JPH09293682A - Plasma generating device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a plasma generating device which is high in degree of freedom of processing substrates variable in shape and size by a method wherein antennas planted in one of opposed electrodes and other antennas planted in the other electrode are so arranged as to be parallel with each other and staggered. SOLUTION: Comblike antennas 5a are planted in an electrode 4a, an electrode 4b is formed surrounding the electrode 4a and the antennas 5a, and comblike antennas 5b are planted in the electrode 4b extending inwards. The antennas 5a and 5b are arranged parallel with each other and staggered. Permanent magnets 7 are arranged in spaces sandwiched in between the antennas 5a and 5b so as to be alternately changed in polarity. By this setup, a plasma generating device can be enhanced in size corresponding to the number of the electrodes 4a and 4b, so that the plasma generating device can be improved in degree of freedom of processing substrates of various shape and size.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plasma generator, and more particularly to a plasma generator that generates plasma to perform surface treatment on a substrate.

[0002]

2. Description of the Related Art In recent years, in the manufacturing process of semiconductors and liquid crystal devices, surface treatments such as thin film formation using high frequency plasma, doping, and dry etching have been performed. As a plasma generator for generating this high-frequency plasma, glow discharge in the RF frequency band (for example, 13.56 MHz) by a flat plate type electrode, or microwave guided by a waveguide (for example, 2.45 GHz) and a magnetic field are applied. An electron cyclotron resonance discharge is used. Further, in recent years, new plasma generators for more precise and highly functional surface treatment have been demanded, and for example, inductively coupled or helicon wave type discharge, pulse-modulated high frequency plasma, or VHF band high frequency plasma is required. There is an attempt to use it.

Generally, in order to perform highly accurate and highly functional surface treatment using plasma, first, low pressure and high density plasma is required. The high density plasma
In the case of dry etching, it is necessary to increase the number of particles and ions involved in the etching and thus increase the etching processing speed. Further, it is necessary that the particles / ions collide with the surface of the substrate as perpendicularly as possible.
This is because the mask pattern formed on the substrate is processed / formed perpendicularly to the surface of the substrate. However, in a high-pressure plasma, the probability of particles colliding with each other increases, and it becomes difficult to maintain the directionality of particles / ions colliding with the substrate. The low pressure plasma reduces the effects of residual gas and the collision of particles and ions,
It is necessary to maintain the reactivity and directivity of the ions.
By using low pressure plasma, the mask pattern is processed / formed perpendicularly to the surface.

However, in such a low-pressure and high-density plasma, since it is necessary to use high energy for plasma generation, particles or ions having high energy are often generated per piece. It has been pointed out that such high-energy particles and ions damage the substrate to be treated or destroy radicals in plasma effective for etching.

The density of the plasma and the energy of the ions are determined by the electron density and the electron temperature, which basically depend on the frequency of the supplied high frequency signal. For example, in the case of glow discharge using a low-frequency high-frequency signal (for example, 13.56 MHz high-frequency signal), both electron density and electron temperature are low, but some particles with high energy are present and the discharge pressure is high. There's a problem.
On the other hand, in the case of electron cyclotron resonance using a high frequency high frequency signal (for example, a 2.45 GHz high frequency signal), a low pressure discharge is possible and the electron density is high, but the electron temperature is uniformly relatively high. Moreover, since a magnet is used, it is difficult to increase the diameter.

In theory, the frequency band of a high-frequency signal capable of generating plasma having a high electron density and a low electron temperature is at least 13.56 MHz to 2.45 GHz.
It is said to exist in the frequency band between.

On the other hand, Japanese Unexamined Patent Publication No. 7-307200 discloses a plasma generator which supplies a high frequency signal having a frequency of 100 MHz to 1 GHz to generate plasma. This prior art discloses an example of the structure of an antenna installed in a plasma generation chamber into which a plasma gas for plasma generation is introduced and providing a high frequency electric field. FIG. 7 is a cross-sectional view showing an example of the structure of the antenna described in this document. As shown in the figure, there is disclosed an antenna structure in a plasma generator in which a plurality of antennas 30a radially extending from the center to the outer periphery and a plurality of antennas 30b extending from the outer periphery to the center are formed in a staggered manner. ing. Each antenna is supplied with a high frequency signal having a phase difference of 180 degrees. According to this document, the frequency of the high-frequency signal is preferably 100 MHz to 1 GHz, and it is considered that plasma with high electron density and low electron temperature is generated. And, according to the description of this document, it is described that a VHF band high frequency electric field can be uniformly and efficiently introduced, and a small and simple plasma processing apparatus can be realized.

[0008]

However, in the plasma generator described in this document, the interval between the antenna 30a extending radially from the center to the outer periphery and the antenna 30b extending from the outer periphery to the center is not uniform. Without
As the diameter increases, the distance increases toward the outer circumference, so uniform plasma processing cannot be expected. In particular, when processing a rectangular substrate such as a liquid crystal display device, it is necessary to prepare a plasma generation chamber of a size sufficient to cover the rectangular substrate. It is difficult to perform uniform surface treatment with the used plasma generator.

[0009]

In order to overcome the above problems, the present invention comprises a plurality of electrodes, for example, a pair of electrodes, and a plurality of antennas respectively implanted in these electrodes,
It is characterized in that the antenna erected on one of the opposing electrodes is arranged so as to be substantially parallel to and disagree with the antenna erected on the other electrode.

According to the present invention, it is possible to obtain a plasma generator having flexibility in the shape and size of a substrate to be processed while using a high frequency electric field in the UHF or VHF band.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A plasma generator according to claim 1 of the present invention comprises a plurality of electrodes facing each other, a plurality of antennas respectively set up on the plurality of electrodes, and at least one of the plurality of electrodes. A high-frequency power supply for supplying a high-frequency signal to the antenna, and the antenna erected on one of the opposing electrodes is arranged substantially parallel to and disagree with the antenna erected on the other electrode. Therefore, uniform plasma processing can be performed by the antennas arranged in parallel to each other, and the outer shape of the electrodes and the antenna formed in the plasma generation chamber can be freely designed while keeping the antennas parallel to each other.

The plasma generator according to a second aspect of the present invention is characterized in that at least one outer contour of the electrodes is a rectangle, and the antennas are kept parallel to each other while the electrodes and the electrodes are kept parallel to each other. The size of the antenna can be freely designed.

In the plasma generator according to a third aspect of the present invention, the plurality of electrodes are circularly arranged concentrically with each other.
The distance between each electrode is characterized in that the antenna erected on one electrode and the antenna erected on the opposite electrode are selected to be substantially parallel to each other,
The antenna erected from circular electrodes arranged concentrically, while being kept substantially parallel to the opposing antenna,
You can freely design the size.

In the plasma generator according to a fourth aspect of the present invention, the distance between the electrodes is such that the difference between the maximum value and the minimum value of the width formed by the opposing antennas is the wavelength of the high frequency signal. The feature is that the distance is selected to be smaller than 20% of 1/4, and since the opposing antennas are kept substantially parallel to each other, uniform plasma processing can be expected.

The plasma generator according to claim 5 of the present invention is characterized in that the frequency of the high frequency signal is selected from the frequency band of 40 MHz to 1 GHz, and the high frequency signal of the VHF band or the UHF band is used. Can be used to control the optimum conditions for the system in which the plasma treatment is performed, such as electron temperature and ion density.

A plasma generator according to a sixth aspect of the present invention is characterized in that at least one electrode of the plurality of electrodes is grounded, and a high frequency signal applied to another electrode can be efficiently provided. And it can be used easily.

A plasma generator according to a seventh aspect of the present invention is characterized in that high-frequency signals whose phases are 180 degrees different from each other are supplied to electrodes facing each other. The high-frequency signal applied between the electrodes can be used more efficiently.

In the plasma generator according to the eighth aspect of the present invention, at least a plurality of supply points in one of the electrodes,
It is characterized by supplying high-frequency signals having different phases, and the efficiency of the applied high-frequency signals can be substantially improved.

A plasma generator according to a ninth aspect of the present invention comprises a phase shift circuit for adjusting the phase of the high frequency signal according to the wavelength of the high frequency signal and the distances between the plurality of supply points. The high frequency signal can be efficiently supplied to the electrode regardless of the position of the supply point on the electrode to which the high frequency signal is supplied.

In the plasma generator according to the tenth aspect of the present invention, the distance from the position on the electrode to which the high frequency signal is supplied to the open end of the antenna is equivalently an integer of 1/4 of the wavelength of the high frequency signal. It is characterized by being doubled,
It is possible to efficiently perform plasma processing with a given high frequency signal.

The plasma generator according to the eleventh aspect of the present invention is characterized by comprising a permanent magnet which is provided in a space between the antennas facing each other and which generates a magnetic field orthogonal to the electric field. A plasma generator using cyclotron resonance can be provided.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is a cross-sectional view showing the configuration of an embodiment of the plasma generator of the present invention. The plasma generator of the present invention comprises a plasma generation chamber 1 and a pair of electrodes 4.
a, 4b, and a plurality of antennas 5a, 5b provided in parallel with the electrodes 4a, 4b, respectively. Although not shown, the plasma generation chamber 1 is provided with an exhaust system, a gas introduction port, and a substrate transfer chamber. Although details of the electrodes 4a and 4b and the antennas 5a and 5b will be described later, a high frequency signal from the high frequency power supply 2 is applied to at least one of the electrodes 4a and 4b through the matching circuit 3. The matching circuit 3 is provided for impedance matching of the electric element group connected in the subsequent stage. These electrodes 4a, 4b
Although the antennas 5a and 5b can be placed in plasma, as shown in the figure, in order to avoid metal contamination during plasma processing, as is often done for the coil portion of the inductively coupled plasma generator. It is preferable to install the antenna via the insulating plate 6. Further, as in the case of utilizing electron cyclotron resonance, it is preferable to dispose the permanent magnet 7 between the antenna and the electrodes. Inside the plasma generation chamber 1, a substrate 8 to be surface-treated is arranged on a substrate electrode 9. An RF signal is supplied from the RF power source 10 to the substrate electrode 9 via the matching circuit 11. Further, one end of the RF power source 10 is grounded.

FIG. 2 is a sectional view showing an example of the structure of electrodes and antennas used in the plasma generator of the present invention. A plurality of antennas 5a are erected on the electrode 4a in a comb shape. An electrode 4b is formed so as to surround the electrodes 4a and the antenna 5a, and a plurality of antennas 5 are formed on the electrode 4b.
b is planted in the shape of a comb and toward the inside. The antennas 5a and 5b are arranged parallel to each other and alternately staggered. Also the antenna 5a
In the space sandwiched between the antenna 5b and the antenna 5b, the permanent magnets 7 are arranged so that their polarities alternate. Further, in this embodiment, the electrode 4b is grounded. A high frequency signal from the high frequency power supply 2 is supplied from one point, for example, the center of the electrode 4a. In order to generate a stable and uniform high frequency electric field, the distance from the supply point of the high frequency signal to each open end of the electrode 5a is equivalently an integral multiple of ¼ of the frequency λ of the high frequency signal. It is preferable. In this embodiment, the high-frequency signal is supplied only to one electrode 4a and the electrode 4b is grounded. However, the high-frequency signal having a phase different from that of the high-frequency signal supplied to the electrode 4a by 180 degrees is supplied to the electrode 4b. May be supplied.

In FIG. 3, the electrodes 4a and 4b have a phase of 18
1 shows an embodiment of a structure of an electrode and an antenna capable of supplying a high frequency signal different by 0 degrees, and one output of the high frequency power supply 2 is supplied to an electrode 4 via a matching circuit 3a.
It is supplied to one point of a, for example, the center point, and the other output is a series consisting of a phase shift circuit 12 for shifting the phase of the high frequency signal from the high frequency power source by 180 degrees, a high frequency amplifier 3b, and a second matching circuit 3b. It is supplied to one point of the electrode 4b through the circuit. That is, the electrode 4b has
A high-frequency signal whose phase is 180 degrees different from that of the high-frequency signal supplied to the electrode 4a is supplied.

The frequency of the high frequency signal supplied from the high frequency power source 2 is from the VHF band (30 MHz to 300 MHz) to the UHF band (3
40MHz to 1GHz is preferable over 00MHz). This is because the electron temperature of the plasma and the ion density can be controlled under desirable conditions, and 1/4 of the wavelength at this time is controlled.
Is in the range of 7.5 cm to 187.5 cm, which is convenient for the size of a substrate to be processed normally. Further, in such a frequency range, the magnetic field strength that satisfies the electron cyclotron resonance condition is about 13 Gauss to 330 Gauss, which is also convenient because a permanent magnet having a magnetic field strength in this range can be easily realized.

According to such an embodiment, the antennas 5a, 5
It is possible to increase the size of the plasma generating apparatus while keeping the void sandwiched by b always constant, and it is possible to provide a plasma generating apparatus that is particularly convenient for surface-treating a rectangular substrate.

Next, the configuration of a further embodiment of the present invention is shown in FIG. In FIG. 4, the electrode 4a has a U shape having two sides parallel to each other, and the antenna 5a
Are planted separately on the parallel sides of the electrode 4a. The electrode 4b has a rectangular shape surrounding the electrode 4a and the antenna 5a, and an electrode 4b 'is further planted on one side facing the open side of the electrode 4a. Antenna 5b
Are erected on the electrodes 4b and 4b ', and are installed parallel to the antenna 5a and alternately staggered from each other. Although the permanent magnet is omitted in the description of this embodiment, it is desirable to dispose the permanent magnet in the gap between the opposing antennas as in the embodiment described with reference to FIG. Further, the high-frequency signal is supplied to at least one of the electrodes, but the distance from the supply point of the high-frequency signal to the open end of each antenna is an integral multiple of 1/4 of the wavelength of the equivalently supplied high-frequency signal. Is desirable.

By forming in this way, a larger-sized plasma generator is provided. Furthermore, the parallel part of the electrode 4a is expanded to three or more, and the electrode 4 facing this is added.
It is also possible to add b.

Next, the configuration of a further embodiment of the present invention is shown in FIG.
Will be described with reference to FIG. FIG. 5 shows an antenna structure of a plasma generator in which a plurality of circular electrodes are concentrically arranged and antennas are arranged so as to alternately face each electrode. That is, for example, a circular electrode 40b surrounding the electrode 40a is arranged concentrically around the electrode 40a. Further, a concentric circular electrode 41a is arranged so as to surround the electrode 40b.
A concentric electrode 41b is arranged so as to surround a. Antennas 50a, 50b, 51 are arranged on the electrodes 40a, 40b, 41a, 41b so as to face each other alternately.
a and 51b are planted. Of course, it is possible to increase the number of electrodes formed in the concentric circles. Here, since each antenna extends radially, strictly speaking, it is not possible to keep the opposing electrodes parallel to each other. However, if the distance between the electrodes is small and the length of the antenna is sufficiently short, it can be considered that the opposing antennas are substantially parallel to each other. Specifically, the difference between the maximum width and the minimum width of the gap formed by the opposing antennas is selected to be 20% or less of 1/4 of the wavelength of the supplied high frequency signal. Therefore, by increasing the number of concentric electrodes without increasing the length of the antenna, it is possible to provide a large-sized plasma generator while maintaining the antennas substantially parallel to each other. It will be possible. Further, it is possible to increase the number of antennas that are set up on the electrodes as the distance to the outer circumference increases. By increasing the number of antennas, the angle formed between the adjacent antennas becomes smaller, and the opposing antennas can also be made to face each other in a closer parallel relationship.

Further, in the embodiment shown in FIG. 5, a high frequency signal is supplied to at least one point of the electrodes 40a and 41a. The electrodes 40b and 41b are grounded, or high frequency signals having a phase difference of 180 degrees from the high frequency signals supplied to the electrodes 40a and 41a are supplied to the electrodes 40b and 41b, respectively. From the supply point of the high frequency signal at each electrode,
The distance to the tip of each antenna is preferably an integral multiple of ¼ of the wavelength of the equivalently supplied high frequency signal.

Further, it is also possible to supply a high frequency signal having a phase difference according to the distance between the electrodes at two or more positions.

For example, as shown in FIG. 6, the electrode 4a
A high-frequency signal is supplied to both ends of each of the two, and the high-frequency signal supplied to one of them is a signal whose phase is adjusted by the phase shift circuit 14. The phase shift circuit 14 adjusts the phase of the high frequency signal according to the wavelength of the high frequency signal and the distance between the supply points on the electrodes to which the high frequency signal is supplied. That is, when a high frequency signal is supplied from one supply point on the electrode and the phase of the high frequency signal appearing at the other supply point is deviated by φ, the phase shift circuit 14 shifts the phase of the high frequency signal by φ. The generated high frequency signal is supplied to the other supply point of the electrode. The supply points of such high-frequency signals are not limited to two points, and it is possible to supply high-frequency signals from more supply points. In this case, the phases of the high-frequency signals can be changed according to the phases appearing at the respective supply points. A phase shift circuit for shifting may be provided.

As is apparent from the above description, the plasma generator according to the present invention has flexibility in the number of electrodes and the number of antennas, and it depends on the shape and size of the substrate to be processed. The number of electrodes and antennas may be set appropriately.

[0034]

As described above, according to the plasma generator of the present invention, a plurality of antennas are arranged on at least a pair of opposing electrodes so as to be substantially parallel to each other. Not only is it possible to increase the size of the plasma generator, but it is also possible to provide a plasma generator having a degree of freedom that matches the size and shape of the substrate to be processed.

[Brief description of drawings]

FIG. 1 is a side view showing a configuration of an embodiment of a plasma generator of the present invention.

FIG. 2 is a configuration diagram showing a configuration of an embodiment of an electrode and an antenna used in the plasma generator of the present invention.

FIG. 3 is a configuration diagram showing a configuration of another embodiment of electrodes and antennas used in the plasma generator of the present invention.

FIG. 4 is a configuration diagram showing the configuration of yet another embodiment of electrodes and antennas used in the plasma generator of the present invention.

FIG. 5 is a configuration diagram showing a configuration of still another embodiment of electrodes and antennas used in the plasma generator of the present invention.

FIG. 6 is a configuration diagram showing a configuration of still another embodiment of electrodes and antennas used in the plasma generator of the present invention.

FIG. 7 is a configuration diagram showing configurations of electrodes and antennas used in a conventional plasma generator.

[Explanation of symbols]

 1 Plasma Generation Chamber 2 High Frequency Power Supply 3 Matching Circuit 4a, 4b Electrodes 5a, 5b Antenna 6 Insulation Plate 7 Permanent Magnet 8 Substrate 9 Substrate Electrode

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Office reference number FI Technical display location H01L 21/3065 H05H 1/46 M 21/31 H01L 21/265 P H05H 1/46 21/302 B

Claims (11)

[Claims] 1. An opposing electrode comprising a plurality of electrodes facing each other, a plurality of antennas respectively set up on the plurality of electrodes, and a high-frequency power source for supplying a high-frequency signal to at least one of the plurality of electrodes. 1. A plasma generator, wherein an antenna erected on one side is arranged so as to be substantially parallel to and disagree with the antenna erected on the other side electrode. 2. The plasma generator according to claim 1, wherein at least one outer contour of the electrode is rectangular. 3. The plurality of electrodes are circularly and concentrically arranged with respect to each other, and the distance between the electrodes is substantially equal to that of an antenna erected on one electrode and an antenna erected on an opposite electrode. 2. The plasma generator according to claim 1, wherein the distance is set to be parallel to. 4. The distance between each of the electrodes is such that the difference between the maximum value and the minimum value of the width formed by the opposing antennas is:
4. The plasma generator according to claim 3, wherein the distance is selected to be smaller than 20% of 1/4 of the wavelength of the high frequency signal. 5. The frequency of the high frequency signal is 40 MHz to 1 GHz
2. The plasma generator according to claim 1, wherein the frequency is selected from the range. 6. The plasma device according to claim 1, wherein at least one of the electrodes is grounded. 7. The electrodes facing each other are in phase with each other.
The plasma generator according to claim 1, wherein high-frequency signals different by 180 degrees are supplied. 8. The plasma generator according to claim 1, wherein high-frequency signals having different phases are supplied to a plurality of supply points on at least one of the electrodes. 9. The plasma generation according to claim 8, further comprising a phase shift circuit that adjusts a phase of the high frequency signal according to a wavelength of the high frequency signal and distances between the plurality of supply points. apparatus. 10. The distance from the position on the electrode to which the high frequency signal is supplied to the open end of the antenna is equivalently an integral multiple of ¼ of the wavelength of the high frequency signal. The plasma generator according to claim 1. 11. The plasma generator according to claim 1, further comprising a permanent magnet provided in a gap between the antennas facing each other to generate a magnetic field orthogonal to the electric field.