Power supply system for supplying a plasma or gas laser process, and method for inducing a plasma

Abstract

The invention relates to a power supply system (2) comprising a power converter (3) which generates a high-frequency power signal and which can be connected to a load (6) in order to supply a plasma or gas laser process with power, wherein: the power converter (3) comprises at least one amplifier stage (40) having a first and a second amplifier path (42, 43) each having an amplifier unit (42a, 43a); the first amplifier path (42) is configured to output a first amplifier-path output signal and the second amplifier path (43) is configured to output a second amplifier-path output signal which has a phase that is shifted relative to the first amplifier-path output signal, said phase being not equal to, in particular greater than, 0° and being not equal to, in particular less than, 180°; the amplifier paths (42, 43) are connected to a phase-position-shifting coupler unit (47) which couples the output signals of the amplifier paths (42, 43) to form a high-frequency power signal, the power supply system being characterized in that the first and second amplifier units (42a, 43a) are in the form of Doherty amplifiers each having the following components: i. a base-load amplifier (103) which is designed to provide a base-load amplifier power; ii. a peak-load amplifier (104) which is designed to provide a peak-load amplifier power; and iii. a power coupler (107) for combining the base-load amplifier power and the peak-load amplifier at the output of the particular first or second amplifier unit (42a, 43a) to form an amplifier output power (Pout).

Description

[0001] Power supply system for supplying a plasma or gas laser process and method for exciting a plasma

[0002] The invention relates to a power supply system comprising a power converter generating a high-frequency power signal, which can be connected to a load for supplying power to a plasma or gas laser process. Furthermore, the invention relates to a plasma system comprising a load and such a power supply system.

[0003] Furthermore, the invention relates to a method for exciting a plasma with a high-frequency power.

[0004] Power supply systems, especially systems that generate power at frequencies > 1 MHz and especially < 200 MHz, and especially < 90 MHz, are used, for example, for laser excitation or in plasma coating systems. Such power supply systems often use multiple amplifiers to generate the total power of the power supply system.

[0005] In such a power supply system, sudden changes in the required power can occur, for example, if an arc occurs in the plasma chamber and the supplied power must be suddenly reduced accordingly. On the other hand, a different power may be required to ignite a plasma than to operate a plasma process. When the plasma state changes, the impedance of the load also changes. Here, too, a sudden change in the load occurs. Impedance matching often cannot be carried out quickly enough, so that power is reflected from the load. This reflected power should be kept away from the amplifiers or amplifier paths if possible to prevent destruction or damage to the power supply system. It is known to use so-called circulators to absorb the reflected power.However, in the frequency range mentioned, such circulators are very large and can no longer be used in practice.

[0006] If there are sudden load changes and also sudden changes in the target power, the output power must be controlled. This can be achieved, for example, by varying the input power of an amplifier unit. However, this also changes the efficiency of the amplifier unit. At low output powers, the amplifier operates in the so-called back-off region. This is the range in which the amplifier only makes a portion of the maximum possible output power available at the output. In this back-off region, the efficiency of the amplifier unit decreases. Depending on the load to be driven, the transistor used in the amplifier must therefore dissipate considerably more power. This makes it considerably hotter. In the event of a mismatch, this behavior changes. Depending on the load angle or reflection factor, the transistor heats up either in the back-off or in the saturation region.This means that controlling the output power via the input power in the event of a mismatch is only possible to a limited extent. To prevent transistor overheating, limiting the maximum output power has often been recommended. However, reducing the maximum output power does not solve this problem, since critical temperatures occur with large mismatches and unfavorable load angles, even at low power levels, not just at high power levels.

[0007] Against this background, the task arises of enabling reliable and efficient operation of a power supply system with strongly fluctuating, for example pulsed, power output.

[0008] To achieve the object, a power supply system according to claim 1 is proposed. The power supply system according to the invention comprises a power converter generating a high-frequency power signal, which can be connected to a load for supplying a plasma or gas laser process with power, wherein the power converter comprises at least one amplifier stage with a first and a second amplifier path, each having an amplifier unit, wherein the first amplifier path is for outputting a first

[0009] amplifier path output signal is configured and the second amplifier path is configured to output a second amplifier path output signal which has a phase shifted compared to the first amplifier path output signal, which is unequal to, in particular greater than, 0° and unequal to, in particular less than, 180°, wherein the amplifier paths are connected to a phase-shifting coupler unit which is designed to couple the output signals of the amplifier paths to form a radio-frequency power signal, wherein the first and the second amplifier unit each have the following components: i. a base load amplifier which is designed to provide a base load amplifier power; ii. a peak load amplifier which is designed to provide a peak load amplifier power; and iii. a power coupler for combining the base load amplifier power and the peak load amplifier power at the output of the respective first and second amplifier units.second amplifier unit to an amplifier output power.

[0010] A phase-shifting coupler unit is understood to be a unit that has a coupler and, for one or optionally several amplifier paths, a phase-shifting network, wherein the input signals of the coupler unit, during intended operation, have a phase position relative to one another that is neither 0° nor 180°, and in particular is greater than 0° and less than 180°. For example, the input signals can be phase-shifted by 90°. A coupler unit whose input signals, during fully coupled operation, have a phase offset of 0° or 180° relative to one another is not understood to be a phase-shifting coupler unit in the present disclosure, since here only the input signals are added without any further phase offset. The phase-shifting coupler unit can be a 90° hybrid coupler. This meets the requirements in an improved manner with reduced component complexity.A phase-shifting coupler unit is also understood to be a unit designed to return reflected power, which is passed from the load through the coupler to the amplifier units, to the amplifier units with a different phase. In the event of a mismatch, for example, a 90° hybrid coupler with two amplifier units of the same impedance connected to its input terminals splits the reflected power between the two amplifier units with a 90° phase shift.A phase-shifting coupler unit is also understood to mean a unit which has a first input impedance at its first input terminal and a second input impedance at its second input terminal, and which is designed such that the input impedances are equal when no reflected power is passed through the coupler unit to the input terminals, and which are unequal when reflected power is passed through the coupler unit to the input terminals.

[0011] The coupler unit can, as described above, be designed to forward the power reflected to its output terminal to its input terminals with a phase shift, and thus to the amplifier units in the amplifier paths. The input impedances at the coupler unit can then change, in particular can be different. This can result in the output impedance of the first amplifier unit assuming a different value than the output impedance of the second amplifier unit. This, in turn, can influence the properties of the coupler unit in such a way that it directs the power of one amplifier unit to the other amplifier unit, so that the amplifier units influence each other. The output impedance of the amplifier units can become negative.Under certain load conditions, this can lead to the first amplifier unit in the first amplifier path supplying power to the second amplifier unit in the second amplifier path. These characteristics led to the discouragement of using a phase-shifting coupler unit in the past. There were concerns that this would cause the amplifier units to become unstable and / or the transistors to overheat.

[0012] A common cause of instability is the very rapid change in the impedance of the load, e.g., the plasma process. The load change occurs so rapidly that neither an impedance matching network connected between the power supply system and the load nor the power control of the power supply system can react quickly enough to the load change. The rapid load change produces reflected power, which is reflected into the amplifier units. This changes the impedance of the amplifier units, as described above. As a result, after the rapid load change, the amplifier units no longer deliver the same power as before the load change.However, in a power supply system with a phase-shifting coupler unit, especially with a 90° hybrid coupler, the change in power per change in load state is much smaller than in a power supply system without such a coupler unit or with non-phase-shifting properties. Therefore, a power supply system with a phase-shifting coupler unit is more stable.

[0013] Examples for the design of such a phase-shifting coupler unit are e.g. in WO2017 / 001598A1 WO2005 / 027258A1 , WO2011 / 110654A1 , EP1699107A1 ,

[0014] DE202010016850U1 or DE202010016732U1. These disclosures are hereby incorporated by reference into the present application in their entirety.

[0015] In one aspect, a first and a second amplifier unit are provided as part of the two amplifier paths. Both the first and second amplifier units have a structure with two different sub-amplifiers, which are referred to here as base load amplifiers and peak load amplifiers. The first and second amplifier units are configured such that the base load amplifier essentially provides a base load of the amplifier output power. The peak load amplifier can be active at a low power level in base load operation, in which the output power is mainly provided by the base load amplifier, or the peak load amplifier can be inactive. The power coupler provided as part of the first and second amplifier units combines the base load amplifier power and the peak load amplifier power at the output of the respective first and second amplifier units to form an amplifier output power.Preferably, the first and second amplifier units, i.e. the two combinations of base load amplifier and peak load amplifier, are each designed as Doherty amplifiers.

[0016] In one aspect, the first and second amplifier units are identical.

[0017] It has been found that the power supply system exhibits significantly lower power dissipation in the event of mismatch than known power supply systems. This can be attributed to the fact that the base load amplifier and the peak load amplifier of the first and second amplifier units can each be operated in a high-efficiency operating range. This increases the efficiency of the first and second amplifier units compared to a conventional push-pull amplifier, particularly a Class AB amplifier. Due to the reduced power dissipation, the first and second amplifier units heat up less, thereby increasing the service life of the amplifier units, particularly the transistors in these amplifier units, and thus also the reliability of the power supply system as a whole. Furthermore, the variation in load power is almost independent of the load angle.

[0018] In one aspect, the power supply system comprises a signal providing device configured to provide signals to the first and second amplifier units for generating the high-frequency power signal within a predetermined power range such that the base-load amplifier power is greater than the peak-load amplifier power at least in part of the predetermined power range. In this power range, which may also be referred to as the base-load range, the base-load amplifier can thus supply the majority of the amplifier output power. The base-load amplifier is preferably located within a high-efficiency operating range. The peak-load amplifier provides only a small amount of power or no power at all within this range, so that it is not necessary for the peak-load amplifier to also be within an efficient operating range within this power range.Preferably, the base load amplifier power in a lower part of the predetermined power range is greater than the peak load amplifier power. In this respect, low power levels can be covered solely or primarily by the base load amplifier without the peak load amplifier having to be active or having to provide high power. In one aspect, it is provided that the peak load amplifier and the base load amplifier each have an amplifying transistor with an input terminal, e.g., a gate terminal. In one aspect, it is provided that a bias voltage at the input terminal of the transistor is adjustable in at least one of the two amplifiers, and during operation the bias voltage in the base load amplifier is different from that in the peak load amplifier.In one aspect, it is provided that a bias current at the input terminal of the transistor is adjustable for at least one of the two amplifiers, and during operation, the bias current for the base-load amplifier is different from that for the peak-load amplifier. A bias voltage is understood here to be a voltage that changes only very slowly or not at all compared to the input signal and is configured to keep the transistor in a predetermined state of conduction at its output terminals.

[0019] A bias current is understood here as a current that changes very slowly or not at all compared to the input signal and is designed to keep the transistor in a predetermined state of conduction at its output terminals. A typical gate bias arrangement is disclosed, for example, in WO2017 / 001594A1. WO2017 / 001594A1 is hereby incorporated in its entirety by reference into the present application.

[0020] In one aspect, it is provided that the base load amplifier is configured as a substantially linear amplifier and the peak load amplifier as a substantially non-linear amplifier. The base load amplifier behaves substantially linearly, particularly in a power range in which the base load amplifier power is greater than the peak load amplifier power, i.e., an output signal of the base load amplifier is proportional to an input signal of the base load amplifier. The peak load amplifier, on the other hand, can be configured such that an output signal of the peak load amplifier is not proportional to an input signal of the peak load amplifier. The aforementioned setting of the bias voltage and / or bias current can be used for this purpose.

[0021] In one aspect, the peak load amplifier and / or the base load amplifier are designed in the form of a push-pull power amplifier. In particular, the peak load amplifier and / or the base load amplifier each have two identical transistors. In particular, the two identical transistors are accommodated in a common housing. In one aspect, the peak load amplifier and / or the base load amplifier are designed in the form of a planar power amplifier, in particular in a design as described, for example, in WO2017 / 001602A1. WO2017 / 001602A1 is hereby incorporated in its entirety by reference into the present application. In one aspect, it is provided that the base load amplifier is configured as a class B amplifier or as a class AB amplifier and the peak load amplifier is configured as a class C amplifier.When configured as a Class-B or Class-AB amplifier, the base-load amplifier can comprise two transistors arranged in a push-pull circuit. In a Class-B amplifier, the two transistors each conduct for 180° of an oscillation period. A Class-B amplifier can achieve an efficiency of up to 78.5%, but exhibits some distortion due to the switching transition between the two transistors. In a Class-AB amplifier, however, the two transistors each conduct for more than 180° of an oscillation period, creating an overlap region in which both transistors conduct. Class-AB amplifiers sacrifice some of the efficiency of a Class-B amplifier but achieve improved linearity. The Class C amplifier has one or more transistors, each of which conducts for a duration of less than 180° of the oscillation period, for example approximately 120°.Class C amplifiers exhibit high signal distortion but can achieve high efficiency, for example, around 80%. The aforementioned bias voltage and / or bias current adjustment can be used to tune these amplifier classes.

[0022] In one aspect, it is provided that the peak load amplifier is configured to provide the peak load amplifier power only when a predetermined base load amplifier power is exceeded. The aforementioned bias voltage and / or bias current at the input of the amplifying transistor of the peak load amplifier can be used for this purpose. Such a configuration offers the advantage that the base load amplifier alone provides the amplifier output power in a base load range. In this respect, the behavior of the first and second amplifier units in the base load range can be substantially influenced by the base load amplifier. Only when a higher power than the base load is provided does the peak load amplifier become active and provide a peak load amplifier power in addition to the base load amplifier power. The peak load amplifier can thus cover power peaks in particular.

[0023] In one aspect, the peak load amplifier is configured to set its output impedance to a higher impedance when the base load amplifier power falls below a predetermined level.

[0024] In one aspect, it is provided that the power supply system comprises a signal providing device which is configured to provide the first and second amplifier unit with signals for generating the high-frequency power signal such that an output signal of the peak load amplifier has a phase offset with respect to an output signal of the base load amplifier, and / or the first and second amplifier unit comprises a phase-shifting splitter which is configured to provide the base load amplifier and the peak load amplifier with signals for generating the high-frequency power signal such that an output signal of the peak load amplifier has a phase offset with respect to an output signal of the base load amplifier.The phase offset between the output signals of the peak load amplifier and the base load amplifier makes it possible to use a power coupler as part of the first and second amplifier unit, which is designed to shift the phase position.

[0025] In one aspect, the signal provision device or the phase-shifting splitter is configured so that the phase offset is adjustable, in particular to a value of 90° or n*180° + 90°. Examples of the design of such a phase-shifting splitter are disclosed, for example, in WO2017 / 001598A1. This disclosure is hereby incorporated by reference in its entirety into the present application.

[0026] In one aspect, it is provided that the power coupler is designed as a phase-shifting power coupler. In this respect, two output signals from the base load amplifier and the peak load amplifier can be combined in phase with a phase offset by means of the phase-shifting power coupler. The phase-shifting power coupler can have an impedance converter and / or a 4-wire line, in particular arranged between the output of the base load amplifier and the peak load amplifier and the output of the first or second amplifier unit. The power coupler can be constructed from discrete components, in particular from a combination of inductance(s) and capacitance(s), particularly preferably from a network with two capacitances connected to ground and an inductance that is connected between the two other terminals of the capacitances and connected to the input or output of the power coupler.The inductance can be configured as a planar inductance on a circuit board. One or both capacitances can be adjusted, at least in part, to ground by the capacitance of the planar inductance. Impedance matching can be achieved via the impedance converter, which increases the efficiency of the first and second amplifier units. In one aspect, the power coupler increases the output impedance at its output relative to the output impedance of the base-load amplifier when the base-load amplifier is operated in overdrive.

[0027] In one aspect, the base load amplifier is provided with a larger output impedance when operating in the linear region than when operating in overdrive.

[0028] In one aspect, the peak load amplifier has a larger output impedance when the base load amplifier is operated in the linear range than when the base load amplifier is operated in overdrive.

[0029] In one aspect, it is provided that the phase of the second amplifier path output signal, which is shifted relative to the first amplifier path output signal, is adjustable. By adjusting the phase, the output power of the power converter can be regulated. Furthermore, it is possible to set an output power that enables the ignition of a plasma. The phase between the first amplifier path output signal and the second amplifier path output signal is adjusted by a signal-providing device configured to provide the first and second amplifier units with signals for generating the high-frequency power signal, or by an adjustable splitter connected to the first and second amplifier units.

[0030] In one aspect, the amplifiers and / or amplifier units each comprise one or more transistors, in particular LDMOS transistors or GaN transistors. LDMOS stands for "laterally diffused metal oxide semiconductor." When used in amplifiers or amplifier units to generate power that can be supplied to a plasma process, these transistors using LDMOS technology have been shown to behave much more reliably than comparable conventional MOSFETs. This can be attributed to a much higher current carrying capacity. LDMOS transistors can be used to construct amplifiers, amplifier units, and power supply systems with a very similar or even identical topology, which can be used at frequencies spanning several decades in the range from 1 MHz to 200 MHz, preferably in the range from 1 MHz to 90 MHz. These are frequencies often used in plasma processes and for gas laser excitation.Conventional MOSFETs often encounter problems when used in plasma processes at these frequencies, as too much of the power supplied to the plasma process is reflected back. Therefore, the generated power often had to be limited to prevent the reflected power from exceeding a critical limit. This meant that the plasma processes could not always be reliably ignited or operated within the desired power range. In addition, complex adjustable impedance matching circuits and combiners were designed to overcome these disadvantages. LDMOS transistors are now particularly advantageous when significant reflected power is to be expected, as is the case, for example, when supplying plasma processes. In conjunction with the phase-shifting coupler unit mentioned above, the advantage of LDMOS transistors is that they can absorb much higher reflected power.This reduces the requirements for additional impedance matching networks connected between the power supply system and the load, and can result in savings in component and control costs for these impedance matching networks. Examples of the design of a previously mentioned phase-shifting power coupler and an amplifier with LDMOS transistors are disclosed, for example, in WO2015 / 091468A1. This disclosure is hereby incorporated in its entirety by reference into the present application.

[0031] In one aspect, multiple amplifier stages are provided, with two amplifier paths of each amplifier stage being connected to a 90° hybrid coupler, in particular directly without the interposition of other coupling devices. Such a configuration can provide greater power.

[0032] In one aspect, the power supply system is configured such that, in the event of a load mismatch, power reflected at the load is at least partially conducted via the coupler unit and at least one power coupler to at least one of the base load amplifier and the peak load amplifier, is at least partially reflected by the latter, and is returned via the at least one power coupler to the coupler unit, which at least partially directs this returned power into a resistor. Preferably, a larger proportion is reflected by the base load amplifier than by the respective peak load amplifier.

[0033] In one aspect, it is provided that several of the amplifier stages disclosed herein are connected in parallel, and the output terminals of these parallel-connected amplifier stages are interconnected via a power coupler cascade or a multiple combiner. Examples of such a power coupler cascade or a multiple combiner are disclosed, for example, in WG2011 / 110652A1, WO2017 / 001595A1, DE102011086557A1, or EP1701376A1, as well as in the as yet unpublished patent application DE102023111812.9. These disclosures are hereby incorporated by reference in their entirety into the present application.

[0034] To solve the problem mentioned above, a plasma system with a load and a power supply system described above and below is also proposed, which has a power converter which is connected to the load, in particular via an impedance matching network.

[0035] To achieve the object stated at the outset, a method for exciting a plasma with high-frequency power is further proposed, in which an analog signal is fed to each of two amplifier paths and amplified in the amplifier path by at least one amplifier unit to form a high-frequency power signal, the high-frequency power signals being fed to a phase-shifting coupler unit which couples the high-frequency power signals in a phase-dependent manner, the first and second amplifier units each having the following components: i. a base load amplifier which provides a base load amplifier power; ii. a peak load amplifier which provides a peak load amplifier power when the base load amplifier power is exceeded; and iii. a power coupler which couples the base load amplifier power and the peak load amplifier power at the output of the respective first and second amplifier units.second amplifier unit combined to an amplifier output power.

[0036] According to an advantageous embodiment of the method, it is provided that the plasma is excited with a pulsed high-frequency power and the high-frequency power signal is a pulsed high-frequency power signal.

[0037] Alternatively or in addition to the advantageous embodiments explained above, the advantageous embodiments and features explained in connection with the device according to the invention can be used in the method.

[0038] Further details and advantages of the development will be explained below using the exemplary embodiments shown in the figures. Herein:

[0039] Fig. 1 shows a power supply system according to an embodiment in a block diagram; Fig. 2 shows a part of the power supply system according to Fig. 1 in a detailed block diagram;

[0040] Fig. 3 shows a DDS module in a block diagram;

[0041] Fig. 4 shows an embodiment of an amplifier unit of the power supply system according to Fig. 2:

[0042] Fig. 5 shows an alternative embodiment of a power converter for the power supply system according to Fig. 2;

[0043] Fig. 6 simulated curves of the load power versus the input power for a power supply system with conventional amplifiers and with amplifier units according to Fig. 5; and

[0044] Fig. 7 simulated curves of the power loss over the load power for a power supply system with conventional amplifiers and with amplifier units according to Fig. 5

[0045] Fig. 1 shows a plasma system 1 comprising a power supply system 2. The power supply system 2, in turn, has a power converter 3, which can be connected to a voltage supply network 4. The power generated at the output of the power converter is supplied via an impedance matching network 5 to a load 6, which can, for example, be a plasma chamber in which a plasma is generated, with the aid of which plasma processing can be carried out in the plasma chamber. In particular, a workpiece can be etched or a material layer can be applied to a substrate. The load 6 can also be a gas laser excitation.

[0046] A comparable power supply system and a method for exciting a plasma are disclosed, for example, in DE 10 2013 226 537 A1. In this power supply system, two amplifier paths are connected to a phase-shifting coupler unit, which couples the output signals of the amplifier paths to a high-frequency power signal. The advantage of using a phase-shifting coupler unit is that the two amplifier paths connected to the coupler unit experience different impedances in the event of a mismatch.Because the amplifier paths have different impedances, the transistors of the amplifiers and / or amplifier units heat up to different degrees in the event of mismatch, in contrast to in-phase combining, with the warmer of the two transistors heating up less even without regulation of the supply voltage than in comparison to the use of conventional combining. In addition, in the event of mismatch, power is not fed back to the amplifier paths, but can be dissipated into an absorption resistor.

[0047] Figure 2 shows the power supply system 2 in a schematic representation with further details. The power supply system 2 has a power converter 3 that generates an output power that can be supplied to the load 6, for example, a plasma process or laser excitation. An impedance matching network 5 can be arranged between the load 6 and the power converter 3.

[0048] The power supply system 2 comprises a digital-to-analog converter (DAC) 31 for generating an analog output signal. The generation of the analog signal will be explained below with reference to the illustration in Fig. 3. A logic circuit unit 32 is assigned to the digital-to-analog converter 31. In particular, sequences of digital values ​​are supplied to the DAC 31 from the logic circuit unit 32, from which the DAC 31 generates the analog output signal. The DAC 31 and the logic circuit unit 32 can be integrated in a so-called direct synthesis module (DDS module) 33, which can also be referred to as a direct digital synthesizer. According to the exemplary embodiment, the logic circuit unit 32 comprises

[0049] 1. a signal data memory in which signal data values ​​for generating the analogue signal form are stored,

[0050] 2. an amplitude data memory in which amplitude data values ​​are stored to influence the amplitude of the analog signals,

[0051] 3. a multiplier for multiplying the signal data values ​​with the amplitude data values ​​and

[0052] 4. a counter which ensures that signal data values ​​are read from the signal data memory and fed to the multiplier at a predetermined rate.

[0053] Both the signal data memory 34 and the amplitude data memory 35 can be designed as so-called look-up tables (LUT).

[0054] As shown in Fig. 2, the generated analog signal is fed to a first amplifier stage 40 and, there, in particular, to a splitter 41. The splitter 41 can be designed as a hybrid coupler that splits the analog signal into two phase-shifted signals, in particular two signals phase-shifted by 90°, with a signal output by the splitter 41 being fed to an amplifier path 42, 43. The first amplifier path 42 has at least one first amplifier unit 42a. The second amplifier path 43 has at least one second amplifier unit 43a. The amplifier units 42a, 43a are designed here as Doherty amplifiers, the structure of which will be discussed further below. The voltage supply to the amplifier paths 42, 43 and thus to the amplifier units 42a, 43a is provided via a voltage supply 44.At the output of each of the amplifier paths 42, 43, an optional output network 45, 46 is provided, which adapts the output impedance of the respective amplifier unit 42a, 43a to the input impedance of a phase-shifting coupler unit 47 and simultaneously filters out unwanted harmonics. In the phase-shifting coupler unit 47, the output signals of the amplifier paths 42, 43 are coupled in a phase-dependent manner to form an output signal, which is ultimately applied to the load 6 via an optional impedance matching network 5. The phase-shifting coupler unit 47 is preferably a 90° hybrid coupler. The output network 45 can have a filter, in particular a low-pass and / or band-pass filter. This allows interfering frequencies to be attenuated.

[0055] The output power at the output of the coupler unit 47 can be measured by corresponding measuring devices 48. The dashed line 49 indicates that the measuring devices 48 are connected to a voltage regulator 50, which in turn controls the voltage supply 44. In particular, the measuring devices 48 can also measure the power delivered to the load 6 and the power reflected by the load 6. From these values, a reflection factor or an absolute value of a reflection factor can be determined, which in turn can be used to implement the voltage regulation.

[0056] The illustration in Fig. 4 shows a first embodiment of the two amplifier units 42a, 43a from Fig. 2. The amplifier units 42a, 43a are designed here as Doherty amplifiers, each comprising the following components: i. a base load amplifier 103, which is configured to provide a base load amplifier power; ii. a peak load amplifier 104, which is configured to provide a peak load amplifier power; and iii. a power coupler 107 for combining the base load amplifier power and the peak load amplifier power at the output of the respective first or second amplifier unit 42a, 43a to form an amplifier output power P ou t. A filter, particularly a low-pass and / or band-pass filter, can be provided at the output of the base-load amplifier 103. This allows interfering frequencies to be attenuated.

[0057] A filter, particularly a low-pass and / or band-pass filter, can be provided at the output of peak-load amplifier 104. This allows interfering frequencies to be attenuated.

[0058] The power Pj nat the input of the first and second amplifier units 42a, 43a, respectively, is split by a phase-shifting splitter 101 into two signal paths with a phase offset, here a phase offset of 90°. The illustration in Fig. 4 shows the functional elements of the phase-shifting splitter 101 as separate elements: splitter 101 and phase shifter 102. Nevertheless, the phase-shifting splitter 100 can be designed as a hybrid coupler, in particular a 90° hybrid coupler. Due to the introduced phase offset, the output signal of the peak-load amplifier 104 also has a phase offset compared to the output signal of the base-load amplifier 103. These output signals are combined by the power coupler 107. The power coupler 107 is also illustrated here as a combination of a phase-shifting impedance inverter 105, for example, a 4-wire line, and an impedance converter 106.The phase-shifting impedance inverter 105 and the impedance converter 106 can also be designed as a single unit, such as a λ / 4 line or a pi-filter, comprising discrete components, in particular a combination of inductance(s) and capacitance(s), particularly preferably a network with two capacitances connected to ground and an inductance connected between the other two terminals of the capacitances and connected to the input or output of the power coupler.

[0059] The first and second amplifier units 42a, 43a are configured such that the base load amplifier 103 essentially provides a base load of the amplifier output power P ou t. The peak load amplifier 104 can be used in a base load mode in which the amplifier output power P out is provided primarily by the base load amplifier 103, may be active at a low power level, or the peak load amplifier 104 may be inactive, i.e., high-impedance. The base load amplifier 103 may be configured as a class B amplifier or as a class AB amplifier, while the peak load amplifier 104 is configured as a class C amplifier. The peak load amplifier 104 may be designed such that the transistor(s) of the peak load amplifier 104 are only conductive for a fraction of half a signal period. In this respect, the peak load amplifier 104 is configured to provide the peak load amplifier power only when a predetermined base load amplifier power is exceeded. The illustration in Fig. 5 shows a further embodiment of an amplifier stage 40 with a first amplifier path 42 comprising a first amplifier unit 42a and a second amplifier path 43 comprising a second amplifier unit 43a.The two amplifier units 42a, 43a are coupled to each other via a phase-shifting coupler unit 47. This is designed here as a 3dB-90° hybrid coupler. The two amplifier units 42a, 43a, in particular their base load amplifier 103 and peak load amplifier 104, are controlled by a signal provision device 99. This is preferably configured to provide signals for generating the high-frequency power signal in a predetermined power range such that the base load amplifier power is greater than the peak load amplifier power at least in a portion of the predetermined power range, preferably in a lower portion of the predetermined power range.

[0060] The power supply system comprising amplifier stage 40 is configured such that, in the event of a mismatch of load 6, power reflected at load 6 is at least partially routed via coupler unit 47 and at least one power coupler 107 to at least one of base load amplifier 103 and peak load amplifier 104. The power is reflected at least at this base load amplifier 103 or peak load amplifier 104 and routed back to coupler unit 47 via power coupler 107. This coupler unit is connected to an absorption resistor 110, which absorbs this returned power.

[0061] The diagram in Fig. 6 compares the simulated load power P of a power supply system with the input power Pi. The two upper diagrams compare a power supply system with conventional amplifiers, referred to here as PA, with a power supply system with amplifiers designed as Doherty amplifiers, referred to here as DPA, in the two lower diagrams. The type of coupler unit 47 is specified as a further parameter: The left-hand diagrams refer to a coupler unit designed as a Wilkinson combiner, while the right-hand diagrams refer to a 3dB-90° hybrid combiner.

[0062] The diagram in Fig. 7 compares the simulated power loss Pv of a power supply system with the load power P . The two upper diagrams compare a power supply system with conventional amplifiers, referred to here as PA, with a power supply system with amplifiers designed as Doherty amplifiers, referred to here as DPA, in the two lower diagrams. The type of coupler unit 47 is specified as a further parameter: The left-hand diagrams refer to a coupler unit designed as a Wilkinson combiner, the right-hand diagrams to a 3dB-90° hybrid combiner.

[0063] In Figs. 6 and 7, it can be seen from the diagram at the bottom right that the combination of Doherty amplifiers and a phase-shifting coupler 47 designed as a 3 dB 90° hybrid combiner generates less power dissipation in the event of mismatch, i.e., with a reflection factor r > 0, than the combination of a Doherty amplifier with a Wilkinson combiner, as shown in the diagram at the bottom left, or the combination of a conventional amplifier with a 3 dB 90° hybrid combiner, as shown in the diagram at the top right, and significantly less power dissipation than the combination of a conventional amplifier and a Wilkinson combiner, as shown in the diagram at the top left. As a result of this reduced power dissipation, the power amplification system according to the invention requires less effort to cool, thereby increasing the service life of the transistors and thus the reliability of the overall system.Furthermore, it can be seen that the variation in the load power P for the combination of Doherty amplifiers and a phase-shifting coupler 47 designed as a 3 dB 90° hybrid combiner (bottom right) is almost independent of the reflection coefficient r. Therefore, a power supply system with Doherty amplifiers and a phase-shifting coupler 47 designed as a 3 dB 90° hybrid combiner can enable reliable and efficient operation with highly fluctuating, for example, pulsed, power output.

Claims

Patent claims:

1. Power supply system (2) with a power converter (3) generating a high-frequency power signal, which can be connected to a load (6) for supplying a plasma or gas laser process with power, wherein the power converter (3) comprises at least one amplifier stage (40) having: - a first amplifier path (42) comprising a first amplifier unit (42a), - a second amplifier path (43) comprising a second amplifier unit (43a), wherein the first amplifier path (42) is configured to output a first amplifier path output signal and the second amplifier path (43) is configured to output a second amplifier path output signal which has a phase shifted relative to the first amplifier path output signal, which is unequal to, in particular greater than, 0° and unequal to, in particular less than, 180°, wherein the amplifier paths (42, 43) are connected to a phase-shifting coupler unit (47) which is designed to couple the output signals of the amplifier paths (42, 43) to form a radio-frequency power signal, characterized in that the first and the second amplifier unit (42a, 43a) each have the following components: i. a base load amplifier (103) which is designed to provide a base load amplifier power; ii. a peak load amplifier (104) which is designed to provide a peak load amplifier power; and iii.a power coupler (107) for combining the base load amplifier power and the peak load amplifier power at the output of the respective first and second amplifier units (42a, 43a) to form an amplifier output power (Pout).

2. Power supply system (2) according to claim 1, characterized in that the power supply system (2) has a signal providing device (99) which is designed to provide the first and second amplifier unit (42a, 43a) with signals for generating the high-frequency power signal in a predetermined power range such that the base load amplifier power at least in part of the predetermined power range, preferably in a lower part of the specified power range, is greater than the peak load amplifier power.

3. Power supply system (2) according to one of the preceding claims, characterized in that the base load amplifier (103) is configured as a substantially linear amplifier and the peak load amplifier (104) is configured as a substantially non-linear amplifier 4. Power supply system (2) according to one of the preceding claims, characterized in that the base load amplifier (103) is configured as a class B amplifier or as a class AB amplifier and the peak load amplifier (104) is configured as a class C amplifier.

5. Power supply system (2) according to one of the preceding claims, characterized in that the peak load amplifier (104) is configured to provide the peak load amplifier power only when a predetermined base load amplifier power is exceeded.

6. Power supply system (2) according to one of the preceding claims, characterized in that the peak load amplifier (104) is designed to set its output impedance to a higher impedance when a predetermined base load amplifier power is undershot.

7. Power supply system (2) according to one of the preceding claims, characterized in that the power supply system (2) has a signal providing device (99) which is configured to provide the first and second amplifier unit (42a, 43a) with signals for generating the high-frequency power signal such that an output signal of the peak load amplifier (104) has a phase offset compared to an output signal of the base load amplifier (103), and / or the first and second amplifier unit (42a, 43a) comprises a phase-shifting splitter (100) which is configured to provide the base load amplifier (103) and the peak load amplifier (104) with signals for generating the high-frequency power signal such that an output signal of the peak load amplifier (104) has a phase offset compared to an output signal of the base load amplifier (103).

8. Power supply system (2) according to claim 7, characterized in that the signal providing device (99) or the phase-shifting splitter (100) are designed so that the phase offset is adjustable, in particular to a value of 90° or n*180° + 90°.

9. Power supply system (2) according to one of the preceding claims, characterized in that the power coupler (107) is designed as a phase-shifting power coupler.

10. Power supply system (2) according to one of the preceding claims, characterized in that the phase of the second amplifier path output signal shifted relative to the first amplifier path output signal is adjustable.

11. Power supply system (2) according to one of the preceding claims, characterized in that the amplifier units (42a, 43a) each have one or more transistors, in particular LDMOS transistors or GaN transistors.

12. Power supply system (2) according to one of the preceding claims, characterized in that a plurality of amplifier stages (40) are provided, wherein two amplifier paths (42, 43) of the amplifier stages (40) are connected to a 90° hybrid coupler, in particular directly without the interposition of other coupling devices.

13. Power supply system (2) according to one of the preceding claims, characterized in that it is configured such that in the event of a mismatch of the load (6), a power reflected at the load (6) is at least partially guided via the coupler unit (47) and at least one power coupler (107) to at least one of the base load amplifier (103) and the peak load amplifier (104), is at least partially reflected by this and is guided back via the at least one power coupler (107) to the coupler unit (47), which guides this returned power at least partially into a resistor (110).

14. Plasma system (1) with a load (6) and a power supply system (2) according to one of the preceding claims, which has a power converter (3) which is connected to the load (6), in particular via an impedance matching network (5).

15. A method for exciting a plasma with a high-frequency power, in which two amplifier paths (42, 43) are each fed with an analog signal and amplified in the amplifier path (42, 43) by at least one amplifier unit (42a, 43a) to form a high-frequency power signal, wherein the high-frequency power signals are fed to a phase-shifting coupler unit (47) which couples the high-frequency power signals in a phase-dependent manner, characterized in that the first and the second amplifier unit (42a, 43a) each have the following components: iv. a base load amplifier (103) which provides a base load amplifier power; v. a peak load amplifier (104) which provides a peak load amplifier power when the base load amplifier power is exceeded; and vi. a power coupler (107) which combines the base load amplifier power and the peak load amplifier power at the output of the respective first and second amplifier units (42a, 43a).second amplifier unit (42a, 43a) combined to form an amplifier output power.

16. The method according to claim 15, characterized in that the plasma is excited with a pulsed radio-frequency power and the radio-frequency power signal is a pulsed radio-frequency power signal.

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