Method for producing a growth substrate, method for producing an epitaxial silicon carbide layer, growth substrate, and epitaxial silicon carbide layer

Abstract

A method for producing a growth substrate (1) for an epitaxial silicon carbide layer (5) is specified, the method comprising : providing an initial wafer (2), wherein the initial wafer (2) comprises silicon carbide and wherein the initial wafer (2) comprises a first dopant, and heating the initial wafer (2) to an annealing temperature within a first gas atmosphere, wherein the first dopant and the first gas comprise the same material element, such that a growth region (4) for the epitaxial silicon carbide layer (5) is produced, wherein a maximum concentration of the first dopant of the growth region (4) is higher than a maximum concentration of the first dopant in an initial wafer region. Furthermore, a method for producing an epitaxial silicon carbide layer (5), a growth substrate (1), an epitaxial silicon carbide layer (5), and a power semiconductor device are provided.

Description

[0001] P2024,0604 WO N / P240008WO01 June 5,2025 -1 - DescriptionMETHOD FOR PRODUCING A GROWTH SUBSTRATE, METHOD FPORODUCINGAN EPITAXIAL SILICON CARBIDE LAYER, GROWTH SUBSTRAT E, ANDEPITAXIAL SILICON CARBIDE LAYERThe present disclosure relates to a method for prod ucing agrowth substrate, a method for producing an epitaxi al siliconcarbide layer, a growth substrate, and an epitaxial siliconcarbide layer.Typically, carbon vacancies in silicon carbide laye rs resultin at least two electrically active levels in the b andgap,which are characteristic of recombination centers a ffectinglifetime and leakage currents in a typical semicond uctordevice.Embodiments of the disclosure relate to a method fo rproducing a growth substrate. Further embodiments r elate to amethod for producing an epitaxial silicon carbide l ayer, agrowth substrate,and an epitaxialsilicon carbide layer.This is achieved by the subject-matter of the indep endentclaims. Further embodiments are evident from the de pendentclaimsand the following description.A method for producing a growth substrate for an ep itaxialsilicon carbide layer is described. The growth subs trate isparticularly a growth substrate for the epitaxial s iliconcarbide layer.The epitaxialsilicon carbide layer isinparticular epitaxially growable on a top surface of thegrowth substrate. P2024,0604 WO N / P240008WO01 June 5,2025 -2 -According to an embodiment of the method for produc ing agrowth substrate, an initial wafer is provided, whe rein theinitial wafer comprises silicon carbide, SiC, and w herein theinitial wafer comprises a first dopant. The initial waferexemplarily has a crystal structure, particularly c omprisinga layered structure. For example, the initial wafer ischaracteristic of a predetermined polytype of silic oncarbide.For example, the first dopant is incorporated in th e siliconcarbide in the crystalstructure.Exemplarily,the initialwafer comprising the first dopant is of a first con ductivitytype. For example, the first conductivity type is a n n-type.“N-type” means here and in the following that the f irstdopant is configured to add electrons to the silico n carbide.Exemplarily, the first dopant is distributed in the initialwafer homogeneously. “Homogeneously” means here and in thefollowing that a maximum concentration of the first dopantvaries in the initial wafer by at most 10% or at mo st 5%.According to the embodiment of the method for produ cing agrowth substrate, the initial wafer is heated to an annealingtemperature within a firstgasatmosphere,wherein the firstdopant and the first gas comprise the same material element.For example, the initial wafer is heated to the ann ealingtemperature within the firstgasatmosphere forapredetermined annealing time. During the predetermi nedannealing time, a top surface region of the initial waferreacts, for example, with the first gas. Exemplaril y, thereaction takes place up to a reaction depth, extend ing from atop surface to a bulkofthe initialwafer. P2024,0604 WO N / P240008WO01 June 5,2025 -3 -Exemplarily, the element material accumulates up to thereaction depth in the top surface region. In partic ular, aconcentration of the first dopant up to the first r eactiondepth is higher than in a bulk region of the initia l wafer.According to the embodiment of the method for produ cing agrowth substrate, the initial wafer is heated to th eannealing temperature within the first gas atmosphe re suchthat a growth region for the epitaxial silicon carb ide layeris produced, wherein a maximum concentration of the firstdopant of the growth region is higher than a maximu mconcentration of the first dopant in the initial wa ferregion.Afterthe annealing temperature and / orthe firstgasatmosphere are applied, the initial wafer is divide d in tworegions, namely the growth region and the initial w aferregion. This means that by the heating and the appl ication ofthe first gas atmosphere, the growth region is gene rated inthe initial wafer up to the reaction depth. The ini tial waferregion is at least mostly not affected by the heati ng and theapplication of the first gas atmosphere in the sens e that theinitialwaferregion hasthe same concentration of the first dopantasthe initialwaferbefore the heating and the application.For example, the maximum concentration of the first dopant isat least one order of magnitude higher than the max imumconcentration of the first dopant in the initial wa ferregion.Such a growth region particularly forms the top sur face ofthe growth substrate.In particular,the epitaxial siliconcarbide layer is epitaxially growable on the top su rfaceformed ofthe growth region. P2024,0604 WO N / P240008WO01 June 5,2025 -4 -In summary, such a method advantageously produces a growthsubstrate for an epitaxial silicon carbide layer, w herein theepitaxial silicon carbide layer can be grown direct ly on thegrowth region. This makes the use of a typical buff er layerunnecessary. Advantageously,a comparativelyhigh concentration ofthe materialelementofthe firstdopantin the growth regionleads to a strain in the crystal structure which, i n turn,leads to the formation of interstitials, in particu larinterstitial carbon atoms. This means that such a g rowthregion advantageously serves as a reservoir of inte rstitialcarbon atoms during a growth of the epitaxial silic on carbidelayer on the growth region, wherein a concentration ofelectrically active levels is advantageously reduce d in suchepitaxial silicon carbide layers grown on top of th e growthregion.According to a further embodiment of the method for producinga growth substrate, a maximum concentration of inte rstitialcarbon atomsin the growth region ishigherthan a maximumconcentration of interstitial carbon atoms in the i nitialwafer region. Exemplarily, the maximum concentratio n ofinterstitial carbon atoms in the growth region is a t leastone order of magnitude higher than the maximum conc entrationof interstitial carbon atoms in the initial wafer r egion. Themaximum concentration ofinterstitialcarbon atoms in thegrowth region is at least 1·10 11 cm -3 and / or at most 1·10 13 cm -3.According to a further embodiment of the method for producinga growth substrate, a polymorph type of the silicon carbide P2024,0604 WO N / P240008WO01 June 5,2025 -5 -is a hexagonal polytype 4H. In particular, the desi gnation"4H" indicates that the hexagonal polytype has a he xagonalcrystal structure. The hexagonal polytype 4H has, i nparticular, a periodicity of 4 in a stacking sequen ce along ac-axis of a hexagonal unit cell. This means that th e siliconcarbide having the hexagonal polytype 4H has a repe atingsequence everyfourbilayersofsilicon and carbon atoms.According to a further embodiment of the method for producinga growth substrate,the firstdopantand the first gascomprise nitrogen as the material element. In parti cular, thefirst dopant is nitrogen, N, and the first gas atmo sphere isan N 2 atmosphere.During the heating to the annealing temperature and theapplication of the first gas atmosphere an N-rich l ayer isproduced in the initial wafer, being the growth reg ion.According to a further embodiment of the method for producinga growth substrate,a maximum concentration ofthe firstdopant in the initial wafer region is at most 4·10 18 cm -3. Inparticular, a maximum concentration of the first do pant inthe initial wafer region is at least 1·10 15 cm -3 and / or atmost 1·10 18 cm -3.According to a further embodiment of the method for producinga growth substrate,a maximum concentration ofthe firstdopant in the growth region is at least 5·10 18 cm -3 and / or atmost 5·10 20 cm -3.Exemplarily, with such concentrations the first dop ant, beingparticularlyN in the N-rich layer,advantageously inducesenough strain in the crystal structure in the growt h region P2024,0604 WO N / P240008WO01 June 5,2025 -6 -for forming the comparatively high maximum concentr ation ofinterstitialcarbon atoms.According to a further embodiment of the method for producinga growth substrate, the annealing temperature is at least1000°C and / oratmost1500°C.According to a further embodiment of the method for producinga growth substrate, the initial wafer is heated for apredetermined annealing time of at least 0.5 h and / or at most5 h.According to a further embodiment of the method for producinga growth substrate, the growth region has a thickne ss of atleast0.01 μm and / oratmost1 μm. Exemplarily,a thicknessof the growth region is at least one order of magni tudesmaller than a thickness of the initial wafer regio n.According to a further embodiment of the method for producinga growth substrate, the growth region has a thickne ss of atleast0.05 μm and / oratleast0.1 μm.Advantageously, with the indicated annealing temper ature andthe indicated predetermined annealing time, the gro wth regionisproduced having a sufficientthicknessand thus beingparticularly suitable for acting a as the reservoir for theinterstitialcarbon atoms.A further embodiment relates to a method for produc ing anepitaxial silicon carbide layer, in particular comp rising thegrowth substrate as produced by the method describe d hereinbefore. Therefore, the features as described in con nectionwith the method for producing a growth substrate ar e also P2024,0604 WO N / P240008WO01 June 5,2025 -7 -applicable to the method for producing an epitaxial siliconcarbide layer,and vice versa.According to an embodiment of the method for produc ing anepitaxial silicon carbide layer, a growth substrate isprovided comprising silicon carbide with a first do pant andcomprising an initial wafer region and a growth reg ion,wherein a maximum concentration of the first dopant in thegrowth region is higher than a maximum concentratio n of thefirstdopantin the initialwaferregion.According to the embodiment of the method for produ cing anepitaxial silicon carbide layer, the growth substra te isheated to a growth temperature. For example, the gr owthtemperature isequalto the annealing temperature. Alternatively,the growth temperature isdifferent from theannealing temperature, in particular the growth tem peratureis higher than the annealing temperature. Exemplari ly, thegrowth temperature is at least 100°C or at least 20 00°Chigherthan the annealing temperature.According to the embodiment of the method for produ cing anepitaxial silicon carbide layer, the epitaxial sili concarbide layer is applied on the growth region. In p articular,the epitaxial silicon carbide layer is applied to a topsurface of the growth substrate being the top surfa ce of thegrowth region.The epitaxialsilicon carbide layer isin particulardirectlyapplied to the growth region.Exemplarily, a plurality of epitaxial silicon carbi de layersis applied to the growth region, accordingly. A pol ymorphtype ofthe epitaxialsilicon carbide layeristhe hexagonal polytype 4H. P2024,0604 WO N / P240008WO01 June 5,2025 -8 -Advantageously, a further buffer layer can be omitt ed as theepitaxial silicon carbide layer can be directly gro wn on thegrowth region.Exemplarily, when the epitaxial silicon carbide lay er isgrown on the growth region,the growth temperature leadsto adiffusion of the interstitial carbon atoms from the growthregion to the grown epitaxial silicon carbide layer , inparticular during growth thereof. The diffused inte rstitialcarbon atoms advantageously occupy native carbon va cancies.In this way, carbon vacancies are greatly reduced i n thefinished epitaxialsilicon carbide layer.According to a further embodiment of the method for producingan epitaxialsilicon carbide layer,during heating and applying,the carbon in the growth region diffuses to theepitaxial silicon carbide layer, occupying carbon v acanciesin the epitaxial silicon carbide layer. Particularl y, duringthe heating and the application of the epitaxial si liconcarbide layer, the interstitial carbon atoms of the growthregion diffuse into the epitaxial silicon carbide l ayer.According to a further embodiment of the method for producingan epitaxial silicon carbide layer, a maximum conce ntrationof carbon vacancies in the produced epitaxial silic on carbidelayer is less than 10 10 cm - . The provided value for themaximum concentration of carbon vacancies in the pr oducedepitaxial silicon carbide layer is particularly a r esolutionlimitofa corresponding measuring process. P2024,0604 WO N / P240008WO01 June 5,2025 -9 -According to a further embodiment of the method for producingan epitaxial silicon carbide layer, the growth temp erature isatleast1300°C and atmost1500°C.According to a further embodiment of the method for producingan epitaxial silicon carbide layer, the epitaxial s iliconcarbide layer and the growth substrate are produced inseparate chambers.According to a further embodiment of the method for producingan epitaxial silicon carbide layer, the epitaxial s iliconcarbide layer and the growth substrate are produced in thesame chamber. A furtherembodimentrelatesto a growth substrate foranepitaxial silicon carbide layer, which can be or is producedby the method described herein before. Therefore, t hefeatures as described in connection with the method forproducing a growth substrate are also applicable to thegrowth substrate,and vice versa.According to an embodiment, the growth substrate co mprises aninitial wafer region comprising silicon carbide wit h a firstdopant.According to the embodiment, the growth substrate c omprises agrowth region comprising silicon carbide with a fir st dopant.According to the embodiment of the growth substrate , thegrowth region is located on the initial wafer regio n. Inparticular, the growth region and the initial wafer regioneach have a main extension plane in lateral directi ons. Thegrowth region and the initial wafer region are stac ked above P2024,0604 WO N / P240008WO01 June 5,2025 -10 - one anotherin a verticaldirection,perpendicular to the initialwaferregion.According to the embodiment of the growth substrate , amaximum concentration of the first dopant in the gr owthregion is higher than a maximum concentration of th e firstdopantin the initialwaferregion.According to a further embodiment of the growth sub strate,the initial wafer region and the growth region each comprisea firstdopant.According to a further embodiment of the growth sub strate, amaximum concentration ofinterstitialcarbon atoms in thegrowth region is higher than a maximum concentratio n ofinterstitial carbon atoms in the initial wafer regi on.A further embodiment relates to an epitaxial silico n carbidelayer, which can be or is produced by the method de scribedherein before. Therefore, the features as described inconnection with the method for producing an epitaxi al siliconcarbide layerare also applicable to the epitaxial silicon carbide layer,and vice versa.According to an embodiment, the epitaxial silicon c arbidelayer comprises a growth substrate comprising silic on carbidewith a first dopant and comprising an initial wafer regionand a growth region. According to the embodiment,the epitaxialsilicon carbide layercomprisesan epitaxialsilicon carbide layer arranged on the growth region. P2024,0604 WO N / P240008WO01 June 5,2025 -11 -According to an embodiment of the epitaxial silicon carbidelayer,a maximum concentration ofthe firstdopant in thegrowth region is higher than a maximum concentratio n of thefirstdopantin the initialwaferregion.A further embodiment relates to a power semiconduct or device,which comprises the epitaxial silicon carbide layer asdescribed herein before. Therefore, the features as describedin connection with the power semiconductor device a re alsoapplicable to the epitaxialsilicon carbide layer, and vice versa.The term “power” here and in the following, for exa mple,refers to power semiconductor devices adapted for p rocessingvoltagesand currentsofmore than 100 V,e.g.650 V or1200 V and / ormore than 10 A. The epitaxialsilicon carbide layerofthe power semiconductordevice can be processed accordingly. The powersemiconductor device is, for example, a power metalinsulating semiconductor field-effect transistor, p owerMISFET for short. The term MISFET shall also compri se metaloxide semiconductor field-effect transistors, MOSFE Ts, whichhave an oxide as an insulating material at the gate . Thepower semiconductor device may also be an insulated -gatebipolartransistor,IGBT. The accompanying Figuresare included to provide a furtherunderstanding. In the Figures, elements of the same structureand / orfunctionalitymaybe referenced bythe same reference signs.Itisto be understood thatthe embodiments shown inthe Figures are illustrative representations and ar e notnecessarilydrawn to scale. P2024,0604 WO N / P240008WO01 June 5,2025 -12 -Figure 1 shows a flow chart of the method for produ cing agrowth substrate for an epitaxial silicon carbide l ayeraccording to an exemplaryembodiment.Figure 2 shows a flow chart of the method for produ cing anepitaxial silicon carbide layer according to an exe mplaryembodiment. Figures3,4 and 5 show method stagesaccording to Figures1and 2, and in particular a growth substrate in Figu re 3, andan epitaxialsilicon carbide layerin Figure 4. Figure 6 showsa deep-leveltransientspectroscopy measurementforan epitaxialsilicon carbide layer according to an exemplaryembodiment. Figures7 and 8 each show an I-V characteristicof a power semiconductorsemiconductordevice according to an exemplary embodiment.In method step S1 according to the exemplary embodi ment ofFigure 1 an initial wafer 2 is provided, wherein th e initialwafer 2 comprises silicon carbide and wherein the i nitialwafer 2 comprises a first dopant. The initial wafer 2particularly comprises silicon carbide of a hexagon alpolytype 4H.The waferisparticularlyprovided in a chamber,which is equipped for example with a heater and a g as deviceconfigured forproviding a gasatmosphere. Subsequently,in method step S3,the initialwafer 2 isheated to an annealing temperature within a first g asatmosphere,wherein the firstdopantand the first gas P2024,0604 WO N / P240008WO01 June 5,2025 -13 -comprise the same material element. The initial waf er 2 isheated and is exposed to the first gas atmosphere f or apredetermined annealing time. In particular, the fi rst dopantisnitrogen,N,and the firstgasatmosphere isan N2atmosphere.During the heating and the exposure to the firstgas atmosphere, particularly nitrogen accumulates a t a topsurface region ofthe initialwafer2.After the heating and the exposure to the first gasatmosphere,in a method step S3,a growth region 4 foranepitaxial silicon carbide layer 5 is produced, wher ein amaximum concentration of the first dopant of the gr owthregion 4 ishigherthan a maximum concentration of the first dopantin an initialwaferregion 3.In particular, nitrogen accumulates at the top surf ace regionup to a reaction depth, extending from a top surfac e of theinitial wafer 2 towards a bulk of the initial wafer 2. Theregion where the nitrogen accumulatesisformed to the growthregion 4, where the maximum concentration of the fi rst dopantis higher, particularly by at least one order of ma gnitudehigher, than the maximum concentration of the first dopant inthe initialwafer2.The restofthe initialwafer 2 isformed to the initial wafer region 3, where the max imumconcentration of the first dopant is smaller, parti cularly byat least one order of magnitude smaller, than the m aximumconcentration of the first dopant in the growth reg ion 4.The produced growth substrate 1 comprises the growt h region 4and the initial wafer region 3, particularly for an epitaxialsilicon carbide layer 5. The growth region 4 is con figured tobe the region on which the epitaxial silicon carbid e layer 5isgrown directly. P2024,0604 WO N / P240008WO01 June 5,2025 -14 -In method step S4 according to the exemplary embodi ment ofFigure 2, a growth substrate 1 comprising silicon c arbidewith a first dopant and comprising an initial wafer region 3and a growth region 4 is provided. The growth subst rate 1 isparticularlythe growth substrate 1 asproduced in connectionwith Figure 1. The wafer is particularly provided i n achamber, which can be a different chamber than acco rding tothe method of Figure 1, which is equipped with a fu rtherheater and an epitaxial evaporation device, for exa mple.Therefore, the maximum concentration of the first d opant inthe growth region 4 is higher than the maximum conc entrationofthe firstdopantin the initialwaferregion 3. Themaximum concentration of the material element of th e firstdopantin the growth region 4 leadsto a strain in a crystal structure ofthe silicon carbide,which leadsto a formationof interstitial carbon atoms. In particular, a maxi mumconcentration of interstitial carbon atoms in the g rowthregion 4 is at least 1·10 11 cm - and / or at most 1·10 13 cm -3.The growth substrate 1 is heated to a growth temper ature inmethod step S5. The growth temperature is, for exam ple,higherthan the annealing temperature according to the method ofFigure 1.During the heating to the growth temperature, the e pitaxialsilicon carbide layer 5 is applied on the growth re gion 4.When the epitaxial silicon carbide layer 5 is appli ed, inparticular is grown, on the growth region 4, the gr owthtemperature leads to a diffusion of the interstitia l carbonatoms from the growth region 4 to the epitaxial sil icon P2024,0604 WO N / P240008WO01 June 5,2025 -15 -carbide layer 5, in particular during an applicatio n,particularduring a growth,thereof.The diffusedinterstitial carbon atoms occupy native carbon vaca ncies inthe epitaxial silicon carbide layer 5. In this way, carbonvacancies are greatly reduced in the finished epita xialsilicon carbide layer 5. A maximum concentration of carbonvacancies in the produced epitaxial silicon carbide layer 5is less than 10 10 cm -3.Figures 3 and 4 correspond to the method steps of F igure 1,particularly to method steps S1 and S2, respectivel y. Theinitialwafer2 according to Figure 3 isformed of siliconcarbide, which is doped with a first dopant. The in itialwafer 2 has a main extension direction, wherein a t op surfaceis formed of a main surface extending along the mai nextension direction.The growth substrate 1 according to Figure 4 compri ses aninitial wafer region 3 and a growth region 4, which arestacked above one another perpendicular to the main extensiondirection. A stacking direction is defined as a ver ticaldirection. A height of the growth region 4 in the v erticaldirection is smaller, particularly at least one ord er ofmagnitude smaller, than a height of the initial waf er region3 in the verticaldirection. Figure 5 correspondsto the method stepsofFigure 2,whereinthe epitaxial silicon carbide layer 5 is applied on thegrowth region 4. Interstitial carbon atoms in the g rowthregion 4 are indicated as black dots. Carbon vacanc ies in theepitaxialsilicon carbide layer5 are indicated as blackcircles. During heating to the growth temperature a nd duringthe application of the epitaxial silicon carbide la yer 5, the P2024,0604 WO N / P240008WO01 June 5,2025 -16 -interstitial carbon atoms of the growth region 4 di ffuse tothe carbon vacancies in the epitaxial silicon carbi de layer 5and occupythem,asindicated byarrows. In the diagram ofFigure 6,deep-leveltransientspectroscopy, DLTS, values in pF are indicated on t he y-axisand a corresponding measurement temperature is indi cated onthe x-axis. A measurement curve comprising a Z 1 / 2 peak ischaracteristic of a typical grown epitaxial silicon carbidelayer. A measurement curve comprising an ON1 and an ON2 peakis characteristic of a grown epitaxial silicon carb ide layer5 according to an exemplaryembodiment,i.e.being grown onthe growth region 4. Exemplarily, the Z 1 / 2 peak ischaracteristicofthe presence ofcarbon vacancies in theepitaxial silicon carbide layer, wherein the ON1 an d the ON2peak is characteristic of no presence of carbon vac ancies inthe epitaxial silicon carbide layer 5. In particula r, the ON1and the ON2 peakrelate to two electricallyactive levels which are known to be related to carbon.The use of the epitaxial silicon carbide layer 5 de scribedherein before, particularly in connection with Figu re 5 canbe employed fora powersemiconductordevice,such asaMOSFET, in particular a 4H-SiC MOSFET. The reductio n ofcarbon vacancies in the epitaxial silicon carbide l ayer 5advantageously leads to a decrease in an on-resista nce, R ON,and to an improvement of the electrical characteris tics ofthe powersemiconductordevice asshown in Figures 7 and 8.In the diagram of Figure 7, a gate source current, I GS, givenin A / cm 2 is indicated on the y-axis and a corresponding gat esource voltage, V GS, given in V is indicated on the x-axis. P2024,0604 WO N / P240008WO01 June 5,2025 -17 -The two curves are characteristic of a drain source voltageof10 V ata temperature of25°C.In the diagram of Figure 8, a drain source current, I DS,given in A / cm 2 is indicated on the y-axis and a correspondingdrain source voltage, V DS, given in V is indicated on the x-axis. The two curves are characteristic of a gate s ourcevoltage of15 V ata temperature of25°C.In both Figures 7 and 8, the upper curves are chara cteristicof the epitaxial silicon carbide layer 5 which is g rown onthe growth region 4 as described herein above. In c ontrast,the lower curves are characteristic of typical epit axialsilicon carbide layers 5 which are not grown on the growthregion 4.The exemplary embodiments, in particular features o f theexemplary embodiments, of the Figures can be combin ed withone another.

[0002] P2024,0604 WO N / P240008WO01 June 5,2025 -18 - Reference Signs 1 growth substrate 2 initialwafer 3 initialwaferregion 4 growth region 5 epitaxialsilicon carbide layer S1..S5 method steps

Claims

P2024,0604 WO N / P240008WO01 June 5,2025 -19 - Claims 1.Method forproducing a growth substrate (1)for an epitaxialsilicon carbide layer(5),comprising:- providing an initial wafer (2), wherein the initi al wafer(2) comprises silicon carbide and wherein the initi al wafer(2)comprisesa firstdopant,and- heating the initial wafer (2) to an annealing tem peraturewithin a first gas atmosphere, wherein the first do pant andthe firstgascomprise the same materialelement,- such that a growth region (4) for the epitaxial s iliconcarbide layer(5)isproduced,wherein a maximumconcentration of the first dopant of the growth reg ion (4) ishigher than a maximum concentration of the first do pant in aninitialwaferregion (3),and wherein- the growth region (4) has a thickness of at least 0.01 μmand / oratmost1 μm. 2.Method according to claim 1,wherein- a maximum concentration of interstitial carbon at oms in thegrowth region (4) is higher than a maximum concentr ation ofinterstitial carbon atoms in the initial wafer regi on (3).

3. Method according to one of claims 1 or 2, wherei n- a polymorph type of the silicon carbide is a hexa gonalpolytype 4H,and / or- the first dopant and the first gas comprise nitro gen as thematerialelement.

4. Method according to one of claims 1 to 3, wherei n- a maximum concentration of the first dopant in th e initialwafer region (3) is at most 4·10 18 cm -3 , and / orP2024,0604 WO N / P240008WO01 June 5,2025 -20 -- a maximum concentration of the first dopant in th e growthregion (4) is at least 5·10and / or at most 5·10 20 cm -3.

5. Method according to one of claims 1 to 4, wherei n- the annealing temperature is at least 1000°C and / or at most1500°C,and / or- the initial wafer (2) is heated for a predetermin edannealing time of at least 0.5 h and / or at most 5 h .

6. Method according to one of claims 1 to 5, wherei n- the growth region (4) has a thickness of at least 0.05 μmand / oratleast0.1 μm.

7. Method for producing an epitaxial silicon carbid e layer(5),comprising:- providing a growth substrate (1) comprising silic on carbidewith a first dopant and comprising an initial wafer region(3) and a growth region (4), wherein a maximum conc entrationof the first dopant in the growth region (4) is hig her than amaximum concentration of the first dopant in the in itialwaferregion (3),- heating the growth substrate (1) to a growth temp erature,and -applying the epitaxialsilicon carbide layer(5) on the growth region (4). 8.Method according to claim 7,wherein- during heating and applying, the carbon in the gr owthregion (4) diffuses to the epitaxial silicon carbid e layer(5), occupying carbon vacancies in the epitaxial si liconcarbide layer(5).

9. Method according to one of claims 7 or 8, wherei nP2024,0604 WO N / P240008WO01 June 5,2025 -21 -- a maximum concentration of carbon vacancies in th e producedepitaxial silicon carbide layer (5) is less than 10 10.

10. Method according to one of claims 7 to 9, where in-the growth temperature isatleast1300°C and at most 1500°C.

11. Method according to one of claims 7 to 10, wher ein- the epitaxial silicon carbide layer (5) and the g rowthsubstrate (1) are produced in separate chambers, or- the epitaxial silicon carbide layer (5) and the g rowthsubstrate (1)are produced in the same chamber.

12. Growth substrate (1) for an epitaxial silicon c arbidelayer(5),comprising- an initial wafer region (3) comprising silicon ca rbide witha firstdopant,and- a growth region (4) comprising silicon carbide wi th a firstdopant,wherein- the growth region (4) is located on the initial w aferregion (3),- the growth region (4) has a thickness of at least 0.01 μmand / oratmost1 μm, and- a maximum concentration of the first dopant in th e growthregion (4) is higher than a maximum concentration o f thefirstdopantin the initialwaferregion (3).

13. Growth substrate (1) according to claim 12, whe rein- the initial wafer region (3) and the growth regio n (4) eachcomprise a firstdopant,and- a maximum concentration of interstitial carbon at oms in thegrowth region (4) is higher than a maximum concentr ation ofinterstitial carbon atoms in the initial wafer regi on (3).P2024,0604 WO N / P240008WO01 June 5,2025 -22 -14. Epitaxial silicon carbide layer (5), comprising- a growth substrate (1) comprising silicon carbide with afirst dopant and comprising an initial wafer region (3) and agrowth region (4),and- an epitaxial silicon carbide layer (5) arranged o n thegrowth region (4),wherein- the growth region (4) has a thickness of at least 0.01 μmand / oratmost1 μm, and- a maximum concentration of the first dopant in th e growthregion (4) is higher than a maximum concentration o f thefirstdopantin the initialwaferregion (3). 15.Powersemiconductordevice,comprising -an epitaxialsilicon carbide layer(5)according to claim

Images