JP2851765B2 - Plasma generation method and apparatus - Google Patents

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

The following is an example of application of the plasma generation method.
A dry etching method suitable for fine processing will be described.

[0004] The progress of modern high-density semiconductor integrated circuits is bringing about a change that can be compared with the industrial revolution. Higher densities of semiconductor integrated circuits are accompanied by miniaturization of element dimensions, improvement of devices, and large area of chip size. It has been realized by the conversion.
The miniaturization of element dimensions has been progressing to the order of the wavelength of light, and the use of excimer lasers and soft X-rays for lithography is being studied. It can be said that dry etching plays an important role in realizing fine patterns, as well as lithography.

[0005] Dry etching is a processing technique for removing unnecessary portions of a thin film or a substrate by utilizing a chemical or physical reaction on a gas-solid surface caused by radicals, ions, or the like existing in plasma. Reactive ion etching (RIE), which is most widely used as a dry etching technique, is to remove an unnecessary portion of a sample surface by exposing the sample to a high-frequency discharge plasma of an appropriate gas to cause an etching reaction. . Necessary portions, that is, portions not to be removed, are usually protected by a photoresist pattern used as a mask.

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

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

FIG. 16 is a schematic view showing a conventional reactive ion etching apparatus using a magnetron discharge. Reactive gas is introduced into the metallic chamber 81 via a gas controller 82, and the inside of the chamber 81 is controlled to an appropriate pressure by an exhaust system 83. An upper portion of the chamber 81 is provided with an anode (anode) 84, and a lower portion thereof is provided with a sample stage 85 serving as a cathode (cathode). 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 sets of a pair of AC electromagnets 88 facing each other are provided in a state where the phases are different from each other by 90 degrees. A rotating magnetic field is applied to the inside of the chamber 81 by the two sets of AC electromagnets 88. And facilitates discharge in a high vacuum. In this case, the electrons move in a cycloid motion due to the rotating magnetic field, so that the movement path of the electrons is lengthened, and the ionization efficiency is increased.

[0009]

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

For example, in a conventional magnetron reactive ion etching apparatus, the local bias of plasma is equalized by averaging over time by a rotating magnetic field. However, the instantaneous plasma density is not uniform. A local potential difference occurs. For this reason, the conventional magnetron reactive ion etching apparatus is
When applied to the I process, the gate oxide film may be broken.

Similarly, in an ECR etching apparatus,
Since the magnetic field is distributed in the radial direction of the chamber, local unevenness of the plasma density occurs, which causes unevenness of the etching species and a local potential difference.
Due to the non-uniformity of the plasma, the uniformity of the etching deteriorates, and it becomes difficult to produce LSIs with a 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 using a thinner gate oxide film.

A conventional parallel plate type magnetron etching apparatus of 13.56 MHz excitation has a frequency of 100 to 200M.
Attempts have also been made to increase the density of plasma by superimposing high-frequency power of Hz, thereby reducing the self-bias voltage and reducing damage to the sample due to high-energy ions.

However, according to this method, although a high density of plasma can be achieved, it is difficult to improve the uniformity of the plasma. Therefore, it is not enough to solve the above-mentioned problem caused by the non-uniformity of the plasma. I can not say.

The present invention has been made in view of the above problems, and provides a plasma generation method and apparatus for the same, which have high density and excellent uniformity under a high vacuum, thereby improving the fine workability and causing less damage to devices. The purpose is to:

[0015]

In order to achieve the above object, the invention according to claims 1 to 6 is directed to a side electrode disposed so as to surround a plasma generating section at the same frequency via a delay circuit. By applying high-frequency power having a different phase, a rotating electric field that causes a rotating motion of electrons in the plasma generating unit is excited in the plasma generating unit.

[0016]

According to a first aspect of the present invention, there is provided a plasma generating method comprising the steps of: arranging three or more side electrodes on a side of a plasma generating portion in a vacuum chamber so as to surround the plasma generating portion; A high-frequency power is supplied from a high-frequency power supply to one of the above-mentioned side electrodes, and a high-frequency power is supplied from the high-frequency power supply to the other one of the three or more side electrodes via a delay circuit. By supplying high-frequency power having the same frequency as the high-frequency power and sequentially having different phases, a rotating electric field that causes the electrons in the plasma generating portion to rotate is excited in the plasma generating portion.

[0018]

[0019]

[0020]

According to a second aspect of the present invention, there is provided a plasma generating apparatus comprising: a plasma generator; and three or more side electrodes provided at positions surrounding a plasma generating part in a vacuum chamber. A high-frequency power supply for supplying high-frequency power to one of the side electrodes, and to the other one of the three or more side electrodes,
The high frequency power received from the high frequency power source is delayed by delaying the high frequency power, and the high frequency power has the same frequency and the phase is sequentially changed. An electric field exciting means for exciting a rotating electric field that causes the electrons in the plasma generating section to make a rotational motion is provided.

According to a third aspect of the present invention, in the configuration of the second aspect , the side wall of the vacuum chamber is formed of a dielectric material.
The side electrodes described above add a configuration provided outside the vacuum chamber.

According to a fourth aspect of the present invention, in addition to the configuration of the second aspect, a configuration in which each of the plurality of delay circuits is a low-pass filter is added.

According to a fifth aspect of the present invention, in the configuration of the second aspect , the delay circuits for sequentially delaying the high-frequency power received from the high-frequency power supply are set to have substantially equal delay times. It is to be added.

According to a sixth aspect of the present invention, in the configuration of the second aspect , the electrons in the plasma generating portion are directed in the same direction as or opposite to the direction of the rotational motion of the electrons caused by the rotating electric field excited by the electric field exciting means. And a magnetic field applying means for applying a magnetic field for giving a swirling motion to the plasma generating section.

The invention of claim 7 to 10, both made different from the frequency of the RF power supplied to the frequency of the RF power supplied to the sample stage disposed a lateral electrodes so as to surround the plasma generation portion, The high frequency power supplied to the sample stage is made to have a high impedance with respect to the frequency of the high frequency power supplied to the side electrode.

According to a seventh aspect of the present invention, there is provided a plasma generating apparatus comprising: a plasma generating device provided in a vacuum chamber at a position surrounding a sample stage provided below a plasma generating unit and surrounding the plasma generating unit; The plasma generator includes three or more side electrodes and first high-frequency power supply means for supplying high-frequency power having the same frequency and different phases sequentially to the three or more side electrodes. Electric field exciting means for exciting a rotating electric field that causes a rotating motion to occur,
High frequency power having a frequency different from the frequency of the high frequency power supplied from the high frequency power supply means through a filter circuit having high impedance characteristics with respect to the frequency of the high frequency power supplied from the first high frequency power supply means. And a second high-frequency power supply means for supplying to the sample stage.

According to an eighth aspect of the present invention, in the configuration of the seventh 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. This configuration adds a configuration in which the frequency of the high-frequency power is supplied through a filter circuit having high impedance characteristics.

According to a ninth aspect of the present invention, in the configuration of the seventh aspect , the frequency of the high-frequency power supplied from the first high-frequency power supply is equal to the frequency of the high-frequency power supplied from the second high-frequency power supply. The configuration is added to be set higher than the above.

According to a tenth aspect of the present invention, in the configuration of the seventh aspect ,
Magnetic field applying means for applying to the plasma generating unit a magnetic field that gives a rotating motion in the same or opposite direction to the direction of the rotational motion of the electrons caused by the rotating electric field excited by the electric field exciting means to the electrons in the plasma generating unit. The configuration of being provided is added.

[0031]

[0032]

[0033]

[0034]

[0035]

[Action] According to the plasma generating method or apparatus according to claim 1 or claim 2, in the plasma generating unit electrons, while being allowed to rotary motion by a rotating electric field is excited in the plasma generating portion, the kinetic energy of the own Proceed along the direction. Such electron motion effectively increases the cross-sectional area of collision between electrons and gas molecules, so that compared to a conventional parallel-plate plasma generator, high ionization efficiency can be obtained even in a high vacuum and discharge can be achieved. It will be easier.

Further, since the high-frequency electric field of the plasma generating section is more uniform than that of the magnetic field distribution by the conventional plasma generating method or apparatus, it is possible to obtain 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 of three or more side electrodes, and the high-frequency power source is supplied to another side electrode. , The high-frequency powers supplied sequentially through the delay circuit from each other can be supplied by a simple circuit.

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

[0039] According to the plasma generating apparatus of claim 7, since the frequency on the side electrode on the side of the plasma generating portion to form a rotating field in the plasma generating portion by applying sequentially different frequency power phases are the same, the Similarly, since the electrons in the plasma generating section move in the direction of their own kinetic energy while rotating, high ionization efficiency can be obtained and discharge can be facilitated even in a high vacuum.

A high frequency power having a frequency different from the frequency of the high frequency power supplied from the first high frequency power supply to the side electrode is supplied to the sample stage from the second high frequency power supply. It is supplied through a filter circuit with high impedance characteristics to the frequency of the high-frequency power supplied to the sample stage from the means, so that it excites the high-frequency power applied to the sample stage and the rotating electric field and mainly contributes to plasma generation Are independent of each other.

[0041] According to the plasma generating apparatus according to claim 6 or 10, electrons in the plasma generating portion is allowed to translating cycloid movement center of rotational movement is translated by rotating the electric field of the aforementioned, translating cycloid motion by the magnetic field of the above The translational motion component of the electron is converted into a swirling motion component that swirls the plasma generating unit. For this reason, the electrons in the plasma generating unit move such that the center of the rotational motion provided by the rotating electric field proceeds on the trajectory of the swirling motion provided by the magnetic field, and the electrons escape from the plasma generating unit. Without making a cycloidal motion accompanied by a rotational motion.

[0042]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A dry etching apparatus to which a plasma generating method according to a first embodiment 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 stage provided at the lower part of the chamber 1, 3 is a sample to be etched formed of a semiconductor wafer mounted on the sample stage 2, and 4 is a chamber. Is a counter electrode of the sample stage 2 provided on the upper part of the sample table. Reference numerals 5, 6, 7, and 8 denote first, second, third, and fourth side electrodes formed of parallel plate electrodes provided on the side of the chamber 1, respectively. 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 having a frequency of 10 MHz from a first high-frequency power supply 9 A via a first matching circuit 10.
Between the first to fourth side electrodes 5 to 8 and the first matching circuit 10, the high frequency power (frequency of 1 MHz in this embodiment) applied to the sample stage 2 is high. A first filter 14 serving as an impedance is inserted.

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

A first delay circuit 11 is provided between the first side electrode 5 and the second side electrode 6. The high frequency power applied to the second side electrode 6 by the first delay circuit 11 has a phase difference of about 90 degrees with respect to the high frequency power applied to the first side electrode 5. Second side electrode 6
A second delay circuit 12 is provided between the second delay circuit 12 and the third side electrode 7. The high frequency power applied to the third side electrode 6 by the second delay circuit 12 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. The high frequency power applied to the fourth side electrode 8 by the third delay circuit 13 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 m is generally selected to be about 1.27. The delay time Td in the first to third delay circuits 11, 12, 13 is represented by Td = (LC) ^1/2 .

An 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 set to 0.1 Pa to 10 Pa by a turbo pump (not shown). Controlled to a 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 DC power supplies or pulse power supplies, whereby a magnetic field in a direction substantially perpendicular to the sample table 2 is applied inside the chamber 1. .

Hereinafter, the operation of the dry etching apparatus configured as described above will be described 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 section 21. Electronic e
While being rotated by the rotating electric field applied to the plasma generating unit 21, it travels in the direction of its own kinetic energy.

Although not shown, the plasma generator 2
1, only the first side electrode 5 and the third side electrode 7 are provided, or only the second side electrode 6 and the fourth side electrode 8 are provided via the plasma generator 21. Alternatively, high-frequency powers having the same frequency and different phases, which are supplied from the same high-frequency power supply and provided with a phase difference of 180 degrees by the delay circuit, may be supplied to the pair of opposed side electrodes. In this way, the electrons in the plasma generation unit 21 travel in the direction of their own kinetic energy while being caused to move in amplitude by the high-frequency electric field applied to the plasma generation unit 21.

FIG. 7 is a graph showing the distance traveled by the electron e during one cycle of the high frequency power as a function of frequency. Here, 20 eV electrons are assumed. 20e in X direction
Electrons e traveling with V energy move about 6 cm during 20 nanoseconds, which is one cycle of 50 MHz high frequency power. Assuming that the distance between the side electrodes is 30 cm, the electrons e have 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 the number of amplitudes during traveling between the side electrodes decreases.

Although it depends on the type of gas, electron energy of about 15 eV or more is generally required to ionize the gas. Since ionization occurs due to collision between the electron e and gas molecules, the longer the traveling distance of the electron e, the greater the probability of collision and the higher the ionization efficiency. Therefore, in the present invention, the traveling distance of the electrons is increased by rotating or oscillating the electrons, thereby increasing the ionization efficiency. It can also be seen that the cross-sectional area of the collision between the electrons and the gas molecules has been effectively increased by the rotation or amplitude motion 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 electron e with high-frequency power to improve the ionization efficiency.
A high frequency of MHz or higher is required. However 50M
Even if high-frequency power of a frequency lower than 1 Hz is applied and the traveling distance of the electron e decreases, the probability that the electron with a low energy makes a rotational motion or an amplitude motion and collides with the chamber wall and disappears. The ionization efficiency is increased because the electron density decreases 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 also perform a swirling motion due to the magnetic field in addition to the rotational motion or the amplitude motion due to the electric field. Efficiency can be realized.

FIG. 4 shows the upper and lower circular coils 17,
3 shows a motion path of electrons e when a magnetic field in a direction perpendicular to the sample stage 2 is applied to the rotating electric field shown in FIG. Thereby, the translational movement of the electrons e traveling toward the side wall of the chamber 1 in the state of FIG. The magnitude of this pivoting motion 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 pivoting motion is perpendicular to both the applied electric and magnetic fields. Direction. As a result,
The electron e performs a motion in which a cyclotron swirling motion caused by a magnetic field is superimposed on a rotating motion caused by a rotating electric field caused by high-frequency power.

FIGS. 5 and 6 show the case where the above-described magnetic field is applied to the electron e in the state of FIG. 3 while changing the strength of the magnetic field.
Shows how the movement path of the subject changes. As described above, by applying an electric field and a magnetic field to the plasma generation unit 21 and causing the electrons of the plasma generation unit 21 to perform a rotating motion or a rotating motion with an amplitude motion, most of the electrons e in the plasma generation unit 21 are converted. The electron e can be confined in the plasma generator 21 and the traveling distance of the electron e can be increased.
Thereby, the density of the electrons e in the plasma generating section 21 increases, and the ionization efficiency increases.

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

When considering the direction crossing from the left side to the right side in the center of the plasma generating portion 21, the density of electrons e decreases in the central portion where the magnetic field intensity is weak, so that the plasma density also decreases and the magnetic field intensity increases. Since the density of the electrons e increases in the outer peripheral portion, the plasma density also increases.
In the conventional dry etching apparatus, the plasma density becomes non-uniform in this way, resulting in non-uniform etching and damage to a 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 section 21 surrounded by the first to fourth side electrodes 5, 6, 7, 8 is determined. And the magnetic field is almost uniform,
As shown in FIG. 9, the locus of the cycloidal motion accompanied by the rotational motion of the electron e becomes almost equal in each place, so that the plasma density becomes almost uniform in the entire region of the plasma generating section 21. Therefore, according to this dry etching apparatus, reactive radicals and ions generated from the reactive gas for etching in the plasma generating section 21 are irradiated almost uniformly on 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 section 21, damage due to charge-up is extremely reduced, and the etching rate is increased due to the high plasma density.

FIG. 10A schematically shows an example in which boron phosphorus glass is etched by a conventional magnetron etching apparatus using a rotating magnetic field. FIG. 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 at the center of the sample stage, the light is incident on the surface of the Si substrate 30. The resulting ion flux I is proportional to the plasma density distribution corresponding to the magnetic field intensity distribution, and becomes sparse at the center as shown in FIG. As shown in FIG. 10C, the etching rate of the oxide film (boron phosphorus glass 31) also substantially follows the ion flux I and becomes non-uniform. Also, non-uniform plasma density causes damage to the device due to uneven distribution of charge.

FIG. 11 (a) schematically shows an example in which boron phosphorus glass is etched by a dry etching apparatus to which the plasma generation method of the present invention is applied. According to this dry etching apparatus, as described above, since substantially uniform plasma is generated, as shown in FIG. 11A, the ion flux II, which is a reaction product for etching, incident on the surface of the Si substrate 30 is also uniform. , And the etching rate becomes high as shown in FIG. Further, since the plasma is uniform, uneven distribution of the charge is small, and damage due to the charge is extremely small. In this case, the gas introduced into the chamber 1 is CHF ₃ +
A gas based on chlorofluorocarbon, such as O ₂ , 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.
m / min.

This dry etching apparatus is particularly suitable for etching a submicron pattern and for etching a semiconductor wafer having a large diameter such as 6 inches or 8 inches. The reason is that ion scattering is small because the pressure in the chamber 1 is low, so that the pattern of the dimensional shift (so-called CD loss), which is the value obtained by subtracting the line width of the sample after etching from the line width of the photoresist pattern, and the pattern of the etching rate This is because the dependence on the dimensions is small, and because the uniformity of the plasma is high, the size of the chamber 1 can be easily increased.

In this embodiment, as described above, the high-frequency power is supplied to the first to fourth side electrodes 5 to 8 that control the plasma density applied to the sample 3 to be etched and generate a 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, a circuit for supplying high-frequency power to the sample stage 2 includes first to fourth side electrodes 5.
A second filter 16 having high impedance characteristics with respect to the frequency of the high-frequency power supplied to .about.8 is inserted. As a result, the circuit for supplying high-frequency power to the first to fourth side electrodes 5 to 8 and the circuit for supplying high-frequency power to the sample stage 2 become independent from each other, and generate stable and uniform plasma. Can be.

FIG. 12 shows a comparison between the conventional dry etching method and the above-described dry etching method, and it can be understood that the 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, and
By applying high-frequency power having the same frequency that differs by about 90 degrees from each other in 8 to rotate the electron e of the plasma generating unit 21 in a vacuum state, it is excellent in high density and uniformity despite high vacuum. Generated plasma can be generated.

By controlling the high-frequency power supplied to the sample stage 2, it is possible to control the selectivity with respect to the base during etching. Further, since there is almost no local deviation of the plasma, damage to the workpiece can be extremely reduced.

In the present 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. The effect of the present invention can be obtained even if the phase difference is different from 90 degrees. 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.

Hereinafter, a plasma generating method according to the second embodiment of the present invention will be described.

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. In this case, the frequency is set higher than 1 MHz which is the frequency of the high frequency power. This is because the object to be etched is a silicon oxide film, which requires relatively high ion energy 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 a 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 radical density, for the halogen gas plasma. It is shown. If the frequency is 1 MHz or more, the ions cannot follow the AC electric field of the bias, so that the sheath voltage decreases. When the frequency is 1 MHz or more, the decomposition of the gas proceeds, and the density of radicals increases. For this reason, when it is desired to obtain a high selectivity with respect to the underlying substrate,
It can be seen that a high frequency bias is desirable to reduce 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 power for bias supplied to the sample stage 2 is set to 13 MHz, and 4
The frequency of the high frequency power for plasma generation supplied to the side electrodes 5 to 8 is set to 50 MHz, and a gas to be introduced is a mixture of chlorine and a small amount of oxygen.

[0074] As the etching gas, SF ₆ gas or oxygen, chlorine, iodine electro negative (negative) of arsenide when using gas, greater effects of the present invention is obtained from the experimental results. In an electronegative (negative) gas plasma, the electron density is low and the resistance is high,
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, 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 the SLSI is extremely small. Etching rate is 200-400nm
/ Min.

In the second embodiment, the case of dry etching of polycrystalline silicon has been described. However, the dry etching apparatus to which the plasma generating method of the present invention is applied is an S
High effects can also be obtained in etching a metal such as an i-compound or Al, or etching a resist in a multilayer resist.

Hereinafter, a CVD apparatus to which the plasma generating method according to the third embodiment of the present invention is applied will be described 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.
For example, the point that the second high-frequency power supply 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 a sample This is a point provided on the table 2. The other points are the same as those of the dry etching apparatus shown in FIG. 1, and the detailed description thereof will be omitted by retaining the same reference numerals.

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

FIG. 15 shows a cross section of a semiconductor chip formed by the CVD apparatus. On the Si substrate 40, a thermal oxide film 41 is formed. 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.
Has been deposited.

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

[0082]

As described above, according to the plasma generating method or the plasma generating apparatus according to the first to tenth aspects of the present invention, the high frequency power having the same frequency and the different phase is applied to the side electrodes on the side of the plasma generating section. Is applied to excite a high-frequency electric field or a rotating electric field in the plasma generating unit, so that electrons in the plasma generating unit perform amplitude motion or rotational motion, and the collision cross section between the electrons and the gas molecules is effectively increased. High ionization efficiency is obtained even in vacuum, and discharge is easy.

Therefore, according to the plasma generating method or the apparatus of the present invention, the high-frequency electric field of the plasma generating portion is more uniform than the conventional magnetic field distribution by the magnetron discharge or the ECR discharge, so that the plasma having excellent uniformity can be obtained. Therefore, the size of the plasma generator can be easily increased.

Further, the plasma generating method or the plasma generating apparatus of the present invention has almost no local bias of plasma, so that when applied to a dry etching apparatus, a higher vacuum is required as compared with a conventional parallel plate dry etching apparatus. Is possible,
Since ion scattering by gas molecules is small, it is possible to obtain high-density and high-uniformity plasma over a wide range under high vacuum. For this reason, it is possible to perform highly anisotropic etching, and it is possible to perform etching with excellent fine processing, high mass productivity, uniformity, and extremely little damage to devices such as gate oxide film destruction. become.

[0085]

According to the first to sixth aspects of the present invention, high-frequency power is supplied from a high-frequency power source to one of the three or more side electrodes, and the other high-frequency power source is supplied to the other side electrodes. Since the high-frequency power supplied through the sequential delay circuit is supplied, the high-frequency power having the same frequency and sequentially different phases can be supplied by a simple circuit.

According to the first to sixth aspects of the present invention, even if the input power is unbalanced between the side electrodes for some reason, the side electrodes are connected to each other by the delay circuit. The input power imbalance is automatically corrected.

According to the invention of claims 7 to 10 , high frequency power having a frequency different from the frequency of the high frequency power supplied to the side electrode is supplied to the sample stage. Since 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 of each other because the power is supplied through a filter circuit that has high impedance characteristics for the frequency of In addition, the control of ion energy is facilitated, and stable and uniform plasma can be generated.

Further, according to the invention of claim 6 or 10 , a magnetic field is applied to the plasma generating section so as to give the electrons in the plasma generating section a turning motion in the same or opposite direction to the rotational motion of the electrons by the rotating electric field. Since electrons traveling in the plasma generating section can be confined in the plasma generating section, the density of plasma generation becomes higher and more uniform.

[Brief description of the drawings]

FIG. 1 is a schematic view showing a structure of a dry etching apparatus to which a plasma generation 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 locus of movement of electrons in a chamber of the dry etching apparatus.

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

FIG. 5 is a schematic diagram showing a case where a movement trajectory of electrons in a chamber of the dry etching apparatus is projected on a horizontal plane.

FIG. 6 is a schematic diagram showing a case where a movement trajectory of electrons in a chamber of the dry etching apparatus is projected on a horizontal plane.

FIG. 7 is a characteristic diagram showing a relationship between a frequency of high-frequency power applied to a side electrode in the dry etching apparatus and a distance traveled by an electron 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.

FIGS. 10A and 10B are diagrams illustrating a state in which boron phosphorus glass is etched using a conventional magnetron etching apparatus, wherein FIG. 10A is a cross-sectional view showing the etched state, and FIG. FIG. 3C is a diagram showing an etching rate.

11A and 11B are diagrams illustrating a state in which boron phosphorus glass is etched using a dry etching apparatus according to an embodiment of the present invention, wherein FIG. 11A is a cross-sectional view illustrating an etched state, and FIG. () 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 the relationship between the frequency and sheath voltage and the relationship between the frequency and the emission intensity of ions and radicals in the halogen gas plasma generated by the plasma generation method according to the second embodiment of the present invention.

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

FIG. 15 is a sectional view of a semiconductor chip produced by the CVD apparatus.

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

[Explanation of symbols]

 Reference Signs List 1 chamber 2 sample table 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

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Mitsuhiro Ohkuni 1006 Kadoma Kadoma, Osaka Prefecture Inside Matsushita Electric Industrial Co., Ltd. (72) Inventor Ichiro Nakayama 1006 Kazuma, Kadoma, Osaka Pref. Matsushita Electric Industrial Co., Ltd. (56) References JP-A-4-167400 (JP, A) (58) Fields investigated (Int. ⁶ , DB name) H05H 1/46 C23F 4/00 H01L 21/3065

Claims (10)

(57) [Claims] At least three side electrodes are arranged on a side of a plasma generating section in a vacuum chamber so as to surround the plasma generating section,
A high-frequency power is supplied from a high-frequency power supply to one of the three or more side electrodes, and a high-frequency power is supplied to the other one of the three or more side electrodes from the high-frequency power supply via a delay circuit. And supplying a high-frequency power having the same frequency as the high-frequency power and having a sequentially different phase, thereby exciting a rotating electric field that causes the electrons in the plasma generating portion to perform a rotational motion in the plasma generating portion. Plasma generation method. 2. A high-frequency power supply for supplying high-frequency power to one or more of the three or more side electrodes provided at a position surrounding the plasma generating unit in the vacuum chamber. A plurality of the three or more side electrodes, each of which supplies high-frequency power received from the high-frequency power source to another side electrode and supplies high-frequency power having the same frequency as the high-frequency power and sequentially different phases. A plasma generating apparatus comprising: a delay circuit group including a delay circuit; and wherein the plasma generating unit includes an electric field exciting unit that excites a rotating electric field that causes a rotating motion of electrons in the plasma generating unit. 3. The plasma generation according to claim 2 , wherein a side wall of the vacuum chamber is formed of a dielectric material, and the three or more side electrodes are provided outside the vacuum chamber. apparatus. 4. The plasma generator according to claim 2 , wherein each of the plurality of delay circuits is a low-pass filter. 5. The claims, characterized in that the delay circuit group is the high frequency power from the receiving sequentially delayed allowed to delay the high frequency power was being set to be substantially equal to each other
Item 3. The plasma generator according to item 2 . 6. A magnetic field that gives a rotating motion in the same or opposite direction to the direction of the rotational motion of the electrons caused by the rotating electric field excited by the electric field exciting means to the electrons in the plasma generating unit. 3. The plasma generating apparatus according to claim 2 , further comprising a magnetic field applying means for applying the magnetic field. 7. A sample stage provided below a plasma generation unit in a vacuum chamber, three or more side electrodes provided at a position surrounding the plasma generation unit, and a frequency equal to the three or more side electrodes. Electric field exciting means for exciting a rotating electric field that causes the electrons in the plasma generating section to make a rotational motion in the plasma generating section; The table has high impedance characteristics with respect to the frequency of the high-frequency power supplied from the first high-frequency power supply means, 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 means for supplying the high-frequency power through a filter circuit. 8. The first high frequency power supply means applies the high frequency power to the three or more side electrodes with high impedance characteristics with respect to the frequency of the high frequency power supplied from the second high frequency power supply means. The plasma generator according to claim 7 , wherein the power is supplied through a filter circuit. 9. 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 7 , wherein: 10. A magnetic field, which gives a rotating motion in the same or opposite direction as the direction of the rotational motion of the electron caused by the rotating electric field excited by the electric field exciting means, to the plasma generating unit, to the electrons in the plasma generating unit. The plasma generating apparatus according to claim 7 , further comprising a magnetic field applying means for applying the magnetic field.