JP2002016046A - Microwave plasma processing apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a microwave plasma processing apparatus which is high in plasma processing uniformity. SOLUTION: A conductor member 12 is provided at the center of a dielectric member 11 of a nearly circular shape, through which microwaves are propagated so as to pass therethrough in the thickness direction. Installation of the conductor member 12 causes presence of strong electric-field regions in a plurality of radial directions of the dielectric member 11, which is distributed nearly symmetrically, with respect to an axis on its diameter. In response to these strong field regions, plasmas are generated in a processing chamber 2 of a reaction vessel 1, and dispersed to provided a uniform plasma. A sample W on a sample base 3 is processed by the plasma, having a uniform density.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art Plasma generated by externally applying energy to a reaction gas is widely used in manufacturing processes of LSIs, LCDs, etc. In particular, use of plasma is an essential basic technology in a dry etching process. I have. Generally, the excitation method to generate plasma includes:
The case where a microwave of 2.45 GHz is used;
In some cases, 6 MHz RF (Radio Frequency) is used. The former has the advantage that a higher-density plasma can be obtained than the latter, and that no electrodes are required for plasma generation, so that contamination from the electrodes can be prevented.

In the basic configuration of a microwave plasma processing apparatus, a microwave oscillated by a microwave oscillator is propagated through a waveguide to a substantially circular plate-shaped dielectric member, and the surface of the dielectric member is exposed. Microwave from surface waves generated in
A sample stage on which a sample to be processed is placed is provided inside, and the sample is introduced into a reaction vessel sealed in a vacuum with a sealing plate, thereby generating plasma in the reaction vessel and processing the sample. Like that.

[0004]

In such a microwave plasma processing apparatus, it is difficult to generate plasma so that the density becomes uniform, particularly when the area of the plasma generation region is widened. There is a problem that it is difficult to improve the uniformity of processing.

Therefore, the applicant of the present application has proposed a microwave plasma processing apparatus capable of generating plasma so as to have a uniform density and improving the uniformity of the plasma processing (Japanese Patent Laid-Open No. 11-1999). 329789).
In this proposal, the plurality of regions where the strength of the electric field due to the standing wave generated by the microwave propagating through the substantially circular plate-shaped dielectric member is relatively concentric with the center of the dielectric member are Discloses that the diameter of the dielectric member is set so as to be distributed substantially symmetrically with respect to the axis on the diameter of the dielectric member.

However, in this microwave plasma processing apparatus, when various conditions such as the reaction gas pressure including the diameter of the dielectric member, the reaction gas type, the microwave power, and the like are optimized, the density is certainly increased. Although uniform plasma can be generated, there remains a problem that when those conditions are changed, plasma cannot be generated at a uniform density, and there is room for improvement.

The present invention has been made in view of such circumstances, and by providing a conductor member at the center of a substantially circular plate-shaped dielectric member through which microwaves are propagated, it is possible to achieve a wide range of conditions. An object of the present invention is to provide a microwave plasma processing apparatus capable of generating uniform plasma and improving the uniformity of plasma processing.

Another object of the present invention is to provide a microwave plasma processing apparatus capable of improving the ignitability of plasma.

[0009]

According to a first aspect of the present invention, there is provided a microwave plasma processing apparatus for processing a sample with plasma generated by using a microwave. An oscillator, a substantially circular plate-shaped dielectric member that propagates microwaves oscillated by the microwave oscillator, and a conductor member provided at a center of the dielectric member so as to penetrate in the thickness direction thereof, A reaction vessel disposed opposite to one main surface of the dielectric member and having a sample stage on which the sample is placed.

[0010] A microwave plasma processing apparatus according to a second aspect of the present invention is a microwave plasma processing apparatus for processing a sample with plasma generated using microwaves.
A microwave oscillator that oscillates the microwave, a waveguide that propagates the microwave oscillated by the microwave oscillator, and the waveguide is connected to a part of an outer peripheral portion thereof, and a connection portion thereof A substantially circular plate-shaped dielectric member having an outer peripheral portion and an upper portion covered by a conductor plate, a conductor member provided at a center of the dielectric member so as to penetrate in the thickness direction thereof, A sample stage, which is disposed to face the lower surface of the member and on which the sample is mounted, a reaction vessel having the sample stage therein, and is provided between the dielectric member and the sample stage. And a sealing plate made of a dielectric for sealing the reaction vessel in a vacuum.

In the microwave plasma processing apparatus of the present invention, since the conductor member is provided at the center of the substantially circular plate-shaped dielectric member through which the microwave propagates, the microwave propagates through the dielectric member. A plurality of regions in which the electric field strength due to the standing wave generated is relatively strong are uniformly distributed, and accordingly, the density of the plasma generated in the reaction vessel becomes uniform,
The uniformity of the plasma treatment on the sample is improved. Also,
By providing the conductor member, the electric field density near the center of the dielectric member is increased, and the ignition stability of the plasma is improved.

A microwave plasma processing apparatus according to a third invention is characterized in that, in the first or second invention, the diameter d of the conductor member satisfies the following condition (A). 10 ≦ d <D-1.3λ _g (unit: mm) (A) where D: diameter of the dielectric member λ _g : microwave wavelength in the tube

When the diameter of the conductor member is smaller than 10 mm, the concentration of the electric field density decreases, and the ignition stability of the plasma does not improve much. On the other hand, when the diameter of the conductor member is equal to or greater than the diameter of the dielectric member minus 1.3 times the guide wavelength of the microwave, a region where the electric field intensity is relatively strong occurs only in one direction. In addition, the electric field density near the waveguide is increased, and the uniformity of the plasma is deteriorated. Therefore, the diameter of the conductor member is made to satisfy the above condition (A), and the effect accompanying the installation of the conductor member is ensured.

[0014]

DETAILED 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 side sectional view showing a structure of a microwave plasma processing apparatus according to the present invention, and FIG. 2 is a plan view of a dielectric member 11 and a conductor member 12 described later.

In FIG. 1, a cylindrical bottomed reaction vessel 1 is shown.
Is formed entirely of aluminum. A microwave introduction window is opened at the upper part of the reaction vessel 1, and the microwave introduction window is sealed in an airtight state by a sealing plate 4.
The sealing plate 4 is made of a dielectric material such as quartz glass or alumina, which has heat resistance and microwave permeability and has small dielectric loss.

A box-shaped conductive cover member 10 for covering the upper portion of the reaction vessel 1 is connected to the reaction vessel 1. A dielectric member 11 is attached to a ceiling portion in the cover member 10, and an air gap 9 is formed between the dielectric member 11 and the sealing plate 4. The dielectric member 11 is made of a dielectric material such as polyfluoroethylene resin, polyethylene resin, or polystyrene resin such as Teflon (registered trademark), and a substantially rectangular incident port portion 11b is provided on a peripheral surface of a disk-shaped main body 11a having a predetermined diameter. The incident port portion 11b is fitted inside a waveguide 21 having a rectangular cross section connected to the peripheral surface of the cover member 10. A conductor member 12 made of aluminum is provided at the center of the dielectric member 11 so as to penetrate in the thickness direction thereof. The diameter (d) of the conductor member 12 is 10 mm or more and less than 365 mm when the diameter (D) of the dielectric member 11 is 510 mm.

A microwave oscillator 20 is connected to the waveguide 21, and the microwave oscillated by the microwave oscillator 20 is incident on the incident port 11 b of the dielectric member 11 by the waveguide 21. The microwave propagates through the entire region of the main body 11a in a propagation mode determined by the shape and size of the dielectric member 11, and the like, and an electric field having a predetermined distribution is formed.

The reaction vessel 1 has a plurality of through-holes penetrating the peripheral wall of the processing chamber 2. A required reaction gas is introduced into the processing chamber 2 from a gas introduction pipe 5 fitted into the through-hole. Is done. At the center of the bottom wall of the processing chamber 2, a sample table 3 on which the sample W is placed is provided.
The high frequency power supply 7 is connected via the. An exhaust port 8 is provided in the bottom wall of the reaction vessel 1 so that the inside of the processing chamber 2 is exhausted from the exhaust port 8.

In order to perform an etching process on the surface of the sample W using such a microwave plasma processing apparatus, the inside of the processing chamber 2 is evacuated to a desired pressure by exhausting from the exhaust port 8 and then the gas introduction pipe 5 To supply the reaction gas into the processing chamber 2. Then, the microwave oscillator 20 outputs 2.45 GHz.
Is oscillated, introduced into the dielectric member 11 through the waveguide 21, and a standing wave is formed therein to generate a leakage electric field having a predetermined distribution. This leaked electric field penetrates through the air gap 9 and the sealing plate 4 and is introduced into the processing chamber 2, thereby generating plasma in the processing chamber 2 and etching the surface of the sample W with the plasma. Thereafter, a surface wave is formed between the surface of the sealing plate 4 and the plasma (plasma sheath), so that the plasma is stabilized.

Next, the results of measurement experiments of the ion current distribution in the present invention example in which the conductor member 12 is provided at the center of the dielectric member 11 and in the conventional example in which such a conductor member is not provided in the dielectric member will be described. explain.

FIG. 3 shows a measurement result in the example of the present invention (a conductor member 12 having a diameter of 10 mm is provided at the center of a dielectric member 11 having a diameter of 510 mm), and FIG. 4 shows a measurement result in a conventional example. In any of the examples, the reaction gas supplied into the processing chamber is C ₄ F ₈ (flow rate 30 SCCM) / O
₂ (flow rate 20 SCCM) / Ar (flow rate 1000 SCC)
M), the internal pressure was 40 mTorr. Further, the output of the microwave oscillator is set to 2 kW, 3 kW, 4 kW.
The measurement was performed for each of the three stages.

3 and 4, the horizontal axis represents the displacement (mm) in the X or Y direction from the center of the dielectric member.
The vertical axis represents the ion current density (arbitrary unit). In FIGS. 3 and 4, ● and ○ indicate ion current distributions in the X and Y directions at 2 kW, and ★ and ☆ indicate ion current distributions in the X and Y directions at 3 kW. , ◇
Indicates the ion current distribution in the X and Y directions at 4 kW. The measurement was performed at a position 60 mm below the sealing plate.

By comparing FIGS. 3 and 4, the current density in the vicinity of the center is higher in the example of the present invention than in the conventional example.
It can be seen that the current density distribution is uniform over a wide range near the center.

Next, the results of observation of the plasma emission intensity in the present invention example in which the conductor member 12 is provided at the center of the dielectric member 11 and in the conventional example in which such a conductor member is not provided in the dielectric member will be described. I do.

On the quartz provided in the reaction chamber, an example of the present invention (the center of the dielectric member 11 having a diameter of 510 mm
Of the conventional example), a microwave was introduced, plasma was generated in the processing chamber, and the light emission state of the plasma on the quartz surface was photographed by a CCD camera. The conditions of the reaction gas in the plasma generation at this time were the same as those in the above-described ion current distribution measurement experiment, and the output of the microwave oscillator was 2 kW.

The observation results obtained in this manner are shown in FIG.
Is shown schematically in FIG. FIG. 5A shows the observation result in the example of the present invention, and FIG. 5B shows the observation result in the conventional example.
In FIG. 5, black dots represent light emitting points. FIG.
By comparing (a) and (b), it can be seen that in the example of the present invention, the light emission state of the plasma is more uniform than in the conventional example. Since the emission intensity of the plasma correlates with the plasma density, it can be seen that a uniform plasma density is obtained in the example of the present invention.

Further, the plasma ignitability of the example of the present invention (the conductor member 12 having a diameter of 10 mm was installed at the center of the dielectric member 11 having a diameter of 510 mm) and the conventional example (the conductor member 12 was not provided) were examined. Was. 3k for ignition in the conventional example
Although a microwave oscillator output of W or more was required, in the example of the present invention, ignition was possible with a microwave oscillator output of 1.2 kW because of the high electric field density at the center.

Next, the diameter of the conductor member 12 provided at the center of the dielectric member 11 in the present invention will be considered. The diameter d (mm) of the conductor member 12 is set so as to satisfy the following condition (1). Here, D is the diameter of the dielectric member 11 (m
m) and λ _g are the guide wavelength (wavelength of the microwave in the waveguide 21) (mm). 10 ≦ d <D-1.3λ _g (1)

When the diameter d of the conductor member 12 is smaller than 10 mm, the concentration of the electric field density at the central portion is small, the ignition stability of the plasma is poor, and the uniform plasma density cannot be realized. Therefore, the value of the diameter d needs to be 10 mm or more.

By the way, in the donut type dielectric,
If the difference between the inner circumference and the outer diameter is less than 1.3Ramuda _g is the standing wave mode antinode into the gap has only one is formed. If there is only one antinode of the standing wave in the gap between the inner and outer circumferences, the electric field intensity near the waveguide connection portion of the dielectric becomes too large, and the electric field intensity distribution in the dielectric becomes uneven. become. Therefore, the gap between the inner circumference and the outer circumference is set to 1.3λ _g so that more than one antinode is formed in the gap.
It has been found by simulation that it is necessary to take more. In the case of the present invention, the gap is represented by D−d, so that D−d> 1.3λ _g , and after deformation, d <D−1.
It is necessary to satisfy 3λ _g .

Next, the diameter of the conductor member 12 in the present invention will be described.
A specific numerical example of d will be described. Tube wavelength λ
_gIs determined by the following (2). Also, in (2)
Λ _cIs shown by the following (3).

[0032]

(Equation 1)

Where λ: wavelength in vacuum free space (122 mm (= velocity of light ÷ frequency of microwave)) ε: relative permittivity of dielectric member 11 a: length of long side of waveguide 21 cross section b: Length of short side of waveguide 21 cross section m: number of modes in long side direction n: number of modes in short side direction

Here, TE10 is filled in a waveguide 21 of a = 96 mm and b = 27 mm filled with Teflon (ε = 2).
When a microwave in the mode (m = 1, n = 0) is propagated, λ _c = 192 mm from the above (2), and the guide wavelength λ _g is specifically 112 mm as shown in the following (4).

[0035]

(Equation 2)

Therefore, 1.3λ _g = 1.3 × 112 = 1
45.6 (mm), and the diameter D of the dielectric member 11 is 5
When it is 10 mm, the upper limit of d is 510-145.6 =
364.4 (mm). Therefore, when the diameter of the conductor member 12 is 365 mm or more, the electric field distribution of the dielectric member 11 becomes non-uniform. The specific condition of the diameter d of the conductor member 12 in this case is as follows (5). 10 ≦ d <
365… (5)

Next, the result of simulating the electric field on the lower surface of the sealing plate by changing the diameter d of the conductor member 12 will be described. The results are shown in FIGS.
6 to 10 show a dielectric member 1 formed by molding Teflon.
1.45 GHz (wavelength in vacuum free space: 122 m)
m) is introduced, a strength of an electric field formed by the propagation of the microwave is obtained by simulation, and points connecting the same electric field strength are shown by lines. FIG.
Shows the case of d = 0 mm (conventional example), and FIGS. 7, 8, 9 and 10 show d = 30 mm, d = 100 mm, and d, respectively.
= 200 m, d = 370 mm.

In the case of the conventional example in which the conductor member 12 is not provided (FIG. 6), a region where the electric field is strong only in the traveling direction of the microwave (the direction connecting the connection portion with the waveguide 21 and the opposite side) is provided. The electric field distribution is not uniform because the region exists and the region where the electric field is strong is linearly distributed. On the contrary,
In the case of the present invention in which the conductor member 12 is provided (FIGS. 7, 8, and 9), there are regions where the electric field is strong in a plurality of radial directions, and the region where the electric field is strong is located with respect to the axis on the diameter. , The electric field distribution is uniform. However, when the diameter d of the conductor member 12 is 370 mm (FIG. 1)
In (0), as in the conventional example, there is a region where the electric field is strong only in the traveling direction of the microwave, and the electric field distribution is not uniform. The result of such a simulation matches the condition of the above (5).

Therefore, by providing the conductor member 12 that satisfies the above conditions (1) and (5), there are regions where the electric field is strong in a plurality of radial directions of the dielectric member 11,
Since they are distributed almost axisymmetrically with respect to the axis on the diameter,
Plasma is generated in portions corresponding to these strong electric field regions, respectively, and these are diffused to obtain uniform plasma.

[0040]

As described above in detail, in the microwave plasma processing apparatus according to the present invention, the conductor member is provided at the center of the dielectric member so as to penetrate in the thickness direction thereof. There are a plurality of regions where the strength of the electric field due to the standing wave of the microwave propagating through is present in a plurality of radial directions, and these are distributed substantially axisymmetrically with respect to the axis on the diameter. Accordingly, the density of the plasma generated can be made uniform, the sample can be processed by the plasma having the uniform density, and the uniformity of the plasma processing can be improved.

Also, since the diameter of the conductor member to be installed is made to satisfy the above condition (A), it is possible to always obtain an axially symmetric and uniform electric field distribution in the dielectric member.

[Brief description of the drawings]

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

FIG. 2 is a plan view of a dielectric member and a conductor member in the microwave plasma processing apparatus of the present invention.

FIG. 3 is a graph showing a result of an experiment for measuring an ion current distribution in an example of the present invention.

FIG. 4 is a graph showing a result of an experiment for measuring an ion current distribution in a conventional example.

FIG. 5 is a view schematically showing observation results of plasma emission in the present invention example and the conventional example.

FIG. 6 is a view showing a simulation result of an electric field distribution on a lower surface of a sealing plate in a conventional example (diameter d of a conductive member = 0 mm).

FIG. 7 is a diagram showing a simulation result of an electric field distribution on a lower surface of a sealing plate in an example of the present invention (diameter d of a conductive member = 30 mm).

FIG. 8 is a diagram showing a simulation result of an electric field distribution on a lower surface of a sealing plate in an example of the present invention (diameter d of a conductive member = 100 mm).

FIG. 9 is a diagram showing a simulation result of an electric field distribution on the lower surface of the sealing plate in the example of the present invention (the diameter d of the conductor member is 200 mm).

FIG. 10 is a diagram showing a simulation result of an electric field distribution on a lower surface of a sealing plate in a comparative example (diameter d of a conductor member = 370 mm).

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Reaction container 3 Sample stand 4 Sealing plate 10 Cover member 11 Dielectric member 11a Main body 11b Incident port part 12 Conductor member 20 Microwave oscillator 21 Waveguide W Sample

Claims (3)

[Claims] 1. A microwave plasma processing apparatus for processing a sample with plasma generated using microwaves, wherein the microwave oscillator oscillates the microwave, and the microwave oscillated by the microwave oscillator propagates. A substantially circular plate-shaped dielectric member to be formed, a conductor member provided at a center of the dielectric member so as to penetrate in the thickness direction thereof, and a dielectric member disposed so as to face one main surface of the dielectric member. And a reaction vessel having a sample stage in which the sample is placed. 2. A microwave plasma processing apparatus for processing a sample with plasma generated by using a microwave, wherein the microwave oscillator oscillates the microwave, and the microwave oscillated by the microwave oscillator propagates. A waveguide member to be connected, the waveguide is connected to a part of the outer peripheral portion thereof, and a substantially circular plate-shaped dielectric member whose outer peripheral portion and upper portion excluding the connection portion are covered with a conductive plate; A conductor member provided at a center of the dielectric member so as to penetrate in a thickness direction thereof, and a sample table which is disposed to face a lower surface of the dielectric member and mounts the sample, A reaction container having the sample stage therein, and a sealing plate provided between the dielectric member and the sample stage and made of a dielectric for sealing the reaction container to a vacuum. Microwave plasma processing equipment Place. 3. The microwave plasma processing apparatus according to claim 1, wherein the diameter d of the conductor member satisfies the following condition (A). 10 ≦ d <D-1.3λ _g (unit: mm) (A) where D: diameter of the dielectric member λ _g : microwave wavelength in the tube