US3627500A - Method of growing semiconductor rods from a pedestal - Google Patents

Method of growing semiconductor rods from a pedestal Download PDF

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Publication number
US3627500A
US3627500A US813267A US3627500DA US3627500A US 3627500 A US3627500 A US 3627500A US 813267 A US813267 A US 813267A US 3627500D A US3627500D A US 3627500DA US 3627500 A US3627500 A US 3627500A
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United States
Prior art keywords
block
pool
pedestal
center
charge
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Expired - Lifetime
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US813267A
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English (en)
Inventor
Theodore F Ciszek
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Dow Silicones Corp
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Dow Corning Corp
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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
    • C30B15/14—Heating of the melt or the crystallised materials
    • C30B15/16—Heating of the melt or the crystallised materials by irradiation or electric discharge
    • 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
    • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10S117/00—Single-crystal, oriented-crystal, and epitaxy growth processes; non-coating apparatus therefor
    • Y10S117/905—Electron beam

Definitions

  • the present invention relates to rod or crystal growth and more particularly to a method of preventing the formation of a rim around the perimeter of a block of material from which a rod is being drawn.
  • Monocrystalline or single crystal rods of semiconductor materials are of great value to the electronics industry. As the use of these monocrystalline rods has expanded, less expensive methods of producing them and methods of reducing the impurities in them have been sought.
  • monocrystalline rods have been grown by melting a block or charge of the desired material in a crucible, dipping a suitable seed crystal into the molten material and drawing that seed crystal out from the molten material at a rate sufficient to draw or grow a crystal.
  • This method is widely known as the Czochralski method for growing crystals, and numerous variations and embodiments of this method have been patented or published in scientific journals.
  • Larsons method is to bombard the central portion of the upper surface of a block of suitable material with an electron beam until a pool of melted material forms in the center of the upper surface and is contained within the perimeter of the block by the unmelted portion of that upper surface.
  • a suitable seed crystal is then immersed in the pool of melted material and pulled from the pool at a rate which allows solidification of the melted material uplifted from the pool on the seed crystal.
  • the pedestal charge can be said to have grown a rim. It has been found that the growth of such a rim on the pedestal charge causes several problems in the growth of crystals by the above-cited method of Larson.
  • the unmelted rim portion of the pedestal charge cannot efficiently be remolded into a new charge for subsequent use. Thus, this expensive raw material is wasted. Further, the diameter and the length of the crystal that can be drawn from such a pedestal is necessarily limited by the width of the unmelted rim portion of the charge that is required to confine the melted portion of the charge without melting away itself. Additionally, it will be realized that for a given pedestal charge of any size, as the total amount of that charge melted and added to the pool of melted material is increased, the size of the crystal that can be drawn from that pool is also increased. Eliminating the growth of an unmelted rim on the charge increases the amount of material added to the pool.
  • the crystal pulling apparatus the power required to raise the charge to its melting point and the time required for starting and terminating each crystal growth, no rim growth on the pedestal charge can be allowed.
  • Still another problem relates to the fact that the thermal field present in the pedestal charge and the pool of melted material directly affects the growth of a crystal and must be carefully controlled. It has been found that the growth of a rim on the pedestal charge causes the thermal field to vary significantly during crystal growth. This variance has been found very difficult to control and frequently has caused the crystal growth to be aborted.
  • Another object is to provide a method of growingsemiconductor rods from a pedestal charge which method provides for optical monitoring of the rod-pool interface at all times and provides a nearly constant thermal field in the pedestal charge and pool of melted material.
  • the present invention a method for the growth of either monocrystalline or polycrystalline semi-conductor rods from a pedestal charge and the simultaneous prevention of the formation of a rim of unmelted material around the perimeter of that pedestal charge.
  • the pedestal charge is first caused to continuously rotate about its vertical axis. Then, an annular beam of electrons is directed onto the upper surface of the pedstal charge so that the center of the annulus defined by the intersection of the annular beam and the upper surface of the pedestal charge is at an offset or different location than the center of the upper surface of the pedestal charge.
  • a portion of the annulus extends to and is substantially in juxtaposition with a portion of the perimeter of the upper surface and another portion of the annulus also extends beyond or is diametrically on the opposite side of the center of the upper surface from that side on which the center of the annulus lies.
  • every portion of the entire upper surface of the pedestal charge is periodically exposed to the heating effect of the annular beam of electrons and caused to become a part of the pool of melted material thereon.
  • a seed crystal is then immersed into and drawn from the pool in the vicinity of the coolest portion of the pool, which generally is in the vicinity of the center of the annulus of electrons. This procedure is then continued until the pedestal charge is substantially consumed and results in the growth of a semiconductor rod.
  • FIG. 1 is a vertical elevation partly in section of an embodiment of this invention
  • FIG. 2 is a perspective view of a cylindrical block of material from which a rod is being drawn according to the method of the present invention.
  • FIG. 3 is a vertical sectional elevation of a prior art pedestal charge showing the formation of a rim thereon.
  • FIG. 1 a semiconductor rod growing furnace comprising an evacuated container which is hermetically sealed to a base 13.
  • the container 10 can be made of quartz or stainless steel and can have a connecting tube 11 for evacuation of the container and a glass window 12 through which the method of the present invention can be observed when carried out inside the container 10.
  • a self-supporting block of material 17, or pedestal charge, from which a semiconductor rod is to be grown is mounted within the container 10 on a pedestal 15 which is preferably maintained at ground level electrical potential and is secured to the end of a reciprocably and rotatably mounted shaft 16, as indicated by the pertinent arrows.
  • the self-supporting block of material 17 can be a block of silicon, germanium or aluminum oxide.
  • the upper surface of the block of material 17 underlies and supports a pool of melted material 19 which was formed by bombarding the upper surface of the block of material 17 with an annular beam of electrons 21 emitted from an electron beam gun 23.
  • the beam of electrons 21 is properly focused on the upper surface of the block of material 17 by an electromagnetic or magnetic focusing coil.
  • Such coils are well known for that purpose.
  • the gun 23 and coil 27 are mounted within the container 10 by conventional mounting means. Obviously, more than one such focusing coil can be used if desired or advantageous.
  • FIG. 1 does show an annular electron beam gun emitting an annular beam which is focused by an annular focusing coil
  • the method of the present invention can be practiced using several individual electron guns and magnetic or electromagnetic focusing coils properly spaced to form an annular beam.
  • a suitable annular electron beam can be obtained by sweeping the beam from one electron gun across the upper surface of the block of material 17 in an annular pattern.
  • annular beam is intended to include both a beam which is continuously annular and a beam which is substantially continuously annular.
  • a specific electron gun suitable for performing the method of the present invention is the self-accelerated electron beam gun described by H. R. Smith, Jr. in the book, Introduction to Electron Beam Technology, Robert Bakish ed., John Wiley and Sons, Inc., New York, N.Y., chapter 7, page 176, fig. 7.5, 1962.
  • an upper holder 33 which is secured to the end of a reciprocably and rotatably mounted shaft 35, as indicated by the pertinent arrows.
  • This shaft 35 serves as the means for drawing a seed crystal and the growing rod 31 from the pool of melted material 19.
  • the shafts -16 and 35, the holder 33 and the pedestal 15 can be made of stainless steel. Further, the shafts 16 and 35 are held in an air-tight or vacuum proof relationship to the container 10 by gaskets, fittings, O-rings, or the like, 41 and 43 respectively. Suitable means for rotating and/ or reciprocating the shafts 16 and 35 and therefore the pedestal 15 and upper holder 33, are well known to those in the crystal growing art and are described in great detail in several prior art patents.
  • the pedestal charge or block of material 17 must be a material which is at least slightly electrically conductive, and it must not be a material which, when in a molten state under a pressure of at least 10- torr, will vaporize to the extent that the pressure in the container 10 will be raised above 1O torr by that vaporization. Silicon, germanium and aluminum oxide can meet that requirement and, therefore, are suitable materials for crystal growth by the method of the present invention.
  • the block of material 17 is placed in the container 10 and adjusted to a desired level by raising or lowering the pedestal 15.
  • the container 10 is then evacuated by means of a suitable vacuum pump through connecting tube 11.
  • the block of material 17 is then rotated continuously in either a clockwise or counterclockwise direction by the similar rotation of the pedestal 15.
  • the block of material 17 can be preheated by radiant heating, for example. But preferably, the electron beam gun 23, or another electron gun mounted within the container 10, can be used to heat the upper surface of the block 17 to its melting point.
  • the electrons emitted from the gun 23 are directed onto the upper surface of the block 17 as an annular beam.
  • the block of material 17 continuously rotates about a vertical axis which intersects its upper surface at C, every portion of its upper surface is subjected to the heating effect of the annular electron beam 21 and melts to form the pool of melted material 19, as illustrated in FIG. 2.
  • the melted material forms an eccentric pool 19 inside of the perimeter of the upper surface of the block 17 and covers nearly all of that upper surface.
  • the annulus 61 has a portion which is substantially in juxtaposition with a portion of the perimeter of the block of material 17. That is, when the block 17 is cylindrical, which it preferably should be, the perimeter of the block 17 and the annulus 61 are substantially tangential or osculatory eccentric circles. Thus, every portion of the perimeter of the upper surface of the block of material 17 is periodically caused to melt and become a part of the pool of melted material 19 as it passes under, or becomes, the point of tangency of the perimeter and beam 21, thereby preventing the formation of a rim around the perimeter of the block of material 17.
  • the volume of the outer edge melted at any one instant is directly related to the relative lengths of the diameters of the block of material 17 and the annulus 61. That is, as those diameters come closer to being equal, their perimeters come closer to being side by side over their entire lengths and, of course, the entire perimeter comes closer to being molten at all times.
  • the diameter of the annulus 61 cannot be greater than 97.5 percent of the diameter of the upper surface of the block 17 and preferably should not be greater than 92 percent thereof.
  • the center B of the annulus 61 must at least be offset from the center C of the upper surface of the block 17 by a distance of 2.5 percent of the diameter of the upper surface and preferably should be offset by at least 8 percent thereof.
  • the melted material also forms an eccentric pool 19 within the perimeter of the upper surface of the block of material 17 and overlies nearly the entire upper surface.
  • the portion of the pool 19 diametrically opposite the center B of the annulus 61 will solidify if at least some portion of the annulus 61 does not extend beyond the center C of the upper surface of the block of material 17.
  • the diameter of the annulus 61 must at least exceed 50 percent of the diameter of the upper surface of the block 17.
  • the radius of the annulus 61 must exceed 25 percent of the diameter of the upper surface of the block 17, and the center B of the annulus 61 must be offset from the center C of the upper surface of the block 17 by a distance less than 25 percent of the diameter of the upper surface of the block of material 17 and preferably less than 20 percent thereof, since a portion of the annulus 61 must be substantially in juxtaposition with a portion of the perimeter of the upper surface and also extend beyond the center C.
  • the block 17 Several factors contribute to the position and flow of the pool of melted material 19 as the block 17 rotates, e.g., centrifugal forces, surface tension, electrical and thermal conductivity, viscosity, and melting temperature of the material in the block 17. It has been found, that when the block -17 is a silicon block, irrespective of its diameter, to avoid spilling the melted material 19 over the edge of the block 17 and to avoid causing too frequent heating of the perimeter, the rate of rotation of the block of material 17 must not exceed 100 revolutions per minute and, preferably, should not exceed 35 revolutions per minute. On the other hand, to keep the pool 19 from freezing while outside of the annulus 61, the block of material 17 must at least make two and preferably should make at least five revolutions per minute.
  • the center of the thermal field, or the coolest portion of the pool 19 is inside the annulus 61.
  • the seed crystal is immersed in the pool 19 in the vicinity of the center of the annulus 61, and the seed crystal and growing rod 31 are withdrawn from the pool of melted material 19 at that same location.
  • the seed crystal is drawn at a rate which allows solidification of the melted material uplifted from the pool 19 on the seed crystal. The continued withdrawal of the seed crystal thereby draws or pulls a semiconductor rod from the block 17.
  • the pedestal 15 can be moved upward while the seed crystal and growing rod 31 are being drawn up from the pool of melted material 19. This causes the upper surface of the block 17 to always be at the same level and allows the annular beam of electrons to be held still while the block 17 is being consumed. Obviously, the beam 21 could be refocused as the upper surface of the block 17 gradually receded if desired. Although other ratios can be used, it has been found that moving the block 17 upward as indicated by the following equation is preferred:

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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)
  • Liquid Deposition Of Substances Of Which Semiconductor Devices Are Composed (AREA)
US813267A 1969-04-03 1969-04-03 Method of growing semiconductor rods from a pedestal Expired - Lifetime US3627500A (en)

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US81326769A 1969-04-03 1969-04-03

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US3627500A true US3627500A (en) 1971-12-14

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US (1) US3627500A (enrdf_load_stackoverflow)
JP (1) JPS4833876B1 (enrdf_load_stackoverflow)
BE (1) BE748377A (enrdf_load_stackoverflow)
DE (1) DE2016101C3 (enrdf_load_stackoverflow)
FR (1) FR2038216B1 (enrdf_load_stackoverflow)
GB (1) GB1249537A (enrdf_load_stackoverflow)
NL (1) NL7004740A (enrdf_load_stackoverflow)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5363796A (en) * 1991-02-20 1994-11-15 Sumitomo Metal Industries, Ltd. Apparatus and method of growing single crystal
US20040255442A1 (en) * 2003-06-19 2004-12-23 Mcdiarmid James Methods and apparatus for processing workpieces
CN112058596A (zh) * 2020-09-14 2020-12-11 河源市璐悦自动化设备有限公司 一种大尺寸lcd光学玻璃的均匀涂胶工艺

Families Citing this family (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS5094103A (enrdf_load_stackoverflow) * 1973-12-21 1975-07-26
DE2649201C2 (de) * 1976-10-28 1983-02-17 Siemens AG, 1000 Berlin und 8000 München Verfahren zum Herstellen von einkristallinen Halbleitermaterialbändern durch senkrechtes Ziehen aus einem Schmelzfilm unter Verwendung eines Formgebungsteils
DE2649223C2 (de) * 1976-10-28 1983-02-17 Siemens AG, 1000 Berlin und 8000 München Verfahren zum Herstellen von einkristallinen Halbleitermaterialbändern durch senkrechtes Ziehen aus einem Schmelzfilm
JPS5420105A (en) * 1977-07-13 1979-02-15 Totsuto Shiyouji Yuugen Production of leather article with backing material
JPS5470401A (en) * 1977-11-12 1979-06-06 Nakatora Kk Multilevel patterning on leather
US4836788A (en) * 1985-11-12 1989-06-06 Sony Corporation Production of solid-state image pick-up device with uniform distribution of dopants
JPH0412083A (ja) * 1990-04-27 1992-01-16 Osaka Titanium Co Ltd シリコン単結晶製造方法
US6126742A (en) * 1996-09-20 2000-10-03 Forshungszentrum Karlsruhe Gmbh Method of drawing single crystals
DE19638563C2 (de) * 1996-09-20 1999-07-08 Karlsruhe Forschzent Verfahren zum Ziehen von Einkristallen

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5363796A (en) * 1991-02-20 1994-11-15 Sumitomo Metal Industries, Ltd. Apparatus and method of growing single crystal
US20040255442A1 (en) * 2003-06-19 2004-12-23 Mcdiarmid James Methods and apparatus for processing workpieces
CN112058596A (zh) * 2020-09-14 2020-12-11 河源市璐悦自动化设备有限公司 一种大尺寸lcd光学玻璃的均匀涂胶工艺
CN112058596B (zh) * 2020-09-14 2022-12-02 河源市璐悦自动化设备有限公司 一种大尺寸lcd光学玻璃的均匀涂胶工艺

Also Published As

Publication number Publication date
FR2038216B1 (enrdf_load_stackoverflow) 1974-12-06
NL7004740A (enrdf_load_stackoverflow) 1970-10-06
BE748377A (fr) 1970-10-02
DE2016101B2 (de) 1973-04-26
GB1249537A (en) 1971-10-13
DE2016101A1 (de) 1970-10-08
FR2038216A1 (enrdf_load_stackoverflow) 1971-01-08
JPS4833876B1 (enrdf_load_stackoverflow) 1973-10-17
DE2016101C3 (de) 1973-11-22

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