JP4074079B2 - Plasma processing apparatus and plasma processing method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a plasma processing apparatus and a plasma processing method that are mounted on a plasma processing apparatus that processes a substrate using plasma, and that prevent a processing failure due to abnormal discharge in the plasma processing apparatus.
[0002]
[Prior art]
Plasma processing apparatus for manufacturing a semiconductor device using plasma to process a substrate, such as a vapor phase growth apparatus and sputtering apparatus for forming a thin film on a substrate such as a semiconductor wafer, an etching apparatus for removing unnecessary thin films, and ions for doping impurities There are injection devices. This type of plasma processing apparatus includes a pair of processing electrodes including an upper electrode and a lower electrode installed in a vacuum processing chamber, fixes a substrate to be processed on the lower electrode, and has a predetermined pressure in the vacuum processing chamber. A configuration is adopted in which processing is performed on a substrate by filling with a process gas and applying a high-frequency voltage between the processing electrodes to convert the process gas into plasma.
[0003]
By the way, abnormal discharge may be a problem in this type of plasma apparatus. For example, a discharge occurs between the substrate and the processing electrode, and a part of the substrate or electrode where the abnormal discharge has occurred melts and scatters to become a foreign substance and adheres to the surface of the substrate. There is a possibility that a member having a defective pattern or an abnormal discharge is damaged and a plasma leak or the like occurs to change the process conditions. In addition, when abnormal discharge occurs on the substrate, disconnection of a circuit formed on the substrate and insulation failure occur, resulting in a decrease in yield.
[0004]
As one of the causes of such abnormal discharge, moisture contained in the atmosphere in which plasma discharge is performed and moisture attached to the inner surface of the substrate or the processing chamber have been pointed out. In order to remove these moistures, a dry etching apparatus described in Japanese Patent Laid-Open No. 63-141319 employs a method of heating a substrate inserted into a vacuum vessel through an inert gas. In addition, in the semiconductor processing apparatus described in Japanese Patent Laid-Open No. 5-198515, abnormal discharge is not particularly mentioned, but in order to remove moisture, the reaction chamber after the wet cleaning and before the start of the process is heated. Moisture is removed.
[0005]
[Problems to be solved by the invention]
However, in the conventional water removal technique, heat treatment is only performed by controlling the heating time obtained empirically, and thus there is a problem in the stability and certainty of water removal and reproducibility. In other words, the moisture in the atmosphere in the processing chamber and the moisture adhering to the substrate and the processing chamber fluctuate depending on the processing method, processing environment, and the elapsed time after processing. This is because these fluctuations cannot be dealt with.
[0006]
An object of the present invention is to provide a plasma processing apparatus and a plasma processing method that can stably and reliably remove moisture with good reproducibility and suitably prevent abnormal discharge due to moisture in the plasma processing apparatus. is there.
[0007]
[Means for Solving the Problems]
The inventor first actually measured the amount of moisture in the processing chamber, which causes abnormal discharge in the plasma processing apparatus. FIG. 5A shows the amount of gas in the processing chamber measured with a mass spectrometer for one cycle of substrate processing, and FIG. 5B shows the operating state of the apparatus for one cycle of substrate processing. is there. Here, O ₂ (oxygen) gas and SF ₆ (sulfur fluoride gas) are supplied as process gases into the processing chamber, and O ₂ gas is generated when plasma is generated by applying RF (radio frequency) power to the processing electrode. Shows about. He (helium) gas is a wafer cooling gas, and N ₂ (nitrogen gas) is a residual gas in the pipe. From FIG. 5 (b), it can be seen that the RF power for generating the plasma is turned on simultaneously with the introduction of the He gas, and stops when the gas is stopped. In FIG. 5A, the time at which He begins to increase is the plasma discharge start time, and the time at which the reactive gas O ₂ begins to decrease is the plasma discharge stop time. The difference between the time of decrease in He and the decrease in O ₂ is thought to be because the molecular weight of He is small and the exhaust is slow. The reason for the rapid increase in the amount of moisture during plasma discharge is that the substrate exposed to the plasma or the wall surface of the processing chamber is locally heated to desorb the adhering moisture.
[0008]
Next, the moisture in the processing chamber when the substrate was continuously processed was measured. FIG. 6A shows a change in the amount of moisture when the substrate is continuously processed immediately after wet cleaning of the processing chamber using water, acid, or organic solvent. There is a tendency that the amount of water in the processing chamber decreases as the number of processing increases. This is considered to be because moisture adhering to the wall surface of the processing chamber is repeatedly desorbed by the plasma discharge and exhausted.
[0009]
On the other hand, FIG. 6B shows a change in the amount of moisture in the processing chamber when 16 substrates are processed after the substrate processing is sufficiently repeated after cleaning and purged with N ₂ gas for 18 hours. Unlike FIG. 6A, the water content increases with an increase in the number of treatments. This is probably because moisture adhering to the wall surface of the processing chamber was removed to a sufficiently low level, so that moisture desorbed mainly from the substrate was observed. Since moisture desorbed from the substrate is repeatedly exhausted before the substrate is sufficiently exhausted, it is expected that moisture accumulates in the processing chamber. That is, even if the moisture attached to the wall surface of the processing chamber is removed by the processing immediately after the wet cleaning, the moisture brought into the processing chamber by the substrate may cause particles and abnormal discharge. In addition, it can be seen that in order to improve the operating rate of the apparatus, it is necessary to remove the moisture accumulated in the processing chamber atmosphere by continuous processing at an optimal timing, or to prevent moisture accumulation.
[0010]
Therefore, a plasma processing apparatus of the present invention includes a mass spectrometer that analyzes the amount of moisture in a processing chamber for processing a substrate by plasma generated by supplying RF power to a processing electrode provided in the processing chamber, and the mass spectrometer. And a control means for controlling an RF power source for supplying RF power to the machining electrode based on the analysis result of the calculation means.
[0011]
Another plasma processing apparatus of the present invention is an RF for generating plasma for processing a substrate in the processing chamber by an output from the calculation means when the amount of moisture in the processing chamber exceeds a predetermined level. The RF power supply from the power supply to the processing electrode is stopped .
[0012]
The plasma processing method of the present invention supplies an RF power to plasma generated in the processing chamber to the processing electrode provided in the processing chamber, the plasma processing method for processing a substrate by the plasma processing chamber prior to processing the substrate In addition to exposing the substrate to plasma at a power that does not allow the substrate to be processed, the amount of water generated in the processing chamber is constantly measured, and after this measured value falls below a predetermined level, the processing electrode from the RF power supply for substrate processing Control for starting the supply of RF power to is performed.
[0013]
Another plasma processing method of the present invention supplies an RF power to the processing electrode provided in the processing chamber to plasma generated in the processing chamber, the plasma processing method for processing a substrate by the plasma, the measured value is predetermined When the level is exceeded, control is performed to stop the RF power supply from the RF power source to the processing electrode for the generation of plasma in the processing chamber .
[0014]
According to the present invention, the amount of moisture in the processing chamber related to the occurrence of abnormal discharge is monitored by a mass spectrometer, and RF power is supplied to the processing electrode only when the amount of moisture is equal to or less than a predetermined value to perform processing by plasma. Thus, abnormal discharge in the processing chamber of the plasma processing apparatus can be prevented. Further, by exposing the board prior to plasma processing in the processing chamber to plasma, to remove moisture in the substrate, to prevent the water content in the process chamber during processing of the substrate by the plasma increases, the processing chamber Abnormal discharge can be prevented. Furthermore, control is performed to stop the supply of RF power from the RF power source to the processing electrode for generating plasma in the processing chamber when the amount of moisture exceeds a predetermined level. As a result, moisture that causes abnormal discharge in the processing chamber can be stably and reliably removed with good reproducibility, and it is possible to cope with unexpected abnormalities.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic configuration diagram of a first embodiment of a plasma processing apparatus according to the present invention. A pair of processing electrodes 20 composed of an upper electrode 21 and a lower electrode 22 are disposed in the vacuum processing chamber 10, and a substrate W to be processed is placed on the lower electrode 22 by a susceptor (not shown) on the lower electrode 22. Secure to. The upper electrode 21 is provided with a process gas introduction port 11 for introducing a process gas into the vacuum processing chamber so that the process gas is supplied between the processing electrodes 20. Further, an exhaust port 12 for vacuuming the inside of the vacuum processing chamber 10 to a predetermined pressure is opened and connected to a vacuum pump or the like not shown. On the other hand, the lower electrode 22 is connected to an adsorption power source 31 for applying a potential for electrostatic adsorption of the substrate W and an RF power source 32 for supplying RF (high frequency) power to the processing electrode 20. ing.
[0016]
Further, a sampling port 13 is opened in the vacuum processing chamber 10 at a position facing the processing electrode 20, and a mass spectrometer 40 for analyzing gas is attached to the sampling port 13. The sampling port 13 is preferably as close to the substrate W as possible. A calculator 50 is connected to the mass spectrometer 40, and the data analyzed by the mass spectrometer 40 is analyzed by the calculator 50 and necessary signals are output to the controller 60. The calculator 50 is set in advance so as to monitor the intensity of the signal corresponding to the amount of water, that is, the signal of the mass number 18 which is the mass number of H ₂ O. For example, the first threshold value TH1 and the second threshold value TH2 are set for the signal strength. The first threshold value TH1 is assigned a signal intensity that occurs at a frequency at which abnormal discharge becomes a problem, and the second threshold value TH2 is assigned a value at which abnormal discharge starts. Since these values vary depending on the configuration and operating conditions of the plasma processing apparatus, they are set based on values measured in advance through experiments and simulations. Further, the controller 60 controls the adsorption power source 31 and the RF power source 32, and supplies various types of processes related to the supply system and the vacuum exhaust system that do not appear in the drawing of the process gas, the temperature of the vacuum processing chamber 10, and the like. It is configured to perform control.
[0017]
A processing method in the plasma processing apparatus having the above configuration will be described with reference to the timing chart of FIG. First, the vacuum processing chamber 10 is cleaned as a preliminary process, and the vacuum processing chamber 10 is evacuated after cleaning. Then, moisture is measured by the mass spectrometer 40 and the computing unit 50, and after confirming that the signal is lower than the second threshold value TH2, processing for the substrate W is started. That is, a process gas is introduced into the vacuum processing chamber 10 and set to a predetermined pressure, the substrate W is heated to a predetermined temperature, and RF power is applied to the processing electrode 20. As a result, plasma is generated in the vacuum processing chamber 10 and processing for the substrate W is executed. Even during the execution of the plasma processing, the measurement of moisture by the mass spectrometer 40 and the calculator 50 is continued, and if the signal exceeds the second threshold value TH2 and is smaller than the threshold value 1, the calculator 50 takes care. Information is output. In this warning, the control by the controller 60 is not particularly changed.
[0018]
Further, when the signal exceeds the first threshold value TH1, an alarm is output from the calculator 50. In response to this alarm, the controller 60 controls each system, and in particular, stops the generation of plasma in the vacuum processing chamber 10 by stopping the application of RF power by the RF power source 32 to substantially process the substrate W. To stop. On the other hand, the vacuum processing chamber 10 continues to be evacuated, the temperature in the vacuum processing chamber 10 is increased as necessary, or a dry inert gas such as N ₂ or Ar (argon) is used as a purge gas to form a vacuum processing chamber. Let it flow into 10 little by little. Thereby, the moisture exhaust efficiency in the vacuum processing chamber 10 is improved, and the moisture in the vacuum processing chamber 10 is reduced. Then, when the signal from the computing unit 50 is reduced below the first threshold value TH1, preferably the second threshold value TH2, the plasma processing is resumed as described above. In this case, the controller 60 may be manually restarted after the operator confirms the restart.
[0019]
Alternatively, the moisture amount at which the probability of occurrence of abnormal discharge is greater than or equal to the allowable range is set as the first threshold value TH1, and an alarm is issued when the state exceeding the first threshold value TH1 becomes longer than a separately set time. It may be. In this case, the purging and the exhausting are continued until reaching the second threshold value TH2 at which the probability of occurrence of abnormal discharge set lower than the first threshold value TH1 becomes substantially “0”.
[0020]
Here, in the plasma processing in the embodiment, after the vacuum processing chamber 10 is cleaned, the substrate W is set, and the substrate W is not processed, or plasma discharge is performed at an RF power with a sufficiently low processing speed, for example, 200 W. The plasma processing for the substrate W may be started when the moisture signal becomes lower than the second threshold value TH2. By exposing the inside of the vacuum processing chamber 10 to the plasma in this way, the detachment of moisture adhering to the wall surface and internal parts of the vacuum processing chamber 10 is promoted, and the time until the plasma processing apparatus can be processed is shortened. it can. Note that a dummy substrate may be used as the substrate in this case, and the substrate may be replaced with a substrate to be processed immediately before starting the plasma processing. The reason why plasma discharge is performed at such a low power that the substrate is not processed is to prevent abnormal discharge.
[0021]
In the first embodiment, a mass spectrometer and a calculator are attached to the conventional vacuum processing chamber, and the software (program) of the controller can be partially changed. It is possible to suppress the high cost. In addition, it is not necessary to use an expensive semiconductor material gas for plasma discharge at the time of processing, and it is inexpensive if dry inert gas such as N ₂ and Ar or oxygen is used. Damage is also reduced.
[0022]
FIG. 3 is a schematic configuration diagram of a plasma processing apparatus according to the second embodiment as a reference example of the present invention. In the second embodiment, an increase in moisture in the vacuum processing chamber 10 due to moisture brought into the vacuum processing chamber 10 by the substrate W, that is, moisture contained in the substrate W, is prevented. The structure of the vacuum processing chamber 10 is the same as that of the first embodiment, and is given the same reference numerals as in FIG. Here, a preliminary processing chamber 10 </ b> A is provided next to the vacuum processing chamber 10, and both are connected by an airtight substrate transfer port 14. The substrate transfer port 14 can transfer the substrate between the preliminary processing chamber 10A and the vacuum processing chamber 10 when opened, and at least seals the vacuum processing chamber 10 when closed. The preliminary processing chamber 10A has basically the same configuration as the vacuum processing chamber 10, and includes a discharge electrode 20A including a pair of upper electrode 21A and lower electrode 22A so that plasma discharge can be performed. A gas inlet 11A is opened in the upper electrode 21A, and a substrate can be fixed to the lower electrode 22. An adsorption power supply 31A for applying a potential for electrostatic adsorption of the substrate, a discharge electrode An RF power source 32A for supplying RF power to 20A is connected.
[0023]
A sampling port 13A is opened in the preliminary processing chamber 10A, and a mass spectrometer 40 is attached to the sampling port 13A. Further, a calculator 50 is connected to the mass spectrometer 40, the data analyzed by the mass spectrometer 40 is analyzed by the calculator 50, and necessary signals are output to the controller 60. The controller 60 is configured to receive at least a signal from the computing unit 50 and to control at least the RF power source 32A of the preliminary processing chamber 10A, other gas supply systems, exhaust systems, and the like not shown.
[0024]
The plasma processing method in the second embodiment will be described with reference to the timing chart of FIG. First, after the substrate W is carried into the preliminary processing chamber 10A, a low RF power is applied so that the substrate W is not processed to generate plasma in the preliminary processing chamber 10A, and the substrate W is exposed to the plasma. At the same time, the mass spectrometer 40 measures moisture in the gas in the pretreatment chamber 10 </ b> A (a signal having a mass number of 18) and outputs a signal from the calculator 50. As shown in FIG. 5A, the moisture in the gas increases during exposure to the plasma discharge, so that the exhaust process is performed after a predetermined time. By repeating this operation, that is, by alternately and intermittently performing the plasma treatment and the exhaust treatment, the moisture peak gradually decreases. During this time, the controller 60 monitors the signal from the computing unit 50, exhausts sufficiently after the moisture peak falls below the predetermined level TH, moves the substrate W from the substrate transfer port 14 to the vacuum processing chamber 10, Processing by plasma processing is started in the vacuum processing chamber 10. In the plasma discharge in the above-described pretreatment chamber 10A, it is not necessary to use an expensive semiconductor material gas, and it is inexpensive if dry inert gas such as N ₂ or Ar or oxygen is used. Damage to walls and internal parts is also reduced.
[0025]
Here, in the second embodiment, since the conventional vacuum processing chamber can be used as it is, it can be realized by attaching the preliminary processing chamber having the above-described configuration. In particular, the preliminary processing chamber having the same configuration as the vacuum processing chamber can be used. Further, in this case, if the vacuum processing chamber is configured so that moisture can be measured by a mass spectrometer, a calculator, and a controller as in the first embodiment, the first embodiment will be described. Similarly to the above, plasma processing can be executed while monitoring moisture.
[0026]
【The invention's effect】
As described above, according to the present invention, the moisture content in the processing chamber related to the occurrence of abnormal discharge is monitored by a mass spectrometer, and RF power is supplied to the processing electrode only when the moisture content is below a predetermined value. By performing the processing, abnormal discharge in the processing chamber of the plasma processing apparatus can be prevented. Further, by exposing the board prior to plasma processing in the processing chamber to plasma, to remove moisture in the substrate, to prevent the water content in the processing chamber during processing by plasma board increases, the processing chamber Abnormal discharge can be prevented. Furthermore, control is performed to stop the supply of RF power from the RF power source to the processing electrode for generating plasma in the processing chamber when the amount of moisture exceeds a predetermined level. As a result, moisture that causes abnormal discharge in the processing chamber can be stably and reliably removed with good reproducibility, and it is possible to cope with unexpected abnormalities. Further, the present invention is fitted with a mass spectrometer to the processing chamber, by simply changing the software of the process control can be applied to existing plasma device, it becomes high versatility.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of a plasma processing apparatus according to a first embodiment of the present invention.
2 is a timing chart for explaining a plasma processing method of the plasma processing apparatus of FIG. 1; FIG.
FIG. 3 is a schematic configuration diagram of a plasma processing apparatus according to a second embodiment of the present invention.
4 is a timing chart for explaining a plasma processing method of the plasma processing apparatus of FIG. 3; FIG.
FIG. 5 is a diagram showing a change in gas amount in one cycle of substrate processing and an apparatus operating state at that time.
FIG. 6 shows changes in the amount of moisture during substrate processing performed immediately after cleaning of the processing chamber, and changes in the amount of moisture during substrate processing after the substrate processing was repeated sufficiently after the processing chamber was cleaned and nitrogen purge was performed. FIG.
[Explanation of symbols]
10 Vacuum processing chamber 11 of plasma apparatus 11 Process gas introduction port 12 Exhaust port 13 Sampling port 14 Substrate transport port 20 Processing electrode 20A Discharge electrode 21, 21A Upper electrode 22, 22A Lower electrode 31, 31A Adsorption power source 32, 32A RF power source 40 Mass spectrometer 50 Calculator 60 Controller W Substrate

Claims (4)

In a plasma processing apparatus for processing a substrate using plasma generated by supplying RF power to a processing electrode provided in a processing chamber, a mass spectrometer for analyzing the amount of moisture in the processing chamber for processing the substrate, and the mass analysis Plasma processing comprising analysis means for analyzing the data of the meter to calculate the amount of moisture, and control means for controlling an RF power source for supplying RF power to the processing electrode based on the analysis result of the calculation means A device,
When the amount of moisture in the processing chamber exceeds a predetermined level, the control unit is configured to output from the RF power source for generating plasma for processing the substrate in the processing chamber to the processing electrode by an output from the calculation unit. A plasma processing apparatus having a function of stopping the RF power supply. In a plasma processing apparatus for processing a substrate using plasma generated by supplying RF power to a processing electrode provided in a processing chamber, a mass spectrometer for analyzing the amount of moisture in the processing chamber for processing the substrate, and the mass analysis Plasma processing comprising analysis means for analyzing the data of the meter to calculate the amount of moisture, and control means for controlling an RF power source for supplying RF power to the processing electrode based on the analysis result of the calculation means When the amount of moisture generated in the processing chamber is lower than a predetermined level when the substrate is exposed to plasma at a power at which the substrate is not processed in the processing chamber The function of starting RF power supply from the RF power source to the processing electrode for generating plasma of power for processing the substrate by the output from the substrate, and the process for processing the substrate When the amount of moisture in the processing chamber in the processing state exceeds a predetermined level, an output from the calculation means causes an RF power source for generating plasma to process the substrate in the processing chamber to the processing electrode. A plasma processing apparatus having a function of stopping the RF power supply. In a plasma processing apparatus for processing a substrate using plasma generated by supplying RF power to a processing electrode provided in a processing chamber, a mass spectrometer for analyzing the amount of moisture in the processing chamber for processing the substrate, and the mass analysis Plasma processing comprising analysis means for analyzing the data of the meter to calculate the amount of moisture, and control means for controlling an RF power source for supplying RF power to the processing electrode based on the analysis result of the calculation means When the amount of moisture generated in the processing chamber is lower than a predetermined level when the substrate is exposed to plasma at a power at which the substrate is not processed in the processing chamber The function of starting RF power supply from the RF power source to the processing electrode for generating plasma of power for processing the substrate by the output from the substrate, and the process for processing the substrate When the amount of moisture in the processing chamber in the processing state exceeds a predetermined level, an output from the calculation means causes an RF power source for generating plasma to process the substrate in the processing chamber to the processing electrode. A function of stopping the RF power supply of the substrate, and an RF power source for generating plasma of power to be processed by the substrate when the amount of moisture in the processing chamber in the stopped state falls below a predetermined level. A plasma processing apparatus having a function of restarting RF power supply.   In a plasma processing method in which RF power is supplied to a processing electrode provided in a processing chamber to generate plasma in the processing chamber, and the substrate is processed by the plasma, the amount of moisture in the processing chamber is constantly measured, and the measured value is predetermined. A plasma processing method characterized by performing control to stop RF power supply from an RF power source to a processing electrode for generating plasma in the processing chamber when the level is exceeded.

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