JPH01236635A - Plasma processing and device therefor - Google Patents

Abstract

PURPOSE:To improve the plasma producing efficiency compared with the case of applying microwaves and obtain a high plasma processing efficiency by using laser beams as electromagnetic waves. CONSTITUTION:A laser beam oscillator 22 is provided to discharge plasma gas by laser beams 4. Since the laser beams 4 are used as the electromagnetic beams to discharge the reactive gas, if the shape and dimension of a vacuum vessel are set up to meet the cavity-resonance requirements for the laser beams 4, the stationary waves can be easily produced in the vacuum vessel due to the even phase and directivity of the laser beams 4. Furthermore, the reactive gas can be provided with the temperature higher than that in the laser beams 4 due to the notably lower entropy in the laser beams 4. Through these procedures, the producing efficiency of plasma can be improved to increase the plasma processing efficiency even if the oscillating power is only 1/250 of the microwaves.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a plasma processing method and apparatus, and particularly to a plasma processing method and apparatus using electron cyclotron resonance (hereinafter referred to as ECR).

(Prior Art) In a conventional plasma processing apparatus using ECR, the electromagnetic waves that ionize the reaction gas are microwaves, and the following are known.

(1) As described in JP-A-56-155535, a plasma generation chamber and a sample chamber are arranged separately, and in the plasma generation chamber, ions are brought into a highly excited state by cyclotron resonance, and further, A device for increasing the efficiency of microwave discharge by making the plasma generation chamber have a shape and dimensions that satisfy the conditions of a microwave cavity resonator.

(2) A device that uses a permanent magnet to generate magnetic flux for causing ECR, as described in Japanese Patent Application Laid-Open No. 58-125820.

FIG. 2 is a schematic diagram of the main parts of the device (1),
Plasma generation chamber 11 plasma processing chamber 3, substrate holder 11 that supports substrate 2, introduction pipe 5 that introduces microwave 21
(The magnetron, which is a microwave oscillator, is not shown)
Electromagnetic wave introduction window 6, magnetic field coil 7 for generating a magnetic field that satisfies ECR conditions, exhaust port 8 (exhaust system not shown),
Reaction gas supply pipe 9.10 (reaction gas supply system not shown)
The reactant gas common supply pipe 9 also serves as a gas common supply pipe for plasma generation), an inlet 12 for the plasma flow 14, and an electromagnetic wave reflection plate 13.

Plasma processing chamber 3 has a diameter of 350 m + eφ and a length of 300 m.
The substrate holder 11 is made of stainless steel with a diameter of 150 m.
It is made of alumina of n+mφ.

The plasma introduction port 12 has a diameter of 100 mmφ, and the distance to the ECR surface generated in the plasma generation chamber 1 is 130 m.
ff! It is.

The plasma generation chamber 1 has a diameter of 200 nmφ and a height of 2
An electromagnetic wave introducing window 6 made of transparent quartz is installed at a position of 60n+m, and a reflecting plate 13 for generating standing waves is installed below.

The magnetic flux density distribution of the magnetic field generated by the magnetic field coil 7 is
The magnetic field distribution is such that it diverges from the electromagnetic wave introducing window 6 toward the substrate 2, and is set so that the plasma flow efficiently flows toward the substrate.

(Problems to be Solved by the Invention) In the method described in the above-mentioned Japanese Patent Application Laid-open No. 56-155535, the conditions of the microwave cavity in the plasma generation chamber 1 are changed in order to improve the degree of excitation of ions. A standing wave was generated within the generation chamber with a satisfactory shape and dimensions.

However, no consideration was given to the propagation characteristics of the introduced high-frequency waves and the absorption characteristics of high-frequency waves by gas-phase particles.

That is, since the microwaves generated by the magnetron are not uniform in phase and directivity, if they are reflected within the generation chamber 1, the microwaves will interfere with each other.

Therefore, there was a problem in that the plasma generation efficiency was low compared to the microwave power introduced into the generation chamber to generate plasma.

Further, all of the above-mentioned conventional techniques utilize highly excited plasma species generated on the ECR surface.

However, the degree of excitation of ions generated on the ECR surface is gradually lost due to energy dissipation and collisions with other particles while reaching the surface to be processed. Moreover, when the distance to the surface to be processed becomes longer than the mean free path of the ions, this condition becomes even more pronounced.

Therefore, when the plasma generation chamber and the sample chamber are arranged separately as in the prior art, the degree of excitation of the ions is lost due to collisions with other particles before reaching the surface to be processed. Plasma treatment efficiency was low.

Furthermore, in the prior art, the ECR surface is not formed parallel to the surface to be processed. However, the quality and thickness of the deposited film are EC
It largely depends on the distance between the R surface and the surface to be processed. Therefore, particularly when processing a large number of objects to be processed simultaneously or when processing a large surface to be processed, there is a problem in that the film thickness and film quality are not uniform between the objects to be processed or on the surface to be processed.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems and to provide a plasma processing method and apparatus that are compact and have high plasma processing efficiency.

(Means for Solving the Problems) In order to solve the above-mentioned problems, the present invention has the following features: 7. In a plasma processing apparatus using child cyclotron resonance, a laser beam is used as an electromagnetic wave for discharging plasma gas. The points are distinctive.

A further feature is that the vacuum vessel serves both as a plasma generation chamber and a plasma processing chamber, and is set in a shape and size that satisfies conditions for cavity resonance of the electromagnetic waves introduced.

Furthermore, the present invention is characterized in that the reaction gas medium contains at least the same substance as the laser beam medium.

A further feature is that the laser beam is incident almost parallel to the surface to be processed, so that the ECR surface is formed parallel and continuously over the entire surface of the object to be processed.

(Function) Since a laser beam is used as the electromagnetic wave to discharge the reactant gas, if the shape and dimensions of the vacuum container are set to satisfy the conditions for cavity resonance of the laser beam, the phase and directivity of the laser beam can be adjusted. Since the properties are uniform, standing waves can be easily generated within the vacuum container.

Additionally, laser beams have significantly lower entropy;
A temperature higher than the temperature of the laser beam can be applied to the reactant gas.

Therefore, plasma generation efficiency is improved, and plasma processing efficiency can be improved.

Furthermore, since the vacuum container serves both as the plasma generation chamber and the sample chamber, the object to be processed can be placed within the mean free path of the ions, and plasma processing efficiency can be improved.

Furthermore, since the reaction gas medium contains at least the same substance as the laser beam medium, the absorption efficiency of laser energy in the gas is increased, and plasma processing efficiency can be improved.

Furthermore, since the laser beam is incident almost parallel to the surface to be processed and the ECR surface is formed approximately parallel and continuously over the entire surface of the object, the distance between the surface to be processed and the ECR surface is becomes constant.

Therefore, plasma processing can be performed simultaneously and uniformly on a plurality of objects to be processed.

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

FIG. 1 is a schematic diagram of the main parts of a plasma processing apparatus that is an embodiment of the present invention, and the same reference numerals as in FIG. 2 represent the same or equivalent parts.

This embodiment is characterized in that it is equipped with a laser beam oscillator 22, and the plasma gas is discharged by the laser beam 4.

The plasma generation chamber 1 has a diameter of 250Iφ and a height of 260Iφ.
An electromagnetic wave introduction window 6 made of transparent quartz and movable in the vertical direction is installed at the +no+ position.

Note that in the apparatuses shown in FIGS. 1 and 2, although the shape and installation position of the plasma generation chamber 1 are slightly different, the magnetic flux density distribution within the plasma generation chamber 1 is the same.

Below, the results of depositing a SiO□ film using the apparatus of the present invention will be explained in comparison with the conventional plasma processing apparatus shown in FIG.

The substrate 2, which is the object to be processed, is a silicon wafer with a diameter of 100 cm.

Oxygen 02 is introduced from the reaction gas supply pipe 9 at a rate of 200 ml/ml, and monosilane S is introduced from the reaction gas supply pipe 10.
iH4 was introduced at a rate of 30 Ill/min.

At the exhaust port 8, exhaust was performed so that the pressure inside the container was maintained at 2 mTorr.

In addition, the magnetic field coil 7 causes the magnetic flux density inside the container to become EC.
A magnetic field of 875 Gauss or higher satisfying the R condition was generated.

In the apparatus of the present invention shown in FIG. 1, an H20 laser beam with an output IW and an oscillation frequency of 2.45 GHz was introduced through the electromagnetic wave introduction window 6.

Furthermore, in the prior art device shown in FIG. 2, microwaves with an output of 250 W and an oscillation frequency of 2.45 GHz were introduced through the electromagnetic wave introduction window 6.

The reaction time at this time is from the time when SiHa is introduced until the time when the introduction is stopped.

FIG. 3 is a diagram showing the relationship between the deposition rate of the S L O2 film and the number of reflections of electromagnetic waves. In particular, the dotted line shows the deposition rate in the case of the conventional technique using microwaves, and the solid line shows the relationship between the deposition rate and the number of reflections of electromagnetic waves. The figure shows the deposition rate when using

Note that the number of reflections of the laser beam within the plasma generation chamber 1 was changed by changing the introduction angle of the laser beam and the height of the electromagnetic wave introduction window 6.

As is clear from the figure, when the number of reflections is one, the deposition rate using the conventional technique is faster, but when the number of reflections exceeds two, the deposition rate of the S102 film using the apparatus of the present invention is faster. It gets faster. Furthermore, when the number of reflections exceeds 15, the deposition rate is more than four times that of the prior art.

From the results of this practical training, we found that if a laser beam with uniform phase and directivity and a low entropy value is used as the electromagnetic wave to excite gas, even if the oscillation power is 1/250 of that of microwaves, It can be seen that the plasma processing efficiency can be improved.

FIG. 4 shows 5102 in the apparatus of the present invention shown in FIG.
It is a diagram showing the relationship between the deposition rate and etching rate of the film and the oscillation frequency of the laser beam, where the mark indicates the relationship between the deposition rate and the oscillation frequency, and the mark X indicates the relationship between the etching rate and the oscillation frequency. It shows.

The etching rate shown on the vertical axis is the etching rate of the SiO2 film using a buffered hydrofluoric acid solution (HF:NH4F-1:6, solution temperature 25°C), and the etching rate of the SiO2 film is
This is a measure of the density of the two films. That is,
A slow etching rate means that the film is highly dense.

The electromagnetic wave used in this example has an oscillation frequency of 1.42GH
z N2 laser, 2.45 GHz H20 laser, 5.9 GHz ruby laser, 29.4 THz CO2
The lasers are a 474 THz He-Ne laser and an 890 THz N2 laser. Laser beam power is IW.

The number of reflections was set to 20.

Note that the other conditions are the same as above.

In this embodiment, in order to generate a magnetic flux density that satisfies the ECR conditions, the magnetic field coil 7 is made of a superconducting material and cooled with liquid nitrogen to generate a magnetic flux density of up to 0. 32
The magnetic flux density of GGauss was generated.

Furthermore, when using a CO2 laser, the electromagnetic wave introduction window 6 was changed to KRS-5 material, which is thallium iodide material.

As is clear from FIG. 4, the deposition rate increases rapidly when the oscillation frequency of the laser beam becomes approximately IGHz or less.

Further, the etching rate becomes slower when the oscillation frequency of the laser beam becomes about IGHz or higher, and finally matches the etching rate of the thermal oxide film (dotted line).

That is, when a SiO3 film is deposited using a laser beam with an oscillation frequency of approximately 1 Hz or more, the denseness of the deposited film is improved.

From the above experimental results, in order to increase the deposition rate, that is, to increase the plasma processing efficiency, the oscillation frequency is approximately IG.
It is presumed that it is desirable to use a laser beam of Hz or less, and that it is desirable to use a laser beam of IGHz or more in order to improve the density of the deposited film.

Next, an embodiment capable of simultaneously processing a large number of processing substrates will be described by comparison with a conventional plasma processing apparatus.

FIG. 5(b) is a cross-sectional view of an embodiment in which the vacuum container 15 is arranged flat in the direction of propagation of electromagnetic waves, and the vacuum container 15 also serves as a plasma generation chamber and a plasma processing chamber. (a) is a plan view with the upper part of the vacuum container 15 partially removed.

The vacuum container 15 has a width (W) of 800 mm and a length (L) of 5 QO.
mm, height (H) 100+++a+, made of stainless steel, and an electromagnetic wave introduction window 6 for entering the laser beam 4;
It is composed of a reactant gas common supply pipe 9, an exhaust port 8, and a magnetic field coil 7.

On the bottom surface of the vacuum container 15, twelve silicon wafers 2 each having a diameter of 100 mm are arranged in a plane.

FIG. 7(a) shows the magnetic flux density distribution inside the vacuum container 15 shown in FIG.

In this example, in order to improve plasma processing efficiency by confining plasma gas, a mirror magnetic field with a high magnetic flux density was generated at both ends of the vacuum chamber.

Further, FIG. 2B is a diagram showing a magnetic flux density distribution when the conventional technique is applied to the above device, and shows a divergent type magnetic flux density distribution.

In the figure, the dotted line represents the magnetic flux density that satisfies the ECR conditions, and the solid line represents the magnetic flux density distribution generated by the magnetic field coil 7.

Further, the ECR surface is a region where the magnetic flux density due to the magnetic field generated by the magnetic field coil 7 satisfies the ECR condition, that is,
It is formed in the area where the dotted line and the solid line intersect.

As described above, this embodiment is characterized in that the ECR surface is formed over the entire surface of the substrate to be processed.

Hereinafter, embodiments of the present invention will be described in comparison with a conventional technique having a divergent magnetic flux density distribution shown in FIG. 7(b).

O2 gas and SiH4 gas are supplied from the reaction gas supply pipe 9 at a rate of 200 ml/min and 30 ml/min, respectively.
are simultaneously introduced at a speed of 1n, and at the exhaust port 8 the vacuum vessel 1
Evacuation is performed so that the pressure inside becomes 2 mTorr.

The electromagnetic wave introduced is an H20 laser beam with an output IW.

At this time, the dimensions and shape of the vacuum chamber 15 and the incident angle of the laser beam 4 are determined so that a standing wave is generated most efficiently when the laser beam is reflected five times on the wall surface of the chamber opposite to the introduction window. is set to .

The magnetic field within the vacuum vessel 15 is generated by a magnetic field coil 7 installed at the bottom of the vacuum vessel 15 .

Under these conditions, an SiO2 film was first deposited with the divergent magnetic flux density distribution shown in Figure 7(b). No significant difference was observed in the direction without.

However, a large difference was observed in the W direction, which is the traveling direction of the laser beam.

Figure 8(a) shows the relationship between the substrate position from the left side of the figure, the film deposition rate (* mark), and the etching rate of the deposited film by the buffered hydrofluoric acid flow (x mark). It is a diagram.

As is clear from the same figure, the substrate placed on the leftmost side in FIG. The substrate closest to the substrate had the highest deposition rate and film density.

Next, the present invention was applied to a device exhibiting the magnetic flux density distribution shown by the solid line in FIG. 7(a), and S 1
The results of depositing the 02 film are shown below.

FIG. 8(b) is a diagram showing the relationship between the substrate position from the left side in the figure, the film deposition rate, and the etching rate of the deposited film by the buffered hydrofluoric acid flow.

As is clear from the figure, when the device of the present invention is used,
than when the film was deposited with the prior art equipment described above.
A uniform and high speed film deposition rate is achieved, and a uniform and dense deposited film quality is achieved.

From the above experimental results, it can be seen that if the ECR plane is continuously formed parallel to the substrate, the uniformity and speed of plasma processing will be improved, and Tendo processing of the substrate will be possible.

Next, the results of forming a film by introducing H2O instead of 02 using the apparatus of the present invention having the magnetic flux density distribution shown in FIG. 7(a) will be described.

The deposition rate of the 12 films at this time was 1.2±0.
Etching rate with 1 μm 1 buffered hydrofluoric acid flow is 0.1
The thickness was 8±0.01 μm, and the deposition rate and density were both 1.5 times higher than those of the above example in which 0□ was introduced.

This means that if the plasma generation gas or reaction gas medium contains at least the same substance as the laser beam medium, the absorption efficiency of laser energy in the gas will be approximately 100%, and the degree of excitation of the gas will increase. This is to do so.

FIG. 6(b) is a cross-sectional view of a plasma processing apparatus in which the EC1 surface is formed over the entire surface of a plurality of substrates, and FIG. 6(a) shows a state where the upper part of the vacuum vessel 15 is partially removed. FIG.

In this figure, the same reference numerals as in FIG. 5 indicate the same or equivalent parts.

The magnetic flux density distribution inside the vacuum vessel 15 at this time is shown in FIG.
).

The feature of this embodiment is that the laser beam is made to enter from three electromagnetic wave introduction windows 6 at the same time.

According to this embodiment, even if the shape of the vacuum container cannot be set so as to satisfy the conditions for cavity resonance of the laser beam, the EC1 surface is formed over the entire surface of the plurality of substrates. Similarly, multiple substrates can be processed simultaneously and uniformly.

In this example, the electromagnetic wave introducing windows were explained as being provided at three locations, but this was done to ensure that the EC1 surface was formed over the entire surface of a plurality of substrates; The number can be any number as long as the purpose is achieved.

Furthermore, in the embodiment shown in FIGS. 5 and 6,
Although the electromagnetic waves introduced are described as laser beams, such characteristics can be achieved even if the electromagnetic waves are microwaves.

That is, the features of the above embodiment are that the magnetic flux density distribution that satisfies the ECR conditions is formed parallel to the surfaces of the plurality of substrates in the vacuum container, as shown in FIG. The surface is formed over the entire surface of the plurality of substrates.

(Effects of the Invention) According to the present invention, since a laser beam is used as the electromagnetic wave, plasma generation efficiency can be increased compared to the case where microwaves are incident.

Therefore, high plasma processing efficiency can be obtained in a small device with low power consumption.

Moreover, since the laser beam is in phase, scattering within the vacuum chamber can be minimized and damage to the workpiece can be minimized; however, when reflected within the vacuum chamber, it tends to generate standing waves. Therefore, the plasma generation efficiency can be further improved.

Furthermore, since the plasma generation chamber also serves as a sample chamber, the object to be processed can be placed within the mean free path of the ions, thereby increasing plasma processing efficiency.

Furthermore, the medium of the reaction gas contains at least the same substance as the medium of the laser beam, and the absorption efficiency of laser energy in the gas is approximately 100%, so the degree of excitation of the gas is improved. However, even higher plasma processing efficiency can be obtained.

Furthermore, since the EC1 plane is formed parallel and continuously over the entire surfaces of the plurality of substrates, plasma processing can be performed simultaneously and uniformly on the plurality of objects to be processed.

Furthermore, since multiple electromagnetic wave introduction windows can be installed in the vacuum vessel, plasma generation efficiency can be increased even when the shape of the vacuum vessel cannot be set to satisfy the conditions for cavity resonance of electromagnetic waves. , plasma processing efficiency can be improved.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of the main parts of a plasma processing apparatus that is an embodiment of the present invention. FIG. 2 is a schematic diagram of the main parts of a conventional plasma processing apparatus. FIG. 3 is a diagram showing the relationship between the deposition rate of the S i 02 film and the number of reflections of the laser beam. FIG. 4 is a diagram showing the relationship between the deposition rate and etching rate of the SiO2 film and the oscillation frequency of the laser beam. FIG. 5 is a sectional view of a plasma processing apparatus according to another embodiment of the present invention. FIG. 6 is a sectional view of a plasma processing apparatus according to still another embodiment of the present invention. FIGS. 7(a) and 7(b) are diagrams showing the magnetic flux density distribution in the apparatus shown in FIG. 5. FIGS. 8(a) and 8(b) are diagrams showing the film deposition rate and etching rate in the apparatus shown in FIG.

Claims (21)

[Claims] (1) Irradiating electromagnetic waves to the reaction gas in the plasma generation chamber,
A plasma processing method in which electron cyclotron resonance is generated in a plasma generation chamber by generating a magnetic field of a predetermined strength, and highly excited plasma generated by the electron cyclotron resonance is introduced into the plasma processing chamber to perform plasma treatment on the object to be processed. A plasma processing method, wherein the electromagnetic wave is a laser beam. (2) The plasma processing method according to claim 1, wherein a standing wave is generated by reflecting a laser beam in the plasma generation chamber. (3) Electromagnetic waves are irradiated to the reaction gas in the vacuum chamber, which serves as both a plasma generation chamber and a plasma processing chamber, and a magnetic field of a predetermined strength is generated to generate electron cyclotron resonance in the vacuum chamber. 1. A plasma processing method for plasma-processing a workpiece using highly excited plasma generated by resonance, wherein the electromagnetic waves are irradiated substantially parallel to a processing surface of the workpiece. (4) The plasma processing method according to claim 3, wherein the electromagnetic wave is a microwave. (5) The plasma processing method according to claim 3, wherein the electromagnetic wave is a laser beam. (6) The plasma processing method according to claim 5, wherein the medium of the reaction gas contains at least the same substance as the medium of the laser beam. (7) The plasma processing method according to any one of claims 3 to 6, wherein a standing wave is generated by reflecting electromagnetic waves in the vacuum container. (8) In the vacuum container, electron cyclotron resonance occurs substantially parallel and continuously over the entire surface of the object to be processed. The plasma processing method described in Crab. (9) The plasma processing method according to any one of claims 3 to 8, wherein the vacuum container is irradiated with electromagnetic waves from a plurality of locations. (10) a plasma generation chamber; a plasma processing chamber; a support stand disposed inside the plasma processing chamber to support a processed object; a means for supplying a reactive gas to the plasma generation chamber; a laser beam introduction window; a means for irradiating a reactant gas within the plasma generation chamber with a laser beam through the laser beam introduction window; and a means for applying a magnetic field with a magnetic flux density necessary to cause cyclotron resonance within the plasma generation chamber. A plasma processing apparatus characterized by comprising a magnetic field coil that generates a magnetic field. (11) The plasma processing apparatus according to claim 10, wherein the plasma generation chamber includes a reflection plate for reflecting a laser beam and generating a standing wave. (12) A vacuum vessel that serves as both a plasma generation chamber and a plasma processing chamber; a support stand located inside the vacuum vessel and capable of supporting an object to be processed; a means for supplying a reaction gas to the vacuum vessel; and a vacuum chamber. It is equipped with a means for irradiating electromagnetic waves to the reactant gas in the container, an electromagnetic wave introduction window provided in the vacuum container, and a magnetic field coil that generates a magnetic field with a magnetic flux density necessary to cause cyclotron resonance inside the vacuum container. 1. A plasma processing apparatus, wherein the electromagnetic waves are irradiated substantially parallel to a processing surface of an object to be processed. (13) The plasma processing apparatus according to claim 12, wherein the electromagnetic wave irradiation means is a microwave irradiation means. (14) The plasma processing apparatus according to claim 12, wherein the electromagnetic wave irradiation means is a laser beam irradiation means. (15) The plasma processing apparatus according to claim 5, wherein the reaction gas medium contains at least the same substance as the laser beam medium. (16) The oscillation frequency of the laser beam is 1 GHz ~
Claim 1 characterized in that the frequency is 10 GHz.
The plasma processing apparatus according to item 4 or 15. (17) The plasma processing apparatus according to any one of claims 12 to 16, wherein the vacuum container has a shape and dimensions that satisfy conditions for cavity resonance of electromagnetic waves. . (18) The magnetic field coil generates a magnetic field necessary to generate cyclotron resonance substantially parallel and continuously over the entire surface of the processing object. The plasma processing apparatus according to any one of Item 17. (19) The plasma processing apparatus according to any one of claims 12 to 18, wherein the vacuum container is provided with a plurality of electromagnetic wave introduction windows. (20) Claims 12 to 19, wherein the magnetic field coil is made of a superconducting material.
The plasma processing apparatus according to any one of paragraphs. (21) The magnetic field generated by the magnetic field coil is a mirror magnetic field in which the magnetic flux density outside the area corresponding to the contour of the processing surface is higher than the magnetic flux density inside the area in the traveling direction of the electromagnetic wave. A plasma processing apparatus according to any one of claims 12 to 20.