Laser or plasma ignition and power supply method, and plasma system or laser system

Abstract

An improved ignition and power supply method for a laser or processing plasma in a discharge chamber 30 includes: a. supplying power from an output port 24 of an amplifier 12 to the discharge chamber 30, where the 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 and being configured to combine signals depending on an amplitude relationship and / or a phase relationship and supply power to the output port 24 and / or the isolation port 26; b. controlling impedance switching units 27, 27a, 27b connected to the isolation port 26 and a ground 39 according to a first control mode to ignite the laser or processing plasma; and c. controlling impedance switching units 27, 27a, 27b connected to the isolation port 26 according to a second control mode to operate the laser or maintain the processing plasma in the discharge chamber 30.

Description

Technical Field

[0001] The present invention relates to an improved method for igniting and powering a gas laser or plasma in a discharge chamber. Further, the present invention relates to a plasma system or a laser system comprising a discharge chamber and an amplifier.

Background Art

[0002] Plasma for processing workpieces, i.e., for example, plasma for etching or coating workpieces in industrial plasma devices, is often excited using high-frequency energy. To ignite the plasma, it is known to apply a full operating power at a voltage higher than normal to the plasma device to ignite the plasma as quickly as possible. In such a system, a so-called balanced amplifier is often used. Such a balanced amplifier usually has two amplifier path sections, each supplying a signal to a coupler (also called a capacitor). At this time, the coupler has an output port and an isolation port, and is configured to combine signals depending on the amplitude relationship and / or phase relationship of the signals and supply power to the output port and / or the isolation port. For this purpose, the amplifier path sections usually operate with a phase difference of 90° from each other. Such a balanced amplifier and its characteristics are also described, for example, in Non-Patent Document 1. In that document, the term "balanced amplifier" is used as an alternative to the term "balancierter Verstaerker".

[0003] In a suitable balanced amplifier designed for operation in a laser or plasma, the output power is basically flat, i.e., basically constant, across the complex load plane. It is difficult to create a power peak (peaking). Spurious peaking can only be achieved by selecting a higher DC supply voltage. A high DC supply voltage for a short time can generate high power for ignition. However, generating a high DC supply voltage for power peaking (power peaking) is very costly.

[0004] In the case of an unbalanced amplifier, especially when there is no coupler, an impedance for ignition that generates a power peak can be selected by an appropriate cable length between the amplifier and the plasma chamber or discharge chamber. Since unbalanced amplifiers have many other drawbacks, they are rarely used in plasma or laser operations.

[0005] One method of igniting such a plasma system or laser system with a balanced amplifier is described, for example, in Patent Document 1 titled "Method for Supplying Power to a Laser or Plasma, and Plasma System or Laser System" filed on August 4, 2022. In that document, the term "balanced amplifier" is used as an alternative to the term "balancierter Verstaerker". During ignition and operation, the phase relationship between the amplifier path sections during the ignition operation is different from the phase relationship during the plasma processing or laser excitation operation. The method described in that document is very effective in many systems, but it cannot ensure satisfactory reliability in all systems.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

[0007] [Non-Patent Document 1] Alexander Alt et al.: “Analysis of high power LDMOS amplifiers for industrial applications under mismatch conditions”, published in 2014 IEEE Topical Conference on Power Amplifiers for Wireless and Radio Applications (PAWR), Electronic ISBN: 978-1-4799-2778-4. [Summary of the Invention] [Problems to be Solved by the Invention]

[0008] The problem of the present invention is to provide a method and apparatus capable of realizing highly reliable ignition of a laser or plasma. [Means for Solving the Problems]

[0009] This problem is solved by an improved ignition and power supply method for a laser or processing plasma in a discharge chamber. This method includes a. a step of supplying power from the output port of an amplifier to a discharge chamber, wherein the amplifier includes at least two amplifier path portions each supplying a signal to a coupler, the coupler has an output port and an isolation port, and is configured to combine signals depending on the amplitude relationship and / or phase relationship of the signals and supply power to the output port and / or the isolation port, b. Controlling an impedance switching unit connected to the insulation port and the ground according to a first control mode to initiate a laser or a processing plasma; c. Controlling an impedance switching unit connected to the insulation port according to a second control mode to operate the laser or to maintain a processing plasma in the discharge chamber.

[0010] According to the present invention, there is provided the use of an impedance switching unit at the insulation port of a coupler. This impedance switching unit replaces a well-known absorption resistor known in the prior art. In this case, the impedance switching unit can be formed and operated to be formed and operate like a conventional absorption resistor in a second control mode. Conventional absorption resistors usually have an impedance of the coupler, usually 50 ohms. In a given form, the resistance value can also be an integer multiple or a fraction of 50 ohms, for example 25 ohms or 100 ohms. By controlling the impedance switching unit, an overvoltage is generated at the output port of the coupler, and in relation thereto, the generation of a power peak suitable for initiating a laser or a processing plasma is ensured.

[0011] As used herein, "ground" means an electrical connection to the reference potential of the amplifier, which is often abbreviated as "GND".

[0012] As used herein, the "impedance switching unit" means a configuration suitable for performing switching between different impedances. In this case, intentionally, instead of changing the impedance analogously and continuously, it is to switch between two or more values. For this purpose, preferably, a switching element can be used. Such a switching element can be, for example, a transistor, particularly an IGBT or a MOSFET. However, an electromechanical switching element or a PIN diode is also conceivable. Such a switching element has a transition time for switching and cannot switch infinitely fast, but it is obvious that in order to achieve highly reliable and fast ignition, it is necessary to make the switching time as short as possible. The switching element can be connected so as to short-circuit the impedance element. Instead, the switching element can be connected so as to isolate the impedance element. Two or more switching elements can also be provided. These switching elements can be connected so as to short-circuit the impedance element and also to isolate the impedance element.

[0013] When the laser or plasma does not ignite, usually, multiple reflections sufficient for ignition do not occur between the amplifier (its output port) and the non-igniting load. This is because most of the energy is absorbed in the impedance element, often also referred to as an absorption resistor, connected to the isolation port. According to the present invention, this impedance element is appropriately switched for the first control mode and absorbs little or only slightly energy. This can cause multiple reflections of power between the amplifier and the non-igniting load. Thereby, a high enough power or voltage is generated to ignite the plasma or laser. In particular, it has been shown that the switching is superior to a controlled or managed continuous change in the impedance of the absorption resistor. This enables, that is, faster and more reliable ignition.

[0014] According to the method of the present invention, plasma or laser can be ignited quickly and surely. In particular, this method can be used when the phase relationship or amplitude relationship of the signals combined in the coupler cannot be adjusted. This may apply when the signals to be combined themselves originate from a coupler, particularly a 3 dB coupler.

[0015] The signals combined by the coupler can have frequencies in the range of 1 MHz to 100 MHz. Furthermore, they can have powers in the range of 0.5 kW to 6 kW. The signals combined in the coupler can have a 90° phase offset.

[0016] The impedance switching unit can be controlled such that the impedance between the insulation port and the ground becomes approximately zero ohms. For this purpose, the impedance switching unit can have a switching element arranged in parallel with the absorption resistor. In this case, the impedance switching unit is arranged between the insulation port and the ground, and the absorption resistor is configured and functions like a conventional absorption resistor known in the art. By switching on the switching element, the absorption resistor can be short-circuited, thereby preventing energy from being absorbed within the impedance switching unit, particularly in the absorption resistor.

[0017] Alternatively, the impedance switching unit can be controlled such that the impedance between the insulation port and the ground becomes approximately infinite. For this purpose, a switching element can be arranged in series with the absorption resistor between the insulation port and the ground, and in this case, the absorption resistor can be configured and function like a conventional absorption resistor known from the prior art. By opening the switching element, the absorption resistor can be disconnected from the insulation port or the ground, so that energy is not absorbed within the impedance switching unit, particularly in the absorption resistor.

[0018] For the ignition of a laser or a processing plasma, the impedance switching unit can be controlled in a first control mode for a predetermined time, particularly in the range of 0.1 μs to 10,000 μs, preferably in the range of 1 μs to 1,000 μs. At this time, this time can be set so as to ensure that a sufficiently large power peak is generated at the output port of the coupler to reliably ignite the laser or the processing plasma.

[0019] Alternatively or additionally, for the ignition of a laser or a processing plasma, the impedance switching unit can be controlled in a first control mode until the ignition of the laser or the plasma is detected. The ignition of the plasma can be monitored optically, for example. However, between the coupler and the discharge chamber, signals such as current, voltage, and power can be detected, and the ignition of the laser or the plasma can also be derived, for example, by determining the reflection coefficient from the detected signals.

[0020] As the coupler, a 3dB coupler, particularly a 90° hybrid coupler, can be used. The 3dB coupler combines two input signals with a 90° phase shift, whereby the combined power is output at the output port and no power is output at the isolation port. At this time, the amplification path parts for generating signals are separated and do not affect each other. The 3dB coupler itself can be ideally lossless. This means that the power of the two amplification path parts can be completely supplied to the load (plasma or laser) connected to the output port.

[0021] To maintain the plasma or the laser, a 90° phase relationship can be set between the signals. In particular, in relation to the 3dB coupler, the maximum power can be supplied to the plasma or the laser.

[0022] The present invention further relates to a plasma system or a laser system, and the plasma system or the laser system includes a. a discharge chamber, and b. An amplifier connected to a discharge chamber, having a combiner and at least two amplifier path sections respectively supplying signals to the combiner, wherein the combiner has an output port and an isolation port, is configured to combine signals depending on their amplitude relationship and / or phase relationship, and supply power to the output port and / or the isolation port. c. An impedance switching section connected between the isolation port and ground, including an impedance element and at least one switch element. d. A controller configured to control the impedance switching section for ignition of a laser or processing plasma in the discharge chamber.

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

[0024] The switch element can be connected in series or in parallel to the impedance element. The switch element is preferably arranged in parallel to the impedance element. Also, it is conceivable to provide the switch element both in series and in parallel to the impedance element. This increases the flexibility regarding the setting of the impedance at the isolation port for igniting a plasma or a laser. The switch element can be formed as a MOSFET.

[0025] An impedance matching device can be arranged between the plasma chamber or the discharge chamber and the balanced amplifier. In that case, the impedance matching device can be connected to the output port via a wiring, and the wiring has a specially selected electrical length that can depend on the wavelength of the connection and the dielectric and magnetic characteristics. This measure enables high-speed ignition of a laser or a plasma.

[0026] The combiner can be formed as a 3dB coupler, particularly as a 90° hybrid coupler. Such a combiner operates particularly with low loss and can combine a plurality of input signals into one output signal having a higher power than the individual input signals.

[0027] The amplifier can supply signals, in particular, at frequencies of 13.56 MHz and / or 27 MHz. Each amplifier path section may have a class-F inverter. The class-F inverter may have an LDMOS transistor.

[0028] 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 figures of the drawings. They will also become apparent from the claims. The various features can be realized in variants of the invention, individually or in any combination.

[0029] In particular, the above method can be combined with the method described in Patent Document 1. Both methods can be used simultaneously, or can be used sequentially in different orders, or can be used repeatedly. For this purpose, Patent Document 1 is fully incorporated into the present application by reference.

[0030] Schematic diagrams show embodiments of the present invention and will be described in the following description.

Brief Description of the Drawings

[0031]

Figure 1

Figure 2

Figure 3

Figure 4a

Figure 4b

Figure 4c

Figure 5a

Figure 5b

Figure 5c

Figure 6a

Figure 6b

Figure 6c

Mode for Carrying Out the Invention

[0032] The plasma system or laser system described in this embodiment is also described in, for example, Patent Document 2, Patent Document 3, and Patent Document 4. These three publications are hereby incorporated by reference in their entirety into this application. The plasma system or laser system described in these cited documents is further developed in this embodiment by an impedance switching unit. The methods and apparatuses described in this embodiment can also be advantageously used and / or incorporated in the methods and apparatuses described in these cited documents.

[0033] The component referred to as "coupler" in this specification can be configured, for example, as a phase shift coupler unit in Patent Document 2 or a "phase shift coupler" in Patent Document 3.

[0034] In this specification, the isolation port of a coupler typically refers to the output port of a coupler that is not normally powered during normal operation without reflection. In other publications, it is also referred to as a compensation port. An absorption resistor is conventionally connected to the isolation port, for example, as in the previously cited publications. This absorption resistor is often also referred to as a compensation resistor or a termination resistor.

[0035] FIG. 1 shows a plasma system or a laser system 10. The plasma system or laser system 10 particularly includes a balanced amplifier 12, and the balanced amplifier 12 has a first amplifier path section 14 and a second amplifier path section 16. The output signals of the first and second amplifier path sections 14, 16 are applied to the 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 an impedance switching unit 27 is connected. The impedance switching unit 27 is connected between the isolation port 26 and the ground 39.

[0036] A discharge chamber 30 is connected to the output port 24 via a wiring 28. An impedance matching device 32 is disposed directly in the discharge chamber 30. The discharge chamber 30 is thus connected to the amplifier 12 via the wiring 28 and the impedance matching device 32 in the illustrated embodiment.

[0037] The coupler 22 is configured to couple the signals input to the input ports 18, 20 to each other depending on their phase relationship and / or amplitude relationship, and output them to the output port 24 and / or the isolation port 26. The input signals to the coupler 22 have a phase relationship and / or an amplitude relationship, and the input signals are guided such that the signals are coupled by the coupler 22, maximum power is output at the output port 24, and ideally, no power is output at the isolation port 26.

[0038] The impedance switching unit 27 is controlled by the controller 34. In particular, one or more switch elements of the impedance switching unit 27 are thereby controlled. Different configurations of the impedance switching unit 27 will be described.

[0039] The existence of further amplifier path portions 14, 16 connected to the combiner 22 is also conceivable. In the illustrated embodiment, the amplifier path portion 14 itself further has amplifier path portions 36, 38, and the output signals thereof are combined by the combiner 40. The output signal of the combiner 40 corresponds to the output signal of the amplifier path portion 14.

[0040] Each of the amplifier path portions 16, 36, 38 can be configured in the same manner as the amplifier path portion 14. It is also possible to configure only a part of the amplifier path portion in the same manner as the amplifier path portion 14.

[0041] The input signals of the amplifier path portions 14, 16 can come from a splitter. The splitter can be configured in the same manner as the combiner 22.

[0042] The first embodiment of the impedance switching unit 27 is indicated by reference numeral 27a in FIG. 2. The impedance switching unit 27a has an impedance element 36 in the form of an absorption resistor, and a switch element 38 is connected in parallel thereto. The switch element 38 is controlled by the controller 34.

[0043] When the switch element 38 is controlled by the controller 34 in the first control mode and the switch element 38 becomes conductive, the impedance element 36 configured as an absorption resistor is short-circuited, and as a result, the energy cannot be absorbed at the isolation port 26. When the laser or plasma has not been ignited in the discharge chamber 30 yet, the power is reflected in the discharge chamber 30. Since this cannot be absorbed by the impedance element 36, power reflection also occurs in the combiner 22. At the output unit 24, a power peak leading to the ignition of the laser or plasma in the discharge chamber 30 occurs.

[0044] After a predetermined time has elapsed or when ignition of the laser or plasma is detected, the switch element 38 is opened in the second control mode, and power can be supplied to the ignited laser or ignited plasma in the normal operation. When a change occurs in the plasma impedance due to plasma dynamics and related mismatches occur, the power reflected in the discharge chamber 30 can be absorbed by the impedance element 36 configured as an absorption resistor.

[0045] A second embodiment of the impedance switching unit 27 is indicated by reference numeral 27b in FIG. 3. The impedance switching unit 27b has an impedance element 36 in the form of an absorption resistor, and a switch element 38 is connected in series therewith. The switch element 38 is controlled by a controller 34.

[0046] When the switch element 38 is controlled by the controller 34 in the first control mode so as to be in an open state, the connection between the insulating port 26 and the ground 39 is disconnected, and as a result, energy cannot be absorbed at the insulating port 26. When the laser or plasma has not yet been ignited in the discharge chamber 30, the power is reflected in the discharge chamber 30. Since this cannot be absorbed by the impedance element 36, power reflection also occurs in the coupler 22. At the output unit 24, this becomes a power peak, leading to ignition of the laser or plasma in the discharge chamber 30.

[0047] After a predetermined time has elapsed or when ignition of the laser or plasma is detected, the switch element 38 is closed in the second control mode, and power can be supplied to the ignited laser or ignited plasma in the normal operation. When a change occurs in the plasma impedance due to plasma dynamics and related mismatches occur, the power reflected in the discharge chamber 30 can be absorbed by the impedance element 36.

[0048] Figure 4a 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 for all reflection coefficients. As a result, the output power characteristic across the load plane 50 becomes flat. In particular, no power peak is seen. The figure shown was generated by a balanced amplifier having a 3 dB coupler as a combiner, where the impedance element 36 formed as an absorption resistor is not short-circuited and the connection to the ground 39 of the isolation port 26 is not disconnected. No power peak occurs for load impedances suitable for plasma or laser ignition.

[0049] Figure 4b is a graph corresponding to the situation of Figure 4a, in which the output power supplied by the amplifier 12 is shown depending on the magnitude of the reflection coefficient. It can be recognized that the power is basically constant and insufficient to ignite a plasma or a laser.

[0050] Figure 4c is a graph corresponding to the situations of Figures 4a and 4b, in which the output power supplied by the amplifier 12 is shown depending on the phase angle φ of the reflection coefficient.

[0051] Figures 5a, 5b, and 5c show graphs corresponding to Figures 4a to 4c, where the switch element 38 of the impedance switching unit 27a is controlled according to the first control mode so as to short-circuit the impedance element 36.

[0052] From Figure 5a, it can be recognized that a basically flat power distribution is not achieved and a power peak, or peaking, occurs in the range 52. From the related Figures 5b and 5c, it can be recognized that when the magnitude of the reflection coefficient is greater than 0.7 and the angle of the reflection coefficient is 0°, a considerably high power suitable for plasma or laser ignition is generated compared to the cases of Figures 4a to 4c.

[0053] Figures 6a, 6b, and 6c show graphs corresponding to FIGS. 4a to 4c, where the switch element 38 of the impedance switching unit 27b is controlled according to the first control mode so as to disconnect the insulation port 26 from the ground 39.

[0054] It can be recognized from FIG. 6a that a basically flat power distribution is not achieved, and power peaks, or peakings, occur in region 54. From the related FIGS. 6b and 6c, it can be recognized that when the magnitude of the reflection coefficient is greater than 0.7 and the angle of the reflection coefficient is about +180° and about -180°, a considerably high power suitable for plasma or laser ignition is generated as compared with the situations of FIGS. 4a to 4c.

Description of Reference Numerals

[0055] 10 Plasma system or laser system 12 Amplifier 14, 16 Amplifier path section 22 Coupler 24 Output port 26 Insulation port 27, 27a, 27b Impedance switching unit 28 Wiring 30 Discharge chamber 32 Impedance matching device 34 Controller 36 Impedance element 38 Switch element 39 Ground

Claims

1. An improved ignition and power supply method for a laser or processing plasma in a discharge chamber (30), comprising: a. Supplying power from an output port (24) of an amplifier (12) to the discharge chamber (30), wherein the 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), and being configured to couple the signals depending on the amplitude relationship and / or phase relationship of the signals and supply power to the output port (24) and / or the isolation port (26); b. Controlling impedance switching units (27, 27a, 27b) connected to the isolation port (26) and ground (39) according to a first control mode to initiate ignition of the laser or processing plasma; c. Controlling the impedance switching units (27, 27a, 27b) connected to the isolation port (26) according to a second control mode to operate the laser or maintain the processing plasma in the discharge chamber (30).

2. The method according to claim 1, wherein step a. includes controlling the impedance switching units (27, 27a) such that the impedance between the isolation port (26) and the ground (39) is substantially zero ohms or substantially infinite.

3. The method according to claim 1 or 2, wherein for ignition of the laser or processing plasma, the impedance switching units (27, 27a, 27b) are controlled in the first control mode for a predetermined time, particularly in the range of 0.1 μs to 10,000 μs, preferably in the range of 1 μs to 1,000 μs.

4. The method according to any one of claims 1 to 3, wherein for ignition of the laser or processing plasma, the impedance switching units (27, 27a, 27b) are controlled in the first control mode until ignition of the laser or plasma is detected.

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

6. An amplifier (12) connectable to a discharge chamber (30), a. A coupler (22) having an output port (24), an isolation port (26), and two input terminals (18, 20), wherein the coupler (22) is configured to supply signals at the input terminals (18, 20) to the output port (24) and / or the isolation port (26) depending on their amplitude relationship and / or phase relationship. b. At least two amplifier path sections (14, 16) configured to supply signals to the input terminals (18, 20) of the coupler (22). c. An impedance switching section (27, 27a, 27b) connected between the isolation port (26) and ground (39), including an impedance element (36) and at least one switch element (38). d. A controller (34) configured to control the impedance switching section (27, 27a, 27b) for ignition of a laser or processing plasma in the discharge chamber (30). An amplifier (12) comprising the above components.

7. A plasma system or laser system (10) comprising: a. A discharge chamber (30); b. An amplifier (12) connected to the discharge chamber (30), having a coupler (22) and at least two amplifier path sections (14, 16) for supplying signals to the coupler (22) respectively. The coupler (22) has an output port (24) and an isolation port (26), and is configured to combine signals depending on their amplitude relationship and / or phase relationship and supply power to the output port (24) and / or the isolation port (26). c. An impedance switching section (27, 27a, 27b) connected between the isolation port (26) and ground (39), including an impedance element (36) and at least one switch element (38). d. A controller (34) configured to control the impedance switching section (27, 27a, 27b) for ignition of a laser or processing plasma in the discharge chamber (30). A plasma or laser system (10) comprising the above components.

8. The plasma system according to claim 7, wherein the switch element (38) is connected in series or parallel with the impedance element (36).

9. An impedance matching device (32) is arranged between the discharge chamber (30) and the amplifier (12). The impedance matching device (32) is connected to the output port (24) via a wiring (28) having a specially selected electrical length that depends on the wavelength, dielectric characteristics, and magnetic characteristics of the connection. The plasma system according to claim 7 or 8, characterized in that.

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

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