Trench Field-Effect Transistor with Segmented Gate Structure and Method for Preparing the Same

Abstract

This application relates to a trench field-effect transistor with a segmented gate structure and a method for manufacturing the same. The transistor includes: a substrate region, a drift region, a body region, a source region, a shielding gate, a control gate, an insulating layer, a source electrode, a drain electrode, and a metal gate electrode; the drift region, the body region, the source region, and the source electrode are sequentially disposed above the substrate region, and the drain electrode is disposed below the substrate region; the control gate and the shielding gate are sequentially disposed on one side of the drift region from top to bottom, and are respectively connected to the drift region, the body region, and the source region through the insulating layer; the control gate and the shielding gate are separated by the insulating layer; the shielding gate is composed of metal materials with different work functions from top to bottom; the control gate is composed of metal materials with different work functions from top to bottom; the source electrode is disposed above the source region; the metal gate electrode is disposed above the control gate. The solution provided by this application can improve the breakdown voltage of the transistor device.

Description

Technical Field

[0001] The present application relates to the field of semiconductor technology, and in particular, to a trench field effect transistor with a segmented gate structure and a method for manufacturing the same. Background Art

[0002] The shielded gate trench field effect transistor (SGT) has advantages such as a low specific on-resistance, small static and dynamic losses, and a fast switching speed. This is because it can effectively isolate the coupling between the control gate and the drain, and has obvious advantages in terms of channel density, charge compensation effect, and shielded gate structure.

[0003] An important aspect restricting the performance improvement of multi-carrier conductive power devices lies in the contradictory relationship between the breakdown voltage and the specific on-resistance. Among them, the main limitation of the breakdown voltage comes from the non-uniform electric field distribution in the breakdown voltage region, and an extremely important limitation in the SGT comes from the electric field concentration effect (E-field Crowding Effect) at the shielded gate corner. Due to the inherent heavily doped polysilicon in the shielded gate structure of the traditional SGT, when the device is in the forward blocking state, it will inevitably cause the electric flux of ionized donor charges in the breakdown voltage region to be overly concentrated at this corner, resulting in a large peak electric field and reducing the ability of the breakdown voltage to play. Summary of the Invention

[0004] To overcome the problems existing in the related art, the present application provides a trench field effect transistor with a segmented gate structure and a method for manufacturing the same, which can improve the breakdown voltage of the transistor device.

[0005] The first aspect of the present application provides a trench field effect transistor with a segmented gate structure, including: a substrate region 1, a drift region 2, a base region 3, a source region 4, a shielded gate 5, a control gate 6, an insulating layer 7, a source electrode 8, a drain electrode 9, and a metal gate; the drift region 2, the base region 3, the source region 4, and the source electrode 8 are sequentially disposed above the substrate region 1, and the drain electrode 9 is disposed below the substrate region 1;

[0006] The control gate 6 and the shielded gate 5 are sequentially disposed on one side of the drift region 2 from top to bottom, and are respectively connected to the drift region 2, the base region 3, and the source region 4 through the insulating layer 7; the control gate 6 and the shielded gate 5 are separated by the insulating layer 7; the shielded gate 5 is composed of metal materials with different work functions from top to bottom; the control gate 6 is composed of metal materials with different work functions from top to bottom;

[0007] The source electrode 8 is disposed above the source region; the metal gate is disposed above the control gate.

[0008] In an embodiment, in the shielded gate 5, the work function of the metal material increases sequentially from top to bottom.

[0009] In one embodiment, in the control gate 6, the work functions of the metal materials increase successively from top to bottom.

[0010] In one embodiment, in the shielding gate 5, the difference in work function between every two adjacent metal materials is 0.2 to 1.

[0011] In one embodiment, in the control gate 6, the difference in work function between every two adjacent metal materials is 0.2 to 1.

[0012] In one embodiment, the number of metal materials constituting the control gate 6 is the same as the number of metal materials constituting the shielding gate 5.

[0013] In one embodiment, the thicknesses of the metal materials in each layer of the shielding gate 5 are the same.

[0014] In one embodiment, the thicknesses of the metal materials in each layer of the control gate 6 are the same.

[0015] In one embodiment, the number of metal materials constituting the control gate is greater than or equal to 3.

[0016] The second aspect of the present application provides a method for manufacturing a trench field effect transistor having a segmented gate structure, including:

[0017] Preparing a substrate region from a heavily doped semiconductor material;

[0018] Epitaxially forming a drift region on the substrate region;

[0019] Forming a base region above the drift region by ion implantation or diffusion;

[0020] Etching a trench on one side of the drift region;

[0021] Sequentially depositing an oxide, metal materials with different work functions, an oxide, and metal materials with different work functions in the trench to form a shielding gate, a control gate, an insulating layer, and a metal gate;

[0022] Doping above the base region to form a source region;

[0023] Depositing source metal above the source region to obtain a source electrode;

[0024] Fabricating and forming a drain electrode below the substrate region.

[0025] The technical solution provided by the present application may include the following beneficial effects:

[0026] The trench-type field-effect transistor with a segmented gate structure provided by the present application has a shielding gate and a control gate, which are different from the uniform polysilicon materials used in existing conventional shielding gates and control gate structures. The gate material is composed of metal materials with different work functions from top to bottom. Due to the different work functions between different metal materials, a more uniform distribution of the channel electric field will be formed at the interfaces of different metal materials of the control gate and on the corresponding channel surface, thereby obtaining a lower on-resistance in the channel region; while the shielding gate is composed of different metal materials from top to bottom, so that when the device is in forward blocking, a relatively flat electric field distribution can be obtained by modulating the electric field in the breakdown voltage region, thereby improving the breakdown voltage of the device.

[0027] It should be understood that the above general description and the following detailed description are only exemplary and explanatory, and cannot limit the present application. Brief Description of the Drawings

[0028] By describing the exemplary embodiments of the present application in more detail in conjunction with the drawings, the above and other objects, features, and advantages of the present application will become more obvious. Among them, in the exemplary embodiments of the present application, the same reference numerals generally represent the same components.

[0029] Figure 1 It is a schematic structural diagram of a trench-type field-effect transistor with a segmented gate structure shown in an embodiment of the present application;

[0030] Figure 2 It is a schematic flow diagram of a manufacturing method of a trench-type field-effect transistor with a segmented gate structure shown in an embodiment of the present application. Detailed Embodiments

[0031] The preferred embodiments of the present application will be described in more detail below with reference to the drawings. Although the preferred embodiments of the present application are shown in the drawings, it should be understood that the present application can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided to make the present application more thorough and complete, and to convey the scope of the present application fully to those skilled in the art.

[0032] The terms used in the present application are only for the purpose of describing specific embodiments and are not intended to limit the present application. The singular forms "a", "the", and "said" used in the present application and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the term "and / or" used herein refers to and includes any and all possible combinations of one or more of the associated listed items.

[0033] It should be understood that although the terms "first", "second", "third", etc. may be used in this application to describe various information, such information should not be limited to these terms. These terms are only used to distinguish information of the same type from each other. For example, without departing from the scope of this application, the first information may also be referred to as the second information, and similarly, the second information may also be referred to as the first information. Thus, features defined with "first" and "second" may explicitly or implicitly include one or more of such features. In the description of this application, "a plurality of" means two or more, unless otherwise specifically defined.

[0034] Embodiment 1

[0035] Due to the inherent polysilicon heavy doping in the shielding gate structure of the traditional SGT, when the device is in forward blocking, it will inevitably cause the electric flux of ionized donor charges in the breakdown voltage region to be overly concentrated at the corner, resulting in a relatively large peak electric field and reducing the ability to exert the breakdown voltage.

[0036] To address the above problems, the embodiment of this application provides a trench field-effect transistor with a segmented gate structure, which has a relatively flat electric field distribution and thus a relatively high breakdown voltage.

[0037] The technical solutions of the embodiments of this application are described in detail below with reference to the accompanying drawings.

[0038] Figure 1 is a schematic structural diagram of a trench field-effect transistor with a segmented gate structure shown in the embodiment of this application.

[0039] See Figure 1 , the trench field-effect transistor with a segmented gate structure includes: a substrate region 1, a drift region 2, a base region 3, a source region 4, a shielding gate 5, a control gate 6, an insulating layer 7, a source electrode 8, a drain electrode 9, and a metal gate;

[0040] Among them, the drift region 2, the base region 3, the source region 4, and the source electrode 8 are sequentially arranged above the substrate region 1, and the drain electrode 9 is arranged below the substrate region 1; the control gate 6 and the shielding gate 5 are sequentially arranged on one side of the drift region 2 from top to bottom and are respectively connected to the drift region 2, the base region 3, and the source region 4 through the insulating layer 7; the control gate 6 and the shielding gate 5 are separated by the insulating layer 7; the source electrode 8 is arranged above the source region 4; the metal gate is arranged above the control gate.

[0041] Furthermore, the shielding gate 5 is composed of metal materials with different work functions from top to bottom; the control gate 6 is composed of metal materials with different work functions from top to bottom.

[0042] Specifically, for the gate material of the shielding gate 5, from top to bottom, the work function of each layer of metal material increases successively; for the gate material of the control gate 6, from top to bottom, the work function of each layer of metal material increases successively.

[0043] In the embodiment of the present application, for the shielding gate and the control gate, there is no strict requirement for the increment value of the work function of each layer of metal material, that is, the work function of each layer of metal material in the gate materials used for the shielding gate and the control gate can increase equally or non-equally from top to bottom. Preferably, the work function of the gate materials used for the shielding gate and the control gate increases equally from top to bottom.

[0044] In the embodiment of the present application, the difference in work function between every two adjacent metal materials in the shielding gate 5 is 0.2 - 1, preferably, the difference in work function between every two adjacent metal materials is 0.5; the difference in work function between every two adjacent metal materials in the control gate 6 is 0.2 - 1, preferably, the difference in work function between every two adjacent metal materials is 0.5.

[0045] It should be noted that in the actual application process, if the gate materials with equal increment of work function are used for both the shielding gate and the control gate, the difference in work function between two adjacent layers of metal materials of the shielding gate and the difference in work function between two adjacent layers of metal materials of the control gate can be set to be the same.

[0046] Furthermore, the number of metal materials in the shielding gate 5 and the control gate 6 can be set to be the same, that is, the number of metal materials constituting the control gate 6 is the same as the number of metal materials constituting the shielding gate 5.

[0047] Even further, the maximum work function of the metal materials in the shielding gate 5 and the control gate 6 can be set to be the same, that is, the structures of the shielding gate 5 and the control gate 6 are the same.

[0048] In the actual application process, theoretically, the more the number of metal materials with different work functions in the shielding gate and the control gate, the better the performance of the transistor. However, considering cost and process, setting the number of metal materials constituting the control gate or the shielding gate to be greater than or equal to 3 can achieve an increase in the breakdown voltage of the transistor. Preferably, the number of metal materials in the shielding gate or the control gate is 3.

[0049] Taking the shielding gate with a three-layer structure as an example, the shielding gate 5 is divided into a first shielding gate layer 51, a second shielding gate layer 52, and a third shielding gate layer 53. Among them, the work function of the metal material of the first shielding gate layer 51 is lower than that of the second shielding gate layer 52 and lower than that of the third shielding gate layer 53;

[0050] Taking the control gate with a three-layer structure as an example, the control gate 6 is divided into a first control gate layer 61, a second control gate layer 62, and a third control gate layer 63. Among them, the work function of the metal material of the first control gate layer 61 is lower than that of the second control gate layer 62 and lower than that of the third control gate layer 63.

[0051] When the gate material is a single material, the electric field distribution along the channel is approximately triangular, and it is not fully utilized for the specific on-resistance of the channel region. If the gate material is designed to have an increasing work function from top to bottom, the approximate triangular electric field distribution in the channel region can be modulated into an approximate rectangular distribution, thereby effectively increasing the specific on-resistance of the channel region.

[0052] Furthermore, the thicknesses of the metal materials in each layer of the shield gate are the same; the thicknesses of the metal materials in each layer of the control gate are the same.

[0053] In the embodiment of the present application, the substrate region 1 is doped with N-type with a heavy doping concentration; the drift region 2 is doped with N-type with a light doping concentration; the substrate region 3 is doped with P-type with a medium doping concentration; the doping concentration of the source region 4 is a heavy doping concentration.

[0054] Furthermore, the source region 4 is divided into an N-type source region 42 and a P-type source region 41.

[0055] In the embodiment of the present application, the value range of the light doping concentration is 1×10 15 cm -3 to 5×10 16 cm -3 ; the value range of the medium doping concentration is 1×10 17 cm -3 to 5×10 18 cm -3 ; the value range of the heavy doping concentration is 1×10 19 cm -3 to 5×10 20 cm -3 .

[0056] For the trench-type field effect transistor with a segmented gate structure provided by the present application, its shield gate and control gate are different from the uniform polysilicon materials used in the existing conventional shield gate and control gate structures. The gate material is composed of metal materials with different work functions from top to bottom. Due to the different work functions between different metal materials, a more uniform distribution of the channel electric field will be formed at the interface of different metal materials in the control gate and on the corresponding channel surface, thereby obtaining a lower on-resistance in the channel region; while the shield gate is composed of different metal materials from top to bottom, so that when the device is in the forward blocking state, by modulating the electric field in the breakdown voltage region, a relatively flat electric field distribution can be obtained, thereby increasing the breakdown voltage of the device.

[0057] Embodiment 2

[0058] Corresponding to the foregoing embodiment of the trench-type field effect transistor with a segmented gate structure, the present application also provides a preparation method and corresponding embodiments of a trench-type field effect transistor with a segmented gate structure.

[0059] Figure 2 It is a schematic flow chart of the preparation method of the trench-type field effect transistor with a segmented gate structure shown in the embodiments of the present application.

[0060] See Figure 2 , the preparation method of the trench-type field effect transistor with a segmented gate structure includes:

[0061] 201. Prepare a substrate region with a heavily doped semiconductor material;

[0062] Specifically: Prepare a substrate region with an N-type heavily doped semiconductor material.

[0063] 202. Epitaxially form a drift region on the substrate region;

[0064] In the embodiments of the present application, different epitaxial processes can be adopted according to actual needs, including but not limited to: Vapour Phase Epitaxy (VPE) or Chemical Vapor Deposition (CVD).

[0065] 203. Form a base region above the drift region by ion implantation or diffusion;

[0066] The ion implantation process is a process of doping silicon materials. In actual application, the power device product is placed at one end of the ion implanter, and the doping ion source is set at the other end of the ion implanter. At the end of the doping ion source, the dopant atoms are ionized, thus carrying a certain charge, and are accelerated to a very high speed by an electric field, passing through the surface layer of the product, and the doping atoms are implanted into the power device by using the momentum of the atoms to form a doped region.

[0067] The diffusion process is a process of doping pure impurity atoms on the surface of silicon materials. In actual application, diborane or phosphine is usually used as the ion source, and the pure impurity atoms are doped into the surface of silicon materials by means of intermittent diffusion or substitutional diffusion.

[0068] It should be noted that the present application does not strictly limit the preparation method adopted for the base region. In actual processes, the above different processes can be selected according to actual needs to complete the preparation of the base region.

[0069] 204. Etch a trench on one side of the drift region;

[0070] 205. Oxides, metal materials with different work functions, oxides, and metal materials with different work functions are sequentially deposited in the trench to form a shielding gate, a control gate, an insulating layer, and a metal gate electrode.

[0071] Exemplarily:

[0072] After oxides, metal materials with different work functions, and oxides are sequentially deposited in the trench, a deposition operation of metal materials with different work functions is performed again according to the last deposition of metal materials with different work functions, obtaining a shielding gate and a control gate structure with consistent structures.

[0073] Among them, taking metal materials with three different work functions as an example, the deposition order of metal materials in each round is to deposit the metal material with a higher work function first, then deposit the metal material with the second-highest work function, and finally deposit the metal material with the lowest work function, so that the gate material of the shielding gate and / or the control gate is composed of metal materials with work functions increasing sequentially from top to bottom.

[0074] Among them, the deposition thickness of each layer of metal material can be the same, so that the shielding gate and the control gate have a metal material layer structure with equal height and increasing work function.

[0075] 206. A source region is doped above the substrate region;

[0076] Specifically: An N-type source region and a P-type source region are doped above the substrate region with an N-type heavily doped semiconductor material and a P-type heavily doped semiconductor material respectively, and the arrangement direction of the N-type source region and the P-type source region is perpendicular to the interface between the insulating layer and the substrate region.

[0077] 207. A source metal is deposited above the source region to obtain a source electrode;

[0078] 208. A drain electrode is formed below the substrate region.

[0079] It should be noted that the above step 208 can be executed after the preparation of the substrate region is completed, that is, the execution timing of step 208 can be after step 201.

[0080] It can be understood that the execution timing of step 208 does not constitute the only limitation to this application.

[0081] The embodiment of the present application provides a preparation method of a trench-type field-effect transistor with a segmented gate structure. By sequentially filling metal materials with different work functions in the etched trenches, a trench-type field-effect transistor with a segmented shielding gate and control gate structure is obtained. Due to the different work functions between different metal materials, a more uniform distribution of the channel electric field will be formed at the interface of different metal materials of the control gate and on the corresponding channel surface, thereby obtaining a lower on-resistance in the channel region; while the shielding gate is composed of different metal materials from top to bottom, so that when the device is in forward blocking, a relatively flat electric field distribution can be obtained by modulating the electric field in the breakdown voltage region, thereby improving the breakdown voltage of the device.

[0082] Regarding the device in the above embodiment, the specific manner in which each module performs operations has been described in detail in the embodiment related to the method, and will not be elaborated here.

[0083] The solution of the present application has been described in detail above with reference to the drawings. In the above embodiments, the descriptions of each embodiment have their own emphases. For the parts not described in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments. Those skilled in the art should also know that the actions and modules involved in the specification are not necessarily essential to the present application. In addition, it can be understood that the steps in the method embodiments of the present application can be adjusted, combined, and deleted according to actual needs, and the modules in the device embodiments of the present application can be combined, divided, and deleted according to actual needs.

[0084] The flowcharts and block diagrams in the accompanying drawings show the possible architectures, functions, and operations of systems and methods according to multiple embodiments of the present application. In this regard, each block in the flowchart or block diagram may represent a module, a program segment, or a part of code, and the module, program segment, or part of code contains one or more executable instructions for implementing the specified logical function. It should also be noted that in some alternative implementations, the functions marked in the blocks may occur in a different order than marked in the accompanying drawings. For example, two consecutive blocks may actually be executed substantially in parallel, and they may sometimes be executed in the reverse order, depending on the functions involved. It should also be noted that each block in the block diagram and / or flowchart, and the combination of blocks in the block diagram and / or flowchart, can be implemented by a dedicated hardware-based system for performing the specified functions or operations, or can be implemented by a combination of dedicated hardware and computer instructions.

[0085] The embodiments of the present application have been described above. The above description is exemplary, not exhaustive, and is not limited to the disclosed embodiments. Many modifications and variations are obvious to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments. The choice of terms used herein is intended to best explain the principles of the embodiments, the practical application, or the improvement of the technology in the market, or to enable other ordinary skill in the art to understand the embodiments disclosed herein.

Claims

1. A trench field effect transistor with a segmented gate structure, characterized in that, Including: A substrate region (1), a drift region (2), a body region (3), a source region (4), a shielding gate (5), a control gate (6), an insulating layer (7), a source electrode (8), a drain electrode (9), and a metal gate; the drift region (2), the body region (3), the source region (4), and the source electrode (8) are sequentially disposed above the substrate region (1), and the drain electrode (9) is disposed below the substrate region (1); The control gate (6) and the shielding gate (5) are sequentially disposed on one side of the drift region (2) from top to bottom, and are respectively connected to the drift region (2), the body region (3), and the source region (4) through the insulating layer (7); the control gate (6) and the shielding gate (5) are separated by the insulating layer (7); the shielding gate (5) is composed of metal materials with different work functions from top to bottom; the control gate (6) is composed of metal materials with different work functions from top to bottom; The source electrode (8) is disposed above the source region; the metal gate is disposed above the control gate; in the shielding gate (5), the work function of the metal material increases sequentially from top to bottom.

2. The trench-type field-effect transistor with a segmented gate structure according to claim 1, wherein in the control gate (6), the work function of the metal material increases sequentially from top to bottom.

3. The trench-type field-effect transistor with a segmented gate structure according to claim 1, wherein in the shielding gate (5), the work function difference between every two adjacent metal materials is 0.2 to 1.

4. The trench-type field-effect transistor with a segmented gate structure according to claim 2, wherein in the control gate (6), the work function difference between every two adjacent metal materials is 0.2 to 1.

5. The trench-type field-effect transistor with a segmented gate structure according to claim 1, wherein the number of metal materials constituting the control gate (6) is the same as the number of metal materials constituting the shielding gate (5).

6. The trench-type field-effect transistor with a segmented gate structure according to claim 1, wherein the thicknesses of the metal materials in each layer of the shielding gate (5) are the same.

7. The trench-type field-effect transistor with a segmented gate structure according to claim 1, wherein the thicknesses of the metal materials in each layer of the control gate (6) are the same.

8. The trench-type field-effect transistor with a segmented gate structure according to claim 5, wherein the number of metal materials constituting the control gate is greater than or equal to 3.

9. A method for manufacturing a trench field effect transistor with a segmented gate structure, characterized in that, Including: A substrate region is prepared from a heavily doped semiconductor material; A drift region is epitaxially formed on the substrate region; A body region is formed above the drift region by ion implantation or diffusion; A trench is etched on one side of the drift region; An oxide, metal materials with different work functions, an oxide, and metal materials with different work functions are sequentially deposited in the trench to form a shielding gate, a control gate, an insulating layer, and a metal gate. Among them, in the shielding gate, the work function of the metal material increases sequentially from top to bottom; A source region is doped above the body region; Deposit source metal above the source region to obtain a source electrode; Fabricate and form a drain electrode below the substrate region.

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