Silicon carbide semiconductor component with edge termination structure

A semiconductor component includes a SiC semiconductor body having an active region and an edge termination structure at least partly surrounding the active region. A drift zone of a first conductivity type is formed in the SiC semiconductor body. The edge termination structure includes: a first doped region of a second conductivity type between a first surface of the SiC semiconductor body and the drift zone, the first doped region at least partly surrounding the active region and being spaced apart from the first surface; a plurality of second doped regions of the second conductivity type between the first surface and the first doped region; and third doped regions of the first conductivity type separating adjacent second doped regions of the plurality of second doped regions from one another in a lateral direction.

BACKGROUND

In vertical power semiconductor components a load current flows between a first load electrode on the front side and a second load electrode on the rear side of the semiconductor component. In the off state, the reverse voltage is dropped in a vertical direction between the first and second load electrodes and in a lateral direction across an edge termination region between a central, active region of the semiconductor component and a structure formed along the lateral side surface of the semiconductor body with the electrical potential of the second load electrode. For the lateral field reduction, power semiconductor components comprise JTE (Junction Termination Extension) regions, for example, the dopant concentration of which may decrease with decreasing distance from the side surface, or near-surface, floating and oppositely doped regions separated from one another (so-called guard rings). In semiconductor components composed of semiconductor materials in which the diffusion coefficients of dopants are small, edge termination structures such as are known from conventional silicon technology are less effective or more complicated to produce owing to the steeper pn junctions.

The present application is directed to a silicon carbide semiconductor component having improved edge termination.

SUMMARY

The present disclosure relates to a semiconductor component comprising an SiC semiconductor body having an active region and an edge termination structure at least partly surrounding the active region. In the SiC semiconductor body a drift zone of a first conductivity type is formed. The edge termination structure comprises a first doped region of a second conductivity type between a first surface of the SiC semiconductor body and the drift zone. The first doped region at least partly surrounds the active region and is spaced apart from the first surface. The edge termination structure additionally comprises a plurality of second doped regions of the second conductivity type between the first surface and the first doped region and third doped regions of the first conductivity type between the second doped regions.

The present disclosure additionally relates to a semiconductor component comprising an SiC semiconductor body having an active region and an edge termination structure at least partly surrounding the active region, wherein in the SiC semiconductor body a drift zone of a first conductivity type is formed. The edge termination structure comprises a first doped region of a second conductivity type between a first surface of the SiC semiconductor body and the drift zone. The first doped region at least partly surrounds the active region and is spaced apart from the first surface. The edge termination structure furthermore comprises a plurality of second doped regions of the second conductivity type between the first surface and the first doped region and third doped regions between the second doped regions.

Further features and advantages of the subject matter disclosed will be apparent to the person skilled in the art upon reading the following detailed description and upon consideration of the drawings.

DETAILED DESCRIPTION

In the following detailed description, reference is made to the accompanying drawings, which form part of the disclosure and show specific exemplary embodiments for illustration purposes. It goes without saying that further exemplary embodiments exist and structural or logical changes can be made to the exemplary embodiments, without in so doing departing from what is defined by the patent claims. The description of the exemplary embodiments is non-limiting in this respect. In particular, elements of exemplary embodiments described below can be combined with elements of others of the exemplary embodiments described, provided that nothing to the contrary is evident from the context.

The terms “have”, “contain”, “encompass”, “comprise” and the like hereinafter are open terms which on the one hand indicate the presence of the stated elements or features, and on the other hand do not exclude the presence of further elements or features. The indefinite articles and the definite articles encompass both the plural and the singular, provided that nothing to the contrary is clearly evident from the context.

Some figures represent relative dopant concentrations by the indication “−” or “+” next to the doping type. By way of example, “n−” denotes a dopant concentration which is less than the dopant concentration of an “n”-doped region, while an “n+”-doped region has a higher dopant concentration than the “n”-doped region. The indication of the relative dopant concentration does not mean that doped regions with the same relative dopant concentration indication must have the same absolute dopant concentration, unless stated otherwise. By way of example, two different “n”-doped regions can have the same or different absolute dopant concentrations.

The term “electrically connected” describes a low-impedance connection between the electrically connected elements, for example a direct contact between the relevant elements or a connection via a metal and/or a highly doped semiconductor. The expression “electrically coupled” includes the fact that one or more intervening elements suitable for signal transmission can be present between the “electrically coupled” elements, e.g. elements which are controllable such that they can produce a low-impedance connection in a first state and a high-impedance decoupling in a second state.

FIGS. 1A to 1Cshow a semiconductor component500comprising a central active region610and comprising an edge termination region690enclosing the active region610on all sides. An element structure601determining the functionality of the semiconductor component500is formed in the active region610. The element structure601can comprise for example a multiplicity of transistor cells TC, a pn junction of a pn diode or an MPS structure. The semiconductor component500can be a pn diode, an MPS diode, an IGBT (insulated gate bipolar transistor) or an IGFET (insulated gate field effect transistor), for example a MOSFET (metal oxide semiconductor FET), wherein the abbreviation MOSFET encompasses not only FETs having a metallic gate electrode but also FETs having a gate electrode composed of a semiconductor material. The semiconductor component500can also be an MGD (MOS-gated diode) or a semiconductor component which also comprises further electronic elements besides transistor cells TC.

The semiconductor component500is based on an SiC semiconductor body100composed of monocrystalline silicon carbide (SiC), for example 2H SiC (SiC of the 2H polytype), 6H SiC or 15R SiC. In accordance with one embodiment, the material of the SiC semiconductor body100is 4H SiC. A first surface101on the front side of the SiC semiconductor body100is planar or ribbed. A normal104to a planar first surface101or to a central plane of a ribbed first surface101defines a vertical direction. Directions parallel to a planar first surface101or to the central plane of a ribbed first surface101are horizontal or lateral directions.

On the rear side the SiC semiconductor body100has a second surface102parallel to the first surface101. The total thickness of the SiC semiconductor body100between the first and second surfaces101,102can be in the range of hundreds of nanometres to hundreds of micrometres. A side surface103forms the lateral outer surface of the SiC semiconductor body100and connects the first surface101to the second surface102. The side surface103can be oriented orthogonally to the first surface101.

A drift structure130is formed in the SiC semiconductor body100, said drift structure comprising at least one highly doped contact section139along the second surface102and a weakly doped drift zone131of a first conductivity type between the first surface101and the highly doped contact section139. Besides the drift zone131and the contact section139, the drift structure130can comprise even further doped regions of the conductivity type of the drift zone131or of the opposite conductivity type.

The edge termination region690is adjacent to the side surface103of the SiC semiconductor body100and comprises none of the semiconductor elements, for example transistor cells, that determine the functionality of the semiconductor component. Instead, an edge termination structure190for lateral field reduction is formed in the edge termination region690. Besides the edge termination structure190for lateral field reduction, the edge termination region690can comprise further edge structures having doped regions, for example a channel stopper region of the conductivity type of the drift zone131, which is more highly doped than the drift zone131and which can extend between the edge termination structure190and the side surface103from the first surface101into the SiC semiconductor body100.

The edge termination structure190comprises a first doped region191of a second conductivity type, which is complementary to the first conductivity type of the drift zone131. The first doped region191is formed between the first surface101and the drift zone131and together with the drift structure130, for example with the drift zone131, forms a pn junction extending predominantly or completely parallel to the first surface101. A vertical extent of the first doped region191can be in the range of 500 nm to 2.5 μm, for example in a range of 0.8 μm to 1.2 μm. A distance between the first doped region191and the first surface101can be between 100 nm and 1 μm. In a lateral direction and parallel to outer edges of the active region610, the dopant concentration is largely constant, at least in straight sections. In a lateral direction and orthogonally to outer edges of the active region610, the dopant concentration in the second doped regions192can be almost constant over a wide region, e.g. over at least 90% of a lateral width w1of the second doped regions192.

The first doped region191is fully depletable of mobile charge carriers under conditions specified in a data sheet for the semiconductor component500within the operating and ambient conditions within the maximum limiting data in off-state operation. By way of example, the dopant dose for the first doped region191is in a range of 2×1012cm−2to 2×1013cm−2, for example in a range of 6×1012cm−2to 1013cm−2.

The edge termination structure190furthermore comprises second doped regions192, which are laterally spaced apart from one another and in each case at least partly enclose the active region610. In accordance with one embodiment, at least one of the second doped regions192forms a closed structure that completely encloses the active region610. Other second doped regions192can be formed along lines that laterally frame the active region610, wherein the second doped regions192are spaced apart from one another along the lines. In accordance with the embodiment inFIG. 1A, all the second doped regions192form closed structures that in each case completely enclose the active region610.

The second doped regions192are formed between the first surface101and the first doped region191and can adjoin for example the first surface101, the first doped region191, or both. In accordance with one embodiment, the second doped regions192extend from the first surface101as far as the first doped region191. A dopant dose for the second doped regions192is higher than a dopant dose for the first doped region191, for example at least four times higher. In accordance with one embodiment, the dopant concentration of the second doped regions192is at least 1×1017cm−3.

The total dopant dose of the edge termination structure190comprising the first doped region191and the second doped regions can be in a range of 2×1013cm−2to 6×1013cm−2, for example in a range of 3×1015cm−2to 5×1013cm−2.

Third doped regions193of the first conductivity type separate adjacent second doped regions192from one another in a lateral direction.

The first doped region191and the innermost second doped region192facing the active region610can be directly adjacent to doped regions of the same conductivity type that are formed within the active region610. A vertical extent of the edge termination structure190can be at least 80% of a distance between the first surface101and a lower edge of the deepest doped region of the second conductivity type within the active region610.

In the off-state case, the second doped regions192contribute to the reduction of the electric field in a lateral direction. The comparatively weakly doped first doped region191shields the still relatively steep lateral pn junctions in silicon carbide between the second doped regions192and the third doped regions193towards the bottom and in this way reduces the maximum field strength occurring at the lateral pn junctions in the edge termination structure190. The buried first doped region191thus enables, inter alia, higher dopant doses in the second doped regions192, such that the influence of charge carriers that may occupy surface states along an interface between the SiC semiconductor body100and a passivation structure bearing on the first surface101is reduced. The dielectric strength of the edge termination structure190thus remains independent of the operating environment and constant over a longer operating duration.

In this case, the passivation structure can consist of a layer composed of a dielectric material or comprise a plurality of layers composed of different dielectric materials, e.g. a silicon oxide produced from an oxidation of silicon carbide, deposited silicon oxide, a silicon oxide containing nitrogen, a glass, for example USG (undoped silicate glass), BSG (borosilicate glass), PSG (phosphosilicate glass) or BPSG (borophosphosilicate glass), or a polyimide.

In comparison with edge termination structures that only comprise weakly doped ring structures of the second conductivity type, for the production of which only one lithographic mask plane is used, the edge termination structure190is significantly less sensitive to lithography fluctuations, i.e. with regard to variations of the distances between the second doped regions192. Moreover, owing to the shielding effect of the first doped region191, significantly lower field strengths occur at the lateral pn junctions, which has a positive effect on stability and reliability of the semiconductor component and improves the scalability to semiconductor components for higher voltage classes.

By comparison with edge termination structures which are based on a multi-zone implantation with a continuous, near-surface edge termination region of the second conductivity type and in which the dopant concentration in the zones decreases as the distance between the zones and the active region increases, the edge termination structure190can be produced with fewer mask planes, e.g. if the production of the first and second doped regions191,192can be linked with the formation of doped regions of the same conductivity type within the active region610.

FIG. 1Cshows the dependence of the breakdown voltage VBD of the edge termination structure190on the dopant dose Dos for the first doped regions191for a semiconductor component comprising an edge termination region610defined for a reverse voltage of 650 V.

The line401represents the dependence of the breakdown voltage VBD on the dopant dose Dos of the first doped regions. The line402indicates the breakdown voltage within the active region610. The scaling of the abscissa relates to the ratio in percent of the dopant dose in the first doped regions191to a constant reference dose of 4×1012cm−2.

The diagram shows that the edge termination structure190permits a very wide process window for the dopant dose for the second doped regions192and the breakdown voltage of the edge termination structure190is therefore largely independent of process fluctuations with regard to the edge termination structure190. The avalanche breakdown of the semiconductor component500is thus reliably bound to the active region610, which significantly improves the stability of the semiconductor component500and the avalanche robustness thereof. In the active region610the avalanche breakdown can then be pinned for example to curvatures of doped regions of the second conductivity type that are formed there.

FIG. 1Dshows second doped regions192formed in columnar fashion and formed along straight frame lines framing the active region610. Doped second regions192lying on the same frame line are separated from one another by further third doped regions193.

In accordance with the embodiment inFIGS. 2A and 2B, the third doped regions193of the edge termination structure190are of the same conductivity type as the second doped regions192and the first doped region191, wherein a dopant dose in the second doped regions192is higher than that in the third doped regions193. In accordance with one embodiment, the dopant dose in the second doped regions192is at least four times the dopant dose in the first doped region191. In accordance with a further embodiment, the dopant concentration in the third doped regions193can approximately correspond to the dopant concentration in the first doped region191, that is to say can deviate from the dopant concentration in the first doped region191by not more than a maximum of 10% of the value of said dopant concentration.

By comparison with JTE structures which comprise alternately more highly and more weakly doped rings and in which the width of the more highly doped rings decreases with increasing distance from the active region610and the width of the more weakly doped rings increases to the same extent, the edge termination structure190according toFIGS. 2A to 2Bproves to be more robust vis-ávis lithography fluctuations, for example in the case of relatively low voltage classes of, for example, 650 V or 1200 V.

FIG. 3shows a semiconductor component500comprising an SiC semiconductor body100having an edge termination region690enclosing a central active region610with transistor cells TC. Planar gate structures150of the transistor cells TC are formed on the front side of the SiC semiconductor body100, wherein at least in the interior of the active region610an individual gate structure150is assigned in each case to two transistor cells TC formed symmetrically with respect to the gate structure150.

The gate structures150comprise a conductive gate electrode155and a gate dielectric151, which is formed directly on the first surface101and separates the gate electrode155from the SiC semiconductor body100. A body region120extending from the first surface101into the SiC semiconductor body100is assigned in each case to two adjacent transistor cells TC, which for their part are assigned to two adjacent gate structures150. Source regions110of the two adjacent transistor cells TC are formed between the first surface101and the body region120. The body region120can comprise a contact region149, in which the dopant concentration is higher than in a main region121of the body region120outside the contact region149. The contact region149adjoins the first surface101between the two source regions110.

A drift structure130having a drift zone131and a contact section139separates the transistor cells TC from a second surface102of the SiC semiconductor body100, wherein the drift structure130, for example the drift zone131or current spreading zones having the same conductivity type as the drift zone131but a higher dopant concentration than the drift zone131, can extend between adjacent body regions120and below the gate electrodes155to the first surface101.

In the switched-on state, the transistor cells TC form lateral inversion channels in channel regions of the body regions120along the gate dielectric151, said inversion channels connecting the source regions110to the sections of the drift structure130that adjoin the first surface101, for example to the drift zone131or the current spreading zones.

An interlayer dielectric210separates the gate electrode155from a first load electrode310on the front side of the SiC semiconductor body100. Contact structures315extending through openings in the interlayer dielectric210electrically connect the first load electrode310to the contact regions149and to the source regions110. A second load electrode320can adjoin the highly doped contact section139of the drift structure130. The gate electrode155is electrically connected or coupled to a gate terminal of the semiconductor component.

In the exemplary embodiment depicted, the semiconductor component500is an n-channel SiC MOSFET. The first conductivity type is the n type and the second conductivity type is the p type. The first load electrode310can form a source terminal S or be electrically connected to a source terminal S. The second load electrode320can form a drain terminal D or be electrically connected to such a terminal. In accordance with other embodiments, the first conductivity type is the p type, and the second conductivity type is the n type.

An edge termination structure190as described above is formed in the edge termination region690. The first doped region191can extend to below the outermost gate structures150or be laterally spaced apart therefrom. A lateral width of the second doped regions192can decrease with increasing distance from the active region610. In addition or as an alternative thereto, a lateral width of the third doped regions193can increase with increasing distance from the active region610.

A dielectric passivation structure, for example a polyimide structure400, can bear directly on at least one section of the first surface101in the edge termination region690, which structure can cover outer edges of the first load electrode310or of the outermost gate structure150. In accordance with another embodiment, in at least one inner partial region of the edge termination region690that is adjacent to the active region610, the interlayer dielectric210can separate the polyimide structure400from the SiC semiconductor body100. At least one further dielectric layer, for example a silicon oxide layer and/or a layer composed of a silicate glass, can be formed at least in sections between the polyimide structure400and the SiC semiconductor body100.

Surface states at the interface between the SiC semiconductor body100and the passivation structure, for example the polyimide structure400, and at the interface between the SiC semiconductor body100and an interlayer dielectric210can be occupied by charge carriers to different extents during the operation of the semiconductor component500, which charge carriers can influence the electric field distribution in the edge termination region610and the breakdown voltage of the edge termination structure190. In accordance with one embodiment, the dopant concentration in the second doped regions192is at least 1×1017cm−3, for example at least 2×1017cm−3, such that charge carriers which at least temporarily occupy the surface states at the boundary layer between the polyimide structure400and the SiC semiconductor body100have only a small influence on the dielectric strength of the edge termination region690.

In accordance with one embodiment, the dopant dose in the second doped regions192is approximately equal to the dopant dose in the contact regions149or approximately equal to the difference between the dopant concentration in the contact regions149and in the body region120, such that the second doped regions192and the contact regions149can be defined in the same implantation step and in the same mask plane.

The doping of the first doped regions191is chosen such that the first doped regions191are fully depletable during the operation of the semiconductor component500. Since the doping of the body regions120is chosen such that the body regions120are not depleted, the formation of the body regions120usually comprises at least one method step that is independent of the formation of the first doped regions191.

A vertical extent v1of the first doped region191in the edge termination region690can correspond to a distance v3between a lower edge of the body regions120and the first surface101or be at least 80%, e.g. at least 85%, of the distance v3, which in this exemplary embodiment corresponds to the vertical extent of the body regions120comprising the contact regions149, as a result of which a dip in the blocking capability at the junction between the body region120and the edge termination structure190can be avoided.

The semiconductor component500inFIG. 4is an SiC TMOSFET (SiC Trench MOSFET) comprising gate structures150formed in shallow trenches having an approximately v-shaped vertical cross-sectional area. The gate electrode155can extend with approximately uniform layer thickness along sidewalls and along the bottom of the gate structures150. Mesa sections180of the SiC semiconductor body100between adjacent gate structures150comprise source regions110formed along the first surface101and body regions120that separate the source regions110from a drift structure130. The body regions120can comprise a more highly doped contact region149, in which the dopant concentration is higher than in a main region121of the body regions120outside the contact region149. The sidewalls of the mesa sections180can be for example (0-33-8) lattice planes.

The SiC TMOSFET comprises a drift structure130and an edge termination structure190as described above. A vertical extent v1of the edge termination structure190can be at least 80% of a distance v3between a lower edge of the body regions120and the first surface101or be e.g. approximately equal to the distance v3, wherein in the exemplary embodiment inFIG. 4the distance v3corresponds to the vertical extent of the body regions120comprising the contact regions149.

The semiconductor component500inFIG. 5is an SiC TMOSFET comprising gate structures150extending from a first surface101into an SiC semiconductor body100, wherein sidewalls of the gate structures150extend vertically to the first surface101. Body regions120are formed in mesa sections180of the SiC semiconductor body100between adjacent gate structures150, said body regions forming, in the mesa sections180, first pn junctions pn1with a drift structure130and second pn junctions pn2with source regions110formed along the first surface101. Side surfaces of the mesa sections180are main lattice planes of the silicon carbide crystal.

Between adjacent gate structures150, trench contacts316extend from the first load electrode310through an interlayer dielectric210and into the mesa sections180. The trench contacts316laterally adjoin the source regions110and connect the latter to the first load electrode310.

The transistor cells TC additionally comprise shielding regions160of the conductivity type of the body regions120, wherein a distance v4between a lower edge of the shielding regions160and the first surface101is greater than a vertical extent v2of the gate structures150. The shielding regions160can have a higher dopant concentration than the body regions120and are laterally spaced apart from the gate structures150. The gate structures150are shielded against the drain potential by in each case two adjacent shielding regions160, which are significantly closer to the second surface102than the gate structures150. Within the active region610, it is possible to pin the avalanche breakdown in the region of the shielding regions160, for example along the lower edges of the shielding regions160. The shielding regions160can comprise highly doped contact regions149formed directly below the trench contacts316.

An edge termination region690of the semiconductor component500comprises an edge termination structure190as described above. In this case, a vertical extent v1of the edge termination structure190can correspond approximately to the distance v4between the lower edge of the shielding regions160and the first surface101, for example can be at least 80% thereof. If the contact regions149are introduced through the bottom of contact trenches before the formation of the trench contacts316, then the second doped regions192can be formed from the same implantations and in the same mask plane as the highly doped contact regions149, wherein an absolute dopant concentration of the second conductivity type in the second doped regions192can correspond approximately to the difference between the dopant concentration of the contact region149and of the shielding region160.

InFIG. 6, the semiconductor component500is an n-channel SiC TMOSFET based on an SiC semiconductor body100having strip-like transistor cells TC and deep trench gate structures150with a transistor channel on one side. For details of the edge termination structure190that are not described below, reference is made to the description concerningFIGS. 1A and 1B.

On a front side the SiC semiconductor body100has a first surface101, which can comprise coplanar surface sections. The first surface101can coincide with a main lattice plane or extend at an angle deviation α obliquely with respect to a main lattice plane, e.g. with respect to the (0001) lattice plane, wherein the angle deviation can be at most 12°, e.g. approximately 4°.

In the embodiment illustrated, the <0001> crystal direction is tilted by an angle deviation α with respect to the normal104. The <11-20> crystal direction is tilted by the same angle deviation α with respect to the horizontal plane and otherwise extends in the cross-sectional plane. The <1-100> crystal direction is orthogonal to the cross-sectional plane.

On the rear side the SiC semiconductor body100has a second surface102parallel to the first surface101. A total thickness of the SiC semiconductor body100between the first surface101and the second surface101,102can be from hundreds of nanometres to hundreds of micrometres.

A drift structure130formed in the SiC semiconductor body100comprises at least one highly doped contact section139adjoining the second surface102, and a weakly doped drift zone131of a first conductivity type between the first surface101and the highly doped contact section139.

The highly doped contact section139is of the same conductivity type as the drift zone131and can be or comprise a substrate section sawn from a crystal or sliced from a crystal or may have resulted completely from an epitaxy method. The contact section139forms an ohmic contact with a second load electrode320, which can directly adjoin the second surface102. Along the second surface102the dopant concentration in the contact section139is high enough to form a low-impedance contact with the second load electrode320.

The drift zone131can be formed in a layer grown on the contact section139by epitaxy. An average dopant concentration in the drift zone131is in a range of 5×1014cm−3to 5×1016cm−3, for example. Besides the drift zone131and the contact section139, the drift structure130can comprise further doped regions, for example field stop zones, blocking or barrier zones and/or current spreading zones of the conductivity type of the drift zone131and/or island-like regions of the complementary conductivity type.

The transistor cells TC on the front side of the SiC semiconductor body100are formed along gate structures150extending from the first surface101into the SiC semiconductor body100, wherein mesa sections180of the SiC semiconductor body100separate adjacent gate structures150from one another.

A longitudinal extent of the gate structures150along a first horizontal direction is greater than a width of the gate structures150along a second horizontal direction orthogonal to the first horizontal direction and transverse with respect to the longitudinal extent. The gate structures150can be long trenches extending from one side of an active region610having the transistor cells TC as far as an opposite side, wherein the length of the gate structures150can be up to hundreds of micrometres or up to a number of millimetres.

In accordance with other embodiments, the gate structures150can be formed along parallel lines extending in each case from one side of the cell array region to the opposite side, and wherein a multiplicity of gate structures150separated from one another are formed in each case along the same line. The gate structures150can also form a lattice with the mesa sections180in the meshes of the lattice.

The gate structures150can be uniformly spaced apart from one another, can have the same width and can form a regular pattern, wherein a centre-to-centre distance between the gate structures150can be in a range of 1 μm to 10 μm, e.g. of 2 μm to 5 μm. A vertical extent of the gate structures150can be 300 nm to 5 μm, e.g. in a range of 500 nm to 2 μm.

Sidewalls of the gate structures150are slightly tilted with respect to the vertical direction, wherein mutually opposite sidewalls can extend parallel to one another or towards one another. In accordance with one embodiment, the width of the gate structures150decreases with increasing distance from the first surface101. By way of example, one sidewall deviates by the angle deviation α and the other sidewall by −α from the vertical.

The mesa sections180have two opposite longitudinal mesa side surfaces181,182, which directly adjoin two adjacent gate structures150. A first mesa side surface181lies in the (11-20) lattice plane, in which the charge carrier mobility is high. The second mesa side surface182situated opposite the first mesa side surface181can be tilted by double the angle deviation α, for example by approximately 8 degrees, with respect to the relevant lattice plane.

The gate structures150comprise a conductive gate electrode155, which can comprise a highly doped polycrystalline silicon layer, an integral or multipartite metal structure or both. The gate electrode155is electrically connected to a gate metallization on the component front side, which forms a gate terminal or is electrically connected or coupled to such a terminal.

Along at least one side of the gate structure150, a gate dielectric151separates the gate electrode155from the SiC semiconductor body100. The gate dielectric151can comprise a semiconductor dielectric, for example a thermally grown or deposited semiconductor oxide, e.g. silicon oxide, a semiconductor nitride, for example a deposited or thermally grown silicon nitride, a semiconductor oxynitride, for example a silicon oxynitride, some other deposited dielectric material or an arbitrary combination of the materials mentioned. The layer thickness of the gate dielectric151can be tens of nanometres and can be chosen such that a threshold voltage of the transistor cells TC is in a range of 1 V to 8 V.

The gate structures150can exclusively comprise the gate electrode155and the gate dielectric151or can comprise further conductive and/or dielectric structures, e.g. isolating dielectrics, in addition to the gate electrode155and the gate dielectric151.

In the mesa sections180, source regions110are formed towards the front side of the SiC semiconductor body100, which source regions can directly adjoin the first surface101and the first mesa side surface181of the respective mesa section180. In this case, each mesa section180can comprise a source region110having sections connected to one another in the SiC semiconductor body100or having at least two sections which are separated from one another in the SiC semiconductor body100and which are connected to one another with low impedance by way of a contact or trench contact adjoining the mesa section180.

The mesa sections180furthermore comprise body regions120that separate the source regions110from the drift structure130and adjoin the first mesa side surface181. The body regions120form first pn junctions pn1with the drift structure130and second pn junctions pn2with the source regions110. In the switched-on state of the transistor cell TC, an inversion channel connecting the source region110to the drift structure130is formed in the body region120along the gate structure150. An extent of the body regions120along the first mesa side surface181corresponds to a channel length of the transistor cells TC and can be 200 nm to 1500 nm.

The mesa sections180additionally comprise at least partial regions of shielding regions160of the conductivity type of the body regions120, wherein the shielding regions160can adjoin the second mesa side surfaces182and form an ohmic contact with the first load electrode310. The shielding regions160or at least partial regions of the shielding regions160can be more highly doped than the body regions120. By way of example, a dopant concentration p2in the shielding regions160along the second mesa side surfaces182can be at least five times higher than a dopant concentration p1in the body regions120along the first mesa side surfaces181.

The shielding regions160are formed between the body regions120and the second mesa side surfaces182and can directly adjoin the body regions120. A vertical extent of the shielding regions160can be greater than a vertical extent of the body regions120, for example greater than a vertical extent of the gate structures150. More highly doped contact regions149can be formed in the shielding regions160, which contact regions can adjoin the contact structure315to the first load electrode310. A partial region of a shielding region160can be formed directly between the bottom of the gate structure150and the second surface102and shield the gate structure150against the potential of the second load electrode320.

A load current that flows through the SiC semiconductor body100between the first and second load electrodes310,320in the switched-on state of the semiconductor component500passes through the body regions120as a minority charge carrier flow in inversion channels induced along the gate dielectric151. The higher dopant concentration in the shielding regions160in comparison with the dopant concentration in the body regions120suppresses the formation of inversion channels along the second mesa side surfaces182during operation within the maximum limiting data.

FIG. 6additionally shows current spreading zones137as part of the drift structure130, wherein the current spreading zones137form the first pn junctions pn1with the body regions120and directly adjoin the drift zone131, and wherein a dopant concentration in the current spreading zones137is higher than in the drift zone131, for example at least double the magnitude of that in said drift zone.

The vertical extent v1of the edge termination region190can be at least 80%, e.g. at least 85%, of the vertical extent v4of the shielding regions160comprising the contact regions149or be equal in magnitude.

The semiconductor component500inFIG. 7is a pn diode, in the active region610of which a p-doped anode region125can be formed as continuous layer. The edge termination structure190can be directly adjacent to the anode region125laterally. A vertical extent v1of the edge termination structure190is at least 80% of a vertical extent v7of the anode region125. In accordance with one embodiment, the vertical extent v1of the edge termination structure190is equal to the vertical extent v7of the anode region125, such that a dip in the blocking capability at the junction between the edge termination structure190and the anode region125can be avoided.

The semiconductor component500inFIG. 8is an MPS diode, in which in the active region610channel sections136of the drift structure130extend as far as the first surface101and form Schottky contacts SC to the first load electrode310. A dopant concentration in the channel sections136can be greater than or equal to the dopant concentration in the drift zone131. Anode regions125of the second conductivity type that extend from the first surface101into the SiC semiconductor body100likewise adjoin the first load electrode310. For a low load range, the MPS diode uses the lower forward voltage of the Schottky contacts SC, while the bipolar current via the pn junctions can increasingly contribute to higher load currents. In the off-state case, space charge zones extending from the anode regions125laterally into the channel sections136pinch off a leakage current path through the channel sections136.

FIGS. 9A to 9Brelate to the lateral dopant distribution in the second and third doped regions192,193of the edge termination structures190as described in the previous figures, wherein a dopant concentration of dopants of the first conductivity type in the third doped regions193corresponds to the dopant concentration ND0of the same dopant in the drift zone131.

The second doped regions192and the third doped regions193have a constant background doping761of the conductivity type of the drift zone131with the dopant concentration ND0in the drift zone131. At least in edge sections of the second doped regions192, the concentration762of dopants of the conductivity type opposite to the conductivity type of the drift zone131continuously decreases, such that along the same direction the net dopant concentration763falls within a lateral distance Δx of at least 200 nm, for example of at least 500 nm, from a maximum value Nmax to a value Nmax/e, wherein e stands for Euler's number. A fall to 1/e corresponds approximately to a fall from 100% to 37%. In central sections of the second doped regions192, the net dopant concentration763can be approximately constant.

FIG. 9Crepresents the lateral profile of the net dopant concentration763along the line B-B for the case where the third doped regions193are completely oppositely doped.

The lateral dopant distribution described inFIGS. 9A to 9Cresults in the case of a corresponding lateral modulation of an ion beam used for forming the second doped regions192by ion implantation. By way of example, the ion beam can be laterally modulated with the aid of an energy filter arranged in the beam path of the ion beam or with the aid of a suitable neutral stepped mask, which is formed for instance by briefly heating a stepped mask, wherein the mask material runs slightly as a result of the heating. A lateral modulation of the ion beam also results if the ion beam is guided at different angles through the openings in a stepped mask of sufficient height.

FIG. 10shows a vertical cross section through an edge termination region690between an active region610and a side surface103of an SiC semiconductor body100of a semiconductor component500. The first doped region191and the innermost second doped region192of an edge termination structure190are directly adjacent to a doped region of the same conductivity type, e.g. a body region or an anode region125in the active region610. The dopant dose in the second doped regions192is for example four times the dopant dose in the first doped region191.

The second doped regions192are introduced by one or more, for example three, implantations of varying energy through openings in an implantation mask. A width ws of substructures195formed in each case from a second doped region192and a third region193adjoining the second doped region192on the side facing away from the active region610remains constant, wherein a lateral width w2of the second doped regions192decreases with increasing distance from the active region610and a lateral width w3of the third doped regions193correspondingly increases with increasing distance from the active region610. The decrease in the lateral width w2and the increase in the lateral width w3can be provided in linear fashion, i.e. in uniform steps.

The followingFIGS. 11A to 13Fshow dopant distribution, avalanche rate and electric field distribution for a structure according toFIG. 10, wherein the dopant dose for the edge termination structure190is varied in each case.

FIGS. 11A, 12A and 13Arelate to a dopant dose of 40%,FIGS. 11B, 12B and 13Brelate to a dopant dose of 120%,FIGS. 11C, 12C and 13Crelate to a dopant dose of 200%,FIGS. 11D, 12D and 13Drelate to a dopant dose of 400%,FIGS. 11E, 12E and 13Erelate to a dopant dose of 680%, and finallyFIGS. 11F, 12F and 13Frelate to a dopant dose of 800% of a reference dose of 1×1013cm−2.

InFIGS. 11A to 11F, the line403in each case represents the boundary of the space charge zone at the instant of the avalanche breakdown. For implantation doses of 120% or more, the breakdown location is pinned independently of the implantation dose within the active region610.

FIGS. 12A to 12Fin each case indicate the distribution of the impact ionization density K and show that the location of the maximum impact ionization density remains unchanged for implantation doses of between 120% and 800%.

FIGS. 13A to 13Fin each case indicate the distribution of the electric field strength E and show a homogenous field distribution increasing with the implantation dose from the inner area outwards over a wide range of the implantation dose from 120% to 800%.

In accordance withFIG. 14, a method for producing a component comprises forming (902) an oppositely doped zone in an initial layer of an SiC semiconductor substrate, wherein the initial layer is of a first conductivity type and the oppositely doped zone partly or completely surrounds an active region of a component region. The method furthermore comprises forming (904) second doped regions of the second conductivity type, which extend from a first main surface of the SiC semiconductor substrate as far as the first doped region, are laterally spaced apart from one another and in each case at least partly or completely surround the active region. The first doped region is formed from at least one section of the oppositely doped zone. The first doped region, the second doped regions and third doped regions between the second doped regions form an edge termination structure.

The second doped regions can be formed with a higher dopant dose than the first doped region. The oppositely doped zone can be formed at a distance from the first main surface, wherein the second doped regions extend from the first main surface as far as the oppositely doped zone and the first doped region is formed by the oppositely doped zone. As an alternative thereto, the oppositely doped zone can be formed in a manner extending from the first main surface, wherein a vertical extent of the second doped regions is less than a vertical extent of the oppositely doped zone, and wherein the first doped region is formed by a section of the oppositely doped zone that is adjacent to the second doped regions in a vertical direction. Forming the second doped regions can comprise introducing a dopant of the second conductivity type into subregions of the initial layer that are laterally spaced apart from one another. Forming the second doped regions can comprise forming a second doped zone of the second conductivity type, said second doped zone extending from the first main surface into the initial layer, and at least partly oppositely doping sections of the second doped zone by a dopant of the first conductivity type. Forming the second or third doped regions can comprise an ion implantation in which the ion beam is laterally modulated, such that in the second or third doped regions a net dopant distribution in a lateral direction falls within at least 200 nm, for example within at least 500 nm, continuously from a maximum net dopant concentration Nmax to a concentration Nmax/e, wherein e is Euler's number.

FIGS. 15A and 15Brelate to a method in which the first doped region191is formed independently of the second doped regions192.

An SiC semiconductor substrate700is provided, comprising a highly doped substrate section790and an initial layer730grown on the substrate section790for example by means of an epitaxy method.

In the exemplary embodiment depicted, both the substrate section790and the initial layer730are n-doped. The initial layer730can be uniformly doped, with an average dopant concentration in the range of 5×1014cm−3to 5×1016cm−3. An oppositely doped zone791is formed at a distance from the first main surface701.

FIG. 15Ashows the formation of the oppositely doped zone791by means of the implantation of a first dopant481through openings485in a first implantation mask480. The implantation for forming the oppositely doped zone791can comprise a single implantation or a plurality of implantations at different implantation energies. An energy filter for vertically spreading an implant can be arranged in the beam path of the ion beam.

A distance between the oppositely doped layer791and the first main surface701can be hundreds of nanometres, for example at least 500 nm and a maximum of 2 μm. At least one partial layer725of a shielding region, of a body region or of an anode region can be formed via further mask openings485in an active region610of a component region.

FIG. 15Bshows the formation of second doped regions192by ion implantation of a second dopant491through openings495in a second implantation mask490. Instead of the second implantation mask490, a correspondingly structured energy filter can be arranged in the beam path of the ion beam. The second doped regions192can be formed such that they extend from the first main surface701as far as the oppositely doped zone791fromFIG. 15A.

The oppositely doped zone791forms the first doped region191of the edge termination structure190. The initial doping of the initial layer730is maintained in the regions between the second doped regions192that are covered by the mask sections of the second implantation mask490. The relevant regions form the third doped regions193of the edge termination structure190. By way of example, contact regions of body regions, contact regions of shielding regions or a contact region149for an anode region125can be formed through further openings495in the second implantation mask490in the active region610.

In accordance with the embodiment illustrated inFIGS. 16A to 16B, the oppositely doped zone791produced using the first implantation mask480extends from the first main surface701into the initial layer730.

FIG. 16Ashows the formation of the oppositely doped zone791, which can comprise a plurality of implantations at different implantation energies. Simultaneously with the oppositely doped zone791, body regions, shielding regions or an anode region125adjacent to the first main surface701can be formed through further mask openings in active regions610.

FIG. 16Bshows the formation of the second doped regions192, which can be defined for example with the aid of the second implantation mask490as described inFIG. 15B. The original doping of the oppositely doped zone791is maintained in the regions of the oppositely doped zone791that are covered by the second implantation mask490. The relevant regions form third doped regions193of the edge termination structure190, wherein in this case the third doped regions193have the same conductivity type as the second doped regions192and are differentiable therefrom only by virtue of a lower dopant concentration. By way of example, the dopant concentration in the third doped regions193is only 25% of the dopant concentration in the second doped regions192. By way of example, the dopant concentration in the third doped regions193is of the same magnitude as in the first doped region191.

FIG. 17Ashows the formation of an oppositely doped zone791extending from the first main surface701into the SiC semiconductor substrate700, wherein an upper section of the oppositely doped zone791between the first main surface701and a lower section is formed with a higher dopant concentration than the lower section.

FIG. 17Bshows a third implantation mask470having mask openings475, which expose regions in which the third doped regions193are formed, said mask covering regions in which the second doped regions192are formed from subsections of the upper section of the oppositely doped zone791. The implantation with a dopant471of the conductivity type of the initial layer730forms the third doped regions193by renewed opposite doping of subregions of the upper section of the oppositely doped zone791.

FIG. 18shows an ion beam modulation device450in the beam path of an ion beam for the second dopant491fromFIG. 15B. The ion beam modulation device450laterally modulates the ion beam, such that in the second doped regions192a net dopant distribution in a lateral direction falls within at least 200 nm, for example within at least 500 nm, continuously from a maximum net dopant concentration Nmax to a concentration Nmax/e, wherein e is Euler's number.

The ion beam modulation device450can comprise for example a laterally structured energy filter having almost non-transmissive first sections451and transmissive second sections452. In the second sections452, energy and emergence angles of the ions are modulated depending on the impingement location such that the ion beam is split into partial beams which expand between the energy filter and the SiC semiconductor substrate700, wherein the ion density in each partial beam decreases continuously towards the outside.

According to another embodiment, the ion beam modulation device450comprises a neutral stepped mask, which is formed for instance by briefly heating a stepped mask, wherein the mask material runs slightly as a result of the heating. A lateral modulation of the ion beam also results if the ion beam is guided at different angles through the openings in a stepped mask of sufficient height.

In the following, further embodiments of the semiconductor component are explained in detail. It is to be understood that the features mentioned above and those yet to be explained below may be used not only in the respective combinations indicated, but also in other combinations or in isolation without departing from the scope of the invention.

In some embodiments, the third doped regions are completely enclosed by the first doped regions and the second doped regions, e.g. by each of the first doped regions and the second doped regions. In addition or as an alternative, each of the first and second doped regions may completely enclose the active region.

According to at least one embodiment, a dopant dose of the second doped regions is higher than a dopant dose of the first doped region. For example, the dopant dose of the second doped regions is at least double the magnitude of the dopant dose of the first doped region.

In some embodiments, a vertical extent of the edge termination structure is at least 80% and at most 100% of a distance between lower edge of the deepest doped region of the second conductivity type within the active region.

In some embodiments, the active region comprises further doped regions of the second conductivity type and a vertical extent of the edge termination structure is at least 80% of a distance between a deepest lower edge of the further doped regions in the active region and the surface. The active region may further comprise at least one of: transistor cells of the second conductivity type gate electrodes formed on the first surface.

In some embodiments, the vertical extent of the edge termination structure is at least 80% of a distance between the first surface and a lower edge of the body regions.

According to at least one embodiment, the semiconductor component comprises gate structures comprising gate electrodes and extending from the first surface into the SiC semiconductor body. It may be possible that each of the body regions extends between two adjacent gate structures.

In addition or as an alternative, the transistor cells may comprise shielding regions of the second conductivity type. A distance between a lower edge of the shielding regions and the first surface may be greater than a vertical extent of the gate structures. The vertical extent of the edge termination structure may be at least 80% of the distance between the first surface and a lower edge of the shielding regions.

In some embodiments, the shielding regions vertically overlap the gate structures. In alternative embodiments, the shielding regions may be laterally spaced apart from the gate structures.

According to at least one embodiment, the active region comprises a continuous anode region of the second conductivity type which adjoins the first surface. Alternatively, the active region comprises a multiplicity of anode regions and channel sections of the drift region, which channel sections are located between the anode regions. The channel sections may adjoin the first surface and form Schottky contacts to a first load electrode.

In some embodiments, a dopant concentration of the third doped region is equal to a dopant concentration of the drift zone. Separately or in combination, the third doped region comprises dopants of the second conductivity type and a dopant concentration of the second conductivity type is equal to a dopant concentration in the first doped region. Separately or in combination, a dopant dose for the first doped region is in a range of 2×1012cm−2to 2×1013cm−2.

In some embodiments, a dopant concentration within the second doped regions is constant in a lateral direction. Separately or in combination, a dopant concentration of the second doped regions is at least 1×1017cm−3.

According to at least one embodiment of the semiconductor component, the further doped regions and/or the anode region comprise(s) highly doped subregions. A dopant concentration of the highly doped subregions may be equal to the dopant concentration in the second doped regions.

According to at least one embodiment of the semiconductor component, a lateral width of the second doped regions decreases with increasing distance from the active region.

In some embodiments, the semiconductor component may comprise substructures. Each of the substructures may be formed from a second doped region and a third region adjoining the second doped region. The third region may adjoin the second region on a side facing away from the active region. A width of each of the substructures may be constant.

Separately or in combination, a lateral net dopant concentration in the second doped regions falls within at least 200 nm (e.g. a lateral distance of at least 200 nm) from a maximum net dopant concentration Nmax to a concentration Nmax/e, wherein e is Euler's number. For example, the lateral net dopant concentration continuously and/or monotonically decrease from Nmax to Nmax/e within a lateral distance of 200 nm.

The third doped region may be of the first conductivity type. Alternatively, the third doped region may be of the second conductivity type. In the latter case, a dopant concentration in the third doped region may be at most 50% of a dopant concentration in the second doped regions and/or a dopant concentration in the third doped region may be equal to the dopant concentration in the first doped region.