Power supply method to 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 a laser is 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 amplifying 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 the operating modes A, AB, B, or C. Here, an inverter mainly operates in a switching operation, that is, typically operates in the operating modes D, E, F, inverse F (F -1which may also be abbreviated as) or the like, and means an inverter operating therein. In the low power region, an amplifier or inverter that operates like an amplifier in the low power region and like an inverter in the high power region is often used to generate high frequency energy. Therefore, in the following, the term "amplifier" is used to generically refer 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 transistor pair, or four transistors connected for a full bridge, multiple amplifiers are often connected via a coupler that combines the power of the individual amplifiers. This is often done by a power coupler with special characteristics, a so-called 3dB coupler, or a 90° coupler, a quadrature coupler, or a hybrid coupler.

[0004] Such a configuration is characterized in that the power-coupled amplifiers operate 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°. The amplifiers coupled in this way are usually referred to as "balanced amplifiers". When 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 input of the coupler is supplied to a compensation resistor connected via a fourth port, where it results in loss and heat generation. That compensation resistor is also called a load compensation resistor, a termination resistor, a compensation load, or a power loss device.

[0005] One of the problems with such balanced amplifiers often occurs when trying to ignite a gas discharge. In a balanced amplifier, the output power is flat across the complex load plane, i.e., basically constant. It is difficult to generate a power peak (peaking) for ignition. So far, 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] In Patent Document 1, an ignition method is described. In this method, by setting the 90° condition of the orthogonal coupler only at the time of ignition, high power is generated in the output section for ignition. Also, an amplifier actually configured as a "balanced amplifier" operates as a "balanced amplifier" having a 90° phase offset only in the ignition mode and operates in a different phase state in normal operation. This is because in this operation method, only a part of the power existing in the input section is coupled to the output section, and the remaining power is coupled to the compensation resistor via the insulation port of the balanced amplifier, leading to its conversion into heat there. It is clearly shown that this is a very lossy method. In particular, during normal operation, that is, the intentionally controlled energy loss during operation has a very adverse effect on efficiency. This is not a preferable method especially for high power.

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Patent Document 5

Patent Document 6

Patent Document 7

Patent Document 8

Summary of the Invention

Problems to be Solved by the Invention

[0008] The object of the present invention is to provide a method and an apparatus capable of realizing highly reliable ignition of a plasma or a laser and maintaining high efficiency during normal operation when using a balanced amplifier.

Means for Solving the Problem

[0009] This problem is solved by a method according to the present invention for supplying power to a processing plasma or a laser in a discharge chamber. In this case, the method is as follows: a. Supplying power from the output port of the balanced amplifier to the discharge chamber, where the balanced amplifier includes at least two amplifier path parts each supplying a signal to a coupler, the coupler having an output port and an isolation port, being configured to combine signals depending on the phase relationship of the signals, and to supply power to the output port and / or the isolation port depending on the phase relationship of the signals; b. Setting a first phase relationship of the signals for a predetermined time to ignite the plasma or the laser; c. Setting a second phase relationship different from the first phase relationship to operate the laser or to maintain the plasma in the discharge chamber, where i. The second phase relationship is set such that the coupler basically supplies all the power to the output port and basically does not supply power to the isolation 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 for ignition and is reflected back from the balanced amplifier to the discharge chamber.

[0010] Here, "basically" means that within the allowable range of the coupler and phase setting, reasonable efforts are made to achieve these values. 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 isolation port. According to the present invention, therefore, it is intended to set two different phase relationships between the 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 made shorter in time than the second setting. At this time, the phase relationship refers to the phase state or phase difference between the phases of two signals. The change in the phase relationship can be performed, 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, by combining with the above-mentioned inconsistency of the first setting, the amplifier can be operated as an unbalanced amplifier or like an unbalanced amplifier.

[0011] In the case of inconsistency, in the second setting, that is, when the balanced amplifier is operating with a 90° phase offset, the power reflected by the discharge chamber returns to the amplifier via the output port of the coupler. Most of this power is reflected again. However, due to the reverse phase state, this reflected power does not return to the output port, that is, the discharge chamber, but reaches the compensation resistor connected via the isolation port. Thereby, no power peak occurs on the wiring and on the plasma. This is very desirable for normal operation, and therefore, the balanced amplifier operating in the discharge chamber typically has a very high tendency to rapid and unpredictable impedance changes, and thereby has a relatively high proportion of reflected power, especially in pulsed operation, and is very preferred by the operator of the processing plasma or laser.

[0012] However, when a phase offset is set, for example, set to 45°, the power reflected back from the amplifier and the power generated in the amplifier are added together, and for certain mismatches, a power peak may occur. This is undesirable because it may lead to instability in the discharge operation. However, this power peak can be advantageously utilized for ignition. Therefore, in this method, it is advantageous if an unignited state is recognized or predicted. And during the period when this state is determined or predicted, the phase is appropriately set so that ignition of the discharge can be obtained. Because during this period, the power reflected from the discharge chamber to the balanced amplifier is reflected from the balanced amplifier to the discharge chamber at a rate large enough for ignition. At that time, as an adverse effect, a part of the generated power is led to a compensation resistor connected here through an insulating port and converted into heat. However, since this setting, that is, this state is maintained for only a very short time, the energy loss can be kept low. Thereafter, in the next state that continues for a considerably long time, the phase is set to the normal operation, that is, 90°. In this case, the coupler basically supplies all the power to the output port, that is, the discharge chamber, and basically does not supply power to the insulating port. Thereafter, power is supplied to the output port only during the period of the first ignition state. This is much more economical than the solution proposed in, for example, Patent Document 1.

[0013] This method can be particularly advantageously used in a pulse operation with a pulse frequency ranging from 10 kHz to 500 kHz. Since the plasma in the discharge chamber often completely disappears during the period between pulses, the discharge has to be reignited at each new pulse. This can be advantageously done using the above method.

[0014] The signal may have a frequency in the range from 1 MHz to 4,000 MHz, particularly in the range from 1 MHz to 200 MHz. Further, the signal may have a power in the range of 1 kW or more, particularly in the range from 1 kW to 3,000 kW, preferably in the range from 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, the setting of the first phase relationship enables the superposition of the reflected power and the power generated by the amplifier. As a result, a power greater than the power normally generated at a 50-ohm load can be generated. This power can be used for the ignition of 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 is varied 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 in front of 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 in front of the discharge chamber) can be set such that the reflection coefficient of the non-ignited plasma or laser discharge is varied, 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. By means of 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 this 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. In particular, by connection with a 3dB coupler, maximum power can be supplied to the plasma or laser.

[0021] For plasma or laser ignition, a phase state 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°, and most preferably, a phase state of 45° or 135° can be set. In particular, at phases of 45° and 135°, power peaks can be generated. These power peaks occur, for example, when the magnitude of the reflection coefficient is greater than 0.8 and the phase of the reflection coefficient is -90° and 90°.

[0022] Within the scope of the present invention, a plasma system or a laser system is included, and the plasma system or the laser system a. a discharge chamber, and b. a balanced amplifier connected to the discharge chamber, the balanced amplifier including a coupler and at least two amplifier path sections for supplying signals to the coupler, where the coupler has an output port and an isolation port, and is configured to couple the signal depending on the phase relationship of the signal and supply power to the output port and / or the isolation port, c. a controller configured to control the amplifier path section so as to set a first phase relationship of the signal for igniting the plasma or the laser in the discharge chamber and set a second phase relationship of the signal for maintaining the plasma or the laser.

[0023] With such a system, it is possible to ignite the plasma or the laser even when using a balanced amplifier.

[0024] It is possible to arrange an impedance matching device between the discharge chamber and the balanced amplifier. At this time, the impedance matching device is connected to the output port via a wiring, and the wiring has a length such that the load angle is close to the voltage peak, particularly coincides with the voltage peak, in the unignited state. This measure assists in the rapid ignition of the plasma or the laser.

[0025] The coupler can be formed as a 3 dB coupler, particularly a 90° hybrid coupler. Such a coupler is also referred to as a quadrature coupler. In particular, such a coupler can operate with low loss and can couple a plurality of input signals into one output signal having a higher power than the individual input signals.

[0026] At least one amplifier path section can comprise a phase setting means for setting the phase of the signal output by the amplifier path section, particularly a DDS (Direct Digital Synthesis) module having a DAC (Digital - to - Analog Converter) or an FPGA for the purpose of setting the phase. Thereby, the phase relationship between signals can be set in a particularly easy way.

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

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

[0029] Each of the amplifier path sections can particularly have a class - D, push - pull, and / or class - F or inverse - class - F (F -1 ) inverter. Such an inverter can particularly have an LDMOS transistor as a switching and / or amplification transistor. It is explicitly stated that an inverter of this class and / or an inverter having such a transistor is particularly suitable for such an ignition operation and at the same time operates 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 the drawings showing essential details of the invention, and from the claims. The various features can be realized individually or in any combination in variations of the present invention.

[0031] Embodiments of the invention are shown in schematic diagrams and described in the following description.

Brief Description of the Drawings

[0032]

Figure 1

Figure 2

Figure 3

Mode for Carrying Out the Invention

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

[0034] Such an amplifier topology having this type of coupler is 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, Patent Document 7.

[0035] In particular, Patent Document 5 and the corresponding Patent Document 8 show, in their Figure 9, the difference in the 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 recognized that the maximum power is obtained at the 50Ω point in the center of the graph, and the power gradually decreases as the reflection coefficient increases. In contrast, in the upper graph of the unbalanced amplifier, it is recognized 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, clearly a large amount of power is supplied, resulting in a power peak. This is similar to the result obtained when a balanced amplifier, that is, a 90° hybrid coupler, is used in this application and the phase state between the amplifier path sections is changed. Therefore, at the time of plasma or laser ignition, it is mentioned in this embodiment that by combining the above first setting and the mismatch, the amplifier operates as an unbalanced amplifier or like an unbalanced amplifier.

[0036] In particular, Patent Document 7 and Patent Document 6 show a method of connecting two or more amplifier path sections to form a particularly high-output arrangement. In this case, as shown in Patent Document 6, it is not always necessary to form all the couplers as 90° hybrid couplers. It is explicitly stated that an arrangement as 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 the input ports 18, 20 to each other according to their phase relationship and output them to the output port 24 and / or the isolation port 26. For normal operation, i.e., to maintain the plasma or laser in the discharge chamber 30, a phase relationship is set between the signals input to the input ports 18, 20. As a result, the coupler 22 couples the signals so that maximum power is obtained at the output port 24 and ideally no power is obtained at the isolation port 26. This is usually 90°.

[0038] The amplifier path sections 14, 16 can be controlled via the controller 34. By the controller 34, in particular, the phase and / or amplitude of the signals output by the amplifier path sections 14, 16 can be set. Thereby, the phase relationship between the signals can be set.

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

[0040] Each of the amplifier path sections 16, 36, 38 can be configured in the same manner as the amplifier path section 14. Also, it is possible to configure only a part of the amplifier path section in the same manner as the amplifier path section 14. The amplifier path sections 14, 16, 36, 38 can be controlled by the controller 34. In particular, the amplifier path sections 14, 16, 36, 38 can include, for example, a DDS module having a subsequent DAC or a phase setting means of an FPGA, and thereby the phase of the output signals of the respective amplifier path sections 14, 16, 36, 38 can be set.

[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 is recognized that the output power at the output port 24 is substantially constant. As a result, the output power characteristic across the load plane 50 becomes flat. In particular, no power peak is seen. The shown output characteristics correspond to those of a balanced amplifier, in which a phase relationship is set between the input signals so that maximum power coupling is obtained at the output port 24. The shown figure was generated by a balanced amplifier having a 3 dB coupler as the coupler and with the input signals phase-shifted by 90°. This corresponds to the normal operation, i.e., the setting of a second phase relationship for maintaining the plasma or operating the laser.

[0042] Figure 3 shows the output power characteristic across the load plane 50 when a first phase relationship or amplitude relationship is set between the input signals, which is different from the setting of the normal operation for maintaining the plasma or the laser. Basically, a flat power distribution is not achieved, but it can be recognized that a power peak occurs in the 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°, for example, a maximum power of 3200 W or more can be generated. In the above example, about 2300 W of power was generated at a load of 50 ohms, and when the magnitude of the reflection coefficient was about 0.8 and the angle of the reflection coefficient was about 105°, a maximum power of 2400 W or more was generated.

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

Explanation of Signs

[0044] 10 Plasma system or laser system 12 Balanced amplifier 14, 16 Amplifier path section 22 Coupler 24 Output port 26 Insulation port 30 Discharge chamber 34 Controller

Claims

1. A method for supplying power to a processing plasma or a laser in a discharge chamber (30), the method 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 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 a first phase relationship of the signals for a predetermined time to ignite the plasma or the laser; c. Setting a second phase relationship different from the first phase relationship to operate the laser or to maintain a plasma in the discharge chamber (30), wherein i. The second phase relationship is set such that the coupler (22) supplies substantially all of the power to the output port (24) and substantially no power to the isolation port (26), or ii. The first phase relationship is set such that the power reflected from the discharge chamber (30) to the balanced amplifier (12) is large enough for the ignition 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, particularly 80% or more, of the combined power is directed to the output port (24).

4. The method according to any one of claims 1 to 3, characterized in that the predetermined time is in the range of 0.1 to 10,000 microseconds, preferably in the range of 1 to 1,000 microseconds.

5. The method according to any one of claims 1 to 4, characterized in that a 3 dB coupler, particularly a 90° hybrid coupler, is used as the coupler (22).

6. The method according to any one of claims 1 to 5, characterized in that a 90° phase state is set between the signals to maintain the plasma.

7. For the ignition of the plasma, a phase state different from 90° between signals, preferably in the range of 5° to 85° or 95° to 175°, preferably in the range of 40° to 50° or 130° to 140°, particularly preferably 45° or 135°, is set, and the method according to any one of claims 1 to 6 is characterized thereby.

8. A plasma system or a laser system (10), comprising: a. A discharge chamber (30); b. A balanced amplifier (12) connected to the discharge chamber (30), the balanced amplifier (12) including a coupler (22) and at least two amplifier path parts (14, 16) for supplying signals to the coupler (22), wherein the coupler (22) has an output port (24) and an isolation port (26), combines the signals depending on the phase relationship of the signals, and is configured to supply power to the output port (24) and / or the isolation port (26); c. A controller (34) configured to control the amplifier path parts (14, 16) so as to set a first phase relationship of the signals for igniting a plasma or a laser in the discharge chamber (30) and to set a second phase relationship of the signals for maintaining the plasma or the laser.

9. The plasma system or the laser system (10) according to claim 8, characterized in that the coupler (22) is formed as a 3 dB coupler, particularly a 90° hybrid coupler.

10. The plasma system or the laser system (10) according to claim 8 or 9, characterized in that at least one of the amplifier path parts (14, 16) is provided with a phase setting means for setting the phase of the signal output by the amplifier path part (14, 16), particularly a DDS module or an FPGA having a subsequent DAC.

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