JP5012317B2 - Plasma discharge state monitoring device - Google Patents

Description

  The present invention relates to a plasma discharge state determination device that is used in a plasma processing apparatus that performs plasma processing on a plate-like processing object such as a substrate, and that monitors the plasma discharge state.

  Plasma treatment is known as a surface treatment method such as cleaning and etching of a processing object such as a substrate on which an electronic component is mounted. In plasma processing, a substrate to be processed is placed in a vacuum chamber that forms a processing chamber, plasma discharge is generated in the processing chamber, and ions and electrons generated as a result are allowed to act on the surface of the substrate. Surface treatment is performed. In order to perform this plasma processing stably with good processing quality, it is premised that plasma discharge is generated correctly according to the discharge conditions set in advance according to the processing purpose. Various means and methods are used for the purpose of monitoring the state of occurrence of discharge.

For example, a method for detecting the influence of a change in plasma discharge due to some factor on the voltage and current of the high-frequency power supply unit, a method for estimating the discharge state by detecting a self-bias voltage generated between electrodes due to plasma discharge, and the like are known. It has been. However, these methods have the disadvantages that detection accuracy is low when it is necessary to generate plasma discharge under low output conditions, and it is difficult to accurately detect the discharge state. A method that can be detected automatically is used (for example, see Patent Document 1). In this method, a discharge detection sensor equipped with a probe electrode for potential detection is attached to a vacuum chamber provided with a processing chamber, and a potential change induced in response to a change in plasma discharge is detected on the probe electrode, The presence or absence of abnormal discharge in the processing chamber is detected.
JP 2003-318115 A

  Since this method can detect the state change of the plasma discharge generated in the processing chamber with high sensitivity, the presence or absence of plasma discharge and discharge abnormality can be correctly monitored even when the output of the high frequency power supply is low. It is possible in principle. However, the above-mentioned patent document examples do not clearly disclose specific application examples necessary for monitoring the presence / absence of plasma discharge and discharge abnormality with high accuracy, and new applications for actual plasma devices are not disclosed. Technology development was desired.

  Therefore, an object of the present invention is to provide a plasma discharge state monitoring device capable of correctly monitoring the presence / absence of plasma discharge and discharge abnormality.

The plasma discharge state monitoring apparatus of the present invention is a plasma discharge state monitoring apparatus that is used in a plasma processing apparatus that accommodates a processing object in a processing chamber and performs plasma processing, and monitors the plasma discharge state in the processing chamber, A plate-like dielectric member mounted on a vacuum chamber forming the processing chamber so that one surface faces the plasma discharge generated in the processing chamber, and a probe electrode disposed on the other surface of the dielectric member A discharge detection sensor having at least a waveform detection unit that detects a predetermined waveform by receiving a potential change induced in response to a change in the plasma discharge at the probe electrode, the waveform detection unit having a potential of An N-type waveform detecting unit that detects an N-type potential change waveform having an N-shaped waveform pattern that returns to a steady value after swinging on both the positive and negative sides; And a V-type waveform detecting section for detecting a V-shaped potential change waveform having a V-shaped waveform pattern back to a steady value after the N-type waveform detecting unit, the previously positive and negative sides are detected potential change The V-shaped waveform detection unit is used to check that the detected potential change is set in advance on both the positive and negative sides. It is confirmed that the threshold level is reached only on the negative side .

  According to the present invention, the plasma discharge state determining means for monitoring and determining the plasma discharge state in the processing chamber includes the plate-like dielectric member mounted in the vacuum chamber and the probe electrode disposed on the dielectric member. An N-type potential change having an N-shaped waveform pattern that receives a change in potential induced by a discharge detection sensor and a probe electrode according to a change in plasma discharge and returns to a steady value after the potential fluctuates on both sides. An N-type waveform detection unit that detects a waveform, and a V-type waveform detection unit that detects a V-type potential change waveform having a V-shaped waveform pattern that returns to a steady value after the potential fluctuates only on the negative side. By adopting the configuration, a specific potential change waveform corresponding to a change in the plasma discharge state can be detected with high accuracy, and the presence or absence or abnormality of the discharge can be correctly monitored.

(Embodiment 1)
FIG. 1 is a cross-sectional view of a plasma processing apparatus according to a first embodiment of the present invention, FIG. 2 is a diagram illustrating the configuration of a discharge detection sensor used in the plasma processing apparatus according to the first embodiment of the present invention, and FIG. FIG. 4 is a block diagram showing a configuration of a plasma discharge state monitoring device in the plasma processing apparatus of Embodiment 1, and FIG. 4 is an explanatory diagram of a potential change waveform and a waveform monitoring time zone in the plasma discharge state monitoring method of Embodiment 1 of the present invention. 5 is a process flow diagram of the discharge state determination process in the plasma discharge state monitoring method of the first embodiment of the present invention, and FIG. 6 is a process flow diagram of maintenance determination process in the plasma discharge state monitoring method of the first embodiment of the present invention. is there.

  First, the structure of the plasma processing apparatus will be described with reference to FIG. In FIG. 1, a vacuum chamber 3 is configured by disposing a lid portion 2 on a horizontal base portion 1 so as to be movable up and down by elevating means (not shown). The vacuum chamber 3 is closed when the lid portion 2 is lowered and is in contact with the upper surface of the base portion 1 via the seal member 4, and the sealed space surrounded by the base portion 1 and the lid portion 2 holds the object to be processed. A processing chamber 3a that accommodates and performs plasma processing is formed. An electrode portion 5 is disposed in the processing chamber 3a, and the electrode portion 5 is attached to an opening portion 1a provided in the base portion 1 via an insulating member 6 from below. An insulator 7 is mounted on the upper surface of the electrode unit 5, and the substrate 9, which is the object to be processed, is guided by the guide member 8 on both sides of the upper surface of the insulator 7 in the substrate transport direction (perpendicular to the paper surface). It is brought in.

  A vent valve 12, a vacuum gauge 15, a gas supply valve 13, and a vacuum valve 14 are connected to the opening 1 b provided in the base portion 1 through a pipe line 11. Further, the gas supply valve 13 and the vacuum valve 14 are connected to a gas supply unit 16 and a vacuum pump 17, respectively. By opening the vacuum valve 14 while the vacuum pump 17 is driven, the inside of the processing chamber 3a is evacuated. The degree of vacuum at this time is detected by the vacuum gauge 15. The vacuum valve 14 and the vacuum pump 17 constitute a vacuum exhaust unit that exhausts the inside of the processing chamber 3a. Further, by opening the gas supply valve 13, a gas for generating plasma is supplied from the gas supply unit 16 into the processing chamber 3a. The gas supply unit 16 has a built-in flow rate adjustment function, and can supply an arbitrary supply amount of plasma generating gas into the processing chamber 3a. By opening the vent valve 12, the atmosphere is introduced into the processing chamber 3a when the vacuum breaks.

  A high frequency power supply unit 19 is electrically connected to the electrode unit 5 via a matching unit 18. By driving the high frequency power supply unit 19 in a state where the processing chamber 3a is evacuated and supplied with gas, a high frequency voltage is applied between the electrode unit 5 and the lid unit 2 grounded to the ground unit 10, Thereby, plasma discharge is generated in the processing chamber 3a. The matching unit 18 has a function of matching the impedance of the high-frequency power supply unit 19 with the plasma discharge circuit that generates plasma discharge in the processing chamber 3a.

  A circular opening 2 a that functions as a viewing window for viewing the inside of the processing chamber 3 a from the outside of the vacuum chamber 3 is provided on the side surface of the lid 2. A discharge detection sensor 23 including a dielectric member 21 and a probe electrode unit 22 is fixed to the opening 2 a from the outside of the lid 2 by a support member 24. Here, the configuration of the discharge detection sensor 23 will be described with reference to FIG. A dielectric member 21 made of optically transparent glass is attached to the opening 2 a provided in the lid 2. Inside the processing chamber 3a, a plasma discharge is generated between the electrode portion 5 and the lid portion 2, and the dielectric member 21 is vacuumed in such a manner that one surface faces the plasma discharge generated in the processing chamber 3a. It is attached to an opening 2 a provided in the chamber 3.

  A probe electrode unit 22 is mounted on the other surface of the dielectric member 21, that is, the surface facing the outside of the vacuum chamber 3. The probe electrode unit 22 is an integral part in which the probe electrode 22b is formed on one surface of the glass plate 22a and the shield electrode 22c is formed on the other surface, and the probe electrode unit 22 is attached to the dielectric member 21 and discharged. When forming the detection sensor 23, the probe electrode 22 b is supported on the lid 2 by a support member 24 made of a conductive metal in a state where the probe electrode 22 b is in close contact with the outer surface (the other surface) of the dielectric member 21. That is, the discharge detection sensor 23 has a plate-like dielectric member 21 attached to the vacuum chamber 3 so that one surface faces the plasma discharge generated in the processing chamber 3a and the other surface of the dielectric member 21. The probe electrode 22b is disposed at least. The probe electrode 22b is connected to the plasma monitoring device 20 through the detection lead wire 22d.

  In a state where plasma discharge is generated inside the processing chamber 3a, the probe electrode 22b is a space charge layer formed at the interface between the dielectric member 21 and the plasma P generated in the processing chamber 3a and the dielectric member 21. It is in a state of being electrically connected to the plasma P through the sheath S. That is, as shown in FIG. 2, an electric circuit is formed in which a capacitor C1 formed by the dielectric member 21, a capacitor C2 having a capacity corresponding to the sheath S, and a resistor R of the plasma P are connected in series, and the probe is formed. A potential corresponding to the state of the plasma P is induced in the electrode 22b. In the present embodiment, the potential of the probe electrode 22b is guided to the plasma monitoring device 20 by the detection lead wire 22d, and the potential change according to the state of the plasma P is monitored by the plasma monitoring device 20, whereby the plasma in the processing chamber 3a is detected. The discharge state is monitored.

  That is, when abnormal discharge or the like occurs around the substrate 9 placed on the electrode unit 5 inside the processing chamber 3a, the state of the plasma P inside the processing chamber 3a changes. This change is detected as a change in the potential of the probe electrode 22b because it changes the impedance of the circuit described above. This potential change is detected with extremely high sensitivity, and it has a feature that it can accurately detect even a weak fluctuation that could hardly be detected by a conventional method. The shield electrode 22c has a function of electrically shielding the outer surface side of the probe electrode 22b, and the electric charge generated in the shield electrode 22c is released to the grounded lid portion 2 through the conductive support member 24. Thereby, the noise with respect to the electric potential change induced by the probe electrode 22b is reduced.

  In the present embodiment, both the probe electrode 22b and the shield electrode 22c are formed by coating the surface of the glass plate 22a with a transparent conductive material such as ITO in the form of a film. Thereby, in a state where the discharge detection sensor 23 is mounted in the opening 2a, the inside of the processing chamber 3a can be visually recognized from the outside of the lid 2 through the opening 2a. That is, in the discharge detection sensor 23 shown in the present embodiment, the dielectric member 21 is optically transparent attached to the opening 2a (view window) for viewing the inside of the processing chamber 3a from the outside of the vacuum chamber 3. The probe electrode 22b is made of an optically transparent conductive material.

  With such a configuration, it is possible to use both the observation window for visually recognizing the inside of the processing chamber 3a and the probe electrode 22b for monitoring the plasma discharge state. Further, since the dielectric member 21 is exposed to the plasma P in the processing chamber 3a, surface wear occurs, and it is necessary to replace it at predetermined intervals. Also in this case, since the probe electrode unit 22 and the dielectric member 21 are separate parts, only the dielectric member 21 as a consumable part needs to be replaced, and the probe electrode unit 22 does not need to be replaced.

  The plasma processing apparatus includes a control unit 25 that performs overall operation control. The control unit 25 controls the vent valve 12, the gas supply valve 13, the vacuum valve 14, the vacuum gauge 15, the gas supply unit 16, the vacuum pump 17, and the high frequency power supply unit 19, thereby performing each operation necessary for plasma processing. Is done. The control unit 25 has a function of controlling the plasma monitoring device 20 and receiving a detection result from the plasma monitoring device 20 and performing necessary control processing. The control unit 25 includes an operation / input unit 26 and a display unit 27. The operation / input unit 26 performs various operation inputs and data inputs during execution of the plasma processing operation. In addition to displaying an operation screen at the time of input by the operation / input unit 26, the display unit 27 displays the determination result determined by the control unit 25 based on the detection result of the plasma monitoring device 20.

  Next, the configuration and functions of the plasma monitoring device 20 and the control unit 25 will be described with reference to FIG. In FIG. 3, the plasma monitoring device 20 includes an AMP (amplifying device) 31, an A / D converter 32, a waveform data temporary storage unit 33, an N-type waveform detection unit 34, a V-type waveform detection unit 35, and a discharge ON waveform counter 36. A discharge OFF waveform counter 37, an abnormal discharge waveform counter 38, and a leak discharge waveform counter 39. The AMP 31 amplifies the potential change of the probe electrode 22b transmitted through the detection lead 22d. The A / D converter 32 AD converts the potential change signal amplified by the AMP 31. The voltage displacement signal AD-converted by the A / D converter 32, that is, a digital signal indicating a voltage change is sent to the waveform data temporary storage unit 33, the N-type waveform detection unit 34, and the V-type waveform detection unit 35.

  The waveform data temporary storage unit 33 temporarily stores the received digital signal indicating the state of potential change as waveform data. The N-type waveform detection unit 34 recognizes the received digital signal as a waveform, compares the recognized waveform with a predetermined condition set in advance, and generates an N-type waveform having an N-shaped waveform pattern from the waveform. If an N-type waveform is detected, a detection signal is output for each detection. Similarly, the V-shaped waveform detection unit 35 recognizes the received digital signal as a waveform, compares the recognized waveform with a predetermined condition set in advance, and has a V-shaped waveform pattern among the waveforms. If a waveform is detected and a V-shaped waveform is detected, a detection signal is output each time it is detected. That is, the N-type waveform detection unit 34 and the V-type waveform detection unit 35 are a plurality of waveform detection units that receive a potential change induced in response to a change in plasma discharge to the probe electrode 22b and detect a predetermined waveform. Each has a function of outputting a detection signal each time a potential change that meets a predetermined condition appears. In the N-type waveform detection unit 34 and the V-type waveform detection unit 35, the predetermined conditions set for waveform detection differ depending on the waveform pattern to be detected, as will be described below.

  Here, the waveform pattern of the waveform detected by receiving a potential change by the discharge detection sensor 23 during operation of the plasma processing apparatus, and the type of abnormal discharge that occurs in the processing chamber 3a accompanying the operation of the plasma processing apparatus. Will be described with reference to FIG. FIG. 4A shows a waveform pattern detected in the process from the start of operation of the plasma processing apparatus to the end of operation, and a predetermined time (first predetermined time Ta) set in advance for detecting these waveform patterns. , Second predetermined time Tb, third predetermined time Tc).

The time chart shown in FIG. 4B shows the setting timings of a plurality of waveform monitoring time zones to which these predetermined times are assigned in association with the start and end timings of the high frequency power supply application by the high frequency power supply unit 19. . Here, the waveform monitoring time zone is set in order to specify the time zone for monitoring and counting the detected waveform for each waveform type. In this embodiment, the first waveform described below is used. Three time zones, the monitoring time zone [A], the intermediate waveform monitoring time zone [B], and the last waveform monitoring time zone [C], are set in association with the predetermined time.

  First, the first predetermined time Ta and the third predetermined time Tc shown in FIG. 4A are the first waveform monitoring time period for detecting a waveform appearing at the start and end of the application of the high frequency power source [ A] and the predetermined time assigned to the last waveform monitoring time zone [C]. The first waveform monitoring time zone [A] includes the application start timing of the high frequency voltage by the high frequency power supply unit 19 (see timing t1 indicating RFon in the time chart of FIG. 4B), that is, the margin time tΔ1 from the timing t1. This is a period of time until a first predetermined time Ta set to a length at which these waveforms can be reliably detected, starting from a retroactive timing. The last waveform monitoring time zone [C] includes the application end timing of the high-frequency voltage by the high-frequency power supply unit 19 (see timing t2 indicating RFoff in the time chart of FIG. 4B), that is, a margin time from timing t2. Starting from the timing delayed by tΔ2, this is a time period retroactive by a third predetermined time Tc set to a length at which these waveforms can be reliably detected.

  In the first waveform monitoring time zone [A] and the last waveform monitoring time zone [C], a waveform pattern peculiar to the change in plasma discharge state due to the start and end of application of the high-frequency power source, that is, shown in FIG. In this manner, an N-type potential change waveform pattern (N1-type waveform WN1) that exhibits an N-shaped waveform pattern that returns to a steady value after the potential fluctuates on both positive and negative sides is detected. The detection of this waveform confirms that it meets a predetermined condition, that is, a condition that the detected potential change has reached either of the threshold levels ± Vth set in advance on both the positive and negative sides. Is done by.

  A time zone sandwiched between the first waveform monitoring time zone [A] and the last waveform monitoring time zone [C], that is, an intermediate waveform monitoring time zone [B] set including the second predetermined time tb, This is a time zone corresponding to normal operation. Here, the appearance of a potential change waveform caused by an abnormal phenomenon other than the potential change waveform accompanying the normal state change at the start and end of application of the high-frequency power source is monitored. That is, as shown in FIG. 4A, in the intermediate waveform monitoring time zone [B], waveforms appearing due to abnormal discharge and leak discharge are monitored.

  The abnormal discharge is an abnormal discharge that occurs between the substrate 9 placed on the electrode unit 5 and the electrode unit 5, and in a state in which the substrate 9 is warped and placed on the electrode unit 5. This occurs when there is a gap between the substrate 9 and the insulator 7. In this case, the potential change waveform indicating the change in potential of the probe electrode 22b with time is an N-shaped waveform pattern that returns to a steady value after the potential greatly fluctuates on both the positive and negative sides, as shown in FIG. Is an N-type potential change waveform pattern (N2-type waveform WN2). Similarly, the detection of the waveform is performed by confirming that the above-mentioned predetermined condition is met.

N-type potential change waveforms such as the N1-type waveform WN1 and the N2-type waveform WN2 are exclusively detected by the N-type waveform detector 34. That is, the N-type waveform detector 34 receives a potential change induced in response to a change in plasma discharge at the probe electrode 22b, and detects a potential change in a specific pattern caused by the abnormal discharge described above. The N-type potential change waveform that meets the above-mentioned predetermined condition is detected, and the detection signal is sent to a discharge ON waveform counter 36, a discharge OFF waveform counter 37, and an abnormal discharge waveform counter 38, which will be described below. Output.

  The N1-type waveform WN1 detected in the first waveform monitoring time zone [A] and the last waveform monitoring time zone [C] and the N2-type waveform WN2 caused by abnormal discharge are similarly changed in N-type potential. Although it belongs to the waveform pattern, there is a large difference in the fluctuation width because the cause of occurrence is different. In the first embodiment, N-type waveforms having different amplitudes are detected by the same N-type waveform detection unit 34 in this way.

  Next, leak discharge will be described. Leakage discharge is a fine discharge that occurs between a portion to which a high-frequency voltage is applied, such as the electrode portion 5 and the guide member 8, and a portion of the surrounding ground potential in the processing chamber 3a. Such a leak discharge is caused by a decrease in insulation due to foreign matter generated and deposited on the guide member 8 or the opening 1a that guides the conveyance of the substrate 9 by the plasma processing. In particular, on the side surface of the guide member 8 and the inner side surface of the opening 1a, the portion of the resin or metal that has been removed from the workpiece by the sputtering action of the plasma treatment is difficult to be removed by the direct plasma irradiation from above. Easy to deposit and deposit fine particles. As a result, the insulating property is lowered at these portions, and a leak discharge is generated between the base member 1 and the grounded member.

  In this case, since the disturbance that the leak discharge exerts on the plasma discharge state in the processing chamber 3a is small, the potential change waveform that shows the potential change of the probe electrode 22b with time is the V-shaped waveform WV shown in FIG. Thus, a V-shaped potential change waveform pattern that exhibits a V-shaped waveform pattern that returns to a steady value after the potential swings only to the negative side is obtained. The detection of the V-shaped waveform is performed by confirming that the detected potential change reaches the threshold level ± Vth set in advance on both the positive and negative sides only on the negative side.

  This V-type potential change waveform is exclusively detected by the V-type waveform detector 35. That is, the V-shaped waveform detector 35 similarly receives a potential change induced in response to a change in plasma discharge to the probe electrode 22b, and detects a potential change waveform of a specific pattern caused by the above-described leak discharge. A second waveform detection unit that detects the above-described V-type potential change waveform that meets a predetermined condition, and outputs a detection signal to the leak discharge waveform counter 39.

  That is, if the N-type waveform detection unit 34 and the V-type waveform detection unit 35 detect waveforms of specific patterns to be detected, the N-type waveform detection unit 34 and the V-type waveform detection unit 35 will be described below. A detection signal indicating that a specific pattern waveform has been detected is output to the counter discharge ON waveform counter 36, the discharge OFF waveform counter 37, the abnormal discharge waveform counter 38, and the leak discharge waveform counter 39. The discharge ON waveform counter 36, the discharge OFF waveform counter 37, the abnormal discharge waveform counter 38, and the leak discharge waveform counter 39 correspond to each of a plurality of waveform detection units (N-type waveform detection unit 34, V-type waveform detection unit 35). The detection signals output from the corresponding waveform detectors are counted to form a plurality of counters that hold the count values.

  First, the discharge ON waveform counter 36, the discharge OFF waveform counter 37, and the abnormal discharge waveform counter 38 that count the detection signals from the N-type waveform detection unit 34 will be described. The discharge ON waveform counter 36, the discharge OFF waveform counter 37, and the abnormal discharge waveform counter 38 are a plurality of counters (first counters) that count the detection signals output from the N-type waveform detector 34 and hold the count values. The plurality of counters record the number of times the N-type waveform detector 34 detects the N-type waveform.

As described above, the waveform monitoring time zone in which the detection signal from the N-type waveform detection unit 34 is to be counted by the above-described plural (here, three) counters is determined in advance for each counter, and each waveform monitoring time is determined. It has a form having three counters corresponding to the band. As shown in FIG. 4B, these waveform monitoring time zones are associated with the application start timing of the high frequency voltage to the electrode unit 5 in the plasma processing apparatus, that is, the driving on / off timing of the high frequency power supply unit 19. It is set in advance.

  That is, the discharge ON waveform counter 36 counts the detection signal of the N1-type waveform WN1 shown in FIG. 4A in the first waveform monitoring time zone [A] set including the application start timing of the high-frequency voltage. Holds the count value. The discharge OFF waveform counter 37 counts and counts the detection signal of the N1-type waveform WN1 shown in FIG. 4A in the last waveform monitoring time zone [C] set including the application end timing of the high-frequency voltage. Holds the value. Further, the abnormal discharge waveform counter 38 has an intermediate time set including a time zone (second predetermined time Tb) sandwiched between the first waveform monitoring time zone [A] and the last waveform monitoring time zone [C]. In the waveform monitoring time zone [B], the detection signal of the N2-type waveform WN2 shown in FIG. 4A is counted and the count value is held. The leak discharge waveform counter 39 is a count unit that performs processing for counting the number of detections of the potential change waveform by the V-type waveform detection unit 35 that is the second waveform detection unit and holding the count value. This is a second counter that stores the number of times the unit 35 has detected the V-shaped waveform WV.

  The control unit 25 includes a counter control unit 41, a waveform data storage unit 42, a discharge state determination unit 43, and a maintenance determination unit 44. The counter control unit 41 includes a plurality of counters (a discharge ON waveform counter 36, a discharge OFF waveform counter 37, and an abnormal discharge waveform counter 38) so as to count detection signals only at timings corresponding to a preset waveform monitoring time zone. To control. That is, the counter control unit 41 is connected to the discharge ON waveform counter 36, the abnormal discharge waveform counter 38, and the discharge OFF waveform counter 37 through the connection port 40 by three counter control channels A, B, and C.

  When the counter control unit 41 controls these counters, as shown in FIG. 4B, each counter uses only the waveform detection time zone assigned to the counter as the detection timing, and the N-type waveform detection unit 34. The detection signals from the V-shaped waveform detector 35 are counted. As a result, it is possible to count only the waveforms that appear at a significant timing in the determination among the many waveform data detected by the N-type waveform detection unit 34 and the V-type waveform detection unit 35. The counter control channels A, B, and C correspond to the first waveform monitoring time zone [A], the intermediate waveform monitoring time zone [B], and the last waveform monitoring time zone [C], respectively.

  The waveform data storage unit 42 determines whether or not the waveform data, that is, the waveform indicating the potential change of the probe electrode 22b matches a predetermined condition to be detected by the N-type waveform detection unit 34 and the V-type waveform detection unit 35. The data for determining is stored. In this waveform data, a threshold value (see threshold value Δvth shown in FIG. 4A) set for determining a potential fluctuation width in a waveform indicating a potential change or until one fluctuation converges. Items that characterize the waveform pattern, such as the shake time required for, can be selected.

The discharge state determination unit 43 determines the state of plasma discharge in the processing chamber 3a based on the count values held by a plurality of counters, that is, the discharge ON waveform counter 36, the discharge OFF counter 37, and the abnormal discharge waveform counter 38. Perform the process. That is, the discharge state determination unit 43 confirms these counter values and compares each count value with a preset allowable value to determine the plasma discharge state. The maintenance determination unit 44 determines whether maintenance is necessary based on the count value held by the leak discharge waveform counter 39, that is, by checking the counter value and comparing it with a preset allowable value. Accordingly, the discharge state determination unit 43 and the maintenance determination unit 44 include a discharge ON waveform counter 36, a discharge OFF waveform counter 37, an abnormal discharge waveform counter 38, and a leak discharge waveform counter 39.
Is configured to determine whether or not maintenance in the vacuum chamber 3 is necessary in addition to the operating state of the plasma processing apparatus, that is, the plasma discharge state described above.

  Further, in the above configuration, the discharge detection sensor 23, the plasma monitoring device 20 and the control unit 25 constitute plasma discharge state monitoring means (plasma discharge state monitoring device) for monitoring the plasma discharge state in the processing chamber 3a. Then, the plasma monitoring device 20 receives the potential change induced in response to the change of the plasma discharge in the probe electrode 22b, and the first waveform monitoring time zone [A] set including the application start timing of the high frequency voltage, The last waveform monitoring time zone [C] set including the application end timing of the high frequency voltage and the time zone sandwiched between the first waveform monitoring time zone [A] and the last waveform monitoring time zone [C] are included. A process of detecting a potential change waveform of a specific pattern in each of the intermediate waveform monitoring time zones [B] set in step B, counting the number of potential change waveform detections for each waveform monitoring time zone, and holding the count value. A data processing unit is configured. The control unit 25 is a determination unit that performs discharge state determination including the presence / absence of plasma discharge and normal / abnormal plasma discharge state based on the count value for each waveform monitoring time period.

  This plasma processing apparatus is configured as described above. Next, a discharge state determination process executed during operation of the plasma processing apparatus will be described along the flow of FIG. Note that K1, K2, and K3 shown in the flow of FIG. 5 mean the count values held by the discharge ON waveform counter 36, the abnormal discharge waveform counter 38, and the discharge OFF waveform counter 37, respectively.

  When the determination process is started, first, the count value K1 of the discharge ON waveform counter 36 is confirmed (ST1), and it is determined whether or not the count value K1 is smaller than a predetermined allowable value 1 (ST2). Here, when the count value K1 is larger than the predetermined allowable value 1, it is determined that an abnormal discharge that should not be detected is occurring, and the display unit 27 notifies the abnormal discharge state to notify the apparatus. Stop (ST14). If the count value K1 is smaller than the predetermined allowable value 1 in (ST2), the process proceeds to the next step, and the elapse of the first predetermined time Ta in the first waveform monitoring time zone [A] is determined ( ST3) If the time has not elapsed, the process returns to (ST1), and the processes of (ST1) and (ST2) are sequentially repeated.

  If the elapse of the first predetermined time Ta is confirmed in (ST3), it is determined whether or not the count value K1 is 0 (zero) (ST4). Here, when the count value K1 is 0 (zero), it is determined that there is no reliable evidence that plasma discharge is normally generated in the processing chamber 3a, and the display unit 27 causes no discharge. To stop the apparatus (ST13). Next, if it is confirmed in (ST4) that the count value K1 is not 0 (zero), it is determined that plasma discharge is occurring in the processing chamber 3a, and the process proceeds to the next step. That is, the count value K2 of the abnormal discharge waveform counter 38 is confirmed (ST5), and it is determined whether the count value K2 is smaller than a predetermined allowable value 2 (ST6). Here, when the count value K2 is larger than the predetermined allowable value 2, it is determined that the abnormal discharge has occurred in the processing chamber 3a exceeding the allowable frequency, and the abnormal discharge state is notified by the display unit 27. Then, the apparatus is stopped (ST14).

  On the other hand, if the count value K2 is smaller than the predetermined allowable value 2, the process proceeds to the next step to determine the elapse of the second predetermined time Tb in the intermediate waveform monitoring time zone [B] (ST7). If it has elapsed, the process returns to (ST5), and the processes of (ST5) and (ST6) are sequentially repeated. If the passage of the second predetermined time Tb is confirmed in (ST6), the process proceeds to the next step. That is, the count value K3 of the discharge OFF waveform counter 37 is confirmed (ST8), and it is determined whether the count value K3 is smaller than a predetermined allowable value 3 (ST9).

  Here, when the count value K3 is larger than the predetermined allowable value 3, it is determined that an abnormal discharge that should not be detected is occurring, and the display unit 27 notifies the abnormal discharge state. The apparatus is stopped (ST14). If the count value K3 is smaller than the predetermined allowable value 3 in (ST9), the process proceeds to the next step to determine the elapse of the third predetermined time tc in the last waveform monitoring time zone [C] ( If the time has not elapsed (ST10), the process returns to (ST8), and the processes of (ST8) and (ST9) are sequentially repeated.

  If the elapse of the third predetermined time Tc is confirmed in (ST10), it is determined whether or not the count value K3 is 0 (zero) (ST11). Here, when the count value K1 is 0 (zero), it is determined that there is no reliable evidence that plasma discharge is normally generated in the processing chamber 3a, and the display unit 27 causes no discharge. To stop the apparatus (ST13). If it is confirmed in (ST11) that the count value K3 is not 0 (zero), the plasma discharge has been performed normally (ST12), thereby ending the discharge state determination process.

  The discharge state determination processing flow is a plasma processing apparatus in which a substrate 9 as a processing object is accommodated in the processing chamber 3a to perform plasma processing, and plasma discharge in the plasma processing apparatus that monitors the plasma discharge state in the processing chamber 3a. Configure state monitoring methods. The method for monitoring the plasma discharge state in the plasma processing apparatus includes a step of receiving a potential change induced in the probe electrode 22b according to a change in plasma discharge in the processing chamber 3a by the plasma monitoring apparatus 20 as a data processing unit. Detecting a potential change waveform of a specific pattern by the N-type waveform detector 34 in each of the first waveform monitoring time zone [A], the last waveform monitoring time zone [C], and the intermediate waveform monitoring time zone [B]. For each waveform monitoring time zone [A], [B], [C], the number of potential change waveform detections is counted by the discharge ON waveform counter 36, abnormal discharge waveform counter 38, and discharge OFF waveform counter 37, The process of performing the process of holding the count values K1, K2, and K3, and the count values K1, K2, for each waveform monitoring time zone [A], [B], [C] 3 on the basis, and has a form and a step of performing plasma discharge state determination including determination of normal or abnormal presence and plasma discharge state of the plasma discharge.

  Next, with reference to FIG. 6, the maintenance determination process performed subsequent to the above-described discharge state determination process will be described. 6 represents the count value held by the leak discharge waveform counter 39. This maintenance judgment process is a maintenance judgment for the purpose of preventing problems caused by the deposition and deposition of foreign substances generated by the plasma treatment in the vacuum chamber 3 in the process of continuing the operation of the plasma processing apparatus. It is executed by the unit 44 and additionally executed after (ST10) in the flow shown in FIG.

  That is, (ST20) shown in FIG. 6 is the same processing as (ST10) described in the description of the flow of FIG. 5, and the third predetermined time in the last waveform monitoring time period [C] in (ST20). If the elapse of tc is confirmed, the count value K4 of the leak discharge waveform counter 39 is confirmed (ST21), and it is determined whether or not the count value K4 is smaller than a predetermined allowable value 4 (ST22). Here, when the count value K4 is smaller than the predetermined allowable value 4, the frequency of occurrence of leakage discharge due to the adhesion of foreign matters in the processing chamber 3a is below the allowable limit, and maintenance for the purpose of removing foreign matters is performed. It is determined that it is not necessary, and the determination process ends. On the other hand, when the count value K4 is larger than the predetermined allowable value 4 in (ST22), the occurrence frequency of the leak discharge exceeds the allowable limit, and there is a possibility that foreign matter adheres and accumulates. It is determined that the value is high, and the display unit 27 notifies that maintenance is necessary (ST23).

As described above, the plasma processing apparatus shown in Embodiment 1 receives a change in potential induced in response to a change in plasma discharge at the probe electrode of the discharge detection sensor mounted in the vacuum chamber, and is caused by a leak discharge. And a V-shaped waveform detecting unit 35 as a second waveform detecting unit for detecting a potential change waveform of a specific pattern generated by the leakage discharge waveform counter 39. Based on the counted value, the necessity of maintenance is determined. That is, a leak discharge having a causal relationship with a high degree of correlation with the adhesion of foreign matter is detected with high sensitivity, and the degree of foreign matter adhesion and accumulation is estimated based on the cumulative frequency of the leak discharge. This is necessary to keep the equipment operating state optimal compared to the conventional technology that uses the method of estimating the maintenance time by measuring the time required to reach the required vacuum level when the equipment is operating. It is possible to accurately determine whether or not the maintenance time to be reached has been reached.

(Embodiment 2)
FIG. 7 is a block diagram showing the configuration of the plasma discharge state monitoring apparatus in the plasma processing apparatus according to the second embodiment of the present invention, and FIG. 8 is a potential change waveform and waveform monitoring in the plasma discharge state monitoring method according to the second embodiment of the present invention. FIG. 9 is a process flow diagram of the discharge state determination process in the plasma discharge state monitoring method according to the second embodiment of the present invention.

  In the second embodiment, the function of the N-type waveform detection unit 34 in the first embodiment is divided according to the waveform pattern to be detected, and two N-type waveform detection units, that is, N1 type waveform detection units 34A and N2 are divided. The mold waveform detector 34B is used. The N1-type waveform detector 34A exclusively detects a waveform pattern of a potential change caused by a normal state change at the start and end of application of a high-frequency power supply, and the N2-type waveform detector 34B detects a waveform pattern of a potential change caused by abnormal discharge. Detect exclusively.

  That is, in the plasma monitoring apparatus 20 shown in FIG. 7, the detection signal from the N1 type waveform detection unit 34A is counted by the discharge ON waveform counter 36 and the discharge OFF waveform counter 37, and the detection signal from the N2 type waveform detection unit 34B is abnormal. Counting is performed by the discharge waveform counter 38. These points differ from the setting of the waveform monitoring time zone when the counter control unit 41 controls the abnormal discharge waveform counter 38, that is, an intermediate waveform monitoring time described later instead of the intermediate waveform monitoring time zone [B]. The plasma monitoring apparatus 20 shown in FIG. 7 is the same as the plasma monitoring apparatus 20 shown in FIG. 5 except that the band [D] is set.

  The functions of the N1-type waveform detection unit 34A and the N2-type waveform detection unit 34B will be described with reference to FIG. FIG. 8A shows the waveform patterns detected in the process from the start of operation of the plasma processing apparatus to the end of operation, and the predetermined time set for detecting these waveform patterns. The time chart shown in FIG. 8B shows the setting timings of a plurality of waveform monitoring time zones to which these predetermined times are assigned in association with the start and end timings of high frequency power supply application by the high frequency power supply unit 19. is there.

  FIG. 8A shows a waveform pattern detected in the process from the start of operation of the plasma processing apparatus to the end of operation, as in FIG. Here, the first predetermined time Ta, the third predetermined time Tc, the first waveform monitoring time zone [A] and the last waveform monitoring time zone [C] are the same as the example shown in FIG. Is omitted.

In the first waveform monitoring time zone [A] and the last waveform monitoring time zone [C], similarly to FIG. 4A, the potential change waveform accompanying the normal state change at the start and end of the application of the high frequency power supply is shown. An N-shaped waveform pattern (N1-type waveform WN1) is detected. At this time, the threshold level set for waveform pattern detection is a level corresponding to the amplitude of the N1-type waveform WN1, that is, the first threshold level equivalent to the threshold level Vth in FIG. ± Vth1 is set. The waveforms associated with the start and end of application of the high frequency power source detected by the N1-type waveform detector 34A in the first waveform monitoring time zone [A] and the last waveform monitoring time zone [C] are the discharge ON waveform counter 36, Each of them is counted by the discharge OFF waveform counter 37.

  Unlike the intermediate waveform monitoring time zone [B] in the first embodiment, the intermediate waveform monitoring time zone [D] includes all of the first predetermined time Ta, the second predetermined time Tb, and the third predetermined time Tc. The time setting is included. That is, here, the intermediate waveform monitoring time zone [D] is a time zone (second predetermined time Tb) sandwiched between the first waveform monitoring time zone [A] and the last waveform monitoring time zone [C]. And further includes a first predetermined time Ta and a third predetermined time Tc. By setting the intermediate waveform monitoring time zone [D] for monitoring the waveform caused by the abnormal discharge to such a setting, the abnormal discharge can be detected in all the operation times from the start to the stop of the plasma processing apparatus. The occurrence can be monitored, and the monitoring accuracy of abnormal discharge can be further improved.

  In the intermediate waveform monitoring time zone [D], as in the example shown in FIG. 4A, the N2-type waveform WN2 due to abnormal discharge in the processing chamber 3a is detected by the N2-type waveform detection unit 34B and leaked. The V-shaped waveform WV that appears due to the discharge is detected by the V-shaped waveform detector 35. At this time, the threshold level set for waveform pattern detection is a level corresponding to the amplitude of the N2-type waveform WN2, that is, the second threshold level higher than the threshold level Vth in FIG. ± Vth2 is set. The N2-type waveform WN2 associated with the abnormal discharge detected in the intermediate waveform monitoring time zone [D] and the V-type waveform WV appearing due to the leak discharge are respectively detected by the abnormal discharge waveform counter 38 and the leak discharge waveform counter 39. Be counted.

  As described above, in the second embodiment, the waveform detection unit that detects the N-type waveform has a plurality of waveform detection units (N1-type waveform detection unit 34A, N2-type waveform detection unit) that detect waveforms having different amplitude fluctuations. 34B). With this configuration, a plurality of types of waveform patterns having the same N-type potential change waveform pattern and different potential change amplitudes are detected by using a plurality of waveform detection units using different threshold levels. A plurality of types of waveform patterns having different appearance causes can be detected while being correctly identified, and the discharge state can be monitored more precisely.

  FIG. 9 shows a discharge state determination process executed during operation of the plasma processing apparatus in the second embodiment. 9, K1, K2, and K3 mean the count values held by the discharge ON waveform counter 36, abnormal discharge waveform counter 38, and discharge OFF waveform counter 37, respectively, as in FIG. is doing. When the determination process is started, first, the count value K2 of the abnormal discharge waveform counter 38 for counting the intermediate waveform monitoring time period [D] including the entire range of the operation time of the plasma processing apparatus is confirmed (ST31). Then, it is determined whether or not the count value K2 is smaller than a predetermined allowable value 2 (ST32).

  Here, when the count value K2 is larger than the predetermined allowable value 2, it is determined that an abnormal discharge that should not be detected is occurring, and the display unit 27 notifies the abnormal discharge state. The apparatus is stopped (ST46). If the count value K2 is smaller than the predetermined allowable value 2 in (ST32), the process proceeds to the next step to determine the elapse of the first predetermined time Ta in the first waveform monitoring time zone [A] ( If the time has not elapsed (ST33), the process returns to (ST31), and the processes of (ST31) and (ST32) are sequentially repeated.

  If the elapse of the first predetermined time Ta is confirmed in (ST33), the count value K1 of the discharge OFF waveform counter 37 is confirmed (ST34), and whether or not the count value K1 is 0 (zero). Judgment is made (ST35). Here, when the count value K1 is 0 (zero), it is determined that there is no reliable evidence that plasma discharge is normally generated in the processing chamber 3a, and the display unit 27 causes no discharge. To stop the apparatus (ST44).

  Next, if it is confirmed in (ST35) that the count value K1 is not 0 (zero), it is determined that plasma discharge is occurring in the processing chamber 3a, and the process proceeds to the next step. That is, the count value K2 of the abnormal discharge waveform counter 38 is confirmed (ST36), and it is determined whether the count value K2 is smaller than a predetermined allowable value 2 (ST37). Here, when the count value K2 is larger than the predetermined allowable value 2, it is determined that an abnormal discharge that should not be generated is generated in the processing chamber 3a, and the abnormal discharge state is notified by the display unit 27. Then, the apparatus is stopped (ST46).

  If the count value K2 is smaller than the predetermined allowable value 2, the process proceeds to the next step. That is, the elapse of the second predetermined time Tb is determined (ST38). If the time has not elapsed, the process returns to (ST37), and the processes of (ST37) and (ST38) are sequentially repeated. If the passage of the second predetermined time Tb is confirmed in (ST38), the process proceeds to the next step. That is, the count value K2 of the abnormal discharge waveform counter 38 is checked again (ST39), and it is determined whether or not the count value K2 is smaller than a predetermined allowable value 2 (ST40).

  Here, when the count value K2 is larger than the predetermined allowable value 2, it is determined that the abnormal discharge that should not be detected has occurred exceeding the allowable frequency, and the display unit 27 detects the abnormal discharge. The state is notified and the apparatus is stopped (ST46). When the count value K2 is smaller than the predetermined allowable value 2 in (ST40), the process proceeds to the next step, and the elapse of the third predetermined time tc in the last waveform monitoring time zone [C] is determined. If the time has not elapsed (ST41), the process returns to (ST40), and the processes of (ST40) and (ST41) are sequentially repeated.

  If the passage of the third predetermined time Tc is confirmed in (ST41), the count value K3 of the discharge OFF waveform counter 37 is confirmed (ST42), and whether or not the count value K3 is 0 (zero). Is determined (ST43). Here, when the count value K3 is 0 (zero), it is determined that there is no reliable proof that the plasma discharge is normally generated in the processing chamber 3a, and the display unit 27 causes no discharge. To stop the apparatus (ST44). If it is confirmed in (ST43) that the count value K3 is not 0 (zero), the plasma discharge has been performed normally, and the discharge state determination process is thereby terminated.

  The discharge state determination processing flow is a plasma processing apparatus in which a substrate 9 as a processing object is accommodated in the processing chamber 3a to perform plasma processing, and plasma discharge in the plasma processing apparatus that monitors the plasma discharge state in the processing chamber 3a. Configure state monitoring methods. The method for monitoring the plasma discharge state in the plasma processing apparatus includes a step of receiving a potential change induced in the probe electrode 22b according to a change in plasma discharge in the processing chamber 3a by the plasma monitoring apparatus 20 as a data processing unit. Detecting a potential change waveform of a specific pattern by the N-type waveform detector 34 in each of the first waveform monitoring time zone [A], the last waveform monitoring time zone [C], and the intermediate waveform monitoring time zone [D]. For each waveform monitoring time zone [A], [D], [C], the number of potential change waveform detections is counted by the discharge ON waveform counter 36, abnormal discharge waveform counter 38, and discharge OFF waveform counter 37, The step of performing processing for holding the count values K1, K2, and K3, and the count values K1, K2, and the like for each waveform monitoring time zone [A], [D], and [C]. 3 on the basis, and has a form and a step of performing plasma discharge state determination including determination of normal or abnormal presence and plasma discharge state of the plasma discharge.

As described above, in the plasma processing apparatus shown in the first or second embodiment, one surface is used as the plasma discharge state monitoring means for monitoring and determining the plasma discharge state in the processing chamber 3a. A discharge detection sensor 23 having a plate-like dielectric member 21 mounted on the vacuum chamber 3 so as to face the plasma discharge generated in the step and a probe electrode 22b disposed on the other surface of the dielectric member 21, and a probe The electrode 22b receives a potential change induced according to a change in plasma discharge, detects a potential change waveform of a specific pattern in a plurality of waveform monitoring time zones, and counts the number of occurrences of these potential change waveforms for each waveform type. The plasma monitoring device 20 is provided as a data processing unit for performing the processing.

  With this configuration, it is possible to perform the discharge state determination including the presence / absence of discharge and normal / abnormal discharge state based on the count value for each waveform type. In this discharge state determination, since the change in plasma discharge in the processing chamber 3a can be detected with extremely high sensitivity by the discharge detection sensor 23, the change in the plasma discharge in the conventional method, that is, the voltage or current in the high frequency power supply unit is detected. More accurate monitoring of plasma discharge status compared to the conventional configuration that uses a method for detecting the effect of the effect and a method for estimating the discharge status by detecting the self-bias voltage generated between electrodes due to plasma discharge It is possible to do in. Therefore, even when it is necessary to generate a plasma discharge under low output conditions, it is possible to detect a change in the plasma discharge state with high accuracy, thereby correctly monitoring the presence / absence or abnormality of the plasma discharge. .

  The plasma discharge state monitoring device of the present invention has an effect of being able to correctly monitor the presence / absence of plasma discharge and discharge abnormality, and is useful in the field of performing plasma processing such as plasma cleaning using a substrate as a processing target. .

Sectional drawing of the plasma processing apparatus of Embodiment 1 of this invention Structure explanatory drawing of the discharge detection sensor used for the plasma processing apparatus of Embodiment 1 of this invention The block diagram which shows the structure of the plasma discharge state monitoring apparatus in the plasma processing apparatus of Embodiment 1 of this invention. Explanatory drawing of the electric potential change waveform and waveform monitoring time slot | zone in the plasma discharge state monitoring method of Embodiment 1 of this invention Process flow diagram of discharge state determination process in plasma discharge state monitoring method of embodiment 1 of the present invention Processing flow diagram of maintenance determination processing in the plasma discharge state monitoring method of Embodiment 1 of the present invention The block diagram which shows the structure of the plasma discharge state monitoring apparatus in the plasma processing apparatus of Embodiment 2 of this invention. Explanatory drawing of the electric potential change waveform and waveform monitoring time slot | zone in the plasma discharge state monitoring method of Embodiment 2 of this invention Process flow diagram of discharge state determination process in plasma discharge state monitoring method of embodiment 2 of the present invention

Explanation of symbols

2 Lid 2a Opening (view window)
DESCRIPTION OF SYMBOLS 3 Vacuum chamber 3a Processing chamber 5 Electrode part 8 Guide member 9 Substrate 15 Vacuum gauge 16 Gas supply part 17 Vacuum pump 18 Matching device 19 High frequency power supply part 21 Dielectric member 22 Probe electrode unit 22b Probe electrode 23 Discharge detection sensor P Plasma WN1 N1 Type waveform WN2 N2 type waveform WV V type waveform [A] First waveform monitoring time zone [B], [D] Intermediate waveform monitoring time zone [C] Last waveform monitoring time zone

Claims (2)

A plasma discharge state monitoring device that is used in a plasma processing apparatus that performs plasma processing by storing a processing object in a processing chamber, and monitors a plasma discharge state in the processing chamber,
A plate-like dielectric member mounted on a vacuum chamber forming the processing chamber so that one surface faces the plasma discharge generated in the processing chamber, and a probe electrode disposed on the other surface of the dielectric member A discharge detection sensor having at least
A waveform detector for detecting a predetermined waveform by receiving a potential change induced in response to a change in the plasma discharge in the probe electrode;
The waveform detector includes an N-type waveform detecting unit that detects an N-type potential change waveform having an N-shaped waveform pattern that returns to a steady value after the potential swings on both the positive and negative sides, and the potential swings only on the negative side. A V-shaped waveform detecting unit that detects a V-shaped potential change waveform having a V-shaped waveform pattern that later returns to a steady value ;
The N-type waveform detection unit confirms that the detected potential change meets the condition that the threshold level set in advance on both the positive and negative sides has been met. The V-shaped waveform detection unit confirms that the detected potential change reaches the threshold level set in advance on both the positive and negative sides only on the negative side, and monitors the plasma discharge state apparatus.   A first counter that records the number of times that the N-type waveform detection unit has detected the N-type waveform; and a second counter that stores the number of times that the V-type waveform detection unit has detected the V-type waveform. The plasma discharge state monitoring device according to claim 1, wherein:

Images