SEMICONDUCTOR DEVICE

BACKGROUND OF THE INVENTION
Field of the Invention

The present disclosure relates to semiconductor devices and, in particular, to a semiconductor device including a plurality of semiconductor elements connected in parallel with one another.

Description of the Background Art

A power semiconductor device includes semiconductor elements as switching elements in many cases. For example, semiconductor dements each having a gate electrode, such as metal oxide semiconductor field effect transistors (MOSFETs) and insulated gate bipolar transistors (IGBTs), are used. In particular, a high power semiconductor device often includes switching elements connected in parallel with one another. In the semiconductor device, positive feedback circuits are sometimes formed by parasitic capacitance and stray inductance of the semiconductor elements to result in occurrence of parasitic oscillations. The severity of parasitic oscillations is likely to increase in proportion to the number of semiconductor elements connected in parallel with one another. A circuit to suppress parasitic oscillations is often provided. According to WO 2017/026,367, a balance resistor unit having a diode is connected to each of semiconductor switching elements.

According to the above-mentioned conventional technology, balance resistor units equal in number to the number of semiconductor switching elements connected in parallel with one another are required. Thus, in a ease where many semiconductor switching elements are connected in parallel with one another, many diodes are required. This results in complication of a configuration of the semiconductor device.

SUMMARY

The present disclosure has been conceived to solve a problem as described above, and it is an object of the present disclosure to provide a semiconductor device having a simple configuration to suppress parasitic oscillations occurring among a plurality of semiconductor dements connected in parallel with one another.

A semiconductor device of the present disclosure includes a plurality of semiconductor elements and a drive circuit. The plurality of semiconductor elements are connected in parallel with one another, and each have a gate electrode. The plurality of semiconductor elements include a plurality of first semiconductor elements and a plurality of second semiconductor elements. The drive circuit is to provide a gate signal to the gate electrode of each of the plurality of semiconductor elements. The drive circuit includes a main circuit and a plurality of inserted circuits. The plurality of inserted circuits include a first inserted circuit and a second inserted circuit. The first inserted circuit is inserted between the main circuit and the plurality of first semiconductor elements. The second inserted circuit is inserted between the main circuit and the plurality of second semiconductor elements. Each of the first inserted circuit and the second inserted circuit includes a first diode having a forward direction toward the main circuit and a second diode connected in anti-parallel with the first diode.

According to the semiconductor device of the present disclosure, in a case where the gate electrode of the first semiconductor elements has a positive voltage with respect to the gate electrode of the second semiconductor elements, a current flowing from the first semiconductor elements to the second semiconductor elements is interrupted unless the positive voltage exceeds the sum of a forward voltage of the first diode of the first inserted circuit and a forward voltage of the second diode of the second inserted circuit. In contrast, in a case where the gate electrode of the second semiconductor elements has a positive voltage with respect to the gate electrode of the first semiconductor elements, a current flowing from the second semiconductor elements to the first semiconductor elements is interrupted unless the positive voltage exceeds the sum of a forward voltage of the first diode of the second inserted circuit and a forward voltage of the second diode of the first inserted circuit. Parasitic oscillations are removed by interruption of these currents while a voltage across the plurality of first semiconductor elements and the plurality of second semiconductor elements is sufficiently low. In other words, parasitic oscillations having small amplitudes are removed. Parasitic oscillations having large amplitudes occurring due to development of parasitic oscillations having small amplitudes are thereby suppressed. On the other hand, the plurality of semiconductor elements are connected to each of the inserted circuits, so that the number of inserted circuits can be smaller than the number of semiconductor elements. A configuration of the semiconductor device can thus be simplified. As described above, parasitic oscillations occurring among the plurality of semiconductor elements connected in parallel with one another can be suppressed by the simple configuration.

These and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view illustrating an example of a configuration of a semiconductor device in Embodiment 1;

FIG. 2 is a block diagram partially showing the configuration of the semiconductor device of FIG. 1;

FIG. 3 is a circuit diagram schematically showing an upper arm portion and a plurality of inserted circuits connected to the upper arm portion of FIG. 2;

FIG. 4 is a circuit diagram showing a state of a freewheeling diode being connected in parallel with each of a plurality of semiconductor elements of FIG. 3;

FIG. 5 is a circuit diagram schematically showing an upper arm portion and a plurality of inserted circuits connected to the upper arm portion of a semiconductor device in Embodiment 2;

FIG. 6 is a circuit diagram schematically showing an upper arm portion and a plurality of inserted circuits connected to the upper arm portion of a semiconductor device in Embodiment 3; and

FIG. 7 is a circuit diagram schematically showing an upper arm portion and a plurality of inserted circuits connected to the upper arm portion of a semiconductor device in Embodiment 4.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiments will be described below based on the drawings. The same or similar components bear the same reference signs in the drawings described below, and description thereof will be not repeated.

Embodiment 1

FIG. 1 is a cross-sectional view illustrating an example of a configuration of a semiconductor device 90 in Embodiment 1. The semiconductor device 90 includes an insulating substrate 10 (a first substrate), a solder joint 21, a solder joint 22, a base plate 31, at least one semiconductor chip 32 (semiconductor component), a plurality of wires 40, a plurality of main electrodes 51, a drive electrode 52, a printed circuit board 60 (second substrate), a case 71, a sealing material 72, and a lid 73. The insulating substrate 10 includes an insulating plate 13 having a first surface (a lower surface in FIG. 1) and a second surface (an upper surface in FIG. 1), a conductor layer 11 located on the first surface, and a conductor layer 12 located on the second surface and having a pattern. The plurality of wires 40 include a main wire 41 and drive wires 42.

The case 71 has a space to be closed by the case 71 being combined with the base plate 31 and the lid 73, and the other members described above are housed in the space. The main electrodes 51 and the drive electrode 52 have been attached to the case 71. The main electrodes 51 are for a high current to be controlled by the semiconductor device 90, and the drive electrode 52 is to receive a drive signal from outside the semiconductor device 90. The conductor layer 11 of the insulating substrate 10 is joined to the base plate 31 by the solder joint 21. The semiconductor chip 32 is joined to the conductor layer 12 of tire insulating substrate 10 by the solder joint 22. The main electrodes 51 are electrically connected to the semiconductor chip 32 through the main wire 41. The drive electrode 52 is electrically connected to the semiconductor chip 32 through the drive wires 42 and the conductor layer 12. The semiconductor chip 32 mounted on the conductor layer 12 and the wires 40 are covered with the sealing material 72 formed of a gel. The sealing material 72 and the outside of the ease 71 are separated by the lid 73. There is a space between the sealing material 72 and the lid 73, and the printed circuit board 60 is disposed in the space.

FIG. 2 is a block diagram partially showing the configuration of the semiconductor device 90 of FIG. 1. The semiconductor device 90 is a power semiconductor device, specifically an inverter device to receive an external control signal while being subjected to application of a reference potential to a terminal N and application of a high voltage to a terminal P to thereby generate high power from a terminal U in response to the control signal. The terminals P, N, and U are configured by the plurality of main electrodes 51 (FIG. 1). Electrical paths from these terminals may be configured using the main wire 41 (FIG. 1). A single phase (“2 in 1”) inverter device can be obtained by the configuration of FIG. 2, but two or three phase inverter device can be configured by providing a plurality of configurations similar to the configuration of FIG. 2, for example.

The semiconductor device 90 includes a high-side drive circuit 200, an upper arm portion 310, a low-side drive circuit 700, and a lower arm portion 810. The high-side drive circuit 200 includes a high-side drive main circuit 201 and a plurality of inserted circuits 210. The plurality of inserted circuits 210 include a first inserted circuit 211 and a second inserted circuit 212. The low-side drive circuit 700 includes a low-side drive main circuit 701 and a plurality of inserted circuits 210. The high-side drive main circuit 201 has a terminal VS and a terminal HO. The high-side drive main circuit 201 generates, from the terminal HO, a gate signal for the upper arm portion 310, using a potential applied to the terminal VS as a reference potential. The low-side drive main circuit 701 generates, from a terminal LO, a gate signal for the lower arm portion 810, using a potential applied to a terminal VN as a reference potential. The inserted circuits 210 of each of the high-side drive circuit 200 and the low-side drive circuit 700 may be mounted, on the printed circuit board 60. Each of the high-side drive main circuit 201 and the low-side drive main circuit 701 has a terminal to receive the external control signal and a terminal to be provided with a power supply voltage, which are not shown.

Each of the high-side drive main, circuit 201 and the low-side drive main circuit 701 may be configured by an integrated circuit (IC) chip, or both the high-side drive main circuit. 201 and the low-side drive main circuit 701 may be configured by a single IC chip. The high-side drive main circuit 201 and the low-side drive main circuit 701 may be mounted on the printed circuit board 60, or may be arranged outside the case 71 without being mounted on the printed circuit board 60. A short-circuit protection circuit may be mounted on the printed circuit board 60 together with the high-side drive main circuit 201 and the low-side drive main circuit 701.

FIG. 3 is a circuit diagram schematically showing the upper arm portion 310 and the plurality of inserted circuits 210 connected to the upper arm portion 310 of FIG. 2. The upper arm portion 310 includes a plurality of semiconductor elements, specifically a plurality of first semiconductor elements EL1 and a plurality of second semiconductor dements EL2. In the present description, the plurality of semiconductor elements including the plurality of first semiconductor elements EL1 and tire plurality of second semiconductor elements EL2 are genetically referred to as semiconductor elements EL. In the present embodiment, the upper arm portion 310 is partitioned into two blocks, a first block BK1 and a second block BK2. From among the plurality of semiconductor elements EL, semiconductor elements EL arranged in the first block BK1 are the first semiconductor elements EL1, and semiconductor demerits EL arranged in the second block BK2 are the second semiconductor elements EL2. The number of first semiconductor elements EL1 and the number of second semiconductor elements EL2 are each any number greater than one. The first semiconductor elements EL1 and the second semiconductor elements EL2 are preferably equal in number.

The plurality of semiconductor elements EL (FIG. 3) are configured by the at least one semiconductor chip 32 (FIG. 1), and are thus mounted on the insulating substrate 10 (FIG. 1). The plurality of semiconductor elements EL are connected in parallel with one another. One end of the parallel connection is connected to the terminal P. The other end of the parallel connection is connected to a terminal A connected to the terminal U. Each of the plurality of semiconductor elements EL is a semiconductor switching element having a gate electrode, and is a MQSFET or an IGBT, for example. In a case of MOSFETs, the above-mentioned parallel connection is configured by substantially short-circuiting source electrodes thereof and also substantially short-circuiting drain electrodes thereof. In a case of IGBTs, the above-mentioned parallel connection is configured by substantially short-circuiting emitter electrodes thereof and also substantially short-circuiting collector electrodes thereof. Although not shown, in FIG. 3, a freewheeling diode DF may be connected in parallel with each of the semiconductor elements EL as shown in FIG. 4.

The high-side drive circuit 200 (FIG. 2) is to provide the gate signal to the gate electrode of each of the plurality of semiconductor elements EL of the upper arm portion 310. The first inserted circuit 211 of the high-side drive circuit 200 is inserted between the high-side drive main circuit 201 (FIG. 2) and gate electrodes of the plurality of first semiconductor elements EL1 (FIG. 3). The second inserted circuit 212 of the high-side drive circuit 200 is inserted between the high-side drive main circuit 201 (FIG. 2) and gate electrodes of the plurality of second semiconductor elements EL2 (FIG. 3). Specifically, the first inserted circuit 211 is inserted between the terminal HO and a terminal HOa. The terminal HOa is electrically connected to the gate electrodes of the plurality of first semiconductor elements EL1, but is not electrically connected to the gate electrodes of the plurality of second semiconductor elements EL2. The second inserted circuit 212 is inserted between the terminal HO and a terminal HOb. The terminal HOb is electrically connected to the gate electrodes of the plurality of second semiconductor elements EL2, but is not electrically connected to tire gate electrodes of the plurality of first semiconductor elements EL1.

A detailed configuration of the lower arm portion 810 (FIG. 2) is not shown, but the lower arm portion 810 has a substantially similar configuration to the upper arm portion 310 (FIG. 3) described in details above. The lower arm portion 810 is different from the upper arm portion 310 in that one end of parallel connection of the plurality of semiconductor elements EL of the lower arm portion 810 is connected to a terminal B connected to the terminal U. The other end of the parallel connection is connected to a terminal C connected to the terminal N. A specific configuration of the lower arm portion 810 corresponds to the configuration of the upper arm portion 310 shown in FIG. 3 in which the terminal HOa, the terminal HOb, the terminal P, and the terminal A have respectively been read as a terminal LOa, a terminal LOb, the terminal B, and the terminal C.

The low-side drive circuit 700 (FIG. 2) is to provide the gate signal to the gate electrode of each of the plurality of semiconductor elements EL of the lower arm portion 810. The first inserted circuit 211 of the low-side drive circuit 700 is inserted between the low-side drive main circuit 701 (FIG. 2) and gate electrodes of the plurality of first semiconductor elements EL1 (FIG. 3). The second inserted circuit 212 of the low-side drive circuit 700 is inserted between the low-side drive main circuit 701 (FIG. 2) and gate electrodes of the plurality of second semiconductor elements EL2 (FIG. 3). Specifically, the first inserted circuit 211 is inserted between the terminal LO and the terminal LOa. The terminal LOa is electrically connected to the gate electrodes of the plurality of first semiconductor elements EL1, but is not electrically connected to the gate electrodes of the plurality of second semiconductor elements EL2. The second inserted circuit 212 is inserted between the terminal LO and the terminal LOb. The terminal LOb is electrically connected to the gate electrodes of the plurality of second semiconductor elements EL2, but is not electrically connected to the gate electrodes of the plurality of first semiconductor elements EL1.

Each of the first inserted circuit 211 and the second inserted circuit 212 of the high-side drive circuit 200 includes a first diode D1 having a forward direction toward the high-side drive main circuit 201 and a second diode D2 connected in anti-parallel with the first diode D1. Each of the first, inserted circuit 211 and the second inserted circuit 212 of the low-side drive circuit 700 similarly includes a first diode D1 having a forward direction toward the low-side drive main circuit 701 and a second diode D2 connected in anti-parallel with the first diode D1.

According to the present embodiment, in a case where the gate electrode of the first semiconductor elements EL1 has a positive voltage with respect to the gate electrode of the second semiconductor elements EL2, a current flowing from the first semiconductor elements EL1 to the second semiconductor elements EL2 is interrupted unless the positive voltage exceeds the sum of a forward voltage of the first diode D1 of the first inserted circuit 211 and a forward voltage of the second diode D2 of the second inserted circuit 212. In contrast, in a case where the gate electrode of the second semiconductor elements has a positive voltage with respect to the gate electrode of the first semiconductor elements, a current flowing from the second semiconductor elements EL2 to the first semiconductor elements EL1 is interrupted unless the positive voltage exceeds the sum of a forward voltage of the first diode D1 of the second inserted circuit 212 and a forward voltage of the second diode D2 of the first inserted circuit 211. Parasitic oscillations occurring between the first block BK1 and the second block BK2 are removed by interruption of these currents while a voltage across the plurality of first semiconductor elements EL1 and the plurality of second semiconductor elements EL2 is sufficiently low. In other words, parasitic oscillations having small amplitudes are removed. Parasitic oscillations having large amplitudes occurring due to development of parasitic oscillations having small amplitudes are thereby suppressed.

On the other hand, the plurality of semiconductor elements EL are connected to each of the inserted circuits 210, so that the number of inserted circuits 210 can be smaller than the number of semiconductor elements EL. The configuration of the semiconductor device 90 can thus be simplified.

As described above, parasitic oscillations occurring among the plurality of semiconductor elements EL connected in parallel with one another can be suppressed by the simple configuration. A case where the plurality of semiconductor elements EL are partitioned into two blocks, the first block BK1 and the second block BK2 (FIG. 3), has been described in the present embodiment, but the number of blocks may be three or more within an acceptable range of complication of the configuration of the device. Parasitic oscillations can more surely be suppressed by increasing the number of blocks.

The semiconductor elements EL (the first semiconductor elements EL1 and the second semiconductor elements EL2) may be silicon carbide semiconductor elements. In this case, the semiconductor device 90 is a semiconductor device using silicon carbide, that is, a silicon carbide semiconductor device. The silicon carbide semiconductor device is often required to perform fast switching operation using properties of a wide-bandgap semiconductor of silicon carbide. Parasitic oscillations are likely to occur in foe fast switching operation. In the present embodiment, however, parasitic oscillations can effectively be suppressed for the above-mentioned reason.

Furthermore, according to the present embodiment, the case 71 and the members housed therein constitute the semiconductor device 90 as a power module, and a configuration to suppress parasitic oscillations can be provided within the power module. In a case where the plurality of inserted circuits 210 (FIG. 2) are mounted on foe printed circuit hoard 60 (FIG. 1) different from the insulating substrate 10 (FIG. 1) on which the plurality of semiconductor dements EL are mounted, the plurality of inserted circuits 210 can easily be mounted. Specifically, there is no need to mount the inserted circuits 210 on the insulating substrate 10 in a case where the inserted circuits 210 are mounted on the printed, circuit board 60, so that the insulating substrate 10 can have a configuration similar to a conventional configuration in which the inserted circuits 210 are not provided. As described above, both suppression of parasitic oscillations and reduction in size of the power module can be provided.

Embodiment 2

Referring to FIG. 5, a semiconductor device in Embodiment 2 includes a plurality of inserted circuits 220 in place of the plurality of inserted circuits 210 (FIG. 3: Embodiment 1). Each of the plurality of inserted circuits 220, that is, each of a first inserted circuit 221 and a second inserted circuit 222 includes a first resistive element R1 connected in series with the first diode D1 and connected in parallel with the second diode D2, and includes a second resistive element R2 connected in series with the second diode D2 and connected in parallel with the first diode D1. The other configuration is substantially the same as the above-mentioned configuration in Embodiment 1, so that the same or similar components bear the same reference signs, and description thereof will be not repeated.

According to the present embodiment, when ja current caused due to parasitic oscillations flows because it is not completely interrupted by the first diode D1 and the second diode D2, each of the first resistive element R1 and the second resistive element R2 causes a voltage drop. Parasitic oscillations are thereby damped, so that parasitic oscillations can more surely be suppressed.

The first resistive element R1 and the second resistive element R2 are respectively provided to the first diode D1 and the second diode D2 pointing in opposite directions. Therefore, resistance involved, at turn-on operation of the semiconductor elements and resistance involved at turn-off operation of the semiconductor elements can separately be set for the gate signal.

Embodiment 3

Referring to FIG. 6, a semiconductor device in Embodiment 3 includes an upper arm portion 320 in place of the upper arm portion 310 (FIG. 5: Embodiment 2). In the upper arm portion 320, a gate resistive element RG is interposed between each of the inserted circuits 220 of the drive circuit and each of the plurality of semiconductor elements EL. Although not shown, the gate resistive element RG is similarly interposed in the lower arm portion. The gate resistive element RG may be a resistive element built in the semiconductor chip 32 in which the semiconductor elements EL are formed, or may be a resistive element added separately from the semiconductor chip.

According to the present embodiment, the plurality of first semiconductor elements EL1 are separated from one another by gate resistive dements RG, and also the plurality of second semiconductor elements EL2 are separated from one another by gate resistive elements RG. Parasitic oscillations are thus less likely to occur among the plurality of first semiconductor dements EL1 and among tire plurality of second semiconductor elements EL2 even if the number of first semiconductor elements EL1 and the number of second semiconductor elements EL2 are relatively large. The number of first semiconductor elements EL1 connected to the first inserted circuit 211 and the number of second semiconductor elements EL2 connected to the second inserted circuit 212 can thus be increased while suppressing parasitic oscillations. In other words, the number of inserted circuits 210 can be even smaller than the number of semiconductor elements EL. On the other hand, the gate resistive element RG required in the present embodiment may be a simple element that can be formed more easily than the diodes. As described above, parasitic oscillations occurring among the plurality of semiconductor elements EL connected in parallel with one another can be suppressed by a simple configuration in which the number of inserted circuits 220 is further reduced.

A case where the gate resistive elements RG are added to the inserted circuits 220 (see FIG. 5) in Embodiment 2 has been described above, but the gate resistive elements RG may be added to the inserted circuits 210 (FIG. 3) In Embodiment 1.

Embodiment 4

Referring to FIG. 7, a semiconductor device in Embodiment 4 includes a plurality of inserted circuits 230 in place of the plurality of inserted circuits 220 (FIG. 6: Embodiment 3). Each of the plurality of inserted circuits 230, that is, each of a first inserted circuit 231 and a second inserted circuit 232 includes a resistive element R5 connected in parallel with the first diode D1 and the second diode D2. To sufficiently maintain the effect of suppressing parasitic oscillations of each of the inserted circuits 220, the resistive element R5 preferably has a sufficiently large size relative to the size of each of the first resistive element R1 and the second resistive element R2.

If the resistive element R5 is not provided, a voltage drop corresponding to the forward voltage of the first diode D1 or the second diode D2 is caused in gate voltage applied to each of the semiconductor elements EL as the control signal. In contrast, in the present embodiment the resistive element R5 provides an electrical path to bypass a parallel circuit of the first diode D1 and the second diode D2 to avoid the above-mentioned voltage drop. This enables stable control of the semiconductor elements EL.

A case where the resistive element R5 is added to each of the inserted circuits 220 (see FIG. 6) in Embodiment 3 has been described above, but the resistive elements R5 may be added to each of the inserted circuits 220 (FIG. 5) in Embodiment 2 or each of the inserted circuits 210 (FIG. 3) in Embodiment 1.

Embodiments can freely be combined with each other, and can be modified or omitted as appropriate.

While the invention has been shown and described in detail, the foregoing description is in all aspects illustrative and not restrictive, it is therefore understood that numerous modifications and variations can be devised without departing from tire scope of the invention.

SEMICONDUCTOR DEVICE

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