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 of high voltage value and / or high current to a capacitive load, in particular 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 part, meaning that the voltage rise on this load implies a high current capability. The capacitive part in such a case is at least 100 pF, preferably more than 200 pF, for example about 500 pF. This can be a load in a plasma process, for example for plasma treatment applications.

[0003] Several plasma processing applications, such as etching or layer deposition, require high voltage (HV), high frequency (HF), rectangular, asymmetrical and pulsed voltage supplies. Especially 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 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; a number of low power (LP) generators, each LP generator providing at its output, in use, 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 an output of the combiner can be obtained which corresponds to an output value of the HP generator, the combiner value being, in use, higher 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 a rise and / or a decay of the pulse at the output of the combiner; The present invention relates to a high power (HP) generator comprising:

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

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

[0009] Some, and in particular each, of the transformers corresponding to 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, providing charge to the loaded stages, i.e., the LP generators connected to a 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 a driver circuit.

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

[0013] Thus, some, and in particular each, of the transformers associated with the LP generators may be connected in an open chain configuration.

[0014] Some of the transformers corresponding to the LP generators, in particular the main windings of each of them, 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, the high voltages and currents can be separated in an efficient and effective manner.

[0016] Some, and in particular each, of the transformers associated with the LP generator, also referred to as "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 by 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 by the start of the pulse. After approximately 10 ns or 100 ns, one or several additional LP generators are activated, which causes 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, which causes the pulse to rise further. For the decay of the pulse, one or several of the LP generators may 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 output delivery of the HP generator. In other words, the control unit may 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 a continuous slope.

[0020] In one embodiment, 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 embodiment, the combiner and control unit is configured to connect the LP generators by switching only.

[0023] In one embodiment, 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 line pulse upon the rising and / or falling edge of the pulse.

[0024] In one embodiment, the number of LP generators is sufficiently large to form, at the output of the combiner, a pulse having a voltage rise and / or fall of a value equal to or higher than the sum of several values ​​of the LP generators, and a staircase line pulse shape, where the value of the step corresponds to a value equal to or higher 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 way, in particular diodes or components that function like diodes, is connected between the two LP generators. For example, the negative output of the energy storage components, in particular capacitors, of some, in particular each LP generator are 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 to an on state" or "switched to a low impedance at its output". "Switch in parallel with the load" means a switching element that, when activated, is responsible for disconnecting the corresponding LP generator from the nearby connected LP generator. In figures 2a, 2b, 4, 5, these are switching elements S1. In figure 3, these are switching elements S2. By connect switches we mean the switching elements that, when activated, are responsible for connecting the corresponding LP generators. In Figures 2a, 2b, 4, 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, in particular all, of the LP generators. Open-chain configuration shall mean that such damping circuits are positioned between all LP generators and the next higher LP generator, but not between the highest and the lowest. The damping circuits may include resistors and / or inductors if the energy storage components are capacitors. The damping circuits may include resistors and / or capacitors if the energy storage components are inductors. The damping circuits between the LP generators may be positioned preferably in series with the balancing circuits. The damping circuits may be used to eliminate parasitic oscillations in the charge handling paths.

[0027] The entire HP generator can be directly liquid cooled. This can be done by immersion in a dielectric cooling liquid, specifically the LP generator is immersed in the dielectric cooling liquid. All components of the HP generator including the transformer can be immersed in the dielectric cooling liquid which provides high cooling capacity while reducing clearance and creepage requirements. This improves the safe operating area usage 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 the control unit may be arranged, at least partially, together with at least the switching unit, in one housing. The coupler may be arranged in the same housing. The transformer and rectifier may be arranged in the housing. The housing may be leak-proof. A dielectric cooling liquid may flow through the housing, thereby improving cooling and insulation. Distances may be reduced. This allows shorter wire lengths to be used, which reduces the inherent inductance, which leads to faster switching capabilities. Temperature differences between the various switches and other components of the LP generator and / or coupler may be reduced by this kind of direct liquid cooling. Thus, a high degree of balancing is possible.

[0029] In one embodiment, the control unit may be configured to select the contribution of the LP generators in a sequential manner through the LP generators. In particular, each pulse sequence may start with a different LP generator, so that all n LP generators are equally loaded after n pulses. This improves the distribution of the load in the LP generator stack and therefore balances the power losses between the 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 embodiment, the control unit may include a switching unit capable of withstanding voltages of about 0.5 kV or more with voltage rise and fall rates of 15 kV / μs or more, whereby extreme pulses with extremely sharp voltage transitions may be achievable, a feature that is highly desirable 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 a dedicated location 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 for example be the full amount.

[0033] In one embodiment, at least one, preferably some, and most preferably all LP generators are equipped with a LP generator value limiting circuit, such as a voltage limiting circuit or a current limiting circuit. This can be an additional resistor with an output dissipation portion or an additional switching element with a variable, eclectically controllable impedance. 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 by controlling the switching unit. The connection between the output of the data processor and the switching unit can be realized by optical fiber or by magnetic coupling. This can help to switch all LP generators effectively and quickly and without time delay to form, for example, 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 such that this group is exclusively activated or deactivated together. It is then possible to use only one galvanically isolated connection for such a group. The reduction in the number of galvanically isolated connections may save costs and also increases the reliability of the HP generator due to fewer components at risk of failure. Advantageously, each switch has its own galvanically isolated connection. However, several transmitters, if integrated, can be controlled by one control signal, which reduces the number of required I / O components.

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

[0036] By "the control unit is configured to select the contribution of the LP generator to the output value of the HP generator" is understood 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 having 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 circuits, allowing it to calculate new data from the incoming data, to come up with decisions related to the incoming and / or calculated data, and to output appropriate data signals to, e.g., control other electrical circuits 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 the pulse output. High voltage value means 4 kV or more. High current means 10 A or more. The HP generator may be configured to affect the voltage and / or charge carrier transfer between the plasma potential and the substrate in the plasma and / or in the plasma process. The energy storage component may be a capacitor or an 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, more preferably at least 1 / 50 of the energy of one pulse of the HP generator. Continuously charging the energy storage component includes charging to a preferred voltage value of the capacitor or a preferred current value of the inductor. The electrical connection of the LP generators in the coupler may be a series connection, a parallel connection or a combination of both. The coupler value may be a voltage, a current or a power. The control unit may determine which LP generator contributes to the output of the HP generator. The control unit may be configured to control the LP generators such that the 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 an HP generator value.

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

[0042] The control unit may comprise switching units, one switching unit associated with each LP generator. Each switching unit may comprise one or two transistors, in particular MOSFETs. MOSFETs provide high switching capabilities and are usable with currents of 50 A or more, allowing voltages of 500 V or more to be switched. If MOSFETs are used, an anti-parallel diode may be provided to each MOSFET, in particular 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 with two switching elements connected in series. One transistor may be configured to connect two of the LP generators when both values ​​of both LP generators are closed so as to 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 it is activated, i.e. when it 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 its 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 an individual safe voltage / current of all LP generators to prevent failures related to overvoltage or overcurrent 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. The driver may be configured to drive a switching unit, in particular a transistor, in particular a MOSFET. 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 of the LP generators, 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, 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] A capacitor may be provided as an energy storage component in parallel with the switching units, especially the half bridges. This allows the output value of the combiner to be stabilized. Each LP generator may 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 may represent a real dynamic voltage source during each pulse, while allowing large output currents and the required fast voltage transitions.

[0048] An inverter with a full bridge circuit, preferably a buck converter, can be connected to the main winding, allowing 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 the steps of: a. sequentially charging energy storage components of multiple low power (LP) generators, each to a predetermined value; b. selectively combining 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 the steps of:

[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 the generation of 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 powers exceeding the power values ​​of their energy storage components. This solution is versatile due to the fact that it is possible to quickly vary the output pulse amplitude with a resolution equal to the number of low power generators. It is inexpensive because a large number of low power generators and low voltage switches can be used, which is 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. A control signal can be provided to the drivers of the switching units, preferably by optical fiber, although other means can be used. All switches of the switching units can be individually controlled from one main control board, but it is also possible for one signal to control an entire stage (e.g., control signals for the connection switches of the switching units could come from the main control board, while signals for the switches in parallel with the loads of the switching units could be generated on the connection switch driver board), one signal can control multiple switches / stages with grouped control, etc. The total power value is the sum of the power values ​​of only the activated / selected LP generators. The total power value 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. By activating one switch, the load is connected to the capacitor. By activating the other switch, the load is shorted. The output of the entire HP generator 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 of a low impedance voltage source and a capacitive load by 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 in the presented topology. A nearly rectangular voltage waveform shape, lower overshoot and significantly reduced power loss can be obtained by the double step transition.

[0054] Several stages, also called "LP generators", can be operated consecutively 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, leading to a more stable wafer voltage, and a better ion energy distribution.

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

[0056] In the schematic drawings examples of the invention are shown in different stages of use and are explained in more detail in the following description. [Brief description of the drawings]

[0057] [Figure 1] 2 shows a series of pulses with varying amplitude. [Figure 2a] 1 shows a first embodiment of an HP generator. [Figure 2b] 2 shows a second embodiment of the HP generator. [Diagram 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. [Diagram 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] 4 shows the waveforms obtained from continuous operation of the LP generator. [Figure 9] 1 shows the result of a cyclic control signal sequence passed 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 having 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 having a galvanically isolated drive. [Figure 18b] 1 illustrates an embodiment of an HP generator having a galvanically isolated drive. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[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] Figure 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 LP generator 14, 16, 18 comprising an energy storage component C1, C2, Cn, embodied in this case as a capacitor. In use, the energy storage component C1 is continuously charged up to a predefined value associated with the energy storage component C1 in order to keep the energy stored therein constant. In use, each LP generator 14, 16, 18 delivers at its output a LP generator value that corresponds to the value of the energy storage component C1 incorporated in the LP generator 14, 16, 18. The LP generators 14, 16, 18 are electrically connected in a combiner 20 so that a combiner value at the output of the combiner 20 corresponding to the output value of the HP generator 10 and higher than the LP generator value at the output of one of the LP generators 14, 16, 18 can be obtained. The control unit 22 is configured to select the contribution of the LP generators 14, 16, 18 to the output value of the HP generator 10 during the power delivery of the HP generator 10. For clarity, only three LP generators are shown. In practice, much more LP generators are used, typically six or more, ten or more, in particular fifteen or more LP generators, to provide a gradual transition of the output that can be smooth depending on the load requirements.

[0060] The control unit 22 comprises a switching unit 24, 26, 28 associated with each LP generator 14, 16, 18. The switching units 24, 26, 28 each comprise 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. Every LP generator is connected to a power supply 34 and comprises a transformer, a rectifier and an inverter connected to the grid, itself comprising a full bridge and a buck converter, as described in more detail below.

[0062] FIG. 2b generally corresponds to FIG. 2a. Thus, 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, Ln. Thus, the electrical connections / wirings within the coupler 20 are slightly different. In general, the energy stored in an inductor turns into a current source. Thus, the energy storage components are connected in parallel with other current sources, resulting in current multiplication.

[0063] In both figures 2a and 2b, the earth potential, also called earth 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 the ground, as shown for example in figure 10 of (US Pat. No. 5,399,411) or in figure 21 of (US Pat. No. 5,499,411). The earth potential can also be connected to the positive output 32 or to the negative output 12. In figures 2a and 2b it is connected to the positive output 32 as an example.

[0064] Figure 3 shows a simplified embodiment of a part of an HP generator 10 with several LP generators 14, 16, 18. To generate high voltage pulses, it is advantageous to build 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 capacitor of the plasma reactor, and a "pull" (S2) used to discharge the capacitor of the plasma reactor. To generate pulses with different amplitudes, the amplitude can be changed quickly between pulses (as shown in Figures 1, 7, 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 Figure 3, the earth potential, also called earth potential PE, is connected to the negative output of the LP generator 18.

[0065] In some circumstances, if both switching elements S1, S2 are not switched on (during a transition state between two operating states) and the LP generators 14, 16, 18 are connected in series and also in series with a load (e.g. a plasma reactor), the switching elements S1, S2 will be destroyed by overvoltage. Therefore, it is advantageous to add diodes D1, D2 in parallel to all switching elements S1, S2 to protect them from voltages higher than the voltage stored in the respective energy storage components. This is especially true when the switching elements S1, S2 are embodied as MOSFETs. If the switching elements are embodied as unipolar transistors, as MOSFETs are typical, the diodes are pre-mounted as part of the transistor or are an integral part of the transistor die. The die, in the context of an integrated circuit, is a small block of semiconductor material on which a given functional circuit is assembled. These diodes can then be used and there is no 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 the ground potential PE). This state can be achieved by switching on the switching element S2 when the 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 the LP generators 14, 16, are connected in series, whereby 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 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 a 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 in the connection of the load to PE. However, the same result as in Figure 3 can be achieved, i.e., voltage pulses of different amplitudes can be realized by selecting the LP generators 14, 16, 18 that contribute to the output voltage pulse by appropriately driving the switching elements S1, S2. In Figure 4, earth potential, also called earth potential PE, is connected to the negative output of the HP generator 10.

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

[0072] Balancing windings BW of transformers T1, T2, Tn work in such a way that if the magnetic flux is the same in both adjacent transformers T1, T2, Tn, then 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, then the induced voltages will be different in the different transformers T1, T2, Tn and hence current will start flowing between this winding BW. Due to this current, the transformer T1, T2, Tn having the higher magnetic flux will be loaded more 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. 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 source 34 and comprises 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, for example the HP generator of FIG. 2a, where a balancing circuit is connected between the two LP generators 14, 16, 18, including components that allow current flow only in one direction, in particular diodes D or components acting like diodes. The switching units 24, 26, 28 comprise switching elements in a half-bridge. These switching elements are shown as transistors, more precisely as bipolar transistors. During intense switching times, the more preferred type of transistor would be MOSFETs, in particular MOSFETs based on SiC or GaN. In this embodiment, the negative terminal of each LP generator 14, 16, 18, also called a stage, is connected at the same potential as the preceding LP generator 14, 16, 18, by a diode D or a circuit containing a diode. This allows the energy stored in the energy storage components of the lower stage to be transferred to the energy storage components of the higher stage when the switching elements are activated and when the voltage of the energy storage components of the lower stage exceeds that of the higher stage. The charge of the highest stage 14 accumulates the 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 a 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, in particular as shown in FIG. 6.

[0075] Connecting a low impedance voltage source, such as a capacitive voltage source, with a capacitive load, which is unavoidable due to any connector inductance, causes current and voltage oscillations. 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 circuits can be dramatically reduced or even avoided. The energy dissipating parts can then be much smaller or avoided altogether. The power losses can be significantly reduced. This is possible in the presented arrangement and is shown in FIG. 7. Waveform 70 shows a single-stage transition from 0 kV to 10 kV at the output of the coupler 20 by instantaneously activating, for example, all 15 stages. This causes a voltage overshoot, as can be seen in FIG. 7. If the stepwise transition follows a first step, e.g. from 0V to 5.5kV by activating only 8 of the 15 stages, and a second step, e.g. from 5.5kV to 10kV by activating the remaining of the 15 stages, delayed by 10 or 100ns, as shown in waveform 71, the results are much better. The resulting waveform 73 has a much lower overshoot peak and the voltage rises slower but is fast enough for the process. As can be seen in waveform 73, the two-stage transition results in a nearly rectangular output waveform and lower overshoot, and therefore little power dissipation, while the single-stage transition results in waveform 74, which shows a voltage overshoot and therefore a significant power loss 75. The same overshoot peak and its reduction can be seen in the descending slope after 1μs, e.g. 3.5μs.

[0076] FIG. 8 shows the gradual increase in amplitude of pulse 80 as a result of successively activating LP generators 14, 16, 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 including fifteen LP generators #01-#015. The diagram shows a timeline t on the horizontal axis as in FIG. 8. On the vertical axis, the activation of fifteen switching elements corresponding to the fifteen LP generators #01...#15 is shown. The diagonally shaded area 92 is the area where the connecting switching elements are activated. The white box area 91 is the area where the switching elements in parallel with the load are activated, so there are no pulses at the output during the time frame where the diagonally shaded area is not present. In the first column, LP generators #01-#06 are switched together with the corresponding connecting 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 connected switching elements. th In the ninth (9th) row, the 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 In the 10th row, the pulse ends and all connected switching elements are deactivated. Then in the 10th row, the next pulse begins, this time starting with LP generators #02 to #07 instead of LP generators #01 to #06. All LP generators in this example have the same output value, but the output value at the output of the 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 the corresponding switching elements are equally loaded after 15 pulses. This results in a better load distribution between the LP generator stacks and therefore a better power loss balance between the switching elements.

[0077] FIG. 10 shows a plasma processing system comprising a plasma chamber 100 in which a plasma 101 is established in a plasma space. Such or similar systems are shown and described, for example, in US Pat. No. 5,399,633, US Pat. No. 5,499,667 or US Pat. No. 5,499,677. In the plasma chamber, an upper electrode 103 may be positioned. Gas inlets and / or outlets, in particular gas supply pipes 104, may be arranged from the outside to the inside of the plasma chamber 100 and may be connected, in particular, to the electrode 103. A substrate 102, in particular a semiconductor wafer, may be arranged on a support 105 comprising a substrate holder inside the plasma chamber 100. In use, the substrate 102 may be treated by the plasma 101, for example, in an etching, ashing or deposition process, in particular in atomic layer deposition. Etching processes may be very challenging, for example when the ratio of the hole diameter to the hole length to be etched is very low, for example <1 / 100, since deep etching processes are often required. An electrically conductive electrode 106 may be arranged in the plasma chamber 100, in particular in the vicinity of the substrate 102, for example around 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 pulsed power supply, where in particular the pulses may be of different lengths, different amplitudes and shapes, as described, for example, in Figs. 11, 14 of (Patent Document 4) or Fig. 2 of (Patent Document 1). By controlling the first power supply 114, the electrically conductive electrode 106 may additionally or alternatively be used as an ion energy and / or ion acceleration direction control, as also described in (Patent Document 4) or (Patent Document 1). A first radio frequency (RF) power supply 118 may be electrically connected to the support 105 via a first power supply rod 119 and 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 and a second matching unit 110 and a second connection unit 111. An electrode 107 may be positioned within or adjacent to 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 pulsed power supply, where in particular the pulses may be of different lengths, different amplitudes and shapes, for example as described in Figures 11, 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 for ion energy and / or ion acceleration direction control, 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, asymmetrical, pulsed voltages. Especially 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-by-pulse charging and discharging process of this load capacitor. Some plasma applications require the pulses to be shaped, for example as described in Figs. 11, 14 of (US Pat. No. 5,399,433) or Fig. 2 of (US Pat. No. 5,499,433).

[0080] Therefore, a series connection of such switches is one possible solution. Series connections require voltage balancing means. These voltage balancing means are not easily realizable 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 integrated 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 Figure 5 and Figure 13 is that in Figure 13 the main windings P1, P2...Pn are connected in parallel with the transformers T1, T2...Tn. A balancing winding is shown, but is 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. A balancing winding BW is used to transfer energy from transformer T1 to T2 and from 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, 18 at the ends 152a, 152b. It can also be connected in parallel with one, some or all of the switching units 24, 26, 28 at the ends 152a, 152b. This LP generator value limiting circuit 151 comprises a series circuit of a diode D15 and a capacitor C15 and clamps the overvoltage present at its ends 152a, 152b to the voltage to which the capacitor C15 is charged. The voltage of the 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 arranged to be cooled very effectively. The transistor T15 is controlled so that it can be switched on or off, thus in a pulsed mode. Thus, the transistor T15 does not dissipate an excessive amount of energy into heat and is kept fairly cool. When the transistor T15 is switched on, the capacitor is discharged and the discharge current flows through the resistor R15, dissipating the energy into heat. Most of the heat is generated in the resistor R15, which is easier and cheaper to keep cool enough than the transistor T15. The transistor T15 is controlled by a voltage control circuit 154 via its control input G15. The voltage control circuit 154 comprises 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 the current-limiting resistor 156 with the second low-voltage Zener diode 158 is connected to the control input G15 of the transistor T15. The voltage control circuit 154 may further comprise a driver 157. The driver 157 may be connected at its input to the junction of the current limiting resistor 156 and the second low voltage Zener diode 158. The driver 157 may be connected at its output to the control input G15 of the transistor T15. A voltage divider 159 may be connected between the output of the driver 157 and the control input G15 of the transistor T15.

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

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

[0088] 17 shows an embodiment of the HP generator 10 with liquid cooling. All electronic components of the HP generator 10, such as the LP generators 14, 16, 18, the switching units 24, 26, 28, the transformers T1, T2, Tn, and the inverter 40, are arranged in a leak-proof housing 171. A liquid reservoir 174 is arranged close to the housing. Between the housing and the reservoir 174 is arranged a liquid pump 173 for circulating the liquid 171 between the housing and the 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 contribution of the LP generators 14, 16, 18 in a galvanically isolated manner, in particular via an optical fiber connection or a 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 help to switch all LP generators 14, 16, 18 effectively, quickly and without time delay to form pulses with sharp edges, for example. 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, it is possible to use only one galvanically isolated connection 181. Galvanic isolation (transmitter and receiver) may 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 Pulse 81 Waveform 82 Waveform 91 Box Area 92 Diagonally shaded area 100 Plasma Chamber 101 Plasma 102 Substrate 103 Electrode 104 Gas supply pipe 105 Support 106 Electrically Conductive Electrodes 107 Electrode 108 Power supply 109 Second Power Supply Rod 110 Second Integrity Unit 111 Second connection unit 112 Second power source 113 Second Connection Line 114 First Power Source 115 First Connection Line 116 First Integrity 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. A high power (HP) generator (10) configured to deliver pulsed high power having a high voltage and / or current value 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), 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) provides, in use, at its output, a LP generator value which corresponds 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 at the output of the combiner (20) can be obtained which corresponds to an output value of the HP generator (10), the combiner value being, in use, higher 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), 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 winding (SW1, SW2...SWn) is connected to rectifiers (X1, X2...Xn), each rectifier (X1, X2...Xn) being connected to the energy storage element (C1, C2, Cn, L1, L2, Ln) of the corresponding LP generator (14, 16, 18); and / or some of said main windings (P1, P2...Pn) of the transformer corresponding to the LP generator, in particular each main winding, are connected in series; A high power (HP) generator (10).

2. A high power (HP) generator (10) configured to deliver pulsed high power having a high voltage and / or current value 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), 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 said 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 at the output of the combiner (20) can be obtained which corresponds to an output value of the HP generator (10), the combiner value being, in use, higher 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), the charging energy of said LP generators (14, 16, 18) is supplied via transformers (T1, T2...Tn), several, in particular each transformer corresponding to an LP generator, may comprise a balancing winding (BW), preferably two balancing windings, preferably one balancing winding (BW) of one transformer (T1) may be connected to a balancing winding of a different transformer (T2); A 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, in particular at the rising and / or falling edges of the pulse and / or during the pulse, - the LP generators (14, 16, 18) are operated continuously for one pulse; at least one amplitude step is less than 1 kV, in particular less than 500 V; - said 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. An HP generator according to claim 1 or 2.

4. the combiner (20) comprises more than four electrically connected LP generators (14, 16, 18), in particular at least six, in particular more than ten, preferably more than fifteen LP generators (14, 16, 18) are combined in one combiner (20) and / or the number of LP generators (14, 16, 18) is at least a pulse having a rise and / or fall in voltage of a value equal to or higher than the sum of the values ​​of several of the LP generators (14, 16, 18), and a staircase line pulse shape, the value of the staircase corresponding to a value equal to or higher than the value or values ​​of said LP generators (14, 16, 18); There are enough of them to form An HP generator according to any one of claims 1 to 3.

5. 5. An HP generator according to any one of claims 1 to 4, in which a balancing circuit is connected between the two LP generators, the balancing circuit comprising a component allowing current flow in only one direction, in particular a diode D or a component acting like a diode.

6. 6. The HP generator according to any one of claims 1 to 5, wherein a damping circuit (50) is positioned in an open chain configuration between some, in particular all, of said LP generators (14, 16, 18), in particular said damping circuit (50) comprising a resistor (R) and / or an inductor (L).

7. 7. The HP generator according to any one of claims 1 to 6, wherein the HP generator (10) is at least partially directly liquid cooled, in particular by immersion in a dielectric cooling liquid, in particular the LP generators (14, 16, 18) being immersed in a dielectric cooling liquid.

8. 8. The HP generator according to any one of claims 1 to 7, 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), in particular each pulse sequence can start with a different LP generator (14, 16, 18).

9. 9. HP generator according to any one of claims 1 to 8, 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. HP generator according to any one of claims 1 to 9, wherein the control unit (22) is configured to select the contribution of the LP generators (14, 16, 18) so as to reduce voltage overshoots at the output of the HP generator (10) and / or at dedicated locations on the load, in particular at a substrate of a plasma process.

11. 11. The HP generator according to any one of claims 1 to 10, wherein at least one, preferably several and most preferably all LP generators (14, 16, 18) comprise a LP generator value limiting circuit (151), such as a voltage limiting circuit or a current limiting circuit.

12. 12. The HP generator according to any one of claims 1 to 11, wherein the control unit (22) is configured to select the contribution of the LP generators (14, 16, 18) in a galvanically isolated manner, in particular via a fiber optic connection or a magnetic coupling.

13. HP generator according to any one of the preceding claims, wherein a capacitor is provided in parallel with the switching unit (24, 26, 28), in particular with the half-bridge.

14. The HP generator according to any one of the preceding claims, 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. 1. A method of supplying high power pulses having variable amplitude provided by a high power generator (10) to a plasma process, comprising: a. continuously charging energy storage components (C1, L1) of a plurality of low power generators (14, 16, 18) via transformers (T1, T2, Tn), respectively, to a predetermined value; b. selectively combining output values ​​of at least some of the LP generators (14, 16, 18) to obtain desired output values ​​of the high power generator (10) corresponding to pulses having a desired vibration by controlling the LP generators (14, 16, 18); The method includes:

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