JPH08111298A - Thermo-plasma device - Google Patents

Abstract

PURPOSE: To provide a heat plasma device which can stable produce plasma for a long period of time. CONSTITUTION: Beams of light in the peripheral part of plasma P produced are put incident to a sensor 22 via a transparent member 21 installed in the upper part of a cylindrical member 2. Beams of light from a number of sensors are spectrally separated by a spectrograph 23, and the intensity of the beam of light having a specific wavelength is sensed. Signals sensed on the basis of these beams of light from the sensors 22 are fed to a computer and stored. In the computer the relation between the shape of plasma and the light emissive intensity due to the specific wavelength of plasma is previously stored as the database. The computer compares the stored ideal light emissive intensity distribution of the light having specific wavelength with the actually measured light emissive intensity distribution. On the basis of the result from comparison, the parameter(s) influencing the plasma shape is/are controlled.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal plasma apparatus such as a high frequency induction thermal plasma apparatus which evaporates or melts a film forming material in plasma and forms a film on a substrate by evaporation or the molten material.

[0002]

2. Description of the Related Art FIG. 1 shows a conventional high frequency induction thermal plasma device. 1 is a torch for plasma generation. The torch 1 is a cylindrical member 2 made of silicon nitride or the like, a gas ring 3 attached to the upper portion of the cylindrical member 2, a cylindrical member 2
It is formed of the high frequency coil 4 and the like arranged on the outside of the. The cylindrical member 2 is formed in a double pipe structure, and the cooling water is supplied to the inside of the double pipe from the cooling water inlet passage 5 and the cooling water is discharged from the outlet passage 6. Gas ring 3
Although not shown, is connected to a plasma gas source or a powder supply source. Gas ring 3 for powder materials and carrier gas
The plasma gas is supplied to the inside of the cylindrical member 2 from the outside of the gas ring 3 from the central portion of each. The cooling water can be circulated in the gas ring 3. Although not shown, the high frequency coil 4 is configured to be supplied with high frequency power from a high frequency power supply.

A chamber 7 is arranged below the torch 1. The inside of the chamber 7 is configured to be evacuated to a vacuum by a vacuum exhaust system (not shown). Also,
A viewing window 8 is provided in the lateral direction of the chamber 7, and
A viewing window 9 is provided diagonally below. Air is blown inside the peep windows 8 and 9,
The inside of 9 is prevented from adhering powder and the like. The operation of such a configuration will be described below.

Plasma gas is supplied into the cylindrical member 2 through the gas ring 3 of the torch 1 and the high frequency coil 4 is also provided.
Supply high frequency power to Then, the plasma P is ignited in the torch by an appropriate means. Then gas ring 3
The powder material to be deposited is supplied into the plasma P together with the carrier gas through the so as to evaporate or melt the material due to the high temperature of the plasma. The evaporated or melted material is attached onto a substrate (not shown) in the chamber 7 to form a film. At this time, in order to perform high quality film formation, the shape of the plasma P must be optimally controlled.

Therefore, it is necessary to monitor the shape of the plasma P from the outside, but the cylindrical member 2 is made of an opaque member such as silicon nitride in order to shield harmful radiation from the plasma. Therefore, viewing windows 8 and 9 are provided in the chamber 7, and the shape of the plasma P is observed with the naked eye or a television camera by observing the shape of the plasma P from the horizontal direction or obliquely below the plasma P through a monitor. Based on the confirmed tail shape of the plasma P, the flow of the gas supplied from the gas ring 3 into the cylindrical member 2 and the high frequency power supplied to the high frequency coil 4 are controlled based on the experience and intuition of the operator. The control of the flow of the plasma gas includes the local control of the flow along the wall surface of the cylindrical member 2 in the radial direction and the control of the flow of the gas rotated and flowed in the cylindrical member 2.

FIG. 2 shows another example of the conventional high-frequency induction thermal plasma apparatus, in which the same or similar components as those of the apparatus of FIG. 1 are designated by the same reference numerals. With the device of FIG.
At the center of the bottom of the chamber 7 is a stainless steel pipe 1.
0 is provided, and a peep window 11 is attached to the lower end thereof. This stainless steel pipe 10 has water 1
It is cooled by the water tank 13 in which 2 is placed. Pipe 1
A television camera 14 is provided in the lower part of 0, and a signal imaged by the camera 14 is supplied to a monitor 15 such as a cathode ray tube. In the conventional device of FIG. 2,
From directly under the plasma P, the TV camera 14 and the monitor 15
The shape of plasma can be observed by.

[0007]

In the conventional thermal plasma apparatus described above, a material such as powder is supplied into the plasma P together with the carrier gas through the gas ring 3, and the material is evaporated by thermal energy of 10,000 degrees or more. Or melted. The material evaporated in this plasma is rapidly cooled and solidified in the chamber 7 into a fine powder. This pulverized material adheres to the inside of the glass viewing windows 8 and 9. This phenomenon occurs even when air is blown inside the peep windows 8 and 9, and it appears remarkably as time passes, and after a certain amount of time, the plasma P is emitted from the peep windows 8 and 9.
Disappears at all. If this happens, the device must be stopped and the sight glass must be cleaned.

Further, depending on the raw material and the supply gas supplied to the plasma, hydrofluoric acid, hydrochloric acid, etc. may be generated during the plasma reaction process, and the reaction gas and the rapidly solidified powder adhere to the observation windows 8 and 9. By doing so, the material of the sight glass is eroded. As a result, the viewing window becomes opaque, making it difficult to observe the plasma P, making it impossible to control the plasma appropriately. Furthermore, the control of plasma in the above-mentioned apparatus is manual, requires skilled work, and lacks reproducibility, so that high-quality film formation cannot be obtained.
Further, problems such as non-uniformity of waste treatment will occur.

The present invention has been made in view of the above points, and an object thereof is to realize a thermal plasma device capable of stably forming plasma for a long time.

[0010]

A thermal plasma device according to the present invention is a thermal plasma device configured to generate a thermal plasma by heating a plasma gas, from the upper part of the formed plasma to the peripheral part of the plasma. A plurality of monitor means for monitoring light and heat are arranged, and a control means for controlling parameters contributing to plasma formation based on signals from the plurality of monitor means is provided.

[0011]

The thermal plasma apparatus according to the present invention monitors the shape of the plasma from the position above the plasma, and controls parameters such as the gas flow contributing to plasma formation in accordance with the monitored state.

[0012]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 3 shows an embodiment of the present invention, in which the same or similar parts as those of the conventional device of FIGS. 1 and 2 are designated by the same reference numerals, and detailed description thereof will be omitted. The gas ring 3 is shown in more detail in FIG. 3, in which a probe 16 is provided in the central part of the gas ring 3. An opening is made in the center of the probe 16 in its longitudinal direction,
Through this opening, the powder material is supplied together with the carrier gas into the cylindrical member 2 from a powder supply unit (not shown). A passage through which cooling water can circulate is provided in the probe 16, and the cooling water enters through an inlet 17 and is discharged through an outlet 18. A cooling water passage 19 is also provided inside the gas ring 3 to supply cooling water.

In the cylindrical member 2 having a double tube structure, the inner tube is made of silicon nitride and the outer tube is made of quartz tube. Although the cylindrical member 2 is mounted between the upper flange 20a and the lower flange 20b, the upper flange 2
An outlet passage 6 for cooling water is provided at 0a, and an inlet passage 5 for cooling water is provided at the lower flange 20b. A ring-shaped transparent member 21 is provided between the gas ring 3 and the upper flange 20a. A plurality of light receiving sensors 22 are arranged outside the transparent member 21. FIG. 4 shows a view seen from above the gas ring 3 and the control system. For example, eight sensors 22 are provided from A to H. The light from each of the sensors A to H is guided to the spectroscope 23 by an optical fiber, and only the light of a specific wavelength is selected and detected by the spectroscope 23.

The signal from each sensor corrected to a specific wavelength or an average value by the spectroscope 23 is AD-converted and then supplied to the computer 24. Computer 2
4 is an external input device 25 such as a keyboard or a monitor 26
It is connected to the. The computer 24 is also connected to an analog centralized control device 27, which controls the plasma gas control device 28, the high frequency oscillator output control device 29, the emergency emergency stop control device 30, and the like. The operation of such a configuration will be described below.

In this embodiment, first, the argon plasma is activated while increasing the high frequency output to the high frequency coil 4. Thereafter, while mixing the bimolecular gas (oxygen, nitrogen, etc.), the plasma P is stabilized by gradually increasing it to a predetermined high frequency output. At this time, the pressure inside the chamber is kept constant at, for example, 200 Torr by an automatic pressure control system (not shown). Next, the powder material is supplied to the central portion of the plasma P from a powder supply device (not shown) together with a carrier gas such as argon gas via the probe 16 located at the center of the gas ring 3.
The powder material is evaporated or melted by an active thermal plasma of 10,000 degrees or more, and further, a chemical reaction such as oxidation or nitridation is caused by the simultaneously supplied bimolecular gas, and then the substrate located under the plasma frame ( (Not shown), resulting in a high quality deposited or sprayed film on the substrate.

The light in the peripheral portion of the plasma P formed in the above process is incident on the sensor 22 via the transparent member 21. Light from the sensors A to H is dispersed by the spectroscope 23, and the intensity of light of a specific wavelength is detected. The signal detected based on the light from each of the sensors A to H is supplied to the monitor 26 via the computer 24, and the intensity of the light of the specific wavelength for each sensor is displayed.
By the way, the computer 24 stores in advance a database of the relationship between the emission intensity of a specific wavelength of plasma and the plasma shape. The computer 24 compares the stored emission intensity distribution of the light of the ideal specific wavelength with the actually measured emission intensity distribution AD-converted and supplied from the spectroscope 23. The parameters that affect the plasma shape are controlled based on the comparison result.

The parameters affecting the plasma shape include the amount of powder material supplied, the amount of carrier gas such as argon, the amount of plasma gas (bimolecular gas such as argon, oxygen and nitrogen) and the flow velocity such as radius and rotation,
For example, high frequency output. The computer 24 determines the plasma gas control device 28 and the high frequency oscillator output control device 29 based on the ideal light emission distribution and the actual light emission distribution by the centralized control device 2.
The value of each parameter is changed so as to obtain an ideal plasma shape. Further, when the shape of the plasma P changes extremely, or when the plasma P disappears, the emergency emergency stop control device 30 is controlled to immediately stop the device.

When only the emission wavelength of argon gas is selected by the spectroscope 23, the control of the argon gas flow is focused, and when only the emission wavelengths of oxygen and nitrogen gas are selected, the respective emission wavelengths are selected. Focus on gas control. Of course, by detecting the light of the specific wavelength of the powder material to be supplied, the supply amount of the powder material can be accurately controlled. Further, although the spectroscope 23 selects the specific wavelength, the parameters for detecting the total intensity of light from the plasma may be controlled.

FIGS. 5A to 5C show the shape of the formed plasma P and the optical signal intensity distributions detected on the monitor 26 through A to H of the respective sensors 22 at that time. Shows. If the distribution shown on monitor 26 of FIG. 4 is based on an ideal plasma shape, then FIG.
In the case shown in (a), the plasma is formed so as to be extremely inclined to the left side in the drawing, and the intensities of the lights incident on A to H of each sensor 22 differ accordingly. In this state,
For example, by controlling the flow of plasma gas supplied to the inside of the cylindrical member 2, as shown in FIG.
To be formed.

Although the plasma P of FIG. 5B is formed straight, it is thin, and the detection signal intensity also weakens accordingly. In this case, for example, the high frequency output is increased. In the case shown in FIG. 5C, the plasma is formed so as to be extremely inclined to the right side in the figure, and the intensities of the lights incident on A to H of the respective sensors 22 differ accordingly.
In this state, similar to the case of FIG.
The plasma gas flow supplied to the inside of the cylindrical member 2 is controlled so that the plasma P is formed straight as shown in FIG.

As described above, when the above-mentioned parameters are out of balance and the plasma is extremely bent or thinned to have a shape unfavorable for film formation, waste treatment, etc., the condition of each parameter is satisfied. , And plasma is formed into an ideal shape. In addition, adjustment of plasma gas is
This is performed by independent mass flow controllers in the radial direction and the rotating direction of the cylindrical member 2. Further, the high frequency output is, for example, a vacuum tube type high frequency oscillator (frequency 4 MH
When z) is used, it is performed by changing the output adjustment signal of the controller of the thyristor adjusting the DC power.

In the structure shown in FIG. 3, the plasma light is monitored via the transparent member 21 between the gas ring 3 and the cylindrical member 2. Since the powder material and each gas are supplied downward from the gas ring 3, a large flow of gas is generated downward from the gas ring, and a solidified powder substance or plasma generation process is generated in the surface direction of the transparent member 2. The hydrofluoric acid or hydrochloric acid generated in 1 does not go toward the transparent member 21. Therefore, the surface of the transparent member 21 is not contaminated for a long time, and it is prevented that the plasma P cannot be monitored. If the plasma monitoring position through the transparent member is above the plasma P, the solidified powder material or the substance that may corrode the transparent member does not go to the transparent member.

FIG. 6 shows another embodiment of the present invention, in which the same parts as those of the first embodiment shown in FIGS. 3 and 4 are designated by the same reference numerals. Further, FIG. 7 is a view of the torch portion of FIG. 6 viewed from above. The difference between this embodiment and the first embodiment is that the transparent member 31 is arranged at a position where the peripheral portion of the plasma P is directly captured. In the first embodiment, the transparent member 21 and the optical sensor 2 are arranged in the horizontal direction of the gas ring 3.
2 has a structure in which the plasma light leaking from the gap between the gas ring 3 and the cylindrical member 2 is indirectly detected, whereas in this embodiment, the plasma P
Since the light in the peripheral part (circumferential direction) can be directly captured, the sensitivity is excellent, and the shape of the plasma P can be guided in a more prompt and accurate stable direction.

Although the embodiment of the present invention has been described above, the present invention is not limited to this embodiment. For example, radiant heat may be detected instead of the radiant light of plasma. In that case, an infrared detector is used as the monitoring means.
Also, because it is less susceptible to powder materials,
The light was taken out from the gas ring, but if the reason is satisfied, the light may be taken out from another position. Furthermore,
The number of sensors can be arbitrarily selected according to the shape of the torch and the size of plasma. Furthermore, although the high frequency induction thermal plasma device has been described as an example, it can be applied to a direct current type thermal plasma, a microwave plasma, a hybrid thermal plasma generator having both a direct current type and an alternating current type, and the like.

[0025]

As described above, the thermal plasma device according to the present invention monitors the shape of the plasma from the upper position of the plasma, and depending on the monitored state, parameters such as gas flow contributing to plasma formation. Configured to control. As a result, plasma control can be automated without relying on a skilled person, and the reproducibility of the plasma shape can be improved. Therefore,
It is possible to perform film formation and waste treatment stably and reliably with good reproducibility. Moreover, since the shape of the plasma is monitored from above the formed plasma, the observation window is not contaminated by the powder material or the like, and the plasma can be reliably monitored for a long time.

[Brief description of drawings]

FIG. 1 is a diagram showing a conventional high-frequency induction thermal plasma device.

FIG. 2 is a diagram showing a conventional high-frequency induction thermal plasma device.

FIG. 3 is a diagram showing a torch portion of a high frequency induction thermal plasma device which is an embodiment of the present invention.

4A and 4B are a view seen from an upper part of a torch portion and a state of controlling plasma in the embodiment of FIG.

5 is a diagram showing a plasma shape and an optical signal intensity distribution on a monitor in the examples of FIGS. 3 and 4. FIG.

FIG. 6 is a view showing a torch portion of a high frequency induction thermal plasma device which is another embodiment of the present invention.

FIG. 7 is a view seen from above the torch portion in the embodiment of FIG.

[Explanation of symbols]

 1 Torch 2 Cylindrical member 3 Gas ring 4 High frequency coil 16 Probe 21 Transparent member 22 Sensor 23 Spectrometer 24 Computer 26 Monitor 27 Central control device 28 Plasma gas control device 29 High frequency oscillator output control device 30 Emergency emergency stop control device

Claims (4)

[Claims] 1. A thermal plasma device configured to generate a thermal plasma by heating a plasma gas, wherein a plurality of means for monitoring light from the upper portion of the formed plasma to the peripheral portion of the plasma are arranged, and a plurality of monitors are provided. A thermal plasma device comprising a control means for controlling a parameter that contributes to plasma formation based on a signal from the means. 2. The thermal plasma apparatus according to claim 1, wherein each monitor means detects the total intensity of light from the peripheral portion of the plasma. 3. The thermal plasma apparatus according to claim 1, wherein each of the monitoring means detects the intensity of light of a specific wavelength among the light from the plasma peripheral portion. 4. A thermal plasma apparatus, which supplies a plasma gas or the like into a plasma chamber to generate a thermal plasma by heating the plasma gas, and monitors radiant heat from an upper portion of the formed plasma to a peripheral portion of the plasma. The thermal plasma apparatus is characterized in that a plurality of means for arranging are arranged, and a control means for controlling parameters contributing to plasma formation based on signals from a plurality of monitor means is provided.