JPS61268730A - Plasma treatment system - Google Patents

Abstract

PURPOSE:To provide the titled system of no variation in its treatability, with the plasma concentration distribution uniform in the reaction chamber, equipped with reaction chamber having a plural of ducts each fitted with both on-off valve and plamsa flow detector and on-off valve control device so as to equalize plasma flow in each duct. CONSTITUTION:In treating the surface of an object by plasma irradiation on said surface in a plasma reaction chamber, a plural of ducts are connected to said chamber, each duct being equipped with on-off valve and plasma flow detection device. Each on-off valve is controlled, based on signal from said device, so that the amount of the plasma emitted through each duct may be equal one another, thus making the distribution of the plasma gas concentration uniform within the chamber to enable uniform plasma treatment on the surface of the object to be accomplished. Said flow detection device is, e.g., differential pressure type flow meter, illuminance sensor capable of detecting plasma flow from its luminous level, etc.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to plasma processing in which the surface of a workpiece made of plastic deck such as polypropylene or polyethylene is irradiated with plasma to treat the surface of the workpiece. Regarding equipment.

(Prior art) In recent years, for example, plastic parts or products made of polypropylene, polyethylene, etc. (for example, plastic bumpers) have been increasingly used in automobiles to reduce weight. It is known that plastics generally have relatively poor adhesion to paint films.

Therefore, when painting the surface of a plastic product such as the one mentioned above, it is necessary to apply a treatment in advance to make it easier for the paint film to adhere to the surface of the product. A plasma processing apparatus is used to perform the processing. This device usually includes a cylindrical plasma reaction chamber in which a plasma gas inlet and an exhaust port are provided facing each other, and a processing gas (mainly oxygen gas is used) to be supplied to this reaction chamber in advance. It mainly consists of a plasma generation device such as a microwave oscillator that generates plasma, and a vacuum pump that reduces the pressure or evacuates the inside of the reaction chamber to enhance the processing effect. Then, in the reaction chamber, the object to be treated is irradiated with the plasma processing gas and brought into contact with the object to form a functional group on the surface of the object, thereby activating the surface and forming a bond with the coating film. It is designed to improve adhesion.

However, in the conventional plasma processing apparatus as described above, the plasma gas introduced into the reaction chamber from the inlet flows toward the exhaust port, and the peripheral part that deviates from the vicinity of the straight line connecting the inlet and exhaust port. Because the plasma gas does not spread sufficiently, the plasma gas distribution within the reaction chamber tends to be uneven.As a result, the processing performance for the object to be processed differs depending on the arrangement and location of the object. there were.

An example of a plasma processing apparatus that addresses this problem is disclosed in Japanese Utility Model Application Publication No. 59-28535. As shown in FIG. 4, this means that a plasma reaction chamber A has a plurality of exhaust ports B, .

B, and opening/closing valves C1..., C are provided in front of these exhaust ports B, . Room A
The multiple valves C2 . . . , C are sequentially opened simultaneously or intermittently while introducing plasma into the chamber. According to this, the plasma introduced into the reaction chamber A from the above-mentioned inlet flows in multiple directions depending on the number and position of each exhaust port B. Differences in processing performance depending on the arrangement state of the can be made relatively small.

However, even with the above configuration, it is not possible to completely eliminate the non-uniformity of the plasma gas distribution within the reaction chamber A, and as a result, there may be slight differences in processability between objects to be processed or between different parts of the same object. I don't like differences.

(Object of the Invention) The present invention addresses the above-mentioned situation in conventional plasma processing apparatuses, and solves this problem by providing a plasma processing apparatus in which the distribution of plasma gas in a plasma reaction chamber is uniform. The purpose is to eliminate differences in processing performance on the surface of a workpiece caused by uneven or uneven distribution of seed plasma gas, thereby ensuring that uniform plasma processing is performed on the surface of the workpiece. .

(Structure of the Invention) That is, the plasma processing apparatus according to the present invention connects a plurality of exhaust passages to a plasma reaction chamber, and each exhaust passage is provided with an on-off valve that opens and closes the passage. The present invention is characterized in that it includes a flow rate detection means for detecting the flow rate of plasma flowing through each of the upper and lower opening/closing valves, and a control means for controlling each on-off valve. The control means controls each of the on-off valves based on the signal from the flow rate detection means so that the amount of plasma discharged from the reaction chamber through each exhaust passage is equal to each other. Here, as the flow rate detection means, for example, a differential pressure type flowmeter or an illuminance sensor that detects the flow rate from the amount of light emitted by the plasma is used, and these are provided corresponding to each exhaust passage.

(Effects of the Invention) According to the above configuration, plasma introduced into the plasma reaction chamber from the inlet flows in multiple directions toward the plurality of exhaust passages connected to the reaction chamber, and moreover, plasma is introduced into the plasma reaction chamber from the inlet and flows in multiple directions toward the plurality of exhaust passages connected to the reaction chamber. Since the amount of discharged plasma is equal to each other, the concentration distribution of plasma 1 within the reaction chamber becomes uniform. As a result, it is possible to eliminate differences in processability between each workpiece or its parts caused by non-uniform plasma concentration distribution in this type of reaction chamber, and to make all parts of the surface of each workpiece uniform. It becomes possible to perform plasma treatment.

(Example) Hereinafter, an example of the plasma processing apparatus according to the present invention will be described.

FIG. 1 schematically shows a side view of a plasma processing apparatus. have The plasma reaction chamber 3 has a double structure having an outer wall 4 and an inner wall 5, as shown in an enlarged cross-section in FIG. A plurality of exhaust chambers partitioned by 6. . . , 6 are formed, and these exhaust chambers 6. ... 96, a plurality of exhaust passages 70 to 78 are connected to each other, respectively. The reaction chamber 3
The pressure inside the chamber is reduced by the pump 8.

Here, the introduction passage 2 is equipped with a microwave oscillator 10, and the processing gas such as oxygen gas passing through the passage 2 is turned into plasma by the microwave from the oscillator 10, and then The water is supplied into the inner wall portion 5 of No. 3 through a Java tube 2a located within the inner wall portion 5.

However, the inside of the inner wall portion 5 has respective exhaust chambers 6.・
. . , 6 are provided with exhaust ports 5a, . . . , 5a that communicate with the exhaust passages 7o, . ..., 6a has each exhaust chamber 6. ..., 6, that is, louvers (opening/closing valves) 110 to 118 for opening and closing the exhaust passages 70 to 78, respectively, are provided. Among these louvers 110 to 118, a louver (hereinafter referred to as a master louver) 11° that opens and closes the exhaust passage 7o connected to a position substantially opposite to the introduction passage 2a is equipped with a servo motor 12 that drives it and A master louver position detector 13 that detects the opening degree of the louver 11o is connected, and each other louver (
Stepping motors 141 to 148 (hereinafter referred to as slave louvers) 111 to 118 also have stepping motors 141 to 148 for driving, and a slave louver position detector 15 for detecting the opening degree of the louvers.
1 to 158 are connected to each other. Further, differential pressure flowmeters 16o-168 are provided in each of the exhaust passages 70-78, respectively.
Orifices 7a, . . . , 7a provided in 78, respectively.
The flow rate of plasma passing through the passages 70 to 78 is detected by detecting the pressure difference between the upstream and downstream sides of the passages 70 to 78. And each of the above louvers 11o to 118
are controlled by a control circuit 17 shown in FIG. 3 so that the amount of plasma discharged from the reaction chamber 3 through each of the exhaust passages 70 to 78 is equal to each other.

Next, the control circuit 17 shown in FIG. 3 will be explained. The control circuit 17 includes the master louver opening setting device 1.
Signal a from 8 and the master louver position detector 1
3, and the signal C from the master louver differential pressure flow meter 16o.
and differential pressure type flowmeters 161 to 168 for each slave louver.
It has a plurality of second subtracters 201 to 208 (same number as slave Louvers) to which signals d1 to d8 from the subtractors 201 to 208 are respectively input. Of these, the first subtractor 19 subtracts the value indicated by the signal I from the value indicated by the signal a, and sends the result as a signal e to the master louver 11o via the third subtractor 21 and the servo amplifier 22. The output is output to the drive servo motor 12, which rotates the motor 12 according to the polarity and current value of the servo amplifier output to stop the master louver 11o at the position set by the opening setting device 18. There is. In addition, the second
Subtractor 201 (hereinafter, other second subtracters 202 to 208
(also configured in the same way for
and is output to the absolute value amplifier 241.

Among these, the polarity discriminator 231 outputs a signal "1" to open the slave louver 111 when the value of "1" is positive, that is, when the plasma flow rate in the exhaust passage 71 is smaller than the plasma flow rate in the exhaust passage 7o. When the opening signal g1 is sent to the driving stepping motor 141, and when the signal f1 shows a negative value, that is, when the plasma flow rate in the exhaust passage 71 is larger than the plasma flow rate in the exhaust passage 7o, the louver 11
1 through the stepping motor amplifiers 251, and outputs a stop signal 11 to the inverter 261 when the signal f1 is zero or a value considered to be zero within a predetermined range. It has become.

On the other hand, the absolute value amplifier 241 is connected to the second subtracter 20
The absolute value of the signal f1 from 1 is amplified and sent to the voltage-frequency converter 271.
After converting the signal r1' into a frequency so that the frequency becomes higher according to the output of the amplified signal f1' (voltage signal), the signal r1' is converted into a frequency and then outputted to the AND circuit 28 as an angle command pulse f1''.
1. In that case, the AND circuit 281 inputs the inverter 26
Only when the signal 11' (inverted signal of signal i) from 1 is ON, the angle pulse j1 is sent to the driving motor 141 of the slave louver 111 via the stepping motor amplifier 251 in response to the input of the angle command pulse f1''. As a result, the motor 141 is driven to rotate at a speed corresponding to the frequency of the signal j1.
When the polarity of the output signal f1 of the second subtracter 201 is zero or a value close to zero, the angle pulse j1 is output from the AND circuit 281.
is no longer output and the operation of the stepping motor 251 is stopped.

The control circuit 17 also includes each of the second subtracters 201 and 201.
An adder 29 is provided which adds all the signals f1-r8 from ~208. This adder 29 is connected to the third subtracter 21 via a mode changeover switch 30, and when the polarity of the output signal is positive, it is sent to the master louver 110 side, and when it is negative, it is sent to the slave louver 110 side. 1
This indicates that excessive plasma gas is flowing to each of the loopers 11 to 118, and when the polarity is zero, it indicates that the amounts of plasma gas flowing to both loopers 110 and 111 to 118 are suspended from each other. It looks like this. In that case, the absolute value of the output of the adder 29 indicates the uneven distribution amount of the plasma gas. In this control circuit 17,
When the selector switch 30 is set to the adder 29 side, the third subtracter 21 subtracts the output signal k of the adder 29 from the output signal e of the first subtracter 19, and uses the result as signal 1. By sending the signal to the servo motor 12 via the servo amplifier 22, the initial opening degree of the master louver 11o set by the master louver opening degree setting device 18 is corrected. The configuration is such that the flow rates of plasma flowing toward the loopers 11o to 118 (that is, flowing into each of the exhaust passages 70 to 78) can be made equal to each other.

Next, the operation of the above embodiment will be explained.

By introducing plasma from the introduction passage 2 into the inner wall 5 of the plasma reaction chamber 3, which has been previously depressurized to a predetermined pressure by the vacuum pump 8, with the objects to be processed X, . . . , X placed at predetermined positions, Object to be processed X.

.

That is, the output signal a of the opening degree setter 18 is the first. Third
By inputting the signal to the master louver driving servo motor 12 via the subtractor 19.21 and the servo amplifier 22, the motor 12 is rotated according to the polarity and current value of the output signal of the servo amplifier 22, and as a result, the master louver As the opening degree of the louver 11o changes, an output signal corresponding to the amount of change is input from the master louver position detector 13 to the first subtractor 19. Then, when the output signal e of the first subtractor 19 becomes zero in accordance with the setting value of the signal a of the opening setting device 18, the servo motor 12 is stopped, so that the master louver is 11
0 is stopped at a predetermined opening position set by the opening setting device 18.

By the way, when the master louver 110 is opened in this way and the slave louvers 111 to 118 are closed as shown by the chain lines in FIG. 3, the plasma is directed toward the master louver 11o. However, according to the above configuration, the exhaust passages 71 to 78 are connected to correspond to each of the slave blue bars 111 to 118, and the distribution of the plasma in the plasma reaction chamber 3a becomes non-uniform. The opening and closing of each louver 11o to 118 is controlled by the control circuit 17 so that the flow rate of plasma flowing therein and the flow rate of plasma flowing inside the exhaust passage 7o opened and closed by the master louver 11o are equal to each other.

That is, the plasma flow rate in the exhaust passage 7o opened and closed by the master louver 11o, and the exhaust passages 71-78 opened and closed by each slave louver 111-118.
The plasma flow rate within is detected by differential pressure type flowmeters 16o and 161-167 provided in each exhaust passage 7o and 71-78, respectively, and compared in each second subtractor 201-20a. If the former plasma flow rate is greater than the latter plasma flow rate, each polarity discriminator 23
When the opening signals g1 to g8 are output from the polarity discriminators 231 to 238, respectively, and the slave bar is moved further in the opening direction than the initial position, or vice versa, the closing signals h1 to h8 are output from the polarity discriminators 231 to 238, respectively. By outputting the output and rotating the slave louvers in the opening direction, the flow rates of plasma flowing through each of the exhaust passages 70 to 78 are made equal to each other, and as a result, the plasma distribution in the plasma reaction chamber 3 is made uniform. It turns out. This eliminates the difference in processability between each workpiece X,..., ..., all parts of the surface of X will be uniformly plasma treated.

In this embodiment, differential pressure flowmeters 16o to 168 are used as a means for detecting the flow rate of plasma flowing in each exhaust passage 70 to 78, but after mixing nitrogen with the processing gas, The amount of light emitted may be detected by an illuminance detector, and the flow rate of the plasma may be detected thereby.

[Brief explanation of drawings]

1 to 3 show an embodiment of the present invention, FIG. 1 is a schematic side view of a plasma processing apparatus according to the embodiment, and FIG. 2 is an enlarged longitudinal section taken along line II-II in FIG. 1. 3 are block diagrams showing the control circuit. Moreover, FIG. 4 is a front view showing a conventional plasma processing apparatus. 1... Plasma processing device, 3... Plasma reaction chamber,
6.70-78...exhaust passage (6...exhaust chamber), 1
1...WUr11 valve (11o...master looper, 111-118...slave blue bar), 16°~
168...Flow rate detection means (differential pressure flowmeter), 17...
- Control means (control circuit). Applicant Mazda Corporation Figure 4

Claims (1)

[Claims] (1) A plasma processing apparatus that processes the surface of a workpiece by irradiating plasma onto the surface of the workpiece in a plasma reaction chamber, the apparatus comprising a plurality of exhaust passages connected to the reaction chamber, and a plurality of exhaust passages connected to the reaction chamber. A plurality of on-off valves are provided to open and close the passages, a flow rate detection means detects the flow rate of plasma flowing in each of the exhaust passages, and an amount of plasma discharged from each of the exhaust passages is equal to each other. and control means for controlling each of the on-off valves based on a signal from the flow rate detection means.