JP3085019B2 - Plasma processing method and apparatus - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plasma processing method for performing etching, thin film formation, and the like using plasma generated by using microwaves.

[0002]

2. Description of the Related Art Microwaves are introduced into a vacuum vessel under a low gas pressure to generate gas discharge to generate plasma, and this plasma is irradiated on the surface of a sample substrate to perform etching, thin film formation, etc. Research and development are being pursued as plasma processing methods and apparatuses for performing the above processing are indispensable for the manufacture of highly integrated semiconductor elements and the like.

[0003] In particular, as a method for generating highly active plasma in a low gas pressure region, a magnetic field microwave plasma apparatus or a method for generating plasma by electron cyclotron resonance excitation is considered promising. FIG. 8 is a longitudinal sectional view of a conventional plasma processing apparatus using an electron cyclotron resonance excitation using a microwave configured as an etching apparatus.
31 and a sample chamber 33.

The plasma generation chamber 31 has a water cooling structure. A microwave introduction window 31b sealed with quartz glass 31a is provided at the center, and the microwave introduction window 31 is provided at the center of the lower wall.
A plasma extraction window 31c is provided at a position opposed to 31b. One end of a waveguide 32 whose other end is connected to a microwave oscillator (not shown) is connected to the microwave introduction window 31b, and a sample chamber 33 is arranged facing the plasma extraction window 31c. An excitation coil 34 is disposed concentrically with the plasma generation chamber 31 and a waveguide 32 connected thereto so as to surround and surround one end of the waveguide.

In the sample chamber 33, the plasma extraction window 31 is provided.
A sample table 37 is disposed at a position opposite to c, on which a sample S such as a wafer is mounted as it is or detachably mounted by means such as electrostatic suction, and a lower wall of the sample chamber 33 or An exhaust port 33a by an exhaust device (not shown) is opened in the side wall. 31g and 33g are gas supply systems.

In such an etching apparatus, after setting the inside of the plasma generation chamber 31 and the sample chamber 33 to a required pressure, a required gas pressure is obtained in the plasma generation chamber 31 through a gas supply system 31g. As described above, a microwave is introduced into the plasma generation chamber 31 through the microwave introduction window 31b while forming a magnetic field with the excitation coil 34, and the gas is resonantly excited using the plasma generation chamber 31 as a cavity resonator. Generate plasma. The generated plasma is drawn out around the sample S in the sample chamber 33 by a divergent magnetic field whose magnetic flux density decreases as it goes to the sample chamber 33 formed by the exciting coil 34, so that the surface of the sample S in the sample chamber 33 is etched. (JP-A-57-133636).

In the conventional apparatus as described above, the microwave introduction window 31b opened in the upper wall of the plasma generation chamber 31 is hermetically sealed by a quartz glass plate 31a made of a microwave material. When viewed from the side of the plasma generation chamber 31 functioning as a cavity resonator, the microwave introduction window 31b is a space, and a step is formed between the microwave introduction window 31b and the inner wall surface of the plasma generation chamber 31. Are reflected abnormally, and the uniformity of the plasma distribution is deteriorated due to this. As a countermeasure, a device as shown in FIG. 9 has already been filed by the present applicant (Japanese Patent Application Laid-Open No. 63-318099).

FIG. 9 is a partial cross-sectional view of a conventional plasma processing apparatus according to the application of the present applicant, and the inside of a microwave introduction window 31b opened to the plasma generation chamber 31 is filled with the wall. Microwave transmitting material on the same plane
48 is interposed. The microwave transmitting material 48 is made of quartz or the like, and is a disc portion closely fitted into the microwave introduction window 31b.
48a and a flange portion 48b connected to the upper portion thereof are integrally formed, and a flange provided at the lower end of the waveguide 32 is provided.
Together with 32a, it is integrally fixed by a stopper 32b.

In such a conventional apparatus, the microwave opening in the upper wall of the plasma generation chamber 31 has a state in which the introduction window 31b is completely filled with the microwave transmitting material 48 without any gap. The reflection is reduced, and the generation of plasma is also made uniform.

[0010] However, in such a conventional device, a rectangular TE ₁₀ as shown in FIG.
Mode or a circular TE ₁₁ mode as shown in FIG. 11 is used, and since these electric field distributions are strong in the central part, there is a problem that the density of generated plasma is also strong in the central part of the plasma generation chamber 31. there were. Therefore, in order to equalize the distribution of microwaves in the plasma generation chamber, a microwave diffusing means such as a concave lens is provided in the microwave introduction window to uniformize the electric field distribution of the microwaves and uniform the generation of plasma. An apparatus has been proposed (JP-A-3-244123).

[0011]

However, in such prior art, although the uniformity of the electric field intensity distribution of the microwave in the plasma generation chamber is slightly improved, the plasma tends to have a strong central portion. However, it is difficult to generate plasma with higher uniformity.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a microwave in a mode in which the electric field intensity is not the strongest at the center, and to focus the electric field by changing the propagation direction of the microwave. In addition to the uneven distribution due to abnormal reflection of microwaves, the unevenness of microwave electric field strength caused by the propagation mode in the waveguide is eliminated, and the uniformity of microwave electric field strength in the plane is improved. It is an object of the present invention to provide a plasma processing method which can improve the uniformity and generate the plasma with good uniformity.

[0013]

The plasma processing method according to the present invention According to an aspect of the circular waveguide of the TM ₀₁ mode or circular waveguide
The microwave of _TE01 mode is introduced into the vacuum vessel by the electric field focusing means, plasma is generated and the sample is processed, and the plasma processing apparatus according to the present invention generates plasma and generates plasma therein. a vacuum container for processing a sample, said generating means of the microwaves introduced into the vacuum vessel, a microwave mode of the generated microwaves to a mode converter or the generator into a TM ₀₁ mode circular waveguide A mode converter for converting a mode to a TE ₀₁ mode of a circular waveguide, and an electric field converging means provided to introduce the converted microwave into a vacuum vessel while uniforming the electric field distribution. And

[0014]

The generation of plasma in the plasma generation chamber tends to be strong at the center. This is partly due to the fact that the commonly used microwave has a strong electric field strength at the center and the properties of the plasma itself. Therefore, in the present invention, a microwave having an electric field distribution in which the electric field is weak in the central portion and the electric field is strong in the peripheral portion, and has a function of focusing the electric field of the microwave, for example, a dielectric having a convex shape To make the electric field distribution of the microwave introduced into the plasma generation chamber uniform or a distribution that is slightly stronger at the periphery than at the center, thereby making it possible to uniformize the generation of plasma in the plasma generation chamber.

When a convex dielectric is used as a microwave electric field focusing means, the degree of focusing is determined by determining the radius of curvature R of the convex portion in accordance with the structure of the microwave introduction portion of each device. To control the electric field distribution of the microwave. However, in determining R, it goes without saying that R = Ｒ is excluded because it is no longer a convex shape.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below with reference to the drawings showing the embodiments. FIG. 1 is a longitudinal sectional view of a plasma processing apparatus according to one embodiment of the present invention, and FIG. 2 is a partially enlarged sectional view of a microwave introduction window 1b. As in the conventional apparatus, the vacuum vessel is composed of a plasma generation chamber 1 and a sample chamber. And 3.

The plasma generation chamber 1 has a hollow cylindrical shape with a double wall surrounding wall and a cooling water flow chamber, and is formed so as to constitute a cavity resonator for microwaves.
A microwave introduction window 1b provided with a microwave transmitting material 8 is provided at the center of the upper wall of the plasma generation chamber 1, and a plasma extraction window 1c is provided at a position opposite to the microwave introduction window 1b at the center of the lower wall. I have.

The microwave introduction window 1b is sealed with a microwave transmitting material 8, one end of the waveguide 2 is connected to the outside, and the plasma extraction window 1c faces the outside. A sample chamber 3 is provided, and an excitation coil 4 is provided around the plasma generation chamber 1 and one end of the waveguide 2 connected thereto.

[0019] In the middle of the waveguide 2 are with intervening mode converter 5, the other end is connected to the microwave oscillator, not shown, the microwave of the rectangular TE ₁₀ mode by the mode converter 5 generated The microwave is converted into a circular TM ₀₁ mode microwave as shown in FIG. 3 or a rectangular TE ₁₀ mode microwave generated by another mode converter 5 is converted into a circular TE ₀₁ mode microwave as shown in FIG. Plasma generation chamber 1
And an electric field is formed here. The exciting coil 4 is connected to a DC power supply (not shown) to form a magnetic field for generating plasma in the plasma generation chamber 1 by passing a DC current, and to reduce the magnetic flux density toward the sample chamber 3 side. Divergent magnetic field,
This diverging magnetic field causes the plasma generated in the plasma generation chamber 1 to be introduced into the sample chamber 3.

The sample chamber 3 is provided with an exhaust port 3a connected to an exhaust device (not shown) on the bottom wall facing the plasma extraction window 1c. The sample stage 7 is provided by
A sample S is provided on the upper surface so as to face the plasma extraction window 1c.

As shown in FIG. 2, the microwave transmitting material 8 is formed by integrally forming a circular flat convex lens portion 8b smaller than the circular plate portion 8a on the lower surface side thereof.
8b is closely fitted to the microwave introduction window 1b, and the circular portion 8a
Is brought into airtight contact with the outer peripheral edge of the upper portion of the microwave introduction window 1b via an O-ring or the like (not shown), and is fixed together with the flange portion 2a of the waveguide 2 by the metal fitting 2b.
In this state, the lower end surface of the lens portion 8b is positioned so as to project slightly below the inner wall surface of the plasma generation chamber 1. Note that the disk portion 8a and the lens portion 8b may be formed separately.

Examples of the microwave transmitting material 8 include quartz glass, alumina (Al ₂ O ₃ ), BN, SiN, and other materials having a relatively high dielectric constant εr such as heat-resistant polymer materials (Teflon, polyimide).
Is used.

In the apparatus of the present invention,
The sample S is placed on the sample stage 7 in the sample chamber 3, and the plasma generation is performed.
After setting the pressures in the chamber 1 and the sample chamber 3 to the required pressure,
Gas is supplied to plasma generation chamber 1 and sample chamber 3 through supply pipes 1g and 3g.
And a DC current is supplied to the exciting coil 4 in this state.
And waveguide 2, mode converter 5, microphone
Round TM through the window 1b and microwave transmitting material 8
₀₁Mode or circular TE ₀₁Mode microwave
It is introduced into the production chamber 1. This allows the gas to be efficiently
Separated, plasma is generated, and the generated plasma is excited
In the sample chamber 3 due to the divergent magnetic field formed by the coil 4
The gas is introduced and activates the gas in the sample chamber 3 to the surface of the sample S.
Is etched or a thin film is formed.

FIGS. 3 and 4 are illustrations of the electromagnetic field distribution of the circular TM ₀₁ mode and the circular TE ₀₁ mode in the circular waveguide 2 near the connection with the plasma generation chamber 1, respectively. 4A and 4A are cross-sectional views thereof, and FIGS. 3B and 4B are longitudinal sectional views thereof. In the figure, the solid line is the electric field,
The dashed lines indicate the magnetic fields, respectively. As is clear from FIGS. 3 and 4, the distribution of the microwave in the waveguide 2 is
Is 0 at the center of the cross section, and the distribution is weak at the center and strong at the periphery.

FIG. 5 is a schematic longitudinal sectional view showing another embodiment of the present invention, in which microwave transmitting materials 9 and 10 are provided in a microwave introducing window 1c. The microwave transmitting material 9 is formed in substantially the same shape as the conventional microwave transmitting material 48 shown in FIG. 9, and is in contact with the upper surface thereof (in this case, the microwave transmitting materials 9 and 10 are integrally formed). The micro is fixed to the permeable material 10 at a small distance between the micro material and the micro material.

FIGS. 6 and 7 are graphs showing test results of the apparatus of the present invention shown in FIGS. Figure 6 shows a rectangular TE ₁₀ mode microwave with a frequency of 2.45 GHz as a microwave.
Mode converter 5 for converting TE ₁₀ mode to circular TM ₀₁ mode
The mode is converted into a microwave circular TM ₀₁ mode, and is introduced into a plasma generation chamber through a plano-convex lens section 8b shown in FIG. It is a graph of density. The curvature radius of the convex portion of the plano-convex lens portion 8b shown in FIG. 2 in the present invention was set to 100 mm. The conditions for plasma generation are as follows. Ar gas: 120sccm Pressure: 1mTorr Microwave power: 1kW

For reference, the conventional apparatus also shown in FIG. 8 (however, the microwave introduction unit is an apparatus having the structure of FIG. 9), and FIG.
In the conventional device shown in FIG. 1 (however, the microwave introduction unit is a device having the configuration shown in FIG. 9), a rectangular TE ₁₀ → a circular TM ₀₁
A similar test was performed on a device provided with the mode converter described above.

[0028] When ○ mark using the present invention method and apparatus in the graph shown in FIG. 6 (introduction through a lens of a plano-convex shape shown in FIG. 2 microwaves of the circular TM ₀₁ mode), also △ mark is the result of the conventional apparatus shown in FIG. 8 (introducing a microwave rectangular TE ₁₀ mode). In addition, the squares indicate the results when a mode converter of rectangular TE ₁₀ → circular TE ₀₁ is provided in the middle of the waveguide 32 in the conventional device (microwave of circular TM ₀₁ mode is introduced).

[0029] As apparent from the graph of FIG. 6, the microwaves introduced into the plasma generation chamber, who introduced the circular TM ₀₁ mode from the rectangular TE ₁₀ mode has a higher uniformity of the saturation ion current density distribution, moreover Figure It can be seen that the uniformity is further improved by using the microwave transmitting material having the convex lens shape shown in FIG.

FIG. 7 is a rectangular TE ₁₀ mode using a mode converter for converting the circular TE ₀₁ mode, the microwave of the rectangular TE ₁₀ mode frequency 2.45GHz circular TE ₀₁ mode conversion as a microwave as a mode converter 5 FIG. 3 is a graph of a saturated ion current density in a radial direction at a sample stage position when plasma is generated by being introduced into a plasma generation chamber through a plano-convex lens portion 8b shown in FIG. 2 and generating plasma. The radius of curvature of the convex portion of the plano-convex lens portion 8b shown in FIG. 2 in the present invention was also set to 100 mm. The conditions for plasma generation are as follows, as in the case of FIG. Ar gas: 120sccm Pressure: 1mTorr Microwave power: 1kW

For reference, the conventional device also shown in FIG. 8 (however, the microwave introduction unit is a device having the structure of FIG. 9), and FIG.
In the conventional device shown in FIG. 3 (however, the microwave introduction unit is a device having the configuration shown in FIG. 9), a rectangular TE ₁₀ → a circular TE ₀₁
A similar test was performed on a device provided with the mode converter described above.

[0032] When ○ mark using the present invention method and apparatus in the graph shown in FIG. 7 of the (introduced through a lens of a plano-convex shape shown in FIG. 2 microwaves of the circular TE ₀₁ mode), also △ mark is the result of the conventional apparatus shown in FIG. 8 (introducing a microwave rectangular TE ₁₀ mode). In addition, the square marks indicate the results when a mode converter of rectangular TE ₁₀ → circular TE ₀₁ is provided in the middle of the waveguide 32 in the conventional apparatus (microwave introduction of circular TE ₀₁ mode).

As is clear from the graph of FIG.
The microwave introduced into the plasma generation chamber is rectangular
It can be seen that the introduction of the circular TE ₀₁ mode has higher uniformity of the saturation ion current density distribution than the TE ₁₀ mode, and that the uniformity is further improved by using the convex lens-shaped microwave transmitting material shown in FIG. . In addition, the result of introducing the circular TE ₀₁ mode was higher than that of introducing the circular TM ₀₁ mode.

The material and the radius of curvature of the microwave transmitting materials 8, 9 and 10 are determined by changing the magnetic field intensity distribution, the characteristics of the plasma generated by the gas pressure, etc., that is, the plasma density, plasma permittivity, and plasma impedance. Since the optimum shape changes depending on the values, numerical values and shapes may be set in accordance with these.

In the above embodiment, the apparatus of the present invention is etched,
Alternatively, the configuration applied to the film forming apparatus has been described. However, the present invention is not limited to this, and can be applied to, for example, a sputtering apparatus.

[0036]

As described above, in the present invention, a uniform plasma distribution can be obtained by controlling the microwave electric field distribution in the plasma generation chamber, and uniform etching and thin film formation of the sample can be performed. It has the effect that it has.

[Brief description of the drawings]

FIG. 1 is a schematic longitudinal sectional view of an apparatus showing an embodiment of the present invention.

FIG. 2 is a partially enlarged cross-sectional view of an apparatus showing an embodiment of the present invention.

[3] FIG. 1 is an explanatory view of an electromagnetic field distribution of a circular TM ₀₁ mode of the waveguides used in the apparatus according to the embodiment of the present invention shown in FIG.

[4] FIG. 1 is an explanatory view of an electromagnetic field distribution of the circular TE ₀₁ mode waveguide used in the apparatus according to the embodiment of the present invention shown in FIG.

FIG. 5 is a partial longitudinal sectional view showing another embodiment of the present invention.

FIG. 6 is a graph showing a comparison test result between the device of the present invention and a conventional device.

FIG. 7 is a graph showing a comparison test result between the device of the present invention and a conventional device.

FIG. 8 is a schematic longitudinal sectional view of a conventional device.

FIG. 9 is a partially enlarged sectional view of another conventional device.

10 is an explanatory view of an electromagnetic field distribution of the rectangular TE ₁₀ mode conventionally used widely.

FIG. 11 is an explanatory diagram of an electromagnetic field distribution of a circular TE ₁₁ mode conventionally widely used.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Plasma generation room 1b Microwave introduction window 1c Plasma extraction window 2 Waveguide 3 Sample room 4 Excitation coil 5 Mode converter 7 Sample table 8, 9, 10 Microwave transmitting material S sample

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) H05H 1/46 C23C 16/50 C23F 4/00 H01L 21/3065

Claims (2)

(57) [Claims] 1. A were introduced into the vacuum container by TE ₀₁ mode microwave the electric field convergence means of TM ₀₁ mode or circular waveguide of the circular waveguide, and comprises treating the sample to generate a plasma Plasma processing method. 2. A vacuum chamber for processing a sample in its interior to generate plasma, and generation means of the microwave introduced into the vacuum vessel, the mode of the generated microwaves to the TM ₀₁ mode circular waveguide A mode converter for converting or the mode of the generated microwave into a circular waveguide TE ₀₁
A plasma processing apparatus, comprising: a mode converter for converting a mode into a mode; and an electric field converging means provided to introduce the converted microwave into a vacuum vessel while making the electric field distribution uniform.