Metallic clamp and lateral local carrier lifetime control method

Abstract

The application relates to the technical field of semiconductors, and discloses a metal clamp and a transverse local carrier lifetime control method, the metal clamp comprising: a bracket for accommodating the power device; and a metal baffle located in the bracket and forming an accommodation space between the bracket and the metal baffle, the metal baffle comprising a stepped baffle, wherein the heights of multiple steps in the stepped baffle are determined according to target irradiation amounts of corresponding regions in the power device, and the multiple steps are non-obtuse-angle steps. According to the application, the irradiation dose of the metal is regulated through the stepped metal baffle without changing the structure of the power device, so that the minority carrier lifetime in different regions of the power device is finely designed, and the off speeds of different regions of the power device are different, the inconsistent off caused by the parasitic impedance is offset, the off current is balanced, and the off capacity is improved.

Description

Technical Field

[0001] This invention relates to the field of semiconductor technology, and more specifically to a metal clamp and a method for controlling the lifetime of lateral local carriers. Background Technology

[0002] An IGCT (Integrated Gate Commutated Thyristor) is a novel semiconductor switching device that integrates the gate drive circuit with the GCT into a single unit. Based on the GTO (gate turn-off thyristor) structure, the GCT not only possesses the same high blocking capability and low on-state voltage drop as the GTO, but also exhibits the same switching performance as the IGBT (Insulated-Gate Bipolar Transistor). In other words, the GCT combines the strengths of both the GTO and IGBT, making it an ideal megawatt-level, medium-to-high voltage switching device widely used in voltage source inverters, current source inverters, choppers, static circuit breakers, and other circuit topologies.

[0003] GCT devices have a whole-wafer structure, consisting of an edge junction termination region 1, an active region 2, and a gate ring region 3 (also known as a gate contact ring region). Figure 1 (See the top view shown). The edge junction termination region 1 surrounds the outermost edge of the chip to reduce electric field concentration at the edge of the active region, widen the depletion layer, and thus improve the device breakdown voltage; the gate ring region 3 is located between the active regions 2 of the chip (e.g., ...). Figure 1 (as shown in the intermediate gate form) or the periphery of the active region 2 (such as...) Figure 2 The external gate region (shown in the diagram) is responsible for transmitting the gate signal. The active region 2, located inside the chip, consists of multiple cathode rings, each composed of multiple parallel GCT units arranged radially in a ring shape, responsible for the current flow of the GCT device. The metal of the gate ring region 3 is connected to the gate metal in the GCT unit. Due to the different distances of each cathode ring from the gate ring region 3 (i.e., different gate parasitic impedances), the gate signals transmitted to each cathode ring in the GCT unit are also different. Cathode rings farther from the gate ring region 3 turn off more slowly, easily leading to current redistribution and turn-off failure.

[0004] Currently, the main solution to improve the turn-off capability of power devices is to optimize the structure of the power devices. However, the process of optimizing the structure of power devices is generally more complex and the cost is relatively high. Summary of the Invention

[0005] The purpose of this invention is to provide a metal clamp and a method for controlling the lateral local carrier lifetime. Without changing the structure of the power device, the method uses a stepped metal baffle to regulate the irradiation dose through the metal, thereby finely designing the minority carrier lifetime in different regions of the power device. This enables precise control of the turn-off speed in different regions of the power device, counteracts the turn-off inconsistency caused by parasitic impedance, and improves turn-off current sharing and turn-off capability.

[0006] To achieve the above objectives, a first aspect of the present invention provides a metal clamp, the metal clamp comprising: a slot for accommodating the power device; and a metal baffle located within the slot, forming an accommodating space between the metal baffle and the slot, the metal baffle comprising a stepped baffle, wherein the height of a plurality of steps in the stepped baffle is determined by the target irradiance of a corresponding area in the power device, and the plurality of steps are non-obtuse angle steps.

[0007] Preferably, the metal baffle engages precisely with the bracket.

[0008] Preferably, the bottom of the stepped baffle is in complete contact with the power device.

[0009] Preferably, the metal baffle further includes: a first positioning structure disposed at the bottom of the stepped baffle, and the metal clamp further includes: a base plate located between the metal baffle and the power device, wherein the base plate includes: a positioning plate and a second positioning structure, and the first positioning structure and the second positioning structure are adapted to each other.

[0010] Preferably, the bottom of the positioning plate is in complete contact with the power device.

[0011] Preferably, the distance between the outer diameter of the metal baffle and the inner diameter of the slot is equal to or greater than the radial dimension of the protective structure of the edge junction terminal of the power device.

[0012] Preferably, the first positioning structure is a positioning pin, and the second positioning structure is a positioning groove.

[0013] Preferably, the stepped baffle includes multiple metal plates of different sizes, and any two adjacent metal plates are positioned by a positioning pin on the lower surface of the upper metal plate and a positioning groove on the upper surface of the lower metal plate, and the steps of the metal plates are non-obtuse angle steps.

[0014] Preferably, the positions of the positioning pin and the positioning groove correspond to the same position on the highest step of the stepped baffle.

[0015] Preferably, the slot is a hollow structure, and the inner diameter of the slot is greater than or equal to the inner diameter of the protective structure of the edge junction terminal of the power device and less than the outer diameter of the protective structure.

[0016] Preferably, the metal clamp further includes a tray for supporting the power device.

[0017] Preferably, the bottom of the tray is flush with the bottom of the slot, and the tray is made of polystyrene.

[0018] Preferably, the slot is a hollow structure, and the inner diameter of the slot is greater than or equal to the inner diameter of the protective structure of the edge junction terminal of the power device and less than the outer diameter of the protective structure.

[0019] Preferably, the metal clamp further includes a tray for supporting the power device.

[0020] Preferably, the bottom of the tray is flush with the bottom of the slot, and the tray is made of polystyrene.

[0021] Preferably, when the power device is a GCT device, the highest step in the stepped baffle corresponds to the gate ring of the GCT device, and the step in the stepped baffle corresponding to the first cathode ring region of the GCT device is higher than the step corresponding to the second cathode ring region of the GCT device, wherein the first cathode ring region is closer to the gate ring than the second cathode ring region.

[0022] Through the above technical solution, this invention creatively controls the irradiation dose passing through the metal precisely by varying the metal thickness, and employs a stepped metal baffle to finely design the minority carrier lifetime in different annular regions. This corrects the dynamic uneven current between cells caused by factors such as stray resistance and inductance, thereby achieving the optimization goal of improving the device's current turn-off capability. Therefore, this invention achieves the goal of controlling the lateral local carrier lifetime of power semiconductor devices without altering the power device structure, with a simple and easy-to-implement process and low cost.

[0023] A second aspect of the present invention provides a method for controlling the lateral local carrier lifetime of a power device, the method comprising: obtaining the position of the gate contact ring of the power device to be irradiated; selecting a metal clamp according to any of the above embodiments based on the position of the gate contact ring to position the power device in the receiving space, wherein the thickness of each step of the stepped baffle is inversely proportional to the distance between the step and the gate contact ring; and irradiating the positioned power device such that different regions of the power device are irradiated with different doses.

[0024] Through the above technical solution, the present invention creatively uses a stepped metal baffle to finely irradiate the minority carrier lifetime in different annular regions, and corrects the dynamic uneven current between cells caused by factors such as stray resistance and inductance, so as to achieve the optimization goal of improving the device's current turn-off capability.

[0025] Other features and advantages of the present invention will be described in detail in the following detailed description section. Attached Figure Description

[0026] The accompanying drawings are provided to further illustrate embodiments of the present invention and form part of the specification. They are used together with the following detailed description to explain the embodiments of the present invention, but do not constitute a limitation thereof. In the drawings: Figure 1 This is a schematic diagram of a GCT device with an intermediate gate configuration. Figure 2 This is a schematic diagram of an external gate type GCT device; Figure 3 This is a structural diagram of a metal clamp provided in an embodiment of the present invention; Figure 4 This is a structural diagram of a metal clamp provided in an embodiment of the present invention; Figure 5 This is a structural diagram of a metal clamp provided in an embodiment of the present invention; Figure 6 This is a structural diagram of a metal clamp provided in an embodiment of the present invention; Figure 7 This is a structural diagram of a metal clamp provided in an embodiment of the present invention; Figure 8 This is a structural diagram of a metal clamp provided in an embodiment of the present invention; Figure 9 This is a structural diagram of a metal clamp provided in an embodiment of the present invention; Figure 10 This is a structural diagram of a metal clamp provided in an embodiment of the present invention; Figure 11 This is a structural diagram of a metal clamp provided in an embodiment of the present invention; Figure 12 This is a structural diagram of a metal clamp provided in an embodiment of the present invention; Figure 13 This is a structural diagram of a metal clamp provided in an embodiment of the present invention; and Figure 14 This is an electron irradiation distribution curve showing the ratio of dose values ​​of the stepped molybdenum metal baffle to that of the irradiated film, provided in an embodiment of the present invention. Detailed Implementation

[0027] The specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0028] Example 1 A structural diagram of a metal clamp for a power device (e.g., GCT device 10) according to an embodiment of the present invention is provided. The metal clamp includes: a slot for accommodating the power device (e.g., GCT device 10); and a metal baffle located within the slot, forming an accommodating space between the metal baffle and the slot. The power device (e.g., GCT device 10) is located within the accommodating space, and the metal baffle is located above the power device. The metal baffle includes a stepped baffle, wherein the height of a plurality of steps in the stepped baffle is determined by the target irradiance of a corresponding region in the power device (e.g., GCT device 10), and the plurality of steps are non-obtuse angle steps.

[0029] Specifically, Figure 3 This is a structural diagram of a metal clamp for a GCT device 10 provided in an embodiment of the present invention. Figure 3 As shown, the metal clamp includes: a slot 20 for accommodating the GCT device 10; and a metal baffle 40 located within the slot 20 and above the GCT device 10. The metal baffle 40 includes a stepped baffle, wherein the height of a plurality of steps in the stepped baffle is determined by the target irradiance of a corresponding area in the GCT device 10, and the plurality of steps are non-obtuse angle steps.

[0030] The bracket 20 is located below the GCT device 10, and the bracket 20 completely contains the GCT device 10.

[0031] The lateral dimensions of each step of the stepped baffle are determined by the target irradiation area, and the longitudinal dimensions (i.e., thickness) of each step are determined by the target irradiation dose. When the metal baffle is made of aluminum, the thickness of the stepped baffle can range from 5 to 40 mm; when the metal baffle is made of molybdenum / lead, the thickness of the stepped baffle can range from 1 to 10 mm.

[0032] In this embodiment, a regionalized irradiation method is employed, using a specially designed metal clamp to precisely control the irradiation dose and the corresponding irradiation area. Specifically, with Figure 3Taking the GCT device shown as an example, irradiation is mainly applied to the region far from the gate ring to reduce the local minority carrier lifetime. The gate ring does not require irradiation or only requires a small amount of irradiation. Therefore, the step corresponding to the gate ring in the stepped baffle is the highest. As the cathode ring is farther from the gate ring, the amount of irradiation required is greater, so the thickness of the corresponding step becomes smaller and smaller (the number of adjacent cathode rings corresponding to one step can be set according to actual needs). Thus, irradiating the GCT device with a metal baffle can alleviate the current concentration in the region far from the gate ring during turn-off.

[0033] Example 2 When the power device is a GCT device, the highest step in the stepped baffle corresponds to the gate ring of the GCT device, and the step in the stepped baffle corresponding to the first cathode ring region of the GCT device is higher than the step corresponding to the second cathode ring region of the GCT device, wherein the first cathode ring region is closer to the gate ring than the second cathode ring region.

[0034] like Figure 1 The shown intermediate gate layout requires localized irradiation of the cathode rings on both sides of the intermediate gate ring (especially the cathode rings furthest from the intermediate gate ring); while... Figure 2 The outer gate layout shown requires localized irradiation of the inner cathode rings of the edge gate rings (especially the two cathode rings on both sides far from the middle gate ring).

[0035] like Figure 3 or Figure 4 The metal fixture shown, from bottom to top, consists of a tray 20, a GCT device 10 (outer gate type), and a metal baffle 40. Since the gate ring is located on the outer side of the wafer, the inner cathode ring needs to be locally irradiated. Furthermore, the radiation dose required increases with the distance between the cathode ring and the gate ring region 3. Therefore, the metal baffle 40 is thickest at the outermost gate ring region 3 (highest step). As the distance from the gate ring increases, the metal thickness of each inner step gradually decreases. By using metal of different thicknesses, the irradiation dose passing through the device can be precisely controlled, thereby allowing for refined design of minority carrier lifetimes in different annular regions, achieving uniform turn-off, and improving current turn-off capability. However, which specific cathode rings correspond to the same step can be rationally set according to actual irradiation requirements. This is not the main improvement point of this application and will not be elaborated upon here.

[0036] like Figure 5The metal fixture shown, from bottom to top, consists of a tray 20, a GCT device 10 (intermediate gate type), and a metal baffle 40. Since the gate ring region 3 is located in the middle of the wafer, localized irradiation of the cathode rings on both sides of the intermediate gate ring is required. Furthermore, the radiation dose required increases with the distance between the cathode rings and the gate ring. Therefore, the metal baffle 40 is thickest (highest step) at the central gate ring region 3. As the distance from the gate ring increases, the metal thickness of each step on both sides gradually decreases. By using metal of different thicknesses, the irradiation dose passing through the device can be precisely controlled, thereby allowing for refined design of minority carrier lifetimes in different annular regions, achieving uniform turn-off, and improving current turn-off capability.

[0037] In this embodiment, the angle of each step is β, which can be a right angle (β=90°) or an acute angle (β<90°). Since the closer the angle is to a right angle, the higher the accuracy of irradiation dose zoning, the structure of right-angled steps can improve the zoning accuracy. In this embodiment, the metal clamp completely shields the edge junction terminal region of the GCT device.

[0038] Example 3 In the above embodiments, the size of the metal baffle can be smaller than the inner diameter of the slot, in which case the relative positioning between the metal baffle and the power device is not very precise; the size of the metal baffle can also be equal to the inner diameter of the slot, in which case a more precise relative positioning between the metal baffle and the power device can be achieved.

[0039] To achieve more precise relative positioning of the metal baffle and the power device, the metal baffle 40 and the bracket 20 are precisely engaged, such as... Figure 3-5 As shown.

[0040] In this embodiment, considering that the metal baffle 40 completely covers the GCT device 10, there is no need for positioning via the base plate 30.

[0041] Of course, the metal thickness in the area corresponding to the protective structure 12 of the edge junction terminal of the power device in the metal baffle can be set, such as... Figure 4-5 As shown, on the one hand, the relative position of the metal baffle and the GCT device can be fixed, and on the other hand, the terminal area can be irradiated as much as possible to reduce leakage current and thus improve the blocking capability.

[0042] Example 4 Based on the above embodiment one, in order to achieve more accurate relative positioning of the metal baffle and the power device, an additional positioning structure can be used.

[0043] like Figure 6As shown, the metal baffle 10 further includes a first positioning structure 402 disposed at the bottom of the stepped baffle 401. The metal clamp further includes a base plate 30 located between the metal baffle 40 and the power device (e.g., GCT device 10), wherein the base plate 30 includes a positioning plate 301 and a second positioning structure 302, the first positioning structure 402 and the second positioning structure 302 being adapted to each other.

[0044] In the above embodiments, since the power device includes a protective structure for the edge junction terminal, an air gap may exist between the positioning plate and the power device, such as... Figure 6-9 As shown, at this point, the positioning plate and the power device are not completely in contact. However, the inventors have discovered that the air gap is proportional to the lateral scattering distance of electrons after passing through the metal. In order to effectively suppress the scattering distance, in this embodiment, the air gap between the positioning plate and the power device can be eliminated by designing the structure of the positioning plate, so that the positioning plate and the power device are completely in contact.

[0045] Specifically, the positioning plate 301 has a T-shaped structure (e.g., Figure 11 As shown), the upper diameter of the positioning plate 301 is the same as the inner diameter of the bracket 20. The lower diameter of the positioning plate 301 is less than or equal to the inner diameter of the protective structure 12 (e.g., red glue structure) at the edge junction terminal of the power device (e.g., GCT device 10). The height of the middle step of the positioning plate 301 is greater than or equal to the inner height of the red glue of the GCT device 10. The bottom of the positioning plate 301 is completely in contact with the GCT device 10 (e.g., ...). Figure 11 As shown in the figure, it can effectively suppress the scattering distance of electrons after passing through the base plate 30, and effectively improve the irradiation dose zoning accuracy of the GCT device 10.

[0046] The first positioning structure can be a positioning pin, and the second positioning structure can be a positioning groove. For example, the positioning groove 302 can be cylindrical, cuboid, or polygonal, etc., and the positioning pin and the positioning groove have complementary shapes and compatible dimensions.

[0047] The base plate 30 is generally made of metal, but can also be made of other materials such as rigid polyvinyl chloride (PVC).

[0048] like Figure 6The metal fixture shown consists of, from bottom to top, a tray 20, a GCT device 10, a base plate 30, and a metal baffle 40. The positional relationship between the GCT device 10 and the metal baffle 40 is determined by three second positioning structures 302 (e.g., cylindrical positioning slots) and three corresponding first positioning structures 402 (e.g., cylindrical positioning pins). This metal fixture design is primarily for external gate GCT devices (e.g., GCT chips). Since the gate is located on the outer side of the wafer, the inner cathode ring of the intermediate gate ring needs to be locally irradiated. Therefore, the metal baffle 40 has the thickest metal at the outermost gate ring position. As the distance from the gate ring increases, the metal thickness of each step on the inner side gradually decreases. By using metal of different thicknesses, the irradiation dose passing through the device can be precisely controlled, thereby allowing for refined design of minority carrier lifetimes in different annular regions, achieving uniform turn-off, and improving current turn-off capability.

[0049] In this embodiment, the angle of each step is β. The angle of the step can be a right angle (β=90°) or an acute angle (β<90°). Since the closer the angle is to a right angle, the higher the accuracy of irradiation dose zoning, the zoning accuracy can be improved by using a right-angled step structure.

[0050] In this embodiment, the metal fixture uses a slot-type positioning scheme to determine the positional relationship between the metal baffle and the wafer, offering high flexibility. The number of slots used for positioning is not limited to three; it can be two or more, or annular slots can be used. The positions of the positioning slots and positioning pins can be interchanged: one configuration has the positioning slot on the lower side and the positioning pin on the upper side, while another configuration has the positioning slot on the upper side and the positioning pin on the lower side.

[0051] Example 5 In the above embodiment three, the metal baffle can be perfectly engaged with the slot, or a region corresponding to the edge junction terminal of the power device can be reserved at both ends so that the edge junction terminal can be irradiated.

[0052] like Figure 6 or Figure 7 As shown, the distance between the outer diameter of the metal baffle 40 and the inner diameter of the slot 20 is equal to or greater than the radial dimension (e.g., length D) of the protective structure 12 (e.g., red glue structure) of the edge junction terminal of the power device (e.g., GCT device 10).

[0053] like Figure 6 or Figure 7 As shown, the edge junction terminal region not covered by the metal baffle can be fully irradiated, effectively reducing leakage current and improving the blocking characteristics of the GCT device.

[0054] Example 6 Based on Embodiment 4, the stepped baffle can be configured as a multi-layered structure with adjacent structures nested together, thereby allowing for flexible selection of one or more layered structures to assemble steps of appropriate thickness as needed.

[0055] like Figure 8 or Figure 9 As shown, the stepped baffle 401 includes multiple metal plates of different sizes. Any two adjacent metal plates are positioned by a positioning pin on the lower surface of the upper metal plate and a positioning groove on the upper surface of the lower metal plate. The steps of the metal plates are non-obtuse angle steps.

[0056] Furthermore, the stepped baffle can be configured as a multi-layered structure with each structure nested within the others. The uppermost metal layer has a flat surface, allowing for the flexible selection of one or more layers to assemble steps of appropriate thickness as needed.

[0057] Preferably, the positions of the locating pin and the locating groove correspond to the same position on the highest step of the stepped baffle. For example, the locating pins and locating grooves of each cylindrical ring are all located at the middle position below the highest step, such as... Figure 8 or Figure 9 As shown.

[0058] Of course, the positions of the positioning pins and the positioning slots can be set according to the actual situation. If the positions are not in the same place, the flexibility when combining multiple metal shelves will be limited. For example, the combination of adjacent metal shelves requires the positions of their positioning pins and positioning slots to match in order to form a combination, so it is necessary to pre-set each group of metal shelves in batches.

[0059] like Figure 8 The metal fixture shown, from bottom to top, consists of a tray 20, a GCT device 10, a base plate 30, and a metal baffle 40. This metal fixture design is primarily for external gate GCT devices (such as GCT chips). The positional relationship between the GCT device 10 and the metal baffle 40 is determined by three cylindrical positioning slots 302 and three cylindrical positioning pins of corresponding sizes. Each step of the metal baffle 40 is composed of multiple nested cylindrical rings (i.e., metal layers) of different sizes, with adjacent cylindrical rings positioned by slots. Compared to the single-piece metal baffle 40 in Embodiment 1, the multi-layered nested cylindrical ring metal baffle allows for more flexible control of the irradiation area.

[0060] like Figure 9The metal fixture shown, from bottom to top, consists of a tray 20, a GCT device 10, a base plate 30, and a metal baffle 40. This metal fixture design is primarily for intermediate gate GCT devices (such as GCT chips). The positional relationship between the GCT device 10 and the metal baffle 40 is determined by three cylindrical positioning slots 302 and three cylindrical positioning pins of corresponding sizes. Each step of the metal baffle 40 is composed of multiple nested cylindrical rings (i.e., metal layers) of different sizes, with adjacent cylindrical rings positioned by slots. Compared to the single-piece metal baffle 40 in Embodiment 1, the multi-layered nested cylindrical ring metal baffle allows for more flexible control of the irradiation area.

[0061] In this embodiment, the angle of each step is β. The angle of the step can be a right angle (β=90°) or an acute angle (β<90°). Since the closer the angle is to a right angle, the higher the accuracy of irradiation dose zoning, the zoning accuracy can be improved by using a right-angled step structure.

[0062] Example 7 In the above embodiments, since the power device includes a protective structure for the edge junction terminal, an air gap may exist between the metal baffle and the power device, such as... Figure 3-5 As shown, at this time, the stepped baffle / metal baffle is not completely attached to the power device. However, the inventors have found that the air gap is proportional to the lateral scattering distance of electrons after passing through the metal. In order to effectively suppress the scattering distance, in this embodiment, the air gap between the metal baffle and the power device can be eliminated by designing the structure of the metal baffle, so that the stepped baffle / metal baffle is completely attached to the power device.

[0063] In the above embodiment three (for example) Figure 3 Based on this, the bottom of the stepped baffle 401 is completely in contact with the power device (e.g., GCT device 10), such as... Figure 10 As shown.

[0064] The bottom of the stepped baffle 401 is provided with a protruding structure, which is consistent with... Figure 3 The air gaps shown are matched to completely eliminate scattering distance, allowing the stepped metal baffle to achieve high-precision irradiation dose zoning.

[0065] for Figure 4-5 The air gap shown can be made to fit the bottom of the stepped baffle 401 / the metal baffle 40 completely with the power device (e.g., GCT device 10) using a similar metal baffle structure (e.g., a stepped baffle with a protruding structure at the bottom).

[0066] This embodiment effectively suppresses scattering distance by eliminating air gap distance, and the irradiation dose step morphology of the region corresponding to each step is relatively obvious, thereby greatly improving the accuracy of dose zoning.

[0067] Example 8 Because the power device includes a protective structure for the edge junction terminal, an air gap may exist between the base plate 30 and the power device, such as... Figure 6 As shown. However, the inventors have found that the air gap is proportional to the lateral scattering distance of electrons after passing through the metal. In order to effectively suppress the scattering distance, in this embodiment, the air gap between the base plate 30 and the power device can be eliminated by designing the structure of the base plate 30, so that the base plate 30 and the power device are completely attached.

[0068] In the above embodiment four (for example) Figure 6 or Figure 7 Based on this, the bottom of the positioning plate 301 is completely attached to the power device (e.g., GCT device 10), such as... Figure 11 or Figure 12 As shown.

[0069] The bottom of the positioning plate 301 is provided with a protruding structure, which is related to... Figure 6 or Figure 7 The air gaps shown are matched to completely eliminate scattering distance, allowing the stepped metal baffle to achieve high-precision irradiation dose zoning.

[0070] for Figure 8 The air gap shown can be addressed using a similar base plate structure (e.g., a protruding structure at the bottom of the positioning plate) to ensure that the bottom of the positioning plate 301 is fully fitted with the power device (e.g., GCT device 10), such as... Figure 13 As shown. Similarly, for Figure 9 The air gap shown can be made using a similar base plate structure (e.g., a protruding structure at the bottom of the positioning plate) so that the bottom of the positioning plate 401 is fully in contact with the power device (e.g., GCT device 10) (not shown).

[0071] This embodiment effectively suppresses scattering distance by eliminating air gap distance, and the irradiation dose step morphology of the region corresponding to each step is relatively obvious, thereby greatly improving the accuracy of dose zoning.

[0072] Example 9 In the above embodiments, the tray can be a hollow structure or a solid structure. In order to effectively suppress the back reflection effect of electrons on the wafer at the bottom tray, the tray can be set as a hollow structure.

[0073] like Figures 10-13 As shown, the slot 20 is a hollow structure, and the inner diameter of the slot 20 is greater than or equal to the inner diameter of the protective structure 12 of the edge junction terminal of the power device and smaller than the outer diameter of the protective structure 12.

[0074] In other words, the bracket 20 is used to support the bottom of the red glue structure of the GCT device 10.

[0075] For example, the hollow radius of the slot 20 is equal to the dimension between the center of the power device (e.g., GCT device 10) and the inner diameter of the outer red adhesive. The side wall height of the slot 20 is higher than the thickness of the outer red adhesive of the power device (e.g., GCT device 10). The material of the slot 20 is generally metal, but it can also be other materials such as rigid polyvinyl chloride (PVC).

[0076] Example 10 Based on the above embodiment nine, a tray can be provided in the receiving space of the slot to support the bottom of the power device.

[0077] The metal clamp also includes a tray located in the receiving space of the slot, the tray being used to support the power device (e.g., GCT device 10).

[0078] The specific structure of the tray can be set according to the actual situation, such as a tray with supporting feet or a tray with a protruding structure.

[0079] like Figure 13 As shown, the bottom of the tray 50 is flush with the bottom of the tray 20, and the tray is made of polystyrene.

[0080] The tray 50 is located in the hollow center of the slot 20. The radius of the tray 50 is less than or equal to the hollow radius of the slot 20. The thickness is the sum of the height of the inner side of the red glue of the GCT device 10 and the thickness of the metal at the bottom of the slot 20. It is generally made of low-density, dust-free and clean polystyrene material, through which electrons can pass directly. It is used to support the bottom of the wafer of the GCT device 10.

[0081] Example 11 This embodiment provides an irradiation dose distribution curve for a stepped fixture that achieves lateral local lifetime control. See details below. Figure 10 and Figure 14 .like Figure 10As shown in the upper part, the stepped baffle in this embodiment is made of molybdenum metal. The angle of the metal baffle step is 90°, and the height of the metal baffle step is 2mm (e.g., corresponding to the cathode rings of rings 1-3), 4mm (e.g., corresponding to the cathode rings of rings 4-7), and 10mm (e.g., corresponding to the cathode rings of rings 8-10). The lower part is an irradiation dose film, which can obtain the irradiation dose ratio under different metal thicknesses. By changing the distance between the bottom of the stepped metal and the film, irradiation dose distribution curves under different air gap distances are obtained. When the air gap is 1.5 mm (corresponding to the gray dose distribution curve in the figure), since the air gap is proportional to the lateral scattering distance of electrons after passing through the metal, the irradiation dose of this distribution curve shows a gradual trend at a step thickness of 4 mm, with no step morphology, indicating low dose zoning accuracy. When the air gap is 0 mm (corresponding to the black dose distribution curve in the figure), the irradiation dose step morphology in each region of this distribution curve is relatively obvious. This verifies that reducing the air gap distance can improve the dose zoning accuracy, and also verifies that the stepped metal baffle can achieve high-precision irradiation dose zoning.

[0082] In the above embodiments, GCT devices are mainly used as examples for explanation and illustration. These GCT devices include not only reverse-resistance IGCT devices but also asymmetric IGCT devices. Of course, this invention is not only applicable to GCT devices but also to IGBTs (Insulated-Gate Bipolar Transistors), MOSFETs (Metal-Oxide-Semiconductor Field-Effect Transistors), GTOs (Gate Turn-Off Thyristors), and other power devices with radial or annular cathode distributions. The substrate material of the power devices is not limited to silicon but can also be third-generation semiconductor materials such as silicon carbide or gallium nitride.

[0083] In summary, this invention creatively controls the irradiation dose passing through the metal precisely by varying the metal thickness, employs a stepped metal baffle to finely design the minority carrier lifetime in different annular regions, and corrects the dynamic uneven current between cells caused by factors such as stray resistance, thereby achieving the optimization goal of improving the device's current turn-off capability. Therefore, this invention achieves the goal of controlling the lateral local carrier lifetime of power semiconductor devices without altering the power device structure, is simple to implement, and has low cost.

[0084] Example 12 This embodiment provides a method for controlling the lateral local carrier lifetime of power devices, the method comprising: Obtain the position of the gate contact ring of the power device to be irradiated.

[0085] Based on the position of the gate contact ring, a metal clamp of any of the above embodiments is selected to position the power device in the receiving space. The thickness of each step of the stepped baffle is inversely proportional to the distance between the step and the gate contact ring. That is, the greater the distance between the step and the gate contact ring, the smaller the thickness of the step. The step closest to the gate contact ring has the largest thickness, and the step farthest from the gate contact ring has the smallest thickness.

[0086] The positioned power devices are irradiated so that different regions of the power devices are irradiated with different doses.

[0087] Specifically, the power devices after positioning can be irradiated using the following irradiation techniques: electron irradiation, neutron irradiation, gamma particle irradiation, etc.

[0088] In summary, this invention creatively employs a stepped metal baffle to precisely irradiate the minority carrier lifetime in different annular regions, correcting the dynamic uneven current between cells caused by factors such as stray resistance and inductance, thereby achieving the optimization goal of improving the device's current turn-off capability.

[0089] The preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the specific details of the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the protection scope of the present invention.

[0090] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not describe the various possible combinations separately.

[0091] Furthermore, various different embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention, they should also be regarded as the content disclosed by the present invention.

Claims

1. A metal clamp, characterized in that, The metal clamp includes: Bracket; A metal baffle is located within the tray, forming a receiving space between the metal baffle and the tray. This receiving space is used to accommodate power devices. The metal baffle includes a stepped baffle and a first positioning structure at the bottom of the stepped baffle. The stepped baffle comprises multiple metal layers of different sizes. Any two adjacent metal layers are positioned by a positioning pin on the lower surface of the upper metal layer and a positioning groove on the upper surface of the lower metal layer. The height of the multiple steps in the stepped baffle is determined by the target irradiance of the corresponding area in the power device, and the steps of the metal layers are non-obtuse angle steps. A base plate is located between the metal baffle and the power device. The base plate includes a positioning plate and a second positioning structure, wherein the first positioning structure is adapted to the second positioning structure.

2. The metal clamp according to claim 1, characterized in that, The metal baffle engages perfectly with the bracket.

3. The metal clamp according to claim 2, characterized in that, The bottom of the stepped baffle is completely in contact with the power device.

4. The metal clamp according to claim 1, characterized in that, The bottom of the positioning plate is completely in contact with the power device.

5. The metal clamp according to claim 1, characterized in that, The distance between the outer diameter of the metal baffle and the inner diameter of the slot is equal to or greater than the radial dimension of the protective structure of the edge junction terminal of the power device.

6. The metal clamp according to claim 1, characterized in that, The first positioning structure is a positioning pin, and the second positioning structure is a positioning groove.

7. The metal clamp according to claim 1, characterized in that, The position of the positioning pin and the positioning groove corresponds to the same position on the highest step in the stepped baffle.

8. The metal clamp according to claim 1, characterized in that, The slot is a hollow structure, and the inner diameter of the slot is greater than or equal to the inner diameter of the protective structure of the edge junction terminal of the power device and less than the outer diameter of the protective structure.

9. The metal clamp according to claim 8, characterized in that, The metal clamp also includes a tray for supporting the power device.

10. The metal clamp according to claim 9, characterized in that, The bottom of the tray is flush with the bottom of the slot, and the tray is made of polystyrene.

11. The metal clamp according to any one of claims 1-10, characterized in that, When the power device is a GCT device, the highest step in the stepped baffle corresponds to the gate ring of the GCT device, and the step in the stepped baffle corresponding to the first cathode ring region of the GCT device is higher than the step corresponding to the second cathode ring region of the GCT device, wherein the first cathode ring region is closer to the gate ring than the second cathode ring region.

12. A method for controlling the lateral local carrier lifetime of power devices, characterized in that, The lateral local carrier lifetime control method includes: Obtain the position of the gate contact ring of the power device to be irradiated; Based on the position of the gate contact ring, a metal clamp as described in any one of claims 1-11 is selected to position the power device in the receiving space, wherein the thickness of each step of the stepped baffle is inversely proportional to the distance between the step and the gate contact ring; The power device, after being positioned, is irradiated so that different regions of the power device are irradiated with different doses.

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