JP6556497B2 - Electromagnet control device and electromagnet control method - Google Patents

Description

  The present invention relates to an electromagnet control device and an electromagnet control method used to control the distribution of plasma density in, for example, a plasma processing apparatus.

  Conventionally, in a plasma processing apparatus such as a plasma etching apparatus, it is known to control the distribution of plasma density generated in a chamber by a magnetic field generated by a magnet. Specifically, in a plasma etching apparatus, for example, a Lorentz force is generated by applying an electric field and a magnetic field in directions orthogonal to each other inside a chamber into which an etching gas is introduced. This Lorentz force causes the electrons to be trapped by the magnetic field lines while performing a drift motion. As a result, the collision frequency between the electrons and the molecules and atoms of the etching gas increases, and high-density plasma is generated. This is also called a so-called magnetron discharge.

  In order to control the plasma density distribution in the chamber, a magnetic field generated by a magnet disposed outside the chamber is manipulated. As a method for operating a magnetic field, for example, it is known to mechanically move a permanent magnet or to control a current applied to an electromagnet. In the method of moving the permanent magnet mechanically, since the magnetic field intensity generated by the permanent magnet is fixed, it is difficult to finely adjust the plasma density distribution. For this reason, conventionally, it is employed to control the current applied to the electromagnet.

  As a method of controlling the current applied to the electromagnet, the current flowing through the electromagnet coil is detected, the detected current value is compared with the target current value, and the current value flowing through the electromagnet coil becomes the target current value. It is known to control the current value (see, for example, Patent Document 1).

JP 2012-74972 A

  When controlling the current applied to the electromagnet as described above, PI control (Proportional Integral control) has been performed. In PI control, it is generally known that a deviation always occurs with respect to a command value. In order to quickly bring the current flowing through the electromagnet close to the command value, it is necessary to set a relatively large value as the proportional gain or integral constant of the PI control. However, if a relatively large value is set as the proportional gain or integral constant, the stability margin of PI control is reduced, which may cause current overshoot. In addition, when machine differences or characteristic changes occur in the control system or electromagnet, the control may become unstable.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide an electromagnet control device and an electromagnet control method capable of causing the current flowing through the electromagnet to approach a command value relatively quickly.

An electromagnet control device according to a first embodiment of the present invention is an electromagnet control device that controls a current supplied to an excitation coil of an electromagnet, a driver for flowing a current through the excitation coil, and a current value flowing through the excitation coil A current value acquisition unit that acquires a signal indicating the current and a current control unit that controls a current flowing through the excitation coil, and the current control unit is preset based on a resistance value of the excitation coil An output voltage command value calculation unit that calculates an output voltage command value for causing a current of a target current value to flow through the exciting coil, and a current deviation between the target current value and a current value indicated by a signal acquired by the current acquisition unit A current deviation calculation unit for calculating the output voltage command value, and an addition unit for adding the current deviation to the output voltage command value, and the current control unit supplies the output voltage command value with the current deviation added to the driver. Sending Configured to.

  The electromagnet control device according to a second aspect of the present invention is the electromagnet control device according to the first aspect, wherein the current control unit includes a memory unit that stores a resistance value of the exciting coil under a predetermined condition, and the output voltage command The value calculation unit calculates the output voltage command value based on the resistance value stored in the memory unit.

  The electromagnet control device according to a third aspect of the present invention is the electromagnet control device according to the first aspect, further comprising a temperature acquisition unit that acquires a signal indicating the temperature of the excitation coil, and the output voltage command value calculation unit includes: A coil resistance value calculating unit configured to calculate a resistance value of the exciting coil based on a temperature of the exciting coil indicated by a signal acquired by the temperature acquiring unit, and the output voltage command value calculating unit includes the coil resistance value calculating unit; The output voltage command value is calculated based on the calculated resistance value of the exciting coil.

  An electromagnet control device according to a fourth aspect of the present invention is the electromagnet control device according to the third aspect, further comprising a temperature detector for detecting the temperature of the exciting coil, and the temperature detector is a signal indicating the detected temperature. Is transmitted to the temperature acquisition unit.

  An electromagnet control device according to a fifth embodiment of the present invention is the electromagnet control device according to any one of the first to fourth embodiments, further including a current detector that detects a current value flowing through the excitation coil, and the current detector Is configured to transmit a signal indicating the detected current value to the current value acquisition unit.

  The electromagnet according to the sixth embodiment of the present invention is an electromagnet controlled by the electromagnet controller described in any one of the first to fifth embodiments.

  An electromagnet control method according to a seventh aspect of the present invention is an electromagnet control method for controlling a current supplied to an excitation coil of an electromagnet, and the current of a target current value is calculated based on a resistance value of the excitation coil. A step of calculating an output voltage command value for flowing through the excitation coil, a step of flowing a current through the excitation coil based on the calculated output voltage command value, and a signal indicating a value of the current flowing through the excitation coil are acquired. A step of calculating a current deviation between the target current value and the current value indicated by the acquired signal; adding the current deviation to the calculated output voltage command value; and adding the current deviation Passing a current through the exciting coil based on the output voltage command value.

  An electromagnet control device according to an eighth aspect of the present invention is the electromagnet control device according to the seventh aspect, wherein the step of calculating the output voltage command value is based on a resistance value of the exciting coil under a predetermined condition. Calculate the value.

  An electromagnet control device according to a ninth embodiment of the present invention is based on the step of obtaining a signal indicating the temperature of the excitation coil and the temperature of the excitation coil indicated by the acquired signal in the electromagnet control device of the seventh embodiment. Calculating the resistance value of the excitation coil, and calculating the output voltage command value calculates the output voltage command value based on the calculated resistance value of the excitation coil. To do.

  According to one aspect of the present invention, it is possible to provide an electromagnet control device and an electromagnet control method capable of bringing the current flowing through an electromagnet close to a command value.

  Further, according to one aspect of the present invention, an output voltage command value for flowing a current having a preset target current value to the excitation coil is calculated based on the resistance value of the excitation coil, and the output voltage command value is calculated. Since it can be transmitted to the driver, the arrival time to the target current value can be shortened and the control accuracy can be made higher than before (the deviation between the target current value and the actual current value can be reduced). it can). As a result, since a highly accurate A / D converter and D / A converter become unnecessary, the cost of an apparatus can be reduced.

  In addition, according to one aspect of the present invention, since the signal indicating the temperature of the exciting coil is configured to be acquired, even if the resistance value of the exciting coil that is the control target varies greatly depending on the temperature, the coil resistance value is reduced. It is possible to accurately estimate, and the current applied to the exciting coil can be accurately controlled.

It is a schematic sectional side view of the plasma processing apparatus in which the electromagnet control apparatus which concerns on 1st Embodiment of this invention is used. It is a block diagram which shows the controller which concerns on 1st Embodiment, and the exciting coil of an electromagnet apparatus. FIG. 3 is a control block diagram of a CPU current control unit according to the first embodiment. It is a block diagram which shows the controller which concerns on 2nd Embodiment, and the exciting coil of an electromagnet apparatus. It is a control block diagram of a CPU current control part concerning a 2nd embodiment.

<First Embodiment>
Hereinafter, a first embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a schematic sectional side view of a plasma processing apparatus in which a controller that is an electromagnet control apparatus according to a first embodiment of the present invention is used. As shown in FIG. 1, the plasma processing apparatus 10 includes a chamber 13, a substrate stage 14 for placing a substrate W, an electromagnet apparatus 11 disposed on the upper surface of the chamber 13, and an electromagnet apparatus 11 for controlling the electromagnet apparatus 11. And a controller 20 (electromagnet controller).

  The substrate stage 14 is disposed in the chamber 13, and the substrate W is placed on the upper surface thereof. The chamber 13 is evacuated by a vacuum pump (not shown). A gas introduction unit (not shown) is provided in the chamber 13, and an etching gas or the like is introduced into the chamber 13 by the gas introduction unit.

  The electromagnet device 11 is configured to form a magnetic field in the chamber 13 via a partition wall (a top plate of the chamber 13). The magnetic field formed by the electromagnet device 11 is a horizontal magnetic field parallel to the surface of the substrate W.

  The controller 20 is electrically connected to the electromagnet device 11. The controller 20 is configured to be able to apply an arbitrary coil current to the electromagnet device 11. The controller 11 is configured to receive temperature information (temperature signal) from a temperature sensor (not shown) provided in the electromagnet device 11. The location of the controller 20 is arbitrary. For example, a device frame may be provided and attached to the device frame.

For example, the plasma processing apparatus 10 can form an electric field in a direction perpendicular to the surface of the substrate 12 by applying a potential difference between the substrate stage 14 and the top plate of the chamber 13. A horizontal magnetic field is formed by the electromagnet device 11 in a direction perpendicular to the vertical electric field. Thereby, high density plasma is generated and the substrate is processed.

Next, the controller 20 according to the embodiment of the present invention shown in FIG. 1 will be described in detail.
FIG. 2 is a block diagram showing the controller 20 and the exciting coil of the electromagnet device 11 shown in FIG. As shown in the figure, the controller 20 according to the first embodiment of the present invention can receive a current command value S1 that is a predetermined target current value from a user / higher-level device interface unit 31 such as a PC (Personal Computer). Composed. The controller 20 is connected to the excitation coil 40 of the electromagnet device 11 shown in FIG. 1 and is configured to apply a predetermined voltage to the excitation coil 40.

  The wiring of the exciting coil 40 is provided with a current detector 42 that detects the current flowing through the exciting coil 40. The current detector 42 is configured to transmit the detected value of the current flowing through the exciting coil 40 to the controller 20.

  The controller 20 includes a CPU (Central Processing Unit) current control unit 30 that receives the current command value signal S1 from the user / host device interface unit 31, and a D / A that receives the output voltage command value S2 from the CPU current control unit 30. It has the conversion part 32 and the amplifier 33 (driver) which receives the output voltage command value S3 from the D / A conversion part 32. In addition, in 1st Embodiment and 2nd Embodiment demonstrated below, it demonstrates as what has the CPU current control part 30, but it replaces with this and provides DSP current control part provided with DSP (Digital Signal Processor). May be.

  The controller 20 also acquires an amplifier 37 (current value acquisition unit) that acquires the current signal S8 indicating the current value of the exciting coil 40 from the current detector 42, and A / D conversion that acquires the current signal S9 from the amplifier 37. Part 36.

  In order to control the current flowing through the exciting coil 40, first, a digital amount of the current command value signal S <b> 1 is transmitted from the user / higher-level device interface unit 31 to the CPU current control unit 30. The CPU current control unit 30 calculates an output voltage based on the received current command value signal, and transmits a digital output voltage command value S 2 to the D / A conversion unit 32. The D / A converter 32 converts the digital output voltage command value S2 into an analog output voltage command value S3, and transmits the analog output voltage command value S3 to the amplifier 33. The amplifier 33 amplifies the output voltage command value S3, applies an analog output voltage to the exciting coil 40, and causes a current to flow through the exciting coil 40.

  The current detector 42 detects a current flowing through the exciting coil 40 and transmits a current signal S8 to the amplifier 37. The amplifier 37 amplifies the current signal S8 and transmits an analog amount of the current signal S9 to the A / D converter 36. The A / D conversion unit 36 transmits a current value signal S10 obtained by converting the analog current signal S9 into a digital value to the CPU control unit 30.

  The CPU current control unit 30 calculates the output voltage command value signal S <b> 2 again based on the received current value signal S <b> 10, and controls the current that flows through the excitation coil 40 via the A / D conversion unit 32 and the amplifier 33.

The CPU current control unit 30 is configured to compare the current value signal S10 received from the A / D conversion unit 36 with the current command value signal S1 from the user / higher-level device interface unit 31. The CPU current control unit 30 calculates a deviation between the current value of the current value signal S10 and the current value of the current command value signal S1, and compares this deviation with a predetermined value stored in the memory of the CPU current control unit 30. . When it is determined that the deviation is equal to or greater than the predetermined value, the CPU current control unit 30 determines that an abnormality has occurred in the exciting coil 40 and issues a warning to an external display unit (not shown). That is, it is determined whether or not the deviation is large by setting the predetermined value to a certain large value. A large deviation means that the value of the current actually flowing through the exciting coil 40 is far from the command value. In this case, for example, a situation where a rare short occurs in the exciting coil 40 is assumed.

FIG. 3 is a control block diagram of the CPU current control unit 30 shown in FIG.
The CPU current control unit 30 includes an output voltage command value calculation unit 21 that calculates an output voltage command value based on the current command value signal S1 illustrated in FIG. 2, and the current value signal S10 and the current command value signal illustrated in FIG. The current deviation signal S12 with respect to S1 is calculated and PI control is performed on the current deviation signal S12. The output signal S14 output from the current deviation calculator 22 and the output voltage output from the output voltage command value calculator 21. And an adder 29 for adding the command value signal S15.

  The current command value calculation unit 21 is based on the memory unit 23 in which the resistance value (series resistance value) of the exciting coil 40 (see FIG. 2) under a predetermined use condition is stored, and the resistance value and the current command value signal S1. And a calculation unit 24 for calculating an output voltage command value.

  The current deviation calculation unit 22 calculates a current deviation from the current command value signal S1 and the current value signal S10 and outputs the current deviation signal S12, and performs an integration operation on the current deviation signal S12, such as a low-pass filter. And a proportional operation unit 27 that performs a proportional operation on the current deviation signal S13 on which the integration operation has been performed.

The CPU current control unit 30 transmits the current command value S1 received from the user / higher-level device interface unit 31 illustrated in FIG. 2 to the output voltage command value calculation unit 21. In the output voltage command value calculation unit 21, the resistance value (R _t ) (digital value) of the exciting coil 40 (see FIG. 2) under a predetermined use condition is read from the memory unit 23 and sent to the calculation unit 24. The calculation unit 24 calculates an output voltage command value (V _o ) from the resistance value (R _t ) and the current command value (I ₀ ) of the current command value signal S1. That is, the output voltage command value (V _o ) is calculated by the calculation formula V _o = I ₀ × R _t according to Ohm's law. The calculated output voltage command value (V _o ) is sent to the adder 29 as an output voltage command value signal S15. Accordingly, the output voltage command value (V _o ) directly corresponding to the current command value (I ₀ ) can be calculated and output in consideration of the resistance value of the exciting coil 40 (see FIG. 2). Compared to the case where the output voltage command value is calculated based only on the deviation, the time (response time) until the current flowing through the exciting coil 40 reaches the target current value (current command value) can be shortened.

  On the other hand, when the current deviation calculation unit 22 receives the current value signal S10, the subtraction unit 25 calculates a current deviation by subtracting the current value indicated by the current value signal S10 from the current value indicated by the current command value signal S1. The subtraction unit 25 outputs the calculated current deviation to the integration operation unit 26 as a current deviation signal S12. The integration operation unit 26 receives the current deviation signal S12 and performs an integration operation on the current deviation signal S12. The proportional operation unit 27 receives the current deviation signal S14 on which the integration operation has been performed from the integration operation unit 26, and performs a proportional operation on the current deviation signal S14. The current deviation signal S14 for which the proportional operation has been performed is sent to the adding unit 29. The adder 29 adds the current deviation signal S14 to the output voltage command value signal S15, and transmits the output voltage command value signal S2 in which the current deviation is taken into account to the D / A converter 32 (see FIG. 2). Thereby, the output voltage value in consideration of the deviation between the current value flowing through the exciting coil 40 and the target current value can be calculated, and the current value flowing through the exciting coil 40 can be controlled.

As described above, in the controller 20 according to the first embodiment, the output voltage command value calculation unit 21 outputs the output voltage based on the resistance value (R _t ) of the exciting coil 40 (see FIG. 2) under a predetermined use condition. Calculate the command value. As a result, the controller 20 can quickly bring the current flowing through the exciting coil 40 close to the current command value without increasing the proportional gain or the integral constant of the current deviation calculation unit 22. In other words, the time (response time) until the current flowing through the exciting coil 40 reaches the target current value (current command value) can be shortened as compared with the case where the output voltage command value is calculated based only on the deviation. . Therefore, the controller 20 according to the first embodiment can realize current control with excellent stability and high accuracy. Moreover, since the output voltage command value in consideration of the resistance value of the exciting coil 40 is calculated and the exciting coil 40 is controlled based on the command value, the time required to reach the target current value can be shortened and the control accuracy is conventionally improved. (The deviation between the target current value and the actual current value can be reduced). As a result, since a highly accurate A / D converter and D / A converter become unnecessary, the cost of an apparatus can be reduced.

Further, in the controller 20 according to the first embodiment, in addition to the resistance value (R _t ), the output voltage command value is set in consideration of the deviation between the current value flowing through the exciting coil 40 and the current command value (target current value). calculate. Therefore, even if the resistance value (R _t ) of the exciting coil 40 under a predetermined use condition stored in advance is greatly different from the actual resistance value (R _t ) of the exciting coil 40, the current value of the exciting coil 40 And the current command value, the current value flowing through the exciting coil 40 can be brought close to the current command value with high accuracy.

<Second Embodiment>
Next, the electromagnet control apparatus of 2nd Embodiment is demonstrated. FIG. 4 is a block diagram showing the controller and the exciting coil of the electromagnet device. The plasma processing apparatus in which the electromagnet control apparatus according to the second embodiment is used is the same as the plasma processing apparatus shown in FIG.

  The second embodiment is different from the first embodiment in that it has a mechanism for detecting the temperature of the exciting coil. Since other configurations are the same as those of the first embodiment, the same configurations as those of the first embodiment are denoted by the same reference numerals and description thereof is omitted.

  As shown in FIG. 4, the excitation coil 40 is provided with a temperature detector 41 such as a temperature sensor. The temperature detector 41 is configured to transmit the detected temperature of the exciting coil 40 to the controller 20.

  The controller 20 includes an amplifier 35 (temperature acquisition unit) that acquires a temperature signal S5 indicating the temperature of the exciting coil 40 from the temperature detector 41, an A / D conversion unit 34 that receives the temperature signal S6 from the amplifier 35, and Have

  The temperature detector 41 detects the temperature of the exciting coil 40 and transmits a temperature signal S5 to the amplifier 35. The amplifier 35 amplifies the temperature signal S5 and transmits an analog amount of the temperature signal S6 to the A / D converter 34. The A / D conversion unit 34 transmits to the CPU control unit 30 a temperature value signal S7 obtained by converting the analog temperature signal S6 into a digital value.

FIG. 5 is a control block diagram of the CPU current control unit 30 according to the second embodiment.
Compared with the CPU current control unit 30 of the controller 20 according to the first embodiment, the CPU current control unit 30 of the controller 20 according to the second embodiment includes an output voltage command value calculation unit 21 that calculates an output voltage command value. The difference is that a resistance value calculation unit 28 is provided. This will be described in detail below.

As shown in FIG. 5, the output voltage command value calculation unit 21 of the CPU current control unit 30 includes a coil resistance value calculation unit 28 that calculates the resistance value of the exciting coil 40 instead of the memory 23 of the first embodiment. . The coil resistance value calculation unit 28 receives the temperature value signal S7 from the A / D conversion unit 34 shown in FIG. The coil resistance value calculation unit 28 calculates the resistance value (R _t ) of the exciting coil 40 based on the coil temperature (T) indicated by the temperature value signal S7. The resistance value (R _t ) is calculated as follows. That is, assuming that the resistance value of the exciting coil 40 at 20 ° C. is R ₂₀ and the temperature coefficient of the resistance value of the exciting coil 40 is α, the resistance value (R _t ) is calculated by R _t = R ₂₀ × (1 + αT). . The resistance value R ₂₀ of the exciting coil 40 at 20 ° C. is stored in advance in a memory included in the coil resistance value calculation unit 28.

The resistance value (R _t ) calculated by the coil resistance value calculation unit 28 is sent to the calculation unit 24. The calculation unit 24 calculates an output voltage command value (V _o ) based on the resistance value (R _t ) calculated by the coil resistance value calculation unit 28 and the current command value (I ₀ ) of the current command value signal S1. The calculated output voltage command value (V _o ) is sent to the adder 29 as an output voltage command value signal S15.

The coil resistance value calculation unit 28 receives the temperature value signal S7 of the exciting coil 40 and calculates a resistance value (R _t ) at predetermined time intervals. Based on the resistance value (R _t ) calculated every predetermined time, the calculation unit 24 calculates an output voltage command value and transmits the output voltage command value signal S15 to the addition unit 29. Therefore, the controller 20 can control the current of the exciting coil 40 based on the appropriate output voltage command value signal S15 corresponding to the temperature change of the exciting coil 40.

As described above, in the controller 20 according to the second embodiment, the temperature of the exciting coil 40 is monitored, and the actual resistance value (R _t ) of the exciting coil 40 is calculated based on the actual temperature of the exciting coil 40. calculate. As a result, the controller 20 can quickly bring the current flowing through the exciting coil 40 close to the current command value without increasing the proportional gain or the integral constant of the current deviation calculation unit 22. In other words, the time (response time) until the current flowing through the exciting coil 40 reaches the target current value (current command value) can be shortened as compared with the case where the output voltage command value is calculated based only on the deviation. . Moreover, since the output voltage command value in consideration of the resistance value of the exciting coil 40 is calculated and the exciting coil 40 is controlled based on the command value, the time required to reach the target current value can be shortened and the control accuracy is conventionally improved. (The deviation between the target current value and the actual current value can be reduced). As a result, since a highly accurate A / D converter and D / A converter become unnecessary, the cost of an apparatus can be reduced.

Further, the controller 20 calculates an output voltage command value based on the calculated actual resistance value (R _t ). For this reason, since the controller 20 according to the second embodiment can accurately estimate the coil resistance value even if the temperature of the excitation coil 40 changes due to disturbance, it is more suitable for the actual temperature of the excitation coil 40. A highly accurate output voltage command value can be output. Therefore, the controller 20 according to the second embodiment can realize current control with excellent stability and higher accuracy.

In addition to the series resistance value (R _t ), the controller 20 according to the second embodiment also takes into account the deviation between the current value of the exciting coil 40 and the current command value in the same manner as the controller 20 according to the first embodiment. To calculate an output voltage command value. Therefore, based on the deviation between the current value of the exciting coil 40 and the current command value, the current value flowing through the exciting coil 40 can be brought close to the current command value with high accuracy.

  In the first embodiment and the second embodiment, the temperature detector 41 and the current detector 42 are provided separately from the controller 20, but the temperature detector 41 and the current detector 42 are the controller. 20 may be configured as a part.

Further, the components of the CPU current control unit 30 shown in FIGS. 3 and 5 can be realized by software stored in the CPU current control unit 30, for example, except for the memory unit 23.

  The magnet control device according to the present invention can be applied to a device that uses a magnetic force to generate plasma, such as a plasma etching device, a sputtering device, and a plasma CVD (Chemical Vapor Deposition) device.

  As mentioned above, although embodiment of this invention was described, embodiment of the invention mentioned above is for making an understanding of this invention easy, and does not limit this invention. The present invention can be changed and improved without departing from the gist thereof, and the present invention includes the equivalents thereof. In addition, any combination or omission of each component described in the claims and the specification is possible within a range where at least a part of the above-described problems can be solved or a range where at least a part of the effect can be achieved. is there.

DESCRIPTION OF SYMBOLS 11 ... Electromagnet apparatus 20 ... Controller 21 ... Output voltage command value calculation part 22 ... Current deviation calculation part 23 ... Memory part 28 ... Coil resistance value calculation part 29 ... Addition part 30 ... CPU current control part 33 ... Amplifier 35 ... Amplifier 37 ... Amplifier 40 ... Excitation coil 41 ... Temperature detector 42 ... Current detector

Claims (9)

An electromagnet control device for controlling a current supplied to an exciting coil of an electromagnet,
A driver for passing a current through the exciting coil;
A current value acquisition unit for acquiring a signal indicating a current value flowing through the exciting coil;
A current control unit for controlling a current flowing through the exciting coil,
The current controller is
An output voltage command value for calculating an output voltage command value for causing the current of the target current value to flow through the excitation coil based on a resistance value of the excitation coil and a preset target current value for flowing through the excitation coil A calculation unit;
A current deviation calculation unit that calculates a current deviation between the target current value and the current value indicated by the signal acquired by the current acquisition unit;
An adder that adds the current deviation to the output voltage command value;
The current control unit is an electromagnet control device configured to transmit an output voltage command value to which the current deviation is added to the driver. The current control unit includes a memory unit that stores a resistance value of the exciting coil under a predetermined condition.
The electromagnet control device according to claim 1, wherein the output voltage command value calculation unit calculates the output voltage command value based on a resistance value stored in the memory unit. A temperature acquisition unit for acquiring a signal indicating the temperature of the excitation coil;
The output voltage command value calculation unit includes a coil resistance value calculation unit that calculates a resistance value of the excitation coil based on a temperature of the excitation coil indicated by a signal acquired by the temperature acquisition unit,
The electromagnet control device according to claim 1, wherein the output voltage command value calculation unit calculates the output voltage command value based on the resistance value of the exciting coil calculated by the coil resistance value calculation unit. A temperature detector for detecting the temperature of the exciting coil;
The electromagnet control device according to claim 3, wherein the temperature detector is configured to transmit a signal indicating the detected temperature to the temperature acquisition unit. A current detector for detecting a current value flowing through the exciting coil;
5. The electromagnet control device according to claim 1, wherein the current detector is configured to transmit a signal indicating the detected current value to the current value acquisition unit. An electromagnet controller according to any one of claims 1 to 5;
An electromagnet controlled by the electromagnet controller;
A plasma processing apparatus comprising: An electromagnet control method for controlling a current supplied to an excitation coil of an electromagnet,
Calculating an output voltage command value for causing the current of the target current value to flow through the excitation coil based on a resistance value of the excitation coil and a preset target current value for flowing through the excitation coil;
Passing a current through the exciting coil based on the calculated output voltage command value;
Obtaining a signal indicating a current value flowing through the exciting coil;
Calculating a current deviation between the target current value and the current value indicated by the acquired signal;
Adding the current deviation to the calculated output voltage command value;
Passing a current through the exciting coil based on an output voltage command value to which the current deviation is added.   8. The electromagnet control method according to claim 7, wherein the step of calculating the output voltage command value calculates the output voltage command value based on a resistance value of the exciting coil under a predetermined condition. Obtaining a signal indicating the temperature of the exciting coil;
Calculating a resistance value of the exciting coil based on the temperature of the exciting coil indicated by the acquired signal,
8. The electromagnet control method according to claim 7, wherein the step of calculating the output voltage command value calculates the output voltage command value based on the calculated resistance value of the exciting coil.

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