阅读说明：本技术 Jfet器件及其制作方法 (JFET device and manufacturing method thereof ) 是由 韩天宇 许昭昭 于 2021-07-07 设计创作，主要内容包括：本申请公开了一种JFET器件及其制作方法,涉及半导体制造领域。该JFET器件包括衬底；位于衬底上的外延层；位于外延层中的隔离结构、第一类阱、第二类阱、第一类掺杂区域、第二类掺杂区域,第一类掺杂区域位于第二类阱中且第一类掺杂区域靠近第二类阱的边缘,第二类掺杂区域位于第一类阱中且第二类掺杂区域靠近第二类阱的边缘；场板结构及第二类重掺杂区、第一类重掺杂区；位于第一类重掺杂区、第二类重掺杂区和场板结构顶部的金属电极；解决了目前BCD工艺平台中制作的JFET器件的电学参数不满足器件需求的问题；达到了优化BCD工艺平台制作的JFET器件的击穿电压和阈值电压,优化JFET器件性能的效果。(The application discloses a JFET device and a manufacturing method thereof, and relates to the field of semiconductor manufacturing. The JFET device comprises a substrate; an epitaxial layer on the substrate; the epitaxial layer comprises an isolation structure, a first type well, a second type well, a first type doping region and a second type doping region, wherein the isolation structure, the first type well, the second type well, the first type doping region and the second type doping region are positioned in the epitaxial layer; the field plate structure, the second-class heavily doped region and the first-class heavily doped region; the metal electrodes are positioned at the top of the first type heavily doped region, the second type heavily doped region and the field plate structure; the problem that the electrical parameters of the JFET device manufactured in the conventional BCD process platform cannot meet the requirements of the device is solved; the effects of optimizing the breakdown voltage and the threshold voltage of the JFET device manufactured by the BCD process platform and optimizing the performance of the JFET device are achieved.)

1. A JFET device, comprising:

a substrate;

an epitaxial layer on the substrate;

the epitaxial layer comprises an isolation structure, a first-class well, a second-class well, a first-class doped region and a second-class doped region, wherein the isolation structure, the first-class well, the second-class well, the first-class doped region and the second-class doped region are positioned in the epitaxial layer, the second-class well is surrounded by the first-class well, the first-class doped region is positioned in the second-class well and is close to the edge of the second-class well, and the second-class doped region is positioned in the first-class well and is close to the edge of the second-class well;

a field plate structure covering the first type of doped region and the isolation structure within the first type of doped region;

a second type heavily doped region is formed in the second type well and the epitaxial layer, and a first type heavily doped region is formed in the second type doped region;

and the metal electrodes are positioned at the top of the first type heavily doped region, the second type heavily doped region and the field plate structure.

2. The JFET device of claim 1, further comprising a second type of auxiliary well, the second type of auxiliary well being located in the second type of well, the second type of auxiliary well having a doping concentration greater than a doping concentration of the second type of well.

3. The JFET device of claim 1 or 2, wherein the field plate structure is comprised of an oxide layer, a polysilicon layer.

4. The JFET device of claim 3, wherein the polysilicon layer in the field plate structure is a doped polysilicon layer.

5. The JFET device of any one of claims 1 to 4, wherein a second type of region is formed on the substrate, and wherein the epitaxial layer is located above the second type of region.

6. The JFET device of any one of claims 1 to 5, wherein the conductivity type of the first type well, the first type doped region and the first type heavily doped region is a first conductivity type;

the conductivity types of the epitaxial layer, the second-class well, the second-class doped region and the second-class heavily doped region are second conductivity types;

the first conductivity type and the second conductivity type are opposite.

7. A method of fabricating a JFET device, the method comprising:

forming an epitaxial layer on a substrate;

forming an isolation structure on the substrate;

forming a first type well, a second type well, a first type doped region and a second type doped region on the substrate through photoetching and ion implantation processes, wherein the first type well is positioned in the epitaxial layer, the second type well is surrounded by the first type well, the first type doped region is positioned in the second type well and is close to the edge of the second type well, and the second type doped region is positioned in the first type well and is close to the edge of the second type well;

forming a field plate structure which covers the first type doping region and the isolation structure in the first type doping region;

forming a second type heavily doped region in the second type well and the epitaxial layer and forming a first type heavily doped region in the second type doped region through photoetching and ion implantation processes;

and forming metal electrodes on the first heavily doped region, the second heavily doped region and the top of the field plate structure.

8. The method of claim 7, wherein prior to forming the first type of doped region and the second type of doped region, the method further comprises:

and forming a second auxiliary well in the second type well through photoetching and ion implantation processes, wherein the doping concentration of the second auxiliary well is greater than that of the second type well.

9. The method according to claim 7 or 8, wherein the implantation energy for forming the first-type doped region is less than the implantation energy for forming the second-type well, and the implantation dose for forming the first-type doped region is less than the implantation dose for forming the second-type well;

the implantation energy for forming the second type doping region is less than the implantation energy for forming the first type well, and the implantation dose for forming the second type doping region is less than the implantation dose for forming the first type well.

10. The method of any of claims 7 to 9, wherein the forming a field plate structure comprises:

forming an oxide layer on the substrate;

forming a polycrystalline silicon layer on the surface of the oxidation layer;

defining a field plate structure pattern through a photoetching process;

and etching the polycrystalline silicon layer and the oxide layer according to the field plate structure pattern to form the field plate structure.

11. The method of claim 10, wherein prior to defining the field plate structure pattern by the lithographic process, the method further comprises:

and doping the polycrystalline silicon layer by an ion implantation process.

12. The method of claim 7, wherein forming an epitaxial layer on a substrate comprises:

forming a second type of region on the substrate;

and forming the epitaxial layer on the second type region.

13. The method according to any one of claims 7 to 12, wherein the conductivity type of the first type well, the first type doped region and the first type heavily doped region is a first conductivity type;

the conductivity types of the second-class well, the second-class doped region and the second-class heavily doped region are second conductivity types;

the first conductivity type and the second conductivity type are opposite.

Technical Field

The application relates to the field of semiconductor manufacturing, in particular to a JFET device and a manufacturing method thereof.

Background

The BCD (Bipolar-CMOS-DMOS) technology is a process technology for integrating high-voltage power devices such as Bipolar, CMOS and DMOS, various resistors, capacitors and diodes on the same chip, and has the characteristics of low cost, easiness in packaging and the like.

A JFET (junction field effect transistor) is a device that uses the depletion layer width to vary the width of the conduction channel to control the magnitude of leakage current. JFET devices are manufactured on the BCD process platform, and the existing process menu and layout level are generally used for saving cost. Fig. 1 shows a schematic structure of a conventional N-type JFET device fabricated on a BCD process platform. Due to the limitation of a BCD process platform, the withstand voltage between the P-type well region 19 and the N-type well region 14 of the N-type JFET device shown in FIG. 1 is low, the electrical parameters of the JFET device cannot meet the index requirements, and the JFET device cannot work under the preset voltage.

Disclosure of Invention

To solve the problems in the related art, the present application provides a JFET device and a method of fabricating the same. The technical scheme is as follows:

in a first aspect, embodiments of the present application provide a JFET device, including:

a substrate;

an epitaxial layer on the substrate;

the epitaxial layer comprises an isolation structure, a first type well, a second type well, a first type doping region and a second type doping region, wherein the isolation structure, the first type well, the second type well, the first type doping region and the second type doping region are positioned in the epitaxial layer;

the field plate structure covers the first type of doping region and the isolation structure in the first type of doping region;

a second type heavily doped region is formed in the second type well and the epitaxial layer, and a first type heavily doped region is formed in the second type heavily doped region;

and the metal electrodes are positioned on the first type heavily doped region, the second type heavily doped region and the top of the field plate structure.

Optionally, the substrate further includes a second-type auxiliary well, the second-type auxiliary well is located in the second-type well, and the doping concentration of the second-type auxiliary well is greater than that of the second-type well.

Optionally, the field plate structure is composed of an oxide layer and a polysilicon layer.

Optionally, the polysilicon layer in the field plate structure is a doped polysilicon layer.

Optionally, a second type region is formed on the substrate, and the epitaxial layer is located above the second type region.

Optionally, the conductivity types of the first type well, the first type doped region, and the first type heavily doped region are a first conductivity type;

the conductivity types of the epitaxial layer, the second-class well, the second-class doped region and the second-class heavily doped region are second conductivity types;

the first conductivity type is opposite to the second conductivity type.

In a second aspect, embodiments of the present application provide a method for fabricating a JFET device, the method comprising:

forming an epitaxial layer on a substrate;

forming an isolation structure on a substrate;

forming a first type well, a second type well, a first type doping region and a second type doping region on the substrate through photoetching and ion implantation processes, wherein the first type well is positioned in the epitaxial layer, the second type well is surrounded by the first type well, the first type doping region is positioned in the second type well and is close to the edge of the second type well, the second type doping region is positioned in the first type well and is close to the edge of the second type well;

forming a field plate structure, wherein the field plate structure covers the first type doping region and the isolation structure in the first type doping region;

forming a second type heavily doped region in the second type well and the epitaxial layer and forming a first type heavily doped region in the second type doped region by photoetching and ion implantation processes;

and forming metal electrodes on the top of the first type heavily doped region, the second type heavily doped region and the field plate structure.

Optionally, before forming the first type doped region and the second type doped region, the method further includes:

and forming a second auxiliary well in the second type well through photoetching and ion implantation processes, wherein the doping concentration of the second auxiliary well is greater than that of the second type well.

Optionally, the implantation energy for forming the first-type doped region is less than the implantation energy for forming the second-type well, and the implantation dose for forming the first-type doped region is less than the implantation dose for forming the second-type well;

the implantation energy for forming the second type doped region is less than the implantation energy for forming the first type well, and the implantation dose for forming the second type doped region is less than the implantation dose for forming the first type well.

Optionally, forming a field plate structure includes:

forming an oxide layer on a substrate;

forming a polycrystalline silicon layer on the surface of the oxide layer;

defining a field plate structure pattern through a photoetching process;

and etching the polysilicon layer and the oxide layer according to the field plate structure pattern to form a field plate structure.

Optionally, before defining the field plate structure pattern by the photolithography process, the method further includes:

and doping the polysilicon layer by an ion implantation process.

Optionally, forming an epitaxial layer on the substrate includes:

forming a second type of region on the substrate;

and forming an epitaxial layer on the second type region.

Optionally, the conductivity types of the first type well, the first type doped region, and the first type heavily doped region are a first conductivity type;

the conductivity types of the second type well, the second type doping area and the second type heavily doped area are a second conductivity type;

the first conductivity type is opposite to the second conductivity type.

The technical scheme at least comprises the following advantages:

the JFET device comprises a substrate, an epitaxial layer, an isolation structure, a first type well, a second type well, a first type doping area, a second type doping area and a field plate structure, wherein the isolation structure is positioned in the epitaxial layer; the second type doping area in the first type well is used for reducing the overall concentration peak value of the first type well, and the first type doping area in the second type well is used for reducing the overall concentration peak value of the second type well, so that the problem that the electrical parameters of a JFET device manufactured in the conventional BCD process platform cannot meet the requirements of the device is solved; the effects of improving the withstand voltage between the first-class well and the second-class well, optimizing the breakdown voltage and the threshold voltage of the JFET device manufactured by the BCD process platform and optimizing the performance of the JFET device are achieved.

Drawings

In order to more clearly illustrate the detailed description of the present application or the technical solutions in the prior art, the drawings needed to be used in the detailed description of the present application or the prior art description will be briefly introduced below, and it is obvious that the drawings in the following description are some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative efforts.

Fig. 1 is a schematic diagram of a prior art JFET device;

fig. 2 is a schematic structural diagram of a JFET device according to an embodiment of the present disclosure;

fig. 3 is a schematic structural diagram of a JFET device according to an embodiment of the present disclosure;

fig. 4 is a flow chart of a method of fabricating a JFET device according to an embodiment of the present disclosure;

fig. 5 is a schematic diagram illustrating an embodiment of a method for manufacturing a JFET device according to an embodiment of the present disclosure;

fig. 6 is a schematic diagram illustrating an embodiment of a method for manufacturing a JFET device according to an embodiment of the present disclosure;

fig. 7 is a schematic diagram illustrating an embodiment of a method for manufacturing a JFET device according to an embodiment of the present disclosure;

fig. 8 is a schematic diagram illustrating an embodiment of a method for manufacturing a JFET device according to an embodiment of the present disclosure;

fig. 9 is a schematic diagram illustrating an embodiment of a method for manufacturing a JFET device according to an embodiment of the present disclosure;

fig. 10 is a schematic diagram illustrating an embodiment of a method for manufacturing a JFET device according to an embodiment of the present disclosure;

figure 11 is a flow chart of a method of fabricating a JFET device according to another embodiment of the present application;

fig. 12 is a schematic diagram illustrating an embodiment of a method for fabricating a JFET device according to another embodiment of the present application;

fig. 13 is a schematic diagram of an embodiment of a method for fabricating a JFET device according to another embodiment of the present application;

fig. 14 is a schematic diagram illustrating an embodiment of a method for fabricating a JFET device according to another embodiment of the present application;

fig. 15 is a schematic diagram illustrating an embodiment of a method for fabricating a JFET device according to another embodiment of the present application;

11, a P-type substrate; 12, a P-type region; 13, P-type epitaxy; 14, an N-type well region; 15, a P-type doped region; 16, an N-type doped region; 17, a P-type doped region; 18, a metal electrode; 19, a P-type well region; 20, STI.

Detailed Description

The technical solutions in the present application will be described clearly and completely with reference to the accompanying drawings, and it is obvious that the described embodiments are some, but not all embodiments of the present application. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.

In the description of the present application, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, and are only for convenience of description and simplicity of description, and do not indicate or imply that the device or element being referred to must have a particular orientation, be constructed and operated in a particular orientation, and thus, should not be construed as limiting the present application. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.

In the description of the present application, it is to be noted that, unless otherwise explicitly specified or limited, the terms "mounted," "connected," and "connected" are to be construed broadly, e.g., as meaning either a fixed connection, a removable connection, or an integral connection; the connection can be mechanical connection or electrical connection; the two elements may be directly connected or indirectly connected through an intermediate medium, or may be communicated with each other inside the two elements, or may be wirelessly connected or wired connected. The specific meaning of the above terms in the present application can be understood in a specific case by those of ordinary skill in the art.

In addition, the technical features mentioned in the different embodiments of the present application described below may be combined with each other as long as they do not conflict with each other.

Referring to fig. 2, a cross-sectional view of a JFET device according to an embodiment of the present disclosure is shown. As shown in fig. 2, the JFET device includes a substrate 21, an epitaxial layer 22 on the substrate 21, an isolation structure 23 in the epitaxial layer 22, a first type well 24, a second type well 25, a first type doped region 26, and a second type doped region 27.

Optionally, the isolation structure 23 is a shallow trench isolation.

The second-type well 25 is surrounded by the first-type well 24.

The first type doped region 26 is located in the second type well 25, and the first type doped region 26 is near the edge of the second type well 25.

The depth of the first type doped region 26 is less than the depth of the second type well 25, and the doping concentration of the first type doped region 26 is less than the doping concentration of the second type well 25.

The first type doping region 26 does not cause the second type well 25 to be inverted. The first-type doped region 26 may reduce the overall concentration peak of the second-type well 25.

The second type doping region 27 is located in the first type well 24 and the second type doping region 27 is near the edge of the second type well 25.

The depth of the second type doped region 27 is less than the depth of the first type well 24 and the doping concentration of the second type doped region 27 is less than the doping concentration of the first type well 24.

The second type doping region 27 does not cause the first type well 24 to be inverted. The second type doping region 27 may reduce the overall concentration peak of the first type well 24.

The field plate structure covers the first type of doped region 26 and the isolation structure 23 within the first type of doped region 26.

The top of the field plate structure, which is formed with a metal electrode 28, helps to improve the breakdown voltage of the JFET device.

The second type well 25 and the epitaxial layer 22 have a second type heavily doped region 29 formed therein and the second type doped region 27 has a first type heavily doped region 30 formed therein.

The top of the first type heavily doped region 30 and the second type heavily doped region 29 are formed with metal electrodes 28.

The substrate and the epitaxial layer have the same conductivity type, and the conductivity type of the epitaxial layer is opposite to that of the first-type well. Such as: the substrate is a P-type substrate, the epitaxial layer is a P-type epitaxial layer, and the first-type well is an N well.

In summary, the JFET device provided by the embodiment of the present application includes a substrate, an epitaxial layer, an isolation structure located in the epitaxial layer, a first type well, a second type well, a first type doped region, a second type doped region, and a field plate structure covering the isolation structure in the first type doped region and the first type doped region, wherein a second type heavily doped region is formed in the second type well and the epitaxial layer, a first type heavily doped region is formed in the second type doped region, and a metal electrode located at the top of the first type heavily doped region, the second type heavily doped region, and the field plate structure; the second type doping area in the first type well is used for reducing the overall concentration peak value of the first type well, and the first type doping area in the second type well is used for reducing the overall concentration peak value of the second type well, so that the problem that the electrical parameters of a JFET device manufactured in the conventional BCD process platform cannot meet the requirements of the device is solved; the effects of improving the withstand voltage between the first-class well and the second-class well, optimizing the breakdown voltage and the threshold voltage of the JFET device manufactured by the BCD process platform and optimizing the performance of the JFET device are achieved.

As shown in fig. 2, the field plate structure is composed of an oxide layer 31 and a polysilicon layer 32. Optionally, the polysilicon layer 32 is a doped polysilicon layer.

As shown in fig. 2, a second type region 33 is formed on the substrate 21, and the epitaxial layer 22 is located above the second type region 33.

The conductivity type of the second type region 33 is the same as the epitaxial layer 22. For example, the epitaxial layer is a P-type epitaxial layer, and the second type region is a P-type region.

In the JFET device, the conductivity types of the first type well 24, the first type doped region 26 and the first type heavily doped region 30 are of a first conductivity type; the conductivity types of the epitaxial layer 22, the second-type well 25, the second-type doped region 27 and the second-type heavily doped region 29 are the second conductivity type; the first conductivity type is opposite to the second conductivity type.

For example, the first conductivity type is N-type, and the second conductivity type is P-type; alternatively, the first conductivity type is P-type and the second conductivity type is N-type.

When the JFET device is an N-type JFET device, the substrate 21, the second type region 33, and the epitaxial layer 22 are P-type, the first type well 24 is an N-well, the second type well 25 is a P-well, the first type doped region 26 is an N-type doped region, the second type doped region 27 is a P-type doped region, the first type heavily doped region 30 is an N-type heavily doped region, and the second type heavily doped region 29 is a P-type heavily doped region.

In order to further reduce the threshold voltage of the JFET device, another JFET device is provided in embodiments of the present application, as shown in fig. 3.

As can be seen by comparing fig. 2 and 3, the JFET device of fig. 3 has a second type auxiliary well 34 added to the second type well 25. The auxiliary wells of the second type 34 are located between the doped regions of the first type 26.

The doping concentration of the second-type auxiliary well 34 is greater than the doping concentration of the second-type well 25. The second-type auxiliary well 34 increases the concentration of the second-type well 25, which helps to deplete the first-type well 24 during operation of the JFET device, resulting in a reduction in threshold voltage.

Referring to fig. 4, a flow chart of a method for fabricating a JFET device according to an embodiment of the present application is shown. The method is suitable for manufacturing the JFET device in the BCD process platform. As shown in fig. 4, the method at least comprises the following steps:

step 401, an epitaxial layer is formed on a substrate.

Alternatively, as shown in fig. 5, the second-type region 33 is formed on the substrate 21. Alternatively, the second-type regions 33 may be formed on the substrate 21 by photolithography and ion implantation processes. The substrate 21 and the second type region 33 are of the same conductivity type.

As shown in fig. 6, the epitaxial layer 22 is formed on the second-type region 33. Optionally, the epitaxial layer 22 is formed on the second-type region 33 by an epitaxial growth process. The conductivity type of the epitaxial layer 22 is the same as the conductivity type of the second type region 33.

At step 402, an isolation structure is formed on a substrate.

Optionally, the isolation structure is a shallow trench isolation. Photolithography is performed on the epitaxial layer 22, the epitaxial layer 22 is etched by an etching process to form a shallow trench, and the shallow trench is filled with silicon dioxide and subjected to CMP processing to form an isolation structure 23, as shown in fig. 7.

In step 403, a first type well, a second type well, a first type doped region and a second type doped region are formed on the substrate through photolithography and ion implantation processes.

And defining a first type trap pattern through a photoetching process, and implanting first type doping ions into the substrate through an ion implantation process to form a first type trap in the epitaxial layer.

And defining a second type trap pattern through a photoetching process, and implanting second type doping ions into the substrate through an ion implantation process to form a second type trap in the first type trap. As shown in fig. 8, the second-type well 25 is surrounded by the first-type 24 well.

Forming a second-type doped region 27 in the first-type well 24 through a photolithography process and an ion implantation process; the first-type doped region 26 is formed in the second-type well 25 through a photolithography process and an ion implantation process. It should be noted that the forming sequence of the first-type doped region 26 and the second-type doped region 27 is determined according to practical situations, and this is not limited in the embodiment of the present application.

As shown in fig. 8, the first-type doped region 26 is located in the second-type well 25 and the first-type doped region 26 is close to the edge of the second-type well 25; the second type doping region 27 is located in the first type well 24 and the second type doping region 27 is near the edge of the second type well 25.

Step 404, a field plate structure is formed, wherein the field plate structure covers the first type of doping region and the isolation structure in the first type of doping region.

And depositing a material for forming the field plate structure, and forming the field plate structure through photoetching and etching processes.

As shown in fig. 9, a field plate structure is formed on the substrate 21, and the field plate structure covers the first type doped region 26 and the isolation structure 23 in the first type doped region.

Step 405, forming a second type heavily doped region in the second type well and the epitaxial layer and a first type heavily doped region in the second type doped region by photolithography and ion implantation processes.

Through photolithography and ion implantation processes, a second type heavily doped region 29 is formed in the second type well 25 and the epitaxial layer 22, and a first type heavily doped region 30 is formed in the second type doped region 27, as shown in fig. 10.

And 406, forming metal electrodes on the top of the first heavily doped region, the second heavily doped region and the field plate structure.

And depositing a metal layer, and forming metal electrodes on the first type heavily doped region, the second type heavily doped region and the top of the field plate structure through photoetching and etching processes to form the JFET device as shown in figure 2.

In summary, in the method for manufacturing the JFET device provided by the embodiment of the present application, the epitaxial layer is formed on the substrate; forming an isolation structure on a substrate; forming a first type well, a second type well, a first type doping region and a second type doping region on a substrate, wherein the first type well is positioned in an epitaxial layer, the second type well is surrounded by the first type well, the first type doping region is positioned in the second type well and is close to the edge of the second type well, the second type doping region is positioned in the first type well and is close to the edge of the second type well; forming a field plate structure, wherein the field plate structure covers the first type doping region and the isolation structure in the first type doping region; forming a second type heavily doped region in the second type well and the epitaxial layer, and forming a first type heavily doped region in the second type doped region; forming metal electrodes on the top of the first type heavily doped region, the top of the second type heavily doped region and the top of the field plate structure; the second type doping area in the first type well is used for reducing the overall concentration peak value of the first type well, and the first type doping area in the second type well is used for reducing the overall concentration peak value of the second type well, so that the problem that the electrical parameters of a JFET device manufactured in the conventional BCD process platform cannot meet the requirements of the device is solved; the effects of improving the withstand voltage between the first-class well and the second-class well, optimizing the breakdown voltage and the threshold voltage of the JFET device manufactured by the BCD process platform and optimizing the performance of the JFET device are achieved.

In order to further reduce the threshold voltage of the JFET device, another embodiment of the present application further provides a flow chart of a method for manufacturing the JFET device, as shown in fig. 11, the method at least comprises the following steps:

step 501, an epitaxial layer is formed on a substrate.

As shown in fig. 5, a second type region 33 is formed on the substrate 21. Alternatively, the second-type regions 33 may be formed on the substrate 21 by photolithography and ion implantation processes. The substrate 21 and the second type region 33 are of the same conductivity type.

As shown in fig. 6, the epitaxial layer 22 is formed on the second-type region 33. Optionally, the epitaxial layer 22 is formed on the second-type region 33 by an epitaxial growth process. The conductivity type of the epitaxial layer 22 is the same as the conductivity type of the second type region 33.

Step 502, an isolation structure is formed on a substrate.

This step is explained in step 402 above and will not be described here.

In step 503, a first type well and a second type well are formed on the substrate through photolithography and ion implantation processes.

And defining a first type trap pattern through a photoetching process, and implanting first type doping ions into the substrate through an ion implantation process to form a first type trap in the epitaxial layer.

And defining a second type trap pattern through a photoetching process, and implanting second type doping ions into the substrate through an ion implantation process to form a second type trap in the first type trap. As shown in fig. 8, the second-type well 25 is surrounded by the first-type 24 well.

The first type of dopant ions and the second type of dopant ions are of opposite conductivity types.

Step 504, forming a second-type auxiliary well in the second-type well through photoetching and etching processes.

The conductivity type of the second type auxiliary well is the same as that of the second type well.

The doping concentration of the second-type auxiliary well is greater than that of the second-type well. The second auxiliary trap enables the doping concentration in the second trap to be increased, and is beneficial to reducing the threshold voltage of the JFET device.

As shown in fig. 12, a second-type auxiliary well 34 is formed in the second-type well 25.

And 505, forming a first type doped region and a second type doped region through a photoetching process and an ion implantation process.

Forming a second-type doped region 27 in the first-type well 24 through a photolithography process and an ion implantation process; the first-type doped region 26 is formed in the second-type well 25 through a photolithography process and an ion implantation process, as shown in fig. 13.

It should be noted that the forming sequence of the first-type doped region 26 and the second-type doped region 27 is determined according to practical situations, and this is not limited in the embodiment of the present application.

As shown in fig. 13, the first-type doped region 26 is located in the second-type well 25 and the first-type doped region 26 is close to the edge of the second-type well 25; the second type doping region 27 is located in the first type well 24 and the second type doping region 27 is near the edge of the second type well 25. The auxiliary wells of the second type 34 are located between the doped regions of the first type 26.

Step 506, a field plate structure is formed, wherein the field plate structure covers the first type of doping region and the isolation structure in the first type of doping region.

And depositing a material for forming the field plate structure, and forming the field plate structure through photoetching and etching processes.

As shown in fig. 14, a field plate structure is formed on the substrate 21, and the field plate structure covers the first type doped region 26 and the isolation structure 23 in the first type doped region.

And 507, forming a second type heavily doped region in the second type well and the epitaxial layer and a first type heavily doped region in the second type doped region through photoetching and ion implantation processes.

Through photolithography and ion implantation processes, a second type heavily doped region 29 is formed in the second type well 25 and the epitaxial layer 22, and a first type heavily doped region 30 is formed in the second type doped region 27, as shown in fig. 15.

And step 508, forming metal electrodes on the top of the first-class heavily doped region, the second-class heavily doped region and the field plate structure.

And depositing a metal layer, and forming metal electrodes on the first type heavily doped region, the second type heavily doped region and the top of the field plate structure through photoetching and etching processes to form the JFET device as shown in figure 3.

In an alternative embodiment based on the embodiments shown in fig. 4 and 11, the step "forming a field plate structure", i.e. step "404" or step "506", may be implemented by:

step 601, forming an oxide layer on the substrate.

Step 602, a polysilicon layer is formed on the surface of the oxide layer.

Optionally, after the polysilicon layer is formed, doping the polysilicon layer by an ion implantation process; the doped ions are N-type ions or P-type ions.

Step 603, defining a field plate structure pattern by a photolithography process.

And step 604, etching the polysilicon layer and the oxide layer according to the field plate structure pattern to form a field plate structure.

As shown in fig. 9 or 10 or 14 or 15, the field plate structure includes an oxide layer 31 and a polysilicon layer 32.

In the manufacturing method of the JFET device shown in fig. 4 or fig. 11, the conductivity types of the first type well, the first type doped region and the first type heavily doped region are the first conductivity type; the conductivity types of the second type well, the second type doping area and the second type heavily doped area are a second conductivity type; the first conductivity type is opposite to the second conductivity type.

It should be noted that, when the JFET device is manufactured on the BCD process platform, various processes for manufacturing the JFET device and other steps can be performed simultaneously with those of other devices according to actual design requirements.

It should be understood that the above examples are only for clarity of illustration and are not intended to limit the embodiments. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. And are neither required nor exhaustive of all embodiments. And obvious variations or modifications of this invention are intended to be covered by the scope of the invention as expressed herein.