Patent Application
20250210306
Embodiments of the present invention relate to an energy refeeding module, to a switching circuit comprising such an energy refeeding module, to a switching embodiment comprising at least one of such a switching circuit, a plasma system comprising such a switching circuit and/or a such switching embodiment, and method of producing rectangular voltage output pulses.
Some plasma treatment applications, such as etching or layer deposition, demand a high voltage (HV), high frequency (HF), rectangular, asymmetrical, pulsed voltage supply. Often the voltage values significantly exceed the voltage handling possibilities of individual semiconductor switches, especially when high frequency operation is required. Therefore, often series connection of such switches is the only possible solution. Series connection requires voltage balancing means. These are not easily realized in HF operation.
Most plasma applications present a load, which contains a capacitive component. Significant power loss is related to the pulse-by-pulse charging and discharging process of this load capacitance. Further problems are low efficiency of pulse generators and unwanted voltage oscillation. Therefore, voltage pulses are required which have an (almost) ideal rectangular shape.
Embodiments of the present invention provide an energy refeeding module for a switching circuit with a switching unit configured to be connectable to a DC voltage source. The energy refeeding module includes a rectifying circuit configured to be connected with a positive end of a DC-side thereof to a positive connection of the DC voltage source, with a negative end of the DC-side thereof to a negative connection of the DC voltage source, and a transformer. The transformer includes a primary winding configured to be connected in series between the switching unit and an output of the energy refeeding module, and configured to have both a stray inductance and parasitic resistance low enough to lead one or a combination of the following: the high value of voltage, the high value of voltage rise, and the high current value. The transformer includes a secondary winding connected to an AC-side of the rectifying circuit.
Subject matter of the present disclosure will be described in even greater detail below based on the exemplary figures. All features described and/or illustrated herein can be used alone or combined in different combinations. The features and advantages of various embodiments will become apparent by reading the following detailed description with reference to the attached drawings, which illustrate the following:
Embodiments of the present invention provide an energy refeeding module, a switching circuit, switching embodiment, plasma processing system and a method for producing high voltage rectangular shape pulses.
According to one aspect of the invention an energy refeeding module is provided for a switching circuit with a switching unit configured to be connectable to a DC voltage source and to deliver at its output one or a combination of the following features:
According to a further aspect of the invention a switching circuit is provided, to be connected to a plasma processing load, comprising
According to a further aspect of the invention a switching circuit is provided configured to deliver high-voltage- (HV-) fast rising pulses to a plasma processing load, comprising:
Such a switching circuit allows generating voltage pulses having nearly ideal rectangular shape. In particular, unwanted voltage oscillations can be prevented. Furthermore, the efficiency of such a switching circuit is very high. If such a switching circuit is used in a high voltage pulse generator, the efficiency of the pulse generator can be increased.
The stray inductance may be 100 μH or less. In particular 10 μH or less.
The parasitic resistance may be 1Ω or less, in particular 0.1Ω or less.
High value of voltage may be 800 V or more, in particular 1.5 kV or more, especially at least 5 kV.
High value of voltage rise may be a voltage rise of at least 1 kV/μs, in particular 10 kV/μs or more, preferred 100 kV/μs or more. With voltage rise could be meant voltage fall as well.
High current value may be at least 30 A, in particular 100 A or more.
High voltage pulse signal may be a pulse signal with a high voltage as defined above, in particular with a high value of voltage rise as defined above.
The module, the units, the circuit, and/or the embodiment may be configured for a power delivery into the plasma load, in particular during a pulse, at the output of at least 10 kW, advantageously 20 kW or more.
The rectifying circuit may be connected with its positive end of the DC-side to the positive connection of the DC voltage source, with its negative end of the DC-side to the negative connection of the DC voltage source, in particular to ground potential.
The energy refeeding module, the switching circuit, and/or the switching unit may be part of a high power generator as described in EP22461510.4, filed 28 Feb. 2022, with the title “High power generator and method of supplying high power pulses”.
The transformer may be a step-up transformer. During generating the pulse the high-side switching element switch may be switched on, so the energy from the voltage source flows to the output connectable to a load, in particular a plasma load having capacitive characteristics. At the beginning of this process almost the entire voltage difference between the voltage source and the voltage on the load occurs on the primary winding of the transformer. At the secondary winding of the transformer a voltage is induced. The value of this voltage is equal to the voltage at the primary winding multiplied by the transformer ratio. If this induced voltage is higher than the supply voltage on the busbar, the rectifying components of the rectifier start to conduct. In this way, the induced voltage at the secondary winding is limited to the value of the voltage on the busbar, i.e. the supply voltage. Because of the transformer ratio, also the voltage at the primary winding is reduced (to a voltage corresponding to the voltage on the busbar divided by the ratio of the transformer). Therefore, at the beginning of charging of the load the transformer represents a relatively low impedance and allows to quickly charge the load. In this state, the transformer's magnetic core does not accumulate any energy, which could cause overvoltage on the load.
When the charging current decreases such that the voltage induced by the secondary winding is not higher than the voltage on the busbar, the current in the secondary winding stops flowing so the transformer merely acts as an inductance. This inductance of the primary winding of the transformer increases, so the current charging the load capacitance decreases. Therefore the charging process decelerates, which reduces unwanted oscillations.
Basically the same occurs when the high-side-switching element is opened and the low-side switching element is closed, i.e. during the falling flank of the output voltage pulse. In that state the energy from the load capacitance is discharged through the low-side-switching element. At the beginning of this process the voltage at the primary winding of the transformer is high enough, that some energy is returned to the busbar by the rectifying circuit.
This process is relatively fast, as the current is limited mainly by the leakage inductance of the transformer. At the end of discharging the capacitive load, the voltage at the primary winding of the transformer is low (the voltage at the secondary winding of the transformer is lower than the voltage at the busbar), so the transformer starts to behave as an ordinary inductance that limits the current and decelerates the discharging process of the load. Once again, the unwanted oscillation is relatively small because the amount of energy stored in the inductance of the transformer is small.
Because for some time some energy is returned back to the busbar and thus to the power source during charging and discharging load capacitance, this circuit has an increased overall efficiency.
The rectifying circuit may comprise one component configured to lead current only in one way, in particular a rectifying diode.
The rectifying circuit may comprise two components configured to lead current only in one way, in particular two rectifying diodes.
The rectifying circuit may comprise four components configured to lead current only in one way, in particular four rectifying diodes, in particular in a bridge circuit. In this way the rectifying circuit can be realized with cheap standard components.
An overvoltage-protecting unit, in particular an overvoltage-protecting diode, may be configured to be connected between the output and the rectifier circuit in order to protect the load against overvoltage.
At least one overvoltage-protecting unit, in particular one overvoltage-protecting diode, may be configured to be connected between the output and at least one connection of the voltage source.
As it was mentioned before, the transformer is charging itself. Therefore, it stores some energy. This can generate some overvoltage (the load capacitance would be charged to a voltage higher than that of the busbar). To avoid this, this overvoltage-protecting unit, in particular overvoltage-protecting diode, can be provided, which protects the load against overvoltage. In this way, unwanted oscillations can be prevented. A first damping resistor may be connected in series to the overvoltage-protecting unit. With that, the energy refeeding module may be even better stabilized. The first damping resistor may have a value from 1Ω to 100Ω, preferably from 20Ω to 70Ω.
A negative-voltage-protecting unit, in particular a negative-voltage-protecting diode, may be configured to be connected between the output and the ground potential in order to protect the load from negative voltage. Moreover, unwanted oscillations can be limited by adding such a negative-voltage-protecting unit, in particular a negative-voltage-protecting diode parallel to the load which prevents the load from charging to a negative voltage. A second damping resistor may be connected in series to the negative-voltage-protecting unit. With that, the energy refeeding module may be further stabilized. The second damping resistor may have a value from 1Ω to 100Ω, preferably from 20Ω to 70Ω.
A diode may be connected in parallel to one, in particular to each of the switching elements. Such, the switching elements may be protected against high voltages. This is particularly true if the switching elements comprise MOSFETS as switching parts. Each switching element may comprise one or more switching parts, for example MOSFETs or bipolar transistors.
One aspect of the invention relates to a switching embodiment with
A further aspect of the invention relates to a plasma system comprising a plasma load and a switching circuit as described in this description above, and/or a switching embodiment described in this description above. Such a plasma system may be used advantageously in semiconductor production processes, in particular for production of 3D-memory devices, such as 3D NAND-memory devices, preferred when etching deep holes for connection of the 3D-structure.
A further aspect of the invention relates to a method of producing rectangular voltage output pulses comprising the steps of:
This method allows generating voltage pulses having nearly ideal rectangular shape. Voltage overshoots and oscillations can be prevented, thus increasing efficiency.
During charging and discharging of a load capacitance connected to the output, energy is fed back to the busbar. This increases the efficiency of the switching circuit. Power loss can largely be prevented.
Oscillations may be reduced by providing diodes connected to the output.
More precise, the oscillations may be reduced by providing
Further features and advantages of the embodiments of the invention are described below on the basis of the figures of the drawing. The features shown there are not necessarily to be understood as being to scale and are shown in such a way that the special features according to embodiments of the invention can be made clearly visible. The various features can be implemented individually or in any combination.
The switching circuit 101 further comprises an energy refeeding module 15. The energy refeeding module 15 is connected with its positive end to the positive connection of the DC voltage source V1 and with its negative end to the negative connection of the DC voltage source V1. The energy refeeding module 15 is further connected to the connection point 16 between the high-side-switching element S1 and the low-side-switching element S2. The energy refeeding module 15 is further connected with the output OUT of the switching circuit 101.
The energy refeeding module 15 comprises a rectifying circuit 14 and a transformer TF1. The rectifying circuit 14 is connected with its positive end of the DC-side to the positive connection of the DC voltage source V1 and with its negative end of the DC-side to the negative connection of the DC voltage source V1, here in particular to ground potential PE. The transformer TF1 comprises a primary winding 18 and a secondary winding 19. The primary winding 18 is connected in series between the output OUT of the switching circuit 101 and the switching unit 24, in particular the connection point 16 between the high-side-switching element S1 and the low-side-switching element S2. The transformer TF1 is configured to have both, a stray inductance and parasitic resistance low enough to lead the afore mentioned high value of voltage, high value of voltage rise, and/or high current value. The secondary winding 19 of the transformer TF1 is connected with both ends to the AC-side of the rectifying circuit 14. The rectifying circuit 14 comprises four diodes DR1-DR4 connected here in a bridge circuit. The rectifying circuit 14 is connected with its DC-side to the voltage source V1 and with its AC-side to a secondary winding of a transformer TF1. The transformer TF1 may comprise a magnetic core.
Diodes D1, D2 are provided in parallel to each of the switching elements S1, S2. They may be used as freewheeling diodes and/or to protect the switching elements S1, S2 against negative voltage.
An overvoltage protection unit, embodied as a further diode D01, is connected between the output OUT and the positive connection of the voltage source V1 to protect the load against overvoltage. A negative-voltage-protecting unit, embodied as an other diode D02, is connected between the negative connection of the voltage source V1, here in particular ground potential PE, and the output OUT, i.e. in parallel to the load 12, in order to protect the load from negative voltages. These diodes D01, D02 may also reduce oscillations. Further, a first damping resistor R1 is connected in series with the overvoltage protection unit, embodies as diode D01. Further, a second damping resistor R2 is connected in series with the negative-voltage-protecting unit, embodied as diode D02. With these resistors oscillations may be reduced even better.
The operation of the switching circuit 101 is as follows. During generating of a pulse, high-side switching element S1 may be switched on so that energy from the voltage source V1 flows to the output OUT. At the beginning of this process almost the entire voltage difference between the voltage source V1 and the voltage on the load 12 occurs on the primary winding of the transformer TF1. Therefore, a voltage will be induced at the secondary winding 19 of the transformer TF1. The value of this voltage is equal to the voltage at the primary winding multiplied by the transformer ratio. If this induced voltage is higher than the voltage on the voltage source V1, the positively biased diodes DR1-DR4 of the rectifier 14 start to conduct, therefore the induced voltage at the secondary winding is limited to the value of the voltage of the voltage source V1. Because of the transformer ratio, also the voltage at the primary winding is reduced, to a voltage corresponding to the voltage on the voltage source V1 divided by the ratio of the transformer. Therefore, at the beginning of charging of the load 12 the transformer TF1 represents a relatively low impedance and allows to quickly charge the load 12. In this state, the transformer's magnetic core does not accumulate any energy, which may cause overvoltage on the load 12.
When the charging current decreases such that the voltage induced by the secondary winding is not higher than the voltage on the busbar V1, the current in the secondary winding stops flowing, so the transformer TF1 merely acts as an inductance. This inductance of the primary winding of transformer TF1 increases, so the current charging the load 12 decreases. Therefore, the charging process decelerates which reduces unwanted oscillations.
The same occurs when high-side switching element S1 is opened and low-side switching element 2 is closed, i.e. during the falling flank of the output voltage pulse. In that state the energy from the load is discharged through low-side switching element S2. At the beginning of this process the voltage at the primary winding of the transformer TF1 is high enough, that some energy is returned to the voltage source V1 by the rectifying circuit 14.
This process is relatively fast, as the current is limited mainly by the leakage inductance of the transformer TF1. At the end of discharging the load, the voltage at the primary winding of the transformer TF1 is low (the voltage at the secondary winding of the transformer TF1 is lower than the voltage at the voltage source V1). So, the transformer TF1 starts to behave as an ordinary inductance that limits the current and decelerates the discharging process of the load 12. Once again, the unwanted oscillation is relatively small because the amount of energy stored in the inductance of the transformer TF1 is small.
Every switching unit 324, 324i, . . . 324n, is connected to a corresponding voltage source V1, Vi, . . . Vn, respectively.
The series combination of switching circuits 301, 301i, . . . 301n may build a switching embodiment 311.
The switching units 324, . . . 324i, . . . 324n are connected in series with one voltage source connection point of one switching circuit 301, 301i connected to the output OUT of the next switching circuit 301i, 301n in the series connection line.
The refeeding modules 315i, . . . 315n are here optional. For the effect only one refeeding module 315 at the output of the switching embodiment 311 may be sufficient.
Every switching unit 424, 424i, . . . 424n, is connected to a corresponding voltage source V1, Vi, . . . Vn, respectively.
The series combination of switching circuits 401, 401i, . . . 401n may build a switching embodiment 411.
The switching units 424, . . . 424i, . . . 424n are connected in series with one voltage source connection point of one switching circuit 401n, 401i connected to the output OUT of the next switching circuit 401i, 401 in the series connection line.
The refeeding modules 415i, . . . 415n are here optional. For the effect only one refeeding module 415 at the output of the switching embodiment 411 may be sufficient. A switching embodiment 411 with such a realization is shown in
In
While subject matter of the present disclosure has been illustrated and described in detail in the drawings and foregoing description, such illustration and description are to be considered illustrative or exemplary and not restrictive. Any statement made herein characterizing the invention is also to be considered illustrative or exemplary and not restrictive as the invention is defined by the claims. It will be understood that changes and modifications may be made, by those of ordinary skill in the art, within the scope of the following claims, which may include any combination of features from different embodiments described above.
The terms used in the claims should be construed to have the broadest reasonable interpretation consistent with the foregoing description. For example, the use of the article “a” or “the” in introducing an element should not be interpreted as being exclusive of a plurality of elements. Likewise, the recitation of “or” should be interpreted as being inclusive, such that the recitation of “A or B” is not exclusive of “A and B,” unless it is clear from the context or the foregoing description that only one of A and B is intended. Further, the recitation of “at least one of A, B and C” should be interpreted as one or more of a group of elements consisting of A, B and C, and should not be interpreted as requiring at least one of each of the listed elements A, B and C, regardless of whether A, B and C are related as categories or otherwise. Moreover, the recitation of “A, B and/or C” or “at least one of A, B or C” should be interpreted as including any singular entity from the listed elements, e.g., A, any subset from the listed elements, e.g., A and B, or the entire list of elements A, B and C.
| Number | Date | Country | Kind |
|---|---|---|---|
| 22460041.1 | Sep 2022 | EP | regional |
This application is a continuation of International Application No. PCT/EP2023/074947 (WO 2024/056624 A1), filed on Sep. 12, 2023, and claims benefit to European Patent Application No. EP 22460041.1, filed on Sep. 12, 2022. The aforementioned applications are hereby incorporated by reference herein.
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/EP2023/074947 | Sep 2023 | WO |
| Child | 19075822 | US |
