JPH1197635A - Capacity element and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the deterioration of the electrical characteristics of a capacity element by a method wherein a component constituting a capacity insulation film, or a component constituting the other metal films coming into contact with a lower electrode or an upper electrode passes through the lower electrode or the upper electrode and diffuses, so that the composition of the capacity insulation film is changed. SOLUTION: A capacity element comprises a lower electrode 11, a capacity insulation film 12 composed of a Bi-based ferroelectric thin film formed on the lower electrode 11, and an upper electrode 13A formed on the capacitive insulation film 12. A first Ti film 14 is formed on the upper electrode 13A. The upper electrode 13A comprises a metal film having a spherical-shape crystalline structure of Pt.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a capacitor, particularly to a capacitor used as a nonvolatile memory of a semiconductor integrated circuit device and a method of manufacturing the same.

[0002]

2. Description of the Related Art In response to demands for high integration, low voltage, and high speed operation of semiconductor integrated circuit devices, non-volatile memories capable of reducing the thickness and writing and reading at low voltage and at high speed. Attention has been paid to ferroelectric memories.

A ferroelectric memory utilizes a phenomenon that the amount of charge flowing into and out of a data line differs depending on whether or not the spontaneous polarization state of a ferroelectric thin film used as a capacitor insulating film is inverted.

FIG. 5 shows a sectional structure of a conventional capacitive element used in a ferroelectric memory. As shown in FIG. 5, a TiO _x (titanium oxide) film 1a having a thickness of 100 nm is provided.
And a Pt (platinum) film 1b having a thickness of 300 nm and a capacitor insulating film 2 formed of a ferroelectric thin film having a layered structure of bismuth (Bi) having a layered structure of bismuth (Bi) on a lower electrode 1 having a laminated structure. Is formed, and Pt is formed on the capacitance insulating film 2.
An upper electrode 3 made of a film is formed. An SiO ₂ (silicon oxide) film 5 as an interlayer insulating film having a contact hole is formed on the capacitive insulating film 2 including the upper electrode 3 via a first Ti (titanium) film 4 having a thickness of 20 nm. Is formed on the SiO ₂ film 5.
m, a first TiN (titanium nitride) film 7 having a thickness of 150 nm, an Al (aluminum) wiring film 8 having a thickness of 800 nm, and 30 n
A second TiN film 9 having a thickness of m is formed.

[0005] The first Ti film 4 is made of SiO ₂ film 5 and Pt.
The second Ti film 6 is formed to improve the adhesion between the first TiN film 7 and the upper electrode 3. The second Ti film 6 is formed to improve the adhesion to the upper electrode 3 made of a film. The first TiN film 7 serves as a barrier layer between the Al wiring film 8 and the upper electrode 3, and the second TiN film 9 serves as an antireflection film at the time of pattern exposure for forming the Al wiring film 8.

Further, since the ferroelectric thin film constituting the capacitive insulating film 2 has a strong oxidizing power, if Au, Si, TiN or the like is used as a material constituting the lower electrode 1 and the upper electrode 3,
Since the lower electrode 1 and the upper electrode 3 are easily oxidized by the capacitance insulating film 2, Pt is used as a material for forming the lower electrode 1 and the upper electrode 3.

[0007]

However, as shown in FIG. 6, since the Pt film constituting the upper electrode 3 has a columnar crystal structure, the first Ti film 4 and the second Ti film 6
Bi atoms (indicated by white circles), which are components of a ferroelectric thin film having a bismuth layered structure constituting the capacitive insulating film 2, and the first Ti film 4
And Ti atoms constituting the second Ti film 6 (indicated by black circles)
Is easily diffused along the crystal grain boundaries of the Pt film. For this reason, the composition of the ferroelectric thin film forming the capacitive insulating film changes, and thus there is a problem that the electrical characteristics of the capacitive element deteriorate.

Such a problem occurs not only when the upper electrode 3 is made of a Pt film, but also when the lower electrode 2 is made of a Pt film. This is not limited to the case where the crystal is formed by, but occurs widely when it has a columnar crystal.

In view of the above, the present invention relates to a capacitor element comprising a lower electrode and an upper electrode, and a capacitor insulating film formed between the lower electrode and the upper electrode. It is possible to prevent a component constituting another metal film which is in contact with the electrode or the upper electrode from diffusing through the lower electrode or the upper electrode, thereby preventing a change in the composition of the capacitor insulating film and a deterioration in electric characteristics of the capacitor. Aim.

[0010]

According to the present invention, in order to achieve the above object, the lower electrode or the upper electrode is formed of a metal film having a spherical crystal structure of a platinum group metal. Specifically, a capacitor according to the present invention includes a capacitor having a lower electrode, a capacitor insulating film formed on the lower electrode, and an upper electrode formed on the capacitor insulating film. At least one of the lower electrode and the upper electrode
One of the electrodes is formed of a metal film having a spherical crystal structure of a platinum group metal.

According to the capacitive element of the present invention, the component constituting the capacitive insulating film or the component constituting the metal film such as the adhesion layer adjacent to the electrode having the spherical crystal structure is composed of the crystal constituting the electrode having the spherical crystal structure. Diffusion is prevented by the grain boundaries between each other.

In the capacitive element of the present invention, the capacitive insulating film is preferably made of a Bi-based ferroelectric thin film.

Further, in the capacitance element of the present invention, the metal constituting the metal film is preferably Pt.

A method of manufacturing a capacitor according to the present invention includes a lower electrode forming step of forming a lower electrode on a substrate, a capacitor insulating film forming step of forming a capacitor insulating film on the lower electrode, The present invention is directed to a method of manufacturing a capacitor including an upper electrode forming step of forming an upper electrode thereon, wherein at least one of the lower electrode forming step and the upper electrode forming step includes an inert gas and oxygen in a chamber. A step of forming a metal film having a spherical crystal structure of a platinum group metal by introducing a discharge gas comprising a mixed gas with the gas and performing sputtering.

According to the method for manufacturing a capacitive element of the present invention, at least one of the lower electrode forming step and the upper electrode forming step includes the step of forming an inert gas and an oxygen gas in a chamber having a target made of a platinum group metal. Since sputtering is performed by introducing a discharge gas consisting of a mixed gas of the above, growth of columnar crystals is hindered by oxygen taken in the film.

In the method for manufacturing a capacitor of the present invention, the platinum group metal is preferably Pt.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION

(First Embodiment) Hereinafter, a capacitor according to a first embodiment and a method of manufacturing the same will be described with reference to FIGS. 1 (a) to 1 (c) and FIG.

First, as shown in FIG. 1A, a 100 nm thick TiO _x (titanium oxide) film 11 a and a 300 nm thick first Pt (platinum) film are formed on a semiconductor substrate 10.
After forming the lower electrode 11 having a laminated structure with the film 11b, a capacitance insulating film 12 made of a ferroelectric thin film having a layered structure of bismuth (Bi) having a thickness of 250 nm is formed on the lower electrode 11. Form.

Next, reactive sputtering is performed by introducing a discharge gas, for example, a mixed gas of 80 vol% argon gas and 20 vol% oxygen gas into a chamber having a target made of, for example, Pt and a room temperature. . By doing so, Pt atoms are ejected from the target, and the ejected Pt atoms are deposited on the capacitive insulating film 12. At this time, since oxygen in the discharge gas is taken into the film, Pt columnar crystal growth is hindered.
Eventually, spherical Pt crystals having an average particle diameter of 100 nm or less are formed, and oxygen precipitates at the grain boundaries. Thus, the second Pt having a spherical crystal structure with an average particle diameter of 100 nm or less and a thickness of 200 nm is formed on the capacitance insulating film 12.
After forming the film 13, the first Tt film is formed on the second Pt film 13.
An i film 14 is deposited.

The processing conditions for the reactive sputtering need not be room temperature, but can be performed in a temperature range from room temperature to 100 ° C. In this case, if reactive sputtering is performed at a temperature of 200 ° C. or more, P
Since the t film 14 does not have a spherical crystal structure but has a columnar crystal structure, the temperature is preferably 100 ° C. or less.

The mixing ratio of the mixed gas of the argon gas and the oxygen gas, which is the discharge gas, is not limited, but the mixing ratio of the oxygen gas is preferably 1 vol% or more.

Next, as shown in FIG. 1B, the second P
When the t film 13 and the first Ti film 14 are patterned,
An upper electrode 13A made of the second Pt film 13 is formed.

Next, as shown in FIG.
After depositing SiO ₂ 15 as an interlayer insulating film on the
A contact hole is formed by etching the first Ti film 14 and SiO ₂ 15. Thereafter, a _second film having a thickness of 25 nm is formed on the SiO ₂ 15.
Ti film 16, first TiN having a thickness of 150 nm
Film 7, Al wiring films 18 and 3 having a thickness of 800 nm
A second TiN film 19 having a thickness of 0 nm is formed.

The first Ti film 14 is formed for improving the adhesion between the SiO ₂ film 15 and the upper electrode 13A, and the second Ti film 16 is formed for the first TiN film 17 and the upper electrode 13A. The first TiN film 17 is formed to improve the adhesion to the upper electrode 1A.
3A, and the second TiN film 19 becomes an anti-reflection film at the time of pattern exposure for forming the Al wiring film 18.

According to the first embodiment, the second Pt film 1
The upper electrode 13A made of No. 3 has a spherical crystal structure with an average particle diameter of 100 nm or less. Therefore, even if heat treatment is performed in a later step, Bi which is a component of the ferroelectric thin film forming the capacitance insulating film 12 is formed. Since the diffusion of the atoms is prevented at the interface of the spherical crystal constituting the upper electrode 13A, the atoms do not diffuse into the first Ti film 4 and the second Ti film 16, and the first Ti
Since the diffusion of the Ti atoms constituting the film 14 and the second Ti film 16 is prevented at the interface of the spherical crystal of the upper electrode 13A,
It does not diffuse into the ferroelectric thin film forming the capacitance insulating film 12.
For this reason, the composition of the ferroelectric thin film forming the capacitive insulating film 12 hardly changes, so that the electrical characteristics of the capacitive element do not deteriorate.

(Second Embodiment) A capacitor according to a second embodiment and a method of manufacturing the same will now be described with reference to FIGS.
This will be described with reference to (c) and FIG.

First, as shown in FIG. 3A, a first Ti film 21 as an adhesion layer is deposited on a semiconductor substrate 20 and then placed in a chamber at room temperature having a target made of, for example, Pt. For example, reactive sputtering is performed by introducing a discharge gas composed of a mixed gas of 80 vol% argon gas and 20 vol% oxygen gas. By doing so, Pt atoms are ejected from the target, and the ejected Pt atoms are deposited on the Ti film 21. At this time, since oxygen in the discharge gas is taken into the film, the growth of the columnar crystal of Pt is hindered, so that a spherical Pt crystal having an average particle diameter of 100 nm or less is finally formed and oxygen is bound at the grain boundary. Precipitates out. Thus, the first
The first electrode to be a 200-nm-thick lower electrode having a spherical crystal structure with an average grain size of 100 nm or less is formed on the Ti film 21 of FIG.
Of the Pt film 22 is formed.

The reactive sputtering may be performed at a temperature in the range of room temperature to 100 ° C., not necessarily room temperature. In this case, if the reactive sputtering is performed at a temperature of 200 ° C. or higher, the first Pt film 22 has a columnar structure instead of a spherical structure. Therefore, the temperature is preferably 100 ° C. or lower.

The mixing ratio of the mixed gas of the argon gas and the oxygen gas serving as the discharge gas is not limited, but the mixing ratio of the oxygen gas is preferably 1 vol% or more.

Thereafter, a capacitor insulating film 23 made of a ferroelectric thin film having a layered structure of bismuth (Bi) is formed on the first Pt film 22, and then on the capacitor insulating film 23,
A second Pt film 24 and a second Ti film 25 are sequentially formed.

Next, as shown in FIG. 3B, the second P
When the t film 24 and the second Ti film 25 are patterned,
An upper electrode 24A made of the second Pt film 24 is formed.

Next, as shown in FIG.
After depositing SiO ₂ 26 serving as an interlayer insulating film,
A contact hole is formed by etching the second Ti film 25 and SiO ₂ 26. Then, on the SiO ₂ 26, the third Ti layer 27, the first T
An iN film 28, an Al wiring film 29, and a second TiN film 30 are formed.

According to the second embodiment, the first Pt film serving as the lower electrode has a spherical crystal structure with an average grain size of 100 nm or less. Bi atoms, which are components of the ferroelectric thin film constituting the film 23, are prevented from diffusing at the interface of the spherical crystal of the first Pt film 22, which is the lower electrode, so that the first Ti film 21,
It does not diffuse into the second Ti film 25 and the third Ti film 27, and does not diffuse into the first Ti film 21, the second Ti film 25, and the third T film 25.
Since the diffusion of the Ti atoms constituting the i-film 27 is prevented at the interface between the spherical crystals of the first Pt film 22, the Ti atoms do not diffuse into the ferroelectric thin film constituting the capacitance insulating film 23. For this reason, the composition of the ferroelectric thin film forming the capacitive insulating film 23 hardly changes, so that the electrical characteristics of the capacitive element do not deteriorate.

In the first and second embodiments, the metal film forming the lower electrode and the upper electrode is not limited to the Pt film, but may be another metal film having a spherical crystal structure, for example, XIII in the periodic table. Of the elements belonging to the group, 4d, 5d
From the metals of the platinum group (or sometimes referred to as the palladium group) such as Ru (ruthenium), Rh (rhodium), Pd (palladium), Os (osmium) or Ir (iridium). Film. The reason is that the oxide of the platinum group metal has conductivity.

Further, the smaller the particle size of the spherical crystals constituting the metal films to be the lower electrode and the upper electrode, the smaller the B
The ability to block the diffusion of i atoms and Ti atoms increases, but the resistance also increases. On the other hand, as the particle size increases, the resistance decreases, but the ability to block the diffusion of Bi atoms and Ti atoms also decreases. Therefore, it is preferable that the particle size is such that the metal film has a plurality of spherical crystals in the vertical direction.

The capacitor insulating film 23 is not limited to a ferroelectric thin film, but may be a high dielectric thin film or an insulating film made of another metal oxide.

The metal film in contact with the lower electrode or the upper electrode is not limited to the Ti film, but may be W (tungsten).
Film, Ta (tantalum) film, Nb (niobium) film, Ir (iridium) film, Ru (ruthenium) film, Pd (palladium) film and the like are used as an adhesion layer of an Al wiring film, and are used as a capacitor insulating film. A film made of a metal that diffuses to change the composition of the capacitor insulating film can be widely used.

[0038]

According to the capacitive element of the present invention, the component constituting the capacitive insulating film or the component constituting the metal film such as the adhesion layer adjacent to the electrode having the spherical crystal structure constitutes the electrode having the spherical crystal structure. Since the diffusion is prevented by the grain boundaries between the crystals, the composition of the capacitor insulating film is unlikely to change, so that the deterioration of the electrical characteristics of the capacitor can be prevented.

In the capacitive element of the present invention, if the capacitive insulating film is a Bi-based ferroelectric thin film, the composition of the Bi-based ferroelectric thin film, whose composition is easily changed by thermal diffusion, can be prevented. .

In the capacitive element of the present invention, even if the metal constituting the metal film is Pt having high oxidation resistance, oxygen contained in the discharge gas consisting of the inert gas and the oxygen gas is taken into the film. Therefore, the Pt atoms flipped off from the target reliably form a spherical crystal structure, so that a change in the composition of the capacitor insulating film can be reliably prevented.

According to the method of manufacturing a capacitive element according to the present invention, at least one of the lower electrode forming step and the upper electrode forming step includes the step of forming an inert gas and an oxygen gas in a chamber having a target made of a platinum group metal. Since sputtering is performed by introducing a discharge gas composed of a mixed gas of the above, the atoms of the platinum group metal become spherical crystals, so that a metal film having a spherical crystal structure of the platinum group metal can be reliably formed.

In the method of manufacturing a capacitive element of the present invention, even if the platinum group metal is Pt having high oxidation resistance, oxygen contained in a discharge gas consisting of an inert gas and an oxygen gas is taken into the film. , Pt flicked off the target
Since the atoms surely form a spherical crystal structure, a metal film having a spherical crystal structure of platinum oxide having conductive properties can be surely formed.

[Brief description of the drawings]

FIGS. 1A and 1B are cross-sectional views showing steps of a method for manufacturing a capacitor according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view showing each step of a method for manufacturing a capacitive element according to the first embodiment of the present invention.

FIGS. 3A and 3B are cross-sectional views illustrating respective steps of a method for manufacturing a capacitive element according to a second embodiment of the present invention.

FIG. 4 is a cross-sectional view showing each step of a method for manufacturing a capacitive element according to a second embodiment of the present invention.

FIG. 5 is a cross-sectional view showing a conventional capacitive element.

FIG. 6 is a cross-sectional view illustrating a problem of a conventional capacitive element.

[Explanation of symbols]

10 semiconductor substrate 11 lower electrode 11a TiO _x film 11b first Pt film 12 capacitive insulating film 13 and the second Pt film 13A upper electrode 14 first Ti film 15 SiO ₂ 16 second Ti film 17 first TiN film Reference Signs List 18 Al wiring film 19 Second TiN film 20 Semiconductor substrate 21 First Ti film 22 First Pt film 23 Capacitive insulating film 24 Second Pt film 24A Upper electrode 25 Second Ti film 26 SiO ₂ 27 Third Ti film 28 First TiN film 29 Al wiring film 30 Second TiN film

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI H01L 21/8247 29/788 29/792 (72) Inventor Yasufumi Izutsu No. 1-1 Kochicho, Takatsuki-shi, Osaka Matsushita Electronics Corporation Inside

Claims (5)

[Claims] 1. A capacitive element comprising: a lower electrode; a capacitive insulating film formed on the lower electrode; and an upper electrode formed on the capacitive insulating film, wherein the lower electrode and the upper electrode At least one of the electrodes is made of a metal film having a spherical crystal structure of a platinum group metal. 2. The capacitive element according to claim 1, wherein said capacitive insulating film is made of a Bi-based ferroelectric thin film. 3. The capacitor according to claim 1, wherein the metal forming the metal film is Pt. 4. A lower electrode forming step for forming a lower electrode on the substrate, a capacitive insulating film forming step for forming a capacitive insulating film on the lower electrode, and forming an upper electrode on the capacitive insulating film. A method of manufacturing a capacitive element comprising an upper electrode forming step, wherein at least one of the lower electrode forming step and the upper electrode forming step includes an inert gas in a chamber having a target made of a platinum group metal. A method for producing a capacitive element, comprising: forming a metal film having a spherical crystal structure of a platinum group metal by introducing a discharge gas comprising a mixed gas of oxygen and an oxygen gas to perform sputtering. 5. The method according to claim 4, wherein the platinum group metal is Pt.