Impedance matching circuit and plasma supply system and method for operating

Abstract

An impedance matching circuit (11), a plasma supply system (1) having such an impedance matching circuit and a method for operating such an impedance matching circuit, in particular in such a plasma supply system having a series circuit (10) attached to a high-frequency connection (RFin), wherein the series circuit comprises at least one reactive element, in particular a capacitor (C1, C2), and at least one switching element (T1, T2) having a control input (G) to which a control circuit (12) is attached, characterized in that the control circuit is attached to an enable signal input via a coupler (13). In this way, a low switching time can be achieved with low losses in one or more switching elements.

Description

Technical Field

[0001] The present invention relates to an impedance matching circuit having a series circuit attached to a high-frequency connector (HF connector), wherein the series circuit includes at least one reactance, particularly a capacitor, and at least one switching element having a control input terminal to which a control circuit is attached.

[0002] The present invention also includes a plasma supply system having such an impedance matching circuit.

[0003] The present invention also includes a method for operating the aforementioned impedance matching circuit, particularly in the aforementioned plasma supply system. Background Technology

[0004] High frequency (HF) here refers to a frequency of 1 MHz or greater. In particular, it refers to a frequency of 10 MHz or greater.

[0005] Reactance can be an inductor, a capacitor, or a combination of both.

[0006] Impedance matching circuits are typically used in HF-excited plasma processes. HF-excited plasma processes are used, for example, for coating (sputtering) and / or etching substrates in the production of architectural glass, semiconductors, photovoltaic elements, flat panel displays, and other products. Impedance in these processes typically changes very rapidly; therefore, impedance matching must be performed very quickly (within milliseconds or less). The power of these processes ranges from several hundred W (e.g., 300 W and above) to several kW or tens of kW. At this power, the voltage within the impedance matching circuit is typically several hundred V (e.g., 300 V and above), and sometimes 1000 V and above. The current in such circuits can be several amperes, typically tens of A, and sometimes 100 A and above. Implementing impedance matching circuits under these voltage and current conditions has always been a significant challenge. The rapid variability of the reactance in such impedance matching circuits presents an additional, very high challenge.

[0007] Such an impedance matching circuit is shown, for example, in DE 10 2015 220 847 A1 and is referred to there as an impedance matching network. The reactances 18, 20, and 22 shown therein can be adjusted in a variable manner to enable impedance matching. One possibility for this variable adjustment is to connect and disconnect reactances of different values ​​using electronically controlled semiconductor switches. Reference is made to the disclosure of DE 10 2015 220 847 A1, which is the subject of this disclosure.

[0008] In such impedance matching circuits, the following requirement exists: the reactance, especially the capacitance, in the connected impedance matching circuit must be dynamically connected to the HF path. This should be achieved as quickly as possible. However, during switching, increased losses occur in the switching element, which may lead to thermal overload and damage to the switching element. Short switching times must be achieved to minimize the risk of losses and damage. Summary of the Invention

[0009] The objective of this invention is to extend the impedance matching circuit mentioned at the beginning, so as to reduce the aforementioned problems when connecting reactance, especially capacitor.

[0010] According to the invention, this task is solved by an impedance matching circuit having a series circuit attached to a high-frequency connector, wherein the series circuit includes at least one reactance, particularly a capacitor, and at least one switching element having a control input terminal to which a control circuit is attached, wherein the control circuit is attached to an enable signal input terminal via a coupler. Thus, a shorter switching time can be achieved with low loss in one or more switching elements. The control circuit is preferably configured to allow control of the control input terminal of at least one switching element, such that the state of at least one switching element can be changed, particularly by turning the switching element on and off. The coupler is used to transmit electrical signals or signal information between two separate potentials, particularly between two galvanicly separated potentials. That is, different potentials may exist at the input and output terminals of the coupler. The coupler is particularly used to transmit switching information to the control circuit. In the context of the invention, the enable signal input terminal is a signal input terminal through which the state of at least one switching element can be changed, particularly by turning the switching element on and off.

[0011] Couplers can be constructed as, for example, optical couplers, magnetic couplers, electromagnetic couplers, or electrical couplers. Magnetic couplers are also known as inductive couplers. Coupling is achieved through a changing magnetic field. For example, converters or transformers can be constructed with or without ferrite as an element to enhance induction. Electrical couplers are also known as capacitive couplers. Coupling is achieved through an electric field. A typical example used for electrical couplers is a capacitor. Electromechanical couplers can be, for example, relays or piezoelectric-based couplers.

[0012] The electrical coupler can be designed to bridge high voltages relative to ground that are greater than the HF voltage appearing in the impedance matching circuit, especially greater than the HF voltage appearing in the series circuit, and especially greater than the HF voltage appearing across at least one reactance, particularly a capacitor, and / or across at least one switching element. This high voltage can be, in particular, 300V or above, and especially 1000V or above.

[0013] Electrical couplers can be designed to decouple high frequencies corresponding to the frequency at which an impedance matching circuit is applied to the high-frequency junction during operation. HF is particularly 1 MHz or higher, especially 10 MHz or higher.

[0014] Impedance matching circuits can be designed to turn one or more switching elements on and off during operation, i.e., when a voltage is applied to the HF connector, and especially to turn off one or more switching elements when an HF current flows through them. The HF current in the flowing state can be 1A or greater, particularly 10A or greater, and preferably 100A or greater.

[0015] When the control circuitry is integrated into the coupler, a particular advantage arises. This allows for a space-saving layout.

[0016] Couplers can be constructed from discrete structural elements. For example, the coupler can be constructed as an optical waveguide combined with an optical coupler, as a transformer, converter, or capacitor, as a combination of individual components, or as a component combining multiple characteristics, such as a converter with magnetic and capacitive coupling.

[0017] Alternatively, the coupler can be constructed as an integrated circuit. In particular, the coupler can be constructed in a digital coupler circuit.

[0018] The control circuit can be constructed from discrete structural components. Alternatively, the control circuit can be constructed as an integrated circuit.

[0019] A series circuit can have two anti-serial connected transistors, particularly field-effect transistors, connected at their source potential in the case of a field-effect transistor or at their emitter potential in the case of a bipolar transistor, and located at a common source or emitter potential. A control circuit located at the common source or emitter potential, resonating with the frequency of the signal to be transmitted through an impedance matching circuit, enables rapid recharging (umladen) of the gate-source capacitance or base-emitter capacitance.

[0020] The control circuit can be attached to the supply voltage via at least one choke. This allows for decoupling of the control circuit. Preferably, two chokes are provided. In particular, one choke is provided between the connector of the supply voltage and the connector of the control circuit. The choke configuration is used to provide the average supply current of the control circuit and possibly the coupler. The choke configuration is used to prevent the transmission of fast switching edges. A fast switching edge refers to an edge duration of 1 ms or less (10% to 90%), especially an edge duration of 100 μs or less, preferably an edge duration of 10 μs or less. The chokes can also have the same inductance.

[0021] The control circuit can be attached, in particular, directly to the source or emitter potential. Specifically, the control circuit can be attached to the junction of a series circuit via a reference circuit, particularly to the source potential. The reference circuit can be configured, and especially can also be used, to bipolarly reference the supply voltage Vbias relative to the source potential. Therefore, it is not necessary to apply a negative supply voltage to the control circuit via an additional choke. The reference circuit can resonate with the frequency of the signal to be transmitted. The bipolar supply voltage facilitates faster recharging of the gate-source capacitance. Additionally, it can compensate for high-frequency signals coupled to the gate-source voltage.

[0022] The connector can be directly connected to a reference circuit. This allows the reference circuit to resonate particularly well with the frequency of the signal to be transmitted.

[0023] The reference circuit may include a voltage divider. This allows a reference to the decoupled supply voltage. The voltage divider may, in particular, have two resistors connected in series. These resistors may, in particular, have the same value.

[0024] The connection point of two resistors connected in series can be connected to the source potential, especially directly.

[0025] The reference circuit may have internal DC voltage sources, particularly two internal DC voltage sources, each of which has a capacitor. Specifically, one or more internal DC voltage sources may each consist of a single capacitor. Each capacitor may be formed by one or more capacitors.

[0026] Two internal DC voltage sources can be connected in series and, in particular, can have the same voltage.

[0027] The common connection point of two series-connected internal DC voltage sources can be connected to the source potential, especially directly.

[0028] The common connection point of two internal DC voltage sources connected in series can be connected to the voltage divider, specifically at the connection point of the two resistors in the voltage divider. Therefore, the voltages of the two voltage sources can remain constant.

[0029] The reference circuit can be attached to the supply voltage via at least one choke. The inductance of the choke can be sized such that the HF current flowing from the control circuit or reference circuit to the supply voltage is negligible.

[0030] The supply voltage can keep the voltage source at a fixed potential, which is adjusted accordingly for switching transistors.

[0031] The series circuit may have a switching transistor with a source potential located on ground.

[0032] This series circuit has at least two switching elements connected in parallel. This increases the current resistance.

[0033] Impedance matching circuits may have multiple series circuits connected in parallel, each series circuit having a control circuit attached to it.

[0034] Reactance, especially capacitance, in a series circuit can have different values.

[0035] The task is also addressed by a plasma supply system having a high-frequency power generator, a load, and the aforementioned impedance matching circuit, wherein the load is in the form of a plasma process for coating or etching a substrate, operating at a high frequency.

[0036] The task is also addressed by a plasma supply system having a high-frequency power generator, a load, and an impedance matching assembly. The load is in the form of a plasma process operating in HF for coating or etching a substrate, and the impedance matching assembly has multiple of the aforementioned impedance matching circuits.

[0037] The task is also accomplished by a method for operating the aforementioned impedance matching circuit, particularly in the aforementioned plasma supply system, the method comprising one or more of the following steps:

[0038] a) In particular, a switching element or multiple switching elements are switched on by a sufficiently large positive voltage between a control connector and a source potential, or between multiple control connectors and multiple source potentials.

[0039] b) Specifically, a switching element or multiple switching elements can be turned off by a sufficient negative voltage between a control connector and a source potential, or between multiple control connectors and multiple source potentials.

[0040] c) Applying a high voltage to the drain terminal of one or more switching elements, wherein the high voltage is numerically greater than the largest voltage between the drain terminal and the source potential.

[0041] d) Disconnect the high voltage from the drain terminal of one switching element or from the drain terminals of multiple switching elements.

[0042] Preferably, steps b) and c) of the above method can be performed simultaneously.

[0043] Preferably, steps a) and d) of the above method can be performed simultaneously.

[0044] Other advantages of the invention will become apparent from the specification and drawings. Similarly, according to the invention, the features mentioned above and further explained can be applied individually or in any combination thereof. The embodiments shown and described are not to be construed as an exhaustive enumeration, but rather as exemplary features used in the narrative of the invention. Attached Figure Description

[0045] Figure 1 A plasma supply system with impedance matching circuitry is shown.

[0046] Figure 2 This shows a portion of an impedance matching circuit;

[0047] Figure 3 The reference circuit is shown. Detailed Implementation

[0048] Figure 1A plasma supply system 1 is shown, which has a high-frequency power generator 40 attached to a load 28, particularly a plasma load, via an impedance matching circuit 11. The impedance matching circuit 11 is part of an impedance matching assembly 9. In the illustrated embodiment, the impedance matching circuit 11 includes reactances 18, 20, and 22, which are controlled by manipulation circuits 12, 14, and 16 to change their reactance values. The manipulation circuits 12, 14, and 16 are controlled by a control device 32. A measuring device 25 is attached to the control device 32, which may have measuring elements 24 and 26 for detecting, for example, current and voltage, forward and reflected power, and / or impedance values ​​and phase angles. Based on the parameters obtained by the measuring device 25, for example, the power reflected at the load 28 or the reflection factor can be determined. Reflected power occurs when a mismatch exists, i.e., when the impedance of the load 28 does not match the output impedance of the power generator 40. Alternatively or additionally, the corresponding measuring device may also be arranged at the input or inside the impedance matching assembly 9. The impedance matching assembly 10 is adapted to transform the load impedance 27 at the input of the load 28 into a transformed load impedance 29 at the input of the impedance matching circuit 11, i.e., on the generator side.

[0049] Figure 2 A portion of the impedance matching circuit 11 is shown. The series circuit 10 here includes two switching elements T1 and T2, which are configured as field-effect transistors. The switching elements T1 and T2 are connected to each other at their source potentials S, i.e., anti-series connected. Additionally, the series circuit 10 here includes capacitors C1 and C2. In a more general form, the series circuit 10 includes at least one reactance, particularly capacitors C1 and C2, and at least one switching element T1 and T2. This series circuit 10 can be... Figure 1 A portion of one of the reactances 18, 20, and 22. The reactance can be an inductor or a capacitor C1 or C2. In particular, the variable reactances 18, 20, and 22 can have multiple series circuits connected in parallel, which are constructed as in the aforementioned series circuit 10.

[0050] exist Figure 2 The arrangement shown is suitable for dynamically connecting capacitors C1 and C2 to the HF path. The connectors to the HF path are indicated by RFin and correspond to the connectors to the power generator 40.

[0051] Figure 2 The operation of the circuit can be described as follows:

[0052] If capacitors C1 and C2 are to be connected in impedance matching circuit 11, then switching elements T1 and T2 are switched on, i.e., switching elements T1 and T2 are switched to conduction. In the current case, this can be achieved by a sufficiently large positive voltage between the two control terminals G and the two source potentials S.

[0053] If capacitors C1 and C2 in impedance matching circuit 11 are to be disconnected, switching elements T1 and T2 are turned off, i.e., switched to non-conductive states. In the current case, this can be achieved with a sufficiently negative voltage between the two control terminals G and the two source potentials S. In the off state, in the defined configuration of switching elements T1 and T2, i.e., in commercially available MOSFETs, the voltage between the source potentials S and drain terminals D1 and D2 of switching elements T1 and T2 cannot be positive, because otherwise switching elements T1 and T2 might become conductive through internal parasitic diodes and could be damaged. However, since an HF voltage can be applied to switching elements T1 and T2 through terminals RFin or RFout in the non-conductive state, this HF voltage can become very high, more precisely, potentially positive or negative, and therefore this requirement must be ensured through external wiring. In the current case, external wiring can be achieved by attaching a high voltage HV. This high voltage HV can be a DC voltage. The high voltage HV should be greater than the maximum negative voltage appearing at one of the drain terminals D1 and D2. This high voltage HV can be connected through an additional switching element T3, that is, when the control circuit 12 turns off the switching elements T1 and T2, i.e. switches them to non-conductive, the additional switching element T3 is turned on during operation, i.e. switches to conductive.

[0054] The other switching element T3 and the high voltage HV can be protected from high-frequency effects by using HF filtering components, especially RL elements. In the current case, the RL elements have one resistor R1, R2 and one inductor L1, L2, which are connected in series.

[0055] When the switching element is turned on again, i.e. switched to conduction, the high voltage HV should be disconnected from the switching elements T1 and T2, i.e., the other switching element T3 should be turned off, i.e. switched to non-conductivity, so that the series circuit 10 is not subsequently loaded through the high voltage.

[0056] Figure 2 The arrangement can be implemented on a circuit board (PCB).

[0057] Switching elements T1 and T2 are controlled by control circuit 12 at its control connector G. This control circuit receives the switching signal from coupler 13, which is attached to the enable signal input. During switching, increased losses occur in switching elements T1 and T2, which may lead to thermal overload and damage to the switching elements T1 and T2. Short switching times must be achieved to minimize the risk of loss and damage.

[0058] Switching elements T1 and T2 are at a common source potential. The control circuit 12, which is located at the common source potential and resonates with the frequency of the high-frequency signal generated by the power generator 40, enables rapid recharging of the gate-source capacitance of switching elements T1 and T2.

[0059] Control circuits 12, 14, and 16 can be constructed identically. Coupler 13 can be integrated into control circuits 12, 14, and 16 or implemented in control device 32. Coupler 13 can be constructed from discrete structural components. Coupler 13 can be implemented as an optocoupler, magnetic coupler, electrical coupler, electromagnetic coupler, or any component for information transmission, particularly as a digital coupler, and especially as an integrated circuit. Control circuit 12 can be implemented from discrete structural components or integrated with coupler 13.

[0060] The control circuit 12 is supplied with a supply voltage Vbias via HF chokes L3 and L4. The control circuit 12 is decoupled via chokes L3 and L4. Chokes L3 and L4 only supply the average supply current of the control circuit 12 and possibly the coupler 13. The fast switching edge (Schaltflanken) is no longer needed via chokes L3 and L4. To prevent the voltage at the supply input of the control circuit 12, for example at the switching edge, from dropping, a reference circuit 17 can be additionally provided at the supply input of the control circuit 12. This reference circuit is configured to stabilize the voltage at the input of the control circuit 12. The additional function of the reference circuit 17 is combined with… Figure 3 To describe.

[0061] exist Figure 2 The potential represented by GND / RFout can be used as the HF output terminal. Capacitor C2 can be replaced by another switching transistor with a source potential located on GND.

[0062] exist Figure 3The reference circuit 17, shown in detail, can be configured, and in particular, used to make the supply voltage Vbias bipolar relative to the source potential. Therefore, it is not necessary to apply a negative supply voltage to the control circuit 12 via an additional choke. The reference circuit 17 can be attached to the potential of the series circuit, particularly to the source potential S. This reference circuit then oscillates at the frequency of the signal generated by the power generator 40. Such a bipolar supply voltage facilitates faster recharging of the gate-source capacitance. Additionally, the HF signal coupled to the gate-source voltage can be compensated. The reference circuit 17 does not necessarily have to generate a bipolar voltage. The connection of the potential to GND via the choke 14 to the source potential (S) is also possible.

[0063] Figure 3 Reference circuit 17 is shown. This reference circuit includes resistors R3 and R4 and capacitors C3 and C4. Reference circuit 17 has voltage dividers R3 and R4 and two internal DC voltage sources V1 and V2, each of which has a capacitor C3 and C4.

[0064] Two resistors, R3 and R4, are connected in series.

[0065] The common connection point of the two resistors R3 and R4 connected in series is connected to the source potential S.

[0066] The common connection point of the two series-connected resistors R3 and R4 is also connected to the common connection point of the two series-connected internal DC voltage sources V1 and V2.

[0067] Two internal DC voltage sources, V1 and V2, are connected in series. Each DC voltage source, V1 and V2, is composed of capacitors C3 and C4, respectively. Each capacitor, C3 and C4, can be implemented by one or more capacitors.

[0068] The common connection point of the two series-connected internal DC voltage sources V1 and V2 is connected to the source potential S.

[0069] The supply voltage Vbias can be configured as a current supply device with a fixed output voltage. This current supply device charges two capacitors C3 and C4 through chokes L3 and L4, that is, it provides charge by means of the current filtered by chokes L3 and L4. The control circuit 12 consumes this charge to control the series circuit 10.

[0070] Such impedance matching circuit 11 is also shown, for example, in DE 20 2020 103 539 U1 and is referred to there as impedance matching component 11. The reactances 18, 20, and 22 shown there are also adjustable in a variable manner to adjust the impedance matching. One possibility for this variable adjustment is to connect and disconnect reactances of different values ​​by means of electronically controlled semiconductor switches. Reference is also made to the disclosure of DE 20 2020 103539 U1, which is the subject of this disclosure. In particular, the series circuit 10 described herein can be configured as in the circuit component 116 described there.

Claims

1. An impedance matching circuit (11) having a series circuit (10) attached to a high-frequency connector (RFin), wherein, The series circuit (10) includes at least one reactor and at least one switching element (T1, T2), the switching element having a control input (G), to which a control circuit (12) is attached. The control circuit (12) is connected to an enable signal input via a coupler (13), the coupler (13) being designed to bridge a high voltage relative to ground greater than the HF voltage present in the impedance matching circuit (11) and / or the HF voltage present in the at least one switching element (T1, T2). The control circuit (12) is connected to the junction of the series circuit (10) via a reference circuit (17), the reference circuit (17) having an internal DC voltage source, wherein the internal DC voltage source (V1, V2) each has a capacitor (C3, C4).

2. The impedance matching circuit according to claim 1, characterized in that, The coupler (13) is constructed as an optical coupler, magnetic coupler, electromagnetic coupler or electrical coupler.

3. The impedance matching circuit according to claim 2, characterized in that, The coupler (13) is designed to decouple high frequencies corresponding to the high frequencies at which the impedance matching circuit is loaded on the high frequency connector (RFin) during operation.

4. The impedance matching circuit according to claim 3, characterized in that, The impedance matching circuit is designed to turn one or more switching elements (T1, T2) on and off during operation, i.e., when a voltage is applied to the high-frequency connector (RFin).

5. The impedance matching circuit according to any one of claims 1-3, characterized in that, The control circuit (12) is integrated into the coupler (13).

6. The impedance matching circuit according to claim 5, characterized in that, The coupler (13) is constructed from discrete structural elements.

7. The impedance matching circuit according to claim 5, characterized in that, The coupler (13) is constructed as an integrated circuit.

8. The impedance matching circuit according to claim 5, characterized in that, The control circuit (12) is constructed from discrete structural components.

9. The impedance matching circuit according to claim 5, characterized in that, The control circuit (12) is constructed as an integrated circuit.

10. The impedance matching circuit according to claim 5, characterized in that, The series circuit (10) has two anti-parallel transistors connected at their source terminals (S) and located at a common source potential.

11. The impedance matching circuit according to claim 5, characterized in that, The control circuit (12) is attached to the supply voltage (Vbias) via at least one choke coil (L3, L4).

12. The impedance matching circuit according to claim 10, characterized in that, The control circuit (12) is attached to the source potential.

13. The impedance matching circuit according to claim 5, characterized in that, The control circuit (12) is attached to the junction of the series circuit (10) via the reference circuit (17).

14. The impedance matching circuit according to claim 13, characterized in that, The connector point is directly connected to the reference circuit (17).

15. The impedance matching circuit according to claim 14, characterized in that, The reference circuit (17) has voltage dividers (R3, R4).

16. An impedance matching circuit, characterized in that, The impedance matching circuit has a series circuit (10) attached to a high-frequency connector (RFin), wherein the series circuit (10) includes at least one reactance and at least one switching element (T1, T2), the switching element having a control input (G), and a control circuit (12) attached to the control input. The control circuit (12) is characterized in that it is attached to an enable signal input via a coupler (13), and the control circuit (12) is attached to the connector of the series circuit (10) via a reference circuit (17), the reference circuit (17) having an internal DC voltage source, wherein the internal DC voltage source (V1, V2) each has a capacitor (C3, C4).

17. The impedance matching circuit according to claim 16, characterized in that, Two internal DC voltage sources (V1, V2) are connected in series.

18. The impedance matching circuit according to claim 17, characterized in that, The series circuit (10) has two anti-parallel connected transistors connected at their source potentials (S) and located at a common source potential, and the common connection point of the two series-connected internal DC voltage sources (V1, V2) is connected to the source potentials (S).

19. The impedance matching circuit according to claim 17, characterized in that, The reference circuit (17) is attached to the supply voltage (Vbias) via at least one choke coil (L3, L4).

20. The impedance matching circuit according to any one of claims 16-19, characterized in that, The series circuit (10) has a switching transistor with a source potential located on ground.

21. The impedance matching circuit according to any one of claims 16-19, characterized in that, The series circuit (10) has at least two switching elements connected in parallel.

22. The impedance matching circuit according to any one of claims 16-19, characterized in that, The impedance matching circuit has a plurality of series circuits (10) connected in parallel, each of which has a control circuit (12) attached to it.

23. The impedance matching circuit according to any one of claims 16-19, characterized in that, The capacitors (C1, C2) set in the series circuit (10) have different values.

24. A plasma supply system (1) comprising a high-frequency power generator (40), a load (28), and an impedance matching circuit (11) according to any one of claims 1-23, wherein the load is in the form of a plasma process for coating or etching a substrate, operating at a high frequency, wherein, The impedance matching circuit includes...

25. A plasma supply system having a high-frequency power generator (40), a load (28), and an impedance matching assembly (9), the load being in the form of a plasma process for coating or etching a substrate operating in HF, and the impedance matching assembly having a plurality of impedance matching circuits (11) according to any one of claims 1-23.

26. A method for operating an impedance matching circuit according to any one of claims 1 to 23 in a plasma supply system according to claim 24 or 25, the method comprising one or more of the following method steps: a) Connect one or more switching elements by a sufficiently large positive voltage between one control terminal and one source terminal, or between multiple control terminals and multiple source terminals. b) Turn off one or more switching elements by a sufficient negative voltage between a control terminal and a source terminal, or between multiple control terminals and multiple source terminals. c) Connect the high voltage to the drain terminal of one or more switching elements, wherein, The high voltage is numerically greater than the maximum voltage between the drain and source terminals. d) Disconnect the high voltage from the drain terminal of one switching element or from the drain terminals of multiple switching elements.

27. The method according to claim 26, wherein, Simultaneously perform method steps b) and c).

28. The method according to any one of claims 26 to 27, wherein, Simultaneously perform method steps a) and d).

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