A single crystal for the manufacture of disk devices surface acoustic waves and the method of its production

 

(57) Abstract:

The invention relates to the production of dependence of frequency-selective devices for surface acoustic wave (saw) and bulk acoustic wave (BAW). The essence of the invention as a single crystal for the manufacture of disk devices on surfactant use monocrystal entangling niobate or entangling tantalate diameter 86-110 mm in the direction of thermostable slice obtained by the Czochralski method by loading in the iridium crucible pre-synthesized single-crystal mixture, which is obtained by fusing synthesized in the form of a shaped tablets polycrystalline mixture obtained by sintering the respective oxides in the space between the inner walls Lungolago crucible with a diameter equal to the diameter iridium crucible for single crystal growth and lundevall tube in its Central part, collected in the form of a hollow cylinder along the Central axis which passes crystallochemical with seed, the internal surface Lungolago crucible and the outer surface lundevall tube cover platinum; creating a protective atmosphere is carried out in two stage is, the lead bare oriented in the direction of thermostable cut crystal in contact with the surface of the melt and pulling on him the crystal. The invention allows to obtain high-quality large single crystals while simplifying the synthesis method and the rational use of raw materials. 2 S. and 2 C.p. f-crystals.

The invention relates to the production of dependence of frequency-selective devices for surface acoustic wave (saw) and bulk acoustic wave (BAW).

Known for single crystal drive devices surfactant-silica (and.with. N 439056, MKI: H 03 H 9/00, 1972). However, he does not have high temperature stability and provides good piezoelectric quality, which limits the possibility of using it in acoustoelectronics.

The closest substance to the claimed is a single crystal entangling silicate, to produce disks for devices surfactant of not more than 75-80 mm (WO 98/40544, MKI: 30 B C 29/34, 15/00, C 01 G 15/00, priority 30.12.97 year). Indications promising single crystal of a piezoelectric material shows not sufficiently high piezoelectric properties, which limits its application.

The known method paluwagan crucible to oriented towards 0001, 1010, 1120 seed, in a flowing atmosphere of a mixture of oxygen and nitrogen, using previously obtained by solid-phase synthesis mixture by sintering in air source compressed oxides of lanthanum, gallium, tantalum or lanthanum, gallium, niobium, respectively (B. M. Mille, A. C. Butashin, ,, Hagavatam and other rare earth Modified gallaty with the structure of Ca3Ga2GeO14. Reports of the USSR Academy of Sciences, 1982, I. 264, No. 6, S. 1385-1389). The disadvantage of this method is the use of pressure equipment for briquetting the mixture, which pollutes the charge at the stage of its preparation ions of the latter, and hence, reduces the quality of the crystals and complicates the process; the cultivation of the platinum crucible does not give the possibility to grow large crystals due to the limited operational capabilities of platinum; and the orientation of the obtained crystals does not provide a rational, low-way cut crystal on drives to SAS.

The closest in technical essence and the achieved result of the claimed method is a method of growing entangling tantalate and entangling niobate by Czochralski method, include the Lee nitrogen with the addition of oxygen (U.S. Pat. RF N 2152462, MKI: 30 B C 15/00; C 30 B 29/22, 10.07.2000,)

However, this method does not provide the required diameter of the grown crystals for the manufacture of standard discs with a diameter of 3 and 4 inches, accepted in the world practice, and the crystals grown in this way have insufficient quality for use in devices, surface acoustic wave (possible defects, cracks).

The technical object of the present invention to provide a high-quality large single crystals entangling tantalate or entangling niobate while simplifying the synthesis method and the rational use of raw materials with the aim of obtaining a high-quality discs that meet the requirements for manufacturing devices on the SAS.

The problem is solved by the fact that as a single crystal for the manufacture of disk devices surfactant with the structure of rare-earth gallates use monocrystal entangling tantalate (langatate) or entangling niobate (langasite) diameter 86-110 mm in the direction of thermostable slice. And in a known way to obtain this monocrystal by Czochralski method, including the loading of iridium SUB>3Ga5,5Nb0,5O14, creating a protective atmosphere of argon and oxygen, the subsequent melting of the material, the introduction of a rotating seed oriented crystal in contact with the surface of the melt, and pulling on it oriented crystal, as charge using single-crystal mixture, the seed crystal entangling tantalate or entangling niobate is oriented in the direction of thermostable slice, and create a protective atmosphere is carried out in two stages: the melting of the charge is injected only one gaseous argon, and after melting the mixture add oxygen. Moreover, single-crystal mixture obtained by fusing pre-synthesized in the form of a shaped tablets mixture obtained by sintering the respective oxides in the space between the inner walls Lungolago crucible with a diameter equal to the diameter iridium crucible for growing crystals, and lundevall tube installed in its Central part, collected in the form of a hollow cylinder along the Central axis which passes crystallochemical with seed. The internal surface Lungolago crucible and the outer surface lundevall trubatch surface acoustic waves langatate or langasite, which show an increase of the piezoelectric properties due to the strong polarizability of the two ions in the deformed node of the octahedron, in comparison with other materials can meet continuously increasing demand for all kinds piezoelectronic devices for industrial and domestic use. The data sizes used single crystals with a diameter of 86-110 mm ensure minimal loss of devices on the periphery of the disc in relation to the total number of products on the entire surface of the disc. When the crystals have a thermostable slice, i.e. the same orientation, which provides reception of these plates oriented with close to zero values of temperature coefficient of frequency, and the absence of crystal scattering centers, controlled optically.

In obtaining single crystals of langatate or langasite using single-crystal mixture composition of La3Ga5,5Ta0,5O14or La3Ga5,5Nb0,5O14causes growing large high-quality single crystals for subsequent manufacture accepted in the world practice standard drives langatate or langasite diameter 76,2 and 101,2 mm

When Orien is langasite crystals grow along the precisely selected thermostable slice, that allows you to cut from the grown crystal disks at an angle of 90 degrees to the longitudinal axis of the crystal (perpendicular to the direction of growth), while ensuring minimal loss of material and near zero temperature coefficient of frequency. The requested orientation of the seed crystal langatate or langasite - thermostable cut - allows you to grow single crystals of langatate or langasite, oriented along the direction of thermostable slice.

Creating a protective atmosphere in two stages, namely the melting of the charge is injected only one gaseous argon, and after melting, add oxygen, prevents oxidation of the inner walls of iridium crucible at the time of melting of the charge, and therefore, prevents the ingress of particles of iridium metal in the melt, and then in crystal.

Growing single-crystal mixture is performed by fusing pre-synthesized mixture in the form of a shaped tablets obtained by sintering in the space between the inner walls Lungolago crucible with a diameter equal to the diameter of the crucible for single crystal growth, and lundevall tube installed in its Central part. In allelucht loss components in contrast to briquetting. In addition, the inner part Lungolago crucible and the outer part lundevall tube for solid-phase synthesis of cover pure platinum Pt is 99.9%, which eliminates the contamination of the charge uncontrollable impurities during its synthesis and sintering.

Shaped tablets mixture corresponding to the composition of La3Ga5,5Ta0,5O14or La3Ga5,5Nb0,5O14collected in the form of a hollow cylinder for fusion in a crucible along a Central axis which passes crystallochemical with seed, this eliminates the possibility of them lowering past the crucible when melting the bottom of tablets in the crucible, and as a result, no loss of charge. The use of molded tablets mixture for the synthesis of single-crystal mixture allows instead of 3-4 cycles to build-up of charge at one time, right after that begins the persecution of the single crystal on a seed crystal, which raskrashivaut to a given diameter, and the pulling of the single crystal. The overmoulding process is carried out in one step, resulting in a composite with the persecution and growth of the single crystal in one technological cycle, which provides a more rational use of expensive Obskoy increases in the perfection of the crystal structure of the crystals.

All the above causes:

- reduction of gas consumption to create a protective atmosphere 3-4 times;

- reducing the number of preliminary operations, reducing the complexity of the process;

- exception violation stoichiometry of the melt for growing single crystals.

Examples of specific performance

Example No. 1.

As a source of chemicals used gallium oxide, qualifications OFS 15-2, meet THE 6-09-3777-80 with the content of the basic substance (Ga2O3) not less than 99.99%, the oxide of lanthanum brand Lao-D that meets THE 48-4-523-90 with the content of the basic substance (La2O3) not less than 99.99%, and the oxide of tantalum, qualifications OFS 14-4, meet THE 6-09-5016-82 with the content of the basic substance (Ta2O5) not less than 99.99%. Polycrystalline mixture is prepared in the form of 9 tablets weight 2290 g, which weighed the source chemicals: oxides of lanthanum mass 1004,03 g, gallium oxide mass 1061,12 g and tantalum oxide mass 226,96 g placed in 9 plastic cans and mixed for 2 hours each. Prepared 9 mixtures fall asleep at nine landowych crucibles with a diameter of 130 mm, a volume of 3 l, in the Central part of which has Alentova tube diameter, Rav Crucibles with a mixture of the original oxide covered with a lid and set in the oven solid-phase synthesis, turn up the heat until 1430oC for 6 hours, then produce exposure for 6 hours and cooled to 200oC. Source polycrystalline mixture, obtained by the claimed method, in compact form, in the form of a shaped tablets with a diameter of 120 mm, with a hole along its axis, corresponds according to x-ray phase analysis of the composition of La3Ga5,5Ta0,5O14. Next for growing high-quality single crystal of langatate diameter 86 mm weight 4390 g used in the future to manufacture discs with a diameter of 76.2 mm, it is necessary to prepare single-crystal mixture, the mass 6580 g, for which three grown single crystal weighing 4400 g of polycrystalline mixture prepared by the method of solid-phase synthesis. What three iridium crucible having a diameter of 120 mm, height 120 mm, wall thickness and bottom of 2 mm, made of iridium brand And is 99.9, download three tablets weight 2290 g each. Then three of the crucible is placed in molds of cultivating plants and produce an Assembly of thermal units. Molds are pumped to a residual pressure of 10-3PA and putting a high-purity argon (99,998%) and produce the complete melting of charge. After melting of the charge and shielding melt DNAs for growing single crystals corresponded to the composition (99% Ar + 1% O2). Later in contact with the surface of the melt is injected rotary oriented in one of the stable directions of the seed crystal langatate and produce growing a single crystal of langatate. Received three single crystal of langatate weight of 4400 g each subjected to analysis for the content of impurities. Controlled mass-spectroscopic analysis of the total content of impurities in the melt does not exceed 510-4wt.%. After this one crystal is cut in half and 2 pure iridium crucible having a diameter of 120 mm, height 120 mm, wall thickness, and the bottom 2 mm, annealed in vacuum better than 10-3PA at 1700oC, is loaded single-crystal mixture according 6300 g in each. Iridium crucibles with the single-crystal mixture are installed in the mold of cultivating plants and Assembly of thermal units. Molds are pumped to a residual pressure of 10-3PA and putting a high-purity argon (99,998%), and produce a complete melting of charge. After melting of the charge and shielding melt the inner walls of iridium crucible into the mould putting oxygen in an amount such that the gas mixture for growing single crystals corresponded from thermostable directions of the seed crystal langatate and produce growing a single crystal of langatate at speeds of Kristallografiya 10.min, the axial gradient of 15 degrees./cm and a growth rate of 2 mm per hour. The control beam He-Ne laser showed no evidence of scattering centers. The grown crystals have orientation thermostable slice. From the obtained high-quality crystal with a diameter of 86 mm, a height of the straight cone (1) - 35 mm, height of the cylindrical part (2) is 100 mm, the height of the inverted cone (3) - 25 mm, weight: 4100 g by cutting perpendicular to the growth axis get 70 thermostable discs cut with a diameter of 76.2 mm (3 inches). Two grown high-quality crystals 140 drives.

Example 2.

As a source of chemicals used gallium oxide, qualifications OFS 15-2, meet THE 6-09-3777-80 with the content of the basic substance (Ga2O3) not less than 99.99%, the oxide of lanthanum brand Lao-D that meets THE 48-4-523-90 with the content of the basic substance (La2O3) not less than 99.99%, and the oxide of tantalum, qualifications OFS 14-4, meet THE 6-09-5016-82 with the content of the basic substance (Ta2O5) not less than 99.99. Polycrystalline mixture is prepared in the form of 10 tablets weight 3360 g, which weighed the source chemicals: oxides of lanthanum mass 1473,17 g, gallium oxide mass 1556,93 g and the oxide of tantalum by weight of 333 g and placed in 10 plastic cans IEMA 5 l, in the Central part of which has Alentova tube diameter equal to the diameter of Kristallografiya. The inner surface landowych crucibles and the outer surface lundevall tube is coated with platinum. The crucible with a mixture of the original oxide covered with a lid and set in the oven solid-phase synthesis include heating to 1400oC for 6 hours, then produce exposure for 6 hours and cooled to 200oC. Source polycrystalline mixture, obtained by the claimed method, in compact form, in the form of a shaped tablets with a diameter of 150 mm, with a hole along its axis, corresponds according to x-ray phase analysis of the composition of La3Ga5,5Ta0,5O14. Next for growing high-quality single crystal of langatate with a diameter of 110 mm and weight 8150 g, subsequently used for the manufacture of disk diameter to 101.2 mm, it is necessary to prepare single-crystal mixture, the mass 16800 g, for which two grown single crystal with a weight of 8400 g of polycrystalline mixture prepared by the method of solid-phase synthesis. To do this in two iridium crucible with a diameter of 160 mm, height 160 mm, wall thickness and bottom of 2 mm, made of iridium brand And is 99.9, download five tablets weight 3360 grams each. Congestion pumped to a residual pressure of 10-3PA and putting a high-purity argon (99,998%), and produce a complete melting of charge. After melting of the charge and shielding the inner walls of iridium crucible into the mould putting oxygen in an amount such that the gas mixture for growing single crystals corresponded to the composition (99% Ar + 1% O2). Later in contact with the surface of the melt is injected rotary oriented in one of the stable directions of the seed crystal langatate and produce growing a single crystal of langatate. Received two single crystal of langatate weight of 8400 g each subjected to analysis for the content of impurities. Controlled mass-spectroscopic analysis of the total content of impurities in the melt does not exceed 510-4wt.%. After that, both of the single crystal is placed in pure iridium crucible with a diameter of 160 mm, height 160 mm, wall thickness, and the bottom 2 mm, annealed in vacuum better than 10-3PA at 1700oC. the Iridium crucible with the single-crystal mixture is set in the mold growth installation and Assembly of thermal node. The mold is pumped to a residual pressure of 10-3PA and putting a high-purity argon (99,998%), and produce a full logo crucible into the mould putting oxygen in such numbers, to gas mixture for growing single crystals corresponded to the composition (99% Ar+ 1% O2). Later in contact with the surface of the melt is injected rotary oriented in one of the stable directions of the seed crystal and produce growing a single crystal of langatate at speeds of Kristallografiya about 10. /min, the axial gradient of 15 degrees./cm and a growth rate of 2 mm per hour. The control beam He-Ne laser showed no evidence of scattering centers. The grown crystals have orientation thermostable slice. From the obtained high-quality crystal with a diameter of 110 mm, a height of the straight cone (1)-40 mm, a height of the cylindrical part (2)-125 mm, the height of the inverted cone (3)-30 mm, weight 8630 g, by cutting perpendicular to the growth axis receive 85 drives thermostable cutoff diameter to 101.2 mm (4 inches).

Example No. 3.

As a source of chemicals used gallium oxide, qualifications OFS 15-2, meet THE 6-09-3777-80 with the content of the basic substance (Ga2O3) not less than 99.99%, the oxide of lanthanum brand Lao-D that meets THE 48-4-523-90 with the content of the basic substance (La2O3) not less than 99.99%, and the oxide of niobium, qualifications OFS 14-4, meet THE 6-09-5016-82 with the content of jus g, why weigh the source chemicals: oxides of lanthanum mass 1017,39 g, gallium oxide mass 1073,87 g and niobium oxide mass 138,26 g placed in 9 plastic cans and mixed for 2 hours each. Prepared 9 mixtures fall asleep at nine landowych crucibles with a diameter of 130 mm, a volume of 3 l, in the Central part of which has Alentova tube diameter equal to the diameter of Kristallografiya. The inner part of the crucibles and the outer part landowych tubes coated with platinum. The crucible with a mixture of the original oxide covered with a lid and set in the oven solid-phase synthesis include heated to 1420oC for 6 hours, then produce exposure for 6 hours and cooled to 200oC. Source polycrystalline mixture, obtained by the claimed method, in compact form, in the form of a shaped tablets with a diameter of 120 mm, with a hole along its axis, corresponds according to x-ray phase analysis of the composition of La3Ga5,5Nb0,5O14. Next for growing high-quality single crystal langasite diameter of 86 mm and a weight of 4300 g used in the future to manufacture discs with a diameter of 76.2 mm, it is necessary to prepare single-crystal mixture weight 6600 g, for which three grown monocrystal is yevich crucible with a diameter of 120 mm, height of 120 mm, wall thickness and bottom of 2 mm, made of iridium brand And is 99.9, download three tablets weight 2230 grams each. Then three of the crucible is placed in molds of cultivating plants and produce an Assembly of thermal units. Molds are pumped to a residual pressure of 10-3PA and putting a high-purity argon (99,998%), and produce a complete melting of charge. After melting of the charge and shielding melt the inner walls of iridium crucible into the mould putting oxygen in an amount such that the gas mixture for growing single crystals corresponded to the composition (99% Ar + 1% O2). Later in contact with the surface of the melt is injected rotary oriented in one of the stable directions of the seed crystal langasite and produce growing single crystal langasite. Received three single crystal langasite weight of 4400 g each subjected to analysis for the content of impurities. Controlled mass-spectroscopic analysis of the total content of impurities in the melt does not exceed 510-4wt. %. After this one crystal is cut in half and 2 pure iridium crucible having a diameter of 120 mm, height 120 mm, wall thickness, and the bottom 2 mm, annealed in vacuum n the e crucibles with the single-crystal mixture are installed in the mold of cultivating plants and Assembly of thermal units. Molds are pumped to a residual pressure of 10-3PA and putting a high-purity argon (99,998%) and produce the complete melting of charge. After melting of the charge and shielding melt the inner walls of iridium crucible into the mould putting oxygen in an amount such that the gas mixture for growing single crystals corresponded to the composition (99% Ar + 1% O2). Later in contact with the surface of the melt is injected rotary oriented in one of the stable directions of the seed crystal langasite and produce growing single crystal langasite at speeds of Kristallografiya 10.min, the axial gradient of 15 degrees. /cm and a growth rate of 2 mm per hour. The control beam He-Ne laser showed no evidence of scattering centers. The grown crystals have orientation thermostable slice. From the obtained high-quality crystal with a diameter of 86 mm, a height of the straight cone (1) - 35 mm, height of the cylindrical part (2) is 100 mm, the height of the inverted cone (3) - 25 mm, weight 4115 g, by cutting perpendicular to the growth axis get 70 thermostable discs cut with a diameter of 76.2 mm (3 inches). Two grown high-quality crystals 140 drives.

The proposed mo is ishemic in turn for manufacturing filters for surfactant systems for mobile and cellular communication and the claimed method of cultivation allows to obtain single crystals with a diameter of 86 and 110 mm With the industrial technology of growing large crystals is environmentally friendly, waste-free, and grown crystals are of high quality and free of scattering centers, controlled optically.

1. A single crystal for the manufacture of disk devices surface acoustic waves with the structure of gallogermanate calcium, characterized in that it uses a single crystal entangling tantalate or entangling niobate diameter 86-110 mm in the direction of thermostable slice.

2. A method of producing single crystal for the manufacture of disk devices surface acoustic waves by the Czochralski method, including loading in the iridium crucible of the mixture corresponding to the composition of La3Ga5,5TA0,5O14or La3Ga5,5Nb0,5O14, creating a protective atmosphere of argon and oxygen, the subsequent distribution of the material, the introduction of a rotating seed oriented crystal in contact with the surface of the melt and pulling on it oriented crystal, characterized in Chile interalliance niobate is oriented in the direction of thermostable slice, while creating a protective atmosphere is carried out in two stages: when fusing enter only gaseous argon, and after melting the mixture add oxygen.

3. The method according to p. 2, wherein the single-crystal mixture obtained by fusing pre-synthesized in the form of a shaped tablets mixture obtained by sintering the respective oxides in the space between the inner walls Lungolago crucible with a diameter equal to the diameter of the crucible for single crystal growth and lundevall tube installed in its Central part, collected in the form of a hollow cylinder along the Central axis which passes crystallochemical with seed.

4. The method according to p. 3, characterized in that the inner surface Lungolago crucible and the outer surface lundevall tube used for solid-phase synthesis, covered with platinum.

 

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FIELD: Czochralski method for crystal growth from melt, in particular crystals of heat-resistant multicomponent compounds.

SUBSTANCE: single crystal lithium aluminate LiAlO2 is obtained by using Czochralski method in inductive heating equipment. Crystal growth process includes batch melting containing lithium aluminate in iridium crucible followed by single crystal drawing from melt onto oriented seed crystal in inert gas atmosphere. Beforehand prepared batch-cake obtained by compounding of aluminum oxide and lithium carbonate, wherein lithium carbonate excess is 2-4 % in respect to stoichiometric ratio, is used as raw batch. Mixture is heat treated in two steps: at temperature 700oC in the first step and at 1050oC in the second one with holding for 3 h in each step. To prevent losses of volatile batch components crystallization is carried out under excess (not less than 0.3 atm) pressure of inert gas, and at the beginning of growth process broader surface square is screened, seed crystal is grown up to diameter equal to 0.8 of crucible one, then crystal is drawn up to desired length while finished diameter is decreased up to 0.5-0.6 of crucible one. As a result reusable crystal part has form of truncated cone. Single crystal lithium aluminate produced according to present invention is useful in disc production served as substrate in epitaxial film growth, in particular gallium nitride (GaN) films.

EFFECT: coarse-grained crystals of high quality.

1 ex, 1 tbl, 1 dwg

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