Bidirectional electrostatic protection device

Abstract

The utility model discloses a bidirectional electrostatic protection device. The device comprises a substrate of a first doping type; the epitaxial layer of the second doping type is located on the substrate, and the second doping type is opposite to the first doping type; the plurality of areas comprise one SCR area and four diode areas or one SCR area and eight diode areas, and the diode areas surround the SCR area; each diode region comprises a diode, and each SCR region comprises an SCR structure; the plurality of isolation structures extend into the substrate from the surface of the epitaxial layer, and a plurality of mutually isolated regions are defined in the epitaxial layer; and the diode and the SCR structure are electrically connected through the metal interconnection structure to form the bidirectional electrostatic protection device. According to the bidirectional electrostatic protection device, the diode and the SCR structure are combined to discharge static electricity, the advantages of the diode and the SCR structure can be considered, and the bidirectional electrostatic protection device has the advantages of being small in capacitance, low in residual voltage, low in trigger voltage, high in maintaining voltage, high in IPP, high in ESD protection capacity and capable of discharging static electricity bidirectionally.

Description

Technical Field

[0001] The utility model relates to the technical field of semiconductors, in particular to a bidirectional electrostatic protection device. Background Art

[0002] Electro-Static Discharge (ESD) protection device is a voltage clamping overvoltage protection device used to protect electronic equipment from damage caused by transient high-energy impact. It can convert the high impedance between its two poles into low impedance at a speed of picoseconds, absorbing surge power of up to several kilowatts, thereby avoiding damage to electronic equipment.

[0003] Traditional electrostatic protection devices are basically voltage regulator type structures with relatively simple manufacturing processes. Generally, PN junctions are directly formed on P+ substrate / N+ substrate by heterogeneous doping. Traditional electrostatic protection devices are mainly used in power, switch, and audio ports in consumer electronic products (such as mobile phones, computers, digital cameras, etc.). This is because such ports are slow and the capacitance requirements of electrostatic protection devices are not high, generally above 20pF. However, for the protection of high-speed communication ports (such as USB3.0 ports, DisplayPort ports, SATA3.0 ports, and HDMI2.0 ports), traditional electrostatic protection devices are not suitable. This is because high-speed communication has extremely high data transmission rates. For example, the data transmission rate of industrial automation networks is greater than 480M / s, and some high-speed data transmission rates reach more than 10G / s. This requires that the capacitance of the electrostatic protection device for line protection is extremely low, not greater than 1.0pF, otherwise it will cause data transmission to be lost and the circuit cannot work properly. At the same time, the ESD capability requirements are extremely high and cannot be lower than 12kV.

[0004] Although the silicon controlled rectifier (SCR) structure has the advantages of high current discharge efficiency, strong anti-static ability, low static leakage, and small parasitic capacitance, its trigger voltage is high, the opening speed is slow, and the holding voltage (VH) is only 1~2V, which is lower than the operating voltage of the protected device and can easily cause latching problems, making it unsuitable for use in power protection circuits. The operating voltage of the power protection circuit is generally above 3.3V, so SCR devices with large hysteresis cannot be used. Therefore, it is necessary to develop a new type of ultra-low capacitance electrostatic protection device that not only meets the requirements of low parasitic capacitance of high-speed communication ports, but also meets the requirements of low clamping voltage and peak current I PP High, high ESD capability and holding voltage (VH) greater than the operating voltage requirements. Utility Model Content

[0005] The utility model aims to provide a bidirectional electrostatic protection device to solve the problems of the prior art.

[0006] According to one aspect of the utility model, a bidirectional electrostatic protection device is provided, comprising: a substrate of a first doping type; an epitaxial layer of a second doping type located on the substrate, the second doping type being opposite to the first doping type; a plurality of regions, the plurality of regions comprising an SCR region and four diode regions, or the plurality of regions comprising an SCR region and eight diode regions; the diode regions surrounding the SCR regions, each of the diode regions comprising a diode, and the SCR regions comprising an SCR structure; a plurality of isolation structures extending from the surface of the epitaxial layer into the substrate, defining the plurality of mutually isolated regions in the epitaxial layer; and a metal interconnect structure electrically connecting the diodes and the SCR structures to form the bidirectional electrostatic protection device.

[0007] Optionally, the bidirectional electrostatic protection device further includes: a first well region and a second well region, both located in the epitaxial layer of the SCR region, the first well region being of a first doping type, and the second well region being of a second doping type; a first doping region of the first doping type being located in the epitaxial layer of each diode region, and in the first well region and the second well region of the SCR region; a second doping region of the second doping type being located in the epitaxial layer of each diode region, and in the first well region and the second well region of the SCR region; and a third doping region being located between the first well region and the second well region in the SCR region , wherein, in each of the diode regions, the adjacent first doped regions and the second doped regions and the epitaxial layer constitute a diode unit, one diode unit constitutes one diode or multiple diode units are connected in parallel to constitute one diode; in the SCR region, the adjacent first well region and the second well region, the first doped regions and the second doped regions within the first well region and the second well region, and the third doped region between the adjacent first well region and the second well region constitute an SCR unit, one SCR unit constitutes one SCR structure or multiple SCR units are connected in parallel to constitute one SCR structure.

[0008] Optionally, the diode region further includes the first well region, the first well region is located in the epitaxial layer, the first doped region is located in the first well region, and the second doped region is located in the epitaxial layer outside the first well region.

[0009] Optionally, in one of the SCR units in the SCR area, the second doped region in the second well region, the second well region, the epitaxial layer, the third doped region, the first well region and the first doped region in the first well region constitute a Zener diode; the first well region and the second well region constitute a parasitic diode, or the first well region and the epitaxial layer constitute a parasitic diode; the first doped region in the second well region, the second well region, the epitaxial layer, the first well region and the first doped region in the first well region constitute a PNP transistor; the second doped region in the second well region, the second well region, the epitaxial layer, the first well region and the second doped region in the first well region constitute an NPN transistor; the first well region and the second well region are also formed with a first body resistor and a second body resistor, respectively.

[0010] Optionally, the first doping region includes a doping region of a first doping type and / or a deep trench filled with a semiconductor material of the first doping type; the second doping region includes a doping region of a second doping type and / or a deep trench filled with a semiconductor material of the second doping type.

[0011] Optionally, a first diode, a second diode, a third diode and a fourth diode are formed in the four diode regions respectively, and the first diode to the fourth diode are symmetrically distributed on both sides of the SCR structure, wherein the first diode and the second diode are distributed on one side of the SCR structure, and the fourth diode and the third diode are distributed on the other side of the SCR structure; the positive electrode of the first diode and the negative electrode of the second diode are connected to the first port, and the positive electrode of the third diode and the negative electrode of the fourth diode are connected to the second port; in the SCR structure, the PNP transistor and the first body resistor are connected in series, and the common node is the first node, and the second body resistor and the NPN transistor are connected in series, and the common node is the first node. The node is the second node; the emitter, base and collector of the PNP transistor are respectively connected to the current inflow end, the second node and the first node of the SCR structure; the emitter, base and collector of the NPN transistor are respectively connected to the current outflow end, the first node and the second node of the SCR structure; the positive and negative electrodes of the parasitic diode are respectively connected to the current outflow end of the SCR structure and the second node; the positive and negative electrodes of the Zener diode are respectively connected to the current outflow end of the SCR structure and the second node; the negative electrode of the first diode and the negative electrode of the third diode are connected to the current inflow end of the SCR structure, and the positive electrode of the second diode and the positive electrode of the fourth diode are connected to the current outflow end of the SCR structure.

[0012] Optionally, the third diode has an area and a structure that are completely identical to those of the first diode, and the fourth diode has an area and a structure that are completely identical to those of the second diode.

[0013] Optionally, a first diode, a second diode, a third diode, a fourth diode, a fifth diode, a sixth diode, a seventh diode and an eighth diode are formed in the eight diode regions respectively, and the first diode to the eighth diode are symmetrically distributed on both sides of the SCR structure, wherein the first diode to the fourth diode are distributed side by side on one side of the SCR structure, and the fifth diode to the eighth diode are distributed side by side on the other side of the SCR structure; the anode of the first diode and the cathode of the second diode are connected to the first port; the anode of the eighth diode and the cathode of the seventh diode are connected to the second port; the cathode of the first diode is connected to the anode of the third diode, and the cathode of the fourth diode is connected to the anode of the second diode; the cathode of the fifth diode is connected to the anode of the seventh diode, and the cathode of the eighth diode is connected to the anode of the sixth diode; In the SCR structure, the PNP transistor and the first body resistor are connected in series, and the common node is the first node; the second body resistor and the NPN transistor are connected in series, and the common node is the second node; the emitter, base and collector of the PNP transistor are respectively connected to the current inflow end, the second node and the first node of the SCR structure; the emitter, base and collector of the NPN transistor are respectively connected to the current outflow end, the first node and the second node of the SCR structure; the positive and negative electrodes of the parasitic diode are respectively connected to the current outflow end and the second node of the SCR structure; the positive and negative electrodes of the Zener diode are respectively connected to the current outflow end and the second node of the SCR structure; the negative electrode of the sixth diode and the negative electrode of the third diode are connected to the current inflow end of the SCR structure, and the positive electrode of the fifth diode and the positive electrode of the fourth diode are connected to the current outflow end of the SCR structure.

[0014] Optionally, the area and structure of the first diode are exactly the same as those of the eighth diode, the area and structure of the second diode are exactly the same as those of the seventh diode, the area and structure of the third diode are exactly the same as those of the sixth diode, and the area and structure of the fourth diode are exactly the same as those of the fifth diode.

[0015] Optionally, the SCR region includes a blocking portion, the blocking portion is located in the first well region and / or the second well region of the SCR structure, and the blocking portion is located in at least one gap among a plurality of gaps formed between every two adjacent doping regions.

[0016] Optionally, in the diode region, the top-view shapes of the first doping region and the second doping region are long strips or rectangles, the length directions of the first doping region and the second doping region extend along the first direction, the first doping region and the second doping region are arranged alternately and in parallel along the second direction, and the first direction is perpendicular to the second direction.

[0017] Optionally, in the SCR region, the top-view shapes of the first doping region, the second doping region and the third doping region are long strips or rectangles; the length directions of the first doping region and the second doping region extend along the first direction, and the first doping region and the second doping region are arranged alternately and in parallel along the second direction; the length direction of the third doping region extends along the first direction, or there are multiple third doping regions, the length directions of the multiple third doping regions extend along the second direction, and the multiple third doping regions are arranged in parallel along the first direction.

[0018] Optionally, the bidirectional electrostatic protection device also includes: a dielectric layer, located on the epitaxial layer and covering the surface of the epitaxial layer, the isolation structure, the first well region, the second well region, the first doped region, the second doped region and the third doped region; and a plurality of conductive pillars, penetrating the dielectric layer and respectively contacting the first doped region and the second doped region in the plurality of regions, the metal interconnection structure electrically connecting the diode and the SCR structure through the conductive pillars.

[0019] The bidirectional electrostatic protection device provided by the utility model uses a diode and an SCR structure to integrate into a bidirectional electrostatic protection device, saving the packaging cost of the device. At the same time, the advantages of the diode's small capacitance, the SCR structure's strong surge and anti-static capabilities per unit area, small leakage current, and small parasitic capacitance are integrated together, which can take into account the advantages of the diode and the SCR structure, has the advantages of low capacitance and low residual voltage, and also avoids the problem of low voltage maintenance and easy latching when the SCR structure is used alone. Thus, a device with low trigger voltage and I PP Bidirectional electrostatic protection device with high ESD capability and high holding voltage.

[0020] Furthermore, the metal pads of the bidirectional electrostatic protection device are all located on the same surface of the device, for example, all on the front side, which solves the limitation that the existing wire bonding package requires two-surface packaging. It is suitable for WLCSP packaging and flip-chip packaging, and has the advantages of high efficiency, low cost and small size.

[0021] Furthermore, since the bidirectional electrostatic protection device shares the SCR structure in the forward and reverse directions, and the forward and reverse diodes are the same, the forward and reverse breakdown voltages of the device are equal, and the forward and reverse breakdown voltages have good consistency.

[0022] Furthermore, four diodes are arranged around the SCR structure, which can greatly reduce the capacitance compared to a single SCR structure, while increasing the holding voltage and avoiding the latch effect, thereby forming a bidirectional electrostatic protection device with low trigger voltage, high holding voltage and extremely small capacitance, which is suitable for the protection of high-frequency circuits below 3.3V; and eight diodes are arranged around the SCR structure, which can further reduce the capacitance and further increase the holding voltage, which is suitable for the protection of high-frequency circuits below 4.5V and has better ESD protection performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The above and other purposes, features and advantages of the present invention will become more apparent through the following description of the embodiments of the present invention with reference to the accompanying drawings, in which:

[0024] Figure 1 A schematic cross-sectional view showing an electrostatic protection device of a thyristor structure in the prior art;

[0025] Figure 2 and Figure 3 A cross-sectional view and a top view of a bidirectional electrostatic protection device according to a first embodiment of the utility model are respectively shown;

[0026] Figure 4 A schematic diagram showing the current flow direction when a high potential is applied to the first port I / O1 and a low potential is applied to the second port I / O2 in the bidirectional electrostatic protection device of the first embodiment of the utility model;

[0027] Figure 5 A schematic diagram of the circuit structure of a bidirectional electrostatic protection device according to the first embodiment of the utility model is shown;

[0028] Figure 6 A schematic diagram showing another implementation of the SCR structure in the bidirectional electrostatic protection device of the first embodiment of the utility model;

[0029] Figures 7a to 7i The cross-sectional views of various stages in the preparation process of the bidirectional electrostatic protection device of the first embodiment of the utility model are shown;

[0030] Figure 8 A top view of a bidirectional electrostatic protection device according to a second embodiment of the utility model is shown;

[0031] Fig. 9 A top view of a bidirectional electrostatic protection device according to a third embodiment of the present utility model is shown;

[0032] Fig.10 and Fig.11 A cross-sectional view and a top view of a bidirectional electrostatic protection device according to a fourth embodiment of the utility model are respectively shown;

[0033] Fig.12A schematic diagram of the circuit structure of a bidirectional electrostatic protection device according to a fourth embodiment of the present utility model is shown;

[0034] Fig.13 A schematic diagram showing the current flow direction when a high potential is applied to the first port I / O1 and a low potential is applied to the second port I / O2 in the bidirectional electrostatic protection device of the fourth embodiment of the utility model;

[0035] Fig.14 A top view of a bidirectional electrostatic protection device according to a fifth embodiment of the present utility model is shown;

[0036] Fig.15 A top view of a bidirectional electrostatic protection device according to a sixth embodiment of the present utility model is shown;

[0037] Fig.16 A characteristic comparison diagram of the electrostatic protection device of the prior art and the electrostatic protection semiconductor device of the utility model is shown. DETAILED DESCRIPTION

[0038] The present invention will be described in more detail below with reference to the accompanying drawings. In each of the accompanying drawings, the same elements are represented by similar reference numerals. For the sake of clarity, the various parts in the accompanying drawings are not drawn to scale. In addition, some well-known parts may not be shown. The present invention can be presented in various forms, some examples of which will be described below.

[0039] Figure 1 The cross-sectional schematic diagram of the electrostatic protection device of the thyristor structure in the prior art is shown. Figure 1As shown, the electrostatic protection device of the SCR structure includes a substrate 10, an N-type well region 30 and a P-type well region 20 adjacent to each other in the substrate 10, a P+ doping region 14 and an N+ doping region 13 are formed in the N-type well region 30, a P+ doping region 12 and an N+ doping region 11 are formed in the P-type well region 20, and a doping region 21 is formed between the P-type well region 20 and the N-type well region 30. A dielectric layer 40 is formed on the surface of the substrate 10, conductive pillars 31, 32, 33 and 34 are formed inside the dielectric layer 40, and a first electrode 50 and a second electrode 60 are formed on the dielectric layer 40. The first electrode 50 is connected to the N+ doping region 11 and the P+ doping region 12 respectively through the conductive pillars 31 and 32, and the second electrode 60 is connected to the N+ doping region 13 and the P+ doping region 14 respectively through the conductive pillars 33 and 34. The passivation layer 70 covers the surfaces of the dielectric layer 40, a portion of the first electrode 50 and the second electrode 60. The first electrode 50 is, for example, a cathode, and the second electrode 60 is, for example, an anode. The SCR structure has a low maintenance voltage, which is prone to latch-up effect, causing the protected circuit to fail to work properly. To this end, the utility model provides a bidirectional electrostatic protection device with a low trigger voltage and a high maintenance voltage, which solves the problem that the voltage characteristics of the current SCR structure exceed the design window, so that the maintenance voltage of the device is higher than the operating voltage of the protected circuit. Figure 2-Figure 16 Give a detailed introduction.

[0040] Figure 2 and Figure 3 The cross-sectional view and top view of the bidirectional electrostatic protection device according to the first embodiment of the utility model are respectively shown.

[0041] like Figure 2As shown, the bidirectional electrostatic protection device of this embodiment includes a substrate 101, an epitaxial layer 102, a plurality of isolation structures 105, a first well region 106, a second well region 104, a plurality of first doped regions 107, a plurality of second doped regions 108, a dielectric layer 109 and a metal interconnection structure. The epitaxial layer 102 is located on the substrate 101, and a plurality of isolation structures 105 extend from the surface of the epitaxial layer 102 toward the substrate 101, penetrate the epitaxial layer 102 and extend to the inside of the substrate 101, and define the epitaxial layer 102 into a plurality of mutually isolated regions. The dielectric layer 109 covers the epitaxial layer 102, and a plurality of conductive pillars 1091 are formed in the dielectric layer 109 to electrically connect the plurality of regions in cooperation with the metal interconnection structure. Among them, the substrate 101 is of a first doping type, and the epitaxial layer 102 is of a second doping type opposite to the first doping type. In this embodiment, the first doping type is, for example, P-type, the second doping type is, for example, N-type, the substrate 101 is, for example, a P-substrate, and the epitaxial layer 102 is, for example, an N-epitaxial layer, but is not limited thereto. The isolation structure 105 includes an isolation trench, a gate oxide layer (not shown in the figure) covering the sidewall and bottom of the isolation trench, and polysilicon filled in the isolation trench, that is, the gate oxide layer is located between the polysilicon and the isolation trench.

[0042] The isolation structure 105 defines multiple regions of the epitaxial layer 102, including an SCR region and multiple diode regions, and multiple diode regions surround one SCR region. A diode is formed in each diode region, and an SCR structure is formed in the SCR region. Figure 2In this embodiment, the multiple regions are respectively an SCR region and four diode regions, the four diode regions are surrounded by the SCR region, and a diode is formed in each diode region. Specifically, the epitaxial layer 102 is separated by the isolation structure 105 to form a first region 1031, a second region 1032, a third region 1033, a fourth region 1034 and a fifth region 1035. Among them, the first region 1031, the second region 1032, the third region 1033 and the fourth region 1034 are diode regions, and the fifth region 1035 is an SCR structure region. The first diode D1, the second diode D2, the third diode D3 and the fourth diode D4 are formed in the first region 1031, the second region 1032, the third region 1033 and the fourth region 1034 respectively. Multiple diode regions are symmetrically distributed on both sides of the SCR region, for example, the first region 1031 and the second region 1032 are distributed on one side of the fifth region 1035, and the fourth region 1034 and the third region 1033 are distributed on the other side of the fifth region 1035, then the first diode D1 and the second diode D2 are distributed on one side of the SCR structure, and the fourth diode D4 and the third diode D3 are distributed on the other side of the SCR structure, but not limited thereto. In this embodiment, the first region 1031, the second region 1032, the third region 1033 and the fourth region 1034 are arranged in a matrix, and the fifth region 1035 is located in the central region of the matrix, but not limited thereto.

[0043] Combination Figure 2 and Figure 3, each diode region includes a plurality of alternatingly arranged first doping regions 107 and second doping regions 108 located in the epitaxial layer 102, the first doping regions 107 are of the first doping type, and the second doping regions 108 are of the second doping type. An adjacent first doping region 107, a second doping region 108 and the epitaxial layer 102 constitute a diode unit, and each diode region contains at least one diode unit. When only one diode unit is included, the one diode unit constitutes a diode, and when multiple diode units are included, multiple diode units are connected in parallel to form a diode. Furthermore, each diode region may also include multiple first well regions 106 of the first doping type. The first well region 106 is located in the epitaxial layer 102, the first doping region 107 is located in the first well region 106, and the second doping region 108 is located in the epitaxial layer 102 outside the first well region 106, that is, the first doping region 107 corresponds to the first well region 106 one by one, and is arranged alternately with the second doping region 108, the first doping region 107 is, for example, a P+ type doping region, the second doping region 108 is, for example, an N+ type doping region, and the first well region 106 is, for example, a P-type well region. Further, the first doping region 107, the second doping region 108 and the first well region 106 are all in the shape of long strips or rectangles, and their lengths extend in the same direction. For example, the length directions of the first doping region 107, the second doping region 108 and the first well region 106 all extend along the first direction, and the first doping region 107 and the second doping region 108 are arranged alternately and in parallel along a second direction perpendicular to the first direction.

[0044] Further, each SCR structure includes a first well region 106 of a first doping type and a second well region 104 of a second doping type located in the epitaxial layer 102, and a third doping region 1081 located between the first well region 106 and the second well region 104. The third doping region 1081 may be of the first doping type or the second doping type. In this embodiment, the first well region 106 is, for example, a P-type well region, the second well region 104 is, for example, an N-type well region, and the third doping region 1081 is, for example, an N-type doping region. The first well region 106 and the second well region 104 are in contact with or separated from each other. In this embodiment, the first well region 106 and the second well region 104 are separated from each other, and the third doping region 1081 is located in the first well region 106, the second well region 104, and the epitaxial layer 102. The first well region 106 and the second well region 104 each include a plurality of second doping regions 108 and a plurality of first doping regions 107 arranged alternately. The first well region 106 may also include only one second doping region 108 and one first doping region 107, and the second well region 104 may also include only one second doping region 108 and one first doping region 107. The first well region 106, the second well region 104, the second doping region 108 and the first doping region 107 in the SCR structure are in the shape of long strips or rectangles, and their length directions all extend along the first direction, and the second doping regions 108 and the first doping regions 107 are arranged alternately and in parallel along the second direction.

[0045] In the SCR structure, the third doping region 1081 may include, for example, a plurality of them, the top view shape of the third doping region 1081 is, for example, a rectangle or a strip, the length direction of the plurality of third doping regions 1081 extends, for example, along the second direction, and the plurality of third doping regions 1081 are arranged in parallel along the first direction. The junction depth of the third doping region 1081 in the epitaxial layer 102 is preferably greater than the junction depth of the first doping region 107 and the second doping region 108, which can improve the antistatic ability of the device. In other embodiments, the junction depth of the third doping region 1081 may also be less than or equal to the junction depth of the first doping region 107 and the second doping region 108. The magnitude of the trigger voltage can be controlled by controlling the implantation dose of the doping impurities in the third doping region 1081 and the overlap width of the third doping region 1081 and the first well region 106.

[0046] Each SCR structure includes at least one SCR unit, each SCR unit includes a first well region 106 and a second well region 104 adjacent to each other and a third doping region 1081 between the first well region 106 and the second well region 104, and the first well region 106 and the second well region 104 both include alternatingly arranged first doping regions 107 and second doping regions 108. When the SCR structure includes a plurality of SCR units, the plurality of SCR units are connected in parallel to form the SCR structure.

[0047] See again Figure 2The number of the first doping region 107 and the second doping region 108 in each region is preferably the same, but can also be different, for example, the first doping region 107 is more than the second doping region 108, or the second doping region 108 is more than the first doping region 107. And the first doping region 107 and the second doping region 108 in each region preferably appear in pairs. In addition, the number of the first doping region 107 and the second doping region 108 in the first well region 106 can be equal to or different from the number of the first doping region 107 and the second doping region 108 in the second well region 104.

[0048] Furthermore, the first doping region 107 includes a doping region of the first doping type and / or a deep trench filled with a semiconductor material of the first doping type; the second doping region 108 includes a doping region of the second doping type and / or a deep trench filled with a semiconductor material of the second doping type.

[0049] Further, in the diode region, the length of the first well region 106 is greater than the length of the first doping region 107 and the second doping region 108, the width of the first well region 106 is greater than the width of the first doping region 107 and the second doping region 108, and the depth of the first well region 106 is greater than the depth of the first doping region 107 and the second doping region 108. In the SCR structure, the length of the first well region 106 and the second well region 104 is greater than the length of the first doping region 107 and the second doping region 108, the width of the first well region 106 and the second well region 104 is greater than the width of the first doping region 107 and the second doping region 108, and the depth of the first well region 106 and the second well region 104 is greater than the depth of the first doping region 107 and the second doping region 108. In this embodiment, the first well region 106 within the diode region (the first region 1031, the second region 1032, the third region 1033 and the fourth region 1034) can make the electric field distribution more uniform, prevent the electric field from breaking down on the device surface, and significantly improve the forward diode's surge and anti-static capabilities, making the device more stable and having better performance.

[0050] See again Figure 3In the first region 1031, a first doped region 107 in a first well region 106, an adjacent second doped region 108 and the epitaxial layer 102 constitute a diode unit, and a plurality of identical diode units are connected in parallel to constitute a first diode D1. Among them, the first doped region 107 in the first region 1031 is the anode of the first diode D1, and the second doped region 108 in the first region 1031 is the cathode of the first diode D1. Similarly, in the second region 1032, a first doped region 107 in a first well region 106, an adjacent second doped region 108 and the epitaxial layer 102 constitute a diode unit, and a plurality of diode units are connected in parallel to constitute a second diode D2. The third region 1033 is similar to the fourth region 1034 and will not be described in detail here. In order to maintain good symmetry, the area, structure and number of the third diode D3 and the first diode D1 are preferably exactly the same; the area, structure and number of the fourth diode D4 and the second diode D2 are preferably exactly the same.

[0051] In a specific embodiment, in the first region 1031, the second region 1032, the third region 1033 and the fourth region 1034, the width of the first doping region 107 and the second doping region 108 is 1.5 μm to 10 μm, the length is 30 μm to 200 μm, and the junction depth is 0.3 μm to 2 μm, but not limited thereto. The width, length and depth of the first doping region 107 in the first region 1031 and the third region 1033 are equal, and the width, length and depth of the second doping region 108 are equal; the width, length and depth of the first doping region 107 in the second region 1032 and the fourth region 1034 are equal, and the width, length and depth of the second doping region 108 are equal, so that the current capacity of the device in both the forward and reverse directions is the same.

[0052] Further, in the fifth region 1035, the second doped region 108 in the second well region 104, the second well region 104, the epitaxial layer 102, the third doped region 1081, the first well region 106, and the first doped region 107 in the first well region 106 constitute a Zener diode DZ. When the first well region 106 and the second well region 104 in the SCR structure are in contact, the first well region 106 and the second well region 104 constitute a parasitic diode D0; when the first well region 106 and the second well region 104 in the SCR structure are separated, the first well region 106 and the epitaxial layer 102 constitute a parasitic diode D0, and the breakdown voltage of the parasitic diode D0 is much higher than the breakdown voltage of the Zener diode DZ. The first doped region 107 in the second well region 104, the second well region 104, the epitaxial layer 102, the first well region 106, and the first doped region 107 in the first well region 106 constitute a PNP transistor. The second doped region 108 in the second well region 104, the second well region 104, the epitaxial layer 102, the first well region 106 and the second doped region 108 in the first well region 106 form an NPN transistor. The first well region 106 and the second well region 104 have respective body resistances Rp and Rn.

[0053] In a specific embodiment, in the fifth region 1035, the width of the first doping region 107 and the second doping region 108 is 0.8μm~10μm, the length is 30μm~300μm, and the junction depth is 0.3μm~2μm; the spacing between adjacent first doping regions 107 and second doping regions 108 is 0.5μm~5μm; the spacing between the first well region 106 and the second well region 104 is 1~5μm, and the depth of the third doping region 1081 is 1~3μm and the width is 1~8μm, but is not limited to this.

[0054] Further, see again Figure 2 The dielectric layer 109 is located on the epitaxial layer 102, covering the surfaces of the epitaxial layer 102, the isolation structure 105, the first well region 106, the second well region 104, the first doped region 107, the second doped region 108 and the third doped region 1081. A plurality of contact holes are opened in the dielectric layer 109, and the contact holes penetrate the dielectric layer 109, exposing the plurality of first doped regions 107 and the plurality of second doped regions 108; the contact holes are filled with metal materials, and the metal materials are in contact with the exposed plurality of first doped regions 107 and the plurality of second doped regions 108, so as to form a plurality of conductive pillars 1091. Further, a metal interconnection structure electrically connected to the plurality of first doped regions 107 and the plurality of second doped regions 108 through the conductive pillars 1091 can be formed.

[0055] Figure 4 The diagram shows the current flow direction when a high potential is applied to the first port I / O1 and a low potential is applied to the second port I / O2 in the bidirectional electrostatic protection device of the first embodiment of the utility model. Figure 5The schematic diagram of the circuit structure of the bidirectional electrostatic protection device of the first embodiment of the utility model is shown.

[0056] like Figure 5 As shown, the bidirectional electrostatic protection device provided in this embodiment includes four diodes and an SCR structure, the positive electrode of the first diode D1 and the negative electrode of the second diode D2 are connected to the first port I / O1, and the positive electrode of the third diode D3 and the negative electrode of the fourth diode D4 are connected to the second port I / O2. In the SCR structure, the body resistor Rn and the transistor NPN are connected in series between the current inflow end and the current outflow end of the SCR structure, and the transistor PNP and the body resistor Rp are also connected in series between the current inflow end and the current outflow end of the SCR structure. The current inflow end of the SCR structure is, for example, a power supply end, which receives a voltage VCC, and the current outflow end is a ground end, which receives a voltage GND, and GND is usually zero voltage. The base of the PNP transistor is connected to the common node of the body resistor Rn and the transistor NPN, and the base of the NPN transistor is connected to the common node of the transistor PNP and the body resistor Rp. At the same time, a parasitic diode D0 and a voltage regulator diode DZ are also connected between the body resistor Rn and the current outflow end. Specifically, the common node of the PNP transistor and the body resistor Rp is the first node Q1, and the common node of the body resistor Rn and the NPN transistor is the second node Q2; the emitter, base and collector of the PNP transistor are respectively connected to the current inflow end of the SCR structure, the second node Q2 and the first node Q1; the emitter, base and collector of the NPN transistor are respectively connected to the current outflow end of the SCR structure, the first node Q1 and the second node Q2; the positive and negative electrodes of the parasitic diode D0 are respectively connected to the current outflow end of the SCR structure and the second node Q2; the positive and negative electrodes of the voltage regulator diode DZ are respectively connected to the current outflow end of the SCR structure and the second node Q2. The cathode of the first diode D1 and the cathode of the third diode D3 are connected to the current inflow end of the SCR structure, that is, connected to the common node of the emitter of the PNP transistor and the body resistor Rn. The anode of the second diode D2 and the anode of the fourth diode D4 are connected to the current outflow end of the SCR structure, that is, connected to the common node of the emitter of the NPN transistor and the body resistor Rp.

[0057] Combination Figure 4 and Figure 5In the bidirectional electrostatic protection device of the first embodiment of the utility model, when the first port I / O1 is applied with a high potential and the second port I / O2 is applied with a low potential, due to the high breakdown voltage of the second diode D2, the current flows from the anode of the first diode D1 (the first doped region 107 in the first region 1031) to the cathode of the first diode D1 (the second doped region 108 in the first region 1031), and further flows into the first doped region 107 and the second doped region 108 in the second well region 104 of the SCR structure, so that the NPN transistor and the PNP transistor are turned on and work, and after passing through the SCR structure, the current flows out from the first doped region 107 and the second doped region 108 in the first well region 106; then the current flows into the second port I / O2 through the fourth diode D4.

[0058] The reverse breakdown voltage of the first port I / O1 to the second port I / O2 can be expressed as:

[0059] V BR1 = V f1 + V H1 + V f4

[0060] Among them, V f1 is the forward voltage drop of the first diode D1; V H1 is the holding voltage of the SCR structure, V H1 The base and emitter voltage V of the NPN transistor BE1 and the emitter-collector voltage V in the saturation region of the PNP transistor CES2 Composition, can be expressed as: V H1 = V BE1 + V CES2 ; V f4 is the forward voltage drop of the fourth diode D4. When the current flowing through the first diode D1 and the fourth diode D4 is 10mA, V f1 and V f4 The base and emitter voltage of the NPN transistor is about 0.9V. BE1 The emitter and collector voltage V in the saturation region of the PNP transistor is about 0.9V. CES2 is about 1.2V, so V H1 The reverse breakdown voltage V of the bidirectional ESD protection device is about 2.1V. BR1 At about 3.9 V, it can be used to protect circuits with a power supply voltage of about 3.3 V. In addition, the SCR structure changes the trigger voltage of the SCR structure by adjusting the impurity concentration and width of the voltage stabilizing diode DZ (mainly the third doping region 1081), which can reduce the trigger voltage of the SCR structure from more than 20 V to 5-10 V, meeting the working window of the bidirectional electrostatic protection device.

[0061] Similarly, when the second port I / O2 is at a high potential and the first port I / O1 is at a low potential, the current flows from the third diode D3 into the second well region 104 of the SCR structure, then flows out from the first well region 106, and flows out from the first port I / O1 via the second diode D2. The reverse breakdown voltage of the second port I / O2 to the first port I / O1 can be expressed as:

[0062] V BR2 = V f3 + V H1 + V f2

[0063] Among them, V f3 is the forward voltage drop of the third diode D3, V f2 is the forward voltage drop of the second diode D2, V H1 is the holding voltage of the SCR structure. Since the first diode D1 is exactly the same as the third diode D3, the second diode D2 is exactly the same as the diode D4, and the SCR structure is the same, V BR1 = V BR2 , the bidirectional voltage is highly consistent, and the forward and reverse breakdown voltages are consistent.

[0064] Although a single SCR structure has good surge and anti-static capabilities per unit area, as well as the advantage of low parasitic capacitance, its maintenance voltage is only about 2.1V, which is not suitable for protecting 3.3V circuits. Therefore, four low-capacitance conduction diodes are integrated with the SCR structure into a bidirectional electrostatic protection device to increase the maintenance voltage. Furthermore, this embodiment uses a diode and an SCR structure to integrate into a bidirectional electrostatic protection device, which can significantly reduce the capacitance of the device. The use of four low-capacitance diodes and an SCR structure to integrate into a bidirectional electrostatic protection device can take into account the advantages of both diodes and SCR structures, and has the characteristics of small capacitance, low residual voltage, and appropriate voltage.

[0065] Specifically, due to the low doping concentration of the epitaxial layer 102, the area of ​​the first diode D1 to the fourth diode D4 is small, and the capacitance of the diode is generally 0.1pF~1pF; the capacitance of the SCR structure is generally 0.05pF~0.5pF, which can be equivalent to a wire. If the low-capacitance diode and the SCR structure are integrated into one device, the circuit can be equivalent to the first diode D1 and the second diode D2 in parallel, the third diode D3 and the fourth diode D4 in parallel, and then the two are connected in series. Assuming that the capacitance C of the first diode D1 D1 The capacitance C of the third diode D3 D3 are equal, and C D1 =C D3 =0.4pF, the capacitance C of the second diode D2 D2 and the capacitance C of the fourth diode D4 D4are equal, and C D2 =C D4 =0.3pF, then the capacitance C of the first port I / O1 to the second port I / O2 T1 It can be expressed as:

[0066] It can be seen from the above formula that by integrating the first diode D1 to the fourth diode D4 and the SCR structure into one device, the capacitance of the bidirectional electrostatic protection device is greatly reduced. Furthermore, the capacitance and the maximum peak pulse current I of the bidirectional electrostatic protection device can be adjusted by adjusting the area of ​​the first diode D1 to the fourth diode D4 and the SCR structure. pp And electrostatic protection ability.

[0067] Therefore, the electrostatic protection device uses four diodes and a low trigger voltage SCR structure to integrate into a low trigger and high maintenance voltage bidirectional electrostatic protection device, which reduces the packaging cost of sealing multiple devices together; it can take into account the advantages of the diode's strong forward current discharge capability and low capacitance and the SCR structure's strong surge and anti-static capabilities per unit area, small leakage current, small parasitic capacitance, and low trigger voltage, while avoiding the problem of latching caused by the low maintenance voltage VH when a single SCR structure is used. At the same time, the pads of the device are all led out from the front of the device (the side away from the substrate 101), which is suitable for WLCSP (Wafer Level Chip Scale Package) packaging or FC-BGA (FlipChip Ball Grid Array) packaging.

[0068] Figure 6 A schematic diagram showing another implementation of the SCR structure in the bidirectional electrostatic protection device of the first embodiment of the utility model is shown.

[0069] The SCR structure of the present invention can be composed in a variety of ways, such as Figure 6 Give one possible way. Figure 6As shown, the SCR structure further includes a barrier, for example, a second barrier 112 formed in the first well region 106 and a first barrier 111 formed in the second well region 104. The first barrier 111 and the second barrier 112 may both be doped regions, and the first barrier 111 is located in the second well region 104. When it is a doped region, its doping type is opposite to that of the second well region 104. For example, when the second well region 104 is N-type doped, the first barrier 111 is P-type doped. Similarly, the second barrier 112 is located in the first well region 106. When it is a doped region, its doping type is opposite to that of the first well region 106. For example, when the first well region 106 is P-type doped, the second barrier 112 is N-type doped. In addition, the first barrier 111 and the second barrier 112 may both be insulating structures, for example, both are composed of an isolation trench and an oxide layer filled in the isolation trench. Alternatively, the first blocking portion 111 is one of the doped region and the insulating structure, and the second blocking portion 112 is the other of the doped region and the insulating structure. In other embodiments, the blocking portion may be located in the first well region 106 and / or the second well region 104 of the SCR structure, and the blocking portion is located in at least one of the multiple gaps formed between each two adjacent doped regions. The existence of the blocking portion can block the current flow path, increase the amplification factor of the transistor, reduce the trigger voltage, and increase the body resistance to increase the holding voltage.

[0070] Figures 7a to 7i The cross-sectional views of various stages in the preparation process of the bidirectional electrostatic protection device of the first embodiment of the utility model are shown below. Figures 7a to 7i The preparation method of the bidirectional electrostatic protection device according to the first embodiment of the utility model is described.

[0071] like Figure 7a As shown, a substrate 101 is provided. The substrate 101 is a semiconductor layer of a first doping type. In this embodiment, the substrate 101 is, for example, a P-type silicon substrate, and the resistivity of the substrate 101 is, for example, 50Ω∙cm to 200Ω∙cm. The parasitic capacitance is reduced by setting the resistivity of the substrate 101.

[0072] like Figure 7b As shown, an epitaxial layer 102 (with a resistivity of about 100-2000 Ω·cm) is formed on a substrate 101. The epitaxial layer 102 is, for example, an N-type epitaxial layer.

[0073] like Figure 7c As shown, a first oxide layer 1051 having an opening 1052 is formed on the epitaxial layer 102 as a hard mask.

[0074] In this step, for example, a first oxide layer 1051 is formed on the epitaxial layer 102 by a deposition process. Further, an opening 1052 is formed in the first oxide layer 1051 by photolithography and etching. The first oxide layer 1051 is, for example, a silicon oxide (SiO2) layer.

[0075] like Figure 7d As shown, an isolation structure 105 is formed.

[0076] In this step, the epitaxial layer 102 and the substrate 101 are etched through the opening 1052 using the first oxide layer 1051 as a hard mask to form a plurality of isolation trenches, wherein each isolation trench penetrates the epitaxial layer 102 and extends to the interior of the substrate 101 .

[0077] Further, a gate oxide layer is formed on the sidewall and bottom of the isolation trench by gate oxide growth, and then the isolation trench is filled with a polysilicon filling process to form an isolation structure 105. The isolation structure 105 divides the epitaxial layer 102 into different regions. In this embodiment, the epitaxial layer 102 is isolated to form a first region 1031, a second region 1032, a third region 1033, a fourth region 1034, and a fifth region 1035. Then, the first oxide layer 1051 is removed.

[0078] like Figure 7e As shown, the second oxide layer 1053 is grown by thermal oxidation.

[0079] In this embodiment, the second oxide layer 1053 is, for example, a silicon oxide (SiO 2 ) layer. The thickness of the second oxide layer 1053 is less than that of the first oxide layer 1051 . The second oxide layer 1053 serves as a masking layer for subsequent ion implantation.

[0080] like Figure 7f As shown, a first well region 106 and a second well region 104 are formed.

[0081] In this step, the second oxide layer 1053 is used as a masking layer, and the first doping type impurities and the second doping type impurities are selectively implanted by a photolithography process, and push-up is performed to form a first well region 106 and a second well region 104. The first well region 106 and the second well region 104 extend from the surface of the epitaxial layer 102 to the inside of the epitaxial layer 102. The plurality of first well regions 106 are respectively located in the epitaxial layer 102 in the first region 1031, the second region 1032, the third region 1033, the fourth region 1034, and the fifth region 1035, and the second well region 104 is located in the epitaxial layer 102 in the fifth region 1035.

[0082] like Figure 7g As shown, a third doping region 1081 , a first doping region 107 and a second doping region 108 are formed.

[0083] In this step, the second oxide layer 1053 is used as a masking layer, and a high concentration of second doping type impurities is selectively injected using a photolithography process, and then a suitable temperature is used to form a third doping region 1081. Then, a high concentration of first doping type impurities is selectively injected using a photolithography process, and annealing is performed to form a first doping region 107, and the first doping region 107 is an injection region; a high concentration of second doping type impurities is selectively injected using a photolithography process, and annealing is performed to form a second doping region 108, and the second doping region 108 is an injection region. In the first region 1031, the second region 1032, the third region 1033, and the fourth region 1034, the first doping region 107 is located in the first well region 106, and the second doping region 108 is located in the epitaxial layer 102, and is alternately distributed with the first doping region 107. In the fifth region 1035, a plurality of second doping regions 108 and first doping regions 107 are arranged alternately in parallel inside the first well region 106 and the second well region 104.

[0084] like Figure 7h As shown, a dielectric layer 109 is formed on the surface of the epitaxial layer 102 , and contact holes and conductive pillars 1091 are formed in the dielectric layer 109 .

[0085] In this step, a dielectric layer 109 is formed on the surface of the epitaxial layer 102 by, for example, a deposition process. The dielectric layer 109 is, for example, a silicon oxide (SiO2) layer. Further, a plurality of contact holes are formed in the dielectric layer 109 by using a photolithography process and an etching process. The contact holes penetrate the dielectric layer 109, exposing a plurality of first doped regions 107 and a plurality of second doped regions 108. Afterwards, a metal of appropriate thickness is deposited in the contact holes to fill the contact holes, and then chemical mechanical polishing (CMP) is used to remove the excess metal, leaving only the metal in the contact holes, to form a plurality of conductive pillars 1091.

[0086] like Figure 7i As shown, further, a metal interconnection structure is formed.

[0087] For example, a metal of a certain thickness is formed by evaporation or sputtering process, and a metal interconnection structure is selectively completed by photolithography and etching to electrically connect multiple diode regions and an SCR region. Finally, a metal pad is led out, and the metal pad is connected to the first port I / O1 and the second port I / O2 respectively. Optionally, a double-layer metal interconnection structure can be formed as needed.

[0088] Further, a passivation layer is deposited, and the passivation layer is photolithographically and etched to expose the metal pad, and the other regions of the device are protected by the passivation layer, thereby improving the stability and reliability of the device; the substrate 101 is thinned to a suitable thickness to adapt to different packaging forms. The above steps are conventional techniques in the art and will not be described in detail here.

[0089] Figure 8A top view of a bidirectional electrostatic protection device according to a second embodiment of the utility model is shown.

[0090] The first region 1031 to the fourth region 1034 of the bidirectional electrostatic protection device structure of this embodiment are the same as those of the first embodiment, and will not be described in detail here. The only difference is that the structure of the fifth region 1035 is different. Figure 8 As shown, in the fifth region 1035, a first well region 106, a second well region 104, a third doping region 1081 connecting the first well region 106 and the second well region 104, a first doping region 107 and a second doping region 108 in the first well region 106, and a first doping region 107 and a second doping region 108 in the second well region 104 constitute an SCR unit. The fifth region 1035 may include a plurality of SCR units, for example Figure 8 Two SCR units are shown in FIG. 1 , and two or more SCR units are connected in parallel to form an SCR structure. The SCR structure includes two or more SCR units, but the first well region 106 of each SCR unit only includes one first doping region 107 and one second doping region 108, and the second well region 104 also only includes one first doping region 107 and one second doping region 108. This structure can reduce the current density per unit area, and can increase the maximum peak pulse current I under the same area. pp In other embodiments, the first well region 106 and the second well region 104 may also include a plurality of first doping regions 107 and a plurality of second doping regions 108 .

[0091] In the first embodiment, the fifth region 1035 includes only one SCR unit, the first well region 106 and the second well region 104 have larger areas, and the first well region 106 and the second well region 104 contain multiple groups of alternatingly arranged first doped regions 107 and second doped regions 108, which are more robust and have stronger surge and anti-static capabilities.

[0092] Fig. 9 A top view of a bidirectional electrostatic protection device according to a third embodiment of the utility model is shown.

[0093] The first region 1031 to the fourth region 1034 of the bidirectional electrostatic protection device structure of this embodiment are the same as those of the first embodiment, and are not described in detail here. The only difference is that the shape of the third doping region 1081 of the fifth region 1035 is different. Fig. 9 As shown, in the fifth region 1035 , there is only one third doping region 1081 , and the top view shape of the third doping region 1081 is a rectangle, and the length direction of the rectangle extends along the first direction.

[0094] Further, in the fifth region 1035, the width of the first doping region 107 and the second doping region 108 is 0.8μm~10μm, the length is 30μm~300μm, and the junction depth is 0.3μm~2μm; the spacing between adjacent first doping regions 107 and second doping regions 108 is 0.5μm~5μm; the spacing between the first well region 106 and the second well region 104 is 1~5μm, and the depth of the third doping region 1081 is 1~3μm, the width is 1~8μm, and the length is 5~300μm, but is not limited to this.

[0095] In the top view, the third doping regions 1081 are connected from multiple intervals to form a whole. After the third doping regions 1081 are connected to form a whole, the maximum peak pulse current I PP Although the capacitance will be slightly larger, the overall capacitance will be reduced by coupling with four diodes, so the overall ESD protection performance is better.

[0096] Fig.10 and Fig.11 The cross-sectional view and top view of the bidirectional electrostatic protection device according to the fourth embodiment of the utility model are respectively shown.

[0097] like Fig.10 As shown, the bidirectional electrostatic protection device includes a substrate 101, an epitaxial layer 102, a plurality of isolation structures 105, a first well region 106, a second well region 104, a plurality of first doped regions 107, a plurality of second doped regions 108, a dielectric layer 109, and a metal interconnection structure. The substrate 101, the epitaxial layer 102, the isolation structure 105, the first well region 106, the second well region 104, a plurality of first doped regions 107, a plurality of second doped regions 108, the dielectric layer 109, the conductive pillars 1091, and the metal interconnection structure in this embodiment are the same as those in the first embodiment and are not described in detail herein. The bidirectional electrostatic protection device in this embodiment differs from that in the first embodiment only in that in this embodiment, there are eight diode regions. Fig.10In this embodiment, the multiple isolation structures 105 divide the epitaxial layer 102 into 9 regions, including eight diode regions and one SCR region. The eight diode regions surround the SCR region. For example, the eight diode regions can be symmetrically distributed on both sides of the SCR region. The eight diode regions are respectively the first region 2031, the second region 2032, the third region 2033, the fourth region 2034, the fifth region 2035, the sixth region 2036, the seventh region 2037 and the eighth region 2038. The SCR region is the ninth region 2039. The first diode D1, the second diode D2, the third diode D3, the fourth diode D4, the fifth diode D5, the sixth diode D6, the seventh diode D7 and the eighth diode D8 are respectively formed in the eight diode regions, and an SCR structure is formed in the SCR region. The first diode D1 to the eighth diode D8 are symmetrically distributed on both sides of the SCR structure, for example, the first diode D1 to the fourth diode D4 are distributed side by side on one side of the SCR structure, and the fifth diode D5 to the eighth diode D8 are distributed side by side on the other side of the SCR structure, but it is not limited thereto. The SCR structure can be exactly the same as that of the first embodiment, and will not be described in detail here. The first diode D1 and the eighth diode D8 can be exactly the same, the second diode D2 and the seventh diode D7 can be exactly the same, the third diode D3 and the sixth diode D6 can be exactly the same, and the fourth diode D4 and the fifth diode D5 can be exactly the same. Or the first diode D1, the third diode D3, the fifth diode D5 and the seventh diode D7 can be exactly the same, and the second diode D2, the fourth diode D4, the sixth diode D6 and the eighth diode D8 can be exactly the same. Or the first diode D1 to the eighth diode D8 are exactly the same. Since the structure, composition and process flow of each diode region have been introduced in the first embodiment, they will not be described one by one here.

[0098] Further, the anode of the first diode D1 and the cathode of the second diode D2 are connected to the first port I / O1; the anode of the eighth diode D8 and the cathode of the seventh diode D7 are connected to the second port I / O2; the cathode of the first diode D1 is connected to the anode of the third diode D3, and the cathode of the fourth diode D4 is connected to the anode of the second diode D2; the cathode of the fifth diode D5 is connected to the anode of the seventh diode D7, and the cathode of the eighth diode D8 is connected to the anode of the sixth diode D6. The cathode of the third diode D3 is connected to the cathode of the sixth diode D6, and is connected to the current inflow end of the SCR structure; the anode of the fourth diode D4 is connected to the anode of the fifth diode D5, and is connected to the current outflow end of the SCR structure. The current inflow end and the current outflow end of the SCR structure are the power supply end (receiving the power supply voltage VCC) and the ground end (receiving the ground voltage GND), respectively.

[0099] like Fig.11As shown, in the top view, every two diode regions are grouped as a group, which are divided into four groups in total and distributed at the four corners of the matrix, and the SCR region is distributed in the center of the rectangle. The first diode D1 and the third diode D3 are grouped as the first group, the fourth diode D4 and the second diode D2 are grouped as the second group, the second group and the first group are distributed on the same side, and the second group is distributed above the first group; similarly, the fifth diode D5 and the seventh diode D7 are grouped as the third group, the eighth diode D8 and the sixth diode D6 are grouped as the fourth group, the third group and the fourth group are distributed on the other side of the SCR region, and the third group is distributed above the fourth group, but not limited to this. The well region and doping region contained in each diode region and SCR region can be the same as those in the first embodiment, and will not be repeated here. Fig.11 The figure also shows a current flow path schematic diagram (indicated by the dotted arrows) of the current flowing from the first port I / O1 through the first diode D1 and the third diode D3 into the SCR structure, and then flowing out of the SCR structure, passing through the fifth diode D5 and the seventh diode D7 and reaching the second port I / O2, which will not be described here. Fig.11 Only one possible distribution mode of each region is given. However, in other embodiments, the distribution of the diode region and the SCR region is not limited thereto.

[0100] Fig.12 A schematic diagram of the circuit structure of a bidirectional electrostatic protection device according to a fourth embodiment of the present utility model is shown; Fig.13 A schematic diagram showing the current flow direction when a high potential is applied to the first port I / O1 and a low potential is applied to the second port I / O2 in the bidirectional electrostatic protection device of the fourth embodiment of the utility model.

[0101] like Fig.12 As shown, the circuit structure of the bidirectional electrostatic protection device of this embodiment is only Figure 5Four diodes are added on the basis of the SCR, and the structure of the SCR remains unchanged. Specifically, in the SCR structure, the body resistor Rn and the transistor NPN are connected in series between the current inflow end and the current outflow end of the SCR structure, and the transistor PNP and the body resistor Rp are also connected in series between the current inflow end and the current outflow end of the SCR structure. The current inflow end of the SCR structure is, for example, a power supply end that receives a voltage VCC, and the current outflow end is a ground end that receives a voltage GND, and GND is usually zero voltage. The common node of the PNP transistor and the body resistor Rp is the first node Q1, and the common node of the body resistor Rn and the NPN transistor is the second node Q2; the emitter, base and collector of the PNP transistor are respectively connected to the current inflow end of the SCR structure, the second node Q2 and the first node Q1; the emitter, base and collector of the NPN transistor are respectively connected to the current outflow end of the SCR structure, the first node Q1 and the second node Q2; the positive and negative electrodes of the parasitic diode D0 are respectively connected to the current outflow end of the SCR structure and the second node Q2; the positive and negative electrodes of the voltage regulator diode DZ are respectively connected to the current outflow end of the SCR structure and the second node Q2. The negative electrode of the sixth diode D6 and the negative electrode of the third diode D3 are connected to the current inflow end of the SCR structure, that is, connected to the common node of the emitter of the PNP transistor and the body resistor Rn. The positive electrode of the fifth diode D5 and the positive electrode of the fourth diode D4 are connected to the current outflow end of the SCR structure, that is, connected to the common node of the emitter of the NPN transistor and the body resistor Rp.

[0102] like Fig.13 As shown, in the bidirectional electrostatic protection device of this embodiment, when the first port I / O1 is applied with a high potential and the second port I / O2 is applied with a low potential, due to the high breakdown voltage of the second diode D2 and the fourth diode D4, the current flows from the anode of the first diode D1 (the first doping region 107 in the first region 2031) to the cathode of the first diode D1 (the second doping region 108 in the first region 2031), and then flows into the anode (the first doping region 107 in the third region 2033) and cathode (the second doping region 108 in the third region 2033) of the third diode D3, and further flows into the first doping region 107 and the second doping region 108 in the second well region 104 of the SCR structure, so that the NPN transistor and the PNP transistor are turned on and work. After passing through the SCR structure, the current flows out from the first doping region 107 and the second doping region 108 in the first well region 106 of the SCR structure; then the current passes through the fifth diode D5, and then flows from the fifth diode D5 to the seventh diode D7, and finally flows into the second port I / O2.

[0103] The reverse breakdown voltage of the first port I / O1 to the second port I / O2 can be expressed as:

[0104] V BR3 = V f1+ V f3 + V H2 + V f5 + V f7

[0105] Among them, V f1 is the forward voltage drop of the first diode D1; V f3 is the forward voltage drop of the third diode D1; V H2 is the holding voltage of the SCR structure, V H2 The base and emitter voltage V of the NPN transistor BE1 and the emitter-collector voltage V in the saturation region of the PNP transistor CES2 Composition, can be expressed as: V H2 = V BE1 + V CES2 ; V f5 is the forward voltage drop of the fifth diode D4; V f7 is the forward voltage drop of the seventh diode D7. When the current flowing through the first diode D1, the third diode D3, the fifth diode D5 and the seventh diode D7 is 10mA, V f1 、V f3 、V f5 and V f7 The base and emitter voltage of the NPN transistor is about 0.9V. BE1 The emitter and collector voltage V in the saturation region of the PNP transistor is about 0.9V. CES2 is about 1.2V, so V H2 The reverse breakdown voltage V of the bidirectional ESD protection device is about 2.1V. BR3 At about 5.7 V, it is used to protect circuits with a power supply voltage of about 4.5 V. In addition, the SCR structure changes the trigger voltage of the SCR structure by adjusting the impurity concentration and width of the voltage stabilizing diode DZ (mainly the third doping region 1081), which can reduce the trigger voltage of the SCR structure from more than 20 V to 5-10 V, meeting the working window of the bidirectional electrostatic protection device.

[0106] Similarly, when the second port I / O2 is at a high potential and the first port I / O1 is at a low potential, the current flows from the eighth diode D8 into the sixth diode D6, then flows into the second well region 104 of the SCR structure, then flows out from the first well region 106, flows to the second diode D2 via the fourth diode D4, and then flows out from the first port I / O1. The reverse breakdown voltage of the second port I / O2 to the first port I / O1 can be expressed as:

[0107] V BR4 = V f8 + V f6 + V H2 + V f4+ V f2

[0108] Among them, V f8 is the forward voltage drop of the eighth diode D8, V f2 is the forward voltage drop of the second diode D2, V f6 is the forward voltage drop of the sixth diode D6, V f4 is the forward voltage drop of the fourth diode D4, V H2 is the holding voltage of the SCR structure. Since the first diode D1 is exactly the same as the eighth diode D8, the second diode D2 is exactly the same as the seventh diode D7, the third diode D3 is exactly the same as the sixth diode D6, the fourth diode D4 is exactly the same as the fifth diode D5, and the SCR structure is the same, so V BR3 =V BR4 , the bidirectional voltage is highly consistent, and the forward and reverse breakdown voltages are consistent.

[0109] Although a single SCR structure has good surge and anti-static capabilities per unit area, as well as the advantage of low parasitic capacitance, its maintenance voltage is only about 2.1V, which is not suitable for protecting 3.3V circuits. Therefore, eight low-capacitance conduction diodes are integrated with the SCR structure into a bidirectional electrostatic protection device, which can increase the maintenance voltage. Furthermore, this embodiment uses a diode and an SCR structure to integrate into a bidirectional electrostatic protection device, which can significantly reduce the capacitance of the device. The use of eight low-capacitance diodes and an SCR structure to integrate into a bidirectional electrostatic protection device can take into account the advantages of both diodes and SCR structures, and has the characteristics of small capacitance, low residual voltage, and appropriate voltage.

[0110] Specifically, due to the low doping concentration of the epitaxial layer 102, the area of ​​the first diode D1 to the eighth diode D8 is small, and the capacitance of the diode is generally 0.1pF~1pF. The capacitance of the SCR structure is generally 0.05pF~0.5pF, which can be equivalent to a wire. If the low-capacitance diode and the SCR structure are integrated into one device, the circuit can be equivalent to the first diode D1 connected in series with the third diode D3, the sixth diode D6, and the eighth diode D8, and the second diode D2 connected in series with the fourth diode D4, the fifth diode D5, and the seventh diode D7, and then the two are connected in parallel. Assume that the capacitance C of the first diode D1 D1 The capacitance of the diode is equal to that of the diode, that is, C D1 = C D3 = C D2 = C D4 = C D5 = C D6 = C D7 = C D8 =0.3pF, then the capacitance C of the first port I / O1 to the second port I / O2T2 It can be expressed as:

[0111] It can be seen from the above formula that by integrating the first diode D1 to the eighth diode D8 and the SCR structure into one device, the capacitance of the bidirectional electrostatic protection device is greatly reduced. Furthermore, the capacitance and the maximum peak pulse current I of the bidirectional electrostatic protection device can be adjusted by adjusting the area of ​​the first diode D1 to the eighth diode D8 and the SCR structure. pp And electrostatic protection ability.

[0112] The preparation method of the bidirectional electrostatic protection device of this embodiment is the same as that of the bidirectional electrostatic protection device of the first embodiment, and will not be repeated here.

[0113] Compared with a single SCR device, the electrostatic protection device that uses a combination of four diodes and an SCR structure can reduce capacitance and increase the holding voltage, making it suitable for the protection of high-frequency circuits below 3.3V. Compared with an electrostatic protection device that uses a combination of eight diodes and an SCR structure, the electrostatic protection device that uses a combination of four diodes and an SCR structure can further reduce capacitance (the capacitance is reduced to 1 / 2 of that of four diodes) and further increase the holding voltage, making it suitable for the protection of high-frequency circuits below 4.5V, with better ESD protection performance.

[0114] Fig.14 A top view of a bidirectional electrostatic protection device according to a fifth embodiment of the utility model is shown.

[0115] like Fig.14 As shown, the bidirectional electrostatic protection device of this embodiment is Fig.11 The devices shown are substantially the same, the only difference being the shape of the third doping region 1081. In this embodiment, in the ninth region 2039, only one third doping region 1081 is included, and the top view shape of the third doping region 1081 is a rectangle, the length direction of the rectangle extends along the first direction, and overlaps with both the first well region 106 and the second well region 104.

[0116] In the top view, the third doping regions 1081 are connected from multiple intervals to form a whole. After the third doping regions 1081 are connected to form a whole, the maximum peak pulse current I PP Although the capacitance will be slightly increased, the overall capacitance will be reduced by coupling with eight diodes, so the overall ESD protection performance is good. Moreover, the first well region 106 and the second well region 104 contain a structure in which two or more groups of first doping regions 107 and second doping regions 108 are alternately arranged. The single first well region 106 and the second well region 104 have a large area, high robustness, and strong surge resistance and anti-static capabilities.

[0117] Fig.15 A top view of a bidirectional electrostatic protection device according to a sixth embodiment of the utility model is shown.

[0118] like Fig.15 As shown, the diode regions 2031 to 2038 of the bidirectional electrostatic protection device structure of this embodiment are Fig.11 The embodiments are the same and will not be described here again. The only difference is that the structure of the ninth region 2039 is different. Fig.15 As shown, in the ninth region 2039, a plurality of SCR units may be included, for example Fig.15 Two SCR units are shown in FIG. 1 , and two or more SCR units are connected in parallel to form an SCR structure. This structure can reduce the current density per unit area and increase the maximum peak pulse current I under the same area. pp .

[0119] And in Fig.15 In the embodiment, the third doping region 1081 of one SCR unit is a structure of multiple spaced-apart structures, and the third doping region 1081 of another SCR unit is an overall rectangular structure, which provides a wider range of use for the device.

[0120] Fig.16 A characteristic comparison diagram of the electrostatic protection device of the prior art and the electrostatic protection semiconductor device of the utility model is shown.

[0121] like Fig.16 As shown, a comparison diagram of the voltage and current curves (IV diagram) of the electrostatic protection semiconductor device of the prior art and the utility model during operation is shown, wherein the horizontal axis represents the voltage and the vertical axis represents the current. The curve graphs of the utility model and the prior art are respectively indicated by solid lines and dotted lines. The power supply voltage for normal operation of the device is VDD, and the trigger voltage of the device is VT, and VT is higher than VDD. Generally, a maximum VT threshold is set, and the voltage difference between VDD and VT threshold is regarded as the design window. The voltage exceeding the maximum VT threshold is regarded as failure, that is, it is in the failure area. The voltage less than the power supply voltage VDD and maintained in this area may be a latch effect, that is, it is in the latch area. Both of the above situations will cause the device to exceed the design window, causing the risk of burning the protected device or failing to work normally, so it is hoped that the voltage of the device falls within the design window when it is working.

[0122] like Fig.16, the SCR structure of the prior art maintains the voltage VH1 below the operating voltage VDD after being triggered, so that the protected circuit works in a low-resistance path, latching occurs, the circuit cannot work normally, and the maintaining current IH1 is high, which is easy to damage the device. At the same time, the trigger voltage VT1 of the SCR structure of the prior art is high, exceeding the design window. However, due to the use of a diode and SCR combined structure, the trigger voltage VT2 of the device is lower than that of the prior art (VT2<VT1), the maintaining voltage VH2 is higher than that of the prior art (VH2>VH1), and the maintaining voltage VH2 is greater than the power supply voltage VDD, and the trigger voltage VT2 is lower than the operating voltage VDD. The device works within the design window, and the latch effect will not occur, which does not affect the normal use of the circuit.

[0123] Therefore, the bidirectional electrostatic protection semiconductor device of the present invention is provided with multiple diodes on the basis of the original SCR structure, so that the holding voltage of the device is improved, the latch effect during electrostatic discharge is avoided, and the electrostatic discharge effect is improved.

[0124] The embodiments of the present invention are described above, and these embodiments do not describe all the details in detail, nor do they limit the present invention to the specific embodiments described. Obviously, many modifications and changes can be made based on the above description. This specification selects and specifically describes these embodiments in order to better explain the principles and practical applications of the present invention, so that those skilled in the art can make good use of the present invention and the modifications based on the present invention. The present invention is limited only by the claims and their full scope and equivalents.

Claims

1. A bidirectional electrostatic protection device, characterized in that: include: a substrate of a first doping type; an epitaxial layer of a second doping type located on the substrate, wherein the second doping type is opposite to the first doping type; a plurality of regions, the plurality of regions comprising one SCR region and four diode regions, or the plurality of regions comprising one SCR region and eight diode regions; The diode region surrounds the SCR region, each of the diode regions includes a diode, and the SCR region includes an SCR structure; A plurality of isolation structures extending from the surface of the epitaxial layer into the substrate, defining the plurality of mutually isolated regions in the epitaxial layer; A metal interconnect structure electrically connects the diode and the SCR structure to form the bidirectional electrostatic protection device.

2. The bidirectional electrostatic protection device according to claim 1, characterized in that: Also includes: A first well region and a second well region, both located in the epitaxial layer of the SCR region, the first well region being of a first doping type, and the second well region being of a second doping type; a first doping region of a first doping type located in the epitaxial layer of each of the diode regions and in the first well region and the second well region of the SCR region; a second doping region of a second doping type located in the epitaxial layer of each of the diode regions and in the first well region and the second well region of the SCR region; as well as a third doping region, located between the first well region and the second well region in the SCR region, Among them, in each of the diode regions, the adjacent first doped regions and the second doped regions and the epitaxial layer constitute a diode unit, one diode unit constitutes one diode or multiple diode units are connected in parallel to constitute one diode; in the SCR region, the adjacent first well region and the second well region, the first doped regions and the second doped regions within the first well region and the second well region, and the third doped region between the adjacent first well region and the second well region constitute an SCR unit, one SCR unit constitutes one SCR structure or multiple SCR units are connected in parallel to constitute one SCR structure.

3. The bidirectional electrostatic protection device according to claim 2, characterized in that: The diode region also includes the first well region, which is located in the epitaxial layer, the first doped region is located in the first well region, and the second doped region is located in the epitaxial layer outside the first well region.

4. The bidirectional electrostatic protection device according to claim 2, characterized in that: In one of the SCR units in the SCR region, The second doped region in the second well region, the second well region, the epitaxial layer, the third doped region, the first well region and the first doped region in the first well region constitute a Zener diode; The first well region and the second well region constitute a parasitic diode, or the first well region and the epitaxial layer constitute a parasitic diode; The first doped region in the second well region, the second well region, the epitaxial layer, the first well region and the first doped region in the first well region constitute a PNP transistor; The second doped region in the second well region, the second well region, the epitaxial layer, the first well region and the second doped region in the first well region constitute an NPN transistor; The first well region and the second well region further form a first body resistor and a second body resistor, respectively.

5. The bidirectional electrostatic protection device according to claim 2, characterized in that: The first doping region includes a doping region of a first doping type and / or a deep trench filled with a semiconductor material of the first doping type; the second doping region includes a doping region of a second doping type and / or a deep trench filled with a semiconductor material of the second doping type.

6. The bidirectional electrostatic protection device according to claim 4, characterized in that: A first diode, a second diode, a third diode and a fourth diode are formed in the four diode regions respectively, and the first diode to the fourth diode are symmetrically distributed on both sides of the SCR structure, wherein the first diode and the second diode are distributed on one side of the SCR structure, and the fourth diode and the third diode are distributed on the other side of the SCR structure; The anode of the first diode and the cathode of the second diode are connected to the first port, and the anode of the third diode and the cathode of the fourth diode are connected to the second port; In the SCR structure, the PNP transistor and the first body resistor are connected in series, and the common node is the first node; the second body resistor and the NPN transistor are connected in series, and the common node is the second node; the emitter, base and collector of the PNP transistor are respectively connected to the current inflow end, the second node and the first node of the SCR structure; the emitter, base and collector of the NPN transistor are respectively connected to the current outflow end, the first node and the second node of the SCR structure; the positive electrode and the negative electrode of the parasitic diode are respectively connected to the current outflow end of the SCR structure and the second node; the positive electrode and the negative electrode of the Zener diode are respectively connected to the current outflow end of the SCR structure and the second node; The cathode of the first diode and the cathode of the third diode are connected to the current inflow end of the SCR structure, and the anode of the second diode and the anode of the fourth diode are connected to the current outflow end of the SCR structure.

7. The bidirectional electrostatic protection device according to claim 6, characterized in that: The third diode has the same area and structure as the first diode, and the fourth diode has the same area and structure as the second diode.

8. The bidirectional electrostatic protection device according to claim 4, characterized in that: A first diode, a second diode, a third diode, a fourth diode, a fifth diode, a sixth diode, a seventh diode and an eighth diode are respectively formed in the eight diode regions, and the first diode to the eighth diode are symmetrically distributed on both sides of the SCR structure, wherein the first diode to the fourth diode are distributed side by side on one side of the SCR structure, and the fifth diode to the eighth diode are distributed side by side on the other side of the SCR structure; The anode of the first diode and the cathode of the second diode are connected to the first port; the anode of the eighth diode and the cathode of the seventh diode are connected to the second port; the cathode of the first diode is connected to the anode of the third diode, and the cathode of the fourth diode is connected to the anode of the second diode; the cathode of the fifth diode is connected to the anode of the seventh diode, and the cathode of the eighth diode is connected to the anode of the sixth diode; In the SCR structure, the PNP transistor and the first body resistor are connected in series, and the common node is the first node; the second body resistor and the NPN transistor are connected in series, and the common node is the second node; the emitter, base and collector of the PNP transistor are respectively connected to the current inflow end, the second node and the first node of the SCR structure; the emitter, base and collector of the NPN transistor are respectively connected to the current outflow end, the first node and the second node of the SCR structure; the positive electrode and the negative electrode of the parasitic diode are respectively connected to the current outflow end of the SCR structure and the second node; the positive electrode and the negative electrode of the Zener diode are respectively connected to the current outflow end of the SCR structure and the second node; A cathode of the sixth diode and a cathode of the third diode are connected to a current inflow end of the SCR structure, and an anode of the fifth diode and an anode of the fourth diode are connected to a current outflow end of the SCR structure.

9. The bidirectional electrostatic protection device according to claim 8, characterized in that: The area and structure of the first diode are exactly the same as those of the eighth diode, the area and structure of the second diode are exactly the same as those of the seventh diode, the area and structure of the third diode are exactly the same as those of the sixth diode, and the area and structure of the fourth diode are exactly the same as those of the fifth diode.

10. The bidirectional electrostatic protection device according to claim 2, characterized in that: The SCR region includes a blocking portion, the blocking portion is located in the first well region and / or the second well region of the SCR structure, and the blocking portion is located in at least one gap among a plurality of gaps formed between every two adjacent doping regions.

11. The bidirectional electrostatic protection device according to claim 2, characterized in that: In the diode region, the top-view shapes of the first doping region and the second doping region are long strips or rectangles, the length directions of the first doping region and the second doping region extend along the first direction, the first doping region and the second doping region are arranged alternately and in parallel along the second direction, and the first direction is perpendicular to the second direction.

12. The bidirectional electrostatic protection device according to claim 11, characterized in that: In the SCR region, the top-view shapes of the first doping region, the second doping region and the third doping region are long strips or rectangles; the length directions of the first doping region and the second doping region extend along the first direction, and the first doping region and the second doping region are arranged alternately and in parallel along the second direction; the length direction of the third doping region extends along the first direction, or there are multiple third doping regions, the length directions of the multiple third doping regions extend along the second direction, and the multiple third doping regions are arranged in parallel along the first direction.

13. The bidirectional electrostatic protection device according to claim 2, characterized in that: Also includes: a dielectric layer, located on the epitaxial layer and covering surfaces of the epitaxial layer, the isolation structure, the first well region, the second well region, the first doped region, the second doped region and the third doped region; as well as A plurality of conductive pillars penetrate the dielectric layer and are respectively in contact with the first doped regions and the second doped regions in the plurality of regions. The metal interconnect structure electrically connects the diode and the SCR structure through the conductive pillars.

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