JPH04199828A - Manufacture of oxide thin film of high dielectric constant - Google Patents

Abstract

PURPOSE:To improve a dielectric strength and reduce a leakage current, by projecting on an oxide film such as a tantalum oxide film, oxygen ions or an oxygen plasma generated in the plasma processing equipment, which utilizes a plasma decomposition using a microwave. CONSTITUTION:For example, an oxygen gas is introduced into a plasma generating chamber 16, and via a waveguide 18, a microwave generated by a microwave power supply 17 is introduced into the oxygen gas to discharge it, and thereby, the generation of oxygen ions or an oxygen plasma is performed. In this case, by applying thereto a magnetic field generated through an electromagnet 19 of a solenoid type, a cyclotron resonance of electron is generated in the plasma generating chamber 16. Further, by setting oxygen in the plasma generating chamber 16, a highly active oxygen plasma having a high ionization rate and a high electron temperature is obtained. This oxygen plasma is introduced into a sample chamber 14 by the potential difference between oxygen ions as well as by a divergent magnetic field, and is projected on an oxide film 11 put on a sample table 12. Thereby, the leakage current and the dielectric strength of the oxide film are improved.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a method for producing a high dielectric constant thin film applied to electronic devices and the like.

BACKGROUND OF THE INVENTION As the degree of integration of VLSIs such as DRAMs increases, the area occupied by the capacitor section can no longer be ignored. In order to reduce the occupied area, it is necessary to use a thin film material that has a high capacitance per unit area, that is, a high dielectric constant. In general, the material must have low leakage current and high dielectric strength. Conventionally, silicon oxide (SiO2), which has a dielectric constant of about 4, and silicon nitride (Si3N4), which also has a dielectric constant of about 7, have been used as capacitor insulating film materials. These insulating film materials have been used so far because of their high dielectric strength and low leakage current, but because of their low dielectric constants, it is becoming difficult to apply them to VLSI, which is becoming increasingly highly integrated.

In addition, as a material to replace these, tantalum oxide ("I"
``a20s), hafnium oxide (Hf02), and other materials with high dielectric constants are considered as candidates.Currently, T
A205 is being considered as a promising material by many research institutions.

Problems to be Solved by the Invention In this way, the conventional SiO
Considering the features of 2,5i3NA, the leakage current is very small, the reliability is high, and the dielectric constant is small, so it is not possible to secure sufficient memory capacity by reducing the cell area due to increased integration. However, it is difficult to summarize.

In addition, Ta205 has a dielectric constant of about 20 to 25.
By using the reactive sputter link method, films with excellent properties such as denseness and high dielectric strength are formed. However, at the film thickness of several tens of η or less required for LSI, so far only the dielectric constant decreases and the leakage current increases. In addition, when considering step coverage, CVD method is an effective technique for forming a film or soaking into super LsI. However, in the CVD method, the decomposition of the raw material and the reaction with oxygen are insufficient, so the film immediately after formation has a low dielectric strength voltage and a large leakage current, making it impractical.

Therefore, by performing heat treatment in an oxidizing atmosphere at a high temperature of usually about 800° C., it is possible to improve dielectric strength and reduce leakage current. However, actually LS
In the step I, when oxidation treatment is performed at a high temperature of about 800° C., mutual diffusion and thermal damage occur between the materials of the F base, causing deterioration of device characteristics, which is a problem.

The present invention aims to solve such conventional problems.

Means for Solving the ProblemsClaim 10: The method for producing a high dielectric constant oxide thin film according to the present invention comprises generating an oxide film such as a tantalum oxide thin film in a plasma processing apparatus using plasma decomposition using microwaves. The above problem is solved by irradiating oxygen ions or oxygen plasma.

Claim 20 Another method for producing a high dielectric constant oxide thin film according to the present invention is to apply plasma generated by applying a high frequency voltage to scum containing at least oxygen on an oxide film such as a tantalum oxide thin film. The above-mentioned problem is solved by installing an electrode set at a predetermined potential between a sample stage on which an oxide film is installed and irradiating it with oxygen ions or oxygen plasma.

Another oxide high dielectric constant 'fiI according to the present invention of claim 3
The manufacturing method II solves the above problem by installing an oxide film such as a tantalum oxide thin film in plasma generated by applying a high frequency voltage to a gas containing at least oxygen.

The present invention according to claim 1 provides plasma decomposition of oxygen gas or the like using microwaves, particularly under electron cyclotron resonance absorption conditions, as oxygen ions or oxygen plasma irradiated onto an oxide film such as tantalum oxide';ii film. When using a material with a high electron density and high dissociation degree generated by plasma decomposition with a magnetic field applied to satisfy the It is possible to reduce the dielectric strength and improve the dielectric strength. Furthermore, the present invention utilizes the kinetic energy of ions or plasma.
It is possible to provide a method for producing a high dielectric constant oxide thin film that can be processed without damage at a relatively low temperature of 00° C. or lower.

The present invention according to claim 2 uses highly active oxygen ions or oxygen plasma generated by applying a high frequency voltage to scum containing at least oxygen as the oxygen ions or oxygen plasma to be irradiated to the oxide film, and furthermore, the plasma and the oxide film are Oxygen ions in the plasma are accelerated by applying a predetermined low electric field between the sample stage and the sample stage, which accelerates oxidation of the irradiated area.
As a result, it is possible to reduce the leakage current of the film and improve the insulation surface and 1 voltage. Further, in the present invention, it is possible to control the degree of oxidation of the irradiated region by changing the ion accelerating electric field. Roughly speaking, the present invention utilizes the kinetic energy of ions or plasma to
It is possible to provide a method for producing a high dielectric constant oxide thin film that can be processed without damage at a relatively low temperature of .degree. C. or lower.

Further, in the present invention of claim 3, since the oxide film is installed so as to be directly exposed to highly active oxidizing plasma generated by applying a high frequency voltage to the scum containing at least oxygen, the films i, ti As a result, the leakage current characteristics of the film can be improved and the dielectric strength can be improved. Furthermore, the present invention
It is possible to provide a method for producing a high dielectric constant oxide thin film that can be processed at a relatively low temperature of 500° C. or lower using plasma motion 1 energy.

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

FIG. 1 shows a schematic cross-sectional view of a manufacturing apparatus used in the method for manufacturing an oxide high dielectric constant thin film according to the first aspect of the present invention.

A substrate 11 on which an oxide film (for example, tantalum oxide 11N) is formed is placed on a sample stage 12 and heated to a predetermined temperature by a heater 13. The inside of the sample chamber 14 is evacuated by a vacuum pump 15.

To generate oxygen ions or oxygen plasma, for example, oxygen gas is introduced into the plasma generation chamber 16, and this gas is heated to a frequency of 2.45 GH generated by the microwave power source 17.
This is done by introducing microwaves of z through the waveguide 18 and causing a discharge.

In this case, a solenoid-type electromagnet 19 placed around the plasma generation chamber 16 generates a central magnetic field of 8750auss.
By applying a magnetic field to a certain degree, electron cyclotron resonance occurs in the plasma generation chamber 16. The oxygen gas pressure in the plasma generation chamber 16 is set to 10-4 to 1O-3To.
By setting to rr, oxygen plasma with high activity, high ionization rate, and high electron temperature can be obtained. This oxygen plasma is introduced into the sample chamber 16 by the divergent magnetic field of the electromagnet 19, and at the same time is introduced by the difference in oxygen ions or potential, and is irradiated onto the oxide film 11 installed on the sample stage 12 in the sample chamber 16. Ru.

The most typical processing conditions are oxygen gas flow rate of 5 seconds,
Oxygen gas pressure lXl0-3 Torr, microwave power 30
0W, processing temperature 300°C. If the processing temperature of the oxide film 11 is a predetermined temperature between 300 and 500°C, the film will be sufficiently oxidized by the highly active oxygen ion plasma, and as a film characteristic, the leakage current will decrease and the dielectric strength will improve. The present inventors have confirmed that.

For example, a tantalum oxide thin film is used as the oxide film to be subjected to the irradiation treatment. For example, a tantalum oxide thin film can be produced under reduced pressure C.
Formed by VD method. Typical formation conditions are shown. A silicon substrate on which 200 nm of polycrystalline silicon is formed is placed in a reaction tube and maintained at 450°C. As the waste source for CVD, Ta(OC2) 1s)s was used, the waste container was kept warm at about 130°C, and the flow rate was 150 sccm.
A: While scraping and buffing, the gas is fed to the reaction tube through a gas feed pipe kept at 200°C. Also, as an oxidizing gas, oxygen gas is fed to the reaction tube at a flow rate of 100 sccm. The degree of vacuum inside the tube is 0.5 Torr.

-250 nm of tantalum oxide formed under the conditions described in F?
The dielectric constant of Ti1lW is 21.5, and the leakage current density is 4.8×10 when an electric field of I MV/cm is applied.
-6A/crn2. By subjecting this tantalum oxide thin film to the oxygen ion plasma irradiation treatment for 30 minutes, the leakage current density at IMV/cm was reduced to 6.5 x 10-8 A/cm2.

Figure 2 shows the electric field dependence of leak current density before and after oxygen ion plasma dissection treatment. The improvement in dielectric strength after treatment is also obvious.

Next, FIG. 3 shows a schematic cross-sectional view of a manufacturing apparatus used in the method of manufacturing a high dielectric constant oxide thin film according to the second aspect of the present invention. A gas containing at least oxygen, for example, oxygen scum, is introduced into the plasma generation chamber 16, and a high frequency signal (13-56MH
z) is applied to generate plasma. By applying a DC voltage between the plasma and the sample stage 12 on which the substrate 11 on which the oxide film is formed is placed, highly active oxygen ions are extracted from the plasma generation chamber 16, and the plasma is placed on the sample stage 12. This is to irradiate the oxide film 11. In this method, the energy of oxygen ions can be controlled by changing the accelerating voltage, thereby making it possible to control the degree of oxidation promotion.

Typical processing conditions are an oxygen gas pressure of 3 x 10-' Torr in the plasma generation chamber 16, a high frequency power of 200 W, an ion acceleration voltage of 1 kV, and a processing temperature of 300°C. Further, the conditions for forming the oxide film are the same as in the first invention.

In this case as well, if the treatment temperature of the oxide film is a predetermined temperature between 300 and 500°C, the irradiated highly active ions
The present inventors have confirmed that the coating can be sufficiently oxidized by plasma, and that properties in the direction of -L can be achieved. By performing the treatment for 30 minutes under the above conditions, the leakage current density was reduced to 3.5 x 10-5. A/c In2
We were able to reduce the current voltage to 7X10-8A/cm2, and increase the voltage per insulation surface to 2-5MV/CIn.

A schematic cross-sectional view of a manufacturing apparatus used in the method of manufacturing a high dielectric constant oxide thin film according to the present invention as claimed in claim 3 is shown in FIG. Oxygen gas, for example, was introduced into the vacuum chamber 41 as a scum containing at least oxygen, a high frequency electric field of 13.56 MHz was applied to the parallel electrodes to cause a discharge, and the scum was heated to a predetermined temperature in the discharge plasma. An oxide film is placed and treated with oxygen. A feature of this method is that the oxidation of the coating can be promoted by directly exposing it to highly active oxygen plasma containing oxygen ions.

Typical processing conditions are an oxygen gas pressure of 1T o in the vacuum chamber.
r r, high frequency power of 200 W, and processing temperature of 300°C. The formation of the oxide film is the same as in the first and second inventions. In this case as well, the treatment temperature for the oxide film is 300 to 500.
At a predetermined temperature between °C, the coating is sufficiently oxidized;
It is possible to improve leakage current characteristics and dielectric strength. By oxygen treatment for 20 to 30 minutes under the above conditions, the leakage current density was reduced from 5 x 10-5 A/cm2 before treatment to 8.5 x 10-8 A/cm2, and the dielectric strength was reduced to 1. What used to be 2MV/cm is now 2.3MV/cm.
I was able to improve it to cm.

As described in detail of the invention, the method for producing a high dielectric constant oxide thin film of the present invention according to claim 1.2 or 3 includes the following steps:
Since highly active oxygen ion plasma is used, it is possible to fill the deficiency in oxygen concentration in oxide films with high dielectric constants such as tantalum oxide, thereby reducing leakage current. It is possible to improve film properties such as an increase in dielectric strength, and by utilizing the kinetic energy of oxygen ion plasma, it is possible to provide a method that allows processing in a low temperature range of 500° C. or lower.

The method for producing a high dielectric constant oxide thin film of the present invention is extremely useful as a method for forming insulating film materials for next-generation VLSIs such as DRAMs of 16 Mbits or more, and the industrial value of the present invention is high.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view of a manufacturing apparatus used in the method for manufacturing a high dielectric constant oxide thin film of the present invention according to claim 1, and FIG. FIG. 3 is a schematic cross-sectional view of a manufacturing apparatus used in the method for manufacturing an oxide high dielectric constant thin film of the present invention according to claim 2. , and FIG. 4 is a schematic cross-sectional view of a manufacturing apparatus used in the method for manufacturing a high dielectric constant oxide thin film of the present invention according to claim 3. DESCRIPTION OF SYMBOLS 11...Substrate with oxide film formed (), 12...Sample stage, 13...Heater, 14...Sample chamber, 1
5... Vacuum pump, 16... Plasma generation chamber, 17
...Microwave power supply, 18...Waveguide, 19...
Electromagnet, 3], 32...electrode, 4]...vacuum chamber. Agent Patent Attorney Matsu 1) Tadashi Michi 1 Figure 2 Figure 3 Figure 1'3 Figure 4

Claims (1)

[Scope of Claims] (1) Forming a high dielectric constant oxide thin film by irradiating the oxide film with oxygen ions or oxygen plasma generated in a plasma processing device using plasma decomposition using microwaves. A method for producing a high dielectric constant oxide thin film characterized by: (2) installing an electrode set to a predetermined potential between the plasma generated by applying a high frequency voltage to a gas containing at least oxygen to the oxide film and the sample stage on which the oxide film is installed; A method for producing a high dielectric constant oxide thin film, the method comprising forming the high dielectric constant oxide thin film by irradiating oxygen ions or oxygen plasma. (3) An oxide high dielectric constant thin film characterized in that the oxide high dielectric constant thin film is formed by installing an oxide film in plasma generated by applying a high frequency voltage to a gas containing at least oxygen. Manufacturing (4) Claims 1 and 2 characterized in that a tantalum oxide thin film is used as the oxide film.
or 3. The method for producing an oxide high dielectric constant thin film according to 3. (5) The method for producing a high dielectric constant oxide thin film according to claim 1, 2 or 3, characterized in that the oxide film is maintained at a predetermined temperature of 300 to 500°C during irradiation with oxygen ions or oxygen plasma. . (6) The method for producing a high dielectric constant oxide thin film according to claim 1, characterized in that the plasma processing apparatus uses a method of applying a magnetic field so as to satisfy electron cyclotron resonance absorption conditions.