JP3003248B2 - Plasma processing equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for utilizing a plasma formed by using a microwave for processing such as forming a thin film on a substrate to be processed or etching. A vacuum vessel having a circular microwave inlet that is hermetically closed by a plate-like microwave transmission window; a microwave generator; and a microwave vessel coupled with the vacuum vessel, through which microwaves are transmitted. The present invention relates to a plasma processing apparatus comprising: a microwave transmission unit formed of a cylindrical hollow conductor; and, more particularly, to a structure near a microwave introduction port.

[0002]

2. Description of the Related Art In a semiconductor manufacturing process, a microwave plasma processing apparatus capable of generating and maintaining a stable plasma even at a low pressure has been used in a film formation and an etching step with the miniaturization of a semiconductor device. I have. Many are electron cyclotron resonance (Electron Cyclotron Res
onance, hereafter also referred to as ECR)
This is an ECR type plasma processing apparatus that generates highly active plasma.

FIG. 5 shows a conventional configuration example of this type of plasma processing apparatus. The apparatus includes a vacuum vessel 1 formed as a stepped cylinder, a plate-shaped microwave transmission window 4 for hermetically closing a microwave introduction port 5 formed at the center of the upper end face of the cylinder, and a microwave generator (not shown). Equipment and vacuum vessel 1
And a microwave transmission unit 22 composed of a hollow conductor through which microwaves oscillated by a microwave generator pass through the atmosphere of the inside, and a solenoid 3 surrounding the vacuum vessel 1 coaxially as main components. I have.

The solenoid 3 is arranged so that its geometric center is located on the atmosphere side of the microwave transmission window 4, and adjusts the current flowing through the solenoid 3 to set the ECR condition on the vacuum side of the microwave transmission window 4. In addition to forming a magnetic field region that satisfies the condition, the microwave oscillated by the microwave generator is introduced into the vacuum vessel 1 through the microwave transmission unit 4 through the microwave transmission unit 22 and is introduced into the vacuum vessel 1. When the film raw material gas is introduced, the gas is efficiently ionized in the ECR magnetic field region and turned into plasma. The gas flows toward the substrate table 13 along the line of magnetic force of the divergent magnetic field formed by the solenoid 3, and a thin film is formed on the surface of the substrate 6. .

[0005]

Since the substrate 6 to be processed is usually circular in shape, the microwave inlet formed in the vacuum vessel is also formed in a circular shape, and is airtightly closed by the circular microwave transmitting window 4. The microwave power is introduced into the vacuum vessel 1 while the vacuum in the vacuum vessel 1 is maintained.

On the other hand, the waveguide main body 10 constituting the microwave transmission section 22 uses a microwave generator of a microwave frequency of 2.45 GHz which is generally used industrially.
A waveguide composed of a waveguide of JIS standard WRJ-2 having a rectangular cross section and a rectangular flange of BRJ-2 is used. The end waveguide 12 constituting the end of the microwave transmission section 22 is also formed in a rectangular shape having the same cross-sectional shape as the main body side.

As described above, in the conventional apparatus, the cross-sectional shape of the microwave transmission section is rectangular over the entire length despite the circular shape of the microwave inlet and the microwave transmission window, so that the size of the substrate to be processed is small. As the size increases, it becomes difficult to form a plasma having a uniform density in a region on the front side of the microwave transmission window and including the area of the substrate, so that the film thickness on the substrate reflects this density distribution. The problem is that the uniformity of distribution cannot be obtained.

An object of the present invention is to provide a plasma processing apparatus capable of forming a uniform plasma in a wide area including a large-sized substrate area on the front side of a microwave transmitting window,
In particular, it is to provide a structure of the microwave introduction part.

[0009]

In order to solve the above-mentioned problems, according to the present invention, there is provided a circular microwave inlet which is formed in a cylindrical shape and has one end face hermetically closed by a plate-like microwave transmitting window. A plasma processing comprising: a formed vacuum container; a microwave generator; and a microwave transmission unit formed by connecting the vacuum container and the microwave generator and having a hollow cylindrical conductor through which microwaves are transmitted. The diameter of the microwave inlet is larger than the diameter of the substrate to be processed.
The opening at the vacuum vessel side end face of the microwave transmission section is formed to have a circular shape having the same diameter as the microwave introduction port, and the inside of the appropriate longitudinal range including the vacuum vessel side end face of the microwave transmission section is formed. It is assumed that the space cross-sectional shape gradually changes from the cross-sectional shape on the output end side of the microwave generator to the circular shape on the vacuum vessel side end face opening.

In this case, the change from the cross-sectional shape on the output end side of the microwave generator to the circular shape of the end surface on the vacuum vessel side in the appropriate longitudinal range including the end face on the vacuum vessel side of the microwave transmission section is included. It may be performed continuously like a trapezoid formed by enclosing a rectangular plate and a circular plate on both end surfaces and enclosing the end surfaces with a single plate along the periphery of both end surfaces. The steps may have a stepped shape in which individual steps having a height determined corresponding to the wave wavelength are sequentially connected.

Further, in a vacuum vessel in which the diameter of the microwave introduction port is larger than the diameter of the substrate to be processed by 40 mm or more, a portion around the introduction port in which the microwave introduction port is formed is formed so as to be separable from the vacuum vessel body. It is suitable.

Further, it is more preferable that the portion around the microwave inlet formed detachably from the main body of the vacuum vessel is formed as a cover plate for closing the end face of the cylindrical portion of the vacuum vessel on the microwave inlet side.

[0013]

When the microwave introduction portion of the vacuum vessel is formed in this manner, the direction of the microwave electric field propagated in the rectangular waveguide from the microwave generator does not change and the vacuum vessel has a wave front wider than the substrate area. Introduced into. As a result, the source gas in the vacuum vessel is turned into plasma in a wider area including the substrate area on the front side of the microwave transmission window, and the density of the plasma flowing toward the substrate along the lines of magnetic force of the diverging magnetic field is increased in the peripheral portion of the substrate. It becomes higher at a considerable position, and the plasma density distribution becomes more uniform. According to experiments, this plasma density distribution is determined by the diameter of the microwave inlet, as described in the Examples section.
The uniformity is significantly higher in a circular area 40 mm smaller. Since the plasma density distribution and the film thickness distribution correspond closely, it is possible to form a thin film with a more uniform film thickness distribution on a larger substrate by configuring the microwave introduction section in this way. Become.

Further, the change from the cross-sectional shape of the output end side of the microwave generator to the circular shape of the end surface of the vacuum vessel side in the appropriate longitudinal range including the end face of the microwave transmission section including the vacuum vessel side is as follows. Microwaves can be introduced into the vacuum vessel without changing the direction of the microwave electric field, even if this change is made continuously or stepwise if the change is performed gradually at an inclination according to the microwave wavelength. can do. Therefore, by selecting and using an easily manufactured shape according to the microwave wavelength to be used and the size of the microwave introduction port, the device can be configured at lower cost.

If the portion around the inlet where the microwave inlet is formed is formed so as to be separable from the vacuum vessel main body, even when processing substrates of different sizes, the vacuum vessel main body can be replaced without being replaced. A microwave inlet having a size corresponding to the size of the substrate can be easily used, and the microwave transmission covering the substrate area by efficiently converting the raw material gas into plasma without excessively reducing the density of the supplied microwave power. The plasma density distribution in the window front side region can be made uniform.

Further, if the portion around the microwave introduction port formed detachably from the vacuum vessel main body is formed as a lid plate that closes the end face of the vacuum vessel cylindrical portion on the microwave introduction port side, the size of the apparatus can be maximized. A uniform surface treatment can be performed up to a large substrate size, and when the upper limit of the substrate size is constant, the apparatus can be downsized. In addition, since the inside of the vacuum vessel is completely opened to the atmosphere during the regular maintenance work inside the vacuum vessel, there is an advantage that the maintenance is easy and complete.

[0017]

FIG. 1 shows a first embodiment of the structure of the microwave introducing part according to the present invention. The end waveguide 11 constituting the vacuum vessel side end of the microwave transmission unit 21 has a rectangular flange 11A on the waveguide body 10 side and a circular flange 11B on the vacuum vessel 1 side.
And a cylindrical hole 11C having a tapered tubular section whose cross section gradually changes in the axial direction between the square hole of the flange 11A and the circular hole of the flange 11B. It is connected to the vacuum vessel 1 through a flange 9 formed with a heating part for being arranged concentrically with the vacuum vessel 4.

The plasma density on the front side of the microwave transmitting window when both the circular hole of the flange 11B and the diameter of the microwave introduction port 5 are 200 mm, and the microwave density in the conventional apparatus in which only the diameter of the microwave introduction port is 200 mm. FIG. 2 shows the measurement results of the plasma density distribution on the front side of the wave transmission window. In the figure, the zero point on the horizontal axis indicates the center position of the microwave inlet, and the measurement position indicates the radial distance from the center of the microwave inlet. Comparing both measurement results, in the device of the present invention, since the circular opening area of the end face of the end waveguide 11 is large,
When the same microwave power is used, the power density on the front side of the microwave transmission window becomes slightly thinner, and the maximum electron density becomes slightly lower, but the electron density at a position corresponding to the periphery of the substrate increases,
It can be seen that the plasma density distribution is flattened.

Further, FIG. 3 shows an apparatus according to the present invention.
The measurement results when the microwave power is changed to increase the uniformity of the plasma density distribution are shown. As can be seen from the measurement results, as the microwave power increases, the plasma density in the peripheral area increases more than in the central area, and the density distribution becomes remarkable in a circular area 40 mm smaller than the diameter of the microwave inlet. At a microwave power of 600 W or more, a uniform plasma having a density distribution of ± 14.6% in the circular region can be obtained.

FIG. 4 shows a second embodiment of the present invention, in which the basic function of the microwave introduction unit structure according to the embodiment of FIG. 1 is not changed and the function in the operation of the plasma processing apparatus is improved. 5 shows an embodiment of a wave introduction unit structure. The point different from FIG. 1 is that the portion around the microwave transmission window of the vacuum container can be separated from the vacuum container main body, and the microwave inlets having different diameters can be used without replacing the vacuum container main body. . That is, a separable portion around the microwave introduction port is formed as a lid plate 7 for closing the end face of the vacuum vessel cylindrical portion, and a lid having a microwave introduction port of a size corresponding to the diameter of the substrate 6 to be processed is formed. By preparing a number of types of plates of a substrate size, uniform plasma can be obtained while the microwave power is effectively used while the vacuum vessel main body is fixed.

[0021]

According to the present invention, since the plasma processing apparatus is configured as described above, the following effects can be obtained.

In the apparatus according to the first aspect, a region having a uniform plasma density can be controlled in accordance with the size of a substrate to be processed, and a uniform surface treatment can be performed by efficiently using plasma generation energy. become.

In the apparatus according to the second and third aspects, any one of them is selectively used in accordance with the difficulty of manufacture depending on the microwave wavelength and the size of the microwave introduction window.
The device can be configured at lower cost.

In the apparatus according to the fourth aspect, the effect of the first aspect can be obtained without replacing the vacuum vessel main body, and the operation of the apparatus becomes easy.

In the apparatus according to the fifth aspect, it is possible to perform a uniform surface treatment up to the maximum possible substrate size due to the dimensions of the apparatus, and to downsize the apparatus when the upper limit of the substrate size is constant. In addition, since the inside of the vacuum vessel is completely opened to the atmosphere during the regular maintenance work inside the vacuum vessel, there is an advantage that the maintenance is easy and complete.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a device showing a first embodiment of a microwave introduction unit structure according to the present invention.

FIG. 2 is a diagram showing a plasma density distribution in the vicinity of a microwave transmission window by the apparatus of the present invention in comparison with a plasma density distribution in the vicinity of a microwave transmission window by a conventional apparatus.

FIG. 3 is a diagram showing how the plasma density distribution in the vicinity of a microwave transmission window changes with the microwave power supplied to plasma generation by the apparatus of the present invention.

FIG. 4 is an apparatus sectional view showing a second embodiment of the microwave introduction unit structure according to the present invention.

FIG. 5 is a cross-sectional view of an example of a structure of a microwave introduction unit in a conventional plasma processing apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Vacuum container 4 Microwave transmission window 5 Microwave introduction port 6 Substrate (substrate to be processed) 21 Microwave transmission part 22 Microwave transmission part

Claims (5)

(57) [Claims] A vacuum vessel having a cylindrical microwave inlet formed on one end face and hermetically closed by a plate-shaped microwave transmission window; a microwave generator;
A microwave transmission unit comprising a cylindrical hollow conductor through which the microwave is transmitted, which couples the vacuum container and the microwave generation device; anda microwave transmission unit configured to transmit the microwave oscillated by the microwave generation device to the microwave transmission unit. In a plasma processing apparatus for transmitting through a microwave transmitting window to be introduced into a vacuum vessel, generating microwave discharge plasma in the vacuum vessel and performing surface treatment on a substrate to be processed in the vacuum vessel, the microwave introduction port The diameter of the microwave transmission section is formed to be larger than the diameter of the substrate to be processed by 40 mm or more, and the opening at the vacuum vessel side end face of the microwave transmission section is formed in a circle having the same diameter as the microwave introduction port, and the vacuum vessel side end face of the microwave transmission section That the cross-sectional shape of the internal space in the appropriate longitudinal range gradually changes from the cross-sectional shape on the output end side of the microwave generator to the circular shape of the end face opening on the vacuum vessel side. Plasma processing apparatus according to symptoms. 2. The plasma processing apparatus according to claim 1, wherein a cross-sectional shape of an internal space in an appropriate longitudinal range including an end face of the microwave transmission unit on a vacuum vessel side is obtained from a cross-sectional shape on the output end side of the microwave generator. The plasma processing apparatus is characterized in that the change of the opening of the vacuum vessel side end surface into a circular shape is performed continuously. 3. The plasma processing apparatus according to claim 1, wherein an internal space cross-sectional shape of an appropriate longitudinal range including a vacuum vessel-side end face of the microwave transmission section is taken from a microwave generator output end-side cross-sectional shape. The plasma processing apparatus is characterized in that the change of the vacuum vessel side end face opening into a circular shape is performed in a stepwise manner. 4. The plasma processing apparatus according to claim 1, wherein the diameter of the microwave introduction port is larger than the diameter of the substrate to be processed.
A plasma processing apparatus characterized in that a vacuum vessel formed to be larger than 40 mm is formed so that a portion around the microwave introduction port is formed from the vacuum vessel body. 5. The plasma processing apparatus according to claim 4, wherein a portion around the microwave introduction port formed detachably from the vacuum vessel body closes an end face of the vacuum vessel cylindrical portion on the microwave introduction port side. A plasma processing apparatus formed as a cover plate.