Freewheel device and power semiconductor device
By introducing a gradient anode structure into the freewheeling device, the contradiction between surge capability, reverse recovery loss, and safe operating area performance is resolved, achieving a balance between high-efficiency surge capability and low loss in the freewheeling device.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-05
- Publication Date
- 2026-04-07
AI Technical Summary
Improving the surge capability of freewheeling devices and reducing reverse recovery losses and improving the performance of the reverse recovery safe operating area are contradictory and difficult to reconcile.
By introducing a gradient anode structure, a P+ type doped structure with a size that decreases from large to small is formed from the center of the freewheeling device outwards. This enhances carrier injection in the central region and reduces the injection efficiency in the surrounding areas near the terminal region.
While improving the surge capability of freewheeling devices, it avoids a significant increase in reverse recovery losses and a decrease in the performance of the reverse recovery safe operating area.
Smart Images
Figure CN121815676A_ABST
Abstract
Description
Technical Field
[0001] This disclosure relates to the field of semiconductor technology, and in particular to a freewheeling device and a power semiconductor device. Background Technology
[0002] Fast recovery diodes (FRDs) are typically used for rectification and freewheeling. In the field of power semiconductor devices, FRDs are generally connected in anti-parallel to power switching transistors (such as insulated gate bipolar transistors, IGBTs) to provide reverse freewheeling. In recent years, the requirements for FRDs have become increasingly stringent, especially in wind power and power grid applications. Because circuits must withstand the effects of various system instabilities, such as current and voltage overloads, this places more stringent demands on FRDs. FRDs must withstand forward surge currents several times or even tens of times their rated current.
[0003] At the chip level, improving the surge current capability of an FRD requires enhancing anode injection and reducing the on-state voltage drop (Vf). However, this leads to a significant increase in reverse recovery losses and increases carrier injection efficiency in the termination region, affecting the performance of the reverse recovery safe operating area. In other words, improving the surge capability of an FRD and reducing reverse recovery losses and improving the performance of the reverse recovery safe operating area are contradictory and difficult to reconcile. Summary of the Invention
[0004] This disclosure provides a freewheeling device and a power semiconductor device to solve the problem of the difficult-to-coordinate contradiction between improving the surge capability of the freewheeling device, reducing reverse recovery loss, and improving the reverse recovery safe operating area performance.
[0005] In a first aspect, this disclosure provides a freewheeling device, including an effective region and a terminal region located outside the effective region. The freewheeling device includes: an anode located in the effective region, the anode including a plurality of first P+ type doped structures, and the width of the plurality of first P+ type doped structures decreasing along a direction parallel to the surface of the effective region and away from the center of the effective region.
[0006] Secondly, this disclosure provides a power semiconductor device, including: a power switch transistor; and the aforementioned freewheeling device, wherein the freewheeling device is connected in reverse parallel with the power switch transistor.
[0007] The technical solution of this application introduces a gradient anode structure to form a P+ type doped structure with a size that gradually decreases from the center of the freewheeling device to the periphery. As a result, when the freewheeling device is turned on, the carrier injection is strong in the central region of the freewheeling device and weak in the surrounding areas near the terminal region. Therefore, it does not enhance the carrier injection in the terminal region. Thus, while improving the surge capability of the freewheeling device, it does not cause a significant increase in reverse recovery loss or a decrease in the reverse recovery safe operating area. Attached Figure Description
[0008] The present disclosure will be described in more detail below based on embodiments and with reference to the accompanying drawings:
[0009] Figure 1 This is a cross-sectional view of the freewheeling device in some embodiments of this application;
[0010] Figure 2 This is a top view of the freewheeling device in some embodiments of this application;
[0011] Figure 3 and Figure 4 This is a top view of the freewheeling device in some embodiments of this application;
[0012] Figure 5 This is a schematic diagram of the P+ type doped structure of the anode in some embodiments of this application;
[0013] Figure 6 This is a cross-sectional view of the effective area of the freewheeling device in some embodiments of this application;
[0014] Figures 7-10 This is a top view of the freewheeling device in some embodiments of this application;
[0015] Figures 11-15 This is a top view of the freewheeling device in some embodiments of this application;
[0016] Figure 16 This is a schematic diagram of the structure of a power semiconductor device in some embodiments of this application.
[0017] In the accompanying drawings, the same parts are referred to by the same reference numerals, and the drawings are not drawn to scale. Detailed Implementation
[0018] To enable those skilled in the art to better understand the technical solutions of this disclosure, and to fully understand and implement the process of how this disclosure applies technical means to solve technical problems and achieve corresponding technical effects, the technical solutions in the embodiments of this disclosure will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this disclosure, not all embodiments. The embodiments of this disclosure and the various features within them can be combined with each other without conflict, and the resulting technical solutions are all within the protection scope of this disclosure. All other embodiments obtained by those skilled in the art based on the embodiments of this disclosure without creative effort should fall within the protection scope of this disclosure.
[0019] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this disclosure are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of this disclosure described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.
[0020] For ease of understanding, the terms used in the technical solutions of this application are explained below.
[0021] Freewheeling devices, mainly including freewheeling diodes, fast recovery diodes, and Schottky diodes, play a role in preventing voltage and current surges in circuits, ensuring circuit stability and safety.
[0022] The effective region refers to the area in a freewheeling device that performs its primary function; it typically refers to the active region of the device. The effective region includes the PN junction, which withstands stress when a reverse withstand voltage is applied.
[0023] The bonding region plays an important role in electronic packaging technology, and it is a key part for interconnecting the chip and the casing.
[0024] The termination region, located around the freewheeling device, occupies a portion of the chip area, but its design is necessary. The main function of the termination region is to improve the device's withstand voltage and reliability, and reduce leakage current. The working principle of the termination region includes mechanisms such as field-limiting loop junction termination and cylindrical junction depletion. By designing the termination region appropriately, the overall performance and stability of the device can be effectively improved.
[0025] In P-type semiconductors, the hole concentration is greater than the electron concentration, meaning that holes are the dominant charge carriers during current flow. The opposite is true for N-type semiconductors, where the electron concentration is greater than the hole concentration, and electrons are the dominant charge carriers.
[0026] P+ type doping and N+ type doping: + indicates heavy doping with high doping concentration; P- type doping and N- type doping: light doping with low doping concentration.
[0027] A diode consists of P-type and N-type semiconductors, with the P-type semiconductor called the anode and the N-type semiconductor called the cathode. They are connected by a PN junction, forming a depletion region. The working principle of a diode is based on the characteristics of a PN junction. When a forward voltage is applied to the anode (i.e., the anode voltage is higher than the cathode voltage), holes in the P-type semiconductor and electrons in the N-type semiconductor recombine in the depletion region, allowing current to flow. In this state, the diode is conducting, known as forward bias. When a reverse voltage is applied to the anode (i.e., the anode voltage is lower than the cathode voltage), the depletion region widens, preventing current flow. In this state, the diode is cut off, known as reverse bias.
[0028] In the field of power semiconductor devices, freewheeling devices are typically connected in antiparallel to power switching transistors (such as insulated-gate bipolar transistors, IGBTs) to provide reverse freewheeling. In recent years, the requirements for freewheeling devices have become increasingly stringent, especially in wind power and power grid applications. Because circuits must withstand the effects of various system instabilities, such as current and voltage overloads, more stringent requirements are placed on freewheeling devices. Freewheeling devices must withstand forward surge currents several times or even tens of times their rated current.
[0029] In related technologies, to improve the surge current capability of freewheeling devices, it is necessary to enhance anode injection to form a P+ type doped structure and reduce the on-state voltage drop Vf. However, this leads to a significant increase in reverse recovery losses and an increase in carrier injection efficiency in the terminal region, affecting the performance of the reverse recovery safe operating region. In other words, improving the surge capability of freewheeling devices and reducing reverse recovery losses and improving the performance of the reverse recovery safe operating region are contradictory and difficult to reconcile.
[0030] To address the aforementioned technical issues, the technical solution of this application introduces a gradient anode structure, forming a P+ type doped structure with a size that gradually decreases from the center of the freewheeling device outwards. As a result, when the freewheeling device is turned on, carrier injection is strong in the central region of the freewheeling device and weak in the surrounding areas near the terminal region. Therefore, it does not enhance carrier injection in the terminal region, thereby improving the surge capability of the freewheeling device without significantly increasing reverse recovery loss or reducing the reverse recovery safe operating area.
[0031] The technical solution of this application will now be described in detail with reference to the accompanying drawings and specific embodiments.
[0032] like Figure 1 As shown, according to some embodiments of this application, a freewheeling device 1 is provided, including an effective area 100 and a terminal area 200 located around the effective area 100.
[0033] The freewheeling device 1 includes an anode 11 located in the effective region 100. The anode 11 includes a plurality of first P+ type doped structures 121, 122, and 123. The widths of the plurality of first P+ type doped structures decrease in a direction parallel to the surface AA of the effective region 100 and away from the center of the effective region 100.
[0034] Therefore, by enhancing the injection of charge carriers into the anode 11, multiple first P+ type doped structures 121, 122, and 123 are formed, thereby improving the surge capability of the freewheeling device 1. Furthermore, by setting the size of the multiple first P+ type doped structures to decrease in a direction parallel to the surface of the effective region 100 and away from the center of the effective region 100, when the freewheeling device 1 is turned on, the carrier injection is strong in the central region of the freewheeling device 1 and weak in the surrounding areas near the terminal region 200. Therefore, it does not enhance the carrier injection within the terminal region 200, thus improving the surge capability of the freewheeling device 1 without significantly increasing reverse recovery loss or reducing the reverse recovery safe operating area. In other words, it effectively solves the contradiction between improving the surge capability of the freewheeling device 1 and reducing reverse recovery loss and improving the performance of the reverse recovery safe operating area.
[0035] like Figure 2 As shown, in some embodiments, the terminal area 200 may be arranged around the periphery of the effective area 100.
[0036] It should be noted that, although attached Figure 2 In the illustrated example, the cross-section of the current-carrying device 1 is square, but in the technical solution of this application, the surface of the current-carrying device 1 can also be other regular or irregular shapes.
[0037] The decreasing width trend of the multiple first P+ type doped structures can mean that: along a direction parallel to the surface AA of the effective region 100 and away from the center of the effective region 100, the width of the multiple first P+ type doped structures decreases sequentially; or, the central P+ type doped structure closest to the center of the effective region 100 has the largest width among the multiple first P+ type doped structures, and the widths of the other peripheral P+ type doped structures are consistent and smaller than the width of the central P+ type doped structure; or, at least two P+ type doped structures closest to the center of the effective region 100 have consistent and largest widths among the multiple first P+ type doped structures, and the widths of the other peripheral P+ type doped structures are consistent and smaller than the widths of the at least two P+ type doped structures.
[0038] The central P+ type doped structure closest to the center of the effective region 100 can refer to the center of the effective region 100 being located within the central P+ type doped structure, or the central P+ type doped structure having the smallest spacing distance from the center of the effective region 100.
[0039] The first P+ type doped structure can be, for example, but is not limited to, a strip structure or a ring structure.
[0040] In one exemplary embodiment, the plurality of first P+ type doped structures include a central P+ type doped structure near the center of the effective region 100 and a plurality of ring-shaped peripheral P+ type doped structures, the peripheral P+ type doped structures being sequentially arranged around the periphery of the central P+ type doped structure. The central P+ type doped structure can be, for example, block-shaped or ring-shaped. In this case, exemplarily, such as... Figure 3 As shown, the width of the central P+ type doped structure 121 can be set to be the largest, while the widths of the annular peripheral P+ type doped structures 122 and 123 are the same and smaller than the width of the central P+ type doped structure.
[0041] In another exemplary embodiment, a plurality of first P+ type doped structures are strip-shaped, extending from one edge BB of the effective region 100 to the opposite edge BB, and the plurality of first P+ type doped structures are distributed in parallel within the effective region 100. In this case, exemplarily, such as Figure 4 As shown, along a direction parallel to the surface AA of the effective region 100 and away from the center of the effective region 100, for one side, the widths of multiple first P+ type doped structures 121, 122, and 123 can be successively reduced.
[0042] According to some embodiments of this application, the first P+ type doped structure is continuously doped along its extension direction in a direction parallel to the surface of the effective region 100 (e.g., ...). Figure 3 and 4 (as shown), or includes multiple discontinuous doped regions (such as...) Figure 5 The schematic first P+ type doped structure 122) can be configured to increase the strength of the anode 11 as needed. The greater the strength, the greater the improvement in surge capability.
[0043] exist Figure 5 In the illustrated example, the first P+ type doped structure 122 is strip-shaped, and the first P+ type doped structure 122 may include multiple discontinuous doped regions along its extension direction. It is understood that if the first P+ type doped structure is of other shapes, such as ring-shaped, it can also be configured in the same way to be continuously doped along its extension direction, or to include multiple discontinuous doped regions.
[0044] In some embodiments, such as Figure 1 As shown, the first P+ type doped structure 123, which is closest to the terminal region 200 among the multiple first P+ type doped structures, has a distance W between itself and the edge BB of the effective region 100 that is greater than a first preset value. This can reduce the injection efficiency of the first P+ type doped structure into the terminal region 200, suppress the increase in reverse recovery loss and the decrease in the reverse safe working area.
[0045] The first preset value can be greater than or equal to 100um, for example.
[0046] In some embodiments, such as Figure 1 As shown, along the direction parallel to the surface AA of the effective region 100, the spacing L between two adjacent first P+ type doped structures in the plurality of first P+ type doped structures is greater than the second preset value, thereby ensuring that the two adjacent first P+ type doped structures are separated from each other after push-bonding.
[0047] The second preset value can be, for example, greater than or equal to twice the depth D of the first P+ type doped structure in a direction parallel to the surface AA of the effective region 100.
[0048] In some embodiments, the first P+ type doped structure 123 closest to the terminal region 200 among the plurality of first P+ type doped structures has a distance W between it and the edge BB of the effective region 100 greater than a first preset value. Simultaneously, along a direction parallel to the surface of the effective region 100, the spacing L between two adjacent first P+ type doped structures among the plurality of first P+ type doped structures is greater than a second preset value. This ensures that two adjacent first P+ type doped structures are separated after push-bonding, facilitating the control of the desired effective gradient structure (i.e., the width of the plurality of first P+ type doped structures decreases along a direction parallel to the surface of the effective region 100 and away from the center of the effective region 100), thereby reducing the implantation efficiency of the first P+ type doped structure into the terminal region 200, suppressing the increase in reverse recovery loss and the decrease in the reverse safe operating region.
[0049] According to some embodiments of this application, the active region includes a P-type semiconductor layer and an N-type semiconductor layer, wherein the P-type semiconductor layer is formed as an anode 11 and the N-type semiconductor layer is formed as a cathode 12. A first P+ type doped structure is located within the P-type semiconductor layer or on the upper part of the N-type semiconductor layer near the surface AA of the effective region 100, and multiple first P+ type doped structures are arranged in a staggered manner along a direction perpendicular to the surface AA of the effective region 100, such as... Figure 6 As shown, this ensures that the two nearest-neighbor first P+ type doped structures are separated from each other after the push-junction, which facilitates the control and realization of the required effective gradient structure.
[0050] In some embodiments, such as Figure 6 As shown, when at least a portion of the multiple first P+ type doped structures are located within the P-type semiconductor layer, at least a portion of the first P+ type doped structures are located in the upper part, middle part, or lower part of the P-type semiconductor layer near the surface of the effective region 100, or away from the surface of the effective region 100AA. The middle part of the P-type conductor layer is located between the upper and lower parts, which facilitates the sequential staggered arrangement of the multiple first P+ type doped structures along the direction perpendicular to the surface AA of the effective region 100, making it easier to control and realize the desired effective gradient structure.
[0051] For example, multiple first P+ type doped structures are distributed in the P-type semiconductor layer and the upper part of the N-type semiconductor layer near the surface AA of the effective region 100. The multiple first P+ type doped structures are staggered in sequence along the direction perpendicular to the surface AA of the effective region 100, so that a sufficient number of first P+ type doped structures can be set according to the requirements, and the multiple first P+ type doped structures are staggered in sequence along the direction perpendicular to the surface AA of the effective region 100, which facilitates the control and realization of the required effective gradient structure.
[0052] Combination Figure 7-10 As shown, according to some embodiments of this application, the effective region 100 can be divided into multiple sub-effective regions 101, and multiple first P+ type doped structures are provided in each sub-effective region 101. The distance W between the edge of the sub-effective region 101 and the edge AA of the effective region 100 is greater than a first preset value. The specific form of the multiple first P+ type doped structures provided in each sub-effective region 101 can refer to the above embodiments, for example, the width setting, specific structure and arrangement of the multiple first P+ type doped structures, and whether they are continuously doped. In other words, a gradually changing first P+ type doped structure is introduced in each sub-effective region 1010, thereby making it easier to control the contradiction between surge capability, reduced reverse recovery loss, and improved reverse recovery safe operating area performance.
[0053] Multiple sub-effective regions 101 can be distributed symmetrically around the center of the effective region 100, such as Figure 7-9 As shown, or, the multiple sub-effective regions 101 include a first sub-effective region 101 near the center of the effective region 100 and multiple annular second sub-effective regions 101, with the multiple second sub-effective regions 101 sequentially arranged around the periphery of the first sub-effective region 101, such as... Figure 10 As shown.
[0054] Referring to Figures 11-15, in some embodiments of this application, the effective region 100 includes: a plurality of bonding regions 300, which are evenly distributed around the center of the effective region 100, so that the current distribution in the freewheeling device 1 is relatively uniform; and no bonding region 300 is provided in the center of the freewheeling device 1 (the temperature rise in the center is the highest), so as to avoid the high temperature in the center of the freewheeling device 1 from affecting the long-term reliability of the package interface, and at the same time, it can prevent the current from accumulating in the center of the freewheeling device 1, which is beneficial to suppressing the temperature rise in the center of the freewheeling device 1.
[0055] In some embodiments, the bonding region may include multiple second P+ type doped structures, and the size of the multiple second P+ type doped structures decreases along a direction parallel to the surface of the effective region and away from the center of the bonding region. That is, the bonding region also introduces the width-gradient P+ type doped structures of this embodiment, realizing the synergistic effect of the freewheeling device structure itself and the packaging structure, and further breaking the contradiction between surge capability and reverse recovery loss reduction and reverse recovery safe operating area performance improvement.
[0056] The specific form of the multiple second P+ type doped structures set in the bonding region can refer to the multiple first P+ type doped structures in the above embodiments, for example, the width setting, specific structure and arrangement of the P+ type doped structures, and whether they are continuously doped.
[0057] Multiple bonding regions 300 can be axially symmetrical about an axis passing through the center of the effective region 100, such as... Figure 12 As shown, or symmetrically distributed around the center of the effective area 100, such as Figure 13 and 15 As shown.
[0058] like Figure 16 As shown, according to some embodiments of this application, a power semiconductor device is also provided, including: a substrate 201, a power switch 2 disposed on the substrate 201, and a freewheeling device 1, wherein the freewheeling device 1 is connected in reverse parallel with the power switch 2. The freewheeling device 1 employs the freewheeling device described in the above embodiments, thereby improving the surge capability of the device without significantly increasing reverse recovery losses or reducing the reverse recovery safe operating area.
[0059] Power semiconductor devices may also include other functional structures such as metallization region 3 and lead 4, which will not be described in detail here.
[0060] It should be noted that, in this disclosure, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element limited by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes that element.
[0061] While the embodiments disclosed herein are as described above, the foregoing content is merely for the purpose of facilitating understanding of this disclosure and is not intended to limit this disclosure. Any person skilled in the art to which this disclosure pertains may make any modifications and changes in form and detail of the implementation without departing from the spirit and scope disclosed herein; however, the scope of patent protection of this disclosure shall still be determined by the scope defined in the appended claims.
Claims
1. A freewheeling device, comprising an active region and a terminal region located around the active region, characterized in that, The freewheeling device includes: The anode is located in the effective region and includes a plurality of first P+ type doped structures. The widths of the plurality of first P+ type doped structures decrease in a direction parallel to the surface of the effective region and away from the center of the effective region.
2. The freewheeling device according to claim 1, characterized in that, The first P+ type doped structure closest to the terminal region among the plurality of first P+ type doped structures has a distance greater than a first preset value between it and the edge of the effective region.
3. The freewheeling device according to claim 2, characterized in that, The first preset value is greater than or equal to 100um.
4. The freewheeling device according to claim 1, characterized in that, Along a direction parallel to the surface of the effective region, the spacing between two adjacent first P+ type doped structures in the plurality of first P+ type doped structures is greater than a second preset value.
5. The freewheeling device according to claim 4, characterized in that, The second preset value is greater than or equal to twice the depth of the first P+ type doped structure in a direction perpendicular to the surface of the effective region.
6. The freewheeling device according to claim 1, characterized in that, The effective region includes a P-type semiconductor layer and an N-type semiconductor layer, wherein the P-type semiconductor layer is formed as the anode; The first P+ type doped structure is located in the P-type semiconductor layer or in the upper part of the N-type semiconductor layer near the surface of the effective region, and the plurality of first P+ type doped structures are arranged in a staggered manner along a direction perpendicular to the surface of the effective region.
7. The freewheeling device according to claim 6, characterized in that, When at least a portion of the plurality of first P+ type doped structures is located within the P-type semiconductor layer, at least a portion of the first P+ type doped structures is located in the upper part, middle part, or lower part of the P-type semiconductor layer near the surface of the effective region, and the middle part of the P-type conductor layer is located between the upper and lower parts.
8. The freewheeling device according to claim 1, characterized in that, Along a direction parallel to the surface of the effective region, the first P+ type doped structure is continuously doped along its extension direction, or includes multiple discontinuous doped regions.
9. The freewheeling device according to claim 1, characterized in that, The plurality of first P+ type doped structures include a central P+ type doped structure near the center of the effective region and a plurality of annular peripheral P+ type doped structures, wherein the peripheral P+ type doped structures are sequentially arranged around the periphery of the central P+ type doped structure.
10. The freewheeling device according to claim 1, characterized in that, The plurality of first P+ type doped structures are strip-shaped, extending from one edge of the effective region to the opposite edge, and are distributed in parallel within the effective region.
11. The freewheeling device according to any one of claims 1-10, characterized in that, The effective region includes multiple sub-effective regions, each of which is provided with the multiple first P+ type doped structures, and the distance between the edge of the sub-effective region and the edge of the effective region is greater than a first preset value.
12. The freewheeling device according to claim 11, characterized in that, The plurality of sub-effective regions are distributed symmetrically around the center of the effective region, or, The plurality of sub-effective regions include a first sub-effective region near the center of the effective region and a plurality of annular second sub-effective regions, wherein the plurality of second sub-effective regions are sequentially arranged around the periphery of the first sub-effective region.
13. The freewheeling device according to any one of claims 1-10, characterized in that, The effective region includes: multiple bonding regions, evenly distributed around the center of the effective region; Each of the bonding regions includes a plurality of second P+ type doped structures, and the widths of the plurality of second P+ type doped structures decrease in a direction parallel to the surface of the effective region and away from the center of the bonding region.
14. A power semiconductor device, characterized in that, include: Power switching transistors; The freewheeling device according to any one of claims 1-13, wherein the freewheeling device is connected in reverse parallel with the power switch.