A fast recovery diode and a preparation method thereof

Abstract

The present invention relates to the field of semiconductor technology, and particularly to a fast recovery diode. The fast recovery diode includes: a substrate, an N-type epitaxial layer, an active region, and a termination region surrounding the active region; the N-type epitaxial layer is located on the substrate. Among them, the N-type epitaxial layer includes an N buffer layer, an N drift layer, and an N-epitaxial layer that are sequentially stacked. In the N-type epitaxial layer, the doping concentration of the N drift layer is the lowest; both the active region and the termination region are located on the N-epitaxial layer. Through this fast recovery diode, effects such as reducing the maximum reverse recovery current Irrm of the fast recovery diode, reducing losses, increasing device reliability, and reducing the failure rate at the application end can be achieved.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor technology, and in particular, to a fast recovery diode and a method for manufacturing the same. Background Art

[0002] A fast recovery diode (FRD) is a diode with a short reverse recovery time and good switching characteristics, and is widely used in contemporary power electronic circuits. The fast recovery diode is mainly used in combination with devices such as an insulated gate bipolar transistor (IGBT) and a metal oxide semiconductor field effect transistor (MOSFET) to play a freewheeling or rectifying role, meeting the application requirements of high power, high frequency, etc. With the increasing demand for the high-power characteristics of the fast recovery diode at the application end, especially the increasing demand for the large-current characteristics of the fast recovery diode, the maximum reverse recovery current Irrm of the fast recovery diode is too large during reverse recovery, resulting in device burnout and increasing the failure rate at the application end. Summary of the Invention

[0003] By providing a fast recovery diode and a method for manufacturing the same in an embodiment of the present application, the technical problem in the prior art that the maximum reverse recovery current Irrm of the fast recovery diode is too large during reverse recovery, resulting in device burnout and increasing the failure rate at the application end, is solved, and technical effects such as reducing the maximum reverse recovery current Irrm of the fast recovery diode and reducing the failure rate at the application end are achieved.

[0004] In a first aspect, an embodiment of the present invention provides a fast recovery diode, including: a substrate, an N-type epitaxial layer, an active region, and a termination region surrounding the active region;

[0005] The N-type epitaxial layer is located on the substrate. Among them, the N-type epitaxial layer includes an N buffer layer, an N drift layer, and an N-epitaxial layer that are sequentially stacked. In the N-type epitaxial layer, the doping concentration of the N drift layer is the lowest;

[0006] Both the active region and the termination region are located on the N-epitaxial layer.

[0007] Preferably, the doping concentration of the N-epitaxial layer is higher than that of the N drift layer, and the doping concentration of the N-epitaxial layer is lower than that of the N buffer layer.

[0008] Preferably, the doping concentration range of the N drift layer is 1E14 / cm3 to 1.5E14 / cm3, and the thickness range of the N drift layer is 40 um to 65 um.

[0009] Preferably, the doping concentration of the N-epitaxial layer is 1.5 to 3 times that of the N-drift layer, and the thickness range of the N-epitaxial layer is 10 μm to 20 μm.

[0010] Preferably, the doping concentration of the N-buffer layer is 7 to 10 times that of the N-drift layer.

[0011] Preferably, the thickness range of the N-buffer layer is 10 μm to 20 μm.

[0012] Preferably, the active region includes a P-type emitter region, an anode metal layer, an active region oxide layer, and an active region isolation layer;

[0013] The P-type emitter region is located in the N-epitaxial layer, and the upper surface of the P-type emitter region is on the same horizontal plane as the upper surface of the N-epitaxial layer;

[0014] The active region oxide layer and the active region isolation layer are located at both ends of the P-type emitter region and on the N-epitaxial layer, and the active region isolation layer is on the active region oxide layer;

[0015] The anode metal layer is on the N-epitaxial layer and covers the P-type emitter region and the active region isolation layer.

[0016] Preferably, it further includes a back metal layer, and the back metal layer is located under the substrate.

[0017] Based on the same inventive concept, in a second aspect, the present invention further provides a method for manufacturing a fast recovery diode, including:

[0018] Forming an N-type epitaxial layer on a substrate, wherein the N-type epitaxial layer includes an N-buffer layer, an N-drift layer, and an N-epitaxial layer that are sequentially stacked. In the N-type epitaxial layer, the doping concentration of the N-drift layer is the lowest;

[0019] Forming an active region and a terminal region surrounding the active region on the N-epitaxial layer.

[0020] Preferably, the doping concentration of the N-epitaxial layer is higher than that of the N-drift layer, and the doping concentration of the N-epitaxial layer is lower than that of the N-buffer layer.

[0021] One or more technical solutions in the embodiments of the present invention have at least the following technical effects or advantages:

[0022] The present invention provides a fast recovery diode, which specifically includes: a substrate, an N-type epitaxial layer, an active region, and a termination region surrounding the active region. The N-type epitaxial layer is located on the substrate. Among them, the N-type epitaxial layer includes an N buffer layer, an N drift layer, and an N-epitaxial layer that are sequentially stacked, that is, the N buffer layer is located on the substrate, the N drift layer is located on the N buffer layer, and the N-epitaxial layer is located on the N drift layer. The N buffer layer is an N-type highly doped buffer layer, the N drift layer is an N-type lightly doped drift layer, and the N-epitaxial layer is an N-type low-doped epitaxial layer. In the N-type epitaxial layer, the doping concentration of the N drift layer is the lowest. Both the active region and the termination region are located on the N-epitaxial layer.

[0023] In this way, an N-type epitaxial layer is provided between the substrate and the active region. The N-type epitaxial layer is a three-layer structure, which are an N buffer layer, an N drift layer, and an N-epitaxial layer that are sequentially stacked. An N-epitaxial layer is provided on the N drift layer so that both the active region and the termination region are provided on the N-epitaxial layer. And in the N-type epitaxial layer, the doping concentration of the N drift layer is the lowest, that is, the doping concentration of the N drift layer is less than the doping concentration of the N-epitaxial layer. Therefore, through the device structure of this fast recovery diode, the conductance modulation effect can be reduced, the carrier injection efficiency is reduced when the device is turned on, so that the reverse recovery charge is reduced, the maximum reverse recovery current Irrm is reduced, the loss is reduced, the reliability of the device is increased, and the failure rate at the application end is reduced. Since the doping concentration of the added N-epitaxial layer is higher than that of the N drift layer, the resistivity of the N-type epitaxial layer decreases, but at the same time, the injection efficiency of the P-type emitter region in the active region decreases, and a better on-state voltage drop can be obtained through compromise adjustment. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] By reading the following detailed description of the preferred embodiments, various other advantages and benefits will become clear to those of ordinary skill in the art. The drawings are only for the purpose of showing the preferred embodiments and are not considered to be a limitation of the present invention. And throughout the drawings, the same reference numerals are used to represent the same components. In the drawings:

[0025] Figure 1 shows a schematic structural diagram of the fast recovery diode in the embodiment of the present invention;

[0026] Figure 2 shows a curve diagram of the doping concentration relationship of the three epitaxial layers in the N-type epitaxial layer in the embodiment of the present invention;

[0027] Figure 3 shows a comparison schematic diagram of the reverse recovery dynamic curves of the existing PN-NN+ structure and this fast recovery diode in the embodiment of the present invention;

[0028] Figure 4 shows a schematic structural diagram of forming an N-type epitaxial layer on the substrate in the embodiment of the present invention;

[0029] Figure 5 Shows a schematic structural diagram of forming an active region oxide layer, a terminal region oxide layer, a P-type emitter region, and a terminal region P-type field limiting ring in an embodiment of the present invention;

[0030] Figure 6 Shows a schematic structural diagram of forming an active region isolation layer, a terminal region isolation layer, an anode metal layer, and a terminal region metal layer in an embodiment of the present invention;

[0031] Figure 7 Shows a schematic structural diagram of forming a passivation layer and a back metal layer in an embodiment of the present invention;

[0032] Figure 8 Shows a schematic flow chart of the steps of a method for manufacturing a fast recovery diode in an embodiment of the present invention.

[0033] In the figure, 100, substrate; 200, N-type epitaxial layer; 300, active region; 400, terminal region; 500, back metal layer;

[0034] 210, N buffer layer; 220, N drift layer; 230, N-epitaxial layer;

[0035] 310, P-type emitter region; 320, anode metal layer; 330, active region oxide layer; 340, active region isolation layer;

[0036] 410, terminal region P-type field limiting ring; 420, terminal region metal layer; 430, terminal region oxide layer; 440, terminal region isolation layer; 450, passivation layer. Detailed implementation manners

[0037] Hereinafter, exemplary embodiments of the present disclosure will be described in more detail with reference to the accompanying drawings. Although the exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided so that the present disclosure can be more thoroughly understood and the scope of the present disclosure can be completely conveyed to those skilled in the art.

[0038] Embodiment 1

[0039] The first embodiment of the present invention provides a fast recovery diode, as Figure 1As shown, it includes: a substrate 100, an N-type epitaxial layer 200, an active region 300, and a terminal region 400 surrounding the active region 300. The N-type epitaxial layer 200 is located on the substrate 100. Among them, the N-type epitaxial layer 200 includes an N buffer layer 210, an N drift layer 220, and an N-epitaxial layer 230 that are sequentially stacked, that is, the N buffer layer 210 is located on the substrate 100, the N drift layer 220 is located on the N buffer layer 210, and the N-epitaxial layer 230 is located on the N drift layer 220. The N buffer layer 210 is an N-type highly doped buffer layer, the N drift layer 220 is an N-type lightly doped drift layer, and the N-epitaxial layer 230 is an N-type low-doped epitaxial layer. In the N-type epitaxial layer 200, the doping concentration of the N drift layer 220 is the lowest. Both the active region 300 and the terminal region 400 are located on the N-epitaxial layer 230. As Figure 1 shown, terminal regions 400 are provided at both ends of the active region 300.

[0040] It should also be noted that the substrate 100 is an N-type substrate. The substrate 100 is an N-type heavily doped substrate such as silicon dioxide or silicon nitride. The materials of the three layers in the N-type epitaxial layer 200 can be the same or different.

[0041] In this embodiment, an N-type epitaxial layer 200 is provided between the substrate 100 and the active region 300. The N-type epitaxial layer 200 is a three-layer structure, which are an N buffer layer 210, an N drift layer 220, and an N-epitaxial layer 230 that are sequentially stacked. An N-epitaxial layer 230 is provided on the N drift layer 220 so that both the active region 300 and the terminal region 400 are provided on the N-epitaxial layer. And in the N-type epitaxial layer 200, the doping concentration of the N drift layer 220 is the lowest, that is, the doping concentration of the N drift layer 220 is less than the doping concentration of the N-epitaxial layer 230. Therefore, through the device structure of the fast recovery diode in this embodiment, the conductance modulation effect can be reduced, the carrier injection efficiency is reduced when the device is turned on, so that the reverse recovery charge is reduced, the maximum reverse recovery current Irrm is reduced, the loss is reduced, the device reliability is increased, and the application end failure rate is reduced. Since the doping concentration of the added N-epitaxial layer 230 is higher than that of the N drift layer 220, the resistivity of the N-type epitaxial layer 200 decreases, but at the same time, the injection efficiency of the P-type emitter region in the active region 300 decreases, and a better on-state voltage drop can be obtained by compromise adjustment.

[0042] Next, in combination with Figure 1 elaborate in detail the structure and principle of the fast recovery diode in this embodiment:

[0043] The doping concentration relationship of the three layers in the N-type epitaxial layer 200 is: the doping concentration of the N-epitaxial layer 230 is higher than that of the N drift layer 220, and the doping concentration of the N-epitaxial layer 230 is lower than that of the N buffer layer 210. Specifically, as Figure 2As shown, the abscissa is the longitudinal cutting depth starting from the surface of the device downward, and the ordinate is the doping concentration. The doping concentration of the N buffer layer 210 is higher than that of the N drift layer 220. The doping concentration of the N-epitaxial layer 230 is higher than that of the N drift layer 220 and lower than that of the N buffer layer 210. It should be noted that the overall thickness of this device is the same as that of the existing fast-recovery diode with a PN-NN+ structure, indicating that the thickness of this device can meet the thickness requirements of the existing fast-recovery diode device, enabling this device not only to achieve effects such as reducing the maximum reverse recovery current Irrm of the fast-recovery diode and reducing the failure rate at the application end, but also to meet the size requirements of the fast-recovery diode device, further reflecting the practical efficiency of this device.

[0044] The N drift layer 220 is mainly used to broaden the depletion region and increase the reverse breakdown voltage of the fast-recovery diode. The doping concentration range of the N drift layer 220 is 1E14 / cm 3 ~1.5E14 / cm 3 , and the thickness range of the N drift layer 220 is 40um - 65um. To ensure the high breakdown voltage of this fast-recovery diode device, the doping concentration of the N-epitaxial layer 230 should not be too high. Therefore, the doping concentration of the N-epitaxial layer 230 is 1.5 to 3 times that of the N drift layer 220, that is, the doping concentration range of the N-epitaxial layer 230 is 1.5E14 / cm 3 ~4.5E14 / cm 3 , and the thickness range of the N-epitaxial layer 230 is 10um - 20um.

[0045] By adding the N-epitaxial layer 230 on the N drift layer 220 and the doping concentration of the N-epitaxial layer 230 being greater than that of the N drift layer 220, the conductance modulation effect can be reduced, the carrier injection efficiency during the conduction of this device can be decreased, thereby reducing the reverse recovery charge, lowering the maximum reverse recovery current Irrm, reducing losses, and increasing the device reliability. The increased doping concentration of the N-epitaxial layer 230 is higher than that of the N drift layer 220, resulting in a decrease in the resistivity of the N-type epitaxial layer 200, but at the same time, the injection efficiency of the P-type emitter in the active region 300 is decreased, and a better on-state voltage drop can be obtained through a compromise adjustment.

[0046] The doping concentration of the N buffer layer 210 is greater than that of the N drift layer 220. The doping concentration of the N buffer layer 210 is 7 to 10 times that of the N drift layer 220, that is, the doping concentration range of the N buffer layer 210 is 7E14 / cm 3 ~1.5E15 / cm 3In this way, during the reverse recovery process of the device, when the depletion region reaches the buffer layer, the expansion slows down. There are still a large number of carriers in the buffer layer that have not been recombined or extracted during reverse recovery, increasing the recombination time and improving the reverse recovery softness of the device. To obtain a better reverse recovery time, the thickness of the N buffer layer 210 should not be too thick, and the thickness range of the N buffer layer 210 is 10um - 20um. The specific doping concentrations and thicknesses of the N buffer layer 210, N drift layer 220, and N-epitaxial layer 230 can be set according to actual requirements.

[0047] In this embodiment, the active region 300 includes: a P-type emitter region 310, an anode metal layer 320, an active region oxide layer 330, and an active region isolation layer 340. The P-type emitter region 310 is a P-type doped emitter region. The P-type emitter region 310 is located in the N-epitaxial layer 230, and the upper surface of the P-type emitter region 310 is on the same horizontal plane as the upper surface of the N-epitaxial layer 230. The active region oxide layer 330 and the active region isolation layer 340 are located at both ends of the P-type emitter region 310 and are above the N-epitaxial layer 230. The active region isolation layer 340 is located on the active region oxide layer 330. As shown in the accompanying drawings, the active region isolation layer 340 can also wrap the active region oxide layer 330. The anode metal layer is above the N-epitaxial layer 230 and covers the P-type emitter region 310 and the active region isolation layer 340.

[0048] This embodiment mainly optimizes the active region 300 to improve the reverse recovery characteristics. The terminal region 400 of this embodiment can be set according to actual requirements. As Figure 1As shown, an example of the terminal region 400 includes: a plurality of terminal region P-type field limit rings 410 (only two terminal region P-type field limit rings are shown in the figure), a terminal region metal layer 420, a terminal region oxide layer 430, a terminal region isolation layer 440, and a passivation layer 450. In the figure, the vertically striped pattern region represents the oxide layer, the dotted pattern region represents the isolation layer, and the diamond pattern region represents the passivation layer 450. The plurality of terminal region P-type field limit rings 410 are arranged at intervals. Each terminal region P-type field limit ring 410 is located in the N-epitaxial layer 230, and the upper surface of the terminal region P-type field limit ring 410 is on the same horizontal plane as the upper surface of the N-epitaxial layer 230. The terminal region oxide layer 430 and the terminal region isolation layer 440 are located above the N-epitaxial layer 230 and at both ends of each terminal region P-type field limit ring 410. The terminal region isolation layer 440 covers the terminal region oxide layer 430 and the inner ends of both sides of the terminal region P-type field limit ring 410. A terminal region metal layer 420 is provided in the opening region between the terminal region isolation layers 440 at both inner ends of each terminal region P-type field limit ring 410 and above the terminal region P-type field limit ring 410 corresponding to this opening region, that is, one terminal region P-type field limit ring 410 is correspondingly provided with one terminal region metal layer 420. The passivation layer 450 covers the terminal region metal layer 420, the terminal region isolation layer 440, and the region adjacent to the active region 300.

[0049] It should also be noted that both the active region oxide layer 330 and the terminal region oxide layer 430 play a role in isolation and protection. The terminal region oxide layer 430 can also cooperate with the terminal region P-type field limit ring 410 (i.e., the protection ring) and the terminal region metal layer 420 to play a voltage withstand role. The active region isolation layer 340 and the terminal region isolation layer 440 also play a role in isolation and protection. Directly depositing metal on the previous field oxide layer may cause the metal to damage the field oxide structure. Using the isolation layer as the interlayer dielectric can improve the silicon surface planarization, and then the deposited metal has better planar contact. Since this diode generally uses USG + BPSG borophosphosilicate glass, in addition to being beneficial to planarization, the boron doped in BPSG can reduce the reflux temperature, the phosphorus doped can resist ions (mainly sodium ions) and moisture, increasing the reliability; USG can prevent the boron and phosphorus precipitated in BPSG from diffusing into the substrate epitaxy, causing pollution. The passivation layer 450 can protect the interior of the metal from corrosion. By forming a dense and well-covering passivation film on the metal surface, it can prevent the direct contact between the metal and the external environment and prevent the metal from being corroded. The passivation layer 450 prevents moisture, humidity, and impurities from entering the device interior through its own barrier performance, preventing mechanical damage, etc., thereby protecting the electronic devices below it and enhancing the reliability.

[0050] This fast recovery diode further includes: a back metal layer 500, and the back metal layer is located under the substrate 100. The back metal layer can be called the cathode metal layer.

[0051] The three-layer N-epitaxial layer design on the N-type substrate 100 of this fast-recovery diode forms a PN-N-(Drift)NN+ structure with the P-type emitter region 310. The first epitaxial layer, a highly doped N buffer layer 210, is grown on the substrate 100 to increase the reverse recovery softness. The second epitaxial layer, a lightly doped N drift layer 220, is grown on the N buffer layer 210 to meet the device breakdown voltage requirements. A third epitaxial layer, an N-epitaxial layer 230, is grown on the N drift layer 220, with a doping concentration slightly higher than that of the N drift layer 220, to reduce the conductance modulation effect, lower the carrier concentration, decrease the maximum current Irrm during reverse recovery, increase the device reliability, and reduce the failure rate at the application end.

[0052] The existing design structure of fast-recovery diodes is to add an N-type buffer layer on the basis of the traditional PIN diode structure to form a PN-NN+ structure. In a specific example of this device, the doping concentration of the N buffer layer 210 of this device is 1E15 / cm 3 , and the doping concentration of the N drift layer 220 is 1E14 / cm 3 , and the doping concentration of the N-epitaxial layer 230 is 2.4E14 / cm 3 . The reverse recovery tests are respectively carried out on the PN-NN+ structure and this device. As Figure 3 shown, Figure 3 in which the abscissa represents the reverse recovery time and the ordinate represents the reverse recovery current. The solid line represents the reverse recovery current curve of this device, and the dashed line represents the reverse recovery current curve of the diode with the PN-NN+ structure. It can be seen from Figure 3 that the reverse recovery current Irrm of this fast-recovery diode device is significantly smaller and the softness is better.

[0053] The manufacturing process of this fast-recovery diode is as follows:

[0054] As Figure 4 shown, an N-type epitaxial layer 200 is formed on the N-type heavily doped substrate 100 by epitaxial growth technology. The doping material of the N-type epitaxial layer 200 includes but is not limited to phosphorus doping. The N-type epitaxial layer 200 includes: an N buffer layer 210 (N buffer) grown on the substrate 100, an N drift layer 220 (N-Drift) grown on the N buffer layer 210, and an N-epitaxial layer 230 grown on the N drift layer 220. The doping concentration of the N drift layer 220 is lower than that of the N buffer layer 210. The doping concentration of the N-epitaxial layer 230 is higher than that of the N drift layer 220, and the doping concentration of the N-epitaxial layer 230 is lower than that of the N buffer layer 210.

[0055] As Figure 5As shown, a field oxide layer is deposited on the side of the N-type epitaxial layer 200 away from the substrate 100. The field oxide layer can be an insulating material such as silicon dioxide or silicon nitride to protect the N-type epitaxial layer 200. Through the patterning process of exposure and development on the surface of the field oxide layer, the opening areas corresponding to the P-type emitter region 310 and the terminal region P-type field limiting ring 410 are etched, and the active region oxide layer 330 and the terminal region oxide layer 430 are formed. The P-type emitter region 310 is formed by using a P ion implantation process (such as boron ions) in the opening area corresponding to the P-type emitter region 310, and the terminal region P-type field limiting ring 410 is formed by using an ion implantation process in the opening area corresponding to the terminal region P-type field limiting ring 410.

[0056] As Figure 6 shown, an insulating layer is grown on the terminal region 400 and the P-type emitter region 310 by physical vapor deposition or chemical vapor deposition. The material of the insulating layer can be an insulating material such as silicon dioxide or silicon nitride. The area of the dotted pattern in the figure represents the isolation layer formed by the insulating layer. Through the patterning process of exposure and development on the insulating layer in sequence, and then etching, the active region isolation layer 340 and the terminal region isolation layer 440 are obtained. A front metal layer is formed by metal deposition such as thermal evaporation or magnetron sputtering on the active region isolation layer 340 and the terminal region isolation layer 440. Among them, the area of the oblique stripe pattern in the figure represents the front metal layer. The front metal layer covers the terminal region 400 and the P-type emitter region 310. The material of the front metal layer can be a metal material such as aluminum. Then, the front metal layer is etched to obtain the anode metal layer 320 and the terminal region metal layer 420.

[0057] As Figure 7 shown, by using growth methods such as thermal evaporation or magnetron sputtering, a passivation material is deposited on the anode metal layer 320 and the terminal region metal layer 420 to obtain a passivation material layer. Through the patterning process of exposure and development on the passivation material layer, a passivation layer 450 corresponding to the terminal region 400 in the orthographic projection on the substrate 100 is formed. The material of the passivation layer 450 can be an insulating material such as silicon dioxide or silicon nitride. Then, by using metal deposition methods such as thermal evaporation or magnetron sputtering, a back metal layer is formed on the side of the substrate 100 away from the N-type epitaxial layer 200. The material of the back metal layer can be a metal material such as titanium nickel silver.

[0058] In the process of manufacturing this fast-recovery diode, through the design of the N-type epitaxial layer 200, three epitaxial layers with different doping concentrations are grown on the substrate 100, namely the N-buffer layer 210, the N-drift layer 220, and the N-epitaxial layer 230. The N-drift layer 220 is lightly doped and mainly used to broaden the depletion region and increase the breakdown voltage. The N-buffer layer 210 is highly doped, and its doping concentration is higher than that of the N-drift layer 220 (the concentration ratio of the two is preferably 7-10). When the fast-recovery diode is in the reverse-recovery process, when the depletion region reaches the buffer layer, the expansion slows down. There are still a large number of carriers in the buffer layer that are not recombined or extracted during reverse recovery, increasing the recombination time and improving the reverse-recovery softness. The doping concentration of the N-epitaxial layer 230 near the P-type emitter region 310 is designed to be greater than that of the N-drift layer 220 (the concentration ratio of the two is preferably 1.5-3), which can reduce the conductance modulation effect, reduce the carrier injection efficiency when the device is conducting, thereby reducing the reverse-recovery charge, reducing the maximum reverse-recovery current Irrm, reducing losses, increasing the reliability of the device, and reducing the failure rate at the application end. Further optimization designs are carried out on the doping concentration of the substrate 100, the base region thickness, the P-type emitter region 310, etc. to improve the on-state and reverse-recovery characteristics of the fast-recovery diode.

[0059] Embodiment 2

[0060] Based on the same inventive concept, the second embodiment of the present invention also provides a method for manufacturing a fast-recovery diode, as Figure 8 shown, including:

[0061] S601, forming an N-type epitaxial layer on the substrate, wherein the N-type epitaxial layer includes an N-buffer layer, an N-drift layer, and an N-epitaxial layer that are sequentially stacked, and in the N-type epitaxial layer, the doping concentration of the N-drift layer is the lowest;

[0062] S602, forming an active region and a terminal region surrounding the active region on the N-epitaxial layer.

[0063] As an optional embodiment, forming an active region on the N-epitaxial layer includes:

[0064] forming an active-region oxide layer on the N-epitaxial layer;

[0065] forming a P-type emitter region in the N-epitaxial layer below both ends of the active-region oxide layer, wherein the upper surface of the P-type emitter region is on the same horizontal plane as the upper surface of the N-epitaxial layer;

[0066] forming an active-region isolation layer on the active-region oxide layer at both ends of the P-type emitter region and on the N-epitaxial layer;

[0067] forming an anode metal layer on the N-epitaxial layer, and the anode metal layer covers the P-type emitter region and the active-region isolation layer.

[0068] As an alternative embodiment, it further includes: forming a back metal layer under the substrate.

[0069] Since the preparation method of the fast recovery diode introduced in this embodiment is the preparation method adopted for the fast recovery diode in Embodiment 1 of the present application, based on the fast recovery diode introduced in Embodiment 1 of the present application, those skilled in the art can understand the specific implementation manners and various variations of the preparation method of the fast recovery diode in this embodiment. Therefore, the implementation of how the preparation method of the fast recovery diode realizes the fast recovery diode in Embodiment 1 of the present application will not be described in detail here. As long as those skilled in the art implement the preparation method adopted for the fast recovery diode in Embodiment 1 of the present application, it falls within the scope of protection of the present application.

[0070] Those skilled in the art should understand that although the preferred embodiments of the present invention have been described, once those skilled in the art know the basic creative concepts, additional changes and modifications can be made to these embodiments. Therefore, the appended claims are intended to be interpreted to include the preferred embodiments and all changes and modifications falling within the scope of the present invention.

[0071] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalent technologies, the present invention also intends to include these changes and modifications.

Claims

1. A fast recovery diode, characterized in that, Including: A substrate, an N-type epitaxial layer, an active region, and a terminal region surrounding the active region; The N-type epitaxial layer is located on the substrate. Among them, the N-type epitaxial layer includes an N buffer layer, an N drift layer, and an N-epitaxial layer that are sequentially stacked. In the N-type epitaxial layer, the doping concentration of the N drift layer is the lowest; Both the active region and the terminal region are located on the N-epitaxial layer; Among them, the doping concentration of the N-epitaxial layer is higher than that of the N drift layer, and the doping concentration of the N-epitaxial layer is lower than that of the N buffer layer to meet the size requirements of the fast recovery diode device and further reflect the practical efficiency of the device; The doping concentration of the N-drift layer ranges from 1E14 / cm 3 ~1.5E14 / cm 3 , and the thickness range of the N-drift layer is 40um to 65um; The doping concentration of the N-epitaxial layer is 1.5 to 3 times that of the N drift layer, and the thickness range of the N-epitaxial layer is 10um to 20um; The doping concentration of the N buffer layer is 7 to 10 times that of the N drift layer, and the thickness range of the N buffer layer is 10um to 20um; The N drift layer is used to broaden the depletion region and increase the reverse breakdown voltage value of the fast recovery diode; The N-epitaxial layer is used to ensure the high breakdown voltage value of the fast recovery diode device, so that the doping concentration of the N-epitaxial layer should not be too high, and a better conduction voltage drop can be obtained through a compromise adjustment.

2. The fast recovery diode according to claim 1, characterized in that, The active region includes: a P-type emission region, an anode metal layer, an active region oxide layer, and an active region isolation layer; The P-type emission region is located in the N-epitaxial layer, and the upper surface of the P-type emission region is on the same horizontal plane as the upper surface of the N-epitaxial layer; The active region oxide layer and the active region isolation layer are located at both ends of the P-type emission region and are located on the N-epitaxial layer. The active region isolation layer is located on the active region oxide layer; The anode metal layer is located on the N-epitaxial layer and covers the P-type emission region and the active region isolation layer.

3. The fast recovery diode according to claim 1, characterized in that, Also including: A back metal layer, and the back metal layer is located under the substrate.

4. A method for preparing a fast recovery diode, characterized in that, Including: Forming an N-type epitaxial layer on the substrate. Among them, the N-type epitaxial layer includes an N buffer layer, an N drift layer, and an N-epitaxial layer that are sequentially stacked. In the N-type epitaxial layer, the doping concentration of the N drift layer is the lowest; Forming an active region and a terminal region surrounding the active region on the N-epitaxial layer; Among them, the doping concentration of the N-epitaxial layer is higher than that of the N drift layer, and the doping concentration of the N-epitaxial layer is lower than that of the N buffer layer to meet the size requirements of the fast recovery diode device and further reflect the practical efficiency of the device; The doping concentration of the N-drift layer ranges from 1E14 / cm 3 ~1.5E14 / cm 3 , and the thickness range of the N-drift layer is 40um to 65um; The doping concentration of the N-epitaxial layer is 1.5 to 3 times that of the N drift layer, and the thickness range of the N-epitaxial layer is 10um to 20um; The doping concentration of the N buffer layer is 7 to 10 times that of the N drift layer, and the thickness range of the N buffer layer is 10um to 20um The N drift layer is used to broaden the depletion region and increase the reverse breakdown voltage value of the fast recovery diode; The N-epitaxial layer is used to ensure a high breakdown voltage of this fast-recovery diode device, so that the doping concentration of the N-epitaxial layer should not be too high, and a better on-state voltage drop can be obtained through a compromise adjustment.

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