JP2590112B2 - Microwave plasma processing equipment - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a microwave plasma processing apparatus using electron cyclotron resonance, and more particularly to a microwave plasma processing apparatus suitable for large-area processing.

[Conventional technology]

As a conventional microwave plasma processing apparatus of this type, the one disclosed in Japanese Patent Application Laid-Open No. 59-3018 is known. In this case, a discharge tube is provided in the vacuum chamber, a coil is attached to this, a magnetic field is applied, and a microwave having the same frequency as the electron cyclotron frequency is introduced through the waveguide to cause a discharge. Thus, the reaction gas introduced into the vacuum tube is decomposed, whereby the processing is performed on a substrate, which is a sample placed in a vacuum chamber.

However, when microwaves are introduced through a waveguide, the size of the waveguide is limited by the size of the waveguide, which makes it difficult to process a large-area substrate.

Microwaves can be introduced not only by waveguide but also by Japanese Journal of Pride.
Physics Vol.23, No.8, August 1984, Pages 1101 to 11
06 pages (JAPANESE JOURNAL OF APPLIED PHYSICS Vo
l.23, No. 8, AUGUST, 1984, pp. 1101 to 1106) using a Lisitano-Coil. In this method, the discharge portion can be enlarged by increasing the diameter of the rigidano coil.

However, even in this microwave introduction method, the area that can be processed is limited by the size of a coil that generates a magnetic field for generating electron cyclotron resonance. Although the size of the coil is not theoretically limited, a large coil is required to enable large-area processing, and the device becomes large and consumes a large amount of power. The method is not economical and not practical.

 As described above, large-area processing has been difficult with the conventional apparatus.

[Problems to be solved by the invention]

The prior art described above has a problem that the economics of the magnetic field forming means are not considered, and a device capable of processing a large area cannot be actually produced.

SUMMARY OF THE INVENTION An object of the present invention is to provide a microwave plasma processing capable of economically generating an effective magnetic field over a large area, introducing microwaves to a large area, and causing a large discharge to perform a large area processing. It is to provide a device.

[Means for solving the problem]

The above object is to form at least a part of the magnetic field forming means by a permanent magnet, and to use a plane radiator as a microwave introducing means in the microwave power supply means,
This is achieved by placing the planar radiator between the permanent magnet and the electron cyclotron resonance point.

As described above, in the present invention, a permanent magnet is used for at least a part of the magnetic field forming means, and an attempt is made to reduce the size of the coil and the current.

However, in this case, a waveguide or a Rigidano coil as a means for introducing microwaves cannot be used because the permanent magnet is an obstacle. The magnetic field produced by the permanent magnet becomes weaker as it gets farther from the surface of the S or N pole, and electron cyclotron resonance occurs when the magnetic field falls to the resonance magnetic field strength determined by the microwave frequency. Microwaves must be introduced between the permanent magnet and this electron cyclotron resonance point. For that purpose, it is necessary to use a flat plate-shaped microwave radiator. A flat radiator having the shape of a slot antenna or a beam antenna is suitable for this.

That is, a plane radiator is provided between the permanent magnet and the electron cyclotron resonance point, and a microwave is radiated from the plane radiator, so that plasma can be generated around the electron cyclotron resonance point.

The permanent magnet used here needs to generate a magnetic field sufficient to cause electron cyclotron resonance via a plane radiator, and needs to be cooperative. Specific examples include rare earth cobalt magnets such as SmCo ₅ , oxide magnets such as barium ferrite (BaO, 6Fe ₂ O ₃ ), and alloy magnets such as alnico.

In order to obtain a microwave plasma processing apparatus capable of processing a large area, a permanent magnet having a large area is required, and barium ferrite which is inexpensive and castable Alnico are practical. The arrangement of the permanent magnet may be either inside or outside the vacuum chamber as long as the electron cyclotron resonance point is in the vacuum chamber.

A microwave power source with a frequency of 2.45 GHz can be obtained at low cost. The electron cyclotron resonance magnetic field strength for the frequency of 2.45 GHz is 875 G. According to the above-mentioned material, a magnetic field strength of 2000 g or more can be obtained on the surface of the permanent magnet, so a plane radiator must be provided until the magnetic field weakens to 875 G Is quite possible. In addition, an electromagnet may be used in combination to supplement the magnetic field strength in the peripheral portion.

Since the plane radiator is an antenna for microwave radiation, it may be made of a good conductor, such as copper or aluminum. In the case of the slot antenna type, the shape of the slot may be any one that can be generally used as an antenna, such as an arrangement of elongated holes, an arrangement of radial holes, and an arrangement of concentric holes. A commonly used beam antenna type may also be used. The flat radiator may be provided outside the vacuum chamber, but in this case, a window such as quartz for transmitting microwaves is required.

 A microwave supply method may use a coaxial line.

The gas required for film formation may be introduced between the flat radiator and the sample.If the discharge gas and the reactant gas are introduced separately, introduce the discharge gas near the flat radiator and close the sample. What is necessary is just to introduce a reaction gas.

The sample is attached to a sample holding means having a built-in heater, and is arranged so as to face the flat radiator.

Evacuation of the vacuum chamber is performed by a molecular turbo pump,
The pressure at the time of film formation may be 10 ^{-5 to 1} Torr.

(Operation)

In the present invention, the plane radiator radiates radio waves in the front-back direction of the plane. The direction of the electric field of the radio wave is parallel to the plane. When a permanent magnet is installed behind the plane radiator so as to form a magnetic field in the vertical direction with respect to the plane radiator, the electrons are complemented by the magnetic field, and the cyclotron resonance satisfies the following condition (1). Cause acceleration.

Where f: rotation frequency = microwave frequency B: magnetic flux density q: electron charge m: electron mass

The emitted microwave energy is absorbed as kinetic energy of electrons.

The accelerated electrons collide with the gas in the vacuum chamber, repel the electrons from the gas, connect the discharge and decompose the reaction gas to generate film-forming active species. The film-forming active species diffuses on the sample surface to form a thin film.

And, in the present invention, since at least a part of the magnetic field forming means for forming a magnetic field necessary for causing electron cyclotron resonance is formed by a permanent magnet, compared to a case where the entire magnetic field forming means is formed by an electromagnet, Power consumption can be reduced.

Further, in the present invention, since the microwave is introduced into the vacuum chamber by the plane radiator, the microwave can be radiated over a large area, so that the sample can be processed in a large area.

〔Example〕

 Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a longitudinal sectional view showing an embodiment of the present invention, and FIGS. 2 and 3 are plan views each showing an embodiment of a slot plate as a plane radiator.

In the microwave plasma processing apparatus of the embodiment shown in FIG. 1, a vacuum chamber 1 and a substrate table 2 as a sample holding means are provided.
A reaction gas introduction pipe 4 as a reaction gas introduction means, a discharge gas introduction pipe 5 as a discharge gas introduction means, an auxiliary coil 6, a permanent magnet 7, a control coil 8, and a slot plate as a plane radiator. 9, a microwave power supply 10, a gas supply system 11, a high vacuum exhaust system, and a deposition prevention plate 20.

The inside of the vacuum chamber 1 is evacuated to a high vacuum by a high vacuum exhaust system. As shown in FIG. 1, the high vacuum evacuation system includes a molecular turbo pump 13 and a rotary pump 14.
, A gate valve 15 and vacuum valves 16 and 17.

As shown in FIG. 1, the substrate table 2 is installed in a vacuum chamber 1, and a substrate 12 as a sample is placed on the upper surface of the substrate table 2. In addition, the substrate 12
The heater 3 for heating is built in. The heater 3 is energized by a power supply 18.

The reaction gas introduction pipe 4 and the discharge gas introduction pipe 5 are installed in the vacuum chamber 1 and connected to a gas supply system 11.
When the reactant gas and the discharge gas flow separately, as shown in FIG. 1, the reactant gas is introduced to the substrate table 2 side, and the reactant gas introduction pipe is supplied so that the protection gas flows to the slot plate 9 side. 4 and a discharge gas introduction pipe 5 are arranged.

The auxiliary coil 6 and the permanent magnet 7 constitute a magnetic field forming means for generating electron cyclotron resonance.

The permanent magnet 7 needs to generate a magnetic field sufficient to cause electron cyclotron resonance via the slot plate 9 and needs to cooperate. Therefore, specific examples of the permanent magnet 7 include rare earth cobalt magnets such as SmCo ₅ , oxide magnets such as barium ferrite (BaO, 6Fe ₂ O ₃ ), and synthetic magnets such as alnico. In order to obtain a microwave plasma processing apparatus capable of large-area processing, a large-area permanent magnet 7 is required, and inexpensive barium ferrite or castable alnico is practical. The arrangement of the permanent magnet 7 may be either inside or outside the vacuum chamber 1 as long as the electron cyclotron resonance point is within the vacuum chamber 1.

The control coil 8 is arranged outside the vacuum chamber 1 and controls the shape of the magnetic field lines of the permanent magnet 7.

The slot plate 9 is provided between the permanent magnet 7 and the electron cyclotron resonance point inside the vacuum chamber 1. The slot plate 9 is made of a good conductor such as copper or aluminum. Also, the slot plate 9
The shape of the slot in is as shown in FIG. 2 and arranged in parallel with the elongated hole, or as shown in FIG. Anything that has the function of an antenna, such as an antenna, may be used. The slot plate 9 is connected to a microwave power supply 10 through a coaxial line 21, and the slot plate 9 and the microwave power supply 10 constitute a microwave power supply unit.

2 and 3, reference numerals 31 and 31 'denote slots formed in the slot plate.

The deposition-preventing plate 20 is formed of quartz or the like, and powder or a film produced by a decomposition product of a reactive gas adheres to the slot plate 9 or the slot plate 9 is sputtered, and its components are deposited on the film on the substrate 12. It prevents it from being taken in.

 Next, more specific examples will be described.

As the slot plate 9, a copper plate having a pattern shown in FIG. 2 was used. The diameter of the slot plate 9 is 200 mm, and the length of each slot is 61 mm. The width of the slot was 5 mm.

As the permanent magnet 7, a sintered body of barium ferrite was used.

A case where a glass substrate having a diameter of 200 mm is used as the substrate 12 and a silicon oxide film is formed on the glass substrate will be described.

That is, the inside of the vacuum chamber 1 was evacuated to a high vacuum (10 ^-8 Torr) with the glass substrate attached to the substrate base 2.

Next, an oxygen gas as a discharge gas flows through the discharge gas introduction pipe 5 at a flow rate of about 15 sccm (15 cm ³ per minute in terms of standard state), and a monosilane gas of 30 sccm flows through the reaction gas introduction pipe 4 as a reaction gas. × 10 ^-4 Torr.

Thereafter, power was supplied from the power supply 18 to the heater 3 built in the substrate table, and the glass substrate was heated to 100 ° C.

When the temperature became stable, a current of about 3 A was passed through the auxiliary coil 6 and a current of 1 A was passed through the control coil 8.

Subsequently, a microwave of 2.45 CHz and 800 W was applied to the slot plate 9 from the microwave power supply 10 through the coaxial line 21 to start discharging.

As a result, a silicon oxide film having a thickness of about 500 nm was formed almost uniformly on the glass substrate having a diameter of 200 nm in 10 minutes.

On the other hand, when microwaves were applied to the auxiliary coil 6 and the control coil 8 without passing a current, a silicon oxide film of about 500 nm was formed in 10 minutes at the center of the glass substrate, but about 500 nm at the periphery. Only a 400 nm silicon oxide film was formed, resulting in uneven film thickness.

In this embodiment, a sintered body of barium ferrite was used for the permanent magnet 7, but this was arranged outside the vacuum chamber 1 in order to avoid the influence of gas release from the sintered body. Further, although the slot plate 9 is disposed inside the vacuum chamber, powder or a film produced by a decomposition product of monosilane adheres to the slot plate 9 or the slot plate 9 is sputtered and its components are taken into the film on the glass substrate. In order to prevent this, a deposition plate 20 made of quartz is provided in front of the slot plate 9.

According to the above embodiment, there is no influence of gas release from the permanent magnet 7, and the slot plate 9 is not contaminated and sputtered components are not taken into the film.

In the present invention, an electromagnet may be used in combination to strengthen the peripheral portion of the magnetic field formed by the permanent magnet 7.

Further, in the present invention, a beam antenna type radiator may be used instead of the slot plate 9 as the planar radiator.

〔The invention's effect〕

According to the present invention described above, since at least a part of the magnetic field forming means for forming the magnetic field necessary for causing electron cyclotron resonance is formed by the permanent magnet, the entire magnetic field is formed by the electromagnet. There is an effect that power consumption can be reduced as compared with the case.

Further, according to the present invention, since microwaves are introduced into the vacuum chamber by the plane radiator, microwaves can be radiated over a large area, and there is an effect that a large area substrate can be processed. .

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing an embodiment of the present invention, and FIGS. 2 and 3 are plan views each showing an embodiment of a slot plate as a plane radiator. 1 ... Vacuum chamber, 2 ... Substrate stand, 3 ... Heater, 4 ... Reaction gas introduction pipe, 5 ... Discharge gas introduction pipe, 6 ... Auxiliary coil, 7 ... Permanent magnet, 8 ... Control coil , 9 ... slot plate, 10 ... microwave power supply, 11 ... gas supply system, 12 ... substrate, 13 ... molecular turbo pump, 14 ... rotary pump, 15 ... gate valve, 16,17 ... Vacuum valve, 18 heater power supply, 20 anti-adhesion plate, 21 coaxial line.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Mitsuo Nakatani 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Prefecture Inside the Hitachi, Ltd. Production Engineering Research Laboratory (72) Inventor Tadashi Sonobe 3-1-1 Sachicho, Hitachi-shi, Ibaraki No. Hitachi, Ltd. Hitachi Plant (56) References JP-A-62-89875 (JP, A)

Claims (4)

(57) [Claims] 1. A microwave plasma processing apparatus comprising a vacuum chamber, a sample holding means, a reaction gas and discharge gas introducing means, a magnetic field forming means for generating electron cyclotron resonance, and a microwave power supply means. A microwave plasma processing apparatus using a flat radiator as the microwave power supply means. 2. The microwave plasma processing apparatus according to claim 1, wherein microwave power is supplied to said planar radiator using a coaxial cable. 3. The method according to claim 1, further comprising: means for separating and protecting the plane radiator by a material that transmits microwaves so that the plane radiator does not come into direct contact with plasma. Characteristic microwave plasma processing apparatus. 4. A microwave plasma processing apparatus according to claim 1, wherein a permanent magnet is used as said magnetic field forming means.