Isolation structure and forming method thereof

Abstract

The invention provides an isolation structure and a forming method thereof. Deep trench isolation penetrates through a P-type epitaxial layer and goes deep into a P-type substrate. And the P-type injection region at the bottom of the deep trench isolation plays a role in preventing the N-type regions on the two sides from penetrating through. The P-type buried layer, the P well and the P-type heavily doped region are formed between the two deep trench isolations, and the P-type heavily doped region is led out from the surface of the substrate between the two deep trench isolations, so that the P-type substrate is always kept at zero potential. According to the invention, the holding voltage Vhold (measuring the NPN opening level) is improved, the breakdown voltage and the current for triggering the NPN opening are improved, the NPN opening is inhibited, and the application of the deep trench isolation structure when the P-type substrate is suspended is satisfied.

Description

Technical Field

[0001] The present invention belongs to the technical field of integrated circuit manufacturing, and in particular relates to an isolation structure and a forming method thereof. Background Art

[0002] Deep trench isolation is an isolation technology used in integrated circuit manufacturing. It uses photolithography and etching techniques to form deep trenches that usually reach the silicon substrate, effectively preventing crosstalk and leakage between devices and achieving higher density device layout.

[0003] Figure 1 To improve the previous deep trench isolation structure, such as Figure 1 As shown, the deep trench isolation 106 penetrates through the P-type epitaxial layer 103 and goes deep into the P-type substrate 101. The P-type implantation region 107 at the bottom of the deep trench isolation 106 plays a role in preventing the N-type regions on both sides from punching through. The N-wells 108 on both sides of the deep trench isolation 106 are led out through the N-type heavily doped regions 110. For example, the N-type heavily doped region 110 on the right side is connected to a high potential, and the N-type heavily doped region 110 on the left side is connected to a low potential.

[0004] Since the deep trench isolation structure needs to meet the working requirement of the P-type substrate 101 being suspended, if the P-type substrate 101 is suspended, the bipolar junction transistor (N-type buried layer 102a / P-type substrate 101 / N-type buried layer 102a) is easily turned on, resulting in isolation failure. If the concentration of the P-type injection region 107 at the bottom of the deep trench isolation 106 is increased to suppress the NPN from turning on, the PN junction breakdown voltage of the deep trench isolation will be reduced. Summary of the invention

[0005] The purpose of the present invention is to provide a method for forming an isolation structure, by forming a P-type buried layer, a P-well and a P-type heavily doped region between two deep trench isolations, and leading out a P-type heavily doped region on the substrate surface between the two deep trench isolations, that is, keeping the P-type substrate at zero potential all the time. The present invention improves the holding voltage V hold (measure of NPN turn-on level), breakdown voltage and current that triggers NPN turn-on, which inhibits NPN turn-on and satisfies the application of deep trench isolation structure when the P-type substrate is suspended.

[0006] The present invention provides a method for forming an isolation structure, comprising:

[0007] Providing a P-type substrate, forming a P-type buried layer located in the middle of the P-type substrate near the upper surface area, and N-type buried layers located on both sides of the P-type buried layer; forming a P-type epitaxial layer covering the P-type buried layer and the N-type buried layer;

[0008] Selectively injecting N-type impurities into the P-type epitaxial layer to form two N-type deep wells located directly above the N-type buried layer on both sides;

[0009] Forming shallow trench isolation, forming a shallow trench isolation at the junction area between the middle P-type epitaxial layer and the N-type deep wells on both sides and close to the upper surface of the P-type epitaxial layer;

[0010] Deep trench isolations are formed, wherein two deep trench isolations respectively penetrate the shallow trench isolation, the boundary regions between the P-type epitaxial layer in the middle and the N-type deep wells on both sides, the boundary regions between the P-type buried layer in the middle and the N-type buried layers on both sides, and the P-type substrate at a certain depth below; a P-type implantation region is formed at the bottom of each deep trench isolation;

[0011] forming an N-well and a P-well, wherein the P-well is located in an upper region of the P-type epitaxial layer between the two deep trench isolations;

[0012] Source and drain ion implantation is performed to form an N-type heavily doped region and a P-type heavily doped region, wherein the P-type heavily doped region is located in an upper region of the P well.

[0013] Furthermore, the two N-wells are respectively located in upper regions of the N-type deep wells on one side of the two shallow trench isolations away from the P-well, and the N-wells are adjacent to the shallow trench isolations.

[0014] Furthermore, the depth of the N-well is greater than the depth of the shallow trench isolation, the depth of the P-well is greater than the depth of the shallow trench isolation, and the depth of the N-well is the same as the depth of the P-well 109 .

[0015] Furthermore, the two N-type heavily doped regions are respectively located in upper regions of the two N-wells.

[0016] Furthermore, the depth of the N-type heavily doped region is less than the depth of the N-well, and the doping concentration of the N-type heavily doped region is greater than the doping concentration of the N-well.

[0017] Furthermore, the N-type regions on both sides of the deep trench isolation are led out through the N-type heavily doped region, the N-type heavily doped region on one side is connected to a high potential, and the N-type heavily doped region on the other side is connected to a low potential.

[0018] The present invention also provides an isolation structure, comprising:

[0019] A P-type substrate, wherein a P-type buried layer is formed in the middle of the P-type substrate near the upper surface, and N-type buried layers are formed on both sides of the P-type buried layer;

[0020] A P-type epitaxial layer, wherein the P-type epitaxial layer covers the P-type buried layer and the N-type buried layer;

[0021] N-type deep wells are respectively formed in the P-type epitaxial layer directly above the N-type buried layers on both sides;

[0022] Shallow trench isolation, wherein a shallow trench isolation is formed at the junction area between the middle P-type epitaxial layer and the N-type deep wells on both sides and close to the upper surface of the P-type epitaxial layer;

[0023] Deep trench isolation, wherein two deep trench isolations respectively penetrate the shallow trench isolation, the boundary area between the P-type epitaxial layer in the middle and the N-type deep wells on both sides, the boundary area between the P-type buried layer in the middle and the N-type buried layers on both sides, and the P-type substrate at a certain depth below; a P-type implantation area is formed at the bottom of each deep trench isolation;

[0024] An N-well and a P-well, wherein the P-well is located in an upper region of the P-type epitaxial layer between the two deep trench isolations;

[0025] An N-type heavily doped region and a P-type heavily doped region, wherein the P-type heavily doped region is located in an upper region of the P well.

[0026] Furthermore, the two N-wells are respectively located in upper regions of the N-type deep wells on one side of the two shallow trench isolations away from the P-well, and the N-wells are adjacent to the shallow trench isolations.

[0027] Furthermore, the two N-type heavily doped regions are respectively located in upper regions of the two N-wells.

[0028] Furthermore, the N-type regions on both sides of the deep trench isolation are led out through the N-type heavily doped region, the N-type heavily doped region on one side is connected to a high potential, and the N-type heavily doped region on the other side is connected to a low potential.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] The present invention provides an isolation structure and a method for forming the same. The method comprises: providing a P-type substrate, forming a P-type buried layer in the middle and an N-type buried layer on both sides of the P-type buried layer in a region close to the upper surface of the P-type substrate; forming a P-type epitaxial layer covering the P-type buried layer and the N-type buried layer; selectively injecting N-type impurities into the P-type epitaxial layer to form two N-type deep wells located directly above the N-type buried layer on both sides; forming shallow trench isolation, forming a shallow trench isolation in the boundary region between the middle P-type epitaxial layer and the N-type deep wells on both sides and close to the upper surface of the P-type epitaxial layer; forming a deep trench isolation; Isolation, two deep trench isolations penetrate the shallow trench isolation, the boundary area between the middle P-type epitaxial layer and the N-type deep wells on both sides, the boundary area between the middle P-type buried layer and the N-type buried layer on both sides, and the P-type substrate at a certain depth below from top to bottom; a P-type injection region is formed at the bottom of each deep trench isolation; an N-well and a P-well are formed, and the P-well is located in the upper area of ​​the P-type epitaxial layer between the two deep trench isolations; source and drain ion implantation is performed to form an N-type heavily doped region and a P-type heavily doped region, and the P-type heavily doped region is located in the upper area of ​​the P-well.

[0031] The present invention provides an isolation structure and a method for forming the same. A deep trench isolation penetrates through a P-type epitaxial layer and penetrates into a P-type substrate. The P-type injection region at the bottom of the deep trench isolation prevents the N-type regions on both sides from punching through. The N-type regions on both sides of the deep trench isolation are led out through N-type heavily doped regions. The N-type heavily doped region on one side is connected to a high potential, and the N-type heavily doped region on the other side is connected to a low potential. The present invention forms a P-type buried layer, a P-well and a P-type heavily doped region between two deep trench isolations, and leads out a P-type heavily doped region on the substrate surface between the two deep trench isolations, that is, keeps the P-type substrate at zero potential at all times. The present invention improves the holding voltage V hold (measure of NPN turn-on level), breakdown voltage and current that triggers NPN turn-on, which inhibits NPN turn-on and satisfies the application of deep trench isolation structure when the P-type substrate is suspended. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 This is a schematic diagram of an isolation structure before improvement.

[0033] Figure 2 Schematic diagram of a method for forming an isolation structure according to an embodiment of the present invention.

[0034] Figure 3 It is a schematic diagram of the isolation structure after forming a P-type epitaxial layer according to an embodiment of the present invention.

[0035] Figure 4 It is a schematic diagram of an isolation structure after forming an N-type deep well according to an embodiment of the present invention.

[0036] Figure 5 It is a schematic diagram of the isolation structure after shallow trench isolation is formed according to the embodiment of the present invention.

[0037] Figure 6 It is a schematic diagram of the isolation structure after forming deep trench isolation according to an embodiment of the present invention.

[0038] Figure 7 It is a schematic diagram of the isolation structure after forming an N-well according to an embodiment of the present invention.

[0039] Figure 8 It is a schematic diagram of the isolation structure after forming the N-type heavily doped region and the P-type heavily doped region according to the embodiment of the present invention.

[0040] Fig. 9 Schematic diagram of the comparison of the isolation structure voltage before and after improvement.

[0041] The reference numerals are as follows:

[0042] 101-P-type substrate; 102a-N-type buried layer; 102b-P-type buried layer; 103-P-type epitaxial layer; 104-N-type deep well; 105-shallow trench isolation; 106-deep trench isolation; 107-P-type implantation region; 108-N-well; 109-P-well; 110-N-type heavily doped region; 111-P-type heavily doped region. DETAILED DESCRIPTION

[0043] The present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. The advantages and features of the present invention will become more apparent from the following description. It should be noted that the accompanying drawings are in a very simplified form and use an inaccurate scale, which is only used to conveniently and clearly assist in explaining the purpose of the embodiments of the present invention.

[0044] For ease of description, some embodiments of the present application may use spatially relative terms such as "above", "below", "top", "below", etc. to describe the relationship between one element or component and another (or other) elements or components as shown in the various figures of the embodiments. It should be understood that in addition to the orientations described in the drawings, the spatially relative terms are also intended to include different orientations of the device in use or operation. For example, if the device in the drawings is turned over, the elements or components described as being "below" or "below" other elements or components will subsequently be positioned as being "above" or "above" other elements or components. The terms "first", "second", etc. below are used to distinguish between similar elements and are not necessarily used to describe a specific order or time sequence. It is to be understood that these terms used in this way are interchangeable where appropriate.

[0045] The embodiment of the present invention provides a method for forming an isolation structure, such as Figure 2 As shown, including:

[0046] S1. Provide a P-type substrate, form a P-type buried layer in the middle and N-type buried layers on both sides of the P-type buried layer in a region close to an upper surface of the P-type substrate, and form a P-type epitaxial layer covering the P-type buried layer and the N-type buried layer;

[0047] S2, selectively injecting N-type impurities into the P-type epitaxial layer to form two N-type deep wells located directly above the N-type buried layers on both sides;

[0048] S3, forming shallow trench isolation, forming a shallow trench isolation at the junction area between the middle P-type epitaxial layer and the N-type deep wells on both sides and close to the upper surface of the P-type epitaxial layer;

[0049] S4, forming deep trench isolations, wherein two deep trench isolations respectively penetrate the shallow trench isolation, the boundary region between the middle P-type epitaxial layer and the N-type deep wells on both sides, the boundary region between the middle P-type buried layer and the N-type buried layers on both sides, and the P-type substrate at a certain depth below, from top to bottom; a P-type implantation region is formed at the bottom of each deep trench isolation;

[0050] S5, forming an N-well and a P-well, wherein the P-well is located in an upper region of the P-type epitaxial layer between two deep trench isolations;

[0051] S6. Perform source and drain ion implantation to form an N-type heavily doped region and a P-type heavily doped region, wherein the P-type heavily doped region is located in an upper region of the P well.

[0052] Combine the following Figures 3 to 9 Each step of the method for forming an isolation structure according to an embodiment of the present invention is described in detail.

[0053] Step S1: Figure 3 As shown, N-type impurity injection and P-type impurity injection are performed in the P-type substrate 101 near the upper surface area to form a P-type buried layer 102b located in the middle and an N-type buried layer 102a located on both sides of the P-type buried layer 102b, and then a P-type epitaxial layer 103 is grown, and the P-type epitaxial layer 103 covers the P-type buried layer 102b and the N-type buried layer 102a.

[0054] The material of the P-type substrate 101 can be single crystal silicon doped with P-type impurities, silicon on insulator (SOI), stacked silicon on insulator (SSOI), stacked silicon germanium on insulator (S-SiGeOI), silicon germanium on insulator (SiGeOI) and germanium on insulator (GeOI), etc., and can also be at least one of the following materials: Si, Ge, SiGe, SiC, SiGeC, InAs, GaAs, InP or other III / V compound semiconductors.

[0055] Step S2: Figure 4As shown, N-type impurities are selectively implanted into the P-type epitaxial layer 103 to form an N-type deep well 104, which is respectively located in the P-type epitaxial layer 103 directly above the N-type buried layer 102a on both sides of the P-type buried layer 102b.

[0056] Step S3: Figure 5 As shown, shallow trench isolation 105 is formed by active area lithography, etching and filling processes; one shallow trench isolation 105 is located at the junction area between the middle P-type epitaxial layer 103 and the N-type deep well 104 on the left, close to the upper surface of the P-type epitaxial layer 103; the other shallow trench isolation 105 is located at the junction area between the middle P-type epitaxial layer 103 and the N-type deep well 104 on the right, close to the upper surface of the P-type epitaxial layer 103.

[0057] Step S4: Figure 6 As shown, a high aspect ratio deep trench is etched, and P-type impurities are firstly injected into the bottom of the deep trench to form a P-type injection region 107, and then the trench is filled to form a deep trench isolation 106. One of the deep trenches sequentially penetrates the shallow trench isolation 105, the boundary region between the middle P-type epitaxial layer 103 and the left N-type deep well 104, the boundary region between the middle P-type buried layer 102b and the left N-type buried layer 102a, and the P-type substrate 101 at a certain depth from top to bottom in a direction perpendicular to the P-type substrate 101; the other deep trench sequentially penetrates the shallow trench isolation 105, the boundary region between the middle P-type epitaxial layer 103 and the right N-type deep well 104, the boundary region between the middle P-type buried layer 102b and the right N-type buried layer 102a, and the P-type substrate 101 at a certain depth from top to bottom.

[0058] Step S5: Figure 7 As shown, the well implantation region is opened by photolithography to form an N-well 108 and a P-well 109. The P-well 109 is located in the upper region of the P-type epitaxial layer 103 between the two deep trench isolations 106. The N-well 108 is located in the upper region of the N-type deep well 104 on the side of the two shallow trench isolations 105 away from the P-well 109, and the N-well 108 is adjacent to the shallow trench isolation 105. The depth of the N-well 108 is greater than the depth of the shallow trench isolation 105, and the depth of the P-well 109 is greater than the depth of the shallow trench isolation 105. The depth of the N-well 108 is approximately the same as the depth of the P-well 109.

[0059] Step S6: Figure 8As shown, source and drain ion implantation is selectively performed to form an N-type heavily doped region 110 and a P-type heavily doped region 111. The P-type heavily doped region 111 is located in the upper region of the P-well 109. The depth of the P-type heavily doped region 111 is less than the depth of the P-well 109. The doping concentration of the P-type heavily doped region 111 is greater than the doping concentration of the P-well 109. The N-type heavily doped region 110 is located in the upper region of the N-well 108. The depth of the N-type heavily doped region 110 is less than the depth of the N-well 108. The doping concentration of the N-type heavily doped region 110 is greater than the doping concentration of the N-well 108.

[0060] The method for forming the isolation structure provided by the present invention is as follows: Figure 8 As shown, the deep trench isolation 106 penetrates through the P-type epitaxial layer 103 and goes deep into the P-type substrate 101. The P-type implantation region 107 at the bottom of the deep trench isolation 106 prevents the N-type regions on both sides from punching through. The N-type regions on both sides of the deep trench isolation 106 are led out through the N-type heavily doped region 110. For example, the N-type heavily doped region 110 on the right is connected to a high potential, and the N-type heavily doped region 110 on the left is connected to a low potential.

[0061] The present invention forms a P-type buried layer 102b, a P-well 109 and a P-type heavily doped region 111 between two deep trench isolations 106, and leads the P-type heavily doped region 111 on the substrate surface between the two deep trench isolations 106, that is, the P-type substrate is always kept at zero potential. Fig. 9 As shown, the isolation structure before improvement maintains the voltage V hold The solid line represents the NPN turn-on level, and the dotted line represents the holding voltage of the improved isolation structure. The present invention improves the holding voltage, breakdown voltage and current that triggers the NPN turn-on, suppresses the NPN turn-on, and satisfies the application of the deep trench isolation structure when the P-type substrate is suspended.

[0062] The present invention also provides an isolation structure, such as Figure 8 As shown, including:

[0063] A P-type substrate 101, wherein a P-type buried layer 102b is formed in the middle of the P-type substrate 101 near the upper surface thereof, and N-type buried layers 102a are formed on both sides of the P-type buried layer 102b;

[0064] A P-type epitaxial layer 103, the P-type epitaxial layer 103 covers the P-type buried layer 102b and the N-type buried layer 102a;

[0065] Two N-type deep wells 104 are formed in the P-type epitaxial layer 103 directly above the N-type buried layers 102a on both sides;

[0066] Shallow trench isolation 105, a shallow trench isolation 105 is formed at the junction area between the middle P-type epitaxial layer 103 and the N-type deep wells 104 on both sides and close to the upper surface of the P-type epitaxial layer 103;

[0067] Deep trench isolation 106, two deep trench isolations 106 respectively penetrate the shallow trench isolation 105, the boundary area between the middle P-type epitaxial layer 103 and the N-type deep wells 104 on both sides, the boundary area between the middle P-type buried layer 102b and the N-type buried layers 102a on both sides, and the P-type substrate 101 at a certain depth below; a P-type implantation region 107 is formed at the bottom of each deep trench isolation 106;

[0068] N-well 108 and P-well 109 , where the P-well 109 is located in the upper region of the P-type epitaxial layer 103 between the two deep trench isolations 106 ;

[0069] An N-type heavily doped region 110 and a P-type heavily doped region 111 , wherein the P-type heavily doped region 111 is located in an upper region of the P-well 109 .

[0070] The two N-wells 108 are respectively located in the upper region of the N-type deep well 104 on the side of the two shallow trench isolations 105 away from the P-well 109, and the N-well 108 is adjacent to the shallow trench isolations 105. The two N-type heavily doped regions 110 are respectively located in the upper region of the two N-wells 108.

[0071] The N-type regions on both sides of the deep trench isolation 106 are led out through the N-type heavily doped regions 110 . The N-type heavily doped region 110 on one side is connected to a high potential, and the N-type heavily doped region 110 on the other side is connected to a low potential.

[0072] In summary, the present invention provides an isolation structure and a method for forming the same, wherein the deep trench isolation penetrates through the P-type epitaxial layer and penetrates into the P-type substrate. The P-type injection region at the bottom of the deep trench isolation prevents the N-type regions on both sides from punching through. The present invention forms a P-type buried layer, a P-well and a P-type heavily doped region between two deep trench isolations, and leads out a P-type heavily doped region on the substrate surface between the two deep trench isolations, that is, keeps the P-type substrate at zero potential at all times. The present invention improves the holding voltage V hold (measure of NPN turn-on level), breakdown voltage and current that triggers NPN turn-on, which inhibits NPN turn-on and satisfies the application of deep trench isolation structure when the P-type substrate is suspended.

[0073] In this specification, each embodiment is described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the embodiments can be referred to each other. For the method disclosed in the embodiment, since it corresponds to the device disclosed in the embodiment, the description is relatively simple, and the relevant parts can be referred to the method part description.

[0074] The above description is only a description of the preferred embodiment of the present invention, and is not any limitation on the scope of rights of the present invention. Any technical personnel in this field can make possible changes and modifications to the technical solution of the present invention by using the methods and technical contents disclosed above without departing from the spirit and scope of the present invention. Therefore, any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention shall fall within the protection scope of the technical solution of the present invention.

Claims

1. A method for forming an isolation structure, characterized in that: include: Providing a P-type substrate, forming a P-type buried layer located in the middle of the P-type substrate near the upper surface area, and N-type buried layers located on both sides of the P-type buried layer; forming a P-type epitaxial layer covering the P-type buried layer and the N-type buried layer; Selectively injecting N-type impurities into the P-type epitaxial layer to form two N-type deep wells located directly above the N-type buried layer on both sides; Forming shallow trench isolation, forming a shallow trench isolation at the junction area between the middle P-type epitaxial layer and the N-type deep wells on both sides and close to the upper surface of the P-type epitaxial layer; Deep trench isolations are formed, wherein two deep trench isolations respectively penetrate the shallow trench isolation, the boundary regions between the P-type epitaxial layer in the middle and the N-type deep wells on both sides, the boundary regions between the P-type buried layer in the middle and the N-type buried layers on both sides, and the P-type substrate at a certain depth below; a P-type implantation region is formed at the bottom of each deep trench isolation; forming an N-well and a P-well, wherein the P-well is located in an upper region of the P-type epitaxial layer between the two deep trench isolations; Source and drain ion implantation is performed to form an N-type heavily doped region and a P-type heavily doped region, wherein the P-type heavily doped region is located in an upper region of the P well.

2. The method for forming an isolation structure according to claim 1, wherein: The two N-wells are respectively located in upper regions of the N-type deep wells on one side of the two shallow trench isolations away from the P-well, and the N-wells are adjacent to the shallow trench isolations.

3. The method for forming an isolation structure according to claim 2, wherein: The depth of the N-well is greater than the depth of the shallow trench isolation, the depth of the P-well is greater than the depth of the shallow trench isolation, and the depth of the N-well is the same as the depth of the P-well.

4. The method for forming an isolation structure according to claim 1, wherein: The two N-type heavily doped regions are respectively located in upper regions of the two N-wells.

5. The method for forming an isolation structure according to claim 4, wherein: The depth of the N-type heavily doped region is less than the depth of the N-well, and the doping concentration of the N-type heavily doped region is greater than the doping concentration of the N-well.

6. The method for forming an isolation structure according to claim 4, wherein: The N-type regions on both sides of the deep trench isolation are led out through the N-type heavily doped region, the N-type heavily doped region on one side is connected to a high potential, and the N-type heavily doped region on the other side is connected to a low potential.

7. An isolation structure, characterized in that: include: A P-type substrate, wherein a P-type buried layer is formed in the middle of the P-type substrate near the upper surface, and N-type buried layers are formed on both sides of the P-type buried layer; A P-type epitaxial layer, wherein the P-type epitaxial layer covers the P-type buried layer and the N-type buried layer; N-type deep wells are respectively formed in the P-type epitaxial layer directly above the N-type buried layers on both sides; Shallow trench isolation, wherein a shallow trench isolation is formed at the junction area between the middle P-type epitaxial layer and the N-type deep wells on both sides and close to the upper surface of the P-type epitaxial layer; Deep trench isolation, wherein two deep trench isolations respectively penetrate the shallow trench isolation, the boundary area between the P-type epitaxial layer in the middle and the N-type deep wells on both sides, the boundary area between the P-type buried layer in the middle and the N-type buried layers on both sides, and the P-type substrate at a certain depth below; a P-type implantation area is formed at the bottom of each deep trench isolation; An N-well and a P-well, wherein the P-well is located in an upper region of the P-type epitaxial layer between the two deep trench isolations; An N-type heavily doped region and a P-type heavily doped region, wherein the P-type heavily doped region is located in an upper region of the P well.

8. The isolation structure according to claim 7, characterized in that: The two N-wells are respectively located in upper regions of the N-type deep wells on one side of the two shallow trench isolations away from the P-well, and the N-wells are adjacent to the shallow trench isolations.

9. The isolation structure according to claim 8, characterized in that: The two N-type heavily doped regions are respectively located in upper regions of the two N-wells.

10. The isolation structure according to claim 7, characterized in that: The N-type regions on both sides of the deep trench isolation are led out through the N-type heavily doped region, the N-type heavily doped region on one side is connected to a high potential, and the N-type heavily doped region on the other side is connected to a low potential.

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