High-power generator and high-power pulse supply method

Abstract

A high power (HP) generator (10) and method for delivering pulsed high power having high voltage and / or current values ​​to a capacitive load, in particular a plasma process, comprising: several low power (LP) generators (14, 16, 18), Each LP generator (14, 16, 18) comprises an energy storage component (C1, L1), and in use, the energy storage component (C1, L1) is charged to a predetermined value associated with the energy storage component; several low power (LP) generators (14, 16, 18), each LP generator (14, 16, 18) providing, in use, at its output an LP generator value corresponding to the value of an energy storage component (C1, C2, Cn, L1, L2, Ln) incorporated in the respective LP generator (14, 16, 18); a combiner (20), in which the LP generators (14, 16, 18) are electrically connected so that a combiner value at an output of the combiner (20) can be obtained which corresponds to an output value of the HP generator (10), the combiner value being higher, in use, than the LP generator value at the output of one of the LP generators (14, 16, 18), at least in some states of the HP generator (10); a control unit (22) configured to select the contribution of the LP generators (14, 16, 18) to the output value of the HP generator (10) during the output delivery of the HP generator (10) in order to cause a rise and / or a decay of the pulses at the output of the combiner (20), A high power (HP) generator (10) and method, wherein charging energy for the LP generators (14, 16, 18) is provided via a transformer (T1, T2...Tn) comprising a main winding (P1, P2...Pn) and a secondary winding (SW1, SW2...SWn) for each LP generator (14, 16, 18).

Description

[Technical Field]

[0001] The present invention relates to a high power (HP) generator configured to deliver pulsed high power at high voltage values ​​and / or high currents to a capacitive load, particularly to a plasma process. The present invention also relates to a method of providing high power pulses to a plasma process. [Background technology]

[0002] By capacitive load is meant a load with a capacitive portion, meaning that a voltage rise across this load implies a high current capability. The capacitive portion in this case is at least 100 pF, preferably 200 pF or more, for example, about 500 pF. This can be a load in a plasma process, for example, for plasma treatment applications.

[0003] Some plasma processing applications, such as etching or layer deposition, require high voltage (HV), high frequency (HF), rectangular, asymmetric, and pulsed voltage supplies. Particularly when high frequency operation is required, the voltage values ​​often greatly exceed the voltage handling capabilities of individual semiconductor switches. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] US Patent No. 10,474,184 B2 [Patent Document 2] US Patent No. 10,607,813 B2 [Patent Document 3] U.S. Patent Application Publication No. 2020 0118794 A1 [Patent Document 4] US Patent No. 9,287,086 B2

[0005] Summary of the Invention It is an object of the present invention to provide a high power generator and method for delivering high power pulses to a plasma that allows for the delivery of rapidly varying power (pulses) to a plasma process.

[0006] According to a first aspect, the present invention provides a high power (HP) generator configured to deliver high power having a high voltage and / or a high current value to a load, in particular a plasma process, comprising: - some low power (LP) generators, each LP generator includes an energy storage component, and in use, the energy storage component is charged to a predetermined value associated with the energy storage component; several low power (LP) generators, each LP generator providing, in use, at its output an LP generator value corresponding to the value of an energy storage component incorporated in the respective LP generator; a combiner to which the LP generator is electrically connected so that a combiner value at the output of the combiner can be obtained which corresponds to an output value of the HP generator, the combiner value being higher, in use, than the LP generator value at one output of the LP generator, at least in some states of the HP generator; a control unit configured to select the contribution of the LP generator to the output value of the HP generator during the output delivery of the HP generator in order to cause an increase and / or an attenuation of the pulses at the output of the combiner; The present invention relates to a high power (HP) generator comprising:

[0007] In one embodiment, charging energy for the LP generators is provided via a transformer with a primary winding and a secondary winding for each LP generator, the secondary windings connected to a rectifier, and each rectifier connected to the energy storage component of the corresponding LP generator. The rectifier may include at least one semiconductor element, such as a diode. The rectifier may include four diodes connected in a bridge rectifier configuration. The rectifier and / or the transformer may be part of the power supply.

[0008] Some, and in particular each LP generator may have its corresponding transformer.

[0009] Some, and in particular each, of the transformers associated with the LP generator may have their own magnetic core.

[0010] Some, and in particular each, transformer associated with an LP generator may be equipped with a balancing winding, preferably two balancing windings.

[0011] This allows the AC supply current to flow freely around the transformer, supplying charge to the loaded stages, i.e., the LP generators connected to the load, and preventing overcharging of the unloaded stages, i.e., the LP generators that are not connected to a load and therefore do not contribute to the output of the HP generator. The same concept can be used to power the driver circuit.

[0012] One balancing winding of one transformer may be connected to a balancing winding of a different transformer.

[0013] Thus, some, and in particular each, transformer corresponding to an LP generator may be connected in an open chain configuration.

[0014] The main windings of some of the transformers associated with the LP generator, in particular the main windings of each, may be connected in series, which may mean that one wire is connected in series through all the transformers and is configured to be fed by the AC supply current.

[0015] If each transformer has its own magnetic core and the only common element is the main winding which can be made by one common wire, high voltages and currents can be separated in an efficient and effective way.

[0016] Some, particularly each, of the transformers corresponding to the LP generator, also called "stages", may be embodied as ring-core transformers.

[0017] According to one embodiment, the output of the combiner and / or the output of the HP generator (10), when in use, is a step function, in particular a real step function without a continuous slope.

[0018] According to one embodiment, the LP generators are activated continuously for one pulse. This means that not all LP generators are activated immediately upon the start of the pulse. Thus, for example, if the pulse has a length of 0.5 μs to 2 μs, the first LP generator, or several stacks of LP generators, are activated upon the start of the pulse. After approximately 10 ns or 100 ns, one or more additional LP generators are activated, causing the pulse at the output of the HP generator to rise. Then, after another approximately 10 ns or 100 ns, the next LP generator or stack of LP generators is additionally activated, causing the pulse to rise further. For pulse decay, one or several of the LP generators can be phased out in the same way. "Activating one or several LP generators" means that the control unit selects these LP generators to contribute to the output value of the HP generator during the HP generator's output delivery. In other words, the control unit can be configured to select the contribution of each LP generator to the output value of the HP generator several times during the pulse at the output of the HP generator.

[0019] According to one embodiment, the combiner comprises more than four electrically connected LP generators, in particular more than six LP generators, preferably more than ten, most preferably more than fifteen LP generators. With such a large number of LP generators it is possible to generate real step functions without continuous slopes.

[0020] In one aspect, the control unit is configured to select the contribution of the LP generator in such a way that at least one amplitude step is less than 500V and / or in such a way that a generator with a continuous slope output is not required.

[0021] With such a solution, a generator that produces a continuous slope is not required, which makes the HP generator more efficient.

[0022] In one aspect, the combiner and control unit is configured to connect the LP generators by switching only.

[0023] In one aspect, the control unit may be configured to select the contribution of the LP generator to the output value of the HP generator to form a staircase pulse upon the rising and / or falling edge of the pulse.

[0024] In one aspect, the number of LP generators is sufficiently large to form pulses at the output of the combiner having voltage rises and / or falls of values ​​equal to or greater than the sum of several values ​​of the LP generators, and a staircase pulse shape, where the staircase values ​​correspond to values ​​equal to or greater than one or more values ​​of the LP generators.

[0025] In one embodiment, a balancing circuit comprising components that allow current to flow in only one direction, particularly diodes or components that function like diodes, is connected between the two LP generators. For example, the negative output of the energy storage components, particularly capacitors, of some, particularly each, LP generator is connected to the same potential of the preceding LP generator with such a balancing circuit. This may allow charge from the energy storage components of the lower LP generator to be transferred to the energy storage components of the higher LP generator when the switch in parallel with the load is activated and when the energy storage component value of the lower LP generator exceeds that of the higher LP generator. "Activated" shall mean: "switched on" or "switched to a low impedance at its output." "Switch in parallel with the load" refers to the switching element responsible for disconnecting the corresponding LP generator from nearby connected LP generators when activated. In Figures 2a, 2b, 4, and 5, these are switching element S1. In Figure 3, these are switching element S2. By connect switches we mean the switching elements that, when activated, are responsible for connecting the corresponding LP generator. In Figures 2a, 2b, 4, and 5, these are switching elements S2. In Figure 3, these are switching elements S1. The energy storage components of the highest LP generators accumulate excess charge from the entire stack. These highest LP generators can therefore be advantageously controlled to provide more power to the load than the other LP generators to remove the excess charge.

[0026] In one aspect, damping circuits may be positioned in an open-chain configuration between some, particularly all, of the LP generators. Open-chain configuration shall mean that such damping circuits are positioned between every LP generator and the next higher LP generator, but not between the highest and lowest. The damping circuits may include resistors and / or inductors if the energy storage components are capacitors. The damping circuits may include capacitors if the resistors and / or energy storage components are inductors. The damping circuits between the LP generators may preferably be positioned in series with a balancing circuit. The damping circuits may be used to eliminate parasitic oscillations in the charge handling path.

[0027] The entire HP generator can be directly liquid cooled. This can be done by immersion in a dielectric cooling liquid, and in particular the LP generator is immersed in a dielectric cooling liquid. All components of the HP generator, including the transformer, can be immersed in a dielectric cooling liquid, which provides high cooling capacity while reducing clearance and creepage requirements. This improves the safe operating area utilization of all components, leading to further size reduction and reduced parasitic inductance and capacitance. This reduces the overall size of the HP generator and improves efficiency.

[0028] Some, in particular all, of the LP generators and control units may be at least partially located in one housing, at least together with the switching unit. The combiner may be located in the same housing. The transformer and rectifier may be located in the housing. The housing may be leak-tight. A dielectric cooling liquid may flow through the housing, thereby improving cooling and insulation. Distances may be reduced, allowing shorter wire lengths to be used, which reduces the inherent inductance and thus faster switching capabilities. Temperature differences between the various switches and other components of the LP generators and / or combiner may be reduced by this type of direct liquid cooling. A high degree of balancing is therefore possible.

[0029] In one embodiment, the control unit can be configured to select the contribution of the LP generators in a sequential manner through the LP generators. In particular, each pulse sequence can start with a different LP generator, so that all n LP generators are equally loaded after n pulses. This improves load distribution within the LP generator stack and therefore balances power losses between switching elements.

[0030] In one embodiment, the control unit may comprise a switching unit having a current rise capability of at least 10 A / μs. Such a high current rise capability makes it possible to charge capacitive loads sufficiently quickly.

[0031] In one aspect, the control unit may include a switching unit capable of withstanding voltages of about 0.5 kV or greater with voltage rise and fall rates of 15 kV / μs or greater, thereby enabling extreme pulses with extremely sharp voltage transitions, a highly desirable feature for many applications such as plasma processing, particularly semiconductor plasma processing.

[0032] In one aspect, the control unit may be configured to select the contribution of the LP generators 14, 16, 18 to reduce voltage overshoot at the output of the HP generators and / or at dedicated locations on the load, in particular at the substrate of the plasma process. This may be done by a first step at the output of the HP generators that is only a fraction, in particular half, of the value of a second step that may be the full amount, for example.

[0033] In one embodiment, at least one, preferably several, and most preferably all LP generators are equipped with an LP generator value limiting circuit, such as a voltage limiting circuit or a current limiting circuit. This can be an additional resistor or an additional switching element with a variable, eclectically controllable impedance along with an output dissipation portion. Such a circuit can make the HP generator much more reliable.

[0034] In one embodiment, the control unit is configured to select the contribution of the LP generators in a galvanically isolated manner, in particular via an optical fiber connection or a magnetic coupling. Some, or preferably each, of the LP generators can be selected by the control unit through control of the switching unit. The connection between the output of the data processor and the switching unit can be realized by an optical fiber or a magnetic coupling. This can be useful for switching all LP generators efficiently, quickly, and without time delay, for example, to form pulses with sharp edges in the voltage. Several switching elements of one switching unit can be connected by one galvanically isolated connection. Several LP generators with corresponding switching units can be combined into one group, which can be configured so that the group is exclusively activated or deactivated together. It is then possible to use only one galvanically isolated connection for such a group. Reducing the number of galvanically isolated connections can save costs and increase the reliability of the HP generator because fewer components are at risk of failure. Advantageously, each switch has its own galvanically isolated connection. However, several transmitters, when integrated, can be controlled by one control signal, which reduces the number of I / O components required.

[0035] In one aspect, the voltages of all LP generators, also called "stages," are equal despite their unbalanced loads. Similarly, main-to-secondary winding isolation (ground-to-HV) is simply obtained by positioning the main path near the middle of the ring-core transformer, while keeping the secondary windings near the core and away from the main windings. Since only stage-to-stage voltage isolation needs to be provided here, the balancing windings can be placed near the secondary windings.

[0036] The meaning of "the control unit is configured to select the contribution of the LP generator to the output value of the HP generator" is understood as the capability and configuration of the circuitry of the HP generator in combination with the program of the control unit to enable the HP generator to select a choice of LP generators with respective LP generator values ​​to provide a contribution to the output value of the HP generator.

[0037] The control unit may comprise a data processor, e.g. embodied as an embedded microcontroller, having a program memory, e.g. embodied as a non-volatile data memory, and a data memory, e.g. embodied as a volatile data memory. Such a control unit typically comprises a data interface for incoming data such as measurement data, control input data, etc., and outgoing data such as control signals, information signals, alert signals, etc. Such a control unit typically comprises a data computing section, data comparison capabilities, and similar circuitry, allowing it to calculate new data from the incoming data, make decisions related to the incoming and / or calculated data, and output appropriate data signals to, e.g., control other electrical circuitry of the HP generator.

[0038] The output of the combiner may be the output of the HP generator. However, it is also possible that some minor additional voltage or current shaping component may be connected between the output of the combiner and the output of the HP generator. This minor additional voltage or current shaping component may be a filter or a small voltage, current or power source with a quantity much smaller than the output value of the combiner.

[0039] "HP generator state" means the different states that the HP generator may be in when in use, depending on the operation of different LP generators and / or switching units and / or switching elements within the HP generator.

[0040] High power means 10 kW or more during pulse output. High voltage means 4 kV or more. High current means 10 A or more. The HP generator can be configured to affect the voltage and / or charge carrier movement in the plasma and / or between the plasma potential and the substrate in the plasma process. The energy storage component can be a capacitor or inductor and / or other energy storage component. It should be understood as an energy storage component configured to store an amount of energy that may be a suitable portion of the output energy of one pulse of the HP generator, i.e., at least 1 / 200, preferably at least 1 / 100, and more preferably at least 1 / 50 of the energy of one pulse of the HP generator. Continuously charging the energy storage component includes charging the capacitor to a desired voltage value or the inductor to a desired current value. The electrical connection of the LP generators within the combiner can be series, parallel, or a combination of both. The combiner value can be voltage, current, or power. The control unit can determine which LP generators contribute to the HP generator output. The control unit may be configured to control the LP generators such that at least two LP generators contribute to the output of the HP generator, i.e., such that the output values ​​of the at least two LP generators are added to form the HP generator value.

[0041] The main advantage is that the energy storage components are charged independently of the state of the control unit, meaning there are no limitations on the generated output values, especially the output pulses, their width and consequently the duty cycle of the average output. A second advantage is that each LP generator has its own energy storage component, which protects the switches in the control unit from overvoltage or overcurrent, respectively. A third advantage is that all components are relatively cheap due to the low power components.

[0042] The control unit may include switching units, one associated with each LP generator. Each switching unit may include one or two transistors, particularly MOSFETs. MOSFETs provide high switching capabilities, allowing currents of 50 A or more to be used and voltages of 500 V or more to be switched. When MOSFETs are used, an anti-parallel diode may be provided for each MOSFET, particularly in parallel with each MOSFET. The MOSFETs may be silicon carbide (SiC)-based or gallium nitride (GaN)-based MOSFETs suitable for rapidly switching voltages of 500 V or more with fast voltage rise and fall times (15 kV / μs or more) and high currents (50 A or more) with fast current rise and fall times (10 A / μs or more).

[0043] Each switching unit may comprise a half-bridge circuit in which two switching elements are connected in series. One transistor may be configured to connect two of the LP generators when closed so that both values ​​of both LP generators affect the value at the output of the combiner. In particular, the output values ​​of both LP generators may be added. The other transistor may be configured to short-circuit the load when activated, i.e., when the transistor is closed or in a conducting state.

[0044] Each half-bridge circuit can be clamped by its storage component, for example by a capacitor. This means that the storage component is directly parallel connected to the half-bridge. This configuration protects both switches from overvoltages below the voltage of the capacitor. The storage component can also be an inductor. This configuration protects both switches from overcurrents below the current in the inductor. This is sufficient to maintain a safe voltage / current individually for all LP generators to prevent failures related to overvoltages or overcurrents, respectively. Each LP generator therefore maintains its operating level within itself. This results in an automatically maintained safe state.

[0045] The control unit may comprise a driver, which may be configured to drive a switching unit, in particular a transistor, in particular a MOSFET, and the control unit, in particular the switching unit, may be part of each LP generator.

[0046] At least 6, preferably 10 or more, more preferably 15 or more LP generators may be combined in one combiner. At least two LP generators may provide equal LP generator values. Preferably, most or even all of the LP generators may provide equal values. It is also possible that at least two LP generators may provide different LP generator values, and in particular all LP generators may provide different values. One LP generator may provide an LP generator value that is half the LP generator value of another LP generator.

[0047] Capacitors can be provided as energy storage components in parallel with the switching units, especially the half-bridges. This stabilizes the output value of the combiner. Each LP generator can have its own capacitor, which is charged to an appropriate voltage level. By activating one switch of the associated switching unit, a load, e.g., a plasma process, is connected to the capacitor. By activating the other switch of the switching unit, the load is shorted. The output of the entire HP generator can represent a real dynamic voltage source during each pulse, allowing for large output currents and the required fast voltage transitions.

[0048] An inverter, preferably a buck converter, with a full bridge circuit can be connected to the main winding, which allows for efficient power delivery to the LP generator.

[0049] In a further aspect, the present invention provides a method of supplying high power pulses having variable amplitude provided by a high power (HP) generator to a plasma process, comprising: a. sequentially charging energy storage components of a number of low power (LP) generators to respective predetermined values; b. selectively combining the output values ​​of at least some of the LP generators to obtain desired output values ​​of the HP generators corresponding to pulses having a desired oscillation by controlling the contribution of the LP generators to the output of the HP generators; The present invention relates to a method comprising:

[0050] By using multiple LP generators, each containing an energy storage component, together with a combiner, it is possible to select how many LP generators contribute to generating the output pulse. This solution is relatively safe, versatile, and inexpensive. It is safe because every LP generator can be configured to protect its associated switch against outputs exceeding the output value of its energy storage component. This solution is versatile due to the fact that it is possible to quickly change the output pulse amplitude with a resolution equal to the number of low-power generators. It is inexpensive because it is possible to use multiple low-power generators and low-voltage switches, which are generally cheaper than a single HP generator and high-power pulse unit.

[0051] In one embodiment, the LP generators, also referred to as "stages," can be controlled individually or in groups. Control signals can be provided to the drivers of the switching units, preferably by optical fiber, although other means can be used. All switches in a switching unit can be individually controlled from one main control panel, but one signal can also control an entire stage (e.g., control signals for the connection switches of a switching unit could come from the main control panel, while signals for switches in parallel with the switching unit's load could be generated on the connection switch driver panel), one signal can control multiple switches / stages with grouped control, etc. The total power output is the sum of the power outputs of only the activated / selected LP generators. The total power output can be varied from pulse to pulse by activating or selecting a different number of LP generators for each pulse.

[0052] In one embodiment, the output value of the LP generators, i.e., the LP generator value, can be dynamically stabilized. Each LP generator can have its own capacitor that is charged to the appropriate voltage level. Activating one switch connects the load to the capacitor. Activating the other switch shorts the load. The overall HP generator output can represent a true dynamic power source during each pulse, allowing for large output currents and the required fast transfer transitions.

[0053] A double-step transition can be realized instead of a single-step output value transition. The inevitable connection between a low-impedance voltage source and a capacitive load due to any connector inductance causes current and voltage oscillations. The load peak voltage reaches twice the applied voltage level. The resistive damping circuit dissipates a large amount of power. By applying a double-step transition, the power loss can be significantly reduced. This is possible with the presented topology. A nearly rectangular voltage waveform shape, lower overshoot, and significantly reduced power loss can be obtained with the double-step transition.

[0054] Several stages, also called "LP generators," can be activated continuously during a persistent output pulse. Activating an LP generator means activating the corresponding connecting switch element. To compensate for the decaying wafer voltage, the output voltage may be increased in several steps. Each step adds its voltage to the total output voltage value. If the voltages of all stages are equal, the resolution of each step is 1 / n times the voltage of the full stack of LP generators. A separate stack may be built to address the compensation feature. This can be controlled separately, resulting in a much finer step resolution, potentially resulting in a more stable wafer voltage and better ion energy distribution.

[0055] Further features and advantages of the present invention emerge from the following detailed description of embodiments of the invention based on the figures of the drawings which show the essential details of the invention, and from the claims. The features shown therein are not necessarily to scale, but are shown so that the particular features according to the invention are clearly visible. The various features can be implemented individually or in any combination in variants of the invention.

[0056] In the schematic drawings, examples of the invention are shown in various stages of use, which are explained in more detail in the following description. [Brief explanation of the drawings]

[0057] [Figure 1] 1 shows a series of pulses with varying amplitudes. [Figure 2a] 1 shows a first embodiment of an HP generator. [Figure 2b] 2 shows a second embodiment of the HP generator. [Figure 3] 1 shows a first embodiment of a portion of an HP generator for generating a positive voltage pulse. [Figure 4] 1 shows a second embodiment of a portion of an HP generator for generating a positive voltage pulse. [Figure 5] 1 illustrates an embodiment of an HP generator with a power source for providing power to an LP generator. [Figure 6] 1 illustrates an embodiment of an HP generator having a balancing circuit and a damping circuit. [Figure 7] The waveform shape and power loss for single and double step transitions are shown. [Figure 8] 1 shows the waveform obtained from continuous operation of the LP generator. [Figure 9] 1 shows the result of a cyclic control signal sequence through an LP generator. [Figure 10] 1 shows a plasma processing system including a plasma chamber. [Figure 11] 1 shows an alternative embodiment of the HP generator. [Figure 12]1 shows an alternative embodiment of the HP generator. [Figure 13] 1 shows an alternative embodiment of the HP generator. [Figure 14] 1 shows an alternative embodiment of the HP generator. [Figure 15] 1 shows an example of an LP generator value limiting circuit. [Figure 16] 1 illustrates an embodiment of an HP generator with a balancing circuit. [Figure 17] 1 illustrates an embodiment of an HP generator with liquid cooling. [Figure 18a] 1 illustrates an embodiment of an HP generator with a galvanically isolated drive. [Figure 18b] 1 illustrates an embodiment of an HP generator with a galvanically isolated drive. DETAILED DESCRIPTION OF THE INVENTION

[0058] Figure 1 shows a series of pulses 1 required for plasma applications. It can be seen that the amplitude of pulse 1 may need to be constant for several pulses, but may also need to vary in amplitude from pulse 1 to pulse 1a.

[0059] FIG. 2 shows a first embodiment of a high-power (HP) generator 10 suitable for generating high-power pulses. The HP generator has a positive output section 32 and a negative output section 12. The HP generator 10 comprises several low-power (LP) generators 14, 16, 18, each of which comprises an energy storage component C1, C2, Cn, embodied in this case as a capacitor. During use, the energy storage component C1 is continuously charged to a predetermined value associated with the energy storage component C1 in order to maintain the energy stored therein constant. During use, each LP generator 14, 16, 18 provides at its output an LP generator value corresponding to the value of the energy storage component C1 incorporated within the LP generator 14, 16, 18. The LP generators 14, 16, and 18 are electrically connected within a combiner 20 so that a combiner value at the output of the combiner 20 that corresponds to the output value of the HP generator 10 and is higher than the LP generator value at the output of one of the LP generators 14, 16, and 18 can be obtained. A control unit 22 is configured to select the contribution of the LP generators 14, 16, and 18 to the output value of the HP generator 10 during power delivery from the HP generator 10. For clarity, only three LP generators are shown. In practice, many more LP generators, typically six or more, ten or more, and especially fifteen or more, would be used to provide a gradual transition in output that may be smooth depending on the load demands.

[0060] The control unit 22 comprises switching units 24, 26, 28 associated with each LP generator 14, 16, 18. The switching units 24, 26, 28 each include a switching element S1, S2. In the illustrated embodiment, the switching elements S1, S2 are connected in series, thus realizing a half-bridge. The switching units 24, 26, 28, and thus the switching elements S1, S2, are driven by a driver 30 of the control unit 22.

[0061] The positive output 32 of the HP generator is connected to ground, also called earth potential PE. All LP generators are connected to a power supply 34, which includes a transformer, a rectifier and an inverter connected to the grid, itself including a full bridge and a buck converter, as described in more detail below.

[0062] FIG. 2b generally corresponds to FIG. 2a. Therefore, similar elements are numbered similarly. The difference between FIG. 2a and FIG. 2b is that in FIG. 2b, the energy storage components are embodied as inductances L1, L2, and Ln. Therefore, the electrical connections / wiring within the coupler 20 are slightly different. In general, the energy stored in an inductor turns into a current source. Therefore, the energy storage component is connected in parallel with another current source, resulting in current multiplication.

[0063] In both Figures 2a and 2b, the earth potential, also referred to as ground potential PE, can be connected to one of the outputs of one of the LP generators 14, 16, 18. Thereby, it is possible to form a voltage signal with positive and negative voltages above ground, as shown for example in Figure 10 of (Patent Document 1) or Figure 21 of (Patent Document 2). The earth potential can also be connected to the positive output 32 or the negative output 12. In Figures 2a and 2b, it is connected to the positive output 32 as an example.

[0064] FIG. 3 shows a simplified embodiment of a portion of an HP generator 10 having several LP generators 14, 16, 18. To generate high-voltage pulses, it is advantageous to construct a push-pull switch, which means that the switching unit should have at least two switching elements S1, S2: a "push" (switching element S1) used to charge the plasma reactor capacitor, and a "pull" (S2) used to discharge the plasma reactor capacitor. To generate pulses with different amplitudes, the amplitude can be changed quickly between pulses (as shown in FIGS. 1, 7, and 8), while it is necessary to combine the outputs of two or more LP generators 14, 16, 18. The LP generators 14, 16, 18 can have the same or different LP generator values, in this case voltage amplitudes. In FIG. 3, earth potential, also referred to as earth potential PE, is connected to the negative output of the LP generator 18.

[0065] In some situations, if both switching elements S1 and S2 are not switched on (during a transition between two operating states) and the LP generators 14, 16, and 18 are connected in series with a load (e.g., a plasma reactor), the switching elements S1 and S2 may be destroyed by overvoltage. Therefore, it is advantageous to add diodes D1 and D2 in parallel to all switching elements S1 and S2 to protect them from voltages higher than the voltage stored in their respective energy storage components. This is particularly true when the switching elements S1 and S2 are embodied as MOSFETs. If the switching elements are embodied as unipolar transistors, as MOSFETs are typically, the diodes may be pre-mounted as part of the transistor or may be an integral part of the transistor die. In the context of integrated circuits, the die is a small block of semiconductor material on which a given functional circuit is assembled. These diodes can then be used, eliminating the need to add them separately.

[0066] It is possible to generate a ground potential at the output of the HP generator (the load is short-circuited to ground potential PE). This state can be achieved by switching on the switching element S2 when ground potential is connected to the negative output 12 or the positive output 32 of the HP generator. The switching element S1 is open (switched off) during this state. To generate a (voltage) pulse at the load, it is necessary to switch on the appropriate number of switching elements S1. The LP generators 14, 16, 18 can provide the same or different LP generator values, in this case voltage amplitudes. By switching on several switching elements S1, the associated LP generators, for example LP generators 14, 16, are connected in series, so that the amplitude of the voltage pulse at the load is equal to the sum of the LP generator values, for example their output voltages.

[0067] The complementary switching element S2 associated with the LP generators 14,16 should be switched off to avoid a short circuit within the LP generators 14,16.

[0068] The switching element S1 associated with the LP generator 18 (or further LP generator) should be switched off, and the switching element S2 can be switched on or off (in either case the current flows through the diode D2).

[0069] The configuration of switching elements that are switched on and off can be rapidly changed, resulting in rapid changes in the amplitude of the pulses produced at the output of the HP generator 10. The number of LP generators 14, 16, 18 supplying the load can be rapidly varied to any accessible number (from 0 to n).

[0070] Figure 4 differs from Figure 3 only in the wiring or interconnection of the LP generators 14, 16, 18 and the connection point of the load to PE. However, the same result as in Figure 3 can be achieved, i.e., by selecting the LP generators 14, 16, 18 that contribute to the output voltage pulse by appropriately driving the switching elements S1, S2, voltage pulses of different amplitudes can be realized. In Figure 4, earth potential, also referred to as ground potential PE, is connected to the negative output of HP generator 10.

[0071] Figure 5 shows the power supply of the LP generators 14, 16, and 18 in more detail. The energy storage components C1, C2, and Cn of the LP generators 14, 16, and 18 are continuously charged by the transformers T1, T2, and Tn, respectively, and by the associated rectifiers X1, X2, and Xn, respectively. It is much simpler and cheaper if all the transformers X1, X2, and Xn have their own magnetic cores, and the only common element is the main windings P1, P2, and Pn, which can be made from a single common wire. To ensure the same voltage regardless of the load, a balancing winding BW is added. The balancing winding BW equalizes the magnetic flux of all the transformers T1, T2, and Tn. If the secondary windings SW1, SW2, and SWn have the same number of wires, the voltage of the energy storage component C1 is equal. The charging voltage of the energy storage component C1 can be changed by changing the number of turns of the secondary windings SW1, SW2, and SWn. In that way it can be ensured that all energy storage components C1 are charged to different voltages.

[0072] The balancing windings BW of the transformers T1, T2, Tn work in such a way that when the magnetic flux is the same in both adjacent transformers T1, T2, Tn, the same voltage will be present in both windings BW and hence no current will flow between the windings BW. If for some reason the magnetic flux of one core is different (say higher) than the next core, the induced voltage will be different in the different transformers T1, T2, Tn and hence current will start flowing between the windings BW. This current will cause the transformer T1, T2, Tn with the higher magnetic flux to be more loaded, while the magnetic flux of the next transformer will be increased by this current. By equalizing the magnetic flux of the magnetic cores, the induced voltages will be equalized. The balancing windings BW should have the same number of turns in both transformers connected using the flux equalization method.

[0073] The main windings P1, P2, Pn are connected to an inverter 40, which is connected to a power grid 42. The inverter 40 is part of the power supply 34 and includes a full bridge 44 and a buck converter 46 upstream of the full bridge 44, which is connected to a rectifier 48.

[0074] FIG. 6 shows an HP generator 10, such as the HP generator of FIG. 2a, in which a balancing circuit including components that allow current flow in only one direction—specifically, diodes D or diode-like components—is connected between two LP generators 14, 16, and 18. The switching units 24, 26, and 28 comprise switching elements in half-bridge configurations. These switching elements are shown as transistors, more precisely, as bipolar transistors. During intense switching times, a more preferred transistor type would be MOSFETs, particularly MOSFETs based on SiC or GaN. In this embodiment, the negative terminal of each LP generator 14, 16, and 18, also referred to as a stage, is connected to the same potential as the preceding LP generator 14, 16, and 18 by a diode D or a diode-containing circuit. This allows the energy stored in the energy storage components of the lower stages to be transferred to the energy storage components of the higher stages when the switching elements are activated and the voltage of the energy storage components of the lower stages exceeds that of the higher stages. The charge of the highest stage 14 accumulates excess charge from the entire stack. Therefore, the highest stage 14 should be controlled to provide maximum power to the load to remove excess charge. The use of a diode D or a circuit containing a diode results in better voltage distribution along the LP generator stack. In particular, a balancing circuit, here a damping circuit 50 in series with the diode D, can be used to eliminate parasitic oscillations in the charge handling path. The damping circuit may include an inductor L and / or a resistor R connected in parallel, as shown in particular in FIG. 6.

[0075] Connecting a low-impedance voltage source, such as a capacitive voltage source, to a capacitive load inevitably results in current and voltage oscillations due to connector inductance. The load peak voltage then reaches twice the applied voltage level. This can damage the load and is highly undesirable. Resistive snubber circuits are often used to damp the peak voltage. These dissipative circuits dissipate a large amount of power and therefore generate a large amount of heat, which is also highly undesirable. By applying a two-stage transition, this overshoot can be controlled, reduced, or even avoided. The dissipated energy of the dissipative circuit can be dramatically reduced or even avoided. The energy-dissipating portion can then be much smaller or even avoided entirely. Power losses can be significantly reduced. This is possible with the proposed arrangement, as shown in FIG. 7. Waveform 70 shows a single-stage transition from 0 kV to 10 kV at the output of the combiner 20 by instantaneously activating, for example, all 15 stages. This causes a voltage overshoot, as can be seen in FIG. 7. If the step-wise transition follows a first step, e.g., from 0 V to 5.5 kV by activating only eight of the 15 stages, and a second step, e.g., from 5.5 kV to 10 kV by activating the remaining 15 stages, delayed by 10 or 100 ns, as shown in waveform 71, the results are much better. The resulting waveform 73 has a much lower overshoot peak, and the voltage rise is slower but still fast enough for the process. As can be seen in waveform 73, the two-step transition results in a nearly rectangular output waveform and lower overshoot, thus dissipating very little power, while the single-step transition results in waveform 74, which shows voltage overshoot and therefore significant power loss 75. The same overshoot peak and its reduction can be seen in the descending slope after 1 μs, e.g., 3.5 μs.

[0076] FIG. 8 shows the gradual increase in amplitude of pulse 80 as a result of sequentially activating LP generators 14, 16, and 18 to contribute to the HP output signal. Waveform 81 shows the voltage at the output of the HP generators, and waveform 82 shows the voltage on the wafer in the plasma chamber. FIG. 9 shows the result of cycling a control signal sequence through an LP generator stack containing fifteen LP generators #01-#015. This diagram, like FIG. 8, shows a timeline t on the horizontal axis. The vertical axis shows the activation of fifteen switching elements corresponding to the fifteen LP generators #01-#15. The diagonally shaded area 92 is the area where the associated switching elements are activated. The white box area 91 is the area where the switching elements in parallel with the load are activated; therefore, there are no pulses at the output during the time periods when the diagonally shaded area is not present. In the first column, LP generators #01-#06 are switched together with their associated switching elements. In the second (2 nd In the third (3) column, LP generators #01 to #10 are switched together with the corresponding connecting switching elements. rd In the fourth (4) column, LP generators #01 to #11 are switched together with the corresponding connecting switching elements. th In the 9th (9th) column, LP generators #01 to #12 are switched together with the corresponding connecting switching elements, etc. In this way, the pulse is shaped as a step function. th ) column, the pulse ends and all connected switching elements are deactivated. Then, in column 10, the next pulse begins, this time starting with LP generators #02-#07 instead of LP generators #01-#06. All LP generators in this example have the same output value, but the output value at the output of combiner 20 is the same as for the first pulse. The advantage is that each pulse sequence starts with a different LP generator stack, so that all 15 LP generators and corresponding switching elements are equally loaded after 15 pulses. This results in better load distribution among the LP generator stacks and therefore better power loss balance among the switching elements.

[0077] FIG. 10 shows a plasma processing system including a plasma chamber 100 in which a plasma 101 is established within a plasma space. Such or similar systems are shown and described, for example, in U.S. Pat. No. 6,279,499, U.S. Pat. No. 6,279,499, or U.S. Pat. No. 6,279,499. An upper electrode 103 may be positioned within the plasma chamber. Gas inlets and / or outlets, particularly gas supply pipes 104, may be arranged from the outside to the inside of the plasma chamber 100 and may be connected to the electrode 103. A substrate 102, particularly a semiconductor wafer, may be placed on a support 105 comprising a substrate holder inside the plasma chamber 100. During use, the substrate 102 may be treated by the plasma 101, for example, in an etching, ashing, or deposition process, particularly atomic layer deposition. Etching processes can be extremely challenging, for example, when the ratio of the hole diameter to the hole length to be etched is very low, e.g., <1 / 100, since deep etching processes are often required. An electrically conductive electrode 106 may be positioned within the plasma chamber 100, particularly near the substrate 102, for example, around the periphery of the substrate 102. The electrically conductive electrode 106 may be an edge ring, sometimes called a focus ring. The electrically conductive electrode 106 may be connected to a first power supply 114 via a first connection line 115. The first power supply 114 may be a DC pulse power supply, where the pulses may be of different lengths, amplitudes, and shapes, as described, for example, in FIGS. 11 and 14 of U.S. Patent No. 5,627,497 or in FIG. 2 of U.S. Patent No. 5,627,497. By controlling the first power supply 114, the electrically conductive electrode 106 may additionally or alternatively be used to control ion energy and / or ion acceleration direction, as also described in U.S. Patent No. 5,627,497 or U.S. Patent No. 5,627,497. A first radio frequency (RF) power supply 118 may be electrically connected to the support 105 via a first power supply rod 119, a first matching unit 116, and a first connection unit 117. A second radio frequency (RF) power supply 108 may be electrically connected to the upper electrode 103 via a second power supply rod 109, a second matching unit 110, and a second connection unit 111. An electrode 107 may be positioned in or near the support 105 and is electrically connected to a second power source 112 via a second connecting line 113 .The second power supply 112 may be a DC pulse power supply, where, in particular, the pulses may be of different lengths, amplitudes, and shapes, as described, for example, in Figures 11 and 14 of (Patent Document 4) or Figure 2 of (Patent Document 1). The substrate 102 may be fixed to the support 105 via an electrode 107, which may function as an electrostatic chuck. Through control of the second power supply 112, the electrode 107 may additionally or alternatively be used to control ion energy and / or ion acceleration direction, as described in (Patent Document 4) or (Patent Document 1).

[0078] Some plasma processing applications, such as etching or layer deposition, require the application of high voltage (HV), high frequency (HF), rectangular, asymmetric, and pulsed voltages. Particularly when high frequency operation is required, the voltage values ​​often greatly exceed the voltage handling capabilities of individual semiconductor switches.

[0079] Some plasma applications require not only pulsing but also pulse-to-pulse amplitude variation. Some plasma applications require sources that deliver high peak currents to achieve short voltage transition times. Most plasma applications present a load, which includes a capacitive component. Significant power losses are associated with the pulse-to-pulse charging and discharging process of this load capacitor. Some plasma applications require pulses to be shaped, for example, as described in Figures 11 and 14 of U.S. Patent No. 5,629,497 or Figure 2 of U.S. Patent No. 5,629,497.

[0080] Therefore, connecting such switches in series is one possible solution. Series connections require voltage balancing means, which are not easily realized in HP operation.

[0081] Figure 11 shows an alternative embodiment of the HP generator as shown in Figure 5. The difference between the HP generators as shown in Figure 5 and Figure 11 is that in Figure 11 the main windings P1, P2...Pn are connected in parallel to the transformers T1, T2...Tn and no balancing winding BW is provided.

[0082] Figure 12 shows a further alternative embodiment of the HP generator as shown in Figure 5. The difference between the HP generators as shown in Figure 5 and Figure 12 is that in Figure 12 all the transformers T1, T2...Tn of Figure 5 are combined into one main transformer T1 having only one core. Only one main winding P is required and no balancing winding BW is provided.

[0083] Figure 13 shows a further alternative embodiment of the HP generator as shown in Figure 5. The difference between the HP generators as shown in Figures 5 and 13 is that in Figure 13 the main windings P1, P2... Pn are connected in parallel with the transformers T1, T2... Tn. Balancing windings are shown, but are also not absolutely necessary in such a configuration.

[0084] Figure 14 shows an alternative embodiment of the HP generator as shown in Figure 5. The difference between the HP generators as shown in Figure 5 and Figure 14 is that in Figure 14, the main winding P1 is connected only to the transformer T1. The balancing winding BW is used to transfer energy from the transformer T1 to T2 and from the transformer T2 to the subsequent transformer.

[0085] FIG. 15 shows an example of an LP generator value limiting circuit 151. This LP generator value limiting circuit 151 is a voltage limiting circuit. It can be connected in parallel with one, some, or all of the LP generators 14, 16, and 18 at terminals 152a and 152b. It can also be connected in parallel with one, some, or all of the switching units 24, 26, and 28 at terminals 152a and 152b. This LP generator value limiting circuit 151 comprises a series circuit of a diode D15 and a capacitor C15, and clamps any overvoltage present at its terminals 152a and 152b to the voltage to which capacitor C15 is charged. The voltage of capacitor C15 is controlled by a discharge circuit 153. The discharge circuit 153 comprises a transistor T15, in this case a MOSFET, and a resistor R15, in this case a power resistor, which is configured to be cooled very effectively. Transistor T15 can be switched on or off, and is therefore controlled in pulse mode. Therefore, transistor T15 does not dissipate an excessive amount of energy into heat and remains fairly cool. When transistor T15 is switched on, the capacitor is discharged, and the discharge current flows through resistor R15, dissipating the energy into heat. Most of the heat is generated within resistor R15, which is easier and cheaper to maintain at a sufficiently low temperature than transistor T15. Transistor T15 is controlled by a voltage control circuit 154 via its control input G15. The voltage control circuit 154 includes a series connection of a first high-voltage Zener diode 155, a current-limiting resistor 156, and a second low-voltage Zener diode 158. The junction of current-limiting resistor 156 and second low-voltage Zener diode 158 is connected to the control input G15 of transistor T15. The voltage control circuit 154 may further include a driver 157. Driver 157 may be connected at its input to the junction of current limiting resistor 156 and second low-voltage Zener diode 158. Driver 157 may be connected at its output to control input G15 of transistor T15. A voltage divider 159 may be connected between the output of driver 157 and control input G15 of transistor T15.

[0086] The driver may have hysteresis at its input and is therefore embodied as a Schmitt trigger, which generates a pulse signal to drive the discharge transistor T15 at a frequency of approximately 2-20 kHz. In such a configuration, more than 90% of the power is dissipated in resistor R15, which keeps the transistor cool enough to operate reliably for long periods of time.

[0087] FIG. 16 shows an embodiment of an HP generator 10 having a balancing circuit with components that allow current flow in only one direction, specifically a diode D or a diode-like component, connected between the two LP generators 14, 16, and 18. The balancing circuit, specifically diode D, is connected between the two negative outputs of the LP generators 14, 16, and 18. This allows energy from the lower-stage energy storage components to be transferred to the higher-stage energy storage components when the switching element S1 is activated and the voltage of the lower-stage energy storage components exceeds that of the higher stages. The charging of the highest stage 14 accumulates excess charge from the entire stack. Therefore, the highest stage 14 is controlled to provide maximum power to the load to remove the excess charge. Using diode D or a circuit including a diode results in better voltage distribution along the LP generator stack.

[0088] 17 shows an embodiment of an HP generator 10 with liquid cooling. All electronic components of the HP generator 10, such as the LP generators 14, 16, 18, switching units 24, 26, 28, transformers T1, T2, Tn, and inverter 40, are disposed within a leak-resistant housing 171. A liquid reservoir 174 is disposed near the housing. A liquid pump 173 is disposed between the housing and reservoir 174 for circulating liquid 171 between the housing and reservoir 174 in a closed liquid loop. The reservoir is in thermal contact with a heat exchanger 175, which transfers heat from the closed cooling liquid loop to the environment.

[0089] 18a and 18b show an embodiment of the HP generator 10 having a galvanically isolated connection 181 between the driver 30 and the switching elements S1, S2.

[0090] Thus, here, the control unit 22 is configured to select the contributions of the LP generators 14, 16, 18 in a galvanically isolated manner, in particular via an optical fiber connection or magnetic coupling. The connection between the output of the data processor and the switching elements 24, 26, 28 can be realized by optical fiber or magnetic coupling. This can be useful for switching all LP generators 14, 16, 18 efficiently, quickly, and without time delay, for example, to form pulses with sharp edges. Several switching elements S1, S2 of one switching unit 24, 26, 28 can be connected by one galvanically isolated connection. Several LP generators 14, 16, 18 with corresponding switching units 24, 26, 28 can be combined into one group, which can be configured in such a way that this group is exclusively activated or deactivated together. Then, in such a group, only one galvanically isolated connection 181 can be used. Galvanic isolation (transmitter and receiver) can be used for all switches. Groups of transmitters can be controlled simultaneously reducing the number of control signals required. Reducing the number of galvanically isolated connections 181 potentially reduces costs and increases the reliability of the HP generator 10 by reducing components at risk of failure. [Explanation of symbols]

[0091] 1 pulse 1a pulse 10 High Power Generator 12 Negative output section 14 Low-power generator 16 Low-power generator 18 Low Power Generator 20 Combiner 22 Control Unit 24 Switching Unit 26 Switching Unit 28 Switching Unit 30 Drive unit 32 Positive output section 34 Power supply 40 inverter 42 Power Grid 44 Full Bridge 46 Buck Converter 48 Rectifier 50 Attenuation circuit 70 waveforms 71 Waveform 73 Waveform 74 Waveform 75 Waveform 80 pulses 81 Waveform 82 Waveform 91 Box Area 92 Diagonally shaded area 100 Plasma Chamber 101 Plasma 102 Circuit Board 103 Electrode 104 Gas supply pipe 105 Support 106 Electrically conductive electrodes 107 Electrode 108 Power supply 109 Second Power Supply Rod 110 Second matching unit 111 Second connection unit 112 Second Power Source 113 Second connecting line 114 First Power Source 115 First connecting line 116 First Integrating Unit 117 First Connection Unit 118 Power supply 119 First Power Supply Rod 151 LP generator value limiting circuit 152a End 152b End 153 Discharge circuit 154 Voltage control circuit 155 High Voltage Zener Diode 156 Current limiting resistor 157 Drive Unit 158 Low-Voltage Zener Diode 159 Voltage Divider 171 Liquid 173 Liquid Pump 174 reservoir 175 Heat exchanger 181 Connection S Switching element C. Energy Storage Components D diode P main winding X rectifier SW Second winding BW Balancing winding T transformer L inductor R resistor PE Earth potential

Claims

1. 1. A high power (HP) generator (10) configured to deliver pulsed high power having a high voltage and / or a high current to a capacitive load, the capacitive load being a plasma process, the high power (HP) generator (10) comprising: several low power (LP) generators (14, 16, 18), each LP generator (14, 16, 18) comprises an energy storage component (C1, L1), said energy storage component (C1, L1) being charged in use to a predetermined value associated with said energy storage component; each LP generator (14, 16, 18), in use, provides at its output an LP generator value corresponding to the value of said energy storage components (C1, C2, Cn, L1, L2, Ln) incorporated in the respective LP generator (14, 16, 18); several low power (LP) generators (14, 16, 18); a combiner (20) in which the LP generators (14, 16, 18) are electrically connected so that a combiner value can be obtained at the output of the combiner (20) that corresponds to the output value of the HP generator (10), the combiner value being higher, in use, than the LP generator value at the output of one of the LP generators (14, 16, 18), at least in some states of the HP generator (10); a control unit (22) configured to select the contribution of the LP generators (14, 16, 18) to the output value of the HP generator (10) during its output delivery in order to cause a rise and / or a decay of the pulses at the output of the combiner (20), the charging energy of the LP generators (14, 16, 18) is supplied via a transformer (T1, T2...Tn) comprising a main winding (P1, P2...Pn) and a secondary winding (SW1, SW2...SWn) for each LP generator (14, 16, 18); the second windings (SW1, SW2... SWn) are connected to rectifiers (X1, X2... Xn), each rectifier (X1, X2... Xn) being connected to the energy storage components (C1, C2, Cn, L1, L2, Ln) of the corresponding LP generators (14, 16, 18); and / or some of the main windings (P1, P2...Pn) are connected in series; High power (HP) generator (10).

2. 1. A high power (HP) generator (10) configured to deliver pulsed high power having a high voltage and / or a high current to a capacitive load, the capacitive load being a plasma process, the high power (HP) generator (10) comprising: several low power (LP) generators (14, 16, 18), each LP generator (14, 16, 18) comprises an energy storage component (C1, L1), said energy storage component (C1, L1) being charged in use to a predetermined value associated with said energy storage component; a number of low power (LP) generators (14, 16, 18), each LP generator (14, 16, 18) providing, in use, at its output, a LP generator value corresponding to the value of the energy storage components (C1, C2, Cn, L1, L2, Ln) incorporated in the respective LP generator (14, 16, 18); a combiner (20) in which the LP generators (14, 16, 18) are electrically connected so that a combiner value can be obtained at the output of the combiner (20) that corresponds to the output value of the HP generator (10), the combiner value being higher, in use, than the LP generator value at the output of one of the LP generators (14, 16, 18), at least in some states of the HP generator (10); a control unit (22) configured to select the contribution of the LP generators (14, 16, 18) to the output value of the HP generator (10) during its output delivery in order to cause a rise and / or a decay of the pulses at the output of the combiner (20), the charging energy of said LP generators (14, 16, 18) is supplied via transformers (T1, T2...Tn), some of which may be equipped with balancing windings (BW); High power (HP) generator (10).

3. The control unit (22) has the following features: the output of the combiner (20) and / or the output of the HP generator (10) is a step function; - the LP generators (14, 16, 18) are operated continuously during one pulse; - at least one amplitude step is less than 1 kV, - the LP generators (14, 16, 18) are connected only by switching, and further configured to select the contribution of the LP generators (14, 16, 18) such that one or a combination of 3. The HP generator according to claim 1 or 2.

4. The combiner (20) comprises more than four electrically connected LP generators (14, 16, 18), and / or the number of LP generators (14, 16, 18) is such that at the output of the combiner (20): pulses with voltage rises and / or falls of values ​​equal to or higher than the sum of several values ​​of said LP generators (14, 16, 18); and a staircase pulse shape, the value of the staircase corresponding to a value equal to or higher than one or more values ​​of said LP generators (14, 16, 18); There are enough of them to form 3. The HP generator according to claim 1 or 2.

5. 3. An HP generator according to claim 1 or 2, wherein a balancing circuit comprising components that allow current flow in only one direction is connected between the two LP generators.

6. 3. The HP generator of claim 1, wherein a damping circuit (50) is positioned in an open chain configuration between some of the LP generators (14, 16, 18).

7. 3. The HP generator of claim 1 or 2, wherein the HP generator (10) is at least partially directly liquid cooled.

8. 3. The HP generator according to claim 1 or 2, wherein the control unit (22) can be configured to select the contribution of the LP generators (14, 16, 18) in a sequential manner through the LP generators (14, 16, 18).

9. 3. The HP generator according to claim 1 or 2, wherein the control unit (22) comprises a switching unit (24, 26, 28) having a current rise capability of at least 10 A / μs and / or capable of withstanding voltages of about 0.5 kV or more with voltage rise and fall rates of 15 kV / μs or more.

10. 3. The HP generator according to claim 1 or 2, wherein the control unit (22) is configured to select the contribution of the LP generator (14, 16, 18) so as to reduce voltage overshoot at the output of the HP generator (10) and / or at a dedicated location on the load.

11. 3. The HP generator according to claim 1 or 2, wherein at least one LP generator (14, 16, 18) comprises an LP generator value limiting circuit (151).

12. 3. The HP generator according to claim 1 or 2, wherein the control unit (22) is configured to select the contribution of the LP generators (14, 16, 18) in a galvanically isolated manner.

13. 3. HP generator according to claim 1 or 2, wherein a capacitor is provided in the switching unit (24, 26, 28).

14. 2. The HP generator of claim 1, wherein an inverter (40) comprising a full bridge circuit (44) and a buck converter (46) is connected to the main windings (PW1, PW2, PWn).

15. 3. A method for supplying high power pulses having variable amplitude provided by a high power generator (10) according to claim 1 or 2 to a plasma process, comprising the steps of: a. sequentially charging the energy storage components (C1, L1) of a plurality of the low-power generators (14, 16, 18) to respective predetermined values ​​via the transformers (T1, T2, Tn); b. selectively combining the output values ​​of at least some of the low-power generators (14, 16, 18) to obtain a desired output value of the high-power generator (10) corresponding to a pulse having a desired vibration by controlling the low-power generators (14, 16, 18); A method comprising:

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