JP2001015298A - Plasma generating device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enlarge the input power by avoiding heating of a high-frequency permeative dielectric substance used in a plasma generating device. SOLUTION: An antenna 4 is arranged outside high-vacuum vessels 1 and 3 for producing high-frequency waves in them 1 and 3, part of which is made of a dielectric material transmitting the high-frequency waves produced by the antenna 4, wherein the dielectric substance has a double shell structure (11 and 12 or 13 and 14) having a hollow through which a cooling fluid flows. Because the double shell structure is cooled from its inside, the high-frequency power supplied to the antenna can be made comparatively large. It has been confirmed that the use of cooling fluid involves no problem. Also it is made practicable to make continuous input of high-frequency power.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a plasma generator, and more particularly to a plasma generator for performing processes such as film formation, etching, and cleaning on a semiconductor substrate surface.

[0002]

2. Description of the Related Art A plasma generator is known as an apparatus for performing processes such as film formation, etching, and cleaning on a semiconductor substrate surface. The semiconductor substrate surface is subjected to processes such as film formation, etching, and cleaning by radical atoms / molecules, ultraviolet rays, and the like generated from the plasma gas.

As shown in FIG. 6, a known plasma processing apparatus for such a process includes a vacuum vessel body 101,
High frequency generator 102 connected to vacuum vessel main body 101
And a magnetic field generator 103 for generating a magnetic field having lines of magnetic force along the machine axis. 3 is provided on the outer peripheral surface side of the cylindrical body structure 104 constituting the high-frequency generator 102
High frequency power supply 1
High-frequency power is supplied from 06 through a matching unit 107, and plasma is generated in the device by the antenna 105. The plasma or ultraviolet rays and radical atoms / molecules generated from the plasma are applied to the semiconductor substrate 1 by the magnetic field generator 103.
Irradiation is performed on the semiconductor substrate 108 physically.

[0004] In an apparatus using an antenna, the cylindrical structure 104 is formed of a dielectric so that high frequencies can be transmitted therethrough. The cylindrical structure 104 comes into contact with an antenna that receives a high frequency and rises in temperature, and comes into contact with a high-temperature plasma gas on the inside to raise the temperature. In order to maintain the condition that the dielectric does not melt, the input high frequency power is limited. Under the condition that helicon waves are excited by the antenna 105 to generate high-density plasma, 13.56 MHz high-frequency power of about 500 W is continuously input to 30 mTorr of hydrogen gas.

When such an input is made, a quartz glass cylindrical structure 104 of a bell jar type dielectric tube having an outer diameter of 57 mm is provided.
In this case, the temperature becomes about 200 ° C., and injecting a high-frequency power higher than that has a risk that the glass tube may be damaged. When a plasma is generated by exciting a helicon wave, or when a plasma is generated by applying a high frequency in a rectangular pulse train, a threshold of a pulse high frequency power for generating the helicon wave is from 500 W to 1 kW.
I know it is between. Therefore, in order to sufficiently excite the wave to generate high density plasma, 2 kW
It was necessary to inject the above high frequency power, and it was not possible to continuously inject such high frequency power. A device for cooling an antenna is known from Japanese Patent Application Laid-Open No. Hei 9-115895. Although this known device has a structure in which a dielectric is cooled as a result of antenna cooling, there is no positive technical significance for dielectric cooling. Gas cooling cannot effectively cool the dielectric.

[0006] It is more important to avoid heating the dielectric material because high-frequency power injection is performed continuously rather than pulsed because the plasma processing speed is high and the power supply cost is low. It is desirable to increase the injected power by avoiding heating of the dielectric used in the plasma generator. In that case, it is desired to suppress a decrease in the high-frequency transmittance of the dielectric.

[0007]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a plasma generator capable of increasing an injection power by avoiding heating of a high-frequency transmitting dielectric. Another object of the present invention is to provide a plasma generator capable of continuously injecting high-frequency power by avoiding heating of a high-frequency transparent dielectric.

[0008]

Means for solving the problem are described as follows. The technical matters corresponding to the claims in the expression are appended with numbers, symbols, etc. in parentheses (). The number, the symbol, etc. are at least one of the technical items corresponding to the claims and the plurality / forms of implementation.
Although the agreement and correspondence with the technical matters of the two forms are clarified, it is not intended to show that the technical matters corresponding to the claims are limited to the technical matters of the embodiment.

A plasma generator according to the present invention is provided for generating a high frequency in a high vacuum container (1,3) and a high vacuum container (1,3) disposed outside the high vacuum container (1,3). The antenna (4, 4 ′) and a part (3) of the high vacuum vessel (1, 3) are made of a dielectric material formed of a dielectric material that transmits a high frequency generated by the antenna (4, 4 ′). And the dielectric is a double shell structure (11, 12) having a hollow inside.
Or 13, 14), through which a cooling fluid is passed.

[0010] Since the double-shell structure is cooled inside the double-shell structure, the high-frequency power supplied to the antenna can be further increased. It has been confirmed that no adverse effect is caused by using the cooling fluid. Continuous injection of high frequency power is also possible.

[0011] The dielectric material is one or more materials selected from the group consisting of glass, ceramics, and plastics, and the cooling fluid is selected from the group consisting of water, oil, chlorofluorocarbon, nitrogen gas, and SF6. One or a plurality of cooling fluids. By performing cooling, it is possible to flexibly and flexibly cope with various types of plasma generators which are distinguished by large size, small size, dielectric shape, and price.

The antenna is formed of a hollow tube having a plurality of turns, and a cooling fluid is also passed through the hollow portion of the hollow tube of the antenna.
Furthermore, heating of the dielectric itself is suppressed. The cooling of the antenna additionally serves to cool the dielectric. The cooling fluid is
Coolant, cooling gas.

The dielectric may be any of a flat plate type, a cylindrical type, and a bell jar type, and it has been confirmed that cooling is effective in any type. The injection of the cooling fluid into the hollow is preferably at least one atmosphere to several atmospheres in order to enhance the cooling effect.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Corresponding to the drawings, an embodiment of a plasma generator according to the present invention is provided with a high vacuum vessel main body and a high frequency generator. As shown in FIG. 1, a high-frequency generator 2 is connected to the vacuum vessel main body 1. The high frequency generator 2 is formed by a double shell structure 3 and a high frequency antenna 4.

The vacuum vessel main body 1 and the double shell structure 3 form a single vessel whose inside is evacuated to a high vacuum. A magnetic field generator 5 formed of two concentric coils is provided outside the vacuum vessel main body 1 and the double shell structure 3. The magnetic field generator 5 generates a magnetic field having magnetic lines of force substantially coinciding with the machine axis L.

The double shell structure 3 is formed of a cylindrical body structure 6 and a hemispherical shell structure 7, and is a bell jar type tube. The high-frequency antenna 4 is formed as a three-turn coil on the outer peripheral surface side of the cylindrical structure 6. The high-frequency antenna 4 is supplied with high-frequency power from a high-frequency power supply 8 via a matching unit 9. The center axis of the high-frequency antenna 4 substantially coincides with the machine axis L. The high-frequency antenna 4 has an inner diameter of 72 mm
And a hollow coil formed by winding a copper pipe having a wire diameter of 6 mm three times.

The cylindrical body structure 6 has a double tube structure, and is formed of an outer glass tube 11 having an outer diameter of 72 mm and an inner glass tube 12 having an inner diameter of 57 mm. The outer glass tube 11 and the inner glass tube 12 are formed concentrically and share a machine axis as a common axis. Hemisphere shell structure 7
Is formed of an outer hemispherical glass shell 13 continuing to the outer glass tube 11 and an inner hemispherical glass shell 14 continuing to the inner glass tube 12, and the double shell structure 3 is a bell jar 2
It forms a heavy shell structure.

The double shell structure 3 has an inlet 1
6 and a discharge port 17 at an upper portion thereof. The cooling fluid is introduced from the inlet 16, circulates inside the double shell structure 3, and is discharged from the outlet 17. The inlet 16 and the outlet 17 are respectively connected to the inlet and outlet of a chiller heat exchanger (not shown), and the cooling fluid circulates through the chiller heat exchanger.

The double shell structure 3 is formed of a dielectric material. As the dielectric material, one or more materials selected from the group consisting of glass, ceramics, and plastics can be used. As the cooling liquid, a fluid having low absorption of high-frequency power is used, and in particular, one or a plurality of cooling fluids selected from the group consisting of water, oil, chlorofluorocarbon, nitrogen gas, and SF6 can be used.

From the gas inlet 21, 30 mTorr
Hydrogen gas is introduced into a container formed by the vacuum container main body 1 and the double shell structure 3. The magnetic field generator 5 generates a magnetic field of 200 to 300 Gauss in the central region of the device. High frequency power is continuously supplied to the double shell structure 3 from the high frequency power supply 8 capable of continuous operation through the matching unit 9.

The hydrogen gas in the container is turned into plasma by such high frequency power. Cooling water 2 from inlet 16
The high-frequency antenna 4 injected into the inside of the heavy shell structure 3
Other cooling water is injected into the water. By such two types of injection of the cooling water, the double-shell structure 3 and the high-frequency antenna 4 are simultaneously and actively cooled. The plasma which is subjected to the magnetic force by the magnetic field generator 5 irradiates ultraviolet rays and radical atoms / molecules along the lines of magnetic force toward the semiconductor substrate 23 arranged in the vacuum vessel main body 1. With such radiation, the semiconductor substrate undergoes various treatments.

FIG. 2 shows the frequency dependence of the relative dielectric constant of pure water used as a cooling fluid. The absorption of high-frequency power is proportional to the product of the imaginary part ε of the relative permittivity and the frequency. 1
At a high frequency of 3.56 MHz, ε is 0.049,
It is about 1/180 of the value 8.7 of the microwave for microwave oven at the frequency of 2.45 GHz. The product of the imaginary part of the relative permittivity and the frequency is 1 compared to 2.45 GHz.
At 3.56 MHz, it is about 1/30000, and 13.
The absorption of high frequency power of 56 MHz into water is very small.

Next, comparing the apparatus of FIG. 1 according to the present invention with the known apparatus of FIG. 6, if the inside diameter of the dielectric cylinder near the antenna where the plasma exists is the same, the antenna of the present invention will Is increased, the interaction between the antenna and the plasma is weakened, and there is a concern that the plasma density may be reduced. In order to examine the effect, the cylindrical type 2 shown in FIG.
A plasma generation test was performed to compare the cylindrical single dielectric tube with the same inner diameter as the heavy dielectric tube 41.

The inner diameter of both dielectric quartz glasses used for the test is 50 mm, which is common, and the outer diameter is 72 mm for a double dielectric tube and 57 mm for a single dielectric tube. The antenna had a structure in which a water-cooled copper pipe having a wire diameter of 6 mm was wound three turns in close contact with the outer diameter of the dielectric.
Plasma measurement, 24c from the antenna to the vacuum vessel
The plasma density was measured with a probe at the position of m. The high frequency (R) of the electron density measured by the double glass tube apparatus of FIG.
F) FIG. 4 shows a comparison between the input dependency and the case of changing to a single glass tube.

In the case of a single glass tube, the high frequency input is 1 k
W was the limit, but there was no problem at 2 kW in the double glass tube. At the same high-frequency input of 1 kW, the electron density is about 90% in the double glass tube compared to the single glass tube.
However, it is considered that they are almost the same, and the loss of high-frequency power to water is considered to be small. From these results, the electron density of the hydrogen plasma was the highest at the cube of 1.5 × (10 12) / cm in the single glass tube, but was 4.2 × (10 × 10) in the double glass tube. 12th power) / cm
And the cooling of the dielectric tube is effective.

FIG. 5 shows another embodiment according to the present invention. The vacuum vessel main body 1 is the same as the vacuum vessel main body 1 of the above-described embodiment. The high frequency generator 2 connected to the vacuum vessel body 1 has a double shell structure 3 and a high frequency antenna 4
This is also the same as the above-described embodiment.

The double shell structure 3 'of this embodiment is disk-shaped, that is, flat. The spiral high-frequency antenna 4 'is in close contact with the outer surface (vertical surface) of a flat double dielectric plate having a double shell structure 3'. The center axis of the spiral high-frequency antenna 4 'coincides with the machine axis L. There is no magnetic field generator in this device. In a device where no magnetic field is formed, the antenna and the plasma have an inductive coupling relationship similar to the relationship between the primary and secondary sides of the transformer.

The plasma generated by such a relationship is called an inductively coupled plasma. In FIG. 1, the magnetic field generator 5
The device from which is removed is an inductively coupled plasma device.
Also in this embodiment, cooling of the dielectric is effective. FIG.
The cooling of the dielectric is also effective when a magnetic field generator is attached to the above device.

The plasma generator shown in FIG. 3 used as a test device is a practical device as it is. In this device, the gas inlet 21 is provided at the rear end of the double glass tube structure 3 ".

An apparatus in which high-frequency power is injected from an antenna into a high-vacuum vessel through a dielectric to be cooled can increase the high-frequency power to be injected.
Plasma density increases, plasma processing such as film formation is accelerated, and dielectric heating damage can be prevented even by continuous high-frequency injection. Can be used.

By changing the material of the dielectric and the cooling fluid and using ceramics whose melting temperature is higher than that of glass, it is possible to further increase the high-frequency power and to cope with a large-sized plasma device. Conversely, a small-sized plasma device using low-output high-frequency can be provided at low cost by using plastics as the dielectric. In large-scale plasma devices and devices that turn materials that react with water into plasma,
Safety can be improved by using a flame-retardant oil as a cooling fluid.

By changing the shape of the dielectric, it is possible to cope with different injection methods of a plasma generator for injecting a high frequency with an antenna. In a helicon wave excitation method that requires a magnetic field in the direction of the central axis of the antenna, cylindrical and bell jar dielectrics are suitable, and cooling of these dielectrics is effective. In an inductive coupling method without a magnetic field, a cylindrical, bell jar, or flat dielectric is suitable, and it is also effective to cool them.

In order to ensure a sufficient cooling effect, it is particularly preferable that the cooling fluid be at least one atmosphere to several atmospheres in the dielectric for increasing the cooling effect.

[0034]

According to the plasma generating apparatus of the present invention, the input high-frequency power can be increased and the input can be made continuous.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing an embodiment of a plasma generator according to the present invention.

FIG. 2 is a graph showing relative permittivity calculation.

FIG. 3 is a sectional view showing a comparative test apparatus according to another embodiment of the present invention.

FIG. 4 is a graph for comparing the relationship between an input value and an electron density.

FIG. 5 is a sectional view showing still another embodiment of the plasma generator according to the present invention.

FIG. 6 is a cross-sectional view showing a known device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... High vacuum container (main part) 3 ... Double shell structure 4, 4 '... Antenna 11 ... Outer glass tube 12 ... Inner glass tube

Continuation of the front page (72) Inventor Takao Abe 1-8-1 Koura, Kanazawa-ku, Yokohama-shi, Kanagawa Prefecture F-term (Reference) 5F004 AA00 BA14 BA15 BA16 BA20 BB13 BB14 BB18 BB29 BC08 5F045 AA08 DP01 DP02 DP03 EH01 EH02 EH11 EH16 EH17 EJ04 EJ05

Claims (4)

[Claims] A high-vacuum container; an antenna disposed outside the high-vacuum container for generating a high-frequency wave in the high-vacuum container; and a part of the high-vacuum container is generated by the antenna. A plasma generating apparatus, comprising: a dielectric formed of a dielectric material that transmits the high frequency; the dielectric forming a double-shell structure having a hollow inside, and a cooling fluid passing through the hollow. 2. The method according to claim 1, wherein the dielectric material is one or more materials selected from the group consisting of glass, ceramics, and plastics, and the cooling fluid is water, oil, Freon, nitrogen gas. , SF
6. A plasma generator, which is one or more cooling fluids selected from the group consisting of: 3. The plasma generator according to claim 2, wherein said cooling fluid is injected into said dielectric at a pressure of 1 atm or more to several atm. 4. The plasma generator according to claim 2, wherein the antenna is formed of a hollow tube, and a cooling fluid is passed through the hollow tube.