JPH05275196A - Method and device for plasma producing and plasma processing method - Google Patents

Abstract

PURPOSE:To produce stable plasma in the large dia. discharge region of a microwave plasma processing device corresponding to a large dia. wafer. CONSTITUTION:A mode filter 20 is installed in a large bore waveguide tube 5, and microwaves which are oscillated from a microwave generator 1 to be propagated in the waveguide tube 5 and have a plurality of modes including a higher order mode, are put incident to a discharge chamber 8 while limited to a microwave in single mode, and thereby inter-mode oscillation is prevented in the discharge region to generate a stable plasma.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing microwave plasma, an apparatus for producing the same, and a plasma processing method, and more particularly, to processing a sample such as a semiconductor element substrate having a large diameter using microwave plasma. The present invention relates to a microwave plasma generation method, a generation apparatus therefor, and a plasma processing method suitable for the above.

[0002]

2. Description of the Related Art Conventional microwave plasma generation technology is
For example, "Semiconductor Plasma Process Technology" published by Sangyo Tosho Co., Ltd. on July 10, 1980 (written by Sugano,
As described in p138 to p141), a magnetic field is applied to a discharge chamber vacuum-sealed with a dielectric quartz tube for passing microwaves and a sample placed under the discharge chamber, and a microwave is applied through a waveguide. Is introduced into a discharge chamber, a microwave discharge is generated in the discharge chamber, and a sample is treated using plasma generated by the microwave discharge.

In recent years, the diameter of a sample to be processed, that is, a wafer has been increasing with the progress of the semiconductor industry, and the uniformity of processing has been required even for such a large diameter wafer.

As a method for solving the processing uniformity, for example, JP-A-63-60530 and Japanese Utility Model Laid-Open No. 2-6.
A microwave plasma generation technique as described in Japanese Patent No. 7637 has been proposed.

The former, Japanese Patent Laid-Open No. 63-60530,
The waveguide has a cross section through which a microwave having a wavelength passing through the first portion is connected to the first portion of the tube connected to the output end of the microwave oscillation circuit and the second portion of the tapered portion. It is possible to form a uniform plasma by being configured with the third portion of the plurality of tubes. When the microwave propagates through each waveguide forming the third portion,
The pointing vector distribution in each tube of the third part is not uniform, but since it is formed by a plurality of tubes,
The pointing vector distribution is fairly uniform over the entire area of, and a relatively uniform plasma can be formed even when the mean free path of ionizing electrons in the plasma is short.

In the latter, Japanese Utility Model Laid-Open No. 2-67637, a metal tube having a size larger than the maximum size of the sample is provided in the waveguide, and the tube and the waveguide are formed of a metallic partition plate to prevent microwaves. The sample is processed by tightening it so as to maintain symmetry in the plane perpendicular to the propagation direction, dividing the microwave in contrast to the sample, and uniformly generating plasma for plasma processing of the sample. This is to prevent unevenness. It has been shown that it is necessary to cover the upper part of the cylinder with a lid to prevent the progress of microwaves when the unevenness of processing cannot be prevented by the local progress of microwaves on the sample.

[0007]

SUMMARY OF THE INVENTION The above-mentioned conventional techniques can spread the microwave electric field strength over a wide range in the waveguide. However, even with these conventional techniques, there are still problems regarding the stability and uniformity of plasma, particularly in large-diameter waveguides.

That is, when the diameter of the wafer is increased, a larger cross-sectional size (aperture or a characteristic length of the waveguide cross section) of the plasma to be formed is required. For this reason, it is also necessary to increase the cross-sectional size (aperture or the characteristic length of the cross-section of the waveguide) of the waveguide that propagates the microwave.
It was also found that simply expanding the electric field strength of the microwave in the waveguide is not enough to generate a stable and uniform plasma. It was found to be in the wave propagation mode. The inside of the large-diameter waveguide has a large cross section with respect to the wavelength of microwaves, and microwaves of many modes including a plurality of higher-order modes can propagate in such a waveguide. This is an important issue especially in generating the large-diameter plasma necessary for processing a large wafer of 8 inches or more. When microwaves of a large number of modes are mixed and propagated to the plasma formation region, the introduction of microwave power to the plasma oscillates between the modes (in other words, the mode transitions to another mode), and the plasma state changes. It becomes unstable, and as a result it is difficult to obtain a stable and uniform plasma, the stability of the surface treatment of the sample is reduced, and high-precision processing cannot be performed.

A first object of the present invention is to provide a plasma generation method and apparatus capable of stably generating plasma in a large-diameter discharge region.

A second object of the present invention is to provide a plasma processing method capable of improving the uniformity in plasma processing of a large-diameter sample.

[0011]

In order to achieve the above-mentioned first object, a means for generating a microwave, a discharge chamber to which a gas for plasma generation is supplied and which is evacuated to a predetermined pressure, and a discharge chamber. In a plasma generation device comprising a waveguide for introducing microwaves into a microwave, a microwave having a plurality of modes including higher-order modes propagating in the waveguide is converted into a substantially single-mode microwave. Propagating a waveguide in a plasma generation method in which a device having a mode limiting means for limiting the number is provided in the waveguide, microwaves are introduced into the discharge chamber through the waveguide, and plasma is generated in the discharge chamber. A microwave having a plurality of modes including a higher-order mode is limited to a substantially single-mode microwave, and the number of propagation modes is limited, and plasma is generated in the discharge chamber by the substantially single-mode microwave. It is obtained by the method.

Further, in order to achieve the first object,
A processing chamber and a plasma forming region in the processing chamber; a waveguide which is composed of a small cross-section portion and a large cross-section portion, which are sequentially arranged in the propagation direction leading to the plasma formation region, and which guides microwaves to the plasma formation region; A predetermined plasma formation mode for a plasma formation region in a large cross section of the wave guide, the plasma formation mode having a predetermined pattern of lines of electric force in the cross section of the waveguide; A mode limiter for selecting propagation, the mode limiter comprising a plurality of divider plates in the waveguide, the divider plate having a conductive surface, and dividing the waveguide into an array of sub-waveguides, Each sub-waveguide has a respective sub-pattern of microwave electric field lines that propagate selectively within it,
The sub-patterns for the combined array of sub-directors are intended to be a plasma generator aligned in a predetermined pattern of a predetermined plasma formation mode.

Further, in order to achieve the second object, a semiconductor substrate is placed on a table in the processing chamber, a plasma forming gas is supplied to the processing chamber, and a magnetic field is applied to a plasma forming region in the processing chamber where the semiconductor is exposed. Is applied and microwaves are made incident on the plasma formation region through a waveguide to form plasma, which is an improved method of plasma treating a semiconductor substrate having a diameter of at least 200 mm. The microwave propagation mode arriving at the region is substantially limited to a single propagation mode by the subdivision of the waveguide.

[0014]

In a waveguide having a large diameter, a plurality of modes of microwaves including higher-order modes propagate. However, due to the mode limiting means provided in the waveguide, a microwave having a plurality of modes is substantially single. The number of modes is limited by the microwaves of the modes and the waves are propagated to the discharge chamber. As a result, there is no mode transition between a plurality of modes when plasma is generated, and plasma is stably generated.

Further, a mode limiter is provided in the large cross section of the waveguide consisting of the small cross section and the large cross section which are sequentially arranged in the propagation direction for guiding the microwaves to the plasma formation region, and it is predetermined. By selectively propagating a microwave having a pattern of electric force lines and aligning it with a predetermined plasma formation mode, the microwave mode is limited, and the mode transition between plural modes at the time of plasma generation. The phenomenon is prevented and plasma is stably generated.

Further, when plasma processing a semiconductor substrate of at least 200 mm, the microwave propagation mode reaching the plasma formation region is divided by the subdivision of the waveguide.
By controlling to a substantially single propagation mode, stable plasma can be generated without mode transition phenomenon in multiple modes at the time of plasma generation, and uniformity in plasma processing of a large-diameter substrate (sample) can be improved. it can.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT In the preferred construction of the invention, each split waveguide in the mode limiting means is individually designed to select the microwave mode that produces the desired plasma in the plasma formation region. Of electric field lines, and when these patterns are combined, they form an overall desired microwave mode electric field line.

The prior art using the dividing plate or the partition plate does not suggest anything about the selection of the microwave mode as a whole as described in the present invention. JP 63-
In the 60530 publication, the pattern of individual lines of electric force propagating in the divided waveguide is not related to the mode of the waveguide as a whole. Mixing of modes occurs when trying to propagate through the tube, increasing instability. Further, since the central circular tube described in Japanese Utility Model Laid-Open No. 2-67637 is larger than the wafer size, it is not possible to specify the mode therein. No idea is given regarding the formation of the mode as a whole.

The most preferable characteristic of the mode limiting means is that the mode is completely limited to one mode after passing through the mode limiting means, but it is desired that 80% or more, preferably 90% or more is selected. The preferred mode to select is the basic mode, eg TE11, TE01, TM
01 is mentioned. Among them, the TE11 mode has a wide uniform electric field in the center and is an easy mode to use.
Further, TE01 and TM01 are effective when the electric field in the vicinity of the center is small and the coupling of microwaves with plasma tends to be concentrated in the center. Although the uniformity of the electric field is somewhat degraded, one higher order mode (for example, T
(E12 mode) may be set.

By using the mode limiting means capable of setting and limiting such a mode, only the specific mode is propagated to the plasma formation region even if the cross-sectional size of the waveguide is increased, and a stable large voltage is obtained. A plasma having a diameter can be formed. Further, by processing the surface to be processed of the sample (wafer) which is the substrate using such plasma, the uniformity of the processing of the large diameter sample is improved.

The concept and some embodiments of the present invention will be described in detail below with reference to the drawings. A conventional plasma processing apparatus using microwaves is shown in FIG. 1'is a microwave generator, 19 'is a microwave waveguide, 7'is a quartz bell jar, 8'is a metal container, 9'is a gas introducing means, 10'
Is an exhaust means, 11 'is a solenoid coil, 12' is a sample, 13 'is a sample stage, 9 "is a ground electrode, and 15' is RF.
It is a generator. The microwave waveguide 19 'is in this case
Rectangular waveguide 2 ', rectangular-circular conversion waveguide 3', small-diameter first portion circular waveguide 4'and large-diameter second portion circular waveguide 6 ', enlarged portion 5'. Consists of.

A processing chamber is constituted by the metal container 8'and the quartz bell jar 7'which is hermetically provided at the upper opening of the metal container 8 '. A predetermined flow rate of processing gas is introduced into the processing chamber by the gas introduction means 9'and the exhaust means 10 ', and
The processing chamber is evacuated to a predetermined pressure. In this case, the microwave generated by the microwave generator 1'is guided into the processing chamber by the microwave waveguide 19 'through the quartz bell jar 7'. Due to the interaction between the magnetic field formed by the solenoid coil 11 'and the microwave electric field, the gas in the processing chamber is efficiently turned into plasma. Ions in the plasma are attracted to the bias voltage generated by the AC voltage applied between the sample stage 13 'and the ground electrode 9 "by the RF generator 15' and incident on the processed surface of the sample 12 'with good directionality. To be done.

An embodiment of the microwave plasma generator of the present invention will be described with reference to FIG. The same parts corresponding to those of the device of FIG. 1 are designated by the same numbers without the dashes. In this device, the enlarged portion of the waveguide is not stepped as in the conventional example, but the tapered waveguide 5 is used. The low pressure process chamber is coupled to the waveguide 19 by a flat quartz window 70 instead of a spherical dome. Most importantly, the waveguide 19 has a mode filter 20, which is a mode limiting means, above the quartz window 70 and below the tapered waveguide 5 in the large-diameter circular cross section. The mode filter 20 controls or selects the microwave mode of the waveguide circle toward the plasma formation region on the sample table (electrode) 13, and limits the number of modes.

Some configuration examples of the mode filter 20 will be described below. First, the mixture of microwave modes will be described. Microwave propagation modes and their patterns are generally well known, for example "Micvowav.
e Engineering and Applica
t-ions "OP Gandhi, Pergamo
n Press. Is shown in. Only one or two simple modes can propagate in the narrow waveguide due to the correlation with the wavelength of the microwave. On the other hand, as the waveguide expands with respect to the wavelength of microwaves, many modes can propagate.

Table 1 shows the diameter (D) of the circular waveguide and the cutoff wavelength (input
The relation with c) and the diameter of the circular waveguide which becomes the cutoff of the microwave for each mode at the frequency f = 2.45 GHz are shown. When the frequency f = 2.45 GHz, modes TE11 to TM41 can exist as shown in Table 1 for a circular waveguide having a diameter of 300 mm. However, as the order becomes higher, the proportion of existing modes decreases, and the proportion of existing modes also changes depending on the symmetry of the electromagnetic field of the excited mode.

[0026]

[Table 1]

FIG. 3 (b) shows the mode content in the output when the TE11 mode is input to the tapered waveguide shown in FIG. 3 (a) with respect to the taper angle θ.
This is made clear by the present inventors. Here, in this case, the circular waveguide 4 part is φ90, and the circular waveguide 6 is φ270. As the taper angle θ increases, T
The content rates of M11 mode and TE12 mode are increasing. FIG. 3 shows an ideal case, but in an actual device, T changes due to fluctuations in plasma that is a load and unevenness of the waveguide.
The content rate of modes other than the E11 mode is further increased.
In the case of stepwise expansion (in the case of θ = 90 ° in FIG. 3), the three modes are almost the same, and the dominant mode disappears. As described above, when the TE11 mode is input, the most mixed modes in the output are the TM11 mode and the TE12 mode, and when excited in the TE01 mode which is one of the other basic modes, the TE11 mode is mixed. It was confirmed that the TE21 mode and the TM21 mode were the most available modes.

The mode filter 20 shown in FIG. 2 suppresses the undesired mixing of modes as described above in an enlarged large diameter tube, resulting in a desired mode, preferably a simple fundamental mode, as the dominant mode of the plasma. It serves to propagate to the formation area. Below, mode filter 2
A specific example of 0 will be described in detail. FIG. 4 shows the mode filter 20.
A preferred configuration example of is shown. In the case of a circular waveguide, the TE11 mode is used because it is the fundamental mode and the electric field of the microwave is wide and uniform in the center. Figure 4 (a) shows T
The electric flux line of E11 mode is shown. FIG. 4B shows a configuration of the mode filter 120, which is divided by a linear dividing plate 121 provided at the center and dividing plates 122 and 123 provided on both sides thereof in an arc shape. These divider plates have a conductive surface (in this case made of Al),
It is provided so as to be orthogonal to the electric line of force of the desired mode (TE11 mode in this case) shown in (a), and the distance between these division plates is limited to a small value so that higher-order modes are less likely to occur. Form a director.

If the mode filter 120 is used, only an electric field almost perpendicular to the respective division plates 121 to 123 can pass therethrough, and the microwave mode that can pass through the mode filter 120 is the TE11 mode in this case. Becomes By doing so, there is little effect on the desired mode, and the effect of preventing mixing in other modes is obtained. The length of the mode filter is preferably an integral multiple of 1/4 of the guide wavelength, but it can be achieved by installing a plurality of short filters in multiple stages. Incidentally, in this case, even if the mode filter 120 was installed in the circular waveguide 4 having a diameter of 110 mm, there was almost no effect of plasma stabilization, but the mode filter 120 was provided in the circular waveguide having a diameter of 300 mm. The plasma was stabilized by installing the.

The mode filter used in this embodiment is TE
Although it corresponds to the 11 mode, when a mode other than the TE11 mode is passed as the desired mode,
For example, a mode filter as shown in FIGS. 5 to 9 may be used.

The mode filter 220 in which a plurality of metal cylinders 221 and 222 having different diameters shown in FIG. 5B are concentrically arranged has a line of electric force as shown in FIG. 5A.
Corresponds to 01 mode.

The mode filter 3 comprising a plurality of metal plates 321 radially arranged in the metal cylinder shown in FIG. 6B.
20 is TE0 which is a line of electric force as shown in FIG.
Corresponds to 1 mode.

Inside the metal cylinder shown in FIG. 7B, the metal plate 4
The mode filter 420 in which the arc-shaped metal plate 422 is divided into four equal parts by 21 and is arranged inward is shown in FIG.
It corresponds to the TE21 mode in which the lines of electric force are as shown in.

The metal plate 5 is placed inside the metal cylinder shown in FIG.
The mode filter 520, which is bisected by 21 and has a small-diameter metal cylinder 522 disposed in each, corresponds to the TM11 mode in which the electric lines of force are as shown in FIG. 8A.

Metal cylinders 6 having different diameters shown in FIG. 9 (b)
21 is arranged concentrically, and the mode filter 620 composed of a plurality of metal plates radially arranged between the metal cylinders is shown in FIG.
It corresponds to the TE12 mode in which the lines of electric force are as shown in (a).

The configuration example of the mode filter is not limited to that shown in the figure. In particular, the number of division plates and the like can be changed in relation to the microwave frequency and wavelength.

In order for the above mode filter to work effectively, it is necessary that the phases of the microwaves in the small spaces which are the sub-waveguides at the exit of the mode filter match. That is, it is necessary that the phase velocities of the microwave modes propagating through the small spaces in the mode filter are equal to each other. In other words, this means that the guide wavelengths of the microwave modes propagating in the respective small spaces (small space guide wavelengths) are equal to each other.

The above-mentioned guide wavelength will be discussed by taking the structure of FIG. 10 as an example. The guide wavelength λg of the microwave mode propagating in the waveguide is the wavelength λ of the microwave propagating in the vacuum, and the cutoff wavelengths λc and 1 / λg ² + 1 / λc ² = determined by the waveguide shape and microwave mode. There is a relationship of 1 / λ ² ... When the frequency of the microwave is 2.45 GHz, λ = 122.4 mm. When the diameter of the small circular waveguide 723 in the center is Db, TE1 propagating in the space B
The cutoff wavelength λc for one mode is λc = 1.71Db. From these values and the formula, TE11 propagating in the space B
The guide wavelength λδb 'of the mode is determined. Also, space C
Is approximated by a rectangle and the inner diameter of the large-diameter circular waveguide 721 is Da, a rectangular waveguide mode TE propagating in the space C is obtained.
The cutoff wavelength λc of 10 is λc = π (Da + Db) / n. n is the number of division plates 722, and in FIG.
It is 6. From these values and formula, T propagating in the space C
The guide wavelength λδc ′ of the E10 mode is determined. The above discussion means that it is necessary to make the values of λδb ′ and λδc ′ thus determined equal.

Incomplete microwave mode matching at the entrance and exit of the mode filter results in microwave reflection. In order to minimize this reflection, it is effective to set the length L of the mode filter to an integral multiple of ¼ of the guide wavelength λδ ′ of the microwave mode propagating in the small space. That is, L = h · λδ ′ / 4. However,
h is a positive integer and is assumed to be λδ ′ = λδb ′ = λδc ′. Also, if L = (2h + 1) λδ ′ / 4,
Greater effect is expected.

Further, the circular waveguide 723 and the dividing plate 722.
If the thickness is too large, the reflection of microwaves at the entrance and exit of the mode filter will be large. On the other hand, if the thickness is too thin, mechanical shape control, that is, strength is reduced, resistance to microwaves is increased, and heat is generated. Practically, it is good to set it to 3 to 0.5 mm.

The configuration of the mode filter of FIG. 10 is shown in FIG.
This will be described in more detail with reference to 12 and 13. The explanation here is different from the embodiments shown in FIGS. The embodiment of FIGS. 10 and 11 has a central circular waveguide 723 with six equally radially spaced divider plates 722 extending to the outer circular waveguide 721. The sizes of the small spaces a to g are made small enough to limit the mode of the microwave propagating in each of them, that is, smaller than the cutoff wavelength of the secondary propagation mode of the microwave.

FIG. 12 shows a desired circular TE11 mode electric flux line pattern of the large-diameter circular waveguide 721.

FIG. 13 shows electric lines of force of a restricted mode which can propagate through a small space of a waveguide which is divided by a mode filter. Unlike the large-diameter waveguide 721 on the outside, the circular waveguide 723 on the inside is small so that modes higher than TE11 cannot propagate. Therefore, the electric lines of force of the TE 11 in the circular waveguide 723 are represented by wavy lines in the center of FIG. On the other hand, each of the small spaces b to g on the outer side behaves like a rectangular waveguide and is small enough to propagate only the mode of the rectangular TE10 type, and the electric lines of force are shown by wavy lines in the periphery of FIG. ing. The electric field lines of each microwave mode propagating in these several small spaces, when combined, are shown in FIG.
It can be seen that the lines of electric force close to the desired TE11 mode of the large-diameter circular waveguide shown in 2 are exhibited. That is, it can be seen that they do not match the other simple modes TE01, TM11, etc. as a whole. Ultimately, this mode filter configuration will facilitate the propagation of the TE11 mode in the main waveguide after passing through the filter. Even if the microwaves reaching the filter are in a mixed state of modes, the small space in the filter is divided into sufficiently small regions that each region must be propagated in a simple mode, resulting in the TE11 mode. It will lead dominantly. In summary, the illustrated configuration is TE1
It can be seen that it acts as a mode filter for one mode.

14 to 17 show another structural example of the mode pass filter. In FIG. 14, the electrical conductor 823
Has a polygonal shape, and a dividing plate 822 is provided at its apex. In FIGS. 15 and 16, the circular waveguide 9
24 and 925 are installed concentrically, and in this case, they are arranged in duplicate and the dividing plate 9 is provided between 921, 924 and 925.
22 and 923 are provided. The arrangement of the dividing plates is different between FIG. 15 and FIG.
3 is provided at the same angle, and in FIG. 16, the dividing plates 1022 and 1023 are provided at different angles. The microwave mode to be propagated can be changed by changing the arrangement of the division plates. In FIG. 17, a plurality of circular waveguides 1125 are
In this case, they are separated from each other, and in this case, they are installed on the circumference of a certain distance from the center, and the division plate 1124 and the division plate 1123 are provided on the circumference of the circumference. This structure is suitable for propagating modes with a unique rotational symmetry. Figure 1
In FIG. 0 and FIG. 14, the angle division around the central axis for disposing the division plate is divided into six equal parts, but it goes without saying that this is not necessarily the case.

18 and 19 show examples of the structure of the mode filter in the rectangular waveguide. FIG. 18 is an example in which the rectangular waveguide 30 is divided into three parts by a dividing plate 32.
In FIG. 19, rectangular waveguides 132 are concentrically provided in the space of the rectangular waveguide 131, and the respective corners are connected by a dividing plate 133. FIG. 18 shows that not only the surrounding small space is surrounded but also the surrounding small space is surrounded.

FIG. 20 shows a plurality of specific waveguide sections L ₁ and L ₂
2 shows an example in which mode filters 201 and 202 are provided. By doing so, the specific microwave mode can be more effectively selected. Furthermore, by changing the mutual structure or relative positional relationship (for example, the rotation angle around the microwave power propagation axis), it becomes possible to select more complicated modes.

21 and 22 show improvements of the mode pass filter corresponding to the TE11 mode shown in FIG. The mode pass filter 1220 has a length L and an inner diameter 2R.
The large-diameter waveguide 1221 is divided into two semi-cylinders by a dividing plate 1223 passing through the center, and an arc-shaped dividing plate 1224 is further provided on each half-cylinder portion. Distance d between the center of large-diameter waveguide 1221 and partition plate 1224
₁ is installed at a position satisfying the relationship of 0.4 ≤ d ₁ / R ≤ 0.6, so that TE11
The passing rate of modes other than the modes can be reduced. It should be noted that, as shown in FIG.
If a slit in the axial direction is provided at a position d ₂ from the center of 21, the passing rate in modes other than the TE11 mode is further reduced.
As d ₂ , the relationship of 0.3 ≦ d ₂ / R ≦ 0.4 is satisfied, and the thickness t _{0 of the} dividing plate 1223 is set.
On the other hand, the effect is remarkable when the width t ₁ of the axial slit satisfies t ₁ / t ₀ ≦ 2. The width t ₁ of the axial slits and the slit interval t ₂ may be t ₁ ≈t ₂ .

As a modification of the mode-pass filter 1220 shown in FIG. 21, a large-diameter waveguide 1321 having an inner diameter of 2R is divided into two half cylinders by a dividing plate 1323 passing through the center as shown in FIG. A plurality of split plates 1324 and 1325 may be provided in the respective semi-cylindrical portions, which are bent in a trapezoidal shape or are formed by connecting three flat plates. Ideally, the dividing plate should be completely perpendicular to the desired microwave electric field in the absence of the dividing plate, but due to the manufacturability, a slight deviation does not pose a practical problem. The distance d ₃ between the center of the large-diameter waveguide 1321 and the division plate 1324 and the distance d ₄ between the center of the large-diameter waveguide 1321 and the partition plate 1325 are 0.35 ≦ d ₃ / R <d ₄ / R. By installing it in a position that satisfies the relation ≤ 0.65, TE11
The passing rate of modes other than the modes can be reduced. Note that FIG. 22 shows four cases as the dividing plate, but in the case of four or more, the same effect can be obtained when four of them satisfy the above formula.

In the above embodiments, the mode filter is located outside the plasma forming region, but it can be said that the same effect can be obtained by setting the mode filter or a part thereof inside the plasma forming region or the vacuum region. There is no end. In addition, it may be necessary to optimize the distance between the plasma formation region and the mode filter. That is, more stable and uniform plasma can be obtained by setting the distance between the plasma formation region and the mode filter to an appropriate value. To do this, change the position of the mode filter (ie,
Being mobile is of special value.

As described above, in this embodiment, the following effects can be obtained. (1) Since a plurality of modes can be limited to a substantially single mode and only a specific microwave mode can be preferentially introduced into the plasma, stable plasma can be formed without oscillation between the modes. Also, this eliminates the instability of the plasma and improves the uniformity. (2) By preferentially passing only a specific mode, a preset highly uniform microwave of a specific mode can be propagated in the discharge chamber, so that a more uniform electric field distribution can be obtained in the entire discharge chamber. You can Therefore, in the discharge chamber, a high-density plasma is generated with good uniformity due to the synergistic effect of the electric field and the magnetic field having a more uniform distribution in the entire discharge chamber, and is sufficiently diffused from the plasma in the discharge chamber to the surface to be processed of the wafer. Sufficient homogeneity is maintained for each of the arriving radical species and the ions for which diffusion is somewhat insufficient. (3) As a result, the ions and radicals in the plasma uniformly reach the surface to be processed of the wafer, and the etching process and the deposition process are performed. Particularly in the etching process, the uniformity of the ions is improved, so that the uniformity of the etching rate and the uniformity and precision of the etching shape within the surface to be processed of the wafer are improved.

Next, another embodiment of the present invention will be described with reference to FIGS. The embodiment shown in FIG. 23 is different from that of FIG. 2 in that the taper tube 5 is provided in the waveguide 19 in FIG. 2 whereas an expansion tube (step tube) 105 is used in this embodiment. Is. Even in the case of such a step tube, the mode filter 20 works effectively, and since it can be formed with a short waveguide, the device can be further downsized.

The embodiment of FIG. 24 differs from that of FIG. 23 in that a spherical quartz discharge tube 207 is provided. In this case, there is an effect that there is less metal contamination to plasma.

The embodiment of FIG. 25 differs from that of FIG. 2 in that the waveguide 19 is enlarged by having a tapered tube portion 305, and the mode filter 20 itself is also formed in a tapered shape to a maximum enlarged tapered portion. It is a point provided. According to this embodiment,
In addition to the same effect as the above-mentioned embodiment, it is possible to form a shorter waveguide, and it is possible to downsize the device.

Further, another embodiment of the plasma processing apparatus of the present invention will be described with reference to FIG. The feature of this drawing is that the metal container 404 also serves as a circular waveguide to form a processing chamber, and that the quartz plate 4 is provided at the upper opening of the metal container 404.
And a point where the microwave waveguide 419 is constituted by a rectangular waveguide 402, a rectangular-circular conversion waveguide 403, and a circular tapered waveguide 405, and a circular tapered waveguide. The point is that the mode filter 20a is provided in the maximum inner diameter portion of 405, and the mode filter 20b is provided in the metal container 404. The inner wall surface of the metal container 404, which serves as the discharge portion, is covered with an insulator to prevent impurities and the like from entering the wafer.

In these embodiments shown in FIGS. 2 to 26, in order to easily propagate the TE11 mode microwave in the large-diameter circular waveguide, the microwave oscillated from the magnetron is guided by the rectangular waveguide. It was designed to be guided to a large-diameter circular waveguide through a wave tube and a rectangular-circular conversion waveguide. However, the present invention is not limited to this, and the rectangle-
Instead of the circular conversion waveguide, a rectangular waveguide using a mode conversion waveguide 501, which is formed by diverging the opening on the outlet side by about 90 degrees at a position offset by 90 °, as shown in FIG. The microwave of TE10 mode may be converted into the microwave of TE20 mode so that the microwave of TE01 mode can be easily propagated in the circular waveguide. In this case, by providing a mode filter 503, which is configured by radially arranging dividing plates as shown in FIG. 28, in the circular waveguide 502, the modes other than the TE01 mode are attenuated and T is attenuated.
It is possible to stably generate the microwave in the E01 mode. As a result, a portion having a high plasma density is made uniform over a wide area, so that a large-diameter sample can be uniformly processed.

[0056]

According to the present invention, it is possible to stably form plasma in a substantially single microwave mode, prevent unstable plasma from being generated, and improve uniformity. Further, by specifying and propagating a mode in which the uniform portion of the electric field distribution is wide, the microwave electric field distribution in the discharge region can be made uniform, and plasma can be generated with good uniformity.

As a result, in the present invention, the distribution of ions in the plasma becomes more uniform, and the processing speed and shape of the sample can be controlled more uniformly and highly accurately.

[Brief description of drawings]

FIG. 1 is a sectional view showing an example of a conventional plasma processing apparatus.

FIG. 2 is a sectional view showing an embodiment of the plasma processing apparatus of the present invention.

3A is a diagram showing a shape of a tapered waveguide, and FIG. 3B is a diagram showing mixing of microwave modes in the tapered waveguide.

FIG. 4 is a diagram showing a specific configuration of a mode filter of the present invention, in which (a) shows electric lines of force of a target mode,
(B) is a block diagram of a mode filter.

5A and 5B are diagrams showing another specific configuration of the mode filter of the present invention, in which FIG. 5A shows electric lines of force of a target mode, and FIG. 5B is a configuration diagram of the mode filter.

6A and 6B are diagrams showing another specific configuration of the mode filter of the present invention, wherein FIG. 6A shows electric lines of force of a target mode, and FIG. 6B is a configuration diagram of the mode filter.

7A and 7B are diagrams showing another specific configuration of the mode filter of the present invention, in which FIG. 7A shows electric flux lines of a target mode, and FIG. 7B is a configuration diagram of the mode filter.

8A and 8B are diagrams showing another specific configuration of the mode filter of the present invention, in which FIG. 8A shows electric lines of force of a target mode, and FIG. 8B is a configuration diagram of the mode filter.

9A and 9B are diagrams showing another specific configuration of the mode filter of the present invention, wherein FIG. 9A shows electric lines of force of a target mode, and FIG. 9B is a configuration diagram of the mode filter.

FIG. 10 is a perspective view of the mode filter unit seen through.

11 is a cross-sectional view of the mode filter of FIG.

FIG. 12 is a diagram showing electric lines of force of a target TE11 mode in a large diameter waveguide.

13 is a TE11 that the mode filter of FIG. 10 approximates.
It is a figure which shows the electric force line of a mode.

FIG. 14 is a sectional view showing another embodiment of the mode filter.

FIG. 15 is a sectional view showing another embodiment of the mode filter.

FIG. 16 is a sectional view showing another embodiment of the mode filter.

FIG. 17 is a sectional view showing another embodiment of the mode filter.

FIG. 18 is a cross-sectional view showing another embodiment of the rectangular waveguide section.

FIG. 19 is a cross-sectional view showing another embodiment of the rectangular waveguide section.

FIG. 20 is a vertical cross-sectional view showing an example in which two mode filters are provided in series.

FIG. 21 is a diagram showing an improved example of the mode filter shown in FIG. 4.

FIG. 22 is a modification view considering the ease of manufacturing a mode filter.

FIG. 23 is a diagram showing another embodiment of the plasma processing apparatus according to the present invention.

FIG. 24 is a diagram showing another embodiment of the plasma processing apparatus according to the present invention.

FIG. 25 is a diagram showing another embodiment of the plasma processing apparatus according to the present invention.

FIG. 26 is a diagram showing another embodiment of the plasma processing apparatus according to the present invention.

FIG. 27 is a detailed view showing another embodiment of the mode conversion waveguide.

28 is a perspective view showing a specific example of a mode filter combined with the mode conversion waveguide of FIG. 27. FIG.

[Explanation of symbols]

1 ... Microwave generator, 19 ... Microwave waveguide, 8 ...
Metal container, 9 ... Gas introducing means, 10 ... Exhausting means, 11 ...
Solenoid coil, 13 ... Sample stand, 15 ... RF generator,
12 ... Sample, 20, 20a, 20b, 120, 201,
202, 220, 320, 420, 503, 520, 6
20, 720, 820, 920, 1020, 1120,
1220, 1320 ... Mode filter, 70 ... Quartz window.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kazuo Nojiri 5-20-1, Kamisuimoto-cho, Kodaira-shi, Tokyo Inside the Musashi Factory, Hitachi, Ltd. (72) Inventor Hiromitsu Enami 2326 Imai, Ome-shi, Tokyo Shares Hitachi, Ltd. Device Development Center (72) Inventor Tetsunori Kaji 794, Higashi-Toyoi, Kudamatsu City, Yamaguchi Prefecture Stock company Hitachi Ltd., Kasado Plant (72) Inventor Seiichi Watanabe 502, Kintachi-cho, Tsuchiura-shi, Ibaraki Co., Ltd. (72) Inventor Yoshifumi Ogawa Higashi-Toyoi, Higashi-Toyoi, Yamaguchi Prefecture

Claims (25)

[Claims] 1. A plasma generation method in which a microwave is introduced into a discharge chamber through a waveguide to generate plasma in the discharge chamber, which has a plurality of modes including higher-order modes propagating in the waveguide. A method of generating plasma, characterized in that the number of propagation modes of microwaves is limited to microwaves of substantially single mode, and plasma is generated in the discharge chamber by the microwaves of substantially single mode. 2. The method for generating plasma according to claim 1, wherein the step of limiting the number of microwave propagation modes causes the propagating microwaves propagating through a plurality of sub-directors in the expanded waveguide. , Adjacently subdivide, and recombine the microwaves from the subwaveguide before reaching the plasma formation region. 3. The plasma generation method according to claim 2, wherein the microwave propagates in each sub-waveguide in a single respective mode. 4. The plasma generation method according to claim 1, wherein the plasma formation region has a diameter of at least 300 mm. 5. The plasma generation method according to claim 1, wherein the number of propagation modes is substantially limited to one, and
The two modes of propagation are the fundamental modes of the extended waveguide. 6. The plasma generation method according to claim 5, wherein the fundamental mode is a circular TE ₁₁ mode. 7. A means for generating a microwave, a discharge chamber which is supplied with a plasma generating gas and is evacuated to a predetermined pressure, and a waveguide for introducing the microwave into the discharge chamber. In the plasma generating apparatus, the mode limiting means for limiting the number of propagation modes of a microwave having a plurality of modes including higher-order modes propagating in the waveguide to a substantially single mode microwave is provided in the waveguide. A plasma generating apparatus having the above-mentioned. 8. The plasma generating apparatus according to claim 7, wherein the mode limiting means comprises a flat plate-shaped dividing plate, the dividing plate having a conductive surface, and a plurality of sub-waveguides extending adjacent to each other. The waveguide into a vessel. 9. The plasma generator according to claim 8, wherein the length of the division plate in the propagation direction is an integral multiple of ¼ of the propagation wavelength of the microwave. 10. The plasma generating apparatus according to claim 7, wherein a predetermined plasma forming mode of the microwave of the waveguide between the mode limiting means and the plasma forming region, and the predetermined plasma forming mode is In order to choose, having a predetermined pattern of lines of electric force, the mode limiting means consists of a plurality of divider plates in the waveguide, the divider plates having a conductive surface and sub-guiding the waveguide. And each sub-waveguide has a respective sub-pattern of microwave electric field lines selectively propagating therein, the sub-pattern for a combined sub-waveguide array being predetermined. Aligned in a predetermined pattern of defined plasma formation modes. 11. The plasma generation device according to claim 10, wherein the predetermined plasma formation mode is a fundamental mode of the waveguide. 12. The plasma generating apparatus according to claim 10, wherein each of the dividing plates extends in a cross section of the waveguide perpendicularly to an electric line of force of a predetermined pattern of a predetermined plasma formation mode. Become. 13. The plasma generating apparatus according to claim 12, wherein the intervals between the continuous dividing plates along the lines of electric force of a predetermined pattern are determined by the secondary propagation mode of the microwave in each sub-waveguide. It is smaller than the cutoff wavelength. 14. A plasma generator according to claim 7, wherein the waveguide comprises a first part and a second part, the first part leading the second part and the second part in the propagation direction. Leading to the plasma formation region, the second portion also has a larger cross section than the first portion; and the mode limiting means are in the second portion of the waveguide. 15. The plasma generating device according to claim 14, wherein the waveguide comprises a non-perpendicular diffusion transition portion between the first portion and the second portion. 16. A plasma treatment chamber and a plasma formation region in the treatment chamber; a plasma generation region, which is composed of a small cross-section portion and a large cross-section portion which are sequentially arranged in a propagation direction leading to the plasma formation region. Waveguide; and a predetermined plasma formation mode for a plasma formation region in a large cross section of the waveguide, the plasma formation mode having a predetermined pattern of lines of electric force in the cross section of the waveguide , And a mode limiter for selecting microwave propagation, the mode limiter is composed of a plurality of dividing plates in the waveguide, the dividing plate having a conductive surface, and the waveguide being a sub-waveguide. Each sub-director has a respective sub-pattern of microwave electric field lines that propagate selectively therein, the sub-pattern for a combined array of sub-directors being predetermined. Was plasma generating apparatus is aligned in a predetermined pattern of plasma-forming mode. 17. The plasma generation device according to claim 16, wherein the predetermined plasma formation mode is a fundamental mode of a large cross section of the waveguide. 18. The plasma generating apparatus according to claim 16, wherein the large cross section of the waveguide has a circular cross section. 19. The plasma generation device according to claim 18, wherein the predetermined plasma formation mode is a TE ₁₁ mode. 20. The plasma generator according to claim 16, wherein the waveguide comprises a non-perpendicular diffusion transition portion between a small cross section and a large cross section. 21. The plasma generator according to claim 16, wherein the large cross section of the waveguide has a diameter of at least 300 mm. 22. The plasma generator according to claim 16, wherein each of the division plates extends perpendicularly to a line of force of a predetermined pattern of a predetermined plasma formation mode in a section plane of the waveguide, and The distance between the continuous division plates is smaller than the cutoff wavelength of the secondary propagation mode of the microwave in each sub-waveguide. 23. The plasma generator according to claim 16,
The pedestal supports the substrate exposed to the plasma formation region. 24. A semiconductor substrate is placed on a table in the processing chamber, a plasma forming gas is supplied to the processing chamber, a magnetic field is applied to a plasma forming region in the processing chamber where the semiconductor is exposed, and via a waveguide. A method for improving the plasma treatment of a semiconductor substrate having a diameter of at least 200 mm by forming a plasma by applying microwaves to the plasma formation region,
The improvement is a plasma processing method characterized in that the microwave propagation mode arriving at the plasma formation region is limited to a substantially single propagation mode by subdivision of the waveguide. 25. The plasma processing method according to claim 24, wherein the single propagation mode is a fundamental mode of the waveguide.