US3906889A - Crystal growing apparatus - Google Patents

Crystal growing apparatus Download PDF

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Publication number
US3906889A
US3906889A US325740A US32574073A US3906889A US 3906889 A US3906889 A US 3906889A US 325740 A US325740 A US 325740A US 32574073 A US32574073 A US 32574073A US 3906889 A US3906889 A US 3906889A
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substrate
ion
crystal
ion beam
crystal substrate
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US325740A
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Itiro Omura
Tadao Kaneko
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Hitachi Ltd
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Hitachi Ltd
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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
    • C30B23/00—Single-crystal growth by condensing evaporated or sublimed materials
    • C30B23/02—Epitaxial-layer growth
    • C30B23/06—Heating of the deposition chamber, the substrate or the materials to be evaporated

Definitions

  • a crystal growing apparatus comprises a Knudsen Ce" source of the surface ionization type, focusing means [52] US. Cl.
  • the present invention relates to a crystal growing apparatus, and more particularly to an apparatus which can control crystal growth two-dimensionally and precisely by scanning the surface of a crystal with an ion beam.
  • FIG. 1 is a schematic view showing the construction of a prior-art crystal growing apparatus
  • FIGS. and 2b are schematic views for explaining the subject matter of the present invention, respectively;
  • FIG. 3 is a schematic view showing the construction of an embodiment of crystal growing apparatus according to the present invention.
  • FIG. 4 is a block diagram showing a control unit suitable for the crystal growing appratus according to the present invention.
  • FIG. 1 is a view shows prior-art crystal growing apparatus using neutral molecular beams.
  • meral l designates a vacuum chamber in which crystal growth is carried out, 2 Knudsen cells (in the illustrated case, two cells) used as a molecular beam source, 3 a crystal substrate to be grown, 4 mass analyzing means (for example, a quadrupole mass filter) for evaluating the ratio of partial pressures within the vacuum chamber l, and 5 an electron gun.
  • Neutral molecular beams emitted from the Knudsen cells 2 are caused to fall on the crystal substrate 3, to grow a single crystal on the substrate 3. It is a common practice in this case that, using an electron beam e generated from the electron gun 5, electron-diffraction patterns of the growing crystal are sequentially observed on a fluorescent screen 6.
  • the control of the crystal growth is effected by a temperature control for the substrate 3.
  • the ratio of partial pressures of the molecules within the vacuum chamber 1 is therefore evaluated by the mass analyzing means 4.
  • the temperature of the substrate. 3 is suitably controlled in response to the magnitude of the ratio of partial pressure. Heating means is omitted from the illustration.
  • the prior-art crystal growing apparatus uses neutral molecular beams, it has disadvantages as stated below.
  • the use of the neutral molecular beams makes it impossible to form a two-dimensional molecular concentration distribution on the substrate.
  • the control of the crystal growth is performed only with the substrate temperature. More specificially, the ratio of partial pressure as evaluated by the mass analyzing means is based on those molecules among the total neutral molecular beams being supplied to the substrate which are not absorbed on the substrate, in other words, the quantity of the molecules absorbed on the substrate.
  • the control of the crystal growth with only changes in the quantity of the molecules does not provide a precise control.
  • the present invention employs a Knudsen cell source of the surface ionization type in order to generate ion beams, and effects crystal growth with the ion beams.
  • the Knudsen cell source of the surface ionization type is an ion source which has hitherto been well known.
  • the atoms are passed through a tungsten porous material, they are ionized according to the Saha-Langmuirs equation at their departure from the surface of the material.
  • the Knudsen cell source of the surface ionization type is at a temperture of approximately 1,000C and can efficiently generate ions by increasing the porosity of the tungsten material.
  • one of the most important factors for the probability of surface ionization is the relation between the ionization potential of the specimen atom and the work function of the porous material.
  • the work function of the employed material is about 5.5 eV
  • about 50% of the atoms which come into contact with the material are ionized as for indium (In) whose ionization potential is 5.79 eV.
  • About 1 to 50% of atoms are ionized, as for an element whose ionization potential is approximately 10 eV.
  • FIGS. 2a and 2b are views for explaining the subject matter of the present invention which makes use of the Knudsen cell source of the surface ionization type.
  • ion beams from the Knudsen cell 7 source of the surface ionization type pass through focusing electrostatic lenses 8, and are focused on a substrate 3.
  • the Knudsen cell source of the surface ionization type consists of two cells, it may be similarly composed of a single cell.
  • the magnitude of the ion beams is detected by means of mesh electrodes and ion detectors 9 which are arranged between the focusing electrostatic lines 8 and the substrate 3.
  • the ion beams focused on the substrate 3 are neutralized by the interaction with low energy-electron rays emanating from an electron gun 11.
  • the crystal based on the neutral molecular beams is grown on the substrate 3. Further, if necess'ary, the growing process is successively observed in such way that electron-diffraction patterns of the crystal by high energy-electron rays emanating from an electron gun are formed on a fluorescent screen 6.
  • FIG. 2b is a view for explaining the state in which the ion beam is scanned on the crystal by a deflecting electrode.
  • the ion beam ejected from the Knudsen cell source 7 of the surface ionization type is focused by the focusing electrostatic lens 8, to reach the surface of the substrate 3.
  • the ion beam having reached the substrate 3 scans the surface of the substrate 3 as, for example, shown by dotted lines in the figure by virtue of the deflecting electrode 10. In this case, the scanning speed is freely changed, whereby the distributed state of a multi-layer film gradually growing on the substrate 3 can be varied as desired.
  • FIG. 3 is a schematic view showing the construction of an embodiment of the present invention.
  • the same symbols as in FIGS. 2a and 2b represent the same or equivalent parts.
  • the Knudsen cell source of the surface ionization type 7 consists of three cells.
  • Reference numerals 1 and 4 designate the same vacuum chamber and mass analyzing means as illustrated in FIG. 1, respectively.
  • Numeral 12 indicates a total ion beam detector by which, in case of utilizing a plurality of ion source cells, an ion beam with the respective ion beams focused into a single one is detected.
  • specimen atom ions ejected from the Knudsen cell source of the surface ionization type 7 are focused on the substrate 3 by the focusing electrostatic lens 8.
  • ion beams generated from the cells of the Knudsen ion source of the surface ionization type are respectively detected by the ion detectors 9-1, 9-2 and 9-3.
  • the total quantity of the ion beams is detected by the total ion beam detector 12.
  • a signal from the total ion beam detector 12 is fed back to the electron gun 11, to control the magnitude of an electron beams so as to neutralize the ion beam on the substrate 3 by the electron beam.
  • the ion beam can scan the surface of the substrate 3 by varying the drive voltage of the deflecting electrode 10.
  • the scanning can be made by signals, such as saw-tooth waves. introduced from deflection voltagesupplying means (not shown),
  • signals from the ion detectors 9-1, 9-2 and 9-3 are compared with the signal from the total ion beam detector 12 (no comparator being shown) so as to evaluate the proportions occupied by the ions of the individual beams relative to the total ions.
  • the ratio of partial pressure of molecules within the vacuum vessel or specimen chamber 1 is detected by the mass analyzing means, for example, a quadrupole mass filter 4.
  • a twodimensional concentration distribution of the molecules can be formed in addition to the threedimensional growth of the crystal in the process of the crystal growthby the scanning of the ion beam. Furthermore, according to the present invention, both the ratio of partial pressure and the proportions occupied by the quantities of the ions of the individual beams (where the Knudsen cell source of the surface ionization type consists of a single cell, the quantity of the ions from the single ion cell corresponds to the above proportions) are produced as output signals. Using the output signals, a precise control for the crystal growth may be made in such a way that the output signals of both the quantities and the substrate temperature as well as the ionic amount are calibrated beforehand, or that the electron-diffraction patterns are observed.
  • the temperature of the substrate and/or the quantity of the ejected ion beam from the ion source may be appropriately controlled so as to effect the desired crystal growth.
  • the heating temperature of a heater may be increased or decreased, while in order to control the quantity of ions ejected from the ion source, the tungsten porosity of the Knudsen cell source of the surface ionization type may be increased or decreased.
  • FIG. 4 is a block diagram of a control unit which, using both the proportions occupied by the quantities of the ions and the ratio of partial pressure as control signals, controls the quantities of the ions and the temperature of the crystal substrate in the apparatus of the embodiment shown in FIG. 3.
  • Reference numeral 13 designates a comparator which compares outputs from the ion detector 9 and the total ion detector 12.
  • a computing device 14 receives, as its inputs, an output from the comparator 13 and an output from the quadrupole mass filter 4 (the ratio of partial pressure as referred to above), and generation a control signal for controlling the quantity of emission of the ions or the temperature of the substrate, namely, for controlling the crystal growth.
  • a deflecting voltagegenerator 15 generates a deflection voltage (saw-tooth wave voltage) for the deflecting electrode 10.
  • Numerals l7 and 18 represent an ion beam-controller (for example, a current amplifier) and a substrate temperturecontroller (for example, a current amplifier), respectively, each of which receives as its input an output from the computing device 14.
  • Shown at 19 is a memory means.
  • Display means 20 is composed of. for example, a Braun tube and displays the concentration of the ion beam.
  • Numeral 21 indicates a heater for heating the crystal substrate3.
  • the ion beams generated from the Knudsen'cell source of the surface ionization type 7 are respectively detected by the ion detector 9.
  • Each output of the detector 9 is one of the inputs of the comparator 13.
  • the focused ion beam is detected by the total ion beam detector 12, whose output is the other input of the comparator l3 and a control signal for the electron gun 11.
  • the electron gun 11 has its grid potential controlled by the control signal from the total ion beam detector 12, and generates an electron beam sufficient for the total ion beam to be neutralized on the crystal substrate 3. Since the deflecting electrode has the saw-tooth wave voltage applied thereto from the deflection voltage-generator 15, the ion beam having passed through the focusing electrode means 10 is scanned on the crystal substrate 3.
  • the proportions occupied by the ions of the individual beams with respect to the total ions are evaluated therein.
  • One of the output signals indicating the proportion is one of the inputs to the computing device 14, while the other output signal is an input to display means 20.
  • a change in the ratio of partial pressures within the vacuum chamber 1 is evaluated by the mass analyzing means 4.
  • the output of the mass analyzing means 4 is the other input of the computing device 14.
  • the computing device 14 calculates, from the ratio of partial pressures of the molecules wiithin the vacuum chamber 1 and the ratio of the quantity of each ion beam to the quantity of all the ion beams, whether a change in, for example, the ratio of partial pressures is due to a change in the temperature of the substrate or due to a change in the quantity of the ion beam ejected from the Knudsen cell source of the surface ionization type 7.
  • the output of the computing device 14 becomes the control signal to the ion beam-controller 17 and/or the substrate temperature-control means 18, and is applied thereto.
  • an output signal from the ion beam-controller 17 or from the substrate temperature-control means 18 adjusts the quantity of the emitted ion beam from the Knudsen cell source of the surface ionization type 7 or the output of the heater 21, accordingly, the temperature of the crystal sub strate.
  • the output of the comparator 13 is applied to display means 20. It is, therefore, possible that the ratio of the quantity of the emitted ions of each beam to the total quantity of the emitted ions, namely, the ion beam concentration is displayed by sweeping the applied output signals with the saw-tooth wave voltage from the deflection voltage-generating means 15. Thus, the ion beam concentration can be observed while the crystal is being grown.
  • the sequence of radiation of the radiated ion beams effecting the crystal growth, the kinds of ions constituting the beams, etc. are stored in the memory means 19.
  • the crystal growth is carried out with the deflection voltage-generating means and the computing device 14 controlled by outputs from the memory means 19. Then, any desired multilayer film can be manufactured.
  • the crystal growth can also be controlled in case where the Knudsen cell source of the surface ionization type consists of a single cell. In this case of the single cell, the total ion beam detector 12 shown in FIG. 4 is unnecessary.
  • the quantity of the ion beam from the Knudsen cell source of the surface ionization type and the ratio of partial pressure fed from the quadrupole mass filter 4 are merely compared and operated, to calculate the control output to be applied to the ion beam-controller l7 and the temperature control means 18.
  • the control of the quantity of the emitting ion beams of the Knudsen cell source of the surface ionization type has been stated as being conducted by the use of the analyzed result obtained from the mass filter and the detected results obtained from the ion detector means and the total ion detector means.
  • the analyzed result need not be used.
  • the arithmetic unit 14 shown in FIG. 4 performs operations on condition that the temperature of the substrate 3 is invariable.
  • a crystal growing apparatus comprising:
  • ion detector means for detecting the quantity of the ion beam irradiated from said ion source
  • focusing means for focusing said ion beam onto said crystal substrate
  • beam deflector means for scanning the focused ion beam on said crystal substrate
  • detector means for detecting the ratio of the partial pressures of the molecules within said vacuum chamber
  • a crystal growing apparatus comprising:
  • a Knudsen cell source of the surface ionization type consisting of a plurality of cells and for irradiating a plurality of ion beams onto said crystal substrate; first ion detector means for detecting the quantity of ions of each of said plurality of ion beams; focusing means for focusing said ion beams onto said crystal substrate; beam deflector means for scanning the focused ion beam on said crystal substrate; second ion detector means for detecting the total quantity of ions of said plurality of ion beams; means for generating an electron beam for neutralizing said focused ion beam on said crystal substrate; detector means for detecting the ratio of the partial pressures of the molecules within said vacuum chamber; means for receiving the outputs from said first and second ion detector means and for evaluating the ratio between said total quantity of ions and said quantity of ions of said each ion beam; and
  • the crystal is so grown as to have a two dimensional distribution of concentrations of the molecules by the scanning of said focused ion beam.
  • a crystal growing apparatus comprising:
  • a vacuum chamber within which a crystal substrate to be grown may be disposed
  • first means for irradiating a crystal substrate disposed within said chamber with particles of opposite charge by at least one ion beam
  • second means coupled to said first means, for detecting the magnitude of said at least one ion beam
  • third means coupled to said chamber, for detecting the ratio of the partial pressures of molecules within said chamber
  • fourth means coupled. to said second and third -means, for controlling the irradiation of said at least one ion beam by said first means in accordance with theoutputs of said second and third means, whereby aresulting neutralized particle is grownuponsthe surface of said substrate.
  • said first meansfurther includes means for focusing said at least one ion beamonto said substrate and for scanning the focusedionbeam on said crystal substrate.
  • said first-means comprises means for irradiating said substrate with a plurality of ion beams.
  • sixth means coupled to the outputs of said second and fifth means, for providing a signal representative of the ratiobetween said total quantity of ions and the quantity of ions of each ion beam, whereinsaid fourth means is coupled to said third and sixth means for controlling the irradiation of said ion beams by said first means in accordance withthe outputs of said third and sixth means.
  • said first means for irradiating said crystal substrate commprises a Knudsen cell source of the surface ionization type having a plurality of cells therein for irradiating said substrate with a plurality of ion beams.
  • An apparatus further comprising display means, responsive to the output of said secondmeans, and being synchronized with said scanning means, for displaying the output of said second means, whereby the ion beam concentration can be observed.
  • An apparatus further comprising means, responsive to the output of said fourth means, for controlling the temperatureof said crystal substrate.
  • An apparatus further comprising seventh means, coupled to said first and fourth means, for controlling the quantity of said at least one ion beam, and i eighth means, coupled to said crystal substrate and said fourth means, for controlling the temperature of said substrate, 6 wherein said fourth means applies a signal to at least i one of said seventh and eighth means as a function of the outputs of said second and third means such that crystal growth on said substrate proceeds in accordance with the crystal growth conditions of quantity of said at least one ion beam and temperature of said substrate.
  • An apparatus further comprising seventh means, coupled to said first and fourth means, for controlling the quantity of said plurality of ion beams, and
  • said fourth means applies a signal to at least one of said seventh and eighth means as a function of the outputs of said third and sixth means such that crystal growth on said substrate proceeds in accordance withthe crystal growth conditions of quantity of said plurality of ion beams and temperature of said substrate.
  • said first means further includes means for focusing said ion beams onto said crystal substrate scanning for acanning said focused beams in said crystal substrate.
  • said first means further includes means for accelerating crystal growth of said substrate by irradiating said substrate with a neutral molecular beam.
  • said first means for irradiating said crystal substrate with a plurality of ion beams comprises a Knudsen cell source substrate.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Physical Deposition Of Substances That Are Components Of Semiconductor Devices (AREA)
  • Crystals, And After-Treatments Of Crystals (AREA)
  • Liquid Deposition Of Substances Of Which Semiconductor Devices Are Composed (AREA)
  • Physical Vapour Deposition (AREA)
US325740A 1972-01-21 1973-01-22 Crystal growing apparatus Expired - Lifetime US3906889A (en)

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Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4639377A (en) * 1984-04-24 1987-01-27 Hitachi, Ltd. Thin film formation technique and equipment
US4855013A (en) * 1984-08-13 1989-08-08 Agency Of Industrial Science And Technology Method for controlling the thickness of a thin crystal film
FR2703077A1 (fr) * 1993-03-24 1994-09-30 Harmand Jean Christophe Dispositif de régulation de flux issus de cellules d'évaporation de matériaux solides, utilisant des vannes asservies à des mesures de pressions partielles.
US6753042B1 (en) * 2000-05-02 2004-06-22 Itac Limited Diamond-like carbon thin film coating process
US20100320045A1 (en) * 2008-04-04 2010-12-23 Muska Martin A System and method for tuning the resonance frequency of an energy absorbing device for a structure in response to a disruptive force

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3547074A (en) * 1967-04-13 1970-12-15 Block Engineering Apparatus for forming microelements
US3563809A (en) * 1968-08-05 1971-02-16 Hughes Aircraft Co Method of making semiconductor devices with ion beams
US3573098A (en) * 1968-05-09 1971-03-30 Boeing Co Ion beam deposition unit
US3602709A (en) * 1968-03-14 1971-08-31 Bell & Howell Co Mass analyzer including magnetic field control means

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3547074A (en) * 1967-04-13 1970-12-15 Block Engineering Apparatus for forming microelements
US3602709A (en) * 1968-03-14 1971-08-31 Bell & Howell Co Mass analyzer including magnetic field control means
US3573098A (en) * 1968-05-09 1971-03-30 Boeing Co Ion beam deposition unit
US3563809A (en) * 1968-08-05 1971-02-16 Hughes Aircraft Co Method of making semiconductor devices with ion beams

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4639377A (en) * 1984-04-24 1987-01-27 Hitachi, Ltd. Thin film formation technique and equipment
US4855013A (en) * 1984-08-13 1989-08-08 Agency Of Industrial Science And Technology Method for controlling the thickness of a thin crystal film
FR2703077A1 (fr) * 1993-03-24 1994-09-30 Harmand Jean Christophe Dispositif de régulation de flux issus de cellules d'évaporation de matériaux solides, utilisant des vannes asservies à des mesures de pressions partielles.
US6753042B1 (en) * 2000-05-02 2004-06-22 Itac Limited Diamond-like carbon thin film coating process
US20100320045A1 (en) * 2008-04-04 2010-12-23 Muska Martin A System and method for tuning the resonance frequency of an energy absorbing device for a structure in response to a disruptive force

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JPS4878871A (enrdf_load_html_response) 1973-10-23

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