalum fluctuates significantly due to heat treatment. However, it is considered that cracks occur in the oxide film. When a thin film tantalum capacitor is formed on the above electronic circuit board, it is essential to form a polyimide thin film as a thin film insulating layer on the capacitor, or to mount an LSI chip or the like on the board by soldering. Since a heat treatment at a temperature around 350 ° C. is applied, it is impossible to apply a capacitor that exhibits a fluctuation in leakage current due to the above-described heating.

As one of means for solving this problem, there is a method in which nitrogen is mixed into tantalum and the base metal is tantalum nitride. This is described in, for example, IEICE Transactions C-II Vol. J76-CI
I No. 8 p576-578 (August 1993), it is believed that nitrogen bonded to tantalum inhibits diffusion of oxygen to the underlying metal. However, the dielectric constant of an oxide film formed of a tantalum film mixed with nitrogen has a smaller dielectric constant than that of pure tantalum, and the value decreases as the nitrogen content increases. Although a certain dielectric constant can be secured by reducing the amount of nitrogen,
The effect of suppressing the increase in leakage current due to heating is lost.

In view of the above problems, an object of the present invention is to form an anodically oxidizable conductor thin film containing two elements as main components, in particular, a tantalum nitride thin film made of tantalum and nitrogen, and anodize the dielectric thin film. To provide a high-quality and high-reliability thin-film capacitor which does not increase leakage current due to heating, has a constant capacity, and has low-resistance electrodes, and a method for manufacturing the same. It is in.

[0009]

In order to achieve the above object, the present invention forms an anodically oxidizable conductive thin film containing two kinds of elements as main components and forms the conductive thin film by anodic oxidation. A thin film capacitor using an oxide film as a dielectric material, wherein the concentration ratio of two elements which are main components in the conductive thin film is changed in the thickness direction of the conductive thin film. .

[0010] The present invention also provides a thin film capacitor in which an anodically oxidizable conductive thin film containing two kinds of elements as main components is formed and an oxide film formed by anodizing the conductive thin film is used as a dielectric. A thin film capacitor characterized by laminating a plurality of the conductor thin films having different concentration ratios of two main components.

The present invention also relates to a thin film capacitor in which an anodically oxidizable conductive thin film containing the above two elements as main components is formed and an oxide film formed by anodizing the conductive thin film is used as a dielectric. , The main component of the conductor thin film 2
A thin film capacitor characterized by using tantalum and nitrogen as elements.

Further, the present invention relates to a thin film capacitor in which an anodically oxidizable conductive thin film mainly composed of two kinds of elements is formed, and an oxide film formed by anodizing the conductive thin film is used as a dielectric. 2 which is the main component in the conductive thin film
A method of manufacturing a thin film capacitor, wherein a concentration ratio of an element is changed in a thickness direction of the conductive thin film.

[0013] The present invention also provides a thin film capacitor in which an anodically oxidizable conductive thin film mainly composed of two kinds of elements is formed and an oxide film formed by anodizing the conductive thin film is used as a dielectric. A method for manufacturing a thin film capacitor, comprising laminating a plurality of conductive thin films having different concentration ratios of two main components.

The present invention also relates to a thin film capacitor having a dielectric thin film formed by anodizing a conductive thin film comprising the above two elements as main components and capable of anodizing the conductive thin film. A method of manufacturing a thin film capacitor, wherein two elements which are main components of the conductive thin film are tantalum and nitrogen.

[0015]

(First Example) As a first example of an embodiment of the present invention, a manufacturing process of a thin film capacitor according to the present invention will be described with reference to FIG.

First, an insulating layer 1 as a base of a thin film capacitor is prepared (FIG. 2A). In this example, a polyimide thin film was used as the insulating layer 1. The formation method is described below. First, a varnish-like polyimide precursor is coated on a substrate made of ceramic or the like by a spin coater. This substrate is made of, for example, an insulator made of ceramic or the like, and C
It may be a substrate in which a wiring conductor composed of a conductor made of u or the like is provided, or may be a substrate made of only an insulator having no conductor. On the other hand, by heating the substrate at 350 ° C. for 60 minutes, the polyimide precursor is imidized to obtain polyimide. In this example, a method of thermally curing a varnish-like precursor was used as a method for forming a polyimide, but other than that, for example, a film-like polyimide film was adhered to a substrate using an adhesive film or the like, and then pressed and heated. A method of forming may be used. Further, a film-like film itself may be used as a base material without using a rigid substrate such as ceramic. Further, through holes or the like for making electrical connection with the underlying substrate may be formed in the insulating layer by using photolithography, laser ablation, or the like in the step of forming the insulating layer.

In this embodiment, the insulating layer 1 is made of polyimide, but may be epoxy resin, benzocyclobutene, or an analog thereof. Further, a conductive thin film may be formed directly on an inorganic insulating substrate such as ceramic or glass without using an organic insulating film such as polyimide. However, the requirements for the base material are satisfied by the fact that the adhesion to the tantalum nitride thin film is good and that the surface of the insulating layer is smooth so that defects such as breakage do not occur in the tantalum nitride film. Material and shape need to be selected.

Next, an anodically oxidizable conductive thin film layer 2 containing two kinds of elements as main components is formed on the insulating layer 1 (FIG. 2B). In the present embodiment, a tantalum nitride thin film made of tantalum and nitrogen was used as the conductive thin film layer 2. A tantalum nitride thin film was formed using a planar magnetron type sputtering apparatus. Tantalum having a purity of 99.95% was used as a sputtering target, and a mixed gas of argon and nitrogen was used as an atmosphere gas during sputtering. The conditions are shown below. First, the substrate was mounted on a sputtering apparatus, and after evacuation,
The solution is kept at 0 ° C. for 1 hour to remove water and the like adsorbed on the polyimide film. Thereafter, the degree of vacuum is 5 × 10 to ⁵ Pa or less, and the temperature is 5
After leaving it at 0 ° C. or less, the pressure of the argon / nitrogen mixed gas was 0.5 Pa, and the sputtering power was 0.4
A tantalum nitride thin film is formed with a kW of 110 minutes (a total film thickness of 500 nm).

Here, the correlation between the partial pressure of nitrogen in the sputtering gas and the film characteristics of the tantalum nitride film formed thereby will be described. FIG. 3 shows a sputtering power of 0.4 k in the sputtering apparatus used in this example.
The correlation between the nitrogen partial pressure in the argon / nitrogen mixed gas at W and the specific resistance and the crystal structure of the tantalum nitride thin film is shown. First, in a region where the partial pressure of nitrogen is 0 to 0.3%, a β having a tetragonal crystal structure equivalent to that when nitrogen is not mixed is used.
It shows a structure called -Ta and the specific resistance hardly fluctuates. In this region, the effect of doping with nitrogen is hardly obtained. If the nitrogen concentration exceeds this range and enters the region of 0.3 to 1%, a so-called α-Ta having a body-centered cubic lattice structure is formed, and the specific resistance decreases. The thin film in this region has a high leakage current even if anodic oxidation is performed, and only a dielectric film having unstable characteristics can be obtained.However, if it is used for the lower electrode of the thin film capacitor by taking advantage of the low specific resistance, It is possible to contribute to improvement of the capacitor characteristics, particularly, suppression of signal attenuation when a high-frequency signal is propagated. When the nitrogen partial pressure is in the range of 1 to 2.5%, the dielectric material becomes Ta ₂ N composed of a hexagonal dense lattice, and the dielectric obtained by anodizing this film has a relatively high dielectric constant as a tantalum nitride base. The leakage current is also relatively small. However, the film in this region also has 3
By performing the heat treatment at about 50 ° C. for several hours, the leakage current increases. When the nitrogen partial pressure is in the range of 2.5 to 3.5%, TaN having the same hexagonal close-packed lattice structure is formed. An oxide film based on this film has a low dielectric constant but a low leakage current, and no increase in leakage current due to heating is observed. If the nitrogen partial pressure exceeds 3.5%, stable film formation cannot be performed.

By changing the nitrogen concentration in the film thickness direction by utilizing the film forming characteristics of the above-mentioned tantalum nitride thin film, there is no increase in leakage current due to heating and a constant capacitance. In addition, a high-quality and highly reliable dielectric having a lower electrode with low electric resistance can be formed. Specifically, during the formation of the tantalum nitride thin film, the partial pressure of nitrogen in the mixed gas was varied as follows. First, the film formation time is 0 to
The nitrogen partial pressure ratio is set to 0.5% for 90 minutes, the nitrogen partial pressure ratio is set to 2.0% for 90 to 108 minutes, and the nitrogen partial pressure ratio is set to 108% for 110 to 110 minutes. Was set to 3.0%. As a result, the tantalum nitride thin film in this example is
A first tantalum nitride layer 11 formed at a nitrogen partial pressure of 0.5%, a second tantalum nitride layer 12 formed at a nitrogen partial pressure of 2.0%, and a film formed at a nitrogen partial pressure of 3.0% The three-layered tantalum nitride layer 13 has a three-layer structure, and the thicknesses thereof are 410 nm, 82 nm, and 9 nm, respectively, and the total thickness of the tantalum nitride thin film 2 is 501 nm. In light of the above-mentioned film forming characteristics of tantalum nitride, the tantalum nitride thin film 2
It can be seen that it is composed of a Ta thin film, a Ta ₂ N thin film as the second tantalum nitride layer 12, and a TaN thin film as the third tantalum nitride layer 13.

The correlation curve between the nitrogen partial pressure and the specific resistance, that is, the tantalum nitride structure in FIG. 3 fluctuates when the sputtering power is different as shown in FIG. Also, when another sputtering apparatus is used, these relations are considered to fluctuate. Therefore, it is very difficult to generalize the correlation between the nitrogen partial pressure and the film structure described above. Therefore, for example, when film formation is performed using another apparatus, it is necessary to newly grasp the correlation between the nitrogen partial pressure and the sputtering apparatus and find new conditions.

In this embodiment, the nitrogen partial pressure is intermittently varied, but it is continuously (smoothly with respect to time).
You can change it. Further, in this embodiment, the three-layer film is formed continuously, but the film formation batch may be changed for each of these films. In this embodiment, three films having different nitrogen concentrations are used. However, two or four or more films may be used. Further, the order of fluctuation of the nitrogen concentration may be different from that of the embodiment. As preferable conditions, a TaN film having no increase in leakage current due to heating is formed on a part of the part to be anodized and becomes a dielectric, and Ta is capable of securing a large dielectric constant for most of the part to be a dielectric. _A 2N film is to be formed, and most of the portion to be a lower electrode is to be an α-Ta film having a small specific resistance.

After a tantalum nitride thin film 2 having a different nitrogen concentration in the film thickness direction is formed, this is anodized to form an oxide film 3 (FIG. 2C). A 0.1 vol% aqueous solution of phosphoric acid was used as an electrolytic solution at the time of anodic oxidation. The conditions were a current density of 0.5 mA / cm ² , a formation voltage of 100 V, and a holding time after constant voltage of 1 hour. FIG. 1 shows a detailed view of a laminated film composed of the tantalum nitride thin film 2 and the anodic oxide film 3 obtained under the above conditions. The right half in the figure shows a portion that did not directly touch the electrolytic solution, that is, a portion that was not anodized. The thickness of the oxide film formed according to this embodiment is 160 nm, which is a layer 21 (140 nm thick) in which a part of the second tantalum nitride layer 12 is anodized.
And the third tantalum nitride layer 11 is composed of an anodized layer 22 (20 nm thick). In other words, most of the anodic oxide film 3 serving as the dielectric of the thin film capacitor is an oxide film 21 obtained by anodizing a Ta ₂ N thin film having a relatively high dielectric constant, thereby securing the capacitance and ensuring the surface layer. By forming an oxide film 22 obtained by anodizing a TaN thin film having high heat resistance, an increase in leakage current due to heating is prevented.

Further, the portion of the tantalum nitride thin film 2 which is close to the base insulating layer 1 and which functions as a lower electrode without being anodized becomes a film having a small specific resistance of about 70 μΩcm, thereby improving the capacitor characteristics. ing.

The method of selecting the thickness of the anodic oxide film and the thickness of the tantalum nitride thin film serving as the base will be described below. The thickness t _O of the anodic oxide film is determined only by the formation voltage V _A , and the relationship is t _O = a · V _A. Here, the constant a is a value specific to the material, and in the case of tantalum and tantalum nitride, approximately a =
1.6 nm / V. Further, the volume ratio R _V = t _O / t _M between the metal film and the anodic oxide film, (t _M = the thickness of the metal film changing into the anodic oxide film) is also a value unique to the material. _V = 2.5.

First, the capacitance per unit area required for the thin film capacitor is set. In this embodiment,
90 nF / cm ² . As is well known, the capacitance per unit area is determined by the dielectric constant ε ′ of the dielectric and the film thickness. The relative dielectric constant of each oxide film is about ε ′ = 17 for the Ta ₂ N thin film base and about ε ′ = 9 for the TaN thin film base.
It is. The thickness of the dielectric is at least 150 n in total in order to prevent a short circuit between the upper and lower electrodes.
About m is necessary. From these values, if the oxide film based on the Ta ₂ N thin film is 140 nm and the 3k film based on the TaN thin film is 20 nm, that is, the total film thickness is 160 nm, the capacitance per unit area is about 90 nF / cm ² . Estimated to reach. From the thickness values of these dielectrics and the volume ratio R _V between the oxide film and the conductor film, the thicknesses of the Ta2N thin film and the TaN thin film are approximately 56 nm (or more) and 8 nm, respectively.

After the anodizing step is completed, the upper electrode layer 4 is formed (FIG. 2D). As a material of the upper electrode, a laminated film of a nickel-chromium film and gold was used, and a vacuum deposition was used as a forming method thereof. The nickel-chromium film has a role of an adhesive layer for securing the adhesiveness between the anodic oxide film and gold, and the thickness thereof is 10 nm. The reason why gold is selected as the upper electrode is to prevent oxygen of the anodic oxide film 3 from moving to the upper electrode. The thickness of the gold film was 500 nm. The conditions required for the material of the upper electrode 4 are that it is less oxidized than tantalum, and that it has good adhesion to the anodic oxide film. In these cases, it is preferable to form chromium, titanium, or an alloy containing these at a very thin interface at the interface in order to ensure the adhesion to the anodic oxide film as with gold. Regarding the formation method, other than vapor deposition, for example, sputtering may be used, but it is necessary to consider the formation conditions so as not to physically damage the anodic oxide film 3.

Finally, patterning of the upper electrode, patterning of the anodic oxide film, and patterning of the tantalum nitride thin film as the lower electrode are successively performed on the laminated film formed as described above. The processing method is as follows. Nickel-chromium / gold is wet etching using aqua regia as an etchant, anodic oxide film is dry etching using argon as an etching gas, and tantalum nitride film as a lower electrode is wet etching using an aqueous solution of hydrofluoric nitric acid as an etching solution. In each step, a resist was used as a mask material.

By going through the above steps, FIG.
The thin film capacitor element shown in FIG. The thin film capacitor completed in this way has low leakage current,
It has high reliability and excellent high-frequency characteristics, in which the increase in leakage current due to the heat treatment is small, the capacitance is constant, and the electric resistance of the lower electrode is small.

(Second Example) As a second example of the embodiment of the present invention, a manufacturing process of an electronic circuit board according to the present invention will be described with reference to FIG.

The process of this embodiment is the same as that of the first embodiment except for the step of forming the tantalum nitride thin film 2 (FIG. 2B). It is exactly the same as the example.

The feature of this embodiment is that the nitrogen concentration in the tantalum nitride thin film 2 is not changed by the change of the nitrogen partial pressure of the argon / nitrogen mixed gas at the time of sputtering.
That is, it is changed by a change in sputtering power during film formation. As shown in FIG. 4, when the sputtering power is different, the correlation curve between the nitrogen partial pressure and the specific resistance shifts. FIG. 5 shows the correlation between the reciprocal of the sputtering power, the specific resistance, and the film structure of the tantalum nitride thin film when the oxygen partial pressure is 3.0%. As can be seen from this figure, it is possible to change the nitrogen concentration of the tantalum nitride thin film in the film thickness direction by changing the sputtering power as in the first example. A specific example of this method is described below.

First, the insulating layer 1, which is the base on which the tantalum nitride thin film 2 is formed, is exactly the same as in the first example. A tantalum nitride thin film 2 is formed on this upper layer, and the apparatus used for the film formation is the same as that of the first example. As for film forming conditions, the substrate was mounted on a sputtering apparatus, evacuated, heated at 200 ° C. for 1 hour, and then reached a degree of vacuum of 5 × 10 to ⁵ Pa or less and a temperature of 50 ° C. or less. The film is formed by fixing the pressure of the nitrogen mixed gas at 0.5 Pa and the partial pressure of the nitrogen gas at 3.0%. That is, they are the same except that the nitrogen partial pressure of the mixed gas is fixed and the sputtering power is changed during the film formation. However, it should be noted that, unlike the first example, when the sputtering power is changed, the film forming speed also changes, and thus the ratio of the film forming time of each layer does not directly become the film thickness ratio of each layer. Therefore, it is necessary to grasp the film forming speed for each sputtering power and set the film forming time accordingly.

FIG. 6 is a diagram showing the correlation between the sputtering power and the deposition rate of the tantalum nitride thin film when the nitrogen partial pressure of the mixed gas is 3.0%. 5 and FIG. 5, the conditions for forming the laminated tantalum nitride thin film shown in FIG. 1 are as follows: the sputtering power is 1.7 kW for the first tantalum nitride layer 11, the deposition time is 24 minutes, the second tantalum nitride layer is 12 has a power of 0.7 kW and a film forming time of 11 minutes, and the third tantalum nitride layer 13 has a power of 0.4 kW and a film forming time of 2 minutes. The total film forming time is 37 minutes. In this embodiment formed under these conditions, a thin film capacitor having the same film structure and thickness as the schematic diagram of FIG. 1 can be obtained.

The steps after the formation of the tantalum nitride thin film 2 are exactly the same as those of the embodiment described in the first example.
A high-quality and high-reliability thin-film capacitor is formed without lowering the leakage current due to heating, obtaining a constant capacitance, and having a lower electrode with low electric resistance.

(Third Example) As a third example of the embodiment of the present invention, a comparison result of the capacitor characteristics between the thin film capacitor according to the present invention and that according to the prior art will be shown.

Here, the thin film capacitor according to the present invention comprises:
Assume that it is formed under the conditions described in the first embodiment. Three types of thin film capacitors according to the prior art were prepared.
These are (1) sputtering power 0.4 kW, nitrogen partial pressure 0%, (2) sputtering power 0.4 kW, nitrogen partial pressure 2%, (3) sputtering power 0.4 kW, nitrogen partial pressure 3%. The conditions were the same as those of the thin film capacitor according to the present invention.

Table 1 shows numerical values indicating the capacitor characteristics of each sample. First, as for the capacitance of each sample, (1) not containing nitrogen has the largest value, and (3) containing most nitrogen has the smallest value. The sample according to the present invention has the second smallest value, but shows almost the same value as (2). This is because a film formed by a nitrogen partial pressure of 2% occupies a large part of the dielectric of the capacitor according to the present invention. Next, the applied voltage of each sample was 10 V
(1) is overwhelmingly high, and other samples containing nitrogen show almost the same value.
Next, the leakage current after the heat treatment in a reducing atmosphere at 350 ° C. for 3 hours is also the highest in (1), which is 1000 times or more the value before heating. Also, in the case of (2), the value of the leakage current is increased about 1000 times by heating. (3) and for the sample according to the invention,
The values are almost the same as when no heat treatment is performed. Lastly, the specific resistance of the lower electrode portion serving as an index of the lower electrode of each sample is shown. Regarding this, the sample according to the present invention in which α-Ta is present in the lower layer has the lowest value, and (3) shows the highest value.

[0039]

[Table 1]

From the above results, the thin film capacitor according to the present invention has a lower electrode which can secure a constant capacitance without increasing the leakage current due to heating and has a low electric resistance, as compared with that according to the prior art. It can be seen that the capacitor has high quality and high reliability.

[0041]

As described above, the present invention relates to an anodically oxidizable conductive thin film containing two elements as main components, particularly to a tantalum nitride thin film composed of tantalum and nitrogen, wherein the nitrogen concentration in the tantalum nitride thin film is reduced. By changing the thickness in the thickness direction, there is an effect that a thin-film capacitor having a lower electrode with a low electric resistance can be formed without increasing the leakage current due to heating, ensuring a constant capacitance.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating an embodiment of a thin film capacitor according to the present invention.

FIG. 2 is a view showing an embodiment of a thin film capacitor according to the present invention and a manufacturing process thereof.

FIG. 3 is a graph showing the correlation between the nitrogen partial pressure of an argon / nitrogen mixed gas and the specific resistance and film structure of a tantalum nitride thin film obtained by sputtering at a sputtering power of 0.4 kW in sputtering.

FIG. 4 is a graph showing a correlation between a nitrogen partial pressure of an argon / nitrogen mixed gas and a specific resistance of a tantalum nitride thin film obtained by the sputtering in sputtering.

FIG. 5 is a graph showing a correlation between a sputtering power, a specific resistance, and a film structure when a nitrogen partial pressure of an argon / nitrogen mixed gas is 3.0% in sputtering.

FIG. 6 is a graph showing a correlation between a sputtering power and a film forming rate when a nitrogen partial pressure of an argon / nitrogen mixed gas is 3.0% in sputtering.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Insulating layer, 2 ... Anodically oxidizable conductor thin film (tantalum nitride) composed of 2 elements, 3 ... Anodized film (tantalum oxide), 4 ... Upper electrode (nickel-chromium / gold), 11 ...
First tantalum nitride layer, 12 ... second tantalum nitride layer, 13
... third tantalum nitride layer, 21 ... second tantalum nitride layer 12
Is an oxide film layer anodized, 22... An oxide film layer anodized on the third tantalum nitride layer 11.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yamazaki Tetsuya 292 Yoshidacho, Totsuka-ku, Yokohama-shi, Yokohama, Kanagawa Prefecture Inside of Hitachi, Ltd. Production Technology Research Laboratories (72) Inventor Kurimochi Akihiro 1 Horiyamashita, Hadano-shi, Kanagawa Prefecture Address Enterprise Server Division, Hitachi, Ltd. (72) Inventor Toshiro Terouchi 1 Horiyamashita, Hadano-shi, Kanagawa Prefecture Enterprise Server Division, Hitachi Ltd. (72) Naoki Mori, Hori, Hadano-shi, Kanagawa No. 1 Yamashita F-term (reference) 4K029 BA58 BC00 BD00 GA00 5E082 AB03 BC40 EE05 EE18 EE23 EE26 EE37 EE47 FF15 FG03 FG27 FG44 FG51 KK01 LL01 LL02 MM23 MM24

Claims (6)

[Claims] An anodically oxidizable conductive thin film mainly composed of two elements is formed, and the oxide thin film formed by anodizing the conductive thin film is used as a dielectric. A thin film capacitor characterized by changing the concentration ratio of two elements as main components in the thickness direction of the conductive thin film. 2. A thin film capacitor in which an anodically oxidizable conductive thin film mainly composed of two kinds of elements is formed and an oxide film formed by anodizing the conductive thin film as a dielectric is used. A thin film capacitor comprising a plurality of conductive thin films having different concentration ratios of certain two elements laminated. 3. The thin film capacitor according to claim 1, wherein two elements which are main components of the conductive thin film capable of being anodized are tantalum and nitrogen. 4. A thin film capacitor in which an anodically oxidizable conductive thin film containing two kinds of elements as main components is formed and an oxide film formed by anodizing the conductive thin film is used as a dielectric material. A method for manufacturing a thin film capacitor, characterized in that the concentration ratio of two elements, which are the main components, is changed in the thickness direction of the conductive thin film. 5. A thin film capacitor in which an anodically oxidizable conductive thin film mainly composed of two kinds of elements is formed, and an oxide film formed by anodizing the conductive thin film is used as a dielectric material. A method for manufacturing a thin film capacitor, comprising: laminating a plurality of conductive thin films having different concentration ratios of certain two elements. 6. The method for manufacturing a thin film capacitor according to claim 1, wherein two elements which are main components of the conductive thin film capable of being anodized are tantalum and nitrogen. .