Reverse Conducting Insulated Gate Bipolar Transistor

Abstract

According to one embodiment, the RC-IGBT (1000) comprises a semiconductor body (100) having an emitter side (101) and a collector side (102), a collector layer (1) on the collector side having at least one pilot region (10) and at least one mixed region (11), and a collector electrode (2) on the collector side and in electrical contact with the collector layer. The pilot region is of a first conductivity type. The mixed region has a first sub-region (111) of the first conductivity type and a second sub-region (112) of the second conductivity type. The doping concentration in the first sub-region is different from the doping concentration in the pilot region.

Description

[Technical field]

[0001] The present disclosure relates to a reverse-conducting insulated gate bipolar transistor, also referred to below as RC-IGBT (Reverse-Conducting Insulated Gate Bipolar Transistor). Furthermore, the present disclosure relates to a method for producing a reverse-conducting insulated gate bipolar transistor. [Background technology]

[0002] WO 2015 / 097157 relates to reverse conducting semiconductor devices. US 2015 / 236143 relates to semiconductor devices and RC-IGBTs having a zone directly adjacent to the back electrode. US 2005 / 017290 relates to insulated gate bipolar transistors incorporating freewheeling diodes. US 2018 / 226397 relates to semiconductor devices and electrical apparatus. Summary of the Invention [Problem to be solved by the invention]

[0003] What is needed is an improved RC-IGBT that has an improved tradeoff between robustness, such as safe operating area (SOA) capability, and static losses, and what is needed is an improved method for producing such RC-IGBTs. [Means for solving the problem]

[0004] SUMMARY OF THE DISCLOSURE Embodiments of the present disclosure relate to RC-IGBTs with improved tradeoff between SOA capability and static losses. SOA stands for safe operation area. Further embodiments relate to methods for producing RC-IGBTs.

[0005] First, we will describe the RC-IGBT. According to one embodiment, an RC-IGBT comprises a semiconductor body having an emitter side and a collector side, a collector layer on the collector side having at least one pilot region and at least one mixed region, and a collector electrode on the collector side and in electrical contact with the collector layer. The pilot region is of a first conductivity type. The mixed region has a first sub-region of the first conductivity type and a second sub-region of the second conductivity type. The doping concentration in the first sub-region is different from the doping concentration in the pilot region.

[0006] By having different doping concentrations for the pilot region and the first sub-region, robustness can be increased without increasing static losses. For example, by decreasing the doping concentration in the pilot region and / or increasing the doping concentration in the first sub-region, the reverse bias SOA (RBSOA) can be increased while maintaining or decreasing static losses. A more uniform current / plasma distribution across the active area of ​​the device can be obtained, especially during high current turn-off (RBSOA).

[0007] The disclosed RC-IGBTs combine the advantages of improved robustness (especially high RBSOA) with no or limited increase in conduction losses. These improvements provide an opportunity to expand the range of possibilities for low-state-loss devices that are not RBSOA limited. This is particularly advantageous for low-frequency High-Voltage DC (HVDC) systems where RC-IGBTs are primarily used. Furthermore, the disclosed RC-IGBTs do not require significant changes to the manufacturing method, at most an additional photolithography step.

[0008] The RC-IGBT with pilot region disclosed herein is also commonly called Bi-mode Integrated Gate Transistor, or BIGT for short. The BIGT constitutes a hybrid structure of an IGBT and a standard RC-IGBT. The IGBT is realized in the area of ​​the pilot region and can therefore also be called pilot IGBT. The standard RC-IGBT is realized in the area of ​​the mixed region. Both the IGBT and the standard RC-IGBT are implemented in a single device or a single chip, respectively. The pilot IGBT is sized to reduce snapback in forward conduction mode, for example at low temperatures. In the following, unless otherwise specified, the expression "RC-IGBT" refers to an RC-IGBT with pilot region and therefore to a BIGT, and not to a standard RC-IGBT forming part of the BIGT.

[0009] The semiconductor body may comprise or consist of silicon. The emitter side and the collector side are, for example, opposite sides that bound the semiconductor body in two opposite directions. The distance between the emitter side and the collector side is the thickness of the semiconductor body.

[0010] The collector layer may be part of the semiconductor body. The collector layer may be made of a semiconductor material, for example silicon. For example, the collector layer forms the collector side.

[0011] The different regions of the collector side, such as the pilot region, the sub-region, and the under-defined edge region, can reach the collector side, i.e. each can form a part or an area of ​​the collector side. The different regions may each extend throughout the entire thickness of the collector layer.

[0012] A collector electrode may be adjacent to the collector side and in electrical contact with the collector layer. The collector electrode may include or consist of a metal.

[0013] The pilot region is of a first conductivity type, for example exclusively of the first conductivity type. The first conductivity type may be either hole-conducting or electron-conducting. Thus, the pilot region may be either p-doped or n-doped. For example, the pilot region is homogeneously doped over its entire volume and / or over its entire lateral expansion.

[0014] Here and below, a homogeneous doping concentration means homogeneous within manufacturing tolerances, for example with a maximum deviation of up to 5% from the average doping concentration.

[0015] In this document, lateral direction is understood to be the direction parallel to the collector side or main extension plane of the collector layer or semiconductor body, respectively.

[0016] The mixed region includes a first sub-region of a first conductivity type, e.g. exclusively of the first conductivity type, and a second sub-region of a second conductivity type, e.g. exclusively of the second conductivity type. The second conductivity type may therefore be electron-conducting or hole-conducting. For example, the first sub-regions are p-doped and the second sub-regions are n-doped, or vice versa. All first sub-regions may have the same doping concentration and / or may be homogeneously doped throughout their respective lateral expansion and / or volume. Similarly, all second sub-regions may have the same doping concentration and / or may be homogeneously doped within manufacturing tolerances throughout their respective lateral expansion and / or volume. For example, the first sub-regions and the second sub-regions are arranged alternately in the mixed region.

[0017] Here and below, the same doping concentration means the same doping concentration within the limits of manufacturing tolerances, for example a maximum deviation of the maximum or average doping concentration of up to 5%.

[0018] The area of ​​the pilot region may be larger than the area of ​​each of the first and / or second subregions, for example at least 5 times or at least 10 times or at least 100 times the area of ​​each of the first and / or second subregions. For example, the area of ​​a region or subregion is understood herein to be the area of ​​the respective region / subregion on the collector side.

[0019] The pilot region and / or the mixed region may be contiguous regions, for example the pilot region is a simply linked region, i.e. a continuous region without interruption.

[0020] The doping concentration of the pilot region differs from the doping concentration of the first sub-region. For example, the doping concentrations differ from each other by a factor of at least 1.1 or at least 1.5 or at least 2 or at least 5 or at least 10. Here and below, the comparison of the doping concentrations of two regions / sub-regions can be a comparison of the average doping concentration and / or the maximum doping concentration of these regions / sub-regions. The comparison can also relate to the doping concentration at the surface of the regions / sub-regions, for example on the collector side. The maximum doping concentration may be at the surface of the region.

[0021] For example, the doping concentration in the pilot region is 1·10 16 cm -3 Over 5-10 19 cm -3 For example, 1·10 15 cm -3 Over 5-10 18 cm -3 The following is the result.

[0022] According to a further embodiment, the doping concentration in the first sub-regions is greater than the doping concentration in the pilot region. For example, the doping concentration in each first sub-region is at least 1.1 times, or at least 1.5 times, or at least 2 times, or at least 5 times, or at least 10 times, the doping concentration in the pilot region. The dopant in the pilot region and the first sub-regions may be the same, for example boron.

[0023] By reducing the doping concentration in the pilot region, the RBSOA and Short Circuit SOA (hot) capabilities are increased, but may have an undesirable effect on the static losses and may increase the on-state losses in the IGBT operating mode. Increasing the doping concentration in the first sub-region of the mixed region reduces the on-state losses in the IGBT operating mode, compensating for the effect of reducing the doping concentration in the pilot region. In this way, it is possible to provide a BIGT device with similar on-state losses as known devices, but with improved RBSOA and SCSOA (hot) capabilities.

[0024] According to a further embodiment, the collector layer further comprises an edge region, which may extend to an edge of the collector layer that laterally bounds the collector layer, for example the edge region forms all edges of the collector layer.

[0025] In the lateral direction, 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.

[0026] According to a further embodiment, the edge region laterally surrounds the pilot region and / or the mixed region. For example, the edge region completely surrounds the pilot region and / or the mixed region in the laterally direction. The edge region may form a frame around the pilot region and / or the mixed region. The area of ​​the edge region may be larger than the area of ​​each first sub-region and / or second sub-region. For example, the edge region has a constant width along its extension around the mixed region and / or the pilot region.

[0027] According to further embodiments, a larger portion (majority) of the edge region is either the first conductivity type or the second conductivity type. A larger portion of the edge region, as used herein, can mean a larger portion of the collector-side area formed by the edge region, or a larger portion of the volume of the edge region. A "larger portion" can mean, for example, more than 50% or at least 75%. A "larger portion," a "major portion," a "major portion," and "most of" are used synonymously herein.

[0028] For example, the edge region includes one subregion, also called the third subregion, that is exclusively of the first conductivity type or the second conductivity type. The third subregion can form a larger portion of the edge region. The third subregion may be a contiguous subregion of the edge region. For example, the third subregion completely surrounds the mixed region and / or the pilot region laterally. The third subregion may be homogeneously doped.

[0029] According to a further embodiment, the larger part of the edge region is of the same conductivity type and has the same doping concentration as the first sub-region.

[0030] According to a further embodiment, the larger portion of the edge region is of the same conductivity type as the first sub-region and has a different doping concentration than the first sub-region. For example, the larger portion of the edge region has a lower doping concentration than the first sub-region. In this way, leakage can be reduced while still improving SCSOA(hot) capability.

[0031] The doping concentration of the edge region may be at most 0.9 times, or at most 0.5 times, or at most 0.1 times, the doping concentration of the first sub-region. For example, the doping concentration of the edge region is the same as the pilot region. Alternatively, the doping concentration of the edge region may be at least 1.1 times, or at least 2 times, or at least 10 times, the doping concentration of the first sub-region.

[0032] According to a further embodiment, a larger portion of the edge region is of the same conductivity type and has the same doping concentration as the pilot region.

[0033] According to a further embodiment, the larger portion of the edge region is of the same conductivity type as the second sub-region. In this case, the larger portion of the edge region may have a different doping concentration than the second sub-region or may have the same doping concentration as the second sub-region. For example, the larger portion of the edge region is n-doped. In this way, the emitter connection portion of the p-type termination region serves as an additional anode area of ​​the internal diode of the BIGT, thereby reducing the on-state losses in the diode operation mode.

[0034] The doping concentration of the larger portion of the edge region may be lower than the doping concentration of the second sub-region in the mixed region, for example, up to 0.9 times or up to 0.5 times or up to 0.1 times the doping concentration of the second sub-region. Additionally or alternatively, the doping concentration of the larger portion of the edge region may be at least 1.1 times or at least 2 times or at least 10 times the doping concentration of the first sub-region. Adjusting the doping profile improves the plasma distribution under the termination region and provides an opportunity to maintain or improve the (termination limited) diode turn-off SOA.

[0035] According to a further embodiment, the second sub-region extends into the edge region. The edge region may consist of a portion of the second sub-region extending into the edge region and a larger portion of the edge region mentioned above. The first sub-region may end before the edge region, i.e. it does not extend into the edge region. For example, the first sub-region is adjacent to the edge region.

[0036] According to a further embodiment, the pilot region is laterally surrounded by the mixing region, e.g. completely laterally surrounded by the mixing region, e.g. the pilot region is spaced from the edge region by the mixing region.

[0037] According to a further embodiment, the pilot region, i.e. the shape of the pilot region, has rotational symmetry with respect to an axis of symmetry. The axis of symmetry may extend obliquely, for example perpendicularly, and / or through the collector layer. Obliquely or perpendicularly to the collector layer means, for example, obliquely or perpendicularly to the main extension plane of the collector layer. The axis of symmetry may extend through the pilot region.

[0038] For example, the pilot region has two-fold, three-fold or four-fold rotational symmetry or circular symmetry about the axis of symmetry. In top view on the collector side, the pilot region can have a circular or cross-shaped or star-shaped or rectangular shape.

[0039] According to a further embodiment, the arrangement of the first and second sub-regions in the mixed region has rotational symmetry with respect to the axis of symmetry, for example, the rotational symmetry is two-fold, three-fold or four-fold, or is circular symmetry.

[0040] According to a further embodiment, the pilot region has at least two arms extending radially from the center of the pilot region. For example, the pilot region has at least three or at least four such arms. The center of the pilot region may coincide with the center of the collector side.

[0041] A radial direction is understood herein to be a lateral direction extending through and pointing toward or outward from the center of the pilot region.

[0042] According to a further embodiment, on the collector side the first and second sub-regions extend from the pilot region in a direction away from the pilot region, for example away from the centre of the pilot region.

[0043] On the collector side, the first sub-regions and the second sub-regions may all extend in parallel in the radial direction. For example, the first sub-regions and the second sub-regions are each formed in a strip. The width of the first sub-regions and / or the second sub-regions may each be smaller than the width of the edge region and / or the pilot region. For example, the width of each of the first sub-regions and / or the second sub-regions is at most 50% or at most 10% or at most 1% of the width of the edge region and / or the pilot region.

[0044] According to a further embodiment, the pilot region is concatenated to one or more first sub-regions and / or one or more second sub-regions, meaning that the pilot region is directly adjacent to one or more first sub-regions and / or one or more second sub-regions.

[0045] According to further embodiments, the total area of ​​the pilot regions is at least 10% or at least 20% of the total area of ​​the mixed region. Additionally or alternatively, the total area of ​​the pilot regions may be up to 60% or up to 45% or up to 35% of the total area of ​​the mixed region.

[0046] According to a further embodiment, the pilot region is a contiguous region, such as a single linked region.

[0047] According to a further embodiment, the semiconductor body further comprises a base layer. The base layer may be of the second conductivity type. For example, the base layer is n-doped. The doping concentration of the base layer may be less than that of the second sub-region.

[0048] According to further embodiments, the semiconductor body comprises at least one well region. For example, the semiconductor body comprises several, for example at least 10 or at least 100, well regions. All features disclosed in relation to one well region are also disclosed for the other well regions. For example, the well region is of a first conductivity type. For example, the well region is p-doped. The doping concentration of the well region may be less than, equal to or greater than the doping concentration of the pilot region and / or the first sub-region.

[0049] The well region may be spaced from the collector layer by a base layer, in other words, the base layer may be disposed between the well region and the collector layer, for example, there is no direct connection between the well region and the collector layer.

[0050] According to further embodiments, the semiconductor body further comprises at least one emitter region. The semiconductor body may include a plurality of emitter regions, for example at least 10 or at least 100. All features disclosed for one emitter region are also disclosed for the other emitter regions.

[0051] The emitter region may be of the second conductivity type. For example, each well region is assigned at least one emitter region. The emitter region may be embedded in the well region. The emitter region may be spaced from the base layer by the well region, i.e. there is no direct contact between the base layer and the emitter region. The doping concentration of the emitter region may be less than, equal to or greater than the doping concentration in the second sub-region. For example, the doping concentration of the emitter region is greater than the doping concentration of the base layer.

[0052] The well region and / or the emitter region may be adjacent to the emitter side of the semiconductor body.

[0053] According to further embodiments, at least one emitter electrode is arranged on the emitter side. The emitter electrode may comprise or consist of a metal. The emitter electrode may be in electrical contact with at least one emitter region. The RC-IGBT may comprise several emitter electrodes. All features disclosed in connection with one emitter electrode are also disclosed for the other emitter electrodes. For example, each emitter region is assigned one individual emitter electrode. The emitter electrodes may adjoin the assigned emitter region on the emitter side.

[0054] According to further embodiments, at least one gate electrode is arranged on the emitter side. The gate electrode may be electrically insulated from at least one well region and / or at least one emitter region. The gate electrode is, for example, arranged above the well region but laterally offset from the emitter region. For example, the gate electrode is electrically insulated from the semiconductor body or any conductive region of the semiconductor body. The RC-IGBT may comprise several gate electrodes. All features disclosed in connection with one gate electrode are also disclosed for the other gate electrodes. For example, each well region is assigned one individual gate electrode. The gate electrode may comprise or consist of at least one of a metal, highly doped polysilicon.

[0055] In the lateral direction, the edge and / or termination regions of the RC-IGBT may not overlap any gate electrode or any emitter electrode or any well region or any emitter region.

[0056] According to further embodiments, the width of the pilot region is at least the same as the thickness of the base layer, or at least twice or at least three times the thickness of the base layer. The width of the first sub-region and / or the second sub-region may be less than the thickness of the base layer, or may be up to twice the thickness of the base layer. The total width of the mixed region may be at least twice the thickness of the base layer.

[0057] Next, a method for producing an RC-IGBT is described. The method is particularly suitable for producing an RC-IGBT according to any one of the embodiments described herein. Thus, all features described in relation to the RC-IGBT are also disclosed for the method and vice versa.

[0058] According to one embodiment of the method, a semiconductor body having an emitter side and a collector side is provided. The semiconductor body comprises a collector layer having at least one pilot region of a first conductivity type and a mixed region having a first subregion of the first conductivity type and a second subregion of a second conductivity type. The first subregion and the pilot region may have the same doping concentration. The doping concentration in the pilot region and / or the first subregion is then varied until the doping concentrations in the pilot region and the first subregion are different.

[0059] To vary the doping concentration, the pilot region can be masked and an additional implantation process can be performed in which the doping concentration in the first sub-region is increased while the doping concentration in the pilot region is unchanged or changed less due to the masking, resulting in a lower doping concentration in the pilot region than in the first sub-region of the mixed region, improving the RBSOA performance. Additionally or alternatively, to vary the doping concentration, a local activation process can be performed in which the first sub-region is annealed while the pilot region is not annealed.

[0060] To improve the diode (third quadrant) performance, the doping concentration of the pilot region can be made higher than that of the first sub-region. To change the doping concentration of the pilot region, the first sub-region can be masked and an additional implantation process can be performed in which the doping concentration in the pilot region is increased while the doping concentration in the first sub-region is not changed or is changed less due to the masking. Additionally or alternatively, to change the doping concentration, a local activation process can be performed in which the pilot region is annealed while the first sub-region is not annealed.

[0061] Hereinafter, the RC-IGBT and the method for producing the RC-IGBT will be described in more detail based on an exemplary embodiment with reference to the drawings. The attached drawings are included to provide further understanding. In the drawings, elements of the same structure and / or function may be referred to by the same reference numerals. It should be understood that the embodiments shown in the drawings are exemplary representations and are not necessarily drawn to scale. Insofar as elements or components correspond to each other in terms of their functions in different figures, the description thereof will not be repeated for each of the following figures. For clarity, elements may not be labeled with corresponding reference numerals in all figures. [Brief description of the drawings]

[0062] [Figure 1] FIG. 2 is a collector side top view illustrating a first exemplary embodiment of an RC-IGBT. [Diagram 2] FIG. 2 is a cross-sectional view illustrating a second exemplary embodiment of an RC-IGBT. [Diagram 3] FIG. 3 shows the cross section of FIG. 2 in more detail. [Figure 4] FIG. 13 is a collector side top view illustrating a second exemplary embodiment of an RC-IGBT. [Diagram 5] FIG. 13 is a collector side top view illustrating a further exemplary embodiment of an RC-IGBT. [Figure 6] FIG. 13 is a collector side top view illustrating a further exemplary embodiment of an RC-IGBT. [Figure 7] FIG. [Figure 8] FIG. [Figure 9] 1 is a flow chart of an exemplary embodiment of a method for producing an RC-IGBT. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0063] 1 shows a first exemplary embodiment of an RC-IGBT 1000 in a top view of the collector side. The RC-IGBT 1000 comprises a semiconductor body having an emitter side and a collector side, and a collector layer on the collector side. The collector layer forming the collector side comprises a pilot region 10 and a mixed region 11 (separated by a dashed line for illustration purposes). The pilot region 10 is of a first conductivity type. The mixed region comprises a first sub-region 11 also of the first conductivity type and a second sub-region 112 of a second conductivity type. For example, the pilot region 10 and the first sub-region 111 are p-doped and the second sub-region 112 is n-doped.

[0064] As shown by the different structuring of the different regions / sub-regions, the doping concentration in the pilot region 10 is different from the doping concentration in the first sub-region 111. For example, the doping concentration of the pilot region 10 is smaller than the doping concentration of the first sub-region 111.

[0065] Figures 2-4 show a second exemplary embodiment of the RC-IGBT 1000. Thus, Figure 2 is a view on cross section AA' of Figure 4. Figure 4 shows the RC-IGBT 1000 in a top view of the collector side of the RC-IGBT. Figure 3 shows the framed portion of Figure 2 in more detail.

[0066] The RC-IGBT 1000 comprises a semiconductor body 100 having a base layer 3, a buffer layer 8, and a collector layer 1. The buffer layer 8 and the base layer 3 may be of a second conductivity type. In this embodiment, the first conductivity type is hole conduction and the second conductivity type is electron conduction. Thus, the base layer 3 and the buffer layer 8 are both n-doped. However, they may have different doping concentrations. For example, the doping concentration of the buffer layer 8 is higher than the doping concentration of the base layer 3. The base layer 3 may be thicker than the buffer layer 8. Also, the base layer 3 and / or the buffer layer 8 may be thicker than the collector layer 1.

[0067] The collector layer 1 comprises a pilot region 10 and a mixed region 11. The mixed region 11 comprises a plurality of first sub-regions 111 and a plurality of second sub-regions 112. The first sub-regions 111 and the pilot region 10 are both of a first conductivity type, but have different doping concentrations. Thus, in this case, they are both p-doped. For example, the doping concentration of the pilot region 10 is, for example, at least two times smaller than the first sub-regions 111.

[0068] The second sub-region 112 is of the second conductivity type and is therefore n-type doped in this case. The collector layer 1 forms the collector side 102 of the semiconductor body 100. The pilot region 10 and the sub-regions 111, 112 reach the collector side 102, i.e. each form part of the collector side 102. The collector electrode 2 is arranged on top of the collector side 102 and is in electrical contact with it. The collector electrode 2 is, for example, made of metal.

[0069] Furthermore, the collector layer 1 comprises an edge region 12. The edge region 12 adjoins or forms a lateral edge of the collector layer 1. The edge region 12 may laterally overlap partially or completely with a termination region of the RC-IGBT, for example the termination region defines the edge region 12.

[0070] The termination region is the region of the RC-IGBT that laterally surrounds the active area of ​​the RC-IGBT. The active area is the region through which the device conducts current during the on-state.

[0071] On the emitter side 101 opposite the collector side 102, the semiconductor body 100 comprises a number of well regions 4 (see FIG. 3 for a better illustration). The well regions 4 are, for example, of a first conductivity type, i.e. p-doped. Embedded in the well regions 4 are emitter regions 5, which are, for example, of a second conductivity type, i.e. n-doped. On top of the emitter side 101, emitter electrodes 6 are arranged, which are in electrical contact with the emitter regions 5. Furthermore, gate electrodes 7 are arranged on the emitter side 101 and are insulated from the semiconductor body 100 by an insulating material 9. The emitter electrodes 6 and the gate electrodes 7 are, for example, made of a metal. The insulating material 9 can be SiO 2 or SiO 2 It may consist of.

[0072] The termination region and / or edge region 12 may be defined by a region on a lateral side of the RC-IGBT that does not overlap in the lateral direction with any emitter electrode 6 and / or any gate electrode 7 and / or any emitter region 5 and / or any well region 4.

[0073] 4, which illustrates a second exemplary embodiment of an RC-IGBT 1000 in a top view on the collector side 101, it can be seen that the pilot region 10 has a cross shape. The center 103 of the pilot region 10 coincides with the center of the collector side 102. The pilot region 10 has four-fold rotational symmetry about an axis of symmetry 20 that extends through the center 103, perpendicular to the drawing plane.

[0074] As can also be seen in Fig. 4, the arrangement of the first sub-region 111 and the second sub-region 112 in the mixed region 11 also follows four-fold rotational symmetry about the axis of symmetry 20. The mixed region 11 completely surrounds the pilot region 10 in the laterally direction. The mixed region 11 and the pilot region 10 are further completely surrounded in the laterally direction by the edge region 12. The boundaries between the mixed region 11 and the pilot region 10 and between the mixed region 11 and the edge region 12 are respectively indicated by dashed lines.

[0075] In the exemplary embodiment of Fig. 4, the area of ​​the pilot region 10 is larger than the area of ​​each of the first sub-region 111 and / or the second sub-region 112, e.g. at least 5 times the area of ​​each of the first sub-region 111 and / or the second sub-region 112. The area of ​​the pilot region 10 is, e.g. 10% to 35% of the area of ​​the mixed region. The width of the pilot region 10 may be at least twice the thickness of the base layer 3.

[0076] The first sub-region 111 and the second sub-region 112 are each formed in a strip shape. The width of each of the sub-regions 111, 112 may be smaller than the thickness of the base layer 3, for example, up to 50% of the thickness of the base layer 3.

[0077] The area of ​​the edge region 12 may also be larger than the area of ​​each of the first sub-region 111 and / or the second sub-region 112, for example at least five times larger.

[0078] 2-4, the second sub-region 112 extends into and forms part of the edge region 12. The remaining edge region 12, i.e. a larger part of the edge region 12, is of the same conductivity type as the pilot region 10 and the first sub-region 111, i.e. the first conductivity type.

[0079] In this exemplary embodiment, the doping concentration of the larger part of the edge region 12 is the same as the first sub-region 111. However, the doping concentration of the pilot region 10 is smaller than the first sub-region 111 and the larger part of the edge region 12.

[0080] The larger portion of the edge region 12 that is of the first conductivity type forms a contiguous sub-region of the edge region that completely surrounds the mixed region 11 and the pilot region 10 .

[0081] 5 shows a further exemplary embodiment of the RC-IGBT 1000. A cross section of this RC-IGBT 100 may look similar to the cross section of FIG. 2. However, compared to the previous exemplary embodiment, the top view on the collector side looks different. In contrast to the previous exemplary embodiment, a larger portion of the edge region 12 does not have the same doping concentration as the first sub-region 111, but has the same doping concentration as the pilot region 11.

[0082] In the exemplary embodiment of Fig. 6, again only the top view of the collector side is shown. Here, in contrast to the previous exemplary embodiment, the larger part of the edge region 12 is not of the first conductivity type but of the second conductivity type. Thereby, the larger part of the edge region may have a different doping concentration than the second sub-region 112 of the mixed region 11.

[0083] All the illustrated exemplary embodiments have in common that the doping concentrations of the pilot region and the first sub-region of the mixed region are different. In the described exemplary embodiments, the first conductivity type was hole conduction and the second conductivity type was electron conduction. However, this is only an example and the opposite case is also possible, i.e. the first conductivity type is electron conduction and the second conductivity type is hole conduction.

[0084] Figure 7 (left side) shows an example of the measured influence of the technology curve for increasing the injection dose (20% or 40%) (see arrows) when both the first sub-region and the pilot region always have the same doping concentration. On the y-axis the turn-off switching losses (i.e. the energy dissipated during the switching event from the on-state to the off-state) are shown. On the x-axis the VCEsat (voltage between emitter and collector at saturation) is shown. As expected, an increase in the injection dose (increasing the doping concentration) reduces the VCEsat, while a corresponding RBSOA reduction is also shown (from 4×Inom to 1.5×Inom in terms of maximum current turn-off capability). For all three points the RBSOA failure location is observed above the pilot region. This shows the pilot region as a weak spot over all doping ranges. This limits the movement towards the low-state loss part of the technology curve, a region that is especially favorable for (low switching frequency) HVDC applications where BIGTs are mainly used. In particular, by tuning the doping in the pilot region for improved RBSOA and in the mixed region for improved on-state estimated SOA performance, improvements can be expected as shown in FIG. 7 (right side).

[0085] Experimental results of the degraded diode on-state both with (left) and without (right) BIGT MOS control are shown in Fig. 8. On the y-axis the conduction loss of the diode mode is shown. In both figures the data points on the left correspond to the case where the edge region under the termination region has the same doping concentration and the same conductivity type as the first sub-region (see Fig. 4). The degraded on-state of the data points on the right is due to the use of an edge region, the larger part of which is of a different conductivity type, e.g. n-doped, than the pilot region or the first sub-region, respectively. Here, as an example, the n-doping in the edge region is equal to the doping of the second sub-region in the mixed region. The improvement of the diode on-state, just like the IGBT on-state, is again a key to improve the system level performance in low frequency HVDC systems. Finally, the improvement of the on-state without MOS control also benefits systems where the BIGT is used as a plug-and-play building block for more common (without MOS control) system topologies.

[0086] 9 shows a flow chart of an exemplary embodiment of a method for producing an RC-IGBT. First, in step S1, a semiconductor body having an emitter side and a collector side is provided. The semiconductor body comprises a collector layer having at least one pilot region of a first conductivity type and a mixed region having a first sub-region of the first conductivity type and a second sub-region of a second conductivity type. The first sub-region and the pilot region have the same doping concentration. Then, in step S2, the doping concentration in the pilot region and / or the first sub-region is changed until the doping concentrations in the pilot region and the first sub-region are different.

[0087] The embodiments shown in Figures 1-6 and 9 above represent exemplary embodiments of the improved RC-IGBT and method. Therefore, they do not constitute an exhaustive list of all embodiments of the improved RC-IGBT and method. The actual RC-IGBT and the actual method may differ from the illustrated embodiments, for example, with respect to the arrangement. [Explanation of symbols]

[0088] Reference sign 1 Collector layer 2 Collector electrode 3. Base layer 4 Well Area 5 Emitter Area 6 Emitter electrode 7 Gate electrode 8 Buffer Layer 9. Insulating Materials 10 Pilot Areas 11 Mixed area 12 Edge Area 20 Axis of Symmetry 100 Semiconductor body 101 Emitter side 102 Collector side 103 center 111 First Sub-area 112 Second Sub-area 1000 Reverse Conducting Insulated Gate Bipolar Transistor S1, S2 method steps

Claims

1. A reverse conducting insulated gate bipolar transistor (1000), a semiconductor body (100) having an emitter side (101) and a collector side (102); a collector layer (1) on said collector side (102) having at least one pilot region (10) and at least one mixed region (11); a collector electrode (2) on the collector side (102) and in electrical contact with the collector layer (1); the pilot region (10) is of a first conductivity type; The mixed region (11) comprises a first sub-region (111) of the first conductivity type and a second sub-region (112) of a second conductivity type, the pilot region (10) is a continuous region, the area of ​​the pilot region (10) on the collector side (102) being greater than the area of ​​each of the first sub-region (111) and / or the second sub-region (112) on the collector side (102); the doping concentration of the first sub-region (111) is different from the doping concentration of the pilot region (10); The collector layer (1) further comprises an edge region (12), said edge region (12) laterally surrounding said pilot region (10) and said mixing region (11); most of said edge region (12) is of the same conductivity type as said first sub-region (111); or most of said edge region (12) is of the same conductivity type as said second sub-region (112) but has a different doping concentration than said second sub-region (112); the second sub-region (112) extends into the edge region (12) and the first sub-region (111) terminates before the edge region (12); A reverse conducting insulated gate bipolar transistor (1000), wherein sub-regions of the edge region (12) forming most of the edge region (12) are exclusively of one conductivity type, are formed contiguously and completely surround the mixed region (11) and the pilot region (10) laterally.

2. The reverse conducting insulated gate bipolar transistor (1000) of claim 1, wherein the doping concentration of the first sub-region (111) is greater than the doping concentration of the pilot region (10).

3. 3. The reverse conducting insulated gate bipolar transistor (1000) of claim 1 or 2, wherein most of the edge region (12) is of the same conductivity type and has the same doping concentration as the pilot region (10).

4. 3. The reverse conducting insulated gate bipolar transistor (1000) of claim 1 or 2, wherein at the collector side (102), the first sub-region (111) and the second sub-region (112) extend from the pilot region (10) in a direction away from the pilot region (10).

5. The reverse conducting insulated gate bipolar transistor (1000) of claim 1 or 2, wherein the pilot region (10) is laterally surrounded by the mixed region (11).

6. the pilot region (10) has rotational symmetry about an axis of symmetry (20) extending obliquely through the collector layer (1); 3. The reverse conducting insulated gate bipolar transistor (1000) of claim 1 or 2, wherein the arrangement of the first sub-region (111) and the second sub-region (112) in the mixed region (11) has rotational symmetry about the axis of symmetry (20).

7. 3. The reverse conducting insulated gate bipolar transistor (1000) of claim 1 or 2, wherein the pilot region (10) has at least two arms (101) extending radially from a center (103) of the pilot region (10).

8. The pilot region (10) is connected to one or more first sub-regions (111), the total area of ​​said pilot zones (10) is at least 10% of the total area of ​​said mixing zones (11); The reverse conducting insulated gate bipolar transistor (1000) of claim 1 or 2, wherein the pilot region (10) is a continuous or singly connected region.

9. The semiconductor body (100) comprises: A base layer (3) of the second conductivity type; at least one well region (4) of said first conductivity type spaced from said collector layer (1) by said base layer (3); at least one emitter region (5) of the second conductivity type spaced from the base layer (3) by the well region (4); At least one emitter electrode (6) is arranged on the emitter side (101) and is in electrical contact with at least one emitter region (5), 3. A reverse conducting insulated gate bipolar transistor (1000) according to claim 1 or 2, wherein at least one gate electrode (7) is arranged on the emitter side (101) and is electrically insulated from the well region (4).

10. A method for producing a reverse conducting insulated gate bipolar transistor (1000), comprising: - providing a semiconductor body (1) having an emitter side (101) and a collector side (102), said semiconductor body (1) comprising a collector layer (1) having at least one pilot region (10) of a first conductivity type and a mixed region (11) having a first sub-region (111) of said first conductivity type and a second sub-region (112) of a second conductivity type, said first sub-region (111) and said pilot region (10) having the same doping concentration; Varying the doping concentration in the pilot region (10) and / or in the first sub-region (111) until the doping concentrations in the pilot region (10) and in the first sub-region (111) are different, the pilot region (10) is a continuous region, the area of ​​the pilot region (10) on the collector side (102) being greater than the area of ​​each of the first sub-region (111) and / or the second sub-region (112) on the collector side (102); The collector layer (1) further comprises an edge region (12), said edge region (12) laterally surrounding said pilot region (10) and said mixing region (11); most of said edge region (12) is of the same conductivity type as said first sub-region (111) or most of said edge region (12) is of the same conductivity type as said second sub-region (112) but has a different doping concentration than said second sub-region (112); the second sub-region (112) extends into the edge region (12) and the first sub-region (111) terminates before the edge region (12); A method according to claim 1, wherein sub-regions of said edge region (12) forming most of said edge region (12) are exclusively of one conductivity type, are formed contiguously and completely surround said mixed region (11) and said pilot region (10) in the lateral direction.

11. To vary the doping concentration, either the pilot region (10) or the first sub-region (111) is masked and an implantation process is carried out, during which the doping concentration of the first sub-region (111) or the pilot region (10) is increased, while the doping concentration of the respective other of the pilot region (10) and the first sub-region (111) is not changed or is changed to a lesser extent by the masking, and / or 11. The method of claim 10, wherein a local activation process is performed in which either the first sub-region (111) or the pilot region (10) is annealed, while the respective other of the pilot region (10) and the first sub-region (111) is not annealed.

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