RC-IGBT device with double reverse freewheeling paths and preparation method thereof

Abstract

The invention discloses an RC-IGBT device with double reverse freewheeling paths and a preparation method, and relates to the technical field of semiconductors, the RC-IGBT device comprises a drift region structure, a first anode structure, a second N-type anode region, a cathode structure and a gate structure, the first anode structure comprises an anode collector, a P-type anode region and a first N-type anode region, and the second anode structure comprises a second N-type anode region. A longitudinal diode structure with a longitudinal conduction current path is formed by a cathode structure, a gate structure, a drift region structure and a first N-type anode region; the cathode structure, the gate structure, the drift region structure and the second N-type anode region form a transverse diode structure with a transverse conduction current path, and the longitudinal conduction current path and the transverse conduction current path are connected in parallel. According to the RC-IGBT device, the technical problems of insufficient current processing capability, non-uniform heat distribution, relatively large conduction loss, relatively long reverse recovery time and relatively large reverse recovery loss due to the fact that only one current conduction path exists during reverse working of an existing RC-IGBT device are solved.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor technology, and in particular to an RC-IGBT device with dual reverse freewheeling paths and a preparation method thereof. Background Art

[0002] The traditional IGBT (Insulated Gate Bipolar Transistor) is a voltage-controlled power semiconductor device commonly used in high-frequency, high-voltage scenarios. However, this type of IGBT has certain limitations. When subjected to reverse voltage, its collector cannot conduct due to reverse bias. To enable reverse current conduction and prevent device breakdown, an antiparallel diode is required when driving the load. In practical applications, a single-transistor IGBT chip is often packaged together with a fast recovery diode (FRD). However, this approach is not only costly but also increases the device's parasitic parameters.

[0003] To overcome these problems, a new type of IGBT device has emerged. By introducing an N+ region into the anode region of the IGBT, a diode structure is successfully integrated into the IGBT chip, thus forming an RC-IGBT (Reverse Conducting-Insulated Gate Bipolar Transistor) device. The RC-IGBT device does not require an additional anti-parallel diode chip. This innovation not only saves chip area and testing costs, but also reduces chip costs. In addition, compared to traditional IGBT devices, RC-IGBT devices have smaller parasitic parameters, better temperature uniformity, and excellent soft shutdown characteristics and power cycling capabilities. Therefore, they are widely used in many fields such as DC-DC conversion, AC-DC conversion, motor control, inverters, electric vehicles, etc.

[0004] At present, there are many existing technologies regarding RC-IGBT devices. For example, patent document CN109860171A discloses a bipolar silicon carbide semiconductor power device with an integrated high-speed reverse freewheeling diode. However, existing RC-IGBT devices usually have only one current conduction path when operating in reverse, resulting in technical problems such as insufficient current handling capability, uneven heat distribution, large conduction loss, long reverse recovery time and large reverse recovery loss. Summary of the Invention

[0005] In response to the deficiencies and defects of the above-mentioned prior art, the present invention proposes an RC-IGBT device with dual reverse freewheeling paths and a preparation method, aiming to solve the technical problems of the existing RC-IGBT devices, such as insufficient current handling capacity, uneven heat distribution, large conduction loss, long reverse recovery time and large reverse recovery loss, which are caused by having only one current conduction path when working in reverse.

[0006] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0007] In a first aspect, the present invention provides an RC-IGBT device with dual reverse freewheeling paths, comprising a drift region structure, a first anode structure, a second N-type anode region, a cathode structure, and a gate structure, wherein:

[0008] The front side of the drift region structure is provided with a terminal region and an active region, the second N-type anode region is provided in the terminal region, and the cathode structure and the gate structure are provided in the active region;

[0009] The first anode structure includes an anode collector, a P-type anode region, and a first N-type anode region, the anode collector is arranged on the back side of the drift region structure, the P-type anode region and the first N-type anode region are arranged on the inner side and the outer side between the drift region structure and the anode collector, respectively, the P-type anode region and the side of the first N-type anode region are in contact, the drift region structure and the P-type anode region form a PN junction barrier, and the anode collector is electrically connected to the second N-type anode region;

[0010] The RC-IGBT device forms a longitudinal diode structure having a longitudinal conduction current path through the cathode structure, gate structure, drift region structure and first N-type anode region; the RC-IGBT device forms a transverse diode structure having a transverse conduction current path through the cathode structure, gate structure, drift region structure and second N-type anode region, and the longitudinal conduction current path and the transverse conduction current path are arranged in parallel.

[0011] The P-type anode region is an independent planar structure, the first N-type anode region is an independent ring structure, the P-type anode region is located on the back side of the terminal region and the back side of the active region, the first N-type anode region is located on the back side of the terminal region, the area of the P-type anode region is larger than the area of the first N-type anode region, and the P-type anode region is located within the first N-type anode region.

[0012] The distance LA between the active area and the inner surface of the first N-type anode area is 50-100 μm.

[0013] The front surface of the second N-type anode region and the front surface of the drift region structure are located in the same plane.

[0014] The width of the first N-type anode region is 100 to 800 μm, and the width of the second N-type anode region is 100 to 800 μm.

[0015] The doping concentrations of the P-type anode region, the first N-type anode region, and the second N-type anode region are all 4×10 18 cm- 3 ~10×10 18 cm- 3 .

[0016] The drift region structure includes an N-type drift layer and an N-type buffer layer, the N-type drift layer is arranged on the front side of the N-type buffer layer, the P-type anode region and the first N-type anode region are both arranged on the back side of the N-type buffer layer, and the cathode structure, the gate structure and the second N-type anode region are all arranged on the front side of the N-type drift layer.

[0017] The N-type drift layer has a doping concentration of 7.7×10 12 cm- 3 ~1×10 15 cm- 3 The N-type silicon wafer is made of N-type, and the thickness of the N-type drift layer is 60 μm to 150 μm; the doping concentration of the N-type buffer layer is 5×10 15 cm -3 ~1×10 17 cm -3 .

[0018] The gate structure includes a polysilicon gate, a gate oxide layer and a P-type base region. The P-type base region is arranged on an N-type drift layer. A plurality of grooves penetrating the P-type base region are provided downward from the front of the N-type drift layer. The polysilicon gate is respectively arranged in the grooves through the gate oxide layer; the cathode structure is arranged above the P-type base region.

[0019] The cathode structure includes a cathode emitter, a P-type cathode region and an N-type cathode region. The P-type cathode region and the N-type cathode region are both arranged above the P-type base region, the P-type cathode region and the N-type cathode region are in contact with each other, two N-type cathode regions are provided between any two adjacent P-type cathode regions, and the N-type cathode region between any two adjacent P-type cathode regions is in contact with the side wall of the gate oxide layer; the front sides of all P-type cathode regions and N-type cathode regions are in contact with the cathode emitter, and the back sides of all P-type cathode regions and N-type cathode regions are in contact with the P-type base region; the vertical diode structure is composed of the cathode emitter, the P-type cathode region, the P-type base region, the N-type drift layer, the N-type buffer layer, the first N-type anode region and the anode collector; the horizontal diode structure is composed of the cathode emitter, the P-type cathode region, the P-type base region, the N-type drift layer and the second N-type anode region.

[0020] The doping concentration of the P-type cathode region is 1×10 18 cm- 3 ~1×10 20 cm- 3, the doping concentration of the N-type cathode region is 1×10 19 cm- 3 ~1×10 20 cm- 3 .

[0021] The thickness of the gate oxide layer is 0.05 μm to 0.15 μm, and the doping concentration of the polysilicon gate is 1×10 20 cm- 3 ~5×10 21 cm- 3 , the doping concentration of the P-type base region is 8×10 15 cm- 3 ~1×10 17 cm- 3 .

[0022] The terminal region is evenly provided with a plurality of field limiting rings, and the field limiting rings are located between the active region and the second N-type anode region.

[0023] In a second aspect, the present invention provides a method for preparing an RC-IGBT device with dual reverse freewheeling paths, comprising the following steps:

[0024] S1: Select an N-type silicon wafer to make an N-type drift layer, implant phosphorus ions on the back side of the N-type drift layer to form an N-type buffer layer, implant boron ions on the front side of the N-type drift layer to form a P-type base region, and implant phosphorus ions on the front side of the N-type drift layer to form a second N-type anode region;

[0025] S2: Etching multiple trenches penetrating the P-type base region downward on the front surface of the N-type drift layer, thermally growing SiO2 on the inner surface of the trench to form a gate oxide layer, and depositing polysilicon in the gate oxide layer to form a polysilicon gate;

[0026] S3: forming a P-type cathode region and an N-type cathode region respectively by implanting boron ions and phosphorus ions above the P-type base region, depositing metal above the P-type cathode region and the N-type cathode region to form a cathode emitter, and depositing metal above the second N-type anode region to form a metal electrode;

[0027] S4: implanting boron ions into the inner side of the N-type buffer layer to form a P-type anode region, and implanting phosphorus ions into the outer side of the N-type buffer layer to form a first N-type anode region;

[0028] S5: Depositing metal on the back of the P-type anode region and the first N-type anode region to form an anode collector, and using metal to connect the anode collector and the second N-type anode region to complete the preparation.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] 1. The RC-IGBT device provided by the present invention forms a longitudinal diode structure having a longitudinal conduction current path through a cathode structure, a gate structure, a drift region structure and a first N-type anode region, and forms a transverse diode structure having a transverse conduction current path through a cathode structure, a gate structure, a drift region structure and a second N-type anode region, and the longitudinal conduction current path and the transverse conduction current path are arranged in parallel. Through the combined design of the aforementioned transverse diode structure and the longitudinal diode structure, the longitudinal conduction current path and the transverse conduction current path can carry current at the same time, thereby improving the current handling capacity of the device; by shunting the current through two paths, the current density of each path reduces the risk of local overheating, can make the heat distribution more uniform, reduce the possibility of hot spot formation, thereby reducing the overall thermal resistance and improving the thermal stability of the device. In addition, the dual-path design can also effectively reduce the on-resistance and effectively improve the reverse recovery time, reduce the conduction loss and reduce the reverse recovery loss, which is conducive to improving the efficiency of the device. The present invention not only realizes an RC-IGBT device with greater reverse freewheeling capability, but also solves the oscillation problem in device applications caused by the voltage foldback phenomenon that occurs in the output curve of the existing RC-IGBT device when it transitions from a unipolar operating mode to a bipolar operating mode during forward conduction.

[0031] 2. The present invention sets the area of the P-type anode region to be larger than the area of the first N-type anode region. On the one hand, this is to ensure the length of the distance LA between the active region and the inner surface of the first N-type anode region, and on the other hand, it is to provide a conductive path in the reverse direction.

[0032] 3. Existing RC-IGBT devices usually still have the technical problem of current misdivision. This is because, due to the introduction of the anode N+ region, in the low current mode, the PN junction of the anode P+ / N- buffer layer of the existing RC-IGBT device cannot be turned on, and the conductivity modulation effect cannot be introduced, and the device operates in unipolar mode. As the current increases, the voltage drop of the PN junction of the anode P+ / N- buffer layer increases, causing the junction to turn on, injecting holes into the N- drift region, reducing the device resistance, and entering the bipolar conduction mode. During this transition process, a rebound phenomenon may occur, resulting in current misdivision. To this end, the present invention optimizes the spacing LA between the active area and the inner surface of the first N-type anode area through several experiments, and specifically limits it to 50 to 100 μm, which can effectively solve the technical problem of current misdivision. It should be noted that if the distance LA between the active area and the inner surface of the first N-type anode area is less than 50μm, the RC-IGBT device will have a large rebound voltage, which will have an adverse effect on the parallel operation of the device; if the distance LA is greater than 100μm, the temperature and dynamic carrier uniformity of the RC-IGBT device will deteriorate, affecting the robustness of the device.

[0033] 4. The present invention sets the front side of the second N-type anode region and the front side of the drift region structure to be located in the same plane, which is beneficial to optimizing the electric field distribution, improving the carrier behavior, simplifying the process and enhancing the thermal management capability, thereby ultimately achieving high voltage resistance, low loss and high reliability of the device.

[0034] 5. Based on comprehensive considerations of electric field optimization, on-resistance control, process feasibility, and thermal management, the present invention has, through extensive experimental development, limited the width of the first N-type anode region to 100-800 μm, and the width of the second N-type anode region to 100-800 μm. This allows the device's voltage resistance, operating efficiency, and cost to be optimized. Exceeding this range will result in decreased device voltage resistance, reduced efficiency, process defects, or increased costs.

[0035] 6. Based on comprehensive considerations of conduction performance, voltage resistance, reverse recovery characteristics, thermal stability and process feasibility, the present invention limits the doping concentrations of the P-type anode region, the first N-type anode region, the second N-type anode region, the P-type cathode region and the N-type cathode region respectively. If the doping concentration exceeds the range of the corresponding doping concentration, it will lead to increased conduction loss, decreased voltage resistance, increased switching loss or reduced reliability. On the contrary, it can effectively ensure that the performance of the device is optimized.

[0036] 7. The present invention specifically limits the thickness of the N-type drift layer, as well as the doping concentrations of the N-type drift layer and the N-type buffer layer, which is beneficial to maintaining the voltage resistance of the device.

[0037] 8. The present invention specifically defines the thickness of the gate oxide layer, the doping concentration of the polysilicon gate and the P-type base region. By thinning the gate oxide layer (↑Cox), increasing the polysilicon gate doping (↑gate control efficiency) and reducing the P-type base region doping (↑μ), the device can form a conductive channel with higher concentration and higher mobility at the same voltage, ultimately achieving a significant improvement in conductivity.

[0038] 9. The field limiting ring (FLR) of the present invention is usually located at the edge of the drift region. The field limiting ring is helpful to improve the terminal electric field distribution of the device and improve the voltage resistance of the device.

[0039] 10. The device structure provided by the present invention is more compact, which is beneficial to saving chip area while maintaining high power density. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 Schematic diagram of the planar structure of the RC-IGBT device of the present invention;

[0041] Figure 2 It is a schematic diagram of the three-dimensional structure of the RC-IGBT device of the present invention.

[0042] The markings in the figure are: 1. cathode emitter, 2. P-type base region, 3. P-type cathode region, 4. N-type cathode region, 5. polysilicon gate, 6. field limiting ring, 7. second N-type anode region, 8. gate oxide layer, 9. N-type drift layer, 10. N-type buffer layer, 11. P-type anode region, 12. first N-type anode region, 13. anode collector. DETAILED DESCRIPTION

[0043] The present invention will be further described below in conjunction with the accompanying drawings. It should be understood that the specific embodiments described herein are only used to explain the present invention, but are not intended to limit the present invention.

[0044] Example 1

[0045] like Figure 1 、 2 As shown, this embodiment provides an RC-IGBT device with dual reverse freewheeling paths, including a drift region structure, a first anode structure, a second N-type anode region 7, a cathode structure, a gate structure, and a field limiting ring structure.

[0046] The front surface of the drift region structure is provided with a termination region and an active region, with a cathode structure and a gate structure disposed in the active region. The second N-type anode region 7 is a ring-shaped structure and is disposed at the outermost edge of the termination region. The front surface of the second N-type anode region 7 is coplanar with the front surface of the drift region structure. Aligning the second N-type anode region 7 with the front surface of the drift region structure avoids conflict with the electric field distribution of the field-limiting ring, further improving the withstand voltage capability.

[0047] The first anode structure includes an anode collector 13, a P-type anode region 11 and a first N-type anode region 12. The anode collector 13 is arranged on the back side of the drift region structure. The P-type anode region 11 and the first N-type anode region 12 are respectively arranged on the inner side and the outer side between the drift region structure and the anode collector 13. The side edges of the P-type anode region 11 and the first N-type anode region 12 are in contact with each other. The drift region structure and the P-type anode region 11 form a PN junction barrier. The anode collector 13 and the second N-type anode region 7 are electrically connected through a metal wire.

[0048] The field limiting ring structure is arranged in the terminal region. The field limiting ring structure specifically includes a plurality of field limiting rings 6 , and the field limiting rings 6 are evenly arranged between the active region and the second N-type anode region 7 .

[0049] The RC-IGBT device comprises a vertical diode structure having a longitudinal conduction current path formed by the cathode structure, the gate structure, the drift region structure and the first N-type anode region 12; and a horizontal diode structure having a horizontal conduction current path formed by the cathode structure, the gate structure, the drift region structure and the second N-type anode region 7, and the longitudinal conduction current path and the horizontal conduction current path are arranged in parallel.

[0050] This embodiment, through the specially designed lateral diode structure and vertical diode structure, enables the RC-IGBT device to have the functions of both lateral and vertical reverse freewheeling paths. When the device is in the reverse conduction mode, the current flows from the emitter (surface) on the front of the device to the anode collector 13. The current flows through the longitudinal conduction current path and the lateral conduction current path. In the longitudinal conduction current path, the current flows through the N-type drift layer 9 to the anode collector 13 on the back; in the lateral conduction current path, the current flows through the surface lateral PN junction to the second N-type anode region 7 and then flows through the metal wire to the anode collector 13 on the back. The two conduction current paths are connected in parallel, which reduces the on-resistance and improves the reverse conduction performance. This embodiment not only realizes an RC-IGBT device with greater reverse freewheeling capability, but also avoids the oscillation problem in device application caused by the voltage foldback phenomenon in the output curve when the device transitions from unipolar operating mode to bipolar operating mode during forward conduction.

[0051] In this embodiment, the P-type anode region 11 is an independent planar structure, and the first N-type anode region 12 is an independent ring structure. The P-type anode region 11 is located on the back side of the terminal region and the back side of the active region at the same time, and the first N-type anode region 12 is located only on the back side of the terminal region. The area of the P-type anode region 11 is larger than the area of the first N-type anode region 12. The P-type anode region 11 is located in the first N-type anode region 12, and the sum of the areas of the P-type anode region 11 and the first N-type anode region 12 is less than or equal to the area of the anode collector 13, thereby providing a conduction path in reverse and improving the reverse freewheeling capability of the device.

[0052] In this embodiment, the width of the first N-type anode region 12 is 100 to 800 μm, and the width of the second N-type anode region 7 is 100 to 800 μm. The width of the first N-type anode region 12 and the width of the second N-type anode region 7 can be the same or different. Preferably, the width of the first N-type anode region 12 is 500 μm, and the width of the second N-type anode region 7 is 200 μm. This can prevent the device from having the problem of current misdivision. Of course, in actual application, the width parameters can also be adjusted according to the specific application scenario (such as high frequency, high voltage) to achieve the optimal balance between performance and reliability.

[0053] In this embodiment, the doping concentrations of the P-type anode region 11, the first N-type anode region 12, and the second N-type anode region 7 are all 4×10 18 cm- 3 ~10×10 18 cm- 3 .

[0054] In this embodiment, if Figure 1 、 2As shown, the drift region structure includes a low-doped N-type drift layer 9 and a low-doped N-type buffer layer 10, the N-type drift layer 9 is arranged on the front side (upper surface) of the N-type buffer layer 10, the P-type anode region 11 and the first N-type anode region 12 are both arranged on the back side (lower surface) of the N-type buffer layer 10, and the cathode structure, the gate structure and the second N-type anode region 7 are all arranged on the front side of the N-type drift layer 9.

[0055] Specifically, in order to maintain the withstand voltage of the device, it is preferred that the N-type drift layer 9 adopts a doping concentration of 7.7×10 12 cm- 3 ~1×10 15 cm- 3 The doping concentration of the N-type buffer layer 10 is 5×10 15 cm -3 ~1×10 17 cm -3 In addition, the thickness of the N-type drift layer 9 is 60 μm to 150 μm, and preferably the thickness of the N-type drift layer 9 is 120 μm.

[0056] In this embodiment, if Figure 1 、 2 As shown, the gate structure includes a polysilicon gate 5, a gate oxide layer 8, and a P-type base region 2. There are multiple sets of polysilicon gates 5. The P-type base region 2 is disposed on an N-type drift layer 9. The front surface of the N-type drift layer 9 has multiple trenches extending downward through the P-type base region 2 and spaced apart from each other. The multiple sets of polysilicon gates 5 are disposed in the trenches through the gate oxide layer 8. The cathode structure is disposed above the P-type base region 2. The thickness of the gate oxide layer 8 is 0.05 μm to 0.15 μm, and preferably, the thickness of the gate oxide layer 8 is 0.13 μm.

[0057] Furthermore, the doping concentration of the polysilicon gate 5 is preferably 1×10 20 cm- 3 ~5×10 21 cm- 3 , the doping concentration of the P-type base region 2 is 8×10 15 cm- 3 ~1×10 17 cm- 3 .

[0058] In this embodiment, if Figure 1 、 2As shown, the cathode structure includes a cathode emitter 1, a heavily doped P-type cathode region 3 and a heavily doped N-type cathode region 4. The P-type cathode region 3 and the N-type cathode region 4 are both arranged above the P-type base region 2. The P-type cathode region 3 is in contact with the N-type cathode region 4. Two N-type cathode regions 4 are provided between any two adjacent P-type cathode regions 3, and the N-type cathode region 4 between any two adjacent P-type cathode regions 3 is in contact with the side wall of the gate oxide layer 8, which is equivalent to any gate oxide layer 8 being located between two adjacent N-type cathode regions 4; the front sides of all P-type cathode regions 3 and N-type cathode regions 4 are in contact with the cathode emitter 1, and the back sides of all P-type cathode regions 3 and the back sides of N-type cathode regions 4 are in contact with the P-type base region 2. The vertical diode structure is composed of a cathode emitter 1, a P-type cathode region 3, a P-type base region 2, an N-type drift layer 9, an N-type buffer layer 10, a first N-type anode region 12 and an anode collector 13; the horizontal diode structure is composed of a cathode emitter 1, a P-type cathode region 3, a P-type base region 2, an N-type drift layer 9 and a second N-type anode region 7.

[0059] Furthermore, in order to enable the P-type cathode region 3 and the N-type cathode region 4 to form a good ohmic contact with the cathode emitter 1, it is preferred that the doping concentration of the P-type cathode region 3 is set to 1×10 18 cm -3 ~1×10 20 cm -3 , the doping concentration of the N-type cathode region 4 is set to 1×10 19 cm -3 ~1×10 20 cm -3 .

[0060] The working principle of the RC-IGBT device provided in this embodiment is as follows:

[0061] Forward conduction mode: When the device is in forward conduction mode, similar to a traditional IGBT, current flows from the anode collector 13 on the back of the device to the cathode emitter 1 on the front, with conduction controlled by the device's polysilicon gate 5. At this point, the polysilicon gate 5 applies an appropriate voltage, forming an electron conduction channel between the P-type base region 2 and the N-type drift layer 9. Electrons flow from the cathode emitter 1 through the electron conduction channel into the N-type drift layer 9 and then to the anode collector 13. Simultaneously, holes are injected from the P-type region of the anode collector 13 into the drift region and out through the cathode-side P-type region and cathode emitter 1, thus forming a forward current. In this process, the lateral and vertical diode structures do not directly participate in the forward conduction; the traditional IGBT conduction mechanism is the primary factor at work.

[0062] Reverse conduction mode: When the device is in reverse conduction mode, the current flows from the cathode emitter 1 (front) to the anode collector 13. At this time, the lateral diode structure and the vertical diode structure work together, and current conduction is achieved through both the longitudinal conduction current path and the lateral conduction current path.

[0063] The working principle of the longitudinal diode structure in this embodiment using the longitudinal conduction current path to conduct current is:

[0064] During reverse conduction, the PN junction formed by the N-type drift layer 9 and the P-type cathode region 3 is in the forward conduction state (reverse conduction mode). Electrons can smoothly flow from the anode collector 13 through the first N-type anode region 12 into the N-type drift layer 9, and then flow through the N-type drift layer 9 to the cathode emitter 1 on the front. Holes from the cathode emitter 1 are injected into the N-type drift layer 9 and extracted by the first N-type anode region 12, forming the forward conduction current of the diode. The vertical diode takes advantage of the chip's vertical structure, fully utilizing the advantages of the N-type drift layer 9 in withstanding high voltages and providing a low-resistance current path. It can carry large currents and has high current density.

[0065] Specifically, when the diode is conducting in reverse freewheeling mode, electrons from the N-type anode collector 13 and holes from the P-type cathode emitter 1 are diffused and injected into the drift region, entering the diode conduction mode and generating a reverse conduction current. This carrier movement and recombination process enables the vertical diode to conduct current efficiently, and due to the presence of the N-type drift region, it can withstand higher reverse voltages.

[0066] The working principle of the lateral diode structure in this embodiment using the lateral conduction current path to conduct current is:

[0067] During reverse conduction, current flows from cathode emitter 1 through the surface lateral PN junction to second N-type anode region 7, and then through the metal wire to the back anode collector 13. The lateral diode utilizes the structure on the chip surface, and its current mainly flows within the lateral plane of the chip.

[0068] During reverse conduction, the surface lateral PN junction is forward biased, and holes in the P-type cathode region 3 and electrons in the second N-type anode region 7 diffuse toward the N-type drift layer 9, generating a lateral conduction current. The lateral diode exhibits surface conduction characteristics, complementing the conduction capability of the vertical diode to a certain extent. Furthermore, its location on the chip surface improves device thermal distribution.

[0069] Dual-path synergy: The two current paths are connected in parallel. During reverse conduction, both the lateral diode and the vertical diode conduct simultaneously, sharing the reverse current. This parallel structure effectively reduces on-resistance because both paths provide current channels, increasing the cross-sectional area for current conduction and thus reducing resistance. According to Ohm's law (I = V / R, where I is current, V is voltage, and R is resistance), at the same reverse voltage, the reduction in on-resistance increases the reverse current, improving the device's reverse conduction performance.

[0070] Example 2

[0071] This embodiment provides an RC-IGBT device with dual reverse freewheeling paths. This embodiment differs from Embodiment 1 in that a distance LA between the active region and the inner surface of the first N-type anode region 12 is 50 to 100 μm. Preferably, a distance LA between the active region and the inner surface of the first N-type anode region 12 is 75 μm.

[0072] The RC-IGBT device provided in this embodiment specifically limits the distance LA between the active area and the inner surface of the first N-type anode region 12 to 50-100 μm. It can effectively avoid the problem of current misdivision in the device while maintaining a suitable temperature of the device and uniformity of dynamic carriers, and is also conducive to improving the robustness of the device.

[0073] Example 3

[0074] The present invention also provides a method for preparing the RC-IGBT device described in Example 1 or Example 2, comprising the following steps:

[0075] S1: Select an N-type silicon wafer to form an N-type drift layer 9, implant phosphorus ions on the back side of the N-type drift layer 9 to form an N-type buffer layer 10, implant boron ions on the front side of the N-type drift layer 9 to form a P-type base region 2, and implant phosphorus ions on the front side of the N-type drift layer 9 to form a second N-type anode region 7;

[0076] S2: Etching a plurality of trenches penetrating the P-type base region 2 downward on the front surface of the N-type drift layer 9, thermally growing SiO2 on the inner surface of the trenches to form a gate oxide layer 8, and depositing polysilicon in the gate oxide layer 8 to form a polysilicon gate 5;

[0077] S3: forming a P-type cathode region 3 and an N-type cathode region 4 above the P-type base region 2 by implanting boron ions and phosphorus ions, respectively, and depositing metal above the P-type cathode region 3 and the N-type cathode region 4 to form a cathode emitter 1, and depositing metal above the second N-type anode region 7 to form a metal electrode;

[0078] S4: implanting boron ions into the inner side of the N-type buffer layer 10 to form a P-type anode region 11 , and implanting phosphorus ions into the outer side of the N-type buffer layer 10 to form a first N-type anode region 12 ;

[0079] S5: Depositing metal on the back of the P-type anode region 11 and the first N-type anode region 12 to form an anode collector 13, and using metal to connect the anode collector 13 and the second N-type anode region 7 to complete the preparation.

[0080] In detail, the method described in this embodiment adopts the same technical means as Example 1 or Example 2 when implemented, and can produce the same technical effects, which will not be repeated here.

[0081] The above description is only a specific embodiment of the present invention. Any feature disclosed in this specification, unless otherwise stated, can be replaced by other equivalent or alternative features with similar purposes; all disclosed features, or all steps in the methods or processes, except for mutually exclusive features and / or steps, can be combined in any way.

Claims

1. An RC-IGBT device with dual reverse freewheeling paths, characterized in that: It comprises a drift region structure, a first anode structure, a second N-type anode region (7), a cathode structure and a gate structure, wherein: The front side of the drift region structure is provided with a terminal region and an active region, the second N-type anode region (7) is provided in the terminal region, and the cathode structure and the gate structure are provided in the active region; The first anode structure comprises an anode collector (13), a P-type anode region (11) and a first N-type anode region (12); the anode collector (13) is arranged on the back of the drift region structure; the P-type anode region (11) and the first N-type anode region (12) are respectively arranged on the inner side and the outer side between the drift region structure and the anode collector (13); the sides of the P-type anode region (11) and the first N-type anode region (12) are in contact with each other; the drift region structure and the P-type anode region (11) form a PN junction barrier; and the anode collector (13) and the second N-type anode region (7) are electrically connected; The RC-IGBT device comprises a cathode structure, a gate structure, a drift region structure and a first N-type anode region (12) to form a longitudinal diode structure having a longitudinal conduction current path; the RC-IGBT device comprises a cathode structure, a gate structure, a drift region structure and a second N-type anode region (7) to form a transverse diode structure having a transverse conduction current path, and the longitudinal conduction current path and the transverse conduction current path are arranged in parallel.

2. The RC-IGBT device with dual reverse freewheeling paths according to claim 1, characterized in that: The P-type anode region (11) is an independent planar structure, and the first N-type anode region (12) is an independent ring structure. The P-type anode region (11) is located on the back side of the terminal region and the back side of the active region at the same time. The first N-type anode region (12) is located on the back side of the terminal region. The area of the P-type anode region (11) is larger than the area of the first N-type anode region (12), and the P-type anode region (11) is located within the first N-type anode region (12).

3. The RC-IGBT device with dual reverse freewheeling paths according to claim 1, characterized in that: The distance LA between the active area and the inner surface of the first N-type anode area (12) is 50-100 μm.

4. The RC-IGBT device with dual reverse freewheeling paths according to claim 1, characterized in that: The front surface of the second N-type anode region (7) and the front surface of the drift region structure are located in the same plane.

5. The RC-IGBT device with dual reverse freewheeling paths according to claim 1, characterized in that: The width of the first N-type anode region (12) is 100 to 800 μm, and the width of the second N-type anode region (7) is 100 to 800 μm; the doping concentrations of the P-type anode region (11), the first N-type anode region (12), and the second N-type anode region (7) are all 4×10 18 cm -3 ~10×10 18 cm -3 .

6. The RC-IGBT device with dual reverse freewheeling paths according to claim 1, characterized in that: The drift region structure comprises an N-type drift layer (9) and an N-type buffer layer (10), the N-type drift layer (9) is arranged on the front side of the N-type buffer layer (10), the P-type anode region (11) and the first N-type anode region (12) are both arranged on the back side of the N-type buffer layer (10), and the cathode structure, the gate structure and the second N-type anode region (7) are all arranged on the front side of the N-type drift layer (9).

7. The RC-IGBT device with dual reverse freewheeling paths according to claim 6, characterized in that: The gate structure comprises a polysilicon gate (5), a gate oxide layer (8) and a P-type base region (2); the P-type base region (2) is arranged on an N-type drift layer (9); a plurality of grooves penetrating the P-type base region (2) are provided on the front side of the N-type drift layer (9); the polysilicon gate (5) is arranged in the grooves through the gate oxide layer (8); and the cathode structure is arranged above the P-type base region (2).

8. The RC-IGBT device with dual reverse freewheeling paths according to claim 7, characterized in that: The cathode structure comprises a cathode emitter (1), a P-type cathode region (3) and an N-type cathode region (4); the P-type cathode region (3) and the N-type cathode region (4) are both arranged above the P-type base region (2); the P-type cathode region (3) and the N-type cathode region (4) are arranged in contact with each other; two N-type cathode regions (4) are arranged between any two adjacent P-type cathode regions (3); the N-type cathode region (4) between any two adjacent P-type cathode regions (3) is arranged in contact with the side wall of the gate oxide layer (8); the front surfaces of all the P-type cathode regions (3) and the N-type cathode regions (4) are in contact with the cathode; The cathode emitter (1) is arranged in contact with the cathode emitter, and the back surfaces of all P-type cathode regions (3) and N-type cathode regions (4) are arranged in contact with the P-type base region (2); the vertical diode structure is composed of the cathode emitter (1), the P-type cathode region (3), the P-type base region (2), the N-type drift layer (9), the N-type buffer layer (10), the first N-type anode region (12) and the anode collector (13); the horizontal diode structure is composed of the cathode emitter (1), the P-type cathode region (3), the P-type base region (2), the N-type drift layer (9) and the second N-type anode region (7).

9. The RC-IGBT device with dual reverse freewheeling paths according to claim 1, characterized in that: The terminal region is evenly provided with a plurality of field limiting rings (6), and the field limiting rings (6) are located between the active region and the second N-type anode region (7).

10. A method for preparing a RC-IGBT device with dual reverse freewheeling paths according to any one of claims 1 to 9, characterized in that The following steps are involved: S1: Select an N-type silicon wafer to make an N-type drift layer (9), implant phosphorus ions on the back side of the N-type drift layer (9) to form an N-type buffer layer (10), implant boron ions on the inner side of the front side of the N-type drift layer (9) to form a P-type base region (2), and implant phosphorus ions on the outer side of the front side of the N-type drift layer (9) to form a second N-type anode region (7); S2: etching a plurality of trenches penetrating the P-type base region (2) downward on the front surface of the N-type drift layer (9), thermally growing SiO2 on the inner surface of the trench to form a gate oxide layer (8), and depositing polysilicon in the gate oxide layer (8) to form a polysilicon gate (5); S3: forming a P-type cathode region (3) and an N-type cathode region (4) above the P-type base region (2) by injecting boron ions and phosphorus ions, respectively, and depositing metal above the P-type cathode region (3) and the N-type cathode region (4) to form a cathode emitter (1), and depositing metal above the second N-type anode region (7) to form a metal electrode; S4: injecting boron ions into the inner side of the N-type buffer layer (10) to form a P-type anode region (11), and injecting phosphorus ions into the outer side of the N-type buffer layer (10) to form a first N-type anode region (12); S5: Depositing metal on the back of the P-type anode region (11) and the first N-type anode region (12) to form an anode collector (13), and using metal to connect the anode collector (13) and the second N-type anode region (7) to complete the preparation.

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