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, wherein the fast recovery diode comprises a first conductive type substrate and a first conductive type semiconductor layer, wherein the first conductive type semiconductor layer is located on the first conductive type substrate, wherein the first conductive type semiconductor layer has at least one doping concentration peak, and the distance between each doping concentration peak and the first conductive type substrate is less than the distance between the doping concentration peak and a side of the first conductive type semiconductor layer away from the first conductive type substrate. The fast recovery diode, based on the structure of the first conductive type semiconductor layer, has at least one doping concentration peak, so that the reverse recovery characteristics and switching loss of the fast recovery diode are improved, and by adjusting the morphological parameters of the doping concentration peak, the fast recovery diode can meet the specific performance requirements of different application scenarios. The manufacturing method has simple overall process steps and is suitable for large-scale production.

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, mainly used in the field of power electronics. Compared with ordinary diodes, fast recovery diodes have faster reverse recovery time and lower forward resistance, and can control the flow of current more effectively. This makes it play an important role in switching power supplies, inverters, motor drives, and power transmission.

[0003] In modern power electronic systems, the requirements for efficiency and response speed are constantly increasing, so fast recovery diodes are widely used in high-frequency power conversion and pulse signal processing. In these application fields, fast recovery diodes not only play the role of freewheeling, but also directly affect the overall performance and reliability of the system. The reverse recovery time and reverse recovery softness of fast recovery diodes are two key performance indicators of fast recovery diodes. Generally speaking, a long reverse recovery time is accompanied by high softness, but a long reverse recovery time will lead to increased switching losses and thermal management problems; while a reverse recovery time that is too short and a poor softness will bring about electromagnetic interference problems, causing current mutations to drive voltage mutations, affecting other components in the system.

[0004] See also Figure 1 , Figure 1 A structural schematic diagram of a fast recovery diode is shown, which includes a cathode layer 101, a drift region 102 and an anode layer 104, and a buffer layer 103 is arranged on the side of the drift region 102 close to the cathode layer 101. The reverse recovery characteristic is improved by the arrangement of the buffer layer 103. However, although the additional arrangement of the buffer layer 103 improves the performance of the fast recovery diode to a certain extent, the working performance of the fast recovery diode still cannot meet the market performance requirements for the fast recovery diode, and needs to be further improved.

[0005] Therefore, how to provide a fast recovery diode and a manufacturing method thereof to improve the working performance of the fast recovery diode 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 technical problem that the working performance of the fast recovery diode in the prior art needs 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 semiconductor layer is located on the first conductive type substrate, and the first conductive type semiconductor layer has at least one doping concentration peak. The distance between each of the doping concentration peaks and the first conductive type substrate is smaller than the distance between the doping concentration peak and a side of the first conductive type semiconductor layer away from the first conductive type substrate.

[0011] Optionally, the morphological parameters of each of the doping concentration peaks are configured based on the target performance parameters of the fast recovery diode; wherein the target performance parameters include at least one of withstand voltage, reverse recovery softness and reverse recovery time; and the morphological parameters include at least one of the width of the doping concentration peak and the peak concentration of the doping concentration peak.

[0012] Optionally, the first conductive type semiconductor layer has a first doping concentration peak and a second doping concentration peak, the second doping concentration peak is located between the first doping concentration peak and the first conductive type substrate, and the concentration peak value of the second doping concentration peak is greater than the concentration peak value of the first doping concentration peak.

[0013] Optionally, the peak concentration range of the first doping concentration peak is 5e14cm -3 ~8e14cm -3 , the peak concentration range of the second doping concentration peak is 1e15cm -3 ~5e15cm -3 ; The width of the first doping concentration peak ranges from 10 μm to 20 μm, and the width of the second doping concentration peak ranges from 3 μm to 6 μm.

[0014] Optionally, along the direction from the first conductive type semiconductor layer to the first conductive type substrate, the first doping concentration peak and the first conductive type semiconductor layer satisfy the following relationship: d / t is 1 / 6 to 1 / 3, wherein d is the distance between the peak position of the first doping concentration peak and the first conductive type substrate; and t is the thickness of the first conductive type semiconductor layer.

[0015] Optionally, along the direction from the first conductive type semiconductor layer to the first conductive type substrate, the first conductive type drift layer includes a first low resistance layer, a first high resistance layer, a second low resistance layer, a second high resistance layer and a drift layer stacked in sequence; wherein,

[0016] The first doping concentration peak is composed of the drift layer, the first low resistance layer and the first high resistance layer, and the peak position of the first doping concentration peak is located in the first low resistance layer;

[0017] The second doping concentration peak is composed of the first high resistance layer, the second low resistance layer and the second high resistance layer, and the peak position of the second doping concentration peak is located in the second low resistance layer.

[0018] Optionally, the resistivity range of the first low resistance layer is 5ohm·cm~10ohm·cm; the resistivity range of the first high resistance layer is 25ohm·cm~35ohm·cm; the resistivity range of the second low resistance layer is 1ohm·cm~5ohm·cm, the resistivity range of the second high resistance layer is 8ohm·cm~12ohm·cm, and the resistivity of the drift layer is less than or equal to the resistivity of the first high resistance layer.

[0019] In a second aspect, the present application also provides a method for manufacturing a fast recovery diode, comprising the following steps:

[0020] providing a first conductive type substrate;

[0021] A first conductive type semiconductor layer is formed on the first conductive type substrate, wherein the first conductive type semiconductor layer has at least one doping concentration peak, and a distance between each of the doping concentration peaks and the first conductive type substrate is smaller than a distance between the doping concentration peak and a side of the first conductive type semiconductor layer away from the first conductive type substrate.

[0022] Optionally, the first conductive type semiconductor layer has a first doping concentration peak and a second doping concentration peak, the second doping concentration peak is located between the first doping concentration peak and the first conductive type substrate, and the concentration peak value of the second doping concentration peak is greater than the concentration peak value of the first doping concentration peak; the method for forming the first conductive type semiconductor layer on the first conductive type substrate comprises a multiple epitaxial growth method; wherein,

[0023] In the direction from the first conductive type semiconductor layer to the first conductive type substrate, the first conductive type drift layer includes a first low resistance layer, a first high resistance layer, a second low resistance layer, a second high resistance layer and a drift layer stacked in sequence; wherein,

[0024] The first doping concentration peak is composed of the drift layer, the first low resistance layer and the first high resistance layer, and the peak position of the first doping concentration peak is located in the first low resistance layer;

[0025] The second doping concentration peak is composed of the first high resistance layer, the second low resistance layer and the second high resistance layer, and the peak position of the second doping concentration peak is located in the second low resistance layer.

[0026] Optionally, characteristic parameters of the drift layer, characteristic parameters of the first low-resistance layer and characteristic parameters of the first high-resistance layer are cooperatively configured based on the first morphological parameters of the first doping concentration peak;

[0027] Based on the second morphological parameters of the second doping concentration peak, the characteristic parameters of the first high resistance layer, the characteristic parameters of the second low resistance layer and the characteristic parameters of the second high resistance layer are cooperatively configured; wherein,

[0028] The first morphological parameter includes at least one of the width of the first doping concentration peak and the peak concentration of the first doping concentration peak; the second morphological parameter includes at least one of the width of the second doping concentration peak and the peak concentration of the second doping concentration peak; any of the characteristic parameters includes at least one of resistivity and thickness.

[0029] As described above, the fast recovery diode of the present application is based on the structure of the first conductive type semiconductor layer, that is, it has at least one doping concentration peak in the area close to the first conductive type substrate, so that the reverse recovery characteristics and switching losses of the fast recovery diode are improved, thereby achieving the improvement of the working performance of the fast recovery diode. And by adjusting the morphological parameters of the doping concentration peak in the first conductive type semiconductor layer, the fast recovery diode can meet the specific performance requirements of different application scenarios, and the overall structure is simple, easy to achieve low-cost, high-efficiency large-scale production, and suitable for market-scale applications. The method for making the fast recovery diode of the present application can produce a fast recovery diode with improved reverse recovery characteristics and switching losses. Furthermore, a relatively mature epitaxial process can be used to make the first conductive type semiconductor layer in the fast recovery diode, and the morphological parameters of the doping concentration peak in the first conductive type semiconductor layer can be accurately controlled. The overall process steps are simple and suitable for low-cost and efficient large-scale production. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a schematic diagram of the structure of a fast recovery diode in the related art.

[0031] Figure 2 Shown is a schematic diagram of the structure of a fast recovery diode provided in an embodiment of the present application.

[0032] Figure 3Shown is a schematic diagram of the doping concentration peak distribution of the fast recovery diode provided in an embodiment of the present application.

[0033] Figure 4 Shown is a schematic diagram comparing the electric field distribution of the fast recovery diode provided in the embodiment of the present application and the comparative example during the reverse recovery process.

[0034] Figure 5 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.

[0035] Description of reference numerals:

[0036] 101 - cathode layer, 102 - buffer layer, 103 - drift region, 104 - anode layer;

[0037] 10-first conductive type substrate; 20-first conductive type semiconductor layer, 201-first doping concentration peak, 202-second doping concentration peak, 21-drift layer, 22-first low resistance layer, 23-first high resistance layer, 24-second low resistance layer, 25-second high resistance layer; 30-second conductive type doping layer. DETAILED DESCRIPTION

[0038] 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.

[0039] See also Figures 1 to 5 It 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.

[0040] In the related art, in order to optimize the performance of the fast recovery diode, especially to optimize the reverse recovery time and reverse recovery softness, for example, it is carried out from the perspective of material selection and process improvement. Although some success has been achieved in improving some performance of the fast recovery diode, there are still the following problems to be solved (the overall working performance of the fast recovery diode still needs to be improved). First, the high on-state voltage drop is a common problem. Since the PIN fast recovery diode is usually composed of a P layer, an I layer and an N layer, the current in the on state needs to pass through these areas, resulting in a large internal resistance and a high on-state voltage drop. In addition to reducing energy efficiency, it also increases heat generation, affecting the long-term stability and performance of the device. Secondly, the traditional PIN structure is prone to show a sharper current change during the reverse recovery process, resulting in a "hard recovery" phenomenon. The hard recovery process not only increases the switching loss, but also may interfere with the surrounding circuits and affect the performance of the entire system. Thirdly, in the fast switching operation, the reverse recovery process requires the device to recover from the on state to the reverse cut-off state. If the recovery time is too long, the fast recovery diode will generate a large reverse current in the reverse process, thereby causing switching losses, which not only affects the efficiency of the circuit, but also may cause the fast recovery diode to overheat and shorten its service life. In addition, as the operating frequency of power electronic equipment continues to increase, the reverse recovery characteristics and switching speed of PIN fast recovery diodes are also affected by frequency. At high frequencies, the parasitic parameters of fast recovery diodes (such as capacitance and inductance) will significantly affect their performance, leading to further degradation of switching characteristics, limiting their application in high-efficiency high-frequency power electronic systems. Finally, in order to improve the conduction characteristics and reverse recovery performance of the diode, it is usually necessary to adjust the PIN structure through a sophisticated doping process. These high-precision manufacturing processes not only increase production costs, but may also affect the yield of fast recovery diodes due to process complexity, limiting their large-scale application.

[0041] Based on the above analysis, an embodiment of the present application provides a fast recovery diode, which can improve the working performance of the fast recovery diode at a lower cost by adjusting the structure and internal electrical characteristics of the fast recovery diode. The specific solution is described as follows.

[0042] The present application embodiment provides a fast recovery diode. Figure 2 , Figure 2 The fast recovery diode comprises a first conductive type substrate 10 and a first conductive type semiconductor layer 20 .

[0043] Specifically, the first conductive type semiconductor layer 20 is located on the first conductive type substrate 10, and the first conductive type semiconductor layer 20 has at least one doping concentration peak, and the distance between each doping concentration peak and the first conductive type substrate 10 is smaller than the distance between the doping concentration peak and a side of the first conductive type semiconductor layer 20 away from the first conductive type substrate 10, that is, the doping concentration peak is present in a side region of the first conductive type semiconductor layer 20 close to the first conductive type substrate 10. Please refer to Figure 3 , Figure 3 A schematic diagram of the doping concentration peak distribution of the reverse recovery diode is shown.

[0044] In an optional embodiment, the morphological parameters of each of the doping concentration peaks are configured based on the target performance parameters of the fast recovery diode. Wherein, the target performance parameters include at least one of withstand voltage, reverse recovery softness and reverse recovery time. The morphological parameters include at least one of the width of the doping concentration peak and the peak concentration of the doping concentration peak. The width of the doping concentration peak is in the same direction as the thickness of a certain structural layer (for example, the first conductive type semiconductor layer 20) mentioned later, that is, along the direction from the first conductive type substrate 10 to the first conductive type semiconductor layer 20.

[0045] In an optional embodiment, the first conductive type semiconductor layer 20 has a first doping concentration peak 201 and a second doping concentration peak 202. The second doping concentration peak 202 is located between the first doping concentration peak 201 and the first conductive type substrate 10. And the concentration peak value of the second doping concentration peak 202 is greater than the concentration peak value of the first doping concentration peak 201. Moreover, in the case where the first conductive type semiconductor layer 20 has a first doping concentration peak 201 and a second doping concentration peak 202, the first morphological parameters of the first doping concentration peak 201 and the second morphological parameters of the second doping concentration peak 202 are collaboratively configured based on the target performance parameters of the fast recovery diode. Among them, the first morphological parameters include at least one of the width of the first doping concentration peak 201 and the peak concentration of the first doping concentration peak 201. The second morphological parameters include at least one of the width of the second doping concentration peak 202 and the peak concentration of the second doping concentration peak 202. That is, the target performance parameters are achieved by collaboratively adjusting the first morphological parameters and the second morphological parameters. It should be noted that, Figure 2 The mark of the first doping concentration peak 201 points to the peak position of the first doping concentration peak 201, and the mark of the second doping concentration peak 202 points to the peak position of the second doping concentration peak 202 ( Figure 2 (shown by the dashed line).

[0046] In the embodiment of the present application, by setting the first doping concentration peak 201 and the second doping concentration peak 202 in the first conductive type semiconductor layer 20, the electric field of reverse recovery is cut off based on the first doping concentration peak 201 to shorten the reverse recovery time, and the reverse recovery electric field is buffered based on the second doping concentration peak 202 to increase the reverse recovery softness. That is, the reverse recovery characteristics of the fast recovery diode are improved synergistically based on the first doping concentration peak 201 and the second doping concentration peak 202, and the reverse recovery time performance can be increased without losing the reverse recovery softness. In addition, based on the performance required by the application scenario of the fast recovery diode, the first morphological parameter of the doping concentration peak 201 and the second morphological parameter of the second doping concentration peak 202 are defined, so that the fast recovery diode can meet the performance requirements in a specific application scenario. For example, when the fast recovery diode is applied to a high voltage and high power scenario (for example, a frequency converter), the fast recovery diode needs to have a strong withstand voltage capability. At this time, the doping width and peak concentration of the first doping concentration peak 201 can be reduced to enhance the withstand voltage capability.

[0047] In an optional embodiment, the fast recovery diode further includes a second conductive type doped layer 30, and the second conductive type doped layer 30 is located on a side of the first conductive type semiconductor layer 20 away from the first conductive type substrate 10. For example, the first conductive type substrate 10 and the first conductive type semiconductor layer 20 are both N-type, and the second conductive type doped layer 30 is P-type. Alternatively, the first conductive type substrate 10 and the first conductive type semiconductor layer 20 are both P-type, and the second conductive type doped 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 doped layer 30 serves as the anode region of the fast recovery diode.

[0048] Now, the working process and performance improvement of the fast recovery diode of the embodiment of the present application are described by way of example, assuming that the first conductive type substrate 10 and the first conductive type semiconductor layer 20 are both N-type, the second conductive type semi-doped layer is P-type, and the first conductive type semiconductor layer 20 has a first doping concentration peak 201 and a second doping concentration peak 202:

[0049] 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 anode region injects holes into the first conductive type semiconductor layer 20, and the cathode region injects electrons into the first conductive type semiconductor layer 20. The carriers (including electrons and holes) diffuse, recombine and accumulate in the first conductive type semiconductor layer 20. At this time, there are a large number of carriers in the first conductive type semiconductor layer 20. Due to the conductivity modulation effect, the conduction voltage drop of the fast recovery diode is reduced, thereby reducing its forward conduction loss. In addition to serving as concentration peaks to increase the injection of carriers, the first doping concentration peak 201 and the second doping concentration peak 202 also act as buffer layers to reduce the electric field strength.

[0050] See also Figure 4 , Figure 4 A schematic diagram showing the comparison of the electric field distribution of the fast recovery diode provided in the embodiment of the present application and the comparative example during the reverse recovery process (with Figure 1 The structure shown is a comparative example). In the reverse recovery stage of the fast recovery diode, the first doping concentration peak 201 can slow down the expansion of the depletion region, so that in the reverse recovery current decreasing stage, more carriers participate in the recombination, slowing down the decreasing speed of the reverse recovery current. Figure 5 , Figure 5 The reverse recovery characteristic curve comparison diagram of the fast recovery diode provided by the embodiment of the present application and the comparative example is shown. Similarly, due to the slowdown of the electric field expansion, the reverse recovery current decreases more slowly. At the end of the reverse recovery process, there are more residual carriers, which makes the recombination current larger and reduces the current oscillation (manifested as Figure 5 In addition, under the same on-state voltage drop, the fast recovery diode of the embodiment of the present application has a smaller reverse recovery current peak value and a similar reverse recovery time (that is, while improving the reverse recovery softness, the reverse recovery time is not increased), which makes its loss smaller.

[0051] In an optional embodiment, the peak concentration range of the first doping concentration peak 201 is 5e14 cm -3 ~8e14cm -3 (including endpoint values), for example, the peak concentration of the first doping concentration peak 201 may be 6e14 cm -3 or 7e14 cm -3 The peak concentration range of the second doping concentration peak 202 is 1e15 cm -3 ~5e15 cm -3 (including endpoint values), for example, the peak concentration of the second doping concentration peak 202 may be 2e14 cm -3 、3e14 cm -3 or 4e14 cm -3.

[0052] In an optional embodiment, the width of the first doping concentration peak 201 ranges from 10 μm to 20 μm (including the endpoint values), for example, the width of the first doping concentration peak 201 can be 12 μm, 15 μm or 18 μm. The width of the second doping concentration peak 202 ranges from 3 μm to 6 μm (including the endpoint values), for example, the width of the second doping concentration peak 202 can be 4 μm or 5 μm.

[0053] In the embodiment of the present application, the specific peak concentration and width of the first doping concentration peak 201 and the second doping concentration peak 202 can be reasonably adjusted within the above-mentioned numerical ranges based on the performance requirements of the actual application scenario of the fast recovery diode to obtain a fast recovery diode with the desired performance. In a specific embodiment, when the width of the first doping concentration peak 201 is 15 μm and the peak concentration is 6e14 cm -3 , and the width of the second doping concentration peak 202 is 5 μm and the peak concentration is 3e15 cm -3 Under such circumstances, the reverse recovery time and reverse recovery softness of the fast recovery diode achieve the best balance, which can meet the performance requirements of most application scenarios.

[0054] In an optional embodiment, along the direction from the first conductive type semiconductor layer 20 to the first conductive type substrate 10, the first doping concentration peak 201 and the first conductive type semiconductor layer 20 satisfy: d / t is 1 / 6 to 1 / 3 (including the endpoint values), wherein d is the distance between the peak position of the first doping concentration peak 201 and the first conductive type substrate 10. t is the thickness of the first conductive type semiconductor layer 20. For example, d / t is 1 / 4. Taking the thickness of the first conductive type semiconductor layer 20 as 60 μm as an example, the distance between the peak position of the first doping concentration peak 201 and the first conductive type substrate 10 ranges from 40 μm to 50 μm, and can be 45 μm or 48 μm. When the above-mentioned d / t range is satisfied between the first doping concentration peak 201 and the first conductive type semiconductor layer 20, the distance between the first doping concentration peak 201 and the second conductive type doping layer 30 is relatively far (that is, based on the overall fast recovery diode structure, its position is relatively deep), which can not only cut off the static electric field, but also slow down the expansion of the depletion region during the reverse recovery process. In the reverse current decreasing stage, more carriers are allowed to participate in the recombination, slowing down the current decrease rate and improving the reverse recovery softness to a certain extent.

[0055] In an optional embodiment, along the direction from the first conductive type semiconductor layer 20 to the first conductive type substrate 10, the first conductive type semiconductor layer 20 includes a first low resistance layer 22, a first high resistance layer 23, a second low resistance layer 24, a second high resistance layer 25 and a drift layer 21 stacked in sequence. The first doping concentration peak 201 is composed of the drift layer 21, the first low resistance layer 22 and the first high resistance layer 23, and the peak position of the first doping concentration peak 201 is located in the first low resistance layer 22. The second doping concentration peak 202 is composed of the first high resistance layer 23, the second low resistance layer 24 and the second high resistance layer 25, and the peak position of the second doping concentration peak 202 is located in the second low resistance layer 24.

[0056] In an optional embodiment, the resistivity range of the first low-resistance layer 22 is 5ohm·cm to 10ohm·cm (including endpoint values). For example, the resistivity of the first low-resistance layer 22 may be 6ohm·cm or 8ohm·cm. The resistivity range of the first high-resistance layer 23 is 25ohm·cm to 35ohm·cm (including endpoint values). For example, the resistivity of the first high-resistance layer 23 is 28ohm·cm, 30ohm·cm and 32ohm·cm. The resistivity range of the second low-resistance layer 24 is 1ohm·cm to 5ohm·cm (including endpoint values). For example, the resistivity range of the second low-resistance layer 24 is 2ohm·cm or 4ohm·cm. The resistivity range of the second high-resistance layer 25 is 8ohm·cm to 12ohm·cm (including endpoint values). For example, the resistivity range of the second high-resistance layer 25 may be 10ohm·cm. The resistivity of the drift layer 21 is less than or equal to the resistivity of the first high-resistance layer 23.

[0057] In an optional embodiment, the thickness of the second high resistance layer 25 is in the range of 5 μm to 10 μm (including the endpoint values). The thickness of the second low resistance layer 24 is in the range of 5 μm to 10 μm (including the endpoint values). For example, the thickness of the second high resistance layer 25 may be 6 μm or 8 μm, and the thickness of the second low resistance layer 24 may be 7 μm or 9 μm.

[0058] In an optional embodiment, when the first conductive type semiconductor layer 20 includes a first low resistance layer 22, a first high resistance layer 23, a second low resistance layer 24, a second high resistance layer 25 and a drift layer 21 stacked in sequence, the first conductive type semiconductor layer 20 can be formed by a multi-layer epitaxial process, that is, multiple epitaxial processes are performed on the first conductive type substrate 10 to grow multiple layers of epitaxial layers, and the parameters in each epitaxial process are controlled to obtain epitaxial layers of different thicknesses and resistivities, and the first conductive type semiconductor layer 20 is obtained based on controlling the peak concentration and width of the first doping concentration peak 201 and the second doping concentration peak 202.

[0059] In the embodiment of the present application, a multi-layer epitaxial process is used to form the first conductive type semiconductor layer, and the morphological parameters of the two doping concentration peaks are precisely controlled, so that the fast recovery diode has good applicability in specific application scenarios. The multi-layer epitaxial process also has higher flexibility. By fine-tuning the resistivity and thickness of the corresponding epitaxial layer by the epitaxial process parameters, a more suitable doping peak morphology can be obtained. Compared with other processes, the epitaxial process is more mature, and the control of material growth and the resistivity of the epitaxial layer is more precise and stable, and the process cost is low and the production efficiency is relatively high.

[0060] It should be noted that in the embodiments of this application Figure 2 and Figure 3 The example of two doping concentration peaks in the first conductive type semiconductor layer 20 is used for explanation. In actual application, the doping concentration peak can be one or more than two (for example, three). That is, under the premise of improving the working performance of the fast recovery diode, the number and morphological parameters of the doping concentration peaks can be adjusted based on actual needs.

[0061] The fast recovery diode of the embodiment of the present application is based on the structure of the first conductive type semiconductor layer, that is, there is at least one doping concentration peak in the region close to the first conductive type substrate, so that the reverse recovery characteristics and switching losses of the fast recovery diode are improved, thereby achieving improved working performance of the fast recovery diode. And by adjusting the morphological parameters of the doping concentration peak in the first conductive type semiconductor layer, the fast recovery diode can meet the specific performance requirements of different application scenarios, and the overall structure is simple, easy to achieve low-cost, high-efficiency large-scale production, and suitable for market-scale applications.

[0062] The present application also provides a method for manufacturing a fast recovery diode, which can be used to manufacture the fast recovery diode described above or other suitable fast recovery diodes. The manufacturing method comprises the following steps:

[0063] Providing a first conductive type substrate 10;

[0064] A first conductive type semiconductor layer 20 is formed on the first conductive type substrate 10, and the first conductive type semiconductor layer 20 has at least one doping concentration peak, and the distance between each doping concentration peak and the first conductive type substrate 10 is smaller than the distance between the doping concentration peak and a side of the first conductive type semiconductor layer 20 away from the first conductive type substrate 10.

[0065] In an optional embodiment, the first conductive type semiconductor layer 20 has a first doping concentration peak 201 and a second doping concentration peak 202, the second doping concentration peak 202 is located between the first doping concentration peak 201 and the first conductive type substrate 10, and the concentration peak value of the second doping concentration peak 202 is greater than the concentration peak value of the first doping concentration peak 201.

[0066] Further, the method of forming the first conductive type semiconductor layer 20 on the first conductive type substrate 10 includes multiple epitaxial growth methods;

[0067] In the direction from the first conductive type semiconductor layer 20 to the first conductive type substrate 10, the first conductive type semiconductor layer 20 includes a drift layer 21, a first low resistance layer 22, a first high resistance layer 23, a second low resistance layer 24 and a second high resistance layer 25 stacked in sequence; wherein,

[0068] The first doping concentration peak 201 is formed based on the drift layer 21, the first low resistance layer 22 and the first high resistance layer 23, and the peak position of the first doping concentration peak 201 is located in the first low resistance layer 22;

[0069] The second doping concentration peak 202 is formed based on the first high resistance layer 23 , the second low resistance layer 24 and the second high resistance layer 25 , and the peak position of the second doping concentration peak 202 is located in the second low resistance layer 24 .

[0070] In an optional embodiment, the characteristic parameters of the drift layer 21, the characteristic parameters of the first low resistance layer 22 and the characteristic parameters of the first high resistance layer 23 are cooperatively configured based on the first morphological parameters of the first doping concentration peak 201. The characteristic parameters of the first high resistance layer 23, the characteristic parameters of the second low resistance layer 24 and the characteristic parameters of the second high resistance layer 25 are cooperatively configured based on the second morphological parameters of the second doping concentration peak 202. The first morphological parameter includes at least one of the width of the first doping concentration peak 201 and the peak concentration of the first doping concentration peak 201. The second morphological parameter includes at least one of the width of the second doping concentration peak 202 and the peak concentration of the second doping concentration peak 202. Any of the characteristic parameters includes at least one of resistivity and thickness. Taking the implementation of the first morphological parameter as an example, it is necessary to select and adjust the thickness and resistivity of the drift layer 21, the thickness and resistivity of the first low resistance layer 22 and the thickness and resistivity of the first high resistance layer 23 based on the pre-obtained width of the first doping concentration peak 201.

[0071] In an optional embodiment, the manufacturing method further includes performing at least one of a carrier lifetime control step and a compensation injection step, wherein the carrier lifetime control process includes at least one of platinum diffusion, gold diffusion and electron irradiation. The above steps can further improve the comprehensive performance of the fast recovery diode without changing the resistivity of each epitaxial structure layer in the first conductive type semiconductor layer 20. Among them, the carrier lifetime control process can introduce uniformly distributed deep energy level impurities or irradiation defects in the first conductive type semiconductor layer 20 to form a carrier recombination center, reduce the carrier lifetime, reduce the amount of charge stored in the first conductive type semiconductor layer 20 during forward conduction, and accelerate the recombination of minority carriers during reverse shutdown, thereby further reducing the reverse recovery time. Compensation injection can adjust the injection efficiency of the anode by controlling the doping concentration and structure of the anode (i.e., the second conductive type doping layer 30) to improve the reverse recovery characteristics and conduction characteristics of the fast recovery diode.

[0072] In an optional embodiment, the manufacturing method also includes the step of forming a second conductive type doping layer 30 on the first conductive type semiconductor layer 20, and the second conductive type doping layer 30 can be formed by ion implantation. After forming the second conductive type doping layer 30, it also includes the step of annealing.

[0073] 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 semiconductor layer 20, and the step of forming an anode metal on a side of the second conductive type doped layer 30 away from the first conductive type semiconductor layer 20, thereby completing the manufacturing of the fast recovery diode.

[0074] In the embodiment of the present application, by precisely controlling the multi-layer epitaxial growth process, epitaxial layers with different doping concentrations are introduced into the structure of the fast recovery diode to obtain a first conductive type semiconductor layer with a doping concentration peak having preset morphological parameters. The design of these layers takes into account the optimization of the electric field distribution, carrier recombination and migration mechanism, so that the entire device can maintain a low on-resistance and a fast reverse recovery time in both the on and off states, and has good softness during the reverse recovery process. Specifically, in the design stage of the fast recovery diode, the material of the first conductive type substrate is first selected based on the application platform of the fast recovery diode, and further, according to the performance requirements of the fast recovery diode required by the application platform, precise epitaxial growth conditions are formulated to ensure the structural uniformity, thickness and doping concentration of each epitaxial layer. Then, epitaxial layers with different resistivity and thickness are deposited layer by layer on the first conductive type substrate 10 by an epitaxial growth process to obtain a first conductive type semiconductor layer 20. Next, a series of precise tests are performed on the electrical characteristics of the first conductive type semiconductor layer 20 to ensure that the fast recovery diode actually manufactured can meet the performance requirements of the target application platform (for example, a high-frequency power electronics application platform).

[0075] In addition, in order to obtain the first conductive type semiconductor layer 20 having at least one doping concentration peak, a hydrogen ion implantation process was attempted to fabricate the structure of the first conductive type semiconductor layer 20 in the fast recovery diode. However, after actual verification, it was found that the peak value of the doping concentration peak formed by hydrogen ion implantation and the width of the doping concentration peak were difficult to control, and the formed doping concentration peak was significantly inferior to the embodiment of the present application in terms of precision control for improving the working performance of the fast recovery diode, and it was difficult to ensure the consistency of product performance. The multilayer epitaxial process used in the embodiment of the present application has higher application flexibility, the number of doping concentration peaks, peak concentration and width are highly controllable, and no additional defects (for example, dislocations and defects inside the structure, etc.) are introduced to cause the loss of other working performances of the fast recovery diode. In addition, the multilayer epitaxial process used in the embodiment of the present application is compatible with other processes and is easy to match. For example, when the cathode region of the fast recovery diode is formed by diffusion, the hydrogen ion implantation process will cause the doping redistribution of the cathode region, causing the electrical characteristics of the cathode region to change, while the multilayer epitaxial process used in the embodiment of the present application will not cause the above problems. In addition, in the multi-layer epitaxial process, various carrier lifetime control processes can be flexibly matched to further optimize the performance of the fast recovery diode (for example, further shorten the reverse recovery time, etc.). That is, the multi-layer epitaxial process used in the embodiment of the present application can avoid the problems of poor uniformity, material damage, difficulty in accurately controlling the morphological parameters of the doping concentration peak, complex process and high cost existing in the hydrogen ion implantation process.

[0076] The method for manufacturing a fast recovery diode provided in the embodiment of the present application can manufacture a fast recovery diode with improved reverse recovery characteristics and switching loss. Furthermore, a relatively mature epitaxial process can be used to manufacture the first conductive type semiconductor layer in the fast recovery diode, and the morphological parameters of the doping concentration peak in the first conductive type semiconductor layer can be accurately controlled. The overall process steps are simple and suitable for low-cost and efficient large-scale production.

[0077] In summary, the fast recovery diode of the present application is based on the structure of the first conductive type semiconductor layer, that is, there is at least one doping concentration peak in the region close to the first conductive type substrate, so that the reverse recovery characteristics and switching losses of the fast recovery diode are improved, thereby achieving the improvement of the working performance of the fast recovery diode. And by adjusting the morphological parameters of the doping concentration peak in the first conductive type semiconductor layer, the fast recovery diode can meet the specific performance requirements of different application scenarios, and the overall structure is simple, easy to achieve low-cost, high-efficiency large-scale production, suitable for market-scale applications. The method for making the fast recovery diode of the present application can produce a fast recovery diode with improved reverse recovery characteristics and switching losses. Further, the first conductive type semiconductor layer in the fast recovery diode can be made by a relatively mature epitaxial process, and the morphological parameters of the doping concentration peak in the first conductive type semiconductor layer can be accurately controlled. The overall process steps are simple, suitable for low-cost and efficient large-scale production. Therefore, the present application effectively overcomes the various shortcomings in the prior art and has a high industrial utilization value.

[0078] 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 semiconductor layer is located on the first conductive type substrate, and the first conductive type semiconductor layer has at least one doping concentration peak. The distance between each of the doping concentration peaks and the first conductive type substrate is smaller than the distance between the doping concentration peak and a side of the first conductive type semiconductor layer away from the first conductive type substrate.

2. The fast recovery diode according to claim 1, characterized in that: The morphological parameters of each of the doping concentration peaks are configured based on the target performance parameters of the fast recovery diode; wherein the target performance parameters include at least one of withstand voltage, reverse recovery softness and reverse recovery time; and the morphological parameters include at least one of the width of the doping concentration peak and the peak concentration of the doping concentration peak.

3. The fast recovery diode according to claim 1 or 2, characterized in that: The first conductive type semiconductor layer has a first doping concentration peak and a second doping concentration peak, the second doping concentration peak is located between the first doping concentration peak and the first conductive type substrate, and the concentration peak value of the second doping concentration peak is greater than the concentration peak value of the first doping concentration peak.

4. The fast recovery diode according to claim 3, characterized in that: The peak concentration range of the first doping concentration peak is 5e14cm -3 ~8e14cm -3 , the peak concentration range of the second doping concentration peak is 1e15cm -3 ~5e15cm -3 ; The width of the first doping concentration peak ranges from 10 μm to 20 μm, and the width of the second doping concentration peak ranges from 3 μm to 6 μm.

5. The fast recovery diode according to claim 3, characterized in that: Along the direction from the first conductive type semiconductor layer to the first conductive type substrate, the first doping concentration peak and the first conductive type semiconductor layer satisfy the following relationship: d / t is 1 / 6 to 1 / 3, wherein d is the distance between the peak position of the first doping concentration peak and the first conductive type substrate; and t is the thickness of the first conductive type semiconductor layer.

6. The fast recovery diode according to claim 3, characterized in that: In the direction from the first conductive type semiconductor layer to the first conductive type substrate, the first conductive type drift layer includes a drift layer, a first low resistance layer, a first high resistance layer, a second low resistance layer and a second high resistance layer stacked in sequence; wherein, The first doping concentration peak is composed of the drift layer, the first low resistance layer and the first high resistance layer, and the peak position of the first doping concentration peak is located in the first low resistance layer; The second doping concentration peak is composed of the first high resistance layer, the second low resistance layer and the second high resistance layer, and the peak position of the second doping concentration peak is located in the second low resistance layer.

7. The fast recovery diode according to claim 6, characterized in that: The resistivity range of the first low resistance layer is 5ohm·cm~10ohm·cm; the resistivity range of the first high resistance layer is 25ohm·cm~35ohm·cm; the resistivity range of the second low resistance layer is 1ohm·cm~5ohm·cm; the resistivity range of the second high resistance layer is 8ohm·cm~12ohm·cm; the resistivity of the drift layer is less than or equal to the resistivity of the first high resistance layer.

8. A method for manufacturing a fast recovery diode, characterized in that: The following steps are involved: providing a first conductive type substrate; A first conductive type semiconductor layer is formed on the first conductive type substrate, wherein the first conductive type semiconductor layer has at least one doping concentration peak, and a distance between each of the doping concentration peaks and the first conductive type substrate is smaller than a distance between the doping concentration peak and a side of the first conductive type semiconductor layer away from the first conductive type substrate.

9. The method for manufacturing a fast recovery diode according to claim 8, characterized in that: The first conductive type semiconductor layer has a first doping concentration peak and a second doping concentration peak, the second doping concentration peak is located between the first doping concentration peak and the first conductive type substrate, and the concentration peak value of the second doping concentration peak is greater than the concentration peak value of the first doping concentration peak; the method for forming the first conductive type semiconductor layer on the first conductive type substrate comprises a multiple epitaxial growth method; wherein, In the direction from the first conductive type semiconductor layer to the first conductive type substrate, the first conductive type drift layer includes a drift layer, a first low resistance layer, a first high resistance layer, a second low resistance layer and a second high resistance layer stacked in sequence; wherein, The first doping concentration peak is composed of the drift layer, the first low resistance layer and the first high resistance layer, and the peak position of the first doping concentration peak is located in the first low resistance layer; The second doping concentration peak is composed of the first high resistance layer, the second low resistance layer and the second high resistance layer, and the peak position of the second doping concentration peak is located in the second low resistance layer.

10. The method for manufacturing a fast recovery diode according to claim 9, characterized in that: Coordinately configuring characteristic parameters of the drift layer, characteristic parameters of the first low-resistance layer, and characteristic parameters of the first high-resistance layer based on first morphological parameters of the first doping concentration peak; Based on the second morphological parameters of the second doping concentration peak, the characteristic parameters of the first high resistance layer, the characteristic parameters of the second low resistance layer and the characteristic parameters of the second high resistance layer are cooperatively configured; wherein, The first morphological parameter includes at least one of the width of the first doping concentration peak and the peak concentration of the first doping concentration peak; the second morphological parameter includes at least one of the width of the second doping concentration peak and the peak concentration of the second doping concentration peak; any of the characteristic parameters includes at least one of resistivity and thickness.

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