JP7130899B2 - Plasma device - Google Patents

Description

The present invention relates to plasma devices.

In Patent Document 1, under reduced pressure below atmospheric pressure, anhydrous magnesium halide is exposed to plasma in a reducing gas atmosphere, and the anhydrous magnesium halide is exothermically reacted with active species to produce anhydrous magnesium halide. A method for producing metallic magnesium is disclosed, which is characterized by reducing to obtain metallic magnesium.

Specifically, microwaves are supplied into the container through the window of the dielectric material to generate microwave surface wave hydrogen plasma, and the microwave surface wave hydrogen plasma reduces anhydrous magnesium halide to convert metallic magnesium are generating.

Patent Document 1 discloses that the plasma reaction is accelerated by heating anhydrous magnesium halide to a sublimation start temperature in a plasma atmosphere.

Japanese Unexamined Patent Application Publication No. 2016-216780

On the other hand, in order to control the reaction between the raw material and the plasma, it is preferable to be able to control the supply amount of the raw material. Thus, it is conceivable to control the supply amount of the gaseous raw material supplied to the reaction chamber.

Therefore, when such a structure is provided, there arises a problem that the powdery raw material stored in the raw material storage unit is spouted into the reaction chamber.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a plasma apparatus capable of suppressing ejection of raw materials into a reaction chamber.

In order to achieve the above objects, the present invention is grasped by the following configurations.
(1) A plasma apparatus of the present invention is a plasma apparatus capable of plasma-processing a raw material in a gaseous state, comprising a reaction chamber for processing the raw material in a gaseous state with the plasma, and vaporizing the raw material in the reaction chamber. A raw material storage unit for storing the raw material to be supplied, and an electron penetration suppressing means for suppressing electrons in the plasma entering the raw material storage unit from the reaction chamber.

(2) In the configuration of (1) above, the electron intrusion suppressing means releases the electrons on a receiving port for receiving the raw material in a gaseous state in the reaction chamber or between the receiving port and the raw material storage section. A magnet is provided to form trapping magnetic field lines.

(3) In the configuration of (1) above, the electron intrusion suppressing means includes a conductive cylindrical member provided at a receiving port for receiving the raw material in a gaseous state in the reaction chamber, and an electrically conductive cylindrical member provided at a receiving port for receiving the gaseous raw material in the reaction chamber. a first power supply for applying a current toward the side; a conductive electrode section disposed in the center of the cylindrical member and spaced apart from the cylindrical member; and applying a voltage between the cylindrical member and the electrode section. and a second power source, wherein the electron intrusion suppressing means forms a Lorentz force that suppresses the electrons from moving from the receiving port to the raw material storage portion.

ADVANTAGE OF THE INVENTION According to this invention, the plasma apparatus which can suppress that a raw material blows out in a reaction chamber can be provided.

4 is a graph showing the boundary between the reaction that proceeds to the right side and the reaction that proceeds to the left side of Equation 2 when the partial pressure of hydrogen atoms is changed. BRIEF DESCRIPTION OF THE DRAWINGS It is sectional drawing for demonstrating the plasma apparatus of 1st Embodiment which concerns on this invention. It is a figure for demonstrating the basic content for generating a Lorentz force. It is a figure for demonstrating the electron intrusion suppression means of 2nd Embodiment which concerns on this invention.

EMBODIMENT OF THE INVENTION Hereinafter, with reference to an accompanying drawing, the form (henceforth, embodiment) for implementing this invention is demonstrated in detail.
The same numbers or symbols are given to the same elements throughout the description of the embodiment.

Hereinafter, using anhydrous magnesium chloride as a raw material, the gaseous raw material is reduced with hydrogen plasma (specifically, microwave surface wave hydrogen plasma) in the reaction chamber 2 to produce a magnesium product containing magnesium hydride ( Hereinafter, the case of obtaining a product containing magnesium hydride will be described as an example.

However, since this reaction cannot be explained from a general reaction formula, the reason why it can be realized will be briefly explained.
Normally, the reaction between anhydrous magnesium chloride and hydrogen is represented by the following formula 1.
MgCl ₂ + H ₂ ⇔ MgH ₂ + Cl ₂ (1)

The problem here is how to set the environment (pressure and temperature) during the reaction so that the right side of Equation 1 becomes stable and the reaction proceeds to the right side.

Which one is more stable can be determined by considering the Gibbs free energy. Assuming that the pressure is 10 Pa to generate hydrogen plasma, the temperature in the reaction chamber 2 must be about 1150° C. or higher in order to advance the reaction to the right.

In such a high temperature state, magnesium hydride itself becomes a gaseous state, so it is necessary to lower the temperature in the reaction chamber 2 in order to deposit it as a solid. Since the reaction to the left of 1 predominates, the material that precipitates as a solid will be anhydrous magnesium chloride, and magnesium hydride will not precipitate.
Therefore, from the general reaction formula (see formula 1), it is concluded that it is difficult to react anhydrous magnesium chloride with hydrogen to obtain magnesium hydride.

However, excited atoms/molecules, radicals (chemically active atoms/molecules), electrons, ions (positive and negative), and neutral atoms/molecules exist in microwave surface wave hydrogen plasma. By considering the reaction formula considering the above state, it is possible to explain that magnesium hydride can be produced by irradiating anhydrous magnesium chloride with microwave surface wave hydrogen plasma.

For example, assuming a reaction formula in which a hydrogen atom exists, as shown in the following formula 2, the boundary between the reaction proceeding to the right and the reaction proceeding to the left is shown in FIG. is.
MgCl ₂ + 2H + H ₂ ⇔ MgH ₂ + 2HCl (2)

In FIG. 1, the pressure in the reaction chamber 2 (see FIG. 2) is 10 Pa, the horizontal axis is the partial pressure (mPa) of hydrogen atoms, and the vertical axis is temperature (° C.). ) is changed, the boundary between the reaction that proceeds to the right and the reaction that proceeds to the left is shown in degrees (° C.).

As can be seen from Fig. 1, when the partial pressure of hydrogen atoms is the same, _MgH2 is produced by lowering the temperature, and at the same temperature, the higher the partial pressure of hydrogen atoms, the more _MgH2 is produced. It has become so.

Here, it should be noted that there is a solution that produces _MgH2 even in a temperature range lower than 100°C, which is the temperature at which _MgH2 begins to decompose into Mg and H2 at ₁₀ Pa, and _MgH2 can be satisfactorily converted into a solid state. It is possible to precipitate as

Therefore, like the plasma apparatus 1 of the first embodiment described below, magnesium hydride is deposited in a range where high-density microwave surface-wave hydrogen plasma in which hydrogen atoms and the like can actually be assumed exists. Adhesion means 80 (see FIG. 2) was provided, and an experiment was conducted to adhere magnesium hydride. Magnesium product adhering to surface 81 (see FIG. 2) of adhesion means 80 violently foamed by simply dripping water droplets to produce hydrogen. It has been confirmed that the plasma device 1 contains magnesium hydride to the extent that it generates .

However, even in a plasma apparatus 1 other than the plasma apparatus 1 in which the adhesion means 80 is provided as in the following embodiment, the powdery raw material stored in the raw material storage unit 51 is ejected into the reaction chamber 2. Therefore, the attachment means 80 is not essential in the present invention.

(First embodiment)
FIG. 2 is a cross-sectional view for explaining the plasma device 1 of the first embodiment according to the present invention.
As shown in FIG. 2, the plasma apparatus 1 includes a housing 10 forming a reaction chamber 2 for plasma-processing gaseous raw materials (anhydrous magnesium chloride in this example). The reaction chamber 2 has a first space F and a second space S by providing a partition 11 having an opening 11A in the housing 10, but the partition 11 may be omitted. , the reaction chamber 2 may be formed as one space.

The plasma apparatus 1 includes a window W made of a dielectric material (for example, quartz or ceramics) provided in a portion of the reaction chamber 2 where microwaves are incident, and a window W for generating microwave surface wave plasma. A microwave generating means 20 (for example, a magnetron) for generating microwaves supplied to the first space F in the reaction chamber 2 via the and a waveguide 21 for guiding.

When microwaves are supplied into the reaction chamber 2 through the window W, a surface wave is formed on the surface of the window W exposed in the reaction chamber 2, and the density is higher than the cutoff angular frequency of the surface wave. A density plasma (high density microwave surface wave plasma) is generated.

Since the microwave surface wave plasma (microwave surface wave hydrogen plasma in this example) has a high electron density, the irradiated microwave is reflected on the surface of the microwave surface wave plasma and does not enter the inside, but the microwave Wave surface waves are propagated along the surface of the plasma.

In this embodiment, the frequency of the generated microwave is 2.45 GHz, but it is not necessary to be limited to this frequency. It may be 6 MHz, 27.1 MHz, 13.56 MHz, and the like.

The plasma apparatus 1 also includes a depressurizing means 30 for discharging the gas in the reaction chamber 2 and reducing the pressure in the reaction chamber 2 .
Specifically, as the decompression means 30, the plasma apparatus 1 is connected to the first space F through a first exhaust pipe 31 provided with a first exhaust valve 31A that determines the presence or absence of exhaust by an opening/closing operation or opening/closing control. The second space S is connected to the second space S through a second exhaust pipe 33 provided with a first vacuum pump 32 connected and a second exhaust valve 33A that determines whether or not to exhaust air by an opening/closing operation or opening/closing control. a vacuum pump 34;

In order to stably generate high-density microwave surface wave plasma (microwave surface wave hydrogen plasma in this example), it is advantageous for the pressure in the reaction chamber 2 to be low. The internal pressure is preferably 1/10 atmospheric pressure or less, more preferably 1/100 atmospheric pressure or less, and even more preferably 1/1000 atmospheric pressure or less.

In the case of a vacuum pump with a weak gas suction force, it takes time to increase the degree of vacuum in the reaction chamber 2. Therefore, in order to eliminate such setup time, the first vacuum pump 32 or the second vacuum pump At least one of 34 is preferably a mechanical booster pump having a high gas suction force.

The plasma apparatus 1 includes a first pressure gauge 32A for measuring the pressure inside the first space F of the reaction chamber 2 and a second pressure gauge 32A for measuring the pressure inside the second space S of the reaction chamber 2. A gauge 34A is provided, for example, based on the pressure measured by the first pressure gauge 32A, so that the pressure in the first space F becomes a predetermined pressure (eg, about 10 Pa), the first vacuum pump 32 and the operation of the first exhaust valve 31A.

For example, the first vacuum pump 32 may be operated (ON), and the operation of the first exhaust valve 31A may be controlled (opening/closing control) based on the pressure measured by the first pressure gauge 32A. Conversely, the operation of the first vacuum pump 32 may be controlled (ON/OFF control) while the first exhaust valve 31A is kept open.

Similarly, for example, based on the pressure measured by the second pressure gauge 34A, the second vacuum pump 34 and the second exhaust valve are adjusted so that the pressure in the second space S becomes a predetermined pressure (eg, about 10 Pa). You may make it control the operation|movement of 33A.

For example, the second vacuum pump 34 may be operated (ON), and the operation of the second exhaust valve 33A may be controlled (opening/closing control) based on the pressure measured by the second pressure gauge 34A. Conversely, the operation of the second vacuum pump 34 may be controlled (ON/OFF control) while the second exhaust valve 33A is kept open.

However, it is not necessary to operate both the two vacuum pumps (the first vacuum pump 32 and the second vacuum pump 34) in order to set the pressures in the first space F and the second space S to the predetermined pressures.

For example, as a preliminary setup, the two vacuum pumps (the first vacuum pump 32 and the second vacuum pump 34) are operated only when the pressure in the reaction chamber 2 is set to a predetermined pressure, and the pressure in the reaction chamber 2 is set to a predetermined pressure. When the pressure reaches , the first exhaust valve 31A is closed to stop the operation of the first vacuum pump 32, and thereafter, based on the pressure measured by the first pressure gauge 32A or the second pressure gauge 34A, the reaction The operations of the second vacuum pump 34 and the second exhaust valve 33A may be controlled so as to maintain the pressure inside the chamber 2 at a predetermined pressure.

The pressure measured by the first pressure gauge 32A and the second pressure gauge 34A was averaged as the measured value of the pressure in the reaction chamber 2 used when maintaining the pressure in the reaction chamber 2 at a predetermined pressure. You may make it use a thing.

The plasma apparatus 1 also includes hydrogen supply means (not shown) for supplying hydrogen as a gas forming a reducing atmosphere into the reaction chamber 2 .
In this embodiment, the gas to be converted into microwave surface wave plasma is hydrogen, so it is called a hydrogen supply means. This hydrogen supply means is only a specific example of the gas supply means for the gas to be turned into microwave surface wave plasma.

For example, the hydrogen supply means includes a hydrogen storage unit (a hydrogen cylinder or a hydrogen storage tank) (not shown) serving as a hydrogen supply source, and a hydrogen supply pipe (in this example, a first A supply pipe 41 and a second supply pipe 42), and a mass flow meter or the like that is provided on the hydrogen supply pipe and controls the amount of hydrogen (gas) supplied to the reaction chamber 2 to be converted into microwave surface wave plasma. supply amount control means (first supply amount control means MFC1 and second supply amount control means MFC2 in this example);

If the hydrogen storage unit is a hydrogen cylinder, it will be replaced with another hydrogen cylinder when the remaining amount of hydrogen in the hydrogen cylinder decreases. Hydrogen supply pipes for supplying hydrogen from the hydrogen storage unit to the reaction chamber 2 (in this example, the first supply pipe 41 and the second The configuration may be limited to up to two supply pipes 42) and may not include a hydrogen storage unit.
That is, in the above description, the portion other than the hydrogen storage unit may be the hydrogen supply means of the plasma device 1 .

In addition, when the gas to be converted to microwave surface wave plasma is other than hydrogen, the hydrogen storage portion naturally becomes a storage portion storing the other gas. It is only a specific example of the gas storage part that stores the gas to be converted.

Furthermore, when the gas to be converted to microwave surface wave plasma is other than hydrogen, the hydrogen supply pipe is a gas supply pipe for supplying gas from the gas storage part storing the gas to be converted to microwave surface wave plasma to the reaction chamber 2. Therefore, the hydrogen supply pipe is only a specific example of the gas supply pipe for supplying the gas from the gas storage unit to the reaction chamber 2 .

Going back to the beginning, specifically, the hydrogen storage unit is connected to the first space F via the first supply pipe 41 so that hydrogen can be supplied to the first space F, and via the second supply pipe 42 It is connected so that hydrogen can be supplied to the second space S.
A first supply amount control means MFC1 is provided on the hydrogen storage section side of the first supply pipe 41, and a first supply valve 41A that determines whether or not supply is to be performed by an opening/closing operation or opening/closing control is provided downstream of the first supply amount control means MFC1. there is

Similarly, a second supply amount control means MFC2 is provided on the side of the hydrogen storage section of the second supply pipe 42, and a second supply valve 42A that determines whether or not supply is to be performed by an opening/closing operation or opening/closing control is provided downstream of the second supply amount control means MFC2. ing.

Further, the plasma apparatus 1 is provided with a raw material supply means 50 for vaporizing anhydrous magnesium chloride as a raw material and supplying it to microwave surface wave plasma (microwave surface wave hydrogen plasma in this example).

Specifically, the raw material supply means 50 includes a raw material storage unit 51 that stores powdery anhydrous magnesium chloride as a raw material, and a microwave surface wave plasma (in this example, a microwave surface wave hydrogen plasma), a straight raw material supply pipe 52 for supplying anhydrous magnesium chloride in the raw material storage unit 51 into the first space F of the reaction chamber 2, and electric power from the first power supply 53A. A first heating unit 53 that heats the raw material supply pipe 52 and the raw material storage unit 51 by generating heat when supplied, and a first thermometer 54 that measures the temperature of the first heating unit 53 are provided.

Then, based on the result of temperature measurement by the first thermometer 54, the amount of electric power supplied from the first power supply 53A to the first heating unit 53 is controlled, and the temperatures of the raw material supply pipe 52 and the raw material storage unit 51 are controlled. By controlling, the supply amount of the gaseous raw material supplied into the first space F from the receiving port 12 for receiving the raw material (in this example, anhydrous magnesium chloride) of the reaction chamber 2 is controlled.

For example, anhydrous magnesium chloride becomes a gaseous state at a temperature of about 700° C., and if the temperature is raised above this temperature, the vaporization speed increases, and the gaseous anhydrous magnesium chloride supplied into the first space F of the reaction chamber 2 The supply amount of magnesium chloride can be increased.
Conversely, if the temperature approaches about 700° C., the rate of vaporization slows down, and the amount of gaseous anhydrous magnesium chloride supplied into the first space F of the reaction chamber 2 can be reduced.

Further, the plasma device 1 is provided in the first space F of the reaction chamber 2 as a heating means 60 for heating the inside of the reaction chamber 2, and is supplied with electric power from the second power supply 61A to generate heat to heat the first space of the reaction chamber 2. A second heating unit 61 that heats the space F is provided.

The plasma apparatus 1 is provided with a second thermometer 62 for measuring the temperature in the first space F of the reaction chamber 2, and the result of the temperature measurement by the second thermometer 62 is different from the set predetermined temperature. The amount of power supplied from the second power source 61A to the second heating unit 61 is controlled so that the temperature in the first space F of the reaction chamber 2 is kept at a predetermined temperature.

Specifically, the second heating unit 61 maintains the temperature in the first space F at a temperature at which anhydrous magnesium chloride can exist as gas.

On the other hand, on the outside of the second heating unit 61, in order to prevent the housing 10 from becoming hot due to the radiant heat from the second heating unit 61, a reflector 70 that reflects the radiant heat is provided. Cooling pipes 71 for water cooling are provided on the outer surface.

As described above, when the plasma apparatus 1 is provided with heat insulating means such as the reflector 70 that prevents heat conduction so that the second heating unit 61 does not heat an excessive portion, the temperature of the housing 10 does not become high. Not only can the deterioration of packings and the like used in various parts of the body 10 be suppressed, but also the heat insulation efficiency can be improved, so that power consumption can be reduced.

In addition, the reflector 70 is provided with an insertion tube 72 that is inserted from the first space F into the second space S through the opening 11A of the partition 11 at a position near the center on the upper side. As will be described later, microwave surface wave hydrogen plasma, magnesium-containing gas, and the like are emitted from the insertion tube 72 into the second space S.

As shown in FIG. 2, the plasma device 1 is provided with a deposition means 80 for depositing a product containing magnesium hydride at a position facing the insertion tube 72. After the plasma device 1 is stopped, the deposition The attachment means 80 is detachably attached to the housing 10 so that the means 80 can be taken out.

The adhesion means 80 has a supply port IN (temperature control medium supply port) for supplying a temperature control medium (in this example, water or gas controlled to a temperature of less than 100° C.) and an outlet OUT for discharging the temperature control medium. (Temperature control medium discharge port) is provided, and the container structure has a temperature control medium storage part that prevents the temperature control medium from leaking into the second space S of the reaction chamber 2 .

Note that the adhesion means 80 is such that the surface 81 on the side facing the insertion tube 72, on which the product containing magnesium hydride is to be adhered, is exposed to a high-density microwave surface wave that allows the luminous state emitted from the insertion tube 72 to be visually confirmed. By arranging at a position where the plasma (microwave surface wave hydrogen plasma) directly contacts, at least the surface 81 is arranged within the range where the microwave surface wave plasma that generates the surface 81 exists.
Therefore, the surface 81 is in a special environment in which the presence of high-density microwave surface-wave hydrogen plasma (for example, hydrogen ions, hydrogen atoms, etc.) can be assumed.

The plasma device 1 is temperature control means for keeping the surface temperature of the surface 81 of the deposition means 80 on which the product containing magnesium hydride is deposited within a predetermined temperature range suitable for depositing the product containing magnesium hydride. (not shown).

The temperature control means, for example, supplies a temperature control medium (in this example, water or gas controlled to a temperature of less than 100° C.) from the supply port IN into the temperature control medium storage portion of the adhesion means 80, and the discharge port OUT. A circulation device (not shown) that circulates the temperature control medium so as to discharge the temperature control medium from the outlet OUT, and a temperature control device (not shown) that adjusts the temperature of the temperature control medium discharged from the discharge port OUT to a set temperature. ) and .
Specifically, in this embodiment, the circulation device (not shown) is a pump or the like, and the temperature control device (not shown) is a heat exchanger or the like.

If the outside air can be used as the temperature control medium, a pump for supplying the outside air may be connected to the supply port IN, and the discharge port OUT may be open to the atmosphere. is unnecessary.

Then, in a special environment where the existence of high-density microwave surface wave hydrogen plasma (for example, hydrogen ions, hydrogen atoms, etc.) can be assumed, and the surface temperature is suitable for depositing products containing magnesium hydride At the surface 81 kept within the predetermined temperature range, the reaction proceeding to the right side in the above-described formula (2) is promoted, and a situation is created in which magnesium hydride can exist without being decomposed. can be done.

For example, if the surface temperature of the surface 81 exceeds 200°C, the ratio of magnesium hydride in the product is significantly reduced, so the predetermined temperature range suitable for depositing the product containing magnesium hydride is 200°C or less. It is preferably in the range, more preferably in the range of 150° C. or lower, and even more preferably in the range of 100° C. or lower.

In an experiment, in the case of a product containing magnesium hydride deposited at a surface temperature exceeding 200°C, water droplets were dropped on the product containing magnesium hydride, and it was found that the bubbling phenomenon associated with the separation of hydrogen was very weak. Confirmed.

On the other hand, in the case of a product containing magnesium hydride deposited at a surface temperature of 100°C or less, it was confirmed that when water droplets were dropped on the product, a violent bubbling phenomenon accompanied by the separation of hydrogen was observed. A hydrogen detector tube is used to confirm that the is hydrogen.

In addition, when the surface temperature exceeds 100 ° C., a reaction in which magnesium hydride decomposes into hydrogen and metallic magnesium also occurs, so the proportion of magnesium hydride in the product containing precipitated magnesium hydride will decrease. Therefore, the predetermined temperature range suitable for precipitation of the product containing magnesium hydride is most preferably 100° C. or less from the viewpoint of suppressing the decomposition reaction of magnesium hydride.

In addition, in the experiment, the amount of precipitation per unit time of the product containing magnesium hydride was larger at about 70°C than when the surface temperature was about 80°C, and the amount per unit time was further increased at about 50°C. Since the result of increasing the amount of precipitation is obtained, the predetermined temperature range suitable for precipitation of the product containing magnesium hydride is preferably a lower temperature range from the viewpoint of the amount of precipitation per unit time. .

That is, the predetermined temperature range suitable for precipitation of the product containing magnesium hydride is preferably 80 ° C. or less, more preferably 70 ° C. or less, and 50 ° C. or less. more preferred.

Depending on the product, the adhesion means 80 may be kept warm instead of being cooled. In this case, the temperature control device is a heater or the like.
For example, when the temperature at which metallic magnesium becomes solid is in the range of 400° C. or lower, and the temperature of the surface 81 is set to 250° C. or higher and 400° C. or lower, the content of magnesium hydride is significantly reduced, while the content of metallic magnesium is reduced. Since precipitation is possible, it is thought that a product with a high proportion of metallic magnesium will be precipitated.

The plasma device 1 also has an air release pipe 90 provided with a leak valve 91 in the middle. ing.

This atmospheric release pipe 90 is for opening the reaction chamber 2 to the atmosphere as an emergency measure when the pressure in the reaction chamber 2 becomes abnormal, and the leak valve 91 is normally closed. , so that the air does not enter the reaction chamber 2 .

By the way, in order to reduce anhydrous magnesium chloride and efficiently produce a product containing magnesium hydride, it is preferable that the density of the microwave surface wave plasma (microwave surface wave hydrogen plasma in this example) is high.

One method for this is to increase the microwave power (microwave intensity) of the microwave supplied into the reaction chamber 2 in order to generate microwave surface wave plasma (microwave surface wave hydrogen plasma in this example). to make it higher.

However, this method means increasing the amount of power to be supplied to the microwave generating means 20 for generating microwaves, resulting in a large increase in the amount of power used on average.

Therefore, in the present embodiment, the microwave generating means 20 generates pulse-like microwaves, and while increasing the peak value of the microwave power (microwave intensity), the average microwave power (microwave intensity) ) is lowered.

However, pulse-like microwaves mean those accompanied by periodic microwave power (microwave intensity), and are not necessarily limited to those whose microwave power (microwave intensity) periodically becomes zero. not to be

Specifically, the microwave generating means 20 has a period of 150 microseconds or less (preferably 100 microseconds or less, more preferably 50 microseconds or less, more preferably 50 microseconds or less) in which the peak value of the microwave power (microwave intensity) of the pulse-like microwave appears. microseconds or less), and supply microwaves having a peak microwave power into the reaction chamber 2 before the plasma (microwave surface wave hydrogen plasma in this example) is significantly attenuated. By doing so, the average power used by the microwave generating means 20 is suppressed while maintaining the microwave surface wave plasma having a density substantially corresponding to the peak value of the microwave power (microwave intensity). .

In this way, when the microwave generating means 20 generates microwaves other than pulsed microwaves with substantially constant microwave power (microwave intensity), the plasma density is 10 ¹² /cm ³ or more. If it is ¹⁴ /cm ³ or less, even if the average microwave power is the same, when the microwave generating means 20 generates pulse-like microwaves, the microwave power (microwave intensity) peak Since the value can be increased, a higher plasma density (for example, a high plasma density of 10 ¹⁵ /cm ³ or more) can be obtained, and even if the average microwave power is the same, a plasma density higher than one order of magnitude can be obtained. be able to.

Therefore, by setting the microwave generating means 20 to generate pulse-like microwaves, high-density microwave It can generate surface wave plasma.
Moreover, when the peak value of the microwave power (microwave intensity) increases, there is also the effect that it becomes easier to ignite the microwave surface wave plasma.

Microwave surface wave plasma has a low electron temperature (e.g., about 1 eV) compared to other plasmas (e.g., high-frequency plasma, DC discharge plasma, etc.), and has a high electron temperature (e.g., about 1 eV) like other plasmas. For example, it has the advantage of less energy loss, unlike plasma that consumes energy to achieve 10 eV or more.
Another feature of microwave surface wave plasma is that the temperature of the ions and molecules in the plasma is significantly lower than that of thermal plasma (almost normal temperature).
Furthermore, the microwave surface wave plasma can uniformly generate the above-described high-density plasma over a large area of, for example, 0.5 m ² or more.

Next, a raw material in a gaseous state (in this example, anhydrous magnesium chloride) is supplied into the reaction chamber 2, and a reduction process is performed with plasma (in this example, microwave surface wave hydrogen plasma) to produce a product different from the raw material. While explaining the process (manufacturing method) for obtaining (in this example, a product containing magnesium hydride), the plasma device 1 will be further explained.
However, the raw material may be anhydrous magnesium halide, metallic magnesium, or the like.

First, as a preparatory step, the pressure reduction means 30 (the first vacuum pump 32 and the second vacuum pump 34) is driven to reduce the pressure in the reaction chamber 2 to a predetermined pressure (for example, about 10 Pa). to implement.

Then, when the pressure in the reaction chamber 2 reaches a predetermined pressure (for example, about 10 Pa), pulse-like microwaves are supplied into the reaction chamber 2 by the microwave generation means 20, and hydrogen is supplied by the hydrogen supply means. is started, and the generation (emission) of microwave surface wave plasma (microwave surface wave hydrogen plasma in this example) is confirmed through an observation window (not shown), for example.
It should be noted that whether or not the microwave surface wave plasma (microwave surface wave hydrogen plasma in this example) is generated may be confirmed by a measuring instrument for measuring the emission spectrum intensity.

At this time, supply amount control means (first supply amount control means MFC1 and second supply amount control means) for controlling the supply amount of the gas (hydrogen in this example) to be supplied to the reaction chamber 2 for microwave surface wave plasma MFC 2) supplies gas (hydrogen in this example) into the reaction chamber 2 while the amount of gas (hydrogen in this example) is controlled.

Then, after confirming the generation (light emission) of the microwave surface wave plasma (microwave surface wave hydrogen plasma in this example), next, the heating means 60 for heating the inside of the reaction chamber 2 is driven to A procedure for raising the temperature in 1 space F to a predetermined temperature (for example, about 700° C.) is performed.

After the microwave surface wave plasma (microwave surface wave hydrogen plasma in this example) is generated in this way, if the heating means 60 for heating the inside of the reaction chamber 2 is driven, the inner wall surface of the reaction chamber 2 will be Even if metallic magnesium or the like adhered during the previous treatment is present in the substrate, the generation of microwave surface wave plasma (microwave surface wave hydrogen plasma in this example) is not hindered.

Specifically, since metallic magnesium reflects microwaves, if a large amount of vaporized metallic magnesium is present in the reaction chamber 2, microwaves supplied from the window W are reflected by the metallic magnesium, resulting in microwave surface waves. It may interfere with the initial ignition (start of generation) of the plasma (in this example, microwave surface wave hydrogen plasma).

On the other hand, if the initial ignition (start of generation) was not hindered and the microwave surface wave plasma (microwave surface wave hydrogen plasma in this example) was generated, the particles adhered to the inner wall surface of the reaction chamber 2 Vaporization of metal magnesium does not affect microwave surface wave plasma (microwave surface wave hydrogen plasma in this example).

Therefore, as described above, it is preferable to drive the heating means 60 after confirming the generation (light emission) of the microwave surface wave plasma (microwave surface wave hydrogen plasma in this example).

However, if the inside of the reaction chamber 2 is kept at about 700° C., the temperature of the inner wall surface of the reaction chamber 2 is basically kept above the vaporization temperature of metallic magnesium. Precipitation of magnesium can be suppressed.

For this reason, after stopping the supply of anhydrous magnesium chloride as a raw material at the end of the treatment, if the heating means 60 is stopped after metallic magnesium is no longer floating in the reaction chamber 2, the reaction Since metallic magnesium can be prevented from adhering to the inner wall surface of the chamber 2, there is no problem even if the heating means 60 is driven before the microwave surface wave plasma (microwave surface wave hydrogen plasma in this example) is generated. Driving the heating means 60 after generating the microwave surface wave plasma is just a precaution.

When the heating means 60 starts heating the inside of the first space F, the temperature control means (not shown) starts supplying the temperature control medium adjusted to the temperature set in the adhesion means 80, and the adhesion means A procedure is performed to keep the surface temperature of the surface 81 of 80 at a surface temperature at which magnesium hydride precipitates (in this example, a temperature within a temperature range of less than 100°C).

Thereafter, the supply of anhydrous magnesium chloride as a raw material is started by the raw material supply means 50, and the anhydrous magnesium chloride as a raw material is heated in the reaction chamber 2 by microwave surface wave plasma (microwave surface wave hydrogen plasma in this example). When the treatment procedure is started, the surface temperature (in this example, the temperature within the temperature range of less than 100 ° C.) for depositing the product containing magnesium hydride is set to the surface 81 within the range where the microwave surface wave plasma exists. The procedure of depositing a magnesium hydride-containing product onto the surface 81 of the deposition means 80 placed in the .

That is, toward the surface 81 of the adhesion means 80, a microwave surface wave plasma (microwave surface wave hydrogen plasma in this example) and a magnesium-containing gas (because it is in the plasma, magnesium atoms, magnesium chloride, magnesium hydride) ) is blown, the temperature in the vicinity of the surface 81 drops sharply, and as shown in FIG. The containing product adheres (deposits) to the surface 81 of the adhesion means 80 .

However, only magnesium hydride is not necessarily deposited on the surface 81 of the adhesion means 80. Of course, it is preferable that the proportion of magnesium hydride is close to 100%. Anhydrous magnesium chloride and the like may also be included.
A product different from the raw material is therefore to be understood as a product containing a substance different from the raw material.

After driving the plasma device 1 for a predetermined time, the driving of the plasma device 1 is stopped, the pressure in the reaction chamber 2 is returned to the atmospheric pressure, and the temperature at which the adhesion means 80 can take out (for example, magnesium hydride is a temperature that does not react violently with moisture in the air), the adhesion means 80 is removed, and a procedure for recovering the product containing magnesium hydride adhering to the surface 81 of the adhesion means 80 is performed.

During the period until the driving of the plasma device 1 is stopped and the deposition means 80 is removed, the reaction chamber 2 contains a gas with a low dew point (for example, air with a low dew point, nitrogen, and a rare gas (helium, argon, etc.). ) is supplied and purged.

In addition, since the surface 81 is under a special environment where the existence of high-density microwave surface-wave hydrogen plasma (for example, high-density hydrogen ions, hydrogen atoms, etc.) can be assumed, the surface 81 of the adhesion means 80 is coated with anhydrous chloride. Some experimental results suggest that even when magnesium is deposited, the reduction reaction proceeds and changes to magnesium hydride.

Therefore, after stopping the supply of anhydrous magnesium chloride as a raw material into the reaction chamber 2, the surface 81 of the adhesion means 80 is continued to be cooled so that the temperature of the product containing magnesium hydride adhered to the surface 81 reaches a predetermined temperature. By continuing to irradiate the microwave surface wave plasma (microwave surface wave hydrogen plasma) under the condition below (in this example, the temperature within the temperature range of less than 100 ° C.), the ratio of magnesium hydride in the product may be increased.

Then, according to the plasma apparatus 1 of the present embodiment, the attaching means 80 for attaching a product different from the raw material (a product containing magnesium hydride in this example) applies the surface 81 to a microwave surface wave plasma (a product containing magnesium hydride in this example). , microwave surface wave hydrogen plasma), and the temperature of the surface 81 of the deposition means 80 for depositing a product different from the raw material is set to a temperature suitable for depositing the product different from the raw material. A temperature control means that keeps the temperature within a predetermined temperature range (in this example, a temperature range of less than 100 ° C.) is set to an appropriate temperature, so a product that is not normally obtained (in this example, a product containing magnesium hydride ) can be obtained.

By the way, when observing the first space F without heating the inside of the first space F by the heating means 60, it is sometimes seen that the raw material (in this example, anhydrous magnesium chloride) is spouting out around the receiving port 12. As a result of investigating the cause, it became clear that the powdery raw material in the raw material storage unit 51 was charged by electrons in the plasma and ejected by electrostatic repulsion.

Therefore, in the present embodiment, as shown in FIG. 2, the plasma apparatus 1 includes an electron penetration suppression means 13 (enlarged view on the right side of FIG. See).

Specifically, the electron intrusion suppressing means 13 has a magnetic line of force that traps electrons from the receiving port 12 for receiving the gaseous raw material (in this example, anhydrous magnesium chloride) in the reaction chamber 2 to the raw material storage unit 51. A pair of magnets are provided so that the south pole and the north pole are opposed to each other.

In this embodiment, the electron intrusion suppressing means 13 is provided with a pair of permanent magnets, and the permanent magnets lose their magnetic force when the temperature reaches the Curie point or higher. , the pair of permanent magnets may be replaced by a pair of electromagnets so as to avoid such concerns.

Alternatively, one of the pair of permanent magnets or electromagnets may be an array of a plurality of permanent magnets or electromagnets, and the other of the pair of permanent magnets or electromagnets may be an array of a plurality of permanent magnets or electromagnets.

Further, the electron penetration suppressing means 13 only needs to prevent electrons in the plasma from entering the raw material storage unit 51 from the inlet 12. It may be provided on the receiving port 12 for receiving (inside the reaction chamber 2).

As described above, the electron penetration suppressing means 13 is provided, and the electrons are trapped by the magnetic lines of force. Then, the magnesium chloride anhydride is not charged, and electrostatic repulsion does not occur.

Therefore, only the gaseous raw material (anhydrous magnesium chloride in this example) is supplied into the reaction chamber 2, and the controllability of the supply amount of the raw material can be improved.

(Second embodiment)
Next, the plasma device 1 of 2nd Embodiment is demonstrated.
In the first embodiment, the case where the electron intrusion suppressing means 13 is composed of a pair of magnets MG has been described. A case will be described in which the suppressing means 13A is configured to utilize the Lorentz force.

Since the second embodiment is similar to the first embodiment except for the electron intrusion suppressing means 13A, the electron intrusion suppressing means 13A will be mainly described below, and the same points as in the first embodiment will be described. may be omitted.

FIG. 3 is a diagram for explaining the basic content for generating the Lorentz force, and FIG. 4 is a diagram for explaining the electron penetration suppressing means 13A of the second embodiment. After explaining the basic content for generating the Lorentz force, the electron penetration suppressing means 13 will be explained with reference to FIG.
In FIG. 3, the left side shows a schematic diagram of the structure for generating the Lorentz force, and the right side shows the state of the Lorentz force generated by the structure.

As shown in FIG. 3, a pair of left and right magnets are arranged so that the S pole and the N pole face each other.
In the arrangement of FIG. 3, looking at the opposing poles between the pair of left and right magnets, the S pole is located on the left side (the S pole of the left magnet is located on the left side) and the N pole is located on the right side (the right side is located on the right side). Since the north pole of the magnet is positioned, the direction of the magnetic field (magnetic flux density) is from right to left.

On the other hand, by arranging a pair of electrodes in a direction perpendicular to the direction of the magnetic field (magnetic flux density) and applying a voltage, one becomes an anode (+ pole) and the other becomes a cathode (- pole).

In FIG. 3, the front side (lower side) is the anode (+ pole), the back side (upper side) is the cathode (- pole), and in the plasma (in this example, in the microwave surface wave hydrogen plasma) 3, the current I flows from the front side (lower side) to the back side (upper side).

The above state is illustrated on the right side of FIG. , the thumb of the left hand points upward, and the force (Lorentz force) is generated upward according to Fleming's left hand rule.

However, Fleming's left-hand rule indicates the force acting when the charge is positive (Lorentz force), and the force acting when the charge is negative (Lorentz force) is in the opposite direction.

Therefore, in the case of the configuration of FIG. 3, an upward force (Lorentz force) acts on positively charged ions (e.g., positive ions such as hydrogen ions in the plasma), and negatively charged ions (e.g., , anions and electrons) will have a downward force (Lorentz force).

In the configuration of FIG. 3, if the facing S and N poles are reversed, that is, if the N pole is positioned on the left side and the S pole is positioned on the right side, the direction of the magnetic field (magnetic flux density) will be reversed. Therefore, the relationship of the Lorentz force is also reversed. and electrons) will be subject to an upward force (Lorentz force).

Similarly, in the configuration of FIG. Since the direction of is reversed, the relationship of the Lorentz force is also reversed. , anions and electrons), an upward force (Lorentz force) acts.

The electron intrusion suppressing means 13A is realized using such a principle, and the configuration of the electron intrusion suppressing means 13A will be specifically described below with reference to FIG.

As shown on the left side of FIG. 4, the electron intrusion suppressing means 13A includes a cylindrical member CM made of a conductive material and an electrode portion made of a conductive material and disposed in the center of the cylindrical member CM. and a rod-shaped member SM.
In addition, the rod-shaped member SM as the electrode portion is arranged in the center of the cylindrical member CM so as to be separated from the cylindrical member CM so as not to short-circuit with the cylindrical member CM.

Referring to FIG. 2, instead of omitting the pair of magnets MG, the cylindrical member CM of the electron intrusion suppressing means 13A (see the dotted frame in the enlarged view on the right side of FIG. 2) is placed between the pair of magnets MG. , and the gaseous raw material (anhydrous magnesium chloride in this example) is supplied into the reaction chamber 2 through the cylindrical member CM.

In this embodiment, the cylindrical member CM is made of stainless steel (SUS), and the rod-shaped member SM is made of tungsten or the like that can withstand high temperatures.
However, if the cross-sectional area of the rod-shaped member SM is large and does not generate much heat, stainless steel (SUS) or the like may be used in the same manner as the cylindrical member CM. Although the shape is a circular column having a diameter of about 5 mm to 10 mm, the cross-sectional shape of the bar-shaped member SM may be polygonal such as hexagonal, or may be star-shaped.
In addition, the larger the inner diameter of the cylindrical member CM, the less pressure loss, so it is preferably 5.0 cm or more, for example.

Further, as shown in FIG. 4, the electron intrusion suppressing means 13A supplies a first power source for causing an electric current I to flow through the cylindrical member CM and a voltage for causing the cylindrical member CM and the rod-shaped member SM to function as a pair of electrodes. and a second power supply for applying.
For example, the first power supply is configured to supply a current I of 30A to 300A to the cylindrical member CM at a voltage of about 0.5V to 1.0V.
Also, the second power supply applies a voltage of about 20V to 80V.

In the configuration shown in FIG. 4, the first power source is provided so as to flow a current I from one side (eg, the upper side of FIG. 4) to the other side (eg, the lower side of FIG. 4) of the cylindrical member CM. , a second power supply is provided to apply a voltage between the cylindrical member CM and the rod-shaped member SM such that the cylindrical member CM is a cathode (negative electrode) and the rod-shaped member SM is an anode (+ electrode). there is

The diagram on the right side of FIG. 4 is a schematic diagram of the diagram on the left side viewed from above. , bottom of FIG. 4), a counterclockwise magnetic field is formed in the internal space of the cylindrical member CM, as indicated by the dotted line on the right side of FIG.

In physics textbooks, etc., it is explained that even if a current I is passed from one side of the cylindrical member CM to the other side, no magnetic field is formed in the internal space of the cylindrical member CM. In the case of a cylindrical member CM having a large inner diameter (for example, an inner diameter of 3.0 cm or more) that does not hinder the flow of the raw material (in this example, anhydrous magnesium chloride), a magnetic field is generated at the center where the rod-shaped member SM is located. A gauss meter confirms that a magnetic field is formed elsewhere, although it is not formed.
However, there is a tendency for the magnetic field to become weaker toward the center.

In addition, since the current I flows in plasma (in this example, microwave surface wave plasma), as shown in the right side of FIG. I flows.
For example, in this embodiment, a current I of approximately 1.0 A flows.

At the point of contact between the current I radially flowing from the bar member SM toward the cylindrical member CM and the counterclockwise magnetic field, a magnetic field oriented in the counterclockwise direction by drawing a tangential line to the magnetic field at the point of contact is occurring.

Therefore, in the case of the configuration shown in FIG. 4, an upward force (Lorentz force) acts on positively charged ions (positive ions such as hydrogen ions in the plasma in this example), and negatively charged. A downward force (Lorentz force) acts on the object (for example, anions and electrons).

If the first power supply is provided so that the direction of the current I flowing through the cylindrical member CM is reversed, a clockwise magnetic field is formed, so the relationship of the Lorentz force is reversed, that is, a positive charge is generated. A downward force (Lorentz force) acts on those with negative charges (e.g., cations), and an upward force (Lorentz force) acts on those with negative charges (e.g., anions and electrons). Become.

Similarly, if a second power source is provided so that the cylindrical member CM is used as an anode (+ pole) and the rod-shaped member SM is used as a cathode (- electrode), the current I flowing between the rod-shaped member SM and the cylindrical member CM is Since the direction is reversed, the Lorentz force relationship is reversed, that is, a downward force (Lorentz force) acts on positively charged objects (e.g., cations), and negatively charged objects (e.g., Anions and electrons) are subject to an upward force (Lorentz force).

Therefore, on either side of the cylindrical member CM, a force (Lorentz force) acting on positively charged substances (eg, cations) is generated, and it acts on negatively charged substances (eg, anions and electrons). Whether to generate a force (Lorentz force) is selected depending on how the first power source or the second power source is provided.

The electron penetration suppressing means 13A shown in FIG. 2 generates a force (Lorentz force) that acts on negatively charged substances (eg, anions and electrons) toward the reaction chamber 2 side.

As described above, in this embodiment, the electron penetration suppressing means 13A includes a conductive cylindrical member CM provided in the receiving port 12 for receiving the gaseous raw material (in this example, anhydrous magnesium chloride) in the reaction chamber 2, A first power supply that applies current to the cylindrical member CM from one side (one end side) to the other side (the other end side), and a conductive electrode that is arranged in the center of the cylindrical member CM and separated from the cylindrical member CM. (bar-shaped member SM in FIG. 4), and a second power source for applying a voltage between the cylindrical member CM and the electrode portion, and the electron penetration suppressing means 13A prevents electrons in the plasma from A Lorentz force is formed which restrains the movement toward the reservoir 51 .

Therefore, as in the first embodiment, the entry of electrons into the raw material storage unit 51 is suppressed, so that the raw material (in this example, anhydrous magnesium chloride) in the raw material storage unit 51 is not charged, and electrostatic repulsion occurs. As a result, the powdery raw material in the raw material storage unit 51 can be prevented from being spouted into the reaction chamber 2 .

As a result, as in the first embodiment, only the gaseous raw material (in this example, anhydrous magnesium chloride) is supplied into the reaction chamber 2, thereby enhancing the controllability of the raw material supply amount. is possible.

Although the present invention has been described above based on specific embodiments, the present invention is not limited to the above specific embodiments.
For example, in the second embodiment, the structure shown in FIG. 3 may be used as the electron penetration suppressing means 13A provided near the inlet 12 in the reaction chamber 2 as it is.

As described above, the present invention is not limited to the embodiments, and suitable modifications and improvements are also included in the technical scope of the present invention. is clear from the description of the range of

1 plasma device 2 reaction chamber 10 housing 11 partition 11A opening 12 reception ports 13, 13A electron penetration suppressing means 20 microwave generating means 21 waveguide 30 decompression means 31 first exhaust pipe 31A first exhaust valve 32 first Vacuum pump 32A First pressure gauge 33 Second exhaust pipe 33A Second exhaust valve 34 Second vacuum pump 34A Second pressure gauge 41 First supply pipe 41A First supply valve 42 Second supply pipe 42A Second supply valve 50 Material supply Means 51 Raw material storage unit 52 Raw material supply pipe 53 First heating unit 53A First power supply 54 First thermometer 60 Heating means 61 Second heating unit 61A Second power supply 62 Second thermometer 70 Reflector 71 Cooling pipe 72 Insertion pipe 80 Attachment Means 81 Surface 90 Atmospheric release pipe 91 Leak valve CM Cylindrical member F First space IN Supply port MFC1 First supply amount control means MFC2 Second supply amount control means MG Magnet OUT Discharge port S Second space SM Bar member W Window

Claims (1)

A plasma apparatus capable of plasma-processing a raw material in a gaseous state,
a reaction chamber in which the raw material in a gaseous state is treated with the plasma;
a raw material storage unit for storing the raw material to be vaporized and supplied to the reaction chamber;
an electron penetration suppressing means for suppressing electrons in the plasma entering the raw material storage unit from the reaction chamber ,
The electron intrusion suppressing means is
a conductive cylindrical member provided at a receiving port for receiving the gaseous raw material in the reaction chamber;
a first power source that applies current to the cylindrical member from one side to the other side;
a conductive electrode portion disposed in the center of the cylindrical member and spaced apart from the cylindrical member;
a second power supply that applies a voltage between the cylindrical member and the electrode unit,
The plasma apparatus , wherein the electron intrusion suppression means forms a Lorentz force that suppresses the electrons from moving from the inlet to the raw material storage section .

Images