A fast recovery diode and its fabrication method

Abstract

This invention provides a fast recovery diode and its fabrication method. The fast recovery diode includes: a drift layer; a back-side doped layer located on one side surface of the drift layer; and a cathode layer, the cathode layer including: a cathode spacer layer penetrating a portion of the back-side doped layer and in contact with the drift layer; and a cathode body layer located on the side surface of the cathode spacer layer and the back-side doped layer opposite to the drift layer; the conductivity type of the back-side doped layer is opposite to that of the cathode layer and the drift layer, respectively. The fast recovery diode of this invention can suppress reverse recovery current oscillation.

Description

Technical Field

[0001] This invention relates to a power semiconductor device and its fabrication method, specifically to a fast recovery diode and its fabrication method. Background Technology

[0002] A fast recovery diode (FRD) is a semiconductor diode characterized by excellent switching characteristics and a short reverse recovery time. It is widely used in various fields such as household appliances, electric vehicles, and rail locomotives, especially in high-voltage equipment such as converter valves and circuit breakers in power systems. The structure of a typical diode is a PN junction formed by the direct contact of P-type and N-type semiconductors. However, a fast recovery diode adds an intrinsic semiconductor i-layer between the P-type and N-type materials of a typical diode, forming a PiN structure. The method for preparing the intrinsic semiconductor i-layer mainly involves forming a low-concentration N-type drift layer between the P-type anode layer and the N-type cathode layer. This N-type drift layer has a much lower doping concentration than the P-type anode and N-type cathode layers, and can be approximated as the intrinsic semiconductor i-layer.

[0003] Although fast recovery diodes have advantages such as low on-state voltage drop, high breakdown voltage, strong anti-static discharge capability, and low high-temperature leakage current, they are prone to current oscillation at the end of the reverse recovery phase. Summary of the Invention

[0004] The technical problem to be solved by this invention is how to suppress the reverse recovery current oscillation phenomenon of fast recovery diodes.

[0005] To address the aforementioned problems, the present invention provides a fast recovery diode, comprising: a drift layer; a back-side doped layer located on one side surface of the drift layer; a cathode layer, the cathode layer comprising: a cathode spacer layer penetrating a portion of the back-side doped layer, the cathode spacer layer being in contact with the drift layer; a cathode body layer located on the side surface of the cathode spacer layer and the back-side doped layer opposite to the drift layer; the conductivity type of the back-side doped layer being opposite to the conductivity type of the cathode layer and the drift layer, respectively.

[0006] Optionally, the doping concentration in the back doped layer is 1 to 2 orders of magnitude lower than the doping concentration in the cathode layer; the doping concentration in the back doped layer is 1 to 4 orders of magnitude higher than the doping concentration in the drift layer.

[0007] Optionally, the thickness of the back doped layer is 11 μm to 20 μm.

[0008] Optionally, the back-side doped layer comprises one or more spaced island structures.

[0009] Optionally, the projected area of ​​the back-side doped layer on the drift layer is 10% to 40% of the cross-sectional area of ​​the drift layer.

[0010] Optionally, the cathode spacer layer penetrates a portion of the back-side doped layer and extends into a portion of the drift layer.

[0011] Optionally, a first trench is provided on the side surface of the cathode body layer facing away from the drift layer; the fast recovery diode further includes: a cathode electrode layer, which covers the cathode body layer and is recessed toward the first trench.

[0012] Optionally, the number of first grooves is several, the spacing between adjacent first grooves is 11μm to 20μm, the depth of the first groove is 1μm to 20μm, and the width of the first groove is 11μm to 20μm.

[0013] Optionally, it may also include: an anode layer located on the side of the drift layer opposite to the back doped layer.

[0014] Optionally, the anode layer also extends into a portion of the drift layer.

[0015] Optionally, the anode layer has a second trench on the side surface opposite to the drift layer; the fast recovery diode further includes an anode electrode layer that covers the anode layer and is recessed toward the second trench.

[0016] Optionally, it further includes: the stepped lifetime control layer, a portion of which is located within the anode layer and a portion of which is located within the drift layer; the stepped lifetime control layer is doped with any one or a combination of H ions, He ions, and platinum ions.

[0017] Optionally, the thickness of the stepped lifetime control layer is 1 nm to 1000 nm.

[0018] The present invention also provides a method for fabricating a fast recovery diode, comprising: forming a drift layer; forming a back-side doped layer and a cathode layer, wherein the back-side doped layer is located on one side surface of the drift layer; the cathode layer comprises: a cathode spacer layer penetrating a portion of the back-side doped layer, the cathode spacer layer being in contact with the drift layer; and a cathode body layer located on the side surface of the cathode spacer layer and the back-side doped layer facing away from the drift layer; wherein the conductivity type of the back-side doped layer is opposite to the conductivity type of the cathode layer and the drift layer, respectively.

[0019] Optionally, the steps of forming the drift layer, the back-side doped layer, and the cathode layer include: providing an initial body layer, the initial body layer including the drift layer; forming an initial back-side doped layer in the initial body layer at the bottom of the drift layer; forming a first trench on the side of the initial back-side doped layer opposite to the drift layer, the first trench being located in a portion of the initial back-side doped layer; forming a cathode layer in the initial back-side doped layer at the bottom of the first trench and in the initial back-side doped layer on the side of the first trench, the thickness of the cathode layer being greater than the depth of the first trench and less than the thickness of the initial back-side doped layer, the initial back-side doped layer outside the cathode layer constituting the back-side doped layer.

[0020] Optionally, the steps of forming the drift layer, the back doped layer, and the cathode layer include: providing an initial body layer, the initial body layer including the drift layer; forming a back doped layer in the initial body layer at the bottom of the drift layer; forming a third trench through the back doped layer; and forming a cathode layer covering the back doped layer and filling the third trench.

[0021] Optionally, in the step of forming the cathode layer, the cathode layer has a first trench on the side opposite to the drift layer, and the position of the first trench corresponds to the position of the third trench.

[0022] Optionally, it may also include: forming a cathode electrode layer that covers the cathode body layer and is recessed toward the first trench.

[0023] Optionally, it further includes: forming an anode layer on the other side of the drift layer; the anode layer is located on the side of the drift layer opposite to the back doped layer.

[0024] Optionally, the step of forming the anode layer includes: providing an initial body layer, the initial body layer including a drift layer; forming an anode layer in the initial body layer of a partial thickness at the top of the drift layer; and forming a second trench on a side surface of the anode layer opposite to the drift layer.

[0025] Optionally, the step of forming the anode layer includes: providing an initial body layer, the initial body layer including a drift layer; forming a second trench in the initial body layer of a partial thickness at the top of the drift layer; and after forming the second trench, forming an anode layer in the initial body layer at the top of the drift layer and in the initial body layer on the side of the second trench, the anode layer having a protrusion on one side surface facing the drift layer.

[0026] Optionally, it also includes: forming an anode electrode layer that covers the anode layer and is recessed toward the second trench.

[0027] Optionally, it further includes: forming a stepped lifetime control layer, a portion of which is located within the anode layer and a portion of which is located within the drift layer; the stepped lifetime control layer is doped with any one or a combination of H ions, He ions, and platinum ions.

[0028] The beneficial effects of this invention are as follows:

[0029] The fast recovery diode provided by this invention includes a back-side doped layer, the conductivity of which is opposite to that of the cathode layer and the drift layer. The cathode layer includes: a cathode spacer layer penetrating a portion of the back-side doped layer and in contact with the drift layer; and a cathode body layer located on the side of the cathode spacer layer and the back-side doped layer facing away from the drift layer. When the fast recovery diode is forward-biased, electrons in the cathode layer sequentially pass through the cathode body layer and the cathode spacer layer into the drift layer. At the end of the reverse recovery phase of the fast recovery diode, holes are injected into the drift layer from the back-side doped layer, optimizing the soft recovery characteristics of the fast recovery diode and thus suppressing reverse recovery current oscillations.

[0030] Furthermore, the back-side doped layer comprises one or more spaced island-like structures. With a fixed projected area of ​​the back-side doped layer on the drift layer surface, the dimensions of the back-side doped layer in all directions are not excessively small, which is beneficial for the fabrication of the back-side doped layer. Secondly, the spaced island-like structures have a relatively small obstruction effect on electron injection during the forward conduction of the fast recovery diode, thus avoiding an increase in the forward voltage drop of the fast recovery diode.

[0031] Furthermore, the cathode spacer layer penetrates a portion of the back-side doped layer and extends into a portion of the drift layer, which can prevent the back-side doped layers on both sides of the cathode spacer layer from connecting together, and make it easier for electrons in the cathode layer to be injected into the drift layer.

[0032] Furthermore, a first trench is formed on the side surface of the cathode body layer facing away from the drift layer, and the cathode electrode layer covers the cathode body layer and is recessed towards the first trench. During press-fit packaging, the cathode electrode layer on the side of the first trench bears the pressure applied to it, and the cathode electrode layer will extend in the horizontal direction perpendicular to the pressure, thereby reducing the vertical pressure on the cathode layer surface and alleviating stress concentration on the surface of the fast recovery diode chip.

[0033] Furthermore, the anode layer has a second trench on its surface opposite to the drift layer, and the anode electrode layer covers the anode layer and is recessed towards the second trench. During press-fit packaging, the anode electrode layer on the side of the second trench bears the pressure applied to it, causing the anode electrode layer to extend in a horizontal direction perpendicular to the pressure, thereby reducing the vertical pressure on the anode layer surface and alleviating stress concentration on the fast recovery diode chip surface. Secondly, the second trench increases the interface area between the anode electrode layer and the anode layer, thus improving hole injection efficiency.

[0034] Furthermore, the anode layer extends into part of the drift layer, increasing the area of ​​the interface between the anode layer and the drift layer, which improves the hole injection efficiency.

[0035] Furthermore, it also includes a stepped lifetime control layer, which is doped with any one or a combination of H ions, He ions, and platinum ions. Part of the stepped lifetime control layer is located within the anode layer, resulting in low leakage current; another part is located within the drift layer, resulting in a high carrier recombination rate during reverse recovery and reducing the reverse recovery current. This improves the electrical performance and robustness of the fast recovery diode. Attached Figure Description

[0036] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0037] Figure 1 This is a schematic diagram of the structure of a fast recovery diode;

[0038] Figure 2 This is a schematic diagram of another type of fast recovery diode;

[0039] Figure 3 This is a schematic diagram of another type of fast recovery diode;

[0040] Figures 4 to 5 This is a schematic diagram of the fabrication process of a fast recovery diode;

[0041] Figures 6 to 7 A schematic diagram illustrating the fabrication process of another type of fast recovery diode;

[0042] Figures 8 to 9 This is a schematic diagram illustrating the fabrication process of another type of fast recovery diode.

[0043] Figure 10This is a comparison graph of the reverse recovery current between Test Example 1 and the comparative example;

[0044] Figure 11 This is a comparison graph of the reverse recovery voltage of Test Example 1 and the comparative example;

[0045] Figure 12 The graph shows a comparison of the forward conduction voltage drop trends between Test Example 2 and the comparative example under different vertical pressure sealing stress conditions.

[0046] Figure label:

[0047] 1, Drift layer; 2, Backside doped layer; 3, Cathode layer; 4, Cathode electrode layer; 5, Anode layer; 6, Anode electrode layer; 7, Stepped lifetime control layer; 1', Drift layer; 5', Anode layer; 1A, Initial body layer. Detailed Implementation

[0048] The technical solutions of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention. Furthermore, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0049] Example 1

[0050] This embodiment provides a fast recovery diode, such as Figure 1 As shown, it includes:

[0051] Drift layer 1;

[0052] The back-side doped layer 2 is located on one side surface of the drift layer 1;

[0053] The cathode layer 3 includes: a cathode spacer layer that penetrates a portion of the back doped layer and is in contact with the drift layer 1; and a cathode body layer located on the side surface of the cathode spacer layer and the back doped layer 2 facing away from the drift layer 1, wherein the conductivity type of the back doped layer 2 is opposite to that of the cathode layer 3 and the drift layer 1, respectively.

[0054] In this embodiment, the back doped layer 2 has a P-type conductivity, the cathode layer 3 has an N-type conductivity, and the drift layer 1 has an N-type conductivity.

[0055] In this embodiment, when the fast recovery diode is forward-biased, electrons in the cathode layer 3 are injected into the drift layer 1 sequentially through the cathode body layer and the cathode spacer layer. Since a back-side doped layer 2 is provided between the drift layer 1 and the cathode layer 3, holes are injected into the drift layer 1 from the back-side doped layer 2 at the end of the reverse recovery process of the fast recovery diode. This optimizes the soft recovery characteristics of the fast recovery diode, suppresses reverse recovery current oscillation, and improves the reverse recovery robustness of the fast recovery diode.

[0056] In one embodiment, the doping concentration of drift layer 1 ranges from 1E10cm⁻¹. -3 Up to 1E20cm -3 .

[0057] In one embodiment, the doping concentration of the back doped layer 2 is 1 to 2 orders of magnitude lower than that of the cathode layer 3. This 1 to 2 order of magnitude reduction in doping concentration of the back doped layer 2 compared to the cathode layer 3 optimizes the soft recovery characteristics of the fast recovery diode without affecting the ohmic contact between the cathode layer 3 and the cathode electrode layer 4, thus achieving low ohmic contact resistance of the cathode.

[0058] In one embodiment, the doping concentration in the back doped layer 2 is 1 to 4 orders of magnitude higher than that in the drift layer 1. Compared to the doping concentration of the drift layer 1, the 1 to 4 orders of magnitude higher doping concentration in the back doped layer 2 ensures a sufficient concentration difference, ensuring that enough holes are injected from the back doped layer 2 to the cathode side during reverse recovery.

[0059] In one embodiment, the thickness of the back doped layer 2 is 11 μm to 20 μm, for example, 15 μm. The thickness of the back doped layer 2 improves the fast recovery diode's resistance to dynamic avalanche and forward surge, prevents forward punch-through under high voltage and high current, and enhances the operating stability of the fast recovery diode.

[0060] The back-side doped layer 2 comprises one or more spaced island-like structures. With a fixed projected area of ​​the back-side doped layer 2 on the surface of the drift layer 1, the dimensions of the back-side doped layer 2 in all directions are not excessively small, which is beneficial for the fabrication of the back-side doped layer. Secondly, the spaced island-like structures have a relatively small obstruction effect on electron injection during the forward conduction of the fast recovery diode, thus avoiding an increase in the forward voltage drop of the fast recovery diode.

[0061] In one embodiment, the projected area of ​​the back-side doped layer 2 on the drift layer 1 is 10% to 40% of the cross-sectional area of ​​the drift layer 1, for example, 20%. Within this range, the island-like doped structure can provide a trade-off optimization for the forward conduction and reverse recovery performance of the diode. Below this range, the optimization effect of the island-like structure on reverse recovery decreases; while above this range, the degrading effect of the conduction structure on the forward voltage drop becomes more pronounced.

[0062] In this embodiment, the cathode spacer layer penetrates a portion of the back-side doped layer 2 and extends into a portion of the drift layer 1. This prevents the back-side doped layers 2 on both sides of the cathode spacer layer from connecting together, making it easier for electrons in the cathode layer 3 to be injected into the drift layer. It should be noted that in other embodiments, the cathode spacer layer penetrates a portion of the back-side doped layer, and the longitudinal thickness of the cathode spacer layer is equal to the thickness of the back-side doped layer, with the cathode spacer layer in contact with the drift layer.

[0063] In this embodiment, reference Figure 1 The cathode body layer has a first trench on the side facing away from the drift layer 1. The fast recovery diode also includes a cathode electrode layer 4, which covers the cathode body layer and is recessed towards the first trench. The cathode electrode layer 4 has a three-dimensional periodic protrusion structure. During press-fit packaging, the cathode electrode layer 4 on the side of the first trench bears the pressure applied to it, causing it to extend in a horizontal direction perpendicular to the pressure. This reduces the vertical pressure on the surface of the cathode layer 3 and alleviates stress concentration on the surface of the fast recovery diode chip.

[0064] In one embodiment, the depth of the first trench is 1 μm to 20 μm, for example, 10 μm. If the depth of the first trench is too small, the degree of reduction in the vertical pressure on the cathode layer surface is reduced; if the depth of the first trench is too large, the distance between the bottom surface of the first trench and the cathode spacer layer is too small, resulting in an excessively thin connection between the cathode spacer layer and the cathode body layer, which is not conducive to the charge transfer between the cathode spacer layer and the cathode body layer.

[0065] In this embodiment, there are several first trenches, and the back doped layer 2 between adjacent first trenches has an island-like structure. In one embodiment, the spacing between adjacent first trenches is 11μm to 20μm, for example, 15μm. The periodically distributed back doped layers 2, with a certain distance, uniformly inject holes from the back doped layers into the drift layer at the end of the reverse recovery process of the fast recovery diode, thereby improving the reverse recovery stability of the fast recovery diode.

[0066] In this embodiment, the width of the first trench is 11 μm to 20 μm, for example, 15 μm. The width of the first trench and the spacing between adjacent first trenches together determine the distribution of the island structure in the back-side doped layer. The spacing between adjacent first trenches determines the width of the island structure in the back-side doped layer, and the width of the first trench determines the spacing between the island structures in the back-side doped layer. After the spacing between adjacent first trenches is determined, the width of the first trench determines the area ratio of the island structure in the back-side doped layer. When the spacing between the first trenches is too small, the area ratio of the island structure in the back-side doped layer is too large, which affects the electron injection from the cathode layer into the drift layer, resulting in adverse consequences such as a large forward conduction voltage drop. When the width of the first trench is too large, the area ratio of the island structure in the back-side doped layer is too small, which affects the hole injection during the reverse recovery process, weakening its effect on optimizing reverse recovery performance.

[0067] It should be noted that in other embodiments, the first trench may not be provided on the side surface of the cathode body layer facing away from the drift layer, so that the cathode electrode layer is planar.

[0068] In this embodiment, reference Figure 1 The fast recovery diode further includes: an anode layer 5 located on the side of the drift layer 1 away from the back doped layer 2; and an anode electrode layer 6 covering the anode layer 5.

[0069] In this embodiment, the conductivity type of the anode layer 5 is P-type.

[0070] In this embodiment, the surface of the anode layer 5 facing away from the drift layer 1 has a second trench, and the anode electrode layer 6 covers the anode layer 5 and is recessed towards the second trench. During press-fit packaging, the anode electrode layer 6 on the side of the second trench bears the pressure applied to it, and the anode electrode layer 6 extends in a horizontal direction perpendicular to the pressure, thereby reducing the vertical pressure on the surface of the anode layer 5 and alleviating stress concentration on the surface of the fast recovery diode chip. Furthermore, the second trench increases the interface area between the anode electrode layer 6 and the anode layer 5, which improves the hole injection efficiency.

[0071] In other embodiments, the second trench may not be provided in the anode layer.

[0072] In this embodiment, the interface between the anode layer 5 and the drift layer 1 is used as an example.

[0073] Example 2

[0074] The difference between this embodiment and Embodiment 1 is that: Figure 2 As shown, the anode layer 5' also extends into a portion of the drift layer 1'. The increased interface area between the anode layer 5' and the drift layer 1' improves the hole injection efficiency.

[0075] The parts in this embodiment that are the same as those in Embodiment 1 will not be described in detail.

[0076] Example 3

[0077] The difference between this embodiment and Embodiment 1 is that: Figure 3 As shown, the fast recovery diode further includes a stepped lifetime control layer 7, a portion of which is located within the anode layer 5 and a portion within the drift layer 1. The stepped lifetime control layer 7 is doped with any one or a combination of H ions, He ions, and platinum ions. Because a portion of the stepped lifetime control layer 7 is located inside the anode layer, during reverse blocking, most of the depletion layer does not reach the stepped lifetime control layer in the anode layer. Therefore, compared to a structure where the stepped lifetime control layer is entirely located inside the drift layer, the reverse blocking leakage current is smaller. Simultaneously, because a portion of the stepped lifetime control layer is located within the drift layer, the electron-hole recombination rate is effectively increased during reverse recovery, reducing the peak reverse recovery current and optimizing the reverse recovery characteristics.

[0078] In one embodiment, the thickness of the stepped lifetime control layer 7 is 1 nm to 1000 nm, for example, 100 nm. The functions of the stepped lifetime control layer 7 include forming a defect layer within the drift layer to accelerate electron-hole recombination during reverse recovery, and forming a high-concentration cation layer in the anode layer to reverse-block leakage current and reduce leakage current during reverse recovery. Therefore, forming a stepped lifetime control layer in the drift layer and anode layer results in a smaller thickness of the layer, leading to a smaller effect of accelerating electron-hole recombination in the cathode layer and a larger effect of reducing leakage current in the anode layer during reverse recovery; conversely, a larger thickness of the layer leads to a larger effect of accelerating electron-hole recombination in the cathode layer and a smaller effect of reducing leakage current in the anode layer during reverse recovery. Considering these factors, the thickness of the stepped lifetime control layer is controlled within the range of 1 nm to 1000 nm, which effectively accelerates electron-hole recombination in the cathode layer and effectively reduces leakage current in the anode layer during reverse recovery.

[0079] It should be noted that, in Figure 2 A stepped life control layer can also be set in the middle.

[0080] Example 4

[0081] This embodiment provides a method for manufacturing a fast recovery diode, such as... Figures 4 to 5As shown, the method includes: forming a drift layer 1'; forming a back-side doped layer 2 and a cathode layer 3, wherein the back-side doped layer 2 is located on one side surface of the drift layer 1'; the cathode layer 3 includes: a cathode spacer layer that penetrates a portion of the back-side doped layer 2 and is in contact with the drift layer 1'; and a cathode body layer located on the side surface of the cathode spacer layer and the back-side doped layer 2 facing away from the drift layer 1'; the conductivity type of the back-side doped layer 2 is opposite to that of the cathode layer 3 and the drift layer 1', respectively.

[0082] In this embodiment, the back doped layer 2 has a P-type conductivity, the cathode layer 3 has an N-type conductivity, and the drift layer 1' has an N-type conductivity.

[0083] In this embodiment, the steps of forming the drift layer 1', the back-side doped layer 2, and the cathode layer 3 include: providing an initial body layer 1A, the initial body layer 1A including the drift layer 1'; forming an initial back-side doped layer in the initial body layer 1A at the bottom of the drift layer 1'; forming a first trench on the side of the initial back-side doped layer opposite to the drift layer 1', the first trench being located in a portion of the initial back-side doped layer; forming a cathode layer in the initial back-side doped layer at the bottom of the first trench and in the initial back-side doped layer on the side of the first trench, the thickness of the cathode layer being greater than the depth of the first trench and less than the thickness of the initial back-side doped layer, the initial back-side doped layer outside the cathode layer constituting the back-side doped layer. The process for forming the initial back-side doped layer includes an ion implantation process. The process for forming the cathode layer includes an ion implantation process.

[0084] In another embodiment, the steps of forming the drift layer, the back-side doped layer, and the cathode layer include: providing an initial body layer 1A, the initial body layer 1A including the drift layer; forming a back-side doped layer in the initial body layer 1A at the bottom of the drift layer; forming a third trench through the back-side doped layer; and forming a cathode layer covering the back-side doped layer and filling the third trench. The process for forming the back-side doped layer includes an ion implantation process. The process for forming the cathode layer includes a deposition process.

[0085] In the step of forming the cathode layer, the cathode layer has a first trench on the side opposite to the drift layer, and the position of the first trench corresponds to the position of the third trench. It should be noted that in other embodiments, the first trench may not be formed in the cathode layer.

[0086] The method for fabricating a fast recovery diode in this embodiment further includes: forming a cathode electrode layer 4 that covers the cathode body layer and is recessed towards the first trench. The process for forming the cathode electrode layer 4 includes a deposition process. At this time, the overall morphology of the cathode electrode layer 4 presents a three-dimensional periodic protrusion structure, which is beneficial to extend the vertical pressure acting on the fast recovery diode chip in the horizontal direction during press-fit packaging, thereby alleviating stress concentration and protecting the fast recovery diode chip.

[0087] In this embodiment, the step of forming the anode layer includes: providing an initial body layer 1A, the initial body layer 1A including a drift layer; forming a second trench in the initial body layer 1A with a portion of the thickness at the top of the drift layer; after forming the second trench, forming an anode layer 5' in the initial body layer at the top of the drift layer and in the initial body layer on the side of the second trench, the anode layer 5' having a protrusion on one side surface facing the drift layer.

[0088] After the second trench is formed, when the anode layer 5' is formed in the initial bulk layer at the bottom of the drift layer and in the initial bulk layer on the side of the second trench, certain depths in the anode layer 5' exhibit alternating light and heavy doping in the horizontal direction. Therefore, the anode layer 5' can regulate the hole injection efficiency. The regulation of hole injection efficiency refers to the fact that different regions in the anode layer 5' have different doping concentrations, thus affecting the hole injection efficiency. When the current density in the anode layer 5' is low, the regions with relatively low doping concentration play a major role in hole injection; when the current density in the anode layer 5' is high, the regions with relatively high doping concentration play a major role in hole injection.

[0089] In this embodiment, the method for manufacturing a fast recovery diode further includes: forming an anode electrode layer 6 that covers the anode layer and is recessed toward the second trench.

[0090] Example 5

[0091] The difference between this embodiment and Embodiment 4 is that the step of forming the anode layer 5' includes: providing an initial body layer 1A, the initial body layer including a drift layer; forming the anode layer 5' in a portion of the thickness of the initial body layer at the top of the drift layer; and further, forming a second trench on the surface of the anode layer 5' facing away from the drift layer. Figures 6 to 7 As shown, the anode layer 5' exhibits alternating heavy and light doping in the horizontal direction. This alternating doping pattern is due to the reduced average doping concentration of the anode layer below the second trench caused by etching, while the average doping concentration is higher in the region where the second trench is not etched. By utilizing the different hole injection efficiencies resulting from varying doping concentrations in different regions of the anode layer 5' when the current density varies, the hole injection efficiency during forward injection can be adjusted.

[0092] The parts in this embodiment that are the same as those in Embodiment 4 will not be described in detail.

[0093] Example 6

[0094] Please refer to Figure 8 and Figure 9 The method for fabricating a fast recovery diode in this embodiment further includes: forming a stepped lifetime control layer 7, a portion of which is located within the anode layer 5 and a portion of which is located within the drift layer 1; the stepped lifetime control layer 7 is doped with any one or a combination of H ions, He ions, and platinum ions.

[0095] Since part of the stepped lifetime control layer 7 is located inside the anode layer 5 above the PN junction, most of the depletion layer does not reach the stepped lifetime control layer 7 in the anode region during reverse blocking. Therefore, the reverse blocking leakage current is smaller compared to the structure where all the stepped lifetime control layers 7 are located inside the drift layer 1. At the same time, since part of the stepped lifetime control layer 7 is located inside the drift layer 1 below the PN junction, the electron-hole recombination rate is effectively increased during reverse recovery, the peak reverse recovery current is reduced, and the reverse recovery characteristics are optimized.

[0096] Comparative example: The structure of the fast recovery diode from bottom to top consists of a cathode electrode layer, a cathode layer, a drift layer, an anode layer, and an anode electrode layer; the oscillation amplitude of the reverse recovery current at the end of the reverse recovery period is about ±1A, the amplitude ratio is ±1%, and the peak value of the reverse recovery current is 206.4A.

[0097] Test Example 1: Peak doping concentration of the cathode layer is 1E17cm -3 The cathode layer thickness is 20 μm; the peak doping concentration of the back doped layer is 1E15cm. -3 The back-side doped layer has a thickness of 12 μm; the first trench has a depth of 10 μm, a width of 12 μm, and a spacing of 12 μm between adjacent first trenches; the cathode electrode layer has a thickness of 8 μm; the second trench has a depth of 5 μm and a spacing of 10 μm between adjacent second trenches; the peak doping concentration of the anode layer is 1E19 cm⁻¹. -3 The anode layer thickness is 10 μm; the anode electrode layer thickness is 8 μm; the distance between the stepped lifetime control layer in the anode layer and the PN junction between the anode layer and the drift layer is 4 μm; and the distance between the stepped lifetime control layer in the drift layer and the PN junction between the anode layer and the drift layer is 1 μm.

[0098] like Figure 10 and Figure 11 As shown, Figure 10 In the diagram, the horizontal axis represents the reverse recovery time of the fast recovery diode, and the vertical axis represents the reverse recovery current during the reverse recovery process of the fast recovery diode. Figure 11In the figure, the horizontal axis represents the reverse recovery time of the fast recovery diode, and the vertical axis represents the reverse recovery voltage during the reverse recovery process of the fast recovery diode. The fast recovery diode in this embodiment can effectively reduce the peak reverse recovery current of the chip by 21.1%, with a peak reverse recovery current of 162.9A. There is no current oscillation or voltage oscillation at the end of the reverse recovery period, thus improving performance.

[0099] Test Example 2: Peak doping concentration of the cathode layer is 1E17cm -3 The cathode layer thickness is 50 μm; the peak doping concentration of the back doped layer is 1E15cm. -3 The back-side doped layer has a thickness of 20 μm; the first trench has a depth of 20 μm, a width of 20 μm, and a spacing of 20 μm between adjacent first trenches; the cathode electrode layer has a thickness of 10 μm; the second trench has a depth of 5 μm and a spacing of 10 μm between adjacent second trenches; the peak doping concentration of the anode layer is 1E19 cm⁻¹. -3 The anode layer thickness is 10 μm; the anode electrode layer thickness is 8 μm; the distance between the stepped lifetime control layer in the anode layer and the PN junction between the anode layer and the drift layer is 3 μm; and the distance between the stepped lifetime control layer in the drift layer and the PN junction between the anode layer and the drift layer is 2 μm.

[0100] like Figure 12 As shown, Figure 12 In the figure, the horizontal axis represents the pressure change experienced by the fast recovery diode during the press-fit packaging process, and the vertical axis represents the forward voltage drop of the fast recovery diode during the press-fit packaging process. In this embodiment, the forward voltage drop of the fast recovery diode decreases by 3% with pressure at the maximum attenuation rate during press-fit packaging, which greatly alleviates the parameter drift of the fast recovery diode caused by uneven press-fit stress when multiple fast recovery diodes are connected in parallel.

[0101] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A fast recovery diode, characterized in that, include: Drift layer; A back-side doped layer located on one side surface of the drift layer; The cathode layer includes: a cathode spacer layer penetrating a portion of the back-side doped layer, the cathode spacer layer being in contact with the drift layer; and a cathode body layer located on the side surface of the cathode spacer layer and the back-side doped layer facing away from the drift layer. The conductivity type of the back doped layer is opposite to that of the cathode layer and the drift layer, respectively; The cathode body layer has a first trench on the side surface facing away from the drift layer; the fast recovery diode further includes: a cathode electrode layer, which covers the cathode body layer and is recessed toward the first trench; Also includes: An anode layer is located on the side of the drift layer opposite to the back doped layer; A stepped lifetime control layer, wherein a portion of the stepped lifetime control layer is located within the anode layer and a portion of the stepped lifetime control layer is located within the drift layer; the stepped lifetime control layer is doped with any one or a combination of H ions, He ions, and platinum ions.

2. The fast recovery diode according to claim 1, characterized in that, The doping concentration in the back doped layer is 1 to 2 orders of magnitude lower than that in the cathode layer; the doping concentration in the back doped layer is 1 to 4 orders of magnitude higher than that in the drift layer.

3. The fast recovery diode according to claim 1, characterized in that, The thickness of the back doped layer is 11 μm to 20 μm.

4. The fast recovery diode according to claim 1, characterized in that, The back-side doped layer comprises one or more spaced island-like structures.

5. The fast recovery diode according to claim 1, characterized in that, The projected area of ​​the back-side doped layer on the drift layer is 10% to 40% of the cross-sectional area of ​​the drift layer.

6. The fast recovery diode according to claim 1, characterized in that, The cathode spacer layer penetrates a portion of the back-side doped layer and extends into a portion of the drift layer.

7. The fast recovery diode according to claim 1, characterized in that, The number of first grooves is several, the spacing between adjacent first grooves is 11μm~20μm, the depth of the first groove is 1μm~20μm, and the width of the first groove is 11μm~20μm.

8. The fast recovery diode according to claim 1, characterized in that, The anode layer also extends into part of the drift layer.

9. The fast recovery diode according to claim 1, characterized in that, The anode layer has a second groove on the side surface opposite to the drift layer; The fast recovery diode further includes an anode electrode layer that covers the anode layer and is recessed toward the second trench.

10. The fast recovery diode according to claim 1, characterized in that, The thickness of the stepped lifetime control layer is 1 nm to 1000 nm.

11. A method for manufacturing a fast recovery diode, characterized in that, include: Formation of drift layer; A back-side doped layer and a cathode layer are formed, wherein the back-side doped layer is located on one side surface of the drift layer; The cathode layer includes: a cathode spacer layer penetrating a portion of the back-side doped layer, the cathode spacer layer being in contact with the drift layer; a cathode body layer located on the side surface of the cathode spacer layer and the back-side doped layer facing away from the drift layer; the conductivity type of the back-side doped layer is opposite to that of the cathode layer and the drift layer; a first trench is formed on the side surface of the cathode body layer facing away from the drift layer; the fast recovery diode further includes: a cathode electrode layer, the cathode electrode layer covering the cathode body layer and recessed towards the first trench; It also includes: forming an anode layer on the other side of the drift layer; the anode layer is located on the side of the drift layer opposite to the back doped layer; It also includes: forming a stepped lifetime control layer, a portion of which is located within the anode layer and a portion of which is located within the drift layer; the stepped lifetime control layer is doped with any one or a combination of H ions, He ions, and platinum ions. The steps of forming the drift layer, the back-side doped layer, and the cathode layer include: providing an initial body layer, the initial body layer including the drift layer; forming a back-side doped layer in the initial body layer at the bottom of the drift layer; forming a third trench through the back-side doped layer; forming a cathode layer covering the back-side doped layer and filling the third trench; the process of forming the back-side doped layer includes an ion implantation process; the process of forming the cathode layer includes a deposition process. In the step of forming the cathode layer, the cathode layer has a first trench on the side opposite to the drift layer, and the position of the first trench corresponds to the position of the third trench; It also includes: forming a cathode electrode layer that covers the cathode body layer and is recessed toward the first trench.

12. The method for manufacturing a fast recovery diode according to claim 11, characterized in that, The step of forming the anode layer includes: providing an initial body layer, the initial body layer including a drift layer; forming an anode layer in the initial body layer of a partial thickness on top of the drift layer; and forming a second trench on a side surface of the anode layer opposite to the drift layer. Alternatively, the step of forming the anode layer includes: providing an initial body layer, the initial body layer including a drift layer; forming a second trench in the initial body layer of a partial thickness at the top of the drift layer; and after forming the second trench, forming an anode layer in the initial body layer at the top of the drift layer and in the initial body layer on the side of the second trench, the anode layer having a protrusion on one side surface facing the drift layer.

13. The method for manufacturing a fast recovery diode according to claim 12, characterized in that, Also includes: An anode electrode layer is formed that covers the anode layer and is recessed toward the second trench.

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