A fast recovery diode and a manufacturing method

Abstract

The application relates to the field of semiconductor technology, in particular to a fast recovery diode and a manufacturing method, the fast recovery diode comprising a substrate, an epitaxial layer, an active region and a terminal region surrounding the active region; the epitaxial layer is arranged on the substrate; the active region and the terminal region are arranged on the epitaxial layer; the terminal region comprises a front P-type transition region and at least two front P-type field limiting rings; the front P-type transition region and the front P-type field limiting rings are both located on the epitaxial layer, the front P-type transition region is in contact with a main junction of the active region, the front P-type field limiting rings are spaced and sequentially surround the front P-type transition region and the active region, the upper surfaces of the main junction of the active region, the front P-type transition region, the front P-type field limiting rings and the epitaxial layer are at the same level; and the front P-type transition region is a smooth double-arc-shaped region. Through the fast recovery diode, the electric field and the current density at the anode edge of the device are reduced, and the reliability and the practicability of the device are enhanced.

Description

Technical Field

[0001] This invention relates to the field of semiconductor technology, and in particular to a fast recovery diode and its manufacturing method. Background Technology

[0002] A fast recovery diode (FRD) is a diode with a short reverse recovery time and good switching characteristics, widely used in modern power electronic circuits. FRDs are mainly used in conjunction with devices such as insulated-gate bipolar transistors (IGBTs) and metal-oxide-semiconductor field-effect transistors (MOSFETs) to provide freewheeling or rectification functions, meeting the requirements of high-power and high-frequency applications.

[0003] Existing fast recovery diodes have a front-side termination structure. On this termination structure, one or more P-ring structures are formed at intervals from the anode edge outwards to reduce the effect of junction bending and weaken the surface electric field strength. However, existing fast recovery diodes are prone to electric field concentration at the anode edge, making the device susceptible to breakdown. During switching, longitudinal current and current in the termination region flow into the active region anode electrode. When the current is large, the excessively high current density at the anode edge can easily cause the device to burn out. Therefore, existing fast recovery diodes suffer from low reliability due to electric field concentration or excessively high current density at the anode edge. Summary of the Invention

[0004] This application provides a fast recovery diode and its manufacturing method, which solves the technical problem of low device reliability caused by electric field concentration or excessive current density at the anode edge of the fast recovery diode in the prior art. It achieves the technical effects of reducing the electric field and current density at the anode edge of the fast recovery diode and enhancing the reliability and practicality of the device.

[0005] In a first aspect, embodiments of the present invention provide a fast recovery diode, comprising: a substrate, an epitaxial layer, an active region, and a terminal region surrounding the active region;

[0006] The epitaxial layer is disposed on the substrate;

[0007] The active region and the terminal region are disposed on the epitaxial layer;

[0008] The terminal area includes: a front-facing P-type transition area and at least two front-facing P-type field limiting loops;

[0009] The front P-type transition region and the front P-type field limiting ring are both located on the epitaxial layer. The front P-type transition region is in contact with the main junction of the active region. The front P-type field limiting rings are spaced apart and sequentially surround the front P-type transition region and the active region. The upper surface of the main junction of the active region, the upper surface of the front P-type transition region, the upper surface of the front P-type field limiting ring, and the upper surface of the epitaxial layer are on the same horizontal plane.

[0010] The front P-shaped transition area is a smoothly connected double-arc region.

[0011] Optionally, the terminal area further includes: a rear P-shaped transition area;

[0012] The back-side P-type transition region is located in the substrate or in the substrate and the epitaxial layer, and the surface of the back-side P-type transition region is at the same level as the bottom surface of the substrate;

[0013] The back-side P-type transition region is vertically aligned with the front-side P-type transition region, such that the back-side P-type transition region is adjacent to the region directly below the main junction of the active region in the vertical direction.

[0014] Optionally, the P-shaped transition area on the back side is a smoothly connected double-arc region.

[0015] Optionally, the terminal region further includes: a plurality of back-side P-type field limiting rings; the back-side P-type field limiting rings are located in the substrate or in the substrate and the epitaxial layer, the surface of the back-side P-type field limiting rings is at the same level as the bottom surface of the substrate, and the back-side P-type field limiting rings sequentially surround the back-side P-type transition region and are distributed at intervals.

[0016] Optionally, the width of the injection opening in a single arc-shaped region of the frontal P-type transition zone ranges from 5 to 10 μm.

[0017] Optionally, the main junction of the active region is a P-type emitter region, which is located in the epitaxial layer, and the upper surface of the P-type emitter region is on the same horizontal plane as the upper surface of the epitaxial layer. Each end of the P-type emitter region is in contact with the front-side P-type transition region.

[0018] Optionally, the active region further includes an anode metal layer; the anode metal layer is located above the epitaxial layer and covers the P-type emitter region.

[0019] Optionally, it further includes: a cathode metal layer; the cathode metal layer is located below the substrate, and the cathode metal layer covers the back-side P-type transition region and the back-side P-type field confinement ring.

[0020] Optionally, the terminal region further includes an insulating layer located above the epitaxial layer, the insulating layer covering the front P-type transition region and the front P-type field limiting ring.

[0021] Based on the same inventive concept, in a second aspect, the present invention also provides a method for manufacturing a fast recovery diode, for manufacturing the fast recovery diode as described in the first aspect, the method comprising:

[0022] An epitaxial layer is formed on the substrate;

[0023] The active region and the terminal region are formed on the epitaxial layer, wherein the terminal region includes: a front-side P-type transition region and at least two front-side P-type field-limiting rings;

[0024] Both the front-side P-type transition region and the front-side P-type field limiting ring are located on the epitaxial layer. The front-side P-type transition region is in contact with the main junction of the active region. The front-side P-type field limiting rings are spaced apart and sequentially surround the front-side P-type transition region. The surfaces of the main junction of the active region, the front-side P-type transition region, the front-side P-type field limiting rings, and the epitaxial layer are on the same horizontal plane. The front-side P-type transition region is a smoothly connected double-arc region.

[0025] One or more technical solutions in the embodiments of the present invention have at least the following technical effects or advantages:

[0026] In this embodiment of the invention, a front-side P-type transition region is provided near the main junction of the active region in the terminal region. This front-side P-type transition region is adjacent to and in contact with the main junction of the active region, thereby reducing the electric field strength at the edge of the main junction (i.e., the anode edge) and laterally reducing the current density at the main junction edge. Furthermore, the front-side P-type transition region is a smoothly connected double-arc region. This introduces a gentle connection point, transforming the single high electric field at the anode edge into two lower electric fields, dispersing the electric field strength at the anode edge, and further improving or reducing the electric field at the anode edge. The smoothly connected double-arc region (i.e., the front-side P-type transition region) makes the current density distribution more uniform, further laterally reducing the current density at the main junction edge and avoiding local current overshoot and excessive thermal stress at the anode edge. Through the structural design of the fast recovery diode in this embodiment of the invention, premature local breakdown of the device is avoided, improving the device's withstand voltage and enhancing its reliability and practicality. Attached Figure Description

[0027] Various other advantages and benefits will become apparent to those skilled in the art upon reading the following detailed description of preferred embodiments. The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings:

[0028] Figure 1 A schematic diagram of the fast recovery diode device in an embodiment of the present invention is shown;

[0029] Figure 2 The diagram illustrates the relationship between the distance and electric field strength between the fast recovery diode device and the edge of the anode main junction in an embodiment of the present invention, as well as a schematic diagram of the relationship between the distance and electric field strength between the fast recovery diode device and the edge of the anode main junction in a comparative device.

[0030] Figure 3 The diagram illustrates the relationship between the distance and current density between the fast recovery diode device and the edge of the anode main junction in an embodiment of the present invention, and provides a schematic diagram of the relationship between the distance and current density between the fast recovery diode device and the edge of the anode main junction in a comparative device.

[0031] Figure 4 The diagram illustrates the relationship between the longitudinal depth and electric field intensity of the fast recovery diode device from the front to the back side in an embodiment of the present invention, and provides a schematic diagram of the relationship between the longitudinal depth and electric field intensity of the device from the front to the back side.

[0032] Figure 5 The reverse recovery current curve of the fast recovery diode device in the embodiment of the present invention is shown, as well as a schematic diagram of the reverse recovery current curve of the comparative device.

[0033] Figure 6 This diagram illustrates a structure in an embodiment of the present invention in which an epitaxial layer, a front-side P-type transition region, and a front-side P-type field confinement ring are formed on a substrate.

[0034] Figure 7 This diagram illustrates a structure in which a P-type emitter region is formed on the epitaxial layer and in the active region, according to an embodiment of the present invention.

[0035] Figure 8 This diagram illustrates a structure in which a back-side P-type transition region and a back-side P-type field confinement ring are formed in the terminal region under the substrate, according to an embodiment of the present invention.

[0036] Figure 9 This diagram illustrates a structure in which an insulating layer is formed on an epitaxial layer according to an embodiment of the present invention.

[0037] Figure 10 This diagram illustrates a structure in which an anode metal layer is formed in the active region above the epitaxial layer, according to an embodiment of the present invention.

[0038] Figure 11 A schematic flowchart of the manufacturing method of a fast recovery diode according to an embodiment of the present invention is shown.

[0039] In the attached figures, 110 is the substrate; 120 is the epitaxial layer; 130 is the active region; 140 is the termination region; and 150 is the cathode metal layer.

[0040] 121. Buffer layer; 122. Drift layer;

[0041] 131. P-type emitter region; 132. Anode metal layer;

[0042] 141. Front P-type transition region; 142. Front P-type field limiting ring; 143. Back P-type transition region; 144. Back P-type field limiting ring; 145. Insulating layer. Detailed Implementation

[0043] Exemplary embodiments of the present disclosure will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.

[0044] Example 1

[0045] The first embodiment of the present invention provides a fast recovery diode, such as... Figure 1 As shown, it includes: a substrate 110, an epitaxial layer 120, an active region 130, and a termination region 140 surrounding the active region 130. The epitaxial layer 120 is disposed on the substrate 110. The active region 130 and the termination region 140 are disposed on the epitaxial layer 120.

[0046] The terminal region 140 includes a front-facing P-type transition region 141 and at least two front-facing P-type field-limiting rings 142. Both the front-facing P-type transition region 141 and the front-facing P-type field-limiting rings 142 are spatially annular and surround the active region 130. For example... Figure 1 As shown in the cross-sectional view of the fast recovery diode, the front-side P-type transition region 141 and the front-side P-type field-limiting ring 142 are both located on the epitaxial layer 120. The front-side P-type transition region 141 is in contact with the main junction of the active region 130, that is, the front-side P-type transition region 141 is provided in the terminal region 140 near the main junction of the active region 130, and the front-side P-type transition region 141 is adjacent to and in contact with the main junction of the active region 130. The front-side P-type field-limiting rings 142 are spaced apart and sequentially surround the front-side P-type transition region 141 and the active region 130, that is, as shown in the diagram. Figure 1As shown, the front-side P-type field-limiting rings 142 are arranged at intervals from the front-side P-type transition region 141 outwards. The front-side P-type field-limiting ring 142 farthest from the active region 130 can also be called the front-side P-type cutoff ring. The upper surface of the main junction of the active region 130, the upper surface of the front-side P-type transition region 141, the upper surface of the front-side P-type field-limiting rings 142, and the upper surface of the epitaxial layer 120 are on the same horizontal plane.

[0047] The front P-shaped transition area 141 is a smoothly connected double-arc region, which can also be called the front P-shaped double-arc transition area. The front P-shaped transition area 141 is formed by two arc-shaped regions (i.e., arc-shaped regions), and the two arc-shaped regions are smoothly connected to introduce a gentle connection point between the two arc-shaped regions, so that there are no sharp points between the two arc-shaped regions and the formation of convex curved corners is avoided.

[0048] It should also be noted that the substrate 110 is an N-type heavily doped substrate. The material of the substrate 110 is silicon dioxide or silicon nitride. The epitaxial layer 120 is an N-type epitaxial layer. The epitaxial layer 120 includes one or more N-type buffer layers 121 located on the substrate 110, and an N-type drift layer 122 located on the N-type buffer layer 121. The doping concentration, thickness, and other parameters of the substrate 110 and the epitaxial layer 120 can be selected and set according to the voltage withstand requirements of different products or actual needs. The device in this embodiment refers to a fast recovery diode device.

[0049] In this embodiment, a front-side P-type transition region 141 is provided in the terminal region 140 near the main junction of the active region 130. The front-side P-type transition region 141 is adjacent to and in contact with the main junction of the active region 130 to reduce the electric field strength at the edge of the main junction of the active region 130 (i.e., the anode edge), and to laterally reduce the current density at the edge of the main junction. Furthermore, the front-side P-type transition region 141 is a smoothly connected double-arc region. The front-side P-type transition region 141 introduces a gentle connection point, transforming the single high electric field at the anode edge into two lower electric fields, dispersing the electric field strength at the anode edge, and further improving or reducing the electric field at the anode edge. The smoothly connected double-arc region (i.e., the front-side P-type transition region 141) makes the current density distribution more uniform, further reducing the current density at the edge of the main junction laterally, avoiding local current overshoot and excessive thermal stress at the anode edge. Through the structural design of the fast recovery diode in this embodiment, premature local breakdown of the device is avoided, the withstand voltage of the device is improved, and the reliability and practicality of the device are enhanced.

[0050] Below, in conjunction with Figure 1 This embodiment details the specific structure and device principle of the fast recovery diode:

[0051] like Figure 1As shown, the terminal region 140 also includes a back-side P-type transition region 143. The back-side P-type transition region 143 is a smoothly connected double-arc region. The back-side P-type transition region 143 is located in the substrate 110 or in the substrate 110 and the epitaxial layer 120, that is, the depth of the back-side P-type transition region 143 from the bottom surface of the substrate 110 to the epitaxial layer 120 can reach into the substrate 110 or into the epitaxial layer 120. The surface of the back-side P-type transition region 143 is at the same horizontal plane as the bottom surface of the substrate 110. The back-side P-type transition region 143 is vertically aligned with the front-side P-type transition region 141, so that the back-side P-type transition region 143 is adjacent to the region directly below the main junction of the active region 130 in the vertical direction.

[0052] The back-side P-type transition region 143 and the front-side P-type transition region 141 form a transition region, which works synergistically. When the device is subjected to reverse bias, the back-side P-type transition region 143 allows additional holes to be injected into the drift layer 122 of the epitaxial layer 120, recombine with electrons, and achieve vertical electric field modulation. This has a certain widening effect on the depletion region and can also reduce the electric field peak at the edge of the main junction. Furthermore, the back-side P-type transition region 143 can block / reduce the vertical current inrush at the edge of the main junction, thereby reducing the current density at the edge of the main junction. Through the combined effect of the front and back-side P-type double-arc transition regions, the current density and electric field strength at the junction edge are reduced, improving device reliability and enhancing device stability and safety.

[0053] It should be noted that in this embodiment, the front side refers to the side of the epitaxial layer 120 facing upwards, and the back side refers to the side of the substrate 110 facing downwards. The front and back sides only indicate different placement positions. In this embodiment, the front P-type transition region 141 and the back P-type transition region 143 are P-type transition regions in different locations, and the same applies to the P-type field limiting ring.

[0054] like Figure 1 As shown, the terminal region 140 further includes a plurality of back-side P-type field-limiting rings 144. The back-side P-type field-limiting rings 144 are located in the substrate 110 or in the substrate 110 and epitaxial layer 120; that is, the depth of the back-side P-type field-limiting rings 144 from the bottom surface of the substrate 110 to the epitaxial layer 120 can reach into the substrate 110 or the epitaxial layer 120. The surface of the back-side P-type field-limiting rings 144 is at the same horizontal plane as the bottom surface of the substrate 110. The back-side P-type field-limiting rings 144 sequentially surround the back-side P-type transition region 143 and are spaced apart. Figure 1 As shown, the rear P-type field limiting rings 144 are arranged at intervals from the rear P-type transition area 143 outwards. The rear P-type field limiting rings 144 can be set in a one-to-one correspondence with the front P-type field limiting rings 142, or they can be set in a staggered manner; no restriction is placed here.

[0055] Both the back-side P-type field limiting ring 144 and the back-side P-type transition region 143 can reduce electron injection at the back cathode during forward conduction, thereby reducing the reverse recovery peak current IRRM. Furthermore, the increased hole introduction during reverse recovery ensures sufficient holes to maintain the tailing current at the end of the process, increasing the reverse recovery softness of the fast recovery diode and preventing device damage caused by oscillations during "hard turn-off." The combined effect of the back-side P-type transition region 143 and the back-side P-type field limiting ring 144 further reduces the electric field strength and current density at the anode edge, improving the device's reliability and practicality.

[0056] Furthermore, each of the back-side P-type field limiting rings 144 is an independent field limiting ring, allowing the peak electric field of the device to be distributed across multiple back-side P-type field limiting rings 144, thus preventing excessively strong local electric fields. The region between adjacent back-side P-type field limiting rings 144 does not affect normal carrier injection and conductance modulation. This reduces the reverse recovery peak current IRRM and increases reverse recovery softness while keeping the forward voltage drop increase within a low range, balancing these two trade-offs and achieving a superior compromise. Moreover, the spaced-out back-side P-type field limiting rings 144 better disperse the thermal stress of the device, further improving its reliability and stability.

[0057] Furthermore, the front P-type transition region 141 and the front P-type field limiting ring 142 have the same structure as the back P-type transition region 143 and the back P-type field limiting ring 144. In the manufacturing process of the device, the front and back of the terminal region 140 can be realized using the same structural photomask, without the need for additional photomasks, without additional processes and costs, thus achieving process compatibility and reducing manufacturing costs.

[0058] The injection opening width of a single arc-shaped region in the front P-type transition region 141 and the injection opening width of a single arc-shaped region in the back P-type transition region 143 are both 5~10µm. The spacing between the injection openings of the two arc-shaped regions of the P-type transition region is 2~7µm. During the fabrication of the P-type transition region, P-type ions are injected through the injection openings of the two arc-shaped regions, forming two smoothly intersecting double-arc-shaped regions after the P-type ions diffuse, i.e., the structure of the P-type double-arc transition region. Although this embodiment sets a P-type transition region in the termination region, the area of ​​the termination region is consistent with that of the existing fast recovery diode, without adding additional termination area. In other words, the P-type transition region is directly added based on the area of ​​the termination region of the existing fast recovery diode, which is compatible with existing processes, reduces process costs, and saves chip area. The ring width of the P-type field limiting ring is 8~12µm, and the ring spacing is 18~28µm.

[0059] like Figure 1As shown, the terminal region 140 also includes an insulating layer 145, which is located above the epitaxial layer 120 and covers the front-side P-type transition region 141 and the front-side P-type field limiting ring 142. The terminal region 140 can also form a metal field plate or a polysilicon field plate, etc., according to actual needs. The specific structure of the terminal region 140 forming a metal field plate or a polysilicon field plate is not specifically limited here.

[0060] like Figure 1 As shown, the main junction of the active region 130 is a P-type emitter region 131, which is located in the epitaxial layer 120. The upper surface of the P-type emitter region 131 is on the same horizontal plane as the upper surface of the epitaxial layer 120, and each end of the P-type emitter region 131 is in contact with the front-side P-type transition region 141. The active region 130 also includes an anode metal layer 132, which is located above the epitaxial layer 120 and covers the P-type emitter region 131. The anode metal layer 132 and the P-type emitter region 131 form the anode of the device. In this embodiment, the electric field strength and current density at the anode edge are improved mainly through the P-type field limiting ring and P-type transition region in the terminal region 140. It can also reduce the reverse recovery peak current IRRM of the device and increase the reverse recovery softness. Therefore, the specific structure of the active region 130 is not limited, and other areas of the active region 130 can be designed according to actual needs.

[0061] The fast recovery diode of this embodiment further includes a cathode metal layer 150. The cathode metal layer 150 is located below the substrate 110 and covers the back-side P-type transition region 143 and the back-side P-type field limiting ring 144. The cathode metal layer 150 forms the cathode of the device.

[0062] The following section will describe in detail the structural principle of the fast recovery diode device of this embodiment by comparing and analyzing it with a comparative device. The comparative device is a fast recovery diode device without the front-side P-type transition region 141, the back-side P-type transition region 143, and the back-side P-type field-limiting ring 144. Other structural features of the comparative device are consistent with those of the fast recovery diode of this embodiment; for example, the structure of the active region 130 of the comparative device is consistent with the structure of the active region 130 of the device of this embodiment, and the structure of the P-type field-limiting ring of the comparative device is consistent with the structure of the P-type field-limiting ring of the device of this embodiment.

[0063] The P-type transition region is a double-arc transition region, i.e., a smoothly connected double-arc region. By having the front-side P-type transition region 141 in contact with each end of the P-type emitter region 131 of the active region 130, the current density at the edge of the anode main junction can be reduced laterally. The smoothly connected double-arc region structure of the front-side P-type transition region 141 transforms a single high electric field peak at the edge of the anode main junction into two lower electric field peaks, thus withstanding the high-intensity electric field at the anode edge. Furthermore, the corresponding arrangement of the front-side P-type transition region 141 and the back-side P-type transition region 143, and their synergistic effect, further reduces the electric field strength and current density at the anode edge, especially the longitudinal current density, which also reduces the reverse recovery peak current IRRM of the device and increases the reverse recovery softness of the device.

[0064] like Figure 2 As shown, Figure 2 The horizontal axis represents the distance from the edge of the anode main junction, that is, the distance from the edge of the P-type emitter region 131 of the active region 130. Figure 2 The vertical axis represents the electric field intensity. From Figure 2 The electric field intensity curves of the comparative device show that the active region 130 of the comparative device has a larger curvature and higher electric field intensity at the edge of the main junction. A very high peak electric field exists at the edge of the active region 130 of the comparative device, exceeding 2.5E5 V / cm. Therefore, the comparative device is prone to breakdown at lower reverse bias voltages, resulting in lower breakdown voltage performance. Figure 2 As can be seen from the electric field intensity curve of the device in this embodiment, the device, through the front-side P-type double-arc transition region structure, introduces a smooth connection point (i.e., an intermediate connection point) between the two arcs in advance through two-stage arc regions. Therefore, the entire depletion layer expansion path is divided into two stages. During the expansion of the depletion layer from the main junction (i.e., the P-type emitter region 131) of the active region 130 to the front-side P-type transition region 141, a gentle redistribution occurs at the intermediate connection point of the front-side P-type transition region 141. This achieves the dispersion and balance of the electric field at the edge of the anode main junction, improves the lateral high electric field intensity at the edge of the anode main junction, and avoids the presence of a local high-intensity electric field at the edge of the anode main junction, preventing premature device breakdown. Therefore, the structural design of the front-side P-type transition region 141 reduces the electric field intensity at the edge of the main junction of the active region 130 (i.e., the anode edge), enhancing the reliability and stability of the device.

[0065] By leveraging the synergistic effect of the double-arc transition regions on the front and back sides of the terminal region 140 located at the edge of the P-type emitter region 131 in the active region 130, the current density at the edge of the anode main junction is reduced both longitudinally and laterally, enhancing device reliability. Since the anode area (i.e., the area of ​​the active region 130 on the front side) of the fast recovery diode is smaller than the cathode area (i.e., the area on the back side), specifically, the terminal region 140 at the edge of the active region 130 occupies a certain area on the front side, while the back side of the device is a full-area cathode. When the device is forward-biased, electrons flow longitudinally from the back side towards the anode and the terminal region 140 at the anode edge, and laterally towards the anode. Therefore, current filament accumulation is significant at the anode edge, resulting in high current density and making the device susceptible to thermal failure and other device damage.

[0066] However, through the device structure configuration of this embodiment, a P-type double-arc transition region (i.e., front P-type transition region 141 and back P-type transition region 143) is provided at the edge of the anode main junction. This allows the current to be distributed along the edge length of the front P-type double-arc transition region, resulting in a more uniform current density distribution. Simultaneously, the back P-type double-arc transition region directly below the edge of the main junction can block and reduce the longitudinal current inrush at the edge of the main junction, also reducing the current density at the edge of the main junction. The combined effect of the front and back P-type double-arc transition regions avoids localized current overshoot and excessive thermal stress at the anode edge, improving the reliability and stability of the device. Figure 3 As shown, Figure 3 The horizontal axis represents the distance from the edge of the anode main junction, that is, the distance from the edge of the P-type emitter region 131 of the active region 130. Figure 3 The vertical axis represents current density. From Figure 3 As can be clearly seen, the current density at the edge of the anode main junction of the comparative device is very high. Through the device structure of this embodiment, and the setting of the front and back P-type double-arc transition regions, the current density at the edge of the anode main junction is greatly reduced.

[0067] During reverse bias, the back-side P-type double-arc transition region at the edge of the main junction receives additional holes injected into the drift layer 122 of the epitaxial layer 120, which recombine with electrons, achieving vertical electric field modulation. This also broadens the depletion region, reduces the peak electric field at the edge of the anode main junction, and provides voltage withstand capability. Figure 4 As shown, Figure 4 The horizontal axis represents the vertical depth of the device from the front to the back. Figure 4 The vertical axis represents the electric field strength of the device. Compared to the comparative device, the device in this embodiment has a significantly smoother electric field distribution, and the electric field strength is lower than that of the comparative device. Through the device structure of this embodiment, and the setting of the front and back P-type double arc transition regions, the electric field strength at the edge of the anode main junction is greatly reduced.

[0068] like Figure 5 As shown, Figure 5 The horizontal axis represents the device's off-time. Figure 5 The vertical axis represents the reverse recovery current of the device. From Figure 5 As can be seen from the electric field intensity curve of the comparison device, the reverse recovery peak current IRRM of the comparison device is relatively large. At the end of the reverse recovery phase of the comparison device, when the current decreases from the reverse peak, the excessive rate of change of current leads to a hard turn-off phenomenon in the comparison device. This results in current oscillations and electromagnetic interference in the circuit of the comparison device, which can easily damage it. Therefore, under high voltage and high current conditions, fast recovery diodes need to have soft recovery characteristics to avoid device damage caused by current oscillations and electromagnetic interference.

[0069] Compared to the comparative device, the reverse recovery peak current IRRM of the device in this embodiment is much smaller than that of the comparative device, indicating that the device structure of this embodiment reduces the reverse recovery peak current IRRM. In the final stage of reverse recovery of the device in this embodiment, as the current decreases from the reverse peak, the curve at the end of the reverse recovery is relatively gentle, indicating a small rate of current change. This significantly increases the reverse recovery softness of the device; that is, the device in this embodiment has more holes to maintain the tail current at the end of the reverse recovery, increasing the reverse recovery softness and avoiding device damage caused by oscillations due to "hard turn-off". Furthermore, the device in this embodiment does not exhibit significant oscillations, improving the reliability and stability of the device.

[0070] In summary, the terminal region 140 structure, which combines the front P-type transition region 141 and the back P-type transition region 143 at the edge of the main junction (i.e., the anode main junction) in the active region 130, along with the spaced P-type field limiting rings on the front and back sides, effectively enhances the high electric field strength peak and current concentration effect at the junction of the active region 130 and the terminal region 140. It also reduces the reverse recovery peak current IRRM and increases the reverse recovery softness. Furthermore, it collaboratively improves the device's reliability and stability by addressing issues such as excessively high local electric field breakdown and overheating caused by excessive local current at the edge of the anode main junction due to high electric field strength and high current density. Moreover, since the back and front sides of the terminal region 140 share the same structure, only one photolithography plate is needed to complete the back structure photolithography, eliminating the need for additional photolithography plates, achieving process compatibility, and avoiding additional costs.

[0071] Below, in conjunction with Figure 1 The manufacturing process of the fast recovery diode device in this embodiment is described in detail:

[0072] like Figure 6As shown, an epitaxial layer 120 is grown on a substrate 110. The epitaxial layer 120 includes one or more N-type buffer layers 121. An N-type drift layer 122 is formed on top of the buffer layer 121. The doping concentration, thickness, and other parameters of the substrate 110 and the epitaxial layer 120 can be selected and set according to the voltage withstand requirements of different products. In this embodiment, the thickness of the example substrate 110 ranges from 10µm to 20µm, and the thickness of the epitaxial layer 120 ranges from 35µm to 75µm.

[0073] like Figure 6 As shown, through patterning processes such as photolithography exposure, development, and etching, an opening region of a front-side P-type transition region 141 and a front-side P-type field confinement ring 142 is formed in the terminal region 140 on the epitaxial layer 120. P-type boron ion implantation is then performed to push the implantation holes, forming the front-side P-type transition region 141 and the front-side P-type field confinement ring 142. The implantation opening width of a single arc-shaped region of the front-side P-type transition region 141 ranges from 5 to 10 μm, the width of the front-side P-type field confinement ring 142 ranges from 8 μm to 12 μm, the spacing between the implantation openings of two arc-shaped regions of the front-side P-type transition region 141 ranges from 2 μm to 7 μm, and the ring spacing of the front-side P-type field confinement rings 142 ranges from 18 μm to 28 μm. The inter-ring distance of the front-side P-type field confinement rings 142 gradually increases by 1 μm to 4 μm from the first to the last field confinement ring. The number of front-side P-type field confinement rings 142 and the ring spacing are set according to the voltage withstand requirements of different products. The implantation energy range for P-type boron ions is 60-80 keV, and the implantation dose range is 5E13cm. This occurs in the opening regions of the frontal P-type transition region 141 and the frontal P-type field confinement ring 142. −2 ~1E15m −2 The actual injected energy and dosage can be adjusted according to different product requirements and process conditions.

[0074] like Figure 7 As shown, P-type boron ion implantation is performed in the active region 130 of the epitaxial layer 120 through patterning processes such as photolithography, development, and etching to form the P-type emitter region 131, which is the anode main junction. The implantation energy range of the P-type emitter region 131 is 60~80 KeV, and the implantation dose range is 2E12cm. −2 ~5E13cm −2 The actual injected energy and dosage can be adjusted according to different product requirements and process conditions.

[0075] like Figure 8As shown, after photolithography exposure and development, a back-side P-type transition region 143 and a back-side P-type field confinement ring 144 are formed on the bottom surface of the substrate 110, followed by P-type boron ion implantation to form the back-side P-type transition region 143 and the back-side P-type field confinement ring 144. The implantation energy range for the back-side P-type transition region 143 and the back-side P-type field confinement ring 144 is 40~80 KeV, and the implantation dose range is 5E15cm⁻¹. −2 ~1E17m −2 The actual implantation energy and dose can be adjusted according to different product requirements and process conditions. It should be noted that the implantation dose of the back-side P-type structure of the termination region 140 > the implantation dose of the front-side P-type structure of the termination region 140 ≥ the implantation dose of the P-type emitter region 131. The implantation dose of the P-type structure of the termination region 140 being ≥ the implantation dose of the P-type emitter region 131 allows the depletion region to extend further into the drift layer 122, resulting in better device breakdown voltage. The higher implantation dose of the back-side P-type structure of the termination region 140 compared to the front-side P-type structure is due to the higher doping concentration of the substrate 110, preventing the back-side P-type structure of the termination region 140 from being diluted by the substrate 110.

[0076] like Figure 9 As shown, an insulating layer 145 of the terminal region 140 is formed on the epitaxial layer 120 by physical vapor deposition or chemical vapor deposition. The insulating layer 145 covers the front P-type transition region 141 and the front P-type field limiting ring 142. The material of the insulating layer 145 can be insulating materials such as silicon dioxide and silicon nitride.

[0077] like Figure 10 As shown, in Figure 9 On the insulating layer 145 formed in the middle, an anode contact hole is formed through patterning processes such as exposure, development, and etching. After the hole is formed, metal is deposited using methods such as thermal evaporation and magnetron sputtering to form an anode metal layer 132 on the epitaxial layer 120. The anode metal layer 132 covers the P-type emitter region 131.

[0078] like Figure 1 As shown, a cathode metal layer 150 is formed by metal deposition on the back side of the substrate 110 using methods such as thermal evaporation and magnetron sputtering.

[0079] In the manufacturing process of this embodiment, it is compatible with the existing fast recovery diode manufacturing process. In the terminal region 140, the same P-type structure is set on the back and front sides. Only one photolithography plate of the terminal region 140 is needed to complete the structural photolithography of the front and back sides. No additional photolithography plate is required, achieving process compatibility and no additional cost.

[0080] Example 2

[0081] Based on the same inventive concept, the second embodiment of the present invention also provides a method for manufacturing a fast recovery diode, used to manufacture the fast recovery diode as described in Embodiment 1, such as... Figure 11 As shown, the manufacturing method includes:

[0082] S201, an epitaxial layer is formed on the substrate;

[0083] S202, the active region and the termination region are formed on the epitaxial layer, wherein the termination region includes: a front-side P-type transition region and at least two front-side P-type field limiting rings;

[0084] Both the front-side P-type transition region and the front-side P-type field limiting ring are located on the epitaxial layer. The front-side P-type transition region is in contact with the main junction of the active region. The front-side P-type field limiting rings are spaced apart and sequentially surround the front-side P-type transition region. The surfaces of the main junction of the active region, the front-side P-type transition region, the front-side P-type field limiting rings, and the epitaxial layer are on the same horizontal plane. The front-side P-type transition region is a smoothly connected double-arc region.

[0085] Since the fast recovery diode manufacturing method described in this embodiment is the same as the manufacturing method used for the fast recovery diode in Embodiment 1 of this application, those skilled in the art can understand the specific implementation method and various variations of the fast recovery diode manufacturing method described in Embodiment 1 of this application based on the fast recovery diode. Therefore, how this fast recovery diode manufacturing method implements the fast recovery diode in Embodiment 1 of this application will not be described in detail here. Anyone skilled in the art who implements the manufacturing method used for the fast recovery diode in Embodiment 1 of this application falls within the scope of protection of this application.

[0086] Those skilled in the art will understand that although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of the invention.

[0087] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A fast recovery diode, characterized in that, include: Substrate, epitaxial layer, active region, and terminal region surrounding the active region; The epitaxial layer is disposed on the substrate; The active region and the terminal region are disposed on the epitaxial layer; The terminal area includes: a front-facing P-type transition region and at least two front-facing P-type field limiting rings; The front P-type transition region and the front P-type field limiting ring are both located on the epitaxial layer. The front P-type transition region is in contact with the main junction of the active region. The front P-type field limiting rings are spaced apart and sequentially surround the front P-type transition region and the active region. The upper surface of the main junction of the active region, the upper surface of the front P-type transition region, the upper surface of the front P-type field limiting ring, and the upper surface of the epitaxial layer are on the same horizontal plane. The front P-shaped transition area is a smoothly connected double arc-shaped region, which is formed by two arc-shaped regions and the two arc-shaped regions are smoothly connected. By providing a front-side P-type transition region near the main junction of the active region in the terminal region, the front-side P-type transition region is adjacent to and in contact with the main junction of the active region, thereby reducing the electric field strength at the edge of the main junction of the active region and laterally reducing the current density at the edge of the main junction. The terminal area also includes: a rear P-shaped transition area; the rear P-shaped transition area is a smoothly connected double arc-shaped region; The back-side P-type transition region is located in the substrate or in the substrate and the epitaxial layer, and the surface of the back-side P-type transition region is at the same level as the bottom surface of the substrate; The back-side P-type transition region is vertically aligned with the front-side P-type transition region, such that the back-side P-type transition region is adjacent to the region directly below the main junction of the active region in the vertical direction.

2. The fast recovery diode as described in claim 1, characterized in that, The terminal area further includes: a plurality of back-side P-type field limiting rings; the back-side P-type field limiting rings are located in the substrate or in the substrate and the epitaxial layer, the surface of the back-side P-type field limiting rings is at the same level as the bottom surface of the substrate, and the back-side P-type field limiting rings sequentially surround the back-side P-type transition region and are distributed at intervals.

3. The fast recovery diode as described in claim 1, characterized in that, The width of the injection opening in a single arc-shaped region of the frontal P-type transition zone ranges from 5 to 10 μm.

4. The fast recovery diode as described in claim 1, characterized in that, The main junction of the active region is a P-type emitter region, which is located in the epitaxial layer. The upper surface of the P-type emitter region is on the same horizontal plane as the upper surface of the epitaxial layer, and each end of the P-type emitter region is in contact with the front P-type transition region.

5. The fast recovery diode as described in claim 4, characterized in that, The active region further includes an anode metal layer; the anode metal layer is located above the epitaxial layer and covers the P-type emitter region.

6. The fast recovery diode as described in claim 2, characterized in that, Also includes: A cathode metal layer; the cathode metal layer is located below the substrate and covers the back P-type transition region and the back P-type field confinement ring.

7. The fast recovery diode as described in claim 1, characterized in that, The terminal region further includes an insulating layer located above the epitaxial layer, the insulating layer covering the front P-type transition region and the front P-type field limiting ring.

8. A method for manufacturing a fast recovery diode, characterized in that, The method for manufacturing a fast recovery diode as described in any one of claims 1-7 comprises: An epitaxial layer is formed on the substrate; The active region and the terminal region are formed on the epitaxial layer, wherein the terminal region includes: a front-side P-type transition region and at least two front-side P-type field-limiting rings; Both the front-side P-type transition region and the front-side P-type field limiting ring are located on the epitaxial layer. The front-side P-type transition region is in contact with the main junction of the active region. The front-side P-type field limiting rings are spaced apart and sequentially surround the front-side P-type transition region. The surfaces of the main junction of the active region, the front-side P-type transition region, the front-side P-type field limiting rings, and the epitaxial layer are on the same horizontal plane. The front-side P-type transition region is a smoothly connected double-arc region.

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