Power circuit

Abstract

To suppress a corona discharge between a high-potential portion to which a high voltage is applied and a ground potential member.SOLUTION: A power supply circuit according to an embodiment comprises: an electrically conductive member at a reference potential; a first insulation member arranged on a front surface of the conductive member; a plurality of switching elements that are arranged on the front surface side opposite the conductive member of the first insulation member, and each have a body part and a terminal part extending from the body part; a sheet-like second insulation member that is interposed between the plurality of switching elements and the first insulation member, and has thermosoftening property; a circuit board that is arranged at a position separated in a direction away from the conductive member as seen from the plurality of switching elements, and is implemented so that the plurality of switching elements are connected in serial by connecting the terminal parts of the plurality of switching elements; and a third insulation member that covers the body parts of the plurality of switching elements and the second insulation member without making contact with the circuit board.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] Embodiments of the present invention relate to a power supply circuit.

Background Art

[0002] In a plasma processing apparatus used in a process of manufacturing a semiconductor device, a liquid crystal substrate, or the like, a power supply device for generating a high voltage may be provided, such as a pulse power supply device for generating a pulse voltage which is, for example, a pulsed voltage (Patent Document 1).

[0003] The pulse power supply device is configured to, for example, convert DC power into AC power by an inverter circuit, then convert the AC power into AC power with different voltage values by a transformer, rectify and smooth it by a rectifier smoothing circuit, and further generate a pulse voltage by a switching circuit or the like.

[0004] In the pulse power supply device as described above, for example, a pulse voltage having a potential of a high voltage with an absolute value of about 10 kV is output. For this reason, in the rectifier smoothing circuit and the switching circuit, a high-potential portion to which a high voltage with an absolute value of about 10 kV is applied by a high voltage application circuit occurs. As is well known, the higher the applied voltage, the easier it is for corona discharge to occur. Therefore, it is necessary to suppress corona discharge at such high-potential portions.

[0005] For example, there is a technique for suppressing the occurrence of corona discharge in a gap around a member having a ground potential in a high voltage application circuit (Patent Document 2). Specifically, a conductor having a ground potential is inserted between a part of a screw hole to which a screw used in the high voltage application circuit is attached and a high-potential portion to suppress electric field concentration in the screw hole.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

[0007] However, the applied voltage in Patent Document 2 is a relatively low voltage of about 3.3kV. For this reason, the disclosure in Patent Document 2 is limited to measures to prevent corona discharge in the air gap around the screw.

[0008] In contrast, when a high voltage of, for example, 10kV or more in absolute value is applied, corona discharge becomes even more likely to occur. Therefore, it is necessary to further strengthen measures to prevent corona discharge between high-potential areas such as conductive regions of circuit boards and switching elements, and components at ground potential. In particular, corona discharge is likely to occur from terminals and angular areas of switching elements, and measures to suppress corona discharge are necessary in these areas.

[0009] This invention has been made in view of these problems, and aims to provide a power supply circuit that can suppress corona discharge between a high-potential portion to which a high voltage is applied and a component at ground potential. [Means for solving the problem]

[0010] The power supply circuit according to the embodiment comprises a conductive member with a reference potential, a first insulating member disposed on the surface of the conductive member, a plurality of switching elements disposed on the surface of the first insulating member opposite to the conductive member and each having a main body and terminals extending from the main body, a second insulating member in the form of a sheet having heat-softening properties and interposed between the plurality of switching elements and the first insulating member, a circuit board disposed at a position away from the conductive member when viewed from the plurality of switching elements, and mounted such that the plurality of switching elements are connected in series by connecting the terminals of the plurality of switching elements, and a third insulating member that covers the main bodies of the plurality of switching elements and the second insulating member in a non-contact manner with the circuit board. [Effects of the Invention]

[0011] According to embodiments of the present invention, corona discharge can be suppressed between a high-potential portion to which a high voltage is applied and a component at ground potential. [Brief explanation of the drawing]

[0012] [Figure 1] Figure 1 is a circuit diagram showing an example of the configuration of a power supply circuit according to an embodiment. [Figure 2] Figure 2 is a circuit diagram showing an example of the configuration of the switching unit according to the embodiment. [Figure 3] Figure 3 is a schematic cross-sectional view showing an example of the physical configuration of the switching unit according to the embodiment. [Figure 4] Figure 4 is a diagram illustrating the height model of the mold resin according to the embodiment. [Figure 5] Figure 5 is an enlarged cross-sectional view showing how an insulating sheet is provided between the insulating member and the switching element according to the embodiment. [Modes for carrying out the invention]

[0013] Hereinafter, embodiments of the power supply circuit according to the present invention will be described with reference to the drawings. However, the present invention is not limited by these embodiments. In the following embodiments, parts with the same reference numerals are considered equivalent, and redundant explanations will be omitted as appropriate.

[0014] (Example of power supply circuit configuration) Figure 1 is a circuit diagram showing an example of the configuration of a power supply circuit 100 according to an embodiment. As shown in Figure 1, the power supply circuit 100 has switching units 10, 20, an output terminal 30, and an output node 40.

[0015] The switching units 10 and 20 are connected to each other via the output node 40. These switching units 10 and 20 output a pulse voltage from the output terminal 30 via the output node 40. In order to generate such a pulse voltage, a DC power supply DC (DCp or DCn) that supplies a DC voltage is connected to the power supply circuit 100.

[0016] When a DC voltage is applied from the DC power supply DC, the switching units 10 and 20 alternately repeat on / off. That is, when the switching unit 10 is on, the switching unit 20 is off, and when the switching unit 10 is off, the switching unit 20 is on. As a result, a pulse voltage is output from the output terminal 30.

[0017] At this time, the frequency of the pulsed voltage waveform is about several hundred kHz. However, depending on the application, various frequencies such as about several tens of kHz or about 1 MHz are used. In addition, since there is a slight delay in the on / off switching of these switching units 10 and 20, a dead time may occur when the pulses are switched, during which both switching units 10 and 20 are off.

[0018] In the example shown in Fig. 1(a), a positive voltage such as 12 kV is applied to the power supply circuit 100. That is, the potential difference between the high-potential side terminal and the low-potential side terminal of the DC power supply DCp is, for example, 12 kV, and the low-potential side terminal of the DC power supply DCp is connected to a ground potential such as 0 kV. Therefore, the potential of the high-potential side terminal becomes 12 kV, and thus the output voltage of the DC power supply DCp becomes +12 kV. As described above, a pulsed voltage between 12 kV and 0 kV is alternately output from the output terminal 30.

[0019] As in the example shown in FIG. 1(b), a negative voltage such as -12 kV may be applied to the power supply circuit 100. That is, the high-potential side terminal of the DC power supply DCn may be connected to a ground potential such as 0 kV, the potential of the low-potential side terminal may be set to -12 kV, and the output voltage of the DC power supply DCn may be set to -12 kV. In this case, a pulsed voltage between -12 kV and 0 kV is alternately output from the output terminal 30.

[0020] Note that the DC voltage of 12 kV or -12 kV applied to the power supply circuit 100 is merely an example, and the power supply circuit 100 of the embodiment assumes that a voltage of 10 kV or more in absolute value is applied. However, a voltage of less than 10 kV in absolute value may be applied to the power supply circuit 100 of the embodiment.

[0021] As described above, the power supply circuit 100 in FIG. 1 that generates a pulsed voltage can be applied to a pulsed power supply device used when performing plasma processing in, for example, a semiconductor manufacturing process.

[0022] FIG. 2 is a circuit diagram showing an example of the configuration of the switching unit 10 according to the embodiment.

[0023] As shown in FIG. 2, the switching unit 10 includes a plurality of sets of switching elements 111, gate drive circuits 121, and isolated DC-DC converters 122, with one set consisting of a switching element 111, a gate drive circuit 121, and an isolated DC-DC converter 122.

[0024] In the example of FIG. 2, the switching unit 10 includes six sets of switching elements 111, gate drive circuits 121, and isolated DC-DC converters 122, but the number of these configurations is not limited to six sets and is arbitrary. Also, as will be described later, each set of the switching element 111, the gate drive circuit 121, and the isolated DC-DC converter 122 may include a capacitor 123.

[0025] Each switching element 111 is configured as, for example, a field-effect transistor (FET). However, the switching element 111 may be an element other than a field-effect transistor, such as an insulated-gate bipolar transistor (IGBT) or other semiconductor switches.

[0026] These switching elements 111 are connected in series and mounted on a circuit board 110, such as a printed circuit board. The circuit board 110 on which these switching elements 111 are mounted functions as an FET board that switches the applied voltage. All switching elements 111 may be mounted on a single circuit board 110, or they may be divided and mounted on multiple circuit boards 110 if there are many switching elements 111.

[0027] A voltage of, for example, 12kV is applied to the switching element 111 at one end of the series connection from the DC power supply DCp mentioned above. The other end of the series connection switching element 111 is connected to the output node 40 mentioned above.

[0028] Each switching element 111 is connected to a gate drive circuit 121. The gate drive circuit 121 controls each switching element 111 corresponding to its gate drive circuit 121 so that these switching elements 111 are turned on or off simultaneously. To turn on a switching element 111, the gate drive circuit 121 supplies a voltage between the gate and source of the switching element 111 such that the potential difference is, for example, 24V.

[0029] Each gate drive circuit 121 receives a control signal from a control circuit (not shown). The gate drive circuit 121 controls the gate voltage of the switching element 111 according to the received control signal.

[0030] The voltage supplied by the gate drive circuit 121 between the gate and source of the switching element 111 is supplied from isolated DC-DC converters 122, each connected to an individual gate drive circuit 121. A DC power supply DCd, for example, 24V, is connected to each of the multiple isolated DC-DC converters 122. The DC power supply DCd is shared among these isolated DC-DC converters 122.

[0031] More specifically, the potential difference between the high-potential terminal and the low-potential terminal of the DC power supply DCd is, for example, 24V, and the low-potential terminal of the DC power supply DCd is connected to ground potential, such as 0kV. Therefore, the potential of the high-potential terminal becomes 24V, and thus the output voltage of the DC power supply DCd becomes 24V. As a result, a voltage of, for example, 24V is supplied from the DC power supply DCd to the isolated DC-DC converter 122.

[0032] Furthermore, each isolated DC-DC converter 122 incorporates a transformer (not shown), which isolates the primary side (input side) from the secondary side (output side).

[0033] If the gate drive circuit 121 consumes a large amount of power, a capacitor 123 may be inserted between the gate drive circuit 121 and the isolated DC-DC converter 122.

[0034] These gate drive circuits 121, isolated DC-DC converters 122, and capacitors 123 are mounted on a circuit board 120, such as a printed circuit board. The circuit board 120 on which the gate drive circuits 121, isolated DC-DC converters 122, and capacitors 123 are mounted functions, for example, as a driver board for driving switching elements 111.

[0035] In this case, all gate drive circuits 121, isolated DC-DC converters 122, and capacitors 123 may be mounted on a single circuit board 120. For example, if multiple switching elements 111 are mounted on multiple circuit boards 110, the gate drive circuits 121, isolated DC-DC converters 122, and capacitors 123 may be mounted on multiple circuit boards 120 corresponding to these circuit boards 110.

[0036] Furthermore, the switching unit 20 shown in Figure 1 above has a circuit configuration similar to that of the switching unit 10 shown in Figure 2. However, the potential supplied to the switching unit 20 is different from that of the switching unit 10.

[0037] When each switching element 111 is turned on, the drain-source connections of these switching elements 111 are electrically connected. As a result, a high voltage of 12kV is applied to the output node 40 via the series-connected switching elements 111.

[0038] Furthermore, when each switching element 111 is off, each switching element of the switching unit 20 is turned on and connected to a ground potential such as 0kV. Therefore, the drain-source potential of each switching element becomes 0kV, and the output node 40 also becomes 0kV.

[0039] At this time, a potential difference of 12kV is generated in the switching unit 10, and this potential difference is shared and borne by each switching element 111 of the switching unit 10, creating a potential difference between the drain and source of each switching element 111.

[0040] As shown in the example in Figure 2, if the switching unit 10 has, for example, six switching elements 111, the potential of the source of each switching element 111 will be, for example, 10kV, 8kV, 6kV, 4kV, 2kV, and 0kV in order from the switching element 111 at the top of the page.

[0041] Similarly, when each switching element 111 is turned on, each switching element in the switching unit 20 is turned off, creating a potential difference of 12kV in the switching unit 20. Therefore, this potential difference is shared and borne by each switching element in the switching unit 20, creating a potential difference between the drain and source of each switching element.

[0042] If the switching unit 20 also has, for example, six switching elements, the potential of the source of each switching element will be, in order from the switching element connected to the output node 40, for example, 10kV, 8kV, 6kV, 4kV, 2kV, and 0kV.

[0043] The same applies when a negative voltage such as -12kV is applied to the power supply circuit 100, as shown in Figure 1(b) above.

[0044] In other words, when the individual switching elements 111 of the switching unit 10 are turned on and the individual switching elements of the switching unit 20 are turned off, a potential difference of -12kV is generated in the switching unit 20. Therefore, the source potentials of the individual switching elements are, in order from the switching element connected to the output node 40, for example, -2kV, -4kV, -6kV, -8kV, -10kV, and -12kV.

[0045] Furthermore, when the individual switching elements 111 of the switching unit 10 are off and the individual switching elements of the switching unit 20 are on, a potential difference of -12kV is generated in the switching unit 10. Therefore, the source potentials of the individual switching elements 111 are, in order from the switching element 111 at the top of the page, for example, -2kV, -4kV, -6kV, -8kV, -10kV, and -12kV.

[0046] Thus, in a switching unit 10 to which a high voltage of 10kV or more in absolute value is applied, the potential difference can be shared among multiple switching elements 111, thereby suppressing dielectric breakdown of individual switching elements 111.

[0047] In other words, based on the magnitude of the potential difference generated in the switching section 10 and the breakdown voltage characteristics of each switching element 111, the number of switching elements 111 to be included in the switching section 10, as well as the number of gate drive circuits 121 and isolated DC-DC converters 122 associated with these switching elements 111, can be determined. The same applies to the number of switching elements in the switching section 20, as well as the number of gate drive circuits and isolated DC-DC converters.

[0048] (Example of switching element configuration) Next, an example of the configuration of the switching element 111 included in the power supply circuit 100 of the embodiment will be described using Figures 3 to 5.

[0049] Figure 3 is a schematic cross-sectional view showing an example of the physical configuration of a switching element 111 according to an embodiment. As shown in Figure 3, the multiple switching elements 111 are arranged at a distance from the circuit board 110, on a conductive member 114 with an insulating member 113 on its upper surface via an insulating sheet 112, and the entire structure is sealed with a molding resin 115.

[0050] As described above, the switching element 111 is prone to generating heat due to the high voltage applied to it and its high-speed operation, such as achieving a switching cycle of several hundred kHz. For this reason, as described above, the switching element 111 is not mounted directly on the circuit board 110, but is placed at a location away from the circuit board 110, for example, on a conductive material 114 with high thermal conductivity, to dissipate the heat from the switching element 111.

[0051] The conductive member 114 is a conductive plate-shaped member, such as a water-cooled copper plate, which has a built-in flow path for a cooling liquid (not shown), and cools the multiple switching elements 111 arranged on its upper surface via the insulating member 113. The conductive member 114 also has a ground potential of 0V or the like by being grounded. The potential of the conductive member 114 is also called the reference potential.

[0052] The first insulating member, the insulating member 113, is a plate-shaped member made of an insulating ceramic such as alumina, silicon nitride, or aluminum nitride, and insulates the space between the multiple switching elements 111 and the conductive member 114. The thickness of the plate-shaped insulating member 113 can be, for example, 10 mm.

[0053] Furthermore, as described above, by making the conductive member 114 and the insulating member 113 flat plates and their contact surfaces being planar, the contact area of ​​the conductive member 114 and the insulating member 113 can be maximized, thereby enhancing the heat dissipation effect of these members.

[0054] The insulating sheet 112, acting as a second insulating member, is placed between each of the multiple switching elements 111 and the insulating member 113. The insulating sheet 112 is a sheet-like resin or the like that has heat-softening properties, and dissipates the heat generated by each switching element 111 towards the conductive member 114. The insulating sheet 112 may be a heat-dissipating sheet or the like that has heat-softening properties.

[0055] Specifically, the insulating sheet 112 should have good thermal conductivity in addition to a certain degree of insulating properties. Furthermore, heat is applied when sealing the multiple switching elements 111 with the molding resin 115. It is desirable that the insulating sheet 112 be made of a material that does not deteriorate or decompose due to the heat generated at this time.

[0056] As an example of a material for the insulating sheet 112 that satisfies the above requirements, a phase change material (PCM) manufactured by Shin-Etsu Silicone can be cited. Among PCM materials, for example, PCS-CR-10 has a thermal conductivity of 2.0 W / m·K and a dielectric breakdown voltage of 8.0 kV / mm.

[0057] For example, since the thermal conductivity of air, which has poor insulating properties, is 0.0241 W / m·K, the insulating sheet 112 only needs to have a thermal conductivity of, for example, 1.0 W / m·K or higher, and PCS-CR-10 can be said to have sufficient thermal conductivity. Furthermore, since the dielectric breakdown voltage of aluminum nitride, one of the candidate materials for the insulating member 113, is 15 kV / mm, the above dielectric breakdown voltage of PCS-CR-10 provides sufficient dielectric strength as a lower component for multiple switching elements 111. In addition, since PCS-CR-10 is thermally softened, it is considered to meet the requirements for thermal resistance as well.

[0058] Each switching element 111 has a main body 11 placed on an insulating sheet 112, and a plurality of terminals 12d, 12g, and 12s extending upward from the upper surface of the main body 11. The main body 11 is a silicon chip or the like on which semiconductor elements such as FETs are mounted. The plurality of terminals 12d, 12g, and 12s pass through the molding resin 115 that encloses the switching element 111 and are connected to the circuit board 110. In this way, each switching element 111 is mounted on the circuit board 110 so that it is connected in series with each other.

[0059] Of the terminals 12d, 12g, and 12s of the switching element 111, terminal 12d, as the first terminal, is the drain terminal connected to the drain of the FET, and a high voltage is applied from the circuit board 110. The applied voltage, which is the voltage of the first potential, is, for example, the voltage supplied from the DC power supplies DCp and DCn shown in Figure 1 above, and is a voltage of, for example, 10kV or more in absolute value.

[0060] Furthermore, terminal 12s, which acts as a second terminal, is a source terminal connected to the source of the FET, and is electrically connected to terminal 12d when the switching element 111 is turned on. Also, terminal 12g, which acts as a third terminal, is a gate terminal connected to the gate of the FET, and receives a voltage signal from the circuit board 110 that controls the on / off state of the switching element 111.

[0061] Note that the arrangement of these terminals 12d, 12g, and 12s is not limited to the example in Figure 3.

[0062] The circuit board 110 is supported above the multiple switching elements 111, separated from them, by, for example, a support column 116 provided on the upper surface of the insulating member 113. The circuit board 110 is a printed wiring board or the like, and has multiple electrodes 13d, 13g, and 13s on its lower surface facing the switching elements 111.

[0063] Of these electrodes 13d, 13g, and 13s, electrode 13d is connected to terminal 12d of the switching element 111 and outputs the applied voltage from the circuit board 110 to terminal 12d. Electrode 13g is connected to terminal 12g of the switching element 111 and outputs the voltage signal from the circuit board 110 to terminal 12g. Electrode 13s is connected to terminal 12s of the switching element 111 and generates a potential difference between the source and drain of the switching element 111 via terminal 12s.

[0064] The molded resin 115, acting as a third insulating material, covers the main body 11 of the multiple switching elements 111 without contacting the circuit board 110. This allows the molded resin 115 to seal the multiple switching elements 111 onto the insulating material 113. Therefore, the molded resin 115 also contains insulating sheets 112 interposed between each switching element 111 and the insulating material 113.

[0065] In the example shown in Figure 3, two switching elements 111 are sealed within the same molded resin 115, but the number of switching elements 111 sealed within a single molded resin 115 is not limited to this. Each switching element 111 may be sealed individually within the molded resin 115, or two or more switching elements 111 may be sealed together within a single molded resin 115, as in the example shown in Figure 3.

[0066] The molding resin 115 is an insulating resin, such as silicone resin. Specifically, it is desirable that the molding resin 115 has good insulating properties and good thermal conductivity.

[0067] For example, since the dielectric breakdown voltage of air is 3.0 kV / mm, it is preferable that the molding resin 115 has a dielectric breakdown voltage greater than 3.0 kV / mm. Since the dielectric breakdown voltage of typical silicone resins is around 20 kV / mm to 30 kV / mm, as mentioned above, sufficient dielectric strength can be obtained by using, for example, silicone resin for the molding resin 115.

[0068] Furthermore, as mentioned above, since the thermal conductivity of air is 0.0241 W / m·K, it is preferable that the molding resin 115 has a thermal conductivity of, for example, 1.0 W / m·K or higher. Since the thermal conductivity of general silicone resins is around 0.1 W / m·K to 5.1 W / m·K, it is possible to select one that satisfies the above requirements from among various silicone resins.

[0069] As an example of a mold resin 115 material that satisfies the above requirements, one example is KE-1897, a silicone resin manufactured by Shin-Etsu Silicone. KE-1897 has a thermal conductivity of 1.6 W / m·K and a dielectric breakdown voltage of 25 kV / mm.

[0070] Furthermore, KE-1897 has high viscosity, and it is presumed that when used, for example, as a molding resin 115 to encapsulate a switching element 111, it will have high adhesion to the switching element 111 and the insulating base material 113. Therefore, it is thought that peeling of the molding resin 115 film will be easily suppressed.

[0071] In this way, by encapsulating multiple switching elements 111 with a mold resin 115 made of a material with a high dielectric breakdown voltage, such as silicone resin, corona discharge between the circuit board 110 or the terminals 12d, 12g, and 12s of the switching elements 111 and the conductive members 114 and other structures beneath them is suppressed.

[0072] Furthermore, the electric field strength tends to be higher at sharp parts such as the corners of the chip-shaped switching element 111, making it prone to corona discharge. Since the corners of the chip shape are covered with the molded resin 115, the occurrence of corona discharge can be suppressed in this respect as well.

[0073] Furthermore, unlike the example shown in Figure 3, if terminals 12d, 12g, and 12s have a bent shape, this portion may also cause corona discharge. In this case as well, corona discharge can be suppressed by covering the bent portions of terminals 12d, 12g, and 12s with the molded resin 115.

[0074] Here, the circuit board 110 is placed on the insulating member 113 at a predetermined distance Ds. The height of the molded resin 115 is within a range less than the distance Ds between the circuit board 110 and the insulating member 113, and is set so that the distance from the top surface of the insulating member 113 to the top surface of the molded resin 115 is a predetermined distance Dm.

[0075] The lengths of the terminals 12d, 12g, and 12s of the switching element 111 have a predetermined upper limit, and in order to suppress the enlargement of the power supply circuit 100 including the switching unit 10, the distance Ds between the circuit board 110 and the insulating member 113 is limited. Therefore, the distance Dm, which is the height of the molded resin 115, becomes an even smaller value.

[0076] On the other hand, near conductive parts of the circuit board 110, such as electrodes 13d, 13g, and 13s, where the absolute voltage is 10kV or higher, the electric field strength is high, making it easy for corona discharge to occur. The appropriate height of the mold resin 115 to suppress such corona discharge will be considered below.

[0077] Figure 4 is a diagram illustrating the height model of the mold resin 115 according to the embodiment.

[0078] As shown in Figure 4, the grounded conductive member 114 has a potential of 0kV.

[0079] Furthermore, if a high voltage such as 12kV as shown in Figure 1(a) above is applied to terminal 12d of the switching element 111, terminal 12s will also reach a high potential when the switching element 111 is turned on. In addition, a voltage such as 24V, as shown in the example in Figure 2 above, is applied to terminal 12g of the switching element 111, which is a voltage that differs from terminal 12s by a predetermined potential difference. Therefore, when the switching element 111 is turned on, terminal 12g will also reach a high potential.

[0080] Therefore, the entire conductive portion of the circuit board 110, including electrodes 13d, 13g, and 13s, will have a high potential of 12kV or higher. Corona discharge occurs when a voltage exceeding the dielectric strength of the components that exist between the high-potential and low-potential portions is applied to these components.

[0081] In the example shown in Figure 4, the materials present between the conductive member 114, which has a potential of 0 kV, and the circuit board 110, which has a potential of 12 kV, are an insulating member 113 such as aluminum nitride, a molded resin 115, and an air layer in the gap between the upper surface of the molded resin 115 and the lower surface of the circuit board 110. Note that the insulating sheet 112 is an extremely thin material, for example, only about 10-20 μm thick, compared to these materials, and is therefore not considered here.

[0082] Here, if we denote the voltages applied to the insulating member 113, the molded resin 115, and the air layer as Vc, Vb, and Va, respectively, and their parasitic capacitances as Cc, Cb, and Ca, then the following relationship exists between these voltages and parasitic capacitances.

[0083] Va:Vb:Vc = 1 / Ca:1 / Cb:1 / Cc

[0084] Furthermore, from the above relationship, the voltage Va applied to the air layer can be calculated as follows.

[0085] Va=12kV×(1 / Ca) / (1 / Ca)+(1 / Cb)+(1 / Cc) =3.59kV

[0086] The parasitic capacitance is a value that can be determined from the dielectric constant ε, thickness d, and area S of the material, as follows.

[0087] C = ε·S / d

[0088] Here, the dielectric constants ε of the insulating member 113, the molded resin 115, and the air layer are 8.5, 6, and 1, respectively, assuming the insulating member 113 is aluminum nitride and the molded resin 115 is silicone resin. Furthermore, the thicknesses d of the insulating member 113, the molded resin 115, and the air layer are assumed to be 10 mm, 7 mm, and 1 mm, respectively. The areas S of the insulating member 113, the molded resin 115, and the air layer are not considered because they cancel each other out during the calculation process of the above formula.

[0089] In such a case, as described above, the voltage Va applied to the air layer is 3.59kV, and the dielectric strength of the 1mm thick air layer at this time is 3kV. Therefore, if the thickness d of the air layer between the molded resin 115 and the circuit board 110 is 1mm, the dielectric strength will be insufficient and corona discharge may occur.

[0090] Based on the above, let's consider a more practical configuration. In the switching unit 10 of the embodiment, the distance Ds between the circuit board 110 and the insulating member 113 shown in Figure 3 above can be 12 mm as an example.

[0091] Based on this premise, in order to increase the dielectric strength of the air layer above the voltage Va applied to the air layer, it is preferable to make the thickness d of the air layer greater than, for example, 1 mm, and for example, 3 mm or more. For example, a voltage Va of 5.82 kV will be applied to a 3 mm thick air layer, and the dielectric strength of a 3 mm thick air layer is 9 kV. Therefore, a 3 mm thick air layer has sufficient dielectric strength against the applied voltage Va, and theoretically, corona discharge will not occur.

[0092] As shown in Figure 3 above, the thickness of the air layer in the gap between the upper surface of the molded resin 115 and the lower surface of the circuit board 110 is the distance (Ds-Dm). Therefore, it is preferable to keep the distance Dm, which is the height of the molded resin 115, to less than 11 mm, and more preferably to keep it to 9 mm or less. This makes it possible to secure an air layer thickness d that is greater than 1 mm, for example, 3 mm or more.

[0093] The configuration shown in Figure 4 can be obtained as follows.

[0094] First, an insulating member 113, such as aluminum nitride, is provided on the upper surface of a conductive member 114, such as a water-cooled copper plate. Multiple switching elements 111 are then arranged on the insulating member 113. At this time, an insulating sheet 112 is interposed between the insulating member 113 and the switching elements 111 to prevent the intrusion of an insulating air layer. This is shown in Figure 5.

[0095] Figure 5 is an enlarged cross-sectional view showing how an insulating sheet 112 is provided between the insulating member 113 and the switching element 111 according to the embodiment.

[0096] As shown in Figure 5(a), multiple switching elements 111 are arranged on the insulating member 113, each with an insulating sheet 112 in between. The insulating member 113 and the switching elements 111 have fine irregularities on their surfaces. Therefore, at this point, there are fine gaps between the insulating member 113 and the insulating sheet 112, and between the insulating sheet 112 and the switching elements 111.

[0097] As shown in Figure 5(b), when the insulating sheet 112 is heated to a predetermined temperature, the insulating sheet 112 softens due to the heat, and the insulating member 113 and the multiple switching elements 111 adhere to each other. At this time, as the insulating sheet 112 softens, it fills in the fine irregularities on the surfaces of the insulating member 113 and the switching elements 111. Therefore, the intrusion of an air layer is suppressed, and the insulating member 113 and the multiple switching elements 111 are in close contact.

[0098] As a result, multiple switching elements 111 are bonded to the insulating member 113 by the insulating sheet 112, and are also thermally connected to the conductive member 114 via the insulating member 113, thus providing a configuration that allows for efficient cooling of the switching elements 111.

[0099] Next, the switching element 111 is sealed with molding resin 115 while terminals 12d, 12g, and 12s protrude from the top surface. The sealing of the switching element 111 with molding resin 115 can be done, for example, using a molding method with a mold.

[0100] Specifically, multiple switching elements 111, bonded to an insulating sheet 112, are placed in a mold on an insulating member 113 provided on the upper surface of a conductive member 114, and a heated and melted silicone resin or the like is injected into the mold. After this, the thermoplastic silicone resin cools and solidifies to form the molded resin 115. As mentioned above, since the insulating sheet 112 is thermosoft, it is prevented from being altered or decomposed by the heat generated during the formation of the molded resin 115.

[0101] Next, the circuit board 110 is supported above the multiple switching elements 111 sealed in the molded resin 115. Furthermore, the terminals 12d, 12g, and 12s that protrude from the upper surface of the molded resin 115 sealing the multiple switching elements 111 are connected to the electrodes 13d, 13g, and 13s of the circuit board 110, respectively, so that the multiple switching elements 111 are mounted on the circuit board 110 in series with each other.

[0102] Based on the above, the configuration shown in Figure 4 is manufactured.

[0103] The configuration of the switching unit 10, mainly consisting of the switching element 111, has been described above using Figures 3 to 5. However, the various configurations described above can also be applied to the switching unit 20.

[0104] (Overview) In plasma processing, which is part of semiconductor manufacturing processes, power supply circuits such as high-voltage pulse power supplies are sometimes used. These power supply circuits use switching elements to output pulse voltages. Insulation measures are taken for switching elements that operate under high voltage.

[0105] However, when the output voltage exceeds, for example, 10kV in absolute value, the electric field strength near the high-voltage components of the switching element increases, making corona discharge more likely. In addition, switching elements that operate at high speeds under high voltage tend to generate heat, and cooling mechanisms such as water-cooled copper plates with aluminum nitride ceramic plates are used to suppress damage due to overheating.

[0106] In the cooling mechanism described above, for example, increasing the thickness of the ceramic plate inserted between the water-cooled copper plate and the switching element allows for a greater distance between the high-potential circuit board and the water-cooled copper plate at the reference potential, thereby making corona discharge less likely to occur. However, increasing the thickness of the ceramic plate moves the switching element further away from the water-cooled copper plate, reducing cooling efficiency.

[0107] Furthermore, as mentioned above, there are constraints on the distance between these components, and given this device configuration, it is difficult to ensure sufficient insulation distance between the switching element and components with potential differences, such as the ceramic plate and the water-cooled copper plate. Therefore, further measures are needed to prevent damage to the switching element due to corona discharge.

[0108] According to the power supply circuit 100 of this embodiment, a molded resin 115 is provided that covers the main body 11 of a plurality of switching elements 111 and an insulating sheet 112, without contact with the circuit board 110. This makes it possible to suppress corona discharge between the high-potential area to which high voltage is applied and the ground potential component.

[0109] According to the power supply circuit 100 of this embodiment, a heat-softening insulating sheet 112 is interposed between each of the multiple switching elements 111 and the insulating member 113. This improves the adhesion between the switching elements 111 and the insulating member 113, making it possible to further suppress corona discharge.

[0110] Furthermore, in previous technologies, when arranging switching elements on a ceramic plate, a thermal grease or similar material was applied to the ceramic plate before arranging the switching elements to prevent an air layer from entering between the switching elements and the ceramic plate, thus preventing insulation.

[0111] However, if such a configuration is sealed with, for example, mold resin, there is a concern that the heat generated during the molding process may cause the thermal grease to volatilize, creating bubbles, or that the oil in the thermal grease may separate, preventing the mold resin from solidifying sufficiently around it, resulting in the inclusion of bubbles.

[0112] As described above, by using a heat-softening insulating sheet 112 instead of thermal grease, for example, it is possible to suppress deterioration and decomposition of the insulating sheet 112 due to heat during molding of the molded resin 115, and to prevent air bubbles from being mixed into the molded resin 115.

[0113] In this way, by sealing the switching element 111 with the mold resin 115, the occurrence of corona discharge can be suppressed, while the heat dissipation effect can be enhanced by using the insulating sheet 112.

[0114] According to the power supply circuit 100 of this embodiment, the distance between the electrodes 13d, 13g, 13s, etc. of the circuit board 110 and the upper surface of the molded resin 115 is set to a distance such that no discharge occurs between the electrodes 13d, 13g, 13s, etc. of the circuit board 110 and the molded resin 115.

[0115] As described above, if the distance (Ds-Dm) between the circuit board 110 and the molded resin 115 is not sufficiently maintained, corona discharge may occur in the air layer between these components. By setting the distance (Ds-Dm) as described above, such corona discharge can be further suppressed.

[0116] Furthermore, corona discharge is suppressed without the need to take measures such as moving the conductive member 114 at the reference potential away from the high-potential circuit board 110. Therefore, for example, there is no need to thicken the insulating member 113, making it possible to maintain good cooling efficiency. In addition, it becomes easier to miniaturize the power supply circuit 100.

[0117] According to the power supply circuit 100 of this embodiment, the voltage applied to the terminal 12d of the switching element 111 is a predetermined potential voltage with an absolute value of 10kV or more. Thus, even when dealing with an applied voltage of 10kV or more in absolute value, for example, the power supply circuit 100 of this embodiment can be applied while suppressing the occurrence of corona discharge with the configuration described above.

[0118] Furthermore, experiments conducted by the inventors have confirmed that corona discharge can be suppressed even when handling applied voltages up to approximately 12kV in absolute value. Considering that conventional power supply circuits experienced corona discharge at an absolute value of approximately 10kV, it can be said that the above configuration of the embodiment provides sufficient protection against corona discharge.

[0119] In the above embodiment, an insulating sheet 112 was interposed between the switching element 111 and the insulating member 113. However, a material similar to, for example, the molding resin 115 may be interposed between these members.

[0120] For example, silicone resin, which can be used as the material for the molding resin 115, has sufficient adhesiveness. Therefore, even when using a molding resin such as silicone resin, the adhesion between the switching element 111 and the insulating member 113 can be improved. Furthermore, molding resins such as silicone resin also have good thermal conductivity. Therefore, the heat dissipation of the switching element 111 can be sufficiently improved even with the molding resin.

[0121] Furthermore, in the above-described embodiment, corona discharge countermeasures were implemented targeting the switching element 111. However, the configuration of the above-described embodiment is applicable not only to the switching element 111 but also to various devices used for high-voltage control.

[0122] (Note) Preferred embodiments of the present invention are described below.

[0123] (Note 1) According to one aspect of the present invention, A conductive member with a reference potential, A first insulating member is disposed on the surface of the conductive member, A plurality of switching elements are arranged on the surface side of the first insulating member opposite to the conductive member, each having a main body and a terminal portion extending from the main body, A heat-softening sheet-like second insulating member is interposed between each of the plurality of switching elements and the first insulating member, A circuit board is mounted such that the multiple switching elements are connected in series, with the terminal portions of the multiple switching elements connected to a position away from the conductive member, as viewed from the multiple switching elements, and the multiple switching elements are arranged at a distance from the conductive member. The circuit board is not in contact with the main body portion of the plurality of switching elements and the third insulating member which covers the second insulating member. A power supply circuit is provided.

[0124] This makes it possible to suppress corona discharge between the high-potential area to which high voltage is applied and the ground potential component.

[0125] (Note 2) In the power supply circuit described in Appendix 1 above, The contact surface between the conductive member and the first insulating member is flat.

[0126] If the contact surfaces of these components are flat, the contact area between them can be maximized, thereby improving heat dissipation.

[0127] (Note 3) In the power supply circuit described in Appendix 1 above, The terminal portion is deformed inside the third insulating member covering the main body portion so that the terminal shape faces the circuit board side.

[0128] Even when the terminal shape is deformed in this way and has a pointed part, the occurrence of corona discharge can be suppressed by covering this part with a third insulating material.

[0129] While several embodiments of the present invention have been described, these embodiments are presented as examples only and are not intended to limit the scope of the invention. These embodiments can be carried out in a variety of other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their variations are included in the scope and spirit of the invention, as well as in the claims and their equivalents. [Explanation of Symbols]

[0130] 10, 20... Switching section, 11... Main body section, 12d, 12g, 12s... Terminals, 13d, 13g, 13s... Electrodes, 30... Output terminal, 40... Output node, 100... Power supply circuit, 110, 120... Circuit board, 111... Switching element, 112... Insulating sheet, 113... Insulating material, 114... Conductive material, 115... Molding resin.

Claims

1. A conductive member with a reference potential, A first insulating member is disposed on the surface of the conductive member, A plurality of switching elements are arranged on the surface side of the first insulating member opposite to the conductive member, each having a main body and a terminal portion extending from the main body, A heat-softening sheet-like second insulating member is interposed between the plurality of switching elements and the first insulating member, A circuit board is mounted such that the multiple switching elements are connected in series, with the terminal portions of the multiple switching elements connected to a position away from the conductive member, as viewed from the multiple switching elements, and the multiple switching elements are arranged at a distance from the conductive member. The circuit board is not in contact with the main body portion of the plurality of switching elements and the third insulating member which covers the second insulating member. power circuit.

2. Each of the switching elements of the plurality of switching elements has a terminal portion, A first terminal connected to the circuit board, to which a voltage of a first potential is applied from the circuit board, A second terminal connected to the circuit board and electrically connected to the first terminal when the switching element is turned on, It has a third terminal connected to the circuit board, to which a voltage signal controlling the on / off state of the switching element is input from the circuit board, The distance between the conductive portion of the circuit board and the upper surface of the third insulating member is set to a distance such that no discharge occurs between the conductive portion of the circuit board and the third insulating member. The power supply circuit according to claim 1.

3. The aforementioned reference potential is the ground potential. The voltage of the first potential is such that the absolute value of the potential is 10 kV or more. The power supply circuit according to claim 2.

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