JPH09266097A - Plasma processing method and device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a plasma processing method and device capable of detecting the initial state of a plasma discharge failure. SOLUTION: High frequency voltage whose output power varies is applied from a high frequency power supply 3 to a plasma generating part 5 in accordance with a voltage from a modulating oscillator 11, and a plasma discharge is produced. A high frequency signal produced as the result of the plasma discharge is detected by a sensor unit 6, a specific higher harmonic spectrum is detected therefrom by a spectrum detecting part 1 and, when a signal whose rate of change with change in voltage from the modulating oscillator 11 is high is detected from the higher harmonic spectrum, a signal showing the initial state of a plasma discharge failure is fed to a control circuit 31. At the control circuit 31 a plasma generating parameter for generating a normal plasma discharge is set in accordance with the signal fed and is stored in memory, and an RF output power control part 33, an electrode-to-electrode gap control part 34, and a gas flow rate control part 35 are controlled so that the normal plasma discharge occurs.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plasma processing method and a plasma processing apparatus for applying a high frequency voltage from a high frequency power source to a pair of electrodes to process an object to be processed by plasma discharge generated between the electrodes. Regarding

[0002]

BACKGROUND ART Currently, in the field of semiconductor manufacturing, CV
For the purpose of D, ashing, etching, surface treatment, or the like, a plasma treatment method in which an object to be treated such as a semiconductor wafer is treated using plasma discharge is widely used. As this plasma processing method, generally, plasma is generated in vacuum, but recently, it has been attempted to generate plasma under atmospheric pressure or a pressure in the vicinity thereof.

Japanese Unexamined Patent Publication No. 7-135098 discloses an RF plasma processing apparatus which performs processing by generating plasma by RF (high frequency) in a chamber, in which a frequency component other than 13.56 MHz which is the frequency of the RF power source is RF.
A technique of detecting from the current and detecting whether or not this RF current is abnormal is disclosed. In the invention of this publication, R
When the F current is abnormal, the generation of spark or arc discharge is detected, and the operation of the RF power supply is stopped and a warning sound is output.

[0004]

By the way, before the occurrence of the spark or arc discharge, a slight abnormal discharge is locally generated. This minute abnormal discharge is considered to be the initial state of abnormal plasma discharge such as spark or arc discharge. It has been confirmed by the present inventors that this minute abnormal discharge locally heats a pair of electrodes or the surface of the object to be processed, which is in contact with the plasma discharge space, to generate a red discolored portion.

In the RF plasma processing apparatus described above, the occurrence of sparks and arc discharges can be detected, but the occurrence of minute abnormal discharges before the sparks and arc discharges cannot be detected.

Here, once abnormal discharge such as spark or arc discharge occurs, there is a high possibility that a large amount of damage will be applied to the object to be processed and the pair of electrodes, and the processing yield will decrease, resulting in interruption of processing. Throughput decreases with repair. Therefore, it has been earnestly desired to prevent abnormal discharge such as spark and arc discharge.

However, as long as a minute abnormal discharge cannot be detected, it has been impossible to prevent abnormal discharges such as sparks and arc discharges that occur subsequently.

The present invention has been made in view of the above problems, and an object thereof is to provide a plasma processing method capable of detecting a minute abnormal discharge which is an initial state of abnormal plasma discharge. Especially.

Another object of the present invention is to detect a minute abnormal discharge, which is the initial state of abnormal plasma discharge, to prevent abnormal discharge such as spark or arc discharge and to prevent electrode or electrode due to the abnormal discharge. An object of the present invention is to provide a plasma processing method and a plasma processing apparatus capable of preventing damage to a target object.

[0010]

According to a first aspect of the present invention, an AC voltage from an AC power source is applied to a pair of electrodes to generate plasma between the pair of electrodes, and the plasma discharge discharges an object to be processed. In the plasma processing method for processing, a spectrum of a specific frequency other than the fundamental frequency of the AC power supply is monitored while changing at least one of a plurality of plasma generation parameters that change the state of the plasma discharge, It is characterized in that the initial state of abnormal plasma discharge is determined based on the rate of change.

At the time of the transition to the initial state when the plasma discharge is abnormal, the change in the spectrum value of the specific frequency itself is slight compared with that before the transition, but the rate of change of the spectrum before the transition and the spectrum after the transition are small. It was found through experiments by the present inventors that it can be clearly distinguished from the change rate of.

Therefore, in the invention of claim 1, the difference in the rate of change of the spectrum of a specific frequency other than the fundamental frequency at the time of plasma discharge reflects the initial state of abnormal plasma discharge. By detecting, it is determined whether or not the initial state of the plasma discharge abnormality.

As described in claim 2, it is preferable that the specific frequency is a harmonic wave with respect to a fundamental frequency of the AC power supply.

This is because the spectrum of a specific harmonic with respect to the fundamental frequency of the AC power source changes, particularly reflecting the initial state of abnormal plasma discharge.

According to a third aspect of the present invention, when it is determined that the plasma discharge abnormality is in the initial state, the fact that the plasma discharge abnormality is in the initial state is generated is recorded as history information of processing of the object. It is preferable to store as.

By using the stored history information, it is possible to determine the object to be processed in which the initial state of abnormal plasma discharge has occurred during the plasma processing after the plasma processing, so that the damaged object to be processed can be separated. You can Alternatively, when a defect of the object to be processed is found in the subsequent inspection process, the history information can be used for investigating the cause of the defect.

When it is determined that the plasma discharge abnormality is in the initial state, at least one of the plurality of plasma generation parameters is controlled to maintain a normal plasma state. It is preferable to set the state.

Since the plasma state can be changed depending on the value of the plasma generation parameter, a normal plasma state can be maintained by controlling at least one of the plurality of plasma generation parameters. In this way, it is possible to prevent an abnormal plasma state such as spark or arc discharge.

According to a fifth aspect of the present invention, by applying an AC voltage from an AC power source to the pair of electrodes, the state of plasma discharge generated between the pair of electrodes is controlled, and the object to be processed is treated by the plasma. In the plasma processing method for processing, while changing at least one of a plurality of plasma generation parameters, a boundary condition for transitioning to the initial state of the plasma discharge abnormality is detected, and based on the boundary condition, the plurality of plasmas are detected. It is characterized in that at least one of the generation parameters is controlled to maintain a normal plasma discharge.

According to the fifth aspect of the invention, the normal generation of plasma discharge that does not shift to the initial state of abnormal plasma discharge is maintained based on the detected boundary condition. Therefore,
After that, not only the abnormal plasma state such as spark and arc discharge can be prevented, but also the transition to the initial state of abnormal plasma discharge can be prevented. Therefore, the processing of the object can be performed in a state where the damage is less.

According to a sixth aspect of the present invention, the at least one plasma generation parameter that is changed is an output power from an AC power source, and the output power can be periodically changed during the generation of the plasma discharge. .

In this way, the initial state of abnormal plasma discharge can be detected during the plasma processing of the object to be processed, and normal plasma discharge can be maintained. Therefore, an abnormal plasma state such as spark or arc discharge can be prevented in advance, and the object to be processed can be processed without being damaged.

Alternatively, as described in claim 7, the output power from the AC power supply can be changed at the start of output.

In this way, the plasma generation parameters for generating normal plasma discharge can be preset at the time of starting the processing of the object to be processed or before that.

According to an eighth aspect of the present invention, in the fourth or fifth aspect, the at least one plasma generation parameter to be controlled is an output power of the AC power supply, and the output power is lower than a value under the boundary condition. It is characterized by doing.

According to a ninth aspect of the present invention, in the fourth or fifth aspect, the at least one plasma generation parameter to be controlled is a distance between the pair of electrodes, and the distance is larger than a value under the boundary condition. It is characterized by doing.

According to a tenth aspect of the present invention, in the fourth or fifth aspect, the at least one plasma generation parameter to be controlled is a gas supplied between the pair of electrodes and added to the plasma discharge gas. It is characterized in that the supply amount of the additive gas is made larger than the value under the boundary condition.

The plasma state can be changed from the initial abnormal state to the normal state by controlling the plasma generation parameters defined in claims 8, 9 and 10 based on the boundary conditions.

According to the invention of claim 11, in claim 9,
The added gas is Ar, Kr, Xe, O ₂ , CF ₄ ,
N ₂ , CO ₂ , SF ₆ and CHF ₃ , at least O, N, F
Alternatively, it is characterized in that it is one or more reactive gas selected from the gas containing Cl or the liquid containing them in the gas phase.

According to the eleventh aspect of the present invention, it has been confirmed that when the amount of these additive gases is increased, the initial state of abnormal plasma is less likely to occur.

According to a twelfth aspect of the present invention, in the plasma processing apparatus for controlling the state of plasma discharge generated between the pair of electrodes by applying an AC voltage from the AC power source to the pair of electrodes, a plurality of plasma generation devices are provided. Detecting means for detecting a boundary condition that shifts to the initial state of the plasma discharge abnormality while changing at least one of the parameters, and based on the detected boundary condition, among the plurality of plasma generation parameters. And a control means for setting and controlling at least one to maintain normal plasma discharge generation.

According to the twelfth aspect of the present invention, generation of normal plasma discharge that does not shift to the initial state of abnormal plasma discharge is maintained based on the detected boundary condition. Therefore, thereafter, not only the abnormal plasma state such as spark and arc discharge can be prevented, but also the transition to the initial state of abnormal plasma discharge can be prevented. Therefore, the processing of the object can be performed in a state where the damage is less.

According to a thirteenth aspect of the present invention, in the twelfth aspect, there is further provided a storage means for storing the at least one plasma generation parameter set based on the detected boundary condition, and the control means stores the storage parameter. Based on the at least one plasma generation parameter
It is characterized by maintaining normal generation of plasma discharge.

According to the thirteenth aspect of the present invention, after the boundary condition is measured and the plasma generation parameter set based on the boundary condition is stored in the storage means, the normal plasma discharge is performed based on the stored information. Is maintained.

[0035]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a schematic configuration of a first embodiment of a plasma processing apparatus according to the present invention. In this plasma processing apparatus, an AC voltage from an AC power supply is applied to a pair of electrodes to generate plasma between the pair of electrodes, and the state of the plasma discharge is controlled to process an object to be processed. .

In particular, the boundary condition for transitioning to the initial state of abnormal plasma discharge is detected while changing at least one of a plurality of plasma generation parameters that change the state of plasma discharge. Then, based on the boundary condition, at least one of the plurality of plasma generation parameters is controlled to maintain normal plasma discharge.

The plasma processing apparatus shown in FIG. 1 mainly comprises a high frequency power source 3, a plasma generating section 5 which is supplied with high frequency power from the high frequency power source 3 to generate plasma discharge, and a high frequency generated by the plasma generating section 5. A sensor unit 6 that detects a signal, a spectrum detector 1 that is a detection unit that detects an initial state of a plasma discharge abnormality using a harmonic spectrum detected by the sensor unit 6, and a detection result from the spectrum detector 1. And a control circuit 31 which is a control means for controlling the plasma generation parameter.

Specifically, in the embodiment of FIG. 1, atmospheric pressure plasma is generated as the plasma treatment, and the output power from the high frequency power source is changed as the plasma generation parameter to process the object to be treated in the atmospheric pressure plasma. A case will be described below in which the boundary condition for transitioning to the initial state of abnormal plasma discharge is detected during the operation.

First, from the modulating oscillator 11 in the spectrum detecting section 50, the high frequency power source 3 is supplied via the coaxial cable 2.
To a traveling wave (Pf) power control voltage. This traveling wave (Pf) power control voltage is shown in FIG.
As shown in, the voltage is periodically changed and output.

The high frequency power source 3 is, for example, 13.56 MHz.
The high frequency voltage of is output. This high frequency power source 3
Based on the control voltage supplied from the modulation oscillator 11, the high-frequency voltage from 1 to is changed and output so that the voltage periodically increases and decreases, as shown in FIG. The high-frequency voltage from the high-frequency power source 3 is matched by the matching device 4 and supplied to the plasma generator 5.

The plasma generator 5 is composed of a pair of electrodes, an upper electrode 5a and a lower electrode 5b which is grounded. A high frequency power is supplied between the upper electrode 5a and the lower electrode 5b, and a plasma generating gas such as He is supplied to generate a plasma discharge. Further, an additive gas described later can be supplied if necessary. The object to be processed is placed on the lower electrode 5b.

Due to the plasma discharge generated by the plasma discharge section 5, the fundamental frequency (traveling wave) is 13.
Various high frequency signals are generated, including 56 MHz and its harmonics. The sensor unit 6 is connected to the upper electrode 5a, for example, and detects these high frequency signals. The sensor unit 6 comprises a capacitor 61 and a resistor 62 grounded. The high frequency signal detected by the sensor unit 6 is transmitted through the coaxial cable 7 to
It is sent to the spectrum detector 1.

The spectrum detector 1 tunes the input high frequency signal to a specific harmonic other than the fundamental frequency of the high frequency power source 3 and detects the spectrum of the higher harmonic.
Further, the spectrum detection unit 1 detects a case where the rate of change of the spectrum of the specific harmonic is large with respect to the change when the RF output power of the high frequency power supply 3 increases or decreases at a predetermined value.

Description of Spectrum Detection Unit The high frequency signal from the sensor unit 6 is passed through the coaxial cable 8 of the spectrum detection unit 1 and the high pass & trap filter 1
2 is supplied. This high pass & trap filter 1
In 2, the fundamental frequency component of the high frequency current flowing in the high frequency conducting path at the time of plasma generation is cut, and the high frequency component above the fundamental frequency is extracted.

The high frequency components extracted by the high pass & trap filter 12 are amplified by the RF amplifier 54,
It is sent to the first frequency converter 14. First frequency converter 1
4 converts the input high frequency signal into a first intermediate frequency (for example, 10.7 MHz), which is the difference between the specific harmonic to be tuned and the first local oscillation frequency from the first local oscillator 13. Output. The first intermediate frequency is amplified by the high frequency amplifier 55 and is passed through the narrow band filter 15, whereby the first intermediate frequency in the narrow band is extracted. The first intermediate frequency signal from the narrow band filter 15 is sent to the second frequency converter 17. The second frequency converter 17 converts to a second intermediate frequency (for example, 455 KHz) which is a difference between the first intermediate frequency and the second local oscillation frequency from the second local oscillator 16, and outputs the second intermediate frequency. The second intermediate frequency from the second frequency converter 17 is amplified by the high frequency amplifier 18 and input to the detector 19. Detector 1
At 9, the tuned signal of the specific harmonic is detected. That is, the detector 19 can detect the spectrum of the specific harmonic.

The spectrum detecting unit 1 detects an initial abnormal plasma state before abnormal discharge such as spark or arc discharge. In this initial plasma abnormal state, the signal level of the harmonic of interest is extremely weak. According to an experiment by the present inventors, the harmonic signal output from the sensor unit 6 is, as shown in FIG.
The signal power is in the range of -70 to -40 dBm.
Converting this harmonic into the effective value of the voltage level,
It is 90 μVrms to 3 mVrms.

In this embodiment, among the harmonics shown in FIG.
For example, the sixth harmonic signal is detected. The signal level of the sixth harmonic is -70 to -60, as shown in FIG.
It is a weak signal power of dBm. This weak signal is
Converted to the effective value of the voltage level, 90 to 200 μVr
ms.

Here, in the case where a simple wide band amplifier is used in order to detect the specific harmonic spectrum in the spectrum detector 1, as shown in FIG. 4, the output frequency from the high frequency power source 3 is as shown in FIG. Since 13.56 MHz is much stronger than the signal strength of each harmonic, the amplifier saturates before the resulting harmonic reaches the desired signal level. Further, when a high gain amplifier is used, it oscillates when the same frequency as each harmonic is amplified, and when a wide band amplifier is used, this amplifier itself generates noise, resulting in S / N. There is the problem of worsening the ratio.

Therefore, in the present embodiment, as described above, the sixth harmonic spectrum can be detected by performing frequency conversion and amplification in a plurality of stages.

The voltage of the detected sixth harmonic wave is, according to the periodic change of the output power from the high frequency power source 3, as shown in FIG. 6 (A), during the normal plasma discharge. Change linearly. This figure 6
The voltage shown in (A) is proportional to the control voltage shown in FIG. On the other hand, in the initial state of abnormal plasma discharge, as shown in FIG. 6B, the output power from the high-frequency power source 3 changes periodically according to the periodic change, but is non-linear within each period. Changes to.

Next, the rate of change of the detected sixth harmonic spectrum with respect to the change of the traveling wave power control voltage is detected.

The divider 20 has a traveling wave power control voltage from the modulating oscillator 11 and a sixth wave from the detector 19.
The harmonic voltage is input. Then, the divider 20 divides the detection voltage of the sixth harmonic detected by the detector 19 by the control voltage from the modulation oscillator 11. When the value obtained by this division is indicated by a voltage, when the plasma discharge is normal, the two voltages input to the divider 20 are in a proportional relationship, and thus the quotient voltage is shown in FIG. As shown, it becomes a constant value, that is, a DC voltage. On the other hand, in the initial state of abnormal plasma discharge, the output of the divider 20 becomes an unstable value, that is, an AC voltage, as shown in FIG. 7B.

The division result from the divider 20 is sent to the AC amplifier 21 and amplified. Here, when the plasma is normal, a DC voltage is input to the AC amplifier 21, so that the output of the AC amplifier 21 is zero. On the other hand, in the initial state of abnormal plasma, the AC voltage is input to the AC amplifier 21, and thus the amplified AC voltage is output as the output of the AC amplifier 21.

The output of the AC amplifier 21 is detected by the wave detector 22 and supplied to the voltage comparator 23. Voltage comparator 23
A detection sensitivity setting volume 24 for presetting a predetermined reference voltage value is connected to the. Voltage comparator 23
Then, the voltage value preset by the detection sensitivity setting volume 24 is compared with the voltage value from the detector 22.

Here, when the plasma is normal, the detector 22
The output of the voltage comparator 23 is low because the output of the voltage comparator is zero. On the other hand, in the initial state of the plasma abnormality, a voltage higher than the reference voltage value is input to the voltage comparator 23, so that the output of the voltage comparator 23 becomes high.

The output of the voltage comparator 23 is the transistor 2
5 is connected to the base. In the initial state of abnormal plasma, the voltage comparator 23 outputs a high signal, so that the transistor 25 is turned on and a current flows through the coil 26. The diode D ₁ turns on the transistor 25.
It prevents the backflow of the current at the time of / OFF.

A switch 27 is provided near the coil 26.
Is provided. The switch 27 has one terminal connected to the terminal 28 and the other terminal composed of a terminal a connected to the terminal 29 and a terminal b connected to the terminal 30. In the initial state of abnormal plasma, a current flows through the coil 26, so that the switch 27 is switched and connected to the terminal b. Thus, when the switch 27 is switch-connected to the terminal b and the terminals 28 and 30 are connected, a signal indicating that the plasma discharge abnormality is in the initial state is output.
On the other hand, the switch 27 is switched and connected to the terminal a, and the terminal 2
When 8 and the terminal 29 are connected, a signal indicating that the plasma discharge is normal is output.

By the above operation, the apparatus of this embodiment detects the initial state of plasma abnormality.

In the present embodiment, the output from the spectrum detector 1 is sent to the control circuit 31. The control circuit 31 determines whether the plasma discharge is normal or the initial state of the plasma discharge abnormality is based on the output from the spectrum detector 1. As a result, when it is determined that the plasma discharge abnormality is in the initial state, control is performed so as to stop the plasma discharge or warn that the plasma discharge is abnormal. It should be noted that the initial state of the abnormal plasma discharge is less persistent than that at the time of abnormalities such as sparking and arcing, and occurs sporadically. Therefore, the warning or the instruction to stop the apparatus may be issued only when the initial state of the above-mentioned abnormal plasma discharge is detected a plurality of times.

Further, the number of the object to be processed in which the initial state of the abnormal plasma discharge has occurred may be recorded as history information on a recording medium such as a disk.

Further, in the control circuit 31, based on the above judgment, a necessary plasma generation parameter among a plurality of plasma generation parameters used when generating plasma discharge is set so as to generate normal plasma discharge. Set.

For example, the control circuit 31 outputs a command for changing the control voltage to the modulation oscillator 11 so that the control circuit 31 recognizes the timing of the change in the RF power from the high frequency power supply 3. You can
Then, based on the signal from the spectrum detection unit 1, the control circuit 31 can recognize the magnitude of the RF power at the time of shifting to the initial state of abnormal plasma discharge. This RF
The magnitude of the power is one of the boundary conditions when shifting to the initial state of abnormal plasma discharge.

In this case, the control circuit 31 controls at least one of the plurality of plasma generation parameters so that the plasma discharge becomes normal than the boundary condition, for example, the plasma density becomes lower than the boundary condition.

As the plasma generation parameter, for example, the RF output power, the gap between the electrodes, the flow rate of the additive gas added to the discharge gas, etc. are used. Control circuit 31
Controls at least one of the RF output power control unit 33, the inter-electrode gap control unit 34, and the gas flow rate control unit 35 using the set plasma generation parameter. The correlation between each parameter and the plasma state will be described later, but at least one of the RF output power, the interelectrode gap, and the gas flow rate is changed and set so that the plasma discharge is always performed normally.

Further, the changed plasma generation parameters can be stored in the memory 32. By doing this, the above-mentioned monitoring process is performed once, and the plasma generation parameters that can maintain a normal plasma state are stored in the memory 3.
If registered in 2, the normal plasma state can be stably maintained thereafter based on the information in the memory 31.

As described above, in the above-described plasma processing apparatus, the case where the RF output power is periodically changed during processing of the object to be processed so that normal plasma discharge is generated is monitored. . In addition to this, when the power of the plasma processing apparatus is turned on, that is, when the output of the voltage from the modulation oscillator 11 is started, the high frequency voltage from the high frequency power source 3 is changed as shown in FIG. The initial state of abnormal plasma discharge may be determined. Then, based on this determination, the plasma generation parameter is set so as to generate a normal plasma discharge, and control is performed using this set plasma generation parameter, so that the object to be processed is processed with normal plasma discharge. It can be performed.

Here, the conditions under which the spectrum detector 1 can accurately detect the initial state of abnormal plasma discharge from a weak input signal will be considered. An operational amplifier is generally used as the voltage comparator 23, and the operating voltage of this operational amplifier is 1
It is V-10V. On the other hand, the voltage of the weak signal input to the spectrum detection unit 1 is 90 μVrms to 3 m in effective value.
It is Vrms. Therefore, in order to amplify the weak signal up to the operating voltage level of the operational amplifier, the total gain of the amplifiers at each stage in the spectrum detector 1 is approximately 330 to 100,000 times. Considering that the effective value of the voltage level of the sixth harmonic is 90 to 200 μVrms, the above-mentioned total gain is approximately 5000 to 1000 times.
00 times. . Further, the selectivity of the frequency spectrum at this time is 3d in the width of ± 50 kHz as shown in FIG.
The narrow band below is preferable because of the characteristic that Bm is reduced.

Next, FIG. 8 shows a schematic configuration of another embodiment of the plasma processing apparatus of FIG.

The difference between FIG. 1 and FIG. 8 is that the configuration of FIG. 8 does not include the modulation oscillator 11 of FIG. 1, and the frequency from this modulation oscillator 11 and the frequency from the detector 19 are different. That is, a subtractor 40 is mounted instead of the divider 20, the AC amplifier 21, and the detector 22 for comparing the frequency and detecting the voltage of the harmonic of the plasma discharge.

In the plasma processing apparatus of FIG. 8, the detector 19
The traveling wave (Pf) power monitor voltage from the high-frequency power supply 3 is subtracted by the subtractor 40 from the sixth harmonic level from.

Here, as shown in FIG. 9 (A), during normal plasma discharge, the high frequency (Pf) monitor power and the sixth harmonic level are in a proportional relationship, and the gain in the spectrum detector 1 is set to a predetermined value. If set to, the sixth harmonic level becomes a straight line a with a predetermined slope that matches the traveling wave (Pf) power monitor voltage and increases as the high frequency power increases. On the other hand, after shifting to the initial state of abnormal plasma discharge, the displacement is changed to the inclination indicated by the straight line b.

Therefore, as the output from the subtractor 40, as shown in FIG. 9B as the corrected signal level, the rate of change of the sixth harmonic level with respect to the change of the high frequency power during normal plasma becomes zero. On the other hand, after the transition to the initial state of abnormal plasma discharge, the rate of change of the sixth harmonic level with respect to the change of the high frequency power becomes a straight line having a predetermined slope. Thus, the rate of change of the sixth harmonic level sharply increases at the high frequency power W shown in FIG. 9B.

In the plasma processing apparatus of FIG. 8, by utilizing the above-mentioned relationship between the higher harmonic power and the sixth higher harmonic level, a low level is output from the subtractor 40 when the plasma is normal, and the initial state of abnormal plasma discharge is entered. After that, high is output.
By inputting the output of the subtractor 40 to the voltage comparator 23, it is possible to detect the transition to the initial state of abnormal plasma discharge in the same manner as in the above embodiment.

In the above-described plasma processing apparatus, it was possible to detect the initial state of abnormal plasma discharge, especially at the sixth harmonic of the fundamental frequency of the high frequency power source. According to experiments by the present inventors, it was found that the initial state of abnormal plasma discharge can be detected even by using the fourth harmonic. This fourth
The relationship between each input signal strength of the harmonic and the sixth harmonic and the output voltage to be monitored is as shown in FIG. In addition,
The specific frequency used for this detection is not limited to the fourth harmonic and the sixth harmonic, and other harmonics or frequencies other than the harmonics can be used.

Next, each plasma generation parameter will be specifically described.

(1) Regarding RF Output Power Dependence of Plasma State As shown in FIG. 11, a dielectric 41 made of aluminum nitride is formed on the upper electrode 5a of the pair of electrodes of the plasma generating section 5.
Is installed, and atmospheric pressure plasma is generated in the line type discharge electrode using the aluminum stage 42 for the lower electrode 5b.
The distance between the dielectric 41 and the aluminum stage 42, that is, the inter-electrode gap GAP is 1 mm, helium He is used as a discharge gas, and the flow rate of He is 15 liters / m 2.
As in, it is made to flow from the direction of arrow A.

In the plasma discharge electrode of FIG. 11,
FIG. 12 shows the relationship between the RF output power and the discharge detection signal when the high frequency levels at the fourth, sixth and eighth harmonics of the fundamental frequency are measured. In FIG. 12, the point at which the discharge detection signal starts to change so as to rapidly increase with the increase in RF output power is a point P. This point P is called, for example, an inflection point. R shown by this inflection point P
When the RF output power is higher than the F output power, the initial state of abnormal plasma discharge occurs. The range in which the initial state of this plasma discharge abnormality occurs is indicated by R. It should be noted that the range R of the initial state of the abnormal plasma discharge shown in FIG.
Indicates a range in which the initial state of abnormal plasma discharge can be visually confirmed.

From FIG. 12, when controlling the RF output power as the plasma generation parameter to be controlled,
By setting and controlling this RF output power value to a value lower than the RF output power value indicated by the inflection point P, it is possible to prevent the occurrence of an initial state of abnormal plasma discharge.

(2) Regarding Dependence of Additive Gas Flow Rate on Plasma State Next, in the plasma discharge electrode of FIG. 11, when the oxygen O ₂ was added at 300 SCCM to helium He as a discharge gas, the fourth fundamental frequency, FIG. 13 shows the relationship between the RF output power and the discharge detection signal at the sixth and eighth harmonics. When oxygen is added as an additional gas, the RF output power is 500 in the initial state of abnormal plasma discharge.
It was not detected unless it was higher than the high output near W. Therefore, by using an additive gas such as oxygen as the plasma generation parameter to be controlled and generating the atmospheric pressure plasma by adding the additive gas, it is possible to control so that the initial state of abnormal plasma discharge does not occur. This is because the intrinsic mobility of electrons in the plasma generated by the additive gas is smaller than the intrinsic mobility of electrons in the plasma generated by the discharge gas, and the plasma damage to the object to be processed is caused. It is assumed that there is a correlation with the reduction of

The additive gas is Ar, Kr, or X.
_{e, O 2, CF 4,} N 2, CO 2, SF 6 and CHF _3, at least O, N, selected from among those which are gaseous state F or gas containing Cl or liquid containing them, 1 Any reactive gas described above may be used.

Next, in the plasma discharge electrode of FIG. 11, when the glass substrate having the MIM element pattern formed thereon is placed on the lower electrode,
FIG. 14 shows the relationship between the RF output power and the discharge detection signal at the sixth and eighth harmonics. It was confirmed that, on the substrate on which the element pattern was formed, the initial state of abnormal plasma discharge occurred at almost the same RF output power as the RF output power at which the initial state of abnormal plasma discharge shown in FIG. 14 occurred. Therefore, when the substrate on which the element pattern is formed is actually processed by plasma discharge, only the RF output power value is set to a value lower than the RF output power value indicated by the inflection point P to generate plasma discharge. Alternatively, an additive gas may be added to the discharge gas to set a predetermined RF output power value to generate plasma discharge.

(3) Dependence of Inter-electrode Gap on Plasma State FIGS. 15 to 18 show the fourth and sixth fundamental frequencies when the inter-electrode gap GAP is changed in the plasma discharge electrode of FIG. And the relationship between the RF output power and the discharge detection signal at the eighth harmonic. The discharge detection signal shown in FIG. 15 is measured using a plasma discharge electrode having an inter-electrode gap of 0.5 mm, and the discharge detection signal shown in FIG. 16 is using a plasma discharge electrode having an inter-electrode gap of 1.0 mm. The discharge electrode signal shown in FIG. 17 is measured using a plasma discharge electrode with an inter-electrode gap of 1.5 mm, and the discharge electrode signal shown in FIG. 18 has an inter-electrode gap of 2.0 mm. It is measured using the plasma discharge electrode of.

From FIGS. 15 to 18, the larger the gap between the electrodes is, the more the initial state of abnormal plasma discharge occurs.
F output power is high. This is because the wider the gap between the electrodes is, the lower the electric field strength between the electrodes is. Therefore, by setting the gap between the electrodes wide, it is possible to prevent the occurrence of the initial state of abnormal plasma discharge.

Next, FIG. 19 shows a schematic configuration of another embodiment of the plasma state detecting apparatus according to the present invention. In this plasma state detecting device, a high frequency signal transmitted as an electromagnetic wave is received from the plasma generating unit, and thereafter, the specific frequency level thereof is detected as in the above-described embodiment, and the initial state of abnormal plasma discharge is detected.

For example, in the configuration shown in FIG. 19, the high frequency voltage output from the high frequency power supply 3 is matched by the matching unit 4 and supplied to the plasma generating unit 5, so that plasma discharge occurs. In the plasma processing apparatus of FIG. 19, a high frequency signal generated due to plasma discharge is received by the antenna 51 and supplied to the spectrum detection unit 1 via the coaxial cables 52 and 53. After that, the initial state of abnormal plasma discharge can be detected in the same manner as in the above embodiment.

According to the embodiment of the wireless system shown in FIG. 19, the detection system consisting of the antenna 51 and the spectrum detecting section 1 can be freely arranged without depending on the position of the plasma generating section 5. Therefore, as compared with the embodiment shown in FIG. 1, the labor for connecting the sensor unit 6 to the electrodes can be saved,
The work for that is unnecessary. Further, since it is a wireless reception system, it can be easily used for detecting an initial state of abnormal plasma discharge in an existing plasma processing apparatus.

Next, as another embodiment of the plasma processing apparatus, the plasma processing for detecting the initial state of the abnormal plasma discharge by detecting the light emission in the initial state of the abnormal plasma discharge to control the plasma discharge. The device will be described below.

FIG. 20 shows a schematic configuration of an embodiment of a plasma processing apparatus using a photodetection method.

In FIG. 20, for example, an RF electrode 72 is provided as a plasma discharge electrode, and a TAB tape 73 is placed and fixed on the stage 71. A fiber 74 is introduced between the stage 71 of the plasma discharge electrode and the RF electrode 72, and the fiber 74 detects light emission generated in the initial state of abnormal plasma discharge. Light emission during plasma discharge has a wavelength according to components such as atoms in plasma. Therefore, the emission wavelength obtained by the fiber 74 is transmitted to the spectroscope 75, and the spectroscope 75 detects the wavelength of each component contributing to plasma discharge. The wavelength of each component detected by the spectroscope 75 is sent to the emission intensity detection unit 76, and the intensity at the time of emission is detected for each component. These emission intensities are sent to the comparator 77 and compared with the preset emission intensities during normal plasma discharge. The comparator 77 sends a signal indicating that the plasma discharge abnormality has occurred to the control circuit 31.

The control circuit 31 sets a plurality of plasma generation parameters so that the initial state of abnormal plasma discharge does not occur. Then, the RF output power control unit 33, the inter-electrode gap control unit 34, and the gas flow rate control unit 35 are controlled using the set plasma generation parameters.

Table 1 shows the plasma processing apparatus of FIG.
Helium He is used as the discharge gas and oxygen O ₂ is used as the additive gas.
The luminescence intensity of helium atoms and oxygen atoms detected by the fiber 74 is shown when is used.

[0093]

[Table 1] The emission wavelength of helium atoms is 706.5 nm, and the emission wavelength of oxygen atoms is 777.3 nm. At this time, the inter-electrode gap is 3 mm and the helium flow rate is 20 liter / min.

The values in Table 1 are shown in FIG. The curve a shows the emission intensity of helium atoms, and the curve b shows the emission intensity of oxygen atoms. From this FIG. 21, it could be confirmed that the initial state of abnormal plasma discharge occurred when the RF output power was higher than 400 W. Therefore,
By setting the plasma generation parameter so that the RF output power is 400 W or less, it is possible to prevent the occurrence of the initial state of abnormal plasma discharge.

[0095]

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an embodiment of a plasma processing apparatus of the present invention.

FIG. 2 is a diagram showing a traveling wave power control voltage.

FIG. 3A is a diagram schematically showing a periodic output change of a high frequency voltage, and FIG. 3B is a diagram schematically showing an output change of a high frequency voltage at the start of voltage output.

FIG. 4 is a characteristic diagram showing selectivity of a detection signal in a spectrum detection unit.

FIG. 5 is a diagram showing selected signal widths.

FIG. 6A is a diagram schematically showing a change state of a harmonic spectrum detected when plasma is normal, and FIG. 6B is a diagram schematically showing a change state of a harmonic spectrum detected when plasma is abnormal. .

7A is a diagram schematically showing a change in a discharge detection signal output when plasma is normal, and FIG. 7B is a diagram schematically showing a change in a discharge detection signal output when plasma is abnormal.

FIG. 8 is a schematic configuration diagram of another embodiment of the plasma processing apparatus according to the present invention.

9A is a diagram schematically showing a detected harmonic level and a traveling wave power monitor voltage, and FIG. 9B is a diagram schematically showing a signal level after the division of both.

FIG. 10 is a diagram showing the relationship between the signal strength and the monitor output voltage at the fourth, sixth, and eighth harmonics.

FIG. 11 is a schematic configuration diagram of electrodes used in a plasma processing apparatus.

12 shows a relationship between RF output power and a plasma discharge detection signal detected by using the electrode of FIG.

FIG. 13 shows the relationship between RF output power and plasma discharge detection signal when oxygen is added.

FIG. 14 shows the relationship between RF output power and plasma discharge detection signal when a glass substrate having an element pattern is used.

FIG. 15 shows the relationship between the RF output power and the plasma discharge detection signal when the gap between the electrodes is 0.5 mm.

FIG. 16 shows the relationship between the RF output power and the plasma discharge detection signal when the gap between the electrodes is 1.0 mm.

FIG. 17 shows the relationship between the RF output power and the plasma discharge detection signal when the gap between the electrodes is 1.5 mm.

FIG. 18 shows the relationship between the RF output power and the plasma discharge detection signal when the gap between the electrodes is 2.0 mm.

FIG. 19 is a schematic configuration diagram of an embodiment of a plasma processing apparatus according to the present invention, which wirelessly receives an electromagnetic wave of plasma discharge.

FIG. 20 is a schematic configuration diagram of an embodiment of a plasma processing apparatus according to the present invention, which uses a light detection method.

FIG. 21 is a diagram showing the relationship between the RF output power and the emission intensity of He atoms and O atoms.

[Explanation of symbols]

 1 Spectrum Detection Section 3 High Frequency Power Supply 4 Matching Device 5 Plasma Generation Section 6 Sensor Unit 11 Modulation Oscillator 12 High Pass & Trap Filter 13 First Local Oscillator 14 First Frequency Converter 15 Narrow Band Filter 16 Second Local Oscillator 17 Second Frequency Oscillator 18 High-frequency amplifier 19, 22 Detector 20 Divider 21 AC amplifier 23 Voltage comparator 24 Detection sensitivity setting volume 25 Transistor 26 Coil 27 Switch 31 Control circuit 32 Memory 33 RF output power control unit 34 Electrode gap control unit 35 Gas Flow rate control unit 40 Subtractor 51 Antenna 71 Stage 72 RF electrode 73 TAB tape 74 Fiber 75 Spectrometer 76 Emission intensity detection unit 77 Comparator

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Internal reference number FI Technical indication H01L 21/66 H01L 21/31 C // H01L 21/31 21/302 E (72) Inventor Yamaguchi Hisao, 2500, Hagizono, Chigasaki, Kanagawa Japan, Japan Vacuum Technology Co., Ltd.

Claims (13)

[Claims] 1. A plasma is generated between the pair of electrodes by applying an AC voltage from an AC power source to the pair of electrodes,
In a plasma processing method for processing an object to be processed by the plasma discharge, while changing at least one of a plurality of plasma generation parameters that changes the state of the plasma discharge, a specific frequency other than a fundamental frequency of the AC power supply is changed. A plasma processing method, wherein a change in spectrum is monitored, and it is determined that the initial state of abnormal plasma discharge is based on the detected rate of change in the spectrum. 2. The plasma processing method according to claim 1, wherein the specific frequency is a harmonic of the fundamental frequency of the AC power supply. 3. The history of processing of the object to be processed according to claim 1, wherein when the initial state of the plasma discharge abnormality is determined, the occurrence of the initial state of the plasma discharge abnormality is generated. A plasma processing method characterized by storing as information. 4. The normal plasma according to claim 1, wherein when it is determined that the plasma discharge abnormality is in an initial state, at least one of the plurality of plasma generation parameters is controlled. A plasma processing method, characterized in that the state is maintained. 5. A plasma treatment method for treating an object to be treated with the plasma by controlling the state of plasma discharge generated between the pair of electrodes by applying an AC voltage from an AC power source to the pair of electrodes. In, while changing at least one of the plurality of plasma generation parameters, a boundary condition for transitioning to the initial state of the plasma discharge abnormality is detected, and based on the boundary condition, at least one of the plurality of plasma generation parameters is detected. A plasma processing method, characterized in that a normal plasma discharge is maintained by controlling one of them. 6. The method of claim 1, wherein the at least one plasma generation parameter that is changed is an output power from the AC power supply, the output power being periodically generated during the generation of the plasma discharge. A plasma processing method, characterized in that: 7. The at least one plasma generation parameter to be changed according to claim 1, wherein the at least one plasma generation parameter is output power from the AC power supply, and the output power is changed at the start of output. Plasma treatment method. 8. The method according to claim 4, wherein the at least one plasma generation parameter to be controlled is an output power of the AC power supply, and the output power is lower than a value in the boundary condition. Plasma treatment method. 9. The method according to claim 4, wherein the at least one plasma generation parameter to be controlled is a distance between the pair of electrodes, and the distance is larger than a value under the boundary condition. Plasma treatment method. 10. The controlled plasma generation parameter according to claim 4, wherein the at least one plasma generation parameter is a gas supplied between the pair of electrodes, and a supply amount of an additive gas added to a plasma discharge gas. Is larger than the value under the boundary condition. 11. The additive gas according to claim 10, wherein the additive gas is Ar, Kr, Xe, O ₂ , CF ₄ ,
N ₂ , CO ₂ , SF ₆ and CHF ₃ , at least O, N, F
Or a gas containing Cl, or a liquid containing them, which is one or more reactive gases selected from those in a gas phase state. 12. A plasma processing apparatus, wherein a plasma is generated between a pair of electrodes by applying an AC voltage from an AC power supply to the pair of electrodes, and a plurality of plasmas are generated in the plasma processing apparatus for processing an object to be processed by the plasma discharge. Detecting means for detecting a boundary condition that shifts to an initial state of the plasma discharge abnormality while changing at least one of the parameters; and a plurality of plasma generation parameters among the plurality of plasma generation parameters based on the detected boundary condition. A plasma processing apparatus comprising: a control unit that controls at least one setting to maintain normal plasma discharge generation. 13. The storage device according to claim 12, further comprising a storage unit that stores the at least one plasma generation parameter set based on the detected boundary condition, wherein the control unit stores the stored at least one of the at least one plasma generation parameter. A plasma processing apparatus, which maintains normal plasma discharge generation based on three plasma generation parameters.