JP2020057510A - Ion gun controller and ion gun control method - Google Patents

Abstract

To provide an ion gun controller and ion gun control method, capable of suppressing degradation in exposure dose.SOLUTION: An ion gun controller 70 includes a gas control section 71 and a voltage control section 72. The gas control section 71 repeats the control for compensating for degradation in a detection value by an increase in a gas flow rate value so that a current detection value is a target current value. The ion gun controller 70 increases a gas flow rate at the completion of a constant voltage period against a gas flow rate at the start of the constant voltage period within the constant voltage period.SELECTED DRAWING: Figure 2

Description

  The present invention relates to an ion gun control device and an ion gun control method.

  BACKGROUND ART An ion gun that irradiates an ion beam to treat a surface of a substrate is known (for example, see Patent Document 1). The ion gun includes a cathode and an anode. The cathode includes a pair of magnetic pole members located with a gap therebetween, and forms a magnetic field in the gap formed by the pair of magnetic pole members. The anode is located such that an electric field is formed in a direction orthogonal to a direction in which the pair of magnetic pole members face each other. The ion gun generates a magnetron discharge by applying a voltage between the electrodes while flowing a gas through a gap formed by the cathode, and irradiates the target with an ion beam.

JP 2012-164677 A

However, the ions generated in the gap sputter each magnetic pole member constituting the cathode, thereby reducing the irradiation amount of the ion beam.
An object of the present invention is to provide an ion gun control device and an ion gun control method capable of suppressing a decrease in irradiation amount.

  A control device for an ion gun for solving the above-mentioned problem includes a first electrode composed of a pair of magnetic pole members having opposing magnetism and located with a gap therebetween, and a second electrode facing the first electrode. And supplying a gas from between the electrodes to between the magnetic pole members during a constant voltage period in which a predetermined voltage is applied between the first electrode and the second electrode. A control device for controlling the driving of the ion gun so as to ionize the gas, wherein the gas flow rate is adjusted so that a detected value of a current flowing between the first electrode and the second electrode becomes a target value. A gas control unit that repeats control to compensate for the decrease in the detected value with an increase, and within the constant voltage period, increases the gas flow at the end of the constant voltage period with respect to the gas flow at the start of the constant voltage period. Is provided.

  A method for controlling an ion gun for solving the above-mentioned problem includes a first electrode composed of a pair of magnetic pole members having opposing magnetism and spaced from each other, and a second electrode facing the first electrode. And supplying a gas from between the electrodes to between the magnetic pole members during a constant voltage period in which a predetermined voltage is applied between the first electrode and the second electrode. A method for controlling the operation of the ion gun so as to ionize the gas, wherein the gas flow rate is adjusted so that a detected value of a current flowing between the first electrode and the second electrode becomes a target value. Repeating the control to compensate for the decrease in the detected value by increasing, and increasing the gas flow rate at the end of the constant voltage period with respect to the gas flow rate at the start of the constant voltage period within the constant voltage period. .

  As the elapse of the constant voltage period progresses, the gap between the magnetic pole members constituting the first electrode increases. The expansion of the gap between the magnetic pole members causes a reduction in ion density between the magnetic pole members, that is, a reduction in the irradiation amount of the ion beam. In this regard, according to each of the above configurations, the decrease in the detected value is compensated for by increasing the gas flow rate so that the detected value becomes the target value, and the gas flow rate at the start of the constant voltage period is fixed within the constant voltage period. The gas flow at the end of the voltage period increases. Therefore, the decrease in the current value is suppressed by the increase in the gas flow rate, whereby the decrease in the irradiation amount due to the increase in the width of the interval can be suppressed.

  The ion gun control device further includes a voltage control unit configured to increase a voltage applied between the first electrode and the second electrode immediately after the end of the current constant voltage period to start the next constant voltage period. The voltage control unit may include, as a condition for ending the current constant voltage period, estimating that the width of the gap is equal to or greater than a period reference value.

  Increasing the width of the gap between the magnetic pole members reduces the ion density between the magnetic pole members and widens the width of the ion beam. In this regard, according to the configuration described above, the voltage applied between the electrodes increases when the width of the gap is estimated to be equal to or greater than the period reference value. That is, when the width of the gap is estimated to be equal to or greater than the period reference value, the speed of ions is increased. As a result, it is possible to suppress the width of the ion beam from expanding in the irradiation target due to the gap width being equal to or greater than the period reference value.

  In the above-described ion gun control device, the voltage control unit may calculate power consumption based on a voltage applied between the first electrode and the second electrode, the detected value, and a usage time of the ion gun. When the amount is equal to or greater than the threshold, the width of the gap may be estimated to be equal to or greater than the period reference value. According to the ion gun control device, it is possible to easily estimate whether the width of the gap is equal to or larger than the period reference value.

  In the ion gun control device, the voltage control unit includes a storage unit that stores a plurality of thresholds different from each other and a set value of a voltage associated with each threshold, and the width of the gap is based on the period reference. In estimating whether the value is equal to or greater than the value, the threshold value larger than the previous constant voltage period is used in the current constant voltage period, and the set value associated with the threshold value used in the current constant voltage period is used in the next constant voltage period. It may be used during the voltage period. According to this ion gun control device, since the threshold of the power consumption is used in ascending order, the above-described effect can be obtained in each constant voltage period even when the constant voltage period continues three times or more. Also.

  In the above-described ion gun control device, the gas control unit includes a storage unit that separately stores a relationship between the target value and the gas flow rate for each set value, and the voltage control unit performs the current constant voltage period. The control of the gas flow rate may be performed based on the above-mentioned relationship associated with the set value used in the above.

  The current flowing between the first electrode and the second electrode increases as the voltage increases. In this regard, according to this configuration, the increase in the current accompanying the increase in the voltage is corrected by the supply of the gas flow rate based on the relationship stored in the storage unit. As a result, when the voltage is switched between the previous constant voltage period and the current constant voltage period, it is possible to suppress the deviation of the irradiation amount due to the increase in the voltage.

FIG. 1 is a configuration diagram showing a configuration of an embodiment of a control device of an ion gun together with an ion gun. FIG. 2 is a block diagram showing an electrical configuration of the control device of the ion gun. The figure which shows the relationship between the threshold value in voltage setting data, and a set value. 7 is a graph showing the relationship between gas flow rate and electric power in gas flow rate setting data. 9 is a flowchart showing a voltage control processing procedure included in the ion gun control method.

An embodiment of the ion gun control device and the ion gun control method will be described below.
[Ion gun]
As shown in FIG. 1, the ion gun 10 includes a first electrode 20, a second electrode 30, a magnet 40, and a gas unit 60.

  The first electrode 20 is composed of a pair of magnetic pole members located with a gap 23 therebetween. The pair of magnetic pole members includes a first magnetic pole member 21 and a second magnetic pole member 22. The first magnetic pole member 21 has a rail shape extending in a direction perpendicular to the paper surface and opening upward. The second magnetic pole member 22 has a plate shape extending in a direction perpendicular to the plane of the paper and filling a part of the opening.

  The magnet 40 has a columnar shape extending along the direction in which the second magnetic pole member 22 extends. The magnet 40 is magnetically connected to the first magnetic pole member 21 and the second magnetic pole member 22. The magnet 40 gives opposite polarities to the separate magnetic pole members 21 and 22, and generates a magnetic field in the gap 23 between the first magnetic pole member 21 and the second magnetic pole member 22.

  The first electrode 20 and the magnet 40 define a discharge space 24 inside the first magnetic pole member 21. The second electrode 30 is located in the discharge space 24. The first electrode 20 and the second electrode 30 are electrically insulated by an insulating material 31. The second electrode 30 is electrically connected to the power supply unit 50. The power supply unit 50 and the first electrode 20 are connected to a ground potential.

  The gas unit 60 communicates with the discharge space 24 through the gas flow channel 61. The gas unit 60 and the power supply unit 50 are electrically connected to a control device 70 (hereinafter, also referred to as a control device 70) of the ion gun.

[Control device for ion gun]
As shown in FIG. 2, the power supply unit 50 includes a power supply 51 and a current monitor 52. The gas unit 60 includes a gas supply source 61S and a mass flow controller (MFC62).

  The power supply 51 applies a predetermined DC voltage between the first electrode 20 and the second electrode 30. The second electrode 30 is an anode to which a positive potential is applied. The first electrode 20 is a cathode connected to the ground potential. The period during which the power supply 51 applies a constant voltage is a single constant voltage period. The power supply 51 changes the voltage stepwise according to a command from the control device 70. Control device 70 causes power supply unit 50 to output a predetermined voltage different from the voltage applied in the current constant voltage period, thereby starting the next constant voltage period.

  The current monitor 52 detects the current output from the power supply 51. The current monitor 52 is connected to a power supply circuit that applies a voltage between the electrodes 20 and 30, and detects a current flowing through the power supply circuit as a current flowing between the electrodes 20 and 30.

  The gas unit 60 introduces gas into the discharge space 24 through the gas passage 61. The introduced gas causes a magnetron discharge by an electric field generated between the first electrode 20 and the second electrode 30 and a magnetic field generated between the magnetic pole members 21 and 22. Gas ions generated by the magnetron discharge are accelerated by an electric field applied between the first electrode 20 and the second electrode 30, and are irradiated from the gap 23 as an ion beam.

  The control device 70 includes a gas control unit 71 and a voltage control unit 72. The current monitor 52 outputs the detection value Ia of the current monitor 52 to the gas control unit 71 and the voltage control unit 72. The current monitor 52 matches the detection value Ia used for processing by the gas control unit 71 with the detection value Ia used for processing by the voltage control unit 72.

The voltage control unit 72 includes a voltage control processor 72P and a voltage control memory 72M that is an example of a storage unit.
The voltage control processor 72P is not limited to one in which all of various processes are performed by software. For example, the voltage control processor 72P may include dedicated hardware (application-specific integrated circuit: ASIC) that executes at least a part of various types of processing. The voltage control processor 72P is configured as a circuit including one or more dedicated hardware circuits such as an ASIC, one or more processors (microcomputers) operating according to a computer program (software), or a combination thereof. .

  The voltage control memory 72M stores the initial value of the set value Vset, the power consumption Pa up to the present, and the voltage setting data D1. The initial value of the set value Vset is used when the ion gun 10 is an unused item. The power consumption Pa up to the present is the power consumption of the ion gun 10 used this time until now. The power consumption Pa up to the present is used when the ion gun 10 used once is continuously used.

  As shown in FIG. 3, the voltage setting data D1 associates the set value Vset with each threshold value Pth of the power consumption Pa. The threshold value Pth included in the voltage setting data D1 is a plurality of different threshold values P0, P1, P2, P3, and P4. The set value Vset included in the voltage setting data D1 is a plurality of different set values V1, V2, V3, V4, and V5. Each set value Vset is a value of a voltage applied between the first electrode 20 and the second electrode 30. Each set value Vset increases as the threshold value Pth corresponding to the set value Vset increases.

  For example, the threshold value P0 is an initial value of the threshold value Pth used when the use of the ion gun 10 is started. The set value V1 associated with the threshold value P0 is a set value Vset used in the next constant voltage period. The threshold value P1 is larger than the threshold value P0. The set value V2 associated with the threshold value P1 is larger than the set value V1. The threshold value P2 is larger than the threshold value P1. The set value V3 associated with the threshold value P2 is larger than the set value V2.

  Prior to the start of the current beam irradiation process, the voltage control processor 72P specifies the set value Vset at the start of the process. For example, when the ion gun 10 is an unused item, the voltage control processor 72P reads the initial value of the set value Vset, and specifies the read initial value as the set value Vset at the start of processing. The voltage control processor 72P reads the power consumption Pa when the used ion gun 10 is continuously used. The voltage control processor 72P refers to the voltage setting data D1, extracts the maximum value from the threshold value Pth smaller than the read power consumption Pa, and sets the set value Vset associated with the maximum value to the voltage setting value. Read from data D1. That is, the voltage control processor 72P specifies the set value Vset set in the previous constant voltage period as Vset at the start of the current process.

Returning to FIG. 2, the gas control unit 71 includes a gas control processor 71P and a gas control memory 71M that is an example of a storage unit.
The gas control processor 71P is not limited to processing all various processes by software. For example, the gas control processor 71P may include dedicated hardware (application-specific integrated circuit: ASIC) that executes at least a part of various processes. The gas control processor 71P is configured as a circuit including one or more dedicated hardware circuits such as an ASIC, one or more processors (microcomputers) operating according to a computer program (software), or a combination thereof. .

  The gas control memory 71M stores a target value Ip and gas flow rate setting data D2. The target value Ip is a current value I targeted in the current beam irradiation processing. The target value Ip is externally input to the control device 70 prior to the current beam irradiation processing. The gas flow rate setting data D2 includes a control gain DP used for PID control of the gas flow rate. The gas flow rate setting data D2 indicates the relationship between the value of the current flowing between the electrodes 20, 30 (current value I) and the flow rate initial value Q. The flow rate initial value Q is a gas flow rate used at the start of the constant voltage period.

  As shown in FIG. 4, the relationship indicated by the gas flow rate setting data D2 is such that the higher the flow rate initial value Q is, the larger the current value I is. The gas flow rate setting data D2 stores the relationship between the current value I and the flow rate initial value Q one by one for each set value Vset. The gas flow rate setting data D2 separately stores the relationship between the current value I and the flow rate initial value Q for each set value Vset.

  For example, the gas flow rate setting data D2 indicates that the current value I increases as the flow rate initial value Q increases with respect to the set value V1. The gas flow rate setting data D2 indicates a relationship with respect to the set value V2 as the current value I increases as the flow rate initial value Q increases, and gives a gradient greater than the relationship with the set value V1. Further, the gas flow rate setting data D2 indicates a relationship that the current value I increases as the flow rate initial value Q increases with respect to the set value V3, and gives a greater gradient than the relationship at the set value V2.

  Prior to the start of the current constant voltage period, the gas control processor 71P refers to the set value Vset in the current constant voltage period and reads the gas flow rate setting data D2 associated with the current set value Vset. The gas control processor 71P determines the initial flow rate associated with the current value I corresponding to the target value Ip based on the read gas flow rate setting data D2 so that the target value Ip can be obtained in the current constant voltage period. Specify the value Q.

  The gas control processor 71P repeats the adjustment of the gas flow rate at a predetermined control cycle throughout the current constant voltage period. In adjusting the gas flow rate, the gas control processor 71P calculates the gas flow rate in the current control cycle and the detected value Ia in the current control cycle so that the detected value Ia increases toward the target value Ip and converges. , The gas flow rate in the next control cycle is calculated. The gas control processor 71P controls the driving of the MFC 62 so that the calculated gas flow rate is supplied. The gas control processor 71P compensates for a decrease in the detected value Ia by increasing the gas flow rate.

  The voltage control processor 72P performs an update process of the power consumption Pa. In the updating process, the detected value Ia during the current constant voltage period, the voltage set value Vset during the current constant voltage period, and the time during which the ion gun was used during the current constant voltage period are used to determine the current constant voltage period. , The power consumption Pa of the ion gun is calculated. The voltage control processor 72P updates the power consumption Pa in the control cycle.

  The voltage control processor 72P monitors that the updated power consumption Pa is less than the current threshold value Pth. Monitoring of the power consumption Pa is estimation of whether or not the width of the gap 23 is equal to or greater than the period reference value. When determining that the power consumption Pa is equal to or greater than the current threshold value Pth, the voltage control processor 72P reads the set value Vset of the voltage associated with the current threshold value Pth based on the voltage setting data D1. The voltage control processor 72P controls the driving of the power supply 51 so that a voltage corresponding to the read set value Vset is output, thereby starting the next constant voltage period.

[Action]
Hereinafter, a control method of the ion gun 10 performed by the control device 70 will be described.
Prior to the start of the beam irradiation process, the voltage control unit 72 specifies, for example, a set value Vset corresponding to the current power consumption Pa. The gas control unit 71 reads out the gas flow rate setting data D2 corresponding to the set value Vset specified by the voltage control unit 72. The gas control unit 71 specifies a flow rate initial value Q corresponding to the current target value Ip based on the read gas flow rate setting data D2. The gas control unit 71 controls the driving of the MFC 62 to start gas supply at the specified flow rate initial value Q. The voltage control unit 72 controls the driving of the power supply 51 to start voltage application at the specified set value Vset. The ion gun 10 generates ions in the gap 23 between the magnetic pole members 21 and 22 and starts irradiating the target with an ion beam.

  Continuation of ion beam irradiation increases the width of the gap 23 by sputtering the magnetic pole members 21 and 22 by electric discharge. When the width of the gap 23 is increased, the ion density in the gap 23 is reduced, and the current flowing between the electrodes 20 and 30 is reduced. As a result, the amount of ions contained in the ion beam is reduced.

  At this point, the controller 70 repeats the control to compensate for the decrease in the detected value Ia by increasing the gas flow rate so that the detected value Ia becomes the target value Ip. Then, within the constant voltage period, the gas flow rate at the end of the constant voltage period increases with respect to the gas flow rate at the start of the constant voltage period. That is, the control device 70 performs control to increase the flow rate of the gas and thereby suppress a decrease in the detection value Ia.

  For example, the gas control processor 71P calculates a difference between the detected value Ia and the target value Ip for each control cycle. The gas control processor 71P calculates the gas flow rate in the next control cycle so that the difference becomes smaller, and controls the driving of the MFC 62 so that the calculated gas flow rate is supplied. In the control of the gas flow rate such that the detected value Ia becomes the target value Ip, the gas flow rate may repeatedly increase and decrease in each control cycle. However, in the constant voltage period that is sufficiently larger than the control cycle, the gas flow at the end of the constant voltage period increases with respect to the gas flow at the start of the constant voltage period.

  Further continuation of the ion beam increases the width of the gap 23 to increase the width of the ion beam. The expanded ion beam reduces the density of the amount of ions arriving at the target.

  In this regard, the control device 70 regards the increase in the power consumption Pa as an increase in the width of the gap 23, and increases the set value Vset in response to the power consumption Pa becoming equal to or larger than the threshold Pth, thereby increasing the irradiation. Control is performed to increase the speed of ions in the direction.

  More specifically, as shown in FIG. 5, the voltage control processor 72P sets the voltage set value Vset to the set value V1 at the start of the beam irradiation processing, and sets the threshold P0 associated with the set value V1 to the threshold Pth. (Step S11). The voltage control processor 72P controls the power consumption Pa from the start of use of the ion gun to the present using the set value Vset in the current control cycle, the detected value Ia in the current control cycle, and the length of the control cycle. It is updated every cycle (step S12).

  The voltage control processor 72P determines whether or not the updated power consumption Pa is equal to or greater than the threshold value Pth in the current constant voltage period (step S13). The voltage control processor 72P updates the power consumption Pa and updates the current power consumption Pa and the current threshold Pth until the updated power consumption Pa becomes equal to or greater than the threshold Pth in the current constant voltage period. A comparison is made (No in step S13).

  When the updated power consumption Pa becomes equal to or greater than the threshold value Pth in the current constant voltage period (Yes in step S13), the voltage control processor 72P refers to the voltage setting data D1 and sets the set value Vset to the current constant voltage. The setting value is changed to the set value Vset associated with the threshold value Pth in the period. That is, the voltage control processor 72P starts the next constant voltage period. Further, the voltage control processor 72P updates the threshold value P1 that is higher by one step than the threshold value Pth in the current constant voltage period as a new threshold value Pth, and repeats the processing of steps S12 and S13 again (step S14). ).

  Here, each of the electrodes 20 and 30 used for discharging also serves as an electrode used for accelerating the ion beam. The increase in the voltage applied to accelerate the ion beam increases the current flowing through the power supply circuit.

  In this regard, when increasing the voltage from the set value Vset in the current constant voltage period to the set value Vset in the next constant voltage period, the gas control processor 71P corresponds to the set value Vset in the next constant voltage period. The gas flow rate setting data D2 is read. Then, the gas control processor 71P calculates the flow rate initial value Q corresponding to the target value Ip based on the read gas flow rate setting data D2 so that the target value Ip is obtained in the next constant voltage period. Then, at the start of the next constant voltage period, the gas control processor 71P temporarily reduces the flow rate initial value Q.

As described above, according to the above embodiment, the following effects can be obtained.
(1) A decrease in the detected value Ia is compensated by an increase in the gas flow rate so that the detected value Ia becomes the target value Ip. Then, within the constant voltage period, the gas flow at the end of the constant voltage period is increased with respect to the gas flow at the start of the constant voltage period. As a result, the gas flow rate is increased so that the detection value Ia approaches the target value Ip, so that a decrease in the irradiation amount of the ion beam can be suppressed.

(2) When the width of the gap 23 is estimated to be equal to or greater than the period reference value, the voltage applied between the electrodes 20 and 30 is increased, and the speed of ions is increased. As a result, it is possible to suppress the width of the ion beam from expanding in the irradiation target due to the width of the gap 23 being equal to or greater than the period reference value.
(3) Since the width of the gap 23 is estimated from the power consumption Pa, it is possible to easily estimate whether the width of the gap 23 is equal to or greater than the period reference value.

  (4) Since the threshold value Pth of the power consumption Pa is used in ascending order, even if the constant voltage period is continuous three or more times, the effect according to the above (1) to (3) is obtained in each constant voltage period. Is obtained.

  (5) When the next constant voltage period is started, the increase in the current accompanying the increase in the voltage is corrected by the supply of the gas flow rate. As a result, when the voltage is switched between the previous constant voltage period and the current constant voltage period, it is possible to suppress the deviation of the irradiation amount due to the increase in the voltage.

The above embodiment can be modified as follows.
The gas flow rate setting data D2 can be changed to a configuration in which the flow rate initial value Q is associated with each set value Vset one by one. Even if the flow rate initial value Q is one for each set value Vset, it is possible to obtain the effects according to the above (1) to (4) as long as the target value Ip is constant. is there. As described in the above embodiment, if the gas flow rate setting data D2 has a configuration in which the relationship between the current value I and the flow rate initial value Q is provided one by one for each set value Vset, the target values Ip are mutually It is possible to obtain an appropriate flow rate initial value Q for two or more different types of beam irradiation processing.

  The voltage control memory 72M may store a map in which the gas flow rate and the detected value Ia are associated with the width of the gap 23 one by one for each set value Vset. Then, the voltage control processor 72P reads the map corresponding to the set value Vset of the current constant voltage period, applies the gas flow rate and the detected value Ia in the current control cycle to the read map, and May be estimated. That is, estimation of whether or not the width of the gap 23 is equal to or greater than the period reference value can be executed based on the gas flow rate, the set value Vset, and the detection value Ia.

  The estimation of whether or not the width of the gap 23 is equal to or greater than the period reference value is not limited to the estimation using various parameters, but is an estimation based on image processing using an imaging result of a camera that images the gap 23. Is also good.

  Ia: detected value, Ip: target value, Pa: power consumption, Pth, P0, P1, P2, P3, P4: threshold value, Vset, V1, V2, V3, V4, V5: set value, 10: ion gun, 20 first electrode, 21 first magnetic pole member, 22 second magnetic pole member, 23 gap, 30 second electrode, 40 magnet, 50 power supply unit, 60 gas unit, 70 control device, 71 ... gas control unit, 72 ... voltage control unit.

Claims (6)

Using an ion gun including a first electrode composed of a pair of magnetic pole members having opposing magnetism and positioned with a gap therebetween, and a second electrode facing the first electrode, the first electrode is An ion for controlling driving of the ion gun so as to supply a gas from between the electrodes to between the magnetic pole members and ionize the gas during a constant voltage period in which a predetermined voltage is applied between the second electrode and the second electrode. A gun control device,
The control for compensating for the decrease in the detected value by increasing the gas flow rate is repeated so that the detected value of the current flowing between the first electrode and the second electrode becomes the target value. A control device for an ion gun, comprising: a gas control unit configured to increase a gas flow rate at the end of the constant voltage period with respect to a gas flow rate at a start of the voltage period. A voltage control unit configured to increase a voltage applied between the first electrode and the second electrode immediately after the end of the current constant voltage period and start a next constant voltage period,
The control device for the ion gun according to claim 1, wherein the voltage control unit estimates that the width of the gap is equal to or larger than a period reference value, as a condition for ending the current constant voltage period. The voltage control unit, when the voltage applied between the first electrode and the second electrode, the detected value, when the amount of power consumption calculated from the usage time of the ion gun is equal to or more than a threshold, The ion gun control device according to claim 2, wherein the width of the gap is estimated to be equal to or greater than the period reference value. The voltage control unit includes a storage unit that stores a plurality of thresholds different from each other and a set value of a voltage associated with each threshold, and determines whether the width of the gap is equal to or greater than the period reference value. In the estimation, a threshold larger than the previous constant voltage period is used in the current constant voltage period, and a set value associated with the threshold used in the current constant voltage period is used in the next constant voltage period. The control device of the ion gun according to the above. The gas control unit includes a storage unit that separately stores a relationship between the target value and the gas flow rate for each set value, and the voltage control unit is associated with a set value used for a current constant voltage period. The control device for an ion gun according to claim 4, wherein the control of the gas flow rate is performed based on the relationship. Using an ion gun including a first electrode composed of a pair of magnetic pole members having opposing magnetism and positioned with a gap therebetween, and a second electrode facing the first electrode, the first electrode is An ion for controlling driving of the ion gun so as to supply a gas from between the electrodes to between the magnetic pole members and ionize the gas during a constant voltage period in which a predetermined voltage is applied between the second electrode and the second electrode. A method of controlling a gun,
The control for compensating for the decrease in the detected value by increasing the gas flow rate is repeated so that the detected value of the current flowing between the first electrode and the second electrode becomes the target value. A method for controlling an ion gun, comprising increasing the gas flow rate at the end of the constant voltage period with respect to the gas flow rate at the start of a voltage period.