JP4341256B2 - Plasma processing equipment - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a plasma processing apparatus using surface wave excitation plasma.
[0002]
[Prior art]
Conventionally, in a semiconductor manufacturing process, plasma technology is often used for film formation, etching, ashing, and the like. Plasma technology is also used for manufacturing solar cells, liquid crystal displays, plasma displays, and the like. If high-density and uniform plasma is generated, a uniform and stable treatment can be performed on the workpiece.
[0003]
As a plasma processing apparatus capable of generating high-density and uniform plasma, an apparatus using surface wave plasma (SWP) is known (for example, see Patent Document 1). This device introduces microwaves propagating in the waveguide from the slot antenna through the dielectric window (microwave introduction window) into the plasma generation chamber, and excites the process gas in the plasma generation chamber by the surface wave generated in the dielectric window. Thus, surface wave excitation plasma is generated.
[0004]
[Patent Document 1]
JP 2000-348898 (2nd page, FIG. 1)
[0005]
[Problems to be solved by the invention]
In this type of plasma processing apparatus, the standing wave mode of the surface wave is determined by the area and thickness of the dielectric window and the dimensions of the hermetic container. Naturally, since the plasma density of the surface wave excited plasma is directly affected by the standing wave mode of the surface wave, the plasma density, so-called discharge mode, is determined for each standing wave mode.
When microwave power or gas pressure in the hermetic container is continuously changed, a phenomenon called mode jump occurs in which the discharge mode changes rapidly. Since the mode jump intermittently fluctuates the plasma density distribution, there is a problem that a plasma having a desired density cannot be obtained.
The present invention provides a plasma processing apparatus that does not cause a mode jump.
[0006]
[Means for Solving the Problems]
(1) A plasma processing apparatus according to claim 1 is a microwave waveguide having a slot antenna on a bottom surface, a microwave introduction window for forming and propagating a surface wave from the microwave introduced through the slot antenna, and a surface A process gas is excited by a wave to generate surface wave excited plasma, and an airtight container for processing an object to be processed by the surface wave excited plasma, and a surface wave propagation path that propagates along the surface of the microwave introduction window. In addition, a part of the surface wave is introduced , the phase of the surface wave is changed by reflecting a part of the introduced surface wave on the reflection surface, and the surface wave whose phase is changed is merged with the surface wave propagating in the propagation path. And a concave portion to prevent generation of a standing wave mode of the surface wave.
(2) A plasma processing apparatus according to claim 2, wherein a microwave waveguide having a slot antenna on the bottom surface, a microwave introduction window for forming and propagating a surface wave from the microwave introduced through the slot antenna, and a surface A process gas is excited by a wave to generate surface wave excited plasma, and an airtight container for processing an object to be processed by the surface wave excited plasma, and a surface wave propagation path that propagates along the surface of the microwave introduction window. A part of the surface wave that has been introduced and the part of the surface wave that has been introduced is reflected by the reflecting surface, so that the propagation direction of the part of the surface wave that propagates along the propagation path is changed, and the propagation direction is changed. A concave portion that changes the phase of the wave and rejoins the propagation path to prevent generation of a standing wave mode of the surface wave.
(3) According to the invention of claim 3, in the plasma processing apparatus of claim 1 or 2, the concave portion is provided with a reflecting plate for reflecting and joining the surface waves entering the concave portion to the propagation path. Features.
(4) The invention of claim 4 is the plasma processing apparatus of claim 3, wherein the reflecting plate is a movable reflecting plate, and the position of the reflecting plate is changed to make the phase of the surface wave variable.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, a plasma processing apparatus according to the present invention will be described with reference to the drawings.
FIG. 1 is an overall configuration diagram schematically showing a plasma processing apparatus according to an embodiment of the present invention. The plasma processing apparatus shown in FIG. 1 includes a microwave waveguide 1, a dielectric plate 2, and a chamber 10 including a chamber body 3 and a flange 4. The dielectric plate 2 is provided on the top of the chamber body 3 so as to be in contact with the inner wall of the chamber body 3. The microwave waveguide 1 is provided on the upper surface of the dielectric plate 2.
[0008]
For example, a microwave having a frequency of 2.45 GHz oscillated from a microwave output unit (not shown) propagates in the microwave waveguide 1 in the direction perpendicular to the paper surface. A plurality of slot antennas 5 for guiding microwaves to the dielectric plate 2 are formed on the bottom plate 1 a of the microwave waveguide 1. The dielectric plate 2 is made of a dielectric material such as quartz, alumina, zirconia, and Pyrex glass (registered trademark of US Corning).
A plurality of metal poles 6 as surface wave scattering members are embedded in the dielectric plate 2. The dielectric plate 2 is provided with a plurality of point reflectors 7 as surface wave absorbers.
[0009]
The metal pole 6 is manufactured from a conductive material or a dielectric material having a dielectric constant different from that of the dielectric plate 2. As the conductive material, a nonmagnetic metal such as stainless steel, aluminum, or an aluminum alloy is used. As the dielectric material, if quartz having a dielectric constant of 3.6 is used as the dielectric plate 2, alumina having a dielectric constant of 9 to 10 and zirconia having a dielectric constant of 7 to 10 can be used. .
[0010]
The point reflector 7 includes a cylinder 11, a reflecting plate 12 fixed to the tip of the piston rod, and an auxiliary plate 13. By extending and contracting this piston rod, the reflector 12 can move in the direction indicated by the arrow in the cylinder 11. The cylinder 11 and the reflecting plate 12 are manufactured from a nonmagnetic metal material such as stainless steel, aluminum, or an aluminum alloy. The auxiliary plate 13 is manufactured from a dielectric material.
[0011]
The chamber body 3 is provided with a gas introduction port 8 and a vacuum exhaust port 9. Process gases such as O ₂ , SiH ₄ , H ₂ , N ₂ , SF ₆ , Cl ₂ , Ar, and He are introduced from the gas inlet 8. By exhausting from the vacuum exhaust port 9 while introducing the process gas, the pressure in the chamber 10 is normally maintained at about 0.1 to 50 Pa. The chamber 10 is manufactured from a nonmagnetic metal material such as stainless steel, aluminum, or an aluminum alloy.
[0012]
The microwaves pass through the slot antenna 5 and enter the dielectric plate 2, propagate as a surface wave S on the surface of the dielectric plate 2 on the chamber body 3 side, and instantaneously spread over the entire surface of the dielectric plate 2. . This surface wave energy excites the process gas introduced into the chamber 10 to generate plasma P. Although not shown, by placing an object to be processed in the plasma P, processes such as film formation, etching, and ashing are performed.
[0013]
Next, the operation of the metal pole 6 and the point reflector 7 will be described.
FIG. 2 is a plan view of the plasma processing apparatus of FIG. 1 taken along line II. The outer edge of the dielectric plate 2 is surrounded by the side wall of the chamber body 3. A plurality of metal poles 6 (shown in a small circular shape) and a plurality of point reflectors 7 (shown in a large circular shape) are arranged on the dielectric plate 2.
[0014]
The microwave M traveling from the left to the right in the microwave waveguide 1 is introduced into the dielectric plate 2 through the slot antenna 5 and propagates through the surface of the dielectric plate 2 as the surface wave S, thereby determining the surface wave. A standing wave mode is formed. When the metal pole 6 or the point reflector 7 is not present, the standing wave mode determined by the dielectric constant, area, thickness, dimension of the hermetic container, microwave power, gas pressure, and gas type of the dielectric plate is maintained.
[0015]
In FIG. 2, the operation of the metal pole 6 and the point reflector 7 will be described in detail with reference to an area 20 surrounded by a two-dot chain line. The arrow in the area 20 schematically shows a mode in which the surface wave is scattered or absorbed by the metal pole 6 or the point reflector 7. Hereinafter, when a part of the surface wave S is taken out and described, numbers are added like the surface waves S1 and S2.
[0016]
<Metal pole>
In FIG. 2, the surface wave S1 propagating on the dielectric plate 2 is scattered by the metal pole 6a. The surface wave S1 goes straight when the metal pole 6a is not present, but when it is present, the straight wave is blocked and takes a course in every direction. This state will be further described with reference to FIG.
[0017]
FIG. 3 is a cross-sectional view taken along the line II-II in FIG. 2 and is a view for explaining the embedded state and operation of the metal pole.
Each of the four metal poles 6 b to 6 e is a cylindrical block, and the height thereof is shorter than the thickness of the dielectric plate 2. The dielectric plate 2 is provided with holes for embedding the metal poles 6b to 6e. As the metal poles 6b to 6e, one type can be appropriately selected from the above-described conductive materials and dielectric materials having a dielectric constant different from that of the dielectric plate 2. Two or more kinds of materials can be used in combination. When the metal pole is not required, a pole made of the same material as that of the dielectric plate 2 may be inserted instead. The number and arrangement of the metal poles are not limited to the present embodiment, and can be freely designed according to parameters such as microwave power and gas pressure.
[0018]
In FIG. 3, how the surface wave propagates on the surface of the dielectric plate 2 is indicated by arrows. The surface wave S5 indicated by the right-pointing arrow is scattered by the metal poles 6b and 6c and becomes a composite wave composed of the surface waves S6 and S7. Since the surface wave S5 before being scattered and the surface waves S6 and S7 after being scattered are different in phase, amplitude and the like, it is difficult for the surface wave S5 to form a standing wave. Similarly, the surface wave S8 indicated by the left-pointing arrow is scattered by the metal poles 6d and 6e, and it is difficult to form a standing wave. As a result, the standing wave mode of the surface wave S disappears, and the mode jump of the surface wave excited plasma does not occur.
[0019]
<Point reflector>
In the area 20 of FIG. 2, a part of the surface wave S2 propagating on the dielectric plate 2 is absorbed by the point reflector 7a, and the propagation direction is somewhat changed. That is, the surface wave S2 propagates while changing the propagation direction as schematically shown by the arrows of the surface waves S3 and S4. This state will be further described with reference to FIG.
[0020]
FIG. 4 is a cross-sectional view taken along the line III-III in FIG. 2 and is a view for explaining the structure and operation of the point reflector.
The two point reflectors 7a and 7b are provided on the upper surface of the dielectric plate 2, that is, on the atmosphere side. For the point reflector 7a, the distance D is the distance between the reflecting plate 12a and the auxiliary plate 13a, and this portion is in an atmospheric pressure environment. For the point reflector 7b, the distance D is set to zero.
[0021]
In FIG. 4, the manner in which the surface wave propagates on the surface of the dielectric plate 2 is indicated by arrows. The surface wave S9 indicated by the arrow pointing to the right is absorbed by the point reflector 7a. The surface wave S10 enters the point reflector 7a through the auxiliary plate 13a and is reflected by the bottom surface of the reflecting plate 12a separated by the distance D. The reflected wave reflected by the reflecting plate 12a merges with the surface wave S9 through the auxiliary plate 13a and the dielectric plate 2. Since the reflected wave is different in phase, amplitude, and the like from the surface wave S9, the surface wave S9 is difficult to form a standing wave.
[0022]
On the other hand, the surface wave S11 indicated by the left-pointing arrow in the figure is not absorbed because the point reflector 7b is present but the distance D is zero. The surface wave S11 is only slightly changed in phase and amplitude due to the scattering action. Therefore, the standing wave mode of the surface wave S11 is hardly disturbed.
However, in reality, since the surface wave propagates two-dimensionally, the standing wave mode of the surface wave S11 is disturbed by the influence of the surface wave S9 propagating rightward. If there is a portion where it is difficult to form a standing wave mode like the surface wave S9, the standing wave mode as a whole of the surface wave S disappears, and the mode jump of the surface wave excited plasma does not occur.
[0023]
From the above, the standing wave mode of the surface wave S can be reliably eliminated by making the distance D of the point reflector 7 variable.
A plurality of point reflectors 7 may be arranged on the upper side of the dielectric plate 2, and the distances D of the respective point reflectors 7 may be different from each other. By such fine adjustment, the standing wave mode of the surface wave S can be surely lost even when parameters such as microwave power and gas pressure are changed. The number and arrangement of the point reflectors are not limited to this embodiment, and can be freely designed according to parameters such as microwave power and gas pressure.
[0024]
The dielectric plate 2 may be provided with either the metal pole 6 or the point reflector 7 or both. By providing it together, the standing wave mode of the surface wave S can be more reliably eliminated.
[0025]
【The invention's effect】
As described above, according to the present invention, it is possible to provide a plasma processing apparatus that does not cause a mode jump.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram schematically showing an entire plasma processing apparatus according to an embodiment of the present invention.
FIG. 2 is a plan view of the plasma processing apparatus according to the embodiment of the present invention viewed along line II.
3 is a cross-sectional view taken along the line II-II in FIG. 2, and is a view for explaining an embedded state and operation of a metal pole.
4 is a cross-sectional view taken along the line III-III in FIG. 2, for explaining the structure and operation of the point reflector.
[Explanation of symbols]
1: Microwave waveguide 2: Dielectric plate (microwave introduction window)
3: Chamber body 4: Flange 5: Slot antenna 6: Metal pole (surface wave scattering member)
7: Point reflector (surface wave absorber)
10: Chamber M: Microwave S: Surface wave P: Plasma

Claims (4)

A microwave waveguide with a slot antenna on the bottom;
A microwave introduction window for forming and propagating a surface wave from the microwave introduced through the slot antenna;
A process gas is excited by the surface wave to generate surface wave excited plasma, and an airtight container for processing an object to be processed by the surface wave excited plasma;
Provided in the propagation path of the surface wave propagating along the surface of the microwave introduction window, a part of the surface wave is introduced, and the phase is changed by reflecting a part of the introduced surface wave on the reflection surface And a concave portion for joining the surface wave whose phase has been changed to the surface wave propagating in the propagation path,
A plasma processing apparatus characterized in that generation of the standing wave mode of the surface wave is prevented. A microwave waveguide with a slot antenna on the bottom;
A microwave introduction window for forming and propagating a surface wave from the microwave introduced through the slot antenna;
A process gas is excited by the surface wave to generate surface wave excited plasma, and an airtight container for processing an object to be processed by the surface wave excited plasma;
Provided in the propagation path of the surface wave propagating along the surface of the microwave introduction window , introducing a part of the surface wave, and reflecting the reflected surface by the part of the introduced surface wave, the propagation Changing the propagation direction of a part of the surface wave propagating through the path, and changing the phase of the surface wave whose propagation direction has changed, and a concave part that rejoins the propagation path,
A plasma processing apparatus characterized in that generation of the standing wave mode of the surface wave is prevented. In the plasma processing apparatus of Claim 1 or 2,
The plasma processing apparatus, wherein the concave portion is provided with a reflecting plate for reflecting and joining the surface wave entering the concave portion to the propagation path. In the plasma processing apparatus of Claim 3,
The plasma processing apparatus, wherein the reflection plate is a movable reflection plate, and the position of the reflection plate is changed to make the phase of the surface wave variable.

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