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
  • C30B15/02—Single-crystal growth by pulling from a melt, e.g. Czochralski method adding crystallising materials or reactants forming it in situ to the melt
  • C30B15/04—Single-crystal growth by pulling from a melt, e.g. Czochralski method adding crystallising materials or reactants forming it in situ to the melt adding doping materials, e.g. for n-p-junction
• • 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
  • C30B15/10—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
  • C30B15/00—Single-crystal growth by pulling from a melt, e.g. Czochralski method
  • C30B15/14—Heating of the melt or the crystallised materials
• • 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
  • C30B15/14—Heating of the melt or the crystallised materials
  • C30B15/16—Heating of the melt or the crystallised materials by irradiation or electric discharge

Definitions

• the present invention relates to a method for pulling a single crystal from semiconductor material using a device with a crucible, such a device and a semiconductor wafer made from single-crystal silicon.
• Single crystals made of semiconductor material such as silicon can be pulled out of a
• melt of the semiconductor material are produced.
• a so-called seedling is usually introduced into the melt and then pulled up.
• This process is also known as the so-called Czochralski method.
• the melt itself is obtained by melting generally polycrystalline, ie solid, semiconductor material, which is usually introduced into the crucible as a bed.
• Contamination in the device or in the components can usually be kept low by using suitable materials.
• semiconductor materials such as the silicon mentioned are usually also coated with an oxide or the semiconductor material oxidizes in air. In the case of silicon, silicon dioxide is created.
• JP 2196082 A it is known, for example, to remove such an oxide layer by heating the semiconductor material in the device to a predetermined temperature for a predetermined period of time. Then the device is evacuated or an inert gas atmosphere is formed therein.
• silicon nitride which avoids the risk of contamination by oxygen from the crucible, as is the case with conventional crucibles made of silicon dioxide or quartz.
• silicon dioxide or quartz As is the case with conventional crucibles made of silicon dioxide or quartz.
• silicon nitride or corresponding other nitrides it can sometimes be very high
• the task arises of using a crucible made of a nitride of a semiconductor material to pull a single crystal out of this semiconductor material to improve the manufacturing process or pulling process.
• the invention relates to a method for pulling a single crystal from semiconductor material using a device with a crucible, which is used to pull the single crystal from a melt in the crucible.
• a crucible is used as the crucible, which consists at least partially, but preferably also completely, of a nitride of the semiconductor material.
• silicon in the particularly preferred case of silicon as the semiconductor material, this is silicon nitride (Si3N 4 ).
• the semiconductor material from which the single crystal is to be formed preferably silicon
• This can in particular also take the form of a bed, ie individual, smaller and / or larger pieces of the semiconductor material are introduced or poured into the crucible.
• such a device generally also has a suitable pulling device for the single crystal from the melt, which - as will be explained later - is obtained from the semiconductor material.
• a heat shield is usually provided, the lower end of which is designed as a type of brim.
• the semiconductor material in the crucible is heated before pulling the single crystal, so that the semiconductor material melts. It is usual or appropriate here
• a partial pressure for nitrogen is set or regulated in the device to a value of at least 0.1 mbar, preferably of at least 1 mbar.
• a total pressure of the atmosphere in the device is preferably set or regulated to a value of at least 50 mbar, preferably at least 200 mbar.
• the pressure can be increased as desired, but if, for example, devices which are actually intended for vacuum are used, an appropriate upper limit may be 800 mbar, since such devices are not suitable for higher pressures.
• At least one neutral gas, in particular argon is expediently provided in the atmosphere in addition to nitrogen. Such a neutral gas serves as a protective gas.
• a partial pressure for nitrogen is set or regulated to a value between 1 mbar and 10 mbar, preferably between 2 mbar and 5 mbar. In this way, as close as possible to a triple point between - in the case of silicon as a semiconductor material - silicon nitride, solid
• Nitrogen and liquid nitrogen can be approached. For a closer
• Semiconductor material is that when the single crystal is pulled from the melt, crystals form from the nitride of the semiconductor material, for example
• Silicon nitride crystals separate.
• the molten semiconductor material dissolves the material of the crucible up to the solubility limit, with maximum solubility generally being highly temperature-dependent.
• Such crystals from the nitride of the semiconductor material grow not only due to temperature differences, but also due to segregation during crystal pulling.
• the growing single crystal contains significantly less nitrogen than the melt, which is why the nitrogen is enriched in the melt.
• it is advisable to use this excess Remove nitrogen from the system at a suitable location so that particles from the nitride of the semiconductor material (so-called segregation) do not lead to the dislocation of the single crystal.
• a cooling plate surrounding the crucible in particular an annular one, is provided, which is in thermal contact with a cooling device surrounding the cooling plate and the crucible.
• a cooling plate is a plate or another shaped unit made of a particularly good heat-conducting material. This allows heat or heat to be conducted away particularly well from the surface of the melt or from the crucible.
• the cooling device can be, for example, water cooling of the system jacket.
• the temperature in the region of the crucible can be kept as low as possible, which prevents or reduces the decomposition of the nitride from the semiconductor material.
• the surface of the melt can be positioned at the level of the cooling plate, if possible, or vice versa.
• a cooling capacity of the cooling plate is set or regulated by means of a cooling plate heating device. This enables a more precise setting or control of the heat dissipated.
• a temperature required for this can be measured at a suitable point, for example by means of a temperature sensor, in particular a pyrometric one
• a cooling capacity of the cooling plate can also be selected or set once by its thickness (i.e. an expansion in the direction of gravity).
• crystal needles are formed or grown from the nitride of the semiconductor material (ie in particular from silicon nitride) on a surface of the crucible facing the melt.
• Such growth of crystals can be achieved, for example, by deliberately changing the partial pressure of the protective gas or neutral gas mentioned and / or by changing the flow of the protective gas or neutral gas mentioned can be varied by the device.
• a bead made of the nitride of the semiconductor material forms on the inside of the crucible at about the level of the surface of the melt, on which beads such crystals can then be selectively grown.
• a coating with crystallization nuclei is provided on the surface of the crucible facing the melt (i.e. on the inside thereof).
• a layer can be produced by chemical vapor deposition (CVD). This is achieved by the fact that CVD process conditions produce particularly strong crystal growth in this crystal direction and so that appropriately oriented nuclei become established. This makes it particularly easy and easy to achieve that the crystal needles then grow in a direction perpendicular to the surface of the crucible, and so a total of a particularly large number of crystal needles can be formed and a particularly large amount of nitrogen can be bound therein.
• Such a heating device can be specifically set or regulated in such a way that a sufficiently wide area around the single crystal remains free from the crystal needles.
• the difference between the temperature, in particular the radiation temperature, the surface of the melt and the (lower) ambient temperature of the melt is preferably between 3 ° C. and 8 ° C. Another point when using crucibles made from a nitride
• Semiconductor material is that as little as possible unnecessary heat into the system, in particular the crucible, should be introduced in order to avoid degradation of the crucible as far as possible.
• the solid and meltable semiconductor material which is located in the crucible
• the crucible from above (seen in the direction of gravity) and / or the crucible from below (also seen in the direction of gravity) in each case at least partially heated directly by heat radiation generated by the heater.
• direct heating is to be understood to mean that the heat radiation generated by the heating device is unimpeded on the relevant one to be heated
• Components such as a susceptor are present, which are also heated and then act as unnecessary or undesirable heat sources.
• the crucible can expediently be moved into a heating position within the device.
• the heating device is or is in particular arranged in such a way that it surrounds the crucible and is bent inwards (in particular in the radial direction) at an upper end above the crucible with respect to gravity.
• the crucible for melting the semiconductor material can thus be moved downwards in a targeted manner and the curved material can be used to directly heat the semiconductor material and so on
• the crucible can then be moved up again so that the single crystal can be pulled.
• the crucible is arranged on a suspension element which has at least one opening, so that the crucible is generated by means of the heating device by means of the heating device Heat radiation that passes through the at least one opening is directly heated.
• a suspension element can be, for example, a tube with openings or recesses in the tube walls, so that the heat radiation
• the semiconductor material must be heated via the crucible.
• Computing unit or control unit can be used.
• the invention further relates to a device for pulling a single crystal from semiconductor material, which has a crucible in which a melt from which the single crystal can be drawn can be kept, the crucible consisting at least partially of a nitride of the semiconductor material.
• the device is set up in such a way that a partial pressure for nitrogen is set or regulated therein during operation to a value of at least 0.1 mbar, preferably of at least 1 mbar.
• a computing unit or control unit can be provided.
• a cooling plate in particular an annular one, surrounding the crucible provided, which is in thermal contact with a cooling device surrounding the cooling plate and the crucible.
• the device is set up such that during operation on one of the melts
• a heating device is provided which is arranged in such a way that the solid and meltable semiconductor material from above and / or the crucible from below can each be at least partially heated directly by heat radiation generated by the heating device.
• the invention further relates to a semiconductor wafer made of single-crystal silicon, which is separated from a single crystal produced according to the invention, for example by means of a wire saw.
• the semiconductor wafer made of single-crystal silicon preferably has a diameter of at least 300 mm and an oxygen content of less than 1 ⁇ 10 16 atoms per cm 3 , the oxygen content being understood in accordance with the new ASTM standard.
• Figure 1 shows schematically in longitudinal section a device according to the invention in a preferred embodiment, with which a method according to the invention can be carried out.
• FIG. 2 shows schematically the device of Figure 1 in a different position.
• FIG. 3 shows a phase diagram for silicon or silicon nitride as a function of temperature and nitrogen partial pressure.
• Figure 4 shows schematically part of a crucible of an inventive
• Figure 5 shows schematically a coating of a surface of a crucible of a device according to the invention in a preferred embodiment.
• FIG. 1 schematically shows a device 100 according to the invention in a preferred embodiment, which is used to pull a single crystal.
• a method according to the invention can be carried out, which in a preferred embodiment is to be explained in more detail below with the aid of the device 100.
• FIG. 2 shows the device 100 from FIG. 1 in a different position while a method according to the invention is being carried out.
• Figures 1 and 2 will be described in a comprehensive manner.
• a crucible 130 is arranged in the device 100, into which solid semiconductor material can be introduced.
• semiconductor material is indicated by reference numeral 153 and is, for example, silicon, here in the form of a bed, ie in the form of many individual pieces, here polycrystalline pieces.
• the crucible 130 in this case consists at least partially, but in particular completely, of a nitride of the flalbonductor material, that is to say, for example, silicon nitride (Si 3 N 4 ).
• This solid semiconductor material is melted, so that a melt or melted semiconductor material 154 results in the crucible 130, as shown in FIG. 2.
• a heating device 135 is provided which surrounds the crucible 130.
• This heating device 135 can be, for example, an oven or the like.
• a heat shield 136 is attached above the semiconductor material 153 or the melt 154 and the crucible 130, which heat shield can serve to retain the heat that is later emitted by the melt 154, so as to reduce the energy consumption.
• a single crystal 150 as can be partially seen or indicated in FIG. 1, can then later be formed from the melt using a pulling device 140.
• a more detailed description of the pulling of the crystal is not intended to be given within the scope of the present invention, since this basically does not differ from known methods.
• a heating position PH heat radiation generated by the heating device 135, here indicated by an arrow W, can directly heat the solid semiconductor material 153.
• the heating device 135 is bent radially inwards at an upper end or region, so that the heat radiation W can reach the solid semiconductor material 153 more directly and over a large area. In this way, indirect heating of the solid
• Semiconductor material 153 can be reduced via the crucible 130 or its wall, which would lead to undesirable heat sources within the device and thus would contribute to the degradation of the crucible 130. It goes without saying that the crucible 130 must be able to be moved into the heating position PH in a suitable manner.
• the crucible can be moved into a pulling position PZ, in which the single crystal 150 can be pulled out of the melt 154, as shown in FIG. 2.
• the crucible 130 is arranged on a support means 161, for example in the form of a tube or the like, which in turn is arranged in or on a collecting trough 160. Openings are now provided in the suspension means 161, designated 162 here by way of example. These openings 162 preferably extend at least 50% of the circumference (with respect to an axis in the direction of gravity) of the suspension element 161. In this way it can be achieved that heat radiation W, which is generated by means of the heating device 135, in particular in the pulling position PZ, directly can reach the crucible 130 or its wall, in particular also at locations or areas that would be covered using conventional suspension means. In this way, undesirable heat sources within the device can be avoided or reduced, which would otherwise contribute to the degradation of the crucible 130.
• a cooling device 120 is provided in the device 100, which surrounds the crucible 130 and which can be, for example, water cooling. Furthermore, an annular cooling plate 121 is provided, which likewise surrounds the crucible 130 (at least in the position shown in FIG. 2) and which is in thermal contact with the cooling device 120.
• the cooling plate in particular has a thermally highly conductive material, for example plates made of isostatically pressed graphite. Above the cooling plate 121 are a number of plates 122 made of thermally insulating material, for example
• Carbon felt or carbon hard felt provided.
• heat that is generated or present in the crucible 130 or the melt 154 can be dissipated particularly effectively and quickly, as is indicated by an arrow F, which represents a heat flow.
• the heat flow can be directed to the outside
• a cooling plate heating device 125 is provided, by means of which the cooling capacity of the cooling plate 121 can be adjusted or regulated.
• a maximum output, to which the cooling plate is designed in connection with the cooling device 120, can be specifically reduced, if necessary.
• the device 100 contains a further, in particular annular,
• Heating device 138 is provided, which faces a surface of the melt 154 and surrounds the single crystal 150 to be pulled.
• Heating device 138 can ensure that crystal needles, which are formed in the melt and on the surface of the crucible facing the melt, do not grow too far to the single crystal 150. For this purpose, also on the
• FIG. 3 shows a phase diagram for silicon or silicon nitride, a pressure p in mbar and a logarithmic representation for a partial pressure of nitrogen over a temperature T in ° C. being plotted.
• Three phases are shown, with P1 showing a phase of solid silicon nitride (ShNU), P2 showing a phase of solid silicon and P3 showing a phase of liquid silicon.
• This phase diagram shows the dependencies of the conversion from silicon to silicon nitride on both the temperature T and the partial pressure of
• Nitrogen P recognizable. This phase diagram shows that at a temperature higher than the melting temperature of silicon (here around 1420 ° C), a certain
• Partial pressure for nitrogen is appropriate to remain in a range (as close as possible to the triple point) in which all phases involved are stable, or the
• the nitrogen required for this can, for example, be introduced into the device 100 via the openings 101 shown in FIGS. 1 and 2 and set or regulated by means of a computing unit 110 designed as a control or regulating unit.
• the atmosphere in the device can contain a neutral gas such as argon, as has already been explained in more detail at the beginning.
• FIG. 4 schematically shows part of a crucible 130 of a device according to the invention in a preferred embodiment, as is shown for example in FIGS. 1 and 2.
• a bulge 155 forms on a surface 131 of the crucible 130 facing the melt on fleas of the surface 151 of the melt.
• the background to this is that the removal of silicon from the melt to form the single crystal increases the proportion of nitrogen in the melt. This creates an imbalance, which is reflected in the formation of crystalline silicon nitride. Crystals made of silicon nitride that float freely in the melt and float freely on the melt surface are undesirable since these can lead to dislocation of the single crystal. For this reason, crystal needles made of silicon nitride are specifically formed on the surface 131 on this bead 155.
• crystal needles are created over the entire height of the inner wall of the crucible, which is smeared by the melting surface.
• Such crystal needles are designated 156 by way of example.
• the region of the melt in which the single crystal is formed or drawn is as free as possible from such floating crystals, so that dislocations in the single crystal occur as far as possible.
• This coating 170 is, in particular, a CVD layer with crystallization nuclei 171, which particularly preferably have triple crystal corners, as designated by way of example at 172.
• This way can be achieved be that the crystal needles to be formed on the surface of the crucible grow inwards as perpendicularly as possible to the crucible wall on the melting surface.
• annular heating device which is explained with reference to FIGS. 1 and 2 and surrounds the single crystal, it can also be achieved that these crystal needles are not too close to the single crystal
• the proposed method and the proposed device can be used to form a particularly low-oxygen single crystal, preferably a single crystal made of silicon, because despite the use of, for example
• Silicon nitride as a material for the crucible the problems that arise or

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Crystallography & Structural Chemistry (AREA)
• Materials Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Crystals, And After-Treatments Of Crystals (AREA)

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Citations (6)

• 2018
  • 2018-06-25 DE DE102018210286.4A patent/DE102018210286A1/de not_active Withdrawn
• 2019
  • 2019-06-04 WO PCT/EP2019/064553 patent/WO2020001939A1/de active Application Filing
  • 2019-06-14 TW TW108120612A patent/TWI707992B/zh not_active IP Right Cessation

Patent Citations (6)

Non-Patent Citations (2)

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