High holding voltage bidirectional scr structure

Abstract

The application provides a high-maintenance-voltage bidirectional SCR structure, which comprises an N-type substrate, a first PWELL region, a second PWELL region, an NWELL region, a first P+ implantation region, a second P+ implantation region, a third P+ implantation region, a fourth P+ implantation region, a fifth P+ implantation region, a sixth P+ implantation region, a first N+ implantation region, a second N+ implantation region, a third N+ implantation region, a first electrode metal line, a first cross-connection metal line, a second cross-connection metal line and a second electrode metal line. The anode current is guided by the cross-connection metal line to enter the cathode, and the current does not pass through the inner surface but passes through the outer body, so that the voltage drop during conduction is increased, the maintenance voltage of the device is improved, the SCR with a completely symmetrical structure design can meet the requirement of bidirectional ESD protection, and the bidirectional electrical parameters are completely consistent.

Description

Technical Field

[0001] This invention belongs to the field of electronic science and technology, and mainly relates to on-chip electrostatic discharge (ESD) protection technology for integrated circuits. Specifically, it relates to a type of bidirectional ESD protection device with strong latch-up resistance. Background Technology

[0002] ESD (Electrical Overstress) is a major cause of electrical overstress (EOS) damage to electronic systems, resulting in permanent damage to electronic products. While most ESD damage is caused by human error, it is difficult to avoid. During the manufacturing, assembly, storage, and handling of electronic products, static electricity accumulates on people, instruments, storage devices, and even the products themselves. When these objects come into contact with electronic components without the user's knowledge, a discharge path is created, leading to damage. Therefore, in addition to strengthening the control of static electricity accumulation during human operation, electronic products themselves must also possess a certain degree of anti-static capability.

[0003] In CMOS integrated circuits, diodes, transistors, MOSFETs, and SCRs can all serve as ESD protection devices, with SCRs capable of withstanding extremely high ESD voltages in a smaller layout area. However, as... Figure 1 As shown, due to the snapback characteristic of SCR, after the ESD stress ends, if the protected port voltage is higher than the SCR's sustaining voltage (V... h If this occurs, the SCR will latch up, causing the original circuit system to malfunction. Therefore, when using an SCR as an ESD protection device, latch-up must be avoided.

[0004] To prevent SCR latch-up, raising its sustaining voltage above the normal operating voltage of the protected port, thus preventing the SCR from maintaining its on-state, is an important research direction in SCR development. Traditional methods for increasing the sustaining voltage can be categorized into three main types: reducing the base transport coefficient of parasitic PNP / NPN transistors, reducing the emitter efficiency of parasitic transistors in the SCR, and embedding other channels. Unlike these three methods, this invention improves the device's sustaining voltage by altering the current distribution when the SCR is on.

[0005] In the protection of some input / output (I / O) ports, bidirectional ESD protection devices are often needed, and the parameters such as on-resistance of two directions should be as same as possible. However, the general SCR is a unidirectional ESD protection device, and the parameters of the device are completely different when used in positive and negative directions. At this time, a bidirectional SCR with symmetrical positive and negative structures is needed. SUMMARY

[0006] The problem to be solved by the present application is: how to design the device structure to change the current distribution when the SCR is turned on, and then improve the holding voltage of the bidirectional SCR under the condition of the process.

[0007] To achieve the above-mentioned application purposes, the technical solutions of the present application are as follows:

[0008] A high holding voltage bidirectional SCR structure comprises: an N-type substrate 01, a first PWELL region 11, a second PWELL region 12, a NWELL region 21, a first P+ implantation region 31, a second P+ implantation region 32, a third P+ implantation region 33, a fourth P+ implantation region 34, a fifth P+ implantation region 35, a sixth P+ implantation region 36, a first N+ implantation region 41, a third N+ implantation region 43, a first electrode metal line 51, a first cross-connection metal line 52, a second cross-connection metal line 53, and a second electrode metal line 54.

[0009] The first P+ injection area 31 is located at the left end of the first PWELL area 11, the third P+ injection area 33 is located at the right end of the first PWELL area 11, the first P+ injection area 31 and the third P+ injection area 33 are connected through the first cross-over metal line 52, the NWELL area 21 is located at the middle of the N-type substrate 01 and is adjacent to the first PWELL area 11, the second PWELL area 12 is located at the right side of the N-type substrate 01 and is adjacent to the NWELL area 21, the third N+ injection area 43 and the fifth P+ injection area 35 are located at the middle of the second PWELL area 12, the third N+ injection area 43 is located at the right side of the fifth P+ injection area 35, the third N+ injection area 43 and the fifth P+ injection area 35 are connected through the second electrode metal line 54 and serve as the second electrode of the device, the fourth P+ injection area 34 and the sixth P+ injection area 36 are located at the two ends of the second PWELL area 12, the fourth P+ injection area 34 is located at the left end, the sixth P+ injection area 36 is located at the right end, and the fourth P+ injection area 34 and the sixth P+ injection area 36 are connected through the second cross-over metal line 53.

[0010] As a preferred mode, the second N+ injection area 42 is located at the middle of the NWELL area 21.

[0011] As a preferred mode, the first P+ injection area 31 is adjacent to the first N+ injection area 41, and the sixth P+ injection area 36 is adjacent to the third N+ injection area 43.

[0012] As a preferred mode, the third P+ injection area 33 is adjacent to the second N+ injection area 42, and the fourth P+ injection area 34 is adjacent to the second N+ injection area 42.

[0013] As a preferred mode, the doping type of each area in the bidirectional SCR structure is changed to the opposite doping type, that is, the P-type doping is changed to N-type doping, and the N-type doping is changed to P-type doping.

[0014] The beneficial effects of the present application are as follows:

[0015] 1. The anode current is guided by the cross-over metal line to take the outside path in the body when entering the cathode, thereby increasing the voltage drop when conducting, that is, improving the maintaining voltage of the device.

[0016] 2. The present application is an SCR with a completely symmetrical structure, which can meet the requirements of bidirectional ESD protection and has completely consistent bidirectional electrical parameters. Attached Figure Description

[0017] Figure 1 A safety design window for conventional ESD devices;

[0018] Figure 2 This is a diagram of a traditional bidirectional SCR structure.

[0019] Figure 3 This is a structural diagram of Example 1;

[0020] Figure 4(a) and Figure 4(b) are schematic diagrams of the working principle of Example 1; wherein, Figure 4(a) is a schematic diagram of the current path before the SCR is turned on; Figure 4(b) is a schematic diagram of the current path when the SCR is turned on;

[0021] Figure 5 This is a structural diagram of Example 2;

[0022] Figure 6 This is a structural diagram of Example 3;

[0023] Figure 7 This is a structural diagram of Example 4;

[0024] Figure 8 This is a comparison chart of the TLP test results of Example 4 and a conventional bidirectional SCR;

[0025] Wherein, 01 is an N-type substrate, 11 is the first PWELL region, 12 is the second PWELL region, 21 is an NWELL region, 31 is the first P+ implantation region, 32 is the second P+ implantation region, 33 is the third P+ implantation region, 34 is the fourth P+ implantation region, 35 is the fifth P+ implantation region, 36 is the sixth P+ implantation region, 41 is the first N+ implantation region, 42 is the second N+ implantation region, 43 is the third N+ implantation region, 51 is the first electrode metal line, 52 is the first bridging metal line, 53 is the second bridging metal line, and 54 is the second electrode metal line. Detailed Implementation

[0026] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0027] Example 1

[0028] like Figure 3As shown, the example provides a high holding voltage bidirectional SCR structure, comprising: an N-type substrate 01, a first P-well region 11, a second P-well region 12, a N-well region 21, a first P+ implantation region 31, a second P+ implantation region 32, a third P+ implantation region 33, a fourth P+ implantation region 34, a fifth P+ implantation region 35, a sixth P+ implantation region 36, a first N+ implantation region 41, a second N+ implantation region 42, a third N+ implantation region 43, a first electrode metal line 51, a first jumper metal line 52, a second jumper metal line 53, a second electrode metal line 54.

[0029] Wherein, the first P-well region 11 is located at the left side of the N-type substrate 01, the first N+ implantation region 41 and the second P+ implantation region 32 are arranged in the middle of the first P-well region 11, the first N+ implantation region 41 is located at the left side of the second P+ implantation region 32, the first N+ implantation region 41 and the second P+ implantation region 32 are connected by the first electrode metal line 51 and serve as the first electrode of the device, the first P+ implantation region 31 and the third P+ implantation region 33 are arranged at the left end and the right end of the first P-well region 11 respectively, the first P+ implantation region 31 is located at the left end, the third P+ implantation region 33 is located at the right end, and the first P+ implantation region 31 and the third P+ implantation region 33 are connected by the first jumper metal line 52; the N-well region 21 is located in the middle of the N-type substrate 01 and is adjacent to the first P-well region 11, and the second N+ implantation region 42 is arranged in the N-well region 21; the second P-well region 12 is located at the right side of the N-type substrate 01 and is adjacent to the N-well region 21, the third N+ implantation region 43 and the fifth P+ implantation region 35 are arranged in the middle of the second P-well region 12, the third N+ implantation region 43 is located at the right side of the fifth P+ implantation region 35, the third N+ implantation region 43 and the fifth P+ implantation region 35 are connected by the second electrode metal line 54 and serve as the second electrode of the device, the fourth P+ implantation region 34 and the sixth P+ implantation region 36 are arranged at the left end and the right end of the second P-well region 12 respectively, the fourth P+ implantation region 34 is located at the left end, the sixth P+ implantation region 36 is located at the right end, and the fourth P+ implantation region 34 and the sixth P+ implantation region 36 are connected by the second jumper metal line 53.

[0030] The working principle of the example is as follows:

[0031] As shown in Figure 4(a), taking the first electrode metal line 51 as the anode and the second electrode metal line 54 as the cathode as an example, since the distance from the fourth P+ injection region 34 to the fifth P+ injection region 35 is greater than the distance from the sixth P+ injection region 36 to the fifth P+ injection region 35, when the ESD voltage is small, the current path is: first electrode metal line 51, second P+ injection region 32, first PWELL region 11, third P+ injection region 33, first PWELL region 11, second N+ injection region 42, second PWELL region 12, fourth P+ injection region 34, second bridging metal line 53, sixth P+ injection region 36, second PWELL region 12, fifth P+ injection region 35, second electrode metal line 54.

[0032] As shown in Figure 4(b), with the increase of ESD voltage, the voltage drop from the sixth P+ injection region 36 to the fifth P+ injection region 35 will also increase. When it increases to about 0.7V, the diode formed by the second PWELL region 12 and the third N+ injection region 43 will turn on, and the current path will become: first electrode metal line 51, second P+ injection region 32, first PWELL region 11, third P+ injection region 33, first PWELL region 11, second N+ injection region 42, second PWELL region 12, fourth P+ injection region 34, second bridging metal line 53, sixth P+ injection region 36, second PWELL region 12, third N+ injection region 43, second electrode metal line 54. Subsequently, with further increases in current, the SCR will turn on.

[0033] In traditional SCRs, the current is concentrated on the surface when initially turned on, following the shortest path. A relatively small voltage is sufficient to maintain the turn-on current. However, in this example SCR, the ESD current has a long path within the base region of the cathode parasitic NPN transistor, resulting in a larger voltage drop. Therefore, the entire device requires a higher voltage to maintain the turn-on current, meaning the holding voltage is increased. In other words, traditional SCRs, due to the surface "shortcut," concentrate the current along this path during initial conduction, resulting in a very small device voltage. This example SCR lacks this "shortcut," forcing a higher voltage to maintain the turn-on state.

[0034] Example 2

[0035] like Figure 5 As shown, the difference between the device structure in this embodiment and that in embodiment 1 is that the first P+ injection region 31 is adjacent to the first N+ injection region 41, and the sixth P+ injection region 36 is adjacent to the third N+ injection region 43.

[0036] The working principle of this example is largely the same as that of Example 1. The difference is that, taking the first electrode metal wire 51 as the anode and the second electrode metal wire 54 as the cathode as an example, the current flowing into the cathode is divided into the right current guided by the bridging metal wire and the left current of the conventional path. Since the sixth P+ injection region 36 is closer to the fifth P+ injection region 35, the right current accounts for a larger proportion, and the design concept of the present invention is better reflected, which can further increase the holding voltage.

[0037] Example 3

[0038] like Figure 6 As shown, the difference between the device structure in this embodiment and that in embodiment 1 is that there is no second N+ injection region 42.

[0039] The working principle of this example is largely the same as that of Example 1. The difference is that, taking the first electrode metal line 51 as the anode and the second electrode metal line 54 as the cathode as an example, after removing the second N+ injection region 42, the original single-sided abrupt junction composed of the second N+ injection region 42 and the second PWELL region 12 becomes a PN junction composed of the NWELL region 21 and the second PWELL region 12. The avalanche breakdown voltage of this PN junction is significantly increased, which can increase the trigger voltage of the device.

[0040] Example 4

[0041] like Figure 7 As shown, the difference between the device structure in this embodiment and that in embodiment 1 is that the third P+ injection region 33 is adjacent to the second N+ injection region 42, and the fourth P+ injection region 34 is adjacent to the second N+ injection region 42.

[0042] The working principle of this example is largely the same as that of Example 1. The difference is that, taking the first electrode metal line 51 as the anode and the second electrode metal line 54 as the cathode as an example, compared with the PN junction composed of the second PWELL region 12 and the second N+ implantation region 42 in Example 1, the PN junction composed of the fourth P+ implantation region 34 and the second N+ implantation region 42 in this example has a higher P-region doping concentration and a smaller avalanche breakdown voltage, which can reduce the trigger voltage of the device.

[0043] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can 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 those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A high holding voltage bidirectional SCR structure, characterized by, Comprise: N-type substrate (01), first PWELL region (11), second PWELL region (12), NWELL region (21), first P+ implantation region (31), second P+ implantation region (32), third P+ implantation region (33), fourth P+ implantation region (34), fifth P+ implantation region (35), sixth P+ implantation region (36), first N+ implantation region (41), third N+ implantation region (43), first electrode metal line (51), first cross-connection metal line (52), second cross-connection metal line (53), second electrode metal line (54); Wherein, the first PWELL region (11) is located in the N-type substrate (01) on the left side, the first N+ implantation region (41) and the second P+ implantation region (32) are arranged in the first PWELL region (11) on the top middle part, the first N+ implantation region (41) is on the left side of the second P+ implantation region (32), the first N+ implantation region (41) and the second P+ implantation region (32) are connected by the first electrode metal line (51) and serve as the first electrode of the device, the first P+ implantation region (31) and the third P+ implantation region (33) are arranged in the first PWELL region (11) on the top two ends, the first P+ implantation region (31) is on the left end, the third P+ implantation region (33) is on the right end, and the first P+ implantation region (31) and the third P+ implantation region (33) are connected by the first cross-connection metal line (52); the NWELL region (21) is located in the N-type substrate (01) on the top middle part and is adjacent to the first PWELL region (11), the second PWELL region (12) is located in the N-type substrate (01) on the right side and is adjacent to the NWELL region (21), the third N+ implantation region (43) and the fifth P+ implantation region (35) are arranged in the second PWELL region (12) on the top middle part, the third N+ implantation region (43) is on the right side of the fifth P+ implantation region (35), the third N+ implantation region (43) and the fifth P+ implantation region (35) are connected by the second electrode metal line (54) and serve as the second electrode of the device, the fourth P+ implantation region (34) and the sixth P+ implantation region (36) are arranged in the second PWELL region (12) on the top two ends, the fourth P+ implantation region (34) is on the left end, the sixth P+ implantation region (36) is on the right end, and the fourth P+ implantation region (34) and the sixth P+ implantation region (36) are connected by the second cross-connection metal line (53).

2. The high-sustaining voltage bi-directional SCR structure of claim 1, wherein: The second N+ implantation region (42) is arranged in the NWELL region (21) on the top.

3. The high-sustaining voltage bi-directional SCR structure of claim 2, wherein: The first P+ implantation region (31) is adjacent to the first N+ implantation region (41), and the sixth P+ implantation region (36) is adjacent to the third N+ implantation region (43).

4. The high-sustaining voltage bi-directional SCR structure of claim 2, wherein: The third P+ implantation region (33) is adjacent to the second N+ implantation region (42), and the fourth P+ implantation region (34) is adjacent to the second N+ implantation region (42).

5. The high-sustaining voltage bidirectional SCR structure according to any one of claims 1 to 4, characterized in that: Each doping type is changed to the opposite doping, that is, the P-type doping is changed to the N-type doping, and the N-type doping is changed to the P-type doping.

Images