JPH11330391A - Capacity element and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a capacity element having excellent electric characteristics and high reliability by flattening a surface of a capacity insulating film and a method for manufacturing it. SOLUTION: The capacity element comprises a supporting board 1, a first electrode 2 formed on the board 1, a first insulating film 5 formed on the electrode 2 and constituted by a ferroelectric material or a high dielectric material, a second insulating film 8 formed on the film 5 and constituted by the same material as that of the film 5, and a second electrode 4 formed on the film 8 in such a manner that a mean particle size of crystal grain of an insulator for constituting the film 8 is smaller than that of the insulator for constituting the film 5.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a capacitive element using a ferroelectric film or a dielectric film having a high dielectric constant incorporated in a semiconductor integrated circuit as a capacitive insulating film, and a method of manufacturing the same.

[0002]

2. Description of the Related Art In recent years, with the increase in the density of many semiconductor devices constituting consumer electronic equipment, the miniaturization of semiconductor elements used has been advanced, and unnecessary radiation, which is electromagnetic noise generated from electronic equipment, has been advanced. Is a big problem. As a countermeasure for reducing this unnecessary radiation, attention is paid to a technology for incorporating a large-capacity capacitive element in a semiconductor integrated circuit using a ferroelectric or a dielectric film having a high dielectric constant (hereinafter referred to as a high dielectric film) as a capacitive insulating film. Is taking a bath.

In addition, with the aim of putting a non-volatile RAM capable of low operating voltage, high speed writing and high speed reading to a practical level, a capacitor element using a ferroelectric film having spontaneous polarization characteristics as a capacitor insulating film has been developed. Technical development for forming on top is being actively carried out.

A method of manufacturing a capacitor using a conventional ferroelectric thin film will be described below with reference to FIGS. A first electrode 2 made of a Pt film is selectively formed on a support substrate 1 by sputtering (a). Next, a capacitance insulating film 3 made of SrBi ₂ Ta ₂ O ₉ is formed on the first electrode 2 by a coating method, a CVD (Chemical Vapor Deposition) method, or a sputtering method to a thickness in a range of 100 to 250 nm. After that, it is sintered at a temperature in the range of 650 to 800 ° C. in an oxygen atmosphere (b). Continue film thickness 100 ~
A second electrode 4 made of a Pt film having a thickness in the range of 300 nm is formed on the surface of the capacitive insulating film 3 by a sputtering method, thereby forming the capacitive element shown in FIG.

[0005]

However, in the above-mentioned conventional manufacturing method, a sufficient amount of spontaneous polarization is required for the capacitor insulating film 3 to obtain a sufficiently high dielectric constant as a high dielectric substance or as a ferroelectric substance. For this, at least about 100nm
It is necessary to form crystal grains of the size of the ferroelectric thin film in the capacitance insulating film 3 having an average thickness of about 200 nm. It will be larger in comparison. Therefore, the surface irregularities of the ferroelectric thin film become large, and when a capacitive element is manufactured using such a ferroelectric thin film, large variations in electrical characteristics such as dielectric strength and dielectric constant or spontaneous polarization may occur. In addition, there is a problem in processing in a process such as disconnection of wiring formed on the capacitor insulating film 3 and a problem in reliability of a semiconductor device having a built-in capacitor.

An object of the present invention is to solve the above-mentioned conventional problems and to provide a capacitive element having excellent electrical characteristics and high reliability by flattening the surface of a capacitive insulating film and a method of manufacturing the same. Aim.

[0007]

In order to achieve the above object, the present invention provides a method for forming a first electrode made of a metal film or a conductive oxide film on one surface of a supporting substrate;
A step of sintering and forming a first insulating film whose main component is a ferroelectric or a dielectric having a high dielectric constant on the electrode of
A step of forming a second insulating film by heat treatment on the first insulating film, and a step of forming a second electrode made of a metal film or a conductive oxide film on the second insulating film. It is provided.

The average grain size of the crystal grains of the material forming the second insulating film is smaller than the average grain size of the material forming the first insulating film, or the material forming the second insulating film is The second insulating film has a main component of the same ferroelectric or high dielectric constant as the main component of the first insulating film. The processing temperature in the step of forming the second insulating film by heat treatment is set to a first temperature.
Is lower than the sintering temperature in the step of forming the insulating film by sintering.

Further, a ferroelectric material containing at least Bi is used as a material constituting the first insulating film.

Therefore, according to the present invention, the first insulating film made of a ferroelectric or a dielectric having a high dielectric constant is sintered, and the surface of the first insulating film having large irregularities on the surface is formed of crystal grains. A capacitor insulating film having a flat surface is obtained by covering with a second insulating film having an average particle size smaller than the average particle size of the first insulating film or including an amorphous region other than a crystal. be able to.

[0011]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a process sectional view for explaining a method of manufacturing a capacitive element according to a first embodiment of the present invention. Note that, in FIG. 1, portions corresponding to those in FIG.

A first electrode 2 made of a Pt film is formed on a supporting substrate 1 to a thickness in the range of 50 to 400 nm (FIG. 1).
(A)). Next, SrBi ₂ Ta ₂ O is formed on the first electrode 2.
The first insulating film 5 of ₉ is formed by spin coating or CVD (C
It is formed to a thickness in the range of 50 to 250 nm using a chemical vapor deposition method or a sputtering method, and sintered at 800 ° C. in an oxygen atmosphere (FIG. 1B). Next, it is crystallized by sintering, and Ta is used as a second insulating film on the surface of the first insulating film 5 where irregularities are generated by crystal grains.
_{A 2} O ₅ thin film 6 is formed (FIG. 1C). Next, the Ta
By forming the second electrode 4 made of a Pt film on the surface of the ₂ O ₅ thin film 6 with a thickness in the range of 50 to 300 nm, the capacitor shown in FIG.

As described above, according to the above embodiment, Sr
The Ta ₂ O ₅ thin film 6 is buried in the concave portion of the uneven portion formed on the surface of the first insulating film 5 made of Bi ₂ Ta ₂ O ₉ , whereby the first insulating film 5 and the second insulating film 5 are flattened. The surface of the capacitive insulating film of the capacitive element composed of the Ta ₂ O ₅ thin film 6 serving as the insulating film forms a flat surface.

In this embodiment, a Ta ₂ O ₅ thin film is used as the second insulating film, but the same effect can be obtained by using another insulating film such as a Bi ₂ O ₃ thin film. .

Next, a second embodiment of the present invention will be described. The manufacturing process of the capacitor in this embodiment is the same as that in the first embodiment, and is different from the first embodiment in that an insulating material used for the second insulating film is different.

As in the case of the first embodiment, a first electrode film 2 and a first insulating film 5 are formed on a support substrate 1, and the surfaces thereof are formed as a second insulating film by spin coating. Ba _x S
After the formation of the r _1-x ) TiO ₃ thin film 7, the second electrode 4 is formed on the surface of the thin film 7, thereby forming the capacitive element according to the second embodiment.

As described above, according to the above embodiment, Sr
Bi ₂ Ta ₂ O ₉ first in concave portions of the concavo-convex portion generated on the surface of the insulating film 5 having a small grain than SrBi ₂ Ta ₂ O ₉ thin film of a crystal made of a thin film _{(Ba x Sr 1-x)} TiO _The surface of the capacitive insulating film of the capacitive element composed of the first insulating film 5 and the (Ba _x Sr _{1 -x} ) TiO ₃ thin film 7 as the second insulating film is planarized by embedding the _three thin films 7. Will form a flat surface.

In this embodiment, the (Ba _x Sr _{1 -x} ) TiO ₃ thin film 7 is used as the second insulating film.
The same effect can be obtained by using another insulator having a smaller grain size than the crystal grains of the first insulating film 5 made of the i ₂ Ta ₂ O ₉ thin film.

Next, a third embodiment of the present invention will be described. The manufacturing process of the capacitor in this embodiment is the same as that of the first embodiment. The difference from the first embodiment is that the insulating material used for the second insulating film is different from that of the first embodiment. The same material is used, but the heat treatment method is different.

As in the first and second embodiments, a first electrode film 2 and a first insulating film 5 are formed on a support substrate 1, and SrBi ₂ as a _second insulating film is formed on the surface thereof. Ta ₂ O ₉
The thin film 8 is formed to a thickness of 20 to 50 nm by spin coating, CVD, or sputtering, and is heat-treated at 600 ° C., and then the second electrode 4 is formed on the surface thereof. The capacitance element according to the third embodiment is formed.

As described above, according to the above embodiment, Sr
The SrBi ₂ Ta ₂ O ₉ thin film having a grain size smaller than that of the first insulating film 5 due to the low heat treatment temperature in the concave portion of the uneven portion formed on the surface of the first insulating film 5 made of the Bi ₂ Ta ₂ O ₉ thin film. 8
Therefore, the surface of the capacitive insulating film of the capacitive element composed of the first insulating film 5 and the SrBi ₂ Ta ₂ O ₉ thin film 8 as the _second insulating film has a flat surface. Become.

Further, in the case of the present embodiment, the sintering temperature of the SrBi ₂ Ta ₂ O ₉ thin film of the first insulating film 5 and the heat treatment temperature of the SrBi ₂ Ta ₂ O ₉ thin film 8 of the second insulating film are different. Although different, and the degree of crystallization is different, the capacitance insulating film can be formed with a single substance, so that it is not necessary to provide facilities for forming the second insulating film, which is advantageous in cost. In addition, since the components are made of the same material, there is an advantage that there is no need to worry about peeling of the film between the first insulating film and the second insulating film (generally, this may occur due to thermal stress or the like).

In the first, second, and third embodiments, the first insulating film 5 is made of ferroelectric SrBi ₂ Ta _2.
Although an O ₉ thin film was used, other dielectric thin films can be used. In particular, when a ferroelectric thin film containing Bi, such as Bi ₄ Ti ₃ O ₁₂ , SrBi ₂ Ta ₂ O ₉ , or SrBi ₂ Nb ₂ O _9, is used as the first insulating film 5, the particle diameter of these particles is small. Since it is larger than other types of dielectric thin films, the manufacturing method according to the present invention is very effective for improving the withstand voltage of the capacitor. Although the Pt film is used as the electrode metal of the first and second electrodes for the capacitor, the same effect can be obtained by using another metal or a conductive oxide such as RuO _2. it can.

[0025]

According to the present invention, there is provided a step of forming a first electrode made of a metal film or a conductive oxide film on one surface of a supporting substrate, and forming a ferroelectric substance or a main component on the first electrode. A step of sintering and forming a first insulating film made of a dielectric having a high dielectric constant, a step of sintering and forming a second insulating film on the first insulating film; Forming a second electrode made of a metal film or a conductive oxide film on the insulating film of (1), another insulating film is formed on the surface of the dielectric thin film having a large step due to unevenness of crystal grains. By laminating the films, an amorphous region where no crystal causing irregularities is formed or a second insulating film made of crystal grains smaller than the crystal grains of the dielectric thin film forming the first insulating film is formed. By covering, a capacitor insulating film with a flat surface can be obtained, The al those that can achieve simplification of the processing steps.

[Brief description of the drawings]

FIG. 1 is a process cross-sectional view illustrating a method for manufacturing a capacitive element according to an embodiment of the present invention.

FIG. 2 is a process sectional view showing a conventional method for manufacturing a capacitive element.

[Explanation of symbols]

Reference Signs List 1 support substrate 2 Pt film (first electrode film) 4 Pt film (second electrode film) 5 SrBi ₂ Ta ₂ O ₉ thin film (first insulating film) 6 Ta ₂ O ₅ thin film (second insulating film) _{) 7 (Ba x Sr 1-} x) TiO 3 thin film (second insulating film) 8 amorphous SrBi ₂ Ta ₂ O ₉ thin film (second insulating film)

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Koji Arita, Inventor 1-1, Yukicho, Takatsuki-shi, Osaka Matsushita Electronics Corporation (72) Inventor Yasuhiro Uemoto 1-1, Yukicho, Takatsuki-shi, Osaka Matsushita Electronics Industrial Co., Ltd.

Claims (12)

[Claims] 1. A support substrate, a first electrode formed on the support substrate, and a first insulating film formed on the first electrode and made of a ferroelectric or high dielectric. A second insulating film formed on the first insulating film and made of the same material as the first insulating film; and a second electrode formed on the second insulating film. Wherein the average grain size of the crystal grains of the insulator forming the second insulating film is smaller than the average grain size of the crystal grains of the insulator forming the first insulating film. element. 2. The method according to claim 1, wherein the first insulating film has a particle size of 100 nm.
The capacitive element according to claim 1, wherein the capacitive element has crystal grains exceeding the number of grains. 3. A support substrate, a first electrode formed on the support substrate, and a first insulating film formed on the first electrode and made of a ferroelectric or a high dielectric. A second insulating film formed on the first insulating film and made of the same material as the first insulating film; and a second electrode formed on the second insulating film. Having the first insulating film,
The second insulating film includes crystal grains having a grain diameter of more than 100 nm, and the average grain diameter of the crystal grains of the insulator constituting the second insulating film is the first grain diameter.
A capacitor element smaller than the average grain size of the crystal grains of the insulator constituting the insulating film. 4. The capacitor according to claim 1, wherein the first insulating film has a thickness of 50 nm to 250 nm. 5. The capacitor according to claim 1, wherein the second insulating film has a thickness of 20 nm to 50 nm. 6. The capacitor according to claim 1, wherein the second insulating film includes an amorphous region. 7. A step of forming a first electrode on a supporting substrate, a step of forming a first insulating film mainly composed of a ferroelectric or a high dielectric on the first electrode, A step of sintering the first insulating film, a step of forming a second insulating film mainly containing a ferroelectric or a high dielectric on the first insulating film, A method for heat-treating the second insulating film at a temperature lower than the sintering temperature; and a step of forming a second electrode on the second insulating film. . 8. The method according to claim 7, wherein a main component of the first insulating film is the same as a main component of the second insulating film. 9. The method according to claim 7, wherein the thickness of the first insulating film is 50 nm to 250 nm. 10. The method according to claim 7, wherein the second insulating film has a thickness of 20 nm to 50 nm. 11. The method according to claim 7, wherein the second insulating film includes an amorphous region. 12. The method according to claim 7, wherein the material forming the first insulating film includes a ferroelectric substance containing bismuth (Bi).