Voltage Generator

Abstract

To effectively prevent insulation breakdown on the basis of floating potential.SOLUTION: A voltage generating device includes a heat sink 21, an inductor 19 having a coil 19S wound around a core 19C, a fixture 23 for fixing the core 19C, an insulating member 22 arranged between the fixture 23 and the heat sink 21, and a short-circuit member 20 for, for example, electrically short-circuiting the core 19C and an output node N1 of a first inverter circuit 17. The short-circuit member 20 gives the core 19C a definite potential rather than a floating potential, thereby effectively preventing dielectric breakdown between the core 19C and the coil 19S.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a voltage generating device. [Background technology]

[0002] A plasma processing apparatus is provided with a voltage generator that generates a pulsed voltage (pulse voltage) (see, for example, Patent Document 1). The voltage generator is configured, for example, to convert a DC voltage into an AC voltage using an inverter circuit, then convert the AC voltage into a different voltage value using a transformer, and further generate a pulse voltage using a switching circuit or the like.

[0003] Such a voltage generator typically has an inductor at its output terminal to suppress inrush current. The voltage generator also uses a heat sink for heat dissipation. This heat sink is made of a conductive material and functions as a ground potential. For insulation, an insulating member made of ceramics or the like is placed on top of the heat sink, and an inverter circuit, inductor, and the like are sometimes placed on top of this insulating member.

[0004] In some cases, an inductor having a core (iron core) is used as the inductor. Such an inductor is composed of a coil wound around the core. The inductor is fixed to an insulating member by a fixture. Therefore, electrically, the core is located between the coil wound around the core and the heat sink, which is at ground potential.

[0005] Here, the inductor core is at a floating potential because it is not connected to any other fixed potential. Furthermore, because the voltage generator has the above-described structure, the potential of the inductor core is influenced by the potential of the coil, the potential of the heat sink, etc. As a result, a large potential difference occurs between the core and the coil, and in some cases, dielectric breakdown may occur between the core and the coil. In particular, if the voltage value (absolute value) of the pulse voltage output from the voltage generator is large, dielectric breakdown is more likely to occur between the inductor coil and core.

[0006] In addition, other circuits such as an inverter circuit may be placed on top of a base member that is placed on top of an insulating member made of the above-mentioned ceramics or the like. The base member is, for example, a member in which an insulating layer is placed on top of a metal substrate, and copper foil is placed on top of that. The metal substrate of the base member has a floating potential, similar to the core described above, and the potential of the metal substrate is a potential influenced by the potential of the copper foil, the potential of the heat sink, etc. Therefore, similar to the core described above, a large potential difference occurs between the copper foil and the metal substrate, and in some cases, dielectric breakdown may occur between the copper foil and the metal substrate. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-125729 Summary of the Invention [Problem to be solved by the invention]

[0008] The present invention provides a voltage generator that can effectively prevent dielectric breakdown due to floating potential. [Means for solving the problem]

[0009] In order to solve the above problems, the voltage generating device of the present invention comprises a first conductive member at ground potential, a first insulating member arranged on top of the first conductive member, a second conductive member to which a first voltage is applied, a third conductive member at floating potential arranged between the second conductive member and the first insulating member, and a short-circuiting member that electrically connects a point at the same potential or approximately the same potential as the third conductive member to a point to which a second voltage is applied. [Effects of the Invention]

[0010] According to the present invention, it is possible to provide a voltage generating device that can effectively prevent dielectric breakdown due to floating potential. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a circuit diagram illustrating a voltage generating device according to a first embodiment of the present invention. [Figure 2] 2 is a cross-sectional view illustrating an example of the configuration of an inductor 19 and a short-circuit member 20 of the voltage generator according to the first embodiment of the present invention. FIG. [Figure 3] FIG. 3 is an explanatory diagram illustrating the effects of the first embodiment. [Figure 4] FIG. 3 is an explanatory diagram illustrating the effects of the first embodiment. [Figure 5] FIG. 4 is a circuit diagram illustrating a modified example of the voltage generating device according to the first embodiment of the present invention. [Figure 6] FIG. 4 is a circuit diagram illustrating a voltage generating device according to a second embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, the present embodiment will be described with reference to the accompanying drawings. In the accompanying drawings, functionally identical elements may be designated by the same numerals. Note that the accompanying drawings show embodiments and implementation examples according to the principles of the present disclosure, but these are for understanding the present disclosure and are not to be used to interpret the present disclosure in a limiting manner. The descriptions in this specification are merely typical examples and are not intended to limit the scope or application of the present disclosure in any way.

[0013] Although the present embodiment has been described in sufficient detail to enable those skilled in the art to implement the present disclosure, it should be understood that other implementations and forms are possible, and that changes in configuration and structure and substitutions of various elements are possible without departing from the scope and spirit of the technical ideas of the present disclosure. Therefore, the following description should not be interpreted as being limited thereto.

[0014] [First embodiment] A voltage generator according to a first embodiment of the present invention will be described with reference to Fig. 1. The voltage generator shown in Fig. 1 is configured to convert a DC voltage into an AC voltage using an inverter circuit, then convert the AC voltage into a different voltage value using a transformer, and further generate a pulse voltage using an inverter circuit or the like.

[0015] The voltage generating device of Figure 1 is configured to include a DC power supply 11, an inverter circuit 12, a transformer 13, a rectifier 14, a smoothing circuit 15, a DC power supply 16, a first inverter circuit 17, a second inverter circuit 18, an inductor 19, and a short-circuiting element 20.

[0016] A first voltage generator X1 is formed by the first inverter circuit 17. Furthermore, a second voltage generator X2 is formed by the inverter circuit 12, the transformer 13, the rectifier 14, the smoothing circuit 15, and the second inverter circuit 18.

[0017] The first inverter circuit 17 forming the first voltage generator X1 is configured by connecting two transistors in series between a power supply node (e.g., −10 kV) and a ground terminal (GND). Therefore, the two transistors are alternately turned on, so that the first voltage generator X1 is configured to output from the output node N1 a first pulse voltage (e.g., a pulse voltage in which 0 V and −10 kV are alternately repeated) based on the DC voltage output from the DC power supply 16 (e.g., −10 kV output). The first pulse voltage output from the output node N1 is output to the outside via the output terminal Vout1.

[0018] The output node N1 of the first inverter circuit 17 is connected to a node N21 of the second inverter circuit 18, forming a so-called floating connection, whereby the second voltage generator X2 generates a second pulse voltage that is superimposed, as an offset, on the first pulse voltage generated by the first voltage generator X1.

[0019] The inverter circuit 12 is, for example, a full-bridge inverter circuit that converts the DC voltage output from the DC power supply 11 into an AC voltage.

[0020] Transformer 13 has a primary winding and a secondary winding arranged opposite to each other, and further converts the AC voltage output by inverter circuit 12 into an AC voltage of a different voltage value. The output voltage of transformer 13 is applied to rectifier 14. Rectifier 14 is a circuit that converts the AC voltage output by transformer 13 into a DC voltage. Smoothing circuit 15 is a circuit that smoothes the output voltage of rectifier 14.

[0021] The second inverter circuit 18 is configured by connecting two transistors in series between the node N21 and the node N22. By alternately turning on the two transistors, the second inverter circuit 18 is configured to output from the output node N2 a second pulse voltage (for example, a pulse voltage in which 0 V and −11.5 kV are alternately repeated) obtained by superimposing the first pulse voltage generated by the first voltage generator X1 as an offset on the output voltage of the smoothing circuit 15. The second pulse voltage output from the output node N2 is output to the outside via the output terminal Vout2.

[0022] The on / off timing of the two transistors of the first inverter circuit 17 and the two transistors of the second inverter circuit 18 is set according to the usage situation. For example, the on / off timing of the two transistors of the first inverter circuit 17 and the on / off timing of the two transistors of the second inverter circuit 18 are synchronized so that when the output level of the first inverter circuit 17 is high (large absolute value), the output level of the second inverter circuit 18 is also high (large absolute value). Of course, this is not limiting. For example, instead of synchronizing the on / off timing as described above, the on / off timing may be staggered. Alternatively, a pulse voltage that alternates between high and low levels (absolute value greater than 0) may be used.

[0023] Inductor 19 includes a ferrite core 19C and a coil 19S (winding) wound around it. One end is connected to the output node N2 of the second inverter circuit 18, and the other end is connected to the output terminal Vout2. Inductor 19 is used to suppress inrush current. That is, when the output of the voltage generator outputs a high pulse voltage to a capacitive load such as a plasma processing apparatus, excessive current flows when the pulse voltage rises or falls. Therefore, inductor 19 is inserted to suppress the excessive current.

[0024] The short-circuiting member 20 electrically shorts the ferrite core 19C and the power line HL, which has the same potential as the output node N1, thereby fixing the potential of the ferrite core 19C to the potential of the power line HL. The power line HL may be, for example, a power line connecting the first inverter circuit 17 and the second inverter circuit 18.

[0025] An example of a specific configuration of the inductor 19 and the short-circuiting member 20 will be described with reference to Fig. 2. As shown in Fig. 2, some of the components in Fig. 1, including the inductor 19, are mounted on a heat sink 21 via an insulating member 22 made of ceramics such as alumina, silicon nitride, or aluminum nitride. In Fig. 2, the rectifier 14, the smoothing circuit 15, the first inverter circuit 17, the second inverter circuit 18, and the inductor 19 are mounted on the heat sink 21 via the insulating member 22. Note that in Fig. 2, the rectifier 14, the smoothing circuit 15, the first inverter circuit 17, and the second inverter circuit 18 are shown as a single block. Furthermore, the heat sink 21 is made of a conductive material and is supplied with a ground potential.

[0026] As described above, the coil 19S is wound around the ferrite core 19C to form the inductor 19. The inductor 19 is provided with a fixture 23 for fixing the inductor 19, and the inductor 19 is mounted on the insulating member 22 via the fixture 23. The fixture 23 is made of a conductive material such as aluminum and is electrically connected to the ferrite core 19C and is capable of fixing the ferrite core 19C. Thus, the inductor 19, including the coil 19S and the ferrite core 19C, is fixed by the fixture 23. Therefore, by attaching the fixture 23 to the insulating member 22, the inductor 19 is mounted on the insulating member 22 via the fixture 23. Furthermore, the ferrite core 19C and the fixture 23 are electrically at the same potential. Therefore, the fixture 23, like the ferrite core 19C of the inductor, is an example of the third conductive member of the present invention.

[0027] Even if the ferrite core 19C and the fixture 23 are not in contact with each other and there is a small gap between them, the ferrite core 19C and the fixture 23 will be at approximately the same electrical potential. This is because the parasitic capacitance between the ferrite core 19C and the fixture 23 is significantly larger than that of metals with other potentials, resulting in a low impedance at high frequencies and almost no potential difference. Therefore, it is possible to insert a soft, insulating sheet between the ferrite core 19C and the fixture 23 to prevent cracking of the ferrite core 19C.

[0028] The short-circuit member 20 electrically connects (short-circuits) the power line HL that connects the second inverter circuit 18 and the inductor 19 to the fixture 23. This allows the fixture 23 and the ferrite core 19C to be fixed to the potential of the power line HL.

[0029] The effects of the first embodiment will be described with reference to Figures 3 and 4. Figure 3 is a schematic diagram for explaining the change in potential of each part when there is no short-circuit member 20, and Figure 4 is a schematic diagram for explaining the change in potential of each part when there is a short-circuit member 20.

[0030] Without the short-circuit member 20, a parasitic capacitance C1 is formed between the heat sink 21 and the ferrite core 19C or the fixing member 23 due to the insulating member 22. Furthermore, a parasitic capacitance C2 is formed between the ferrite core 19C or the fixing member 23 and the coil 19S. Note that this discussion is based on the assumption that there is no air gap between the heat sink 21 and the fixing member 23, and only the insulating member 22 exists. Furthermore, it is assumed that there is only an air gap between the ferrite core 19C and the coil 19S.

[0031] In this case, for example, the facing area S1 between the heat sink 21 and the fixture 23 is 0.0025 m 2 If the distance d1 between them is equivalently estimated to be 0.01 m, the parasitic capacitance C1 is approximately 20 pF. On the other hand, if the opposing area S2 of the coil 19S and the core 19C is 0.0025 m 2 If the distance d2 between them is equivalently estimated to be 0.002 m, the parasitic capacitance C2 is approximately 11 pF. If the insulating member 22 is made of ceramics such as alumina, silicon nitride, or aluminum nitride, the dielectric constant is large (εr=approximately 7 to 10), and therefore the parasitic capacitance C1 tends to be larger than the parasitic capacitance C2.

[0032] When such parasitic capacitances C1 and C2 (C1>>C2) are generated, if a voltage of 11.5 kV is applied to the coil 19S, a voltage of approximately 4.1 kV is applied to the parasitic capacitance C1, and a voltage of approximately 7.4 kV is applied to the parasitic capacitance C2. In other words, a large voltage tends to be applied between the coil 19S and the ferrite core 19C, which tend to have a lower withstand voltage than the insulating member 22, which has a high withstand voltage, and this can cause a dielectric breakdown.

[0033] Therefore, in this embodiment, as shown in FIG. 4, the ferrite core 19C or a fixture 23 electrically connected thereto is connected to the power line HL by a short-circuiting member 20. As a result, the ferrite core 19C and the fixture 23 are not at a floating potential but are given the potential of the power line HL. In this embodiment, the potential of the power line HL is the potential of the output node N1 of the first inverter circuit 17, i.e., the first pulse voltage. Therefore, without the short-circuiting member 20, a potential difference of approximately 7.4 kV occurs between the coil 19S and the ferrite core 19C. However, by using the short-circuiting member 20, this potential difference can be significantly reduced to 1.5 kV, which is the voltage of the smoothing circuit 15.

[0034] In this way, by applying the potential of the power line HL to the ferrite core 19C and the fixture 23, the voltage across the parasitic capacitance C2 becomes relatively lower than in the case of Fig. 3. On the other hand, the voltage across the parasitic capacitance C1 becomes higher than in the case of Fig. 3, but this does not pose a problem because the withstand voltage of the insulating member 22 is high. Therefore, according to the first embodiment, it is possible to provide a voltage generator that can effectively prevent dielectric breakdown due to floating potential.

[0035] FIG. 5 is a circuit diagram illustrating a modification of the voltage generator of the first embodiment. As described above, in FIG. 1, the power line HL and the fixture 23 are electrically connected (short-circuited) by the short-circuiting member 20. However, for example, the node N22 and the fixture 23 may be electrically connected (short-circuited) by the short-circuiting member 20. In this case, the potential difference between the coil 19S and the ferrite core 19C is smaller than in the case of FIG. 1, but the potential difference between the ferrite core 19C (which has the same potential or approximately the same potential as the fixture 23) and the heat sink 21 is larger. However, this is not a problem because the withstand voltage of the insulating member 22 is high. That is, by appropriately selecting the voltage at the point electrically connected (short-circuited) to the fixture 23, the potential difference between the inductor coil 19S and the inductor ferrite core 19C (which has the same potential as the fixture) can be reduced. Therefore, dielectric breakdown between the inductor coil 19S and the inductor ferrite core 19C can be made less likely.

[0036] The configuration of the voltage generator shown in Figures 1 and 5 is just one example, and similar short-circuiting members can also be used in voltage generators with other circuit configurations in which an inductor is mounted on a heat sink 21 via an insulating member 22.

[0037] [Second embodiment] Next, a voltage generator according to a second embodiment will be described with reference to Fig. 6. The overall configuration of the voltage generator may be the same as that of the first embodiment, so duplicated explanations will be omitted.

[0038] Fig. 6 is a cross-sectional view of some of the components included in the voltage generator of the second embodiment. The same components as those in Fig. 2 are given the same reference numerals in Fig. 6, and therefore, redundant explanations will be omitted.

[0039] In the voltage generator of the second embodiment, other circuits (14, 15, 17, 18) such as an inverter circuit are disposed on top of a base member 2 that is disposed on top of an insulating member 22 made of ceramic or the like. The base member 2 is a member in which an insulating layer 25 is disposed on top of a metal substrate 24, and a copper foil 26 is disposed on top of that. Note that the other circuits (14, 15, 17, 18) such as the inverter circuit and the inductor 19 are not shown in FIG. 6. The copper foil 26 functions as a power line and is connected, for example, to the output node N2 (see FIG. 1) of the first embodiment, to which the second pulse voltage is applied.

[0040] The metal substrate 24 of the base member 2 is at a floating potential, similar to the above-described ferrite core 19C. Therefore, the potential of the metal substrate 24 is influenced by the potential of the copper foil 26, the potential of the heat sink 21, and the like, and therefore, similar to the above-described ferrite core 19C, a large potential difference occurs between the copper foil 26 and the metal substrate 24, and in some cases, dielectric breakdown may occur between the copper foil 26 and the metal substrate 24.

[0041] 6, in the second embodiment, the metal substrate 24 and the copper foil 26 are short-circuited by a short-circuit member 27. This allows the metal substrate 24 to be given the potential of the copper foil 26, rather than a floating potential.

[0042] By applying the potential of the copper foil 26 to the metal substrate 24, a high voltage is prevented from being applied to the parasitic capacitance between the metal substrate 24 and the copper foil 26. Therefore, according to the second embodiment, it is possible to provide a voltage generator that can effectively prevent dielectric breakdown due to floating potential. Note that, as in the first embodiment, for example, the metal substrate 24 and the location to which the voltage of the node N22 is applied may be electrically connected (short-circuited) by a short-circuit member 27.

[0043] The effects of the first and second embodiments described above are as follows. Without short-circuit member 20, the third conductive member (e.g., ferrite core 19C of the inductor, metal substrate 24) is at a floating potential. As a result, the potential is influenced by the potential of the second conductive member (e.g., coil 19S of the inductor, copper foil 26) to which the first voltage is applied, the potential of the first conductive member (e.g., heat sink 21), and the like. This creates a large potential difference between the second conductive member and the third conductive member, which may result in dielectric breakdown between the second conductive member and the third conductive member. However, by electrically connecting a location at the same potential or approximately the same potential as the third conductive member to a location to which the second voltage is applied using a short-circuit member, the potential of the third conductive member can be made the same potential or approximately the same potential as the location to which the second voltage is applied (e.g., output node N1). In other words, by appropriately selecting the second voltage, the potential difference between the second conductive member and the third conductive member can be reduced. This makes it less likely that dielectric breakdown will occur between the second conductive member and the third conductive member. In this way, the potential difference between the first conductive member and the third conductive member becomes large, but this does not pose a problem because the withstand voltage of the first insulating member is high.

[0044] The present invention is not limited to the above-described embodiments and includes various modifications. For example, the above-described embodiments have been described in detail to clearly explain the present invention, and the present invention is not necessarily limited to those including all of the described configurations. Furthermore, it is possible to replace part of the configuration of one embodiment with the configuration of another embodiment, or to add the configuration of another embodiment to the configuration of one embodiment. Furthermore, it is possible to add, delete, or replace part of the configuration of each embodiment with other configurations. [Explanation of symbols]

[0045] 11…DC power supply 12...Inverter circuit 13...Transformer 14... Rectifier 15...Smoothing circuit 16…DC power supply 17...First inverter circuit 18...Second inverter circuit 19...Inductor 19C...Ferrite core (an example of a third conductive member) 19S... Coil (winding) (an example of the second conductive member) 20...Short-circuit member 21...heat sink (an example of a first conductive member) 22...insulating member (an example of a first insulating member) 23...Fixing device (an example of a third conductive member) 24...metal substrate (an example of a third conductive member) 25...insulating layer 26... Copper foil (power line) (an example of the second conductive member) X1: First voltage generator X2: Second voltage generator

Claims

1. a first conductive member at ground potential; a first insulating member disposed on the first conductive member; a second conductive member to which a first voltage is applied; a third conductive member at a floating potential disposed between the second conductive member and the first insulating member; a short-circuiting member that electrically connects a portion of the third conductive member that has the same potential or substantially the same potential as the third conductive member and a portion to which a second voltage is applied; Equipped with the location to which the second voltage is applied is selected so that the potential difference between the second conductive member and the third conductive member is smaller than that in a case where the short-circuit member is not connected; Voltage generator.

2. an inductor having a coil wound around a core; a fixture made of a conductive material that fixes the core, the second conductive member is a coil of the inductor, the third conductive member is a core of the inductor, The voltage generator according to claim 1 , wherein the short-circuiting member electrically connects the fixture and a location to which the second voltage is applied.

3. an insulating layer is provided on an upper portion of a metal substrate, and a base member having a power line disposed thereon is disposed on an upper portion of the insulating layer; and the second conductive member is the power line, the third conductive member is the metal substrate, The voltage generator according to claim 1 , wherein the short-circuiting member electrically connects the metal substrate and a location to which the second voltage is applied.

Images