Pulse power supply device

Abstract

This pulse power supply device generates a pulse of a discretionary waveform having a plurality of prescribed voltage gradients by superimposing a constant voltage DC-voltage and a broken-line waveform voltage. The broken-line waveform voltage includes a broken-line waveform voltage in which a plurality of linear waveform voltages are connected, such voltages changing over time from a ground potential according to a plurality of prescribed voltage change rates dV / dt. The pulse power supply device: generates the broken-line waveform voltage by inverter control; generates the discretionary waveform voltage by superimposing the DC voltage and the broken-line waveform voltage; and generates a pulse waveform from the discretionary waveform voltage, and thereby generates, without using a current source, a pulse having a discretionary voltage gradient.

Description

Pulse Power Supply

[0001] The present invention relates to a pulse power supply device that generates a pulse output containing an arbitrary waveform whose voltage changes with a predetermined slope.

[0002] The pulse output generated by the pulse power supply is used for plasma processing such as film formation processing and etching processing, and can also be applied to various industrial devices other than plasma processing. For example, in etching processing of semiconductor devices, a negative voltage relative to ground is applied to a substrate to generate a substantially uniform negative voltage across the entire surface of the substrate when plasma processing a conductor.

[0003] In plasma etching and deposition processes, it is known to use a pulsed bias waveform comprising a broad negative pulse during the etching phase and a short positive pulse during the discharge phase.

[0004] It is known to apply a bias with a pulsed waveform to compensate for the ion deposition effect on the dielectric substrate during the etching or deposition phase. The pulsed waveform consists of a negative voltage gradient that decreases to compensate for the rise in substrate potential during the etching or deposition phase, and a positive voltage pulse to attract electrons to maintain the charge bias during the discharge phase. Configurations that generate a negative voltage gradient by incorporating ion current compensation, such as a current source, into a switch-mode power supply are known (see Patent Documents 1 and 2).

[0005] Patent No. 7214046 Patent No. 6181792

[0006] In order to supply an ion current that maintains the substrate voltage at a constant voltage, it is necessary to set a predetermined negative voltage gradient. In the conventional pulse power supply described above, the relationship between the negative voltage gradient and the ion current is determined by a predetermined function, so an ion current compensation current source such as a current source is used to realize the negative voltage gradient.

[0007] However, current sources with high resistance have the problem that the time constant of the circuit that constitutes the current source becomes large due to the influence of distributed capacitance, and the problem of low high-speed response becomes more pronounced at high pulse frequencies.

[0008] In addition to the issue of high-speed response mentioned above, there are other points to consider with current sources. Generally, current sources are affected by internal resistance and temperature fluctuations, so temperature compensation and feedback compensation are required, which increases the cost of the components of the pulsed power supply device. As mentioned above, pulsed power supplies that output high-frequency pulses using a current source have issues such as high-speed response and cost due to the use of the current source.

[0009] SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems of the prior art and to provide a pulse power supply device equipped with an arbitrary waveform voltage generating section that can obtain a negative voltage gradient without using a current source.

[0010] The pulse power supply of the present invention generates pulses of arbitrary waveforms having a plurality of predetermined voltage gradients by superimposing a constant DC voltage on a broken-line waveform voltage. The broken-line waveform voltage has a broken-line waveform voltage formed by connecting a plurality of linear waveform voltages that change over time from a ground potential at a plurality of predetermined voltage change rates dV / dt. The pulse power supply of the present invention generates this broken-line waveform voltage by inverter control, generates an arbitrary waveform voltage by superimposing the DC voltage on the broken-line waveform voltage, and generates a pulse waveform from the arbitrary waveform voltage, thereby generating pulses with arbitrary voltage gradients without using a current source.

[0011] The pulse power supply device of the present invention includes a first DC power supply that generates a first voltage of a DC voltage, an arbitrary waveform voltage generation unit that generates a voltage of an arbitrary waveform using a plurality of linear waveforms connecting two voltages, and a switch unit that generates a pulse waveform by switching between a ground potential and the arbitrary waveform voltage, and outputs pulses by repeating the pulse waveform at a predetermined cycle.

[0012] The switch section supplies a pulse-period current to the load by switching between an application phase in which a periodic pulse is applied to the load side and a discharge phase in which the charge accumulated on the load side is discharged.

[0013] The arbitrary waveform voltage generating unit generates a broken line waveform voltage in which a plurality of linear waveform voltages having different voltage change rates dV / dt are connected together, starting from a ground potential by inverter control, and generates an arbitrary waveform voltage by superimposing the generated broken line waveform voltage on a first voltage of the first DC power supply.

[0014] The arbitrary waveform voltage is the output voltage of a pulse output in the application phase of the pulse period of the switch section, with the voltage at the start of the application phase being the first voltage and the voltage at the end of the application phase being the terminal voltage of the broken line waveform voltage biased with the first voltage.

[0015] The arbitrary waveform voltage generating unit includes a second DC power supply, an inverter circuit that converts the DC voltage of the second DC power supply into an AC voltage, a rectifier circuit that converts the AC voltage of the inverter circuit into a DC voltage, and a voltage superposition circuit that superimposes the output of the first DC power supply and the output of the rectifier circuit.

[0016] In inverter control for DC-AC voltage conversion, the inverter circuit generates an arbitrary waveform voltage by adjusting: (a) the time width of the application phase; (b) the inflection point where the linear waveform voltage of the broken-line waveform voltage switches; and (c1) the voltage change rate dV / dt of each linear waveform voltage of the broken-line waveform voltage, or (c2) the voltage of the inflection point.

[0017] By adjusting the time width (Ton) of the application phase of the output pulse period T, the time width of the pulse output is adjusted.

[0018] An inflection point is a point where multiple linear waveform voltages that form a broken-line waveform voltage are connected, and the linear waveform voltages before and after this inflection point have different voltage change rates dV / dt. Because adjacent linear waveforms are connected, an inflection point can be identified by the time between the inflection points, the starting voltage of the application phase, and the voltage change rate dV / dt of each linear waveform voltage.

[0019] Furthermore, since the end voltages at the connection points of adjacent linear waveform voltages before and after the inflection point are the same, once the starting voltage of the application phase is identified, the inflection point can be identified by the end voltage at one end.

[0020] As described in the Problems section, there is a demand for generating a substantially uniform negative voltage across the entire surface of the substrate, but during the application phase, the power supply output Vout or the output current Iout is not necessarily constant and may vary depending on the load state, etc. Therefore, in order to supply an ion current that maintains the substrate voltage at a constant voltage, it is necessary to set a predetermined negative voltage gradient according to the power supply output Vout or the output current Iout.

[0021] In response to this problem, the present invention forms an arbitrary waveform voltage using a piecewise linear waveform voltage obtained by connecting a plurality of linear waveform voltages having different voltage change rates dV / dt, and supplies an output to a load based on this arbitrary waveform voltage, thereby maintaining the power supply output Vout or output current Iout at a constant value and applying a substantially uniform negative voltage across the entire surface of the substrate.

[0022] The rectifier circuit rectifies the output of the inverter circuit to generate a broken-line waveform voltage, and the voltage superposition circuit superposes a first voltage output from the first DC power supply and the broken-line waveform voltage output from the rectifier circuit to generate an arbitrary waveform voltage in which a plurality of linear waveform voltages having different voltage change rates dV / dt are switched and connected at inflection points, with the first voltage of the first DC power supply as a starting voltage.

[0023] The inverter further includes a control unit for controlling the inverter circuit, and performs inverter control based on predetermined control values. The control unit has control values ​​for determining the following values ​​as control parameters for inverter control: (a) the duration of the application phase, (b) the time between inflection points for switching the linear waveform voltage of the broken-line waveform voltage, and (c1) the voltage change rate dV / dt of each linear waveform voltage, or (c2) the voltage at the inflection point.

[0024] When the change in load over time can be predicted, the control parameters can be estimated or measured in advance and acquired, and the control parameters or control values ​​based on the control parameters can be stored in a storage device or the like, and can be read out as needed to control the inverter. The control unit controls the inverter based on the control values ​​for these control parameters and generates a broken-line waveform voltage formed by connecting multiple linear waveform voltages.

[0025] The broken-line waveform voltage can be set based on the control value in a plurality of setting modes.

[0026] (Setting mode 1) At each time point when the time between inflection points reaches the control value for the time between inflection points, the control unit sets the control value for the voltage change rate dV / dt as the slope of the linear waveform voltage, and sequentially switches the linear waveform voltage from the broken line waveform voltage to generate the broken line waveform voltage.

[0027] (Setting mode 2) At each time point when the time between the inflection points reaches the control value for the time between the inflection points, the control unit sets the slope of the linear waveform voltage to a slope determined based on the control values ​​for the voltage of the inflection points at that time point and the next time point and the control value for the time between the inflection points, and sequentially switches the linear waveform voltage of the broken line waveform voltage to generate a broken line waveform voltage.

[0028] (Setting mode 3) At each time point when the time between inflection points reaches the control value for the time between inflection points, the control unit determines a voltage fluctuation by comparing the control value for the voltage at the inflection point at that time with the detected value of the output voltage at that time, and when a voltage fluctuation is determined, the control unit sets a slope determined based on the detected value of the output voltage at that time and the control value for the voltage at the inflection point at the next time as the slope of the linear waveform voltage, and sequentially switches between the broken line waveform voltages to generate a broken line waveform voltage.

[0029] The voltage superposition circuit superposes the broken-line waveform voltage rectified by the rectification circuit on the first voltage of the first DC power supply to generate a voltage with an arbitrary waveform.

[0030] The broken-line waveform voltage output from the rectifier circuit exhibits a voltage waveform formed by connecting multiple linear waveform voltages, each of which varies linearly over time, with the voltage at the start of each application phase being ground potential and varying over time from ground potential. The arbitrary waveform voltage is formed by superimposing a first voltage on the broken-line waveform voltage, resulting in a linear waveform voltage that varies linearly over time at a predetermined voltage change rate dV / dt, with the first voltage as the starting voltage, and other linear waveform voltages with different voltage change rates dV / dt that are switched at inflection points. By controlling the voltage change rate dV / dt of each connected linear waveform voltage in response to changes in the power supply output Vout or the output current Iout due to fluctuations in the load state, etc., the power supply output Vout or the output current Iout is kept constant, and an ion current that maintains the substrate voltage at a constant voltage is supplied.

[0031] The switch unit synchronizes the start of pulse generation in the switch unit with the start of output from the arbitrary waveform voltage generator, and generates a pulse waveform by switching between 0 V (ground potential) and the arbitrary waveform voltage generated by the arbitrary waveform voltage generator. The generated pulse waveform has a first section where the potential is ground potential, and a second section where a piecewise linear waveform voltage is formed by connecting multiple linear waveform voltages that change linearly over time from the first voltage at a predetermined voltage change rate dV / dt. There is a potential difference of the first voltage between 0 V in the first section and the first voltage at the start of the second section.

[0032] The voltage at the start point of the arbitrary waveform voltage is determined by the first voltage of the first DC power supply, and the voltage at the end point of the arbitrary waveform voltage is determined by the voltage change rate dV / dt of the broken line waveform voltage and the time width of the second section of the broken line waveform voltage.

[0033] The switch unit generates a pulse waveform from the arbitrary waveform voltage as one pulse, and outputs a periodic pulse by repeating this pulse waveform at a predetermined period. The time width of one pulse is the sum of the time width of the first section and the time width of the second section, and is determined according to the pulse period.

[0034] In the case of a negative polarity arbitrary waveform voltage, the switch unit outputs a periodic pulse, one pulse of which is a voltage waveform consisting of two voltage sections: a first section of 0 V and a second section of an arbitrary waveform voltage that changes over time from the negative first voltage to a broken-line waveform voltage.

[0035] In the arbitrary waveform voltage generating section of the present invention, the voltage superimposing circuit can be arranged in a number of different positions.

[0036] (First Configuration) In the first configuration, the voltage superposition circuit is disposed in a rectifier circuit, and as an example, one output terminal of the rectifier circuit is connected to the output terminal of the first DC power supply.

[0037] (Second embodiment) A transformer is provided between the inverter circuit and the rectifier circuit of the second embodiment, the voltage superposition circuit is disposed in this transformer, and the output terminal of the first DC power source is connected to one end of the secondary side of the transformer.

[0038] As described above, the pulse power supply device of the present invention can achieve high-speed response by including an arbitrary waveform voltage generating section that can obtain a predetermined voltage gradient without using a current source.

[0039] FIG. 1 is a diagram for explaining a schematic configuration of a pulse power supply according to the present invention; FIG. 2 is a timing chart for explaining an example of operation of the pulse power supply according to the present invention; FIG. 3 is a diagram for explaining an example of the waveform of a broken line waveform voltage; FIG. 4 is a flowchart for explaining setting example 1 of a broken line waveform voltage; FIG. 5 is a flowchart for explaining setting example 3 of a broken line waveform voltage; FIG. 6 is a diagram for explaining an example of operation in the discharge phase of the pulse power supply according to the present invention; FIG. 7 is a diagram for explaining an example of operation in the discharge phase of the pulse power supply according to the present invention; FIG. 8 is a diagram for explaining an example of operation in the application phase of the pulse power supply according to the present invention; FIG. 9 is a diagram for explaining an example of operation in the application phase of the pulse power supply according to the present invention; FIG. 10 is a schematic configuration diagram of a first example of an arbitrary waveform voltage generating section according to the present invention; FIG. 11 is a timing chart of the first example of an arbitrary waveform voltage generating section according to the present invention; FIG. 12 is a schematic configuration diagram of a second example of an arbitrary waveform voltage generating section according to the present invention; FIG. 13 is a timing chart of the second example of an arbitrary waveform voltage generating section according to the present invention; FIG. 14 is a diagram for explaining an example of the configuration of a voltage superposition circuit according to the present invention; FIG. 15 is a diagram for explaining a configuration example of a voltage superposition circuit according to the present invention; FIG. 16 is a diagram for explaining a smoothing circuit according to the present invention; FIG. 17 is a diagram for explaining a first embodiment including a smoothing circuit according to the present invention; FIG. 18 is a diagram for explaining a second embodiment including a smoothing circuit according to the present invention; and FIG. 19 is a diagram for explaining waveform examples of a smoothing circuit according to the present invention. 1 is a diagram showing an example of a waveform of a smoothing circuit of the present invention; 2 is a diagram for explaining an example in which the load of the pulse power supply device of the present invention is a plasma load; 3 is a diagram showing an example of a switch drive signal Vgate, a power supply output Vout, and an output current Iout; 4 is a diagram showing a switch drive signal Vgate, a wafer voltage Vsh, a power supply output Vout, and an ion current Ip;

[0040] (1) General Configuration and Operational Example of the Pulse Power Supply Device of the Present Invention The general configuration and operational example of the pulse power supply device of the present invention will be described below with reference to FIGS. 1 to 6. FIG.

[0041] The pulse power supply device 1 includes a power supply unit 10, a switch unit 13, and a control unit 15. The power supply unit 10 includes a first DC power supply 11 that generates a first constant voltage as a first power supply, and an arbitrary waveform voltage generating unit 12 that generates an arbitrary waveform voltage as a second power supply.

[0042] The arbitrary waveform voltage generating unit 12 generates a broken-line waveform voltage Vline formed by connecting a plurality of linear waveform voltages whose voltage changes at a predetermined voltage change rate dV / dt starting from the ground potential, and by superimposing the first voltage of the first DC power supply 11 on this broken-line waveform voltage Vline, it generates an arbitrary waveform voltage whose voltage changes at a predetermined voltage change rate dV / dt starting from the first voltage, and outputs a pulse of the arbitrary waveform voltage output Vopt.

[0043] The switch unit 13 supplies current to the load by alternately repeating a discharge phase in which electric charge accumulated on the load side is discharged by switching operation and an application phase in which periodic pulses are applied to the load side. The switch unit 13 includes a pulse switch unit 13a for outputting pulses of the arbitrary waveform voltage output Vopt to the load in the application phase, and a discharge circuit 13b for discharging electric charge accumulated in the load. The switching operations of the pulse switch unit 13a and the discharge circuit 13b are controlled by the control unit 15.

[0044] In the application phase, the switch unit 13 applies the arbitrary waveform voltage generated by the arbitrary waveform voltage generation unit 12 to the load as one periodic pulse waveform. In the discharge phase, the charge accumulated on the load side is discharged and the output of the switch unit 13 becomes 0 V, so the output of the switch unit 13 at the start of the application phase changes from 0 V to the first voltage. The pulse output output from the switch unit 13 is supplied to the load 21 as a power supply output.

[0045] The pulse power supply 1 may be configured to include a smoothing circuit. The smoothing circuit may be configured in two ways: a first way in which the smoothing circuit is connected to the output terminal of the arbitrary waveform voltage generator 12; and a second way in which the smoothing circuit is connected to the output terminal of the pulse switch unit 13a of the switch unit 13. The smoothing circuit of the first way suppresses noise contained in the output of the arbitrary waveform voltage generator. The smoothing circuit of the second way suppresses voltage oscillations such as overshoot and undershoot that occur in the switch unit 13 due to voltage changes between the discharge phase and the application phase. Note that the smoothing circuit is not shown in FIG. 1 .

[0046] The control unit 15 controls the arbitrary waveform voltage generating unit 12 and the switch unit 13. At this time, the output control of the arbitrary waveform voltage output Vopt of the arbitrary waveform voltage generating unit 12 and the pulse control of the switch unit 13 are performed in synchronization.

[0047] 2 is a timing chart illustrating an example of the operation of the pulse power supply device of the present invention. The power supply unit 10 includes a first power supply, a first DC power supply 11, and a second power supply, an arbitrary waveform voltage generator 12. The first DC power supply 11 of the first power supply generates a constant first voltage V1. The arbitrary waveform voltage generator 12 of the second power supply generates a broken-line waveform voltage Vline that varies at a predetermined voltage change rate dV / dt starting from the ground potential, and superimposes the first voltage V1 on this broken-line waveform voltage Vline to generate a trapezoidal waveform voltage.

[0048] The arbitrary waveform voltage generating unit 12 generates a broken-line waveform voltage Vline based on a control signal from the control unit 15, and superimposes the generated broken-line waveform voltage Vline on a first voltage V1 to generate an arbitrary waveform voltage, which is output as an arbitrary waveform voltage output Vopt.

[0049] The control signal of the arbitrary waveform voltage generating unit 12 has the same output pulse period T as the switch control signal that controls the switch unit 13, and is synchronized with the switch control signal. The generation of the broken-line waveform voltage Vline by the control signal of the arbitrary waveform voltage generating unit 12 and the start of the pulse application phase by the switch control signal occur at the same time A. The end of the broken-line waveform voltage Vline by the control signal of the arbitrary waveform voltage generating unit 12 and the end of the pulse application phase and the start of the discharge phase by the switch control signal occur at the same time B.

[0050] Here, when the duty ratio with respect to the output pulse period T (= Ton + Toff) is Ton / T, the on time of the control signal of the arbitrary waveform voltage generating unit 12 and the time of the application phase are the same Ton, and the off time of the control signal of the arbitrary waveform voltage generating unit 12 and the time of the discharge phase are the same Toff.

[0051] The broken-line waveform voltage Vline changes from 0 V at the start of the application phase at a predetermined voltage change rate dV / dt for each of the multiple linear waveform voltages, and becomes a voltage ΔV determined by the product of the voltage change rate dV / dt and Ton (Ton × dV / dt) at the end of the application phase. The arbitrary waveform voltage output Vopt changes from the first voltage V1 at the start of the application phase at a predetermined voltage change rate dV / dt, and becomes a voltage (V1 + ΔV) obtained by superimposing a voltage ΔV on the first voltage V1 at the end of the application phase.

[0052] The voltages ΔV and (V1+ΔV) are voltages that depend on the voltage change rate dV / dt and Ton or the duty ratio of the periodic pulse, because ΔV is the product (Ton×dV / dt) of the voltage change rate dV / dt and Ton. Therefore, if the voltage change rate dV / dt, Ton, or the duty ratio of the periodic pulse is changed, the voltages ΔV and (V1+ΔV) will have different values.

[0053] The smoothing circuit of the first type suppresses noise contained in the arbitrary waveform voltage output Vopt, and the smoothing circuit of the second type suppresses voltage oscillations due to overshoot and undershoot contained in the switch output of the switch unit 13. The power output of the pulse power supply device 1 is supplied to a load 21.

[0054] In FIG. 2 , (A) indicates the voltage V1 of the first DC power supply 11, (B) indicates a control signal for controlling the inverter provided in the arbitrary waveform voltage generating unit 12, (C) indicates the broken-line waveform voltage Vline, (D) indicates the arbitrary waveform voltage output Vopt, (E) indicates a control signal for controlling the switches SWA and SWB of the switch unit 13, (F) indicates the output Vsw of the switch unit 13, and (G) indicates the power supply output Vout.

[0055] The broken-line waveform voltage Vline of (C) is formed based on the inverter control signal at Ton during the output pulse period T shown in (B), but is not formed at Toff during the output pulse period T. The arbitrary waveform voltage output Vopt shown in (D) is formed by superimposing the voltage V1 of the first DC power supply 11 shown in (A) and the broken-line waveform voltage Vline shown in (C).

[0056] The broken-line waveform voltage Vline shown in (C) and the arbitrary waveform voltage output Vopt shown in (D) have inflection points, namely, a start point P0, an inflection point P1, an inflection point P2, and an end point P3, and a plurality of linear waveform voltages connecting these inflection points. Note that, although the figure shows a total of four inflection points, including the start point P0 and the end point P3, the number of inflection points can be any number of at least three, including the start point, intermediate point, and end point.

[0057] By superimposing the voltage V1 and the broken-line waveform voltage Vline, the voltage at the start point P0 of the arbitrary waveform voltage output Vopt becomes V1, and the voltage at the end point P3 becomes V3. The voltage V3 at the end point P3 becomes a voltage that corresponds to the voltage changes of the multiple linear waveform voltages, and the voltage difference ΔV between the start point and the end point of the broken-line waveform voltage Vline is (V1-V3).

[0058] The control signals of the switches SWA and SWB (E) are synchronized with the control signals of the inverter (B), the control signal SWA controls the on / off of the pulse switch unit 13a, and the control signal of the switch SWB controls the on / off of the discharge circuit 13b.

[0059] In (F), the section marked with Ph_dis represents the discharge phase, and the section marked with Ph_app represents the application phase. During the discharge phase, the switch SWA of the pulse switch unit 13a is in the OFF state, and the switch SWB of the discharge circuit 13b is in the ON state. On the other hand, during the application phase, the switch SWA of the pulse switch unit 13a is in the ON state, and the switch SWB of the discharge circuit 13b is in the OFF state.

[0060] The switch SWA of the pulse switch unit 13a switches from the discharge phase to the application phase by switching from the off state to the on state, and outputs the arbitrary waveform voltage output Vopt as a pulse output during the application phase Ton.

[0061] The switch SWB of the discharge circuit 13b switches from the OFF state to the ON state, thereby switching from the application phase to the discharge phase, discharging the charge accumulated in the load during Toff of the discharge phase to ground, and setting the voltage of the arbitrary waveform voltage output Vopt to 0 V.

[0062] (F) and (G) both show output waveforms, with (F) showing the output waveform of the pulse switch unit, and (G) showing the output waveform of the power supply after the output of the pulse switch unit has been smoothed.

[0063] (Waveform Example of Broken Line Waveform Voltage) An example of a broken line waveform voltage will be described using Figures 3A and 3B. Here, an example of a broken line waveform voltage having two inflection points P1 and P2 between a start point P0 and an end point P3 is shown, but the number of inflection points can be any number. In Figures 3A and 3B, the linear waveform voltage indicated by the dashed line represents a waveform in which a single straight line connects the start point P0 and the end point P3.

[0064] 3A shows an example of a broken-line waveform voltage in which, compared to the linear waveform voltage shown by the dashed line, the voltage V1 at the inflection point P1 is lower and the voltage V2 at the inflection point P2 is higher. In this waveform example, the voltage change rate dV / dt of the linear waveform voltage connecting the start point P0 and the inflection point P1 is expressed as V1 / T1, the voltage change rate dV / dt of the linear waveform voltage connecting the inflection point P1 and the inflection point P2 is expressed as (V2-V1) / T2, and the voltage change rate dV / dt of the linear waveform voltage connecting the inflection point P2 and the end point P3 is expressed as (V3-V2) / T3. Note that T1 is the time width between the start point P0 and the inflection point P1, T2 is the time width between the inflection point P1 and the inflection point P2, and T3 is the time width between the inflection point P2 and the end point P3.

[0065] 3B, compared to the linear waveform voltage indicated by the dashed line, the voltage V1 at inflection point P1 is higher and the voltage V2 at inflection point P2 is lower. In this waveform example, the voltage change rate dV / dt of the linear waveform voltage connecting start point P0 and inflection point P1 is expressed as V1 / T1, the voltage change rate dV / dt of the linear waveform voltage connecting inflection point P1 and inflection point P2 is expressed as (V2-V1) / T2, and the voltage change rate dV / dt of the linear waveform voltage connecting inflection point P2 and end point P3 is expressed as (V3-V2) / T2.

[0066] (Setting of Broken Line Waveform Voltage) The setting of the broken line waveform voltage by the control unit will be described with reference to Figures 4 and 5. Note that the following describes a case in which, in a pulse period for generating one pulse, a switching operation is performed to apply a periodic pulse to the load side in an application phase, and a discharge phase is performed to discharge charge accumulated on the load side, and the current generated by repeating this pulse period is supplied to the load.

[0067] When generating a broken-line waveform voltage in inverter control, the control unit sets the following control values ​​as control parameters: (a) time width T of the application phase, (b) time Tk between inflection points at which the broken-line waveform voltage is switched to the linear waveform voltage, and (c1) voltage change rate dV / dt of each linear waveform voltage, or (c2) voltage at the inflection point

[0068] (Setting Mode 1) Setting Mode 1 of the broken-line waveform voltage will be described using Fig. 4. In Setting Mode 1, an example is shown in which the voltage change rate dV / dt of each linear waveform voltage constituting the broken-line waveform voltage is set when the time width T of the application phase and the time Tk between inflection points are set and the inflection points are determined, among the control values ​​described above. Note that in the flowchart of Fig. 4, the steps are indicated by the symbols S1 to S7.

[0069] The control values ​​for determining the inflection points are the time width T of the application phase, the time T between the inflection points, and the voltage change rate dV / dt of the linear waveform voltage, which is a control value for determining the slope of the linear waveform between the inflection points. These control values ​​can be readably stored in any storage device.

[0070] First, the voltage change rate dV / dt of the linear waveform voltage at the first point of the application phase, which has been set as an initial value, is read (S1), the voltage change rate dV / dt of the initial linear waveform voltage is set, and a linear waveform voltage is generated using this voltage change rate dV / dt (S2).

[0071] Thereafter, it is determined whether an inflection point has been reached based on whether the elapsed time since the start of outputting the linear waveform voltage has reached the time Tk between the inflection points (S3). If an inflection point has been reached, the voltage change rate dV / dt of the next linear waveform voltage is read (S4), and the voltage change rate dV / dt of the read linear waveform voltage is changed (S5).

[0072] It is determined whether the inflection point is the end point of the broken-line waveform voltage, and if it is not the end point, steps S3 to S5 are repeated (S6). If the inflection point is the end point in S6, one application phase ends, and after the discharge phase, a pulse period in which one pulse is formed ends, and then steps S1 to S6 are repeated in the next pulse period (S7).

[0073] (Setting Mode 2) While the above-described setting mode 1 is an example in which a predetermined voltage change rate dV / dt of a linear waveform voltage is used, in setting mode 2, the broken-line waveform voltage may be set using the voltage of an inflection point instead of the voltage change rate dV / dt. In this case, the voltage change rate dV / dt of the first linear waveform voltage is calculated by dividing the voltage difference (V1-V0) between the voltage V0 at the start point P0 of the broken-line waveform voltage and the voltage V1 at the inflection point P1 by the time width T1, and the voltage change rate dV / dt of the next linear waveform voltage is calculated by dividing the voltage difference (V2-V1) between the voltage V1 at the inflection point P1 and the voltage V2 at the inflection point P2 by the time width T2. The linear waveform voltages of the other sections can be calculated in a similar manner.

[0074] (Setting Mode 3) Setting Mode 3 of the broken-line waveform voltage will be described using Fig. 5. In Setting Mode 3, among the control values ​​described above, the time width T of the application phase and the time Tk between inflection points have been set, the inflection points have been determined, and the output voltage Vk at each inflection point has been determined. In the flowchart of Fig. 5, the steps are indicated by the reference numerals S11 to S21.

[0075] First, calculate the voltage change rate dV / dt of the linear waveform voltage at the beginning of the application phase. This voltage change rate dV / dt is the voltage V at the starting point P0. ０ and the voltage V1 at the first inflection point P1 (V1-V0) is divided by the time width T1 (S11). The calculated voltage change rate dV / dt is set as an initial value (S12).

[0076] At the inflection point Pk after the time width of the linear waveform voltage has elapsed (S13), the output voltage Vk set at the inflection point Pk is read (S14), and the output voltage Vo at that time is detected (S15). The detected output voltage Vo is compared with the read output voltage Vk to determine whether the detected output voltage Vo has deviated from the set output voltage Vk. This determination can be made, for example, based on whether the difference between the output voltage Vo and the output voltage Vk exceeds a preset threshold value. If it is determined that there is no voltage fluctuation, steps S13 to S15 are repeated (S16).

[0077] If it is determined that there is a voltage fluctuation, the voltage Vk+1 at the next inflection point Pk+1 is read (S17), and the voltage difference (Vk+1-Vo) between the output voltage Vo and the read voltage Vk+1 at the inflection point Pk+1 is divided by the time width Tk to calculate the voltage change rate dV / dt as ((Vk+1)-Vo) / Tk (S18), and the voltage change rate dV / dt is updated (S19). Then, steps S13 to S19 are repeated until the end point of the broken line waveform voltage (S20), and after one application phase ends, and the pulse period forming one pulse ends via the discharge phase, steps S11 to S20 are repeated in the next pulse period (S21).

[0078] (Example of operation in the discharge phase) Figure 6 is a diagram for explaining an example of operation in the discharge phase, and Figures 6A and 6B respectively show the operating state at the time when the power supply output Vout rises from V2 to 0 V and the operating state when the power supply output Vout becomes 0 V in the discharge phase Ph_dis in (F) of Figure 2.

[0079] The discharge phase Ph_dis1 in Fig. 6A is the point in time when the switch SWA of the pulse switch unit 13a is switched off and the switch SWB of the discharge circuit 13b is switched on. This point in time corresponds to the section indicated by Dis1 in Fig. 2F. During Dis1, the power supply output Vout rises from V3 to 0 V, and the output current Iout sharply decreases toward 0 A as a discharge current. The current Ir in the application phase corresponds to the ion current Ip in the case of a plasma load.

[0080] In the discharge phase Ph_dis2 in Fig. 6B, the switch SWA of the pulse switch unit 13a is in the OFF state, and the switch SWB of the discharge circuit 13b is in the ON state. This state corresponds to the section indicated by Dis2 in Fig. 2. In this Dis2, the power supply output Vout is 0 V, and the output current Iout is 0 A.

[0081] (Example of operation in application phase) Figure 7 is a diagram for explaining an example of operation in the application phase, and Figures 7A and 7B respectively show the operating state at the time when the power supply output Vout falls from 0 V to V1 and the operating state when the power supply output Vout changes from V1 to V2 in the application phase Ph_app in (F) of Figure 2.

[0082] The application phase Ph_app1 in Fig. 7A is the point in time when the switch SWA of the pulse switch unit 13a is switched on and the switch SWB of the discharge circuit 13b is switched off. This point in time corresponds to the point in time indicated by App1 in Fig. 2(F). At this point in time App1, the power supply output Vout falls from 0 V to V1, and a current Iq flows toward the load. The voltage change at the point in time App1 is determined by the time constant of the circuit connected downstream of the switch unit.

[0083] In the application phase Ph_app2 of FIG. 7B, the switch SWA of the pulse switch unit 13a is on, and the switch SWB of the discharge circuit 13b is off. This state corresponds to the section indicated by App2 in FIG. 2F. In App2, the power supply output Vout changes from V1 at a voltage change rate dV / dt, and at the end of App2, the power supply output Vout becomes V3. In the case of a plasma load, a constant current Ir corresponding to the ion current Ip determined based on the voltage change rate dV / dt flows in the output current Iout. An example of the current Ir and the current Iq is shown in FIG. 18.

[0084] (2) Arbitrary Waveform Voltage Generator The arbitrary waveform voltage generator 12 of the present invention includes an inverter circuit that converts a DC voltage into an AC voltage, a rectifier circuit that converts the AC voltage of the inverter circuit into a DC voltage, and a voltage superposition circuit that generates a trapezoidal waveform voltage by superimposing the output of the DC power supply of the first power supply and the broken-line waveform voltage Vline output via the rectifier circuit, and outputs the trapezoidal waveform voltage as an arbitrary waveform voltage output Vopt.

[0085] The arbitrary waveform voltage generating unit of the present invention can be configured in a plurality of forms in which the voltage superimposing circuit that superimposes the output of the DC power supply and the broken-line waveform voltage Vline is arranged at different positions in the circuit of the arbitrary waveform voltage generating unit.

[0086] First and second configuration examples of the arbitrary waveform voltage generator of the present invention will be described below with reference to Figs. 8 to 11. Figs. 8 and 9 are diagrams for explaining the first configuration example of the arbitrary waveform voltage generator, and Figs. 10 and 11 are diagrams for explaining the second configuration example of the arbitrary waveform voltage generator. Also, Fig. 12 is a diagram for explaining a configuration example of a voltage superposition circuit.

[0087] (a) First Configuration Example of Arbitrary Waveform Voltage Generator FIG. 8 shows a schematic configuration of a first configuration example of an arbitrary waveform voltage generator of the present invention, and FIG. 9 shows a timing chart of the first configuration example of the arbitrary waveform voltage generator of the present invention.

[0088] The arbitrary waveform voltage generating unit 12A of the first configuration example includes a second DC power supply 12a, an inverter circuit 12b, a transformer 12c, and a rectifier circuit 12d, and the voltage superposition circuit 12e is provided within the rectifier circuit 12d.

[0089] The second DC power supply 12a may be an AC / DC power supply that converts AC to DC and outputs a DC voltage, or may be a normal DC power supply. The AC (alternating current) source may be either an external power supply or an internal power supply. The inverter circuit 12b converts the input DC voltage into an AC voltage and adjusts the voltage value of the converted AC voltage before outputting it. The transformer 12c converts the amplitude of the AC voltage from the inverter circuit 12b based on a transformation ratio determined by a predetermined winding ratio. The rectifier circuit 12d rectifies the AC voltage from the transformer 12c and converts it into a DC voltage.

[0090] The inverter circuit 12b is inverter-controlled based on a control command output from the control unit 15. The control command from the control unit 15 may be generated based on a feedback signal of the voltage and / or current output from the arbitrary waveform voltage generator, or may be generated based on an external signal from an external device (not shown).

[0091] The inverter circuit 12b is driven at a high frequency of, for example, several hundred kHz to several tens of MHz, and may be a single-transistor flyback inverter using one switching element, a two-transistor half-bridge inverter using two switching elements, or a four-transistor full-bridge inverter using four switching elements.

[0092] The voltage superposition circuit 12e is incorporated into the rectifier circuit 12d and superimposes the first voltage V1 of the first DC power supply 11 on the rectified output of the rectifier circuit 12d. Fig. 12A shows an example configuration of the voltage superposition circuit 12e incorporated into the rectifier circuit 12d. Here, an example circuit formed of a diode bridge is shown as the rectifier circuit 12d. In the circuit configuration example of Fig. 12A, the output terminal of the voltage superposition circuit 12e is connected to one output terminal of the rectifier circuit 12d, and the rectified output on which the first voltage V1 is superimposed is output as an arbitrary waveform voltage output.

[0093] 9 shows a case where PWM control is used for inverter control. Inverter control is performed during an on-time Ton based on a duty ratio within an output pulse period T, and resumes after an off-time Toff has elapsed. PWM control controls the pulse width for each inverter period Tinv (=1 / f_inv) determined by the drive frequency f_inv. The output voltage is adjusted by gradually increasing or decreasing the pulse width to increase or decrease the peak value of the output voltage.

[0094] When generating the broken-line waveform voltage Vline and the gradient waveform of the voltage of the arbitrary waveform voltage output Vopt by inverter control, the drive frequency f_inv of the PWM control that performs the inverter control needs to be higher than the output pulse frequency f_pulse, taking into consideration the responsiveness when a smoothing circuit is connected downstream of the arbitrary waveform voltage generating unit 12, and is preferably at least five times higher.

[0095] The transformer 12c adjusts the peak value of the inverter output from the inverter circuit 12b based on a transformation ratio determined by the turns ratio, and outputs the adjusted value to the rectifier circuit 12d. The rectifier circuit 12d rectifies the inverter output and outputs a broken-line waveform voltage whose voltage changes at a predetermined voltage change rate dV / dt. The broken-line waveform voltage is output during an on-time Ton and not during an off-time Toff. The voltage superposition circuit 12e superimposes a first voltage V1 on the rectified output from the rectifier circuit 12d to generate a superposed output.

[0096] (b) Second Configuration Example of Arbitrary Waveform Voltage Generator FIG. 10 shows a schematic configuration of a second configuration example of the arbitrary waveform voltage generator of the present invention, and FIG. 11 shows a timing chart of the second configuration example of the arbitrary waveform voltage generator of the present invention.

[0097] The arbitrary waveform voltage generating unit 12B of the second configuration example includes a second DC power supply 12a, an inverter circuit 12b, a transformer 12c, and a rectifier circuit 12d, and includes a voltage superposition circuit 12e in the transformer 12c.

[0098] The arbitrary waveform voltage generating unit 12B of the second configuration example includes a second DC power supply 12a, an inverter circuit 12b, a transformer 12c, and a rectifier circuit 12d, similar to the arbitrary waveform voltage generating unit 12A of the first configuration example, but differs in that a voltage superposition circuit 12e is incorporated into the transformer 12c. Here, a description of the second DC power supply 12a, the inverter circuit 12b, the transformer 12c, and the rectifier circuit 12d will be omitted, and only the voltage superposition circuit 12e will be described.

[0099] The voltage superposition circuit 12e is configured to be incorporated in the transformer 12c, and superimposes the first voltage V1 of the first DC power supply 11 on the inverter output of the inverter circuit 12b. Fig. 12B shows an example of the configuration of the voltage superposition circuit 12e.

[0100] In the circuit configuration example of FIG. 12B, the first DC power supply 11 is connected to one output terminal on the secondary side of the transformer 12c, so that the first voltage V1 is superimposed on the inverter output voltage converted by the transformer 12c.

[0101] 11, like FIG. 9, shows a case where PWM control is used for inverter control. Inverter control is performed during an on-time Ton based on a duty ratio within an output pulse period T, and resumes after an off-time Toff has elapsed. PWM control controls the pulse width for each inverter period Tinv determined by the drive frequency f_inv. The output voltage is adjusted by gradually increasing or decreasing the pulse width to increase or decrease the peak value of the output voltage.

[0102] As in the first configuration example, when generating the broken-line waveform voltage Vline and the voltage gradient waveform of the arbitrary waveform voltage output Vopt by inverter control, taking into consideration the responsiveness when a smoothing circuit is connected downstream of the arbitrary waveform voltage generating unit 12, the drive frequency f_inv of the PWM control that performs the inverter control needs to be higher than the output pulse frequency f_pulse, and preferably is at least five times higher.

[0103] The transformer 12c adjusts the peak value of the inverter output from the inverter circuit 12b based on a transformation ratio.

[0104] The voltage superposition circuit 12e superposes the first voltage V1 on the inverter output converted by the transformer 12c to generate a transformer output, which is output to the rectification circuit 12d. The rectification circuit 12d rectifies the inverter output and outputs a broken-line waveform voltage whose voltage changes at a predetermined voltage change rate dV / dt. The broken-line waveform voltage is output during the on-time Ton and is not output during the off-time Toff.

[0105] (3) Smoothing Circuit Fig. 13 shows an example of the configuration of the smoothing circuit 14. The smoothing circuit 14 is configured as an LC circuit having an inductor Lp connected in series and a capacitor Cp connected in parallel. Note that this smoothing circuit 14 is just an example, and the present invention is not limited to this LC circuit.

[0106] The smoothing circuit of the pulse power supply 1 of the present invention can be configured in a first form in which the smoothing circuit is connected to the output terminal of the arbitrary waveform voltage generating unit 12, or in a second form in which the smoothing circuit is connected to the output terminal of the pulse switch unit 13a of the switch unit 13. The smoothing circuit of the first form suppresses noise contained in the arbitrary waveform voltage output. The smoothing circuit of the second form suppresses voltage oscillations such as overshoot and undershoot that occur in the switch unit 13 due to voltage changes between the discharge phase and the application phase.

[0107] (a) First embodiment of smoothing circuit A first embodiment of a smoothing circuit 14A will be described with reference to Fig. 14. Fig. 14 shows a configuration example of an arbitrary waveform voltage generating unit 12A that performs voltage superposition in a rectifying circuit 12d.

[0108] The smoothing circuit 14A is connected between the output terminal of the rectifier circuit 12d of the arbitrary waveform voltage generator 12A and the input terminal of the switch unit 13, and suppresses high-frequency noise components contained in the arbitrary waveform voltage output generated by the rectifier circuit, etc. In this circuit configuration, even when the switch SWA of the pulse switch unit 13a in the switch unit 13 is switched to the off state, the voltage charged in the capacitor in the smoothing circuit 14A does not drop to the voltage of the V1 power supply. Therefore, in the first form, a discharge circuit 17 is connected to discharge the voltage charged in the capacitor in the smoothing circuit 14A.

[0109] (b) Second embodiment of smoothing circuit A second embodiment of the smoothing circuit 14B will be described with reference to Figures 15 and 16. Figure 15 shows a configuration example of an arbitrary waveform voltage generating unit 12A that performs voltage superposition in a rectifying circuit 12d, and Figure 16 shows an example of a waveform of the smoothing circuit 14B.

[0110] The smoothing circuit 14B of the second embodiment is connected between the pulse switch section 13a and the discharge circuit 13b in the switch section 13. Due to the switching operation performed by the pulse switch section 13a of the switch section 13, the voltage changes abruptly from V3 to the first voltage V1 during discharge, and also changes abruptly from the ground potential of 0V to the first voltage V1. This voltage change causes an overshoot or undershoot in the output waveform.

[0111] When the switch SWA of the pulse switch unit 13a is in the ON state, the capacitor of the smoothing circuit 14B is charged. After that, when the switch SWA of the pulse switch unit 13a is switched to the OFF state, the voltage charged in the capacitor of the smoothing circuit 14B is discharged because the discharge circuit 13b is switched to the ON state. As a result, between the discharge phase and the application phase, when the pulse switch unit 13a switches between the ON state and the OFF state, voltage oscillations such as overshoot and undershoot caused by voltage changes are suppressed, the voltage value of the power supply output is settled at a predetermined time constant, and a power supply output Vout with suppressed fluctuations is output.

[0112] 16A and 16B show examples of waveforms of the smoothing circuit 14B, where Fig. 16A shows a case where the constants of the inductor Lf and the capacitor Cf are small, and Fig. 16B shows a case where the constants of the inductor Lf and the capacitor Cf are large.

[0113] By selecting small constants for the inductor Lf and the capacitor Cf, the time constant of the LC circuit is set to a small value, thereby shortening the voltage rise time. If the time constant of the LC circuit is large, the voltage rise time t2 becomes long, making it necessary to set a long discharge time, which affects the setting of the high-frequency output pulse frequency f_pulse. It is desirable that the voltage rise time t1 be shorter than, for example, 10% of the pulse period.

[0114] (4) Example of Plasma Load An example of the load of the pulse power supply of the present invention will be described with reference to Fig. 17. In the case of a plasma load, the plasma load in the plasma chamber 2 is represented by capacitors Cw and Cp and an ion current Ip. Capacitor Cw is the intrinsic capacitance of components of the plasma chamber, such as the substrate, and Cp is the variable capacitance of the sheath capacitance and stray capacitance.

[0115] In the plasma chamber 2, the ion current Ip supplied to the substrate placed in the chamber is required to be constant, thereby maintaining the wafer voltage Vsh of the substrate at a constant voltage.

[0116] The pulse power supply device of the present invention supplies the above-mentioned constant ion current Ip and supplies the load in the plasma chamber 2 with power to maintain the substrate wafer voltage Vsh at a constant voltage.

[0117] The pulse power supply device of the present invention feeds back the power output Vout and / or output current Iout detected by the detector 16 to the control unit 15, generates a control value that keeps the power output Vout or the output current Iout at a constant value, and controls the switch SWA of the pulse switch unit 13a and the switch SWB of the discharge circuit 13b.

[0118] FIG. 18 shows an example of a drive signal Vgate for driving a switch, a power supply output Vout, and an output current Iout, and FIG. 19 shows the drive signal Vgate, a wafer voltage Vsh, a power supply output Vout, and an ion current Ip.

[0119] When switching from the discharge phase to the application phase, the power supply output Vout changes from 0 V, which is the ground potential, to V1 with the time constant of the smoothing circuit 14B, and a current Iq flows for a time tq. After the time tq has elapsed, the power supply output Vout changes at a voltage change rate dV / dt, and the current Iq is maintained at a constant current.

[0120] At the end of the application phase, the power supply output Vout becomes voltage V2. This voltage V2 has a value determined by the voltage change rate dV / dt and the duration of the application phase. The duration of the gradient section of the application phase corresponds to the on-time Ton of the output pulse period T.

[0121] The pulse power supply device of the present invention can be applied to a load that requires a constant voltage pulse output, in addition to being applied to plasma processing.

[0122] REFERENCE SIGNS LIST 1 Pulse power supply device 2 Plasma chamber 10 Power supply unit 12, 12A, 12B Arbitrary waveform voltage generation unit 12b Inverter circuit 12c Transformer 12d Rectifier circuit 12e Voltage superposition circuit 13 Switch unit 13a Pulse switch unit 13b Discharge circuit 14, 14A, 14B Smoothing circuit 15 Control unit 16 Detector 17 Discharge circuit 21 Load Cf, Cp, Cw Capacitor Iout Output current Ip Ion current Lf, Lp Inductor P0 Start point P1, P2, Pk Inflection point P3 End point Ph_dis Discharge phase Ph_add Application phase SWA, SWB Switch T Output pulse period Tinv Inverter period Toff Off time Ton On time Vopt Arbitrary waveform voltage output Vk, Vo: Output voltage Vline: Linear waveform voltage Vout: Power supply output Vsh: Wafer voltage dV / dt: Voltage change rate f_inv: Drive frequency f_pulse: Output pulse frequency ΔV: Voltage difference

Claims

1. A pulse power supply comprising: a first DC power supply that generates a first DC voltage; an arbitrary waveform voltage generation unit that generates an arbitrary waveform voltage using a plurality of linear waveforms connecting two voltages; and a switch unit that generates a pulse waveform by switching between a ground potential and the arbitrary waveform voltage and outputs pulses by repeating the pulse waveform at a predetermined cycle, wherein the arbitrary waveform voltage is the output voltage in an application phase of the pulse, and the application phase is made up of a first application section that falls from the ground potential to the first voltage, and a second application section that runs from the first voltage to a second voltage that is a voltage obtained by biasing the first voltage to a terminal voltage of the linear waveform voltage, and the arbitrary waveform voltage generation unit generates, by inverter control, a broken-line waveform voltage in which a plurality of linear waveform voltages with different voltage change rates dV / dt are connected together, starting from the ground potential, and generates the arbitrary waveform voltage by superimposing the broken-line waveform voltage in the second application section on the first voltage.

2. The pulse power supply according to claim 1, wherein said arbitrary waveform voltage generating unit comprises: a second DC power supply; an inverter circuit that converts the DC voltage of said second DC power supply into an AC voltage; a rectifier circuit that converts the AC voltage of said inverter circuit into a DC voltage; and a voltage superposition circuit that superimposes the output of said first DC power supply and the output of said rectifier circuit, wherein said inverter circuit adjusts, in the DC-AC voltage conversion, the time width of the application phase, the inflection point at which the broken-line waveform voltage is switched to a linear waveform voltage, the voltage change rate dV / dt of each linear waveform voltage, or the voltage of the inflection point, said rectifier circuit rectifies the output of said inverter circuit to generate a broken-line waveform voltage, and said voltage superposition circuit voltage-superimposes said first voltage of the output of said first DC power supply and the broken-line waveform voltage of the output of said rectifier circuit, and generates an arbitrary waveform voltage in which a plurality of linear waveform voltages with different voltage change rates dV / dt are switched and connected at the inflection point, with said first voltage of said first DC power supply as a starting point voltage.

3. A pulse power supply according to claim 2, further comprising a control unit for controlling said inverter circuit, said control unit having control values ​​for determining the time width of said application phase, the time between inflection points for switching the linear waveform voltage of said broken-line waveform voltage, and the voltage change rate dV / dt of each linear waveform voltage, or the voltage of the inflection point, and performing inverter control based on said control values ​​to generate a broken-line waveform voltage formed by connecting a plurality of linear waveform voltages.

4. A pulse power supply device according to claim 2, further comprising a control unit for controlling said inverter circuit, wherein said control unit feeds back power supply output Vout and / or output current Iout, determines control values ​​for keeping power supply output Vout or output current Iout at a constant value, the time width of said application phase, the time and voltage of the inflection point at which the broken-line waveform voltage is switched to a linear waveform voltage, and a duty ratio that determines each linear waveform voltage, and performs inverter control based on said control values ​​to generate a broken-line waveform voltage formed by connecting a plurality of linear waveform voltages.

5. A pulse power supply according to claim 2, wherein the voltage superposition circuit is provided in the rectifier circuit, and an output terminal of the first DC power supply is connected to one output terminal of the rectifier circuit.

6. The pulse power supply according to claim 2, further comprising a transformer between said inverter circuit and said rectifier circuit, said voltage superposition circuit being provided in said transformer, and an output terminal of said first DC power supply being connected to one end of the secondary side of said transformer.

7. The pulse power supply according to claim 3, wherein the control unit sets the control value of the voltage change rate dV / dt as the slope of the linear waveform voltage at each time point when the time between inflection points reaches the control value of the time between inflection points, and sequentially switches the linear waveform voltage from one broken-line waveform voltage to another to generate a broken-line waveform voltage.

8. The pulse power supply according to claim 3, wherein, at each time point when the time between inflection points reaches the control value for the time between inflection points, the control unit sets the slope of the linear waveform voltage to a slope determined based on the control values ​​for the voltage of the inflection point at that time point and the next time point and the control value for the time between inflection points, and sequentially switches the linear waveform voltage to generate the broken-line waveform voltage.

9. The pulse power supply according to claim 3, wherein, at each time point when the time between inflection points reaches a control value for the time between inflection points, the control unit determines a voltage fluctuation by comparing the control value for the voltage at the inflection point at that time with the detected value of the output voltage at that time, and when determining the voltage fluctuation, sets the slope of the linear waveform voltage to a slope determined based on the detected value of the output voltage at that time and the control value for the voltage at the inflection point at the next time, and sequentially switches between the linear waveform voltages to generate a broken-line waveform voltage.

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