US3805044A - Computerized process control system for the growth of synthetic quartz crystals - Google Patents

Computerized process control system for the growth of synthetic quartz crystals Download PDF

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Publication number
US3805044A
US3805044A US00131916A US13191671A US3805044A US 3805044 A US3805044 A US 3805044A US 00131916 A US00131916 A US 00131916A US 13191671 A US13191671 A US 13191671A US 3805044 A US3805044 A US 3805044A
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United States
Prior art keywords
autoclave
crystal
temperature
zone
tau
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Expired - Lifetime
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US00131916A
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English (en)
Inventor
R Bhattacharyya
A Fiore
D Rudd
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AT&T Corp
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Western Electric Co Inc
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Priority to US00131916A priority Critical patent/US3805044A/en
Priority to CA127,660A priority patent/CA957251A/en
Priority to DE19722215998 priority patent/DE2215998A1/de
Priority to IT89565/72A priority patent/IT975681B/it
Priority to GB1593272A priority patent/GB1385234A/en
Priority to IL39146A priority patent/IL39146A/xx
Priority to FR7212139A priority patent/FR2132727B1/fr
Priority to BE781750A priority patent/BE781750A/xx
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Publication of US3805044A publication Critical patent/US3805044A/en
Assigned to AT & T TECHNOLOGIES, INC., reassignment AT & T TECHNOLOGIES, INC., CHANGE OF NAME (SEE DOCUMENT FOR DETAILS). EFFECTIVE JAN. 3,1984 Assignors: WESTERN ELECTRIC COMPANY, INCORPORATED
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D9/00—Crystallisation
    • B01D9/02—Crystallisation from solutions
    • 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
    • Y10T117/1096—Apparatus for crystallization from liquid or supercritical state including pressurized crystallization means [e.g., hydrothermal]

Definitions

  • G06f 15/46 n n algorithm y which a g p nt [58] Field of Search 235/1511, 151.12; computer can make adaptive changes to the currents 23/301 R supplied to heating elements associated with the upper and lower zones of the autoclave, during the 25 day [56] References Cited growth cycle, to yield a superior crystal of high Q.
  • this invention relates to the growth of synthetic crystals. More particularly, in a preferred embodiment, this invention relates to a computercontrolled process for growing synthetic crystals having substantially uniform mechanical properties throughout all crystallographic regions of the crystal.
  • quartz silicon dioxide
  • quartz has proved to be most suitable for use in electronic circuitry. This is due to the superior physical properties possessed by quartz, for
  • An important factor in analyzing the performance of a vibrating piezoelectric crystal is its internal friction.
  • This parameter may be defined as the ratio of the energy which is converted into heat within the crystal to the total energy supplied to the crystal when resonating at its natural frequency.
  • the internal friction is related to imperfections in the crystal structure. Because this energy loss is low, the numerical value for the internal friction of mostcrystals is a very small number. It is, thus, more convenient to define a quality factor, Q, equal to the reciprocal of the internal friction.
  • This mechanical Q is analogous to the Q of a tuned L,R,C circuit defined as Q (wL/R) (l/mCR) where w Zrr X the frequency of resonance.
  • the excellent circuit properties of uartz are due, in part, to the very high ratio of mass to elastance (this is equivalent to a high L/C ratio in a conventional tuned circuit) and to the very high ratio of mass to damping (this is equivalent to a high Q in a conventional tuned circuits).
  • the Q of a natural quartz crystal is in the order of from 10,000 to 30,000 with values ranging up to 500,000 or more for specially treated crystals mounted in a vacuum.
  • quartz crystals are employed, for example, in the channel filters associated with frequency multiplex carrier systems, and as frequency control elements in the oscillators associated with coaxial cable carrier systems, and the like.
  • the telephone industry has been BEST AVAILABLE COPY forced to use carrier systems having carrier frequencies and sidebands which fall higher and higher in the frequency spectrum.
  • the Q requirements of a typical quartz resonator have been found to be as follows: from 0 to Khz a Q of about l00,000 is required; from 100 to 300 Khz a Q of about 300,000 is required; from 300 Khz to about I Mhz a Q of from 400,000 to 800,000 is required; and from 1 to 10 Mhz crystals having Qs up to 1,000,000 are required.
  • Silicon dioxide or natural quartz, is believed to constitute approximately 1/10 of the earth's crust.
  • EDT ethylene diamine tartrate
  • the remaining volume of the autoclave is filled to about 80 percent capacity with a solvent which is capable of dissolving quartz.
  • a solvent which is capable of dissolving quartz.
  • a solvent which is capable of dissolving quartz.
  • a solvent which is capable of dissolving quartz.
  • a solvent which is capable of dissolving quartz.
  • a solvent which is capable of dissolving quartz.
  • a solvent which is capable of dissolving quartz.
  • a solvent which is capable of dissolving quartz.
  • a solvent which is capable of dissolving quartz.
  • a solvent which is capable of dissolving quartz.
  • NaOl-I sodium hydroxide
  • dopants such as lithium nitrate (LiNO may be added to the solution to improve the characteristics of the crystals.
  • the vessel is then sealed and heat is applied to the upper and lower zones of the autoclave. Typically, the upper zone is heated to about 630F and the lower zone to about 700F.
  • the action of the heat causes the nutrient quartz to dissolve in the alkaline solution and, because the upper zone is relatively cooler than the lower zone, the solvated quartz flows by convection to the upper end of the autoclave.
  • the baffle plate which separates the two halves of the autoclave contains a plurality of small holes, and serves to maintain two essentially isothermal zones within the vessel. In addition, the baffle plate helps to channel the convected flow of solvated quartz from the lower zone to the upper zone.
  • the action of the heat which is applied to the autoclave causes the aqueous solution of a sodium hydroxide within the autoclave to expand, generating pressures in the order of 25,000 pounds per square inch.
  • the upper, or crystallization zone is some 70F cooler than the lower zone, when the aqueous solution arrives at the upper zone, it cools and quartz precipitates out of solution and nucleates onto the seed crystals in the form of a single crystal.
  • the process varies in time, depending upon the size of the crystals desired, but nominal growing times are in the order of from three to four weeks.
  • the seed crystals grow in X, Y, and Z directions.
  • the above-described crystal growing process is referred to as a fast Z-growth, or fast basal growth process. 5
  • the synthetic crystals are removed from the autoclave for further processing. Crystal units are then cut from the synthetic crystals and, as is well known, these cuts may be made in any of several orientations, for example, X cut, Y cut, BT cut, CT cut, etc. For telecommunication purposes, however, most quartz crystal devices operate in the lower and middle frequency ranges.
  • the Q of a basal cut slice will vary throughout the slice and the average Q, from slice to slice, will also vary.
  • the problem is to find a technique for growing synthetic crystals whereby the crystals may be made to exhibit predetermined mechanical properties throughout selected crystallographic regions thereof.
  • a substantially vertically disposed autoclave is charged with a crystal growing nutrient, the autoclave being functionally divided into two essentially isothermal zones.
  • the autoclave is then partially filled with a solvent capable of dissolving said nutrient, and at least one seed crystal suspended, proximate the upper zone of the autoclave.
  • the autoclave then is sealed and heat is applied to the upper and lower zones thereof to increase the pressure and temperature above the levels required to dissolve the nutrient in the solvent.
  • the temperature of the lower zone is established at a higher value than that of the upper zone to permit a convective flow of solvated nutrient over the surfaces of the seed crystal.
  • the temperature differential between the upper and lower zones is altered selectively as time proceeds so as to change t e tale 0f BEST AVAILABLE COPY flow of solvated nutrient over the seed crystal.
  • the growth rate of the crystal is selectively altered thereby causing the crystal to exhibit the desired predetermined mechanical properties.
  • One illustrative apparatus for practicing the above method comprises a substantially vertically disposed autoclave which is functionally divided into an upper and a lower zone.
  • the autoclave is adapted to receive a charge of crystal growing nutrient in the lower zone and of being substantially filled with a solvent capable of dissolving the nutrient.
  • the apparatus further includes means for suspending at least one seed crystal within the autoclave, proximate the upper zone thereof as well as first and second heating means which are respectively associated with the upper and lower zones.
  • a source of energy for the first and second heating means is also provided as well as computer means for respectively adjusting the amount of energy supplied to the first and second heating means from said source, whereby the temperature differential between the upper and lower zones of the autoclave is selectively altered during the crystal growing process.
  • FIG. 1 is a partially cut-away, isometric view of an hydrothermal autoclave of a type suitable for use with the present invention
  • FIG. 2 is a graph depicting the relationship between crystal growth and growth rate, as a function of time, for a crystal grown in the autoclave of FIG. 1;
  • FIG. 3 is a graph depicting the relationship between the Q of a crystal and the elapsed time for a crystal grown in the autoclave of FIG. 1;
  • FIG. 4 is a drawing, prepared from an actual photography of a shadowgram, showing how the Q of a crystal is assigned to different physical locations within the body of the crystal;
  • FIG. 5 is a graph depicting the relationship between the Q of a crystal and its growth rate for a crystal grown in the autoclave of FIG. 1;
  • FIG. 6 depicts an illustrative profile of the desired temperatures for the upper and lower zones of a computer-controlled autoclave according to the present invention
  • FIG. 7 is a graph which depicts the autocorrelation between samples in the mathematical model of the autoclave of the present invention.
  • FIG. 8 is a graph depicting the root mean square error, as a function of time, for the mathematical model of the autoclave of the present invention.
  • FIG. 9 depicts a graph of the estimated value of the parameter w, as a function of y, for region 4 of the upper zone in the mathematical model of the autoclave of the present invention.
  • FIG. 10 is a graph depicting the relationship between the upper and lower zone temperatures, as a function of time, during the warm-up phase of the autoclave of FIG. 1;
  • FIG. 11 depicts the formula used to predict the temperature of the autoclave of FIG. 1;
  • FIG. 12 depicts the formulae used to compute the heater currents for the heating elements associated with the autoclave of FIG. 1;
  • FIG. 13 depicts the formulae used to update the value of the parameter K in the mathematical model of the autoclave of FIG. 1;
  • FIG. 14 depicts the values of the estimated off-line parameters for the mathematical model of an experimental hydrothermal autoclave actually built and tested
  • FIG. 15 depicts one illustrative apparatus configuration for practicing the present invention.
  • FIGS. 16 22 depict an illustrative logical flow chart for implementing the algorithm of the present invention
  • FIG. 23 illustrates the manner in which FIGS. 16 22 should be assembled
  • FIG. 24 depicts a graph of the estimated value of the parameter w, as a function of 7, for region 4 of the lower zone in the mathematical model of the autoclave of FIG. 1;
  • FIG. 25 depicts a graph of the estimated value of the parameter w, as a function of y, for region 1 of the upper zone in the mathematical model of the autoclave of FIG. 1.
  • This invention is based upon the discovery that the uniformity of synthetically-grown crystals may be improved by controllably increasing the temperature differential between the upper and lower zones of an autoclave, throughout the growth cycle, to maintain a relatively constant rate of flow of solvated nutrient over the seed crystals.
  • the crystal growing process must be mathematically characterized so that the temperature differential necessary to maintain a constant rate of convective flow can be calculated for any instant of time during the growth cycle.
  • a real-time, direct digital control algorithm must be derived so that appropriate changes may be made to the current which is supplied to the heating coils associated with the upper and lower zones of the autoclave to produce the desired temperature differential for the time period of interest.
  • the illustrative embodiment of the invention pertains to the growth of synthetic quartz crystals.
  • One skilled in the art will appreciate that the invention is not so limited, and may be used with equal facility in any hydrothermal crystal growing process.
  • the use of the invention to grow crystals other than quartz merely requires modification of the parameters of the control algorithm and the crystal growing equations.

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  • Chemical & Material Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Crystals, And After-Treatments Of Crystals (AREA)
US00131916A 1971-04-07 1971-04-07 Computerized process control system for the growth of synthetic quartz crystals Expired - Lifetime US3805044A (en)

Priority Applications (8)

Application Number Priority Date Filing Date Title
US00131916A US3805044A (en) 1971-04-07 1971-04-07 Computerized process control system for the growth of synthetic quartz crystals
CA127,660A CA957251A (en) 1971-04-07 1971-11-15 Computerized process control system for the growth of synthetic quartz crystals
DE19722215998 DE2215998A1 (de) 1971-04-07 1972-04-01 Von einem elektronischen Rechner gesteuertes Kristallzüchtungsverfahren
GB1593272A GB1385234A (en) 1971-04-07 1972-04-06 Crystal growing
IT89565/72A IT975681B (it) 1971-04-07 1972-04-06 Sistema di comando di processo computorizzato per l accrescimento di cristalli di quarzo sintetici
IL39146A IL39146A (en) 1971-04-07 1972-04-06 Method and apparatus for controlling the rate of growth of synthetic crystals
FR7212139A FR2132727B1 (de) 1971-04-07 1972-04-06
BE781750A BE781750A (fr) 1971-04-07 1972-04-06 Procede de regulation de la croissance de cristaux de quartz synthetiques par ordinateur

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US00131916A US3805044A (en) 1971-04-07 1971-04-07 Computerized process control system for the growth of synthetic quartz crystals

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US3805044A true US3805044A (en) 1974-04-16

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US (1) US3805044A (de)
BE (1) BE781750A (de)
CA (1) CA957251A (de)
DE (1) DE2215998A1 (de)
FR (1) FR2132727B1 (de)
GB (1) GB1385234A (de)
IL (1) IL39146A (de)
IT (1) IT975681B (de)

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3922527A (en) * 1974-12-26 1975-11-25 Nat Forge Co Temperature control apparatus
US3971876A (en) * 1974-12-26 1976-07-27 National Forge Company Temperature control apparatus
US4401487A (en) * 1980-11-14 1983-08-30 Hughes Aircraft Company Liquid phase epitaxy of mercury cadmium telluride layer
US5135603A (en) * 1982-03-11 1992-08-04 The United States Of America As Represented By The United States Department Of Energy Quartz crystal growth
US6238480B1 (en) * 1997-04-30 2001-05-29 Sawyer Research Products, Inc. Method and apparatus for growing crystals
US20090222124A1 (en) * 2008-02-29 2009-09-03 Fisher Controls International Llc Estimation of process control parameters over predefined travel segments
US8236102B1 (en) * 2008-01-30 2012-08-07 Solid State Scientific Corporation Hydrothermal methods of fabricating trivalent-metal-ion-doped sapphire crystals

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3183063A (en) * 1961-05-31 1965-05-11 Western Electric Co Autoclave for growing quartz crystals
US3621213A (en) * 1969-11-26 1971-11-16 Ibm Programmed digital-computer-controlled system for automatic growth of semiconductor crystals

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3183063A (en) * 1961-05-31 1965-05-11 Western Electric Co Autoclave for growing quartz crystals
US3621213A (en) * 1969-11-26 1971-11-16 Ibm Programmed digital-computer-controlled system for automatic growth of semiconductor crystals

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3922527A (en) * 1974-12-26 1975-11-25 Nat Forge Co Temperature control apparatus
US3971876A (en) * 1974-12-26 1976-07-27 National Forge Company Temperature control apparatus
US4401487A (en) * 1980-11-14 1983-08-30 Hughes Aircraft Company Liquid phase epitaxy of mercury cadmium telluride layer
US5135603A (en) * 1982-03-11 1992-08-04 The United States Of America As Represented By The United States Department Of Energy Quartz crystal growth
US6238480B1 (en) * 1997-04-30 2001-05-29 Sawyer Research Products, Inc. Method and apparatus for growing crystals
US8236102B1 (en) * 2008-01-30 2012-08-07 Solid State Scientific Corporation Hydrothermal methods of fabricating trivalent-metal-ion-doped sapphire crystals
US20090222124A1 (en) * 2008-02-29 2009-09-03 Fisher Controls International Llc Estimation of process control parameters over predefined travel segments
US7996096B2 (en) * 2008-02-29 2011-08-09 Fisher Controls International Llc Estimation of process control parameters over predefined travel segments

Also Published As

Publication number Publication date
CA957251A (en) 1974-11-05
IL39146A (en) 1975-07-28
BE781750A (fr) 1972-07-31
IL39146A0 (en) 1972-06-28
IT975681B (it) 1974-08-10
FR2132727B1 (de) 1974-08-02
DE2215998A1 (de) 1972-10-19
GB1385234A (en) 1975-02-26
FR2132727A1 (de) 1972-11-24

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