JP2000331797A - Plasma machining method and plasma machining device used for implementation thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a plasma machining method and a plasma machining device capable of uniforming generated plasma density without changing the electric field strength distribution of a microwave. SOLUTION: An exciting coil 14 forms a vertical magnetic field, and also forms a divergent magnetic field, having lower magnetic flux density toward a sample compartment 13. Plasma is introduced into the sample compartment 13 by this divergent magnetic field. A dipole ring magnet 1 is disposed on the periphery of a plasma generating compartment 11 inside the exciting coil 14. The dipole ring magnet 1 forms a horizontal magnetic field, that is a magnetic field perpendicular to the magnetic field by the exciting coil 14.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plasma processing method and apparatus for performing processing such as etching and thin film formation, and more particularly to a plasma processing method in which a microwave having an electric field of a propagation direction component and an orthogonal direction component such as TM mode is introduced. TECHNICAL FIELD The present invention relates to a plasma processing method for generating plasma and a plasma processing apparatus used for carrying out the method.

[0002]

2. Description of the Related Art Microwaves are introduced into a vacuum vessel under reduced pressure and low gas pressure to generate plasma, and the plasma is applied to a sample such as a semiconductor device substrate to perform etching, thin film formation, and the like. Can be applied to the sample. As such an apparatus, an apparatus that generates plasma by electron cyclotron resonance (ECR) excitation is known. In this apparatus, a plasma generation chamber and a sample chamber communicating below the plasma generation chamber are provided in a vacuum vessel, a microwave introduction tube is connected to the upper part of the plasma generation chamber, and an excitation coil is concentrically formed on the outer periphery of the plasma generation chamber. Is provided. The plasma generation chamber has a microwave introduction window on the upper surface and a plasma outlet on the lower surface. The microwave introduction window is sealed with a quartz glass microwave introduction window, and one end of a microwave introduction tube connected to the microwave supply unit is connected. On the other hand, the plasma outlet faces the sample chamber, and a sample stage on which the sample is placed is arranged in the sample chamber.

[0003] A sample such as a wafer is removably mounted on a sample stage. After decompression of the plasma generation chamber and the sample chamber, a gas is supplied to the plasma generation chamber, and a microwave is generated while a DC magnetic field is formed by an excitation coil. The microwave is introduced into the plasma generation chamber through the introduction pipe. At this time, plasma is generated in the plasma generation chamber, and the divergent magnetic field whose magnetic flux density decreases toward the sample chamber side draws the plasma into the sample chamber to perform plasma processing on the sample surface.

By the way, in order to generate plasma by ECR, it is necessary to supply a microwave electric field in a direction substantially orthogonal to a DC magnetic field. The microwave frequency is 2.4
It is known that a magnetic field of 875 Gauss is required for 5 GHz. In the plasma processing apparatus as described above, since the DC magnetic field is applied in the traveling (propagating) direction of the microwave, the microwave electric field component in the direction orthogonal to the DC magnetic field turns the gas introduced into the plasma generation chamber into plasma. .

[0005] As a microwave for generating ECR plasma, a TE mode such as a TE11 mode, a TM mode such as a TM01 mode, and the like are often used. When the vacuum vessel has a cylindrical cross section, the circular mode is used,
In the case of a rectangular cross section, the rectangular mode is used. Usually, a circular cylindrical mode is used, and a circular TE mode with small transmission loss and easy handling is used. In recent years, a circular TM mode with high microwave absorption efficiency is being used. However, the electric field component (Ez) in the microwave traveling direction (for example, vertical direction) of the circular TM mode is smaller than the electric field component (Ex, Ey) in the direction (horizontal direction) perpendicular to the microwave direction. The distribution is significantly different.

[0006]

FIG. 4 shows a circular TM01.
5 is a graph showing an electric field strength distribution of a mode microwave component in a waveguide. The vertical axis indicates the microwave electric field intensity. The horizontal axis indicates the radial position of the waveguide,
The left side is the center of the tube, and the right side is the outer peripheral side. '○-in the graph
“○” indicates the total electric field strength of the horizontal component (Ex, Ey), and “xx” indicates the electric field strength of the vertical component (Ez). As shown in the graph, on the center side in the waveguide, the electric field component (Ez) in the direction of microwave propagation is higher in intensity than the electric field components (Ex, Ey) in the horizontal direction, and conversely, on the peripheral side of the waveguide. It can be seen that the intensity of the horizontal electric field component (Ex, Ey) is higher than the vertical component (Ez).

Since microwaves are introduced from the upper center in the plasma generation chamber, the vertical electric field component (Ez) concentrates in the center of the plasma generation chamber, and the generated plasma density is reduced. In addition, since the electric field components (Ex, Ey) in the horizontal direction are concentrated in a ring shape at the peripheral portion of the plasma generation chamber and the plasma density increases, there is a problem that the plasma density becomes non-uniform in the plasma generation chamber.

In order to solve this problem, a method has been proposed in which the microwave distribution is artificially changed to thereby make the plasma density distribution uniform. For example, the applicant of the present application has proposed, in Japanese Patent Application Laid-Open No. 6-69161, a plasma processing apparatus in which a microwave lens is disposed at an inlet of a waveguide into a plasma generation chamber to change a microwave electric field intensity distribution. are doing. Japanese Patent Application Laid-Open No. Hei 7-263348 proposes a plasma processing apparatus in which a dielectric block is disposed in a waveguide to change the electric field distribution of microwaves to make the plasma density uniform.

Thus, the electric field intensity distribution of the microwave in the waveguide can be changed, but the electric field intensity distribution of the microwave after being introduced into the plasma generation chamber cannot be changed. Therefore, the uniformity of the plasma density may not be sufficient. Also, since the microwave electric field intensity distribution is determined based on the mode, a significant change in the distribution will disturb the mode, and when a higher-order mode is generated, the reflection will increase and microwave energy will be transferred to the plasma generation chamber. There was a problem that it could not be supplied.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and the electric field components in both directions of the microwave propagation direction and the direction intersecting the microwave propagation direction are involved in the generation of the ECR plasma. It is an object of the present invention to provide a plasma processing method capable of increasing and making the generated plasma density uniform without any change, and a plasma processing apparatus used for carrying out the method.

[0011]

According to a first aspect of the present invention, there is provided a plasma processing method comprising: applying a magnetic field while introducing a raw material gas and a microwave into a plasma generation chamber to generate plasma in the plasma generation chamber; A plasma processing method of performing a plasma process on the plasma generating chamber, a step of introducing a microwave into the plasma generation chamber, a step of applying a magnetic field in a direction along a propagation direction of the microwave in the plasma generation chamber, Applying a magnetic field in an intersecting direction.

According to the first aspect of the invention, the magnetic fields in the directions corresponding to the microwave propagation direction and the direction perpendicular thereto are applied so that the electric field components in both directions are turned into plasma. Even when microwaves having different electric field intensity distributions in different directions are used, the plasma density in the plasma generation chamber can be increased and made uniform.

[0013] A plasma processing method according to a second aspect of the present invention comprises the first
In the invention, the microwave introduced into the plasma generation chamber has a circular TM01 mode as a main mode.

The circular TM01 mode has an electric field strength distribution in which the electric field intensity is higher at the center of the waveguide than at the periphery, and the vertical electric field component is concentrated at the center of the waveguide, and the horizontal electric field component is concentrated at the periphery. In the second invention, even when the circular TM01 mode is used, plasma is generated in both the vertical and horizontal electric field components, so that the plasma density in the plasma generation chamber is made uniform.

A plasma processing apparatus according to a third aspect of the present invention is a plasma processing apparatus for applying a magnetic field while introducing a raw material gas and a microwave into a plasma generation chamber to generate plasma in the plasma generation chamber and performing plasma processing on a sample. In the apparatus, first magnetic field generating means for forming a magnetic field in a direction along a propagation direction of the microwave in the plasma generation chamber,
And a second magnetic field generating means for generating a magnetic field in a direction intersecting with the propagation direction.

According to the third aspect of the present invention, both the electric field component in the propagation direction (for example, vertical direction) of the microwave in the plasma generation chamber and the electric field component (horizontal electric field component) orthogonal thereto generate plasma. Therefore, even when a microwave whose electric field intensity distribution in the plasma generation chamber is significantly different between the propagation direction component and the orthogonal direction component is used, the density of the plasma generated in the plasma generation chamber is made uniform.

A plasma processing apparatus according to a fourth aspect of the present invention has
In the invention, the apparatus further includes a microwave supply unit that supplies the microwave having the TM mode as a main mode.

According to the fourth aspect of the invention, the TM mode is a mode having an electric field component in both the microwave propagation direction and the direction orthogonal to the microwave propagation direction. The plasma density in the chamber is made uniform.

The plasma processing apparatus according to the fifth invention has a third
Alternatively, in the fourth invention, the second magnetic field generating means includes a plurality of magnets arranged in an annular shape on the outer periphery of the plasma generation chamber and arranged so that the magnetization direction rotates one half of the ring. Features.

In the fifth invention, a so-called dipole ring magnet is used as the second magnetic field generating means, so that a uniform magnetic field in a direction orthogonal to the microwave propagation direction can be applied. In addition, the plasma density in the plasma generation chamber is made more uniform.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below with reference to the drawings showing the embodiments. FIG. 1 is a schematic vertical sectional view showing the structure of the plasma processing apparatus of the present invention.
The plasma processing apparatus includes a plasma generation chamber 11 and a sample chamber 13.
And a vacuum container comprising: Plasma generation chamber 11
Has a hollow cylindrical shape and is formed so as to constitute a cavity resonator for microwaves. A microwave introduction port 11c is provided at the center of the upper wall of the plasma generation chamber 11, and is sealed by a microwave introduction window 11b made of a microwave transmitting material such as quartz glass. One end of a circular waveguide 12 is connected to the outer surface of the microwave introduction window 11b, and the other end is connected to the microwave supply unit 9. The microwave supply unit 9 supplies the circular TM01 mode to the waveguide 12. Further, a gas supply system 11g is communicated with a peripheral portion of the upper wall of the plasma generation chamber 11.

In the center of the lower wall of the plasma generation chamber 11, a plasma outlet 11d is provided at a position facing the microwave introduction window 11b. A sample chamber 13 is provided facing the plasma outlet 11d, and a sample table 17 on which the sample S is mounted is disposed in the sample chamber 13. The sample stage 17 may be provided with an electrostatic suction means, and the sample S is removably mounted. An exhaust port 13 a communicating with an exhaust device (not shown) is opened on the bottom wall of the sample chamber 13, and a gas supply system 13 g is communicated with a side wall of the sample chamber 13.

The plasma generation chamber 11 of such a vacuum vessel
An excitation coil (first magnetic field generating means) 14 is provided around one end of the waveguide 12. The excitation coil 14 is connected to a DC power supply (not shown), and forms a magnetic field (vertical magnetic field, Z-directional magnetic field) for generating plasma in the plasma generation chamber 11 by the flow of the DC current, and the sample chamber 13. A divergent magnetic field whose magnetic flux density decreases toward the side is formed, and the plasma generated in the plasma generation chamber 11 by the divergent magnetic field is introduced into the sample chamber 13. And the plasma generation chamber 1
The dipole ring magnet 1, which is the second magnetic field generating means, which is a feature of the present invention, is disposed inside the exciting coil 14 on the outer periphery of the magnet 1.

FIG. 2 is a plan view showing the structure of the dipole ring magnet, and also shows the positional relationship between the plasma generation chamber 11 and the waveguide 12. The dipole ring magnet 1 has a plurality of magnets 10 a, 10 b... 10 p arranged concentrically around the plasma generation chamber 11, and these magnets 10 are fixed to the yoke 15. In the present embodiment, 16 magnets are arranged in a ring. The yoke 15 is configured to be rotatable in a horizontal plane, and can rotate the dipole ring magnet 1 during the plasma processing. The first magnet 10a is the waveguide 1
The second magnet 10 is magnetized in a direction toward the center of the second magnet 10.
b is disposed at a position making an angle θ with the first magnet 10a around the waveguide 12, and its magnetization direction is the first magnet 10a.
Is a direction rotated by an angle 2θ with respect to the magnetic field direction.
The magnets 10c, 10d... 10p have the same relationship between the arrangement position and the magnetizing direction and the first magnet 10a, and the magnet 10i at the position θ = 180 ° with the first magnet 10a One magnet 10a is magnetized in the same direction. The magnets located symmetrically with respect to the center of the waveguide 12 are magnetized in the same direction. That is, the 16 magnets are magnetized so as to make one rotation around a half circumference of the ring.

The dipole ring magnet 1 having such a configuration has a magnetic field in the direction of the white arrow shown in FIG.
A magnetic field in the same direction as the first magnet 10a is formed in a horizontal plane (xy plane). This is a magnetic field in a direction substantially orthogonal to the magnetic field formed by the exciting coil 14. Also, since the dipole ring magnet 1 is rotatable in a horizontal plane,
Magnetic fields in all directions perpendicular to the magnetic field formed by the exciting coil 14 can be formed. Further, it is known that the dipole ring magnet 1 can form a uniform magnetic field. Therefore, the first and second magnetic field generating means of the present embodiment generate the magnetic fields in both the direction (z direction) along the propagation direction of the microwave and the directions (x, y directions) substantially perpendicular to the direction of plasma generation. It can be applied to the chamber 11.

In the plasma processing apparatus shown in FIG.
The dipole ring magnet 1 is provided inside the excitation coil 14, but is not limited to this, and may be provided around the excitation coil 14.

When performing plasma processing on the sample S using the above-described plasma processing apparatus, first, the sample S is placed on the sample stage 17 of the sample chamber 13 and the inside of the plasma generation chamber 11 and the inside of the sample chamber 13 are kept in a predetermined state. After the gas is exhausted to the pressure, the gas is supplied from the gas supply pipe 11g into the plasma generation chamber 11 and from the gas supply pipe 13g into the sample chamber 13, and set to a predetermined pressure. In this state, a DC current is passed through the exciting coil 4 to generate a magnetic field satisfying the cyclotron resonance conditions, and a circular TM0 is introduced from the waveguide 12 into the plasma generation chamber 11.
One mode of microwave is introduced. At this time, the dipole ring magnet 1 generates a magnetic field that satisfies the cyclotron resonance condition in a direction substantially orthogonal to the propagation direction (travel direction) of the microwave, so that the electric field component (Ez) in the travel direction of the microwave is Plasma is generated by the magnetic field of the ring magnet 1. At the same time, the electric field components (Ex, Ey) in the direction orthogonal to the traveling direction generate plasma by the magnetic field formed by the exciting coil 14. The generated plasma is introduced into the sample chamber 13 by a divergent magnetic field formed by the excitation coil, and activates the gas in the sample chamber 13,
The sample S is subjected to plasma processing.

FIG. 3 is a graph showing an electric field intensity distribution in a waveguide of a microwave component involved in plasma generation according to the present embodiment. In the present embodiment, since both the horizontal electric field component (Ex, Ey) and the vertical electric field component (Ez) participate in plasma generation, the vertical axis represents the vertical component and the horizontal component of the microwave. The total electric field strength is shown. The horizontal axis indicates the radial position of the waveguide, the left side is the tube center, and the right side is the outer peripheral side. As shown in the graph, the electric field intensity of the microwave shows a substantially uniform value on the center side and the outer peripheral side in the waveguide. Therefore, the intensity of the electric field of the microwave introduced into the plasma generation chamber 11 is uniform on the center side and the peripheral side, and the density of the generated plasma is made uniform.

Since the dipole ring magnet 1 is rotatable in the horizontal plane as described above, the direction of the generated magnetic field can be changed by 360 ° in the horizontal plane, and the plasma density can be made more uniform.

Further, in the present embodiment, the case where the circular TM mode microwave is used has been described. However, the present invention is not limited to this, and the same effect can be obtained even when the rectangular TM mode is used. it can. In addition to the TM mode, a microwave is used, in which the electric field intensity distribution in the waveguide is different between the center and the periphery of the waveguide, and the intensity of the electric field component is significantly different in the direction of microwave propagation and the direction orthogonal to the microwave. In such a case, the present invention can be applied.

[0031]

As described above, in the present invention, the electric field intensity distribution in the microwave waveguide is different between the center side and the peripheral side, and the electric field intensity distribution is significantly different in both the propagation direction and the vertical direction. Since a magnetic field that satisfies the ECR condition is formed for the electric field component, the density of the plasma generated in the plasma generation chamber can be increased and made uniform. In addition, since the electric field intensity distribution of the microwave itself based on the mode is not changed, no higher-order mode is particularly generated, sufficient microwave energy can be supplied to the plasma generation chamber, and good plasma can be generated with a uniform density. The present invention has excellent effects.

[Brief description of the drawings]

FIG. 1 is a schematic longitudinal sectional view showing a structure of a plasma processing apparatus of the present invention.

FIG. 2 is a plan view showing a structure of a dipole ring magnet used in the present embodiment.

FIG. 3 is a graph showing an electric field intensity distribution in a waveguide of a microwave component involved in plasma generation according to the present embodiment.

FIG. 4 is a graph showing a conventional electric field intensity distribution in a waveguide of a microwave component of a circular TM mode.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 dipole ring magnet (second magnetic field generating means) 9 microwave supply unit 10 a to 10 p magnet 11 plasma generation chamber 12 waveguide 13 sample chamber 14 excitation coil (first magnetic field generating means) S sample

 ────────────────────────────────────────────────── ─── Continuing from the front page (72) Inventor Ekunori Murase 1-8 Fuso-cho, Amagasaki-shi, Hyogo Sumitomo Metal Industries, Ltd. Electronics Research Laboratory F-term (reference) 5F004 AA01 BA14 BA16 BB07 BB11 BB14 BB19 BC08 5F045 AA08 AA10 BB01 BB02 DP11 DQ10 EH01 EH03 EH16 EH17

Claims (5)

[Claims] 1. A plasma processing method for applying a magnetic field while introducing a raw material gas and a microwave into a plasma generation chamber to generate plasma in the plasma generation chamber and performing plasma processing on a sample. Introducing into the plasma generation chamber;
A plasma processing method comprising: applying a magnetic field in a direction along a propagation direction of the microwave in the plasma generation chamber; and applying a magnetic field in a direction crossing the propagation direction. 2. The plasma processing method according to claim 1, wherein the microwave introduced into the plasma generation chamber has a circular TM01 mode as a main mode. 3. A plasma processing apparatus for applying a magnetic field while introducing a raw material gas and a microwave into a plasma generation chamber to generate plasma in the plasma generation chamber and performing a plasma process on a sample, wherein: Plasma processing comprising: first magnetic field generation means for forming a magnetic field in a direction along a propagation direction in a plasma generation chamber; and second magnetic field generation means for forming a magnetic field in a direction intersecting with the propagation direction. apparatus. 4. The plasma processing apparatus according to claim 3, further comprising a microwave supply unit that supplies the microwave having a TM mode as a main mode. 5. The second magnetic field generating means includes a plurality of magnets arranged annularly around the plasma generation chamber and arranged so that the magnetization direction makes one rotation around a half circumference of the ring. Or the plasma processing apparatus according to 4.