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
  • C30B25/00—Single-crystal growth by chemical reaction of reactive gases, e.g. chemical vapour-deposition growth
  • C30B25/02—Epitaxial-layer growth
  • C30B25/14—Feed and outlet means for the gases; Modifying the flow of the reactive gases
• • 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
  • C30B25/00—Single-crystal growth by chemical reaction of reactive gases, e.g. chemical vapour-deposition growth
• • 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
  • C30B29/36—Carbides

Definitions

• the present invention relates to a system for growing silicon carbide crystals according to the preamble to Claim 1-
• Nisshin Steel in mSi this is described in European patent EPSSMD 1 I?.
• IU0DD/M3S77 - Hakarov's concept provides for reaction gases containing silicon and carbon to be admitted separately to a reaction chamber at high-temperature and to be put in contact in the vicinity of a substrate so that the silicon and the carbon are deposited directly on the substratei growing a crystal 1 .
• Hakarov's invention proposed that deposits of silicon carbide along the walls of the chamber be prevented! and therefore provided for silicon carbide to be caused to form solely in the vicinity of the substratei that is ⁇ of the growing crystal-
• the object of the present invention is to provide a third and basic proposal which is different from the previous ones and improved in comparison therewith- This object is achieved by the system for growing silicon carbon crystals having the characteristics set forth in independent
• the concept underlying the present invention is to cause reaction gases containing carbon and gases containing silicon to enter a chamber by means of separate input means and to cause those gases to come into contact in a central zone of the chamber remote from the growth substrate-
• the concentration profile and the velocity profile are thus substantially constant radially (clearly! there are inevitable edge effects) ⁇ a constant growth rate! a uniform crystalline structure! and a uniform chemical composition are thus achieved throughout the cross-section of the substrate.
• FIG. 1 is a schematic sectioned view which assists in understanding the description of the teachings of the present invention!
• Figure 5 shows a first embodiment of the present invention in a simplifiedn sectioned view ⁇
• Figure 3 shows a second embodiment of the present invention! in a simplified! sectioned view.
• the system for growing silicon carbide crystals on substrates comprises a chamber which extends along an axisi typically! the axis is verticals the chamber has:
• the input means for gases containing silicon are positioned! shaped and dimensioned in a manner such that the gases containing silicon enter in a second end zone of the chamberi the input means for the gases containing carbon are positioned! shaped and dimensioned in a manner such that the carbon and the silicon come substantially into contact in a central zone of the chamber remote both from the first end zone and from the second end zone-
• the chamber is indicated In the space enclosed by the chamber is indicated IDi the input means for gases containing silicon are indicated BT the input means for gases containing carbon are indicated 3-, the substrate support means are indicated M (a substrate is shown fitted on the means >4 and indicated by a black line) T the exhaust output means are indicated Sn an evaporation cell of the means 5 (which will be mentioned and described below) is indicated Sl ⁇ two possible embodiments of central cores of the means ⁇ (which will be mentioned and described below) are indicated ⁇ A and 52Bn a level indicative of the first end zone of the chamber is indicated ZIn a level indicative of the second end zone of the chamber is indicated Z ⁇ and a level indicative of the central zone of the chamber is indicated ZC- Moreover!
• the concentration profile and the velocity profile through the system specified above are substantially constant radially! at least in the first end zone of the chamber (clearly! there are inevitable edge effects)! a constant growth rat ⁇ i a uniform crystalline structure! and a uniform chemical composition are thus achieved over the entire cross-section of the substrate disposed on the support means- Moreover- since the input zone for the gases containing silicon is remote from the zone of mixing with the gases containing carbon (the central zone ZOn and since the chamber is at a very high temperaturen any liquid silicon particles that are formed at the input to the chamber or upstream of the input to the chamber evaporate and there is therefore no risk of the formation of solid silicon carbide particles owing to contact of the carbon with the liquid particles ⁇ such solid silicon carbide particles are difficult to break up by sublimation (particularly if they are large) and are very dangerous since they irremediably spoil the growing crystal if they strike its surface.
• the input zone for the gases containing silicon is remote from the zone of mixing with the gases containing carbon (the central zone ZOn it is possible to arrange for the concentration profile and the velocity profile of the gases containing silicon ⁇ upon their meeting ⁇ to be substantially constant radially (clearly ⁇ there are inevitable edge effects).
• a first end zone (Zl) i a central zone (ZC) ⁇ and a second end zone (ZE)-
• the chamber has a substantially cylindrical shape and extends mainly substantially vertically (the most advantageous selection) ⁇ the first end zone Zl corresponds to the upper zone of the cylinder and the second end zone Z ⁇ corresponds to the lower zone of the cylinder- If low gas-flows are used in a system according to the present invention (as is preferable)! the vertical orientation of the chamber causes any liquid silicon particles (particularly if they are large) to tend to remain at the bottom until they evaporate.
• the second end zone may extend from the base up to a height of about SD mm ⁇ the central zone may extend from a height of about IDD mm to a height of about ISD m ⁇ H and the first end zone may extend from a height of about HDD mm to a height of about SSD mm.
• Ulith appropriate selections of the various gas output means and of the flow-rates and velocities of the gas-flows ⁇ the lengths of th ⁇ various zones and the distances between the various zones can be reduced considerably to less than half.
• the compounds containing silicon and the compounds containing carbon enter the chamber in gaseous form and since there is a very large degree of lateral diffusion because of the high temperature!
• the exhaust output means may serve to discharge everything: reaction products! compounds and elements ⁇ hich have not reacted and/or have not been deposited-! carrier gases-i etching gases and! possibly (!) ⁇ solid particles detached from the walls of the chamber and/or from the growing crystal-
• the temperature of about lflOD°C corresponds approximately to the temperature limit of normal CVD processes for the growth of silicon carbide ⁇ moreover! this temperature of about ISDD 0 C constitutes a boundary temperature: typically! below lflDD°C there is 3C-type nucleation of the SiC and typically above lflDD°C there is bH-type or MH-type nucleation of the SiCi finally! this temperature of about lfiDD°C ensures that the silicon is in the gaseous phase in the range of pressures (D-l-l-D atmosphere) and dilutions (.Y/.-E ⁇ X) that are of interest.
• the input means for the gases containing carbon are positioned! shaped and dimensioned in a manner such that the carbon and the silicon come substantially into contact in a zone 1 which is also remote from the chamber walls (as is ⁇ in part! the case in Figure l) ⁇ the deposits of silicon carbide along the internal walls of the chamber are much more limited.
• the chamber of the system according to the present invention may advantageously have input means for anti-nucleation gas ⁇ these may be positioned! shaped and dimensioned in many different ways! possibly combined with one another ⁇ hydrochloric acid CHCl]I may advantageously be used as anti-nucleation gas ⁇ this compound reacts with the silicon in the gaseous phase!
• the chamber of the system according to the present invention may advantageously have input means for etching gas ⁇ these may be positioned! shaped and dimensioned in many different ⁇ aysi possibly combined with one another ⁇ hydrochloric acid EHCl]] may advantageously be used as etching gas ⁇ this compound attacks the solid deposits and the solid silicon and silicon carbide particles (in particular if they are polycrystalline) ⁇ hydrochloric acid may advantageously be used in combination with hydrogen •
• Input means for etching gas may be positioned! shaped and dimensioned so as to admit gas in the first end zone of the chamber (as in the embodiments of Figure S and Figure 3) ⁇ that isi in the vicinity of the support means and of the exhaust output means-
• These means may serve to prevent the exhaust output means from being obstructed because of deposits of material-
• these means comprise a hollow sleeve (which also acts as a wall of the chamber in the upper zone of the chamber) which is in communication with a suitable duct and has a plurality of holes facing towards the interior of the chamber- Input means for anti-nucleation gas may be positioned!
• these means may serve to reduce the presence of liquid silicon particles in the chamber! in particular in the second zone of the chamber-
• these means comprise a plurality of nozzles arranged in a ring and oriented at an angle of about MS° towards the centre of the chamber- Input means for anti-nucleation gas may be positioned!
• These means may serve to reduce the presence of liquid silicon particles in the chamber in particular in the central zone of the chamber- Input means for etching gas may be positioned! shaped! and dimensioned in a manner such as to create a gas-flow substantially only along the walls of the chamber.
• These means may serve to remove and/or prevent deposits of silicon carbide along the walls of the chambers in providing such a flow of etching gas along the ⁇ alls ⁇ however! it is necessary to take account of its effect on the walls of the chamber which must be adequately protected.
• the input means for etching gas may be adapted for causing a etching gasn typically hydrochloric acid! associated with a carrier gasn typically hydrogen! (alternatively! argoti ⁇ helium-i or a mixture of two or more of those gases) to enter the chambers the proportions between etching gas and carrier gas may bei for example! ID slm for hydrogen and 1- ⁇ slm for hydrochloric acid.
• the support means of the system according to the present invention may also advantageously have input means for etching gas (as in the embodiment of Figure 5 and Figure 3)i these may be positioned!
• the support means may be constituted! for examplei by a thick disc provided with an internal cavity and mounted on a tube which is in communication with the cavity (as in the embodiments of Figure E and Figure 3)i the tube is thermally insulated and chemically isolatedi the etching gas is injected into the tube! flows through the cavity ⁇ and emerges from a plurality of holes formed in the periphery of the disc
• the system according to the present invention may advantageously comprise means for rotating the support means during the growth process (as in the embodiments of Figure ⁇ and Figure ⁇ ). An improved uniformity of the growth conditions in the region of the crystal surface is thus obtained.
• the system according to the present invention may advantageously comprise means for retracting the support means during the growth process (as in the embodiments of Figure ⁇ and Figure 3).
• the crystal surface is thus substantially always in the same position in the chambers irrespective of the length of the crystal that has grown and it is therefore easier to control the growth conditions in the region of the crystal surface-
• the means for moving the support means may advantageously be protected both from the heat and from the chemical environment of the reaction chamber (as in the embodiments of Figure ⁇ and Figure ⁇ ) •
• the support means can support a single substratei which is the simplest situation-
• the input means for gases containing silicon may be positioned! shaped and dimensioned in many different ways-
• the mouth of the duct in the chamber may advantageously be formed with a flow-dynamic distributor adapted for rendering the velocity profiles uniform and preventing lateral vortices.
• the most typical and the simplest way of evaporating the liquid silicon particles is by heating ⁇ in fact
• Figure 1 shows schematically a graphite sleeve covered with a suitable material which can be heated by induction and by radiation-
• the duct may advantageously have a central core in the region of an end portion of the duct:, the central core may be heated by radiation from the walls of the duct ⁇ the core may be of various shapes and sizes ⁇ particular shapes and/or sizes may be designed to maximize heat exchanges between the duct walls and the core and between the core and the gas-
• the duct may advantageously have a central core in the region of an end portion of the duct ⁇ the core may be of various shapes and sizesi particular shapes and/or sizes may be designed to prevent vortices and to control possible condensation along the walls.
• the central core is suitably shaped and dimensioned! it can thus serve both to heat and to distribute the gas- Figure 1 shows ⁇ by way of indication ⁇ only two examples of such cores (to be precise ⁇ this drawing shows them in section and not yet mounted in the end portion of the duct) ⁇
• the first corei indicated i2A ⁇ has a cylindrical shape with two hemispherical ends and can be inserted completely in the end portion of the ducti
• the second core ⁇ indicated 25Bn has an inverted conical shape with a spherical cap in the base region and can be disposed above the outlet of the duct so that the tip of the cone is inserted in the duct but without blocking it.
• the input means for gases containing silicon may advantageously comprise a cup-shaped element having an opening facing towards the duct (as in the embodiment of Figure 3).
• the cup is thus heated by radiation from the chamber walls and the gas which flows through the cup is heated quickly to high temperature by the walls of the cup ⁇ rapid heating is very advantageous since the time during which the silicon is at a temperature below the silicon dew pointi and hence the growth time for silicon particles ⁇ (and therefore their size) are thus reduced ⁇ moreover ⁇ any particles (in particular liquid silicon particles) tend to be retained in the cup until they evaporate.
• Figure 3 shows a cylindrical cup! the cup may be suitably shaped and dimensioned both with regard to the outer surface and with regard to the inner surfaced particular shapes and/or sizes may be designed to prevent vortices ⁇ to maximize heat exchanges between the chamber walls and the cup and between the cup and the gas ⁇ and to control possible condensation along the walls-
• the input means for gases containing carbon may be positioned! shaped and dimensioned in many different ways-
• the input means for gases containing carbon may comprise a plurality of nozzles arranged in a ring and opening into the second zone of the chamber (as in the embodiment of Figure ⁇ in which the nozzles are facing substantially upwards) i for a vertical ⁇ cylindrical chamber! the ring and the chamber are typically coaxial and the ring is typically positioned on the base of the cylinder (as in the embodiment of Figure H) or on the lower portion of the cylindrical wall-
• the nozzles should be shaped and dimensioned in a manner such that the jet of gas containing carbon is substantially in contact with the silicon in a central zone of the chambers the shape of a nozzle determines the direction and the shape of the gas jet-
• the input means for gases containing carbon may comprise a plurality of ducts which are arranged in a ring and which open 1 into the central zone of the chamber (as in the embodiment of Figure 3)i for a vertical! cylindrical chamber! the ring and the chamber are typically coaxial and the ducts are typically all identical and parallel ⁇ for a good result! the mean diameter of the ring may be selected so as to be approximately equal to ⁇ /3 of the inside diameter of the chamber-
• these ducts are in communication with a hollow disc adjacent the base of the chambers a series of small ducts opens in the cavity of the disci the small ducts extend as branches from a large coaxial duct-
• the input means for gases containing carbon may comprise a ring- shaped duct which opens in the central zone of the chambers for a verticaln cylindrical chambers the ring and the chamber are typically coaxial ⁇ to permit a good distribution of the gases containing silicon (which enter in the second zone of the chamber) T the mean diameter of the ring is advantageously only slightly less than the inside diameter of the chambers in this case ⁇ a ring-shaped duct for etching gas may be provided in additionn positioned around the ring-shaped duct for gases containing carbon and close to the walls of the chamber so as to keep the chamber walls clear of silicon carbide deposits-
• the input means for gases containing carbon should be designed so as to try to achieve good mixing with the gases containing silicon and a wide and uniform distribution of the gases in the chamber and to try to prevent vortices ⁇ it is also advantageous to take account of the possible diffusion of the gases containing carbon back towards the input for the gases containing silicon- Both with regard to the input means for the gases containing silicon and with regard to the input means for the gases
• the input means for precursor gases are typically adapted for admitting to the chamber a precursor gas associated withi and hence diluted inn a carrier gas which may be hydrogen ⁇ argon ⁇ helium ⁇ or a mixture of two or more of those gases ⁇ the proportions between precursor gas and carrier gas may bei for examplen ID slm for the carrier gas and 1- ⁇ slm for the precursor gas-
• the precursor gases carrying carbon may be propane ECgHgIDn ethylene ECgH ⁇ ll ⁇ or acetylene ECgHgIOi of thesen the compound which is most stable at high temperature is acetylenei the easiest to handle is propane ⁇ and the compromise compound is ethylene-
• the heating means are advantageously of the induction type and are adapted for heating the chamber wallsi the heating means are not shown in any of the drawings- It is preferable to maintain a predetermined temperature profiled in particular the temperature of the central zone of the chamber is advantageously very high (52OD 0 C-HbDD 0 On whereas the temperature of the first zone (and hence of the substrate and of the growing crystal) is a little lower (IaDD 0 C-SSDD 0 C) to promote condensation of the silicon carbidei the temperature of the first zone (the input zone for the gases containing silicon) should be very high (22DD 0 C-ELiDO 0 C) but may also be slightly lower (EDDD 0 C-S 1 IDD 0 C) than the temperature of the central zone- In a first embodiment! the heating means may therefore be adapted for producing the following temperatures in the chamber:
• the heating means may therefore be adapted for producing the following temperatures in the chamber:
• the support means in the second zonen a temperature within the range of 55DD-SbDD degrees ⁇ preferably about 51DD degrees- It is advantageous to arrange for the support means to comprise temperature control means.
• the support means of the system according to the present invention are typically made of graphite coated with a layer of SiC or TaCi these therefore also act as heating elements both by the induction effect and by the radiation effect-
• a gas-flown for example-i of hydrogenn may advantageously be used to control the temperature of the support means ⁇ a hydrogen flow of 55 slm absorbs a power of about 1 kU in order to be heated to ⁇ DDD°C from ambient temperature.
• the support means may be constituted!
• the gas-flow inside the support means can advantageously be used both for etching and for temperature control-

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• Chemical & Material Sciences (AREA)
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• Inorganic Chemistry (AREA)
• Crystals, And After-Treatments Of Crystals (AREA)
• Silicon Compounds (AREA)
• Carbon And Carbon Compounds (AREA)

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• 2003
  • 2003-06-13 IT IT001196A patent/ITMI20031196A1/it unknown
• 2004
  • 2004-06-09 EP EP04739749A patent/EP1636404A1/en not_active Withdrawn
  • 2004-06-09 CN CNB2004800164824A patent/CN100350082C/zh not_active Expired - Lifetime
  • 2004-06-09 RU RU2006101147/15A patent/RU2341595C2/ru not_active IP Right Cessation
  • 2004-06-09 KR KR1020057022349A patent/KR20060017810A/ko not_active Withdrawn
  • 2004-06-09 WO PCT/EP2004/006244 patent/WO2004111316A1/en not_active Ceased
  • 2004-06-09 JP JP2006515874A patent/JP2006527157A/ja active Pending
• 2005
  • 2005-04-27 US US11/116,145 patent/US20060283389A1/en not_active Abandoned

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