JP2000164392A - Microwave plasma treating device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the evenness of a plasma treatment. SOLUTION: The optical width corresponding to the width of a microwave guide window in a region pinched by the outer periphery of an upper electrode 18 facing a sample bed 3 and the inner periphery of a ring member 10 and annularly exposed to a treating chamber 2 (the width obtained by multiplying the actual width and the square root of the relative dielectric constant of a medium) is set to the half-wavelength or above in vacuum of the microwaves generated by a microwave oscillator 20. The microwaves guided to an annular waveguide type antenna section 12a from the microwave oscillator 20 are introduced into the treating chamber 2 through a microwave guide window with high efficiency. The evenness of the density of the plasma generated in the treating chamber 2 is improved, and the evenness of the plasma treating applied to a sample substrate W is increased.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to etching, ashing, and CVD (chemical vapor deposition) using plasma on a large-diameter semiconductor substrate, a glass substrate for a large-sized liquid crystal display, and the like.
The present invention relates to a microwave plasma processing apparatus suitable for use for performing such processing.

[0002]

2. Description of the Related Art In processes for manufacturing LSIs (Large Scale Integrated Circuits), LCDs (Liquid Crystal Displays), and the like, plasma generated when external energy is applied to a reaction gas is widely used. In particular, dry etching technology using plasma, in these processes,
It has become an essential basic technology.

[0003] Generally, as excitation means for generating plasma, there are cases where a microwave of 2.45 GHz is used,
It is known that 13.56 MHz RF (Radio Frequency) is used. When using microwave,
Compared to the case of using RF, there is an advantage that high-density plasma can be obtained and no electrode is required for generating plasma, so that contamination from the electrode can be prevented.

However, in a conventional plasma processing apparatus using microwaves, it has been difficult to generate plasma so that the plasma area is large and the plasma density is uniform. Therefore, it has been difficult to employ a dry etching process using microwaves in processing a large-diameter semiconductor substrate (semiconductor wafer) or a large LCD glass substrate.

[0005] In this regard, as a plasma processing apparatus capable of uniformly generating microwave plasma over a large area, a system utilizing surface-wave electric field-excited plasma has been proposed. No., JP-A-62-99
No. 481 discloses this. In this plasma processing apparatus, an upper wall of a processing container is sealed with a heat-resistant plate that can transmit microwaves, and a dielectric line connected to a microwave waveguide is disposed above the sealing plate. Then, plasma is generated by the surface wave electric field leaking from the surface of the dielectric line.

FIG. 7 is a side sectional view of the former plasma processing apparatus, and FIG. 8 is a plan view of the plasma processing apparatus shown in FIG. In this conventional apparatus 150, a sealing plate 84 is provided above a processing container 81 made of a metal conductor, and the processing chamber 82 is hermetically sealed by these. Further, a cover member 90 that covers the upper portion of the processing container 81 and the sealing plate 84 is connected to the processing container 81, and a waveguide 71 is connected between the cover member 90 and the microwave oscillator 70. I have. A dielectric line 91 is attached to the ceiling portion of the cover member 90 while securing an air gap 93 between the dielectric plate 91 and the sealing plate 84. The dielectric line 91 is formed by the width of the waveguide 71 and the processing container 81.
Is formed in a substantially pentagonal shape in a plan view having a tapered portion 91a that extends to a width enough to cover.

[0007] A sample table 83 for mounting a sample substrate W is disposed in the processing vessel 81 at a position facing the sealing plate 84.
The F bias circuit 87 is connected. Processing container 8
An exhaust port 88 connected to an exhaust device (not shown) is formed in a lower wall of the processing container 81, and a gas supply pipe 85 for supplying a required reaction gas is connected to one side wall of the processing container 81.

When a predetermined process is to be performed on the sample substrate W placed on the sample table 83 by using the microwave plasma processing apparatus 150 configured as described above, first, the exhaust port 88 is evacuated. Is performed to set the inside of the processing chamber 82 to a required degree of vacuum, and then a reaction gas is supplied from the gas supply pipe 85.
Next, a microwave is generated in the microwave oscillator 70, and is introduced, via the waveguide 71, into the dielectric line 91 including the tapered portion 91 a for expanding the microwave.

Then, an electric field is formed below the dielectric line 91, and the formed electric field passes through the air gap 93 and the sealing plate 84 and is supplied to the processing chamber 82. As a result, plasma is generated in the processing chamber 82, and the sample substrate W
Is subjected to a process such as etching. At this time, an RF bias is applied to the sample table 83 by the RF bias circuit 87 as needed. RF
The ions in the plasma are accelerated by the bias potential formed in the processing chamber 82 by the bias and guided to the sample substrate W, whereby the surface of the sample substrate W can be subjected to, for example, anisotropic etching. It becomes possible.

In the conventional apparatus 150, a large-diameter sample substrate W
Even if the width of the processing chamber 82 is set large to process the pressure, a uniform electric field is formed directly below the sealing plate 84, and as a result,
A uniform plasma can be obtained. Therefore, a predetermined process can be performed on the large-diameter sample substrate W.

[0011]

The conventional device 1
In 50, the dielectric line 91 is provided with a tapered portion 91 a projecting horizontally from the edges of the sealing plate 84 and the processing container 81 in order to uniformly expand the microwave.
Therefore, when the apparatus 150 is installed, the processing container 8
In order to store the tapered portion 91a protruding from one edge, it is necessary to secure an extra space in the horizontal direction.

With the recent increase in the diameter of the sample substrate W, a microwave plasma processing apparatus in which the width of the processing chamber 82 is larger has been required. In addition, at a manufacturing site for semiconductor devices and the like, there is a need not to secure a new installation site for the device, that is, to be able to install the device in a space as narrow as possible.

However, in the conventional device 150, the size of the tapered portion 91a is determined according to the area of the dielectric line 91.
In other words, it is determined according to the width of the processing chamber 82. Therefore, in order to process a large-diameter sample substrate W, it is necessary to secure a larger space so that a large tapered portion 91a can be accommodated. As described above, the conventional apparatus 150 has a problem that it is not possible to simultaneously satisfy the requirement to process a large-diameter sample substrate W and the requirement to reduce the installation space of the apparatus as much as possible.

Further, in the conventional device 150, due to its structure,
Since the surface facing the sample stage 83, that is, the lower surface of the sealing plate 84 cannot be grounded, the side wall of the processing vessel 81 and the like function as an effective counter electrode against RF bias by being grounded. As a result, there is a problem that the side walls of the processing container 81 are damaged by the ion collision. Further, since the effective counter electrode is located in a direction not facing the sample substrate W, for example, obliquely upward, the directivity of ions incident on the sample substrate W is poor, and the process such as etching anisotropy is difficult. There was a problem that performance was low.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems in the conventional apparatus, and enables processing of a large-diameter sample, space saving, and
It is an object of the present invention to provide a microwave plasma processing apparatus capable of improving the directivity of incident ions, and in particular, to obtain a microwave plasma processing apparatus capable of improving the uniformity of processing.

[0016]

According to the apparatus of the present invention, a microwave is introduced into a processing chamber in which a sample stage on which a sample to be processed is placed is stored, plasma is generated by the microwave, and the plasma is generated. A microwave plasma processing apparatus for performing processing on the sample using the first conductive body facing the sample stage, and an annular flat plate microwave introduction plate disposed around the first conductive body. A second conductor disposed along the outer periphery of the microwave introduction plate; and a conductive tubular member disposed on the microwave introduction plate. An opening is formed in a portion facing the introduction plate, and a surface of the microwave introduction plate exposed to the processing chamber between an outer periphery of the first conductor and an inner periphery of the second conductor. The optical width in the direction along It is set to be more than half the wavelength in vacuum filtered.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS 1. Basic Configuration of Apparatus FIG. 1 is a side sectional view of a microwave plasma processing apparatus according to an embodiment, and FIG. 2 is a plan view of the apparatus shown in FIG. FIG. 1 corresponds to a cross-sectional view taken along line AA of FIG.
In this apparatus 101, a ring member 10 having a groove formed on the inner peripheral surface is attached to the upper end of a cylindrical processing container 1 having a bottom. The processing container 1 is made of a metal such as aluminum, for example, and the ring member 10 is also made of a metal.

Further, the annular microwave introduction plate 4 is supported by the ring member 10 by fitting its outer peripheral edge into the groove of the ring member 10. The material of the annular microwave introduction plate 4 is required to have heat resistance, microwave permeability, and small dielectric loss.
For example, a dielectric such as quartz glass or alumina is employed.

On the upper surface of the ring member 10, a substantially cylindrical block member having an outer diameter substantially equal to the outer diameter of the ring member 10 and having an inner diameter substantially equal to the inner diameter of the microwave introduction plate 4 described above. 25 is screwed to the ring member 10. This block member 25 is formed of a metal such as aluminum. An annular plate member 16 also made of a metal such as aluminum is provided on the bottom of the block member 25.
Are fitted. The plate member 16 includes a plurality of slits 15.
Are provided at a predetermined distance in the circumferential direction.

An annular cavity 47 having a rectangular cross section is formed by the block member 25 and the plate member 16. On the outer peripheral wall of the block member 25, a groove having a rectangular cross section communicating with the annular cavity 47 is formed. The groove forms a rectangular hole 48 by being covered with the upper surface of the ring member 10. The dielectric 14 is fitted in the annular cavity 47 and the rectangular hole 48. As a material of the dielectric 14, for example, a fluororesin such as Teflon (registered trademark), a polyethylene resin, or a polystyrene resin is adopted, and preferably, a fluororesin is used.

An annular waveguide type antenna unit is constituted by a tubular member which is constituted by a block member 25 and a plate member 16 and defines an annular cavity 47 therein, and a portion of the dielectric material 14 filling the cavity 47. 12a are formed. Also,
The introduction portion 12b is formed by the portion of the block member 25 and the portion of the ring member 10 which define the rectangular hole 48 therein, and the portion of the dielectric material 14 filling the rectangular hole 48. The annular waveguide type antenna unit 12a and the introduction unit 12b constitute an antenna 13 together.

Inlet 4 formed in the outer peripheral wall of the tubular member
9, an annular cavity 47 defined in the tubular member;
The rectangular hole 48 defined in the introduction part 12b communicates. One end of the waveguide 21 is connected to the introduction portion 12b,
The microwave oscillator 20 is connected to the other end of the waveguide 21. Therefore, the microwave (for example, an electromagnetic wave having a frequency of 300 MHz to 30 GHz) generated by the microwave oscillator 20 is supplied to the inside of the waveguide 21 and the introduction unit 1.
The annular waveguide type antenna unit 1 is formed through the rectangular hole 48 of FIG.
It is introduced into the cavity 47 of 2a.

Cavity 47 of annular waveguide type antenna section 12a
The standing wave can be generated in the cavity 47 by appropriately setting the length in the circumferential direction to, for example, approximately an integral multiple of the wavelength of the propagating microwave. Specifically, two traveling waves traveling in the opposite directions in the annular waveguide antenna section 12a collide at a position facing the introduction section 12b to generate a standing wave. Due to the wall standing wave, a wall current having a maximum value flows at predetermined intervals on the inner surface of the annular waveguide antenna section 12a, that is, on the wall surface of the cavity 47.

As the dielectric 14, for example, the relative dielectric constant ε =
When 2.1 Teflon is employed, the mode of the microwave propagating in the circular waveguide antenna portion 12a, to the rectangular TE _10, which is a basic propagation mode, the frequency of the microwave is 2.45 GHz In this case, the dimensions inside the annular waveguide antenna section 12a, that is, the cross-sectional dimension along the radial direction of the cavity 47 may be set to a height of 27 mm and a width of 66.2 mm. The microwave of the rectangular TE ₁₀ propagates uniformly inside the annular waveguide antenna section 12a with little loss.

Further, the outer diameter is 380 mm and the inner diameter is 180 to 200 m
When the microwave introduction plate 4 having a thickness of 20 mm and a thickness of 20 mm is used, the distance from the center of the annular waveguide antenna section 12a to the center in the width direction of the annular waveguide antenna section 12a is: It can be set to 141 mm. In this case, the circumferential length (about 886 mm) of the circle connecting the center in the width direction of the annular waveguide antenna section 12a is determined by the length of the annular waveguide antenna section 1a.
It is substantially an integral multiple of the wavelength (approximately 110 mm) of the microwave propagating in 2a.

For this reason, the microwave resonates in the annular waveguide type antenna portion 12a, and the above-mentioned standing wave becomes a high voltage / low current at the antinode position and a low voltage / high current at the node position. The Q value of the antenna 13 is improved. This standing wave generates an electric field from the slit 15 to the processing chamber 2 via the sealing plate 4. Therefore, it is desirable that the slit 15 is arranged at the position of the antinode of the standing wave.

The block member 25 is provided with a heating block 26 made of aluminum in a columnar shape such that the lower surface thereof is slightly higher than the lower surface of the microwave introducing plate 4.
It is detachably fitted inside via a sheet-shaped insulator 31. As a material of the insulator 31, for example, quartz or ceramic is used. In the heating block 26, a heater 28 as a heating source is embedded.

Further, a cylindrical concave portion is provided at the center of the lower surface of the heating block 26. This concave portion is closed by an upper electrode 18 formed by shaping a conductive material such as a conductor or a semiconductor, that is, a conductor (hereinafter, referred to as a “conductor” including a semiconductor) into a disk shape. Thus, the gas diffusion chamber 30 is formed. The conductor 45 is formed by the upper electrode 18 and the heating block 26.

The gas diffusion chamber 30 communicates with the gas supply pipe 5 penetrating the heating block 26, and the upper electrode 18 has a plurality of through holes (not shown).
By supplying the reaction gas from the gas supply pipe 5, the reaction gas can be uniformly introduced into the processing chamber 2.
The upper electrode 18 is made of, for example, a silicon-based material.

The part where the processing vessel 1, the ring member 10, the annular microwave introduction plate 4, the block member 25 and the heating block 26 are joined to each other is sealed with a heat-resistant O. An (O) ring 17 is interposed.

At the center of the bottom of the processing vessel 1, a sample table 3 on which a sample substrate W is placed is provided so as to be able to move up and down. An RF bias circuit 7 is connected to the sample table 3 via a matching circuit 6. Further, an exhaust port 81 is provided on a side wall of the processing container 1, and the inside air of the processing chamber 2 can be exhausted by an exhaust mechanism (not shown).

FIG. 1 shows an example in which the upper electrode 18 is electrically grounded through a wiring, but an RF bias circuit different from the RF bias circuit 7 and a matching circuit different from the matching circuit 6 are shown. May be connected in the same manner as the sample table 3. Alternatively, the sample table 3 may be grounded, and a matching circuit and an RF bias circuit may be connected only to the upper electrode 18. When the upper electrode 18 is grounded, the insulator 31 may not be provided.

Since the apparatus 101 is configured as described above, an electric field is formed in the processing chamber 2, and a plasma is generated in the processing chamber 2 by the electric field. The plasma processing is performed on the sample substrate W placed on the sample table 3 by the plasma. The electric field in the processing chamber 2 forms a microwave standing wave in the annular waveguide-type antenna portion 12a provided in an annular shape so as to surround the conductor 45 facing the sample stage 3, and this Microwaves are generated from the standing wave by propagating to the processing chamber 2.

Therefore, the uniformity of the generated plasma is relatively good, and the plasma processing can be performed on the large-diameter sample substrate W. Moreover, unlike the conventional device 150, the tapered portion 91a is not required, and the annular waveguide type antenna portion 12a is introduced through the introduction portion 12b.
Since microwaves can be directly incident, no extra installation space is required around the processing vessel 1.

Further, since an RF bias is applied between the sample table 3 and the upper electrode 18 opposed thereto, the directivity of ions incident on the sample substrate W is high. Therefore, plasma etching with good anisotropy becomes possible, and fine processing with a high aspect ratio can be performed on the sample substrate W. Moreover, since it is not necessary to use the side wall and the like of the processing container 1 as an effective counter electrode, wear of the side wall and the like due to ion collision is suppressed, and the life of the processing container 1 and the like is increased.

<2. Optimization of Width of Microwave Introducing Window> The region exposed between the outer periphery of the conductor 45 and the inner periphery of the ring member 10 and exposed to the processing chamber 2 has a circular conduction shape. It functions as a microwave introduction window through which microwaves pass when introduced into the processing chamber 2 from the waveguide antenna unit 12a.
The radial width D of the microwave introduction window (that is, the distance between the outer periphery of the conductor 45 and the inner periphery of the ring member 10 in the direction along the surface of the microwave introduction plate 4) is a certain optimum value. Range exists. In the apparatus 101, the width D is set so as to satisfy this optimum range.

FIG. 3 is a cross-sectional view of the apparatus 101 taken along the line BB of FIG. FIG. 4 is a partially enlarged cross-sectional view of the apparatus 101 taken along the line CC of FIG. An annular ring member 10, an annular microwave introduction plate 4 having a width D1, an annular insulator 31 having a width D2, and a circular upper electrode having a diameter L are provided in order from the periphery to the center of the processing chamber 2. 18
(The conductor 45) is exposed. The width D of the annular microwave introduction window is given by the sum of the width D1 and the width D2.

The optimum range of the width D is found through experiments, as shown by the data described later, and is expressed as follows. That is, it is desirable that the optical width corresponding to the width D (in other words, the distance between the position P and the position Pb) is set to １ ／ or more times the wavelength λ of the microwave in a vacuum. The optical width means a width obtained by multiplying the actual width by the square root of the dielectric constant of the medium, that is, a width converted into a vacuum medium.

This optimum condition is equivalent to the case where the insulator 31 is not present, and the actual width D is equal to or more than 倍 of the wavelength of the microwave transmitted through the microwave introduction plate 4.
That is, the optimum condition when the insulator 31 does not exist is:
The following equation 1: D ≧ 1/2 · λ1 (Equation 1) Here, λ1 is the wavelength of the microwave in the microwave introduction plate 4.

When the insulator 31 exists, the optimal condition is as follows: D1 · (ε1) ^1/2 + D2 · (ε2) ^1/2 ≧ ^1/2 · λ (Formula 2) ). Here, ε1 is the relative permittivity of the microwave introduction plate 4, and ε2 is the relative permittivity of the insulator 31.

The wavelength λ of the microwave in a vacuum is
The following Expression 3: λ = 2πc / ω (Expression 3) Where c is the speed of light in a vacuum and ω
Is the angular frequency of the microwave generated by the microwave oscillator 20.

As shown in FIG. 4, the microwave propagates through the slit 15 from the annular waveguide antenna section 12a to the microwave introduction plate 4. The microwave is obtained by leaking a traveling wave propagating through the annular waveguide antenna section 12a, and its wavelength in vacuum is given by Expression 3.

In the microwave leaked to the microwave introducing plate 4, there is a component traveling toward the conductor 45 as the traveling wave Q1. This traveling wave Q1 is reflected on the outer peripheral surface of the conductor 45, and as a result, the reflected wave Q2 further propagates into the microwave introduction plate 4 (and the insulator 31).
Then, by combining them, a standing wave Q3 is formed near the outer peripheral surface of the conductor 45. The wavelength of the standing wave Q3 in a vacuum is also given by Expression 3.

Therefore, the above-mentioned optimum conditions are obtained by excluding the nodes on the outer peripheral surface of the conductor 45 among the nodes (generally plural) of the standing wave Q3 formed near the outer peripheral surface of the conductor 45. Regarding the position Pa of the node closest to the conductor 45, this is equivalent to setting the position P on the inner circumference of the ring member 10 to be farther than the position Pa of the node when viewed from the conductor 45. In other words, the above-described optimum condition is equivalent to setting the actual width D to be equal to or greater than the actual width Da with respect to the actual width Da between the node position Pa and the outer peripheral position Pb of the conductor 45. That is, the optimum condition can be expressed by the following Expression 4: D ≧ Da (Equation 4). The optical width corresponding to the actual width Da corresponds to half the wavelength λ of the microwave in a vacuum. If the insulator 31 is not provided, the actual width Da matches the half-wavelength of the microwave in the microwave introduction plate 4, that is, 1/2 ・ λ1.

<3. Verification Data> Next, experimental results supporting the above-mentioned optimum conditions will be described. In the experiment, conditions regarding the configuration and operation of the device 101 were set as follows. First, the frequency of the microwave output from the microwave oscillator 20 was set to 2.45 GHz. Also,
The upper electrode 18 was electrically grounded. Therefore, the insulator 31 is not provided, and the inner periphery of the microwave introduction plate 4 is in contact with the outer periphery of the conductor 45. Therefore, width D is width
The optimum condition for the width D, which coincides with D1, is expressed by Expression 1. Further, a quartz plate (relative permittivity ε1 = 4.0) was used for the microwave introduction plate 4, and a silicon-based material was used for the upper electrode 18.

The wavelength λ given by Equation 3 is λ = 122.4
mm. Therefore, using the relative dielectric constant ε1 = 4.0 of quartz and calculating the width Da based on the following equation 5: Da · (ε1) ^1/2 = ^1/2 · λ (Equation 5), Da = 1/2 · λ1 = 6
1 mm is obtained.

When the experiment is started, first, the processing chamber 2 is set to a predetermined pressure with a process gas (mixed gas of C ₄ F ₈ , CO, O ₂ , and Ar), and then the microwave oscillator 20 is started. And
Thereby, the microwave was injected into the antenna 13. The generated microwave is introduced into the processing chamber 2 from the annular waveguide antenna section 12a through the slit 15 and the microwave introduction plate 4. As a result, plasma is generated by the process gas.

At substantially the same time, the RF bias circuit 7 was activated to apply a high frequency to the sample stage 3.
As the substrate to be processed W mounted on the sample stage 3, a semiconductor substrate having an 8-inch diameter was used. An oxide film was formed on the surface of the sample substrate W, and the oxide film was subjected to plasma etching. The processing container 1 and the ring member 10 were heated to a predetermined temperature.

Under the above conditions, the distribution of the etching rate in the surface of the sample substrate W was measured while changing the diameter L of the upper electrode 18 (conductor 45). 1 of diameter L
Since the inner peripheral radius of the ring member 10 corresponding to the sum of 倍 times and the width D is constant, the width D changes as the diameter L changes.

FIG. 5 shows three typical widths D (diameter L).
FIG. 14 is a distribution chart showing the results of an experiment for. The sign (a) is
This shows an experimental result when the upper electrode 18 does not exist, the diameter L is zero, and the width D is set to 140 mm corresponding to the inner radius of the ring member 10. The symbol (b) indicates that the diameter L is 156 mm and the width D is slightly larger than the half-wavelength of the microwave in the microwave introduction plate 4: 1/2 · λ1 = 61 mm. Shows the experimental results when set to mm. Further, the symbol (c) has a diameter L = 164 mm,
The width D is 58 mm, which is slightly smaller than 1/2 ・ 1 = 61 mm
Represents the experimental results when set to. FIG.
, The “microwave incident direction” means a direction in which the microwave is incident on the antenna 13 through the waveguide 21.

The etching rate was measured over 25 points on the surface of the sample substrate W. In each of the experimental results of symbols (a) to (c), the bold line is a contour line indicating an etching rate corresponding to the average value of the measured values at 25 points, and each contour line represented by a thin line has an etching depth of , Are drawn every 20 nm from the average. The symbol “+” indicates an etching rate higher than the average value,
The symbol "-" indicates an etching rate lower than the average value. Positions marked with “+” and “−”
It corresponds to a measurement point.

Among the three experimental results of symbols (a) to (c),
The respective average values were approximately the same as each other. Further, as shown by the experimental result of the code (c), the width D is 1/2 · λ1 =
If it is smaller than 61 mm, the etching rate increases as the distance from the microwave incidence side increases, and decreases as the distance increases. That is, the etching rate shows a distribution biased toward the microwave incident side.

On the other hand, in the experimental results of the codes (a) and (b) corresponding to the case where the width D is larger than 1/2 ・ λ1 = 61 mm, the distribution of the etching rate and the incident direction of the microwave Is weak, and the interval between contour lines is wider than the result of the code (c). That is, the code
In the results of (a) and (b), the uniformity of the etching rate is better than the result of code (c).

In order to quantitatively evaluate the uniformity of the etching rate, the “etching rate non-uniformity” is calculated by the following equation (6): non-uniformity (%) = {(M−m) / (M + m)} × 100 ··· (Equation 6) Here, M is the maximum value among the measured values over 25 points, and m is the minimum value.

Based on the definition of Equation 6, the non-uniformity of the etching rate is ± 4.0% in the experimental result of the code (a),
The calculated value was ± 3.6% in (b) and ± 31% in (c). That is, the quantitative evaluation is that the width D is 1/21 / 2λ1 = 61
When the distance is larger than mm, it is clearly shown that the uniformity of the etching rate is dramatically improved as compared with the case where the distance is smaller.

FIG. 6 is a graph showing the result of calculating the non-uniformity of the etching rate based on the results of an experiment conducted by changing the width D at finer intervals. As shown in FIG. 6, the nonuniformity of the etching rate is such that the width D is ・ · λ1.
= Shorter than 61 mm, the width is relatively high and the width D is 1/2
It becomes lower in the region longer than λ1 = 61 mm. Moreover,
As the width D increases beyond 61 mm, the etch rate non-uniformity decreases dramatically.

This indicates that the uniformity of the density of the plasma generated in the processing chamber 2 changes drastically as the width D changes at 1/2 ・ λ 1 = 61 mm. ing. That is, when the width D is set to 1/21 / 2λ1 = 61 mm or more, the uniformity of the plasma density is remarkably improved as compared with the case where the width D is set to less than 1/2 ・ λ1.

This also means that the width D is given by the following equation (1).
When the optimum conditions shown by 2 and 4 are satisfied, it also means that the efficiency of introduction of the microwave into the processing chamber 2 is dramatically increased. This phenomenon can be explained by a mechanism in which the strength of the standing wave Q3 shown in FIG.

As described above, it was confirmed that the width D had selectivity and that the width Da had a critical value on the basis of the uniformity in the density of the plasma generated in the processing chamber 2. Proven by As can be seen from the distribution diagram of FIG. 5 and the graph of FIG. 6, even in an apparatus in which the width D is set to be less than the width Da, the non-uniformity of the plasma density
In processing the sample substrate W, the practicality is not impaired. However, in order to further improve the uniformity of the processing on the sample substrate W, it is more preferable to set the apparatus 101 so as to satisfy the optimum conditions expressed by Expressions 1, 2, and 4.

<4. Modifications> (1) The opening formed at the bottom of the tubular member constituting the annular waveguide antenna section 12a is used to increase the efficiency of microwave propagation to the processing chamber 2. As shown in FIG. 2, it is desirable that the slits 15 are formed at predetermined intervals in the circumferential direction. However, the shape of the opening is not generally limited to this example, and various shapes can be adopted. For example, the opening may be formed as a slit continuous at a constant width along the circumferential direction.

(2) Instead of the annular waveguide type antenna section 12a having an annular tubular member, instead of surrounding the upper electrode 18,
One end (corresponding to an “inlet”) of a cavity formed inside is arranged in a “C” shape or a spiral shape in plan view and communicates with the waveguide 21, and the other end is closed. An antenna including a tubular member configured to perform the above operation may be employed.

(3) In the apparatus 101 shown in FIG. 1, the ring member 10 covers the bottom surface in the vicinity of the outer periphery of the microwave introduction plate 4, so that the inner periphery of the ring member 10 exposed to the processing chamber 2 is formed. , The width D of the microwave introduction window. On the other hand, in the microwave plasma processing apparatus of the present invention, the ring member 10 does not cover the bottom surface near the outer periphery of the microwave introduction plate 4, for example, the microwave introduction plate 4 is placed on the upper end of the processing vessel 1. It is also possible to adopt a form of being directly installed on the vehicle.

In this example, the inner periphery of the upper end of the processing vessel 1 corresponds to the outer end of the microwave introduction window having a width D. That is, the “second conductor” in the present invention includes:
Not limited to the ring member 10, various members of the apparatus (for example, the processing container 1) may correspond to the form of the apparatus.

[0064]

According to the apparatus of the present invention, microwaves are applied to a tubular member provided on a microwave introduction plate disposed annularly around a first conductor arranged opposite to a sample stage. Introduced, and further, by introducing microwaves into the processing chamber through the opening and the microwave introduction plate,
Plasma is formed in the processing chamber, and the sample is processed by the formed plasma. Therefore, it is possible to perform processing on a large-diameter sample.

Moreover, unlike the conventional apparatus, the microwave can be directly incident on the tubular member without the need for the tapered portion, so that no extra installation space is required around the processing vessel. Further, since the first conductor facing the sample stage is provided, between the sample stage and the first conductor,
By applying the RF bias, the directivity of ions incident on the sample can be improved. Further, since it is not necessary to make the wall surface or the like of the processing chamber an effective counter electrode, wear of the wall surface or the like due to ion collision is suppressed, and the life of the apparatus is improved.

Further, a region exposed between the outer periphery of the first conductor and the inner periphery of the second conductor and exposed to the processing chamber, that is, along the surface of the microwave introduction plate of the microwave introduction window. The optical width in the vertical direction is set to be at least half the wavelength of the microwave in a vacuum, so the efficiency of introducing the microwave into the processing chamber is high and the uniformity of the plasma density in the processing chamber is high. Is improved. Therefore, the uniformity of the plasma processing performed on the sample is improved.

[Brief description of the drawings]

FIG. 1 is a side sectional view of an apparatus according to an embodiment.

FIG. 2 is a plan view of the device according to the embodiment.

FIG. 3 is a sectional view taken along the line BB of FIG. 1;

FIG. 4 is a partially enlarged sectional view taken along the line CC of FIG. 2;

FIG. 5 is a distribution diagram of an etching rate of a sample substrate.

FIG. 6 is a graph showing the dependence of etching rate non-uniformity on the width of a microwave introduction window.

FIG. 7 is a side sectional view of a conventional device.

FIG. 8 is a plan view of a conventional device.

[Explanation of symbols]

 Reference Signs List 2 processing chamber 3 sample table 4 microwave introduction plate 10 ring member (second conductor) 15 slit (opening) 16 plate member (tubular member) 18 upper electrode (first conductor) 25 block member (tubular member) 26 Heating block (first conductor) 45 Conductor 47 Cavity W Sample substrate (sample)

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Claims (1)

[Claims] 1. A method for introducing a microwave into a processing chamber containing a sample stage on which a sample to be processed is placed, generating plasma using the microwave, and performing processing on the sample using the plasma. A microwave plasma processing apparatus, comprising: a first conductor facing the sample stage; an annular flat plate microwave introduction plate disposed around the first conductor; and an outer periphery of the microwave introduction plate. A second conductive member disposed along the microwave introducing plate, and a conductive tubular member disposed on the microwave introducing plate, wherein an opening is formed in a portion of the tubular member facing the microwave introducing plate. The optical width between the outer circumference of the first conductor and the inner circumference of the second conductor in a direction along the surface of the microwave introduction plate exposed to the processing chamber is reduced.波長 of the wavelength of the microwave in a vacuum Microwave plasma processing equipment set to more than double.