Shield grid power device capable of improving terminal electric field

Abstract

The invention discloses a shield gate power device capable of improving a terminal electric field, which relates to the field of power semiconductor devices and comprises an active region and a terminal region surrounding the active region. The active region comprises a plurality of long cell grooves and short cell grooves which are alternately arranged in parallel along a first direction; the terminal area internally comprises N terminal grooves surrounding the active area, and each terminal groove comprises two vertical parts parallel to the first direction and a horizontal part perpendicular to the vertical parts; for the terminal groove adjacent to the active region, at least one horizontal part is connected with a plurality of lug bosses vertical to the horizontal part, and the lug bosses are in one-to-one correspondence with the short cell grooves; the protruding parts vertically extend from the connected horizontal parts to one ends of the corresponding short cell grooves, the distance between one ends, close to the corresponding protruding parts, of the short cell grooves and the corresponding protruding parts is T2, the distance between the two ends of the long cell grooves and the corresponding horizontal parts is T1, and T1 is larger than T2. The device can improve terminal electric field distribution and improve the reliability of the device.

Description

Technical Field

[0001] This invention relates to the field of power semiconductor devices, and in particular to a shielded gate power device that can improve the terminal electric field. Background Technology

[0002] Shielded-gate power MOSFETs enhance the two-dimensional depletion of the device drift region through the bulk shielded gate electrode, optimizing the peak electric field in the drift region. This allows for a reduction in the resistivity of the epitaxial layer while achieving the same breakdown voltage as conventional trench devices. However, the introduction of the shielded gate introduces instability in avalanche breakdown, affecting device reliability.

[0003] Traditional shielding gate terminal arrangement methods, such as Figure 1 As shown, the spacing between trenches within the cell region is T1, and the spacing between the trenches in the cell region and the terminal trench is T2. If the spacing of T2 is too small, the breakdown voltage of the device will be too low; if the spacing of T2 is too large, the breakdown curve will exhibit a walking-in phenomenon, meaning the breakdown voltage will decrease after multiple tests. As is well known, power devices are composed of tens of thousands of cells arranged in parallel, and the T2 structure within the dashed box in the transition region also contains tens of thousands of such structures. Therefore, the spacing of T2 is particularly important; even slight process variations can cause changes in the T2 spacing in the transition region, thus affecting the breakdown voltage of the device. Summary of the Invention

[0004] To address the aforementioned problems and technical requirements, the inventors have proposed a shielded gate power device that can improve the terminal electric field. The technical solution of this invention is as follows: A shielded gate power device that can improve the terminal electric field includes an active region located in the central region of a semiconductor substrate, and a terminal region surrounding the active region. The active region includes a plurality of strip-shaped long cell grooves and short cell grooves arranged in parallel and alternately along a first direction, wherein the length of the long cell grooves is greater than the length of the short cell grooves. The terminal area includes N terminal trenches surrounding the active area. For any terminal trench, the terminal trench includes two vertical parts parallel to the first direction and two horizontal parts perpendicular to the vertical parts. The vertical parts and the horizontal parts are connected end to end in sequence. For the terminal trench adjacent to the active region, at least one horizontal portion is connected to a plurality of protrusions perpendicular to the horizontal portion, and the plurality of protrusions correspond one-to-one with a plurality of short cell trenches. The protrusion extends vertically from the connected horizontal portion to one end of the corresponding short cell groove, and the distance between the end of the short cell groove near the corresponding protrusion and the corresponding protrusion is T2. The distance between the two ends of the long cell groove and the corresponding horizontal portion is T1, and T1 is greater than T2.

[0005] A further technical solution is that when there are multiple protrusions perpendicular to the horizontal part connected to only one horizontal part in the terminal groove, the end of the short cell groove away from the corresponding protrusion is flush with the long cell groove.

[0006] A further technical solution is that the width of the protrusion is the same as the width of the corresponding short cell groove, the distance between the adjacent long cell groove and the short cell groove is T1, and the distance between the protrusion and the adjacent long cell groove is also T1.

[0007] A further technical solution is that the vertical part is connected to the horizontal part through a bent part, the angle formed by the bent part and the connected vertical part is 135°, and the angle formed by the bent part and the connected horizontal part is also 135°.

[0008] A further technical solution is that, when N=3, a first terminal trench, a second terminal trench, and a third terminal trench are sequentially formed in the terminal region along the direction from the active region to the terminal region. The width of the first terminal trench is the same as the width of the second terminal trench and is greater than the width of the third terminal trench.

[0009] A further technical solution is that the depth of the first terminal trench and the depth of the second terminal trench are greater than the depth of the third terminal trench.

[0010] A further technical solution is that the distance between the first terminal groove and the second terminal groove is smaller than the distance between the second terminal groove and the third terminal groove.

[0011] The further technical solution is that the distance between the first terminal trench and the second terminal trench is 0.8T1, and the distance between the second terminal trench and the third terminal trench is T1.

[0012] The further technical solution is that the width of all long cell trenches and short cell trenches is W1, the width of the first terminal trench and the width of the second terminal trench are 1.15W1, and the width of the third terminal trench is W1.

[0013] A further technical solution is that the inner wall of the terminal trench is covered with an insulating oxide layer, and the terminal trench is filled with polysilicon, wherein the polysilicon is isolated from the inner wall of the terminal trench by the insulating oxide layer. The polysilicon in the terminal trench adjacent to the active region is in ohmic contact with the first electrode metal layer above the semiconductor substrate used to form the first electrode.

[0014] The beneficial technical effects of this invention are: This invention alternately arranges long and short cell trenches within the active region, and provides a protrusion on at least one horizontal portion of the terminal trench adjacent to the active region. The protrusion corresponds to a short cell trench, and maintains a T2 gap at one end of the corresponding short cell trench to form a transition region. This structure reduces the number of locations requiring T2 gap maintenance by half compared to conventional designs, and adjacent locations requiring T2 gap maintenance can be isolated by long cell trenches. In conventional designs, a T2 gap affected by process variations can easily impact adjacent T2 gaps; however, this invention avoids this problem through the isolation effect of long cell trenches, thus reducing the overall degree to which T2 gaps are affected by process variations. Furthermore, the electric field depletion structure at the transition region in this invention is simpler than that of conventional transition regions, optimizing the terminal electric field distribution, mitigating instability caused by avalanche breakdown, and improving device reliability. In addition, this invention provides bends at the four corners of the terminal trenches, which, compared to conventional rounded corners, avoids electric field concentration, thereby further improving the device's withstand voltage. Attached Figure Description

[0015] Figure 1 This is a partial schematic diagram of the terminal arrangement of a conventional shielded gate power device provided by the present invention.

[0016] Figure 2 This is a schematic diagram of the layout of the shielded gate power device that can improve the terminal electric field provided by the present invention.

[0017] Figure 3 This is a partial schematic diagram of the layout of the shielded gate power device that can improve the terminal electric field provided by the present invention.

[0018] Figure label: 1-Long cell groove, 2-Short cell groove, 3-Terminal groove, 31-First terminal groove, 32-Second terminal groove, 33-Third terminal groove, 4-Vertical part, 5-Horizontal part, 6-Bending part, 7-Protrusion. Detailed Implementation

[0019] The specific embodiments of the present invention will be further described below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the scope of this disclosure.

[0020] The present invention discloses a shielded gate power device that can improve the terminal electric field, including an active region located in the central region of a semiconductor substrate, and a terminal region surrounding the active region; The active region includes a plurality of strip-shaped long cell grooves 1 and short cell grooves 2 arranged alternately in parallel along the first direction. The length of the long cell grooves 1 is greater than the length of the short cell grooves 2. The terminal region includes N (N is a positive integer and N≥1) terminal grooves 3 surrounding the active region. For details, please refer to Figure 2-3For a power device, it generally includes an active region located in the center of a semiconductor substrate and a termination protection zone surrounding the active region. The specific functions and distribution of the active region and termination protection zone can be consistent with existing technologies. The active region typically contains several parallel-distributed trench-type cells. The long and short cell trenches are part of the trench-type cell structure. Specifically, the trench-type cells can be shielding gate trench-type cells, and their specific form can be consistent with existing technologies. The semiconductor substrate can use commonly used materials, such as silicon substrates or SiC substrates, to meet application requirements.

[0021] For any terminal groove 3, the terminal groove 3 includes two vertical portions 4 parallel to the first direction and two horizontal portions 5 perpendicular to the vertical portions 4. Please refer to [reference needed]. Figure 2 That is, a horizontal part 5 is provided on the upper and lower sides of the active area, and a vertical part 4 is provided on the left and right sides of the active area. The vertical part 4 and the horizontal part 5 are connected end to end in sequence to form a terminal groove 3 that surrounds the active area. The specific connection method can be referred to the following description.

[0022] For the terminal trench 3 adjacent to the active area, at least one horizontal part 5 is connected to a plurality of protrusions 7 perpendicular to the horizontal part 5, and the plurality of protrusions 7 correspond one-to-one with a plurality of short cell trenches 2; the protrusions 7 are disposed between one end of the corresponding short cell trench 2 and the connected horizontal part 5, and the distance between the end of the short cell trench 2 near the corresponding protrusion 7 and the corresponding protrusion 7 is T2, and the distance between the two ends of the long cell trench 1 and the corresponding horizontal part 5 is T1, where T1 is greater than T2.

[0023] like Figure 3 As shown, taking the example of multiple protrusions 7 provided on the horizontal portion 5 below the active region, the protrusions 7 extend vertically from the horizontal portion 5 to one end of the corresponding short cell groove 2, and are spaced T2 apart from the short cell groove 2, forming Figure 3 The transition area is shown within the dashed box. The width of the protrusion 7 is the same as the width of the corresponding short cell groove 2. The distance between adjacent long cell grooves 1 and short cell grooves 2 is T1, and the distance between the protrusion and the adjacent long cell groove 1 is also T1. Generally, T2 can be 60%-80% of T1.

[0024] Because long cell trenches 1 and short cell trenches 2 are alternately arranged in the active region, and the protrusions 7 correspond one-to-one with the short cell trenches 2, adjacent protrusions 7 on the same side of the horizontal portion 5 are all connected by long cell trenches 1. The long cell trenches 1 can act as isolation, preventing the distance T2 between a certain protrusion 7 and its corresponding short cell trench 2 from being affected by the process, thus reducing the degree of process influence on the transition region. Furthermore, compared to traditional terminal structure designs, the structure proposed in this application has a simpler electric field depletion in the transition region, which can improve the instability of avalanche breakdown. Figure 1 and Figure 3 The transition area shown (the area within the dashed box). Figure 1 The electric field depletion of a traditional terminal structure is influenced by the terminal trench's effect on two adjacent cell trenches, the effect between the two cell trenches, and the effect of the terminal trench on the region between the two cell trenches. Figure 3 The transition region formed in this application is only affected by the short cell trench 2 corresponding to the protrusion 7 and the long cell trench 1 on both sides of the protrusion. Therefore, the electric field depletion of the transition region formed in this application is simpler and less affected by process fluctuations. This can optimize the terminal electric field distribution, improve the unstable situation of device avalanche breakdown, and enhance the reliability of the device.

[0025] Optionally, for any short cell trench 2, protrusions 7 can be provided at both ends or only at one end. That is, protrusions 7 can be provided on the horizontal portions 5 above and below the active region or only on the horizontal portion on one side of the active region. When protrusions 7 are provided at both ends of the short cell trench 2, the distance between both ends of the short cell trench 2 and the protrusions 7 is T2, and both ends form a transition region. When a protrusion 7 is provided at only one end of the short cell trench 2, that is, when only one horizontal portion 5 in the terminal trench 3 is connected to multiple protrusions 7 perpendicular to the horizontal portion 5, the end of the short cell trench 2 away from the corresponding protrusion 7 is flush with the long cell trench 1. That is, one end of the short cell trench 2 is T2 away from the protrusion 7 on the horizontal portion 5 on one side of the active region, and the other end of the short cell trench 2 is T1 away from the horizontal portion 5 on the other side of the active region.

[0026] Furthermore, the vertical portion 4 in the terminal groove 3 is connected to the horizontal portion 5 via a bending portion 6. The angle formed by the bending portion 6 and the connected vertical portion 4 is 135°, and the angle formed by the bending portion 6 and the connected horizontal portion 5 is also 135°. Figure 3 As shown, the terminal groove 3 has four bends 6, and each vertical part 4 is connected to the horizontal part 5 through the bend 6, thereby forming an obtuse-angle bend shape at the four corners of the terminal groove 3. Figure 1 Compared to the traditional rounded corners shown, this design avoids electric field concentration at the rounded corners, further improving the device's withstand voltage. It should be noted that... Figure 2 The diagram only shows local areas at the four corners of the power device layout, omitting the middle areas in the length and width directions. In actual implementation, the length and width values ​​of the power device layout can be set according to actual needs.

[0027] When the terminal area is provided with multiple terminal trenches 3 (N>1), the geometric centers of all terminal trenches 3 are consistent. In one embodiment of the present invention, N=3, and a first terminal trench 31, a second terminal trench 32, and a third terminal trench 33 are sequentially formed in the terminal area along the direction from the active area to the terminal area. Please refer to [reference needed]. Figure 2 The width of the first terminal trench 31 is the same as the width of the second terminal trench 32 and is greater than the width of the third terminal trench 33. The depth of the first terminal trench 31 is greater than the depth of the second terminal trench 32 and is greater than the depth of the third terminal trench 33. The distance between the first terminal trench 31 and the second terminal trench 32 is less than the distance between the second terminal trench 32 and the third terminal trench 33, so as to ensure a uniform transition of the electric field.

[0028] In one embodiment of the present invention, the distance between the first terminal groove 31 and the second terminal groove 32 is 0.8T1, and the distance between the second terminal groove 32 and the third terminal groove 33 is T1. The width of all long cell grooves 1 and short cell grooves 2 is W1, the width of the first terminal groove 31 and the width of the second terminal groove 32 are 1.15W1, and the width of the third terminal groove 33 is W1. Figure 2-3 As shown, to ensure the aforementioned spacing is formed between the first terminal groove 31, the second terminal groove 32, and the third terminal groove 33, the lengths of the vertical portion 4, the horizontal portion 5, and the bent portion 6 in the first terminal groove 31, the second terminal groove 32, and the third terminal groove 33 gradually increase. In specific implementations, the values ​​of N, T1, T2, and W1 can be determined according to the actual needs of the formed power device.

[0029] Furthermore, the inner wall of the terminal trench 3 is covered with an insulating oxide layer, and the terminal trench 3 is filled with polysilicon, which is isolated from the inner wall of the terminal trench 3 by the insulating oxide layer; the polysilicon in the terminal trench 3 adjacent to the active region has an ohmic contact with the first electrode metal layer above the semiconductor substrate used to form the first electrode metal, and the polysilicon filled in other terminal trenches 3 is floating. Specifically, the power device can be a MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor) device or an IGBT (Insulated Gate Bipolar Transistor) device. For a MOSFET device, the first electrode is the source; for an IGBT device, the first electrode is the emitter.

[0030] In summary, this invention alternately arranges long and short cell trenches within the active region, and provides a protrusion on at least one horizontal portion of the terminal trench adjacent to the active region. The protrusion corresponds to a short cell trench and forms a transition region with one end of the corresponding short cell trench at a T2 distance, thereby optimizing the electric field distribution, mitigating instability caused by avalanche breakdown, and improving device reliability. Simultaneously, the terminal trench forms obtuse-angled bends at the four corners to further improve the device's withstand voltage.

[0031] In the description of this specification, the terms "first," "second," "third," and "fourth" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0032] The use of terms such as "one embodiment / mode," "some embodiments / modes," "example," "specific example," or "some examples," etc., refers to a specific feature, structure, material, or characteristic described in connection with that embodiment / mode or example, which is included in at least one embodiment / mode or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment / mode or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments / modes or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments / modes or examples described in this specification, as well as the features of different embodiments / modes or examples.

[0033] In the description of this application, if terms such as "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential" appear, these terms indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0034] In this application, unless otherwise expressly specified and limited, the terms "installation," "connection," "joining," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise expressly limited. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0035] The above descriptions are merely preferred embodiments of the present invention, and the present invention is not limited to the above embodiments. It is understood that other improvements and variations that can be directly derived or conceived by those skilled in the art without departing from the spirit and concept of the present invention should be considered to be included within the protection scope of the present invention.

Claims

1. A shielded gate power device capable of improving the electric field at the termination, characterized by, The active region is located in the center of the semiconductor substrate, and the terminal region surrounds the active region; The active region comprises a plurality of long cell trenches and short cell trenches arranged alternately in parallel along a first direction, and the length of the long cell trenches is greater than the length of the short cell trenches; The terminal region comprises N terminal trenches surrounding the active region, and for any terminal trench, the terminal trench comprises two vertical portions parallel to the first direction and two horizontal portions perpendicular to the vertical portions, and the vertical portions and the horizontal portions are connected end to end in sequence; For the terminal trench adjacent to the active region, at least one horizontal portion is connected with a plurality of protruding portions perpendicular to the horizontal portion, and the plurality of protruding portions correspond to the plurality of short cell trenches one by one; The protruding portion vertically extends from the connected horizontal portion to one end of the corresponding short cell trench, and the distance between the end of the short cell trench close to the corresponding protruding portion and the corresponding protruding portion is T2, and the distance between the two ends of the long cell trench and the corresponding horizontal portion is T1, and T1 is greater than T2.

2. The shielded gate power device with improved termination electric field according to claim 1, wherein, When only one horizontal portion of the terminal trench is connected with a plurality of protruding portions perpendicular to the horizontal portion, the end of the short cell trench away from the corresponding protruding portion is flush with the long cell trench.

3. The shielded gate power device with improved termination electric field according to claim 1, wherein, The width of the protruding portion is the same as the width of the corresponding short cell trench, the spacing between adjacent long cell trenches and short cell trenches is T1, and the spacing between the protruding portion and the adjacent long cell trench is also T1.

4. The shielded gate power device with improved termination electric field according to claim 1, wherein, The vertical portion is connected with the horizontal portion through a bending portion, the included angle between the bending portion and the connected vertical portion is 135°, and the included angle between the bending portion and the connected horizontal portion is also 135°.

5. The shielded gate power device with improved termination electric field according to claim 1, wherein, When N=3, the first terminal trench, the second terminal trench and the third terminal trench are sequentially formed in the terminal region along the direction from the active region to the terminal region, wherein the width of the first terminal trench is the same as the width of the second terminal trench and greater than the width of the third terminal trench.

6. The shielded gate power device with improved termination electric field according to claim 5, wherein, The groove depth of the first terminal trench and the groove depth of the second terminal trench are greater than the groove depth of the third terminal trench.

7. The shielded gate power device with improved termination electric field according to claim 6, wherein, The spacing between the first terminal trench and the second terminal trench is less than the spacing between the second terminal trench and the third terminal trench.

8. The shielded gate power device with improved termination electric field according to claim 7, wherein, The spacing between the first terminal trench and the second terminal trench is 0.8T1, and the spacing between the second terminal trench and the third terminal trench is T1.

9. The shielded gate power device with improved termination electric field according to claim 8, wherein, The width of all long cell trenches and short cell trenches is W1, the width of the first terminal trench and the width of the second terminal trench are 1.15W1, and the width of the third terminal trench is W1.

10. The shielded gate power device with improved termination electric field according to claim 1, wherein, The inner wall of the terminal trench is covered with an insulating oxide layer, and the terminal trench is filled with polysilicon, and the polysilicon is isolated from the inner wall of the terminal trench by the insulating oxide layer; The polysilicon in the terminal trench adjacent to the active region is in ohmic contact with the first electrode metal layer above the semiconductor substrate for forming the first electrode.

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