HF generator for a plasma processing system, and such a plasma processing system

Abstract

An HF generator (3) for a plasma processing system (1) comprises an amplifier unit (10) which is designed to amplify an HF signal. Furthermore, a voltage supply unit (12) is provided which is designed to generate a supply voltage (20) and to supply same to the amplifier unit (10). The voltage supply unit (12) comprises a DC converter (14) which can be operated in a switching operation mode, and the DC converter (14) which can be operated in the switching operation mode is designed to convert an input direct current supplied to the DC converter into a first output voltage (18a). The voltage supply unit (12) comprises a DC converter (15) which can be operated in a linear operation mode, and the DC converter (15) which can be operated in the linear operation mode is designed to convert an input direct current supplied to the DC converter into a second output voltage (18b). The voltage supply unit (12) comprises a voltage output unit (19), wherein the first and the second output voltage (18a, 18b) can be supplied to the voltage output unit (19), and the voltage output unit (19) is designed to generate the supply voltage (20) from the first and second output voltage (18a, 18b) and / or output the supply voltage.

Description

[0001] RF generator for a plasma processing system and such a plasma processing system

[0002] The invention relates to an RF generator for a plasma processing system and such a plasma processing system.

[0003] The surface treatment of workpieces using plasma and gas lasers is an industrial process in which a plasma is generated, particularly in a plasma chamber, using direct current or a high-frequency alternating signal with an operating frequency in the range of a few 10 kHz up to the GHz range.

[0004] The plasma chamber is connected to a high-frequency generator (HF generator) via additional electronic components such as coils, capacitors, cables, or transformers. These additional components can represent resonant circuits, filters, or impedance matching circuits.

[0005] Plasma processes represent a highly variable load for a high-frequency generator, depending on the conditions in the plasma chamber. In particular, the properties of the workpiece, electrodes, and gas conditions are important.

[0006] High-frequency generators have a limited operating range depending on the impedance of the connected electrical load. If the load impedance exceeds a permissible range, the required energy / power cannot be delivered to the load. Damage to the HF generator is also possible.

[0007] For this reason, an impedance matching circuit, also called a “matchbox”, is often used to transform the impedance of the load to a nominal impedance of the generator output.

[0008] The technical requirements for the RF generator are also constantly increasing. The purpose of the RF generator is to transfer radio-frequency energy into the plasma chamber. This RF energy is used to ionize gases in the chamber, thus generating the plasma. Furthermore, the RF energy helps to keep the plasma stable and control its density and temperature. By adjusting the RF power, different plasma states can be achieved, which are required for different applications. In semiconductor manufacturing and materials processing, plasma chambers are often used for sputtering processes. In this process, ions from the plasma are directed onto a target (target material), knocking atoms out of the target and depositing them on a substrate. The RF generator enables control of the energy input into the plasma and thus control of the sputtering process.In CVD (chemical vapor deposition) processes, reactive gases are also introduced into the plasma chamber. The energy from the RF generator helps break down these gases and form reactive particles, which then settle on a substrate and form solid layers. The energy of the plasma can also be used to clean surfaces of contaminants, as the reactive particles in the plasma react with the contaminants on the surface and remove them. The RF generator is therefore a crucial tool for generating and controlling plasma in a plasma chamber, enabling a wide variety of industrial and scientific processes. Plasma processing systems have long been used to process substrates, such as semiconductor wafers or flat panel displays, into integrated circuits or other electronic products.Common plasma processing systems may include capacitively coupled plasma processing (CCP) systems or inductively coupled plasma processing (ICP) systems.

[0009] In general, the processing of plasma substrates involves a balance of ions and radicals. As electronic devices become smaller and / or more complex, etching requirements such as selectivity, uniformity, high aspect ratio, aspect-dependent etching, etc. have increased. While it was possible to perform etching on previous generations of products by modifying certain parameters such as pressure, RF bias, power, etc., the next generation of smaller and / or more sophisticated products requires different etching capabilities. The fact that ions and radicals cannot be more effectively decoupled and independently controlled with current technology has limited, and in some cases impractical, the performance of some etching processes for fabricating these smaller and / or more sophisticated electronic devices in some plasma processing systems.

[0010] It is therefore the object of the present invention to provide an RF generator for a plasma processing system with which the requirements described above can also be met for the next generation of products.

[0011] The object is achieved by the RF generator for a plasma processing system according to claim 1 and by the plasma processing system according to claim 20. Claims 2 to 19 describe advantageous developments of the RF generator, and claim 21 describes an advantageous development of the plasma processing system. The RF generator for a plasma processing system comprises an amplifier unit designed to amplify an RF signal. Furthermore, the RF generator comprises a voltage supply unit designed to generate a supply voltage and supply it to the amplifier unit. The voltage supply unit comprises a DC converter operable in switching mode, which has an output terminal, wherein the DC converter operable in switching mode is designed to convert an input DC voltage supplied to it into a first output voltage and output this at the output terminal.The output terminal of the DC converter operable in switching mode can also be referred to as the first output terminal. The voltage supply unit further comprises a DC converter operable in linear mode, which has an output terminal, wherein the DC converter operable in linear mode is designed to convert a DC input voltage supplied to it into a second output voltage and output this at the output terminal. The output terminal of the DC converter operable in linear mode can also be referred to as the second output terminal. The voltage supply unit further comprises a voltage output unit having a first and a second input terminal. The output terminal of the DC converter operable in switching mode is connected to the first input terminal, and the output terminal of the DC converter operable in linear mode is connected to the second input terminal.The first output voltage and the second output voltage can thereby be supplied to the voltage output unit, wherein the voltage output unit is designed to generate and / or output the supply voltage from the first output voltage and the second output voltage and to supply the supply voltage to the amplifier unit.

[0012] Providing a supply voltage, as well as a first or second output voltage, involves providing a voltage source. Providing a voltage source has the advantage that the voltage remains stable, at least within specified limits, independent of the load. The voltage can be adjusted very precisely, efficiently, and quickly.

[0013] It is particularly advantageous that the power supply unit comprises a DC converter operable in switched mode and a DC converter operable in linear mode, and that the output voltage generated by both DC converters is used to power the amplifier unit. The use of these different topologies allows the supply voltage to be generated particularly quickly and with good efficiency. The DC converter operable in linear mode can set the desired output voltage particularly quickly, whereas the DC converter operable in switched mode generates the supply voltage very efficiently.

[0014] The amplitude of an RF signal, which is fed to the amplifier unit, amplified by the amplifier unit, and output as an amplified RF signal, can thus be adjusted very quickly and in a particularly efficient manner. This rapid adjustment is necessary to reliably control new plasma processes. In this case, the level of the RF signal fed to the amplifier unit can be left constant. This ensures that the amplifier unit always operates in the linear range. In this case, the change in the amplitude of the amplified RF signal takes place solely via a rapid change in the supply voltage of the amplifier unit by the power supply unit. This makes it very easy to generate multilevel pulses or an arbitrary waveform.

[0015] An arbitrary waveform signal is a signal whose envelope can follow any waveform. Unlike multi-level pulses, not only individual levels and the transitions from one level to the next can be set as the envelope, but also any desired curve that can change continuously or jump between two values.

[0016] Such multilevel pulses or an arbitrary waveform offer various advantages. For example, pulsing the plasma can reduce heat generation. This is particularly important for temperature-sensitive samples or substrates. Using different pulse modes, the temperature of the substrate or sample can be regulated during the process. Such RF signals can also positively influence the layer quality in deposition processes or the selectivity in etching processes. Furthermore, continuous plasma treatment can lead to damage in some materials. Pulsing allows the plasma to act more "gentlely" and minimize potential damage. In certain applications, different pulse modes can achieve greater process efficiency by activating and deactivating the plasma at optimal intervals. Different pulse modes can be used in processes based on chemical reactions, such as etching.Plasma-enhanced chemical vapor deposition (PECVD) helps control the reaction dynamics and the formation of specific species. The term "species" in this context refers to the various reactive components generated in the plasma and responsible for the chemical deposition on the substrate. Overall, the ability to use different pulse patterns and frequencies offers the user greater flexibility in adapting the plasma process to specific needs or materials.

[0017] The use of a DC converter operating in linear mode allows for very rapid adjustment of the desired supply voltage. A DC converter operating in switching mode, for example in the form of a buck converter, can only quickly adjust the desired output voltage with a small output capacitance. In this case, however, the output voltage is subject to ripple. To smooth this ripple while still achieving fast transient response, the switching frequency would have to be increased, which in turn leads to higher switching losses and lower efficiency. The present development addresses this problem by combining the DC converter operating in switching mode with the DC converter operating in linear mode, thus enabling the supply voltage to be adjusted quickly and efficiently.

[0018] In one aspect, the amplifier unit is configured to generate and output multilevel pulses and / or an arbitrary waveform.

[0019] In one aspect, the amplifier unit is designed to receive an RF signal of constant amplitude and to convert and output this (?) into a multilevel pulse and / or an arbitrary waveform merely by varying the amplitude of the supply voltage.

[0020] In one aspect, the DC converter operable in linear mode reaches its preset second output voltage faster than the DC converter operable in switching mode reaches its preset first output voltage. This is especially true when both output voltages are the same.

[0021] In one aspect, the frequency of the RF signal that can be supplied to the amplifier unit is at least 10, 50, 100, 1000 times higher than the frequency with which the supply voltage is changed in its amplitude by the voltage supply unit.

[0022] In one aspect, the RF generator comprises a signal generation unit for generating an RF signal that can be fed to the amplifier unit. The signal generation unit comprises a signal source and optionally a mixer and / or filter and / or divider. The signal source can be, for example, an oscillator, such as an LC oscillator, quartz oscillator, Gunn diode oscillator, or a YIG oscillator. A direct digital synthesizer (DDS) can also be used, which generates the corresponding RF signal using a phase accumulator, look-up table, and digital-to-analog converter.

[0023] In one aspect, the switching-mode DC converter and the linear-mode DC converter are arranged in parallel, i.e., connected in parallel. This allows the switching-mode DC converter and the linear-mode DC converter to operate independently of each other.

[0024] In one aspect, the voltage output unit is configured to output the higher of the first and second output voltages as the supply voltage. This makes it very simple for the DC converter operable in linear mode, which can be regulated more quickly, to generate the supply voltage first, while the DC converter operable in switched mode takes over as soon as it generates a sufficiently high voltage. As a result, the required supply voltage is available very quickly, and later, in particular automatically, switching occurs to the more efficient DC converter operable in switched mode, thereby reducing power consumption and the cooling requirements of the RF generator.

[0025] In one aspect, the voltage output unit comprises a first diode unit with at least one first diode and a second diode unit with at least one second diode. The use of such a diode unit allows the higher of the first and second output voltages to be output as the supply voltage in a very simple manner. If the first output voltage has a level of 40 V and the second output voltage has a level of 41 V, the at least one first diode is blocking, whereas the at least one second diode is conducting. In this case, the supply voltage is formed solely from the second output voltage. If the first output voltage later rises to 42 V, the at least one first diode becomes conducting, whereas the at least one second diode is blocking. In this case, the supply voltage is formed solely from the first output voltage.

[0026] The voltage output unit and the DC converter operable in switching mode and / or the DC converter operable in linear mode do not have to be clearly separated modules. For example, the first diode unit may be located in the DC converter operable in switching mode, and the second diode unit may be located in the DC converter operable in linear mode. In this case, the voltage output unit would simply comprise a common node to which the supply voltage is applied.

[0027] In one aspect, the first diode unit is connected with its input to the output terminal of the DC converter operable in switching mode. The second diode unit is connected with its input to the output terminal of the DC converter operable in linear mode. The first diode unit and the second diode unit are connected with their respective outputs to a common star point, which in turn is connected to the amplifier unit. The supply voltage to be output is applied to the star point. Preferably, the at least one first diode of the first diode unit is connected with its anode to the output terminal of the DC converter operable in switching mode. The at least one first diode of the first diode unit is preferably connected with its cathode to the star point. Preferably, the at least one second diode of the second diode unit is connected with its anode to the output terminal of the DC converter operable in linear mode.The at least one second diode of the second diode unit is preferably connected to the star point with its cathode.

[0028] In one aspect, the voltage output unit comprises a switching unit, wherein the switching unit is configured, depending on the switch position, to connect either the DC converter operable in switching mode or the DC converter operable in linear mode to the amplifier unit. The switching unit comprises, in particular, active switches, i.e., semiconductor switches. An active switch preferably comprises at least one transistor.

[0029] In one aspect, a first active switch is connected by its input to the output terminal of the DC converter operable in switching mode. A second active switch is connected by its input to the output terminal of the DC converter operable in linear mode. The first and second active switches are connected by their respective outputs to a common star point, which in turn is connected to the amplifier unit.

[0030] In one aspect, a control unit, in particular a local one, is provided which is designed to measure the voltage at the output terminal of the DC converter operable in switching mode and the voltage at the output terminal of the DC converter operable in linear mode and, depending on the voltage level, to control the switching unit of the voltage output unit accordingly, in particular to control it in such a way that the DC converter whose output voltage is closer to a target value for the supply voltage is connected to the amplifier unit.

[0031] In one aspect, the voltage output unit is designed to first generate the supply voltage from the second output voltage or to first output the second output voltage as a supply voltage when a setpoint value for the supply voltage changes, in particular when it increases, in order to generate the supply voltage from the first output voltage or to output the first output voltage as a supply voltage at a later time.

[0032] In one aspect, the voltage supply unit is configured to supply the amplifier unit at a time only via the DC converter operable in switching mode or via the DC converter operable in linear mode. This ensures that the supply voltage is applied very quickly by the DC converter operable in linear mode, and that the supply voltage is generated very efficiently during subsequent operation via the DC converter operable in switching mode. In this case, only one of the two DC converters serves to supply the amplifier unit at a time.

[0033] In one aspect, the voltage supply unit is configured to switch off the DC converter operable in linear mode when the amplifier unit is supplied via the DC converter operable in switched mode. Preferably, the input DC voltage supplied to the DC converter operable in linear mode can be switched away from the DC converter via a switching unit. It is also conceivable for a control unit to be configured to control the DC converter operable in linear mode such that it generates a second output voltage that is at or approximately at 0 V. This saves further energy.

[0034] In one aspect, the voltage supply unit is configured to control the DC converter operable in linear mode such that it generates the second output voltage that lies below a setpoint for the desired supply voltage. This makes it particularly easy for the DC converter operable in switching mode to take over the supply of the amplifier unit as soon as the first output voltage is closer to the setpoint for the desired supply voltage.

[0035] In one aspect, the second output voltage is in the range of 90% to 95%, 97%, or 98% of the setpoint for the desired supply voltage.

[0036] In one aspect, the voltage supply unit is configured to control the DC converter operable in switching mode such that it generates the first output voltage that approximately corresponds to the setpoint for the desired supply voltage and / or that differs from the setpoint for the desired supply voltage by a difference that is smaller than a difference between the second output voltage and the setpoint for the desired supply voltage and / or that is greater than the second output voltage. This achieves in a simple manner that the supply voltage is only generated by the DC converter operable in switching mode as soon as its second output voltage reaches a certain level.

[0037] In one aspect, the power supply unit comprises a discharge unit.

[0038] The discharge unit is designed to transfer energy from the DC converter operable in switching mode and / or an intermediate circuit capacitor arranged therein to at least one discharge resistor when the DC converter operable in switching mode reduces the first output voltage, thus, for example, converting it into heat or feeding it back into a power grid. This ensures that the new setpoint for the supply voltage, which is below a previous setpoint, is reached as quickly as possible. In particular, an intermediate circuit capacitor within the DC converter operable in switching mode is discharged via the discharge unit.

[0039] In one aspect, the discharge unit comprises a switching unit and at least the discharge resistor, wherein the switching unit is designed to connect the discharge resistor in order to dissipate energy from the DC converter operable in switching mode and / or an intermediate circuit capacitor arranged therein towards a reference ground, for example via a resistor. Alternatively, the discharge unit comprises a switching unit, wherein the switching unit is designed to electrically connect the DC converter operable in linear mode to the output terminal of the DC converter operable in switching mode, such that the DC converter operable in linear mode draws energy from the DC converter operable in switching mode and / or an intermediate circuit capacitor arranged therein and preferably feeds it back into the energy network or dissipates it towards a reference ground, for example via a resistor.

[0040] In one aspect, the discharge unit comprises a further DC converter operable in switching mode, which is designed to extract energy from the intermediate circuit capacitor. Additionally or alternatively, the discharge unit comprises a further DC converter operable in linear mode, which is designed to extract energy from the DC converter operable in switching mode and / or an intermediate circuit capacitor arranged therein.

[0041] In one aspect, the additional DC converter operable in switching mode is a buck converter. Additionally or alternatively, the additional DC converter operable in linear mode is a linear regulator.

[0042] In one aspect, the discharge unit extracts the energy at the star point where the supply voltage is applied.

[0043] In one aspect, the DC input voltage that can be supplied to the switching-mode DC converter is the same DC input voltage that can be supplied to the linear-mode DC converter. Alternatively, the DC input voltage that can be supplied to the switching-mode DC converter is a different DC input voltage than the DC input voltage that can be supplied to the linear-mode DC converter.

[0044] In one aspect, the switching-mode DC converter is a buck converter, a boost converter, a combination buck and boost converter, an OC converter, or a SEPIC converter. A buck converter is an electronic circuit that converts a higher input voltage to a lower output voltage. A boost converter is a type of DC-DC converter that increases an input voltage to a higher output voltage. The OC converter is a voltage converter that can produce both higher and lower output voltages than the input voltage while providing an inverted voltage level. The SEPIC converter (Single Ended Primary Inductance Converter) is a voltage converter that can transform an input voltage to an output voltage that is either higher or lower than the input voltage without inverting it.

[0045] In one aspect, the power supply unit comprises a rectifier unit for generating the respective input DC voltage for the DC converter operable in switching mode and the DC converter operable in linear mode from an AC voltage. A single-phase AC voltage, e.g., 230 V, or a three-phase AC voltage, e.g., 400 V, can be supplied to the rectifier unit.

[0046] In one aspect, the supply voltage is selected with its voltage profile such that the amplifier unit is configured to output an amplified RF signal in the form of a multilevel pulse or an arbitrary waveform. This applies in particular when the amplifier unit is supplied with a constant RF signal to be amplified, the amplitude of which always has the same maximum.

[0047] In one aspect, the amplifier unit comprises at least a first and a second amplifier, which are arranged in parallel to one another, wherein the same supply voltage can be supplied to both amplifiers. Alternatively, the amplifier unit comprises at least a first and a second amplifier, which are arranged in parallel to one another, wherein the DC converter operable in switching mode and the DC converter operable in linear mode are designed to supply the first amplifier with electrical energy, i.e. with a first supply voltage, and wherein the voltage supply unit comprises an additional DC converter operable in switching mode and an additional DC converter operable in linear mode, which are designed to supply the second amplifier with electrical energy, i.e. with a second supply voltage. The first and second supply voltages can be the same or different.

[0048] The disclosed plasma processing system comprises at least one RF generator as described above. Furthermore, an impedance matching circuit is provided, which is connected to the output terminal of the RF generator. Furthermore, a central control device is provided, which is designed to control the RF generator such that it sets the supply voltage for the amplifier unit to a specific value. The supply voltage can be continuously changed so that the amplifier unit generates specific pulse patterns or an arbitrary waveform.

[0049] The development is described below purely by way of example with reference to the drawings. They show:

[0050] Figure 1 : an embodiment of the plasma processing system with a

[0051] RF generator;

[0052] Figure 2: an embodiment of the RF generator;

[0053] Figure 3: an embodiment of a voltage supply unit with a DC converter operable in switching mode, a DC converter operable in linear mode, and a voltage output unit; Figure 4A: an embodiment of the DC converter operable in switching mode with a discharge unit;

[0054] Figure 4B: another embodiment of the discharge unit; and

[0055] Figure 5: using diagrams of signals the functioning of the

[0056] Power supply unit with the DC converter that can be operated in switching mode and the DC converter that can be operated in linear mode.

[0057] Figure 1 shows a plasma processing system 1 which comprises a central control device 2. The plasma processing system 1 further comprises an RF generator 3, an impedance matching circuit 4 and at least one consumer 5, in particular in the form of a plasma chamber. The RF generator 3 is designed to provide a radio-frequency signal 21, in particular in the form of a pulsed radio-frequency signal 21 and / or an arbitrarily modulated radio-frequency signal 21, with a nominal power PNenn and a frequency fo and to output it at an output terminal 3a. The impedance matching circuit 4 comprises an input terminal 4a, wherein the RF generator 3 is connected with its output terminal 3a to the input terminal 4a via a first cable connection 6a. The impedance matching circuit 4 further comprises an output terminal 4b. The output terminal 4b is connected to the at least one consumer 5 via a second cable connection 6b.The first and / or second cable connection 6a, 6b may comprise one or more cables, for example, connected in series and / or in parallel. Coaxial cables are preferably used.

[0058] The consumer 5, i.e., the plasma chamber, comprises at least one electrode 7 for generating a plasma 8. The electrode 7 is connected to the output terminal 4b of the impedance matching circuit 4. In this embodiment, a camera system 91 is arranged in the plasma chamber 5, which is designed to observe the plasma 8.

[0059] The central control device 2 is preferably a processor and / or FPGA and / or microcontroller and / or ASIC, which is programmed according to its suitability or configuration. The central control device 2 can also include, among other things, a memory device for this purpose.

[0060] The central control device 2 is designed to control the RF generator 3, in particular to activate or deactivate it. Additionally or alternatively, the central control device 2 is also designed to change the power and / or frequency of the RF signal by appropriately controlling the RF generator 3. Additionally or alternatively, the central control device 2 is designed to change the waveform 22 of the high-frequency signal 21 by appropriately controlling the RF generator 3. This can relate, for example, to: the type of the high-frequency signal 21, modulation of the RF signal 21, pulse durations, pulse repetition rate. The central control device 2 is also designed to specify an arbitrary waveform to the RF generator 3, which the generator generates and outputs at its output terminal 3a.

[0061] The central control device 2 is preferably also designed to control the impedance matching circuit 4. In particular, the central control device 2 is designed to change the transformation ratio within the impedance matching circuit 4 and / or to specify an impedance at the output terminal 4b. Additionally or alternatively, the central control device 2 is designed to specify the impedance at the input terminal 4a, which acts on the RF generator 2.

[0062] The plasma processing system 1 further comprises an output measuring unit 92. The output measuring unit 92 is preferably arranged between the RF generator 3 and the impedance matching circuit 4. The output measuring unit 92 is designed, for example, to measure a power Pi transmitted from the RF generator 3 toward the impedance matching circuit 4 and a power Pr reflected back toward the RF generator 3. In principle, the output measuring unit 92 can also be designed to measure an impedance value at the input terminal 4a of the impedance matching circuit 4.

[0063] For this purpose, the output measuring unit 92 comprises, for example, a directional coupler unit. Via the directional coupler unit, the output measuring unit 92 can measure the power of a forward and return high-frequency signal on the first cable connection 6a in order to calculate the respective power or impedance at the input terminal 4a from this. The output measuring unit 92 can alternatively also comprise a current sensor and a voltage sensor. The central control device 2 is configured to calculate the respective power or impedance at the input terminal 4a, which the RF generator 3 sees, based on the measurement result of the directional coupler unit or the current sensor and the voltage sensor.

[0064] The plasma processing system 1 preferably comprises an operating unit 93. The operating unit 93 is preferably a screen, in particular a touch-sensitive screen. In addition to a screen, the operating unit 93 can also comprise input devices such as a keyboard and / or mouse. The operating unit 93 can also be a web server that provides data and receives user input. The central control device 2 is designed to display current settings of the RF generator 3 and / or the impedance matching circuit 4 on the operating unit 93.

[0065] The central control device 2 is preferably designed to receive setpoint specifications, for example for the power of the high-frequency signal 21, from the control unit 93. Additionally or alternatively, the frequency of the high-frequency signal 21 and / or the waveform 22 of the high-frequency signal and / or the pulse rate and / or the pulse duration for the high-frequency signal 21 can be received by the control unit 93. A desired impedance at the output terminal 4b of the impedance matching circuit 4 can also be received via the control unit 93. From this, corresponding manipulated variables for the RF generator 3 and control data for the impedance matching circuit 4 can be generated and transmitted to the latter.

[0066] Figure 2 shows an embodiment of the RF generator 3. The RF generator 3 comprises an amplifier unit 10, a signal generation unit 11 and a voltage supply unit 12.

[0067] In this exemplary embodiment, the amplifier unit 10 comprises a first amplifier 10a and a second amplifier 10b. The first amplifier 10a and the second amplifier 10b are preferably transistor amplifiers. The first amplifier 10a and the second amplifier 10b are connected in parallel. The output of the first amplifier 10a and the output of the second amplifier 10b are connected to a combiner 13, which combines both output signals and outputs them as an amplified RF signal. The output of the combiner 13 is connected to the impedance matching circuit 4 via the first cable connection 6a.

[0068] The Combiner 13 is preferably a Wilkinson Combiner or a hybrid Combiner.

[0069] In principle, it is conceivable for the amplifier unit 10 to comprise more than two amplifiers 10a, 10b. Preferably, the first amplifier 10a is constructed identically to the second amplifier 10b.

[0070] The signal generation unit 11 is designed to generate the RF signal to be amplified by the amplifier unit 10. The signal generation unit 11 comprises a signal source and optionally a mixer and / or filter and / or divider. The signal source can be, for example, an oscillator, such as an LC oscillator, quartz oscillator, Gunn diode oscillator, or a YIG oscillator.

[0071] A direct digital synthesizer (DDS) can also be used, which generates the corresponding RF signal using a phase accumulator, look-up table and digital-to-analog converter.

[0072] Preferably, the same RF signal is supplied to the first amplifier 10a and the second amplifier 10b. In this case, the signal generation unit 11 comprises the divider, particularly in the form of a Wilkinson divider or hybrid divider.

[0073] In principle, it is also conceivable that the signal generation unit 11 comprises a separate signal source for each amplifier 10a, 10b.

[0074] The signal source of the signal generation unit 11 is preferably designed to generate an RF signal in any desired form and at any desired frequency and / or amplitude. As described with reference to Figure 1, the type of RF signal to be generated can be set via the central control device, which in turn receives input from the control unit 12.

[0075] The voltage supply unit 12 comprises a DC converter 14 operable in switching mode and a DC converter 15 operable in linear mode.

[0076] An input DC voltage can be supplied to both the DC converter 14, which can be operated in switching mode, and the DC converter 15, which can be operated in linear mode. The DC converter 14, which can be operated in switching mode, converts this input DC voltage into a first output voltage 18a. The DC converter 15, which can be operated in linear mode, converts this input DC voltage into a second output voltage 18b. The first and / or second output voltage 18a, 18b can be lower or higher than the respective input DC voltage.

[0077] In order to generate the corresponding input DC voltage, the voltage supply unit 12 comprises a rectifier unit 16. The rectifier unit

[0078] In this case, a 3-phase alternating voltage 17, in particular of 400 V, can be supplied to 16. Preferably, the rectifier unit 16 is a full-bridge rectifier with 6 diodes to convert the 3-phase alternating voltage

[0079] 17. Both the positive and negative half-waves of each phase are rectified. To smooth the direct current and reduce voltage ripple, the rectifier unit 16 may include at least one filter, in particular an intermediate circuit capacitor.

[0080] The voltage supply unit 12 also includes a voltage output unit 19. The voltage output unit 19 is arranged at the output of the DC converter 14 operable in switching mode and at the output of the DC converter 15 operable in linear mode. The first output voltage 18a and the second output voltage 18b of the respective DC converters 14, 15 are supplied to the voltage output unit 19. The voltage output unit 19 is designed to generate and / or output the supply voltage 20 from the first and second output voltages 18a, 18b.

[0081] An output of the voltage output unit 19 is connected to a respective supply input of the first amplifier 10a and the second amplifier 10b of the amplifier unit 10. This allows the supply voltage 20 to be supplied to the first amplifier 10a and the second amplifier 10b of the amplifier unit 10.

[0082] By appropriately controlling the DC converter 14, which can be operated in switching mode, and the DC converter 15, which can be operated in linear mode, the supply voltage can be pulsed or have an arbitrary waveform, whereby the amplified RF signal at the output of the RF generator 3 is also a multi-level pulse signal or an arbitrary waveform signal.

[0083] The DC converter 14 operable in switching mode and the DC converter 15 operable in linear mode are arranged in parallel to each other.

[0084] The voltage output unit 19 is designed to output the higher of the first and second output voltages 18a, 18b as the supply voltage 20.

[0085] The voltage output unit 19 is also designed to, in the event of a change, in particular an increase, of a setpoint value for the supply voltage 20, first generate the supply voltage 20 from the second output voltage 18b, or to output the second output voltage 18b first as the supply voltage 20, in order to generate the supply voltage 20 from the first output voltage 18a at a later time, or to output the first output voltage 18a as the supply voltage 20.

[0086] The amplifier unit 10 and thus the first and second amplifiers 10a, 10b are supplied with electrical energy, i.e. the supply voltage 20, at the same time only via the DC converter 14 which can be operated in switching mode or via the DC converter 15 which can be operated in linear mode.

[0087] The current setpoint for the first output voltage 18a and the second output voltage 18b can be supplied to the RF generator 3 via the central control device 2. In principle, a corresponding curve for the first output voltage 18a and the second output voltage 18b can also be stored in a memory unit in the RF generator 3, wherein this curve is tracked by the DC converter 14 operable in switching mode and the DC converter 15 operable in linear mode. For this purpose, the RF generator 3 can have a local control unit. This local control unit is preferably designed to control the signal generation unit 11 and / or the DC converter 14 operable in switching mode and / or the DC converter 15 operable in linear mode.

[0088] Figure 3 shows an embodiment of the voltage supply unit 12 with the DC converter 14 operable in switching mode, the DC converter 15 operable in linear mode and the voltage output unit 19.

[0089] The DC converter 14, which can be operated in switched mode, is a buck converter. The buck converter comprises a switch 25, a diode 26, at least one inductor 27, and at least one intermediate circuit capacitor 28. The switch 25, which is preferably a transistor, in particular a MOSFET, is connected to an input terminal 14a of the DC converter 14, which can be operated in switched mode. The input DC voltage from the rectifier unit 16 can be supplied via this input terminal 14a. The switch 25, on the other hand, is connected to both the at least one inductor 27 and the diode 26. The diode 26, in turn, is connected to a reference ground, whereas the at least one inductor 27 is connected to an output terminal 14b of the DC converter 14, which can be operated in switched mode. The output terminal 14b is also connected to the reference ground via the at least one intermediate circuit capacitor 28.Of course, multiple inductors 27 connected in series and / or parallel to one another can be used. Of course, multiple intermediate circuit capacitors 28 connected in series and / or parallel to one another can also be used. The first output voltage 18a is applied to the output terminal 14b.

[0090] During a switch-on phase of the buck converter, switch 25 is closed, i.e., switched on. An input current flows through the at least one inductor 27, and energy is stored in the at least one inductor 27. The diode 26 is blocking during this phase. During a switch-off phase of the buck converter, switch 25 is open, i.e., blocking the input current. The energy stored in the at least one inductor 27 is delivered to the load via the diode 26. The at least one intermediate circuit capacitor 28 ensures that the first output voltage 18a remains largely constant and is not influenced by the switching operations of switch 25. The first output voltage 18a can be controlled by the duty cycle, i.e., the ratio of the switch-on time to the total time of switch 25. If switch 25 is closed for a longer period, the first output voltage 18a approaches the input voltage.

[0091] Such a buck converter operates very efficiently, especially at low output voltages. It is also very compact, and the first output voltage 18a can be easily varied by changing the duty cycle. Control is preferably achieved via a discrete-time control unit, which is implemented, for example, in the local control unit. This takes into account, in particular, the dead times of the microcontroller and / or the FPGA.

[0092] Preferably, the buck converter also includes overcurrent protection, overtemperature protection and / or undervoltage protection.

[0093] If the first output voltage 18a is to be as smooth as possible, the settling time for modern plasma processes is often no longer sufficient. Therefore, the voltage supply unit 12 includes the DC converter 15, which can be operated in linear mode. In this embodiment, the DC converter 15, which can be operated in linear mode, is a linear regulator.

[0094] The linear regulator comprises a transistor 30 and preferably an operational amplifier 31. A collector of the transistor 30 is connected to an input terminal 15a of the DC converter 15 operable in linear mode. The input DC voltage is supplied to the input terminal 15a. An emitter of the transistor 30 is connected to an output terminal 15b of the DC converter 15 operable in linear mode. A first input of the operational amplifier 31 serves to supply a control voltage. A second input, in particular an inverting input, of the operational amplifier 31 is connected to the emitter of the transistor 30. By changing the control voltage, the second output voltage 18b at the emitter can be regulated to a specific target value. The linear regulator regulates to the desired output voltage 18b more quickly than the buck converter.However, the switching losses are higher than with the buck converter, especially for low output voltages 18b in relation to the supplied DC input voltage.

[0095] The voltage output unit 19 comprises a first diode unit with at least one first diode 35 and a second diode unit with at least one second diode 36. The first diode 35 is connected with its anode to the output terminal 14b of the DC converter 14 operable in switching mode. The first diode 35 is connected with its cathode to a star point 37. The second diode 36 is connected with its anode to the output terminal 15b of the DC converter 15 operable in linear mode. The second diode 36 is connected with its cathode to the star point 37. The supply voltage 20 is output at the star point 37. The star point 37 is connected to the amplifier unit 10 and thus preferably to the first amplifier 10a and the second amplifier 10b. The higher voltage of the first output voltage 18a and the second output voltage 18b is therefore always present at the star point 37.Because the DC converter 15 operable in linear mode reaches the setpoint for the second output voltage 18b more quickly than the DC converter 14 operable in switching mode, the supply voltage 20 is initially formed from the second output voltage 18b when a desired change in the supply voltage 20 occurs. At a later point in time, the first output voltage 18a then exceeds the level of the second output voltage 18b, whereby from this point onward the DC converter 14 operable in switching mode takes over the supply of the amplifier unit 10, and the supply voltage 20 is formed from the first output voltage 18a.

[0096] This is achieved because the voltage supply unit 12 is designed to control the DC converter 14, which can be operated in switching mode, such that it generates the first output voltage 18a, which is in particular greater than the second output voltage 18b. Preferably, the setpoint value for the second output voltage 18b is slightly lower than the setpoint value for the supply voltage 20 to be set, so that the DC converter 14, which can be operated in switching mode, takes over the supply of the amplifier unit 10 when the first output voltage 18a approximately corresponds to the setpoint value of the supply voltage 20 to be set.

[0097] Figure 4A shows an embodiment of the DC converter 14 operable in switching mode with a discharge unit 40. The discharge unit 40 is designed to draw energy from the DC converter 14 operable in switching mode and / or an intermediate circuit capacitor 28 arranged therein in the event that the DC converter 14 operable in switching mode reduces the first output voltage 18a. For this purpose, the discharge unit 40 comprises a switching unit 41 and a resistor 42. The resistor 42 can be connected to the resonant circuit of the DC converter 14 operating in switching mode via the switching unit 41. In particular, the switching unit 41 is connected to the output terminal 14b. The resistor 42 itself is preferably connected to the reference ground. As a result, the first output voltage 18a can be reduced significantly more quickly than would be possible without such a discharge unit.Instead of dissipating the energy from the resonant circuit into resistor 42, the energy can of course also be fed back into a power grid.

[0098] Figure 4B shows a further exemplary embodiment of how the discharge unit 40 can be constructed. The discharge unit 40 comprises a further DC converter 45 operable in switching mode, which is designed to draw energy from the first DC converter 14 operable in switching mode and / or an intermediate circuit capacitor 28 arranged therein. The further DC converter 45 operable in switching mode is also designed in the form of a buck converter. This DC converter 45 comprises a switch 46, a diode 47, and at least one inductor 48. Optionally, the DC converter 45 comprises at least one smoothing capacitor 49. The switch 46, which is preferably a transistor, in particular a MOSFET, is connected to the star point 37. It can also be connected to the output terminal 14b of the first DC converter 14 operable in switching mode.The switch 46, on the other hand, is connected to both the at least one inductor 48 and the diode 47. The diode 47 is in turn connected to a reference ground, whereas the at least one inductor 48 is connected to an output terminal 45b of the further DC converter 45, which can be operated in switching mode. The output terminal 45b is also connected to the reference ground via the at least one smoothing capacitor 49. A resistor is preferably connected to the reference ground at the output terminal 45b, via which the discharge takes place. In this exemplary embodiment, the voltage output unit 19 comprises a third diode 38, which is connected between the star point 37 and the further DC converter 45, which can be operated in switching mode.In this exemplary embodiment, the discharge unit 40 comprises a further DC converter 50 operable in linear mode, which is designed to draw energy from the DC converter 14 operable in switched mode and / or an intermediate circuit capacitor 28 arranged therein. This further DC converter 50 operable in linear mode is preferably a linear regulator. The linear regulator comprises a transistor 51 and preferably an operational amplifier 52. A collector of the transistor 51 is connected to the star point 37. It can also be connected to the output terminal 14b of the DC converter 14 operable in switched mode. An emitter of the transistor 51 is connected to an output terminal 50b of the further DC converter 50 operable in linear mode. A first input of the operational amplifier 52 serves to supply a control voltage.A second input, in particular an inverting input, of operational amplifier 52 is connected to the collector of transistor 51. By changing the control voltage, an output voltage at the emitter can be regulated to a specific target value. The linear regulator regulates to the desired output voltage more quickly than the buck converter. In this exemplary embodiment, voltage output unit 19 comprises a fourth diode 39, which is connected between star point 37 and the further DC converter 50 operable in linear mode. Transistor 51 can also be designed, for example, as an FET, e.g., as a MOSFET; in this case, the emitter terminal and the collector terminal would each be replaced by a drain and source terminal, respectively.

[0099] In the event that energy is to be extracted as quickly as possible by the discharge unit 40, both the additional DC converter 45 operable in switching mode and the additional DC converter 50 operable in linear mode can extract energy from the star point 37 or energy from the DC converter 14 operable in switching mode. This can be done in parallel using the third and fourth diodes 38, 39, with the additional DC converter 50 operable in linear mode regulating to the corresponding output voltage more quickly. Figure 5 shows, using diagrams of signals, in particular a voltage U over time t, the functioning of the voltage supply unit 12 with the DC converter 14 operable in switching mode and the DC converter 15 operable in linear mode for generating the supply voltage 20. A desired curve for the supply voltage 20 is shown in the first figure (a) of Figure 5.This is a typical supply voltage 20 for multilevel pulse operation.

[0100] An exemplary course of an arbitrary waveform is shown in the fifth figure (e), as well as in figures 1 and 2. The waveform 22 can be seen as the envelope of a high-frequency signal 21 with the arbitrary course over time t.

[0101] For an RF signal 21 with a waveform 22 as envelope, the supply voltage 20 would look different than in figure (a), namely that it would follow the waveform 22.

[0102] A portion of the first figure (a) is shown enlarged in the second figure (b). The supply voltage 20 is intended to rise to a specific value at time t1. To achieve this, the RF generator 3, in particular the local control unit of the RF generator 3, activates both the DC converter 15, which can be operated in linear mode, and the DC converter 14, which can be operated in switching mode. An example curve of the second output voltage 18b is shown in the third figure (c). At time t1, the second output voltage 18b rises very quickly to a specific setpoint. An example curve of the first output voltage 18a is shown in the fourth figure (d). At time t1, the first output voltage 18a rises more slowly to a specific setpoint than the second output voltage 18b.In this case, the second diode 36 of the voltage output unit 19 is conductive and the first diode 35 of the voltage output unit 19 is blocking, and the supply voltage 20 is formed solely by the second output voltage 18b. At time t2, the level of the first output voltage 18a exceeds the level of the second output voltage 18b. In this case, the first diode 35 of the voltage output unit 19 is conductive and the second diode 36 of the voltage output unit 19 is blocking, and the supply voltage 20 is formed solely by the first output voltage 18a. At time t2, the DC converter 15, which can be operated in linear mode, is switched off, and the amplifier unit 10 is supplied solely via the DC converter 14, which can be operated in switching mode.

[0103] This allows a very rapid change of the supply voltage 20 to be achieved, whereby the amplifier unit 10 operates equally efficiently.

[0104] The development is not limited to the described embodiments. Within the scope of the development, all described and / or drawn features can be combined with one another in any way, unless otherwise stated.

Claims

Claims 1. RF generator (3) for a plasma processing system (1) having the following features: - an amplifier unit (10) designed to amplify an RF signal; - a voltage supply unit (12) which is designed to generate a supply voltage (20) and to supply it to the amplifier unit (10); - the voltage supply unit (12) comprises a DC converter (14) operable in switching mode, which comprises an output terminal (14b), wherein the DC converter (14) operable in switching mode is designed to convert an input DC voltage supplied to it into a first output voltage (18a) and to output this at the output terminal (14b); - the voltage supply unit (12) comprises a DC converter (15) operable in linear mode, which comprises an output terminal (15b), wherein the DC converter (15) operable in linear mode is designed to convert an input DC voltage supplied to it into a second output voltage (18b) and to output this at the output terminal (15b); - the voltage supply unit (12) comprises a voltage output unit (19) having a first and a second input terminal, wherein the output terminal (14b) of the DC converter (14) operable in switching mode is connected to the first input terminal and wherein the output terminal (15b) of the DC converter (14) operable in linear mode is connected to the second input terminal, so that the The voltage output unit (19) can be supplied with the first and second output voltages (18a, 18b), and the voltage output unit (19) is designed to generate and / or output the supply voltage (20) from the first and second output voltages (18a, 18b).

2. RF generator (3) according to claim 1, characterized by the following feature: - the DC converter (14) operable in switching mode and the DC converter (15) operable in linear mode are arranged in parallel to each other.

3. RF generator (3) according to claim 1 or 2, characterized by the following feature: - the voltage output unit (19) is designed to output the higher of the first and second output voltages (18a, 18b) as the supply voltage (20).

4. RF generator (3) according to claim 3, characterized by the following feature: - the voltage output unit (19) comprises a first diode unit with at least one first diode (35) and a second diode unit with at least one second diode (36); or - the voltage output unit (19) comprises active switches.

5. RF generator (3) according to claim 4, characterized by the following features: - the first diode unit is connected by its input to the output terminal (14b) of the DC converter (14) operable in switching mode; the second diode unit is connected by its input to the output terminal (15b) of the DC converter (15) operable in linear mode; the first diode unit and the second diode unit are connected with their respective outputs to a common star point (37), which in turn is connected to the amplifier unit (10); and / or - a first active switch is connected by its input to the output terminal (14b) of the DC converter (14) operable in switching mode; a second active switch is connected by its input to the output terminal (15b) of the DC converter (15) operable in linear mode; the first and second active switches are connected by their respective outputs to a common star point (37), which in turn is connected to the amplifier unit (10).

6. RF generator (3) according to one of the preceding claims, characterized by the following feature: - the voltage output unit (19) is designed to generate the supply voltage (20) first from the second output voltage (18b) or to output the second output voltage (18b) first as a supply voltage (20) in the event of a change, in particular an increase, of a setpoint value for the supply voltage (20), in order to generate the supply voltage (20) from the first output voltage (18a) or to output the first output voltage (18a) as a supply voltage (20) at a later time.

7. RF generator (3) according to one of the preceding claims, characterized by the following feature: - the voltage supply unit (12) is designed to supply the amplifier unit (10) at the same time only via the DC converter (14) operable in switching mode or via the DC converter (15) operable in linear mode.

8. RF generator (3) according to claim 7, characterized by the following feature: - the voltage supply unit (12) is designed to switch off the DC converter (15) operable in linear mode when the amplifier unit (10) is supplied via the DC converter (14) operable in switching mode.

9. RF generator (3) according to one of the preceding claims, characterized by the following feature: - the voltage supply unit (12) is designed to control the DC converter (15) operable in linear mode in such a way that it generates the second output voltage (18b) which is below a setpoint value for the desired supply voltage (20).

10. RF generator (3) according to claim 9, characterized by the following feature: - the second output voltage (18b) is in the range of 90% to 97% of the setpoint for the desired supply voltage (20).

11. RF generator (3) according to claim 9 or 10, characterized by the following features: - the voltage supply unit (12) is designed to control the DC converter (14) operable in switching mode such that it generates the first output voltage (18a) which: a) corresponds approximately to the setpoint value for the desired supply voltage (20); and / or b) differs from the setpoint value for the desired supply voltage (20) by a difference which is smaller than a difference between the second output voltage (18b) and the setpoint for the desired supply voltage (20); and / or c) is greater than the second output voltage (18b).

12. RF generator (3) according to one of the preceding claims, characterized by the following features: - the voltage supply unit (12) comprises a discharge unit (40); - the discharge unit (40) is designed to extract energy from the intermediate circuit capacitor (28) and to discharge it into at least one discharge resistor (42) or to feed it back into a power grid in the event that the DC converter (14) which can be operated in switching mode reduces the first output voltage (18a).

13. RF generator (3) according to claim 12, characterized by the following features: - the discharge unit (40) comprises a switching unit (41) and at least one discharge resistor (42), wherein the switching unit (41) is designed to connect the discharge resistor (42) in order to dissipate energy from the DC converter (14) operable in switching mode and / or an intermediate circuit capacitor (28) arranged therein in the direction of the reference ground; or - the discharge unit (40) comprises a switching unit (41), wherein the switching unit (41) is designed to connect the DC converter (15) operable in linear mode to the output terminal (14b) of the DC converter (14) operable in switching mode, so that the DC converter (15) operable in linear mode draws energy from the DC converter (14) operable in switching mode and / or an intermediate circuit capacitor (28) arranged therein.

14. RF generator (3) according to claim 12, characterized by the following features: - the discharge unit (40) comprises a further DC converter (45) operable in switching mode, which is designed to extract energy from the DC converter (14) operable in switching mode and / or an intermediate circuit capacitor (28) arranged therein; and / or - the discharge unit (40) comprises a further DC converter (50) operable in linear mode, which is designed to extract energy from the DC converter (14) operable in switching mode and / or an intermediate circuit capacitor (28) arranged therein.

15. RF generator (3) according to one of the preceding claims, characterized by the following features: - the input DC voltage that can be supplied to the DC converter (14) operable in switching mode is the same input DC voltage that can be supplied to the DC converter (15) operable in linear mode; or - the input DC voltage that can be supplied to the DC converter (14) operable in switching mode is a different input DC voltage than that that can be supplied to the DC converter (15) operable in linear mode.

16. RF generator (3) according to one of the preceding claims, characterized by the following feature: - the DC converter (14) operable in switching mode is a buck converter or a boost converter or a combination of buck and boost converter or an Öuk converter or a SEPIC converter.

17. RF generator (3) according to one of the preceding claims, characterized by the following feature: - the voltage supply unit (12) comprises a rectifier unit (16) in order to convert an alternating voltage into the respective input direct voltage for the DC converter (14) operable in switching mode and the DC converter (15) operable in linear mode.

18. RF generator (3) according to one of the preceding claims, characterized by the following feature: - the supply voltage (20) is selected in terms of its voltage curve such that the amplifier unit (10) is designed to output an RF signal in the form of a multilevel pulse or an arbitrary waveform.

19. RF generator (3) according to one of the preceding claims, characterized by the following feature: - the amplifier unit (10) comprises at least a first and a second amplifier (10a, 10b) arranged in parallel to one another, wherein the same supply voltage (20) can be supplied to both amplifiers (10a, 10b); or - the amplifier unit (10) comprises at least a first and a second amplifier (10a, 10b) which are arranged in parallel to one another, wherein the DC converter (14) which can be operated in switching mode and the DC converter (15) which can be operated in linear mode are designed to supply the first amplifier (10a) with electrical energy and wherein the voltage supply unit (12) comprises an additional DC converter which can be operated in switching mode and an additional DC converter which can be operated in linear mode, which are designed to supply the second amplifier (10b) with electrical energy.

20. Plasma processing system (1) with at least one RF generator (3) constructed according to one of the preceding claims, characterized by the following features: - an impedance matching circuit (4) is provided which is connected to the output terminal (3a) of the RF generator (3); - a central control device (2) is provided which is designed to control the RF generator (3) in such a way that it sets the supply voltage (20) for the amplifier unit (10) to a specific value. 21 . Plasma processing system according to claim 20, characterized by the following features: - an output measuring unit (92) is provided and designed to: a) measure a power output by the RF generator (3); or b) measure a power output by the impedance matching circuit from the RF generator (3); - the central control device (2) is designed to set the setpoint value for the supply current (20) as a function of the power.

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