A fast recovery diode and a method for preparing the same

Abstract

The present invention discloses a fast recovery diode and a preparation method thereof, and relates to the field of semiconductor technology. The fast recovery diode comprises: a semiconductor body, including a terminal region and an active region; wherein the terminal region is doped with a first recombination center impurity, and the first recombination center impurity is used to recombine minority carriers in the terminal region to adjust the lifetime of minority carriers in the terminal region; in the direction from the terminal region to the active region, the doping concentration of the first recombination center impurity gradually decreases; a first groove is located on the first surface of the semiconductor body, and is located in the region of the terminal region away from the active region; wherein the semiconductor body also includes a first surface and a second surface arranged oppositely; the first groove is used as a diffusion center of the first recombination center impurity, and the first recombination center impurity diffuses from the first groove to the terminal region. The technical solution provided by the present invention improves the performance and reliability of the fast recovery diode.

Description

Technical Field

[0001] The embodiments of the present invention relate to the field of semiconductor technology, and in particular to a fast recovery diode and a preparation method thereof. Background Art

[0002] Insulated Gate Bipolar Transistor (IGBT), Metal Oxide Semiconductor Field Effect Transistor (MOSFET) and other power switching devices usually need to be connected in parallel with a fast recovery diode (FRD) in the application to discharge the excess current in the circuit load and reduce the high induced voltage of the parasitic inductance caused by the reverse current of the load. As the switching speed of power devices continues to increase, the performance requirements for the fast recovery diodes used with them are also getting higher and higher, requiring them to have a short turn-off time (trr) and soft reverse recovery characteristics and reliability.

[0003] In order to achieve low trr and high softness factor at the same time, it is necessary to control the minority carrier lifetime of the fast recovery diode. Minority carrier lifetime control technology refers to reducing the minority carrier lifetime by introducing recombination centers inside the device, optimizing the carrier distribution, and thus improving the reverse recovery characteristics of the device. Traditional minority carrier lifetime control technology is a global lifetime control technology, which usually adopts the method of introducing deep energy level impurities and electron irradiation. Deep energy level metal impurities have a very high diffusion coefficient, and electron irradiation produces uniformly distributed recombination centers, and cannot produce a local narrow recombination center distribution. Local lifetime technology provides greater design freedom for device performance optimization. Compared with the traditional lifetime control technology that introduces recombination centers in a large range throughout the device, local lifetime control technology selectively introduces deep energy level recombination centers inside the semiconductor device, that is, only introduces high-concentration recombination centers in the area where the turn-off time is most effective, forming a local low lifetime area, while no or very few recombination centers are introduced in other areas to further improve the performance of the device.

[0004] However, regardless of whether global lifetime control or local lifetime control is used, only the minority carrier lifetime distribution in the longitudinal direction (perpendicular to the chip) is adjusted, without considering the optimization of the minority carrier lifetime in the lateral direction, which affects the performance and reliability of the fast recovery diode. Summary of the invention

[0005] The embodiment of the present invention provides a fast recovery diode and a preparation method thereof, so as to improve the performance and reliability of the fast recovery diode.

[0006] According to one aspect of the present invention, there is provided a fast recovery diode, comprising:

[0007] A semiconductor body, including a terminal region and an active region;

[0008] The terminal region is doped with a first recombination center impurity, and the first recombination center impurity is used to recombine minority carriers in the terminal region to adjust the lifetime of minority carriers in the terminal region; in the direction from the terminal region to the active region, the doping concentration of the first recombination center impurity gradually decreases;

[0009] A first groove is located on the first surface of the semiconductor body and in an area of ​​the terminal region away from the active region; wherein the semiconductor body also includes a first surface and a second surface arranged opposite to each other; the first groove is used as a diffusion center for a first recombination center impurity, and the first recombination center impurity diffuses from the first groove into the terminal region.

[0010] Optionally, the first surface includes a first terminal region surface located in the terminal region and a first active region surface located in the active region;

[0011] Wherein, the surface of the first active region includes a first doped region of a first conductivity type, and the conductivity type of the semiconductor body between the first doped region of the first conductivity type and the second surface is a second conductivity type;

[0012] The surface of the first terminal region includes a first conductivity type second doped region, and the conductivity type of the semiconductor body between the first conductivity type second doped region and the second surface is the second conductivity type.

[0013] Optionally, the first recombination center impurities include platinum and / or gold.

[0014] Optionally, the fast recovery diode further includes:

[0015] a blocking structure extending from the first surface into the semiconductor body;

[0016] The blocking structure is used to block the first recombination center impurities in the terminal region from diffusing into the active region.

[0017] Optionally, the blocking structure includes:

[0018] The second groove is located on the first surface and in a region of the terminal region adjacent to the active region.

[0019] Optionally, the blocking structure further includes:

[0020] A barrier layer is located in the second groove; wherein a distance from a surface of the barrier layer away from the first surface to the first surface is greater than or equal to a distance from a surface of the first conductive type first doped region away from the first surface to the first surface, and greater than or equal to a distance from a surface of the first conductive type second doped region away from the first surface to the first surface.

[0021] Optionally, the semiconductor body includes a substrate and a semiconductor epitaxial layer located on one side of the substrate; the first surface is a surface of the semiconductor epitaxial layer away from the substrate, and the second surface is a surface of the substrate away from the semiconductor epitaxial layer;

[0022] In which, the semiconductor body is also doped with a second composite center impurity; in a direction perpendicular to the substrate, the doping concentration of the second composite center impurity gradually decreases from the interface between the substrate and the semiconductor epitaxial layer to the first conductive type first doping region, and gradually decreases from the interface between the substrate and the semiconductor epitaxial layer to the first conductive type second doping region.

[0023] Optionally, the first conductivity type second doping region includes a plurality of first conductivity type second doping sub-regions;

[0024] A plurality of first conductivity type second doped sub-regions are sequentially arranged at intervals in a direction from the terminal region to the active region.

[0025] According to another aspect of the present invention, a method for preparing a fast recovery diode is provided, which is used to prepare the fast recovery diode according to any embodiment of the present invention, comprising:

[0026] forming a semiconductor body; the semiconductor body comprising a terminal region and an active region;

[0027] A first recombination center impurity is doped in the terminal region; the recombination center impurity is used to recombine minority carriers in the terminal region to adjust the lifetime of minority carriers in the terminal region; the doping concentration of the recombination center impurity gradually decreases in the direction from the terminal region to the active region; the first surface of the semiconductor body includes a first groove, and is located in a region of the terminal region away from the active region; the first groove is used as a diffusion center of the first recombination center impurity, and the first recombination center impurity diffuses from the first groove into the terminal region.

[0028] Optionally, the forming of the semiconductor body includes:

[0029] providing a substrate;

[0030] A semiconductor epitaxial layer is formed on one side of the substrate; wherein the semiconductor body comprises a first surface and a second surface arranged opposite to each other, the first surface is a surface of the semiconductor epitaxial layer away from the substrate, and the second surface is a surface of the substrate away from the semiconductor epitaxial layer; the first surface comprises a first terminal region surface located in the terminal region and a first active region surface located in the active region;

[0031] A first conductive type first doping region is formed on the surface of the first active region, and a first conductive type second doping region is formed on the surface of the first terminal region; wherein the conductivity type of the semiconductor body between the first conductive type first doping region and the second surface, and the conductivity type of the semiconductor body between the first conductive type second doping region and the second surface is the second conductive type;

[0032] Doping the first recombination center impurity in the terminal region comprises:

[0033] Forming a first groove on the first surface; the first groove is located in a region of the terminal region away from the active region;

[0034] Filling the first groove with a first recombination center impurity, and heating the semiconductor body to diffuse the first recombination center impurity toward the terminal region;

[0035] Before filling the first recombination center impurities in the first groove, the method further includes:

[0036] A blocking structure is formed in the semiconductor body; the blocking structure extends from the first surface into the semiconductor body, and the blocking structure is used to block the first recombination center impurities in the terminal region from diffusing into the active region.

[0037] The embodiment of the present invention provides a fast recovery diode and a preparation method thereof, wherein the fast recovery diode comprises: a semiconductor body, including a terminal region and an active region; a first recombination center impurity is doped in the terminal region, and the recombination center impurity is used to recombine minority carriers in the terminal region to adjust the lifetime of minority carriers in the terminal region; and the doping concentration of the recombination center impurity gradually decreases in the direction from the terminal region to the active region. The technical solution provided by the embodiment of the present invention, by doping the recombination center impurity used to recombine minority carriers in the terminal region in the terminal region, and setting the doping concentration of the recombination center impurity to gradually decrease in the direction from the terminal region to the active region, makes the minority carrier lifetime decrease from the junction of the active region and the terminal region to the terminal region in the lateral direction, while the minority carrier lifetime in the active region remains unchanged, which can reduce the number of unbalanced minority carriers stored in the terminal region during forward conduction, and make the unbalanced minority carriers in the terminal region disappear faster through recombination during reverse recovery, so as to improve the performance and reliability of the device during reverse recovery.

[0038] It should be understood that the contents described in this section are not intended to identify the key or important features of the embodiments of the present invention, nor are they intended to limit the scope of the present invention. Other features of the present invention will become easily understood through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0040] Figure 1 is a schematic structural diagram of a fast recovery diode provided by an embodiment of the present invention;

[0041] Figure 2 yes Figure 1 The lifetime distribution of minority carriers in the lateral direction in the structure shown;

[0042] Figure 3 yes Figure 1 The lifetime distribution of minority carriers in the vertical direction in the structure shown;

[0043] Figure 4 is a schematic structural diagram of another fast recovery diode provided by an embodiment of the present invention;

[0044] Figure 5 is a flow chart of a method for preparing a fast recovery diode provided by an embodiment of the present invention;

[0045] Figure 6 is a structural cross-sectional view corresponding to step S110 in a method for preparing a fast recovery diode provided in an embodiment of the present invention;

[0046] Figure 7 is a structural cross-sectional view corresponding to step S120 in a method for preparing a fast recovery diode provided in an embodiment of the present invention;

[0047] Figure 8 is a structural cross-sectional view corresponding to step S130 in a method for preparing a fast recovery diode provided in an embodiment of the present invention;

[0048] Figure 9~Figure 10 is a structural cross-sectional view corresponding to step S200 in a method for preparing a fast recovery diode provided in an embodiment of the present invention;

[0049] Fig.11 is a structural cross-sectional view corresponding to step S210 in a method for preparing a fast recovery diode provided in an embodiment of the present invention;

[0050] Fig.12 It is a structural cross-sectional view corresponding to step S220 in a method for preparing a fast recovery diode provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0051] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0052] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0053] An embodiment of the present invention provides a fast recovery diode. Figure 1 is a schematic diagram of the structure of a fast recovery diode provided by an embodiment of the present invention, with reference to Figure 1 , fast recovery diodes include:

[0054] A semiconductor body 1 includes a terminal region Q2 and an active region Q1; wherein the terminal region Q2 is doped with a first recombination center impurity, and the recombination center impurity is used to recombine minority carriers in the terminal region Q2 to adjust the lifetime of minority carriers in the terminal region Q2; in the direction from the terminal region Q2 to the active region Q1, the doping concentration of the recombination center impurity gradually decreases.

[0055] The first groove 30 is located on the first surface 11 of the semiconductor body 1 and in a region of the terminal region Q2 away from the active region Q1; wherein the semiconductor body 1 includes a first surface 11 and a second surface 12 arranged opposite to each other; the first groove 30 is used as a diffusion center for the first recombination center impurities, and the first recombination center impurities diffuse from the first groove 30 into the terminal region Q2.

[0056] Specifically, the semiconductor body 1 includes a terminal region Q2 and an active region Q1 , and the terminal region Q2 is located on at least one side of the active region Q1 . Figure 1 In the semiconductor body 1 shown, the terminal region Q2 is located on opposite sides of the active region Q1. The active region Q1 of the semiconductor body 1 is used to form a diode, and the terminal region Q2 of the semiconductor body 1 is used to form a lateral variation of doping (VLD) structure or to form a plurality of field limiting rings (FLR). The semiconductor body 1 can be formed by at least one semiconductor epitaxial layer 20. The semiconductor body 1 can also include a substrate 10, that is, the semiconductor body 1 includes a substrate 10 and at least one semiconductor epitaxial layer 20 located on one side of the substrate 10. The material of the substrate 10 is the same as the material of the semiconductor epitaxial layer 20, or the material of the substrate 10 is different from the material of the semiconductor epitaxial layer 20. The material of the substrate 10 may include semiconductor materials such as Si and SiC, and the material of the semiconductor epitaxial layer 20 may include semiconductor materials such as Si and SiC.

[0057] The semiconductor body 1 includes a first surface 11 and a second surface 12 that are arranged opposite to each other. When the semiconductor body 1 includes only a semiconductor epitaxial layer 20, the second surface 12 is a surface of the semiconductor body 1 close to the substrate 10, and the first surface 11 is a surface of the semiconductor body 1 away from the substrate 10. When the semiconductor body 1 includes a substrate 10 and at least one semiconductor epitaxial layer 20, the second surface 12 is a surface of the substrate 10 away from the semiconductor epitaxial layer 20, and the first surface 11 is a surface of the semiconductor epitaxial layer 20 farthest from the substrate 10 away from the substrate 10. The conductivity type of the semiconductor body 1 is the second conductivity type. Among them, Figure 1 The semiconductor body 1 shown includes a substrate 10 and a semiconductor epitaxial layer 20 located on one side of the substrate.

[0058] The reverse recovery time (trr) of a fast recovery diode refers to the time required for the internal stored charge to be cleared and the reverse current to drop to a certain proportion (usually 10%) when the diode switches from the forward conduction state to the reverse cutoff state. This time reflects the speed of carrier recombination inside the diode and is an important parameter for measuring the switching performance of the diode. The reverse recovery time of a fast recovery diode is usually shorter than that of an ordinary diode and can be at the level of several hundred nanoseconds (ns), which makes the fast recovery diode suitable for high-frequency and high-power applications, because the shorter recovery time can reduce switching losses and improve the efficiency and reliability of the circuit.

[0059] The minority carrier lifetime of the fast recovery diode can be controlled to achieve a low reverse recovery time of the fast recovery diode. The terminal region Q2 is doped with a first recombination center impurity, which serves as a recombination center for recombination of minority carriers in the terminal region Q2. Figure 2 yes Figure 1The lifetime distribution of minority carriers in the lateral direction in the structure shown is shown in Figure 2. Figure 2 , the horizontal axis x refers to the horizontal position of the minority carrier, and the vertical axis τ refers to the lifetime of the minority carrier; in the embodiment of the present invention, the doping concentration of the first recombination center impurity in the terminal region Q2 is set to gradually decrease in the direction X pointing from the terminal region Q2 to the active region Q1, so that the lifetime of the minority carriers in the terminal region Q2 decreases from the junction of the active region Q1 and the terminal region Q2 to the terminal region Q2, while the minority carrier lifetime in the active region Q1 remains unchanged, so that the non-equilibrium minority carriers in the terminal region Q2 disappear faster through recombination during the reverse recovery process, thereby shortening the trr of the fast recovery diode.

[0060] In addition, in the prior art, when the device is forward-conducted, a large number of unbalanced minority carriers will exist in the terminal region Q2. During the reverse recovery process, these minority carriers cannot flow out of the terminal region Q2, but can only flow to the active region Q1 and flow out of the active region Q1. Therefore, it is easy to cause current concentration at the boundary of the active region Q1, and even cause thermal burnout. In the embodiment of the present invention, the life of the minority carriers in the terminal region Q2 is controlled to decrease from the junction of the active region Q1 and the terminal region Q2 to the terminal region Q2, while the life of the minority carriers in the active region Q1 remains unchanged, and the number of unbalanced minority carriers stored in the terminal region Q2 during forward conduction can also be reduced, avoiding the problem of current concentration and thermal burnout at the boundary of the active region Q1, thereby improving the reliability of the device during the reverse recovery process.

[0061] The fast recovery diode provided by the embodiment of the present invention comprises: a semiconductor body 1, comprising a terminal region Q2 and an active region Q1; the terminal region Q2 is doped with a first recombination center impurity, the recombination center impurity is used to recombine minority carriers in the terminal region Q2, so as to adjust the lifetime of minority carriers in the terminal region Q2; in the direction from the terminal region Q2 to the active region Q1, the doping concentration of the recombination center impurity gradually decreases. The technical solution provided by the embodiment of the present invention, by doping the recombination center impurity used to recombine minority carriers in the terminal region Q2 in the terminal region Q2, and setting the doping concentration of the recombination center impurity to gradually decrease in the direction X from the terminal region Q2 to the active region Q1, so that in the lateral direction, the minority carrier lifetime decreases from the junction of the active region Q1 and the terminal region Q2 to the terminal region Q2, while the minority carrier lifetime in the active region Q1 remains unchanged, which can reduce the number of unbalanced minority carriers stored in the terminal region Q2 during forward conduction, and at the same time make the unbalanced minority carriers in the terminal region Q2 disappear faster through recombination during the reverse recovery process, so that the reliability of the device during the reverse recovery process can be improved.

[0062] Based on the above embodiments, Figure 1Optionally, the semiconductor body 1 includes a first surface 11 and a second surface 12 arranged opposite to each other; wherein the first surface 11 includes a first terminal region surface located in the terminal region Q2 and a first active region surface located in the active region Q1; the first active region surface includes a first conductive type first doping region 21, and the conductive type of the semiconductor body 1 between the first conductive type first doping region 21 and the second surface 12 is the second conductive type; the first terminal region surface includes a first conductive type second doping region 22, and the conductive type of the semiconductor body 1 between the first conductive type second doping region 22 and the second surface 12 is the second conductive type.

[0063] Specifically, the semiconductor body 1 includes a first conductive type first doping region 21, which is located on the surface of the first active region of the semiconductor body 1, and the conductivity type of the semiconductor body 1 between the first conductive type first doping region 21 and the second surface 12 is the second conductive type. The semiconductor body 1 also includes a first conductive type second doping region 22, which is located on the surface of the first terminal region of the semiconductor body 1, and the conductivity type of the semiconductor body 1 between the first conductive type second doping region 22 and the second surface 12 is the second conductive type.

[0064] The first conductive type first doping region 21 and the first conductive type second doping region 22 are doped with the first conductive type doping ions; the semiconductor body 1 between the first conductive type first doping region 21 and the second surface 12, and the semiconductor body 1 between the first conductive type second doping region 22 and the second surface 12 are doped with the second conductive type doping ions. If the first conductive type is N-type, the second conductive type is P-type; if the first conductive type is P-type, the second conductive type is N-type. Among them, the N-type doping ions can be P (phosphorus) or N (nitrogen) ions, and the P-type doping ions can be Al (aluminum) ions or B (boron) ions. In the embodiment of the present invention, the first conductive type is P-type and the second conductive type is N-type. The N+ shown in the figure indicates that the doping concentration of the N-type doping ions in this area is high, and the N- indicates that the doping concentration of the N-type doping ions in this area is low.

[0065] Based on the above embodiments, Figure 1 Optionally, the semiconductor body 1 includes a substrate 10 and a semiconductor epitaxial layer 20 located on one side of the substrate 10; the first surface 11 is a surface of the semiconductor epitaxial layer 20 away from the substrate 10, and the second surface 12 is a surface of the substrate 10 away from the semiconductor epitaxial layer 20; the doping concentration of the second conductive type doped ions in the substrate 10 is greater than the doping concentration of the second conductive type doped ions in the semiconductor epitaxial layer 20;

[0066] Among them, the semiconductor body 1 is also doped with second composite center impurities; in the direction Y perpendicular to the substrate 10, the doping concentration of the second composite center impurities gradually decreases from the interface between the substrate 10 and the semiconductor epitaxial layer 20 to the first conductive type first doping region 21, and gradually decreases from the interface between the substrate 10 and the semiconductor epitaxial layer 20 to the first conductive type second doping region 22.

[0067] Specifically, the softness factor of a fast recovery diode is a parameter that measures its recovery characteristics, which reflects the length of time it takes for minority carriers to disappear due to recombination during the reverse recovery process of the diode. The larger the softness factor, the longer the minority carriers disappear during the reverse recovery of the diode, and the softer the recovery process, which means that the voltage spike generated by the diode during the recovery process is lower and has less impact on the circuit. Soft recovery characteristics can reduce switching losses, improve efficiency, and reduce interference with other circuit components.

[0068] Figure 3 yes Figure 1 The lifetime distribution of minority carriers in the vertical direction in the structure shown is shown in Figure 2. Figure 3 , the horizontal axis y refers to the position of the minority carrier in the vertical direction, and the vertical axis τ refers to the lifetime of the minority carrier; in the vertical direction (in the direction Y perpendicular to the substrate 10), the doping concentration of the second composite center impurity is set to gradually decrease from the interface between the substrate 10 and the semiconductor epitaxial layer 20 to the first conductive type first doping region 21, and the doping concentration of the second composite center impurity is set to gradually decrease from the interface between the substrate 10 and the semiconductor epitaxial layer 20 to the first conductive type second doping region 22, which can reduce the minority carrier injection from the first conductive type first doping region 21 to the second conductive type doping region located between the first conductive type first doping region 21 and the substrate 10 when the device is forward-conducted. At the same time, during the reverse recovery process of the device, the minority carrier disappearance speed at the interface between the substrate 10 and the semiconductor epitaxial layer 20 is slower than the minority carrier disappearance speed at the interface between the first conductive type first doping region 21 and the second conductive type doping region below, thereby increasing the softness factor of the device reverse recovery process.

[0069] Among them, the first conductive type first doping region 21 is a P-type region, and the first conductive type second doping region 22 is a P-type region; the second conductive type doping region between the first conductive type first doping region 21 and the substrate 10 is an N-type region, and the second conductive type doping region between the first conductive type second doping region 22 and the substrate 10 is an N-type region. The concentration of N-type doping ions in the substrate 10 is greater than that of N-type doping ions in the second conductive type region in the semiconductor epitaxial layer 20. Therefore, a P / N-junction is formed between the first conductive type first doping region 21 in the semiconductor epitaxial layer 20 and the second conductive type region in the semiconductor epitaxial layer 20, and an N- / N+ junction is formed between the second conductive type region in the semiconductor epitaxial layer 20 and the substrate 10. The doping concentration of the second composite center impurity is set to gradually decrease from the interface between the substrate 10 and the semiconductor epitaxial layer 20 to the first conductive type first doping region 21, so that the minority carrier lifetime can be reduced from the N- / N+ junction to the P / N-junction in the vertical direction, and the minority carrier injection from the P region to the N-region when the device is forward-conducted can be reduced. At the same time, during the reverse recovery process of the device, the minority carrier disappearance rate at the N- / N+ junction is slower than the minority carrier disappearance rate at the P / N-junction, thereby increasing the softness factor of the reverse recovery process.

[0070] The technical solution provided by the embodiment of the present invention requires controlling the minority carrier lifetime of the fast recovery diode in order to achieve both low trr and high softness factor. In the horizontal direction, the minority carrier lifetime decreases from the junction of the active region Q1 and the terminal region Q2 to the terminal region Q2, and the minority carrier lifetime in the active region Q1 remains unchanged. In the vertical direction, the minority carrier lifetime decreases from the N- / N+ junction to the P / N- junction, so that the carrier distribution is optimized, thereby improving the reverse recovery characteristics of the device.

[0071] Based on the above embodiments, please continue to refer to Figure 1 , Optionally, the first recombination center impurities include platinum and / or gold.

[0072] Specifically, the control of the minority carrier lifetime in the terminal region Q2 in the lateral direction can be achieved by a platinum diffusion process or a gold diffusion process, that is, the first composite center impurity doped in the terminal region Q2 can be platinum, or the first composite center impurity doped in the terminal region Q2 can be gold, or the first composite center impurity doped in the terminal region Q2 can include platinum and gold. In the process of preparing a fast recovery diode, a semiconductor epitaxial layer 20 can be formed on a substrate 10, and a first conductive type first doping region 21 and a first conductive type second doping region 22 are formed on the surface of the semiconductor epitaxial layer 20 away from the substrate 10. Then, a first groove 30 is formed outside the terminal region Q2, and platinum and / or gold are formed in the first groove 30. Platinum diffusion and / or gold diffusion are completed by a high temperature process. The first groove 30 is used as a diffusion center for the first composite center impurity. The first composite center impurity diffuses from the first groove 30 to the terminal region Q2. The diffusion temperature and time are controlled, thereby controlling the distribution of the first composite center impurity, forming a distribution that decreases from the terminal region Q2 to the active region Q1. After the platinum expansion process and / or the gold expansion process, the first groove 30 may still contain platinum and / or gold, or may not contain platinum and / or gold.

[0073] Among them, the depth of the first groove 30 is less than or equal to the depth of the first conductive type second doping region 22, and less than or equal to the depth of the first conductive type first doping region 21, so as to reduce the distance between the position where the concentration peak of the first composite center impurity is located and the P / N junction in the longitudinal direction, and even make the position where the concentration peak of the first composite center impurity is located at the P / N junction in the longitudinal direction, thereby further improving the reverse recovery characteristics of the device.

[0074] Based on the above embodiments, please continue to refer to Figure 1 , optional, fast recovery diodes, and also include:

[0075] A blocking structure 40 extending from the first surface 11 into the semiconductor body 1;

[0076] The blocking structure 40 is used to block the first recombination center impurities in the termination region Q2 from diffusing into the active region Q1 .

[0077] Specifically, the blocking structure 40 extends from the first surface 11 into the semiconductor body 1 and is located in the terminal region Q2 near the active region Q1. The blocking structure 40 is used to block the diffusion of the first recombination center impurities to the active region Q1, which helps to form the required minority carrier lifetime distribution in the lateral direction. At the same time, the blocking structure 40 can also block the unbalanced minority carrier current in the terminal region Q2 from flowing from the device surface to the active region Q1, preventing the reliability risks caused by the surface hot carrier effect and heat accumulation.

[0078] Optionally, the blocking structure 40 includes a second groove 41. The second groove 41 is located on the first surface 11 and is located in the region of the terminal region Q2 near the active region Q1. By providing a groove between the active region Q1 and the terminal region Q2, the first recombination center impurities in the terminal region Q2 are prevented from diffusing to the active region Q1, which helps to form the required minority carrier lifetime distribution in the lateral direction. At the same time, the second groove 41 can also block the unbalanced minority carrier current in the terminal region Q2 from flowing from the device surface to the active region Q1, preventing the reliability risks caused by the surface hot carrier effect and heat accumulation.

[0079] Furthermore, Figure 4 is a schematic diagram of the structure of another fast recovery diode provided by an embodiment of the present invention, referring to Figure 4 , a barrier layer 42 may be provided in the second groove 41, and the barrier structure 40 further includes a barrier layer 42 located in the second groove 41. The distance from the surface of the barrier layer 42 away from the first surface 11 to the first surface 11 is greater than or equal to the distance from the surface of the first conductive type first doping region 21 away from the first surface 11 to the first surface 11, and is greater than or equal to the distance from the surface of the first conductive type second doping region 22 away from the first surface 11 to the first surface 11. The material of the barrier layer 42 may be an insulating material such as silicon dioxide or silicon nitride. By providing the barrier layer 42 in the second groove 41, the flatness of the first surface 11 of the semiconductor body 1 may be improved, which is beneficial to the subsequent preparation process of the fast recovery diode.

[0080] Based on the above embodiments, optionally, the second recombination center impurity may include H + Ion or He + ions, by implanting H + Ion or He + ions, achieving vertical control of minority carrier lifetime. + Ion or He + The peak position of the ion is located near the P / N-junction, forming a distribution in which the minority carrier lifetime decreases from the N- / N+ junction to the P / N-junction, increasing the softness factor of the reverse recovery process. + Ion or He + Ion implantation into the semiconductor body 1 can reduce the minority carrier lifetime in the semiconductor body 1 and shorten the trr of the fast recovery diode.

[0081] Based on the above embodiments, Figure 1 and Figure 4Optionally, the first conductive type second doping region 22 includes a plurality of first conductive type second doping sub-regions 221; the plurality of first conductive type second doping sub-regions 221 are sequentially arranged at intervals in the direction X from the terminal region Q2 to the active region Q1. Each first conductive type second doping sub-region 221 can be understood as a field limiting ring surrounding the active region Q1, and a plurality of spaced field limiting rings are arranged in the terminal region Q2.

[0082] The embodiment of the present invention further provides a method for preparing a fast recovery diode, which is used to prepare the fast recovery diode described in any embodiment of the present invention. Figure 5 is a flow chart of a method for preparing a fast recovery diode provided by an embodiment of the present invention, with reference to Figure 5 , the preparation method of the fast recovery diode includes:

[0083] S10, forming a semiconductor body; the semiconductor body includes a terminal region and an active region.

[0084] S20, doping a first recombination center impurity in the terminal region; the recombination center impurity is used to recombine the minority carriers in the terminal region to adjust the lifetime of the minority carriers in the terminal region; in the direction from the terminal region to the active region, the doping concentration of the recombination center impurity gradually decreases.

[0085] The first surface of the semiconductor body includes a first groove, and is located in a terminal region away from the active region; the first groove is used as a diffusion center for first recombination center impurities, and the first recombination center impurities diffuse from the first groove into the terminal region.

[0086] Specifically, the semiconductor body 1 includes a terminal region Q2 and an active region Q1, the active region Q1 of the semiconductor body 1 is used to form a diode, and the terminal region Q2 of the semiconductor body 1 is used to form a VLD structure or to form a plurality of FLR structures. The semiconductor body 1 can be formed by at least one semiconductor epitaxial layer 20. The semiconductor body 1 can also include a substrate 10, that is, the semiconductor body 1 includes a substrate 10 and at least one semiconductor epitaxial layer 20 formed on one side of the substrate 10. The material of the substrate 10 is the same as the material of the semiconductor epitaxial layer 20, or the material of the substrate 10 is different from the material of the semiconductor epitaxial layer 20.

[0087] The terminal region Q2 is doped with a first recombination center impurity, which serves as a recombination center for recombination of minority carriers in the terminal region Q2. The first recombination center impurity is arranged in the direction X from the terminal region Q2 to the active region Q1, and the doping concentration of the first recombination center impurity in the terminal region Q2 gradually decreases, so that the life of the minority carriers in the terminal region Q2 decreases from the junction of the active region Q1 and the terminal region Q2 to the terminal region Q2, while the life of the minority carriers in the active region Q1 remains unchanged, so that the non-equilibrium minority carriers in the terminal region Q2 disappear faster through recombination during the reverse recovery process, thereby shortening the trr of the fast recovery diode.

[0088] In addition, in the prior art, when the device is forward-conducted, a large number of unbalanced minority carriers will exist in the terminal region Q2. During the reverse recovery process, these minority carriers cannot flow out of the terminal region Q2, but can only flow to the active region Q1 and flow out of the active region Q1. Therefore, it is easy to cause current concentration at the boundary of the active region Q1, and even cause thermal burnout. In the embodiment of the present invention, the life of the minority carriers in the terminal region Q2 is controlled to decrease from the junction of the active region Q1 and the terminal region Q2 to the terminal region Q2, while the life of the minority carriers in the active region Q1 remains unchanged, and the number of unbalanced minority carriers stored in the terminal region Q2 during forward conduction can also be reduced, avoiding the problem of current concentration and thermal burnout at the boundary of the active region Q1, thereby improving the reliability of the device during the reverse recovery process.

[0089] The method for preparing a fast recovery diode provided in an embodiment of the present invention dopes a recombination center impurity used to recombine minority carriers in the terminal region Q2 in the terminal region Q2, and sets the doping concentration of the recombination center impurity to gradually decrease in the direction X from the terminal region Q2 to the active region Q1, so that in the lateral direction, the minority carrier lifetime decreases from the junction of the active region Q1 and the terminal region Q2 toward the terminal region Q2, while the minority carrier lifetime in the active region Q1 remains unchanged, which can reduce the number of unbalanced minority carriers stored in the terminal region Q2 during forward conduction, and at the same time make the unbalanced minority carriers in the terminal region Q2 disappear faster through recombination during the reverse recovery process, thereby improving the performance and reliability of the device during the reverse recovery process.

[0090] Optionally, step S10 of forming a semiconductor body includes:

[0091] S110 , providing a substrate.

[0092] Specifically, refer to Figure 6 , providing a substrate 10, which may be a heavily doped N-type substrate.

[0093] S120. Form a semiconductor epitaxial layer on one side of the substrate; wherein the semiconductor body includes a first surface and a second surface that are arranged opposite to each other, the first surface is a surface of the semiconductor epitaxial layer away from the substrate, and the second surface is a surface of the substrate away from the semiconductor epitaxial layer; the first surface includes a first terminal region surface located in the terminal region and a first active region surface located in the active region.

[0094] Specifically, refer to Figure 7 , a semiconductor epitaxial layer 20 is formed on one side of the substrate 10 , and the semiconductor epitaxial layer 20 may be a lightly doped N-type semiconductor epitaxial layer.

[0095] S130, forming a first conductive type first doped region on the surface of the first active region and a first conductive type second doped region on the surface of the first terminal region; wherein the conductivity type of the semiconductor body between the first conductive type first doped region and the second surface, and the conductivity type of the semiconductor body 1 between the first conductive type second doped region and the second surface are the second conductive type.

[0096] Specifically, refer to Figure 8 The first conductive type first doping region 21 and the first conductive type second doping region 22 can be formed in the same ion implantation process or in different ion implantation processes. Preferably, the first conductive type first doping region 21 and the first conductive type second doping region 22 can be formed in the same ion implantation process, which can simplify the device preparation process.

[0097] A mask may be formed on a side of the semiconductor epitaxial layer 20 away from the substrate 10, and the mask window shape and the parameter values ​​of the window are set according to the shapes and parameters of the first conductive type first doping region 21 and the first conductive type second doping region 22. Based on the mask, the first conductive type ions are implanted into the first surface 11 of the semiconductor body 1, and through a diffusion process, the first conductive type first doping region 21 is formed in the active region Q1, and the first conductive type second doping region 22 is formed in the terminal region Q2.

[0098] Optionally, after forming the semiconductor body in step S10, the step further includes:

[0099] S200, forming a blocking structure in the semiconductor body; the blocking structure extends from the first surface into the semiconductor body, and the blocking structure is used to block the first recombination center impurities in the terminal region from diffusing into the active region.

[0100] Among them, reference Fig. 9 The blocking structure 40 includes a second groove 41. The blocking structure 40 is formed in the semiconductor body 1, including: forming a second groove 41 on the first surface 11, the second groove 41 is located in the terminal region Q2 near the active region Q1. The depth of the second groove 41 is greater than or equal to the depth of the first conductive type first doping region 21, and greater than or equal to the depth of the first conductive type second doping region 22.

[0101] For further reference, Fig.10 The blocking structure 40 further includes a blocking layer 42, and the blocking layer 42 is located in the second groove 41. Forming the blocking structure 40 in the semiconductor body 1 further includes: forming the blocking layer 42 in the second groove 41. The material of the blocking layer 42 may include insulating materials such as silicon dioxide or silicon nitride.

[0102] Optionally, step S20 of doping the terminal region with a first recombination center impurity includes:

[0103] S210, forming a first groove 30 on the first surface 11; the first groove 30 is located in a region of the terminal region Q2 away from the active region Q1. (Refer to Fig.11 )

[0104] S220, filling the first recombination center impurities in the first groove 30, and heating the semiconductor body 1, so that the first recombination center impurities diffuse to the terminal region Q2. (Refer to Fig.12 )

[0105] Optionally, after doping the first recombination center impurities in the terminal region Q2 in step S20, the step further includes:

[0106] A second composite center impurity is doped in the semiconductor body 1; in a direction perpendicular to the substrate 10, the doping concentration of the second composite center impurity gradually decreases from the interface between the substrate 10 and the semiconductor epitaxial layer 20 to the first conductive type first doping region 21, and gradually decreases from the interface between the substrate 10 and the semiconductor epitaxial layer 20 to the first conductive type second doping region 22.

[0107] Specifically, doping the semiconductor body 1 with the second recombination center impurity may include: injecting H into the semiconductor body 1 through an irradiation process. + or He + , in order to control the longitudinal minority carrier lifetime. + or He + The peak position of the injection is located near the P / N-junction, thus forming a distribution in which the minority carrier lifetime decreases from the N- / N+ junction to the P / N-junction.

[0108] Note that the above are only preferred embodiments of the present invention and the technical principles used. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein, and that various obvious changes, readjustments and substitutions can be made by those skilled in the art without departing from the scope of protection of the present invention. Therefore, although the present invention has been described in more detail through the above embodiments, the present invention is not limited to the above embodiments, and may include more other equivalent embodiments without departing from the concept of the present invention, and the scope of the present invention is determined by the scope of the appended claims.

Claims

1. A fast recovery diode, characterized in that: include: A semiconductor body, comprising a terminal region and an active region; wherein the terminal region is doped with a first recombination center impurity, the first recombination center impurity being used to recombine minority carriers in the terminal region to adjust the lifetime of minority carriers in the terminal region; and the doping concentration of the first recombination center impurity gradually decreases in a direction from the terminal region to the active region; A first groove is located on the first surface of the semiconductor body and in an area of ​​the terminal region away from the active region; wherein the semiconductor body also includes a first surface and a second surface arranged opposite to each other; the first groove is used as a diffusion center for the first recombination center impurity, and the first recombination center impurity diffuses from the first groove into the terminal region; the first recombination center impurity includes platinum and / or gold.

2. The fast recovery diode according to claim 1, characterized in that: The first surface includes a first terminal region surface located in the terminal region and a first active region surface located in the active region; Wherein, the surface of the first active region includes a first doped region of a first conductivity type, and the conductivity type of the semiconductor body between the first doped region of the first conductivity type and the second surface is a second conductivity type; The surface of the first terminal region includes a first conductivity type second doped region, and the conductivity type of the semiconductor body between the first conductivity type second doped region and the second surface is the second conductivity type.

3. The fast recovery diode according to claim 2, characterized in that: Also includes: a blocking structure extending from the first surface into the semiconductor body; The blocking structure is used to block the first recombination center impurities in the terminal region from diffusing into the active region.

4. The fast recovery diode according to claim 3, characterized in that: The blocking structure comprises: The second groove is located on the first surface and in a region of the terminal region adjacent to the active region.

5. The fast recovery diode according to claim 4, characterized in that: The blocking structure further comprises: A barrier layer is located in the second groove; wherein a distance from a surface of the barrier layer away from the first surface to the first surface is greater than or equal to a distance from a surface of the first conductive type first doped region away from the first surface to the first surface, and greater than or equal to a distance from a surface of the first conductive type second doped region away from the first surface to the first surface.

6. The fast recovery diode according to claim 2, characterized in that: The semiconductor body comprises a substrate and a semiconductor epitaxial layer located on one side of the substrate; the first surface is a surface of the semiconductor epitaxial layer away from the substrate, and the second surface is a surface of the substrate away from the semiconductor epitaxial layer; In which, the semiconductor body is also doped with a second composite center impurity; in a direction perpendicular to the substrate, the doping concentration of the second composite center impurity gradually decreases from the interface between the substrate and the semiconductor epitaxial layer to the first conductive type first doping region, and gradually decreases from the interface between the substrate and the semiconductor epitaxial layer to the first conductive type second doping region.

7. The fast recovery diode according to claim 2, characterized in that: The first conductivity type second doping region includes a plurality of first conductivity type second doping sub-regions; A plurality of first conductivity type second doped sub-regions are sequentially arranged at intervals in a direction from the terminal region to the active region.

8. A method for preparing a fast recovery diode, characterized in that: Used to prepare the fast recovery diode according to any one of claims 1 to 7, comprising: forming a semiconductor body; the semiconductor body comprising a terminal region and an active region; A first recombination center impurity is doped in the terminal region; the first recombination center impurity is used to recombine minority carriers in the terminal region to adjust the lifetime of minority carriers in the terminal region; the doping concentration of the first recombination center impurity gradually decreases in the direction from the terminal region to the active region; the first surface of the semiconductor body includes a first groove, and is located in a region of the terminal region away from the active region; the first groove is used as a diffusion center of the first recombination center impurity, and the first recombination center impurity diffuses from the first groove into the terminal region.

9. The method for preparing a fast recovery diode according to claim 8, characterized in that: The forming of the semiconductor body comprises: providing a substrate; A semiconductor epitaxial layer is formed on one side of the substrate; wherein the semiconductor body comprises a first surface and a second surface arranged opposite to each other, the first surface is a surface of the semiconductor epitaxial layer away from the substrate, and the second surface is a surface of the substrate away from the semiconductor epitaxial layer; the first surface comprises a first terminal region surface located in the terminal region and a first active region surface located in the active region; A first conductive type first doping region is formed on the surface of the first active region, and a first conductive type second doping region is formed on the surface of the first terminal region; wherein the conductivity type of the semiconductor body between the first conductive type first doping region and the second surface, and the conductivity type of the semiconductor body between the first conductive type second doping region and the second surface is the second conductive type; Doping the first recombination center impurity in the terminal region comprises: Forming a first groove on the first surface; the first groove is located in a region of the terminal region away from the active region; Filling the first groove with a first recombination center impurity, and heating the semiconductor body to diffuse the first recombination center impurity toward the terminal region; Before filling the first recombination center impurities in the first groove, the method further includes: A blocking structure is formed in the semiconductor body; the blocking structure extends from the first surface into the semiconductor body, and the blocking structure is used to block the first recombination center impurities in the terminal region from diffusing into the active region.

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