Reverse conducting insulated gate bipolar transistor and method for fabricating a reverse conducting insulated gate bipolar transistor

Abstract

According to one embodiment, an RC-IGBT (100) comprises a semiconductor body (10) having an emitter side (11) and a collector side (19). The semiconductor body comprises at least one mixed region (18) on the collector side. The mixed region is of a first conductivity type and includes a plurality of first-type regions (15) laterally spaced from one another by semiconductor material of a second conductivity type. When viewed from above on the collector side, the first-type regions of the mixed region are each elongated and each extend radially away from a reference point of the mixed region. The number of first-type regions of the mixed region increases in a stepwise manner in a direction away from the reference point.

Description

[Technical Field]

[0001] The present disclosure relates to a reverse conducting insulated gate bipolar transistor and a method for fabricating a reverse conducting insulated gate bipolar transistor. [Background technology]

[0002] There is a need for improved reverse conducting insulated gate bipolar transistors, e.g., those having improved reverse conduction characteristics and / or improved secondary snapback events. Additionally, there is a need for methods for fabricating such reverse conducting insulated gate bipolar transistors. Summary of the Invention [Means for solving the problem]

[0003] SUMMARY Embodiments of the present disclosure relate to reverse conducting insulated gate bipolar transistors and methods for fabricating reverse conducting insulated gate bipolar transistors.

[0004] First, a reverse-conducting insulated gate bipolar transistor is specified. In the following, the abbreviation RC-IGBT is used for the expression "Reverse-Conducting Insulated Gate Bipolar Transistor".

[0005] According to one embodiment, an RC-IGBT includes a semiconductor body having an emitter side and a collector side. The semiconductor body includes at least one mixed region on the collector side. The mixed region is of a first conductivity type and includes a plurality of first-type regions laterally spaced from one another by semiconductor material of a second conductivity type. When viewed from above the collector side, the first-type regions of the mixed region are each elongated and each extend radially away from a reference point of the mixed region. The number of first-type regions of the mixed region increases in a stepwise manner in a direction away from the reference point.

[0006] The radial and step-wise arrangement of the first type of regions allows for the desired diode area to be achieved while at the same time providing a snapback-free device.

[0007] The RC-IGBT described herein is specifically a power device. It may be configured to carry a current of at least 10 A and / or handle a voltage of at least 600 V and / or at most 6500 V. For example, the RC-IGBT is a low-voltage device for operation between 1000 V and 2000 V.

[0008] The semiconductor body may be based on silicon or silicon carbide. The thickness of the semiconductor body, measured in a vertical direction from the collector side to the emitter side, is, for example, at least 60 μm and / or at most 700 μm. For example, the thickness of the semiconductor body is at most 150 μm. The emitter side and the collector side are opposite sides of the semiconductor body and vertically delimit the semiconductor body.

[0009] A first main electrode, the so-called "emitter electrode," may be located on the emitter side and is in electrical contact with the semiconductor body, and a second main electrode, the so-called "collector electrode," is located on the collector side and is in electrical contact with the semiconductor body, in particular with the mixed region.

[0010] The mixed regions are collector-side regions, i.e., they are adjacent to or form part of the collector side, respectively. The mixed regions include a plurality of first-type regions, e.g., at least 20 or at least 50 first-type regions, which are also adjacent to the collector side, i.e., each forms part of it.

[0011] An RC-IGBT may comprise multiple mixed regions, and all features disclosed herein with respect to one mixed region are also disclosed with respect to the other mixed regions.

[0012] The first type region is of a first conductivity type, which may be n-type. Thus, the first type region may be n-doped. However, the first conductivity type may alternatively be p-type.

[0013] The first-type regions are laterally spaced apart from one another in a lateral direction, the lateral direction being perpendicular to the vertical direction, specifically a direction parallel to the collector side of the semiconductor body and / or parallel to the main extension plane. For example, when viewed from above the collector side, each of the first-type regions is formed continuously and uninterrupted.

[0014] The first-type regions are separated from each other by semiconductor material of a second conductivity type. The second conductivity type is opposite to the first conductivity type. Thus, if the first conductivity type is n-type, the second conductivity type is p-type. Each first-type region may be completely surrounded laterally by semiconductor material of the second conductivity type. The second conductivity type semiconductor material disposed between the first-type regions also abuts, or forms part of, the collector side.

[0015] The first-type regions are elongated when viewed from above the collector location. For example, the first-type regions are all formed in stripes. Furthermore, when viewed from above the collector side, the first-type regions extend radially away from a reference point of the mixing region. That is, some or all of the first-type regions are oriented primarily or entirely radially. The radial direction is the lateral direction pointing away from the reference point. In particular, the primary extension direction of some or all of the elongated first-type regions is parallel or nearly parallel to the radial direction.

[0016] For example, when viewed from above on the collector side, the main extension direction of some or all of the elongated first type regions extends perpendicular to the contour of a circle or ellipse, with the reference point being the centre of the circle or ellipse.

[0017] The number of first-type regions in the mixed region increases stepwise in the direction away from the reference point. This means that, considering a specific azimuthal sector (polar sector) covered by the mixed region, the number of first-type regions that are completely located within this azimuthal sector is greater in regions farther from the reference point than in regions closer to the reference point. The azimuthal sector may be 360°, or it may be a smaller azimuthal sector, for example, of at most 20° and / or at least 5°. The azimuthal angle or azimuthal sector is defined relative to the reference point.

[0018] "Graded" means that the number of first-type regions increases stepwise, rather than continuously. Each stage is assigned a fixed area of ​​mixing region when viewed from above the collector side. The stages are arranged in order, moving away from the reference point. For example, the stage closest to the reference point has the fewest number of first-type regions, and the stage farthest from the reference point has the most. When comparing the number of first-type regions in different stages, only first-type regions within the same azimuthal sector are counted.

[0019] For example, in each stage, or at least in the stage closest to the reference point, all of the first-type regions have the same length, the length being measured along the main extension direction of each first-type region. The first-type regions of different stages may have different lengths.

[0020] For example, the mixed region comprises two or more stages, in particular three or more stages, for which the number of regions of the first type increases the further the stages are from the reference point, for example the mixed region comprises at most 10 such stages arranged one after the other in the direction away from the reference point.

[0021] According to a further embodiment, the semiconductor body comprises a pilot region on the collector side. The pilot region is adjacent to the mixed region. The pilot region is of the second conductivity type. The RC-IGBT can therefore be a so-called "Bi-Mode Insulated Gate Transistor", or BIGT for short. The terms "pilot region" and "BIGT" are familiar to those skilled in the art. The pilot region forms part of the collector side.

[0022] The pilot region is the region of the device that is a pure IGBT, and the mixed region is the region where the RC-IGBT is actually formed. In particular, the pilot region is a continuous region, e.g., an unbroken region, on the emitter side.

[0023] When viewed from above on the collector side, the pilot region has an area that is larger than each of the first-type regions, for example, at least five times or at most ten times larger. The pilot region is, for example, adjacent to the collector electrode. The size of the pilot region is selected to reduce snapback. On the other hand, to keep the area of ​​the RC-IGBT large, it may be advantageous to select the pilot region as small as possible. For example, the area of ​​the pilot region, when viewed from above on the top surface, is at least d·d and / or at most 100·d·d and / or at most 90% of the active area, where d is the thickness of the semiconductor body measured in the vertical direction. This range has been found to satisfy the above-mentioned conditions.

[0024] According to a further embodiment, when viewed from above on the collector side, the reference point lies within the pilot region, for example coinciding with the centroid of the pilot region.

[0025] The reference point is located within the pilot region, and the first type of region extends radially away from the pilot region. Due to the arrangement of the first type of region, uniform plasma distribution along the length of the RC-IGBT can also be achieved for low voltage applications, i.e., relatively thin thicknesses of the semiconductor body, as well as good thermal performance.

[0026] According to a further embodiment, when viewed from above on the collector side, the mixing region completely surrounds the pilot region, i.e., the pilot region is completely surrounded laterally by the mixing region, which means that the mixing region covers an azimuthal sector of 360°.

[0027] According to a further embodiment, when viewed from above on the collector side, the second-type region of the second conductivity type extends continuously from the pilot region to the edge of the mixed region. The edge of the mixed region is the part of the mixed region farthest from the reference point. The second-type region may, for example, be a continuous region bounded by several first-type regions. The second-type region may extend over the entire azimuthal sector covered by the mixed region. For example, the second-type region may extend over a 360° azimuthal sector, i.e., completely surround the reference point and / or the pilot region. In particular, the second-type region is formed by a semiconductor material of the second conductivity type arranged between the first-type regions.

[0028] Such continuously formed second type regions further help to uniformly distribute the plasma generated during operation.

[0029] According to a further embodiment, when viewed from above on the collector side, the first-type regions are uniformly distributed around the reference point, e.g., for each pair of adjacent first-type regions within one stage, the minimum distance between adjacent first-type regions is the same.

[0030] Additionally or alternatively, when viewed from above on the collector side, the mixing region may have n-fold rotational symmetry about a reference point, where integer n is, for example, at least 10, or at least 30, or at least 50, or at least 100.

[0031] According to a further embodiment, each step of the step increase is assigned an area on the collector side, viewed from above on the collector side.

[0032] According to a further embodiment, the area allocated to at least one stage is shaped as a ring, for example an elliptical ring or a circular ring. For example, the areas allocated to two or more stages are rings. The rings are concentric with each other.

[0033] For example, each of the first type of regions has a first longitudinal end closest to the reference point and a second longitudinal end farthest from the reference point. When viewed from above the collector side, the first longitudinal ends of the first type of regions may lie on different elliptical or circular contours around the reference point. These contours define the boundaries of the annular regions of the stage.

[0034] For example, when viewed from above, a first such contour enclosing a smallest area intersects the first longitudinal edges of a first number, the first number being, for example, at least 10. A second such contour enclosing a larger area intersects the first longitudinal edges of a second number, the second number being greater than the first number, for example, at least twice as great as the first number. Furthermore, there may be a third such contour enclosing an even larger area intersects the first longitudinal edges of a third number, the third number being greater than the second number. The contours may be concentric with respect to a reference point.

[0035] According to further embodiments, the number of regions of the first type varies from one stage to the adjacent stage by at least 2-fold or at least 3-fold or at least 5-fold.

[0036] According to a further embodiment, within a stage, i.e., within the area assigned to this stage, the distance between two adjacent first-type regions, particularly the distance between each pair of adjacent first-type regions, has a first value in the region closest to the reference point and a second value in the region farthest from the reference point. The second value is greater than the first value. That is, the distance between two adjacent first-type regions, particularly the distance between each pair of adjacent first-type regions, increases as the distance from the reference point increases. For example, the distance increases gradually or continuously, respectively.

[0037] When referring to adjacent first-type regions within a stage, this means that the first-type regions are adjacent in the azimuth direction. In the radial direction, two adjacent first-type regions may be at the same height or position, respectively.

[0038] According to a further embodiment, the second value is at most four times the first value. In particular, the mixed region is formed such that when moving away from the reference point and before the ratio of the second value to the first value exceeds the number 4, a next stage with an increased number of first-type regions begins. For example, in a region azimuthally located between two adjacent first-type regions, when moving from one stage to the next, a new first-type region is formed with an increased number of first-type regions.

[0039] As an example, some first type regions begin within a stage and extend from there across one or more further stages that are further away from the reference point than the stage in which the first type regions begin.

[0040] For example, at least some or all of the first-type regions may extend over only one stage, i.e., these first-type regions may be uniquely assigned to one stage. However, some or all of these first-type regions in at least one stage may be assigned an associated first-type region in a subsequent stage that is further away from the reference point, and the first-type regions and the assigned associated first-type regions may be oriented in the same direction and / or have the same azimuthal position, i.e., have the same position in the azimuthal direction.

[0041] According to a further embodiment, the maximum distance between two adjacent first-type regions in one stage is greater than the minimum distance between two adjacent first-type regions in a next stage located downstream of the one stage in a direction away from the reference point.

[0042] According to further embodiments, the width of the first type regions, measured perpendicular to their respective main direction of extension, is at most half of the first value, or at most 1 / 4 of the first value, or at most 1 / 6 of the first value.

[0043] According to a further embodiment, the RC-IGBT further comprises a plurality of transistor half cells arranged one after the other in a first lateral direction. Each transistor half cell comprises, for example, one implanted region, also called a source region, of a first conductivity type. The implanted region is in electrical contact with an emitter electrode arranged on the top surface. For example, the implanted region is adjacent to the emitter electrode. For example, the implanted region extends to the emitter side. The implanted region may be, for example, a continuous, uninterrupted region. Each transistor half cell may be assigned exactly one implanted region in a one-to-one correspondence.

[0044] In addition to the implantation region, the semiconductor body includes at least one base region and a drift region. The drift region is of a first conductivity type. The drift region is disposed vertically between the emitter side and the mixed region and / or pilot region. The drift region may be adjacent to the mixed region and / or pilot region. The at least one base region is disposed vertically between the emitter side and the drift region. The at least one base region is of a second conductivity type. Each implantation region is spaced from the drift region by at least one base region, e.g., laterally and / or vertically. For example, each implantation region, and therefore each transistor half cell, may be assigned an individual base region. All transistor half cells may be formed identically within manufacturing tolerance limits.

[0045] The RC-IGBT can be made with a planar architecture or a trench architecture. The trench architecture means that there are several trenches (e.g., two per half cell) extending from the emitter side into the semiconductor body. The gate electrode of the RC-IGBT extends into at least some of the trenches. In the planar architecture, the gate electrode is located on the emitter side of the semiconductor body.

[0046] According to a further embodiment, the area of ​​the transistor half-cell measured in the first lateral direction is smaller than the width of the first-type region. For example, the ratio between the width of the first-type region and the area of ​​the transistor half-cell is at least 1.2 and / or at most 5. The area of ​​the transistor half-cell is, for example, defined as the pitch between two adjacent transistor half-cells in the first lateral direction. Each two adjacent half-cells may be adjacent to each other and may be formed as mirror images of each other.

[0047] According to a further embodiment, the pilot region has a round shape when viewed from above on the collector side. For example, the pilot region has a circular or elliptical shape. In particular, the pilot region has a diameter of x 2 / a 2 +y2 / b 2 The area may be delimited by a contour that follows the relationship x=0, y=1, where x and y are coordinates on the collector side, the center of the pilot region has coordinates x=0 and y=0, and a and b are fixed numbers. The center of the pilot region may be the centroid of the pilot region. The center of the pilot region may coincide with a reference point. For example, the main extension direction of the first type region is perpendicular to this contour.

[0048] According to a further embodiment, the collector side has a rectangular shape, the edges of which have a length L and a width W, whereby L≧W. For example, L and W are at least 1 mm and / or at most 30 mm or at most 20 mm.

[0049] According to a further embodiment, the area and shape of the pilot region are selected depending on the area and shape of the collector side according to the following rules.

[0050] - if L<2·W, the collector side comprises only one pilot region surrounded by a mixing region, the contours delimiting the pilot region satisfy 0.1≦(2·a) / L≦0.5, 0.1≦(2·b) / W≦0.5, and (2·a) / L=(2·b) / W; - For L ≥ 2·W, the collector side comprises several pilot regions, each surrounded by a mixed region, each delimited by a contour satisfying 0.1 ≤ (2·a) / L' ≤ 0.5, 0.1 ≤ (2·b) / W ≤ 0.5, and (2·a) / L' = (2·b) / W, where L'·c = L, c is an integer and the number of pilot regions. In particular, L' ≥ W.

[0051] In other words, if the length L is less than twice the width W, the RC-IGBT has only one pilot region and one mixed region on the collector side. If the length L is at least twice as large as the width W but less than three times the width W, the RC-IGBT has exactly two mixed regions and exactly two assigned pilot regions, etc. Moreover, if the collector side is square in shape, the pilot regions are circular. In the case of several pilot regions, the pilot regions are laterally spaced apart from each other.

[0052] These design rules for the size of the pilot region provide a good compromise between snapback reduction and uniform plasma contribution.

[0053] According to a further embodiment, L≧2·W and the collector side comprises several pilot regions each surrounded by a mixing region, each pilot region being delimited by a contour satisfying 0.1≦(2·a) / L′≦0.5, 0.1≦(2·b) / W≦0.5, and (2·a) / L′=(2·b) / W, where L′·c=L, c being an integer and the number of pilot regions. In particular, L′≧W.

[0054] According to a further embodiment, the semiconductor body comprises an edge region on the collector side, which may extend to an edge of the collector side and laterally delimit the collector side, for example, the edge region forms the edge of the collector side.

[0055] According to a further embodiment, the edge region is of the first conductivity type. Alternatively, the edge region is of the second conductivity type. In particular, the edge region is a continuous region of only one conductivity type.

[0056] According to a further embodiment, the edge region laterally surrounds the mixing region and / or the pilot region. For example, the edge region completely surrounds the mixing region and / or the pilot region in the laterally direction. That is, when viewed from above on the collector side, the edge region may completely surround the mixing region and / or the edge region. For example, when viewed from above, the edge region forms a frame around the mixing region and / or the pilot region.

[0057] When viewed from above on the collector side, the edge region may overlap the termination region of the RC-IGBT, for example, the edge region completely or partially overlaps the termination region of the RC-IGBT.

[0058] The area of ​​the edge region may be greater than the area of ​​each of the first type regions, for example at least 10 times greater, when viewed from above on the collector side. The edge region may have a constant width along its extent around the mixing region and / or the pilot region.

[0059] According to further embodiments, the edge region is of a second conductivity type. For example, the edge region has a lower doping concentration than the semiconductor material of the second conductivity type in the mixed region disposed laterally between the first-type regions. For example, the doping concentration is at least one order of magnitude or at least two orders of magnitude less than the doping concentration of the semiconductor material of the second conductivity type in the mixed region. In this way, leakage can be reduced while SCSOA(hot) performance is further improved.

[0060] According to a further embodiment, the edge region is of the first conductivity type. The doping concentration may be the same as or different from the doping concentration in the first-type region. In such an edge region, the emitter connection portion of the p-type termination region serves as an additional anode region for the BIGT's internal diode, thereby reducing on-state losses in diode operation mode.

[0061] Next, a method for fabricating an RC-IGBT is specified. The method may be used to fabricate the RC-IGBTs specified herein. Accordingly, all features disclosed in relation to the RC-IGBT are also disclosed in relation to the method, and vice versa.

[0062] According to one embodiment, the method includes providing information representing a length L and a width W that the collector side of the RC-IGBT to be manufactured should have, where L≧W. Then, a semiconductor body having an emitter side and a collector side is manufactured in response to the provided information. The semiconductor body is manufactured such that the semiconductor body includes at least one mixed region on the collector side. The mixed region is of a first conductivity type and includes a plurality of first-type regions laterally spaced from one another by semiconductor material of a second conductivity type. When viewed from above the collector side, the first-type regions of the mixed region are each elongated and each extend radially away from a reference point of the mixed region. The number of first-type regions of the mixed region increases in a stepwise manner in a direction away from the reference point. If L≧2·W, a semiconductor body having two or more such mixed regions is manufactured. If L<2·W, a semiconductor body having only one such mixed region is manufactured. [Brief explanation of the drawings]

[0063] DETAILED DESCRIPTION OF THE INVENTION

[0064] Hereinafter, an RC-IGBT and a method for manufacturing an RC-IGBT will be described in more detail with reference to the drawings based on exemplary embodiments. The accompanying figures are included to provide further understanding. In the figures, elements of the same structure and / or function may be referred to by the same reference symbols. It should be understood that the embodiments shown in the figures are exemplary representations and are not necessarily drawn to scale. To the extent that elements or components correspond to each other in terms of their function in different figures, their description will not be repeated for each of the following figures. For clarity, elements may not appear with corresponding reference symbols in all figures.

[0065] Figures 1-3 show in cross-section a first exemplary embodiment of an RC-IGBT 100. Figure 2 shows in more detail the area of ​​Figure 1 indicated by the dashed rectangle. Figure 3 shows in more detail a portion of Figure 2.

[0066] The RC-IGBT comprises a semiconductor body 10 having an emitter side 11 and a collector side 19 positioned vertically opposite each other. The semiconductor body 10 is based on Si or SiC, for example.

[0067] On the collector side 19, the semiconductor body 10 comprises alternating first-type regions 15 and second-type regions 16, which form a mixed region 18. The regions 15 and 16 are in electrical contact with a collector electrode 3 arranged on the bottom surface 19. The collector electrode 3 is made of, for example, a metal.

[0068] The first type region 15 is of a first conductivity type, hereinafter n-type, and the second type region 16 is of a second conductivity type, hereinafter p-type.

[0069] Furthermore, the semiconductor body 10 comprises an edge region 18" that forms part of the collector side 19 and forms the edge of the collector side 19. The edge region 18" is herein of the second conductivity type, but may alternatively be of the first conductivity type.

[0070] The drift region 14 is disposed between the emitter side 11 and the collector side 19. The drift region 14 is of a first conductivity type, i.e., n-type. The drift region 14 is adjacent to a region 15 of the first type and a region 16 of the second type.

[0071] A plurality of trenches 51, 52 extend from emitter side 11 into semiconductor body 10 and into drift region 14. Trench 51 is a first type of trench, also referred to herein as an active trench, and trench 52 is a second type of trench, also referred to herein as an inactive trench or dummy trench.

[0072] The first-type trenches 51 are filled with a conductive material that is electrically isolated from the semiconductor body 10 by an electrical insulating layer 40, referred to herein as the "gate insulating layer." Therefore, there is no direct electrical contact between the semiconductor body 10 and the conductive material in the first-type trenches 51. The gate insulating layer 40 is formed, for example, from an oxide such as SiO2. The conductive material in the first-type trenches 51 may be highly doped polysilicon. The conductive material in the first-type trenches 51 is part of the gate electrode 4 of the semiconductor device 100.

[0073] The second type of trench 52 is also filled with a conductive material, e.g., highly doped polysilicon, that is electrically isolated from the semiconductor body 10 by an electrically insulating layer, which is similar to the gate insulating layer 40. The conductive material in the second type of trench 52 is part of the emitter electrode 2 that is disposed on the emitter side 11. The first base region 13a is adjacent to and in electrical contact with the emitter electrode 2 at a first contact region 6a, also referred to as the "Rb prime region."

[0074] Semiconductor body 10 comprises several base regions 13a, 13b, 13c arranged vertically between drift region 14 and emitter side 11. Base regions 13a, 13b, 13c are all of the second conductivity type, i.e., p-type, and they all adjoin drift region 14 as well as emitter side 11. First base region 13a and second base region 13b are shallower (have less vertical extent) than trenches 51, 52. Third base region 13c is deeper than trenches 51, 52, i.e., extends further into semiconductor body 10.

[0075] As can be seen in FIG. 1 , the semiconductor device 100 is subdivided into a plurality of so-called “transistor half-cells.” One such transistor half-cell HF is shown in more detail in FIG. 3 . The transistor half-cell HF is the structure between the vertical dashed lines in FIG. 3 . In FIGS. 1 and 2 , several such transistor half-cells HF are arranged one after the other in a first horizontal direction extending from left to right. Two adjacent half-cells HF are mirror images of each other in a plane extending perpendicular to the first horizontal direction and through the third base region 13c (see the right vertical dashed line in FIG. 3 ). Each half-cell has a lateral extent W4 in the first horizontal direction.

[0076] As shown in FIG. 3 , the half-cell HF includes a portion (half) of the first base region 13c, a first-type trench 51, a second base region 13b, a second-type trench 52, and a portion (half) of the third base region 13c, which are arranged in this order along the first lateral direction. The half-cell HF further includes an implantation region 12 (source region 12) of a first conductivity type, i.e., n-type, vertically disposed between the first base region 13c and the upper surface 11. The implantation region 12 is adjacent to the first base region 13c and the first-type trench 51. The implantation region 12 is also adjacent to and in electrical contact with the emitter electrode 2.

[0077] FIG. 4 shows the RC-IGBT 100 of FIGS. 1-3 as viewed from above on the collector side 19. As can be seen, the semiconductor body 10 comprises, in addition to the mixed region 18, a pilot region 18'. The pilot region 18' is also of the second conductivity type, i.e., p-type. It can further be seen that the mixed region 18 completely surrounds the pilot region 18' laterally. The edge region 18'' completely surrounds the mixed region 18 and the pilot region 18' laterally.

[0078] The pilot region 18' has a circular, i.e., circular, shape. The first type regions 15 of the mixing region 18 are all elongated stripes and extend radially relative to a reference point Z that coincides with the center of the pilot region 18'.

[0079] As can be further seen in Figure 4, the number of first type regions 15 in the mixing region 18 increases in stages in the direction away from the reference point Z. In fact, the mixing region 18 can be subdivided into three stages. Each stage is assigned an area that completely surrounds the pilot region 18'. The area assigned to the innermost stage is annular. The area assigned to the next radially outer stage is also annular. The area of ​​the outermost stage is delimited by a square outline.

[0080] The number of first-type regions 15 increases from the innermost stage (innermost ring) to the middle stage (middle ring), and then increases again from the middle stage to the outermost stage. Such a gradual increase in the number of first-type regions 15 allows the desired diode area to be maintained.

[0081] In particular, as can be seen in Figure 4, the density of the first type regions 16 decreases monotonically within each stage as one moves away from the reference point Z. At the transition to the next stage, the density increases sharply, and then decreases monotonically again within this next stage.

[0082] Also, in FIG. 4, it can be seen that the second type region 16 of the second conductivity type extends continuously from the pilot region 18′ to the edge region 18″. This allows the electron-hole plasma generated during operation to be uniformly distributed throughout the entire extent of the RC-IGBT 100.

[0083] This design minimizes snapback due to the large pilot region resulting from the circular design. This is particularly important for LV ultrathin devices, where the design rules for initial snapback elimination and pilot IGBT design depend on the device thickness. Accordingly, the intermixing region surrounding the pilot region, which consists of alternating p-type and n-type regions, is designed to minimize secondary snapback and increase SOA limits. In fact, if the intermixing region is not properly designed and distributed around the pilot region, non-uniform carrier injection can occur after the initial snapback event. During IGBT conduction, the plasma density is highest in the center of the active region, directly above the pilot region protruding from it. As a result, the temperature in the center of the RC-IGBT is significantly higher compared to conventional discrete diode and IGBT approaches. This is exacerbated in LV ultrathin devices, where plasma distribution can already be an issue. Furthermore, during IGBT turn-off, dynamic electron avalanches, which primarily contribute to increased turn-off losses at low temperatures and low currents, begin earlier in the cells located directly above the pilot region, which compromises BiGT device reliability. Here, the intermixing region design is chosen to ensure smooth electrical characteristics and SOA performance.

[0084] 5 shows a further exemplary embodiment of the RC-IGBT 100, again viewed from above on the collector side 19. Here, the collector side 19 is rectangular in shape with a length L and a width W that vary. The pilot region 18' is therefore selected to be elliptical rather than circular. The first-type regions 15 of the mixing region 18 still extend primarily radially, but now they all extend perpendicular to the elliptical contour that defines and delimits the pilot region 18'.

[0085] 4 and 5, the length L is less than twice the width W. The outline that defines or defines the pilot region 18' is x 2 / a 2 +y 2 / b 2= 1, where x and y are coordinates on collector side 19, the center of pilot region 18' has coordinates x = 0 and y = 0, and a and b are fixed numbers. Furthermore, in both Figures 4 and 5, the following is satisfied: 0.1 ≤ (2 a) / L ≤ 0.5, 0.1 ≤ (2 b) / W ≤ 0.5, and (2 a) / L = (2 b) / W. In the case of Figure 4, W = L and a = b.

[0086] 6 shows a further exemplary embodiment of the RC-IGBT 100 as viewed from above the collector side 19. In this case, L≧2·W. Thus, the collector side 19 includes two mixed regions 18, each surrounding a uniquely assigned pilot region 18′. The pilot regions 18′ each satisfy 0.1≦(2·a) / L′≦0.5, 0.1≦(2·b) / W≦0.5, and (2·a) / L′=(2·b) / W, where L′·c=L, where c is an integer and is the number of pilot regions 18′. In this case, L′=L / 2.

[0087] FIG. 7 shows in more detail a portion of the collector side 19 of FIG. 4. As can be seen, the distance between two adjacent first-type regions 15 within one stage, measured in a direction perpendicular to the radial direction, i.e., in the azimuthal direction, increases continuously as it moves radially outward, i.e., from a first value W1 to a second value W2. The following constraints are thereby met: W2 > W1 and W2 ≦ 4 W1. When moving to the next stage, the number of first-type regions 15 increases, so that in the next stage, the value W1 is again smaller than the value W2 of the previous stage.

[0088] Moreover, the width W3 of each first-type region 15 is smaller than the first value W1. Furthermore, the extent W4 of the transistor half-cell HF shown in Figure 3 is smaller than the width W3.

[0089] 8 shows a flowchart of an exemplary embodiment of a method for manufacturing an RC-IGBT. In step S1, information I representing the length L and width W of the collector side 19 of the RC-IGBT to be manufactured is provided, where L≧W.

[0090] In step S2, a semiconductor body 10 having an emitter side 11 and a collector side 19 is produced according to the provided information I, so that the semiconductor body 10 comprises at least one mixed region 18 on the collector side 19.

[0091] The mixed region 18 is of a first conductivity type and includes a plurality of first-type regions 15 laterally spaced apart from one another by semiconductor material of a second conductivity type. When viewed from above on the collector side 19, the first-type regions 15 of the mixed region 18 are each elongated and each extend radially away from a reference point Z of the mixed region 18. The number of first-type regions 15 of the mixed region 18 increases in stages in the direction away from the reference point Z. If L≧2·W, a semiconductor body is produced having two or more such mixed regions 18, and if L<2·W, a semiconductor body is produced having only one such mixed region.

[0092] 1-8 described above represent exemplary embodiments of the improved RC-IGBTs and improved methods for manufacturing RC-IGBTs, and therefore, they do not constitute an exhaustive list of all embodiments of the improved RC-IGBTs and methods. Actual RC-IGBTs and methods may differ from the illustrated embodiments with respect to, for example, layout, devices, and method steps. [Explanation of symbols]

[0093] Reference sign 2 Emitter electrode 3 Collector electrode 4 gate electrode 10 Semiconductor body 11 Emitter side 12 Injection area 13 Base Area 13a first base region 13b Second base region 13c Third base region 14 Drift Region 15 Areas of the first type 16 Second type of area 18 Mixed area 18' pilot area 18” edge area 19 Collector side 40 Electrical insulating layer / gate insulating layer 51 First type trench 52 Second type trench 100 RC-IGBT W width L length W1 First value W2 Second value W3 width W4 range I Information S1,S2 method steps

Claims

1. a semiconductor body (10) having an emitter side (11) and a collector side (19); A reverse conducting insulated gate bipolar transistor (100) comprising: - said semiconductor body (10) comprises at least one mixed region (18) on said collector side (19), - said mixed region (18) is of a first conductivity type and comprises a plurality of first type regions (15) laterally spaced apart from one another by semiconductor material of a second conductivity type; - seen from above on said collector side (19), - the first type of regions (15) of the mixing zone (18) are each elongated and each extend radially away from a reference point (Z) of the mixing zone (18); - the number of first type regions (15) of said mixed region (18) increases stepwise in the direction away from said reference point (Z), - said semiconductor body (10) comprises at least one pilot region (18') adjacent to said mixed region (18) on said collector side (19), - said pilot region (18') is of said second conductivity type, - when viewed from above on the collector side (19), said reference point (Z) is within said pilot area (18'); the area of ​​said pilot region (18') is at least d·d and at most 100·d·d, where d is the thickness of said semiconductor body (10); A reverse conducting insulated gate bipolar transistor (100).

2. - when viewed from above on the collector side (19), the mixing zone (18) completely surrounds the pilot zone (18'); The reverse conducting insulated gate bipolar transistor (100) of claim 1.

3. - when viewed from above on the collector side (19), the second type region (16) of the second conductivity type extends continuously from the pilot region (18') to the edge of the mixed region (18); A reverse conducting insulated gate bipolar transistor (100) according to claim 1 or 2.

4. - when viewed from above on said collector side (19), said first type of areas (15) are uniformly distributed around said reference point (Z); A reverse conducting insulated gate bipolar transistor (100) according to any one of the preceding claims.

5. - when viewed from above on said collector side (19), each step of said step increase is assigned an area of ​​said collector side (19), - the area assigned to at least one stage is annular; A reverse conducting insulated gate bipolar transistor (100) according to any one of the preceding claims.

6. - said number of regions (15) of the first type varies by at least a factor of two from one stage to the adjacent stage, A reverse conducting insulated gate bipolar transistor (100) according to any one of the preceding claims.

7. - in a step, the distance between each adjacent first type region (15) has a first value (W1) in the region closest to said reference point (Z) and a second value (W2) in the region farthest from said reference point (Z), - said second value (W2) is greater than said first value (W1), but is at most four times said first value (W1); A reverse conducting insulated gate bipolar transistor (100) according to any one of the preceding claims.

8. the width (W3) of said first type regions (15), measured perpendicular to their respective main direction of extension, is at most half of said first value (W1); The reverse conducting insulated gate bipolar transistor (100) of claim 7.

9. a first plurality of laterally arranged transistor half-cells (HC) arranged one after the other; Furthermore, - said extent (W4) of said transistor half-cell (HC), measured in said first lateral direction, is smaller than said width (W3) of said first type area (15); A reverse conducting insulated gate bipolar transistor (100) according to any one of the preceding claims.

10. - when viewed from above on the collector side (19), the pilot area (18') has a round shape, x ２ / a ２ +y ２ / b ２ = 1, where x and y are coordinates on said collector side (19), the centre of said pilot region (18') has coordinates x = 0 and y = 0, a and b are fixed numbers, - said collector side (19) has a rectangular shape with rectangular edges having a length L and a width W, L≧W; The area and shape of the pilot area (18') depend on the area and shape of the collector side (19) according to the following rules: -L<2 W, the collector side (19) comprises only one pilot region (18') surrounded by a mixing region (18), and the contour delimiting the pilot region (18') satisfies 0.1≦(2·a) / L≦0.5, 0.1≦(2·b) / W≦0.5, and (2·a) / L=(2·b) / W; - if L≧2·W, the collector side (19) comprises several pilot regions (18′) each surrounded by the mixing region (18), each pilot region (18′) being delimited by a contour satisfying 0.1≦(2·a) / L′≦0.5, 0.1≦(2·b) / W≦0.5, and (2·a) / L′=(2·b) / W, where L′·c=L, c is an integer and is the number of pilot regions (18′); Selected according to A reverse conducting insulated gate bipolar transistor (100) according to any one of the preceding claims.

11. -L≧2 W, said collector side (19) comprises several pilot regions (18') each surrounded by a mixing region (18), each pilot region (18') being delimited by a contour satisfying 0.1≦(2·a) / L′≦0.5, 0.1≦(2·b) / W≦0.5, and (2·a) / L′=(2·b) / W, where L′·c=L, c being an integer and the number of pilot regions (18'); The reverse conducting insulated gate bipolar transistor (100) of claim 10.

12. - said semiconductor body (10) comprises an edge region (18") on said collector side (19), said edge region (18") being of said first conductivity type or said second conductivity type and laterally surrounding said mixed region (18); A reverse conducting insulated gate bipolar transistor (100) according to any one of the preceding claims.

13. - said edge regions (18") are of said second conductivity type and have a lower doping concentration than said semiconductor material of said second conductivity type arranged laterally between said regions (15) of said first type; The reverse conducting insulated gate bipolar transistor (100) of claim 12.

14. - said edge region (18") is of said first conductivity type; The reverse conducting insulated gate bipolar transistor (100) of claim 12.

15. A method for fabricating a reverse conducting insulated gate bipolar transistor (100), comprising: - providing information (I) representing the length L and width W that the collector side (19) of the fabricated reverse conducting insulated gate bipolar transistor (100) should have, where L≧W; - producing a semiconductor body (10) having an emitter side (11) and a collector side (19) according to the information (I) provided; and, as a result, - said semiconductor body (10) comprises at least one mixed region (18) on said collector side (19), - said mixed region (18) is of a first conductivity type and comprises a plurality of first type regions (15) laterally spaced apart from one another by semiconductor material of a second conductivity type; - seen from above on said collector side (19), - the first type of regions (15) of the mixing zone (18) are each elongated and each extend radially away from a reference point (Z) of the mixing zone (18); - the number of first type regions (15) of said mixed region (18) increases stepwise in the direction away from said reference point (Z), - if L<2·W, two or more such mixed regions (18) are produced in the semiconductor body (10), and if L≧2·W, only one such mixed region (18) is produced in the semiconductor body (10); method.

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