US3085031A - Method of zone-melting rod-shaped bodies - Google Patents

Method of zone-melting rod-shaped bodies Download PDF

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US3085031A
US3085031A US7573A US757360A US3085031A US 3085031 A US3085031 A US 3085031A US 7573 A US7573 A US 7573A US 757360 A US757360 A US 757360A US 3085031 A US3085031 A US 3085031A
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zone
aperture
rod
bore
reaches
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US7573A
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Adrianus Van Wieringen
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US Philips Corp
North American Philips Co Inc
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US Philips 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
    • C30B13/00—Single-crystal growth by zone-melting; Refining by zone-melting
    • C30B13/08—Single-crystal growth by zone-melting; Refining by zone-melting adding crystallising materials or reactants forming it in situ to the molten zone
    • C30B13/10—Single-crystal growth by zone-melting; Refining by zone-melting adding crystallising materials or reactants forming it in situ to the molten zone with addition of doping materials
    • 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
    • Y10S438/00—Semiconductor device manufacturing: process
    • Y10S438/914—Doping
    • Y10S438/925—Fluid growth doping control, e.g. delta doping

Definitions

  • This invention relates, to methods of zone-melting rodshaped bodies, hereinafter referred to as rods, which methods are to be understood to mean the local heating of such rods so as to obtain a molten zone, whereafter the heat source and the rod are relatively moved so that the zone advances through the rod in the direction of its length.
  • rods which methods are to be understood to mean the local heating of such rods so as to obtain a molten zone, whereafter the heat source and the rod are relatively moved so that the zone advances through the rod in the direction of its length.
  • the material of the rod is melted at the front side of the zone, the so-called melting front, whereas such material recrystallises at the rear side of the zone.
  • the melting front is approximately flat and is substantially at right angles to the direction of length of the rod.
  • the method is frequently used for zone refining semi-conductive materials, such as germanium, silicon and intermetallic compounds, but also for adding to such materials certain elements, hereinafter referred to as dopes, which may act upon the conductivity and/ or conductivity type, for instance in a way named zone levelling, and described at pages 161-164 of the above mentioned book of Pfann.
  • Such a dope often consists of a solid material which is disposed on the body in the form of a pill or powder and dissolved in the molten zone as soon as the latter reaches the location of the pill. It will be evident that this method is not applicable if the rod is in a vertical position such as with zone-rnelting without a crucible, sometimes referred to as floating-zone melting. For this application it has been suggested to provide the activating material in a cavity provided transversely to the direction of length of the rod.
  • the dope partly evaporates before being absorbed by the melt. It also frequently happens that the pill keeps floating on the melt for some time so that not only does the evaporation process last longer, but also the moment of the addition of the dope to the melt becomes uncertain.
  • An object of the invention is inter alia to mitigate these disadvantages.
  • the dope is provided in a bore the direction of length of which is at an angle to the melting front, the zone being led through the rod in a direction such that the melting front reaches the opening of the bore sooner than the dope.
  • the bore preferably has a depth such that the opening is closed by melting before the dope is reached by the melting front.
  • the bore when starting from a lateral face of the rod, may be provided in inclined position with respect to the direction of length, but it is also possible, when starting at one end of the rod, to provide it in the direction of length itself.
  • FIG. 1 is a diagrammatic sectional view of a device for zone-melting of a horizontal rod.
  • FIG. 2 shows a similar device for zone-melting of a vertical rod.
  • the device shown in FIG. 1 comprises an elongated crucible 1, in which a rod 2, for example. of germanium, is disposed,
  • a movable source of energy represented by a high-frequency coil 3, may bring about in the rod a molten zone 4 which may advance in the direction of the arrow.
  • the rod 2 consists of very pure. zone-refined germanium and has a length of 30 cm., a height of 2.5 cm. and a crosssectional area of 4 cm?.
  • the molten zone 4 having a length of about 3 cm. advances at a rate of 2 mm. per minute.
  • the dope may consist of 0.085 mgr. of arsenic and the pill having a diameter of about 1 mm. may consist of germanium in which the arsenic has been dissolved.
  • a bore 6 has been provided, on the bottom of which the pill 7 is laid.
  • the bore 6 may have a length of about 1.5 cm. and a diameter of about 2 min.
  • the longitudinal direction of the bore may be at an angle of 45 with the longitudinal direction of the rod 2.
  • the melting front 8 reaches the bore at its opening firstly. This opening will thus be closed by melting before the arsenic in the pill 7 has been enabled to evaporate strongly and before the pill 7 will tend to float on the melt.
  • the figure shows, in dotted line, a second bore 9 which extends in the direction of length of the rod.
  • a rod 11 is arranged in vertical position, while an energy source 12 is vertically movable with respect to the rod, resulting in a molten zone 13 which is held between the ends of the rod due to surface tension.
  • a dope may in this case be added by again providing an inclined bore 14, the opening of which lies higher than its bottom.
  • the dope in the form of a pill 15 is laid in the bore.
  • the molten zone is now advancing downwards with respect to the rod 11, so that the opening of the bore may be closed by melting by means of the melting front 16 before the pill 15 is strongly heated.
  • a method of doping an elongated body of semiconductor material comprising providing from a surface of the body an elongated aperture which extends into the body a substantial depth, placing solid doping material in the aperture within the body through the opening at the surface, forming in the body a molten zone having front and rear surfaces with the front surface being inclined toward the said extended aperture and being closer to the aperture opening at the surface, and advancing the molten zone through the body in a direction at which its front reaches the aperture opening before it reaches and melts the solid doping material, the angle of inclination 3 between the aperture and the front surface of the molten zone and the location of the solid doping material being such that the said front surface reaches and melts the furthest point of the aperture wall at the surface before it reaches and melts the solid doping material.
  • a method of doping an elongated body of semiconductor material comprising providing from a surface of the body an elongated bore which extends into the body at least partially in the direction of length of the body and at an angle to a direction transverse to the body, placing solid doping material at the bottom of the bore within the body through the opening at the surface, forming in the body a transverse molten zone having front and rear surfaces with the front surface closer to the bore opening than its bottom, and advancing the molten zone through the body in its length direction at which the molten front reaches the bore opening before the front reaches and melts the solid doping material, the angle of the bore and its depth being such that the said molten front reaches and melts the furthest point of the bore wall at the surface before it reaches and melts the solid doping material.

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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)
  • Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)

Description

A. VAN WlERlNGEN 3,085,031
METHOD OF ZONE-MELTING ROD-SHAPED BODIES Filed Feb. 9, 1960 April 9, 1963 uuul w- FIG.4
INVENTOR ADRIANUS VAN WIERINGEN United States, Patent F 3,085,031 METHOD SF ZfiNE-MELTING ROD=HAPEB BGDiES Adrianne van Wieringen, Nijmegen, Netherlands, assignor to North Americanlhilips (Iompany, Inn, New York, N.Y., a corporation of Delaware Filed-Feh.- 9, 196i), Ser. No. 7,573 Claims priority, application Netherlandsl eb. 17, 1959 4. Claims. (Cl. Mil-15).
This invention relates, to methods of zone-melting rodshaped bodies, hereinafter referred to as rods, which methods are to be understood to mean the local heating of such rods so as to obtain a molten zone, whereafter the heat source and the rod are relatively moved so that the zone advances through the rod in the direction of its length. Such methods are for instance described in the book Zone Melting by W. G. Pfann (John Wiley and Sons, New York) (1958). I
The material of the rod is melted at the front side of the zone, the so-called melting front, whereas such material recrystallises at the rear side of the zone. The melting front is approximately flat and is substantially at right angles to the direction of length of the rod. The method is frequently used for zone refining semi-conductive materials, such as germanium, silicon and intermetallic compounds, but also for adding to such materials certain elements, hereinafter referred to as dopes, which may act upon the conductivity and/ or conductivity type, for instance in a way named zone levelling, and described at pages 161-164 of the above mentioned book of Pfann.
Such a dope often consists of a solid material which is disposed on the body in the form of a pill or powder and dissolved in the molten zone as soon as the latter reaches the location of the pill. It will be evident that this method is not applicable if the rod is in a vertical position such as with zone-rnelting without a crucible, sometimes referred to as floating-zone melting. For this application it has been suggested to provide the activating material in a cavity provided transversely to the direction of length of the rod.
In the said methods it may occur that the dope partly evaporates before being absorbed by the melt. It also frequently happens that the pill keeps floating on the melt for some time so that not only does the evaporation process last longer, but also the moment of the addition of the dope to the melt becomes uncertain.
An object of the invention is inter alia to mitigate these disadvantages.
According to the invention, the dope is provided in a bore the direction of length of which is at an angle to the melting front, the zone being led through the rod in a direction such that the melting front reaches the opening of the bore sooner than the dope. The bore preferably has a depth such that the opening is closed by melting before the dope is reached by the melting front.
The bore, when starting from a lateral face of the rod, may be provided in inclined position with respect to the direction of length, but it is also possible, when starting at one end of the rod, to provide it in the direction of length itself.
In order that the invention may be readily carried into effect, two embodiments will now be described in detail, by way of example, with reference to the accompanying drawing.
FIG. 1 is a diagrammatic sectional view of a device for zone-melting of a horizontal rod.
FIG. 2 shows a similar device for zone-melting of a vertical rod.
It is to be noted that parts of these devices which are $385,031 Fatented- Apr. 9, 1963 ice not essential to the invention, such as envelopes and supporting members, are omitted.
The device shown in FIG. 1 comprises an elongated crucible 1, in which a rod 2, for example. of germanium, is disposed, A movable source of energy, represented by a high-frequency coil 3, may bring about in the rod a molten zone 4 which may advance in the direction of the arrow.
Let it be assumed that a dope is to be added to the zone at the area. indicated by 5, which dope has been given the form of a pill in the usual manner. Neither the form and the composition of the pill, nor the composition of the rod are essential to the invention. As an example the rod 2 consists of very pure. zone-refined germanium and has a length of 30 cm., a height of 2.5 cm. and a crosssectional area of 4 cm?. The molten zone 4, having a length of about 3 cm. advances at a rate of 2 mm. per minute. The dope may consist of 0.085 mgr. of arsenic and the pill having a diameter of about 1 mm. may consist of germanium in which the arsenic has been dissolved.
In inclined direction a bore 6 has been provided, on the bottom of which the pill 7 is laid. The bore 6 may have a length of about 1.5 cm. and a diameter of about 2 min. The longitudinal direction of the bore may be at an angle of 45 with the longitudinal direction of the rod 2.
It will be evident that, due to the direction in which the zone 4 advances, the melting front 8 reaches the bore at its opening firstly. This opening will thus be closed by melting before the arsenic in the pill 7 has been enabled to evaporate strongly and before the pill 7 will tend to float on the melt.
By a further advance of the melting front 8 of for instance about 1 cm. after the moment at which the opening of the bore 6 was closed, the pill 7 is dissolved completely.
The figure shows, in dotted line, a second bore 9 which extends in the direction of length of the rod. By means of such a bore, which must be at least as deep as the length of the zone 4, it is possible to add a dope in a similar manner to that described above.
In the device shown in FIG. 2, a rod 11 is arranged in vertical position, while an energy source 12 is vertically movable with respect to the rod, resulting in a molten zone 13 which is held between the ends of the rod due to surface tension.
A dope may in this case be added by again providing an inclined bore 14, the opening of which lies higher than its bottom. The dope in the form of a pill 15 is laid in the bore. The molten zone is now advancing downwards with respect to the rod 11, so that the opening of the bore may be closed by melting by means of the melting front 16 before the pill 15 is strongly heated.
It will be evident that the angle made by the bore with respect to the melting front is important for the effect to be obtained. The larger this angle, that is to say, the more the bore extends in the direction of length of the rod, the greater is the effect obtained.
What is claimed is:
1. A method of doping an elongated body of semiconductor material, comprising providing from a surface of the body an elongated aperture which extends into the body a substantial depth, placing solid doping material in the aperture within the body through the opening at the surface, forming in the body a molten zone having front and rear surfaces with the front surface being inclined toward the said extended aperture and being closer to the aperture opening at the surface, and advancing the molten zone through the body in a direction at which its front reaches the aperture opening before it reaches and melts the solid doping material, the angle of inclination 3 between the aperture and the front surface of the molten zone and the location of the solid doping material being such that the said front surface reaches and melts the furthest point of the aperture wall at the surface before it reaches and melts the solid doping material. I
2. A method as set forth in claim 1 wherein the bore extends into the body at an acute angle relative to its length direction.
3. A method of doping an elongated body of semiconductor material, comprising providing from a surface of the body an elongated bore which extends into the body at least partially in the direction of length of the body and at an angle to a direction transverse to the body, placing solid doping material at the bottom of the bore within the body through the opening at the surface, forming in the body a transverse molten zone having front and rear surfaces with the front surface closer to the bore opening than its bottom, and advancing the molten zone through the body in its length direction at which the molten front reaches the bore opening before the front reaches and melts the solid doping material, the angle of the bore and its depth being such that the said molten front reaches and melts the furthest point of the bore wall at the surface before it reaches and melts the solid doping material.
4. A method as set forth in claim 3 wherein the bore extends into the body from one end in its length direction.
References Cited in the file of this patent UNITED STATES PATENTS 2,739,088 Pfann Mar. 20, 1956 2,789,039 Jensen Apr. 16, 1957 2,813,048 Pfann Nov. 12, 1957 2,841,559 Rosi July 1, 1958 2,898,249 Jensen Aug. 4, 1959 2,902,350 Jenny et a1 Sept. 1, 1959 OTHER REFERENCES Kolb et al.: Electrochemical Society Journal, vol. 106,
20 No. 7, July 1959, pages 597-599.

Claims (1)

1. A METHOD OF DOPING AN ELONGATED BODY OF SEMICONDUCTOR MATERIAL, COMPRISING PROVIDING FROM A SURFACE OF THE BODY AN ELONGATED APERTURE WHICH EXTENDS INTO THE BODY A SUBSTANTIAL DEPTH, PLACING SOLID DOPING MATERIAL IN THE APERTURE WITHIN THE BODY THROUGH THE OPENING AT THE SURFACE, FORMING IN THE BODY A MOLTEN ZONE HAVING FRONT AND REAR SURFACES WITH THE FRONT SURFACE BEING IN CLINED TOWARD THE SAID EXTENDED APERTURE AND BEING CLOSER TO THE APERTURE OPENING AT THE SURFACE, AND ADVANCING THE MOLTEN ZONE THROUGH THE BODY IN A DIRECTION AT WHICH ITS FRONT REACHES THE APERTURE OPENING BEFORE IT REACHES AND MELTS THE SOLID DOPING MATERIAL, THE ANGLE OF INCLINATION BETWEEN THE APERTURE AND THE FRONT SURFACE OF THE MOLTEN ZONE AND THE LOCATION OF THE SOLID DOPING MATERIAL BEING SUCH THAT THE SAID FRONT SURFACE REACHES AND MELTS THE FURTHEST POINT OF THE APERTURE WALL AT THE SURFACE BEFORE IT REACHES AND MELTS THE SOLID DOPING MATERIAL.
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DE1235875B (en) * 1963-11-13 1967-03-09 Siemens Ag Process for the production of neodymium-doped calcium fluoride single crystals for lasers

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2739088A (en) * 1951-11-16 1956-03-20 Bell Telephone Labor Inc Process for controlling solute segregation by zone-melting
US2789039A (en) * 1953-08-25 1957-04-16 Rca Corp Method and apparatus for zone melting
US2813048A (en) * 1954-06-24 1957-11-12 Bell Telephone Labor Inc Temperature gradient zone-melting
US2841559A (en) * 1955-04-27 1958-07-01 Rca Corp Method of doping semi-conductive materials
US2898249A (en) * 1954-06-10 1959-08-04 Rca Corp Method of preparing semi-conductor alloys
US2902350A (en) * 1954-12-21 1959-09-01 Rca Corp Method for single crystal growth

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
AT194444B (en) * 1953-02-26 1958-01-10 Siemens Ag Method and device for treating an elongated semiconductor crystal arrangement

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2739088A (en) * 1951-11-16 1956-03-20 Bell Telephone Labor Inc Process for controlling solute segregation by zone-melting
US2789039A (en) * 1953-08-25 1957-04-16 Rca Corp Method and apparatus for zone melting
US2898249A (en) * 1954-06-10 1959-08-04 Rca Corp Method of preparing semi-conductor alloys
US2813048A (en) * 1954-06-24 1957-11-12 Bell Telephone Labor Inc Temperature gradient zone-melting
US2902350A (en) * 1954-12-21 1959-09-01 Rca Corp Method for single crystal growth
US2841559A (en) * 1955-04-27 1958-07-01 Rca Corp Method of doping semi-conductive materials

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DK94963C (en) 1962-12-10

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