JP2761172B2 - Plasma generator - 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 generator using a high-frequency discharge.

[0002]

2. Description of the Related Art Plasma generation methods using high-frequency discharge are used in various fields such as dry etching for fine processing, sputtering and plasma CVD for thin film formation, and ion implantation equipment. Plasma generation in a high vacuum is required for miniaturization and high-precision control of film quality.

The following is an example of application of the plasma generation method.
Dry etching 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 device dimensions has been progressing to the order of the wavelength of light, and the use of excimer lasers and X-rays for lithography is promising. It can be said that dry etching plays an important role in realizing fine patterns along with 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 between a gas phase and a 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 protected by a host resist pattern usually 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. It is effective to increase the degree of vacuum of the plasma generator to increase the mean free path of ions in order to make the directionality of ions uniform. However, if the degree of vacuum in the plasma chamber is increased, high-frequency discharge is difficult to occur. There is.

Therefore, as a countermeasure, a method of applying a magnetic field to the plasma chamber to facilitate the generation of discharge, for example, a magnetron RIE or ECR dry etching technique has been developed.

FIG. 13 is a schematic diagram showing a conventional ion etching apparatus using magnetron discharge. A reactive gas is introduced into the metallic chamber 51 via a gas controller 52, and an exhaust system 53 is provided in the chamber 51.
Is controlled to an appropriate pressure. Chamber 51
An anode 54 is provided on the upper part of the sample, and a sample stage 55 serving as a cathode is provided on the lower part. An RF power supply 57 is connected to the sample stage 55 via an impedance matching circuit 56, so that high-frequency discharge can be generated between the sample stage 55 and the anode 54. On each side of the chamber 51, a pair of AC electromagnets 58 facing each other have a phase of 90.
Two sets are provided in different states, and a rotating magnetic field is applied into the chamber 51 by the two sets of AC electromagnets 58, thereby facilitating 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.

FIG. 14A shows a conventional magnetron RI.
E and ECR dry etching equipment show an example of etching boron phosphorus glass.
0 is a Si substrate, 61 is boron phosphorus glass, and 62 is a photoresist pattern.

[0010]

However, the conventional apparatus as described above has a problem that the device element is damaged as described below. In the conventional magnetron RIE apparatus, the local bias of the plasma is averaged over time by the rotating magnetic field to equalize the bias of the plasma. However, as shown in FIG. Has a distribution in the radial direction, the unevenness of the etching type occurs due to the local density of the plasma density, and a local potential difference occurs.
For this reason, a conventional magnetron RIE device is replaced with a MOSLS.
When applied to the I process, there is a problem that a gate oxide film is broken.

Similarly, in the ECR apparatus, since the magnetic field generally has a distribution in the radial direction of the chamber, there is a local variation in the plasma density, which causes non-uniformity of the etching species and a local potential difference. There was a problem to do.

Therefore, in Japanese Patent Application No. 2-402319, the phase of the vacuum chamber and the N first electrodes provided at substantially equal intervals in the vacuum chamber are shifted by approximately (360 / N) degrees. A first high-frequency power supply for applying high-frequency power of a frequency to the first electrodes in the order in which they are arranged, and a plasma generator surrounded by the first electrodes by a rotating electric field formed by the first electrodes Generating means for generating high-density plasma at a second electrode, a second electrode and a ground electrode provided in the vacuum chamber, and a second electrode connected to the second electrode.
There has been proposed a plasma generating apparatus including an ion extracting means for extracting ions from the plasma generated in the plasma generating section, the ion generating means being composed of a second high frequency power supply for applying a high frequency power of a frequency.

According to this plasma generator, high-density and uniform plasma can be generated under high vacuum. However, the present invention can generate more uniform plasma. Accordingly, it is an object of the present invention to provide a plasma generator having excellent fine workability and extremely little damage to a device.

[0014]

In order to achieve the above-mentioned object, according to the first aspect of the present invention, the electric field formed by the second electrode of the plasma extracting means and the ground electrode is the first electrode of the plasma generating means. Specifically, a vacuum chamber and N (N is an integer of 2 or more) N-th vacuum chambers provided at substantially equal intervals in the vacuum chamber are prevented. 1 electrode and phase is approximately (360 / N)
A first high-frequency power supply for applying high-frequency power of a first frequency, which is shifted every time, to the first electrode in the order in which they are arranged, the first electrode being supplied to the first electrode by a rotating electric field formed by the first electrode; A plasma generating means for generating high-density plasma in the enclosed plasma generating portion; a second electrode and a ground electrode provided in the vacuum chamber; and a second electrode for applying high-frequency power of a second frequency to the second electrode. A plasma generating apparatus comprising: a high-frequency power supply source and an ion extracting means for extracting ions from plasma generated in the plasma generating section;
The electric field formed by the ground electrode and the second electrode is provided at a position where it does not interfere with the rotating electric field formed by the first electrode.

According to a second aspect of the present invention, in the configuration of the first aspect, the first electrode is provided on each side of the vacuum chamber, and the second electrode and the ground electrode are provided at the bottom of the vacuum chamber. Are added to the configuration.

According to a third aspect of the present invention, in addition to the configuration of the second aspect, a configuration is provided in which the ground electrode is formed in a ring shape and is provided around the second electrode.

According to a fourth aspect of the present invention, the distance between the first electrode and the ground electrode is greater than the distance between the second electrode and the ground electrode. This is to add a configuration that is set to be large.

According to a fifth aspect of the present invention, in the configuration of the first to fourth aspects, the first frequency of the high-frequency power applied to the first electrode is equal to the second frequency of the high-frequency power applied to the second electrode. This is to add a configuration that the frequency is set higher than the frequency.

According to a sixth aspect of the present invention, in addition to the first to fifth aspects, a configuration in which the wall surface of the vacuum chamber is insulated is added.

According to a seventh aspect of the present invention, in the configuration of the first to sixth aspects, the surface of the first electrode is covered with a protective film for preventing sputter from adhering to the first electrode. The configuration is added.

According to an eighth aspect of the present invention, a configuration is provided in which the degree of vacuum in the vacuum chamber is set to 10 Pa or less to the configurations of the first to seventh aspects.

[0022]

According to the first aspect of the present invention, the rotation of electrons induced by the rotating electric field formed by the first electrode of the plasma generating means or the movement of drawing a Lissajous figure such as a cycloid makes it possible to maintain a high level even in a high vacuum. High ionization efficiency is obtained, and high-density plasma is generated in the plasma generation section.
Compared with the conventional magnetron discharge or ECR discharge by a magnetic field, the uniform electric field provides plasma with excellent uniformity, and the apparatus can be easily enlarged. Also, since there is almost no local deviation of the plasma, damage to the workpiece is extremely small.

Further, the ground electrode of the ion extraction means is provided at a position where the electric field formed by the ground electrode and the second electrode does not interfere with the rotating electric field formed by the first electrode. The phenomenon that the electric field formed by the second electrode and the ground electrode disturbs the high-density plasma generated by the rotating electric field formed by the first electrode is suppressed.

According to the second aspect of the present invention, the first electrode is provided on the side of the vacuum chamber, and the second electrode and the ground electrode are provided on the bottom of the vacuum chamber. Can reliably suppress the phenomenon of disturbing the high-density plasma generated by the rotating electric field formed by the first electrode.

According to the third aspect of the present invention, since the ground electrode is formed in a ring shape and is provided around the second electrode, the electric field formed by the second electrode and the ground electrode is the same as that of the first embodiment. The phenomenon of disturbing the high-density plasma generated by the rotating electric field formed by the one electrode can be more reliably suppressed.

According to the fourth aspect of the present invention, the distance between the first electrode and the ground electrode is set to be larger than the distance between the second electrode and the ground electrode. Plasma is generated between the first electrode and the ground electrode, in combination with the fact that the electric field formed by the electrode and the rotating electric field formed by the first electrode do not interfere with each other. However, since plasma is generated only between the second electrode and the ground electrode, the plasma generated between the second electrode and the ground electrode is generated by the plasma generated between the first electrode and the ground electrode. It will not be disturbed.

According to the fifth aspect of the present invention, the first frequency of the high-frequency power applied to the first electrode is set higher than the second frequency of the high-frequency power applied to the second electrode.
Since the first high frequency applied to the first electric field is higher, the radius of rotation of the electrons in the plasma is reduced, and a higher density plasma is generated by the rotating electric field formed by the first electrode. Further, since the first frequency is higher than the second frequency, not only ions but also electrons follow the electric field formed by the second electrode and the ground electrode, and the direction of the ions is disturbed by the electrons following the ions. That phenomenon can be avoided.

According to the structure of claim 6, since the wall surface of the vacuum chamber is insulated, the wall surface of the vacuum chamber is charged more negatively than the plasma potential, so that the loss of plasma is reduced.

According to the seventh aspect of the present invention, since the surface of the first electrode is covered with the protective film, no sputter adheres to the first electrode, and the first electrode is insulative because the protective film is insulating. The efficiency of secondary electron emission from the substrate is improved.

According to the structure of claim 8, since the degree of vacuum in the vacuum chamber is set to 10 Pa or less, the free path distance of electrons is short, and the density of plasma increases.

[0031]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a first embodiment of the present invention, where N =
3 shows the structure of a dry etching apparatus as a plasma generator in the case of No. 3. FIG. 2 shows a longitudinal sectional structure of the dry etching apparatus, and FIG. 3 shows a transverse sectional structure of the dry etching apparatus. In FIG. 1, reference numeral 1 denotes a grounded chamber having a wall surface covered with an insulator such as ceramic, Teflon or quartz, and the inside of the chamber 1 constitutes a vacuum chamber. Instead of covering the wall surface 1a of the chamber 1 with an insulator, a separate member from the chamber 1 such as an inner chamber made of quartz or the like may be provided inside the chamber 1.

The first wall 1a of the chamber 1 has
, Three side electrodes 2A, 2B, 2C are provided at substantially equal intervals, that is, circumferentially at angular positions of 120 °. Each of the side electrodes 2A, 2B, and 2C has the first discharge power from the first high-frequency power supply sources 3A, 3B, and 3C, which has the same discharge power but different power phases by about 120 °.
High frequency power of a frequency is applied. That is, the phase of the side electrode 2B leads the phase of the side electrode 2A by 120 °, and the phase of the side electrode 2C lags the phase of the side electrode 2A by 120 °. Each side electrode 2A, 2B, 2
C is adjusted to 3 MHz from 15 MHz via a matching circuit (not shown).
Although high-frequency power of 00 MHz is applied, in this embodiment, each of the side electrodes 2A, 2B, 2C
Is applied with high-frequency power having a frequency of 50 MHz. A phase shifter (not shown) realizes a phase difference of 120 ° between the high-frequency powers supplied to the side electrodes 2A, 2B, 2C.

The above-mentioned three side electrodes 2A, 2B, 2C
And the first high-frequency power supply sources 3A, 3B, 3C constitute a plasma generating means.
A high-density plasma is generated in the plasma generating portion inside each of the side electrodes 2A, 2B, 2C by the rotating electric field formed by the high-frequency power applied to A, 2B, 2C. In this case, the side electrodes 2A, 2B, 2C do not need to be grounded. The reason is that the three side electrodes 2A, 2B, and 2C to which high-frequency powers having different phases are sequentially applied play a role with each other.

A sample stage 4 as a second electrode is provided at the bottom of the chamber 1, and a ring-shaped earth electrode 5 is provided outside the sample stage 4. The sample table 4 is supplied from the second high frequency power supply 6 to a second frequency, for example, 13.56 M.
Hz high frequency power is applied.

In the first embodiment, the shape of the chamber 1 is cylindrical, the diameter of the chamber 1 is 400 mm,
The height of the chamber 1 is 400 mm, and the side electrodes 2A, 2
The height of B and 2C is 50 mm, and the diameter of the sample stage 4 is 200 m
m. The distance between each lateral electrodes 2A, 2B, 2C and the ground electrode 5: L ₁ is 200 mm, the distance between the sample stage 4 and the earth electrode 4: L ₂ is 30 mm.

Further, an etching gas is introduced into the chamber 1 through an inlet 1b via an asflow controller (not shown), and the introduced etching gas is exhausted from an outlet 1c to the outside. The pressure inside the chamber 1 is controlled to about 0.1 Pa to 10 Pa by a turbo pump (not shown).

FIG. 4 shows the result of measuring the electron density by the Langmuir probe method in the above etching apparatus. The measurement area is composed of three side electrodes 2A, 2B,
Ar gas is used as an etching gas below the plasma generating section surrounded by 2C, and the pressure inside the chamber 1 is 1 Pa. And each side electrode 2A, 2B, 2
C has a phase shift of 120 ° and a frequency of 50 MH
30 W of high-frequency power, which is z
The frequency of 13.56 MHz is set on the sample stage 4 on which a is mounted.
Of 30 W high frequency power was applied. Then, the probe 7 shown in FIG. 2 is inserted at a height position between each of the side electrodes 2A, 2B, 2C and the sample table 4 inside the chamber 1, and from the center of the sample table 4 in the horizontal direction from -100 mm. +
The electron density was measured at a position up to 100 mm.

As shown in FIG. 4, a highly uniform plasma is generated without using a magnetic field under a high vacuum of 1 Pa due to the rotating electric field and the confinement of electrons. The degree of vacuum greatly affects the uniformity of the plasma. At a degree of vacuum of 10 Pa or more, the plasma is localized near the side electrodes 2A, 2B, and 2C, so that the uniformity of the plasma is slightly reduced.

FIG. 5 shows that the position of the ground electrode 5 is changed so that the distance from the center of the sample table 4 to the horizontal direction is from -100 mm to +100 mm.
The result of having measured the electron density in the position up to mm is shown. FIG. 5A shows a case where the ground electrode 5 is installed on the upper part of the chamber 1, and FIG. 5B shows a case where the ground electrode 5 is placed almost in the middle between the side electrodes 2 A, 2 B and 2 C and the sample table 4. FIG. 5C shows the case of this embodiment, that is, each side electrode 2.
A, 2B, the distance between the 2C and the ground electrode 5: L ₁ 2
And the distance between the sample stage 4 and the ground electrode 5:
The L ₂ respectively show when set to 30 mm.

In the case of FIG. 5A, the electric field formed by the sample stage 4 and the ground electrode 5 is applied to each of the side electrodes 2A, 2A.
Since it interferes with the rotating electric field formed by B and 2C, the plasma generated by the side electrodes 2A, 2B and 2C is disturbed, and the plasma density is not uniform. This is because a strong discharge occurs between each side electrode 2A, 2B, 2C and the ground electrode 5 to generate plasma, and a discharge between the sample stage 4 and the ground electrode 5 becomes weak. It is believed that there is. In the case of FIG. 5B, the plasma density is made uniform as compared with the case of FIG. 5A, but the plasma density is not uniform at the periphery of the sample stage 4. this is,
It is considered that the same level of discharge occurs between both the side electrodes 2A, 2B, 2C and the ground electrode 5 and between the sample stage 4 and the ground electrode 5, and plasma is generated on both sides. On the other hand, in the case of FIG. 5C, the plasma density is also uniform at the periphery of the sample table 4. This is considered to be because no discharge occurs between each of the side electrodes 2A, 2B, 2C and the ground electrode 5, and no plasma is generated.

Hereinafter, the relationship between the first frequency f ₁ of the high-frequency power applied to each of the side electrodes 2A, 2B, 2C and the second frequency f ₂ of the high-frequency power applied to the sample table 4 will be considered.

In the case of the first embodiment, each side electrode 2A, 2
A high frequency power of a frequency of 50 MHz is applied to B and 2C, and a high frequency power of a frequency of 13.56 MHz is applied to the sample stage 4. The frequency of the high-frequency power applied to the sample table 4 without changing other parameters is 50 MHz
Changing to, the uniformity of the plasma deteriorated. When the frequency of the high-frequency power applied to the sample stage 4 is changed to 70 MHz, the power density of the plasma stage is highly dependent on the sample stage 4, and it becomes difficult to independently control the ion energy and the plasma density.

By setting the first frequency f ₁ higher than the second frequency f ₂ , the rotating electric field formed by the side electrodes 2 A, 2 B, and 2 C is applied to plasma generation, and the sample table 4 and the ground electrode 5 are connected to each other. Can be applied to the extraction of ions from the plasma generated in the plasma generator. The energy obtained by a charge in a high-frequency electric field is approximately inversely proportional to its mass. Since the mass of an ion is several thousand times or more than the mass of an electron,
Ions cannot follow a high-frequency electric field of MHz or more, but only electrons follow. By setting the first frequency f ₁ to about 10 MHz or higher and higher than the second frequency f ₂ , only the electrons follow the rotating electric field generated by the side electrodes 2A, 2B, 2C, and the first frequency f ₁ Can be used exclusively for plasma generation. Also, the second frequency f ₂
Less than the first frequency f ₁ , preferably 10 MHz
If below, the ion energy incident on the sample stage 4 can be controlled by the high-frequency power of a second frequency f _2.

FIG. 6A shows a state in which the first frequency f ₁ is higher than the second frequency f ₂ , and FIG.
Frequency f ₁ indicates a state in the second less than the frequency f _2. In the case of FIG. 6A, since the electrons of the plasma generating unit do not follow the electric field formed by the sample table 4 and the ground electrode 5, the direction of the ions is not disturbed by the electrons. In the case of 6 (b), not only the ions of the plasma generating part but also the electrons follow the electric field formed by the sample table 4 and the ground electrode 5, and the direction of the ions is disturbed by the electrons following the ions. . Therefore, FIG.
In the case of (a), it is possible to independently control the plasma generated in the plasma generating unit and the ions extracted from the plasma, but in the case of FIG. 6 (b), the plasma generated in the plasma generating unit is controlled. And the ions extracted from the plasma are difficult to control independently.

Hereinafter, the insulating property of the wall surface 1a of the chamber 1 will be considered.

In the first embodiment, the wall surface 1a of the chamber 1 was covered with an insulator such as ceramic, Teflon or quartz. However, the case where the wall surface 1a of the chamber 4 was exposed to metal was examined. If the metal is exposed,
Each side electrode 2A, 2B, 2C and wall surface 1a of chamber 1
And the discharge between the side electrodes 2A, 2B and 2C is not stable, so that the plasma density is
a was less than half of that in the case where it was covered with an insulator.

In the case of the first embodiment, each side electrode 2A, 2
The surfaces of B, 2C and the sample stage 4 are covered with a protective film made of alumina. This means that when coated with alumina, the plasma density is 10 to 30% lower than when the metal is exposed.
This is because what can be increased has been experimentally obtained. Further, when each of the side electrodes 2A, 2B, 2C is covered with an insulating protective film, sputtering to each of the side electrodes 2A, 2B, 2C does not occur, and metal contamination in the chamber 1 due to sputtering is prevented. can do.

Hereinafter, results of dry etching performed using the dry etching apparatus according to the first embodiment will be described.

First, the etching of the polysilicon film will be described with reference to FIG. The structure of the film is shown in FIG.
As shown in FIG.
O ₂ 12 is formed, n ⁺ Pol on the thermal SiO ₂ 12
A y-Si film 13 is formed, and an n ⁺ Poly-Si film 13 is formed.
Is formed thereon. The etching conditions were such that the flow rate of the etching gas Cl ₂ was 80 sccm,
The degree of vacuum is 1 Pa, the frequency of the high frequency power applied to the sample stage 4 is 13.56 MHz, the power is 30 W, and the frequency of 50 MHz is applied to each of the side electrodes 2A, 2B, 2C.
Of high-frequency power of 30 W and 40 W, respectively.
Dry etching was performed while changing to W, 50 W, 60 W, and 70 W. As a result, as shown in FIG.
Regarding the etching shape, a good vertical shape was obtained under all conditions.

FIG. 8 shows the power dependence of the etching characteristics of the n ⁺ Poly-Si film 13 on the side electrodes 2A, 2B, 2C. Although the etching rate increases in proportion to the increase in power, the uniformity of the etching rate
Under all conditions, it is within the range of 1 to 5%. A selectivity (to a thermal oxide film) of 250 was obtained at an etching rate of 600 nm / min, which was excellent.

From this result, it is possible to obtain a low-power and low-power n ⁺ Poly-Si film 13 without using a deposition gas (for example, HBr) and applying a magnetic field as compared with the conventional dry etching apparatus. It has been found that good etching characteristics (uniform etching, high etching rate, high selectivity, and vertical shape) can be obtained.

Next, the etching of the aluminum silicon film will be described with reference to FIG. The structure of the film is as shown in FIG. 9A, in which a BPSG film 15 is formed on a silicon substrate 11, and an BPSG film 15 is formed on the BPSG film 15.
An l-Si (1%)-Cu (0.5%) film 16 is formed, and a resist 14 is formed on the Al-Si (1%)-Cu (0.5%) film 16. Etching conditions are
The etching gas is BCl ₃ / Cl ₂ = 50/60 scc
m, the degree of vacuum is 0.5 Pa, and each side electrode 2A, 2A
The frequency of the high frequency power applied to B and 2C is 200 MHz
The power was set to 100 W, the frequency of the high-frequency power applied to the sample stage 4 was set to 2 MHz, and the power was set to 50 W. As a result, as shown in FIG. 9B, a favorable vertical shape was obtained under an optimized condition for the etched shape.

FIG. 10 shows a graph of Al—Si (1%) — Cu
(0.5%) shows the dependence of the etching characteristics of the film 16 on the N ₂ gas flow rate. As shown in FIG.
The etching rate is 600 n under the condition that the shape of the Si (1%)-Cu (0.5%) film 16 becomes a forward taper.
At the time of m / min, the selectivity (to resist) 5 is obtained,
It was good. Further, the uniformity of the etching rate is within the range of 1 to 5% under all conditions.

From these results, it can be seen that, compared to the conventional dry etching apparatus, Al—Si (1%) is used at a lower power and without using a deposition gas (eg, CHCl 3 or HBr) and without applying a magnetic field. ) -Cu (0.
5%) It was found that good etching characteristics could be obtained for the film 16.

Next, the etching of the BPSG film (silicon oxide film containing boron and phosphorus) 16 will be described with reference to FIG. The structure of the film is as shown in FIG.
Is formed, and a resist 14 is formed on the BPSG film 15. The etching conditions are etching gas CF ₄
At a flow rate of 50 sccm, and an etching gas CH ₂ F ₂
And the vacuum degree is 0.7 Pa
And the frequency of the high-frequency power applied to the sample stage 4 is 600
The frequency was 30 kHz and the power was 30-100 W. The frequency of the high frequency power applied to each of the side electrodes 2A, 2B, 2C was 30 MHz, and the power was changed to perform dry etching. As a result, as shown in FIG. 11B, a favorable vertical shape was obtained for the etched shape. The etching rate increases with an increase in high-frequency power. Then, a selectivity (to silicon) of 90 was obtained at an etching rate of 400 nm / min, which was excellent. Further, the uniformity of the etching rate is within the range of 1 to 5% under all conditions. Further, a phenomenon in which the etching rate decreases with an increase in the aspect ratio, that is, a so-called microloading effect, was not detected when the aspect ratio was 5 or less. Further, charge-up damage evaluation using a MOS structure TEG was performed, but no damage was detected even for a gate oxide film having a thickness of 10 nm. This is considered to be due to good plasma uniformity.

From these results, it was found that the BPSG film 15 can obtain good etching characteristics without a microloading effect and no damage as compared with the conventional dry etching apparatus.

FIG. 12 shows a second embodiment of the present invention.
4 shows the structure of a dry etching apparatus as a plasma generating apparatus when = 4.

The same members as those in the first embodiment are denoted by the same reference numerals as those in the first embodiment, and the detailed description is omitted. Inside the wall surface 1a of the chamber 1, four side electrodes 2A, 2B, 2C, 2D as first electrodes are provided at substantially equal intervals, that is, at circumferentially angular positions at 90 ° intervals. . Each side electrode 2A, 2B, 2C, 2D has a first
From the high frequency power supply sources 3A, 3B, 3C, and 3D, the high frequency power of the first frequency having the same discharge power but different power phases by about 90 ° is applied. That is, the side electrode 2B is ahead of the side electrode 2A by 90 °, the side electrode 2C is ahead of the side electrode 2A by 180 °, and the side electrode 2D is the side electrode 2A. 270 degrees ahead. Each side electrode 2A, 2B, 2
30 MHz for C and 2D via a matching circuit (not shown)
, And a 90 ° phase difference between the high-frequency powers is realized by a phase shifter (not shown). The side electrodes 2A, 2B, 2C,
The height relationship between 2D and the chamber 1 is the same as in the first embodiment.

The sample stage 4 is a fifth electrode, and the ground electrode 5 is provided around the sample stage 4 as in the first embodiment.
And at an interval of about 30 mm.

As in the first embodiment, the chamber 1
, An etching gas is introduced via an asflow controller (not shown), and the pressure inside the chamber 1 is controlled to about 0.1 Pa to 10 Pa by a turbo pump (not shown).

In the first embodiment, N = 3,
Although N = 4 in the second embodiment, N can be appropriately selected from integers of 2 or more.

In the first and second embodiments, an etching apparatus is described as a plasma generator. However, the plasma generator of the present invention is not limited to an ion source such as a plasma CVD apparatus or a sputter ion implantation apparatus. It goes without saying that the present invention can be applied to an apparatus that requires high-density plasma under a high vacuum.

Further, in the first and second embodiments, the phase difference of the high-frequency power is set to 120 ° or 9 °, respectively.
Although the case where the angle is fixed to 0 ° has been described, the phase difference of the high-frequency power may be changed as a function of time.

[0065]

As described above, according to the plasma generator according to the first aspect of the present invention, the earth electrode of the ion extracting means is configured such that the electric field formed by the earth electrode and the second electrode is the first electric field. Since it is provided at a position that does not interfere with the rotating electric field formed by the electrodes, the electric field formed by the second electrode and the ground electrode generates a high-density plasma generated by the rotating electric field formed by the first electrode. Since the scattering phenomenon is suppressed, the plasma in the plasma generating section becomes dense and uniform. Therefore, according to the plasma generator according to the first aspect of the present invention, fine processing is excellent and damage to the device is reduced.

According to the second aspect of the present invention, the first electrode is provided on the side of the vacuum chamber and the second electrode is provided on the side of the vacuum chamber.
And the earth electrode are provided at the bottom of the vacuum chamber, so that the electric field formed by the second electrode and the earth electrode generates high-density plasma generated by the rotating electric field formed by the first electrode. Disturbing phenomena can be reliably suppressed.

According to the third aspect of the present invention, since the ground electrode is formed in a ring shape and provided around the second electrode, the ground electrode is formed by the second electrode and the ground electrode. The phenomenon in which the generated electric field disturbs the high-density plasma generated by the rotating electric field formed by the first electrode can be more reliably suppressed.

According to the plasma generator according to the fourth aspect of the present invention, the distance between the first electrode and the ground electrode is set larger than the distance between the second electrode and the ground electrode. The electric field formed by the second electrode and the ground electrode is provided at a position that does not interfere with the rotating electric field formed by the first electrode. Does not generate plasma, the plasma generated between the second electrode and the ground electrode is not disturbed by the plasma generated between the first electrode and the ground electrode. Plasma becomes more uniform.

According to the fifth aspect of the present invention, the first frequency of the high-frequency power applied to the first electrode is set higher than the second frequency of the high-frequency power applied to the second electrode. Since the first high frequency applied to the first electric field is high, a higher density plasma is generated by the rotating electric field formed by the first electrode, and the first frequency is higher than the second frequency. Therefore, the electrons do not follow ions extracted by the electric field formed by the second electrode and the ground electrode, and the directionality of the ions is not disturbed, so that the anisotropic etching can be reliably performed.

According to the plasma generating apparatus of the present invention, the wall surface of the vacuum chamber is insulated and is charged more negatively than the plasma potential, so that the loss of plasma is reduced. Good plasma generation can be realized.

According to the plasma generating apparatus of the present invention, the surface of the first electrode is covered with the protective film, and the sputter does not adhere to the first electrode. Can be prevented from deteriorating due to sputtering, and the phenomenon that the vacuum chamber is contaminated and the device being processed is contaminated with impurities, and since the protective film has insulating properties, secondary electrons from the first electrode can be prevented. The emission efficiency is increased, and the density of the plasma is improved.

According to the plasma generating apparatus of the present invention, since the degree of vacuum in the vacuum chamber is set to 10 Pa or less, the free path distance of electrons is shortened and the plasma density is increased.

[Brief description of the drawings]

FIG. 1 is a schematic view showing a dry etching apparatus as a first embodiment of a plasma generating apparatus according to the present invention.

FIG. 2 is a longitudinal sectional view of the dry etching apparatus of the first embodiment.

FIG. 3 is a cross-sectional view of the dry etching apparatus of the first embodiment.

FIG. 4 is a view showing a result of measuring an electron density by a Langmuir probe method in the dry etching apparatus of the first embodiment.

FIGS. 5A and 5B show the results of measuring the electron density by changing the position of the ground electrode in the dry etching apparatus of the first embodiment, and FIG. 5A shows the case where the ground electrode is installed in the upper part of the chamber; Indicates a case where the ground electrode is located substantially in the middle between the side electrode and the sample table, and FIG. 4C shows a case where the distance between the side electrode and the ground electrode is larger than the distance between the sample table and the ground electrode. .

FIGS. 6A and 6B show the relationship between the magnitude of the first frequency and the second frequency and the plasma generation state in the dry etching apparatus of the first embodiment, and FIG.
(B) is a case where the first frequency is lower than the second frequency.

FIGS. 7A and 7B show a state where dry etching is performed on a polysilicon film using the dry etching apparatus according to the first embodiment, FIG. 7A shows a state before dry etching, and FIG. This is the later state.

FIG. 8 is a diagram showing the power dependence of etching characteristics on a side electrode when dry etching is performed on a polysilicon film using the dry etching apparatus according to the first embodiment.

FIGS. 9A and 9B show a state where dry etching is performed on an aluminum silicon film using the dry etching apparatus according to the first embodiment, FIG. 9A shows a state before dry etching, and FIG. This is the later state.

FIG. 10 is a diagram showing the dependence of etching characteristics on the flow rate of N ₂ gas when dry etching is performed on an aluminum silicon film using the dry etching apparatus according to the first embodiment.

11A and 11B show a state in which dry etching is performed on the BPSG film using the dry etching apparatus according to the first embodiment, FIG. 11A shows a state before dry etching, and FIG. 11B shows a state after dry etching. It is a state of.

FIG. 12 is a schematic view showing a dry etching apparatus as a second embodiment of the plasma generating apparatus according to the present invention.

FIG. 13 is a schematic diagram showing a dry etching apparatus as a conventional plasma generator.

FIG. 14A shows a state in which boron phosphorus glass is etched by a conventional dry etching apparatus, and FIG.
Shows the distribution of the magnetic field above the sample stage when the dry etching is performed.

[Explanation of symbols]

 Reference Signs List 1 chamber 1a wall surface 1b inlet 1c outlet 2A, 2B, 2C, 2D side electrode (first electrode) 3A, 3B, 3C, 3D first high-frequency power supply source 4 sample table (second electrode) 5 Earth electrode 6 Second high frequency power supply 7 Probe

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI H01L 21/205 H01L 21/205 21/3065 21/302 B (72) Inventor Nakayama Ichiro 1006 Kazuma Kazuma, Kadoma City, Osaka Matsushita Electric (72) Inventor Norihiko Tamaki 1006 Oaza Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (56) References JP-A-3-30424 (JP, A) JP-A-4-215430 ( JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) H05H 1/00-1/54 C23C 14/34 C23C 16/50 C23F 4/00 H01L 21/205 H01L 21/302

Claims (8)

(57) [Claims] 1. A vacuum chamber and a first electrode (N is an integer of 2 or more) provided at substantially equal intervals in the vacuum chamber and having a phase shifted by approximately (360 / N) degrees. A first high-frequency power supply for applying high-frequency power of a frequency to the first electrodes in the order in which they are arranged, and a plasma generator surrounded by the first electrodes by a rotating electric field formed by the first electrodes Generating means for generating high-density plasma, a second electrode and a ground electrode provided in the vacuum chamber, and a second high-frequency power supply for applying a high-frequency power of a second frequency to the second electrode A plasma generating apparatus comprising an ion extracting means for extracting ions from the plasma generated in the plasma generating unit.
The plasma generation, wherein the ground electrode is provided at a position where an electric field formed by the ground electrode and the second electrode does not interfere with a rotating electric field formed by the first electrode. apparatus. 2. The method according to claim 1, wherein the first electrode is provided on a side of the vacuum chamber, and the second electrode and a ground electrode are provided on a bottom of the vacuum chamber. Item 2. The plasma generator according to item 1. 3. The plasma generator according to claim 2, wherein the ground electrode is formed in a ring shape and is provided around the second electrode. 4. A distance between the first electrode and the ground electrode is set to be larger than a distance between the second electrode and the ground electrode. The plasma generator according to any one of claims 1 to 3. 5. The apparatus according to claim 1, wherein a first frequency of the high-frequency power applied to the first electrode is set higher than a second frequency of the high-frequency power applied to the second electrode. Item 5. The plasma generator according to any one of Items 1 to 4. 6. The plasma generator according to claim 1, wherein a wall surface of the vacuum chamber is insulated. 7. The method according to claim 1, wherein a surface of said first electrode is covered with an insulating protective film for preventing sputter from adhering to said first electrode. The plasma generator according to claim 1. 8. The plasma generator according to claim 1, wherein the degree of vacuum in the vacuum chamber is set to 10 Pa or less.