IGBT device with power clamping function

Abstract

The utility model discloses an IGBT device with a power clamping function. The IGBT device comprises a P region, an N-type buffer region, an N-drift region, a P-type body region, an N + region, a P + region, a front trench gate structure, collector metal and emitter metal. The P region is provided with a back trench gate structure extending upwards into the N-type buffer region, and the back trench gate structure forms an SBR structure on the back of the IGBT device. According to the utility model, the back trench gate structure is additionally arranged on the IGBT device, and the resistance reduction amplitude of the drift region can be limited when the IGBT device is subjected to large voltage impact, so that the current flowing through the IGBT device is prevented from being obviously increased, and the service life of the IGBT device under such severe working conditions is prolonged.

Description

Technical Field

[0001] This utility model belongs to the field of power semiconductor technology, and in particular relates to an IGBT device with power clamping function. Background Technology

[0002] An IGBT (Insulated Gate Bipolar Transistor) is a composite, fully controllable, voltage-driven power semiconductor device composed of a BJT (Bipolar Junction Transistor) and a MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor). It combines the advantages of a MOSFET's high input impedance and a GTR's low on-state voltage drop. In applications with the same voltage, a GTR has a low saturation voltage drop and high current density, but requires a larger drive current; a MOSFET has very low drive power and fast switching speed, but a large on-state voltage drop and low current density. The IGBT combines the advantages of both devices, requiring low drive power and having a low saturation voltage drop. Therefore, IGBTs are well-suited for applications in converter systems with DC voltages of several hundred volts and above, such as AC motors, frequency converters, switching power supplies, lighting circuits, and traction drives.

[0003] Due to the large operating current, the application of IGBT devices inevitably involves the induced voltage surges caused by inductive loads or parasitic inductance during switching. When traditional IGBT devices are turned off under conditions of high current and high switching frequency, the ratio between the total collector-emitter voltage and the power bus voltage, as well as the ratio between the current and the normal turn-off current, often reach a relatively large value, such as 2-3 times or even more. This makes it more likely that the maximum instantaneous power will exceed the actual maximum power allowed by the IGBT device, causing traditional IGBTs to fail during their turn-off process. Utility Model Content

[0004] In view of the shortcomings of the prior art, the technical problem to be solved by this utility model is to provide an IGBT device with power clamping function.

[0005] To solve the above-mentioned technical problems, this utility model provides the following technical solution:

[0006] An IGBT device with power clamping function includes a P-region, an N-type buffer, and an N-drift region arranged sequentially from bottom to top. A collector metal is disposed at the lower end of the P-region. The P-region has a back trench gate structure extending upwards into the N-type buffer, forming an SBR structure on the back side of the IGBT device. A P-type body region is disposed above the N-drift region, and a front trench gate structure is disposed within the P-type body region, extending downwards through the P-type body region and into the N-drift region. An N+ region is disposed on each side of the upper part of the P-type body region corresponding to the front trench gate structure, and a P+ region is disposed on the side of the N+ region away from the front trench gate structure. A dielectric layer is disposed at the upper end of the P-type body region, and an emitter metal is disposed on the dielectric layer. The emitter metal is connected to the P+ region and the N+ region through contact holes formed in the dielectric layer.

[0007] Furthermore, the P-region is P-type doped, the N-type buffer zone is N-type doped, the N-drift region is lightly N-type doped, the P-type body region is P-type doped, the N+ region is heavily N-type doped, and the P+ region is heavily P-type doped.

[0008] Furthermore, the back trench gate structure extends upward through the P region and into the N-type buffer zone.

[0009] Furthermore, the front trench gate structure includes a front trench extending downward through the P-type body region and into the N-drift region, a front gate oxide layer formed on the trench wall of the front trench, and a front gate filled in the front trench.

[0010] Furthermore, the thickness of the N-type buffer ranges from 5 μm to 25 μm.

[0011] Furthermore, the back trench gate structure includes a back trench extending upward from the lower end of the P region through the P region and into the N-type buffer, a back gate oxide layer formed on the trench wall of the back trench, and a back gate filled in the back trench.

[0012] Furthermore, the depth of the back groove is 0.3μm to 5μm.

[0013] Furthermore, the thickness of the back-side gate oxide layer is 30 Å to 150 Å.

[0014] Furthermore, the doping concentration of the P-region is 1E15cm⁻¹. -3 ~1E17cm -3 .

[0015] Furthermore, the P region is provided with multiple back groove structures, and the center-to-center distance between adjacent back groove structures is 0.5μm to 10μm.

[0016] In this invention, by adding a back trench gate structure connected to the collector on the IGBT device and adjusting the doping concentration of the P-region, the hole injection amount can be adjusted appropriately to limit conductance modulation for power clamping. Under large voltage surges, the decrease in resistance of the drift region can be limited, preventing a significant increase in the current flowing through it; the maximum instantaneous power of the induced voltage can be significantly reduced, thereby achieving the effect of trigger power clamping and improving the lifespan of the IGBT device under such harsh operating conditions. Attached Figure Description

[0017] The accompanying drawings, which are included to provide a further understanding of this application and form part of this application, illustrate exemplary embodiments and are used to explain this application, but do not constitute an undue limitation of this application. In the drawings:

[0018] Figure 1 This is a schematic diagram of an embodiment of an IGBT device with power clamping function according to the present invention.

[0019] Figure 2 This is a schematic diagram of the structure after the emitter metal has been removed.

[0020] The diagrams in the instruction manual are labeled as follows:

[0021] P-region -100; N-type buffer zone -210; N-drift region -220; P-type body region -310; P+ region -320; N+ region -330; dielectric layer -400; contact hole -410; front trench gate structure -500; front trench -510; front gate oxide layer -520; front gate -530; emitter metal -600; back trench gate structure -700; back trench -710; back gate oxide layer -720; back gate -730; collector metal -800. Detailed Implementation

[0022] The following specific examples illustrate the implementation of this utility model. The illustrations provided in the following embodiments are only schematic representations of the basic concept of this utility model. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0023] When a traditional IGBT device is turned off under conditions of high current and high switching frequency, the instantaneous extreme value of the induced voltage may exceed the power supply bus voltage, and the total voltage between the collector and emitter may exceed twice the power supply bus voltage. Since the pn junction voltage drop between the collector and the N-drift region also increases, the amount of holes injected from the collector into the N-drift region also increases proportionally. This can lead to a sudden drop in the resistance of the N-drift region, resulting in a significant decrease in the on-resistance of the traditional IGBT. Therefore, when turned off under conditions of high current and high switching frequency, both the total voltage and current between the collector and emitter of a traditional IGBT increase simultaneously, resulting in higher instantaneous power. In extreme cases, such as a hard turn-off signal at the gate drive terminal, and where there is no sufficiently effective power limit in the application circuit, the ratio between the total voltage between the collector and emitter and the power supply bus voltage, and the ratio between the current and the normal turn-off current, often reach a relatively large value, such as 2-3 times or even more. In this case, the maximum instantaneous power is more likely to exceed the maximum power actually allowed by the traditional IGBT device, thereby causing the traditional IGBT to fail during its turn-off process.

[0024] Please see Figure 1 , Figure 1 This is a schematic diagram of an embodiment of the IGBT device with power clamping function according to this utility model. The IGBT device with power clamping function in this embodiment includes a P-region 100, an N-type buffer 210, and an N-drift region 220 arranged sequentially from bottom to top. The P-region 100 is P-type doped, the N-type buffer 210 is N-type doped, and the N-drift region 220 is lightly N-type doped. The thickness of the N-type buffer 210 is generally in the range of 5μm to 25μm, and the thickness range of the N-drift region 220 is related to the voltage withstand capability of the IGBT device, generally 650V / 50μm.

[0025] A collector metal 800 is provided at the lower end of the P-region 100, and a back trench gate structure 700 extending upward into the N-type buffer 210 is provided in the P-region 100. By adding a back trench gate structure 700 to the back of the IGBT device, an SBR (Super Barrier Rectifier) ​​structure can be formed; thereby suppressing the decrease in resistance of the drift region when the IGBT device experiences a large induced voltage surge.

[0026] A P-type body region 310 is disposed on the upper part of the N-drift region 220, and the P-type body region 310 is P-type doped. A front trench gate structure 500 is disposed on the P-type body region 310, and the front trench gate structure 500 penetrates downward through the P-type body region 310 and extends into the N-drift region 220. In this embodiment, the front trench gate structure 500 includes a front trench 510 that penetrates downward through the P-type body region 310 and extends into the N-drift region 220, a front gate oxide layer 520 formed on the trench wall of the front trench 510, and a front gate 530 filled in the front trench 510. The front gate oxide layer 520 is generally formed by a thermal oxidation process, and the front gate 530 is generally formed by depositing polysilicon and then etching back.

[0027] An N+ region 330 is disposed on each side of the upper part of the P-type body region 310 corresponding to the two sides of the front trench gate structure 500. The N+ region 330 is heavily N-type doped. A P+ region 320 is disposed on the side of the N+ region 330 away from the front trench gate structure 500. The P+ region 320 is heavily P-type doped. A dielectric layer 400 is disposed at the upper end of the P-type body region 310. An emitter metal 600 is disposed on the dielectric layer 400. The emitter metal 600 is connected to the P+ region 320 and the N+ region 330 through a contact hole 410 formed in the dielectric layer 400.

[0028] In this embodiment, the back trench gate structure 700 includes a back trench 710 extending upward from the lower end face of the P-region 100 through the P-region 100 and into the N-type buffer 210, a back gate oxide layer 720 formed on the trench wall of the back trench 710, and a back gate 730 filled in the back trench 710; thereby forming an SBR structure on the back side of the IGBT device. The back gate oxide layer 720 is generally formed by a thermal oxidation process, and the back gate 730 is generally formed by depositing polysilicon and then etching back.

[0029] The turn-on voltage of the SBR structure can be adjusted by the depth of the back trench gate structure 700, the thickness of the back gate oxide layer 720, and the doping concentration of the P-region 100. The thinner the back trench gate structure 700 or the thinner the back gate oxide layer 720, or the lower the doping concentration of the P-region 100, the lower the turn-on voltage of the SBR structure. The P-region 100 typically has multiple back trench gate structures 700. The degree to which the SBR structure suppresses the decrease in drift region resistance can be adjusted by the turn-on voltage of the SBR and the pitch of the back trench gate structures 700 (i.e., the center-to-center distance between adjacent back trench gate structures 700). The lower the turn-on voltage of the back trench gate structure 700 or the smaller the pitch of the back trench gate structure 700, the higher the degree of suppression of the decrease in drift region resistance, and the more obvious the power clamping effect. Therefore, the structural parameters of this embodiment can be optimized according to specific application requirements to achieve better application performance. After determining the pitch of the back trench gate structure 700, the number of back trench gate structures 700 is also determined.

[0030] The depth of the back trench 710 (i.e., the depth of the back trench gate structure 700) is typically 0.3 μm to 5 μm; the thickness of the P-region 100 is less than the depth of the back trench 710. The thickness of the back gate oxide layer 720 is typically 30 Å to 150 Å; the doping concentration of the P-region 100 is typically 1E15cm⁻¹. -3 ~1E17cm -3 The center-to-center spacing between adjacent back trenches 710 (i.e., the center-to-center spacing between adjacent back trench grid structures 700) is generally 0.5 μm to 10 μm.

[0031] In this embodiment, when the induced voltage surge is small and insufficient to turn on the SBR structure, the IGBT device is in the corresponding operating mode of a traditional IGBT device, that is, the operating process is the same as that of a traditional IGBT device, and the back trench gate structure 700 does not function.

[0032] When the IGBT device experiences a large induced voltage surge, the voltage drop between the collector metal 800 and the N-type buffer 210 (or N-drift region 220) increases. When the voltage reaches the turn-on voltage of the SBR structure formed by the back trench gate structure 700, an N-type conductive channel is formed between the collector and the N-type buffer 210 (or N-drift region 220) and directly connected. This reduces the pn junction voltage drop between the collector and the N-type buffer 210 (or N-drift region 220), thus limiting the amount of holes injected from the collector into the N-drift region 220 and limiting the resistance of the N-drift region 220 from further decreasing, thereby preventing the current from continuing to increase. Compared with traditional IGBT devices, this achieves the effect of trigger power clamping.

[0033] When the voltage drop between the collector and the N-buffer (or N-drift region 220) drops below the turn-on voltage of the SBR structure, the SBR structure will immediately turn off, and the performance of the IGBT device in this embodiment will return to the corresponding state of the traditional IGBT device.

[0034] IGBT devices are inevitably subjected to induced voltage surges during application. The IGBT device using the structure of this embodiment can promptly activate the SBR structure integrated on the collector when subjected to a large voltage surge, limiting the amount of holes injected from the collector into the N-drift region 220. This limits the decrease in resistance of the drift region, thus preventing a significant increase in the current flowing through it. This significantly reduces the maximum instantaneous power of the induced voltage, achieving a trigger power clamping effect, thereby widening the safe operating area of ​​the IGBT device and improving its lifespan under such harsh conditions. In terms of specific parameters, compared to traditional IGBT devices of the same specifications, the structure of this embodiment allows the IGBT device to withstand a larger dV / dt (voltage change rate) between the collector and emitter. Furthermore, in fixed-voltage applications or testing environments, it appropriately reduces the short-circuit current, increasing the short-circuit time it can withstand.

[0035] The above embodiments only illustrate preferred implementations of this utility model, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the utility model patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this utility model, and these all fall within the protection scope of this utility model. Therefore, the protection scope of this utility model patent should be determined by the appended claims.

Claims

1. An IGBT device having a power clamping function, characterized by: The IGBT device comprises, from bottom to top, a P region, an N-type buffer region and an N-drift region, the lower end of the P region is provided with a collector metal, the P region is provided with a back trench gate structure extending into the N-type buffer region, the back trench gate structure forms an SBR structure on the back of the IGBT device, the upper part of the N-drift region is provided with a P-type body region, the P-type body region is provided with a front trench gate structure, the front trench gate structure penetrates the P-type body region downward and extends into the N-drift region, the upper part of the P-type body region corresponds to the two sides of the front trench gate structure and is respectively provided with an N+ region, the side of the N+ region away from the front trench gate structure is provided with a P+ region, the upper end of the P-type body region is provided with a dielectric layer, the dielectric layer is provided with an emitter metal, and the emitter metal is connected with the P+ region and the N+ region through a contact hole formed in the dielectric layer.

2. The IGBT device having a power clamping function according to claim 1, characterized by: The P region is P-type doped, the N-type buffer region is N-type doped, the N-drift region is N-type lightly doped, the P-type body region is P-type doped, the N+ region is N-type heavily doped, and the P+ region is P-type heavily doped.

3. The IGBT device having a power clamping function according to claim 1, wherein: The back trench gate structure penetrates the P region upward and extends into the N-type buffer region.

4. The IGBT device having a power clamping function according to claim 1, wherein: The front trench gate structure comprises a front trench penetrating the P-type body region downward and extending into the N-drift region, a front gate oxide layer formed on the slot wall of the front trench, and a front gate filled in the front trench.

5. The IGBT device having a power clamping function according to claim 1, wherein: The thickness of the N-type buffer region ranges from 5 μm to 25 μm.

6. The IGBT device having a power clamping function according to claim 1, wherein: The back trench gate structure comprises a back trench penetrating the P region from the lower end surface of the P region upward and extending into the N-type buffer region, a back gate oxide layer formed on the slot wall of the back trench, and a back gate filled in the back trench.

7. The IGBT device having a power clamping function according to claim 6, wherein: The depth of the back trench ranges from 0.3 μm to 5 μm.

8. The IGBT device having a power clamping function according to claim 6, wherein: The thickness of the back gate oxide layer ranges from 30 A to 150 A.

9. The IGBT device having a power clamping function according to claim 6, wherein: The P region has a doping concentration of 1E15 cm -3 ~1E17 cm -3 .

10. The IGBT device having a power clamping function according to claim 6, wherein: The P region is provided with a plurality of back trench structures, and the center distance between adjacent back trench structures ranges from 0.5 μm to 10 μm.

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