EP0000123B1 - Method for growing monocrystalline layers from the liquid phase by the sliding boat system. - Google Patents

Method for growing monocrystalline layers from the liquid phase by the sliding boat system. Download PDF

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EP0000123B1
EP0000123B1 EP78100110A EP78100110A EP0000123B1 EP 0000123 B1 EP0000123 B1 EP 0000123B1 EP 78100110 A EP78100110 A EP 78100110A EP 78100110 A EP78100110 A EP 78100110A EP 0000123 B1 EP0000123 B1 EP 0000123B1
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melt
substrate
slide
melts
substrates
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German (de)
French (fr)
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EP0000123A1 (en
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Claus Weyrich
Werner Hosp
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Siemens AG
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B09—DISPOSAL OF SOLID WASTE; RECLAMATION OF CONTAMINATED SOIL
    • B09B—DISPOSAL OF SOLID WASTE
    • B09B1/00—Dumping solid waste
    • B09B1/008—Subterranean disposal, e.g. in boreholes or subsurface fractures
    • 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
    • C30B19/00—Liquid-phase epitaxial-layer growth
    • C30B19/06—Reaction chambers; Boats for supporting the melt; Substrate holders
    • C30B19/063—Sliding boat system
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
    • H01L21/02104—Forming layers
    • H01L21/02365—Forming inorganic semiconducting materials on a substrate
    • H01L21/02367—Substrates
    • H01L21/0237—Materials
    • H01L21/02387—Group 13/15 materials
    • H01L21/02395—Arsenides
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
    • H01L21/02104—Forming layers
    • H01L21/02365—Forming inorganic semiconducting materials on a substrate
    • H01L21/02436—Intermediate layers between substrates and deposited layers
    • H01L21/02439—Materials
    • H01L21/02455—Group 13/15 materials
    • H01L21/02463—Arsenides
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
    • H01L21/02104—Forming layers
    • H01L21/02365—Forming inorganic semiconducting materials on a substrate
    • H01L21/02518—Deposited layers
    • H01L21/02521—Materials
    • H01L21/02538—Group 13/15 materials
    • H01L21/02546—Arsenides
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
    • H01L21/02104—Forming layers
    • H01L21/02365—Forming inorganic semiconducting materials on a substrate
    • H01L21/02612—Formation types
    • H01L21/02617—Deposition types
    • H01L21/02623—Liquid deposition
    • H01L21/02625—Liquid deposition using melted materials

Definitions

  • the invention relates to a method for depositing single-crystalline layers according to the liquid-phase shift epitaxy, as specified in the preamble of claim 1.
  • Such a sliding epitaxy method and a device for carrying out this method are described, for example, in US Pat. No. 3,753,801.
  • double heterostructure diodes e.g. a (Ga, Al) As-GaAs diode
  • US Re 28 140 From US Re 28 140 it is known to grow an epitaxial layer on successive substrates. There is a single storage container 10-12, from which melt is removed in portions by means of a first slide 13 into an opening 18 and then applied to a substrate wafer by displacement. If a further pane is to be coated, a further slide 14 is to be provided, with which the substrate slices and the portion opening 18 of the first slide have to be displaced relative to one another and with respect to the one storage container. For re-deposition, reheating to the original starting temperature is planned. In addition, US Re 28 140 only mentions coating several substrates in tandem. The possibility of depositing several layers on top of one another is also mentioned, for which purpose additional storage containers and additional portion openings have to be provided in an extended first slide. The substrate disc is probably again in the second slide.
  • Layer sequences are usually produced using sliding devices in which the substrate disks are located in suitably designed depressions in a graphite “boat” and in which a movable slide is present which has several Has chambers for different melts of different compositions.
  • the substrate disks are arranged one behind the other or concentrically at the same distance, and the chambers of the slide are also arranged one behind the other or concentrically with the appropriate distance.
  • the thickness of the grown layer is determined by the size of the lowering of the temperature of the melt and by the thickness of the melt above the substrate, and, unless the amount of dissolved substance corresponding to the lowering of the temperature is entirely deposited on the substrate, also by the cooling rate of the melt. If very thin layers are to be deposited on a substrate, then melts which are saturated with the material of the substrate must be used for the deposition, so that when the melt is pushed on, there is no uncontrolled dissolution of the substrate crystal on its surface and, as a result, an uncontrolled layer growth .
  • the object of the invention is to provide a method for the deposition of single-crystalline layers after the liquid phase shift epitaxy, with which it is possible to provide a plurality of substrate wafers simultaneously with a multilayer structure, without the need for such pre-substrates and which allows the number of to reduce the chambers of the slide provided for the melts to be pushed open.
  • the advantage of the method according to the invention is that the individual layers are deposited on the respective substrate wafers from the same melt, and that the temperature is reduced by the same amount for the individual melts. To control the thickness of the layer deposited in each case, the thickness of the melt located above the substrate wafer is varied accordingly.
  • the respective melt from which the layer in question is to be deposited in single crystal remains on the substrate crystal until it is in equilibrium with it.
  • the substrate wafers to be coated are arranged one behind the other in the apparatus used to carry out the method according to the invention at the same distance as the distance between the slider chambers provided for the melts.
  • the substrate disks or the chambers provided for the melts can be arranged linearly or also on concentric circles.
  • a first melt is pushed onto a first substrate.
  • the first melt can optionally have been brought into solution equilibrium via a pre-substrate.
  • the arrangement is cooled by a certain temperature interval T, which is, for example, approximately 1 ° C.
  • Material that is dissolved in the melt is deposited epitaxially on the substrate surface.
  • the melt is left on the substrate until the melt has reached the solution equilibrium prevailing at this new temperature, ie until the melt is exhausted for the deposition. It can be assumed that the growth out of the melt is determined by the diffusion of the substance dissolved in the melt, for example in the case of the deposition of GaAs by the diffusion of the As in the Ga melt.
  • the minimum residence time of the melt on the substrate after the cooling is completed by the equation. given, where W max is the greatest thickness of the melt used for deposition and D is the diffusion coefficient of the dissolved material in the melt.
  • a prerequisite for the necessity of this minimum dwell time is that the equation ⁇ ⁇ ⁇ T ⁇ t min is fulfilled, where ⁇ is the reciprocal cooling rate, AT is the cooling interval. If the equation ⁇ ⁇ ⁇ T> t min applies instead of this last equation, the minimum dwell time can be kept correspondingly lower after cooling. If the reciprocal cooling rate of the melt is kept sufficiently high, a holding time of the melt on the substrate without a simultaneous lowering of the temperature could even be omitted entirely.
  • the thickness of the melt is proportional to the thickness of the melt located over the respective substrate wafer.
  • ⁇ T 1 ° C.
  • the thickness of the melt must be approximately 1 mm in order to grow a 1 ⁇ m thick GaAs layer, taking the hold time according to the equation with D approximately equal to 5.10 -5 cm 2 sec -1 must be approximately 200 sec.
  • the first melt is then pushed onto the second substrate by sliding the slide; at the same time, the second melt is then pushed onto the first substrate to deposit the second layer.
  • the arrangement is then cooled again by the same amount of temperature, in the example given by 1 ° C.
  • the first melt is then pushed onto the third substrate wafer, the second melt onto the second substrate wafer, and the third melt onto the first substrate wafer, and then the entire arrangement cooled again by 1 ° C.
  • Fig. 2 shows the temperature profile of the entire arrangement.
  • the initial temperature T A is, for example, 800 ° C.
  • the temperature is gradually lowered by an amount AT, for example by 1 ° C.
  • the final temperature T E is in a process in which ten substrate wafers are coated with a 4-layer structure, for example 14 ° C. lower than the initial temperature.

Description

Die Erfindung betrifft ein Verfahren zum Abscheiden einkristalliner Schichten nach der Flüssigphasen-Schiebeepitaxie, wie es im Oberbegriff des Patentanspruches 1 näher angegeben ist.The invention relates to a method for depositing single-crystalline layers according to the liquid-phase shift epitaxy, as specified in the preamble of claim 1.

Zur Herstellung bestimmter Halbleiterbauelemente, z.B. zur Herstellung von Lumineszenzdioden oder Laserdioden, ist es notwendig, auf einem Halbleiterkristall eine oder mehrere Schichten aus Halbleitermaterial epitaxial abzuscheiden. Insbesondere zur Herstellung von Halbleiterbauelementen aus intermetallischen III-V-Verbindungen und deren Mischkristalle wird dazu die Technik der Flüssigphasen-Schiebeepitaxie angewendet. Bei dieser Methode wird mit Hilfe eines Schiebers eine Schmelze, die das abzuscheidende Material enthält, auf die Oberfläche eines Substrates aufgeschoben und sodann durch leichtes Abkühlen der Schmelze Material auf der Substratoberfläche einkristallin abgeschieden. Sobald mit dem Abscheiden die vorgesehene Schichtdicke der einkristallinen Schicht erreicht ist, wird mit Hilfe des Schiebers die restliche Schmelze von der Substratoberfläche bzw. der aufgewachsenen Epitaxieschicht abgeschoben. Ein solches Schiebeepitaxie-Verfahren sowie eine Vorrichtung zur Durchführung dieses Verfahrens sind beispielsweise in der US-Patentschrift 3 753 801 beschrieben. Zur Herstellung von kohärent und inkohärent strahlenden Doppelheterostruktur-Dioden, z.B. einer (Ga, AI) As-GaAs-Diode, sowie auch bei Mikrowellen-Bauelementen mit Heterestruktur ist es notwendig, aufeinander mehrere Schichten epitaxial abzuscheiden. Diese Schichten unterscheiden sich dabei in ihrer Zusammensetzung, z.B. bei einer GaAs-(GaA1)As-Schichtfolge, im Aluminiumgehalt.For the manufacture of certain semiconductor devices, e.g. for the production of luminescent diodes or laser diodes, it is necessary to epitaxially deposit one or more layers of semiconductor material on a semiconductor crystal. In particular for the production of semiconductor components from intermetallic III-V compounds and their mixed crystals, the technique of liquid phase shifting epitaxy is used. In this method, a melt containing the material to be deposited is pushed onto the surface of a substrate with the aid of a slide, and material is then deposited in a single crystal on the substrate surface by slightly cooling the melt. As soon as the intended layer thickness of the single-crystalline layer has been reached with the deposition, the remaining melt is pushed off the substrate surface or the grown epitaxial layer with the aid of the slide. Such a sliding epitaxy method and a device for carrying out this method are described, for example, in US Pat. No. 3,753,801. For the production of coherently and incoherently radiating double heterostructure diodes, e.g. a (Ga, Al) As-GaAs diode, as well as in the case of microwave components with a heterostructure, it is necessary to epitaxially deposit several layers on top of one another. These layers differ in their composition, e.g. with a GaAs (GaA1) As layer sequence, in the aluminum content.

Aus der US-Re 28 140 ist bekannt, je eine Epitaxieschicht auf aufeinanderfolgende Substrate aufwachsen zu lassen. Es ist dort ein einziger Vorratsbehälter 10-12 vorhanden, aus dem mit einem ersten Schieber 13 in eine Öffnung 18 portionsweise Schmelze entnommen und dann durch Verschieben auf eine Substratscheibe aufgebracht wird. Soll eine weitere Scheibe beschichtet werden, ist ein weiterer Schieber 14 vorzusehen, mit dem die Substratscheiben und die Portionsöffnung 18 des ersten Schiebers gegeneinander und gegenüber dem einen Vorratsbehälter verschoben werden müssen. Für die erneute Abscheidung ist vorherige Wiedererwärmung auf die ursprüngliche Ausgangstemperatur vorgesehen. Zusatzlich ist in der US-Re 28 140 noch lediglich erwähnt, mehrere Substrate in Tandemweise zu beschichten. Auch ist die Möglichkeit, mehrere Schichten aufeinander abzuscheiden, erwähnt, wozu zusätzliche Vorratsbehälter und zusätzliche Portionsöffnungen in einem verlängerten ersten Schieber vorzusehen sind. Die Substratscheibe befindet sich wohl wieder im zweiten Schieber.From US Re 28 140 it is known to grow an epitaxial layer on successive substrates. There is a single storage container 10-12, from which melt is removed in portions by means of a first slide 13 into an opening 18 and then applied to a substrate wafer by displacement. If a further pane is to be coated, a further slide 14 is to be provided, with which the substrate slices and the portion opening 18 of the first slide have to be displaced relative to one another and with respect to the one storage container. For re-deposition, reheating to the original starting temperature is planned. In addition, US Re 28 140 only mentions coating several substrates in tandem. The possibility of depositing several layers on top of one another is also mentioned, for which purpose additional storage containers and additional portion openings have to be provided in an extended first slide. The substrate disc is probably again in the second slide.

Schichtfolgen, wie sie beispielsweise für Doppelheterostruktur-Laserdioden oder -Lumineszenzdioden benötigt werden, werden üblicherweise mit Schiebeapparaturen hergestellt, bei denen sich in einem Graphit- "Boot" in geeignet ausgebildeten Vertiefungen die Substratscheiben befinden, und bei denen ein beweglicher Schieber vorhanden ist, der mehrere Kammern für die verschiedenen Schmelzen unterschiedlicher Zusammensetzung aufweist. Die Substratscheiben sind dabei hintereinander oder konzentrisch im gleichen Abstand angeordnet, und die Kammern des Schiebers sind ebenfalls hintereinander oder konzentrisch mit dem entsprechenden Abstand angeordnet. Durch Weiterschieben bzw. Drehen des Schiebers werden die Schmelzen nacheinander über den jeweiligen Substratkristall geschoben, wobei jedes Mal durch Abkühlen der Schmelze um einen gewissen Temperaturbetrag auf der Substratscheibe eine einkristalline Schicht aufwächst. Die Dicke der aufgewachsenen Schicht wird durch die Größe der Temperaturabsenkung der Schmelze und durch die Dicke der Schmelze über dem Substrat, und, sofern nicht die der Temperaturabsenkung entsprechende Menge gelöster Substanz zur Gänze auf dem Substrat abgeschieden wird, auch durch die Abkühlgeschwindigkeit der Schmelze festgelegt. Wenn auf einem Substrat sehr dünne Schichten abgeschieden werden sollen, so müssen zum Abscheiden Schmelzen verwendet werden, die mit dem Material des Substrates gesättigt sind, damit beim Aufschieben der Schmelze nicht eine unkontrollierte Auflösung des Substratkristalles an seiner Oberfläche und als deren Folge ein unkontrolliertes Schichtwachstum auftritt. Eine exakte Sättigung der Schmelzen wird am einfachsten dadurch bewerkstelligt, daß die jeweils verwendete Schmelze durch genügend langes Verweilen auf einem Vorsubstrat in ein Lösungsgleichgewicht gebracht wird, bevor sie auf das eigentliche Substrat aufgeschoben wird. Bei tatsächlich ausgeführten Apparaturen, in denen mehrere Substratscheiben gleichzeitig beschichtet werden, ist für jede abzuscheidende Schicht einer jeden Substratscheibe eine gesonderte Kammer in dem Schieber vorgesehen worden. Zur Herstellung einer 4-Schichtstruktur, bei der zur Abscheidung der einzelnen Schichten jeweils unterschiedliche Abkühlintervalle angewendet werden, ist ein Schieber eingesetzt worden, dessen Kammerzahl 4 mal so groß ist wie die Zahl der zu beschichtenden Substratscheiben. Dies hat bereits bei einer kleinen Anzahl von Substratscheiben zu einer sehr komplizierten Konstruktion des Schiebers bzw. des "Bootes" geführt. Ferner konnte die hohe Anzahl von Kammern bei der Beschickung dieser "Boote" leicht zu Fehlern führen. Bei der Verwendung von Vorsubstraten ist bei diesem Verfahren darüber hinaus auch die doppelte Anzahl von Substratscheiben erforderlich, was die Kosten des Verfahrens zusätzlich erhöht.Layer sequences, as are required, for example, for double heterostructure laser diodes or luminescent diodes, are usually produced using sliding devices in which the substrate disks are located in suitably designed depressions in a graphite “boat” and in which a movable slide is present which has several Has chambers for different melts of different compositions. The substrate disks are arranged one behind the other or concentrically at the same distance, and the chambers of the slide are also arranged one behind the other or concentrically with the appropriate distance. By pushing or turning the slide, the melts are pushed one after the other over the respective substrate crystal, each time a single-crystal layer growing on the substrate wafer by cooling the melt by a certain amount of temperature. The thickness of the grown layer is determined by the size of the lowering of the temperature of the melt and by the thickness of the melt above the substrate, and, unless the amount of dissolved substance corresponding to the lowering of the temperature is entirely deposited on the substrate, also by the cooling rate of the melt. If very thin layers are to be deposited on a substrate, then melts which are saturated with the material of the substrate must be used for the deposition, so that when the melt is pushed on, there is no uncontrolled dissolution of the substrate crystal on its surface and, as a result, an uncontrolled layer growth . The easiest way to achieve exact saturation of the melts is to bring the melt used in each case into a solution equilibrium by lingering on a pre-substrate for a sufficiently long time before it is pushed onto the actual substrate. In actually implemented apparatuses in which several substrate wafers are coated at the same time, a separate chamber has been provided in the slide for each layer to be deposited on each substrate wafer. To produce a 4-layer structure, in which different cooling intervals are used to separate the individual layers, a slide has been used, the number of chambers of which is 4 times as large as the number of substrate wafers to be coated. Even with a small number of substrate disks, this has led to a very complicated construction of the slide or the "boat". Furthermore, the high number of Chambers can easily lead to errors when loading these "boats". When using pre-substrates, this method also requires twice the number of substrate wafers, which additionally increases the cost of the method.

Aufgabe der Erfindung ist es, ein Verfahren zum Abscheiden einkristalliner Schichten nach der Flüssigphasen-Schiebeepitaxie anzugeben, mit dem es möglich ist, mehrere Substratscheiben gleichzeitig mit einer Vielschicht-Struktur zu versehen, ohne daß derartige Vorsubstrate notwendig sind und das es erlaubt, die Zahl der für die aufzuschiebenden Schmelzen vorgesehenen Kammern des Schiebers zu vermindern.The object of the invention is to provide a method for the deposition of single-crystalline layers after the liquid phase shift epitaxy, with which it is possible to provide a plurality of substrate wafers simultaneously with a multilayer structure, without the need for such pre-substrates and which allows the number of to reduce the chambers of the slide provided for the melts to be pushed open.

Diese Aufgabe wird bei einem wie im Oberbegriff des Patentanspruches 1 angegebenen Verfahren erfindungsgemäß nach der im kennzeichnenden Teil des Patentanspruches 1 angegebenen Weise gelöst.This object is achieved in a method as specified in the preamble of claim 1 according to the invention in the manner specified in the characterizing part of claim 1.

Vorteilhafte Ausgestaltungen der Erfindung sind in den Unteransprüchen angegeben.Advantageous embodiments of the invention are specified in the subclaims.

Der Vorteil des erfindungsgemäßen Verfahrens besteht einmal darin, daß die einzelnen Schichten auf den jeweiligen Substratscheiben jeweils aus derselben Schmelze abgeschieden werden, und daß weiterhin die Temperaturabsenkung für die einzelnen Schmelzen jeweils um den gleichen Betrag erfolgt. Zur Steuerung der Dicke der jeweils abgeschiedenen Schicht wird die Dicke der über der Substratscheibe befindlichen Schmelze entsprechend variiert.The advantage of the method according to the invention is that the individual layers are deposited on the respective substrate wafers from the same melt, and that the temperature is reduced by the same amount for the individual melts. To control the thickness of the layer deposited in each case, the thickness of the melt located above the substrate wafer is varied accordingly.

Die jeweilige Schmelze, aus der heraus die betreffende Schicht einkristallin abgeschieden werden soll, verbleibt solange auf dem Substratkristall, bis sie sich mit diesem im Gleichgewicht befindet. Die zu beschichtenden Substratscheiben sind in der für die Durchführung des erfindungsgemäßen Verfahrens verwendeten Apparatur hintereinander im gleichen Abstand wie der Abstand der für die Schmelzen vorgesehenen Kämmern des Schiebers angeordnet. Die Substratscheiben bzw. die für die Schmelzen vorgesehenen Kammern können linear oder auch auf konzentrischen Kreisen angeordnet sein.The respective melt from which the layer in question is to be deposited in single crystal remains on the substrate crystal until it is in equilibrium with it. The substrate wafers to be coated are arranged one behind the other in the apparatus used to carry out the method according to the invention at the same distance as the distance between the slider chambers provided for the melts. The substrate disks or the chambers provided for the melts can be arranged linearly or also on concentric circles.

Zum Abscheiden der ersten einkristallinen Schichten wird eine erste Schmelze auf ein erstes Substrat aufgeschoben. Die erste Schmelze kann gegebenenfalls auch über ein Vorsubstrat in das Lösungsgleichgewicht gebracht worden sein. Nachdem die erste Schmelze auf das erste Substrat aufgeschoben worden ist, wird die Anordnung um ein bestimmtes Temperaturintervall T, das beispielsweise etwa 1 °C beträgt, abgekühlt. Dabei scheidet sich Material, das in der Schmelze gelöst ist, auf der Substratoberfläche epitaktisch ab. Die Schmelze wird solange auf dem Substrat belassen, bis die Schmelze das bei dieser neuen Temperatur herrschende Lösungsgleichgewicht erreicht hat, d.h. bis die Schmelze für die Abscheidung erschöpft ist. Man kann davon ausgehen, daß das Wachstum aus der Schmelze heraus durch die Diffusion des in der Schmelze gelösten Stoffes bestimmt wird, beispielsweise bei der Abscheidung von GaAs durch die Diffusion des As in der Ga-Schmelze. In diesem Falle ist die Mindestverweilzeit der Schmelze auf dem Substrat nach Abschluß der Abkühlung durch die Gleichung.

Figure imgb0001
gegeben, wobei Wmax die größte Dicke der zum Abscheiden verwendeten Schmelze und D der Diffusionskoeffizient des gelösten Materials in der Schmelze ist. Voraussetzung für die Notwendigkeit dieser Mindestverweilzeit ist, daß die Gleichung α·ΔT<<tmin erfüllt ist, wobei α die reziproke Abkühlungsgeschwindigkeit, AT das Abkühlungsintervall ist. Gilt statt dieser letzten Gleichung die Gleichung α·ΔT>tmin, so kann nach erfolgter Abkühlung die Mindestverweildauer jedoch entsprechend niedriger gehalten werden. Wird die reziproke Abkühlungsgeschwindigkeit der Schmelze hinreich groß gehalten, so könnte eine Haltezeit der Schmelze auf dem Substrat ohne gleichzeitige Temperaturabsenkung sogar gänzlich entfallen. Dadurch, daß die Schmelzen, die zum Abscheiden der jeweiligen Schicht auf die Substrate aufgeschoben werden, unterschiedlich dick gehalten werden, können trotz des für alle Schmelzen gleichen Abkühlintervalles dennoch verschieden dicke Schichten auf den jeweiligen Substratscheiben aufgewachsen werden, da unter den angegebenen Bedingungen die Dicke der jeweils abgeschiedenen Schicht der Dicke der über der jeweiligen Substratscheibe befindlichen Schmelze proportional ist. Beispielsweise muß bei einem Abkühlintervall ΔT=1°C und einer Ausgangstemperatur von beispielsweise 800°C für eine Abscheidung von GaAs aus einer Ga-As-Schmelze die Dicke der Schmelze etwa 1 mm betragen, um eine 1 ,um dicke GaAs-Schicht aufzuwachsen, wobei die Haltezeit nach der Gleichung
Figure imgb0002
mit D ungefähr gleich 5.10-5cm2sec-1 etwa 200 sec betragen muß. Nach dieser Haltezeit wird sodann die erste Schmelze durch Weiterschieben des Schiebers auf des zweite Substrat geschoben; gleichzeitig wird dann die zweite Schmelze auf das erste Substrat zur Abscheidung der zweiten Schicht geschoben. Die Anordnung wird sodann wieder um den gleichen Temperaturbetrag, in dem angegebenen Beispiel also um 1 °C, abgekühlt. Danach wird sodann die erste Schmelze auf die dritte Substratscheibe, die zweite Schmelze auf die zweite Substratscheibe, und die dritte Schmelze auf die erste Substratscheibe aufgeschoben, und dann die gesamte Anordnung wiederum um 1°C abgekühlt. Diese Verfahrensschritte werden entsprechend der Zahl der Substrate und der abzuscheidenden Schichten fortgeführt. Sollen beispielsweise zehn Substratscheiben mit einer 4-Schichtstruktur versehen werden, so sind also vier Kammern für die Schmelzen vorzusehen, und es sind insgesamt vierzehn Schiebeschritte erforderlich. Daraus ergibt sich eine Gesamtabkühlung von 14°C, wenn bei jedem einzelnen Schiebeschritt die Abkühlung um 10C erfolgt. Innerhalb eines Temperaturintervalles von 14°C können die Temperaturabhängigkeiten der Löslichkeit bzw. der Verteilungskoeffizienten der Komponenten und Dotierstoffe in der Schmelze vernachlässigt werden, so daß für die Substratscheiben die abgeschiedenen Schichten gleiche Schichtdicken aufweisen.To deposit the first single-crystalline layers, a first melt is pushed onto a first substrate. The first melt can optionally have been brought into solution equilibrium via a pre-substrate. After the first melt has been pushed onto the first substrate, the arrangement is cooled by a certain temperature interval T, which is, for example, approximately 1 ° C. Material that is dissolved in the melt is deposited epitaxially on the substrate surface. The melt is left on the substrate until the melt has reached the solution equilibrium prevailing at this new temperature, ie until the melt is exhausted for the deposition. It can be assumed that the growth out of the melt is determined by the diffusion of the substance dissolved in the melt, for example in the case of the deposition of GaAs by the diffusion of the As in the Ga melt. In this case, the minimum residence time of the melt on the substrate after the cooling is completed by the equation.
Figure imgb0001
 given, where W max is the greatest thickness of the melt used for deposition and D is the diffusion coefficient of the dissolved material in the melt. A prerequisite for the necessity of this minimum dwell time is that the equation α · ΔT << t min is fulfilled, where α is the reciprocal cooling rate, AT is the cooling interval. If the equation α · ΔT> t min applies instead of this last equation, the minimum dwell time can be kept correspondingly lower after cooling. If the reciprocal cooling rate of the melt is kept sufficiently high, a holding time of the melt on the substrate without a simultaneous lowering of the temperature could even be omitted entirely. Characterized in that the melts that are pushed onto the substrates for the deposition of the respective layer are kept of different thicknesses, despite the cooling interval being the same for all melts, layers of different thicknesses can nevertheless be grown on the respective substrate wafers, since the thickness of the each deposited layer is proportional to the thickness of the melt located over the respective substrate wafer. For example, with a cooling interval ΔT = 1 ° C. and an initial temperature of, for example, 800 ° C. for the deposition of GaAs from a Ga-As melt, the thickness of the melt must be approximately 1 mm in order to grow a 1 μm thick GaAs layer, taking the hold time according to the equation
Figure imgb0002
 with D approximately equal to 5.10 -5 cm 2 sec -1 must be approximately 200 sec. After this holding time, the first melt is then pushed onto the second substrate by sliding the slide; at the same time, the second melt is then pushed onto the first substrate to deposit the second layer. The arrangement is then cooled again by the same amount of temperature, in the example given by 1 ° C. The first melt is then pushed onto the third substrate wafer, the second melt onto the second substrate wafer, and the third melt onto the first substrate wafer, and then the entire arrangement cooled again by 1 ° C. These process steps are continued in accordance with the number of substrates and the layers to be deposited. If, for example, ten substrate wafers are to be provided with a 4-layer structure, four chambers must be provided for the melts and a total of fourteen sliding steps are required. This results in a total cooling of 14 ° C, if the cooling by 10C takes place with each individual sliding step. The temperature dependencies of the solubility or the distribution coefficients of the components and dopants in the melt can be neglected within a temperature interval of 14 ° C., so that the deposited layers have the same layer thicknesses for the substrate wafers.

Im folgenden wird die Erfindung anhand eines in den Figuren dargestellten Ausführungsbeispiels beschrieben und näher erläutert.

  • Fig. 1 zeigt schematisch die für die Durchführung des erfindungsgemäßen Verfahrens verwendete Apparatur,
  • Fig. 2 zeigt schematisch, wie die Temperatur der gesamten Anordnung zur Abscheidung einzelner Schichten auf den jeweiligen Substratscheiben abgesenkt werden wird.
Fig. 1 zeigt schematisch den Verfahrensgang zur Herstellung einer 4-Schichtstruktur auf GaAs-Substraten. In einem "Boot" 1, das beispielsweise aus Graphit besteht, befinden sich die Substratscheiben 11, 12, 13, 14 und 15. Auf diesem Boot 1 ist ein Schieber 2 aufgesetzt, der vier Kammern enthält, in denen die Schmelzen 21, 22, 23 und 24 enthalten sind. Die Dicke der jeweiligen Schmelzen über den Substraten wird durch die Menge der eingefüllten Schmelze eingestellt. Mit Stempeln 3 wird verhindert, daß bei kleinen Schmelzdicken sich die Schmelze aufgrund Oberflächenspannung zu einem Tropfen zusammenzieht. Zum Abscheiden einer 4-Schichtstruktur auf den Substraten wird der Schieber zunächst in eine Position gebracht, bei der sich über dem Substrat 11 die Schmelze 21 befindet. Dabei wird auf dem Substrat 11 eine Schicht 111 abgeschieden. Sodann wird der Schieber in die nächste Position gebracht, so daß die Schmelze 21 sich über dem Substrat 12 befindet. Die Temperatur der Anordnung wird jetzt wiederum um einen Betrag von etwa 1°C abgesenkt. Dabei scheidet sich auf dem Substrat 12 eine Schicht 121 einkristallin ab, aus der jetzt über dem Substrat 11 befindlichen Schmelze 22 scheidet sich eine Schicht 112 auf dem Substrat 11 ab. Im nächsten Verfahrensschritt wird der Schieber 2 wiederum in Pfeilrichtung weitergeschoben, so daß die Schmelze 21 sich jetzt über dem Substrat 13 befindet. Dieser Zustand ist in Fig. 1 dargestellt. Die Temperatur der Anordnung wird wiederum um den Betrag AT = 1 °C abgesenkt. Dabei scheidet sich auf dem Substrat 13 dann die erste epitaxiale Schicht, auf dem Substrat 12 die zweite und auf dem Substrat 11 die dritte epitaxiale Schicht ab. Danach wird der Schieber 2 wiederum um eine Stellung weitergeschoben, so daß die Schmelze 21 nun über dem Substrat 14, die Schmelze 24 über dem Substrat 11 vorhanden ist. In entsprechender Weise wird fortgefahren, bis alle Substrate mit einer 4-Schichtstruktur überzogen sind.The invention is described and explained in more detail below with reference to an exemplary embodiment shown in the figures.
  • 1 schematically shows the apparatus used to carry out the method according to the invention,
  • 2 shows schematically how the temperature of the entire arrangement for depositing individual layers on the respective substrate wafers will be reduced.
1 schematically shows the process for producing a 4-layer structure on GaAs substrates. The substrate disks 11, 12, 13, 14 and 15 are located in a "boat" 1, which consists, for example, of graphite. 23 and 24 are included. The thickness of the respective melts over the substrates is adjusted by the amount of the melt filled. Stamps 3 prevent the melt from contracting into a drop due to surface tension at small melt thicknesses. To deposit a 4-layer structure on the substrates, the slide is first brought into a position in which the melt 21 is located above the substrate 11. A layer 111 is deposited on the substrate 11. The slide is then brought into the next position so that the melt 21 is above the substrate 12. The temperature of the arrangement is then lowered again by an amount of approximately 1 ° C. In this case, a layer 121 is deposited on the substrate 12 in a single crystal, and a layer 112 is deposited on the substrate 11 from the melt 22 now located above the substrate 11. In the next process step, the slide 2 is again pushed in the direction of the arrow, so that the melt 21 is now above the substrate 13. This state is shown in Fig. 1. The temperature of the arrangement is again reduced by the amount AT = 1 ° C. The first epitaxial layer then deposits on the substrate 13, the second epitaxial layer on the substrate 12 and the third epitaxial layer on the substrate 11. Thereafter, the slide 2 is again moved one position so that the melt 21 is now above the substrate 14, the melt 24 is above the substrate 11. The procedure continues in a corresponding manner until all substrates have been coated with a 4-layer structure.

Fig. 2 zeigt den Temperaturverlauf der gesamten Anordnung. Die Anfangstemperatur TA beträgt beispielsweise 800°C. Entsprechend der vorhandenen Anzahl von Substraten sowie der Zahl der abzuscheidenden Schichten erfolgt eine schrittweise Temperaturabsenkung jeweils um einen Betrag AT, beispielsweise um 1 °C. Die Endtemperatur TE liegt bei einem Verfahren, bei dem zehn Substratscheiben mit einer 4-Schichtstruktur überzogen werden, beispielsweise 14°C tiefer als die Anfangstemperatur.Fig. 2 shows the temperature profile of the entire arrangement. The initial temperature T A is, for example, 800 ° C. Depending on the existing number of substrates and the number of layers to be deposited, the temperature is gradually lowered by an amount AT, for example by 1 ° C. The final temperature T E is in a process in which ten substrate wafers are coated with a 4-layer structure, for example 14 ° C. lower than the initial temperature.

Claims (3)

1. Process for the deposition of monocrystalline layers on substrates by liquid phase slide epitaxy, in which different monocrystalline layers are deposited on one another at the same time on a plurality of substrates by applying melts to the substrates by means of a slide and removing them by further movement of the slide after the deposition of the particular layer, wherein a slide is used which possesses a plurality of equidistantly arranged chambers which contain the melts of the materials to be deposited, and wherein the deposition of the individual layers is effected by lowering the temperature of the melt which is present on the particular substrate, characterised in that the substrates are uniformly arranged, each distance being equal to the distance of the chambers of the slide, that in each depositing step, the temperature of all the melts which are present on a substrate in each case is lowered by the same amount, that for the deposition of monocrystalline layers of predetermined thickness the thickness of the melt which is present on the particular substrate is kept at a value which corresponds to the layer thickness to be deposited, and that after the termination of the lowering of the temperature until the removal of the melt, a minimum duration tmln is observed whose magnitude is determined in accordance with the formulae
Figure imgb0007
and
Figure imgb0008
wherein Wmax is the greatest thickness of the melts in the arrangement, D is the diffusion coefficient of the material dissolved in the melt, a is the reciprocal rate of cooling and AT the amount of the lowering of temperature of the individual cooling step.
2. Process as claimed in Claim 1 for the production of monocrystalline layers on III-V-compound semiconductors, characterised in that a melt of the III-component is selected as the melt in which material of the V-component is dissolved.
3. Use of a process as claimed in one of the Claims 1 or 2 for the production of heterostructure-semiconductor crystals.
EP78100110A 1977-07-05 1978-06-07 Method for growing monocrystalline layers from the liquid phase by the sliding boat system. Expired EP0000123B1 (en)

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DE2730358A DE2730358C3 (en) 1977-07-05 1977-07-05 Process for the successive deposition of monocrystalline layers on a substrate according to liquid phase shift epitaxy

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EP0000123B1 true EP0000123B1 (en) 1981-02-25

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NL7712315A (en) * 1977-11-09 1979-05-11 Philips Nv METHOD FOR EPITAXIAL DEPOSITION OF SEVERAL LAYERS.
DE3036643C2 (en) * 1980-09-29 1984-09-20 Siemens AG, 1000 Berlin und 8000 München Device for liquid phase epitaxy
US4319937A (en) * 1980-11-12 1982-03-16 University Of Illinois Foundation Homogeneous liquid phase epitaxial growth of heterojunction materials
US4342148A (en) * 1981-02-04 1982-08-03 Northern Telecom Limited Contemporaneous fabrication of double heterostructure light emitting diodes and laser diodes using liquid phase epitaxy
US4547230A (en) * 1984-07-30 1985-10-15 The United States Of America As Represented By The Secretary Of The Air Force LPE Semiconductor material transfer method
JPH07115987B2 (en) * 1986-09-26 1995-12-13 徳三 助川 Fabrication of superstructures and multilayers
TW460604B (en) 1998-10-13 2001-10-21 Winbond Electronics Corp A one-sided and mass production method of liquid phase deposition
CN102995115B (en) * 2012-12-27 2015-07-29 中国电子科技集团公司第十一研究所 A kind of graphite boat for rheotaxial growth and liquid-phase epitaxial growth process

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USRE28140E (en) * 1971-11-29 1974-08-27 Bergh ctal
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US3933538A (en) * 1972-01-18 1976-01-20 Sumitomo Electric Industries, Ltd. Method and apparatus for production of liquid phase epitaxial layers of semiconductors
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US3899371A (en) * 1973-06-25 1975-08-12 Rca Corp Method of forming PN junctions by liquid phase epitaxy
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