JP5145699B2 - Plasma processing apparatus and plasma processing method - Google Patents

Description

  The present invention relates to a plasma processing apparatus and a plasma processing method for introducing a pulse wave from the outside into a plasma processing chamber to generate plasma to perform a predetermined process on an object, and in particular, in a high-frequency plasma processing apparatus, severe impedance matching is performed. The present invention relates to a plasma processing apparatus and a plasma processing method suitable for being performed appropriately and instantaneously.

Chemical vapor deposition (CVD) is a technology for depositing reaction products in the form of a film on the surface of an object to be processed by vapor phase growth in a high-temperature atmosphere using a processing gas that does not react at room temperature. It is widely used in the manufacture of metal and surface modification of metals and ceramics.
Recently, CVD has also been applied as a low pressure plasma CVD for surface modification of plastic containers, particularly for improving gas barrier properties.

Plasma CVD is a method for growing thin films using plasma. Basically, it is generated by dissociating and combining gases containing a processing gas under a reduced pressure with electric energy of a high electric field. This is a method of depositing the processed material on the processing object by chemical reaction in the gas phase or on the processing object.
The plasma state is realized by glow discharge, corona discharge, arc discharge, etc. For example, as a method of glow discharge, a method using a direct current glow discharge, a method using a microwave discharge (microwave plasma CVD). ), A method using high-frequency glow discharge (high-frequency plasma CVD), and the like are known.

Among these, the microwave plasma CVD includes a cylindrical chamber, a nozzle that feeds a raw material gas into the interior space of an inverted container in the chamber, and a waveguide that introduces microwaves into the chamber. This is an apparatus for forming a thin film on the inner surface of a container by converting a raw material gas into plasma by introducing a microwave.
As described above, the microwave plasma CVD can greatly simplify the configuration of the apparatus, and the degree of decompression in the apparatus can be reduced only when the inner surface of the plastic container is processed. Since it suffices to generate it, it is not necessary to maintain the entire apparatus in a high vacuum, which is excellent in terms of ease of operation and productivity.

On the other hand, the high-frequency plasma CVD includes a plasma processing chamber in which the inside is evacuated, an external electrode that constitutes a part of the plasma processing chamber, and an internal electrode that is inserted into the internal space of a container disposed in the plasma processing chamber. And a gas supply means for supplying a source gas into the container. When a source gas is allowed to flow inside the container under a vacuum and a high frequency is applied to the external electrode, a bias voltage is generated between the external electrode and the internal electrode. This is an apparatus that generates a raw material gas into plasma and forms a thin film on the inner surface of the container (see, for example, Patent Document 1).
This high-frequency plasma CVD is suitable for processing objects with a simple shape because the wavelength is large and the plasma tends to stand up uniformly, and because the electrodes are brought close to each other. It can be said that the device is suitable for a membrane.

Incidentally, impedance matching is one of the important techniques related to the plasma CVD method.
In this method, a matching unit provided between the pulse wave power source and the electrode in the plasma processing chamber matches the impedance of the pulse wave power source and the impedance of the plasma viewed from the electrode.
If the impedances are different, there is a risk that the pulse wave power source may be damaged by the reflected power as well as not being able to supply sufficient power to the plasma because the power is reflected by the electrodes. This is done to avoid this.

However, the impedance value to be matched differs before and after the generation of plasma. For this reason, an automatic matching device is generally used so that the change can be followed.
Here, the configuration of a conventional automatic matching device is shown in FIG. As shown in the figure, the automatic matching unit 100 includes a matching circuit 110, a current detection circuit 120, a voltage detection circuit 130, and a control circuit 140.
The matching circuit 110 includes a first variable capacitor 112 connected between the input terminal 150 and the ground 111, a second variable capacitor 113 and a coil 114 connected in series between the input terminal 150 and the output terminal 160. It has.

The first variable capacitor 112 and the second variable capacitor 113 are to change their capacitances by adjusting the distance from other electrodes while rotating the variable electrode by a motor. Impedance matching of the matching unit 100 is performed by changing the capacitances of the variable capacitors 112 and 113.
The current detection circuit 120 and the voltage detection circuit 130 are used for measuring traveling wave power and reflected wave power. The current detection circuit 120 measures the current flowing through the input terminal 150, and the voltage detection circuit 130 measures the voltage at the input terminal 150. These measured current and voltage are output to the control circuit 140.

The control circuit 140 calculates traveling wave power and reflected wave power based on the current measured by the current detection circuit 120 and the voltage detected by the voltage detection circuit 130, and in response to these calculated values, the control circuit 140 The capacitance, that is, the impedance of the matching circuit 110 is controlled.
Various inventions for improving the matching device having such a configuration have been proposed in the past (see, for example, Patent Documents 2 and 3).
JP-A-8-53117 JP 2005-325395 A JP 2006-213967 A (FIG. 4)

  However, the conventional matching unit takes time because the impedance is varied by a mechanical method of adjusting the electrode interval by rotating the variable electrode by a motor. Specifically, the matching speed took at least 0.4 seconds or more. For this reason, there has been a problem that plasma emission delay may occur and a film with good performance cannot be formed.

  As described above, if impedance matching by the matching unit is not performed instantaneously, the plasma is not ignited and no film is formed, or even if the film is ignited, the film formation time is shorter than a predetermined time. In this case, a bottle with insufficient gas barrier properties is generated. In the worst case, it is assumed that the pulse wave power source is damaged by the reflected power.

Here, Patent Document 2 described above discloses a configuration including a spark generating means for forcibly emitting plasma in order to avoid a situation in which plasma does not emit light due to delay in impedance matching in the matching unit. .
However, with this technology, the plasma emits light when the impedance is not matched, so there is a problem that sufficient power cannot be supplied to the plasma and there is a risk that the pulse wave power supply may be damaged by reflected power. Still remained.

  The present invention has been considered in view of the above circumstances, and can supply sufficient power to the plasma, avoid the risk of damage to the pulse wave power source due to reflected power, and eliminate the emission delay of the plasma. An object of the present invention is to provide a plasma processing apparatus and a plasma processing method capable of forming a film with high performance.

In order to achieve this object, a plasma processing apparatus of the present invention is a plasma processing apparatus to which a matching unit for matching impedance between a power source that supplies a pulse wave and an electrode in the plasma processing chamber is connected, and plasma emission The first matching unit that matches the previous impedance, the second matching unit that matches the impedance after plasma emission, and the impedance in the high output period that increases the high-frequency output that is output during the ON time of the pulse wave are matched. A third matching unit; and a switching unit that switches between the first matching unit, the second matching unit, and the third matching unit . The switching unit is connected to the first matching unit before the plasma is generated, and the plasma emits light. Then, the first matching unit is switched to the second matching unit, and the second matching unit is switched to the third matching unit when shifting to the high output period .

When the plasma processing apparatus has such a configuration, switching from the first matching unit to the second matching unit can be instantaneously performed by the switching unit, so that a plasma emission delay is eliminated and a film with good performance can be formed.
In addition, since impedances are instantaneously matched after plasma emission, sufficient power can be supplied to the plasma, and the risk of damage to the pulse wave power source due to reflected power can be avoided.

Further, when the plasma processing apparatus has such a configuration, impedance can be immediately matched with the shift to the high output stage.

Further, when the plasma processing apparatus has such a configuration, even in a high-frequency plasma processing apparatus with severe impedance matching, impedance after plasma emission can be matched immediately.

The plasma processing apparatus of the present invention further includes a light emission detecting means for detecting that the plasma has emitted light, and the switching means detects that the light emission detecting means detects the light emission of the plasma, and then the first matching device to the second matching device. It can be set as the structure switched to.
If the plasma processing apparatus has such a configuration, switching from the first matching unit to the second matching unit can be performed when plasma is emitted.

Moreover, the plasma processing apparatus of this invention can make the impedance of the matching circuit in a 1st matching device and / or a 2nd matching device into the fixed impedance matched beforehand.
When the plasma processing apparatus has such a configuration, impedance can be matched immediately when the plasma processing apparatus is switched to the second matching unit. Therefore, it is possible to eliminate the plasma emission delay and to form a film with good performance. Further, by finding the impedance matching constant of the matching circuit in the first matching unit in advance in the batch system and fixing it, the impedance can be instantly matched by the first matching unit even during the induction period.

The plasma processing method of the present invention is a plasma processing method for matching impedance between a power source for supplying a pulse wave and an electrode in the plasma processing chamber by a matching device, and before the emission of plasma, the first matching device The high output period during which the impedance is matched and the emission of plasma is detected, the impedance is matched by switching to the second matching unit that has been matched to the fixed impedance in advance, and the high frequency output that is output during the ON time of the pulse wave is increased. At the time of transition, the second matching device is switched to the third matching device to match the impedance .

  If the plasma processing method is such a method, when plasma emission is detected, it is possible to instantaneously switch to the impedance to be matched after the plasma emission, so that there is no delay in plasma emission and a film with good performance can be formed. .

As described above, according to the present invention, the first matching device, the second matching device, and the switching device are provided, and the second matching device is previously matched with a fixed impedance. Can be switched to its fixed impedance.
As a result, it is possible to eliminate the delay in light emission of the plasma, avoid the risk of the pulse wave power supply being damaged by the reflected power, and supply a sufficient power to the plasma to form a film with good performance.

  Hereinafter, preferred embodiments of a plasma processing apparatus and a plasma processing method according to the present invention will be described with reference to the drawings.

(Plasma processing equipment)
First, an embodiment of the plasma processing apparatus of the present invention will be described with reference to FIG.
This figure is a schematic diagram showing the configuration of the plasma processing apparatus of the present embodiment.

As shown in the figure, the plasma processing apparatus 1a includes a plasma processing chamber 10, a high-frequency power source 20, a matching unit 30 (30-1, 30-2), a switching unit 40a, a plasma emission sensor 50, and a switching unit. And a control means 60.
Here, the plasma processing chamber 10 is inserted into an external electrode 11 provided so as to surround the bottle A (processing object), a shield cover 12 that shields the outside of the external electrode 11, and an internal space of the bottle A. Gas nozzle (internal electrode) 13, and the gas nozzle 13 is grounded.

  The high frequency power source (pulse wave power source) 20 outputs a pulse wave as shown in FIG. 2 and supplies it to the plasma processing chamber 10. The waveform of the ON time of the pulse wave is formed by a high frequency as shown in FIG. That is, a high frequency is output during the ON time of the pulse wave. Thereby, the performance of the thin film can be improved by performing control such that the ON time of the pulse wave is shortened in the induction period and the holding period (see FIG. 3) and the output is increased in the high output period.

The matching unit 30 is a device that matches the impedance of the high-frequency power source 20 with the impedance of the plasma viewed from the external electrode 11. In the present embodiment, the matching unit 30 includes a first matching unit 30-1 for a vacuum state and a second matching unit 30-2 for plasma.
The first matching unit 30-1 performs impedance matching when the inside of the plasma processing chamber 10 is in a vacuum state (induction period until plasma is emitted). The impedance of the matching circuit of the first matching unit 30-1 can be adjusted and fixed in advance by a batch system. Thereby, impedance matching in the induction period can be performed instantaneously.

The second matching unit 30-2 performs impedance matching after the plasma emission. In the second matching unit 30-2, the impedance of the matching circuit is adjusted and fixed in advance. For this reason, impedance is matched when switched to the second matching device 30-2.
Note that the matching unit 30 itself may be any conventionally known matching unit as shown in FIG.

The switching device 40a switches between the first matching device 30-1 and the second matching device 30-2 based on a control signal from the switching control means 60.
For example, when switched to the terminal 1 side, the first matching unit 30-1 is connected between the high frequency power supply 20 and the external electrode 11. On the other hand, when switched to the terminal 2 side, the second matching unit 30-2 is connected.
As the switch 40a, for example, a contact switch (for example, a relay) or a contactless switch (for example, a semiconductor element) can be used.

When the plasma emission sensor (emission detection means) 50 detects the emission of plasma that has occurred inside the plasma processing chamber 10, it outputs a detection signal.
When the detection signal output from the plasma emission sensor 50 is input, the switching control means 60 causes the switching device 40a to perform a switching operation.

The switching control means 60 has a plasma light emitting sensor amplifier and a matching unit switching controller.
The plasma light emission sensor amplifier amplifies the detection signal from the plasma light emission sensor 50.

  The matching unit switching controller, when receiving the amplified detection signal, sends a control signal to the switching unit 40a to perform the switching operation. The switcher 40a performs a switching operation so as to connect to the first matching unit 30-1 before receiving the control signal and to connect to the second matching unit 30-2 when receiving the control signal. The switching time in the switching device 40a is preferably within one pulse (10 ms or less).

The plasma processing apparatus 1 can be configured as shown in FIG. 4 instead of FIG. That is, three matching units 30 can be provided, and the switching unit 40 can switch between them.
In this case, as shown in FIG. 4, the matching unit 30 includes a first matching unit 30-1 for a vacuum state, a second matching unit 30-2 for low power plasma, and a third for high power plasma. Three matching units 30-3 are provided.
Of these, the first matching unit 30-1 matches the impedance before plasma emission. The second matching unit 30-2 matches impedance in a holding period (low output period, see FIG. 3) after plasma emission. The third matching unit 30-3 matches the impedance in the high output period (see FIG. 3). Further, in the third matching unit 30-3, the impedance of the matching circuit can be set to a fixed value in advance. Thereby, impedance can be matched instantaneously in a high output period.

The switching unit 40b switches among the first matching unit 30-1, the second matching unit 30-2, and the third matching unit 30-3 based on a control signal from the switching control means 60. For example, in the induction period, the terminal 1 is switched to connect only the first matching unit 30-1 between the high frequency power supply 20 and the plasma processing chamber 10. In the holding period, the terminal 2 is switched to connect only the second matching unit 30-2. In the high output period, the terminal 3 is switched to connect only the third matching unit 30-3.
The switching from the first matching unit 30-1 to the second matching unit 30-2 is performed when plasma emission is detected by the plasma emission sensor 50. On the other hand, switching from the second matching unit 30-2 to the third matching unit 30-3 is performed, for example, when a predetermined time (time required for the holding period) has elapsed.

(Operation procedure of plasma processing equipment)
Next, the operation procedure of the plasma processing apparatus will be described.
The inside of the plasma processing chamber 10 is evacuated by a vacuum pump (not shown). Next, a processing gas is supplied from a gas nozzle (internal electrode) 13 inserted in the center of the bottle 20. Subsequently, a high frequency voltage is applied to the external electrode 11. As a result, a bias voltage is generated between the external electrode 11 and the internal electrode 13, plasma is generated inside the bottle A, and a thin film is formed on the inner surface of the bottle A.

Here, the high frequency voltage applied to the external electrode 11 is controlled as shown in FIG.
That is, the output is increased (induction period) from the start of introduction of the high frequency (pulse wave) until (t1) until the plasma emits light (t2).
After plasma ignition, in order to form an adhesion layer, the high-frequency output is held in a constant state (E1) for a predetermined time (holding period (low output period)).
After the elapse of a predetermined time (t3), the high-frequency output is further increased (transition period), and when the predetermined output is reached (t4), the barrier layer is formed and maintained at its high output state (E2) (high Output period).

(Impedance matching adjustment and pulse wave)
Next, the impedance matching adjustment and the pulse wave of this embodiment will be described with reference to FIGS.
5 and 6 are waveform diagrams showing the impedance matching adjustment and the pulse wave of this embodiment. FIG. 5 shows the pulse wave in the method I and FIG. 6 shows the pulse wave in the method II, respectively.
In addition, (a) in each figure shows the timing of the plasma processing for every bottle. Moreover, in the following description, the plasma processing apparatus 1a having the configuration shown in FIG. 1 will be described.

・ Method I
Method I finds the impedance matching constant of the second matching unit 30-2 in advance, performs a constant adjustment step for fixing the constant to the second matching unit 30-2, a film forming process, and the above-described method. And a film forming process step of performing impedance matching after plasma emission with a fixed value.
As shown in FIG. 5B, in the constant adjustment step, an adjustment pulse wave is introduced from the high frequency power supply 20 into the plasma processing chamber 10. This adjustment pulse wave is a pulse wave having an ON time of 1 ms or less. When plasma is generated in the plasma processing chamber 10, the impedance of the second matching unit 30-2 is adjusted, and a fixed value of the matching constant is obtained.

In the film forming process stage, first, a pulse wave for vacuum is introduced from the high frequency power supply 20 into the plasma processing chamber 10, and then a pulse wave for processing is introduced. This processing pulse wave has, for example, an ON time of 1 ms or less in the induction period or holding period (adhesion layer stage), and a repetition frequency of 100 Hz in the barrier layer stage (high output period).
When the output is increased during the induction period and plasma is emitted in the plasma processing chamber 10, this emission is detected by the plasma emission sensor 50, a control signal is output from the switching control means 60, and the switcher 40a receiving this control signal. The switching operation from the first matching unit 30-1 to the second matching unit 30-2 is performed. Thereby, in the holding period, impedance matching is performed by the fixed impedance of the second matching unit 30-2.
As described above, the method I can immediately switch to the second matching unit 30-2 whose impedance is fixed at the time of plasma emission in the film forming process. For this reason, Method I is applied when the adhesion layer is important in terms of performance.

  When the plasma processing apparatus 1b shown in FIG. 4 is used, when switching from the holding period to the high output period, the switching unit 40b causes the second matching unit 30-2 to move to the third matching unit 30-3. A switching operation is performed. Thereby, in the high output period, impedance matching is performed by the fixed impedance of the third matching unit 30-3.

・ Method II
Method II is a method of adjusting and fixing the impedance of the second matching unit 30-2 in the adhesion layer stage (holding period) and switching to a matching unit that matches the plasma of the barrier layer in the barrier layer stage.
As shown in FIG. 6C, an adjustment pulse wave is introduced from the high frequency power supply 20 into the plasma processing chamber 10 during the induction period and the holding period. This adjustment pulse wave is a pulse wave having an ON time of 1 ms or less. And when a plasma generate | occur | produces in the plasma processing chamber 10, the impedance of the 2nd matching device 30-2 will be adjusted and a fixed value will be calculated | required. When this fixed value is obtained, the adjustment pulse wave is introduced as a processing pulse wave.

Thereafter, in the barrier layer stage, a processing pulse wave is introduced from the high frequency power source 20 into the plasma processing chamber 10. This processing pulse wave can be a pulse wave having a frequency of 13.56 MHz, 27 MHz, or the like and a duty ratio of 50%.
In this barrier stage, when the switching control means 60 detects that the output of the plasma emission sensor 50 has become high, the switching unit 40 controls the first matching unit 30- Switching operation from 1 to the second matching unit 30-2 is performed. Thereafter, impedance matching is performed by the fixed impedance of the second matching unit 30-2.
As described above, since the method II adjusts the impedance of the second matching unit 30-2 in the adhesion layer stage, the adhesion layer is not so problematic because the plasma is in an unstable state during the time of adjusting the impedance. It is applied when it does not become.

  As described above, according to the plasma processing apparatus and the plasma processing method of the present embodiment, the first matching unit for vacuum state, the second matching unit for plasma, and the switching device for switching between these, By adopting a configuration in which the second matching unit is fixed in advance to the impedance matching constant after plasma generation, the impedance is instantly matched when switching from the first matching unit to the second matching unit due to plasma emission. Therefore, it is possible to eliminate the delay of plasma emission and form a thin film with good performance.

The preferred embodiments of the plasma processing apparatus and the plasma processing method of the present invention have been described above. However, the plasma processing apparatus and the plasma processing method according to the present invention are not limited to the above-described embodiments, and the scope of the present invention. Needless to say, various modifications can be made.
For example, in the above-described embodiment, the configuration includes two or three matching devices. However, the present invention is not limited to this configuration. For example, two matching circuits are configured in one matching device, and the matching circuits are configured. You can also switch between them.

  Since the present invention is an invention related to impedance matching in a plasma processing apparatus, it can be used for apparatuses and devices that require impedance matching.

It is the schematic which shows the structure of the plasma processing apparatus of this invention. It is a wave form diagram which shows the pulse wave output from a high frequency power supply. It is a graph which shows the change of the high frequency output in film-forming processing. It is the schematic which shows the other structure of the plasma processing apparatus of this invention. It is a wave form diagram which shows impedance matching adjustment and pulse wave control (method I). It is a wave form diagram which shows impedance matching adjustment and pulse wave control (method II). It is a circuit diagram which shows the structure of the conventional automatic matching device.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1a, 1b Plasma processing apparatus 10 Plasma processing chamber 20 High frequency power supply 30-1 1st matching device (for vacuum conditions)
30-2 Second matcher (for (low power) plasma)
30-3 Third matcher (for high power plasma)
40a, 40b switching device 50 plasma emission sensor 60 switching control means

Claims (4)

A plasma processing apparatus to which a matching unit for matching impedance between a power source for supplying a pulse wave and an electrode in the plasma processing chamber is connected,
A first matching device for matching the impedance before plasma emission;
A second matching unit for matching the impedance after plasma emission;
A third matching unit for matching the impedance in a high output period for increasing the output of the high frequency output during the ON time of the pulse wave;
Switching means for switching between the first matching unit, the second matching unit and the third matching unit ;
The switching means is
Before plasma generation, connect to the first matcher,
When the plasma emits, switch from the first matcher to the second matcher,
The plasma processing apparatus , wherein the second matching unit is switched to the third matching unit at the time of transition to the high output period . A light emission detecting means for detecting that the plasma emits light,
The plasma processing apparatus according to claim 1, wherein the switching unit switches from the first matching unit to the second matching unit when plasma emission is detected by the light emission detection unit. The plasma processing apparatus according to claim 1, wherein an impedance of a matching circuit in the first matching unit and / or the second matching unit is a fixed impedance that is matched in advance. A plasma processing method for matching impedance between a power source for supplying a pulse wave and an electrode in a plasma processing chamber by a matching device,
Before the plasma emission, the impedance is matched by the first matching device,
When the plasma emission is detected, the impedance is matched by switching to a second matching unit that is previously matched to a fixed impedance,
At the time of transition to a high output period in which the high frequency output that is output during the ON time of the pulse wave is increased, the impedance is matched by switching from the second matching device to the third matching device.
And a plasma processing method.

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