CN108054202B - Semiconductor structure and forming method thereof - Google Patents

Semiconductor structure and forming method thereof Download PDF

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CN108054202B
CN108054202B CN201810026243.0A CN201810026243A CN108054202B CN 108054202 B CN108054202 B CN 108054202B CN 201810026243 A CN201810026243 A CN 201810026243A CN 108054202 B CN108054202 B CN 108054202B
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channel
drift
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doping type
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CN108054202A (en
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陆阳
黄必亮
周逊伟
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Joulwatt Technology Co Ltd
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Joulwatt Technology Hangzhou Co Ltd
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    • H01L29/76—Unipolar devices, e.g. field effect transistors
    • H01L29/772—Field effect transistors
    • H01L29/78—Field effect transistors with field effect produced by an insulated gate
    • H01L29/7833—Field effect transistors with field effect produced by an insulated gate with lightly doped drain or source extension, e.g. LDD MOSFET's; DDD MOSFET's
    • H01L29/7835—Field effect transistors with field effect produced by an insulated gate with lightly doped drain or source extension, e.g. LDD MOSFET's; DDD MOSFET's with asymmetrical source and drain regions, e.g. lateral high-voltage MISFETs with drain offset region, extended drain MISFETs
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    • H01L29/66477—Unipolar field-effect transistors with an insulated gate, i.e. MISFET
    • H01L29/66674—DMOS transistors, i.e. MISFETs with a channel accommodating body or base region adjoining a drain drift region
    • H01L29/66681—Lateral DMOS transistors, i.e. LDMOS transistors
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    • H01L29/0642—Isolation within the component, i.e. internal isolation
    • H01L29/0649—Dielectric regions, e.g. SiO2 regions, air gaps
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    • H01L29/1045—Channel region of field-effect devices of field-effect transistors with insulated gate, e.g. characterised by the length, the width, the geometric contour or the doping structure with a non-uniform doping structure in the channel region surface the doping structure being parallel to the channel length, e.g. DMOS like
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    • H01L29/7816—Lateral DMOS transistors, i.e. LDMOS transistors

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Abstract

The invention provides a semiconductor structure and a forming method thereof, wherein the forming method comprises the following steps: providing a semiconductor substrate, and forming a body region in the semiconductor substrate; forming a drift region in the body region, wherein the doping type of the drift region is opposite to that of the body region; forming a channel region in the body region, wherein the channel region partially extends towards the direction of the drift region to form at least one channel extension region, the at least one channel extension region and the drift region form interdigital distribution, and the doping type of the channel region is the same as that of the body region; forming an isolation region within the drift region, an end of the at least one channel extension region being located below the isolation region; forming a grid structure on the surface of the semiconductor substrate; and forming a source region in the channel region on one side of the gate structure, and forming a drain region in the drift region, wherein the drain region is positioned on one side of the isolation region, which is far away from the channel region.

Description

Semiconductor structure and forming method thereof
The present application is filed as a divisional application of application No. 2015100782107, application date 2015, 2/13, entitled "semiconductor structure and method for forming the same".
Technical Field
The present invention relates generally to semiconductor manufacturing, and more particularly to a semiconductor structure and a method for forming the same.
Background
The lateral double-diffused metal oxide semiconductor (LDMOS) device is a lightly-doped MOS device, has very good compatibility with a CMOS process, has good thermal stability and frequency stability, high gain and durability and low feedback capacitance and resistance, and is widely applied to radio frequency circuits.
In the BCD process, a P-type LDMOS device with a drain capable of bearing high voltage is generally required. In the prior art, the structure of a conventional P-type LDMOS device is shown in fig. 1 and 2, and includes: a semiconductor substrate 100, an N-well 101 located on the semiconductor substrate; a channel region 102 and a drift region 103 located within the N-well 101; an isolation region 104 located within the drift region 103; a gate 105 crosses the channel region 102, the N-well 101, and the drift region 103 and partially covers the isolation region 104; the drain region 106 is located in the drift region 103 and the source region 107 is located in the channel region 102. As can be seen from fig. 2, the surface electric field of the active region at the boundary between the drain-side gate and the isolation region of the P-type LDMOS with the structure is large, the breakdown voltage of the device is limited by the surface electric field of the active region at the boundary between the drain-side gate and the isolation region, and the breakdown voltage is low.
In order to increase the breakdown voltage of the P-type LDMOS, the current method is to additionally implant an implant region with a conductivity type opposite to that of the drift region in the drain region, and the implant region can change the charge distribution and depletion region of the device, thereby increasing the breakdown voltage of the device. However, in the manufacturing process, an additional layer of mask is required to be added for increasing the P-type LDMOS of the implantation region, which not only increases the manufacturing process, but also greatly increases the manufacturing cost.
Disclosure of Invention
The invention provides a semiconductor structure with high breakdown voltage and a forming method thereof, aiming at overcoming the problem of low breakdown voltage of the existing LDMOS device.
In order to achieve the above object, an embodiment of the present invention provides a method for forming a semiconductor structure, including: providing a semiconductor substrate, and forming a body region in the semiconductor substrate; forming a drift region in the body region, wherein the doping type of the drift region is opposite to that of the body region; forming a channel region in the body region, wherein part of the channel region extends towards the direction of the drift region to form at least one channel extension region, the at least one channel extension region and the drift region are distributed in an interdigital manner, and the doping type of the channel region is the same as that of the body region; forming an isolation region in the drift region, an end of the at least one channel extension region being located below the isolation region; forming a grid structure on the surface of the semiconductor substrate; and forming a source region in the channel region on one side of the gate structure, and forming a drain region in the drift region, wherein the drain region is positioned on one side of the isolation region far away from the channel region.
In one embodiment of the present invention, the formation process of at least one channel extension region includes: and forming a channel region mask layer on the surface of the semiconductor substrate, wherein the channel region mask layer is provided with at least one channel region injection window extending towards the direction of the drift region, the channel region mask layer is used as a mask for injection, and a channel extension region is formed in a body region corresponding to the at least one channel region injection window.
In an embodiment of the invention, at least one channel extension region is in contact with the drift region.
In an embodiment of the invention, at least one of the channel extension regions has a predetermined distance from the drift region.
In an embodiment of the present invention, when the semiconductor structure is a P-type LDMOS, the doping type of the body region and the doping type of the channel region are both N-type, and the doping type of the drift region, the doping type of the source region, and the doping type of the drain region are P-type; when the semiconductor structure is an N-type LDMOS, the doping types of the body region and the channel region are both P-type, and the doping types of the drift region, the source region and the drain region are all N-type.
In an embodiment of the invention, the implantation concentration of the channel region is greater than that of the drift region, and both the implantation concentration of the channel region and that of the drift region are 1017cm-3Magnitude.
The technical scheme of the invention also provides a semiconductor structure which comprises a semiconductor substrate, a body region, a drift region, a channel region, an isolation region, a grid structure, a source region and a drain region. The body region is positioned in the semiconductor substrate; the drift region is positioned in the body region, and the doping type of the drift region is opposite to that of the body region; the channel region is positioned in the body region, part of the channel region extends towards the direction of the drift region to form at least one channel extension region, interdigital distribution is formed between the at least one channel extension region and the drift region, and the doping type of the channel region is the same as that of the body region; the isolation region is positioned in the drift region, and the end part of the at least one channel extension region is positioned below the isolation region; the grid structure is positioned on the surface of the semiconductor substrate; the source region is positioned in the channel region at one side of the grid structure; the drain region is located in the drift region and located on one side of the isolation region away from the channel region.
In an embodiment of the invention, at least one of the channel extension regions has an elongated rectangular or trapezoidal shape.
In an embodiment of the invention, at least one channel extension region is in contact with the drift region.
In an embodiment of the invention, at least one of the channel extension regions has a predetermined distance from the drift region.
In an embodiment of the present invention, when the semiconductor structure is a P-type LDMOS, the doping type of the body region and the doping type of the channel region are both N-type, and the doping type of the drift region, the doping type of the source region, and the doping type of the drain region are P-type; when the semiconductor structure is an N-type LDMOS, the doping type of the body region and the doping type of the channel region are both P-type, and the doping type of the drift region, the doping type of the source region and the doping type of the drain region are N-type.
In an embodiment of the invention, the isolation region is a local field oxide isolation region or a shallow trench isolation region.
Compared with the prior art, the technical scheme of the invention has the following advantages:
the invention provides a semiconductor structure and a forming method thereof.A channel region and a drift region are formed in a body region, and the channel region extends towards the direction of the drift region to form at least one channel extension region. An interdigitated distribution is formed between the at least one channel extension region and the drift region. The arrangement enables the semiconductor structure provided by the invention to form a depletion region at a longitudinal PN junction between the body region and the drift region, and simultaneously form a transverse depletion region between the channel extension region and the drift region, and the transverse depletion region enables the surface electric field of the active region at the junction of the drain-end gate and the isolation region to be reduced, thereby improving the breakdown voltage of the device.
Further, a channel extension region and a drift region contact can be arranged, a lateral PN junction is formed between the channel extension region and the drift region, and lateral depletion can be achieved by the lateral PN junction under a small reverse bias voltage. However, since the vertical PN junction between the body region and the drift region is depleted in the vertical direction and also depleted in the lateral direction, the channel extension region and the drift region may not be in direct contact with each other at a predetermined distance during design. When the longitudinal PN junction between the body region and the drift region enters the channel extension region when the transverse depletion occurs, the drift region and the channel extension region are gradually depleted along the transverse direction along with the increase of the external voltage, and the effect of reducing the surface electric field of the active region at the junction of the drain terminal gate and the isolation region can also be achieved. In order to facilitate the production of the device and meet the design rule, the shape of the channel extension region is rectangular or trapezoidal.
In order to make the aforementioned and other objects, features and advantages of the present invention comprehensible, preferred embodiments accompanied with figures are described in detail below.
Drawings
Fig. 1 is a schematic structural diagram of a conventional P-type LDMOS device.
Fig. 2 is a schematic cross-sectional view of the P-type LDMOS device shown in fig. 1 along line AA'.
Fig. 3 to 9 are schematic structural diagrams illustrating a process of forming a semiconductor structure according to an embodiment of the invention.
Fig. 10 is a schematic structural diagram of a semiconductor structure according to an embodiment of the invention.
Detailed Description
Please refer to fig. 1 and fig. 2, wherein fig. 2 is a schematic cross-sectional view taken along line AA' of fig. 1. In the existing manufacturing process of the P-type LDMOS device, the surface electric field limits the breakdown voltage of the P-type LDMOS device because the active region at the junction of the drain-terminal gate and the isolation region has a larger surface electric field. The inventor finds that the breakdown voltage of the LDMOS device can be effectively improved by reducing the surface electric field of the active region at the junction of the drain-terminal gate and the isolation region.
Therefore, the invention provides a semiconductor structure and a forming method thereof, wherein channel regions and drift regions are distributed in an interdigital mode in a body region, and lateral depletion is formed between a channel extension region and the drift region on the channel region. The transverse drain extends to the whole active region where the drain end gate and the isolation region are intersected in the length direction of the gate structure, and the surface electric field of the active region where the drain end gate and the isolation region are intersected can be effectively reduced by the arrangement, so that the effect of improving the breakdown voltage of the semiconductor structure is achieved.
The following detailed description of specific embodiments of the invention refers to the accompanying drawings. In describing the embodiments of the present invention in detail, the drawings are not to be considered as being enlarged partially in accordance with the general scale, and the drawings are only examples, which should not be construed as limiting the scope of the present invention. In addition, the three-dimensional dimensions of length, width and depth should be included in the actual fabrication.
Fig. 3 to 9 are schematic structural diagrams illustrating a forming process of the semiconductor structure according to this embodiment. Wherein the positions of the hatching of fig. 7 to 9 are the same as those of fig. 5.
First, as shown in fig. 3, a semiconductor substrate 200 is provided, a body region 201 is formed in the semiconductor substrate 200, the doping type of the body region 201 is opposite to that of the semiconductor substrate 200, and a PN junction isolation is formed between the two. In the present embodiment, the material of the semiconductor substrate 200 is silicon, and the doping type thereof is P. However, the present invention is not limited thereto. In other embodiments, the semiconductor material 200 may be germanium, silicon carbide, silicon-on-insulator, or germanium-on-insulator.
In the present embodiment, the body region 201 is formed by epitaxy. The epitaxially formed body region 201 has a uniform impurity distribution with a doping concentration of 1016cm-3Magnitude. However, the present invention is not limited thereto. In other embodiments, body region 201 may be formed using a well implant process. Since the semiconductor structure provided by this embodiment is a P-type LDMOS, the body region 201 is doped with N-type impurity ions, which include one or more of phosphorus ions, arsenic ions, or antimony ions. However, the present invention is not limited thereto. In other embodiments, when the semiconductor structure is an N-type LDMOS, the body region 201 is doped with P-type impurity ions, including one or more of boron ions, gallium ions, or indium ions.
Next, fig. 4 to 6 are referred to. Fig. 4 is a top view after forming drift region 204 and channel region 203 in body region 201. Fig. 5 is a schematic cross-sectional view taken along line BB 'of fig. 4, and fig. 6 is a schematic cross-sectional view taken along line CC' of fig. 4.
First, a drift region mask layer is formed on the body region 201, the drift region mask layer has a drift region injection window, and P-type impurity ions are injected into the drift region injection window through a well to form a drift regionAnd (5) moving the region 204. However, the present invention is not limited thereto. When the formed semiconductor structure is an N-type LDMOS, the body region 201 may be formed by implanting N-type impurity ions through a well to form a drift region. To increase the breakdown voltage, the drift region 204 is provided with a lower doping concentration of 1017cm-3Magnitude. Preferably, the doping concentration of the drift region 204 is set to 1E17cm-3. However, the present invention is not limited thereto.
Next, a channel region 203 is formed in the body region 201, and the specific forming process is as follows: forming a channel region mask layer on the surface of the body region 201, wherein the channel region mask layer is provided with at least one channel region injection window extending towards the direction of the drift region 204, and performing well injection on the channel region 203 by taking the channel region mask layer as a mask, wherein the injection concentration is 1017cm-3Magnitude. The body region 201 corresponding to the channel region implant window forms a channel extension region 205. Preferably, the doping concentration of the channel region 203 is set to 5E17cm-3. However, the present invention is not limited thereto.
In the present embodiment, the channel region implantation window has a rectangular shape, and the doping type of the channel region 203 is the same as the doping type of the body region 201, and is all N-type impurity ions. However, the present invention is not limited in this regard. In other embodiments, the channel region implantation window on the channel mask layer may be in other patterns, such as a trapezoid, etc., that meet design rules; when the semiconductor structure is an N-type LDMOS, the impurities implanted into the channel region 203 are P-type impurity ions.
In the present embodiment, the channel region mask layer has a channel region implantation window extending toward the drift region 204, and correspondingly, the implanted channel region 204 has a channel extension region 205 thereon. However, the present invention is not limited thereto. In other embodiments, there may be more than two channel extensions 205 on the channel region 204.
In this embodiment, the channel mask layer and the drift mask layer are both made of silicon oxide. However, the present invention is not limited thereto. In other embodiments, the channel region mask layer and the drift region mask layer may both be silicon nitride.
Since the implantation concentration of the channel region 203 is higher than that of the drift region 204, the channel extension region 205 may invert the drift region 204, forming a PN junction. Therefore, the present invention does not limit the specific structure of the mask layer in the drift region. The specific structure of the drift region mask layer can be a finger matched with the channel region mask layer, a long strip rectangle in the traditional LDMOS structure or other structures meeting the design rule.
After implantation of the channel region, the structure shown in fig. 4 is finally formed. In this structure, cross-sectional views are formed for a position where the channel extension region 205 exists and a position where the channel extension region 205 does not exist, respectively. Fig. 5 is a cross-sectional view taken along line BB 'of fig. 4, and fig. 6 is a cross-sectional view taken along line CC' of fig. 4.
In fig. 5, the channel extension region 205 is in contact with the drift region 204, a lateral PN junction is formed between the two, and when a reverse bias is applied between the drain and the source, the channel extension region 205 and the drift region 204 are laterally depleted and the laterally depleted region extends to the entire active region where the drain terminal gate and the isolation region interface in the length direction of the gate structure 206. Lateral depletion causes the surface electric field of the drift region 204, especially the surface electric field of the active region where the drain-side gate and the isolation region border, to be reduced after the isolation region is formed. The reduction of the surface electric field tends to increase the breakdown voltage.
In fig. 6, the structure is the same as that of the conventional P-type LDMOS, and thus, when a forward bias is applied between the drain and the source, the parameters such as the on-resistance are not changed. Therefore, the semiconductor structure provided by this embodiment forms an interdigital distribution between the channel region 203 and the drift region 204 through the optimized design of the drain terminal, and can obtain a higher breakdown voltage without changing other characteristics of the device. Furthermore, as the leakage end injection is not required to be added, a layer of mask plate is reduced at the production moment, and the production cost is greatly reduced.
In the semiconductor structure shown in fig. 4, in addition to the lateral PN junction between the channel region 203 and the drift region 204, there is also a longitudinal PN junction between the drift region 204 and the body region 201. Therefore, in other embodiments, the channel extension region 205 and the drift region 204 may be disposed with a set distance therebetween that is less than a depletion distance of the vertical PN junction between the drift region 204 and the body region 201 in the lateral direction. When reverse bias is applied between the drain and the source, the longitudinal PN junction is depleted along the transverse direction and enters the channel extension region 205, and transverse depletion is formed between the channel extension region 205 and the drift region 204, so that the purpose of reducing the surface electric field of the active region at the boundary of the drain end gate and the isolation region 202 and improving the breakdown voltage is also achieved.
Referring to fig. 7, isolation regions 202 are formed within the drift region 204, with ends of the channel extension regions 205 located below the isolation regions 202. In this embodiment, the isolation region 202 is a shallow trench isolation region, and the specific forming process is as follows: an isolation groove with a depth smaller than that of the drift region 204 is formed on the surface of the drift region 204 through masking, photoetching and etching, an isolation material is filled in the isolation groove to finally form a shallow groove isolation region, and the isolation material can be silicon oxide, silicon nitride and the like. However, the present invention does not limit the specific structure of the isolation region 202 and the formation sequence thereof. In other embodiments, the isolation region 202 may be formed in the body region 201 first, and then the well implantation is performed to form the channel region 201 and the drift region 204, and the isolation region 202 may also be a local field oxide isolation region formed by local field oxidation and in a bird's beak shape.
Next, referring to fig. 8, a gate structure 206 is formed on the semiconductor substrate 200 where the channel region 203 and the drift region 204 are formed. The gate structure 206 is located over the channel region 203 on one side and over the isolation region 205 on the other side. The gate structure 206 includes a gate dielectric layer 207 on the surface of the semiconductor substrate 200, a gate electrode 208 on the gate dielectric layer 207, and sidewalls (not shown) on both sidewalls of the gate dielectric layer 207 and the gate electrode 208. In this embodiment, the gate dielectric layer 207 may be silicon oxide, the gate electrode 208 may be polysilicon, and the sidewall spacers include silicon oxide and silicon nitride. However, the present invention is not limited thereto. In other embodiments, gate dielectric layer 207 may be a high-k material and gate electrode 208 may be a metal.
Finally, referring to fig. 9, a source region 209 is formed in the channel region 203 on one side of the gate structure 206, and a drain region 210 is formed in the drift region 204 on the other side of the gate structure 206, wherein the drain region 210 is located on one side of the isolation region 202 away from the channel region 203. In the present embodiment, the source region 209 and the drain region 210 are both formed by ion implantation, and the doping type of the source region 209 and the doping type of the drain region 210 are both P-type, which are opposite to the doping type of the body region 201. However, the present invention is not limited thereto. In other embodiments, when the semiconductor structure is an N-type LDMOS, the doping type of the source region 209 and the doping type of the drain region 210 are both N-type.
In the semiconductor structure formed by the above method, the channel region 203 extends in the direction of the drift region 204, and the channel extension region 205 and the drift region 204 are distributed in an interdigital manner. When reverse bias is applied between the drain and the source, the channel extension region 205 and the drift region 204 are laterally depleted, which can effectively reduce the surface electric field of the active region between the drain-side gate and the isolation region 205, thereby achieving the purpose of improving the breakdown voltage. In addition, the structure of the other parts of the semiconductor structure formed by the above method except the channel extension region 205 is the same as that of the conventional P-type LDMOS, and the electrical characteristics of the conventional P-type LDMOS can still be maintained.
Corresponding to the above method for forming a semiconductor structure, the present embodiment further provides a semiconductor structure, and specifically refers to fig. 10. Fig. 10 is a top view of the semiconductor structure provided in this embodiment. The semiconductor structure provided by the embodiment comprises:
a semiconductor substrate 200, in the present embodiment, the doping type of the semiconductor substrate is P-type;
a body region 201 of a doping type N located within the semiconductor substrate 200. However, the present invention is not limited thereto. In other embodiments, when the semiconductor structure is a P-type LDMOS, the doping type of the body region 201 is P-type, and correspondingly, the doping type of the semiconductor substrate 200 is N-type.
A drift region 204 located within the body region 201, the drift region 204 having a doping type opposite to the doping type of the body region 201. The doping type of the drift region 204 is P-type in this embodiment. However, the present invention is not limited thereto. In other embodiments, when the semiconductor structure is a P-type LDMOS, the doping type of the drift region 204 is N-type.
A channel region 203 located in the body region, a doping type of the channel region 203 is the same as a doping type of the body region 201, and in the present embodiment, the doping type of the channel region 203 is N-type. The channel region 203 extends partially in the direction of the drift region 204 to form at least one channel extension region 205, and an interdigital distribution is formed between the at least one channel extension region 205 and the drift region 204. In the present embodiment, the channel region 203 has a channel extension region 205 thereon. However, the present invention is not limited thereto. In other embodiments, there may be more than two channel extensions 205 on the channel region 203.
An isolation region 202 located within the drift region 204. In the present embodiment, the isolation region 202 is a shallow trench isolation region having a depth smaller than that of the body region 201. However, the present invention is not limited thereto. In other embodiments, the isolation region 202 may be a local field oxide isolation region.
And a gate structure 206 located on the surface of the semiconductor substrate 200, wherein one side of the gate structure 206 is located above the channel region 203, and the other side is located above the isolation region 202. In the present embodiment, the gate structure 206 includes a gate dielectric layer 207 on the surface of the semiconductor substrate 200, a gate electrode 208 on the gate dielectric layer 207, and sidewalls on both sidewalls of the gate dielectric layer 207 and the gate electrode 208.
A source region 209 in the channel region 203 on one side of the gate structure 206;
a drain region 210 located within the body region 201 and on a side of the isolation region 202 remote from the channel region 203. In the present embodiment, the doping type of the source region 209 is the same as the doping type of the drain region 210, and both are P-type. However, the present invention is not limited thereto. In other embodiments, when the semiconductor structure is an N-type LDMOS, the doping type of the source region 209 and the doping type of the drain region 210 are the same and both are N-type.
Compared with the prior art, the technical scheme of the invention has the following advantages:
according to the semiconductor structure and the forming method thereof provided by the invention, the channel region 203 and the drift region 204 are formed in the body region 201, the channel region 203 partially extends towards the direction of the drift region 204, and at least one channel extension region 205 is formed. An interdigitated distribution is formed between the at least one channel extension region 205 and the drift region 204. The arrangement enables the semiconductor structure provided by the invention to form a depletion region at a longitudinal PN junction between the body region 201 and the drift region 204, and simultaneously form a transverse depletion region between the channel region extension region 205 and the drift region 204, and the transverse depletion region enables the surface electric field of an active region at the boundary of a drain terminal gate and an isolation region to be reduced, so that the breakdown voltage of the device is improved.
Further, the channel extension region 205 and the drift region 204 may be disposed in contact with each other to form a lateral PN junction therebetween, which may achieve lateral depletion under a small reverse bias. However, since the vertical PN junction between the body region 201 and the drift region 204 is depleted longitudinally and also depleted laterally, the channel extension region 205 and the drift region 204 may be set to be not in direct contact during design, and a set distance is provided between the two regions, when the vertical PN junction between the body region 201 and the drift region 204 is depleted laterally, the vertical PN junction enters the channel region 203, and with the increase of the applied voltage, the drift region 204 and the channel region 203 are gradually depleted laterally, which may also achieve the effect of reducing the surface electric field of the active region at the interface of the drain gate and the isolation region. In order to facilitate the production of the device and meet the design rule, the shape of the channel extension region is rectangular or trapezoidal.
Although the present invention has been described with reference to the preferred embodiments, it should be understood that various changes and modifications can be made therein by those skilled in the art without departing from the spirit and scope of the invention as defined by the appended claims.

Claims (4)

1. A method of forming a semiconductor structure, comprising:
providing a semiconductor substrate, and forming a body region in the semiconductor substrate;
forming a drift region in the body region, wherein the doping type of the drift region is opposite to that of the body region;
forming a channel region in the body region, wherein the channel region partially extends towards the direction of the drift region to form at least one channel extension region, the at least one channel extension region and the drift region form interdigital distribution, and the doping type of the channel region is the same as that of the body region;
forming an isolation region within the drift region, an end of the at least one channel extension region being located below the isolation region;
forming a grid structure on the surface of the semiconductor substrate;
forming a source region in the channel region on one side of the gate structure, and forming a drain region in the drift region, wherein the drain region is located on one side of the isolation region away from the channel region;
when the semiconductor structure is a P-type LDMOS, the doping type of the body region and the doping type of the channel region are both N-type, and the doping type of the drift region, the doping type of the source region and the doping type of the drain region are all P-type; when the semiconductor structure is an N-type LDMOS, the doping type of the body region and the doping type of the channel region are both P-type, and the doping type of the drift region, the doping type of the source region and the doping type of the drain region are all N-type;
the injection concentration of the channel region is greater than that of the drift region, and the injection concentration of the channel region and that of the drift region are both 1017cm-3Magnitude;
the at least one channel extension region has a set distance from the drift region that is less than a depletion distance of a vertical PN junction between the drift region and the body region in a lateral direction.
2. The method of claim 1, wherein the at least one channel extension region is formed by: and forming a channel region mask layer on the surface of the semiconductor substrate, wherein the channel region mask layer is provided with at least one channel region injection window extending towards the direction of the drift region, the channel region mask layer is used as a mask for injection, and a channel extension region is formed in the body region corresponding to the at least one channel region injection window.
3. A semiconductor structure, comprising:
a semiconductor substrate;
a body region located within the semiconductor substrate;
a drift region located in the body region, the drift region having a doping type opposite to that of the body region;
the channel region is positioned in the body region, part of the channel region extends towards the direction of the drift region to form at least one channel extension region, interdigital distribution is formed between the at least one channel extension region and the drift region, and the doping type of the channel region is the same as that of the body region;
an isolation region located within the drift region, an end of at least one channel extension region being located below the isolation region;
the grid structure is positioned on the surface of the semiconductor substrate;
the source region is positioned in the channel region on one side of the grid structure;
the drain region is positioned in the drift region and positioned on one side, far away from the channel region, of the isolation region;
the at least one channel extension region has a set distance from the drift region that is less than a depletion distance of a vertical PN junction between the drift region and the body region in a lateral direction.
4. The semiconductor structure of claim 3, wherein when the semiconductor structure is a P-type LDMOS, the doping type of the body region and the doping type of the channel region are both N-type, and the doping type of the drift region, the doping type of the source region, and the doping type of the drain region are all P-type; when the semiconductor structure is an N-type LDMOS, the doping type of the body region and the doping type of the channel region are both P-type, and the doping type of the drift region, the doping type of the source region and the doping type of the drain region are all N-type.
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