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 power supply unit (12) is provided in order to generate a supply current (20) and supply same to the amplifier unit (10). The power supply unit (12) comprises a DC converter (14) which can be operated in a switching operation mode and which converts an input direct current supplied to the DC converter into a first output current (18a) and outputs same at an output connection (14b). The power supply unit (12) comprises a DC converter (15) which can be operated in a linear operation mode and which converts an input direct current supplied to the DC converter into a second output current (18b) and outputs same at an output connection (15b). The output connection (14b) of the DC converter (14) which can be operated in the switching operation mode and the output connection (14b) of the DC converter (15) which can be operated in the linear operation mode are connected to one another at a star point (37), as a result of which the first output current (18a) and the second output current (18b) add up to form the supply current (20).

Description

[0001] TRUMPF Hüttinger GmbH + Co. KG

[0002] RF generator for a plasma processing system and such a plasma processing system

[0003] The invention relates to an RF generator for a plasma processing system and such a plasma processing system.

[0004] 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.

[0005] 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.

[0006] "HF" is the abbreviation for "high frequency." "HF" refers to frequencies from a few tens of kHz up to the GHz range. "HF" preferably refers to frequencies from 1 MHz to 300 MHz.

[0007] 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.

[0008] RF 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 RF generator is also possible.

[0009] 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.

[0010] An RF generator for a plasma process is typically designed for an output power greater than 500 W, preferably 1 kW or more, especially 3 kW or more. For plasma processes with particularly high demands and power requirements, an output power of 10 kW or more is also possible. Controlling such power levels stably, precisely, and reliably presents a major challenge.

[0011] 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 deposit 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 and remove the contaminants on the surface. 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.

[0012] 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 can include capacitively coupled plasma (CCP) or inductively coupled plasma (ICP) systems.

[0013] 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.

[0014] 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.

[0015] 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. Advantageous developments of the RF generator and the plasma processing system are disclosed in the dependent claims and the description.

[0016] The RF generator for a plasma processing system comprises an amplifier unit configured to amplify an RF signal. Furthermore, the RF generator comprises a power supply unit configured to generate a supply current and supply it to the amplifier unit. The power supply unit comprises a DC converter operable in switching mode, which has an output terminal. The DC converter operable in switching mode is configured to convert an input direct current supplied to it into a first output current and output it 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 power supply unit also 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 an input direct current supplied to it into a second output current and to output this at the output terminal. The output terminal of the DC converter operable in linear mode can also be referred to as a second output terminal. Furthermore, the output terminal of the DC converter operable in switched mode and the output terminal of the DC converter operable in linear mode are connected to one another at a star point, whereby the first output current and the second output current are added to the supply current. Preferably, the amplifier unit is connected directly to the star point. The provision of a supply current, as well as a first or second output current, each means the provision of a current source.Current sources have the advantage that they can be interconnected at their outputs without additional circuitry. The output current is summed in such an arrangement. The current sources can operate in parallel at their outputs without affecting each other.

[0017] 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 current generated by both DC converters is used jointly to power the amplifier unit. The use of these different topologies allows the supply current to be generated particularly quickly and with good efficiency. The DC converter operable in linear mode can set the desired supply current particularly quickly, whereas the DC converter operable in switched mode generates the supply current very efficiently.

[0018] The amplitude of the 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 is always operated 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 current of the amplifier unit through the power supply unit. This makes it very easy to generate multilevel pulses or an arbitrary waveform. An arbitrary waveform signal is a signal whose envelope can follow any desired curve shape.In contrast to multi-level pulses, not only individual levels and the transitions from one level to the next can be set as an envelope, but any desired curve that can change continuously but can also jump between two values.

[0019] 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. Different pulse modes can regulate the temperature of the substrate or sample 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 "gentle" 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.

[0020] The use of a DC converter operating in linear mode allows for very rapid adjustment of the desired supply current. A DC converter operating in switching mode, for example in the form of a buck converter, can only quickly adjust the desired output current with a small output capacitance. In this case, however, the output current 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 through the combined use of a DC converter operating in switching mode and a DC converter operating in linear mode, thus enabling the supply current to be adjusted quickly and efficiently.

[0021] In one aspect, the amplifier unit is configured to generate and output multilevel pulses and / or an arbitrary waveform.

[0022] In one aspect, the amplifier unit is designed to receive an RF signal with a constant amplitude and to convert and output this signal into a multilevel pulse and / or an arbitrary waveform merely by varying the amplitude of the supply current that can be supplied to the amplifier unit.

[0023] In one aspect, the DC converter operable in linear mode reaches its preset second output current faster than the DC converter operable in switching mode reaches its preset first output current. This is especially true when both output currents are equal.

[0024] 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 current is changed in amplitude by the power supply unit.

[0025] 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.

[0026] 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.

[0027] In one aspect, the DC converter operable in linear mode is configured to generate the second output current at a level that corresponds to a difference between a setpoint supply current and the first output current. This allows the DC converter operable in switching mode to increase its first output current as quickly as desired, because the DC converter operable in linear mode can easily provide the difference through faster regulation. This achieves the maximum possible efficiency.

[0028] In one aspect, a first measuring unit is provided and arranged downstream of the output terminal of the DC converter operable in switching mode, wherein the first measuring unit is designed to measure a level of the first output current. The DC converter operable in linear mode is designed to generate the second output current as a function of the setpoint value of the supply current and the measured first output current. In one aspect, a first diode unit with at least one first diode is provided, wherein the first diode unit is arranged between the output terminal of the DC converter operable in switching mode and the star point. Additionally or alternatively, a second diode unit with at least one second diode is provided, wherein the second diode unit is arranged between the output terminal of the DC converter operable in linear mode and the star point.The use of such a diode unit ensures that current flows only from the respective output terminal to the star point, but not in the other direction.

[0029] In one aspect, the first diode unit is connected with its input to the output terminal of the DC converter operable in switched 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 the common star point, which in turn is connected to the amplifier unit. The desired supply current 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 switched 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.

[0030] In one aspect, the current output unit comprises a switching unit, wherein the switching unit is designed, depending on the switch position, to connect either the DC converter operable in switched mode or the DC converter operable in linear mode, or both DC converters at the same time, 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. In the event that the DC converter operable in switched mode generates the supply current completely itself, i.e., at the level of the predetermined target value, the DC converter operable in linear mode can be switched away from the star point.

[0031] In one aspect, a control unit, in particular a local one, is provided, which is in particular designed to measure the current at the output terminal of the DC converter operable in switching mode and the current at the output terminal of the DC converter operable in linear mode and, depending on the measured current levels, to control the DC converter operable in linear mode in such a way that it only regulates a difference between the first output current generated by the DC converter operable in switching mode and the setpoint value for the supply current or provides it as a second output current.

[0032] In one aspect, the power supply unit is designed to generate the additionally required supply current when a setpoint value for the supply current changes, in particular when it increases, first by controlling the DC converter operable in linear mode, which increases the second output current, wherein the DC converter operable in switching mode is correspondingly readjusted in the current level for the first output current.

[0033] In one aspect, the power supply unit is designed to supply the amplifier unit simultaneously via both the DC converter operable in switched mode and the DC converter operable in linear mode. This ensures that the supply current is applied very quickly at its desired level through the simultaneous use of both DC converters and that, during further operation, the DC converter operable in linear mode reduces its second output current by the amount by which the DC converter operable in switched mode increases its first output current. The reduction of the second output current occurs as soon as the sum of the first and second output currents corresponds to the predetermined target value for the supply current or deviates therefrom by less than a, in particular adjustable, threshold value.

[0034] In one aspect, the switching DC converter is configured to generate the setpoint for the supply current alone.

[0035] In one aspect, the power 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 direct current 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 current that is at or approximately at 0 A. This saves further energy.

[0036] In one aspect, the power supply unit is configured to switch off the DC converter operable in linear mode when the first output current generated by the DC converter operable in switching mode reaches the setpoint for the supply current or when the first output current deviates from the setpoint of the supply current by less than 5%, 3%, or 2%.

[0037] In one aspect, the power supply unit is designed to control the DC converter operable in switching mode such that it generates the first output current at a level that lies below a setpoint for the desired supply current. This makes it particularly easy for the DC converter operable in linear mode to apply the difference even in the presence of a ripple in the first output current and to reliably regulate the difference, ensuring that the supply current thus generated does not exceed the setpoint for the supply current. At the same time, the predominant portion of the supply current is formed by the first output current and can therefore be generated very efficiently by the DC converter operable in switching mode.

[0038] In one aspect, the first output current is in the range of 90% to 95%, 97%, or 98% of the setpoint for the desired supply current.

[0039] In one aspect, the power supply unit is configured to control the DC converter operable in switching mode such that it generates the first output current which approximately corresponds to the setpoint for the desired supply current and / or which is greater than the second output current.

[0040] 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.

[0041] In one aspect, the power supply unit comprises a discharge unit. The discharge unit is configured to extract energy from the DC converter operable in switching mode and / or an intermediate circuit capacitor arranged therein and dissipate it, e.g., to convert it into heat or feed it back into a power grid, in the event that the DC converter operable in switching mode reduces the first output current. This ensures that the new setpoint for the supply current, 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.In one aspect, the discharge unit comprises a switching unit, wherein the switching unit is designed to dissipate energy from the DC converter operable in switching mode and / or an intermediate circuit capacitor arranged therein directly towards a reference ground or indirectly, 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.

[0042] In one aspect, the discharge unit comprises a further DC converter operable in switching mode, which is configured to draw energy from the DC converter operable in switching mode and / or an intermediate circuit capacitor arranged therein. Additionally or alternatively, the discharge unit comprises a further DC converter operable in linear mode, which is configured to draw energy from the DC converter operable in switching mode and / or an intermediate circuit capacitor arranged therein.

[0043] 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.

[0044] In one aspect, the discharge unit extracts the energy at the neutral point where the supply current is applied. In one aspect, the DC converter operable in linear mode and the further DC converter operable in linear mode are configured to smooth ripple on the first output current.

[0045] 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.

[0046] In one aspect, a path between the star point and the amplifier unit is free of a discrete component, in particular in the form of a capacitance, which in particular connects the path to the reference ground.

[0047] In one aspect, the switching-mode DC converter is free of any overriding voltage regulation. This allows the initial output current to be set very quickly.

[0048] In one aspect, the DC converter operable in switching mode comprises a voltage limiting unit configured to limit an output voltage at the output terminal of the DC converter operable in switching mode to a maximum value. Such a voltage limiting unit can be formed, for example, by a Zener diode or a suppressor diode. A varistor, a voltage-regulated integrated circuit, or a transistor-based circuit can also be used for voltage limitation.

[0049] In one aspect, the power supply unit comprises a rectifier unit for generating the respective input direct current for the DC converter operable in switching mode and the DC converter operable in linear mode from an alternating current. The rectifier unit can be supplied with, for example, a single-phase alternating voltage, e.g., 230 V, or a three-phase alternating voltage, e.g., 400 V. In one aspect, the supply current is selected in terms of its current profile such that the amplifier unit is designed 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 high maximum.

[0050] In one aspect, the amplifier unit comprises at least a first and a second amplifier arranged in parallel, wherein the same supply current can be supplied to both amplifiers. Alternatively, the amplifier unit comprises at least a first and a second amplifier arranged in parallel, 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 current, and wherein the power 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 current. The first and second supply currents can be the same or different.

[0051] The 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 current for the amplifier unit to a specific target value. The supply current can be continuously changed so that the amplifier unit generates specific pulse patterns or an arbitrary waveform. In one aspect, an output measuring unit is provided and designed to measure a power output by the RF generator or to measure a power received by the impedance matching circuit from the RF generator. The central control device is designed to set the target value for the supply current as a function of the power.The power output by the RF generator is higher than the power input by the impedance matching circuit. The power input by the impedance matching circuit does not include the portion of the power reflected back toward the RF generator.

[0052] The development is described below purely by way of example with reference to the drawings. They show:

[0053] Figure 1 : an embodiment of the plasma processing system with a

[0054] RF generator;

[0055] Figure 2: an embodiment of the RF generator;

[0056] Figure 3: another embodiment of the RF generator;

[0057] Figure 4: an embodiment of a power supply unit with a

[0058] A DC converter operable in switching mode and a DC converter operable in linear mode;

[0059] Figure 5: an embodiment of the DC-

[0060] converter with a discharge unit; and

[0061] Figure 6: another embodiment of the discharge unit. Figure 1 shows a plasma processing system 1, which includes a central control device 2. The plasma processing system 1 further includes 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 includes 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 includes 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 can comprise one or more cables, for example, connected in series and / or in parallel. Coaxial cables are preferably used.

[0062] 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.

[0063] 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.

[0064] 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.

[0065] 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.

[0066] 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 transmitted from the RF generator 3 toward the impedance matching circuit 4 and to measure a power 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.

[0067] 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.

[0068] 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.

[0069] 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 operating unit 93. Additionally or alternatively, the frequency of the high-frequency signal 21 and / or the waveform 22 of the high-frequency signal 21 and / or the pulse rate and / or the pulse duration for the high-frequency signal 21 can be received by the operating unit 93. A desired impedance at the output terminal 4b of the impedance matching circuit 4 can also be received via the operating 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. An exemplary course of an arbitrary waveform is shown 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.

[0070] 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 power supply unit 12.

[0071] 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.

[0072] The Combiner 13 is preferably a Wilkinson Combiner or a hybrid Combiner.

[0073] In principle, it is conceivable that the amplifier unit 10 comprises more than two amplifiers 10a, 10b.

[0074] Preferably, the first amplifier 10a is constructed identically to the second amplifier 10b.

[0075] 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. 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.

[0076] 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.

[0077] In principle, it is also conceivable that the signal generation unit 11 comprises a separate signal source for each amplifier 10a, 10b.

[0078] 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 2, which in turn receives an input from the operating unit 92.

[0079] The power supply unit 12 comprises a DC converter 14 operable in switching mode and a DC converter 15 operable in linear mode.

[0080] An input direct current 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 direct current into a first output current 18a. The DC converter 15, which can be operated in linear mode, converts this input direct current into a second output current 18b. The first and / or second output current 18a, 18b can be lower or higher than the respective input direct current. In order to generate the corresponding input direct current, the power supply unit 12 comprises a rectifier unit 16. In this case, a 3-phase alternating voltage 17, in particular of 400 V, can be supplied to the rectifier unit 16. The rectifier unit 16 is preferably a full-bridge rectifier with 6 diodes in order to rectify the 3-phase alternating voltage 17.Both the positive and negative half-waves of each phase are rectified. To smooth the direct current and reduce voltage and current ripples, the rectifier unit 16 can include at least one filter, in particular an intermediate circuit capacitor 28.

[0081] The power supply unit 12 comprises a star point 37, from which the first output current 18a and the second output current 18b are added and form the supply current 20.

[0082] The star point 37 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 current 20 to be supplied to the first amplifier 10a and the second amplifier 10b of the amplifier unit 10.

[0083] 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 current can be pulsed or have an arbitrary waveform, whereby the amplified RF signal at the output of the RF generator 3 is also a multilevel pulse signal or an arbitrary waveform signal.

[0084] The DC converter 14, which can be operated in switching mode, and the DC converter 15, which can be operated in linear mode, are arranged in parallel. The DC converter 15, which can be operated in linear mode, is designed to generate the second output current 18b at a level that corresponds to a difference between a setpoint value of the supply current 20 and the first output current 18a.

[0085] Basically, the power supply unit 12 is designed to supply the amplifier unit 10 at the same time via the DC converter 14 operable in switching mode and via the DC converter 15 operable in linear mode.

[0086] The current setpoint for the supply current 20 can be supplied to the RF generator 3 via the central control device 2. The RF generator 3 can also be configured to calculate the setpoint for the supply current 20 from a desired power at the output of the RF generator 3. Such a power can be supplied via the central control device 2.

[0087] Figure 3 shows another embodiment of the RF generator 3. Figure 3 describes the operation of the power supply unit 12 in more detail. Control connections, which can carry analog or digital signals, are shown in dashed lines. Reference to a control voltage also includes a control current.

[0088] An input direct current is supplied via the rectifier unit 16 to the DC converter 14, which can be operated in switching mode, and to the DC converter 15, which can be operated in linear mode.

[0089] A first measuring unit 60 is provided, which is arranged at the output terminal 14b of the DC converter 14 operable in switching mode. The first measuring unit 60 is designed to measure a level of the first output current 18a. The measurement signal from the first measuring unit 60 is fed to a differential amplifier 61. The measurement signal is preferably fed to an inverting input of the differential amplifier 61. The DC converter 15 operable in linear mode is designed to generate the second output current 18b as a function of the setpoint value of the supply current 20 and the measured first output current 18a. For this reason, the setpoint value of the supply current 20 is fed to the differential amplifier 61. This is preferably fed to the non-inverting input of the differential amplifier 61. An output of the differential amplifier 61 is connected to the DC converter 15 operable in linear mode.The DC converter 15, which can be operated in linear mode, generates a second output current 18b, the magnitude of which corresponds to a difference between the setpoint value of the supply current 20 and the first output current 18a.

[0090] Units of measurement that measure current may be marked in the figures with an arrow and the letter “I”.

[0091] The setpoint for the supply current 20 can be received directly from the central control device 2. However, the setpoint for the supply current 20 can also be provided by a local control unit 62 of the RF generator 3. This local control unit 62 is connected to the higher-level central control device 2 in Figure 3.

[0092] Furthermore, in this exemplary embodiment, a second measuring unit 63 is provided, which is arranged at the output terminal 15b of the DC converter 15 operable in linear mode and upstream of the star point 37. The second measuring unit 63 is designed to measure the second output current 18b and to transmit the measured second output current 18b to the DC converter 15 operable in linear mode.

[0093] In this exemplary embodiment, a third measuring unit 64 is also provided, which is arranged between the star point 37 and the amplifier unit 10. The third measuring unit 64 is designed to measure the supply current 20. The measured supply current 20 can be transmitted to the local control unit 62. Depending on the measured supply current 20 and the setpoint for the supply current 20, the local control unit 62 is designed to adjust the setpoint for the supply current 20. In principle, the measured supply current 20 can also be transmitted to the central control device 2.

[0094] In this exemplary embodiment, a power of the RF signal Pi output from the amplifier unit 10 and a power of the RF signal Pr reflected back into the amplifier unit 10 are also measured. This result is transmitted to the local control unit 62. It could also be transmitted to the central control device 2. Depending on this result, the setpoint for the supply current 20 can be adjusted. These power values ​​can be measured with the output measuring unit 92 or with another measuring unit, which is arranged, for example, in the housing of the RF generator 3.

[0095] Figure 4 shows an embodiment of the power supply unit 12 with the DC converter 14 operable in switching mode and the DC converter 15 operable in linear mode.

[0096] 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 direct current 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 current 18a is applied to the output terminal 14b.

[0097] 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. 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 diode 26. The at least one intermediate circuit capacitor 28 ensures that the first output current remains largely constant and is not influenced by the switching operations of switch 25. The first output current 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 current 18a approaches the input current.

[0098] Such a buck converter operates very efficiently, especially at low output currents. It is also very compact, and the first output current 18a can be easily varied by changing the duty cycle. Control is preferably performed 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. Preferably, no overlying voltage regulation is provided. This makes the buck converter very fast.

[0099] Preferably, the buck converter also comprises overcurrent protection, overtemperature protection and / or undervoltage protection and / or overvoltage protection.

[0100] The first measuring unit 60, which measures the first output current 18a, is arranged at the output terminal 14b. Depending on the magnitude of the first output current 18a, the switch 25 is controlled accordingly. Not shown is that the first measuring unit 60 can also be connected to the differential amplifier 61 (see Figure 3) in this case.

[0101] If the first output current 18a is to be as smooth as possible, the settling time for modern plasma processes is often no longer sufficient. The power supply unit 12 therefore 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.

[0102] 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 current 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, in particular a non-inverting input, 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. In particular, an output of the second measuring unit 63 is connected to the second input of the operational amplifier 31. By changing the control voltage, the second output current 18b at the emitter can be regulated to a specific target value.The linear regulator regulates to the desired output current 18b more quickly than the buck converter. However, the switching losses are higher than with the buck converter, especially for low output currents 18b relative to the supplied DC input current.

[0103] Furthermore, a first diode unit with at least one first diode 35 and a second diode unit with at least one second diode 36 are provided. 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 the 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 summed supply current 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.

[0104] Because the DC converter 15 operable in linear mode reaches the setpoint for the second output current 18b more quickly than the DC converter 14 operable in switching mode, when a desired change in the supply current 20 is required, the supply current 20 is initially formed predominantly from the second output current 18b. At a later point in time, the first output current 18a then exceeds the level of the second output current 18b, whereby from this point onward the DC converter 14 operable in switching mode takes over the predominant supply of the amplifier unit 10. The second output current 18b can be continuously reduced further the more the first output current 18a increases toward the setpoint for the supply current 20.

[0105] Preferably, the DC converter 14 operable in switching mode is designed to generate the first output current 18a at a level that is greater than 90% of the setpoint for the supply current 20 and less than the supply current 20, wherein the DC converter 15 operable in linear mode is designed to continuously adjust a level of the second output current 18b to the difference between the first output current 18a and the setpoint for the supply current 20. As a result, no supply current 20 is output that is higher than its setpoint, or the supply current 20 only minimally exceeds its setpoint. The DC converter 15 operable in linear mode is also designed to compensate for ripples in the course of the first output current 18a. Therefore, in particular, no capacitance is required at the input of the amplifier unit 10, whereby very fast multilevel pulses or a very rapidly changing arbitrary waveform can be set.

[0106] Figure 5 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 current 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 current 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.

[0107] Figure 6 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 further DC converter 45 can comprise 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 operable in switching mode. The output terminal 45b is also connected to the reference ground via the at least one smoothing capacitor 49. A resistor to reference ground, via which the discharge takes place, is preferably connected to the output terminal 45b. In this exemplary embodiment, a third diode 38 is provided, which is connected between the star point 37 and the further DC converter 45 operable in switching mode. The switch 46 is preferably controlled as a function of the current flowing into the further DC converter 45 operable in switching mode.

[0108] 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 current at the emitter can be regulated to a specific target value. The linear regulator regulates to the desired output current more quickly than the additional DC converter 45, which can be operated in switching mode. In this exemplary embodiment, a fourth diode 39 is provided, which is connected between star point 37 and the additional DC converter 50, which can be operated 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.

[0109] In the event that energy is to be extracted as quickly as possible by the discharge unit 40, both the further DC converter 45 operable in switching mode and the further 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.

[0110] Diodes 35, 36, 37 and / or 38 are only optional.

[0111] 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 power supply unit (12) designed to generate a supply current (20) and to supply it to the amplifier unit (10); - the power 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 direct current supplied to it into a first output current (18a) and to output this at the output terminal (14b); - the power 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 direct current supplied to it into a second output current (18b) and to output this at the output terminal (15b); - the output terminal (14b) of the DC converter (14) operable in switching mode and the output terminal (14b) of the DC converter (15) operable in linear mode are connected to one another at a star point (37), whereby the first output current (18a) and the second output current (18b) add up to the supply current (20).

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 one another.

3. RF generator (3) according to claim 1 or 2, characterized by the following feature: - the DC converter (15) operable in linear mode is designed to generate the second output current (18b) at a level that corresponds to a difference between a desired value of the supply current (20) and the first output current (18a).

4. RF generator (3) according to one of the preceding claims, characterized by the following features: - a first measuring unit (60) is provided and arranged at the output terminal (14b) of the DC converter (14) operable in switching mode, wherein the first measuring unit (60) is designed to measure a level of the first output current (18a); - the DC converter (15) operable in linear mode is designed to generate the second output current (18b) as a function of the setpoint value of the supply current (20) and the measured first output current (18a).

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

6. RF generator (3) according to one of the preceding claims, characterized by the following feature: - the power supply unit (12) is designed to switch off the DC converter (15) operable in linear mode when the amplifier unit (10) is completely supplied via the DC converter (14) operable in switching mode.

7. RF generator (3) according to one of the preceding claims, characterized by the following feature: - the power supply unit (12) is designed to switch off the DC converter (15) operable in linear mode when the first output current (18a) generated by the DC converter (14) operable in switching mode reaches the setpoint value for the supply current (20) or is less than 5%, 3% or 2% lower than the setpoint value of the supply current (20).

8. RF generator (3) according to one of the preceding claims, characterized by the following feature: - the DC converter (14) operable in switching mode is designed to generate the first output current (18a) at a level that is greater than 90% of the setpoint value for the supply current (20) and less than the supply current (20), wherein the DC converter (15) operable in linear mode is designed to continuously adapt a level of the second output current (18b) to the difference between the first output current (18a) and the setpoint value for the supply current (20).

9. RF generator (3) according to one of the preceding claims, characterized by the following features: - the power supply unit (12) is designed to control the DC converter (14) operable in switching mode in such a way that it generates the first output current (18a) which: a) approximately corresponds to the setpoint for the desired supply current (20); and / or b) is greater than the second output current (18b).

10. RF generator (3) according to one of the preceding claims, characterized by the following features: - the power supply unit (12) comprises a discharge unit (40); - the discharge unit (40) is designed to extract energy from the DC converter (14) operable in switching mode and / or an intermediate circuit capacitor (28) arranged therein and to dissipate it or to feed it back into a power grid in the event that the DC converter (14) operable in switching mode reduces the first output current (18a).

11. RF generator (3) according to claim 10, characterized by the following features: - the discharge unit (40) comprises a switching unit (41), wherein the switching unit (41) is designed to dissipate energy from the DC converter (14) operable in switching mode and / or an intermediate circuit capacitor (28) arranged therein directly or via a discharge resistor (42) towards 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.

12. RF generator (3) according to one of the preceding claims 10 or 11, 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.

13. RF generator (3) according to one of the preceding claims, characterized by the following feature: - the DC converter (15) operable in linear mode and the further DC converter (50) operable in linear mode are designed to smooth ripples on the first output current (18a).

14. RF generator (3) according to one of the preceding claims, characterized by the following feature: - a path between the star point (37) and the amplifier unit (10) is free of a discrete component, in particular in the form of a capacitance.

15. RF generator (3) according to one of the preceding claims, characterized by the following feature: - the DC converter (14) which can be operated in switching mode is free from any superimposed voltage regulation.

16. RF generator (3) according to one of the preceding claims, characterized by the following feature: - the DC converter (14) operable in switching mode comprises a voltage limiting unit which is designed to set an output voltage at Output terminal (14b) of the DC converter (14) operable in switching mode to be limited to a maximum value.

17. 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.

18. RF generator (3) according to one of the preceding claims, characterized by the following feature: - the supply current (20) is selected in terms of its current profile 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 current (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 power supply unit (12) comprises an additional DC converter (14) which can be operated in switching mode and an additional DC converter (15) 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 current (20) for the amplifier unit (10) to a specific target 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.

Images