JP2002280197A - Igniter for generating plasma - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an igniter capable of easily generating plasma even in a plasma generating chamber having a pressure as low as 10<-2> Torr, in the plasma generating device using a microwave. SOLUTION: A permanent magnet 27 is embedded in a part of the plasma generating chamber 21, a zone 28 for partial electronic cyclotron resonance is formed by the magnetic field of the permanent magnet 27 produced in the plasma generating chamber 21 and microwave power Po radiated into the plasma generating chamber 21, and surface wave plasma 29 is ignited with the zone 28 as seed plasma at the initial stage of supplying the microwave power.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ignition device for generating plasma by supplying microwave power to a plasma generation chamber maintained at a predetermined pressure to generate plasma.

[0002]

2. Description of the Related Art Clean surfaces of metals, semiconductors, insulators, and the like.
One of processing means such as polishing, etching, or depositing a thin film on the surface is a plasma generator.

[0003] There are various types of plasma generators, one example of which is shown in FIG. The plasma generation device shown in FIG. 2 is known as a surface wave excitation type plasma generation device using microwave power Po.

This plasma generating apparatus includes a dielectric plate 13 at a boundary between a plasma generating chamber 11 and a waveguide 12, and the plasma generating chamber of the dielectric plate 13 is supplied with microwave power Po supplied from the waveguide 12. A surface wave is generated on the side, and gas is separated by the surface wave to generate plasma 14.

[0005] The dielectric plate 13 is connected to the plasma generation chamber 11.
A dielectric window for isolating the air from the atmosphere is formed, and a quartz plate, an alumina plate, or the like is used. In addition, in this figure, 15 is a vacuum pump, and 16 is a gas supply pipe.

[0006]

The above-described plasma generating apparatus supplies microwave power Po to the plasma generating chamber 11 to ionize gas molecules and generate plasma.
It is necessary to maintain the gas pressure in the plasma generation chamber 11 at 10 ⁻¹ Torr or more.

However, at a gas pressure of 10 ⁻¹ Torr or more, the mean free path of ions and neutral radicals is several mm.
As described below, the application range of the plasma generator is limited.
From this, a plasma generating apparatus capable of easily generating plasma even under conditions in which the gas pressure of the plasma generating chamber 11 is increased by about two orders of magnitude and having an average free path of several tens to several hundreds of mm Is desired.

The present invention has been made in view of the above situation, and
^An object of the present invention is to provide an ignition device for plasma generation that can reliably generate plasma in a plasma generation chamber having a low pressure of ⁻² Torr or less.

[0009]

According to a first aspect of the present invention, there is provided a plasma generating apparatus for generating a plasma by supplying microwave power to a plasma generating chamber. A magnetic field generating member is provided in part, and a seed plasma generating means for generating a local electron cyclotron resonance region by a magnetic field of the magnetic field generating member and the microwave power in an initial stage of supplying the microwave power is provided. The present invention proposes an ignition device for generating plasma characterized in that the ignition device is configured to ignite.

In this plasma generator, when microwave power is supplied, a seed plasma is generated in the initial stage, so that plasma ignited by this seed plasma is generated at once.

The gas pressure in the plasma generation chamber is 10 ⁻² To.
Plasma is reliably generated even at a low pressure of rr or less. Therefore, the mean free path of ions and neutral radicals can be increased. Once the plasma is generated, the plasma density becomes higher than the cut-off density that does not allow the propagation of microwave power, and the microwave power is absorbed by the plasma. Has no effect.

According to a second aspect of the present invention, there is provided the above-described plasma generating apparatus, further comprising a magnetic field generating member for moving back and forth in a part of the plasma generating chamber, and after ignition of the plasma, seed plasma generating for moving the magnetic field generating member out of the plasma generating chamber. An ignition device for generating plasma characterized by providing means is proposed.

In this plasma generator, the magnetic field generating member is moved out of the plasma generation chamber after the plasma is ignited, whereby the influence of the magnetic field on the object to be processed by the plasma can be prevented.

[0014]

Next, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows a mechanism diagram of a plasma generating apparatus embodying the present invention.
A predetermined gas is injected from the gas supply pipe 22 and is maintained at a gas pressure of about 10 ⁻² Torr by the vacuum pump 23.

The waveguide 2 is provided in the plasma generation chamber 21.
4 is radiated through the coupling hole 25 (microwave radiation hole) and the dielectric window 26. Note that the dielectric window 26 is formed of a quartz plate, an alumina plate, or the like, as in the conventional example, and shields the plasma generation chamber 21 from atmospheric pressure.

On the other hand, a small permanent magnet 27 is embedded in the side wall of the plasma generation chamber 21. This permanent magnet 27
A magnetic field is generated in the plasma generation chamber 21, and the magnetic field and the microwave power constitute a seed plasma generating means for generating an electron cyclotron resonance region. The wall of the plasma generation chamber 21 is made of a specific magnetic material such as stainless steel or aluminum, and allows the magnetic field of the permanent magnet 27 to pass therethrough.

The plasma generator configured as described above has
When the microwave power Po is supplied by the waveguide 24, the microwave power Po is radiated into the plasma generation chamber 21 through the coupling hole 25 and the dielectric window 26.

Therefore, the electron cyclotron resonance zone 28 is locally generated in the plasma generation chamber 21 by the magnetic field of the permanent magnet 27 and the microwave power Po.

[0019] Note that the electron cyclotron resonance, and the frequency fm of the microwave power Po in use, and the magnetic flux density of the permanent magnet 27 B is that the relation of fm = eB / 2πm _e. Here, e and _{m e} is the charge and mass of each electron, when the 2.45 GHz 875Gaus
The s magnetic field corresponds.

The electron cyclotron resonance zone 28 generated as described above becomes a seed plasma, and a surface wave plasma 29 is ignited at once at the room side of the dielectric window 26.

Even if the configuration of the magnetic field is far from the optimum condition for confining the plasma, the ignition can be easily performed even at a low gas pressure of about 10 ⁻² Torr if the above-mentioned resonance condition is satisfied. Therefore, the mean free path of ions and neutral radicals is increased (for example, several tens mm to several hundred mm).
The generated plasma can be generated, and the application range of the plasma generator can be expanded.

As described above, a single magnet (permanent magnet 27)
In the magnetic field configuration described above, there is no effect of confining the plasma and only low-density plasma is generated.
1 sufficiently functions as a seed plasma causing discharge breakdown.

Further, once the surface wave plasma 29 is generated, the density of the plasma becomes higher than the cut-off density which does not allow the propagation of the microwave power Po.
o is absorbed by the plasma near the dielectric window 26,
The magnetic field of the permanent magnet 27 does not affect the plasma characteristics.

The cut-off density Nc of the plasma is (Nc
= The _{^{4π 2 ε o m e / e}} 2) f 2. Here, ε _o is the dielectric constant of vacuum, and f is the frequency.

On the other hand, as another embodiment of the present invention, a fitting recess for the permanent magnet 27 is provided in a part of the plasma chamber 21,
The configuration is such that the permanent magnet 27 is moved to a position where the permanent magnet 27 is advanced into the fitting recess and a position where the permanent magnet 27 is retracted from the fitting recess.

That is, the seed plasma is generated as described above with the permanent magnet 27 advanced, and after the plasma 29 is ignited, the permanent magnet 27 is withdrawn. Thus, the object to be processed by the plasma 29 is not affected by the magnetic field of the permanent magnet 27.

Also, the present invention provides a permanent magnetic field generating member.
Even if an electromagnet is provided instead of the magnet 27, the seed plasma is similarly generated.
Can be generated. It should be noted that the plasma generator of the present invention
When performing the etching process, ₂, F₂
When depositing a gas such as₄, C₂H₆
Such gas is supplied from a gas supply pipe 22.

[0028]

As described above, the ignition device of the present invention generates a local electron cyclotron resonance region using the magnetic field of the magnetic field generating member provided in the plasma generation chamber and the microwave power, and generates the seed plasma in the plasma generation chamber. Is generated, the plasma is reliably ignited by this kind of plasma even in a plasma generation chamber at a low pressure of about 10 ⁻² Torr.

As a result, it is easy to implement the plasma generator using microwaves, and the plasma generator has a wide range of application.

[Brief description of the drawings]

FIG. 1 is a mechanism diagram of a plasma generator shown as one embodiment of the present invention.

FIG. 2 is a mechanism diagram of a plasma generator shown as a conventional example.

[Explanation of symbols]

 Reference Signs List 21 Plasma generation chamber 22 Gas supply pipe 23 Vacuum pump 24 Waveguide 25 Coupling hole 26 Dielectric window 27 Permanent magnet 28 Resonant zone 29 Plasma

Claims (2)

[Claims] 1. A plasma generating apparatus for generating a plasma by supplying microwave power to a plasma generating chamber, comprising: a magnetic field generating member provided in a part of the plasma generating chamber; A seed plasma generating means for generating a local electron cyclotron resonance region by using the magnetic field and the microwave power, and igniting the plasma with the seed plasma. 2. The plasma generating ignition device according to claim 1, further comprising: a magnetic field generating member that moves forward and backward in a part of the plasma generating chamber, and after the plasma is ignited, the magnetic field generating member moves out of the plasma generating chamber. An ignition device for generating plasma, comprising a seed plasma generating means for causing generation.