JP2020036460A - Semiconductor device and power supply device - Google Patents

Abstract

To achieve total area reduction of a semiconductor device, loss reduction in a snubber resistance, and improvement of surge voltage suppression effect of a snubber circuit.SOLUTION: A semiconductor device 20 is provided with: semiconductor elements 21 and 22 turning on and off; and a snubber circuit 30 for suppressing surge voltage generated when the semiconductor elements 21 and 22 turn off. The snubber circuit 30 is incorporated in the semiconductor elements 21 and 22 and has a snubber diode 31 for flowing the surge current, generated when the semiconductor elements 21 and 22 turn off, to the prescribed direction, and a snubber capacitor 32 disposed near the snubber diode 31 and for absorbing the surge current. A snubber resistance 33 is provided inside or outside of the semiconductor elements 21 and 22.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a semiconductor device having a semiconductor element and a snubber circuit, and a power supply device such as a switching power supply using the semiconductor device.

  Patent Literature 1 discloses a semiconductor device having a protection diode for protecting a gate insulating film of a GaN-based transistor from overvoltage. Patent Document 2 discloses a semiconductor device in which a surge voltage generated when a high electron mobility transistor having no body diode (hereinafter, referred to as “GaN-HEMT”) is turned off is protected by a clamp diode.

2. Description of the Related Art Conventionally, various snubber circuits for suppressing a spike-like high voltage (hereinafter referred to as “surge voltage”) generated when a switching element or a rectifying diode is turned off are known.
Snubber circuits include an individual snubber circuit that is connected one-to-one to all semiconductor elements to be protected, and a collective snubber circuit that is collectively connected between DC wirings. The individual snubber circuits include, for example, an RC snubber circuit, a charge / discharge type RCD snubber circuit, and a discharge prevention type RCD snubber circuit, and the collective snubber circuits include, for example, a C snubber circuit and an RCD snubber circuit.

5A, 5B, 5C, 5D, and 5E are circuit diagrams showing a conventional snubber circuit.
5A is a circuit diagram showing an RC snubber circuit, FIG. 5B is a circuit diagram showing a C snubber circuit, FIG. 5C is a circuit diagram showing an RCD snubber circuit, FIG. 5D is a circuit diagram showing a discharge blocking RCD snubber circuit, and FIG.

  In the circuit of FIG. 5A, two semiconductor elements (for example, a MOS type field effect transistor, hereinafter referred to as "MOSFET") 2- connected in series between the DC positive electrode wiring 1P and the negative electrode wiring 1N. RC snubber circuits 10A-1 and 10A-2 are connected in parallel to 1 and 2-2, respectively. The drain / source of one of the two MOSFETs 2-1 and 2-2 is connected to the positive wiring 1P and the connection point 1C. The drain and source of the other MOSFET 2-2 are connected to the connection point 1C and the negative wiring 1N. A body diode 2a, which is a parasitic diode, is connected in anti-parallel between the drain and source of each of the MOSFETs 2-1 and 2-2. Each of the RC snubber circuits 10A-1 and 10A-2 is configured by a series circuit of a snubber resistor 11 and a snubber capacitor 12.

  When the two MOSFETs 2-1 and 2-2 are turned on / off alternately and the switching speed is high, a surge voltage is generated at the time of turn-off. This surge voltage is applied to each of the RC snubber circuits 10A-1 and 10A-2. Is suppressed. At this time, the surge current is absorbed by the snubber capacitor 12, and the accumulated charge in the snubber capacitor 12 is discharged by the snubber resistor 11.

  In the circuit of FIG. 5B, one C snubber circuit 10B is connected in parallel to two MOSFETs 2-1 and 2-2 connected in series. The C snubber circuit 10B is constituted by one snubber capacitor 12, and a surge current generated when the two MOSFETs 2-1 and 2-2 are turned off is absorbed by the snubber capacitor 12, and the surge voltage is suppressed. Note that a snubber resistor 11 for discharging the accumulated charge of the snubber capacitor 12 in series with the snubber capacitor 12, that is, for preventing vibration, may be provided.

  In the circuit of FIG. 5C, one RCD snubber circuit 10C is connected in parallel to two MOSFETs 2-1 and 2-2 connected in series. The RCD snubber circuit 10C includes a snubber diode 13 and a snubber capacitor 12 connected in series, and a snubber resistor 11 connected in parallel to the snubber diode 13. The snubber diode 13 snubbers a surge current generated when the two MOSFETs 2-1 and 2-2 turn off (that is, a surge current due to an electromotive force generated by inductance due to turn-off during the switching operation of the MOSFETs 2-1 and 2-2). It has a function of flowing to the capacitor 12.

  Without the snubber diode 13, the snubber resistor 11 must be set to a small value when applied to the large-capacity MOSFETs 2-1 and 2-2. Therefore, the drain current at the time of turning on the MOSFETs 2-1 and 2-2 increases, and the duty of the MOSFETs 2-1 and 2-2 becomes strict. As a countermeasure, the snubber diode 13 is added, so that the snubber resistance value can be increased, and the problem of responsibility at the time of turning on the MOSFETs 2-1 and 2-2 can be avoided.

  In the circuit of FIG. 5D, two discharge blocking RCD snubber circuits 10D-1 and 10D-2 are respectively connected in parallel to two MOSFETs 2-1 and 2-2 connected in series. One RCD snubber circuit 10D-1 includes a snubber capacitor 12, a snubber diode 13, and a snubber resistor 11-1. Snubber capacitor 12 and snubber diode 13 in RCD snubber circuit 10D-1 are connected in series, and this series circuit is connected in parallel to MOSFET 2-1. The snubber resistor 11-1 on the RCD snubber circuit 10D-1 side is connected between a connection point between the snubber capacitor 12 and the snubber diode 13 in the RCD snubber circuit 10D-1 and the negative wiring 1N. Similarly, the other RCD snubber circuit 10D-2 includes a snubber diode 13, a snubber capacitor 12, and a snubber resistor 11-2. The snubber diode 13 and the snubber capacitor 12 are connected in series. It is connected in parallel to MOSFET 2-2. The snubber resistor 11-2 on the RCD snubber circuit 10D-2 side is connected between the positive wiring 1P and a connection point between the snubber diode 13 and the snubber capacitor 12 in the RCD snubber circuit 10D-2.

  Discharge to snubber resistor 11-1 on the side of RCD snubber circuit 10D-1 is prevented by snubber diode 13 in RCD snubber circuit 10D-1, and the RCD snubber diode 13 in RCD snubber circuit 10D-2. Discharge to the snubber resistor 11-2 on the circuit 10D-2 side is prevented.

  In the circuit of FIG. 5E, two charge / discharge RCD snubber circuits 10E-1 and 10E-2 are connected in parallel to two MOSFETs 2-1 and 2-2 connected in series. Each of the snubber circuits 10E-1 and 10E-2 is connected in parallel with each of the MOSFETs 2-1 and 2-2, and is composed of a series circuit including a snubber diode 13 and a snubber capacitor 12, and a parallel circuit with the snubber diode 13. , And a snubber resistor 11 connected to each other. In each of the charge / discharge type RCD snubber circuits 10E-1 and 10E-2, the snubber resistor 11 charges and discharges the snubber capacitor 12 with the snubber diode 13.

JP 2013-12692 A JP 2017-123359 A

  In order to protect the semiconductor elements (for example, MOSFETs) 2-1 and 2-2, the conventional RC snubber circuits 10A-1 and 10A-2 of FIG. 5A and the C snubber circuit 10B of FIG. In some cases, the snubber resistor 11 is attached.), The loss generated in the snubber resistor 11 is large, and there is a problem in mounting. When the RCD snubber circuits 10C, 10D-1, 10D-2, 10E-1, and 10E-2 shown in FIGS. 5C, 5D, and 5E are used to reduce the loss of the snubber resistor 11, the semiconductor element and the snubber circuit are reduced. When a power module is configured by housing a semiconductor device having the same in a package, the number of components is large, so that mounting restrictions on the power module may occur. Also, if the wiring distance between the snubber diode 13 and the snubber capacitor 12 is long, a surge voltage is generated at the time of turn-off due to wiring inductance, so that the surge caused by the snubber circuits 10C, 10D-1, 10D-2, 10E-1, 10E-2. The voltage suppression effect may not be obtained.

A semiconductor device of the present invention is a semiconductor device including a semiconductor element that performs on / off operation, and a snubber circuit that suppresses a surge voltage generated when the semiconductor element is turned off, wherein the snubber circuit includes a semiconductor element. It has a built-in snubber diode for flowing a surge current generated when the semiconductor element is turned off in a predetermined direction.
The snubber circuit may be provided with, for example, a snubber capacitor arranged near the snubber diode and absorbing the surge current, and further, a snubber resistor discharging the accumulated charge of the snubber capacitor.

  A power supply device of the present invention is characterized in that power conversion is performed using the semiconductor device.

According to the semiconductor device of the present invention and the power supply device using the same, since the snubber diode is built in the semiconductor element, the total area (the entire formation area) of the semiconductor device is smaller than when the snubber diode is externally mounted. , The loss in the snubber resistance, and the effect of suppressing the surge voltage of the snubber circuit can be improved.
For example, since the snubber resistor is used for discharging the snubber capacitor, even if the wiring distance is long from the snubber capacitor, it does not adversely affect the surge voltage suppressing effect. Further, when a compound semiconductor element such as GaN-HEMT is used as the semiconductor element, it can be formed into a horizontal structure, so that it can be easily formed into one chip, and more effective surge voltage suppression can be expected during high-speed hard switching.

1 is a schematic cross-sectional view schematically illustrating a semiconductor device according to a first embodiment of the present invention. Schematic plan view of FIG. Circuit diagram of FIG. FIG. 4 is a circuit diagram showing a configuration example of a power supply device having the semiconductor device 20 of FIG. Circuit diagram showing a conventional RC snubber circuit Circuit diagram showing a conventional C snubber circuit Circuit diagram showing a conventional RCD snubber circuit Circuit diagram showing a conventional discharge blocking RCD snubber circuit Circuit diagram showing a conventional charge / discharge type RCD snubber circuit

  Embodiments of the present invention will become apparent from the following description of the preferred embodiments when read in light of the accompanying drawings. However, the drawings are for explanation only, and do not limit the scope of the present invention.

(Configuration of Embodiment 1)
FIG. 1 is a schematic cross-sectional view schematically illustrating a semiconductor device according to a first embodiment of the present invention. FIG. 2 is a schematic plan view of FIG. FIG. 3 is a circuit diagram of FIG.
In order to simplify the illustration, FIG. 2 is a schematic plan view of a semiconductor device portion 20A surrounded by a two-dot chain line in the semiconductor device 20 surrounded by a broken line in FIG. Is schematically shown in FIG.

  As shown in FIG. 3, the semiconductor device 20 including the semiconductor device portion 20A of the first embodiment is housed in a package 20a constituting a power module. A positive terminal 23P for power, a negative terminal 23N for ground, and a connection terminal 23C are provided outside the package 20a. In the package 20a, a plurality (for example, two) of semiconductor elements (for example, MOSFETs) 21 and 22 are connected in series between the positive terminal 23P and the negative terminal 23N. One of the two MOSFETs 21 and 22 has a drain connected to the positive terminal 23P, a source connected to the connection terminal 23C, and a body diode 21a connected in anti-parallel between the drain and the source. The MOSFET 21 is an element that is turned on / off by a switching drive voltage applied to the gate. Similarly, the other MOSFET 22 has a drain connected to the connection terminal 23C, a source connected to the negative terminal 23N, and a body diode 22a connected in anti-parallel between the source and the drain.

A snubber circuit (for example, an RCD snubber circuit) 30 is connected in parallel between the drain of one MOSFET 21 and the source of the other MOSFET 22. The RCD snubber circuit 30 has a snubber diode 31, a snubber capacitor 32, and a snubber resistor 33, and the snubber diode 31 and the snubber capacitor 32 are connected in series. A snubber resistor 33 is connected in parallel between the anode and the cathode of the snubber diode 31.
The snubber resistor 33 may be externally provided outside the package 20a.

In the semiconductor device portion 20 </ b> A shown in FIG. 2, the MOSFET 21 is formed on the drain substrate 41. A snubber diode 31, a snubber capacitor 32, and a snubber resistor 33 that constitute the RCD snubber circuit 30 are formed so as to be built in the MOSFET 21. The snubber capacitor 32, snubber diode 31, and snubber resistor 33 are formed in the vicinity. On the outer periphery of the MOSFET 21, a wiring 48 on the 21G side connected to the gate Poly-Si is formed.
The snubber capacitor 32 and the snubber resistor 33 may be formed outside the MOSFET 21 or may be configured to be externally provided outside the semiconductor device 20.

In the semiconductor device portion 20A shown in FIG. 1, an adjacent MOSFET formation region 21A and a snubber circuit formation region 30A are provided.
In the MOSFET formation region 21A, the drain substrate 41 corresponding to the drain 21D of the MOSFET 21 is formed of, for example, Ti-Ni-Ag. On this drain substrate 41, a high-concentration impurity N ⁺ layer 42 and a low-concentration impurity N ⁻ region 43 constituting the MOSFET 21 are stacked. A plurality of high-concentration impurity P ⁺ regions 44 are formed in the upper portion of the N ⁻ layer 43. A high concentration impurity N ⁺ region 45 is formed in a part of the upper part of the plurality of P ⁺ regions 44. On a part of the plurality of N ⁺ regions 45, for example, a source 21S including a wiring 48 of an Al-Si metal film is formed via a conductive Poly-Si film 48a. On the other P ⁺ region 44, for example, a gate 21G including a wiring 48 is formed via an insulating film 46 formed of a SiO ₂ film, an insulating film 47 formed of a PSG film, and a conductive Poly-Si film 48a. Is formed. Part of the source 21S and the gate 21G are covered with a passivation film 49 made of, for example, a Polyimide insulating film.
The region including the source 21S, the gate 21G, and the drain 21D including the drain substrate 41 constitutes a vertical MOSFET 21.

In the snubber circuit formation region 30 ^</ b ^{> A} , an N ⁺ layer 42 is formed on the drain substrate 41. On the N ⁺ layer 42, a P ⁺ -type buried layer 51 of a high-concentration impurity for separating from the drain substrate 41 is formed so as to surround the snubber circuit formation region 30 ^</ b ^> A. An N ⁻ layer 43 is formed in the P ⁺ type buried layer 51. A P ⁺ region 44 is formed in a part of the upper portion in the N ⁻ layer 43. An insulating film 46 is formed on a part of the N ⁻ layer 43. A wiring 48 is formed on the insulating film 46 and a wiring 48 is also formed on the P ⁺ region 44.
The N ⁻ layer 43, the insulating film 46, and the wiring 48 formed thereon form the snubber capacitor 32. Furthermore, snubber diode 31 is constituted by P ⁺ region 44 and N ⁻ layer 43. The wiring 48 on the snubber capacitor 32 side and the wiring 48 on the snubber diode 31 side are insulated by an insulating film 47 and a passivation film 49.

  A snubber resistor 33 is mounted on the snubber circuit forming area 30A. The snubber resistor 33 is formed on the insulating film 46 by, for example, a strip-shaped resistive Poly-Si film, and two electrodes 52 and 53 made of, for example, an Al-Si film are formed at both ends. One electrode 52 opens the insulating film 46 and is connected to the N− layer 43. The other electrode 53 is connected to the wiring 48 in a series shape.

(Operation of Embodiment 1)
In the semiconductor device 20 of the first embodiment, a switching drive voltage for turning on / off the two MOSFETs 21 and 22 alternately to prevent a through current is applied to the gate of the MOSFET 21 and the gate of the MOSFET 22, respectively. . When the two MOSFETs 21 and 22 alternately perform on / off operations, if the switching speed is high, a surge voltage is generated at the time of turn-off. The charge of the surge voltage is accumulated in the snubber capacitor 32 through the snubber diode 31 and the snubber resistor 33. Thus, the surge voltage is suppressed by the RCD snubber circuit 30.

(Modification of First Embodiment)
The first embodiment may be modified, for example, as in the following (a) to (c).
(A) The semiconductor element is composed of two MOSFETs 21 and 22, and the semiconductor element is an insulated gate bipolar transistor (hereinafter referred to as “IGBT”), a compound semiconductor element such as GaN-HEMT, a GaN diode, or the like. Rectifier diode or the like. For example, when the semiconductor element is formed of an IGBT, the N ⁺ layer 42 in the MOSFET formation region 21A in FIG. 1 may be changed to a P layer. Further, the number of the semiconductor elements may be one or three or more.
(B) The cross-sectional structure in FIG. 1 and the planar structure in FIG. 2 of the semiconductor device 20 may be modified to other structures. For example, the snubber diode 31 may be configured using a PN junction region in the MOSFET formation region 21A of FIG. Further, a snubber resistor 33 made of a resistive layer such as non-doped polysilicon may be formed in the snubber circuit formation region 30A or the MOSFET formation region 21A.
(C) The RCD snubber circuit 30 is replaced with a snubber circuit of another configuration such as a discharge blocking RCD snubber circuit of FIG. 5D, a charge / discharge RCD snubber circuit of FIG. 5E, or a snubber circuit having only the snubber diode 31. May be.

(Effect of Embodiment 1)
According to the semiconductor device 20 of the first embodiment, since the snubber diodes 31 are built in the MOSFETs 21 and 22, the total area of the semiconductor device 20 (the entire formation area) is smaller than when the snubber diodes 31 are externally mounted. , The loss in the snubber resistor 33, and the surge voltage suppression effect of the RCD snubber circuit 30 can be improved. Since the snubber resistor 33 is used for discharging the snubber capacitor 32, even if the wiring distance is long from the snubber capacitor 32, it does not adversely affect the surge voltage suppressing effect.
Further, when a compound semiconductor element such as GaN-HEMT is used as the semiconductor element, it can be formed into a horizontal structure, so that it can be easily formed into one chip, and more effective surge voltage suppression can be expected during high-speed hard switching.

(Configuration of Second Embodiment)
FIG. 4 is a circuit diagram showing a configuration example of a power supply device having the semiconductor device 20 of FIG. 1 according to the second embodiment of the present invention.
The power supply device 60 is a three-phase inverter circuit that converts a single-phase DC voltage DCin into a three-phase AC voltage ACout, and has an input capacitor 61 that stores the DC voltage DCin. One-phase, two-phase, and three-phase semiconductor devices 20-1, 20-2, and 20-3 are connected in parallel to the input capacitor 61, and these one-phase, two-phase, and three-phase semiconductor devices 20-1 are connected. 20-3 are supplied to a load ZL such as a three-phase motor.

  Each of the semiconductor devices 20-1 to 20-3 has the same configuration as the semiconductor device 20 of FIG. That is, the one-phase semiconductor device 20-1 has two MOSFETs 21-1 and 22-1 connected in series. Body diodes 21a and 22a are connected in anti-parallel to the MOSFETs 21-1 and 22-1, respectively. An RCD snubber circuit 30-1 is connected in parallel to the two MOSFETs 21-1 and 22-1. The RCD snubber circuit 30-1 has a snubber diode 31 and a snubber capacitor 32 connected in series, and a snubber resistor 33 is connected in parallel to the snubber diode 31. Similarly, the two-phase semiconductor device 20-2 includes two MOSFETs 21-2 and 22-2 and an RCD snubber circuit 30-2, and the three-phase semiconductor device 30-3 also has two MOSFETs 21-3 and 22. -3 and an RCD snubber circuit 30-3.

(Operation of Embodiment 2)
In the power supply device 60 according to the second embodiment, when a single-phase DC voltage DCin is input, the DC voltage DCin is stored in the input capacitor 61. The accumulated DC voltage DCin is alternately turned on / off by the first switching drive voltage (not shown) in the one-phase semiconductor device 20-1, and the two MOSFETs 21-1 and 22-1 are turned on and off to a one-phase AC voltage. Is converted. At this time, the surge voltage generated at the time of turning off the MOSFETs 21-1 and 22-1 that alternately turn on / off is suppressed by the RCD snubber circuit 30-1.

  Next, the two MOSFETs 21-2 and 22-2 in the two-phase semiconductor device 20-2 are alternately turned on / off by a second switching drive voltage (not shown) whose phase is delayed by 120 ° from the first switching drive voltage. Then, the DC voltage DCin is converted into a two-phase AC voltage. At this time, the surge voltage generated at the time of turning off the MOSFETs 21-2 and 22-2 that alternately turn on / off is suppressed by the RCD snubber circuit 30-2. Furthermore, the two MOSFETs 21-3 and 22-3 in the three-phase semiconductor device 20-3 alternately turn on / off by a third switching drive voltage (not shown) whose phase is delayed by 120 ° from the second switching drive voltage. , DC voltage DCin is converted into a three-phase AC voltage. At this time, the surge voltage generated at the time of turning off the MOSFETs 21-3 and 22-3 that are turned on / off alternately is suppressed by the RCD snubber circuit 30-3. The converted three-phase AC voltage ACOut is supplied to the load ZL.

(Modification of Embodiment 2)
The power supply device 60 according to the second embodiment may be changed to a power supply device having a configuration other than the three-phase inverter circuit.

(Effect of Embodiment 2)
According to the power supply device 60 of the second embodiment, the same effects as those of the first embodiment can be obtained.

20, 20-1 to 20-3 Semiconductor device 20A Semiconductor device portion 21, 22, 21-1 to 21-3, 22-1 to 22-3 MOSFET
21A MOSFET forming region 30, 30-1 to 30-3 RCD snubber circuit 30A snubber circuit forming region 31 snubber diode 32 snubber capacitor 33 snubber resistor 41 drain substrate 60 power supply device

Claims (9)

A semiconductor element that performs on / off operation,
A snubber circuit that suppresses a surge voltage generated when the semiconductor element is turned off,
A semiconductor device comprising:
The snubber circuit,
Having a snubber diode built in the semiconductor element and causing a surge current generated when the semiconductor element is turned off to flow in a predetermined direction,
A semiconductor device characterized by the above-mentioned. The snubber circuit,
A snubber capacitor that is disposed near the snubber diode and absorbs the surge current,
The semiconductor device according to claim 1, wherein: The snubber diode and the snubber capacitor,
Connected in series,
3. The semiconductor device according to claim 2, wherein: The snubber circuit,
A snubber resistor is provided inside or outside the semiconductor element, and has a snubber resistance for discharging accumulated charge of the snubber capacitor.
4. The semiconductor device according to claim 2, wherein: The snubber resistor is connected in series with the snubber capacitor,
The snubber diode is connected in parallel to the snubber resistor,
5. The semiconductor device according to claim 4, wherein: The semiconductor element and the snubber circuit are formed on the same substrate,
The semiconductor device according to claim 1, wherein: The semiconductor element and the snubber circuit,
Housed in the package that constitutes the power module,
The semiconductor device according to claim 1, wherein: The semiconductor element is
MOS field-effect transistors, insulated gate bipolar transistors, compound semiconductor devices, and devices including rectifying diodes,
The semiconductor device according to claim 1, wherein:   A power supply device that performs power conversion using the semiconductor device according to claim 1.

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