RF Generator

Abstract

A radio frequency (RF) generator, particularly for plasma applications, includes: at least one cooling element having an upper surface and a lower surface; at least one DC power source; at least one power stage for amplifying an RF signal and connected to the upper surface of the at least one cooling element, the power stage comprising one or more power amplifiers; and a driver for feeding the power amplifiers of the at least one power stage and connected to the upper surface of the at least one cooling element; at least one DC power source connected to the power amplifiers and driver by bus bars and supplying a DC voltage V busbarが , is supplied to the power amplifier and driver through a bus bar, which is connected between ground and the bus bar, V busbar a damping network comprising a plurality of capacitors configured to shape the above transients.

Description

[Technical Field]

[0001] The present invention relates to radio-frequency (RF) generators, especially for plasma applications. [Background technology]

[0002] Plasma processing is a highly versatile and precise technique for modifying material surfaces, particularly in semiconductor chip manufacturing. Plasma processing systems use RF power signals to excite gaseous compounds, forming free electrons and ions. Various process parameters allow for precise control of the plasma composition, i.e., the amount of ions, electrons, neutrons, and various radicals. Such plasma processes are used many times in semiconductor manufacturing, preferably to deposit layers on semiconductor wafers or to etch the surface of semiconductor wafers, both with high uniformity and great precision across the entire surface.

[0003] Plasma processing tools are typically operated with RF power signals at frequencies ranging from 0.3 MHz to 300 MHz and at power levels of 50 W or greater, preferably 500 W or greater.

[0004] The use of pulsed-mode operation to modulate the envelope of the RF power signal has several advantages. In particular, the amount of power dissipated into the semiconductor wafer over a period of time can be adjusted to prevent detrimental effects on the wafer and associated materials. Furthermore, the ratio of different reactive species can be varied by power modulation, allowing different reactive species to dominate at various pulse stages. This allows for tailoring of the chemical processes occurring at the wafer surface.

[0005] Pulsed mode operation is challenging for RF generators. Typical pulse rates range from 1 Hz to 100 kHz, but can be as high as 1 MHz. As a result, the output of an RF generator must be modulated accordingly, for example, to adjust a sequence of different power levels in a repeating pattern. Rapid changes in output power can cause internal fluctuations that affect the stability of the DC power delivered to all parts of the circuit.

[0006] Ideally, the DC power supply of an RF generator provides a stable, programmable voltage to the RF power amplifier (PA) input. In fast pulse mode operation, the DC power supply operates at a constant set point and powers the PA, which generates the carrier signal. Modulation of the output power can be achieved by modulating the gate voltage of the PA via a driver circuit.

[0007] DC voltage V busbar is distributed via rails ("busbars") and fed to the RF generator's driver circuitry and the PA. Ideally, the output waveform of an RF generator operating in pulsed mode would be an amplified copy of the PA input, i.e., square edges as the power level changes with very fast rise and fall times.

[0008] In reality, there are parasitic impedances between the DC power supply and the PA. If the required output current changes suddenly due to modulation, for example, during RF turn-on and turn-off, power level changes, or periodically in pulsed mode operation, the DC voltage V at the driver and PA input will busbar This can cause transient voltage fluctuations and oscillations in the signal, resulting in additional undesirable signal modulation, such as reduced rise and fall times, overshoot and undershoot.

[0009] Overshoot and undershoot tolerances, as well as the rise and fall times required for power level changes, are typically given tolerances by the RF generator user. Additional boundary conditions and limitations on components may be required to ensure reliable, stable, and safe operation of the DC power supply and PA.

[0010] Therefore, to meet output signal specifications, component optimization is required to stabilize the RF generator output against multiple boundary conditions.

[0011] V on busbar busbar The standard solution to avoid transients is to use a bank of large electrolytic capacitors that completely suppress all voltage fluctuations, where total capacitance of 1000 μF or more, or even 2000 μF or more, is usually implemented with electrolytic capacitors, which are an easy way to provide such large capacitance in a relatively compact space. Summary of the Invention [Problem to be solved by the invention]

[0012] However, electrolytic capacitors are very sensitive in terms of reliability. To operate without failure for several years (as required in semiconductor manufacturing), their operating temperature must be kept below a specified value, which requires cooling. Due to their geometry, these capacitors cannot be properly mounted on a cold plate, and only air cooling with a fan is possible.

[0013] Power RF generators of 2 kW or more generally use water cooling, with all circuit components requiring cooling placed on a cooling plate through which water circulates. If electrolytic capacitors are used in such power generators, additional air cooling is required, which increases cost and space. Furthermore, at power levels above 2 kW, the required number of electrolytic capacitors typically fits into a 19-inch wide enclosure, but not into a 19.5-inch wide enclosure because efficient air cooling requires a certain spacing between capacitors.

[0014] Electrolytic capacitors, in particular, have a large capacitance value, so when replacing them with replacement capacitors, many more replacement capacitors are required, which have a smaller capacitance. However, the large number of replacement capacitors required necessitates a much larger space requirement than electrolytic capacitors of a similar capacitance.

[0015] Therefore, it is necessary to avoid the use of electrolytic capacitor banks in the RF generator, but at the same time, it is necessary to fit a high-power RF generator into a 1 9 / 2 inch wide enclosure.

[0016] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide an RF generator that overcomes the drawbacks of the prior art. [Means for solving the problem]

[0017] This problem is solved by a radio frequency (RF) generator according to claim 1.

[0018] The present invention provides an RF generator, particularly for plasma applications. The RF generator generates RF power and includes at least one cooling element having an upper surface and a lower surface. The cooling element may be configured as a cold plate including one or more channels or pipes through which a coolant can flow to cool the cold plate. Alternatively, the cooling element may be configured as a heat sink cooled by airflow. The RF generator further includes at least one DC power source. Preferably, the RF generator includes two or more DC power sources. One or more DC power sources may be connected to and cooled via the cooling element. Alternatively, the DC power source may be separated from the cooling element and cooled by an independent cooling element, e.g., an airflow generated by an independent fan.

[0019] The RF generator includes at least one power stage that amplifies an RF signal, the power stage being connected to the top surface of the at least one cooling element. The power stage is comprised of one or more power amplifiers (PAs). When there is more than one power stage, the RF generator may include a power combiner to combine the amplified RF signals of two or more power stages. Additionally or alternatively, each power stage may include one or more PAs, and the amplified RF signals of each PA are combined by a combiner, which may be part of the power stage or an individual component.

[0020] Therein, by connecting at least one power stage to a cooling element, the at least one power stage is efficiently cooled by the cooling element.

[0021] The RF generator further comprises a driver supplying the PA of the at least one power stage, the driver being connected to a top surface of the at least one cooling element for cooling the driver.

[0022] At least one DC power supply is connected to the PA and the driver by a bus bar, and a DC voltage V is supplied to the PA and the driver via the bus bar. busbar The busbar includes a damping network with multiple capacitors connected between ground and the busbar, and V busbar The damping network is configured to shape the transients on V busbar This reduces transient voltage fluctuations and oscillations on the power supply, improving the reliability, stability, and safety of DC power supplies, PAs, and other components, while also meeting the tolerance requirements for rise and fall times required for power level changes.

[0023] Preferably, the bus bar is at least partially constituted by a PCB connecting the DC power supply to the PA and driver, and more preferably, the bus bar is constituted entirely by a PCB.

[0024] Preferably, the busbar is at least partially configured as a metal bar or stripe. Therefore, the busbar can be configured as a combination of a PCB and a metal bar or stripe. The metal bar or stripe preferably has a width that is 10 times, more preferably 20 times, greater than the height of the stripe. In particular, the metal stripe can have a height or thickness between 0.5 mm and 3 mm, and a width between 15 mm and 30 mm.

[0025] Preferably, the busbars have an inductance of 50 nH or less, more preferably 40 nH or less. These values ​​ensure that the DC voltage V at the input of the driver and PA is busbar This can reduce the effects of transient voltage fluctuations and vibrations that occur in the

[0026] Preferably, the damping network capacitor is configured as a ceramic capacitor. Ceramic capacitors have the advantage of a longer lifespan than electrolytic or metal film capacitors, thereby improving the lifespan and operational reliability of the RF generator. Furthermore, ceramic capacitors have a high thermal tolerance, so they require less or no additional cooling.

[0027] Preferably, the ceramic capacitor is connected to a cooling element for cooling. Using a ceramic capacitor in this way allows for efficient cooling. Alternatively, if the ceramic capacitor cannot be directly connected to the cooling element, an indirect connection to the cooling element can be implemented. This indirect connection can include an array of vias connecting the solder pads of the ceramic resistor to a similar area on the bottom side of the PCB where the ceramic capacitor is attached. In this way, heat loss is distributed over a larger area of ​​the PCB. Furthermore, thermally conductive metal standoffs, spacers, or bolts to which the PCB is screwed can thermally connect specific areas of the bottom side of the PCB for cooling to the cooling element. Alternatively or additionally, convection air cooling can be used for cooling.

[0028] Preferably, the sum or total capacitance of all capacitors in the damping network is less than 200 μF, preferably less than 100 μF, more preferably less than 50 μF, even more preferably less than 10 μF, and most preferably less than 5 μF. To provide a compact size for the RF generator, particularly to accommodate RF generators in 1 9 / 2-inch enclosures, it is desirable to reduce the space required by the damping network capacitors. At the same time, reducing the capacitance of the damping network limits the current drawn from the DC power supply when loading the damping network capacitors.

[0029] As the capacitance of the damping network decreases, the time constant of the LC network of the busbar inductance and the capacitance of the damping network can become 10 μs or less. This shifts the resonant frequency to a region above the pulse frequency of the RF generator. In the prior art, when using capacitors with a total capacitance of 1000 μF or more, the resonant frequency was within the range of the pulse frequency of the RF generator.

[0030] For example, a modern damping network with a busbar inductance in the range of 20 nH to 50 nH and an electrolytic capacitor with a total capacitance of 1 mF to 5 mF will have a resonant frequency in the range of 10 kHz to 35 kHz, which is within the commonly used pulse rate range of 1 Hz to 100 kHz. In contrast, if the capacitance of the damping network according to the present invention is much smaller, for example, 2 to 10 μF, the resonant frequency will be 220 kHz to 800 kHz, which is much higher than the usual pulse rate.

[0031] When the RF power changes suddenly from one level to another in pulsed mode operation, the time constants of the overshoot and undershoot are derived from the resonant frequencies of the busbar inductance and the capacitance of the damping network. As a result, in the above example, state-of-the-art damping networks using electrolytic capacitors have time constants in the range of 30-100 microseconds, while the solution according to the present invention has time constants of 1-4 microseconds.

[0032] In the case of electrolytic capacitor solutions, such overshoots and undershoots with long time constants can be compensated for by the regulation loop controlling the RF output power. However, this is not possible in all cases, depending on the required speed of regulation. Furthermore, operating electrolytic capacitors at pulse frequencies within the above-mentioned resonance range increases ripple currents, generates heat losses, and severely impacts the lifespan of the electrolytic capacitors. This is a particular disadvantage of state-of-the-art solutions in RF generators operating in pulsed mode compared to the damping network, which has a much smaller capacitance as proposed in this invention.

[0033] The significantly reduced capacitance configurations possible with the ceramic capacitors of this invention avoid the lifespan issues of electrolytic capacitors. Because the overshoot and undershoot time constants are short, they are always much shorter than the pulse length and located near the rising and falling edges of the pulse pattern. The resistance and capacitance combination of the RC damping network is specially designed to limit the amplitude of the overshoot and undershoot to within a specified deviation from the power setting.

[0034] Because the total capacitance of the damping network is reduced, the damping network can be realized using only ceramic capacitors, improving the reliability and lifespan of the RF generator.

[0035] Preferably, one or more capacitors of the damping network constitute a damping resistor or are connected in series with a damping resistor to form an RC combination. In this way, the damping resistor provides a voltage drop across V busbar Attenuation of the above transients is achieved.

[0036] Preferably, two or more damping resistors have different resistance values, preferably all damping resistors have different resistance values, or alternatively, all damping resistors have the same resistance value.

[0037] Preferably, the capacitors of the damping network have different capacitances, where at least two capacitors of the damping network have different capacitances, or each capacitor of the damping network can have a different capacitance, thereby enabling efficient damping of transient phenomena of different time scales.

[0038] Preferably, the damping network is composed of RC combinations with different time constants. Therefore, the time constants of the combinations of capacitors and damping resistors are different for at least two RC combinations, or are different for each RC combination of the damping network. Among them, the RC combination with a smaller capacitance has a smaller resistance. In other words, the smaller the capacitance of the capacitor in the RC combination, the smaller the resistance of the resistor in the RC combination.

[0039] Preferably, the damping network is located on a separate PCB, preferably one PCB for each power stage, where the PCB may be separate from the driver PCB and / or the power stage. Using separate PCBs in this manner facilitates placement of the damping network within the RF generator housing, resulting in a compact RF generator. In particular, two or more PCBs can be stacked in a three-dimensional arrangement, resulting in a compact arrangement that fits within the RF generator's 1 9 / 2-inch wide housing.

[0040] Preferably, the PCB of the damping network is positioned above the power stage. The PCB is positioned on the opposite side of the power stage from the cooling element. In particular, the PCB is positioned at a distance from the power stage and connected to the power stage by one or more connectors, such as metal bolts, spacers, or standoffs. This allows for a compact arrangement of the damping network and facilitates connection to the power stage.

[0041] Preferably, the DC power supply is connected to the same cooling element as the power stage and / or driver, thus creating a compact RF generator and reducing the number of cooling elements required. Alternatively, the DC power supply is located on a separate cooling element. Alternatively, the DC power supply may not be connected to any cooling element of the RF generator and may be cooled by the airflow generated by the fan in the DC power supply.

[0042] Preferably, the DC power supply is located on the underside of the at least one cooling element.

[0043] Preferably, at least one cooling element has an opening for feeding a bus bar from the lower surface to the upper surface of the cooling element.

[0044] Preferably, the busbars are connected to the underside of the cooling elements and an insulating layer is disposed between the busbars and the at least one cooling element. The use of an electrically insulating and thermally conductive layer between the busbars and the at least one cooling element facilitates cooling of the busbars.

[0045] Preferably, the RF generator is comprised of two or more DC power supplies, all connected to the same busbar. In this way, the use of two or more DC power supplies can increase the available output power of the RF generator.

[0046] Preferably, the RF generator produces an RF power of 2 kW or more, more preferably 5 kW or more.

[0047] Preferably, the RF generator is disposed in a housing, which preferably has a standardized 19 / 2 inch or 19 inch size. In this way, a compact RF generator is provided.

[0048] Preferably, the busbar includes an RF decoupling network, the RF decoupling network including one or more capacitors, wherein the decoupling network functions as a low-pass filter. In particular, the capacitors are connected to ground. Preferably, the capacitors have a total or combined capacitance of less than 1000 nF, preferably less than 500 nF, and more preferably less than 250 nF.

[0049] Preferably, the driver comprises a MOSFET with a drain-gate feedback connection that connects V to the gate. busbar Preferably, the capacitor has a capacitance of less than 2000 pF, more preferably less than 1000 pF, and even more preferably less than 100 pF.

[0050] Preferably, the PA is constructed as a MOSFET, particularly a laterally-diffused metal-oxide semiconductor (LDMOS), with a drain-gate feedback connection between V busbar In particular, the capacitor has a capacitance of 2000 nF or less, preferably 500 nF or less, and more preferably 200 nF or less.

[0051] Preferably, the driver comprises an output network comprising a DC blocking capacitor, preferably having a capacitance of less than 10 nF, more preferably less than 5 nF, even more preferably less than 2 nF, wherein the output network may be disposed between the driver and the PA, in particular the gate of the PA MOSFET.

[0052] Preferably, the driver output network comprises a series RC circuit in parallel with a DC blocking capacitor, wherein the series RC circuit comprises a resistor and a capacitor connected in series, preferably the resistor has a resistance between 0.5 kΩ and 1.5 kΩ, and the capacitor of the RC circuit has a capacitance between 0.5 nF and 2 nF.

[0053] Preferably, the RF power has rise and fall times of less than 1.5 μs, more preferably less than 1 μs, where the rise and fall times are defined as a change from 10% to 90% of full power up or 90% to 10% of full power down, e.g., from a power change of 1000 W to 100 W, the time to go from 910 W to 190 W is less than 1.5 μs, preferably less than 1 μs.

[0054] Preferably, the output RF power deviates from the set point by within ±5%, which means that transient output power overshoots and undershoots stay within ±5% of the set power. [Effects of the Invention]

[0055] In this way, in the RF generator of the present invention, the V supplied from the DC power supply due to the parasitic impedance of the bus bar busbarTo reduce voltage transients, a damping network is used. This network typically consists solely of ceramic capacitors, which extends the RF generator's lifespan. However, to further compensate for the reduced capacitance of ceramic capacitors compared to, for example, electrolytic capacitors, the RF generator can be equipped with additional measures to avoid or mitigate transients and their impact on the amplified RF output. Such measures include one or more of an optimized RF decoupling network, an optimized drain-gate feedback connection in the driver and / or PA, or an optimized DC blocking capacitor between the driver and PA. In this way, the overshoot and undershoot tolerances and the required rise and fall times for power level changes in the RF generator can be met. Additional component boundary conditions and constraints can be met to ensure reliable, stable, and safe operation of the DC power supply and PA. [Brief explanation of the drawings]

[0056] In the following the invention will be explained in more detail with reference to the accompanying drawings.

[0057] The diagram shows:

[0058] [Figure 1] FIG. 1 is a schematic diagram of an RF generator. [Figure 2] 1 shows in detail a top view an RF generator according to the invention. [Figure 3] FIG. 3 is a side view of the RF generator according to FIG. 2. [Figure 4] Details of the dumping network. [Figure 5] 1 is a schematic RF generating circuit according to the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0059] 1, which shows a schematic RF generator 10. The RF generator 10 comprises at least one power amplifier (PA) 14 that amplifies an RF signal provided by a driver 20 to produce an amplified version of the RF signal at output 18 as an RF output. Connection 43 is used to provide an RF modulated input signal to the driver 20. Therein, the driver 20 and power amplifier 14 are supplied from a DC power supply 22 that is connected to the PA 14 and driver 20 via a bus bar 24. The bus bar 24 provides a DC voltage V busbar is applied to the PA 14 and driver 20. The RF generator 10 according to the present invention can output an amplified RF signal from the output 18 with an output power of 2 kW or more, preferably 5 kW or more. The RF signal has a frequency of 0.3 to 300 MHz, particularly 13.56 MHz, 27.12 MHz, 40.68 MHz, or 60 MHz. In pulsed-mode operation of the RF generator 10, the envelope of the RF output signal is shaped by variations in the driver output power. Typical pulse rates range from 1 Hz to 100 kHz, and can be as high as 1 MHz. This pulsed-mode operation can cause internal fluctuations that can affect the stability of the DC power supply and / or other components of the RF generator. In particular, V busbar There is a possibility that transient phenomena may occur in the power supply, which must be suppressed.

[0060] 2 and 3, which show the RF generator 10 in a top view and a side view, respectively. In FIG. 2, modules and components with solid borders are located above or above the cooling element 12, while modules and components with dashed borders are located below or below the cooling element 12. In the example of FIG. 2, the RF generator 10 includes a cooling element 12 configured as a cold plate, which may be cooled by water or another coolant flowing through channels within the cooling element 12. As shown in FIGS. 2 and 3, the cooling element 12 includes an upper surface 13 and a lower surface 15. A driver 20 is disposed on the upper surface 13 of the cooling element 12. Furthermore, in the example of FIGS. 2 and 3, two power stages 17 are disposed to amplify the RF signal from the driver 20. Each power stage 17 may include one or more PAs 14, and the signals of the PAs 14 of one power stage 17 may be combined by a combiner (not shown). The outputs 29 of each power stage 17 are combined in a power combiner 16 and fed to an output coupler 18 .

[0061] In the example of FIGS. 2 and 3 , two DC power sources 22 are disposed on the underside 15 of the cooling element 12. The two DC power sources 22 are connected to the busbar 24 via brackets 26. Alternatively, in other embodiments, there may be more or fewer DC power sources and / or one or more DC power sources may be at least partially disposed on the top side 13 of the cooling element 12. Thus, in the example of FIGS. 2 and 3 , the DC power sources 22, the power stage 17, the power combiner 16, and the driver 20 share a common cooling element 12. Alternatively, there may be more than one cooling element 12; for example, the DC power sources 22 may be disposed on separate cooling elements. Alternatively, one or more DC power sources may not be cooled by a cooling element, but instead may be cooled by airflow generated by a fan.

[0062] The DC power source 22 is connected to the power stage 17 by a bus bar 24. In the example of FIGS. 2 and 3, the bus bar 24 is at least partially configured as a metal strip or ribbon. The bus bar 24 is partially disposed on the lower surface 15 of the cooling element 12 and partially disposed above the upper surface 13 of the cooling element 12, with the bus bar 24 routed from the lower side to the upper side of the cooling element through an opening 35 in the cooling element. In particular, the bus bar 24 is partially disposed between the DC power source 22 and the lower surface 15 of the cooling element 12. To avoid short circuits between the bus bar 24 and the cooling element 12, an insulating layer 30 can be disposed between the bus bar 24 and the lower surface 15 of the cooling element 12. To guide the bus bar 24 from the lower surface 15 to the upper surface 13 of the cooling element 12, the cooling element 12 can define an opening 35 through which the bus bar extends toward the upper surface 13 of the cooling element 12. A substantially vertical portion 32 of the bus bar 24 extends above the power stage 17 through the opening 35.

[0063] Preferably, the bus bars 24 are connected to the individual power stages 17 by connection PCBs 28, in which the connection PCBs 28 are above and separate from the power stages 17. The connection PCBs 28 are connected to the power stages 17 by connectors 34, such as metal bolts, spacers, or standoffs, and V busbar The voltage is supplied to the power stages 17, i.e. the PA 14, in which, in particular, for each power stage 17, a separate connection PCB 28 is implemented.

[0064] In embodiments where the DC power supply 22 is located on the top side 13 of the cooling element 12 or laterally alongside the top side 13 of the cooling element 12 (i.e., the DC output is on the same side as the power stage 17 but may be located on a different cooling element, or may be located without a cooling element), the busbar may be implemented by only the connecting PCB 28, without any metal stripes.

[0065] 5, which shows a simplified circuit diagram of the RF generator 10, in which connection 44 is connected to one or more DC power supplies 22. Connection 43 may be connected to an RF signal source for providing an RF modulated signal to the driver 20. Connected to the bus bar 24 is a damping network 42, which may be located on a respective connection PCB 28. The damping network 42 is described in more detail with reference to FIG. 4. The damping network 42 may be integrated into the bus bar 24 by connectors 36, 37. The damping network 42 comprises capacitances C1, C2, ..., C i , ..., C n The damping network 42 is made up of a plurality of capacitors 40 each having a capacitance of Σ i C i is less than 200 μF, preferably less than 100 μF, and more preferably less than 50 μF. In particular, all capacitors 40 are constructed as ceramic capacitors. Ceramic capacitors are more reliable and have a longer life than electrolytic capacitors. Typically, V busbar To suppress voltage transients, the capacitance of the damping network 42 is intended to be large. Increasing the capacitance reduces the losses required to suppress resonance. Therefore, the design uses the maximum capacitance possible within the available space to minimize heat generation. However, such high capacitances could only be achieved with electrolytic or metal film capacitors, which are vulnerable to thermal stress and have a short lifespan. Therefore, the present invention proposes reducing the capacitance of the damping network 42, allowing the use of more reliable ceramic capacitors without increasing the space required for the RF generator 10. Reducing the capacitance of the capacitor 40 in the damping network 42 shortens the time constant and adjusts the resonant frequency of the damping network 42 to be higher than the operating frequency of the RF generator 10. V busbarTo dampen voltage transients and suppress overshoots and undershoots, one or more, and preferably all, of the capacitors 40 are connected in series with damping resistors 38, as depicted in FIG. 4, where the damping resistors 38 are each made up of resistors R1, R2, ..., R n It has.

[0066] Among them, for example, all the capacitances C1,...,C n may be the same or different. Similarly, all resistors R1,...,R n may be the same or different.

[0067] In a first embodiment, the resistance of resistor 38 and the capacitance of capacitor 40 are selected to be the same value as follows:

[0068] [Table 1]

[0069] In another embodiment, the capacitance and resistance of capacitor 40 and resistor 38 each have two different values. In one embodiment, the resistance and capacitance can be selected as follows:

[0070] [Table 2]

[0071] This allows different RC combinations to efficiently damp transients of different time scales. In particular, the smaller the capacitance of the capacitor 40 in the RC combination, the smaller the resistance value of the damping resistor 38 can be selected. In another example, all capacitors and all resistors have different values ​​and can be selected as follows:

[0072] [Table 3]

[0073] 4 and 5 show only one capacitor 40 and one resistor 38 for each RC combination, the resistance as well as the capacitance of a single RC combination can be formed by a combination of multiple capacitors and / or multiple resistors, respectively. Furthermore, while the above tables show specific numbers of resistors and their resistance values, and specific values ​​of capacitors and their capacitances, these are merely examples and should not be construed in any limiting sense.

[0074] By implementing the damping network 42 according to Figure 4, V busbar Voltage transients can be efficiently damped using one or more time constants.

[0075] By reducing the capacitance of the damping network 42, the space required for the ceramic capacitors is maintained and is smaller than when using electrolytic capacitors. Therefore, the RF generator can be housed in a standard 19.5 inch or 19 inch enclosure.

[0076] To further reduce the effect of transients on the RF output, the busbar 24 may have at least one capacitor 57 connected to ground and may be further connected to an RF decoupling network 58 configured as a low-pass filter made up of resistors, wherein the capacitance of the capacitor 57 may be less than 1000 nF, preferably less than 500 nF, more preferably less than 250 nF.

[0077] The driver 20 may include a MOSFET 52 including a drain-gate feedback connection 46, where the drain-gate feedback connection 46 is comprised of at least one capacitor 45. The capacitor 45 of the drain-gate feedback connection 46 may have a capacitance of less than 2000 pF, preferably less than 1000 pF, and more preferably less than 100 pF. The capacitor 45 may be combined with a resistor 47. The resistance of the resistor 47 may be 10 kΩ or less, preferably 5 kΩ or less, and more preferably 2 kΩ or less.

[0078] The driver 20 is connected to the PA 14 of the power stage 17, and at the connection thereto is disposed a DC blocking capacitor 48. Therein, the DC blocking capacitor 48 may have a capacitance of less than 10 nF, preferably less than 5 nF, and more preferably less than 2 nF.

[0079] PA 14 includes a MOSFET 56, preferably configured as an LDMOS. MOSFET 56 includes a drain-gate feedback connection 51, which may include a capacitor 49. The capacitor 49 of drain-gate feedback connection 51 may have a capacitance of 1000 nF or less, preferably 500 nF or less, and more preferably 200 nF or less. Furthermore, drain-gate feedback connection 51 may include a resistor 50, which may have a resistance of less than 1 kΩ, preferably less than 800 Ω, and more preferably less than 600 Ω.

[0080] Additional filters 60, 60' can be implemented at the output of the power stage 14 and the output of the driver 20 to shape the RF signals. Thus, according to the present invention, the use of ceramic capacitors 40 in the damping network 42 reduces the total capacitance of the damping network 42 without increasing the required space, while still providing sufficient suppression of transients on the busbar 24 and their effect on the RF output. Additional means can be implemented to provide an interference-free RF signal at the output of the RF generator, thereby ensuring a deviation of less than ±5% between the generated RF output signal and a set value corresponding to the intended RF signal power.

[0081] The solution of the present invention allows for a more reliable and stable operation of the RF generator over a longer lifetime: transient overvoltages on the included MOSFETs are kept within safe operating limits, allowing the driver as well as the PA to operate in a stable operating region.

Claims

1. A cooling element having an upper surface and a lower surface, At least one DC power supply, An RF signal is amplified, and at least one power stage is connected to the upper surface of the at least one cooling element, wherein the power stage comprises one or more power amplifiers, A driver that supplies power to the power amplifier of the at least one power stage, the driver being connected to the upper surface of the at least one cooling element, comprising: The at least one DC power supply is connected to the power amplifier and the driver by a busbar, and the DC voltage V ｂｕｓｂａｒ However, it is supplied to the power amplifier and the driver via the busbar, The busbar is connected between the ground and the busbar, and the DC voltage V ｂｕｓｂａｒ An RF generator that produces RF output for plasma applications, featuring a damping network with multiple capacitors configured to shape transient phenomena.

2. The RF generator according to claim 1, characterized in that the plurality of capacitors in the damping network are configured as ceramic capacitors.

3. The RF generator according to claim 1 or 2, characterized in that the total capacitance of all capacitors in the damping network is less than 200 μF.

4. The RF generator according to claim 1, characterized in that one or more capacitors in the damping network are provided with damping resistors or are connected in series with damping resistors to form an RC combination.

5. The RF generator according to claim 4, characterized in that two or more damping resistors have different resistance values.

6. The RF generator according to claim 4 or 5, characterized in that the damping network is composed of RC combinations having different time constants.

7. The RF generator according to claim 1, characterized in that the damping network is arranged on a separate PCB, and the damping network consists of one PCB for each power stage.

8. The RF generator according to claim 7, characterized in that the PCB of the damping network is located above the power stage.

9. The RF generator according to claim 1, characterized in that the DC power supply is located on the lower surface of the at least one cooling element.

10. The RF generator according to claim 9, characterized in that the at least one cooling element has an opening for supplying the busbar from the lower surface to the upper surface.

11. The RF generator according to claim 9 or 10, characterized in that the busbar is connected to the lower surface of the at least one cooling element, and an insulating layer is disposed between the busbar and the at least one cooling element.

12. The RF generator according to claim 1, wherein the housing is located inside a standardized 19 / 2-inch or 19-inch enclosure.

13. The RF generator according to claim 1, characterized in that the busbar constitutes an RF decoupling network, and the RF decoupling network is composed of one or more capacitors having a total capacitance of less than 1000 nF.

14. The RF generator according to claim 1, characterized in that the driver comprises a MOSFET having a drain-gate feedback connection, and the drain-gate feedback connection comprises a capacitor having a capacitance of less than 2000 pF.

15. The RF generator according to claim 1, characterized in that the power amplifier comprises a MOSFET having a drain-gate feedback connection, and the drain-gate feedback connection comprises a capacitor having a capacitance of less than 1000 nF.

16. The RF generator according to claim 1, characterized in that the driver comprises an output network having a DC blocking capacitor having a capacitance of less than 10 nF.

17. The RF generator according to claim 16, wherein the output network comprises a series RC circuit in parallel with the DC blocking capacitor, the resistance value of the resistor in the series RC circuit is 0.5 kOhm to 1.5 kOhm, and the capacitance of the capacitor in the series RC circuit is 0.5 nF to 2 nF.

Images