JP2000164570A - Plasma processing equipment - Google Patents

Abstract

(57) [Summary] [PROBLEMS] A plasma processing apparatus capable of extending the life of the inner wall surface of a reaction vessel. SOLUTION: An inner upper wall 11a, an inner lower wall 11b, and an outer wall 11c are connected to each other in a reaction vessel 11, and a reaction chamber 12 is formed inside. An alumite film 1, which is an insulating film, is formed on the inner wall surface of the inner lower wall 11b, and an edge portion of the inner sample transfer port 21b of the inner lower wall 11b,
An alumina film 2 as an insulating film is formed on each edge portion of the lower end portion 110. Since the insulating film at the edge has a thickness in which the alumite film 1 and the alumina film 2 are laminated, the electric field concentration is reduced. As a result, excessive spatter at the edge portion is prevented, and the life of the container is extended.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a semiconductor device substrate,
Etching, ashing, CVD (Chemical Vapor Depositio) on glass substrates for liquid crystal displays (LCD)
The present invention relates to a plasma processing apparatus for performing processes such as n), and more particularly to a plasma processing apparatus used for etching a silicon oxide film.

[0002]

2. Description of the Related Art In an LSI manufacturing process, it is widely practiced to apply external energy to a reaction gas to generate a plasma, and to perform processing such as etching, ashing, and CVD using the plasma. In particular, a dry etching technique using plasma has become an essential basic technique for this LSI manufacturing process.

As an apparatus for performing such plasma processing, there are an apparatus for generating plasma using high frequency, an apparatus for generating plasma using microwave and applying high frequency to control the plasma. By selecting an appropriate high frequency, generation of plasma and control of ions in the plasma can be easily performed.

However, in a plasma processing apparatus using a high frequency, the inner wall surface of the reaction vessel is constantly exposed to plasma containing radicals and ions having high chemical activity. Therefore, it is important to select a material for the inner wall surface of the reaction vessel. By properly selecting the material of the inner wall surface or coating with an appropriate material, the plasma processing characteristics are improved,
The life of the inner wall surface is prolonged. For example, it is possible to improve the selectivity with respect to the base during etching, or to suppress generation of particles due to sputtering of the inner wall surface.

For example, there has been proposed a plasma etching apparatus using high-purity alumina (Al ₂ O ₃ ) as a material for an inner wall surface of an etching chamber (Japanese Patent Application Laid-Open Nos. 63-326442 and 61-289634). No.). Also, a plasma etching apparatus using anodized aluminum as a material for the inner wall surface has been proposed (Japanese Patent Application Laid-Open No. 4-299529). As described above, a predetermined insulating film is formed on the inner wall surface of the reaction container according to the type of the etching target and the reaction gas.

[0006]

Normally, since the reaction vessel is electrically grounded, the inner wall surface also partially serves as a ground electrode for high frequencies. When the plasma is generated at a high frequency by using the inner wall surface of the reaction vessel as a ground electrode, the plasma is stabilized. When the plasma is controlled by the bias potential generated by applying a high frequency to the mounting table on which the sample is mounted, the bias potential is stabilized.

[0007] Since the state of the plasma is affected by the inner wall surface of the reaction vessel serving as the ground electrode, the thickness of the insulating film is important when an insulating film is provided on the inner wall surface. That is, the inner wall surface functions as a ground electrode when there is no insulating film, and the effect of the ground electrode weakens as the insulating film becomes thicker. When the thickness exceeds a predetermined thickness, the inner wall does not function as a ground electrode at all.

Therefore, when the inner wall surface of the reaction vessel is used as a ground electrode, particularly when no counter electrode is provided, it is necessary to reduce the thickness of the insulating film provided on the inner wall surface. However,
When the insulating film is thin, the inner wall surface is sputtered by the plasma, the insulating film peels off, and the inner wall surface is exposed. As a result, there is a problem that the life until the inner wall surface of the reaction vessel is exposed is shortened.

The present invention has been made in view of such circumstances, and an object of the present invention is to maintain the life of the inner wall surface long while the inner wall surface of the reaction vessel functions as a ground electrode. An object of the present invention is to provide a plasma processing apparatus.

[0010]

According to a first aspect of the present invention, there is provided a plasma processing apparatus for applying a high frequency to a container and processing a sample by plasma, wherein the container has an inner wall surface coated with an insulating film. Preferably, the insulating film is formed thicker at an edge portion of the inner wall surface than at other portions.

The inventor of the present application has presumed that the high frequency electric field is concentrated on the edge portion provided on the inner wall surface serving as the ground electrode, so that this portion is sputtered quickly. Here, the edge portion refers to a portion where the shape of the inner wall surface of the container changes, such as a corner portion, an edge portion, and a tip portion. Specifically, the edge portion of the sample transfer port, the edge of the lower end of the inner wall, and the like. And the edges of other openings.

In the first invention, the thickness of the insulating film at the edge portion where the high-frequency electric field is particularly likely to concentrate on the inner wall surface of the container is formed thicker than other portions. The edge portion where the insulating film is formed thicker acts as a ground electrode weaker than other portions, so that the electric field concentration is reduced. This suppresses excessive sputtering of the insulating film at the edge portion. In addition, there is an effect of extending the life due to the fact that the insulating film is simply formed thick. Further, since the thickness of the other portion of the insulating film is as usual, it sufficiently functions as a ground electrode on the inner wall surface, and stabilizes high frequency application.

A plasma processing apparatus according to a second aspect of the present invention is characterized in that plasma is generated in the container by introducing microwaves through the microwave window into a container provided with a microwave window, and the plasma is generated in the container. In a plasma processing apparatus that applies a high frequency to the mounting table provided in the processing table and guides the generated plasma to the sample mounted on the mounting table to process the sample, the container has an inner wall surface coated with an insulating film,
The insulating film is formed to be thicker at an edge portion of the inner wall surface than at other portions.

According to the second aspect of the present invention, in a device for generating plasma by introducing a microwave and controlling the plasma by applying a high frequency, the thickness of the insulating film on the inner wall surface of the container is formed thick at the edge portion. The reaction vessel is a ground electrode for high frequency, and the edge portion is easily sputtered quickly. However, the electric field concentration is reduced by forming the insulating film thicker than other portions. This suppresses excessive sputter at the edge portion. In addition, since the insulating film is thick, it is possible to prolong the service life. Further, the other portion of the insulating film sufficiently functions as a ground electrode, stably generates a high frequency bias on the mounting table, and can improve the plasma processing characteristics. .

[0015] A plasma processing apparatus according to a third aspect of the present invention comprises:
Alternatively, in the second invention, the edge portion is a region including an edge of a sample transfer port formed on the inner wall surface.

The plasma processing apparatus is provided with a sample transfer port for loading a sample into a container, disposing the sample on a mounting table, and carrying out the sample after plasma processing. In the third invention, an insulating film thicker than other portions is formed in a region including an edge of the sample transfer port formed on an inner wall surface of the container. By forming the insulating film at the edge portion thicker than other portions, the electric field concentration is reduced. This suppresses excessive sputter at the edge portion. In addition, since the insulating film is thick, it is possible to prolong the life. Further, the other portion of the insulating film sufficiently functions as a ground electrode, and stabilizes the application of high frequency.

According to a fourth aspect of the present invention, in the plasma processing apparatus according to the first, second or third aspect, the insulating film formed on an edge portion of the inner wall surface of the container contains alumina.

In the fourth aspect of the present invention, at least the surface of the insulating film at the edge portion is formed of alumina (Al ₂ O ₃ ). Therefore, even when sputtered, contamination of the sample by impurities such as heavy metals is prevented. Reduced.

The plasma processing apparatus according to the fifth invention has a first
In any one of the fourth to fourth inventions, after forming an alumite film with a predetermined thickness by an anodizing method on the inner wall surface of the container, the insulating film is formed by spraying alumina on the edge portion. Features.

In the fifth invention, an alumite film is formed on the entire inner wall surface by anodic oxidation, and only the edges are coated with alumina on the surface of the alumite film by thermal spraying. By using the thermal spraying method, a dense film can be formed to a required thickness. Therefore, an insulating film having a thicker edge portion and a thinner other portion can be easily formed.

[0021] The plasma processing apparatus according to the sixth aspect of the present invention comprises:
In any one of the fifth to fifth inventions, the thickness of the insulating film formed on the edge portion is at least 100 μm.

In the sixth invention, the thickness of the insulating film at the edge portion formed of, for example, only alumina, only alumite, or a laminate of alumite and alumina is 100 μm.
When the thickness is smaller, the effect of relaxing the electric field concentration is small.
It preferably has a thickness of at least 00 μm.

A plasma processing apparatus according to a seventh aspect of the present invention comprises:
In any one of the sixth to sixth inventions, the method is characterized by being used for etching a silicon oxide film on the sample.

In etching a silicon oxide film, control of ions is extremely important. Etching of the silicon oxide film uses a large high frequency power, a high frequency lower than 13.56 MHz, such as 2 MHz or 400 kHz, or a low pressure of several tens mTorr or less. Such processing conditions increase the level of high frequency electric field concentration, and the electric field concentration at the edge becomes a more serious problem. According to the seventh aspect of the present invention, when the silicon oxide film is etched, the electric field concentration is reduced by using a container in which the insulating film at the edge portion is formed thick, and a great effect is obtained.

[0025]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below with reference to the drawings showing the embodiments. FIG. 1 is a side sectional view showing a structure of a plasma processing apparatus according to an embodiment of the present invention. FIG. 2 is an enlarged view of an area A shown in FIG. In the figure, reference numeral 11 denotes a bottomed cylindrical reaction vessel made of a conductive metal such as aluminum or stainless steel. As described later, the reaction vessel 11 has an inner upper wall 11a,
The inner lower wall 11b and the outer wall 11c are connected, and a reaction chamber 12 is formed inside the lower wall 11b and the outer wall 11c. Reaction vessel 1
The reason why 1 has a double structure of an inner side and an outer side is that the temperature can be efficiently and stably controlled only on the inner side, and only the inner side can be replaced and used.

The upper opening of the reaction vessel 11 is
With the introduction window 14, the O-ring 32 is interposed and hermetically sealed.
Has been stopped. The microwave introduction window 14 has heat resistance and
Quartz glass with low wave loss and low dielectric loss
(SiO_Two), Alumina (Al _TwoO_Three) Etc.
Has been established.

A disk-shaped dielectric layer 36 is arranged in parallel above the microwave introduction window 14 with a space layer 35 at a predetermined interval, and the upper part of the dielectric layer 36 is a metal cover plate 37 made of, for example, aluminum. Covered with. One side of the dielectric layer 36 is connected to a microwave oscillator 39 via a waveguide 38. The dielectric layer 36 is made of a material having a small dielectric loss,
For example, it is formed of a synthetic resin such as a fluororesin, polyethylene, and polystyrene. As the frequency of the microwave, for example, 2.45 GHz is used.

On the lower surface of the microwave introduction window 14, an introduction region of the microwave introduced into the reaction chamber 12 is formed.
A limiting plate 9 for limiting to a central portion of the frame is disposed.
The limiting plate 9 is an annular plate having conductivity, and is fixed so that an inner peripheral edge of the limiting plate 9 abuts on an annular microwave window convex portion 14 a protruding below the microwave introduction window 14. ing. The lower surfaces of the limiting plate 9 and the microwave window projection 14a are covered and protected by the quartz cover 10. A heater 31 is embedded on the outer peripheral side of the limiting plate 9.

FIG. 2 is an enlarged view of the area A shown in FIG. 1 and shows the detailed structure of the side wall of the reaction vessel. As shown in FIG. 2, the reaction vessel 11 includes an inner upper wall 11a, an inner lower wall 11b, and an outer wall 11c, and is made of aluminum. The outer side wall 11c has a substantially cylindrical shape with a bottom, and the inner upper wall 11a and the inner lower wall 11b are vertically mounted to form a cylindrical shape, and are disposed inside the outer wall 11c. Separating means 2 for inner upper wall 11a and outer wall 11c
3, 25 and the insulating O-rings 24, 26 are detachably connected to each other. The two are thermally separated by separating means 23, 25, and the O-rings 24, 26 improve the airtightness in the reaction chamber 12. Is held. The inner upper wall 11a, the inner lower wall 11b, and the outer wall 11c are electrically grounded.

The outer wall 11c is provided with an outer reaction gas introduction hole 19a for introducing a gas into the reaction chamber 12, and an exhaust port 20 connected to an exhaust device (not shown). Further, an outer sample transfer port 21a for loading the sample S into the reaction chamber 12 and unloading the processed sample S out of the reaction vessel 11 is provided below the outer reaction gas introduction hole 19a. I have. The opening of the outer sample transfer port 21a has a size slightly larger than the size of the sample S to be subjected to plasma processing using this apparatus.

Further, a cooling gas introduction hole 30a and a cooling gas exhaust hole 30b are provided on the outer side wall 11c. For example, N ₂ gas is introduced from the cooling gas introduction hole 30a and discharged from the cooling gas exhaust hole 30b. By the inner upper wall 1
Cooling space 28 between 1a and outer wall 11c is cooled,
The temperature rise of the outer side wall 11c is suppressed. The heater 27 is embedded in the inner upper wall 11a, and the heating temperature of the inner upper wall 11a can be controlled.

The inner lower wall 11b is attached to the lower surface of the inner upper wall 11a, and the inner wall surfaces of the inner lower wall 11b and the inner upper wall 11a are formed flush. The inner lower wall 11b is vertically suspended slightly away from the outer wall 11c toward the inner peripheral side, and the lower end portion 110 is located at a position lower than the outer reaction gas introduction hole 19a and is separated from the bottom surface of the reaction vessel 11 by a predetermined length. I have. A gas supply passage 19c is provided over the entire periphery of the upper portion of the inner lower wall 11b at a position where the gas can flow from the outer reaction gas introduction hole 19a, and the O-ring 33 maintains airtightness with the outer wall 11c. I have. On the inner wall surface of the inner lower wall 11b, a plurality of inner reaction gas introduction holes 19b are formed in the circumferential direction so as to communicate with the gas supply passage 19c. Inner lower wall 11
b, an inner sample transfer port 21b is formed at a position below the inner reaction gas inlet 19b and opposite to the outer sample transfer port 21a. The opening of the inner sample transfer port 21b has substantially the same size as or slightly larger than the outer sample transfer port 21a.

An alumite film 1 is formed on the inner wall surfaces of the inner upper wall 11a and the inner lower wall 11b by anodic oxidation. FIG. 3 is an enlarged partial cross-sectional view showing the configuration of the insulating film on the inner lower wall. As shown in FIG. 3, the alumite film 1, which is an insulating film, includes an inner wall surface of an inner lower wall 11b continuous with the inner upper wall 11a, an opening of the inner sample transfer port 21b, and a lower end 110 of the inner lower wall 11b. And is formed to cover. Further, the alumite film 1 is provided on the outer sample transfer port 21 of the outer wall 11c.
It is formed so as to cover the inner wall surface below a.

An alumina film 2 as an insulating film is formed by spraying on the edge portion, that is, the region including the edge of the opening portion of the inner sample transfer port 21b and the region including the edge of the lower end portion 110. I have. The region including the edge of the opening portion is the opening surface, the inner peripheral surface and the outer peripheral surface of the inner lower wall 11b continuous with the opening surface. The region including the edge of the lower end portion 110 is the lower end surface and the inner peripheral surface and the outer peripheral surface of the inner lower wall 11b continuous therewith. The alumina film 2 is formed so as to be superimposed on the alumite film 1. As a feature of the present invention, the edge of the inner sample transfer port 21b and the edge of the inner lower wall 11b are thicker than the other portions. The insulating film is formed thicker by that much. Although not shown in the present embodiment, the alumina film 2 may be sprayed near the exhaust port 20 and the thickness of the insulating film covering the edge portion may be formed to be thicker than other portions.

As shown in FIG. 1, a mounting table 15 is disposed in the reaction chamber 12 at a position facing the microwave introduction window 14, and is carried in from outside (inside) sample transfer ports 21a and 21b. The sample S is mounted on the mounting table 15. The mounting table 15 is fixed on a base 16 provided at the bottom of the reaction vessel 11, and is insulated from the reaction vessel 11 by an insulating member 18. A high frequency power supply 40 is connected to the mounting table 15. The frequency of the high frequency power supply 40 is 4
00 kHz, 2 MHz, 13.56 MHz or the like is used. Further, the mounting table 15 includes a suction mechanism (not shown) such as an electrostatic chuck for fixing the sample S and a circulation mechanism (not shown) for circulating a medium for maintaining the sample S at a constant temperature. ing. The periphery of the mounting table 15 is covered with a plasma shield member 17. The mounting table 15 has a structure in which alumina is sprayed on the surface of an aluminum electrode body in order to provide an electrostatic chuck function.
Alumina is used for the insulating member 18 and the plasma shield member 17.

When performing plasma processing on the surface of the sample S using the plasma processing apparatus having the above configuration, first,
The sample S is mounted on the mounting table 15, and the mounting table 15, the inner upper wall 11a, and the inner lower wall 11b are maintained at a predetermined temperature. Next, the inside of the reaction chamber 12 is evacuated from the exhaust port 20 to a predetermined pressure, and then the outside (inside) reaction gas introduction holes 19a, 19b
To supply a reaction gas into the reaction chamber 12. Then, a microwave is oscillated from the microwave oscillator 39 and the waveguide 3
Microwaves are introduced into the dielectric layer 36 through 8. As a result, a surface wave electric field is formed in the space layer 35, and transmits through the microwave introduction window 14 to generate plasma in the reaction chamber 12.

Simultaneously with the generation of plasma, the high-frequency power supply 40
Is applied to the mounting table 15 to generate a bias voltage on the surface of the sample S. While controlling the energy of ions in the plasma by this bias voltage, the sample S
The sample S is subjected to plasma treatment by irradiating the surface of the sample with ions. At this time, the inner upper wall 11a and the inner lower wall 11b function as ground electrodes, and the insulating film formed of the alumite film 1 and the alumina film 2 is subjected to plasma sputtering. Edge portion of inner wall surface, ie, inner sample transfer port 2
Since an insulating film thicker than the other portions by the thickness of the alumina film 2 is formed at the edge of the lower edge portion 1b and the lower end portion 110 of the inner lower wall 11b, the electric field concentration on the edge portion is reduced, and excessive sputtering occurs. Never be.

[0038]

EXAMPLES Using the above-described plasma processing apparatus of the present embodiment, the life of the inner wall surface of the reaction vessel 11 and the concentration of aluminum mixed in the sample S at that time were tested. In the apparatus of Example 1, an alumite film 1 was formed as an insulating film to have a thickness of 50 μm by anodic oxidation treatment, and an alumina film 2 was spray-formed to a thickness of 100 μm on an edge portion. Therefore, the thickness of the insulating film at the edge is 150 μm. For comparison, the life of the conventional plasma processing apparatus was similarly tested. In the conventional device, only the alumite film 1 was formed as an insulating film on the inner wall surface and the edge portion with a thickness of 50 μm. The plasma processing conditions were discharge conditions of 15 mTorr, microwave power of 1.6 kW, high frequency power of 1.4 kW, and frequency of 400 k.
Hz, the reaction gas supplied CHF ₃ at 35 sccn.

As a result of the test, the life of the conventional apparatus was about 150 hours, and the aluminum mixed concentration at that time was 1.5 ×
Although it was 10 ¹⁴ (atm / cm ² ), the life of the apparatus of Example 1 was 300 hours or more, and the aluminum mixed concentration at that time was 6 × 10 ¹³ (atm / cm ² ). From this result, it was found that in the plasma processing apparatus of Example 1, the life of the inner wall surface was maintained long while the reaction vessel functioned as the ground electrode.

In the above-described embodiment, the case where the reaction vessel 11 has a double structure of the inner side wall and the outer side wall has been described. However, the present invention is not limited to this. However, the present invention is applied. In that case, the insulating film at the edge of the sample transfer port opened on the inner wall surface of the container is formed thicker than other portions. Further, the shape of the reaction vessel 11 and the shape of the dielectric layer 36 are not limited to the shapes described above.

Further, in the above-described embodiment, the case where the alumina film 2 is formed on the surface of the alumite film 1 is described as the insulating film formed on the edge portion. However, the present invention is not limited to this. It may be formed of only two. In order to prevent the sample S from being contaminated during the plasma processing, it is preferable that the alumina film 2 is formed on at least the surface of the insulating film. However, the present invention is not limited to this.

Furthermore, in the above-described embodiment, an apparatus of a type in which plasma is generated by using a microwave and the plasma is controlled by applying a high frequency is described, but the present invention is not limited to this. The present invention can also be applied to a device that generates plasma by using a so-called parallel plate type device.

[0043]

As described above, in the present invention, an insulating film thicker than other portions is formed on the edge portion of the inner wall surface of the container. Concentration is eased. Thus, the insulating film at the edge portion can be prevented from peeling off more quickly than the other portions due to the sputtering, and the life of the container can be extended. Further, by forming at least the surface side of the insulating film formed at the edge portion with alumina, the present invention has excellent effects such as reduction of contamination of the sample due to heavy metal impurities.

[Brief description of the drawings]

FIG. 1 is a side sectional view showing a structure of a plasma processing apparatus according to an embodiment of the present invention.

FIG. 2 is an enlarged view of a side wall of a reaction vessel provided in the plasma device of FIG.

FIG. 3 is an enlarged partial cross-sectional view showing a configuration of an insulating film on a side wall of FIG. 2;

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 alumite film 2 alumina film 11 reaction vessel 11 a inner upper wall 11 b inner lower wall 11 c outer wall 14 microwave introduction window 15 mounting table 21 a outer sample transport port 21 b inner sample transport port 36 dielectric layer 38 waveguide 39 microwave oscillator 110 Lower end S sample

Claims (7)

[Claims] 1. A plasma processing apparatus for applying a high frequency to a container and processing a sample by plasma, wherein the container has an inner wall surface covered with an insulating film, and another part is provided at an edge portion of the inner wall surface. A plasma processing apparatus characterized in that the insulating film is formed thicker than in (1). 2. A plasma is generated in the container by introducing microwaves through the microwave window into a container provided with a microwave window, and a high frequency is applied to a mounting table provided in the container. In the plasma processing apparatus, which applies the applied plasma and guides the generated plasma to the sample mounted on the mounting table to process the sample, the container has an inner wall surface coated with an insulating film, and an edge portion of the inner wall surface. A plasma processing apparatus, wherein the insulating film is formed thicker than other portions. 3. The plasma processing apparatus according to claim 1, wherein the edge portion is a region including an edge of a sample transfer port formed on the inner wall surface. 4. The plasma processing apparatus according to claim 1, wherein the insulating film formed on an edge portion of an inner wall surface of the container contains alumina. 5. The method according to claim 1, wherein an alumite film is formed to a predetermined thickness on an inner wall surface of the container by an anodizing method, and then the edge portion is sprayed with alumina to form the insulating film. The plasma processing apparatus according to any one of the above. 6. The plasma processing apparatus according to claim 1, wherein the thickness of the insulating film formed on the edge portion is 100 μm or more. 7. The plasma processing apparatus according to claim 1, which is used for etching a silicon oxide film on the sample.