JPH0645095A - Method for generating plasma and device therefor - Google Patents

Abstract

PURPOSE:To generate a plasma with high density and excellent uniformity under high vacuum, thereby improving fine workability, and minimizing the damage to a device. CONSTITUTION:First to fourth side electrodes 5-8 are arranged on the sides of a plasma generating part laid in vacuum state to enclose the plasma generating part. A high frequency power is supplied to the first side electrode 5 from a first high frequency power source 9A, a high frequency power is supplied to the second side electrode 6 from the first high frequency power source 9A through a first delay circuit 11, a high frequency power is supplied to the third side electrode 7 from the first high frequency power source 9A through first and second delay circuits 11, 12, and a high frequency power is supplied to the fourth side electrode 8 from the first high frequency power source 9A through first-third delay circuits 11, 12, 13. Thus, high frequency powers having the same frequency and successively differed in phases are applied to the first- fourth side electrodes 5-8, respectively, and a rotating field as rotating electrons in the plasma generating part is excited in the plasma generating part.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plasma generating method and apparatus for generating plasma.

[0002]

2. Description of the Related Art A plasma generating method using a high frequency discharge is used in various fields such as a dry etching apparatus for fine processing, a sputtering apparatus for forming a thin film, a plasma CVD apparatus, an ion implantation apparatus and the like. , For the miniaturization of processing dimensions and high-precision control of film quality,
Plasma generation in high vacuum is required.

Hereinafter, as an application example of the plasma generation method,
A dry etching method suitable for fine processing will be described.

The progress of modern high-density semiconductor integrated circuits is bringing about a change comparable to the industrial revolution, and the higher density of semiconductor integrated circuits means miniaturization of device dimensions, improvement of devices, and large area of chip size. Have been realized by
The miniaturization of device dimensions has advanced to about the wavelength of light, and the use of excimer lasers and soft X-rays is being considered for lithography. It can be said that dry etching plays an important role along with lithography for the realization of fine patterns.

Dry etching is a processing technique for removing an unnecessary portion of a thin film or a substrate by utilizing a chemical or physical reaction on a gas-solid phase surface due to radicals, ions, etc. existing in plasma. Reactive ion etching (RIE), which is most widely used as a dry etching technique, causes an etching reaction by exposing a sample to a high-frequency discharge plasma of an appropriate gas to remove an unnecessary portion of the sample surface. . The required portion, that is, the portion that is not removed is usually protected by the photoresist pattern used as a mask.

For the miniaturization, it is necessary to make the directionality of ions uniform, but for this purpose, it is essential to reduce the scattering of ions in plasma. In order to make the directionality of the ions uniform, it is effective to increase the vacuum degree of the plasma generator to increase the mean free path of the ions, but if the vacuum degree of the plasma chamber is increased, it is difficult for high frequency discharge to occur. There's a problem.

Therefore, as a countermeasure, a method for applying a magnetic field to the plasma chamber to facilitate discharge, such as a magnetron reactive ion etching technique or an ECR (electron cyclotron resonance) etching technique, has been generally developed.

FIG. 16 is a schematic diagram showing a reactive ion etching apparatus using a conventional magnetron discharge. A reactive gas is introduced into the metallic chamber 81 via a gas controller 82, and the inside of the chamber 81 is controlled to have an appropriate pressure by an exhaust system 83. An anode (anode) 84 is provided above the chamber 81, and a sample table 85 serving as a cathode (cathode) is provided below the chamber 81. An RF power source 87 is connected to the sample stage 85 via an impedance matching circuit 86 so that high frequency discharge can be generated between the sample stage 85 and the anode 84. On each side of the chamber 81, two pairs of facing AC electromagnets 88 are provided with their phases differing from each other by 90 degrees, and a rotating magnetic field is applied to the inside of the chamber 81 by the two pairs of AC electromagnets 88. , Facilitates discharge in high vacuum. By doing so, the electrons make a cycloidal motion due to the rotating magnetic field, so that the motion path of the electrons becomes long and the ionization efficiency becomes high.

[0009]

However, according to the above-mentioned magnetron discharge or ECR discharge, it is difficult to perform fine etching processing due to the non-uniform plasma density and the sample to be processed is damaged. There was a problem.

For example, in the conventional magnetron reactive ion etching apparatus, the local bias of the plasma is made uniform by temporally averaging it by the rotating magnetic field, but the instantaneous plasma density is not uniform. A local potential difference occurs. Therefore, the conventional magnetron reactive ion etching system is
When applied to the I process, breakdown may occur in the gate oxide film.

Similarly, in the ECR etching apparatus,
Since the magnetic field is distributed in the radial direction of the chamber, the plasma density is locally dense and dense, which causes nonuniform etching species and a local potential difference.
Due to this nonuniformity of plasma, the uniformity of etching deteriorates, which makes it difficult to produce LSIs with high yield. The non-uniformity of the plasma means that it is difficult to perform accurate etching when performing dry etching on an ultrafine pattern LSI or a large-diameter wafer in which an even thinner gate oxide film is used.

In addition, the conventional parallel plate type magnetron etching apparatus of 13.56 MHz excitation is 100 to 200M.
A method has also been attempted in which plasma is densified by superimposing a high frequency power of Hz to reduce the self-bias voltage and damage to a sample due to high-energy ions.

However, according to this method, although the density of plasma can be increased, it is difficult to improve the uniformity of plasma. Therefore, it is not sufficient to solve the above-mentioned problems caused by the nonuniformity of plasma. I can not say.

In view of the above-mentioned problems, the present invention provides a plasma generating method and an apparatus therefor, which have high density and excellent uniformity under high vacuum, which improves microfabrication and causes less damage to devices. The purpose is to

[0015]

In order to achieve the above-mentioned object, the inventions of claims 1 to 10 are arranged at the same frequency through a delay circuit on the side electrodes arranged so as to surround the plasma generating portion. By applying high-frequency power having different phases, a rotating electric field that excites the electrons in the plasma generating unit to rotate is excited in the plasma generating unit.

[0016] Specifically, the solution means taken by the invention of claim 1 is a plasma generating method, wherein a pair of side electrodes are arranged at positions facing each other through a plasma generating portion in a vacuum chamber, and the pair of side electrodes are arranged. High frequency power is supplied from one of the electrodes to a high frequency power source, and the other side electrode of the pair of side electrodes is supplied from the high frequency power source via a delay circuit to the high frequency power. By supplying high-frequency power having the same frequency but different phases, a high-frequency electric field that causes electrons in the plasma generating section to perform amplitude motion is excited in the plasma generating section.

According to a second aspect of the present invention, there is provided a plasma generating method, wherein three or more side electrodes are arranged on a side of a plasma generating portion in a vacuum chamber so as to surround the plasma generating portion, High frequency power is supplied from one high frequency power source to one of the above side electrodes, and is supplied from the high frequency power source to another side electrode of the three or more side electrodes via a delay circuit. By supplying high-frequency power having the same frequency as that of the high-frequency power but sequentially different phases, a rotating electric field that causes the electrons in the plasma generating section to make a rotational motion is excited in the plasma generating section.

According to a third aspect of the present invention, a plasma generator is provided with a pair of side electrodes provided at positions facing each other with a plasma generator in the vacuum chamber, and the pair of side electrodes. A high frequency power source for supplying high frequency power to one of the side electrodes, and delaying the high frequency power received from the high frequency power source to the other side electrode of the pair of side electrodes so as to delay the high frequency power and the frequency. And a delay circuit for supplying high-frequency power having the same phase but different phases, and the plasma generating section is provided with an electric field excitation means for exciting a high-frequency electric field that causes the electrons in the plasma generating section to make an amplitude motion. is there.

According to a fourth aspect of the invention, in the structure of the third aspect, the side wall of the vacuum chamber is formed of a dielectric material, and the pair of side electrodes are provided outside the vacuum chamber. Is added.

According to a fifth aspect of the invention, the delay circuit is a low pass filter in addition to the configuration of the third aspect.

According to a sixth aspect of the present invention, there is provided a plasma generating device, comprising: three or more side electrodes provided in a position surrounding a plasma generating portion in a vacuum chamber; and three or more side electrodes. A high-frequency power source for supplying high-frequency power to one side electrode, and other side electrodes of the three or more side electrodes,
A delay circuit group composed of a plurality of delay circuits for delaying high-frequency power received from the high-frequency power source to respectively supply high-frequency power having the same frequency and sequentially different phases to the high-frequency power, An electric field excitation means for exciting a rotating electric field that causes electrons in the plasma generating portion to make a rotational motion is provided.

According to a seventh aspect of the present invention, in the structure of the sixth aspect, the side wall of the vacuum chamber is formed of a dielectric material, and
The above lateral electrodes are added to the structure provided outside the vacuum chamber.

According to an eighth aspect of the present invention, in addition to the configuration of the sixth aspect, a configuration in which each of the plurality of delay circuits is a low pass filter is added.

According to a ninth aspect of the present invention, in the configuration of the sixth aspect, the delay times for sequentially delaying the high frequency power received from the high frequency power supply by the delay circuit group are set to be substantially equal to each other. It is something to add.

The invention of claim 10 is based on the structure of claim 6,
A magnetic field applying means for applying to the plasma generating part a magnetic field that gives the electrons in the plasma generating part a swirling motion in the same direction or in the opposite direction to the rotational motion of the electrons caused by the rotating electric field excited by the electric field exciting means. Is added.

According to the invention of claims 11 to 14, the frequency of the high-frequency power supplied to the sample stage is made different from the frequency of the high-frequency power supplied to the side electrodes arranged so as to surround the plasma generating portion. The high frequency power supplied to the sample stage has a high impedance with respect to the frequency of the high frequency power supplied to the side electrodes.

Specifically, the solution means taken by the invention of claim 11 is that the plasma generator is provided in a sample stage provided below the plasma generator in the vacuum chamber and at a position surrounding the plasma generator. Electrons in the plasma generating part are composed of three or more side electrodes and first high frequency power supplying means for supplying high frequency power having the same frequency and sequentially different phases to the three or more side electrodes. An electric field excitation means for exciting a rotating electric field that causes a rotational movement to a high frequency power, and a high frequency power having a frequency different from the frequency of the high frequency power supplied from the first high frequency power supply means are supplied from the first high frequency power supply means. Second high frequency power supply means for supplying to the sample stage via a filter circuit having a high impedance characteristic with respect to the frequency of the high frequency power. It is intended.

According to a twelfth aspect of the present invention, in the configuration of the eleventh aspect, the first high-frequency power supply means supplies the high-frequency power to the three or more side electrodes from the second high-frequency power supply means. The configuration in which the high frequency power is supplied through a filter circuit having a high impedance characteristic is added.

According to a thirteenth aspect of the present invention, in the configuration of the eleventh aspect, the frequency of the high frequency power supplied from the first high frequency power supply means is the frequency of the high frequency power supplied from the second high frequency power supply means. The configuration is set to be higher than the above.

According to a fourteenth aspect of the present invention, in the structure of the eleventh aspect, the electrons in the plasma generating portion are in the same direction as or opposite to the direction of the rotational movement of the electrons brought about by the rotating electric field excited by the electric field exciting means. A configuration is additionally provided in which a magnetic field applying means for applying a magnetic field that gives a turning motion to the plasma generating section is provided.

[0031]

According to the plasma generating method or apparatus of the first or third aspect, the electrons in the plasma generating portion are oscillated by the high frequency electric field excited by the plasma generating portion, Proceed in line with the direction. Since such electron motion effectively increases the collision cross-section between electrons and gas molecules, it is possible to obtain a high ionization efficiency even in a high vacuum and discharge as compared with the conventional parallel plate plasma generator. It will be easier.

Further, since the high-frequency electric field in the plasma generating section is more uniform than the magnetic field distribution obtained by the conventional plasma generating method or apparatus, it is possible to obtain a plasma having excellent uniformity.

As a method of forming the high frequency electric field as described above, one side electrode of the pair of side electrodes is supplied with high frequency power from the high frequency power source, and the other side electrode is delayed from the high frequency power source. By supplying the high frequency power supplied via the circuit, it is possible to supply the high frequency power having the same frequency but different phases with a simple circuit.

In this way, even if the input power is unbalanced for some reason between the side electrodes, the side electrodes are connected to each other by the delay circuit, so that the input power is automatically unbalanced. Will be corrected.

According to the plasma generating method or the apparatus of claim 2 or 6, the electrons in the plasma generating portion are rotatively moved by the rotating electric field excited by the plasma generating portion and are Proceed in line with the direction. Since such electron motion effectively increases the collision cross-section between electrons and gas molecules, it is possible to obtain a high ionization efficiency even in a high vacuum and discharge as compared with the conventional parallel plate plasma generator. It will be easier.

Further, since the high-frequency electric field in the plasma generating section is more uniform than the magnetic field distribution obtained by the conventional plasma generating method or apparatus, it is possible to obtain a plasma having excellent uniformity.

As a method for forming the rotating electric field as described above, a high frequency power is supplied from a high frequency power source to one side electrode of the three or more side electrodes, and the high frequency power source is supplied to the other side electrode. By respectively supplying the high frequency powers sequentially supplied from the above through the delay circuit, it is possible to supply the high frequency powers having the same frequency and sequentially different phases with a simple circuit.

In this way, even if the input power is unbalanced for some reason between the side electrodes, since the side electrodes are connected to each other by the delay circuit, the input power is automatically unbalanced. Will be corrected.

According to the plasma generator of claim 11,
In order to form a rotating electric field in the plasma generating part by applying high-frequency power having the same frequency and sequentially different phases to the side electrodes on the side of the plasma generating part, the electrons in the plasma generating part perform the rotational motion as described above. However, since it advances in the direction of its own kinetic energy, high ionization efficiency can be obtained even in a high vacuum and discharge can be facilitated.

The high frequency power having a frequency different from the frequency of the high frequency power supplied from the first high frequency power supply means to the side electrodes is supplied to the sample stage from the second high frequency power supply means. Since it is supplied through a filter circuit having a high impedance characteristic with respect to the frequency of the high frequency power supplied from the means to the sample stage, the high frequency power applied to the sample stage and the rotating electric field are excited to contribute mainly to plasma generation. It is independent of the high frequency power generated.

According to the plasma generating apparatus of the tenth or fourteenth aspect, the electrons in the plasma generating portion are caused to undergo a translational cycloidal motion in which the center of the rotational motion is translated by the above-mentioned rotating electric field, and the translational cycloidal motion is caused by the above-mentioned magnetic field. The translational motion component of the electron that moves is converted into a swirl motion component that swirls the plasma generating portion. For this reason, the electrons in the plasma generation section move such that the center of the rotational movement caused by the rotating electric field advances on the locus of the swirling movement caused by the magnetic field, so that the electrons escape from the plasma generation section. Without a cycloid motion accompanied by rotational motion.

[0042]

EXAMPLE A dry etching apparatus to which the plasma generating method according to the first example of the present invention is applied will be described below.

FIG. 1 is a schematic diagram showing the structure of this dry etching apparatus. In FIG. 1, 1 is a rectangular parallelepiped chamber (vacuum chamber), 2 is a sample table provided under the chamber 1, 3 is a sample to be etched made of a semiconductor wafer placed on the sample table 2, and 4 is a chamber. Is an opposite electrode of the sample table 2 provided on the upper part of the. Reference numerals 5, 6, 7, and 8 denote first, second, third, and fourth side electrodes, which are parallel plate electrodes provided on the sides of the chamber 1. A portion surrounded by the sample stage 2, the counter electrode 4, and the first to fourth side electrodes 5 to 8 is a plasma generation region.

The first to fourth side electrodes 5, 6, 7, 8 are supplied with high frequency power of 10 MHz from the first high frequency power supply 9A via the first matching circuit 10.
Between the first to fourth side electrodes 5 to 8 and the first matching circuit 10, a high frequency power (1 MHz in this embodiment) applied to the sample stage 2 is high. The 1st filter 14 used as impedance is inserted.

A high frequency power having a frequency of 1 MHz is supplied to the sample table 2 from a second high frequency power source 9B via a second matching circuit 15. A second filter having a high impedance between the sample stage 2 and the second matching circuit 15 with respect to the high frequency power (10 MHz in this embodiment) applied from the first high frequency power supply 9A. 16 is inserted.

A first delay circuit 11 is provided between the first side electrode 5 and the second side electrode 6. Due to the first delay circuit 11, the high frequency power applied to the second side electrode 6 has a phase difference of about 90 degrees with respect to the high frequency power applied to the first side electrode 5. Second lateral electrode 6
The second delay circuit 12 is installed between the third delay electrode 12 and the third side electrode 7. Due to the second delay circuit 12, the high frequency power applied to the third side electrode 6 has a phase difference of about 90 degrees with respect to the high frequency power applied to the second side electrode 5. A third delay circuit 13 is provided between the third side electrode 7 and the fourth side electrode 8. Due to the third delay circuit 13, the high frequency power applied to the fourth side electrode 8 has a phase difference of about 90 degrees with respect to the high frequency power applied to the third side electrode 7.

First to third delay circuits 11, 12, 13
Is a so-called m-type low-pass filter (low-pass filter) as shown in FIG. 2, and generally, about 1.27 is selected for m. The delay time Td in the first to third delay circuits 11, 12 and 13 is represented by Td = (LC) ^1/2 .

Etching gas is introduced into the chamber 1 from an inlet (not shown) via a mass flow controller (not shown), and the pressure in the chamber 1 is 0.1 Pa to 10 Pa by a turbo pump (not shown). It is controlled to a certain degree.

In addition, above and below the chamber 1,
An upper circular coil 17 and a lower circular coil 18 are provided respectively. Upper and lower circular coils 17, 18
Is supplied with current from power supplies 19 and 20 which are a DC power supply or a pulse power supply, whereby a magnetic field in a direction substantially perpendicular to the sample stage 2 is applied inside the chamber 1. .

The operation of the dry etching apparatus configured as described above will be described below with reference to FIG.

FIG. 3 is a diagram schematically showing the trajectory of electrons e when high frequency power is applied to the first to fourth side electrodes 5 to 8 surrounding the plasma generating part 21. Electron e is
While being rotated by the rotating electric field applied to the plasma generator 21, the plasma generator 21 proceeds in the direction of its own kinetic energy.

Although not shown, the plasma generator 2
1 to provide only the first side electrode 5 and the third side electrode 7 or to provide only the second side electrode 6 and the fourth side electrode 8 via the plasma generator 21. Alternatively, the pair of side electrodes facing each other may be supplied with high-frequency power supplied from the same high-frequency power source and having the same frequency with a phase difference of 180 degrees given by the delay circuit but different phases. By doing so, the electrons in the plasma generating unit 21 travel in the direction of their own kinetic energy while undergoing amplitude motion by the high-frequency electric field applied to the plasma generating unit 21.

FIG. 7 is a graph showing the distance traveled by the electron e during one cycle of high frequency power as a function of frequency. Here, 20 eV electrons are assumed. 20e in X direction
The electron e traveling with the energy of V moves by about 6 cm in 20 nanoseconds, which corresponds to one cycle of high-frequency power of 50 MHz. Assuming that the distance between the side electrodes is 30 cm, the electron e has an amplitude of about 5 times while traveling the distance. When the energy of the electron e is large, the traveling speed is high, and thus the number of amplitudes during traveling between the side electrodes decreases.

Although it depends on the gas species, generally, electron energy of about 15 eV or more is required to ionize the gas. Since the ionization is caused by the collision between the electron e and the gas molecule, the longer the traveling distance of the electron e, the more the probability of collision and the higher the ionization efficiency. Therefore, according to the present invention, the traveling distance of the electrons is lengthened by rotating or oscillating the electrons, thereby increasing the ionization efficiency. It can also be seen that the cross-sectional area where electrons and gas molecules collide with each other has effectively increased due to the rotational movement or amplitude movement of the electrons.

Since the distance between the opposing side electrodes is usually several tens of cm, it is necessary to rotate or oscillate the electrons e by high frequency power to improve the ionization efficiency by about 50 cm.
A high frequency of MHz or higher is required. However, 50M
Even if the high-frequency power having a frequency lower than Hz is applied and the traveling distance of the electron e decreases, the electron with low energy makes a rotational motion or an amplitude motion, so that there is a probability that the electron collides with the chamber wall and disappears. The ionization efficiency is increased because the electron density is decreased and the electron density is prevented from decreasing.

Further, as will be described later, when a magnetic field is applied to the chamber 1, the electrons perform not only rotational motion or amplitude motion due to the electric field but also swirl motion due to the magnetic field, so that high ionization is achieved even at a frequency lower than 50 MHz. Efficiency can be realized.

FIG. 4 shows the upper and lower circular coils 17,
By supplying a direct current to 18, a movement path of the electron e when a magnetic field in a direction perpendicular to the sample stage 2 is applied to the rotating electric field shown in FIG. 3 is shown. As a result, the translational movement of the electrons e moving toward the side wall of the chamber 1 in the state of FIG. 3 is converted into the movement in the direction in which the plasma generating portion 21 is swung. The magnitude of this swirl is proportional to the product of the magnitude of the applied electric field and the magnitude of the applied magnetic field, and the direction of this swirl is perpendicular to both the applied electric and magnetic fields. It is in the right direction. As a result,
The electron e performs a motion in which the cyclotron swirl motion due to the magnetic field is superimposed on the rotary motion caused by the rotary electric field due to the high frequency power.

FIG. 5 and FIG. 6 show that when the above magnetic field is applied to the electron e in the state of FIG. 3 while changing the strength of the magnetic field, the electron e
It shows how the movement path of the robot changes. As described above, by applying an electric field and a magnetic field to the plasma generating unit 21 and causing the electrons of the plasma generating unit 21 to perform a swirling motion accompanied by a rotational motion or an amplitude motion, most of the electrons e in the plasma generating unit 21 are removed. The traveling distance of the electron e can be lengthened by confining it in the plasma generation unit 21.
As a result, the density of the electrons e in the plasma generator 21 is increased, and the ionization efficiency is increased.

According to the conventional magnetron etching apparatus using the rotating magnetic field, the magnetic flux distribution 22 immediately above the sample table 2 at a certain moment is non-uniform as shown in FIG. 8 (a). For this reason, the electrons e in the chamber 1 (black circles in FIG. 8B) rotate with an orbital radius that is inversely proportional to the magnetic field strength, so that the upper and lower parts of the chamber 1 where the magnetic field strength is weak and the outer periphery of the plasma generation region. In the area, the orbital radius of the electron e becomes large, so the electron e collides with the wall of the chamber 1 and disappears.

Further, when considering the direction crossing from the left side to the right side in the central part of the plasma generating part 21, the density of the electrons e decreases in the central part where the magnetic field strength is weak, so the plasma density becomes low and the magnetic field strength is strong. Since the density of electrons e increases in the outer peripheral portion, the plasma density also increases.
In the conventional dry etching apparatus, thus, the plasma density becomes non-uniform, resulting in non-uniform etching and damage to the workpiece.

On the other hand, according to the dry etching apparatus to which the plasma generating method of the present invention is applied, the electric field in the plasma generating portion 21 surrounded by the first to fourth side electrodes 5, 6, 7, 8 is formed. And the magnetic field is almost uniform,
As shown in FIG. 9, the loci of the cycloidal motion accompanied by the rotational motion of the electrons e are substantially equal at each place, so that the plasma density is substantially uniform in the entire area of the plasma generation unit 21. Therefore, according to this dry etching apparatus, the reactive radicals and ions generated from the reactive gas for etching in the plasma generating part 21 are almost uniformly irradiated to the entire surface of the sample 3 to be etched. Therefore, etching is uniformly performed in the entire region of the sample 3 to be etched facing the plasma generating portion 21, damage due to charge-up is extremely reduced, and the etching rate is increased due to the high plasma density.

FIG. 10 (a) schematically shows an example in which boron phosphorus glass is etched by a conventional magnetron etching apparatus using a rotating magnetic field. Figure 10 (a)
In the above, 30 is a Si substrate, 31 is boron phosphorus glass,
32 is a photoresist pattern. As shown in FIG. 10B, when the instantaneous magnetic field intensity distribution immediately above the Si substrate 30, that is, immediately above the sample stage has a minimum value in the central portion of the sample stage, it is incident on the surface of the Si substrate 30. The flux I of incoming ions is proportional to the plasma density distribution corresponding to the magnetic field strength distribution, and becomes sparse in the center as shown in FIG. As shown in FIG. 10C, the etching rate of the oxide film (boron phosphorus glass 31) substantially follows the ion flux I and becomes nonuniform. In addition, the nonuniform plasma density causes damage to the device due to uneven distribution of charges.

FIG. 11A schematically shows an example in which boron phosphorus glass is etched by a dry etching apparatus to which the plasma generating method of the present invention is applied. According to this dry etching apparatus, since substantially uniform plasma is generated as described above, the ion flux II, which is the reaction product for etching, incident on the surface of the Si substrate 30 is also uniform, as shown in FIG. As a result, the etching rate becomes highly uniform as shown in FIG. 11 (b). Further, since the plasma is uniform, the uneven distribution of charges is small, and the damage caused by the charges is extremely small. In this case, CHF ₃ + is used as the gas introduced into the chamber 1.
A gas based on Freon gas such as O ₂ or CF ₄ + CH ₂ F ₂ was used, and the gas pressure was 0.1 to 10 Pa. The etching rate at this time is 100 to 350 n.
It was m / min.

This dry etching apparatus is particularly suitable for etching a submicron pattern and a large-diameter semiconductor wafer of 6 inches or 8 inches. The reason is that since the pressure inside the chamber 1 is low, the amount of ion scattering is small, so that the dimension shift (so-called CD loss) or the etching rate pattern, which is the value obtained by subtracting the line width of the sample after etching from the line width of the photoresist pattern. This is because the dependence on dimensions is small, and because the uniformity of plasma is high, it is easy to increase the size of the chamber 1.

In this embodiment, as described above, the high-frequency power is supplied to the first to fourth side electrodes 5 to 8 which control the plasma density with which the sample 3 to be etched is irradiated and which generate the rotating electric field. The circuit has a first impedance having a high impedance with respect to the frequency of the high frequency power supplied to the sample stage 2.
Filter 14 is inserted. On the other hand, the circuit for supplying high-frequency power to the sample table 2 includes the first to fourth side electrodes 5
The second filter 16 having a high impedance characteristic with respect to the frequency of the high frequency power supplied to 8 is inserted. As a result, a circuit that supplies high-frequency power to the first to fourth side electrodes 5 to 8 and a circuit that supplies high-frequency power to the sample stage 2 are independent of each other, and stable and uniform plasma is generated. You can

FIG. 12 shows a comparison between the conventional dry etching method and the above dry etching method, and it can be understood that the above dry etching method is superior to the conventional method.

As described above, according to this embodiment, the first to fourth side electrodes 5, 6, 7, which surround the plasma generating portion 21,
By rotating the electrons e of the plasma generating portion 21 in the vacuum state by applying high frequency power of the same frequency, which has a phase difference of about 90 degrees to 8, the density is high and the uniformity is excellent despite the high vacuum. Generated plasma can be generated.

By controlling the high frequency power supplied to the sample stage 2, the selection ratio with respect to the base during etching can be controlled. Furthermore, since there is almost no local bias in the plasma, damage to the work piece can be extremely reduced.

In this embodiment, the case where the phase difference of the high frequency power is set to 90 degrees is shown. This is because when the phase difference is set to 90 degrees, the power input efficiency to the plasma is good, Even if the phase difference is different from 90 degrees, the effect of the present invention can be obtained. Further, the phase of the high frequency power applied to the first to fourth side electrodes 5 to 8 may be changed as a function of time.

The plasma generating method according to the second embodiment of the present invention will be described below.

In the first embodiment, the frequency of the high frequency power supplied to the first to fourth side electrodes 5 to 8 mainly contributing to plasma generation is 10 MHz and is applied to the sample stage 2 as a bias. The case where the frequency is set higher than 1 MHz which is the frequency of the high frequency power is shown. This is because the etching target is a silicon oxide film and relatively high ion energy is required for etching. On the other hand, in the second embodiment, the second frequency of the high frequency power applied to the sample stage 2 as the bias is set lower than the first frequency of the high frequency power contributing to plasma generation.

FIG. 13 shows the relationship between the frequency (MHz) and the sheath voltage (V) corresponding to the ion energy, and the relationship between the frequency (MHz) and the emission intensity proportional to the ion density or the radical density for the halogen gas plasma. Is shown. When the frequency is 1 MHz or more, the ions cannot follow the alternating electric field of the bias, and the sheath voltage decreases. Further, when the frequency is 1 MHz or higher, the decomposition of gas proceeds and the density of radicals increases. From this, in order to obtain a high selection ratio for the base substrate,
It can be seen that a high frequency bias is desirable to reduce the ion energy.

When the plasma generation method of the present invention is applied to dry etching of phosphorus-doped polycrystalline silicon, the frequency of the high frequency bias power supplied to the sample stage 2 is set to 13 MHz, and the first to the first Four
The frequency of the high-frequency power for plasma generation supplied to the side electrodes 5 to 8 is set to 50 MHz, and the gas to be introduced is a mixture of chlorine and a small amount of oxygen.

It was found from the experimental results that the effect of the present invention is great when SF ₆ gas or an electronegative gas such as oxygen, chlorine or iodine is used as the etching gas. In the plasma of electronegative gas, the density of electrons is low and the resistance is high.
Electric potential gradient in plasma is electropositive
Since it is larger than gas, the effect of the present invention is particularly large.

Also in this case, the first to fourth side electrodes 5 to 5
Since the electric field inside 8 is uniform, a plasma with good uniformity can be obtained, and the uniformity of etching is also good.
Also, since there is almost no local bias of plasma, MO
The damage to the device such as the destruction of the gate oxide film of SLSI is extremely small. Etching rate is 200-400nm
/ Min value is obtained.

In the second embodiment, the case of dry etching of polycrystalline silicon is shown, but the dry etching apparatus to which the plasma generating method of the present invention is applied is S.
It is possible to obtain a high effect also for etching of i compound, metal such as Al, etching of a resist in a multilayer resist, and the like.

A CVD apparatus to which the plasma generating method according to the third embodiment of the present invention is applied will be described below with reference to FIG.

The CVD apparatus to which the third embodiment is applied is different from the dry etching apparatus shown in FIG. 1 to which the first embodiment is applied, except that a means for supplying high-frequency power to the sample stage 2 is used.
For example, the second high-frequency power source 9B, the second matching circuit 15, the second filter 16 and the counter electrode 4 shown in FIG. 1 are not provided, and the heater 23 for controlling the thickness of the deposited film is the sample. This is the point provided on the stand 2. Since the other points are the same as those of the dry etching apparatus shown in FIG. 1, the same reference numerals are given and detailed description thereof is omitted.

In this CVD apparatus, the chamber 1
It is preferable that N ₂ gas of 15 sccm and SiH ₄ gas of 15 sccm are introduced into the chamber, the pressure of these gases is set to 0.07 Pa, and the temperature of the sample stage 2 is set to 400 ° C.

FIG. 15 shows a cross section of a semiconductor chip produced by the above CVD apparatus. A thermal oxide film 41 is formed on the Si substrate 40. Aluminum 42 deposited by sputtering to a thickness of 0.8 μm
Is processed into a wiring having a width of 0.8 μm by photolithography and dry etching. The SiN film 43 is formed on the aluminum 42 by the above-mentioned CVD apparatus.
Have been deposited.

This CVD apparatus is suitable for a CVD method for a large-diameter semiconductor wafer of 6 inches or 8 inches. The reason for this is that, as explained in the case of the dry etching apparatus, this CVD apparatus can increase the spatial uniformity of plasma, so that the deposited film can be realized uniformly over the entire wafer. Is.

[0082]

As described above, according to the plasma generating method or the plasma generating apparatus of the invention of claims 1 to 14, high frequency power having the same frequency but different phases is applied to the side electrodes on the side of the plasma generating portion. Is applied to excite a high-frequency electric field or a rotating electric field in the plasma generating part, the electrons in the plasma generating part make an amplitude motion or a rotational motion, and the collision cross section of the electron and the gas molecule is effectively increased. High ionization efficiency is obtained even in vacuum, and discharge is easy.

Therefore, according to the plasma generation method or the apparatus thereof of the present invention, the high-frequency electric field of the plasma generation portion is more uniform than that of the conventional magnetic field distribution by magnetron discharge or ECR discharge, so that plasma with excellent uniformity can be obtained. Therefore, it is easy to increase the size of the plasma generator.

In addition, since the plasma generating method or its generating apparatus of the present invention has almost no local bias of plasma, when applied to a dry etching apparatus, a higher vacuum than that of a conventional parallel plate dry etching apparatus is applied. Is possible,
Since there is little ion scattering by gas molecules, it is possible to obtain a high density plasma in a wide range with high uniformity under high vacuum. Therefore, it is possible to perform highly anisotropic etching, which has excellent fine workability, high mass productivity, good uniformity, and extremely small damage to the device such as destruction of the gate oxide film. become.

Further, according to the invention of claim 1 or claims 3 to 5, high-frequency power is supplied from a high-frequency power source to one side electrode of the pair of side electrodes, and the other side electrode is provided with the high-frequency power. Since the high frequency power supplied from the high frequency power supply via the delay circuit is supplied, the high frequency power having the same frequency but different phases can be supplied by a simple circuit.

According to the second or sixth to tenth aspects of the invention, one of the three or more side electrodes is supplied with high frequency power from the high frequency power source, and the other side electrode is provided with the high frequency power. Since the high frequency powers supplied from the power supply through the delay circuits are supplied respectively, it is possible to supply the high frequency powers having the same frequency but different phases sequentially with a simple circuit.

Further, according to the inventions of claims 1 to 10, even if the input power is unbalanced for some reason between the side electrodes, the side electrodes are connected to each other by a delay circuit. Input power imbalance is automatically corrected.

According to the invention of claims 11 to 14,
For the sample stage, high-frequency power having a frequency different from that of the high-frequency power supplied to the side electrodes is passed through a filter circuit having high impedance characteristics with respect to the frequency of the high-frequency power supplied to the side electrodes. Since it is supplied, the high frequency power applied to the sample stage and the high frequency power that excites the rotating electric field and mainly contributes to plasma generation are independent from each other, so that the ion energy can be easily controlled and a stable and uniform plasma can be obtained. Can be generated.

Further, according to the invention of claim 10 or 14, a magnetic field is applied to the plasma generating part to give electrons in the plasma generating part a swirling motion in the same direction or in the opposite direction to the rotational motion of the electrons due to the rotating electric field. Since the electrons traveling in the plasma generating portion can be confined in the plasma generating portion, the generation of plasma becomes more dense and more uniform.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a structure of a dry etching apparatus to which a plasma generating method according to a first embodiment of the present invention is applied.

FIG. 2 is a circuit diagram showing an example of a delay circuit in the dry etching apparatus.

FIG. 3 is a schematic diagram showing a motion trajectory of electrons in a chamber of the dry etching apparatus.

FIG. 4 is a schematic diagram showing a motion locus of electrons in a chamber of the dry etching apparatus.

FIG. 5 is a schematic view of a case in which a motion locus of electrons in a chamber of the dry etching apparatus is projected on a horizontal plane.

FIG. 6 is a schematic view of a case where a motion locus of electrons in a chamber of the dry etching apparatus is projected on a horizontal plane.

FIG. 7 is a characteristic diagram showing the relationship between the frequency of the high frequency power applied to the side electrodes in the dry etching apparatus and the distance traveled by electrons during one cycle of the high frequency power.

FIG. 8 is a schematic diagram showing magnetic flux distribution and electron rotation in a conventional magnetron etching apparatus.

FIG. 9 is a schematic diagram showing rotation of electrons in the dry etching apparatus.

10A and 10B are diagrams illustrating a state in which boron phosphorus glass is etched by using a conventional magnetron etching apparatus, in which FIG. 10A is a sectional view showing an etched state, and FIG. 10B is a distribution of magnetic field strength. And FIG. 6C is a diagram showing the etching rate.

FIG. 11 is a diagram illustrating a state in which boron phosphorus glass is etched by using the dry etching apparatus according to the embodiment of the present invention, in which (a) is a cross-sectional view showing the etched state, and (b) is a sectional view. ) Is a diagram showing an etching rate.

FIG. 12 is a table comparing a dry etching apparatus according to an embodiment of the present invention with a conventional dry etching apparatus.

FIG. 13 is a characteristic diagram showing a relationship between frequency and sheath voltage in halogen gas plasma generated by the plasma generating method according to the second embodiment of the present invention, and a relationship between frequency and emission intensity of ions and radicals.

FIG. 14 is a schematic view showing the structure of a CVD apparatus to which the plasma generation method according to the third embodiment of the present invention is applied.

FIG. 15 is a cross-sectional view of a semiconductor chip created by the CVD device.

FIG. 16 is a schematic view showing a reactive ion etching apparatus using a conventional magnetron discharge.

[Explanation of symbols]

 1 chamber 2 sample stage 3 sample to be etched 4 counter electrode 5 first side electrode 6 second side electrode 7 third side electrode 8 fourth side electrode 9A first high frequency power supply 9B second High frequency power supply 10 First matching circuit 11 First delay circuit 12 Second delay circuit 13 Third delay circuit 14 First filter 15 Second matching circuit 16 Second filter 17 Upper circular coil 18 Lower circular Coil 19, 20 Power supply 21 Plasma generator

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Reference number within the agency FI Technical display location H01L 21/302 C 9277-4M (72) Inventor Mitsuhiro Oguni 1006 Kadoma, Kadoma-shi, Osaka Matsushita Electric Sangyo Co., Ltd. (72) Inventor Noboru Nomura Osaka Prefecture Kadoma City 1006 Kadoma Matsushita Electric Industrial Co., Ltd. (72) Inventor Ichiro Nakayama Osaka Kadoma City Kadoma 1006 Matsushita Electric Industrial Co., Ltd.

Claims (14)

[Claims] 1. A pair of side electrodes are arranged at positions facing each other through a plasma generating section in a vacuum chamber, and a high frequency power is supplied from a high frequency power source to one side electrode of the pair of side electrodes. The plasma generation is performed by supplying high-frequency power, which is supplied from the high-frequency power source through the delay circuit and has the same frequency as the high-frequency power but a different phase, to the other side electrode of the pair of side electrodes. The method for generating plasma according to claim 1, wherein a high-frequency electric field that excites the electrons in the plasma generating portion to perform an amplitude motion is excited. 2. Three or more lateral electrodes are arranged on the side of the plasma generating portion in the vacuum chamber so as to surround the plasma generating portion,
High frequency power is supplied from a high frequency power supply to one of the three or more side electrodes, and high frequency power is supplied to the other side electrode of the three or more side electrodes from the high frequency power supply via a delay circuit. Is supplied to the plasma generating part to excite a rotating electric field that causes electrons in the plasma generating part to rotate. Plasma generation method. 3. A high frequency power supply for supplying high frequency power to a pair of side electrodes provided at positions facing each other through a plasma generating portion in the vacuum chamber, and one side electrode of the pair of side electrodes. From a power supply and a delay circuit that delays high-frequency power received from the high-frequency power supply to the other side electrode of the pair of side electrodes to supply high-frequency power having the same frequency as the high-frequency power but a different phase. In addition, the plasma generating device is provided with an electric field excitation means for exciting a high frequency electric field that causes the electrons in the plasma generating part to perform an amplitude motion. 4. The plasma generator according to claim 3, wherein the side wall of the vacuum chamber is made of a dielectric material, and the pair of side electrodes is provided outside the vacuum chamber. . 5. The plasma generator according to claim 3, wherein the delay circuit is a low pass filter. 6. A high frequency power source for supplying high frequency power to one or more side electrodes of the three or more side electrodes, the three or more side electrodes being provided in a position surrounding a plasma generating portion in the vacuum chamber. A plurality of high frequency powers having the same frequency as the high frequency power but sequentially different phases are delayed by delaying the high frequency power received from the high frequency power supply to the other side electrode among the three or more side electrodes. A plasma generating apparatus comprising: a delay circuit group including a delay circuit, wherein the plasma generating unit is provided with an electric field excitation means for exciting a rotating electric field that causes electrons in the plasma generating unit to make a rotational motion. 7. The plasma generation according to claim 6, wherein the side wall of the vacuum chamber is made of a dielectric material, and the three or more side electrodes are provided outside the vacuum chamber. apparatus. 8. The plasma generator according to claim 6, wherein each of the plurality of delay circuits is a low-pass filter. 9. The plasma generator according to claim 6, wherein delay times for sequentially delaying the high frequency power received from the high frequency power supply by the delay circuit group are set to be substantially equal to each other. 10. A magnetic field that imparts to the electrons in the plasma generating section a swirling motion in the same direction or in the opposite direction to the rotational motion of the electrons produced by the rotating electric field excited by the electric field exciting means, to the plasma generating unit. The plasma generator according to claim 6, further comprising magnetic field applying means for applying the magnetic field. 11. A sample stage provided under a plasma generating section in a vacuum chamber, three or more side electrodes provided at positions surrounding the plasma generating section, and the same frequency for the three or more side electrodes. An electric field excitation means for exciting a rotating electric field that causes the electrons in the plasma generating portion to rotate in the plasma generating portion; The pedestal has high impedance characteristics with respect to the frequency of the high frequency power supplied from the first high frequency power supply means, and the high frequency power having a frequency different from the frequency of the high frequency power supplied from the first high frequency power supply means. And a second high-frequency power supply unit that supplies the high-frequency power via a filter circuit. 12. The first high frequency power supply means has high impedance characteristics with respect to the frequency of the high frequency power supplied from the second high frequency power supply means to the three or more side electrodes. The plasma generator according to claim 11, wherein the plasma generator is supplied through a filter circuit having the same. 13. The frequency of the high-frequency power supplied from the first high-frequency power supply means is set higher than the frequency of the high-frequency power supplied from the second high-frequency power supply means. The plasma generator according to claim 11. 14. A magnetic field for giving electrons in the plasma generating section a swirl motion in the same direction as or in a direction opposite to the rotational motion of the electrons produced by the rotating electric field excited by the electric field exciting means, in the plasma generating unit. The plasma generator according to claim 11, further comprising magnetic field applying means for applying the magnetic field.