Power combiner for coupling RF signals for a plasma process supply system and a plasma process system

Abstract

The invention relates to a power combiner (1) for coupling RF signals, in particular designed for a plasma process supply system and a plasma process system, the power combiner (1) being designed for a predefined operating frequency range with a frequency in the range of 2 MHz to 200 MHz, in particular in the range of 10 MHz to 50 MHz, designed for an output power ≥ 2 kW, preferably ≥ 4 kW, said power combiner comprising: e) a plurality of inputs (In1-In4) designed for connecting RF power amplifier stages (AS1-AS4), f) a main output (OUT), g) a plurality of coupling elements, in particular in the form of inductors (L1-L4), wherein each coupling element connects one input (In1-In4) to the main output (OUT), h) a balancing circuit (B) which connects the inputs (In1-In4) to one another, having: iii) an energy absorber, in particular in the form of a resistor (R1-R4), and a balancing line (W1-W4) with a fixed characteristic impedance and a length of n*λ / 2, where n ∈ ℕ.

Description

[0001] Power combiner for coupling RF signals for a plasma process supply system and a plasma process system

[0002] Description:

[0003] The present invention relates to a power combiner for coupling RF signals, in particular designed for a plasma process supply system and a plasma process system, the power combiner being designed for powers > 2 kW, preferably > 4 kW and frequencies in the range from 2 MHz to 200 MHz, in particular in the range from 10 MHz to 50 MHz,

[0004] The present invention further relates to an RF power amplifier unit comprising such a power combiner as well as a plasma process supply system and a plasma process system.

[0005] It also includes a method for supplying a load, in particular a plasma process.

[0006] A plasma process supply system is configured to supply a plasma process assembly. A plasma process assembly is an assembly in which a plasma is generated and maintained to start and maintain a process. This can involve gas laser excitation. In particular, it can be a plasma processing assembly. With such a plasma processing assembly, materials, and in particular their surfaces, can be processed, for example, by coating, etching, or activating them. Such plasma processing assemblies are used, for example, in the manufacture of architectural glass, photovoltaic modules, displays, semiconductor components such as microcontrollers or semiconductor memory chips, etc.Since these are high-precision processes, the demands on such plasma process arrangements and consequently also on the plasma process supply systems that supply them with electrical power are extremely high, with regard to measurement and control accuracy, reliability, continuous operation, efficiency, etc. Such a plasma process supply system is often designed for power levels > 2 kW, preferably > 4 kW, and frequencies in the range from 2 MHz to 200 MHz, particularly in the range from 10 MHz to 50 MHz. Such a plasma process supply system frequently comprises one or more high-frequency signal sources designed to jointly provide this required power and to regulate it according to the process specifications. In addition, a plasma process supply system often comprises one or more impedance matching circuits designed to match the impedance at the output of the high-frequency signal source(s) to the impedance at the input of the plasma process.

[0007] The output power of high-frequency signal sources, especially RF power amplifier stages with transistor amplifiers, is limited by currently available transistors to a few hundred watts to a few kW. To achieve higher output power, multiple high-frequency signal sources must be interconnected using a power combiner. The power combiners should exhibit the lowest possible losses while providing a wide bandwidth. High-frequency signal sources for plasma process supply systems, in particular, require such power combiners. As the demands on measurement and control accuracy, as well as stability, of plasma process supply systems are constantly increasing, the corresponding demands on the power combiners used in these systems are also constantly growing.

[0008] At the same time, the power combiner inputs to which the high-frequency signal sources are connected should be as well decoupled from each other as possible to avoid cross-feeding of the high-frequency signal sources and uneven distribution of reflected output power. Unequal amplitudes, phases, or internal impedances of the high-frequency signal sources connected to the power combiner create a push-pull signal that is harmful to the high-frequency signal sources. Additionally or alternatively, unequal distribution of the reflected power can change the phases and / or amplitudes, as well as the load impedance of the individual amplifiers. This can lead to excessive stress on the amplifier with the highest load.

[0009] Therefore, the inputs of power combiners are usually connected via so-called balancing circuits. Such balancing circuits can, for example, contain a resistance and / or a capacitance. The inputs are often connected to each other via the balancing circuit, especially via a common star point.

[0010] A power combiner for such processes is known, for example, from DE 20 2016 008 958 Ul.

[0011] The disadvantage of such a power combiner is that it is only suitable for a limited power output. This is due to the limited space available for the number of high-frequency signal sources that can be arranged around it.

[0012] The present invention is therefore based on the object of providing a power combiner suitable for higher power levels. This object is achieved by a power combiner according to independent claim 1. Advantageous developments of the invention emerge from the subclaims and / or the description.

[0013] According to the present invention, a power combiner is therefore proposed, designed for a predetermined operating frequency range for coupling RF signals with a frequency in the range from 2 MHz to 200 MHz, in particular in the range from 10 MHz to 50 MHz, designed for an output power of > 2 kW, preferably > 4 kW, comprising: a) a plurality of inputs, designed for the connection of RF power amplifier stages, b) a main output, c) a plurality of coupling elements, in particular designed as inductors, wherein each coupling element connects a respective input to the main output, d) a compensation circuit which connects the inputs to one another, comprising: i) an energy absorber, in particular designed as a resistor, and ii) a compensation line with a fixed characteristic impedance and a length of n* / 2 with ne I.

[0014] An 'operating frequency range' refers to the frequency range within which the power combiner and the RF power amplifier stages connected to it operate, i.e., for which they are designed. This can be a very narrowband operating frequency range, e.g. 13.54 MHz - 13.58 MHz, or a somewhat broader one, e.g. 13.06 MHz to 14.06 MHz. In both cases, the center frequency would be 13.56 MHz. An operating frequency range is usually specified by the manufacturer of a power combiner as the nominal frequency range. This will vary depending on the power combiner's area of ​​application. If a power combiner is part of an RF power amplifier unit, it is also designed for at least this operating frequency range.

[0015] Here, "n" generally refers to the wavelength of the high-frequency signals within the corresponding line, i.e., within the compensating line, at a frequency within the operating frequency range, specifically the center frequency of the operating frequency range. "n" N means that n can be a natural number, i.e., n = 1, 2, 3, 4, . . .

[0016] An energy absorber can be a component capable of extracting electrical energy from the power combiner and converting it into heat, for example, like a resistor. It is also conceivable, however, that this component is designed to at least partially convert the energy and make it available again at another location.

[0017] A coupling element can be, for example, an inductance or a coupling line with a predetermined length, e.g., X / 4. If the multiple coupling elements are all inductances, they can advantageously always have the same inductance value, in particular, they can be of identical construction. The multiple RF power amplifier stages often cannot be arranged very close to one another because they

[0018] - often generate so much heat that they have to be cooled by cooling units, and / or

[0019] - due to their high power generation, they carry such high currents and voltages that they would negatively influence each other by emitting high-frequency fields.

[0020] One solution is to space the RF power amplifier stages further apart and / or to shield them appropriately. In both cases, the outputs of the RF power amplifier stages can only be spaced apart. This results in a distance that is disadvantageous for the power combiner.

[0021] If the inputs of a power combiner are located far apart, the compensation line from the compensation circuit to the neutral point can become long and deviate from the theoretically ideal 0 mm. Such a long compensation line between the compensation circuit and the neutral point can result in unwanted coupling with phase delay. This would impair the coupling and input matching. Attempts to compensate for this coupling with compensation circuits or attenuators have so far been unsuccessful and / or have led to undesirable power losses, which, in addition to the loss of efficiency at these power levels, regularly lead to undesirably high heat generation.

[0022] In such arrangements, however, the compensating line with the described design and in particular with the described length can lead to great advantages.

[0023] The coupling elements can be arranged in such a way that they hardly influence each other, or in particular, they do not influence each other at all. "Hardly" here means such a small influence that, according to the laws of physics, it is insignificant. The specified characteristic impedance of the compensating line can, in particular, be equal to the characteristic impedance at the corresponding input.

[0024] The specified characteristic impedance of the compensation line can in particular be equal to an integer multiple of the characteristic impedance at the corresponding input.

[0025] The specified characteristic impedance of the compensation line can in particular be equal to an integer divisor of the characteristic impedance at the corresponding input.

[0026] The specified characteristic impedance of the compensating line can in particular be equal to 25 Q, 50 Q or 100 Q.

[0027] By using such a compensation line with a length of n* / 2 in the compensation circuit of the power combiner, deterioration of the coupling and input matching of the power combiner can be avoided. In a further embodiment, the length of the compensation line of the power combiner can be used to bridge distances, especially long distances, between the inputs of the power combiner.

[0028] Wide spacing means spacing of > / 16.

[0029] This provides a power combiner that functions efficiently and faithfully despite the large distances between individual components.

[0030] The ability to choose from various discrete compensating line lengths allows for freely selectable spacing between the individual components of the power combiner. This allows for highly flexible design and application of the power combiner.

[0031] Furthermore, the power combiner's compensation circuit can include an additional capacitance. This capacitance can be connected in series or parallel to the energy absorbers, particularly resistors, of the compensation circuit. This can increase the decoupling bandwidth.

[0032] Furthermore, the compensating line with a length of n* / 2 can be implemented at least partially as a coaxial cable or microstrip line. In particular, the portion implemented as a coaxial cable or microstrip line can be longer than the remaining portions of the compensating line. This prevents interference that could be transmitted from the compensating line to other components, e.g., RF power amplifier stages, or, conversely, prevents interference that could be transmitted from other components, e.g., RF power amplifier stages, to the compensating line.

[0033] Furthermore, the power combiner can have a capacitance that connects the output to a ground terminal. This capacitance, together with the coupling elements, particularly in the form of inductors, can be used as a low-pass filter, which can be used to filter out unwanted harmonics.

[0034] Additional capacitors can also be used, which are connected to a ground terminal before the inductors. This creates a so-called pi circuit consisting of two capacitors and one inductor, which in turn can serve as a low-pass filter. The power combiner can be arranged on a cooling unit. The cooling unit can be fluid-cooled. This cooling unit can have at least one channel for a fluid to flow through. The cooling unit can be made of copper, for example.

[0035] The cooling unit can be at least partially designed as a cooling plate. The cooling unit can be composed of several parts made of different materials. Examples of such a cooling unit are disclosed and described in detail in the following published applications: WO 2019 / 072894 A1, WO 2013 / 068004 A1, WO 2014 / 207185 A1. Thus, the power combiner can be used for the high power levels described in this disclosure, since process heat generated by the components, such as the energy absorbers, in particular designed as resistors, of the compensation circuit, can be dissipated directly via the fluid in the cooling unit. The power combiner can, in particular, be distributed across several cooling units, preferably across several cooling units spaced apart from one another as described above.

[0036] Furthermore, the coupling elements, in particular designed as inductors, and the energy absorber(s), in particular designed as resistors, as well as any capacitors of the power combiner, can be arranged on a circuit board. The circuit board can be made of FR-4, for example. Such an arrangement of the components on a circuit board can be easily manufactured and can enable uncomplicated contacting of the components.

[0037] The circuit board material can, in particular, be made of a polytetrafluoroethylene-based material, also known as PTFE. This material is particularly suitable due to its low dielectric constant and low losses.

[0038] The designation FR-4 stands for a class of flame-resistant and flame-retardant composite materials consisting of epoxy resin and fiberglass fabric. The abbreviation FR stands for "flame retardant." Polytetrafluoroethylene-based material, also abbreviated to PTFE, is several times more expensive than FR-4, but it can be used for circuit boards in the RF range because of its particularly low-loss performance in this frequency range. The circuit boards can be designed thinner because this material has a lower dielectric constant and also a higher dielectric strength against high electric fields.

[0039] In one embodiment, the coupling elements are designed as RF line sections with a fixed characteristic impedance and a length of n* / 4 with ne I. Particularly at higher frequencies, e.g., > 40 MHz, such RF line sections can be used advantageously and with low losses as an alternative or in addition to inductors.

[0040] The power combiner can have a further configuration:

[0041] - a first power combiner part,

[0042] - a second power combiner part

[0043] - wherein the two power combiner sections are connected to a previously described compensation line with a fixed characteristic impedance and a length of n* / 2 with n e N. Thus, the power combiner can be largely implemented on a circuit board as described in this disclosure. The compensation line can be routed from one power combiner section to the other.

[0044] In particular, the heat-generating part of the power combiner, i.e., the part through which the aforementioned high power flows, can be cooled by the cooling unit described in this disclosure. The compensation line, which generally does not generate as much heat, can be routed freely.

[0045] One of these, in particular several, preferably all power combiner parts can have or can have in a further embodiment:

[0046] - several coupling elements, in particular designed as inductors for connecting one input each to the main output and / or

[0047] - one, in particular several, energy absorbers, in particular configured as resistors. In this way, the power combiner can also be implemented largely on a circuit board as described above. The compensation line can be routed from one power combiner section to the other.

[0048] In this way, the heat-generating part of the power combiner, i.e. the part through which the previously mentioned high power flows, in particular the coupling elements, can also be cooled by the cooling unit described in this disclosure.

[0049] By connecting RF power amplifier stages to the dedicated inputs of the power combiner, the power combiner can be expanded to form an RF power amplifier unit. This RF power amplifier unit then represents a functional unit for coupling multiple RF power sources and can supply other loads or processes with its output power. The connected RF power amplifier stages can be, for example, RF transistor amplifiers.

[0050] In a further embodiment, the RF power amplifier unit may additionally comprise two heat sink sections, wherein

[0051] - a first RF power amplifier stage, in particular a first group of RF power amplifier stages, is / are arranged on a first heat sink section, and

[0052] - a second RF power amplifier stage, in particular a second group of RF power amplifier stages, is / are arranged on a second heat sink section, and

[0053] - the two heat sink sections are arranged at a distance from each other, and the compensation circuit connects the outputs of the RF power amplifier stages and the compensation line connects the RF power amplifier stages of the first heat sink section to those of the second heat sink section.

[0054] In a further embodiment, the RF power amplifier unit may additionally comprise two cooling units, wherein

[0055] - a first RF power amplifier stage, in particular a first group of RF power amplifier stages, is / are arranged on a first cooling unit, and

[0056] - a second RF power amplifier stage, in particular a second group of RF power amplifier stages, is / are arranged on a second cooling unit, and - the two cooling units are arranged at a distance from one another, and the compensation circuit connects the outputs of the RF power amplifier stages and the compensation line connects the RF power amplifier stages of the first cooling unit to those of the second cooling unit.

[0057] In this way, the high power levels described in this disclosure can be generated particularly well for plasma processes. The RF power amplifier stages can be distributed across multiple cooling units or heat sink sections. This allows for very effective heat dissipation. Furthermore, the RF power amplifier stages interfere with each other less due to the spacing.

[0058] One or both cooling units and / or heatsink sections can be arranged between two RF power amplifier stages. The cooling units and / or heatsink sections can thus provide shielding between these two RF power amplifier stages, further improving signal quality and reliability.

[0059] The spacing can be at least 10 mm, in particular at least 20 mm, measured at the shortest distance between the two cooling units and / or heat sink sections.

[0060] The power combiner can be divided into several power combiner sections, as previously described. Each power combiner section can be arranged on the cooling unit or heat sink section to which it is assigned a group of RF power amplifier stages, i.e., whose power levels it is designed to combine. This also allows the power combiner sections to be advantageously cooled.

[0061] A heat sink section refers to a part of a cooling unit. The cooling unit can be designed at least partially as a cooling plate. The cooling unit can be composed of several parts made of different materials. Examples of such a cooling unit are disclosed and described in detail in the following published applications: WO 2019 / 072894 A1, WO 2013 / 068004 A1, WO 2014 / 207185 A1. The object is also achieved by a plasma process supply system comprising at least one RF power amplifier unit as described above and an impedance matching circuit connected downstream thereof. Thus, a power combiner as described above can be used particularly advantageously and ensure particular reliability and stability of the system.

[0062] The object is also achieved by a plasma process system comprising a plasma process supply system as described above and a plasma process arrangement which is connected to the impedance matching circuit.

[0063] For example, a power combiner as described above can be used particularly advantageously and ensure particular reliability and stability of the system.

[0064] The object is also achieved by a method for supplying a load, in particular a plasma process arrangement with a previously described power amplifier unit and in particular with an impedance matching circuit connected downstream thereof, which in turn is particularly preferably connected to a plasma process arrangement, wherein

[0065] - RF power signals are supplied from RF power amplifier stages to the inputs of the power combiner,

[0066] - These RF power signals are combined by the power combiner at its output,

[0067] - And compensating currents flow via a compensating line between the inputs, which has a length of n* / 2 with ne N and a fixed characteristic impedance.

[0068] In this way, the task can be solved particularly advantageously.

[0069] Preferred embodiments of the invention are illustrated schematically in the drawings and are explained in more detail below with reference to the figures of the drawing.

[0070] There are shown: Fig. 1a, 1b two embodiments of a power amplifier unit each with two cooling units;

[0071] Fig. 2 shows an embodiment of a power amplifier unit with three cooling units;

[0072] Fig. 3 shows an embodiment of a power amplifier unit with four cooling units;

[0073] Fig. 4a, 4b two embodiments of a power amplifier unit with two cooling units each;

[0074] Fig. 5 schematic view of a power amplifier unit

[0075] Fig. 6 a plasma process system with a plasma process supply system.

[0076] Fig. 1a and b show two embodiments of power amplifier units 10 according to the invention. The power amplifier units 10 each have a power combiner 1, two RF power amplifier stages AS1, AS2 and two cooling units CP1, CP2. The power combiners 1 comprise two inputs In1, In2, a main output OUT, two coupling elements designed as inductors LI, L2 and a compensation circuit B. The RF power amplifier stages AS1, AS2 are connected to the inputs In1, In2, with the first RF power amplifier stage AS1 being connected to the first input In1 and the second RF power amplifier stage AS2 being connected to the second input In2. The inductors LI, L2 connect the inputs In1, In2 to the main output OUT, with the first inductor LI connecting the first input In1 and the second inductor L2 connecting the second input In2 to the main output OUT.The inductors LI, L2 and RF power amplifier stages AS1, AS2 are arranged on the cooling units CPI, CP2.

[0077] The first RF power amplifier stage AS1 and the first inductor LI are arranged on the first cooling unit CP1. The second RF power amplifier stage AS2 and the second inductor L2 are arranged on the second cooling unit CP2.

[0078] The compensation circuit B connects the two inputs Inl, In2 of the power combiner 1. In Fig. 1a, the compensation circuit B has two energy absorbers designed as resistors RI, R2 and two compensation lines Wl, W2 with a length of n* / 2. Both inputs Inl, In2 of the power combiner 1 are connected to a common star point S via the two resistors RI, R2 and the two compensation lines Wl, W2.

[0079] In Fig. 1b, the compensation circuit B has two energy absorbers designed as resistors RI, R2 and a compensation line Wl with a length of n* / 2. The two inputs Inl, In2 are connected to each other via the two resistors RI, R2 and the compensation line Wl.

[0080] In Fig. 1a and b, both resistors RI, R2 of the compensation circuit B are each arranged on one of the two cooling units CP1, CP2. The first resistor RI is arranged on the first cooling unit CP1 and connected to the first input In1. The second resistor R2 is arranged on the second cooling unit CP2 and connected to the second input In2.

[0081] In contrast to the power combiner 1 in Fig. 1a, the power combiner 1 in Fig. 1b has a capacitance C which connects the main output OUT to a ground terminal GND.

[0082] If the energy absorber is designed as a resistor, its value can advantageously be equal to the characteristic impedance at the corresponding input.

[0083] The resistance specified as an energy absorber can in particular be equal to an integer multiple of the characteristic impedance at the corresponding input.

[0084] The resistance used as an energy absorber can, in particular, be equal to an integer divisor of the characteristic impedance at the corresponding input. The resistance used as an energy absorber can, in particular, be equal to 25 Ω, 50 Ω, or 100 Ω.

[0085] Fig. 2 also shows an embodiment of a power amplifier unit 10 according to the invention. The power amplifier unit 10 is largely identical to the embodiment in Fig. 1a, wherein it has a third RF power amplifier stage AS3 and a third cooling unit CP3. The power combiner 1 has, in addition to the components described in the description of Fig. 1a, a third input In3 and a third coupling element designed as an inductor L3. In this embodiment, the compensation circuit B comprises a third compensation line W3 of length n* / 2 and a third energy absorber designed as a resistor R3. The third RF power amplifier stage AS3 is connected to the third input In3. The third input In3 is connected to the main output OUT via the third inductor L3.The third RF power amplifier stage AS3, the third inductor L3, and the third resistor R3 of the compensation circuit B are arranged on the third cooling unit CP3. The three inputs Inl-In3 are connected via the compensation circuit B via the resistors R1-R3 and the compensation lines W1-W3 of length n* / 2 to a common star point S. The first resistor RI and the first compensation line W1 are connected to the first input Inl, the second resistor R2 and the second compensation line W2 are connected to the second input In2, and the third resistor R3 and the third compensation line W3 are connected to the third input In3.

[0086] Fig. 3 again shows an embodiment of a power amplifier unit 10 according to the invention. This power amplifier unit 10 is largely identical to the embodiment in Fig. 2, wherein it has a fourth RF power amplifier stage AS4 and a fourth cooling unit CP4. In addition to the components described in the description of Figs. 1a and 2, the power combiner 1 has a fourth input In4 and a fourth coupling element designed as an inductor L4. In this embodiment, the compensation circuit B comprises a fourth compensation line W4 of length n* / 2 and a fourth energy absorber designed as a resistor R4. The fourth RF power amplifier stage AS4 is connected to the fourth input In4. The fourth input In4 is connected to the main output OUT via the fourth inductor L4.The fourth RF power amplifier stage AS4, the fourth inductor L4, and the fourth resistor R4 of the equalizing circuit B are arranged on the fourth cooling unit CP4. The four inputs Inl-In4 are connected via the equalizing circuit B to a common star point S via the resistors R1-R4 and the equalizing lines W1-W4 of length n* / 2. The first resistor RI and the first equalizing line W1 are connected to the first input Inl, the second resistor R2 and the second equalizing line W2 are connected to the second input In2, the third resistor R3 and the third equalizing line W3 are connected to the third input In3, and the fourth resistor R4 and the fourth equalizing line W4 are connected to the fourth input In4. Figs. 4a and b show further embodiments of power amplifier units 10 according to the invention.The power amplifier units 10 each comprise a power combiner 1, four RF power amplifier stages AS1-AS4, and two cooling units CP1, CP2. The power combiner 1 comprises four inputs Inl-In4, a main output OUT, four coupling elements configured as inductors L1-L4, and a compensating circuit B. The RF power amplifier stages AS1-AS4 are connected to the inputs Inl-In4. The inductors L1-L4 connect the inputs Inl-In4 to the main output OUT.

[0087] In Fig. 4a, the four inputs Inl-In4 are directly connected to the main output OUT via the four inductors L1-L4.

[0088] In Fig. 4b, the first two inputs Inl, In2 are connected via the first two inductors L1, L2 to a first output O1, and the second two inputs In3, In4 are connected via the second two inductors L3, L4 to a second output O2. The two outputs O1, O2 are then connected to the main output OUT.

[0089] The four inductors L1-L4 and the four RF power amplifier stages AS1-AS4 are arranged on the two cooling units CP1, CP2. The first two inductors LI, L2 and the first two RF power amplifier stages AS1, AS2 are arranged on the first cooling unit CP1. The RF power amplifier stages AS1, AS2 and the components of a first power combiner section 1a, namely the coupling elements designed here as inductors LI, L2 and the energy absorbers designed here as resistors RI, R2, together form a first RF power amplifier stage arrangement AU1. The second two inductors L3, L4 and the second two RF power amplifier stages AS3, AS4 are arranged on the second cooling unit CP2.The RF power amplifier stages AS3, AS4, and the components of a second power combiner part lb, namely the coupling elements designed here as inductors L3, L4 and the energy absorbers designed here as resistors R3, R4 together form a second RF power amplifier stage arrangement AU2.

[0090] The compensation circuit B has four energy absorbers designed as resistors R1-R4 and a compensation line W1 with a length n* / 2. The four inputs Inl-In4 are connected to one another using the compensation circuit B. For this purpose, the first two inputs Inl, In2 are connected to one another via the first two resistors RI, R2, arranged on the first cooling unit CP1. The first resistor RI is connected to the first input Inl and the second resistor R2 is connected to the second input In2. Likewise, the second two inputs In3, In4 are connected to one another via the second two resistors R3, R4, arranged on the second cooling unit CP2. The third resistor R3 is connected to the third input In3 and the fourth resistor R4 is connected to the fourth input In4. The compensation line W1 then connects all four inputs Inl-In4 to one another.

[0091] In this way, two, and in particular more than two, RF power amplifier stage arrangements AU1, AU2 can be interconnected. If more than two RF power amplifier stage arrangements AU1, AU2 are interconnected, several compensating lines can be interconnected in a star configuration, as shown analogously in Figs. 2 and 3 for more than two RF power amplifier stages.

[0092] Individual, in particular several, particularly preferably all, RF power amplifier stage arrangements AU1, AU2 can also have more than two RF power amplifier stages AS1, AS2. Accordingly, these can then also have more than two components of the power combiner parts 1a, 1b, i.e., more than two coupling elements configured here as inductors LI, L2, and more than two energy absorbers configured here as resistors RI, R2.

[0093] Fig. 4b also shows a possible connection arrangement of the two outputs 01, 02 of the two RF power amplifier stage arrangements AU1, AU2 with the main output OUT.

[0094] The first output O1 of the first RF power amplifier stage arrangement AU1 is connected to a first transmission line arrangement TL1. The first transmission line arrangement TL1 has a first signal conductor SL1 and a first reference conductor BL1. The second output O2 of the second RF power amplifier stage arrangement AU2 is connected to a second transmission line arrangement TL2. The second transmission line arrangement TL2 has a second signal conductor SL2 and a second reference conductor BL2. The two signal conductors SL1, SL2 are designed to transmit the respective output signals of the RF power amplifier stage arrangements AU1, AU2. The two reference conductors BL1, BL2 represent the reference potential for the two signal conductors SL1, SL2 and are electrically connected to a potential that is constant relative to the reference ground. In this case, this potential is the reference ground GND itself.

[0095] The two transmission line arrangements TL1, TL2 are combined and connected to a coupling line arrangement TLC. The coupling line arrangement TLC has a coupling signal line SLC and a coupling reference line BLC. The coupling signal line SLC is designed to transmit the combined output signals of the two RF power amplifier stage arrangements AU1, AU2, i.e., the sum of the output signals of the two RF power amplifier stage arrangements AU1, AU2. The coupling reference conductor BLC represents the reference potential of the coupling signal conductor SLC and is electrically connected to a potential that is constant relative to the reference ground. In this case, this potential is the reference ground GND itself. The coupling line arrangement TLC is connected to the main output OUT of the power amplifier unit 10.

[0096] In this case, the two transmission line arrangements TL1, TL2 can be designed as microstrip lines MSL.

[0097] In this case, the coupling line arrangement (TLC) can also be implemented as microstrip lines (MSL). Another design for carrying RF power signals, such as a coaxial line, is also conceivable.

[0098] Fig. 5 shows a further embodiment of a power amplifier unit 10 according to the invention. The power amplifier unit 10 is very similar to the power amplifier unit 10 in Fig. 4b, only in a different view, and the connection arrangement of the two outputs O1, O2 of the two RF power amplifier stage arrangements AU1, AU2 to the main output OUT is implemented as a coaxial line CXL. The descriptions of the two transmission line arrangements TL1, TL2, the two signal conductors SL1, SL2, the two reference conductors BL1, BL2, the coupling line arrangement TLC, the coupling signal line SLC, and the coupling reference conductor BLC can be found in the description of Fig. 4b.

[0099] The two cooling units CP1, CP2 can each have a heat sink section CS1, CS2. It is also conceivable for multiple heat sink sections CS1, CS2 to be arranged on a common cooling plate, but spatially spaced from one another (not shown in the figures). For example, the first heat sink section CS1 can be arranged on a first side of a cooling unit, and the second heat sink section CS2 can be arranged on the rear side of the same cooling unit.

[0100] In contrast to the power amplifier unit 10 in Fig. 4b, the power amplifier unit 10 here has two combiner circuit boards PCB1, PCB2. The first combiner circuit board PCB1 is arranged on the first heat sink section CS1 and thus, in this embodiment, also on the first cooling unit CP1. The second combiner circuit board PCB2 is arranged on the second heat sink section CS2 and thus, in this embodiment, also on the second cooling unit CP2. The power amplifier unit 10 also has the power combiner 1 from Fig. 4b. This shows the four RF power amplifier stages AS1-AS4, each divided into the RF power amplifier stage arrangements AU1, AU2. Also shown are the four coupling elements embodied as inductors L1-L4, the main output OUT, and the compensation circuit B. The compensation circuit B comprises the four energy absorbers embodied as resistors R1-R4 and the compensation line W1 of length n* / 2.

[0101] The first two RF power amplifier stages AS1, AS2 are arranged on a first amplifier circuit board PCB12. The first two RF power amplifier stages AS1, AS2 are arranged with this first amplifier circuit board PCB12 on the first heat sink section CS1 and thus, in this embodiment, also on the first cooling unit CP1. The second two RF power amplifier stages AS3-AS4 are arranged on a second amplifier circuit board PCB34. The second two RF power amplifier stages AS3-AS4 are arranged with this second amplifier circuit board PCB34 on the second heat sink section CS2 and thus, in this embodiment, also on the second cooling unit CP2.

[0102] The first combiner board PCB1 can also be combined with the first amplifier board PCB12 to form a single circuit board. The second combiner board PCB2 can also be combined with the second amplifier board PCB34 to form a single circuit board. This simplifies manufacturing and reduces the number of cable connections between circuit boards, making the overall system more reliable. The first two inductors L1, L2 and the first two resistors R1, R2 are arranged on the first combiner board PCB1. The second two inductors L3, L4 and the second two resistors R3, R4 are arranged on the second combiner board PCB2.

[0103] Fig. 6 shows a plasma process system 17 with a plasma process supply system 12.

[0104] The plasma process supply system 12 comprises a power amplifier unit 10 with a power combiner 1. These can be designed as previously described.

[0105] The plasma process supply system 12 also has an impedance matching circuit 11.

[0106] The main output OUT of the power combiner 1 is connected to the input of the impedance matching circuit 11. The output terminal of the impedance matching circuit 11 is connected to the load, in this case a plasma processing arrangement in a plasma chamber 13.

[0107] The plasma chamber 13 has:

[0108] - a substrate 15 that is processed by the plasma 16, e.g. coated or etched,

[0109] - an electrode 14 with which the RF power is coupled into the plasma chamber 13 in order to ignite and maintain the plasma 16.

[0110] The impedance matching circuit 11 is designed to transform the input impedance of the plasma process at its output to the output impedance of the power amplifier unit 10. Embodiments of such plasma process systems and / or impedance matching circuits are described, for example, in the following published patent applications: DE 10 2009 001 355 A1, DE 10 2011 007 597 A1, DE 10 2011 007 598 A1, WO 2021 / 209390 A1, WO 2021 / 255250 A1.

Claims

1. Power combiner (1) for coupling RF signals, in particular designed for a plasma process supply system and a plasma process system, the power combiner (1) being designed for a predetermined operating frequency range with a frequency in the range from 2 MHz to 200 MHz, in particular in the range from 10 MHz to 50 MHz, designed for an output power of > 2 kW, preferably > 4 kW, comprising: a) a plurality of inputs (Inl-In4) designed for the connection of RF power amplifier stages (AS1-AS4), b) a main output (OUT), c) a plurality of coupling elements, in particular designed as inductors (Ll-L4), wherein a coupling element in each case connects one input (Inl-In4) to the main output (OUT), d) a compensation circuit (B) which connects the inputs (Inl-In4) to one another, comprising: i) an energy absorber, in particular designed as a resistor (R.1-R4), and ii) a compensating line (W1-W4) with a fixed characteristic impedance and a length of n* / 2 with ne I.

2. Power combiner (1) according to the preceding claim 1, wherein the compensation circuit (B) may additionally comprise a capacitance.

3. Power combiner (1) according to one of the preceding claims, wherein the compensating line (W1-W4) with a length of n* / 2 at least partially comprises a coaxial cable or a microstrip line and in particular the part which is designed as a coaxial cable or microstrip line is longer than the remaining parts of the compensating line.

4. Power combiner (1) according to one of the preceding claims, wherein the power combiner has a capacitance (C) connecting the main output (OUT) to a ground terminal (GND).

5. Power combiner (1) according to one of the preceding claims, wherein the power combiner (1) is arranged on at least one cooling unit (CP1-CP4), e.g., a fluid-cooled cooling plate.

6. Power combiner (1) according to one of the preceding claims, wherein the coupling elements, in particular designed as inductors (L1-L4), of the power combiner (1) and the energy absorbers, in particular designed as resistors (R.1-R4), of the compensation circuit (B) are arranged on a printed circuit board, in particular on a combiner printed circuit board (PCB1, PCB2).

7. Power combiner (1) according to one of the preceding claims, comprising: - a first power combiner part (la), - a second power combiner section (lb), - wherein the two power combiner parts (la, lb) are connected to a compensating line (Wl) with a fixed characteristic impedance and a length of n* / 2 with ne N.

8. Power combiner (1) according to claim 7, wherein one, in particular several, preferably all power combiner parts (la, lb) comprise: - several coupling elements, in particular designed as inductors (L1-L4) for connecting one input each (Inl - In4) to the main output (OUT) and / or - one, in particular several energy absorbers, in particular designed as a resistor (R.1-R4).

9. RF power amplifier unit (10) comprising a power combiner (1) according to one of the preceding claims, wherein RF power amplifier stages (AS1-AS4), e.g., RF transistor amplifiers, are connected to the inputs (In1-In4) of the power combiner (1).

10. RF power amplifier unit (10) according to claim 9, additionally comprising two cooling units (CPI, CP2) wherein - a first RF power amplifier stage (AS1), in particular a first group of RF power amplifier stages (AS1, AS2), are arranged on a first cooling unit (CP1), - a second RF power amplifier stage (AS3), in particular a second group of RF power amplifier stages (AS3, AS4), are arranged on a second cooling unit (CP1) and - the two cooling units (CP1, CP2) are arranged at a distance from each other, and the compensation circuit (B) connects the outputs of the RF power amplifier stages (AS1, AS2, AS3, AS4) and the compensation line (Wl) connects the RF power amplifier stages (AS1, AS2, AS3, AS4) of the first cooling unit (CP1) with those of the second cooling unit (CP2).

11. RF power amplifier unit (10) according to claim 9, additionally comprising two heat sink sections (CS1, CS2) wherein - a first RF power amplifier stage (AS1), in particular a first group of RF power amplifier stages (AS1, AS2), is arranged on a first heat sink section (CS1), - a second RF power amplifier stage (AS3), in particular a second group of RF power amplifier stages (AS3, AS4), is arranged on a second heat sink section (CS2) and - the two heat sink sections (CS1, CS2) are arranged at a distance from one another, and the compensation circuit (B) connects the outputs of the RF power amplifier stages (AS1, AS2, AS3, AS4) and the compensation line (Wl) connects the RF power amplifier stages (AS1, AS2, AS3, AS4) of the first heat sink section (CS1) with those of the second heat sink section (CS2).

12. Plasma process supply system (12) comprising at least one RF power amplifier unit (10) according to one of the preceding claims 9 to 11, and an impedance matching circuit (11) connected downstream thereof.

13. Plasma process system (17) comprising a plasma process supply system (12) according to claim 12 and a plasma process arrangement, which is connected to the impedance matching circuit (11).

14. Method for supplying a load, in particular a plasma process, with a power amplifier unit (10) according to one of the preceding claims 9 to 11, and in particular with an impedance matching circuit (11) connected downstream thereof, which in turn is particularly preferably connected to a plasma process arrangement, wherein - RF power signals from RF power amplifier stages (AS1 - AS4) are supplied to the inputs (Inl - In4) of the power combiner, - These RF power signals are combined by the power combiner (1) to its main output (OUT), - And a compensating current flows via a compensating line (Wl) between the inputs (Inl - In4), whereby the compensating line (Wl) has a length of n* / 2 with ne N and a fixed characteristic impedance.

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