Flow rate control method and plasma processing apparatus

Abstract

To improve controllability and to reduce cost by reducing the number of parts.SOLUTION: The controller 119 of the plasma etching processing apparatus 100 controls the flow rate of the cooling water of the coil 107. After the start of the process treatment, the control device 119 controls the flow rate of the cooling water so that the coil temperature does not exceed the rated temperature based on the output set value of the coil 107 in the process treatment. When the coil temperature calculated from the resistance value of the coil 107 reaches a preset target temperature, the control device 119 controls the flow rate of the cooling water so that the coil temperature is maintained at the target temperature. When the power supply of the coil 107 is changed from the ON state to the OFF state, the control device 119 controls the flow rate of the cooling water until a preset necessary cooling time necessary for cooling is exceeded so that the coil temperature becomes equal to or lower than the target temperature.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to a technique such as a method for controlling the flow rate of cooling water that cools a coil for generating a magnetic field in a plasma processing apparatus. [Background technology]

[0002] Plasma processing apparatuses are known that process a substrate-shaped sample, such as a semiconductor wafer, placed on a sample stage in a processing chamber inside a vacuum vessel using plasma generated by supplying a processing gas into the processing chamber. One such plasma processing apparatus uses electromagnetic ion cyclotron resonance (Ion Cyclotron Resonance). In this type of plasma processing apparatus, a voltage is applied to a magnetic field-generating coil, which generates a magnetic field to convert the processing gas into plasma. When current flows through the magnetic field-generating coil, the coil generates heat due to Joule heating. To prevent damage to the coil due to the temperature rise caused by the heat generation, plasma processing apparatuses typically use water-cooling systems that circulate cooling water through the coil to prevent the coil from overheating.

[0003] Patent Document 1 below proposes a technique for controlling an adsorption heat pump in which the required cooling water flow rate of a heat medium is controlled using a value measured by a temperature sensor that individually detects the temperature of the heat medium as a factor. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-522623 Summary of the Invention [Problem to be solved by the invention]

[0005] In order to determine the flow rate of the cooling water based on the coil temperature and water temperature, as in the technology of Patent Document 1, it is necessary to add a water thermometer and a coil thermometer, which increases the number of parts in the plasma processing apparatus. Therefore, the first problem is that the cost of the plasma processing apparatus increases.

[0006] Next, for users of equipment to which this technology is applied, it is desirable to reduce the flow rate of the cooling water used for the coil during operation as much as possible. To achieve this, it is necessary to control the coil temperature to a value close to the threshold value and minimize the corresponding flow rate of the cooling water. Therefore, the second challenge is to control the coil temperature by cooling the coil with as little water as possible.

[0007] Concerns about setting the cooling water flow rate so that the coil temperature is just above the threshold are that the coil may be damaged if the temperature exceeds the threshold, and that leaving too much margin will result in wasted cooling water.In order to accurately control the cooling water flow rate, it is necessary to optimize the cooling water flow rate control depending on the operating status of the coil power supply.

[0008] An object of the present disclosure is to provide a technique for controlling the flow rate of cooling water in a plasma processing apparatus that can improve controllability and reduce the number of parts to reduce costs. [Means for solving the problem]

[0009] A representative embodiment of the present disclosure has the following configuration. A cooling water flow rate control method according to one embodiment controls the flow rate of cooling water for cooling a coil for generating a magnetic field in a plasma processing apparatus. The plasma processing apparatus includes a cooling water pipe unit that circulates the cooling water and a control device that controls the flow rate of the cooling water by controlling a control valve provided in the cooling water pipe unit. The flow rate control method includes a first step in which, after starting a process treatment in which a sample is treated according to process conditions using a plasma-converted process gas generated using the coil, the control device controls the flow rate of the cooling water based on an output setting value of the coil in the process treatment so that the coil temperature does not exceed a rated temperature of the coil; a second step in which, when the coil temperature calculated from the resistance value of the coil reaches a predetermined target temperature, the control device controls the flow rate of the cooling water so that the coil temperature remains at the target temperature; and a third step in which, when the power supply to the coil is switched from an ON state to an OFF state, the control device controls the flow rate of the cooling water until a predetermined required cooling time elapses so that the coil temperature remains below the target temperature.

[0010] In one embodiment, a plasma processing apparatus includes a cooling water pipe unit that circulates cooling water through a magnetic field generating coil, and a control device that controls a control valve provided in the cooling water pipe unit to control the flow rate of the cooling water. The control device executes the following three controls: a first control, in which the control device controls the flow rate of the cooling water based on an output setting value of the coil during the process after starting a process in which a sample is treated with a plasma-converted process gas generated using the coil according to process conditions, so that the coil temperature does not exceed a rated temperature of the coil; a second control, in which the control device controls the flow rate of the cooling water when the coil temperature calculated from a resistance value of the coil reaches a predetermined target temperature, so that the coil temperature is maintained at the target temperature; and a third control, in which the control device controls the flow rate of the cooling water when the power supply of the coil is switched from an ON state to an OFF state, so that the coil temperature remains below the target temperature until a predetermined required cooling time elapses. [Effects of the Invention]

[0011] According to a representative embodiment of the present disclosure, a technique for controlling cooling water in a plasma processing apparatus can be provided, which improves controllability and reduces the number of parts, thereby reducing costs. Problems, configurations, effects, etc. other than those described above will be described in the description of the embodiment. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a vertical cross-sectional view showing an outline of the configuration of a plasma processing apparatus according to an embodiment of the present invention; [Figure 2] 1 is a schematic diagram of a control system configuration according to an embodiment of the present invention. [Figure 3] 4 is a flowchart showing an example of a first control according to the embodiment of the present invention. [Figure 4] 6 is a flowchart showing an example of a second control according to the embodiment of the present invention. [Figure 5] 6 is a flowchart showing an example of a third control according to the embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0013] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. In the drawings, identical parts are generally designated by the same reference numerals, and repeated explanations will be omitted. In the drawings, the representation of components may not represent their actual positions, sizes, shapes, ranges, etc., in order to facilitate understanding of the invention.

[0014] <Technical philosophy> The plasma processing apparatus according to the present disclosure performs cooling water flow rate control in three stages, first to third, to control the coil temperature by using as little cooling water as possible depending on the operating state of the coil power supply. These stages are used for FF (feedforward) control and FB (feedback) control. The first to third stages are defined, for example, as follows:

[0015] The first control is a control of the period from OFF to ON of the coil power supply. The first control is a control performed until the current value of the coil power supply reaches a steady state after a transient phenomenon and data is collected that enables feedback control based on resistance values. The plasma processing apparatus performs FF control after the start of process processing based on the output setting value of the coil power supply for the process processing so that the cooling water volume does not exceed the rated coil temperature. This makes it effective to incorporate FF control that minimizes the cooling water flow rate into the plasma processing apparatus.

[0016] The second control is performed from the start of FB control until the coil is powered off. The second control calculates the coil temperature from the coil resistance value, and when the target temperature is reached, calculates the cooling water flow rate and performs PID control to adjust the cooling water flow rate so as to maintain the target temperature. This makes it effective to incorporate FB control that minimizes the cooling water flow rate into the plasma processing apparatus even if the plasma processing apparatus does not have a water thermometer or coil thermometer.

[0017] The third control is control of the period after the coil is powered off. After the coil is powered off, the third control calculates the required cooling time for the coil from the cooling water flow rate set in the second control, and performs FF control of the cooling water flow rate based on that time. This is because when the coil power is off, the plasma processing device cannot read the voltage value, and the apparent resistance value becomes 0, making FB control impossible. Since the coil retains heat even after the coil current value becomes 0, it must continue to be cooled to a certain extent. Therefore, it is effective to incorporate FF control into the plasma processing device, which continues to flow cooling water after the coil power supply output is turned from ON to OFF until the cooling time required to reach below the target temperature has elapsed.

[0018] <Application to plasma processing equipment> An embodiment of controlling the flow rate of cooling water for cooling the coil in the plasma processing apparatus using the above first to third controls will be described below.

[0019] In the first control, the plasma processing apparatus performs FF control to cool the coil with as little flow rate as possible and control the coil temperature based on the output setting value of the power supply for the coil under conditions such as gas type, pressure, and temperature (hereinafter referred to as "process conditions") for processing a sample on a substrate such as a semiconductor wafer. This allows the plasma processing apparatus to determine the operating state of the coil before operation and control the flow rate of cooling water to suppress or reduce the problem of Problem 2 described above.

[0020] In the second control, the plasma processing apparatus performs PID control according to the resistance value. The plasma processing apparatus estimates the coil temperature from the resistance value calculated from the monitored voltage and current values ​​of the DC power supply that applies voltage to the coil, and controls the flow rate of the cooling water so that the coil temperature reaches a predetermined target value, thereby solving the above-mentioned problems 1 and 2.

[0021] In the third control, the plasma processing apparatus continues to flow the cooling water at the flow rate in the second control, calculates the cooling time required for the coil temperature to fall below the target temperature, and controls the flow rate of the cooling water based on the calculated time, thereby performing FF control to control the coil temperature.The plasma processing apparatus solves the above-mentioned problems 1 and 2 by determining the required cooling time for the coil from the state of the coil temperature in the second control and controlling the flow rate of the cooling water.

[0022] An example of a process for controlling the control layer device of the plasma processing apparatus will be outlined below.

[0023] The coil resistance at a given temperature and the resistance at the rated temperature are calculated in advance. The recipe settings for wafer processing conditions in the wafer processing unit are read, and the power output setting for the coil for the processing is transmitted to the control device and stored in advance. With the power output setting stored in the control device, the coil power supply changes from OFF to ON. Until the current value of the coil power supply (e.g., DC power supply) passes through a transient phenomenon and reaches a steady state, the control device calculates the required cooling water flow rate from the output setting, cools the coil with as little cooling water as possible, and performs FF control to control the coil temperature. After that, the control device initiates PID control as soon as the current value of the coil power supply reaches the set value. The voltage and current values ​​monitored by the coil power supply are sent to the control device. The control device calculates the coil temperature based on the resistance calculated from the output values ​​(or the supplied current and voltage) from these power supplies. The control device then applies FB control based on the calculated coil temperature to control the cooling water flow rate. When the coil's power supply is switched from ON to OFF and it becomes impossible to calculate the coil's resistance value from the voltage and current values, the control device calculates the required cooling time until the coil temperature drops below the target temperature, and performs FF control to keep the cooling water flowing for the calculated required cooling time.

[0024] (Embodiment) Embodiments of the present disclosure will be described with reference to the drawings. The plasma processing apparatus includes, for example, a coil for generating a magnetic field and controls the flow rate of cooling water for cooling the coil. The plasma processing apparatus also includes, for example, a cooling water pipe unit for circulating cooling water through the coil, and a control device for controlling the flow rate of the cooling water by controlling a control valve provided in the cooling water pipe unit. The plasma processing apparatus will be described in detail below.

[0025] <Configuration of plasma processing apparatus> Fig. 1 is a longitudinal cross-sectional view showing a schematic outline of the configuration of a plasma processing apparatus according to this embodiment. Fig. 1 shows a plasma etching processing apparatus, as an example of a plasma processing apparatus, which uses a microwave electric field as an electric field for generating plasma, generates ECR (Electron Cyclotron Resonance) between the microwave electric field and magnetic field to generate plasma, and uses the generated plasma to etch a substrate-like sample such as a semiconductor wafer. Hereinafter, a plasma etching processing apparatus 100, as an example of the plasma processing apparatus, will be described.

[0026] 1, the plasma etching processing apparatus 100 has a vacuum vessel 101 equipped with a processing chamber 104 inside where plasma is generated. The vacuum vessel 101 has a cylindrical shape and an open top, and a dielectric window 103 (made of, for example, quartz) for introducing microwaves is arranged on the top as a cover member, forming the processing chamber 104 with the inside and outside airtightly separated.

[0027] A vacuum exhaust port 110 is disposed at the bottom of the vacuum vessel 101. The vacuum exhaust port 110 is connected to a vacuum exhaust device (not shown) disposed below and connected to the vacuum vessel 101.

[0028] Furthermore, a shower plate 102 that forms the ceiling surface of a processing chamber 104 is provided below the lower surface of a dielectric window 103 that forms the upper cover member of the vacuum vessel 101. The shower plate 102 has a plurality of gas inlet holes 102a arranged in the center. Gas for etching is introduced into the processing chamber 104 through the plurality of gas inlet holes 102a. The shower plate 102 is a circular plate made of a dielectric material such as quartz.

[0029] An electric field and magnetic field generating unit 160 is disposed above and outside the vacuum vessel 101, and generates an electric field and a magnetic field for forming the plasma 116. The electric field and magnetic field generating unit 160 includes the following components and is provided in the plasma etching processing apparatus 100.

[0030] In the electric field / magnetic field generating unit 160, a waveguide 105 is disposed above the dielectric window 103. An electric field is transmitted inside the waveguide 105 to supply a high-frequency electric field of a predetermined frequency into the processing chamber 104 for forming the plasma 116. Furthermore, the electric field transmitted inside the waveguide 105 is generated by oscillation in an electric field generating power supply 106. The frequency of the electric field is not particularly limited, but in this embodiment, microwaves of 2.45 GHz are used.

[0031] In addition, magnetic field generating coils (hereinafter referred to as "coils") 107 that form a magnetic field are arranged above the dielectric window 103 of the processing chamber 104, on the side wall of the vacuum vessel 101 that forms the cylindrical portion of the processing chamber 104, and on the outer periphery of the lower end of the waveguide 105, surrounding these.

[0032] The electric field of the microwaves generated by the electric field generating power supply 106 propagates through the inside of the waveguide 105 , passes through the dielectric window 103 and the shower plate 102 , and is supplied to the processing chamber 104 from above.

[0033] Furthermore, an ECR (Electron Cyclotron Resonance) is generated by the interaction between the electric field of the microwaves generated by the electric field generating power supply 106 and the magnetic field generated by the coil 107 and supplied into the processing chamber 104 .

[0034] Then, by exciting and dissociating atoms or molecules of the processing gas introduced into the processing chamber 104 through the gas introduction holes 102a of the shower plate 102, a high-density plasma 116 is formed in the processing chamber 104.

[0035] Furthermore, a wafer-mounting electrode (electrode) 120 constituting a sample stage is provided in the lower part of the processing chamber 104, below the space where the plasma 116 is generated. The wafer-mounting electrode (hereinafter referred to as the "sample stage") 120 has a mounting surface on which a semiconductor wafer (hereinafter simply referred to as the "wafer") 109, which is the sample (processing object), is placed. The sample stage 120 is disposed so that the mounting surface faces the shower plate 102 or the dielectric window 103.

[0036] The upper surface of the sample stage 120 is covered with a dielectric film 140 that forms the mounting surface. Inside the dielectric film 140, multiple conductive films (electrostatic attraction electrodes) 111 for electrostatic attraction are arranged, connected to a DC power supply 127 via a high-frequency filter 126 shown in FIG. 1. The conductive film 111 forms the mounting surface of the sample stage 120. The conductive film 111 is a film-like electrostatic attraction electrode to which DC power for electrostatically attracting a wafer is supplied. In this embodiment, the conductive film 111 may be bipolar, in which one of the multiple film-like electrodes is given a different polarity, or may be monopolar, in which the same polarity is given, but is shown as monopolar in this embodiment.

[0037] Further, a high frequency power supply 131 and a matching box 129 are arranged near the conductive film 111. In this embodiment, the high frequency power supply 131 and the matching box 129 are arranged below the vacuum exhaust port 110. The high frequency power supply 131 and the matching box 129 are connected to a conductive electrode substrate 108 having a circular or cylindrical shape and arranged inside the sample stage 120. The high frequency power supply 131 is connected to the ground 112.

[0038] High frequency power of a predetermined frequency is supplied from the high frequency power supply 131 to the electrode substrate 108, and during processing of the wafer 109, a bias potential is formed above the wafer 109, which is attracted and held on the upper surface of the sample stage 120. In other words, the sample stage 120 has a wafer-mounting electrode to which high frequency power is supplied from the high frequency power supply 131 while the plasma 116 is being generated.

[0039] Inside the electrode substrate 108, in order to remove the transferred heat and cool the sample stage 120, multiple coolant flow paths 152 are arranged spirally or concentrically around the central axis in the vertical direction of the electrode substrate 108 or the sample stage 120. A cooling coolant for cooling the electrode substrate 108 flows through these coolant flow paths 152.

[0040] Furthermore, a recessed portion is disposed on the outer periphery of the upper portion of the sample stage 120, surrounding the outer periphery of the mounting surface. In this recessed portion, a susceptor ring 113, which is a ring-shaped member made of a dielectric material such as quartz or ceramics such as alumina, is placed on the ring-shaped upper surface formed lower than the mounting surface of the sample stage 120.

[0041] When the upper surface of the susceptor ring 113 is placed in the recess, the upper surface of the susceptor ring 113 has a dimension that makes it higher than the mounting surface of the sample stage 120. The susceptor ring 113 is disposed on the outer periphery of the mounting surface of the sample stage 120 and covers the surface of the sample stage 120.

[0042] Specifically, the susceptor ring 113 is configured to cover the upper surface of the recess, the cylindrical side wall surface of the recess, and the cylindrical side wall surface of the sample stage 120 below the recess.

[0043] In the plasma etching processing apparatus 100 described above, an unprocessed wafer 109 is placed on the tip of an arm of a wafer transfer robot disposed in a vacuum transfer chamber, which is a separate vacuum chamber connected to the side wall of the vacuum chamber 101 and whose pressure has been reduced to the same level as that of the processing chamber 104 inside the vacuum transfer chamber. A gate, which is a passage connecting the vacuum transfer chamber and the processing chamber 104, is opened by operating a valve disposed in the vacuum transfer chamber, and the unprocessed wafer 109 placed on the tip of the arm of the robot is transferred into the processing chamber 104. The wafer 109 is then transferred to above a mounting surface of a sample stage 120 in the processing chamber 104, where it is transferred onto the lift pins by vertical movement of the lift pins, and then placed on the mounting surface, where it is attracted to and held on the mounting surface of the sample stage 120 by electrostatic force generated by DC power applied from a DC power supply 127.

[0044] In this state, the etching gas has its flow rate or speed adjusted by a mass flow controller (not shown) and is introduced into the space between the dielectric window 103 and the quartz shower plate 102. After diffusing in this space, the gas is introduced into the processing chamber 104 through the gas introduction holes 102a of the shower plate 102.

[0045] Thereafter, by operating a vacuum exhaust device (not shown), gas and particles inside the processing chamber 104 are exhausted through the vacuum exhaust port 110. Depending on the balance between the amount of gas supplied from the gas inlet holes 102a of the shower plate 102 and the amount of gas exhausted from the vacuum exhaust port 110, the pressure inside the processing chamber 104 is adjusted to a predetermined value within a range suitable for processing the wafer 109.

[0046] Furthermore, while the wafer 109 is being held by suction on the sample stage 120, a thermally conductive gas such as He (helium) is supplied from an opening (not shown) in the upper surface of the dielectric film 140 to the gap between the wafer 109 and the upper surface of the dielectric film 140, which is the mounting surface of the sample stage 120. This supply of gas promotes heat transfer between the wafer 109 and the sample stage 120.

[0047] A coolant adjusted to a temperature within a predetermined range flows and circulates through a coolant flow path 152 disposed in the electrode substrate 108 of the sample stage 120, thereby adjusting the temperature of the sample stage 120 or the electrode substrate 108 before the wafer 109 is placed on it. Therefore, by heat transfer between the sample stage 120 or the electrode substrate 108, which have a large heat capacity, the temperature of the wafer 109 is adjusted to be close to these temperatures before processing, and even after processing begins, heat is transferred from the wafer 109 to adjust the temperature of the wafer 109.

[0048] A voltage is applied to the coil 107 by the coil power supply 115, thereby supplying a magnetic field to the processing chamber 104. The current value and voltage value of the coil power supply 115 at this time are transmitted from an ammeter 117 and a voltmeter 118 to a control device 119. Based on the transmitted current value and voltage value, the control device 119 can also detect the ON / OFF state of the coil power supply 115.

[0049] Cooling water supplied from chiller 121 is introduced into an outward cooling water pipe 123 for cooling coil 107 through a cooling water pipe and manifold (not shown). A flow control valve 122 is attached to outward cooling water pipe 123. Control device 119 issues an instruction to valve control unit 125 to open or close flow control valve 122. Upon receiving the opening / closing instruction, valve control unit 125 adjusts the opening / closing amount of flow control valve 122 so that the flow rate of cooling water introduced into coil 107 is as small as possible relative to the amount of heat generated by the coil.

[0050] The cooling water discharged from the outlet of the coil 107 returns to the chiller 121 through the return cooling water pipe 124 and a manifold (not shown). The temperature of the cooling water is adjusted again in the chiller 121, and the cooling water is circulated to cool the coil 107.

[0051] In this state, a microwave electric field and magnetic field are supplied into the processing chamber 104, and plasma 116 is formed using the gas. Once plasma 116 is formed, radio frequency (RF) bias power is supplied to the electrode substrate 108 from a radio frequency power supply 131. When a bias potential is formed above the upper surface of the wafer 109, charged particles such as ions in the plasma 116 are attracted to the upper surface of the wafer 109 in accordance with the potential difference between the bias potential and the potential of the plasma 116. The attracted charged particles then collide with a mask previously placed on the upper surface of the wafer 109 and with the surface of the film layer, including the film layer, of the wafer 109, thereby performing an etching process. During the etching process, the processing gas introduced into the processing chamber 104 and particles of reaction products generated during the process are exhausted from a vacuum exhaust port 110.

[0052] Next, in the plasma etching processing apparatus 100 of this embodiment, during plasma processing, high-frequency power is supplied from the high-frequency power source 132 to the conductor ring 130 arranged on the upper outer periphery of the sample stage 120 via a power supply connector 161 provided on the sample stage 120 and having an elastic conductive member.

[0053] In the sample stage 120 of this embodiment, the AC high voltage generated by the radio frequency power supply 132 is supplied to a conductor ring 130 made of a conductive material and disposed within the susceptor ring 113 via a load matching box 128 and a load impedance variable box 133. With this configuration, the load impedance variable box 133, which is adjusted to a suitable impedance value, combined with a relatively high impedance portion disposed above the susceptor ring 113, can relatively reduce the impedance value for radio frequency power from the radio frequency power supply 132 through the electrode substrate 108 to the outer periphery of the wafer 109. This allows radio frequency power to be effectively supplied to the outer periphery and outer periphery of the wafer 109, reducing the concentration of the electric field at the outer periphery and outer periphery, and attracting charged particles such as ions in the plasma to the upper surface of the wafer 109 in a desired direction.

[0054] High frequency power supply 132 is connected to ground 112. The frequency of high frequency power supply 132 in this embodiment is preferably set to the same value as that of high frequency power supply 131 or to a value that is a constant multiple of that.

[0055] <System configuration> Next, a control system for controlling the flow rate of cooling water for cooling the coil according to this embodiment will be described in more detail. FIG. 2 is a schematic diagram of the configuration of a control system 201.

[0056] 2, control system 201 is included in plasma etching processing apparatus 100. Control system 201 includes coil 107, coil power supply 115, control device 119, valve control unit 125, flow control valve 122, manifold 210, flow meter 211, and manifold 212. Plasma etching processing apparatus 100 also includes chiller 121, outward cooling water pipe 123, and return cooling water pipe 124. Chiller 121, outward cooling water pipe 123, and return cooling water pipe 124 form a cooling water pipe section.

[0057] The coil power supply 115 includes an ammeter 117 that measures the current flowing through the coil 107 and a voltmeter 118 that measures the voltage applied to the coil 107. During operation of the plasma etching processing apparatus 100, the control device 119 obtains the current value of the current supplied from the coil power supply 115 to the coil 107 from the ammeter 117 and obtains the voltage value of the voltage applied to the coil 107 from the voltmeter 118.

[0058] One end of the outward cooling water pipe 123 is connected so that cooling water is introduced from the chiller 121 into the outward cooling water pipe 123. The other end of the outward cooling water pipe 123 is connected so that cooling water is introduced to the coil 107 after passing through the manifold 210 and the flow control valve 122. One end of the return cooling water pipe 124 is connected to the coil 107 so that cooling water is introduced from the coil 107. The other end of the return cooling water pipe 124 is connected to the chiller 121 via the flow meter 211 and the manifold 212 so that cooling water introduced from the coil 107 is introduced into the chiller 121.

[0059] In this way, the cooling water flowing out from chiller 121 flows into chiller 121 via manifold 210, flow control valve 122, coil 107, flow meter 211, and manifold 212. In other words, the cooling water is configured to circulate through chiller 121, outward cooling water pipe 123, manifold 210, flow control valve 122, coil 107, flow meter 211, and return cooling water pipe 124. By calculating the temperature drop of the cooling water in chiller 121 and the temperature rise of the cooling water in coil 107, control device 119 controls the temperature of the cooling water to maintain a constant temperature.

[0060] More specifically, the control device 119 acquires the voltage value and current value of the coil power supply 115 and calculates the flow rate of cooling water required to cool the coil 107. Next, the control device 119 instructs the valve control unit 125 to adjust the opening of the flow rate control valve 122 so that the calculated flow rate can flow through the coil 107. Upon receiving the instruction, the valve control unit 125 adjusts the flow rate control valve 122 to control the flow rate of cooling water introduced into the coil 107.

[0061] Next, a method for controlling the flow rate of cooling water that cools the coil 107 according to an embodiment will be described. Figures 3, 4, and 5 are flowcharts showing an example of flow rate control executed by the control device 119. This flowchart shows an example of a method for controlling the flow rate of cooling water in three stages depending on the operating state of the coil power supply 115.

[0062] 3 is a flowchart showing an example of the first control. In the first control, after the start of a process in which wafer 109 is processed according to process conditions using a process gas plasma generated using coil 107, controller 119 controls the flow rate of cooling water based on the output setting value of coil 107 in the process so that the coil temperature of coil 107 does not exceed the rated temperature of coil 107.

[0063] 4 is a flowchart showing an example of the second control, in which, when the coil temperature calculated from the resistance value of the coil 107 reaches a preset target temperature, the control device 119 controls the flow rate of the cooling water so that the coil temperature is maintained at the target temperature.

[0064] 5 is a flowchart showing an example of the third control. In the third control, when the power supply of the coil 107 is switched from an ON state to an OFF state, the control device 119 controls the flow rate of the cooling water until a predetermined required cooling time required for cooling is exceeded so that the coil temperature becomes equal to or lower than the target temperature.

[0065] In step S300 of FIG. 3, the control device 119 calculates in advance the resistance value R of the coil at an arbitrary temperature. C1 and temperature rating R C2 The resistance values ​​thus determined may be stored in a predetermined memory in the control device 119.

[0066] With the resistance value stored in the control device 119, the first control is started. After the first control is started, in step S301, the control device 119 reads the recipe setting values ​​(setting contents) of the process conditions. Here, the recipe setting values ​​are, for example, parameters of the process conditions during plasma etching processing. The control device 119 can acquire the output setting value of the coil power supply from the recipe setting values. The control device 119 confirms the output setting value of the coil power supply in the process conditions and proceeds to the processing of step S302.

[0067] Next, in step S302, the control device 119 starts the flow rate control of the cooling water. After the flow rate control of the cooling water is started, the process proceeds to step S303.

[0068] In step S303, the control device 119 changes the cooling water flow rate to a value that does not exceed the rated coil temperature according to the set current value set in the output setting value. The control device 119 calculates the cooling water flow rate that does not exceed the rated coil temperature according to the set current value, and sends an instruction to the valve control unit 125 to adjust the valve opening so that the cooling water flows at the calculated flow rate. As a result, the cooling water is introduced into the coil 107 so that the coil 107 does not exceed the rated coil temperature described above.

[0069] In step S304, the control device 119 determines whether the current value of the coil power supply 115 has passed through a transient state and reached a steady state. The control device 119 acquires the current value of the current supplied from the coil power supply 115 to the coil 107, and makes a determination based on whether the acquired current value has reached a steady state. A steady state is, for example, when the current value remains within a certain range for a predetermined time. If it is determined that the steady state has not been reached (No in S304), the determination in step S304 is repeated. If the control device 119 determines that the steady state has been reached (Yes in S304), the process proceeds to step S305.

[0070] In step S305, the control device 119 ends the FF control based on the current value of the coil power supply 115, that is, the first control process, and starts the second control process.

[0071] The second control shown in FIG. 4 starts from step S306. In step S306, the control device 119 calculates the coil temperature from the following equation (1), which can express the coil resistance value Rc(Tc) at the coil temperature Tc, the coil resistance value Rc1(t) at an arbitrary temperature t of the coil, and the coil resistance temperature coefficient α as a function. Then, the processing proceeds to the processing of step S307. The control device 119 can calculate the coil resistance value Rc(Tc) at the coil temperature Tc using the current value acquired from the ammeter 117 and the voltage value acquired from the voltmeter 118. Tc=t+1 / α*{Rc(Tc)-Rc1(t)} / Rc1(t)...Equation (1)

[0072] In step S307, the control device 119 determines whether the temperature of the coil 107 is the target temperature. The target temperature is a preset value obtained from a recipe setting value as a target value for the temperature of the coil 107. If it is determined that the temperature of the coil 107 is the target temperature (S307: Yes), the process proceeds to step S308.

[0073] In step S308, the control device 119 starts PID (Proportional-Integral-Differential Controller) control, which calculates the cooling water flow rate xn so as to maintain the coil temperature Tc constant using the following equation (2), which can express the coil temperature Tc as a function. PID control is a type of feedback control in control engineering, and is a method of controlling an input value using three elements: the deviation between the output value and the target value, its integral, and its derivative. After the control device 119 calculates the cooling water flow rate, the process proceeds to step S309. xn=f(Tc) (2)

[0074] In step S309, the control device 119 issues an instruction to change the flow rate of the cooling water to the valve control unit 125. Upon receiving the instruction, the valve control unit 125 adjusts the flow rate control valve 122 to the instructed opening degree. This adjusts the flow rate of the cooling water flowing through the outbound cooling water pipe 123. After the flow rate control, the process proceeds to step S310.

[0075] In step S310, the control device 119 determines whether the coil power supply output is OFF. For example, the control device 119 may acquire the voltage value of the voltage applied to the coil 107 from the coil power supply 115, and determine whether the voltage is OFF based on whether the acquired voltage value is 0. If the control device 119 determines that the coil power supply output is not OFF (S310: No), the process proceeds to step S311.

[0076] In step S311, the control device 119 calculates the temperature of the coil 107 using the above-described formula (1). After the temperature of the coil 107 is calculated, the process proceeds to step S308. As a result, the process of calculating the temperature of the coil 107 and adjusting the flow rate of the cooling water is repeated.

[0077] Furthermore, in step S310, if it is determined that the control device 119 is OFF (S310: Yes), the process proceeds to step S312. That is, the control device 119 ends the FB control, which is the second control, and starts the process of the third control.

[0078] On the other hand, in step S307, if the control device 119 determines that the temperature of the coil 107 is not the target temperature (S307: No), the process proceeds to step S313.

[0079] In step S313, the control device 119 instructs the valve control unit 125 to change the flow rate of the cooling water to 0 L / min. Upon receiving the instruction, the valve control unit 125 adjusts the flow rate control valve 122 to the instructed opening. This adjusts the flow rate of the cooling water flowing through the outward cooling water pipe 123. In other words, the cooling water stops flowing to the coil 107, allowing the temperature of the coil 107 to increase. After the cooling water flow rate control, the process proceeds to step S314.

[0080] In step S314, the control device 119 determines whether the output of the coil power supply 115 is OFF. If it is determined that the output of the coil power supply 115 is OFF (S314: Yes), in step S315, the control device 119 ends the FB control. This ends the control of the cooling water of the plasma etching processing device 100.

[0081] Furthermore, if the control device 119 determines that the output of the coil power supply is not OFF (S314: No), the process proceeds to step S306, and the processes of steps S306 and S307 are repeated. As a result, the cooling water does not flow to the coil 107 until the temperature of the coil 107 reaches the target temperature.

[0082] The third control shown in FIG. 5 starts from the process of step S316 after step S312 shown in FIG.

[0083] In step S316, the control device 119 continues to flow the cooling water at the flow rate set in the second control described above so that the temperature of the coil 107 becomes equal to or lower than the target temperature. With the cooling water flowing in this manner, the process proceeds to step S317.

[0084] In step S317, the control device 119 calculates the required cooling time required for the temperature of the coil 107 to become equal to or lower than the target temperature, and after the required cooling time is calculated, determines whether the required cooling time has exceeded. If the control device 119 determines that the required cooling time has not exceeded (S317: No), the process proceeds to step S318.

[0085] In step S318, the control device 119 determines whether the next process has started. If the control device 119 determines that the next process has started (S318: Yes), the process proceeds to the first control (S321). Specifically, the process proceeds to step S302 shown in FIG. 1.

[0086] Furthermore, if the control device 119 determines that the next process has not started (S318: No), the process proceeds to the process of step S317 described above. In step S317, the control device 119 again determines whether the required cooling time described above has been exceeded. As a result, if the process for the next sample has not started, cooling water continues to flow through the coil 107, continuing to cool the coil 107, until the required cooling time has elapsed. In step S317, if the control device 119 determines that the required cooling time has elapsed (S317: Yes), the process proceeds to the process of step S319.

[0087] In step S319, the control device 119 instructs the valve control unit 125 to change the cooling water flow rate to 0 L / min. Upon receiving the instruction, the valve control unit 125 adjusts the flow rate control valve 122 to the instructed opening. This adjusts the flow rate of the cooling water flowing through the outbound cooling water pipe 123. In other words, the cooling water stops flowing through the coil 107. After the flow rate control, the process proceeds to step S320.

[0088] In step S320, the control device 119 ends the FF control, thereby completing the flow rate control of the cooling water in the plasma etching processing device 100.

[0089] <Effects> As described above, the plasma etching processing apparatus 100 of this embodiment can provide a cooling water control method that improves controllability and reduces the number of parts to reduce costs.

[0090] More specifically, the cooling water flow rate control can be divided into three types of control, first to third, depending on the operating state of the coil power supply 115, and FB control can be performed while FF control is performed. In other words, the plasma etching processing apparatus 100 can select the optimal control method from the first to third controls depending on the operating state of the coil power supply 115. This can improve the accuracy and responsiveness of the cooling water flow rate control of the plasma etching processing apparatus 100.

[0091] Specifically, the flow rate control of the cooling water using the voltage value obtained from the coil power supply 115 and the resistance value calculated from the current value allows the amount of heat to be predicted faster than the heat propagates through the equipment and reaches the temperature sensor, thereby enabling the plasma etching processing apparatus 100 to improve the responsiveness of the cooling water control.

[0092] Although the embodiments of the present disclosure have been specifically described above, they are not limited to the above-described embodiments and various modifications are possible without departing from the spirit of the present disclosure. In each embodiment, components can be added, deleted, or replaced, except for essential components. Unless otherwise specified, each component may be singular or plural. Combinations of the embodiments and their modifications are also possible. Some or all of the above-described configurations, functions, processing units, etc. may be realized by hardware, such as an integrated circuit design, or by software in which a processor interprets and executes a program. Data and information such as programs, tables, and files that realize each function can be stored in a storage device such as a memory, hard disk, or SSD, or on a storage medium such as an IC card, SD card, or DVD. [Explanation of symbols]

[0093] 100... plasma etching processing apparatus (plasma processing apparatus), 107... coil, 109... wafer (sample), 115... coil power supply, 116... plasma, 117... ammeter, 118... voltmeter, 119... control device, 123... outward cooling water pipe, 124... return cooling water pipe, 125... valve control unit, 201... control system

Claims

1. A flow rate control method for controlling a flow rate of cooling water for cooling a coil for generating a magnetic field of a plasma processing apparatus, comprising: The plasma processing apparatus includes: a cooling water pipe portion for circulating the cooling water; a control device that controls a control valve provided in the cooling water pipe section to control the flow rate of the cooling water, The flow rate control method includes: a first step in which, after starting a process treatment in which a sample is treated according to process conditions with a plasma-converted treatment gas formed using the coil, the control device controls the flow rate of the cooling water based on an output setting value of the coil in the process treatment so that the coil temperature does not exceed a rated temperature of the coil; a second step in which, when the coil temperature calculated from the resistance value of the coil reaches a predetermined target temperature, the control device controls the flow rate of the cooling water so that the coil temperature is maintained at the target temperature; a third step in which, when the power supply of the coil is changed from an ON state to an OFF state, the control device controls the flow rate of the cooling water until a predetermined required cooling time required for cooling is exceeded so that the coil temperature becomes equal to or lower than the target temperature; A flow rate control method comprising:

2. 2. The flow rate control method according to claim 1, In the second step, the flow rate of the cooling water is controlled by PID control. Flow control method.

3. 2. The flow rate control method according to claim 1, the first step includes a process in which the control device reads the output setting value of the coil corresponding to the process operation, Flow control method.

4. 2. The flow rate control method according to claim 1, When the power supply of the coil is in an OFF state, the control device performs the flow rate control of the first step, After the power supply of the coil is changed from the OFF state to the ON state and the current value of the power supply reaches a steady state, the control device performs the flow rate control of the second step. Flow control method.

5. 2. The flow rate control method according to claim 1, In the second step, the control device reads a current value and a voltage value from a power supply of the coil, calculates a resistance value of the coil from the read current value and voltage value, calculates a coil temperature of the coil from the calculated resistance value, and calculates a flow rate of the cooling water from the calculated coil temperature; Flow control method.

6. 6. The flow rate control method according to claim 5, In the second step, the control device determines whether the calculated coil temperature is the target temperature, and when it determines that the coil temperature is the target temperature, controls the flow rate of the cooling water by PID control so as to maintain the target temperature. Flow control method.

7. 2. The flow rate control method according to claim 1, In the third step, when the power supply of the coil is changed from an ON state to an OFF state, the control device controls the flow rate of the cooling water based on the output setting value of the coil so that the coil temperature becomes equal to or lower than the target temperature, and then the control device determines whether the required cooling time has elapsed. Flow control method.

8. a cooling water pipe section for circulating cooling water through a coil for generating a magnetic field; a control device that controls a control valve provided in the cooling water pipe section to control the flow rate of the cooling water, The control device a first control in which, after starting a process treatment in which a sample is treated according to process conditions with a plasma-converted treatment gas formed using the coil, the control device controls the flow rate of the cooling water based on an output setting value of the coil in the process treatment so that the coil temperature does not exceed a rated temperature of the coil; a second control in which, when the coil temperature calculated from the resistance value of the coil reaches a predetermined target temperature, the control device controls the flow rate of the cooling water so that the coil temperature is maintained at the target temperature; a third control in which, when the power supply of the coil is changed from an ON state to an OFF state, the control device controls the flow rate of the cooling water until a predetermined required cooling time required for cooling is exceeded so that the coil temperature becomes equal to or lower than the target temperature; A plasma processing apparatus that performs the above steps.

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