EP1871926A1 - Method for growing thin semiconductor ribbons - Google Patents

Method for growing thin semiconductor ribbons

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Publication number
EP1871926A1
EP1871926A1 EP06726209A EP06726209A EP1871926A1 EP 1871926 A1 EP1871926 A1 EP 1871926A1 EP 06726209 A EP06726209 A EP 06726209A EP 06726209 A EP06726209 A EP 06726209A EP 1871926 A1 EP1871926 A1 EP 1871926A1
Authority
EP
European Patent Office
Prior art keywords
filaments
support strip
semiconductor material
silicon
ribbon
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.)
Withdrawn
Application number
EP06726209A
Other languages
German (de)
French (fr)
Inventor
Claude Remy
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.)
Solarforce
Original Assignee
Solarforce
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 Solarforce filed Critical Solarforce
Publication of EP1871926A1 publication Critical patent/EP1871926A1/en
Withdrawn legal-status Critical Current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
    • 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
    • C30B15/00—Single-crystal growth by pulling from a melt, e.g. Czochralski method
    • C30B15/20—Controlling or regulating
    • C30B15/22—Stabilisation or shape controlling of the molten zone near the pulled crystal; Controlling the section of the crystal
    • 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
    • C30B15/00—Single-crystal growth by pulling from a melt, e.g. Czochralski method
    • C30B15/34—Edge-defined film-fed crystal-growth using dies or slits
    • 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
    • C30B29/08—Germanium
    • 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
    • C30B29/40—AIIIBV compounds wherein A is B, Al, Ga, In or Tl and B is N, P, As, Sb or Bi
    • C30B29/42—Gallium arsenide
    • 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
    • H01L31/18—Processes or apparatus specially adapted for the manufacture or treatment of these devices or of parts thereof

Definitions

  • the subject of the present invention is a method for drawing semiconductor tapes, in particular polycrystalline silicon, of small thickness from a molten silicon bath.
  • the most used semiconductor ribbons are polycrystalline silicon ribbons.
  • the following description therefore relates to silicon ribbons, but bearing in mind that the invention also relates to ribbons of other semi-conductive materials, such as for example germanium or gallium arsenide.
  • a strip of thin thickness and generally of carbon scrolls vertically, from bottom to top and at a constant speed, in a bath of molten silicon.
  • a thin layer of silicon is deposited on each of the two faces of the carbon band.
  • the strip emerging from the bath is a composite strip consisting of a carbon core inserted between two layers of silicon.
  • the carbon core is subsequently removed by burning in a high temperature oven.
  • two silicon strips of small thickness are obtained which are cut into plates.
  • the RST process is for example described in patents FR 2,386,359, FR 2,550,965 and FR 2,561,139.
  • the other method, the method STR is illustrated schematically in FIG. 1.
  • a draft crucible 10 contains a molten silicon bath 12.
  • the bottom of the crucible is pierced with two orifices through which penetrate two filaments 14 and 16 parallel, vertical and spaced from each other. These filaments scroll at a constant speed, from bottom to top, in the silicon bath.
  • a seed initially allows crystallization of the silicon to begin between the two filaments on the surface of the silicon bath.
  • a self-supporting ribbon 18 can then be pulled between the two filaments, which serve to stabilize or anchor the edges of the ribbon.
  • the growth of the ribbon 18 is developed by the meniscus 20 which is formed by capillarity over a height of about 7 mm above the surface of the silicon bath between the filaments 14 and 16.
  • Patent application WO 2004/035877 describes a form of implementation of the STR method, as well as means for reducing or eliminating the meniscus deformation that sometimes occurs.
  • the STR method has other disadvantages. For example, it has low productivity due to its low draw speed, of the order of 1.7 cm / min. Beyond this pulling speed occurs a warpage of the ribbon due to thermal stresses that deform the surface of the silicon ribbon. It was then proposed to perform in parallel several draws in the same building. However, the parallel draw is hampered by the problem of interference between free liquid menisci. Indeed, menisci tend to attract to reduce surface energy, which leads to flatness defects ribbons. This problem is partly solved by the patent application WO 2004/042122 A1, at the cost of a complication of the method, with the establishment around the ribbons of control elements of the shape of the meniscus in the lateral part of the ribbon .
  • STR system Another disadvantage of the STR system lies in the fact that in practice the thickness of the ribbon is hardly less than 250 micrometers. Below this thickness, the silicon ribbon becomes left and fragile and is difficult to handle in the steps of manufacturing photovoltaic cells.
  • the STR process includes a priming phase, germination, which is critical and delicate at the start of the ribbon draw or restart after accidental breaks in the liquid meniscus.
  • the present invention aims to improve the STR method by overcoming one or more of the aforementioned drawbacks.
  • the invention relates to a method of drawing at least one ribbon of a semiconductor material in which two parallel filaments spaced from each other pass vertically, from bottom to top and continuously the surface of a bath of said molten semiconductor material, said ribbon being formed from a meniscus located between said filaments and substantially at said surface.
  • a support strip is interposed between the filaments and contained in the plane defined by the filaments, the support strip traversing vertically, from bottom to top and continuously, the bath surface of the molten semiconductor material to the same speed of travel as the filaments, the ribbon of semiconductor material forming on one of the two faces of the support strip and being supported by said face.
  • the filaments are carbon or silica and their diameter is between 0.3 and 1 mm. They can be covered with a thin layer of pyrolytic graphite.
  • the support strip is carbon and its thickness is between 200 and 350 microns.
  • the molten semiconductor material is contained in a drawing crucible provided with a substantially horizontal bottom, said bottom comprising a slot through which the support strip and the filaments penetrate.
  • the slot preferably has a rectangular horizontal section whose width is slightly greater than the thickness of the support strip and, at each of the two ends of the rectangular section, a circular horizontal section through which the filaments pass.
  • the semiconductor material may be based on a semiconductor element such as silicon or germanium or a congruent or quasi-congruent semiconductor compound, such as, for example, gallium arsenide.
  • FIG. 1 schematically illustrates the method STR according to the prior art
  • FIG. 2 illustrates the method according to the present invention
  • FIGS. 3 and 4 show, in horizontal section along horizontal planes at heights respectively indicated by III and IV in FIG. 2, the two filaments and the two semiconductor ribbons, silicon in the example described, surrounding the carbon support band;
  • FIG. 5 shows schematically in horizontal section the slot of the draft crucible through which pass the support strip and the filaments.
  • a support band preferably made of carbon, is used in the STR method while retaining the two filaments of carbon.
  • the support strip has the effect of reinforcing the anchoring of the liquid silicon meniscus on the edges of the strip by wetting effect.
  • the drawing crucible made for example of silica or carbon, is filled with silicon made liquid by raising its temperature.
  • the support strip is contained in the vertical plane defined by the two longitudinal axes of symmetry of the filaments 24 and 26 (which have a substantially cylindrical shape but not necessarily a revolution, a rectangular section for example being possible).
  • This slot 28, also shown in horizontal section in Figure 5, has the shape of an elongated rectangle 30 terminated at each of its two ends by a circular surface 32 or 34.
  • the width of the rectangle 30 is slightly greater than the width of the support strip 22 and the diameter of the circular surfaces 32 and 34 is slightly greater than the diameter of the filaments so that the support strip 22 and the two filaments 24 and 26 pass through the slot 28.
  • the distance between the edges of the slot 28 of the support strip 22 and filaments 24-26 is such that the molten silicon contained in the crucible does not flow through the slot.
  • the width of the section rectangular 30 of the slot may be of the order of 600 micrometers and the diameter of the circular sections 32-34 of the order of 1 mm.
  • the support strip 22 and the filaments 24-26 pass through the slot 28 and pass vertically, from bottom to top, the drawing crucible filled with liquid silicon. Unrepresented means pull vertically at a constant speed the assembly formed by the strip 22 and the filaments 24-26, in the direction of the arrow 36.
  • the drawing speed can reach values close to 5 cm / min, without appearance of effect of warping of the surfaces of the composite, for silicon strips of about 200 microns thick and 10 cm / min for ribbons of about 80 microns thick.
  • the maximum draw speed in the conventional STR process is about 1.7 cm / min, so about 3 to 6 times lower.
  • a meniscus is formed at the junction 38 of the surface of the liquid silicon with the support strip 22 and the filaments 24-26.
  • FIGS 3 and 4 show in section, in horizontal planes at heights respectively indicated by III and IV relative to the silicon bath, the shapes of the ribbons 40 and 42 adhering to the support strip 22 and 24-26 filaments.
  • the silicon has cooled and crystallized to form the silicon ribbons while at the height of the IV plane, at a height of a few millimeters (typically less than 6 mm) relative to the surface of the molten silicon, the silicon 44 is not yet solidified and forms a meniscus.
  • the filaments 24 and 26 are identical, made of carbon or silica, optionally coated with pyrolytic graphite, and their diameter is between 0.3 and 1 mm. They are spaced from the edges of the support strip 22 by about 100 microns so as to prevent any contact likely to deform the support strip.
  • the thickness of the support strip 22 is between 200 and 350 microns, preferably between 200 and 300 microns.
  • This support strip is preferably made of carbon, for example flexible graphite made from expanded natural graphite and then rolled.
  • the support strip 22 may be delivered in rolls one meter in width and several hundred meters in length. However, for the embodiment described here, a width, for example between five and twenty centimeters, is preferably used. After drawing, a composite strip is obtained consisting of the support strip 22, the two filaments 24-26 and the two silicon strips 40-42 supported by the support strip and the filaments.
  • the next step is firstly, by means of a laser for example, to cut into composite plates, generally rectangular, the composite strip and to cut the edges of the composite strip or composite plates so as to expose the song of carbon ribbons.
  • the filaments 24-26 are thus eliminated.
  • the support band 22 is destroyed by burning, for example in air, at high temperature (about 1000 ° C) to obtain two polycrystalline silicon plates.
  • the faces of the plates, previously free or located opposite the support strip 22, then undergo a light etching to remove the oxide layer, silica, which is formed on the surface.
  • This oxidized layer is very thin, of the order of a few tenths of a micrometer. Stripping can be done by various conventional routes.
  • the support band thanks to its thermophysical characteristics, brings additional advantages to the conventional two-filament STR process, which avoids or minimizes the formation of a composite strip with left surfaces. Indeed, on the one hand, the participation of the support band in the extraction of the latent heat of crystallization relatively decreases the temperature gradient in the silicon band at the level of the crystallization front, which delays the appearance of the phenomenon.
  • the presence of the support strip in the draft crucible divides by two the width of the molten silicon bath, which attenuates the thermal convection currents that tend to develop in the bath and as a consequence the displacement of the isotherm of crystallization that they can induce.
  • the presence of the support strip considerably reduces the possibility of displacement of the crystallization meniscus due to the disturbances that it undergoes by the variations of the connection angle of the liquid surface with the walls of the impression crucible and / or by the presence of a neighboring meniscus when several ribbons are drawn simultaneously from the same molten silicon bath.
  • the presence of the support band physically maintains the point of attachment of the liquid meniscus in an almost fixed vertical plane, with a possibility of displacement in a direction perpendicular to the support band typically less than ⁇ 100 micrometers.
  • the present invention therefore makes it possible, compared with the conventional STR method, to obtain silicon ribbons of smaller thickness, for example less than 150 micrometers, with better flatness and at higher draw speeds (and therefore with higher productivity).
  • the invention is therefore particularly well suited to the production of photovoltaic cells by using the silicon ribbons thus produced.
  • a single ribbon can be produced, instead of two simultaneously, by preventing the deposition of silicon on one of the two faces of the support strip.
  • the support strip and the two filaments do not penetrate into the silicon bath by the bottom of the frame but by the side walls or dive directly into the bath from above and, by a return mechanism, also emerge from the top of the bath.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Manufacturing & Machinery (AREA)
  • Physics & Mathematics (AREA)
  • Condensed Matter Physics & Semiconductors (AREA)
  • Electromagnetism (AREA)
  • General Physics & Mathematics (AREA)
  • Computer Hardware Design (AREA)
  • Microelectronics & Electronic Packaging (AREA)
  • Power Engineering (AREA)
  • Inorganic Chemistry (AREA)
  • Crystals, And After-Treatments Of Crystals (AREA)
  • Silicon Compounds (AREA)

Abstract

The invention relates to a method for growing at least one ribbon made of a semiconductor material (40-42) according to which two parallel and interspaced filaments (24-26) vertically pass through, upward and at a continuous speed, the surface of a bath of this molten semiconductor material, the ribbon (40-42) being formed from a meniscus located between the filaments and essentially at the level of said surface. According to the invention, a supporting strip (22) is placed between the filaments (24-26), the supporting strip (22) vertically passing through, upward and at a continuous speed, the surface of the molten semiconductor material at the same speed as the filaments, the semiconductor ribbon (40-42) thus being formed on one of the two sides of the supporting strip and being supported by this side. The invention serves to produce polycrystalline silicon ribbons for manufacturing photovoltaic cells.

Description

Procédé de tirage de rubans de semi-conducteur de faible épaisseur Method for drawing thin semiconductor ribbons
La présente invention a pour objet un procédé de tirage de rubans de semi-conducteur, notamment du silicium polycristallin, de faible épaisseur à partir d'un bain de silicium fondu.The subject of the present invention is a method for drawing semiconductor tapes, in particular polycrystalline silicon, of small thickness from a molten silicon bath.
Les rubans de semi-conducteur les plus utilisés, notamment pour la réalisation de cellules photovoltaïques, sont des rubans de silicium polycristallin. L'exposé qui suit se rapporte donc aux rubans de silicium, mais en gardant à l'esprit que l'invention concerne également des rubans d'autres matières semi -conductrices, telles que par exemple le germanium ou l'arséniure de gallium.The most used semiconductor ribbons, especially for producing photovoltaic cells, are polycrystalline silicon ribbons. The following description therefore relates to silicon ribbons, but bearing in mind that the invention also relates to ribbons of other semi-conductive materials, such as for example germanium or gallium arsenide.
La réalisation de rubans minces de silicium est une solution préférée à l'obtention de plaques de silicium par sciage de lingots pour fabriquer des cellules photovoltaïques. En effet, cette solution permet une forte réduction de la consommation de silicium, la suppression de l'opération coûteuse du sciage en plaques et la réduction de la consommation de produits chimiques toxiques.The production of thin silicon ribbons is a preferred solution for obtaining silicon wafers by sawing ingots to produce photovoltaic cells. Indeed, this solution allows a strong reduction of the silicon consumption, the suppression of the expensive operation of the sawing in plates and the reduction of the consumption of toxic chemicals.
Parmi les nombreuses solutions de tirage de rubans de silicium qui ont été développées, deux procédés de tirage vertical se sont révélés les plus performants pour l'obtention de rubans minces, l'un appelé "RST" pour Ruban sur Substrat Temporaire et l'autre "STR" (abréviation de "STring Ribbon").Among the many silicon ribbon drawing solutions that have been developed, two vertical printing processes have proven to be the most successful in obtaining thin ribbons, one called "RST" for Temporary Substrate Ribbon and the other one "STR" (abbreviation of "STring Ribbon").
Selon le procédé RST, une bande de faible épaisseur et généralement en carbone défile verticalement, de bas en haut et à vitesse constante, dans un bain de silicium fondu. Une couche mince de silicium se dépose sur chacune des deux faces de la bande de carbone. Après solidification, la bande qui sort du bain est une bande composite constituée d'une âme en carbone insérée entre deux couches de silicium. L'âme en carbone est ultérieurement éliminée par brûlage dans un four à haute température. On obtient ainsi deux rubans de silicium de faibles épaisseurs qui sont découpés en plaques. Le procédé RST est par exemple décrit dans les brevets FR 2 386 359, FR 2 550 965 et FR 2 561 139. L'autre procédé, le procédé STR, est illustré schématiquement sur la figure 1. Un creuset de tirage 10, muni de moyens de chauffage non représentés, contient un bain de silicium fondu 12. Le fond du creuset est percé de deux orifices par lesquels pénètrent deux filaments 14 et 16 parallèles, verticaux et espacés l'un de l'autre. Ces filaments défilent à vitesse constante, de bas en haut, dans le bain de silicium. Un germe permet au départ d'amorcer la cristallisation du silicium entre les deux filaments à la surface du bain de silicium. Un ruban autosupporté 18 peut alors être tiré entre les deux filaments, lesquels servent à stabiliser ou à ancrer les bords du ruban. La croissance du ruban 18 se développe par le ménisque 20 qui se forme par capillarité sur une hauteur d'environ 7 mm au-dessus de la surface du bain de silicium entre les filaments 14 et 16. Après solidification du silicium, les filaments sont incorporés dans le ruban de silicium sur ses bords. La demande de brevet WO 2004/035877, par exemple, décrit une forme de mise en œuvre du procédé STR, ainsi que des moyens permettant de réduire ou de supprimer la déformation du ménisque qui se produit parfois.According to the RST method, a strip of thin thickness and generally of carbon scrolls vertically, from bottom to top and at a constant speed, in a bath of molten silicon. A thin layer of silicon is deposited on each of the two faces of the carbon band. After solidification, the strip emerging from the bath is a composite strip consisting of a carbon core inserted between two layers of silicon. The carbon core is subsequently removed by burning in a high temperature oven. Thus, two silicon strips of small thickness are obtained which are cut into plates. The RST process is for example described in patents FR 2,386,359, FR 2,550,965 and FR 2,561,139. The other method, the method STR, is illustrated schematically in FIG. 1. A draft crucible 10, provided with heating means (not shown), contains a molten silicon bath 12. The bottom of the crucible is pierced with two orifices through which penetrate two filaments 14 and 16 parallel, vertical and spaced from each other. These filaments scroll at a constant speed, from bottom to top, in the silicon bath. A seed initially allows crystallization of the silicon to begin between the two filaments on the surface of the silicon bath. A self-supporting ribbon 18 can then be pulled between the two filaments, which serve to stabilize or anchor the edges of the ribbon. The growth of the ribbon 18 is developed by the meniscus 20 which is formed by capillarity over a height of about 7 mm above the surface of the silicon bath between the filaments 14 and 16. After solidification of the silicon, the filaments are incorporated in the silicon ribbon on its edges. Patent application WO 2004/035877, for example, describes a form of implementation of the STR method, as well as means for reducing or eliminating the meniscus deformation that sometimes occurs.
Ces procédés de tirage vertical, bien que performants, sont cependant confrontés au problème de l'instabilité du ménisque de silicium liquide à chaque extrémité du ruban en raison des forces capillaires qui tendent à sectionner ce ménisque. Diverses améliorations du procédé ont été proposées. Par exemple, pour le procédé RST, le brevet FR 2 550 965 propose d'utiliser des éléments fixes placés au voisinage des bords du ruban afin d'ajuster la forme du ménisque et l'épaisseur de la couche de silicium sur ces bords. De même, pour le procédé STR, la demande de brevet WO 01/04388 A3 propose des moyens pour stabiliser le bord du ménisque en élevant le niveau du bain de silicium fondu à proximité des filaments. Ces solutions ne donnent cependant pas entière satisfaction.These vertical drawing processes, although efficient, are however confronted with the problem of the instability of the liquid silicon meniscus at each end of the ribbon due to the capillary forces that tend to cut this meniscus. Various improvements of the process have been proposed. For example, for the RST method, patent FR 2 550 965 proposes to use fixed elements placed in the vicinity of the ribbon edges in order to adjust the shape of the meniscus and the thickness of the silicon layer on these edges. Likewise, for the STR method, patent application WO 01/04388 A3 proposes means for stabilizing the edge of the meniscus by raising the level of the molten silicon bath near the filaments. These solutions, however, are not entirely satisfactory.
Le procédé STR présente d'autres inconvénients. Par exemple, il a une faible productivité due à sa faible vitesse de tirage, de l'ordre de 1 ,7 cm/mn. Au-delà de cette vitesse de tirage se produit un gauchissement du ruban dû à des contraintes d'origine thermique qui déforment la surface du ruban de silicium. Il a alors été proposé d'effectuer en parallèle plusieurs tirages dans un même bâti. Cependant, le tirage en parallèle se heurte au problème de l'interférence entre les ménisques liquides libres. En effet, les ménisques tendent à s'attirer pour réduire l'énergie de surface, ce qui conduit à des défauts de planéité des rubans. Ce problème est en partie résolu par la demande de brevet WO 2004/042122 A1 , au prix d'une complication du procédé, avec la mise en place autour des rubans d'éléments de contrôle de la forme du ménisque dans la partie latérale du ruban. Un autre inconvénient du système STR réside dans le fait qu'en pratique l'épaisseur du ruban est difficilement inférieure à 250 micromètres. En dessous de cette épaisseur, le ruban de silicium devient gauche et fragile et est difficile à manipuler dans les étapes de fabrication de cellules photovoltaïques. De plus, le procédé STR comporte une phase d'amorçage, la germination, qui est critique et délicate au démarrage du tirage du ruban ou au redémarrage à la suite de ruptures accidentelles du ménisque liquide.The STR method has other disadvantages. For example, it has low productivity due to its low draw speed, of the order of 1.7 cm / min. Beyond this pulling speed occurs a warpage of the ribbon due to thermal stresses that deform the surface of the silicon ribbon. It was then proposed to perform in parallel several draws in the same building. However, the parallel draw is hampered by the problem of interference between free liquid menisci. Indeed, menisci tend to attract to reduce surface energy, which leads to flatness defects ribbons. This problem is partly solved by the patent application WO 2004/042122 A1, at the cost of a complication of the method, with the establishment around the ribbons of control elements of the shape of the meniscus in the lateral part of the ribbon . Another disadvantage of the STR system lies in the fact that in practice the thickness of the ribbon is hardly less than 250 micrometers. Below this thickness, the silicon ribbon becomes left and fragile and is difficult to handle in the steps of manufacturing photovoltaic cells. In addition, the STR process includes a priming phase, germination, which is critical and delicate at the start of the ribbon draw or restart after accidental breaks in the liquid meniscus.
La présente invention a pour but d'améliorer le procédé STR en remédiant à un ou plusieurs des inconvénients mentionnés précédemment.The present invention aims to improve the STR method by overcoming one or more of the aforementioned drawbacks.
A cette fin, l'invention concerne un procédé de tirage d'au moins un ruban d'un matériau semi-conducteur selon lequel deux filaments parallèles et espacés l'un de l'autre traversent verticalement, de bas en haut et de façon continue, la surface d'un bain dudit matériau semi-conducteur fondu, ledit ruban se formant à partir d'un ménisque situé entre lesdits filaments et sensiblement au niveau de ladite surface. Selon l'invention, une bande support est interposée entre les filaments et contenue dans le plan défini par les filaments, la bande support traversant verticalement, de bas en haut et de façon continue, la surface du bain du matériau semi-conducteur fondu à la même vitesse de défilement que les filaments, le ruban de matériau semiconducteur se formant sur l'une des deux faces de la bande support et étant supporté par ladite face. De préférence, deux rubans de matériau semi-conducteur sont formés simultanément, l'un sur l'une des deux faces de la bande support et l'autre sur l'autre face. De façon avantageuse, les filaments sont en carbone ou en silice et leur diamètre est compris entre 0,3 et 1 mm. Ils peuvent être recouverts d'une fine couche de graphite pyrolytique.To this end, the invention relates to a method of drawing at least one ribbon of a semiconductor material in which two parallel filaments spaced from each other pass vertically, from bottom to top and continuously the surface of a bath of said molten semiconductor material, said ribbon being formed from a meniscus located between said filaments and substantially at said surface. According to the invention, a support strip is interposed between the filaments and contained in the plane defined by the filaments, the support strip traversing vertically, from bottom to top and continuously, the bath surface of the molten semiconductor material to the same speed of travel as the filaments, the ribbon of semiconductor material forming on one of the two faces of the support strip and being supported by said face. Preferably, two ribbons of semiconductor material are formed simultaneously, one on one of the two faces of the support strip and the other on the other side. Advantageously, the filaments are carbon or silica and their diameter is between 0.3 and 1 mm. They can be covered with a thin layer of pyrolytic graphite.
Selon une forme de réalisation préférée, la bande support est en carbone et son épaisseur est comprise entre 200 et 350 micromètres. Le matériau semi-conducteur fondu est contenu dans un creuset de tirage muni d'un fond sensible ment horizontal, ledit fond comprenant une fente par laquelle pénètrent la bande support et les filaments.According to a preferred embodiment, the support strip is carbon and its thickness is between 200 and 350 microns. The molten semiconductor material is contained in a drawing crucible provided with a substantially horizontal bottom, said bottom comprising a slot through which the support strip and the filaments penetrate.
La fente a de préférence une section horizontale rectangulaire dont la largeur est légèrement supérieure à l'épaisseur de la bande support et, à chacune des deux extrémités de la section rectangulaire, une section horizontale circulaire par laquelle traversent les filaments.The slot preferably has a rectangular horizontal section whose width is slightly greater than the thickness of the support strip and, at each of the two ends of the rectangular section, a circular horizontal section through which the filaments pass.
Le matériau semi-conducteur peut être à base d'un élément semiconducteur tel que le silicium ou le germanium ou d'un composé semi- conducteur à fusion congruente ou quasi-congruente, tel que par exemple l'arséniure de gallium.The semiconductor material may be based on a semiconductor element such as silicon or germanium or a congruent or quasi-congruent semiconductor compound, such as, for example, gallium arsenide.
D'autres avantages et caractéristiques de l'invention apparaîtront au cours de la description qui suit d'un mode de réalisation de l'invention, donné à titre d'exemple non limitatif, en référence aux dessins annexés et sur lesquels :Other advantages and features of the invention will become apparent from the following description of an embodiment of the invention, given by way of non-limiting example, with reference to the accompanying drawings and in which:
- la figure 1 illustre schématiquement le procédé STR selon l'art antérieur;FIG. 1 schematically illustrates the method STR according to the prior art;
- la figure 2 illustre le procédé selon la présente invention;FIG. 2 illustrates the method according to the present invention;
- les figures 3 et 4 montrent, en coupe horizontale selon des plans horizontaux à des hauteurs indiquées respectivement par III et IV sur la figure 2, les deux filaments et les deux rubans de semi-conducteur, silicium dans l'exemple décrit, entourant la bande support de carbone; etFIGS. 3 and 4 show, in horizontal section along horizontal planes at heights respectively indicated by III and IV in FIG. 2, the two filaments and the two semiconductor ribbons, silicon in the example described, surrounding the carbon support band; and
- la figure 5 représente schématiquement en coupe horizontale la fente du creuset de tirage à travers laquelle passent la bande support et les filaments.- Figure 5 shows schematically in horizontal section the slot of the draft crucible through which pass the support strip and the filaments.
Selon l'invention, une bande support, de préférence en carbone, est utilisée dans le procédé STR tout en conservant les deux filaments de carbone. La bande support a notamment pour effet de renforcer l'ancrage du ménisque de silicium liquide sur les bords de la bande par effet de mouillage.According to the invention, a support band, preferably made of carbon, is used in the STR method while retaining the two filaments of carbon. In particular, the support strip has the effect of reinforcing the anchoring of the liquid silicon meniscus on the edges of the strip by wetting effect.
Sur la figure 2, une bande support verticale 22 encadrée par deux filaments verticaux 24 et 26 pénètre de bas en haut dans un creuset de tirage (non représenté) par une fente 28 située au fond du creuset. Le creuset de tirage, réalisé par exemple en silice ou en carbone, est rempli de silicium rendu liquide par élévation de sa température. La bande support est contenue dans le plan vertical défini par les deux axes de symétrie longitudinaux des filaments 24 et 26 (qui ont une forme sensiblement cylindrique mais pas nécessairement de révolution, une section par exemple rectangulaire étant possible). Cette fente 28, également représentée en coupe horizontale sur la figure 5, a la forme d'un rectangle allongé 30 terminé à chacune de ses deux extrémités par une surface circulaire 32 ou 34. La largeur du rectangle 30 est légèrement supérieure à la largeur de la bande support 22 et le diamètre des surfaces circulaires 32 et 34 est légèrement supérieur au diamètre des filaments de sorte que la bande support 22 et les deux filaments 24 et 26 passent à travers la fente 28. La distance séparant les bords de la fente 28 de la bande support 22 et des filaments 24-26 est telle que le silicium fondu contenu dans le creuset ne s'écoule pas à travers la fente. A titre d'exemple, pour une épaisseur de bande support de 300 micromètres, pour un diamètre de filament de 0,6mm et pour une hauteur de 1 cm de silicium fondu contenu dans le creuset au droit de la fente, la largeur de la section rectangulaire 30 de la fente peut être de l'ordre de 600 micromètres et le diamètre des sections circulaires 32-34 de l'ordre de 1 mm.In Figure 2, a vertical support strip 22 flanked by two vertical filaments 24 and 26 penetrates upwardly in a draft crucible (not shown) by a slot 28 at the bottom of the crucible. The drawing crucible, made for example of silica or carbon, is filled with silicon made liquid by raising its temperature. The support strip is contained in the vertical plane defined by the two longitudinal axes of symmetry of the filaments 24 and 26 (which have a substantially cylindrical shape but not necessarily a revolution, a rectangular section for example being possible). This slot 28, also shown in horizontal section in Figure 5, has the shape of an elongated rectangle 30 terminated at each of its two ends by a circular surface 32 or 34. The width of the rectangle 30 is slightly greater than the width of the support strip 22 and the diameter of the circular surfaces 32 and 34 is slightly greater than the diameter of the filaments so that the support strip 22 and the two filaments 24 and 26 pass through the slot 28. The distance between the edges of the slot 28 of the support strip 22 and filaments 24-26 is such that the molten silicon contained in the crucible does not flow through the slot. For example, for a support strip thickness of 300 micrometers, for a filament diameter of 0.6 mm and for a height of 1 cm of molten silicon contained in the crucible at the right of the slot, the width of the section rectangular 30 of the slot may be of the order of 600 micrometers and the diameter of the circular sections 32-34 of the order of 1 mm.
La bande support 22 et les filaments 24-26 passent à travers la fente 28 et traversent verticalement, de bas en haut, le creuset de tirage rempli de silicium liquide. Des moyens non représentés tirent verticalement à vitesse constante l'ensemble formé par la bande 22 et les filaments 24-26, dans le sens de la flèche 36. La vitesse de tirage peut atteindre des valeurs proches de 5 cm/mn, sans apparition d'effet de gauchissement des surfaces du composite, pour des rubans de silicium d'environ 200 micromètres d'épaisseur et de 10 cm/mn pour des rubans d'environ 80 micromètres d'épaisseur. Par comparaison, la vitesse de tirage maximale dans le procédé STR classique est d'environ 1 ,7 cm/mn, donc environ 3 à 6 fois inférieure. Un ménisque se forme à la jonction 38 de la surface du silicium liquide avec la bande support 22 et les filaments 24-26. Les deux cotés de la bande support 22 se recouvrent d'une mince couche de silicium qui cristallise en se refroidissant. On obtient ainsi simultanément deux rubans 40 et 42 de silicium polycristallin. Les figures 3 et 4 montrent en coupe, selon des plans horizontaux à des hauteurs indiquées respectivement par III et IV par rapport au bain de silicium, les formes des rubans 40 et 42 adhérant à la bande support 22 et aux filaments 24-26. A la hauteur du plan III, le silicium s'est refroidi et cristallisé pour former les rubans de silicium alors qu'à la hauteur du plan IV, à une hauteur de quelques millimètres (typiquement inférieure à 6 mm) par rapport à la surface du silicium fondu, le silicium 44 n'est pas encore solidifié et forme un ménisque.The support strip 22 and the filaments 24-26 pass through the slot 28 and pass vertically, from bottom to top, the drawing crucible filled with liquid silicon. Unrepresented means pull vertically at a constant speed the assembly formed by the strip 22 and the filaments 24-26, in the direction of the arrow 36. The drawing speed can reach values close to 5 cm / min, without appearance of effect of warping of the surfaces of the composite, for silicon strips of about 200 microns thick and 10 cm / min for ribbons of about 80 microns thick. By comparison, the maximum draw speed in the conventional STR process is about 1.7 cm / min, so about 3 to 6 times lower. A meniscus is formed at the junction 38 of the surface of the liquid silicon with the support strip 22 and the filaments 24-26. The two sides of the support strip 22 are covered with a thin layer of silicon which crystallizes while cooling. Two ribbons 40 and 42 of polycrystalline silicon are thus simultaneously obtained. Figures 3 and 4 show in section, in horizontal planes at heights respectively indicated by III and IV relative to the silicon bath, the shapes of the ribbons 40 and 42 adhering to the support strip 22 and 24-26 filaments. At the height of the plane III, the silicon has cooled and crystallized to form the silicon ribbons while at the height of the IV plane, at a height of a few millimeters (typically less than 6 mm) relative to the surface of the molten silicon, the silicon 44 is not yet solidified and forms a meniscus.
Dans un mode de réalisation préféré, les filaments 24 et 26 sont identiques, réalisés en carbone ou en silice, éventuellement recouvert de graphite pyrolytique, et leur diamètre est compris entre 0,3 et 1 mm. Ils sont écartés des bords de la bande support 22 d'environ 100 micromètres de façon à prévenir tout contact susceptible de déformer la bande support.In a preferred embodiment, the filaments 24 and 26 are identical, made of carbon or silica, optionally coated with pyrolytic graphite, and their diameter is between 0.3 and 1 mm. They are spaced from the edges of the support strip 22 by about 100 microns so as to prevent any contact likely to deform the support strip.
L'épaisseur de la bande support 22 est comprise entre 200 et 350 micromètres, de préférence entre 200 et 300 micromètres. Cette bande support est de préférence réalisée en carbone , par exemple en graphite souple réalisé à partir de graphite naturel expansé puis laminé. La bande support 22 peut être livrée en rouleaux d'un mètre de largeur et de plusieurs centaines de mètres de longueur. Cependant, pour le mode de réalisation décrit ici, on utilise de préférence une largeur par exemple comprise entre cinq et vingt centimètres. Après tirage, on obtient une bande composite constituée de la bande support 22, des deux filaments 24-26 et des deux rubans de silicium 40-42 supportés par la bande support et les filaments. L'étape suivante consiste tout d'abord, au moyen d'un laser par exemple, à couper en plaques composites, généralement rectangulaires, la bande composite et à découper les bords de la bande composite ou des plaques composites de façon à mettre à nu le chant des rubans de carbone. Les filaments 24-26 sont donc ainsi éliminés. Puis la bande support 22 est détruite par brûlage, par exemple sous air, à haute température (environ 1000 °C) afin d'obtenir deux plaques de silicium polycristallin. Les faces des plaques, précédemment libres ou situées en regard de la bande support 22, subissent ensuite un léger décapage pour éliminer la couche oxydée, de la silice, qui s'est formée en surface. Cette couche oxydée est de très faible épaisseur, de l'ordre de quelques dixièmes de micromètres. Le décapage peut se faire par différentes voies classiques.The thickness of the support strip 22 is between 200 and 350 microns, preferably between 200 and 300 microns. This support strip is preferably made of carbon, for example flexible graphite made from expanded natural graphite and then rolled. The support strip 22 may be delivered in rolls one meter in width and several hundred meters in length. However, for the embodiment described here, a width, for example between five and twenty centimeters, is preferably used. After drawing, a composite strip is obtained consisting of the support strip 22, the two filaments 24-26 and the two silicon strips 40-42 supported by the support strip and the filaments. The next step is firstly, by means of a laser for example, to cut into composite plates, generally rectangular, the composite strip and to cut the edges of the composite strip or composite plates so as to expose the song of carbon ribbons. The filaments 24-26 are thus eliminated. Then the support band 22 is destroyed by burning, for example in air, at high temperature (about 1000 ° C) to obtain two polycrystalline silicon plates. The faces of the plates, previously free or located opposite the support strip 22, then undergo a light etching to remove the oxide layer, silica, which is formed on the surface. This oxidized layer is very thin, of the order of a few tenths of a micrometer. Stripping can be done by various conventional routes.
Les modifications du procédé STR qui viennent d'être décrites permettent d'améliorer la productivité du procédé classique par une vitesse de tirage plus élevée et par l'obtention simultanée de deux rubans de silicium, de diminuer la consommation de silicium en diminuant l'épaisseur des rubans jusqu'à des valeurs inférieures à 100 micromètres et d'améliorer la planéité des rubans. Ce dernier avantage est dû à plusieurs effets. Tout d'abord, la bande support, grâce à ses caractéristiques thermophysiques, apporte des atouts supplémentaires au procédé STR classique à deux filaments, qui évitent ou minimisent la formation d'une bande composite avec des surfaces gauches. En effet, d'une part, la participation de la bande support à l'extraction de la chaleur latente de cristallisation diminue relativement le gradient de température dans la bande de silicium au niveau du front de cristallisation, ce qui retarde l'apparition du phénomène de flambage due aux contraintes thermomécaniques et permet des vitesses de tirage très élevées et, d'autre part, son inertie thermique stabilise le champ thermique au voisinage du ménisque réduisant ainsi le déplacement de l'isotherme de cristallisation. De plus, la présence de la bande support dans le creuset de tirage divise par deux la largeur du bain de silicium fondu, ce qui atténue les courants de convection thermique qui tendent à se développer dans le bain et en corollaire le déplacement de l'isotherme de cristallisation qu'ils peuvent induire. Egalement, la présence de la bande support diminue considérablement la possibilité de déplacement du ménisque de cristallisation due aux perturbations qu'il subit par les variations d'angle de raccordement de la surface liquide avec les parois du creuset de tirage et/ou par la présence d'un ménisque voisin lorsque plusieurs rubans sont tirés simultanément d'un même bain de silicium fondu. En effet, la présence de la bande support maintient physiquement le point d'attachement du ménisque liquide dans un plan vertical quasiment fixe, avec une possibilité de déplacement dans une direction perpendiculaire à la bande support typiquement inférieure à ± 100 micromètres. La présente invention permet donc, par rapport au procédé STR classique, d'obtenir des rubans de silicium d'épaisseur plus faible, par exemple inférieure à 150 micromètres, avec une meilleure planéité et à des vitesses de tirage plus élevées (et donc avec une productivité plus grande). L'invention est donc tout particulièrement bien adaptée à la réalisation de cellules photovoltaïques par utilisation des rubans de silicium ainsi produits.The modifications of the method STR which have just been described make it possible to improve the productivity of the conventional method by a higher drawing speed and by simultaneously obtaining two silicon ribbons, to reduce the silicon consumption by decreasing the thickness. ribbons up to values less than 100 micrometers and improve the flatness of the ribbons. This last advantage is due to several effects. First of all, the support band, thanks to its thermophysical characteristics, brings additional advantages to the conventional two-filament STR process, which avoids or minimizes the formation of a composite strip with left surfaces. Indeed, on the one hand, the participation of the support band in the extraction of the latent heat of crystallization relatively decreases the temperature gradient in the silicon band at the level of the crystallization front, which delays the appearance of the phenomenon. of buckling due to thermomechanical stresses and allows very high pulling speeds and, on the other hand, its thermal inertia stabilizes the thermal field in the vicinity of the meniscus thus reducing the displacement of the crystallization isotherm. In addition, the presence of the support strip in the draft crucible divides by two the width of the molten silicon bath, which attenuates the thermal convection currents that tend to develop in the bath and as a consequence the displacement of the isotherm of crystallization that they can induce. Also, the presence of the support strip considerably reduces the possibility of displacement of the crystallization meniscus due to the disturbances that it undergoes by the variations of the connection angle of the liquid surface with the walls of the impression crucible and / or by the presence of a neighboring meniscus when several ribbons are drawn simultaneously from the same molten silicon bath. Indeed, the presence of the support band physically maintains the point of attachment of the liquid meniscus in an almost fixed vertical plane, with a possibility of displacement in a direction perpendicular to the support band typically less than ± 100 micrometers. The present invention therefore makes it possible, compared with the conventional STR method, to obtain silicon ribbons of smaller thickness, for example less than 150 micrometers, with better flatness and at higher draw speeds (and therefore with higher productivity). The invention is therefore particularly well suited to the production of photovoltaic cells by using the silicon ribbons thus produced.
Des modifications ou variations évidentes pour l'homme du métier pourront être apportées à la mise en œuvre du procédé qui vient d'être décrite sans sortir du cadre de la présente invention. Par exemple, un seul ruban peut être produit, au lieu de deux simultanément, en empêchant le dépôt de silicium sur l'une des deux faces de la bande support. De plus, on pourrait aisément imaginer que la bande support et les deux filaments ne pénètrent pas dans le bain de silicium par le fond du bâti mais par les parois latérales ou plongent directement dans le bain par le dessus et, par un mécanisme de renvoi, en ressortent également par le dessus du bain. Modifications or variations obvious to those skilled in the art may be made to the implementation of the method which has just been described without departing from the scope of the present invention. For example, a single ribbon can be produced, instead of two simultaneously, by preventing the deposition of silicon on one of the two faces of the support strip. In addition, one could easily imagine that the support strip and the two filaments do not penetrate into the silicon bath by the bottom of the frame but by the side walls or dive directly into the bath from above and, by a return mechanism, also emerge from the top of the bath.

Claims

REVENDICATIONS
1. Procédé de tirage d'au moins un ruban de matériau semi-conducteur (40-42) selon lequel deux filaments (24-26) parallèles et espacés l'un de l'autre traversent verticalement, de bas en haut et à vitesse continue, la surface d'un bain dudit matériau semi-conducteur fondu, ledit rubanA method of drawing at least one ribbon of semiconductor material (40-42) in which two filaments (24-26) parallel and spaced apart from one another pass vertically from bottom to top and at a speed continuous, the surface of a bath of said molten semiconductor material, said ribbon
(40-42) se formant à partir d'un ménisque situé entre lesdits filaments et sensiblement au niveau de ladite surface, ledit procédé étant caractérisé en ce qu'une bande support (22) est interposée entre lesdits filaments (24-26) et contenue dans le plan défini par lesdits filaments, ladite bande support (22) traversant verticalement, de bas en haut et à vitesse continue, ladite surface dudit bain de matériau semi-conducteur fondu à la même vitesse de défilement que lesdits filaments, ledit ruban de matériau semi-conducteur (40-42) étant alors formé sur l'une des deux faces de ladite bande support et étant supporté par ladite face. (40-42) forming from a meniscus located between said filaments and substantially at said surface, said method being characterized in that a support strip (22) is interposed between said filaments (24-26) and contained in the plane defined by said filaments, said support strip (22) traversing vertically, from bottom to top and at a continuous speed, said surface of said bath of semiconductor material melted at the same speed of movement as said filaments, said strip of semiconductor material (40-42) being then formed on one of the two faces of said support strip and being supported by said face.
2. Procédé selon la revendication 1 caractérisé en ce que deux rubans de matériau semi-conducteur (40-42) sont formés simultanément, l'un sur l'une des deux faces de ladite bande support et l'autre sur l'autre face. 2. Method according to claim 1 characterized in that two ribbons of semiconductor material (40-42) are formed simultaneously, one on one of the two faces of said support strip and the other on the other side .
3. Procédé selon l'une des revendications précédentes caractérisé en ce que lesdits filaments (24-26) sont en carbone ou en silice. 3. Method according to one of the preceding claims characterized in that said filaments (24-26) are carbon or silica.
4. Procédé selon la revendication 3 caractérisé en ce que le diamètre desdits filaments (24-26) est compris entre 0,3 et 1 mm. 4. Method according to claim 3 characterized in that the diameter of said filaments (24-26) is between 0.3 and 1 mm.
5. Procédé selon l'une des revendications 3 et 4 caractérisé en ce que lesdits filaments (24-26) sont recouverts d'une fine couche de graphite pyrolytique. 5. Method according to one of claims 3 and 4 characterized in that said filaments (24-26) are covered with a thin layer of pyrolytic graphite.
6. Procédé selon l'une des revendications précédentes caractérisé en ce que ladite bande support (22) est en carbone.6. Method according to one of the preceding claims characterized in that said support strip (22) is carbon.
7. Procédé selon la revendication 6 caractérisé en ce que l'épaisseur de ladite bande support (22) est comprise entre 200 et 300 micromètres.7. The method of claim 6 characterized in that the thickness of said support strip (22) is between 200 and 300 micrometers.
8. Procédé selon l'une des revendications précédentes caractérisé en ce que l'épaisseur du ruban de matériau semi-conducteur (40-42) est inférieure à 250 micromètres. 8. Method according to one of the preceding claims characterized in that the thickness of the ribbon of semiconductor material (40-42) is less than 250 micrometers.
9. Procédé selon l'une des revendications précédentes caractérisé en ce que ledit matériau semi-conducteur fondu est contenu dans un creuset de tirage muni d'un fond sensiblement horizontal, ledit fond comprenant une fente (28) par laquelle pénètrent ladite bande support (22) et lesdits filaments (24-26).9. Method according to one of the preceding claims characterized in that said molten semiconductor material is contained in a draw crucible provided with a substantially horizontal bottom, said bottom comprising a slot (28) through which penetrate said support strip ( 22) and said filaments (24-26).
10. Procédé selon la revendication 9 caractérisé en ce que ladite fente (28) a une section horizontale rectangulaire (30) dont la largeur est légèrement supérieure à l'épaisseur de ladite bande support (22) et, à chacune des deux extrémités de la section rectangulaire, une section horizontale circulaire (32-34) par laquelle traversent lesdits filaments.10. The method of claim 9 characterized in that said slot (28) has a rectangular horizontal section (30) whose width is slightly greater than the thickness of said support strip (22) and, at each of the two ends of the rectangular section, a circular horizontal section (32-34) through which said filaments pass.
11. Procédé selon l'une des revendications précédentes caractérisé en ce que ledit matériau semi-conducteur est à base d'un élément semiconducteur ou d'un composé semi -conducteur à fusion congruente ou quasi-congruente. 11. Method according to one of the preceding claims characterized in that said semiconductor material is based on a semiconductor element or a semi-conductive compound with congruent or quasi-congruent fusion.
12. Procédé selon la revendication 11 caractérisé en ce que ledit matériau semi-conducteur est du silicium.12. The method of claim 11 characterized in that said semiconductor material is silicon.
13. Procédé selon l'une des revendications précédentes caractérisé en ce que les bords de la bande support sont distants des filaments d'au moins 100 micromètres de façon à prévenir tout contact susceptible de déformer ladite bande support. 13. Method according to one of the preceding claims characterized in that the edges of the support strip are spaced from the filaments of at least 100 microns so as to prevent contact likely to deform said support strip.
EP06726209A 2005-04-22 2006-03-01 Method for growing thin semiconductor ribbons Withdrawn EP1871926A1 (en)

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FR0551032A FR2884834B1 (en) 2005-04-22 2005-04-22 METHOD OF DRAWING LOW THICK SEMICONDUCTOR RIBBONS
PCT/FR2006/050185 WO2006111668A1 (en) 2005-04-22 2006-03-01 Method for growing thin semiconductor ribbons

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EP06726209A Withdrawn EP1871926A1 (en) 2005-04-22 2006-03-01 Method for growing thin semiconductor ribbons

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JP (1) JP2008536793A (en)
CN (1) CN101128625A (en)
AU (1) AU2006238527A1 (en)
FR (1) FR2884834B1 (en)
WO (1) WO2006111668A1 (en)

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DE102009044249B3 (en) * 2009-10-14 2011-06-30 ReiCat GmbH, 63571 Process and apparatus for separating argon from a gas mixture
US9464364B2 (en) * 2011-11-09 2016-10-11 Varian Semiconductor Equipment Associates, Inc. Thermal load leveling during silicon crystal growth from a melt using anisotropic materials
CN106521622A (en) * 2016-12-20 2017-03-22 常州大学 Heating device for horizontal pulling of silicon wafers

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US4299648A (en) * 1980-08-20 1981-11-10 The United States Of America As Represented By The United States Department Of Energy Method and apparatus for drawing monocrystalline ribbon from a melt
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CN101128625A (en) 2008-02-20
WO2006111668A1 (en) 2006-10-26
AU2006238527A1 (en) 2006-10-26
US20090050051A1 (en) 2009-02-26
JP2008536793A (en) 2008-09-11
FR2884834A1 (en) 2006-10-27
FR2884834B1 (en) 2007-06-08

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