Power diodes

Abstract

The present invention discloses a power diode. A power diode includes a semiconductor body, which is coupled to an anode metallization and a cathode metallization of the power diode. The semiconductor body has a drift region of a first conductivity type and an anode region of a second conductivity type. The anode region includes: a contact region arranged to contact the anode metallization; a field stop region arranged below the contact region; and a body region arranged below the field stop region and above the drift region. The electrically activated dopant concentration of the anode region exhibits a distribution diagram, which along the vertical direction, according to the distribution diagram: a first maximum value exists in the contact region; a second maximum value exists in the field stop region; and the dopant concentration decreases continuously from the first maximum value to a local minimum value, and increases continuously from the local minimum value to the second maximum value.

Description

Technical Field

[0001] The present description relates to embodiments of power diodes and to embodiments of methods for processing power diodes. In particular, the present description relates to embodiments of power diodes having a specific semiconductor anode structure and to corresponding processing methods. 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 devices. For example, insulated gate bipolar transistors (IGBTs), metal oxide semiconductor field effect transistors (MOSFETs), and power diodes, to name a few, have been used in a variety of applications including but not limited to switches in power supplies and power converters.

[0003] A power diode generally includes a semiconductor body configured to conduct a load current along a load current path between two load terminals of the diode if a voltage in the forward direction is applied between the terminals. If a voltage in the reverse direction is applied, the power diode generally exhibits a blocking state and the flow of the load current is inhibited.

[0004] The load terminals of a power diode are generally referred to as an anode terminal and a cathode terminal, and the transition of the power diode from a conducting state to a blocking state may follow a reverse recovery behavior of the power diode.

[0005] In certain applications, it may be desirable to avoid too high a charge carrier concentration near the anode terminal so that high current peaks during reverse recovery can be avoided. Summary of the invention

[0006] According to an embodiment, a power diode comprises a semiconductor body coupled to an anode metallization and a cathode metallization of the power diode. The semiconductor body has a drift region of a first conductivity type and an anode region of a second conductivity type. The anode region comprises: a contact region arranged to be in contact with the anode metallization; a field stop region arranged below the contact region; and a body region arranged below the field stop region and above the drift region. The electrically activated dopant concentration of the anode region exhibits a profile, which, along a vertical direction, according to the profile: a first maximum value exists in the contact region; a second maximum value exists in the field stop region; and the dopant concentration decreases continuously from the first maximum value to a local minimum value, and increases continuously from the local minimum value to the second maximum value.

[0007] According to another embodiment, a method for processing a power diode includes: providing a semiconductor body having a drift region of a first conductivity type; creating an anode region of a second conductivity type in the semiconductor body; providing an electrically activated dopant concentration in the anode region, the dopant concentration exhibiting a distribution diagram along a vertical direction, according to the distribution diagram: a first maximum value exists in a contact region of the anode region; a second maximum value exists in a field stop region of the anode region; and the dopant concentration continuously decreases from the first maximum value to a local minimum value, and continuously increases from the local minimum value to the second maximum value.

[0008] Those skilled in the art will recognize additional features and advantages upon reading the following detailed description, and upon viewing the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] The parts in the drawings are not necessarily to scale, instead emphasis is placed on illustrating the principles of the present invention. In addition, in the drawings, the same reference numerals designate corresponding parts. In the drawings:

[0010] Figure 1 schematically and exemplarily illustrates a section of a vertical cross-section of a power diode according to one or more embodiments; and

[0011] Figure 2 schematically and exemplarily illustrates the course of charge carrier concentration present in the semiconductor body of a power diode; and

[0012] Figure 3 schematically and exemplarily illustrates the course of charge carrier concentration present in a semiconductor body of a power diode according to one or more embodiments;

[0013] Figure 4 schematically and exemplarily illustrates the paths of electric fields and charge carrier concentrations present in a semiconductor body of a power diode according to one or more embodiments; and

[0014] Figure 5 Aspects of a method of processing a power diode according to one or more embodiments are schematically and exemplarily illustrated. DETAILED DESCRIPTION

[0015] 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.

[0016] In this regard, directional terms, such as "top", "bottom", "below", "front", "rear", "back", "leading", "trailing", "above", etc., may be used with reference to the orientation of the figure being described. Because the various parts of the embodiments can be positioned in many 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.

[0017] 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 by way of explanation and is not meant to be a limitation of the invention. For example, features illustrated or described as part of one embodiment may be used on other embodiments or used in conjunction with other embodiments to produce yet other embodiments. It is intended that the 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 designated by the same reference numerals in different drawings.

[0018] 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, the surface of a semiconductor wafer or die or chip. 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.

[0019] 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. parallel to the normal direction of the surface of the semiconductor wafer / chip / die. 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. The extension direction Z is also referred to herein as the "vertical direction Z".

[0020] In this specification, n-doping is referred to as the “first conductivity type” and p-doping 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.

[0021] In the context of this specification, the terms "in ohmic contact", "in electrical contact", "in ohmic connection" 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 of a semiconductor device and a part or component thereof. Further, in the context of this specification, the term "in contact" 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.

[0022] Additionally, in the context of this specification, if not stated otherwise, the term "electrically insulated" is used in its generally reasonably understood context, and is thus intended to describe two or more components that 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 nevertheless be coupled to each other, such as mechanically and / or capacitively and / or inductively. To give an example, two electrodes of a capacitor may be electrically insulated from each other and simultaneously mechanically and capacitively coupled to each other, such as by means of an insulating portion (e.g., a dielectric).

[0023] The specific embodiments described in this specification relate to power semiconductor devices that can be used in power converters or power supplies, but are not limited thereto. Thus, in an embodiment, such a device can be configured to carry a load current, which will be fed to a load and / or provided by a power source accordingly. For example, a power semiconductor device can include one or more active power semiconductor units, such as a monolithically integrated diode unit, and / or a monolithically integrated transistor unit, and / or a monolithically integrated IGBT unit, and / or a monolithically integrated RC-IGBT unit, and / or a monolithically integrated MOS gate-controlled diode (MGD) unit, and / or a monolithically integrated MOSFET unit and / or its derivatives. Such a diode unit and / or such a transistor unit can be integrated in a power semiconductor module. A plurality of such units can constitute a unit field, which is arranged together with the active area of ​​the power semiconductor device.

[0024] The description further relates to a power semiconductor device in the form of a power diode.

[0025] The term "power diode" as used in this specification is intended to describe a semiconductor device on a single chip having high voltage blocking and / or high current carrying capabilities. In other words, such a power diode is 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, and the high voltages being typically above 15V, more typically 100V and above, such as up to at least 500V.

[0026] For example, the power diodes described below may be semiconductor devices configured to be employed as power components in low, medium and / or high voltage applications. For example, the term "power diode" as used in this specification does not refer to logic semiconductor devices used, for example, to store data, calculate data, and / or other types of semiconductor-based data processing.

[0027] As is known, a power diode may include a semiconductor body in which an anode region and a drift region are provided. Typically, the anode region is coupled to a first load terminal, such as an anode port, and the drift region is coupled to a second load terminal, such as a cathode port of the power diode. Typically, the drift region has a first conductivity type and the anode region has a second conductivity type. The drift region is typically configured according to the specified blocking voltage of the power diode. The anode region should provide a good ohmic contact with the first load terminal on one side and, on the other side, provide a suitable emitter efficiency. In this regard, Figure 2 The course of dopant concentrations that may be present in a power diode is illustrated by way of example, wherein the dashed line indicates the concentration of dopants of a first conductivity type and the solid line indicates the concentration of dopants of a second conductivity type. For example, in order to provide a good contact, the anode region may have a concentration of dopants of the second conductivity type that exhibits a peak 70 near a first load terminal, wherein the first load terminal may dock with the anode region at position Z=0. After the peak 70, the dopant concentration decreases rapidly. For example, such a peak 70 may be provided by subjecting the semiconductor body to an implantation. In the main part of the anode region, the dopant concentration remains substantially below the value at the peak 70. Further along the vertical direction Z, the anode region docks with the drift region, thereby forming a pn junction, for example approximately therein. Figure 2 Where the dashed line intersects the solid line.

[0028] The course of the dopant concentration in the anode region near the load terminal has a significant influence on the characteristics of the power diode, for example regarding the static and / or dynamic blocking capability, on-state losses and the emitter efficiency of the anode region, and therefore on the dynamic behavior of the power diode, for example its reverse recovery behavior.

[0029] Figure 1 A section of a vertical cross section of a power diode 1 according to one or more embodiments is schematically and exemplarily illustrated.

[0030] The power diode 1 comprises a semiconductor body 10 coupled to an anode metallization 11 and a cathode metallization 12 of the power diode 1. The anode metallization 11 may be part of a first load terminal and the cathode metallization 12 may be part of a second load terminal of the power diode 1. The power diode 1 may exhibit a vertical configuration according to which the anode metallization 11 is arranged at a front side of the power diode 1 and according to which the cathode metallization 12 is arranged at a back side of the power diode 1.

[0031] During the on-state, the power diode 1 may be configured to conduct a load current between the anode metallization 11 and the cathode metallization 12, e.g., along the vertical direction Z. The on-state may be achieved by applying a voltage between the anode metallization 11 and the cathode metallization 12, wherein the potential present at the anode metallization 11 is greater than the potential present at the cathode metallization 12. During the off-state / blocking state, the power diode 1 may be configured to block a blocking voltage applied between the anode metallization 11 and the cathode metallization 12, wherein the potential present at the cathode metallization 12 is greater than the potential present at the anode metallization 11.

[0032] The power diode 1 may be configured for a load current of at least 1A, at least 5A or even greater than 10A.

[0033] The semiconductor body 10 has a drift region 100 of a first conductivity type and an anode region 101 of a second conductivity type. The drift region 100, for example its total extension along the vertical direction Z and / or its dopant concentration can be configured for a blocking voltage of at least 300V, at least 500V, or for a blocking voltage even greater than 700V.

[0034] In an embodiment, the total extension of the anode region 101 in the vertical direction Z is in the range of 500 nm to 15000 nm, in the range of 1000 nm to 10000 nm, or in the range of 3000 nm to 6000 nm.

[0035] Furthermore, the total extension of the drift zone 100 in the vertical direction Z (eg the distance between the pn junction 1010 and the cathode metallization 12 along the vertical direction Z) may be in the range of 10 μm to 1000 μm, in the range of 30 μm to 500 μm, or in the range of 50 μm to 200 μm.

[0036] The power diode 1 may be implemented in a wafer having a thickness in the vertical direction Z in the range of 10 μm to 1000 μm, in the range of 30 μm to 750 μm or in the range of 50 μm to 650 μm.

[0037] In an embodiment, the total extension of the anode region 101 in the vertical direction Z amounts to no more than 20% of the total extension of the drift region 100 (which may include the cathode region 102 , see next paragraph) in the vertical direction Z, or amounts to no more than 10% thereof.

[0038] The drift region 100 may include a dopant of a first conductivity type. For example, the drift region 100 is n-doped. The drift region 100 may exhibit a first conductivity type. 12 cm -3 To 5*10 14 cm -3 For example, as indicated above, the dopant concentration of the drift zone 100 and its total extension along the vertical direction Z are selected depending on the rated voltage (eg maximum blocking voltage) for which the power diode 1 should be designed.

[0039] For example, the semiconductor body 10 further comprises a cathode region 102, wherein the drift region 100 can be coupled to the cathode metallization 12 by means of the cathode region 102. For example, the cathode region 102 is arranged in contact with the cathode metallization 12 and can exhibit a 5*10 19 cm -3 To 5*10 20 cm -3 In an embodiment, the cathode region 102 may act as a field stop region of the first conductivity type. The cathode region 102 may also be understood to form a lower portion of the drift region 100, and it exhibits a significantly greater dopant concentration than the remainder of the drift region 100. Therefore, in an embodiment, the dopant concentration of the drift region 100 may vary along the vertical direction Z. In the lower portion, which may form up to 20% of the total extension of the drift region 100 in the vertical direction Z, the maximum concentration of the dopant of the first conductivity type may exceed the concentration of the dopant of the first conductivity type in at least a portion of the remaining region of the drift region 100 by at least 10 times. Again, it should be understood that the lower portion of the drift region 100 may be formed by means of the cathode region 102.

[0040] The anode region 101 may include a dopant of the second conductivity type. For example, the anode region 101 is p-doped.

[0041] In an embodiment, the power diode 1 may thus exhibit a structure consisting of an anode region 101 (p-doped), a drift region 100 (I (intrinsic) or n-doped). - doped) and the cathode region 102 (n-doped) to form a PIN or PN - N structure.

[0042] The anode region 101 may include: a contact region 1011 arranged to be in contact with the anode metallization 11; a field stop region 1012 arranged below the contact region 1011; and a body region 1013 arranged below the field stop region 1012 and above the drift region 100. According to the foregoing, the term “below” indicates that the field stop region 1012 is arranged at a deeper level with respect to the vertical direction Z than the contact region 1011. Furthermore, the body region 1013 is arranged at a deeper level with respect to the vertical direction Z than the field stop region 1012.

[0043] For example, the field stop region 1012 is sandwiched between the contact region 1011 and the body region 1013. The contact region 1011 may form an upper termination of the semiconductor body 10 and, for example, exhibit a surface 111. The surface 111 may abut against the anode metallization 11, for example directly or with its diffusion barrier section (not shown separately). The body region 1013 may abut against the drift region 100, wherein the transition between the body region 1013 and the drift region 100 may form a pn junction (see Figure 1 , 3 and reference number 1010 in 4).

[0044] As will be explained in more detail below, the anode region 101 may be provided by creating a larger p-well within the semiconductor body 10, for example by performing a diffusion process step. For example, such a p-well may form a body region 1013. Thereafter, a first implant process step may be performed to form a field stop region 1012, and a second implant process step may be performed to form the contact region 1011. The implantation may be followed by a temperature annealing process step in order to provide an electrically activated dopant concentration also within the contact region 1011 and the field stop region 1012.

[0045] In an embodiment, the total extension of the contact region 1011 in the vertical direction Z is in the range of 10 nm to 700 nm, in the range of 30 nm to 500 nm, or in the range of 50 nm to 400 nm.

[0046] Furthermore, the total extension of the field stop zone 1012 in the vertical direction Z may be in the range of 50 nm to 2000 nm, in the range of 100 nm to 1500 nm or in the range of 300 nm to 1000 nm.

[0047] Furthermore, the total extension of the body region 1013 in the vertical direction Z may be in the range of 300 nm to 15000 nm, in the range of 500 nm to 10000 nm, or in the range of 1000 nm to 5000 nm.

[0048] Now refer to Figure 3, which exemplarily and schematically illustrates the existence of Figure 1 The dopant concentration (concentration N A (p-type dopant) and the concentration N D (n-type dopant)), in an embodiment, the electrically activated dopant concentration of the anode region 101 exhibits a distribution profile along the vertical direction Z, according to which:

[0049] (i) the first maximum value 31 exists in the contact area 1011;

[0050] (ii) the second maximum value 32 exists within the field stop region 1012; and

[0051] (iii) The dopant concentration decreases continuously from the first maximum value 31 to a local minimum value 33 , and increases continuously from the local minimum value 33 to the second maximum value 32 .

[0052] In an embodiment, the transition between the contact area 1011 and the field stop diagram 1012 occurs at the local minimum 33 .

[0053] In this specification, the term "electrically activated dopant concentration" refers to a dopant concentration that provides and / or increases electrical conductivity. For example, the term "electrically activated dopant concentration" does not refer to a damage concentration. In an embodiment, neither the contact region 1011 nor the field stop region 1012 is damaged, or each does not include a damaged region (where of course it is almost impossible to completely avoid the smallest crystal defects, such as vacancies, especially very close to the surface 111). On the contrary, in an embodiment, at least in the contact region 1011 and the field stop region 1012, the conductivity, such as the thin layer conductivity, is substantially proportional to the electrically activated dopant concentration. The proportionality factor can be defined as the temperature-dependent carrier mobility. The carrier mobility is affected by the concentration of doping atoms (acceptors and donors) present in the semiconductor region because the doping atoms cause Coulomb scattering of mobile carriers, that is, the higher the doping concentration, the lower the mobility of mobile carriers. The carrier mobility in a region that does not provide or only provides marginal crystal defects as stated above can be defined as bulk mobility, which depends on the concentration of donors and acceptors in the region. Thus, it should be understood that starting from the position of the first maximum 31 and continuing along the vertical direction Z, for example until the pn junction 1010, in an embodiment, the charge carrier mobility and / or lifetime is not disturbed by damaged regions and the like. For example, the carrier mobility in a region starting at the position of the first maximum 31 and continuing along the vertical direction Z, for example until the pn junction 1010, in an embodiment, can differ from the bulk mobility by a maximum of 20%. For example, the first maximum 31 is the first maximum of the electrically activated dopant concentration occurring along the vertical direction Z (starting at Z=0, i.e. at the surface 111), and the second maximum 32 is the second maximum of the electrically activated dopant concentration occurring along the vertical direction Z. Between the first maximum 31 and the second maximum 32, the electrically activated dopant concentration does not drop below the local minimum 33. Instead, the dopant concentration decreases continuously from the first maximum value 31 to the local minimum value and increases continuously from the local minimum value 33 to the second maximum value 32. Furthermore, in an embodiment, between the second maximum value 32 and the inflection point 34 (explained in more detail below), the electrically activated dopant concentration does not drop below the value present at the inflection point 34, but decreases continuously from the second maximum value to the inflection point.

[0054] In an embodiment, the anode region 101 exhibits five equal parts along the vertical direction Z, wherein each of the first maximum 31 and the second maximum 32 is positioned within the uppermost equal part, i.e. within the upper 20% of the total extension of the anode region 101 along the vertical direction. For example, each of the first maximum 31 and the second maximum 32 is positioned within a distance of 2000 nm from the anode metallization 11, the distance being measured along the vertical direction Z from the transition between the contact area 1011 and the anode metallization 11, e.g. measured from the surface 111 along the vertical direction Z. The distance may be less than 2000 nm, e.g. less than 1000 nm or even less than 750 nm.

[0055] Furthermore, the first maximum 31 may occur within a distance (which is along the vertical direction) of less than 300 nm, less than 200 nm or even less than 100 nm. According to an embodiment, the first maximum 31 may occur in the contact region 1011 at the transition between the contact region 1011 and the anode metallization 11 .

[0056] The distance between the first maximum 31 and the second maximum along the vertical direction Z may be in the range of 100 nm to 2000 nm, in the range of 200 nm to 1000 nm, or in the range of 300 nm to 750 nm.

[0057] In an embodiment, the second maximum value 32 is in the range of 70% to 130% of the first maximum value 31. Thus, it should be understood that the second maximum value 32 may be greater than the first maximum value 31. The second maximum value 32 may therefore be the absolute maximum value of the dopant concentration of the anode region 101. The electrically activated dopant concentration at each of the first maximum value 31 and the second maximum value 32 may be greater than 10 17 cm -3 The local minimum 33 may be in the range of 10% to 50% of the first maximum 31. Furthermore, within the body region 1013, for example, the maximum electrically activated dopant concentration at each position of the body region 1013 along the vertical direction Z may be in the range of 1 / 50 to 1 / 5 of the electrically activated dopant concentration present at any one of the first maximum 31 and the second maximum 32. Of course, at a position closer to the field stop region 1012, the electrically activated dopant concentration of the body region 1013 may be greater than the electrically activated dopant concentration at a position closer to the drift region 100.

[0058] Further along the vertical direction Z, according to the profile, the electrically activated dopant concentration can decrease continuously from the second maximum value 32 to an inflection point 34, at which the rate of change (hereinafter referred to as gradient) of the dopant concentration with respect to the vertical direction Z exhibits a local maximum. The dopant concentration can then decrease continuously from the inflection point 34 throughout the body region 1013 until the transition formed between the body region 1013 and the drift region 100, i.e. the pn junction 1010.

[0059] The first concentration gradient existing above the inflection point 34 may be greater than the second concentration gradient existing below the inflection point 34, such as Figure 3 , for example, at least three times thereof. In an embodiment, the mean gradient of the dopant concentration between the second maximum value 32 and the inflection point 34 along the vertical direction Z, i.e., the difference between the dopant concentrations at the second maximum value 32 and the inflection point 34 divided by the distance between the second maximum value 32 and the inflection point 34 along the vertical direction Z may be the first concentration gradient, and is therefore greater than the second concentration gradient present below the inflection point 34. The second concentration gradient may be a dopant concentration gradient between the inflection point 34 and the concentration of the second conductivity type dopant present at the pn junction 1010 along the vertical direction Z, i.e., the difference between the dopant concentration at the inflection point 34 and the concentration of the second conductivity type dopant present at the pn junction 1010 divided by the distance between the inflection point 34 and the position of the pn junction 1010 along the vertical direction Z. The first gradient may be at least 3 times, at least 5 times, or at least 10 times the second gradient.

[0060] The electrically active dopant concentration present at the inflection point can be 10 15 cm -3 By May 10 16 cm -3 According to an embodiment, the electrically activated dopant concentration present at the inflection point 34 may be lower than the doping of the local minimum 33 .

[0061] Figure 4 Corresponds to Figure 3 , and additionally illustrates an exemplary course of the electric field E (dashed line) during the static blocking state of the power diode 1 . In an embodiment, the electric field stops below the inflection point 34 .

[0062] Thus, the anode region 101 can be configured so as to ensure that the electric field does not extend until the second maximum 32 during the static blocking state, but stops appropriately before (i.e. below) it, for example below the inflection point 34. For example, the distance (along the vertical direction) between the electric field peak during the blocking state of the power diode 1 and the second maximum 32 amounts to at least 500 nm. For example, during forward conduction of the power diode 1, the drift region 100 is filled with more mobile electrons and holes compared to the background doping concentration, thereby providing a low on-state voltage of the power diode 1. Upon commutation of the power diode 1, i.e. when changing from the forward conduction state ("on state") to the blocking state, excess charge must be moved out of the drift region 100. The stored mobile holes are removed via the anode region 101 and the anode metallization 11. The positive charge of the mobile holes during commutation may result in a temporarily further penetration of the electric field in the direction towards the anode metallization 11 ( Figure 4 ). The electric field can be stopped before reaching the second maximum value 32 or before reaching the first maximum value 31. The risk of accidental breakdown can thus be reduced. In addition, based on the proposed structure, according to which the two maxima 31 and 32 can act redundantly with respect to avoiding field penetration towards the anode metallization 11, the production method can be designed to be more robust.

[0063] Also proposed herein is a method for processing a power diode, for example a method for manufacturing a power diode according to one of the embodiments presented above. Figure 5 A flow chart of an exemplary embodiment of a method 2 for processing a power diode is schematically illustrated in FIG. Figure 5 .

[0064] In a first step 20, a semiconductor body is provided, which has a drift region of a first conductivity type. Then, in a step 21, an anode region of a second conductivity type is created in the semiconductor body. Subsequently, in a step 22, the electrically activated dopant concentration in the anode region is provided with a profile according to which: a first maximum value is present in a contact region of the anode region; a second maximum value is present in a field stop region of the anode region; and the dopant concentration decreases continuously from the first maximum value to a local minimum value and increases continuously from the local minimum value to the second maximum value.

[0065] Already mentioned above Figure 1 as well as Figure 3 and 4The features of the explained exemplary embodiment of the power diode 1 are equally applicable to the exemplary embodiment of the method 2. Therefore, repeating these optional features again is avoided. However, for reasons of clarity, the reference signs adopted above for explaining the exemplary embodiment of the power diode 1 will now be used likewise for explaining the exemplary embodiment of the method 2. However, it should be understood that the method presented herein is not necessarily limited to providing the exemplary embodiment of the method 2 already described above with respect to Figure 1 as well as Figure 3 and 4 The explained embodiment of the power diode 1 . Nevertheless, the features of the alternative embodiment of the method 2 described below are equally applicable to the embodiment of the power diode 1 described above.

[0066] For example, providing (see step 22) an electrically activated dopant concentration in the anode region 101 comprises carrying out a diffusion process step in order to provide a base dopant concentration with respect to the anode region 101, for example by using boron as dopant material. This may exclude an implantation step followed by a diffusion process step for introducing a dopant of the second conductivity type into the semiconductor body 10. For example, a larger p-well may thereby be formed, which substantially exhibits the dimensions of the anode region 101 and provides an electrically activated base dopant concentration exhibiting the same as in Figure 3 and 4 Before creating the field stop region 1012 and the contact region 1011 , the path of the base dopant concentration will continue to extend toward the vertical direction Z according to the path existing in the body region 1013 .

[0067] Furthermore, providing (see step 22) an electrically activated dopant concentration in the anode region 101 may comprise carrying out a first implantation process step with a first implantation energy for producing the second maximum value 32, and carrying out a second implantation process step with a second implantation energy for producing the first maximum value 31. As already explained above, the second maximum value 32 may be greater than the first maximum value 31.

[0068] For example, the second implantation treatment step is carried out with an implantation energy of less than 30 keV or less than 20 keV. For example, the second implantation treatment step is carried out so that the mean distance of the implanted ions that have been penetrated by the implanted ions measured from the surface 111 of the provided semiconductor body 10 amounts to less than 100 nm. The mean distance can be even shorter, for example shorter than 80 nm, shorter than 70 nm or even shorter than 50 nm. Possible measures for adjusting the mean distance are not only the implantation energy applied during the second implantation treatment step, but also the thickness of a thin layer at the surface 111 that can be formed during the preparation of a single ion implantation treatment step, for example an oxide layer (not shown).

[0069] For example, the second implantation process step is performed with an implantation energy that is less than the implantation energy applied during the first implantation. The implantation doses for each of the first implantation and the second implantation may, for example, be substantially the same as each other, for example, the doses may each total 4*10 12 cm -2 In another embodiment, the implantation dose applied during the first implantation may be greater than the dose applied during the second implantation, for example in order to provide the second maximum value 32 having a greater value than the value of the first maximum value 31. However, it should be understood that in another embodiment, the second maximum value 32 may also be provided with a smaller value than the value of the first maximum value 31.

[0070] During each of the first and second implants, boron may be implanted.

[0071] Providing (see step 22) the electrically activated dopant concentration in the anode region 101 may further comprise performing a high temperature annealing step in order to substantially completely repair defects caused by the first implantation step or respectively by the first and second implantation steps, thereby providing the electrically activated dopant concentration in the contact region 1011 and the field stop region 1012. According to an embodiment, the high temperature annealing step may comprise heating the semiconductor body 10 to a temperature of at least 800° C., 900° C. or 1000° C. for at least one second, one minute, or several minutes.

[0072] As already explained above, in an embodiment, none of the contact region 1011 and the field stop region 1012 is damaged. For example, a damaging implant can be performed by implanting particles into the semiconductor body and subsequently avoiding the implementation of a high temperature annealing process step, or correspondingly subsequently implementing only a short and / or low temperature annealing process step, according to which the defects caused by the implantation are not completely repaired. According to an exemplary embodiment of method 2, a temperature annealing process step is performed in order to substantially completely repair the defects caused by the implantation(s).

[0073] In an embodiment, at least one of the first implantation process step and the second implantation process step is performed by using an energy filter.The use of energy filters for obtaining certain dopant concentration profiles is likewise known to the skilled person.

[0074] Therefore, the profile of the electrically activated dopant concentration in the body region 1013 may be a diffusion profile, and the profile of the electrically activated dopant concentration in each of the contact region 1011 and the field stop region 1012 may be an implantation profile. The dose for each of the contact region 1011 and the field stop region 1012 may be less than 2*10 13 cm -2 , can be less than 1*1013 cm -2 Or it can be less than 5*10 12 cm -2 , and the dose to the main area 1013 can be less than 1*10 13 cm -2 , can be less than 6*10 12 cm -2 Or it can be less than 3*10 12 cm -2 .

[0075] In another embodiment, creating a profile of electrically activated dopant concentration within at least one of the contact region 1011 and the field stop region 1012 may involve performing an epitaxial processing step.

[0076] In the above, embodiments of power diodes and corresponding processing methods are explained. For example, these power diodes are based on silicon (Si). Accordingly, single-crystalline semiconductor regions or layers, such as semiconductor body 10 and its regions / regions, such as regions 100, 101, 102, etc., can be single-crystalline Si regions or Si layers. In other embodiments, polycrystalline or amorphous silicon can be used.

[0077] However, it should be understood that the semiconductor body 10 and its regions / areas can be made of any semiconductor material suitable for manufacturing power diodes. Examples of such materials include, but are not limited to, the following: 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 gallium indium arsenide phosphide (InGaAsP); and binary or ternary II-VI semiconductor materials, such as cadmium telluride (CdTe) and mercury cadmium telluride (HgCdTe), to name a few. 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 include, but are not limited to, the following: 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.

[0078] Spatially relative terms such as "below," "below," "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 encompass different orientations of the corresponding devices in addition to those different orientations depicted in the figures. Further, terms such as "first," "second," and the like are also used to describe various elements, regions, sections, and the like, and are also not intended to be limiting. Throughout this description, the same terms refer to the same elements.

[0079] As used herein, the terms “having,” “containing,” “including,” “comprising,” “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.

[0080] 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 by the accompanying drawings. Instead, the present invention is limited only by the following claims and their legal equivalents.

Claims

1. A power diode (1) comprising a semiconductor body (10) coupled to an anode metallization (11) and a cathode metallization (12) of the power diode (1), wherein the semiconductor body (10) has a drift region (100) of a first conductivity type and an anode region (101) of a second conductivity type, the anode region (101) comprising: - a contact region (1011) arranged in contact with the anode metallization (11); - a field stop region (1012) arranged below the contact region (1011); - a body region (1013) arranged below the field stop region (1012) and above the drift region (100); The electrically activated dopant concentration of the anode region (101) exhibits a profile along the vertical direction (Z) according to which: - a first maximum (31) exists within the contact area (1011); - a second maximum (32) exists within the field stop region (1012); - the dopant concentration decreases continuously from the first maximum value (31) to a local minimum value (33), and increases continuously from the local minimum value (33) to the second maximum value (32); and The second maximum value (32) is in the range of 70% to 130% of the first maximum value (31), wherein according to the profile, the dopant concentration decreases continuously from the second maximum value (32) to an inflection point (34), at which the rate of change of the dopant concentration with respect to the vertical direction (Z) has a local maximum, and wherein during the blocking state of the power diode (1), the electric field stops below the inflection point (34).

2. The power diode (1) according to claim 1, wherein the second maximum (32) is an absolute maximum of the dopant concentration of the anode region (101).

3. The power diode (1) according to claim 1 or 2, wherein the local minimum (33) is in the range of 10% to 50% of the first maximum (31).

4. The power diode (1) according to claim 1 or 2, wherein the electrically activated dopant concentration at each of the first maximum (31) and the second maximum (32) is greater than 10 17 cm -3 .

5. The power diode (1) according to claim 1 or 2, wherein the maximum electrically active dopant concentration within the body region (1013) is in the range of 1 / 50 to 1 / 5 of the electrically active dopant concentration present at any one of the first maximum value (31) and the second maximum value (32).

6. The power diode (1) according to claim 1 or 2, wherein: At least within the contact region (1011) and the field stop region (1012), the electrical conductivity is substantially proportional to the electrically activated dopant concentration.

7. The power diode (1) according to claim 1, wherein According to the profile, the dopant concentration decreases continuously from the inflection point (34) throughout the body region (1013) until a transition (1010) formed between the body region (1013) and the drift region (100).

8. The power diode (1) according to claim 7, wherein a first concentration gradient existing above the inflection point (34) is at least three times greater than a second concentration gradient existing below the inflection point (34).

9. The power diode (1) according to any one of claims 1-2 and 7-8, wherein the anode region (101) exhibits five equal parts along the vertical direction (Z), wherein each of the first maximum value (31) and the second maximum value (32) is positioned in the uppermost equal part.

10. A power diode (1) according to one of claims 1-2 and 7-8, wherein each of the first maximum (31) and the second maximum (32) is located within a distance of 2000 nm from the anode metallization (11), the distance being measured along the vertical direction (Z) from the transition (111) between the contact area (1011) and the anode metallization (11).

11. The power diode (1) according to any one of claims 1-2 and 7-8, wherein - the total extension of the anode region (101) in the vertical direction (Z) amounts to no more than 20% of the total extension of the drift region (100) in the vertical direction (Z); and / or wherein - the total extension of the anode region (101) in the vertical direction (Z) is in the range of 500 nm to 15000 nm; and / or wherein - the total extension of the drift region (100) in the vertical direction (Z) is in the range of 10 μm to 1000 μm, - The power diode (1) is realized in a wafer having a thickness in the vertical direction (Z) in the range of 10 μm to 1000 μm.

12. The power diode (1) according to one of claims 1-2 and 7-8, wherein the profile within each of the contact region (1011) and the field stop region (1012) is an injection profile.

13. The power diode (1) according to claim 9, wherein the dose to each of the contact region (1011) and the field stop region (1012) is less than 2*10 13 cm -2 .

14. The power diode (1) according to any one of claims 1-2, 7-8 and 13, wherein the dose to the body region (1013) is less than 1*10 13 cm -2 .

15. The power diode (1) according to any one of claims 1-2, 7-8 and 13, wherein the profile within the body region (1013) is a diffuse profile.

16. The power diode (1) according to one of claims 1-2, 7-8 and 13, wherein the distance between the electric field peak during the blocking state of the power diode (1) and the second maximum (32) amounts to at least 500 nm.

17. The power diode (1) according to one of claims 1-2, 7-8 and 13, wherein the drift region (100) is configured for a blocking voltage of at least 500V.

18. The power diode (1) according to one of claims 1-2, 7-8 and 13, wherein the semiconductor body (10) further comprises a cathode region (102) of the first conductivity type, wherein the drift region (100) is coupled to the cathode metallization (12) by means of the cathode region (102).

19. A method (2) for processing a power diode (1), comprising: - providing (20) a semiconductor body (10) having a drift region (100) of a first conductivity type; - creating (21) an anode region (101) of a second conductivity type in the semiconductor body (10); - providing (22) an electrically activated dopant concentration in the anode region (101), said electrically activated dopant concentration exhibiting a profile along the vertical direction (Z) according to which: - a first maximum (31) exists in the contact region (1011) of the anode region (101); - a second maximum (32) exists in the field stop region (1012) of the anode region (101); - the dopant concentration decreases continuously from the first maximum value (31) to a local minimum value (33), and increases continuously from the local minimum value (33) to the second maximum value (32); and The second maximum value (32) is in the range of 70% to 130% of the first maximum value (31), wherein according to the profile, the dopant concentration decreases continuously from the second maximum value (32) to an inflection point (34), at which the rate of change of the dopant concentration with respect to the vertical direction (Z) has a local maximum, and wherein during the blocking state of the power diode (1), the electric field stops below the inflection point (34).

20. The method of claim 19, wherein the electrically activated dopant concentration present at the second maximum (32) is greater than the electrically activated dopant concentration present at the first maximum (31).

21. The method according to claim 19 or 20, wherein: - providing (22) an electrically active dopant concentration in said anode region (101) comprises performing a diffusion treatment step so as to provide a base dopant concentration with respect to the anode region (101).

22. The method according to claim 19 or 20, wherein: - providing (22) an electrically activated dopant concentration in the anode region (101) comprises performing a first implantation process step with a first implantation energy for producing a second maximum (32), and, optionally, performing a second implantation process step with a second implantation energy for producing the first maximum (31); and / or wherein - Providing (22) an electrically activated dopant concentration in the anode region (101) comprises performing a high temperature annealing step to substantially completely repair defects caused by the first implantation step or respectively by the first and second implantation steps, thereby providing an electrically activated dopant concentration in the contact region (1011) and the field stop region (1012).

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