Impedance matching module, impedance matching circuit, plasma process supply system and plasma process system

Abstract

The invention relates to an impedance matching module for powers of ≥500 W and frequencies in the range from 2 to 100 MHz for an impedance matching circuit, a plasma process supply system and a plasma process system, having a) an insulating circuit board (3), b) planar conductor tracks (2), arranged on an top side (3a) and a bottom side (3b) of the insulating circuit board (3), c) a plurality of semiconductor switching elements (5), in particular transistors or PIN diodes, d) a substrate (4), in particular a ceramic plate, e) wherein the planar conductor tracks (2) are designed to connect the semiconductor switching element connections (5a) to one another and to other components, f) wherein the semiconductor switching elements (5) are arranged on the top side (3a) of the insulating circuit board (3) and are designed to connect and disconnect reactances (6), for example capacitors and / or coils, in order to change an impedance from the input to the output of an impedance matching circuit (11), g) wherein the substrate (4) is thicker than the insulating circuit board (3) and is fixedly connected to the surface of the insulating circuit board (3) over the majority of the bottom side (3b) of the circuit board (3), and h) wherein the substrate (4) is designed such that the planar conductor tracks (2) can be spaced apart, by means of said substrate (4), from a cooling body (7) in order to be electrically insulated from same, and i) wherein the substrate (4) and the connection of the circuit board (3) to the substrate are configured to dissipate the heat of the planar conductor tracks (2) and semiconductor switching elements (5) to a cooling body (7).

Description

[0001] Impedance matching module, impedance matching circuit, plasma process supply system and plasma process system

[0002] The present invention relates to an impedance matching module for an impedance matching circuit, a plasma process supply system and a plasma process system for mounting on a, in particular metallic, heat sink, designed for powers > 500 W, preferably > 2 kW and frequencies in the range from 2 MHz to 100 MHz, in particular in the range from 10 MHz to 50 MHz, an impedance matching circuit, a plasma process supply system and a plasma process system.

[0003] Such an impedance matching module can be used in an impedance matching circuit in a system in which a load is supplied with electrical power, particularly high-frequency power. "High frequency" is also abbreviated to "HF" below. Here, "HF" refers to frequencies in the range from 2 MHz to 100 MHz, particularly in the range from 10 MHz to 50 MHz.

[0004] In such a system, the load impedance should be matched to the impedance of the power supply, otherwise power reflection may occur. Power reflection has a direct impact on the efficiency of a system; it reduces its efficiency.

[0005] An example system in which an impedance matching circuit may be used may be a plasma processing system.

[0006] Such a plasma processing system may, for example, be a system in which a load, e.g. a plasma processing arrangement, is supplied with electrical power.

[0007] Such a plasma processing arrangement can, for example, be a plasma processing chamber that is used for industrial plasma processes such as the surface treatment of workpieces, semiconductor manufacturing with plasma or the processing of workpieces with gas lasers.

[0008] In such an application, the plasma processing arrangement serves to generate plasma. For this purpose, a plasma processing arrangement may comprise an electrode that is fed with a high-frequency power signal for generating the plasma, hereinafter referred to as the RF power signal.

[0009] Typically, a high-power and especially high-voltage power supply is required, for which the plasma processing arrangement can be connected to a high-frequency power supply, hereinafter referred to as RF power supply.

[0010] The plasma process occurring in the plasma processing system has the problem that the electrical load impedance of the plasma processing system, which occurs during the process, depends on the conditions within the plasma processing system and can vary greatly. In particular, the properties of the workpiece, electrode, and gas conditions are important.

[0011] For this reason, an impedance matching circuit is usually required to transform the load impedance to a nominal impedance of the RF power supply. Such an impedance matching circuit is typically placed between an RF power supply and the plasma processing device, usually in close proximity to the plasma processing device.

[0012] An impedance matching circuit is typically an arrangement that may contain inductances and / or capacitances.

[0013] For complex problems where it is important to be able to change the impedance quickly, semiconductor-switched impedance matching circuits are often used. These semiconductor switching elements can be used to switch inductances and / or capacitances in impedance matching circuits on and off. Control circuits can be used to control the switching on and off of the semiconductor switching elements. An example of such a semiconductor-switched impedance matching circuit is disclosed and described in DE 20 2020 102 084 U1. With ever increasing performance requirements in this area, the circuits in which the actual semiconductor switching elements are arranged are becoming increasingly complex. These complex circuits are generally intended to implement universal switching elements that function in both parallel and series configurations. DE 20 2020 103 539 U1 discloses and describes with Fig.Figure 3 shows an example of such a more complex circuit, referred to there as a switchable reactance unit. This circuit contains semiconductor switching elements in both parallel and series configurations.

[0014] Particularly in series configurations, parasitic capacitances arise due to the necessary cooling of the semiconductor switching elements. These parasitic capacitances negatively impact the electrical performance of such a circuit.

[0015] A compact design, i.e. one that is designed to save as much space as possible, is very desirable.

[0016] The present invention is therefore based on the object of providing an impedance matching module for powers > 500 W and frequencies in the range from 2 to 100 MHz, which allows complex structures for the arrangement of semiconductor switching elements in parallel and series configuration in a compact design and can be realized with high-performance cooling and reduced parasitic capacitance.

[0017] This object is achieved by an impedance matching module according to independent claim 1. Advantageous developments of the invention emerge from the subclaims and / or the description.

[0018] According to the present invention, an impedance matching module for an impedance matching circuit, a plasma process supply system and a plasma process system for mounting on a, in particular metallic, heat sink, designed for powers > 500 W and frequencies in the range from 2 MHz to 100 MHz is proposed, comprising a) an insulating circuit board, b) planar conductor tracks, arranged on the top and / or bottom of the insulating circuit board, c) a plurality of semiconductor switching elements, in particular transistors or PIN diodes, d) a substrate, in particular a ceramic plate, e) wherein the planar conductor tracks are designed to connect the semiconductor switching element terminals to one another and to other components, f) wherein the semiconductor switching elements are arranged on the top of the insulating circuit board and are designed to have reactances, e.g.Capacitors and / or coils, to be switched on and off in order to change an impedance from the input to the output of an impedance matching circuit, g) wherein the substrate is thicker than the insulating circuit board and is firmly connected to the insulating circuit board over most of the underside of the circuit board, and h) wherein the substrate is designed such that the planar conductor tracks can be spaced apart from a heat sink, in particular a metallic heat sink, by this substrate in order to be electrically insulated therefrom, and i) wherein the substrate and the connection of the circuit board to the substrate are designed to dissipate the heat of the planar conductor tracks and semiconductor switching elements to a heat sink.

[0019] By constructing an insulating, thermally conductive substrate combined with an insulating circuit board on which a complex layout of planar conductor tracks can be structured, on which components can be arranged, the problem of a complex circuit, high-performance cooling and minimal parasitic capacitance can be solved.

[0020] For the substrate, a plate made of aluminum oxide or aluminum nitride ceramic can be used, for example. The insulating circuit board can be made of conventional circuit board material, such as FR-4, or, in particular, polytetrafluoroethylene-based material, also known as PTFE. This material is particularly suitable due to its low dielectric constant and low losses.

[0021] The designation FR-4 stands for a class of flame-resistant and flame-retardant composite materials consisting of epoxy resin and fiberglass fabric. The abbreviation FR stands for "flame retardant." Polytetrafluoroethylene-based material, also abbreviated to PTFE, is several times more expensive than FR-4, but it can be used for circuit boards in the RF range because of its particularly low-loss performance in this frequency range. The circuit boards can be designed thinner because this material has a lower dielectric constant and also a higher dielectric strength against high electric fields.

[0022] "Permanently connected" means a connection between the circuit board and the substrate that cannot slip during operation, cannot come loose, and in which no air pockets are located or can form. Such air pockets often occur in components connected with thermal paste. These have the disadvantage that high electric fields can arise at the edge of the air pockets, which in turn can lead to harmful partial discharges. In addition, the thermal conductivity is negatively affected. The "permanent connection" is advantageously created by pressing and / or gluing, especially under pressure combined with heat. A "large part" means a surface area that makes up at least 60%, in particular at least 80% of the total surface. For example, if the underside of the circuit board is 100 cm 2 large, the "majority of the underside" should be at least 60 cm 2 , in particular at least 80 cm 2 be.

[0023] The planar conductor tracks are made of an electrically conductive material, particularly copper. Arranging the conductor tracks on the top and bottom of the insulating circuit board enables a highly flexible and complex layout. At certain points, the conductor tracks on the top and bottom sides can be electrically connected via vias. The top side of the insulating circuit board can be further coated.

[0024] Metal oxide semiconductor field-effect transistors (MOSFETs) can be used for the semiconductor switching elements. The semiconductor switching elements can be attached, for example, by soldering them onto the planar conductor tracks on the top side of the insulating circuit board. In addition to the semiconductor switching elements, reactances such as coils and / or capacitors can also be arranged on the top side of the insulating circuit board. These reactances are designed to be switched on and off by the semiconductor switching elements. By arranging the reactances directly on the insulating circuit board, their heat can also be dissipated via the substrate.

[0025] Furthermore, resistors can be arranged on top of the insulating circuit board, designed to prevent overloading of individual semiconductor switching elements. This makes the entire assembly more robust, and even in the event of a fault, the expensive semiconductor switching elements can remain undamaged. By arranging the resistors directly on the insulating circuit board, their heat can also be dissipated via the substrate.

[0026] Furthermore, circuit board connection options can be arranged on the top side of the insulating circuit board, via which several further circuit boards can be connected and, in particular, stacked above the first circuit board. The circuit board connection options can be electrical circuit board connection options that electrically connect the individual circuit boards to one another, and mechanical circuit board connection options that secure the circuit boards and ensure a distance between the circuit boards. The further added circuit boards can have further reactances, referred to here as additional reactances, such as capacitors and / or coils, which can be switched on and off via the semiconductor switching elements. The added circuit boards can have conventional circuit board material such as FR-4 or, for example, polytetrafluoroethylene-based material.The ability to add additional circuit boards with additional reactances makes the impedance matching module modularly expandable and thus more scalable.

[0027] Furthermore, the insulating circuit board and the substrate of the impedance matching component can be bonded by heating and pressing a prepreg between them. "Prepreg" is a common material name, short for "preimpregnated." This typically refers to pre-impregnated, usually flat, sheet-like textile semi-finished products with a thermoplastic or thermosetting matrix, such as unidirectional layers of threads, fabrics, or scrims, often with perpendicularly arranged threads.

[0028] Prepregs are cured under heat and pressure to produce components. They are prefabricated, for example, in sheet form, wound on rolls. The term prepreg encompasses not only unidirectionally reinforced or flat semi-finished products, but also other preforms of essentially any shape, consisting, in the broadest sense, of a fiber-filled, uncured thermoset matrix. The matrix is ​​in a partially cross-linked state and is pasty to solid, but can be liquefied again by heating.

[0029] Prepregs are machine-processable and are therefore frequently used in automated processes. They produce consistent, high-quality products. Advantages include their low undulation and high fiber volume fraction. Curing at high temperatures enables short cycle times in further processing. Processing requires significant investment, e.g., for autoclaves, placement robots, and refrigerated storage. Such prepregs are generally used to join several circuit boards together to form a multilayer circuit board. To ensure a secure and long-lasting joint, the materials to be joined should have very similar properties regarding their expansion under heat. However, this is not necessarily the case for the circuit board and the substrate, especially if the substrate is made of ceramic. This initially spoke against such a bond.However, ceramic exhibits very good thermal conductivity and, at the same time, very good electrical insulating properties, as well as low dielectric losses when isolating high-frequency signals with high voltages. Contrary to expectations, however, tests have shown that, even with small dimensions, a secure and long-lasting joining of materials with different properties, such as ceramic with FR-4 and / or ceramic with PTFE material, is possible. "Small dimensions" here means a bonding area of ​​less than 400 cm. 2and / or with a maximum length of 20 cm. The entire impedance matching component can be applied via the substrate to a heat sink, which dissipates the heat from the planar inductors. Such a heat sink can preferably be metallic, in particular made of aluminum and / or copper. The heat sink can also be a fluid heat sink, which has at least one cooling channel through which a fluid flows, through which the heat is dissipated. A thermal paste can be applied between the heat sink and the substrate, and the impedance matching component can be attached to the heat sink using brackets.

[0030] Furthermore, the impedance matching module can be used in an impedance matching circuit in a plasma process supply system or a plasma process system.

[0031] Such a plasma process supply system can comprise an RF power supply in addition to the impedance matching circuit. Such an impedance matching circuit can comprise, in addition to the impedance matching component, additional reactances, referred to here as additional impedances, such as coils and / or capacitors, as well as a control circuit. The additional reactances can be implemented as planar reactances and, like the existing reactances, can be switched on and off via the semiconductor switching elements. The switching on and off using the semiconductor switching elements can be controlled via the control circuit.

[0032] The entire impedance matching circuit can be connected to the RF power supply on the one hand and can be designed to be connected to a plasma processing arrangement on the other hand.

[0033] In a plasma processing system, such a plasma processing arrangement may be present and connected to the impedance matching circuit. The plasma processing arrangement may be supplied with electrical power provided by the RF power supply via the impedance matching circuit. Preferred embodiments of the invention are schematically illustrated in the drawings and are explained in more detail below with reference to the figures of the drawing. They show:

[0034] Fig. 1 is a plan view of a first embodiment of a top side of an insulating circuit board of an impedance matching module according to the invention

[0035] Fig. 2 is a schematic view of a first embodiment of an impedance matching module according to the invention arranged on a heat sink in cross section

[0036] Fig. 3 is a schematic view of an embodiment of a plasma processing system

[0037] Fig. 1 shows a plan view of a first embodiment of a top side of an insulating circuit board 3 of an impedance matching module 1 according to the invention. Also indicated are the substrate 4, which is arranged beneath the circuit board 3, and the heat sink 7, which is arranged beneath the substrate 4, which is shown again in Fig. 2. The top side of the insulating circuit board 3 has semiconductor switching elements 5, reactances 6 in the form of capacitors, resistors 14, and various connection options 19a, 19b, 20, 21, 22. The planar conductor tracks 2 (shown in Fig. 2) of the impedance matching module 1 are covered in this figure by a coating on the top side 3a of the insulating circuit board 3 or attached to the underside 3b of the insulating circuit board 3 and are therefore not visible.The connection options 19a, 19b, 20, 21, 22 are divided into signal connection options 19a, 19b, mechanical circuit board connection options 20, electrical circuit board connection options 21, and heat sink connection options 22. The signal connection options 19a, 19b can be further divided into integrated signal connection options 19a, which are integrated into the insulating circuit board 3, and applied signal connection options 19b, which are applied to the insulating circuit board 3. The impedance matching module 1 can be supplied with RF power signals or control signals from the control circuit 18, for example, via the signal connection options 19a, 19b, and can be integrated into the overall impedance matching circuit 11. Additional circuit boards 15 can be attached to the insulating circuit board 3 at a distance via the mechanical circuit board connection options 20 (shown in Fig. 2).The mechanical circuit board connection options 20 can be implemented as cylindrical attachments with a height corresponding to the desired spacing of the circuit boards on the insulating circuit board 3. These cylindrical attachments can have a threaded hole in their center, through which the additional circuit boards 15 can be fixed with screws.

[0038] With the electrical circuit board connection options 21, the individual circuit boards can be electrically connected to one another, so that possible additional reactances 16 on possible further circuit boards 15 can be integrated into the circuit on the insulating circuit board 3.

[0039] The impedance matching module 1 can be attached to a possible heat sink 7 via the heat sink connection options 22.

[0040] The mechanical circuit board connection options 20 and the heat sink connection options 21 can be connected to a ground potential if required.

[0041] In addition, the semiconductor switching elements 5 can have semiconductor switching element terminals 5a. These can be used to contact the semiconductor switching elements 5 and to connect them to other semiconductor switching elements 5 and / or other components via the planar conductor tracks 2. When a MOSFET is used as the semiconductor switching element 5, the semiconductor switching element terminals 5a can, for example, comprise a gate, a drain, and a source terminal.

[0042] Fig. 2 shows a first embodiment of an impedance matching module 1 according to the invention arranged on a heat sink 7. The cross section shown also shows the insulating circuit board 3 and the substrate 4 of the impedance matching module 1. The insulating circuit board 3 is arranged on the substrate 4 and firmly connected to it. The insulating circuit board 3 has planar conductor tracks 2 on the top and bottom sides 3a, 3b of the insulating circuit board 3. The planar conductor tracks 2 connect the semiconductor switching element terminals 5a to one another and to other components, such as the reactances 6 and resistors 14. The substrate 4 is arranged on the heat sink 7 and connected to it. Due to the thickness of the substrate, the insulating circuit board 3 is spaced from the heat sink 7 and electrically insulated from it. Two further circuit boards 15 are stacked on the insulating circuit board 3.The additional circuit boards can be connected to one another via several circuit board connection options 20, 21. Firstly, there are mechanical circuit board connection options 20, which serve to mechanically secure and space the individual circuit boards 3, 15. Secondly, there are electrical circuit board connection options 21, via which the individual circuit boards are electrically connected to one another. A more detailed description of the connection options can be found in the description of Fig. 1. Additional reactances 16, such as capacitors and / or coils, can be arranged on the additional circuit boards 15.

[0043] The heat sink 7 is shown as a fluid heat sink having a plurality of cooling channels 7a which are designed to be flowed through by a fluid, e.g. water, through which heat can be dissipated.

[0044] Fig. 3 shows an embodiment of an exemplary plasma processing system 9. The plasma processing system 9 comprises a plasma processing supply system 8 and a plasma processing arrangement 10. The plasma processing supply system 8 comprises an impedance matching circuit 11 as described above and an RF power supply 12. The impedance matching module 1 according to the invention is integrated into the impedance matching circuit 11. In addition, the impedance matching circuit 11 comprises further additional reactances 17, such as capacitors and / or coils, as well as a drive circuit 18.

[0045] Such a typical additional reactance 17 is described, for example, in patent application DE 10 2023 104 958.5, filed on February 28, 2023, entitled "Impedance matching module, impedance matching circuit, plasma process supply system, and plasma process system," which is hereby fully incorporated by reference into the present application. In particular, the additional impedance matching module (1) described in the cited application can further develop the additional reactance 17 with individual or all of its features. Such a typical impedance matching circuit 11 is described, for example, in patent application DE 10 2023 104 942.9, filed on February 28, 2023, entitled "Impedance matching circuit, plasma process supply system, and plasma process system," which is hereby fully incorporated by reference into the present application.In particular, the further impedance matching circuit (1) described in the said application can further develop the present impedance matching circuit 11 with individual or all of its features.

[0046] Such a typical plasma processing system 9 is described, for example, in patent application DE 10 2023 104 955.0, filed on February 28, 2023, entitled "Impedance matching circuit for a plasma processing system and a plasma processing system with such an impedance matching circuit," which is hereby fully incorporated into the present application by reference. In particular, the second impedance matching unit (7) described in said application can be configured with the features of the impedance matching module 1 described here.

[0047] Such a typical plasma process system 9 is described, for example, in patent application DE 10 2023 104 948.8, filed on February 28, 2023, entitled "Impedance matching circuit, plasma process supply system, and plasma process system," which is hereby incorporated into the present application in its entirety by reference. In particular, the second impedance matching unit (7, 7a-7f) described in the aforementioned application can be configured with the features of the impedance matching module 1 described herein.

[0048] With the features described above, the number of components, such as semiconductor switching elements or reactances, such as coils and / or capacitors as well as capacitances and / or inductances, can be kept lower, thus achieving an even more compact design.

Claims

Claims 1. Impedance matching module (1) for an impedance matching circuit (11), a plasma process supply system (8) and a plasma process system (9) for mounting on a, in particular metallic, heat sink (7), designed for power levels > 500 W and frequencies in the range from 2 MHz to 100 MHz, comprising: a) an insulating circuit board (3), b) planar conductor tracks (2) arranged on the top side (3a) and bottom side (3b) of the insulating circuit board (3), c) a plurality of semiconductor switching elements (5), in particular transistors or PIN diodes, d) a substrate (4), in particular a ceramic plate, e) wherein the planar conductor tracks (2) are designed to connect the semiconductor switching element terminals (5a) to one another and to other components, f) wherein the semiconductor switching elements (5) are arranged on the top side (3a) of the insulating circuit board (3) and are designed to have reactances (6), e.g.Capacitors and / or coils, to be switched on and off in order to change an impedance from the input to the output of an impedance matching circuit (11), g) wherein the substrate (4) is thicker than the insulating circuit board (3) and is firmly connected to the insulating circuit board (3) over a large part of the underside (3b) of the circuit board (3), and h) wherein the substrate (4) is designed such that the planar conductor tracks (2) can be spaced from a heat sink (7) by this substrate (4) in order to be electrically insulated therefrom, and i) wherein the substrate (4) and the connection of the circuit board (3) to the substrate (4) are designed to dissipate the heat of the planar conductor tracks (2) and semiconductor switching elements (5) to a heat sink (7).

2. Impedance matching module (1) according to the preceding claim 1, wherein reactances (6), such as capacitors and / or coils, are arranged on the upper side (3a) of the insulating circuit board (3) and are designed to be switched on or off by the semiconductor switching elements (5).

3. Impedance matching module (1) according to the preceding claims 1 and 2, wherein resistors (14) are arranged on the upper side (3a) of the insulating circuit board (3) and are designed to prevent overloading of individual semiconductor switching elements (5).

4. Impedance matching module (1) according to one of the preceding claims, wherein on the upper side (3a) of the insulating circuit board (3) there are mechanical and electrical circuit board connection possibilities (20, 21), via which one or more further circuit boards (15) are connected and in particular stacked over the first insulating circuit board (4).

5. Impedance matching module (1) according to the preceding claim 4, wherein added further circuit boards (15) have additional reactances (16), such as capacitors and / or coils, which can be switched on and off by the semiconductor switching elements (5).

6. Impedance matching module (1) according to one of the preceding claims, wherein the fixed connection of the insulating circuit board (3) to the substrate (4) is produced by pressing and / or gluing, in particular under pressure combined with heat.

7. Impedance matching module (1) according to one of the preceding claims, wherein the substrate (4) is connected to the insulating circuit board (3) via a prepreg (13) inserted therebetween by heating and pressing together.

8. Impedance matching module (1) according to one of the preceding claims, wherein the impedance matching module (1) is connected via the substrate (4) to a heat sink (7), in particular a metallic heat sink.

9. Impedance matching module (1) according to claim 8, wherein the heat sink (7) is a fluid heat sink having at least one cooling channel (7a) through which a fluid flows, via which the heat can be dissipated.

10. Impedance matching module (1) according to one of the preceding claims, wherein the upper side (3a) of the insulating circuit board (3) is covered with a coating.

11. Impedance matching module (1) according to one of the preceding claims, wherein the impedance matching module (1) is modularly expandable.

12. Impedance matching circuit (11), comprising: a) an impedance matching module (1) according to one of the preceding claims, b) further additional reactances (17), e.g., capacitors and / or coils, c) a control circuit (18), d) wherein the semiconductor switching elements (5) of the impedance matching module (1) can be controlled by the control circuit (18).

13. Impedance matching circuit (11) according to claim 12, wherein the further additional reactances (17) can be switched on and off via the semiconductor switching elements (5) and are in particular designed to be planar.

14. Plasma process supply system (8) comprising an RF power supply (12) for providing an RF power signal and an impedance matching circuit (11) according to one of the preceding claims 12 or 13, wherein the impedance matching circuit is electrically connected to the RF power supply (12) and is designed to be connected to a plasma process arrangement (10).

15. Plasma process system (9) comprising a plasma process supply system (8) according to the preceding claim 14 and a plasma process arrangement (10), wherein the plasma process arrangement (10) is connected to the plasma process supply system (8) and wherein the plasma process supply system (8) is configured to supply the plasma process arrangement (10) with power of an RF power signal.

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