WO2000012784A1 - Method for producing a defect-free monocrystalline silicon carbide layer - Google Patents

Method for producing a defect-free monocrystalline silicon carbide layer Download PDF

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Publication number
WO2000012784A1
WO2000012784A1 PCT/DE1999/002671 DE9902671W WO0012784A1 WO 2000012784 A1 WO2000012784 A1 WO 2000012784A1 DE 9902671 W DE9902671 W DE 9902671W WO 0012784 A1 WO0012784 A1 WO 0012784A1
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Prior art keywords
substrate
layer
surface layer
sic
porous surface
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PCT/DE1999/002671
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German (de)
French (fr)
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Klaus Heyers
Wilhelm Frey
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Robert Bosch Gmbh
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Publication of WO2000012784A1 publication Critical patent/WO2000012784A1/en

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    • C—CHEMISTRY; METALLURGY
    • C30—CRYSTAL GROWTH
    • C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
    • C30B23/00—Single-crystal growth by condensing evaporated or sublimed materials
    • C30B23/02—Epitaxial-layer growth
    • C—CHEMISTRY; METALLURGY
    • C30—CRYSTAL GROWTH
    • C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
    • C30B25/00—Single-crystal growth by chemical reaction of reactive gases, e.g. chemical vapour-deposition growth
    • C30B25/02—Epitaxial-layer growth
    • C—CHEMISTRY; METALLURGY
    • C30—CRYSTAL GROWTH
    • C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
    • C30B29/00—Single crystals or homogeneous polycrystalline material with defined structure characterised by the material or by their shape
    • C30B29/10—Inorganic compounds or compositions
    • C30B29/36—Carbides

Definitions

  • the invention is based on a method for producing a defect-free silicon carbide layer according to the type of the main claim, which have hitherto only been available as surface layers of afer made from silicon carbide single crystals.
  • the use of SiC components is limited by the currently extremely high costs for the SiC single crystals. It has therefore been attempted for a long time to deposit low-defect SiC layers on inexpensive silicon wafers, so that the cost advantage of a cheap substrate with the physical advantages of semiconductors with a large band gap, e.g. SiC, is connected. In all direct deposition processes, however, the large lattice mismatch of almost 20% leads between that
  • the inventive method of independent method claim 1 has the advantage that thanks to the porous substrate surface which is generated by anodization (electrochemical etching), the elastic properties of the substrate, in particular an Si substrate, are modified, but the crystal structure is not damaged. Similar to a sponge structure, the porous silicon layer is able to relieve tension through elastic deformation. If SiC is deposited on this porous substrate surface, the porous serves
  • Substrate surface layer as a nucleation nucleus for a cubic crystal lattice of a single-crystal SiC layer and is able to compensate for the lattice mismatch to a large extent and thus greatly reduce the occurrence of defects due to lattice mismatch. Because porous layers can be produced on large silicon wafers and the deposition of SiC on large silicon wafers is possible, this method enables large-area SiC layers with a low defect density to be produced.
  • FIG. 1 shows an etching basin used in the manufacturing method according to the invention.
  • FIG. 2 shows a semiconductor produced according to the invention.
  • the porous surface layer shown in the enlarged representation according to FIG. 2 on the surface 12 of a Substrate wafer 10 is produced by anodization.
  • the substrate wafer 10 is electrically contacted on the back and exposed on the front to an electrolyte in the form of dilute hydrofluoric acid (5-25% in water with ethanol or methanol).
  • the contact can optionally be made via electrolyte in the etching basin 101, as shown in FIG. 1, or via metal contact by means of a metal ring which is produced by metallizing the back of the substrate wafer 10, for example using Al, Pt, Cr or Cu.
  • FIG. 1 shows, a current flow is impressed between the electrolyte of the etching medium 108 and the substrate wafer 104, the typical values of which are between 1 and 50 mA / cm 2 .
  • the substrate surface 12 of the substrate disk 103 is now evenly removed by means of electropolishing or, if the abovementioned upper limit of the current coating is observed, locally etched from surface defects in the form of thin channels.
  • porous Si both p-doped silicon and n-doped silicon can be used as the substrate. Since the silicon is etched thanks to defect electrons (holes), holes have to be created in the n-docuated Si, in particular by lighting.
  • the pore size of the porous surface layer 14 ranges from a few nm to approximately 100 nm.
  • the density of these channels is generally so great that a porous layer with degrees of porosity of over 90% is formed, the density of which depends on the etching time.
  • the concentration of the hydrofluoric acid solution and the chosen potential or current density can influence both the porosity (from ⁇ 10 to over 90%) and the geometry of the remaining substrate areas. Enlarging the pores enables effective stress absorption in the SiC Deposition 16 on the porous surface layer 14.
  • the mechanical stability of a highly porous layer is relatively low, which means that a mechanical lift off
  • a low-porosity layer is less suitable for stress absorption, but enables the deposition of high-quality epitaxial layers, since in this case more germ cells are available to grow a high-quality layer. For this reason, a porosity of the porous surface layer 14 of 10 to 60% is preferred, in particular 20 to 50%.
  • Porosity on the surface 12 of the substrate wafer 10 up to large degrees of porosity at the transition to bulk silicon is advantageous in order to ensure both good stress decoupling and a high level directly on the surface on which epitaxial deposition is to be carried out
  • the porous areas are monocrystalline and have the same crystal structure as the underlying compact substrate 10.
  • the thickness of the porous surface layer 14 produced is in the range from 100 nm, preferably from 500 nm to 5 ⁇ m.
  • porous silicon Due to the high reactivity of the porous silicon, this is advantageous shortly before epitaxy e.g. dipped in hydrofluoric acid to remove the native oxide.
  • hydrogen can be used as the carrier gas during the deposition process.
  • the SiC layer 16 is separated from the gas phase as follows:
  • the substrate wafer 10 is exposed to an atmosphere which, in addition to a carrier gas, contains gases which contain the starting materials Si and C.
  • the gases are split up thermally or by means of plasma support and reach the surface layer 14 by diffusion.
  • the substrate 10 is also kept at an elevated temperature (> 200-1000 ° C.) in order to operate the deposition reaction close to the thermodynamic equilibrium.
  • the substrate temperature can be reduced by bombarding the surface 12 with low-energy ions, which are generated, for example, in a plasma and by means of a
  • Substrate bias on the sample Due to the interaction of the ions with the crystal atoms of the substrate, energy is coupled in close to the surface, which leads to heating of only the substrate surface 12 without thermally stressing the entire structure.
  • the SiC layer 16 can also be deposited by means of molecular beam epitaxy (MBE).
  • MBE molecular beam epitaxy
  • Substrate atoms so strong that there are no collisions between the particles.
  • the transport of the evaporated atoms is therefore determined exclusively by the thermal energy of the source.
  • the substrate temperature can reach a few hundred Degrees can be reduced, down to temperatures of around 400 ° C, while high-quality layers are realized.
  • substrates made of Ge can also be used for the method according to the invention for producing low-defect SiC layers, since they have similar crystal structures.
  • the porous surface layer 14 is generated in an apparatus according to FIG. 1 in an etching basin 101.
  • the silicon wafer 103 is fastened by means of a holder 102 and divides the etching basin 101 into two sub-basins 111 and 112.
  • the first sub-basin 111 is connected via the cathode 109 to the negative pole 106 of a voltage source.
  • the positive pole 107 of this voltage source is electrically connected to the anode 110, which is located in the second sub-basin.
  • the electrodes are made from a palladium-platinum alloy or preferably from pure platinum.
  • the partial pools 111, 112 are filled with the etching solution, the typical composition of which is 25% hydrofluoric acid, 25% water and 50% ethanol. At current densities of a few 10 mA / cm 2 , after anodizing for a few minutes, typical porous layer thicknesses in the range of a few micrometers are generated.
  • the silicon wafer 103 is then exposed to an atmosphere which, in addition to a carrier gas, for example hydrogen, contains gases which contain the starting materials Si and C, usually SiH 4 , SiCl 2 H 2 and C 2 H 2 or similar hydrocarbons.
  • gases which contain the starting materials Si and C, usually SiH 4 , SiCl 2 H 2 and C 2 H 2 or similar hydrocarbons.
  • the gases are split up thermally or by means of plasma support and the substrate 10, 103 is kept at a high temperature, which is from 200 ° to 1000 ° C.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Inorganic Chemistry (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • General Chemical & Material Sciences (AREA)
  • Crystals, And After-Treatments Of Crystals (AREA)

Abstract

The invention relates to a method for producing a defect-free, monocrystalline, preferably large-surface, silicon carbide (SiC) layer on a substrate, preferably on an Si substrate, especially for use in power electronics and sensors. The method consists of the anodization of a porous surface layer (14) on the substrate (10) on which an SiC layer (16) is precipitated from a gas phase comprising the parent substances Si and C in a carrier gas. Alternatively, it is possible to carry out the precipitation of the SiC layer (16) using molecular beam epitaxy.

Description

Verfahren zur Herstellung einer defektarmen, einkristallinen Silizium-Carbid-SchichtProcess for producing a low-defect, single-crystal silicon carbide layer
Stand der TechnikState of the art
Die Erfindung geht aus von einem Verfahren zur Herstellung einer defektarmen Silizium-Carbid-Schicht nach der Gattung des Hauptanspruchs, welche bislang nur als Oberflächenschichten von aus Silizium-Carbid-Einkristallen hergestellten afern zur Verfügung stehen. Der Einsatz von SiC-Bauelemente wird durch die derzeit extrem hohen Kosten für die SiC-Einkristalle beschränkt. Es wird daher seit längerem versucht, defektarme SiC-Schichten auf preisgünstigen Siliziumwafern abzuscheiden, damit der Kostenvorteil eines billigen Substrates mit den physikalischen Vorteilen von Halbleitern mit großem Bandabstand, wie z.B. SiC, verbunden wird. Bei allen direkten Abscheideverfahren führt jedoch die große Gitterfehlanpassung von nahezu 20 % zwischen demThe invention is based on a method for producing a defect-free silicon carbide layer according to the type of the main claim, which have hitherto only been available as surface layers of afer made from silicon carbide single crystals. The use of SiC components is limited by the currently extremely high costs for the SiC single crystals. It has therefore been attempted for a long time to deposit low-defect SiC layers on inexpensive silicon wafers, so that the cost advantage of a cheap substrate with the physical advantages of semiconductors with a large band gap, e.g. SiC, is connected. In all direct deposition processes, however, the large lattice mismatch of almost 20% leads between that
Siliziumsubstrat und der SiC Epitaxie-Schicht zu sehr großen Defektdichten, die eine Anwendung dieses Materials bei Elektronikbauteilen bisher nicht erlaubten. Vorteile der ErfindungSilicon substrate and the SiC epitaxial layer to very large defect densities, which previously have not allowed the use of this material in electronic components. Advantages of the invention
Das erfindungsgemäße Verfahren des unabhängigen Verfahrensanspruchs 1 hat den Vorteil, daß dank der porösen Substratoberfläche die durch Anodisierung (elektrochemisches Ätzen) erzeugt wird, die elastischen Eigenschaften des Substrats, insbesondere eines Si-Substrats, modifiziert sind, die Kristallstruktur jedoch nicht geschädigt ist. Ähnlich einer Schwammstruktur ist die poröse Siliziumschicht in der Lage, Verspannungen durch elastische Verformung abzubauen. Wenn auf dieser porösen Substratoberfläche SiC abgeschieden wird, dient die poröseThe inventive method of independent method claim 1 has the advantage that thanks to the porous substrate surface which is generated by anodization (electrochemical etching), the elastic properties of the substrate, in particular an Si substrate, are modified, but the crystal structure is not damaged. Similar to a sponge structure, the porous silicon layer is able to relieve tension through elastic deformation. If SiC is deposited on this porous substrate surface, the porous serves
Substratoberflächenschicht als Nukleationskeim für ein kubisches Kristallgitter einer einkristallinien SiC-Schicht und ist in der Lage, die Gitterfehlanpassung zu einem großen Teil aufzufangen und somit die Entstehung von gitterfehlanpaεsungsbedingten Defekten stark zu verringern. Dadurch, daß poröse Schichten auf großen Siliziumscheiben erzeugt werden können und die Abscheidung von SiC auf großen Siliziumscheiben möglich ist, wird durch dieses Verfahren eine Herstellung von großflächigen SiC-Schichten mit geringer Defektdichte möglich.Substrate surface layer as a nucleation nucleus for a cubic crystal lattice of a single-crystal SiC layer and is able to compensate for the lattice mismatch to a large extent and thus greatly reduce the occurrence of defects due to lattice mismatch. Because porous layers can be produced on large silicon wafers and the deposition of SiC on large silicon wafers is possible, this method enables large-area SiC layers with a low defect density to be produced.
Zeichnungdrawing
Die Figur 1 zeigt ein beim erfindungesgemäßen Herstellungsverfahren eingesetztes Ätzbecken. Die Figur 2 stellt einen erfindungsgemäß erzeugten Halbleiter dar.FIG. 1 shows an etching basin used in the manufacturing method according to the invention. FIG. 2 shows a semiconductor produced according to the invention.
Beschreibung von AusführungsbeispielenDescription of exemplary embodiments
Die in der vergrößerten Darstellung gemäß Figur 2 gezeigte poröse Oberflächenschicht auf der Oberfläche 12 einer Substratscheibe 10 wird durch Anodisierung erzeugt. Die Substratscheibe 10 wird rückseitig elektrisch kontaktiert und vorderseitig einem Elektrolyten in Form von verdünnter Flußsäure (5 - 25 % in Wasser mit Ethanol oder Methanol) ausgesetzt. Die Kontaktierung kann wahlweise über Elektrolyt im Ätzbecken 101, wie in Figur 1 abgebildet, erfolgen oder über Metallkontakt mittels einem Metallring, der durch Metallisierung der Rückseite der Substratscheibe 10, beispielsweise mit AI, Pt , Cr oder Cu erzeugt wird.The porous surface layer shown in the enlarged representation according to FIG. 2 on the surface 12 of a Substrate wafer 10 is produced by anodization. The substrate wafer 10 is electrically contacted on the back and exposed on the front to an electrolyte in the form of dilute hydrofluoric acid (5-25% in water with ethanol or methanol). The contact can optionally be made via electrolyte in the etching basin 101, as shown in FIG. 1, or via metal contact by means of a metal ring which is produced by metallizing the back of the substrate wafer 10, for example using Al, Pt, Cr or Cu.
Wie Figur 1 zeigt, wird ein Stromfluß zwischen dem Elektrolyten des Ätzmediums 108 und der Substratscheibe 104 aufgeprägt, dessen typische Werte zwischen 1 und 50 mA/cm2 liegen. Je nach angelegtem elektrischem Potential wird nun die Substratoberfläche 12 der Substratscheibe 103 mittels Elektropolitur gleichmäßig abgetragen oder, bei Einhaltung der zuvor genannten Obergrenze des Strombelags , startend von Oberflächendefekten lokal in Form dünner Kanäle angeätzt. Zur Herstellung von porösem Si können sowohl p-dotiertes Silizium als n-dotiertes Silizium als Substrat eingesetzt werden. Da das Ätzen des Siliziums dank Defektelektronen (Löchern) erfolgt, müssen jedoch im n-docierten Si Löcher erzeugt werden, insbesondere durch Beleuchtung.As FIG. 1 shows, a current flow is impressed between the electrolyte of the etching medium 108 and the substrate wafer 104, the typical values of which are between 1 and 50 mA / cm 2 . Depending on the applied electrical potential, the substrate surface 12 of the substrate disk 103 is now evenly removed by means of electropolishing or, if the abovementioned upper limit of the current coating is observed, locally etched from surface defects in the form of thin channels. For the production of porous Si, both p-doped silicon and n-doped silicon can be used as the substrate. Since the silicon is etched thanks to defect electrons (holes), holes have to be created in the n-docuated Si, in particular by lighting.
Die Porengröße der porösen Oberflächenschicht 14 reicht von wenigen nm bis zu ca. lOOnm. Die Dichte dieser Kanäle ist im allgemeinen so groß, daß eine poröse Schicht mit Porositätsgraden bis über 90 % entsteht, deren Dichte von der Ätzdauer abhängt. Hierbei kann durch die Konzentration der Flußsäure-Lösung und das gewählte Potential- bzw. die Stromdichte sowohl die Porosität (von <10 bis über 90 %) als auch die Geometrie der verbleibenden Subtratbereiche beeinflußt werden. Eine Vergrößerung der Poren ermöglicht eine effektive Streßaufnahme bei der erfindungsgemäßen SiC- Abscheidung 16 auf der porösen Oberflächenschicht 14. Aber die mechanische Stabilität einer hochporöεen Schicht ist relativ gering, wodurch ein mechanisches Abheben einerThe pore size of the porous surface layer 14 ranges from a few nm to approximately 100 nm. The density of these channels is generally so great that a porous layer with degrees of porosity of over 90% is formed, the density of which depends on the etching time. The concentration of the hydrofluoric acid solution and the chosen potential or current density can influence both the porosity (from <10 to over 90%) and the geometry of the remaining substrate areas. Enlarging the pores enables effective stress absorption in the SiC Deposition 16 on the porous surface layer 14. However, the mechanical stability of a highly porous layer is relatively low, which means that a mechanical lift off
Schicht, die sich über einer hochporösen Schicht befindet, stattfinden kann. Eine niedrigporöse Schicht ist zur Streßaufnahme weniger geeignet, ermöglicht aber die Abscheidung qualitativ guter epitaktischer Schichten, da in diesem Falle mehr Keimzellen zur Verfügung stehen, um eine hochwertige Schicht wachsen zu lassen. Deswegen wird eine Porosität der porösen Oberflächenschicht 14 von 10 bis 60 % bevorzugt, insbesondere von 20 bis 50 %.Layer that is over a highly porous layer can take place. A low-porosity layer is less suitable for stress absorption, but enables the deposition of high-quality epitaxial layers, since in this case more germ cells are available to grow a high-quality layer. For this reason, a porosity of the porous surface layer 14 of 10 to 60% is preferred, in particular 20 to 50%.
Der Einbau eines Poroεitätsgradienten von niedrigerThe incorporation of a porosity gradient of lower
Porosität an der Oberfläche 12 der Substratscheibe 10 bis zu großen Porositätsgraden am Übergang zum Bulksilizium ist vorteilhaft, um sowohl gute Streßentkopplung zu gewährleisten als auch unmittelbar an der Oberfläche, auf der epitaktisch abgeschieden werden soll, eine hohePorosity on the surface 12 of the substrate wafer 10 up to large degrees of porosity at the transition to bulk silicon is advantageous in order to ensure both good stress decoupling and a high level directly on the surface on which epitaxial deposition is to be carried out
Keimzellendichte für hochwertige Schichten zu haben. Die porösen Bereiche sind monokristallin und haben die gleiche Kristallstruktur wie das darunterliegende kompakte Substrat 10. Die Dicke der erzeugten porösen Oberflächenschicht 14 liegt im Bereich von 100 nm, vorzugsweise von 500nm bis 5μ.m.To have germ cell density for high-quality layers. The porous areas are monocrystalline and have the same crystal structure as the underlying compact substrate 10. The thickness of the porous surface layer 14 produced is in the range from 100 nm, preferably from 500 nm to 5 μm.
Aufgrund der hohen Reaktivität des porösen Siliziums wird dieses kurz vor Epitaxie vorteilhaft z.B. in Flußsäure getaucht, um das native Oxid zu entfernen. Alternativ dazu kann mit Wasserstoff als Trägergaε während des Abscheidungsverfahren gearbeitet werden.Due to the high reactivity of the porous silicon, this is advantageous shortly before epitaxy e.g. dipped in hydrofluoric acid to remove the native oxide. Alternatively, hydrogen can be used as the carrier gas during the deposition process.
Die Abεcheidung der SiC-Schicht 16 aus der Gasphase erfolgt folgendermaßen : Die Substratscheibe 10 wird einer Atmosphäre ausgesetzt, die neben einem Trägergas Gase enthält, die die Ausgangsstoffe Si und C enthalten. Die Gase werden thermisch oder mittels Plasmaunterstützung aufgespalten und gelangen mittels Diffusion zur Oberflächenschicht 14. Das Substrat 10 wird ebenfalls auf erhöhter Temperatur gehalten (> 200 - 1000 °C) , um derart die Abεcheidereaktion nahe am thermodynamisehen Gleichgewicht zu betreiben. Gleichzeitig ermöglicht die erhöhte Oberflächendiffusion der Si- und C-Atome den Aufbau epitaktischer Schichten. Die Reduzierung der Substrattemperatur ist möglich durch einen Beschüß der Oberfläche 12 mit niederenergetiεchen Ionen,, die z.B. in einem Plasma erzeugt werden und mittels einerThe SiC layer 16 is separated from the gas phase as follows: The substrate wafer 10 is exposed to an atmosphere which, in addition to a carrier gas, contains gases which contain the starting materials Si and C. The gases are split up thermally or by means of plasma support and reach the surface layer 14 by diffusion. The substrate 10 is also kept at an elevated temperature (> 200-1000 ° C.) in order to operate the deposition reaction close to the thermodynamic equilibrium. At the same time, the increased surface diffusion of the Si and C atoms enables the formation of epitaxial layers. The substrate temperature can be reduced by bombarding the surface 12 with low-energy ions, which are generated, for example, in a plasma and by means of a
Substratvorspannung auf die Probe geleitet werden. Durch die Wechselwirkung der Ionen mit den Kristallatomen des Substrates wird oberflächennah Energie eingekoppelt, die zu einer Aufheizung nur der Substratoberfläche 12 führt, ohne das gesamte Gefüge thermisch zu belasten. Durch dieseSubstrate bias on the sample. Due to the interaction of the ions with the crystal atoms of the substrate, energy is coupled in close to the surface, which leads to heating of only the substrate surface 12 without thermally stressing the entire structure. Through this
Methode ist es möglich, die im allgemeinen notwendige hohe Substrattemperatur, die für gute Schichtqualität erforderlich ist, zu reduzieren, und damit einer Schädigung der empfindlichen porösen Siliziumschicht vorzubeugen.Method, it is possible to reduce the high substrate temperature required in general for good layer quality, and thus to prevent damage to the sensitive porous silicon layer.
Die Abscheidung der SiC-Schicht 16 kann auch mittels Molekularstrahl-Epitaxie (MBE) erfolgen. Diese Weiterentwicklung der Aufdampftechnik, deren gesamter Vorgang im Ultrahochvakuum abläuft, erhöht die freie Weglänge der von der Elektronenkanone abgedampftenThe SiC layer 16 can also be deposited by means of molecular beam epitaxy (MBE). This further development of vapor deposition technology, the entire process of which takes place in an ultra-high vacuum, increases the free path of the vaporized by the electron gun
Substratatome so stark, daß keine Kollisionen der Teilchen vorkommen. Deshalb ist der Transport der abgedampften Atome ausschließlich von der thermischen Energie der Quelle bestimmt. Die Substrattemperatur kann auf wenige hundert Grad reduziert werden, bis herab zu Temperaturen um 400 °C, gleichzeitig werden hochwertige Schichten realisiert. AlsSubstrate atoms so strong that there are no collisions between the particles. The transport of the evaporated atoms is therefore determined exclusively by the thermal energy of the source. The substrate temperature can reach a few hundred Degrees can be reduced, down to temperatures of around 400 ° C, while high-quality layers are realized. As
Substrat für das erfindungsgemäße Verfahren zur Herstellung von defektarmen SiC-Schichten können neben Scheiben aus Si, insbesondere p-dotiertem Si, auch Substrate aus Ge eingesetzt werden, denn sie haben ähnliche Kristallεtrukturen.In addition to disks made of Si, in particular p-doped Si, substrates made of Ge can also be used for the method according to the invention for producing low-defect SiC layers, since they have similar crystal structures.
Die poröse Oberflächenschicht 14 wird bei einer Vorrichtung gemäß Figur 1 in einem Ätzbecken 101 erzeugt. Die Siliziumscheibe 103 wird mittels einer Halterung 102 befestigt und teilt das Ätzbecken 101 in zwei Teilbecken 111 und 112. Das erste Teilbecken 111 iεt über die Kathode 109 mit dem Minuspol 106 einer Spannungsquelle verbunden. Der Pluspols 107 dieser Spannungsquelle iεt mit der Anode 110, die sich im zweiten Teilbecken befindet, elektrisch verbunden. Die Elektroden sind auε einer Palladium- Platin- Legierung oder vorzugsweise aus reinem Platin. Die Teilbecken 111, 112 εind mit der Ätzlösung ausgefüllt, deren typische Zusammensetzung 25 % Flußsäure, 25 % Wasser und 50 % Ethanol ist. Bei Stromdichten von einigen 10 mA/cm2 , nach Anodisierung von wenigen Minuten, werden typische poröse Schichtdicken im Bereich einiger Mikrometer erzeugt .The porous surface layer 14 is generated in an apparatus according to FIG. 1 in an etching basin 101. The silicon wafer 103 is fastened by means of a holder 102 and divides the etching basin 101 into two sub-basins 111 and 112. The first sub-basin 111 is connected via the cathode 109 to the negative pole 106 of a voltage source. The positive pole 107 of this voltage source is electrically connected to the anode 110, which is located in the second sub-basin. The electrodes are made from a palladium-platinum alloy or preferably from pure platinum. The partial pools 111, 112 are filled with the etching solution, the typical composition of which is 25% hydrofluoric acid, 25% water and 50% ethanol. At current densities of a few 10 mA / cm 2 , after anodizing for a few minutes, typical porous layer thicknesses in the range of a few micrometers are generated.
Die Siliziumscheibe 103 wird dann einer Atmosphäre ausgesetzt, die neben einem Trägergas, z.B. Wasserstoff, Gase enthält, die die Ausgangsstoffe Si und C enthalten, üblicherweise SiH4, SiCl2H2 und C2H2 oder ähnliche Kohlenwasserstoffe. Die Gase werden thermisch oder mittels Plasmaunterstützung aufgespalten und das Substrat 10, 103 auf hoher Temperatur gehalten, die bei 200° bis 1000 °C liegt. The silicon wafer 103 is then exposed to an atmosphere which, in addition to a carrier gas, for example hydrogen, contains gases which contain the starting materials Si and C, usually SiH 4 , SiCl 2 H 2 and C 2 H 2 or similar hydrocarbons. The gases are split up thermally or by means of plasma support and the substrate 10, 103 is kept at a high temperature, which is from 200 ° to 1000 ° C.

Claims

Anεprüche Claims
1. Verfahren zur Herεtellung einer defektarmen, einkristallinen, vorzugsweise großflächigen Siliziumcarbid (SiC) -Schicht auf einem Substrat, vorzugsweise auf einem Si-Substrat, insbesondere für Anwendungen in der Leistungεelektronik und Senεorik, dadurch gekennzeichnet, daß durch Anodisierung eine poröεe Oberflächenschicht (14) auf dem Substrat (10) erzeugt wird, auf welcher eine SiC-Schicht (16) aus einer Gasphase mit den Ausgangsstoffen Si und C in einem Trägergas abgeschieden wird.1. A process for producing a low-defect, single-crystalline, preferably large-area silicon carbide (SiC) layer on a substrate, preferably on a Si substrate, in particular for applications in power electronics and sensor technology, characterized in that a porous surface layer (14) is produced by anodization. is produced on the substrate (10), on which an SiC layer (16) is deposited from a gas phase with the starting materials Si and C in a carrier gas.
2. Verfahren nach Anspruch 1, dadurch gekennzeichnet, daß das Aufspalten der Silizium und Kohlenstoff enthaltenden Gase thermiεch oder mittels Plasmaunterstützung erfolgt.2. The method according to claim 1, characterized in that the splitting of the silicon and carbon-containing gases takes place thermiεch or by means of plasma support.
3. Verfahren zur Herstellung einer defektarmen, einkristallinen, vorzugsweise großflächigen SiC-Schicht auf einem Substrat, vorzugsweise auf einem Siliziumsubstrat, insbesondere für Anwendung in der Leistungselektronik -und sensorik, dadurch gekennzeichnet, daß durch Anodisierung eine poröse Oberflächenschicht (14) auf dem Substrat (10) erzeugt wird, auf welcher die Abscheidung der SiC-Schicht mittels Molekularstrahl-Epitaxie realisiert wird.3. Process for producing a low-defect, single-crystal, preferably large-area SiC layer on a substrate, preferably on a silicon substrate, in particular for use in the Power electronics and sensors, characterized in that anodization produces a porous surface layer (14) on the substrate (10) on which the SiC layer is deposited by means of molecular beam epitaxy.
4. Verfahren nach einem der vorhergehenden Ansprüche, dadurch gekennzeichnet, daß als Substrat (10) Silizium, insbesondere p-dotiertes Silizium, oder Germanium eingesetzt wird.4. The method according to any one of the preceding claims, characterized in that silicon, in particular p-doped silicon, or germanium is used as the substrate (10).
5. Verfahren nach einem der vorhergehenden Ansprüche, dadurch gekennzeichnet, daß das Ätzmedium (108) für die5. The method according to any one of the preceding claims, characterized in that the etching medium (108) for the
Anodisierung eine verdünnte Flußsäure, vorzugsweiεe ein Gemisch aus Flußεäure mit Waεser und Ethanol oder Methanol iεt .Anodization is a dilute hydrofluoric acid, preferably a mixture of hydrofluoric acid with water and ethanol or methanol.
6. Verfahren nach einem der vorhergehenden Ansprüche, dadurch gekennzeichnet, daß das Ätzmedium (108) 5 - 25 % Flußsäure enthält.6. The method according to any one of the preceding claims, characterized in that the etching medium (108) contains 5 - 25% hydrofluoric acid.
7. Verfahren nach einem der vorhergehenden Ansprüche, dadurch gekennzeichnet, daß der Anodisierungεεtrom zwiεchen 1 und 50 raA/cm2 liegt.7. The method according to any one of the preceding claims, characterized in that the anodization current lies between 1 and 50 raA / cm 2 .
8. Verfahren nach einem der vorhergehenden Ansprüche, dadurch gekennzeichnet, daß die Porengröße der porösen Oberflächenschicht (14) von einigen nm bis 100 nm reicht . 8. The method according to any one of the preceding claims, characterized in that the pore size of the porous surface layer (14) ranges from a few nm to 100 nm.
9. Verfahren nach einem der vorhergehenden Ansprüche , dadurch gekennzeichnet, daß die Porosität der porösen Oberflächenschicht in einem Bereich von 10 bis 60 %, vorzugsweise von 20 bis 50 % liegt.9. The method according to any one of the preceding claims, characterized in that the porosity of the porous surface layer is in a range from 10 to 60%, preferably from 20 to 50%.
10. Verfahren nach einem der vorhergehenden Ansprüche, dadurch gekennzeichnet, daß ein Porösitatsgradient von hoher zu niedriger Porosität vom Substrat (10) zur10. The method according to any one of the preceding claims, characterized in that a porosity gradient from high to low porosity from the substrate (10) to
Oberfläche der porösen Oberflächenschicht (14) erzeugt wird.Surface of the porous surface layer (14) is generated.
11. Verfahren nach einem der vorhergehenden Ansprüche, dadurch gekennzeichnet, daß die Dicke der porösen11. The method according to any one of the preceding claims, characterized in that the thickness of the porous
Oberflächenschicht (14) einen Bereich von lOOnm bis 5μm, vorzugsweiεe von 500nm biε 5μm, hat.Surface layer (14) has a range from 100 nm to 5 μm, preferably from 500 nm to 5 μm.
12. Verfahren nach einem der vorhergehenden Anεprüche, dadurch gekennzeichnet, daß daε Oxid, daε sich an der12. The method according to any one of the preceding claims, characterized in that daε oxide, daε on the
Oberfläche der porösen Oberflächenschicht (14) bildet, durch Reduktion gelöst wird, bevor die einkristalline SiC-Schicht (16) aufgebracht wird.Surface of the porous surface layer (14) forms, is dissolved by reduction before the single-crystal SiC layer (16) is applied.
13. Verfahren nach einem der vorhergehenden Ansprüche, dadurch gekennzeichnet, daß die Oberflächenschicht (14) vor und/oder während des Abscheidens der SiC-Schicht (16) mit niederenergetischen Ionen beschossen wird. 13. The method according to any one of the preceding claims, characterized in that the surface layer (14) is bombarded with low-energy ions before and / or during the deposition of the SiC layer (16).
PCT/DE1999/002671 1998-08-27 1999-08-25 Method for producing a defect-free monocrystalline silicon carbide layer WO2000012784A1 (en)

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US7718469B2 (en) 2004-03-05 2010-05-18 The University Of North Carolina At Charlotte Alternative methods for fabrication of substrates and heterostructures made of silicon compounds and alloys
US20130256143A1 (en) * 2012-03-30 2013-10-03 GM Global Technology Operations LLC Anodized inserts for coulomb damping or frictional damping

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