SILICON-BASED CERAMIC COATINGS FOR QUARTZ CRUCIBLES FOR CZOCHRALSKI GROWTH OF SILICON SINGLE CRYSTALS, SIMILAR UNIDIRECTIONAL GROWTH METHODS AND SIMILAR SEMICONDUCTOR MATERIALS, AND OTHER APPLICATIONS REQUIRING REDUCED CHEMICAL REACTIVITY OF FUSED SILICA

摘要

1. The invention provides a new process for the unidirectional growth ofsingle crystal ingots of semiconductor materials such as silicon, germaniumandsilicon/germanium alloys, by coating the quartz crucibles holding the moltenmaterial. The coating process of quartz crucibles films aims at reducingchemicalcontamination of the single crystal, and/or enhance wetting properties of thecrucible with respect to the contained molten materials. The ceramic coatingmayconsist of silicon carbide, and/or silicon oxycarbide, silicon carbonitride,siliconcarboronitride, or any other multilayered structure comprising at least one ofthese films. The unidirectional growth methods include Czochrralski (Cz),Magnetic Czochralski (MCz), Liquid Encapsulated Czochralski (LEC), Bridgman-Stockbarger, Vertical Gradient Freeze, Pedestal, Heat Exchange Method (HEM),Casting, Ribbon/Sheet Growth, etc. The synthesis of the coating includevariousmethods, such as Chemical Vapour Deposition and related methods, polymer-derived methods, sputtering, Vapor Deposition Transport, laser ablation, etc.2. The invention provides a new method for the confinement of themolten material during the unidirectional growth of semiconductor materials,bydepositing a ceramic thin film on the inner and/or outer walls of the quartzcrucible. The method of improving the quartz crucible holding the moltensemiconductor material during a crystal growing process, consists of thedeposition on the surface of the crucible of a film of silicon carbide, ofsiliconoxycarbide, or any multi layered structure coating comprising a film of theabovementioned materials at the interface with the molten silicon and/or at theinterfacewith the holder/susceptor. The quartz crucible improved this way may be usedforthe Czochralski growth of single crystal, polycrystalline,or amorphoussemiconductor silicon, germanium, or silicon /germanium alloys. The methodresults in:a) a reduced contamination with oxygen from SiO2 by reduced SiOformation at the SiO2/Si interfaceb) a reduced contamination with carbon via CO-dissolution from thegas phase, andc) a reduced contamination with SiC-particles produced thegaseous atmosphere are sought.Since SiO, CO and SiC are responsible for the contamination of thesemiconductor product with oxygen, carbon, and induce crystalline defects(stacking faults, dislocations, precipitates, resistivity instability viageneration ofthermal donors, etc), control of the formation of all these defects may beachieved via the use of the new crucible3. The invention provides a new method for solid-source doping directlyfrom the coated quartz crucible during the unidirectional growth ofsemiconductormaterials, permitting control of the optimum delivery from/through the ceramicfilm of doping impurities such as B, Al, Ga, In, N, P, As, Sb, H that can becontained in the quartz wall or in the ceramic film. Also, incorporation ofoptimumconcentrations of essential elements, such as oxygen and carbon, can beachieved below the saturation limit. Doping with S, Se, Te becomes alsofeasiblein the case of silicon, germanium, silicon/germanium alloys and diamond-likesemiconductor materials.4. The invention provide an improved quartz crucible for theunidirectional growth of single crystal ingots of semiconductor silicon,germanium,and silicon/germanium alloys, characterized by reduced transfer of SiO and/orCO into the melt from the crucible/melt and/or the crucible/holder interface.Thecrucible includes a body of vitreous silica having an inner surface which isincontact during the growth process with molten silicon, and an outer surfacewhichis in contact with the graphite holder. The chemical reactivity of SiO2(silica,quartz) produces SiO and CO at the two mentioned interfaces, species that arethe main sources responsible for the contamination of the single crystal withoxygen and carbon the crucible unstable during. These two impurities are themain impurities in the semiconductor crystal, and the induced defects relatedtothe presence of oxygen, carbon, and other species resulted from the chemicalreactions involving these (such as in situ formation of SiC) in the singlecrystalinclude stacking faults, oxygen precipitates, formation of thermal donors,formation of dislocations, and others. Control over the production of thesetwospecies during the silicon melting and crystal growing process resultsimplicitly incontrolling the physical and chemical properties affected by the inclusion oftheseimpurities in the crystal.5. The invention provide a method of coating with silicon carbide/siliconoxycarbide films that can be used in applications where reduced chemicalreactivity of SiO2 is sought, either for the protection of the silicamaterial, or for toavoid contamination with silicon or oxygen from silica.6. The invention provides s solid source of doping with oxygenconsisting of an ultrathin silicon carbide/oxycarbide ceramic film depositedon ahigh purity quartz rod which is introduced in the molten zone duringunidirectionalsolidification of the material. The ceramic ultrathin film acts as a barrierwithcontrolled porosity against oxygen diffusion from the inner silica walltowards thesemiconductor melt contained in the quartz crucible.7. The invention provides a solid source for doping with elements fromthe series N,P,As,Bi,B,Al,Ga,In,S,Se,As,B,H, from thin silicon-based ceramicfilms deposited on quartz crucibles during unidirectional solidification ofsemiconductor materials.The invention provide a new process for the unidirectional growth of singlecrystal ingots of semiconductor materials such as silicon, germanium andsilicon/germanium alloys, by coating the quartz crucibles holding the moltenmaterial. Thequartz crucibles are coated with ceramic films aims at reducing chemicalcontamination ofthe single crystal, and/or enhance wetting properties of the crucible withrespect to thecontained molten materials.The ceramic coating comprises silicon carbide, and/or silicon oxycarbide,siliconcarbonitride, silicon carboronitride, or any other multilayered structurecomprising at leastone of these films.. The unidirectional growth methods include Czochrralski(Cz),Magnetic Czochralski (MCz), Vapor Controlled Czochralski (VCz), LiquidEncapsulatedCzochralski (LEC), Bridgman-Stockbarger, Vertical Gradient Freeze, Pedestal,HeatExchange Method (HEM), Casting, Ribbon/Sheet Growth, etc. The synthesis of thecoating include various methods, such as Chemical Vapour Deposition andrelatedmethods, polymer-derived methods, sputtering, Vapor Deposition Transport,laserablation, etc.The invention provides a new method for the confinement of the moltenmaterial during the unidirectional growth of semiconductor materials, bydepositing aceramic thin film on the inner and outer walls of the quartz crucible.The invention provides a new method for solid-source doping directly from thecoated quartz crucible during the unidirectional growth of semiconductormaterials,permitting control of the optimum delivery from/through the ceramic film ofdopingimpurities such as B, Al, Ga, In, N, P, As, Sb, H that can be contained in thequartz wallor in the ceramic film. Also, incorporation of optimum concentrations ofessentialelements, such as oxygen and carbon, can be achieved below the saturationlimit.Doping with S, Se, Te becomes also feasible in the case of silicon, germanium,silicon/germanium alloys and diamond-like semiconductor materials.The invention provide an improved quartz crucible for the unidirectionalgrowthof single crystal ingots of semiconductor silicon, germanium, andsilicon/germaniumalloys, characterized by reduced transfer of SiO and/or CO into the melt fromthecrucible/melt and/or the crucible/holder interface.The invention provide a method of coating with silicon carbide/siliconoxycarbide films that can be used in applications where reduced chemicalreactivity ofSiO2 is sought, either for the protection of the silica material, or for toavoid contaminationwith silicon or oxygen from silica.