Plasma processing system and plasma ignition assist method

Abstract

The present invention provides a plasma processing system and a plasma ignition assisting method. A control device of the plasma processing system executes a collection process, a first determination process, a second determination process, and an ignition process. In the collection process, values of respective adjustable variables related to matching of impedance between a power supply unit and a plasma are collected, and measurement values representing the impedance matching state are collected. In the first determination process, a passing point corresponding to the value of the variable having the largest slope of change of the measurement value with respect to a vector from a point corresponding to each variable to a matching point is determined, where the matching point is a point corresponding to the measurement value in a state of the most matching impedance. In the second determination process, a point on a straight line including the passing point and the matching point and farther from the matching point than the passing point is determined as a start point of control. In the ignition process, each variable is controlled from the start point along the straight line toward the matching point, thereby igniting plasma in the plasma processing device.

Description

Technical Field

[0001] The present disclosure relates to a plasma processing system and a plasma ignition assist method. Background Art

[0002] In recent years' semiconductor manufacturing processes, plasma processing apparatuses that use plasma to process substrates are used. In a plasma processing apparatus, a processing gas is supplied into a processing chamber to adjust the pressure in the processing chamber to a predetermined pressure. Further, by supplying high-frequency power into the processing chamber, the processing gas is plasmaized, and plasma processing such as etching is performed on the substrate accommodated in the processing chamber by the plasma.

[0003] Prior Art Documents

[0004] Patent Documents

[0005] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2010-153274 Summary of the Invention

[0006] Problems to be Solved by the Invention

[0007] The present disclosure provides a plasma processing system and a plasma ignition assist method capable of stably igniting plasma.

[0008] Solutions for Solving the Problems

[0009] A plasma processing system according to one aspect of the present disclosure includes a plasma processing apparatus and a control device. The plasma processing apparatus has a processing chamber that accommodates a substrate, and performs plasma processing on the substrate by generating plasma in the processing chamber. The control device controls the plasma processing apparatus. Further, the control device executes a collection process, a first determination process, a second determination process, and an ignition process. In the collection process, values of respective adjustable variables related to impedance matching between a power supply unit that supplies high-frequency power to the co-directional plasma and the plasma are collected, and measurement values indicating the impedance matching state between the power supply unit and the plasma are collected. In the first determination process, a point corresponding to the value of the variable having the largest slope of the change in the measurement value with respect to the vector from the point corresponding to each variable to the matching point is determined as the passing point, where the matching point is the point corresponding to the measurement value in the state of the most impedance matching. In the second determination process, a point on the straight line including the passing point and the matching point that is farther from the matching point than the passing point is determined as the start point of control. In the ignition process, each variable is controlled so that the measurement value changes from the start point along the straight line toward the matching point, thereby igniting plasma in the plasma processing apparatus.

[0010] Effects of the Invention

[0011] According to various aspects and embodiments of the present disclosure, stable plasma ignition can be achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 FIG. is an example of a plasma processing system showing an embodiment of the present disclosure.

[0013] Figure 2 FIG. is an example of a diagram showing the structure of a matcher.

[0014] Figure 3 FIG. is an example of a diagram showing the relationship between a control variable and the light emission intensity of plasma.

[0015] Figure 4 FIG. is an example of a diagram showing a method of adjusting a variable.

[0016] Figure 5 FIG. is an example of a diagram showing a method of adjusting a variable.

[0017] Figure 6 FIG. is an example of a diagram for explaining a method of determining a control direction.

[0018] Figure 7 FIG. is an example of a diagram showing the change in the power of a reflected wave.

[0019] Figure 8 FIG. is an example of a diagram for explaining a limit point and a limit line.

[0020] Figure 9 FIG. is an example of a diagram for explaining the control of a control variable during the execution of a process.

[0021] Figure 10 FIG. is a flowchart showing an example of data collection processing.

[0022] Figure 11 FIG. is a flowchart showing an example of ignition assist processing.

[0023] Figure 12 FIG. is an example of a diagram showing a computer for implementing the functions of a control device. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0024] Hereinafter, embodiments of the disclosed plasma processing system and plasma ignition assist method will be described in detail based on the drawings. In addition, the disclosed plasma processing system and plasma ignition assist method are not limited by the following embodiments.

[0025] In addition, a matching circuit is provided between the power supply unit and the processing space where plasma is generated to efficiently supply high-frequency power from the power supply unit to the plasma in the processing space. The matching circuit operates to match the output impedance of the power supply unit with the impedance of the plasma in the processing space. In addition, hereinafter, generating plasma in the processing space is referred to as plasma ignition.

[0026] During the plasma ignition process, the impedance of the plasma changes. Therefore, when the matching circuit operates during the plasma ignition process, sometimes the matching operation progresses in a state where the plasma has not yet ignited, and the matching operation becomes stable in a state where the plasma has not ignited. In addition, when the matching circuit operates during the plasma ignition process, even if the plasma ignites temporarily, sometimes the plasma will extinguish again due to the matching operation. Thus, when the plasma ignition and the matching operation are performed in parallel, it is difficult to stably ignite the plasma.

[0027] Therefore, the present disclosure provides a technique capable of stably igniting plasma.

[0028] [Structure of Plasma Processing System 1]

[0029] Figure 1 FIG. is an example of a plasma processing system 1 showing an embodiment of the present disclosure. The plasma processing system 1 includes a plasma processing apparatus 100 and a control apparatus 200. The plasma processing apparatus 100 excites a processing gas remaining between electrodes by high-frequency power supplied to at least one of two opposing electrodes. Thereby, the plasma processing apparatus 100 generates plasma in the processing chamber of the processing container, and performs plasma processing such as etching on the semiconductor wafer W by the generated plasma. In the present embodiment, the plasma processing apparatus 100 is a plasma processing apparatus using capacitively coupled plasma (CCP).

[0030] The plasma processing apparatus 100 is formed in a cylindrical shape (e.g., a cylindrical shape) from a metal such as aluminum, and has a processing container 102 for accommodating a semiconductor wafer W as an example of a substrate. The processing container 102 is grounded. In addition, the shape of the plasma processing system 103 is not limited to a cylindrical shape, and may be, for example, a square tubular shape (e.g., a box shape).

[0031] A mounting stage 110 for mounting the semiconductor wafer W is provided in the processing container 102. The mounting stage 110 is formed in a substantially columnar shape (e.g., a cylindrical shape) from aluminum or the like. In addition, the shape of the mounting stage 110 is not limited to a cylindrical shape, and may be, for example, a prismatic shape (e.g., a multi-prismatic shape). Although not shown, an electrostatic chuck for electrostatically adsorbing and holding the semiconductor wafer W, a temperature adjustment mechanism for adjusting the temperature of the semiconductor wafer W, etc. are provided on the mounting stage 110.

[0032] At the upper part of the processing container 102, an upper electrode 104 formed in a plate shape of a conductive body such as silicon is provided via an insulating member 106. The insulating member 106 is formed in a ring shape of, for example, ceramics and can be provided on the outer periphery of the upper electrode 104. The upper electrode 104 is provided above the mounting stage 110 so as to face the mounting stage 110. The space surrounded by the processing container 102 and the upper electrode 104 is defined as a processing chamber 161.

[0033] A gas introduction port 121 is formed in the side wall of the processing container 102, and the gas introduction port 121 is connected to a gas supply mechanism 120 via a pipe 123. The gas supply mechanism 120 includes a gas supply source 122, a flow controller 124, and a valve 126. The gas supply source 122 is a supply source of a processing gas such as CF4 gas. The flow controller 124 controls the flow rate of the processing gas supplied from the gas supply source 122 into the processing chamber 161. The valve 126 controls the supply and stop of the processing gas from the gas supply source 122 into the processing chamber 161.

[0034] In Figure 1 In order to simplify the description, it is shown that the gas supply mechanism 120 supplies a single type of processing gas into the processing container 102, but it is not limited to the case where the gas supply mechanism 120 supplies a single type of processing gas, and multiple types of processing gases can also be supplied. In addition, in Figure 1 In, the processing gas supplied from the gas supply mechanism 120 is supplied into the processing chamber 161 from the gas introduction port 121 provided on the side wall of the gas supply mechanism 120, but as another example, the processing gas can also be supplied into the processing chamber 161 from the approximate center of the upper electrode 104. In addition, the upper electrode 104 may have a shower head structure.

[0035] An exhaust pipe 132 is connected to the bottom of the processing container 102, and an exhaust device 130 having a vacuum pump or the like is connected to the exhaust pipe 132. The gas in the processing chamber 161 can be exhausted by the exhaust device 130 to control the pressure in the processing chamber 161 to a desired pressure.

[0036] An opening 134 is formed in the side wall of the processing container 102, and the opening 134 is opened and closed by a gate valve 136. When loading the semiconductor wafer W, the gate valve 136 is opened, and the semiconductor wafer W is loaded into the processing chamber 161 by a transfer mechanism such as a transfer arm (not shown) and placed on the mounting stage 110. Then, after the transfer mechanism withdraws from the processing chamber 161, the gate valve 136 is closed, and the semiconductor wafer W is processed.

[0037] In addition, a window 108 formed of quartz or the like is provided on the side wall of the processing container 102. The window 108 is connected to a measuring device 170 that measures the light emission intensity of the plasma generated in the processing chamber 161. Information on the light emission intensity of the plasma measured by the measuring device 170 is output to the control device 200. The information on the light emission intensity of the plasma measured by the measuring device 170 is an example of a measured value indicating the matching state of the impedance between the power supply unit and the plasma.

[0038] The upper electrode 104 is connected to the high-frequency power supply 150 via the matcher 152. The high-frequency power supply 150 is an example of a power supply unit. The high-frequency power supply 150 supplies high-frequency power of a predetermined frequency (e.g., 60 MHz) to the upper electrode 104. The magnitude of the high-frequency power output from the high-frequency power supply 150 is controlled by the control device 200. In addition, the frequency of the high-frequency power supplied to the upper electrode 104 is not limited to 60 MHz, and may be 13.56 MHz, 27 MHz, 100 MHz, or the like. In addition, the high-frequency power supply 150 may be connected to the stage 110 via the matcher 152. In this case, the stage 110 is used as a lower electrode.

[0039] Figure 2 It is a diagram showing an example of the structure of the matcher 152. The matcher 152 has a VC1 (varicap) and a VC2 whose capacitances can be controlled. VC1 is connected in series between the high-frequency power supply 150 and the upper electrode 104, and VC2 is connected between the high-frequency power supply 150 and the ground potential (GND potential) in parallel with the high-frequency power supply 150. VC1 and VC2 operate to match the output impedance of the high-frequency power supply 150 with the impedance of the plasma in the processing chamber 161. The capacitances of VC1 and VC2 are controlled by the control device 200. In addition, the matcher 152 outputs information indicating the magnitude of the power of the reflected wave with respect to the high-frequency power supplied from the high-frequency power supply 150 to the upper electrode 104 to the control device 200.

[0040] Due to the high-frequency power supplied to the upper electrode 104, a potential difference is generated between the upper electrode 104 and the stage 110. Moreover, due to the generated potential difference, electrons existing in the processing chamber 161 are accelerated and collide with the processing gas supplied to the processing chamber 161, thereby exciting the processing gas supplied to the processing chamber 161 to ionize the processing gas in the processing chamber 161. Then, a predetermined process such as etching is performed on the semiconductor wafer W on the stage 110 by ions and active species contained in the plasma.

[0041] The control device 200 includes a memory, a processor, an input / output interface, etc. Process data, programs, etc. are stored in the memory. The processor reads and executes the programs stored in the memory. Further, the processor controls each part of the plasma processing apparatus 100 via the input / output interface based on the process data, etc. stored in the memory.

[0042] [Relationship between Control Variables and Plasma]

[0043] Figure 3 is a diagram showing an example of the relationship between a control variable and the light emission intensity of plasma. In Figure 3 this example, the control amounts of VC1 and VC2 included in the matcher 152 are used as an example of control variables. The control amounts of VC1 and VC2 are amounts corresponding to the overlapping area between the electrodes of the stator and the electrodes of the rotor, and are control amounts when the control amount in the state where the capacitance value of the electrode plate is the lowest is set to 0% and the control amount in the state where the capacitance value is the highest is set to 100%. The control variable is an example of an adjustable variable related to the matching of the impedance between the high-frequency power supply 150 and the plasma.

[0044] For example, as Figure 3 shown, the light emission intensity of the plasma varies according to the combination of the control amounts of VC1 and VC2. In Figure 3 it is shown that the higher the light emission intensity of the plasma, the more efficiently the high-frequency power from the high-frequency power supply 150 can be supplied to the plasma, and the better the impedance matching between the high-frequency power supply 150 and the plasma. Among them, the maximum point P M corresponds to the light emission intensity of the plasma in the state where the impedance between the high-frequency power supply 150 and the plasma is most matched. The maximum point P M is an example of a matching point.

[0045] For example, when graphing the distribution of the light emission intensity of the plasma in the direction along the straight line L passing through the maximum point P Figure 3 it is, for example, as M shown in Figure 4 and Figure 5 like that. Figure 4 and Figure 5 are diagrams showing an example of a method for adjusting a variable. For example, as Figure 4 shown, the change amount of the light emission intensity of the plasma (i.e., the slope of the change in the light emission intensity) with respect to the change amount of the control variable in the direction along the straight line L varies according to the value of the control variable.

[0046] Here, when controlling the control variable in the direction from the direction with a gentle slope of the change in the light emission intensity along the straight line L toward the maximum point P M where the light emission intensity is the maximum, the light emission intensity of the plasma is, for example, asFigure 4 changes as indicated by the solid-line arrow. In this case, during the control of the control variable along the straight line L towards the maximum point P M even if the plasma is ignited during the process of controlling the control variable, due to overshoot of the control or the like, the light emission intensity sometimes decreases sharply as Figure 4 indicated by the dashed-line arrow. As a result, the ignited plasma sometimes extinguishes.

[0047] On the other hand, for example, as Figure 5 shown, in the case of controlling the control variable along the straight line L towards the maximum point P from the direction where the slope of the change in the light emission intensity is steep M the light emission intensity of the plasma changes, for example, as Figure 5 indicated by the solid-line arrow. In this case, during the process of controlling the control variable along the straight line L towards the maximum point P M the plasma is ignited, and due to overshoot of the control or the like, the light emission intensity decreases as Figure 5 indicated by the dashed-line arrow. However, after passing through the maximum point P M the light emission intensity decreases slowly. Therefore, it is possible to perform fine adjustment of the control variable before the plasma extinguishes, and it is possible to make the light emission intensity of the plasma approach the maximum point P again M . As a result, it is possible to stably ignite the plasma.

[0048] Therefore, preferably, in the relationship between the control variable and the light emission intensity of the plasma, the control direction of the control variable where the slope of the change in the light emission intensity is steep is determined, and the control variable is controlled along the determined control direction towards the maximum point P where the light emission intensity is maximum M to control the control variable.

[0049] [Method for determining the control direction]

[0050] In order to determine the control direction of the control variable, first, in the state where the plasma is ignited, the light emission intensity of the plasma is measured while controlling the control variable and measuring the value of each control variable. Moreover, for example, as Figure 6 shown, the measured values of the light emission intensity collected are marked on the coordinates with each control variable as the axis. Figure 6 is a diagram for explaining an example of the method for determining the control direction. In Figure 6 this example, the control amount of VC1 and the control amount of VC2 included in the matcher 152 are used as an example of the control variable.

[0051] Next, the point corresponding to the combination of the control variables with the maximum measured value of the light emission intensity among the measured values of the light emission intensity marked on the coordinates is determined as the maximum point P M .

[0052] Next, the measurement point P with the steepest slope of the change in the measured value of the emission intensity with respect to the vector V starting from the point (measurement point P) corresponding to the combination of each control variable and ending at the maximum point P M is determined as the passing point P P . The passing point P P is the point where the slope of the change in the emission intensity in the direction towards the maximum point P M is the steepest.

[0053] Next, the vector V starting from the passing point P P and ending at the maximum point P M is determined P . The direction of the vector V P is the control direction of the control variable.

[0054] In addition, the ratio of the difference between the emission intensity at the maximum point P M and the emission intensity at the measurement point P to the magnitude of the vector V is calculated as the slope of the change in the measured value of the emission intensity at the measurement point P. When the measured value of the emission intensity is regarded as a function of the control variable, the directional derivative in the direction indicated by the vector V can be calculated as the slope of the change in the measured value of the emission intensity at the measurement point P. Additionally, it is necessary to make the determined passing point P P a point in the direction indicated by the vector V P such that: on the vector V P from the passing point P M to the maximum point P P , the measured value of the emission intensity increases monotonically. Therefore, when the measured value of the emission intensity decreases in at least a part of the vector V P in the direction indicated by the vector V P from the passing point P M to the maximum point P P , it is not determined as the passing point P P .

[0055] Next, the straight line L1 including the determined vector V is determined. Moreover, on the straight line L1, the point corresponding to the combination of the control variables in the region where the plasma is not ignited and further away from the maximum point P P than the passing point P M is determined as the start point P S of the control. In addition, regarding the start point P S , it is desirable that the measured value of the emission intensity is constant or increases monotonically on the straight line L1 from the start point P S to the passing point P P .

[0056] [Ignition Control]

[0057] ​​​​​​​​​​​​​​​​​​​In the process actually performed using plasma, each control variable is controlled so that the luminous intensity of the plasma changes from the starting point P S along the straight line L1 towards the maximum point P M . At this time, for example, as Figure 7 shown, the magnitude of the power of the reflected wave with respect to the high-frequency power supplied from the high-frequency power supply 150 to the upper electrode 104 is measured. Figure 7 is a diagram showing an example of the change in the power of the reflected wave.

[0058] Next, the point corresponding to the combination of the values of the control variables at the timing t p when the slope of the decrease in the power of the reflected wave is the largest is determined as the limit point P L . Moreover, after the plasma is actually ignited, for example, as Figure 8 shown, on the coordinates with each control variable as an axis, the straight line passing through the limit point P L and orthogonal to the straight line L1 is determined as the limit line L2. Figure 8 is a diagram for explaining an example of the limit point P L and the limit line L2. Moreover, the control variables on the side closer to the maximum point P M than the limit line L2 are used to adjust the plasma. Thus, in the adjustment of the control variables performed after ignition, the values of the control variables on the side closer to the starting point P S than the limit line L2 are not used, so that the extinction of the plasma can be suppressed.

[0059] Thus, in the process actually performed using plasma, each control variable is controlled, for example, as Figure 9 shown, so that the luminous intensity of the plasma changes. Figure 9 is a diagram for explaining an example of the control of the control variables during the execution of the process.

[0060] First, each control variable is controlled so that the luminous intensity of the plasma changes along the straight line L1 from the starting point P S towards the maximum point P M . Moreover, the limit point P L is determined based on the change in the power of the reflected wave, and the ignition of the plasma is detected. After the plasma is ignited, the control variables on the side closer to the maximum point P L than the limit point P M (the values of the control variables included in the range ΔL) are used to adjust the plasma. In the range ΔL, the change in the luminous intensity of the plasma is gentle, so that even if there is a slight overshoot in the control, the risk of plasma extinction is small. Therefore, in the adjustment of the control variables performed after ignition, the extinction of the plasma can be suppressed.

[0061] In addition, in Figure 8On the illustrated straight line L1, a point P S closer to the limit point P L than the starting point P S is updated to a new starting point P S . Thus, when plasma ignition is performed next time, the time required from the start of control to plasma ignition can be shortened.

[0062] [Data collection and processing]

[0063] Figure 10 is a flowchart showing an example of data collection and processing. In Figure 10 the illustrated data collection and processing, the light emission intensity of the plasma is measured for each combination of control variables, and the maximum point P M is determined based on the distribution of the measured light emission intensity of the plasma, and the point P P and the starting point P S are passed through. Figure 10 The illustrated data collection and processing is implemented by the control device 200 controlling each part of the plasma processing device 100.

[0064] First, plasma is generated in the processing chamber 161 under the control amounts of the predetermined VC1 and VC2 (S10).

[0065] Next, the control device 200 selects an unselected control amount value from the predetermined control amount values of VC1 (S11). In step S11, the control device 200 sequentially selects the control amount values of VC1 at a step of 1% among the control amount values of VC1 from 0% to 100%, for example.

[0066] Next, the control device 200 selects an unselected control amount value from the predetermined control amount values of VC2 (S12). In step S12, the control device 200 sequentially selects the control amount values of VC2 at a step of 1% among the control amount values of VC2 from 0% to 100%, for example.

[0067] Next, the measuring device 170 measures the light emission intensity of the plasma in the processing chamber 161 (S13). The control device 200 stores the information on the light emission intensity of the plasma measured by the measuring device 170 in the memory corresponding to the control amount selected in step S11 and the control amount selected in step S12.

[0068] Next, the control device 200 determines whether all the control amount values among the predetermined control amount values of VC2 have been selected (S14). If there is an unselected control amount value (S14: "No"), the control device 200 executes the process shown in step S12 again.

[0069] On the other hand, when all the control quantity values have been selected (S14: "Yes"), the control device 200 determines whether all the control quantity values among the predetermined VC1 control quantity values have been selected (S15). When there are unselected control quantity values (S15: "No"), the control device 200 executes the process shown in step S11 again. The processes of steps S10 to S15 are an example of a collection process.

[0070] On the other hand, when all the control quantity values have been selected (S15: "Yes"), the control device 200 uses the collected data to determine the passing point P P (S16). For example, with respect to the light emission intensity of the plasma, the control device 200 calculates the slope of the change in the measured value of the light emission intensity with respect to the vector V starting from the point corresponding to each control variable and ending at the maximum point P M in the relationship of the control variables (the control quantity of VC1 and the control quantity of VC2). Moreover, the control device 200 determines the point corresponding to the combination of the control variable values with the maximum slope of the change in the measured value of the light emission intensity with respect to the vector V as the passing point P P . Step S16 is an example of a first determination process.

[0071] Next, the control device 200 uses the determined passing point P P to determine the starting point P S (S17). For example, the control device 200 includes the vector V P from the passing point P M to the maximum point P P and determines the point on the straight line L1 that is farther from the maximum point P P than the passing point P M as the control starting point P S . Step S17 is an example of a second determination process. Then, the data collection process shown in this flowchart ends.

[0072] [Ignition assistance process]

[0073] Figure 11 is a flowchart showing an example of the ignition assistance process. Figure 11 The illustrated ignition assistance process is implemented by the control device 200 controlling each part of the plasma processing apparatus 100. In addition, before starting Figure 11 the illustrated ignition assistance process, the semiconductor wafer W has been placed on the mounting table 110, the processing gas has been supplied into the processing chamber 161, and the inside of the processing chamber 161 has been adjusted to a predetermined pressure.

[0074] First, the control device 200 controls the high-frequency power supply 150 and the matcher 152 to set the control amount of VC1 and the control amount of VC2 to values corresponding to the starting point P S (S20). Then, the control device 200 determines whether plasma has been ignited in the processing chamber 161 (S21). In the present embodiment, when the magnitude of the reflected wave power output from the matcher 152 decreases below a predetermined threshold, the control device 200 determines that plasma has been ignited in the processing chamber 161. Step S21 is an example of a measurement process.

[0075] In addition, the control device 200 may determine that plasma has been ignited in the processing chamber 161 when the light emission intensity output from the measuring device 170 increases above a predetermined threshold. Further, the control device 200 may determine that plasma has been ignited in the processing chamber 161 when the magnitude of the reflected wave power output from the matcher 152 decreases below a predetermined threshold and the light emission intensity output from the measuring device 170 increases above a predetermined threshold.

[0076] When plasma has not been ignited in the processing chamber 161 (S21: "No"), for example, as Figure 8 described, the control device 200 changes the control amount of VC1 and the control amount of VC2 by a specified amount so that the light emission intensity of the plasma changes along the straight line L1 toward the maximum point P M (S22). Then, the process shown in step S21 is executed again. Step S22 is an example of an ignition process.

[0077] On the other hand, when plasma has been ignited in the processing chamber 161 (S21: "Yes"), the control device 200 determines the limit point P L based on the history of the magnitude of the reflected wave power output from the matcher 152 (S23). For example, as Figure 7 and Figure 8 described, the control device 200 determines the point corresponding to the combination of the control amount values of VC1 and VC2 at which the slope of the decrease in the reflected wave power is the largest as the limit point P L . Step S23 is an example of a third determination process.

[0078] Then, for example, as Figure 8 described, the control device 200 determines the straight line passing through the limit point P L and orthogonal to the straight line L1 as the limit line L2 (S24). Then, the control device 200 updates the point P S closer to the limit point P L than the starting point P S ' as the new starting point P S(S25). Step S25 is an example of an update process.

[0079] Next, the control device 200 performs stable control of the plasma (S26). In step S26, the control amounts of VC1 and VC2 corresponding to the points on the side closer to the maximum point P than the limit line L2 are used to adjust the control amounts of VC1 and VC2 so that the impedance between the high-frequency power supply 150 and the plasma is further matched. Specifically, the control amounts of VC1 and VC2 are adjusted so that the magnitude of the reflected wave power output from the matcher 152 becomes smaller. In addition, the adjustment of the control amount of VC1 and the adjustment of the control amount of VC2 can be performed simultaneously, alternately, or only one of them. Step S26 is an example of a stable control process. M Next, the control device 200 determines whether the plasma processing for the semiconductor wafer W has ended based on the process stored in the memory (S27). If the plasma processing has not ended (S27: "No"), the process shown in step S26 is executed again.

[0080] On the other hand, if the plasma processing has ended (S27: "Yes"), the control device 200 stops the supply of high-frequency power. Then, the processed semiconductor wafer W is taken out of the processing chamber 161, and the ignition assist processing shown in this flowchart ends.

[0081] In addition, in the example of

[0082] In addition, in the example of Figure 11 the process of updating the start point P (S25) is performed between the process of determining the limit line L2 (S24) and the process of performing stable control of the plasma (S26), but the disclosed technology is not limited to this. For example, the process of updating the start point P (S25) can be performed after the plasma processing ends (S27: "Yes"). In addition, the process of updating the start point P (S25) can be performed before starting the ignition assist processing for the next semiconductor wafer W, or can be performed immediately before the process of setting the control amounts of VC1 and VC2 to the values corresponding to the start point P (S20). S the process of updating the start point P (S25) is performed between the process of determining the limit line L2 (S24) and the process of performing stable control of the plasma (S26), but the disclosed technology is not limited to this. For example, the process of updating the start point P (S25) can be performed after the plasma processing ends (S27: "Yes"). In addition, the process of updating the start point P (S25) can be performed before starting the ignition assist processing for the next semiconductor wafer W, or can be performed immediately before the process of setting the control amounts of VC1 and VC2 to the values corresponding to the start point P (S20). S the process of updating the start point P (S25) can be performed after the plasma processing ends (S27: "Yes"). In addition, the process of updating the start point P (S25) can be performed before starting the ignition assist processing for the next semiconductor wafer W, or can be performed immediately before the process of setting the control amounts of VC1 and VC2 to the values corresponding to the start point P (S20). S the process of updating the start point P (S25) can be performed before starting the ignition assist processing for the next semiconductor wafer W, or can be performed immediately before the process of setting the control amounts of VC1 and VC2 to the values corresponding to the start point P (S20). S the process of updating the start point P (S25) can be performed immediately before the process of setting the control amounts of VC1 and VC2 to the values corresponding to the start point P (S20).

[0083] [Hardware]

[0084] The control device 200 is implemented by a computer 90 having a structure as shown in Figure 12 for example. Figure 12FIG. 0 is a diagram showing an example of a computer 90 that implements the functions of the control device 200. The computer 90 includes a CPU (Central Processing Unit) 91, a RAM (Random Access Memory) 92, a ROM (Read Only Memory) 93, an auxiliary storage device 94, a communication I / F (Interface) 95, an input / output I / F 96, and a media I / F 97.

[0085] The CPU 91 operates based on a program stored in the ROM 93 or the auxiliary storage device 94 to control each part. The ROM 93 stores a startup program executed by the CPU 91 when the computer 90 starts up, a program depending on the hardware of the computer 90, and the like.

[0086] The auxiliary storage device 94 is, for example, an HDD (Hard Disk Drive) or an SSD (Solid State Drive), and stores a program executed by the CPU 91, data used by this program, and the like. The CPU 91 reads the program from the auxiliary storage device 94 and loads it onto the RAM 92, and executes the loaded program.

[0087] The communication I / F 95 communicates with the plasma processing device 100 via a communication line such as a LAN (Local Area Network). The communication I / F 95 receives data from the plasma processing device 100 via the communication line and sends it to the CPU 91, and sends the data generated by the CPU 91 to the plasma processing device 100 via the communication line.

[0088] The CPU 91 controls an input device such as a keyboard and an output device such as a display via the input / output I / F 96. The CPU 91 obtains a signal input from the input device via the input / output I / F 96 and sends it to the CPU 91. In addition, the CPU 91 outputs the generated data to the output device via the input / output I / F 96.

[0089] The media I / F 97 reads the programs or data stored in the storage medium 98 and stores them in the auxiliary storage device 94. The storage medium 98 is, for example, an optical recording medium such as a DVD (Digital Versatile Disc), a PD (Phase change rewritable Disk), a magneto-optical recording medium such as an MO (Magneto-Optical disk), a tape medium, a magnetic recording medium, or a semiconductor memory. The process steps of the process, the data collected through data collection processing, the maximum point P M and the passing point P P are stored in the auxiliary storage device 94, along with the straight line L1, the starting point P S and the limiting point P L and the limiting line L2 and other information.

[0090] The CPU 91 of the computer 90 reads the program loaded onto the RAM 92 from the recording medium 98 and stores it in the auxiliary storage device 94. However, as another example, the program can also be obtained from another device via a communication line and stored in the auxiliary storage device 94.

[0091] One embodiment has been described above. As described above, the plasma processing system 1 in this embodiment includes a plasma processing device 100 and a control device 200. The plasma processing device 100 has a processing container 102 for accommodating the semiconductor wafer W, and performs plasma processing on the semiconductor wafer W by generating plasma in the processing container 102. The control device 200 controls the plasma processing device 100. In addition, the control device 200 executes a collection process, a first determination process, a second determination process, and an ignition process. In the collection process, values of various adjustable variables related to the matching of the impedance between the high-frequency power supply 150 that supplies high-frequency power to the co-directional plasma and the plasma are collected, and measured values indicating the matching state of the impedance between the high-frequency power supply 150 and the plasma are collected. In the first determination process, the point corresponding to the value of the variable with the largest slope of the change in the measured value with respect to the vector V from the point corresponding to each variable to the maximum point P M is determined as the passing point P P , and the maximum point P M is the point corresponding to the measured value in the state of the best impedance match. In the second determination process, a point on the straight line L1 including the passing point P P and the maximum point P M that is farther from the maximum point P P than the passing point P M is determined as the starting point P S for control. In the ignition process, each variable is controlled so that the measured value changes from the starting point P SAlong the straight line L1 towards the maximum point P M varies, thereby igniting the plasma within the plasma processing apparatus 100. Thereby, stable plasma ignition can be achieved.

[0092] In addition, in the above-described embodiment, the slope of the change in the measured value in the first determination step is obtained by dividing the difference between the measured value at the maximum point P M and the measured value at the point corresponding to the same variable by the magnitude of the vector V. Thereby, the slope of the change in the measured value in the direction towards the maximum point P M can be calculated.

[0093] In addition, in the above-described embodiment, when the measured value is regarded as a function of the variable, the slope of the change in the measured value in the first determination step is the directional derivative in the direction of the vector V. Thereby, the slope of the change in the measured value in the direction towards the maximum point P M can be calculated.

[0094] In addition, in the above-described embodiment, the measured value representing the matching state of the impedance between the high-frequency power supply 150 and the plasma is the light emission intensity of the plasma. Thereby, the matching state of the impedance between the high-frequency power supply 150 and the plasma can be estimated with high precision.

[0095] In addition, in the above-described embodiment, after plasma ignition, the control device 200 executes a stabilization control step, in which the values of the respective variables are adjusted to further match the impedance between the high-frequency power supply 150 and the plasma. Thereby, the impedance between the high-frequency power supply 150 and the plasma can be matched with higher precision.

[0096] In addition, in the above-described embodiment, the control device 200 further executes a measurement step and a third determination step. In the measurement step, the power of the reflected wave of the high-frequency power from the upper electrode 104 is measured during the ignition step. In the third determination step, the point corresponding to the value of the variable when the slope of the decrease in the power of the reflected wave is the maximum is determined as the limit point P L . In the stabilization control step, the values of a plurality of variables closer to the maximum point P L than the straight line L2 passing through the limit point P M and orthogonal to the straight line L1 are used for adjustment. Thereby, plasma extinction can be suppressed.

[0097] In addition, in the above-described embodiment, the control device 200 further executes updating the point P S on the straight line L1 closer to the limit point P L than the start point P S ' to a new start point P SThe update process. Thereby, when plasma ignition is performed next time, the time required from the start of control to plasma ignition can be shortened.

[0098] In addition, in the above-described embodiment, the adjustable variables related to the impedance matching between the high-frequency power supply 150 and the plasma can be multiple variables. In this case, in the collection process, for each combination of values of the multiple adjustable variables related to the impedance matching between the high-frequency power supply 150 and the plasma, a measured value indicating the impedance matching state between the high-frequency power supply 150 and the plasma is collected. In addition, in the first determination process, the point corresponding to the combination of variable values with the maximum slope of the change in the measured value with respect to the vector V from the point corresponding to each variable of the multiple variables to the maximum point P M is determined as the passing point P P . Thereby, variables that are more in line with the actual system can be used, and plasma ignition can be stably achieved.

[0099] In addition, in the above-described embodiment, the multiple variables include at least one of the control amount of VC1 and the control amount of VC2 included in the matcher 152 connected between the upper electrode 104 that supplies high-frequency power to the plasma processing apparatus 100 and the high-frequency power supply 150. Thereby, the impedance matching between the high-frequency power supply 150 and the plasma can be easily adjusted.

[0100] [Other]

[0101] In addition, the disclosed technology is not limited to the above-described embodiments, and various modifications can be made within the scope of its gist.

[0102] For example, in the above-described embodiment, the light emission intensity of the plasma is used as the measured value indicating the impedance matching state between the high-frequency power supply 150 and the plasma. However, the disclosed technology is not limited thereto. For example, the magnitude of the power of the reflected wave with respect to the high-frequency power supplied from the high-frequency power supply 150 to the plasma, the ratio of the high-frequency power supplied from the high-frequency power supply 150 to the plasma to the power of the reflected wave, or the ratio of V pp of the high-frequency power to V dc can be used as the measured value indicating the impedance matching state between the high-frequency power supply 150 and the plasma. Alternatively, a value selected from the group including these values and the light emission intensity of the plasma or a combination of two or more values can be used as the measured value indicating the impedance matching state between the high-frequency power supply 150 and the plasma. In addition, V pp of the high-frequency power is the difference between the maximum value and the minimum value of the voltage waveform, and V dc of the high-frequency power is the DC bias voltage superimposed on the high-frequency power.

[0103] In addition, in the above-described embodiment, as an example of an adjustable variable related to the matching of the impedance between the high-frequency power supply 150 and the plasma, the control amounts of VC1 and VC2 in the matcher 152 are used, but the disclosed technology is not limited thereto. For example, in Figure 2 's example, two variable capacitors (VC1 and VC2) are provided in the matcher 152, but a variable inductor (VL) based on a coil can be used to replace at least one variable capacitor. In addition, in Figure 2 's example, VC2 is connected between the node between the high-frequency power supply 150 and VC1 and the ground potential, but VC2 can also be connected between the node between VC1 and the upper electrode 104 and the ground potential, and an additional variable capacitor VC3 can be connected to the node between VC1 and the upper electrode 104.

[0104] In addition, in the above-described embodiment, the high-frequency power supply 150 supplies high-frequency power of a predetermined single frequency to the upper electrode 104, but the disclosed technology is not limited thereto. For example, the high-frequency power supply 150 can supply high-frequency power of a frequency modulated by ±2% to 20% or so with respect to a fundamental frequency (e.g., 60 MHz) to the upper electrode 104. In this case, the control device 200 modulates the frequency of the high-frequency power output from the high-frequency power supply 150 so that the output impedance of the high-frequency power supply 150 matches the impedance of the plasma in the processing chamber 161. As an adjustable variable related to the impedance matching, for example, a control amount related to the frequency of the high-frequency power that can be modulated with respect to the fundamental frequency and is represented by a ratio [%] can be used.

[0105] In addition, as adjustable variables related to the matching of the impedance between the other high-frequency power supply 150 and the plasma, the type of the processing gas, the pressure of the processing gas, the flow rate of the processing gas, the pressure in the processing chamber 161, the temperature of the semiconductor wafer W, etc. can be used. In addition, the variables used at the time of plasma ignition and the variables used for the stable control of the plasma after plasma ignition can be the same or different.

[0106] In addition, in the above-described embodiment, the impedance matching between the high-frequency power supply 150 and the plasma is performed by adjusting a plurality of variables, but the disclosed technology is not limited thereto, and the matching can also be performed by adjusting one variable. For example, the control amount of VC2 and other variables can be fixed, and a series of controls can be performed only by the control amount of VC1.

[0107] In addition, in the above-described embodiment, the maximum point P determined based on the data collected and processed through data collection processing Mis used as a point corresponding to the state of the most optimal impedance matching between the high-frequency power supply 150 and the plasma, but the disclosed technology is not limited thereto. For example, in the stable control after plasma ignition, the actual most optimal impedance matching point P between the high-frequency power supply 150 and the plasma M is used to update the maximum point P M . At the maximum point P M when it is updated, the updated maximum point P M is used to update the vector V P , the straight line L1, and the starting point P S . Thus, it is possible to control the ignition of the plasma based on the measured values obtained in the environment where the process is actually carried out.

[0108] Alternatively, it may be that when the maximum point P M is updated, in order to make the end point coincide with the updated maximum point P M the vector V P is translated in parallel, and thus the starting point of the vector V P , that is, the passing point P P is updated. In this case, the updated maximum point P M and the passing point P P are used to update the straight line L1 and the starting point P S .

[0109] In addition, in the above-described embodiment, as an example of the plasma source, the plasma processing system 1 that uses capacitively coupled plasma (CCP) for processing has been described, but the plasma source is not limited thereto. As plasma sources other than capacitively coupled plasma, for example, inductively coupled plasma (ICP), microwave-excited surface wave plasma (SWP), electron cyclotron resonance plasma (ECP), helicon wave-excited plasma (HWP), etc. are listed. That is, it is not limited to a plasma source that uses a high-frequency power supply and an electrode such as capacitively coupled plasma (CCP), and the same control can also be performed in a plasma source that has adjustable variables related to the impedance matching between the plasma generation power supply and the plasma, such as inductively coupled plasma (ICP) that uses a high-frequency power supply and an antenna, and microwave-excited surface wave plasma (SWP) that uses a microwave power supply and a waveguide.

[0110] Furthermore, it should be considered that the embodiments disclosed this time are illustrative in all aspects and not restrictive. In fact, the above-described embodiments can be specifically implemented in various ways. In addition, the above-described embodiments can be omitted, replaced, and changed in various ways without departing from the appended claims and their gist.

Claims

1. A plasma processing system, comprising: A plasma processing apparatus having a processing container for accommodating a substrate, and performing plasma processing on the substrate by generating plasma in the processing container; and A control device for controlling the plasma processing apparatus, Among them, The control device performs the following processes: A collection process of collecting measured values representing the impedance matching state between the power supply unit that supplies high-frequency power to the plasma and the plasma for each adjustable variable value related to the impedance matching; A first determination process of determining, as a passing point, the value of the variable corresponding to the point where the slope of the change in the measured value with respect to the vector from the point corresponding to each variable to the matching point is the largest, the matching point being the point corresponding to the measured value in the state of the best impedance match; A second determination process of determining, as a start point of control, the point on the straight line including the passing point and the matching point that is farther from the matching point than the passing point; And An ignition process of controlling each variable so that the measured value changes from the start point along the straight line to the matching point, thereby igniting plasma in the plasma processing apparatus.

2. The plasma processing system according to claim 1, wherein In the first determination process, the slope of the change in the measured value is obtained by dividing the difference between the measured value at the matching point and the measured value at the point corresponding to the variable by the magnitude of the vector.

3. The plasma processing system according to claim 1, wherein In the first determination process, when the measured value is regarded as a function of the variable, the slope of the change in the measured value is the directional differential value in the direction indicated by the vector.

4. The plasma processing system according to any one of claims 1 to 3, wherein The measured value representing the impedance matching state between the power supply unit and the plasma is one value or a combination of two or more values selected from the group including the following values: the light emission intensity of the plasma; the magnitude of the power of the reflected wave of the high-frequency power supplied from the power supply unit to the plasma; The ratio of the high-frequency power supplied from the power supply unit to the plasma to the power of the reflected wave; And the ratio of the difference between the maximum value and the minimum value of the voltage waveform of the high-frequency power to the DC bias voltage superimposed on the high-frequency power.

5. The plasma processing system according to any one of claims 1 to 3, wherein A stable control process is performed after the plasma ignition. In the stable control process, the values of each variable are adjusted to further match the impedance between the power supply unit and the plasma.

6. The plasma processing system according to claim 5, wherein The control device further performs the following processes: A measurement process of measuring the power of the reflected wave of the high-frequency power from the conductor that supplies high-frequency power to the inside of the plasma processing apparatus during the ignition process; and a third determination step of determining, as a limit point, a point corresponding to a value of the variable having the steepest slope of decrease in the power of the reflected wave In the stable control step, adjustment is performed using a value of the variable closer to the matching point side than a straight line passing through the limit point and orthogonal to the straight line 7. The plasma processing system according to claim 6, wherein the control device further performs an update step in which a point on the straight line closer to the limit point than the start point is updated as a new start point 8. The plasma processing system according to any one of claims 1 to 3, wherein the variable is a plurality of variables in the collection step, for each combination of values of the plurality of adjustable variables related to matching of the impedance between the power supply unit that supplies high-frequency power to the plasma and the plasma, a measurement value indicating the matching state of the impedance between the power supply unit and the plasma is collected in the first determination step, a point corresponding to a combination of values of the variable having the steepest slope of change in the measurement value with respect to a vector from a point corresponding to each variable of the plurality of variables to the matching point is determined as the passing point 9. The plasma processing system according to any one of claims 1 to 3, wherein the variable includes at least one of a control amount of a variable capacitor included in a matcher connected between a conductor that supplies high-frequency power to the plasma processing apparatus and a high-frequency power source and a control amount related to the frequency of the high-frequency power 10. A plasma ignition assist method, comprising the following steps a collection step of collecting, in a plasma processing apparatus, for each value of each adjustable variable related to matching of the impedance between a power supply unit that supplies high-frequency power to the plasma and the plasma, a measurement value indicating the matching state of the impedance between the power supply unit and the plasma a first determination step of determining, as a passing point, a point corresponding to a value of the variable having the steepest slope of change in the measurement value with respect to a vector from a point corresponding to each of the variables to a matching point, the matching point being a point corresponding to the measurement value in a state of optimal impedance matching a second determination step of determining, as a start point of control, a point on a straight line including the passing point and the matching point and farther from the matching point than the passing point and an ignition step of controlling each of the variables so that the measurement value changes from the start point along the straight line toward the matching point, thereby igniting plasma in the plasma processing apparatus 11. The plasma ignition assist method according to claim 10 a stable control step is performed after the plasma ignition, in which the values of each of the variables are adjusted to further match the impedance between the power supply unit and the plasma 12. The plasma ignition assist method according to claim 11, further performing the following step A measurement step of measuring the power of the reflected wave of the high-frequency power from a conductor that supplies high-frequency power to the inside of the plasma processing apparatus in the ignition step; and A third determination step of determining a limit point as the point corresponding to the value of the variable with the maximum slope of the decrease in the power of the reflected wave, In the stable control step, adjustment is performed using the value of the variable closer to the matching point side than the straight line passing through the limit point and orthogonal to the straight line.

13. The plasma ignition assist method according to claim 12, An update step is further performed, in which a point on the straight line closer to the limit point than the start point is updated as a new start point.

14. The plasma ignition assist method according to any one of claims 10 to 13, characterized in that The variable is a plurality of variables, In the collection step, for each combination of values of the plurality of adjustable variables related to the matching of the impedance between the power supply unit that supplies high-frequency power to the plasma and the plasma, a measured value indicating the matching state of the impedance between the power supply unit and the plasma is collected, In the first determination step, the point corresponding to the combination of the values of the variables with the maximum slope of the change in the measured value with respect to the vector from the point corresponding to each variable of the plurality of variables to the matching point is determined as the passing point.

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