JPH11214245A - Thin film monolithic capacitor and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thin film monolithic capacitor having a good dielectric property and less changes of characteristics with the elapse of time, and a method for manufacturing such a thin film monolithic capacitor. SOLUTION: A thin film monolithic capacitor 10 includes a board 12. On the board 12, a thin film dielectric layer 14, an electrode layer 16, and an outer electrode 18 connected to the electrode layer 16 are formed. A protective film 20 is formed at a part corresponding to the part where the dielectric layer 14 is formed. To produce this thin film monolithic capacitor 10, the thin film dielectric layer 14, the electrode layer 16 and the outer electrode 18 are formed on the board 12 by a CVD method or the like. The multilayer body thus obtained is heat-treated under the partial pressure of oxygen. After that, the protective film 20 is formed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thin-film multilayer capacitor and a method of manufacturing the same, and more particularly to, for example, a small-sized and relatively large-capacity thin-film multilayer capacitor and a method of manufacturing the same.

[0002]

2. Description of the Related Art In recent years, in the field of electronic components, further miniaturization and higher performance of capacitors and the like have been desired with the increase in circuit density. As such a small high-performance capacitor, for example, there is a multilayer ceramic capacitor. To manufacture multilayer ceramic capacitors,
First, an electrode paste is printed on a ceramic green sheet cut to a predetermined size, dried, and then a plurality of ceramic green sheets are stacked. After the laminated ceramic green sheets are pressed, they are further cut into a predetermined size and fired to obtain a fired body. An external electrode paste is applied to the fired body and baked to form a multilayer ceramic capacitor.

However, when a multilayer ceramic capacitor is manufactured by such a method, it is impossible to make the dielectric layer thinner than the ceramic raw material powder. At present, it is difficult to produce a dielectric layer having a thickness of 3 μm or less. For this reason, there has been a limit in reducing the size and increasing the capacity of the multilayer ceramic capacitor.

In order to solve such a problem, Japanese Patent Application Laid-Open No. Sho 56-144523 discloses a method of manufacturing a multilayer ceramic capacitor in which a dielectric layer is formed by sputtering. Here, Al ₂ O ₃ , SiO _2
2 , a method of forming a thin film and an electrode of TiO ₂ and BaTiO ₃ by sputtering is disclosed.

However, Al ₂ O ₃ , SiO ₂ , T
Since the material itself has a low dielectric constant such as iO ₂ , it is necessary to make the film very thin in order to increase the capacitance as a capacitor, and there is a problem in the reliability as an electronic device such as leakage current and dielectric strength. Come out. On the other hand, in addition to BaTiO ₃ , SrTiO ₃ , (Ba, S
r) TiO ₃ , PbTiO ₃ , Pb (Zr, Ti)
Dielectrics such as O ₃ and Pb (Mg, Nb) O ₃ have a high dielectric constant as a material, but if it is desired to obtain a high dielectric constant in a thin film state, it is necessary to improve the crystallinity of the thin film by high-temperature deposition. There is.

[0006]

SUMMARY OF THE INVENTION However, CVD
In the case of forming an oxide dielectric layer under reduced pressure, such as a method or sputtering, when an oxide dielectric layer and an electrode layer are alternately formed to produce a multilayer capacitor, the number of stacked layers increases, The phenomenon that the dielectric loss tangent tan δ becomes abnormally large appears. This phenomenon does not appear remarkably when the number of dielectric layers of the multilayer capacitor is small.

[0007] As a result of analyzing such a thin film laminate, an increase in oxygen deficiency was observed in the lower layer formed in the initial stage. This is because, when a thin film laminate is manufactured by the above-described method, oxygen or an oxidizing agent is supplied to the film formation surface during dielectric film formation, but the already formed oxide dielectric layer has a low oxygen content. Since it was exposed to high temperature under pressure, it is considered that oxygen desorption occurred. As a result, it is considered that the abundance of OH groups and the like in the lower layer increases, and tan δ increases.

Further, the thin film laminate produced by these methods easily adsorbs moisture in the air, and its dielectric properties are greatly different between those measured in the air and those measured in a reduced pressure. When measured, tan δ increases. Furthermore, due to the adsorption of moisture, its dielectric properties change with time in the atmosphere.

SUMMARY OF THE INVENTION Therefore, a main object of the present invention is to provide a thin film multilayer capacitor having good dielectric characteristics and little change in characteristics over time. Another object of the present invention is to provide a method of manufacturing a thin film multilayer capacitor having good dielectric characteristics and little change in characteristics over time.

[0010]

According to the present invention, there is provided a thin-film multilayer capacitor in which an oxide dielectric thin film layer and an electrode layer are stacked, having a protective film for shielding the oxide dielectric thin film layer from the outside. Characteristic is a thin film multilayer capacitor. Specifically, the substrate includes a laminate of an oxide dielectric thin film layer and an electrode layer formed on the surface of the substrate, and external electrodes connected to the electrode layers formed at both ends of the laminate. Characterized in that the oxide dielectric thin film layer exposed to the outside is covered with a protective film. Further, the present invention provides a method for manufacturing a thin film multilayer capacitor including a laminate of at least two or more oxide dielectric thin film layers and an electrode layer, wherein at least a final oxide dielectric thin film layer is formed, A method for manufacturing a thin film multilayer capacitor, comprising performing heat treatment in an oxygen partial pressure higher than the oxygen partial pressure at the time of forming an oxide dielectric thin film layer. Further, after the heat treatment, a protective film for blocking the oxide dielectric thin film layer from the outside may be formed.

The presence of the protective film for shielding the oxide dielectric thin film layer from the outside prevents moisture in the air from being adsorbed, thereby reducing the influence of the moisture in the air. In particular, in the case of a thin film multilayer capacitor in which the oxide dielectric thin film layer is exposed to the outside, the influence of moisture in the air can be reduced by covering the outermost oxide dielectric thin film layer with a protective film. Further, when producing a thin film laminated capacitor, after forming a thin film laminated body, by performing a heat treatment under a high oxygen partial pressure, oxygen deficiency in a lower layer can be reduced.

The above objects, other objects, features and advantages of the present invention will become more apparent from the following detailed description of embodiments with reference to the drawings.

[0013]

FIG. 1 is an illustrative view showing one example of a thin film multilayer capacitor of the present invention. The thin-film multilayer capacitor 10 includes a substrate 12. On the substrate 12, a plurality of thin film dielectric layers 14 and electrode layers 16 are alternately laminated to form a laminate. As the thin film dielectric layer 14, for example, an oxide dielectric thin film layer such as (Ba, Sr) TiO ₃ is used. Then, the laminated electrode layers 16 are alternately drawn out to both ends in the width direction of the substrate 12 and connected to two external electrodes 18. Further, a protective film 20 is formed so as to cover the portion where the thin film dielectric layer 14 is formed.

In order to manufacture such a thin-film multilayer capacitor 10, thin-film dielectric layers 14 and electrode layers 16 are alternately formed on a substrate 12 by, for example, a CVD method. At this time, the external electrodes 18 are formed by sequentially laminating the electrode layers on both ends in the width direction of the substrate 12. The laminate thus obtained is heat-treated in a high oxygen partial pressure. Then, a protective film 20 is formed corresponding to the portion where the thin film dielectric layer 14 is formed.

In the thin-film multilayer capacitor 10, since the protective film 20 is formed, moisture in the air is not adsorbed on the thin-film dielectric layer 14, so that deterioration of the dielectric characteristics due to the moisture can be prevented. Further, since the adsorption of moisture is suppressed, it is possible to suppress a change with time of the dielectric characteristics during use of the thin film multilayer capacitor 10. Further, during the manufacturing, after all the thin film dielectric layers 14 are formed, by performing a heat treatment at a high oxygen partial pressure, oxygen vacancies generated in the thin film dielectric layers 14 during film formation can be reduced.
Therefore, it is possible to prevent the deterioration of the dielectric characteristics due to such oxygen deficiency.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG.
FIG. 2 is an illustrative view showing an OCVD apparatus. MOCVD equipment 30
Includes a plurality of raw material vaporizers 32a, 32b, 32c.
The raw material vaporizer 32a stores a substance that is a raw material of a thin film dielectric layer to be manufactured. Ar gas as a carrier gas is introduced into the raw material vaporizer 32a via a valve 36 and a mass flow controller (MFC) 34 for controlling the flow rate of the carrier gas. In addition, the raw material vaporizer 3
A control valve 38 for controlling the flow rate is attached to the discharge side of 2a. Further, a bypass valve 40 is provided between the control valve 38 and the valve 36. A pressure gauge 42 is attached to the primary side of the valve 36.

The raw material vaporizer 32b has an MFC 44
And Ar via the valve 46 as a carrier gas.
Gas is introduced. Further, a pressure gauge 48 and a control valve 50 for controlling a flow rate are attached to the discharge side of the raw material vaporizer 32b. A bypass valve 52 is provided between the control valve 50 and the valve 46.
Ar gas as a carrier gas is introduced into the raw material vaporizer 32c via the MFC 54 and the valve 56. Further, a control valve 58 for controlling the flow rate is attached to the discharge side of the raw material vaporizer 32c. Then, a bypass valve 60 is attached between the control valve 58 and the valve 56. A pressure gauge 62 is attached to the primary side of the valve 56.

The control valves 38, 50, 58 are connected to a mixer 64 for mixing the source gas. Mixer 64
Is connected via a valve 66 to a gas nozzle 70 attached to a film forming chamber 68. Further, O ₂ gas as an oxidizing gas is supplied to the gas nozzle 70 via the MFC 72 and the valve 74. Film forming chamber 68
Is connected to a mechanical booster pump 78 and a rotary pump 80 via a control valve 76. Also,
A bypass valve 82 is attached between the mixer 64 and the mechanical booster pump 78. Further, a pressure gauge 84 is attached to the film forming chamber 68,
The pressure in the film forming chamber 68 is controlled.

A portion surrounded by a dotted line between the raw material vaporizers 32a to 32c and the film forming chamber 68 is heated to vaporize the raw material. That is, the raw material vaporizers 32a to 32a
By introducing Ar gas while heating 2c,
Raw materials can be vaporized. At this time, when the raw material is solid, it can be vaporized by blowing Ar gas on the raw material surface, and when the raw material is liquid, it can be vaporized by blowing Ar gas into the raw material and bubbling. .

The raw material gas obtained by vaporizing the raw material is mixed in a mixer 64 and supplied to a gas nozzle 70. Then, from the gas nozzle 70, the source gas and the O ₂ gas are blown onto the substrate 90 placed in the film forming chamber 68. The inside of the film forming chamber 68 is set at a predetermined temperature, and is set at a predetermined pressure by a mechanical booster pump 78 and a rotary pump 80.
Then, the raw material gas and the O ₂ gas are brought into contact with the substrate 90 in the film forming chamber 68, and the raw material gas undergoes thermal decomposition or combustion reaction, and a dielectric thin film or the like is formed on the substrate 90.

Using this MOCVD apparatus 30, a (Ba, Sr) TiO ₃ thin film (BST thin film) was formed as a dielectric layer. The film forming conditions are as shown in Table 1. That is, Ba (DPM) ₂ (phen) ₂ is used as a Ba raw material, and Sr (DPM) ₂ (phen) is used as a Sr raw material.
₂ and Ti (OiC ₃ H ₇ ) as a Ti raw material
₄ was used to generate the source gas. Where DPM
Is dipivaloylmethane C ₁₁ H ₁₉ O ₂ (2,2,6,6
-Tetramethyl-3,5-heptanedione), and phen is an abbreviation for phenanthroline. The Ba raw material is vaporized at 215 ° C., the Sr raw material is vaporized at 200 ° C., and the Ti raw material is vaporized at 3 ° C.
Vaporized at 5 ° C. Further, the temperature of the mixer 64 is set to 250 ° C.
The temperature in the film forming chamber 68 was set to 650 ° C., and the pressure was set to 667 Pa.

[0022]

[Table 1]

Before forming the BST thin film, a Pt film was formed on the substrate 90. As the substrate 90, 1.0 × 1.0
As shown in FIG. 3, a P-shaped pattern 92 is formed on one side of the substrate 90 in the width direction.
A t film was formed. The Pt film was produced using an RF sputtering apparatus under the film forming conditions shown in Table 2. The time for forming the Pt film is 120 seconds, and the thickness is about 200 nm.

[0024]

[Table 2]

Next, under the conditions shown in Table 1, a BST thin film was formed at the center of the substrate 90 in a rectangular pattern 94 shown in FIG. The film formation time is 120 minutes and the film thickness is 300
nm. Further, in order to absorb the thickness of the formed BST thin film, a Pt film was formed on one side and the other side in the width direction of the substrate 90 with the pattern 96 shown in FIG. P
The film forming conditions of the t film are as shown in Table 2, the film forming time is 180 seconds, and the film thickness is 300 nm, which is the same as the BST thin film. Further, on the other side in the width direction of the substrate 90, FIG.
A Pt film was formed in a “convex” pattern 98 as shown in FIG. The film forming conditions are as shown in Table 2, the film forming time is 120 seconds, and the film thickness is 200 nm. Therefore, B
The ST thin film is composed of the Pt film of the pattern 92 and the Pt film of the pattern 98.
t film.

As described above, a Pt film and a BST thin film were alternately formed to produce a thin film laminate. In this thin film laminate, the order of film formation on the substrate 90 is as follows.
BST thin film of pattern 94, Pt film of pattern 96, Pt film of pattern 98, BST thin film of pattern 94 ...
The pattern 94 becomes the BST thin film and the pattern 96 becomes the Pt film, and the last is either the pattern 92 Pt film or the pattern 98 Pt film. That is, the BS of pattern 94
On both surfaces of the T thin film, a Pt film of a pattern 92 drawn to one side in the width direction of the substrate 90 and a Pt film of a pattern 98 drawn to the other side in the width direction of the substrate 90 are formed.
The dimension of the overlapping portion between the pattern 92 and the pattern 98 is 0.4 × 0.4 mm.

Thus, 120 thin film laminates having 12 BST thin films were produced. Next, forty of each of the prepared thin film laminates were subjected to (1) 1
Heat treatment was performed at 3.3 kPa at 650 ° C. for 20 hours, and (2) in air at 650 ° C. for 20 hours.
For the thin film laminate subjected to the heat treatment (1) and the heat treatment (2) and the thin film laminate not subjected to the heat treatment,
The capacitance and the dielectric loss tangent (tan δ) were measured at 1 kHz in the air and under a reduced pressure of 4 Pa. And
Table 3 shows the average value of the capacitance and tan δ and the short-circuit rate.

[0028]

[Table 3]

As can be seen from Table 3, the properties measured in the air were subjected to a heat treatment to obtain ta.
Both nδ and the short-circuit rate decreased significantly. This is because oxygen is desorbed from the previously formed BST thin film during formation of a plurality of thin film dielectric layers and Pt layers because the oxygen partial pressure is low in the film forming chamber 68, and tan δ and short circuit rate are reduced. It is thought that it will decrease. On the other hand, it is considered that by performing the heat treatment under a high oxygen partial pressure, oxygen vacancies in the previously formed BST thin film are reduced, and tan δ and short-circuit rate are improved.

When the characteristics are measured under reduced pressure, both the capacitance and tan δ are lower than those measured in the air. The one that has been heat treated is 1
The value of tan δ was reduced to a practically acceptable level of about 2%. This is presumably because, when measured in the atmosphere, moisture in the atmosphere is adsorbed on the BST thin film, whereas the effect of moisture is small under reduced pressure.

Further, heat treatment (1) and heat treatment (2)
A silicon oxide film was formed as a protective film with a pattern 100 shown in FIG. The protective film was formed so as to cover the BST thin film. The film forming conditions at this time are as shown in Table 4.

[0032]

[Table 4]

For the sample on which the protective film was formed,
At kHz, the capacitance and tan δ were measured.
Table 5 shows the average values of the measured capacitance and tan δ, and the short-circuit rate.

[0034]

[Table 5]

In the sample on which the protective film was formed, a value almost equal to the measurement result of the sample on which the protective film was not formed under reduced pressure was obtained. This is considered to be due to the fact that the effect of moisture in the atmosphere was eliminated by the protective film, and the same effect as that obtained by measuring the characteristics under reduced pressure was obtained. Therefore, a thin-film multilayer capacitor having a very high capacitance per unit volume and low loss can be obtained by forming a thin-film laminate, heat-treating it under a high oxygen partial pressure, and further forming a protective film. .

In the above example, the oxygen partial pressure is 13.3 k.
Although heat treatment was performed in Pa and the atmosphere (oxygen partial pressure: about 21.3 kPa), the present invention is not limited to this. For example, heat treatment in oxygen (oxygen partial pressure: 101 kPa) is effective. Needless to say,

Further, in the above example, the heat treatment is performed after all the oxide dielectric layers are formed. However, the present invention is not limited to this. For example, each oxide dielectric layer may be formed. It has been confirmed that the same effect can be obtained by performing the heat treatment after forming the uppermost oxide dielectric layer even if the heat treatment is performed each time the film is formed.

[0038]

According to the present invention, it is possible to obtain a thin-film multilayer capacitor which is not affected by moisture in the atmosphere and has little deterioration of characteristics and little change with time. Furthermore, by using the manufacturing method of the present invention, a dielectric thin film having a high capacitance can be formed, so that a small-sized and high-performance thin film multilayer capacitor can be manufactured. Moreover, since the obtained thin film laminate has low tan δ and short ratio,
A highly reliable thin-film multilayer capacitor can be obtained.

[Brief description of the drawings]

FIG. 1 is an illustrative view showing one example of a thin-film multilayer capacitor of the present invention;

FIG. 2 is an illustrative view showing an MOCVD apparatus for manufacturing a thin film multilayer capacitor using the method for manufacturing a thin film multilayer capacitor of the present invention.

FIG. 3 is a plan view showing a pattern of a Pt film formed on a substrate.

FIG. 4 is a view showing B formed on a Pt film having the pattern shown in FIG. 3;
It is a top view which shows the pattern of ST thin film.

FIG. 5 is a plan view showing a pattern of a Pt film formed to absorb the thickness of the BST thin film having the pattern shown in FIG. 4;

6 is a plan view showing a pattern of a Pt film formed on the BST thin film having the pattern shown in FIG. 4;

FIG. 7 is a plan view showing a pattern of a protective film for protecting the BST thin film.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Thin film laminated capacitor 12 Substrate 14 Thin film dielectric layer 16 Electrode layer 18 External electrode 20 Protective film 30 MOCVD apparatus 32a-32c Raw material vaporizer 64 Mixer 68 Film formation chamber 78 Mechanical booster pump 80 Rotary pump 90 Substrate

Claims (4)

[Claims] 1. A thin-film multilayer capacitor in which an oxide dielectric thin-film layer and an electrode layer are stacked, comprising a protective film for shutting off the oxide dielectric thin-film layer from the outside. . 2. A semiconductor device comprising: a substrate; a laminate of an oxide dielectric thin film layer and an electrode layer formed on the surface of the substrate; and external electrodes connected to the electrode layers formed at both ends of the laminate. A thin-film multilayer capacitor characterized in that an oxide dielectric thin-film layer exposed to the outside is covered with a protective film. 3. A method for manufacturing a thin film multilayer capacitor including a laminate of at least two or more oxide dielectric thin film layers and an electrode layer, wherein at least a final oxide dielectric thin film layer is formed. A method for producing a thin film multilayer capacitor, comprising performing heat treatment in an oxygen partial pressure higher than the oxygen partial pressure at the time of forming an oxide dielectric thin film layer. 4. The method according to claim 3, wherein after performing the heat treatment, a protective film for blocking the oxide dielectric thin film layer from the outside is formed.