High-voltage bidirectional NPN electrostatic protection device and preparation method thereof

Abstract

The invention provides a high-voltage bidirectional NPN electrostatic protection device and a preparation method thereof. The high-voltage bidirectional NPN electrostatic protection device comprises a P-type substrate, an N-type buried layer on the P-type substrate and a bidirectional NPN device structure on the N-type buried layer, the bidirectional NPN device structure comprises a P-type epitaxial layer, a P-type buried layer at the bottom of the P-type epitaxial layer, a first N-type well, a P-type well, a second N-type well, a first floating P + injection region in the P-type well, a second floating P + injection region in the first N-type well and a third floating P + injection region in the second N-type well, the M N + injection regions are arranged on the outer side of the second floating P + injection region at intervals; the M N + injection regions are arranged on the outer side of the third floating P + injection region at intervals; m is a natural number greater than or equal to 2. The bidirectional ESD protection circuit is suitable for a high-voltage port needing bidirectional ESD protection, the discharge capacity of ESD current and the maintaining voltage of a bidirectional NPN triode are improved, and the bidirectional ESD protection circuit has high area efficiency and high latch-up resistance.

Description

Technical Field

[0001] The invention relates to the field of electrostatic protection, and in particular to a high-voltage bidirectional NPN electrostatic protection device and a preparation method thereof. Background Art

[0002] With the advancement of semiconductor process technology, the failure of integrated circuit chips and electronic products caused by ESD has become more and more serious. ESD protection for electronic products and integrated circuit chips has become one of the main problems faced by product engineers. For terminal products or electronic systems, electrostatic discharge is one of the main causes of reliability problems. This type of high-voltage integrated circuit often works in an environment with strong interference, high current and high voltage, and has high requirements for the robustness of ESD devices. At present, the ESD device protection capability in the ESD solutions provided by semiconductor process manufacturers is often low and the area is large. Therefore, in some chips that require high ESD protection capabilities, new on-chip electrostatic protection devices must be developed to meet such high ESD protection requirements.

[0003] As one of the active devices, the NPN transistor structure has excellent ESD protection capabilities. The traditional NPN transistor is a snapback device (voltage hysteresis device) under the ESD current state, so its ability to discharge current is significantly stronger than that of the PNP transistor structure, and it is superior to the PNP transistor structure in both on-resistance and discharge efficiency. However, in high-voltage ESD applications, its lower holding voltage may have a latching risk, and the holding voltage of the NPN transistor is not easy to adjust, and its size is related to the thickness of the epitaxial layer of the process and the characteristics of the N-type buried layer. NPN transistors are widely used in high-voltage ports of some power chips that have high chip reliability requirements. However, the discharge efficiency of the NPN transistor structure is still much lower than that of the thyristor structure, and there are obstacles to the application of the NPN transistor structure in some low-cost high-voltage ports.

[0004] At the same time, in chips where the voltage fluctuation range transmitted by the I / O pins is positive or negative, bidirectional ESD protection is required. The most commonly used method is to use two unidirectional NPN devices back to back to meet the forward and reverse voltage withstand requirements of the ESD device, but this method will cause the ESD device layout area to be too large.

[0005] The cross-section diagram of a traditional unidirectional NPN electrostatic protection device is as follows: Figure 1 Its equivalent circuit diagram is shown as Figure 2As shown. When an ESD pulse is applied to the unidirectional NPN anode, the N-type well forms a reverse biased PN junction with the P-type epitaxial layer and the P-type well. When the pulse voltage is higher than the avalanche breakdown voltage of the reverse biased PN junction, a large amount of avalanche current will be generated inside the device. The current flow path is the N+ injection connected to the anode, the N-type well, the P-type epitaxial layer and the P-type well, and finally flows to the cathode through the N+ injection connected to the cathode. At this time, the NPN transistor is turned on and begins to discharge the large ESD current. The traditional unidirectional NPN has a fast turn-on speed and high process consistency, but the disadvantages are also very obvious, that is, the structural area efficiency is relatively low and the maintenance voltage is low. The low maintenance voltage leads to a large latch-up risk in the high-voltage ESD protection port of the power chip. In the bidirectional ESD protection port, it is necessary to improve the back-to-back form of two unidirectional devices, and the disadvantage of relatively low area efficiency is more obvious.

[0006] Therefore, how to provide a bidirectional ESD protection device with strong discharge capability, high area efficiency and high sustaining voltage has become one of the problems to be solved urgently by those skilled in the art.

[0007] It should be noted that the above introduction to the technical background is only for the convenience of providing a clear and complete description of the technical solutions of the present invention and for the convenience of understanding by those skilled in the art. It cannot be considered that the above technical solutions are well known to those skilled in the art simply because these solutions are described in the background technology section of the present invention. Summary of the invention

[0008] In view of the above-mentioned shortcomings of the prior art, the purpose of the present invention is to provide a high-voltage bidirectional NPN electrostatic protection device and a preparation method thereof, which are used to solve the problems of weak discharge capability, low area efficiency, low holding voltage, etc. of the NPN ESD protection device in the prior art.

[0009] In order to achieve the above-mentioned object and other related objects, the present invention provides a high-voltage bidirectional NPN electrostatic protection device, which at least includes:

[0010] A P-type substrate, an N-type buried layer disposed on the P-type substrate, and a bidirectional NPN device structure disposed on the N-type buried layer;

[0011] Wherein, the bidirectional NPN device structure includes a P-type epitaxial layer, a P-type buried layer arranged at the bottom of the P-type epitaxial layer, a first N-type well, a P-type well and a second N-type well arranged in sequence above the P-type buried layer, a first floating P+ injection region arranged in the P-type well, a second floating P+ injection region arranged in the first N-type well, a third floating P+ injection region arranged in the second N-type well, M N+ injection regions arranged in the first N-type well and arranged in sequence from the outside to the inside of the high-voltage bidirectional NPN electrostatic protection device on the outside of the second floating P+ injection region, and M N+ injection regions arranged in the second N-type well and arranged in sequence from the outside to the inside of the high-voltage bidirectional NPN electrostatic protection device on the outside of the third floating P+ injection region;

[0012] The M N+ injection regions in the first N-type well are connected together and serve as the anode of the high-voltage bidirectional NPN electrostatic protection device, and the M N+ injection regions in the second N-type well are connected together and serve as the cathode of the high-voltage bidirectional NPN electrostatic protection device; M is a natural number greater than or equal to 2.

[0013] Optionally, the high-voltage bidirectional NPN electrostatic protection device also includes: a first field oxygen isolation region arranged outside the outermost N+ injection region in the first N-type well, a second field oxygen isolation region arranged outside the outermost N+ injection region in the second N-type well, a third field oxygen isolation region arranged between the first floating P+ injection region and the second floating P+ injection region; a fourth field oxygen isolation region arranged between the first floating P+ injection region and the third floating P+ injection region; M field oxygen isolation regions arranged between each injection region in the first N-type well; and M field oxygen isolation regions arranged between each injection region in the second N-type well.

[0014] Optionally, M is set to 3; the first N+ injection region, the second N+ injection region and the third N+ injection region are arranged in sequence from the outside to the inside of the high-voltage bidirectional NPN electrostatic protection device; the fourth N+ injection region, the fifth N+ injection region and the sixth N+ injection region are arranged in sequence from the outside to the inside of the high-voltage bidirectional NPN electrostatic protection device.

[0015] More optionally, the high-voltage bidirectional NPN electrostatic protection device further includes an isolation structure disposed at the periphery of the bidirectional NPN device structure.

[0016] More optionally, the isolation structure includes: a first high-voltage N-well and a second high-voltage N-well arranged on the upper layer of the N-type buried layer and located outside the P-type epitaxial layer, a third N-type well arranged on the first high-voltage N-well, a first floating N+ injection region arranged in the third N-type well, a fourth N-type well arranged on the second high-voltage N-well, and a second floating N+ injection region arranged in the fourth N-type well.

[0017] More optionally, the isolation structure further includes: a fifth field oxygen isolation region disposed outside the first floating N+ implantation region, and a sixth field oxygen isolation region disposed outside the second floating N+ implantation region.

[0018] To achieve the above-mentioned purpose and other related purposes, the present invention provides a method for preparing the above-mentioned high-voltage bidirectional NPN electrostatic protection device, and the method for preparing the high-voltage bidirectional NPN electrostatic protection device comprises:

[0019] Step 1) forming an N-type buried layer in a P-type substrate, and forming a P-type buried layer at the bottom of the P-type epitaxial layer on the N-type buried layer;

[0020] Step 2) forming a first N-type well, a second N-type well and a P-type well in the P-type epitaxial layer;

[0021] Step 3) forming a first floating P+ injection region in the P-type well, forming a second floating P+ injection region and M N+ injection regions sequentially arranged from the outside to the inside of the high-voltage bidirectional NPN electrostatic protection device in the first N-type well, and forming a third floating P+ injection region and M N+ injection regions sequentially arranged from the outside to the inside of the high-voltage bidirectional NPN electrostatic protection device in the second N-type well;

[0022] Step 4) performing annealing treatment on each implantation region to eliminate the migration of impurities in the implantation region;

[0023] Step 5) Connect the N+ injection regions in the first N-type well together and use them as the anode of the high-voltage bidirectional NPN electrostatic protection device, and connect the N+ injection regions in the second N-type well together and use them as the cathode of the high-voltage bidirectional NPN electrostatic protection device.

[0024] Optionally, between step 1) and step 2), the method further includes: forming a field oxygen isolation region between each implantation region of the bidirectional NPN device structure on the surface of the P-type epitaxial layer.

[0025] More optionally, the method further includes forming an isolation structure around the bidirectional NPN device structure:

[0026] Step 2) further includes: forming a first high-voltage N-well and a second high-voltage N-well on the N-type buried layer, forming a third N-type well on the first high-voltage N-well, and forming a fourth N-type well on the second high-voltage N-well;

[0027] Step 3) also includes: forming a first floating N+ injection region in the third N-type well, and forming a second floating N+ injection region in the fourth N-type well.

[0028] More optionally, between step 1) and step 2), the method further includes: forming a field oxygen isolation region outside the isolation structure.

[0029] As described above, the high-voltage bidirectional NPN electrostatic protection device and the preparation method thereof of the present invention have the following beneficial effects:

[0030] 1. The present invention floats the base region of the NPN structure and symmetrically processes the emitter and collector of the NPN to form a bidirectional NPN structure, which can be applied to high-voltage ports that require bidirectional ESD protection.

[0031] 2. The present invention embeds at least one N+ injection in the N-type well and connects to the anode and cathode of the device respectively. The additionally embedded N+ injection can form additional parasitic NPN transistors; and these additional parasitic NPN transistors share the same P-well base region. This design can effectively increase the failure current of the bidirectional NPN transistor structure and increase its ESD current discharge capacity while keeping the area basically unchanged. Compared with the traditional method of directly increasing the ESD current discharge capacity by increasing the index of the bidirectional NPN transistor, the nested multi-injection method can make multiple parasitic NPN transistors share a relatively large base region of the layout area, which can save area to the maximum extent and has higher area efficiency.

[0032] 3. The present invention embeds a first floating P+ injection region in the P-type well of the base region, and embeds a second floating P+ injection region and a third floating P+ injection region in the first N-type well and the second N-type well, respectively. The embedding of the floating injection region can effectively reduce the carrier mobility of the area below the floating injection, thereby forcing the ESD current path to become deeper and flow deeper into the device, ultimately achieving the purpose of significantly increasing the holding voltage of the bidirectional NPN transistor. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 Shown is a cross-sectional schematic diagram of a unidirectional NPN electrostatic protection device.

[0034] Figure 2 Shown is the equivalent circuit diagram of a unidirectional NPN electrostatic protection device.

[0035] Figure 3 Shown is a cross-sectional schematic diagram of a high-voltage bidirectional NPN electrostatic protection device of the present invention.

[0036] Figure 4 Shown is a schematic diagram of an equivalent circuit of a high-voltage bidirectional NPN electrostatic protection device of the present invention.

[0037] Component number description

[0038] 1 High voltage bidirectional NPN electrostatic protection device

[0039] 101 P-type substrate

[0040] 201 N-type buried layer

[0041] 11 Bidirectional NPN device structure

[0042] 301 P-type buried layer

[0043] 401 P-type epitaxial layer

[0044] 501~502 First and second high voltage N wells

[0045] 601~604 First, second, third, fourth N-type well

[0046] 701 P-type well

[0047] 801~812 The first to twelfth oxygen isolation area

[0048] 901~903 First, second and third floating P+ injection regions

[0049] 904-909 First, second, third, fourth, fifth, sixth N+ implantation regions

[0050] 910~911 First and second floating N+ implantation regions DETAILED DESCRIPTION

[0051] The following describes the embodiments of the present invention through specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention.

[0052] See also Figure 3-4 It should be noted that the illustrations provided in this embodiment are only used to illustrate the basic concept of the present invention in a schematic manner, and the drawings only show components related to the present invention rather than being drawn according to the number, shape and size of components in actual implementation. In actual implementation, the type, quantity and proportion of each component may be changed arbitrarily, and the component layout may also be more complicated.

[0053] like Figure 3 As shown, the present invention provides a nested multi-injection high-voltage bidirectional NPN electrostatic protection device 1 with a high holding voltage, and the high-voltage bidirectional NPN electrostatic protection device 1 includes:

[0054] A P-type substrate 101 , an N-type buried layer 201 disposed on the P-type substrate 101 , and a bidirectional NPN device structure 11 disposed on the N-type buried layer 201 .

[0055] like Figure 3 As shown, the P-type substrate 101 is arranged at the bottom layer of the device, the N-type buried layer 201 is located on the upper layer of the P-type substrate 101, and the bidirectional NPN device structure 11 is located on the N-type buried layer 201. The bidirectional NPN device structure 11 is separated from the P-type substrate 101 by the N-type buried layer 201 to avoid the influence of the substrate potential on the bidirectional NPN device structure 11.

[0056] like Figure 3 As shown, the bidirectional NPN device structure 11 includes a P-type epitaxial layer 401, a P-type buried layer 301, a first N-type well 601, a P-type well 701, a second N-type well 602, a first floating P+ injection region 901, a second floating P+ injection region 902, a third floating P+ injection region 903 and 2M N+ injection regions, where M is a natural number greater than or equal to 2.

[0057] Specifically, the P-type epitaxial layer 401 is located on the upper layer of the N-type buried layer 201. The P-type buried layer 301 is located at the bottom of the P-type epitaxial layer 401 and is used to separate the N-type buried layer 201 from the well regions (the first N-type well 601, the P-type well 701, and the second N-type well 602) of the bidirectional NPN device structure 11.

[0058] Specifically, the first N-type well 601, the P-type well 701 and the second N-type well 602 are arranged at intervals in the P-type epitaxial layer 401 and are located above the P-type buried layer 301, wherein the P-type well 701 is located in the central area of ​​the device, the first N-type well 601 and the second N-type well 602 are respectively located on both sides of the P-type well 701, the first N-type well 601 and the P-type well 701 are separated by the P-type epitaxial layer 401, and the second N-type well 602 and the P-type well 701 are separated by the P-type epitaxial layer 401.

[0059] Specifically, the first floating P+ injection region 901 is disposed in the P-type well 701, the second floating P+ injection region 902 is disposed in the first N-type well 601, and the third floating P+ injection region 903 is disposed in the second N-type well 602. In this embodiment, M is set to 3. The first N+ injection region 904, the second N+ injection region 905, and the third N+ injection region 906 are disposed in the first N-type well 601, located outside the second floating P+ injection region 902, and are arranged in sequence from the outside to the inside of the high-voltage bidirectional NPN electrostatic protection device 1; that is, in this embodiment, the first N+ injection region 904, the second N+ injection region 905, the third N+ injection region 906, and the second floating P+ injection region 902 are located on the left side of the device, and are close to the center area of ​​the device from left to right. The fourth N+ injection area 907, the fifth N+ injection area 908 and the sixth N+ injection area 909 are arranged in the second N-type well 602, located outside the second N+ floating injection area 903, and are arranged in sequence from the outside to the inside of the high-voltage bidirectional NPN electrostatic protection device 1; that is, in this embodiment, the fourth N+ injection area 907, the fifth N+ injection area 908, the sixth N+ injection area 909 and the third floating P+ injection area 903 are located on the right side of the device, and approach the center area of ​​the device from right to left. It should be noted that the outer side of the high-voltage bidirectional NPN electrostatic protection device 1 mentioned in the present invention is the side away from the central base area, and the inner side of the high-voltage bidirectional NPN electrostatic protection device 1 is the side close to the central base area. In actual use, the number of M can be set according to actual needs, and the parallel structure of at least two NPN transistors is realized by nesting.

[0060] like Figure 3 As shown, the M N+ injection regions in the first N-type well 601 are connected together and serve as the anode of the high-voltage bidirectional NPN electrostatic protection device 1, and the M N+ injection regions in the second N-type well 602 are connected together and serve as the cathode of the high-voltage bidirectional NPN electrostatic protection device 1.

[0061] As another implementation of the present invention, Figure 3As shown, the high-voltage bidirectional NPN electrostatic protection device 1 also includes: a first field oxygen isolation region 801, a second field oxygen isolation region 802, a third field oxygen isolation region 803, a fourth field oxygen isolation region 804 and 2M field oxygen isolation regions. The first field oxygen isolation region 801 is located outside the first N+ injection region 904 (the outermost N+ injection region in the first N-type well 601); in this embodiment, the first field oxygen isolation region 801 is located at the surface at the junction of the P-type epitaxial layer 401 and the first N-type well 601. The second field oxygen isolation region 802 is located outside the fourth N+ injection region 907 (the outermost N+ injection region in the second N-type well 602); in this embodiment, the second field oxygen isolation region 802 is located at the surface at the junction of the P-type epitaxial layer 401 and the second N-type well 602. The third field oxygen isolation region 803 is located between the first floating P+ implantation region 901 and the second floating P+ implantation region 902; in this embodiment, the third field oxygen isolation region 803 is located at the interface surface of the first N-type well 601, the P-type epitaxial layer 401 and the second N-type well 602. The fourth field oxygen isolation region 804 is located between the first floating P+ implantation region 901 and the third floating P+ implantation region 903; in this embodiment, the fourth field oxygen isolation region 804 is located at the interface surface of the second N-type well 602, the P-type epitaxial layer 401 and the first N-type well 601. In this example, three field oxygen isolation regions are set in the first N-type well 601, which are respectively recorded as the seventh field oxygen isolation region 807, the eighth field oxygen isolation region 808, and the ninth field oxygen isolation region 809; three field oxygen isolation regions are set in the second N-type well 602, which are respectively recorded as the tenth field oxygen isolation region 810, the eleventh field oxygen isolation region 811, and the twelfth field oxygen isolation region 812. Among them, the seventh field oxygen isolation region 807 is located on the surface of the first N-type well 601 between the first N+ injection region 904 and the second N+ injection region 905; the eighth field oxygen isolation region 808 is located on the surface of the first N-type well 601 between the second N+ injection region 905 and the third N+ injection region 905; the ninth field oxygen isolation region 809 is located on the surface of the first N-type well 601 between the third N+ injection region 906 and the second floating P+ injection region 902; the tenth field oxygen isolation region 810 is located on the surface of the second N-type well 602 between the fourth N+ injection region 907 and the fifth N+ injection region 908; the eleventh field oxygen isolation region 811 is located on the surface of the second N-type well 602 between the fifth N+ injection region 908 and the sixth N+ injection region 909; the twelfth field oxygen isolation region 812 is located on the surface of the second N-type well 602 between the sixth N+ injection region 909 and the third floating P+ injection region 903.

[0062] As another implementation of the present invention, the high voltage bidirectional NPN electrostatic protection device 1 further includes an isolation structure disposed on the periphery of the bidirectional NPN device structure 11. Figure 3As shown, the isolation structure includes: a first high-voltage N-well 501, a second high-voltage N-well 502, a third N-type well 603, a fourth N-type well 604, a first floating N+ injection region 910, and a second floating N+ injection region 911. The first high-voltage N-well 501 and the second high-voltage N-well 502 are located on the N-type buried layer 201 and on both sides of the P-type epitaxial layer 401. The third N-type well 603 is located on the first high-voltage N-well 501, and the first floating N+ injection region 910 is arranged in the third N-type well 603. The fourth N-type well 604 is located on the second high-voltage N-well 502, and the second floating N+ injection region 911 is arranged in the fourth N-type well 604. Further, the isolation structure also includes: a fifth field oxygen isolation region 805 and a sixth field oxygen isolation region 806. The fifth field oxygen isolation region 805 is located outside the first floating N+ implantation region 910; in this embodiment, the fifth field oxygen isolation region 805 is located on the surface at the junction of the P-type substrate 101 and the third N-type well 603. The sixth field oxygen isolation region 806 is located outside the second floating N+ implantation region 911; in this embodiment, the sixth field oxygen isolation region 806 is located on the surface at the junction of the P-type substrate 101 and the fourth N-type well 604.

[0063] like Figure 3 As shown, the third N+ injection region 906, the first N-type well 601, the P-type well 701, the second N-type well 602 and the sixth N+ injection region 909 constitute the first lateral parasitic NPN transistor NPN1; the second N+ injection region 905, the first N-type well 601, the P-type well 701, the second N-type well 602 and the fifth N+ injection region 908 constitute the second lateral parasitic NPN transistor NPN2; the first N+ injection region 904, the first N-type well 601, the P-type well 701, the second N-type well 602 and the fourth N+ injection region 907 constitute the third lateral parasitic NPN transistor NPN3. The isolation structure formed by the first floating N+ injection region 910 , the third N-type well 603 , the first high-voltage N-well 501 , the N-type buried layer 201 , the second high-voltage N-well 502 , the fourth N-type well 604 and the second floating N+ injection region 911 completely isolates the bidirectional NPN device structure 11 from the P-type substrate 101 .

[0064] like Figure 3As shown, when the ESD high voltage pulse reaches the anode of the device, the first N+ injection region 904, the second N+ injection region 905 and the third N+ injection region 906 are at high potential, and the fourth N+ injection region 907, the fifth N+ injection region 908 and the sixth N+ injection region 909 at the other end are low potential cathodes. The PN junction composed of the first N-type well 601, the P-type epitaxial layer 401 and the P-type well 701 is reverse biased. When the pulse voltage is higher than the avalanche breakdown voltage of the reverse biased PN junction, a large amount of avalanche current will be generated inside the device. The avalanche current flows through the second N-type well 602 and flows into the cathode. Since the parasitic NPN1 current path composed of the third N+ injection region 906 and the sixth N+ injection region 909 is the shortest, the parasitic NPN1 is turned on first, and then drives the outer parasitic NPN2 and NPN3 to turn on in sequence. From the equivalent circuit diagram Figure 4 It can be seen that when the voltage drop caused by the avalanche current on the parasitic resistance of the P-type well 701 is large enough, the parasitic NPN1 is turned on, and after the parasitic NPN1 is turned on, the parasitic NPN2 and the parasitic NPN3 are also gradually turned on and discharge the ESD current together.

[0065] Similarly, when a positive ESD pulse appears at the cathode, the fourth N+ injection region 907, the fifth N+ injection region 908 and the sixth N+ injection region 909 are at high potential, and the first N+ injection region 904, the second N+ injection region 905 and the third N+ injection region 906 at the other end are low potential cathodes. The reverse biased PN junction composed of the second N-type well 602, the P-type epitaxial layer 401 and the P-type well 701 undergoes avalanche breakdown, and the avalanche current flows through the first N-type well 601 and flows into the anode. The equivalent circuit diagram Figure 4 It can be seen that when the voltage drop caused by the avalanche current on the parasitic resistance of the P-type well 701 is large enough, the parasitic NPN1 is turned on first, and then the parasitic NPN2 and the parasitic NPN3 are gradually turned on and discharge the ESD current together, and a reverse ESD current discharge path is formed.

[0066] Due to the existence of the first floating P+ injection region 901, the second floating P+ injection region 902 and the third floating P+ injection region 903, the local carrier mobility below the three floating P+ injection regions will decrease, causing the resistivity of the region to increase, thereby reducing the ESD current close to the device surface, making the ESD current deeper, and the ESD discharge path longer, ultimately increasing the sustaining voltage.

[0067] The present invention also provides a method for preparing the above-mentioned high-voltage bidirectional NPN electrostatic protection device, comprising the following steps:

[0068] Step 1) forming an N-type buried layer 201 in a P-type substrate 101, and forming a P-type buried layer 301 at the bottom of a P-type epitaxial layer 401 on the N-type buried layer.

[0069] Specifically, as an example, before forming the N-type buried layer 201, step 1) also includes the step of pre-treating the P-type substrate 101; including: forming a growth inhibition layer on the P-type substrate 101 (for example, the growth inhibition layer includes but is not limited to a stacked silicon dioxide layer and a silicon nitride layer), spin coating a photoresist layer on the growth inhibition layer and exposing and developing based on a mask to form an isolation pattern to divide the device preparation area, removing the growth inhibition layer in the device preparation area and removing the isolation pattern.

[0070] Specifically, as an example, after forming the P-type buried layer 301, it also includes: forming a field oxygen isolation region between each implantation region of the bidirectional NPN device structure 11 on the surface of the P-type epitaxial layer 401. In this embodiment, a first field oxygen isolation region 801 is formed outside the outermost N+ implantation region in the first N-type well 601, a second field oxygen isolation region 802 is formed outside the outermost N+ implantation region in the second N-type well 602, a third field oxygen isolation region 803 is formed on the surface at the junction of the first N-type well 601 and the P-type well 701, a fourth field oxygen isolation region 804 is formed on the surface at the junction of the second N-type well 602 and the P-type well 701, a seventh field oxygen isolation region 807, an eighth field oxygen isolation region 808 and a ninth field oxygen isolation region 809 are formed between each implantation region in the first N-type well 601, and a tenth field oxygen isolation region 810, an eleventh field oxygen isolation region 811 and a twelfth field oxygen isolation region 812 are formed between each implantation region in the second N-type well 602.

[0071] Furthermore, when the high-voltage bidirectional NPN electrostatic protection device 1 includes an isolation structure, a field oxygen isolation region outside the isolation structure is formed while forming each injection region of the bidirectional NPN device structure 11. Specifically, a fifth field oxygen isolation region 805 is formed outside the first floating N+ injection region 910, and a sixth field oxygen isolation region 806 is formed outside the second floating N+ injection region 911.

[0072] It should be noted that when the field oxygen isolation region is formed, the implantation regions have not yet been formed, and the position of the field oxygen isolation region is determined based on the predetermined field oxygen isolation region position and the implantation region position.

[0073] Step 2) forming a first N-type well 601 , a second N-type well 602 and a P-type well 701 in the P-type epitaxial layer 401 .

[0074] Specifically, when the high-voltage bidirectional NPN electrostatic protection device 1 includes an isolation structure, step 2) also includes: forming a first high-voltage N-well 501 and a second high-voltage N-well 502 on the N-type buried layer 201, forming a third N-type well 603 on the first high-voltage N-well 501, and forming a fourth N-type well 604 on the second high-voltage N-well 502.

[0075] Step 3) A first floating P+ injection region 901 is formed in the P-type well 701, a second floating P+ injection region 902 and M N+ injection regions arranged in sequence from the outside to the inside of the high-voltage bidirectional NPN electrostatic protection device 1 are formed in the first N-type well 601, and a third floating P+ injection region 903 and M N+ injection regions arranged in sequence from the outside to the inside of the high-voltage bidirectional NPN electrostatic protection device 1 are formed in the second N-type well 602.

[0076] Specifically, when the high-voltage bidirectional NPN electrostatic protection device 1 includes an isolation structure, step 3) also includes: forming a first floating N+ injection region 910 in the third N-type well 603 , and forming a second floating N+ injection region 911 in the fourth N-type well 604 .

[0077] Step 4) performing annealing treatment on each implantation region to eliminate the migration of impurities in the implantation region;

[0078] Step 5) Connect the N+ injection regions in the first N-type well 601 together and use them as the anode of the high-voltage bidirectional NPN electrostatic protection device 1 , and connect the N+ injection regions in the second N-type well 602 together and use them as the cathode of the high-voltage bidirectional NPN electrostatic protection device 1 .

[0079] Specifically, in this embodiment, the first N+ injection region 904, the second N+ injection region 905 and the third N+ injection region 906 are connected together through the lead-out electrode and serve as the anode of the device, and the fourth N+ injection region 907, the fifth N+ injection region 908 and the sixth N+ injection region 909 are connected together through the lead-out electrode and serve as the cathode of the device.

[0080] The preparation method of the nested multi-injection high-voltage bidirectional NPN electrostatic protection device of the present invention is simple in process and easy to operate. The prepared high-voltage bidirectional NPN electrostatic protection device structure can be applied to high-voltage bidirectional ESD ports, and can provide a design reference for the ESD protection device of high-voltage bidirectional ESD ports. At the same time, the present invention also adopts the technology of nested multi-injection, and at least one N+ injection is additionally embedded in the N-type well and connected to the anode and cathode of the device respectively. The additional embedded N+ injection can form an additional parasitic NPN triode, and the design can effectively increase the failure current of the bidirectional NPN triode structure and increase its discharge capacity for ESD current. Compared with the traditional method, that is, directly increasing the discharge capacity for ESD current by increasing the index of the bidirectional NPN triode, the nested multi-injection method can make multiple parasitic NPN triodes share a relatively large base area of ​​the layout area, which can save area to the maximum extent, and the area efficiency is higher. In addition, the floating P+ injection is embedded in the emitter and base areas of the bidirectional NPN triode structure, which can effectively increase the holding voltage of the device and reduce the risk of latching between the device and the circuit. The device of the present invention adopts 0.18 μm high-voltage BCD process.

[0081] In summary, the present invention provides a high-voltage bidirectional NPN electrostatic protection device and a preparation method thereof, comprising: a P-type substrate, an N-type buried layer arranged on the P-type substrate, and a bidirectional NPN device structure arranged on the N-type buried layer; wherein the bidirectional NPN device structure comprises a P-type epitaxial layer, a P-type buried layer arranged at the bottom of the P-type epitaxial layer, a first N-type well, a P-type well and a second N-type well arranged in sequence above the P-type buried layer, a first floating P+ injection region arranged in the P-type well, a second floating P+ injection region arranged in the first N-type well, a third floating P+ injection region arranged in the second N-type well, and a P-type buried layer arranged at the bottom of the P-type epitaxial layer. M N+ injection regions are placed in the first N-type well and are arranged in sequence from the outside to the inside of the high-voltage bidirectional NPN electrostatic protection device at intervals on the outside of the second floating P+ injection region, and M N+ injection regions are placed in the second N-type well and are arranged in sequence from the outside to the inside of the high-voltage bidirectional NPN electrostatic protection device at intervals on the outside of the third floating P+ injection region; the M N+ injection regions in the first N-type well are connected together and serve as the anode of the high-voltage bidirectional NPN electrostatic protection device, and the M N+ injection regions in the second N-type well are connected together and serve as the cathode of the high-voltage bidirectional NPN electrostatic protection device; M is a natural number greater than or equal to 2. The present invention is suitable for high-voltage ports that require bidirectional ESD protection, improves the discharge capacity of ESD current and the holding voltage of the bidirectional NPN transistor, and has a higher area efficiency and a stronger anti-latch capability. Therefore, the present invention effectively overcomes the various shortcomings of the prior art and has a high industrial utilization value.

[0082] The above embodiments are merely illustrative of the principles and effects of the present invention, and are not intended to limit the present invention. Anyone familiar with the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by a person of ordinary skill in the art without departing from the spirit and technical concept disclosed by the present invention shall still be covered by the claims of the present invention.

Claims

1. A high voltage bidirectional NPN electrostatic protection device, characterized in that: The high voltage bidirectional NPN electrostatic protection device at least comprises: A P-type substrate, an N-type buried layer disposed on the P-type substrate, and a bidirectional NPN device structure disposed on the N-type buried layer; Wherein, the bidirectional NPN device structure includes a P-type epitaxial layer, a P-type buried layer arranged at the bottom of the P-type epitaxial layer, a first N-type well, a P-type well and a second N-type well arranged in sequence above the P-type buried layer, a first floating P+ injection region arranged in the P-type well, a second floating P+ injection region arranged in the first N-type well, a third floating P+ injection region arranged in the second N-type well, M N+ injection regions arranged in the first N-type well and arranged in sequence from the outside to the inside of the high-voltage bidirectional NPN electrostatic protection device on the outside of the second floating P+ injection region, and M N+ injection regions arranged in the second N-type well and arranged in sequence from the outside to the inside of the high-voltage bidirectional NPN electrostatic protection device on the outside of the third floating P+ injection region; The M N+ injection regions in the first N-type well are connected together and serve as the anode of the high-voltage bidirectional NPN electrostatic protection device, and the M N+ injection regions in the second N-type well are connected together and serve as the cathode of the high-voltage bidirectional NPN electrostatic protection device; M is a natural number greater than or equal to 2.

2. The high voltage bidirectional NPN electrostatic protection device according to claim 1, characterized in that: The high-voltage bidirectional NPN electrostatic protection device also includes: a first field oxygen isolation region arranged outside the outermost N+ injection region in the first N-type well, a second field oxygen isolation region arranged outside the outermost N+ injection region in the second N-type well, a third field oxygen isolation region arranged between the first floating P+ injection region and the second floating P+ injection region; a fourth field oxygen isolation region arranged between the first floating P+ injection region and the third floating P+ injection region; M field oxygen isolation regions arranged between each injection region in the first N-type well; and M field oxygen isolation regions arranged between each injection region in the second N-type well.

3. The high voltage bidirectional NPN electrostatic protection device according to claim 1, characterized in that: M is set to 3; the first N+ injection area, the second N+ injection area and the third N+ injection area are arranged in sequence from the outside to the inside of the high-voltage bidirectional NPN electrostatic protection device; the fourth N+ injection area, the fifth N+ injection area and the sixth N+ injection area are arranged in sequence from the outside to the inside of the high-voltage bidirectional NPN electrostatic protection device.

4. The high voltage bidirectional NPN electrostatic protection device according to any one of claims 1 to 3, characterized in that: The high-voltage bidirectional NPN electrostatic protection device also includes an isolation structure arranged at the periphery of the bidirectional NPN device structure.

5. The high voltage bidirectional NPN electrostatic protection device according to claim 4, characterized in that: The isolation structure includes: a first high-voltage N-well and a second high-voltage N-well arranged on the upper layer of the N-type buried layer and located outside the P-type epitaxial layer, a third N-type well arranged on the first high-voltage N-well, a first floating N+ injection region arranged in the third N-type well, a fourth N-type well arranged on the second high-voltage N-well, and a second floating N+ injection region arranged in the fourth N-type well.

6. The high voltage bidirectional NPN electrostatic protection device according to claim 5, characterized in that: The isolation structure further includes: a fifth field oxygen isolation region disposed outside the first floating N+ implantation region, and a sixth field oxygen isolation region disposed outside the second floating N+ implantation region.

7. A method for preparing a high voltage bidirectional NPN electrostatic protection device according to any one of claims 1 to 6, characterized in that: The preparation method of the high-voltage bidirectional NPN electrostatic protection device comprises: Step 1) forming an N-type buried layer in a P-type substrate, and forming a P-type buried layer at the bottom of the P-type epitaxial layer on the N-type buried layer; Step 2) forming a first N-type well, a second N-type well and a P-type well in the P-type epitaxial layer; Step 3) forming a first floating P+ injection region in the P-type well, forming a second floating P+ injection region and M N+ injection regions sequentially arranged from the outside to the inside of the high-voltage bidirectional NPN electrostatic protection device in the first N-type well, and forming a third floating P+ injection region and M N+ injection regions sequentially arranged from the outside to the inside of the high-voltage bidirectional NPN electrostatic protection device in the second N-type well; Step 4) performing annealing treatment on each implantation region to eliminate the migration of impurities in the implantation region; Step 5) Connect the N+ injection regions in the first N-type well together and use them as the anode of the high-voltage bidirectional NPN electrostatic protection device, and connect the N+ injection regions in the second N-type well together and use them as the cathode of the high-voltage bidirectional NPN electrostatic protection device.

8. The method for preparing a high voltage bidirectional NPN electrostatic protection device according to claim 7, characterized in that: The method further includes between step 1) and step 2): forming a field oxygen isolation region between each implantation region of the bidirectional NPN device structure on the surface of the P-type epitaxial layer.

9. The method for preparing a high voltage bidirectional NPN electrostatic protection device according to claim 7 or 8, characterized in that: The step of forming an isolation structure around the bidirectional NPN device structure is also included: Step 2) further includes: forming a first high-voltage N-well and a second high-voltage N-well on the N-type buried layer, forming a third N-type well on the first high-voltage N-well, and forming a fourth N-type well on the second high-voltage N-well; Step 3) also includes: forming a first floating N+ injection region in the third N-type well, and forming a second floating N+ injection region in the fourth N-type well.

10. The method for preparing a high voltage bidirectional NPN electrostatic protection device according to claim 9, characterized in that: The method further includes forming a field oxygen isolation region outside the isolation structure between step 1) and step 2).

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