A fast recovery diode and a method for manufacturing the same

Abstract

The present application provides a fast recovery diode and a manufacturing method thereof. The fast recovery diode comprises a first conductive type substrate and a first conductive type drift layer. The first conductive type drift layer is located above the first conductive type substrate. The first conductive type drift layer comprises a first region and a second region. The second region is located between the first region and the first conductive type substrate. In the direction from the first conductive type drift layer to the first conductive type substrate, the doping concentration of the first region gradually decreases; there is a high doping concentration peak in the second region, and the doping concentration of the high doping concentration peak is higher than the lowest value of the doping concentration of the first region. The fast recovery diode, based on the first conductive type drift layer, improves the distribution and movement of carriers in the forward conduction and reverse recovery process, reduces switching losses and electromagnetic interference, and improves the reverse recovery characteristics under the full current state, thereby improving reliability. The manufacturing method has simple manufacturing steps.

Description

Technical Field

[0001] The present application belongs to the field of semiconductor devices and manufacturing technology, and relates to a fast recovery diode and a manufacturing method thereof. Background Art

[0002] Fast Recovery Diode (FRD) is a semiconductor device that can switch quickly in high-frequency applications and is widely used in the field of power electronics. Compared with ordinary diodes, FRD has a shorter reverse recovery time and lower forward resistance, and can control the flow of current more efficiently.

[0003] With the rapid development of modern energy, FRD is gradually being applied to the field of energy, such as energy vehicles, photovoltaic wind power, etc. In these application scenarios, FRD is not only responsible for the freewheeling function, but also directly affects the overall performance and stability of the system. The key performance indicators of FRD include reverse recovery time and reverse recovery softness. Among them, reverse recovery time refers to the time required to switch from the on state to the reverse blocking state. A shorter reverse recovery time can effectively reduce switching losses and improve system efficiency. Reverse recovery softness refers to the ratio of the rise time to the fall time of the reverse recovery current during the reverse recovery process. A higher reverse recovery softness usually means better system safety.

[0004] However, the reverse recovery time and reverse recovery softness of FRD are usually difficult to balance. The longer the reverse recovery time, the higher the reverse recovery softness, but this will also cause some problems. For example, long reverse recovery will increase switching losses, because more energy is consumed during each switching process, reducing the energy efficiency of the system. The increased loss will cause device heating problems, which may cause temperature rise, thereby affecting the service life and stability of the FRD. For example, although a reverse recovery time that is too short can help reduce switching losses, it may lead to insufficient reverse recovery softness, thereby causing electromagnetic interference (EMI) problems. Since the rapid change of current can cause a sudden change in voltage, this sudden change may affect other components in the system and cause instability (especially at low currents, sudden changes in current can cause serious system problems). Therefore, in the design stage of FRD, the reverse recovery time and reverse recovery softness of FRD must be comprehensively considered so that the two can reach a balance, thereby optimizing the working performance of FRD. However, in the actual application of FRD, it was found that the reverse recovery process of the fast recovery diode was significantly different under the rated current and the small current (where the small current is less than the rated current). For example, when the FRD is at the rated current, it has better reverse recovery softness to achieve a smoother reverse recovery process, thereby reducing switching losses and electromagnetic interference. When the current is small or the load is low, the reverse recovery characteristics of the FRD will change significantly. For example, it will show a sudden change in the current waveform, which will cause a series of problems and affect the reliability and stability of the FRD.

[0005] Therefore, how to provide a fast recovery diode and a manufacturing method thereof to improve the working performance and reliability of the FRD has become an important technical problem that needs to be solved urgently by those skilled in the art.

[0006] It should be noted that the above introduction to the technical background is only for the convenience of providing a clear and complete description of the technical solutions of the present application and for the convenience of understanding by those skilled in the art. It cannot be considered that the above technical solutions are well known to those skilled in the art simply because they are described in the background technology section of the present application. Summary of the invention

[0007] In view of the above-mentioned shortcomings of the prior art, the purpose of the present application is to provide a fast recovery diode and a manufacturing method thereof, so as to solve the problem that the working performance and reliability of FRD in the prior art need to be improved.

[0008] To achieve the above objectives and other related objectives, in a first aspect, the present application provides a fast recovery diode, comprising:

[0009] a first conductive type substrate;

[0010] A first conductive type drift layer is located above the first conductive type substrate, the first conductive type drift layer includes a first region and a second region, the second region is located between the first region and the first conductive type substrate, wherein in the direction from the first conductive type drift layer to the first conductive type substrate, the doping concentration of the first region gradually decreases; and there is a high doping concentration peak in the second region, and the doping concentration of the high doping concentration peak is higher than the lowest value of the doping concentration of the first region.

[0011] Optionally, the doping concentration range of the first region is 1e14 cm -3 ~7e14 cm -3 , the doping concentration of the high doping concentration peak is less than the maximum doping concentration of the first region.

[0012] Optionally, the distance between the high doping concentration peak and the first conductive type substrate is in the range of 5 μm to 10 μm; and / or,

[0013] A ratio between a thickness of the first region and a thickness of the first conductive type drift layer is 85% to 95%.

[0014] Optionally, the first region includes multiple epitaxial layers, and in the direction from the first conductive type drift layer to the first conductive type substrate, the resistivity of the multiple epitaxial layers gradually increases, and the thickness of the multiple epitaxial layers gradually increases.

[0015] Optionally, the first region includes a diffusion layer, and in a direction from the first conductive type drift layer to the first conductive type substrate, a distribution concentration of impurity elements in the diffusion layer gradually decreases.

[0016] Optionally, the second region includes a doped epitaxial layer having the high doping concentration peak; or, the second region includes a diffusion injection layer having a hydrogen ion injection region, and the hydrogen ion injection region constitutes the high doping concentration peak.

[0017] In a second aspect, the present application also provides a method for manufacturing a fast recovery diode, comprising the following steps:

[0018] providing a first conductive type substrate;

[0019] forming a first conductive type drift layer on the first conductive type substrate, wherein the first conductive type drift layer comprises a first region and a second region, wherein the second region is located between the first region and the first conductive type substrate;

[0020] Among them, in the direction from the first conductive type drift layer to the first conductive type substrate, the doping concentration of the first region gradually decreases; there is a high doping concentration peak in the second region, and the doping concentration of the high doping concentration peak is higher than the maximum value of the doping concentration of the first region.

[0021] Optionally, forming the first conductive type drift layer on the first conductive type substrate comprises the following steps:

[0022] forming a first semiconductor layer on the first conductive type substrate;

[0023] forming a second semiconductor layer on the first semiconductor layer; wherein,

[0024] The method of forming the first semiconductor layer on the first conductive type substrate is the same as or different from the method of forming the second semiconductor layer on the first semiconductor layer.

[0025] Optionally, the first semiconductor layer and the second semiconductor layer constitute the first conductive type drift layer, and the manufacturing method comprises the following steps:

[0026] Forming a first semiconductor layer on the first conductive type substrate based on an epitaxial growth method, wherein the first semiconductor layer has the high doping concentration peak;

[0027] A second semiconductor layer is formed on the first semiconductor layer based on an epitaxial growth method. The second semiconductor layer includes multiple epitaxial layers. In a direction from the second semiconductor layer to the first semiconductor layer, the doping concentration of the multiple epitaxial layers gradually decreases.

[0028] Optionally, the manufacturing method further comprises the following steps:

[0029] Diffusion is performed based on a side of the second semiconductor layer away from the first semiconductor layer;

[0030] Performing annealing so that the elements diffused into the second semiconductor layer and the first semiconductor layer are distributed in a predetermined manner;

[0031] Hydrogen ion implantation is performed based on a surface of the first conductive type substrate away from the first semiconductor layer to form the high doping concentration peak in the first semiconductor layer.

[0032] As described above, the fast recovery diode of the present application, based on the design of the doping concentration distribution in the first conductive type drift layer, forms a gradual electric field in the first conductive type drift layer and cuts off the electric field at the high doping concentration peak, thereby improving the distribution and movement of carriers during forward conduction and reverse recovery, reducing switching losses and reducing electromagnetic interference, and also improving the reverse recovery characteristics of the fast recovery diode under the full current state, and improving the reliability of the fast recovery diode. The method for manufacturing the fast recovery diode of the present application can produce a fast recovery diode with improved working performance and reliability, especially improved reverse recovery characteristics under the full current state, and the manufacturing steps are simple, and the manufacturing method of the first conductive type drift layer can be flexibly selected based on actual needs, which is suitable for large-scale production. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 It is a schematic diagram of the structure of a fast recovery diode in the related art.

[0034] Figure 2 Shown is a schematic diagram of the structure of a fast recovery diode provided in an embodiment of the present application.

[0035] Figure 3 Shown is a schematic diagram of the doping concentration distribution of the fast recovery diode provided in an embodiment of the present application.

[0036] Figure 4 Shown is a schematic diagram comparing the reverse recovery characteristics of the fast recovery diodes provided in the embodiment of the present application and the comparative example.

[0037] Description of reference numerals:

[0038] 101 - cathode layer, 102 - buffer layer, 103 - drift region, 104 - anode layer;

[0039] 10 - first conductivity type substrate; 20 - first conductivity type drift layer, 21 - first region, 22 - second region, 220 - high doping concentration peak; 30 - second conductivity type semiconductor layer. DETAILED DESCRIPTION

[0040] The following describes the implementation of the present application through specific examples, and those skilled in the art can easily understand other advantages and effects of the present application from the contents disclosed in this specification. The present application can also be implemented or applied through other different specific implementations, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present application.

[0041] See also Figures 1 to 4It should be noted that the illustrations provided in this embodiment are only used to illustrate the basic concept of the present application in a schematic manner, and the drawings only show components related to the present application rather than being drawn according to the number, shape and size of components in actual implementation. In actual implementation, the type, quantity and proportion of each component may be changed arbitrarily, and the component layout may also be more complicated.

[0042] After analyzing the problem mentioned in the background technology that the two parameters of FRD reverse recovery time and reverse recovery softness have been comprehensively balanced in the FRD design stage, but there are significant differences between rated current and low current in actual application, it is found that the main application scenarios of FRD include switching power supplies, PWM pulse width modulators, inverters and other electronic circuits. These application scenarios usually involve large currents and high-frequency switching operations, that is, optimizing the reverse recovery performance of FRD under large currents can better meet market demand. Therefore, in the relevant technology, the performance optimization of FRD is basically focused on the optimization and balance of reverse recovery time and reverse recovery softness under rated current state, and little attention is paid to the fact that under low current state, the performance of FRD may be very different from or even opposite to that under rated current. For example, please refer to Figure 1 , Figure 1 A schematic diagram of the structure of a fast recovery diode in the related art is shown, and the fast recovery diode includes a cathode layer 101, a buffer layer 102, a drift region 103 and an anode layer 104 stacked in sequence, and the reverse recovery characteristics of the FRD are improved by the setting of the buffer layer 102. However, in actual application, in some application scenarios, there will be a situation where the FRD works in a low current state most of the time, for example, in the field of new energy vehicles. Therefore, the reverse recovery softness of the FRD under low current is also crucial to the reliability and stability of the electrical system. Among them, the rated current is tens of amperes to hundreds of amperes, and the low current is several milliamperes to several amperes. For example, the rated current ranges from 10A to 375A, and the low current is 1mA to 10A.

[0043] After analyzing the reverse recovery characteristics of FRD under different current states, it is found that in practical applications, the carrier recombination process of FRD is relatively uneven under low current conditions compared to the rated current state. This unevenness will cause more dramatic changes in reverse recovery time and tail current. Due to the violent oscillation of the reverse recovery tail current (that is, the reverse recovery current switches back and forth between forward and reverse), the current and voltage will change rapidly, thereby causing electromagnetic interference. This not only affects the stability of the system, but may also cause overvoltage and overcurrent phenomena, and increase switching losses and heat loads. These excessive losses not only increase the difficulty of thermal management, but may also cause overheating, accelerated aging, and even failure of the fast recovery diode. Therefore, the current fluctuations caused by the oscillation of FRD under low current conditions will have a significant impact on the electrical safety, reliability, and efficiency of the system.

[0044] Based on the above content, an embodiment of the present application provides a fast recovery diode, which mainly reduces reverse recovery loss and improves current oscillation problems under small currents through the doping concentration distribution in the drift region of the fast recovery diode, thereby improving the working performance and reliability of the FRD.

[0045] The present application embodiment provides a fast recovery diode. Figure 2 , Figure 2 The fast recovery diode includes a first conductive type substrate 10 and a first conductive type drift layer 20 .

[0046] Specifically, the first conductive type drift layer 20 is located above the first conductive type substrate 10, and the first conductive type drift layer 20 includes a first region 21 and a second region 22, and the second region 22 is located between the first region 21 and the first conductive type substrate 10. In the direction from the first conductive type drift layer 20 to the first conductive type substrate 10, the doping concentration of the first region 21 gradually decreases. There is a high doping concentration peak 220 in the second region 22. The doping concentration of the high doping concentration peak 220 is higher than the lowest value of the doping concentration of the first region 21. Please refer to Figure 3 , Figure 3 The doping concentration distribution diagram of the fast recovery diode is shown (along Figure 2 in the direction indicated by the dashed arrow).

[0047] In an optional embodiment, the doping concentration range of the first region 21 is 1e14 cm -3 ~7e14 cm -3 (including endpoint values). For example, in the first region 21, the doping concentration of the region with the lowest concentration is 1e14 cm -3 The doping concentration in the highest concentration region is 1e14 cm -3 ~7e14 cm -3 , the doping concentrations of other regions are within the above range. Of course, the doping concentrations of the lowest concentration region and the highest concentration region in the first region 21 may also be other doping concentration values ​​within the above range. Among them, the doping concentration of the high doping concentration peak 220 is less than the highest doping concentration value of the first region 21.

[0048] In an optional embodiment, if Figure 2As shown, the distance d between the high doping concentration peak 220 and the first conductive type substrate 10 ranges from 5 μm to 10 μm (including the endpoint values). For example, the distance d between the high doping concentration peak 220 and the first conductive type substrate 10 is 6 μm or 8 μm. It should be noted that the above distance d is the distance between the area corresponding to the peak value of the high doping concentration peak 220 and the first conductive type substrate 10.

[0049] In an optional embodiment, the ratio between the thickness t1 of the first region 21 and the thickness t2 of the first conductive type drift layer 20 is 85% to 95% (including the end point values). For example, the ratio between the thickness t1 of the first region 21 and the thickness t2 of the first conductive type drift layer 20 is 88%, 90% or 92%. In the first conductive type drift layer 20, since the first region 21 mainly assumes the role of forming a gradient electric field and withstand voltage, the distribution of carriers is optimized by the gradient electric field, so that the carriers migrate more smoothly to reduce the probability of oscillation during reverse recovery, and the second region 22 mainly assumes the role of effective electric field cutoff, therefore, the first region 21 should occupy most of the first conductive type drift layer 20 compared to the second region 22. Furthermore, due to the electric field cutoff effect of the high doping concentration peak 220 in the second region 22, the high doping concentration peak 220 needs to be close to the first conductive type substrate 10, so that the high doping concentration peak 220 can quickly remove carriers to avoid carrier retention, which will prolong the reverse recovery time and may cause current and voltage oscillations, and may even cause other problems that damage the fast recovery diode. Therefore, when the ratio of the thickness t1 of the first region 21 to the thickness t2 of the first conductive type drift layer 20 is within the above range, a fast recovery diode with better reverse recovery time and reverse recovery softness can be achieved.

[0050] In the embodiment of the present application, two implementation methods of the first conductive type drift layer 20 are provided, which are as follows:

[0051] Mode 1: The first region 21 includes multiple epitaxial layers, and in the direction from the first conductive type drift layer 20 to the first conductive type substrate 10, the resistivity of the multiple epitaxial layers gradually increases, and the thickness of the multiple epitaxial layers gradually increases. Wherein, the thickness of any of the epitaxial layers is 5μm to 15μm (including the end value), for example, the thickness of the epitaxial layer can be 8μm, 10μm or 12μm, and the number of epitaxial layers included in the first region 21 is adjusted based on actual needs, for example, the first region 21 includes 8 epitaxial layers or 10 epitaxial layers, etc.

[0052] Furthermore, the second region 22 includes a doped epitaxial layer, and the doped epitaxial layer has the high doping concentration peak 220 .

[0053] In this embodiment, the first region 21 and the second region 22 are both formed based on an epitaxial growth method, and by controlling the doping concentration in different epitaxial growth steps, the first conductive type drift layer 20 is formed based on multiple layers of the epitaxial layer and the doped epitaxial layer. From this perspective, the first conductive type drift layer 20 is a split-molded structure.

[0054] Mode 2: The first region 21 includes a diffusion layer, and the distribution concentration of impurity elements in the diffusion layer gradually decreases in the direction from the first conductive type drift layer 20 to the first conductive type substrate 10 .

[0055] Furthermore, the second region 22 includes a diffusion injection layer, the diffusion injection layer has a hydrogen ion injection region, and the hydrogen ion injection region constitutes the high doping concentration peak 220 .

[0056] In this embodiment, a semiconductor layer can be formed on the first conductive type substrate 10, and the semiconductor layer is diffused with impurity elements (i.e., doping diffusion) so that the impurity elements are distributed in a preset manner in the semiconductor layer. The slope and width of the doping concentration change in the first region 21 are controlled based on parameters such as the dose and energy of the diffused impurity elements and the temperature of the post-diffusion annealing process. Then, hydrogen ion implantation is performed based on the side of the first conductive type substrate 10 away from the semiconductor layer to form a hydrogen ion implantation region in the semiconductor layer close to the first conductive type substrate 10 and at a certain distance from the first conductive type substrate 10. The first conductive type drift layer 20 is formed based on the diffusion layer and the diffusion implantation layer. From this perspective, the first conductive type drift layer 20 is an integrated structure.

[0057] In an optional embodiment, the fast recovery diode further includes a second conductive type semiconductor layer 30, and the second conductive type semiconductor layer 30 is located on a side of the first conductive type drift layer 20 away from the first conductive type substrate 10. For example, the first conductive type substrate 10 and the first conductive type drift layer 20 are both N-type, and the second conductive type semiconductor layer 30 is P-type. Alternatively, the first conductive type substrate 10 and the first conductive type drift layer 20 are both P-type, and the second conductive type semiconductor layer 30 is N-type. The first conductive type substrate 10 serves as the cathode region of the fast recovery diode, and the second conductive type semiconductor layer 30 serves as the anode region of the fast recovery diode.

[0058] Assuming that the first conductive type substrate 10 and the first conductive type drift layer 20 are both N-type, and the second conductive type semiconductor layer 30 is P-type, the working process of the fast recovery diode in the embodiment of the present application is described by way of example:

[0059] In the freewheeling stage of the fast recovery diode, when the fast recovery diode is forward-conducted, under the action of the forward voltage, the second conductive type semiconductor layer 30 (i.e., the anode region) injects holes into the first conductive type drift layer 20, and the first conductive type substrate 10 (i.e., the cathode region) injects electrons into the first conductive type drift layer 20. The carriers (including electrons and holes) diffuse, recombine and accumulate in the first conductive type drift layer 20 to form a large number of carrier groups. In this process, due to the conductivity modulation effect, the conductivity of the first conductive type drift layer 20 is improved, so that the conduction voltage drop is reduced, thereby reducing the forward conduction loss of the fast recovery diode to optimize the conduction performance and overall working efficiency of the device.

[0060] In the reverse recovery stage of the fast recovery diode, such as Figure 4 As shown, since the doping concentration of the first region 21 in the first conductive type drift layer 20 is gradually distributed from high to low along the direction close to the first conductive type substrate 10 (i.e., the cathode region), and then cut off by the high doping concentration peak 220 in the second region 22, the electric field on the side of the first conductive type drift layer 20 close to the second conductive type semiconductor layer 30 (i.e., the anode region) is stronger, which helps to accelerate the diffusion of carriers from the second conductive type semiconductor layer 30 (i.e., the anode region) to the first conductive type drift layer 20, so that during the reverse recovery process, the carriers can be removed more quickly, thereby shortening the reverse recovery time. In addition, since the gradually doped region can make the diffusion process of the carriers smoothly transition, and the highly doped region can quickly remove the carriers, it can avoid a sharp change in the current, smooth the attenuation process of the current, reduce the current peak value during the reverse recovery process, and thus improve the reverse recovery softness. In addition. The smoother current attenuation avoids the oscillation phenomenon of the tail current, helps to reduce the electromagnetic interference generated during the switching process, so that the fast recovery diode is well applied in high-frequency and high-voltage application scenarios.

[0061] See also Figure 4 , Figure 4 A comparison diagram of the reverse characteristic curves of the fast recovery diode provided by the comparative example and the embodiment of the present application is shown, wherein Figure 1 The structure shown is used as a comparative example. The fast recovery diode in the related art usually adopts a uniformly doped drift region structure, for example Figure 1In the comparative structure shown, the doping concentrations of various regions in the drift region 103 are basically consistent. In the reverse recovery stage, after the carriers are exhausted at the PN junction between the anode layer 104 and the drift region 103, the electric field quickly expands to the drift region 103, and quickly sweeps the carriers stored in the freewheeling stage out of the fast recovery diode, resulting in a very fast decline in the reverse recovery current in the falling stage (reflected in the steepness of the curve in the falling stage), and a high di / dt (current change rate), resulting in large reverse recovery current, poor reverse recovery softness, and long reverse recovery time during the switching process, which in turn leads to high switching losses. In addition, due to the rapid change of the reverse recovery current, the tail current is prone to oscillation under low current conditions (such as Figure 4 The solid line curve in the dotted box shows an oscillation peak), which affects the reverse recovery characteristics of the fast recovery diode, and further affects the overall efficiency of the circuit and the working performance of the fast recovery diode, which can easily cause the power device to fail.

[0062] Compared with the comparative example, in the embodiment of the present application, the switching performance of the fast recovery diode can be improved by gradually decreasing the gradient distribution of the doping concentration of the first region 21, based on the improvement of the distribution of carriers in the forward conduction and reverse recovery processes, for example, reducing switching losses and reducing electromagnetic interference. Specifically, based on the gradual distribution of the doping concentration in the first region 21, a gradual electric field is generated in the first conductive type drift layer 20, so that the diffusion process of the carriers is smoother, and the current is prevented from changing sharply, so that the attenuation process of the current in the reverse recovery process is smoother, and the current peak value in the reverse recovery process is reduced, and the reverse recovery softness is improved. At the same time, smoother current decay can reduce the probability of tail current oscillation and even avoid the occurrence of tail current oscillation. Not only effectively reduce switching losses to improve the working efficiency of the fast recovery diode. It also helps to reduce the electromagnetic interference generated during the switching process, improve the electrical compatibility of the system, and make the fast recovery diode suitable for high frequency, high voltage and other application scenarios. At the same time, the doping concentration gradually decreases from the anode region to the cathode region, so that the electric field strength on the side of the first region 21 close to the anode region is higher than the electric field strength on the side of the first region 21 close to the cathode region, which helps to accelerate the diffusion of carriers from the anode region to the first conductive type drift layer 20, thereby reducing the residence time of carriers in the reverse recovery process, improving the reverse recovery speed, and thus shortening the reverse recovery time. In addition, the doping concentration gradient distribution in the first conductive type drift layer 20 also improves the thermal characteristics of the fast recovery diode, reduces the risk of failure due to overheating, and further improves the reliability of the fast recovery diode.

[0063] In addition, in the embodiment of the present application, a high doping concentration peak 220 is set in the second region 22 after the doping concentration gradient distribution. In the process of carriers moving from the first region 21 to the cathode region, when they diffuse to the region close to the anode region, the diffusion process is cut off by the high doping concentration peak 220 and the carriers are recombined to be removed, thereby maintaining the reverse recovery softness as much as possible. Moreover, the high doping concentration peak 220 can also act as a buffer layer in the reverse withstand voltage process to delay the expansion of the electric field and cut off the electric field.

[0064] The fast recovery diode provided in the embodiment of the present application is based on the design of the doping concentration distribution in the first conductive type drift layer, forms a gradual electric field in the first conductive type drift layer and cuts off the electric field at the high doping concentration peak, improves the distribution and movement of carriers during forward conduction and reverse recovery, reduces switching losses and reduces electromagnetic interference, and also improves the reverse recovery characteristics of the fast recovery diode under full current (covering both low current and rated current ranges) and improves the reliability of the fast recovery diode.

[0065] The present application also provides a method for manufacturing a fast recovery diode, which can be used to manufacture the above-mentioned fast recovery diode or other suitable fast recovery diodes. Figure 2 The structure shown in the figure is understood, and the manufacturing method includes the following steps:

[0066] Providing a first conductive type substrate 10;

[0067] forming a first conductive type drift layer 20 on the first conductive type substrate 10, wherein the first conductive type drift layer 20 includes a first region 21 and a second region 22, wherein the second region 22 is located between the first region 21 and the first conductive type substrate 10;

[0068] Among them, in the direction from the first conductive type drift layer 20 to the first conductive type substrate 10, the doping concentration of the first region 21 gradually decreases; there is a high doping concentration peak 220 in the second region 22, and the doping concentration of the high doping concentration peak 220 is higher than the maximum value of the doping concentration of the first region 21.

[0069] In an optional embodiment, forming the first conductive type drift layer 20 on the first conductive type substrate 10 includes the following steps:

[0070] forming a first semiconductor layer on the first conductive type substrate 10;

[0071] forming a second semiconductor layer on the first semiconductor layer; wherein,

[0072] The method of forming the first semiconductor layer on the first conductive type substrate 10 is the same as or different from the method of forming the second semiconductor layer on the first semiconductor layer.

[0073] In one embodiment, the first semiconductor layer and the second semiconductor layer directly constitute the first conductive type drift layer 20. At this time, the first semiconductor layer is formed on the first conductive type substrate 10 based on an epitaxial growth method, and the first semiconductor layer has the high doping concentration peak 220.

[0074] A second semiconductor layer is formed on the first semiconductor layer based on an epitaxial growth method. The second semiconductor layer includes multiple epitaxial layers. In a direction from the second semiconductor layer to the first semiconductor layer, the doping concentration of the multiple epitaxial layers gradually decreases.

[0075] In another embodiment, the first semiconductor layer and the second semiconductor layer do not directly constitute the first conductive type drift layer 20. On the basis of forming the first semiconductor layer and the second semiconductor layer, the manufacturing method further includes the following steps:

[0076] Diffusion is performed based on a side of the second semiconductor layer away from the first semiconductor layer;

[0077] Performing annealing so that the elements diffused into the second semiconductor layer and the first semiconductor layer are distributed in a predetermined manner;

[0078] Hydrogen ion implantation is performed on a surface of the first conductive type substrate 10 away from the first semiconductor layer to form the high doping concentration peak 220 in the first semiconductor layer.

[0079] Furthermore, forming a first semiconductor layer on the first conductive type substrate 10 and forming a second semiconductor layer on the first semiconductor layer are formed based on the same step, and the first semiconductor layer and the second semiconductor layer are an integrated structure.

[0080] In an optional embodiment, the manufacturing method also includes the step of forming a second conductive type semiconductor layer 30 on the first conductive type drift layer 20, and the second conductive type semiconductor layer 30 can be formed by ion implantation. After forming the second conductive type semiconductor layer 30, an annealing step is also included.

[0081] In an optional embodiment, the manufacturing method also includes the step of forming a cathode metal on a side of the first conductive type substrate 10 away from the first conductive type drift layer 20, and the step of forming an anode metal on a side of the second conductive type semiconductor layer 30 away from the first conductive type drift layer 20, thereby completing the manufacturing of the fast recovery diode.

[0082] The method for manufacturing a fast recovery diode provided in the embodiment of the present application can produce a fast recovery diode with improved working performance and reliability, especially improved reverse recovery characteristics under the full current state. The manufacturing steps are simple, and the manufacturing method of the first conductive type drift layer can be flexibly selected based on actual needs, which is suitable for large-scale production.

[0083] In summary, the fast recovery diode of the present application, based on the design of the doping concentration distribution in the first conductive type drift layer, forms a gradual electric field in the first conductive type drift layer and makes the electric field cut off at the high doping concentration peak, improves the distribution and movement of carriers in the forward conduction and reverse recovery process, reduces switching losses and reduces electromagnetic interference, and also improves the reverse recovery characteristics of the fast recovery diode under the full current state, and improves the reliability of the fast recovery diode. The method for manufacturing the fast recovery diode of the present application can produce a fast recovery diode with improved working performance and reliability, especially improved reverse recovery characteristics under the full current state, and the manufacturing steps are simple, and the manufacturing method of the first conductive type drift layer can be flexibly selected based on actual needs, which is suitable for large-scale production. Therefore, the present application effectively overcomes the various shortcomings in the prior art and has a high industrial utilization value.

[0084] The above embodiments are merely illustrative of the principles and effects of the present application and are not intended to limit the present application. Anyone familiar with the technology may modify or change the above embodiments without violating the spirit and scope of the present application. Therefore, all equivalent modifications or changes made by a person of ordinary skill in the art without departing from the spirit and technical ideas disclosed in the present application shall still be covered by the claims of the present application.

Claims

1. A fast recovery diode, characterized in that: include: a first conductive type substrate; A first conductive type drift layer is located above the first conductive type substrate, the first conductive type drift layer includes a first region and a second region, the second region is located between the first region and the first conductive type substrate, wherein in the direction from the first conductive type drift layer to the first conductive type substrate, the doping concentration of the first region gradually decreases; and there is a high doping concentration peak in the second region, and the doping concentration of the high doping concentration peak is higher than the lowest value of the doping concentration of the first region.

2. The fast recovery diode according to claim 1, characterized in that: The doping concentration of the first region ranges from 1e14 cm -3 ~7e14 cm -3 , the doping concentration of the high doping concentration peak is less than the maximum doping concentration of the first region.

3. The fast recovery diode according to claim 1, characterized in that: The distance between the high doping concentration peak and the first conductive type substrate is in the range of 5 μm to 10 μm; and / or, A ratio between a thickness of the first region and a thickness of the first conductive type drift layer is 85% to 95%.

4. The fast recovery diode according to claim 1, characterized in that: The first region includes multiple epitaxial layers. In a direction from the first conductive type drift layer to the first conductive type substrate, the resistivity of the multiple epitaxial layers gradually increases, and the thickness of the multiple epitaxial layers gradually increases.

5. The fast recovery diode according to claim 1, characterized in that: The first region includes a diffusion layer, and in a direction from the first conductive type drift layer to the first conductive type substrate, a distribution concentration of impurity elements in the diffusion layer gradually decreases.

6. The fast recovery diode according to any one of claims 1 to 5, characterized in that: The second region includes a doped epitaxial layer, and the doped epitaxial layer has the high doping concentration peak; or, The second region includes a diffusion injection layer, wherein the diffusion injection layer has a hydrogen ion injection region, and the hydrogen ion injection region constitutes the high doping concentration peak.

7. A method for manufacturing a fast recovery diode, characterized in that: The following steps are involved: providing a first conductive type substrate; forming a first conductive type drift layer on the first conductive type substrate, wherein the first conductive type drift layer comprises a first region and a second region, wherein the second region is located between the first region and the first conductive type substrate; Among them, in the direction from the first conductive type drift layer to the first conductive type substrate, the doping concentration of the first region gradually decreases; there is a high doping concentration peak in the second region, and the doping concentration of the high doping concentration peak is higher than the maximum value of the doping concentration of the first region.

8. The method for manufacturing a fast recovery diode according to claim 7, characterized in that: Forming the first conductive type drift layer on the first conductive type substrate comprises the following steps: forming a first semiconductor layer on the first conductive type substrate; forming a second semiconductor layer on the first semiconductor layer; wherein, The method of forming the first semiconductor layer on the first conductive type substrate is the same as or different from the method of forming the second semiconductor layer on the first semiconductor layer.

9. The method for manufacturing a fast recovery diode according to claim 8, characterized in that: The first semiconductor layer and the second semiconductor layer constitute the first conductive type drift layer, and the manufacturing method comprises the following steps: Forming a first semiconductor layer on the first conductive type substrate based on an epitaxial growth method, wherein the first semiconductor layer has the high doping concentration peak; A second semiconductor layer is formed on the first semiconductor layer based on an epitaxial growth method. The second semiconductor layer includes multiple epitaxial layers. In a direction from the second semiconductor layer to the first semiconductor layer, the doping concentration of the multiple epitaxial layers gradually decreases.

10. The method for manufacturing a fast recovery diode according to claim 8, characterized in that: The production method further comprises the following steps: Diffusion is performed based on a side of the second semiconductor layer away from the first semiconductor layer; Performing annealing so that the elements diffused into the second semiconductor layer and the first semiconductor layer are distributed in a predetermined manner; Hydrogen ion implantation is performed based on a surface of the first conductive type substrate away from the first semiconductor layer to form the high doping concentration peak in the first semiconductor layer.

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