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

Abstract

The invention relates to an impedance matching module (1) for an impedance matching circuit (11), a plasma process supply system (8) and a plasma process system (9) for assembly on a cooling body (7) designed for powers of ≥ 500 W and frequencies in the range from 2 to 100 MHz, having: a) a planar inductor (2), b) an insulating circuit board (3), c) a substrate (4), in particular a ceramic plate, d) wherein the planar inductor (2) is divided into two equally long planar conductor tracks (2a, 2b) which are connected in parallel and which are arranged on both sides of and congruently on the insulating circuit board (3), e) wherein the two conductor tracks (2a, 2b) are electrically connected at their ends by terminals (5a, 5b, 5c, 5d, 5e) and / or vias (6a, 6b, 6c, 6d), f) 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 underside (3b) of the insulating circuit board (3), and g) wherein the planar conductor tracks (2a, 2b) can be spaced apart, by way of the substrate (4), from a cooling body (7) in order to be electrically insulated therefrom, and h) wherein the substrate (4) and the connection of the circuit board (3) to the substrate (4) is suitable for dissipating the heat of the planar conductor tracks 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 and frequencies in the range from 2 MHz to 100 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 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 can, for example, be a system in which a load, e.g., a plasma processing assembly, is supplied with electrical power. Without a connected plasma processing assembly, a plasma processing system can be referred to as a plasma processing supply system.

[0007] 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] The higher the power to be transmitted, the more difficult it becomes to build compact impedance matching circuits. The larger the power to be transmitted, the larger the impedance matching circuits become. This size makes their use space-consuming and, in many configurations, allows little variability in their design. However, a compact design, that is, one that is as space-saving as possible, is highly desirable.

[0014] DE 20 2016 008 958 UI discloses a solution for reducing installation space and simplifying manufacturing for a power combiner. A planar structure is used for the power combiner. In planar structures, current displacement occurs in inductors and lines, resulting in unwanted hotspots. These hotspots reduce the efficiency of an impedance matching circuit.

[0015] In addition, the quality of inductors and lines used in an impedance matching circuit should generally be maximized, as this is also responsible for the efficiency and thus quality of an impedance matching circuit.

[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 MHz to 100 MHz, which can be realized in a planar structure in the smallest possible space, avoiding hot spots and having inductances and lines with a high quality factor.

[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 heat sink, in particular a metallic one, is proposed, designed for powers > 500 W and frequencies in the range from 2 MHz to 100 MHz, comprising a) a planar inductor, b) an insulating circuit board, c) a substrate, in particular a ceramic plate, d) wherein the planar inductor is divided into two planar conductor tracks of equal length, electrically connected in parallel, which are arranged on both sides and congruently on the insulating circuit board, e) wherein the two conductor tracks are electrically connected at their ends via terminals and / or vias, in particular are electrically connected exclusively at their ends,f) 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 insulating circuit board, and g) wherein the planar conductor tracks can be spaced apart from a heat sink, in particular a metallic heat sink, by the substrate in order to be electrically insulated therefrom, and h) wherein the substrate and the connection of the circuit board to the substrate are designed to dissipate the heat of the planar conductor tracks to a heat sink.

[0019] By doubling the conductor tracks on the top and bottom surfaces of an insulating circuit board, the current in a planar inductor or line is split into two paths. Due to the essentially identical current flow geometry with twice the conductor cross-section, losses are reduced for the same inductance. This results in an inductance with higher quality. By splitting the current between two lines, local hot spots are avoided. "Essentially identical current flow geometry" refers to a geometry that has identical geometric dimensions under typical manufacturing conditions, particularly those typical for circuit board manufacturing. Minor modifications to accommodate other conditions, such as fastening devices, contacts, safety clearances, etc., may also fall under the term "essentially."

[0020] The conductor tracks forming the inductance are made of an electrically conductive material, particularly copper. When selecting the material for the insulating circuit board, it is preferable to ensure that the material is suitable for high-frequency applications. For the insulating circuit board, typical PCB materials such as FR-4 or polytetrafluoroethylene-based materials are therefore ideal. Polytetrafluoroethylene-based materials, also known as PTFE, are particularly suitable due to their low dielectric constant and low losses. For the substrate, an aluminum oxide or aluminum nitride ceramic, for example, can be used.

[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] This provides an impedance matching component that is compact due to its planar design and also avoids the formation of local heat points, also called 'hotspots', and has inductances and lines with a high quality.

[0024] The two conductor tracks can be connected to each other exclusively at their ends at the terminals and vias. This forces the current flow, especially in non-straight sections, to remain in the respective conductor track and cannot escape to the other one. This improves the quality of the inductance by reducing current displacement. Furthermore, the insulating circuit board and the substrate of the impedance matching component can be connected by heating and pressing together a prepreg sandwiched 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.

[0025] 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.

[0026] 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 heating. 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 at high voltages. Contrary to expectations, however, tests have shown that, even with small dimensions, a secure and long-lasting bonding of materials with different properties, such as ceramic with FR-4 and / or ceramic with PTFE material, is possible. With small dimensions, a bonding area of ​​less than 400 cm2 is possible. 2 and / or with a maximum length of 20 cm.

[0027] The entire impedance matching component can be applied via the substrate to a heat sink, which dissipates the heat from the planar conductor tracks. 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 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.

[0028] Furthermore, the impedance matching module can be used in an impedance matching circuit in a plasma process supply system or a plasma process system.

[0029] 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, further reactances, such as coils and / or capacitors, semiconductor switching elements, and a control circuit. The reactances can be switched on and off via the semiconductor switching elements in order to change the impedance from the input to the output of the impedance matching circuit. The semiconductor switching elements can be, for example, metal-oxide-semiconductor field-effect transistors (MOSFETs). The switching on and off using the semiconductor switching elements can be controlled via the control circuit. The control circuit (16) can be designed for this purpose.

[0030] 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.

[0031] 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:

[0032] Fig. 1 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

[0033] Fig. 2 is a schematic view of the top side of the insulating circuit board of the impedance matching module according to the invention. Fig. 3 is a schematic view of an embodiment of the bottom side of the insulating circuit board of the impedance matching module according to the invention.

[0034] Fig. 4 is a schematic view of an embodiment of a plasma processing system

[0035] Fig. 5 a perspective view of the impedance matching module

[0036] Detailed description of the drawings:

[0037] Fig. 1 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 connected to it. The substrate 4 is arranged on the heat sink 7 and connected to it. The thickness of the substrate spaced the insulating circuit board 3 from the heat sink 7 and electrically insulated from it. An inductor 2 is arranged as a planar conductor track 2a on the top side 3a and as a planar conductor track 2b on the bottom side 3b of the insulating circuit board 3. The heat sink 7 is shown as a fluid heat sink having a plurality of cooling channels 7a through which a fluid, e.g. water, flows, via which any heat generated can be dissipated.

[0038] Fig. 2 shows an embodiment of the top side 3a of the insulating circuit board 3 of the impedance matching module 1. This top side 3a of the insulating circuit board 3 has a planar conductor track 2a, connections 5a, b, c, d, e and vias 6a, b, c, d. The planar inductor 2 has two planar conductor tracks 2a, 2b, of which only one planar conductor track 2a is visible on the top side 3a. The other planar conductor track 2b is arranged essentially congruently on the bottom side 3b, as shown in Fig. 3. The two planar conductor tracks 2a, 2b have an asymmetric shape, in particular the two conductor tracks 2a, 2b have a meandering course. The planar inductance 2 with its two planar conductor tracks 2a, 2b has straight track sections 20 followed by non-straight track sections 21, here in particular with a strong curve shape, whereby the planar conductor tracks 2a, 2b reverse their direction.The change of these sections occurs several times in succession, with the curve shapes being alternating right and left curves, so that the planar inductance 2 can utilize the area of ​​the insulated circuit board 3 and exhibit the desired properties.

[0039] In addition, terminals 5a, b, c, d, e are located on the top side 3a of the insulating circuit board 3, which are connected to the planar inductor 2. These terminals allow the impedance matching module 1 to be integrated into an impedance matching circuit 11. The vias 6a, b, c, d, which have a round shape, serve to electrically connect the planar inductor 2 on the top side 3a of the insulating circuit board 3 to the planar inductor on the bottom side 3b. Terminals for, for example, an RF power signal can also be applied to the vias 6a, b, c, d on the top side 3a of the insulating circuit board 3.

[0040] Fig. 3 shows an embodiment of a bottom side 3b of the insulating circuit board 3 of the impedance matching module 1. The bottom side 3b represents the reverse side of the top side 3a described in Fig. 2 and therefore has the same components. The description of the components can accordingly be derived from the description of Fig. 2. The fundamental distinction between the top and bottom sides of the insulating circuit board 3 is that, in the respective top view, the planar conductor track 2b of the bottom side 3b is arranged mirror-inverted to the planar conductor track 2a of the top side 3a. This results in the two planar conductor tracks 2a, 2b being arranged exactly one above the other, i.e., congruent, but electrically separated by the circuit board 3.

[0041] Terminals 5a, 5b, 5c, 5d, 5e can each represent one end of the conductor tracks 2a, 2b. They serve to adjust the desired inductance or frequency by connecting the following components of an impedance matching circuit 11 to one of the corresponding terminals 5a, 5b, 5c, 5d, 5e.

[0042] The vias 6a, 6b, 6c, 6d can each represent an end of the conductor tracks 2a, 2b. They serve to adjust the desired inductance or frequency by connecting additional components of an impedance matching circuit 11 to one of the corresponding vias 6a, 6b, 6c, 6d.

[0043] The two conductor tracks 2a, 2b are only connected to each other at the terminals 5a, 5b, 5c, 5d, 5e and vias 6a, 6b, 6c, 6d. This forces the current flow, especially in the non-straight track sections 21, to remain in the respective conductor track 2a, 2b and cannot escape to the other one. This improves the quality of the inductance by reducing current displacement.

[0044] In Fig. 2 and 3, the position of a possible substrate 4 is also indicated as a dashed border.

[0045] Fig. 5 shows a perspective view of the impedance matching module 1. The same reference symbols are used here as in Figs. 1, 2 and 3.

[0046] Fig. 4 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 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 reactances 14, such as capacitors and / or coils, semiconductor switching elements 15, and a drive circuit 16.

[0047] 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 incorporated into the present application in its entirety by reference. In particular, the further impedance matching circuit (1) described in the aforementioned application can further develop the present impedance matching circuit 11 with some or all of its features.

[0048] 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, at least one of the coils (15, 18, 19, 24, 25) described in the cited patent application can be configured with the features of the impedance matching module 1 described here.

[0049] Such a typical plasma process system 9 is also 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 in its entirety by reference into the present application. In particular, at least one of the inductors (L2a, L2b, L3a, L3d, L3e, L3f) described in the cited patent application can be configured with the features of the impedance matching module 1 described here. With the features described above, the number of components, for example, semiconductor switching elements or reactances, e.g., coils and / or capacitors, as well as capacitances and / or inductors, 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 powers > 500 W and frequencies in the range from 2 MHz to 100 MHz, comprising: a) a planar inductor (2), b) an insulating printed circuit board (3), c) a substrate (4), in particular a ceramic plate, d) wherein the planar inductor (2) is divided into two planar conductor tracks (2a, 2b) of equal length, electrically connected in parallel, which are arranged on both sides and congruently on the insulating printed circuit board (3), e) wherein the two conductor tracks (2a, 2b) are electrically connected at their ends via connections (5a, 5b, 5c, 5d, 5e) and / or vias (6a, 6b, 6c, 6d) are,f) wherein the substrate (4) is thicker than the insulating circuit board (3) and is firmly connected to the insulating circuit board (3) over most of the underside (3b) of the insulating circuit board (3), and g) wherein the planar conductor tracks (2a, 2b) can be spaced from a heat sink (7) by the substrate (4) in order to be electrically insulated therefrom, and h) wherein the substrate (4) and the connection of the circuit board (3) to the substrate (4) are suitable for dissipating the heat of the planar conductor tracks to a heat sink (7).

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

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

4. Impedance matching module (1) according to claim 3, 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.

5. 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.

6. Impedance matching module (1) according to one of the preceding claims, wherein the two conductor tracks (2a, 2b) are connected to one another exclusively at their ends at the terminals and vias.

7. Impedance matching module (1) according to one of the preceding claims, wherein the two conductor tracks (2a, 2b) have a meander-shaped course.

8. Impedance matching module (1) according to one of the preceding claims, wherein the two conductor tracks (2a, 2b) have a plurality of connections (5a, 5b, 5c, 5d, 5e) along their course, each of which has a possibility of connecting further components and thus can each represent an end of the conductor tracks (2a, 2b).

9. Impedance matching module (1) according to one of the preceding claims, wherein the two conductor tracks (2a, 2b) have a plurality of vias (6a, 6b, 6c, 6d) along their course, each of which has a possibility of connecting further components and can thus each represent an end of the conductor tracks (2a, 2b).

10. Impedance matching circuit (11), comprising: a) an impedance matching module (1) according to one of the preceding claims, b) further reactances, e.g., capacitors and / or coils, c) semiconductor switching elements (15), in particular transistors or PIN diodes, d) a control circuit (16), e) wherein the semiconductor switching elements (15) are designed to switch the reactances on and off in order to change the impedance from the input to the output of the impedance matching circuit (11), f) wherein the control circuit (16) is designed to be able to control the switching on and off of the reactances by the semiconductor switching elements (15).

11. Impedance matching circuit (11) according to claim 10, designed to be connected on the one hand to an RF power supply (12) and on the other hand to a plasma processing arrangement (10).

12. 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 10 or 11, wherein the impedance matching circuit (11) is electrically connected to the RF power supply (12) and is designed to be connected to a plasma process arrangement (10).

13. Plasma process system (9) comprising a plasma process supply system (8) according to the preceding claim 12 and a plasma process arrangement (10), wherein the plasma process arrangement (10) is connected to the plasma process supply system (8) and 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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