Power semiconductor transistors

Abstract

A power semiconductor transistor (1) comprises a semiconductor body (10) having a front side (10‑1) and a back side (10‑2), the back side (10‑2) having a back side surface (10‑20), wherein the semiconductor body (10) comprises a drift region (100) of a first conductivity type and a field stop region (105) of the first conductivity type, the field stop region (105) being arranged between the drift region (100) and the back side (10‑2) and extending in a vertical direction from the back side (10‑2) to the front side (10‑1). The cross-section of (Z) includes a concentration profile of a donor of a first conductivity type, the concentration profile exhibiting: a first local maximum (1051) at a first distance (d1) from a back surface (10‑20), a front width (B) at half-maximum associated with the first local maximum, and a back width (A) at half-maximum associated with the first local maximum (1051), wherein the front width (B) at half-maximum is less than the back width (A) at half-maximum and totals at least 8% of the first distance (d1).

Description

Technical Field

[0001] The present description relates to embodiments of a power semiconductor transistor. In particular, the present description relates to embodiments of a power semiconductor transistor comprising a field stop zone and to embodiments of processing and / or producing such a power semiconductor transistor. Background Art

[0002] Many functions of modern devices in automotive, consumer and industrial applications, such as converting electrical energy and driving electric motors or motors, rely on power semiconductor transistors. For example, insulated gate bipolar transistors (IGBTs) and metal oxide semiconductor field effect transistors (MOSFETs), to name a few, have been used in a variety of applications including, but not limited to, switches in power supplies and power converters (e.g., in traction applications).

[0003] A power semiconductor transistor typically includes a semiconductor body configured to conduct a load current along a load current path between two load terminals of the device. For example, in a vertical arrangement of such a power semiconductor transistor, a first load terminal may be coupled to the front side of the semiconductor body and a second load terminal may be coupled to the back side of the semiconductor body. The load current path typically passes through a drift region of a first conductivity type (e.g., n-type).

[0004] Furthermore, the load current path may be controlled by means of the insulated electrode, which is sometimes referred to as a gate electrode. For example, upon receiving a corresponding control signal from, for example, a driver unit, the control electrode may selectively set the power semiconductor transistor to one of a conducting state and a blocking state.

[0005] Typically, the semiconductor body comprises a field stop zone of the first conductivity type (sometimes also referred to as a buffer zone), wherein the field stop zone can, for example, be arranged between the drift zone and the back side. The field stop zone can be configured to influence the course of the electric field during the blocking state of the power semiconductor transistor. The field stop zone can exhibit a higher concentration of donors of the first conductivity type than the drift zone. For example, the electric field drop in the blocking state in a direction pointing from the front side to the back side can thus be increased. The field stop zone of the semiconductor transistor can, for example, be formed by means of proton implantation through the back side of the semiconductor body.

[0006] The field stop region may have an impact on a number of further properties of the power semiconductor transistor.It is generally desirable to provide a power semiconductor transistor that is optimized with respect to certain electrical properties, such as short circuit strength, thermal leakage current, and / or turn-off softness. Summary of the invention

[0007] According to a first aspect of the present disclosure, a power semiconductor transistor includes a semiconductor body having a front side and a back side with a back side surface. The semiconductor body includes a drift region of a first conductivity type and a field stop region of the first conductivity type. The field stop region is arranged between the drift region and the back side, and includes a concentration profile of a donor of the first conductivity type in a cross section along a vertical direction from the back side to the front side, the concentration profile exhibiting: a first local maximum at a first distance from the back side surface, a front width at half maximum value associated with the first local maximum value, and a back width at half maximum value associated with the first local maximum value, wherein the front width at half maximum value is less than the back width at half maximum value, and totals at least 8% of the first distance.

[0008] According to a second aspect, a method for processing a power semiconductor transistor comprises: providing a semiconductor body having a front side and a back side, the back side having a back side surface; and creating a field stop zone inside the semiconductor body by means of at least one proton implantation step, wherein the implantation is performed through the back side surface at an implantation angle relative to a normal to the back side surface, the implantation angle being in the range from 20° to 60°. Furthermore, the implantation is performed with an implantation energy in the range from 100 keV to 800 keV and with an implantation dose that produces an integral of a resulting donor concentration profile in the field stop of at least 20% of the penetration charge specific for the semiconductor body material.

[0009] According to a third aspect, a method for processing a power semiconductor transistor comprises: providing a semiconductor body having a front side and a back side, the back side having a surface defined by a back side surface normal; structuring the back side so as to form a plurality of surface portions which differ from each other in that they have different orientations relative to the back side surface normal; and creating a field stop zone inside the semiconductor body by means of at least one proton implantation step performed through the back side surface, wherein the proton beam is deflected by the plurality of surface portions during the proton implantation step.

[0010] A fourth aspect of the invention relates to a method for producing a power semiconductor transistor, wherein the power semiconductor transistor is a power semiconductor transistor according to the first aspect, the method comprising method steps according to at least one of the second and third aspects.

[0011] A person skilled in the art will recognize additional features and advantages when reading the following detailed description and when viewing the accompanying drawings. It should be noted that the power semiconductor transistor according to the first and second aspects of the invention may have been processed or produced with the aid of the method steps according to the third and / or fourth aspects of the invention. Thus, the features of the invention described above and to be described below with respect to the power semiconductor transistor may be applied analogously to the processing and / or production method and vice versa. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] The various parts in the figures are not necessarily to scale, instead the emphasis is placed on illustrating the principles of the present invention. In addition, in the figures, the same reference numerals designate corresponding parts. In the accompanying drawings:

[0013] Figure 1 schematically and exemplarily illustrates a section of a vertical cross-section of a power semiconductor transistor according to one or more embodiments;

[0014] Figure 2 schematically and exemplarily illustrates a section of a vertical cross-section of a power semiconductor transistor according to one or more embodiments;

[0015] Figure 3 schematically and exemplarily illustrates a donor concentration profile inside a field stop zone according to one or more embodiments;

[0016] Figure 4 schematically and exemplarily illustrates a donor concentration profile inside a field stop zone according to one or more embodiments;

[0017] Figure 5 schematically and exemplarily illustrates a donor concentration profile inside a field stop zone according to one or more embodiments;

[0018] Figure 6 schematically and exemplarily illustrates a donor concentration profile inside a field stop zone according to one or more embodiments;

[0019] Fig. 7A -B each schematically and exemplarily illustrates a proton implantation step for creating a field stop zone according to one or more embodiments;

[0020] Figure 8 illustrates schematically and exemplarily a structured back side of a semiconductor body according to one or more embodiments; and

[0021] Fig. 9 An amorphous backside surface of a semiconductor body according to one or more embodiments is schematically and exemplarily illustrated. DETAILED DESCRIPTION

[0022] In the following detailed description, reference is made to the accompanying drawings which form a part hereof, and in which is shown by way of illustration specific embodiments in which the invention may be practiced.

[0023] In this regard, directional terms such as "top", "bottom", "below", "front", "rear", "back", "leading", "trailing", "below", "above", etc. may be used with reference to the orientation of the figure being described. Since the various parts of the embodiments can be positioned in a plurality of different orientations, the directional terms are used for illustrative purposes and are in no way limiting. It is to be understood that other embodiments may be utilized and structural or logical changes may be made without departing from the scope of the present invention. Therefore, the following detailed description is not to be construed in a limiting sense, and the scope of the present invention is defined by the appended claims.

[0024] Reference will now be made in detail to various embodiments, one or more examples of which are illustrated in the drawings. Each example is provided as an explanation and is not intended to be a limitation of the present invention. For example, features illustrated or described as part of one embodiment may be used in other embodiments or in combination with other embodiments to produce yet other embodiments. It is intended that the present invention includes such modifications and variations. Examples are described using specific language, which should not be interpreted as limiting the scope of the appended claims. The drawings are not to scale and are for illustrative purposes only. For clarity, if not otherwise stated, the same elements or manufacturing steps have been indicated by the same reference numerals in different drawings.

[0025] The term "horizontal" as used in this specification is intended to describe an orientation substantially parallel to a horizontal surface of a semiconductor substrate or semiconductor structure. This may be, for example, a surface of a semiconductor wafer or die. For example, both the first lateral direction X and the second lateral direction Y mentioned below may be horizontal directions, wherein the first lateral direction X and the second lateral direction Y may be perpendicular to each other.

[0026] The term "vertical" as used in this specification is intended to describe an orientation that is generally arranged perpendicular to a horizontal surface, i.e., for example, parallel to a normal direction of the surface of the semiconductor wafer. For example, the extension direction Z mentioned below may be an extension direction perpendicular to both the first lateral direction X and the second lateral direction Y.

[0027] In this specification, n-doped is referred to as the “first conductivity type” and p-doped is referred to as the “second conductivity type.” Alternatively, the opposite doping relationship may be adopted, such that the first conductivity type may be p-doped and the second conductivity type may be n-doped.

[0028] Furthermore, within this specification, the terms "charge carrier concentration", "dopant concentration" and "donor concentration" may refer to the average charge carrier / dopant / donor concentration of a particular semiconductor region or semiconductor area, or to the mean charge carrier / dopant / donor concentration, or to the surface charge carrier / dopant / donor concentration, respectively. Thus, for example, a statement that a particular semiconductor region exhibits a certain donor concentration that is higher or lower than the donor concentration of another semiconductor region may indicate that the respective mean concentrations of the semiconductor regions are different from each other.

[0029] In the context of this specification, the terms "ohmic contact", "electrical contact", "ohmic connected" and "electrically connected" are intended to describe the presence of a low-ohmic electrical connection or a low-ohmic current path between two regions, sections, areas, parts or components of a semiconductor device, or between different terminals of one or more devices, or between a terminal or metallization or electrode and a part or component of a semiconductor device. Furthermore, in the context of this specification, the term "contacted" is intended to describe the presence of a direct physical connection between two elements of the respective semiconductor device; for example, a transition between two elements in contact with each other may not include additional intermediate elements, etc.

[0030] Furthermore, in the context of this specification, if not stated otherwise, the term "electrically insulated" is used in the context of its general, well-informed understanding and is thus intended to describe that two or more components are located separately from each other and there is no ohmic connection connecting those components. However, components that are electrically insulated from each other may nonetheless be coupled to each other, for example mechanically and / or capacitively and / or inductively. To give an example, two electrodes of a capacitor may be electrically insulated from each other, for example by means of an insulation (e.g., a dielectric), and at the same time mechanically and capacitively coupled to each other.

[0031] The specific embodiments described in this specification relate to power semiconductor transistors exhibiting a strip unit or pin unit configuration, such as can be used in a power converter or power supply, without limitation thereto. Thus, in an embodiment, the semiconductor transistor is configured to carry a load current, which is to be fed to a load and / or provided by a power source accordingly. For example, the semiconductor device may include one or more active power unit cells, such as a monolithically integrated IGBT cell, and / or a monolithically integrated RC-IGBT cell, and / or a monolithically integrated MOSFET cell, and / or derivatives thereof. Such a transistor cell can be integrated in a power semiconductor module. A plurality of such cells can constitute a cell field, which is arranged together with the active area of ​​the power semiconductor device.

[0032] The term "power semiconductor transistor" as used in this specification is intended to describe a semiconductor transistor on a single chip having high voltage blocking and / or high current carrying capabilities. In other words, such power semiconductor devices are intended for high currents and / or high voltages, the high currents being typically in the ampere range, such as up to tens or hundreds of amperes or even up to several kA, and the high voltages being typically above 100V, more typically 500V and above, such as up to at least 1kV, up to at least 6 kV. For example, the semiconductor devices described below may be semiconductor devices exhibiting a strip cell configuration or a pin cell configuration, and may be configured for use as power components in low, medium and / or high voltage applications.

[0033] For example, the term "power semiconductor transistor" as used in this specification does not refer to a logic semiconductor device used for, for example, storing data, computing data, and / or other types of semiconductor-based data processing.

[0034] Figure 1 and 2 Each schematically and exemplarily illustrates a section of a vertical cross section of a power semiconductor transistor 1 according to one or more embodiments. The illustrated vertical cross section extends in a plane defined by a first lateral direction X and a vertical direction Z and orthogonal to a second lateral direction Y. Each of the illustrated components may also extend along the second lateral direction Y. In the following, reference will be made to Figure 1 and 2 Each one of them.

[0035] The semiconductor transistor 1 comprises a semiconductor body 10 having a front side 10-1 and a back side 10-2 having a back side surface 10-20. The semiconductor body 10 is coupled to each of a first load terminal structure 11 and a second load terminal structure 12 of the power semiconductor transistor 1. The first load terminal structure 11 may, for example, be an emitter terminal or a source terminal (depending on the type of power semiconductor transistor), which is, for example, coupled to the front side 10-1 of the semiconductor body 10. The second load terminal structure 12 may, for example, be a collector terminal or a drain terminal, which is, for example, coupled to the back side 10-2 of the semiconductor body 10. For example, the first load terminal structure 11 and / or the second load terminal 12 may comprise respective front side or back side metallizations.

[0036] The semiconductor body 10 comprises a drift region 100 of a first conductivity type, which is configured to conduct a load current between a first load terminal structure 11 and a second load terminal structure 12. The drift region 100 may comprise a dopant of the first conductivity type (eg n-type). In an embodiment, the drift region 100 is an n-doped semiconductor region.

[0037] Furthermore, the power semiconductor transistor 1 may include one or more control units 14, each of which extends at least partially into the semiconductor body 10 at the front side 10-1. The one or more control units 14 may be configured to control the load current by switching the power semiconductor transistor 1 into one of a conducting state and a blocking state. In other words, the one or more control units 14 may be configured to selectively conduct the load current or block the blocking voltage depending on the switching state of the power semiconductor device 1.

[0038] Such a control unit 14 may for example comprise a control structure, such as a MOS control structure, such as Figure 2 As shown in the figure. Figure 2 The exemplary embodiment shown in corresponds to an IGBT configuration of the power semiconductor transistor 1. However, the present description is not limited to a specific kind of configuration of the one or more control units 14. Rather, the control unit 14 may exhibit any configuration that is common for power semiconductor transistors such as IGBTs or MOSFETs. The skilled person is familiar with these kinds of configurations. Accordingly, in Figure 1 In the present description, the one or more control units 14 are illustrated only schematically, since the exact configuration is not the primary subject of the present description.

[0039] For example, Figure 2 The control unit 14 depicted in FIG. 1 may exhibit a strip configuration, which may extend, for example, through the active area of ​​the semiconductor body 10 along the second lateral direction Y. In another embodiment, the control unit 14 may exhibit a honeycomb configuration, for example having a horizontal cross-section exhibiting at least one of the following: a quadratic shape, a rectangular shape, a rectangular shape with rounded corners, a circular shape, and an elliptical shape.

[0040] like Figure 2 As further illustrated in , each control unit 14 may, for example, include a trench-gate structure. For example, the trench-gate structure may be arranged in one of a strip configuration and a honeycomb configuration (e.g., exhibiting a quadratic or rectangular shape in a horizontal cross-section), as mentioned above. For example, each of the control units 14 may include a control electrode 141 arranged inside the trench, wherein the control electrode 141 may be configured to receive a control signal, such as a gate voltage, from a control terminal (not shown) of the power semiconductor transistor 1. For example, within each control unit 14, the control electrode 141 may be electrically insulated from the first load terminal structure 11 by means of an insulating block 143, such as an oxide block, as is well known to those skilled in the art.

[0041] Furthermore, each of the cells 14 may include a body region 102 of a second conductivity type (e.g., p-type) complementary to the first conductivity type (e.g., n-type) and at least one source region 104 arranged to be in contact with the first load terminal 11, wherein the body region 102 isolates the at least one source region 104 from the drift region 100. Figure 2 As shown in FIG. 1 , the transition between the body region 102 and the drift region 100 forms a pn junction 103, which is configured to block a blocking voltage applied in a forward direction between the first load terminal 11 and the second load terminal 12. Each of the control units 14 may include a portion of the drift region 100.

[0042] Inside each control unit 14, a corresponding control electrode 141 may be electrically insulated from each of the source region 104, the body region 102 and the drift region 100 by means of an insulating structure 142 (such as an oxide) included in the trench. For example, the control electrode 141 may be configured to induce a transport channel, such as, for example, an n-channel, in the body region 102 between the source region 104 and the drift region 100 depending on a control signal, thereby enabling a conducting state of the power semiconductor device 1. Instead of Figure 2 In addition to such a vertical trench cell 14 illustrated in FIG, the power semiconductor device 1 may be equipped with a so-called planar switching cell (not shown), in which the gate electrode is positioned vertically above the semiconductor body 10. The skilled person is familiar with the principles and variants of such a trench-based or planar switching cell 14 configuration and will therefore not explain them in further detail.

[0043] As is also known to the person skilled in the art, the semiconductor body 10 may further include a backside emitter region 107 of a second conductivity type (eg p-type), which may be arranged at the backside 10 - 2 in contact with the second load terminal 12 , see Figure 2 . In this case, the power semiconductor device 1 can be configured as an IGBT. In another variant, in which the power semiconductor device 1 is configured as a MOSFET, for example, such a back emitter region 107 of the second conductivity type may not be present and a highly doped n-type region may be provided. For example, the back emitter region 107 may have been formed by a diffusion process and / or an implantation process through the back surface 10-20, followed by a subsequent annealing step at a temperature below 440°C. In some embodiments, producing the back emitter region 107 may further involve an activation process by means of a laser, wherein irradiation with the laser is performed through the back side 10-2.

[0044] Furthermore, the semiconductor body 10 comprises a field stop zone 105 of the first conductivity type. The field stop zone 105 is arranged between the drift zone 100 and the back side 10-2. It should be noted that in this context, the relation "between" is to be understood in a broad sense, i.e. further elements may be arranged between the field stop zone 105 and the back side 10-2, such as a back side emitter zone 107 (see Figure 2 ). As is known in principle to a person skilled in the art, such a field stop zone 105 can be provided for influencing the course of the electric field, in particular during the blocking state of the power semiconductor transistor 1. The field stop zone 105 can include donors of the first conductivity type in a higher concentration than the drift zone 100. For example, the electric field drop in the blocking state in a direction pointing from the front side 10-1 to the back side 10-2, i.e. in a direction opposite to the vertical direction Z, can thereby be increased. The field stop zone 105 can have been formed, for example, by means of a proton implantation through the back surface 10-20 of the semiconductor body 10. For example, such an implantation process can be followed by a subsequent annealing step at a temperature below 440°C.

[0045] In accordance with Figure 2 In an embodiment, a second pn junction 108 is formed at the transition between the backside emitter region 107 and the field stop region 105. For example, the second pn junction 108 is positioned at a distance d8 from the backside surface 10-20 nm, wherein the distance d8 is in the range from 100 nm to 500 nm (see also Figure 4 ).

[0046] In a cross section along a direction pointing from the back side 10-2 to the front side 10-1 (i.e. along a direction defined by a normal N on the back side surface 10-2 or equivalently along a vertical direction Z), the field stop zone 105 may include a concentration profile of donors of the first conductivity type, the concentration profile being Figure 1 and 2 Each of the above is exemplarily depicted in FIG. Figures 4 to 6 A more detailed illustration of a section of such a donor concentration profile inside the field stop zone 105 is schematically and exemplarily shown in FIG. Figures 1 to 6 The donor concentration profile is shown in each of the .

[0047] In an embodiment, at least 80% (such as at least 60%) of the donors in the field stop zone 105, i.e. at least 80% (such as at least 60%) of the donors forming the donor concentration profile, are hydrogen induced donors. For example, such hydrogen induced donors may have been created by means of an implantation process followed by an annealing process, as will be further described below.

[0048] The donor concentration profile may exhibit a first local maximum 1051 at a first distance d1 from the back side 10-2 (i.e., from the back side surface 10-2). For example, the first distance d1 is equal to or less than 4 μm, such as at most 3.75 μm. In other words, the first local maximum 1051 may be located relatively shallowly with respect to the back side surface 10-2. On the other hand, in an embodiment, the first distance d1 may be equal to or greater than 0.3 μm, such as at least 0.350 μm.

[0049] Furthermore, the donor concentration profile may exhibit a half-maximum front width B associated with the first local maximum 1051 , wherein the half-maximum front width B amounts to at least 8%, such as at least 10%, at least 12%, or even at least 20%, of the first distance d1 .

[0050] In the following, reference will be made to Figure 1-3 , 5 and 6 to explain the definition of the front width B at half maximum. It should be noted that Figure 4 and 5 In the figure, the solid line represents the donor concentration curve according to the present invention, while the dotted line is a reference curve shown for comparison purposes. In the following, if not stated otherwise, reference will be made to the solid curve. As can be seen, for example, in Figure 3 , 5 In each of 10 and 6, the first local maximum 1051 of the donor concentration CC exhibits a concentration height H, which is defined as the difference between the donor concentration CC at the first local maximum 1051 and the donor concentration CC at a local minimum that is adjacent to the first local maximum 1051 in the direction toward the front side 10-1 (i.e., it is located farther in the vertical direction Z). For example, in Figure 3 and 5 In an exemplary embodiment of the present invention, the local minimum may be located at the rightmost edge of the concentration profile (or even at Figure 3 and 5 The concentration height H is thus the concentration at the first local maximum 1051 and Figure 3 and 5 The middle bottom line (i.e. Figure 3 and 5 ) at the far right edge of the diagram shown in . In contrast, Figure 6 In the exemplary embodiment of , a local minimum is positioned between the first local maximum 1051 and the second local maximum 1052 .

[0051] The front width B at half maximum is defined as the distance between the position d1 of the first local maximum 1051 and the point of the donor concentration curve at which the donor concentration CC has dropped to half of the concentration height H when moving away from the first local maximum 1051 in the direction of the front side 10-1 (i.e., in the vertical direction Z). Figure 3 and 5 In the exemplary embodiment of , the ordinate indicates the donor concentration CC in units normalized to the height H. In other words, the concentration CC at the first local maximum 1051 is 1.0, and the concentration CC at the local minimum is 0.0. Thus, in Figure 3 and 5 In the normalized scale of , the front width B at half maximum is measured at a value of 0.5.

[0052] Correspondingly, the back width A at half maximum value associated with the first local maximum 1051 is defined as the distance between the position d1 of the first local maximum 1051 and the following point of the donor concentration curve: when moving away from the first local maximum 1051 in the direction of the back side 10-2 (i.e., in the direction opposite to the vertical direction Z), at this point, the donor concentration has dropped to half of the concentration height H. The sum of the front width B at half maximum value and the back width A at half maximum value corresponds to the full width A+B at half maximum value.

[0053] In accordance with Figures 1 to 6 In each of the embodiments, the front width B at half maximum is less than the back width A at half maximum. For example, the front width B at half maximum may even be less than half of the back width A at half maximum.

[0054] In accordance with Figures 1 to 6 In an embodiment of each of the above, the front width B at half maximum is at least 0.225 μm, such as at least 0.250 μm, at least 0.275 μm, or even at least 0.375 μm. In addition, in an embodiment, the back width A at half maximum associated with the first local maximum 1051 can be at least 0.675 μm, such as at least 0.700 μm or even at least 0.725 μm. For example, the full width A+B at half maximum associated with the first local maximum 1051 is at least 0.9 μm, such as at least 1.0 μm or even at least 1.1 μm.

[0055] In addition, according to Figure 5 (solid curve), the concentration profile may be characterized in that at a distance of 250 nm from the location of the first local maximum 1051 in the direction of the front side 10 - 1 , the donor concentration is at least 35% of the donor concentration at the first local maximum 1051 .

[0056] In addition, according to Figure 5 In the embodiment of (solid curve), the donor concentration profile may be characterized in that at a distance of 375 nm from the position of the first local maximum 1051 in the direction of the front side 10 - 1 , the donor concentration is at least 5% of the donor concentration at the first local maximum 1051 .

[0057] In addition, according to Figure 5 (solid curve), the donor concentration profile may be characterized in that, in the direction of the back side 10 - 2 at a distance of 500 nm from the location of the first local maximum 1051 , the donor concentration amounts to at least 60% of the donor concentration at the first local maximum 1051 .

[0058] In addition, according to Figure 5 In the embodiment of (solid curve), the concentration profile may be characterized in that at a distance of 1500 nm from the location of the first local maximum 1051 in the direction of the back side 10 - 2 , the donor concentration is at least 25% of the donor concentration at the first local maximum 1051 .

[0059] For comparison, Figure 5 A donor concentration profile (point reference curve) that does not exhibit all of the characteristic features of the bottom layer of the present invention is also depicted. For example, although the local maximum of the point reference curve is approximately located at the same distance d1 from the back surface 10-20 as the first maximum 1051 of the solid curve, it has a front width at half maximum that is less than 8% of the distance d1. In addition, the full width at half maximum of the reference curve is less than 0.9 μm.

[0060] In an embodiment, the donor concentration of the first conductivity type inside the field stop zone 105 may be relatively homogeneous in a lateral direction, such as in one or both of the first and second lateral directions X, Y (see, e.g. Figure 1 and 2 ). For example, along at least 80% of the extension of the field stop zone 105 along a lateral direction, such as along one or both of the first and second lateral directions X, Y perpendicular to the vertical direction Z, the donor concentration at the first local maximum 1051 may vary by less than 10%. Additionally or alternatively, in the active region of the power semiconductor transistor 1, the donor concentration at the first local maximum 1051 may vary by less than 10% along the lateral directions X, Y perpendicular to the vertical direction Z.

[0061] In accordance with Figure 2In an embodiment, wherein the semiconductor body 10 comprises a back emitter region 107 of the second conductivity type, and wherein a second pn junction 108 is formed at a transition between the back emitter region 107 and the field stop region 105, the current amplification factor of the partial transistor formed by the back emitter region 107, the field stop region 105, the drift region 100, and the body region 102 of the control unit 14 is The current amplification factor may vary by less than 10% along the lateral directions X, Y perpendicular to the vertical direction Z. For example, the lateral homogeneity of the donor concentration at the first local maximum 1051 described above may be promoted. Such lateral homogeneity.

[0062] In accordance with Figure 6 In an embodiment of the present invention, the field stop zone 105 may include a plurality of local maxima 1051, 1052, 105n-1, 105n, wherein a first local maximum 1051 is located closer to the backside surface 10-20 than each of the other local maxima 1052, 1053, 105n-1, 105n of the plurality of local maxima. The first local maximum 1051 may also be referred to as a "shallowest peak" because it is the shallowest of the local maxima 1051, 1052, 105n-1, 105n relative to the backside surface 10-20. In addition, an nth local maximum 105n of the plurality of local maxima 1051, 1052, 105n-1, 105n is located farther from the backside surface 10-20 than each of the other local maxima 1051, 1052, 105n-1 of the plurality of local maxima. The nth local maximum may be referred to as the "deepest peak" because it is the deepest of the local maxima 1051, 1052, 105n-1, 105n relative to the backside surface 10-20. Figure 6 In an exemplary embodiment of , the donor concentration profile inside the field stop zone exhibits four local maxima (n=4). In other embodiments, a different number of local maxima may be provided, such as 2, 3, 5, 6 or even more than 6 local maxima.

[0063] In an embodiment, the donor concentration at the first local maximum 1051 is higher than the donor concentration at each of the other local maxima 1052, 105n-1, 105n in the plurality of local maxima. For example, the donor concentration at the first local maximum 1051 may exceed the corresponding donor concentration at each of the other local maxima 1052, 105n-1, 105n in the plurality of local maxima by at least 50% or at least 100%, such as, for example, at least 5 times.

[0064] In an embodiment, the donor concentration at the first local maximum 1051 is at least 1e15 cm -3, such as at least 2e15cm -3 . Furthermore, in an embodiment, the donor concentration at the first local maximum 1051 is in a range from 10 to 5000 times, such as in a range from 20 to 2500 times, of the donor concentration of the drift region 100. For example, the donor concentration at the first local maximum 1051 may be in a range from 10 to 5000 times, such as in a range from 20 to 2500 times, of the mean concentration of dopants of the first conductivity type in the drift region 100.

[0065] Furthermore, according to an embodiment, the donor concentration at the nth local maximum (ie at the deepest donor concentration peak inside the field stop zone 105 ) may be equal to or less than 500 times the donor concentration of the drift region 100 , such as the mean donor concentration of the drift region 100 .

[0066] For example, in an embodiment, the donor concentration at the nth local maximum 105n may be equal to or less than 2e15 cm -3 For example, in an embodiment, the donor concentration at the nth local maximum 105n may be equal to or less than 5e14 cm -3 .

[0067] In an embodiment, the corresponding donor concentration at each of the multiple local maxima 1051, 1052, 105n-1, 105n is in the range from 2 times to 5000 times the donor concentration of the drift region 100, or in the range from 5 times to 1000 times the donor concentration of the drift region 100, wherein the donor concentration of the drift region 100 may be the average donor concentration inside the drift region 100.

[0068] For example, in an embodiment, the corresponding donor concentration at each of the plurality of local maxima 1051, 1052, 105n-1, 105n is in the range of 3e13 cm -3 to 5e16 cm -3 in the range of 1e14 cm -3 and 1e16 cm -3 In the range between.

[0069] Furthermore, in an embodiment, a corresponding donor concentration at each of the plurality of local maxima 1052, 105n-1, 105n except the first local maximum 1051 may be in a range from 2 times the donor concentration of the drift region 100 to 400 times the donor concentration of the drift region 100, wherein the donor concentration of the drift region 100 may be the mean donor concentration in the drift region 100. Furthermore, in an embodiment, a corresponding donor concentration at each of the plurality of local maxima 1052, 105n-1, 105n except the first local maximum 1051 may be in a range from 2 times the donor concentration of the drift region 100 to 125 times the donor concentration of the drift region 100, wherein the donor concentration of the drift region 100 may be the mean donor concentration in the drift region 100. Furthermore, in an embodiment, the corresponding donor concentration at each of the multiple local maxima 1052, 105n-1, 105n except the first local maximum 1051 may be in a range from 2 times the donor concentration of the drift region 100 to 100 times the donor concentration of the drift region 100, wherein the donor concentration of the drift region 100 may be the average donor concentration in the drift region 100.

[0070] In an embodiment, the corresponding donor concentration at each of the plurality of local maxima 1052, 105n-1, 105n except the first local maximum 1051 may be in the range from 5e13 cm -3 to 1.6e15 cm -3 In an embodiment, the corresponding donor concentration at each of the plurality of local maxima 1052, 105n-1, 105n except the first local maximum 1051 may be in the range from 5e13 cm -3 to 5e14 cm -3 In an embodiment, the corresponding donor concentration at each of the plurality of local maxima 1052, 105n-1, 105n except the first local maximum 1051 may be in the range from 5e13 cm -3 to 4e14 cm -3 in the range.

[0071] Furthermore, in an embodiment, the donor concentration at the plurality of local maxima 1052, 105n-1, 105n other than the first local maximum 1051 is constant or increases when going from one local maximum to an adjacent local maximum in a direction toward the backside surface 10-20.

[0072] According to another embodiment (not shown), the donor concentration at the nth local maximum 105n is equal to or greater than the donor concentration at the (n-1)th local maximum 105n-1 adjacent to the nth local maximum 105n, the (n-1)th local maximum 105n-1 being located closer to the backside surface 10-20 than the nth local maximum 105n.

[0073] Embodiments of the method for processing and / or producing a power semiconductor transistor correspond to the embodiments of the power semiconductor transistor described above with respect to the figures. Thus, for example, the features of the embodiments of the power semiconductor device described above with reference to the figures can be realized by implementing corresponding processing method steps. Embodiments of the method for processing a power semiconductor device can thus comprise: providing a semiconductor body 10; and forming corresponding structures arranged in / on the semiconductor body 10 by processes such as masked or unmasked implantation and / or semiconductor layer and / or oxide layer deposition.

[0074] In an embodiment, a method for processing a power semiconductor transistor 1 comprises: providing a semiconductor body 10 having a front side 10-1 and a back side 10-2, the back side 10-2 having a back side surface 10-20; and creating a field stop zone 105 inside the semiconductor body 10 by means of at least one proton implantation step and a subsequent annealing step, wherein the implantation is performed through the back side surface 10-20. In addition to protons, other n-doping species may be used, such as phosphorus, selenium, etc.

[0075] In accordance with Fig. 7A -B, the proton implantation is performed at an implantation angle β relative to a back surface normal N pointing from the back side 10-2 to the front side 10-1 (i.e. along the vertical direction Z), wherein the implantation angle β is in the range of 20° to 60°. In addition, the implantation may be performed at an implantation energy in the range of 100 keV to 800 keV, such as in the range of 100 keV to 600 keV. For example, in an embodiment, the implantation may be performed at an implantation energy in the range of 200 keV to 400 keV. The implantation dose may be selected so that the resulting integrated hydrogen-related donor profile amounts to at least 20% or at least 30%, such as at least 50%, of the penetration charge specific to the material of the semiconductor body 10. For example, the penetration charge for silicon is typically in the range of 0.5e12 cm -2 to 2.0e12 cm -2 in the range.

[0076] For example, including the above reference Figures 1 to 6 The field stop zone 105 of the described donor concentration profile may be formed by means of the at least one proton implantation step and a subsequent annealing step.

[0077] In an embodiment, the method comprises a plurality (eg at least two) of such proton implantation steps, which may differ from each other in that the implantation is performed from different azimuthal directions relative to the backside surface 10-20. Fig. 7A - The solid arrows in B may represent a first implantation step at an implantation angle β performed from a first azimuth angle, and the dotted arrows may represent a second implantation step performed at the same implantation angle β but from a second azimuth angle offset by 180° relative to the first azimuth angle.

[0078] For example, corresponding to Figure 4 The solid curve donor concentration profile in is the result of so-called quadruple-mode injection (i.e., injection from four different azimuthal angles). Figure 4 In each of the four implantation steps of the donor concentration profile illustrated in the solid curve in , the implantation angle relative to the surface normal of the back side 10-20 is β=34°. For comparison, Figure 4 The dotted curve in shows the donor concentration profile resulting from a single-mode implantation, ie an implantation carried out from only one azimuthal direction at an implantation angle of β = 7° relative to the surface normal at the back side 10-20°. Figure 4 The dashed and dotted lines in show that as a result of the quadruple mode injection at a relatively large injection angle of β = 34° as compared to the single mode process at a small injection angle of β = 7°, the (logarithmically expressed) "slopes" on both sides of the local maximum 1051 are quite shallow. At the same time, the corresponding injection depths (i.e. the positions of the corresponding peaks) are very similar.

[0079] It has been found that by means of one or more implants at relatively large implant angles β and possibly from several different azimuthal directions, as with standard implant conditions (cf. Figure 4 The “slope” of the proton peak (e.g. Figure 4 105 ) can be varied continuously in the range from 0% to -100%. For example, the vertical extension of the falling branch of the peak 1051 in the direction of the front side 10-1 can thus be increased so as to amount to at least 15% or even at least 25% of the penetration depth at the end of the range of the proton implantation. For example, such a relatively shallow reduction towards the front side 10-1 can result in a softer turn-off behavior and better short-circuit strength, as compared to a standard donor concentration profile in the field stop zone 105. For example, by means of a stepwise or continuous variation of the injection angle β and / or the azimuth angle, a stepwise or continuous variation of the injection angle β and / or the azimuth angle can be achieved. Figure 4 Continuous transition between the two exemplary donor concentration profiles illustrated in .

[0080] In an embodiment, one or more implantation steps as described above may be combined with further implantation steps performed at a smaller implantation angle or even at an implantation angle of β=0°. Figure 6 The plurality of further peaks 1052 , 105 n - 1 , 105 n exemplarily illustrated in FIG. 1 may be formed by implantation steps at smaller implantation angles.

[0081] Furthermore, in an embodiment, creating the field stop zone 105 may further comprise helium irradiation through the backside surface 10-20. In other words, the implantation described above may be combined with the helium irradiation. For example, the lateral homogeneity of the donor distribution within the field stop zone 105 may thereby be further improved. For example, such helium irradiation may be implemented as an implantation through the backside surface 10-20 at a suitable implantation angle (e.g. at 7°) and a suitable implantation energy (e.g. at 1.3 MeV) in order to induce vacancies in the field stop zone 105, wherein the local maximum of the concentration of vacancies may be roughly located at a first distance d1 from the backside surface 10-20, i.e. at or close to the position of the first local maximum 1051. For example, during the previously mentioned annealing step, the vacancies induced by the helium irradiation may be modified by hydrogen, thereby "closing" defects in the main hydrogen profile.

[0082] In addition, according to Fig. 7A In the embodiment of -B, during the at least one proton implantation step, a plurality of particles P may be present on the backside surface 10-20, such as, for example, resist residues, silicon particles, oxide particles, etc. Fig. 7A In FIG. 1-B, only one representative particle P is shown for illustration purposes. For example, the particle may have a maximum lateral extension E. The exemplary particle P may be modeled as a cylindrical particle having a diameter E and a radius E / 2. For example, the diameter E may amount to 10 μm. As explained above, in Fig. 7A In -B, two implantations are performed at the same implantation angle β=45° but from two different azimuth angles (corresponding to the solid arrow and the dotted arrow, respectively), which differ from each other by 180°. The first implantation (solid arrow) creates a first doped region inside the field stop zone 105, which is Fig. 7A -B is hatched from the upper left corner to the lower right corner. The second implant (dotted arrow) creates a second doped region inside the field stop zone 105. The second doped region is Fig. 7A -B is hatched from the lower left corner to the upper right corner. In addition, the checkered area inside the field stop area 105 marks the area where both the first and second injections have reached. In other words, the respective range ends of the first and second injections are at Fig. 7A -B overlaps in the checkerboard area.

[0083] from Fig. 7AIn comparison with B, it is evident that such an overlap region may or may not form beneath the particle P, depending on the implantation angle β and the penetration depth c (which in turn depends on the implantation energy). Figure 7B As shown in , if the penetration depth c is too small and / or if the injection angle β is too large, "holes" or relatively weakly doped regions may remain in the field stop zone 105. In order to ensure the presence of overlapping regions, i.e. to avoid such "holes", the injection parameters must be selected so that the lateral penetration f (i.e. the projection of the penetration depth c on the back surface 10-20) amounts to at least the radius E / 2. For example, in the case of particles having a diameter of E=10 µm, the lateral penetration f should amount to at least the radius E / 2 = 5 µm in order to ensure a laterally continuous field stop zone 105, as shown in . Fig. 7A In contrast, Figure 7B In an exemplary embodiment of the present invention, the lateral penetration f′ is smaller than the radius E / 2, resulting in a lateral interruption of the field stop zone 105 .

[0084] In an embodiment, the implantation angle β and / or the implantation energy are selected such that the resulting penetration depth c satisfies the equation:

[0085]

[0086] Thus, it can be ensured that the resulting field stop zone is not interrupted laterally.

[0087] Additionally or alternatively, the implantation angle β and / or the implantation energy may be selected such that the resulting penetration depth c satisfies the equation:

[0088]

[0089] This ensures that the end of the resulting range of the first donor concentration peak 1051, i.e., the first distance d1 (see Figure 1-5 ) is not too large. For example, the resulting first distance d1 may thus be in the range from 0.3 μm to 4 μm, as explained above.

[0090] In an embodiment, the method may further comprise an annealing step after the at least one proton implantation step, wherein the annealing step is performed at a temperature in the range from 360° C. to 440° C. or in the range from 380° C. to 420° C. Furthermore, the annealing step may be performed for a duration in the range from 30 minutes to 4 hours.

[0091] In addition, according to Figure 8In an embodiment of the invention, the method for processing a power semiconductor transistor 1 comprises the steps of structuring the back side 10-2 of the semiconductor body 10 so that a plurality of surface portions 10-21 are formed. The surface portions 10-21 differ from each other in that they have different orientations relative to a back side surface normal N. For example, the structuring of the back side 10-2 comprises an etching process, such as by means of potassium hydroxide (KOH). A field stop zone 105 inside the semiconductor body 10 may then be created by means of at least one proton implantation step carried out through the back side surface 10-20, wherein the proton beam b is deflected by the plurality of surface portions 10-21 during the proton implantation step. For example, such an implantation process may be used instead of or in combination with an implantation at a relatively large implantation angle in order to create a relatively shallow and / or laterally homogeneous field stop zone 105.

[0092] In accordance with Fig. 9 In the embodiment of the present invention, the amorphous surface can be used for the same purpose. For example, a plurality of small scattering centers 10-23 can be arranged on the back surface 10-20, wherein the scattering centers 10-23 can have a similar effect as the plurality of surface portions 10-21, as already described above with reference to Figure 8 Explained.

[0093] The embodiments described above include the recognition that relevant properties of a power semiconductor transistor, such as an IGBT, may be severely affected by the detailed routing of the donor concentration profile inside the field stop region of the device.

[0094] For example, it has been recognized that an improvement with respect to short circuit strength and / or with respect to thermal leakage current can be achieved by providing a laterally homogeneous donor concentration inside the field stop zone, wherein a first peak of a vertical donor concentration profile inside the field stop zone is located relatively shallowly with respect to the backside surface of the device. For example, by providing a lateral homogeneity amplification factor of a portion of transistors formed inside an IGBT as a result of such a laterally homogeneous donor concentration in the field stop zone , the short-circuit strength of the IGBT can be enhanced. One reason for this is that the homogeneity of the field stop zone can prevent unfavorable current filamentation. Therefore, it is possible to generally increase the amplification factor As a result, in the event of a short circuit, due to the homogeneous injection of holes, the unfavorable Umklapp effect of the electric field in front of the p-emitter of the IGBT can be avoided even at very high current densities.

[0095] In addition, by avoiding the amplification factor The local increase of can reduce the risk of transistor latch-up which may occur due to a locally enhanced hole density at the front side (possibly through dynamic avalanche enhancement).

[0096] Local enlargement amplification factor A significant increase of thermal leakage currents may also result, leading to detrimental hot spots. Thus, by providing a laterally homogeneous field stop zone, it is also possible to reduce thermal leakage currents. An improvement in the thermal short-circuit strength of a power semiconductor transistor may thus be achieved.

[0097] Furthermore, the detailed course of the vertical donor concentration profile may influence the change in current and voltage at the end of the switching process of the power semiconductor transistor. Thus, for example, the turn-off softness of the transistor may be improved by providing a relatively smooth decay of the shallowest field stop peak in the direction of the drift region. In other words, for example, a relatively large front width at half maximum of the shallowest peak may contribute to increasing the turn-off softness.

[0098] According to one or more embodiments, a power semiconductor transistor includes a field stop zone, wherein in a cross section along a vertical direction pointing from the back side to the front side, a donor concentration profile exhibits a first local maximum at a first distance from a back side surface of the device and a front width at half maximum value associated with the first local maximum value, wherein the front width at half maximum value totals at least 8% of the first distance.

[0099] Furthermore, according to one or more embodiments, it is proposed to create a field stop zone of a power semiconductor transistor, which may have some or all of the properties described above, by means of one or more proton implantation steps, wherein the implantation is performed at an implantation angle in the range from 20° to 60°, at an implantation energy in the range from 100keV to 1600keV, from 100keV to 800keV, from 100keV to 600keV, or from 200keV to 400keV, and with an implantation dose that produces an integral of the resulting donor concentration profile in the field stop zone of at least 20% of the penetration charge specific for the semiconductor body material. By means of such an implantation process at various angles, the donor concentration profile can be continuously varied, thereby providing a tool for tailoring the switching behavior of the transistor.

[0100] Furthermore, according to one or more embodiments, a method for processing a power semiconductor transistor comprises: structuring the back side of a semiconductor body so as to form a plurality of surface portions which differ from one another in that they have different orientations relative to a normal to the back side surface; and creating a field stop zone inside the semiconductor body by means of at least one proton implantation step carried out through the back side surface, wherein during the proton implantation step a proton beam is deflected by the plurality of surface portions.

[0101] Features of further embodiments are defined in the dependent claims. Features of further embodiments as well as features of the embodiments described above may be combined with each other to form additional embodiments, as long as the features are not explicitly described as alternatives to each other.

[0102] In the above, embodiments related to power semiconductor transistors (such as IGBTs or MOSFETs) and corresponding processing and production methods are explained. For example, these devices are based on silicon (Si). Accordingly, single-crystal semiconductor regions or layers (such as semiconductor body 10 and its regions / areas 100, 102, 103, 104, 105 and 107) can be single-crystal Si regions or Si layers. In other embodiments, polycrystalline or amorphous silicon can be used.

[0103] However, it should be understood that the semiconductor body 10 and its doped regions / areas may be composed of any semiconductor material suitable for use in fabricating semiconductor devices. Examples of such materials include, but are not limited to, elemental semiconductor materials such as silicon (Si) or germanium (Ge); Group IV compound semiconductor materials such as silicon carbide (SiC) or silicon germanium (SiGe); binary, ternary or quaternary III-V semiconductor materials such as gallium nitride (GaN), gallium arsenide (GaAs), gallium phosphide (GaP), indium phosphide (InP), indium gallium phosphide (InGaPa), aluminum gallium nitride (AlGaN), aluminum indium nitride (AlInN), indium gallium nitride (InGaN), aluminum gallium indium nitride (AlGaInN) or indium gallium arsenide phosphide (InGaAsP); and binary or ternary II-VI semiconductor materials such as cadmium telluride (CdTe) and mercury cadmium telluride (HgCdTe). The previously mentioned semiconductor materials are also referred to as "homojunction semiconductor materials". When two different semiconductor materials are combined, a heterojunction semiconductor material is formed. Examples of heterojunction semiconductor materials are not limited here to include aluminum gallium nitride (AlGaN)-aluminum gallium indium nitride (AlGaInN), indium gallium nitride (InGaN)-aluminum gallium indium nitride (AlGaInN), indium gallium nitride (InGaN)-gallium nitride (GaN), aluminum gallium nitride (AlGaN)-gallium nitride (GaN), indium gallium nitride (InGaN)-aluminum gallium nitride (AlGaN), silicon-silicon carbide (SixC1-x) and silicon-SiGe heterojunction semiconductor materials. For power semiconductor device applications, Si, SiC, GaAs and GaN materials are currently used.

[0104] Spatially relative terms such as "below," "below," "above," "lower," "above," "upper," and the like are used for ease of description to explain the positioning of one element relative to a second element. These terms are intended to cover different orientations of the respective devices in addition to orientations different from those depicted in the figures. In addition, terms such as "first," "second," and the like are also used to describe various elements, regions, sections, and the like, and are not intended to be limiting. The same terms refer to the same elements throughout the description.

[0105] As used herein, the terms “having,” “comprising,” “including,” “including,” “exhibiting,” and the like are open-ended terms that indicate the presence of stated elements or features, but do not preclude additional elements or features.

[0106] With the above range of variations and applications in mind, it should be understood that the present invention is not limited by the foregoing description, nor is it limited by the accompanying drawings. Instead, the present invention is limited only by the following claims and their legal equivalents.

Claims

1. A power semiconductor transistor (1), comprising a semiconductor body (10) having a front side (10-1) and a back side (10-2), the back side (10-2) having a back side surface (10-20), The semiconductor body (10) comprises a drift region (100) of a first conductivity type and a field stop region (105) of a first conductivity type, The field stop zone (105) is arranged between the drift zone (100) and the back side (10-2) and comprises, in a cross section along a vertical direction (Z) pointing from the back side (10-2) to the front side (10-1), a concentration profile of a donor of the first conductivity type, the concentration profile exhibiting: a first local maximum (1051) at a first distance (d1) from the back side surface (10-20), a front width (B) at half maximum value associated with the first local maximum (1051), and a back width (A) at half maximum value associated with the first local maximum (1051), Wherein the front width at half maximum (B) is less than the back width at half maximum (A) and amounts to at least 8% of the first distance (d1).

2. The power semiconductor transistor (1) according to claim 1, wherein the front width (B) at half maximum is less than half the back width (A) at half maximum.

3. The power semiconductor transistor (1) according to one of the preceding claims 1-2, wherein the integral of the donor concentration profile in the field stop zone (105) amounts to at least 20% of the penetration charge specific for the material of the semiconductor body (10).

4. The power semiconductor transistor (1) according to one of the preceding claims 1-2, wherein the first distance (d1) is equal to or smaller than 4 μm and / or equal to or larger than 0.3 μm.

5. The power semiconductor transistor (1) according to one of the preceding claims 1 to 2, wherein the front width (B) at half maximum is at least 0.225 μm and / or wherein the back width at half maximum (A) is at least 0.675 μm and / or Wherein a full width at half maximum (A+B) associated with the first local maximum (1051) is at least 0.9 μm.

6. The power semiconductor transistor (1) according to one of the preceding claims 1-2, wherein at least 80% of the donors in the field stop zone (105) are hydrogen-induced donors.

7. A power semiconductor transistor (1) according to one of the preceding claims 1-2, wherein the concentration profile is characterized in that, in the direction of the front side (10-1), at a distance of 250 nm from the position of the first local maximum (1051), the donor concentration is at least 35% of the donor concentration at the first local maximum (1051).

8. A power semiconductor transistor (1) according to one of the preceding claims 1-2, wherein the concentration profile is characterized in that, in the direction of the front side (10-1), at a distance of 375 nm from the position of the first local maximum (1051), the donor concentration is at least 5% of the donor concentration at the first local maximum (1051).

9. A power semiconductor transistor (1) according to one of the preceding claims 1-2, wherein the concentration profile is characterized in that, in the direction of the back side (10-2), at a distance of 500 nm from the position of the first local maximum (1051), the donor concentration is at least 60% of the donor concentration at the first local maximum (1051).

10. A power semiconductor transistor (1) according to one of the preceding claims 1-2, wherein the concentration profile is characterized in that, in the direction of the back side (10-2), at a distance of 1500 nm from the position of the first local maximum (1051), the donor concentration is at least 25% of the donor concentration at the first local maximum (1051).

11. A power semiconductor transistor (1) according to one of the preceding claims 1-2, wherein along at least 80% of the extension of the field stop zone (105) along a lateral direction (X, Y) perpendicular to the vertical direction (Z), the donor concentration at the first local maximum (1051) varies by less than 10%, and / or wherein in the active area of ​​the power semiconductor transistor (1), the donor concentration at the first local maximum (1051) varies by less than 10% along the lateral direction (X, Y) perpendicular to the vertical direction (Z).

12. A power semiconductor transistor (1) according to one of the preceding claims 1-2, wherein the semiconductor body (10) comprises a back emitter region (107) of a second conductivity type complementary to the first conductivity type, the back emitter region (107) being arranged at the back side (10-2), wherein a second pn junction (108) is formed at the transition between the back emitter region (107) and the field stop region (105).

13. The power semiconductor transistor (1) according to claim 12, wherein the current amplification factor α of the part of the transistor formed by the back emitter region (107), the field stop region (105), the drift region (100), and the body region (102) of at least one control unit (14) is pnp / npn The variation along the lateral directions (X, Y) perpendicular to the vertical direction (Z) is less than 10%.

14. A power semiconductor transistor (1) according to one of the preceding claims 1 to 2, wherein the field stop zone (105) comprises a plurality of local maxima (1051, 1052, 105n-1, 105n), a first local maximum (1051) being located closer to the back side surface (10-20) than each of the other local maxima (1052, 105n-1, 105n) of the plurality of local maxima, and an nth local maximum (105n) of the plurality of local maxima (1051, 1052, 105n-1, 105n) being located further away from the back side surface (10-20) than each of the other local maxima (1051, 1052, 105n-1) of the plurality of local maxima, wherein a donor concentration at the first local maximum (1051) is higher than a donor concentration at each of the other local maxima (1052, 105n-1, 105n) of the plurality of local maxima.

15. The power semiconductor transistor (1) according to claim 14, wherein the donor concentration at the first local maximum (1051) is at least 1e15 cm -3 .

16. The power semiconductor transistor (1) according to claim 14, wherein the donor concentration at the nth local maximum (105n) is equal to or less than 2e15 cm -3 And / or wherein the donor concentration at the nth local maximum (105n) is equal to or less than 500 times the donor concentration in the drift region (100).

17. The power semiconductor transistor (1) according to claim 14, wherein the corresponding donor concentration at each of the plurality of local maxima (1051, 1052, 105n-1, 105n) is in the range of 3e13 cm -3 to 5e16cm -3 in the range of.

18. The power semiconductor transistor (1) according to claim 14, wherein: The respective donor concentration at each of the plurality of local maxima (1052, 105n-1, 105n) other than the first local maximum (1051) is in the range from 2 times the donor concentration of the drift region (100) to 400 times the donor concentration of the drift region (100), and / or wherein, The corresponding donor concentration at each of the plurality of local maxima (1052, 105n-1, 105n) other than the first local maximum (1051) is in the range of 5e13 cm -3 to 1.6e15cm -3 in the range.

19. A power semiconductor transistor (1) according to claim 14, wherein the donor concentration at multiple local maxima (1052, 105n-1, 105n) other than the first local maximum (1051) is constant or increases when going from one local maximum to an adjacent local maximum in the direction towards the back surface (10-20).

20. The power semiconductor transistor (1) according to claim 14, wherein the donor concentration at the nth local maximum (105n) is equal to or greater than the donor concentration at the (n-1)th local maximum (105n-1) adjacent to the nth local maximum (105n), the (n-1)th local maximum (105n-1) being located closer to the back surface (10-20) than the nth local maximum (105n).

21. A method for processing a power semiconductor transistor (1), comprising: - providing a semiconductor body (10) having a front side (10-1) and a back side (10-2), the back side (10-2) having a back side surface (10-20); as well as - creating a field stop zone (105) inside the semiconductor body (10) by means of at least one proton implantation step, wherein the implantation is carried out through the back side surface (10-20) as follows: - at an implantation angle (β) relative to the backside surface normal (N), the implantation angle (β) being in the range from 20° to 60°, - with an implantation energy in the range from 100 keV to 800 keV, and - using an implantation dose that produces an integral of the resulting donor concentration profile in the field stop zone (105) of at least 20% of the penetration charge specific for the material of the semiconductor body (10).

22. A method according to claim 21, comprising a plurality of such proton implantation steps which differ from each other in that the implantation is carried out from different azimuthal directions relative to the backside surface (10-20).

23. The method according to claim 21 or 22, wherein a plurality of particles (P) are present on the backside surface (10-20), the particles (P) having a maximum lateral extension (E), and wherein the implantation angle (β) and / or the implantation energy are selected such that the resulting penetration depth (c) satisfies the equation:

24. The method of claim 23, wherein the implantation angle (β) and / or the implantation energy are selected such that the resulting penetration depth (c) satisfies the equation:

25. The method according to one of claims 21 to 22, wherein creating the field stop zone (105) further comprises helium irradiation through the backside surface (10-20).

26. The method according to one of claims 21 to 22, further comprising an annealing step after the at least one proton implantation step, wherein the annealing step is performed at a temperature in the range from 360°C to 440°C for a duration in the range from 30 minutes to 4 hours.

27. A method for processing a power semiconductor transistor (1), comprising: - providing a semiconductor body (10) having a front side (10-1) and a back side (10-2), the back side having a surface (10-20) defined by a back side surface normal (N); - structuring the back side (10-2) so that a plurality of surface portions (10-21) are formed which differ from one another in that they have different orientations relative to the back side surface normal (N); as well as - Creating a field stop zone (105) inside the semiconductor body (10) by means of at least one proton implantation step performed through the backside surface (10-20), wherein during the proton implantation step the proton beam (b) is deflected by the plurality of surface portions (10-21).

28. Method for processing a power semiconductor transistor (1) according to claim 27, wherein the field stop zone (105) as defined in one of claims 1 to 20 is formed by means of the at least one proton implantation step.

29. A method for producing a power semiconductor transistor (1), wherein the power semiconductor transistor (1) is a power semiconductor transistor (1) according to one of claims 1 to 20, the method comprising the method steps according to at least one of claims 21 to 28.

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