JP2000195842A - Plasma processing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a plasma processing device, wherein even if a reactor vessel has a large diameter, the overall size of the device can be reduced as much as possible, while the inside surface of a vessel is prevented from wearing. SOLUTION: On the upper surface of a cover member 10, an annular waveguide type antenna part 11a, with a U-shaped cross section is molded into an annular shape, is provided circumferentially with the center axis of the reactive device 1 while its opening facing the cover member 10, and a plurality of slits 15 are opened at a part facing the annular waveguide antenna part 11a of the cover member 10. A limiting plate 9, which with a conductive plate molded into an annular shape, limits the inlet region for microwave is provided to face the inside surface of a microwave window 4. The outer peripheral part of the limiting plate 9 is held and fixed between the upper end of the reactive device 1 and the outer peripheral part of the microwave window 4, while the inner peripheral part of the limiting plate 9 is made to face at an appropriate position near the end part on the outer peripheral side of the annular waveguide type antenna part 11a of the slits 15.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for performing processing such as etching or ashing on a semiconductor substrate, a glass substrate for a liquid crystal display, or the like by using plasma generated by using microwaves.

[0002]

2. Description of the Related Art Plasma generated by giving energy to a reaction gas from the outside is widely used in a manufacturing process of an LSI or an LCD. In particular, the use of plasma has become an indispensable basic technology in the dry etching process. As the size of a substrate processed by the plasma increases, it is required to uniformly generate the plasma over a wider area. Therefore, the applicant of the present application has disclosed Japanese Patent Application Laid-Open Nos. 62-5600 and 62-9948.
The following device is proposed in Japanese Patent Publication No. 1 and the like.

FIG. 13 shows Japanese Patent Application Laid-Open No. 62-5600 and
FIG. 14 is a side sectional view showing a plasma processing apparatus of the same type as the apparatus disclosed in JP-A-62-99481, and FIG. 14 is a plan view of the plasma processing apparatus shown in FIG. Rectangular box-shaped reactor 31
Is formed entirely of aluminum. Reactor
A microwave window 34 is arranged on the upper part of the reactor 31, and the upper part of the reactor 31 is hermetically sealed by the microwave window 34. The microwave window 34 is formed of a dielectric material such as quartz glass or alumina, which has heat resistance and microwave permeability and has a small dielectric loss.

[0004] A rectangular box-shaped cover member 40 for covering the upper part of the reactor 31 is connected to the reactor 31. A dielectric line 41 is attached to a ceiling portion in the cover member 40.
The dielectric line 41 is formed by molding a dielectric such as a fluororesin such as Teflon (registered trademark), a polyethylene resin, or a polystyrene resin into a plate shape having a protrusion at a vertex of a substantially pentagon formed by combining a rectangle and a triangle. The projection is fitted inside a waveguide 51 connected to the peripheral surface of the cover member 40. The microwave oscillator 50 is connected to the waveguide 51, and the microwave oscillated by the microwave oscillator 50 is incident on the projection of the dielectric line 41 by the waveguide 51.

As described above, the base end side of the convex portion of the dielectric line 41 is formed into a tapered portion 41a having a substantially triangular shape in plan view, and the microwave incident on the convex portion follows the tapered portion 41a. And is spread in the width direction thereof and propagates throughout the dielectric line 41. The microwave is reflected at the end face of the cover member 40 facing the waveguide 51, and the incident wave and the reflected wave are superimposed to form a standing wave on the dielectric line 41.

[0006] The interior of the reactor 31 is a processing chamber 32,
A required gas is introduced into the processing chamber 32 from a gas introduction pipe 35 fitted in a through hole penetrating the peripheral wall of the processing chamber 32. At the center of the bottom wall of the processing chamber 32, a mounting table 33 on which the sample W is mounted is provided. The mounting table 33 is connected to an RF power supply 37 of several hundred kHz to several tens of MHz via a matching box 36. I have. An exhaust port 38 is provided in the bottom wall of the reactor 31 so that the inside air of the processing chamber 32 is exhausted from the exhaust port 38.

In order to perform an etching process on the surface of the sample W using such a plasma processing apparatus, the inside of the processing chamber 32 is evacuated to a desired pressure by evacuating from the exhaust port 38, and then the processing is performed through the gas introduction pipe 35. A reaction gas is supplied into the chamber 32. Then
Microwaves are oscillated from a microwave oscillator 50 and introduced into the dielectric line 41 via the waveguide 51. At this time,
The microwave is uniformly spread in the dielectric line 41 by the tapered portion 41a, and forms a standing wave in the dielectric line 41. Due to this standing wave, a leaked electric field is formed below the dielectric line 41, and this is transmitted through the microwave window 34 and introduced into the processing chamber 32. In this way, the microwave propagates into the processing chamber 32. As a result, plasma is generated in the processing chamber 32, and the surface of the sample W is etched by the plasma. This allows the reactor to process large-diameter sample W
Even if the diameter of 31 is increased, microwaves can be uniformly introduced into the entire region of the reactor 31, and a large-diameter sample W can be relatively uniformly plasma-treated.

[0008]

In the conventional plasma processing apparatus, in order to spread the microwave uniformly on the dielectric line 41, the microwave is projected horizontally from the microwave window 34 and the edge of the reactor 31. A tapered portion 41a is provided, and the tapered portion 41a is set to a predetermined size in accordance with the area of the dielectric line 41, that is, the diameter of the processing chamber 32. Therefore, when installing a conventional plasma processing apparatus, an extra horizontal space for accommodating the tapered portion 41a protruding from the peripheral edge of the reactor 31 must be secured. By the way, sample W
As the diameter of the reactor increases, a plasma processing apparatus in which the diameter of the reactor 31 is further increased is required. At this time, it is also required that the installation place of the apparatus need not be treated, that is, it can be installed in a space as narrow as possible. However, in the conventional apparatus, since the size of the tapered portion 41a is determined according to the diameter of the reactor 31, there is a problem that both of the above requirements cannot be satisfied.

On the other hand, in the conventional plasma processing apparatus, the plasma generated near the inner peripheral surface of the reactor 31 may sputter the inner peripheral surface of the reactor 31. When the inner peripheral surface of the reactor 31 is sputtered, particles are generated thereby, and the particles W contaminate the sample W.

The present invention has been made in view of such circumstances, and an object of the present invention is to reduce the size of the entire apparatus as much as possible even if the diameter of the reactor is large, and to reduce the inner surface of the vessel. It is an object of the present invention to provide a plasma processing apparatus capable of preventing wear of a plasma processing apparatus.

[0011]

The inventor of the present invention provides a microwave by an endless annular or end annular waveguide antenna provided with a slit for emitting microwaves facing the microwave window. It has been found that plasma can be uniformly generated in the container by a configuration in which microwaves are introduced into the container through the wave window, that is, even in a configuration in which a microwave supply unit is not provided at the center. In addition, there is a problem in the past, and the microwave supply to the inner peripheral surface of the container is increased by radiating the microwave by the endless annular or end annular waveguide type antenna, and the plasma becomes strong near the inner peripheral surface. With respect to the possibility of generation, the present inventors have found that the generation of plasma near the inner peripheral surface of the container can be effectively suppressed by providing the microwave limiting member, and completed the present invention.

That is, a plasma processing apparatus according to a first aspect of the present invention is a plasma processing apparatus comprising: an annular waveguide type antenna having a slit disposed on a surface facing the microwave window and having a slit in the container provided with the microwave window. A microwave is radiated, plasma is generated by introducing microwaves into the container through the microwave window, and a sample mounted on a mounting table provided in the container is processed by the generated plasma. A microwave processing apparatus, wherein a microwave limiting member for limiting a microwave introduction region to a central portion is provided in the container.

[0013] A plasma processing apparatus according to a second aspect of the present invention is a plasma processing apparatus comprising: an annular waveguide type antenna having a slit provided on a surface facing the microwave window and arranged in a container provided with an annular microwave window; A microwave is radiated to generate plasma by introducing microwaves into the container through the microwave window, and is fitted into a mounting table provided in the container and / or the microwave window. A plasma processing apparatus for applying a high frequency to a counter electrode provided to guide a generated plasma to a sample mounted on a mounting table and processing the sample, wherein the microwave introduction region is located in the center of the container. A microwave limiting member for limiting the part is provided.

[0014] A plasma processing apparatus according to a third aspect of the present invention comprises:
Alternatively, in the second invention, the microwave limiting member is in contact with the microwave window.

A plasma processing apparatus according to a fourth aspect of the present invention has a first
In any one of the third to third inventions, the step between the lower surface of the microwave limiting member and the lower surface of the microwave window is equal to or more than the skin thickness δ of the plasma represented by the following equation. . δ = c / ωp ωp = √ {(N · e 2) / (ε 0 · m e)} where, c: velocity of light in a vacuum (2.997 × ¹⁰ 10 cm / se
c) N: the plasma density (cm ^-3) e: charge ^{(1.602 × 10 -19 C) ε} 0: vacuum dielectric constant ^{(8.85 × 10 -10 F / cm} ) m e: electron mass (9.11 × 10 ^-31 kg )

According to a fifth aspect of the present invention, there is provided a plasma processing apparatus comprising:
In any one of the third to third aspects, a step between the lower surface of the microwave limiting member and the lower surface of the microwave window is 7.5 m.
m or more.

The plasma processing apparatus according to the sixth invention has a third
In any one of the fifth to fifth inventions, the microwave window is provided with an annular convex portion that follows the inner peripheral surface of the microwave limiting member, and the microwave limiting member is externally fitted to the annular convex portion. There is a feature.

The plasma processing apparatus according to the seventh aspect of the present invention has a third
In any one of the sixth to sixth inventions, a protection member for protecting a surface of the microwave limiting member opposite to a surface in contact with the microwave window is provided.

The plasma processing apparatus according to the eighth invention has a first
In any one of the seventh to seventh inventions, an endless annular waveguide antenna is provided.

The plasma processing apparatus according to the ninth invention has a first
In any one of the seventh to seventh inventions, an endless annular waveguide antenna is provided.

According to a tenth aspect of the present invention, in the plasma processing apparatus according to the ninth aspect, the waveguide antenna is formed in a C shape or a spiral shape.

In the plasma processing apparatus according to the first, second and eighth to tenth aspects of the present invention, the endless annular or endless annular waveguide provided with a slit for emitting microwaves facing the microwave window. The antenna is configured to supply microwaves by using a type antenna, so even if there is no part that spreads the microwaves uniformly, such as a tapered portion provided on the dielectric line, the microwaves are placed inside the container so that the plasma is generated uniformly. Waves can be supplied. The annular arrangement of slits from which microwaves are radiated, that is, the diameter of the annular waveguide antenna, the shape and arrangement of the slits, the cross-sectional shape of the waveguide, and the microwave propagation mode may be appropriately considered.

Accordingly, there is no protrusion such as a tapered portion provided on the dielectric line, and the size of the plasma processing apparatus can be reduced as much as possible. In addition, since a microwave limiting member that limits the microwave introduction region to the central portion is provided, the arrangement of the microwave limiting member blocks microwave propagation from above, which has been a problem in the past. ,
In addition, the use of the annular waveguide antenna can solve the problem of wear on the inner surface of the container, which may be a problem.

Further, in the plasma processing apparatus of the second invention, the microwave window is made annular by adopting an endless annular or end annular waveguide type antenna structure. A configuration in which a counter electrode is provided by being fitted inside becomes possible. By applying a high frequency to the counter electrode or electrically grounding the counter electrode, more advanced control of plasma can be performed.

A dielectric such as Teflon (registered trademark) such as a fluororesin, a polyethylene resin or a polystyrene resin may be inserted into the endless annular or endless annular waveguide type antenna.

In the plasma processing apparatus of the third invention,
Since the microwave limiting member is in contact with the microwave window, the propagation of microwaves near the inner peripheral surface of the container is suppressed, and the generation of plasma strongly near the inner peripheral surface of the container is suppressed. The contact surface of the limiting member to the microwave window can be protected from sputtering by plasma.

In the plasma processing apparatus of the fourth invention,
The step between the lower surface of the microwave limiting member that limits the region into which the microwave is introduced and the lower surface of the microwave window is expressed by the following formulas (1) and (2):
That's it. δ = c / ωp ... (1 ) ωp = √ {(N · e 2) / (ε 0 · m e)} ... (2) where, c: velocity of light in a vacuum (2.997 × ¹⁰ 10 cm / se
c) N: the plasma density (cm ^-3) e: charge ^{(1.602 × 10 -19 C) ε} 0: vacuum dielectric constant ^{(8.85 × 10 -10 F / cm} ) m e: electron mass (9.11 × 10 ^-31 kg )

In the inside of the container, plasma is 5 × 10 ¹¹ c
The plasma is generated at a density of about m ^{−3 to} 5 × 10 ¹² cm ^−3.
Microwaves cannot penetrate into the generated plasma because they are sufficiently larger than ¹⁰ cm ^-3 . At this time, if the step is smaller than the skin thickness δ of the plasma, the microwave introduced into the container via the microwave limiting member propagates on the surface of the plasma, and the surface wave may reach the inner surface of the container. There is. However, in the present invention, the step is plasma skin thickness δ.
As described above, the above-mentioned surface wave is limited to the inside of the opening of the microwave limiting member, and is prevented from reaching the inner surface of the container through the lower surface of the microwave limiting member. Therefore,
The microwave introduction region can be reliably limited to the central portion of the container, and the inner surface of the container can be reliably prevented from being worn.

[0029] In the plasma processing apparatus of the fifth invention,
The step between the lower surface of the microwave limiting member and the lower surface of the microwave window is the maximum value of the skin thickness δ of the plasma, 7.5.
mm or more, the surface wave is prevented from reaching the inner surface of the side wall of the container as before. Therefore, the microwave introduction region can be reliably limited to the central portion of the container, and the inner surface of the container can be reliably prevented from being worn.

In the plasma processing apparatus of the sixth invention,
Since the inner peripheral edge of the microwave limiting member is protected from plasma sputtering by the annular convex portion of the microwave window, generation of particles from the inner peripheral edge of the microwave limiting member is suppressed.

In the plasma processing apparatus of the seventh invention,
The surface of the microwave limiting member opposite to the microwave window side is protected by the protection member from sputtering by plasma, so that generation of particles from this portion can be prevented.

[0032]

Embodiments of the present invention will be specifically described below with reference to the drawings. (Embodiment 1) FIG. 1 is a side sectional view showing a structure of a plasma processing apparatus according to the present invention, and FIG. 2 is a plan view of the plasma processing apparatus shown in FIG. Bottomed cylindrical reactor 1
Is formed entirely of a conductive metal, and the reactor 1 is electrically grounded. The upper opening of the reactor 1 is hermetically sealed by a microwave window 4. The microwave window 4 is formed of a dielectric material such as quartz glass or alumina, which has heat resistance and microwave permeability and has a small dielectric loss.

A cover member 10 formed by molding a conductive metal into a circular lid shape is externally fitted to the microwave window 4, and the cover member 10 is fixed on the reactor 1. An antenna 11 for introducing microwaves into the reactor 1 is fixed on an upper surface of the cover member 10. The antenna 11 is formed by forming an annular waveguide-type antenna portion 11a formed by molding a member having a U-shaped cross section into an endless annular shape, with its opening facing the cover member 10, and concentric with the central axis of the reactor 1. A plurality of slits 15, 15,... Are formed in a portion of the cover member 10 facing the annular waveguide antenna portion 11a. That is, in the present embodiment, the annular waveguide antenna unit 11a
The portion of the cover member 10 in which the slits 15, 15,... Are opposed to the annular waveguide antenna portion 11a constitutes an annular waveguide antenna.

The annular waveguide antenna 11a is connected to the reactor 1
Is provided slightly concentric with the central axis of the reactor 1 slightly inside the inner peripheral surface of the reactor, and around the opening provided on the outer peripheral surface thereof for introducing microwaves to the annular waveguide antenna portion 11a. Are connected so as to extend in the diametrical direction of the annular waveguide antenna section 11a. Teflon (registered trademark) is provided in the introduction section 11b and the annular waveguide antenna section 11a.
A dielectric 14 such as a fluororesin, a polyethylene resin or a polystyrene resin (preferably Teflon) is fitted therein.

A waveguide 29 extending from a microwave oscillator 30 is connected to the introduction section 11b. Microwaves oscillated by the microwave oscillator 30 pass through the waveguide 29 to the introduction section 11b of the antenna 11. Incident. This incident wave is introduced from the introduction part 11b to the annular waveguide type antenna part 11a. The microwaves introduced into the annular waveguide antenna section 11a are converted into traveling waves propagating through the annular waveguide antenna section 11a in opposite directions to each other in the dielectric 14 in the annular waveguide antenna section 11a. , And the traveling waves are superimposed to generate a standing wave in the annular waveguide antenna section 11a. Due to this standing wave, a wall current showing a maximum value flows at a predetermined interval through the inner surface of the annular waveguide antenna section 11a.

At this time, an annular waveguide type antenna unit in which Teflon (registered trademark) having a relative permittivity εr of 2.1 is inserted.
In order to change the mode of the microwave propagating in the inside 11a to the rectangular TE10 which is the fundamental propagation mode, the annular waveguide antenna section 11a is set in accordance with the microwave frequency of 2.45 GHz.
May be 27 mm high and 66.2 mm wide. The microwave in this mode propagates through the dielectric 14 in the annular waveguide antenna 11a with almost no energy loss.

The microwave window 4 having a diameter of 380 mm
When Teflon (registered trademark) with εr = 2.1 is internally fitted into the annular waveguide antenna 11a, the width of the annular waveguide antenna 11a from the center of the annular waveguide antenna 11a is used. The dimension up to the center in the direction may be 141 mm.
In this case, the circumferential length (approximately 886 mm) of the circle C connecting the center in the width direction of the annular waveguide antenna section 11a is determined by the wavelength of the microwave propagating in the annular waveguide antenna section 11a. (Approximately 110 mm). Therefore, the microwave resonates in the annular waveguide antenna portion 11a, and the above-described standing wave becomes a high voltage / low current at the antinode position, and becomes a low voltage / high current at the node position, and the antenna Q value is improved.

Incidentally, the annular waveguide type antenna portion 11a may be hollow without inserting the dielectric material 14. However, when the dielectric 14 is inserted into the annular waveguide antenna 11a, the wavelength of the microwave incident on the annular waveguide antenna 11a is increased by 1 / √ (εr) by the dielectric 14. (Εr is the relative dielectric constant of the dielectric). Therefore, when the annular waveguide type antenna unit 11a having the same diameter is used, the annular waveguide type antenna unit when the dielectric 14 is mounted is more than when the dielectric 14 is not mounted. There are many locations where the current flowing through the wall of 11a is maximized,
15, 15, ... can be established a lot. Therefore, the microwave can be more uniformly introduced into the processing chamber 2.

FIG. 3 shows the slit 1 shown in FIG. 1 and FIG.
It is explanatory drawing explaining 5, 15, .... As shown in FIG. 3, the slits 15, 15,...
The portion facing the annular waveguide-type antenna portion 11a is directed in the diametrical direction of the annular waveguide-type antenna portion 11a, that is, perpendicularly to the traveling direction of the microwave propagating in the annular waveguide-type antenna portion 11a. It is set up in the shape of a strip. When the annular waveguide antenna 11a has the dimensions described above, each slit 1
The length of 5, 15,... Is 50 mm, the width is 20 mm, and the distance between adjacent slits 15, 15 is approximately 55 m. That is, Yes in two slits 15, 15 provided from the intersection point P ₁ to be described later to the position of 27.5 mm, both slits 15, 15
Other slits 15, 15,... Are provided at an interval of 55 mm from.

That is, each of the slits 15, 15,.
The intersection point P, which is a side of the two points where the extension line L extending the center line of the center line 11b intersects the above-described circle C, which is separated from the introduction portion 11b.
_{From 1} to both following the circle C, (2n−
1) · λg / 4 (n is an integer, λg is the wavelength of microwave propagating in the annular waveguide antenna)
Two slits 15 and 15 are opened. Both slits 15 and 15
, A plurality of other slits 15, 15,... Are respectively formed at intervals of m · λg / 2 (m is an integer) on both sides following the circle C. That is, the slits 15, 15,... Are provided at positions where the nodes of the standing wave described above are formed. Thereby, microwaves can be efficiently radiated from each of the slits 15, 15,....

FIG. 4 is an explanatory diagram for explaining the result of simulating the intensity of the electric field distributed on the dielectric 14 in the antenna 11 shown in FIG. A microwave of 2.45 GHz is incident on a dielectric formed by molding Teflon into a shape in which a rod is provided on the outer periphery of a perfect circular ring, and is formed by microwave propagation from the end of the rod. The electric field strength was simulated, and the same electric field strength positions were connected by lines. As a result, as shown in FIG. 4, a plurality of regions having a strong electric field strength are formed on the dielectric so as to be symmetric with respect to the axis passing through the center of the annular body and the center of the rod.

Each of the slits 15, 15,... Described above is located substantially at the center (node) between a plurality of regions (antinodes) of high electric field strength, and the micro-radiation emitted from each slit 15, 15,. The waves pass through the microwave window 4 and are introduced into the reactor 1.

In the present embodiment, the slits 15, 1
5, ... are opened so as to be orthogonal to the traveling direction of the microwave propagating in the annular waveguide type antenna portion 11a.
The present invention is not limited to this, and a slit may be opened so as to obliquely intersect the traveling direction of the microwave, or may be opened in the traveling direction of the microwave. Due to the plasma generated in the reactor 1, the wavelength of the microwave propagating in the antenna 11 changes, and the annular waveguide antenna 11
The position where the maximum value of the current flowing through the peripheral wall of a may change, but in the slit opened in the direction of microwave propagation or the slit opened in the direction of microwave propagation, the current The change in the position showing the maximum value can be captured in the area of the slit.

As described above, each of the slits 15, 15,.
Since the cover member 10 is provided substantially radially, the microwave is uniformly introduced into the entire region in the reactor 1. On the other hand, FIG.
As shown in the above, since the antenna 11 is provided on the cover member 10 having the same diameter as the diameter of the reactor 1 without protruding from the periphery of the cover member 10, even if the diameter of the reactor 1 is large, The size of the plasma processing apparatus is as small as possible, so that it can be installed in a small space.

At the center of the bottom wall of the processing chamber 2, there is provided a mounting table 3 on which the sample W is mounted, and a high frequency power supply 7 is connected to the mounting table 3 via a matching box 6. A through hole is formed in the peripheral wall of the processing chamber 2 and penetrates the peripheral wall. A gas introduction pipe 5 for introducing a reaction gas into the processing chamber 2 is fitted into the through hole. Further, an exhaust port 8 is provided on the bottom wall of the processing chamber 2, and the inside air of the processing chamber 2 is discharged from the exhaust port 8.

A limiting plate 9, which is opposed to the inner surface of the microwave window 4 and limits the introduction region where the microwave is introduced into the processing chamber 2 to the center of the processing chamber 2, contacts the microwave window 4. It is arranged. The limiting plate 9 is formed by shaping a conductive plate into an annular shape, and the outer peripheral edge of the limiting plate 9 is sandwiched and fixed between the upper end of the reactor 1 and the outer peripheral edge of the microwave window 4. The inner peripheral edge of the limited plate 9
Annular waveguide antenna with slits 15, 15, ...
11a is opposed to an appropriate position near the end on the outer peripheral surface side. The limiting plate 9 is electrically grounded.

To perform an etching process on the surface of the sample W using such a plasma processing apparatus, the interior of the processing chamber 2 is evacuated to a desired pressure by exhausting from the exhaust port 8, and then the processing is performed through the gas introduction pipe 5. A reaction gas is supplied into the chamber 2. Then
A microwave of 2.45 GHz is oscillated from the microwave oscillator 30 and introduced into the antenna 11 through the waveguide 31.
The standing wave is formed in the annular waveguide antenna section 11a. The electric field radiated from the slits 15, 15,... Of the annular waveguide antenna section 11a is transmitted through the microwave window 4 and introduced into the processing chamber 2, and plasma is generated in the processing chamber 2. The surface of the sample W on the mounting table 3 is etched by this plasma.

Further, high frequency may be applied to the mounting table 3 from the high frequency power supply 7 via the matching box 6 simultaneously with the oscillation by the microwave oscillator 30. By applying a high frequency to the mounting table 3, the surface of the sample W on the mounting table 3 can be etched while controlling ions in the plasma.

At this time, since the ring-shaped limiting plate 9 electrically grounded is in contact with the inner surface of the microwave window 4, the microwave is introduced into the opening of the limiting plate 9,
There, plasma is generated. Thereby, the position where the plasma is generated can be separated from the inner peripheral surface of the reactor 1, and the inner peripheral surface of the reactor 1 is prevented from being worn by the plasma.

On the other hand, the limited plate 9 electrically grounded
However, it acts as a counter electrode of the mounting table 3 to which a high frequency is applied, and the directivity of the plasma guided on the sample W can be improved.

By the way, the thickness dimension d of the limiting plate 9
Is preferably not less than the skin thickness δ of the plasma determined by the following equations (1) and (2) (δ ≦
d). δ = c / ωp ... (1 ) ωp = √ {(N · e 2) / (ε 0 · m e)} ... (2) where, c: velocity of light in a vacuum (2.997 × ¹⁰ 10 cm / se
c) N: the plasma density (cm ^-3) e: charge ^{(1.602 × 10 -19 C) ε} 0: vacuum dielectric constant ^{(8.85 × 10 -10 F / cm} ) m e: electron mass (9.11 × 10 ^-31 kg )

The plasma in the reactor 1 is usually 5 × 10 ¹¹
It is generated at a density of about cm ^{−3 to} 5 × 10 ¹² cm ⁻³ ,
This plasma density is 7.45 × 1 which is the cutoff density.
Microwaves cannot penetrate into the generated plasma because they are sufficiently larger than 0 ¹⁰ cm ^-3 . At this time, when the thickness dimension d of the limiting plate 9 is smaller than the skin thickness δ of the plasma, the microwave introduced into the opening of the limiting plate 9 propagates on the surface of the plasma to cause the limiting plate 9 of the reactor 1. May reach the lower side of When the plasma density N is 5 × 10 ¹¹ cm ⁻³ and 5 × 10 ¹² cm ⁻³ , respectively, the skin thickness δ of the plasma is 7.5 mm and 2.4 mm, respectively.

However, in the plasma processing apparatus shown in FIG. 1, the thickness d of the limiting plate 9 is limited to the normal value of the plasma density N of 5 × 10 ¹¹ cm ^{−3 to} 5 × 10 ¹² cm ⁻³ . By setting the plasma skin thickness δ at 7.5 mm or more, which is the maximum value of the plasma skin thickness δ in the range, the region where the microwave propagates can be more reliably limited within the opening of the limiting plate 9.

(Embodiment 2) FIG. 5 is a plan view showing Embodiment 2 of the present invention. In the figure, parts corresponding to those in FIG. 2 are denoted by the same reference numerals, and description thereof is omitted. On the cover member 10, one end side is bent into a C shape (arc shape) or a single spiral shape (C shape in FIG. 5), and an end-shaped ring having an end closed. The waveguide type antenna 12 is provided, and a waveguide 29 connected to a microwave oscillator 30 is connected to the other end of the waveguide type antenna 12. A plurality of slits are formed in a portion of the cover member 10 facing the waveguide type antenna 12.
15, 15, ... are established.

FIG. 6 shows the slits 15, 15,... Shown in FIG.
FIG. As shown in FIG. 6 orthogonal slits 15, 15, ... is the portion opposed to the waveguide antenna 12 of the cover member 10 (see FIG. 5), the center axis L ₁ of the waveguide antenna 12 It is set up so that each slit 1
The opening positions of 5, 15,... Are determined at m · λg / 2 from the closed end of the waveguide antenna 12.

Although the present embodiment has been described with reference to a case where one end is bent into a C-shape and an end-shaped annular waveguide type antenna 12 whose end is closed is provided. However, the present invention is not limited to this. As shown in FIG. 2, an end-shaped annular waveguide type antenna having a partition wall for reflecting microwaves is provided at an appropriate position in the annular waveguide type antenna unit. It goes without saying that it is good.

(Embodiment 3) FIG. 7 is a side sectional view showing Embodiment 3 in which the inner peripheral surface of the above-described limiting plate 9 is protected. FIG. 8 is a partially enlarged view of the plasma processing apparatus shown in FIG. In both figures,
Portions corresponding to those shown in FIG. 1 are denoted by the same reference numerals, and description thereof is omitted. As shown in FIGS. 7 and 8, on the surface of the microwave window 4 on the processing chamber 2 side, an annular convex portion 4 a having substantially the same height as the thickness of the limiting plate 9 is provided. It is provided so as to contact the peripheral surface.

In such a plasma processing apparatus,
As before, the limiting plate 9 prevents the inner surface of the reactor 1 from being worn. On the other hand, the inner peripheral surface of the limiting plate 9 may be gradually worn out due to exposure to the plasma, but the inner peripheral surface of the limiting plate 9 is covered with the annular projection 4a of the microwave window 4 as described above. Therefore, the inner peripheral surface of the limiting plate 9 is isolated from the plasma, thereby preventing the plasma from being worn by the plasma. Therefore, generation of particles due to wear of the limiting plate 9 is suppressed.

(Embodiment 4) FIG. 9 is a side sectional view showing Embodiment 4 and FIG. 10 is a partially enlarged view of the plasma processing apparatus shown in FIG. In the present embodiment, in addition to the inner peripheral surface of the limiting plate 9, the portion of the limiting plate 9 facing the processing chamber 2 is also prevented from being worn.
Note that, in both figures, portions corresponding to the portions shown in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted.

As shown in FIGS. 9 and 10, on the inner surface of the microwave window 4, an annular convex portion 4 a having substantially the same size as the thickness of the limiting plate 9 abuts on the inner peripheral surface of the limiting plate 9. It is provided as follows. Further, at the upper end of the reactor 1 and at the edge on the processing chamber 2 side, a step portion 1a which is one step lower than other portions is provided, and a dielectric (preferably quartz glass) is provided on the step portion 1a. The outer peripheral edge of the protection plate 19 for protecting the limiting plate 9 is fitted into the
Is held between the step portion 1a and the limiting plate 9. The inner diameter of the protection plate 19 is substantially equal to the inner diameter of the annular projection 4a. The portion of the limiting plate 9 protruding into the processing chamber 2 is covered with the microwave window 4, the annular convex portion 4a, and the protection plate 19, so that the limiting plate 9 is not worn by the plasma. 9 is prevented from being generated due to wear.

(Fifth Embodiment) FIG. 11 is a side sectional view showing a fifth embodiment, and FIG. 12 is a plan view of the plasma processing apparatus shown in FIG. The entire bottomed cylindrical reactor 1 is formed of a metal such as aluminum. At the upper end of the reactor 1, a ring member 21 having a groove on the inner peripheral surface is attached.
The annular microwave window 24 is a ring member
Supported by 21.

On the upper surface of the ring member 21, a cylindrical block member 25 having an outer diameter substantially the same as the outer diameter of the ring member 21 and an inner diameter substantially the same as the inner diameter of the annular microwave window 24 described above is provided. It is screwed to the member 21. The block member 25 is formed of a metal such as aluminum. An annular waveguide-type antenna section in which a rectangular groove is formed in a cross section at a portion of the block member 25 facing the annular microwave window 24.
11a is formed, and on the peripheral surface of the block member 25, an introduction portion 11b formed with a rectangular hole communicating with the annular waveguide type antenna portion 11a is formed. An annular plate member 16 made of aluminum is provided at the bottom of the annular waveguide type antenna portion 11a.
The plate member 16 has a plurality of slits 15, 1
5, ... are established at a predetermined distance in the circumferential direction. A dielectric 14 is fitted inside the introduction section 11b and the annular waveguide antenna section 11a. That is, in the present embodiment, the annular waveguide antenna section 11a and the plurality of slits 15, 15,.
An annular waveguide antenna is constructed from the plate member 16 in which is opened.

On the peripheral surface of the block member 25, the introduction portion 11
A waveguide 29 extending from the microwave oscillator 30 is connected to the periphery of the opening of b, and the microwave oscillated by the microwave oscillator 30 passes through the waveguide 29 and enters the introduction portion 11b of the antenna 11.
Is incident on.

The above-mentioned block member 25 is provided with a heating block 26 formed by molding aluminum into a columnar shape so that the lower surface of the heating block 26 is slightly higher than the lower surface of the annular microwave window 24. The heating block 26 has a heater 28 embedded therein as a heating source.

At the center of the lower surface of the heating block 26, a cylindrical concave portion is provided. The concave portion is closed by a counter electrode 18 formed by molding a conductor or semiconductor material into a disk, and a gas diffusion chamber 20 is provided. It is. The counter electrode 18 is detachably screwed to the heating block 26, and the counter electrode 18 is connected to a changeover switch 60.
Thus, it is possible to switch between electrically grounding and connecting to the high frequency power supply 7b via the matching box 6b. Further, the reactor 1, the ring member 21, the annular microwave window 24, the block member 25, and the heating block 26
Are connected to each other, heat-resistant O-rings 17, 17,... (Partially omitted) are interposed to seal them in an airtight state.

The position of the lower surface of the counter electrode 18 is arranged so as to be substantially flush with the lower surface of the annular microwave window 24.

The position of the lower surface of the counter electrode 18 is
Below the position of the lower surface of the
Should not protrude beyond the skin thickness δ of
As shown in this example, the lower surface of the counter electrode 18 is
More preferably, it should be approximately flush with the lower surface of window 24
No. As described above, the microwave plasma having such a configuration is used.
Of the plasma generated in the reactor 1 in the
Density is 5 × 10¹¹cm ^-3~ 5 × 10¹²cm^-3And
Plasma density N is 5 × 10¹¹cm^-3And 5 × 10
¹²cm^-3, The skin thickness δ of the plasma is
7.5 mm and 2.4 mm. Therefore, this counter
The position of the lower surface of the pole 18 is the position of the lower surface of the annular microwave window 24.
Below that is the minimum value of the plasma skin thickness δ
It is better not to protrude beyond 2.4mm
As shown in this example, the lower surface of the counter electrode 18 is
It is more preferable that the lower surface of the window 24 be substantially flush with the lower surface.
No.

As described above, when plasma exceeding the cutoff density is generated in the reactor 1, microwaves cannot penetrate into the generated plasma, and the skin thickness of the plasma on the surface of the plasma is about δ. A surface wave propagating in the region is formed. Therefore, by preventing the lower surface of the counter electrode 18 from projecting beyond the skin thickness δ of the plasma below the lower surface of the annular microwave window 24, the microwave The surface wave can be propagated (spread), and more uniform plasma can be generated.

On the other hand, the thickness dimension of the limiting plate 9 described later is set to 7.5 mm or more, which is the maximum value of the skin thickness δ of the plasma. Within.

The gas diffusion chamber 20 communicates with the gas introduction pipe 5 passing through the heating block 26. The gas supplied from the gas introduction pipe 5 to the gas diffusion chamber 20 is diffused and homogenized there, and then through a plurality of through-holes formed in the counter electrode 18, the gas is supplied to the processing chamber 2.
Introduced into. At the center of the bottom wall of the processing chamber 2, a mounting table 3 on which the workpiece W is mounted is provided so as to be able to move up and down, and a high frequency power supply 7 is connected to the mounting table 3 via a matching box 6. Further, an exhaust port 8 is provided in a peripheral wall of the processing chamber 2, and the inside air of the processing chamber 2 is exhausted from the exhaust port 8.

The outer edge of the limiting plate 9 is provided in the groove of the ring member 21, and the limiting plate 9 is an annular microwave window.
The limiting plate 9 is fitted so as to abut the inner surface of the plate 24, and is electrically grounded. Opposite to the lower surface of the limiting plate 9, the cross-sectional view has a substantially curved shape and an annular protective member 19 a
The inner peripheral surface and the lower surface of the limiting plate 9 are protected by the protective member 19a.

In such a plasma processing apparatus,
As before, the limiting plate 9 prevents the inner surface of the reactor 1 from being worn. Further, the microwave window 4 and the protection member 19a
Since the entire surface of the portion of the limiting plate 9 protruding into the processing chamber 2 is covered, the limiting plate 9 is not worn by the plasma, and the generation of particles due to the wearing of the limiting plate 9 is prevented.

[0073]

In the plasma processing apparatus according to the first, second, third and eighth to tenth aspects, the horizontal dimension of the plasma processing apparatus can be made as small as possible. In addition, the introduction region of the microwave introduced into the container is limited by the limiting member, and the position where plasma is generated is separated from the inner peripheral surface of the container, so that the inner peripheral surface of the container is prevented from being worn by the plasma. You. Therefore, generation of particles is prevented, and contamination of the sample is avoided.

In the fourth and fifth aspects of the invention, the microwave introduced into the container via the microwave limiting member propagates on the surface of the plasma, and the surface wave propagates beyond the opening of the microwave limiting member. This prevents the microwave introduction region from being limited to the central portion of the container, thereby reliably preventing the inner surface of the container from being worn.

In the plasma processing apparatus according to the sixth and seventh aspects of the present invention, since the above-described limiting member is protected from the plasma by the protection member, the limiting member is prevented from being worn by the plasma. Therefore, the present invention has excellent effects, such as generation of particles due to wear of the limiting member and prevention of contamination of the sample.

[Brief description of the drawings]

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

FIG. 2 is a plan view of the plasma processing apparatus shown in FIG.

FIG. 3 is an explanatory diagram illustrating a slit shown in FIGS. 1 and 2.

FIG. 4 is an explanatory diagram illustrating a result of simulating the intensity of an electric field distributed on a dielectric in the antenna illustrated in FIG. 2;

FIG. 5 is a plan view showing the second embodiment.

FIG. 6 is an explanatory diagram illustrating the slit shown in FIG.

FIG. 7 is a side sectional view showing a third embodiment.

8 is a partially enlarged view of the plasma processing apparatus shown in FIG.

FIG. 9 is a side sectional view showing a fourth embodiment.

10 is a partial enlarged view of the plasma processing apparatus shown in FIG.

FIG. 11 is a side sectional view showing a fifth embodiment.

FIG. 12 is a plan view of the plasma processing apparatus shown in FIG.

FIG. 13 is JP-A-62-5600 and JP-A-62-99481.
FIG. 1 is a side sectional view showing a plasma processing apparatus of the same type as the apparatus disclosed in Japanese Patent Application Laid-Open Publication No. H10-209,026.

FIG. 14 is a plan view of the plasma processing apparatus shown in FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Reactor 2 Processing room 4 Microwave window 9 Limited plate 11 Antenna 11a Annular waveguide type antenna part 15 Slit 19 Protection plate 19a Protection member

Claims (10)

[Claims] A microwave is radiated from an annular waveguide-type antenna having a slit on a surface facing the microwave window in a container provided with the microwave window, and the microwave is radiated from the annular waveguide type antenna. A plasma processing apparatus for generating plasma by introducing microwaves into the container through a wave window, and processing a sample mounted on a mounting table provided in the container with the generated plasma, A plasma processing apparatus, wherein a microwave limiting member for limiting a microwave introduction region to a central portion is provided in a container. 2. In a container provided with an annular microwave window, microwaves are radiated from an annular waveguide antenna having a slit on a surface facing the microwave window and having a slit on the facing surface. Plasma is generated by introducing microwaves into the container through the microwave window, and a counter electrode provided to be fitted in the mounting table and / or the microwave window provided in the container. A plasma processing apparatus for applying a high frequency to the sample and guiding the generated plasma to a sample mounted on a mounting table to process the sample, wherein a microwave introduction region is limited to a central portion in the container. A plasma processing apparatus comprising a member. 3. The plasma processing apparatus according to claim 1, wherein the microwave limiting member is in contact with the microwave window. 4. The plasma processing apparatus according to claim 1, wherein a step between the lower surface of the microwave limiting member and the lower surface of the microwave window is equal to or more than a skin thickness δ of plasma expressed by the following equation. The plasma processing apparatus as described in the above. δ = c / ωp ωp = √ {(N · e 2) / (ε 0 · m e)} where, c: velocity of light in a vacuum (2.997 × ¹⁰ 10 cm / se
c) N: the plasma density (cm ^-3) e: charge ^{(1.602 × 10 -19 C) ε} 0: vacuum dielectric constant ^{(8.85 × 10 -10 F / cm} ) m e: electron mass (9.11 × 10 ^-31 kg ) 5. The plasma processing apparatus according to claim 1, wherein a step between the lower surface of the microwave limiting member and the lower surface of the microwave window is 7.5 mm or more. 6. The microwave window is provided with an annular convex portion that follows the inner peripheral surface of the microwave limiting member, and the microwave limiting member is externally fitted to the annular convex portion.
6. The plasma processing apparatus according to any one of claims 1 to 5. 7. The plasma processing according to claim 3, further comprising a protection member for protecting a surface of the microwave limiting member opposite to a surface in contact with the microwave window. apparatus. 8. The plasma processing apparatus according to claim 1, wherein an endless annular waveguide antenna is arranged. 9. The plasma processing apparatus according to claim 1, wherein an end-shaped annular waveguide antenna is arranged. 10. The plasma processing apparatus according to claim 9, wherein said waveguide antenna is formed in a C shape or a spiral shape.