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WO1987007313A1 - Croissance epitaxiale - Google Patents

Croissance epitaxiale Download PDF

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Publication number
WO1987007313A1
WO1987007313A1 PCT/US1987/001261 US8701261W WO8707313A1 WO 1987007313 A1 WO1987007313 A1 WO 1987007313A1 US 8701261 W US8701261 W US 8701261W WO 8707313 A1 WO8707313 A1 WO 8707313A1
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WO
WIPO (PCT)
Prior art keywords
dispersion
constituents
growth
temperature
substrate
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
PCT/US1987/001261
Other languages
English (en)
Inventor
Barbara G. Bryskiewicz
Tadeusz R. Bryskiewicz
Ferdynand P. Dabkowski
Jacek Laqowski
Harry C. Gatos
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Massachusetts Institute of Technology
Original Assignee
Massachusetts Institute of Technology
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Massachusetts Institute of Technology filed Critical Massachusetts Institute of Technology
Publication of WO1987007313A1 publication Critical patent/WO1987007313A1/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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Classifications

    • 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
    • C30B19/08—Heating of the reaction chamber or the substrate
    • 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
    • C30B19/02—Liquid-phase epitaxial-layer growth using molten solvents, e.g. flux
    • C30B19/04—Liquid-phase epitaxial-layer growth using molten solvents, e.g. flux the solvent being a component of the crystal composition

Definitions

  • This invention relates to materials growth and, more particularly, to epitaxial growth.
  • U. S. Patent No. 4,186,045 discloses a method of liquid phase epitaxial growth in which such compounds are grown from a solution by precipitation of the constituents of the solution onto a seed or substrate.
  • the substances of which the material is formed are melted together to provide a liquid solution that includes the constituents of the material, the solution is brought into contact with the appropriate seed or substrate, and the material to be grown is then precipitated from the solution onto the interface between the solution and seed.
  • precipitation is effected by electromigration.
  • it is caused by other mechanisms, such as Peltier cooling at the seed-solution interface.
  • the solution from which growth proceeds must be in equilibrium, i.e., it must be a saturated solution of the constituents of the to-be-grown compound, at the growth temperature.
  • the growth temperature is typically well below the melting point of the compound, the relative percentages of the constituents present in the saturated solution is typically quite different from that in the compound produced, and the solubility of one or more of the constituents in another also varies with temperature. All of this makes it difficult to provide- the necessary equilibrated solution.
  • One aspect of the present invention features forming such an equilibrium growth dispersion by heating the constituents of the to-be produced compound in the desired predetermined proportions to above the temperature at which growth will occur, homogenizing the mixture, and then rapidly quenching it.
  • such an equilibrium growth dispersion is placed in intimate contact
  • the growth dispersion and substrate are heated to a temperature above the melting point of the constituent that is the major component of the equilibrium growth dispersion to provide complete wetting between the dispersion and substrate, and both are then cooled to bond the dispersion and substrate together into a unitary growth assembly.
  • One of the constituents may be, e.g., arsenic, phosphorous, antimony or cadmium; another may be, for example, gallium, indium, tin or tellurium.
  • Preferred practices of the invention include both aspects, and feature also heating the dispersion and the substrate under vacuum to a temperature sufficient to vaporize and permit removals of hydroxide or oxide impurities, but below the temperature of which any of the constituents is signi icantly (e.g., greater than about 0.05%) soluble in any other, prior to placing the dispersion into contact with the substrate.
  • the invention is particularly useful in connection with the epitaxial growth of binary and mixed II-VI, III-V, and IV-IV compounds.
  • exemplary such compounds include materials grown from a saturated solution in which tellurium is the solvent and major constituent and in which smaller amounts of any other constituents are dissolved (such as CdTe, HgCdTe, MnTe, PbTe and PbSnTe), materials grown from a saturated solution of other constituents in selenium (such as CdSe), and materials grown from saturated solutions in which the solvent is gallium or indium (such as GaAs, GaAlAs, GaP, GaSb, GaAlP, GaAlSb, InSb, InAs and InP), together with other compounds which the aforementioned U. S. Patent No. 4,186,045 says may be produced using the electroepitaxial growth process described therein.
  • Figure 1 schematically illustrates a system useful for producing an equilibrium growth dispersion.
  • Figure 2 schematically illustrates a procedure for forming the desired interface between an equilibrium growth dispersion pellet and a substrate.
  • Figure 3 schematically illustrates expitaxial growth from the pellet-substrate assembly of Figure 2.
  • Figures 4 and 4A are gallium-arsenic phase diagrams.
  • a quartz ampoule 10 is cleaned and its inner surfaces 12 pyrolitically covered with a thin layer of carbon.
  • Predetermined quantities of the constituents of the compound to be grown are cleaned, weighed, and placed within the ampoule.
  • the relative percentages of the constituents are chosen so that, when melted together at the temperature at which growth is to take place, they will produce an equilibriated, i.e., saturated, solution of the constituents.
  • the exact relative proportions chosen will depend, of course, on the particular compound and selected growth temperature.
  • the ampoule with the constituents in it, is evacuated (typically to a pressure of 5 x 10 ⁇ 6 torr or less), and sealed in such a way as to minimize the free space above the charge.
  • the sealed ampoule 10 is then placed into a furnace 14, as shown in Figure 1, and the furnace is heated to a temperature 30 to 50 degrees above the planned growth temperature. Theoretically, the entire charge within the ampoule would melt and form a saturated solution at the planned growth temperature. The 30 to 50 degree superheat insures total dissolution.
  • the charge is homogenized at the superheat temperature for a period of 24 hours, typically by slow rotation of the ampoule 10 about its vertical axis while it is in place within the furnace 14.
  • the ampoule 10 containing the essentially saturated solution is rapidly - 5 -
  • the quenched product i.e., the quenched product in the material forming the major fraction (i.e., the solvent, typically decreases with decreasing temperature, it will be recognized that normal cooling of a saturated solution would result in precipitation of particles of the solute constituent(s) ; the resulting product at room temperature would be various sized particles of the solute constituent(s) unevenly distributed through (typically on the top of) the major fraction constituent (the solvent). Rapid quenching prevents such precipitation. As previously indicated, the quenched product (i.e.
  • the equilibrium growth dispersion is an essentially homogeneous dispersion of fine particles of the solute constituent(s) (e.g., the constituent(s) forming the minor fraction of the saturated solution) in the solvent (e.g., the major) ' fraction constituent.
  • the dispersion is solid at room temperature.
  • the solid-at-room-temperature equilibrium growth dispersion is then removed from the ampoule, typically by breaking the ampoule; and thereafter may be used to provide the solution from which epitaxial growth of the desired compound will proceed.
  • the equilibrium growth dispersion from ampoule 10 provides a disc-shaped pellet, designated 32, which may be placed on the substrate 40 upon which epitaxial growth is to proceed.
  • a disc-shaped pellet designated 32
  • the substrate 40 For successful epitaxial growth, there should be complete wetting of the substrate 40 by the growth solution. Without such complete wetting, e.g., if any bubbles of trapped gas or other impurities exist at the interface 42 between the equilibrium growth dispersion pellet 32 and the substrate 40, proper growth will not be accomplished. Complete wetting, and elimination of possible impurities at the interface 42, is accomplished by placing both the substrate 40 and pellet 32 in a furnace (not shown) and heating, under reduced pressure, to a temperature sufficient to vaporize and remove impurities (Fig. 3A) .
  • such heating may convert hydroxides of one of the constituents to an oxide which will vaporize and be removed from the system. While the system is still at elevated temperature, the furnace chamber is filled with pure inert gas and the pellet 32 is placed on and lightly pressed into contact with the substrate 40 (Fig. 3B) . It will be recognized that the temperature sufficient to vaporize and remove impurities is (or alternatively the furnace temperature will be increased to) above the melting point of the major constituent (i.e., the solvent) of the equilibrium growth dispersion.
  • the major constituent i.e., the solvent
  • the pellet 32 and substrate 40 are then pressed together, eliminating any trapped gas bubbles between the pellet and the substrate and insuring that there is complete wetting of the substrate-pellet interface.
  • the pellet-substrate structure is then cooled, resolidifying pellet 32 and bonding it to the substrate, thus forming a unitary pellet-substrate assembl -44 that can be loaded into the growth system.
  • the substrate and pellet are simply heated and then brought into contact with each other in an inert gas atmosphere. Heating, typically to a temperature of between 10 and 30 degrees above the melting point of the major constituent, causes slight melting and the pellet and substrate may then be pressed together to form the desired void-free interface. On cooling, the two bond together and form the unitary pellet- substrate assembly.
  • FIG. 3 illustrates, somewhat schematically, a system for conducting epitaxial growth using the pellet-substrate assembly 44 of the present invention.
  • the pellet-substrate assembly 44 is fitted into a stepped, cylindrical boron-nitride housing 50, with the growth pellet 32 fitting closely into a central axial bore 52 of housing 50 and the substrate 40 • fitted into an annular recess 54 in the base of a threaded cylindrical cavity 56 in the bottom 55 of housing 50.
  • a cylindrical graphite insert 60 fits into a cavity 62, coaxial with bore 52, recess 54 and cavity 56.
  • a replenishing source 64 (e.g., a source of the minor fraction constituent(s) which will melt and during growth will provide the additional material necessary to maintain the growth solution at equilibrium as growth proceeds) is placed on top of the pellet 32 of the pellet- substrate system 44, in an annular recess 66 in the base of a cavity 74 in insert 60.
  • Cylindrical graphite electrodes 70, 72 are screwed into place in cavities 74 and 56, with the upper electrode 70' contacting the top of source 64 and the lower electrode 72 in contact with substrate 40.
  • a conductive contact layer 76 typically a material, such as gallium to which some aluminum has been added, that will melt and provide complete wetting and electrical contact
  • the complete assembly (typically already provided in a furnace (not shown)) is then heated to the desired growth temperature, typically under reduced pressure.
  • the pellet 32 melts during heat-up and forms a solution, supersaturated at temperatures below the growth temperature and saturated and in thermodynamic equilibrium with both the substrate 40 and replenishing source 50 when the growth temperature is reached.
  • electric current is applied across electrodes 70, 72, as taught in the aforementioned U.S. Patent, causing the compound constituents in the saturated solution provided by pellet 32 to precipitate onto the interface 42 between the solution and the substrate, forming the desired compound (schematically indicated at 78).
  • the relative percentages of the constituents in the compound being grown is typically very different from that in the saturated solution.
  • the saturated solution from which a compound is grown typically will contain far more of one compound (the solvent) than the other (the solute).
  • the solute in the solution must be continuously replenished - with material from replenishing source 64 as growth proceeds.
  • Such combining and reshaping may be accomplished by placing one or more pellets 32 (the number depending on the desired total solution required for subsequent crystal growth) in a quartz reforming ampoule of the desired diameter (the inside of the reforming ampoule, like ampoule 10, is typically pyrolitically coated with a layer of carbon) , and then heating the reforming ampoule with the pellet(s) in it to a temperature some 50 to 70 degrees above the melting point of the major constituent of the pellet(s); but below that which the solute constituent(s) is, to any significant extent, soluble in the major fraction constituent (the solute).
  • the equilibrium growth dispersion pellet(s) will melt sufficiently to flow and form new growth pellet of diameter equal to that of ampoule 30, and upon subsequent cooling, the mixture will remain an essentially homogeneous dispersion of fine particles of the minor constituent(s) in the major constituent, i.e., an equilibrium growth dispersion, typically solid at room temperature.
  • an equilibrium growth dispersion typically solid at room temperature.
  • One particular useful application of the above- described invention is in the growth of gallium arsenide. In such growth, predetermined quantities of gallium and either elemental arsenic or gallium arsenide are cleaned, weighed, and placed within the ampoule 10 of Figure 1.
  • the relative percentages of gallium and arsenic or gallium arsenide to be loaded into ampoule 10 are determined from the phase diagrams of Figures 4 and 4A. If, for example, the epitaxial growth process is to be accomplished at a temperature of 850 degrees Centigrade, it will be seen from the phase diagrams of Figures 4 and 4A that an equilibrium solution at that temperature contains about 3.83% (by atomic percent, e.g., the atomic fraction expressed as a percent) arsenic and 96.17% gallium.
  • the amount of arsenic (or gallium arsenide which is, of course, 50% arsenic and 50% gallium by atomic percent) added to the gallium is chosen so that the total amount of arsenic in the ampoule is, by atomic percent, equal to 3.83% of the total.
  • equilibrium is provided by different relative proportions.
  • an equilibrium growth dispersion for epitaxial growth at 850°C may be proposed by heating together 0.26 grams of gallium arsenide and 3 g. of gallium; while, by way of comparison, an equilibrium growth dispersion for growth at 900°C. may be prepared, by adding 0.43 g.
  • melting and homogenization of the materials in the ampoule is provided by heating to about 880-900° C. (i.e., 30 to 50 degrees C above the planned 850°C. growth temperature) for a period of 24 hours; and the ampoule is then quenched.
  • the resulting desired equilibrium growth dispersion consists of fine particles of arsenic (with, perhaps, a minor amount of gallium arsenide particles) uniformly dispersed throughout the gallium) .
  • Complete wetting, and elimination of possible impurities at the interface 42 between the gallium arsenide equilibrium growth dispersion pellet 32 so formed and a gallium arsenide substrate 40 is preferably accomplished by placing both the substrate 40 and pellet 32 in a furnace (not shown) and heating, under reduced pressure, to about 400-500 degrees C. (as discussed previously and shown in Fig. 2A) Such heating converts any gallium hydroxide present to gallium oxide, and the oxide vaporizes and is removed from the system. While the system is still at elevated temperature, the pellet 32 and substrate are placed in contact with each other, and the system is then cooled, thus providing the desired pellet-substrate assembly 44 (as shown in Fig. 2B).

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Liquid Deposition Of Substances Of Which Semiconductor Devices Are Composed (AREA)

Abstract

Dispersion de croissance en équilibre destinée à être utilisée dans une culture épitaxiale liquide à une température de croissance prédéterminée d'un composé comprenant au moins deux constituants. Des quantités prédéterminées de chaque constituant sont placées dans une fiole en quartz scellée (10). La fiole est nettoyée et ses surfaces internes (12) sont recouvertes par un procédé pyrolitique d'une mince couche de carbone. Les quantités prédéterminées sont telles que les proportions relatives totales des constituants permettent d'obtenir une solution saturée de l'un des constituants dans un autre des constituants à la température de croissance et la fiole contenant les quantités prédéterminées est chauffée dans un organe chauffant (14) à une température non inférieure à la température de croissance pour dissoudre les constituants et est maintenue à cette température pendant un laps de temps suffisant pour produire une solution de l'un des constituants dans l'autre. On provoque ensuite la solidification rapide de la solution, généralement en la refroidissant dans un bain (16), pour former la dispersion de croissance en équilibre qui comprend une dispersion essentiellement homogène de particules d'un constituant (le soluté) dans l'autre (le solvant).
PCT/US1987/001261 1986-05-28 1987-05-26 Croissance epitaxiale Ceased WO1987007313A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US86813686A 1986-05-28 1986-05-28
US868,136 1986-05-28

Publications (1)

Publication Number Publication Date
WO1987007313A1 true WO1987007313A1 (fr) 1987-12-03

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PCT/US1987/001261 Ceased WO1987007313A1 (fr) 1986-05-28 1987-05-26 Croissance epitaxiale

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Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3278342A (en) * 1963-10-14 1966-10-11 Westinghouse Electric Corp Method of growing crystalline members completely within the solution melt
US3677228A (en) * 1970-04-17 1972-07-18 Bell Telephone Labor Inc Crystal growth apparatus
US3810794A (en) * 1970-09-24 1974-05-14 Varian Associates Preparation of gap-si heterojunction by liquid phase epitaxy
US3950195A (en) * 1975-02-21 1976-04-13 Bell Telephone Laboratories, Incorporated Lpe technique for reducing edge growth
US4026735A (en) * 1976-08-26 1977-05-31 Hughes Aircraft Company Method for growing thin semiconducting epitaxial layers
US4142924A (en) * 1976-12-16 1979-03-06 Massachusetts Institute Of Technology Fast-sweep growth method for growing layers using liquid phase epitaxy
US4283247A (en) * 1979-06-21 1981-08-11 Texas Instruments Incorporated Liquid phase epitaxial process for magnetic garnet
US4529027A (en) * 1982-06-14 1985-07-16 U.S. Philips Corporation Method of preparing a plurality of castings having a predetermined composition

Patent Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3278342A (en) * 1963-10-14 1966-10-11 Westinghouse Electric Corp Method of growing crystalline members completely within the solution melt
US3677228A (en) * 1970-04-17 1972-07-18 Bell Telephone Labor Inc Crystal growth apparatus
US3810794A (en) * 1970-09-24 1974-05-14 Varian Associates Preparation of gap-si heterojunction by liquid phase epitaxy
US3950195A (en) * 1975-02-21 1976-04-13 Bell Telephone Laboratories, Incorporated Lpe technique for reducing edge growth
US4026735A (en) * 1976-08-26 1977-05-31 Hughes Aircraft Company Method for growing thin semiconducting epitaxial layers
US4142924A (en) * 1976-12-16 1979-03-06 Massachusetts Institute Of Technology Fast-sweep growth method for growing layers using liquid phase epitaxy
US4283247A (en) * 1979-06-21 1981-08-11 Texas Instruments Incorporated Liquid phase epitaxial process for magnetic garnet
US4529027A (en) * 1982-06-14 1985-07-16 U.S. Philips Corporation Method of preparing a plurality of castings having a predetermined composition

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