JPH08171998A - Micro wave plasma processing device and plasma processing method - Google Patents

Abstract

PURPOSE: To evenly process a sample at a high speed by using the micro wave so as to appropriately set the high density area of the plasma to be generated in a plasma processing chamber. CONSTITUTION: A resonator 24 for resonantly oscillating the micro wave at the specified mode is fitted to a micro wave transmitting means 2 for supplying the micro wave, which is generated by a micro wave generator 1, to a plasma generating space 4. A waveguide 26 for gradually changing the diameter of the cross section of an opening formed over from the resonator 24 to the plasma generating space 4 is fitted.

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 and a plasma processing method, and more particularly to a microwave plasma processing apparatus suitable for performing plasma processing such as etching and film formation on a wafer at high speed and uniformly. And a plasma processing method.

[0002]

2. Description of the Related Art A conventional microwave plasma processing apparatus is
For example, as described in the semiconductor plasma process technology (edited by Takuo Sugano, published by Sangyo Tosho, (1980), P139), a quartz discharge chamber is formed in a waveguide that propagates microwaves, and the quartz discharge chamber is arranged outside the discharge chamber. It is known that plasma is generated in the discharge chamber by the action of the magnetic field generated by the coil and the electric field of the microwave, and the plasma is used to perform plasma treatment on the surface of the semiconductor wafer.

[0003]

In the microwave plasma processing apparatus, the microwave oscillated from the magnetron is introduced into the plasma processing chamber, for example, the etching processing chamber via the microwave waveguide, and is introduced into the etching processing chamber. The introduced microwave energy is efficiently supplied to plasma mainly in the electron cyclotron resonance (ECR) region, and high-density plasma is generated in the etching processing chamber. Further, the plasma generated in the etching processing chamber is transported to the wafer side where the etching processing is performed along the magnetic lines of force formed in the etching processing chamber. Therefore, in order to uniformly etch the wafer,
It is necessary to make the plasma density on the wafer on which the plasma processing is performed uniform over a wide range as much as possible. Furthermore, in order to make the plasma distribution on the wafer uniform,
The microwave mode introduced into the etching chamber must be uniform.

In the microwave plasma processing apparatus as in the above-mentioned prior art, the microwave waveguide for introducing microwaves from the magnetron into the etching processing chamber has a constant diameter for transmitting microwaves in a specific mode. It was manufactured and the diameter and shape of the waveguide were not changed.

On the other hand, in order to advance the mode of the microwave passing through the inside of the waveguide while keeping it in a constant mode,
It is known to use a waveguide in which the diameter of the microwave waveguide is gradually increased to reach the etching processing chamber.

When attempting to generate a high-density plasma using these conventional microwave waveguides, the central portion in the etching chamber has a high density, which is a medium-high (convex) shape.
The plasma density distribution was as follows, and it was not possible to obtain high density and uniform plasma.

Therefore, in the past, in order to process the wafer as fast and uniformly as possible, the vicinity of the central portion where the plasma density was high and the plasma density was relatively uniform was used, but the uniformity over the entire wafer is insufficient. there were. Therefore, in the case of processing a wafer having a large diameter of 8 inches or more, since the plasma density in the peripheral portion of the wafer becomes lower, the etching rate becomes slower than that in the central portion of the wafer, and the entire wafer should be uniformly etched. Was difficult. Further, in order to uniformly etch the entire wafer, it is necessary to further increase the inner diameter of the etching processing chamber to expand the region of high plasma density in the central portion, which causes a problem of increasing the size of the apparatus.

In order to increase the density of plasma on the wafer, it is necessary to increase the power of the microwave incident on the etching chamber and to efficiently propagate the microwave in the microwave waveguide. There must be. In particular, if there is a surface in the microwave waveguide that is orthogonal to the traveling direction of the microwave, the microwave will be reflected by this surface and the microwave energy will be efficiently transmitted to the plasma. Can't do it.
When the transmission efficiency of microwave energy deteriorates, conventionally, the supply of microwave power is increased to deal with it.
It could not be said that the plasma density was efficiently increased.

The object of the present invention is to solve the above-mentioned problems of the prior art. It is possible to set a high-density plasma region to be generated in the plasma processing chamber and to make the sample high-speed and high-speed.
An object of the present invention is to provide a microwave plasma processing apparatus and a plasma processing method capable of performing uniform processing.

[0010]

SUMMARY OF THE INVENTION In the microwave plasma processing apparatus, the above object is to resonate the microwave in a specific mode by the microwave propagation means for supplying the microwave generated by the microwave oscillator to the plasma generation space. A device with a resonator attached and a waveguide that gradually changes the cross-sectional area (aperture) of the resonator from this resonator to the plasma generation space is used. On the other hand, it is achieved by a method in which the propagation area is gradually changed and introduced into the plasma generation region, and the processing gas is made into plasma using the microwave to process the sample.

Further, by making the opening of the waveguide on the side of the plasma generation space smaller than the inner diameter of the inside of the chamber forming the plasma generation space, high density plasma can be obtained in the peripheral portion.

[0012]

Operation: While supplying the microwave generated by the microwave oscillator to the plasma generation space, a resonator for resonating the microwave in a specific mode is attached, and an opening cross-sectional area from the resonator to the plasma generation space is gradually increased. By changing to, it is possible to set the microwave mode introduced into the plasma generation space to a desired mode. For example, it is possible to supply the TE ₀₁ mode microwave having a ring-shaped strong electric field intensity of a desired size (radial direction) in the cross section in the traveling direction of the microwave to the plasma generation space. As a result, a plasma having a ring-shaped high-density plasma distribution can be generated on the ECR surface, and due to the diffusion of the plasma from the ECR surface to the sample side, a medium-high (convex) plasma distribution on the sample causes It is possible to obtain a plasma distribution with improved uniformity to a (concave) plasma distribution, and it is possible to perform processing with an optimum plasma distribution corresponding to the processing of the sample, and to process the sample at high speed and uniformly. You can

Further, the plasma generation space side opening (aperture) of the microwave waveguide entering the plasma generation space is made smaller by the waveguide side inner diameter inside the chamber forming the plasma generation space, so that plasma is generated once. It is also possible to prevent the microwave supplied to the room forming the space from escaping from the room by reflection or the like, and it is possible to obtain high-density plasma in the peripheral portion.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is a vertical sectional view of a microwave plasma processing apparatus. Reference numeral 1 is a magnetron which is a microwave oscillator, and oscillates a microwave of 2.45 GHz, for example. Reference numeral 2 is a microwave propagation means for propagating the microwave oscillated from the magnetron 1,
In this case, the rectangular waveguide 21, the circular rectangular conversion waveguide 22, the circular waveguide 23, the resonator 24, and the reduction waveguide 26 are sequentially connected to the magnetron 1. In this case, the rectangular waveguide 21 is set to have a size for propagating the microwave of the rectangular TE ₁₁ mode, and has a matching device 27 for impedance matching of the microwave in the middle thereof. In this case, the circular waveguide 23 is set to a size capable of propagating a microwave of circular TE ₁₁ mode. The resonator 24 has a slit plate 25 between the resonator 24 and the reduction waveguide 26,
In this case, a plurality of slit holes arranged radially are formed as shown in FIG. Resonator 24, in this case, is set so as to emit microwaves of TE ₀₁ mode from the slit plate 25 together with the resonating microwaves of TE ₀₁ mode. The reduction waveguide 26 has a tapered inner surface in this case so that the opening cross-sectional area thereof gradually decreases in the traveling direction of the microwave. In this case, the tapered shape of the reduction waveguide 26 is such that the microwave entrance diameter is substantially the same as the inner diameter of the resonator 24, and the microwave exit diameter is incident on the microwave introduction side of the plasma processing chamber 4 (described later). It is almost the same as the caliber.

Reference numeral 4 is a chamber for forming a plasma generating space, and in this case, it is a plasma processing chamber which also serves as plasma processing. The plasma processing chamber 4 is made of a conductor, for example, high-purity aluminum or the like, and the inner surface thereof is subjected to hard alumite processing and the like, and also functions as a microwave waveguide. The plasma processing chamber 4 is formed by providing the quartz plate 3 between the plasma processing chamber 4 and the reduction waveguide 26, and the space on the reduction waveguide 26 side and the processing chamber space are isolated. The plasma processing chamber 4 is connected to and communicates with the vacuum chamber 5. A sample table 8 is supported on the bottom of the vacuum chamber 5 via an electrically insulating material. Sample table 8
Is a sample in a space formed by the plasma processing chamber 4 and the vacuum chamber 5, and in this case, the surface where the wafer 10 is arranged is provided so as to face the quartz plate 3.

In this case, the vacuum chamber 5 is a gas capable of uniformly supplying a processing gas for processing such as etching or film formation to the wafer 10 on the sample stage 8 from the periphery of the inner surface of the upper part of the plasma processing chamber 4. A supply means 12 is provided, and a vacuum exhaust means 11 capable of reducing the pressure inside the vacuum chamber 5 to a predetermined pressure is connected. A high-frequency power source 9, which is a power source for applying a bias voltage to the sample stage 8, is connected to the sample stage 8. Reference numeral 28 is a gate valve that partitions the vacuum chamber 5 and is connected to the plasma processing chamber 4 to form a processing chamber.

Solenoid coils 6 and 7 for forming a magnetic field in the plasma generation chamber 4 are wound around the resonator 24, the reduction waveguide 26 and the plasma processing chamber 4. In the apparatus of the present embodiment, the solenoid coil 6 can generate a stronger magnetic field than the solenoid coil 7, and is set so as to form a flat ECR surface in the plasma processing chamber 4 by being combined with the magnetic field of the solenoid coil 7. There is.

In the microwave plasma processing apparatus configured as described above, the microwave emitted from the magnetron 1 is transmitted through the rectangular waveguide 21, the matching device 27, the circular rectangular conversion waveguide 22, and the circular waveguide 23. Through microwave resonator 2
Guided to 4. The microwave guided to the resonator 24 is internally resonated in a specific microwave mode, and is also guided to the reduction waveguide 26 through the slit plate 25 that emits in the specific mode. The microwave that has passed through the reduction waveguide 26 is guided into the etching processing chamber 4 through the quartz plate 3. The microwaves introduced into the etching process chamber 4 act on the magnetic field formed in the etching process chamber by the solenoid coils 6 and 7 so that the plasma processing chamber 4 is affected.
The processing gas inside is turned into plasma. At this time, the microwave emitted from the magnetron 1 is the resonator 2 of the microwave.
4 and the reduced waveguide 26 are introduced into the etching processing chamber 4 so that the density and distribution of the plasma generated in the etching processing chamber 4 becomes a high density and uniform improved plasma. Results were obtained.

FIG. 3 shows the result of measuring the distribution of the ion current density of the plasma incident on the sample stage (electrode) depending on the presence or absence of the resonator 24 and the presence or absence of the reduction waveguide 26. In this case, the Al film is replaced with BCl ₃ by using the photoresist as a mask.
It is an experimental result at the time of etching using the mixed processing gas of / Cl ₂ . Etching by this apparatus is performed at a processing pressure of 5 to 50 mTorr and a processing gas flow rate of 50 to 300.
ml, processing gas mixing ratio: 0.5 to 1.5 (BCl ₃ ) / 1
(Cl ₂ ), high frequency power output: 25 to 250 W, microwave output: 200 W to 1.5 KW. A curve A shows an ion current density distribution when the resonator 24 and the reduction waveguide 26 are provided. A curve B shows an ion current density distribution when the resonator 24 is provided and the reduction waveguide 26 is not provided. Curve C shows the resonator 24 and the reduced waveguide 26.
The ion current density distribution when not provided is shown.

According to FIG. 3, in the case of the prior art in which the resonator 24 and the reduction waveguide 26 are not provided, the ion current density in the central part of the sample stand is high as shown by the curve C, and the outer peripheral part of the sample stand is high. It is small, and it is clearly seen that the ion current density on the sample stage is non-uniform, that is, the plasma density on the sample stage 8 in the plasma processing chamber 4 is non-uniform. When the etching process is performed under such a plasma condition, particularly when the Al film having a step structure is etched because the selectivity ratio to the resist in the wafer central portion is small, the chip portion in the wafer central portion in the thin portion of the resist film in the step portion However, there is a problem in that the etching removal is performed faster than the chip portion in the peripheral portion of the wafer, and the etched shape of the Al film in the step portion cannot be maintained.

When the resonator 24 is provided and the reduction waveguide 26 is not provided, the ion current density at the center of the sample stand is slightly lowered as shown by the curve B, but the ion current density at the periphery of the sample stand is reduced. It can be seen that the uniformity of the ion current density is improved over the entire surface of the sample table, that is, the uniformity of the plasma density on the sample table 8 is improved. This is because the resonator 26 having the slit plate 25 specifies a ring-shaped strong electric field strength distribution mode, in this case, a TE ₀₁ mode microwave, and guides the microwave to the plasma processing chamber 4. It is considered that this results in a strong ring-shaped plasma density distribution on the ECR surface, and the plasma is diffused toward the wafer. When the etching process is performed under such a plasma condition, the difference in the selectivity ratio to the resist between the central portion and the peripheral portion of the wafer is significantly improved, the uniformity with respect to the resist selection ratio is improved, and the above-mentioned problems are solved. I was able to. The etching uniformity of the Al film at this time was not affected.

Further, the resonator 24 and the reduction waveguide 26 are provided.
In the case of the present embodiment, the ion current density is improved on the entire surface of the sample table while maintaining the uniformity of the curve B as shown by the curve A, that is, a high density plasma having an increased plasma density is provided on the sample table 8. It can be seen that in (1) and (2), the uniformity is improved. When the etching process is performed under such plasma conditions, the process uniformity and the process speed of the wafer can be improved.

As described above, by mounting the resonator 24 on a part of the waveguide of the microwave propagation means, the uniformity of the ion current density on the sample stage is improved, and further, the reduced waveguide 2
6 is provided between the resonator 24 and the quartz plate 3 to increase the value of the ion current density while keeping the distribution state of the ion current density on the sample table almost constant, that is, the plasma on the sample table. Can be uniformly improved with high density.
As a result, the processing speed can be improved and the wafer 10 can be uniformly processed when performing processing such as etching or film formation.

Next, a second embodiment of the microwave plasma processing apparatus of the present invention will be described with reference to FIG. FIG. 4 shows the microwave propagation means and the plasma processing chamber portion of the apparatus in FIG. 1, which are the same as the members shown in FIG. The difference between this figure and FIG. 1 is that in the reduced waveguide for guiding the microwave to the plasma processing chamber 4, which is provided in the subsequent stage of the resonator 24 (with respect to the traveling direction of the microwave), the plasma of the waveguide is reduced. The point is that the reduced waveguide 26a is formed by gradually reducing the diameter reaching the processing chamber 4 side. In this case, the reduction waveguide 26
With respect to the wavelength of the microwave passing through a, the degree of decrease in the diameter of the microwave reducing waveguide 26a is set to a negligible stepwise decrease. With this configuration, the same effect as that of the above-described embodiment can be obtained. Further, in the case of the reduced waveguide in which the aperture is gradually reduced, the reduced waveguide 26a can be easily configured by stacking donut-shaped disks having different apertures. The shape of 26a can be easily changed.

Next, a third embodiment of the microwave plasma processing apparatus of the present invention will be described with reference to FIG. FIG. 5 shows the microwave propagation means and the plasma processing chamber of the apparatus shown in FIG. 1, which are the same as the members shown in FIG. This drawing is different from FIG. 1 in that the reduced waveguide 26b has a smaller diameter on the side of the plasma processing chamber 4 of the reduced waveguide than the diameter of the microwave introduction portion of the etching processing chamber 4. By doing so, it was possible to further increase the ion current density particularly in the outer peripheral portion of the wafer 10 as compared with the above-described apparatus of FIG. This is because microwaves once introduced into the plasma processing chamber 4 via the reduction waveguide 26b and the quartz plate 3 are unlikely to be emitted from the inside of the plasma processing chamber 4 to the outside of the plasma processing chamber 4 via the quartz plate 3. It is thought to be because.

The above-mentioned curve shape of FIG. 3 changes depending on the processing gas used, that is, the ion current density changes depending on the processing gas. The distribution tendency of the ion current density depends on the presence or absence of the resonator and the reduced waveguide. In the relationship between the size of the plasma treatment chamber side diameter of the reduced waveguide and the size thereof, there is a tendency similar to that shown in FIG. Therefore, as described above, by providing the resonator and the reduction waveguide in the microwave propagation means and adjusting the diameter of the reduction waveguide on the side of the plasma processing chamber 4, the high-density region of plasma on the wafer can be reduced. Since it can be generated at a desired position, it is possible to generate optimum plasma conditions for processing such as etching or film formation. For example, in order to make the resist selection ratio uniform within the wafer surface, the plasma density in the upper part of the wafer is made higher than in the central part.

Next, a fourth embodiment of the microwave plasma processing apparatus of the present invention will be described with reference to FIG. FIG. 6 shows the microwave propagation means and the plasma processing chamber of the apparatus in FIG. 1, which are the same as the members shown in FIG. The difference between this figure and FIG. 1 is that instead of the reduced waveguide 26, the diameter of the opening cross section in the waveguide is gradually expanded toward the plasma processing chamber 4 side, that is, with respect to the traveling direction of microwaves. That is, the enlarged waveguide 29 is used. This also makes it possible to change the high-density region of the plasma generated in the plasma processing chamber 4 and obtain the optimum plasma state for processing the sample.

According to these embodiments, the microwave of the specific mode set by the resonator is introduced into the plasma processing chamber by using the reduction waveguide or the expansion waveguide.
The high-density distribution region of plasma can be changed from the conventional middle-height state to the optimum position in the peripheral direction, and the optimum plasma state for sample processing can be created, so that the sample can be processed uniformly and at high speed. You can

When appropriately adjusting the diameters of the reduction waveguide and the expansion waveguide on the side of the plasma processing chamber 4 in the above-described embodiments, for example, a portion corresponding to the inner surface of the reduction waveguide is made of a conductor. By adopting a contracting or enlarging waveguide that can automatically change the aperture, such as a conical plate that is rounded into a conical shape and slideable by overlapping the ends, the plasma density distribution can be adjusted during processing and etching can be performed. In the case of processing, the reduction waveguide shape is changed during etching and during overetching, etc., and the plasma distribution is changed so as to improve the selection ratio with respect to the resist or the underlayer, so that etching processing with even higher yield is performed. You can Further, the control of plasma distribution during the process can be applied during the film forming process, if necessary.

These plasma distribution adjusting techniques can be applied to etching treatment of metals, gates, and oxide films other than Al film, and can be applied to treatment using microwave plasma such as film forming treatment other than etching treatment.

Further, in the apparatus shown in FIG. 1, the magnetic field generated by the solenoid coils 6 and 7 is used for generating plasma, but the apparatus can be applied to the apparatus which does not use the magnetic field. When the electron density of plasma generated in the plasma processing chamber is 7 × 10 ¹⁰ pieces / cm ³ or more in the absence of a magnetic field (1 × 10 ¹¹ pieces / cm ³ or more in the presence of a magnetic field), the plasma is microwave. It has a reflection boundary surface of and reflects a part of the incident microwave. At this time, the energy of the microwave is efficiently transferred to the plasma and the plasma density is improved by providing a space having a size such that the microwave resonates between the boundary surface and the slit plate. The dimensions of the waveguide are preferably set in consideration of this point as well.

Further, in the apparatus shown in FIG. 1, the processing gas is supplied to the wafer from around the inner surface above the processing chamber. However, the processing gas is supplied from the quartz window portion facing the wafer. Can be changed as appropriate.

[0033]

According to the present invention, a microwave propagation means for supplying microwaves to the plasma generation space causes the microwave propagation means to resonate and radiate microwaves of a specific mode, and the resonator to reach the plasma generation space. By providing a waveguide that gradually changes the cross-sectional area of the opening, the high-density region of the plasma generated in the plasma processing chamber can be set as appropriate, and the plasma on the sample can be optimized for processing the sample. The effect is that the sample can be uniformly processed.

[Brief description of drawings]

FIG. 1 is a longitudinal sectional view showing a microwave plasma processing apparatus according to one embodiment of the present invention.

FIG. 2 is a diagram showing details of a slit plate in the apparatus of FIG.

FIG. 3 is a diagram showing the relationship between the presence or absence of a microwave resonator and a reduction waveguide and the ion current density distribution.

FIG. 4 is a vertical sectional view showing a microwave propagation means portion of a microwave plasma processing apparatus according to a second embodiment of the present invention.

FIG. 5 is a vertical sectional view showing a microwave propagation means portion of a microwave plasma processing apparatus according to a third embodiment of the present invention.

FIG. 6 is a vertical sectional view showing a microwave propagation means portion of a microwave plasma processing apparatus according to a fourth embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Magnetron, 2 ... Microwave propagation means, 3 ... Quartz plate, 4 ... Plasma processing chamber, 24 ... Resonator, 26, 26
a, 26b ... Reduced waveguide, 29 ... Expanded waveguide.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yoshiaki Sato 794 Azuma Higashitoyo, Kudamatsu City, Yamaguchi Prefecture Stock Company Hitachi Ltd. Kasado Factory

Claims (10)

[Claims] 1. A microwave oscillated by a microwave oscillator is introduced into a plasma generation space through a microwave propagation means, and a sample is processed using the plasma generated in the plasma generation space by using the microwave. In the microwave plasma processing apparatus, the microwave propagation means comprises
A resonator for resonating a microwave propagating through the means in a specific mode, and a waveguide in which an opening cross-sectional area of a space from the resonator to the plasma generation space gradually changes in a propagation direction of the microwave. And a microwave plasma processing apparatus. 2. The microwave plasma processing apparatus according to claim 1, wherein the waveguide side of the resonator is a slit plate. 3. The microwave plasma processing apparatus according to claim 1, wherein an opening cross-sectional area of the waveguide gradually decreases and changes in a propagation direction of the microwave. 4. The microwave plasma processing apparatus according to claim 1, wherein an opening cross-sectional area of the waveguide gradually expands and changes in a propagation direction of the microwave. 5. The microwave plasma processing apparatus according to claim 3, wherein the opening cross-sectional area of the waveguide is changed stepwise. 6. The microwave plasma processing apparatus according to claim 1, wherein the opening on the plasma generation space side of the waveguide is substantially the same as the inside diameter of the waveguide in the chamber forming the plasma generation space. . 7. The microwave plasma processing apparatus according to claim 1, wherein the opening on the plasma generation space side of the waveguide is smaller than the inside diameter of the waveguide in the chamber forming the plasma generation space. 8. A microwave is propagated in a specific mode, and the propagation area is gradually changed with respect to the traveling direction of the microwave and introduced into the plasma generation region, and the processing gas is plasmaized using the microwave to sample the sample. A plasma processing method, characterized in that the processing is performed. 9. A plasma density is increased in a peripheral portion on a wafer,
Alternatively, the plasma processing method is characterized in that the plasma density is reduced in the central portion and the selectivity ratio to the resist is increased to etch the material to be etched under the resist mask. 10. A plasma processing method, characterized in that, in a plasma having an electron density of 1 × 10 ¹¹ pieces / cm ³ or more, the peripheral portion of the wafer has a higher plasma density than the central portion, and the sample is treated. .