Bidirectional low-residual-voltage SCR device structure for ESD protection

Abstract

The utility model relates to an SCR (Selective Catalytic Reduction) device structure, in particular to a bidirectional low-residual-voltage SCR device structure for ESD (Electro-Static Discharge) protection, which is characterized in that a plurality of first P-type diffusion regions and two first N-type diffusion regions distributed on two sides of the plurality of first P-type diffusion regions are arranged on a first P-type well; a second P-type diffusion region is arranged on the first N-type well; a second N-type diffusion region is arranged at the joint of the first N-type well and the second P-type well; a third N-type diffusion region is arranged on the third P-type well; a third P-type diffusion region is arranged at the joint of the third P-type well and the second N-type well; the bottom of the first front metal layer is connected with the first P-type diffusion region and the first N-type diffusion region; the bottom of the second front metal layer is connected with the second P-type diffusion region and the second N-type diffusion region; and the bottom of the third front metal layer is connected with the third P-type diffusion region and the third N-type diffusion region. According to the ESD protection device, the maintaining voltage of the device can be obviously reduced, the ESD protection performance is improved, and the strict requirement of a miniaturized chip on ESD protection is met.

Description

Technical Field

[0001] The utility model relates to the structure of an SCR device, in particular to a bidirectional low-residual voltage SCR device structure for ESD protection. Background Art

[0002] In the field of electrostatic discharge (ESD) protection of integrated circuits, with the continuous reduction of chip size, the performance requirements for ESD protection devices are also increasing day by day. SCR (Silicon Controlled Rectifier) devices have become an important choice for ESD protection in miniaturized chips due to their strong surge current capacity and low holding voltage.

[0003] Currently, the mainstream bidirectional SCR devices compatible with the CMOS process generally include two parts in structure: an SCR structure (IO→GND) and a forward PN junction diode (GND→IO), which are respectively used to handle ESD events in the IO to GND and GND to IO directions. However, the limitation of this design is that as the current in the GND to IO direction increases, the voltage drop of the forward PN junction diode also increases accordingly, making it difficult to further reduce the holding voltage of the bidirectional SCR device and difficult to meet the increasingly strict ESD protection standards. Summary of the Utility Model

[0004] The purpose of the utility model is to solve the technical problem that it is difficult to further reduce the holding voltage of the existing bidirectional SCR device, and to provide a bidirectional low-residual voltage SCR device structure for ESD protection.

[0005] To solve the above technical problem, the technical solution provided by the utility model is as follows:

[0006] A bidirectional low-residual voltage SCR device structure for ESD protection, comprising a P-type substrate and an isolation layer disposed on the top of the P-type substrate;

[0007] On the P-type substrate, there is a first P-type well with its top connected to the bottom of the isolation layer, and two groups of first N-type wells, second P-type wells, second N-type wells, and third P-type wells that are symmetrically distributed on both sides of the first P-type well and are connected in sequence from inside to outside;

[0008] On the first P-type well, there are a plurality of first P-type diffusion regions with their tops connected to the bottom of the isolation layer, and two first N-type diffusion regions distributed on both sides of the plurality of first P-type diffusion regions;

[0009] On the first N-type well, there is a second P-type diffusion region with its top connected to the bottom of the isolation layer; at the junction of the first N-type well and the second P-type well, there is a second N-type diffusion region with its top connected to the bottom of the isolation layer;

[0010] A third N-type diffusion region with its top connected to the bottom of the isolation layer is provided on the third P-type well; a third P-type diffusion region with its top connected to the bottom of the isolation layer is provided at the junction of the third P-type well and the second N-type well;

[0011] On the top of the isolation layer, there is a first front metal layer, and second and third front metal layers distributed on both sides of the first front metal layer;

[0012] The bottom of the first front metal layer is connected to the first P-type diffusion region and the first N-type diffusion region; the bottom of the second front metal layer is connected to the second P-type diffusion region and the second N-type diffusion region; the bottom of the third front metal layer is connected to the third P-type diffusion region and the third N-type diffusion region.

[0013] Further, via holes corresponding to the first P-type diffusion region, the first N-type diffusion region, the second P-type diffusion region, the second N-type diffusion region, the third P-type diffusion region, and the third N-type diffusion region are formed on the isolation layer;

[0014] The bottom of the first front metal layer passes through the isolation layer through the via hole and is connected to the first P-type diffusion region and the first N-type diffusion region as the GND of the SCR device structure; the bottom of the second front metal layer passes through the isolation layer through the via hole and is connected to the second P-type diffusion region and the second N-type diffusion region as the IO of the SCR device structure; the bottom of the third front metal layer passes through the isolation layer through the via hole and is connected to the third P-type diffusion region and the third N-type diffusion region as the GND of the SCR device structure.

[0015] Further, the material of the P-type substrate is silicon with a <100> crystal orientation and a resistivity of 8 - 20 Ω·cm.

[0016] Further, the doping material of the first P-type well, the second P-type well, and the third P-type well is boron; the doping material of the first N-type well and the second N-type well is phosphorus.

[0017] Further, the doping material of the first P-type diffusion region, the second P-type diffusion region, and the third P-type diffusion region is boron; the doping material of the first N-type diffusion region, the second N-type diffusion region, and the third N-type diffusion region is arsenic.

[0018] Further, the material of the isolation layer is borophosphosilicate glass.

[0019] Further, the first front metal layer, the second front metal layer, and the third front metal layer are silicon-aluminum alloy, and the thickness of the silicon-aluminum alloy is 1.5 - 2 μm.

[0020] Compared with the prior art, the beneficial effects of the present utility model are:

[0021] The structure of the bidirectional low-residual-voltage SCR device for ESD protection provided by the present utility model is characterized in that a first N-type well, a second P-type well, a second N-type well and a third P-type well which are connected in sequence are respectively arranged on both sides of the first P-type well, and a second N-type diffusion region and a third P-type diffusion region are respectively arranged at the joints of the first N-type well and the second P-type well and the joint of the second N-type well and the third P-type well. Among them, the third P-type diffusion region, the third P-type well, the P-type substrate, the second P-type well and the second N-type diffusion region form a first current path (PN junction), and the third P-type diffusion region, the second N-type well, the second P-type well and the second N-type diffusion region form a second current path (PNPN junction). Since the PNPN junction is prone to latch-up conduction, the PNPN will turn on under a relatively small current, generating a negative resistance effect, which can significantly reduce the holding voltage of the device and improve the ESD protection performance, meeting the strict requirements of miniaturized chips for ESD protection. Description of the Drawings

[0022] Figure 1 It is a schematic structural diagram of an embodiment of the present utility model.

[0023] Description of the reference numerals: 1 is a P-type substrate, 2 is an isolation layer, 3 is a first P-type well, 4 is a first N-type well, 5 is a second P-type well, 6 is a second N-type well, 7 is a third P-type well, 8 is a first P-type diffusion region, 9 is a first N-type diffusion region, 10 is a second P-type diffusion region, 11 is a second N-type diffusion region, 12 is a third P-type diffusion region, 13 is a third N-type diffusion region, 14 is a first front metal layer, 15 is a second front metal layer, and 16 is a third front metal layer. Detailed Embodiment

[0024] Next, the technical solutions in the present utility model will be clearly and completely described in conjunction with the drawings. Obviously, the described embodiments are only a part of the embodiments of the present utility model, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present utility model without creative efforts shall fall within the protection scope of the present utility model.

[0025] As Figure 1 shown, a structure of a bidirectional low-residual-voltage SCR device for ESD protection includes a P-type substrate 1 and an isolation layer 2 disposed on the top of the P-type substrate 1;

[0026] A first P-type well 3 whose top is connected to the bottom of the isolation layer 2 is provided on the P-type substrate 1, and two groups of first N-type wells 4, second P-type wells 5, second N-type wells 6 and third P-type wells 7 which are symmetrically distributed on both sides of the first P-type well 3 and are connected in sequence from inside to outside;

[0027] On the first P-type well 3, there are multiple first P-type diffusion regions 8 with their tops connected to the bottom of the isolation layer 2, and two first N-type diffusion regions 9 distributed on both sides of the multiple first P-type diffusion regions 8;

[0028] On the first N-type well 4, there is a second P-type diffusion region 10 with its top connected to the bottom of the isolation layer 2; at the junction of the first N-type well 4 and the second P-type well 5, there is a second N-type diffusion region 11 with its top connected to the bottom of the isolation layer 2;

[0029] On the third P-type well 7, there is a third N-type diffusion region 13 with its top connected to the bottom of the isolation layer 2; at the junction of the third P-type well 7 and the second N-type well 6, there is a third P-type diffusion region 12 with its top connected to the bottom of the isolation layer 2;

[0030] On the top of the isolation layer 2, there is a first front metal layer 14, and second front metal layers 15 and third front metal layers 16 distributed on both sides of the first front metal layer 14;

[0031] On the isolation layer 2, there are lead holes corresponding to the first P-type diffusion region 8, the first N-type diffusion region 9, the second P-type diffusion region 10, the second N-type diffusion region 11, the third P-type diffusion region 12, and the third N-type diffusion region 13;

[0032] The bottom of the first front metal layer 14 passes through the isolation layer 2 through the lead hole and is connected to the first P-type diffusion region 8 and the first N-type diffusion region 9 as the GND of the SCR device structure; the bottom of the second front metal layer 15 passes through the isolation layer 2 through the lead hole and is connected to the second P-type diffusion region 10 and the second N-type diffusion region 11 as the IO of the SCR device structure; the bottom of the third front metal layer 16 passes through the isolation layer 2 through the lead hole and is connected to the third P-type diffusion region 12 and the third N-type diffusion region 13 as the GND of the SCR device structure.

[0033] In this embodiment, the materials of each part in the bidirectional low-residual-voltage SCR device structure are as follows:

[0034] The material of the P-type substrate 1 is silicon with <100> crystal orientation, and its resistivity is 8 - 20 Ω.cm.

[0035] The doping material of the first P-type well 3, the second P-type well 5, and the third P-type well 7 is boron, with an implantation energy of 80 - 100 kev and a dose of 6E12 - 4e13; the doping material of the first N-type well 4 and the second N-type well 6 is phosphorus, with an implantation energy of 100 - 120 kev and a dose of 1e13 - 2E13; the formation temperature of the first P-type well 3, the second P-type well 5, the third P-type well 7, the first N-type well 4, and the second N-type well 6 is 1150 °C, and the formation time is 1.5 h - 2 h.

[0036] The doping material of the first P-type diffusion region 8, the second P-type diffusion region 10, and the third P-type diffusion region 12 is boron, with an implantation energy of 25 - 40 keV and a dose of 2 - 4E15; the doping material of the first N-type diffusion region 9, the second N-type diffusion region 11, and the third N-type diffusion region 13 is arsenic, with an implantation energy of 80 keV and a dose of 5 - 7E15.

[0037] The material of the isolation layer 2 is borophosphosilicate glass, which is deposited at 5 - 8K.

[0038] The first front metal layer 14, the second front metal layer 15, and the third front metal layer 16 are aluminum-silicon alloy layers, and the thickness of the aluminum-silicon alloy is 1.5 - 2 μm.

[0039] The bidirectional low-residual voltage SCR device structure for ESD protection provided by the present utility model has the following specific manufacturing steps:

[0040] 1) Use photo, implant, and drive-in processes to form a first P-type well 3 on the P-type substrate 1, and first N-type wells 4, second P-type wells 5, second N-type wells 6, and third P-type wells 7 symmetrically distributed on both sides of the first P-type well 3;

[0041] 2) Use Photo and implant processes to form a first P-type diffusion region 8 and a first N-type diffusion region 9 on the first P-type well 3;

[0042] And use Photo and implant processes to form a second P-type diffusion region 10, a second N-type diffusion region 11, a third N-type diffusion region 13, and a third P-type diffusion region 12 at the first N-type well 4, the junction of the first N-type well 4 and the second P-type well 5, the third P-type well 7, and the junction of the third P-type well 7 and the second N-type well 6;

[0043] 3) Use an etching process to etch lead holes corresponding to the first P-type diffusion region 8, the first N-type diffusion region 9, the second P-type diffusion region 10, the second N-type diffusion region 11, the third P-type diffusion region 12, and the third N-type diffusion region 13 on the isolation layer 2;

[0044] The bottom of the first front metal layer 14 passes through the isolation layer 2 through the lead hole and is connected to the first P-type diffusion region 8 and the first N-type diffusion region 9 as the GND of the SCR device structure;

[0045] The bottom of the second front metal layer 15 passes through the isolation layer 2 through the lead hole and is connected to the second P-type diffusion region 10 and the second N-type diffusion region 11 as the IO of the SCR device structure;

[0046] The bottom of the third front metal layer 16 is connected to the third P-type diffusion region 12 and the third N-type diffusion region 13 through a via hole passing through the isolation layer 2 to serve as the GND of the SCR device structure.

[0047] As described above, only the specific embodiments of the present invention are provided, but the protection scope of the present invention is not limited thereto. Any changes or substitutions within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention should be subject to the protection scope of the claimed rights.

Claims

1. A bidirectional low-residual voltage SCR device structure for ESD protection, characterized in that: It includes a P-type substrate (1) and an isolation layer (2) disposed on the top of the P-type substrate (1); On the P-type substrate (1), there is a first P-type well (3) whose top is in contact with the bottom of the isolation layer (2), and two groups of first N-type wells (4), second P-type wells (5), second N-type wells (6) and third P-type wells (7) that are symmetrically distributed on both sides of the first P-type well (3) and are connected in sequence from the inside to the outside; On the first P-type well (3), there are multiple first P-type diffusion regions (8) whose tops are in contact with the bottom of the isolation layer (2), and two first N-type diffusion regions (9) distributed on both sides of the multiple first P-type diffusion regions (8); On the first N-type well (4), there is a second P-type diffusion region (10) whose top is in contact with the bottom of the isolation layer (2); at the junction of the first N-type well (4) and the second P-type well (5), there is a second N-type diffusion region (11) whose top is in contact with the bottom of the isolation layer (2); On the third P-type well (7), there is a third N-type diffusion region (13) whose top is in contact with the bottom of the isolation layer (2); at the junction of the third P-type well (7) and the second N-type well (6), there is a third P-type diffusion region (12) whose top is in contact with the bottom of the isolation layer (2); On the top of the isolation layer (2), there is a first front metal layer (14), and second front metal layers (15) and third front metal layers (16) distributed on both sides of the first front metal layer (14); The bottom of the first front metal layer (14) is in contact with the first P-type diffusion region (8) and the first N-type diffusion region (9); the bottom of the second front metal layer (15) is in contact with the second P-type diffusion region (10) and the second N-type diffusion region (11); the bottom of the third front metal layer (16) is in contact with the third P-type diffusion region (12) and the third N-type diffusion region (13).

2. The bidirectional low-residual voltage SCR device structure for ESD protection according to claim 1, characterized in that: On the isolation layer (2), lead holes corresponding to the first P-type diffusion region (8), the first N-type diffusion region (9), the second P-type diffusion region (10), the second N-type diffusion region (11), the third P-type diffusion region (12), and the third N-type diffusion region (13) are opened; The bottom of the first front metal layer (14) passes through the isolation layer (2) through the lead hole and is in contact with the first P-type diffusion region (8) and the first N-type diffusion region (9) to serve as the GND of the SCR device structure; the bottom of the second front metal layer (15) passes through the isolation layer (2) through the lead hole and is in contact with the second P-type diffusion region (10) and the second N-type diffusion region (11) to serve as the IO of the SCR device structure; the bottom of the third front metal layer (16) passes through the isolation layer (2) through the lead hole and is in contact with the third P-type diffusion region (12) and the third N-type diffusion region (13) to serve as the GND of the SCR device structure.

3. The bidirectional low-residual voltage SCR device structure for ESD protection according to claim 1, wherein: The material of the P-type substrate (1) is silicon with a <100> crystal orientation and its resistivity is 8 - 20 Ω.cm.

4. The bidirectional low-residual voltage SCR device structure for ESD protection according to claim 1, characterized in that: The doping material of the first P-type well (3), the second P-type well (5) and the third P-type well (7) is boron; the doping material of the first N-type well (4) and the second N-type well (6) is phosphorus.

5. The bidirectional low-residual voltage SCR device structure for ESD protection according to claim 1, characterized in that: The doping material of the first P-type diffusion region (8), the second P-type diffusion region (10), and the third P-type diffusion region (12) is boron; the doping material of the first N-type diffusion region (9), the second N-type diffusion region (11), and the third N-type diffusion region (13) is arsenic.

6. The bidirectional low-residual voltage SCR device structure for ESD protection according to claim 1, characterized in that: The material of the isolation layer (2) is borophosphosilicate glass.

7. The bidirectional low-residual voltage SCR device structure for ESD protection according to claim 1, characterized in that: The first front metal layer (14), the second front metal layer (15), and the third front metal layer (16) are aluminum-silicon alloy layers, and the thickness of the aluminum-silicon alloy is 1.5 - 2 μm.

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