Laterally diffused metal oxide semiconductor device and method of manufacture thereof

Abstract

The laterally diffused metal oxide semiconductor device includes a substrate, a body region, a drift region, a field oxide structure, and a drain region, the body region having a first conductivity type and formed in the substrate, the drift region having a second conductivity type and formed in the substrate and adjacent to the body region, the field oxide structure formed on the drift region, the drain region having the second conductivity type and formed in an upper surface layer of the drift region and contacting an end of the field oxide structure remote from the body region. A method of manufacturing a laterally diffused metal oxide semiconductor device includes forming a field oxide structure, the lower surface of the end of the field oxide structure adjacent to the body region being flush with the upper surface of the substrate and having an upwardly extending sloping surface, the lower surface of the end of the field oxide structure remote from the body region being lower than the upper surface of the substrate, and the thickness of the field oxide structure gradually increasing from the end of the field oxide structure adjacent to the body region to a preset value toward the end of the field oxide structure remote from the body region.

Description

[Technical field]

[0001] This application relates to the field of semiconductor technology, and more particularly to laterally diffused metal oxide semiconductor devices and methods for fabricating same. [Background technology]

[0002] NLDMOS is the core device in BCD, and breakdown voltage and on-resistance are the main indicators of LDMOS device performance. In order to ensure that LDMOS devices have a sufficiently large breakdown voltage and at the same time a sufficiently small on-resistance, it is necessary to modulate the impurity distribution in the drift region used for breakdown voltage and the field plate structure. In a typical manufacturing process, a vertical breakdown voltage field plate is generally fabricated using a LOCOS structure or an STI structure, and the performance of the LDMOS device can be predicted by modulating the thickness and length of the field plate structure.

[0003] For LDMOS devices, a graded field plate must be formed to improve the electric field distribution and increase device reliability, i.e., the field plate must be located close to the JFET region of the device and have a smaller field plate thickness than the drift region. Although the LOCOS field plate can have a large bird's beak and the LOCOS structure can be used to provide a field plate with a smaller thickness in the JFET region than in the drift region, a LOCOS structure with a bird's beak that is too long increases the pitch of the entire LDMOS device, increasing the on-resistance of the device. Summary of the Invention [Problem to be solved by the invention]

[0004] Based on this, a laterally diffused metal oxide semiconductor device and a method for fabricating the same are provided.

[0005] The laterally diffused metal oxide semiconductor device includes a substrate, a body region, a drift region, a field plate structure, and a drain region.

[0006] The body region has a first conductivity type and is formed in the substrate.

[0007] The drift region has a second conductivity type and is formed in the substrate and adjacent to the body region, the second conductivity type being opposite the first conductivity type.

[0008] A field plate structure is formed on the drift region, the lower surface of one end of the field plate structure adjacent to the body region being flush with the upper surface of the substrate and having an upwardly extending inclined surface, the lower surface of one end of the field plate structure away from the body region being lower than the upper surface of the substrate, and the thickness of the field plate structure gradually increasing from the end adjacent to the body region to the end away from the body region to a preset value.

[0009] The drain region has the second conductivity type and is formed in the upper surface layer of the drift region and contacts one end of the field plate structure remote from the body region.

[0010] In one embodiment, the included angle between the sloping surface and a bottom surface of one end of the field plate structure adjacent to the body region is greater than or equal to 30 degrees and less than or equal to 60 degrees.

[0011] In one embodiment, the field plate structure includes a first oxidation structure and a second oxidation structure.

[0012] The first oxidation structure is formed on the drift region at one end of the field plate structure adjacent to the drain region, and a top surface of the first oxidation structure is not lower than a top surface of the substrate, the first oxidation structure sequentially includes a first end and a second end in a direction from the body region to the drift region, and a thickness of the first oxidation structure gradually increases from the first end to the second end to a preset value.

[0013] The second oxide structure is formed on the top surface of the drift region adjacent to the body region and extends along the top surface of the first end to the interface between the first end and the second end, the inclined surface being the top surface of the second oxide structure adjacent to the body region.

[0014] In one embodiment, the thickness of the second oxide structure is less than or equal to 1500 Angstroms.

[0015] In one embodiment, the first oxidation structure includes a local silicon isolation oxide structure, and the local silicon isolation oxide structure is fabricated by a dip process.

[0016] In one embodiment, the laterally diffused metal oxide semiconductor device further includes a source region, a polysilicon gate, and a shallow trench isolation structure.

[0017] The source region has the second conductivity type and is formed in the upper surface layer of the body region.

[0018] A polysilicon gate is formed over and extends along the field plate structure to cover the substrate between the source region and the field plate structure.

[0019] A shallow trench isolation structure is formed in the substrate, the shallow trench isolation structure contacting the drain region and a portion of a bottom surface of the shallow trench isolation structure contacting the drift region.

[0020] In the above-mentioned laterally diffused metal oxide semiconductor device, a field plate structure is formed on the drift region, the lower surface of one end of the field plate structure adjacent to the body region is flush with the upper surface of the substrate and has an upwardly extending inclined surface, the lower surface of one end of the field plate structure away from the body region is lower than the upper surface of the substrate, and the thickness of the field plate structure gradually increases from the end adjacent to the body region to the end away from the body region to a preset value. By providing a field plate structure whose lower surface at one end adjacent to the body region is flush with the upper surface of the substrate and has an upwardly extending inclined surface, and the thickness of the field plate structure gradually increases from the end adjacent to the body region to the end away from the body region to a preset value, the length of the field plate structure whose lower surface is lower than the upper surface of the substrate does not increase (the spacing of the LDMOS device does not increase), and at the same time, a field plate structure whose thickness gradually increases at the position of the JFET region is formed, which improves the electric field distribution on the device surface and at the same time increases the reliability of the device.

[0021] A method for fabricating a laterally diffused metal oxide semiconductor device includes the following steps.

[0022] A substrate is provided.

[0023] Adjacent body and drift regions are formed in the substrate, the body region having a first conductivity type and the drift region having a second conductivity type opposite the first conductivity type.

[0024] A field plate structure is formed on the drift region, the lower surface of one end of the field plate structure adjacent to the body region being flush with the upper surface of the substrate and having an upwardly extending inclined surface, the lower surface of one end of the field plate structure away from the body region being lower than the upper surface of the substrate, and the thickness of the field plate structure gradually increasing from the end adjacent to the body region to the end away from the body region to a preset value.

[0025] A drain region of the second conductivity type is formed in the upper surface layer of the drift region, the drain region contacting one end of the field plate structure remote from the body region.

[0026] In one embodiment, the step of forming a field plate structure on the drift region includes:

[0027] A first oxidation structure is formed on the drift region, the first oxidation structure sequentially including a first end and a second end in a direction from the body region to the drift region, and a thickness of the first oxidation structure gradually increases from the first end to the second end to a preset value.

[0028] A second oxidation structure is formed on an upper surface of the drift region adjacent to the body region, the second oxidation structure extending along an upper surface of the first end to an interface between the first end and the second end.

[0029] The first oxidation structure is an end of the field plate structure away from the body region, the inclined surface is an upper surface of the second oxidation structure adjacent to the body region, and the included angle between the inclined surface and a lower surface of the end of the field plate structure adjacent to the body region is greater than or equal to 30 degrees and less than or equal to 60 degrees.

[0030] In one embodiment, the first oxidation structure comprises a local silicon isolation oxide structure, and the step of forming the first oxidation structure in the drift region comprises:

[0031] A hard mask layer is formed on the substrate, the hard mask layer being provided with a recess, the recess exposing the substrate in a first oxide structure pre-defined area.

[0032] A sidewall structure is formed on the sidewall of the trench in contact with the hard mask layer, the lower surface of the sidewall structure being flush with the bottom of the trench.

[0033] A localized thermal oxidation process is performed to form a first oxide structure at the bottom of the trench.

[0034] In one embodiment, the step of forming a second oxide structure on an upper surface of the drift region adjacent to the body region includes:

[0035] A thin oxide film is formed on the top surface of the substrate.

[0036] A photoresist mask layer is formed on the thin oxide film, the photoresist mask layer covering the thin oxide film in the second oxide structure pre-established area.

[0037] A wet etching process is performed to remove the excess thin oxide film, and a second oxide structure is obtained, which is constituted by the thin oxide film remaining in the second oxide structure pre-defined area.

[0038] In one embodiment, the thickness of the thin oxide film is greater than or equal to 300 Angstroms and less than or equal to 1500 Angstroms.

[0039] In one embodiment, the method of fabricating a laterally diffused metal oxide semiconductor device further comprises:

[0040] A shallow trench isolation structure is formed in the substrate, the shallow trench isolation structure contacting the drain region and a portion of a bottom surface of the shallow trench isolation structure contacting the drift region.

[0041] A source region having a second conductivity type is formed in the upper surface layer of the body region.

[0042] A polysilicon gate is formed over the field plate structure, the polysilicon gate extending along the field plate structure and covering the substrate between the source region and the field plate structure.

[0043] In the above-mentioned method for manufacturing a laterally diffused metal oxide semiconductor device, a field plate structure is formed on the drift region, the lower surface of one end of the field plate structure adjacent to the body region is flush with the upper surface of the substrate and has an upwardly extending inclined surface, the lower surface of one end of the field plate structure away from the body region is lower than the upper surface of the substrate, and the thickness of the field plate structure gradually increases from the end adjacent to the body region to the end away from the body region to a preset value. By forming a field plate structure whose lower surface at one end adjacent to the body region is flush with the upper surface of the substrate and has an upwardly extending inclined surface, and the thickness of the field plate structure gradually increases from the end adjacent to the body region to the end away from the body region to a preset value, the length of the field plate structure whose lower surface is lower than the upper surface of the substrate does not increase (the spacing of the LDMOS device does not increase), and at the same time, a field plate structure whose thickness gradually increases at the position of the JFET region is formed, which improves the electric field distribution on the device surface and at the same time increases the reliability of the device. [Brief description of the drawings]

[0044] [Figure 1] FIG. 1 is a flow chart of a method for fabricating a laterally diffused metal oxide semiconductor device in one embodiment. [Diagram 2] FIG. 2 is a flow chart for forming a field plate structure on a drift region in one embodiment. [Diagram 3] FIG. 3 is a flow chart for forming a first oxidation structure in the drift region in one embodiment. [Figure 4] FIG. 4 illustrates a cross-sectional view of a device after a hard mask layer has been formed over a substrate in one embodiment. [Diagram 5] FIG. 5 is a cross-sectional view of a device after sidewall structures have been formed in one embodiment. [Figure 6] FIG. 6 is a cross-sectional view of a device after a first oxidation structure has been formed in one embodiment. [Figure 7]FIG. 7 illustrates a cross-sectional view of a device after a photoresist mask layer has been formed in one embodiment. [Figure 8] FIG. 8 is a cross-sectional view of a device after a second oxidation structure has been formed in one embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0045] In order to more clearly describe the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces drawings required in the description of the embodiments or the prior art. However, the drawings described below are only some of the embodiments of the present application, and it is obvious that a person skilled in the art can obtain other drawings based on these drawings without requiring any creative efforts. In order to facilitate the understanding of the present application, the present application will now be described more completely with reference to the associated drawings. Although the drawings show embodiments of the present application, the present application can be realized in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure in the present application clearer and more complete.

[0046] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art of this application. The terms used herein are for the purpose of describing specific embodiments only and are not intended to be limiting of the present application.

[0047] It should be clear that when a component or layer is referred to as being "on," "adjacent to," "connected to," or "bonded to" another component or layer, it may be directly on, directly adjacent to, or directly connected to or bonded to the other component or layer, or there may be intervening components or layers. Conversely, when a component is referred to as being "directly on," "directly adjacent to," "connected to," or "bonded to" another component or layer, there are no intervening components or layers. It should be clear that, although terms such as first, second, third, etc. may be used to describe various components, members, regions, layers, doping types, and / or portions, these components, members, regions, layers, doping types, and / or portions should not be limited by these terms. These terms are merely intended to distinguish one component, member, region, layer, doping type, or portion from another component, member, region, layer, doping type, or portion. Thus, without departing from the teachings of the present invention, a first component, member, region, layer, doping type or portion discussed below can be referred to as a second component, member, region, layer or portion. For example, a first doping type can be a second doping type, and similarly, a second doping type can be a first doping type. The first doping type and the second doping type are different doping types, for example, the first doping type can be P-type and the second doping type can be N-type, or the first doping type can be N-type and the second doping type can be P-type.

[0048] For example, spatial relationship terms such as "under," "on the underside," "below," "under," "on top of," "on top of," and the like may be used herein to describe the relationship of one component or feature to another component or feature depicted in the figures. It should be clear that in addition to the orientation depicted in the figures, spatial relationship terms also include different orientations of the device in use or operation. For example, if the device in the figures is rotated, a description of "under another component," "under another component," or "under another component" would result in the orientation of the component or feature being "above" the other component or feature. Thus, the exemplary terms "under" and "under" can include both the orientations of above and below. Additionally, the device can include other orientations (e.g., rotated 90 degrees or other orientations) and the spatial description terms used herein should be interpreted accordingly.

[0049] As used herein, the singular forms "a," "an," and "the" can also include the plural, unless the context clearly indicates otherwise. It should be further understood that terms such as "comprising" or "having" refer to the presence of stated features, wholes, steps, operations, assemblies, parts, or combinations thereof, but do not exclude the possibility that one or more other features, wholes, steps, operations, assemblies, parts, or combinations thereof may be present or added. At the same time, as used herein, the term "and / or" includes any and all combinations associated with the listed items.

[0050] Embodiments of the invention are described herein with reference to cross-sectional views that are intended to be schematic illustrations of idealized embodiments (and intermediate structures) of the invention. In this manner, variations in the shapes shown can be expected, for example, due to manufacturing techniques and / or tolerances. Thus, embodiments of the invention are not limited to the particular shapes of the regions shown herein, but include shape deviations that arise, for example, due to manufacturing techniques. For example, an implanted region shown as a rectangle may have generally rounded or curved features at its edges and / or have an implant concentration gradient rather than a binary transition from implanted to non-implanted regions. Similarly, a buried region formed by implantation may have some implantation occurring in the region between the buried region and the surface through which the implantation is performed. Thus, the regions shown in the figures are schematic in nature, and their shapes are not indicative of the actual shape of the regions of a device and are not intended to limit the scope of the invention.

[0051] For LDMOS devices, in an ideal situation, it is desirable to have a certain field plate thickness close to the JFET region, which is used to improve the electric field distribution in this area and increase the reliability of the LDMOS device. The thickness of the field plate should be smaller than that of the drift region field plate and larger than the oxide layer thickness of the gate oxide. When using an STI structure field plate, it is not possible to realize the manufacture of a field plate with a gradually changing thickness by the primary process. When using a LOCOS structure field plate, a LOCOS structure with a large bird's beak can be manufactured by the primary process to obtain a field plate with a gradually changing thickness, but a bird's beak that is too long will affect the pitch of the entire LDMOS device, increasing the on-resistance of the device.

[0052] Please refer to Figure 1. It is a flow chart of a method for manufacturing a laterally diffused metal oxide semiconductor device in one embodiment.

[0053] In order to solve the above problems, in one embodiment, the present application provides a method for manufacturing a laterally diffused metal oxide semiconductor device, as shown in Figure 1, the method includes steps S102, S104, S106 and S108.

[0054] In step S102, a substrate is provided.

[0055] The substrate may be made of undoped single crystal silicon, impurity-doped single crystal silicon, silicon-on-insulator (SOI), silicon-on-insulator stack (SSOI), silicon-germanium-on-insulator stack (S-SiGeOI), silicon-germanium-on-insulator (SiGeOI), germanium-on-insulator (GeOI), etc. As an example, in this embodiment, single crystal silicon is selected and used as the constituent material of the substrate.

[0056] In step S104, adjacent body and drift regions are formed in the substrate.

[0057] The body region has a first conductivity type, and the drift region has a second conductivity type opposite to the first conductivity type. When the first conductivity type is P type, the second conductivity type is N type, and when the first conductivity type is N type, the second conductivity type is P type. In this embodiment, the first conductivity type is P type, and the second conductivity type is N type.

[0058] In step S106, a field plate structure is formed on the drift region.

[0059] The lower surface of one end of the field plate structure adjacent to the body region is flush with the upper surface of the substrate and has an upwardly extending inclined surface, the lower surface of one end of the field plate structure away from the body region is lower than the upper surface of the substrate, and the thickness of the field plate structure gradually increases from the end adjacent to the body region to the end away from the body region to a preset value.

[0060] In step S108, a drain region of a second conductivity type is formed in the upper surface layer of the drift region, the drain region being in contact with one end of the field plate structure remote from the body region.

[0061] In the above-mentioned method for manufacturing a laterally diffused metal oxide semiconductor device, a field plate structure is formed on the drift region, and the lower surface of one end of the field plate structure adjacent to the body region is flush with the upper surface of the substrate and has an upwardly extending inclined surface, the lower surface of one end of the field plate structure away from the body region is lower than the upper surface of the substrate, and the thickness of the field plate structure gradually increases from the end adjacent to the body region to the end away from the body region to a preset value. By forming a field plate structure whose lower surface is flush with the upper surface of the substrate and has an upwardly extending inclined surface and whose thickness gradually increases from the end adjacent to the body region to the end away from the body region to a preset value, the length of the field plate structure whose lower surface is lower than the upper surface of the substrate does not increase (the spacing of the LDMOS device does not increase), and at the same time, a field plate structure whose thickness gradually increases at the position of the JFET region is formed, which improves the electric field distribution on the device surface and at the same time increases the reliability of the device.

[0062] In one embodiment, the order of steps S104 and S106 is adjusted according to actual requirements. For example, step S104 is performed first and then step S106, or step S106 is performed first and then step S104. For example, step S104 is performed first and then step S106.

[0063] Please refer to Figure 2. A flow chart of forming a field plate structure on a drift region in one embodiment.

[0064] As shown in FIG. 2, in one embodiment, step S106 includes step S202 and step S204.

[0065] In step S202, a first oxide structure is formed on the drift region.

[0066] The first oxidation structure sequentially includes a first end and a second end in a direction from the body region toward the drift region, and a thickness of the first oxidation structure gradually increases from the first end to the second end to a preset value. The first oxidation structure is an end of the field plate structure away from the body region, and a lower surface is not higher than an upper surface of the substrate.

[0067] In one embodiment, before step S104, the method further includes forming a shallow trench isolation structure in a substrate, and a field plate structure is formed on the substrate between adjacent shallow trench isolation structures. In the present application, a manufacturing process commonly used by those skilled in the art can be selected to form the shallow trench isolation structure.

[0068] See Figure 3. A flow chart of forming a first oxidation structure in the drift region in one embodiment.

[0069] In one embodiment, the first oxidation structure includes a local silicon isolation oxide structure.As shown in Figure 3, step S202 includes step S302, step S304 and step S306.

[0070] In step S302, a hard mask layer is formed on a substrate, the hard mask layer being provided with a recess, the recess exposing the substrate in a first oxide structure pre-defined region.

[0071] See Figure 4, which is a cross-sectional view of a device after a hard mask layer has been formed on a substrate in one embodiment.

[0072] 4, first, a substrate 10 is obtained, a shallow trench isolation structure 102 is formed in the substrate 10, and then adjacent body regions 101 and drift regions 103 are formed in the substrate between the adjacent shallow trench isolation structures 102. Furthermore, a hard mask layer 20 is formed on the substrate 10 between the adjacent shallow trench isolation structures 102. A groove 202 is provided in the hard mask layer 20, which is located above the drift region 103, and the groove 202 exposes the substrate (drift region 103) in the first oxidation structure pre-setting region.

[0073] Specifically, a hard mask thin film is formed on the substrate surface, and then the hard mask thin film in the first oxidation structure pre-setting region located above the drift region 103 is removed by a photoresist and etching process, and then a hard mask layer 20 composed of the remaining hard mask thin film is obtained, and a groove 202 is formed at the position of the first oxidation structure pre-setting region.

[0074] In one embodiment, the hard mask layer 20 includes a stack of an oxide layer, a nitride layer, or both. As an example, in this embodiment, the hard mask layer 20 is selected to be a silicon nitride mask layer.

[0075] In step S304, a sidewall structure is formed on the sidewall of the groove in contact with the hard mask layer, the lower surface of the sidewall structure being flush with the bottom of the groove.

[0076] See Figure 5, which is a cross-sectional view of a device after sidewall structures have been formed in one embodiment.

[0077] As shown in FIG. 5, a sidewall structure 204 in contact with the hard mask layer 20 is formed on the sidewall of the groove 202. Specifically, first, a sidewall thin film is formed on the substrate 10. The sidewall thin film covers the surface of the first oxidation structure presetting region (the drift region 103 exposed from the bottom of the groove 202) and extends along the sidewall of the groove 202 to the surface of the hard mask layer 20. Then, the excess sidewall thin film is removed by a photoresist process and a dry etching process to obtain a sidewall structure 204 composed of a sidewall thin film covering the sidewall of the groove 202. The lower surface of the sidewall structure 204 is flush with the bottom of the groove 202 (the upper surface of the drift region 103). By forming the sidewall structure 204, it is possible to reduce oxygen penetrating under the hard mask layer 20 adjacent to the sidewall of the trench 202 when a local thermal oxidation process is performed later, and by shortening the bird's beak length of the local silicon isolation oxidation structure (first oxidation structure) to be formed, it is possible to eliminate the effect of the bird's beak length on the pitch of the entire device.

[0078] In one embodiment, the sidewall structure 204 is a silicon nitride structure. In practical applications, one can choose the sidewall structure 204 made of different materials according to requirements.

[0079] In step S306, a local thermal oxidation process is performed to form a first oxide structure at the bottom of the groove.

[0080] Please refer to Figure 6, which is a cross-sectional view after a first oxidation structure is formed in one embodiment.

[0081] 6, after forming the sidewall structure 204, a local thermal oxidation process is performed to form a LOCOS structure (local silicon isolation structure) with a short bird's beak at the bottom (first oxidation structure pre-setting region) of the groove 202, i.e., a first oxidation structure 206. The first oxidation structure 206 includes a first end 206A adjacent to the body region 101 and a second end 206B away from the body region 101, and the thickness of the first end 206A increases from the part adjacent to the body region 101 to the position of the second end 206B. In a subsequent process, a source region is formed in the body region 101 on the first end 206A side, and a drain region is formed in the drift region 103 on the second end 206B side. The thickness of one side of the second end 206B adjacent to the first end 206A is a preset value, i.e., the first end 206A is adjacent to the body region 101, and the boundary (intersection) between the first end 206A and the second end 206B is a position where the thickness of the first oxide structure 206 changes from less than the preset value to the preset value. Then, the hard mask layer 20 and the sidewall structure 204 on the substrate 10 are removed.

[0082] In step S204, a second oxidation structure is formed on the top surface of the drift region adjacent to the body region, the second oxidation structure extending along the top surface of the first end to an interface between the first end and the second end.

[0083] A second oxidation structure 108 is formed on an upper surface of the drift region 103 adjacent to the body region 101, the second oxidation structure 108 extending along an upper surface of the first end 206A to a location where a thickness of the first oxidation structure 206 changes from less than a preset value to a preset value. The beveled surface is an upper surface of the second oxidation structure adjacent to the body region, and an included angle between the beveled surface and a lower surface of one end of the field plate structure adjacent to the body region is greater than or equal to 30 degrees and less than or equal to 60 degrees.

[0084] In one embodiment, step S204 includes a first stage, a second stage and a third stage. In the first stage, a thin oxide film 104 is formed on the upper surface of the substrate 10. In the second stage, a photoresist mask layer 106 is formed on the thin oxide film 104. The photoresist mask layer 106 covers the thin oxide film 104 in the second oxide structure pre-setting region. In the third stage, a wet etching process is performed to remove the excess thin oxide film 104, and a second oxide structure 108 is obtained, which is composed of the remaining thin oxide film 104 in the second oxide structure pre-setting region.

[0085] See Figure 7, which is a cross-sectional view of a device after a photoresist mask layer is formed in one embodiment. See Figure 8, which is a cross-sectional view of a device after a second oxidation structure is formed in one embodiment.

[0086] As shown in Figures 7 and 8, first, a thin oxide film 104 is formed on the upper surface of the substrate 10. Then, a photoresist mask layer 106 is formed on the thin oxide film 104. The photoresist mask layer 106 covers the thin oxide film 104 in the second oxide structure pre-setting region on the side adjacent to the body region 101. The projection of the photoresist mask layer 106 on the substrate 10 surrounds the first end 206A, and the projection of the photoresist mask layer 106 on the substrate 10 on one side adjacent to the first oxide structure 206 is flush with the boundary between the first end 206A and the second end 206B. The projection of the photoresist mask layer 106 on the substrate 10 on one side away from the first oxide structure 206 is located on the drift region 103 between the body region 101 and the first oxide structure 206, that is, has a certain distance from the first end 206A. Furthermore, a wet etching process is performed to remove excess oxide thin film 104, and a second oxide structure 108 is obtained, which is composed of the oxide thin film 104 remaining in the second oxide structure preset region. The second oxide structure 108 covers the upper surface of the substrate 10, and extends along the upper surface of the first end 206A to the boundary between the first end 206A and the second end 206B. That is, the second oxide structure 108 covers a part of the drift region 103 on the side close to the body region 101 and the upper surface of the first end 206A. The sum of the thicknesses of the second oxide structure 108 covering the first end 206A and the first end 206A is equal to or less than the thickness of the flat region (region where the thickness does not change) of the second end 206B, that is, the sum of the thicknesses of the second oxide structure 108 covering the first end 206A and the first end 206A is equal to or less than the preset value. This causes the thickness of the field plate structure to gradually increase, and the electric field distribution in the polycrystalline silicon gate structure 116 formed on the field plate structure to gradually change. The upper surface 110 of the second oxide structure 108 adjacent to the body region is an inclined surface of the field plate structure, and the included angle φ between the upper surface 110 and the upper surface of the substrate 10 (the interface between the field plate structure and the upper surface of the substrate 10) is greater than or equal to 30 degrees and less than or equal to 60 degrees.The second oxide structure 108 together with the first oxide structure 206 constitutes a field plate structure, and by adjusting the adhesion between the photoresist mask layer 106 and the thin oxide film 104, the etching rate of the wet etching process, and the etchant, the magnitude of the included angle φ can be adjusted, and the rate at which the thickness of the field plate structure gradually changes from the body region to the drift region can be adjusted, thereby adjusting the performance of the device.

[0087] In another embodiment, the overlap between the second oxide structure 108 and the first oxide structure 206 is adjusted based on the shape of the first oxide structure 206 .

[0088] Compared to using only the first oxidation structure 206, by covering the first end 206A of the first oxidation structure 206 with the second oxidation structure 108, the rate at which the thickness of the field plate structure formed by the first oxidation structure 206 and the second oxidation structure 108 gradually changes can be adjusted, and a field plate structure with a gradually changing thickness is formed.

[0089] In one embodiment, both the first oxide structure 206 and the second oxide structure 108 are silicon dioxide structures.

[0090] In one embodiment, the thin oxide film 104 is formed on the top surface of the substrate 10 by a chemical vapor deposition process.

[0091] In one embodiment, the thickness of thin oxide film 104 is greater than or equal to 300 Angstroms and less than or equal to 1500 Angstroms.

[0092] In one embodiment, the method for fabricating a laterally diffused metal oxide semiconductor device further comprises a first stage and a second stage.

[0093] In a first step, a source region having a second conductivity type is formed in the upper surface layer of the body region 101. In a second step, a polysilicon gate is formed on the field plate structure, the polysilicon gate extending along the field plate structure and covering the substrate between the source region and the field plate structure.

[0094] 8, a doping process is performed to form a source region 112 having a second conductivity type in the upper surface layer of the body region 101, and a drain region 114 having a second conductivity type is formed in the drift region 103 between the first oxidation structure 206 and the shallow trench isolation structure 102, one end of the drain region 114 contacts the first oxidation structure 206 and the other end contacts the shallow trench isolation structure 102. Then, a polysilicon gate structure 116 is formed on the field plate structure. The polysilicon gate structure 116 extends along the field plate structure to cover the substrate 10 between the source region 112 and the field plate structure, i.e., the polysilicon gate structure 116 extends along the field plate structure to cover the substrate 10 between the source region 112 and the second oxidation structure 108.

[0095] In one embodiment, the method for manufacturing a laterally diffused metal oxide semiconductor device further includes forming a heavily doped region 118 of the first conductivity type in the body region 101 between the source region 112 and the shallow trench isolation structure 102.

[0096] In one embodiment, the method for fabricating a laterally diffused metal oxide semiconductor device further comprises forming a gate oxide layer, a metal interconnect layer.

[0097] It should be understood that although the steps in the flowchart of FIG. 1 are shown in sequence as indicated by the arrows, the steps do not necessarily have to be performed in the order indicated by the arrows. Unless otherwise specified in this specification, the order of the steps is not strictly limited, and the steps can be performed in other orders. In addition, at least some of the steps in FIG. 1 may include multiple steps or multiple stages, and these steps or stages do not have to be completed at the same time, but can be performed at different times, and the order of the steps or stages does not have to be sequential, but can be performed alternately or alternately with other steps or at least some of the steps or stages in other steps.

[0098] As shown in FIG. 8, in one embodiment, the present application further provides a laterally diffused metal oxide semiconductor device, including a substrate 10, a body region 101, a drift region 103, a field plate structure, and a drain region 114.

[0099] The substrate 10 may be made of undoped single crystal silicon, impurity-doped single crystal silicon, silicon-on-insulator (SOI), silicon-on-insulator-laminated (SSOI), silicon-germanium-on-insulator-laminated (S-SiGeOI), silicon-germanium-on-insulator (SiGeOI), germanium-on-insulator (GeOI), etc. As an example, in this embodiment, single crystal silicon is selected as the constituent material of the substrate 10.

[0100] A body region 101 has a first conductivity type and is formed in the substrate 10 .

[0101] The drift region 103 has a second conductivity type and is formed in the substrate 10 and adjacent to the body region 101, the second conductivity type being opposite to the first conductivity type. When the first conductivity type is P type, the second conductivity type is N type, and when the first conductivity type is N type, the second conductivity type is P type. In this embodiment, the first conductivity type is P type and the second conductivity type is N type.

[0102] The field plate structure is formed on the drift region 103. The bottom surface of one end of the field plate structure close to the body region 101 is flush with the top surface of the substrate 10 and has an upwardly extending inclined surface 110, the bottom surface of one end of the field plate structure away from the body region 101 is lower than the top surface of the substrate 10, and the thickness of the field plate structure gradually increases from the end close to the body region 101 to the end away from the body region 101 to a preset value.

[0103] A drain region 114 has a second conductivity type and is formed in an upper surface layer of the drift region 103 and contacts one end of the field plate structure remote from the body region 101 .

[0104] In one embodiment, the included angle φ between the sloped surface 110 and the underside of one end of the field plate structure adjacent the body region 101 is greater than or equal to 30 degrees and less than or equal to 60 degrees. By adjusting the magnitude of the included angle φ, the rate at which the thickness of the field plate structure gradually changes from the body region 101 to the drift region 103 can be adjusted to tune the performance of the device.

[0105] In one embodiment, the field plate structure includes a first oxidation structure 206 and a second oxidation structure 108 .

[0106] The first oxidation structure 206 is one end of the field plate structure adjacent to the drain region 114, and is formed on the drift region 103, and the top surface of the first oxidation structure 206 is not lower than the top surface of the substrate 10. The first oxidation structure 206 sequentially includes a first end and a second end in a direction from the body region 101 to the drift region 103, and the thickness of the first oxidation structure 206 gradually increases from the first end to the second end to a preset value. The boundary portion between the first end and the second end is a position where the thickness of the first oxidation structure 206 changes from less than the preset value to the preset value.

[0107] The second oxide structure 108 is formed on the top surface of the drift region 103 adjacent to the body region 101 and extends along the top surface of the first end to the boundary between the first end and the second end. The inclined surface 110 is the top surface of the second oxide structure adjacent to the body region.

[0108] In one embodiment, the thickness of the second oxide structure 108 is less than or equal to 1500 Angstroms.

[0109] In one embodiment, the first oxidation structure 206 includes a local silicon isolation oxide structure, which is fabricated by a dip process.

[0110] In one embodiment, the laterally diffused metal oxide semiconductor device further includes a source region 112 , a polysilicon gate 116 and a shallow trench isolation structure 102 .

[0111] The source region 112 has a second conductivity type and is formed in an upper surface layer of the body region 101 .

[0112] A polysilicon gate 116 is formed over and extends along the field plate structure to cover the substrate 10 between the source region 112 and the field plate structure.

[0113] The shallow trench isolation structure 102 is formed in the substrate 10. The shallow trench isolation structure 102 contacts the drain region 114, and a portion of the bottom surface of the shallow trench isolation structure 102 contacts the drift region 103.

[0114] In the above-mentioned laterally diffused metal oxide semiconductor device, a field plate structure is formed on the drift region, the lower surface of one end of the field plate structure adjacent to the body region is flush with the upper surface of the substrate and has an upwardly extending inclined surface, the lower surface of one end of the field plate structure away from the body region is lower than the upper surface of the substrate, and the thickness of the field plate structure gradually increases from the end adjacent to the body region to the end away from the body region to a preset value. By providing a field plate structure whose lower surface of one end adjacent to the body region is flush with the upper surface of the substrate and has an upwardly extending inclined surface, and the thickness of the field plate structure gradually increases from the end adjacent to the body region to the end away from the body region to a preset value, the length of the field plate structure whose lower surface is lower than the upper surface of the substrate does not increase (the spacing of the LDMOS device does not increase), and at the same time, a field plate structure whose thickness gradually increases at the position of the JFET region is formed, which improves the electric field distribution on the device surface and at the same time increases the reliability of the device.

[0115] In the present specification, the reference words "some embodiments," "other embodiments," "ideal embodiment," and the like mean that the specific features, structures, materials, or characteristics described with reference to the embodiment or example are included in at least one embodiment or example of the present invention. In the present specification, the general description in the above terms does not necessarily refer to the same embodiment or example.

[0116] The technical features of the above-described embodiments can be combined in any way. For the sake of brevity, all possible combinations of the technical features of the above-described embodiments have not been described, but any combination of these technical features that does not cause a contradiction should be considered to be within the scope of the present specification.

[0117] The above-mentioned embodiments merely represent some implementation means of the present application, and are described in detail, but should not be understood as limiting the scope of the patent to be applied for. It should be noted that a person skilled in the art may make some modifications and improvements without departing from the concept of the present application, and all of these are within the scope of protection of the present application. Therefore, the scope of protection of the patent of the present application should be defined by the accompanying claims.

Claims

1. 1. A laterally diffused metal oxide semiconductor device, comprising: a substrate, a body region, a drift region, a field plate structure, and a drain region; the body region having a first conductivity type and formed in the substrate; the drift region having a second conductivity type and formed in the substrate and adjacent to the body region, the second conductivity type being opposite to the first conductivity type; the field plate structure is formed on the drift region, a lower surface of one end of the field plate structure adjacent to the body region is flush with an upper surface of the substrate and has an upwardly extending inclined surface, a lower surface of one end of the field plate structure away from the body region is lower than the upper surface of the substrate, and a thickness of the field plate structure gradually increases from the one end adjacent to the body region to the one end away from the body region to a preset value; the drain region having the second conductivity type and formed in an upper surface layer of the drift region and contacting one end of the field plate structure remote from the body region.

2. 2. The laterally diffused metal oxide semiconductor device of claim 1, wherein an included angle between the inclined surface and a bottom surface of one end of the field plate structure adjacent to the body region is greater than or equal to 30 degrees and less than or equal to 60 degrees.

3. the field plate structure includes a first oxidation structure and a second oxidation structure; the first oxidation structure is an end of the field plate structure away from the body region and formed on the drift region, and a top surface of the first oxidation structure is not lower than a top surface of the substrate, the first oxidation structure sequentially includes a first end and a second end in a direction from the body region toward the drift region, and a thickness of the first oxidation structure gradually increases from the first end toward the second end to the preset value; 2. The laterally diffused metal oxide semiconductor device of claim 1 , wherein the second oxidation structure is formed on an upper surface of the drift region adjacent to the body region and extends along an upper surface of the first end portion to a boundary portion between the first end portion and the second end portion, and the inclined surface is an upper surface of the second oxidation structure adjacent to the body region.

4. 4. The laterally diffused metal oxide semiconductor device of claim 3, wherein the thickness of said second oxide structure is less than 1500 Angstroms.

5. 4. The laterally diffused metal oxide semiconductor device of claim 3, wherein the first oxide structure comprises a local silicon isolation oxide structure.

6. further comprising a source region, a polysilicon gate, and a shallow trench isolation structure; the source region has the second conductivity type and is formed in an upper surface layer of the body region; the polysilicon gate is formed on and extends along the field plate structure to cover the substrate between the source region and the field plate structure; 2. The laterally diffused metal oxide semiconductor device of claim 1 , wherein the shallow trench isolation structure is formed in the substrate, the shallow trench isolation structure contacts the drain region, and a portion of a bottom surface of the shallow trench isolation structure contacts the drift region.

7. 1. A method for manufacturing a laterally diffused metal oxide semiconductor device, comprising the steps of: Providing a substrate; forming adjacent body and drift regions in the substrate; forming a field plate structure on the drift region; forming a drain region of a second conductivity type in an upper surface layer of the drift region and in contact with one end of the field plate structure away from the body region; the body region has a first conductivity type and the drift region has the second conductivity type opposite the first conductivity type; a bottom surface of an end of the field plate structure adjacent to the body region being flush with an upper surface of a substrate and having an upwardly extending inclined surface, a bottom surface of an end of the field plate structure away from the body region being lower than an upper surface of the substrate, and a thickness of the field plate structure gradually increasing from the end adjacent to the body region to the end away from the body region to a preset value.

8. The step of forming a field plate structure on the drift region includes: forming a first oxidation structure on the drift region; forming a second oxidation structure on an upper surface of the drift region adjacent to the body region; the first oxidation structure sequentially includes a first end and a second end in a direction from the body region toward the drift region, and a thickness of the first oxidation structure gradually increases from the first end toward the second end to the preset value; the second oxide structure extends along a top surface of the first end to an interface between the first end and the second end; 8. The method of claim 7, wherein the first oxidation structure is an end of the field plate structure away from the body region, the inclined surface is an upper surface of the second oxidation structure adjacent to the body region, and an included angle between the inclined surface and a lower surface of the end of the field plate structure adjacent to the body region is greater than or equal to 30 degrees and less than or equal to 60 degrees.

9. the first oxidation structure comprises a local silicon isolation oxide structure; forming a first oxidation structure in the drift region; forming a hard mask layer on the substrate, the hard mask layer having a recess that exposes the substrate in a first oxide structure pre-defined region; forming a sidewall structure on a sidewall of the groove, the sidewall structure being in contact with the hard mask layer and having a lower surface flush with a bottom of the groove; 9. The method of claim 8, further comprising: performing a local thermal oxidation process to form a first oxide structure at the bottom of the groove.

10. forming a second oxidation structure on an upper surface of the drift region adjacent to the body region; forming a thin oxide film on an upper surface of the substrate; forming a photoresist mask layer on the thin oxide film, the photoresist mask layer covering the thin oxide film in the second oxide structure pre-setting region; and performing a wet etching process to remove the excess thin oxide film to obtain a second oxide structure constituted by the remaining thin oxide film in the second oxide structure pre-defined area.

11. 11. The method according to claim 10, wherein the thickness of the thin oxide film is 300 angstroms or more and 1500 angstroms or less.

12. forming a shallow trench isolation structure in the substrate, the shallow trench isolation structure contacting the drain region and having a portion of a lower surface contacting the drift region; forming a source region having a second conductivity type in an upper surface layer of the body region; 8. The method of claim 7, further comprising forming a polysilicon gate on the field plate structure, extending along the field plate structure and covering a substrate between the source region and the field plate structure.

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