JP3071814B2 - Plasma processing apparatus and processing method thereof - Google Patents

Description

The present invention relates to a plasma processing apparatus for performing plasma processing of a semiconductor such as a VLSI, and particularly to a plasma processing of a VLSI having a fine structure with a wiring width of 0.8 μm or less. The present invention relates to a plasma processing apparatus and a processing method capable of generating high-density plasma in a high vacuum (pressure of 10 ⁻³ Torr or less) and performing uniform and high-speed plasma processing on a substrate to be processed.

[Conventional technology]

As a plasma processing apparatus capable of stably generating high-density plasma in a high vacuum, there is a plasma processing apparatus using an electron cyclotron resonance phenomenon, for example, an apparatus described in Japanese Patent Application Laid-Open No. 55-141729.

[Problems to be solved by the invention]

As the integration of LSIs advances, the element structure becomes finer and more complicated, and the number of steps increases. For this reason, the chip unit price of the LSI increases, and the price per bit increases. Therefore, in order to reduce the price per bit below the current level, it is necessary to manufacture many LSIs at once, and the diameter of the substrate has been increased from 150 mm in diameter to 200 mm in diameter. Therefore, a processing apparatus capable of performing plasma processing with high uniformity is demanded. Further, with the miniaturization of the element structure, it is necessary to perform plasma processing to desired dimensions with high accuracy. In order to perform high-precision plasma processing, it is effective to perform processing in a high vacuum region where the mean free path of collision of atmospheric gas molecules in the processing chamber is long. The present invention intends to generate high-density plasma uniformly over a large area at a low pressure and to perform highly accurate plasma processing with good uniformity.

In a conventional plasma processing apparatus, since direct current or high frequency power is used as energy for plasma generation,
In particular, it was difficult to generate high-density plasma in a high vacuum region where the pressure was 10 ⁻³ Torr or less. On the other hand, electron cyclotron resonance (Electron C) is a plasma processing device that can generate high-density plasma even in a high vacuum region.
There is an apparatus (hereinafter, referred to as an ECR apparatus) using yclotron resonance. In a plasma processing apparatus using an electromagnetic wave, such as an ECR apparatus, in order to introduce an electromagnetic wave from the atmosphere into a low-pressure processing chamber while maintaining the processing chamber at a predetermined pressure, a component made of a derivative that transmits the electromagnetic wave (hereinafter, referred to as “ Windows) are indispensable.

However, in the ECR system, plasma with a size similar to the size of the "window" is generated in the vicinity of the "window". The size of the "window" is required. Therefore, in response to the increase in the diameter of the substrate, it is necessary to increase the diameter of the “window”, the means for generating a static magnetic field, and the means for introducing microwaves.
The whole device becomes huge. Therefore, it is considered that it is practically difficult to cope with a future increase in the diameter of the substrate. Further, as described later, since the microwave has a short wavelength, a standing wave of the microwave is generated in parallel with the substrate surface, the plasma density distribution becomes non-uniform, and there is a problem that the processing is likely to be non-uniform. .

An object of the present invention is to provide a plasma processing apparatus capable of generating high-density plasma even in a high vacuum and performing high-speed uniform plasma processing on a large-area substrate. Another object of the present invention is to provide a plasma processing apparatus having a configuration capable of performing the high-speed and uniform plasma processing without increasing the size of the apparatus, and a processing method thereof.

[Means for solving the problem]

In order to generate high-density plasma, it is necessary to efficiently absorb the power for plasma generation into the plasma. Further, in order to make the plasma distribution uniform, it is necessary to make the distribution of the power for plasma generation uniform. In general, the power of electromagnetic waves in an electromagnetically closed space, such as a plasma processing chamber, usually has a spatial distribution on the order of the wavelength. Therefore, it is effective to use electromagnetic waves having a long wavelength for uniformity.

Therefore, in the present invention, in order to efficiently absorb a high frequency having a longer wavelength than a microwave into a plasma, the above-described problem can be solved by providing a configuration including an antenna for exciting an electromagnetic wave called a Heusler wave in the plasma. I made it.

[Action]

An electromagnetic wave having a frequency lower than the electron cyclotron frequency that propagates in a plasma to which a static magnetic field is applied in a direction parallel to the static magnetic field is called a Heusler wave.

The amount of electromagnetic wave energy absorbed into the plasma can be evaluated by the product of the square of the current flowing in the plasma and the electrical resistance of the plasma. When energy is absorbed, an increase in plasma density, an increase in electron temperature, and the like occur. The loss of plasma is mainly caused by the absorption of electrons in the plasma on the wall of the processing chamber. Therefore, in order to generate high-density plasma, it is effective to absorb electromagnetic wave energy at a position distant from the processing chamber wall surface. The magnitude of the current flowing by the electromagnetic wave is proportional to the high-frequency magnetic flux density. Therefore, for high-density plasma generation, it is desirable to realize an electromagnetic field distribution in which the high-frequency magnetic flux density of the electromagnetic wave introduced into the plasma generation chamber becomes high in the center of the plasma generation chamber.

In order to effectively excite the Heusler wave, it is preferable to use an antenna corresponding to the wavelength of the Heusler wave. The wavelength λ of the Heusler wave can be theoretically expressed as in equation (1).

Here, λ: wavelength of Heusler wave (m) c: speed of light (= 3.0 × 10 ⁸ m / s): frequency of electromagnetic wave (Hz) _c : electron cyclotron frequency (Hz) _p : plasma frequency (Hz) The electron cyclotron frequency _c and the plasma frequency _p in the above equation are expressed as follows by the strength of the static magnetic field and the plasma density, respectively.

Here, e: charge of electron (C) B _o : magnetic flux density (T) _me : mass of electron (kg) _ne : plasma density (/ m ³ ) ε: dielectric constant of vacuum (F / m) is there.

In FIG. 9 shows an example of calculation of the relationship between the wavelength of the plasma density n _e and whistler wave the magnitude of the static magnetic field as a parameter to be applied. However, the frequency of the electromagnetic wave was 13.56 MHz. From this figure, it can be seen that, for example, when the plasma density is 10 ¹² / cm ³ , the wavelength is several tens of cm at a magnetic flux density of several hundred G (Gauss).

Here, when there is a relationship of { _c } _p (4) between the frequency of the electromagnetic wave, the electron cyclotron frequency _c , and the plasma frequency _p , the expression (1) becomes Can also be approximated.

By using the above equation (1) or equation (5), the size of the antenna for efficiently exciting the Heusler wave can be determined.

In general, in order to efficiently excite an electromagnetic wave, a half-wavelength antenna having a length of λ _o / 2 (λ _o is the wavelength of the electromagnetic wave) or an antenna having a length of an integral multiple of λ _o / 2 is used. Good. However, it is usually desirable to use a half-wavelength antenna from the viewpoint of miniaturization and reduction of loss of the antenna.

In the case of a semiconductor processing apparatus that performs single-wafer processing, the size of a processing chamber is approximately the same as the size of a substrate to be processed. Therefore, to excite the Heusler wave in this processing chamber,
The wavelength of the Heusler wave must be comparable to the size of the substrate to be processed. Wavelength of whistler wave, as shown in equation (1) or Formula (5), determined by the plasma density n _e and the magnetic flux density magnitude B _o. Here, while it is difficult to control the plasma density independently of other parameters, the magnitude of the magnetic flux density can be easily controlled. Therefore,
The magnitude of the magnetic flux density is selected so that the wavelength of the Heusler wave in the processing chamber is approximately the same as the size of the substrate to be processed, and by using an antenna corresponding to this wavelength, the energy input efficiently is used for plasma generation. be able to.

The plasma density n _o in conventional plasma processing apparatus 10
¹¹ is a to 10 ¹³ / cm ³ order. Plasma frequency _p is determined only by the plasma density n _e, as shown in equation (3), the _p corresponding to the plasma density range 2.84GHz
~ 28.4 GHz. Therefore, for example, in the case of a plasma density of 10 ¹² / cm ³ , in order to make the wavelength of the Heusler wave by the electromagnetic wave having a frequency of 13.56 MHz about 20 cm, the magnetic flux density is 20
It should be about 0G.

In order to make the plasma processing uniform, the plasma density distribution must be made uniform. Therefore, it is necessary to make the distribution of electric power used for plasma generation uniform. One of the causes of the non-uniformity of the plasma processing in the plasma processing apparatus using microwaves is that the wavelength is in the same order as the size of the processing chamber, so that the plasma processing apparatus stands in the processing chamber in a direction parallel to the substrate to be processed. A wave is generated.

It is known that in a plasma to which a static magnetic field is applied, an electromagnetic wave has different propagation characteristics depending on whether the propagation direction of the wave is parallel to or perpendicular to the static magnetic field. Normal
In the ECR device, since the static magnetic field is almost perpendicular to the substrate to be processed, one of the causes of the non-uniformity of the plasma processing in the ECR device is that an electromagnetic wave propagates in a direction perpendicular to the static magnetic field. It is considered that a standing wave is generated. Therefore, in order to eliminate non-uniformity due to this, it is only necessary to prevent waves from propagating in a direction perpendicular to the static magnetic field. There are two types of waves that propagate in a direction perpendicular to the static magnetic field: abnormal waves and normal waves. Of these, it is known that an abnormal wave does not theoretically propagate below the frequency _L represented by the following equation (6).

This frequency _L is in the microwave band in a normal plasma processing apparatus. Therefore, if an electromagnetic wave having a lower frequency is used, nonuniformity due to propagation of an abnormal wave can be avoided.

FIG. 10 shows the relationship between the wavelength and the frequency of the normal wave. The normal wave has the property that the propagation characteristics are determined only by the plasma density without being influenced by the magnitude of the static magnetic field, and that only the electromagnetic wave having the plasma frequency or higher can propagate. Therefore, if an electromagnetic wave having a frequency equal to or lower than the plasma frequency is used, generation of a standing wave in a direction perpendicular to the static magnetic field can be prevented. In a normal plasma processing apparatus, the plasma frequency is a number as described above.
Since it is in the same frequency range as microwaves on the order of GHz, the use of electromagnetic waves in a lower frequency range can prevent normal waves from propagating in the direction perpendicular to the static magnetic field, and achieve uniform plasma processing. it can.

〔Example〕

Hereinafter, embodiments of the present invention will be described with reference to the drawings. First
FIG. 1 shows a schematic configuration of a sputtering apparatus embodying the present invention. In the drawing, a processing chamber 1 is maintained at a predetermined pressure suitable for processing by a vacuum exhaust system and a gas introduction system (not shown). An electromagnet 3 is provided on the back surface of the target 2, and the generated static magnetic field confines the plasma on the surface of the target 2 at a high density.
A static magnetic field for adjusting the wavelength of the Heusler wave is generated therein. A substrate 4 to be processed is placed facing the target 2. A bias power supply 5 is connected to the substrate 4 to be processed, so that a bias potential suitable for processing can be given.
The processing chamber 1 further includes an antenna 7 connected to a high-frequency power source 6 having an oscillation frequency of, for example, 13.56 MHz.
A high-density plasma can be generated by radiating a Heusler wave into the inside. The antenna 7 is arranged so that its central axis is substantially parallel to the direction of the static magnetic field generated by the electromagnet 3. In FIG. 1, what is indicated by reference numeral 20 is a sputtering power supply.

As will be described in detail later, the antenna 7 has a structure in which two curved plates made of a highly conductive material are opposed to each other as shown in FIG. However, the antenna shown in FIGS. 6 to 8 may be used as the antenna 7.

When a conductive material is formed, it is preferable that the material of the antenna be the same as the material for the film in consideration of the possibility that the antenna is sputtered and mixed into the film as an impurity.

2 and 3 show another example of the sputtering apparatus embodying the present invention. The apparatus shown in FIGS. 2 and 3 has the same configuration as that of the sputtering apparatus shown in FIG. 1 except that the position of the antenna 7 is different. That is, FIG. 2 shows an example in which the antenna 7 is installed near the periphery of the substrate 4 to be processed.
The figure shows an example in which an antenna 7 is installed at the center of the target 2. In both cases, similarly to the embodiment shown in FIG. 1, the central axis of the antenna 7 is arranged so as to be substantially parallel to the direction of the static magnetic field generated by the electromagnet 3. In the example shown in FIG. 1, the plasma density in the processing chamber 1 is uniformly increased, whereas in the example shown in FIG. 2, a high-density plasma can be generated near the substrate 4 to be processed. The amount of ions in the plasma incident on the substrate 4 to be processed can be easily controlled by the high-frequency power applied to the antenna 7. In the example shown in FIG. 3, by disposing the antenna 7 at the center of the electromagnet 3, it is possible to prevent film-forming particles sputtered from the target 2 and moving linearly from adhering to the antenna 7. As the antenna 7, similarly to the embodiment shown in FIG. 1, an antenna shown in FIGS. 6 to 8 may be used in addition to the antenna shown in FIG.

FIG. 4 shows a schematic configuration of an etching apparatus embodying the present invention. In the figure, a processing chamber 10 is maintained at a predetermined pressure suitable for processing by a processing gas introduction system including a gas introduction port 8 and a vacuum exhaust system (not shown).
A substrate 4 to be processed is installed in the processing chamber 10. A bias power supply 9 is connected to the substrate 4 to be processed, and a bias potential suitable for processing can be applied. Above the processing chamber 10, a plasma generating chamber 11 made of a dielectric such as quartz having a small loss of electromagnetic waves is provided in connection with the processing chamber 10. Around the plasma generation chamber 11, there is an antenna 7 connected to a high frequency power supply 13 having an oscillation frequency of 13.56 MHz, for example. Further, an electromagnet 12 is provided outside the electromagnet 12 to generate a static magnetic field suitable for processing in the plasma generation chamber 11. The antenna 7 is arranged so that its central axis is substantially parallel to the direction of the static magnetic field generated by the electromagnet 12. Although the antenna shown in FIG. 5 is used here as the antenna 7, the antenna shown in FIG.
8 to 8 may be used. According to this embodiment, high-density plasma can be generated with high uniformity even in a high vacuum region, so that high-quality and high-speed processing can be achieved. In addition,
The present invention was implemented by changing the processing gas in the same configuration.
A CVD device can be configured.

In the above description, the case where the antenna 7 is located outside the plasma generation chamber 11 has been described.
It may be arranged inside 11. In this case, the plasma generation chamber
The material 11 may be a material other than the dielectric, for example, a metal such as aluminum.

Next, the antenna 7 will be described in detail. 5 to 8 show the shape of the antenna 7. Each of these antennas can be used in each of the embodiments shown in FIGS. First, FIG. 5 shows an antenna having a structure in which two curved plates 15 made of a material having a small electric resistance such as copper are opposed to each other. As shown, plate 15
Is λ / 2 (where λ is the wavelength of the Heusler wave). The oscillation frequency of the two plates 15 is, for example, 13.56 M
A high-frequency power supply 14 Hz is connected, and a Heusler wave can be excited by a high-frequency electric field generated between the plates 15.

FIG. 6 shows what is called a double loop antenna.
As shown in the figure, the height is λ / 2. The material is made of a wire 16 having a small electric resistance such as copper, for example, and a high-frequency power supply 14 having an oscillation frequency of 13.56 MHz is connected thereto. A Heusler wave can be excited by a high-frequency magnetic field generated by a high-frequency current flowing through the wire 16.

FIGS. 7 and 8 show a structure in which the antenna shown in FIGS. 5 and 6, respectively, is twisted by 180 °. It is known that a Heusler wave is a circularly polarized wave in which the plane of polarization makes a half rotation when traveling a half wavelength. Therefore, by employing the structure shown in FIGS. 7 and 8, it is possible to more efficiently excite a circularly-polarized Heusler wave. Other features are the same as those of the antenna shown in FIGS.

In the above description, FIGS. 5 to 8 all show an example in which the length is λ / 2, but a length having an integral multiple of λ / 2 may be used. In this case, the twist angle of the antenna shown in FIGS. 7 and 8 is 180 ° for the length λ / 2.

〔The invention's effect〕

According to the present invention, it is possible to obtain a plasma processing apparatus capable of generating high-density plasma with high spatial uniformity even in a high vacuum region and enabling stable and uniform processing in a high vacuum region.

[Brief description of the drawings]

1 to 3 are schematic diagrams of a sputtering apparatus embodying the present invention, FIG. 4 is a schematic diagram of an etching apparatus embodying the present invention, and FIGS. FIG. 9 is a perspective view showing an antenna for exciting a wave, FIG. 9 is a graph showing the relationship between the wavelength of a Heusler wave and the plasma density, and FIG. 10 is a graph showing the relationship between the wavelength of a normal wave and the frequency. DESCRIPTION OF SYMBOLS 1 ... Processing chamber 2 ... Target 3 ... Electromagnet 4 ... Substrate to be processed 5 ... Bias power supply 6 ... High frequency power supply 7 ... Antenna 8 ... Gas inlet 9 ... Bias Power supply, 10 Processing chamber 11 Plasma generation chamber 12 Electromagnet 13, 14 High frequency power supply 15 Plate, 16 Wire rod

Continuation of the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) C23C 14/00-14/58 H01L 21/3065 H01L 21/203 H01L 21/205

Claims (4)

(57) [Claims] 1. A plasma processing apparatus comprising a static magnetic field generating means and an electromagnetic wave generating means for plasma processing an object to be processed installed in a processing chamber, wherein the plasma processing apparatus excites a Heusler wave in the processing chamber. A plasma processing apparatus characterized in that the antenna means has a structure twisted by half a rotation per half wavelength of a Heusler wave in a direction substantially parallel to the static magnetic field. 2. A plasma processing apparatus comprising a static magnetic field generating means and an electromagnetic wave generating means for plasma processing an object to be processed installed in a processing chamber, wherein the plasma processing apparatus excites a Heusler wave in the processing chamber. A plasma processing apparatus, comprising: a plurality of opposed flat plates having a length corresponding to a half wavelength of a Heusler wave in a direction substantially parallel to the static magnetic field. . 3. A plasma processing method in which an object to be processed installed in a processing chamber is plasma-processed by a plasma generated in the processing chamber by generating a static magnetic field and introducing an electromagnetic wave, wherein the processing chamber includes an antenna. A plasma processing method characterized by using means for exciting a Heusler wave having a wavelength substantially equal to the length of the surface of the object to be processed. 4. A plasma processing method for performing plasma processing on an object placed in a processing chamber with plasma generated in the processing chamber by generating a static magnetic field and introducing an electromagnetic wave, wherein the frequency of the electromagnetic wave is in a microwave band. A plasma processing method using an antenna having a frequency lower than that of the plate and having a length almost half of the wavelength of the electromagnetic wave and introducing the electromagnetic wave into the processing chamber.