JPS5935169B2 - capacitor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to improvements in capacitors that use tantalum oxide films as dielectrics.

Conventionally, capacitors using tantalum oxide films as dielectrics have been widely used.

Tantalum oxide films are physically and chemically more stable than aluminum oxide or other dielectrics. Therefore, the obtained capacitor is also smaller and exhibits superior characteristics compared to other capacitors. However, even though tantalum oxide film capacitors exhibit such excellent characteristics, in order to keep up with the rapid technological progress of recent years, there is a strong desire for the emergence of a capacitor that can exhibit characteristics superior to those currently available. The present invention was made in view of these circumstances, and its purpose is to maximize the characteristics of tantalum oxide film and exhibit characteristics superior to existing tantalum oxide film capacitors in all respects. The objective is to provide a capacitor that can

Hereinafter, details of the present invention will be explained with reference to illustrated embodiments.
In FIG. 1, 1 is a substrate made of glass, silicon, sapphire, alumina, etc.
An arsenic tantalum film 2 having a predetermined thickness is provided on the upper surface of the anode.

The arsenic content of the arsenic tantalum film 2 is 0.8 to 3.
．． It is 0% by weight. Therefore, the arsenic tantalum film 2
An arsenic-containing tantalum oxide film 3 serving as a dielectric is formed on the upper surface. The arsenic content of the arsenic-containing tantalum oxide film 3 is also uniformly contained in the range of 0.8 to 3.0% by weight. A metal film 4 made of nichrome alloy, aluminum, tantalum, etc. is provided on the upper surface of the arsenic tantalum oxide film 3 as a cathode, and this metal film 4 and the arsenic tantalum film 2 can be used as electrodes. It is becoming available. Note that 5 in the figure indicates an insulator. Since the arsenic tantalum oxide film 3 containing 0.8 to 3.0% by weight of arsenic is used as a dielectric material, as shown in the experimental results described later, a simple tantalum oxide film or a phosphorous-doped tantalum oxide film Compared to the dielectric, the capacitance is 615 to 915 times, the width δ is 1/4 to 1/2, the equivalent series resistance is 1/25 to 2/15, and the withstand voltage is 2 to 2. A three-fold improved capacitor is obtained.

FIG. 2 shows another embodiment of the present invention, in which the same parts as in FIG. 1 are designated by the same reference numerals.

Therefore, the explanation of the overlapping parts will be omitted. In this embodiment, a lead dioxide film T is interposed between a graphite film 6 and an arsenic-containing tantalum oxide film 3 instead of the metal layer film 1 shown in FIG. 1, which serves as the cathode side electrode. . Even with this configuration, the same effects as in the above embodiment can be expected. Incidentally, in manufacturing such a capacitor, it is effective to adopt the following means.

That is, an arsenic-containing tantalum film is formed on the substrate surface by reactive sputtering of tantalum in an arsenic or arsine atmosphere. The arsenic-containing tantalum film formed by this sputtering contains arsenic in a uniform distribution state. Next, the surface of the arsenic-containing tantalum oxide film may be oxidized by an oxidizing means such as anodic oxidation to form an arsenic-containing tantalum oxide film of a predetermined thickness, and this arsenic-containing tantalum oxide film may be used as a dielectric. . The precautions and conditions for the above-mentioned series of manufacturing processes are listed below. [A] Sputtering process (1) Substrate material: borosilicate glass, sapphire, silicon, gold, quartz,
Silicon carbide, alumina, aluminum nitride ceramic ivy, glass, metal polyimide polymer film, etc. can be used.

(2) Atmosphere (a) Arsenic, arsine or a mixed gas atmosphere thereof,
(b) A mixed gas atmosphere of noble gases such as argon and neon containing arsenic or arsine, (c) Nitrogen, oxygen, acid ratio nitrogen, sulfuric acid gas, ammonia, etc. containing arsenic or arsine,
Tantalum metal is reactively sputtered onto the surface of the substrate in either a mixed gas atmosphere consisting of water vapor and hydrogen.

At this time, the partial pressure of arsenic or arsine is 10-9 to 10-
3t0rr, preferably 10-6 to 10-4t0rr. If other gases are included, the partial pressure of these gases should be approximately 10-7 to 10-1t0rr, preferably 10
-5 to 10-1t0rr. (3) Cathode voltage -7000V to -2000V1 preferably -6000V
~-3000V.

J(4) Anode voltage -500V to 300V, preferably -200 to 200V.

(5) Cathode current density varies depending on the type of substrate and surface condition, but JO. Ol
~50mA/Cft. Preferably 0.1-1.0mA/
Let it be CTl.

(6) Substrate temperature The temperature is 200 to 1000°C, preferably 300 to 600°C, although it is affected by the type and surface condition of the substrate.

(7) Annealing at 400-600℃ after sputtering for 20-200℃
Hold for a minute.

[B] Oxide film formation process (anodic oxidation) (1) Chemical liquid water, ammonia sulfite, ethylene glycol, acetonitrile, ethylene carbonate, dimethylforiaside, dimethylsulfone, ethyneanaside, hexamethylphosphoroacide, diethyl sulfate, methylpyrrolidone , mineral acids such as sulfuric acid, phosphoric acid, and their salts (sodium, magnesium, nickel, tin zinc, chromium, aluminum, cerium, thorium, ammonium, ethylene diammonium, guadinium, tetraphenyl arsonium) in solvents such as glacial acetic acid, etc. , pyridinium, etc.) or acetic acid, citric acid, acrylic acid, benzenesulfonic acid, phenolicyanuric acid, phenylphosphonic acid, salicylic acid,
Organic acids and their salts such as ethyl phosphoric acid, tetrafluoroboric acid, or tetrafluoroboric acid, perchloric acid,
In an electrolyte solution obtained by dissolving an electrolyte such as inorganic acids and their salts such as iolic acid, chromic acid, selenic acid, aluminic acid, permanganic acid, tetraboric acid, tetrathionic acid, or potassium nitrate, sodium nitrate, bisulfuric acid. It is immersed in a molten salt solution of lithium, tetraethylammonium benzoate, ammonium phosphite dihydrate, ammonium formate, etc. together with a counter electrode made of platinum, tantalum, gold, or stainless steel.
Chemical formation is performed using the counter electrode as a cathode and the arsenic tantalum film as an anode.

(2) Temperature -11 to 300°C, preferably 50 to 120°C.

(3) Chemical current density 100μ~500mAA preferably 500 μ to 10 mA//Cll.

(4) Aging time Aging is carried out at a voltage of x (0.7 to 1.0) for 30 to 400 minutes, preferably 100 to 200 minutes.

(5) Annealing treatment After aging, wash with water and store in oxygen or air atmosphere for 20 minutes.
20 under the conditions of 0~350℃, 100~800t0rr
Heat treatment for ~100 minutes improves the electrical characteristics of the finished capacitor.

After obtaining this process, aluminum, tantalum, nichrome alloy, gold, nickel,
A metal film for an electrode is formed by vapor depositing or sputtering tin, silver, indium, graphite, and a tin-lead alloy.

Note that a semiconductor layer of manganese dioxide, lead dioxide, silver oxide, nickel sesquioxide, thallium sesquioxide, aluminum phosphide, cadmium sulfide, or the like may be interposed between the arsenic-containing tantalum oxide film and the metal film for the electrode. . As the metal film for the electrode, a paste in which metal powder is dispersed may be applied and dried. Next, an experimental example of a capacitor formed in accordance with the gist of the present invention will be described.

Experimental example 1 Aluminoborosilicate glass was used as a substrate. After leaving 0.5 d of the slide surface of this substrate and masking the other parts with resist, it was placed in a sputtering device, the inside of the device was replaced with an argon atmosphere, and then a trace amount of Arsine gas was injected.

Maintain arsine gas partial pressure at 1 x 10-3t0rr, cathode voltage -6000V1 anode voltage -200V1 cathode current density 0
．． 1mA/Cllt. Under sputtering conditions with a substrate temperature of 300°C, tantalum was reactively sputtered onto the substrate surface.
After forming an arsenic-containing tantalum film with a thickness of 000λ, the atmosphere was changed to an argon atmosphere of 1 × 10 -4 t0rr, and then the substrate temperature was raised to 400°C and held for 200 minutes to anneal the arsenic-containing tantalum film. . After cooling the substrate slowly, it was taken out from the apparatus and immersed in an aqueous sodium hydroxide solution at room temperature to remove the resist. Next, the substrate was immersed in a 1X10-2M citric acid aqueous solution at 50°C, and a direct current was applied to it for 50 minutes using the arsenic tantalum film as an anode and the platinum counter electrode as a cathode.
00μAA? was applied at a constant current density of , and chemical conversion was performed until the potential difference between the two electrodes reached 100V. Potential difference is 100V
After this potential difference was reached, this potential difference was maintained for 100 minutes for aging treatment. The thickness of the arsenic-containing tantalum oxide film after the machining treatment was 1,900 mm. After aging, the substrate was thoroughly washed with distilled water, then transferred to a deposition apparatus and subjected to 5x
The nichrome alloy was preheated to 200° C. in an argon atmosphere of 10 −4 t0rr and evaporated at 1350° C., and then deposited on the tantalum oxide film to form a 2000λ thick nichrome alloy layer, which was used as a cathode. Then, lead wires were attached to the cathode and the tantalum metal part to form a capacitor as shown in FIG. Reference experiment example 1 Using the same substrate as that used in experiment example 1, 1X1
After sputtering tantalum on the substrate surface under the same conditions as in Experimental Example 1 in an argon atmosphere of 0-3t0rr to form an arsenic-free tantalum film, 8X10-3 at 50°C
A tantalum oxide film was formed on the surface of the tantalum film by immersing it in M phosphoric acid under the same chemical formation and aging conditions as in Experimental Example 1, and then a nichrome alloy electrode was attached in the same manner to form a capacitor.

As a result of analyzing the two types of capacitors obtained in Experimental Example 1 and Reference Experimental Example 1 in this way, it was found that the dielectric layer of the former contained 0.8% by weight of arsenic in a uniformly distributed state. .

The latter dielectric layer also contained 0.8% by weight of phosphorus. The electrical characteristics of both were as shown in the attached table. Experimental Example 2 A silicon single crystal wafer with a length of 0.7 cm, a width of 0.7 cm, and a thickness of 0.5 mm was used as a substrate. This substrate was placed in a sputtering device and degassed, and then placed in an arsenic atmosphere of 1 x 10-4 t0rr. After that, cathode voltage - 3000, anode voltage 2
00, cathode current density 0.5mA/Crlts substrate temperature 6
After forming a 2000λ thick arsenic-containing tantalum film on the substrate surface by reactive sputtering of tantalum under sputtering conditions of 00°C, the arsenic-containing tantalum film was annealed by holding the substrate temperature at 600°C for 20 minutes. .

Next, the parts of the substrate not covered with the arsenic tantalum film were insulated with a resist, and then immersed in an ethylene glycol solution of 1×10-4M5 ammonium borate and heated to 90°C. Graphite, the counter electrode, was set as the cathode, and direct current was applied at a constant current density of 10 mA/CTl, and anodization was performed until the potential difference between the two electrodes rose to 60 V. After the potential difference reached 60 V, the potential difference was reduced to 50 V. The arsenic tantalum oxide film was then aged for 200 minutes. The thickness of the formed arsenic-containing tantalum oxide film was 1000A. Next, insert the board 1
It was immersed in an ethylene glycol solution containing 0.02M lead perchlorate and 0.2M perchloric acid at 30°C, and a direct current of 50°C was applied using the arsenic tantalum metal as the anode and the counter electrode, platinum, as the cathode. A current density of IA/C7i was applied and the current was applied for 100 minutes to form two β-type lead dioxide layers on the arsenic tantalum oxide film.
It was formed to a thickness of 0.000. Subsequently, the resist was dissolved and removed, and a colloidal aqueous solution of graphite was sprayed onto the lead dioxide layer and baked at 120° C. for 20 minutes to form a graphite layer with a thickness of 5000λ. Next, the graphite layer was used as a cathode, the arsenic tantalum metal layer was used as an anode, lead wires were attached, and then an insulating resin was coated to form a capacitor as shown in FIG. Reference experiment example 2 Using the same substrate as that used in experiment example 2, 1×1
After sputtering tantalum under the same sputtering conditions as in Experimental Example 2 in a neon atmosphere of 0-3t0rr to form a 2000λ thick tantalum film that does not contain arsenic on the substrate surface,
A tantalum oxide film with a thickness of 1000λ was formed by immersion in an ethylene glycol solution of 2M ammonium dihydrogen arsenate at 90°C and anodized and aged under the same conditions as in Experimental Example 2, followed by electrodeposition of lead dioxide in the same manner as above. After baking graphite, it was made into a capacitor.

As a result of analyzing the capacitors obtained in Experimental Example 2 and Reference Experimental Example 2 in this way, it was found that the dielectric layer, that is, the tantalum oxide layer of each capacitor contained 3.0% by weight of arsenic.

In addition, the electrical characteristics of each were as shown in the attached table. Experimental example 3 Alumina ceramic was used as a substrate, and the surface of this substrate was coated with 0.5C11P! ．． After covering the other parts with resist, it is placed in a sputtering device, and the inside of the device is heated to arsine gas partial pressure of 5×10-4t0rr1 ammonia gas partial pressure of 2×1.
0-5t0rr1 Phosphine gas partial pressure 3×10-5t0
It was filled with a mixed gas atmosphere of rr.

Next, cathode voltage -5000V1 cathode voltage 0V1 cathode current density 1.0mA/CTL. After forming an arsenic-containing tantalum film containing arsenic, phosphorus, and nitrogen on the substrate surface by reactive sputtering with a substrate temperature of 450°C, the substrate was slowly cooled and removed from the apparatus. Out u
The resist was dissolved and removed at room temperature. Next, the board is 120
Immersed in ammonium formate solution at ℃, and applied a direct current of 2 mA/C with the arsenic tantalum membrane as the anode and the counter electrode of platinum as the cathode.
Anodic formation was performed by applying a constant current density of 7 liters, and when the potential difference between the two electrodes rose to 120, the potential difference between the two electrodes was increased to 80
V and maintained in a molten salt at 120° C. for 120 minutes for aging. Next, the washed and dried substrate was
It was transferred to an air atmosphere at 50° C. and 800 t0rr and annealed for 30 minutes. The thickness of the formed arsenic tantalum oxide layer was 2500λ. Subsequently, the substrate was slowly cooled to room temperature, transferred to a vapor deposition apparatus, heated to 100°C in an arsenic atmosphere of 5 x 10' TOrr, and then aluminum was heated to 700°C.
It was heated to 0.degree. C. to evaporate, and the vapor was condensed and deposited on the arsenic-containing tantalum oxide film. Then, the aluminum layer was used as a cathode, and the tantalum metal layer was used as an anode, and lead wires were attached to each to complete a capacitor as shown in FIG. Reference Experimental Example 3 Using the same substrate as that used in Experimental Example 3, a phosphine gas partial pressure of 2 x 10-4 was applied to 0.5d of the surface of this substrate.
t0rr1 Ammonium gas partial pressure 4×10-7 TOrr
After forming a tantalum film containing phosphorus and nitrogen with a thickness of 3500λ under the same sputtering conditions as in Experimental Example 3 in a mixed gas atmosphere of
Anodization was performed under the same formation conditions as in Experimental Example 3 by immersing it in molten ammonium formate salt containing dissolved ammonium hydrogen.
Further, the same annealing process was performed to form an arsenic-containing tantalum oxide layer having a thickness of 2500λ.

Next, aluminum was deposited on the arsenic tantalum oxide layer to complete the capacitor. In this way, Experimental Example 3
As a result of analyzing the two types of capacitors obtained in Reference Experimental Example 3, it was found that each dielectric layer contained 2.1% by weight of arsenic.

In addition, the electrical characteristics of each were as shown in the attached table. Experimental example 4 Using sapphire as a substrate, the surface of this substrate was
Cr1t8. The other parts were covered with resist and placed in a sputtering machine together with nickel foil.

Arsenic gas partial pressure 4×10-5t0rr1 Arsine gas partial pressure 4×10-5t0rr1 Helium gas partial pressure 1X
Ventilate to 10-3t0rr, cathode voltage -4000V1 anode voltage 100, cathode current density 0.7mA/d foil temperature 50
An arsenic-containing tantalum film having a thickness of 2500λ was formed on the substrate surface by sputtering tantalum under sputtering conditions at 0°C.
Keep the substrate temperature at 500℃＼, 1×10-3t0r
After annealing the tantalum film in a helium atmosphere of 60°C, annealing the tantalum film in a helium atmosphere of 60°C, and then annealing the tantalum film in a helium atmosphere of 60°C.
- Arsenic tantalum oxide with a thickness of 550λ was immersed in a 3M sodium sulfate aqueous solution, applying a direct current of 30 mA/CTI between the two electrodes with the tantalum layer as an anode and the counter electrode as a cathode to perform constant voltage formation for 150 minutes. A layer was formed. Next, the substrate was transferred into a sputtering device and heated in advance at 500°C in a neon atmosphere of 1 x 10-2 t0rr for 30 minutes, and then the cathode voltage -500V1 anode voltage -
Tantalum was sputtered on the arsenic tantalum oxide layer under sputtering conditions of 50V1 cathode current density 3mA/Clt.
A tantalum layer with a thickness of 0.00 mm was formed and heated at 500°C, 1×10
-After annealing by holding in a neon atmosphere of 2t0rr for 200 minutes, the resist was removed and lead wires were attached to the inner tantalum metal layer and the surface tantalum metal layer to form the shape shown in Figure 1. A non-polar capacitor was formed. Reference Experimental Example 4 The same substrate as used in Experimental Example 4 was coated with resist in the same manner, and then placed in a sputtering device to form a 1×1
Tantalum was sputtered on the substrate surface to a thickness of 25 mm under the same sputtering conditions as in Experimental Example 4 in a neon atmosphere of 0-2 t0rr.
After forming a tantalum layer of 00λ, 2×1 at 60℃
It was immersed in an aqueous solution that dissolved 0-3M sodium sulfate and the same concentration of sodium arsenite, and was chemically formed under the same chemical formation conditions as in Experimental Example 4 to form a tantalum oxide layer. A non-polar capacitor was formed using this as an electrode.

In this way, the electrical characteristics of the two types of capacitors obtained in Experimental Example 4 and Reference Experimental Example 4 were investigated, and the results shown in the table below were obtained.

All measured values were taken at 20°C, 30% RE, and an applied DC of 1
It was determined under the conditions of 0V1 applied and AC 1V (Vbell). As is clear from the above table, the capacitors of the present invention (for example, Experimental Examples 1, 2, 3, and 4) are different from the conventional capacitors (Reference Experimental Examples 1, but 2, 3, and 4 are not included).

) is superior in all respects. This seems to be due to the effective effect of arsenic contained in the tantalum oxide film. Note that Reference Experimental Examples 2, 3, and 4 are included in the present invention, but as is clear from the explanation of the manufacturing process, arsenic is doped when anodizing the tantalum film, so oxidation is not possible. This is thought to be the reason why the distribution of arsenic in the tantalum film is not uniform and the characteristics are slightly deteriorated. Therefore, Experimental Example 1
, 2, 3, and 4, it is preferable to dope arsenic when forming the tantalum film. Furthermore, the amount of arsenic contained in the tantalum oxide film is effective within the range of 0.8 to 3.0% by weight, and if it is outside this range, no significant effect can be expected. In addition,
The present invention can also be applied to electrolytic capacitors each having a tantalum sintered foil wire film as a base. As described in detail above, according to the present invention, it is possible to provide a capacitor using a tantalum oxide film that can exhibit excellent characteristics.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal cross-sectional view of one embodiment of the present invention, and FIG. 1 is a longitudinal cross-sectional view of another embodiment of the present invention. 1...Substrate, 2...Arsenic-containing tantalum film, 3...Arsenic-containing tantalum oxide film, 4...
・Metal film.

Claims (1)

[Claims] 1. A capacitor characterized in that a dielectric is formed of a tantalum oxide film containing 0.8 to 3.0% by weight of arsenic.