Trench gate controlled composite power device with low on-state voltage and low switching loss

Abstract

This invention belongs to the field of power semiconductor technology, specifically relating to a trench gate-controlled composite power device with low on-state voltage and low switching losses. The device is a non-fully symmetrical composite structure, integrating an IGBT unit structure and a trench MOS gate-controlled thyristor (MCT) unit structure on the same semiconductor substrate. The device includes an anode structure, an electric field cutoff layer, an N-type drift region, a base region structure, a cathode structure, and a trench gate structure. The trench gate penetrates the base region and extends into the drift region, enabling the modulation of carriers in different regions. During conduction, the MCT structure triggers a PNPN conduction mechanism, enhancing the conductivity modulation effect and reducing the on-state voltage. During turn-off, the trench gate forms a carrier extraction channel within the N-type base region, accelerating minority carrier removal and thus reducing switching losses. This structure achieves synergistic optimization of conduction and switching performance by controlling the spatiotemporal distribution of carrier injection and extraction, making it suitable for high power density and high-frequency power electronics applications.

Description

Technical Field

[0001] This invention belongs to the field of power semiconductor device technology, specifically relating to a trench gate-controlled composite power device with low on-state voltage and low switching loss characteristics. Background Technology

[0002] With the rapid development of new energy power generation, electric vehicle drive systems and high-frequency power electronic conversion technology, higher requirements are being placed on the comprehensive performance of power devices in terms of conduction loss and switching loss.

[0003] Traditional IGBT devices possess excellent gate control capabilities and superior switching performance. Their MOS control structure enables fast turn-on and turn-off speeds, making them suitable for high-frequency applications. However, because their conduction primarily relies on bipolar conduction modulation, their on-state voltage drop remains relatively high, limiting their efficiency performance in high-current-density applications.

[0004] On the other hand, MOS gate-controlled thyristors (MCTs) achieve strong conductivity modulation through a PNPN structure, exhibiting a low on-state voltage drop, which has significant advantages in high-current conduction scenarios, such as... Figure 1 As shown. However, traditional MCT devices have a strong carrier storage effect, and their turn-off process depends on carrier recombination and extraction, resulting in a slow turn-off speed and large switching losses.

[0005] Therefore, how to simultaneously achieve the fast switching capability of IGBT and the low conduction loss characteristics of MCT in the same device has become an important direction for power device structure optimization. Summary of the Invention

[0006] The purpose of this invention is to provide a trench gate-controlled composite power device with low on-state voltage and low switching loss. By integrating IGBT structure and trench MCT structure in the same cell, the synergistic optimization of conduction performance and switching performance is achieved.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] A trench gate-controlled composite power device with low on-state voltage and low switching loss includes an anode metal 1, a P+ anode region 2, an N-type electric field cutoff layer 3, and an N-type drift region 4 stacked sequentially from bottom to top; it also includes a trench gate structure, wherein the trench of the trench gate structure extends from the upper surface of the device along the vertical direction of the device into the N-type drift region 4, and a trench gate oxide layer 5 is provided at the bottom and sides of the trench, and a polysilicon gate 6 is filled in the trench, with the sides and bottom of the polysilicon gate 6 covered by the trench gate oxide layer 5;

[0009] The trench gate structure isolates the active part of the device into two units along the lateral direction of the device: an IGBT unit and a MOS gate-controlled thyristor unit.

[0010] The IGBT unit includes a first P-type base region 71, a first N+ cathode region 91, and a first P+ cathode region 101. The first P-type base region 71 is located on the upper surface of the N-type drift region 4. The first N+ cathode region 91 and the first P+ cathode region 101 are located side by side on the upper layer of the first P-type base region 71. The first P-type base region 71 and the first P+ cathode region 101 are in contact with the trench gate structure. A first cathode metal 111 is provided on the upper surface of the first P+ cathode region 101. The first cathode metal 111 extends towards the trench gate structure to cover the upper surface of the first N+ cathode region 91.

[0011] The MOS gate-controlled thyristor unit includes a second P-type base region 72, an N-type base region 8, a second N+ cathode region 92, and a second P+ cathode region 102. The second P-type base region 72 is located on the upper surface of the N-type drift region 4, the N-type base region 8 is located on the upper surface of the second P-type base region 72, and the second N+ cathode region 92 and the second P+ cathode region 102 are located side by side on the upper layer of the N-type base region 8. The second P-type base region 72, the N-type base region 8, and the second P+ cathode region 102 are in contact with the trench gate structure. A second cathode metal 112 is provided on the upper surface of the second N+ cathode region 92, and the second cathode metal 112 extends towards the trench gate structure to cover the upper surface of the second P+ cathode region 102.

[0012] The anode metal 1 and the P+ anode region 2 constitute the anode structure. The IGBT unit and the MOS gate-controlled thyristor unit share the N-type drift region 4, the N-type electric field cutoff layer 3, and the anode structure.

[0013] The device includes a trench gate oxide layer 5 and a polysilicon gate 6. The trench gate oxide layer 5 extends downward from the device surface, with its depth exceeding the lower surface of the P-type base region 7. The lower surface of the trench gate oxide layer 5 and the lower part of its outer surface are in contact with the N-type drift region 4, and the upper part of the outer surface of the trench gate oxide layer 5 is in contact with the right-side P-type base region 7, N-type base region 8, and P+ cathode region 10 in sequence. The polysilicon gate 6 is located inside the trench gate oxide layer 5. The lead-out terminal of the polysilicon gate 6 is the gate.

[0014] The cell is a non-perfectly symmetrical composite structure, including an IGBT cell structure and a trench MOS gate-controlled thyristor (MCT) cell structure. The two are integrated in the same semiconductor substrate and share the drift region, electric field cutoff layer structure and anode structure to form a composite conductive path.

[0015] The beneficial effects of this invention are as follows: By introducing a trench MOS gate-controlled thyristor structure into the cell, the device forms a PNPN structure conduction path in the on-state, enhancing the conductivity modulation effect in the drift region, improving the carrier injection level, and significantly reducing the drift region resistance, thereby achieving a lower on-state voltage. Furthermore, the composite structure of this invention achieves decoupled control of conductivity modulation intensity and carrier storage by regulating the spatiotemporal distribution of carrier injection and extraction. During the turn-off process, it can form an effective carrier extraction channel in the N-type base region, enabling the minority carriers stored in the drift region to be quickly extracted. The rapid removal of the PNPN structure reduces its regenerative effect and shortens the turn-off time. The trench gate structure of this invention reduces the coupling area between the gate and the drift region, lowers the equivalent gate-drain capacitance of the device, and thus reduces the energy loss caused by voltage and current overlap during switching. By integrating the IGBT structure and the trench MOS gate-controlled thyristor structure in the same cell, this invention enables the device to have strong conductivity modulation capability during conduction, while having effective carrier regulation and extraction paths during switching, thereby achieving a good trade-off between low on-state voltage and low switching loss. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of a conventional planar gate MOS gate-controlled thyristor;

[0017] Figure 2 This is a schematic diagram of the trench gate-controlled composite power device structure of the present invention;

[0018] Figure 3 This is a comparison chart of the input / output capabilities of the present invention and conventional planar gate MOS gate-controlled thyristors;

[0019] Figure 4 This is a comparison chart of the turn-on losses of the present invention and conventional planar gate MOS gate-controlled thyristors;

[0020] Figure 5 This is a comparison chart of the turn-off losses of the present invention and conventional planar gate MOS gate-controlled thyristors. Detailed Implementation

[0021] The invention will now be further described with reference to the accompanying drawings.

[0022] This invention proposes a trench gate-controlled composite power device with low on-state voltage and low switching loss, the structure of which is as follows: Figure 2 As shown, the structure is a vertical conductive structure, which includes, from bottom to top, an anode structure, an electric field cutoff layer structure, a voltage withstand layer structure, a base region structure, a cathode structure, and a trench gate structure. The structural relationships of each part have been given in the claims.

[0023] In terms of lateral structure, the device consists of a left IGBT unit and a right trench MOS gate thyristor unit. The two share the N-type drift region and the N-FS layer, and share the anode region, thus forming a composite conductive path.

[0024] During device turn-on, when a forward voltage is applied to the gate, in the left IGBT structure, the trench gate forms an inversion electron channel on the sidewall of the P-type base region 71, allowing electrons to be injected from the N+ cathode region 91 into the N-type drift region 4, thus establishing a MOS-controlled turn-on path. Simultaneously, in the right trench MOS gate-controlled thyristor structure, the PNPN structure is triggered to turn on under the action of electron injection, and the P+ anode 2 injects holes into the N-type drift region 4, forming a strong conductivity modulation effect in the N-type drift region 4, which significantly increases the carrier concentration and thus reduces the device's on-state voltage. Thus, the left IGBT structure provides a controlled electron injection channel, and the right MCT structure provides a strong conductivity modulation turn-on path. Both participate in the establishment of the turn-on path, with the MCT structure playing a dominant role in the steady-state turn-on stage.

[0025] During device turn-off, when the gate voltage decreases, the inversion electron channel on the sidewall of the P-type base region 71 in the left IGBT structure rapidly disappears, cutting off the electron injection channel and suppressing continuous current input. Simultaneously, in the right trench MOS gate-controlled thyristor structure, the trench gate forms a carrier extraction channel in the N-type base region 8, allowing the minority carriers stored in the drift region to be rapidly released towards the cathode, thus weakening the regeneration effect of the PNPN structure and accelerating its exit from the conduction state. Therefore, the left IGBT structure achieves rapid turn-off control of current injection, while the right MCT structure achieves effective extraction of stored carriers; the two work together to complete the rapid turn-off process. Thus, throughout the switching process, the trench gate regulates the electron conduction channel and carrier extraction channel in different regions, enabling both the IGBT and MCT structures to participate in the dynamic behavior of the device during both the turn-on and turn-off phases, achieving unified optimization of conduction and switching performance.

[0026] Furthermore, the trench gate structure improves gate control efficiency by increasing channel density and reducing parasitic capacitance, thereby reducing energy loss during switching while decreasing Miller plateau duration, compared to the performance of conventional devices. Figure 3 , Figure 4 and Figure 5 The simulation diagram.

[0027] In summary, this invention achieves synergistic optimization of low on-state voltage and low switching loss through a composite design of IGBT structure and trench MCT structure, and has good prospects for engineering applications.

Claims

1. A trench gate-controlled composite power device with low on-state voltage and low switching loss, characterized in that, The device includes an anode metal (1), a P+ anode region (2), an N-type electric field cutoff layer (3), and an N-type drift region (4) stacked sequentially from bottom to top; it also includes a trench gate structure, wherein the trench of the trench gate structure extends from the upper surface of the device along the vertical direction of the device into the N-type drift region (4), and has a trench gate oxide layer (5) at the bottom and sides of the trench, and is filled with a polysilicon gate (6), the sides and bottom of the polysilicon gate (6) being covered by the trench gate oxide layer (5); The trench gate structure isolates the active part of the device into two units along the lateral direction of the device: an IGBT unit and a MOS gate-controlled thyristor unit. The IGBT unit includes a first P-type base region (71), a first N+ cathode region (91), and a first P+ cathode region (101), wherein the first P-type base region (71) is located on the upper surface of the N-type drift region (4), the first N+ cathode region (91) and the first P+ cathode region (101) are located side by side on the upper layer of the first P-type base region (71), and the first P-type base region (71) and the first P+ cathode region (101) are in contact with the trench gate structure; a first cathode metal (111) is provided on the upper surface of the first P+ cathode region (101), and the first cathode metal (111) extends towards the trench gate structure to cover the upper surface of the first N+ cathode region (91); The MOS gate-controlled thyristor unit includes a second P-type base region (72), an N-type base region (8), a second N+ cathode region (92), and a second P+ cathode region (102). The second P-type base region (72) is located on the upper surface of the N-type drift region (4), the N-type base region (8) is located on the upper surface of the second P-type base region (72), the second N+ cathode region (92) and the second P+ cathode region (102) are located side by side on the upper layer of the N-type base region (8), and the second P-type base region (72), the N-type base region (8), and the second P+ cathode region (102) are in contact with the trench gate structure. A second cathode metal (112) is provided on the upper surface of the second N+ cathode region (92), and the second cathode metal (112) extends towards the trench gate structure to cover the upper surface of the second P+ cathode region (102). The anode metal (1) and the P+ anode region (2) constitute the anode structure. The IGBT unit and the MOS gate-controlled thyristor unit share the N-type drift region (4), the N-type electric field cutoff layer (3), and the anode structure. It includes a trench gate oxide layer (5) and a polysilicon gate (6); the trench gate oxide layer (5) extends downward from the surface of the device, and its depth exceeds the lower surface of the P-type base region (7). The lower surface of the trench gate oxide layer (5) and the lower part of the outer surface are in contact with the N-type drift region (4), and the upper part of the outer surface of the trench gate oxide layer (5) is in contact with the right P-type base region (7), the N-type base region (8) and the P+ cathode region (10) in sequence; the polysilicon gate (6) is located inside the trench gate oxide layer (5); the lead-out terminal of the polysilicon gate (6) is the gate. The cell is a non-perfectly symmetrical composite structure, including an IGBT cell structure and a trench MOS gate-controlled thyristor (MCT) cell structure. The two are integrated in the same semiconductor substrate and share the drift region, electric field cutoff layer structure and anode structure to form a composite conductive path.

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