US3870477A - Optical control of crystal growth - Google Patents

Optical control of crystal growth Download PDF

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Publication number
US3870477A
US3870477A US269985A US26998572A US3870477A US 3870477 A US3870477 A US 3870477A US 269985 A US269985 A US 269985A US 26998572 A US26998572 A US 26998572A US 3870477 A US3870477 A US 3870477A
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Prior art keywords
melt
capillary
meniscus
growing
growth
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US269985A
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English (en)
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Jr Harold E Labelle
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Saint Gobain Ceramics and Plastics Inc
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Tyco Laboratories Inc
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Priority to US269985A priority Critical patent/US3870477A/en
Priority to CA165,978A priority patent/CA998922A/en
Priority to GB1333073A priority patent/GB1374065A/en
Priority to IT49012/73A priority patent/IT979997B/it
Priority to NL7305454A priority patent/NL7305454A/xx
Priority to BE130864A priority patent/BE799237A/xx
Priority to FR7316790A priority patent/FR2191943B1/fr
Priority to CH665273A priority patent/CH575777A5/xx
Priority to DE2325104A priority patent/DE2325104C3/de
Priority to JP48054173A priority patent/JPS5147432B2/ja
Priority to BR3955/73A priority patent/BR7303955D0/pt
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Assigned to SAPHIKON, INC., A CORP. OF NEW HAMPSHIRE reassignment SAPHIKON, INC., A CORP. OF NEW HAMPSHIRE ASSIGNMENT OF ASSIGNORS INTEREST. Assignors: TYCO LABORATORIES, INC., A CORP. OF MA.
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    • 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
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T117/00—Single-crystal, oriented-crystal, and epitaxy growth processes; non-coating apparatus therefor
    • Y10T117/10—Apparatus
    • Y10T117/1004—Apparatus with means for measuring, testing, or sensing
    • Y10T117/1008—Apparatus with means for measuring, testing, or sensing with responsive control means
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T117/00—Single-crystal, oriented-crystal, and epitaxy growth processes; non-coating apparatus therefor
    • Y10T117/10—Apparatus
    • Y10T117/1024—Apparatus for crystallization from liquid or supercritical state
    • Y10T117/1032—Seed pulling
    • Y10T117/1036—Seed pulling including solid member shaping means other than seed or product [e.g., EDFG die]
    • Y10T117/104—Means for forming a hollow structure [e.g., tube, polygon]

Definitions

  • Bolj 17/00 It consists of optically monitoring the height of a vertical liquid meniscus in the region of the growth Zone [58] Fleld of Search 23/273 301 SP and adjusting the rate of heating or the rate of crystal pulling to maintain the height of the liquid meniscus [56] References cued between selected limits, with the result that outside UNITED STATES PATENTS dimensions of the crystalline product, eg the outside 3,033,660 5/1962 Okkerse 23/301 diameter of a sapphire tube, will be substantially unlg varying and will meet preset tolerances. uc er 3,499,736 3 1970 Zwaneburg.
  • My U.S. Pat. No. 3,,59l,348 describes how to grow crystalline bodies according to what is called the edgedefined, film-fed growth technique (also now known as the EFG process).
  • the shape of the crystalline body is determined by the external or edge configuration of the end surface of a forming member which for want of a better name is called a die.
  • the process involves growth on a seed from a liquid film of feed material sandwiched between the growing body and the end surface of the die, with the liquid in the film being continuously replenished from a suitable melt reservoir via one or more capillaries in the die member.
  • the film By appropriately controlling the pulling speed of the growing body and the temperature of the liquid film, the film can be made to spread (under the influence of the surface tension at its periphery) across the full expanse of the end surface of the die until it reaches the perimeter or perimeters thereof formed by intersection of that surface with the side surface or surfaces of the die.
  • the angle of intersection of the aforesaid surfaces of the die is such relative to the contact angle of the liquid film that the liquids surface tension will prevent it from overrunning the edge or edges of the dies end surface.
  • the angle of intersection is a right angle whch is simplest to achieve and thus most practical to have.
  • the growing body grows to the shape of the film which conforms to the edge configuration of the dies end surface.
  • a continuous hole may be grown in the crystalline body by providing in that surface a blind hole of the same shape as the hole desired in the growing body, provided however, that any such hole in the dies end surface is made large enough so that surface tension will not cause the film around the hole to fill in over the hole.
  • the forming member is mounted so that the capillary is connected to a reservoir pool of melt, whereby the capillary is self-filling. Accordingly, the process is sometimes known as the SFT method, the term SFT being an abbreviation of the phrase self-filling tube" used to denote the forming member used to grow rods or filaments.
  • temperature measuring instrument An obvious choice of temperature measuring instrument is an optical pyrometer, but because of the disposition and relatively small size of the growth interface, the emissivity of the forming member and any radiation shields that may be associated with the forming member tends to cause the pyrometer to yield an erroneous reading.
  • a change in temperature does not necessarily means that the o.d. of a growing tube has changed (a change in pulling speed may offset a change in temperature enough so that no change in tube o.d. will result).
  • the temperature of the growing tube is within the tolerance limits or exceeds the lower or upper limit, and hence the operator does not know whether the temperature needs to be adjusted, or in what direction and by how much. 1f the growth interface temperature is too hot, the tube will grow to a smaller diameter, while if it is too cold, stress and grain boundaries may occur in i the product and the melt may start to solidify to the forming member.
  • the problem is complicated when several like crystalline bodies are being pulled simultaneously at the same speed from different die members fed by a common melt supply. Measuring the'growth interface temperature at one die member, even if 'it could be done accurately, does not suffice as a measurement of the growth temperatures at all of the dies since one die may be at a higher or lower temperature than the others.
  • the primary object of this invention is to provide a method of monitoring and controlling crystal growth so that the outside dimensions of the growing body, notably the o.d. of a tubular body, is within prescribed limits.
  • a further object is to improve upon the methods described and claimed in said U.S. Pat. Nos. 3,591,348 and 3,471,266 by providing a method of monitoring the crystal growth and maintaining the cross-sectional size of the growing body substantially constant.
  • FIG. 1 is a sectional view in elevation of a crucible and die assembly and illustrates growth of a crystalline tube according to the EFG process;
  • FIG. 2 is a view like FIG. 1 but on a reduced scale of a crucible and die assembly for growing a crystalline tube according to the SFT process;
  • FIG. 3 is a fragmentary enlargement of the apparatus of FIG. 2 and shows growth of a crystalline tube according to the SFT process;
  • FIG. 4 is a fragmentary sectional view in elevation showing an optical apparatus associated with a crystalgrowing furnace for monitoring crystal growth according to this invention.
  • FIG. 5 is a plan view of the crucible and die used in arrangement embodying four dies of the type shown in FIG. 1, as used in the apparatus of FIG. 4.
  • the height of the meniscus is affected by the temperature of the melt in the region of the growth interface and the pulling speed, and I have determined that, within limits, the outer diameter of a hollow tube or a solid rod will decrease as the outer meniscus height increases (an increase in the same diameters occurs if the outer meniscus height decreases). It is to be noted also that the inner diameter of a hollow tube will increase or decrease as the outer meniscus height increases or decreases respectively. I have also determined that a relatively small change in the outer diameter of a tube or rod is reflected by a relatively large percentage change in meniscus height.
  • the essence of the invention is to directly measure the height of the meniscus, rather than the melt temperature at the growth interface, and to use that measurement as a basis for determining how to vary the rate of heating to achieve a substantially constant outside diameter for a hollow tube or a solid rod.
  • the same technique may be used to grow other shapes, e.g., flat ribbons, to prescribed sizes.
  • Other features of the invention are described below.
  • FIG. 1 shows a crucible-die assembly for use in growing a tubular body according to the process of my U.S. Pat. No. 3,591,348.
  • the assembly comprises a crucible 2 containing a die assembly or forming member 4 which consists of a round rod 6 that has a coaxial cavity or blind hole 8 of circular cross-section at its top end so that its substantially flat top and surface 10 is annular.
  • Rod 6 is made of a material that is wetted by and will not react with or dissolve in the melt material.
  • Hole 8 must have a diameter large enough so that the film 20 (described below) will not close over its upper end.
  • hole 8 may be made so that it extends for the full length of rod 6, i.e., so that its bottom end is open to the melt in the crucible. If such is the case, its diameter must be large enough so that it cannot fill with melt by action of capillary rise.
  • the round rod 6 also has a plurality of small diameter of longitudinally extending bores 12 (only two of which are visible in FIG. 1) that are spaced substantially uniformly about its axis, bores 12, are sized to function as capillaries for the melt 14 contained in the crucible.
  • Rod 6 is affixed to a plate 16 that rests on ashoulder 18 formed at the top end of the crucible.
  • Rod 6 is mounted in a center hole in plate 16 and projects slightly above its top surface. The bottom end of rod 6 is spaced from the bottom of the crucible.
  • FIG. 1 The apparatus of FIG. 1 is mounted in a suitable crystal growing furnace, e.g. of the type disclosed in my aforesaid U.S. patents, and a charge of material to be grown is placed in the crucible and melted. The molten liquid will flow up into the capillaries 12 by action of capillary rise. Essentially each capillary contains a column of melt.
  • the cross-sectional sizes of the capillaries 12 and the length of rod 6 are preferably set so that for a given melt material, e.g.
  • the capillary action is sufficient to cause the melt to fully fill the capillaries so long as the level of the melt supply in the crucible is high enough to trap the bottom end of the rod, i.e., high enough for the bottom end of the rod to be immersed in the melt supply.
  • the choice of materials used to form the crucible and die assembly depends upon the composition of the melt.
  • the melt is alumina
  • the crucible and die assembly are preferably made of molybdenum or tungsten.
  • a film of melt is established on the upper end surface 10 of the forming member, as shown at 20.
  • the film 20 overlies and conforms to the configuration of the end surface 10 (the orifices of capillaries 12 are ignored in determining the configuration of surface 10).
  • the film may be formed by bringing a seed crystal into contact with melt in one of the capillaries and adjusting the temperature of the melt in the capillaries and also the pulling speed of the crystal so that crystal growth will occur on the seed and so that, as the seed is withdrawn, surface tension will cause the melt in contact with the seed to move up out of the capillary and spread out onto the upper surface 10 to form the film 20.
  • the growing body will have a crosssectional shape conforming to the shape of surface 10.
  • An alternative and preferred mode of establishing film 20 is to bring a seed (preferably one whose cross-sectional shape corresponds to the shape of surface into contact with the end surface 10, and hold the seed there long enough for some of it to melt and cover the end surface 10 as well as connect with the melt in the capillary or capillaries. Then the seed is withdrawn at a rate and with the melt film at a temperature such that crystal growthwill occur on the seed at all points along the interface of the seed and the film 20.
  • the growing body With the apparatus of FIG. 1, the growing body will be a hollow tube 22.
  • the melt film is characterized by a meniscus 24 at its outer edge and a meniscus 26 at its inner edge.
  • Each of the menisci extends between an edge of the dies upper surface 10 and the growth interface and is concave, i.e. the two menisci are bowed inwardly toward one another, as shown. It is to be understood that as a practical matter it is not possible to observe the inner meniscus 26 during crystal growth and for this reason only the outer meniscus is measured and used as a basis for monitoring and controlling the outer diameter of the growing tube 22.
  • the height h (and the degree of bowing) of meniscus 24 will vary if a change is made in pulling speed and/or the temperature off film 20, and the inner and outer diameters of the growing tube 22 will change as the height of the meniscus changes. More specifically, the inner and outer diameters of the growing body will increase and decrease respectively as the height of meniscus 24 increases and will decrease and increase respectively when the meniscus height decreases. However, the minimum size of the inner diameter and the maximum size of the outer diameter of the growing body are determined by the corresponding diameters of end surface 10 since the melt film 20 cannot expand beyond the inner and outer edges of end surface 10.
  • FIG. 2 shows a crucible 30 containing a die or forming member assembly 32 designed for growing a tubular body according to the process disclosed in my U.S. Pat. No. 3,471,266.
  • the forming member 32 consists of a plate 34 that rests on the bottom of the crucible and a capillary unit that comprises a round tube 36 surrounding and concentric with a solid rod 38.
  • the elements of the capillary unit are made of a material that is wetted by and will not react with or dissolve in the melt material.
  • Tube 36 and rod 38 are disposed in depressions in plate 34 and are welded thereto.
  • the bottom end of tube 36 is slotted or has holes as at 40 so as to provide inlet ports whereby melt can flow into the annular space 42 between it and rod 38.
  • the radial distance or gap between rod 38 and the inside surface of tube 36 is such as to allow the space 42 to function as a capillary for the melt material 44 contained in the crucible.
  • the upper end of tube 36 is bevelled as shown at 46 to provide a sharp top edge.
  • the upper end of rod 38 is formed with a conical cavity 48 as shown so that it also has a sharp top edge.
  • tube 36 and rod 38 are level with each other as shown and the height of the capillary unit is set so that, for the given radial distance or gap between the tube and rod, capillary action will cause melt to rise within and fully fill the capillary so long as there is enough melt in the crucible to trap the ports 40.
  • a cover 50 for the crucible is Completing the assembly. The latter has a center hole to accommodate the upper end of the capillary unit which projects a short distance above the cover as shown. Cover 50 functions as a radiation shield for the melt.
  • crucible, die and cover material depends upon the composition of the melt.
  • these components are preferably made of molybdenum or tungsten.
  • the apparatus of FIG. 2 is mounted in a suitable crystal growing furnace, e.g. of the type and in the manner disclosed in my U.S. Pat. No. 3,471,266.
  • a charge of material to be grown is placed in the crucible and melted, and when this occurs, the molten liquid will fill capillary 42.
  • Crystal growth is initiated by inserting an appropriate seed into the column of melt 52 in the capillary, and adjusting the thermal distribution in the upper end of the melt column 52 so that crystal growth will occur and be sustained as the seed crystal is withdrawn at an appropriate speed.
  • the crystal growth will spread horizontally to the annular cross-sectional shape of the melt column so that the growth product will assume the shape of a hollow tube as shown at 54in FIG. 3.
  • a previously grown tube, of a'size suitable for introduction into the column of melt in the capillary may be used as a seed with the apparatus of FIG.
  • FIG. 3 illustrates the growth interface using the apparatus of FIG. and how the growth interface may be monitored in accordance with this invention.
  • surface tension causes the column of melt 52 to adhere to it and to rise above the level of the top edges of the capillary unit. Crystal growth occurs at all pointsalong the top end of the column of melt, due to the surface tension effect noted above, and the melt will form a vertical meniscus at each top edge'as' shown at'56 arid 58. Each meniscus extends between an upper'edge of the capillary unit and the growth interface.
  • the shape of the menisci is similar to that of the menisci 24 and 26 of FIG. 1.
  • Crystal growth occurs at all points along the crystalmelt interface which tends to be both within and above the capillary as shown.
  • shape of the growing body is determined by the temperature and the temperature gradients of the upper end of the column of melt, and the temperature gradients are shaped by the capillary unit. Also the cross-sectional size of the growing body is affected by the pulling rate and the temperature of the meltcolumn.
  • the height of the outer meniscus 56 (the dimension h in FIG. 3) will depend upon the pulling speed and the temperature at the upper end of the melt column, i.e. at the growth interface, and that the greater the height h, the smaller the o.d. and the larger the i.d. of the growing tube. Similarly, the less the height h, the larger the o.d. and the smaller the i.d. of the growing tube.
  • the temperature is raised or lowered, and will cause the meniscus height (typically in the order of 0.007 inch) to change from 60-100% (depending on the pulling speed). Since the meniscus height can be measured very. accurately, i.e. to within about 0.0005 inch, the effect of a change in heating rate on the meniscus height can be readily determined and the power input to the crucible heating means of the furnace can be adjusted so as to produce relatively precise incremental changes in meniscus height, and thereby provide close control over the o.d. of the growing tube.
  • the meniscus height may be precisely measured using a microscope with a recticle in its eyepiece focus.
  • Other suitable commercially-available optical devices are known to persons skilled in the art and may be used to measure meniscus height.
  • the operator adjusts the power input to the heating means of the furnace so that the observed meniscus is maintained at a height which, as determined from prior runs, using the same constant pulling speed, will cause the crystal body to grow with an o.d. that is within the prescribed limits.
  • the operator can determine by measuring the meniscus height whether the o.d. of the growing tube is on the high or low limits side of the desired o.d. size and can, by appropriately adjusting the heating rate, adjust the meniscus, if necessary, to bring or maintain the o.d. within the prescribed tolerance limits. Since a tube may tend to grow slightly oval, the preferred procedure is to maintain the observed meniscus height at a value which assures that the maximum and minimum outer diameters of the tube are within the high and low tolerance limits respectively.
  • Both of the processes described in my US. Pat. Nos. 3,591,348 and 3,471,266 have the advantage that a plurality of crystal bodies of like (or different) crosssectional shape and size may be grown simultaneously using a plurality oflike (or different) forming members or dies mounted in a common crucible and a common pulling mechanism.
  • the present invention facilitates growth of several like bodies, e.g. tubes, simultaneously so that the o.d. of each body is within prescribed tolerance limits. In such case, only one of the several growing bodies is optically monitored to determine meniscus height, and the power input to the heating means of the furnace is adjusted so that the meniscus height of the monitored growth zone is kept at a value that assures that the body growing at that zone will have an o.d.
  • FIG. 4 illustrates how a furnace of the type shown in my aforesaid US. Patents is modified to permit optical monitoring and measurement of meniscus height by means of a microscope system.
  • the furnace contains a crucible-multiple die arrangement for growing a plurality of crystalline bodies simultaneously according to the EFG process, it is to be understood that the illustrated crucible-die arrangement may be replaced by one suitable for growing bodies according to the SET process.
  • a crucible 2 is mounted within the furnace enclosure which consists of two spaced quartz tubes 60 and 62 that define an annular space (which is closed off at its top and bottom ends) through which cooling water is circulated for the purpose of keeping the quartz at a safe temperature and also to absorb infra-red energy so as to make it easier for the operator to comfortably observe growth of the product.
  • the plate 16 supported by the crucible carries three die assemblies 4 (a, b and c) constructed as shown in FIG. 1, plus a hollow filler tube 59 (FIG. 4) that is made of the same material as the die assemblies.
  • a delivery tube 61 made of quartz or other suitable heat-resistant material extends through and is sealed to the furnace tubes 60 and 62 as shown.
  • the bottom end of tube 61 is located in line with and terminataes close to but does not engage the upper end of filler tube 59.
  • the purpose of filler tube 59 and delivery tube 61 is to permit replenishing the melt in the crucible without interrupting crystal growth.
  • a tubular body is grown from a melt film supported on the upper end surface of each die assembly as described above in connection with FIG. 1. Only die assembly 40 and filler tube 59 are visible in FIG. 4.
  • a short section of transparent quartz pipe 64 is inserted into aligned holes formed in the furnace tubes 60 and 62 and sealed thereto so as to preserve the integrity of the cooling water jacket.
  • the inner end of pipe 64 is open but its outer end is closed off by an end wall 66 so as to prevent escape of the inert gas or vacuum that customarily is provided within the furnace.
  • the pipe 64 is inclined outwardly and is located so that its axis is directed at the upper end of one of the three die assemblies, e.g. die assembly 4c.
  • the pulling mechanism (not shown) associated with the furnace has a pulling rod 68 that corresponds to pulling rod 32 shown in FIG. 1 of my US. Pat. No. 3,471,266.
  • Attached to the pulling rod is a seed holder 70 which is adapted to hold a selected number, in this case three, seeds 72.
  • Each of the three seeds 72 (of which only one is shown) is held by holder 70 in vertical alignment with a different one of the three die assemblies 4a-c.
  • Seed holder 70 has a slot 73 large enough for it to clear delivery tube 61, whereby to prevent the latter from obstructing the up and down movement.
  • a microscope 74 attached to a holder 76 that is adjustably mounted to a suitable fixed support 78 which preferably but not necessarily is part of or secured to a stationary portion of the furnace apparatus.
  • the microscope may be a stereomicroscope.
  • An essential requirement of the microscope is that it be adapted with a recticle device for precisely measuring the meniscus height as herein described.
  • Model 562B-LI Stereostar Zoom microscope manufactured by American Optical Company, Instrumental Division, Buffalo, N.Y., that is fitted with x eyepieces and has a suitable linear division recticle or eyepiece disc mounted in one of its eyepieces, e. g., American Optical eyepiece disc Catalog No. 1428, which has 200 divisions each 0.001 inch at 2X magnification.
  • the eyepiece disc is oriented so that the graduated scale is a vertical image and the microscope is aimed along pipe 64 so that the scale is focused on the meniscus to be monitored and measured.
  • the crystalline body grows from a pool of melt that is a continuation of a column of melt in the capillary, and that the pool of melt is characterized by at least one meniscus that extends from the growth interface down to a top edge of the capillary forming member.
  • the growth pool of melt is the film that overlies the top end surface 10 and the meniscus 24 extends from the outer edge of the surface 10 up to the edge of the growth interface.
  • the height of the meniscus can be controlled by adjusting the film temperature and/or the pulling speed, surface tension will cause the bottom end of the meniscus to remain substantially at the edge of the surface 10 despite changes (within limits) of its height h.
  • the growth pool of melt is less sharply defined in the process illustrated in FIG. 3, but it is to be understood as being the upper portion of the column of melt that forms the interface with the growing body and notably includes that portion of the column of melt that is bounded by the two menisci 56 and 58.
  • the growth interface may be tapered as shown or may be substantially flatter. The growth interface tends to be less tapered as the radial dimension of the capillary decreases (due apparently to a more isothermal condition in the growth pool of melt) and also as the pulling speed is increased.
  • FIGS. 1-3 are for growing tubular bodies, it is to be understood that forming members for growing other shapes, e.g. rods, filaments, ribbons, etc., according to the EFG and SFT processes, also may be used in the practice of this invention since, regardless of the shape of the growing body, the growth pool of melt is still characterized by at least one meniscus. In the case of rods, filaments and ribbons, there is only one meniscus (at the outside of the growth pool of melt) since the growing body is as a solid. Growth of tubular bodies other than round tubes, e.g. hollow bodies having a rectangular, square or triangular cross-section, also is characterized by both inner and outer menisci.
  • the EFG and SFT processes improved according to this invention may be used to grow crystalline bodies of a wide variety of materials, including but not limited to alumina (sapphire) ruby, barium titanate, beryllium oxide, titanium dioxide, chromium oxide (C50,), lithium niobate, lithium fluoride (LiF), calcium fluoride (CaF and sodium chloride.
  • alumina sinoladium
  • barium titanate titanium dioxide
  • Crmium oxide Crohn'stylium oxide
  • LiF lithium fluoride
  • CaF calcium fluoride
  • sodium chloride sodium chloride
  • EXAMPLE An EFG molybdenum die arrangement substantially as shown in FIGS. 4 and 5 is assembled with a molybdenum crucible and the crucible is filled with a supply of solid particles of high purity (99*%) alumina.
  • the crucible and die assembly are mounted in a crystal growing furnace of the type shown in my US. Pat. Nos. 3,591,348 and 3,471,266.
  • IE1 crucible 2 is mounted on short tungsten rods within a cylindrical carbon heat susceptor 82 which in turn is attached to and supported by a tungsten rod 84 that is mounted in the bed plate (not shown) of the furnace, substantially in the manner illustrated in the aforementioned U. S. Patents.
  • a cylindrical radiation shield 85 made of carbon cloth. is wrapped around the carbon susceptor.
  • the R.F. heating coil 86 of the furnace is disposed so that it surrounds the carbon susceptor 82 as shown.
  • the three die assemblies 4a-c are identical. Each is made of molybdenum, as is the plate 16 and filter tube 59. Delivery tube 61 is made of alumina. With reference to FIGS. 1 and 4, the annular upper end surface 10 of each capillary rod 6 has an outside diameter of 0.378 inch and an inside diameter (i.e. the diameter of hole 8) of 0.315 inch while each of the capillaries 12 has a diameter of 0.012 inch.
  • the crucible has an internal depth of about 1% inch and an internal diameter of about 1% inch.
  • Each rod 6 has an overall length of about 1% inch and its bottom end is spaced about oneeighth inch from the bottom of the crucible.
  • Filler tube 59 has an o.d. of about 0.378 inch and an inner diameter of about 0.325 inch, and its length is such that its bottom end is about one-eighth inch from the bottom of the crucible and its top end projects about one-sixteenth inch above plate 16.
  • Three idential seeds 72 are attached to holder 70.
  • the seeds are substantially monocrystalline alumina tubes previously grown by means of the same cruciblecapillary arrangement. Cooling water is introduced in the water jacket defined by quartz tubes 60 and 62 and the furnace enclosure 88 is evacuated and then filled with argon to a pressure of about 1 atmosphere.
  • the RF coil is energized by a 500 KHz power supply which is operated so that the alumina charge in crucible 2 is melted and the upper surface of the die is at an average temperature of about l20C above the melting point of alumina. In this molten condition, the alumina rises in and fully fills each of the capillaries 12. Then the furnaces pulling mechanism is actuated and operated so that the three seeds are lowered into contact with the upper end surfaces 10 of the three die units 4a-c.
  • the seed crystals are allowed to rest in contact with the die units for about 5-l0 seconds, during which time the ends of the seeds melt and form films as shown at 20 in FIG. 1 which overlie and substantially fully cover the end surfaces 10.
  • the film 20 connects with the columns of melt in the capillaries 12.
  • the pulling mechanism is operated so as to withdraw the three tubular seeds at a rate of about one-fourth to onefifth inch/minute.
  • the initial withdrawal of the seeds is accompanied by solidification of melt therein from the films and as the seeds continue to be withdrawn continuous crystal growth occurs on the end of each seed.
  • the crystal growth on the seeds tends to deplete the films 20, but the films are replenished by additional melt fed by the capillaries.
  • the meniscus 24 of the film 20 overlying the upper end surface of the capillary unit 4c is optically monitored by means of an American Optical Model 562B-L1 stereo-microscope disposed as shown in FIG. 4 and modified with eyepieces and an eyepiece disc as previously described. it is desired to maintain the height of the meniscus 24 to approximately halfway between the limits of 0.004 and 0.001 inch. Accordingly, as the crystal growth occurs, the power input to the RF heating coil 86 is modified to raise or lower the temperature of the melt films 20 so as to increase or decrease the height of the meniscus 24 of the unit 40 as required. The pulling speed is maintained constant at the aforementioned rate as crystal growth processes.
  • Additional powdered alumina is periodically delivered to the crucible via tubes 59 and 61 to replenish the supply of melt.
  • the crystal growth is continued for approximately 4 hours, at which time the pulling rate is increased to approximately 1.0 inch per hour so as to cause the growing crystal to be pulled free from the melt films 20.
  • the power supply to the heater is then turned off and the furnace allowed to cool. Then the seeds and grown tubes are removed from the seed holder.
  • Crystalline bodies grown according to the procedure of this Example are tubular and substantially monocrystalline. Furthermore, at substantially all points along their lengths each of the bodies has a diameter which is within the limits of 0.375 inch 1 0.003 inch.
  • the advantages of the invention can be readily determined by modifying the procedure of the foregoing example in either of two ways.
  • the first modification consists of the same procedure except that (a) the height of the film meniscus is not measured and (b) the rate of power input to the RF coil is maintained constant during crystal growth at the level which was found adequate to initially raise the temperature of the upper end surface of the die to about -20C above the melting point of alumina.
  • the second modification consists of the same procedure as in the Example except that (a) the height of the film meniscus is not measured and (b) the temperature of the edge of the film is constantly. measured with an optical pyrometer and the rate of power input to the RF coil is adjusted as required so that the apparent temperature of the edge of the film is kept within l020C above the melting poing of alumina.
  • the tubes have varying outside diameters and the differences in o.d. at different points along one tube typically will exceed 0.003 inch and not all of the three tubes will meet the o.d. requirement of 0.375 inch i 0.003 inch.
  • the invention may be practiced by maintaining the temperature at the solidliquid interface substantially constant, and varying the pulling speed so as to maintain the height of the meniscus 24 (or the meniscus 56 in the case of the SFT process) within limits that will assure production of bodies of substantially constant outside dimensions that meet predetermined tolerances.
  • a method of growing a crystalline body of a selected material so that said body has a selected crosssectional shape for an indefinite distance along its length comprising growing and pulling said crystalline body from a growth pool of melt which is replenished via a capillary member by action of capillary rise from a reservoir supply of melt, said growth pool of melt also being characterized by a vertical meniscus which extends between the interface thereof with said crystalline body and an edge of said capillary member, the improvement comprising:
  • said capillary member comprises a single capillary filled with said column of melt and said growth pool of melt has substantially the same crosssectional shape as said capillary.
  • a method of growing a crystalline body of a selected material comprising establishing a growth pool of melt from a reservoior supply of melt by means of a capillary member having at least one capillary whose bottom end is positioned so that melt will fill said capillary by action of capillary rise from said reservoir supply, growing a substantially monocrystalline body from said growth pool of melt and pullling said body from said growth pool of melt as growth occurs thereon, said growth pool of melt being an extension of a column of melt in said at least one capillary and being bounded by a meniscus that extends from the interface thereof with said growing body down to an edge of said capillary member, optically monitoring and measuring the height of said meniscus, holding substantially constant the rate at which said growing body is pulled from said growth pool of melt, and adjusting the temperature of said growth pool of melt as required to maintain the height of said meniscus substantially constant within predetermined limits.
  • a method of growing a substantially monocrystalline body of a selected material so that said body has a controlled cross-sectional size comprising:

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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)
  • Oxygen, Ozone, And Oxides In General (AREA)
  • Liquid Deposition Of Substances Of Which Semiconductor Devices Are Composed (AREA)
US269985A 1972-07-10 1972-07-10 Optical control of crystal growth Expired - Lifetime US3870477A (en)

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Application Number Priority Date Filing Date Title
US269985A US3870477A (en) 1972-07-10 1972-07-10 Optical control of crystal growth
CA165,978A CA998922A (en) 1972-07-10 1973-03-13 Optical control of crystal growth
GB1333073A GB1374065A (en) 1972-07-10 1973-03-20 Optical control of crystal growth
IT49012/73A IT979997B (it) 1972-07-10 1973-03-23 Procedimento per l accrescimento di corpi cristallini sagomati
NL7305454A NL7305454A (fi) 1972-07-10 1973-04-18
BE130864A BE799237A (fr) 1972-07-10 1973-05-08 Reglage optique de la croissance de cristaux
FR7316790A FR2191943B1 (fi) 1972-07-10 1973-05-09
CH665273A CH575777A5 (fi) 1972-07-10 1973-05-10
DE2325104A DE2325104C3 (de) 1972-07-10 1973-05-17 Verfahren zum Ziehen eines langgestreckten, kristallinen Körpers
JP48054173A JPS5147432B2 (fi) 1972-07-10 1973-05-17
BR3955/73A BR7303955D0 (pt) 1972-07-10 1973-05-28 Aperfeicoamentos em ou relativos ao controle otico do crescimento de cristal

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BE (1) BE799237A (fi)
BR (1) BR7303955D0 (fi)
CA (1) CA998922A (fi)
CH (1) CH575777A5 (fi)
DE (1) DE2325104C3 (fi)
FR (1) FR2191943B1 (fi)
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Cited By (14)

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Publication number Priority date Publication date Assignee Title
DE2611056A1 (de) * 1975-03-17 1976-09-30 Tyco Laboratories Inc Vorrichtung und verfahren zum ziehen von kristallkoerpern aus der schmelze
US4032390A (en) * 1974-02-25 1977-06-28 Corning Glass Works Plural crystal pulling from a melt in an annular crucible heated on both inner and outer walls
US4116641A (en) * 1976-04-16 1978-09-26 International Business Machines Corporation Apparatus for pulling crystal ribbons from a truncated wedge shaped die
US4213940A (en) * 1976-07-20 1980-07-22 Siemens Aktiengesellschaft Apparatus for pulling monocrystalline ribbon-like bodies out of a molten crystalline film
DE3001259A1 (de) * 1979-01-15 1980-07-24 Mobil Tyco Solar Energy Corp Verfahren, system und vorrichtung zur ueberwachung und gegebenenfalls steuerung des ziehwachstums eines kristallkoerpers aus der schmelze
US4217165A (en) * 1978-04-28 1980-08-12 Ciszek Theodore F Method of growing a ribbon crystal particularly suited for facilitating automated control of ribbon width
US4318769A (en) * 1979-01-15 1982-03-09 Mobil Tyco Solar Energy Corporation Method of monitoring crystal growth
US4334948A (en) * 1981-02-23 1982-06-15 Rca Corporation Method of and apparatus for growing crystal ribbon
US4915773A (en) * 1986-11-26 1990-04-10 Kravetsky Dmitry Y Process for growing shaped single crystals
US5360599A (en) * 1993-06-21 1994-11-01 General Electric Company Crucible support heater for the control of melt flow pattern in a crystal growth process
US5431124A (en) * 1991-05-30 1995-07-11 Chichibu Cement Co., Ltd. Rutile single crystals and their growth processes
US5458083A (en) * 1992-05-29 1995-10-17 Chichibu Cement Co., Ltd. Growth method for a rod form of single oxide crystal
CN101519797B (zh) * 2009-01-20 2012-05-02 洛阳金诺机械工程有限公司 晶体碎料拉制硅芯的方法及实施该方法的一种装置
CN104088011A (zh) * 2014-07-15 2014-10-08 天津市恒瑜晶体材料制造有限公司 一种蓝宝石微毛细管的制备方法及其使用的模具

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JPS609000B2 (ja) * 1977-05-25 1985-03-07 工業技術院長 帯状シリコン結晶の成長装置
JPS5453927U (fi) * 1977-09-22 1979-04-14
JPS5488884A (en) * 1977-12-26 1979-07-14 Nippon Telegr & Teleph Corp <Ntt> Plate crystal producing equipment
US4440728A (en) * 1981-08-03 1984-04-03 Mobil Solar Energy Corporation Apparatus for growing tubular crystalline bodies
DE102006041736A1 (de) * 2006-09-04 2008-03-20 Schott Solar Gmbh Verfahren und Anordnung zur Herstellung eines Rohres
CN113280906B (zh) * 2021-06-18 2022-05-10 太原理工大学 基于计算机视觉的泡生法籽晶最佳接种时机振动感知方法

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US3033660A (en) * 1959-05-05 1962-05-08 Philips Corp Method and apparatus for drawing crystals from a melt
US3291650A (en) * 1963-12-23 1966-12-13 Gen Motors Corp Control of crystal size
US3428436A (en) * 1963-12-16 1969-02-18 Monsanto Co Methods and apparatus for zone melting
US3499736A (en) * 1965-10-06 1970-03-10 Philips Corp X-ray or gamma ray use in control of crystal diameter
US3621213A (en) * 1969-11-26 1971-11-16 Ibm Programmed digital-computer-controlled system for automatic growth of semiconductor crystals
US3650703A (en) * 1967-09-08 1972-03-21 Tyco Laboratories Inc Method and apparatus for growing inorganic filaments, ribbon from the melt
US3692499A (en) * 1970-08-31 1972-09-19 Texas Instruments Inc Crystal pulling system

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US3291574A (en) * 1963-12-23 1966-12-13 Gen Motors Corp Semiconductor crystal growth from a domical projection
US3591348A (en) * 1968-01-24 1971-07-06 Tyco Laboratories Inc Method of growing crystalline materials

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US3033660A (en) * 1959-05-05 1962-05-08 Philips Corp Method and apparatus for drawing crystals from a melt
US3428436A (en) * 1963-12-16 1969-02-18 Monsanto Co Methods and apparatus for zone melting
US3291650A (en) * 1963-12-23 1966-12-13 Gen Motors Corp Control of crystal size
US3499736A (en) * 1965-10-06 1970-03-10 Philips Corp X-ray or gamma ray use in control of crystal diameter
US3650703A (en) * 1967-09-08 1972-03-21 Tyco Laboratories Inc Method and apparatus for growing inorganic filaments, ribbon from the melt
US3621213A (en) * 1969-11-26 1971-11-16 Ibm Programmed digital-computer-controlled system for automatic growth of semiconductor crystals
US3692499A (en) * 1970-08-31 1972-09-19 Texas Instruments Inc Crystal pulling system

Cited By (15)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4032390A (en) * 1974-02-25 1977-06-28 Corning Glass Works Plural crystal pulling from a melt in an annular crucible heated on both inner and outer walls
DE2611056A1 (de) * 1975-03-17 1976-09-30 Tyco Laboratories Inc Vorrichtung und verfahren zum ziehen von kristallkoerpern aus der schmelze
US4116641A (en) * 1976-04-16 1978-09-26 International Business Machines Corporation Apparatus for pulling crystal ribbons from a truncated wedge shaped die
US4213940A (en) * 1976-07-20 1980-07-22 Siemens Aktiengesellschaft Apparatus for pulling monocrystalline ribbon-like bodies out of a molten crystalline film
US4217165A (en) * 1978-04-28 1980-08-12 Ciszek Theodore F Method of growing a ribbon crystal particularly suited for facilitating automated control of ribbon width
US4318769A (en) * 1979-01-15 1982-03-09 Mobil Tyco Solar Energy Corporation Method of monitoring crystal growth
DE3001259A1 (de) * 1979-01-15 1980-07-24 Mobil Tyco Solar Energy Corp Verfahren, system und vorrichtung zur ueberwachung und gegebenenfalls steuerung des ziehwachstums eines kristallkoerpers aus der schmelze
US4334948A (en) * 1981-02-23 1982-06-15 Rca Corporation Method of and apparatus for growing crystal ribbon
US4915773A (en) * 1986-11-26 1990-04-10 Kravetsky Dmitry Y Process for growing shaped single crystals
US5431124A (en) * 1991-05-30 1995-07-11 Chichibu Cement Co., Ltd. Rutile single crystals and their growth processes
US5458083A (en) * 1992-05-29 1995-10-17 Chichibu Cement Co., Ltd. Growth method for a rod form of single oxide crystal
US5360599A (en) * 1993-06-21 1994-11-01 General Electric Company Crucible support heater for the control of melt flow pattern in a crystal growth process
CN101519797B (zh) * 2009-01-20 2012-05-02 洛阳金诺机械工程有限公司 晶体碎料拉制硅芯的方法及实施该方法的一种装置
CN104088011A (zh) * 2014-07-15 2014-10-08 天津市恒瑜晶体材料制造有限公司 一种蓝宝石微毛细管的制备方法及其使用的模具
CN104088011B (zh) * 2014-07-15 2017-01-18 牛玥 一种蓝宝石微毛细管的制备方法及其使用的模具

Also Published As

Publication number Publication date
DE2325104C3 (de) 1980-10-09
JPS4953176A (fi) 1974-05-23
FR2191943A1 (fi) 1974-02-08
GB1374065A (en) 1974-11-13
JPS5147432B2 (fi) 1976-12-15
BR7303955D0 (pt) 1974-02-12
FR2191943B1 (fi) 1978-06-30
BE799237A (fr) 1973-11-08
IT979997B (it) 1974-09-30
NL7305454A (fi) 1974-01-14
CA998922A (en) 1976-10-26
DE2325104B2 (de) 1980-02-21
DE2325104A1 (de) 1974-01-24
CH575777A5 (fi) 1976-05-31

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