A three-dimensional square cell structure, preparation method and device thereof

Abstract

The present invention discloses a three-dimensional square cell structure, comprising: a first-conductivity-type epitaxial region, a second-conductivity-type well region located within the first-conductivity-type epitaxial region, a meandering first-conductivity-type source region located within the second-conductivity-type well region, and a second-conductivity-type body region located within the meandering first-conductivity-type source region; wherein the second-conductivity-type body region is convex; along the horizontal and vertical directions, the first-conductivity-type epitaxial region, the second-conductivity-type well region, and the meandering first-conductivity-type source region are each provided with a plurality of protrusions of the same width and height, thereby forming a plurality of protruding mesas in the horizontal and vertical directions, respectively, and simultaneously forming a cross-shaped mesa structure intersecting with the second-conductivity-type body region on the square cell structure. This structure enables the device to have both parallel and perpendicular channels to the cell surface, thereby increasing the channel density, reducing the on-resistance of the channel, and improving the current flow capacity of the device.

Description

Technical Field

[0001] The present invention belongs to the field of microelectronics technology, and in particular relates to a three-dimensional square cell structure, a preparation method and a device thereof. Background Art

[0002] Semiconductor technology has played a decisive role in the development of the power electronics industry. Power semiconductor devices have long been considered key components of power electronics. MOSFETs (Metal-Oxide-Semiconductor Field-Effect Transistors) and IGBTs (Insulated Gate Bipolar Transistors) are two typical and widely used semiconductor devices.

[0003] As a power semiconductor device, MOSFET can reduce converter conversion losses, increase power density, lower heat dissipation requirements, and reduce system size and complexity, significantly improving system performance. Furthermore, its high-temperature, high-voltage, and low-loss characteristics make MOSFETs suitable for a variety of systems, including power supplies, rail transit, motor control, electric vehicles, and aerospace. IGBTs are composite, fully controlled, voltage-driven power semiconductor devices composed of a BJT (bipolar junction transistor) and a MOS (insulated-gate field-effect transistor). They combine the advantages of a MOSFET's high input impedance with the GTR's low on-state voltage drop. They are ideally suited for applications in power conversion systems with DC voltages of 600V and above, such as AC motors, inverters, switching power supplies, lighting circuits, and traction drives.

[0004] However, the common MOSFET or IGBT cell structures are mostly planar. Due to process limitations, this planar cell structure cannot further increase the channel density and reduce the device channel resistance, thereby affecting the device's current capacity and limiting its application. Summary of the Invention

[0005] In order to solve the above problems existing in the prior art, the present invention provides a three-dimensional square cell structure, a preparation method and a device thereof. The technical problem to be solved by the present invention is achieved by the following technical solutions:

[0006] In a first aspect, the present invention provides a three-dimensional square cell structure, comprising: a first conductive type epitaxial region, a second conductive type well region located within the first conductive type epitaxial region, a meandering first conductive type source region located within the second conductive type well region, and a second conductive type body region located within the meandering first conductive type source region; wherein,

[0007] The second conductive type body region is convex;

[0008] Along the horizontal and vertical directions, a number of protrusions with the same width and height are provided on the first conductive type epitaxial region, the second conductive type well region and the meandering first conductive type source region to form a number of protruding mesas in the horizontal and vertical directions respectively, and at the same time, a cross-shaped mesa structure intersecting with the second conductive type body region is formed on the square cell structure.

[0009] In one embodiment of the present invention, the width of each of the raised mesas does not exceed the inner edge of the second conductivity type well region.

[0010] In one embodiment of the present invention, the width of the raised mesa is 1-5 μm, and the height is 0.1-1 μm.

[0011] In one embodiment of the present invention, the first conductivity type is N-type, and the second conductivity type is P-type.

[0012] In a second aspect, the present invention further provides another three-dimensional square cell structure, comprising: a first conductive type epitaxial region, a second conductive type well region located in the first conductive type epitaxial region, a meandering first conductive type source region located in the second conductive type well region, and a second conductive type body region located in the meandering first conductive type source region; wherein,

[0013] Along the horizontal and vertical directions, a number of grooves with the same width and depth are symmetrically provided on the first conductive type epitaxial region, the second conductive type well region and the meander-shaped first conductive type source region on both sides of the second conductive type body region to form a number of grooves in the horizontal and vertical directions respectively, and at the same time, a cross-shaped groove structure intersecting with the second conductive type body region is formed on the upper surface of the square cell structure.

[0014] In one embodiment of the present invention, the width of each of the grooves does not exceed the inner edge of the second conductivity type well region.

[0015] In one embodiment of the present invention, the width of the groove is 1-5 μm and the depth is 0.1-1 μm.

[0016] In a third aspect, the present invention provides a method for preparing a three-dimensional square cellular structure, comprising:

[0017] preparing a first conductivity type epitaxial region;

[0018] forming a second conductivity type well region, a meandering first conductivity type source region, and a second conductivity type body region in sequence on the first conductivity type epitaxial region by an ion implantation process;

[0019] The obtained sample is etched to form a cross-shaped mesa structure or a groove structure on the surface of the sample.

[0020] In a fourth aspect, the present invention provides a MOSFET device comprising any one of the three-dimensional square cell structures described in the above embodiments.

[0021] In a fifth aspect, the present invention provides an IGBT device comprising any one of the three-dimensional square cell structures described in the above embodiments.

[0022] Beneficial effects of the present invention:

[0023] 1. The present invention forms a three-dimensional square cellular structure by adding a mesa structure or a groove structure on the surface of the cellular structure. In addition to parallel channels parallel to the cellular surface, the device also has vertical channels perpendicular to the cellular surface, thereby increasing the channel density, reducing the on-resistance of the channel, and thus improving the current flow capacity of the device.

[0024] 2. The present invention designs the mesa structure and the groove structure into a cross shape, which can improve the channel of the cell from two directions at the same time, making the channel density improvement effect more obvious.

[0025] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 Schematic diagram of a three-dimensional square cell structure with a group of raised mesas provided in Example 1 of the present invention;

[0027] Figure 2 is a top view of a three-dimensional square cellular structure having a group of raised mesas provided in Example 1 of the present invention;

[0028] Figure 3 is a cross-sectional view of a three-dimensional square cellular structure having a group of raised mesas provided in Example 1 of the present invention;

[0029] Figure 4 Schematic diagram of a three-dimensional square cell structure with two groups of raised mesas provided by an embodiment of the present invention;

[0030] Figure 5 Schematic diagram of a three-dimensional square cell structure with a set of grooves provided in the second embodiment of the present invention;

[0031] Figure 6 is a top view of a three-dimensional square cellular structure having a set of grooves provided in the second embodiment of the present invention;

[0032] Figure 7 is a cross-sectional view of a three-dimensional square cellular structure having a set of grooves provided in Example 2 of the present invention;

[0033] Figure 8 Schematic diagram of a three-dimensional square cell structure with two groups of grooves provided by an embodiment of the present invention;

[0034] Figure 9 This is a schematic flow chart of a method for preparing a three-dimensional square cellular structure provided in Example 3 of the present invention. DETAILED DESCRIPTION

[0035] The present invention will be further described in detail below with reference to specific examples, but the embodiments of the present invention are not limited thereto.

[0036] Example 1

[0037] This embodiment provides a three-dimensional square cell structure with a raised mesa structure, which includes: a first conductive type epitaxial region 1, a second conductive type well region 2 located in the first conductive type epitaxial region 1, a meandering first conductive type source region 3 located in the second conductive type well region 2, and a second conductive type body region 4 located in the meandering first conductive type source region 3; wherein,

[0038] The second conductive type body region 4 is convex;

[0039] Along the horizontal and vertical directions, a number of protrusions with the same width and height are provided on the first conductive type epitaxial region 1, the second conductive type well region 2 and the meander-shaped first conductive type source region 3 to form a number of protruding mesas 5a in the horizontal and vertical directions respectively, and at the same time, a cross-shaped mesa structure 6a intersecting with the second conductive type body region 4 is formed on the square cell structure.

[0040] In this embodiment, the width d of each of the raised mesas 5a does not exceed the inner edge of the second conductive type well region 2, so as to ensure that the second conductive type well region 2 has raised mesas in both horizontal and vertical directions, thereby forming vertical and horizontal channels in the second conductive type well region 2.

[0041] Optionally, the width of the raised mesa 5a is 1-5 μm, and the height is 0.1-1 μm.

[0042] Specifically, this embodiment takes a square cell structure with a group of raised terraces as an example for detailed description. Figure 1 , Figure 1 3D square cell structure with a group of raised mesas provided in the first embodiment of the present invention; wherein the width d of the raised mesas 5a is the same as the width of the second conductive type body region 4.

[0043] In this embodiment, the first conductivity type is N-type and the second conductivity type is P-type. In addition, the first conductivity type can also be set to P-type and the second conductivity type to N-type. In this embodiment, the first conductivity type is preferably N-type and the second conductivity type is P-type.

[0044] Furthermore, the N-type epitaxial region 1 and the P-type well region 2 are lightly doped regions, and the N-type source region 3 and the P-type body region 4 are heavily doped regions. Thus, the three-dimensional square cell structure provided by this embodiment includes the N-epitaxial region 1, the P-well region 2, the N+ source region 3 and the P+ body region 4. Figure 2-3 , Figure 2 is a top view of a three-dimensional square cellular structure having a group of raised mesas provided in Example 1 of the present invention; Figure 3 1 is a cross-sectional view of a three-dimensional square cellular structure having a group of raised mesas provided in Example 1 of the present invention.

[0045] Since the cross-type mesa structure in this embodiment includes a group of raised mesas, the total width of the cross-type mesa structure 6 a is the same as the width d of a single raised mesa 5 a , and both are equal to the width of the second conductivity type body region 4 .

[0046] It should be noted that, in another embodiment of the present invention, the cross-shaped table structure may also include multiple sets of parallel raised table surfaces. For example, see Figure 4 , Figure 4 3D square cell structure with two groups of raised mesas provided by an embodiment of the present invention; wherein, the edges at both ends of the two raised mesas 5a do not exceed the inner edge of the second conductive type well region 2.

[0047] This embodiment forms a three-dimensional square cellular structure by adding a raised table structure to the surface of the cellular structure, so that in addition to having parallel channels parallel to the cellular surface, the device also has a vertical channel perpendicular to the cellular surface. Compared with the traditional two-dimensional structure cell, the channel is only in the horizontal direction and the channel width cannot be further improved. This embodiment adds a vertical channel (the side wall of the table is the vertical channel) on the basis of the horizontal channel of the cell by setting a table structure without reducing the horizontal channel, thereby effectively improving the total channel width of the entire cellular structure. It can be seen that the height of the table side wall determines the width of the vertical channel. The introduction of the vertical channel effectively improves the cellular channel density, reduces the on-resistance of the channel, and thus improves the flow capacity of the device.

[0048] In addition, in this embodiment, the mesa structure is designed to be cross-shaped, which can improve the channel of the cell from two directions at the same time, making the channel density improvement effect more obvious.

[0049] Example 2

[0050] This embodiment provides a three-dimensional square cell structure with a groove structure, which includes: a first conductive type epitaxial region 1, a second conductive type well region 2 located in the first conductive type epitaxial region 1, a meandering first conductive type source region 3 located in the second conductive type well region 2, and a second conductive type body region 4 located in the meandering first conductive type source region 3; wherein,

[0051] Along the horizontal and vertical directions, a number of grooves of the same width and depth are symmetrically provided on the first conductive type epitaxial region 1, the second conductive type well region 2 and the meander-shaped first conductive type source region 3 on both sides of the second conductive type body region 4 to form a number of grooves 5b in the horizontal and vertical directions respectively, and at the same time, a cross-shaped groove structure 6b intersecting with the second conductive type body region 4 is formed on the upper surface of the square cell structure.

[0052] In this embodiment, the width of each groove 5b does not exceed the inner edge of the second conductive type well region 2 to ensure that the second conductive type well region 2 has raised mesas in both horizontal and vertical directions, thereby forming vertical and horizontal channels in the second conductive type well region 2.

[0053] Optionally, the groove 5b has a width of 1-5 μm and a height of 0.1-1 μm.

[0054] Specifically, this embodiment takes a square cell structure with a set of grooves as an example for detailed description. Figure 5 , Figure 5 3D square cell structure with a set of grooves provided in the second embodiment of the present invention; wherein the width D of the groove 5b is the same as the width of the second conductive type body region 4.

[0055] In this embodiment, the first conductivity type is preferably N-type and the second conductivity type is P-type. Furthermore, the N-type epitaxial region 1 and the P-type well region 2 are lightly doped regions, and the N-type source region 3 and the P-type body region 4 are heavily doped regions. Thus, the three-dimensional square cell structure provided by this embodiment includes the N-epitaxial region 1, the P-well region 2, the N+ source region 3, and the P+ body region 4. See Figure 6-7 , Figure 6 is a top view of a three-dimensional square cellular structure having a group of groove structures provided in the second embodiment of the present invention; Figure 7 It is a cross-sectional view of a three-dimensional square cell structure having a group of groove structures provided by the second embodiment of the present invention.

[0056] Since the cross-shaped groove structure in this embodiment includes a group of grooves, the total width of the cross-shaped groove structure 6 b is the same as the width D of a single groove 5 b , and both are equal to the width of the second conductive type body region 4 .

[0057] It should be noted that, in another embodiment of the present invention, the cross-shaped groove structure may also include multiple sets of parallel grooves. For example, see Figure 8 , Figure 8 3D square cell structure with two groups of grooves provided by an embodiment of the present invention; wherein, the edges at both ends of the two grooves 5b do not exceed the inner edge of the second conductive type well region 2.

[0058] This embodiment forms a three-dimensional square cellular structure by adding a groove structure to the surface of the cellular structure, so that in addition to parallel channels parallel to the cellular surface, the device also has a vertical channel perpendicular to the cellular surface. Compared with the traditional two-dimensional structure cell, the channel is only in the horizontal direction and the channel width cannot be further improved. This embodiment sets a table structure on the basis of the horizontal channel of the cell, and adds a vertical channel (the side wall of the table is the vertical channel) without reducing the horizontal channel, thereby effectively improving the total channel width of the entire cellular structure. It can be seen that the height of the side wall of the table determines the width of the vertical channel. The introduction of the vertical channel effectively improves the cell channel density, reduces the on-resistance of the channel, and thus improves the flow capacity of the device.

[0059] In addition, the groove structure is designed into a cross shape in this embodiment, which can improve the channel of the cell from two directions at the same time, making the channel density improvement effect more obvious.

[0060] Example 3

[0061] Based on the above-mentioned embodiment 1 and embodiment 2, this embodiment provides a method for preparing a three-dimensional square cell structure. Figure 9 , Figure 9 Schematic diagram of a process for preparing a three-dimensional square cellular structure provided in Example 3 of the present invention, comprising the following steps:

[0062] Step 1: Prepare a first conductivity type epitaxial region.

[0063] Generally speaking, the epitaxial region is located on a conductive substrate of the same type, and preferably the first conductive type is N-type.

[0064] Specifically, an N-epitaxial layer is formed on an N+ substrate. The specific thickness and doping concentration of the N-epitaxial layer are not specifically limited in this embodiment. For example, the thickness of the N-epitaxial layer can be set to 35 μm and the doping concentration can be set to 1×10 15 cm -3 .

[0065] Step 2: using an ion implantation process to sequentially form a second conductivity type well region, a meandering first conductivity type source region, and a second conductivity type body region on the first conductivity type epitaxial region.

[0066] First, P-type ions are implanted into the N-epitaxial layer obtained in step 1 to form a P-well region. The junction depth of the P-well region can be 0.7 μm, and the doping concentration can be 4×10 17 cm -3 .

[0067] Then, N-type ions are continuously implanted on the above sample to form a meandering N+ source region. The junction depth of the N+ source region can be 0.2 μm, and the doping concentration can be 1×10 19 cm -3 .

[0068] Finally, P-type ions are implanted into the meandering N+ source region in the middle of the sample to form a P+ body region. The junction depth of the P+ body region can be 0.2 μm, and the doping concentration can be 1×10 19 cm -3 .

[0069] It should be noted that this embodiment does not specifically limit the order of forming the second conductivity type well region, the meandering first conductivity type source region, and the second conductivity type body region, and those skilled in the art may adjust it as needed.

[0070] Step 3: Etching the obtained sample to form a cross-shaped mesa structure or groove structure on the sample surface.

[0071] In this embodiment, Si etching or SiC etching process can be used to etch the periphery of the sample obtained in step 2 according to whether the epitaxial layer material is Si or SiC, respectively, to remove the peripheral epitaxial layer to form a cross-shaped mesa structure in the middle of the sample.

[0072] Alternatively, the middle of the sample obtained in step 2 is etched to remove the epitaxial layer in the middle, so as to form a cross-shaped groove structure in the middle of the sample.

[0073] It should be noted that the specific process parameters can be implemented with reference to existing etching processes and are not specifically limited in this embodiment.

[0074] The preparation method provided in this embodiment can prepare the three-dimensional square cell structure provided in the above-mentioned embodiment 1 or embodiment 2. As a result, the prepared device structure also has parallel channels parallel to the cell surface and vertical channels perpendicular to the cell surface, thereby increasing the channel density, reducing the on-resistance of the channel, and helping to improve the current flow capacity of the device.

[0075] Example 4

[0076] Based on the above-mentioned embodiment one and embodiment two, this embodiment provides a MOSFET device, which includes the three-dimensional square cell structure with a raised mesa structure provided in the above-mentioned embodiment one, or includes the three-dimensional square cell structure with a groove structure provided in the above-mentioned embodiment two.

[0077] In this embodiment, Si or SiC material may be used to form an epitaxial layer of a three-dimensional square cell structure.

[0078] Preferably, this embodiment uses SiC material to form a MOSFET device having a three-dimensional square cell structure. In the SiC MOSFET device provided in this embodiment, each mesa structure 5a can have a width of 1-5 μm and a height of 0.1-1 μm; alternatively, each groove structure 5b can have a width of 1-5 μm and a depth of 0.1-1 μm.

[0079] Regarding other structural parameters of the MOSFET device, reference may be made to existing devices, and this embodiment will not be described in detail here.

[0080] Therefore, the SiC MOSFET device provided in this embodiment has a higher channel density and a lower channel resistance, and thus has good current flow capability.

[0081] Example 5

[0082] Based on the above-mentioned embodiment 1 and embodiment 2, this embodiment provides an IGBT device, which includes the three-dimensional square cellular structure with a raised mesa structure provided in the above-mentioned embodiment 1, or includes the three-dimensional square cellular structure with a groove structure provided in the above-mentioned embodiment 2.

[0083] In this embodiment, the specific structural parameters of the IGBT device can be modified and set according to the existing device structure and actual conditions, and will not be described in detail in this embodiment.

[0084] Therefore, the IGBT device provided by this embodiment also has a higher channel density and a lower channel resistance, and thus has a good current carrying capacity.

[0085] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise" and the like to indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0086] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of the technical features being referred to. Thus, a feature identified as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, "plurality" means two or more, unless otherwise specifically defined.

[0087] In the description of the present invention, reference to the terms "one embodiment," "some embodiments," "examples," "specific examples," or "some examples" means that the specific features, structures, materials, or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in any suitable manner in any one or more embodiments or examples. In addition, those skilled in the art can combine and combine different embodiments or examples described in this specification.

[0088] The above is a further detailed description of the present invention in conjunction with specific preferred embodiments, and the specific implementation of the present invention should not be considered to be limited to these descriptions. For those skilled in the art of the present invention, without departing from the concept of the present invention, several simple deductions or substitutions can be made, which should be considered to fall within the scope of protection of the present invention.

Claims

1. A three-dimensional square cell structure, characterized in that: include: A first conductive type epitaxial region (1), a second conductive type well region (2) located in the first conductive type epitaxial region (1), a meandering first conductive type source region (3) located in the second conductive type well region (2), and a second conductive type body region (4) located in the meandering first conductive type source region (3); wherein, The second conductive type body region (4) is convex; Along the horizontal and vertical directions, a plurality of protrusions of the same width and height are provided on the first conductive type epitaxial region (1), the second conductive type well region (2) and the meander-shaped first conductive type source region (3), so as to form a plurality of protruding mesas (5a) in the horizontal and vertical directions respectively, and at the same time, a cross-shaped mesa structure (6a) intersecting with the second conductive type body region (4) is formed on the square cell structure.

2. The three-dimensional square cellular structure according to claim 1, characterized in that: The width of each of the raised mesas (5a) does not exceed the inner edge of the second conductive type well region (2).

3. The three-dimensional square cellular structure according to claim 1, characterized in that: The width of each raised mesa (5a) is 1-5 μm, and the height is 0.1-1 μm.

4. The three-dimensional square cellular structure according to claim 1, characterized in that: The first conductivity type is N-type, and the second conductivity type is P-type.

5. A three-dimensional square cell structure, characterized in that: include: A first conductive type epitaxial region (1), a second conductive type well region (2) located in the first conductive type epitaxial region (1), a meandering first conductive type source region (3) located in the second conductive type well region (2), and a second conductive type body region (4) located in the meandering first conductive type source region (3); wherein, Along the horizontal and vertical directions, a plurality of grooves of the same width and depth are symmetrically provided on the first conductive type epitaxial region (1), the second conductive type well region (2) and the meander-shaped first conductive type source region (3) on both sides of the second conductive type body region (4), so as to form a plurality of grooves (5b) in the horizontal and vertical directions respectively, and at the same time, a cross-shaped groove structure (6b) intersecting with the second conductive type body region (4) is formed on the upper surface of the square cell structure.

6. The three-dimensional square cellular structure according to claim 5, characterized in that: The width of each groove (5b) does not exceed the inner edge of the second conductive type well region (2).

7. The three-dimensional square cellular structure according to claim 5, characterized in that: Each of the grooves (5b) has a width of 1-5 μm and a depth of 0.1-1 μm.

8. A method for preparing a three-dimensional square cellular structure, characterized in that: include: preparing a first conductivity type epitaxial region; An ion implantation process is used to sequentially form a second conductivity type well region, a meandering first conductivity type source region, and a second conductivity type body region on the first conductivity type epitaxial region; wherein the second conductivity type well region is located within the first conductivity type epitaxial region, the meandering first conductivity type source region is located within the second conductivity type well region, and the second conductivity type body region is located within the meandering first conductivity type source region; Etching the obtained sample in the horizontal and vertical directions to form a plurality of protrusions of the same width and height on the first conductive type epitaxial region, the second conductive type well region, and the meander-shaped first conductive type source region, thereby forming a plurality of protruding mesas in the horizontal and vertical directions, respectively, and forming a cross-shaped mesa structure intersecting with the second conductive type body region on the square cell structure; Alternatively, the obtained sample is etched along the horizontal and vertical directions to form a number of symmetrical grooves with the same width and depth on the first conductive type epitaxial region, the second conductive type well region and the meander-shaped first conductive type source region on both sides of the second conductive type body region, thereby forming a number of grooves in the horizontal and vertical directions respectively, and at the same time forming a cross-shaped groove structure on the upper surface of the square cell structure that intersects with the second conductive type body region.

9. A MOSFET device, characterized in that: It comprises the three-dimensional square cellular structure according to any one of claims 1 to 4 or the three-dimensional square cellular structure according to any one of claims 5 to 7.

10. An IGBT device, characterized in that: It comprises the three-dimensional square cellular structure according to any one of claims 1 to 4 or the three-dimensional square cellular structure according to any one of claims 5 to 7.

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