JPH10233294A - Plasma treatment device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a plasma treatment device capable of improving uniformity of electric field intensity distribution. SOLUTION: In a plasma treatment device wherein a microwave generated in a microwave generator 60 is transmitted into wave guides 62, 64 and then introduced into a treatment container where plasma treatment is performed for a body W to be treated, the device is constructed such that the wave guides 62, 64 are equipped with a mode filter means 65 for removing a microwave component of a specific oscillation mode out of the microwave transmitted thereinto. With this, a microwave component of an unnecessary oscillation mode is removed by the mode filter means 65, whereby electric field intensity is uniformly distributed in the treatment container.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plasma processing apparatus in which energy for generating plasma is supplied by microwaves to generate plasma.

[0002]

2. Description of the Related Art In recent years, a plasma processing apparatus has been used for processing such as film formation, etching, ashing, and the like in a semiconductor product manufacturing process in accordance with high density and high miniaturization of a semiconductor product. , 0.1 to several tens mTorr
A microwave plasma apparatus that generates high-density plasma by combining a microwave and a magnetic field from a ring-shaped coil is used because a plasma can be stably generated even in a high vacuum state having a relatively low pressure of about r. There is a tendency.

Conventionally, as this kind of microwave plasma apparatus, an apparatus as disclosed in Japanese Patent Application Laid-Open No. HEI 3-17273 is known. In this device, a waveguide for introducing microwaves is connected to a plasma generation chamber having a magnetic field forming means, and the microwaves introduced from the waveguides cause electron cyclotron resonance to generate high-density plasma. It is supposed to. FIG. 7 is a schematic configuration diagram showing an example of this type of a conventional plasma processing apparatus, in which a processing vessel 2 is shown.
A microwave introduction window 4 is provided on the ceiling of the device, and a microwave generated by a microwave generator 6 is supplied to, for example, a rectangular waveguide 8.
And microwave introduction window 4 via conical waveguide 10
And is introduced into the processing container 2.
The microwave introduced into the processing container 2 is combined with a vertical magnetic field generated by a magnet 12 provided outside the upper portion of the processing container 2 and an ECR (Electron Cyclo).
(Tron Resonance), and a high-density plasma is generated.

[0004]

By the way, in the above-mentioned apparatus example, the microwave oscillating in the rectangular waveguide 8 in, for example, the TE10 mode is transmitted to the TM converter by the mode converter 9.
Although the TM01 mode is basically an axisymmetric electric field mode, the TM01 mode has an axially symmetric and substantially uniform electric field intensity distribution in the processing container. Was expected to be obtained. However, the actually obtained plasma density is not uniform in the wafer plane.
As shown in (1), the thickness of the film formed on the wafer surface is partially increased in the peripheral portion of the wafer as shown by oblique lines 13, and the uniformity of the plasma processing cannot be maintained. was there. The reason why the electric field intensity distribution becomes non-uniform is that the vibration mode of the microwave introduced into the processing chamber 2 is not only the TM01 mode but also some other vibration modes, for example, the plasma as shown in FIG. Considering the non-uniformity of the processing, it is considered that a vibration component of the TE11 mode is included. In particular, as the wafer size increases from 8 inches to 12 inches, it becomes more difficult to increase the uniformity of the plasma density, and it is strongly desired to solve the above problems.

[0005] The present invention focuses on the above problems,
It was created to solve this effectively. An object of the present invention is to provide a plasma processing apparatus capable of improving the uniformity of the electric field intensity distribution by removing a microwave component of an unnecessary vibration mode, for example, a TE11 mode.

[0006]

The inventor of the present invention has conducted intensive studies on the non-uniformity of the plasma processing, and as a result, it has been determined whether the light is generated from the mode converter or the reflected wave generated when the microwave is introduced. Although unknown, the microwaves introduced contain a small amount of unnecessary vibration mode components in addition to the main vibration modes. This has led to the invention.

That is, in order to solve the above-mentioned problems, the present invention propagates a microwave generated by a microwave generator into a waveguide and introduces the microwave into a processing vessel for performing a plasma processing on an object to be processed. In the plasma processing apparatus described above, the waveguide is provided with a mode filter for removing a microwave component of a specific vibration mode from the microwave propagating through the waveguide.

Thus, when the microwave propagates through the waveguide, a specific unnecessary vibration mode, for example, a microwave component of the TE11 mode is removed by the mode filter. Therefore, only a specific major vibration mode, for example, the microwave component of the TM01 mode is introduced into the processing container, and the uniformity of the electric field intensity distribution can be improved. Such a mode filter can be formed by providing a large number of slits along a propagation direction in a cylindrical conductor. This slit consists of a long hole extending along the propagation direction, for example,
The waveguides are arranged in a staggered manner in the circumferential direction, and are provided such that the ends of the slits overlap the ends of the slits adjacent to the circumferential direction in the propagation direction.

As a result, the wall current flowing in the circumferential direction is effectively suppressed, and the propagation of the microwave component of an unnecessary vibration mode, for example, the TE11 mode is prevented, and this is efficiently removed. . In addition, since a microwave component of an unnecessary vibration mode, for example, a TE11 mode, is radiated outward from the slit as a radio wave, a microwave absorber made of a material having a high dielectric loss factor is provided to absorb this. Ensure safety.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the plasma processing apparatus according to the present invention will be described below in detail with reference to the accompanying drawings. FIG.
FIG. 2 is a configuration diagram showing a plasma processing apparatus according to the present invention, FIG. 2 is an enlarged longitudinal sectional view showing a mode filter used in the apparatus shown in FIG. 1, and FIG. 3 is an enlarged transverse sectional view showing a mode filter used in the apparatus shown in FIG. FIG. 4 is a perspective view showing a mode filter used in the apparatus shown in FIG.

In this embodiment, a case where the plasma processing apparatus is applied to a plasma film forming apparatus will be described. As shown in the figure, the plasma film forming apparatus 14 as a plasma processing apparatus has a processing container 16 in which a side wall and a bottom portion are formed of a conductor such as aluminum and the whole is formed in a cylindrical shape. Is configured as a closed processing space S. In the processing container 16, a mounting table 1 on which, for example, a semiconductor wafer W as an object to be processed is mounted on an upper surface.
8 are accommodated. The mounting table 18 is formed in a substantially columnar shape with a central portion made of, for example, anodized aluminum or the like, and the lower portion thereof is supported by a supporting table 20 also formed in a columnar shape by aluminum or the like. In addition, the support base 20 is installed on the bottom of the processing container 16 via an insulating material 22.

On the upper surface of the mounting table 18, an electrostatic chuck or a clamping mechanism (not shown) for holding the wafer by suction is provided. The mounting table 18 is connected to a matching box 26 via a power supply line 24. And for example 13.56 MH
z is connected to a bias high frequency power supply 28. A cooling jacket 3 for flowing cooling water or the like for cooling a wafer during plasma processing is provided on a support 20 for supporting the mounting table 18.
0 is provided.

A processing gas supply nozzle 32 made of, for example, a quartz pipe for introducing a film-forming gas into the container, for example, is provided in a side wall of the processing container 16 and defining a processing space S. The nozzle 32 is connected to a processing gas source 40 via a gas flow path 34 via a mass flow controller 36 and an on-off valve 38. The film forming gas as the processing gas is, for example, SiH ₄ , SiF ₄ , SiH ₂ F ₂ ,
C ₂ H ₂ , O ₂ , H ₂ gas or the like can be used. A gas nozzle 42 made of quartz for supplying an inert gas such as argon as a plasma gas is provided in front of the processing space S.
Gas is supplied here. A ring-shaped magnet 44 for ECR is provided outside the upper part of the processing chamber 16 so as to apply a vertical magnetic field for generating ECR to the processing space S.

A gate valve 46 is provided on the outer periphery of the side wall of the container so as to open and close when a wafer is loaded into and unloaded from the inside of the container. An exhaust port 48 connected to a vacuum pump (not shown) is provided at the bottom of the container.
If necessary, the inside of the processing vessel 16 can be evacuated to a predetermined pressure.

On the other hand, in the ceiling portion of the processing container 16, an opening 5 having a size substantially equal to or slightly larger than the diameter of the mounting table 18 for introducing microwaves into the container is provided.
A microwave introduction window 54 made of, for example, AlN (aluminum nitride) is hermetically provided in the opening 50 via a sealing member 52 such as an O-ring.

On the other hand, a microwave generator 60 for supplying microwaves to the microwave introduction window 54 generates microwaves of, for example, 2.45 GHz, and these initially have a rectangular waveguide. 62, for example TE
Microwaves in 10 vibration modes are transmitted, and a mode converter 64 is provided on the way to convert the transmission mode to the TM01 mode. The mode converter 64 is connected to a mode filter 65 which is a feature of the present invention.
The mode filter 65 is connected to a tapered waveguide 66 having a conical shape, for example, as a waveguide.
The microwave introduction window 54 is connected to the lower end side of the tapered waveguide 66 so that microwaves can be introduced into the processing chamber 16. The waveguide 66 is not limited to a conical tapered waveguide, but may be a cylindrical waveguide.

Accordingly, the microwave mode-converted by the mode converter 64 is introduced into the processing chamber 16 through the tapered waveguide 66. At this time, the unnecessary vibration mode, For example, a microwave component of the TE11 mode is removed. As shown in FIGS. 2 to 4, the mode filter 65 is formed into a cylindrical shape and has a waveguide 68 for transmitting microwaves.
And a large number of slits 70 formed on the wall surface of the waveguide section 68. Specifically, the waveguide portion 68 is formed in a cylindrical shape by a conductor such as copper or aluminum, and the flange portion 72 at one end is fixed to the flange portion 64A on the mode converter 64 side by a bolt 74. The other end of the flange portion 76 is fixed to the flange portion 66A of the tapered waveguide 66 by a bolt 78. The waveguide 68 may be formed by coating a defective conductor such as a cylindrical resin with silver plating or the like.

Each of the slits 70 is formed by a long hole formed along the microwave propagation direction, and at predetermined intervals along the microwave propagation direction and the circumferential direction of the cylindrical waveguide section 68. Many are provided. Regarding the dimensions of each member, the thickness of the waveguide section 68 is about several mm, and the diameter is about 1 mm.
The width W1 of the slit 70 is about several mm, and the length L1 is about 50 to 70 mm, while it is about 0 cm.
The slits 70 are arranged in a zigzag manner in the circumferential direction of the cylindrical waveguide section 68, and the end of each slit 70 is connected to the end of the slit adjacent to the propagation direction. It is formed so as to overlap by a small distance L2 in the circumferential direction. As a result, the wall current that is to flow in the circumferential direction of the waveguide 68 is converted into an electromagnetic wave at the slit 70 and emitted, and the flow of this current can be efficiently prevented.

In the illustrated example, two rows of slits 70 and three rows of three slits 70 are alternately arranged along the microwave propagation direction, and these rows are arranged at equal intervals along the circumferential direction. Although 16 columns are provided (see FIG. 3), it is needless to say that the present invention is not limited to these numerical examples. In order to absorb the electromagnetic waves of the microwaves emitted from each slit 70, a rectangular microwave absorber 80 divided into eight as shown in FIG. Is provided. As the microwave absorber 80, a material having a large dielectric constant and a large dielectric loss, for example, a dielectric such as SiC can be used. Further, a cylindrical shield 82 made of, for example, aluminum is provided outside the microwave absorber 80 so as to cover the entirety of the conductor portion 78, and the microwave leaking from the inside is almost completely removed. Seals are provided to further improve safety.

Next, the operation of the embodiment constructed as described above will be described. First, the semiconductor wafer W is accommodated in the processing chamber 16 by the transfer arm via the gate valve 46, and the lifter pins (not shown) are moved up and down to place the wafer W on the mounting surface on the upper surface of the mounting table 18. I do.
Then, the inside of the processing container 16 is maintained at a predetermined process pressure, for example, in the range of 0.1 to several tens mTorr, and the above-described film forming gas is supplied from the processing gas supply nozzle 32 while controlling the flow rate together with the carrier gas. I do. Further, an Ar gas is supplied from the gas nozzle 42 as a plasma gas.

In some cases, the Ar gas is not supplied. At the same time, the microwave from the microwave generator 60 is
Rectangular waveguide 62, mode converter 64, mode filter 6
5 and the taper waveguide 66, and the microwave is introduced into the processing space S through the microwave introduction window 54 to form an electric field in this space, thereby generating plasma and performing a film forming process. . At this time, the plasma generates electron cyclotron resonance due to the vertical magnetic field from the magnet 44 disposed outside the processing chamber 16, and the plasma density increases.

Here, the microwave of, eg, 2.45 GHz generated by the microwave generator 60 is, for example, TE1
Propagation in the rectangular waveguide 62 by the 0 mode vibration is converted into, for example, TM01 mode vibration by the mode converter 64, and the unnecessary vibration mode microwave included in the microwave, for example, TE11 here. The mode microwaves are removed by the mode filter 65. Further, the microwave propagates through the tapered waveguide 66 and is supplied into the processing container 16. Here, the mode filter 65 propagates the microwave of the TM01 mode, which is the main vibration mode, and the TE mode, which is an unnecessary vibration mode.
The function of removing the 11-mode microwave will be described in detail with reference to FIGS.

FIG. 5 is a diagram schematically showing a state in which wall currents in the TE11 mode and TM01 mode flow along the waveguide having no slit, and FIG. 6 shows the TE11 mode along the waveguide of the mode filter. It is a figure which shows typically the state which the wall current of the mode and the TM01 mode flows. As is well known, the wall current in the TE11 mode includes a current component C1 flowing in the propagation direction and a current component C2 flowing in a direction perpendicular to the propagation direction, that is, in the circumferential direction. Is only the current component C3 flowing along the propagation direction, and there is no current component flowing along the circumferential direction.

In such a situation, as shown in FIG. 5, on the wall surface of the waveguide 84 having no slit as shown in FIG. 5, there is no obstacle obstructing the flow of the wall current. Both the wall current in the mode and the wall current in the TM01 mode flow well, and therefore, the microwaves in both vibration modes propagate without attenuation. On the other hand, when a large number of slits 70 are provided along the propagation direction on the wall surface of the waveguide section 68 as in the present invention, FIG.
As shown in (A), of the wall current in the TE11 mode, the current component C1 flowing along the propagation direction flows with almost no attenuation, but the current component C2 trying to flow along the circumferential direction is reduced by the slit 70. And the flow tends to be obstructed. Therefore, TE
The eleven mode microwaves are now greatly attenuated and removed. That is, the energy of the microwave in the TE11 mode is emitted to the outside as a microwave electromagnetic wave due to the generation of a magnetic dipole due to the magnetic field in the gap of the slit 70.

TE1 removed by the slit 70
The one-mode microwave propagates from the mode converter 64 side in FIG. 1 as well as the TE11-mode microwave generated by reflection at the microwave introduction window 54 side as well as being attenuated. In contrast, FIG.
As shown in (B), the wall current of the TM01 mode is only the current component C3 flowing along the propagation direction of the microwave, and therefore, even if a large number of slits 70 are provided in the waveguide 68, the flow hardly flows. There is no hindrance, and therefore, the microwave in the TM01 mode propagates with almost no attenuation.

In this manner, the microwave mode-converted by the mode converter 64 is passed through the mode filter 65, so that only unnecessary TE11 mode microwaves are almost cut off, and the main vibration mode TM01 mode , It is possible to greatly improve the uniformity of the electric field density in the processing space S in the processing chamber 16. In addition, the TE11 mode microwave removed by the mode filter 65 is absorbed by the microwave absorber 80 disposed outside the slit 70 and converted into heat. Further, even if the microwave leaks out, the microwave can be completely shut off by the shield 82 provided outside the microwave, so that the safety can be maintained at a high level.

Further, as shown in FIG. 2, if the slits 70 are arranged in a zigzag manner in the circumferential direction so that both ends thereof are overlapped, the wall current flowing in the circumferential direction is almost surely cut off. Therefore, the microwave attenuation efficiency of the TE11 mode can be further increased. As shown in FIGS. 2 and 3, when 16 rows of slits were provided at equal intervals along the circumferential direction of the waveguide section 68, the TE11 mode microwave could be attenuated by approximately 6 to 8 dB. When eight slit rows are provided at regular intervals along the circumferential direction of the waveguide section 68, microwaves in the TE11 mode are transmitted at approximately 3 dB or more.
The attenuation was 3.8 dB. As a result, in both cases, the electric field intensity distribution in the processing space S was made more uniform, and the in-plane uniformity of the film thickness of the plasma processing, for example, the film formation could be greatly improved.

The length and number of the slits 70 are not limited to those of the present embodiment as described above, and for example, the length of the slit may be set to the full length of the waveguide. Here, the conical tapered waveguide 66 is used immediately before the microwave introduction window, but a cylindrical waveguide may be used instead. In this embodiment, the case where the plasma processing apparatus is applied to the plasma film forming apparatus has been described as an example, but the present invention is not limited to this.
The present invention can be applied to other plasma devices, for example, a plasma etching device, a plasma ashing device, a sputtering device, and the like. In addition, the present invention can be applied not only to an ECR type plasma device but also to other types of plasma devices.

[0029]

As described above, according to the plasma processing apparatus of the present invention, the following excellent operational effects can be exhibited. A mode filter is provided in the waveguide to remove unnecessary vibration modes such as TE11 mode microwave components, so that only a specific single vibration mode such as TM01 mode microwave components is introduced into the processing chamber. it can. Therefore, the uniformity of the distribution state of the electric field intensity in the processing space can be greatly improved, and the uniformity of the plasma processing, for example, in the case of the film forming processing, the in-plane uniformity of the film thickness can be greatly improved. it can. Further, by providing the microwave absorber, the removed microwave energy of the vibration mode can be absorbed, and its safety can be maintained at a high level.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing a plasma processing apparatus according to the present invention.

FIG. 2 is an enlarged vertical sectional view showing a mode filter used in the apparatus shown in FIG.

FIG. 3 is an enlarged cross-sectional view showing a mode filter used in the apparatus shown in FIG.

FIG. 4 is a perspective view showing a mode filter used in the apparatus shown in FIG.

FIG. 5 shows TE1 along a waveguide without slits.
It is a figure which shows typically the state which the wall current of 1 mode and TM01 mode flows.

FIG. 6 is a diagram schematically showing a state in which wall currents in the TE11 mode and the TM01 mode flow along the waveguide of the mode filter.

FIG. 7 is a schematic configuration diagram showing an example of a conventional plasma device.

FIG. 8 is an explanatory diagram showing a film formation state when film formation is performed using the apparatus shown in FIG. 7;

[Explanation of symbols]

 Reference Signs List 14 plasma film forming apparatus (plasma processing apparatus) 16 processing container 18 mounting table 54 microwave introduction window 60 microwave generator 62 rectangular waveguide 64 mode converter 65 mode filter 66 taper waveguide 68 waveguide section 70 slit 80 microwave absorber 82 shield S processing space W semiconductor wafer (workpiece)

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI H01P 1/16 H01P 1/16

Claims (6)

[Claims] In a plasma processing apparatus, a microwave generated by a microwave generator is propagated into a waveguide and introduced into a processing container for performing plasma processing on an object to be processed. And a mode filter for removing a microwave component of a specific vibration mode from the microwave propagating to the plasma processing apparatus. 2. The mode filter according to claim 1, wherein the mode filter includes a waveguide for transmitting the micro-waves and a plurality of slits formed in the waveguide for eliminating a wall current. Plasma processing equipment. 3. The plasma processing apparatus according to claim 2, wherein the slit comprises a long hole extending along a propagation direction of the microwave. 4. The slits are arranged in a zigzag manner in the circumferential direction of the waveguide, and the ends of the slits are connected to the ends of the slits adjacent to the circumferential direction in the propagation direction. The plasma processing apparatus according to claim 2, wherein the plasma processing apparatuses overlap each other. 5. A microwave absorber that absorbs microwaves of a specific vibration mode emitted from the slit is provided on an outer periphery of the waveguide section. Plasma processing equipment. 6. The specific vibration mode to be removed is TE
The plasma processing apparatus according to any one of claims 1 to 5, wherein the mode is an eleven mode.