A fast recovery diode and a method for preparing the same

Abstract

A fast recovery diode comprises: a first conductive type semiconductor layer; a drift layer located on the first conductive type semiconductor layer; a second conductive type doped layer located in the drift layer; the fast recovery diode further comprises: a first recombination region, the first recombination region is located in the drift layer at the bottom of the second conductive type doped layer, the first recombination region comprises a plurality of transversely arranged first sub-recombination regions, adjacent first sub-recombination regions have different depths in the drift layer; and / or a second recombination region, the second recombination region is located in the second conductive type doped layer, the second recombination region comprises a plurality of transversely arranged second sub-recombination regions, adjacent second sub-recombination regions have different depths in the second conductive type doped layer. The fast recovery diode provided by the present invention has a lower reverse recovery peak current and a faster reverse recovery speed.

Description

Technical Field

[0001] The invention relates to the technical field of diodes, and in particular to a fast recovery diode and a preparation method thereof. Background Art

[0002] Fast recovery diodes (FRDs) are generally used for rectification and freewheeling. This patent studies freewheeling diodes. In the field of semiconductor power devices, freewheeling diodes are generally connected in reverse parallel to power switch tubes (such as insulated gate bipolar transistors (IGBTs), thyristors, etc.) to play a role in reverse freewheeling. This device is collectively referred to as a switching device. Switching devices are used in inverters, power systems, locomotive traction and other fields, involving voltages ranging from tens to thousands of volts.

[0003] Fast recovery diodes are traditionally described as pin structures. In fact, the structure of fast recovery diodes is quite complex, generally a pn-nn+ structure. The top layer is the p-type emitter on the anode side, followed by a uniformly doped n-layer, followed by an n-type buffer layer with gradually increasing concentrations, and finally a heavily doped n+ emitter on the cathode side. The n-type buffer layer can compromise and optimize the chip's reverse recovery characteristics and forward conduction voltage drop.

[0004] A good fast recovery diode should not only have low conduction voltage drop and low switching loss, but also have the advantages of fast reverse recovery speed, good reverse recovery softness, high dynamic avalanche resistance and strong forward surge resistance. In the preparation of fast recovery diodes, the service life control is often used to optimize the performance of the device and achieve a better dynamic and static compromise. The main method is to introduce a spatially appropriately distributed recombination center into the device. Commonly used lifetime control technologies include global lifetime control technology and local lifetime control technology. The essence of the lifetime control area is to use defects formed by electron irradiation, heavy metal diffusion or proton / helium ion implantation. The energy poles of these defects are closer to the bandgap center than the impurity energy poles, and have a greater effect on the recombination of carriers, so they can effectively enhance the reverse recovery characteristics of the fast recovery diode. The lifetime control methods of fast recovery diodes mainly include global lifetime control and local lifetime control. Among them, global lifetime control is generally formed by electron irradiation technology or heavy metal diffusion to control the overall lifetime of the fast recovery diode; local lifetime control is generally formed by proton or helium ion implantation to control the lifetime of specific parts of the fast recovery diode.

[0005] In the prior art, the fast recovery diode has a long reverse recovery time and a large reverse recovery peak current. Summary of the invention

[0006] Therefore, the technical problem to be solved by the present invention is to overcome the long reverse recovery time and large reverse recovery peak current of the fast recovery diode in the prior art, thereby providing a fast recovery diode and a preparation method thereof.

[0007] The present invention provides a fast recovery diode, comprising: a first conductive type semiconductor layer; a drift layer located on the first conductive type semiconductor layer; a second conductive type doped layer located in the drift layer; the fast recovery diode further comprises: a first recombination region, the first recombination region is located in the drift layer at the bottom of the second conductive type doped layer, the first recombination region comprises a plurality of transversely arranged first sub-recombination regions, adjacent first sub-recombination regions have different depths in the drift layer; and / or a second recombination region, the second recombination region is located in the second conductive type doped layer, the second recombination region comprises a plurality of transversely arranged second sub-recombination regions, adjacent second sub-recombination regions have different depths in the second conductive type doped layer.

[0008] Optionally, the plurality of laterally arranged first sub-composite areas include a first first sub-composite area to an Nth first sub-composite area arranged in sequence, where N is an integer greater than or equal to 2; when k is an even number, the center depth of the k-1th first sub-composite area and the center depth of the k+1th first sub-composite area are both lower than the center depth of the kth first sub-composite area, or, the center depth of the k-1th first sub-composite area and the center depth of the k+1th first sub-composite area are both higher than the center depth of the kth first sub-composite area, where N is an integer greater than or equal to 3, and k is an integer greater than or equal to 2 and less than or equal to N-1.

[0009] Optionally, when j is an odd number greater than or equal to 3, the central depth of the j-1th first sub-composite area and the central depth of the j+1th first sub-composite area are both higher than the central depth of the kth first sub-composite area, or, the central depth of the j-1th first sub-composite area and the central depth of the j+1th first sub-composite area are both lower than the central depth of the kth first sub-composite area, N is an integer greater than or equal to 4, and j is less than or equal to N-1.

[0010] Optionally, the thickness of the first sub-recombination region is 0.2 μm to 10 μm.

[0011] Optionally, the first recombination zone is doped with defect ions, and the defect ions include protons or helium ions.

[0012] Optionally, the plurality of laterally arranged second sub-composite areas include a first second sub-composite area to an Mth second sub-composite area arranged in sequence, where M is an integer greater than or equal to 2; when q is an even number, the center depth of the q-1th second sub-composite area and the center depth of the q+1th second sub-composite area are both lower than the center depth of the qth second sub-composite area, or, the center depth of the q-1th second sub-composite area and the center depth of the q+1th second sub-composite area are both higher than the center depth of the qth second sub-composite area, M is an integer greater than or equal to 3, and q is an integer greater than or equal to 2 and less than or equal to M-1.

[0013] Optionally, when w is an odd number greater than or equal to 3, the central depth of the w-1th second sub-composite area and the central depth of the w+1th second sub-composite area are both higher than the central depth of the wth second sub-composite area, or, the central depth of the w-1th second sub-composite area and the central depth of the w+1th second sub-composite area are both lower than the central depth of the wth second sub-composite area, M is an integer greater than or equal to 4, and w is less than or equal to M-1.

[0014] Optionally, the thickness of the second sub-recombination region is 0.2 μm to 10 μm.

[0015] Optionally, the difference between the distance between the bottom surface of the second composite region and the bottom surface of the second conductive type doped layer and the first distance is greater than or equal to 1 μm; the first distance is the width of the space charge region in the second conductive type doped layer when the fast recovery diode is reversely broken down.

[0016] Optionally, the second recombination zone is doped with defect ions, and the defect ions include protons or helium ions.

[0017] Optionally, it also includes: an anode structure, which is located on the surface of the second conductive type doped layer.

[0018] Preferably, the anode structure includes: a first anode layer, located on the surface of the second conductive type doped layer; a second anode layer, located on at least a portion of the surface of the first anode layer facing away from the second conductive type doped layer, and the second anode layer is made of a different material from the first anode layer.

[0019] Optionally, it further includes: a barrier layer located on a surface of a portion of the first anode layer that is away from the second conductive type doping layer; and the second anode layer also covers the barrier layer.

[0020] Optionally, the first conductive type semiconductor layer is doped with protons or helium ions.

[0021] The present invention also provides a method for preparing a fast recovery diode, comprising: providing a drift layer; forming a first conductive type semiconductor layer on one side of the drift layer; forming a second conductive type doped layer on the other side of the drift layer; forming a first recombination region in the drift layer at the bottom of the second conductive type doped layer, the first recombination region comprising a plurality of laterally arranged first sub-recombination regions, adjacent first sub-recombination regions having different depths in the drift layer; and / or forming a second recombination region in the second conductive type doped layer, the second recombination region comprising a plurality of laterally arranged second sub-recombination regions, adjacent second sub-recombination regions having different depths in the second conductive type doped layer.

[0022] Optionally, it also includes: before forming the first composite region and the second composite region, forming a patterned barrier layer on the second conductive type doped layer; using the patterned barrier layer as a mask, performing a first ion implantation into the drift layer at the bottom of the second conductive type doped layer to form the first composite region; using the patterned barrier layer as a mask, performing a second ion implantation into the second conductive type doped layer to form the second composite region.

[0023] Optionally, the method further includes: before performing the first ion implantation and the second ion implantation, forming an anode structure on a surface of the second conductive type doped layer facing away from the drift layer, wherein the anode structure is located on a surface of the second conductive type doped layer.

[0024] Preferably, the step of forming a patterned barrier layer on the second conductive type doped layer is: forming a patterned barrier layer on the side of the anode structure away from the drift layer; ions of the first ion injection and the second ion injection pass through the anode structure; after forming the first recombination area and the second recombination area, removing the patterned barrier layer.

[0025] Preferably, the step of forming the anode structure includes: forming a first anode layer on the surface of the second conductive type doped layer; forming a second anode layer on the surface of a part of the first anode layer facing away from the second conductive type doped layer, the second anode layer and the first anode layer having a different material; the step of forming a patterned barrier layer on the drift layer includes: before forming the second anode layer, forming a patterned barrier layer on the surface of a part of the first anode layer facing away from the second conductive type doped layer; after forming the second anode layer, the second anode layer also covers the patterned barrier layer; after forming the second anode layer, performing a first ion implantation and a second ion implantation.

[0026] Optionally, the step of forming the first conductive type semiconductor layer is performed before forming the second conductive type doped layer, or after forming the second conductive type doped layer.

[0027] Preferably, the method further comprises: thinning the back side of the drift layer; after thinning the back side of the drift layer, performing a third ion implantation on the back side of the drift layer, and performing laser annealing on the region implanted with the third ions to form an ohmic contact layer.

[0028] Preferably, the step of forming the first conductive type semiconductor layer includes: performing a fourth ion implantation in a portion of the drift layer adjacent to the ohmic contact layer; after performing the fourth ion implantation, annealing the fourth ion implanted area to form a first conductive type semiconductor layer, wherein the first conductive type semiconductor layer has protons or helium ions.

[0029] The technical solution of the present invention has the following advantages:

[0030] A fast recovery diode provided by the present invention comprises: a first conductive type semiconductor layer; a drift layer located on the first conductive type semiconductor layer; and a second conductive type doped layer located in the drift layer; the fast recovery diode further comprises: a first recombination region, the first recombination region being located in the drift layer at the bottom of the second conductive type doped layer, the first recombination region comprising a plurality of laterally arranged first sub-recombination regions, adjacent first sub-recombination regions having different depths in the drift layer; and / or a second recombination region, the second recombination region being located in the second conductive type doped layer, the second recombination region comprising a plurality of laterally arranged second sub-recombination regions, adjacent second sub-recombination regions having different depths in the second conductive type doped layer. In the present invention, when a first recombination zone is set in the drift layer, the depths of adjacent first sub-recombination zones in the drift layer are different, the interface between the first recombination zone and the drift layer increases, and when the external voltage of the fast recovery diode changes from forward to reverse, the recombination speed of carriers in the first recombination zone increases, the reverse recovery peak current decreases, and the recovery speed increases; when a second recombination zone is set in the drift layer, the depths of adjacent second sub-recombination zones in the second conductive type doped layer are different, the interface between the second recombination zone and the second conductive type doped layer increases, and when the external voltage of the fast recovery diode changes from forward to reverse, the recombination speed of carriers in the second recombination zone increases, the reverse recovery peak current decreases, and the reverse recovery speed increases.

[0031] If the first recombination zone and the second recombination zone are formed at the same time, the position of the recombination center increases, which effectively reduces the carrier concentration in the drift layer and the second conductive type doping layer. When the external voltage of the fast recovery diode changes from forward to reverse, the reverse recovery peak current decreases. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0033] Figure 1 A preparation flow chart of a method for preparing a fast recovery diode according to Example 1 of the present invention;

[0034] Figures 2 to 8 This is a schematic diagram of the process structure of a method for preparing a fast recovery diode according to Example 1 of the present invention;

[0035] Figures 9 to 12This is a schematic diagram of the process structure of a method for preparing a fast recovery diode according to Example 3 of the present invention. DETAILED DESCRIPTION

[0036] The technical solution of the present invention will be described clearly and completely below in conjunction with the accompanying drawings. 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 are within the scope of protection of the present invention.

[0037] In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", and "third" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance.

[0038] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0039] In addition, 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.

[0040] Example 1

[0041] This embodiment provides a method for preparing a fast recovery diode. Figure 1 , including the following steps:

[0042] S1: provides drift layer;

[0043] S2: forming a first conductive type semiconductor layer on one side of the drift layer;

[0044] S3: forming a second conductive type doped layer on the other side of the drift layer;

[0045] S4: forming a first recombination zone in the drift layer at the bottom of the second conductive type doped layer, the first recombination zone comprising a plurality of laterally arranged first sub-recombination zones, adjacent first sub-recombination zones having different depths in the drift layer; and / or forming a second recombination zone in the second conductive type doped layer, the second recombination zone comprising a plurality of laterally arranged second sub-recombination zones, adjacent second sub-recombination zones having different depths in the second conductive type doped layer.

[0046] A fast recovery diode provided by the present invention comprises: a first conductive type semiconductor layer; a drift layer located on the first conductive type semiconductor layer; and a second conductive type doped layer located in the drift layer; the fast recovery diode further comprises: a first recombination region, the first recombination region being located in the drift layer at the bottom of the second conductive type doped layer, the first recombination region comprising a plurality of laterally arranged first sub-recombination regions, adjacent first sub-recombination regions having different depths in the drift layer; and / or a second recombination region, the second recombination region being located in the second conductive type doped layer, the second recombination region comprising a plurality of laterally arranged second sub-recombination regions, adjacent second sub-recombination regions having different depths in the second conductive type doped layer. In the present invention, when a first recombination zone is set in the drift layer, the depths of adjacent first sub-recombination zones in the drift layer are different, the interface between the first recombination zone and the drift layer increases, and when the external voltage of the fast recovery diode changes from forward to reverse, the recombination speed of carriers in the first recombination zone increases, the reverse recovery peak current decreases, and the recovery speed increases; when a second recombination zone is set in the drift layer, the depths of adjacent second sub-recombination zones in the second conductive type doped layer are different, the interface between the second recombination zone and the second conductive type doped layer increases, and when the external voltage of the fast recovery diode changes from forward to reverse, the recombination speed of carriers in the second recombination zone increases, the reverse recovery peak current decreases, and the reverse recovery speed increases.

[0047] If the first recombination zone and the second recombination zone are formed at the same time, the position of the recombination center increases, which effectively reduces the carrier concentration in the drift layer and the second conductive type doping layer. When the external voltage of the fast recovery diode changes from forward to reverse, the reverse recovery peak current decreases.

[0048] In this embodiment, the formation of the first recombination area and the second recombination area is taken as an example. Figures 2 to 11 The preparation method of fast recovery diode is introduced in detail.

[0049] refer to Figure 2 , providing a drift layer 100. In this embodiment, the drift layer 100 is an N-type silicon semiconductor. In other embodiments, the drift layer 100 can be made of other materials.

[0050] refer to Figure 3, the drift layer 100 is subjected to surface oxidation treatment to form an initial first oxide layer 101 and an initial second oxide layer 102. The initial first oxide layer 101 is located on one side of the drift layer 100, and the initial second oxide layer 102 is located on the other side of the drift layer 100.

[0051] In one embodiment, the thickness of the initial first oxide layer 101 is 800nm-2000nm, for example, 900nm, 1200nm, 1400nm or 1800nm; the thickness of the initial second oxide layer 102 is 800nm-2000nm, for example, 900nm, 1200nm, 1400nm or 1800nm. Figure 4 , the initial first oxide layer 101 is removed, and after the initial first oxide layer 101 is removed, a first conductive type semiconductor layer 103 is formed on a side of the drift layer 100 facing away from the initial second oxide layer 102 .

[0052] refer to Figure 5 A second conductive type doped layer 105 is formed on a side of the drift layer 100 facing away from the first conductive type semiconductor layer 103 .

[0053] In this embodiment, the method further includes: patterning the initial first oxide layer 101 so that the initial first oxide layer 101 forms a second oxide layer 104 , wherein the second oxide layer 104 has an active area window penetrating the second oxide layer 104 .

[0054] In this embodiment, the step of forming the second conductive type doped layer 105 includes: using the second oxide layer 104 as a mask to inject P-type conductive ions into the drift layer 100 at the bottom of the active area window; then, annealing and activating the P-type conductive ions injected into the drift layer 100 to form the second conductive type doped layer 105.

[0055] The thickness of the second conductive type doped layer 105 is less than the thickness of the drift layer 100. The thickness of the second conductive type doped layer 105 is 5 μm-20 μm, for example, 5 μm, 8 μm, 10 μm or 15 μm.

[0056] In one embodiment, the method further includes: before forming the second conductive type doped layer 105, forming a protective layer on the surface of the drift layer 100 exposed in the active area window, wherein the material of the protective layer includes silicon oxide, and the thickness of the protective layer is less than the thickness of the second oxide layer 104. In one embodiment, the thickness of the protective layer is 30nm-50nm.

[0057] During the process of forming the second conductive type doped layer 105 , the protective layer can protect the surface of the drift layer 100 from being damaged by the ion implantation process.

[0058] In this embodiment, the second conductive type doping layer 105 is doped with P-type conductive ions, such as boron ions, with an implantation dose of 1e 13 atom / cm 2 -1e 15 atom / cm 2 , for example: 1e 13 atom / cm 2 , 5e 13 atom / cm 2 , 1e 14 atom / cm 2 or 5e 14 atom / cm 2 .

[0059] In this embodiment, the temperature used for annealing and activating the P-type conductive ions implanted into the drift layer 100 is 1150° C.-1250° C., for example, 1200° C., and the annealing atmosphere is nitrogen.

[0060] The step of injecting P-type conductive ions into the drift layer 100 at the bottom of the active area window using the second oxide layer 104 as a mask may be one injection or two injections. When two injections are used to inject P-type conductive ions into the drift layer 100, the specific process is as follows: injecting P-type conductive ions into the drift layer 100 at the bottom of the active area window for the first time using the second oxide layer 104 as a mask, and then performing an annealing activation treatment on the P-type conductive ions injected for the first time; then, injecting P-type conductive ions into the surface of the drift layer 100 for the second time using the second oxide layer 104 as a mask, and then performing an annealing activation treatment on the P-type conductive ions injected for the second time.

[0061] The second sub-implantation of P-type conductive ions in the drift layer has the following functions: reducing the contact resistance between the second conductive type doped layer 105 and the subsequent anode structure.

[0062] In this embodiment, after forming the second conductive type doping layer 105, the protective layer is removed. In this embodiment, it also includes: forming a patterned barrier layer on the second conductive type doping layer 105; using the patterned barrier layer as a mask, performing a first ion implantation on the drift layer 100 at the bottom of the second conductive type doping layer 105 to form the first recombination region; using the patterned barrier layer as a mask, performing a second ion implantation on the second conductive type doping layer 105 to form the second recombination region.

[0063] In this embodiment, the method further includes: forming an anode structure on a surface of the second conductive type doped layer 105 facing away from the drift layer, wherein the anode structure is located on a surface of the second conductive type doped layer 105 .

[0064] In this embodiment, specifically, after removing the protective layer, an anode structure is formed.

[0065] In one embodiment, before the first ion implantation and the second ion implantation, an anode structure is formed on a surface of the second conductive type doped layer 105 facing away from the drift layer, and the anode structure is located on the surface of the second conductive type doped layer 105. If the anode structure is formed after the first ion implantation and the second ion implantation, the high temperature generated during the formation of the anode structure may affect the effects of the first ion implantation and the second ion implantation.

[0066] refer to Figure 6 The step of forming the anode structure includes: forming a first anode layer 106 on the surface of the second conductive type doping layer 105.

[0067] The first anode layer 106 also covers the surface of the second oxide layer 104 .

[0068] The material of the first anode layer 106 includes Al.

[0069] refer to Figure 7 The step of forming the anode structure further includes: forming a second anode layer 108 on a surface of a portion of the first anode layer 106 that is away from the second conductive type doped layer 105 .

[0070] The second anode layer 108 and the first anode layer 106 are made of different materials.

[0071] The material of the second anode layer 201 includes one of Ti, Ni or Ag.

[0072] The step of forming the patterned barrier layer 107 on the second conductive type doped layer is: before forming the second anode layer 108 , forming the patterned barrier layer on a surface of a portion of the first anode layer 106 facing away from the second conductive type doped layer 105 .

[0073] The material of the barrier layer 107 is one or more of Si3N4, SRN or SiO2, wherein SRN is silicon-rich silicon nitride. In other embodiments, the material of the barrier layer 107 can be other dielectric materials. The thickness of the barrier layer 107 is 0.5 μm-2 μm, for example, 0.5 μm, 0.7 μm, 0.9 μm or 1.2 μm.

[0074] If the thickness of the blocking layer 107 is less than 0.5 μm, it cannot effectively play the role of blocking the subsequent ion implantation; if the thickness of the blocking layer 107 is greater than 2 μm, the ion implantation cannot pass through the blocking layer 107 .

[0075] After the second anode layer 108 is formed, the second anode layer 108 also covers the patterned barrier layer 107 .

[0076] refer to Figure 8 After forming the second anode layer 108, the patterned barrier layer 107 is used as a mask to perform a first ion implantation on the drift layer 100 at the bottom of the second conductive type doped layer 105 to form the first recombination region 110; the patterned barrier layer 107 is used as a mask to perform a second ion implantation on the second conductive type doped layer 105 to form the second recombination region 111.

[0077] Ions of the first ion implantation and the second ion implantation pass through the anode structure.

[0078] The first recombination region 110 includes a plurality of first sub-recombination regions arranged laterally, and adjacent first sub-recombination regions have different depths in the drift layer.

[0079] The thickness of the first sub-recombination region is 0.2 μm-10 μm, for example, 1 μm, 2 μm, 3 μm or 5 μm. If the thickness of the first sub-recombination region is less than 0.2 μm, the number of generated recombination centers is small, and the reduction of the reverse recovery peak current of the fast recovery diode is small.

[0080] The first recombination region 110 is doped with defect ions, and the defect ions include protons or helium ions.

[0081] The plurality of transversely arranged first sub-composite regions include a first first sub-composite region to an Nth first sub-composite region arranged in sequence, where N is an integer greater than or equal to 2.

[0082] When k is an even number, the central depth of the k-1th first sub-composite area and the central depth of the k+1th first sub-composite area are both lower than the central depth of the kth first sub-composite area, or the central depth of the k-1th first sub-composite area and the central depth of the k+1th first sub-composite area are both higher than the central depth of the kth first sub-composite area, N is an integer greater than or equal to 3, and k is an integer greater than or equal to 2 and less than or equal to N-1.

[0083] When j is an odd number greater than or equal to 3, the central depth of the j-1th first sub-recombination region and the central depth of the j+1th first sub-recombination region are both greater than the central depth of the kth first sub-recombination region, or the central depth of the j-1th first sub-recombination region and the central depth of the j+1th first sub-recombination region are both lower than the central depth of the kth first sub-recombination region, N is an integer greater than or equal to 4, and j is less than or equal to N-1. The second recombination region 111 includes a plurality of second sub-recombination regions arranged laterally, and adjacent second sub-recombination regions have different depths in the second conductive type doped layer 105.

[0084] The thickness of the second sub-recombination region is 0.2 μm-10 μm, for example, 1 μm, 2 μm, 3 μm or 5 μm. If the thickness of the second sub-recombination region is less than 0.2 μm, the number of generated recombination centers is small, and the reduction of the reverse recovery peak current of the fast recovery diode is small.

[0085] The difference between the distance between the bottom surface of the second composite region 111 and the bottom surface of the second conductive type doped layer 105 and the first distance is greater than or equal to 1μm; the first distance is the width of the space charge region in the second conductive type doped layer 105 when the fast recovery diode is reversely broken down.

[0086] If the difference between the distance between the bottom surface of the second recombination region 111 and the bottom surface of the second conductive type doped layer 105 and the first distance is greater than or equal to 1 μm, the reverse leakage current of the fast recovery diode is relatively large.

[0087] The second recombination region 111 is doped with defect ions, and the defect ions include protons or helium ions.

[0088] The plurality of transversely arranged second sub-composite regions include a first second sub-composite region to an Mth second sub-composite region arranged in sequence, where M is an integer greater than or equal to 2.

[0089] When q is an even number, the central depth of the q-1th second sub-composite area and the central depth of the q+1th second sub-composite area are both lower than the central depth of the qth second sub-composite area, or the central depth of the q-1th second sub-composite area and the central depth of the q+1th second sub-composite area are both higher than the central depth of the qth second sub-composite area, M is an integer greater than or equal to 3, and q is an integer greater than or equal to 2 and less than or equal to M-1. When w is an odd number greater than or equal to 3, the central depth of the w-1th second sub-composite area and the central depth of the w+1th second sub-composite area are both higher than the central depth of the wth second sub-composite area, or the central depth of the w-1th second sub-composite area and the central depth of the w+1th second sub-composite area are both lower than the central depth of the wth second sub-composite area, M is an integer greater than or equal to 4, and w is less than or equal to M-1.

[0090] It should be noted that, during the first ion implantation and the second ion implantation, the second oxide layer 104 also serves as a mask.

[0091] In one embodiment, before performing the first ion implantation and the second ion implantation and after forming the anode structure, a passivation layer 109 is formed on a side of the portion of the second oxide layer 104 away from the drift layer. The material of the passivation layer 109 includes a polyimide film. The passivation layer 109 is used to protect the terminal from being contaminated by foreign impurities.

[0092] After forming the first recombination region 110 and the second recombination region 111, electron irradiation is performed on the drift layer 100, the first recombination region 110, the second conductivity type doped layer 105, the second recombination region 111, and the first conductivity type semiconductor layer 103. The electron irradiation has the effect of increasing the number of recombination centers in the drift layer 100, the first recombination region 110, the second conductivity type doped layer 105, the second recombination region 111, and the first conductivity type semiconductor layer 103.

[0093] After electron irradiation, the drift layer 100, the first recombination region 110, the second conductive type doped layer 105, the second recombination region 111 and the first conductive type semiconductor layer 103 are annealed at a temperature of 250° C. to 400° C., for example, 250° C., 300° C., 350° C., 400° C. The annealing process is used to solidify the position of the recombination center and reduce the leakage current of the fast recovery diode.

[0094] In this embodiment, after annealing the drift layer 100, the first recombination region 110, the second conductive type doped layer 105, the second recombination region 111 and the first conductive type semiconductor layer 103, a cathode electrode is formed on the surface of the first conductive type semiconductor layer 103 facing away from the drift layer 100. The cathode electrode material includes one of AlTiNiAg, TiNiAg, AlTiAu and AlTiPbAu.

[0095] It should be noted that the step of forming the first conductive type semiconductor layer 103 may be performed before forming the second conductive type doping layer 105 , or may be performed after forming the second conductive type doping layer 105 .

[0096] In this embodiment, before forming the second conductive type doped layer 105, it also includes: thinning the back side of the drift layer 100; after thinning the back side of the drift layer, performing a third ion implantation on the back side of the drift layer, and performing laser annealing on the third ion implanted area to form an ohmic contact layer.

[0097] The third ions include phosphorus ions, which function as N-type doping ions.

[0098] In this embodiment, the step of forming the first conductive type semiconductor layer includes: performing a fourth ion implantation in a portion of the drift layer 100 adjacent to the ohmic contact layer; after performing the fourth ion implantation, annealing the region implanted with the fourth ion to form the first conductive type semiconductor layer 103. The first conductive type semiconductor layer 103 contains protons or helium ions.

[0099] In this embodiment, the fourth ion implantation may be performed multiple times, and the implantation depths of the multiple fourth ion implantations are different. For example, the fourth ion implantation may be performed 1 to 5 times.

[0100] The fourth ion implantation implants protons or helium ions into a portion of the drift layer 100 .

[0101] After the fourth ion implantation, the fourth ion implanted region is annealed at a temperature of 300° C.-550° C., for example, 300° C., 350° C., 400° C. or 450° C. The purpose of the annealing is to anneal the implanted protons or helium ions to achieve an N-type doping effect, thereby reducing the conduction voltage drop of the fast recovery diode and shortening the electric field expansion width of the fast recovery diode.

[0102] The first conductive type semiconductor layer 103 has a width of 1 μm-20 μm, for example, 1 μm, 5 μm, 10 μm or 20 μm. If it is less than 1 μm, it cannot effectively reduce the conduction voltage drop of the device and shorten the electric field expansion width.

[0103] When the fourth ion injection can be performed multiple times, in the first conductive type semiconductor layer 103, the first conductive type ion concentration fluctuates in the depth direction of the first conductive type semiconductor layer 103, and the peak decreases sequentially from the surface of the first conductive type semiconductor layer 103 facing away from the drift layer 100, which can effectively avoid the diode from tripping during reverse recovery and improve stability.

[0104] In other embodiments, the step of forming the first conductive type semiconductor layer 103 may be: placing the back side of the drift layer 100 in a chamber with a POCl3 atmosphere, at 1100°C-1300°C, for example, 1150°C, 1200°C, 1250°C or 1300°C, so that P in the POCl3 diffuses into the back side of the drift layer 100 to form the first conductive type semiconductor layer 103. If the first conductive type semiconductor layer 103 is formed by this step, then in the first conductive type semiconductor layer 103, the concentration of the first conductive type ions in the first conductive type semiconductor layer 103 gradually decreases from the side of the first conductive type semiconductor layer facing away from the drift layer to the side facing the drift layer.

[0105] If the P in POCl3 is diffused into the back side of the drift layer 100 to form the first conductive type semiconductor layer 103, the formation of the first conductive type semiconductor layer 103 needs to be completed before the first ion implantation and the second ion implantation. If the formation of the first conductive type semiconductor layer 103 is completed after the first ion implantation and the second ion implantation, the diffusion of the P in POCl3 into the back side of the drift layer 100 during the formation of the first conductive type semiconductor layer 103 requires a higher temperature, which may destroy the implantation effects of the first ion implantation and the second ion implantation.

[0106] Example 2

[0107] This embodiment provides a fast recovery diode, referring to Figure 8 , including: a first conductive type semiconductor layer 103; a drift layer 100 located on the first conductive type semiconductor layer 103; a second conductive type doped layer 105 located in the drift layer 100; a first recombination region 110, the first recombination region is located in the drift layer 100 at the bottom of the second conductive type doped layer 105, the first recombination region 110 includes a plurality of laterally arranged first sub-recombination regions, and adjacent first sub-recombination regions have different depths in the drift layer 100; and / or, a second recombination region 111, the second recombination region 111 is located in the second conductive type doped layer 105, the second recombination region 111 includes a plurality of laterally arranged second sub-recombination regions, and adjacent second sub-recombination regions have different depths in the second conductive type doped layer 105.

[0108] A fast recovery diode provided by the present invention comprises: a first conductive type semiconductor layer 103; a drift layer 100 located on the first conductive type semiconductor layer 103; a second conductive type doped layer 105 located in the drift layer 100; the fast recovery diode further comprises: a first recombination region 110, the first recombination region 110 is located in the drift layer at the bottom of the second conductive type doped layer 105, the first recombination region 110 comprises a plurality of transversely arranged first sub-recombination regions, adjacent first sub-recombination regions have different depths in the drift layer; and / or a second recombination region 111, the second recombination region 111 is located in the second conductive type doped layer 105, the second recombination region 111 comprises a plurality of transversely arranged second sub-recombination regions, adjacent second sub-recombination regions have different depths in the second conductive type doped layer 105. In the present invention, when a first recombination region 110 is provided in the drift layer 100, the depths of adjacent first sub-recombination regions in the drift layer 100 are different, the interface between the first recombination region 110 and the drift layer 100 increases, and when the external voltage of the fast recovery diode changes from forward to reverse, the recombination velocity of carriers in the first recombination region 110 increases, the reverse recovery peak current decreases, and the recovery velocity increases; when a second recombination region 111 is provided in the drift layer 100, the depths of adjacent second sub-recombination regions in the second conductive type doped layer 105 are different, the interface between the second recombination region 111 and the second conductive type doped layer 105 increases, and when the external voltage of the fast recovery diode changes from forward to reverse, the recombination velocity of carriers in the second recombination region 111 increases, the reverse recovery peak current decreases, and the reverse recovery velocity increases.

[0109] If the first recombination region 110 and the second recombination region 111 are formed at the same time, the position of the recombination center increases, which effectively reduces the carrier concentration in the drift layer 100 and the second conductive type doped layer 105. When the external voltage of the fast recovery diode changes from forward to reverse, the reverse recovery peak current decreases.

[0110] The plurality of transversely arranged first sub-composite areas include a first first sub-composite area to an Nth first sub-composite area arranged in sequence, N being an integer greater than or equal to 2; when k is an even number, the center depth of the k-1th first sub-composite area and the center depth of the k+1th first sub-composite area are both lower than the center depth of the kth first sub-composite area, or, the center depth of the k-1th first sub-composite area and the center depth of the k+1th first sub-composite area are both higher than the center depth of the kth first sub-composite area, N is an integer greater than or equal to 3, and k is an integer greater than or equal to 2 and less than or equal to N-1.

[0111] When j is an odd number greater than or equal to 3, the central depth of the j-1th first sub-composite area and the central depth of the j+1th first sub-composite area are both higher than the central depth of the kth first sub-composite area, or the central depth of the j-1th first sub-composite area and the central depth of the j+1th first sub-composite area are both lower than the central depth of the kth first sub-composite area, N is an integer greater than or equal to 4, and j is less than or equal to N-1.

[0112] The thickness of the first sub-recombination region is 0.2 μm-10 μm, for example, 1 μm, 2 μm, 3 μm or 5 μm.

[0113] The first recombination region 110 is doped with defect ions, and the defect ions include protons or helium ions.

[0114] The plurality of transversely arranged second sub-composite regions include a first second sub-composite region to an Mth second sub-composite region arranged in sequence, where M is an integer greater than or equal to 2.

[0115] When q is an even number, the central depth of the q-1th second sub-composite area and the central depth of the q+1th second sub-composite area are both lower than the central depth of the qth second sub-composite area, or the central depth of the q-1th second sub-composite area and the central depth of the q+1th second sub-composite area are both higher than the central depth of the qth second sub-composite area, M is an integer greater than or equal to 3, and q is an integer greater than or equal to 2 and less than or equal to M-1.

[0116] When w is an odd number greater than or equal to 3, the central depth of the w-1th second sub-composite area and the central depth of the w+1th second sub-composite area are both higher than the central depth of the wth second sub-composite area, or the central depth of the w-1th second sub-composite area and the central depth of the w+1th second sub-composite area are both lower than the central depth of the wth second sub-composite area, M is an integer greater than or equal to 4, and w is less than or equal to M-1.

[0117] The thickness of the second sub-recombination region is 0.2 μm-10 μm, for example, 1 μm, 2 μm, 3 μm or 5 μm.

[0118] The difference between the distance between the bottom surface of the second composite region 111 and the bottom surface of the second conductive type doped layer 105 and the first distance is greater than or equal to 1μm; the first distance is the width of the space charge region in the second conductive type doped layer 105 when the fast recovery diode is reversely broken down.

[0119] The second recombination region 111 is doped with defect ions, where the defect ions include protons or helium ions.

[0120] The fast recovery diode further includes: an anode structure, and the anode structure is located on the surface of the second conductive type doped layer 105 .

[0121] The anode structure includes: a first anode layer 106, located on the surface of the second conductive type doped layer 105; a second anode layer 108, located on the surface of a portion of the first anode layer 106 facing away from the second conductive type doped layer 105, and the second anode layer 108 is distinguished from the characteristic layer of the first anode layer in that the metal material is different.

[0122] The fast recovery diode further includes: a barrier layer 107 located on a surface of a portion of the first anode layer 106 facing away from the second conductive type doped layer 105 ; and the second anode layer 108 also covers the barrier layer 107 .

[0123] The fast recovery diode further includes: a second oxide layer 104 , which is located on a surface of a portion of the drift layer 100 that is away from the first conductive type semiconductor layer 103 , and has an active region window penetrating the second oxide layer 104 .

[0124] The passivation layer 109 is located on a side of the second oxide layer 104 away from the drift layer 100. The material of the passivation layer 109 includes a polyimide film, and the passivation layer 109 is used to protect the terminal from being contaminated by foreign impurities.

[0125] The fast recovery diode further includes: a cathode electrode, which is located on a surface of the first conductive type semiconductor layer 103 facing away from the drift layer 100, and the cathode electrode material includes one of AlTiNiAg, TiNiAg, AlTiAu and AlTiPbAu.

[0126] In one embodiment, the first conductive type semiconductor layer is doped with protons or helium ions.

[0127] It should be noted that, in other embodiments, the first conductive type semiconductor layer may not be doped with protons or helium ions.

[0128] Example 3

[0129] refer to Figures 2 to 6 The preparation method of the fast recovery diode of Example 1 is described.

[0130] refer to Fig. 9 , Fig. 9 For Figure 6 Based on the schematic diagram of FIG. 1 , the step of forming the anode structure includes: forming a second anode layer 201 on a surface of a portion of the first anode layer 106 which is away from the second conductive type doped layer 105 .

[0131] The second anode layer 108 and the first anode layer 106 are made of different materials.

[0132] The material of the second anode layer 201 includes one of Ti, Ni or Ag.

[0133] refer to Fig.10 , forming a patterned barrier layer 202 on the second conductive type doped layer, the steps are: forming a patterned barrier layer 202 on a surface of a portion of the second anode layer 201 away from the second conductive type doped layer 105 .

[0134] The material of the blocking layer 202 includes a patterned photoresist layer or a patterned molybdenum sheet. The thickness of the blocking layer 202 is 0.5 μm-2 μm, for example, 0.5 μm, 0.7 μm, 0.9 μm or 1.2 μm.

[0135] If the thickness of the blocking layer 202 is less than 0.5 μm, it cannot effectively serve as a barrier for subsequent ion implantation; if the thickness of the blocking layer 202 is greater than 2 μm, ion implantation cannot pass through the blocking layer 202 .

[0136] refer to Fig.11 After forming a patterned barrier layer 202, the patterned barrier layer 202 is used as a mask to perform a first ion implantation on the drift layer 100 at the bottom of the second conductive type doped layer 105 to form the first recombination region 203; the patterned barrier layer 202 is used as a mask to perform a second ion implantation on the second conductive type doped layer 105 to form the second recombination region 204.

[0137] Ions of the first ion implantation and the second ion implantation pass through the anode structure.

[0138] It should be noted that, during the first ion implantation and the second ion implantation, the second oxide layer 104 also serves as a mask.

[0139] In one embodiment, before performing the first ion implantation and the second ion implantation and after forming the anode structure, a passivation layer 205 is formed on a side of the portion of the second oxide layer 104 away from the drift layer 100, wherein the material of the passivation layer 205 includes a polyimide film, and the passivation layer 205 is used to protect the terminal from being contaminated by foreign impurities.

[0140] After forming the first recombination region 203 and the second recombination region 204, electron irradiation is performed on the drift layer 100, the first recombination region 203, the second conductivity type doped layer 105, the second recombination region 204 and the first conductivity type semiconductor layer 103. The electron irradiation has the effect of increasing the number of recombination centers in the drift layer 100, the first recombination region 203, the second conductivity type doped layer 105, the second recombination region 204 and the first conductivity type semiconductor layer 103.

[0141] After electron irradiation, the drift layer 100, the first recombination region 203, the second conductive type doped layer 105, the second recombination region 204 and the first conductive type semiconductor layer 103 are annealed at a temperature of 250° C. to 400° C., for example, 250° C., 300° C., 350° C. or 400° C. The annealing process is used to solidify the position of the recombination center and reduce the leakage current of the fast recovery diode.

[0142] refer to Fig.12 After the drift layer 100 , the first recombination region 203 , the second conductive type doped layer 105 , the second recombination region 204 and the first conductive type semiconductor layer 103 are annealed, the barrier layer 202 is removed.

[0143] In this embodiment, after removing the barrier layer 202, a cathode electrode is formed on the surface of the first conductive type semiconductor layer 103 facing away from the drift layer 100. The cathode electrode material includes one of AlTiNiAg, TiNiAg, AlTiAu and AlTiPbAu.

[0144] It should be noted that the step of forming the first conductive type semiconductor layer 103 may be performed before forming the second conductive type doping layer 105 , or may be performed after forming the second conductive type doping layer 105 .

[0145] It should be noted that the step of forming the first conductive type semiconductor layer 103 may be performed before forming the second conductive type doping layer 105 , or may be performed after forming the second conductive type doping layer 105 .

[0146] In this embodiment, before forming the second conductive type doped layer 105, it also includes: thinning the back side of the drift layer 100; after thinning the back side of the drift layer, performing a third ion implantation on the back side of the drift layer, and performing laser annealing on the third ion implanted area to form an ohmic contact layer.

[0147] The third ions include phosphorus ions, which function as N-type doping ions.

[0148] In this embodiment, the step of forming the first conductive type semiconductor layer includes: performing a fourth ion implantation in a portion of the drift layer 100 adjacent to the ohmic contact layer; after performing the fourth ion implantation, annealing the region implanted with the fourth ion to form the first conductive type semiconductor layer 103. The first conductive type semiconductor layer 103 contains protons or helium ions.

[0149] In this embodiment, the fourth ion implantation may be performed multiple times, and the implantation depths of the multiple fourth ion implantations are different. For example, the fourth ion implantation may be performed 1 to 5 times.

[0150] The fourth ion implantation implants protons or helium ions into a portion of the drift layer 100 .

[0151] After the fourth ion implantation, the fourth ion implanted region is annealed at a temperature of 300° C.-550° C., for example, 300° C., 350° C., 400° C. or 450° C. The purpose of the annealing is to anneal the implanted protons or helium ions to achieve an N-type doping effect, thereby reducing the conduction voltage drop of the fast recovery diode and shortening the electric field expansion width of the fast recovery diode.

[0152] The first conductive type semiconductor layer 103 has a width of 1 μm-20 μm, for example, 1 μm, 5 μm, 10 μm or 20 μm. If it is less than 1 μm, it cannot effectively reduce the conduction voltage drop of the device and shorten the electric field expansion width.

[0153] When the fourth ion injection can be performed multiple times, in the first conductive type semiconductor layer 103, the first conductive type ion concentration fluctuates in the depth direction of the first conductive type semiconductor layer 103, and the peak decreases sequentially from the surface of the first conductive type semiconductor layer 103 facing away from the drift layer 100, which can effectively avoid the diode from tripping during reverse recovery and improve stability.

[0154] In other embodiments, the step of forming the first conductive type semiconductor layer 103 may be: placing the back side of the drift layer 100 in a chamber with a POCl3 atmosphere, at 1100°C-1300°C, for example, 1150°C, 1200°C, 1250°C or 1300°C, so that P in the POCl3 diffuses into the back side of the drift layer 100 to form the first conductive type semiconductor layer 103. If the first conductive type semiconductor layer 103 is formed by this step, then in the first conductive type semiconductor layer 103, the concentration of the first conductive type ions in the first conductive type semiconductor layer 103 gradually decreases from the side of the first conductive type semiconductor layer facing away from the drift layer to the side facing the drift layer.

[0155] If the P in POCl3 is diffused into the back side of the drift layer 100 to form the first conductive type semiconductor layer 103, the formation of the first conductive type semiconductor layer 103 needs to be completed before the first ion implantation and the second ion implantation. If the formation of the first conductive type semiconductor layer 103 is completed after the first ion implantation and the second ion implantation, the diffusion of the P in POCl3 into the back side of the drift layer 100 during the formation of the first conductive type semiconductor layer 103 requires a higher temperature, which may destroy the implantation effects of the first ion implantation and the second ion implantation.

[0156] Example 4

[0157] This embodiment provides a fast recovery diode, referring to Fig.12 , which is different from the fast recovery diode in Example 2 in that: the first anode layer above the second conductive type doped layer is in complete contact with the second anode layer.

[0158] Obviously, the above embodiments are merely examples for the purpose of clear explanation, and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived therefrom are still within the scope of protection of the invention.

Claims

1. A fast recovery diode, characterized in that: include: a first conductivity type semiconductor layer; a drift layer located on the first conductive type semiconductor layer; a second conductivity type doped layer located in the drift layer; The fast recovery diode also includes: a first recombination region, the first recombination region is located in the drift layer at the bottom of the second conductive type doping layer, the first recombination region includes a plurality of laterally arranged first sub-recombination regions, adjacent first sub-recombination regions have different depths in the drift layer, the first recombination region is doped with defective ions, and the defective ions include protons or helium ions; and / or, a second recombination region, the second recombination region is located in the second conductive type doping layer, the second recombination region includes a plurality of laterally arranged second sub-recombination regions, adjacent second sub-recombination regions have different depths in the second conductive type doping layer.

2. The fast recovery diode according to claim 1, characterized in that: The plurality of transversely arranged first sub-composite areas include a first first sub-composite area to an Nth first sub-composite area arranged in sequence, where N is an integer greater than or equal to 2; When k is an even number, the central depth of the k-1th first sub-composite area and the central depth of the k+1th first sub-composite area are both lower than the central depth of the kth first sub-composite area, or the central depth of the k-1th first sub-composite area and the central depth of the k+1th first sub-composite area are both higher than the central depth of the kth first sub-composite area, N is an integer greater than or equal to 3, and k is an integer greater than or equal to 2 and less than or equal to N-1.

3. The fast recovery diode according to claim 2, characterized in that: When j is an odd number greater than or equal to 3, the central depth of the j-1th first sub-composite area and the central depth of the j+1th first sub-composite area are both higher than the central depth of the kth first sub-composite area, or the central depth of the j-1th first sub-composite area and the central depth of the j+1th first sub-composite area are both lower than the central depth of the kth first sub-composite area, N is an integer greater than or equal to 4, and j is less than or equal to N-1.

4. The fast recovery diode according to claim 1, characterized in that: The thickness of the first sub-recombination region is 0.2 μm to 10 μm.

5. The fast recovery diode according to claim 1, characterized in that: The plurality of transversely arranged second sub-composite areas include a first second sub-composite area to an Mth second sub-composite area arranged in sequence, where M is an integer greater than or equal to 2; When q is an even number, the central depth of the q-1th second sub-composite area and the central depth of the q+1th second sub-composite area are both lower than the central depth of the qth second sub-composite area, or the central depth of the q-1th second sub-composite area and the central depth of the q+1th second sub-composite area are both higher than the central depth of the qth second sub-composite area, M is an integer greater than or equal to 3, and q is an integer greater than or equal to 2 and less than or equal to M-1.

6. The fast recovery diode according to claim 5, characterized in that: When w is an odd number greater than or equal to 3, the central depth of the w-1th second sub-composite area and the central depth of the w+1th second sub-composite area are both higher than the central depth of the wth second sub-composite area, or the central depth of the w-1th second sub-composite area and the central depth of the w+1th second sub-composite area are both lower than the central depth of the wth second sub-composite area, M is an integer greater than or equal to 4, and w is less than or equal to M-1.

7. The fast recovery diode according to claim 1, characterized in that: The thickness of the second sub-recombination region is 0.2 μm to 10 μm.

8. The fast recovery diode according to claim 1, characterized in that: A difference between a distance between a bottom surface of the second recombination region and a bottom surface of the second conductive type doped layer and the first distance is greater than or equal to 1 μm; The first distance is the width of the space charge region in the second conductivity type doped layer when the fast recovery diode is reversely broken down.

9. The fast recovery diode according to claim 1, characterized in that: The second recombination zone is doped with defect ions, wherein the defect ions include protons or helium ions.

10. The fast recovery diode according to claim 1, characterized in that: Also includes: An anode structure is located on the surface of the second conductive type doped layer.

11. The fast recovery diode according to claim 10, characterized in that: The anode structure includes: a first anode layer located on the surface of the second conductive type doped layer; a second anode layer located on at least a portion of the first anode layer on a surface facing away from the second conductive type doped layer, and the second anode layer is made of a different material from the first anode layer.

12. The fast recovery diode according to claim 11, characterized in that: Also includes: A barrier layer is located on a surface of a portion of the first anode layer that is away from the second conductive type doping layer; The second anode layer also covers the barrier layer.

13. The fast recovery diode according to claim 1, characterized in that: The first conductive type semiconductor layer is doped with protons or helium ions.

14. A method for preparing a fast recovery diode, characterized in that: include: Providing a drift layer; forming a first conductive type semiconductor layer on one side of the drift layer; forming a second conductive type doped layer on the other side of the drift layer; A first recombination zone is formed in the drift layer at the bottom of the second conductive type doped layer, the first recombination zone includes a plurality of laterally arranged first sub-recombination zones, and adjacent first sub-recombination zones have different depths in the drift layer; and / or a second recombination zone is formed in the second conductive type doped layer, the second recombination zone includes a plurality of laterally arranged second sub-recombination zones, and adjacent second sub-recombination zones have different depths in the second conductive type doped layer.

15. The method for preparing a fast recovery diode according to claim 14, characterized in that: Also includes: Before forming the first recombination region and the second recombination region, forming a patterned barrier layer on the second conductive type doped layer; Using the patterned barrier layer as a mask, performing a first ion implantation on the drift layer at the bottom of the second conductive type doping layer to form the first recombination region; Using the patterned barrier layer as a mask, a second ion implantation is performed on the second conductive type doped layer to form the second recombination region.

16. The method for preparing a fast recovery diode according to claim 15, characterized in that: Also includes: Before performing the first ion implantation and the second ion implantation, an anode structure is formed on a surface of the second conductive type doped layer facing away from the drift layer, and the anode structure is located on a surface of the second conductive type doped layer.

17. The method for preparing a fast recovery diode according to claim 16, characterized in that: The steps of forming a patterned barrier layer on the second conductive type doped layer are: forming a patterned barrier layer on the side of the anode structure away from the drift layer; ions of the first ion implantation and the second ion implantation pass through the anode structure; after forming the first recombination area and the second recombination area, removing the patterned barrier layer.

18. The method for preparing a fast recovery diode according to claim 16, characterized in that: The steps of forming the anode structure include: forming a first anode layer on the surface of the second conductive type doped layer; forming a second anode layer on the surface of a part of the first anode layer away from the second conductive type doped layer, the second anode layer and the first anode layer having a different material; the steps of forming a patterned barrier layer on the drift layer include: before forming the second anode layer, forming a patterned barrier layer on the surface of a part of the first anode layer away from the second conductive type doped layer; after forming the second anode layer, the second anode layer also covers the patterned barrier layer; after forming the second anode layer, performing a first ion implantation and a second ion implantation.

19. The method for preparing a fast recovery diode according to claim 14, characterized in that: The step of forming the first conductive type semiconductor layer is performed before forming the second conductive type doped layer, or after forming the second conductive type doped layer.

20. The method for preparing a fast recovery diode according to claim 19, characterized in that: Also includes: thinning the back side of the drift layer; After the back side of the drift layer is thinned, a third ion implantation is performed on the back side of the drift layer, and a laser annealing process is performed on the region implanted with the third ions to form an ohmic contact layer.

21. The method for preparing a fast recovery diode according to claim 19, characterized in that: The step of forming the first conductive type semiconductor layer includes: performing a fourth ion implantation in a portion of the drift layer adjacent to the ohmic contact layer; after performing the fourth ion implantation, annealing the fourth ion implanted area to form a first conductive type semiconductor layer, wherein the first conductive type semiconductor layer has protons or helium ions.

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