Method for supplying power to a plasma or laser, and plasma system or laser system

Abstract

A method of supplying power to a processing plasma or a laser in a discharge chamber (30), comprising: a. supplying power from an output port (24) of a balanced amplifier (12) to the discharge chamber (30), wherein the balanced amplifier (12) includes at least two amplifier path portions (14, 16) each supplying a signal to a coupler (22), the coupler (22) having an output port (24) and an isolation port (26), configured to combine signals depending on the phase relationship of the signals and supply power to the output port (24) and / or the isolation port (26) depending on the phase relationship of the signals; b. setting a first phase relationship of the signals for a predetermined time to initiate the plasma or the laser; and c. setting a second phase relationship different from the first phase relationship to operate the laser or maintain the plasma in the discharge chamber (30).

Description

Technical Field

[0001] The present invention relates to a method for supplying power to a processing plasma or a laser in a discharge chamber. Further, the present invention relates to a plasma system or a laser system including a discharge chamber and a balanced amplifier.

Background Art

[0002] A processing plasma, that is, a work processing plasma, that is, for example, in an industrial plasma device for semiconductor manufacturing, a plasma for etching or coating a work is often excited in a discharge chamber, also called a plasma chamber, using high-frequency energy having a frequency of 2 MHz or more and high power of, for example, 3 kW or more. In order to ignite the plasma as quickly as possible, it is known to apply full operating power using a higher voltage to the plasma device for plasma ignition. Similarly, such high-frequency energy is used to supply power to a laser in a discharge chamber. Such lasers are also used, for example, for cutting and melting metals, glass, semiconductors, and for generating EUV light sources for lithography in semiconductor manufacturing.

[0003] To generate high-frequency energy, an amplifier or an inverter operated by a transistor for amplification of a high-frequency signal is used. Here, an amplifier means an amplifier that mainly operates in the linear region and partly operates in compression, that is, typically operates in operation modes A, AB, B, or C. Here, an inverter mainly operates in a switching operation, that is, typically operates in operation modes D, E, F, inverse F (F -1It refers to an inverter that operates in a low-power region (sometimes abbreviated as ), or similar. Amplifiers or inverters that operate like amplifiers in the low-power region and like inverters in the high-power region are often used to generate high-frequency energy, so below, the term "amplifier" will be used to refer collectively to both types of inverters and amplifiers. Since the required power is often greater than the power that can be generated by one transistor, one pair of transistors, or four transistors connected for a full bridge, multiple amplifiers are often connected via couplers that combine the power of the individual amplifiers. This is often done by power couplers with special characteristics, so-called 3dB couplers, as well as 90° couplers, orthogonal couplers, or hybrid couplers.

[0004] Such a configuration is characterized in that the power-coupled amplifier operates with a 90° phase offset during normal operation. Therefore, the coupler is designed to couple power at its output only when the power signal at its input is phase-shifted by 90°. Such a coupled amplifier is typically called a "balanced amplifier." If the power signal at the input of such a coupler is not phase-shifted by 90°, depending on the phase state, a significant portion of the power applied to the coupler's input is supplied to a compensating resistor connected via a fourth port, resulting in losses and heat generation. This compensating resistor is also called a load compensating resistor, termination resistor, compensating load, or power loss device.

[0005] One of the problems with such balanced amplifiers often arises when attempting to ignite a gas discharge. In a balanced amplifier, the output power is flat across the complex load plane, meaning it is essentially constant. Generating a power peak (peaking) for ignition is difficult. Until now, pseudo-peaking could only be achieved by selecting a higher DC supply voltage. However, generating a high DC supply voltage for a power peak is very costly.

[0006] Patent Document 1 describes an ignition method in which high power is generated at the output for ignition by setting a 90° condition for the orthogonal coupler only during ignition. Furthermore, an amplifier actually configured as a "balanced amplifier" operates as a "balanced amplifier" with a 90° phase offset only in ignition mode, and operates in a different phase state during normal operation. This means that in this operating method, only a portion of the power present at the input is coupled to the output, and the remaining power is coupled to a compensation resistor via the isolation port of the balanced amplifier, where it is converted into heat. This is clearly a very lossy method. In particular, the intentionally controlled energy loss during normal operation, i.e., during operation, has a very negative impact on efficiency. This is not a desirable method, especially for high power. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] German Utility Model Specification No. 202017103327U [Patent Document 2] U.S. Patent No. 7512387B2 [Patent Document 3] U.S. Patent No. 7452443B [Patent Document 4] U.S. Patent No. 7745955B2 [Patent Document 5] U.S. Patent No. 10026593B2 [Patent Document 6] International Publication No. 2011 / 110652A1 Pamphlet [Patent Document 7] German Patent Application Publication No. 102011086557B4 Specification [Patent Document 8] German Patent Application Publication No. 102013226537A1 Specification [Overview of the Initiative] [Problems that the invention aims to solve]

[0008] The object of the present invention is to provide a method and apparatus that can achieve reliable ignition of a plasma or laser while maintaining high efficiency during normal operation when using a balanced amplifier. [Means for solving the problem]

[0009] This problem is solved by the method for supplying power to a processing plasma or laser in a discharge chamber according to the present invention. In this method, a. Power is supplied to the discharge chamber from the output port of a balanced amplifier, and in this case, the balanced amplifier includes at least two amplifier paths, each supplying a signal to a coupler, the coupler having an output port and an isolation port, and is configured to couple signals depending on the phase relationship of the signals and to supply power to the output port and / or isolation port depending on the phase relationship of the signals. b. Setting a first phase relationship of the signal for a predetermined time in order to ignite a plasma or laser, c. Setting a second phase relationship different from the first phase relationship in order to operate the laser or to maintain the plasma in the discharge chamber, and in doing so, i. Set a second phase relationship such that the coupler essentially supplies all power to the output port and essentially does not supply power to the isolated port, or ii. The first phase relationship is set such that the power reflected from the discharge chamber to the balanced amplifier is large enough to ignite and is reflected back from the balanced amplifier to the discharge chamber.

[0010] Here, "basically" means that reasonable efforts are made to achieve these values ​​within the tolerance range of the coupler and phase setting. In this case, if a better setting cannot be reasonably achieved within the range of the amplifier, 5-10% of the power may be supplied to the isolated port. According to the present invention, it is therefore intended to set two different phase relationships between signals supplied to the coupler. The first setting is used to ignite the plasma or laser, and the second setting is used to maintain the plasma or laser. In this case, the first setting can be shorter in duration than the second setting. Here, the phase relationship is the phase state, or phase difference, between the phases of two signals. A change in the phase relationship can be made, for example, by changing the phase of one or more signals so that the phase state between the two signals is different from before. In particular, when igniting the plasma or laser, the amplifier can be made to operate as an unbalanced amplifier, or like an unbalanced amplifier, by combining the first setting and mismatch described above.

[0011] In the event of mismatch, in the second setting, i.e., when the balanced amplifier is operating with a 90° phase offset, the power reflected by the discharge chamber returns to the amplifier via the coupler's output port. Most of this power is reflected again. However, in the reverse phase state, this reflected power does not return to the output port, i.e., the discharge chamber, but instead goes to the connected compensation resistor via the isolation port. This prevents power peaks from occurring on the wiring and plasma. This is highly desirable for normal operation, and therefore, balanced amplifiers operating in discharge chambers typically have a very high tendency to respond to rapid and unpredictable impedance changes, and thus have a relatively high proportion of reflected power, especially in pulsed operation, making them very popular with operators of processing plasmas or lasers.

[0012] However, if a phase offset is set, for example to 45°, the power reflected back from the amplifier and the power generated in the amplifier are added together, and a power peak may occur for certain mismatches. This is undesirable as it can lead to instability in the discharge operation. However, this power peak can be used to the advantage of ignition. Therefore, in this method, it is advantageous if an unignited state is recognized or predicted. The phase is then appropriately set so that ignition of the discharge is obtained during the period when this state is confirmed or predicted. This is because, during this period, a sufficiently large proportion of the power reflected from the discharge chamber to the balanced amplifier is reflected back from the balanced amplifier to the discharge chamber for ignition. As an unfavorable effect, some of the generated power is directed through the isolation port to the compensation resistor connected thereto and converted into heat. However, since this setting, i.e., this state, is maintained for only a very short time, energy loss is kept low. Subsequently, in the next state which lasts for a considerable period of time, the phase is set to normal operation, i.e., 90°, in which case the coupler essentially supplies all power to the output port, i.e., the discharge chamber, and essentially no power to the isolation port. Then, power is supplied to the output port only for the duration of the initial ignition state. This is far more economical than the solution proposed in, for example, Patent Document 1.

[0013] This method is particularly advantageous for pulsed operation with pulse frequencies ranging from 10 kHz to 500 kHz. Since the plasma in the discharge chamber often completely extinguishes during the interval between pulses, the discharge must be reignited with each new pulse. This can be advantageously accomplished using the method described above.

[0014] The signal may have a frequency in the range of 1 MHz to 4,000 MHz, particularly in the range of 1 MHz to 200 MHz. Furthermore, the signal may have a power of 1 kW or more, particularly in the range of 1 kW to 3,000 kW, preferably in the range of 1 kW to 3 kW.

[0015] The first phase relationship can be selected such that there is a mismatch from the balanced amplifier to the plasma or laser, or the discharge chamber. In the case of a mismatch, the power reflected in the discharge chamber is also reflected in the switching or amplification element (especially the transistor) of the amplifier, and most of it is consumed in the resistor connected to the isolation port. In the case of a mismatch, by setting the first phase relationship, superposition of the reflected power and the power generated by the amplifier becomes possible. As a result, power greater than the power normally generated at a 50-ohm load can be generated. This power can be used for igniting the plasma or laser.

[0016] The second phase relationship can be selected such that 50% or more, especially 80% or more, of the combined power is directed towards the output port. This corresponds to the normal operation where the phase relationship of the signal is set so that as much power as possible is supplied to the output port.

[0017] The predetermined time is in the range of 0.1 to 10000 μs, preferably in the range of 1 to 1000 μs, or can be selected. Therefore, the first phase relationship can be set only for a relatively short period. This is sufficient for igniting the plasma or laser.

[0018] As described above, the power peak achievable by this method can occur particularly at very specific reflection coefficients. The reflection coefficient is usually a complex number and has a real part and an imaginary part. The reflection coefficient can be represented, for example, on a Smith chart. The reflection coefficient varies along the length of the wiring. This can be graphically confirmed, for example, as a displacement within the Smith chart. Thereby, the wiring length between the balanced amplifier and the discharge chamber or impedance matching device (which can be connected before the discharge chamber) can be used to positively influence ignition when there is a predetermined phase angle between the amplifier path sections and a predetermined reflection in the non-ignited state. The length of the wiring between the balanced amplifier and the discharge chamber or impedance matching device (which can be connected before the discharge chamber) can be set such that the reflection coefficient of the non-ignited plasma or laser discharge is changed, thereby causing the reflection coefficient seen from the balanced amplifier to approach and particularly match the power peak.

[0019] As a coupler, a 3dB coupler, particularly a 90° hybrid coupler, can be used. With a 3dB coupler, two 90° phase-shifted input signals can be combined, whereby the combined power is output at the output port and no power is output at the isolation port. At that time, the amplifier path sections that generate the signals are decoupled and do not affect each other. The 3dB coupler itself can ideally be lossless. This means that the power of the two amplifier path sections can be fully supplied to the load (plasma or laser) connected to the output port.

[0020] For the maintenance of the plasma or laser, a 90° phase state can be set between the signals. Particularly, by connecting with a 3dB coupler, maximum power can be supplied to the plasma or laser.

[0021] For ignition of plasma or laser, phase states different from 90° can be set between signals, preferably in the range of 5° to 85°, or 95° to 175°, preferably in the range of 40° to 50°, or in the range of 130° to 140°, most preferably in the range of 45° or 135°. In particular, power peaks can be generated at phases of 45° and 135°. These power peaks occur, for example, when the magnitude of the reflection coefficient is greater than 0.8 and the phases of the reflection coefficient are -90° and 90°.

[0022] Within the scope of the present invention, a plasma system or a laser system is included, and such plasma system or laser system is a. Discharge chamber and b. A balanced amplifier connected to a discharge chamber, the balanced amplifier including a coupler and at least two amplifier paths supplying signals to the coupler, wherein the coupler has an output port and an isolation port, and is configured to couple the signals depending on the phase relationship of the signals and to supply power to the output port and / or isolation port. c. A controller configured to control the amplifier path to set a first phase relationship of the signal in order to ignite a plasma or laser within the discharge chamber, and a second phase relationship of the signal in order to maintain the plasma or laser.

[0023] Such a system makes it possible to ignite plasma or lasers even when using a balanced amplifier.

[0024] An impedance matching device can be placed between the discharge chamber and the balanced amplifier, in which case the impedance matching device is connected to the output port via wiring, and the length of the wiring is such that the load angle is close to, in particular, the voltage peak in the unignited state, and coincides with the voltage peak. This measure assists in the rapid ignition of the plasma or laser.

[0025] The coupler can be formed as a 3dB coupler, particularly as a 90° hybrid coupler. Such a coupler is also called an orthogonal coupler. In particular, such a coupler can operate with low loss and can couple multiple input signals into a single output signal that has higher power than each individual input signal.

[0026] At least one amplifier path may include phase setting means for setting the phase of the signal output by that amplifier path, in particular a DDS (Direct Digital Synthesis) module or FPGA having a DAC (Digital-to-Analog Converter). This allows the phase relationship between signals to be set in a particularly easy manner.

[0027] The amplifier path can also obtain the amplified signal via a splitter that sets the phase state to 90°. This can be, for example, a 90° 3dB splitter. In this case as well, a phase setting means can be provided in at least one amplifier path for phase setting.

[0028] The amplifier can supply signals, particularly at frequencies from 2 MHz to 60 MHz, and especially from 10 MHz to 16 MHz. Within this range, the ignition behavior can be set particularly well.

[0029] The amplifier path is, in particular, Class D, push-pull, and / or Class F or inverse Class F (F) respectively. -1 ) may have an inverter. Such an inverter may have an LDMOS transistor in particular as a switching and / or amplifying transistor. It has been explicitly stated that inverters of this class and / or inverters having such transistors are particularly suitable for such ignition operations and at the same time operate very stably and economically in normal operation.

[0030] Further features and advantages of the present invention will become apparent from the following detailed description of embodiments of the invention with reference to drawings illustrating details essential to the invention, and from the claims. Various features can be realized individually or in any combination in modifications of the invention.

[0031] An embodiment of the present invention is shown in a schematic diagram and described in the following description. [Brief explanation of the drawing]

[0032] [Figure 1] This is a schematic diagram illustrating a plasma system or laser system. [Figure 2] This figure shows the output characteristics of a balanced amplifier across the load plane during normal operation. [Figure 3] This figure shows the output characteristics of the amplifier's output power when the first phase relationship is set. [Modes for carrying out the invention]

[0033] Figure 1 shows a plasma system or laser system 10. The plasma system or laser system 10 includes a balanced amplifier 12, which has a first amplifier path section 14 and a second amplifier path section 16. The output signals of the first and second amplifier paths 14 and 16 are applied to the input ports 18 and 20 of a coupler 22. Therefore, the first and second amplifier paths 14 and 16 are connected to the input ports 18 and 20 of the coupler 22. The coupler 22 has an output port 24 and an isolated port 26 to which a resistor 27 is connected. The resistor 27 is also called a compensating resistor. A discharge chamber 30 is connected to the output port 24 via wiring 28. The length of the wiring 28 is configurable. An impedance matching device 32 is located directly on the discharge chamber 30. In the illustrated embodiment, the discharge chamber 30 is thus connected to the balanced amplifier 12 via wiring 28 and an impedance matching device.

[0034] Such amplifier topologies having this type of coupler are described, for example, in the following documents: Patent Document 2, Patent Document 3, Patent Document 4, Patent Document 5, Patent Document 1, Patent Document 6, and Patent Document 7.

[0035] In particular, Patent Document 5 and its corresponding Patent Document 8 show in Figure 9 the difference in measured output power via the complex reflection coefficient for an unbalanced amplifier (non-phase-shift coupler unit, upper graph) and a balanced amplifier (with 90° hybrid coupler, lower graph). In the lower graph, it is clearly evident that the maximum power is obtained at the 50Ω point in the center of the graph, and that the power gradually decreases as the reflection coefficient increases. In contrast, in the upper graph for the unbalanced amplifier, it is evident that the maximum power is not supplied at the 50Ω point in the center of the graph. When there is a mismatch in the direction of φ=11π / 6, a large amount of power is clearly supplied. This results in a power peak. This is similar to the result obtained in this application when a balanced amplifier, i.e., a 90° hybrid coupler, is used and the phase state between the amplifier path sections is changed. Therefore, in this embodiment, it is mentioned that by combining the above first setting and mismatch when a plasma or laser is ignited, the amplifier may operate as an unbalanced amplifier, or behave like an unbalanced amplifier.

[0036] In particular, Patent Documents 7 and 6 show a method for connecting two or more amplifier path sections to form a particularly high-power configuration. In this case, it is not necessarily required that all couplers be formed as 90° hybrid couplers, as shown in Patent Document 6. It is explicitly stated that the configuration shown in Figure 4 or Figure 5 of Patent Document 6 is particularly advantageous.

[0037] The coupler 22 is configured to couple the signals input to input ports 18 and 20 according to their phase relationship and output them to output port 24 and / or isolated port 26. For normal operation, i.e., to maintain the plasma or laser within the discharge chamber 30, a phase relationship is set between the signals input to input ports 18 and 20. As a result, the signals are coupled by the coupler 22 such that maximum power is obtained at output port 24 and ideally no power is obtained at isolated port 26. This is typically 90°.

[0038] The amplifier paths 14 and 16 can be controlled via the controller 34. The controller 34 allows for the setting of the phase and / or amplitude of the signals output by the amplifier paths 14 and 16. This enables the setting of the phase relationship between the signals.

[0039] The existence of further amplifier paths 14 and 16 connected to coupler 22 is also conceivable. In the illustrated embodiment, amplifier path 14 itself further has amplifier paths 36 and 38, and their output signals are coupled by coupler 40. The output signal of coupler 40 corresponds to the output signal of amplifier path 14.

[0040] Each amplifier path section 16, 36, and 38 can be configured in the same way as amplifier path section 14. Alternatively, only a portion of the amplifier path section can be configured in the same way as amplifier path section 14. The amplifier path sections 14, 16, 36, and 38 can be controlled by the controller 34. In particular, the amplifier path sections 14, 16, 36, and 38 can be equipped with, for example, a DDS module with a subsequent DAC or a phase setting means for an FPGA, which can be used to set the phase of the output signals of each amplifier path section 14, 16, 36, and 38.

[0041] Figure 2 shows the load plane 50 in the form of a Smith chart. The real part of the reflection coefficient is plotted on the x-axis, and the imaginary part of the reflection coefficient is plotted on the y-axis. The output power is shown on the z-axis. Here, it can be seen that the output power at output port 24 is almost constant. As a result, the output power characteristics across the load plane 50 are flat. In particular, no power peaks are observed. The output characteristics shown correspond to those of a balanced amplifier, in which the phase relationship between the input signals is set to obtain maximum power coupling at output port 24. The shown figure was generated by a balanced amplifier having a 3dB coupler as the coupler, and the input signal is phase-shifted by 90°. This corresponds to the setting of a second phase relationship for normal operation, i.e., to maintain the plasma or operate the laser.

[0042] Figure 3 shows the output power characteristics across the load plane 50 when a first phase relationship or amplitude relationship is set between the input signals, and this relationship differs from the normal operating settings for maintaining the plasma or laser. Although a basically flat power distribution is not achieved, it can be seen that a power peak occurs in range 52. In particular, when the magnitude of the reflection coefficient is about 0.8 and the angle of the reflection coefficient is about 110°, a maximum power of, for example, more than 3200W can be generated. In the above example, a power of about 2300W was generated at a load of 50 ohms, and a maximum power of more than 2400W was generated when the magnitude of the reflection coefficient was about 0.8 and the angle of the reflection coefficient was about 105°.

[0043] The power peak in range 52 can be used to achieve plasma or laser ignition. [Explanation of Symbols]

[0044] 10 Plasma system or laser system 12. Balanced Amplifier 14, 16 Amplifier Path Section 22 Couplers 24 output ports 26 isolated ports 30 Discharge Chamber 34 controllers

Claims

1. A method for supplying power to a processing plasma or laser in a discharge chamber (30), the method being: a. Power is supplied to the discharge chamber (30) from the output port (24) of the balanced amplifier (12), and in doing so, the balanced amplifier (12) includes at least two amplifier path sections (14, 16) each supplying a signal to a coupler (22), the coupler (22) has an output port (24) and an isolation port (26), and is configured to couple the signals depending on the phase relationship of the signals and to supply power to the output port (24) and / or the isolation port (26) depending on the phase relationship of the signals. b. Setting the first phase relationship of the signal for a predetermined time in order to ignite the plasma or the laser, c. Setting a second phase relationship different from the first phase relationship in order to operate the laser or to maintain the plasma in the discharge chamber (30), in which case, i. The second phase relationship is set such that the coupler (22) basically supplies all power to the output port (24) and basically does not supply power to the isolation port (26), and ii. A method for setting the first phase relationship such that the power reflected from the discharge chamber (30) to the balanced amplifier (12) is large enough to ignite and is reflected back from the balanced amplifier (12) to the discharge chamber (30).

2. The method according to claim 1, characterized in that the first phase relationship is selected such that there is a mismatch from the balanced amplifier (12) to the discharge chamber (30).

3. The method according to claim 1 or 2, characterized in that the second phase relationship is selected such that 50% or more of the coupled power is directed toward the output port (24).

4. The method according to claim 3, characterized in that the second phase relationship is selected such that 80% or more of the coupled power is directed toward the output port (24).

5. The method according to claim 1 or 2, characterized in that the predetermined time is in the range of 0.1 to 10,000 microseconds.

6. The method according to claim 5, characterized in that the predetermined time is in the range of 1 to 1,000 microseconds.

7. The method according to claim 1 or 2, characterized in that a 3 dB coupler is used as the coupler (22).

8. The method according to claim 7, characterized in that a 90° hybrid coupler is used as the coupler (22).

9. The method according to claim 1 or 2, characterized in that a 90° phase state is set between signals in order to maintain the plasma.

10. The method according to claim 1 or 2, characterized in that a phase state different by 90° is set between signals for igniting the plasma.

11. The method according to claim 10, characterized in that a phase state in the range of 5° to 85° or 95° to 175° is set between signals for igniting the plasma.

12. The method according to claim 11, characterized in that a phase state of 45° or 135° is set between signals for ignition of the plasma.

13. A plasma system or laser system (10), a. Discharge chamber (30) and b. A balanced amplifier (12) connected to the discharge chamber (30), the balanced amplifier (12) including a coupler (22) and at least two amplifier paths (14, 16) that supply signals to the coupler (22), wherein the coupler (22) has an output port (24) and an isolation port (26), and is configured to couple the signals depending on the phase relationship of the signals and to supply power to the output port (24) and / or the isolation port (26), c. A controller (34) configured to control the amplifier path sections (14, 16) to set a first phase relationship of the signal in order to ignite the plasma or laser within the discharge chamber (30) and to set a second phase relationship of the signal in order to maintain the plasma or laser, The controller (34) sets the second phase relationship such that the coupler (22) supplies essentially all power to the output port (24) and essentially no power to the isolation port (26), and sets the first phase relationship such that the power reflected from the discharge chamber (30) to the balanced amplifier (12) is large enough to ignite and is reflected back from the balanced amplifier (12) to the discharge chamber (30), the plasma system or laser system (10).

14. The plasma system or laser system (10) according to claim 13, characterized in that the coupler (22) is formed as a 3 dB coupler.

15. The plasma system or laser system (10) according to claim 14, characterized in that the coupler (22) is formed as a 90° hybrid coupler.

16. The plasma system or laser system (10) according to any one of claims 13 to 15, characterized in that at least one amplifier path section (14, 16) is provided with phase setting means for setting the phase of the signal output by the amplifier path section (14, 16).

17. The plasma system or laser system (10) according to claim 16, characterized in that at least one amplifier path section (14, 16) comprises a DDS module or FPGA having a subsequent DAC for setting the phase of the signal output by the amplifier path section (14, 16).

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