JP6878031B2 - Pulse power supply - Google Patents

Description

The present invention relates to a pulse power supply device.

As a technique in this field, the plasma light source described in Patent Document 1 is known. This plasma light source uses the energy (electricity) stored in the capacitor to generate a potential difference between the center electrode and the external electrode in a state where the steam of the plasma medium is supplied between the center electrode and the external electrode. This causes a discharge.

A technique for recovering and reusing energy (electric power) used for electric discharge is known (see, for example, Patent Document 2). In the apparatus described in Patent Document 2, discharge is performed using a pair of electrodes, the energy reflected from the discharge is inverted and recharged in the capacitor, and the recharged energy is used for the next discharge.

Japanese Unexamined Patent Publication No. 2013-254693 Japanese Unexamined Patent Publication No. 2005-185092

Even in the plasma light source described in Patent Document 1, it is conceivable to recover and reuse the electric power. However, the amount of electric power recovered may differ for each external electrode due to the difference in impedance or the like. When a discharge is generated using this electric power, the discharge current flowing between the center electrode and each external electrode is different, and the initial plasma may become non-uniform. As described above, when plasma is generated by using a plurality of pairs of electrodes, it is desired to make the supplied electric power uniform.

The present invention provides a pulse power supply device capable of reducing variations in the reused electric power in a configuration in which electric power is supplied to each of a plurality of pairs of electrodes.

The pulse power supply device according to one aspect of the present invention is a device that supplies output power for pulse discharge between a center electrode and each of a plurality of external electrodes arranged so as to be separated from the center electrode. This pulse power supply device includes a primary side circuit and a plurality of secondary side circuits provided corresponding to each of the plurality of external electrodes. The primary side circuit includes a first coil portion wound around the core. Each of the plurality of secondary side circuits includes an output capacitor for supplying output power to the corresponding external electrode and center electrode corresponding to the secondary side circuit among the plurality of external electrodes, and one end and output of the output capacitor. A second coil portion provided between the other end of the capacitor and wound around the core is provided. The primary side circuit charges the output capacitor. Each of the plurality of secondary side circuits supplies the output power by supplying the power stored in the output capacitor so as to return from one end of the output capacitor to the other end via the center electrode and the corresponding external electrode.

In this pulse power supply, the primary side circuits charge the output capacitors of a plurality of secondary side circuits. Then, the power stored in each output capacitor is supplied from one end of the output capacitor to the other end of the output capacitor via the center electrode and the corresponding external electrode, so that the center electrode and the corresponding external electrode are supplied from each output capacitor. Output power for pulse discharge is supplied between the electrodes. Therefore, after the output power is supplied, the output capacitor stores the power having the opposite polarity to the power before the supply. Since a second coil portion is provided between one end and the other end of each output capacitor, a current flows from the other end of the output capacitor toward one end via the second coil portion. At this time, since the second coil portions of the plurality of secondary side circuits are wound around the same core, they are magnetically coupled to each other. Therefore, in the secondary circuit where the magnitude of the power stored in the output capacitor is the largest, that is, the voltage of the output capacitor, which is the potential of one end with respect to the potential of the other end of the output capacitor, is the lowest, in addition to the output capacitor. Current flows from one end to the other, and the output capacitor is recharged. In the process of regenerative charging of the output capacitor, if the voltage of the output capacitor becomes the same as the voltage of the capacitors of the other secondary side circuits, it flows to each secondary side circuit so that the voltage of each output capacitor becomes equal. While the currents interact with each other, they flow from the other end to one end of the output capacitor, and each output capacitor is regenerated and charged. As a result, the electric power stored in the output capacitor is made uniform. This makes it possible to reduce the variation in the reused electric power.

Each of the plurality of secondary side circuits may include a switching element for electrically connecting or electrically disconnecting one end and the other end via a second coil portion. In this case, the switching element makes it possible to start regenerative charging by electrically connecting one end and the other end of the output capacitor via the second coil portion.

The pulse power supply device of one embodiment may include a control device that controls a primary side circuit and a plurality of secondary side circuits. By controlling the switching element, the control device performs regenerative charging that returns the power returned to the other end to one end, and charges the output capacitor until the power stored in the output capacitor reaches a predetermined amount after regenerative charging. In addition, the primary side circuit may be controlled. In this case, since the output capacitor is charged after the regenerative charging is performed, the electric power can be reliably reused. Therefore, it is possible to reduce the power consumption.

According to the present invention, it is possible to reduce the variation in the reused electric power.

It is a schematic block diagram of the plasma light source including the pulse power supply device which concerns on one Embodiment. It is sectional drawing of the coaxial electrode along the cross section perpendicular to the central axis. It is a schematic circuit diagram of the pulse power supply device shown in FIG. It is a timing chart for demonstrating the operation of the pulse power supply apparatus shown in FIG. It is a figure for demonstrating the operation at the time of charging of the pulse power supply device shown in FIG. It is a figure for demonstrating the operation at the time of discharge of the pulse power supply apparatus shown in FIG. It is a figure for demonstrating the operation at the time of regenerative charging of the pulse power supply apparatus shown in FIG. It is a figure for demonstrating the mechanism of the regenerative charging shown in FIG. FIG. 8 is an enlarged view showing the vicinity of time point P2 in FIG.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the description of the drawings, the same reference numerals are used for the same or equivalent elements, and duplicate description is omitted.

A plasma light source including a pulse power supply device according to an embodiment will be described with reference to FIGS. 1 and 2. FIG. 1 is a schematic configuration diagram of a plasma light source including a pulse power supply device according to an embodiment. FIG. 2 is a cross-sectional view of a coaxial electrode along a cross section perpendicular to the central axis. The plasma light source 1 shown in FIG. 1 is a facing plasma focus type light source, and is applied to, for example, an exposure apparatus for manufacturing a semiconductor element. The plasma light source 1 is configured to be capable of generating, for example, extreme ultraviolet light (EUV light) having a wavelength of 13.5 nm. The plasma light source 1 enables photolithography to generate fine patterns by generating EUV light. When the plasma light source 1 is used in an exposure apparatus, continuous EUV light is required. Therefore, the plasma light source 1 is required to repeatedly output EUV light emitted in a pulsed manner at a high frequency.

The plasma light source 1 holds a pair of coaxial electrodes 10 that generate plasma, a voltage application device 20 that causes a potential difference between the coaxial electrodes 10, a laser device 30 that irradiates a plasma medium with laser light, and a plasma medium. A plasma medium supply unit 41 is provided.

The pair of coaxial electrodes 10 generate plasma that emits extreme ultraviolet light and confine the plasma. The pair of coaxial electrodes 10 are housed in the chamber 2 and are arranged so as to face each other. The pair of coaxial electrodes 10 are arranged plane-symmetrically with respect to the virtual central surface P extending between them. A certain distance (space) is provided between the pair of coaxial electrodes 10. The chamber 2 is provided with one or more exhaust pipes 3, and a vacuum pump (not shown) is connected to the exhaust pipe 3. The inside of the chamber 2 is maintained at a predetermined degree of vacuum. Chamber 2 is grounded.

As shown in FIGS. 1 and 2, each coaxial electrode 10 includes one center electrode 11, a plurality of external electrodes 12, and one insulator 13. One coaxial electrode 10 and the other coaxial electrode 10 have a common and single central axis AX.

The center electrode 11 is a rod-shaped conductor extending along the central axis AX. The central axis AX is located at the center of the center electrode 11. The center electrode 11 is made of a metal that is not easily damaged by high temperatures. The center electrode 11 is made of a refractory metal such as tungsten and molybdenum. The central axis AX is common to the pair of coaxial electrodes 10. The center axis AX of the center electrode 11 is orthogonal to the above-mentioned center surface P. The tip surface of the center electrode 11 facing the center surface P has a hemispherical shape, for example. The side surface of the center electrode 11 has a conical shape, for example.

The external electrode 12 is a rod-shaped conductor arranged around the center electrode 11. The external electrode 12 is made of a metal that is not easily damaged by high temperatures. The external electrode 12 is made of a refractory metal such as tungsten and molybdenum. The tip surface of the external electrode 12 facing the central surface P may be a curved surface such as a hemisphere or a flat surface.

The external electrode 12 has a predetermined distance from the center electrode 11. The plurality of external electrodes 12 are arranged at equal intervals (that is, rotationally symmetric) in the circumferential direction about the central axis AX. Specifically, the plasma light source 1 is provided with six external electrodes 12. The six external electrodes 12 are arranged at intervals of 60 ° with respect to the central axis AX. The number of external electrodes 12 is not limited to 6, and may be appropriately set according to the size and shape of the center electrode 11 and the external electrode 12, the spacing between them, and the like.

By arranging the plurality of external electrodes 12 around the center electrode 11, an initial discharge can be generated between the center electrode 11 and the external electrode 12. This initial discharge leads to a planar discharge. The planar discharge is also called a current sheet or a plasma sheet.

The insulator 13 is made of, for example, ceramic. The insulator 13 has a disk shape, for example. The insulator 13 supports each base of the center electrode 11 and the external electrode 12 and defines the distance between them. The insulator 13 electrically insulates the center electrode 11 and the external electrode 12.

The voltage applying device 20 creates a potential difference by applying a discharge voltage having the same polarity or the opposite polarity to each coaxial electrode 10. The voltage application device 20 includes two pulse power supply devices 21 and 21. Details of the pulse power supply device 21 will be described later.

The laser device 30 includes a laser generator 31 that irradiates the plasma medium supply unit 41 with the laser beam 32. The laser generator 31 emits a plasma medium by irradiating the laser beam 32 to generate an initial discharge (that is, planar discharge) of the plasma. The laser generator 31 is, for example, a YAG laser, and outputs a fundamental wave or a double wave of the fundamental wave as a short pulse laser beam for ablation. This laser beam is split into at least two laser beams 32a and 32b by an optical element such as a beam splitter (half mirror) 34 and a mirror 35. The laser beams 32a and 32b irradiate the plasma medium supply unit 41. On the surface of the plasma medium 43 irradiated with the laser beams 32a and 32b, a part of the plasma medium 43 becomes a neutral gas or ions (medium steam MV) which is a plasma medium by ablation, and the center electrode 11 and the external electrode 12 Is released between and.

When the laser beams 32a and 32b are irradiated, the discharge voltage by the voltage applying device 20 is applied to the center electrode 11 and the external electrode 12 of each coaxial electrode 10. When the above-mentioned ablation occurs, a discharge between the center electrode 11 and each external electrode 12 is induced, and further, a planar discharge is formed by this discharge. It is preferable that a plurality of (at least two) laser beams are simultaneously irradiated at intervals in the circumferential direction of the central axis AX. It is desirable that the smaller the number of irradiation points of the laser beam, the more the laser beam is irradiated at a position rotationally symmetric with respect to the center electrode 11. In the plasma light source 1, the laser irradiation points are set at two opposite points (see FIG. 2). Simultaneous irradiation of a plurality of laser beams can be easily achieved by forming a plurality of optical paths having a matching optical path length by using optical elements such as a beam splitter and a mirror.

The plasma medium supply unit 41 holds a plasma medium used for generating plasma light. The plasma medium supply unit 41 includes a plasma medium 43 that is a solid or a liquid, and a holding unit 42 that holds the plasma medium 43. The plasma medium 43 can be selected depending on the wavelength of ultraviolet light required. For example, when ultraviolet light of 13.5 nm is required, at least one of lithium (Li), xenon (Xe), tin (Sn) and the like is used as the plasma medium 43. When ultraviolet light of 6.7 nm is required, at least one plasma medium such as gadolinium (Gd) and terbium (Tb) is used.

The plasma light source 1 has two plasma medium supply units 41 for one coaxial electrode 10. The number of plasma medium supply units 41 is not limited to two, and may be appropriately set according to the size and shape of the coaxial electrode 10. The pair of plasma medium supply units 41 are arranged around the coaxial electrode 10.

Next, the details of the pulse power supply device will be described with reference to FIG. FIG. 3 is a schematic circuit diagram of a pulse power supply device according to an embodiment. Since the pulse power supply devices 21 and 21 have the same circuit configuration, one of the pulse power supply devices 21 will be described here.

The pulse power supply device 21 is a device that supplies output power for pulse discharge between the center electrode 11 and each of the plurality of external electrodes 12 arranged so as to be separated from the center electrode 11. The pulse power supply device 21 includes a terminal 22 and a plurality of terminals 23 (23a to 23f). The terminal 22 is connected to the center electrode 11 of the coaxial electrode 10, and the terminals 23a to 23f are connected to the external electrode 12 corresponding to each terminal 23. The pulse power supply device 21 supplies output power by applying a discharge voltage so that the potential of the center electrode 11 is higher than the potential of the external electrode 12. The pulse power supply device 21 may supply output power by applying a discharge voltage so that the potential of the center electrode 11 is lower than the potential of the external electrode 12.

The pulse power supply device 21 includes a single primary side circuit 50, a plurality of secondary side circuits 60 (60a to 60f), and a control device 70. The primary side circuit 50 and the plurality of secondary side circuits 60 are magnetically coupled to each other. Specifically, the primary side circuit 50 and the plurality of secondary side circuits 60 are magnetically coupled via a single core (iron core) B. The core B is made of a material having a high magnetic permeability such as iron. The core B has, for example, an annular shape. A step-up transformer is composed of a core B, a coil portion 51 (first coil portion) and a coil portion 61 (second coil portion), which will be described later.

The primary side circuit 50 is a circuit on the primary side of the step-up transformer. The primary side circuit 50 charges the capacitor C2 (output capacitor) of the secondary side circuit 60, which will be described later. The primary side circuit 50 includes a coil unit 51, a power supply 52, a capacitor C1, switching elements SW1 and SW2, diodes D1 to D4, and an inductor L.

The coil unit 51 transmits and receives electric power to and from the coil unit 61, which will be described later. The coil portion 51 is a conducting wire wound (wound) around the core B, and is magnetically coupled to the coil portion 61 via the core B. The power supply 52 is a power supply for charging the capacitor C1. The power supply 52 supplies a high DC voltage to the capacitor C1. The capacitor C1 is a power storage unit for supplying the power charged by the power supply 52 to the secondary circuit 60.

The switching elements SW1 and SW2 are elements that can switch between electrical opening and closing. That is, it can be switched between an on state in which both ends (collector and emitter) of the switching elements SW1 and SW2 (collector and emitter) are in a conductive state and an off state in which the switching elements are cut off. As the switching elements SW1 and SW2, for example, an IGBT (Insulated Gate Bipolar Transistor), a MOSFET (Metal Oxide Semiconductor Field Effect Transistor), a bipolar transistor and the like are used. In the example shown in FIG. 3, the switching elements SW1 and SW2 are IGBTs. Drive signals are supplied from the control device 70 to the gates (control terminals) of the switching elements SW1 and SW2, respectively. The switching elements SW1 and SW2 switch between an on state and an off state according to a drive signal output from the control device 70.

The diodes D1 and D2 are freewheeling diodes that are electrically connected in parallel with the switching elements SW1 and SW2, respectively. Specifically, the cathodes of the diodes D1 and D2 are connected to the collectors of the switching elements SW1 and SW2, respectively, and the anodes of the diodes D1 and D2 are connected to the emitters of the switching elements SW1 and SW2, respectively. The diodes D3 and D4 are diodes for regenerating the induced energy of the coil portion 51. The inductor L is provided to suppress the inrush current.

One end of the capacitor C1 is connected to the collector of the switching element SW1 and the cathode of the diode D3. The other end of the capacitor C1 is connected to the emitter of the switching element SW2 and the anode of the diode D4. The emitter of the switching element SW1 and the cathode of the diode D4 are connected to each other, and the collector of the switching element SW2 and the anode of the diode D3 are connected to each other. The connection point between the emitter of the switching element SW1 and the cathode of the diode D4 and the connection point between the collector of the switching element SW2 and the anode of the diode D3 are connected via the inductor L and the coil portion 51.

The secondary side circuit 60 is a circuit on the secondary side of the step-up transformer. The secondary side circuit 60 is provided corresponding to each of the plurality of external electrodes 12. In the present embodiment, since the number of external electrodes 12 is 6, six secondary side circuits 60 (60a to 60f) are provided. Since the secondary side circuits 60a to 60f have the same configuration, the secondary side circuits 60a will be described here. In the following description, when distinguishing the elements of the secondary side circuits 60a to 60f, a to f are added to the symbols representing the elements.

The secondary side circuit 60a supplies output power between the external electrode 12a (corresponding external electrode) corresponding to the secondary side circuit 60a among the plurality of external electrodes 12 and the center electrode 11. The secondary side circuit 60a includes a coil portion 61, a capacitor C2 (output capacitor), a switching element SW3, and diodes D5 to D8.

The coil unit 61 transmits and receives electric power to and from the coil unit 51. The coil portion 61 is provided between one end and the other end of the capacitor C2. The coil portion 61 is a conducting wire wound around the core B, and is magnetically coupled to the coil portion 51 via the core B. The capacitor C2 is a power storage unit for supplying output power between the external electrode 12a and the center electrode 11.

The switching element SW3 is an element capable of electrically switching between opening and closing. That is, it is switched between an on state in which both ends (collector and emitter) of the switching element SW3 are in a conductive state and an off state in which the switching element SW3 is in a cutoff state. As the switching element SW3, for example, an IGBT, a MOSFET, a bipolar transistor, or the like is used. In the example shown in FIG. 3, the switching element SW3 is an IGBT. A drive signal is supplied from the control device 70 to the gate (control terminal) of the switching element SW3. The switching element SW3 switches between an on state and an off state according to a drive signal output from the control device 70.

The diode D5 is a freewheeling diode electrically connected in parallel with the switching element SW3. Specifically, the cathode of the diode D5 is connected to the collector of the switching element SW3, and the anode of the diode D5 is connected to the emitter of the switching element SW3. The diodes D6 to D8 are diodes for preventing backflow.

The other end of the capacitor C2 is connected to the anode of the diode D6 via the coil portion 61. The cathode of the diode D6 is connected to the collector of the switching element SW3. The emitter of the switching element SW3 is connected to one end of the capacitor C2. Further, one end of the capacitor C2 is connected to the anode of the diode D7, and the other end of the capacitor C2 is connected to the cathode of the diode D8. The cathode of the diode D7 is connected to the terminal 22. The anode of the diode D8 is connected to the terminal 23a. The switching element SW3 can be said to be a switch for switching the electrical connection between one end of the capacitor C2 and the other end of the capacitor C2.

The secondary circuit 60a is provided with a voltmeter 71 and an ammeter 72. The voltmeter 71 is connected in parallel with the capacitor C2, and measures the voltage across the capacitor C2. The voltmeter 71 measures the voltage by various methods. The voltage is measured, for example, by using a resistance voltage divider. The voltmeter 71 has a positive value (positive voltage) when the potential at one end of the capacitor C2 is higher than the potential at the other end, and a negative value (positive voltage) when the potential at the other end of the capacitor C2 is higher than the potential at one end. The voltage value is output as (negative voltage). The voltmeter 71 outputs the measured voltage value to the control device 70. The ammeter 72 is provided in series between the other end of the capacitor C2 and the coil portion 61, and measures the current from the other end of the capacitor C2 toward one end. The ammeter 72 measures the current by various methods. The current is measured by, for example, a CT method, a Hall element method, a Rogoski coil method, or the like. The ammeter 72 outputs a current value with the current from the other end to one end of the capacitor C2 as positive. The ammeter 72 outputs the measured current value to the control device 70. In the following description, it may be expressed as "voltage of capacitor C2", but the voltage of capacitor C2 means the potential of one end with reference to the potential of the other end of the capacitor C2.

The control device 70 is a controller that controls the primary side circuit 50 and the plurality of secondary side circuits 60. The control device 70 is a computer including, for example, a CPU (Central Processing Unit) and hardware such as a memory such as a RAM (Random Access Memory) and a ROM (Read Only Memory). The function of the control device 70 is realized by operating each hardware under the control of the CPU based on the computer program stored in the memory.

Specifically, the control device 70 controls the primary side circuit 50 and the plurality of secondary side circuits 60 based on the voltage value measured by each voltmeter 71 and the current value measured by each ammeter 72. To do. For example, the control device 70 performs a charging process for charging the capacitor C2 by controlling the switching elements SW1 to SW3. The control device 70 performs a regenerative process of reversing the polarity of the electric power stored in the capacitor C2 by controlling the switching elements SW1 to SW3. By passing a current from the other end of the capacitor C2 to one end, the polarity of the power stored in the capacitor C2 is reversed in a state where the potential of the other end of the capacitor C2 is higher than the potential of one end, and one end of the capacitor C2. Charging to make the potential of is higher than the potential of the other end is called regenerative charging.

Next, the operation of the pulse power supply device 21 will be described with reference to FIGS. 4 to 7. FIG. 4 is a timing chart for explaining the operation of the pulse power supply device shown in FIG. FIG. 5 is a diagram for explaining the operation of the pulse power supply device shown in FIG. 3 during charging. FIG. 6 is a diagram for explaining the operation of the pulse power supply device shown in FIG. 3 at the time of discharge. FIG. 7 is a diagram for explaining the operation of the pulse power supply device shown in FIG. 3 during regenerative charging.

When the operation of the plasma light source 1 is started, power is not stored in the capacitor C2 of each secondary circuit 60. Therefore, first, the voltage application device 20 charges the capacitor C2. Specifically, the control device 70 starts charging the capacitor C2 by first turning on the switching elements SW1 to SW3 (time t0). Then, as shown in FIG. 5, a current I1 flows from one end of the capacitor C1 through the switching element SW1, the inductor L, the coil portion 51, and the switching element SW2 in order and returns to the other end of the capacitor C1. When the current I1 flows through the coil portion 51, an induced electromotive voltage is generated in the coil portion 61 by electromagnetic induction, and returns from the other end of the capacitor C2 to one end of the capacitor C2 through the coil portion 61, the diode D6, and the switching element SW3. A current I2 flows in the path. As a result, the potential at one end of the capacitor C2 becomes lower than the potential at the other end, and the capacitor C2 is charged. That is, the primary side circuit 50 charges the capacitor C2 via the coil portion 51 and the coil portion 61.

While charging the capacitor C2, the control device 70 determines whether or not the voltage value measured by at least one of the voltmeters 71 of each secondary circuit 60 has reached the specified value. .. This voltage value is a value obtained by measuring the voltage VP of the capacitor C2 with a voltmeter 71. The specified value is the voltage value of the capacitor C2 when the specified power used for discharging is charged to the capacitor C2, and is set to, for example, 5 kV. This determination is repeated periodically until the voltage value reaches the specified value. Then, when it is determined that the voltage value has reached the specified value, the control device 70 turns off the switching elements SW1 to SW3 and stops charging the capacitor C2 (time t1). At this time, the voltage applying device 20 supplies output power between the center electrode 11 and the external electrode 12. That is, the voltage applying device 20 applies a discharge voltage between the center electrode 11 and the external electrode 12. Then, the control device 70 determines whether or not the discharge (radiation of plasma light) has been performed.

Here, the emission of plasma light is performed as follows. With the discharge voltage applied, the laser device 30 irradiates the plasma medium 43 of the plasma medium supply unit 41 with the laser beams 32a and 32b. Immediately after that, an electric discharge occurs between each of the plurality of external electrodes 12 and the center electrode 11 (time t2). As a result, as shown in FIG. 6, the current I3 (discharge current) passes from one end of the capacitor C2 through the diode D7, the center electrode 11, the external electrode 12, and the diode D8 in order and returns to the other end of the capacitor C2. Flows, and a planar discharge distributed over the entire circumference of the center electrode 11 is obtained. In FIG. 6, for convenience of drawing, the path of the current I3 is shown in a simplified manner. Therefore, the current I3 is drawn so as not to pass through the center electrode 11 and the external electrode 12, but the center electrode is actually used. It goes through the 11 and the external electrode 12. After that, the planar discharge reaches the tip of the center electrode 11, and the starting point of the discharge current shifts from the side surface of the center electrode 11 to the tip surface. Due to this current transfer, the lithium-containing plasma that has moved with the pair of planar discharges converges to a high density and high temperature.

Since this phenomenon proceeds at the coaxial electrodes 10 sandwiching the central surface P (see FIG. 1), the initial plasma is pushed out from one coaxial electrode 10 toward the other coaxial electrode 10. As a result, the initial plasma receives pressure from both directions along the central axis AX (see FIG. 1) and moves to an intermediate position where the coaxial electrodes 10 face each other (that is, the position of the central surface P), and the plasma medium is used as a component. A single plasma is formed. While the planar discharge is occurring, the density and temperature of the plasma are increased, and the ions containing lithium are ionized. As a result, plasma light including extreme ultraviolet light is emitted from the plasma. Since this plasma light is radiated in a pulsed manner, the series of discharges may be referred to as a pulse discharge.

In this way, plasma light is emitted, and the potential of the other end of the capacitor C2 becomes higher than the potential of one end. In order to determine whether or not discharge (radiation of plasma light) has been performed, the control device 70 determines, for example, a voltage value measured by at least one of the voltmeters 71 of each secondary circuit 60. It is determined whether the voltage is lower than the predetermined voltage threshold. The voltage threshold value is a voltage value of the capacitor C2 capable of determining that the discharge has ended, and is set to, for example, 0V. This determination is repeated periodically until the voltage value becomes lower than the voltage threshold.

Then, when it is determined that the voltage value becomes lower than the voltage threshold value, the control device 70 can determine that the discharge has been performed, and therefore operates the timer (not shown). Then, the control device 70 determines whether a predetermined time has elapsed from the end of the discharge. The predetermined time is a time for preventing re-discharging when the capacitor C2 is regeneratively charged, and is set longer than the pulse width (time width) of the pulse discharge. The pulse discharge is continued, for example, for about 2 microseconds. This determination is periodically repeated until a predetermined time has elapsed.

Then, when it is determined that the predetermined time has elapsed, the control device 70 turns on the switching element SW3 of each secondary circuit 60 and starts regenerative charging (time t3). At this time, the switching elements SW1 and SW2 remain in the off state. As a result, as shown in FIG. 7, a current I4 (regenerative current) flows from the other end of the capacitor C2 through the coil portion 61, the diode D6, and the switching element SW3 in order and returns to one end of the capacitor C2. When the current I4 flows through the coil portion 61, an induced electromotive voltage is generated in the coil portion 51 by electromagnetic induction, and the capacitor C1 passes through the diode D4, the inductor L, the coil portion 51, and the diode D3 in order from the other end of the capacitor C1. The current I5 flows in the path returning to one end of the. As a result, the capacitor C1 is also regeneratively charged.

For example, when the capacity of the capacitor C1 is larger than the capacity of the capacitor C2, the charge accumulated in the capacitor C1 decreases when the capacitor C2 is charged, but the reduced amount of charge is not large with respect to the capacity of the capacitor C1. .. Therefore, at time t3, the regenerative charging of the capacitor C1 and the regenerative charging of the capacitor C2 start at the same time, but the regenerative charging of the capacitor C1 ends immediately. On the other hand, since the regenerative charging of the capacitor C2 is synchronized with the regenerative charging of the capacitor C1 at the start, a large current I4 flows, but after that, the regenerative charging of the capacitor C2 is performed slowly. Therefore, the waveform of the current I4 and the waveform of the current I5 are the waveforms shown in FIG.

When the current I4 flows from the other end of the capacitor C2 to one end, the electric power charged in the capacitor C2 with a negative voltage is inverted and charged to a positive voltage. At this time, among the plurality of secondary side circuits 60, the current I4 flows in the secondary side circuit 60 in which the negative voltage of the capacitor C2 is the largest (that is, the voltage VP of the capacitor C2 is the lowest), and the capacitor C2 is positive. Charged to voltage. When the voltage VP of the capacitor C2 becomes the same as the voltage VP of the capacitor C2 of the other secondary side circuits 60 in the process of regenerative charging of the capacitor C2, the regenerative charging is synchronously performed by those secondary side circuits 60. Will be done. Since the secondary side circuits 60 are magnetically coupled to each other via the core B, the currents I4 flowing through the secondary side circuits 60 interact with each other to be regeneratively charged.

Here, regenerative charging will be described in detail with reference to FIGS. 8 and 9. FIG. 8 is a diagram for explaining the mechanism of regenerative charging shown in FIG. 7. FIG. 9 is an enlarged view showing the vicinity of time point P2 in FIG. First, regenerative charging when only the secondary side circuits 60a and 60b are present will be described. In FIG. 8A, the switching element SW3 is omitted.

As shown in FIG. 8A, the capacitor C2a is reverse-charged so that the voltage VPa of the capacitor C2a connected to the external electrode 12a becomes -4000V after discharging, and the capacitor is connected to the external electrode 12b. It is assumed that the capacitor C2b is reverse-charged so that the voltage VPb of C2b becomes −1000V. When the switching elements SW3a and SW3b are turned on at time t3, the secondary side circuits 60a and 60b become LC circuits. When the secondary side circuits 60a and 60b are independent, the negative voltage charged in the capacitors C2a and C2b is inverted and the regenerative charging becomes a positive voltage continuously. However, since the coil portions 61a and 61b are magnetically coupled by the core B (transformer), they operate as follows.

First, in the phase P1 shown in FIG. 8B, since the voltage VPa of the capacitor C2a is lower than the voltage VPb of the capacitor C2b, inversion (regenerative charging) starts in the secondary circuit 60a. That is, in the secondary circuit 60a, the current I4a passes through the coil portion 61a and the diode D6a in order from the other end of the capacitor C2a and flows into one end of the capacitor C2a. As a result, the voltage VPa of the capacitor C2a increases. At this time, when the current I4a flows through the coil portion 61a, an induced electromotive voltage is generated in the coil portion 61b by electromagnetic induction. However, since the diode D6b is provided, no reverse current flows through the secondary circuit 60b. In the secondary circuit 60a, regenerative charging is continued until the voltage VPa of the capacitor C2a reaches −1000 V, which is the voltage VPb of the capacitor C2b (time point P2).

Then, in the phase P3, as shown in FIG. 9A, when the voltage VPa of the capacitor C2a becomes higher than the voltage VPb of the capacitor C2b, the current I4a flowing in the secondary circuit 60a decreases in a sinusoidal manner. To do. As a result, an induced electromotive voltage is generated in the coil portion 61b, and in the secondary circuit 60b, the current I4b begins to flow from the other end of the capacitor C2b through the coil portion 61b and the diode D6b in order toward one end of the capacitor C2b. The current I4b increases in a sinusoidal manner in the opposite phase to the current I4a.

The voltage VPb of the capacitor C2b increases as the current I4b flows in the secondary circuit 60b. Then, when the voltage VPb of the capacitor C2b becomes higher than the voltage VPa of the capacitor C2a, the current I4b decreases in a sinusoidal manner. As a result, an induced electromotive voltage is generated in the coil portion 61a, and the current I4a in the secondary side circuit 60a increases in a sinusoidal manner in the opposite phase to the current I4b. While repeating this operation, regenerative charging proceeds in the secondary side circuits 60a and 60b.

Then, in the phase P4, the regenerative charging is completed, and the voltage VPa of the capacitor C2a and the voltage VPb of the capacitor C2b become the same voltage. When the loss is negligibly small, the voltages VPa and VPb of the capacitors C2a and C2b are values obtained by reversing the polarities of the average values of the voltages VPa and VPb that were inverting and charged to the capacitors C2a and C2b before the regenerative charging ( + 2500V).

Subsequently, the regenerative charging when the secondary side circuits 60a, 60b, and 60c are present will be described. After discharging, the capacitor C2a is inverted and charged so that the voltage VPa of the capacitor C2a connected to the external electrode 12a becomes -4000V, and the voltage VPb of the capacitor C2b connected to the external electrode 12b becomes -3000V. It is assumed that C2b is reverse-charged and the capacitor C2c is reverse-charged so that the voltage VPc of the capacitor C2c connected to the external electrode 12c becomes −2000V.

Since the voltage VPa of the capacitor C2a is the highest as in the case where the number of secondary side circuits is two, inverting charging (regenerative charging) is started in the secondary side circuit 60a. At this time, an induced electromotive voltage is generated in the coil portions 61b and 61c, but since the diodes D6b and D6c are present, the reverse current does not flow and the voltages VPb and VPc of the capacitors C2b and C2c do not fluctuate. In the secondary circuit 60a, regenerative charging continues until the voltage VPa of the capacitor C2a reaches the voltage VPb of the capacitor C2b-3000V.

When the voltage VPa of the capacitor C2a becomes higher than the voltage VPb of the capacitor C2b, the currents I4a and the current I4b flow alternately in the same manner as in the above-mentioned phase P3, and the voltages VPa and VPb of the capacitors C2a and C2b increase. .. At this time, the voltage VPa of the capacitor C2a and the voltage VPb of the capacitor C2b are substantially the same. This operation continues until the voltages VPa and VPb of the capacitors C2a and C2b reach -2000 V, which is the voltage VPc of the capacitors C2c.

When the voltages VPa and VPb of the capacitors C2a and C2b become higher than the voltage VPc of the capacitors C2c, the currents I4a and I4b flowing in the secondary circuits 60a and 60b decrease in a sinusoidal manner. As a result, an induced electromotive voltage is generated in the coil portion 61c, and in the secondary circuit 60c, the current I4c begins to flow from the other end of the capacitor C2c through the coil portion 61c and the diode D6c in order toward one end of the capacitor C2c. The current I4c increases in a sinusoidal manner. There is a slight difference between the voltage VPa of the capacitor C2a and the voltage VPb of the capacitor C2b when the current I4c starts to flow, and which of the voltage VPa of the capacitor C2a and the voltage VPb of the capacitor C2b is higher depends on the timing. Here, it is assumed that the voltage is higher in the order of voltage VPc, voltage VPb, and voltage VPa.

The voltage VPc of the capacitor C2c increases as the current I4c flows in the secondary circuit 60c. When the voltage VPc of the capacitors C2c becomes higher than the voltages VPa and VPb of the capacitors C2a and C2b, the current I4c decreases in a sinusoidal manner. As a result, an induced electromotive voltage is generated in the coil portion 61b, and the current I4b increases in a sinusoidal shape in the secondary side circuit 60b. The voltage VPb of the capacitor C2b increases as the current I4b flows in the secondary circuit 60b. When the voltage VPb of the capacitors C2b becomes higher than the voltages VPa and VPc of the capacitors C2a and C2c, the current I4b decreases in a sinusoidal manner. As a result, an induced electromotive voltage is generated in the coil portion 61a, and the current I4a increases in a sinusoidal shape in the secondary side circuit 60a.

While repeating such an operation, regenerative charging proceeds in the secondary side circuits 60a, 60b, 60c. By such an operation, sinusoidal currents I4a, I4b, I4c having different phases flow through the secondary side circuits 60a, 60b, 60c. The voltages VPa, VPb, and VPc of the capacitors C2a, C2b, and C2c have substantially the same voltage macroscopically, although they have sine wave waveform shapes with different phases microscopically.

Then, the inverting charging is completed, and the voltages VPa, VPb, and VPc of the capacitors C2a, C2b, and C2c become the same voltage. When the loss is negligibly small, the voltages VPa, VPb, and VPc of the capacitors C2a, C2b, and C2c are the average of the voltages VPa, VPb, and VPc that were reverse-charged to the capacitors C2a, C2b, and C2c before the regenerative charging. The value (+ 3000V) is obtained by reversing the polarity of the value.

Similarly, even when there are six secondary side circuits 60, regenerative charging starts from the secondary side circuit 60 having the lowest voltage of the capacitor C2, and the voltage of the capacitor C2 becomes the same voltage as the secondary side circuit 60 having the next lowest voltage. At that point, regenerative charging proceeds while interacting with each other. Similar operations proceed one after another, and finally, regenerative charging proceeds while the six secondary circuit 60s interact with each other. Finally, the voltages VPa to VPf of the capacitors C2a to C2f reach a value obtained by reversing the polarity of the average value of the voltages VPa to VPf that were reversely charged to the capacitors C2a to C2f before the regenerative charging, and the regenerative charging is completed. To do.

Returning to FIG. 4, the description of the operation of the pulse power supply device 21 will be continued. After starting the regenerative charging, the control device 70 determines whether or not the regenerative charging is completed. This determination is made using, for example, the time variation of the voltage value measured by at least one of the voltmeters 71 of each secondary circuit 60. Specifically, the control device 70 determines whether or not the time change of the voltage value is within the predetermined first range. When the regenerative charging is completed, the voltage change of the capacitor C2 is almost eliminated, so that the first range is set to the time change of the voltage value at which it can be determined that the regenerative charging is completed. The control device 70 determines that the regenerative charging has been completed if the time change of the voltage value is within the first range, and determines that the regenerative charging has not been completed if it is outside the first range.

Further, this determination may be performed using the difference between the maximum voltage value and the minimum voltage value among the voltage values measured by the voltmeter 71 of each secondary circuit 60. In this case, the control device 70 determines whether or not the difference is within a predetermined second range. When the regenerative charging is completed, the voltage of the capacitor C2 of each secondary circuit 60 becomes substantially the same voltage. Therefore, the second range is the difference between the maximum voltage value and the minimum voltage value at which it can be determined that the regenerative charging is completed. Is set to. If the difference is within the second range, the control device 70 determines that the regenerative charging has been completed, and if it is outside the second range, it determines that the regenerative charging has not been completed. The control device 70 further determines whether or not the time change of the minimum voltage value is within the first range, the difference is within the second range, and the time change of the minimum voltage value is the first. If it is within the range, it may be determined that the regenerative charging is completed.

Further, the control device 70 may determine whether or not the regenerative charging is completed by comparing the current value measured by the ammeter 72 of each secondary circuit 60 with a predetermined current threshold value. Good. When the regenerative charging is completed, the current I4 hardly flows, so the current threshold value is set to a current value at which it can be determined that the regenerative charging is completed. Specifically, the control device 70 determines that the regenerative charging is completed when the current value measured by the ammeter 72 is smaller than the current threshold value, and the current value measured by the ammeter 72 is equal to or higher than the current threshold value. In some cases, it is determined that the regenerative charging has not been completed.

The control device 70 may determine whether or not the regenerative charging is completed by combining the determination using the voltage value and the determination using the current value. Further, the control device 70 may calculate the power value from the voltage value and the current value, and determine whether or not the regenerative charging is completed based on the time change of the power value. For example, the control device 70 determines whether or not the time change of the power value is within a predetermined power range. When the regenerative charging is completed, the power change of the capacitor C2 is almost eliminated, so that the power range is set to the time change of the power value that can determine that the regenerative charging is completed. The control device 70 determines that the regenerative charging has been completed if the time change of the power value is within the power range, and determines that the regenerative charging has not been completed if it is out of the power range.

This determination is periodically repeated until the regenerative charging is completed. Then, when it is determined that the regenerative charging is completed, the control device 70 turns on the switching elements SW1 and SW2 and starts charging (time t4). At this time, the switching element SW3 remains in the ON state. Then, the control device 70 determines whether or not the voltage value measured by at least one of the voltmeters 71 of each secondary circuit 60 has reached the specified value. After that, the above operation is repeated.

In this way, each of the plurality of secondary side circuits 60 returns the electric power stored in the capacitor C2 from one end of the capacitor C2 to the other end of the capacitor C2 via the center electrode 11 and the corresponding external electrode 12. Output power is supplied by supplying. By controlling the switching element SW3, the control device 70 performs regenerative charging that returns the power returned to the other end of the capacitor C2 to one end, and the capacitor until the power stored in the capacitor C2 reaches the specified power after the regenerative charging. The primary side circuit 50 is controlled so as to charge C2.

As described above, in the pulse power supply device 21, the single primary side circuit 50 charges the capacitors C2 of the plurality of secondary side circuits 60. Then, the electric power stored in each capacitor C2 is supplied so as to return from one end of the capacitor C2 to the other end of the capacitor C2 via the center electrode 11 and the external electrode 12, so that the center electrode 11 and the center electrode 11 and each capacitor C2 Output power for pulse discharge is supplied between the external electrodes 12. Therefore, after the output power is supplied, the capacitor C2 stores the power having the opposite polarity to the power before the supply. The electrical resistance of plasma is so small that plasma consumes very little power. Therefore, most of the output power supplied from the capacitor C2 returns to the capacitor C2.

Since a coil portion 61 is provided between one end and the other end of each capacitor C2, an LC circuit is formed by the capacitor C2 and the coil portion 61. As a result, a current I4 flows from the other end of the capacitor C2 toward one end via the coil portion 61, and the capacitor C2 is regeneratively charged. Then, each capacitor C2 is recharged by the primary side circuit 50 to make up for the insufficient power, so that the output power for each pulse discharge is made uniform. For example, suppose that after pulse discharging with an output power at which the voltage of the capacitor C2 becomes 5 kV, the power at which the voltage of the capacitor C2 becomes −4.5 kV is recovered by the capacitor C2. By reversing the polarity by regenerative charging and replenishing the power for a voltage of 0.5 kV by the primary side circuit 50, charging for the next pulse discharge is completed. In this way, the electric power used for the pulse discharge can be reused, and the electric power consumption in the plasma light source 1 can be reduced.

However, the power recovered may differ for each capacitor C2 due to differences in impedance and the like. When the polarity of this power is simply reversed, the power stored in each capacitor C2 cannot be made uniform even if the lacking power is supplemented by the primary side circuit 50. That is, since each capacitor C2 is recharged at the same time by the primary side circuit 50, the charge amount cannot be changed for each capacitor C2. Therefore, if the power stored in the capacitor C2 in the regeneratively charged state is non-uniform, the power stored in the capacitor C2 after being recharged by the primary circuit 50 is also non-uniform. If pulse discharge is performed in such a state, the initial plasma becomes non-uniform, and the temperature and density of the converged plasma may not increase. As a result, there is a concern that the emission intensity of plasma light may decrease.

On the other hand, in the pulse power supply device 21, since the coil portions 61 of the plurality of secondary side circuits 60 are wound around the same core B, they are magnetically coupled to each other. Therefore, in the secondary circuit 60 in which the magnitude (negative voltage) of the power stored in the capacitor C2 after supplying the output power is the largest, that is, the voltage of the capacitor C2 is the lowest, from the other end of the capacitor C2. A current I4 flows through one end, and the capacitor C2 is recharged. When the voltage of the capacitor C2 becomes the same as the voltage of the capacitor C2 of the other secondary circuit 60 in the process of regenerative charging of the capacitor C2, each secondary side circuit so that the voltage of each capacitor C2 becomes equal. While the current I4 flowing through the 60 interacts with each other, it flows from the other end of the capacitor C2 to one end, and each capacitor C2 is regenerated and charged. As a result, the electric power stored in each of the capacitors C2 of the plurality of secondary side circuits 60 after regenerative charging is made uniform. This makes it possible to reduce the variation in the reused electric power.

Then, by supplementing the insufficient power with the primary side circuit 50, the output power supplied from each capacitor C2 can be made uniform, and the output power for each pulse discharge can be made uniform. Since the output power is homogenized for each of the external electrodes 12, the initial plasma is homogenized, the convergence of the plasma is improved, and a high-temperature and high-density plasma can be formed. Further, by stabilizing the output power supplied for each pulse discharge, it is possible to suppress the variation in the emission intensity of the plasma light for each pulse discharge. As a result, the stability of the plasma light source 1 can be improved.

Each of the plurality of secondary side circuits 60 includes a switching element SW3 for electrically connecting or electrically disconnecting one end and the other end of the capacitor C2 via the coil portion 61. An LC circuit is formed by electrically connecting one end and the other end of the capacitor C2 via the coil portion 61 by the switching element SW3. This makes it possible to start regenerative charging. When one end and the other end of the capacitor C2 are always connected via the coil portion 61, the electric power returned to the capacitor C2 is regeneratively charged during pulse discharge, and re-discharge can be performed. There is sex. Therefore, the re-discharge can be reliably prevented by turning on the switching element SW3 by the control device 70 at a timing later than the time required for the pulse discharge after the pulse discharge is started.

Then, the primary side circuit 50 is controlled so as to charge the capacitor C2 until the electric power stored in the capacitor C2 reaches a predetermined amount after the regenerative charging. In this case, since the capacitor C2 is charged after the regenerative charging is performed, the electric power can be reliably reused. Therefore, it is possible to further reduce the power consumption of the plasma light source 1.

Although the embodiment of the present invention has been described above, the present invention is not limited to the above embodiment. For example, the pulse power supply device 21 can be used in addition to the plasma light source 1. The pulse power supply device 21 can be applied to a device (a device that requires pulse power at a high repetition cycle) in which the pulse power supply device 21 is repeatedly charged in a pulsed manner and the same voltage is applied to a plurality of electrode pairs.

Further, the primary side circuit 50 may be a high frequency power supply.

Further, the pulse power supply device 21 may supply output power by applying a discharge voltage so that the potential of the center electrode 11 is lower than the potential of the external electrode 12. In this case, terminals 22 are provided for each secondary circuit 60, and the cathode of the diode D7 of each secondary circuit 60 is connected to the corresponding terminal 22. Then, each terminal 22 is connected to an external electrode 12 corresponding to the secondary side circuit 60. Further, the pulse power supply device 21 has one terminal 23, and the anode of the diode D8 of each secondary circuit 60 is connected to the terminal 23. Then, the terminal 23 is connected to the center electrode 11.

1 Plasma light source 2 Chamber 3 Exhaust pipe 10 Coaxial electrode 11 Center electrode 12, 12a, 12b, 12c External electrode 13 Insulator 20 Voltage application device 21 Pulse power supply device 22 Terminals 23, 23a, 23b, 23c, 23d, 23e, 23f Terminal 30 Laser device 31 Laser generator 32, 32a, 32b Laser light 34 Beam splitter 35 Mirror 41 Plasma medium supply section 42 Holding section 43 Plasma medium 50 Primary circuit 51 Coil section (first coil section)
52 Power supply 60, 60a, 60b, 60c, 60d, 60e, 60f Secondary circuit 61, 61a, 61b, 61c Coil section (second coil section)
70 Control device AX Center axis B Core C1 Capacitor C2, C2a, C2b, C2c, C2d, C2e, C2f Capacitor (output capacitor)
D1 diode D2 diode D3 diode D4 diode D5 diode D6, D6a, D6b, D6c diode D7 diode D8 diode L inductor P center surface SW1 switching element SW2 switching element SW3, SW3a, SW3b switching element MV medium steam

Claims (2)

A pulse power supply device that supplies output power for pulse discharge between a center electrode and each of a plurality of external electrodes arranged so as to be separated from the center electrode.
Primary side circuit and
A plurality of secondary side circuits provided corresponding to each of the plurality of external electrodes, and
With
The primary side circuit includes a first coil portion wound around a core.
Each of the plurality of secondary side circuits includes an output capacitor for supplying the output power to the corresponding external electrode, the center electrode, and the output corresponding to the secondary side circuit among the plurality of external electrodes. A second coil portion provided between one end of the capacitor and the other end of the output capacitor and wound around the core, and the one end and the other end are electrically connected via the second coil portion. , Or with a switching element for electrical disconnection ,
The primary side circuit charges the output capacitor and
Each of the plurality of secondary side circuits supplies the output power stored in the output capacitor so as to return from one end to the other end via the center electrode and the corresponding external electrode. Supply, pulse power supply. A control device for controlling the primary side circuit and the plurality of secondary side circuits is provided.
By controlling the switching element, the control device performs regenerative charging of returning the electric power returned to the other end to the one end, and until the electric power stored in the output capacitor reaches a predetermined amount after the regenerative charging. to charge said output capacitor, and controls the primary-side circuit, the pulse power supply device according to claim 1.

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