阅读说明：本技术 功率半导体器件的制备方法 (Preparation method of power semiconductor device ) 是由 贺东晓 于 2020-05-13 设计创作，主要内容包括：本发明提供了一种功率半导体器件的制备方法。该制备方法包括顺序形成有源区和终端区的步骤,形成终端区的步骤包括：在衬底上形成多个第一场板,各第一场板沿由有源区到终端区的方向间隔设置,且相邻各第一场板具有相等的第一间距,第一间距为0.1～8μm。对制备完成上述器件施加的偏置电压突变时,每个场板电容也将均匀的同时变化,从而不会造成电压在场板上的突变而导致的不稳定,降低了场板/场限环之间发生放电击穿的风险。此外,由于间隔设置的场板形成串联电容,从而能够牢牢地控制界面电势的梯度变化,进而能够消除外来的可动离子对终端电压的影响。(The invention provides a preparation method of a power semiconductor device. The preparation method comprises the steps of sequentially forming an active region and a terminal region, wherein the step of forming the terminal region comprises the following steps: and forming a plurality of first field plates on the substrate, wherein the first field plates are arranged at intervals along the direction from the active region to the terminal region, and adjacent first field plates have equal first spacing, and the first spacing is 0.1-8 mu m. When the bias voltage applied to the prepared device is suddenly changed, the capacitance of each field plate is uniformly and simultaneously changed, so that the instability caused by sudden change of the voltage on the field plate is avoided, and the risk of discharge breakdown between the field plate/the field limiting ring is reduced. In addition, the field plates arranged at intervals form a series capacitor, so that the gradient change of the interface potential can be firmly controlled, and the influence of external movable ions on the terminal voltage can be eliminated.)

1. A method of manufacturing a power semiconductor device comprising the steps of sequentially forming an active region and a termination region, wherein the step of forming the termination region comprises:

and forming a plurality of first field plates on the substrate, wherein the first field plates are arranged at intervals along the direction from the active region to the terminal region, and adjacent first field plates have equal first spacing, and the first spacing is 0.1-8 mu m.

2. The method of manufacturing according to claim 1, further comprising, before the step of forming the first field plate, the steps of:

forming a field limiting ring in a substrate such that the field limiting ring surrounds the active region;

forming a field isolation structure on the substrate such that the field isolation structure is disposed in contact with the field limiting ring,

after the step of forming the first field plate, the first field plate is located on a side of the field isolation structure away from the substrate.

3. The production method according to claim 2,

forming the field limiting ring in the substrate to have a doping concentration of the field limiting ring decreasing in a direction from the active region to the termination region; or

Forming said field limiting ring in a substrate to taper a PN junction depth formed between said field limiting ring and said substrate in a direction from said active region to said termination region; or

And forming the field limiting ring in the substrate so that the doping concentration of the field limiting ring and the junction depth of a PN junction formed between the field limiting ring and the substrate are reduced in the direction from the active region to the terminal region.

4. The method of claim 2, wherein a plurality of the field limiting rings are formed in the substrate such that the field limiting rings are spaced apart in a direction from the active region to the termination region, the centerlines of adjacent field limiting rings are equally spaced, and the width of each field limiting ring decreases.

5. The method of manufacturing of claim 2, wherein the step of forming the field limiting ring comprises:

arranging a mask structure on the surface of the substrate, wherein the mask structure is provided with a plurality of annular injection windows penetrating through the substrate, each annular injection window surrounds the active region, and the width of each annular injection window is gradually reduced along the direction from the active region to the terminal region;

performing ion implantation on the implantation window at one side of the substrate with the mask structure to form the field limiting ring;

and removing the mask structure.

6. The method of claim 5, wherein a spacing between adjacent ones of said implantation windows increases in a direction from said active region to said termination region.

7. The method of claim 6, wherein the distance between the centers of adjacent injection windows is a fixed value.

8. The method according to any one of claims 1 to 7, wherein the first field plates are formed to have the same first width.

9. The method of manufacturing according to any one of claims 1 to 7, wherein the first field plate is a metal field plate or a polysilicon field plate.

10. The production method according to any one of claims 1 to 7, characterized in that, after the step of forming the first field plate, the production method further comprises the steps of:

forming an interlayer dielectric layer on one side of the first field plate, which is far away from the substrate;

and forming a plurality of second field plates on one side of the interlayer dielectric layer, which is far away from the first field plate, wherein the second field plates are arranged at intervals along the direction from the active region to the terminal region, and adjacent second field plates have equal second intervals, and the second intervals are 0.1-8 μm.

11. The method of manufacturing of claim 10, wherein each of the second field plates is formed to have a same second width.

12. The method of manufacturing of claim 10, wherein the first field plate is a polysilicon field plate and the second field plate is a metal field plate.

13. The production method according to any one of claims 1 to 7, characterized in that, after the step of forming the first field plate, the production method further comprises the steps of:

and forming a passivation layer on one side of the first field plate far away from the substrate.

14. The method according to claim 13, wherein the passivation layer has a thickness of 0.01 to 2 μm.

Technical Field

The invention relates to the technical field of semiconductor devices, in particular to a preparation method of a power semiconductor device.

Background

The IGBT (insulated gate bipolar transistor) is widely applied to the field of power electronics, is a core switch device for current signal processing, has high input impedance and low breakover voltage, is very suitable for signal processing of large current and high power, and is widely applied to the fields of motor control, UPS, inverter welding machines, household appliances and the like at present.

The chip of the power semiconductor device is mainly composed of two parts: the first is an active region (also called a meta-packet region) which switches on and off current when the power semiconductor device is switched on in the forward direction; and the second is a terminal area which is used for bearing the blocking voltage of the power semiconductor device together with the meta-packet area when the power semiconductor device is in reverse and forward blocking.

Since power semiconductor devices are well suited to handle high current, high power signals, the on-current is from a few amperes to hundreds of amperes and the off-voltage is from hundreds of volts to thousands of volts. If the blocking voltage is unstable, the breakdown failure of the device is easily caused, so that the whole equipment is in failure and even in danger of explosion, and therefore, the provision of the reliable and stable blocking voltage is one of the most core elements of the IGBT chip design.

However, when the voltage of the device rises from zero to the maximum voltage or drops from the maximum voltage to zero, the electric field change between some field plates/field limiting rings is relatively severe because the voltage borne by each field plate is different from that borne by each field plate, so that discharge breakdown easily occurs between the field plates/field limiting rings; in addition, in the prior art, the distance between the field plates is wide, and the electric field lines between the field plates are not completely in the horizontal plane, so that the risk of breakdown of the passivation layer exists, and therefore, the terminal of the power semiconductor device needs a thicker passivation layer for protection and isolation.

Disclosure of Invention

The invention mainly aims to provide a preparation method of a power semiconductor device, which aims to solve the problem that in the prior art, a terminal of the power semiconductor device is easy to generate discharge breakdown.

In order to achieve the above object, according to one aspect of the present invention, there is provided a method of manufacturing a power semiconductor device, including the steps of sequentially forming an active region and a termination region, the step of forming the termination region including: and forming a plurality of first field plates on the substrate, wherein the first field plates are arranged at intervals along the direction from the active region to the terminal region, and adjacent first field plates have equal first spacing, and the first spacing is 0.1-8 mu m.

Further, before the step of forming the first field plate, the preparation method further comprises the steps of: forming a field limiting ring in the substrate so that the field limiting ring surrounds the active region; and forming a field isolation structure on the substrate so that the field isolation structure is arranged in contact with the field limiting ring, wherein the first field plate is positioned on one side of the field isolation structure, which is far away from the substrate, after the step of forming the first field plate.

Further, forming a field limiting ring in the substrate, so that the doping concentration of the field limiting ring is decreased gradually in the direction from the active region to the terminal region; or forming a field limiting ring in the substrate so as to enable the junction depth of a PN junction formed between the field limiting ring and the substrate to be gradually reduced in the direction from the active region to the terminal region; or forming a field limiting ring in the substrate, so that the doping concentration of the field limiting ring and the junction depth of a PN junction formed between the field limiting ring and the substrate are reduced in the direction from the active region to the terminal region.

Further, a plurality of field limiting rings are formed in the substrate, so that in the direction from the active region to the terminal region, the field limiting rings are arranged in the substrate at intervals, the distance between the central lines of adjacent field limiting rings is equal, and the width of each field limiting ring is decreased gradually.

Further, the step of forming the field limiting ring includes: arranging a mask structure on the surface of the substrate, wherein the mask structure is provided with a plurality of annular injection windows penetrating through the substrate, each annular injection window surrounds the active region, and the width of each annular injection window is gradually reduced along the direction from the active region to the terminal region; carrying out ion implantation on the implantation window at one side of the substrate with the mask structure to form a field limiting ring; and removing the mask structure.

Further, the spacing between adjacent injection windows increases in the direction from the active region to the termination region.

Furthermore, the distance between the center positions of the adjacent injection windows is a fixed value.

Further, the first field plates are formed to have the same first width.

Further, the first field plate is a metal field plate or a polysilicon field plate.

Further, after the step of forming the first field plate, the manufacturing method further includes the steps of: forming an interlayer dielectric layer on one side of the first field plate far away from the field isolation structure; and forming a plurality of second field plates on one side of the interlayer dielectric layer, which is far away from the first field plate, wherein the second field plates are arranged at intervals along the direction from the active region to the terminal region, and adjacent second field plates have equal second spacing which is 0.1-8 mu m.

Further, the second field plates are formed to have the same second width.

Furthermore, the first field plate is a polysilicon field plate, and the second field plate is a metal field plate.

Further, after the step of forming the first field plate, the manufacturing method further includes the steps of: a passivation layer is formed on a side of the first field plate away from the substrate.

Furthermore, the thickness of the passivation layer is 0.01-2 μm.

According to the technical scheme, the first field plates with equal spacing and small spacing (between 0.1-8 mu m) are formed on the field isolation structure, so that the adjacent field plates form effective capacitance when the device bears voltage, the capacitance values are approximately equal, and the capacitance values formed by the adjacent field plates are approximate, so that the voltage born by each capacitor is also approximate, and the voltage of the device can form gradient change with a certain slope from the field plates to the active region. When the bias voltage applied to the prepared device is suddenly changed, the capacitance of each field plate is uniformly and simultaneously changed, so that instability caused by sudden change of the voltage on the field plates is avoided, and the risk of discharge breakdown between the field plates is reduced. In addition, the field plates arranged at intervals form a series capacitor, so that the gradient change of the interface potential can be firmly controlled, and the influence of external movable ions on the terminal voltage can be eliminated. Furthermore, due to the presence of the effective capacitance, the surface field lines are almost completely in the horizontal direction, so that the device does not need a too thick or special passivation layer for protection.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of this specification, are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification, illustrate exemplary embodiments of the invention and together with the description serve to explain the invention and not to limit the invention. In the drawings:

fig. 1 is a schematic cross-sectional view illustrating a base body after a field limiting ring is formed in a substrate in a method for manufacturing a power semiconductor device according to an embodiment of the present disclosure, wherein a PN junction depth formed between the field limiting ring and the substrate decreases in a direction from an active region to a termination region;

fig. 2 is a schematic cross-sectional view illustrating a substrate after a mask structure having an implantation window is disposed on a surface of the substrate in a method for manufacturing a power semiconductor device according to an embodiment of the present disclosure;

fig. 3 shows a partially enlarged schematic view of the region b in the power semiconductor device shown in fig. 2;

FIG. 4 is a schematic diagram showing a cross-sectional structure of the substrate shown in FIG. 3 after ion implantation is performed on the implantation window at the side of the substrate having the mask structure to form field limiting rings and the mask structure is removed, wherein the doping concentration of the field limiting rings decreases in the direction from the active region to the terminal region;

fig. 5 is a schematic cross-sectional view of the substrate shown in fig. 3 after ion implantation is performed on the implantation window at the side of the substrate having the mask structure to form a plurality of field limiting rings, and the mask structure is removed, wherein the width of each field limiting ring decreases in the direction from the active region to the terminal region;

FIG. 6 is a schematic cross-sectional view of the body after forming field isolation structures on the substrate shown in FIG. 4;

fig. 7 is a schematic diagram illustrating a cross-sectional structure of the body after forming a plurality of first field plates on a side of the field isolation structure of fig. 6 away from the substrate;

fig. 8 is a partially enlarged schematic view of a region a in the power semiconductor device shown in fig. 7;

fig. 9 is a schematic diagram showing a cross-sectional structure of the body after forming a passivation layer on a side of the first field plate away from the field isolation structure shown in fig. 8;

fig. 10 is a schematic diagram illustrating a cross-sectional structure of the substrate after forming an interlayer dielectric layer on a side of the first field plate away from the field isolation structure shown in fig. 8;

fig. 11 is a schematic diagram illustrating a cross-sectional structure of a substrate after forming a plurality of second field plates on a side of the interlayer dielectric layer of fig. 10 away from the first field plates;

fig. 12 is a schematic diagram showing a cross-sectional structure of the substrate after forming a passivation layer on the side of the second field plate away from the field isolation structure shown in fig. 11.

Wherein the figures include the following reference numerals:

10. a substrate; 20. a field limiting ring; 30. a field isolation structure; 40. a first field plate; 50. an interlayer dielectric layer; 60. a second field plate; 70. a passivation layer; 100. a mask structure; 110. and (4) injecting the window.

Detailed Description

It should be noted that the embodiments and features of the embodiments may be combined with each other without conflict. The present invention will be described in detail below with reference to the embodiments with reference to the attached drawings.

In order to make the technical solutions of the present invention better understood, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. 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 invention.

It should be noted that the terms "first," "second," and the like in the description and claims of the present invention and in the drawings described above are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order. It is to be understood that the data so used may be interchanged under appropriate circumstances in order to facilitate the description of the embodiments of the invention herein. Furthermore, the terms "comprises," "comprising," and "having," and any variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, system, article, or apparatus that comprises a list of steps or elements is not necessarily limited to those steps or elements expressly listed, but may include other steps or elements not expressly listed or inherent to such process, method, article, or apparatus.

Because interface charges exist on the interface of the substrate and an oxide layer due to field oxide oxidation and other pollution in the manufacturing process of the semiconductor device, the change of the interface charges can influence the bending distribution of potential lines around a field limiting ring so as to influence the voltage stability of a terminal; in addition, other mobile ions can reach the interface through the passivation layer on the outer layer of the power semiconductor device with the change of time and environment, and the voltage stability of the terminal is influenced. In the power semiconductor device, the field plate mainly plays a role in stabilizing and controlling the influence of interface charges, so that the device is ensured to have good and stable blocking voltage when being reversely biased.

The mechanism of the terminal withstand voltage is as follows: when the device has forward bias to reverse bias conversion, the voltage of the field limiting ring is gradually increased to a final reverse bias voltage relative to the voltage of the active region; when the device has reverse bias to forward bias conversion, the voltage of the field limiting ring is gradually reduced to the final forward bias voltage relative to the voltage of the active region; each field limiting ring bears a portion of the voltage, and the sum of the voltages is equal to the bias voltage. And, because the interval between the field plates is great, the electric field line between the field plates is crooked outwards.

When the power semiconductor device rises from zero to the maximum voltage or falls from the maximum voltage to zero, the electric field change between some field plates/field limiting rings is relatively severe because the voltages borne by each field plate and each field limiting ring are different, so that discharge breakdown is easy to occur between the field plates/field limiting rings.

Moreover, the distance between the field plates is wide, and the electric field lines between the field plates are not completely in the horizontal plane, so that there is a risk of breakdown of the passivation layer, and therefore, the power semiconductor device generally needs a thicker passivation layer for protection and isolation.

In order to solve the above technical problems, the present applicant provides a method for manufacturing a power semiconductor device, including a step of sequentially forming an active region and a termination region, the step of forming the termination region including: and forming a plurality of first field plates on the substrate, wherein the first field plates are arranged at intervals along the direction from the active region to the terminal region, and adjacent first field plates have equal first spacing, and the first spacing is 0.1-8 mu m.

According to the method, the first field plates with equal spacing and small spacing (between 0.1-8 mu m) are formed on the field isolation structure, so that the adjacent field plates form effective capacitance when the device bears voltage, the capacitance values are approximately equal, and the capacitance formed by the adjacent field plates has the approximate capacitance value, so that the voltage born by each capacitor is also approximate, and the voltage of the device can form gradient change with a certain slope from the field plates to the active region.

When the bias voltage applied to the prepared device is suddenly changed, the capacitance of each field plate is uniformly and simultaneously changed, so that instability caused by sudden change of the voltage on the field plates is avoided, and the risk of discharge breakdown between the field plates is reduced.

In addition, the field plates arranged at intervals form a series capacitor, so that the gradient change of the interface potential can be firmly controlled, and the influence of external movable ions on the terminal voltage can be eliminated. Furthermore, due to the presence of the effective capacitance, the surface field lines are almost completely in the horizontal direction, so that the device does not need a too thick or special passivation layer for protection.

An exemplary embodiment of a method for manufacturing a power semiconductor device according to the present invention will be described in more detail with reference to fig. 1 to 12. These exemplary embodiments may, however, be embodied in many different forms and should not be construed as limited to only the embodiments set forth herein. It should be understood that these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the concept of these exemplary embodiments to those skilled in the art.

Firstly, forming a plurality of first field plates on one side of the field isolation structure far away from the substrate, wherein the first field plates are arranged at intervals along the direction from the active region to the terminal region, and adjacent first field plates have equal first intervals, and the first intervals are 0.1-8 mu m.

Before the step of forming the first field plate, the manufacturing method of the present invention may further include the steps of: the field limiting ring 20 is formed in the substrate 10 such that the field limiting ring 20 surrounds the active region, as shown in fig. 1 to 5.

The field limiting rings 20 may be formed as continuous field limiting rings, and in order to further reduce the risk of discharge breakdown between the field limiting rings/field plates, it is preferable to form the field limiting rings 20 in the substrate 10 such that the doping concentration of the field limiting rings 20 decreases in the direction from the active region to the termination region; or forming a field limiting ring 20 in the substrate 10 to decrease the junction depth of the PN junction formed between the field limiting ring 20 and the substrate 10 in the direction from the active region to the termination region; alternatively, the field limiting rings 20 are formed in the substrate 10 such that the doping concentration of the field limiting rings 20 and the junction depth of the PN junction formed between the field limiting rings 20 and the substrate 10 are both decreased in the direction from the active region to the termination region.

It is desirable to have the implant depth of the field limiting ring 20 in the direction from the active region to the termination region decrease uniformly so that the PN junction depth formed between the field limiting ring 20 and the substrate 10 decreases as shown in fig. 1. The continuous field limiting rings 20 may also have a doping concentration that decreases uniformly in the direction from the active region to the termination region.

In the step of forming the continuous field limiting ring, the distance between the center positions of the adjacent implantation windows 110 is set to be a fixed value, and the width of each implantation window 110 is gradually decreased along the direction from the active region to the termination region, so that the distance between the adjacent implantation windows 110 is gradually decreased, thereby forming the field limiting ring 20 with the doping concentration changing in a gradient manner.

The field limiting rings 20 formed are not limited to the above-described structure of continuous field limiting rings, and in another preferred embodiment, a plurality of field limiting rings 20 are formed in the substrate 10, and the field limiting rings 20 are disposed in the substrate 10 at intervals in the direction from the active region to the terminal region, the distances between the center lines of adjacent field limiting rings 20 are equal, and the widths of the field limiting rings 20 decrease gradually.

After step S1, a continuous field limiting ring structure with a gradient of concentration is obtained, or a plurality of spaced field limiting rings 20 are obtained, and the field limiting rings 20 enable the device voltage to form a constant gradient along the field limiting rings 20 to the active region. When the bias voltage applied to the prepared device is suddenly changed, the voltage on the field limiting ring 20 is changed in a uniform gradient manner, and the capacitance of each field plate is also changed uniformly and simultaneously, so that instability caused by sudden change of the voltage on the field limiting ring 20 and the field plate is avoided, and the risk of discharge breakdown between the field plate and the field limiting ring 20 is further reduced.

In order to form the field limiting ring 20, it is preferable that the step of forming the field limiting ring 20 includes: providing a mask structure 100 on the surface of the substrate 10, wherein the mask structure 100 has a plurality of annular implantation windows 110 penetrating through the substrate 10, each annular implantation window 110 surrounds the active region, and the width of each annular implantation window 110 decreases in the direction from the active region to the termination region, as shown in fig. 2; the implantation window 110 is ion implanted at the side of the substrate 10 having the mask structure 100 to form the field limiting rings 20, and then the mask structure 100 is removed, as shown in fig. 4 and 5.

In the step of performing ion implantation on the implantation windows 110, the spacing and the width of the implantation windows 110 may be adjusted to obtain a plurality of field limiting rings 20 with consecutive field limiting rings and intervals, for example, fig. 4 shows that the doping concentration of the field limiting rings 20 decreases in the direction from the active region to the terminal region, while fig. 5 shows that the field limiting rings 20 are multiple, in the direction from the active region to the terminal region, the field limiting rings 20 are arranged in the substrate 10 at intervals, the spacing of the center lines of adjacent field limiting rings 20 is equal, and the width of each field limiting ring 20 decreases.

A person skilled in the art can reasonably select the material of the mask structure 100 according to the prior art, and the material of the mask structure 100 may be silicon dioxide, photoresist, or the like; the process conditions of the ion implantation can be reasonably set by those skilled in the art according to the prior art, such as the dose of the ion implantation is 1E 15-5E 13, and the energy is 20-150K.

The total voltage V of the field limiting ring 20 between A and A' in FIGS. 1, 4 and 5_AA＇Satisfies the following conditions:

wherein the content of the first and second substances,toRespectively, the voltage shared by the field limiting ring 20 region formed through each of the implantation windows 110 in the direction from the termination region toward the active region.

As shown in FIGS. 2 and 3, adjacent implantation windows 110 in the mask structure 100 have a centerline spacing D_iEach of the implantation windows 110 has a width L in a direction from the active region to the termination region_iAnd a distance d is formed between adjacent implantation windows 110_iWherein, the ith injection window 110 in the direction from the active region to the termination region satisfies:

D₁＝L₁+d₁；

the parameters (D) for reasonably designing the implantation window 110 are calculated according to the voltage class of the designed device₁、L₁And d₁；D_i、L_iAnd d_i) I.e. a continuous field limiting ring can be obtained, and a plurality of spaced field limiting rings 20 can also be obtained by increasing the spacing of the implantation windows 110 or decreasing the width of the implantation windows 110.

In order to achieve a stable gradient of the voltage across the field limiting ring 20 and at the same time facilitate the process design, in a preferred embodiment, the width difference between adjacent implantation windows 110 in the mask structure 100 is the same, and at this time, the width of each implantation window 110 along the direction from the termination region to the active region is increased by a fixed value.

In the preferred embodiment, the adjacent implantation windows 110 in the mask structure 100 have the same center line distance D, and the width L of each implantation window 110 in the direction from the active region to the termination region_iGradually decreases and the distance d between the adjacent implantation windows 110_iGradually increasing, if the width difference between adjacent implantation windows 110 in the mask structure 100 is defined as a fixed value k, the ith implantation window is formed from the active region to the termination regionThe port 110 satisfies:

D＝L₁+d₁；

L_i-L_i+1＝k；

parameters for the rational design of the implant window 110 are calculated (D, L) based on the voltage class of the device being designed₁And d₁；D、L_iAnd d_i) Thus, continuous field limiting rings with gradient doping concentration can be obtained, the distance between the central lines of adjacent field limiting rings 20 is equal, and the width of each field limiting ring 20 decreases progressively in the direction from the active region to the terminal region.

By adopting the design concept, a continuous field limiting ring with more uniform doping concentration change can be designed, a plurality of field limiting rings 20 at intervals can also be designed, and the width difference values of the adjacent field limiting rings 20 are the same.

After the step of forming the above-described field limiting ring 20, the above-described manufacturing method of the present invention further includes the steps of: a field isolation structure 30 is formed on the substrate 10 such that the field isolation structure 30 is disposed in contact with the field limiting rings 20, as shown in fig. 6.

In the step S2, a person skilled in the art may use a deposition process conventional in the art to form the field isolation structure 30, and a person skilled in the art may also make a reasonable choice of the material for forming the field isolation structure 30 according to the prior art, such as the field isolation structure 30 may be SiO₂。

After the step of forming the field isolation structure 30, the plurality of first field plates 40 are formed on a side of the field isolation structure 30 remote from the substrate 10, as shown in fig. 7.

In step S3, a person skilled in the art can form the first field plate 40 by using a deposition process and an etching process that are conventional in the art, where the first field plate 40 can be a metal field plate or a polysilicon field plate.

In order to avoid the non-uniform and synchronous electric field variation at the same position on the surface caused by the excessive potential deviation between the field limiting ring 20 and the first field plate 40, in a preferred embodiment, the width of the first field plate 40 is kept constant, and the number of the implantation windows 110 in the first field plate 40 and the mask structure 100 is the same.

In the above step S3, as shown in fig. 7 and 8, adjacent first field plates 40 have the same first pitch C₁Adjacent first field plates 40 have a first centerline spacing H_iAnd each first field plate 40 has a first width W_iAnd the ith field plate in the direction from the active region to the termination region satisfies the following conditions:

in a preferred embodiment, adjacent first field plates 40 are made to have the same centerline spacing H₁And each of the first field plates 40 is formed to have the same first width W₁At this time, the first pitch C between the adjacent first field plates 40₁H above₁And the above W₁Satisfies the following conditions:

H₁＝W₁+C₁。

the parameters (C) of the first field plate 40 are rationally designed by calculation according to the voltage class of the designed device₁、H_iAnd W_i；C₁、H₁And W₁) And obtaining the field plate structure with the series coupling capacitor.

By adopting the design thought, taking a 3300V device as an example, a power semiconductor device with a continuous field limiting ring and a field plate structure with a series coupling capacitor can be designed: d is 21 μm, L₁＝20μm；d₁＝1μm；k＝0.4μm，C₁＝0.5μm；W₁20 μm, resulting in a very stable termination structure.

After the step of forming the first field plate 40, the manufacturing method of the present invention may further include the steps of: a passivation layer 70 is formed on the side of the first field plate 40 remote from the substrate 10, as shown in fig. 9. Due to the existence of the effective capacitance in the first field plate 40, the surface electric field lines of the device are almost completely in the horizontal direction, so that a too thick or special passivation layer 70 is not needed for protection, and in this case, the passivation layer 70 may be a conventional material in the prior art, such as silicon nitride, and the thickness is preferably 0.01 to 2 μm.

The termination region of the present invention may further adopt a combination structure of a polysilicon field plate and a metal field plate, and in order to obtain the dual-layer field plate, in a preferred embodiment, after the step of forming the first field plate 40, the preparation method of the present invention may further include the steps of: s4, forming an interlayer dielectric layer 50 on the side of the first field plate 40 away from the substrate 10, as shown in fig. 10; and S5, forming a plurality of second field plates 60 on the side of the interlayer dielectric layer 50 away from the first field plates 40, as shown in fig. 11, wherein the second field plates 60 are arranged at intervals along the direction from the active region to the termination region, and adjacent second field plates 60 have an equal second pitch, and the second pitch is 0.1-8 μm.

In the step S4, a person skilled in the art may use a conventional deposition process in the prior art to form the interlayer dielectric layer 50, and a person skilled in the art may also reasonably select a material for forming the interlayer dielectric layer 50 according to the prior art, where the interlayer dielectric layer 50 may be made of, for example, celp, silicon dioxide, or the like.

In the step S5, a person skilled in the art may use a deposition process and an etching process that are conventional in the prior art to form the second field plates 60, and the center lines of adjacent second field plates 60 are equal, so that the formed second field plates 60 have the same second width, and the design concept of the second field plates 60 may be the same as that of the first field plates 40, which is not described herein again.

In one embodiment of the present invention, the first field plate 40 formed in step S3 is a polysilicon field plate and the second field plate 60 formed in step S5 is a metal field plate. In the above embodiment, since the metal field plates generally have a greater thickness than the polysilicon field plates, it is preferable that the second pitch of adjacent second field plates 60 is greater than the first pitch of adjacent first field plates 40.

In order to avoid the influence of an excessively large potential deviation between the metal field plate and the polysilicon field plate on the device, in the above embodiment, preferably, the number of the metal field plate and the polysilicon field plate is the same, or n number of the metal field plates is n, n +1 number of the polysilicon field plates is n, and n is a natural number greater than 1.

In one embodiment of the present invention, steps S3 and S5 are performed sequentially such that the termination region includes both first field plates 40 and second field plates 60, each first field plate 40 has the same first width, each second field plate 60 has the same second width, and the sum of each first width and each first pitch is equal to the sum of each second width and each second pitch.

In an embodiment of the present invention, step S3 and step S5 are performed sequentially, so that the termination region includes both the first field plates 40 and the second field plates 60, the spacing regions between adjacent first field plates 40 correspond to the second field plates 60, and the spacing regions between adjacent second field plates 60 correspond to the first field plates 40, as shown in fig. 11. In the above embodiment, the spaced-apart region between adjacent ones of the first field plates 40 may correspond to the centerline of each of the second field plates 60.

In another embodiment of the present invention, steps S3 to S5 are performed sequentially, so that the termination region includes both the first field plates 40 and the second field plates 60, a first spacing region is provided between each adjacent first field plate 40, a second spacing region is provided between each adjacent second field plate 60, and each first spacing region and each second spacing region are arranged in a one-to-one correspondence.

When the first field plate 40 and the second field plate 60 are sequentially formed in the above manufacturing method of the present invention, the passivation layer 70 may also be formed on the side of the second field plate 60 away from the substrate 10, as shown in fig. 12. Due to the existence of the effective capacitance in the first field plate 40 and the second field plate 60, the surface electric field lines of the device are almost completely in the horizontal direction, so that a too thick or special passivation layer 70 is not needed for protection, and at this time, the passivation layer 70 can be a conventional material in the prior art, such as silicon nitride, and the thickness is preferably 0.01-2 μm.

From the above description, it can be seen that the above-described embodiments of the present invention achieve the following technical effects:

1. the capacitance formed by adjacent field plates in the device obtained by the preparation method has approximate capacitance value, so that the voltage born by each capacitance is also approximate, the voltage of the device can form gradient change with a certain slope from the field plate to the active region, when the bias voltage of the device is suddenly changed, the capacitance of each field plate is uniformly and simultaneously changed, the instability caused by sudden change of the voltage on the field plate can not be caused, and the risk of discharge breakdown between the field plate/the field limiting ring is reduced;

2. because the field plates arranged at intervals form a series capacitor, the gradient change of the interface potential can be firmly controlled, and the influence of external movable ions on the terminal voltage can be eliminated;

3. due to the existence of the effective capacitance, the surface electric field lines are almost completely in the horizontal direction, so that the device does not need a thick or special passivation layer for protection;

4. by enabling the doping concentration of the field limiting rings to decrease progressively along the direction far away from the active region or enabling the junction depth of PN junctions formed between the continuous field limiting rings and the substrate in the direction to decrease progressively, the voltage of the device can form a fixed gradient change from the field limiting rings to the active region, when the bias voltage of the device changes suddenly, the voltage on the field limiting rings is changed uniformly in a gradient manner, and the capacitance of each field plate is also changed uniformly and simultaneously, so that instability caused by sudden changes of the voltage on individual field limiting rings and field plates can be avoided, and the risk of discharge breakdown between the field plates/the field limiting rings is further reduced.

The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.