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
  • C30B29/00—Single crystals or homogeneous polycrystalline material with defined structure characterised by the material or by their shape
  • C30B29/02—Elements
  • C30B29/06—Silicon
• • 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
  • C30B11/00—Single-crystal growth by normal freezing or freezing under temperature gradient, e.g. Bridgman-Stockbarger method
  • C30B11/002—Crucibles or containers for supporting the melt
• • 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
  • C30B21/00—Unidirectional solidification of eutectic materials
  • C30B21/02—Unidirectional solidification of eutectic materials by normal casting or gradient freezing
• • 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
  • C30B28/00—Production of homogeneous polycrystalline material with defined structure
  • C30B28/04—Production of homogeneous polycrystalline material with defined structure from liquids
  • C30B28/06—Production of homogeneous polycrystalline material with defined structure from liquids by normal freezing or freezing under temperature gradient
• • 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
  • C30B29/12—Halides
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
  • H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
  • H01L31/0248—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by their semiconductor bodies
  • H01L31/036—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by their semiconductor bodies characterised by their crystalline structure or particular orientation of the crystalline planes
  • H01L31/0368—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by their semiconductor bodies characterised by their crystalline structure or particular orientation of the crystalline planes including polycrystalline semiconductors
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
  • Y02E10/00—Energy generation through renewable energy sources
  • Y02E10/50—Photovoltaic [PV] energy

Definitions

• the invention relates to a process for the production of multicrystalline silicon.
• Multicrystalline silicon is used to manufacture photovoltaic solar cells.
• the crystal has different
• Feedstock for the production of monocrystalline or multicrystalline silicon is polycrystalline silicon.
• the polycrystalline silicon is usually produced by means of the Siemens process.
• a bell-shaped reactor (“Siemens reactor") thin filament rods ("thin rods") of silicon are heated by direct current passage and a reaction gas containing a silicon-containing component and hydrogen introduced.
• a reaction gas containing a silicon-containing component and hydrogen introduced.
• An alternative is the production of polycrystalline silicon granules in a fluidized bed reactor. This is done by fluidization of silicon particles by means of a gas flow in a fluidized bed, which is heated by a heater to high temperatures. By adding a silicon-containing reaction gas, a deposition reaction takes place on the hot
• TCS Terichlorosilane
• Single-crystalline silicon can be produced by means of crucible pulling (Czochralski or CZ process) or by zone melting (float zone or FZ process).
• the solidification of the silicon is usually carried out in Quarzguttiegeln, with
• Silicon nitride are coated.
• the silicon nitride prevents the silicon from adhering to the crucible. In the case of adhesion, cracks in the silicon material and loss of the crystallized silicon may occur.
• the silicon is heated until it melts. When completely melted, the silicon solidifies from bottom to top. After solidification, the crystal is slowly cooled controlled.
• the crystal After the crystal has cooled, the crystal can be removed and processed into wafers.
• the crystal blocks are first separated by means of a réellelochsäge into smaller blocks or bricks (raw and finished columns).
• the smaller bricks are then cut into wafers using a wire saw.
• the approach is pursued to influence the initial crystal microstructure on the bottom of the crucible by moderation of the axial heat transfer.
• US 201 1/239933 A1 discloses a method for producing silicon blocks comprising the following steps:
• the removal of the heat takes place in such a way that sets in the region of the bottom on the inside of the vessel at least temporarily an inhomogeneous temperature distribution.
• the temperature distribution comprises one
• Production of silicon ingots comprising the following steps: providing a container for receiving a silicon melt,
• liquid silicon may be brought into contact with a substrate having a temperature below the melting temperature of silicon.
• the substrate preferably consists of a fine-grained raw material such as silicon, silicon carbide, silicon nitride or graphite having a mean grain size in the range of 0.1 mm to 3 mm, which is placed directly on a bottom of the container and in particular a thickness in the range of 1 cm to 5 cm.
• the temperature in the fine-grained layer is below the silicon melting temperature and the melting and
• Solidification process can take place either in the same or two different crucibles and the crystallized silicon block has a height of at least 50 cm.
• the number of grains should decrease from the bottom to the cap and thereby decrease at least 20%, in particular at least 30%. It is reported that the electrically recombination-active defect content remains constant above a certain block height.
• US 2013/136918 A1 discloses a process for producing a crystalline
• Forming tool wherein the mold itself sets a vertical direction
• crystalline silicon block having a lower portion and defining a vertical direction, characterized in that the crystalline silicon block has a plurality of vertically grown ones
• the rate of increase of the defect density in the vertical direction of the block is in a range of 0.01 to 10% / mm.
• Nucleation promotion layer should consist of irregular particles with a size of less than 50 mm and composed of silicon and silicon carbide particles. Furthermore, the nucleation promoting layer may consist of a plate having a melting point above that of silicon and having a roughness of 300 to 1000 ⁇ m.
• the crystal material (block and wafer) should have predominantly crystal orientations of the silicon grains between (001) and (1 1 1), wherein a volume percentage of the silicon grains with the predominant
• Crystal orientations should be greater than 50%.
• Providing a temperature control device for controlling the temperature of the silicon melt in the container Arranging raw material in the container comprising silicon and at least one nucleating agent to promote heterogeneous nucleation in the silicon melt, and
• the nucleating agent comprises nanoscale particles.
• nucleating agents for heterogeneous nucleation in the silicon melt.
• the specification of the additional nucleating agents takes place in the vicinity of the bottom of the crucible, preferably in an area where the nucleating agent concentration is greater than the saturation concentration of the elements involved.
• the nucleating agents should have a surface area of at least 2 m 2 / g, the particles optionally
• Getterzentren be for metal atoms, consisting of at least a portion of silicon and at least one element of C, O and N. 90% of the nucleating particles should have a size of at most 1 ⁇ .
• a silicon ingot having a longitudinal axis, a first end in the direction of the longitudinal axis, a second end in the direction of the longitudinal axis, a length (L) in the direction of the longitudinal axis, a multicrystalline structure and a grain density, which in the region of the first end at least 400 dm “2 , in particular at least 600 dm " 2 , in particular at least 800 dm "2 .
• a silicon wafer of multicrystalline silicon is known, with a wafer surface and with particles, wherein at least 90% of the particles have a
• Diameter of at most 1 ⁇ have, and the particles have a proportion of a compound of silicon and at least one of the elements selected from the group of carbon, oxygen and nitrogen.
• silicon wafers which have an area ratio of at least 80 and up to 95% and a dislocation density of less than 10 5 cm "2.
• Production of silicon ingots comprising the steps of providing a crucible for receiving a silicon melt, having a bottom and a plurality of side walls connected to the bottom; Attaching germs at least on an inner side of the bottom of the crucible, wherein the seeds have a melting temperature which is greater than the melting temperature of silicon; Filling the crucible with the silicon melt; Solidification of the silicon melt on the seeds starting and removing the solidified silicon from the crucible.
• the process leads to an initially fine-grained crystal structure.
• the necessary germ density is in the range of 0.001 to 100 / cm 2 , the seed size in the range of 0.01 to 50,000 ⁇ .
• materials to be used one or more compounds of the elements of III., IV. And / or V. main group are described, but in particular AI2O3, SiC, SiO, SiO2, Si3N4, BN, BP, AIAs, AIN or BeO.
• DE 10 201 1 003 578 A1 and US 201 1/203517 A1 describe a method for the production of silicon blocks comprising the following steps:
• a vessel for receiving a silicon melt which has on at least one vessel wall at least in regions a nucleation-suppressing surface and at least one seed target on the inside provided with the nucleation-suppressing surface on an inner side of at least one vessel wall; arranging a silicon melt; Melt in the vessel by pouring liquid silicon or by melting solid silicon,
• materials to be used are silicon carbide, graphite, silicon nitride,
• nucleation-promoting layer and a diffusion-inhibiting layer is constructed and may consist of various Ba compounds, oxides, carbides, nitrides, etc.
• the processes described in the prior art are technologically complex due to the costly adjustment of the heat transfer and the longer process times, eg. B. when germinating on Siliciunnrohstoff.
• the problem of the invention resulted.
• the object was multicrystalline silicon with a lower electrically recombination-active surface area and thus higher
• the object of the invention is achieved by a method for producing multicrystalline silicon, comprising the following steps:
• the bottom of the crucible has a coating comprising one or more compounds selected from the group consisting of Si 3 N 4, Si 3 N 4 and oxidized S1O2,
• the silicon layer releases a reducing agent upon heating of the crucible and / or melting of the silicon layer.
• the silicon layer comprises a silicon raw material conditioned to release a reducing agent. This changes the wetting behavior of the Crucible coating against the silicon melt produced from the polycrystalline silicon. This wetting behavior varies with the oxygen content of the crucible coating. A chemical attack by the reducing agent reduces the oxygen content of the crucible coating, thereby influencing the wetting properties. This allows the initial
• the silicon layer comprises polycrystalline silicon produced by means of the previously described Siemens process and then added to
• the silicon-containing component of the reaction gas is monosilane or a halosilane, e.g. Trichlorosilane mixed with hydrogen. Hydrogen and halogens are thereby added e.g. enclosed in the granular silicon particles.
• the silicon layer comprises polycrystalline silicon having a
• Hydrogen in silicon can be measured by "inert gas fusion thermal conductivity / infrared detection method" analogously to ASTM E 1447.
• the silicon layer comprises polycrystalline silicon with a
• the silicon layer comprises polycrystalline silicon having a
• Halogens or chloride can be analyzed via SEMI PV 10, "Test Method for Instrumental, Neutron Activation Analysis (INAA) of Silicon” or also
• the silicon layer comprises granular polycrystalline silicon with a particle size of 50 to 4000 ⁇ m. Particularly preferred is a grain size of 50 to 400 ⁇ .
• the determination of the particle size can be carried out by means of an optical particle size analyzer. This is the dynamic
• the silicon layer in one embodiment is placed in the crucible so as to cover at least 30% of the area of the bottom of the crucible. Preferably, at least 50% of the bottom surface of the crucible is covered. In one embodiment, the silicon layer completely covers the bottom surface of the crucible.
• the silicon layer preferably has a height of 50 ⁇ to 100 cm, more preferably 50 ⁇ to 10 cm and most preferably 50 ⁇ to 1 cm.
• polycrystalline silicon may be fractions (Siemens process) or polycrystalline silicon granules.
• the crucible coating at least 200 ⁇ , preferably 300-500 ⁇ thick, the chemical attack by the reducing agent, which is released from the silicon layer, only in the upper part of the crucible coating (50-150 ⁇ thickness). Only in the upper range does the wetting behavior change. Under the chemically attacked upper part of the coating remains a non-wetting coating that prevents complete penetration of the silicon melt to the crucible bottom.
• the silicon layer has no contact with the inside of the crucible.
• the distance to the inside of the crucible should be at least 1 mm. In one embodiment, the distance is at least 1 cm. This can be done
• the directional solidification of the silicon melt preferably produces a multicrystalline silicon block or a crude and finished column (Brick), hereinafter referred to as a silicon column having an average particle size of less than 12.5 mm 2 , more preferably less than 5 mm 2 , most preferably less than 2.5 mm 2 in the bottom region of the multicrystalline silicon block or the multicrystalline silicon column.
• a silicon column having an average particle size of less than 12.5 mm 2 , more preferably less than 5 mm 2 , most preferably less than 2.5 mm 2 in the bottom region of the multicrystalline silicon block or the multicrystalline silicon column.
• the bottom area extends from the bottom of the silicon block or the bottom of the silicon column to a height of the block of 5 cm (range 0-5 cm from the floor).
• the mean grain size can be determined for example by means of the identification and
• the multicrystalline silicon block, the multicrystalline silicon column and a multicrystalline silicon wafer made therefrom have a maximum mean grain size - measured on an area of 156 x 156 mm 2 - of 12.5 mm 2 , more preferably 10 mm 2 and most preferably 7 mm 2 ,
• the multicrystalline silicon block, the multicrystalline silicon column and a multicrystalline silicon wafer produced therefrom preferably have a homogeneous areal distribution of the grain orientation.
• individual grain orientations should not have an area fraction on an area of 156 ⁇ 156 mm 2 of block, column or wafer of greater than 50%, particularly preferably greater than 25%.
• Individual grain orientations should have an area fraction of less than 25%, more preferably less than 10%, and most preferably less than 5%.
• a microstructure of multicrystalline silicon block, multicrystalline silicon pillar, and a multicrystalline silicon wafer made thereof should have one
• Block-close wafers preferably have an electrically recombination-active area fraction of 0.2-2.5%.
• Multicrystalline silicon wafers with the lowest electrically recombination active area fraction from the block cap, ie at the end of solidification, preferably have an average particle size of 6-1 1 mm 2 .
• the crucible is preferably a quartz crucible, the one
• Coating containing Si3N has.
• the resulting silicon layer comprises silicon, which releases an agent that chemically attacks oxide-containing surfaces.
• Siliciumeinwaage (silicon seed layer and arranged above it polycrystalline silicon) can be melted within the crucible, thus the process takes less time and then can be germinated small-grained on the wetting crucible coating. In addition, the expansion of the bad bottom area, which is due to solid-state diffusion from the crucible and the coating, is reduced.
• the initial seeding in the directional solidification of multicrystalline silicon can be controlled by the presentation of a specific silicon raw material in the form of Siliciunn- layer.
• the spatial variation of the addition also allows the spatial structure of the wetting behavior to be defined.
• a local or locally varied template is possible.
• the crucible may consist of S1O2, Si3N or C.
• the coating may be composed of Si3N particles, which in turn have an oxidized surface. It can also be different
• Crucible coatings can be combined: one crucible coating can slow down or even prevent the chemical attack induced by the silicon layer, while the second crucible coating promotes chemical attack.
• the silicon layer which is in direct contact with the oxidized Si3N-based crucible coating, can be arranged in the crucible in different ways: it can be either full-surface or locally confined to the crucible
• Fig. 1 shows a coated crucible with silicon layer and polycrystalline silicon in cross-section.
• Fig. 2 shows a coated crucible with silicon layer and polycrystalline silicon in cross-section.
• Fig. 3 shows a coated crucible with silicon layer and polycrystalline silicon in plan view.
• Fig. 4 shows a coated crucible with silicon layer and polycrystalline silicon in cross-section.
• Fig. 5 shows a coated with two different materials crucible with silicon layer and polycrystalline silicon in cross section.
• Fig. 6 shows defect content and average grain size over the height of the crystal block for Example and Comparative Example. List of reference numbers used
• Fig. 1 shows the sketch of a crucible 3 in cross section, consisting of side walls and a crucible bottom. You can see from the outside in the crucible 3, the
• silicon-releasing material namely the silicon layer 1 is filled and the area which is filled with "normal” silicon raw material, namely with polycrystalline silicon
• Figs. 2 and 3 show sketches of a crucible 3 in cross section, consisting of
• Fig. 4 shows the sketch of a crucible 3 in cross section, consisting of side walls and a crucible bottom.
• the specification of the silicon layer 1 takes place here in such a way that the silicon layer 1 does not come in direct contact with the side walls of the crucible 3.
• Fig. 5 shows the sketch of a crucible 3 in cross section, consisting of side walls and a crucible bottom. You can see from the outside in the crucible 3, the
• the crucible coating 41 is characterized in that the silicon layer 1 slows down induced chemical attack or does not take place at all.
• Crucible coating 42 is characterized in that the induced by silicon layer 1 chemical attack proceeds favorably.
• the inventive process A is characterized by the specification of a polycrystalline silicon granules, which was deposited on trichlorosilane in a fluidized bed, with a grain size of 0 to 4000 ⁇ and a chlorine content of greater than 35 ppmw.
• the standard process B is characterized by the specification of broken polycrystalline silicon on the crucible bottom, produced by the Siemens process, with a grain size of 0-15 mm and a chlorine content of less than 1 ppmw.
• Fig. 6 shows a comparison of the defect content and the average grain size over the block height for the presentation of a silicon layer 1 on the crucible bottom, which releases a suitable reducing agent (process A), compared to the template of polycrystalline silicon 2 on the crucible bottom, which is not a suitable reducing agent contains (process B).
• Process A are lower over the entire block height than process B.

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• 2015
  • 2015-02-05 DE DE102015201988.8A patent/DE102015201988A1/de not_active Withdrawn
• 2016
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