A bidirectional scr electrostatic protection device

Abstract

This invention provides a bidirectional SCR electrostatic discharge (ESD) protection device, comprising a P-type substrate, an N-type buried layer, a P-type epitaxial layer, a deep N-type well, a first P-type well, a second P-type well, an N-type well, a high-voltage N-type well, heavily doped P-type material, a first shallow trench isolation layer, heavily doped N-type material, a first field oxygen isolation layer, and a floating field plate. The P-type substrate is located at the bottom layer, and the N-type buried layer is located above the P-type substrate, with their surfaces flush. The P-type epitaxial layer is located above the P-type substrate. The deep N-type well, the first P-type well, the second P-type well, the N-type well, the high-voltage N-type well, the heavily doped P-type material, and the heavily doped N-type material are all formed within the P-type epitaxial layer via ion implantation. This invention reduces the device's turn-on voltage through the floating field plate, and achieves sequential or simultaneous turn-on of different current discharge paths through two current discharge paths and the length of the field oxygen isolation layer, controlling the device's double hysteresis characteristics to avoid latch-up effects. The centrosymmetric structure increases the longitudinal current, improving the overall current capability of the device.

Description

Technical Field

[0001] This invention relates to the field of electronic device technology, and in particular to a bidirectional SCR electrostatic discharge protection device. Background Technology

[0002] Electrostatic discharge (ESD) is one of the main threats causing damage or failure of integrated circuits (ICs). Silicon rectifier (SCR) devices are widely used in ESD protection due to their low on-resistance and high current handling capability (i.e., high robustness). In many applications, such as those requiring simultaneous protection against both forward and reverse ESD impacts on I / O ports or power lines, ESD protection devices need to have bidirectional withstand voltage and bidirectional discharge capabilities. Utilizing the ease of forming symmetrical or quasi-symmetrical structures using SCRs, bidirectional SCR devices can be realized.

[0003] Traditional SCRs (including bidirectional ones) generally suffer from high turn-on voltage and low holding voltage, making them unable to turn on in time or prone to latch-up. In power integrated circuits, bidirectional SCRs are more widely used. In most cases, the holding voltage and turn-on voltage will shift in the same direction; that is, to increase the holding voltage, the turn-on voltage is also reduced, and to reduce the turn-on voltage, the holding voltage is also reduced. Summary of the Invention

[0004] To address the issues of high turn-on voltage and latch-up susceptibility in existing SCR electrostatic discharge (ESD) protection devices, this invention proposes a bidirectional SCR ESD protection device. By introducing a floating field plate, the device's turn-on voltage is reduced with almost no decrease in the holding voltage. By designing two current discharge paths and the length of the field-oxygen isolation, the current capability of the device in the holding state is improved. The device can also achieve sequential or simultaneous turn-on of different current discharge paths, controlling the device's double hysteresis characteristics to avoid latch-up. By designing a centrally symmetrical structure, the longitudinal current is increased, and the current can be discharged in multiple directions, from the center to the periphery or from the periphery to the center, thereby improving the overall current capability of the device.

[0005] A bidirectional SCR electrostatic discharge protection device includes: a P-type substrate, an N-type buried layer, a P-type epitaxial layer, a deep N-type well, a first P-type well, a second P-type well, an N-type well, a high-voltage N-type well, a heavily doped P-type layer (P+), a first shallow trench isolation layer, a heavily doped N-type layer (N+), a first field oxygen isolation layer, and a floating field plate. The P-type substrate is located at the bottom layer, the N-type buried layer is located inside and above the P-type substrate, and the surfaces of the two layers are flush. The P-type epitaxial layer is located above the P-type substrate. The deep N-type well, the first P-type well, and the second P-type well are also included. The deep N-type well, high-voltage N-type well, and heavily doped P-type well are all formed within the P-type epitaxial layer via ion implantation. Above the P-type substrate are sequentially arranged P-type epitaxial layers and deep N-type wells, with the outermost layer being the P-type epitaxial layer. Except for the outermost P-type epitaxial layer, the remaining P-type epitaxial layers and deep N-type wells are located above the N-type buried layer. Above the outermost P-type epitaxial layer is the first P-type well, and the heavily doped P-type well is located above and within the first P-type well. Both surfaces are flush. The first P-type well and the heavily doped P-type well... A P-type ring is formed. Above the deep N-type well adjacent to the outermost P-type extension is an N-type well. Above the N-type well is a first shallow trench isolation. The deep N-type well, the N-type well, and the first shallow trench isolation form an isolation ring. Above the deep N-type well near the middle is a high-pressure N-type well. Above the high-pressure N-type well is a first field oxygen isolation. Above the first field oxygen isolation is a floating field plate. The deep N-type well, the high-pressure N-type well, and the first field oxygen isolation form an electrode isolation ring. Between the isolation ring and the electrode isolation ring is a second electrode ring composed of a second P-type well and a P+ / N+ structure. The P+ / N+ structure is located inside and above the second P-type well, and their surfaces are flush. The second P-type well is located above the P-type extension. Adjacent to the inner side of the electrode isolation ring is a first electrode structure composed of a second P-type well and an N+ / P+ / N+ structure. The N+ / P+ / N+ structure is located inside and above the second P-type well, and their surfaces are flush. The high-pressure N-type well is located between the N+ / P+ / N+ structure and the second P-type well below the P+ / N+ structure.

[0006] Furthermore, the entire electrostatic protection device has a centrally symmetrical structure, with the P-type heavy doping in the N+ / P+ / N+ structure as the center of symmetry. The electrode isolation ring is arranged around the first electrode structure, the second electrode ring is arranged around the electrode isolation ring, the isolation ring is arranged around the second electrode ring, and the P-type ring is arranged around the isolation ring.

[0007] Furthermore, in the N+ / P+ / N+ structure, P+ is located at the center, and N+ surrounds P+.

[0008] Furthermore, the floating field plate is a polycrystalline silicon field plate or a through-hole field plate, and the floating field plate has a ring-shaped, island-shaped or strip-shaped structure, and there are one or more of them.

[0009] Furthermore, the isolation ring and the N-type buried layer isolate the main body of the electrostatic protection device from the substrate. The first P-type well and the heavily doped P-type layer located above the first P-type well connect the substrate potential or perform floating treatment. The heavily doped N-type layer located above the second P-type well serves as the emitter of the NPN when the device is turned on. The high-voltage N-type well, the deep N-type well, and the N-type buried layer serve as the collector of the NPN. The second P-type well and the P-type epitaxial layer serve as the base of the NPN. The second P-type well and the P-type epitaxial layer below the N+ / P+ / N+ structure and the heavily doped P-type layer connecting their potentials serve as the emitter or collector of the PNP, respectively. The high-voltage N-type well and the deep N-type well serve as the base of the PNP. The N-type buried layer, the P-type epitaxial layer, and the second P-type well form a diode DIODE. Specifically, the N-type buried layer, the P-type epitaxial layer below the second electrode, and the second P-type well form DIODE1, and the N-type buried layer, the P-type epitaxial layer below the first electrode, and the second P-type well form DIODE2.

[0010] Furthermore, a second shallow trench isolation or a second field oxygen isolation is added between P+ and N+, located within the second P-type trap.

[0011] Furthermore, the floating field plate is a through-hole field plate, and a first metal layer is provided above the through-hole field plate. The first metal layer is electrically connected to the through-hole field plate. The material of the first metal layer is copper or aluminum, and the filling material of the through-hole field plate is tungsten.

[0012] Furthermore, the entire electrostatic protection device has a centrally symmetrical structure, with the P-type heavy doping in the first electrode as the center of symmetry. This allows the device to discharge current both laterally and longitudinally, and the current can be discharged from the center to the surroundings or from the surroundings to the center in multiple directions. By adjusting the field oxygen isolation length (L), the device's double hysteresis and the device's turn-on voltage can be adjusted, thereby regulating the device's current-carrying capacity. By adjusting the total length and spacing of the floating field plate and the structure, the device's turn-on voltage can be adjusted. SG can be positive, negative, or zero, where G is the length of the high-voltage N-type well and S is the total length of the floating field plate. By adjusting these structural dimensions, the device can be adapted to different application requirements.

[0013] Furthermore, when the first electrode is the cathode and the second electrode is the anode, when ESD occurs, avalanche breakdown occurs between the second P-type well below the N+ / P+ / N+ structure and the high-voltage N-type well, generating a large avalanche breakdown current. This current flows through the second P-type well and P-type epitaxial layer below the N+ / P+ / N+ structure, creating a voltage difference between the N+ / P+ / N+ structure and the interior of the second P-type well and P-type epitaxial layer. Once this voltage difference reaches the diode's turn-on voltage, the PN junction formed by the N+ in the N+ / P+ / N+ structure and the second P-type well below it conducts. This causes the transistor NPN1, consisting of the N+ in the N+ / P+ / N+ structure as the emitter, the second P-type well and P-type epitaxial layer below it as the base, and the high-voltage N-type well and deep N-type well as the collector, to turn on, and the junction with the N+ / P+ / N+ structure... In the + / N+ structure, N+ acts as the emitter, the second P-type well and P-type epitaxial layer below the N+ / P+ / N+ structure act as the base, and the N-type buried layer acts as the collector. Due to avalanche breakdown between the high-voltage N-type well and the second P-type well, PNP is activated, which uses the second P-type well and P-type epitaxial layer below the P+ / N+ structure, along with the heavily doped P-type layer connecting their potentials, as the emitter, the high-voltage N-type well and deep N-type well as the base, and the second P-type well and P-type epitaxial layer below the N+ / P+ / N+ structure, along with the heavily doped P-type layer connecting their potentials, as the collector. The activation of NPN1, NPN2, and PNP can all discharge ESD current. Furthermore, the collector of NPN1 provides current to the base of PNP, and the collector of PNP provides current to the base of NPN1, forming a positive feedback and enhancing the ESD current discharge capability.

[0014] When the second electrode is the cathode and the first electrode is the anode, the working principle is the same, the difference is that the tubes that are turned on are NPN3, NPN4 and PNP.

[0015] Furthermore, when the second electrode is the anode and the first electrode is the cathode, the paths containing NPN1 and NPN2 are open, and their total current can be divided into three parts: 1) In the NPN2 path, the current flows through R1 第二P型阱+P型外延 DIODE1, R N型埋层 1) NPN2 flows from the anode to the cathode; 2) In the NPN1 path, the current flows through R1 第二P型阱+P型外延 PN junction in PNP, R 高压N型阱+深N型阱 1) NPN1 flows from the anode to the cathode; 3) In the PNP path, the current flows through R1 第二P型阱+P型外延 PNP, R2 第二P型阱+P型外延The current flows from the anode to the cathode. The collector of NPN1 provides current to the base of the PNP, and the collector of the PNP provides current to the base of NPN1, forming positive feedback and enhancing current discharge capability. Conversely, when the first electrode is the anode and the second electrode is the cathode, the paths containing NPN3 and NPN4 are open, and the total current can be divided into three parts: 1) In the NPN4 path, the current flows through R2... 第二P型阱+P型外延 DIODE2, R N型埋层 1) NPN4 flows from the anode to the cathode; 2) In the NPN3 path, the current flows through R2. 第二P型阱+P型外延 PN junction in PNP, R 高压N型阱+深N型阱 1) NPN3 flows from the anode to the cathode; 2) In the PNP path, the current flows through R2. 第二P型阱+P型外延 PNP, R1 第二P型阱+P型外延 The current flows from the anode to the cathode. The collector of NPN3 provides current to the base of PNP, and the collector of PNP provides current to the base of NPN3, forming positive feedback and enhancing the current discharge capability.

[0016] When L (field-oxygen isolation length) is short, the high-voltage N-type well is short, and it is more easily depleted by the second P-type well. Therefore, the device turn-on voltage is low, and the distance between N+ and the high-voltage N-type well is close, making it easier for NPN1 or NPN3 to turn on. As the current gradually increases, the emitter current can cross the second P-type well and the P-type epitaxial layer to reach the N-type buried layer, allowing NPN2 or NPN4 to turn on, resulting in secondary hysteresis. Therefore, the smaller L is, the smaller the turn-on voltage, and the more the discharge current tends to discharge through NPN1 or NPN3 first, and then through NPN2 or NPN4, exhibiting double hysteresis. The larger L is, the larger the turn-on voltage, and the more the discharge current tends to turn on NPN1 and NPN2 or NPN3 and PNP4 simultaneously, exhibiting single hysteresis. In the case of double hysteresis, the device turn-on voltage is low, and the initial current capability is weak, but the current capability increases during the second hysteresis. In the case of single hysteresis, the device turn-on voltage is high, but the current capability is strong after turn-on. Therefore, by adjusting L, the device's turn-on voltage, current magnitude, current path, and hysteresis can be adjusted according to the actual needs of the circuit, providing high flexibility.

[0017] The present invention also provides another bidirectional SCR electrostatic protection device, which has the same structure as the above-mentioned bidirectional SCR electrostatic protection device, except that the high-voltage N-type well and the deep N-type well below the first field oxygen isolation are replaced by a deep high-voltage N-type well.

[0018] The beneficial technical effects of this invention are as follows:

[0019] This invention introduces a floating field plate above the field oxygen isolation. Since the potential of the floating field plate is not zero when the device is working, it attracts electrons or holes in the second P-type well and the high-voltage N-type well, which helps to form a current path in advance and reduces the turn-on voltage of the device with almost no reduction in the holding voltage. By designing two current discharge paths and adjusting the length L of the field oxygen isolation, the current capability of the device in the holding state is improved, and the turn-on voltage of the device and the two current discharge paths can be controlled to be turned on simultaneously or sequentially (NPN1 and NPN3 are the same current discharge paths under different electrode settings, and NPN2 and NPN4 are another same current discharge path under different electrode settings), thereby controlling the double hysteresis characteristics of the device and avoiding latch-up effect. At the same time, by designing a centrally symmetrical structure, the longitudinal current is increased, and the current can be discharged in multiple directions from the center to the periphery or from the periphery to the center, improving the overall current capability of the device. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the 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 the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 This is a cross-section of a bidirectional SCR electrostatic protection device provided in an embodiment of the present invention. Figure 1 ;

[0022] Figure 2 This is a top view of a bidirectional SCR electrostatic protection device provided in an embodiment of the present invention;

[0023] Figure 3 This is a cross-section of a bidirectional SCR electrostatic protection device provided in an embodiment of the present invention. Figure 2 ;

[0024] Figure 4 This is a cross-section of a bidirectional SCR electrostatic protection device provided in an embodiment of the present invention. Figure 3 ;

[0025] Figure 5 This is a cross-section of a bidirectional SCR electrostatic protection device provided in an embodiment of the present invention. Figure 4 ;

[0026] Figure 6 This is a cross-section of a bidirectional SCR electrostatic protection device provided in an embodiment of the present invention. Figure 5 ;

[0027] Figure 7 This is a cross-section of a bidirectional SCR electrostatic protection device provided in an embodiment of the present invention. Figure 6 ;

[0028] Figure 8 These are examples of top views of various field plate arrangements provided in the embodiments of the present invention, wherein (a) is an example of a single ring-shaped field plate structure, (b) is an example of multiple ring-shaped field plate structures, (c) is an example of an island-shaped field plate structure, and (d) is an example of a strip-shaped field plate structure.

[0029] Figure 9 This is an equivalent circuit diagram of a bidirectional SCR electrostatic protection device provided in an embodiment of the present invention;

[0030] Figure 10 These are comparison diagrams of transverse TLP simulation curves when the first electrode is grounded as the cathode according to the embodiments of the present invention. Among them, (a) is the TLP simulation curve without the floating field plate, (b) is the TLP simulation curve with the floating field plate and S=S1, (c) is the TLP simulation curve with the floating field plate and S=S2, and (d) is the TLP simulation curve with the floating field plate and S=S3. Detailed Implementation

[0031] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0032] Under normal circumstances, if the holding current is large enough to exceed the maximum operating current of the circuit (i.e., the SCR hysteresis curve does not touch the circuit's operating region), the latch-up effect can be effectively avoided. Therefore, given the limited ability to increase the holding voltage, increasing the holding current is also one of the methods to avoid the latch-up effect.

[0033] Example 1:

[0034] This invention proposes a bidirectional SCR electrostatic protection device, such as... Figure 1 As shown, the electrostatic discharge protection device includes: a P-type substrate, an N-type buried layer, a P-type epitaxial layer, a deep N-type well, a first P-type well, a second P-type well, an N-type well, a high-voltage N-type well, a heavily doped P-type layer (P+), a first shallow trench isolation layer, a heavily doped N-type layer (N+), a first field oxygen isolation layer, and a polycrystalline silicon field plate.

[0035] The P-type substrate is located at the bottom layer, and the N-type buried layer is located inside and above the P-type substrate. The surfaces of the two are flush. The P-type epitaxial layer is located above the P-type substrate. The deep N-type well, the first P-type well, the second P-type well, the N-type well, the high-voltage N-type well, the P-type heavy doping, and the N-type heavy doping are all formed in the P-type epitaxial layer by ion implantation.

[0036] Above the P-type substrate are P-type epitaxial layers and deep N-type wells arranged sequentially. The outermost layer is the P-type epitaxial layer. Except for the outermost P-type epitaxial layer, the remaining P-type epitaxial layers and deep N-type wells are all located above the N-type buried layer. Above the outermost P-type epitaxial layer is the first P-type well. The heavily doped P-type layer is located inside and above the first P-type well. The surfaces of the two are flush. The first P-type well and the heavily doped P-type layer form a P-type ring. Above the deep N-type well adjacent to the outermost P-type epitaxial layer is an N-type well. Above the N-type well is the first shallow trench isolation layer. The deep N-type well, the N-type well, and the first shallow trench isolation layer form an isolation ring.

[0037] Above the deep N-type well near the center is a high-pressure N-type well, above which is the first field oxygen isolation, and above the first field oxygen isolation is a floating field plate. The deep N-type well, the high-pressure N-type well, and the first field oxygen isolation form an electrode isolation ring. Between the isolation ring and the electrode isolation ring is a second electrode ring composed of a second P-type well and a P+ / N+ structure. The P+ / N+ structure is located inside and above the second P-type well, and their surfaces are flush. The second P-type well is located above the P-type extension. Adjacent to the inner side of the electrode isolation ring is a first electrode structure composed of a second P-type well and an N+ / P+ / N+ structure. The N+ / P+ / N+ structure is located inside and above the second P-type well, and their surfaces are flush. The high-pressure N-type well is located between the N+ / P+ / N+ structure and the second P-type well below the P+ / N+ structure. In the N+ / P+ / N+ structure, P+ is located in the center, and N+ surrounds P+.

[0038] The entire electrostatic protection device has a centrally symmetrical structure, with the P-type heavy doping in the N+ / P+ / N+ structure as the center of symmetry. The electrode isolation ring is arranged around the first electrode structure, the second electrode ring is arranged around the electrode isolation ring, the isolation ring is arranged around the second electrode ring, and the P-type ring is arranged around the isolation ring.

[0039] An isolation ring and an N-type buried layer isolate the electrostatic discharge (ESD) device body from the substrate. Simultaneously, the N-type buried layer is also part of the device body and participates in device operation. The first P-type well and the heavily doped P-type layer above it connect the substrate potential or perform a floating treatment. The heavily doped N-type layer above the second P-type well acts as the emitter of the NPN when the device is turned on. The high-voltage N-type well, deep N-type well, and N-type buried layer act as the collector of the NPN, and the second P-type well and P-type epitaxial layer act as the base of the NPN. The second P-type well and P-type epitaxial layer below the N+ / P+ / N+ structure and the heavily doped P-type layer connecting their potentials act as the emitter or collector of the PNP, respectively. That is, the second P-type well and P-type epitaxial layer below the N+ / P+ / N+ structure and the heavily doped P-type layer connecting their potentials act as the emitter or collector of the PNP. The PNP diode is formed by the emitter of the P+ / N+ structure, the second P-type well and the P-type epitaxial layer below the P+ / N+ structure, and the heavily doped P-type layer connecting their potentials as the collector of the PNP diode. Alternatively, the PNP diode is formed by the second P-type well and the P-type epitaxial layer below the N+ / P+ / N+ structure, and the heavily doped P-type layer connecting their potentials as the collector of the PNP diode. The PNP diode is formed by the second P-type well and the P-type epitaxial layer below the P+ / N+ structure, and the heavily doped P-type layer connecting their potentials as the emitter of the PNP diode. The high-voltage N-type well and the deep N-type well serve as the base of the PNP diode. The N-type buried layer, the P-type epitaxial layer, and the second P-type well form a diode DIODE. Specifically, the N-type buried layer, the P-type epitaxial layer below the second electrode, and the second P-type well form DIODE1, and the N-type buried layer, the P-type epitaxial layer below the first electrode, and the second P-type well form DIODE2.

[0040] Where L is the field oxygen isolation length, G is the high-voltage N-type well length, and S is the total length of the polysilicon field plate. By adjusting L, the double hysteresis condition and the turn-on voltage of the device can be adjusted, as well as the current capability of the device in the holding state. By adjusting S, the turn-on voltage of the device can be adjusted. SG can be positive, negative, or zero. Through these structural dimension adjustments, the device can be adapted to different application requirements.

[0041] The entire electrostatic discharge protection device has a centrally symmetrical structure, as shown in the top view below. Figure 2 As shown, due to the multiple layers, Figure 2 The diagram only shows a partial view of the structure. The P-type heavy doping in the N+ / P+ / N+ structure is taken as the center of symmetry, and other structures are arranged around P+. This allows the device to discharge current in both the lateral and longitudinal directions, and the current can be discharged from the center to the surroundings or from the surroundings to the center in multiple directions, improving the overall current capability of the device. The only difference between the lateral and longitudinal directions is the length T of P+ in the first electrode; the other structures and dimensions are the same.

[0042] The first P-type trap and the second P-type trap can be the same trap or different traps, depending on the actual situation.

[0043] The first and second electrodes can be used as cathodes or anodes, respectively, to achieve bidirectional ESD protection.

[0044] When an ESD event occurs, the SCR device can quickly discharge the ESD current, protecting the internal circuitry from ESD damage. This invention provides two current discharge paths: Current discharge path one: N+, second P-type well + P-type epitaxial layer, high-voltage N-type well + deep N-type well, second P-type well + P-type epitaxial layer; Current discharge path two: N+, second P-type well + P-type epitaxial layer, N-type buried layer, second P-type well + P-type epitaxial layer. Having two discharge paths can improve the overall current discharge capability of the SCR device, increase the holding current to further reduce the risk of latch-up effect, and increase the failure current to enhance the robustness of the device.

[0045] When the first electrode is the cathode and the second electrode is the anode, when ESD occurs, avalanche breakdown occurs between the second P-type well below the N+ / P+ / N+ structure and the high-voltage N-type well, generating a large avalanche breakdown current. This current flows through the second P-type well and P-type epitaxial layer below the N+ / P+ / N+ structure, creating a voltage difference between the N+ / P+ / N+ structure and the interior of the second P-type well and P-type epitaxial layer. Once this voltage difference reaches the diode's turn-on voltage, the PN junction formed by the N+ in the N+ / P+ / N+ structure and the second P-type well below it conducts. This causes the transistor NPN1, consisting of the N+ in the N+ / P+ / N+ structure as the emitter, the second P-type well and P-type epitaxial layer below it as the base, and the high-voltage N-type well and deep N-type well as the collector, to turn on. In the N+ structure, N+ acts as the emitter, the second P-type well and P-type epitaxial layer below the N+ / P+ / N+ structure act as the base, and the N-type buried layer acts as the collector. Due to avalanche breakdown between the high-voltage N-type well and the second P-type well, PNP is activated, which consists of the second P-type well and P-type epitaxial layer below the P+ / N+ structure, as well as the heavily doped P-type layer connecting their potentials, acting as the emitter, the high-voltage N-type well and deep N-type well, as the base, and the second P-type well and P-type epitaxial layer below the N+ / P+ / N+ structure, as well as the heavily doped P-type layer connecting their potentials, acting as the collector. The activation of NPN1, NPN2, and PNP can all discharge ESD current. Furthermore, the collector of NPN1 provides current to the base of PNP, and the collector of PNP provides current to the base of NPN1, forming a positive feedback and enhancing the ESD current discharge capability.

[0046] When the second electrode is the cathode and the first electrode is the anode, the working principle is the same, the difference is that the tubes that are turned on are NPN3, NPN4 and PNP.

[0047] Example 2:

[0048] This embodiment also provides a bidirectional SCR electrostatic protection device, such as Figure 3 As shown, the difference between Embodiment 2 and Embodiment 1 is that a second shallow trench isolation or a second field oxygen isolation is added between P+ and N+ located in the second P-type well. When avalanche breakdown occurs, the breakdown current increases the path due to the presence of the shallow trench isolation or field oxygen isolation, so that the voltage difference generated between the N+ / P+ / N+ or P+ / N+ structure and the second P-type well and the P-type epitaxial layer can reach the turn-on voltage of the PN junction formed by N+ and the second P-type well more quickly. Therefore, the device can turn on more quickly when an ESD event occurs.

[0049] Example 3:

[0050] This embodiment also provides a bidirectional SCR electrostatic protection device, such as Figure 4 As shown, the difference between Example 3 and Example 1 is that the high-pressure N-type trap and the deep N-type trap are replaced with a deep high-pressure N-type trap, which can save costs.

[0051] Example 4:

[0052] This embodiment also provides a bidirectional SCR electrostatic protection device, such as Figure 5 As shown, the difference between Example 4 and Example 1 is that the floating field plate is a plurality of polycrystalline silicon structures located above the first field oxygen isolation, and the total length S of the field plate and the spacing d between the field plates can be set according to actual conditions.

[0053] Example 5:

[0054] This embodiment also provides a bidirectional SCR electrostatic protection device, such as Figure 6 As shown, the difference between Example 5 and Example 1 is that the floating field plate is a through-hole field plate, the filler is preferably the common metal tungsten, but it can also be other metals, a first metal layer is provided above the through-hole field plate, the first metal layer is electrically connected to the through-hole field plate, and the material of the first metal layer is copper or aluminum.

[0055] Example 6:

[0056] This embodiment also provides a bidirectional SCR electrostatic protection device, such as Figure 7 As shown, the difference between Example 6 and Example 1 is that the floating field plate is a through-hole field plate, and there are multiple through-hole field plates. The total length S of the field plate and the distance d between the field plates can be set according to actual conditions. The filler is preferably the common metal tungsten, but it can also be other metals. A first metal layer is provided above the through-hole field plate. The first metal layer is electrically connected to the through-hole field plate. The material of the first metal layer is copper or aluminum.

[0057] Figure 8 This is a top view example of various field plate arrangements, applicable to both polycrystalline silicon field plates and through-hole field plates. The field oxide isolation length L, the total length S of the floating field plate, and the field plate spacing d correspond to the previous embodiments. Figure 8 (a) is a monolithic annular field plate structure based on [the structure], and Figure 1 , 3 Matching 4 and 6, (b) is a structure of multiple annular field plates, with Figure 5 , 7 Matching the structure, (c) is an island-shaped field plate structure and (d) is a strip-shaped field plate structure. Different field plate structures will result in different device characteristics. The selection should be based on a comprehensive consideration of specific requirements, process conditions, hierarchical structure, etc.

[0058] Figure 9 The equivalent circuit diagram of this invention shows that when the second electrode is the anode and the first electrode is the cathode, the paths containing NPN1 and NPN2 are open, and the total current can be divided into three parts: 1) In the NPN2 path, the current flows through R1 第二P型阱+P型外延 DIODE1, R N型埋层 1) NPN2 flows from the anode to the cathode; 2) In the NPN1 path, the current flows through R1 第二P型阱+P型外延 PN junction in PNP, R 高压N型阱+深N型阱 1) NPN1 flows from the anode to the cathode; 3) In the PNP path, the current flows through R1 第二P型阱+P型外延 PNP, R2 第二P型阱+P型外延 The current flows from the anode to the cathode. The collector of NPN1 provides current to the base of the PNP, and the collector of the PNP provides current to the base of NPN1, forming positive feedback and enhancing current discharge capability. Conversely, when the first electrode is the anode and the second electrode is the cathode, the paths containing NPN3 and NPN4 are open, and the total current can be divided into three parts: 1) In the NPN4 path, the current flows through R2... 第二P型阱+P型外延 DIODE2, R N型埋层 1) NPN4 flows from the anode to the cathode; 2) In the NPN3 path, the current flows through R2. 第二P型阱+P型外延 PN junction in PNP, R 高压N型阱+深N型阱 1) NPN3 flows from the anode to the cathode; 2) In the PNP path, the current flows through R2. 第二P型阱+P型外延 PNP, R1 第二P型阱+P型外延 The current flows from the anode to the cathode. The collector of NPN3 provides current to the base of PNP, and the collector of PNP provides current to the base of NPN3, forming positive feedback and enhancing the current discharge capability.

[0059] When L is short, the high-voltage N-type well is shorter, and it is more easily depleted by the second P-type well. Therefore, the device turn-on voltage is lower, and the distance between N+ and the high-voltage N-type well is closer, making it easier for NPN1 or NPN3 to turn on. As the current gradually increases, the emitter current can cross the second P-type well and the P-type epitaxial layer to reach the N-type buried layer, allowing NPN2 or NPN4 to turn on, resulting in secondary hysteresis. Therefore, the smaller L is, the smaller the turn-on voltage and turn-on current, and the more likely the discharge current is to flow through NPN1 or NPN3 first, then through NPN2 or NPN4, exhibiting double hysteresis. The larger L is, the larger the turn-on voltage, and the more likely the discharge current is to turn on NPN1 and NPN2 or NPN3 and PNP4 simultaneously, exhibiting single hysteresis. In the case of double hysteresis, the device turn-on voltage is lower, and the initial current capability is weaker, but the current capability increases during the second hysteresis. In the case of single hysteresis, the device turn-on voltage is higher, but the current capability is stronger after turn-on. Therefore, by adjusting L, the device's turn-on voltage, current magnitude, current path, and hysteresis can be adjusted according to the actual needs of the circuit, providing high flexibility.

[0060] The total length, spacing, and structure (ring, island, or strip) of the floating field plate will affect the electric field distribution of the device, thus affecting the device's turn-on voltage.

[0061] Figure 10 The figures show a comparison of simulation curves of transverse transmission line pulses (TLP) with and without a floating field plate when the first electrode is used as the cathode. (a) shows the effect without a floating field plate, (b) with a floating field plate and S=S1, (c) with a floating field plate and S=S2, and (d) with a floating field plate and S=S3. Figure 10 It can be observed that, compared with the non-floating field plate, the turn-on voltage of the bidirectional SCR electrostatic protection device proposed in this invention is reduced by 6.5V (S=S1), 7V (S=S2), and 3V (S=S3), respectively, while maintaining the voltage basically unchanged. Therefore, the turn-on voltage of the device can be adjusted by adjusting the total length, spacing, and structure of the floating field plate.

[0062] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A bidirectional SCR electrostatic protection device, characterized in that, The device includes: a P-type substrate, an N-type buried layer, a P-type epitaxial layer, a deep N-type well, a first P-type well, a second P-type well, an N-type well, a high-voltage N-type well, a heavily doped P-type layer (P+), a first shallow trench isolation layer, a heavily doped N-type layer (N+), a first field oxygen isolation layer, and a floating field plate. The P-type substrate is located at the bottom layer, the N-type buried layer is located inside and above the P-type substrate, and their surfaces are flush. The P-type epitaxial layer is located above the P-type substrate. The deep N-type well, the first P-type well, the second P-type well, the N-type well, and the high-voltage N-type well are also included. The N-type well, P-type heavy doping, and N-type heavy doping are all formed within the P-type epitaxial layer via ion implantation. Above the P-type substrate are sequentially arranged P-type epitaxial layers and deep N-type wells, with the outermost layer being the P-type epitaxial layer. Except for the outermost P-type epitaxial layer, the remaining P-type epitaxial layers and deep N-type wells are located above the N-type buried layer. Above the outermost P-type epitaxial layer is the first P-type well, and the P-type heavy doping is located above and within the first P-type well. Both surfaces are flush, and the first P-type well and the P-type heavy doping form a P-type ring. Above the deep N-type well adjacent to the outermost P-type epitaxial layer is an N-type well. Above the N-type well is a first shallow trench isolation. The deep N-type well, the N-type well, and the first shallow trench isolation form an isolation ring. Above the deep N-type well near the middle is a high-pressure N-type well. Above the high-pressure N-type well is a first field oxygen isolation. Above the first field oxygen isolation is a floating field plate. The deep N-type well, the high-pressure N-type well, and the first field oxygen isolation form an electrode isolation ring. Between the isolation ring and the electrode isolation ring is a second electrode ring composed of a second P-type well and a P+ / N+ structure. The P+ / N+ structure is located inside and above the second P-type well, and their surfaces are flush. The second P-type well is located above the P-type epitaxial layer. Adjacent to the inner side of the electrode isolation ring is a first electrode structure composed of a second P-type well and an N+ / P+ / N+ structure. The N+ / P+ / N+ structure is located inside and above the second P-type well, and their surfaces are flush. The high-pressure N-type well is located between the N+ / P+ / N+ structure and the second P-type well below the P+ / N+ structure.

2. The bidirectional SCR electrostatic protection device according to claim 1, characterized in that, The entire electrostatic protection device has a centrally symmetrical structure, with the P-type heavy doping in the N+ / P+ / N+ structure as the center of symmetry. The electrode isolation ring is arranged around the first electrode structure, the second electrode ring is arranged around the electrode isolation ring, the isolation ring is arranged around the second electrode ring, and the P-type ring is arranged around the isolation ring.

3. The bidirectional SCR electrostatic protection device according to claim 1, characterized in that, In the N+ / P+ / N+ structure, P+ is located at the center, and N+ surrounds P+.

4. The bidirectional SCR electrostatic protection device according to claim 1, characterized in that, The floating field plate is a polycrystalline silicon field plate or a through-hole field plate. The floating field plate has a ring-shaped, island-shaped, or strip-shaped structure, and there are one or more of them.

5. The bidirectional SCR electrostatic protection device according to claim 1, characterized in that, An isolation ring and an N-type buried layer isolate the main body of the electrostatic protection device from the substrate. The first P-type well and the heavily doped P-type layer located above the first P-type well connect the substrate potential or perform floating treatment. The heavily doped N-type layer located above the second P-type well serves as the emitter of the NPN when the device is turned on. The high-voltage N-type well, the deep N-type well, and the N-type buried layer serve as the collector of the NPN. The second P-type well and the P-type epitaxial layer serve as the base of the NPN. The second P-type well and the P-type epitaxial layer below the N+ / P+ / N+ structure and the P+ / N+ structure, as well as the heavily doped P-type layer that connects their potentials, serve as the emitter or collector of the PNP, respectively. The high-voltage N-type well and the deep N-type well serve as the base of the PNP. The N-type buried layer, the P-type epitaxial layer, and the second P-type well form a diode (DIODE).

6. The bidirectional SCR electrostatic protection device according to claim 1, characterized in that, A second shallow trench isolation or a second field oxygen isolation is added between P+ and N+, located within a second P-type trap.

7. The bidirectional SCR electrostatic protection device according to claim 4, characterized in that, The floating field plate is a through-hole field plate, and a first metal layer is provided on the top of the through-hole field plate. The first metal layer is electrically connected to the through-hole field plate. The material of the first metal layer is copper or aluminum, and the filling material of the through-hole field plate is tungsten.

8. A bidirectional SCR electrostatic protection device, characterized in that, The structure of the bidirectional SCR electrostatic protection device as described in any one of claims 1-7 is different in that the high-voltage N-type well and the deep N-type well below the first field oxygen isolation are replaced by a deep high-voltage N-type well.

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