WO2008034578A1 - Procédé de production d'alliages de silicium comportant du germanium - Google Patents

Procédé de production d'alliages de silicium comportant du germanium Download PDF

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Publication number
WO2008034578A1
WO2008034578A1 PCT/EP2007/008091 EP2007008091W WO2008034578A1 WO 2008034578 A1 WO2008034578 A1 WO 2008034578A1 EP 2007008091 W EP2007008091 W EP 2007008091W WO 2008034578 A1 WO2008034578 A1 WO 2008034578A1
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WO
WIPO (PCT)
Prior art keywords
process according
bearing
alloy
gecl
sicl
Prior art date
Application number
PCT/EP2007/008091
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English (en)
Inventor
Eric Robert
Tjakko Zijlema
Original Assignee
Umicore
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
Priority claimed from EP06019824A external-priority patent/EP1903007A1/fr
Application filed by Umicore filed Critical Umicore
Publication of WO2008034578A1 publication Critical patent/WO2008034578A1/fr

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Classifications

    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B33/00—Silicon; Compounds thereof
    • C01B33/02—Silicon
    • C01B33/021—Preparation
    • C01B33/027—Preparation by decomposition or reduction of gaseous or vaporised silicon compounds other than silica or silica-containing material
    • C01B33/033—Preparation by decomposition or reduction of gaseous or vaporised silicon compounds other than silica or silica-containing material by reduction of silicon halides or halosilanes with a metal or a metallic alloy as the only reducing agents
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B33/00—Silicon; Compounds thereof
    • C01B33/02—Silicon
    • C01B33/037—Purification

Definitions

  • the invention relates to the manufacture of Ge-bearing solar grade silicon as a feedstock material for the manufacture of crystalline silicon solar cells.
  • the alloy is obtained by direct reduction Of GeCl 4 and SiCl 4 , which are commonly available in high purity grades.
  • the Si is sometimes alloyed with Ge.
  • the addition of about 2 wt. % of Ge has indeed been reported to have the potential to enhance the efficiency of polycrystalline Si solar cells through an increase of minority carrier lifetime and/or optical absorption coefficient.
  • Silicon suitable for application in solar cells is commonly manufactured by the thermal decomposition of SiHCl 3 according to the Siemens process or its variants. The process delivers very pure silicon, but it is slow, highly energy consuming, and requires large investments.
  • SiCl 4 An alternative route towards the formation of Si for solar cells is the reduction of SiCl 4 with metals such as Zn. This process has the potential for significant cost reduction because of lower investment costs and reduced energy consumption.
  • high purity Ge-bearing Si alloy is obtained by a process for converting SiCl 4 and GeCl 4 to a Ge-bearing Si alloy, comprising the steps of: - contacting SiCl 4 and GeCl 4 with a liquid metal phase containing Zn, thereby obtaining a Si- and Ge-bearing metal phase and Zn-chloride;
  • the total amounts of SiCl 4 and GeCl 4 introduced in contacting step are preferably chosen so as to obtain a Ge-bearing Si alloy with 1 to 5 wt.% of Ge.
  • the Si- and Ge-bearing metal phase as obtained in the contacting step can advantageously contain, besides Si as solute, also at least some Si in the solid state, e.g. as suspended particles. Formation of particular Si may indeed occur during the contacting step, when the Zn metal gets saturated in Si.
  • Solid state Si and Ge can also be obtained by cooling the Si- and Ge-bearing metal phase as obtained in the contacting step, preferably to a temperature of between 450 and 600 °C.
  • the solids can preferably be separated from the bulk of the molten phase, e.g. after settling. They form an enriched Si- and Ge-bearing metal phase, which is however still impregnated with Zn and has to be further processed in the purification step.
  • Gas flow rates up to 50 kg/min per m 2 of bath surface are compatible with the abovementioned low Si losses.
  • the gaseous SiCl 4 and GeCl 4 are adequately dispersed in the bath, e.g. by using multiple submerged nozzles, a submerged nozzle equipped with a porous plug, a rotating gas injector, or any other suitable mean or combination of means.
  • the SiCl 4 and GeCl 4 can be injected along with a carrier gas such as N 2 .
  • a flow rate over 10, and preferably 12 or more kg/min per m 2 of bath surface is advised to perform the process in a more economical way.
  • the obtained Zn-chloride can be subjected to molten salt electrolysis, thereby recovering Zn, which can be recycled to the contacting step, and chlorine, which can be recycled to a Si and/or Ge chlorination process for the production of SiCl 4 and/or GeCl 4 ;
  • the purification step can be condensed and recycled to the contacting step; and/or- the fraction of SiCl 4 and GeCl 4 that exits the contacting step un-reacted can be recycled to the contacting step.
  • the purification step is performed above the melting point of the Ge-bearing Si alloy, the alloy can be solidified only once, using e.g. ribbon growth or directional solidification.
  • the ribbon growth method includes its variants, such as ribbon-growth- on-substrate (RGS), which directly yields RGS Si wafers.
  • the molten silicon can be granulated, the granules being fed to a melting furnace, preferably in a continuous way, whereupon the molten silicon can be solidified in a single step, again using e.g. ribbon growth or directional solidification.
  • the solid material obtained can then be further processed to solar cells, directly or after wafering, according to the solidification method used.
  • suitable amounts of SiCl 4 and Of GeCl 4 are injected into liquid Zn. Both products can be injected simultaneously or sequentially, in any order. It is experienced that the conversion yield of GeCl 4 is nearly quantitative, whilst the conversion of SiCl 4 typically is somewhat lower. The exact yields will depend on the specific configuration of the reactor and of the chosen temperatures and gas flow rates. The operator will thus have to monitor the Ge to Si alloying ratio and adapt the flow rates of SiCl 4 and GeCl 4 in a straightforward and known way to correct any deviation from the desired ratio. Making use of the same apparatus for Ge-alloying as for the Si production renders this scheme particularly attractive and economic. GeCl 4 is indeed a relatively cheap source of ultra-pure Ge, and the direct reduction with liquid zinc avoids the multiple steps according to the usual ultra-pure Ge production process.
  • a Ge- and Si-bearing Zn alloy containing both dissolved and solid Si can be obtained, while the chlorinated Zn either forms a separate liquid phase, or is formed as a vapour.
  • Zn can be retrieved from its chloride, e.g. by molten salt electrolysis, and reused in de contacting step.
  • the alloy can be purified at high temperatures, above the boiling points of both Zn and Zn-chloride, but below the boiling point of the Si ( 2355 0 C).
  • the evaporated Zn can be retrieved and reused. Any other volatile element is also removed in this step. It is thus possible to close the loop on Zn, thereby avoiding the introduction of impurities into the system through fresh additions.
  • gaseous GeCl 4 and SiCl 4 are contacted with liquid Zn at atmospheric pressure, at a temperature above the boiling point OfZnCl 2 (732 °C) and below the boiling point of Zn (907 0 C).
  • the preferred operating temperature is 750 to 880 °C, a range ensuring sufficiently high reaction kinetics, while the evaporation of metallic Zn remains limited.
  • the molten Zn is placed in a reactor, preferably made of quartz or of another high purity material such as graphite.
  • a reactor preferably made of quartz or of another high purity material such as graphite.
  • Both SiCl 4 and GeCl 4 which are liquid at room temperature, are injected via a submerged tube. The injection is performed in the lower part of the Zn-containing vessel.
  • the liquid chlorides are heated during their transit in the tube, and are actually injected as gases. They can also be vaporized in a separate evaporator, and the obtained vapours are then injected in the melt.
  • the end of the injection tube can be provided with a dispersion device such as a porous plug or fritted glass. It is indeed important to have a good contact between the gaseous chlorides and the Zn to get a high reduction yield. If this is not the case, partial reduction could occur. Finely dispersing the gasses is an important factor in limiting the entrainment of particulate Si with the gaseous flow.
  • the reduction process produces ZnCl 2 . It has a boiling point of 732 °C, and is gaseous at the preferred operating temperature. It leaves the Zn-containing vessel via the top. The vapours are condensed and collected in a separate crucible.
  • the process also produces metallic Si and Ge. Both dissolve in the molten Zn up to their solubility limit.
  • the Si solubility in the Zn increases with temperature but remains limited to about 4% at 907 °C, the atmospheric boiling point of pure Zn. Ge is markedly more soluble.
  • the injected amount of SiCl 4 is such that the solubility limit of Si in Zn is exceeded. Solid, particulate Si is produced, which may remain in suspension in the molten Zn bath and/or aggregate so as to form dross. This results in a Zn metal phase with total (dissolved, suspended and drossed) Si concentration of preferably more than 10%, i.e. considerably higher than the solubility limit.
  • any particulate Si is however subject to losses by entrainment with the gaseous ZnCl 2 stream.
  • the particulate Si can be subject to losses by entrainment with the ZnCl 2 gaseous stream, however, in practice the Si loss by entrainment is less than 15% of the total Si input, and this is to be considered as acceptable.
  • the Si-and Ge- bearing Zn alloy is allowed to cool down to a temperature somewhat above the melting point of the Zn, e.g. 600 °C.
  • a major part of the initially dissolved Si crystallizes together with some Ge, and accumulates together with any solid Si that was already present in the bath in an upper solid fraction.
  • the lower liquid fraction of the metal phase is Si- and Ge-depleted, and can be separated by any suitable means, e.g. by pouring. This metal can be directly re-used in a subsequent contacting step.
  • the upper solid fraction is subjected to the purification as mentioned above, with the advantage that the amount of Zn to be evaporated is considerably reduced.
  • the Zn can be separated from the Ge-bearing Si alloy by vaporisation at a temperature above the boiling point of Zn (907 °C). A purity of 5N to 6N is then obtained. A special high temperature sparging or bubbling step with a gaseous Si or Ge chloride or with Cl 2 typically leads to an even superior purity. For this operation, the temperature is further increased above the melting point (about 1400 0 C) but below the boiling point of (about 2355 °C) of the Si. Some of the elements that can be eliminated by this process step are Cr, Cu, Mn, Al, Ca, B and P. It is noteworthy that Ge is not eliminated during this process.
  • a further advantage of the invention is that the Ge-bearing Si alloy can be recovered in the molten state at the end of the purification process. Directly obtaining the Ge- bearing Si alloy in the molten state allows for a better integration of the feedstock production with the steps towards wafer production, providing an additional reduction in the total energy consumption of the process as well as in the cost of the wafer manufacturing.
  • the liquid alloy can indeed be solidified in a single step, directly yielding ingots, or substrates if a ribbon growth method is used.
  • the following example illustrates the invention.
  • 8500 g of metallic Zn is heated to 850 0 C in a graphite reactor.
  • the height of the bath is about 19 cm and its diameter is 9 cm.
  • a MinipulsTM peristaltic pump is used to introduce GeCl 4 in the reactor via a quartz tube.
  • the immersed extremity of the tube is fitted with a porous plug made of quartz.
  • the GeCl 4 vaporises in the immersed section of the tube and is dispersed as a gas in the liquid Zn.
  • 50g Of GeCl 4 is injected, with a flow rate of ca. 250 g/h.
  • the ZnCl 2 which evaporates during the reaction, condenses in a graphite tube connected to the reactor and is collected in a separate vessel. Any un-reacted GeCl 4 is collected in a wet scrubber connected to the ZnCl 2 vessel.
  • the formed Ge dissolves completely in the zinc.

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  • Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Inorganic Chemistry (AREA)
  • Silicon Compounds (AREA)

Abstract

L'invention concerne la production d'alliages de silicium comportant du germanium qui présentent un degré de pureté élevé, et qui sont utilisés en tant que matériau de base pour produire des cellules solaires à base de silicium. Les composés SiCl4 et GeCl4, qui se trouvent à l'état gazeux, sont convertis en des métaux par contact de ces composés avec du Zn liquide, ce qui permet d'obtenir un alliage de Si comportant du Ge ainsi que du chlorure de Zn, cet alliage et ces composés étant ensuite séparés. Puis, l'alliage est purifié par chauffage à une température supérieure au point de fusion du Zn. Ce procédé peut être effectué sans utiliser de technologie compliquée, et permet de conserver le degré de pureté élevé des composés SiCl4 et GeCl4 jusqu'a l'obtention du produit final. Le seul autre réactif employé est Zn, qui peut être obtenu à des degrés de pureté très élevés, et qui peut être recyclé après l'électrolyse du chlorure de Zn.
PCT/EP2007/008091 2006-09-22 2007-09-18 Procédé de production d'alliages de silicium comportant du germanium WO2008034578A1 (fr)

Applications Claiming Priority (6)

Application Number Priority Date Filing Date Title
EP06019824A EP1903007A1 (fr) 2006-09-22 2006-09-22 Procédé de production d'alliages de silicium contenant du germanium
EP06019824.9 2006-09-22
US84673906P 2006-09-25 2006-09-25
US60/846,739 2006-09-25
EP07010413 2007-05-25
EP07010413.8 2007-05-25

Publications (1)

Publication Number Publication Date
WO2008034578A1 true WO2008034578A1 (fr) 2008-03-27

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WO (1) WO2008034578A1 (fr)

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2468892A (en) * 2009-03-25 2010-09-29 Tate & Lyle Technology Ltd A molten salt treatment system and process
US20110318250A1 (en) * 2010-06-08 2011-12-29 Kaner Richard B Rapid solid-state metathesis routes to nanostructured silicon-germainum
US8591758B2 (en) 2010-06-23 2013-11-26 California Institute Of Technology Mechanochemical synthesis and thermoelectric properties of magnesium silicide and related alloys
CN108823637A (zh) * 2018-07-30 2018-11-16 孟静 提纯多晶硅的装置
CN108842183A (zh) * 2018-09-10 2018-11-20 孟静 多晶硅片的制备方法

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH1111925A (ja) * 1997-06-25 1999-01-19 Sumitomo Metal Ind Ltd 多結晶シリコンおよび塩化亜鉛の製造方法
JPH1192130A (ja) * 1997-09-11 1999-04-06 Sumitomo Sitix Amagasaki:Kk 高純度シリコンの製造方法
WO2006034802A1 (fr) * 2004-09-29 2006-04-06 Umicore Procede de production de ge consistant a reduire geci4 au moyen de metal liquide
WO2006100114A1 (fr) * 2005-03-24 2006-09-28 Umicore Procede de fabrication de si par reduction de sicu a l’aide de zn liquide
WO2007013644A1 (fr) * 2005-07-28 2007-02-01 Sumitomo Chemical Company, Limited Procédé servant à produire du silicium polycristallin

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH1111925A (ja) * 1997-06-25 1999-01-19 Sumitomo Metal Ind Ltd 多結晶シリコンおよび塩化亜鉛の製造方法
JPH1192130A (ja) * 1997-09-11 1999-04-06 Sumitomo Sitix Amagasaki:Kk 高純度シリコンの製造方法
WO2006034802A1 (fr) * 2004-09-29 2006-04-06 Umicore Procede de production de ge consistant a reduire geci4 au moyen de metal liquide
WO2006100114A1 (fr) * 2005-03-24 2006-09-28 Umicore Procede de fabrication de si par reduction de sicu a l’aide de zn liquide
WO2007013644A1 (fr) * 2005-07-28 2007-02-01 Sumitomo Chemical Company, Limited Procédé servant à produire du silicium polycristallin

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
DATABASE WPI Week 200719, Derwent World Patents Index; AN 2007-192504, XP002462659 *

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2468892A (en) * 2009-03-25 2010-09-29 Tate & Lyle Technology Ltd A molten salt treatment system and process
US20110318250A1 (en) * 2010-06-08 2011-12-29 Kaner Richard B Rapid solid-state metathesis routes to nanostructured silicon-germainum
US8808658B2 (en) 2010-06-08 2014-08-19 California Institute Of Technology Rapid solid-state metathesis routes to nanostructured silicon-germainum
US8591758B2 (en) 2010-06-23 2013-11-26 California Institute Of Technology Mechanochemical synthesis and thermoelectric properties of magnesium silicide and related alloys
CN108823637A (zh) * 2018-07-30 2018-11-16 孟静 提纯多晶硅的装置
CN108842183A (zh) * 2018-09-10 2018-11-20 孟静 多晶硅片的制备方法

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