US3814827A - Method and apparatus for floating zone melting of a semiconductor rod - Google Patents

Method and apparatus for floating zone melting of a semiconductor rod Download PDF

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Publication number
US3814827A
US3814827A US00400702A US40070273A US3814827A US 3814827 A US3814827 A US 3814827A US 00400702 A US00400702 A US 00400702A US 40070273 A US40070273 A US 40070273A US 3814827 A US3814827 A US 3814827A
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United States
Prior art keywords
rod
diameter
stage
zone
control
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Expired - Lifetime
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US00400702A
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English (en)
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H Stut
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Siemens AG
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Siemens AG
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Priority claimed from DE19722247651 external-priority patent/DE2247651C3/de
Priority claimed from DE19732332968 external-priority patent/DE2332968C3/de
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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
    • C30B13/28—Controlling or regulating
    • C30B13/30—Stabilisation or shape controlling of the molten zone, e.g. by concentrators, by electromagnetic fields; Controlling the section of the crystal
    • 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
    • Y10T117/1068—Seed pulling including heating or cooling details [e.g., shield configuration]
    • 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
    • Y10T117/1076—Apparatus for crystallization from liquid or supercritical state having means for producing a moving solid-liquid-solid zone
    • Y10T117/1088—Apparatus for crystallization from liquid or supercritical state having means for producing a moving solid-liquid-solid zone including heating or cooling details

Definitions

  • the energy which is directed to the melting zone must be adjusted to the volume of the'required melting zone, as well as to the cooling conditions and the electrical coupling relations between the induction coil creating the melting zone and the melting zone itself.IThis is the case, for example, if a small core crystal is joined to a storage rod which is to be remelted by zone melting and has a larger diameter, and if the melting zone is at first createdat the border between the core and the storage rod.
  • the foregoing object isachieved in that information concerning the volume of the melting zone,proper angles and the melting and the solidifying front and at the turning point during the course of the melt-liquid part of a volume control system interposed in the actual di-;
  • the diameter at the solidifying front and the angles at the projecting points; solidifying front, melting front and turning point are determined from the pulses of the linearly scanned melting zone.
  • the geometric form of the conical rod part is determined by the respective diameter and the respective angle whereby the diameter and the corresponding angle constitute a function of the distance which was covered by the solidifying front. Accordingly, the diameter and the angles of projection are dependent in the form of a cosine function on the distance which has covered by 1 the solidifying front.
  • the first method wherein the volume is maintained at a constant level is sufficient for a quasi-stationary operation, whereby neither the traveling speedof the melting zone nor the diameters or the diameter relation, respectively, of the two rod parts, nor the radial or axial heat flowconditions change.
  • r is the radius of the core crystal
  • R is the radius of the finished cylindrical cosine-shaped junction, which preferably corresponds approximately to the diameter of the rod to be melted.
  • the'function of the angle of diameter a f (d) can be derived from the two functions of the diameter and the respective angle depending on the covered distance d f (x).
  • the application of this function for controlling the angle can also be advantageous if, due
  • changes of thegeometric and thermal conditions are to be expected if the melting zone approaches the rod end, or if the storage rod exhibits irregular diameters, of if the surrounding atmosphere changes or is changed, for example, the protective gas or vacuum, of if a doping gas flow strikes the melt-liquid zone.
  • a program is, for example, fed into a data processing arrangement 11.
  • the program which reflects the dependency of the rod diameter beginning at the core crystal and on which the distance covered by the phase border or the induction heating coil 12, respectively, is dependent on the functional course of the method which is to be described.
  • a television camera'20 scans the melting zone 2 of nism comprises an automatic volume control amplifier 4, which is subjacent to the actual diameter control loop comprising a control amplifier and an amplifier 5 for adjusting the diameter deviation to the desired volume value.
  • the energy supply to the heating coil 12 is controlled by way of a frequency generator 18 .(oscillater) from acontrol amplifier 6 having a parallel angle
  • These two automatic control systems are coupled with each other by way of a third geometry" automatic control system and the program unit ll in such a way that the desired geometric form of the junction is created without rendering the melt-liquid zone unstable, which means without causing the melt-liquid zone to freeze or flow off.
  • the melting zone is supervised by means of a television camera under constantly maintained recording conditions, whereby from the pictures of the melting zone recorded by the television camera electrical pulses are conducted by way of an optoelectronic image transformation.
  • This method is characterized in that the information is gained from the pulses supplied by the television camera, concerning the volume of the melting zone, projection angles at the melting front and the solidifying front, as well as the turning point during the course of the melt-liquid part of the melting zone and the diameter of the semiconductor rod at the solidifying front, in that this information is used for changing the distance of the rod ends to limit the melting zone and for changing the supplied energy, whereby the distance changing of the rod ends limits the melting zone for achieving a given diameter and is carried out by way of an automatic volume control system connected subjacent to the actual diameter automatic control system and in that the angle deviation of the projection angles from their desired value is employed for the correction of the energy supplied to the melting zone.
  • the present invention achieves improvement in crucible-free zone melting of a semiconductor rodv disclosed in the aforementioned patent application.
  • the invention concerns a device for floating zone melting of a semiconductor rod, whereby the vertically oriented semiconductor rod, which is supported at its ends by rod mountings which can be shifted in the direction of the rod axis, is surrounded coaxially by an induction heating coil creating the melting zone and which can be shifted axially, whereby furthermore an automatic control of the energy supplied automatic control system by which the angle of a respective diameter is adjusted to the desired. value.
  • control value d supplied by the data processing arrangement to the input stage of a first cascade automatic control system and the control value a (x supplied to the input stage of a second cascade automaticcontrol system experiences a comparison with the respective actual value supplied by the electronic camera by way of an evaluation calculator, while a signal in proportion to the respective control deviation is created as an input signal for the second stage of the respective cascade automatic control system;
  • a semiconductor rod 1 whichis to be the semiconductor rod 1, for example the lower mounting la, is designed to be axially shiftable in the direction indicated by the double headed arrow 9' relative to the second mounting so that a melting zone 2 covers the entire cross section of the semiconductor rod and the two rod parts separated by the melting zone can be brought closer to or moved further apart from each other.
  • a compressionstretch mechanism the mechanism controlling this movement is usually referred to as a compressionstretch mechanism.
  • various possibilities are known so that an illustration in the drawing anda corresponding discussion in the specification is superfluous.
  • the drive of the stretchmompression mecha-' nism is supplied by-a motor 8 which is controlledby the output of a first cascade automatic control system'.
  • the induction heating coil 12 issupplemented in the usual manner by a capacitor 12a connected in parallel thereto to form a high frequency resonant circuit with a fixed setting.
  • This high frequency resonant circuit is loosely coupled with a high frequency generator 18 by way of a coupling inductor 19.
  • the frequency of the electrical oscillations supplied by the generator 18 can be continuously changed in a frequency range contain ing the resonant frequency of the resonant circuit formed by the induction heating coil 12 and a capacitor 12a. so that activation of the adjustment of the HF generator 18, the energy which is transferred to the induc tion heating coil 12 can be changed.
  • a conventional television recording camera which can be coupled with a television playback device in order to make a visual control possible of the television picture of the melting zone 2 is employed as a control sensor to monitor the melting zone 2.
  • a suitable orientation of the electronic camera 20 in respect to the melting zone 2 and the constant maintenance of the recording conditions is provided for in such a way that each pulse supplied by the camera 20 per scanning cycle contains a definite information concerning a certain diameter of the picture recorded by the camera 20. This is the very case if the scanning lines on the target of the camera 20 are oriented vertical to the picture of the axis of the semiconductor rod 1 and if the optical axis of the recording lens which is directed onto the melting zone 2 maintains its length and inclination with respect to the rod axis.
  • the location x of the crystalization front of the melting zone 2 is supervised and the values corresponding to the location coordinate x preferably distance between crystalization front of the melting value and calculates with this numerical value the respective control value of d (x and at (x that is the values d (x and a (x)
  • the equation d k) o R (R r )cosx 1r/p. can be employed for determining the value d (x which is also used as a basis for the corresponding value a (x under consideration of the volume change.
  • r is the radius of the core crystal
  • R is the radius of the thicker normal rod
  • the coordination supervision device 21 may also operate, however, in such a way that any time the crystalization front has covered a distances, for example s 0.5 mm, a signal will appear by means of which the values ofd (x and a (x can be determined, according to a program which can be called upon from the data processing arrangement 11, in this case being designed as a memory. It is thereby possible to provide the signals a different character in case of a forward movement of the crystalization front than in the case of a backward movement, so that in case of a backward movement values which were already called upon can be prepared for a renewed call from storage.
  • the signal supplied by the integration stage is directed to the input of acorrection or control amplifier 4 by way of the line 4!).
  • a second input of the amplifier 4 is supplied with a magnitude as an actual value which was also obtained by integration, via the line 4a, which signal is binding for the geometric condition of the melting zone 2.
  • the output signal which is supplied by the amplifier 4 is directed to a third control stage formed by a recoupled amplifier 7 of the cascade forming the first control loop.
  • a recoupled amplifier 7 of the cascade forming the first control loop For the purpose of recoupling, the shaft of the motor 8 of the stretch-compression mechanism, which is operated by the third control stage, is firmly coupled with a tachometer generator 8a and the voltage supplied therefrom is applied to a second input of the amplifier 7. Therefore, stable rates of revolution of the motor 8 and a definite operation of the stretchcompression mechanism are achieved.
  • the previously mentioned controller-output a (x is applied to the input of the second cascade control loop or system of the arrangement according to the invention by way of the line 6!) and the respective actual value via the line 6a in the form of voltages which are in proportion to the actual values.
  • the first stage of this second cascade control system is provided by a correction or control amplifier 6 which creates a signal in proportion to the deviation of the value a (x This signal is directed to the second stage of the cascade automatic control system.
  • This control cascade is formed by a motor 13, a potentiometer l4 which is connectedto a non-illustrated direct current voltage source, and a correction or control amplifier 15.
  • the P] control character of this stage is provided by the motor 13 which changes the tapping point of the potentiometer l4 and therefore the direct voltage which is supplied as a value via the potentiometer 14.
  • the actual value is supplied by a resonant circuit containing the capacitor 12a and the induction heating coil 12. It should constitute a measure for the energy which is supplied to the resonant circuit, and therefore to the induction heating coil 12. I i
  • the alternating voltage at the capacitor 12a supplies. after rectification and possible smoothing by the rectifier arrangement 24, a voltage U which can be read at 21 volt meter 22 and which forms a measure for the energy accepted by the resonant circuit.
  • This voltage is applied-to one input of an amplifier 15 by way of the line 15b.
  • the voltage supplied by the potentiometer 14 is applied as a control value to the outer input of the amplifier 15' by way of the line 15b.
  • the motor 13 is activated as soon as a profile deviation ofa (x occurs. If it is zero, a balance should be given at the amplifier 15 between the value supplied by the potentiometer l4 and the voltage value U,. as the actual value supplied by the arrangement 24, which can be easily achieved by corresponding adjustment of the potentiometer setting. If the energy supply from the generator 18 for the coupling between the melting zone 2 and the induction heating coil 12 should change, the voltage U and also the actual value a (x will likewise change. In such a case, the control stages 6 and 15 will be activated until a balance is again established at the amplifier l5 and the deviation of a (x has disappeared. t
  • the output of-the second control stage 15 of the second cascade control system is connected to a recoupled third control stage comprising the amplifier 16, whose output operates a motor l7 to incluence the adjustment -9 of the generator 18.
  • the recoupling or feedback is provided by a resistor 23 connected between the output of the amplifier 16 and a second input of the amplifier. Contrary to the feedback conditions of the first cascade control system, this feedback system does not deal with a tachometer generator recoupling, but with an armature voltage recoupling which is sufficient in this case.
  • the amplitudes (pulse levels or height) only serve for selecting the various pulses, in particular the pulse relating to the-crystalization front and therefore the pulse P corresponding to the diameter d (x and the above mentioned neighboring pulse corresponding to the diameter d (.r,,- )t).
  • control values d (x and a (.r,,) are made available, which values are necessary for the input stages of the two cascade control systems, whereby these control values are called upon according to the location x of the crystalization front of the melting zone 2.
  • the control-deviation is generated in the first cascade control system and servesfor controlling the distance of the two mountings 1a and lbof the semiconductor rod 1 which is tobe melted, by means of time integration to a control magnitude which only causes the motor 8'energization to disappear if the diameter of the rod growing from the melting zone 2 is to remain constant and a deviationdoes not exist.
  • the respective actual value is the sum v is ear which is in proportion to the volume of the melting zone 2 (or a part of this volume which can be observed) and which should border the crystalization front.
  • the influencing of the energy supply to the induction heating coil 12 takes place in a similar manner byway of a second cascade automatic control system of the arrangement according to the invention.
  • the deviation of the marginal angle a(.r,,) which is applied at its input amplifier controls the second control system by way of an actuator or motor 13 which is similar to the integrator in the integration effect, whereby as a control magnitude for the second stage of this cascade the energy supply of the induction heating coil 12 is employed.
  • the electronic television camera 20 is used as a control sensor for the determination of the sum S
  • a different control sensor namely a rectifying and filter circuit 24 is employed.
  • a recoupled output stage 16 which influences the control path is employed to control the motor 17 to, in turn, control the frequency of the generator 18. Also, the rate of revolution of the motor 17 becomes, due to the feedback provided by the resistor 23, approximately proportional to the deviation of the energy.
  • control value d (x),) and a (x,,) is in any case selected insuch a way that it is'in accordance with the stability of the melting zone 2.
  • a method for the floating zone melting of a semiconductor rod, in particular a rod consisting of silicon comprising the steps of supplying energy to a zone of the rod for melting the zone; monitoring the molten zone with a television camera under constantly maintained recording conditions; generating electrical pulses from the recorded image representing volume of the molten zone, projection angles of the zone, the solidifying front and the turning point over the course of the melt-liquid partof the molten zone and the diameter of the semiconductor rod at the solidifying front; limiting the melting zone in responseto the information obtained from the generated pulses to obtain a desired diameter; and controlling the energy supplied in response to information from the electrical pulses concerning the angle deviations of the projection angles.
  • Apparatus for floating-zone melting of a semiconductor rod, particularly a silicon semiconductor rod comprising: I
  • a rod mount actuator connected to one of said rod mounts for axially moving said one mount
  • variable energizing supply means connected to said coil for energizing said coil to heat the rod and cre ate a melting zone
  • a supply actuator connected to said supply means for controlling the energy supplied to the rod
  • an electronic television camera operating to linearly scan the melting zone perpendicular to the rod axis and produce actual value information signals corresponding to rod diameter and profile angle of the melting zone and the crystalization front thereof;
  • a data processor receiving the information signals
  • first and second multi-stage control systems connected to said data processor and'to said rod mount actuator and said supply actuator, respectively;
  • monitoring means adjacent the rod for monitoring the position of the crystalization front and requesting first and second magnitudes from said data processor corresponding to the diameter at the crystalization front and to,the angle of the melting zone profile at the crystalization front, respectively, said first magnitude applied to said first control system and said second magnitude applied to said second control system;
  • a calculator connected between said television camera and said control systems for providing respective signals which are proportional to the signals representing actual value information;
  • first comparison stages in the respective control systems for comparing the respective values received from said calculator with those received from said data processor to provide respective control signals
  • said data processor is a calculator for calculating respective control signals representing rod diameter and profile angle at a monitored position, and said data processor is connected to said first stages of said control system.
  • said data processor includes a memoryfor storing information corresponding to rod diameter and profile angle and is responsive to said monitoring means to provide signals associated with the monitored position. to said first stages of said control systems.
  • said first control system comprises said first stage, an integrating stage as a part of said integrating means connected to said first stage as a second stage and an amplifier having inputs connected to said calculator and to said integrator and an output connected to said third stage.
  • Apparatus according to claim 9 wherein said calculator comprises means for supplying a sum of the squares of the pulses per scanning cycle generated by the television camera and a diameter value assigned to the image of the actual melting zone, and operates to evaluate'the pulses as to rod diameter.
  • said third stage includes an amplifier connected to said rod mount actuator, 21 tachometer included in the feedback circuit of said-third stage and connected to and operated by said rod mount actuator to create a feedback voltage, and means connecting said feedback voltage to said amplifier of said third stage.
  • said first stage of said second control system is operable to provide a signal which is proportional to the deviation of the profile angle, and comprising a potentiometer connected to an auxiliary voltage source, a potentiometer actuator connected to said first stage and operated thereby to provide a control value, a correction amplifier in said second stage of said second control system connected to receive said control value and connected to said heating coil to receive a signal value representative of heating coil energization.
  • connection between said correction amplifier and said heating coil includes rectifier means.
  • variable energizing supply means includes a high frequency generator variable in frequency for supplying high frequency energy to said induction heating coil, a resonant circuit including said heating coil loosely coupled to said high frequency generator, said high frequency generator being steadily variable over a frequency range which includes the resonant frequency of said resonant circuit.

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  • Chemical & Material Sciences (AREA)
  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Engineering & Computer Science (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Crystals, And After-Treatments Of Crystals (AREA)
US00400702A 1972-09-28 1973-09-25 Method and apparatus for floating zone melting of a semiconductor rod Expired - Lifetime US3814827A (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE19722247651 DE2247651C3 (de) 1972-09-28 1972-09-28 Vorrichtung zur Steuerung des Durchmessers eines Halbleiterstabes
DE19732332968 DE2332968C3 (de) 1973-06-28 1973-06-28 Vorrichtung zur Steuerung des durchmessers eines Halbleiterstabes

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US3814827A true US3814827A (en) 1974-06-04

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US00400702A Expired - Lifetime US3814827A (en) 1972-09-28 1973-09-25 Method and apparatus for floating zone melting of a semiconductor rod

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US (1) US3814827A (de)
DD (1) DD110182A5 (de)
DK (1) DK141784C (de)
FR (1) FR2201132B1 (de)
GB (1) GB1451622A (de)
HK (1) HK26477A (de)
IT (1) IT993934B (de)

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4162367A (en) * 1977-07-11 1979-07-24 Siemens Aktiengesellschaft Method of crucible-freeze zone-melting a semiconductor rod and apparatus for carrying out the method
US4845332A (en) * 1987-09-16 1989-07-04 National Steel Corp. Galvanneal induction furnace temperature control system
US4866230A (en) * 1987-04-27 1989-09-12 Shin-Etu Handotai Company, Limited Method of and apparatus for controlling floating zone of semiconductor rod
US4931945A (en) * 1987-12-05 1990-06-05 Shin-Etsu Handotai Company Limited Method of controlling floating zone
US6498327B1 (en) * 1998-12-04 2002-12-24 Ulf Thelander Method for inductive heating and monitoring

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3243509A (en) * 1962-04-27 1966-03-29 Siemens Ag Apparatus for measuring the molten zone diameter in zone-melting processes

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3243509A (en) * 1962-04-27 1966-03-29 Siemens Ag Apparatus for measuring the molten zone diameter in zone-melting processes

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4162367A (en) * 1977-07-11 1979-07-24 Siemens Aktiengesellschaft Method of crucible-freeze zone-melting a semiconductor rod and apparatus for carrying out the method
US4866230A (en) * 1987-04-27 1989-09-12 Shin-Etu Handotai Company, Limited Method of and apparatus for controlling floating zone of semiconductor rod
US4845332A (en) * 1987-09-16 1989-07-04 National Steel Corp. Galvanneal induction furnace temperature control system
US4931945A (en) * 1987-12-05 1990-06-05 Shin-Etsu Handotai Company Limited Method of controlling floating zone
US6498327B1 (en) * 1998-12-04 2002-12-24 Ulf Thelander Method for inductive heating and monitoring

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Publication number Publication date
DD110182A5 (de) 1974-12-12
DK141784C (da) 1980-11-03
FR2201132B1 (de) 1980-04-30
IT993934B (it) 1975-09-30
DK141784B (da) 1980-06-16
HK26477A (en) 1977-06-10
GB1451622A (en) 1976-10-06
FR2201132A1 (de) 1974-04-26

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