Bidirectional scr electrostatic protector

Abstract

The application discloses a bidirectional SCR electrostatic protector, and relates to the field of electrostatic protection devices, which comprises a first electrostatic protection unit and a second electrostatic protection unit. The first electrostatic protection unit comprises a first P-type region, a first N-type region and a second P-type region arranged in sequence along a first direction. The second electrostatic protection unit comprises a third P-type region, a second N-type region and a fourth P-type region arranged in sequence along the first direction. The first P-type region and the third P-type region are both provided with a first P-well, a first N-well and a second P-well, the first N-type region and the second N-type region are both provided with a second N-well above, and the second P-type region and the fourth P-type region are both provided with a third P-well, a third N-well and a fourth P-well. The second end of the first electrostatic protection unit is electrically connected with the first end of the second electrostatic protection unit. In the case of maintaining the trigger voltage unchanged, the maintaining voltage is improved.

Description

Technical Field

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

[0002] With the development of high-voltage integrated circuits such as automotive electronics, power management chips, and industrial control chips, chip operating voltages have gradually increased to 40V, 60V, and even higher. Silicon Controlled Rectifiers (SCRs) are widely used in electrostatic discharge (ESD) protection designs due to their advantages such as high ESD carrying capacity per unit area, low on-resistance, and high chip area utilization. However, traditional SCR structures still have the following technical drawbacks: low sustaining voltage, typically only a few volts to a dozen volts, which easily leads to latch-up effects in high-voltage bipolar-complementary metal-oxide-semiconductor-double-diffused metal-oxide-semiconductor (BCD) processes; structural adjustments made to increase the sustaining voltage are often accompanied by an increase in the trigger voltage, resulting in a compressed ESD design window; furthermore, single-stage high sustaining voltage SCRs struggle to simultaneously achieve high sustaining voltage and high ESD robustness.

[0003] Therefore, the present invention provides a bidirectional SCR electrostatic discharge protector to solve the technical problem that current SCR electrostatic discharge protectors are unable to simultaneously achieve a high sustaining voltage and a low trigger voltage. Summary of the Invention

[0004] The purpose of this invention is to provide a bidirectional SCR electrostatic discharge protector to solve the technical problem that current SCR electrostatic discharge protectors are unable to balance a high sustaining voltage and a low trigger voltage.

[0005] To solve the above-mentioned technical problems, the present invention provides a bidirectional SCR electrostatic discharge protector, including a first electrostatic discharge protection unit and a second electrostatic discharge protection unit; the first electrostatic discharge protection unit includes a first P-type region, a first N-type region and a second P-type region arranged sequentially along a first direction; the second electrostatic discharge protection unit includes a third P-type region, a second N-type region and a fourth P-type region arranged sequentially along the first direction; The first P-type region and the third P-type region are each provided with a first P-well, a first N-well and a second P-well, the first N-type region and the second N-type region are each provided with a second N-well above them, and the second P-type region and the fourth P-type region are each provided with a third P-well, a third N-well and a fourth P-well. The surface of the first P-well is provided with a first P-doped region, the surface of the first N-well is provided with a first N-doped region, the surface of the third N-well is provided with a third N-doped region, and the surface of the fourth P-well is provided with a fourth P-doped region. The first end of the first electrostatic discharge (ESD) protection unit and the second ESD protection unit are connected to the first P-doped region and the first N-doped region, and the second end of the first ESD protection unit and the second ESD protection unit are connected to the third N-doped region and the fourth P-doped region; the second end of the first ESD protection unit is electrically connected to the first end of the second ESD protection unit.

[0006] Optionally, it also includes a P-type substrate, wherein the first electrostatic discharge protection unit and the second electrostatic discharge protection unit are disposed on one side surface of the P-type substrate.

[0007] Optionally, the first electrostatic protection unit further includes a first N-type buried layer, which is disposed below the first P-type region, the first N-type region, and the second P-type region; The second electrostatic protection unit further includes a second N-type buried layer, and the second N-type region is disposed above the second N-type buried layer; The central region of the second N-type region has a first protrusion, and the third P-type region and the fourth P-type region are located on both sides of the first protrusion, with the top of the first protrusion flush with the top of the third P-type region and the fourth P-type region.

[0008] Optionally, one side surface of the P-type substrate is provided with the first N-type buried layer, the second N-type buried layer, and an isolation structure located between the first N-type buried layer and the second N-type buried layer.

[0009] Optionally, the system further includes an isolation structure, wherein the isolation structure is provided on opposite sides of the first electrostatic protection unit along the first direction, on opposite sides of the second electrostatic protection unit along the first direction, and between the first P-well, the first N-well, the second P-well, the second N-well, the third P-well, the third N-well, and the fourth P-well.

[0010] Optionally, the first P-type region is a first deep P-well, the second P-type region is a second deep P-well, and the first N-type region is a first high-pressure deep N-well. The third P-type region is the first P-type body region, the fourth P-type region is the second P-type body region, and the second N-type region is the second high-pressure deep N-well.

[0011] Optionally, the width of the second P-well and the width of the third P-well of the first electrostatic protection unit are both 1.6 micrometers; The width of the second P-well and the width of the third P-well in the second electrostatic protection unit are both 1.6 micrometers.

[0012] Optionally, in the first electrostatic protection unit, the spacing between the second P-well and the adjacent edge of the first P-type region, and the spacing between the third P-well and the adjacent edge of the second P-type region are both 1.4 micrometers to 1.6 micrometers. In the second electrostatic protection unit, the spacing between the second P-well and the adjacent edge of the third P-type region, and the spacing between the third P-well and the adjacent edge of the fourth P-type region are both 3 micrometers to 4 micrometers.

[0013] Optionally, the first end of the first electrostatic discharge protection unit and the second electrostatic discharge protection unit are used as the anode, and the second end of the first electrostatic discharge protection unit and the second electrostatic discharge protection unit are used as the cathode. Alternatively, the first end of the first electrostatic discharge protection unit and the second electrostatic discharge protection unit can be used as the negative terminal, and the second end of the first electrostatic discharge protection unit and the second electrostatic discharge protection unit can be used as the positive terminal.

[0014] Optionally, both the first N-type region and the second N-type region are equipped with SCR high-pressure deep N-wells; The SCR high-voltage deep N-well is provided with a second N-well and a second N-doped region located on the surface of the second N-well.

[0015] The bidirectional SCR electrostatic discharge (ESD) protector provided by this invention includes a first ESD protection unit and a second ESD protection unit. The first ESD protection unit includes a first P-type region, a first N-type region, and a second P-type region arranged sequentially along a first direction. The second ESD protection unit includes a third P-type region, a second N-type region, and a fourth P-type region arranged sequentially along the first direction. A first P-well, a first N-well, and a second P-well are provided on both the first P-type region and the third P-type region. A second N-well is provided above both the first N-type region and the second N-type region. A third P-well, a third N-well, and a fourth P-well are provided on both the second P-type region and the fourth P-type region. A first P-doped region is provided on the surface of the first P-well, a first N-doped region is provided on the surface of the first N-well, a third N-doped region is provided on the surface of the third N-well, and a fourth P-doped region is provided on the surface of the fourth P-well. A first end of the first ESD protection unit and the second ESD protection unit is connected to the first P-doped region and the first N-doped region, and a second end of the first ESD protection unit and the second ESD protection unit is connected to the third N-doped region and the fourth P-doped region. The second end of the first ESD protection unit is electrically connected to the first end of the second ESD protection unit.

[0016] As can be seen, this bidirectional SCR electrostatic discharge (ESD) protector includes a first ESD protection unit and a second ESD protection unit. The first ends of the first and second ESD protection units are connected to the first P-doped region and the first N-doped region, respectively. The second ends of the first and second ESD protection units are connected to the third N-doped region and the fourth P-doped region, respectively. The second end of the first ESD protection unit is electrically connected to the first end of the second ESD protection unit, forming a series structure. When static electricity needs to be discharged, the first and second ESD protection units are triggered collaboratively, forming a complete ESD discharge path from the first end of the first ESD protection unit to the second end of the second ESD protection unit. Simultaneously, both the first and second ESD protection units include mutually coupled PNP and NPN transistors; the second N-well is the base region of the PNP transistor and the collector of the NPN transistor; the second P-well and the first P-type region, the second P-well and the third P-type region, the third P-well and the second P-type region, and the third P-well and the fourth P-type region all constitute the base region of the NPN transistor; the ESD discharge path is formed based on the PNP and NPN transistors. Compared with the current SCR electrostatic protector structure, the bidirectional SCR electrostatic protector provided in this application increases the base region width of the NPN transistor and weakens the current amplification factor of the NPN transistor, thereby significantly improving the holding voltage of the unit while maintaining the trigger voltage basically unchanged. Attached Figure Description

[0017] To more clearly illustrate the technical solutions of 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 only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a schematic diagram of the structure of an existing SCR electrostatic protector; Figure 2 The diagram shows the forward transmission line pulse current-voltage characteristic curve of an existing SCR electrostatic protection device. Figure 3 The negative transmission line pulse current-voltage characteristic curve of existing SCR electrostatic protection devices; Figure 4 This is a schematic diagram of the structure of a bidirectional SCR electrostatic protector provided in an embodiment of the present invention; Figure 5 A curve illustrating the transmission line pulse test current-voltage characteristic of a bidirectional SCR electrostatic protector provided in an embodiment of the present invention; Figure 6A graph illustrating the leakage current characteristics of a transmission line pulse test for a bidirectional SCR electrostatic protector provided in an embodiment of the present invention; In the figure: 1. P-type substrate, 2. First N-type buried layer, 3. Second N-type buried layer, 4. First deep P-well, 5. First high-voltage deep N-well, 6. Second deep P-well, 7. First P-type bulk region, 8. Second high-voltage deep N-well, 9. Second P-type bulk region, 10. First P-well, 11. First N-well, 12. Second P-well, 13. Second N-well, 14. Third P-well, 15. Third N-well, 16. Fourth P-well, 17. First P-doped region, 18. First N-doped region, 19. Second P-doped region, 20. Second N-doped region, 21. Third P-doped region, 22. Third N-doped region, 23. Fourth P-doped region. 101. P-type substrate, 102. N-type buried layer, 103. First SCR high-voltage deep N-well, 104. First P-type epitaxial layer, 105. Second SCR high-voltage deep N-well, 106. Second P-type epitaxial layer, 107. Third SCR high-voltage deep N-well, 108. First N-well, 109. First P-well, 110. Second N-well, 111. Second P-well, 112. Third N-well, 113. First P-doped region, 114. First N-doped region, 115. Second P-doped region, 116. Second N-doped region, 117. Isolation structure. Detailed Implementation

[0019] The core of this invention is to provide a bidirectional SCR electrostatic discharge protector. Please refer to [link / reference needed]. Figures 1 to 3 , Figure 1 This is a schematic diagram of the structure of an existing SCR electrostatic protector; Figure 2 The diagram shows the forward transmission line pulse current-voltage characteristic curve of an existing SCR electrostatic protection device. Figure 3 This shows the negative transmission line pulse current-voltage characteristic curve of a conventional SCR electrostatic discharge (ESD) device. (See also...) Figures 1 to 3The existing SCR electrostatic discharge protector includes: a P-type substrate 101 and an N-type buried layer 102 located on the P-type substrate 101; a first SCR high-voltage deep N-well 103, a first P-type epitaxial layer 104, a second SCR high-voltage deep N-well 105, a second P-type epitaxial layer 106, and a third SCR high-voltage deep N-well 107 are sequentially disposed on the N-type buried layer 102 along a first direction; a first P-well 109 is disposed in the first P-type epitaxial layer 104, and a second P-well 111 is disposed in the second P-type epitaxial layer 106; it also includes a first N-well 108 and a second N-well 109. 10 and a third N-well 112, wherein the second N-well 110 is located between the first P-well 109 and the second P-well 111; the first P-well 109 is provided with a first P-doped region 113 and a first N-doped region 114, and the second P-well 111 is provided with a second P-doped region 115 and a second N-doped region 116, and an isolation structure 117 is provided between each P-doped region and the N-doped region; the first P-doped region 113 and the first N-doped region 114 are connected to the anode, and the second P-doped region 115 and the second N-doped region 116 are connected to the cathode, and the device has a symmetrical structure. When the device is working, taking the anode under a positive high voltage pulse as an example: the first P-well 109 and the second N-well 110 are forward-biased first; when the voltage rises to about 70 volts, the second N-well 110 and the second P-well 111 undergo avalanche breakdown, and holes are injected into the second P-well 111, causing its potential to rise. When the potential of the second P-well 111 is 0.7 volts higher than that of the second N-doped region 116, the corresponding PN junction is forward-biased and the NPN transistor is turned on; after the NPN is turned on, it drives the PNP to be turned on, and the PNP continues to inject holes into the second P-well 111, forming a positive feedback, and a low-resistance discharge channel is formed between the anode and the cathode.

[0020] from Figures 2 to 3 As can be seen, the trigger voltage of this SCR electrostatic discharge (ESD) protector is approximately 70 volts, the sustaining voltage is only 22 volts, the maximum overcurrent capability is 13.2 amperes, the total width is 644 micrometers, and the overcurrent capability per unit width is 20.5 mA per micrometer. Due to the low sustaining voltage, there is a risk of latch-up when applied to higher voltage domains. Therefore, there is a need to provide a bidirectional SCR ESD protector to increase the sustaining voltage of the SCR ESD protector while maintaining a substantially constant trigger voltage.

[0021] To enable those skilled in the art to better understand the present invention, the invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. Obviously, the described embodiments are merely 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.

[0022] Please refer to Figures 4 to 6 , Figure 4This is a schematic diagram of the structure of a bidirectional SCR electrostatic protector provided in an embodiment of the present invention; Figure 5 A curve illustrating the transmission line pulse test current-voltage characteristic of a bidirectional SCR electrostatic protector provided in an embodiment of the present invention; Figure 6 A graph showing the leakage current characteristics of a transmission line pulse test for a bidirectional SCR electrostatic protector provided in an embodiment of the present invention.

[0023] See Figure 4 This invention provides a bidirectional SCR electrostatic discharge (ESD) protector, comprising a first ESD protection unit and a second ESD protection unit. The first ESD protection unit includes a first P-type region, a first N-type region, and a second P-type region arranged sequentially along a first direction. The second ESD protection unit includes a third P-type region, a second N-type region, and a fourth P-type region arranged sequentially along the first direction. A first P-well 10, a first N-well 11, and a second P-well 12 are provided on both the first and third P-type regions. A second N-well 13 is provided above both the first and second N-type regions. A third P-well 14 and a third N-well are provided on both the second and fourth P-type regions. The first P-well 10 has a first P-doped region 17 on its surface, the first N-well 11 has a first N-doped region 18 on its surface, the third N-well 15 has a third N-doped region 22 on its surface, and the fourth P-well 16 has a fourth P-doped region 23 on its surface. The first ends of the first and second electrostatic discharge (ESD) protection units are connected to the first P-doped region 17 and the first N-doped region 18, and the second ends of the first and second ESD protection units are connected to the third N-doped region 22 and the fourth P-doped region 23. The second end of the first ESD protection unit is electrically connected to the first end of the second ESD protection unit. The bidirectional SCR ESD protector of this embodiment includes a first ESD protection unit and a second ESD protection unit. The first and second ESD protection units are sequentially disposed on the substrate along a first direction. Both the first and second ESD protection units are bidirectional SCR ESD protection devices, meaning that the same ESD discharge effect can be achieved regardless of whether the current flows from the first end to the second end or from the second end to the first end. Furthermore, the symmetrical design of the well region, doped region, and connection method of the first and second electrostatic protection units provides a structural basis for the bidirectional discharge performance of the bidirectional SCR electrostatic protector formed after the first and second electrostatic protection units are connected.

[0024] In terms of device structure, the first electrostatic discharge (ESD) protection unit includes a first P-type region, a first N-type region, and a second P-type region arranged sequentially along a first direction; the second ESD protection unit includes a third P-type region, a second N-type region, and a fourth P-type region arranged sequentially along the first direction. A first P-well 10, a first N-well 11, and a second P-well 12 are each disposed on the first P-type region and the third P-type region, wherein the first P-well 10, the first N-well 11, and the second P-well 12 are arranged sequentially along the first direction on the corresponding P-type regions (i.e., the first P-type region and the second P-type region). A second N-well 13 is disposed above both the first N-type region and the second N-type region. A third P-well 14, a third N-well 15, and a fourth P-well 16 are each disposed on the second P-type region and the fourth P-type region, wherein the third P-well 14, the third N-well 15, and the fourth P-well 16 are arranged sequentially along the first direction on the corresponding P-type regions (i.e., the third P-type region and the fourth P-type region). The above-described structure provided in this embodiment provides a carrier transport channel and a barrier structure for the positive feedback loop of the bidirectional SCR ESD protection device.

[0025] Regarding electrode connections, the surface of the first P-well 10 is provided with a first P-doped region 17, the surface of the first N-well 11 is provided with a first N-doped region 18, the surface of the third N-well 15 is provided with a third N-doped region 22, and the surface of the fourth P-well 16 is provided with a fourth P-doped region 23. The first ends of the first and second electrostatic discharge (ESD) protection units are connected to the first P-doped region 17 and the first N-doped region 18, and the second ends of the first and second ESD protection units are connected to the third N-doped region 22 and the fourth P-doped region 23. Specifically, the first P-doped region 17 and the first N-doped region 18 both serve as ohmic contact regions at the first ends of the first and second ESD protection units. The first P-doped region 17 and the first N-doped region 18 are connected in parallel, enabling the first ends to simultaneously inject holes into the first P-well 10 and electrons into the first N-well 11, providing a carrier injection path for triggering the bidirectional SCR ESD protection device. Both the third N-doped region 22 and the fourth P-doped region 23 serve as ohmic contact regions at the second ends of the first and second electrostatic discharge (ESD) protection units. The third N-doped region 22 and the fourth P-doped region 23 are connected in parallel, enabling the second ends to simultaneously inject electrons into the third N-well 15 and holes into the fourth P-well 16. In this embodiment, the first and second ESD protection units are connected in series, meaning the second end of the first ESD protection unit is electrically connected to the first end of the second ESD protection unit. Specifically, the second end of the first ESD protection unit is electrically connected to the first end of the second ESD protection unit via a metal wire. The second end of the first ESD protection unit and the first end of the second ESD protection unit are electrically connected via a conductive interconnect layer. The material and thickness of the conductive interconnect layer in this embodiment can be referenced from related technologies and will not be elaborated here. In this embodiment, the conductive interconnect layer is a metal wire.

[0026] In this embodiment, the first electrostatic discharge (ESD) protection unit and the second ESD protection unit are connected in series, and they have a synergistic triggering effect. When the anode terminal is subjected to a positive high-voltage ESD pulse, the high-voltage pulse is first applied to the first terminal of the first ESD protection unit, causing avalanche breakdown inside the first ESD protection unit and triggering SCR positive feedback, entering a low-resistance conduction state. After the first ESD protection unit is turned on, the potential at the second terminal of the first ESD protection unit is pulled up. This potential is transmitted to the first terminal of the second ESD protection unit through the metal wire, which is equivalent to applying a high-voltage signal to the first terminal of the second ESD protection unit, thereby triggering avalanche breakdown and positive feedback inside the second ESD protection unit. The trigger voltage of the bidirectional SCR ESD protector provided in this embodiment is approximately equal to the sum of the trigger voltages of the first ESD protection unit and the second ESD protection unit, achieving a multiplication of the trigger voltage.

[0027] In this embodiment, the first end of the first electrostatic discharge (ESD) protection unit and the second ESD protection unit serve as the anode, and the second end of the first ESD protection unit and the second ESD protection unit serve as the cathode; or, the first end of the first ESD protection unit and the second ESD protection unit serve as the cathode, and the second end of the first ESD protection unit and the second ESD protection unit serve as the anode. Specifically, the bidirectional SCR ESD protector has a first end and a second end: the first end of the first ESD protection unit serves as the first end of the bidirectional SCR ESD protector, and the second end of the second ESD protection unit serves as the second end of the bidirectional SCR ESD protector, and the second end of the first ESD protection unit is electrically connected to the first end of the second ESD protection unit. That is, the first end of the first ESD protection unit serves as the first end of the bidirectional SCR ESD protector, and the second end of the second ESD protection unit serves as the second end of the bidirectional SCR ESD protector. Specifically, the cathode of the first ESD protection unit is connected to the anode of the second ESD protection unit, or the cathode of the second ESD protection unit is connected to the anode of the first ESD protection unit. In this embodiment, since both the first and second electrostatic discharge (ESD) protection units are bidirectional symmetrical devices, and the bidirectional SCR ESD protector formed by the series connection of the first and second ESD protection units still maintains symmetry, the anode and cathode terminals of the entire bidirectional SCR ESD protector can be interchanged. Specifically, the anode of the first ESD protection unit is the anode of the bidirectional SCR ESD protector, and the cathode of the second ESD protection unit is the cathode of the bidirectional SCR ESD protector. That is, current can either flow into the first terminal of the first ESD protection unit, pass through the first and second ESD protection units, and then flow out from the second terminal of the second ESD protection unit, or it can flow into the second terminal of the second ESD protection unit, pass through the second and first ESD protection units, and then flow out from the first terminal of the first ESD protection unit. Under these two current directions, in both modes, the electrical parameters such as the trigger voltage and the sustaining voltage are symmetrical, thus achieving bidirectional ESD protection.

[0028] In this embodiment, both the first and second electrostatic discharge (ESD) protection units include PNP and NPN transistors, forming an ESD discharge path. Specifically, the first ESD protection unit includes: a first PNP transistor formed by a first P-well 10, a second N-well 13, and a fourth P-well 16; a first NPN transistor formed by a second N-well 13, a third P-well 14, and a third N-well 15; and a second NPN transistor formed by a first N-well 11, a first P-type region, and a second N-well 13. The second ESD protection unit includes: a second PNP transistor formed by a first P-well 10, a second N-well 13, and a fourth P-well 16; a third NPN transistor formed by a second N-well 13, a fourth deep P-well, and a third N-well 15; and a fourth NPN transistor formed by a first N-well 11, a third P-type region, and a second N-well 13.

[0029] In this embodiment, the second N-well 13 serves as both the base region of the PNP transistor and the collector of the NPN transistor; the second P-well 12 and the first P-type region, as well as the third P-well 14 and the second P-type region, all constitute the base region of the NPN transistor in the first electrostatic discharge (ESD) unit. The second P-well 12 and the third P-type region, as well as the third P-well 14 and the fourth P-type region, all constitute the base region of the NPN transistor in the second ESD unit. This embodiment, through the arrangement of well regions and doped regions, forms three parasitic transistors within both the first and second ESD units.

[0030] The working principles of the first and second electrostatic discharge (ESD) protection units are described below, taking the first terminal as the anode and the second terminal as the cathode in the first and second ESD protection units as examples, from the direction of current inflow.

[0031] When the anode is subjected to a positive high-voltage electrostatic pulse, the current flows in from the first end (anode) of the first electrostatic protection unit, passes through the first electrostatic protection unit and the second electrostatic protection unit in sequence, and then flows out from the second end of the second electrostatic protection unit.

[0032] Specifically, in the first electrostatic discharge protection unit, the first terminal is connected to the first P-doped region 17 and the first N-doped region 18. The first P-doped region 17 and the first N-doped region 18 are connected in parallel as the anode. The first P-doped region 17 is located on the surface of the first P-well 10, and the first N-doped region 18 is located on the surface of the first N-well 11. When a forward high-voltage pulse is applied to the first terminal, a forward-biased PN junction is formed between the first P-well 10 and the second N-well 13. Holes in the first P-well 10 are injected into the second N-well 13, causing the potential of the second N-well 13 to rise. As the potential of the second N-well 13 continues to rise, the PN junction between the second N-well 13 and the second P-type region undergoes avalanche breakdown, and the first PNP transistor composed of the first P-well 10, the second N-well 13, and the fourth P-well 16 is turned on. As avalanche breakdown progresses, the potential of the second P-well 12 increases. When it rises sufficiently, the PN junction between the second P-well 12 and the third N-well 15 becomes forward-biased, and the first NPN transistor, formed by the second N-well 13, the second P-well 12, and the third N-well 15, turns on. The first PNP transistor and the first NPN transistor form a positive feedback loop, creating a low-resistance discharge path within the first electrostatic discharge unit. It should be noted that during this process, in the second NPN transistor formed by the first N-well 11, the first P-type region, and the second N-well 13, the PN junction between the first N-well 11 and the first P-type region is reverse-biased under forward high voltage and does not participate in the main discharge path within the first electrostatic discharge unit.

[0033] After the first electrostatic discharge (ESD) protection unit is turned on, the potential at its second terminal is pulled up. This potential change is transmitted to the second ESD protection unit through the electrical connection between the second terminal of the first ESD protection unit and the first terminal of the second ESD protection unit. In the second ESD protection unit, after the first terminal of the second ESD protection unit receives this potential change, the PN junction between the first P-well 10 and the second N-well 13 is forward-biased. Holes are injected into the second N-well 13, causing its potential to rise. The PN junction between the second N-well 13 and the fourth P-type region undergoes avalanche breakdown, and the second PNP transistor composed of the first P-well 10, the second N-well 13, and the fourth P-well 16 is turned on.

[0034] As the potential of the fourth P-type region rises sufficiently, the PN junction between the fourth P-type region and the third N-well 15 becomes forward-biased, and the third NPN transistor, formed by the second N-well 13, the fourth P-type region, and the third N-well 15, turns on. The second PNP transistor and the third NPN transistor form a positive feedback loop, creating a low-resistance discharge path within the second electrostatic discharge unit. This constitutes a complete electrostatic current discharge path for the bidirectional SCR electrostatic discharge device, from the first terminal of the first electrostatic discharge unit to the second terminal of the second electrostatic discharge unit (i.e., from the anode to the cathode of the bidirectional SCR electrostatic discharge device).

[0035] When the cathode terminal is subjected to a reverse high-voltage electrostatic pulse, current flows in from the second terminal (cathode) of the second electrostatic protection unit, passes through the second electrostatic protection unit and the first electrostatic protection unit in sequence, and then flows out from the first terminal (anode) of the first electrostatic protection unit. Specifically, in the second electrostatic protection unit, the second terminal is connected to the third N-doped region 22 and the fourth P-doped region 23, which are connected in parallel. The third N-doped region 22 is located on the surface of the third N-well 15, and the fourth P-doped region 23 is located on the surface of the fourth P-well 16.

[0036] Since both the first and second electrostatic discharge (ESD) protection units are bidirectional symmetrical devices, and the bidirectional SCR ESD protector formed by connecting the first and second ESD protection units in series has a symmetrical structure, the current flows in from the second end of the second ESD protection unit and flows out from the first end of the first ESD protection unit. Its working principle is symmetrical to that of a positive high-voltage electrostatic pulse, and will not be elaborated further here.

[0037] To improve the sustaining voltage of the bidirectional SCR electrostatic discharge (ESD) protector, compared to the structure of a conventional SCR ESD protector, the bidirectional SCR ESD protector provided in this embodiment adds a second P-well 12, a third P-well 14, a second P-doped region 19 located on the surface of the second P-well 12, and a third P-doped region 21 located on the surface of the third P-well 14. In this embodiment, the width of the second P-well and the width of the third P-well in the first ESD protection unit are both 1.6 micrometers; the width of the second P-well and the width of the third P-well in the second ESD protection unit are both 1.6 micrometers.

[0038] Furthermore, in the first electrostatic discharge (ESD) protection unit, the spacing between the second P-well 12 and the adjacent edge of the first P-type region, and the spacing between the third P-well 14 and the adjacent edge of the second P-type region, are both 1.4 micrometers to 1.6 micrometers. In the second ESD protection unit, the spacing between the second P-well 12 and the adjacent edge of the third P-type region, and the spacing between the third P-well 14 and the adjacent edge of the fourth P-type region, are both 3 micrometers to 4 micrometers.

[0039] Compared to traditional SCR electrostatic discharge (ESD) devices, the bidirectional SCR ESD protector provided in this application effectively increases the base region width of the NPN transistor through the aforementioned dimensional settings. This increased base region width reduces emitter injection efficiency, thereby weakening the current amplification factor of the NPN transistor and reducing the positive feedback strength. Consequently, while maintaining a relatively constant trigger voltage, the sustaining voltage of the unit is significantly increased. This eliminates the risk of traditional SCR ESD protectors entering a latch-up state due to voltage fluctuations within the normal operating voltage range.

[0040] The bidirectional SCR electrostatic discharge protector of this embodiment also includes a P-type substrate 1, and a first electrostatic discharge protection unit and a second electrostatic discharge protection unit are disposed on one side surface of the P-type substrate 1. The P-type substrate 1 serves as the carrier unit of the device.

[0041] In one feasible embodiment, a first N-type buried layer 2, a second N-type buried layer 3, and an isolation structure 24 located between the first N-type buried layer 2 and the second N-type buried layer 3 are disposed on one side surface of the P-type substrate 1.

[0042] In this embodiment, the first electrostatic discharge protection unit further includes a first N-type buried layer 2, which is disposed below the first P-type region, the first N-type region, and the second P-type region; the second electrostatic discharge protection unit further includes a second N-type buried layer 3, which is disposed above the second N-type buried layer 3; the central region of the second N-type region has a first protrusion, and the third P-type region and the fourth P-type region are respectively located on both sides of the first protrusion, and the top of the first protrusion is flush with the top of the third P-type region and the fourth P-type region.

[0043] In one feasible embodiment, the first P-type region is a first deep P-well 4, the second P-type region is a second deep P-well 6, the first N-type region is a first high-pressure deep N-well 5; the third P-type region is a first P-type body region 7, the fourth P-type region is a second P-type body region 9, and the second N-type region is a second high-pressure deep N-well 8.

[0044] In one feasible embodiment, the central region of the P-type substrate 1 has a second protrusion, and the first N-type buried layer 2 and the second N-type buried layer 3 are located on both sides of the second protrusion. In the first electrostatic discharge protection unit, the first deep P-well 4 (i.e., DPW), the first high-voltage deep N-well 5 (i.e., HDNW), and the second deep P-well 6 (i.e., DPW) are arranged sequentially along the first direction and located on the surface of the first N-type buried layer 2 facing away from the P-type substrate 1. The first deep P-well 4, the first high-voltage deep N-well 5, and the second deep P-well 6 have the same depth. The surface of the first deep P-well 4 is provided with the first P-well 10, the second N-well 13, and the second P-well 12 sequentially along the first direction. The surface of the first high-voltage deep N-well 5 is provided with the second N-well 13, and the second deep P-well 6... The surface of the first P well 10 is provided with a third P well 14, a third N well 15 and a fourth P well 16 in sequence along the first direction; and the surface of the first P well 10 is provided with a first P doped region 17, the surface of the first N well 11 is provided with a first N doped region 18, the surface of the second P well 12 is provided with a second P doped region 19, the surface of the second N well 13 is provided with a second N doped region 20, the surface of the third P well 14 is provided with a third P doped region 21, the surface of the third N well 15 is provided with a third N doped region 22, and the surface of the fourth P well 16 is provided with a fourth P doped region 23.

[0045] In the second electrostatic protection unit, the second high-voltage deep N-trap 8 is located above the second N-type buried layer 3; the central region of the second high-voltage deep N-trap 8 has a first protrusion, the first P-type body region 7 and the second P-type body region 9 are located on both sides of the first protrusion, and the top of the first protrusion is flush with the top of the first P-type body region 7 and the second P-type body region 9. The tops of the first P-type body region 7, the second high-pressure deep N-well 8, and the second P-type body region 9 are flush; the surface of the first P-type body region 7 (i.e., the Pbody region) is provided with a first P-well 10, a first N-well 11, and a second P-well 12 in sequence along the first direction; the surface of the second high-pressure deep N-well 8 is provided with a second N-well 13; the surface of the second P-type body region 9 (i.e., the Pbody region) is provided with a third P-well 14, a third N-well 15, and a fourth P-well 16 in sequence along the first direction; and the surface of the first P-well 10 is provided with a first P-doped region 17; the surface of the first N-well 11 is provided with a first N-doped region 18; the surface of the second P-well 12 is provided with a second P-doped region 19; the surface of the second N-well 13 is provided with a second N-doped region 20; the surface of the third P-well 14 is provided with a third P-doped region 21; the surface of the third N-well 15 is provided with a third N-doped region 22; and the surface of the fourth P-well 16 is provided with a fourth P-doped region 23.

[0046] In one feasible embodiment, in the first electrostatic discharge (ESD) protection unit, the first P-well 10, the first N-well 11, and the second P-well 12 are all recessed into the interior of the first deep P-well 4; the second N-well 13 is recessed into the interior of the first high-voltage deep N-well 5; and the third P-well 14, the third N-well 15, and the fourth P-well 16 are all recessed into the interior of the second deep P-well 6. In the second ESD protection unit, the first P-well 10, the first N-well 11, and the second P-well 12 are all recessed into the interior of the first P-type body region 7; the second N-well 13 is recessed into the interior of the second high-voltage deep N-well 8; and the third P-well 14, the third N-well 15, and the fourth P-well 16 are all recessed into the interior of the second P-type body region 9.

[0047] To achieve electrical isolation between the first electrostatic discharge (ESD) protection unit, the second ESD protection unit, and the internal doped regions, the P-type substrate 1 of the bidirectional SCR ESD protector provided in this embodiment further includes an isolation structure 24. Isolation structures 24 are provided on opposite sides of the first ESD protection unit along the first direction, on opposite sides of the second ESD protection unit along the first direction, and between the first P-well 10, the first N-well 11, the second P-well 12, the second N-well 13, the third P-well 14, the third N-well 15, and the fourth P-well 16. In this embodiment, the isolation portion employs shallow trench isolation and is disposed between the first ESD protection unit and the second ESD protection unit, as well as between adjacent edges of adjacent well regions, to prevent surface leakage and define the active region boundaries.

[0048] In this embodiment, the bidirectional SCR electrostatic discharge (ESD) protector is provided with SCR high-voltage deep N-wells 25 in both the first N-type region and the second N-type region. A second N-well 13 and a second N-doped region 20 are disposed on the surface of the second N-well 13. These SCR high-voltage deep N-wells 25 are located inside the first and second N-type regions, achieving lateral isolation between them. In the first ESD protection unit, the SCR high-voltage deep N-well 25 is in contact with the first N-type buried layer 2; in the first ESD protection unit, the SCR high-voltage deep N-well 25 is in contact with the second N-type buried layer 3. In this embodiment, the SCR high-voltage deep N-well 25 is CRL08. For information on the materials and thickness of CRL08, please refer to relevant technologies; details will not be elaborated here.

[0049] In this embodiment, the first P-well 10, the first N-well 11, the second P-well 12, the second N-well 13, the third P-well 14, the third N-well 15, and the fourth P-well 16 have the same thickness. The first P-doped region 17, the first N-doped region 18, the second P-doped region 19, the second N-doped region 20, the third P-doped region 21, the third N-doped region 22, and the fourth P-doped region 23 have the same thickness. The first P-well 10, the first N-well 11, the second P-well 12, the second N-well 13, the third P-well 14, the third N-well 15, and the fourth P-well 16 of the first electrostatic discharge (ESD) unit and the second ESD unit have the same doping concentration, size, distance between adjacent well regions, and distance between adjacent doped regions. The first deep P-well 4 and the second deep P-well 6, the first P-type body region 7 and the second P-type body region 9, and the first N-type buried layer 2 and the second N-type buried layer 3 have the same doping concentration and size. In this embodiment, the thickness, width, material, doping concentration, and size of each well region, doped region, and layer, as well as the dimensions of adjacent well regions / doped regions, are all based on values ​​and materials commonly used by those skilled in the art, and will not be elaborated further here.

[0050] In this embodiment, in P-type doping, the doping concentration of the P-doped region is greater than the doping concentration of the P-well, which is greater than the doping concentration of the deep P-well; the doping concentration of the P-doped region is greater than the doping concentration of the P-type body region, which is greater than the doping concentration of the deep P-well. In N-type doping, the doping concentration of the N-doped region is greater than the doping concentration of the N-well, which is greater than the doping concentration of the high-voltage deep N-well; the doping concentration of the N-doped region is greater than the doping concentration of the N-well, which is greater than the doping concentration of the SCR high-voltage deep N-well.

[0051] This embodiment also performs a transmission line pulse test on the bidirectional SCR electrostatic protector to obtain a curve of the transmission line pulse test current-voltage characteristic of the bidirectional SCR electrostatic protector. Figure 5) and the curve of leakage current characteristics of the transmission line pulse test of the bidirectional SCR electrostatic protector ( Figure 6 ).

[0052] See Figure 5 and Figure 6 The good symmetry of the transmission line pulse curve in both positive and negative directions indicates that the anode and cathode terminals of the bidirectional SCR electrostatic discharge protector provided in this embodiment can be interchanged, further verifying the bidirectional electrostatic protection capability of the bidirectional SCR electrostatic discharge protector. The transmission line pulse test results also show that the bidirectional SCR electrostatic discharge protector of this embodiment can achieve a trigger voltage of 76 volts, a sustaining voltage greater than 60 volts, a peak discharge current as high as 8 amperes, and an electrostatic discharge capability per unit width of up to 20 mA per micrometer. The higher trigger voltage is achieved through the coordinated triggering of two medium-voltage thyristor rectifier units connected in series; the overall trigger voltage is approximately equal to the sum of the trigger voltages of the two units.

[0053] This embodiment increases the base region width of the NPN transistor by adding a second P-well 12, a third P-well 14, a second P-doped region 19 on the surface of the second P-well 12, and a third P-doped region 21 on the surface of the third P-well 14 to the first and second electrostatic protection units, thereby reducing the current amplification factor of the NPN transistor and significantly improving the holding voltage of the unit while maintaining the trigger voltage basically unchanged.

[0054] Because the bidirectional SCR electrostatic discharge protector provided in this embodiment has a sustaining voltage of over 60 volts, it completely eliminates the latch-up risk that is common in traditional SCR electrostatic discharge protection devices within an operating voltage range of 60 volts and below. Furthermore, this bidirectional SCR electrostatic discharge protector achieves a high human body model electrostatic discharge protection level with a small layout area. Its bidirectional symmetrical structure effectively protects against both positive and negative electrostatic discharge pulses on signal lines, eliminating the need for an additional rectifier bridge, thus saving design costs and chip area. It can be safely applied to electrostatic discharge protection for various power domains and input / output interfaces at 60 volts and below.

[0055] The bidirectional SCR electrostatic discharge (ESD) protector provided by this invention includes a first ESD protection unit and a second ESD protection unit. The first ends of both units are connected to a first P-doped region and a first N-doped region, respectively. The second ends of both units are connected to a third N-doped region and a fourth P-doped region, respectively. The second end of the first unit is electrically connected to the first end of the second unit, forming a series structure. When static discharge is required, the first and second units trigger collaboratively, forming a complete ESD discharge path from the first end of the first unit to the second end of the second unit. Both units include mutually coupled PNP and NPN transistors. The second N-well serves as the base region of the PNP transistor and the collector of the NPN transistor. The second P-well and the first P-type region, the second P-well and the third P-type region, the third P-well and the second P-type region, and the third P-well and the fourth P-type region all constitute the base region of the NPN transistor. The ESD discharge path is formed based on the PNP and NPN transistors. Compared with the current SCR electrostatic protector structure, the bidirectional SCR electrostatic protector provided in this application increases the base region width of the NPN transistor and weakens the current amplification factor of the NPN transistor, thereby significantly improving the holding voltage of the unit while maintaining the trigger voltage basically unchanged.

[0056] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the apparatus disclosed in the embodiments, since it corresponds to the method disclosed in the embodiments, the description is relatively simple; relevant parts can be referred to in the method section.

[0057] Those skilled in the art will further recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, computer software, or a combination of both. To clearly illustrate the interchangeability of hardware and software, the components and steps of the various examples have been generally described in terms of functionality in the foregoing description. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementations should not be considered beyond the scope of this invention.

[0058] The steps of the methods or algorithms described in conjunction with the embodiments disclosed herein can be implemented directly by hardware, a software module executed by a processor, or a combination of both. The software module can be located in random access memory (RAM), main memory, read-only memory (ROM), electrically programmable ROM, electrically erasable programmable ROM, registers, hard disk, removable disk, CD-ROM, or any other form of storage medium known in the art.

[0059] Finally, it should be noted that in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes the element.

[0060] The bidirectional SCR electrostatic discharge protector provided by this invention has been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of this invention. The descriptions of the embodiments above are merely for the purpose of helping to understand the method and core ideas of this invention. It should be noted that those skilled in the art can make various improvements and modifications to this invention without departing from its principles, and these improvements and modifications also fall within the protection scope of this invention.

Claims

1. A bidirectional SCR electrostatic discharge protector, characterized in that, It includes a first electrostatic discharge (ESD) protection unit and a second ESD protection unit; the first ESD protection unit includes a first P-type region, a first N-type region and a second P-type region arranged sequentially along a first direction; the second ESD protection unit includes a third P-type region, a second N-type region and a fourth P-type region arranged sequentially along the first direction. The first P-type region and the third P-type region are each provided with a first P-well, a first N-well and a second P-well, the first N-type region and the second N-type region are each provided with a second N-well above them, and the second P-type region and the fourth P-type region are each provided with a third P-well, a third N-well and a fourth P-well. The surface of the first P-well is provided with a first P-doped region, the surface of the first N-well is provided with a first N-doped region, the surface of the third N-well is provided with a third N-doped region, and the surface of the fourth P-well is provided with a fourth P-doped region. The first end of the first electrostatic discharge protection unit and the second electrostatic discharge protection unit are connected to the first P-doped region and the first N-doped region, and the second end of the first electrostatic discharge protection unit and the second electrostatic discharge protection unit are connected to the third N-doped region and the fourth P-doped region. The second end of the first electrostatic discharge protection unit is electrically connected to the first end of the second electrostatic discharge protection unit.

2. The bidirectional SCR electrostatic protector according to claim 1, characterized in that, It also includes a P-type substrate, and the first electrostatic protection unit and the second electrostatic protection unit are disposed on one side surface of the P-type substrate.

3. The bidirectional SCR electrostatic protector according to claim 2, characterized in that, The first electrostatic discharge protection unit further includes a first N-type buried layer, which is disposed below the first P-type region, the first N-type region, and the second P-type region; The second electrostatic protection unit further includes a second N-type buried layer, and the second N-type region is disposed above the second N-type buried layer; The central region of the second N-type region has a first protrusion, and the third P-type region and the fourth P-type region are located on both sides of the first protrusion, with the top of the first protrusion flush with the top of the third P-type region and the fourth P-type region.

4. The bidirectional SCR electrostatic protector according to claim 3, characterized in that, The P-type substrate has a first N-type buried layer, a second N-type buried layer, and an isolation structure located between the first N-type buried layer and the second N-type buried layer on one side surface.

5. The bidirectional SCR electrostatic protector according to claim 1, characterized in that, It also includes isolation structures, wherein the isolation structures are provided on opposite sides of the first electrostatic protection unit along the first direction, on opposite sides of the second electrostatic protection unit along the first direction, and between the first P-well, the first N-well, the second P-well, the second N-well, the third P-well, the third N-well and the fourth P-well.

6. The bidirectional SCR electrostatic protector according to claim 1, characterized in that, The first P-type region is a first deep P-well, the second P-type region is a second deep P-well, and the first N-type region is a first high-pressure deep N-well; The third P-type region is the first P-type body region, the fourth P-type region is the second P-type body region, and the second N-type region is the second high-pressure deep N-well.

7. The bidirectional SCR electrostatic protector according to claim 1, characterized in that, The width of the second P-well and the width of the third P-well in the first electrostatic protection unit are both 1.6 micrometers; The width of the second P-well and the width of the third P-well in the second electrostatic protection unit are both 1.6 micrometers.

8. The bidirectional SCR electrostatic protector according to claim 1, characterized in that, In the first electrostatic protection unit, the spacing between the second P-well and the adjacent edge of the first P-type region, and the spacing between the third P-well and the adjacent edge of the second P-type region are both 1.4 micrometers to 1.6 micrometers. In the second electrostatic protection unit, the spacing between the second P-well and the adjacent edge of the third P-type region, and the spacing between the third P-well and the adjacent edge of the fourth P-type region are both 3 micrometers to 4 micrometers.

9. The bidirectional SCR electrostatic protector according to claim 1, characterized in that, The first end of the first electrostatic discharge protection unit and the second electrostatic discharge protection unit are used as the anode, and the second end of the first electrostatic discharge protection unit and the second electrostatic discharge protection unit are used as the cathode. Alternatively, the first end of the first electrostatic discharge protection unit and the second electrostatic discharge protection unit can be used as the negative terminal, and the second end of the first electrostatic discharge protection unit and the second electrostatic discharge protection unit can be used as the positive terminal.

10. The bidirectional SCR electrostatic protector according to claim 1, characterized in that, Both the first N-type region and the second N-type region are equipped with SCR high-voltage deep N-wells; The SCR high-voltage deep N-well is provided with a second N-well and a second N-doped region located on the surface of the second N-well.

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