JPH0528254B2 - - Google Patents

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a plasma processing apparatus that performs surface treatment on a workpiece made of plastic such as polypropylene or polyethylene by irradiating plasma onto the surface of the workpiece. Regarding.

(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 generally known that adhesion to paint films is relatively poor. Therefore,
When painting the surface of a plastic product as described 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 for this purpose. 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. 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. and,
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 functional groups on the surface of the object, thereby activating the surface and improving adhesion to the coating film. It is starting to improve.

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 portions that are outside the vicinity of the straight line connecting the inlet and exhaust port are Because the plasma gas does not spread sufficiently in the reaction chamber, the plasma gas distribution within the reaction chamber tends to be uneven, and as a result, the processing performance of the object to be processed differs depending on the arrangement and location of the object. There were flaws.

An example of a plasma processing apparatus that addresses this problem is disclosed in Japanese Utility Model Application Publication No. 59-28535. This is as shown in Figure 4.
The plasma reaction chamber A is provided with a plurality of exhaust ports B, ..., B, and each of these exhaust ports B, ..., B is provided with an on-off valve C, ..., C, and a plasma introduction port D provided in the reaction chamber A is provided. The above-mentioned valves C, while introducing plasma into the reaction chamber A through the shower pipe D'.
..., C are opened sequentially or simultaneously or intermittently. According to this, the plasma introduced into the reaction chamber A from the introduction port D flows in multiple directions depending on the number and position of each exhaust port B, ..., B, so the arrangement of the objects to be processed in the reaction chamber A Differences in processability depending on the state 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 therefore some processing may occur between objects to be processed or between different parts of the same object. I don't like the fact that there are gender differences.

(Objective of the Invention) The present invention addresses the above-mentioned actual situation in conventional plasma processing apparatuses, and by providing a plasma processing apparatus in which the distribution of plasma gas in a plasma reaction chamber is uniform, this type of plasma processing apparatus can be improved. The purpose is to eliminate differences in processing performance on the surface of a workpiece caused by uneven or uneven distribution of plasma gas, and to ensure that uniform plasma processing is performed on the surface of the workpiece. do.

(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 by comprising flow rate detection means for respectively detecting the flow rate of plasma, and control means for controlling each of the on-off valves. 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 flow meter 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 a plurality of exhaust passages connected to the reaction chamber, and is discharged from each exhaust passage. Since the amount of discharged plasma becomes equal to each other, the concentration distribution of plasma in the reaction chamber becomes uniform. This makes it possible to eliminate differences in processability between each object to be processed or between its parts, which is caused by non-uniform plasma concentration distribution in this type of reaction chamber.
All parts of the surface of each workpiece can be uniformly plasma-treated.

(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, and as shown in the figure, the processing apparatus 1 has a cylindrical plasma reaction chamber 3 connected to an introduction passage 2 for introducing plasma. This plasma reaction chamber 3, as shown in an enlarged cross section in FIG.
It has a double structure having an outer wall part 4 and an inner wall part 5,
A plurality of partitioned exhaust chambers 6, . A plurality of exhaust passages 7 ₀ to 7 ₈ are connected to each other. Each of the exhaust passages 7 ₀ to 7 ₈ is connected via a pipe 9 to a separately provided vacuum pump 8, for example, a rotary pump, so that the pressure inside the reaction chamber 3 is reduced by the pump 8. It is becoming more and more like this. 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 It is designed to be supplied into the inner wall 5 of the reaction chamber 3 via a shower pipe 2a located within the inner wall 5.

The inner wall portion 5 _is provided with exhaust ports _6a , . The exhaust ports 6a, . . . , 6a are provided with louvers (opening _/ closing valves) _{11 0 to} 11 ₈ for opening and closing the exhaust chambers 6, . Of these louvers 11 ₀ to 11 ₈ , the louver (hereinafter referred to as master louver) 11 ₀ that opens and closes the exhaust passage 7 ₀ connected to the position substantially opposite to the introduction passage 2a is equipped with a servo motor that drives it. 12 and the louver 11
The master louver position detector 13 that detects the opening degree of ₀ is connected, and each of the other louvers (hereinafter referred to as slave louvers) 11 ₁ to 11 ₈
Similarly, there is a stepping motor 14 ₁ for driving.
14 ₈ and slave louver position detectors 15 ₁ to 15 ₈ for detecting the opening degree of the louver are respectively connected. Further, differential pressure type flowmeters ₁₆₀ to ₁₆₈ are provided in each of the exhaust passages ₇₀ to 78, respectively, and these flowmeters are connected to orifices _7a provided in each of the exhaust passages ₇₀ to ₇₈ , respectively. , ..., 7a, the flow rate of plasma passing through the passages 7 0 to 7 8 is detected by detecting the pressure difference between the upstream and downstream sides of the passages 7 ₀ to 7 ₈ . And each of the above louvers 11 ₀ to 11 ₈
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 7 ₀ to 7 ₈ is equal to each other.

Next, the control circuit 17 shown in FIG. 3 will be explained. The control circuit 17 receives the signal a from the master louver opening setting device 18 and the signal b from the master louver position detector 13, respectively. _A first subtractor ₁₉ , _{a plurality of} ( and second subtracters 20 ₁ to 20 ₈ (same number as slave blue bars). Of these, the first subtracter 19 subtracts the value indicated by the signal b from the value indicated by the signal a, and sends the result as a signal e to the above-mentioned The output is sent to the drive servo motor 12 of the master louver 11 ₀ , which rotates the motor 12 in accordance with the polarity and current value of the servo amplifier output to move the master louver 11 ₀ to the position set by the opening setting device 18. It is designed to be stopped. Further, the second subtractor 20 ₁ (hereinafter, other second subtracters 20 ₂ to
20 ₈ ) subtracts the value indicated by the signal d from the value indicated by the signal c, and uses the result as the signal f ₁
The signal is output to the polarity discriminator 23 ₁ and the absolute value amplifier 24 ₁ as a signal. Among them, the polarity discriminator 23 ₁ selects the slave louver _{11 when the signal f 1} shows a positive value, that is, when the plasma flow rate in the exhaust passage 7 ₁ is smaller than the plasma flow rate in the exhaust passage 7 ₀ .
In order to open the driving stepping motor ₁₄₁ , an opening signal _g1 is sent to the driving stepping motor ₁₄₁ , and when the signal _f1 shows a negative value, that is, the plasma flow rate in the exhaust passageway ₇₁ is higher than the plasma flow rate in the exhaust passageway ₇₀ . When the flow rate is larger, a closing signal _h1 for closing the louver ₁₁₁ is outputted via the stepping motor amplifier ₂₅₁ , and the signal _f1 is zero or a value considered to be zero within a predetermined range. When this is indicated, a stop signal _i1 is output to the inverter ₂₆₁ . On the other hand, the absolute value amplifier 24 ₁ amplifies the absolute value of the signal f ₁ from the second subtracter 20 ₁ and sends it to the voltage-frequency converter _{27 1 .}
The amplified signal f ₁ ′ (voltage signal) is converted into a frequency so that the frequency becomes higher according to the output of the signal f ₁ ′, and then outputted to the AND circuit 28 ₁ as an angle command pulse f ₁ ″. In that case, the AND circuit 28 ₁ receives the angle command pulse only when the signal i ₁ ' (inverted signal of the signal i) from the inverter 26 ₁ inputted thereto is ON.
Stepping motor amplifier 2 receives input of f ₁ ″
An angular pulse j ₁ is output to the drive motor 14 ₁ of the slave lever 11 ₁ through the signal j 5 ₁ , so that the motor 14 ₁ is rotationally driven at a speed corresponding to the frequency of the signal j ₁ . There is. That is, when the polarity of the output signal f ₁ of the second subtractor 20 ₁ is zero or a value close to zero, the angle pulse j ₁ is no longer output from the AND circuit 28 ₁ and the operation of the stepping motor 25 ₁ is interrupted. Configured to stop.

The control circuit 17 is also provided with an adder 29 that adds all the signals f ₁ to f ₈ from the second subtracters 20 ₁ to 20 ₈ . This adder 29
is connected to the third subtracter 21 via the mode changeover switch 30, and when the polarity of the output signal k is positive, it is sent to the master louver 11 ₀ side, and when it is negative, it is sent to the slave louver 11 ₁ - This indicates that excess plasma gas is flowing to the 11 ₈ side, and if the polarity is zero, both louvers 11 ₀ and 1
This shows that the amount of plasma gas flowing to the 1 ₁ to 11 ₈ sides is suspended from each other. 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 changeover switch 30 is selected to the adder 29 side, the third subtracter 21 converts the output signal e of the first subtracter 19 into the adder 29.
The output signal k of 9 is subtracted, and the result is sent to the servo motor 12 via the servo amplifier 22 as a signal l.
By sending the data to the master louver 11 ₀ set by the master louver opening setting device 18,
As a result, regardless of the initial opening amount, the air always flows toward each of the louvers 11 ₀ to 11 ₈ (that is, it flows into each exhaust passage 7 ₀ to 7 ₈ ).
The configuration is such that the plasma flow rates 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, Workpiece X,
…, the surface of X is processed, but in that case,
First, the initial opening degree of the master louver ₁₁₀ is set by the master louver opening degree setting device 18 shown in FIG. That is, by inputting the output signal a of the opening setting device 18 to the master louver driving servo motor 12 via the first and third subtracters 19 and 21 and the servo amplifier 22, the motor 12 is activated by the servo amplifier. As a result, the opening degree of the master louver ₁₁₀ changes, and an output signal b corresponding to the amount of change is first subtracted from the master louver position detector 13. The signal is input to the device 19. Then, the signal b matches the setting value of the signal a of the opening setting device 18, and the output signal e of the first subtractor 19
When becomes zero, the servo motor 12 stops, and the master louver ₁₁₀ is stopped at the predetermined opening position set by the opening setting device 18.

By the way, in this way, master louver 1
For example, when the slave louvers 11 ₁ to 11 ₈ are closed as shown by the chain lines in FIG. 3 while the master louver 11 _{0 is open, the plasma flows toward the master louver 11 0 and} a plasma reaction occurs. Room 3
Although the distribution of the plasma within a becomes uniform, according to the above configuration, each slave louver 11
Exhaust passages 7 ₁ to _{7 8} are connected in correspondence with the exhaust passages _{7 1} to 7 ₈ , and the exhaust passages 7 ₀ are opened and closed depending on the flow rate of plasma flowing through the exhaust passages 7 1 to _{7 8 and the master louver 11 0 .} The opening and closing of the louvers 11 ₀ to 11 ₈ are controlled by the control circuit 17 so that the flow rates of the flowing plasma are equal to each other.

That is, the plasma flow rate in the exhaust passage 7 ₀ opened and closed by the master louver 11 ₀ and the plasma flow rate in the exhaust passages 7 ₁ to 7 ₈ opened and closed by each slave louver 11 ₁ to 11 ₈ are the same. Differential pressure flowmeter 1 provided in each exhaust passage 7 ₀ and 7 ₁ to 7 ₈
6 ₀ and 16 ₁ to 16 ₈ respectively, and compared in each second subtractor 20 ₁ to 20 ₈ . If the former plasma flow rate is greater than the latter plasma flow rate, each polarity discriminator 23 ₁
~ 23 ₈ output the opening movement signals g ₁ ~ g ₈ respectively, and if the slave blue bar is moved further in the opening direction than the initial position, or vice versa, each polarity discriminator 23 ₁ ~
Closing motion signals h ₁ to _{h 8} are outputted from the respective exhaust passages 7 0 to 7 8 and the respective slave louvers are rotationally driven in the closing direction, so that the flow rates of _plasma flowing through the exhaust passages 7 ₀ to 7 ₈ are made equal to each other. As a result, the plasma distribution within the plasma reaction chamber 3 is made uniform. As a result, the difference in processability between the objects to be processed X,..., ,X
All parts of the surface will be uniformly plasma treated.

In this embodiment, each exhaust passage 7 ₀ to 7 ₈
Differential pressure flowmeters 16 ₀ to 16 ₈ were used as means for detecting the flow rate of plasma flowing through the chamber, but nitrogen was mixed with the processing gas and the amount of light emitted from the nitrogen plasma was detected by an illuminance detector. , The flow rate of the plasma may be detected thereby.

[Brief explanation of the drawing]

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, FIG. 2 is an enlarged longitudinal sectional view taken along the line of FIG. FIG. 3 is a block diagram 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, 6,7 ₀ to 7 ₈ ... Exhaust passage (6... Exhaust chamber),
11... Opening/closing valve (11 ₀ ... Master louver,
11 ₁ ~ 11 ₈ ... slave blue bar), 16 ₀ ~ 1
6 ₈ ...Flow rate detection means (differential pressure flowmeter), 17...
Control means (control circuit).

Claims (1)

[Claims] 1 A plasma processing apparatus for treating the surface of a workpiece by irradiating plasma onto the surface of the workpiece in a plasma reaction chamber, which includes a plurality of exhaust passages connected to the reaction chamber, and a plurality of exhaust passages provided in each exhaust passage. a plurality of on-off valves for opening and closing the passages; a flow rate detection means for respectively detecting the flow rate of plasma flowing in each of the exhaust passages; A plasma processing apparatus comprising: control means for controlling each of the on-off valves based on a signal from the flow rate detection means.