JPH09246082A - Capacitance element and method of manufacturing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a capacitance element without the peeling off of an adhering layer or the deterioration of an electric characteristic by suppressing the diffusion of the metal components of the adhering layer in the method of manufacturing the capacitance element with the capacitance insulating film of ferroelectric material. SOLUTION: An adhering layer 13 made of metal or metal oxide and a lower electrode 14 made of platinum are formed on a supporting substrate 11. Together with forming the capacitance insulating film 15 made of the metal oxide, an upper electrode 16 is formed. In the step of forming the lower electrode 14, the sputtering method is used to form the platinum film of the internal tensile stress of 2×10<9> dyne/cm<2> or less after the film forming by setting the temperature of the substrate at 200 deg.C to 600 deg.C, and forming the platinum film of dense film quality, the diffusion of the metal components of the adhered layer is suppressed, the peeling off of the adhesion layer is prevented and the deterioration of the electric characteristic is prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a capacitive element using a metal oxide having ferroelectricity as a capacitive insulating film and a method for manufacturing the same.

[0002]

2. Description of the Related Art A capacitive element having a ferroelectric film having a spontaneous polarization characteristic as a capacitive insulating film is formed on a semiconductor integrated circuit in order to put a nonvolatile RAM capable of low operating voltage, high speed writing and high speed reading into practical use. The technology development for doing so is being actively done.

A conventional capacitive element and a method of manufacturing the same will be described below with reference to process sectional views of FIGS.

As shown in FIG. 6A, a silicon oxide film to be an interlayer insulating film 2 is formed on a supporting substrate 1 made of a silicon substrate. Next, as shown in FIG. 6B, metal titanium having a film thickness of about 20 nm to be the adhesion layer 3 and platinum having a film thickness of 300 nm to be the lower electrode 4 are formed on the interlayer insulating film 2.
It is continuously formed at room temperature by a sputtering method using argon gas. Next, as shown in FIG. 6C, the composition forming the capacitive insulating film 5 on the lower electrode 4 is SrBi ₂ Ta ₂ O.
_The ferroelectric film of No. ₉ is applied by the spin-on method and baked at 800 ° C. Next, as shown in FIG. 6D, platinum serving as the upper electrode 6 is formed on the capacitive insulating film 5 by the sputtering method. Further, as shown in FIG. 6E, processing is performed by a photo-etching method and a dry etching method to form a capacitive element.

[0005]

However, in the conventional structure and the manufacturing method thereof, since platinum forming the lower electrode 4 is formed at room temperature, it has a rough film quality in which columnar crystal grains are lined up, and therefore, through the grain boundaries. The metal component of the adhesion layer 3 is
There is a problem that it is easy to diffuse to the lower electrode 4, the adhesion layer 3 disappears, the adhesion strength deteriorates and peeling occurs, and further, it diffuses to the capacitance insulating film 5 and the electrical characteristics of the capacitance element deteriorate. It was

The present invention solves the above-mentioned conventional problems, and an object of the present invention is to provide a capacitive element which is free from peeling and deterioration of electric characteristics by forming a dense film of platinum, and a manufacturing method thereof. .

[0007]

In order to achieve this object, the capacitance element of the present invention is such that platinum forming the lower electrode formed on the adhesion layer has a tensile strength of 2 × 10 ⁹ dyn / cm ² or more. It has internal stress, and its manufacturing method is to form platinum forming the lower electrode by a sputtering method using argon gas at a substrate temperature of 200 ° C. or higher and 600 ° C. or lower.

According to the present invention, it is possible to form a dense film of platinum, and to obtain a capacitive element free from peeling and deterioration of electrical characteristics.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The invention according to claim 1 of the present invention is an adhesion layer made of a metal or a metal oxide formed on a supporting substrate, and formed on the adhesion layer with a tensile stress of 2 ×. A lower electrode made of platinum of 10 ⁹ dyn / cm ² or more, a capacitive insulating film made of a metal oxide formed on the lower electrode, and an upper electrode formed on the capacitive insulating film. Therefore, since platinum has a dense film quality, it has an effect of suppressing diffusion of a metal component forming the adhesion layer to the lower electrode formed of platinum.

According to a second aspect of the present invention, a step of forming an adhesion layer made of a metal or a metal oxide on the supporting substrate,
Argon gas was used on the adhesion layer to increase the substrate temperature to 20.
A step of forming platinum by a sputtering method set to 0 ° C. or more and 600 ° C. or less to form a lower electrode; a step of forming a capacitive insulating film made of a metal oxide on the lower electrode; and an upper portion of the capacitive insulating film. And a step of forming an electrode, whereby the tensile stress of platinum forming the lower electrode can be set to 2 × 10 ⁹ dyn / cm ² or more, and platinum can be made into a dense film quality. . As a result, the metal component forming the adhesion layer can be suppressed from diffusing into the lower electrode formed of platinum.

According to a third aspect of the present invention, the sputtering method according to the second aspect is a parallel plane type magnetron DC electric field sputtering method, whereby platinum can be made into a more dense film quality.

A capacitive element and a method of manufacturing the same according to one embodiment of the present invention will be described below with reference to the process sectional views of FIGS.

(First Embodiment) As shown in FIG. 1A, a silicon oxide film to be an interlayer insulating film 12 is formed on a supporting substrate 11 made of a silicon substrate. Next, FIG.
As shown in (b), the adhesion layer 13 is formed on the interlayer insulating film 12.
Forming a titanium metal film having a film thickness of about 20 nm, a platinum film having a film thickness of 300 nm to be the lower electrode 14, and setting the substrate temperature at 200 ° C. to 600 ° C. and using a parallel plane type using argon gas. It is formed by a magnetron DC electric field sputtering method. Next, as shown in FIG. 1C, the composition forming the capacitive insulating film 15 on the lower electrode 14 is SrBi ₂ Ta ₂
Apply a ferroelectric film of O ₉ by spin-on method and 800 ℃
Baking. Next, as shown in FIG. 1 (d), platinum serving as the upper electrode 16 is formed thereon by a sputtering method. Further, as shown in FIG. 1E, processing is performed by a photo-etching method and a dry etching method to form a capacitive element.

By the way, in the sputtering of platinum for forming the lower electrode 14 of FIG. 1B, a dense film of platinum is required to prevent the diffusion of metallic titanium of the adhesion layer 13 into the lower electrode 14. 2 to 4 show the relationship between the platinum film forming conditions and the internal stress of platinum. The larger the internal stress in the tensile direction, the denser the film. This will be described below. FIG. 2 is a diagram showing the Ar gas pressure dependency of the internal stress of platinum under the conditions of room temperature and a sputtering power of 0.72 kW. FIG. 3 is a diagram showing the sputtering power dependence of the internal stress of platinum under the conditions of room temperature and Ar gas pressure of 8 mTorr. Fig. 4 shows sputtering power 0.72kW
FIG. 4 is a diagram showing the substrate temperature dependence of the internal stress of platinum under the condition of Ar gas pressure of 8 mTorr. As can be seen from the figure, the internal stress of platinum does not change much depending on the Ar gas pressure and the sputtering power. In comparison with these, the internal stress of platinum has a large dependence on the substrate temperature, and the higher the substrate temperature, the stronger the internal stress in the tensile direction. In FIG.
Substrate temperature under conditions of Ar gas pressure of 8 mTorr and sputtering power of 0.72 kW for adhesion strength between platinum of the lower electrode 14 after formation of the capacitive element and the silicon oxide film of the interlayer insulating film 12 formed on the supporting substrate 11. Show dependencies. The adhesion strength was evaluated as a critical load when the film was peeled off by a scanning scratch tester. The higher the substrate temperature, the larger the critical load. From this, it is understood that the greater the tensile stress of platinum, the greater the critical load, that is, the adhesion strength. As a result, it can be seen that as the substrate temperature increases, in other words, as the tensile stress of platinum increases, the diffusion of titanium forming the adhesion layer 13 is suppressed and the adhesion strength increases. As a result of the above, the platinum film forming conditions are such that the critical load shown in FIG.
By forming a dense film having a tensile stress of 2 × 10 ⁹ dyn / cm ² or more at a temperature of not less than 0 ° C., titanium diffusion can be substantially suppressed and deterioration of adhesion can be eliminated.

The upper limit of the substrate temperature is set to 600 ° C. because if it is set to 600 ° C. or higher, the diffusion proceeds too much and the metal film is likely to have hillocks.

In this embodiment, a simple silicon substrate is used as the supporting substrate, but a silicon substrate having an integrated circuit built therein, a quartz substrate, a GaAs substrate or the like may be used. In addition, in this embodiment, as the capacitor insulating film, B
Although SrBi ₂ Ta ₂ O ₉ having a typical composition having an i-based layered perovskite structure was used, Pb (Zr _1-x Ti _x ) O _{3 was used.}
Other ferroelectric films such as or (Ba _1-x Sr _x ) TiO ₃ may be used, or other metal oxides such as tantalum oxide may be used.

Further, although the capacitor insulating film is formed by the spin-on method in the present embodiment, it may be formed by the sputtering method or the chemical vapor deposition method.

In this embodiment, titanium metal is used for the adhesion layer, but other metals such as tantalum and other metal oxides such as ruthenium oxide and iridium oxide may be used.

[0019]

In the capacitive element of the present invention, the platinum forming the lower electrode has an internal stress of tensile stress of 2 × 10 ⁹ dyn / cm ² or more. It is characterized in that it is formed at a substrate temperature of 200 ° C. to 600 ° C., thereby forming a dense film quality of platinum to suppress the diffusion of metal components of the adhesion layer to the lower electrode side, and the adhesion layer becomes thin. It is possible to prevent the peeling and the metal component of the adhesion layer from diffusing to the capacitive insulating film and deteriorating the electrical characteristics of the capacitive insulating film.

[Brief description of drawings]

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

FIG. 2 is a diagram showing the argon gas pressure dependence of internal stress of platinum.

FIG. 3 is a diagram showing the sputtering power dependence of the internal stress of platinum.

FIG. 4 is a diagram showing substrate temperature dependence of internal stress of platinum.

FIG. 5 is a diagram showing the substrate temperature dependence of the adhesion between the platinum lower electrode and the supporting substrate.

FIG. 6 is a process cross-sectional view showing a method of manufacturing a capacitive element in a conventional example.

[Explanation of symbols]

 11 Support Substrate 12 Interlayer Insulation Film 13 Adhesion Layer 14 Lower Electrode 15 Capacitance Insulation Film 16 Upper Electrode

Claims (3)

[Claims] 1. An adhesion layer made of a metal or a metal oxide formed on a supporting substrate, and a lower electrode formed of platinum having a tensile stress of 2 × 10 ⁹ dyn / cm ² or more formed on the adhesion layer. And a capacitive insulating film made of a metal oxide formed on the lower electrode, and an upper electrode formed on the capacitive insulating film. 2. A step of forming an adhesion layer made of a metal or a metal oxide on a supporting substrate, and a sputtering method in which argon gas is used on the adhesion layer and the substrate temperature is set to 200 ° C. or higher and 600 ° C. or lower. A step of forming platinum to form a lower electrode; a step of forming a capacitive insulating film made of a metal oxide on the lower electrode; and a step of forming an upper electrode on the capacitive insulating film. A method of manufacturing a characteristic capacitive element. 3. The method of manufacturing a capacitive element according to claim 2, wherein the sputtering method is a parallel plane magnetron DC electric field sputtering method.