JP2007329189A - Thin-film capacitor, and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thin-film capacitor in which peeling of an electrode film from a dielectric film can be sufficiently prevented while sufficiently ensuring the electrical conductivity of the electrode film, even if inexpensive Cu is used as the electrode. <P>SOLUTION: The thin-film capacitor 100 is provided on a substrate 1, and has a pair of electrode films 2, 6 and the dielectric film 4 provided between the pair of electrode films 2 and 6. In this capacitor 100, the pair of electrode films 2, 6 are each a Cu electrode film containing Cu, coherent layers 3, 5 containing Cu<SB>2</SB>O are provided between the electrode films 2, 6 and the dielectric film 4, and the dielectric film 4 is an oxide dielectric film. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a thin film capacitor used in a small electronic circuit formed on a substrate and a method for manufacturing the same.

  Conventionally, a thin film capacitor as a passive element formed on a substrate is widely known. Such passive elements are required to have high reliability and miniaturization, and in order to satisfy these requirements, it is desired that each of the substrate surface, the electrode film, and the dielectric film be smooth.

  By the way, as an electrode material of the electrode film, a noble metal such as platinum (Pt) or palladium (Pt) has been conventionally used in consideration of oxidation resistance and heat resistance. However, these noble metals are expensive, and there has been a problem that they are not suitable in terms of cost when considering the lamination with the demand for larger capacity. Therefore, it is desirable to use an inexpensive metal such as copper (Cu), nickel (Ni), or aluminum (Al) as an electrode. However, when Cu, Ni, or Al is used as an electrode, it is more easily oxidized than a noble metal such as platinum. Therefore, it is desirable that the dielectric is formed in a reducing atmosphere in which the electrode material is not oxidized.

  If the electrode film is made of a metal material, while the dielectric film is made of an oxide dielectric, smoothing the electrode film and the dielectric film reduces the substantial bonding area due to the reduction in the unevenness of the thin film. Engagement at the joint surface is also reduced. For this reason, the dielectric film and the electrode film are in close contact mainly due to the affinity between the electrode material and the dielectric film material, and the mutual adhesion is weak. Therefore, when the thin film capacitor is placed in a high temperature state, the electrode material and the dielectric film material have different thermal expansion coefficients, causing separation between the electrode film and the dielectric film, resulting in a decrease in the capacitance of the capacitor. It is difficult to ensure the reliability of the formed thin film capacitor.

In this way, peeling is likely to occur between the electrode and the dielectric film due to the stress generated by the difference in thermal expansion coefficient between the electrode material and the dielectric film material. A method of providing a metal layer having a thermal expansion coefficient between them and Ta or Nb between a dielectric (for example, Pb (Mg _1/3 Nb _2/3 ) O ₃ ) (for example, Patent Document 1 below) Reference), a first electrode made of copper, and a second electrode made of a composite material of copper and cuprous oxide, and a method of adjusting the thermal expansion coefficient and Young's modulus of the electrode layer (for example, the following Patent Document 2), eg, between the Pt electrode and the dielectric (e.g. _{Pb (Mg 1/3 Nb 2/3) O} 3), an intermediate containing oxygen and a metal element constituting the dielectric A method of providing a layer (for example, see Patent Document 3 below) is proposed. To have.
Japanese Patent Application Laid-Open No. 11-243032 JP 2001-185443 A Japanese Patent Laid-Open No. 7-45475

  However, in Patent Document 1, since the metal element in the metal layer that is the adhesion layer is different from the metal element in the electrode film and the metal element that constitutes the dielectric film, the stress generated due to the difference in thermal expansion coefficient. Of course, this does not increase the adhesion between the electrode material and the dielectric film material. In Patent Document 2, when priority is given to the adjustment of the thermal expansion coefficient, the ratio of cuprous oxide in the composite material of copper and cuprous oxide is increased in the second electrode (of the ratio of cuprous oxide). (Optimum is 55% or more) The conductivity is lowered. On the other hand, in order to improve the electrical conductivity, it is necessary to increase the ratio of copper in the composite material of copper and cuprous oxide, and eventually, peeling easily occurs between the dielectric film and the electrode. Further, in Patent Document 3, since the metal element constituting the dielectric is a metal element in the intermediate layer, the adhesion between the dielectric and the intermediate layer is good, but the metal element in the intermediate layer is in the electrode. Therefore, the adhesion between the intermediate layer and the electrode is not good, and there is a problem that peeling is likely to occur between the intermediate layer and the electrode.

  Therefore, an object of the present invention is to provide a thin film capacitor having sufficient adhesion between the electrode film and the dielectric film, while sufficiently ensuring the conductivity of the electrode film even when inexpensive Cu is used as the electrode, And a method of manufacturing a thin film capacitor.

In order to solve the above problems, the present inventors have conducted intensive research. As a result, by providing an adhesion layer containing at least Cu ₂ O between the Cu electrode film and the dielectric film of the thin film capacitor, the conductivity of the electrode film can be improved. The present invention has been completed by finding that both the rate and the strong adhesion between the electrode film and the dielectric film can be achieved. That is, the present invention provides a thin film capacitor provided on a substrate and having a pair of electrode films and a dielectric film provided between the pair of electrode films, wherein at least one of the pair of electrode films includes a Cu electrode containing Cu. An adhesion layer containing Cu ₂ O is provided between the Cu electrode film and the dielectric film, and the dielectric film is an oxide dielectric film.

Here, the thickness of the Cu electrode film is preferably 50 nm to 1 μm, and the average value of the thickness of the adhesion layer is preferably more than 0% and less than 10% with respect to the Cu electrode film. Since Cu ₂ O has electrical conductivity but higher electrical resistance than Cu, the average value of the thickness of the adhesion layer is less than 10% with respect to the Cu electrode film, as compared with the case of 10% or more. An increase in resistance between the electrodes can be more sufficiently prevented.

  In the thin film capacitor according to the present invention, the dielectric film preferably has a thickness of 50 nm to 1 μm.

  Furthermore, in the thin film capacitor according to the present invention, it is preferable that both of the pair of electrode films are the Cu electrode films. In this case, an electrode film, an adhesion layer, a dielectric film, an adhesion layer, and an electrode film are sequentially provided on the substrate, and peeling between the dielectric film and the two electrode films is sufficiently prevented by the adhesion layer. Therefore, the reliability of the thin film capacitor can be further increased.

  In the thin film capacitor according to the present invention, the dielectric film has two or more layers between a pair of electrode films, the Cu electrode film is between the dielectric films, and the Cu electrode film The adhesion layer may be provided between the dielectric film.

Further, the present invention provides a method of manufacturing a thin film capacitor element provided on a substrate and having a pair of electrode films and a dielectric film provided between the pair of electrode films, and the pair of electrodes on the substrate. Forming a first electrode film of the films, forming the dielectric film, and forming the other electrode film of the pair of electrode films on the dielectric film. And at least one of the pair of electrode films is a Cu electrode film containing Cu, and includes a step of forming an adhesion layer containing Cu ₂ O between the Cu electrode film and the dielectric film. And

  In the manufacturing method, it is preferable that both of the pair of electrode films are the Cu electrode films. In this case, since the peeling between the dielectric film and the two Cu electrode films is sufficiently prevented while sufficiently ensuring the conductivity of the electrode film, the reliability of the thin film capacitor can be further improved.

  The thin film capacitor of the present invention can sufficiently prevent peeling between the electrode film and the dielectric film while ensuring sufficient conductivity of the electrode film even when inexpensive Cu is used as the electrode. High reliability can be realized.

  Hereinafter, embodiments of the present invention will be described in detail. In all the drawings, the same reference numerals are assigned to the same members.

[First Embodiment]
FIG. 1 is a schematic cross-sectional view showing a thin film capacitor according to this embodiment. As shown in FIG. 1, the thin film capacitor 100 of this embodiment is provided on a substrate 1, and is interposed between a lower electrode film 2, an upper electrode film 6, a lower electrode film 2, and an upper electrode film 6. And a dielectric film 4 to be provided. Here, the lower electrode film 2 is provided on the substrate 1, and the upper electrode film 6 is disposed on the opposite side of the dielectric film 4 from the lower electrode film 2. Each of the lower electrode film 2 and the upper electrode film 6 is a Cu electrode film containing Cu as a main component, between the lower electrode film 2 and the dielectric film 4, and between the upper electrode film 6 and the dielectric film 4. Are provided with adhesion layers 3 and 5 made of Cu ₂ O, respectively. The adhesion layer 3 is in direct contact with each of the lower electrode film 2 and the dielectric film 4, and the adhesion layer 5 is in direct contact with each of the upper electrode film 6 and the dielectric film 4. The dielectric film is an oxide dielectric film containing an oxide.

  That is, in the thin film capacitor 100, oxygen atoms are included in the adhesion layer 3, and oxygen atoms are also included in the dielectric film 4, so that the adhesion between the adhesion layer 3 and the dielectric film 4 is improved. Become strong. Further, the metal element contained in the adhesion layer 3 is Cu, which is the same as Cu that is a metal element constituting the lower electrode film 2. For this reason, the adhesion between the adhesion layer 3 and the lower electrode film 2 is also strengthened. Therefore, peeling between the dielectric film 4 and the lower electrode film 2 is sufficiently prevented by the adhesion layer 3.

  On the other hand, the adhesion layer 5 contains oxygen atoms, and the dielectric film 4 contains oxygen atoms, so that the adhesion between the adhesion layer 5 and the dielectric film 4 becomes strong. The metal element contained in the adhesion layer 5 is Cu, which is the same as Cu that is a metal element constituting the upper electrode film 6. For this reason, the adhesion between the adhesion layer 5 and the upper electrode film 6 is also strengthened. Therefore, peeling between the dielectric film 4 and the upper electrode film 6 is sufficiently prevented by the adhesion layer 5.

On the other hand, since the adhesion layer 3 made of Cu ₂ O is provided separately from the lower electrode film 2, the adhesion between the dielectric film 4 and the lower electrode film 2 is ensured while sufficiently ensuring the conductivity of the electrode film 2. Can be improved. Similarly, since the adhesion layer 5 made of Cu ₂ O is provided separately from the upper electrode film 6, the dielectric film 4 and the upper electrode film 6 have a sufficient conductivity while ensuring the conductivity of the electrode film 6. Adhesion can be improved.

  As described above, according to the thin film capacitor 100, even when Cu is used for the electrode film, the dielectric film 4, the lower electrode film 2, the upper electrode film 6 and the like can be obtained while sufficiently ensuring the conductivity of the electrode film. Is sufficiently prevented. For this reason, high reliability can be realized.

  A substrate adhesion film 11 may be provided between the substrate 1 and the lower electrode film 2.

  Hereinafter, each component of the thin film capacitor 100 of this embodiment will be described in detail.

As the substrate 1, a silicon single crystal substrate, or alumina (Al ₂ O ₃ ), magnesia (MgO), forsterite (2MgO · SiO ₂ ), steatite (MgO · SiO ₂ ), mullite (3Al ₂ O ₃ · 2SiO) is used. ₂ ), beryllia (Be ○), zirconia (ZrO ₂ ), aluminum nitride (AlN), silicon nitride (Si ₃ N ₄ ), ceramic polycrystalline substrate such as silicon carbide (SiC) magnesia, or fired at 1000 ° C. or lower A glass ceramic substrate (LTCC substrate) made of alumina (crystal phase) and silicon oxide (glass phase), a glass substrate such as quartz glass, a single crystal substrate such as sapphire, MgO, SrTiO ₃ , or Al -Metal substrates, such as a Ni-Cu alloy and a Fe-Ni alloy, are illustrated. The substrate 1 may be any material as long as it is chemically and thermally stable, generates little stress, and can maintain the smoothness of the surface. What is necessary is just to select suitably based on the target dielectric constant and baking temperature. Among the substrates, it is preferable to use a silicon single crystal substrate having good substrate surface smoothness. When a silicon single crystal substrate is used, it is preferable to form a thermal oxide film (Si ₂ film) on the surface in order to ensure insulation. The thermal oxide film may be formed by raising the temperature of the silicon substrate and oxidizing the surface of the silicon single crystal substrate in an oxidizing atmosphere. The thickness of the board | substrate 1 is not specifically limited, For example, it is 100-1000 micrometers.

  Note that the surface of the substrate may be smoothed by subjecting it to mirror polishing (policing) such as substrate grinding (lapping) or CMP (Chemical Mechanical Polishing). Further, via electrodes may be formed on the substrate 1 as necessary.

The dielectric film 4 is composed of an oxide dielectric containing an oxide. Examples of such an oxide dielectric include BST (barium strontium titanate), BaTiO ₃ , (Ba) (Ca _{1− X} ) TiO ₃ , (Ba _X Sr _1-X ) TiO ₃ , PbTiO ₃ , Pb (Zr _X Ti _1-X ) _3, etc. (strong) dielectric materials, Pb (Mg _1/3) Composite perovskite relaxor type ferroelectric materials typified by Ni _2/3 ) O _3, bismuth layered compounds typified by Bi ₄ Ti ₃ O ₁₂ , SrBi ₂ Ta ₂ O ₉ , (Sr _X Ba _{1- X 2} ) Tungsten bronze ferroelectric materials represented by Nb ₂ O ₆ , PbNb ₂ O _{6 and the} like are used. Among these, ferroelectric materials having a perovskite structure such as BST, BaTiO ₃ and PZT are preferable because they have a high dielectric constant and can be easily synthesized at a relatively low temperature. The film thickness of the dielectric film 4 is not particularly limited, but is preferably set to 50 nm or more and 1 μm or less. If the film thickness is less than 50 nm, sufficient dielectric constant may not be obtained, and the leakage current may exceed the allowable range. On the other hand, when the film thickness exceeds 1 μm, a sufficient capacitance value cannot be obtained. In order to control the characteristics of the dielectric, an additive substance may be added as a subcomponent as appropriate.

  The electrode material of the lower electrode film 2 and the upper electrode film 6 is a material mainly composed of Cu and includes a Cu-based alloy. Here, the main component refers to a component contained in the electrode material by 50% by volume or more. The reason why Cu is the main component is that there is an advantage that the electric resistance is lower than that when Ni and Al are the main components. The electrode material is most preferably composed only of Cu because it is inexpensive and has high conductivity. The film thicknesses of the lower electrode film 2 and the upper electrode film 6 are not particularly limited, but when they are thin, defects such as pinholes are likely to occur, and when they are thick, peeling due to internal stress is likely to occur. It is preferable to set to. The film thickness of each electrode film is more preferably 50 to 200 nm.

The adhesion layers 3 and 5 are made of Cu ₂ O. By forming the adhesion layers 3 and 5, unlike the technique described in Patent Document 2, the affinity with the dielectric film 4 is increased over the entire surface, so that the adhesion can be enhanced. The average thickness of the adhesion layers 3 and 5 is preferably more than 0% and less than 10% with respect to the thickness of each of the lower electrode film 2 and the upper electrode film 6 which are Cu electrode films. That is, if the thickness of the lower electrode film 2 and the upper electrode film 6 is 50 nm, for example, the thickness of the adhesion layers 3 and 5 is less than 5 nm, and the thickness of the lower electrode film 2 and the upper electrode film 6 is 1 μm. The thickness of the adhesion layers 3 and 5 is preferably less than 100 nm. Here, the average value of the thickness of the adhesion layer is obtained by cutting a thin film capacitor in a FIB (focused ion beam) apparatus to obtain a thin layer sample having an exposed cross section, and observing this with a TEM (transmission electron microscope). A value calculated from data. The ratio of the average value of the thicknesses of the adhesion layers 3 and 5 to the thicknesses of the lower electrode film 2 and the upper electrode film 6 that are Cu electrode films is more preferably 1% or more and less than 10%, and further preferably 2%. .5% or more and 5% or less. Since Cu ₂ O has conductivity but has an electric resistance higher than that of Cu, the average thickness of the adhesion layers 3 and 5 is 10 with respect to the thicknesses of the lower electrode film 2 and the upper electrode film 6 which are Cu electrode films. If it is less than%, an increase in resistance between the electrode films 2 and 6 can be prevented more sufficiently than in the case of 10% or more, and deterioration of the performance of tan δ and league characteristics can be suppressed. .

Examples of the substrate adhesion layer 11 include TiO _x , TiO _x / SiO ₂ , and TaN. _{Incidentally,} TiO X / SiO ₂ means a laminate of TiO _X layer and the SiO ₂ layer. In this case, the SiO ₂ layer is provided on the substrate side. A protective layer made of an inorganic material such as TiO ₂ , SiO ₂ , or Al ₂ O _3, or an organic material such as an epoxy resin or a polyimide resin may be provided on the upper electrode film 10 for the purpose of electrode protection.

Next, a method for manufacturing the thin film capacitor 100 will be described with reference to FIG. In the method of manufacturing the thin film capacitor 100, a thin film capacitor using a substrate in which the surface of a silicon single crystal substrate is thermally oxidized to form a SiO ₂ layer will be described as an example.

<Formation of substrate adhesion layer>
As shown in FIG. 2A, first, a substrate adhesion layer 11 is formed on the substrate 1 for the purpose of improving the adhesion between the substrate 1 and the lower electrode film 12. The substrate adhesion layer 11 can be formed by vapor deposition using physical vapor deposition (PVD) or chemical vapor deposition (CVD). These vapor deposition methods may be selected appropriately depending on the vapor deposition material. For example, TiO ₂ may be formed of TiO ₂ layer by sputtering a target. The formation of the substrate adhesion layer 11 may be performed as necessary in consideration of the combination of the substrate 1 and the lower electrode film 2.

<Formation of lower electrode film>
Next, as shown in FIG. 2B, the lower electrode film 2 made of a material mainly composed of Cu is formed on the substrate adhesion layer 11. The lower electrode film 2 is produced by a normal thin film forming method, and a physical vapor deposition method such as a PVD method or a pulse laser vapor deposition method (PLD) can be used. PVD methods include resistance vapor deposition or vacuum deposition such as electron beam heating, DC sputtering, high frequency sputtering, magnetron sputtering, various sputtering methods such as ECR sputtering or ion beam sputtering, high frequency ion plating, activated vapor deposition, or arc. Illustrative examples include various ion plating methods such as ion plating, molecular beam epitaxy, laser ablation, ionized cluster beam deposition, and ion beam deposition. More specifically, for example, a Cu lower electrode is formed by DC sputtering using a Cu metal target at room temperature.

<Formation of adhesion layer made of Cu ₂ O>
Next, as shown in FIG. 2C, an adhesion layer 3 made of Cu ₂ O is formed on the lower electrode film 2 made of a material containing Cu as a main component. The adhesion layer 3 made of Cu ₂ O can be formed by adjusting a partial pressure of oxygen and applying a normal thin film forming method. However, the lower electrode film formed of a material mainly composed of Cu It is easier to form the outermost surface layer 2 by thermal oxidation. For example, the adhesion layer 3 made of Cu ₂ O is formed on the surface of the lower electrode film 2 under the condition of thermal oxidation at 200 ° C. for 5 minutes in an oxygen atmosphere. Note that the thickness of the adhesion layer 3 can be controlled by increasing the heating time.

<Formation of dielectric film>
Next, as shown in FIG. 2D, a dielectric film (for example, BST) 4 is formed on the adhesion layer 3. The dielectric film 4 is formed using a film coating technique such as a solution coating and firing method such as a sol-gel method or a MOD method (organometallic compound deposition method), a PVD method such as a sputtering method, or a CVD method. According to these film forming methods, when a perovskite ferroelectric such as BaTiO ₃ or PZT is taken as an example, a normal ceramic powder sintering method requires a high temperature process of 900 to 1000 ° C. or more, but 400 to 400 It can be formed at a low temperature of about 850 ° C. In order to suppress the oxidation of the lower electrode film 2, the film formation is performed in a reducing atmosphere in which Cu is not oxidized.

<Formation of adhesion layer made of Cu ₂ O>
Next, as shown in FIG. 2E, an adhesion layer 5 made of Cu ₂ O is formed on the dielectric film 4. The adhesion layer 5 can be formed, for example, by using a Cu metal target and forming a film by DC sputtering in an oxygen-argon atmosphere at a substrate temperature of 200 ° C. Thereby, Cu is oxidized and the adhesion layer 5 made of Cu ₂ O is formed. The film thickness of the adhesion layer 5 can be increased by increasing the film formation time by sputtering.

<Formation of upper electrode film>
Next, as shown in FIG. 2F, an upper electrode film 6 made of a material containing Cu as a main component is formed on the adhesion layer 5. The upper electrode film 6 is produced by a thin film forming method similar to that for the lower electrode film 2. That is, for example, the upper electrode film 16 can be formed by DC sputtering using a Cu metal target with an argon atmosphere and a substrate temperature of 200 ° C.

An annealing process may be performed after the upper electrode film 6 is formed. The annealing treatment may be performed at a temperature of pO ₂ = 20 to 100% and 400 to 1000 ° C. Further, a passivation layer (not shown) is formed as necessary. In addition, when forming each said layer, you may perform predetermined patterning using a photolithographic technique each time. Through the above process, the thin film capacitor 100 is obtained.

  By manufacturing the thin film capacitor 100 by the manufacturing method shown in FIG. 2, peeling between the dielectric film 4 and the two electrode films 2 and 6 was sufficiently prevented while sufficiently ensuring the conductivity of the electrode film. The thin film capacitor 100, that is, the highly reliable thin film capacitor 100 can be manufactured.

[Second Embodiment]
Next, a second embodiment of the thin film capacitor of the present invention will be described. FIG. 3 is a schematic cross-sectional view showing the thin film capacitor of the present embodiment. As shown in FIG. 3, in the thin film capacitor 400 of this embodiment, two dielectric films 4a and 4b are provided between the upper electrode film 6 and the lower electrode film 2, and between the dielectric films 4a and 4b. First, in that the electrode film 10 containing Cu is provided, the adhesion layers 7 and 9 made of Cu ₂ O are provided between the electrode film 10 and the dielectric films 4a and 4b, respectively, and the substrate adhesion layer 11 is omitted. Different from the thin film capacitor 100 of the embodiment.

Here, the dielectric layers 4 a and 4 b have the same configuration as that of the dielectric layer 4, and the adhesion layers 7 and 9 contain Cu ₂ O like the adhesion layers 3 and 5.

  The thin film capacitor 400 of the present embodiment also prevents peeling between the dielectric film 4a and the upper electrode film 6 and peeling between the dielectric film 4b and the lower electrode film 2, as well as the electrode film 10. And the dielectric film 4a and the separation between the electrode film 10 and the dielectric film 4b are sufficiently prevented. For this reason, according to the thin film capacitor 400, even when Cu is used for the electrode film, the separation between the dielectric film 4a and the lower electrode film 2 while ensuring sufficient conductivity of the electrode film, Peeling between the dielectric film 4b and the upper electrode film 6 and peeling between the dielectric films 4a and 4b and the electrode film 10 are sufficiently prevented. For this reason, high reliability can be realized.

  The present invention is not limited to the above embodiment. For example, in the first embodiment, the adhesion layers 3 and 5 are provided on both sides of the dielectric film 4, but when the upper electrode film 6 does not contain Cu, as shown in FIG. The adhesion layer 5 may be omitted. When the lower electrode film 2 does not contain Cu, the adhesion layer 3 may be omitted as shown in FIG. 4A and 4B, the substrate adhesion tank 11 is omitted.

In the second embodiment, two dielectric films 4a and 4b are provided between the upper electrode film 6 and the lower electrode film 2, but three or more dielectric films containing oxide are provided. An electrode film containing Cu may be provided between the dielectric films. In this case, an adhesion layer containing Cu ₂ O may be provided between the electrode film containing Cu and the dielectric film. Even in this case, similarly to the thin film capacitor 400 according to the second embodiment, in addition to realizing high reliability, it is possible to realize large capacity.

  Next, the present invention will be described more specifically with reference to examples, but the present invention is not limited to the following examples.

Example 1
First, a thin film capacitor was manufactured according to the manufacturing method shown in FIG. First, the surface of the silicon single crystal substrate in the substrate forming the SiO ₂ layer by thermal oxidation to form a TiO ₂ layer by sputtering of TiO ₂ as a target. The substrate temperature was room temperature and the film was formed in an oxygen atmosphere. The film thickness of the TiO ₂ layer was 20 nm.

Next, a Cu lower electrode film was formed on the TiO ₂ layer. That is, a Cu lower electrode film was formed by DC sputtering using a Cu metal target at room temperature. The film thickness of the Cu lower electrode film was 200 nm.

Next, an adhesion layer made of Cu ₂ O was formed on the Cu lower electrode film. That is, an adhesion layer made of Cu ₂ O was formed on the surface of the Cu lower electrode film by using thermal oxidation conditions at 200 ° C. for 5 minutes in an oxygen atmosphere. In this case, the thickness of the Cu ₂ O adhesive layer was 2 nm. As a result, the thickness of the Cu lower electrode film became 198 nm.

Next, a BST thin film was formed on the Cu ₂ O adhesion layer. A BST thin film (composition formula (Sr _0.6 Ba _0.4 ) TiO ₃ ) having a film thickness of 150 nm was obtained by sputtering using a BST target at a substrate temperature of 200 ° C. in an argon atmosphere.

  At this time, since the BST thin film was formed in an argon atmosphere, the Cu lower electrode film was not oxidized by the formation of the BST thin film.

Next, a Cu ₂ O adhesion layer was formed on the BST thin film. The Cu ₂ O adhesion layer was formed by DC sputtering using a Cu metal target at a substrate temperature of 200 ° C. in an oxygen-argon atmosphere. The film thickness was 5 nm. Next, a Cu upper electrode film was formed on the surface of the Cu ₂ O adhesion layer. That is, a Cu upper electrode film was formed by DC sputtering using a Cu metal target with an argon atmosphere and a substrate temperature of 200 ° C. The film thickness was 200 nm. The Cu upper electrode film was a circular electrode film having a diameter of 100 μm. Through the above steps, a thin film capacitor was obtained on the substrate.

(Example 2)
Except that the thickness of the _two Cu ₂ O adhesion layers was 10 nm by forming two Cu ₂ O adhesion layers in an oxygen atmosphere under thermal oxidation conditions at 200 ° C. for 10 minutes, the same as in Example 1. Thus, a thin film capacitor was obtained on the substrate.

(Comparative Example 1)
A thin film capacitor was obtained on the substrate in the same manner as in Example 1 except that the Cu ₂ O adhesion layer was not provided between the lower electrode film and the dielectric film and between the dielectric film and the upper electrode film. It was.

(Example 3)
Two of Cu 2 _O adhesion layer in an oxygen atmosphere, is in the same manner as in Example 1 except that a 20nm thickness of two Cu 2 _O adhesion layer by forming a thermal oxidation conditions 200 ° C. 20 min Thus, a thin film capacitor was obtained on the substrate.

(Comparative Example 2)
A thin film capacitor was obtained on the substrate in the same manner as in Example 1 except that a TiO ₂ adhesion layer was provided between the lower electrode film and the dielectric layer. The TiO ₂ adhesion layer was formed by a sputtering method using a TiO ₂ target. The thickness of the TiO ₂ adhesion layer was 10 nm.

(Evaluation)
For Examples 1 and 2 and Comparative Examples 1 and 2, the relative dielectric constant k (100 kHz), tan δ (%), leakage characteristics (100 kV / cm voltage applied) and peel strength (N / cm ² ) were measured. . The relative dielectric constant of the thin film capacitor is determined by using an impedance analyzer (manufactured by Hewlett Packard, model: HP4194A) under conditions of room temperature and frequency of 100 kHz (AC 1 V), and the electrode dimensions of the thin film capacitor, And it computed from the distance between electrodes of a thin film capacitor. Further, the leak characteristics were measured using a semiconductor parameter analyzer (manufactured by Agilent Technologies, model: 4156C) under the conditions of room temperature and electrolytic strength of 100 kV / cm. As shown in FIG. 5, the peel strength was obtained by bonding the sample S on the sample stage 20 with a tape, and further bonding the upper surface of the sample S with the bottom surface of the prismatic metal jig 21 with the tape 22. The peel strength was measured by testing this with a tensile tester (manufactured by Aiko Engineering) using the load cell 23. The results are shown in Table 1. The sample S is a thin film capacitor provided on a substrate, and the upper surface of the sample S is the surface of the upper electrode film.

From the results shown in Table 1, in Examples 1-2, the peel strength is 1.9 times or more compared to Comparative Examples 1-2, and the electrode film and the dielectric film are firmly adhered. I understood that. The Examples 1-2 also electrode film eventually has become a Cu, since the adhesion layer made of Cu 2 _O is provided separately, is considered the conductivity of the electrode film is sufficiently secured.

  As described above, according to the present invention, even when inexpensive Cu is used as an electrode, it is possible to sufficiently prevent peeling between the electrode film and the dielectric film while sufficiently ensuring the conductivity of the electrode film, It was confirmed that high reliability of the capacitor could be realized.

It is a schematic sectional drawing which shows one Embodiment of the thin film capacitor which concerns on this invention. It is a figure which shows a series of manufacturing processes of the thin film capacitor of FIG. It is a schematic sectional drawing which shows other embodiment of the thin film capacitor which concerns on this invention. Furthermore a diagram illustrating another embodiment, (a) shows the embodiment which is provided only on the Cu 2 _O adhesion layer between the lower electrode film and the dielectric film of the thin film capacitor according to the present invention, (b) the upper electrode A mode in which a Cu ₂ O adhesion layer is provided only between the film and the dielectric film is shown. It is a conceptual diagram which shows the method of the peeling strength measurement test using a load cell.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Substrate 2 Lower electrode film 3, 5, 7, 9 Adhesion layer 4, 4a, 4b Dielectric film 6 Upper electrode film 10 Electrode film 11 Substrate adhesion layer 100, 200 Thin film capacitor

Claims (7)

In a thin film capacitor provided on a substrate and having a pair of electrode films and a dielectric film provided between the pair of electrode films,
At least one of the pair of electrode films is a Cu electrode film containing Cu,
An adhesion layer containing Cu ₂ O is provided between the Cu electrode film and the dielectric film,
A thin film capacitor, wherein the dielectric film is an oxide dielectric film.   2. The thickness of the Cu electrode film is 50 nm to 1 μm, and the average value of the thickness of the adhesion layer is more than 0% and less than 10% with respect to the thickness of the Cu electrode film. The thin film capacitor described.   The thin film capacitor according to claim 1, wherein the dielectric film has a thickness of 5.0 nm to 1 μm.   The thin film capacitor according to any one of claims 1 to 3, wherein both of the pair of electrode films are the Cu electrode films.   The dielectric film has two or more layers between the pair of electrode films, the Cu electrode film is between the dielectric films, and the Cu electrode film and the dielectric film The thin film capacitor according to claim 1, further comprising an adhesion layer. In a method for manufacturing a thin film capacitor element provided on a substrate and having a pair of electrode films and a dielectric film provided between the pair of electrode films,
Forming one of the pair of electrode films on the substrate;
Forming the dielectric film;
Forming the other electrode film of the pair of electrode films on the dielectric film,
At least one of the pair of electrode films is a Cu electrode film containing Cu,
A method of manufacturing a thin film capacitor, comprising a step of forming an adhesion layer containing Cu ₂ O between the Cu electrode film and the dielectric film. 7. The method of manufacturing a thin film capacitor according to claim 6, wherein both of the pair of electrode films are the Cu electrode films.

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