A compact symmetric bidirectional electrostatic protection device with high holding voltage

Abstract

The application provides a compact symmetrical bidirectional electrostatic protection device with high holding voltage, which comprises a substrate, two first-conductivity-type buried layers arranged on the substrate, and a first bidirectional SCR structure and a second bidirectional SCR structure arranged above the two first-conductivity-type buried layers respectively, a first isolation structure is arranged between the first bidirectional SCR structure and the second bidirectional SCR structure, and the first bidirectional SCR structure and the second bidirectional SCR structure are symmetrically arranged with the first isolation structure as the center; when working in a forward direction, the first bidirectional SCR structure serves as a main current discharge path, and the second bidirectional SCR serves as a holding voltage regulation path; when working in a reverse direction, the second bidirectional SCR structure serves as a main current discharge path, and the first bidirectional SCR serves as a holding voltage regulation path. The application can effectively improve the holding voltage of the device and greatly avoid the risk of latch-up failure of the device under high-voltage working conditions.

Description

Technical Field

[0001] This invention relates to an electrostatic discharge (ESD) protection device, specifically a compact, symmetrical, bidirectional ESD protection device with a high sustaining voltage. Background Technology

[0002] Electronic circuit systems are highly susceptible to damage from transient energies such as Electrical Over Stress (EOS) and Electrostatic Discharge (ESD). Therefore, appropriate ESD protection devices must be designed to protect the corresponding ports. Furthermore, due to the different functions of the ports, port signals may exhibit both positive and negative voltages. For example, CAN interfaces, commonly used in automotive and industrial control applications, require devices with bidirectional ESD protection capabilities.

[0003] Among the various bidirectional ESD protection devices currently available, the bidirectional silicon controlled rectifier (SCR) has become an important ESD protection device due to its bidirectional protection capability, strong discharge current capability, and high area utilization.

[0004] The structure of a typical electrostatic discharge (ESD) protection scheme for bidirectional SCRs in the prior art is as follows: Figure 1 As shown in Figure 200, this is a traditional bidirectional SCR structure. In this structure, 201 represents the first I / O port, 202 represents the second I / O port, 203 represents the substrate, 204 and 210 represent heavily P-type doped regions, 206 and 208 represent heavily N-type doped regions, 210, 212, and 214 represent high-voltage deep N-wells, 216 and 218 represent P-wells, and 220 represents an N-type buried layer. The heavily N-type doped region 206, P-well 216, and high-voltage deep N-well 214 constitute the emitter, base, and collector regions of a parasitic NPN BJT, respectively. The heavily N-type doped region 208, P-well 218, and high-voltage deep N-well 214 constitute the emitter, base, and collector regions of a parasitic NPN BJT, respectively. The P-well 216, P-well 218, and high-voltage deep N-well 214 constitute the emitter / collector, emitter / collector, and base regions of a parasitic bidirectional PNP BJT, respectively.

[0005] The equivalent circuit diagram of this typical electrostatic discharge (ESD) protection scheme is as follows: Figure 2As shown, 100 is a traditional bidirectional SCR circuit diagram, 101 represents the first I / O port, 102 represents the second I / O port, 104 and 112 represent P-well resistors, 106 and 110 represent parasitic NPN type BJT (Bipolar Junction Transistor), and 108 represents parasitic bidirectional PNP type BJT. The principle is as follows: When an ESD event occurs at the first I / O port 101, a large voltage drop occurs across the reverse PN junction of the base-collector junction of the parasitic bidirectional PNP BJT 110. When the voltage is high enough, avalanche breakdown occurs, establishing a voltage across the P-well resistor 112. When the voltage reaches a level sufficient to forward conduct the base-emitter junction of the parasitic NPN BJT 110, the parasitic NPN BJT 110 turns on, and its collector current also triggers the parasitic bidirectional PNP BJT 108 to turn on. A positive feedback loop is formed between the two BJTs, establishing a low-impedance path, ultimately turning on the entire bidirectional SCR structure. Because the bidirectional SCR structure is symmetrical, the same principle applies when an ESD event occurs at the second I / O port 102.

[0006] This ESD protection scheme has a strong discharge current capability, enabling rapid bidirectional ESD discharge. However, due to the low sustaining voltage of the bidirectional SCR in this typical ESD protection scheme, latch-up is prone to occur under higher operating voltages, leading to damage to the ESD protection device. Therefore, it is necessary to find ways to increase the sustaining voltage of the bidirectional SCR, thereby expanding the design window and meeting higher design standards. Summary of the Invention

[0007] To address the problem of low sustaining voltage and latch-up effect in existing technologies, this invention provides a compact symmetrical bidirectional electrostatic discharge (ESD) protection device with high sustaining voltage. This effectively improves the sustaining voltage of the bidirectional SCR protection device, significantly avoids the risk of latch-up failure under high-voltage operating conditions, and significantly enhances the device's operational stability and long-term reliability.

[0008] This invention relates to a compact, symmetrical, bidirectional electrostatic discharge (ESD) protection device with high sustaining voltage. It includes a substrate, two buried layers of a first conductivity type disposed on the substrate, and a first bidirectional electrostatic discharge (SCR) structure and a second bidirectional SCR structure respectively disposed above the two buried layers. A first isolation structure is provided between the first and second bidirectional SCR structures, and the devices are symmetrically arranged with the first isolation structure as the center. The first bidirectional SCR structure includes a first conductivity type high-voltage deep well and second conductivity type well regions disposed on both sides of the first conductivity type high-voltage deep well. The upper surfaces of the two second conductivity type well regions are respectively provided with mutually isolated first conductivity type heavily doped regions and two second conductivity type heavily doped regions. The first conductivity type heavily doped regions are respectively disposed between the two first conductivity type heavily doped regions. The first bidirectional SCR structure has a first port at one end and a first connection terminal at the other end for connecting to a second bidirectional SCR structure. The second bidirectional SCR structure has a second port at one end and a second connection terminal at the other end for connecting to the first bidirectional SCR structure. The first port is connected to a first conductivity type heavily doped region and one of the second conductivity type heavily doped regions on the upper surface of the second conductivity type well region. The second connection terminal is connected to another second conductivity type heavily doped region. The first connection terminal is connected to a first conductivity type heavily doped region and one of the second conductivity type heavily doped regions on the upper surface of another second conductivity type well region. The other second conductivity type heavily doped region is interconnected with the second conductivity type heavily doped region of the second bidirectional SCR structure via a wire. The output terminals of the first and second connection terminals are respectively provided with signal isolation structures to prevent backflow of current signals. When operating in the forward direction, the first bidirectional SCR structure serves as the main current discharge path, and the second bidirectional SCR serves as the sustaining voltage regulation path; when operating in the reverse direction, the second bidirectional SCR structure serves as the main current discharge path, and the first bidirectional SCR serves as the sustaining voltage regulation path.

[0009] Furthermore, the signal isolation structure includes a diode, an electronic switch, or a MOSFET.

[0010] Furthermore, the first conductivity type is N-type, the second conductivity type is P-type, the first conductivity type high-voltage deep well is a high-voltage deep N-well, and the second conductivity type well region is a P-well.

[0011] Furthermore, deep N-wells are provided on both sides of the P-well to isolate the substrate, and an isolation structure is provided above the deep N-wells to prevent the deep N-wells from contacting the P-type heavily doped region on the upper surface of the P-well.

[0012] Furthermore, the first bidirectional SCR structure connects the N-type heavily doped region, P-well, and high-voltage deep N-well at the first port to form a parasitic NPN type BJT (310), the P-well, high-voltage deep N-well, and the N-type heavily doped region connected to the first connection end to form a parasitic NPN type BJT (314), and the high-voltage deep N-well and the P-wells on both sides to form a parasitic bidirectional PNP type BJT (312). The second bidirectional SCR structure connects the N-type heavily doped region, P-well, and high-voltage deep N-well at the second port to form a parasitic NPN type BJT (324), the P-well, high-voltage deep N-well, and the N-type heavily doped region connected to the second connection end to form a parasitic NPN type BJT (328), and the high-voltage deep N-well and the P-wells on both sides to form a parasitic bidirectional PNP type BJT (326). The base region of the parasitic NPN type BJT (314) is connected to the base region of the parasitic NPN type BJT (328).

[0013] Furthermore, the parasitic NPN type BJT (314) and parasitic bidirectional PNP type BJT (312) of the first bidirectional SCR structure form a first PNPN structure, and the parasitic NPN type BJT (324) and parasitic bidirectional PNP type BJT (326) of the second bidirectional SCR structure form a second PNPN structure. When the first bidirectional SCR structure discharges static electricity, the first PNPN structure forms a positive feedback path for static discharge, and the second PNPN structure forms a sustaining voltage regulation path. When the second bidirectional SCR structure discharges static electricity, the second PNPN structure forms a positive feedback path for static discharge, and the first PNPN structure forms a sustaining voltage regulation path.

[0014] Furthermore, the two ends of the parasitic bidirectional PNP type BJT (312) are respectively connected to the first port and the first connection terminal through a parasitic P-well resistor, and the two ends of the parasitic bidirectional PNP type BJT (326) are respectively connected to the second port and the second connection terminal through a parasitic P-well resistor.

[0015] Compared with existing technologies, the advantages of this invention are: it effectively improves the sustaining voltage of the device, significantly avoids the risk of latch-up failure under high-voltage operating conditions, and significantly improves the device's operational stability and long-term reliability. At the same time, it broadens the application scenarios of bidirectional ESD protection devices, applicable to a wider range of operating voltages, and can be adapted to more high-voltage automotive and industrial communication port protection scenarios, resulting in stronger product adaptability and market versatility.

[0016] This invention employs two bidirectional SCR structures. In forward operation, the first bidirectional SCR serves as the primary current discharge path, while the second bidirectional SCR serves as the sustaining voltage regulation path. In reverse operation, their functions switch, with the second bidirectional SCR acting as the primary current discharge path and the first bidirectional SCR as the sustaining voltage regulation path. This sustaining voltage regulation path disrupts the positive feedback in the bidirectional SCR structure, increasing the difficulty of maintaining conduction and thus improving the sustaining voltage. Furthermore, by switching between the primary and auxiliary paths during forward and reverse current discharge, this invention significantly saves the overall device area, facilitating miniaturized integration design and reducing costs. Attached Figure Description

[0017] To more clearly illustrate the solutions in this invention or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0018] Figure 1 This is a schematic diagram of a typical electrostatic discharge (ESD) protection solution in the prior art; Figure 2 The equivalent circuit diagram is shown for a typical electrostatic discharge (ESD) protection scheme in the prior art. Figure 3 This is a schematic diagram of an embodiment of the compact symmetrical bidirectional electrostatic protection device with high sustaining voltage according to the present invention; Figure 4 This is an equivalent circuit diagram of an embodiment of the compact symmetrical bidirectional electrostatic protection device with high sustaining voltage of the present invention; Figure 5 This is a schematic diagram of current discharge and voltage maintenance regulation during the forward operation of the present invention; Figure 6 This is a schematic diagram illustrating the current discharge and voltage maintenance regulation when the present invention operates in reverse. Figure 7 This is a schematic diagram comparing the TLP curves of the present invention and a typical electrostatic protection scheme obtained from TCAD simulation. Detailed Implementation

[0019] Unless otherwise defined, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains; the terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the invention; the terms "comprising" and "having," and any variations thereof, in the specification, claims, and foregoing drawings are intended to cover non-exclusive inclusion. The terms "first," "second," etc., in the specification, claims, or foregoing drawings are used to distinguish different objects, not to describe a particular order.

[0020] In this invention, the reference to "embodiment" means that a specific feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of the invention. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor is it a mutually exclusive, independent, or alternative embodiment to other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described in this invention can be combined with other embodiments.

[0021] To enable those skilled in the art to better understand the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings.

[0022] like Figure 3 As shown, the present invention has a compact symmetrical bidirectional electrostatic discharge protection device 400 with high sustaining voltage, including a substrate 403, two first conductivity type buried layers 438 and 450 disposed on the substrate 403, and a first bidirectional SCR structure and a second bidirectional SCR structure respectively disposed above the two first conductivity type buried layers. A first isolation structure is provided between the first bidirectional SCR structure and the second bidirectional SCR structure, and the first isolation structure is symmetrically arranged around the first isolation structure.

[0023] The first bidirectional SCR structure includes a first conductivity type high-voltage deep well and second conductivity type well regions disposed on both sides of the first conductivity type high-voltage deep well. The upper surfaces of the two second conductivity type well regions are respectively provided with mutually isolated first conductivity type heavily doped regions and two second conductivity type heavily doped regions. The first conductivity type heavily doped regions are respectively disposed between the two first conductivity type heavily doped regions. The first bidirectional SCR structure has a first port 401 at one end and a first connection terminal 411 at the other end for connecting to the second bidirectional SCR structure. The second bidirectional SCR structure has a second port 402 at one end and a second connection terminal 417 at the other end for connecting to the first bidirectional SCR structure. Typically, the first port 401 is connected to the first I / O port of the protected circuit, and the second port 402 is connected to the second I / O port of the protected circuit.

[0024] The first port 401 is connected to the first conductivity type heavily doped region and one of the second conductivity type heavily doped regions on the upper surface of the second conductivity type well region. The second connection terminal 417 is connected to another second conductivity type heavily doped region. The first connection terminal is connected to the first conductivity type heavily doped region and one of the second conductivity type heavily doped regions on the upper surface of the other second conductivity type well region. The other second conductivity type heavily doped region is interconnected with the second conductivity type heavily doped region of the second bidirectional SCR structure through a wire. The output terminals of the first connection terminal 411 and the second connection terminal 417 are respectively provided with signal isolation structures 444 and 446 to prevent backflow of current signals.

[0025] When operating in the forward direction, the first bidirectional SCR structure serves as the main current discharge path, and the second bidirectional SCR serves as the sustaining voltage regulation path; when operating in the reverse direction, the second bidirectional SCR structure serves as the main current discharge path, and the first bidirectional SCR serves as the sustaining voltage regulation path.

[0026] In this example, the signal isolation structures 444 and 446 are diodes. Of course, the signal isolation structures 444 and 446 in this example can also be set as electronic switches, MOSFETs, or combinations thereof, as long as a fixed potential difference can be established at both ends.

[0027] In one embodiment of the present invention, the substrate is a P-type substrate, the first conductivity type is N-type, the second conductivity type is P-type, the first conductivity type high-voltage deep well is a high-voltage deep N-well, and the second conductivity type well region is a P-well. Of course, the first conductivity type can also be P-type, and the second conductivity type can be N-type; the working principle remains the same.

[0028] like Figure 3 As shown, the first bidirectional SCR structure in this example includes a high-voltage deep N-well 430, and a P-well 434 on the left and a P-well 436 on the right of the high-voltage deep N-well 430. A high-voltage deep N-well 428 is located on the left side of the P-well 434, and a high-voltage deep N-well 432 is located on the right side of the P-well 436, thereby isolating the first bidirectional SCR structure from the substrate 403. An isolation structure is also provided above the high-voltage deep N-wells 428, 430, and 432 to prevent contact between the deep N-wells and the heavily p-type doped regions on the upper surface of the P-wells. In this example, the isolation structure is a trench structure; however, it can also be configured as a shielding gate or other semiconductor isolation structures. The second bidirectional SCR structure is axially symmetrical to the first bidirectional SCR structure of this invention.

[0029] In this example, 404, 408, 410, 414, 416, 420, 422, and 426 represent heavily p-type doped regions, 406, 412, 418, and 424 represent heavily n-type doped regions, 428, 430, 432, 440, 442, and 452 represent high-voltage deep n-wells, and 434, 436, 454, and 448 represent p-wells. The heavily n-type doped region 406, the p-well 434, and the high-voltage deep n-well 430 constitute the emitter, base, and collector regions of the parasitic NPN BJT, respectively. Similarly, the heavily n-type doped region 412, the p-well 436, and the high-voltage deep n-well 430 constitute the emitter, base, and collector regions of the parasitic NPN BJT, respectively. P-wells 434 and 436, along with a high-voltage deep N-well 430, constitute the emitter / collector, emitter / collector, and base regions of a parasitic bidirectional PNP BJT, respectively. Heavy N-type doped regions 418, 454, and 442 constitute the emitter, base, and collector regions of a parasitic NPN BJT, respectively. Heavy N-type doped regions 424, 448, and 442 constitute the emitter, base, and collector regions of a parasitic NPN BJT, respectively. P-wells 454, 448, and 442 constitute the emitter / collector, emitter / collector, and base regions of a parasitic bidirectional PNP BJT, respectively.

[0030] like Figure 4 As shown in the equivalent circuit diagram 300 of the compact symmetrical bidirectional electrostatic discharge (ESD) protection device with high sustaining voltage of the present invention, 301 is the first port, 321 is the first connection terminal of the first bidirectional SCR structure, 302 is the second port, and 317 represents the second connection terminal of the second bidirectional SCR structure. Typically, 301 is connected to the first I / O port of the protected circuit, and 302 is connected to the second I / O port of the protected circuit. 304 represents the first bidirectional SCR structure, 306 represents the second bidirectional SCR structure, 308, 316, 322, and 330 represent P-well resistors, 310, 314, 324, and 328 represent parasitic NPN type BJTs, 310-1 represents the base region of parasitic NPN type BJT 310, 314-1 represents the base region of parasitic NPN type BJT 314, 324-1 represents the base region of parasitic NPN type BJT 324, and 328-1 represents a parasitic NPN type BJT... The base region of 328, 312 and 326 represent parasitic bidirectional PNP type BJTs, and 318 and 320 represent diodes.

[0031] The two ends of the parasitic bidirectional PNP type BJT 312 are connected to the first port 301 and the first connection terminal 321 respectively through a parasitic P-well resistor 308 and 316. The two ends of the parasitic bidirectional PNP type BJT 326 are connected to the second port 302 and the second connection terminal 317 respectively through a parasitic P-well resistor 322 and 330.

[0032] The emitter region of the parasitic NPN type BJT 314 is connected to the base region of the parasitic NPN type BJT 324 through diode 320. The base region of the parasitic NPN type BJT 314 is connected to the base region of the parasitic NPN type BJT 328. The emitter region of the parasitic NPN type BJT 328 is connected to the base region of the parasitic NPN type BJT 310 through diode 318.

[0033] In this example, the parasitic NPN type BJT 314 and parasitic bidirectional PNP type BJT 312 of the first bidirectional SCR structure form a first PNPN structure, and the parasitic NPN type BJT (324) and parasitic bidirectional PNP type BJT (326) of the second bidirectional SCR structure form a second PNPN structure. When the first bidirectional SCR structure discharges static electricity, the first PNPN structure forms a positive feedback path for static discharge, and the second PNPN structure forms a sustaining voltage regulation path. The working principle of this example is as follows: like Figure 5 As shown, when an ESD event arrives at the compact symmetrical bidirectional electrostatic protection device of the embodiment from the first port 301 of the first bidirectional SCR structure, current flows through the P-well resistor 308, the bidirectional parasitic PNP type BJT 312, the parasitic NPN type BJT 314, the diode 320 and the parasitic NPN type BJT 324, forming a positive high current discharge path 501. Meanwhile, because current is injected from the outside into the base region 324-1 of the parasitic NPN BJT 324 of the second bidirectional SCR structure in the positive high current discharge path 501, the parasitic NPN BJT 324 will turn on, causing positive feedback to turn on the second bidirectional SCR structure. At this time, the second bidirectional SCR structure can draw current from the base region 314-1 of the parasitic NPN BJT 314, pulling down the voltage at the junction of the base region 314-1 of the parasitic NPN BJT 314, thereby destroying the positive feedback effect in the first bidirectional SCR, making it more difficult to maintain conduction, thereby achieving the purpose of increasing the holding voltage. The red curve is the holding voltage regulation path 502.

[0034] like Figure 6As shown, when an ESD event arrives at the compact symmetrical bidirectional electrostatic protection device of this embodiment from the second port 302 of the second bidirectional SCR structure, the current will flow through the P-well resistor 322, the bidirectional parasitic PNP type BJT 326, the parasitic NPN type BJT 328, the diode 318 and the parasitic NPN type BJT 310, forming a reverse high current discharge path 503. Meanwhile, because current is injected from the outside into the base region 310-1 of the parasitic NPN BJT 310 of the second bidirectional SCR structure in the reverse high current discharge path 503, the parasitic NPN BJT 310 is turned on, causing positive feedback to turn on the first bidirectional SCR structure. At this time, the turned-on first bidirectional SCR structure can draw current from the base region 328-1 of the parasitic NPN BJT 328, pull down the voltage at the junction of the base region 328-1 of the parasitic NPN BJT 328, thereby destroying the positive feedback effect in the second bidirectional SCR, making it more difficult to maintain conduction, thereby achieving the purpose of improving the holding voltage. The red curve is the holding voltage regulation path 504.

[0035] The compact symmetrical bidirectional electrostatic protection device of this invention was compared with a traditional typical electrostatic protection scheme using TCAD simulation tests. The TLP images obtained from the TCAD simulation tests are shown below. Figure 7 As shown in the figure, the horizontal axis represents the sustaining voltage and the vertical axis represents the current. From this TLP image, it can be seen that the sustaining voltage of the compact symmetrical bidirectional electrostatic protection device of the present invention is 33.2V, while the sustaining voltage of the traditional bidirectional SCR under the same conditions is 21.2V. The sustaining voltage of the new structure is increased by 12V, which is a very significant improvement.

[0036] As can be seen from the above, the beneficial effects of the present invention are: 1. This invention employs an integrated architecture that combines a main bidirectional SCR structure, a voltage-regulating bidirectional SCR structure, and a connection circuit to achieve high-sustaining-voltage ESD clamping of the bidirectional SCR, fundamentally avoiding latch-up effects and significantly improving device operational stability and long-term reliability. Simultaneously, it broadens the application scenarios of bidirectional ESD protection devices, applicable to a wider range of operating voltages, and can be adapted to more high-voltage automotive and industrial communication port protection scenarios, resulting in stronger product adaptability and market versatility.

[0037] 2. This invention breaks away from the existing technical approach of designing the ESD discharge main path and the sustaining voltage regulation circuit separately. The first bidirectional SCR structure and the second bidirectional SCR structure can perform functional substitution when dealing with positive and reverse ESD events. This design method can minimize the area of ​​the ESD protection circuit, which is conducive to the miniaturization and integration design of the device and saves costs.

[0038] The specific embodiments described above are preferred embodiments of the present invention and are not intended to limit the specific scope of the present invention. The scope of the present invention includes, but is not limited to, these specific embodiments. All equivalent changes made in accordance with the present invention are within the protection scope of the present invention.

Claims

1. A compact, symmetrical, bidirectional electrostatic discharge protection device with high sustaining voltage, characterized in that: The device includes a substrate, two buried layers of a first conductivity type disposed on the substrate, and a first bidirectional SCR structure and a second bidirectional SCR structure disposed above the two buried layers of the first conductivity type, respectively. A first isolation structure is provided between the first bidirectional SCR structure and the second bidirectional SCR structure, and the structures are symmetrically arranged with the first isolation structure as the center. The first bidirectional SCR structure includes three parallel high-voltage deep wells of a first conductivity type and two second conductivity type well regions spaced apart between the three first conductivity type high-voltage deep wells. The first conductivity type high-voltage deep wells on both sides are used to isolate the first bidirectional SCR structure from the substrate. The upper surfaces of the two second conductivity type well regions are respectively provided with mutually isolated first conductivity type heavily doped regions and two second conductivity type heavily doped regions. The first conductivity type heavily doped regions are respectively disposed between the two second conductivity type heavily doped regions. An isolation structure is also provided above the first conductivity type high-voltage deep wells to prevent the first conductivity type high-voltage deep wells from contacting the second conductivity type heavily doped regions. The first bidirectional SCR structure has a first port at one end and a first connection terminal at the other end for connecting to a second bidirectional SCR structure. The second bidirectional SCR structure has a second port at one end and a second connection terminal at the other end for connecting to the first bidirectional SCR structure. The first port is connected to a first conductivity type heavily doped region and one of the second conductivity type heavily doped regions on the upper surface of the second conductivity type well region. The second connection terminal is connected to another second conductivity type heavily doped region. The first connection terminal is connected to a first conductivity type heavily doped region and one of the second conductivity type heavily doped regions on the upper surface of the other second conductivity type well region. The other second conductivity type heavily doped region is interconnected with the remaining second conductivity type heavily doped region of the second bidirectional SCR structure via a wire. The output terminals of the first and second connection terminals are respectively provided with signal isolation structures to prevent backflow of current signals. When operating in the forward direction, the first bidirectional SCR structure serves as the main current discharge path, and the second bidirectional SCR structure serves as the sustaining voltage regulation path; when operating in the reverse direction, the second bidirectional SCR structure serves as the main current discharge path, and the first bidirectional SCR serves as the sustaining voltage regulation path.

2. The compact symmetrical bidirectional electrostatic discharge protection device with high sustaining voltage according to claim 1, characterized in that: The signal isolation structure includes a diode, an electronic switch, or a MOSFET.

3. The compact symmetrical bidirectional electrostatic discharge protection device with high sustaining voltage according to claim 1, characterized in that: The first conductivity type is N-type, the second conductivity type is P-type, the first conductivity type high-voltage deep well is a high-voltage deep N-well, and the second conductivity type well region is a P-well.

4. The compact symmetrical bidirectional electrostatic discharge protection device with high sustaining voltage according to claim 3, characterized in that: Both sides of the P-well are provided with deep N-wells that isolate the substrate, and an isolation structure is provided above the deep N-wells to prevent the deep N-wells from contacting the P-type heavily doped region on the upper surface of the P-well.

5. The compact symmetrical bidirectional electrostatic discharge protection device with high sustaining voltage according to claim 4, characterized in that: The first bidirectional SCR structure connects the N-type heavily doped region, P-well, and high-voltage deep N-well at the first port to form a parasitic NPN type BJT (310). The P-well, high-voltage deep N-well, and N-type heavily doped region connected to the first connection end form a parasitic NPN type BJT (314). The high-voltage deep N-well and the P-wells on both sides form a parasitic bidirectional PNP type BJT (312). The second bidirectional SCR structure connects the N-type heavily doped region, P-well, and high-voltage deep N-well at the second port to form a parasitic NPN type BJT (324). The P-well, high-voltage deep N-well, and N-type heavily doped region connected to the second connection end form a parasitic NPN type BJT (328). The high-voltage deep N-well and the P-wells on both sides form a parasitic bidirectional PNP type BJT (326). The base region of the parasitic NPN type BJT (314) is connected to the base region of the parasitic NPN type BJT (328).

6. The compact symmetrical bidirectional electrostatic discharge protection device with high sustaining voltage according to claim 5, characterized in that: The parasitic NPN type BJT (314) and parasitic bidirectional PNP type BJT (312) of the first bidirectional SCR structure form a first PNPN structure, and the parasitic NPN type BJT (324) and parasitic bidirectional PNP type BJT (326) of the second bidirectional SCR structure form a second PNPN structure. When the first bidirectional SCR structure discharges static electricity, the first PNPN structure forms a positive feedback path for static discharge, and the second PNPN structure forms a sustaining voltage regulation path. When the second bidirectional SCR structure discharges static electricity, the second PNPN structure forms a positive feedback path for static discharge, and the first PNPN structure forms a sustaining voltage regulation path.

7. The compact symmetrical bidirectional electrostatic discharge protection device with high sustaining voltage according to claim 5, characterized in that: The two ends of the parasitic bidirectional PNP type BJT (312) are respectively connected to the first port and the first connection terminal through a parasitic P-well resistor, and the two ends of the parasitic bidirectional PNP type BJT (326) are respectively connected to the second port and the second connection terminal through a parasitic P-well resistor.

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