JP2008287999A - Plasma treatment device and its control method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a plasma treatment device and its control method, capable of stabilizing plasma treatment characteristics and easily carrying out troubleshooting, in one of bias voltage control system. <P>SOLUTION: A bias voltage measurement part 17 obtains a direct-current component of bias high-frequency power between a lower electrode 13 loading a workpiece 16 and a matching unit 15. A bias power source control part 18 controls output power of the bias high-frequency power source 14 in a state in which the direct-current component is at a given value. Further, a power value grasping part 31 grasps a power value of the bias high-frequency power. A waveform generating part to be provided by the calculating part 32 generates waveforms on time of the power value grasped. A decision part 33 compares an average value of power values grasped during a given period of the plasma treatment and a preset reference value, and at the same time, compares the waveforms generated and the preset reference waveform to decide existence of impedance changes caused by failures of the device. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a plasma processing apparatus that excites plasma in a reaction chamber by applying high-frequency power and performs plasma processing on an object to be processed accommodated in the reaction chamber, and a control method thereof.

  Conventionally, in a manufacturing process of a semiconductor device, a plasma processing apparatus is frequently used for a film forming process for various material films, a dry etching process for forming wirings, contact holes, and the like. For example, in a dry etching apparatus used in a dry etching process, a reactive process gas is introduced into a reaction chamber in a reduced pressure environment, and plasma of the process gas is excited in the reaction chamber using high-frequency power, a magnetic field, or the like. The object to be etched on the object is removed by being exposed to plasma in the reaction chamber.

  Further, with the recent miniaturization of semiconductor devices, it is required to ensure the processing uniformity of plasma processing. For this reason, it is very important to keep the plasma state in the reaction chamber constant.

  FIG. 8 is a schematic configuration diagram showing a high-density plasma dry etching apparatus represented by an ICP (Inductively Coupled Plasma) system. As shown in FIG. 8, the dry etching apparatus includes a lower electrode 13 that also serves as a mounting table for an object to be processed 16 such as a semiconductor substrate, in an airtight reaction chamber 1. At a position facing the lower electrode 13, a shower head 9 having a large number of gas ejection holes for ejecting gas is disposed toward the object 16. A reactive process gas whose flow rate is controlled by a mass flow controller 8 (MFC 8) is supplied to the shower head 9 through a gas introduction pipe 6. The gas supply pipe 6 on the downstream side of the MFC 8 is provided with an opening / closing valve 7 for switching connection / disconnection between the MFC 8 and the reaction chamber 1. A gas exhaust pipe 2 is connected to the bottom of the reaction chamber 1, and the reaction chamber 1 is evacuated by an exhaust means 4 such as a pump connected to the other end of the gas exhaust pipe 2. The gas exhaust pipe 2 is provided with an exhaust amount adjusting means 3 such as a butterfly valve. For example, the exhaust amount is adjusted so that the pressure in the reaction chamber 1 measured by the pressure measuring device 5 becomes a predetermined pressure. The

  On the other hand, an antenna coil 10 is disposed outside the reaction chamber 1 above the shower head 9 to excite plasma of the process gas in the reaction chamber 1 by inductive coupling. The antenna coil 10 is connected to a source high frequency power source 11 that applies high frequency power via a matching unit 12. The lower electrode 13 is connected to a bias high frequency power source 14 for applying high frequency power via a matching unit 15.

  In the dry etching apparatus having the above configuration, when the object to be processed 16 is placed on the lower electrode 13 via a transport mechanism (not shown), the exhaust unit 4 starts depressurization in the reaction chamber 1. Next, the opening / closing valve 7 is opened, and a process gas whose flow rate is controlled by the MFC 8 is introduced into the reaction chamber 1. The process gas introduced into the reaction chamber 1 diffuses into the reaction chamber 1 through the shower head 9. At this time, the exhaust amount is adjusted by the exhaust amount adjusting means 3, and the inside of the reaction chamber 1 is maintained at a predetermined pressure.

  In this state, when the source high frequency power supply 11 applies high frequency power to the antenna coil 10, process gas plasma is generated in the reaction chamber 1. At this time, the bias high frequency power supply 14 applies high frequency power to the lower electrode 13. As a result, a bias is generated in the lower electrode 13. Due to the bias, ions are incident on the object to be processed 16 from the plasma, and the etching target film on the object to be processed 16 is etched.

  In the dry etching apparatus as shown in FIG. 8, it is necessary to generate plasma stably with high reproducibility in order to reduce the process variation for each plasma process on the workpiece 16. Conventionally, a high-frequency power control method for changing the high-frequency power applied to the antenna coil 10 and the lower electrode 13 has been widely used for controlling the plasma state. However, with the progress of miniaturization of semiconductor devices, the process margin is reduced, and it is difficult to sufficiently reduce processing variations in the high frequency power control method.

  As one of the solutions, for example, the plasma state is controlled by feedback control that fluctuates the high-frequency power applied to the lower electrode 13 so that the bias voltage (the DC voltage component of the bias high-frequency power) of the lower electrode 13 is maintained at a predetermined value. A bias voltage control system is used to control (see, for example, Patent Document 1). The bias voltage is measured by a bias voltage measuring unit 17 connected between the lower electrode 13 and the matching unit 15.

  In the bias voltage control method, since the bias voltage is maintained at a predetermined value, the amount of sputtering due to ions incident on the object 16 from the plasma is stabilized. Therefore, the amount of sputtering of a mask such as a resist pattern formed on the film to be etched and the amount of reaction products deposited on the etched portion side wall of the film to be etched that are not covered with the mask are stabilized. As a result, it is possible to stabilize the processing characteristics (selection ratio, dimensions, etc.) for each plasma processing of the film to be etched, and to ensure reproducibility.

  On the other hand, when the etching of the film to be etched on the object to be processed 16 proceeds mainly due to a chemical reaction between the radical generated in the plasma and the film to be etched, the plasma is in order to stabilize the processing characteristics. It is necessary to stabilize the amount of radicals. The ion current density of plasma can be used as an index of the amount of radicals in plasma. In the high frequency power control method, the traveling wave power W of the high frequency power, the ion current density I, and the bias voltage Vpp satisfy the relationship of Equation 1.

  W = I × Vpp (1)

  According to Equation 1, the ionic current density I can be calculated by measuring the traveling wave power W and the bias voltage Vpp. Therefore, it is possible to control the ion current density I to a predetermined value.

  On the other hand, in the bias voltage control method, the bias high frequency power supply 14 is controlled so that the bias voltage Vpp becomes a predetermined value. The bias voltage Vpp is expressed by the following formula 2 by the plasma impedance Z and the ion current density I.

  Vpp = I × Z (2)

In the bias voltage control method, the bias voltage Vpp is a predetermined value in Equation 2, but the ion current density I and the plasma impedance Z are unknown variables. Therefore, the amount of radicals when the bias voltage is Vpp cannot be grasped. For example, when an aluminum-copper (Al-Cu) film is etched to form a metal wiring, a gas such as chlorine gas (Cl ₂ , BCl ₃ ) is introduced into the reaction chamber 1 as a process gas. The In this case, as the ion current density I increases, the side etching amount on the side surface of the Al pattern increases. As a result, the Al pattern becomes narrower than the desired line width (opening width of the resist mask), and wiring resistance abnormality occurs. In the bias voltage control method, since an increase in the amount of chlorine radicals in the plasma cannot be detected by the ion current density I, such an abnormality cannot be detected.

  By the way, according to Equation 2, if the plasma impedance Z is known, the ion current density I can be calculated. Therefore, the above problem can be solved by monitoring the plasma impedance Z during the plasma processing (see, for example, Patent Document 2). When monitoring the plasma impedance, for example, using a voltage / current probe (VI probe), the bias voltage, the current of the high frequency power and the phase angle are measured between the lower electrode 13 and the matching unit 15, and the impedance is calculated by calculation. Z is calculated.

  The plasma impedance Z is composed of a combined resistance of the actual resistance component R and the reactance component X as shown in Equation 3 below.

  Z = R + jX (3)

In this method, since the phase angle of the traveling wave power is 90 ° in the reaction chamber 1 maintained in a vacuum, the actual resistance component R (ground resistance of the reaction chamber) of the dry etching apparatus is regarded as 0. . That is, it is assumed that the reactance component X is a main component of the plasma impedance Z, and the plasma impedance Z is monitored only by the reactance component X.
Special table 2003-510833 gazette JP-T-2006-501611

  However, in an actual dry etching apparatus, the actual resistance component R constituting the impedance Z is not 0Ω (ohms). Further, for example, the actual resistance component R changes depending on the state of attachment of the built-in parts in the reaction chamber 1 due to maintenance or the like. That is, the impedance monitoring method described above cannot obtain an accurate impedance Z. Therefore, even if the ion current density I is stabilized using the obtained plasma impedance Z (reactance component X), the plasma processing characteristics cannot be systematically stabilized.

  In addition, Patent Document 2 discloses that the presence or absence of an apparatus abnormality is determined based on the obtained reactance component X. However, a specific failure part cannot be specified, and it takes time for failure diagnosis. There are also problems.

  In view of the above-described conventional problems, the present invention provides a plasma processing apparatus capable of stabilizing plasma processing characteristics and easily performing failure diagnosis even in a bias voltage control type plasma processing apparatus. It aims at providing the control method.

  In order to solve the above problems, the present invention employs the following technical means. First, a plasma processing apparatus according to the present invention is premised on a plasma processing apparatus that excites plasma in a reaction chamber by applying high-frequency power and performs plasma processing on an object to be processed accommodated in the reaction chamber. And the plasma processing apparatus which concerns on this invention is provided with the sample stand in which a to-be-processed object is mounted in reaction chamber. A bias high-frequency power source for applying a bias high-frequency power is connected to the sample stage via a matching unit. In addition, the bias voltage measurement unit acquires a DC component of the bias high frequency power between the sample stage and the matching unit. The bias high frequency power supply is controlled by the bias power supply control unit so that the DC component becomes a predetermined value. In the plasma processing apparatus, the power value acquisition unit acquires the power value of the bias high-frequency power output from the bias high-frequency power source. The waveform generation unit generates a waveform for the time of the acquired power value. The determination unit compares the power value acquired within a predetermined period during plasma processing with a preset reference value, and compares the generated waveform with a preset reference waveform. Based on the comparison result of the power value and the comparison result of the waveform, the presence / absence of the plasma impedance fluctuation due to the apparatus abnormality is determined.

  According to this configuration, the fluctuation of the actual resistance component superimposed on the plasma impedance can be reliably detected in the plasma processing apparatus of the bias voltage control method, and the fluctuation of the plasma processing characteristics due to the apparatus abnormality can be prevented. Can do.

  The plasma processing apparatus calculates a control value for setting a power value of bias high-frequency power that obtains predetermined plasma processing characteristics based on a correspondence relationship between a plasma processing characteristic for the object to be processed and a bias high-frequency power acquired in advance. And a means for adjusting the bias high-frequency power so that the bias high-frequency power becomes a set power value during the plasma processing.

  According to this configuration, it is possible to easily maintain the plasma ion current density at a predetermined value in a state where there is no fluctuation in plasma impedance due to an apparatus abnormality. The adjustment of the bias high-frequency power can be performed, for example, by adjusting the internal pressure of the reaction chamber. Or it can implement by adjusting the output electric power value of the source high frequency power source which excites plasma in the reaction chamber.

  Moreover, the determination part can determine with the plasma impedance fluctuation | variation resulting from apparatus abnormality, when there exists a shift or drift in the acquired electric power value as a result of the comparison of an electric power value and a waveform. When it is determined that there is plasma impedance fluctuation due to the apparatus abnormality, it is preferable to further include a notification means for notifying abnormality, and when it is determined that there is plasma impedance fluctuation due to the apparatus abnormality, the apparatus control unit performs plasma processing. More preferably, it is configured to stop.

  Further, the reference value can be set based on the power value of the bias high-frequency power acquired in the plasma processing that is normally performed under the same processing conditions. The reference waveform can be set based on the waveform of the bias high-frequency power acquired in the plasma processing that is normally performed under the same processing conditions.

  On the other hand, in another aspect, the present invention provides a method for controlling a plasma processing apparatus that excites plasma in a reaction chamber by applying high-frequency power and performs plasma processing on an object to be processed accommodated in the reaction chamber. Can do. That is, in the method for controlling a plasma processing apparatus according to the present invention, first, bias high frequency power is applied to a sample stage on which an object to be processed is placed. Next, the DC component of the bias high frequency power applied to the sample stage is acquired. The bias high-frequency power is maintained in a state where the DC component becomes a predetermined value. Under the situation, the power value of the bias high-frequency power is acquired, and a waveform with respect to the time of the acquired power value is generated. The power value acquired within a predetermined period during the plasma processing is compared with a preset reference value and a generated waveform is compared with a preset reference waveform. Based on these comparison results Thus, the presence / absence of plasma impedance fluctuation due to the apparatus abnormality is determined.

  According to the present invention, in the bias voltage control type plasma processing apparatus, it is possible to detect the fluctuation of the actual resistance component superimposed on the plasma impedance, and to ensure that the fluctuation of the plasma processing characteristics due to the apparatus abnormality occurs. Can be prevented. In addition, it is possible to specify the site of the device failure.

  Further, in the present invention, the bias voltage is maintained at a predetermined value and the bias high-frequency power is maintained at a predetermined power value in a situation where the occurrence of impedance fluctuation due to device abnormality is excluded. For this reason, the ion current density of plasma can be maintained at a predetermined value, and fluctuations in dimensions, selection ratio, and the like due to fluctuations in plasma processing characteristics can be suppressed. As a result, plasma processing can be stably performed with good reproducibility.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following embodiments, the present invention is embodied as a high-density plasma type dry etching apparatus typified by an ICP method and a control method thereof.

  FIG. 1 is a schematic configuration diagram showing a plasma processing apparatus in one embodiment of the present invention. The physical structure around the reaction chamber of this plasma processing apparatus is the same as that of the dry etching apparatus shown in FIG. For this reason, in FIG. 1, the same code | symbol is attached | subjected to the component similar to the conventional dry etching apparatus shown in FIG. 8, and the detailed description below is abbreviate | omitted.

  As shown in FIG. 1, the plasma processing apparatus of this embodiment includes a power value acquisition unit 31, a calculation unit 32, a storage unit 33, a notification unit 34, and a device control unit 35. FIG. 2 is a functional block diagram illustrating a configuration of the calculation unit 32. As shown in FIG. 2, the calculation unit 32 includes an average power value calculation unit 51, a waveform generation unit 52, a determination unit 53, and a control value calculation unit 54. Each unit constituting the calculation unit 32 is stored in, for example, a dedicated calculation circuit, hardware including a processor and a memory such as a RAM (Random Access Memory) or a ROM (Read Only Memory), and the processor. It can be realized as software operating on the above.

  For example, the power value acquisition unit 31 acquires the power value of the bias high-frequency power output from the bias high-frequency power supply 14 continuously or at a predetermined sampling period. The power value of the bias high-frequency power can be calculated based on, for example, the current value and voltage value of the bias high-frequency power measured by the VI probe. The average power value calculation unit 51 calculates the average power value within the predetermined period from the power value of the predetermined period acquired by the power value acquisition unit 31 during one plasma process. The waveform generation unit 52 generates a correspondence relationship between the power value and time, that is, a time waveform, from the power value acquired by the power value acquisition unit 31. Based on the time waveform generated by the waveform generation unit 52 and the average power value calculated by the average power value calculation unit 51, the determination unit 53 determines the presence or absence of impedance fluctuation of the plasma generated in the reaction chamber 1. . The control value calculation unit 54 and the notification unit 34 will be described later. The operation of each part of the dry etching apparatus is controlled by the apparatus control unit 35.

  As described above, in the bias voltage control method, when the bias voltage Vpp is a predetermined value, the ion current density I and the plasma impedance Z are unknown variables (see Equation 2). However, under the situation where the bias voltage Vpp is a predetermined value, even if the plasma impedance Z is unknown, the ion current density I is maintained at a constant value if the plasma impedance Z does not change. . Therefore, in the dry etching apparatus of the present embodiment, whether or not the ion current density I is maintained at a constant value by determining the presence or absence of impedance fluctuation during plasma processing in a state where the bias voltage Vpp is controlled to a predetermined value. Determine whether.

  Hereinafter, the determination method of the presence or absence of the impedance fluctuation which the plasma processing apparatus of this embodiment implements is demonstrated. In the plasma processing apparatus of this embodiment, in order to accurately detect the presence or absence of plasma impedance fluctuations, the presence or absence of fluctuations in the actual resistance component R shown in Equation 3 (fluctuations in plasma impedance caused by the apparatus) is confirmed.

  FIG. 3 is a schematic diagram showing a time waveform generated by the waveform generator 52 during one plasma processing. In FIG. 3, the horizontal axis corresponds to time, and the vertical axis corresponds to the power value of the bias high frequency power. FIG. 3A shows a time waveform when a desired processing result is obtained (hereinafter referred to as normal) while the plasma processing apparatus performs a plurality of times of plasma processing. b) and FIG. 3C are time waveforms when a desired processing result is not obtained (hereinafter referred to as abnormal). In FIG. 3B and FIG. 3C, the time waveform at normal time (FIG. 3A) is indicated by a dotted line with the time axis shifted for comparison. In the plasma processing apparatus of this embodiment, the bias power supply control unit 18 sets the output of the bias high frequency power supply 14 based on the measurement result of the bias voltage measurement unit 17 so that the bias voltage becomes a predetermined value during the plasma processing. Feedback control is performed (bias voltage control method). Moreover, each time waveform shown in FIG. 3 is a time waveform at the time of implementing a dry etching process on the same process conditions.

  It can be understood that the time waveform in FIG. 3B and the time waveform in FIG. 3C have different power values compared to the time waveform in FIG. That is, in the time waveform at the time of abnormality shown in FIG. 3B, the power value is larger in the time domain B and the time domain C than in the time waveform at the normal time shown in FIG. Further, in the time waveform at the time of abnormality shown in FIG. 3C, the power value suddenly increases in the time domain B and the time domain C as compared with the time waveform at the normal time shown in FIG. Or decrease.

  FIG. 4 is a diagram showing a change with time of the average power value calculated by the average power value calculation unit 34 over a plurality of plasma treatments. FIG. 4A shows the change over time in the average power value when the normal state changes to the state of FIG. 3B, and FIG. 4B shows the state of FIG. 3C from the normal state. The time-dependent change of the average power value when the state is reached is shown. In FIG. 4, the horizontal axis corresponds to time, and the vertical axis corresponds to the average power value. In FIG. 4A and FIG. 4B, maintenance work is performed on the plasma processing apparatus during the time indicated by the broken line.

  In FIG. 4A, after the maintenance work, the average power value is shifted in the higher direction. That is, after the maintenance work, the abnormal state shown in FIG. In FIG. 4B, after the maintenance work, the average power value fluctuates between a high value and a low value (hereinafter referred to as drift). That is, after the maintenance work, the abnormal state shown in FIG.

  As a result of analyzing the plasma processing apparatus in which the phenomenon shown in FIG. 4 (a) occurred, the parts in the reaction chamber 1 were replaced in the maintenance work, so that the electrical grounding resistance R of the parts (actual resistance component R in Equation 3) ) Is usually higher than 10Ω. The bias traveling wave power W (average power value) is proportional to the ground resistance R as shown in Equation 4 below.

W = I ² × Z = I ² × (R + jX) (4)

  That is, as a result of an increase in the ground resistance R of the parts due to maintenance or the like, the average power value is shifted in a higher direction. Therefore, in the bias voltage control method, when the ground resistance R of the parts in the reaction chamber 1 fluctuates, the average power value shifts in a higher direction as shown in FIG.

  Further, as a result of analyzing the cause of the plasma processing apparatus in which the phenomenon shown in FIG. 4B has occurred by exchanging the cathode electrode 13 and the matching unit 15, the output impedance of the bias high-frequency power source 14 fluctuates. Turned out to be. Further, in FIG. 4B, under the situation where the power value drift occurs, as shown in FIG. 3C, the drift occurs even in the time waveform during one plasma processing. Yes. From the above, in the bias voltage control system, when drift occurs in the average power value of the bias high frequency power 14 with time and the time waveform of the bias high frequency power 14, the output impedance of the bias high frequency power supply 14 is not stable. It can be determined that this is a sign of a failure of the state, that is, the bias high-frequency power supply 14.

  Thus, the actual resistance component shown in Equation 3 is obtained by acquiring the power value of the bias high-frequency power source 14 during the plasma processing and monitoring the temporal change of the average power value for each plasma processing and the time waveform of the bias high-frequency power. R variation (abnormality of plasma processing apparatus) can be detected. Further, in the present embodiment, when the fluctuation of the actual resistance component R occurs, the factor, that is, the location where an abnormality has occurred in the plasma processing apparatus can be specified. It should be noted that there is no abnormality in parts installation in the reaction chamber 1 despite the detection of the power value shift, or there is an abnormality in the bias high-frequency power supply in spite of the detection of the power value drift. If not, the VI probe is abnormal.

  The plasma processing apparatus of the present embodiment detects an abnormality of the plasma processing apparatus as described above, and stabilizes the plasma processing characteristics as follows. FIG. 5 is a diagram showing the relationship between the bias high-frequency power value and the wiring resistance value under the condition that the bias voltage is controlled to be constant. In FIG. 5, the horizontal axis corresponds to the bias high frequency power value, and the vertical axis corresponds to the wiring resistance. FIG. 5 illustrates the cross-sectional shape of the wiring when the bias high-frequency power value is a and the cross-sectional shape of the wiring when the bias high-frequency power value is b (a <b).

  As described above, the wiring pattern dimensions can be stabilized by controlling the bias high-frequency power so that the bias voltage becomes a predetermined value. As a result, the wiring resistance, which is an evaluation item in the final inspection of the semiconductor device, can also be stabilized.

  However, as shown in FIG. 5, when the bias high-frequency power is less than a, the etching rate decreases as the bias high-frequency power decreases, even under the condition that the bias voltage is controlled to a predetermined value. As a result, the wiring pattern dimension increases. In this case, since the wiring resistance is lowered, the desired device characteristics cannot be satisfied. At this time, the ion current density I decreases as the bias high frequency power decreases. When the bias high-frequency power exceeds b, the etching rate increases with the increase of the bias high-frequency power, even under the condition that the bias voltage is controlled to a predetermined value. As a result, the amount of side etching in the side wall direction of the wiring pattern increases, and the wiring pattern dimension decreases. In this case, since the wiring resistance is reduced, the desired device characteristics cannot be satisfied. At this time, the ion current density I increases as the bias high-frequency power increases.

  Therefore, the plasma processing characteristics can be stabilized by maintaining the bias high-frequency power within a predetermined range, that is, maintaining the bias high-frequency power within the range of a to b. As a result, it becomes possible to stably produce semiconductor devices.

  The plasma processing apparatus according to the present embodiment automatically diagnoses a failure during the plasma processing and stabilizes the plasma processing characteristics based on the above knowledge. FIG. 6 is a flowchart showing a process performed by the plasma processing apparatus of the present embodiment during the plasma process in order to detect the presence / absence of impedance fluctuation caused by the apparatus abnormality.

  When the plasma processing is started, as shown in FIG. 6, first, the power value acquisition unit 31 acquires the power value of the bias high-frequency power output from the bias high-frequency power source 14 continuously or at a predetermined sampling period. The waveform generation unit 52 generates a time waveform of the bias high-frequency power based on the power value acquired by the power value acquisition unit 31. Further, the average power value calculation unit 51 acquires a power value acquired within a predetermined period set in advance from the power value acquisition unit 31, and calculates an average power value (step S1). In the present embodiment, the time waveform generated by the waveform generation unit 52 and the average power value calculated by the average power value calculation unit 51 are associated with the information specifying the plasma process from which the power value is acquired in the storage unit 33. It is configured to be stored.

  The time waveform generated by the waveform generation unit 52 and the average power value calculated by the average power value calculation unit 51 are input to the determination unit 53. The determination unit 53 first determines whether or not a shift has occurred in the average power value based on the input average power value (step S2). This determination is performed by comparing the input average power value with a preset reference value. Here, this determination is made based on whether or not the input average power value is within the standard range. The standard range is, for example, a predetermined range (reference value) based on an average power value that is normally performed in the plasma processing among the average power values that are stored in the storage unit 33 and that correspond to the existing plasma processing. Can be set.

  As a result of the determination, if there is a shift in the bias high frequency power, the determination unit 53 instructs the apparatus control unit 35 to stop the plasma processing (steps S2 Yes, S5). Thereby, the plasma processing is stopped. In addition, at this time, the determination unit 53 determines that the bias high-frequency power has shifted in the manufacturing unit (MES: Manufacturing Execution System) 40 that collectively manages the notification unit 34 and the manufacturing equipment in the production line. Notice. At this time, the notification unit 34 issues an alarm by an arbitrary method capable of notifying the operator of an abnormality such as sound, light, warning display, and the like, and a display (not shown) indicating that there is an abnormality in parts mounting in the reaction chamber 1 (Step S6). Further, the MES 40 recognizes that the plasma processing apparatus is abnormal in response to the notification, and takes measures to cause the other semiconductor processing apparatus to process the semiconductor substrate that is scheduled to be processed by the plasma processing apparatus.

  On the other hand, if the result of determination is that there is no shift of the bias high-frequency power, the determination unit 53 determines whether or not a drift has occurred in the input average power value and time waveform (steps S2 No, S3). In this determination, when the input average power value is out of the preset standard range and a drift has occurred in the time waveform, it is determined that there is a drift of the bias high-frequency power. In addition, the presence or absence of the drift of the time waveform is, for example, the time waveform in which the plasma processing is normally performed among the input time waveform and the time waveform corresponding to the already-executed plasma processing stored in the storage unit 33. It can be determined by the presence or absence of a sign change of the difference at each time corresponding to (reference waveform).

  As a result of the determination, if there is a drift of the bias high frequency power, the determination unit 53 instructs the apparatus control unit 35 to stop the plasma processing (steps S3 Yes, S7). Thereby, the plasma processing is stopped. At this time, the determination unit 53 notifies the notification unit 34 and the MES 40 that a drift has occurred in the bias high frequency power. At this time, the notification unit 34 issues an alarm by an arbitrary method capable of notifying the operator of the abnormality, and displays on the display unit (not shown) that the bias high frequency power supply 14 is abnormal (step S8). In addition, the MES 40 recognizes that the plasma processing apparatus is abnormal in response to the notification, and takes action to cause the other semiconductor processing apparatus to process the semiconductor substrate that is scheduled to be processed by the plasma processing apparatus.

  If the result of determination is that there is no drift of the bias high-frequency power, the plasma processing is continued (step S4). The above-described abnormality detection process may be configured to be periodically performed during facility management, for example, weekly management or daily management.

  On the other hand, FIG. 7 is a flowchart showing a process performed by the plasma processing apparatus of the present embodiment during the plasma process for stabilizing the plasma process. This processing is repeatedly performed at predetermined intervals during plasma generation in the plasma processing apparatus of the present embodiment.

  When plasma is generated in the plasma processing apparatus, the control value calculation unit 54 determines the control setting value of the bias high-frequency power based on the relationship between the pattern dimensions exemplified in FIG. 5 and the bias high-frequency power. Here, the control value calculation unit 54 stores the relationship between the pattern dimension and the bias high-frequency power acquired in advance. The determined control setting value is input to the bias power supply control unit 18 through the device control unit 35 (step S11). The bias power source control unit 18 controls the bias high frequency power source 14 so that the bias voltage becomes a predetermined value and the control set value to which the bias high frequency power is input.

  At this time, the control value calculation unit 54 notifies the control setting value of the bias high-frequency power to the device control unit 35, and then acquires the control value and the power value acquired by the power value acquisition unit 31 and input to the control value calculation unit 54. The value is compared (step S12). As a result of the comparison, if the power value and the set value are the same, the control value calculation unit 54 ends the process (step S12 Yes). Here, the same includes substantially the same that can be regarded as substantially the same.

  On the other hand, as a result of the comparison, if the power value and the set value are not the same, the control value calculation unit 54 adjusts the internal pressure of the reaction chamber 1 (steps S12 No, S13). By changing the reaction chamber pressure, the density of process gas molecules in the reaction chamber changes. For this reason, the ion current density of plasma fluctuates according to the internal pressure of the reaction chamber 1, and the power value of the bias high-frequency power also changes. Therefore, the feedback high frequency power can be feedback controlled to a desired value by changing the internal pressure of the reaction chamber 1. The direction in which the reaction chamber pressure is adjusted (pressure increase or depressurization) or the control set value of the reaction chamber pressure is determined based on, for example, the relationship between the reaction chamber pressure and the bias high-frequency power obtained in advance through experiments. Can do.

  The pressure adjustment instruction is input to the exhaust amount control unit 19 through the device control unit 35. The exhaust amount control unit 19 adjusts the exhaust amount by the exhaust amount adjusting means 3 in accordance with the input instruction, and adjusts the internal pressure of the reaction chamber 1. At this time, the control value calculation unit 54 notifies the device control unit 35 of a pressure adjustment instruction, and then compares the power value acquired by the power value acquisition unit 31 and input to the control value calculation unit 54 with the control set value. (Step S12). As a result of the comparison, if the power value and the set value are the same, the process ends (Yes in step S12). The adjustment of the pressure is continued until the acquired power value becomes the same as the set value (No in step S12).

  As a result, even in the bias power control system, the bias high frequency power can be kept constant and the ion current density can be kept constant. As a result, the pattern dimension is stabilized.

  In the above description, the example in which the power value of the bias high-frequency power is feedback-controlled to a desired value by adjusting the pressure in the reaction chamber 1 has been described. However, the power value of the bias high frequency power can also be controlled to a predetermined value by adjusting the output power value of the source high frequency power supply 11. Therefore, instead of the configuration for adjusting the pressure in the reaction chamber 1, by adjusting the output power value of the source high-frequency power source 11, the power value of the bias high-frequency power is feedback-controlled to a desired value. Similar effects can be obtained.

  As described above, according to the present invention, it is possible to detect the fluctuation of the actual resistance component superimposed on the plasma impedance in the plasma processing apparatus of the bias voltage control system, and to improve the plasma processing characteristics due to the apparatus abnormality. Variations can be reliably prevented. As a result, plasma processing characteristics can be stably performed with good reproducibility. In addition, it is possible to specify the site of the device failure.

  In addition, according to the present invention, the plasma ion current density I can be easily monitored, the plasma state can be stabilized, and the processing characteristics (selection ratio, dimensions, etc.) can be stabilized. Furthermore, by automating failure diagnosis, it is possible to minimize processing loss and device operation loss.

  The present invention is not limited to the embodiment described above, and various modifications and applications are possible without departing from the technical idea of the present invention. For example, in the above-described embodiment, as a particularly preferable mode, the power value compared by the determination unit is the average power value, but instead of the average power value, the power value acquired within a predetermined period is used for comparison as it is. Is also possible. Further, in the above-described embodiment, an example in which the plasma processing apparatus is applied to an inductively coupled dry etching apparatus has been described. However, the present invention is applicable to any plasma excitation apparatus that excites plasma by applying high-frequency power such as a CVD (Chemical Vapor Deposition) apparatus. The present invention can also be applied to a plasma processing apparatus.

  The present invention can realize stabilization of equipment and stabilization of plasma processing characteristics, and is useful as a plasma processing apparatus and a control method thereof.

1 is a schematic configuration diagram showing a plasma processing apparatus in one embodiment of the present invention. The functional block diagram which shows the structure of the calculating part in one Embodiment of this invention. The schematic diagram which shows the time waveform in one Embodiment of this invention The figure which shows the time-dependent change of the average electric power value in one Embodiment of this invention. The figure which shows the relationship between the bias high frequency electric power and wiring resistance value in one Embodiment of this invention The flowchart which shows the apparatus abnormality detection process in one Embodiment of this invention. The flowchart which shows the plasma stabilization process in one Embodiment of this invention. Schematic configuration diagram showing a conventional plasma processing apparatus

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Reaction chamber 3 Exhaust amount adjustment means 5 Pressure measuring device 7 Mass flow controller 10 Antenna coil 11 Source high frequency power source 13 Lower electrode 14 Bias high frequency power source 16 Processed object 17 Bias voltage measurement circuit 18 Bias power source control unit 19 Exhaust amount control unit 31 Value acquisition unit 32 Calculation unit 34 Notification unit 35 Device control unit 40 Factory MES
51 Average Power Value Calculation Unit 52 Waveform Generation Unit 53 Determination Unit 54 Control Value Calculation Unit

Claims (22)

In a plasma processing apparatus for exciting plasma in a reaction chamber by applying high-frequency power and performing plasma processing on an object to be processed accommodated in the reaction chamber,
A sample stage on which a workpiece is placed;
A bias high frequency power source for applying a bias high frequency power to the sample stage via a matching unit;
Means for obtaining a DC component of the bias high-frequency power between the sample stage and the matching unit;
Means for controlling the bias high-frequency power source so that the direct current component has a predetermined value;
Means for obtaining a power value of bias high-frequency power output from the bias high-frequency power source;
Means for generating a waveform with respect to time of the acquired power value;
Means for comparing the power value acquired within a predetermined period during plasma processing with a preset reference value;
Means for comparing the waveform with a preset reference waveform;
Based on the comparison result of the power value and the comparison result of the waveform, means for determining the presence or absence of fluctuations in plasma impedance caused by an apparatus abnormality;
A plasma processing apparatus comprising: Means for setting a power value of bias high-frequency power that obtains predetermined plasma processing characteristics based on a correspondence relationship between plasma processing characteristics for the object to be processed and the bias high-frequency power acquired in advance;
Means for adjusting the bias high-frequency power to a state where the bias high-frequency power becomes the set power value during plasma processing;
The plasma processing apparatus according to claim 1, further comprising:   The plasma processing apparatus according to claim 2, wherein the bias high frequency power is adjusted by adjusting an internal pressure of the reaction chamber.   The plasma processing apparatus according to claim 2, wherein the bias high-frequency power is adjusted by adjusting an output power value of a source high-frequency power source that excites plasma in the reaction chamber.   5. The plasma processing apparatus according to claim 1, wherein, as a result of the comparison of the power values and the comparison of the waveforms, when there is a shift or drift in the acquired power value, it is determined that there is a plasma impedance variation caused by the apparatus abnormality. .   The plasma processing apparatus according to any one of claims 1 to 5, further comprising means for notifying abnormality when it is determined that there is plasma impedance fluctuation caused by the apparatus abnormality.   The plasma processing apparatus according to any one of claims 1 to 6, further comprising means for stopping the plasma processing when it is determined that there is a plasma impedance fluctuation caused by an apparatus abnormality.   The plasma processing apparatus according to any one of claims 1 to 7, wherein the reference value is set based on a power value of a bias high-frequency power acquired in a plasma processing normally performed under the same processing conditions.   9. The plasma processing apparatus according to claim 1, wherein the reference waveform is set based on a waveform of a bias high-frequency power acquired in a plasma processing normally performed under the same processing conditions.   The plasma processing apparatus according to claim 1, wherein the power value used for the comparison is an average value of power values acquired within a predetermined period. In a control method of a plasma processing apparatus for exciting plasma in a reaction chamber by applying high-frequency power and performing plasma processing on an object to be processed accommodated in the reaction chamber,
Applying a bias high frequency power to a sample stage on which the object is placed;
Obtaining a direct current component of bias high frequency power applied to the sample stage;
Maintaining the bias high-frequency power in a state where the DC component is a predetermined value;
Obtaining a power value of the bias high frequency power;
Generating a waveform with respect to time of the acquired power value;
Comparing the power value acquired within a predetermined period during plasma processing with a preset reference value;
Comparing the waveform with a preset reference waveform;
Based on the comparison result of the power value and the comparison result of the waveform, the step of determining the presence or absence of fluctuations in plasma impedance due to device abnormality;
A method for controlling a plasma processing apparatus, comprising: A step of setting a power value of bias high-frequency power that obtains predetermined plasma processing characteristics based on a correspondence relationship between the plasma processing characteristics for the object to be processed and the bias high-frequency power acquired in advance;
During the plasma treatment, the bias high-frequency power, a state in which the DC component becomes a predetermined value, and a state in which the set power value is set,
The method for controlling a plasma processing apparatus according to claim 11, further comprising:   The method of controlling a plasma processing apparatus according to claim 12, wherein the bias high frequency power is set to the set power value by adjusting an internal pressure of the reaction chamber.   13. The method of controlling a plasma processing apparatus according to claim 12, wherein the bias high-frequency power is set to the set power value by adjusting a power value of source high-frequency power for exciting plasma in the reaction chamber.   The plasma processing apparatus according to any one of claims 11 to 14, wherein when there is a shift or drift in the acquired power value as a result of the power value comparison and the waveform comparison, it is determined that there is a plasma impedance fluctuation caused by the apparatus abnormality. Control method.   The method for controlling a plasma processing apparatus according to claim 11, further comprising a step of notifying an abnormality when it is determined that there is a plasma impedance fluctuation caused by the apparatus abnormality.   The method for controlling a plasma processing apparatus according to any one of claims 11 to 16, further comprising a step of stopping the plasma processing when it is determined that there is a plasma impedance fluctuation caused by an apparatus abnormality.   The method for controlling a plasma processing apparatus according to claim 11, wherein the reference value is set based on a power value of a bias high-frequency power acquired in a plasma process that is normally performed under the same processing condition.   The method of controlling a plasma processing apparatus according to any one of claims 11 to 17, wherein the reference waveform is set based on a waveform of a bias high-frequency power acquired in a plasma processing normally performed under the same processing conditions.   The method for controlling a plasma processing apparatus according to claim 11, wherein the power value used for the comparison is an average value of power values acquired within a predetermined period.   The method for controlling a plasma processing apparatus according to claim 15, wherein when there is a shift in the acquired power value as a result of the power value comparison and the waveform comparison, it is determined that there is an abnormal mounting of a part in the reaction chamber.   The method of controlling a plasma processing apparatus according to claim 15, wherein when there is a drift in the acquired power value as a result of the power value comparison and the waveform comparison, it is determined that the high frequency power supply to which the bias high frequency power is applied is abnormal.

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