LDMOS device and forming method thereof

Abstract

The LDMOS device structurally comprises a first field oxide structure located in a drift region, the first field oxide structure is provided with a first side wall and a second side wall which are opposite to each other, the first side wall is step-shaped, the second side wall is inclined, and the included angle between the second side wall and the bottom of the first field oxide structure is an obtuse angle; the gate structure is located on the surface of the substrate, part of the gate structure is located on the body region, and the other part of the gate structure is located on the drift region; the source region is positioned in the body region on one side of the gate structure; the first field oxide structure is located between the drain region and the gate structure, the first side wall is close to the gate structure, and the second side wall is close to the drain region, so that the breakdown voltage can be improved, the hot carrier effect can be inhibited, local electric field concentration can be weakened, and the reliability of the device can be improved. And the reliability of the device is improved on the whole.

Description

LDMOS devices and their fabrication methods Technical Field

[0001] This invention relates to the field of semiconductor manufacturing technology, and in particular to an LDMOS device and a method for forming the same. Background Technology

[0002] Lateral double-diffused metal-oxide-semiconductor field-effect transistors (LDMOS) are widely used in the automotive industry due to their numerous advantages, such as high voltage resistance, high gain, low distortion, process compatibility, and design efficiency. These applications include areas like emission reduction, energy saving, advanced driver assistance systems, and enhancing personalization and comfort. They are also used in the medical field, such as ultrasound imaging and advanced power management control.

[0003] However, the performance of existing LDMOS devices needs further improvement. Summary of the Invention

[0004] The technical problem solved by this invention is to provide an LDMOS device and a method for forming the same, so as to improve the performance of the formed device.

[0005] To address the aforementioned technical problems, the present invention provides an LDMOS device, comprising: a substrate; a body region and a drift region adjacent to each other within the substrate; a first field oxygen structure located within the drift region, the first field oxygen structure having opposing first and second sidewalls, the first sidewall being stepped, the second sidewall being inclined, and the angle between the second sidewall and the bottom of the first field oxygen structure being obtuse; a gate structure located on the surface of the substrate, the gate structure being partially located on the body region and partially located on the drift region; a source region located within the body region on one side of the gate structure; and a drain region located in the drift region on the other side of the gate structure, the first field oxygen structure being located between the drain region and the gate structure, the first sidewall being close to the gate structure, and the second sidewall being close to the drain region.

[0006] Optionally, the first field oxygen structure includes a first field oxygen layer, a second field oxygen layer, and a third field oxygen layer arranged and adjacent to each other along a first direction, the first direction being parallel to the substrate surface, the second field oxygen layer being located between the first field oxygen layer and the third field oxygen layer, the depth of the second field oxygen layer being less than the depth of the first field oxygen layer, and the depth of the third field oxygen layer being less than the depth of the second field oxygen layer.

[0007] Optionally, the substrate includes an isolation region and an active region, the isolation region being located on the sidewall of the active region, and the body region and the drift region being located in the active region; the LDMOS device further includes an isolation structure located within the isolation region, wherein the depth of the second field oxide layer is equal to the depth of the isolation structure.

[0008] Optionally, the first field oxygen structure portion also extends to the bottom of the gate structure.

[0009] Optionally, it further includes: a second field oxygen structure located on the surface of the substrate, the second field oxygen structure being located on the surface of the first field oxygen structure and adjacent to the gate structure.

[0010] Optionally, it may also include a contact field plate located on the second field oxygen structure.

[0011] Optionally, the gate structure includes a gate oxide layer and a gate layer located on the surface of the gate oxide layer, wherein a portion of the gate layer extends onto the second field oxide structure and is separate from the contact field plate.

[0012] Optionally, it may also include: a plurality of metal field plates located on the second field oxygen structure, wherein the plurality of metal field plates are distributed from dense to sparse in the direction from the source region to the drain region.

[0013] Optionally, the corners of the first oxygen structure are arc-shaped.

[0014] Accordingly, the present invention also provides a method for forming an LDMOS device, comprising: providing a substrate; forming a first field oxygen structure in the substrate, the first field oxygen structure having opposing first sidewalls and second sidewalls, the first sidewall being stepped, the second sidewall being inclined, and the angle between the second sidewall and the bottom of the first field oxygen structure being obtuse; forming adjacent body regions and drift regions in the substrate, the first field oxygen structure being located in the drift region; forming a gate structure on the surface of the substrate, the gate structure being partially located on the body region and partially located on the drift region; forming a source region in the body region on one side of the gate structure; forming a drain region in the drift region on the other side of the gate structure, the first field oxygen structure being located between the drain region and the gate structure, the first sidewall being close to the gate structure, and the second sidewall being close to the drain region.

[0015] Optionally, the method for forming the first field oxygen structure includes: forming a first groove in the substrate using a first etching process; forming a first field oxygen layer in the first groove; forming a second groove in the substrate using a second etching process, wherein the sidewalls of the second groove expose the first field oxygen layer and its depth is less than the depth of the first groove; forming a second field oxygen layer in the second groove; forming a third groove in the substrate using a third etching process, wherein the sidewalls of the third groove expose the second field oxygen layer and its depth is less than the depth of the second groove; forming a third field oxygen layer in the third groove, thereby forming the first field oxygen structure with the first field oxygen layer, the second field oxygen layer, and the third field oxygen layer, wherein the first field oxygen layer, the second field oxygen layer, and the third field oxygen layer are arranged along a first direction, the first direction being parallel to the substrate surface.

[0016] Optionally, the method further includes: after the first etching process and before the formation of the first field oxide layer, using a first repair process to round the bottom corner of the first groove to make it arc-shaped; after the second etching process and before the formation of the second field oxide layer, using a second repair process to round the bottom corner of the second groove to make it arc-shaped; and after the third etching process and before the formation of the third field oxide layer, using a third repair process to round the bottom corner of the third groove to make it arc-shaped.

[0017] Optionally, the substrate includes an isolation region and an active region, the isolation region being located on the sidewall of the active region; the method further includes: forming the body region and the drift region within the active region; simultaneously forming the second groove, employing the second etching process to form an isolation trench within the isolation region; and simultaneously forming the second field oxide layer, forming an isolation structure within the isolation trench.

[0018] Optionally, before forming the gate structure, the method further includes: forming a second field oxygen structure on the surface of the first field oxygen structure; and after forming the second field oxygen structure, forming a gate oxide layer and a gate layer located on the surface of the gate oxide layer on the substrate surface, wherein the gate structure includes the gate oxide layer and the gate layer, and the gate structure is adjacent to the second field oxygen structure.

[0019] Optionally, it also includes forming a contact field plate on the second field oxygen structure.

[0020] Optionally, the gate layer portion also extends onto the second field oxygen structure and is separate from the contact field plate.

[0021] Optionally, it further includes: forming a plurality of metal field plates on the second field oxygen structure, wherein the plurality of metal field plates are distributed from dense to sparse in the direction from the source region to the drain region.

[0022] Optionally, the gate structure portion is formed on the surface of the first field oxygen structure.

[0023] Compared with the prior art, the technical solution of the embodiments of the present invention has the following beneficial effects:

[0024] In the LDMOS device formation method provided by the present invention, a first field oxygen structure with a special shape is set. The first field oxygen structure is stepped on the side near the gate structure. Under the condition of increased average electric field in the drift region, the electric field concentration problem on the surface of the drift region can be reduced, which is conducive to improving the breakdown voltage and suppressing the hot carrier effect. At the same time, since the first field oxygen structure is inclined on the side near the drain region and the angle between the second sidewall and the bottom of the first field oxygen structure is obtuse, the local electric field concentration can be weakened, thereby improving the overall reliability of the device.

[0025] In the LDMOS device provided by the present invention, a first field oxygen structure with a special shape is provided. The first field oxygen structure is stepped on the side near the gate structure. Under the condition that the average electric field in the drift region increases, the electric field concentration problem on the surface of the drift region can be reduced, which is conducive to improving the breakdown voltage and suppressing the hot carrier effect. At the same time, since the first field oxygen structure is inclined on the side near the drain region and the angle between the second sidewall and the bottom of the first field oxygen structure is obtuse, the local electric field concentration can be weakened, thereby improving the overall reliability of the device. Attached Figure Description

[0026] Figure 1 is a schematic cross-sectional view of an LDMOS device;

[0027] Figures 2 to 14 are schematic diagrams of the steps in the formation method of an LDMOS device according to an embodiment of the present invention. Detailed Implementation

[0028] It should be noted that the terms "surface" and "on" in this specification are used to describe the relative spatial position and are not limited to whether there is direct contact.

[0029] As described in the background section, the performance of LDMOS devices manufactured using existing technologies urgently needs improvement. This paper will now illustrate and analyze this issue using an LDMOS device as an example.

[0030] Figure 1 is a schematic cross-sectional view of an LDMOS device.

[0031] Please refer to Figure 1. The LDMOS device includes: a substrate 100; a body region 101 and a drift region 102 located adjacent to each other within the substrate 100; a gate structure 103 located on the substrate 100, with a portion of the gate structure 103 located on the body region 101 and another portion of the gate structure located on the drift region 102; a field oxide layer 104 located within the drift region 102; a source doped region 105 located within the body region 101 on one side of the gate structure 103; and a drain doped region 106 located within the drift region 102 on the other side of the gate structure 103, wherein the field oxide layer 104 is closer to the gate structure 103 than the drain doped region 106.

[0032] For the aforementioned LDMOS devices, breakdown voltage and on-resistance are a pair of parameters constrained by physical laws and must be balanced. How to reasonably mitigate the contradiction between breakdown voltage and on-resistance while ensuring high stability is a pressing issue. Furthermore, for high-voltage (e.g., >40V) devices, the drain must withstand high voltage, resulting in significant hot carrier injection (HCI), which can lead to severe device degradation. Therefore, under the same breakdown voltage, how to reduce the electric field strength near the field oxide layer 104, thereby reducing the hot carrier effect, is also a pressing problem to be solved.

[0033] To address the aforementioned issues, the LDMOS device and its formation method provided by this invention incorporate a specially shaped first field oxygen structure. This first field oxygen structure is stepped on the side near the gate structure. Under conditions where the average electric field in the drift region increases, it can reduce the electric field concentration on the surface of the drift region, thereby improving the breakdown voltage and suppressing the hot carrier effect. Simultaneously, since the first field oxygen structure is inclined on the side near the drain region, and the angle between the second sidewall and the bottom of the first field oxygen structure is obtuse, it can weaken the local electric field concentration, thus improving the overall reliability of the device.

[0034] To make the above-mentioned objectives, features and beneficial effects of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0035] Figures 2 to 14 are schematic diagrams of the steps in the formation method of an LDMOS device according to an embodiment of the present invention.

[0036] Please refer to Figure 2, which provides substrate 200.

[0037] The substrate 200 has an N-type or P-type conductivity.

[0038] In this embodiment, the substrate 200 includes a substrate (not shown in the figure) and an epitaxial layer (not shown in the figure) located on the surface of the substrate. Subsequent bulk regions, drift regions, and first field oxygen structures are formed within the epitaxial layer.

[0039] In this embodiment, the substrate 200 is of P-type conductivity and is used to form an NMOS device.

[0040] In another embodiment, the substrate is of N-type conductivity and is used to form a PMOS device.

[0041] In this embodiment, the substrate 200 is made of silicon.

[0042] In other embodiments, the substrate material includes silicon carbide, silicon germanium, a multi-element semiconductor material composed of group III-V elements, silicon-on-insulator (SOI), or germanium-on-insulator (GOI). The multi-element semiconductor material composed of group III-V elements includes InP, GaAs, GaP, InAs, InSb, InGaAs, or InGaAsP.

[0043] In this embodiment, the substrate 200 includes an isolation region (not shown) and an active region (not shown), with the isolation region located on the sidewall of the active region. Subsequently, the body region and the drift region are formed within the active region.

[0044] Subsequently, a first field oxygen structure is formed within the substrate 200. The first field oxygen structure has opposing first and second sidewalls. The first sidewall is stepped, the second sidewall is inclined, and the angle between the second sidewall and the bottom of the first field oxygen structure is obtuse.

[0045] In this embodiment, the first sidewall is a three-tiered staircase.

[0046] In other embodiments, the first sidewall may be two or more steps.

[0047] In this embodiment, the method for forming the first field oxygen structure is shown in Figures 3 to 10.

[0048] Please refer to Figure 3. A first groove 201 is formed in the substrate 200 using a first etching process.

[0049] In this embodiment, after the first etching process and before the formation of the first field oxygen layer, please also refer to Figure 4.

[0050] Please refer to Figure 4. The bottom corner of the first groove 201 is rounded using the first repair process to make it arc-shaped (as shown by the dotted circle).

[0051] The first repair process includes one or both of dry etching and wet etching. In this embodiment, the first repair process is wet etching.

[0052] Please refer to Figure 5, where a first field oxygen layer 202 is formed in the first groove 201.

[0053] The method for forming the first field oxygen layer 202 includes: forming a first insulating material layer (not shown in the figure) in the first groove 201 and on the surface of the substrate 200; and patterning the first insulating material layer until the surface of the substrate 200 is exposed.

[0054] The formation process of the first insulating material layer includes a high-density plasma chemical vapor deposition process.

[0055] In this embodiment, the material of the first insulating material layer is silicon oxide.

[0056] In this embodiment, before forming the first insulating material layer, a first inner lining material layer (not shown in the figure) is also formed on the sidewall and bottom surface of the first groove 201; the material of the first inner lining material layer is silicon nitride or silicon oxide.

[0057] Please refer to Figure 6. A second etching process is used to form a second groove 203 in the substrate 200. The sidewalls of the second groove 203 expose the first field oxide layer 202, and its depth is less than the depth of the first groove 201.

[0058] In this embodiment, after the second etching process and before the formation of the second field oxide layer, a second repair process is used to round the bottom corner of the second groove 203, making it arc-shaped.

[0059] In this embodiment, while forming the second groove 203, the second etching process is also used to form an isolation trench 204 in the isolation area.

[0060] Please refer to Figure 7, where a second field oxygen layer 205 is formed in the second groove 203.

[0061] While the second field oxygen layer 205 is being formed, an isolation structure 206 is being formed within the isolation trench 204. The isolation structure 206 is used to form electrical insulation between different devices.

[0062] The method for forming the second field oxygen layer 205 and the isolation structure 206 includes: forming a second insulating material layer (not shown) in the second groove 203 and on the surface of the substrate 200; and patterning the second insulating material layer until the surface of the substrate 200 is exposed.

[0063] The process for forming the second insulating material layer includes a high-density plasma chemical vapor deposition process.

[0064] In this embodiment, the material of the second insulating material layer is silicon oxide.

[0065] In this embodiment, before forming the second insulating material layer, a second inner lining material layer (not shown in the figure) is also formed on the sidewall and bottom surface of the second groove 204; the material of the second inner lining material layer is silicon nitride or silicon oxide.

[0066] Please refer to Figure 8. A third groove 207 is formed in the substrate 200 using a third etching process. The sidewalls of the third groove 207 expose the second field oxide layer 204, and its depth is less than the depth of the second groove 203.

[0067] In this embodiment, after the third etching process and before the formation of the third field oxide layer, a third repair process is also used to round the bottom corner of the third groove 207, making it arc-shaped.

[0068] Please refer to Figures 9 and 10. Figure 10 is a partial enlarged view of Figure 9. A third field oxide layer 208 is formed in the third groove 207. The first field oxide structure is formed by the first field oxide layer 202, the second field oxide layer 204 and the third field oxide layer 208. The first field oxide layer 202, the second field oxide layer 204 and the third field oxide layer 208 are arranged along a first direction X, which is parallel to the surface of the substrate 200.

[0069] Thus, the first field oxygen structure formed has a first sidewall a1 and a second sidewall a2 with opposite sides. The first sidewall a1 is stepped, the second sidewall a2 is inclined, and the angle α between the second sidewall a2 and the bottom of the first field oxygen structure is an obtuse angle.

[0070] In this embodiment, the method for forming the third field oxygen layer 208 includes: forming a third insulating material layer (not shown in the figure) in the third groove 207 and on the surface of the substrate 200; and patterning the third insulating material layer until the surface of the substrate 200 is exposed.

[0071] The formation process of the third insulating material layer includes a high-density plasma chemical vapor deposition process.

[0072] In this embodiment, the material of the third insulating layer is silicon oxide.

[0073] In this embodiment, before forming the third insulating material layer, a third inner lining material layer (not shown in the figure) is also formed on the sidewall and bottom surface of the third groove 207; the material of the third inner lining material layer is silicon nitride or silicon oxide.

[0074] In this embodiment, the angle α between the second sidewall a2 and the bottom of the first field oxygen structure is greater than 135 degrees. The purpose of setting the above-mentioned angle range is to further reduce the problem of local electric field concentration, which is beneficial to improving the breakdown voltage and suppressing the hot carrier effect.

[0075] In this embodiment, the corners of the first field oxygen structure are arc-shaped (as shown by the dashed circle in Figure 10). Making the corners of the first field oxygen structure arc-shaped further reduces the problem of local electric field concentration, which is beneficial for increasing the breakdown voltage and suppressing the hot carrier effect.

[0076] It should be noted that the corner specifically refers to the corner of the stepped edge of the first sidewall a1, the corner formed by the first sidewall a1 and the bottom of the first field oxygen structure, and the corner formed by the second sidewall a2 and the bottom of the first field oxygen structure.

[0077] Please refer to Figure 11. Adjacent body regions 209 and drift regions 210 are formed in the substrate 200, and the first field oxygen structure is located in the drift region 210.

[0078] Specifically, the body region 209 and the drift region 210 are formed within the active region.

[0079] The body region 209 and the drift region 210 have different conductivity types.

[0080] In this embodiment, the body region 209 is P-type and the drift region 210 is N-type.

[0081] In another embodiment, the body region is N-type and the drift region is P-type.

[0082] Please refer to Figure 12. A gate structure is formed on the surface of the substrate 200. Part of the gate structure is located on the body region 209, and another part is located on the drift region 210.

[0083] In this embodiment, the gate structure portion is formed on the surface of the first field oxygen structure. Forming the gate structure portion on the surface of the first field oxygen structure further helps to suppress the hot carrier effect.

[0084] In another embodiment, the second field oxygen structure is not located at the bottom of the gate structure, but only between the gate structure and the drain region.

[0085] In this embodiment, the gate structure includes a gate oxide layer 211 and a gate layer 212 located on the surface of the gate oxide layer 211.

[0086] In this embodiment, before forming the gate structure, a second field oxygen structure 213 is also formed on the surface of the first field oxygen structure.

[0087] In this embodiment, after the second field oxygen structure 213 is formed, the gate structure is formed on the surface of the substrate 200, and the gate structure is adjacent to the second field oxygen structure 213.

[0088] In this embodiment, a portion of the gate layer 212 extends onto the second field oxygen structure 213. This extension of the gate layer 212 onto the second field oxygen structure 213 further improves the electric field distribution, which is beneficial for increasing the device breakdown voltage.

[0089] Please refer to Figure 13. A source region 214 is formed in the body region 209 on one side of the gate structure; a drain region 215 is formed in the drift region 210 on the other side of the gate structure. The first field oxygen structure is located between the drain region 215 and the gate structure. The first sidewall is close to the gate structure, and the second sidewall is close to the drain region 215.

[0090] Thus, by setting a first field oxygen structure with a special shape, which is stepped on the side near the gate structure, the electric field concentration problem on the surface of the drift region 210 can be reduced under the condition of increased average electric field in the drift region 210, which is beneficial to improving the breakdown voltage and suppressing the hot carrier effect. At the same time, since the first field oxygen structure is inclined on the side near the drain region 215, and the angle between the second sidewall and the bottom of the first field oxygen structure is obtuse, the local electric field concentration can be weakened, thereby improving the overall reliability of the device.

[0091] In this embodiment, the leak region 215 is adjacent to the first field oxygen structure.

[0092] In another embodiment, the leak region may be at a certain distance from the first field oxygen structure.

[0093] The source region 214 and the drain region 215 have the same conductivity type, and their conductivity type is the same as that of the drift region 210.

[0094] In this embodiment, the source region 214 and the drain region 215 are of the N-type conductivity.

[0095] In another embodiment, the source region and the drain region are of P-type conductivity.

[0096] In this embodiment, an outlet region 216 is also formed within the body region 209.

[0097] The conductivity type of the lead-out region 216 is the same as that of the body region 209.

[0098] In this embodiment, the conductivity type of the lead-out region 216 is P-type.

[0099] Please refer to Figure 14. A contact field plate 217 is formed on the second field oxygen structure 213, and the gate layer 212 and the contact field plate 217 are separate from each other.

[0100] The purpose of setting the contact field plate 217 is to further reduce the electric field concentration problem on the surface of the drift region 210, which is beneficial to improve the breakdown voltage and suppress the hot carrier effect.

[0101] In another embodiment, the contact field plate may not be formed.

[0102] In this embodiment, a plurality of metal field plates (not shown in the figure) are also formed on the second field oxygen structure 213. The plurality of metal field plates are distributed from dense to sparse in the direction from the source region 214 to the drain region 215. Here, the purpose of setting the second field oxygen structure 213 is to further reduce the electric field concentration problem on the surface of the drift region 210, which is beneficial to improving the breakdown voltage and suppressing the hot carrier effect.

[0103] In another embodiment, it may be unnecessary to form several of the aforementioned metal field plates.

[0104] Specifically, a first dielectric layer (not shown in the figure) is formed on the surface of the substrate and the second field oxygen structure 213; the contact field plate 217 is formed in the first dielectric layer; a second dielectric layer is formed on the first dielectric layer; and a plurality of the metal field plates are formed in the second dielectric layer (not shown in the figure).

[0105] Accordingly, this embodiment of the invention also provides an LDMOS device formed using the above method. Please continue to refer to FIG14, including: a substrate 200; a body region 209 and a drift region 210 located adjacent to each other within the substrate 200; a first field oxygen structure located within the drift region 210, the first field oxygen structure having opposing first sidewalls a1 (as shown in FIG10) and second sidewalls a2 (as shown in FIG10), the first sidewall a1 being stepped, the second sidewall a2 being inclined, and the second sidewall a2 being adjacent to the substrate of the first field oxygen structure. The included angle α of the part (as shown in Figure 10) is an obtuse angle; the gate structure is located on the surface of the substrate 200, with part of the gate structure located on the body region 209 and another part located on the drift region 210; the source region 214 is located in the body region 209 on one side of the gate structure; the drain region 215 is located in the drift region 210 on the other side of the gate structure, the first field oxygen structure is located between the drain region 215 and the gate structure, the first sidewall a1 is close to the gate structure, and the second sidewall a2 is close to the drain region 215.

[0106] Thus, by setting a first field oxygen structure with a special shape, which is stepped on the side near the gate structure, the electric field concentration problem on the surface of the drift region 210 can be reduced under the condition of increased average electric field in the drift region 210, which is beneficial to improving the breakdown voltage and suppressing the hot carrier effect. At the same time, since the first field oxygen structure is inclined on the side near the drain region 215, and the angle between the second sidewall and the bottom of the first field oxygen structure is obtuse, the local electric field concentration can be weakened, thereby improving the overall reliability of the device.

[0107] In this embodiment, the first field oxygen structure includes a first field oxygen layer 202, a second field oxygen layer 204, and a third field oxygen layer 208 arranged and adjacent to each other along a first direction X. The first direction X is parallel to the surface of the substrate 200. The second field oxygen layer 204 is located between the first field oxygen layer 202 and the third field oxygen layer 208. The depth of the second field oxygen layer 204 is less than the depth of the first field oxygen layer 202, and the depth of the third field oxygen layer 208 is less than the depth of the second field oxygen layer 204.

[0108] In this embodiment, the substrate 200 includes an isolation region (not shown in the figure) and an active region (not shown in the figure). The isolation region is located on the sidewall of the active region, and the body region and the drift region are located in the active region.

[0109] In this embodiment, the LDMOS device further includes an isolation structure 206 located within the isolation region, wherein the depth of the second field oxide layer 204 is equal to the depth of the isolation structure 206.

[0110] In this embodiment, the first field oxygen structure portion further extends to the bottom of the gate structure.

[0111] In this embodiment, the LDMOS device further includes a second field oxygen structure 213 located on the surface of the substrate 200. The second field oxygen structure 213 is located on the surface of the first field oxygen structure and is adjacent to the gate structure.

[0112] In this embodiment, the LDMOS device further includes a contact field plate 217, which is located on the second field oxygen structure 213.

[0113] In this embodiment, the gate structure includes a gate oxide layer 211 and a gate layer 212 located on the surface of the gate oxide layer 211. The gate layer 212 extends to the second field oxide structure 213 and is separate from the contact field plate 217.

[0114] In this embodiment, the LDMOS device further includes a plurality of metal field plates (not shown in the figure) located on the second field oxygen structure 213, wherein the plurality of metal field plates are distributed from dense to sparse in the direction from the source region 214 to the drain region 215.

[0115] In this embodiment, the corners of the first field oxygen structure are arc-shaped.

[0116] While the present invention has been disclosed above, it is not limited thereto. Any person skilled in the art can make various modifications and alterations without departing from the spirit and scope of the invention; therefore, the scope of protection of the present invention should be determined by the scope defined in the claims.

Claims

1. An LDMOS device, characterized in that, include: Substrate; Located within the substrate, adjacent bulk and drift regions; A first field oxygen structure located within the drift region, the first field oxygen structure having opposing first and second sidewalls, the first sidewall being stepped, the second sidewall being inclined, and the angle between the second sidewall and the bottom of the first field oxygen structure being an obtuse angle; a gate structure located on the substrate surface, the gate structure being partially located on the body region and partially located on the drift region; The source region located within the body region on one side of the gate structure; The drain region of the drift region is located on the other side of the gate structure. The first field oxygen structure is located between the drain region and the gate structure. The first sidewall is close to the gate structure, and the second sidewall is close to the drain region.

2. The LDMOS device as described in claim 1, characterized in that, The first field oxygen structure includes a first field oxygen layer, a second field oxygen layer, and a third field oxygen layer arranged and adjacent to each other along a first direction, the first direction being parallel to the substrate surface, the second field oxygen layer being located between the first field oxygen layer and the third field oxygen layer, the depth of the second field oxygen layer being less than the depth of the first field oxygen layer, and the depth of the third field oxygen layer being less than the depth of the second field oxygen layer.

3. The LDMOS device as described in claim 2, characterized in that, The substrate includes an isolation region and an active region, the isolation region being located on the sidewall of the active region, and the bulk region and the drift region being located in the active region; The LDMOS device further includes an isolation structure located within the isolation region, wherein the depth of the second field oxide layer is equal to the depth of the isolation structure.

4. The LDMOS device as described in claim 1, characterized in that, The first field oxygen structure portion also extends to the bottom of the gate structure.

5. The LDMOS device as described in claim 1, characterized in that, Also includes: A second field oxygen structure is located on the surface of the substrate, the second field oxygen structure is located on the surface of the first field oxygen structure, and is adjacent to the gate structure.

6. The LDMOS device as described in claim 5, characterized in that, Also includes: A contact field plate, which is located on the second field oxygen structure.

7. The LDMOS device as described in claim 6, characterized in that, The gate structure includes a gate oxide layer and a gate layer located on the surface of the gate oxide layer. The gate layer also extends onto the second field oxide structure and is separate from the contact field plate.

8. The LDMOS device as described in claim 5, characterized in that, Also includes: A plurality of metal field plates are located on the second field oxygen structure, and the plurality of metal field plates are distributed from dense to sparse in the direction from the source region to the drain region.

9. The LDMOS device as described in claim 1, characterized in that, The corners of the first oxygen structure are arc-shaped.

10. A method for forming an LDMOS device, characterized in that, include: A substrate is provided; a first field oxygen structure is formed within the substrate, the first field oxygen structure having opposing first and second sidewalls, the first sidewall being stepped, the second sidewall being inclined, and the angle between the second sidewall and the bottom of the first field oxygen structure being obtuse; adjacent body regions and drift regions are formed within the substrate, the first field oxygen structure being located within the drift region; a gate structure is formed on the surface of the substrate, a portion of the gate structure being located on the body region and another portion being located on the drift region; A source region is formed within the body region on one side of the gate structure; A drain region is formed in the drift region on the other side of the gate structure. The first field oxygen structure is located between the drain region and the gate structure. The first sidewall is close to the gate structure, and the second sidewall is close to the drain region.

11. The method for forming an LDMOS device as described in claim 10, characterized in that, The method for forming the first field oxygen structure includes: forming a first groove in a substrate using a first etching process; forming a first field oxygen layer in the first groove; forming a second groove in the substrate using a second etching process, wherein the sidewalls of the second groove expose the first field oxygen layer and its depth is less than the depth of the first groove; forming a second field oxygen layer in the second groove; forming a third groove in the substrate using a third etching process, wherein the sidewalls of the third groove expose the second field oxygen layer and its depth is less than the depth of the second groove; forming a third field oxygen layer in the third groove, thereby forming the first field oxygen structure with the first field oxygen layer, the second field oxygen layer, and the third field oxygen layer, wherein the first field oxygen layer, the second field oxygen layer, and the third field oxygen layer are arranged along a first direction, which is parallel to the surface of the substrate.

12. The method for forming an LDMOS device as described in claim 11, characterized in that, Also includes: After the first etching process and before the formation of the first field oxide layer, a first repair process is used to round the bottom corner of the first groove to make it arc-shaped; after the second etching process and before the formation of the second field oxide layer, a second repair process is used to round the bottom corner of the second groove to make it arc-shaped; after the third etching process and before the formation of the third field oxide layer, a third repair process is used to round the bottom corner of the third groove to make it arc-shaped.

13. The method for forming an LDMOS device as described in claim 11, characterized in that, The substrate includes an isolation region and an active region, the isolation region being located on the sidewall of the active region; the method further includes: forming the body region and the drift region within the active region; simultaneously forming the second groove, employing the second etching process to form an isolation trench within the isolation region; and simultaneously forming the second field oxide layer, forming an isolation structure within the isolation trench.

14. The method for forming an LDMOS device as described in claim 10, characterized in that, Before forming the gate structure, the method further includes: forming a second field oxygen structure on the surface of the first field oxygen structure; and after forming the second field oxygen structure, forming a gate oxide layer and a gate layer located on the surface of the gate oxide layer on the substrate surface, wherein the gate structure includes the gate oxide layer and the gate layer, and the gate structure is adjacent to the second field oxygen structure.

15. The method for forming an LDMOS device as described in claim 14, characterized in that, Also includes: A contact field plate is formed on the second oxygen structure.

16. The method for forming an LDMOS device as described in claim 15, characterized in that, The gate layer portion also extends onto the second field oxygen structure and is separate from the contact field plate.

17. The method for forming an LDMOS device as described in claim 14, characterized in that, Also includes: A plurality of metal field plates are formed on the second field oxygen structure, and the plurality of metal field plates are distributed from dense to sparse in the direction from the source region to the drain region.

18. The method for forming an LDMOS device as described in claim 10, characterized in that, The gate structure portion is formed on the surface of the first field oxygen structure.

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